DISTRIBUTION OF SILICA IN RICE HUSKS AND ITS EFFECT ON THE FORMATION OF SILICON-CARBIDE

An investigation into the distribution of silica in raw rice husk and its effect on the formation of SiC particles and whiskers is carried out by a detailed study of raw rice husks, burnt rice husks and converted rice husks through XPS, XRD and SEM analyses. The present study has revealed that silica is present all over the rice husk. However, the protuberances and hairs on the outer epidermis and the inner epidermis adjacent to the rice kernel are shown to be rich in silica. The XPS and XRD results indicate that silicon in raw rice husk is bonded to organic material. The SEM analysis of the converted rice husks shows that the part of the rice husk rich in carbon (organic material) tends to form a SiC skeleton structure. It appears that the part of the rice husk rich in silica is the main source of SiO for the formation of SiC whiskers through gaseous reaction between SiO and CO.