[in Japanese]

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Production technology examination by a simple method suitable for utilization was performed about the fiber strengthening porous SiC composite material without the necessity for an interface layer.

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Fracture behavior and toughness of discontinuous carbon fiber dispersed SiC matrix composite under mode_I_loading has been investigated. During the loading, micro damage accumulation behavior was observed in SiC phase. Damage accumulation behavior near the notch tip strongly depends on distribution of carbon fiber bundle. A simple model is proposed and the effect of microscopic fracture behavior on apparent fracture toughness was discussed.

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Fracture toughness of discontinuous carbon fiber dispersed SiC matrix composite with long and short crack have been evaluated by fracture toughness test. Fracture behavior and fracture toughness of DCF/SiC composite strongly depends on length of the initial crack. In the present research, relationship between the crack length and microstructure was discussed based on the experimental results.

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Ni or NiO nanoparticles about 10~100 nm in grain size were uniformly precipitated on Ti-C-N (TiN, TiC and TiCN) powder by rotary chemical vapor deposition (RCVD). The NiO coated on Ti-C-N powder was reduced to Ni during SPS. The relative density, hardness and fracture toughness of Ni precipitated Ti-C-N composite was much higher than pure Ti-C-N and Ni mixed Ti-C-N powder.

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The high-temperature tensile testing of the fully dense (ZrO₂-3mol%Y₂O₃)₈₀(Al₂O₃)₂₀ with the crystalline size of 40 nm was carried out, in order to deduce the strain rate sensitivity (m) for the superplastic flow inherent to nanocrystalline structure; the m is dependent on strain rate. Then, compression is being conducted for the amorphous and/or nanocrystalline (ZrO₂-3mol%Y₂O₃)₈₀(Al₂O₃)₂₀(CeO₂)₂₀, as consolidated to a nearly full-density without additive, by employing the instrumented electric current type thermomechanical testing method.

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[in Japanese]

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The indentation on film/substrate systems with a point-sharp indenter is simulated with the finite element method. The drop in the indentation load P vs. penetration depth h curve is observed when the film/substrate interface slips. The penetration depth at the drop increases with an increase of the interfacial shear strength, the ratio of film Young's modulus to substrate one, and the apex angle of the indenter, and with a decrease of the yield strength of the film. The shear strength is quantitatively discussed in various conditions.

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[in Japanese]

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SiC fiber-reinforced SiC porous matrix composites with no interface between fiber and matrix have been successfully developed in Kyoto University. The composites exhibit unique fracture behavior, which consists of long non-linear region, followed from linear elastic region with high modulus. The objective of this study is to clarify the crack propagation mechanism and investigate mechanical properties after exposure at 1100 oC for 10 h in air. The many crack deflections were detective in the porous matrix area and relatively long fiber pull-outs were observed, which contributed to the non-brittle fracture behavior of the composites. The no degradation in strength after the exposure was demonstrated.

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Impact damages of pressureless sintered boron carbide ceramics joined with aluminum were evaluated using a SUJ2 sphere with φ4mm in diameter as a projectile with the velocity of about 300 m/sec. The result showed that the amount of cracks generated in the boron carbide ceramics joined with aluminum were less than those of monolithic boron carbide ceramics.

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We report the fabrication of fully dense, uniformly dispersed multi-walled CNT (MWCNT)-alumina ceramic matrix nanostructured composites by a scalable self-assembly process of individually dispersed, oppositely charged MWCNT and alumina nanostructures in water followed by a pressure/DC current-assisted consolidation process.

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For the dispersion behavior control of carbon black, CB, nanoparticles in aqueous suspension, poly ethylene imine (PEI) with molecular structure design by Toluoyl groups was prepared and added into suspension. By using Toluoyl -PEI, the suspension viscosity was remarkably decreased. The estimated action mechanism of adsorbed toluoyl-PEI on CB surface was analyzed by colloid probe AFM method. It is estimated that the increase of repulsive interaction by toluoyl-PEI adsorption promoted CB particle dispersion.

