Dynamic fatigue behaviors of structural ceramics were investigated in both air and vacuum (10^-5 Torr) at room temperature. Experimental results were summarized as follows:
(1) The slow crack growth was observed in oxide ceramics and in non-oxide ceramics with oxide additives. Those ceramics did not show the slow crack growth in vacuum. In reaction bonded ceramics and ceramics with non-oxide additives and small oxygen contents, the slow crack growth was not observed in air.
(2) In air, the fatigue parameter of nonoxide ceramics which shows the slow crack growth decreased with increasing oxygen content.
(3) The slow crack growth originated from surface flaw predominated in air.
It is concluded that (1) the slow crack growth of ceramics at room temperature results from the stress corrosion induced by water vapour in air and it occurs within glassy phase at polycrystalline grain boundaries and (2) the oxygen content affects the fatigue parameter of non-oxide ceramics with oxide additives.

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The thermal decomposition of europium (III) acetate tetrahydrate has been studied by thermal analysis, X-ray diffraction, IR, gas chromatography and chemical analysis. The dehydration of tetrahydrate begins at 70°C and two unknown hydrates are produced in the process of the dehydration, which occurs in three steps. Two unknown hydrates are found to be monohydrate and hemihydrate. Anhydrous europium (III) acetate obtained by this study is a new polymorph. The anhydride slowly decomposes to europium (III) oxide carbonate above 280°C, passing through an intermediate compound. Finally, europium (III) oxide is produced. The intermediate compound shows a new X-ray diffraction pattern and is estimated to be EuOCH₃COO.

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Particle size effects on HIP sintering were studied by using three different silicon nitride powders (specific surface areas of 2.0, 4.9 and 12.0m²/g) with yttria and alumina additives up to 6mol% in total. The experimental conditions of HIP were temperatures between 1723-1973K and pressures of 60-200MPa. The influences of particle size of raw materials, additive ratio and HIP condition on the HIP sintering were investigated. The effects of specific surface area (or particle size), temperature, and pressure on the relative density of the sintered body by a specially developed dimensionless analysis were also evaluated. Within the frame of the present work the following results were obtained:
(1) HIP sintering temperature is about 7-25 times more effective than other factors by the dimensionless analysis.
(2) Increasing the specific surface area of silicon nitride from 2.0 to 12.0m²/g the sintering temperature could be lowered to about 200K.
(3) The specific surface area of silicon nitride and the HIPping pressure have almost the same effect on the achieved relative density. This implies that liquid phase sintering was dominant.
(4) The particle size of silicon nitride has a more profound effect than the additive ratio.
(5) The second important variable affecting the relative density is the specific surface area of yttria.
(6) Alumina seems to be better than yttria as sintering aid. The difference is remarkable at low sintering temperatures (below 1873K).
(7) Within the range of this study the effect of oxygen content in the raw materials is smaller than that of the particle size.

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Electroconductive sialon-titanium nitride ceramic composite was machined with the electro-discharge machining method. Surface damage caused during machining in machined members was evaluated with the three point bend test. The machined and fracture surface were observed with a scanning electron microscope (SEM). The effects of machining conditions on the surface damage were discussed. Heat treatment of machined members was carried out in air for recovering their strength. Effects of the pulse duration and duty factor on the strength of machined members were noticiable. The flexural strength of machined member increased with decreases in pulse current and duty factor. Annealing in air had a good effect on the strength of a machined member. The highest strength of machined member attained after annealing was 856MPa, which was about the average flexural strength of the original body.

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The effect of precursor salt on the sinterability and properties of Mn-Co-Ni oxide thermistors has been studied using nitrates and sulfates. The starting samples were obtained by firing the nitrates or sulfates of Mn, Co and Ni with molar ratio of 3:2:1, at 1000°. In order to pursue the differences in the two samples fired between 1000°C and 1400°C, their sinterability, phase changes during firing and complex impedance properties were investigated. When sintered at 1100°C in air, the shrinkage rate was greater with sulfate than nitrate. X-ray diffraction analysis revealed the structure change in both samples fired above 1200°C. When fired above 1200°C, phase separation into Ni-rich and Mn-rich phases was observed by EPMA in both samples, and the amount of Ni-rich phase increased with increasing temperature. When fired at 1400°C, a remarkable microstructural difference was observed between nitrates and sulfates sample. In the case of the sample prepared from nitrates, closely linked Mn-rich phase existed in Ni-rich phase matrix. On the other hand, in the case of the sample prepared from sulfates, Mn-rich phase existed isolatedly in Ni-rich phase matrix. In the Cole-Cole plots, different shape of circular paths were observed in the two samples, and the resistivity of the sample from sulfates was greater than that from nitrates. These results correspond to the results of EPMA.

