[in Japanese]

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Amorphous calcium phosphate (ACP) is one of the precursors of hydroxyapatite (HAp) at wet synthesis. ACP transform into low crystalline HAp at body temperature. The low crystalline HAp is bone-like apatite. Thus, when low crystalline HAp cement body can be prepared about 0ºC, this body is expected to be a controlled released material. In this study, behavior of these cement bodies in a body environment was investigated. We prepared cement bodies from ACP and from calcium phosphate cement (CPC) consisting of calcium hydrogenhposphate dihydrate (DCPD) and tetracalcium phosphate (TTCP). After soaking in simulated body fluid (SBF) for 7 days, cement body from ACP was broken, and the weight of cement body from CPC decreased. These cements have a potential of drug controlled release material.

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[in Japanese]

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A protein-immobilized apatite layer can be formed in a supersaturated calcium phosphate solution (CP solution) supplemented with protein. Efficiency of protein immobilization (percentage of protein immobilized in the apatite layer among all the protein supplemented to the CP solution) was not correlated with molecular weight of the protein, but well correlated with isoelectric point of the protein. This might be because electrostatic interaction between protein and apatite crystal is crucial in formation of the protein-immobilized apatite layer in the CP solution.

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The aim of this research is to study the optimum firing condition for pink-red color development in high temperature glaze by Cr2O3-SnO2-CaO-SiO2 system pigments. The experiment in various firing condition based on Malayaite(CaSnSiO5), the main structure of the color using with CrCl3 as a chromophore, were carried out. Synthesized pigments were analyzed by XRD, FT-IR, Raman Spectroscopy and UV-Vis.

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Using rice husk ash as silica, the influence of the firing temperature and keeping time on the color intensity of the Pr-ZrSiO4 Pigments were investigeted.The Pr-yellow pigments were calcined at 500, 700, 800, 900, 950, 1000, 1100 by ceramic method. The synthesized pigments were chracterised by DT-TG thermal analysis, X-ray diffraction, UV-Vis spectroscopy, SEM-EDAX analysis. The relationship of Zircon phase formation-growth and Pr-yellow color development were evaluated and optimum firing conditions has been determined.

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[in Japanese]

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[in Japanese]

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The natural clinoptilolite, available in Akita prefecture, Japan, was modified chemically and mechanically with changing time duration of sodium hydroxide treatment and ball to powder mass ratio in wet ball milling, respectively. The ammonium ions retention capacity of thus obtained modified clinoptilolites were found sharply increased with either increasing alkaline metal cations content or increasing specific surface area (decreasing particle size) with changing crystal structure to amorphous.

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[in Japanese]

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Various bismuthates including Bi5+ was examined for photocatalytic property by using decomposition of methylene blue. The methylene blue molecule was decomposed under existence of LiBiO3, AgBiO3, BaBi2O6, SrBi2O6 and NaBiO3. Changes of methylene blue concentration confirmed that NaBiO3 and LiBiO3 have relatively large photocatalytic activity for methylene blue decomposition.

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[in Japanese]

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The microstructure of Al2O3 based composite catalyst and its development at high temperatures are examined for heat stable cataltst support. The novel porous ceramics are formd via solid state reactions with highly dispersed nano-particles in alumina matirix.

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[in Japanese]

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Dry rice hulls contain 71-87 wt% organic matter such as cellulose and lignin and 13-29 wt% inorganic matter such as SiO₂ and K₂O depending on the species, climate and geographic location. The inorganic matter is composed of SiO₂ (87-97 wt%) with small amount of alkali and other trace elements. The SiO₂ in the rice hull was localized in the outer and inner epidermis of rice hull. The silica coexists with organic matter and the distance between SiO₂ and organic matter is close conjunctively. Activated carbon with specific surface area of 3270m²/g was produced by the removal of SiO₂ by the reaction of coked rice hulls prepared at 700˚C for 1 h in flowing N₂ with KOH.

