膨張黒鉛のミクロ空隙を利用したサブミクロンβ-SiC微粉末の合成

抄録

A process to synthesize fine β-SiC particles was developed utilizing microspaces of exfoliated graphite (EG). Two types of low molecular weight silicone and a catalyst were dissolved into a silicone oil and they were impregnated into EG by sorption, and then heated in air to cure the compounds. Formed precursors were black flakes of a few millimeters in diameter. Only by the heat treatment of precursors at 1500℃ for 5 h or at 1550-1600℃ for 1 h in Ar, β-SiC of a few tens to hundreds nanometers in size was obtained. In the present process, EG plays two important roles; one is as reaction spaces and the other is as a reductant that functions at elevated temperatures. Initially the cured silicone is coating the graphite sheets of EG as thin films of less than 1μm, and above 1300℃ they start to decompose and form small particles of a few tens to 100 nm in diameter on the graphite sheets. These intermediate particles are composed of the Si-C-O composites and SiO₂ and they spontaneously decompose to β-SiC from around 1400℃, and between 1400 and 1500℃ the reduction of remaining intermediates by graphite sheets occur and form well crystallized fine β-SiC particles. In the present work, further development of the process was made: (1) solventless preparation of precursors was found to be possible, (2) finer particles were obtained by either grinding the precursor prior to the heat treatment or preparing the precursor using shorter chain-type silicone compound, and (c) the yield of β-SiC increased up to 41% by curing silicone compounds at lower temperature and shorter period. The process is simple and raw materials are not expensive so that it is promising for industrial applications.