Sciences : histoire orale

HAGENMULLER Paul, 2001-06-12

Sophie Jourdin — 2011-11-03T15:23:16Z

Paul Hagenmuller, born in Alsace in 1921, developed solid-state chemistry in France. He first initiated a research program at the University of Rennes (1956-60). In 1960 he set up a dynamic laboratory in Bordeaux. In 1964, Hagenmuller organized an international conference dedicated to the relations between structure and physical properties in oxides of the transition elements. The meeting gathered together chemists, crystallographers and solid-state physicists and prompted the establishment of an international community of solid-state chemists. In Bordeaux, Hagenmuller became the head of a research school working, at the interface between physics and chemistry, on the relation between atomic/electronic structure and physical properties, with a strong emphasis on industrial applications.

The Bordeaux research school has attracted scientists and students from all over the world (both developed and emerging countries) and many brilliant chemists of the next generation such as Jean Rouxel were trained in Bordeaux. Paul Hagenmuller retired in 1994. A jubilee celebration was organized at the Maison de la chimie in Paris in 1997. In 2001, his 80th birthday was celebrated in a special issue of the journal Solid State Chemistry.

HERVE ARRIBART (HA) : Pouvez vous retracer votre formation, vos débuts dans la carrière ?

PAUL HAGENMULLER (PH) : Depuis que je m'intéresse à la science je me suis préoccupé de la physique. Je me suis demandé pourquoi les matériaux avaient telle ou telle couleur, tel ou tel comportement électrique, magnétique, optique ... J'ai donc été porté vers la physique, plus tard vers la mécanique par extension, dès que j'ai entrepris mes études de science. Ces études ont eu lieu en 1940 à l'université de Strasbourg, repliée à Clermont Ferrand. Mon statut était celui d'un réfugié politique puisque j'avais quitté l'Alsace pour échapper au système politique allemand et parce que je me refusais d'être un jour mobilisé dans l'armée allemande. A Clermont, pour des raisons financières j'ai fait le choix de la chimie, séduit par la diversité des méthodes de préparation mais choqué parce que la chimie était alors très descriptive et n'était pas encore une science déductive, de réflexion.
Sur place, je suis entré en résistance, je faisais du sabotage. J'ai été arrêté en 1943 et envoyé en camp de concentration à Buchenwald. Là j'ai appris à me taire. J'ai travaillé sur les V2. J'ai appris le russe avec les prisonniers russes ; j'avais de bons contacts avec les communistes allemands. Puis j'ai été envoyé à Dora où c'était plus dur.
Après la guerre, André Chrétien m'a proposé un sujet de thèse sur la formation de nitrites complexes en solution aqueuse, puis une recherche sur la réduction de divers oxydes par des hydrures d'alcalino-terreux. J'ai accepté parce qu'il y avait un appareil mathématique. Puis au lendemain de ma thèse je me suis dit : il faut que je travaille sur des choses plus concrètes, les matériaux. J'ai voulu revenir à mes anciennes amours les matériaux. Je suis parti au Vietnam dans le cadre d'un accord avec la direction de l'enseignement supérieur et moi. Je partais pour deux ans 1954-56, au moment où la France se désengageait et voulait garder des relations culturelles. Au retour il était entendu que je pourrai choisir un poste de maître de conférences parmi ceux qui étaient disponibles en chimie. Ces deux ans de Vietnam ont été pour moi une période de décantation, de réflexion. Et quand je suis revenu j'ai voulu, d'une part, me préoccuper de physique ce qui suppose la détermination des structures atomiques - pour comprendre les propriétés physiques il faut savoir quelles sont les positions des atomes - et, d'autre part, il faut une certaine habileté à préparer des matériaux par des techniques nouvelles fort différentes.

HA : Quelles étaient alors les relations entre physique des solides et chimie des matériaux en France ?

PH : Aujourd'hui la physique s'est beaucoup rapprochée de la chimie parce que, de part et d'autre, on a compris que c'était indispensable pour faire des matériaux à propriétés spécifiques intéressantes sur le plan de la science fondamentale et intéressantes aussi sur le plan des applications. Au début des années 60, on en était à se chercher. Moi, j'avais fait un choix très clair : faire une chimie orientée vers la physique, plus tard vers la mécanique. Maintenant c'est devenu presque de routine, ne serait-ce que par ce que les chimistes pour bien connaître leurs matériaux sont obligés d'utiliser des méthodes de caractérisation physiques. La physique s'est imposée dans les perspectives de la recherche comme par les nécessités quotidiennes : savoir où sont les atomes et les électrons.
Donc au retour du Vietnam mon objectif était d'associer la physique et la chimie. J'ai eu la chance que dans mon poste à Rennes il y avait quantité d'excellents étudiants, mais en chimie personne ne voulait faire de la recherche sous prétexte qu'il n'y avait pas de moyens. J'ai décidé que j'allais lancer des thèses dans ce domaine à l'interface de la physique et de la chimie. On a d'abord tâtonné. On a travaillé sur le bore, sur les hydrures. Parmi les études réalisées à Rennes se trouvait la réduction d'oxydes par l'hydrure de lithium. On était intéressé par les hydrures de bore et d'aluminium qui comportaient des liaisons dites pont-hydrogène originales. Ceci m'a donc amené à réduire le V2O5 par l'hydrure de lithium et nous avons constaté qu'il y avait des phases intermédiaires qui devaient être les futurs bronzes de vanadium et de lithium, qu'on a appelées plus tard b et g. La phase a étant la solution solide de lithium dans V2O5. Alors j'ai pensé que ces matériaux étaient intéressants : s'il y a là un domaine d'existence, les propriétés physiques doivent varier à l'intérieur de ce domaine et si, par chance, ce domaine est suffisamment grand on peut faire ce qui est plus difficile dans les solutions solides limitées, de type oxydes non stœchiométriques. On s'est préoccupé de manière systématique des bronzes de vanadium qu'on a préparés par voie synthétique. Dans les années qui ont suivi - de 1960 à 70, j'étais alors à Bordeaux où un grand nombre de chercheurs de Rennes m'avaient suivi - on a préparé un grand nombre de phases de bronzes de vanadium par analogie avec les bronzes de tungstène qui avaient déjà été signalés. On a fait systématiquement des études magnétiques et électriques pour caractériser le mode de conductivité. Il est apparu que lorsqu'on insérait le lithium dans le réseau, on remplissait les états électroniques du vanadium, qui forment la bande de conduction. Les électrons devenaient donc de plus en plus délocalisés au fur et à mesure que leur nombre augmentait et on passait d'un état semi-conducteur à l'état métallique.

BERNADETTE BENSAUDE-VINCENT (BBV) : Quelles étaient vos relations avec le groupe de Robert Collongues ?

PH : Collongues avait été élève de Georges Chaudron, comme André Michel, Paul Lacombe, Jacques Bénard. J'avais d'excellentes relations avec Collongues. Nos domaines se recouvraient partiellement sur la non-stœchiométrie mais on avait des approches différentes. Lui enlevait des ions, nous on faisait de la chimie d'insertion. Collongues aimait bien se singulariser par rapport à moi mais dans la pratique nous avions la même politique sur des matériaux différents. Il y avait chez lui le même désir de systématique et de réflexion en profondeur. Collongues considérait que la bonne expérience était importante mais qu'elle devait illustrer une réflexion de fond. Il pensait que la science était avant tout la réflexion intellectuelle.
J'ai fait de la chimie sous pression à la manière d'un tailleur : choisir une structure cristallographique, écrire la formule d'une composition chimique, puis la stabiliser dans un degré d'oxydation élevé. Après avoir discuté la structure puis la formule, on préparait sous haute pression. C'était du design pour la conductivité électronique, les propriétés magnétiques, ou les propriétés magnéto-optiques et plus tard également pour la conductivité ionique.
Nous nous intéressions systématiquement à l'évolution de toute propriété physique originale en fonction de la composition et de la structure. Un nœud important dans cette évolution fut le colloque organisé à Bordeaux en 1964 sur les oxydes d'éléments de transition.

HA : Quelle fut la portée de ce colloque de 1964 ?

PH : Ce fut le moment où s'est constituée une communauté internationale de chimie du solide. Le colloque a rassemblé les chimistes qui nous étaient familiers, des cristallographes (Erwin-Felix Bertaut, Charles Guillaud), des physiciens (Jacques Friedel). Parmi les étrangers Mike Sienko, John Goodenough du Lincoln Laboratory au MIT qui est venu pour la première fois à Bordeaux ; des Allemands : Wilhelm Klemm, Rudolf Hoppe, Harold Schäfer ; des Hollandais, des Belges, etc. Il est apparu qu'une conjugaison des méthodes de mesure physique, des méthodes de détermination structurale et une certaine flexibilité pour les changements de composition, pouvaient permettre d'optimiser un certain nombre de propriétés physiques. D'abord le magnétisme, ensuite il y a eu la ferro-électricité - comment accroître la distortion ferro-électrique et par voie de conséquence la polarisation ; enfin, la conductivité ionique, d'abord dans des matériaux isolants au point de vue électronique et ensuite dans des matériaux dits cathodiques utilisables dans des batteries parce que conducteurs mixtes.
Je dois dire que ce qui fut déterminant pour l'avenir de la chimie du solide ce fut la venue de John Goodenough à ce congrès parce qu'il a popularisé parmi nous l'idée de l'importance de la liaison chimique. On a compris qu'on pouvait renforcer ou atténuer la liaison chimique en modifiant la composition, en particulier en jouant sur la liaison antagoniste. Par exemple si on compare le zirconate de baryum avec le titanate de baryum, la liaison baryum-oxygène est renforcée dans le zirconate par rapport au titanate. Inversement si on remplace dans le titanate de baryum, le baryum par le strontium comme la liaison strontium -oxygène est plus forte que la liaison baryum-oxygène, la liaison titane-oxygène est affaiblie, ce qui peut amener une variation très forte de la polarisation en fonction de la température, juste en dessous de la température de Curie. Et on peut avoir ainsi des matériaux aux propriétés intéressantes.

HA : Le rapprochement de la physique et de la chimie avec une orientation vers les applications constituerait-il donc l'identité de la chimie du solide à cette époque ?

PH : Oui nous avions un besoin civique de justifier les crédits que nous demandions par une application dans la vie économique. De plus, le travail avec des industriels fait naître des problèmes inattendus qui sont des challenges et qui sont nourrissants.
Une deuxième date importante dans l'institutionnalisation de la chimie du solide est 1978. Sur mon initiative la Société française de Chimie a créé en 1976 une division de chimie du solide, dont j'ai naturellement été le président. J'ai organisé la même année un premier colloque national de chimie du solide à Nantes. Sur ma proposition et sous ma présidence s'est tenu à Strasbourg en 1978 le premier congrès européen de chimie du solide, organisé par Jean-Claude Bernier (Strasbourg a été choisi pour une raison stratégique,). L'intervalle entre deux congrès consécutifs est maintenant de 3 ans ; le huitième congrès européen a lieu en juillet 2001 à Oslo.

HA : Quel était l'état des relations entre science et industrie en France à cette époque ?

PH : Il y avait une tradition de collaboration en métallurgie et en chimie : Chaudron et ses élèves, Lacombe, Bénard étaient très impliqués. Robert Collongues l'était aussi dans le domaine des monocristaux. Mais il y avait une forte hostilité syndicale au nom des grands principes : il ne faut pas mettre la science au service des grands intérêts privés. Les choses se sont atténuées à la veille de l'élection présidentielle de 1981. J'ai eu la visite de M. Kahane, longtemps doyen à Orsay, qui s'était rallié à la collaboration avec l'industrie privée. Cela a facilité cette évolution qui, de ma part, ne rencontrait aucune résistance car j'étais un scientifique et je n'avais pas à me poser des problèmes de déontologie qui me paraissaient un peu artificiels. Mais une partie de mon entourage était réticente à travailler avec l'industrie.

HA : Est-ce la crise pétrolière de 1973 qui a contribué à anoblir le rapprochement entre science et industrie ?

PH : Oui. Du fait de notre préoccupation entre propriétés physique et composition, nous avons été conduits à travailler sur des composés non-stœchiométriques d'intercalation et nous avons constaté après 1973 qu'il y avait possibilité d'intercalation ou désintercalation à basse température grâce à l'électrochimie comme on le faisait aux Etats Unis. Exxon et Bell étaient plus concernés que nous par la crise de l'énergie.
Les recherches sur la conductivité ionique ont été encouragées par la crise de l'énergie. Après la zircone déjà exploitée par Nernst, puis étudiée par la NASA et par Collongues ; il y avait eu AgI. Puis il y a eu l'alumine-b qui a suscité de nombreux travaux. CGE a dépensé beaucoup d'argent. L'alumine-b est un matériau très particulier. J'étais très sceptique. On a abaissé la température de fonctionnement, mais c'est encore trop haut pour un véhicule électrique. Et puis le soufre attaque la membrane. Finalement on a renoncé, pensant qu'avec des batteries au lithium on irait plus loin. Les derniers efforts de développement visaient plutôt le stockage d'énergie en période creuse. Les nasicons eux ne sont pas attaqués et ils présentent un avantage au plan fondamental car leur structure est plus simple. Ils ont de bonnes performances, qu'on pouvait maîtriser avec une juste proportion de sodium.

HA : Pouvez vous évoquer vos travaux sur la conduction ionique ?

PH : Avant 1973, on a publié un grand nombre de documents sur des conducteurs ioniques. On s'inspirait comme modèle de réflexion des bronzes de tungstène bien que la plupart des travaux publiés à l'époque fussent des études structurales et que les bronzes de tungstène soient métalliques. On avait également préparé une série de nouveaux bronzes de tungstène. Ce travail s'est étendu à des bronzes oxyfluorés, à des bronzes de vanadium et de molybdène contenant les deux cations vanadium et molybdène plus le sodium et le lithium. Puis au début des années 1970, on s'est attaqué aux premiers bronzes de manganèse NaxMnO2 et puis aux bronzes de cobalt KxCoO2.
Sur ces entrefaites il y a eu la grande crise pétrolière de 1973. Les pays occidentaux ont eu peur de manquer d'énergie et donc on s'est occupé de sources d'énergie non fossile et de stockage d'énergie. Un certain nombre de gens ont voulu faire des batteries. Exxon et la Bell Telephon, Whittingham et Murphy en particulier, ont travaillé sur ces matériaux non plus comme nous l'avions fait vers 500°C avec des phases en équilibre thermodynamique mais à basse température par intercalation ou désintercalation électrochimique.
Une spécialité à Bordeaux c'était les fluorures conducteurs. On remplaçait systématiquement l'oxygène par du fluor parce qu'il a la même taille et présente une liaison plus faible. On pouvait ainsi atténuer les interactions magnétiques. Comme pour la zircone, on dope les fluorures systématiquement. Watanabe avait déjà préparé les premières batteries au fluor.
Jean Rouxel s'était intéressé à l'époque où il était mon élève aux sulfures, aux sulfures à couche en particulier. Entre les couches de FeOCl et FeSCl par exemple, on pouvait intercaler beaucoup de choses, comme l'ammoniac ou les amines. Jean Rouxel a préparé NaxTiS2, un matériau qui avait été préparé par Rudorf à Fribourg, qui le considérait comme une curiosité. Mais Rouxel a très vite réalisé qu'il devait y avoir un domaine d'existence. Or il s'est avéré que Li xTiS2 avait un large domaine d'existence. Jean Rouxel a poussé dans cette voie et il a étudié un grand nombre de sulfures et sélénures à feuillets alors que nous nous intéressions plutôt aux oxydes. Il y avait une sorte d'accord empirique entre nous : Nantes les sulfures, Bordeaux, les oxydes. Nous avons étudié des matériaux sur le plan de la synthèse, dans des conditions d'équilibre thermodynamique plus que par intercalation désintercalation.
Il y a une grande variété de méthodes topologiques ou non de relative basse-température qui permettent d'obtenir des matériaux nouveaux. Mettre un mélange très fin de poudres sous hautes pression pour que se déclenche une réaction brutale qui prend fin lorsque l'un des deux constituants initiaux a disparu. Donc c'est un échauffement brutal suivi d'une trempe. Ce qui permet d'obtenir des borures ou des silicium stables seulement à haute température.
Beaucoup de ces matériaux sont métastables mais on peut les utiliser dans des dispositifs.
Jean Rouxel a apporté beaucoup dans le domaine des réactions d'intercalation-désintercalation. Les oxydes lorsqu'on les désintercale perdent des électrons cationiques. C'est une oxydation cationique. Lorsqu'on part de LixCoO2 vers CoO2 on perd des Li+, mais on perd également des électrons qui proviennent des niveaux d. Mais pour les séléniures, ce sont les niveaux anioniques qui sont les plus élevés. Et lorsqu'on oxyde, c'est l'anion qu'on oxyde. On passe de Se2- à Se- et de Se- à Se pour des raisons de stabilité de liaison. Et Jean Rouxel a montré qu'il y avait une évolution graduelle pour les éléments 3d à l'état de sulfure entre TiS2, qui a une structure à couches, et CuS2 qui a une structure avec un ion S de type pyrite. Il a fait une analyse précise dans les cas douteux où les niveaux cationiques et anioniques sont à peu près de même énergie. L'analyse très fine des distances inter-atomiques lui a montré si c'était le cation ou l'anion qui était oxydé. Il a également fait beaucoup de choses sur les bidimensionnels qui sont ici hors sujet.

HA : Qu'est-ce qui a manqué en France alors que les compétences étaient là pour donner l'impulsion sur les batteries au Lithium ?

PH : Il y a un très grand nombre de batteries réversibles au lithium pour des applications diverses depuis les montres jusqu'aux batteries de taille moyenne utilisées par les militaires pour observation spatiale avant bombardement. Mais le marché important, c'est le véhicule électrique, non polluant. Du moins en partie car on s'est résigné au véhicule hybride. Le véritable marché ce serait la voiture électrique -éventuellement hybride- ce qui suppose des batteries de grande taille. Probablement l'électrolyte sera un polymère PEO imprégné d'un sel de lithium avec un gros anion, type matériau Armand. La cathode sera probablement riche en cobalt ce sera un matériau voisin de LixCoO2, plutôt un oxyde qu'un sulfure parce que la tension est plus élevée. Mais pour l'anode ce n'est pas encore évident. Si on pouvait faire mieux que les composés d'intercalation du lithium on serait content. Mais actuellement il n'y a pas encore de solution. Il y a donc premièrement un problème de matériau qui freine cette évolution. Deuxièmement il y a un problème de prix. Ajoutez à cela qu'une batterie au lithium doit être scellée car le lithium est sensible à l'atmosphère et vous voyez que ce n'est pas évident. Une solution concurrente est la batterie hydrogène consistant à stocker l'hydrogène dans un alliage métallique et puis à libérer l'hydrogène. Ce modèle permet des puissances plus élevées que la batterie au lithium mais là aussi il y a un problème de vieillissement car après un certain nombre de cycles, l'alliage s'oxyde car l'oxyde est plus stable que l'hydrure. Ce problème n'est pas encore résolu avec un coût acceptable pour l'utilisateur. A cet égard, il y a une coupure entre le scientifique et l'utilisateur.

