Novel Temperature Dependent Process for α-Al2O3 Platelets

Abstract

α-Al2O3 platelets were prepared in the interface of Na2O-CaO-SiO2 glass induced by Al. Phase identification was accomplished by X-ray diffraction analysis. The morphology of the platelets was observed using an Environmental Scanning Electron Microscopy (ESEM). The changes for the mixtures of the Al powders and the glass powders that occurred during heating were characterized by a combination of differential scanning calorimetry (DSC) and thermalgravimety(TG) on a multi-functional instrument. Confirmed by XRD and ESEM, at 1200°C, the prepared platelets have mean diameters between 400nm and 1000nm. Most of them are aggregated and part of them through intergrowth. The crystals develop from the interface between glass and Al, and can form good moistening with the glass matrix. DSC/TG shows that γ-Al2O3 formed by oxidation of Al, transforms into α-Al2O3 and grow into the platelet α-Al2O3 crystals owing to the molten Al and the molten glass. On the other hand, part of the molten Al erodes into the glass and makes the deviation of the Na2O-CaO-SiO2 ternary system into Na2O-Al2O3-SiO2 ternary system, resulting in the formation of NaAlSiO4.