Preparation of ZrC/Al2O3 Fine Composite Powders by Thermite Reaction.

Abstract

Preparation conditions and formation process of ZrC/Al2O3 composite powders from the ZrO2-Al-carbon black or ZrO2-CH4 system were examined. The ZrC/Al2O3 fine composite powders were prepared from the former system by heating the powder mixture of ZrO2:Al:C molar ratio=3:4:3 at 950°-1000°C for 1h. The formation process of the ZrC/Al2O3 Composite powders was composed of three main reactions: (i) the reduction of ZrO2 With Al and the formation of Al2O3, (ii) the formation of Al3Zr With Zr and Al, and (iii) the decomposition of Al3Zr with carbon black and the formation of ZrC. The process (i) was interfered by the process (ii). Al4C3 was not formed by the process (m). On the other hand, in case of the ZrO2-Al-CH4 system, preparation of ZrC/Al2O3 composite powder was difficult because of Al2C3 and ZrC were formed by reaction between Al3Zr and CH4. For the preparation of the ZrC/Al2O3 composite powder, it was most important to suppress the formation of Al4C3 by controlling the reactivity between Al and carbon source.