MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Al2O3, Si3N4, SiC, AND ZrO2(PSZ) CERAMICS FOR SLURRY VALVES.

In order to use ceramics as a material for slurry valves, which are exposed to a flow of slurry containing hard particles of coal or ash, the bending strength of alumina (Al//2O//3), silicon nitride (Si//3N//4), silicon carbide (SiC) and partially stabilized zirconia (PSZ) was examined under the practical condition (400 degree C, slurry dipped condition). Fracture took place from the structural weak points, that is, pores, large crystal grains and the impurity phases. In the case of ceramics with uniformly small crystalline particles and very little pores, fracture seems to occur through the impurity phases.