HA : Concernant les relations entre physique et chimie qu'est-ce qui a favorisé le rapprochement ?

PH : Les physiciens ont fait des efforts pour parler un langage plus proche de celui des chimistes. J'ai parlé déjà de John Goodenough. Nevil Mott aussi était un homme qui s'exprimait dans un langage compréhensible pour un chimiste. Par exemple, lorsqu'il a obtenu des transitions isolantes par changement de composition au sein d'un domaine d'existence, on comprenait ses préoccupations et il comprenait les nôtres bien qu'on raisonne sur des modèles un peu différents. On est ainsi arrivé à préparer dans des bronzes de tungstène oxyfluorés des matériaux qui sans changement de structure manifestaient une transition métal-isolant. Les physiciens ont fait des progrès. L'équipe de Friedel était très préoccupée de parler un langage qui nous était commun. Je pense à Denis Jérôme, Claude Berthier à Grenoble.

HA : Le travail de physiciens sur la caractérisation très fine vous a-t-il aidé ?

PH : Je me souviens de discussions à Orsay sur les hexaborures. Les physiciens voulaient des matériaux qu'on appelait thermo-ioniques - mais c'est un mot malheureux : on devrait plutôt dire thermo-électronique - c'est à dire ayant un faible potentiel d'ionisation et susceptibles de cracher un jet d'électrons relativement puissant sous tension faible. On en a fait une étude systématique et on a essayé de préparer des cristaux.

HA : Et quel était l'enjeu ?

PH : L'enjeu était d'avoir ponctuellement un faisceau d'électrons puissant, par exemple pour des soudures, des soudures localisées. Outre la collaboration avec les physiciens d'Orsay on a aussi collaboré avec ceux de Grenoble. Plus que ceux d'Orsay, les physiciens de Grenoble avaient un langage très compréhensible. Il y avait un grand homme à Grenoble, Louis Néel. Il avait publié son travail sur le ferrimagnétisme en s'appuyant sur des modèles structuraux très clairs. La répartition des cations entre les sites tétraédriques et les sites octaédriques de la structure spinelle. Donc on comprenait pourquoi on avait des interactions d'abord anti-ferromagnétiques - ce qui constitue la base du ferrimagnétisme - entre des sites tétraédriques A et des sites octaédriques B, et pourquoi l'aimantation résultante était accrue lorsque le réseau prévalent contenait des cations avec beaucoup d'électrons d célibataires. Tous ces travaux - encouragés par les recherches militaires - ont permis une collaboration très fructueuse avec Grenoble. Je pense à Bertaut en particulier. Nous avons été encouragés, par exemple, à faire des études basse-température par Pauthenay qui nous a dit : c'est aux basses- températures qu'on détecte les phénomènes peu énergétiques.
Alors c'est l'époque où nous avons manqué le prix Nobel - Je dis cela en plaisantant, bien sûr !-. Nous avons préparé les premiers oxydes purs de Cu3+ : par exemple SrLaCuO4. Nous avions une telle habitude des solutions solides qu'on pouvait imaginer de préparer une solution solide avec La2CuO4 contenant du Cu2+. Mais pour nous, les solutions solides, c'était du travail secondaire. On cherchait à préparer des oxydes purs. Si on avait été préoccupé des solutions solides on aurait pu trouver des oxydes contenant à la fois du cuivre Cu 2+ et 3++. Comme par routine on caractérisait tous nos matériaux jusqu'à la température de l'hélium liquide, on aurait trouvé la supraconductivité. On ne l'a pas fait parce qu'on voulait des phases pures et non pas des solutions solides.
Bernard Raveau l'a fait avant Alex Müller. Il avait un objectif : comprendre ce qui se passait au point de vue des corrélations. Passer d'un semi-conducteur à un métal. Müller était un très grand physicien. Il a été surpris aussi mais il a tout de suite expliqué. Raveau a fait ses solutions solides. C'est même moi qui ai transmis sa publication au M[aterials] R[esearch] B[ulletin] mais j'ai regretté à l'époque qu'il n'ait pas fait de mesure à l'hélium liquide.

HA : Après avoir évoqué vos collaborations en France, pourriez vous parler de vos liens avec l'étranger ? Vous avez été précurseur pour les relations scientifiques avec les pays en voie de développement comme la Chine, le Maroc et l'Inde. Quelles étaient vos motivations ? Comment voyez-vous la science des matériaux dans ces pays ?

PH : J'ai toujours été persuadé que la science devait être internationale. Cela me distingue de beaucoup de mes compatriotes. Je suis toujours étonné que l'on fasse des quêtes pour aider la recherche en France sur le SIDA. Toute la recherche sur le SIDA, toute recherche de pointe est internationale et ce n'est pas parce que la France dépensera un peu plus d'argent que nécessairement, il y aura des progrès significatifs. La science doit être internationale.
J'ai donc eu des liens d'abord avec les pays développés car dans ce type de relation on se fait connaître mais aussi on apprend. Je suis allé souvent aux Etats Unis, moins par enthousiasme culturel, que parce qu'on y rencontre des gens de qualité. J'ai rencontré Goodenough, Al Cotton... j'ai rencontré à Berkeley ou à Stanford des gens de grande qualité. J'ai eu des relations suivies pendant un temps avec la Grande Bretagne mais les Anglais ont un sentiment de quant à soi. J'espère qu'avec le temps la Grande Bretagne va évoluer vers une intégration dans l'Europe. Les Allemands sont très favorables à cette intégration. Dès 1961 j'avais pris l'initiative d'emmener tout mon laboratoire en Allemagne pour un voyage de 15 jours. On est allé à Stuttgart, Karlsruhe, Heidelberg, Darmstadt, Giessen, Göttingen etc.. On a été très bien reçu par Wilhelm Klemm avec qui j'ai toujours entretenu d'excellentes relations. Mais ses élèves étaient jaloux. Les Allemands se sont sentis bousculés parce qu'un peu jaloux de gens qui faisaient beaucoup de bruit. Ils avaient une bonne tradition de chimie préparative, en relation avec l'industrie. Les Allemands ont compris que pour faire des matériaux nouveaux il fallait des techniques nouvelles comme la haute pression. Mais leur but c'était la performance tandis que le nôtre c'était de stabiliser des structures électroniques peu usuelles, grâce à la synthèse. Les Allemands se sont senti un peu gênés. Les gens leur disaient : vous utilisez des équipements de haute pression mais ce que vous faites c'est de la botanique alors qu'il faudrait réfléchir. Le but d'un équipement est de faire des matériaux à façon pour répondre à des problèmes déterminés. Les collègues allemands avaient un autre point de vue et je regrette qu'il n'y ait pas eu davantage de liens.
En revanche, toujours parmi les pays développés, j'ai eu beaucoup de liens avec l'Europe de l'Est. Pour deux raisons. D'abord, il y avait des gens de qualité chez les Soviétiques, les Polonais et les Tchèques. De plus j'étais un peu agacé de cette Europe coupée en deux du fait de la guerre froide. Donc je trouvais raisonnable qu'il y ait une présence de la France là où c'était relativement facile, c'est à dire la science. C'était intéressant pour eux et pour nous car nous avons eu de ces pays des personnes remarquables. J'ai eu des relations systématiques avec des laboratoires à Prague, Cracovie, à Moscou, à Kiev, Novosibirsk, à Sofia. Avec la Roumanie, c'était impossible car Madame Ceaucescu interdisait aux scientifiques de discuter avec des étrangers.
Avec les pays en voie de développement, la situation change d'un pays à l'autre. J'ai eu des relations avec le Maroc parce que l'université de Bordeaux et l'université de Rabat avaient des liens traditionnels. Je suis allé y faire cours. Il y avait de très bons étudiants je les ai encouragés à faire une thèse. Le nombre a crû considérablement. 30 ou 35 Marocains ont fait des thèses avec moi. J'avais une politique de sélection impitoyable ; je prenais les meilleurs et je les surpayais. Je voulais qu'ils n'aient pas de souci matériel pendant leur thèse. J'ai eu des liens plus occasionnels avec la République du Congo et quelques Tunisiens mais ils préféraient Marseille.
Avec la Chine j'ai fait un choix politique. J'ai compris que la Chine était un potentiel économique et humain. La France devait être présente à un moment où la Chine était exclusivement tournée vers les Etats-Unis. Je suis allé souvent en Chine. J'ai fait venir des étudiants chinois en les choisissant bien sûr excellents. Mes espoirs ont été dépassés par le succès car ils ne sont pas retournés en Chine mais partis au Canada ou aux Etats-Unis comme professeurs ou dans l'industrie. Ils se sont bien débrouillés. Maintenant c'est différent ; une majorité d'étudiants chinois reviennent en Chine.
L'Inde est aussi un pays avec lequel j'ai eu des relations. C'est une société où le savoir est respecté, une science de caste malgré l'abolition officielle des castes. Thaïlande, Malaisie, Indonésie...j'ai privilégié les pays asiatiques par rapport aux pays africains car la culture asiatique favorise la réflexion métaphysique et par conséquent scientifique. Néanmoins j'ai eu aussi des collaborations avec le Brésil, le Chili et l'Argentine. Le but étant d'aider ces pays dans leur développement industriel. Je suis d'ailleurs membre de l'Académie des sciences brésilienne depuis 1988.
Vis à vis des étudiants du tiers monde, j'ai toujours considéré comme ma responsabilité de leur donner une thèse originale et non pas, comme on le fait souvent, de leur faire remplir des vides dans le laboratoire ou de servir de main d'œuvre. Les étudiants du tiers monde que l'on fait venir en Europe il faut bien les choisir et bien les former pour qu'ils deviennent des maîtres.

HA : Je serai curieux de connaître votre point de vue sur l'évolution de la chimie des matériaux et le rapprochement avec la biologie.

PH : Je ne me sens pas compétent dans l'interface chimie/biologie. Mais mon expérience à l'interface physique et chimie me rend plutôt sympathique cette perspective d'une ouverture de la chimie vers la biologie. Elle est défendue par Pierre Pottier, Guy Ourisson, Corriu.
Sur l'interface physique/chimie, cela s'est moins bien passé. Peut-être que je n'ai pas su convaincre. Quand on prêche, on se fait des adeptes mais aussi des ennemis. Cela est vrai au CNRS. Celui qui prêche secoue les caciques, les gens en place. Quelqu'un comme Fernand Gallais était fermement hostile à mon projet d'interface avec la physique. Par contre j'ai rencontré beaucoup de sympathies du côté de Pottier, de Jacques Livage.
Pour revenir aux oxydes supraconducteurs, il s'agit d'un cas intéressant de collaboration entre physiciens et chimistes. Très vite, j'ai compris que l'on avait plafonné et puis à un moment donné il était clair que Tc était d'autant plus élevé que la bande de conduction était plus étroite. Et plus la bande de conduction est étroite plus le matériau est instable et a tendance à se dismuter en donnant un mélange de deux phases. J'ai compris cela très vite mais beaucoup ne l'ont pas compris. Il y a donc eu un emballement. Il a rapproché les chimistes des physiciens. Il est dommage que personne n'ait proposé un modèle simple permettant aux chimistes d'innover de manière simple comme on avait innové dans le domaine de la conductivité ionique, du magnétisme, de la ferroélectricité, des magnéto-optiques ... ou même des composites thermo-structuraux. Il a manqué quelqu'un qui propose un modèle intuitif liant les propriétés à la liaison chimique. Goodenough aurait pu le faire mais il était trop vieux, trop pressé de publier des matériaux miracles. Les matériaux miracles sont difficiles à reproduire. Celui qui essaie il n'a pas le même four ... Ces matériaux sont métastables, ils ne sont jamais parfaitement purs. Ils n'ont jamais le même nombre de lacunes d'oxygène. Donc ce n'est jamais parfaitement répétitif. Cela exclut toute réplication sérieuse parce qu'un matériau n'est utilisable industriellement que s'il est relativement simple à préparer et à utiliser. Telle est la raison de l'échec de la diode Josephson sur laquelle IBM a dépensé beaucoup d'argent. A l'époque j'étais d'ailleurs conseiller d'IBM.

BBV : Est-ce qu'il y a eu des matériaux sortis de vote laboratoire qui ont été industrialisés ?

PH : Il y a d'abord eu les varistors. J'ai fait beaucoup avec la Thomson CSF dans ce domaine. Il y a eu LixCoO2 et puis il y a les céramiques composites de R. Naslain : fibres de carbone infiltrées par SiC qui permet de travailler à des hautes températures pour les matériaux de rentrée de la fusée ou du satellite dans l'atmosphère. Car lorsque l'engin revient dans l'atmosphère, il y a un risque d'oxydation. L'astuce consistait à infiltrer - non pas déposer en surface - SiC à partir d'une phase vapeur. Alors à l'air SiC s'oxyde en donnant SiO2 qui s'infiltre dans le matériau à base de carbone et permet de le prolonger.

BBV : Pourriez vous préciser quelles étaient vos relations avec l'industrie et comment elles ont évolué ?

PH : J'ai toujours eu des relations avec l'industrie. Quand j'étais à Rennes j'ai été contacté par Raymond Paul, un des responsables de la recherche à Rhône Poulenc et il m'a vivement encouragé à travailler avec Rhône Poulenc. J'ai eu plusieurs bourses de thèses payées par l'industrie - parfois il fallait publier des résultats plus tard. Rhône Poulenc a payé la thèse de Michel Pouchard sur les bronzes de vanadium au début des années 60. Ensuite il m'a paru tout naturel de travailler avec l'industrie. J'ai travaillé avec Saint-Gobain sur les verres, en particulier sur les verres conducteurs du lithium et du sodium avec Levasseur, sur les verres sulfurés à base de B2S3. Les verres sont un matériau merveilleux. Ils ont une composition qui est flexible. Vous tombez un peu à côté, cela n'a pas d'importance les propriétés ne sont guère modifiées. Vous n'avez pas le problème des matériaux cristallins où, par suite de la moindre erreur, de la moindre difficulté de préparation, une deuxième phase d'impuretés se forme à côté. Là il vous reste une phase. D'autant plus qu'on peut préparer les verres par trempe brutale donc énormément de matériaux sont vitreux alors qu'il y a 30 ou 40 ans c'était différent.
J'ai eu beaucoup de liens avec l'industrie locale : Aérospatiale et SNECMA, avec SNPA (société nationale des pétroles d'aquitaine : ancêtre d'Elf) sur comment purifier le gaz de Lacq...Ma porte était toujours ouverte, on élargissait le champ de nos recherches à la demande car l'industrie n'est pas un boulet.

BBV : Est-ce que ces liens étaient encouragés par le CNRS ?

PH : Le CNRS était informé bien sûr. Et puis quand on est devenu un laboratoire propre en 1966 Curien était très favorable aux relations avec l'industrie. On a un des contrats avec Saint-Gobain, avec Rhône Poulenc devenu Rhodia, avec Ugine Kuhlman devenu Péchiney. Nous avons même eu des liens avec General Electric aux USA pour les borures, avec BASF sur le di-oxyde de chrome pour les bandes d'enregistrement.

BBV : Quelles sont les méthodes et techniques utilisées dans votre laboratoire ? Et comment ont-elles évolué au cours de votre carrière ?

PH : Au début le B-A-BA c'était la diffraction X. Puis pour bien comprendre la structure on a eu un équipement pour des monocristaux. On a préparé des mono-cristaux pour déterminer les structures. Maintenant on a fait de gros progrès et on peut sur des spectres de poudres lorsque la poudre est de bonne qualité déterminer la structure par les méthodes Riedveld en faisant des hypothèses simples sur la structure la plus probable. La diffraction X a été fondamentale et a débouché ensuite sur la microscopie électronique en transmission qui permet de voir les défauts locaux. C'est merveilleux. La diffraction X était une méthode à grande distance. Par contre la microscopie électronique en transmission vous donne les défauts localisés et étendus. C'est une préoccupation que j'ai eu beaucoup à propos de non-stœchiométrie. Quand on passe d'une phase perovskite ABO3 à une phase brownmillérite A2B2O5, on perd de l'oxygène. Alors à haute température les lacunes d'oxygène sont désordonnées. A température plus basse, elles s'ordonnent en fonction du cation B. Quand c'est du fer ou du gallium, un cation isotrope, on a soit des tétraèdres parce qu'il y a pas de lacune, soit des octaèdres car les lacunes marchent par deux. Donc dans une structure brownmillérite on a une séquence octaèdre,-tétraèdre, octaèdre-tétraèdre, et dans la structure perovskite c'est octaèdre-octaèdre-octaèdre. Alors on peut trouver à condition de faire des recuits à température assez basse - quelques centaines de degrés - des phases intermédiaires avec 2 couches octaèdres, 1 couche tétraèdre, 3 couches octaèdres, 1 couche tétraèdre. Et bien sûr quand on chauffe le désordre s'installe à cause de l'entropie d'empilement. On a étudié de manière systématique comment on passe de défauts isolés aux défauts ordonnés, étendus. Et cela a des conséquences au point de vue de la conductivité de l'ion oxygène. Parce que maintenant on a de nouvelles préoccupations. On veut par exemple extraire l'oxygène de l'air par des membranes de perovskite lacunaire ou détruire les traces de CO en oxydant par l'eau. Dans ce cas, vous avez CO2 - qui est quand même moins toxique que CO, sauf sur le plan idéologique - et vous avez de l'hydrogène. On utilise des perovskites lacunaires qui doivent être conducteurs de l'oxygène - ce qui est normal - mais aussi conducteurs électroniques car le transfert se fait sous tension donc il faut que les ions O2- migrent à travers les lacunes de la structure. Il y a donc un aspect pratique pour les capteurs d'oxygène, la purification des gaz. Les Norvégiens utilisent ces méthodes massivement pour transformer le gaz de la Mer du Nord en un gaz exempt de CO. Norsk-Hydro dépense des sommes considérables pour cela. J'ai été invité pour parler avec les gens impliqués par ces recherches.
Donc pour résumer : nos efforts se sont situés à l'interface entre physique et chimie et se concentraient sur l'étude des relations entre composition, structure et propriétés avec la perspective d'applications industrielles.

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Pour citer l'entretien :

« Entretien avec Paul Hagenmuller », par Bernadette Bensaude-Vincent et Hervé Arribart, 12 juin 2001 Sciences : histoire orale, https://sho.spip.espci.fr/spip.php?article124.
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Entretien avec Paul Hagenmuller, par Bernadette Bensaude-Vincent et Hervé Arribart, 12 juin 2001

Lieu : Paris, France

Support : enregistrement sur cassette

Transcription : Bernadette Bensaude-Vincent et Hervé Arribart

Edition en ligne : Sophie Jourdin

BOILOT Jean-Pierre, 2000-12-12

Sophie Jourdin — 2011-10-28T12:00:58Z

Jean-Pierre Boilot worked on b-alumina in the 1970s and subsequently on ionic conductors within the framework of chimie douce.

BERNADETTE BENSAUDE-VINCENT (BBV) : Quel fut votre parcours individuel ?

