Effect of some technological parameters on structure formation in materials based on reaction-sintered silicon carbide

Abstract

Results of petrographic, x-ray, chemical, and spectral investigations of the structure and composition of materials based on SiC fabricated by reaction sintering of preforms pressed from grainy silicon carbide and its mixtures with petroleum coke in molten and volatilized silicon are presented. It is shown that the structure and composition of reaction-sintered silicon carbide materials can be controlled by changing the proportion of silicon carbide and petroleum coke in the pressed preform, the coarseness of carbide and carbon particles, the density of the pressings, and the temperature of reaction sintering. It is established experimentally that secondary silicon carbide formed as a result of the reaction between petroleum coke and silicon binds the grains of the initial carbide into a dense silicon carbide skeleton, whereas the retained pores are filled with free silicon. A single-phase material consisting entirely of silicon carbide can hardly be obtained by the method of reaction sintering. In practice, this method gives double-phase (SiC-Si) and triple-phase (SiC-Si-C) materials with a maximum content of the principal phase (SiC) equal to 94–96% (mass fractions).