The effect of heat-treatment on the performance of sub-micron SiC_p-reinforced α-β sialon composites: I. Preparation of agglomerate-free starting powders

In order to prepare good-quality, dense, SiC_p-reinforced α-β sialon composites by hot-pressing, a technique was developed to prevent agglomeration of the SiC grains during powder processing. For this purpose, the surfaces of the SiC particles were selectively covered with long organic molecular chains by soaking in a solution of polyethylene glycol in isopropanol; the resulting powder not only resisted re-agglomeration, but was also readily dispersible within the sialon matrix. Infra-red absorption was used to demonstrate that the PEG-modified SiC grains had been successfully coated with OH groups. The dispersion role of PEG is mainly influenced by the molecular weight of the surfactant, the surfactant concentration, the pH value of the suspension and the soaking time of the SiC powder in the solution.