JPB : Je suis entré au laboratoire Collongues en 1971, étant assistant à l'Ecole de céramique de Sèvres où j'enseignais la chimie. Mon sujet de thèse portait sur l'alumine-b plus exactement sur les gallates. On cherchait à améliorer la conduction ionique en remplaçant l'aluminium par du gallium. On connaissait, bien sûr, les travaux de Yao et Kummer et on savait déjà échanger les ions sodium par d'autres. Mais ceci n'a constitué qu'un chapitre de ma thèse qui devait en avoir 5 ou 6.
Après j'ai eu un rôle très particulier : travailler à l'interface de la physique et de la chimie. Cette expérience de collaboration de la physique et de la chimie du solide, c'était une innovation. Seul Yves Le Car avait commencé avant moi. Lui avait un financement industriel, avec CGE qui est devenu Alcatel. Cette collaboration est issue de discussions entre Robert Collongues et André Guinier qui était responsable d'un groupe de physique du solide à Orsay au bâtiment 510. Le Car a commencé à faire de la diffusion des rayons X, organisation des ions de conduction dans alumine-b. J'ai poursuivi dans cette voie. La collaboration s'est étendue. Je passais 50% de mon temps au labo Collongues et 50% en physique chez Guinier et chez Jérôme, un autre groupe de physique du solide qui faisait de la RMN. Une grande partie de ma thèse concernait des problèmes fondamentaux : comment les ions s'organisent, ordre désordre, stœchiométrie.

BBV : Quels étaient les modèles théoriques à l'époque ?

JPB : Peu de choses pour comprendre les mécanismes de conduction. C'est venu plus tard. Les physiciens durs ont attaqué le problème plus tard.
J'ai soutenu ma thèse d'Etat en 1975 devant un jury très impressionnant : Jacques Friedel, Jean Rouxel, Michel Fayard, qui est devenu directeur du secteur chimie au CNRS, Jeanine Théry et Robert Collongues. Je me souviens avoir été mauvais, je n'étais pas fier de moi.

BBV : Avez-vous poursuivi sur alumine-b ?

JPB : Oui de 1975 à 82 j'ai travaillé avec Gaston Colin, cristallographe et avec Philippe Colomban qui est arrivé au labo Collongues. Je l'avais eu comme étudiant à l'école de céramique. On a travaillé essentiellement sur deux aspects : alumine-b stœchiométrique et alumine-b''. Même type de base : compréhension, organisation des ions en utilisant les paramètres fondamentaux du solide : répulsion entre ions, transition au désordre etc.

BBV : Y avait-il alors une communauté française de chercheurs sur l'alumine-b ?

JPB : Oui, il y avait des séminaires organisés ici à Polytechnique par Bernard Sapoval->http://pmc.polytechnique.fr/bs/english.html] et Hervé Arribart. Les gens ici ont commencé à travailler sur l'alumine-b avec des porteurs de protons et ils utilisaient la RMN.
Donc si l'on fait le bilan de ces 10 ans, il y a deux caractéristiques propres à ce sujet

- C'étaient les premières recherches fondamentales menées parallèlement à la recherche industrielle car CGE en France, Ford, General Electric aux USA faisaient des recherches plus appliquées sur les accumulateurs sodium-soufre. C'était particulièrement motivant de voir qu'il y avait des possibilités d'application.
- Deuxième caractéristique : c'était la possibilité de travaux à l'interface physique-chimie. Ces deux aspects là se retrouvent plus tard dans les recherches sur les supra-conducteurs au cours des années 90.

BBV : Aviez-vous des contacts avec l'industrie ?

JPB : On avait des contacts avec CGE et on allait parfois à Marcoussis voir M. Dumas de CGE. Mais on faisait de la recherche fondamentale.
Des contacts avec l'industrie, il y en avait sans doute au labo Collongues. Mais je n'étais pas au courant. Par contre, au laboratoire Collongues, Didier Goureyet était plus proche des préoccupations industrielles, tout en étant en recherche fondamentale.

BBV : Avez-vous ressenti un certain pessimisme industriel sur l'alumine-b au cours de ces années ?

JPB : Non, il y eut une effervescence de 1970 à 76. Le pessimisme est venu après. Il y avait peut être des problèmes pour les gens qui ne travaillaient pas sur le sujet. C'est faux de dire qu'il y avait un pessimisme dans les années 70. Pour les années 80, c'est une autre histoire. Plus de problème d'énergie, d'autres problématiques sont arrivées : utiliser des systèmes. On savait que les batteries sodium-soufre ne seraient pas commerciales. Elles ne le seront peut-être jamais. Donc du point de vue industriel, c'était un tout petit peu moins motivant.

BBV : Avez-vous participé aux congrès internationaux des années 70-80 ?

JPB : Bien sûr je pourrai vous donner la liste. C'est un autre aspect important : il y avait une compétition internationale, essentiellement avec les Américains, avec les gens de General Electric - Roth - et les gens de Bell Telephon. J'ai commencé à participer en 1976 Schenectady ; 1979 Lake Geneva (USA), Gatlinburg (Tennessee) en 1981, Grenoble en 1983, Lake Tahoe en 1985 ; Garmisch en 1987. Outre cette série des Solid State Ionics il y avait Rome (1976) et Saint-Andrews en Ecosse, en 1978. A chaque fois on avait des papiers dans ces conférences.

BBV : Y-a-t-il eu une évolution ou réorientation de vos recherches sur cette période ?

JPB : On a pousuivi les mêmes pistes de recherche sur les deux alumines-b.
Philippe Colomban, chimiste, s'est consacré à l'élaboration des mono-cristaux d'alumine-b. Seuls deux groupes au niveau international savaient faire la synthèse des alumines-b : Colomban au laboratoire Collongues et Farrington chez General Electric. C'était un procédé à haute température avec quelques subtilités chimiques pour parvenir à faire l'alumine stoechiométrique. Mais il n'y eut pas de brevets sur les mono-cristaux. L'objectif était purement fondamental car les applications se faisaient sur un milieu polycristallin, céramique.
Parallèlement à partir de 1978, on a commencé à travailler sur d'autres conducteurs ioniques qui pouvaient remplacer l'alumine. Ils faisaient partie d'une série qu'on appelait nasicons : c'étaient des phosphates ou des phospho-silicates avec des ions sodium.
Le choix du sodium repose sur des arguments très simples : il faut un ion monovalent, de la bonne taille. S'il est trop gros il ne diffuse pas facilement ; s'il est trop petit (cas du proton ou du lithium) il vient se coller sur le réseau ; ou on a une interaction trop forte avec les anions (les chimistes disent trop polarisants). Les meilleurs ions sont Na+ et Ag+. Ensuite le choix dépend des applications. A cette époque là le problème était le stockage d'énergie, on visait des accumulateurs de haute puissance pour faire du stockage. Les critères de densité d'énergie massique portaient le choix sur les éléments légers, donc le sodium plutôt que l'argent.

BBV : Est-ce que la crise d'énergie a infléchi les recherches au labo Collongues ?

JPB : Peut-être mais à cette époque j'étais trop concentré sur ma thèse et je n'avais pas de vue d'ensemble. Pour revenir aux applications, les nasicons ont eu moins d'intérêt car ils sont moins stables, ils résistent moins bien au sodium liquide. Ils n'ont pas eu le succès de l'alumine-b mais des gens travaillent encore dessus. Il y a eu beaucoup de travail sur cette famille : diversité de compositions et de phases. Elle présente un intérêt pour la compréhension des paramètres fondamentaux du solide mais moins que l'alumine-b.

BBV : Rétrospectivement considérez vous que ce travail sur les nasicons a été positif ?

JPB : Oui on aurait peut-être pu arrêter un peu plus tôt. On a travaillé là dessus de 1978 à 1984 mais toujours en parallèle avec l'alumine-b. C'est un travail qui se faisait à Polytechnique où je suis venu en 1981. C'est un sujet qu'on a développé ici avec Colomban, toujours en liaison avec les physiciens du solide (Collin) d'Orsay dans le groupe de Robert Gomès qui avait pris la succession de Guinier.
Après on a pris un virage vers les sols-gels. La transition s'est faite par le biais des nasicons. On avait dans l'idée d'élaborer des phases amorphes pour conducteurs ioniques. Elles étaient dérivées du nasicon. On a préparé les premiers verres organo-minéraux en s'inspirant des conducteurs ioniques type nasicons. Notre modèle à nous était le conducteur ionique. Puis on a eu des résultats intéressants sur ces matériaux, sans rapport avec la conduction ionique. Ces hybrides organo-minéraux, à la frontière entre organique et minéral sont faits à température ambiante avec une chimie douce.

BBV : N'est-ce pas un paradoxe que de la chimie à haute température du labo Collongues sorti une chimie à température ambiante ?

JPB : Oui à la même époque Jacques Livage faisait des gels V205.

BBV : Qu'est-ce qui a motivé votre virage vers les verres ?

JPB : Du point de vue industriel, l'alumine-b c'était moins motivant et, du point de vue fondamental, on avait fait le tour. De plus, je démarrais un groupe ici à Polytechnique, c'était le moment de passer à un nouveau projet.

BBV : Est-ce que ce virage vers les verres organo-minéraux a changé votre place dans la recherche ?

JPB : Au niveau du CNRS, non, car on appartient toujours à la famille chimie du solide. Mais on a eu des contacts industriels nouveaux avec Saint-Gobain (Silor). Bien sûr pendant deux ans, on a eu un peu de ralentissement dans la production de publications. Mais le virage se fait bien.

BBV : Quelles sont les activités de votre laboratoire actuellement ?

JPB : Actuellement on est toujours sur la chimie douce. En plus des hybrides organo-minéraux, on travaille sur des objets nanométriques. On part de molécules et on essaie de construire des solides à partir de ces molécules. Ce sont essentiellement des matériaux pour l'optique : lasers ou stockage de l'information optique.

BBV : Quelles sont les techniques que vous utilisez ? Sont-elles totalement différentes de celles qu'on utilisait au laboratoire de Collongues ?

JPB : C'est de la chimie classique avec des béchers mais pas de haute température. C'est bien différent des labos d'alumine où on avait des fours à 2000°C. Le labo Collongues était surtout tourné vers l'élaboration de matériaux alors que maintenant on fait surtout de la caractérisation. Comme maintenant on dispose de nombreuses techniques, on peut faire des thèses sur la caractérisation avec peu de chimie.
Ce que m'a appris l'alumine-b c'est qu'il faut faire de la chimie. C'est le matériau qui est intéressant. C'est le message le plus important. Toutes les avancées qu'on a eues au laboratoire Collongues, c'est parce qu'on a su faire de la synthèse de matériaux avant et mieux que les autres. Notre premier travail est de faire de l'innovation en matériaux, mais on a beaucoup de collaboration en physique.
Notre troisième thème est la pile à combustible. Il est arrivé avec un ancien du laboratoire de Collongues : Philippe Barboux. Il travaillait sur les films minces de céramique et prépare maintenant des membranes conductrices ioniques pour les piles à combustibles. C'est donc un retour à la tradition d'origine.
Mais il y a un lien entre les verres, les particules nanométriques et les piles à combustibles. Ce sont toujours des procédés à basse-température. On travaille sur la diffusion de molécules comme autrefois on travaillait sur la diffusion des ions.

BBV : Combien de personnes travaillent dans votre groupe ?

JPG : Actuellement notre groupe de chimie du solide comprend 10 personnes et il est l'une des composantes de l'UMR-CNRS intitulée Laboratoire de Physique de la matière condensée qui comprend 50 personnes.

BBV : Quels sont vos liens avec l'étranger ?

JPB : Nous avons gardé des relations avec Bruce Dunn de UCLA (nous avons ici un chercheur permanent qui a fait son post-doc là bas). Nous avons également une collaboration avec un laboratoire allemand. Pas de programme européen, c'est trop de paperasses.

BBV : Comment voyez-vous la chimie du solide française sur la scène internationale ? Est-ce qu'elle n'a pas d'une certaine manière fait obstacle à l'essor d'une science des matériaux en France ?

JPB : C'était suite au démarrage de la physique du solide. Il y a avait a deux pôles de chimie du solide en France, celle de Hagenmuller à Bordeaux et celle de Collongues à Paris. L'une plus mandarinale que l'autre. Des gens comme Rouxel, je les mets dans la famille Hagenmuller. En fait, si on prend les labos actuels de chimie du solide, ce sont tous des descendants d'Hagenmuller ou des descendants de Collongues.
Les deux écoles sont tournées vers la science fondamentale plus que vers les applications. C'est totalement différent de l'approche science des matériaux aux USA. Elle n'existe pas en France. L'approche Materials Science est plus tournée vers les applications. En France, il y a eu beaucoup de recherche fondamentale. L'originalité française n'est pas dans la collaboration avec l'industrie mais dans l'approche physique, dans la collaboration entre chimistes et physiciens du solide. Je défends l'approche française. Si les gens avaient été très proches du milieu industriel, je ne crois pas qu'on aurait été aussi forts en chimie du solide.

BBV : Peut-on associer une coloration politique à cette discipline ?

JPB : Traditionnellement en France, les physiciens sont plutôt à gauche et les chimistes plutôt à droite. Quant à la couleur de ces deux écoles de chimie du solide, je dirais que Hagenenmuller était un gaulliste bon teint ; il serait plutôt proche de Pasqua aujourd'hui ; Collongues, lui, était plutôt centre droite, bon vivant.

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« Entretien avec Jean-Pierre Boilot », par Bernadette Bensaude-Vincent, 12 décembre 2000 Sciences : histoire orale, https://sho.spip.espci.fr/spip.php?article121.

—

Entretien avec Jean-Pierre Boilot, par Bernadette Bensaude-Vincent, 12 décembre 2000

Lieu : Ecole polytechnique, Palaiseau, France

Support : non communiqué

Transcription : Bernadette Bensaude-Vincent

Edition en ligne : Sophie Jourdin

DRESSELHAUS Mildred S., 2001-10-25

Sophie Jourdin — 2011-06-18T22:59:55Z

Mildred Dresselhaus est née en 1930 à Broolkyn, New York. Elle étudie la physique au Cavendish laboratory de l'University of Cambridge en 1951-1952. De retour aux États-Unis, elle obtient en 1953 un Master Degree au Radcliffe college et un PhD en physique à l'Université de Chicago en 1958. Elle se consacre alors à la physique du solide, à la supraconductivité et à la magnéto-optique. Elle intègre ensuite le Lincoln lab du Massachusetts institute of technology (MIT). Avec son mari Gene Dresselhaus, elle oriente alors ses travaux vers l'étude de la structure électronique des semi-métaux – et en particulier du graphite. En 1967, Mildred intègre le département d'Electrical engineering du MIT comme Professeur associé. Elle dirige ensuite le Center for materials science and engineering du MIT. Elle devient Professeur de physique en 1983. En 1985, elle est la première femme à être nommée Institute Professor - le plus haut titre d'un membre de la Faculté du MIT. Mildred Dresselhaus accède ensuite à des postes à haute responsabilité en matière de politique scientifique et de financement de la recherche où elle soutient activement les programmes de recherche en nanotechnologies. Milldred Dresselhaus est particulièrement connue pour son travail sur les propriétés électroniques et photophysiques des allotropes du carbone : le graphite et ses composés d'intercalation, le carbone microporeux, le charbon activé, les fibres de carbone, les aérogels de carbone, les fullerènes, les nanotubes de carbone et les matériaux thermoélectriques de basse dimensionnalité (de zéro- à 2-dimensions). Mildred Dresselhaus a coécrit plusieurs livres sur la science du carbone. Elle a aussi travaillé sur des matériaux autres que carbonés, tels les nanofils de bismuth. Elle a reçu de nombreuses distinctions scientifiques, et a été récompensée à plusieurs reprises pour ses efforts visant à promouvoir la participation accrue des femmes en sciences et en ingénierie. Enfin, "Millie" a encadré plus de 60 PhD, a quatre enfants adultes et plusieurs petits-enfants.

Biographie détaillée

BERNADETTE BENSAUDE-VINCENT (BBV) : How did you make the choice of superconductivity at the University of Chicago in the 1950s ?

MILDRED DRESSELHAUS (MD) : We were encouraged to be independent. Brian Pippard from Cambridge was there for a year and helped define a topic for my thesis. He had been working on Fermi surface of copper. He suggested studying the response of a superconductor in a magnetic field. I made many measurements with various materials in various conditions. And I got unexpected results.

BBV : Was it before the BCS theory ?

MD : Yes it was before the BCS theory and when I published my results Bardeen became interested in them because they could not be explained by their theory. He gave the problem of finding an explanation for it to someone else. I worked with my husband on the model but we did not get a good one. Somebody solved the problem 20 years ago. It was not a consequence of BCS and it was not an important effect for superconductivity.

BBV : What was the situation at the Lincoln Lab when you moved there ?

MD : It was a Defense Lab there was a bunch of interesting projects going on. These were the wonderful years in solid-state physics. Lasers came. I was given so much freedom that I did not have to work on lasers.

BBV : How did you choose your new research topic ?

MD : It was a wonderful career change. I started up magneto-optics. There were new techniques to be learnt, optics in particular. I was working at the High Field Lab, in the basement of Building 4. John Goodenough was my neighbor. I wanted to be independent. Each material has its material science. I decided to work on graphite. There was no competition at that time. The materials science on graphite came from the UK. A highly oriented pyrolytic graphite came from Imperial College in London. The synthesis of diamond had raised interest in the phase diagram. There was an interest in carbon because of its different phases, interesting especially for space programs.
For my experiments I needed a good crystalline structure for the electrons to circle. For the theory problem Joel McClure from Chicago University helped me. A paper was published in the IBM Journal for Research and Development in 1963. Then every year we improved the model. With my second graduate student we turned the established view of the structure of graphite upside down : we put holes were electrons were supposed to be and vice versa. The paper came out in 1968. It turned out to provide the explanation of many effects. It was a real pleasure to hear McClure at the Conference of Low Dimensional Materials in 1970.

ARNE HESSENBRUCH (AH) : Did you have any connections with the Interdisciplinary Laboratory that was set up at MIT in these years ?

MD : I had contacts with A. von Hippel. He was a good friend. The whole idea that Materials Science was interdisciplinary was his idea. He had suggested interdisciplinary laboratories in 1936 and WWII reinforced his view. He started an interdisciplinary laboratory of his own. The Magnet Lab where I was working was separated from von Hippel's. Ben Lax had started a new interdisciplinary lab with Defense money.
I was at home in an Interdisciplinary Lab. My PhD thesis was prepared in an interdisciplinary environment. The Institute of Metals at Chicago University had been sponsored by industry. There were chemists, physicists, all disciplines. The Institute's chair, Cyril S. Smith, advocated interdisciplinarity. He became an historian like his wife in the last 20 years of his life. He did both physics and history.
At MIT, Gordon Brown, the Dean of Engineering, had the idea that engineers should think like physicists. I was asked to teach physics to engineers not in the physics department. This is the MIT tendency to emphasize the practical side rather than the theoretical side.
I had no prejudice for engineers because I needed them for what I was doing. I was affiliated with Electrical Engineering before I got a Chair.

AH : What was the situation when you became Director of the MSE Department in 1977 ?

