To obtain a composite material having enhanced mechanical properties such as thermal shock resistance, breaking strength, hardness, elastic modulus and machinability by sintering silicon carbide power surface-coated with t-BN in such a way that a specified vol.% of h-BN is uniformly dispersed in the grain boundaries or grains of a formed silicon carbide matrix.
Urea and boric acid as sources of BN are dissolved in a solvent and intimately mixed with clean SiC powder, the solvent is removed by drying and reduction treatment is carried out under heating in a reducing atmosphere to form a t-BN(turbulent layer structure BN) coating. A sintering aid is optionally added to the SiC powder surface-coated with a fine h-BN precursor and they are mixed, dried and sintered. The h-BN precursor is converted into h-BN and 5-50 vol.% fine h-BN particles having ≤400 nm average particle diameter are uniformly dispersed in the grain boundaries of a formed SiC matrix or in the grain boundaries and grains to inhibit the grain growth of SiC in sintering.
KUSUSE HISAFUMI
KAWASE TAKESHI
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