Alumina/Glass Composites Fabricated by Melt-Infiltration of Glass into Porous Alumina

Alumina/glass composites were successfully fabricated by melt-infiltration of glass into porous alumina pellets. Alumina powder was first pressed uniaxially at 100MPa to form disc-shaped pellets, then, heated up to 1200°C for 2 h to form porous pellets with moderate strength for subsequent infiltration. A mixture of calcium aluminosilicate and magnesium borosilicate glass powders were melt-infiltrated into porous alumina at 1200°C ~1250°C by capillary pressure to form composites. The infiltration depths varied with the square root of infiltration time. And the activation energy of the infiltration process was estimated to be 621 KJ/mole. After complete infiltration, the composite had bulk density approaching 3.3 g/cm3 (~ 96% of theoretical density) and open porosity reaching zero, with slight expansion of 0.5% in diameter. Its flexural strength was 150MPa and its Vickers microhardness was about 1000 Kg/mm2.