Synthesis of a Ceramic Alloy Powder in the SiC-AIN System by Direct Reaction between the Constituent Elements

摘要

SiC-AIN alloy powders were prepared by reaction sintering of a powder mixture of Si, C, and AI in a nitrogen atmosphere through direct reaction between the constituent elements, i.e. Si + C + xAI + (x/2)N2 = SiC:xAIN. This paper describes the full processing details of the powder preparation and the properties of the synthesized powders and their sintered compacts. Experiments showed that the nitridation of AI occurred actively from 1073 K, followed by the reaction between Si and C at higher temperature. The formation of Si3N4. resulting from the reaction between Si and N, which was not intended in the present process, can be avoided by conducting the reaction sintering in N, gas (contalning 10H2) at 1073 K and subsequently in Ar gas at 1773 K. Such a process produceded SiC-AIN alloys without other phases, and hence fine powders were prepared by ball milling the porous reaction products . Dense compacts of the obtained powders can be fabricated not only by hot-isostatic pressing without external additives but also by pressureless sintering with Y2O3 as sintering additives at relatively low temporattire (2123 K). The microhardness, fracture strength, and fracture toughness of the HIP-sintered SiC-AlN alloys were investigated.