SiCウイスカー/Si_3N_4複合セラミックス・ホットプレス体の室温機械的性質の異方性

概要

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The anisotropies of the mechanical properties of SiC whisker (SiC(w))/Si_3N_4 composite ceramics prepared by hot pressing under 15 MPa at 2073 K for 7.2 ks were investigated by using three kinds of specimens (VV, PV, PP), in which the tensile surface and longitudinal axis are vertical (V) or parallel (P) to the hot press direction. The results were compared with those of hot-pressed Si_3N_4 monolith (M) and SiC(p)/Si_3N_4 composite ceramics (P). The results obtained were as follows; (1) Both the flexural strength (FS) and fracture toughness (K_<IC>) of the composites were nearly the same for VV and PV specimens, and the properties of PP specimens were fairly lower than those of VV or PV specimens. The higher the aspect ratio of SiC(w), the larger the anisotropy of K_<IC>. The anisotropies of K_<IC> of the composites were larger than those of M and P ceramics. For both composites and monolith, the anisotropy of hardness was very small in comparison with those of FS and K_<IC>. (2) The anisotropy of mechanical properties of the SiC(w)/Si_3N_4 composites was ascribed to the orientation anisotropies of acicular β-Si_3N_4 grains as well as of SiC(w). (3) The anisotropy of FS was larger than that of K_<IC>, which was attributed to the larger size of the fracture source of PP specimens.
社団法人日本セラミックス協会の論文
1992-11-01