Sr-anorthite glass ceramic with enhanced crack resistance, reinforced with silicon nitride particles

Abstract

It is demonstrated that composite materials based on Sr-anorthite glass ceramic can be synthesized with finely dispersed α-Si3N4 and β-Si3N4 powders introduced as fillers. A study of the influence exerted by the polymorphic forms of fillers, their morphology, dispersity, and concentration and also by the nature of the matrix on the synthesis, structure, and properties of the composites demonstrated that the mechanism and temperature range of sintering in syntheses of materials are determined by the nature of the matrix and the degree of densification and the structure of the composite depend on the concentration, dispersity, and shape of filler particles, their phase composition, and wettability of the glass-phase matrix. In syntheses of glass-crystalline composites by the hot compaction method, raising the filler content from 10 to 70 vol % leads to a substantial decrease in the density of the materials (by 20%); the maximum content of the filler should not exceed 30 vol %. The use of both α-Si3N4 and β-Si3N4 in an amount of 30% made it possible to raise the critical stress intensity coefficient of the strontium-aluminosilicate matrix by more than a factor of 2. A study of the thermal properties of the composites demonstrated that the glass-crystalline matrix can protect nonoxide fillers from oxidation by atmospheric oxygen at elevated temperatures, with the oxidation onset temperature increased by 300°. The developed class of composites is promising for application in airspace technology, chemical industry, and motor-vehicle construction.