Grain boundary strength in porous SiC ceramics measured using microcantilever beam specimens

Reference Presenter Authors
09-083 Junichi Tatami Tatami, J.(Yokohama National University); Iijima, M.(Yokohama National University); Takahashi, T.(Kanagawa Industrial Institute of Science and Technology); Imoto, Y.(Yokohama National University); Yahagi, T.(Kanagawa Industrial Institute of Science and Technology); Porous SiC ceramics are used for diesel particulate filter. Their higher strength is desired to improve the thermal shock resistance. Because they are usually broken from the grain boundary of a neck, the grain boundary strength should be a dominant factor of the strength of the porous ceramics. In this study, we directly measured the grain boundary strength of a neck in porous SiC ceramics using microcantilever beam specimens. Porous SiC having particle size of about 10 mm was used in this study. Microcantilever beam specimens were made by the focused ion beam technique. Their width, thickness and length were about 1, 3 and 10 μm, respectively, and the section profile was pentagonal. A grain boundary existed at the end of the microcantilever beam specimen. Bending test was carried out to measure the fracture load using a nanoindentor. The fractography showed that the fracture in the microcantilever beam specimens occurred in the grain boundary, which means that the measured strength should be the grain boundary strength. The measured bending strength was 18.8 GPa, which is much higher strength than the bending strength of the dense and porous bulk SiC ceramics. The strength of the porous SiC ceramics was quantitively explained by the grain boundary strength of a neck, pore size, neck radius and its size effect in the Weibull distribution.
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