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Following the previous paper on the dissolution of hydroxyapatite (HAp), the dissolution mechanism of other calcium phosphate compounds was studied for the filtrate after treating ca. 300mg of the sample powders with 0-3.0g of H-R (strongly acidic ion exchange resin, H-form) in aqueous media. Dissolved amounts of Ca, PO₄ and P₂O₇ were determined using ion chromatography and isotachophoresis. Variations of pH value and specific conductivity during the dissolution process were also measured to compare the dissolution rate. The results obtained are summarized as follows;
(1) Ca₃(PO₄)₂(TCP), Ca₈H₂(PO₄)₆⋅5H₂O(OCP), Ca₄(PO₄)₂O(TeCP) and Ca_2.67Al_0.22(PO₄)₂(β-TCP*, a solid solution of AlPO₄ and TCP) dissolve in a similar way to HAp to give Ca(H₂PO₄)₂ according to the Eq. (1) and is followed by the successive ion exchange reaction Eq. (2), for example, Ca₃(PO₄)₂+4(H-R)→Ca(H₂PO₄)₂+2(Ca-R₂) (1) Ca(H₂PO₄)₂+2(H-R)→Ca-R₂+2H₃PO₄ (2)
(2) Reaction between Ca₂P₂O₇ and H-R can be expressed by the following equation to yield a new soluble compound CaH₂(H₂P₂O₇)₂, 2Ca₂P₂O₇+6(H-R)→CaH₂(H₂P₂O₇)₂+3(Ca-R₂)

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The production technique of porous compacts of ceramics containing fine pores have been developed. The mixtures of silica ultrafine particles (pre-treated with solvents) and liquid paraffin were pressed under 300kg/cm² and then fired at 800°-920°C, and the characteristics of the compacts obtained were measured. Mixtures of ultrafine silica which was pretreated by colloidal solution of silica and liquid paraffin of large quantities gave porous compacts containing fine pores. Better results were obtained when 1-18% colloidal silica was added in pre-treatment and the firing temperature was about 850°C. Apparent porosity was 60-80% for the obtained compacts. The mean pore diameter was 0.04μm for the compacts fired at 800°C, which remained virtually with increasing firing temperature, but decreased with increasing content of colloidal silica. Specific surface area was 130m²/g for the compacts fired at 850°C, and decreased with an increase both in temperature and content of colloidal silica, respectively.

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A Zr-O-Si alkoxide complex was synthesized and its hydrolysis-condensation reaction was studied using small angle X-ray scattering. Transparent and homogeneous Zr-O-Si alkoxide solutions were formed by reacting Zr(OC₃H₇)₄ with Si(OC₂H₅)₄ hydrolyzed with one mole of water per one mole of Si(OC₂H₅)₄ and HCl catalyst, whereas the solutions hydrolyzed with NH₄OH catalyst or without any catalyst resulted in precipitation of ZrO₂ crystals. Homogeneous Zr-O-Si alkoxide solutions were hydrolyzed with 0 to 8 moles of water to metal alkoxide, whose X-ray scattering curves were analyzed in both power law and Guinier law. The synthesized Zr-O-Si alkoxide consisted of chain like polymers, which were aggregated into three dimensional branched polymers with water content up to 4 moles per 1 mole metal alkoxide and their size increased up to 65Å in the Guinier radius. However, no further changes in size and shape of aggregated polymers were observed with more than 4 moles of water.

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Surface analysis of the ceramic-steel interface joined with an active metal and brazing metal foils was carried out by SEM, TEM, EDX and XPS. The analyzed specimen was the sintered silicon nitride joined to SNCM steel by Ti metal and Ag/Cu (72/28) brazing metal.
(1) Two reaction layers were produced between Si₃N₄ and braze.
(2) A reaction layer facing Si₃N₄ (layer I) was about 300nm thick and composed mainly of titanium nitride (TiN).
(3) The other reaction layer (layer II) between layer I and the braze was composed of titanium nitride (TiN) and silicide (Ti₅Si₃). The thickness of this layer was about 3μm.

