The capability of preparing carbonates and hydroxides that decompose in air at high temperatures is one of the advantages of hydrothermal reactions as a preparation technique for inorganic materials. In this study, new hydrothermal techniques to prepare single crystals of calcite (carbonate) and hydroxyapatite (hydroxide) were described. For hydrothermal crystal growth of calcite, organic salt solutions were used as a mineralizer for the first time and a solution of ammonium acetate was found to be an excellent mineralizer to obtain high growth rate under mild hydrothermal conditions. Single crystals of hydroxyapatite were prepared from chlorapatite single crystals by ion exchange in alkaline solutions under hydrothermal conditions. The transformation mechanism was explained by dissolution and precipitation of clusters.

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Increasing accumulation of municipal incinerator residue (hereafter called MIR) have been becoming a serious social problem in view of environmental loading, and its reuse or recycling as starting materials of ceramics products is urgently required. Since the glass-ceramics of the CaO-Al₂O₃-SiO₂ system have been promising as construction materials, we have investigated the preparation technique of this glass-ceramics from MIR by the bulk crystallization method. The structures of glass-ceramics were investigated by means of video microscope (VMS), scanning electron microscope (SEM), powder X-ray diffraction (XRD), and so on. Batches were prepared by mixing the various weight ratios in order to get the composition; MIR:SiO₂:CaCO₃:FeS:Na₂SO₄=100:10-30:10-30:3-5:0-5. Glass samples were produced by melting the batches at 1450°C. From those batch compositions, the homogenous glasses were produced. They were reheated at 800°C for 1 h to induce nucleation in the glasses. Further, the glasses were reheated at 1100°C for 2 h, to make them transform into glass-ceramics. The results of VMS photographs, SEM photographs and powder XRD patterns of the obtained glass-ceramics showed the homogeneous precipitations of the prismatic crystals (about 0.5×2 μm) of Anorthite (CaO•Al₂O₃•2SiO₂) and Wollastonite (CaO•SiO₂) by the bulk crystallization, accompanied by a small quantity of Gehlenite (2CaO•Al₂O₃•SiO₂) and/or Nepheline (NaO₂•Al₂O₃•2SiO₂).

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In this study, porous hydroxyapatite microspheres with the size range 9-80 μm have been prepared by a spray-drying method and the possibility using this kind of microspheres as carrier for peptides has been investigated with insulin being chosen as a model drug. In adsorption experiment, many factors (i.e., incubation temperature, incubation duration, pH and concentration of insulin solution) had influences on insulin adsorption on obtained microspheres. More than 90% insulin in solution could be loaded with optimal combination of these factors and drug loading of more than 3% could be achieved. In desorption experiment, the concentration of dipotassium hydrogen phosphate solution in many effecting factors had greatest influence on insulin release from insulin-adsorbed microspheres. More than 90% loaded-insulin could be released at dipotassium hydrogen phosphate solution at concentration around 10 mM. All these results suggested that there was possibility of fabrication of proteinic drug delivery system with porous hydroxyapatite microspheres.

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The influences of suspension pH and the added amount of the cationic polyethylenimine (PEI) dispersant on the stability of SiC suspensions have been investigated by measuring their zeta potential, rheological properties and adsorption behavior. The PEI adsorption state on the SiC surfaces under different pH conditions played a key role in the modification of the particle surface charges and the stability of suspensions. The pH range of stable suspensions was determined depending on the added amount of PEI.

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This work compares the induction period for the nucleation of apatite, rate of crystal growth, and adhesive strength of apatite formed on polyamide films containing either carboxyl or sulfonic groups incorporated with calcium chloride by immersing them in 1.5SBF, whose ion concentrations are 1.5 times those of a simulated body fluid (SBF). The induction period for apatite nucleation on polyamide containing-SO₃H was shorter than for polyamide containing-COOH, while the rate of crystal growth did not depend on the kind of functional group, but depended on the degree of supersaturation of the surrounding solution. The more ready association of sulfonic groups with calcium ions may lead to a shorter induction period for apatite nuclei than that with carboxyl groups. Adhesive strength of apatite layer with polyamide film containing -SO₃H was significantly lower than that with -COOH depending not only on the chemical interactions but also on the mechanical properties of the polyamide film.

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We succeeded in the in situ observation of liquid-liquid phase separation of glass under microgravity at the Japan Microgravity Center (JAMIC), which provides a 10 s microgravity duration. The microgravity level is 10^-5 g (g≡gravitational field at Earth's surface). We constructed an apparatus for the observation of phase separation suitable for the experimental facility. The melt of 3BaO•97B₂O₃ (mol%) was held as a film on a Pt wire loop. The sample was initially heated above the immiscibility temperature and held at that temperature. After the homogenization stage, the melt was cooled. Liquid-liquid phase separation of the melt was observed directly with a video camera. It was found that the nucleation and growth of phase-separated particle under microgravity are slower than in the case of 1-g, and the delay time of phase separation between the case of microgravity and 1-g depends on the flow rate of the melt under microgravity. These observations could be interpreted in terms of Marangoni convection and a change of diffusion.

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Cermet electrodes for Sm-doped ceria electrolyte (SDC) with a composition Ce_0.8Sm_0.2O_1.9 were prepared by freeze drying of the SDC-H₂PtCl₆-Cu(NO₃)₂ suspension (cathode) and the SDC-Ni(NO₃)₂-SnO₂ suspension (anode). The freeze-dried powders decomposed at 873 K and were sintered at 1323-1573 K in air to investigate phase compatibility, microstructures and electrical conductivity. The dominant factors for the terminal voltage drop of the present fuel cell were the resistance of solid electrolyte and the overpotentials at both electrodes. Addition of CuO to SDC-Pt cathode and addition of SnO₂ to SDC-Ni anode reduced the overpotentials at the electrodes and increased the terminal voltage and power density of the cell with SDC electrolyte (500 μm thickness) using a 97 vol% H₂-3 vol% H₂O fuel. The highest power density was 183 mW/cm² at 1073 K.

