A comparative study on physio-mechanical properties of silica compacts fabricated using rice husk ash derived amorphous and crystalline silica

Abstract

Rice husks, an agricultural waste, are widely used as a cheap source of silica to fabricate silica-based composites. Though a lot of research work has been reported related to the utilization of rice husk ash (RHA) as a silica source, no concrete information is available on the behaviour of RHA obtained at different temperatures. We herein report a systematic study on the physical and mechanical behaviour of silica compacts prepared using amorphous and crystalline silica obtained from RHA. Phase analysis of RHA treated at various temperatures is carried out using XRD. Amorphous silica is obtained above 400 °C and below 800 °C. A phase transformation occurs in the temperature range of 800°C–900 °C, after which RHA converts to the crystalline phase. Crystalline silica consists of mostly cristobalite and tridymite phases. Particle size and surface area of obtained RHA are in the range of 552.2 nm–1212 nm and 0.258 m2 g-1-72.96 m2 g-1, respectively. Physical and mechanical properties of silica compacts fabricated using RHA treated at different temperatures have been studied. Green density of silica compacts prepared using crystalline silica is high compared to amorphous silica attributing to the finer size and disorganized nature of amorphous silica. In contrast to green density, sintered silica compacts prepared using amorphous silica shows more relative density and better strength compared to crystalline silica. The above phenomenon can be attributed to the less viscous nature of amorphous silica and better conversion rate of amorphous silica to the cristobalite phase. The developed silica compacts possess bulk density and compressive strength in the range of 1.59 g/cm3-1.97 g/cm3 and 20 MPa–52 MPa, respectively. Obtained results were correlated with the SEM micrograph. © 2022