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Sintering behavior of large size, Sm-doped ceria solid electrolyte disk
Yoshihiro Hirata,Yukio Yoshimura,Soichiro Sameshima,Hidekazu Sueyoshi,Toshiya Doi,Teruhisa Horit 한양대학교 세라믹연구소 2004 Journal of Ceramic Processing Research Vol.5 No.4
The sinterability of a submicrometre-sized Sm-doped ceria solid solution powder(SDC, powder A) with a composition of Ce0.8Sm0.2O1.9 and a mechanically mixed submicrometre-sized Sm2O3-CeO2 powder (powder B) was studied at 1300-1550 oC in air in order to make a practical solid electrolyte disk of 150 mm diameter. No phase change was observed in powder A heated at 600-1550 oC. The Sm2O3 component in powder B dissolved into the CeO2 powder at temperatures above 1500 oC. The sinterability of powder A was higher than powder B. The formation of SDC in powder B at 1500-1550 oC enhanced the sinterability. No cracks and no warps were observed in the small (10 mm diameter) and large (150 mm diameter) disks after sintering at 1300-1550 oC. The uniformity of microstructure was higher for the disk from powder A than from powder B.
Hot-pressing and mechanical properties of SiC ceramics with polytitanocarbosilane
Yoshihiro Hirata,Nobuhiro Hidaka,Soichiro Sameshima,Hidekazu Sueyoshi 한양대학교 세라믹연구소 2004 Journal of Ceramic Processing Research Vol.5 No.4
An SiC power of median size 0.8 µm was mixed with an Al2O3 powder of median size 0.2 µm in a 0.3 M-Y(NO3)3 solution at pH 5 to distribute homogeneously the sintering additives (Al2O3+Y3+ ions) around the SiC particles. In a 30 vol% SiC suspension, the network structure of SiC particles was formed by the heterocoagulation through the adsorbed Al2O3 and Y3+ions. The aqueous suspension of the SiC-Al2O3 (1.17 vol%)- Y3+ ions (0.94 vol% Y2O3) system was consolidated by filtration through a gypsum mold and formed green compacts of 52-55% of theoretical density. Polytitanocarbosilane (PTC) of 0.04-5.2 vol% was infiltrated into the calcined SiC compact. The SiC compacts with and without PTC were hot-pressed under a pressure of 39 MPa at 1950oC in an Ar atmosphere. Addition of PTC to the SiC compact increased the sinterability, flexural strength and fracture toughness of SiC and suppressed the grain growth during the hot-pressing. The measured mechanical values of SiC with 1.3 vol% PTC were as follows: average four-point flexural strength 711 MPa, fracture toughness 5.9 MPa·m1/2, Vickers hardness 19-21 GPa, and Weibull modulus 12.5.