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With a combination of excellent properties, including extremely high melting temperatures, high hardness, low volatilities, good thermal and electrical conductivities, ZrB2-based ultra high temperature ceramics (UHTCs) become viable candidates for high-temperature structural applications. ZrB2 owns AlB2-type hexagonal structure (P6/mmm) and shows high anisotropy in single-crystal form, platelet ZrB2 grains could be formed in reactive hot pressed ZrB2-MoSi2 at temperature of 1650 C. In present work, textured ZrB2 and ZrB2-MoSi2 ceramics were fabricated via strong magnetic field alignment during slip casting, followed by spark plasma sintering. The results on sintering and microstructure of the received textured ceramics will be reported.

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LiCoO₂, which has layered rock-salt structure, is used as positive electrode material for Li-ion batteries. In this study we attempt to produce crystalline-oriented LiCoO₂ by slip casting in a strong magnetic field. And we characterized the relationship between the battery performance and the crystal orientation. As a result, it was revealed that the c-plane oriented electrode have a superior electrochemical performance than the c-axis oriented electrode.

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The sinterability of Y₂O₃ is sensitively influenced by the doping of cation with the doping amount of 1mol%. For instance, the sintering temperature required for full-densification in Y2O3 can be reduced from 1700C to 1300C by Zn²⁺-doping. The sinterability of the cation-doped Y₂O₃ depends on the dopant cation species. High-resolution transmission electron microscope (HRTEM) observations and nano-probe X-ray energy dispersive spectroscopy (EDS) analysis revealed that the doped cation tends to segregate in the vicinity of grain boundaries without forming amorphous layer. The doping effect on the microstructure and high temperature matter transport of the sintered Y₂O₃ will be discussed.

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[in Japanese]

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In this study, we fabricated cermet materials comprising copper and ZrW₂O₈, which had a negative thermal expansion coefficient. The bulk cermet material, consists of a copper matrix containing 0-50 vol% ZrW₂O₈, which has high density was obtained by SPS heat treatment at 873 K for 10 min. The coefficient of thermal expansion of the samples, which depends on the amount of ZrW₂O₈ contained in the matrix, changed from 7.86x10^-6 (Cu:ZrW₂O₈=50:50 vol%) to 17.4x10^-6 K^-1 (Cu100%). The thermal conductivity could also be controlled, varying from 120 (Cu:ZrW₂O₈=50:50 vol%) to 300 Wm^-1K^-1 (Cu100%).

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The microstructures of sintering bodies become anisotropic in constrained sintering of a thin film on rigid substrate, as well as in stress-assisted densifications such as sinter forging and hot pressing. The deformation and the stress states in the body have been described by general constitutive equations using sintering stress tensor and viscosity tensor. These macroscopic quantities were determined from local microstructure and microscopic kinetics for the special case of face-centered tetragonal structure. The simulation results were applied to the cases of sinter-forging and constrained sintering and qualitatively compared to the experimental results available in the literature.

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[in Japanese]

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Aerosol deposition is a method of forming the dense ceramic films by impacting the ceramic particles to the substrate at room temperature. In order to increase the deposition efficiency, the relationship between the deformation energy of Al₂O₃ particles and the deposition efficiency was investigated. It was found that the deformation energy depends on the process of preparing the particles and the lower deformation energy the particles show, the higher deposition efficiency can be achieved.

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[in Japanese]

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To fabricate meso-porous ZnO films on plastic substrates, we propose two low-temperature conversion methods via layered hydroxide zinc acetate (LHZA) films; a dissolution-precipitation method and a pyrolysis method. The former is to immerse the LHZA films in various liquid media facilitating the conversion reaction, and the latter is to pyrolyze the LHZA films at 90 ºC in a dry oven. When the plastic dye-sensitized solar cells were actually constructed by these porous ZnO films on ITO-coated plastic substrates (ITO-PEN), a high conversion efficiency over 3% was achieved for the ZnO electrode obtained by the pyrolysis method.

