| Ultrafine β-SiC powders have sucessfully synthesized from industrial silica sol and carbonblack by sol-gel method.The powders contained SiC up to 98%, showed spheric particles and narrow size distribution,had a mean size about 0.10.2μm and were not or soft agglomerate. When boronic acid or boron powder was introduced into silica sol, a β-SiC/B composite powder was obtained by the same method.This powder is sinterable without additional additives.The thermodynamic and kinetic investigations about the mechanism of SiC synthesis have carried out. Results showed that free energy enthalpy (ΔGT°) was limited to explain the synthetic process of SiC powders in the system of Si-O-C, as the real temperature of SiC yielded was lower than that calculated from (ΔGT°). Author has explained the thermodynamic process in the view of vapour equilibu-lium pressure in the systeym.Kinetic process was discussed according to the determination of SiC yield and observation of TEM micrographs of powders synthesized at differert temperatures. Mechanism was suggested about the synthesis of SiC powders. The main factors affecting the properties of SiC powders and idea technique have been reported.When boron resource was introduced into the synthetic system,the starting temperature of SiC yielded decreased resulting from the decrease of the active energy in the system. It has been found that boron developed the growth of β-SiC particles and limited the formation of α-SiC phase.The state of B existed in β-SiC powders has inverstigated with the help of X-ray diffraction and IR spectra analysis.Results showed that B entered into the lattice of SiC by means of exchanging with Si. In other words, a SiC-B4C solid solution was formed in β-SiC/B powder.Al, B and C were used as sintering adds for hot-pressing of SiC powders in the present paper. Sintering mechanism, properties and microstructures of HP-SiC bodies prepared from different SiC powders have been widely researched by variying additives and temperatures.
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