Sintering behaviour and mechanical properties of Al2O3 platelet-reinforced glass matrix composites obtained by powder technology

A cold-pressing and pressure-less viscous flow sintering treatment for the manufacturing of dense alumina platelet-reinforced glass matrix composites was investigated. The sintering behaviour of mixtures of powdered borosilicate glass cullet, coming from the pharmaceutical industry, and Al2O3 platelets was studied respecting the retardation in sintering caused by the introduction in glass of rigid, non-sintering, inclusions. Despite the relatively low Al2O3 platelet addition significant increases in bending strength, microhardness and, above all, fracture toughness were achieved, due to the homogeneity of mechanical dispersion of platelets and the development of residual stresses, caused by the thermo-elastic mismatch between the constituent phases. A crack deflection toughening mechanism, due to the specific reinforcement, was found to be effective.