ZnO films were prepared from an aqueous nitrate solution containing acetylacetone by a method combining chemical solution deposition and UV-irradiation. It was clarified by X-ray diffraction analysis that irradiating ZnO precursor films with UV induces crystallization at relatively lower temperatures compared with a non-irradiation processes. Changes in the structural bonds of the precursor films before and after irradiation were studied by infrared spectroscopy. The effects of UV-irradiation on film transparency and morphology were discussed based on UV spectroscopy and scanning electron microscopy observations.

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The products of reaction between Pb(Zr_0.53Ti_0.47)O₃ (PZT) and glasses in the PbO-SiO₂ and PbO-B₂O₃-SiO₂ systems at 850°C were studied using powder and bulk PZT samples. A reaction zone was formed between bulk PZT and the glass. The microstructure of the reaction zone changed with the amount of PZT dissolved in the glass phase, which was dependent on the activity of PbO in both the glass phase and PZT. When the amount of dissolved PZT was small, as in the reaction between PZT and 60mol% PbO⋅40mol% SiO₂ glass, the glass phase penetrated into grain boundaries of PZT, and no solid reaction product was formed. When the amount of dissolved PZT was intermediate, as in that between PZT and 40mol% PbO⋅60mol% SiO₂ glass, the glass phase penetrated into the PZT pellet and ZrO₂ particles were precipitated in the glass phase. When the amount of dissolved PZT was large, as in those between PZT and 60mol% PbO⋅20mol% B₂O₃⋅20mol% SiO₂ glass and 40mol% PbO⋅30mol% B₂O₃⋅30mol% SiO₂ glass, the reaction zone was formed, which was composed of Ti-rich PZT and ZrO₂ particles dispersed in the glass phase.

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Indium tin oxide (ITO) films were deposited on acrylics by low temperature reactive magnetron sputtering. The effects of oxygen flow and film thickness on the internal stress and adhesion of ITO films on acrylics were evaluated. Results from the measurement of lattice parameters suggested that the internal compressive stress parallel to the film surface increased with increasing oxygen flow rate. This was possibly due to the peening effects of bombarding particles and the decrease in oxygen vacancies at relatively high oxygen flow. Observation of scratched surface after adhesion test showed that tensile bending moments occur within the coating as it was pushed down underneath the adhesion test indenter. The critical scratching load of ITO films invariably increased with oxygen flow and decreased with increasing thickness.

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Crystallographic orientation of individual grains on the surface of the thick specimen was successfully determined by polarized Raman spectroscopy.
(1) Depth resolution of a few μm in Raman-microprobe polarization was achieved using a high-magnification objective lens and a pinhole plate. This enables determination of the crystallographic orientation of single grains in ceramics.
(2) Raman tensor elements of sapphire, c and d, belonging to the Eg mode were analyzed. The analysis leads to c>>d for 378cm-1 line. As a result, the intensity of Raman scattering was expressed as S378cm-1//∝{1-sin2θcos2(φ-φExp)}sin2θ×cos2(φ-φExp).
(3) Three-dimensional c-axis orientations of translucent alumina grains were successfully determined by polarized Raman lines at 645 and 378cm-1.

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A high purity, sub-micron, α-alumina powder produced by the hydrolysis of aluminum alkoxide method and a thermally hydrated product of the as-received powder have been investigated. The powders were divided into two particle size range fractions. The intensity of aluminum trihydroxide polymorph bands is larger in the diffuse reflectance infrared Fourier transform (DRIFT) spectra of the large particle size fractions of the as-received, as well as the hydrated product. The amount of aluminum trihydroxide polymorphs in the hydrated powder was large enough to be detected in the X-ray diffraction (XRD) pattern of the powder. Scanning electron microscope (SEM) observation of the powders shows the presence of large agglomerates in the hydrated powder. A smaller amount of agglomerates is also noticeable in the as-received powder. Transmission electron microscope (TEM) images of the as-received and hydrated alumina powders revealed the presence of a surface layer interconnecting neighboring α-alumina particles. It is concluded that Al(OH)₃ surface structures of adjacent particles can form hydrogen bonding creating crystalline structures similar to the aluminum trihydroxide polymorphs. These structures are believed to be responsible for the formation of hard agglomerates even in the as-received alumina powder.

