SiCウイスカー/Si_3N_4複合セラミックスのSi_3N_4粒度と破壊靱性に及ぼす希土類系酸化物焼結助剤種の影響

概要

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In order to find the sintering aids for obtaining SiC whisker (SiC(w))/Si_3N_4 composite ceramics with high fracture toughness, the effect of nine rare earth oxides on the β-Si_3N_4 acicular grain size in the monolith was investigated in the first step. In the second step, the fracture toughness of SiC (w)/Si_3N_4 composite ceramics with addition of main four rare earth oxides was investigated in relation to the Si_3N_4 grain size. It was found that the Si_3N_4 grain size in the monolith was largely affected by the chemical species of rare earth oxides and that the order of the grain size was expressed as follows; Y_2O_3>Er_2O_3 ≃ Dy_2O_3>pr_2O_3>Sm_2 O_3 ≃ Gd_2O_3>Tb_4O_7>Nd_2O_3>MgO>Eu_2O_3. The Si_3N_4 grain size in SiC (w)/Si_3N_4 composites was nearly equal to that in the corresponding monolith with the same sintering aid, and the values of K_<IC> of the composites were higher for larger β-Si_3N_4 grains than for the smaller β-Si_3N_4 grains, in the same manner as the monolith.
1992-07-01