Sintering of Al 2O 3–SiC composite from sol–gel method with MgO, TiO 2 and Y 2O 3 addition

Abstract

Al 2O 3–SiC composite ceramics were prepared by pressureless sintering with and without the addition of MgO, TiO 2 and Y 2O 3 as sintering aids. The effects of these compositional variables on final density and hardness were investigated. In the present article at first α-Al 2O 3 and β-SiC nano powders have been synthesized by sol–gel method separately by using AlCl 3, TEOS and saccharose as precursors. Pressureless sintering was carried out in nitrogen atmosphere at 1600 °C and 1630 °C. The addition of 5 vol.% SiC to Al 2O 3 hindered densification. In contrast, the addition of nano MgO and nano TiO 2 to Al 2O 3–5 vol.% SiC composites improved densification but Y 2O 3 did not have positive effect on sintering. Maximum density (97%) was achieved at 1630 °C. Vickers hardness was 17.7 GPa after sintering at 1630 °C. 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.