Microstructural and Mechanical Properties of Alumina (Al2O3) Matrix Composites Reinforced with SiC from Rice Husk by Spark Plasma Sintering

Alumina (Al2O3) suffers from low fracture toughness and low bending strength which restrict its application in the industry for some advanced components. The incorporation of submicron SiC into Al2O3 matrix improves mechanical properties of the matrix. However, the high cost of SiC has delayed the industrial interest of synthesizing Al2O3-SiC composites. Rice husk, an agricultural waste material, is a potential source of low-cost SiC. Therefore, this study presents a simple approach to synthesizing SiC from locally sourced rice husk and using it to reinforce alumina. Rice husk was pyrolysed in a tube furnace under argon atmosphere at different temperatures (1000 degrees C - 1500 degrees C) and reaction times (60 - 120 min). Furthermore, Alumina powder was admixed with 5 - 20 vol% SiC derived from rice husk, and then sintered at temperatures between 1300 degrees C - 1600 degrees C by spark plasma sintering. Maximum yield of SiC was obtained from rice husk at 1500 degrees C and 120 min. Materials with theoretical densities higher than 95% were achieved for the sintered composites. The hardness of sintered composites reached a maximum of 20.2 +/- 1.4 GPa, while a maximum of 4.7 +/-.7 MPa.m(0.5) was obtained for the fracture toughness.