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Residual strain and atomic structures in the vicinity of the grain boundaries were investigated for (2310)[0001] Σ21, (4510)[0001]Σ7 and (0112)[2110]RΣ7 symmetrical tilt grain boundaries of Al₂O₃ bicrystals using convergent beam electron diffraction (CBED) and high-resolution electron microscopy (HRTEM). CBED measurement clearly showed that the RΣ7 grain boundary has a relatively small strain across the boundary. On the other hand, there is strain of about 0.06-0.07% in the area 10 nm from the grain boundaries in both the Σ21 and Σ7 grain boundaries. It was found that signs of strain distribution in the vicinity of the grain boundary observed in the Σ21 specimen were opposite to those observed in the Σ7 specimen. The interplanar distances of (2110) a-plane and (0001) c-plane in the Σ21 boundary were confirmed to increase and decrease, respectively, in the vicinity of the grain boundary. In contrast, the respective interplanar distances in the Σ7 boundary decrease and increase, respectively. The difference in the change of interplanar distance observed in the Σ21 and Σ7 boundaries is considered to be closely related to the atomic density at the respective grain boundaries.

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Aluminum nitride is used for the quick removal of exothermic heat from MPU (Micro Processing Unit) used in computers and from the power module for application to hybrid cars. It has high thermal conductivity, but this property varies with method of manufacturing material powder. Thermal conductivity of sintered body from direct nitrided powder is lower than that of sintered body from reduction nitrided powder. The decreasing of thermal conductivity caused by direct nitrided powder was larger than that of impurities in raw powder as oxygen and metal. Thus, the direct nitrided powder is thought to have another mechanism of the decreasing of thermal conductivity of AlN sintered body. We found that sintered body from direct nitrided powder has many dislocations in grains. These dislocations are thought to be the cause of the decreasing of thermal conductivity. In addition, we found that dislocations occurred in crashing process and occurred at the time of crystal breaking within 300 μm from cracks.

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The objective of this study was to form a polycrystalline oxide film on an Al substrate in electrolytic solutions of sodium phosphate using micro-arc-technology, and to consider a mechanism for the formation of the oxide film by type of sodium phosphate. Micro-arc on the Al substrate did not occur in electrolytic solutions of Na₃PO₄, Na₂HPO₄ or NaH₂PO₄, which were mono-sodium phosphate, preventing micro-arc-processing. However, micro-arc-processing was possible on the Al substrate and crystalline Al₂O₃ films were formed in electrolytic solutions of Na₄P₂O₇ and Na₅P₃O₁₀, which were poly phosphoric acid. Micro-arc may not have occurred in the mono-phosphoric acid electrolytic solutions because the resistance value of phosphoric acid radical impurities barrier layer is small in comparison with poly phosphoric acid sodium.

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Halloysite transformed into intermediate compound with two dimensional structure at 1223 K before fully converting to the spinel compound above 1473 K. This reaction was studied by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD) and thermogravimetric and differential thermal analysis (TG-DTA). Heat treatment at 1223 K provided the oriented intermediate phase with two dimensional structure which was characterized by the selected area diffraction (SAD) with tilting the specimen in TEM. A small amount of fine spinel crystal in nanometric size was also confirmed with the two dimensional intermediate phase by TEM and XRD. Most of the spinel compound formed at the temperature higher than 1473 K decomposed and subsequently formed both of mullite and silica at 1673 K.

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Density functional theory calculations were performed to analyze atomic and electronic structures of cordierite. The most stable configuration of Al and Si atoms in the six-membered ring of a unit cell was decided by geometry optimizations for sixteen different initial structures. A correlation was observed between the number of Al-O-Al bonds in a unit cell and the lattice energy. We concluded that the number of Al-O-Al bonds is a determining factor of the lattice stability. The structural parameters of the most stable crystal structure obtained by geometry optimization agreed well with the experimental observation. According to the distribution of atomic charges and analysis of bond order, the followings were clarified: (i) the covalent bond in a T1 tetrahedron was stronger than that in a T2 tetrahedron, (ii) the covalent bond of a cation in six-membered ring with O atoms in a T1 tetrahedron was the weakest, and (iii) Mg in the cordierite is of ionic nature.

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SiO_x:OH films containing a high concentration of Si-OH bonds deposited by using a direct current (DC) reactive magnetron sputtering with added H₂O. We have discussed the photocatalytic characteristics of SiO_x:OH/TiO₂ multi-layer films, in which various SiO_x:OH films were deposited onto photocatalytic TiO₂ films. As a result, ultra-hydrophilic properties were observed under ultraviolet (UV) irradiation of 10 μW/cm². The concentration of hydrogen in the SiO_x:OH films could be controlled by changing the pressure of H₂O that was used during the process. The hydrogen in the layers is believed to take the form of either Si-OH or H₂O bonds; however, the Si-OH bonding dominates. The hydrophilic properties of the layers are considered to be improved by the presence of the -OH groups in the SiO_x:OH film.

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Glass capillaries with silica gel layer on the inner surface were prepared by applying phase separation during sol-gel reaction of tetraethyl orthosilicate in the presence of poly (ethylene glycol) with number-average molecular weight of 20000. According to this technique, we can coat the internal surface with uniform silica gel layer for silica capillary with diameter up to 0.1 mm. In the gas chromatographic analysis of hydrocarbons using the capillary column with silica gel layer, light hydrocarbons up to C4 can be analyzed with high resolution and within short experimental time at ambient temperature.

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