コロイドプロセッシングによるムライトマトリックス複合材料の合成

概要

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CVD-processed ultrafine mullite powder (<0.1μm)-micrometer size Si_3N_4-whisker or mullite-whisker were dispersed in H_2O-C_2H_5OH-C_3H_8O_3 with a low surface tension at pH 4.0 to prevent cracking during drying of wet green compacts consolidated by filtration. The rheological behavior of suspensions, consolidation process of the solids by filtration, and the pore structures of green compacts were studied to understand the formation of crack-free dense powder compacts with uniformly dispersed whiskers in the nanometer size matrix mullite. The crack-free powder compacts were hot-pressed at 1500℃ for 1 h at 10 to 39 MPa in N_2 atmosphere or pressureless-sintered at 1600° to 1650℃ for 4 or 10 h in air or vacuum. The monolithic mullite (99.9% T.D.) and 10% mullite-whisker-added mullite (91.2% T.D.) with the average strengths of 468 MPa and 242 MPa, respectively, showed little degradation of strength at 1300℃. The composite with 10 vol% Si_3N_4-whisker (99.8% T.D.) showed a high average strength (632 MPa) at room temperature, while the strength decreased to 341 MPa at 1300℃. The fracture toughness (1.68 MPa・m^<0.5>) of the monolithic mullite was increased to 2.94 MPa・m^<0.5> by the addition of 10% Si_3N_4-whisker.
社団法人日本セラミックス協会の論文
1992-04-01