Preparation of Al2O3 - SiC In-Situ Composite Powder Mixtures by Carbothermal Reduction of Kaolinite

Abstract

A1,,O3-SiC,, composite powder mixtures were prepared by carbothermal reduction of kaolinite (A],03.2SiO,.2H,O) in argon atmosphere at constant gas pressure of 0.15 MPa. The reactions were carried out with different mole ratios of silica (in the precursor) and carbon (4.5-9.0), with two types of carbon i.e.carbon black (300m2/g)and activated charcoal (1000m2/g) and at different temperatures in the temperature range of 1550-17000C with one hour of soaking to find the progress of the reaction in all the cases. It was observed that the reactions were complete at 17000C. The reactions were carried out with higher soaking time to optimise the process. It was noted that mullite forms as the intermediate phase at lower temperatures which converts progressively later to a mixture of A1,O, and SiC,, composite product at higher temperatures,