MD : I was the 3rd director. The Lab was in big trouble because the NSF grant was about to be lost. I tried to keep funding coming in like all directors.

BBV : How did you come to the subject of intercalation compounds ?

MD : I entered the field in 1964. Ted Gaballe of Bell Labs had discovered superconductivity in alkali metal intercalated graphite. How could it be superconducting when none of its constituent were ? He knew my work on the electronic structure of graphite. So he asked me to look at the structure after intercalation. I had no idea of what the experiments should be. In 1971 Moore from Imperial College did the first experiment. So in 1973 I decided to the same with optics.
I wrote a proposal to get funds after some exploratory work. For the first time the proposal was refused. The reason was that my proposal concerned a complicated chemistry that I could not possibly get into : I did not get the money. I received my first grant on intercalation in 1977.

BBV : What was the situation in intercalation compounds when you entered the field ?

MD : There was an important conference in France at [?] near Nice organized by Jack Fischer and Vogo, a company manager who was influential in raising money. In fact the participants did not know each other and they started talking together. This conference had a great scientific impact. I wrote a review article for my students in 1978 that was published in 1981. It turned out to be quoted often, and often because I had few results to report. I pointed out it should go like this and that was the way it did go.

AH : Did you interact with Stan Whittingham ?

MD : Whittingham was there but I had no connection with him

BBV : Did you meet with Jean Rouxel ?

MD : Oh yes, I met him in Nantes two months before his death.

AH : Who were the leaders in intercalation compounds ?

MD : Researchers in few countries are active in this field. The US has been active for a time. France had been active long before the USA and to a certain extent Germany also. Japan entered the field later with batteries but are still there. The first patent was taken in 1972.
We worked on intercalation compounds until 1989. Then I stopped because I did not have ideas big enough. You know the MIT rule : each PhD thesis should be innovative, bring something new.

BBV : Would you say that conferences and review essays were crucial in the emergence of this research field ?

MD : Yes review essays are a pedagogical style useful for shaping fields. I was asked to do the same for fullerenes and later for carbon fibers.

BBV : You've had a number of international collaborations. Did you notice different national styles in the domain of Materials Science and Engineering ?

MD : There are more personal styles than national styles. Science is a universal language.

Fin de l'enregistrement

BERNADETTE BENSAUDE-VINCENT (BBV) : So, we want to focus on certain materials on this site, because we want to discover, especially because it's imploding or exploding and one major problem, we have always put some stuff on on solid state batteries, intercalation compounds that you know very well.

MILDRED DRESSELHAUS (MD) : Yes, I know my contribution to the battery business is much more limited than the big deal of intercalation physics.

BBV : Yes, and also you've been working on superconductivity and especially materials when it was quite unusual and in the 1950s, so if you could just tell us, try to remember, the situation with superconductivity in the late 1950s when you came to Chicago University.

MD : OK so that's where you want to start... well that's kind of the beginning of my foray into materials science. So I was a graduate student at the University of Chicago and looking around for research topics because at the University of Chicago at that time the students worked very independently. They found their own topics and figured out how to work them out and they basically did everything, sort of, very much different from today. But I was a special case, so I did it even more independently than others who did it independently. It was a little bit of a sociological thing (I don't know if in the history of science, you like to have a lot of things that we don't report in our regular papers...). I had an advisor that believed that women should not be graduate students, and that it was a big waste of resources to have us, there were very very few of us at that time, about two percent of the graduate student body nationwide - in these fields. So, because I got so much harassment from him, I stayed away from him therefore I worked a lot more independently than I would have, so I didn't have many people to go to to ask questions. He was the only advisor for materials physics or solid state physics. Well I stumbled upon this field partly because of a visit of Brian Pippard who came to the University of Chicago in 1955 for a year to work out the Fermi Surface of Copper, which was a big breakthrough, it was how to do an experiment back then to predict in detail and also measure what was there. So he was there, and he was a big man also with superconductivity at that time, so he interacted with me a lot for the year I was there and we started on this project, he gave me a bunch of ideas, which was very helpful. So it wasn't that I was totally in a vacuum because it started out with an interaction. Then he left, to go back to Cambridge University, and I stayed on and we had intermittent contact by letter, or maybe we had three or four letter exchanges until my thesis was done so it wasn't very much. But for me, I learned, and reading the papers that he and others had written that you could measure something about superconductors by measuring microwave properties. So that's what I learned from him and then formulated a problem to see what a magnetic field does. As you know magnetic fields kills superconductivity at the transition temperature. When you put on a high enough magnetic field, it's the end of the superconducting phase - and it goes normal. So my project was to monitor what happened on the way to ending superconductivity, on the way to the phase transition. And so I measured several materials. My main material was tin because it was a convenient temperature range and you could make the samples pretty easily. But I also studied other samples.... (MD turns off machine). Okay it's off. So I had magnetic field and different superconducting materials with different transition temperatures, and therefore also critical different magnetic fields. I did different orientations of the magnetic field. You know... all the various things you might think of, but I was stuck with one frequency range, because when you build microwave apparatus you're in one frequency range because everything hooks together and this was all homemade equipment because I had no money. But that was the time that you made your own equipment, it was all war surplus stuff that I found in some kind of stock room and throw it away here or there, and most of my equipment was like that, the rest of it I just made in the shop. So I learned how to do that get people in the shop to get me some instructions.

ARNE HESSENBRUCH (AH) : So you did have help on that score at least.

MD : No, I built it myself and designed it, but I had instruction because I never built equipment, I was just a graduate student I never was learning how to do all of this. But people were very helpful, so I got a lot of training like that, but that was the way we did a thesis in that time.

BBV : And did you have any idea of the BCS theory ?

MD : No it wasn't yet, no that came at the very end. So I go along here and I came up with some results that were somewhat counterintuitive. Because I expected that when you go from here to there it would be a continuous thing but instead I'm going toward the normal state before it got to the normal state it got sort of more superconducting, before it went normal. So it was a kind of anomalous effect. I saw it under many conditions and it always would seem to be there. And that was before BCS. I had all these results before BCS and then when BCS came out, BCS had nothing to say about anything anomalous like this. So, Bardeen was actually very interested in my results, because it couldn't be explained by his theory. Bardeen is B of BCS, a Senior person. So he invited me down to University of Illinois to talk to BCS. But I gave a colloqium there as a graduate student - which was pretty amazing - and I just remembered that because I just did a lecture series earlier this week at the University of Illinois, and I could tell them I was there in 1957, giving a lecture, and that I'm still alive and kicking ! They were kind of interested in that. So, well he got interested in my effect and he gave somebody else a project of trying to develop a theory, a detailed theory of application of BCS to microwaves and magnetic fields, et cetera. So it started a research direction for him, and from the experimental side, Pippard was surprised at what I got, so he assigned this project to two other students both of whom became probably people that you're interviewing, became well known in their own right.

AH : This was back in Cambridge then, right ?

MD : Well, it's a little more complicated. One of them was Paul Richards, who was an American who happened to be there, he may be on your list of people that you're interviewing. He was a postdoc, maybe he was a graduate student, I think he was a postdoc at the time, working in the Pippard group. So he did it at one frequency and Brian Josephson was another person probably on your list, he did it at another frequency after Richards. Paul Richards was, after me, he did it at a different frequency. One did lower, one did higher, something like that. They got basically the same results, more or less. Of course, different frequencies, different circumstances. So that was what happened and now their results spilled over into the 1960s, and my papers were published by 1958. They went on for maybe another three years, in different frequency ranges doing complementary experiments. But what happened to me, I didn't stay with this project for very long. I wanted to do more with it and I tried to develop some model with my husband who I got married to in 1958. So we worked on this, I don't know that we really got a good model, we didn't get a model for it, I would say we tried to follow up and improve what we had done.

AH : Sorry, your model, did you incorporate BCS and then try to also explain the effects from your experiment ?

MD : Yeah, what we were trying to do, take into account the details of fields and external fields, and we had RF fields [radio frequency fields] and external fields. We had different directions, RF fields and external fields.

AH : So what was your model ?

MD : I don't remember a whole lot about what we did at that time ! So many years ago ! And part of the reason I don't remember so much about it is that it didn't really have a big impact on anything. And for me, I had to switch fields, because when I got my next first job that was at Lincoln lab, I was told that that wasn't an area to work on because everything was solved. Of course my problem wasn't solved but it turned out that it was actually solved by somebody maybe ten or twenty years later... quite a long time later. And it turned out to be kind of an obscure, not so interesting effect that didn't have that much to do with BCS theory, but had something to do with the intricacies of all of these things interacting and the internal perturbations between them. But it wasn't an important effect as far for electromagnetic theory and it was not an important effect about superconductivity, although a lot of people's attention was attracted and there was some good work that was done, that is, the electrodynamics of BCS was worked out as a result of this. But that stood its test of time when later on high-TC [High-temperature superconductors] came along and gave another push looking at these things. So I moved off into a totally different field.

BBV : Who told you that you had to work on another field ?

AH : Did you choose it yourself ?

BBV : How was the prevision of working on this field formulated ?

MD : Well, you start a job, and you discuss what you're going to do and they were very delighted to have me, to do pretty much anything I wanted. I was working in a Defense lab, you know Lincoln Lab was a Defense lab, and they had a whole bunch of different projects that they had to get done. But they had a few people like me that could do anything they wanted in sort of the basic research area, we don't have jobs like that, so it's hard to explain to somebody what I was doing. But when somebody needed some advice about some solid-state physics topic, that was working on some kind of Defense project, so they would come around and I'd tell them what I knew about it, that was sort of the way that part worked. So I had a lot of freedom, and so, I came around there, I saw what people were working on, and it was just so many exciting things going on. This was really the heyday of solid-state physics. I arrived there in June 1960, these were wonderful years in solid state physics. Lasers came along in 1960, and in fact, most of the people in the division, solid state division, went to work in lasers. But I didn't, I was one of the people that had so much freedom, that I didn't even have to do lasers like when everyone else had to do lasers, was sort of doing what they wanted, but was urged to go into lasers, but I didn't do that. So I started in this magneto-optics business because I thought that this was a really hot topic. And I was right. So I learned totally new technique, I didn't know anything about it, and so it was a lot of new things that I had to learn to do all those experiments.

AH : What's the new technique ?

MD : Well, optics, I had never done optics before, and it was magnetic field research. Well I've done magnetic fields, but that was little tiny fields that I worked with, that I was doing superconductivity work with ; 1000 Gauss was as high as we went. These are little solenoids was all I worked with, and I had a chance to work in that high-field facility. That was just, just beginning to come online. That was a very good research direction, I worked in that field until the Magnet Lab disappeared from MIT, mid-nineties. So I worked in that area for many years, not necessarily on magneto-optics, I worked on a lot of things with applied magnetic fields. So this career change that was imposed on me was wonderful, it was an exciting field. It's good when you're young to work in areas that are new, and maybe superconductivity was not as active at that point. Now when you turn around and look at high-TC superconductivity, we could have discovered it at that time, because I knew about this, and my almost next door neighbor was John Goodenough, who was working on just those materials that were involved in High-TC. Actually we talked to each other but we never worked on any project, because it wasn't, I wasn't supposed to be working with him. No, we didn't have an idea to try his materials, down at low temperatures with the superconductivity, no one had an idea like that.

BBV : How can you explain, because you tried a lot of materials, you were free...?

MD : No, I didn't try a lot of materials, I wasn't doing superconductivity. I made a switch to semiconductor physics basically at that point. So I was doing something different, and he was working with highly correlated materials. But not only studying magnetism, not studying superconductivity, that was.... But very very soon, after I learned of what they were doing I moved, I didn't want to work in the same areas that everybody was working on there was quite a large group, and most of them were doing very similar things. To me, the physics was not different, of course every material has a little different materials science, but there were no really new concepts, not much, it was working out a lot of details for each new material, which I could do. But I decided that I didn't want to do that, so that's how I started into graphite. My first work in graphite was maybe 1961 could have been the end of 1960, but 1961 for sure, and I've been there ever since, as you know. But I got the idea, there were several events - you know you never write about this exactly, so this is history of science - there were several events that happened in 1960 that made this all possible, and for some reason, I happen to know about some of this. In the UK, there was this discovery of how to make HOPG : Highly Oriented Pyrolytic Graphite. To do the experiments that I needed to do with the high magnetic fields we had to have samples that were a little bit bigger than the flakes of graphite that are normally found in nature. So the materials science of this project was worked out in the UK.

AH : What did they come out of ? Was there an industrial interest in this or what ?

MD : Well, different bases of carbon were interesting in 1960 because that's what I was going to mention to you, the year that diamond was artificially synthesized. So there was interest in the phase diagram of carbon diamond, and perhaps the work of Opaloda [?] in making HOPG was related to it.

AH : Do you know what the institutional setting was ?

MD : Yes, certainly, that was Imperial College in England, London, and I had occasion to visit him very very soon thereafter because there was a conference. The conference where the Josephson effect was announced, maybe, could have been that one, or could have been one before that. But I happened to be in the UK, and I dropped in at Imperial College and we met at that very early time, but when we met I already had quite a number of results. So we had something to talk about, because otherwise he wouldn't have been that interested in meeting a young person whom he didn't know anything about. So one thing was the material, and the second thing was there was kind of an interest in the field of carbon. Carbon became interesting when it was understood that were different faces... it wasn't only graphite which people had known well people knew diamonds but they didn't know how to go from one to the other, that wasn't really understood.

BBV : Were they trying to make carbon fibers over there ?

MD : The carbon fiber business came a little later, and my entry into it came later. If you want to go into that, I can, after. But maybe we should talk a little bit how the experiment started because that's never written up any place, so you might find some of that interesting. So all the different carbons that I tried because Raytheon was making carbons for, I don't know, military purposes, and the space program was already starting around that time and carbon was a lightweight material so there was quite a lot of interest. I tried some of their graphites but they didn't work, they just didn't have enough good crystalline quality. To do the experiments that I was after, an electron has to go through a whole cyclotron orbit before being scattered, that was the criteria. So if you have defects, impurities, whatever, that would interfere with that process. So I needed to have a high-quality crystalline material. Maybe a single crystal would be good but it wasn't big enough to get enough signal. I was looking for small defects.

AH : You're doing a magneto-...

MD : Optics, experiment. Well see ! I started out in the beginning doing my first couple of papers were magneto-optics and what other people were doing and that was kind of my learning experience ; and then I took a sidestep and I started another area which people considered too hard so we had virtually no competition because people considered the system too hard. It had a whole bunch of couple bands, four bands, and all people at that time only were thinking about two bands, valence and conduction bands. Anything beyond that was too complicated. So and the experiments could have been tough because it was a materials science problem and all that. But my materials science problem was solved by Opaloda, and there was a fellow at General Electric Laboratory that I found out about in 1960 and he was working in the US with this process of Opaloda. He followed the original work and he made me a sample and the first time we tried it it was beautiful So we were launched. So that might have been the beginning of 1961. We began to get a lot of spectra. Then we tried to figure out what it was that we were seeing. We now had a theory problem. Unfortunately, I don't remember exactly how this happened but when I was a graduate student at the University of Chicago, one of my colleagues, maybe two years older than me, but somebody I knew pretty well, was Joel McClure. He figures into this picture because somehow I made contact with him because he had moved into this graphite area, he wasn't doing that when he was a graduate student, but he became the person that developed the theory for the energy band structure of graphite. So we made contact and I remember him visiting me maybe the fall of 1962, before my third child was born. We were talking about how to deal with the band structure of graphite, explained all the spectrum, and I really got a lot of seminal ideas from him. My husband Gene understood immediately how to translate what he was doing to the experiments that I was doing. We developed a theory, and for our case adapted what McClure had done and extended it to explain the experiment and it worked very well. And so we were able, for the first time at that time to understand many of the details about the electronic structure of graphite. So that was 1962 or so, and I remember publishing a paper the first time this became kind of known on the outside was I was invited to an IBM conference, I don't know exactly the dates of that, but it must have been either late 1962 or early 1963. And that paper is published in the proceedings of the IBM journal. The IBM journal had a special issue for this particular conference and it was my paper on the Fermi surfaces of graphite. So that was one of the very early papers on Fermi surfaces of graphite, and we learned a lot of things. You know that it wasn't just ellipsoids that had more things associated with it and that was, we really did very detailed things with it. And actually what we did, that was interesting and new, and inspired by the work of McClure, but also kind of different as we had some kind of model that is still used today, basically. But it changed - I'll explain all the changes that happened because that's an interesting story for history of science maybe. So we have electrons in holes in graphite, and they were understood at that time and then I... (see every year, science moved slowly in those days relative to now, and I think we wrote a lot of papers on different aspects of this always getting better). Then some time in the mid-1960s, my very first graduate student, Sam Williamson and we did cyclotron resonance and van der Hofstad-Alfven effect, all of those things explaining about the Fermi surface. So we brought to bear all the different experimental techniques we could think of to look at this, and Sam Williamson went on to a very distinguished career. And he has a similar position to what I have at NYU, Institute Professor is my title here [at MIT]. He has similar position, but that was my first student. But his claim to fame isn't this, although his thesis I think was really very good. But he had an interesting career : he went to Rockwell International, got into semiconductor physics, like many of us did and superconductivity after that, and SQUIDS, magnetometers, came in at that time so he learned that technique and he had the idea just around 1970 of using that technique to look at the human brain. That's how he's known, a big name in brain science, using this technique. Yes, but related to what we were doing back, not so far off from what we were doing together in the late 60s. And with my second student after that we went (maybe he was my third student, but it was in very early times), we had the idea that if we took polarized light, doing the experiment in polarized light rather than circularly polarized light, we would be able to look at specific transitions, linear. Electrons go like this and they have different charge, the electron goes this way, the hole goes that way and they rotate in different ways, so we would be able to separate the transitions, and as soon as we did that everything fell apart because what we thought should have been electrons seemed to be holes, and what was holes seemed to be electrons. So this was pretty crazy ! Basically, the result of doing that polarized experiment, we found that everything that had been done on the electronic structure of graphite up until that point was reversed. That the electrons were holes and holes were electrons. Which was very sensible on the basis of fairly elementary considerations. That's why we thought that we were right. So when I submitted my first paper on this subject to the Physical Review, maybe it was Physical Review Letters, I don't remember exactly, but one of those journal articles, the reviewer was Joe McClure. And he was an obvious reviewer of this kind of paper, because he is a most knowledgeable person. And he revealed his identity ; they're not supposed to do that, but he revealed his identity. And he told me, "You don't want to publish this, people have been doing for the last twenty years all kinds of work with electrons this and holes that and how could you reverse it ? You must have something wrong with your experiment". So we checked and we checked and we checked and we said to him that "we think that we're right and if we're wrong, OK, we'll take our chances". And we went ahead and we published it. And as soon as it came out, the paper came out, we started getting letters and comments from different people. "So this is the explanation of this effect, and this is the explanation of that effect", and they had all these data in their drawers and they wouldn't publish them because they couldn't understand what was going on. A : The Emperor's New Clothes ! And then when we straightened out the electron/holes everything started fitting into place. And I had the real pleasure, so this is 1968 or so when we discovered that effect. In 1972, or maybe it was 1970, they had an international conference on low dimensional materials in Dallas, TX. And Joel McClure gave the invited talk on semimetals, or graphite semimetals, something like that. And he focused the entire talk on turning the electronic structure of graphite upside down bringing everybody's work, well we had done that also, but he did it on this occasion for everybody, and it was a very nice thing. And at that time, I gave the corresponding talk on the group V semimetals business because we had been working on that as well, in those early days, working out the electonic structure, the relation of all the group V semimetals. So that was kind of that early period when I was in magneto-optics. I was already at MIT because I joined the faculty in 1967. So 1968 when we turned the band structure of graphite upside down was my first year on the faculty.

