Multiorganometallic compounds made by modifying the synthetic method studied by Thomas were used to prepare high purity submicron-size MgAl₂O₄ powders. Hydrolytic decomposition of MgAl₂(i-OC₃H₇)₈ and the subsequent calcination process produced submicron powders of MgAl₂O₄ of more than 99.98+% purity: 50Å to 100Å at 800°C and about 0.1μm at 1200°C, and with purity of 99.98+% The major contaminant was Si from silicon grease. Homogeneity and stoichiometry of the powders after calcination were studied by transmission electron microscopy and chemical analysis. X-ray and infrared analyses indicated that the formation process of MgAl₂O₄ from MgAl₂(i-OC₃H₇)₈ depends strongly on the atmosphere in hydrolysis of MgAl₂(i-OC₃H₇)₈ and the subsequent calcination temperature.

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Samples of amorphous calcium phosphate (ACP) were prepared under the conditions of various degrees of supersaturation in aqueous reaction mixtures, as measured by the solution product [Ca²⁺] [PO₄^3-]mM² before precipitation. Thermal change of ACP's precipitated from the mixtures in the solution product range of 2.5×10² to 2.5×10⁶mM² was studied by X-ray diffractometry and thermal analyses. Metastable α-Ca₂(PO₄)₂ was obtained at 600°-650°C by thermal crystallization of ACP's from the mixtures with the solution products of more than 10⁴mM². Concerning the ACP samples prepared by the rapid mixing of Ca²⁺ and PO₄^3-, the apparent activation energies for thermal crystallization of ACP and transition of metastable α-Ca₃(PO₄)₂ to β-Ca₃(PO₄)₂ depended on the solution product. From the reaction mixtures in Ca/P atomic ratio from 0.5 to 2.0 ACP's were obtained and changed into α- or β-Ca₃(PO₄)₂.

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Physical and chemical properties of silicon nitride powders treated by explosive shock wave (100kbar, 300kbar) and fine grinding were investigated by X-ray diffraction analysis and Temperature-Programmed Desorption. The surface activity of the activated-powders, as determined by the Temperature-Programmed Desorption of NH₃, was highest with 300kbar explosive shock wave followed by in the decreasing order, fine grinding and 100kbar explosive shock wave. It is shown that the fine grinding promotes fragmentation of crystallites rather than lattice strain. Explosive shock wave of 100kbar increased only the lattice strain, while that of 300kbar promoted fragmentation of crystallites and an increase of lattice strain. The specific surface area indicated that the sintering of silicon nitride powders is accelerated by the explosive shock wave. X-ray diffraction angles of Si₃N₄ decreased by fine grinding but increased by explosive shock wave. A dissolution experiment of Si₃N₄ powders revealed that the activation by fine grinding occurred near the surface layer and that the activation by explosive shock wave penetrated deeply into the bulk of powder particles.

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Absorption spectra of Ni²⁺ ions in PbO-GeO₂-R₂O (R=K or Na) and PbO-GeO₂-K₂O-Na₂O glasses were measured. The ligand field strength and the Racah parameter were calculated from the absorption wave numbers. The state of coordination of Ni²⁺ ions was elucidated from the peak positions. With increasing alkali content in FbO-GeO₂-R₂O-NiO (R=K or Na) glasses, the peak wave number corresponding to the ligand field strength increased and the-Racah parameter decreased. In PbO-GeO₂-K₂O-Na₂O-NiO glasses, the ligand field strength and the Racah parameter were not calculated. Ni²⁺ ions were considered to be predominantly in the 6 coordinated state in PbO-GeO₂ glasses. The increase in alkali content in PbO-GeO₂-R₂O (R=K or Na) glass resulted in the tetragonal and tetrahedral structures. The result obtained suggests that GeO₆^8- ions are formed by adding alkali ions to the glass network.

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Electronic ceramics, which require cofiring for metallization and sintering, are fired in a reducing atmosphere to prevent oxidation of metals. The burn-out of the organic binder in a reduced atmosphere is recognized as one of the most difficult precesses. In the first report, the firing of 92% alumina ceramics (Al₂O₃-MgO-SiO₂) with the polyvinyl butyral binder in a reducing atmosphere (H₂+N₂+H₂O) was studied referring to the mechanisms of binder burn-out, sintering of ceramics and interaction of both. In the second report, the effect of mixing condition of materials on the mechanisms of burn-out and sintering was studied. In this report, the modifications of various conditions responsible for the wide dispersion of firing shrinkage were discussed. Anisotropic shrinkage depends upon the sample size or shape, because of change on the frictional resistance between the setter and sample during firing (Figs. 7-9). As the green thickness depends upon effective air permeability (K_p/t), the increasing thickness which decreases K_p/t retards the evaporation of binder in firing, from which the wide dispersion in shrinkage results (Figs. 10, 12). Decreasing of glass-matrix volume in the final products provides the increase of K_p. To keep low glass-matrix volume, wet mixing duration combinated with dry mixing must be minimized (Figs. 14, 15). The dispersion in shrinkage decreases with increasing K_p (Fig. 13) and decreasing sample thickness.

