Bulk Crystallization of Ceramic Whiskers from Borate-Based Glass

Abstract

Bulk crystallization of B2O3-SiO2-Al2O3-BaO-MgO glass system was investigated. Controlled heat treatment process was carried out between 900 and 1200°C to form glass-ceramics. Phase evolution in the crystallized glasses was studied by X-ray diffraction. Microstructures of the chemically etched surfaces were revealed by scanning electron microscope and micro-hardness was measured by Vickers hardness tester. High aspect ratio of aluminium borate whiskers were in the nano to micro regime and dispersed within the residual glass matrix. Whiskers had different sizes and compositions depending on the heat treatment temperature, which affected the surface hardness of the glass-ceramics. In general, increasing heat treatment temperature led to an increase in crystal size and length as well as the surface hardness (4.8 to 5.5 GPa). The whisker crystals oriented uniformly within the residual glass matrix leading to interlocking microstructure. The synthesized glass-ceramics in this study can be applied as machinable materials in various industries because their microstructures can resist microcracking and hence increase fracture toughness.