Characterization of alumina microspheres produced by combustion torch remelting

Abstract

The present work investigates the thermal treatment of alumina powderwith a purpose built oxygen-Liquefied Petroleum Gas torch, pursuing a low-costalumina microsphere production process. In this dry process, irregularly shapedalumina particles are re-melted, acquiring a spherical shape due to surfacetension. Microspheres were produced starting from two different alumina powders,both having a granule size of approximately 80 µm. Two different startingmaterials with different porosity were tested. In both cases the resulting microspherespresent similar surface texture and the predominant crystalline phase isα-alumina. Microspheres smaller than 42 μm show a dendritic morphology on thesurface with minor presence of γ-alumina. In contrast, microspheres larger than103 μm present a smoother surface with rhombohedral grains and no significant presenceof γ-alumina.