Utilization of Chemically Synthesized Fine Powders of SiC/Al2O3 Composites for Sintering

Fine powders of (Al₂O₃)_100–x(SiC)_x (0 ≤ x ≤ 50) composites were prepared by chemical route (named as pyrophoric technique) to achieve a uniform mixture of SiC in an alumina matrix. The chemically synthesized fine SiC/Al₂O₃ composite powders were sintered to form composites at 1450°C which is well below the sintering temperature of SiC. Sintering was performed in an argon atmosphere. Highly dense SiC/Al₂O₃ microstructures were achieved. An improvement in bulk density and hardness has been achieved for SiC/Al₂O₃ composites with 20 wt% of SiC. Hexagonal-shaped grains have been obtained in (Al₂O₃)₅₀(SiC)₅₀ composite with well-connected grain boundaries. The peak position of alumina in SiC/Al₂O₃ composites shifts toward lower wavenumbers in Fourier transform infrared spectroscopy and higher wavenumbers in Raman spectroscopy due to the incorporation of SiC in the composites. The optical band gap decreases with the addition of SiC and the composite behaves more like a semiconductor rather than an insulator. These properties make SiC/Al₂O₃ composites attractive for various industrial applications.