We used a high-concentration sol-gel process and an electrophoretic deposition technique to synthesize BaTiO₃ films. The particles were prepared by hydrolyzing a high-concentration alkoxide precursor solution. At the hydrolysis stage, it was important to use a sufficient amount of water to produce the particles, and to cool the hydrolyzed precursor solution with a cooling device to prevent gel from forming. When voltage was applied across the pair of electrodes, a gel film was deposited at the cathode. Heating the gel films at low temperature yielded stoichiometric BaTiO₃ films. The process appears to be due to the deposition by electrophoresis of particles from the high-concentration sol. The gel films that were formed had a two-layer structure. The lower layer that firmly adhered to the electrode plate was dense, and this layer was overlaid with the upper layer of a loose gel film.

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Pechini process was known as an excellent method for the synthesis of LiNiO₂ powder. Compared with the result of solid state reaction using NiO and Li₂CO₃ as reactants, Ni₂O₃ was the new compound found in Pechini-processed powder. In the present work, the role of Ni₂O₃ and the reaction mechanism for the synthesis of Pechini-processed LiNiO₂ were studied. XRD and DTA/TG analysis were used to investigate the phases present and the thermal reaction in the Pechini process studied. It was found that Ni₂O₃ was obtained from nickel citrate and nickel acetate which released a large amount of heat during calcination. Based on the thermodynamic calculation, Ni₂O₃ is not a stable compound in the oxidizing environment. As a result, Ni₂O₃ decomposes into NiO, and the decomposed NiO reacts with Li₂CO₃ and forms LiNiO₂ at 700°C. An isothermal kinetics study was performed on the mixture of NiO, Ni₂O₃ and Li₂CO₃ at 700°C. The result indicates that the decomposition of Ni₂O₃ into NiO takes place at the beginning hour of the isothermal reaction. Consequently, NiO and Li₂CO₃ are consumed due to the formation of LiNiO₂. Based on the results obtained, the reactions for Pechini-processed LiNiO₂ may be described by the following reactions:
Citrate complex→Li₂CO₃+NiO+Ni₂O₃
Ni₂O₃→2NiO+1/2 O₂
x/2Li₂CO₃+(2-x)NiO+x/4 O₂→Li_xNi_2-xO₂+x/2 CO₂ (0<x≤1)
This reaction is rationalized on the basis of the instability of Ni₂O₃ and the structural similarity between NiO and LiNiO₂.

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Si-C-O ceramics were prepared by the interchange reaction of methyltriethoxysilane (MTES) with 1, 4-butanediol (BD) and the subsequent pyrolysis. The structures of gels before and after pyrolysis were analyzed by NMR and IR. Carbon-13 CP/MAS NMR spectrum of the gel indicated the interchange reaction with the ethoxy groups of precursor, MTES. Silicon-29 MAS NMR spectra of the pyrolyzed gel revealed that SiC₂O₂ and SiC₄ units existed upon higher temperature heat treatment. The cleavage of BD and the formation of free carbon phase in the pyrolyzed products were certified through TG-MS and ¹³C MAS NMR. ²⁹Si MAS NMR, IR and XRD indicated the reaction of the free carbon with silica to form β-SiC above 1300°C.

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Hexagonal β-Co(OH)₂ platelets with high crystallinity (0.3-10μm in average diameter and -5 in aspect ratio) have been synthesized. The platelets of 0.3-0.5μm in diameter were prepared by a precipitation method, and their sizes were affected by the cobalt ion concentration in the suspensions. Adding rate of precipitant, stirring rate of solution, and aging temperature gave little effect on their morphologies. The platelets with well developed facets were synthesized with high reproducibility, when chloride salt was used as a Cosource and the suspension was aged at room temperature for 86.4 ks. The platelets have been enlarged up to 5-10μm with maintaining morphology (hexagonal shape, -5 in aspect ratio) by hydrothermal treatment (at 393K for 86.4 ks in 12mol/dm³ NaOH aqueous solution).

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The pressureless sintering of calcite was performed doped with lithium fluoride in CO₂ atmosphere. Sintering with grain growth occurred>525°C, and the bulk densities of the sintered specimens reached 2.24g·cm^-3 at 650°C. Phases detected in the sintered specimens were CaCO₃, LiF, CaF₂, and Li₂CO₃. The latter two phases were considered to be formed by the reaction CaCO₃+2LiF→CaF₂+Li₂CO₃. DTA analysis suggested liquid sintering processes had a eutectic composition in the system CaCO₃-Li₂CO₃-LiF, and the ratio of the eutectic composition for CaCO₃:CaF₂:LiF was 0.25:0.15:0.60. The liquid played an important role in the sintering process. The microstructure of a grain-boundary model supported the above-described mechanism.

