CHARACTERIZATION OF ALUMINA MICROSPHERES PRODUCED BY COMBUSTION TORCH REMELTING

Abstract

The present work investigates the thermal treatment of alumina powder with a purpose built oxygen-Liquefied Petroleum Gas torch, as a of low-cost alumina microsphere production process. In this dry process, irregularly shaped alumina particles are re-melted, acquiring a spherical shape due to surface tension. Microspheres of the stable alpha alumina phase were produced starting from two different alumina powders, both having a granule size of approximately 80 µm. In one case the initial granules are formed of micrometric crystalline particles while in the other the crystalline particles are nanometric. In both cases the resulting microspheres present similar surface texture and the predominant crystalline phase is ?-alumina. Microspheres smaller than 42 µm show a dendritic morphology on the surface with minor presence of ?-alumina. In contrast, microspheres larger than 103 µm present a smoother surface with rhombohedral grains and presence of ?-alumina.