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

Abstract

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 °C – 1500 °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 °C – 1600 °C by spark plasma sintering. Maximum yield of SiC was obtained from rice husk at 1500 °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.

Keywords:
Sintering; microstructure; X-ray diffraction; mechanical properties; rice husk; Silicon carbide.