Sintering of Al2O3aSiC composite from sol-gel method with MgO, TiO2 and Y2O3 addition

Al2O3aSiC composite ceramics were prepared by pressureless sintering with and without the addition of MgO, TiO2 and Y2O3 as sintering aids. The effects of these compositional variables on final density and hardness were investigated. In the present article at first I--Al2O3 and I2-SiC nano powders have been synthesized by sol-gel method separately by using AlCl3, TEOS and saccharose as precursors. Pressureless sintering was carried out in nitrogen atmosphere at 1600ADGC and 1630ADGC. The addition of 5vol.% SiC to Al2O3 hindered densification. In contrast, the addition of nano MgO and nano TiO2 to Al2O3a5vol.% SiC composites improved densification but Y2O3 did not have positive effect on sintering. Maximum density (97%) was achieved at 1630ADGC. Vickers hardness was 17.7GPa after sintering at 1630ADGC. SEM revealed that the SiC particles were well distributed throughout the composite microstructures. The precursors and the resultant powders were characterized by XRD, STA and SEM.