Production of silica-based ceramics sintered under nitrogen atmosphere from rice husk and sugarcane bagasse ash

Abstract

Nitride silica-based ceramics were prepared by sintering under nitrogen atmosphere using rice husk ash and bagasse ash as raw materials. X-ray Fluorescence Spectrometry (XRF) and X-ray Diffractometor (XRD) studies revealed that the main phase of rice husk ash (after calcined at 600°C for 6 h.) was amorphous silica, whereas the sugarcane bagasse ash contained quartz and CaCO₃. Thus, both ashes would be a good source for silica. Two batches of the 100 wt% rice husk ash (RHA100) and the mixture of 50 wt% rice husk ash and 50 wt% bagasse ash (RHA50BA50) were wet milled using planetary ball milling machine, and were then dried at 90°C. The powders were uniaxially pressed at the pressure of 150 MPa. The disk shape samples were sintered at 1300-1500°C in the nitrogen atmosphere with gas flow rate of 600 ml/min. The physical and mechanical properties of the sintered disk shape samples were determined. The phase structure and microstructure of the samples were investigated using XRD and SEM techniques, respectively. The main phases obtained after sintering were cristobalite, tridymite, α and β-silicon nitride and SiC. The RHA50BA50 sample sintered at 1450°C showed the optimum properties with low firing shrinkage, low water absorption and high strength.