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CaO-ZrO₂ composite was sintered at 1500°C by addition of ZrO₂ to 20 mol%. ZrO₂ reacted with CaO to form CaZrO₃ that promoted densification of the clinker by restraining growth of CaO grains. The formed CaZrO₃ was mainly located within CaO grains when a small amount of ZrO₂ was doped, while it localized at CaO boundaries with increasing the amount of added ZrO₂. Protective layer, consisting of CaZrO₂ crystalline that encompassed most of CaO grains, formed when the content of ZrO₂ was increased to 20 mol%. The slaking resistance was effectively increased owing to the promotion of densification when a small amount of ZrO₂ was added, and it was increased further by conversion of free CaO into CaZrO₃ with increasing the content of ZrO₂. Especially when a protective layer was formed, the slaking resistance of the clinker increased significantly. The mass gain of CaO clinker without ZrO₂ was 5.8% which decreased to 0.4% by increasing ZrO₂ content to 20 mol% after slaking for 96h at 70°C in 90% humidity.

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Nano-structured γ-Al₂O₃ ceramics have been pelletized under a pressure of 2.5 GPa on uniaxial compaction of nano-size particles. Although the obtained γ-Al₂O₃ ceramics show low density, they have a good transparency. For estimating the influence of particle size on the transparency of nano-structured γ-Al₂O₃ ceramics, nano-sized particles with four different sizes have been used. Nano-structured γ-Al₂O₃ ceramics made of particles whose size is <10nm show a transmittance above 40%. Transmittance decreases with increasing particle diameter. In the case of particle size >20nm the transmittance is less than 20%. This phenomenon is explained by Rayleigh scattering, which is applicable to a particle diameter much smaller than the wavelength of the incident light. The change in transmittance of nano-structured alumina ceramics on heat treatment is not observed below 1123K. However the transmittance remarkably decreases at above 1223K because of rapid grain growths with phase transition, although this temperature is 250K lower than the γ->α-phase transition temperature (1473K) of bulk alumina. When the sample produced from 11.2nm particles was heat-treated at 1173K, the transmittance was maintained for 2h and then decreased with increasing the annealing time. At this time, the transmittance slowly decreased with grain growth without phase transition between 2h and 6h, and then it steeply decreased with grain growth after 6h with phase transition.

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A Monte Carlo simulation method for modeling grain growth of solid particles in a liquid phase was developed to analyze the connectivity of a solid phase in a solid-liquid system on a two or three dimensional lattice. The mean size, contiguity and connectivity of the solid particles were analyzed as a function of the fraction of solid phase (f_S) and interface energy (γ_SL) between solid and liquid phases. The differences between results from 2D and 3D simulations were also examined. The connectivity increased with increasing f_S and γ_SL, 3D simulations producing a much larger connectivity than 2D simulations. The unrealistically low values obtained from 2D simulations proved that 3D simulation is necessary for a reliable analysis of phase connectivity. The connectivity results from 3D simulations could be divided into two groups; in the first group, the microstructures were close to 100% connectivity, while in the second group, the connectivity decreased. This decrease was caused by grain growth, lowering of f_S and γ_SL and increasing of the distance from the edge plane. A plot of connectivity vs. contiguity indicated that there was a critical value of contiguity (approximately 5%) above which close to 100% connectivity could be maintained, and below which the connectivity decreased approximately linearly. Our computational method may be applied to the design of microstructures of materials containing solid and liquid phases when a particular connectivity is desired.

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A gradient index (GRIN) lens is the optical device, which has the distribution of the refractive index in the glass medium. A chromatic aberration is very important when the GRIN lens is used for the optical systems under a source of white light such as a camera and microscope. So, we designed r-GRIN glass composition, which has an improvement in refractive index and a low dispersion distribution to reduce a chromatic aberration, and we also examined suitable preparation method. Then we chose SiO₂-TiO₂-BaO-K₂O glass system and sol-gel process. The theoretical proof of the selection of the SiO₂-TiO₂-BaO-K₂O glass system and the promising composition of the low distributed dispersion r-GRIN lens with large Δn were shown by this study.

