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9. Etude de la réactivité et de la structure des noirs de carbone
355
ABSTRACTS
7. High temperature
tensile creep of graphite+
E. J. Seldin (Research Laboratory of National Carbon Company, Divisicwt of Union Carbide Corporation, Parma, Ohio). Tensile creep tests with durations of 90-120 min were performed on several different types of graphite over the temperature range of 2300 to 2900°C. For ATJ graphite, the creep rate was found to vary with the fourth power of the stress on specimens oriented both “with-the-grain” and “against-the-grain”. An activation energy of 124 kcal/mole was determined from the temperature dependence of the creep rate. This activation energy was found to be the same for both grain orientations and for all of the graphites which were tested. The influence on the creep of anisotropy,grain orientation, density, and the relative proportions of filler and binder coke in the graphite will be discussed. “The subject research was sponsored in part by the Aeronautical Systems Division, Air Force Systems Command, United States Air Force.
8. Reactions of carbon with carbon dioxide activated by low voltage electrons
K. T. Claxton and R. F. Strickland-Constable (Imperial College, London, England). An oxide coated emitter provides electrons which are accelerated in a field of 25 V in a low pressure of CO, gas; a film of carbon deposited on metal foil is also present in the same vessel. The excited CO, reacts with the unheated carbon, with an efficiency rising to 4 p/, of the emitted electrons: the rate of attack is independent of the sign of any electric potential applied to the carbon. The excited species are therefore uncharged and are probably 0 atoms. In the presence of carbon the electron emission current remains substantially constant; but if the carbon is omitted from the reaction vessel the electron current falls rapidly. In the latter case the active species presumably attack the oxide coated filament (which is at 900°C). In the former case they must react preferentially with the cold carbon. 9. Etude de la rkactivitb et de la structure des noirs de carbone J. B. Donnet (Ecole Sup&we de Chimie, Mulhouse (Haut-Rhin), France). L’etude de la reactivite chimique superficielle des noirs de carbone a CtC effect&e sur des Cchantillons progressivement oxydes. On a determine par differentes methodes chimiques et physiques le taux de fonctions carboxyles, hydroxyles et quinone. De plus le taux de radicaux libres superficiels a et6 determine par voie chimique et par resonance paramagnetique Clectronique. Les resultats obtenus permettent d’etablir la stabilite et la structure de ces differentes fonctions chimiques superficielles ainsi que leur attitude dans les reactions radicalaire. La relation entre le taux de quinones superficielles et le taux d’electrons libres sera examinee ainsi que l’hypothese de la structure aroxylique de ces fonctions. D’autre part, une etude systematique des noirs oxydes au microscope Clectronique a permis de mettre en evidence une nette difference de structure interne entre les noirs Furnace et les noirs Thermal. Tandis que les premiers sont attaques de facon desordonnee les noirs prepares par craking thermique presentent des zones sensibles g l’attaque oxydante et ces zones sont disposees de facon concentrique. Ce processes a peu etre confirm& par l’examen au microscope Clectronique, de coupes minces a l’ultramicrotome. Au vu de ces resultats on est conduit g penser que la repartition des domaines microcristallines que semble bien Ctre statistique dans les noirs au four et les noirs channels serait plutat en couches concentriques dans les noirs thermiques avec dans chaque couche une orientation des microcristallites parallele a la surface de la particule. 10. Reactions of graphite with carbon dioxide at 1000 to 1500°C under flow conditions
E. A. Gulbransen, K. F. Andrew, and F. A. Brassart (Westinghouse Pennsylvania). The reaction of high purity graphite with dry carbon of 2-38 torr and for flow rates of 1.5 x 10” to 2.9 x 10”’ carbon dioxide effects were minimized by the use of high flow rates. In contrast to was found for spalling. The rate of reaction of carbon dioxide with
Research Laboratories, Pittsburgh, dioxide was studied at pressures molecules per sec. Gas diffusion the oxygen reaction no evidence carbon at 15OO”C, a pressure of
ABSTRACTS
7. High temperature
tensile creep of graphite+
E. J. Seldin (Research Laboratory of National Carbon Company, Divisicwt of Union Carbide Corporation, Parma, Ohio). Tensile creep tests with durations of 90-120 min were performed on several different types of graphite over the temperature range of 2300 to 2900°C. For ATJ graphite, the creep rate was found to vary with the fourth power of the stress on specimens oriented both “with-the-grain” and “against-the-grain”. An activation energy of 124 kcal/mole was determined from the temperature dependence of the creep rate. This activation energy was found to be the same for both grain orientations and for all of the graphites which were tested. The influence on the creep of anisotropy,grain orientation, density, and the relative proportions of filler and binder coke in the graphite will be discussed. “The subject research was sponsored in part by the Aeronautical Systems Division, Air Force Systems Command, United States Air Force.
