Effect of crystallized phase on mechanical strength of hot-pressed composites of MgO-B2O3-Al2O3 type glass and Al2O3 filler

We optimized the crystallized phase for imparting high mechanical strength to a composite Of MgO-B2O3-Al2O3 glass and Al2O3 filler by hot-press sintering to achieve densification at low temperature and annealing to induce crystallization. The selective crystallization of Al4B2O9 and/or AlBO3 successfully yielded a composite with high mechanical strength and low porosity. This required the use of a glass with a high Al2O3 Content that retained its glassy character even when its entire Al2O3 content was converted to crystalline Al4B2O9. The composite of MgO-B2O3-Al2O3 type glass and Al2O3 filler exhibited a higher mechanical strength than conventional borosilicate glass and Al2O3 filler composites, a porosity of about 1%, a low coefficient of thermal expansion, and was highly waterproof. (C) 2008 The Ceramic Society of Japan. All rights reserved.