Effect of Composition, Sintering Parameters and Morphologies on Densification and Mechanical Behaviour of Alumina Borosilicate Glass Composite

Abstract

Alumina-borosilicate glass composites with x Glass + (1-x) Al2O3 (x = 5, 10, 30 and 50 vol. %) were prepared by pressure-less viscous flow sintering route. A moderately high sintering temperature of 1000–1400oC with an annealing time of 2 and 4 hours respectively were employed in order to prepare the composites. Two different morphologies of alumina particles viz., near-platelet and irregular-shape were also used in the present study. The effect of glass addition, sintering parameters (temperature/time) and the morphology of alumina particles on densification behaviour and mechanical characteristics of the composites were investigated in details. An increment in glass content of the composition reduced the densification of the compact. In general, an increase in sintering temperature resulted in an increase of density, as obvious in the case of viscous flow densification. But densification was hindered by the increase in annealing time. The formation of residual porosities (nearly about 30%) in the compact containing higher glass (for e.g. 50%) sintered at a higher temperature and annealing time (4 hours) is believed to be responsible for the reduction in density. The effect of the morphology of the alumina particles appeared to be more pronounced at higher temperature and annealing time due to more wetting of irregular-shaped alumina particles by viscous glass compared to that of near-platelet particles. By tuning the sintering conditions, proper composition and morphologies, it was possible to produce porous, lightweight yet higher compressive strength composite (about 46 MPa). The compressive strength of the composite obtained in the present study is much higher compared to that of the commercially available marble/granite and can be thought of a better replacement in the application area that demands higher compressive load bearing capacity at room temperatures.