TiO₂-coated hollow glass microspheres (HGMSs) for use in lightweight photocatalysis were developed from titania-hydrate-coated fine volcanic glass (FVG) particles by heat treatment at 940°C for a few seconds. FVG particles were coated with titania hydrate by adding a precipitant dropwise into a suspension in which a raw material of coating layer was dissolved. The change in pH of the suspension, due to decomposition of precipitant, and the stirring speed, had a pronounced effect on the nature of the surface layer and the crystal structure. At an addition rate of 0.6ml/min of precipitant and a stirring speed of 1000rpm, smooth coverage of the FVG particles was achieved, and the crystal structure was amorphous and had traces of the anatase phase. At 0.1ml/min and 300rpm, a thick and rough layer developed on the FVG particles; its structure was amorphous and had traces of the rutile phase. The crystals of anatase and rutile increased in number with heat treatment temperature and finally the surface of HGMS was entirely covered by TiO₂. TiO₂-coated HGMSs from the titania-hydrate-coated FVG are advantageous in particles with low density and high strength, and can be used as photocatalytic fillers.

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In this paper, a numerical technique for analyzing one-dimensional steady-state and transient temperature distributions in a plate of functionally graded ceramic-metal-based materials (FGMs), in relation to both the temperature-dependent thermal properties and continuous/gradual variation of the thermal properties of the FGM, is presented. The FGM plate is assumed to initially have a steady-state temperature gradient, being exposed to high temperature on the ceramic surface and to low temperature on the metallic surface, similar to its in-service state. The FGM plate is then rapidly cooled from the ceramic surface side by cold medium. The steady-state and transient temperature distributions in the FGM plate are analyzed numerically for a model alumina-nickel FGM system. The proposed analytical technique for determining the temperature distribution is relatively simple and widely applicable compared with methods recently proposed by other researchers.

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β-SiAlON ceramics with a relative density of 98.0±0.2% were fabricated from carbothermally synthesized SiAlON powders (z=2.45) without any sintering additives by HIPing under N₂ gas pressure of 150MPa at 1300 to 1900°C for 2h. It was found by SEM observation that the grain growth hardly occurs with hexagonalshaped grains of 2-4μm in size. The mechanical properties of the ceramics are reported; Young's modulus and Poisson's ratio were obtained using an ultrasonic pulse-echo method while the hardness was measured by the Vickers indentation technique, from which the fracture toughness was also calculated. Oxidation of the ceramics was carried out in the temperature range 1400 to 1600°C in an oxygen-containing atmosphere. XRD and ²⁹Si MAS-NMR spectroscopy indicated that the oxide scale consists of amorphous silica and crystalline mullite. Many pores were included in the oxide scale, probably due to N₂ gas formation. The kinetics deduced from both the weight gain and scale thickness suggested that the oxidation rate of these SiAlON ceramics is limited by a nitrogen diffusion process.

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The height of the potential barrier originating at the grain boundaries of recrystallized SiC was experimentally controlled by varying the nitrogen pressure during sintering. The variation in electrical properties with respect to the variation of the potential barrier height was simulated using a computer. There are two conduction mechanisms for recrystallized SiC. One is thermal excitation conduction over the potential barrier and the other is tunnel conduction through the potential barrier. The WKB (Wentzel, Kramers, Brillouin) approximation was applied to calculate the number of carriers that pass through the potential barrier by the tunnel effect. The variation of electrical properties was calculated by varying the height of the potential barriers, and the result corresponded fairly well with the experimentally determined variation of these properties. This simulation method will be useful in designing the electrical properties of recrystallized SiC.

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3Y-TZP/20 mass% La {Co_0.5Fe_0.5(Fe_0.9Al_0.1)₁₁}O₁₉ composites were successfully synthesized in situ during sintering from a mixture of 3mol% Y₂O₃-ZrO₂, La(Fe_0.9Al_0.1)O₃, Fe₂O₃, Al₂O₃ and CoO powders. Platelike La{Co_0.5Fe_0.5(Fe_0.9Al_0.1)₁₁}O₁₉ crystals were grown stably in a 3Y-TZP matrix over a temperature range of 1200 to 1325°C, which is wider than that of La(Fe, Al)₁₂O₁₉. Vickers hardness was 9.0GPa for the composite sintered from 1150 to 1325°C. 3Y-TZP/20 mass% La{Co_0.5Fe_0.5(Fe_0.9Al_0.1)₁₁}O₁₉ composite, which was sintered at 1325°C, exhibited a fracture strength of 630MPa. The composite which was sintered from 1200 to 1325°C exhibited a constant saturation magnetization of 7.2emu/g. The composite which was sintered at 1225°C exhibited a maximum coercivity of 3.8kOe.

