MgO based nanocomposites including ferromagnetic iron particle dispersions, with a volume content <40vol%, were fabricated by a reduction/sintering of MgO and iron oxide powder mixtures. The oxide powder mixtures were prepared by solution chemical processes to obtain a suitable microstructure of ceramic/metal nanocomposites. Iron-nitrate as a source of metal dispersion was dissolved into alcohol and mixed with MgO powder. After calcination in air, the iron oxide in the powder mixture was reduced by hydrogen. Dense nanocomposites were obtained by pulse electric current sintering (PECS) process. Phase analysis of the synthesized powders as a function of calcination temperature and reduction process was carried out using a system for thermogravimetry and differential thermal analysis (TG-DTA), concurrently with X-ray diffraction (XRD) analysis. According to this preparation process, an MgO/Fe nanocomposite material with enhanced fracture toughness and ferromagnetic responses was successfully fabricated.

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The structural and ferroelectric properties of new compounds (Pb_1-X²⁺La_2X/3³⁺)₅Nb₁₀O₃₀ (X=0.00-0.50) were studied with respect to La³⁺ ion substitution of Pb²⁺ ion in Pb₅Nb₁₀O₃₀ having the orthorhombic tungsten bronze structure. Phase identification shows that the structure of compounds will change from orthorhombic to tetragonal symmetry along with the increase of La³⁺ amount. The co-existence of two ferroelectric phases between 0.20<X<0.30 was confirmed by XRD analysis. Result of dielectric measurement also reveals the dielectric abnormality in this narrow compositional area, i.e., a rapid change of both the Curie temperature and the dielectric constant. In addition, the hysteresis loop measurement suggests that it also has significantly improved polarization properties. This set of evidences implies that the new compounds (Pb_1-X²⁺La_2X/3³⁺)₅Nb₁₀O₃₀ show a morphotropic phase boundary (MPB) between 0.20<X<0.30.

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Highly dispersive loading of Y³⁺ ions, as a sintering aid, on Si₃N₄ powder via aqueous processing has been presented. The chemical stability of Si₃N₄ powder in pressured and saturated water vapor was improved by a chemical surface modification with dicarboxylic sebacic acid, while maintaining hydrophilic surface. The treatment of the sebacic acid-modified powder with yttrium acetate tetrahydrate resulted in strong immobilization of Y³⁺ ions at a highly dispersive level on the Si₃N₄ powder surface through ion-exchange with the free carboxyl groups of the sebacic acid molecules attached to the Si₃N₄ surface. The highly dispersive sintering aid promoted hot-press densification of Si₃N₄ even with a small loading amount, in comparison with materials added with Y₂O₃ powder as a sintering aid.

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A screening field at or below which 30% of the titania samples broke electrically was applied to titania ceramics with differently finished surfaces. After high-voltage screening, the survived samples were subjected to three-point bending strength measurement, and the resultant strength distribution was compared to the original distribution. After screening, the Weibull plots of the samples placed rough face down became a convex curve, while plots in the high strength region remained unchanged, indicating that weak samples were selectively eliminated by the high-voltage screening. On the other hand, the apparent screening effect on samples placed with the rough face up was very small. There was a correlation between the mechanical and dielectric strengths, with a correlation coefficient of 0.62 in the former case and 0.3 in the latter case. Surface cracks induced by grinding are thought to act both as fracture origins and as a cause of dielectric breakdown when located on the tensile side. However, surface flaws located on the compression side do not act as fracture origins, but are the starting point of dielectric breakdown.

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Compact bodies of α-alumina with an average particle size of 0.22μm were hot-pressed at heating rates of 5 and 500°C/min. A specimen with a relative density of 99.5% was obtained with adopting a heating rate of 500°C/min up to 1310°C, for a holding time of 2min under a uniaxial pressure of 50MPa. The average grain size was 1.5μm. Both densification and grain growth were enhanced by rapid heating. A rationale for this result was given under the assumption that an increase in defect concentration in the alumina grains was produced by rapid heating.

