Liquid phase sintering of Al2O3/SiC nanocomposites

Al2O3/SiC nanocomposites are usually prepared by hot pressing or using high sintering temperatures, viz. 1700 degrees C. This is due to the strong inhibiting effect of the nano-sized SiC particles on the densification of the material. Liquid phase sintering (LPS) can be used to improve densification. This work explored two eutectic additive systems, namely MnO2. SiO2 (MS) and CaO . ZnO . SiO2 (CZS). The additive content in Al2O3/5 wt% SiC nanocomposite material varied from 2 to 10 wt%. Densities of up to 99% of the theoretical value were achieved at temperatures as low as 1300 degrees C. Characterisation of the materials by XRD, indicated the formation of secondary crystalline phases in addition to Al2O3 and SiC. SEM and TEM analysis showed the presence of a residual glassy phase in the grain boundaries, and an increase in the average grain size when compared to nanocomposites processed without LPS additives. (C) 1999 Elsevier Science Limited. All rights reserved.