DEVELOPMENT OF SIC-WHISKER-REINFORCED LITHIUM ALUMINOSILICATE MATRIX COMPOSITES BY A MIXED COLLOIDAL PROCESSING ROUTE

Abstract

Based on the surface properties of aqueous silica, boehmite, and SiC-whisker dispersions, SiC-whisker-reinforced lithium aluminosilicate (LAS) matrix composites were fabricated by a mixed colloidal processing route. The composites were characterized by a uniform spatial distribution of SiC whiskers throughout the matrix. The fracture toughness increased from 1.3 MPa.m1/2 for the LAS specimen to 5.0 MPa.m1/2 for the hot-pressed composite (950-degrees-C and 20 MPa for 20 min) containing 20 wt% SiC whisker. The increase in fracture toughness appears to result mainly from crack deflection and crack bridging by whiskers with some additional toughenings from load transfer and whisker pullout.