AH : I wanted to ask you about the beginnings of the Interdisciplinary Laboratory at MIT. We actually talked to John Goodenough and I asked him if he had anything to do with it and he said "no, no, no, sitting out there at the Lincoln Lab, there was nothing", and it was almost a hostile atmosphere, they didn't want to have anything to do with him.

MD : Well, I was kind of a part of it. Let me give you a little background. You may have some difficulty but some of the people are still alive. The person who really started all of that was Arthur von Hippel. It's hard to interview him now ; you missed your window with him. He will have his 102nd birthday on the 19th of November [2001]. But he was a big factor in my early life ; he really liked all the things that we were doing. Now, when you're a young faculty member – a young female faculty member - it's maybe not so easy. But to have people who appreciate what you're doing makes things a lot better. So, he was always a good friend. Of course he escaped from the Nazis and all that. He came to the US. He came here, maybe '36 or '37, many years before me, and he started the Interdisciplinary Laboratory, which grew. They worked on many things, properties of dielectrics. See, we had this common background. That's a little bit how we met in the early times. They had ferroelectrics, piezoelectrics, they were growing crystals of all kinds, and phases of ice. There were a lot of books written. He was a big influence on the early solid-state physics. It's too bad because he was coherent until about five years ago, '97 or '96. He knew everything still. He was with it, but now he doesn't even recognize me. I think this is off-base, but there may be some people who know details about the lab. There's John Gelatis who is a microwave person and worked in this laboratory. He is still alive ; he must be in his 80s. He retired a long time ago. He wasn't really a PhD scientist, but he worked in the lab and might be a useful source. He may be able to tell you some other people who may still be alive. Most of the people that I can think of are no longer with us. There's George Pratt, who is faculty still, who came to MIT before I did and had quite a lot of contact with von Hippel, but I don't think he was a member of the lab per se. And he came after the 60s. In 1960, the Interdisciplinary Lab was formed, that I became Director of, but the origin of the lab goes back to the 1936 period and it evolved with von Hippel and he had different groups doing different things. It was his idea.

AH : Here at MIT ? The whole idea that materials science was all fields was his and he was ridiculed and took a lot of flak for that. But when the war came, the lab that he had and the people that he had were very much appreciated. That was the way to solve problems. So he got very heavily involved with war work. And he was anxious to be that because he had had such a bad time in Europe. A lot is written about this, I am sure the history books... You can find out a lot about it.

But you said that when the IDL was set up you were involved.

MD : Well, I wasn't involved. The idea was von Hippel's. I came and started working in the lab in 1960. I was working in the High-field [lab] which wasn't on campus. The High-field lab is not at Lincoln Lab. I was an employee of Lincoln Lab and maybe I analyzed some of my data, did some of the calculations, at the Lincoln Lab, but when I was actually doing the experiments I was here. And it was in the basement of Building 4. That basement of Building 4 is still there. I could show you exactly where that whole thing started. But von Hippel was in a different location : that was the Magnet lab. The Magnet Lab was really separate. The Magnet Lab had people doing all different things, so it was very interdisciplinary in the Magnet Lab. The Magnet Lab had, when I started, maybe a handful of people – we ran our own experiments. In 1962 or maybe 1963, Ben Lax who was my boss got the idea to start something called the national magnet facility and got the funding from the Airforce. They built the building in a bakery over in Albany Street and that became the Magnet lab but the pre-magnet lab, when I worked on it, was in Building 4. When we discovered the magneto-optics of graphite, that was done there, in Building 4.

AH : With all this interdisciplinarity, I presume you felt like a physicist. So, when the IDL was started with the name of Materials Science & Engineering, did you feel that this was a strange concept ?

MD : No. There were two reasons that I was very much at home in it. When I did my PhD-thesis I did it in an interdisciplinary environment. This will sound very strange to you but I got my degree at the University of Chicago. The laboratory where I had my equipment and where I was actually working was called the Institute of Metals. It had physics, chemistry, and metals. It was Cyril Smith, who was boss of the lab. He was the person I knew. It was totally funded by industry. Have you done any work on Cyril Smith ?

AH : No, but we have his books here in the basement – he bequeathed them to the Burndy Library.

BBV : Is he still alive ?

MD : No, no. He died in 1988 or something. He would be a lot older than me.

AH : He has left his papers to MIT.

MD : He had an impact on many things. His wife was an historian and the last 20-30 years of his life he did both history and science. He was a very interdisciplinary guy. He had been in industry and we had an id atmosphere. I didn't have much help doing my thesis but the people that helped me were from different people of all walks of life. I got people who knew how to do machining, vacuum systems, I got chemists. I used all these types of people that I felt comfortable with. So later at the Lincoln Lab we were also solving all kinds of things, and then you need all kinds of people. So I was very comfortable with talking to people, explaining physics principles to them. That was my function. I was brought to MIT as professor to teach physics to engineering students. I had a mentality already. The physicists here didn't want to teach physics to engineering students. They wanted the engineering students to come and take the physics courses exactly as they were doing it. They made no effort to have the physics have any relevance to what they were doing. This was the year of semiconductors and they weren't teaching the physics in any way related to that. When I came Gordon Brown was Dean of Engineering and he had the idea that the engineers missed out on WWII because they didn't know enough physics, and he wanted it changed by having people trained in physics teaching them, in addition to having experience with the engineering side, which I did. That's why I was attractive to them : because I had this dual background and didn't have a prejudice against engineers.

BBV : Did you adapt your physics course to engineers, and how ?

MD : Oh yes, ever since I have been here I have been teaching physics to engineers. I get physics students who come in also. Over the course of the years the physics department's students have moved towards what I was doing, because physics now has a lot of solid-state whereas when I arrived it had nearly none at all. Ben Lax, my boss, was a member of the physics department and he didn't get along very well with the others on the department, so that wasn't a great help in getting this... But he's still alive. You might want to interview him. And he is in order upstairs. He is still working in the lab.

AH : Well, we talked to Sam Schweber, who is also working with us on this project, and he has given me an account of the development of physics at Brandeis from theoretical physics asking philosophical questions towards a physics that can be used, towards engineering.

MD : They have focused a lot on theory at Brandeis, but the MIT experience was somewhat different, because it was favored a lot by WWII. The Radiation Lab, and also the materials group developed. There was a practical side also here. But it was not in the physics department. There was something in the Physics Department, but it wasn't very much. There was John Slater.

AH : Would you tell us something about your time as Director ; if it's not jumping too many years.

MD : Well that's 1977, so it's jumping a lot. I was the 3rd Director and when I took over the Lab was in big trouble ; it was about to lose its NSF funding. I had to keep the money coming in. That's what a Director has to do. The first Director was from Physics, the second was from Materials Science, and I was from Electrical Engineering. I did get a Chair in 1973 which gave me some independence and also some funds to do what I wanted. That's how the intercalation work started.

AH : Shall we drop the IDL and turn to the intercalation story ?

BBV : Yes please.

MD : My first contact in intercalation physics was Ted Gaballe.

AH : We have talked to Stan Whittingham, by the way, so we do have that perspective. I don't know whether that helps you.

MD : There was no contact between us for a long time so we both entered it very much independently I entered the field my first contact with intercalation physics came in 1965 or maybe 1964.

BBV : That early ?

MD : It's not written down, so you wouldn't know. But you could verify it. I got into it through a person called Ted Geballe he is a very well known person in this area. I strongly recommend that you talk to him. He is about 10 years older than I am. Because he really knows a huge amount of the early history. He was involved in many, many things in this field he is retired now but works pretty much every day in the lab. He discovered superconductivity in intercalation compounds when you add potassium in an alkaloid metal to graphite, it becomes an intercalation compound and he found that these materials were superconducting That's 1965 or 1964. I think it's referred to in my list [on the web].

AH : Yes, it is.

MD : Because it was a very important part of my thinking. He knew about my work on the electronic structure of graphite. We hadn't turned it around yet, it was still the old way. But he knew about our magneto-optics work and was sufficiently impressed with that and wanted me to do some kind of experiment that would illuminate what happened to the electronic structure after you made an intercalation compound out of it. Okay ? So that was what he wanted. And he invited me down to Bell Labs and we talked and I listened to what he had to say and I put it somewhere in the back of my mind. I didn't have an idea of what the experiment should be, so I didn't do anything and then in 1970 or 1971, there was a paper by a fellow called Moore (maybe something else) an Englishman, I think also from Imperial College He did the first experiment on the Hausser-Alfven effect in one of the intercalation compounds he showed that you could have cyclotron orbits long enough that you could get magnetic resonance data. When I saw that I knew that if I did an experiment that was similar with what he did with optics it would [?] We tried to make the samples and did the experiment, and I guess our first experiment would have been done about 1973. Because it took me a little while to find out about this paper I didn't see it the day it was published the reason that I mention this Chair is that doing this experiment was that I had this income that I could use for hare-brain experiments and things that maybe you couldn't get funding for. You always try to do an experiment first to make sure that it works before you send off the proposal, because if it's not going to work... I don't want to work there either so you do a little exploratory work - I think everybody does. It's certainly the way we do it. I used a little resources from my Chair to check it out and we got some interesting, encouraging results, so I said well, uh I'll put a student on it to solve it for a season and then of course we had to fund the student with research money so I tried to get money. In my career there have been very few proposals that have not been successful because I am really very modest. I don't ask for money unless I really need it and have a good idea I think that's the reason I have been successful in getting funding but that was one where I was not successful. The comments of the reviewers basically said, that a person with a physics background and my kind of background should not be mucking around with chemistry-related things that were so complicated that we would never understand. So there was a big potential barrier put up by funding agencies. I wasn't able to get anything. And those were the heydays when it was very easy to get money. Maybe I got a tiny little bit of money from the Materials Center, but they said : hush hush, don't tell anybody that you're doing this ! But I believe that as soon we began to get some more results and publications, I think I got my first grant in 77 so it was quite a few years when we were quite unable to get funding. What happened in 1977 was the first conference in intercalation ; the first big conference ever, in southern France, [Lanapour ?]. It's near Nice. Southern Riviera, very nice ! It was a very influential conference it was well attended and had an impact on almost everybody that went there. It revealed what was going on in intercalation physics and chemistry, it was mostly chemistry.

BBV : Who was the organizer ?

MD : Jack Fischer and somebody called Vogel whom you probably don't know he dropped out, he had a company he dropped out of the whole business five years after. He was an influential person in making it all happen maybe not so much for the science.

AH : I am sure Stan Whittingham was there ? You must have met him there ?

MD : Yes well, we could look back and find out. I believe he was there and there were people from all over the place that was the very first time that I met any of these people - total news for me.

AH : Because they were chemists ?

MD : No, almost everybody was new to the field. I'd been there much longer, but nobody knew I was there. Publishing in all these different journals there was no connection and listening to all the things they said ; then I knew what to do. You know, it had a big scientific impact and we came back to MIT and we started working in all the areas. I all of a sudden had a really good picture of what was going on in the field and then my students had a very hard time understanding what was going on in the field and I wrote an article now that article must have started about 1978 or very early 1979 ; I must have been Director of the Materials Center at the time, right ? Because 1977, when I went to Lanapour I must already have been Director because I am just figuring out the dates here - so anyway.

BBV : So you wrote this article.

MD : You know it takes a while to write these articles. Okay, so the article has a lot that should go like this, and it turned out that it should go like this is the way much of this did go. So that article is still referred to now, if somebody wants to look at the article on intercalation compound they often go to that ancient article that was written very early in the time of the field. Because of that, I was asked to do a similar thing for fullerenes, that's my big black book on fullerenes, and that came from Bell Labs researchers who felt that my pedagogic style was useful for researchers. And I guess they said, "I'm an old lady now, it's ok if I spend a few years studying everything that's been done in the field and digesting it and telling students what to do". But I'd done another one on carbon fibers, since you asked about carbon fibers, I did that one many years earlier.

BBV : So you suggest that this kind of review articles take a lot of time.

MD : They take a lot of time.

BBV : They are very useful to shape a discipline.

MD : Yes, and I had the opportunity to shape a few fields in this way. And the first one was the intercalation, you know at the time I was doing it, I of course had no idea that it was going to affect other people, I did it for my own students because they were working across such disparate areas and it was hard for them to figure out what it is that we were really doing. Because there's a lot of interdisciplinary research, and somebody's doing X-rays, someone's doing magnets, and another ones doing optics or infrared. Many many different things, and so they had to learn the field that they were doing, they learned the techniques and so forth, and they had to learn intercalation physics and see how it goes together and how it goes together with all the other guys. So having the review article helped a lot and it helped them in writing chapter one of their thesis too. So I found out how useful that was and that encouraged me to write more things like that later on. We were in intercalation physics until roughly 1990. I did a couple more things later on with with fast optics. We did some kind of elegant work.

BBV : And why did you stop ?

MD : Why did I stop ? Because I got into fullerenes and nanotubes, and their behavior too. It wasn't that ... I didn't have so many ideas, we'd done so many things already, the field had become mature as a result of other people who'd moved in, moved out. But I moved somewhere else and I, everybody's finite, you can't work on everything.

BBV : Do you have students who went, or are working on intercalation compounds because they need the technique ?

MD : No, not really, not really, let me explain about that. Maybe when you interview other people on the project, the ground rules are different. I'm at MIT and the expectation of the graduate student here is that they develop a new field, basically. So when I give a thesis topic, we develop some kind of thesis topic, every thesis I try to make like they're breaking some really new ground. There's a finite number of things that you could do. So maybe one thesis was on the structural properties of intercalation and we got into some interesting things with electron diffraction and we could do the surfaces. And then Raman processes. But after I finished all of those forays, big things, then I moved to something else. Okay ?

BBV : So you moved to fullerenes.

MD : Yeah, well I saw fullerenes as opening up totally new areas so and it's something I could understand in depth because it's only graphite that's rolled up in a scroll, I already knew about that. When I select topics, you know people always ask me, "How do you know what to work on ?" This is graduate students, so I say : you want to work on something new that people don't know much about, and so you take your chances, maybe it will develop into something, maybe it won't. But if it does, then you have a chance at doing something that's really quite new. Otherwise, you're just doing the same thing as somebody else did, and that's not really an MIT PhD. Being a thesis advisor here, I'm a little bit limited, sometimes I have some ideas, oh it'd be nice to do this and this, but that's just an extension of what somebody else did, and that's not appropriate for a PhD thesis. So you asked me about why I got out of intercalation physics. Well I didn't have ideas that were big enough and it's hard to find, when you get to the point where the field is mature, it's hard to find these kinds of good ideas.

BBV : And just one more question about intercalation compounds, did you have contacts with the French people in Nantes, Rouxel...?

MD : Oh yes, oh yes, I did. Yes. And in fact, still. I was with Rouxel two months before he died. We had an interview with the French TV, the two of us together I don't know, we had some kind of interview, it was in Nantes. They had a conference and somehow they sort of took me one day some place, and he was there, I was with him because he had ... Yes, the French, now I see why you're interested in intercalation physics, and chemistry in fact, is not sort of spread around the globe. There are few countries, the US was a player, for a while it was a big player, but only for a short time. France was working on it long before the US, we had one person here that was at Argonne National Lab who passed away, dear heart, I've just forgotten. But he was the big person, he was a giant in the field, but he was working in isolation. He passed away in 1965 approximately. He was originally from Europe, maybe came during World War II, or because of World War II, something like that. The French were very big, and the Germans were somewhat into it, but not as big as the French. And then the Japanese entered later and stayed longer. They're still there. And they were the ones that really started the battery business or aspects of the battery business in a big way. I think they had some of the very early patents on them.

BBV : Yes, on intercalation compounds. The French are not much interested in industrial applications.

MD : Well, yes, that's right, but the Japanese companies have pursued that. It was the first patent, I think in 1972 and well I remember that.

BBV : One question I would like to ask you because you give a lot of collaboration with the Japanese. Carbon fiber.

MD : Yes, oh you want to know that ? Well that happened because of intercalation. In 1980, there were some important collaborations in my career. The first one was not with carbon fibers, it was with Jean Paul [Lycee ?]. And that happened in 1970, we were in Dallas, TX, for this conference that I told you Joe McClure explained about the band structure of graphite and I was explaining about the group five semimetals. Well, they had the conference, it was a very small conference, and that evening, one of the evenings of the conference I went to a concert and I was on a bus going from the conference site to wherever the concert was. And on this bus was Jean Paul Lycee. And I had my badge and he had his badge. We were the only people on the bus with the badges. So I walked over and I introduced myself, I was older than him by a few years. It was okay to approach him I thought, and he of course knew who I was, but didn't know me. That was how we met, and then we started talking about our science. At that time he was working on bismuth, or antimony or something like that, and so I heard what he was doing, and I said, "Oh I know about that, and I know about that" and we started working together and we're still working. I just had something from him yesterday, so we're still working together.

BBV : You have been working together on different topics ?

MD : Oh, we worked on many many topics, we must have a hundred joint papers. But it started on that bus, going to the concert. And that was the beginning of, later on, twenty years later, of low dimensional thermal electricity that came from that meeting because I don't know if that would have happened otherwise. Because we had a dinner party and he invited somebody from France to meet me, and wanted to talk about the, the French navy wanted to know something about thermoelectrics, they had a guy from the ministry that came, and that conversation started the field, so, interesting thing, but I've written that out for the conference proceedings. Did I cover what you wanted on Endo ? Yes, let me tell you about Endo, because he started... 1970 was EC. We met at a conference. And 1980 I met Endo at another conference, and that was the second conference on intercalation physics. The first one was in France in [Lanapour ?], and the second one was in Provincetown, Massachusetts. And he came to that conference, and I was absolutely blown away by his talk on carbon fibers, it was nothing intercalation, well maybe he had intercalated by that time. But what I saw was that he could make these very long thin things and I said that those would be wonderful agents to do transport measurements. I just saw this vision when I heard his talk of all the things that we could do with those samples. And I didn't know that these things existed until that day. And I went up to him and I said, "I just loved your talk. Wonderful ! And we should do an experiment together", I said something like that, and we've been working ever since. So we have many papers too. Yes, but my collaboration with the Japanese is much older than Endo. Endo was not my first Japanese collaborator. But he's my first sort of applied. He's in applied areas, the other people that I worked with before are in more fundamental physics areas.

BBV : And when you have collaborated with Belgians and Japanese, would you say that you noticed different national styles in the field of intercalation ?

MD : Well, yes, there's national styles but there's personal styles too. Yes, not every Japanese is like every other Japanese and not every Frenchman… and Jean Paul Lycee is originally from Alexandria. He was born in Alexandria, Egypt, so I'm not sure he's exactly a typical Belgian either. So maybe he is, maybe he isn't.