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In this work, the hot-corrosion behavior of silicon nitride-bonded silicon carbide composite (SCN) in aluminum melt are studied especially on the similar environment to the actual working condition. The thermal shock resistance and cyclic thermal shock behavior of this composite are also studied. Pre-oxidized specimens corroded more extensively than as-cut specimens in Al melt at the same temperature. The specimens, which were pre-oxidized and immersed in Al melt, showed a severe reduction in their mean compressive strength. The mass changes of SCN oxidized at 850°C-1200°C followed parabolic kinetics but pore neck blocking happened at 1200°C. The activation energy was found to be 223kJ/mol. In water quenching test of SCN composite, the critical thermal shock temperature difference was about 425°C. The repeated thermal stress by the cyclic heating and cooling caused the decrease in strength.

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A new intergrowth bismuth layer-structured ferroelectric, Bi₂WO₆-Bi₃TaTiO₉ (BW-BTT), was successfully synthesized by solid-state reaction, and the regular intergrowth structure was confirmed by the Rietveld method. Differential thermal analysis measurements suggested that the BW-BTT underwent ferroelectric phase transitions twice at around the Curie temperatures of the constituent compounds of BW and BTT. The structural analysis of the BW-BTT showed that there are two kinds of Bi ions in the bismuth oxide layers, and that one Bi ion was displaced to the polarization direction by about 2% of the lattice constant a from the corresponding position in the parent tetragonal structure. This displacement of Bi in the bismuth oxide layers is the structural feature which was found for the first time for both conventional and intergrowth bismuth layered structures.

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The synthesis and properties of ZSM-5 film on a porous mullite honeycomb have been investigated using Malaysia kaolin. Amorphous silica-glass in the kaolin honeycomb sintered at 1450°C was used as a source for ZSM-5 formation. The honeycomb was hydrothermally treated in NaOH, tetrapropylammonium bromide, and water to prepare a novel ZSM-5/mullite honeycomb composite via in-situ crystallization at 160 to 180°C. This paper describes the formation of mullite from Malaysia kaolin at 1400 to 1500°C, the effects of hydrothermal conditions such as reaction temperature, time, and concentration of NaOH solution on the formation of ZSM-5 crystals on the honeycomb, and on the porous properties of the composite.

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Ferrimagnetic glass-ceramics are useful as thermoseeds for hyperthermia of cancers, especially those located at deep parts of the body, since cancers are locally heated by hysteresis loss of the magnetite. When, after implantation at around the cancer, they are placed under an alternating magnetic field. In the present study, a glass of composition 40Fe₂O₃, 29CaO, 31SiO₂, 3P₂O₅ (weight ratio) was heat-treated at a rate of 5°C·min^-1 in 90CO₂+10H₂ atmosphere. Magnetite started to precipitate at 650°C, increased its crystallite size and volume fraction with increasing heat treatment temperature to reach 150nm and 36mass%, respectively at 1150°C. The saturation magnetization of heat-treated specimens increased with increasing heat treatment temperature to reach 32.4emu·g^-1 after treatment at 1150°C. The coercive force of the heat-treated specimen increased with increasing heat treatment temperature to reach 430Oe at 950°C, and then decreased to reach 150Oe at 1150°C. The specimen heat-treated at 1150°C showed the maximum heat generation, 7.5W·g^-1, under 300Oe and 100kHz.