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We have fabricated c-axis oriented thin films of the oxide thermoelectric material Ca₃Co₄O₉(CCO) on MgO(100), SrTiO₃(100) (STO), YSZ polycrystal and YSZ(100) substrates by pulsed laser deposition. The resistivity of CCO thin films on SrTiO₃ and YSZ substrates hardly varied with increasing temperature from 300 to 700 K. On the other hand, the resistivity of the films on MgO was relatively high, because of an impurity phase grown on the surface and the change of lattice constant at high temperature. From the microstructure of the CCO films on STO observed by transmission electron microscopy (TEM) techniques, a main structure of cobaltite [Ca₂CoO₃]_xCoO₂ has been found with identical a, b₁ and c parameters: a=0.48nm, b=0.45nm and c=1.07nm. The composition ratios of the main phase and secondary phase in the CCO films were Ca:Co=0.98:1.0 and Ca:Co=0.39:1.0, respectively.

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Frictional properties of 10 mass%-Fe₃O₄ added Si₃N₄ were investigated and the following results were obtained: 1) A series of sliding tests, which were done changing the combination of the material of the plate and pin, revealed that 10 mass%-Fe₃O₄ added Si₃N₄ provided the smallest frictional coefficient, improvement in anti-scuffing and wear properties as well: 2) Wear tracks were not observed on the sliding surface of chilled cast iron pin when 10 mass%-Fe₃O₄ added Si₃N₄ was applied to the plate: 3) Piston-rings and cylinder-liners made of 10 mass%-Fe₃O₄ added Si₃N₄ were installed in a real engine and then tested. The results proved an actual reduction of friction loss. These experimental results confirmed that a new material with “high oilphilic characteristics” for sliding parts was actually developed.

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We examined a new method of sol preparation using planetary mixer stirring to expand the Δn of SiO₂-TiO₂-BaO-K₂O systems r-GRIN glass upon increasing the amount of Barium content at the sol preparation step. It was found that the planetary mixer stirring enables very quick preparation (100 times shorter) of clear sols over very wide preparation conditions, as compared to conventional stirring. Therefore, it becomes possible to add a barium content three times higher than that formerly reported in the sol preparation step, thus expanding the Barium concentration distribution.

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Various metal oxides coated with a thin silica layer were prepared by two different liquid-phase deposition methods; one is the deposition of silica on the corresponding metal hydroxides using tetraethyl orthosilicate (TEOS), and the other is the hydrothermal treatment of the metal hydroxides with silica glass in basic solution. The TEOS treatment is more effective for depositing silica on the precursor hydroxides than the hydrothermal treatment employing the process of dissolution-deposition of silica. The silica-coated metal oxides of MgO, Fe₂O₃, NiO, Y₂O₃, ZrO₂, SnO₂, and Dy₂O₃ have high specific surface areas >200m²g^-1 after heating at 773K.

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Using Mg-α-SiAlON powders synthesized by carbothermal reduction-nitridation, fabrication of Mg-α-SiAlON ceramics was attempted through gas pressure sintering method. Furthermore, the effect of Si₃N₄ addition on densification of the synthesized powders was investigated. As a result, as-synthesized powders were transformed into β-SiAlON and did not densify during firing. On the other hand, in the case of samples with α-Si₃N₄ powder, it was found that full densification occurred and the Mg-α-SiAlON phase did not change upon gas pressure sintering, namely, dense Mg-α-SiAlON ceramics, composed of fine and uniform grains, could be obtained through firing at 1950°C for 2h.

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Young's modulus, E, Vickers hardness, H_v, crack initiation load, L_c, and fracture toughness, K_c, of 30RO-10Al₂O₃-60SiO₂, B₂O₃, P₂O₅ (mol%) (RO: MgO, CaO, SrO, BaO) system glasses were measured and the compositional dependence of deformation and fracture behaviors was systematically evaluated. Vickers hardness H_v and E had similar dependence on composition. The relationship between E and H_v was found to be expressed by H_v=0.07E. Fracture toughness K_c and L_c were in the order of Mg>Ca>Sr>Ba, depending upon the size of modifier ions, for all glasses with three different network formers. The result of the present study suggests that L_c very sensitively reflects the relationship between composition and fracture behavior of glasses.

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