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PbTiO₃ single crystals with various quantities of added Mg²⁺ ions were grown by the flux cooling method using a platinum crucible. As-grown and poled PbTiO₃ single crystals were used for measurement of pyroelectric properties.
(1) The added Mg²⁺ ions showed no significant effects on the crystal size and yield, but affected the crystal completeness.
(2) The PbTiO₃ single crystals were reddish brown and highly transparent when the quantity of added MgO was in the range of 4000 to 6000ppm. Using a microscope to observe the domain structure, it was confirmed that the crystals are composed of multidomains consisting of 180° and 90° domains.
(3) The axial ratio and the theoretical density of the crystal decreased with increasing MgO content. Based on the data of undoped crystals, the maximum decreases in the axial ratio and the theoretical density of Mg²⁺-doped crystals were approximately 1.88% and 3.31%, respectively.
(4) From the measurement of pyroelectric constants, the pyroelectric coefficient P and the figure of merit F. M. exhibited the highest values when the quantity of added MgO was 6000ppm, reaching 2.7×10^-8C/cm²·K and 0.6×10^-10C·cm/J, respectively.

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The effect of surface treatment of Al₂O₃ powder has been studied on the moldability of mulled materials of oxide powder and resin for injection molding. Al₂O₃ powder was surface-treated by boiling with stearylamine dissolved in toluene for two hours. The amount of surface-adsorbed stearylamine was measured by thermogravimetric analysis. Comparison of wettability of treated and untreated powders for water or acetone showed that the treated powder is more lipophilic because of surface adsorbed stearylamine. Materials for injection molding experiments were prepared by mulling treated and untreated Al₂O₃ powders with polyethylene resin in a volume fraction of Al₂O₃ powder ranging from 50 to 80%. The dispersion of Al₂O₃ powder in resin was estimated from thin sections of these mulled materials with a microscope and by image-processing of the micrographs. The surface treated powder exhibited better dispersion than untreated one. Mulled materials of the surface-treated powder showed markedly large plasticity. For example, a mulled material of 50vol% of surface-treated powder showed about 10⁴ times larger plasticity than that of a material of untreated powder. Even in high powder concentrations, such as a mulled material of 80vol% of the treated powder showed 10 times larger plasticity than that of a material of 50vol% of the untreated powder.

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The temperature distribution in glass material was estimated by calculating the heat transfer in a transient state between glass and a metal mold for forming glass. It was followed by a comparison of the above-calculated data with Trier's experimental result to study any effect on the infrared-ray absorption on glass and the clearance between glass and a metal mold, with the results being is as follows:
(1) With regards to the effect of infrared-ray absorption on the cylindrical shape of glass, the temperature is low near the surface of colorless glass, but in slightly inside, the temperature is lower on green glass. In other words, temperature gradient is larger on colorless glass. This tendency accords with the result of Trier's experiment. In addition, in the center of glass, colorless glass having a smaller absorption coefficient shows a lower temperature.
(2) If the clearance between glass and a mold is supposed to remain unchanged in the result of Trier's experiment, the clearance on colorless glass and green glass is 46 and 40μm, respectively. If the calculation is conducted by varying the clearance between glass and the mold so as to match it to the results of the experiment, the clearance becomes 20-30μm 2s later, 80-90μm 4s later, 40-50μm 6s later and shows only a slight variation thereafter.

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Mechanical and dielectric strength were measured for three types of BaTiO₃ thick films prepared under the different processing conditions. In any case, Weibull moduli for both strength distributions were identical in each type of films, though they differed among three types. The results indicated that dielectric strength measurement is a promising alternative method to distinguish the structural reliability change as influenced by processing parameters before firing within the framework of the same fabrication method.

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Surface electrical resistance along the interface of acid base hetero-contact using TiO₂ or NiO substrate was measured at 20°C under controlled humidity. Humidity-sensitivity of acid TiO₂ was suppressed by the contact with basic oxides and that of basic NiO was enhanced by the contact with an acid oxide. A model in which protons transfer from acid to basic surface by acid base interaction was proposed.

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