BBV : It's much more personal ?

MD : Well, you know science is a universal language, so we can relate to everybody doing our science ; it breaks down all barriers. When I was doing something, I was president of AAAS and I was advocating with Madeline Albright the importance of the state department, this is the US state department, it should have scientific attaches at as many embassies as possible, because that was a ground where Americans at least would be respected and could talk to people. Rather than being hated and staking the battle on military operations. Think about things we could do together, we could, amount this crazy war on terrorism but maybe if we had a way to work with the populations that are disadvantaged, all the money that's spent on the bombs were spent on food, and improving people's living standards, maybe we would be much better off in the end.

BBV : So you still think that science wins peace among the people.

MD : Well it also brings war, all these tools for more destruction than ever before. So it's kind of a double, science has to be used in the right way too. Well I think we're all getting tired, and we have other things to do, maybe we could get together another time after you get a chance to look at what you have, and what you still need.

BBV : Yes, you can go and have a look on the site.

MD : Here ? Oh I used to be an advisor, I was on the board here in the institute for two full terms. I was here doing my thing until I started working for the US government, you know I was working for the Department of Energy. So I had to relinquish everything I was doing in the private sector.

AH : Why did you participate here [at the Dibner Institute] ? Why are you interested in history of science ?

MD : Well I was always interested in the History of Science and well I knew so many of these people, I was a student of Fermi, I just gave a talk for Fermi, on being a teacher and well so I gave the talk and I thought I had such interesting material it wasn't scholarly in the sense that I did a lot of research about Fermi but I just told stories that I knew. And I thought maybe someone would invite me to write an article on it because I thought it was, maybe, a little bit unique perspective, I just gave my talk, if people liked it, maybe they would record it, and that's it.

AH : So why don't you write it ?

MD : Well I don't have enough time. I always do things when I'm invited. You know how it is, we're pretty busy individuals. Well I have been interested in science and I've known just, you know when I started science was so small, everybody knew everybody. I'm talking about my student years, it was just handfuls of people. This wasn't like today, two orders or magnitude smaller. So many of the people that you're interested in, I knew them. Maybe most of them. In one way or another, our paths crossed. Even if we didn't write papers together, maybe we had some influence. But you know when I, I didn't realize it was Dibner, nobody tells me E56, they say Dibner Institute, I say, Oh okay I know that place. I've been here many times.

BBV : Do you think that you could help us to make contact with the Japanese materials scientists because we would like to have a case study of the US, and a case study on France.

MD : Are you willing to go over there ?

BBV : Yes we would go to interview people in Japan. For that we would need introductions. So if you could be kind enough to give us a number of names and contacts it would be really helpful for us, because it's very difficult, we cannot just come and say.

AH : Japan requires special entry.

MD : Okay, I'm very well known in Japan.

BBV : Especially in carbon fiber, because it is the topic we would like to investigate and you know everybody in the field.

MD : I do, well I don't, I wouldn't say I know everybody : I know a lot of people. I think that the book I wrote maybe was helpful. That book is out of print now, they want me to do a second edition. No time. But I'll do it, I'll do it. Carbon nanotubes are so exciting now that I'm- I don't have the time to write a book like the one I did the first time. It needs to go back in the literature for twenty years, I haven't been involved in everybody's doing, just what I'm interested in. Write a book it's a little different, you have to do the scholarly stuff. When nanotubes subside a little bit maybe it's a good time for me, basically if anybody's still interested. Well I'd be happy, what's your time scale ?

BBV : I'm leaving on Sunday but Arne is still here.

AH : To go to Japan, we were thinking the first half of 2002.

BBV : Sometime in there.

MD : Well, I'll get Endo, I'm going to see him in two week, I'm going to his lab he runs me ragged, he brings me to lecture in two different places in one day and that's my regular schedule there, it's kind of unbelievable because it's long distances and running around, very tiring, and you can't and every lecture is on a different subject of course.

BBV : But you can write on the train.

MD : (laughter)

AH : Well thank you very much !

BBV : It was really very rich for us.

MD : I'm not exactly sure what you're after so you'll have to sort of tell us a little bit.

Fin de l'enregistrement

Pour citer l'entretien :

« Entretien avec Mildred Dresselhaus », par Bernadette Bensaude-Vincent et Arne Hessenbruch, 25 octobre 2001, Sciences : histoire orale, /spip.php ?article82.

Pour citer l'entretien :

« Entretien avec Mildred Dresselhaus », par Bernadette Bensaude-Vincent et Arne Hessenbruch, 25 octobre 2001, Sciences : histoire orale, https://sho.spip.espci.fr/spip.php?article82.

Lieu : Dibner Institute, MIT, USA.

Support : enregistrement sur cassette.

Transcription : Bernadette Bensaude-Vincent, Helena Fu, Arne Hessenbruch.

Édition en ligne : Sophie Jourdin, Sacha Loeve.

ARRIBART Hervé, 2001-02-19, 05-29, 02-20

Sophie Jourdin — 2011-06-16T07:31:17Z

Hervé Arribart is the Scientific Director of Saint-Gobain Recherche, an international company of French origin with an emphasis on glass manufacture. He took his PhD from the Ecole Polytechnique in Paris in the mid-1970s and subsequently researched ionic transport using nuclear magnetic resonance. In the late 1970s he worked with Jean Rouxel's group at the University of Nantes. In 1981 he joined the company Elf to work in research and development. In 1985 he moved to Saint-Gobain, where at first a large portion of his research was closely related to the practical problems of production. In 1990 he started a laboratory (a joint venture of Saint-Gobain and the CNRS) on the basic science of glass surfaces, using a diverse set of tools and especially the Atomic Force Microscope. In 1999 he moved to the more managerial position of Scientific Director. Hervé is also on the staff of this project.

2001-02-19 :

HERVE ARRIBART (HA) : I studied at the École Polytechnique in Paris. The selection to the school is done mainly on mathematics. But during my studies I learnt to appreciate physics in particular. I decided to pursue research in solid-state physics. It was a good place to study physics. While in my last year as an undergraduate I did a Diplome d'Étude Approfondie in parallel (an intermediary between an M.Sc. and a PhD typically done for a year before starting one's PhD studies). In Orsay, near the École Polytechnique, there is a very famous place in solid state physics, a lab started by Jacques Friedel - a great name in solid-state physics. I followed this course and afterwards I did the PhD at the École Polytechnique in the field of condensed matter physics. In principle I ought to have started with a topic distant from materials science. I extracted spin-polarized electrons from semiconductors. This was in 1974.

ARNE HESSENBRUCH (AH) : How did one extract spin-polarized electrons in 1974 ?

HA : It is true of all solids, but in semiconductors it is especially interesting that when light falls upon a surface there is a coupling between the spin of photons (in classical physics : the polarization of light) and the spin of electrons. Electrons in the upper layer absorb light photons depending upon the spin. If by some technique you can extract electrons from the conduction band of the semiconductor, you can find ways to select electrons of specific spins. This was quite important at the time because at big-science institutions such as LEP [Large Electron Positron collider] or SLAC [Stanford Linear Accelerator Center], there was a need for spin-polarized electrons. And of course you then needed solid-state physics to do it. But the man who in principle was my supervisor decided to do something else. His name is Claude Weisbuch, and he is now a good friend of mine. For a few years he was the scientific director of the French Department of Defense. He is still working in solid-state physics, in the optics of semiconductors. But he decided to do something else and Bernard Sapoval, another professor at the lab, proposed that I work on new materials. At that time there was little contact between solid-state physics and solid-state chemistry. The idea was to link up with chemists. This is why very early on in my career I had contact with chemists. We worked with Parisian solid state chemists on a new material. We found a new way to draw single crystals of an already existing material. It was very nice because we could examine transport and NMR phenomena. And the material, a copper vanadium sulfide exhibited astonishing properties : a large spread of conductivity that one can measure in a standard experiment. We suspected that this was due to mixed conduction properties. Mixed conductivity refers to conductivity by both electrons and ions. The experiment appeared to verify our a priori suspicion. This gave me the possibility to present a model for mixed conduction in this material and to understand the influence of ion transport and electron transport. I also used NMR in order to understand which ions moved. It turned out that the copper ions moved. So, this was the subject of my first thesis. At the time, in France, there were two theses. The first one was called "thèse de troisième cycle". The second was the "Docteur es sciences". This degree does not exist any longer. The thesis that is done now is shorter.

I decided to continue to work with chemists. I decided to combine NMR and transport measurements. I changed my collaborators, turning to two different groups. In my PhD there had been two chapters on NMR. But I wanted to study proton transport. I had two reasons. One was that protons give a strong NMR signal. The second reason was that two reasons had been given for proton transport. In one, protons move in individual jumps. In the other the proton is a part of a more complex molecule such as the ammonium ion (NH4+) or hydroxonium (H30+). In the former case we can see the transport phenomenon as a result of molecule rotation and proton jump. The molecule would turn and the proton jumps to the neighboring molecule, which again turns and so on. This was called the rotation-jump model. The second model was for the whole complex ion to jump. This was called the vehicle model because the whole molecule acts as a vehicle. So I worked with one group of chemists in Nantes, at the Institut de Matériaux de l'Université de Nantes. It had just been created by Jean Rouxel, a chemist. With them I worked on a substance called antimony acid - a solid. I was able to show using NMR that transport occurred in this case with rotation-jump. Protons used H30+ as a complex rotator. I was also able to show that the jump was due to quantum mechanics within a certain temperature range. It was not the usual ion transport of classical mechanics.

AH : A tunneling effect ?

HA : Yes, this is one aspect of protons, because protons are very light ions allowing for this quantum effect. The other material I studied was ammonium beta alumina. This was the standard beta aluminium in which the sodium had been ion exchanged with ammonium. This material was very interesting from the perspective of NMR. All kinds of ionic motion took place at different temperatures. At the lowest temperatures, that of liquid helium (1-4K), there was rotational quantum motion. As the temperature increases the motion becomes classical.

AH : If I may make a comparison with Stanley Whittingham here. You were working on some of the same materials, you were using some of the same tools (NMR), but you were asking very different questions, right ?

HA : Yes, that is true. I was not at all involved in the application. For two reasons : French chemists were interested in materials and did not look to the application. And chemists were between me and the application, so I had no contact with attitudes such as Whittingham's. I was very happy working on the solid-state physics problems.

AH : And we are talking about the late 1970s now ?

HA : Yes, I began the proton transport research, I think, in 1976.

AH : And it went on for how long ?

HA : For five or six years.

AH : And you lived in Nantes ?

HA : No, I remained in Paris while collaborating with the Nantes group.

AH : Were you employed in Nantes ?

HA : No, not at all. At the beginning I was employed at the Ecole Polytechnique as a research assistant, and then I was hired by the CNRS - in 1977.

AH : So, the CNRS paid your salary, you were able to do basically whatever you wanted, and you collaborated with Jean Rouxel and coworkers because you found it interesting ?

HA : Yes. It was a chance to work with an outstanding chemist. French chemists were really very good. The problem, as we just said, was that there was little interest in application.

AH : What did you do next ?

HA : After my PhD thesis, I found it interesting to go to industry.

AH : I imagine that there were many advantages and disadvantages to leaving academia for industry. For instance, where was status greater, what paid better, where were working conditions better ?

HA : First of all, it was rare, even more so than today, for CNRS people, or people within the public system, to go to industry. I cannot give you a clear answer about my motivation - it was not even clear to myself at the time. I did get a higher salary in industry. I also had personal reasons for leaving Paris and going to the Elf company. I went to an Elf research lab in the Southwest of France, in a very nice place in the Pyrénées. I had small children at the time and it was much better for them to grow up in the countryside and in a very nice climate. I was also curious. So the decision involved many elements. And anyway, it was not irreversible. The CNRS allowed me to take a three-year leave after which I could have gone back. With regard to the working conditions : I was of course less free than I had been at the CNRS, but I found it more stimulating because there were a lot of different problems on the horizon, arriving almost every day. We could easily get the necessary equipment at the CNRS and at Elf, so there were no differences there.

AH : The restrictions at Elf had to do with what you were allowed to study ?

HA : Yes.

AH : What did Elf want you to do ?

HA : In principle I was hired to work on solid-state sensors. Because it was not in the direct line of my previous work I proposed that I work on solid-state sensors and ion conduction. We developed a family of sensors named ISFETs (Ion Sensitive Field Effect Transistors). It was a new kind of transistor at the time but now it is very common. You control the electrode using field effects, opening and closing the circuit between the two other electrodes. This is the way the transistor works. My idea - not an original one - was to replace this way of controlling the electrode, the gate, to replace it with a membrane, selective to such and such an ion. If you put the device in a solution containing the ion for which you have designed the system, the membrane will be charged. This charge will change the state of the solid-state transistor. It worked all right for protons. We could use the device to measure pH and afterwards we just had to change the nature of the membrane, choosing a different solid electrolyte, such as calcium fluoride.

AH : Your toolkit remained the same and you still used NMR ?

HA : Not NMR, but yes. You need large samples in order to do NMR. So it was mainly electrochemistry and surface analysis. This was between 1982 and 1985. But as I told you, in industry new projects can arrive almost every day. I had developed some skills in electronics using instrumentation at the École Polytechnique. Elf applied for a patent for a medical analysis system, a small instrument to be sold to private practitioners, as opposed to hospitals. This had nothing to do with solid-state ionics. But the people working on this project needed someone who knew about electronics, and so I got progressively more involved. After one or two years it had become my main project. This worked very well. I was very proud to design an electronic system that required no manual setting. It was set in the factory forever. This was a critical issue, because we thought that doctors could not be expected to deal with electronics - and I am sure that we were right in this. So there was nothing to check or calibrate - the system was self-calibrating. So it worked very well, and after only two or three years Elf built a plant and people were hired. But in 1984 and 1985 there were big changes in chemistry. And there was a great redistribution of all chemical industries. And Elf, that had been an oil company, in this period expanded to become also a chemical company. As a result a lot of the more diversified lines of business lost in importance. Many projects like ours were discontinued. But because we were already quite advanced we found a way to keep going. In fact it was Dupont de Nemours that found that our system was complimentary to some of theirs. The result was that Elf shipped the patent and everything else to Dupont. For a few months I considered following the project to Dupont and to the United States. In the end I decided against. I still wanted to work in solid-state physics and not to work completely in the instrument making business. But for one or two years I continued as a consultant.

2000-05-29 :

HA : For both personal and professional reasons, I decided to stay in Paris, and then Saint-Gobain offered me a position, working in a new research field : polymer adhesion on glass and other materials. It was a new topic for me too. At the time adhesion was not even considered a science. It was before Pierre-Gilles de Gennes's Nobel Prize in polymer adhesion [1991]. It was rather considered an art. Even though I had no background in the field I was interested. What interested me in the Saint-Gobain proposal was that real breakthroughs were to be expected in the science of adhesion when two materials are brought into contact. In fact this was my first real industrial experience. Of course CNRS had not been an industrial experience at all, and even at Elf I was always in the research lab. As I explained, my work at Elf had nothing to do with the industrial activities. I never visited factories. At Saint-Gobain I had to do this, at least in the beginning.

AH : Did you not say that your development of the medical analysis system resulted in the setting up of a plant ?

HA : Yes. I did participate in the design of the plan, in order to make it efficient. But I had no role in the plant itself after construction. It was also a small plant for high-tech activity.

AH : You had nothing to do with the fabrication side of it, situated in the plant – merely the R&D before the plant became functional ?

HA : Yes, exactly. Saint-Gobain of course has many plants all over France and Europe, and even the United States. But at that time, the company was still franco-français [French through and through] in its general spirit and culture, despite the many factories in other countries. There were only French directors and the system was based on the French system of education. There is a hierarchy from the École Polytechnique through the École des Mines and the École Centrale to lesser schools, and you carry the status of your school within you for the rest of your life. I remember that I strongly felt the weight of tradition when I first joined the company. It is true that winds of change were already blowing then, but they were barely noticeable and needed a couple of years before really expressing themselves. But eventually the company changed its culture, and now the company considers itself an international one. I think a deep change has taken place during my 15 years with the company.

So, anyway, this was the first time I gained experience of the industrial aspect of research. My first task was to examine and synthesize different kinds of adhesion in Saint-Gobain's products and processes. I decided to simultaneously pursue fundamental reflection and a practical approach, helping the factories improve their processes. This was a very instructive experience. I learnt many things although I am not sure that I helped the factories all that much. I certainly learnt for myself that I preferred to stay within R&D and not to progress into production. On the fundamental side, I developed a network of contacts in public labs in France and the US. This became useful later on. After three years in the field, and having created a small research lab, I decided to gain some distance from the practical aspect of my work. It was also obvious to me that fundamental research was required first. Progressively the idea came to me to propose the creation a special laboratory dedicated to the basic aspects of polymer adhesion - and of course also to related issues such as the surface science of glass. But I knew that Saint-Gobain was not ready to have a laboratory for basic science by itself, so my idea was to set up a lab jointly with the CNRS. This was in 1988. From the administrative point of view this was feasible : a number of such joint ventures already existed, an example of which is Rhône-Poulenc. Of course I had to convince both Saint-Gobain and the CNRS of the utility of the project which was not straightforward. Although I managed to convince Saint-Gobain in a manner of hours, CNRS needed more prompting.

AH : Would you explain the nature of Saint-Gobain's research before your proposed laboratory ?

HA : It was a quite common kind of R&D geared towards problem solving. Helping the development of new products and solving problems within production.

AH : So the research agenda was driven by questions arising out of production ?

HA : Yes, and my idea was to get a more fundamental understanding of the questions which would enable us to help with such questions in a much better way.

Figure 1. Saint-Gobain Recherche, Paris

At Saint-Gobain I had to sell the idea primarily to the Vice-President of R&D. He took the decision just before retiring. The CNRS process was more complex. It has a democratic organization where decisions are taken by committees. The members consist of both elected researchers and individuals named by the Ministry of Research. They are divided up into different scientific sections. So here I had to convince a diverse group of people, and not just one person, as at Saint-Gobain. As I mentioned, I had developed a network of relationships in the fields of adhesion and surface science and now this turned out to be useful. I knew that many people approved of my research agenda. My project was accepted without much fanfare, but it still took a while because of the administrational hoops that a proposal has to jump through within the CNRS. They meet only twice a year, and every decision has to be validated by the CNRS directors and so on. It took maybe 12 months. The laboratory started on January 1, 1990. But there was only a building and neither instruments nor people.

Figure 2. Joint lab : Saint-Gobain Recherche & CNRS

The three yellow arrows point to the units of the joint lab within the Saint-Gobain Recherche building.

In the meantime I conferred with scientists in many other labs trying to recruit people. Of course the CNRS could not order people to go, so I had to entice scientists away. I estimated that I needed three scientists from the CNRS in addition to three scientists from Saint-Gobain. Two of the latter had already worked with me, and they followed me to the new project. A further researcher came from somewhere else – it was a young Chinese woman. We also had two or three technicians and some PhD students. Altogether, it took a year or so to gather everyone together. We also had to buy instruments and the process of getting the laboratory shipshape lasted altogether something like 2 years. We began to actually do some research in late 1990. And from then on the activities progressed rapidly. In two to three years we reached a plateau of 20 people, a level that had been stipulated by the CNRS. A third of the people had come from the CNRS, a third from Saint-Gobain, with PhD students constituting the last third.