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Three different non-oxide ceramics, Si₃N₄, SiAlON, and SiC were characterized with respect to their high-temperature micromechanical deformation behavior employing both transmission electron microscopy and the internal friction technique. The latter method was utilized to gain a direct measure of the high-temperature response of the respective material, i.e., the effect of the interfacial glass phase commonly observed in liquid-phase sintered ceramics on externally applied shear stress. Transmission electron microscopy provides complementary information about the structure and chemistry of internal grain boun-daries, which are known to dominate the high-temperature mechanical behavior of the bulk ceramic polycrystal. In addition, the presence and distribution of amorphous or crystalline secondary phases were characterized by electron microscopy. It is shown that, apart from the overall microstructure, the interface structure and/or the local chemical composition is the main parameter affecting the internal friction behavior. As a consequence, this technique allows one to determine the effective interface viscosity of ceramic polycrystals and to reveal as to whether a bimodal grain-boundary structure has developed, e.g., if both wetted and non-wetted interfaces are present, as is shown for the SiC ceramic.

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Platelike BaMnAl₁₁O_19-α particles were grown in a Ce-TZP matrix by the solid-state reaction of Ce-TZP, BaCO₃, MnCO₃ and α-Al₂O₃ powders. The addition of Mn was found to be effective in lowering the formation temperature of single-phase barium hexaaluminate (BaMnAl₁₁O_19-α) by 400°C. The Ce-TZP/20 mass% BaMnAl₁₁O_19-α composites sintered above 1500°C had a homogeneous microstructure dispersed with BaMnAl₁₁O_19-α platelet crystals. BaAl₁₂O₁₉ crystals were found to form by the preferential diffusion of Ba²⁺ ions in the Ce-TZP matrix. The bending strength of Ce-TZP/20 mass% BaMnAl₁₁O_19-α composites sintered at above 1500°C was 575MPa which is slightly higher than that of Ce-TZP ceramics (500MPa).

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The tetragonal-to-monoclinic phase transformation of 3mol% and 4mol% Y₂O₃-doped ZrO₂ (Y-PSZ) was investigated by annealing at 140°C in hot water. Sintered bodies of 3Y-PSZ and 4Y-PSZ were prepared by sintering at 1350°C for 0-10h, in air, and sintering at 1400 or 1450°C, respectively. A 3mol% and 4mol% Y-PSZ fine powder, synthesized by means of the hydrolysis method was used, as a starting powder. It was revealed that the Y₂O₃ concentration within the 3Y-PSZ tetragonal phase decreased and grain size was nearly constant as the holding time at 1350°C increased. When the sintered bodies of 3Y-PSZ were subjected to annealing in hot water, the phase transformation rate increased as the holding time increased. This behavior can be explained by considering the Y₂O₃ concentration within the tetragonal phase at constant grain size. In order to confirm the effect of grain size, a similar characterization was performed on 4Y-PSZ, which shows higher grain size than the 3Y-PSZ. It is shown that the behavior upon annealing in hot water depends only on the Y₂O₃ concentration within the tetragonal phase and not on the grain size. In addition, the phase-transformation behavior abruptly changes at the critical concentration of 2.75mol% of Y₂O₃, which reveals that, for fractions >3.0mol%, the phase transformation is completely controlled by the Y₂O₃ concentration within the tetragonal phase.

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In the starting step of durability testing, the elements removed in relaxing from each electric side because of the measuring of impedance and velocity by ultrasonic wave and density of elements. The electromechanical coupling factor decreased with an increase in resonance resistance. The decrease of velocity was shown due to submicron-crack and residual stress caused by lattice mismatch that occurred by domain switching. The occurrences of submicron-crack and residual stress were suggested by the decrease of pellets bending strength. From these results, the total discussion was performed for the degradation process.

