Effect of ethylene glycol on the mullite crystallization

Mullite is one of the most important aluminosilicate due to its unique thermal properties. In this work, mullite was obtained by sol–gel process at low temperature using sodium metasilicate, water, aluminum nitrate and ethylene glycol. The samples were prepared with a volume ratio of ethylene glycol/water equal to 0/1, 1/1, 2/1 and 3/1. The ethylene glycol effect on mullite crystallization was studied by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and Differential Thermal Analysis (DTA). The sample prepared without ethylene glycol, the less homogeneous one, formed amorphous silica, spinel-phase and α-alumina at 1000 °C, and then crystallized mullite at 1200 °C, with an alumina molar fraction of 0.58. The other samples formed amorphous silica at 900 °C and crystallized mullite as the only crystalline phase at 1000 °C. However, the alumina content in mullite formula depends on the thermal treatment, reaching 0.58 at 1250 °C.