AH : Where did they come from ?

HA : The latter were doing industrial PhDs (Contrat à Durée Déterminée) with Saint-Gobain, and their salary came jointly from the French Ministry of Research and from Saint-Gobain. Of the entire staff, about half each came from chemistry and physics. It was crucial that we develop knowledge and expertise in both these fields. Later we also developed an interest in mechanical problems.

Figure 3. The SPM from Park Scientif Instrument

AH : What was the instrumentation ?

HA : There was a conjunction of the beginning of our lab with the very early days of scanning probe microscopy. This new kind of instrumentation offered a very exciting opportunity. There was a risk in this. We purchased the first Atomic Force Microscope (AFM) ever in France. We bought it from Park Scientific Instruments. Later we built the first AFM for UHV purposes. There were many people then who thought the instrument had no future, so it was a risk to invest time and money in it.

AH : Why did people think it had no future ?

HA : The objection was that it was not clear that atomic resolution could actually be achieved with the AFM. It was not until 1993 that Binnig showed true atomic resolution.

AH : Well, yes, but before he had claimed to achieve atomic resolution. In 1993 he only claimed that so far he had been mistaken and only in 1993 did he achieve true resolution. Is that not right ?

HA : Yes. But in 1993 the community was convinced. The reason I did not hesitate was that atomic resolution was not actually the big issue for our purposes. Even a resolution of 1 nanometer amounted to a great deal. Much could be done with such a resolution in the field of adhesion, and also in fracture mechanics and surface chemistry.

AH : I have the impression that since 1995 or so many people argue that atomic resolution is not really that important, and that in the early 1990s it was still considered the holy grail. So you were unusual in that you had this attitude so early ?

HA : You are right that atomic resolution had a special ring to it in those days.

AH : Did you emphasize the issue of atomic resolution in your application to the CNRS ?

HA : I am not sure. Even today, nobody has achieved atomic resolution in glass. So it would have been a hard sell, also then. The same goes for polymers. And those two were our substances under investigation.
There is a difference between STM and AFM. They obey two different logics. The STM has remained a tool of basic research, in surface science. The AFM, even early on (and this would be interesting to discuss with Calvin Quate or Gerd Binnig), there was a hope that it could be useful, for example in other fields of science, such as mine, or in technology, such as process control, microelectronics, semiconductors, and so on. Generally speaking, in early phases there are always many people who think that a novelty will never become common. We have to remember that in 1987 or 1988 solid probe microscopes were still big and unwieldy instruments. Of course miniaturization had set in by 1990, but it was a novelty. Only very few people were convinced that the AFM would become so common. Calvin Quate is one of the few. The STM has revolutionized basic research on metals and semiconductors. There was a reaction against it, because surface science was done using diffraction techniques working in reciprocal space. Surface scientists were formed in this mode of research. They resisted the change, feeling that newcomers would enter their field without the kind of abstraction that had hitherto been key to access to the field. Working in ordinary space was too easy ! Of course it has not actually become easy because the instrument has brought its own problems, and there are still people working with diffraction and in reciprocal space. The two complement each other.

AH : So this is the background against which your decision has to be seen. You went out on a limb.

HA : Yes. The beginning of my lab coincided with the first commercial scanning probe microscopes (SPMs). We had to grasp the opportunity.

AH : How did you know about the AFM ? Was it a very visible instrument at the time ?

HA : No. I knew about it from publications, but in order to actually see an instrument, I had to travel to California - although I guess I could have seen one at IBM Zurich. There was an STM at Marseille, because two physicists there (Salvan and Humbert) had worked at IBM Zurich, and they had brought one back with them. But they had no experience with the AFM. So I went to the US and visited the very few labs with AFM, both academic labs and the start-up companies of PSI [Park Scientific Instruments] and DI [Digital Instruments]. At Stanford University I met Calvin Quate and at UC Santa Barbara I met Paul Hansma.

AH : Was there a relationship between Paul Hansma and DI ?

HA : I don't remember. But at any rate it was not as close as the one between Quate and Park. I think Park was a former student of Quate's.

AH : So you purchased an AFM from Park. What about the other kinds of instrumentation you purchased for your lab ?

HA : Yes, we had to get other instruments, partly because it took a long time for the AFM to arrive. I had to go to the US to compare the DI and the Park instruments, and I discussed it with the physicists and chemists in our lab before ordering, and then we had to wait for the delivery – maybe 4 months or so. We got a 40% discount, because we were the first French customers, and they hoped that we would open the French market for them. I had very good discussions with Quate, and I think he trusted me to be a good advertisement for him in France. I think we paid 400,000 French Francs, so that the catalogue price was in the order of 800,000 French Francs [approximately US$100,000].

We bought also an infra-red spectrometer, in order to study molecular grafting on oxides. This we used as a complement to the AFM. And as I said in a previous part of the interview, our approach was to combine the traditional surface science (very clean surfaces) with “true surfaces” interacting with the environment. The infra-red spectrometer, XPS (X-ray Photoelectron Spectroscopy), and LEED (Low-Energy Electron Diffraction) were good tools for the traditional surface science approach working in UHV Ultra-High Vacuum). And also HR-EELS (High-Resolution Electron Energy Loss Spectroscopy). Our choice was risky, but it turned out to be correct. Our decision to build bridges between the two approaches was taken in 1992 or 1993. Quite early on in our project we built a surface force apparatus (SFA). It is not at all an AFM – there is no concept of high resolution, but it is similar in that you can get a direct measurement of the force interacting between two objects only a few Ångstroms apart. The idea is to make the measurement quantitative in order to study whether the interaction is due to van der Waals or electrostatic forces. In fact this project took six years – not for technical reasons but simply because we had to get the right people.

AH : Each instrument had its strengths and weaknesses in terms of resolution and the scale of the surface analyzed. And each instrument required special skills. The AFM, for example, requires quite some expertise to disentangle signal from instrumental artifacts, right ?

HA : Yes, artefacts were a real concern at the beginning, when we all had very limited experience. We had to pay much attention in order to ascertain the results.

AH : Can you explain how one separates signal from artefact ?

HA : There are different kinds of artefact. One that now seems quite natural but was hard to understand then is the tip effect. If the surface under examination has sharper topographic features than the tip, then the tip will be imaged rather than the surface. We had trouble with this kind of artefact. In fact, when studying tin oxide deposits on some substrate we got very nice images that we at first interpreted as small crystals having the similar orientation. We were very excited to find a growth mechanism of specific orientations on isotropic surfaces such as glass. I decided to present this result at a small meeting in Davos, Switzerland. The topic there was in fact “The AFM for Technological Applications”. Famous scientists attended, including Calvin Quate, Jim Gimzewski, and Heinrich Rohrer. There were only some 10 people there, because this was very early, maybe 1991. The night before my presentation, I began to wonder that the result was really too beautiful to be true. I telephoned my lab and asked people there to turn the sample by some angle and do the experiment again. That way, the features should have changed if they belonged to the surface. But they did not, and so we knew that the features belonged to the tip. So I did not present that particular slide in my talk.

AH : So rotating the sample by some degree is one way of identifying artefacts.

HA : Yes, that will eliminate this kind of artefact, the tip effect. There are also adhesion artefacts, some of which have been solved in the meantime thanks to new recording techniques such as the tapping mode.

AH : Digital Instruments has a patent for the tapping mode, right ?

HA : Yes.

AH : So the Park instrument that you bought did not have the tapping mode ?

HA : No it did not. The tapping mode did not become available until 1993 or so. Later on, Park Scientific Instruments did do something similar, but they may not call it tapping mode. The DI patent covers the name. And in the straightforward contact mode many artefacts were possible ; for example when looking at soft materials and polymers surface scratches easily occur. If you do that you image the substrate only. One way to identify this effect is to scan again with a smaller tip-surface interaction. In some cases you will find miniature small squares where the surface had been damaged in the course of the first scan. Some artefacts are very common, others are quite specific and harder to identify.

AH : In what you have explained, the identification of artefacts is internal to the instrument itself. It is not that you can go and compare the results of an AFM scan with those from a different instrument ?

HA : You can change the tip, and you should identify artefacts unless you are very unlucky to get the same tip. Everybody understood that the AFM has great potential not just as an imaging instrument but also to measure adhesion, hardness and so on.

AH : Using force-distance curves ?

HA : Yes, force-distance curves. This turned out to be very useful for us. For instance in order to understand the electrostatic interaction between oxide and a silicon nitride tip under water. This was original work. For example, in polymer adhesion we checked if it stayed on the substrate and what scratching would do. Of course such ideas were floating around at the time.

AH : Were you important to the subsequent spread of the AFM in France ?

HA : Yes, people came to our lab. Another lab, at the Institut Curie, that got an AFM at almost the same time. For a while we were a small community but then gradually we grew larger and larger. Yes, we were the pioneers. It was exciting.

2001-02-20 :

HA : I went with one of my sons who was 11 years old at the time to see Park Scientific Instruments. There were no more than 10 people working there, in fact I think it was more like three. It was very small and familial. We discussed and had tea. I enjoyed discussing with these people. It was nothing like an established company.

AH : What did it look like ? Did they work out of a garage ?

HA : Something like between a home and a garage. It was a small house. Even Digital Instruments started out like this. Already in those days DI, and especially Virgil Elings, was much more commercially aggressive, but they were very small too at the time.

AH : Did you stay in touch with some of these guys ?

HA : I stayed in touch with Calvin Quate for five or six years, until 1996. After that I lost the contact but he will probably remember me because we had many discussions. It was curious to see his impact upon materials science. In fact it was very difficult for him to get the first paper on the AFM accepted in Physical Review Letters. Some of it was considered just a pure mechanical profilometer. It had good resolution but it was not really anything new. His project now is very interesting from what I can tell reading his articles in the scientific journals. And he really is a very nice person. Maybe the last time I saw him is when I invited him to give a talk at Saint-Gobain Recherche.

AH : So you stayed in touch with him in the early 1990s, while you were developing your own AFM. I guess the use of the AFM changed the project from what you had originally envisaged ? Did you continue using all the other tools or did you focus exclusively on the AFM ?

HA : We used the other tools.

AH : What did you buy for your laboratory ?

HA : Infrared spectrometer, XPS, HR-EELS (High Resolution Electron Energy Loss Spectrometer), LEED. Quite quickly we had three AFMs. I wanted to develop a PSTM working in the infrared but unfortunately that particular project died because the physicist we had working on it left.

AH : What journals show the history of these instruments best ?

HA : In the beginning it was mainly in the general physics journals such as Applied Physics, Applied Physics Letters, Physical Review Letters, Surface Science. Now there are specialized journals. A journal like Journal of Scientific Instruments is not so important in this respect. Langmuir is also important for soft matter.

AH : Do any of these journals have review articles ?

HA : I am almost sure that all of them do.

AH : We were talking about the various instruments you had in your lab. How did you apply them to your research project ?

HA : The idea was to have two parallel approaches. We were mainly interested in adhesion, molecular grafting and so on. One approach is the classical view of surface science, the ideal surface approach. The other is the REAL surface approach, taking the environment as a part of the system.

AH : Not working in Ultra-High Vacuum (UHV) ?

HA : Yes. But we were trying to make the two approaches meet.

AH : So when you started working with the AFM in UHV, the point was to simplify the experiment ?

HA : Yes.

Figure 4. UHV Chamber et AFM in UHV Chamber

If a probe were to be introduced directly into the UHV chamber, it would take days of pumping to achieve UHV. Instead, it is first introduced into an antechamber, whereupon a vacuum is produced there. Only then can walls be opened without reducing the UHV too much. By pushing the rods labelled 1 and 2, the sample is transported in successive stages into the central chamber. Several instruments are attached to the chamber, including an XPS. On the right, an AFM can be discerned in the UHV chamber.

AH : How did the various instruments complement each other ?

HA : The spectrometers provided structural information. They give a chemical signature. One point of interest was silver on magnesium oxide. In order to have a simple model of glass we chose to study this problem within pure single crystal. We had the probe in situ in the same UHV chamber where we had the instruments to add the deposition techniques. In the case of silver it was just thermal evaporation. We wanted in situ real-time studies of the atoms arriving upon the substrate, the oxide surface. There were two models in this problem. One was that the atoms remain isolated or form small islands, so that the growth process is two-dimensional, so that you first get a perfect monolayer before a second layer is started upon. The other is that growth is three-dimensional with occasional collapses into flatness. To study this it is of course useful both to look directly and to use diffraction techniques. But in order to understand the process you need to grasp the interaction between the silver and the oxide. And only spectroscopic techniques will help here. We always tried to look at a problem from two differing points of view – in this case geometrical and chemical.

AH : You make it sound easy. You just use one tool and you get the topography, and then you use another and you get the chemical composition.

HA : Well of course it is not at all easy. It was very difficult because for instance, the STM works very well when you have a smooth surface but when you have corrugation it becomes much more difficult, because this corrugation interferes with the instrument. In spectroscopy you integrate over the size of the beam which is much larger than the surface scanned by the AFM. So you have to do many different experiments to see what effect the temperature has and so on. You also have to model the interaction. This was a little known problem. What is the mechanism of very small silver clusters on magnesium oxide with other silver clusters in the neighborhood ? It was a new problem. So it took time to understand the system.

AH : What is the measure of success ? It was partly CNRS, so you were under pressure to publish ?

HA : Yes.

AH : And since it was partly Saint-Gobain you had to get patents ?

HA : We had to do both. It was an interesting exercise in communication. In my position as head of the lab, I could not use the same words, the same way of presenting things when addressing different audiences. From time to time it was necessary to gather the scientific and the industrial people together under one roof.

AH : And what language did you speak then ?

HA : Fortunately everyone was happy with this lab, so it was not quite so difficult. The conditions were good. Nonetheless your question is quite correct. It was interesting.

AH : How did you convince Saint-Gobain that this would have a pay-off ? And how did you negotiate long- and short-term goals ?

HA : The short term was a problem. It was not straightforward to plan a new product for the company. The pay-off was very diffuse and difficult to identify. One way of motivating the directors was the argument that we trained very good PhD researchers for Saint-Gobain. And this was not expensive for Saint-Gobain, because they shared all the expenses with CNRS. Up until now this has not been a problem.

AH : Stanley Whittingham told me that in the last 15 years or so there has been a tremendous shift in company planning towards the short term in industry. Partly this was due to the MBA education and the fanning out of this new generation of business administrators into all nooks and crannies of industry. As a result the long-term disappeared, because everything had to fit into the financial year so that you have something to show to your shareholders.

HA : It is true that this has taken hold in industry. We had the good fortune that it was not very developed in Saint-Gobain. But also, the time required for the development of new glass materials just is acknowledged to be greater than that in electronics or informatics. When we start new projects, we are simply not able to show a product six months later. So we are less exposed than people in other fields, but the general development that you alluded to certainly has taken place. Maybe our situation will also change in the future. We may be excessive.

AH : Has the accountancy changed for you ? Did you have to write annual reports ? And has it changed over the last ten years ?

HA : In general ?

AH : Well, for the CNRS I can sort of imagine it. In academia you would specify the number of publications that you have produced and that is the measure. End of story. And that is very simple accountancy. But if you account to a company, keeping in mind the increasing influence of MBAs : did you have to account for your expenses in ever greater detail ?

HA : I do not think there has been such a change in the last decade.

AH : And do you write annual reports ?

HA : Bi-annual. But I am not in this lab anymore ; I left two years ago.

AH : Okay, so during the 1990s up until two years ago you wrote biannual reports to the company and in that period the structure of the reports did not change.

HA : That is correct.

AH : Did you have to specify just how much money you spent ?

HA : Yes, but also there, no change took place. And I always reported to the same person within Saint-Gobain. He was basically content with what we did, so it was never critical. It is true, it might have changed with a different person in charge.

AH : So, how did the instrumentation change throughout the 1990s ? The AFM became commercially available to an ever greater extent, you were able to buy many more things off the shelf. Is that true also of all the other instruments ?

HA : Yes, there are different aspects to your question. We used to build many instruments ourselves, and this was of great use for training. And this has changed. A reason the French PhD has been shortened is that equipment is being bought and not made in-house. That is a general trend. Science is changing as a result, because using a commercial instrument is not the same. When you develop an instrument yourself you know exactly how to get the result. In the specific case of AFM/STM : probably the AFM has been developed much more than the STM. In the STM the major breakthrough was with the driver and that was quite early. I think it was possible to purchase an STM driver already by 1992. Variable temperature was a little more difficult, but it was certainly available by 1994. Different ways of scanning and acquiring information were developed. Otherwise the evolution was purely technical : cheaper, and more diverse (such as an STM expressly for electrochemical research). By contrast the AFM has developed rapidly. Tapping mode and other modes where you measure not only the distance but also hardness, conductivity, adhesion, chemistry. It has become possible to map all these parameters. This explains why more and more people use the AFM.

AH : It has also become cheaper, right ?

HA : Yes.

AH : It has certainly become more user-friendly, adaptable to different circumstances.

HA : Yes. For the STM : there have very beautiful studies made of the coupling between tunneling and modulation. You might modulate the tunneling current with light for instance. You can even leverage the spin of the tunneling electrons. So you can do beautiful physics. But this contributes little to the democratization of the technique.

AH : I have the sense that Calvin Quate, by contrast, is working hard to increase throughput.

HA : Yes, that is right. There can be two reasons for doing that. To make the investigated part of the surface larger – of use in the semiconductor industry. And to shorten the time required for a scan. He is trying to use the system technologically.

AH : Okay. Two years ago you left your lab. Your own lab. Why ?

HA : I wanted to try something new and I was lucky to find someone who was well capable of taking over and for whom I have a lot of respect. He is from a different background. So now it is a different group. I became the Scientific Director of Saint-Gobain Recherche. There are two parts to the job ; one is to be the scientific manager, the other is to establish contacts in the outside world, and to promote innovations within the company, for instance with the marketing people.

AH : You were promoted ?

HA : Yes.

AH : And you have become slightly removed from lab work ?

HA : Yes, completely, I am now involved in organizational work.

AH : In fact, our project resembles your job in the sense that we stand back and look at the scientific research and try to gain a perspective ?

HA : Yes, you could say that.

Fin de l'enregistrement

Pour citer l'entretien :

« Entretien avec Hervé Arribart », par Arne Hessenbruch, 19 février, 29 mai et 20 février 2001, Sciences : histoire orale, /spip.php ?article47.

Pour citer l'entretien :

« Entretien avec Hervé Arribart », par Arne Hessenbruch, 19 février, 29 mai et 20 février 2001, Sciences : histoire orale, https://sho.spip.espci.fr/spip.php?article47.

Lieu : dans le salon (les 19 février et 29 mai 2001) et dans la petite salle de réunion (le 20 février 2001) du Dibner Institute, Etats-Unis.

Support : enregistrement sur cassette.

Transcription : Arne Hessenbruch.

Édition en ligne : Sophie Jourdin, Sacha Loeve.

