SiC-YAG sintered composites from hydroxy hydrogel powder precursors

Yttrium hydroxide and aluminium hydroxide hydrogel were derived from yttriu m nitrate and aluminium nitrate through hydroxy hydrogel route in which SiC particles were kept dispersed. The gel-like mass was heat treated at 900 d egreesC in ambient atmosphere followed by heat treatment at 1400 degreesC i n Ar atmosphere. The specimens were then sintered in the temperature range of 1800-1950 degreesC in Ar atmosphere with 30 min soaking. The phases were identified by XRD analysis. Microstructure of the sintered materials were analysed by scanning electron micrograph. With this new method of preparati on:of powder precursors, the process of sintering was easier and almost the oretical density was achieved with moderate hardness. The mechanism of dens ification was postulated to be a solid-state initiated liquid phase sinteri ng and the overall process of which was activated by the reactive species f ormed from hydroxy hydrogel powder precursors. (C) 2000 Elsevier Science Lt d and Techna S.r.l. All rights reserved.