SINTERING AND MECHANICAL-PROPERTIES OF BETA-WOLLASTONITE

Detailed microstructural studies have been carried out on porous beta- wollastonite (CaSiO3) ceramics with 40-60% of the theoretical density. Xonotlite (Ca6Si6O17(OH)(2)) was used as starting material, and the r eaction and sintering behaviour were systematically examined in the ra nge 800-1200 degrees C in air. Analysis of the mechanical properties s howed that the strength degradation of beta-wollastonite ceramics was certainly induced by the change of microstructure. Isothermal annealin g at 1100 degrees C, however, did not preferentially affect the micros tructure or the mechanical properties of sintered beta-wollastonite. T hese observations lead to the conclusion that the measured bending str ength and Vickers hardness of porous beta-wollastonite ceramics can be substantially modified and improved by controlling the microstructure , in particular due to the shape of randomly oriented grains in the ma trix.