Abstract
The oxidation of two kinds of NbC, powder and single-crystal samples, was carried out isothermally at temperatures of 390 to 610°C at an oxygen partial pressure of 8 kPa using an electromicrobalance. The kinetics results suggested that the oxidation of both powder and crystal samples proceeds essentially by a phase-boundary-controlled reaction. It was found that cracking of grains or particles in the powder samples, which occurs in the later stage, accelerates oxidation below 485°C, and extremely rapid reaction proceeds above that temperature. Simultaneous TG-DTA-MS measurement showed that the reaction above 485°C is due to a large heat evolution resulting from rapid oxidation of bare NbC surfaces produced by cracking of grains or particles, which was partly caused by immediate release of CO2 accumulated in them. Scanning electron microscopy of the crystals showed that columnar, porous grains with the major axis normal to the surface formed, which were responsible for the phase-boundary-controlled reaction of the oxidation of both powder and crystal samples.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
S. Shimada and T. Ishii,J. Am. Ceram. Soc. 73, 2084 (1990).
S. Shimada, M. Inagaki, and T. Matsui,J. Am. Ceram. Soc. 75, 2671 (1992).
S. Shimada, M. Nishisako, and M. Inagaki, Proc. 3rd IUMRS Int. Conf. Advanced Materials (in press).
S. Shimada, M. Nishisako, M. Inagaki, and K. Yamamoto,J. Am. Ceram. Soc. (in press).
S. Shimada and M. Inagaki,Solid State Ionics 63–65, 312 (1993).
A. Szokefalvi-Nagy and H. Jehn,Z. Metall. 75, 389 (1984).
P. Kofstad and H. Kjollesdal,Trans. Metall. Soc. AIME 221, 285 (1961).
J. S. Sheasby,J. Electrochem. Soc. 115, 695 (1968).
J. S. Sheasby and W. W. Smeltzer,Oxid. Met. 15, 215 (1981).
T. P. Hennessey and J. E. Morral,Oxid. Met. 38, 163 (1992).
S. Shimada, T. Koyama, A. Tsunashima, K. Kodaira, and T. Matsushita,J. Cryst. Growth 62, 557 (1983).
S. Shimada, M. Mukaide, K. Kodaira, and T. Matsushita,Yogyo-Kyokai-Shi 93, 768 (1985).
S. Otani, T. Tanaka, and Y. Ishizawa,J. Cryst. Growth 62, 211 (1983).
C. P. Kempter,J. Chem. Phys. 32, 1477 (1960).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Shimada, S. A kinetic and thermoanalytical study on oxidation of powder and single-crystal samples of niobium carbide. Oxid Met 42, 357–373 (1994). https://doi.org/10.1007/BF01046755
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF01046755