SYNTHESIS OF NANOCRYSTALLINE SIC AT AMBIENT-TEMPERATURE THROUGH HIGH-ENERGY REACTION MILLING

This study investigated the in-situ synthesis of nanosized crystalline SiC powders at room temperature through high energy ball milling of e lemental silicon and carbon mixtures. Milling conditions including the mill design, the milling speed, the milling time and the ball-to-powd er weight ratio (i.e. the charge ratio) necessary for the in-situ synt hesis were studied. It was found that uniform formation of nanosized c rystalline SiC powders within the powder charge could be achieved with a correctly designed attritor and the contamination could be minimize d with proper selections of milling conditions. The crystalline beta-S iC powders synthesized were themselves in nanosize scale, quite differ ent from many previous studies which have shown that it is the interna l grain structure of milled powders that is the ''nanocrystalline'' co mponent of the powders (typically 5 - 20 nm), while the powders are th emselves typically 0.1 mu m to > 1 mu m in size. Furthermore, it was f ound that the product structures generated by high energy reaction mil ling depended strongly on the milling speed, the charge ratio and the milling time. Copyright (C) 1996 Acta Metallurgica Inc.