SYNTHESIS AND MECHANISM OF SiC-ZrC COMPOSITE POWDERS BY CARBOTHERMAL REDUCTION METHOD

Abstract

SiC-ZrC composite powders were synthesised by the carbothermal reduction method using starch as the carbon source, zirconium dioxide as the zirconium source, and silica sol as the silicon source. The effects of the reaction temperature on the phase composition and microstructure of the SiC-ZrC composite powders were investigated. The reaction process was thermodynamically analysed and calculated, and the synthesis mechanism of the SiC-ZrC composite powder was analysed. The synthesised powder samples were characterised and analysed by X-ray diffraction, scanning electron microscopy, and other testing methods. The results show that the optimum reaction condition for the synthesis of SiC-ZrC composite powders is at 1550 °C-1600 °C for 1.5 h. A high temperature and a low pressure are beneficial in conducting the synthesis reaction. The SiC-ZrC composite powders synthesised by calcining at 1550 °C and holding for 1.5 h are mainly composed of a certain amount of whiskers, spherical particles, floc particles, and other structures. Moreover, their grain size is small (100-200 nm). The powder samples synthesised at 1600 °C produced a larger number of whiskers. The length of the whiskers was mostly 10 μm, the arrangement was complex and irregular, and a diverse microstructure was formed.