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VOCs are causative substance for the sick house syndrome. Several adsorbents for air cleaning are effective and widely used in civil and industrial processes. We evaluated the adsorption and desorption characteristics of rarefired VOC on some inorganic substances.

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La_0.6Sr_0.4Co_0.2Fe_0.8O₃-La₂NiO_4+δ(LSCF-LNO) system was designed as the cathode material for IT-SOFC. No chemical reaction between the two constituents was detected in the binary system sintered at 1400°C. Among the LSCF-LNO system, 50 vol% LSCF-50 vol% LNO shows the relative density above 96% from 1200°C sintering and sufficient electrical conductivity of 157.7 S/cm at 800°C. This composition has moderate thermal expansion coefficient of 14.5 x 10^-6 K^-1 between 20 and 800°C for IT-SOFC and shows the polarization resistance of 1.05 Ω·cm² at 800°C.

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Mg₂X (X=Si, Ge, and Sn) and their solid solutions have been considered as candidates for high-performance thermoelectric materials. We have fabricated oxidation-resistant FeSi₂ films on sintered Mg₂X by RF magnetron sputtering in order to improve the oxidation resistance of Mg₂X. The sputtering condition was investigated in detail to optimize the thickness of FeSi₂ thin film. The thermoelectric Mg₂X materials coated by FeSi₂ thin film show good oxidation resistance.

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La-doped BaSnO₃ powders prepared by polymerized complex method using metal citrates were densified by spark plasma sintering, and the electrical conductivity and Seebeck coefficient of the ceramics were measured at 373 – 1073 K in air to evaluate the thermoelectric power factor. The solubility of La in Ba_1-xLa_xSnO₃ was estimated to be x = 0.03 from the change in the lattice parameter for the La content at room temperature. The changes in the electrical conduction behavior and thermoelectric power factor for the doped La content at high temperatures were investigated.

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Dye-sensitized solar cells have attracted a great deal of attention as next generation solar cells. We report the fabrication of the SnS-nanoparticles-sensitized TiO2 photoelectrodes and their performance in photoelectrochemical solar cells. By controlling the size of SnS at the nano scale, the improvement of the cell performance is expected because of quantum size effect. SnS nanoparicles were deposited on the TiO2 electrodes by the SILAR (successive ionic layer adsorption and reaction) methods reported by B.Ghosh et al1). The TiO2-SnS electrodes were analyzed by various methods, such as UV-vis, SEM, EDX, and so on. Electric power generation with the TiO2-SnS electrodes was confirmed. With increasing the number of coating of SnS, the current density and the conversion efficiency increased.

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Due to the high surface-to-volume ratio and the superiority in light and electronic transport properties, one dimensional (1D) TiO2 is promising candidate for applications in dye-sensitized solar cells, photocatalysts and gas sensors. In this study, we have attempted to synthesize new types of TiO2 nanorod arrays from TiCl4 with a catalyst on FTO substrate by a low-cost and environment-friendly liquid process.

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TiO2 nano rod were synthesized by hydrothermal method with H2TiO3, H2O2, NH3 to improve the conversion efficiency of dye-sensitized solar cells (DSSC). The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM). As a result, the sample was anatase TiO2 and had the length of 480nm and the diameter of 65nm.

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Layered photocatalyst H3OTi2NbO7 is well known to possess various unique properties such as ion-exchange, intercalation, delamination and so on. CsTi2NbO7 which was the percursor the H3OTi2NbO7 was prepared by soild-state reaction method. The sample treated with aqueous solution of urea, which were dried and then calcined to synthesize a nitrogen-doped titanoniobate. The weight ratio with H3OTi2NbO7 and urea is 1:0.5, 1:1 and 1:2. The prepared samples showed remarkable absorption in the wavelength region of 450-520nm with a red shift of the absorption edge.

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Layered photocatalyst KTiTaO5 is well known to possess various unique properties such as ion-exchange, intercalation delamination and so on. KTiTaO5 was prepared by two methods. One was solid-state reaction method and the other was polymerizable complex method. Iron oxide particles were intercalated into the interlayer of the sample. The prepared samples showed remarkable absorption in the wavelength range of 500-600 nm.