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[in Japanese]

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Al doped ZnO(AZO) nanocrystals were prepared by a hydrothermal treatment with cetyltrimethyl ammonium-bromide (CTAB). It was found from TEM observation that the morphology of ZnO and AZO was changed to rods and spheres, respectively, in comparison with that without CTAB. AZO single phase was synthesized until Al content x=3 but ZnAl₂O₄ was precipitated over x=5. The lattice constants were linearly decreased up to x=5. A simple model calculation revealed that Al amount into ZnO was 1~1.5%.

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Aluminum doped zinc oxide (AZO) is expected material because of highly conductivity and excellent optical properties such as UV adsorption and visible transparency. Enhancing these properties, it was necessary that more fine particle of AZO was prepared. The present study was performed to elucidate the optimum preparing conditions to obtain fine AZO particle by hydrothermal reaction. AZO was synthesized from zinc nitrate solution and aluminum nitrate solution, which was regulated high pH by hydrothermal reaction. The morphology and crystal structure of synthesized particles were evaluated by scanning electron microscopy and x-ray diffraction.

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[in Japanese]

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Linear Polyethyleneimine (LPEI) has been successfully employed to prepare silica nano fibers (SNF). The varied morphologies of crystalline LPEI can be easily changed by controlling the cooling rate of hot LPEI aggregates, which leads to the formation of SNF-based different microstructures containing LPEI inside. The aqueous zinc ions were easily inserted into the well-structured SNF via the coordination interactions between LPEI included on the SNF and Zn²⁺ions. After sintered the Zn²⁺ions-captured SNF at about 773K, the thermally stable nano ZnO particles sized at 1-5 nm were formed in the resulting composite of ZnO@SNF, which has a strong and wide-ranged PL emission from 380 nm to 600 nm under an irradiation of UV light (360 nm).

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This study reported a simple eco-friendly synthesis of semi-amorphous hollow calcium silicate hydrates nanoparticles (HCSHNP). Results showed that HCSHNP is relatively in uniform hollow nano-size ranges from (60 to 100) nm and exhibited stable surface morphology (ultra microporous). Hence, it contains an external and internal surface that can be selectively functionalized with multiple organic and inorganic groups. Hence, this work may open a new route to prepare new hybrid hollow bio-active particles for biological and nano-cement science application.

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We succeeded in synthesis for new (NH₄)_2XLa_1-XSr_X[Fe(CN)₆]•nH₂O (La-Sr-Fe) heteronuclear complex using coprecipitation for (1-X)(NH₄)₂Sr[Fe^II(CN)₆] and XLa[Fe^III(CN)₆]•nH₂O complexes. The XRD peaks for synthesized complexes moved into higher-angle than peaks of LaFe complexes without peaks of SrFe complexes. The Sr content in synthesized complex was smaller than that of starting material. Furthermore, the La-Sr-Fe complex was synthesized by a mechanochemical process using a planetary ball-mill.

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Pure titanium and titanium alloys are used for orthopedic and dental prostheses. Nevertheless, their biocompatibility improvements have still been required. In this study, new preparation technology based on surface modification of titanium-based metals by alkali treatmen has been attempted and reported. After the treatment, surface morphologies were observed by scanning and transmission electron microscopy (SEM, TEM). Chemical composition of the treated surfaces was investigated X-ray fluorescence analysis (XRF). Dissolved elements in the reaction solution were analyzed by inductively coupled plasma (ICP). It was found that the surface morphology consisted from low-dimensional nanostructures was confirmed after the solution chemical treatment.

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[in Japanese]

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Various mesoporous silica and titania thin films on substrates were prepared by a sol-gel technique. Gold nanoparticles (GNPs) were then deposited in the mesopores by chemical reduction, UV irradiation, or heat treatment methods. Electron microscope observations showed that GNPs of various shapes were formed in the films.

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