希土類酸化物を伴った炭化ケイ素の液相焼結と力学特性

概要

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A SiC powder of median size 0.8 μm was mixed with polyacrylic acid (PAA, dispersant) in a 0.3 mol/l-R(NO_3)_3 solution (R=Yb, Y, Gd, Sm, Nd and La) at pH 5 to adsorb uniformly the sintering additive (R^<3+> ion) on the SiC surface. The aqueous 30 vol% SiC suspension with 0.52 mass% PAA and 1.50 mass% R_2O_3 (as R(NO_3)_3), relative to SiC, was consolidated by filtration through a gypsum mold to form green compacts of 50-52% of theoretical density. The consolidated green compacts were densified with grain growth to 76-99% relative density by hot-pressing under a pressure of 39 MPa at 1950℃ for 2 h in an Ar flow. The addition of R_2O_3 of smaller R^<3+> ion was effective to enhance the sinterability of SiC and also to achieve smaller grain size of SiC. This result was discussed based on the additional experiment result on the chemical interaction between SiC compact and the SiO_2-R_2O_3 liquid. The average flexural strength and Weibull modulus of dense SiC were 612 MPa and 5.1, 719 MPa and 6.7, and 731 MPa and 9.8 for Gd_2O_3, Y_2O_3 and Yb_2O_3 addition, respectively.
社団法人日本セラミックス協会の論文
2006-03-01