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[in Japanese]

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We fabricated ZnO nano rod substrate of DSSC which was grown on FTO glass. The nano rod has the diameter of 60nm and length of 7μm. Then we coated MgO thin film covering ZnO nano rod. We have improved Voc and conversion efficiency by MgO coating. Namely, Voc was 627mV and efficiency was 0.125% for ZnO nano rod substrate. Voc was 660mV and efficiency was 0.130% after MgO coating.

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[in Japanese]

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The crystal structure and the neutron scattering length density maps of LiCo_1/3Ni_1/3Mn_1/3O₂were studied by the Rietveld method and the maximum entropy method using the neutron powder diffraction. The crystal structure could be refined with the space group, R-3m. Though Li, (Co, Ni, Mn) and O atoms were mainly occupied at 3a, 3b and 6c sites, 3.8% of 3a site was substituted by Ni atom. According to the neutron scattering length density maps obtained by MEM, it is assumed that the Li atom was diffused through the 3a-9c-3a sites

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Ternary oxides of Ca₆Ti₂Ta₈O₃₀, Sr₆Ti₂Ta₈O₃₀, Ba₆Ti₂Ta₈O₃₀, Sr₃Ti₄Ta₄O₂₁, Ba₃Ti₄Ta₄O₂₁, Ba₃Ti₅Ta_3.2O₂₁ characteristic for the simultaneous presence of Ti and Ta as constituents, were synthesized by amorphous metal complex (AMC) method. Samples loaded with Pt cocatalyst exhibited high H₂ generating activities over 1 mmol / h from MeOH – water mixed solution under UV irradiation. The optimization of calcinations condition and amount of Pt loaded led Ba₃Ti₄Ta₄O₂₁ to have a very high activity reaching 9.7 mmol / h.

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Novel layered perovskite nanosheets with Li-ions at perovskite A-site were synthesized. The A-site substituted Li₂SrTa₂O₇with layered perovskite-type structure was prepared by a solid statet reaction. The nanosheets were obtained by the exfoliation of A-site substituted Li₂SrTa₂O₇ using tetramethylammonium hydroxide. The observation by atomic force microscope showed that the obtained crystallites were the nanosheets with sizes of 100 ~ 400 nm in width, 4 ~ 10 nm in thickness. It was found from element analysis and XRD analysis that the layered perovskite nanosheets with Li-ions at perovskite A-site were obtained for the first time.

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A new compound Na_2.7MnTi₃O₉ with the Na_3-xTi₄O₉-type tunnel structure was synthesized by solid-state reaction at 1173K. It crystallizes in the monoclinic system, space group C2/m, and lattice parameters of a = 2.301 nm, b = 0.2918 nm, c = 1.068 nm, β= 102.9. We have also successfully prepared the isostructural compound Li_2.7MnTi₃O₉ by the ion-exchange technique in the molten LiNO₃ salt. The electrochemical lithium extraction and insertion properties of the obtained Li_2.7MnTi₃O₉ were examined.

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[in Japanese]

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Yttrium hydroxyl carbonate (Y(OH)CO3) precursor nanoparticles were synthesized by the homogeneous precipitation method with the presence of polyacrylic acid (PAAc). Resultant precursor particle size is about 20-30 nm with narrow distribution whereas the particle size is smaller than those acquired by the absence of PAAc. The particle size of the precipitated precursor without the PAAc addition has 230 nm with wide distributions. It was demonstrated that calcination of precursor materials at 1100 ⁰C eventually removes the organic residues and inorganic anions from the precursors and subsequently provided well crystalline Y2O3 nanoparticles which was evident from FT-IR, XRD, FE-SEM and TEM analysis. Likewise, Er3+ doped Y2O3 nanoparticles obtained by the above method gives bright green (550 nm) and red (660 nm) upconversion emission under 980 nm excitation which are useful as bio-imaging probe.

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