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Solid solubility of SnO₂ in In₂O₃ was investigated in the interval between 1000 to 1500°C. Samples were prepared using In₂O₃ powder and tin alkoxide solution, as well as mixed solution of indium and tin alkoxides. X-ray diffraction analysis revealed a solubility limit of SnO₂ in In₂O₃ 0.5, 2, 3.5, and 5% at 1000, 1300, 1400 and 1500°C, respectively. The densities of the solid solutions agreed with calculations based on interstitial oxide ions as a resultant defect. Rietveld analysis revealed that the low solubility of SnO₂ was due to the smaller size of the interstitial sites compared to the ionic radius of the oxide ion.

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High-speed laser drilling using low laser power and flexible circuit layout changes was applied to form 3-dimensional circuits in multilayer ceramics to fabricate miniaturized chip inductors and high-frequency power amplifier modules. The optimized combination of pulse YAG laser energy and the laser absorption coefficient of machined materials enabled ultra-fine through-holes to be formed in thin ceramic green sheets without damaging supporting plastic film where ceramic slurry was cast. Drilling basically involved thermal ablation

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The existence of a liquid-liquid miscibility gap in Fe₃O₄-SiO₂ system has been reported. In this study, phaseseparated glasses of 5Fe₃O₄⋅95SiO₂ (mol%) were prepared by melting sintered rods of the same composition at 1800°C (in immiscible region) using an infrared imaging furnace and, subsequently, quenching with elongation of the melts at a constant rate. The glass quenched without elongation exhibited a binodal type phase separation texture consisting of discrete spherical Fe₃O₄-rich particles. On the contrary, in the sample quenched with elongation, Fe₃O₄-rich particles were stretched and oriented along the direction of elongation. The length of the stretched particles was proportional to the elongation distance and was not independent of the elongation rate within short elongation distance. However, the stretching of the particles was less pronounced for the long elongation ranges. This suggests that the spherical particles grown by phase separation in the binodal region, were stretched by viscous flow in the early stage of elongation and the stretching in the latter stage was reduced by restoration due to viscoelastic behavior and/or to a steep increase of viscosity. The deformation and orientation of phase separation texture could be achieved in this process, though this deformation proceeded under non-equilibrium conditions. Therefore, the operated elongation process of two-liquid immiscible melts may enable one to fabricate high-functional composite materials owing to morphology control of phase separation texture.

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The behavior of Al₈B₄C₇ in CO(g) and its effect as an antioxidant in both Al₂O₃-C and MgO-C have been investigated, and the corresponding mechanisms have been discussed. Al₈B₄C₇ markedly inhibits the oxidation of the carbon-containing refractories. The added Al₈B₄C₇ reacts with CO(g) quickly above 1400°C to give B₂O₃. The B₂O₃ further reacts with MgO or Al₂O₃ in the refractories to form Mg₃B₂O₆ or Al₁₈B₄O₃₃. Mg₃B₂O₆ is stable till 1400°C in air, but Al₁₈B₄O₃₃ begins to decompose above 1300°C. Al₈B₄C₇ is more effective as an antioxidant in MgO-C refractories than in Al₂O₃-C refractories, due to the different stability characteristics of Mg₃B₂O₆ and Al₁₈B₄O₃₃.

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The surface of alumina and silica-alumina fibers was coated with ceria to avoid the sintering between the fibers and alumina matrix and to promote the pull-out of fibers in the oxide fibers/alumina matrix composites. A cerium nitrate solution of 0.25-0.50M at pH 2.0-6.0 was infiltrated into the spaces of woven fabric of the oxide fibers. The infiltrated cerium nitrate was thermally decomposed at 400°C in air to form a cerium oxide layer. No reaction was observed in the X-ray diffraction patterns for the alumina-ceria system at 1300-1500°C. In the alumina-silica-ceria system, α-alumina, mullite (3Al₂O₃⋅2SiO₂) and ceria coexisted at 1300-1500°C in air. The ceria-coated alumina fabric was immersed in a well-dispersed alumina suspension of 15-25vol% solid to form the alumina matrix. The treated fabric of 16 sheets was hot-pressed at 1200°C to produce a dense composite of ceria-coated alumina fiber (47.5-56.6vol%)/alumina matrix (43.4-52.5vol%) with 98.4% of theoretical density. These composites fractured in the absence of plastic deformation.

