Development and characterization of new ceramics.

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Collaborative research on development and characterization of new ceramics has been carried out by our group and the group of Prof. O'Connor in Curtin Univ. of Tech. in Australia. For collaborative experiments and discussion, mutual visits were held eight times. The main results of the research are as follows : On partially stabilized zirconia ceramics containing ytria, tetragonal to monoclinic phase transformation during isothermal aging was intermittently observed using an atomic force microscope, which showed that the transformation occurred at grain boundaries, and propagated to the gram interior, and the spread to the neighboring grains. Addition of small amount of alumina improved mechanical property (K_<IC>), which is believed to be due to amorphous layer formed at gram boundaries. From analyses of X-ray diffraction patterns and collaborative discussion, Predominant, crystal planes formed in sintered and then aged zirconia specimens differed from those formed in powder zirconia. New ceramic, Ti_3SiC_2, having unusual electrical, thermal and mechanical properties was prepared by me group in Curtin Univ. Texture analyses and microstructural observations using high resolution electron microscopes in Himeji Institute of Technology were carried out and the microstructures in Ti_3SiC_2 have process. The ceramics showed high strength in the surface layer and high toughness in the interior region.