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The effect of the addition of Y₂O₃-Al₂O₃ additive on the phase formation and densification process of in situ SiC-BN composite has been investigated. The in situ reaction started at 1450°C despite the addition of Y₂O₃-Al₂O₃ additive. However, when Y₂O₃-Al₂O₃ was added the reaction was much faster and completed after hot pressing at 1700°C. In addition, dense material with well-crystallized SiC and BN grains could be obtained. It was found that denitrification occurred during the reaction process for both specimens with and without Y₂O₃-Al₂O₃ additive. However, denitrification occurred continuously at temperatures higher than 1700°C for the specimen without Y₂O₃-Al₂O₃ additive and eventually resulted in decrease of nitrogen content. The above results were explained based on the following mechanism, that is, the Y₂O₃-Al₂O₃ additive formed a Y-Al-Si-O liquid phase with SiO₂ present in Si₃N₄ raw powder, enhancing diffusion of the elements of the reactants.

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A polyacrylic ammonium (PAA) of molecular weight 10000 was used as a dispersant of aqueous suspensions for submicrometer-sized In₂O₃(90mass%)-SnO₂(10mass%) powder with an isoelectric point pH 2.5. The adsorption of PAA on the particle surfaces at pH 9-10 approached a saturated value of 0.3-0.4mg/m² at about 1.0mg/m² of PAA addition. The apparent viscosity and the pressure filtration rate of suspensions with 35vol% solid, and density of the consolidated powder compacts were closely related to the relative amounts of adsorbed PAA chains and free PAA chains. A well-dispersed suspension, showing the lowest viscosity, was densely consolidated by filtration under a pressure of 196kPa.

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A suitable spark plasma sintering (SPS) condition for densifying iron silicides was examined using three kinds of starting powders: Fe+Si mixture, α-FeSi₂+ε-FeSi mixture, and β-FeSi₂. Dense iron silicides composed of α-FeSi₂+ε-FeSi with a relative density >95% were fabricated at 800°C for 5min, under 30MPa. Below 700°C, density of the sample sintered from β-FeSi₂ powder is much lower than that from the powder of α-FeSi₂+ε-FeSi mixture. Moreover, the grain size of the sample sintered at 800°C from β-FeSi₂ powder was larger than that of samples from the α-FeSi₂+ε-FeSi mixture. It is concluded that a semiconducting β-FeSi₂ phase affects the microstructure as well as the densification behavior of the sintered samples.

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The molecular structure of a heterobimetallic alkoxide formed in a highly concentrated (1.2mol/l) Ba, Ti alkoxides solution with methanol/2-methoxyethanol mixed solvent (60/40 in volume), which is suitable for preparation of BaTiO₃ ceramics via powderless sol-gel process, has been investigated using FT-IR, ¹H NMR, XANES and ICP-AES. Data obtained from the analyses indicate that reaction between barium ethoxide and titanium isopropoxide, used as the starting alkoxides, occurred to form a heterobimetallic alkoxide BaTi(OMe)₄(OEt)(OEtOMe) with a Ba/Ti ratio of 1 in the highly concentrated alkoxides solution.

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Eutectic composite of Al₂O₃/Y₃Al₅O₁₂ (YAG) was prepared by an arc discharge method and its microstructure and stability were investigated. The eutectic composition of Al₂O₃/YAG determined by electron probe micro analysis (EPMA) was Al₂O₃:Y₂O₃=81.6:18.4mol%. Basic eutectic microstructure was a twinned single crystal of Al₂O₃ and YAG. The size of crystals was about 0.2-1μm in width. The fine eutectic microstructure about 0.4μm in width was oriented. The eutectic composite was stable at 1773K for 28.8ks in air, but resulted in grain growth at 1873K.