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Sintering behavior of ZnO with and without 2mol% rare earth oxides (Y₂O₃, La₂O₃, Sm₂O₃, Eu₂O₃ and Er₂O₃) was investigated by dilatometry, microscopy and electrical resistivity measurement. Raw materials were prepared by two mixing procedures; wet mixing of ZnO with rare earth oxide, and mixing of ZnO with ethanol solution of rare earth nitrate. The addition of rare earth oxide delayed the initial sintering of ZnO. For nitrate powder the shrinkage starts 50°-100°C higher than that in oxide powder. The addition of rare earth oxide also prevented grain growth of ZnO. When specimens were fired at 1300°C for 1h, grain size of ZnO was 2-3μm and about 10μm for nitrate and oxide powders respectively, while it was 20-30μm for without additives. These results suggested that the rare earth oxide particles on the grain boundaries prevented the contact among ZnO grains and thus suppressed both initial sintering and grain growth of ZnO and that this tendency was more effective for nitrate powder than oxide powder because of difference of dispersion of rare earth oxide. In specimens with relative bulk density lower than 80%, the room-temperature resistivity decreased exponentially with an increase of bulk density. In specimens with higher bulk densities, the electrical resistivity was proportional to the number of grain boundaries between electrodes. The calculated electrical resistivity per grain boundary was about 0.3Ω.

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Reaction bonded silicon carbide (RB-SiC), which is electroconductive and containing free silicon, was machined by electro-discharge machining (EDM). The electric resistance of the workpiece was 0.08ohm·cm. Pure copper was used as a positive tool electrode. It is shown that RB-SiC is able to be machined without surface cracking, if the pulse current is limited to small amperage. When the pulse duration was more than 100μs and the pulse current was under 9A, the wear of the tool electrode was negligible. Thus, the precision machining can be achieved by EDM. The surface roughness after machining decreased with the decrease in both pulse current and pulse duration. However, many small open pores, formed by vaporization of free Si, remained at the surface after machining with a low energy single pulse. Therefore, it was difficult to obtain the surface roughness smaller than the average diameter of SiC crystals.

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The surface hydroxyl groups on porous glasses pretreated at various temperatures was determined by the successive-ignition-loss method and by means of active hydrogen analyses, and their hydroxyl groups have been classified into two types (isolated and gem type OH groups). The surface of the porous glass consists of three types of OH groups, isolated, gem type and H-bond OH groups. The isolated OH groups were stable up to 500°C, but the elimination of these groups took place gradually above 500°C. On the other hand, the gem type and H-bond OH groups were removed rapidly below 600°C and disappeared above 800°C. The surface of porous glass pretreated at 800°C for 4h contained only isolated OH groups, and the concentration of the isolated OH groups was found to be about 0.7OH's/100Ų. For water vapor adsorption, the surface OH groups play an important role as adsorption sites, and water molecules are adsorbed more strongly on gem type or H-bond OH groups than on isolated OH groups. In porous glass, the ignition-loss method was inadequate to determine the amount of surface OH groups, since water molecules diffused from inside the glass to its surface during heat treatment.

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The relationship between heat-treated adsorbent and its adsorption behavior is studied by using crystalline hydrated titania, H₂Ti₄O₉⋅nH₂O and H₂Ti₂O₅⋅nH₂O fibers. The adsorption behavior of uranium from sea water was observed by using the adsorbents heat-treated at various temperatures, and was compared with that of cesium and strontium from aqueous solutions to find the adsorption mechanism. The fibrous H₂Ti₂O₅⋅nH₂O adsorbent heat-treated at 300°C gave the uranium uptake of 45.8μg/g in maximum after 5 days. The uranium uptake was independent on the exchangeable protons in interlayers, and was maximum on a most disordered intermediate phase during structural modification by heat-treatment. Anatase fibers modified by heat-treatment above 500°C gave the uptake of 25μg/g under the same conditions. The adsorption behavior of cesium and strontium is different from that of uranium, because the uptake of them decreases with the increase of heat-treatment temperature.

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The distribution coefficients for alkaline earth metal ions on heat-treated crystalline hydrated titania fibers were determined as a function of pH at 25°C. The exchange behavior of these ions was well explained by their ion-exchange reaction with hydrogen-ion in the fibers. The ion-exchange ability of these fibers was not affected when these fibers were heat-treated between 25°C and about 70°C, but the value of distribution coefficients decreased when the heat-treatment temperature exceeds 80°C. This behavior is related to the change in the interlayer distance of crystalline hydrated titania.

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