[in Japanese]

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The oxygen storage capability was investigate for Ca2(AlxMn1-x)2O5+d (x = 0.50-0.67) with a brownmillerite-type structure. This oxide was found to store/release a large amount of excess oxygen reversibly in response to variations in temperature and the surrounding atmosphere. The oxygen storage capacity at 400°C reached 2.9 wt% for x = 0.50, while it rapidly decreased with increasing x. Owing to the strong temperature dependence of excess oxygen amount, this oxide showed remarkable ability to intake/release oxygen when temperature swinging between 500°C and 700°C is applied.

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Ceria (CeO2)-based materials have been recognized as an important component of the three-way catalysts (TWCs) because of their excellent oxygen storage capacity (OSC). Since the 1990s, many studies have been devoted to CeO2-ZrO2 solid solutions, to reduce the emission of toxic pollutants (CO, NOx, hydrocarbons, etc.) from automobile exhaust due to their enhanced OSC in automotive TWCs, oxidation-reduction behavior and improved thermal stability at elevated temperatures. Herein, we describe the preparation and characterization of Ce0.5Zr0.5-xAlxOy solid solutions via a facile solvothermal route.

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We investigated CO₂ absorption behavior of Li₂CuO₂ at room temperature. Li₂CuO₂ was pulverized by planetary ball milling under CO₂ atmosphere at room temperature. The thermogravimetric analysis (TG) and X-ray diffraction (XRD) of the pulverized samples were performed to evaluate the CO₂ absorption behavior. From the result of TG and XRD, we found that the smaller the particle size of the sample, the more CO₂ absorption of that.

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Layered double hydroxides (A²⁺_1-kB³⁺_k(OH)₂X^m-_k/m·nH₂O, A:Co, Ni, B:Al, Fe, Mn) were prepared by hydrothermal process, and were examined for soft-chemical reaction and for application to porous materials. The hydrothermally-synthesized LDHs composed of CoAl, NiAl and NiFe can be intercalated with sodium dodecyl sulfate due to relatively high crystallinity. However, the intercalation seems to be difficult for LDH composed of CoFe.

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We report facile exfoliation of 2D nanosheets from Ti₃SiC₂. Currently the most voraciously researched 2D material-graphene is an exceedingly simple system. Our work opens up new horizon to the research in complex 2D materials in the group of layered hexagonal ternary carbides and nitrides - MAX phases. The alkaline extraction technique optimized at ambient conditions is benign to the environment. TEM characterizations reveal distinct individual layers of nanosheets.

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The morphology-controlled synthesis and near-infrared absorption properties of W18O49 were systematically investigated for the application of innovative energy-saving windows. Various morphologies of W18O49, such as nanorods, nanosheres, etc. with various sizes were successfully synthesized by solvothermal reactions using various alcohols as reaction media and, W(EtO)6 and WO3 sol as W source. The W18O49 nanorods of less than 50 nm in length showed the best optical performance as an effective solar filter, which can realize high transmittance in the visible region as well as excellent shielding properties of near infrared light.

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Titanium oxide is useful as an electrode for fuel cell, solar cell, or electrolysis of water, since it can fix the catalyst, dye and enzyme on its surface. In the present study, Ti metal was chemically and thermally treated to form titanium oxide with high specific surface area, high conductivity and ability for catalyst fixation on its surface. A nano network structure was formed by NaOH and HCl treatments and remained even after subsequent heat treatments below 900ºC. The titanium nitride and titanium oxide with oxygen defects were formed by heat treatment in N2 atmosphere. The oxide was mainly formed at the top surface, while titanium nitride was in deeper region. Their conductivities increased with increasing temperature of heat treatment. A redox catalyst such as ferrocene with phosphate end group was able to be fixed on the surface of the Ti metal prepared by chemical and heat treatments.