8. Reactions of carbon with carbon dioxide activated by low voltage electrons
K. T. Claxton and R. F. Strickland-Constable (Imperial College, London, England). An oxide coated emitter provides electrons which are accelerated in a field of 25 V in a low pressure of CO, gas; a film of carbon deposited on metal foil is also present in the same vessel. The excited CO, reacts with the unheated carbon, with an efficiency rising to 4 p/, of the emitted electrons: the rate of attack is independent of the sign of any electric potential applied to the carbon. The excited species are therefore uncharged and are probably 0 atoms. In the presence of carbon the electron emission current remains substantially constant; but if the carbon is omitted from the reaction vessel the electron current falls rapidly. In the latter case the active species presumably attack the oxide coated filament (which is at 900°C). In the former case they must react preferentially with the cold carbon. 9. Etude de la rkactivitb et de la structure des noirs de carbone J. B. Donnet (Ecole Sup&we de Chimie, Mulhouse (Haut-Rhin), France). L’etude de la reactivite chimique superficielle des noirs de carbone a CtC effect&e sur des Cchantillons progressivement oxydes. On a determine par differentes methodes chimiques et physiques le taux de fonctions carboxyles, hydroxyles et quinone. De plus le taux de radicaux libres superficiels a et6 determine par voie chimique et par resonance paramagnetique Clectronique. Les resultats obtenus permettent d’etablir la stabilite et la structure de ces differentes fonctions chimiques superficielles ainsi que leur attitude dans les reactions radicalaire. La relation entre le taux de quinones superficielles et le taux d’electrons libres sera examinee ainsi que l’hypothese de la structure aroxylique de ces fonctions. D’autre part, une etude systematique des noirs oxydes au microscope Clectronique a permis de mettre en evidence une nette difference de structure interne entre les noirs Furnace et les noirs Thermal. Tandis que les premiers sont attaques de facon desordonnee les noirs prepares par craking thermique presentent des zones sensibles g l’attaque oxydante et ces zones sont disposees de facon concentrique. Ce processes a peu etre confirm& par l’examen au microscope Clectronique, de coupes minces a l’ultramicrotome. Au vu de ces resultats on est conduit g penser que la repartition des domaines microcristallines que semble bien Ctre statistique dans les noirs au four et les noirs channels serait plutat en couches concentriques dans les noirs thermiques avec dans chaque couche une orientation des microcristallites parallele a la surface de la particule. 10. Reactions of graphite with carbon dioxide at 1000 to 1500°C under flow conditions
E. A. Gulbransen, K. F. Andrew, and F. A. Brassart (Westinghouse Pennsylvania). The reaction of high purity graphite with dry carbon of 2-38 torr and for flow rates of 1.5 x 10” to 2.9 x 10”’ carbon dioxide effects were minimized by the use of high flow rates. In contrast to was found for spalling. The rate of reaction of carbon dioxide with
Research Laboratories, Pittsburgh, dioxide was studied at pressures molecules per sec. Gas diffusion the oxygen reaction no evidence carbon at 15OO”C, a pressure of