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Ethyl acetoacetate aluminium diisopropoxide, magnesium acetate tetrahydrate, titanium tetraisopropoxide, zirconium tetra-n-butoxide, tetraethyl orthosilicate and boric acid were used to prepare graphite powders coated with Al₂O₃-based oxides. The coating effect with Al₂O₃-based oxides on oxidation resistance of the graphite powders were studied. The oxidation resistance of the graphite powders coated with Al₂O₃-ZrO₂, Al₂O₃-TiO₂, Al₂O₃-B₂O₃ and Al₂O₃-SiO₂ was higher than that of the graphite powder coated with Al₂O₃ monoxide, and the graphite powders coated with 90Al₂O₃⋅10SiO₂ (mass%) showed the highest oxidation resistance. The coating layer of 90Al₂O₃⋅10SiO₂ (mass%) showed the lower true density, higher specific surface area and lower linear shrinkage than those of Al₂O₃. It is considered that these properties of 90Al₂O₃⋅10SiO₂ (mass%) coated graphite determined the high oxidation resistance of the graphite powders.

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Crystallization of glass phase to cristobalite was investigated in mullite-glass ceramics with excess SiO₂ compositions (5.3-16.4mass%), namely, higher than stoichiometric mullite. Starting powders were prepared by alkoxide hydrolysis method. Compact specimens were sintered at 1600°C above the eutectic temperature (1587°C) for 2h. Crystallization treatment was carried out at 1500°C, below the eutectic temperature, for times from 4h to 96h. Crystallization of glass phase proceeded from the surface of the specimen toward its inner part, in linear dependence on the annealing time. At the polished surface of the specimen, crystallization started in large glass pockets and the crystallized area extended spherically toward the inner part. This phenomenon suggests that nucleation occurs at the minimum parts in the elastic energy generated by the volume change involved in the crystallization of glass phase to cristobalite.

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Materials enabling intelligent humidity control were synthesized using fumed silica, tetraethylorthotitanate and quaternary alkylammonium surfactant (decyl-, dodecyl-, tetradecyl and hexadecyltrimethylammonium chlorides) as a liquid-crystal template under hydrothermal conditions. X-ray diffraction profiles and transmission electron micrographs indicated that a homogeneous hexagonal structure of SiO₂-TiO₂ was formed from those products. The mesostructured products had high BET surface areas from 540 to 863m²/g, with uniform pore diameters of 1.5-3nm. These physical quantities were controlled by varying the size of the organic template. Water vapor adsorption isotherms for these materials experienced a sharp increase in adsorption when the relative water vapor pressure (P/P₀) was in the range of 0.4-0.6. Over this range of pressures, the maximum amount of adsorbed water was between 20 and 50mass%. The isotherms were classified as type V in the IUPAC notation, showed an unusually large hysteresis. The large hysteresis could be explained by the difference in contact angle between adsorption and desorption. For both the 2nd and 3rd. water vapor adsorption-desorption isotherms, any morphological change was not observed in the isotherms, meaning that these materials have high durability in their humidity control ability. A small shift of the broad Q^{4 29}Si-MAS/NMR spectra indicated that a wider distribution of the Si-O-Si angles in the SiO₄ tetrahedra when titanium was incorporated into the silica matrix.

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Stoichiometric oxide compound MgCr₂O₄ were sintered with varying the holding time in the range 10min-100h. All the samples were single-phase spinel structure and p-type semiconductor. Oxygen partial pressure dependence of electrical resistivity was measured at 1000°C in a P_O2 of 10⁰-10^-18atm. Oxygen partial pressure dependence of electrical resistivity was clearly divided into two groups according to the difference of holding time during sintering. The oxygen partial pressure dependence at longer holding time was well described by-2 ionized Cr vacancy model. However, the behavior at shorter holding times could not be explained by invoking Cr vacancy models. Under very low oxygen partial pressure, resistivity of all samples showed roughly the same value. It is shown that in such a low oxygen partial pressure atmosphere, Cr vacancy could not exist, and the sample conduction is dominated by an intrinsic conduction mechanism without formation of Cr vacancy.

