Preparation of zirconia and silicon carbide whisker biphasic powder mixtures by carbothermal reduction of zircon powders

Panda, PK and Mariappan, L and Jaleel, VA and Kannan, TS and Amroune, A and Dubois, J and Fantozzi, G (1996) Preparation of zirconia and silicon carbide whisker biphasic powder mixtures by carbothermal reduction of zircon powders. Journal of Materials Science , 31. pp. 4277-4288. ISSN 0022-2461

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Abstract

Carbothermic reduction of zircon powders has been studied under argon and nitrogen gas pressures of 0.15 MPa in order to obtain biphasic composite powder mixtures containing zirconia and silicon carbide whiskers. The reduction has been carried out using different mole ratios of carbon and zircon. Carbon was used in the form of activated charcoal (specific surface area ,-~1000 m2g -1) or carbon black (specific surface area -~300 m2g-1). Whilst complete decomposition to m-ZrO2 was obtained in the argon atmosphere at 1700 ~ under the nitrogen atmosphere the conversion was incomplete even at 1700~ However, the extent of conversion to zirconia at 1650~ under nitrogen was found to be more than that under argon gas. In a few cases, particularly under the nitrogen atmosphere, minor amounts of other forms of zirconia e.g., tetragonal (t)-ZrO2 or orthorhombic (o)-ZrO2 were formed along with the major monoclinic (m)-ZrO2 phase. The rate of reaction was found in general to increase with an increase in the carbon content. The studies particularly indicate that activated charcoal is a better reducing agent than carbon black owing probably to its enormous surface area. Further, it was also noted that cobalt chloride and sodium chloride act as a catalyst and a space forming agent respectively. They aid silicon carbide whisker formation and growth and hence the reaction is appreciably accelerated and reaches completion at 1650~ in the argon atmosphere.

Item Type: Article
Additional Information: Copyright to this article belongs to M/s. Chapman and Hall
Uncontrolled Keywords: Zirconia;Silicon carbide;Zircon powders
Subjects: CHEMISTRY AND MATERIALS > Chemistry and Materials (General)
Depositing User: Users 11 not found.
Date Deposited: 31 Oct 2012 04:20
Last Modified: 31 Oct 2012 04:20
URI: http://nal-ir.nal.res.in/id/eprint/11332

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