Preparation of refractory cordierite using amorphous rice husk silica for thermal insulation purposes

This study aims to investigate the effect of sintering temperatures on the phase formation and physical characteristics of refractory cordierite prepared from rice husk silica, Al2O3, and MgO powders. The samples were subjected to sintering temperatures of 1050-1350 °C, and development of structures was characterized using Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction (XRD) coupled with Rietveld analysis, scanning electron microscopy (SEM) and dilatometry. The results obtained indicated the significant role of sintering temperatures on phase transformation of spinel and cristobalite into cordierite, in which at sintering temperatures of 1230-1350 °C the cordierite emerges as a dominant phase, while spinel and cristobalite are practically undetected. Formation of cordierite was followed by decrease in density, porosity, and thermal expansion coefficient, while for hardness and bending strength the opposite was true. Thermal expansion coefficient of the sintered sample at 1350 °C is 3.3×10−6/°C and the XRD analysis demonstrated that the main crystalline phase is cordierite. Based on these characteristics, the samples are considered as insulator, suggesting their potential use in refractory devices.