The existence of hydroxide ion and inner water of colloidal calcium carbonate was confirmed, and those properties were investigated. It was confirmed that one particle of the colloidal calcium carbonate was a solitary crystal of the calcite from the TEM observation and the ED measurement. A surface hydroxide ion, a crystal internal hydroxide ion, and crystal inner water were evaluated from the FT-IR measurement and the XRD measurement. As a result, the following conclusions were obtained. It was confirmed that a surface hydroxide ion and crystal inner water existed in colloidal calcium carbonate. It has been realized that the surface hydroxide ion is a free type hydroxide ion without hydrogen bond among them. Moreover, it was suggested that the surface hydroxide ion be a base property from exchange adsorptivity.

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The bone repair material strongly required porous calcium phosphate cement with pore diameters of above 100, um for the introduction of osteoblast in vivo. The present work dealt with the preparation conditions of porous calcium phosphate cement by adding calcium carbonate (CaCO₃) as a foaming agent to the mixtures of amorphous tricalcium phosphate (ATCP) -hydroxyapatite (HAp) -citric acid-chitosan. The porous cement was prepared under the following conditions : the liquid/solid weight ratio, 1.0-1.6; HAp wisker/ ATCP weight ratio, 0.4; CaCO₃/ATCP molar ratio, 0.34; citric acid solution, 2.0 mol dm^-3, and the amount of chitosan, 4.0 mass%. The products were characterized by X-ray diffractometry, thermal analysis (TG-DTA), the measurement of pore size distribution annd scanning electron microscopy (SEM). The compressive and bending strengths were improved with increasing amount of chitosan in cement. In addition, the large pores were created by adding CaCO₃. The optimum conditions for the preparation of porous cement having pore diameters of above 100, μm were as follows : the liquid/solid weight ratio, 1.5; the amount of chitsan, 4.0 mass%; and CaCO₃/ATCP molar ratio, 0.09. The main products after hydration were octacalcium phosphate (OCP) and dicalcium phosphate dihydrate (DCPD). The addition of CaCO₃ promoted the formation of large pores and crystallization from ATCP.

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In case of extrusion moulding of particle reinforced cementitious materials, the stress condition of shear stress and extruding pressure in tapered barrel is required to predict extrusion characteristics of it under various material conditions and machinery ones. In the first place, experiments with various kinds of substances and mix proportions were carried out, and extruding pressure and single shear characteristics, namely cohesion and coefficient of internal friction as two indicators were obtained. From the relationships between shear stress and extruding pressure, plastic processing law under a constant machinery condition was clarified. Secondly, the similar experiment was carried out with various kinds of die opening geometries as machinery condition. The concept of effective thickness was adopted as the evaluation method of plastic processing. The results of experiments lead to propose a comprehensive plastic processing law. It was verified that extruding pressure under various conditions of materials and machine could be estimated through this new law.

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Seven kinds of the spinel (MgAl₂O₄) -zirconia (ZrO₂) composite powders were prepared by an ultrasonic spray pyrolysis. The aqueous solutions (100 cm³) containing 0.100-0.200mol·dm^-3 Mg (NO3) ₂, 0.200-0.400mol·dm^-3 Al (NO3) 3, 0.0108-0.0970 mol·dm^-3 ZrOCl₂ and 6.67×10^-4-6.00×10^-3 mol·dm^-3 YCl₃ were spray-pyrolysed at 900°C. The molar ratio of MgO to Al₂O₃ was 1, 00 and that of Y₂O₃ to (ZrO₂+Y₂O₃) was 0.03. The powders calcined at 900°C for 10 min contained spinel and tetragonal zirconia polycrystals (TZP).The spinel compacts with various TZP contents were fired at 1700°C for 10 h. The relative density of the spinel compact was reduced down to 51.1% with TZP content up to 48.51 mol%. The sintered spinel compact with TZP of 48.51 mol% was composed of the grains with an average size of 4.6 μm and pores with an average size of 7.4μm. The open and closed porosities of this sintered compact were 22.8% and 26.1%, respectively.

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Solid solutions containing aniline between phenylphosphonate zirconium and zirconium phosphate, Zr [(O₃PC₆H₅) _x (O₃POH) _2-x] _yC₆H₅NH₂·nH₂O, were prepared under the hydrothermal conditions. Crystallinity and specific surface area of the products were improved much by the addition of aniline and organic derivatives of zirconium phosphate with specific surface area > 200m²·g^-1 were obtained. The products were also found to have higher selectivity to oxygen than that to nitrogen, unlike zeolites and active carbons.

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