Effect of Sintering Additive and Pyrolysis Temperatures on Porous Silicon Carbide

Abstract

Rice husk was used as a raw material to fabricate silicon carbide (SiC) ceramics. Carbothermal reduction was used together with in-situ reaction bonding as the preparation method. Rice husk was carbonized at the temperature around 700 °C in an incineration furnace. Carbonized rice husk was ground and treated with hydrochloric acid solution. After grinding, the sample powders were mixed with silicon metal powder and sintering additives (alumina (Al2O3) and magnesia (MgO)). The mixed powders were pressed and then pyrolyzed at various temperatures and pyrolysis patterns in argon atmosphere. Silicon carbide, as the main crystalline phase, was obtained in all pyrolized samples. Cristobalite was found together with silicon carbide in the samples which pyrolized only lower than 1500 °C. Amount of silicon carbide particle was increased at higher pyrolysis temperature while silicon carbide whisker was decreased. Weight loss, shrinkage and porosity of the pyrolized samples were investigated. Weight loss and shrinkage of the samples increased when increasing pyrolysis temperature while porosity decreased.