ARMAND Michel B., 2001-09-18

2009-12-24T01:38:28Z

Michel Armand, né en 1946, a été formé à la chimie à l'École Normale Supérieure de Saint-Cloud. Après l'obtention d'une maîtrise en chimie inorganique (matière principale, électrochimie) et un séjour au Département de Science et d'Ingénierie des Matériaux à l'Université de Stanford, il entame une thèse sur les composés d'intercalation pour les batteries à l'état solide au Laboratoire d'Ionique des solides de Grenoble (renommé ensuite Laboratoire d'Ionique et d'Électrochimie du solide, puis rattaché en 1995, avec d'autres laboratoires, au Laboratoire d'Électrochimie et de Physicochimie des Matériaux et des Interfaces (LEPMI). En 1974, Michel Armand rejoint le CNRS où il passera le reste de sa carrière française, avant de devenir, en 1995, professeur de chimie à l'Université de Montréal (Canada). Michel Armand s'attacha à dégager les propriétés électroniques des complexes d'intercalation sels de lithium-polymères. Il a contribué à la mise au point de batteries à base de lithium-polymère pour les véhicules électriques.

Biographie détaillée

MICHEL B. ARMAND (MA) : Just to introduce my career, devoted to solid state chemistry, I would remind you that in France we have a special educational system – with universities on the one hand, and the competitive grandes ecoles on the other. I came from one of these schools, the Ecole normale supérieure de Saint Cloud, where most of the students were meant to go all the way through the system. I chose to go into research. Graduating after 4 years, I applied for a student fellowship to study in the US. When I obtained a Fulbright fellowship, I went to Stanford. My supervisor was Robert Huggins and one of his post-docs was Stan Whittingham. In fact I left before submitting my PhD because I wanted to choose a research topic, namely intercalation compounds and solid-state batteries. My advisor wanted me to work on crystals and bronzes which effectively are very nice-looking but without interest for me. So I returned to France in 1972. I joined the CNRS shortly after, in 1974. The CNRS did not bother me when I did not publish for 5 years and let me supervise students before defending my thesis. I benefitted from great tolerance all through my career. I have far less publications than patents : 80 approximately. I have been on leave from the CNRS for the past 5 years while being associated with the Université de Montréal.

BERNADETTE BENSAUDE-VINCENT (BBV) : How did you get into intercalation chemistry ?

MA : Insertion or intercalation, that was the subject of my thesis. I had envisaged titanium disulfide (TiS2) as a potential candidate for intercalation but it was too expensive, too rare, so I dropped it. My doctoral research mainly consisted in trying several simple molecules as potential electrode materials. Insertion chemistry has been developed in France by Jean Rouxel. He supervised a number of doctoral students who inserted metallic ions into various compounds but he never envisaged the electrochemical applications of this kind of compounds. [En Français :] Il dirigeait un certain nombre de thésards qui rentraient des ions métalliques dans des composés mais il n'avait pas envisagé les applications électrochimiques de ce genre de composés. De même à Nancy, [Albert] Hérold travaillait sur des composés d'insertion dans le graphite mais sans penser aux applications. The first steps into intercalation of graphite were made in Germany in the 1830s by a German chemist. The ionic compounds were discovered by Faraday. He demonstrated that silver sulfide behaves as an ionic conductor. Bronzes with their beautiful rainbow colors were also known in the nineteenth century. Nineteenth-century chemistry was something fabulous. However since organic chemistry captured the attention of most chemists, they did not exploit conductivity. Moreover Dalton had won over Berthollet. They mainly considered stoichiometric compounds, and inorganic non-stoichiometric compounds were ignored. Intercalation compounds prove that Berthollet was right. English chemists name them berthollides. They had only one application in the nineteenth century : it was the famous Nernst's glower. It was a commercial success. Doped "zircone" [zirconium dioxide] is still an interesting material. One more illustration of the well-known law : on commence toujours par tomber sur le bon modèle.

HERVÉ ARRIBART (HA) : How did you begin with polymer electrolytes ?

MA : The best way to use intercalation compounds was to use a soft electrolyte. I mean the electrolytes known at that time like silver compounds and beta-alumina were not suitable because their volume changed and you cannot maintain a good interface. Plastic materials seem more suitable. So it was mainly out of pragmatic motivations that I turned my attention to polymer electrolytes.

HA : At that time intercalation compounds had been studied for about 10 years. Did you participate in this development ?

MA : In the 1970s two schools were concerned with intercalation compounds in France because solid state chemistry was well developed in this country. One was with Professor Hérold in Nancy who studied graphite intercalation compounds. The other was Professor Rouxel's. They worked on TiS2,.... and selenides and all these well-known dichalcogenides...So the chemistry was known. But nobody had thought of using intercalation compounds as electrode materials. In 1970, Stan Whittingham was a post-doc with Bob Huggins at Stanford. He was using bronzes to make measurements of the conductivity of beta-alumina. And they were making good contacts and observing the passage of ions between the two compounds because they were non-stochiometric compounds. But there was no concept of using this compound as a source of ions for storing energy. It emerged in fact in 1972. It was during a NATO conference held at Belgirate in Italy where Brian Steele suggested TiS2, what he called solid-solution electrode and suggested its possible use as an electrode material. At the same time, my own presentation was dealing with graphite intercalation compounds. After that, the field almost exploded. I mean there was an explosion of scientific publications, because first, Stan Whittingham became involved with Exxon in the program for making batteries using TiS2 as an electrode material. Second, the electrochemical community had realized the potential of these compounds. So there was an enormous activity around these compounds which peaked around let's say 1989.

HA : Would you say that the Belgirate conference was the first event ? Who participated ?

MA : You would find the major actors in solid state electrochemistry : Brian Steele, a well-known metallurgist, you had Bob Huggins, Stan Whittingham well-known for the intercalation compounds, Hagenmuller, Jean Rouxel, and the people working on beta-aluminas at that time with Wynn Jones and the people from Ford and from the British programme. The British Railway company was working in this field at that time. So this conference – unfortunately the book is out of print - was the outset of the solid-state chemistry's large role in batteries. Formerly it was known that fuel cells used ceramic compounds but then intercalation compounds would also be used for batteries.

HA : Would you say that solid-state chemistry was a discipline in itself at that time ? And which were the respective roles of American and European scientists ?

BBV : Did you consider yourself as a member of the solid-state chemistry community ?

MA : Yes, I was working in Grenoble, working in a laboratory which specialized in solid-state chemistry, spanning over high-temperature ceramics, beta-aluminas, interfacial phenomena : A quite well-known lababoratory. So I have been, I believe, soaked into this field at an early stage in my career. And also you have to say that there was a definite prominence of France in solid-state chemistry which still lasts although it is not as obvious as it used to be 15 years ago.

HA : This lab that you mentioned, its tradition was also in electrochemistry ?

MA : It was devoted to all aspects of solid-state electrochemistry. It was unique, having a big team of about 40 people solely working on solid state electrochemistry.

BBV : What was the name of the lab ?

MA : At that time it was Laboratoire d'Ionique des Solides. The name was changed when it merged with other laboratories. But at that time it was mainly a solid state laboratory partly working on liquid electrolytes. They were precursors in organic electrolytes. Back to Belgirate : suddenly the people in electrochemistry could benefit from the knowledge on intercalation compounds. I mean the chemistry of intercalation compounds : the crystallography, interpreting structure. This allowed a rapid progress.

HA : Could you say more about the French solid-state chemistry schools ?

MA : In Grenoble there was a tradition of electrochemistry dating back to the nineteenth century. It is an heritage. There is a school of engineering there because there is a need for electrochemists. There was this group which sort of nucleated around Professor Desportes and developed research on high temperature ceramics and spread into all aspects of solid-state conductors, mixed conductors, ionic conductors : oxides, glasses, silver compounds, and so there was a common attitude which was more pragmatic than that of other groups.

HA : What was the status of Solid-State Chemistry in the USA ?

MA : It was mainly pragmatic. It was part of Materials Science departments. There was no per se solid state chemistry groups. When I moved to Stanford, Bob Huggins was in a Materials Science department. There was a strong tradition of solid-state electrochemistry in the USSR. And our lab had strong bonds with laboratories in Moscow working on high-temperature fuel cells and also electrodes for MHD (magneto-hydrodynamics), a possible source for transforming fossil fuels into energy.

HA : Your own background was not in organic chemistry. How did you get this idea of polymer electrolytes ?

MA : Polymer electrolytes emerged from the fact that we needed soft electrolytes for using intercalation compounds. I had no knowledge myself of what a polymer was. I thought that polymers were a perfectly disordered state of matter that they could turn into a glass. On the other hand, the electrochemical community had also missed the fact that soft matter deserved some attention. Solid state electrochemistry was inorganic chemistry. Bridging the gap took at least 5 years.

HA : What was the role of Peter Wright, the British polymerist ?

MA : Oh he deserves credit for having made officially the first polymer electrolyte. He realized that dissolving sodium or lithium salts in poly-ethylene oxide (PEO) which at that time was used as an additive for inks or for enhancing the viscosity of water. He realized that if you make complexes and if you heat this complex it becomes conductive. But what he did not realize, because of the gap between polymer chemistry and electrochemistry, was that such complexes had an enormous potential for making batteries when working in conjunction with intercalation compounds. So when I started myself to consider PEO as a solid electrolyte, while I was in Stanford, I had not heard of Wright's paper. It was natural to think of polymers because the problem was the variation in the volume of the electrolyte. I called a colleague of mine in Grenoble to ask him which macromolecule could be used. He mentioned PEO. I ordered it. I mixed it with lithium bromide, I measured the conductivity. Nothing. I dropped the subject. Later when I read Wright's paper in 1975, I understood that I had lacked intuition. Had I heated above 50°C, I would have observed conductivity. When I saw Peter Wright's paper I thought he had found the compound. Now it has to be generalized. So what was lacking was 1) were these coumponds any real conductors ; 2) could they be made for the metal whose intercalation chemistry was prevalent, i.e. lithium. This was very rapidly approved. There was this presentation in St Andrews and people jumped into the field from both sides : electrochemists started making or buying polymers or and polymer chemists started measuring conductivities.

HA : It seems that understanding the mechanisms of conductivity in polymer proved to be difficult.

MA : Oh yes. The theories were there but there was no common application. The polymerists were well aware that the diffusion or transport of material in an amorphous structure was obeying a special law which was called the free volume law. Polymer chemists knew a theory first proposed in the twenties or the thirties which pointed to a temperature which plays the crucial role from a thermodynamical point of view : the glass transition temperature which determines everything. In solid state electrochemistry, the classical Arrhenius law was obeyed most of the time. In fact if you look after 20 years you realize that the situation is not so simple that in some polymers Arrhenius law was sometines obeyed, and that in very high temperature beta-alumina the free volume is sometimes interfering.

HA : Were there colleagues of yours in Grenoble working on amorphous solids ? Did it help you ?

MA : We had good relationships, scientific discussions about the discrepancies between glasses and polymers. Discrepancies and also frustration because the best conductors not especially for lithium are glasses, compounds which are brittle, hard and in which you imagine that it would be more difficult for ions to crawl than in soft matter like polymers. And to our surprise polymers were very good conductors at 60-80°C, warm, lukewarm temperatures. At room temperature conductivity dropped to almost insulators while glasses remained conductors. This situation has been kept for almost 25 years. Trying to break the tg barrier to avoid having a drop of conductivity barrier when you get close to the glass transition temperature of soft matter of activation energy has been the main challenge of research.

HA : When you started to have contacts with industrial companies did you get into trouble with the CNRS. How did you arrange the contracts ?

MA : As soon as we made the first polymer battery and realized its potential we applied for a patent through the CNRS. We did not realize that the patent filing was delayed a couple of days after the presentation in St Andrews. For us it was not very important because in a naive belief we thought that if you speak publicly you may not have your idea stolen from you. But in fact no, according to the French law, if you disclose your invention it is no longer patentable. In the US you are supposed to be able to disclose your invention and you have ten years to file your patent. You are protected because you are the inventor. But stupidly enough because we did not realize, not knowing the law, the patent was extended one year after its filing date and not the date of the St Andrews presentation. In fact the patent was not cancelled but a number of our claims were withdrawn. Surprisingly, it was possible to keep most of the claims in the European litigation but a re-issue was asked at the patent office in the US. It became a nightmare. I will be very frank and provocative in saying that the US patent office displayed a kind of protectionism : the file was lost two times, the examinor was changed many times. We finally ended up sending a lawyer especially to discuss with the examinor and he said that it was absolutely obvious that the examination should have been made before and so on. Finally the patent was re-issued with one claim just one year before the end of its life. In any case this did not deter Elf Aquitaine to start doing common research on this subject. At this time, oil companies were trying to diversify their activity, -solar energy and so on - trying to have a green image. For a while we worked together and we were joined very rapidly by Morselus Contender which was the electricity utility of Hydro-Quebec which is like PTNE or in the US, Edison or like EDF in France. This company mostly relies on hydro-electric power with a lot of hydro-electric possibilities. The cheapest electricity in the world is in Quebec. And they were interested in my goal, my dream : having an electric car, for pollution reasons.

BBV : Which were the terms of the collaboration between Hydro-Quebec, Elf-Aquitaine and the CNRS ?

MA : This is also a subject of controversy. I will be very frank. The CNRS did something that it would not do anymore because it has learnt the lesson. It gave the property of the patent to Elf-Aquitaine who then sold back 50% of the co-property to Hydro-Quebec. In this sense, I think that whatever the country where I work, the state research bodies – NSF or CNRS or any other agency – should never give up patent property. This was the cause of many troubles because it gave Elf Aquitaine complete power over the future of the project.

BBV : What was the reaction of the CNRS when Elf sold its part of the project ?

MA : CNRS could not object because they had made this mistake of giving the property of patent instead of giving the license. Which should never be the case. The government should always be in a position to make the best use of the research which uses tax money. It should be in control of the output of public research.

BBV : Why did you chose to work in Montreal instead of staying in Grenoble ?

MA : It was supposed to be for one year. And we felt five years ago that we were in the final part of the race. A start-up company was making prototypes. The USABC, United State Advanced Battery Consortium, made the choice to invest heavily in solid state batteries. So I thought that it would be easier to work in Montreal than crossing the Atlantic four times a year.

HA : You mentioned the role of electric vehicle in your research program. How would you characterize the role of state programs ? And the private programs conducted by automobile companies.

MA : In the early eighties there was no serious program in electric cars. There was a small activity. People were interested but they did not believe that the electric vehicle would be emblematic (?) before the mid twenty-first century.

BBV : What was the role of EDF (Electricité de France) ?

MA : They were not interested, in the assumption that nuclear power was so abundant that they would not need it. They did not have the expertise : they needed to work in the field of batteries. They left this role to companies such as CGE (Compagnie Générale d'Electricité). They were certainly interested in batteries for load-leveling but they did not invest into batteries which seemed in any case too far away from applications. The people in charge of developing companies were CGE in France or Duracell in the US or whatever battery companies. People did not realize that the solid-state polymer battery is completely different from conventional batteries in terms of technology : it's more akin to paper mill, or printing technology : we are speaking about thin films, and high speed. Solid state polymer batteries have a high surface, thin film configuration. Inspiration and information came from the paper and the film technologies or printing technology. Batteries and fuel cells are still some of the best for producing electricity locally as a co-generator. Intercalation compounds are used for portable items.

HA : After 30 years what is your feeling about the role of Solid State Ionics ?

MA : Its importance has been reinforced recently by the concern for batteries and fuel cells. Most of the driving forces for Solid State chemistry were in the field of energy, the batteries and the fuel cells.

HA : How do you see the future ?

MA : The future ? We need to use energy more efficiently, to reduce pollution... Definitely the near future will be hybrid cars in which we decrease by a factor 2 or possibly 3 the consumption of the car by coupling a normal internal combustion engine well attuned for working at its maximum efficiency with batteries. The batteries are here to provide power for acceleration and also to absorb power every time you break. That way you make better use of your fossil fuel. This is what Japanese car makers Toyota and Honda are going to commercialize. These companies are losing on these cars but they were overwhelmed by the demand. People creating these hybrid cars are so enthusiastic about the feeling of a soft ride, almost noiseless, and low consumption. Taxi companies in Lausanne are among the first. There is also a niche for truly electric cars. Solid-state batteries are ready. If our information are good, there will be solid-state batteries at the Hydro-Quebec. The company will make them available to be tested by the public at the next electrical vehicle (EV) meeting in Montreal next month. This car can be driven for 200 or 300 km on a single charge which makes it suitable for daily commuters, especially for people with a recharging facility in their garage. These cars are ready and it is just a question of political will. On the other hand, there is definitely some lobbying from oil companies, and car companies are not yet willing to change their habits. They are going to sub-contract the making of electronics for EV, the batteries for the electric motor. So they are going to have a less dominating role in the making of the cars. There is some resistance against such a change. Now that the California law has been passed prescribing 10% of the new vehicles with 0% emission hybrid cars are taken seriously unlike in the eighties. They still have to reach political acceptance.

HA : Beta-aluminas have been considered as model-materials and they prompted industrial developments. Do you consider that there is a future for this material ?

MA : The sodium-sulfur batteries produced by Zebra companies have demonstrated their ability to be used for the EV. It's a question of price. There was also a concern for safety because we are speaking of batteries operating at 300°C but most of these issues have been addressed. The main problem is the cost. It makes sense to work on this Zebra batteries for load-leveling. This battery has an almost endless life. In this case the investment can reach very high levels because there will be a return of investment over 10 to 20 years. So the price is less drastic than for a car whose lifetime is 5 to 7 years depending on the countries. And polymer batteries working between 60 and 80°C are very easy to manage. I believe that 20$ per KW/h for stored energy can be made with a polymer battery because the technology is different from that of conventional batteries. They can be made with a very high volume of production, high speed, high conductivity. The same way paper is not expensive although the machinery used to make paper is extremely expensive. The productivity is enormous. Polymer batteries have the same characteristics.

BBV : The EV is your dream. What attempts did you make to convince and get support from state agencies and car companies ?

MA : There are 3 stages : research, R&D and development. I never had problems at the research level. This was science, we had the CNRS resources. We were lucky in having Hydro-Quebec joining the research team. Michel Gauthier who was the head of the research group in Hydro-Quebec convinced this company to invest heavily in R&D. Several millions of dollars a year for R&D invested in long-term research. By contrast the investment by oil-companies was only superficial. That is why Elf sold the project to a Japanese company who did not contribute to its advance.

Fin de l'enregistrement

Pour citer l'entretien :

« Entretien avec Michel B. Armand », par Bernadette Bensaude Vincent et Hervé Arribart, 18 septembre 2001, Sciences : histoire orale, /spip.php ?article8.

Pour citer l'entretien :

« Entretien avec Michel B. Armand », par Bernadette Bensaude Vincent et Hervé Arribart, 18 septembre 2001, Sciences : histoire orale, https://sho.spip.espci.fr/spip.php?article8.

Lieu : Paris, France.

Support : enregistrement sur cassette.

Transcription : Bernadette Bensaude-Vincent.

Édition en ligne : Sacha Loeve.