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Optimal slip conditions for molding of iron-disilicide were determined. The chemical compositions of the starting material were Fe_0.91Mn_0.09Si₂ and Fe_0.98Co_0.02Si₂. The mean particle diameters of both kinds of powder were approximately 6μm. The slip were prepared by adding distilled water to the powder, then, the hydrogen exponent (=pH) of the slips was controlled by adding 3% aqua ammonia. Ammonium alginate was used as a deflocculant as well as a binder. When the pH was greater than 7 for the Fe_0.98Co_0.02Si₂ slip and greater than 8.5 for the Fe_0.91Mn_0.09Si₂ slip, the apparent viscosity was low enough to enable casting. The pHs of the Fe_0.98Co_0.02Si₂ slip and the Fe_0.91Mn_0.09Si₂ slip were determined to be 7 and 8.5, respectively, because a higher pH slip corroded the plaster faster. Although the apparent viscosity increased with the powder concentration, castability was satisfied and the density of the sintered specimen did not depend on the powder concentration under the slip and sintering conditions of this study. Accordingly, the powder concentration was determined to be 77%, because the apparent viscosity of the slip was the lowest at this concentration. The shrinkage of the specimen before and after sintering was 17.1±0.3% and was independent of both the powder concentration and starting material. The ammonium alginate provided stability to the slip and improved the strength of the green body.

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An attempt was made to prepare granules with high water content for semi-dry press forming with a stirring granulator. The agglomerate structure and compaction behavior of the granules were compared with those of spray-dried granules generally used for press forming. Dense granules containing water above 10% were obtained and showed high fluidity in comparison with the spray-dried granules. The obtained granules were more easily deformed and crushed at low forming pressure than spray-dried granules, because they contained large amount of water and had a loose agglomerate structure. Accordingly, the volume change in powder beds of the granules in pressing was larger than that of the spray-dried granules, resulting in high relative density of powder compacts at low pressure.

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The AC impedance analysis was applied to the non-destructive testing of cracks in concrete. Superposed cement boards were measured as a model of concrete with internal cracks. The interface between the cement boards were clearly detected as an independent electric equivalent circuit in the complex impedance plots. This indicates that the AC impedance analysis allows the non-destructive testing of internal cracks in concrete.

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Uniformly open-porous CaZrO₃/MgO composites were prepared by pressureless reactive sintering, and their gas sensing properties to CH₄ and high-temperature strength were studied. The results suggested that the porous material can be used not only for high-temperature filters as reported before, but also for gas sensors. Thus, it is possible to produce multi-functional filters, i.e., simultaneous hot gas-filtering and gas-sensing in one component.

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BaTiO₃-based multilayer capacitors are rich with the science of crystal chemistry, defect chemistry, phase transition theory, ferroelectricity, and processing. State-of-the-art multilayer capacitors are fabricated with base metals, submicron grains and have thickness of layers approaching one micron. There are, however, needs to keep improving the volumetric efficiency of capacitance, improve reliability in thin layers, and increase the number of active layers. This paper summarizes and reviews some of the studies our group is performing to scientifically aid progress in this fast moving field. Specifically, we will review size effect issues, the role of rare-earth doping in improving degradation resistance, and the potential of electrophoretic deposition to produce multilayer structures with nanopowders.

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Thermal conductivity is one of significant physical properties of engineering materials. It has been confirmed through the thermal conductivity measurements of natural and synthetic materials, and from theoretical calculations that the theoretical conductivities of diamond, BN, SiC, BeO, BP and AlN are larger than 300W·m^-1·K^-1 at room temperature, being classed as high thermal conductivity solids. Non-oxide ceramic polycrystals with conductivities close to those of single crystals have been developed through the advances in ceramic processing. In recent years, the thermal conductivity exceeding 150W·m^-1·K^-1 has been reported for β-Si₃N₄ ceramics, joining a group of high thermal conductivity solids. The non-oxide ceramics have been progressively used as heat-dissipating substrates for highly integrated circuits and optoelectronics, structural components for producing semi-conductors, engine-related material components and so on. Accordingly, the significance of high thermal conductivity non-oxide ceramics has been highly recognized in many industrial fields. In this review, the test results of thermal conductivity of non-oxide ceramics, such as SiC, AlN and Si₃N₄, are summarized, and then, the effects of processing and microstructural parameters on their thermal conductivities are discussed. Based on the experimental data, the mechanisms of thermal conduction in non-oxide ceramics are examined. The processing strategy leading to high thermal conductivity non-oxide ceramics is also addressed.

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