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Metal oxide nanoparticles with controlled nanostructures were synthesized by using a wet chemical process and applied to various energy conversion devices. First, we succeeded to prepare a TiO2 nanotube (TNT) thin film by using an alternate layer deposition method. TNT thin film showed excellent photocatalytic and unique electrochemical properties. Second, we found that thermoelectric property of ZnO was improved by co-doping with Y and Al. The maximum value of the dimensionless figure-of-merit (ZT) of 0.41@1000 degree C was obtained for Y and Al co-doped ZnO, prepared by using a pre-doped ZnO nanopowder synthesized by a wet process.

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One of the applications of quantum dots is quantum dot-sensitized solar cells. At present, however, their energy conversion efficiency is not high enough for commercialization. One of the reasons is the loss of energies when electron transfers from quantum dots to TiO₂ particles. In order to avoid this energy loss, we coated TiO₂ directly on the surface of the quantum dots using titanium alkoxide. Photoluminescence efficiency of the TiO₂-coated quantum dots is only slightly reduced. This indicates that the surface state of the quantum dots is maintained after TiO₂ coating.

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[in Japanese]

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Electrolyte membranes for all-solid-state alkaline fuel cells were fabricated using Mg-Al layered double hydroxide (LDH) powder with glass paper or Pt-catalyst-loaded carbon cloth as a supporter. Membranes with a thickness of about 100-150 μm were obtained. Fuel cells using those membranes as a electrolyte were confirmed to show OCV of more than 0.9 V. These cells showed higher power density compared with a fuel cell using the Mg-Al LDH pellet as the electrolyte.

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In this work, two kinds of materials, conductive porous alumina (CPA) and Ni foam were used as the backup layer of gas diffusion electrode (GDE). The CPA prepared by the novel gel-casting method combined both of the sintered alumina grains and nano-carbon network and the porosity reached to 72 vol%. A novel Ag/C nanocomposite was used as the catalysts in both of these two kinds of GDEs. The results of electrochemical tests illustrated that the GDE combined with CPA exhibited a higher activity forward oxygen reduction reaction comparing with that of Ni foam. However, the GDE with Ni foam exhibited a higher electric conductivity.

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We fabricated electrolyte membrane and pseudo-electrode using phosphoric acid treated gypsum. We assembled the pseudo-electrodes onto the electrolyte membrane under some conditions. The resistance of the interface between the membrane and the electrode was measured by AC impedance method and evaluated by using equivalent circuit. The resistance was largely lowered by fabricating electrode on the membrane directly.

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[in Japanese]

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The protonic conducting zinc phosphate glasses containing barium ions were prepared by a melt-quenching method. The glass structures were evaluated by ³¹P MAS-NMR spectroscopy. The peaks of QP2 shifted to the side of lower magnetic fields with increasing the barium amount. The peak intensities of Q⁰ and Q¹ appeared strongly for the samples containing 10-30 mol% barium. These phosphate groups are expected be designed for improving the proton conductivity.

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[in Japanese]

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Butane is suitable for portable fuels because of easy liquefaction. However, the solid carbon can be deposited on the nickel catalyst at low humidities in hydrocarbon fuels, which causes the rapid degradation of the anode performance. In this study, the fuel flexibility was investigated for the anode-supported microtubular SOFCs at the carbon deposition condition.

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[in Japanese]

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There is an increasing demand for SiC components with large size and complicated shape, and one important method of manufacturing these components is by joining SiC sintered parts using various joining techniques. In this work, Si-SiC ceramic parts were joined by a reactive sintering method based on outward diffusion of Si. Mechanical properties of the joined parts were evaluated. The joined Si-SiC parts exhibit high flexural strength without any serious deterioration by heating.

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MD simulations carried out to examine the effect of B- and/or C-doping on the properties of amorphous silicon bonded to SiC crystals are reported. The Tersoff potential form is used to model strongly covalent interactions in systems of amorphous silicon with small amounts of B and/or C, as well as of systems in which the amorphous silicon phase is sandwiched between two identical SiC surfaces, either 6H-SiC(0001), 6H-SiC(2-1-10) or 3C-SiC(001). Systems were simulated between 300 and 1700 K. After relaxation of the structures at zero pressure, diffusion coefficients were extracted from mean square displacement calculations and correlated with structural features.

