Formation mechanism of facture origin in alumina ceramics and suppression of strength variation through novel characterization method

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The aim of the research is to clarify effects of processing factors on the formation of fracture origins in alumina ceramics made through the compaction processes. Very important conclusions obtained in the study are as follows.The raw powder contains coarse particles, which can not be eliminated by conventional processing route, forming fracture origins in high performance alumina ceramics. Dispersion of powder in slurry affects the characteristics of granules, and thus the structure and the formation of fracture origins as well as the deformation in sintering. Forming conditions, especially the moisture affects the structures and properties of ceramics. CIP treatment can be detrimental in the deformation of products. Novel examination on machining flaws as well as structure flaws shows that strength of ceramics are very well explained by these flows. The well-known empirical relationship between the grain size and strength of ceramics can be quantitatively explained from the size distribution of flaws in ceramics.New characterization tools were also developed to conduct the research. They include, confocal laser scanning fluorescent microscopy, liquid immersion infrared microscopy, and quantitative analysis of particle orientation by the liquid immersion polarized light microscopy.In conclusion, the research was successfully competed with many new findings on the formation mechanisms, mechanisms of deformation as well as various new characterization tools, which will be a solid foundation for the development of reliable ceramics in the future.