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The antibacterial activities of samples prepared from oxidation of ZnS powder were studied by measuring the change in electrical conductivity with the growth of Escherichia coli. Oxidation of ZnS occurred at above 550°C in air and then the amount of ZnO increased with increasing the oxidizing temperature. The obtained crystal structure of ZnO was a zinc-blende type. From results of antibacterial tests on ZnS powder samples before and after oxidation, the antibacterial activity was found to increase with increasing the oxidizing temperature. However, no activity of ZnS was observed, irrespective of the powder concentration. The pH value after dispersing the powder samples in physical saline solution was in the range between 5.5 and 8.0, increasing with the formation of ZnO.

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The Zr3d spectrum in the XPS measurement of PZT ceramics was found to vary according to their crystalline phases. The Zr3d spectrum of the rhombohedral phase was deconvoluted to the Zr3d_5/2 profile at 181.3±0.2eV (denoted as A1) and the Zr3d_3/2 profile at 183.6±0.2eV (A2), corresponding to a single chemical state. In contrast, those of both the tetragonal phase and the MPB were deconvoluted to four profiles, Zr3d_5/2 at 182.1±0.2eV (B1) and Zr3d_3/2 at 184.5±0.2eV (B2) in addition to A1 and A2, corresponding to double chemical states. The area ratios of (B1+B2)/ (A1+A2) for the tetragonal phase and the MPB were 0.6 and 0.3, respectively. These results indicate that XPS has potential for a novel analytical application to PZT ceramics.

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Superconducting NdBa₂Cu₃O_7-δ (Nd123) thin films were prepared by a sol-gel method. Nd and Ba-alkoxides and Cu(OH)₂ were used as metal sources, and isopropanol and dimethylaminoethanol were used as solvents. Sols were spin-coated on polycrystalline Ag metal substrates, dried at 80°C and finally heated at 800°C, resulting in the formation of single-phase Nd123. The films exhibited preferred orientation along the c-axis after coating two times. However, the orientation was disturbed when the number of coatings increased. This behavior is attributable to the interfacial reaction between the film and the substrate to form liquid phases and/or structural relaxation of the gel film upon heating. Superconducting transition was observed at 90K after annealing the films in O₂ with superconducting quantum interference device (SQUID) measurements.

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Ultrafine BaTiO₃ particles were prepared by micro-emulsion charring method (MEC method). The MEC method consisted of two steps. The first steps is preparation of water/oil micro-emulsion with BaTiO₃ elements. And the second is low temperature firing process in N₂ atmosphere, which includes charring of oil in emulsion and powdering BaTiO₃ particles with char. The char formed around BaTiO₃ particles prevent an agglomeration of BaTiO₃ particles during firing. In the present experiment, the W/O ratio and an amount of emulsifier greatly influenced on size of droplets of emulsion. The charring temperature was another important experimental factor in order to obtain desired BaTiO₃ particles. Finally obtained BaTiO₃ charring powders were monodispersed spherical particles and particle size was 0.1μm to 0.5μm.

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The plasticity of Georgia kaolin was studied to clarify the factors affecting the uniaxial compression behavior before and after ion-exchange in 1N CH₃COONH₄ solution. Georgia kaolin, a kaolinitic clay, showed a very small amount of dissolution of divalent cations and a similar zeta-potential change before and after the ion-exchange. According to an analysis of the uniaxial compression test, the plasticity degraded at pH 7, however, improved at pH 4.9. It was found that the plasticity was more affected by the pH and zeta-potential value than by the adsorbed ions.

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In this report, we describe the optical characteristics of periodic multilayer films composed of Faraday glass. The evaluation indicates that the multilayer film made of FR5 and BK7 exhibits an enhanced Faraday effect and that the Faraday rotation exceeds 40 degree with a film thickness less than 20μm. Taking an advantage of the paramagnetic nature for FR5, the film can function as an optical switch driven by magnetic field and a magnetic field sensor element.

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In order to reveal the interface reaction mechanism between platinum and 50PbO⋅50SiO₂ glass melts, the redox reaction of platinum was studied electrochemically by cyclic voltammetry with platinum electrodes between 800°C and 1000°C. On cyclic voltammogram, two anodic peaks and one cathodic peak were observed. These peaks were due to redox of platinum in the glass melt. On the electrodes, it was observed that the interface between platinum and glass was uniform after platinum was oxidized by electrolysis. On the other hand, many pores were found near the electrode surface after platinum was reduced, These pores were found to be filled with melt. The mechanisms of redox reaction on the electrode were analyzed.

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