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The thermal softening behavior of poly (phezylsilsesquioxane) (PhSiO_3/2) and poly (benzylsilsesquioxane) (BnSiO_3/2) particles during heat treatment has been investigated from the results of gel permeation chromatography, thermal and structural analyses of the particles. Both PhSiO_3/2 and BnSiO_3/2 particles thermally softened, and the on-set temperature of thermal sintering was about 140 and 50°C for PhSiO_3/2 and BnSiO_3/2, respectively. The thermal sintering of the PhSiO_3/2 and BnSiO_3/2 particles was caused by the decrease of viscosity at temperatures higher than the glass transition temperatures. Glass transition was observed for BnSiO_3/2 in the repeated heating runs, while for PhSiO_3/2 glass transition was appreciable only in the first heating run. From ²⁹Si nuclear magnetic resonance spectra, the development of siloxane network during heat treatment was found to be more significant in PhSiO_3/2 than in BnSiO_3/2. The difference in the structural evolution during heat treatment makes PhSiO_3/2 particles thermosetting and BnSiO_3/2 ones thermoplastic.

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This paper reports about synthesis and fluorescence properties of Ce³⁺ and Mn²⁺ codoped calcium carbonate phosphor emitting by black light irradiation. Ce³⁺ and Mn²⁺ codoped vaterite phosphor was synthesized with liquid phase reaction by adding 0.10mol·dm^-3 (NH₄)₂CO₃ solution into 0.10mol·dm^-3 CaCl₂ solution including Ce(NO₃)₂ and MnCl₂ at 35°C. The optimum excitation wavelength of Ce³⁺ doped vaterite phosphor with Ce/Ca atomic ratio 0.006 was observed at 322nm. The emission wavelength of the vaterite phosphor excited with 322nm light was 367 and 385nm in the near ultraviolet radiation region. The emission of Ce³⁺ and Mn²⁺ codoped vaterite phosphor excited with 322nm light was observed about 640nm and the emitted color was red emission. The largest emission was observed to the vaterite phosphor prepared from synthetic conditions of (Ce+Mn)/Ca atomic ratio 0.058 and Mn/(Ce+Mn) atomic ratio 0.67.

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In order to evaluate statistical characteristics of both static and cyclic fatigue strength in HIP and normal sintered silicon nitrides, namely toughened Si₃N₄ and SN1, load, P-increasing (quasi-static loading) test and load range, ΔP-increasing (cyclic loading) test were conducted in the room air. Acoustic emission (AE) method was attempted during the fatigue tests for the toughened Si₃N₄. The SN1 exhibited static fatigue behavior, while the static strength of the toughened Si₃N₄ was independent of time, i.e., no static fatigue. However, cyclic fatigue behavior appeared in the both materials. ΔP-increasing tests with different initial value of maximum stress, σ_{max, i}, enabled to evaluate cyclic loading condition under which fatigue damage nucleated. The result suggested that σ_{max, i} influenced on the maximum stress at failure, σ_{max, f}, for statistically weak specimens in the both materials, and thus fatigue damage was nucleated at lower stress levels for these specimens. Although this behavior could not be confirmed by AE analysis, AE waveform simulation revealed that the crack volume nucleated under the cyclic loading were smaller than those under quasi-static loading. Based on the above results, observation of fracture surfaces and finite element analysis, the fracture mechanisms of static and cyclic fatigue were discussed in detail.

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We investigated the relation between cathode performance and the thermodynamic stability of the spinel Li_1+xMn_2-xO₄ (x=0-0.1) as a cathode active material for lithium secondary battery. The Mn valence was controlled by annealing conditions or changing the Li content. The heats of dissolution of the samples were measured by the solution calorimetry method. The standard enthalpy of formation, Δ_fH°, and the enthalpy change of reaction, ΔH, were calculated from the heat of dissolution. Δ_fH° and ΔH decreased and Mn valence increased with increasing Li content or higher P_O2 annealing treatment, leading to a good cycle performance in spite of a moderate decrease of initial capacity.