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High-capacitance MLCC technology road map always shows thinner dielectric and inner electrode layer to obtain higher capacitance with smaller case size. Thinner MLCC ceramic layer means smaller grain size of BaTiO ₃, naturally milling and mixing of smaller BaTiO₃ powder and/or the raw material using beads miller with smaller PSZ (partial stabilized zirconia) is indispensable. Conventional PSZ bead for mill is a sintered type. On the other hands, plasma process can fabricate nano-sized powder effectively. We characterized the two different types of 50um PSZ beads by HR-STEM (high-resolution scanning transmission electron microscopy).

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Microstructural developments during sintering in 3 and 8 mol% Y₂O₃-stabilized ZrO₂ polycrystals (3Y and 8Y) were systematically investigated in the sintering temperature range of 1100-1500ºC. Grain growth in 8Y was much faster than that in 3Y. In the grain-boundary faces, Y³⁺ ions segregated at the grain boundaries within a width of about 10 nm. The amount of segregated Y³⁺ ions in 8Y was significantly less than that in 3Y. This indicates that an increase in segregated Y³⁺ ions retards grain growth. Therefore, grain-growth behavior can be reasonably explained by the solute-drag mechanism of Y³⁺ ions segregating along the grain boundary.

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Effect of dopants on mutual grain-boundary (GB) transport of Al and oxygen in polycrystalline Al2O3 wafer that was exposed under steep oxygen potential gradients was evaluated at temperatures of up to 1923K. The diffusion parameters such as chemical potentials, GB diffusion coefficients, and the flux of aluminum and oxygen were determined as functions of position in the depth direction of the wafers. The flux of both Al and oxygen at the outflow sides was significantly larger than at the inflow sides. When only the mobility of oxygen was decreased by GB segregation of Lu, the driving force of Al diffusion was reduced nearby the outflow side, resulting in decrease of flux of both oxygen and Al at the outflow sides.

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[in Japanese]

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Porous alumina is used as support carrier of separation membrane materials. In an actual application, it is exposed in high thermal stress condition. Thermal shock fracture test was performed on porous alumina ceramics, which have various porosities and pore sizes. Fracture strength, fracture toughness, Young modulus, thermal expansion coefficient and thermal conductivity, which affect to the thermal shock property, were also estimated. All properties except for thermal expansion coefficient and thermal shock strength tend to be decreased with the increase in porosity and pore size. On the other hand, the nitrogen permeability was increased with the increase in porosity and pore size. Properties of porous alumina with well-growth grain necking were higher than that of smaller pore size at the same porosity.

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In this study,porous ceramics possessing new pore structure were prepared by emulsion method. Firstly, non-aqueous slurry containing silicon carbide powder and oleic acid was emulsified in aqueous slurry containing alumina powder, monomer, dispersant and cross-linker. Then the emulsion was polymerized by gelcasting method using initiator and catalyst. Thus prepared green body was dried for 4 days and was subsequently sintered at 1700C for 2h in air atmosphere. Pore structure of the porous ceramics was observed by microscopes, and, porosity and pore size distribution was evaluated. We tried to control the porosity and pore size distribution by changing the volume of non-aqueous slurry and aqueous slurry.

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Recently, blended cement is needed in order to lower the energy consumption and CO2 emission from cement industries. Therefore, waste management and environmental loading reduction is also requested by using by-product from other industries, such as BFS and FA. Blended cement can be resulted in good performance for long time hydration. However, the early strength and hydration reaction of blended cement is low and not enough. This paper investigates on using High Alite Cement to improve the early hydration of blended cement. The result shows that High Alite Cement can be suitable for blended cement with both BFS and FA.

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