LOW-TEMPERATURE SYNTHESIS OF ZRC POWDER BY CYCLIC REACTION OF MG IN ZRO2-MG-CH4

We investigated the conditions for low-temperature synthesis of ZrC fi ne powder from ZrO2-Mg-CH4. The synthesis utilizes a thermite-type rea ction, with Mg as the reducing agent, and a reaction between Mg and CH , gas as a carbon source. The Mg/ZrO2 molar ratio as well as the heati ng rate were varied. Because C can be continuously fed into the reacti on group by the cyclic reaction of Mg through the formation and decomp osition of Mg2C3 (2Mg + 3CH4 --> Mg2C3 + 6H-2 --> 2Mg + 3C), a molar r atio of 2.2 for Mg/ZrO2, was sufficient for the synthesis of single-ph ase ZrC. ZrC powders were synthesized under the following conditions: Mg/ZrO2 molar ratio = 2.2, heating rate = 20-degrees-C/min, and temper ature maintained at 750-degrees-C for 30 min. The amount of reaction h eat produced in the reduction reaction of ZrO2 by Mg depended on the M g/ZrO2 molar ratio, specifically, the amount of ZrO2 contained. Moreov er, the cyclic reaction of Mg-Mg2C3-Mg was influenced by the amount of reaction heat described above and by the heating rate. The ZrC fine p owder showed little aggregation and high dispersibility.