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SiC/SiC composites have been considered one of the attractive materials for high temperature structural applications. The fabrication processes for SiC/SiC composites are typically divided into four types, which are chemical vapor infiltration (CVI), precursor impregnation and pyrolysis (PIP), hot pressing (HP) and reaction sintering (RS) method. Particularly, PIP and RS methods have capability for making near-net complex shapes. In this work, the microstructure characteristics of two SiC/SiC composites, which were fabricated by PIP and RS processes, were evaluated using the mercury intrusion method. The influence of their microstructural feature on some properties, such as bending strength, thermal conductivity and oxidation resistance, were discussed.

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The reactions of Y₂SiO₅-SiC and Y₃Al₅O₁₂-SiC in Y₂SiO₅/RBSiC layered composites were investigated with regard to gas generation in the interface regions. In these composites, Y₂SiO₅ and Y₃Al₅O₁₂ were found to have existed as grain-boundary phases in SiC in a 300μm thick layer from the interface. From the results of thermal analysis of Y₂SiO₅-SiC and Y₃Al₅O₁₂-SiC mixed powders and mass analysis of gases generated from the layered composite during heating to 1500°C, it was found that both grain-boundary phases reacted with SiC to generate the gases. This gas generation brings about void formation at the interface, which lead to exfoliation of the layer. Therefore, these reactions between grain-boundary phases and SiC are responsible for limiting the heat resistance of the Y₂SiO₅/SiC layered composite.

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Hydroxyapatite (HAp) was sprayed onto titanium substrates in argon-hydrogen thermal plasma or onto titanium (IV) oxide substrates in argon-oxygen thermal plasma. In the latter case, no adhesive strength by a tensile test could be measured because of high fragility of the titanium (IV) oxide. Comparison of the width of peeled-off layers by a scratch test suggested a higher adhesive strength of HAp layers sprayed onto titanium (IV) oxide than onto titanium substrates. It seemed that the surface oxide layer of the titanium substrate would give a positive contribution to adhesion. In both the above experiments, adhesive strength increased with the substrate temperature up to 1130°C and the maximum adhesive strength was 19.2MPa for layers sprayed onto titanium.

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This paper is the first issue out of the serial studies on crazing phenomenon caused in chinaware glaze by Mr. Hiroshi Inada, which came out in public on Yogyo-Kyokai-Shi in 1977 and 1978.
Through the study, Mr. Inada established quite a new optical method to measure the stress in glaze of chinaware, which was entirely different from the way at that time. And he developed his study with lots of the data gotten from measurement using that method and finally made clear in mechanism how the stress was generated in chinaware glaze.
As a result of long study, he has settled up firmly a new technology to protect chinaware as an industrial product from the crazing in glaze.
The new method by Mr. Inada is just based on the principle of the retardation, which is able to directly measure and determine the stress in glaze of the final chinaware products. It is more simple and so much capable that should be extremely practical as compared with the previous one.
It is the most reliable and direct method of evaluation for the fitness of chinaware body and glaze as well as an effective means of the quality control in the field of industrial chinaware production.
Due to the above new optical method, it has turned out possible to measure the stress in glaze caused in the process of heating and cooling.
It can be said that he has exactly made clear whole mechanism of craze-generation in chinaware, which used to be estimated judging from curves of thermal expansions of the body and glaze so far. Accordingly he has settled an evaluation method for the fitness of the body and glaze by using the data of the stress in glaze.
Furthermore he expanded his consideration with so many data to the study of the effects of stress in the glaze for the reaction of the body and glaze, delayed-crazing of semi-vitreous chinaware, and crazes effected by various conditions of production.
In that way, he directed the basic guide to the plan of chinaware materials to prevent the craze.
According to his memoirs (FC Report 16, No. 12, 300-311 (1998)), this practical study as above had been done between 1958 to 1960 and the method was practically applied to an actual production field at Nippon Toki K.K. (Noritake Co., Limited). It served there so much to the study on chinaware material and quality control. In this way, after his theory had been put in practice, whole the study was released in public.
After that, his new theory and method have been spread widely in the industrial ceramic field in Japan by his own lectures or serial publications in “Yogyo-Kyokai-Shi” and made a great contribution to the advancement of chinaware quality and its productivity.

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