Nonoxide glasses composed of halides and/or chalcogenides (sulfides, selenides, and tellurides) as their main components have been extensively investigated due to their characteristic structures and properties. Among them, the present review focuses on glass formation based on nonfluoride-halide (halides other than fluoride) systems and the structure of the glasses as well as the transition properties of rare-earth ions in the nonoxide glasses. Systematic examination of glass formation in nonfluoride-halide systems based on AX_n-MX-M′X₂ with a single halide ion revealed that the systems of A=Zn, Cd, Ag, Cu and Li are vitrified by a conventional melting-cooling method, where X=Cl, Br, or I, M=alkali metal (K, Rb, Cs), and M′=alkaline earth metal (Ba). The coordination structure around the cations, Aⁿ⁺, was investigated by means of X-ray absorption spectroscopy and other methods. The structural model for these halide glasses is also discussed. The studies about the transition properties of rare-earth ions in the nonoxide glasses showed that the multiphonon relaxation rates are strongly suppressed. Detailed analyses on the fluorescent decay curves for Er³⁺-doped Ga₂S₃-based glasses are presented.

抄録全体を表示

Three types of nanostructured silicon carbide ceramics were prepared with additives of Al₂O₃ and Y₂O₃ as the primary sintering additives, together with 1 mass% CaO, 1 mass% MgO or 0.73 mass% AlN. The silicon carbides (SiC) containing tens of nanometers of grains were successfully fabricated using a two-step sintering process. The mechanical properties and contact damages of the nanostructured SiC ceramics were investigated in this study. The nanostructured SiC ceramics exhibited a hardness of~20 GPa, a strength of 400-700 MPa, and a toughness of 3.0 MPa•m^1/2. The nature of the contact damage exhibited classical ring or cone cracks formed in a region of weak tension outside the contact rather than microcracks in the diffuse quasi-plastic zones as observed in heterogeneous microstructures consisting of micron-sized elongated grains.

抄録全体を表示

S-doped titanium dioxide thin films were found to undergo hydrophilic conversion under visible light irradiation. The water contact angle for the S-doped TiO₂ thin film reached to 15° under visible light irradiation. The photocatalyzed decomposition of acetaldehyde (ALD) in gas phase on TiO₂ thin films was investigated in a batch-type photocatalytic reactor. The photocatalytic activities of TiO₂ thin films for decomposition of ALD were investigated by analyzing amount of ALD consumed and CO₂ generated under visible light irradiation at wavelengths longer than 420 nm.

抄録全体を表示

The larger scale production of nanoporous silica spherical particles was investigated. The particles formed from aqueous solution containing cetyltrimethylammonium chloride, tetraethoxysilane (TEOS), methanol, and ammonia at room temperature and subsequent calcination in air at 550°C led the transformation of the particles to be nanoporous with retaining the original particle morphology. The increase in the TEOS amount in the starting solution was effective for larger scale synthesis without significant loss of particle size distribution. Average particle size varied from 50 nm to 320 nm and the BET surface area varied from 240 to 850 m² g^-1. Maximum product weight achieved was ca. 1 g from 100 g of starting solution; the value is one order greater than those obtained by previously reported starting solutions, where TEOS amount is much smaller. The particle size (to 1721 nm) and surface area (up to 1020 m² g^-1) were changed by the surfactant amount in the starting solutions.

抄録全体を表示

Energy storage devices with high energy density have been used in many electronic devices in recently years. A supercapacitor is one such device, but lower energy density has limited its applications. In this study, manganese oxide deposited on a titanium substrate at various deposition temperatures using the galvanostatic electrodeposition method as the electrodes of a supercapacitor was investigated. The specific capacitance of a supercapacitor is depended on the deposition temperature and is affected by the surface morphology and roughness of the electrode surface. At a deposition temperature of 15°C, manganese oxide showed a needle-like appearance, a roughness of 60.0 nm, and a maximum specific capacitance of 225.3 Fg^-1. The charging/discharging behavior of a supercapacitor was analyzed in 0.1 M Na₂SO₄ aqueous electrolyte at various measuring temperatures and operating potential voltage ranges. The supercapacitor achieved a high energy density of 37.70 Whkg^-1 in a 0.1 M Na₂SO₄ electrolyte at 25°C in an operation range of 0 to 1.3 V.

抄録全体を表示

Synthesis and CO₂ absorption property of Li₄TiO₄ oxide were studied by X-ray powder diffraction and thermogravimetry. Samples were prepared by the solid state method using Li₂CO₃ and Anatase or Rutile TiO₂ as starting reagents. From the results of XRD, it was found that single phase Li₄TiO₄ can be obtained from Anatase TiO₂ and Li₂CO₃ with 1 : 2.1 molar ratio in an alumina cell in atmosphere of Ar : H₂=80 vol% : 20 vol% gas mixture (150 mL/min of flow rate) by heat-treatment up to 1000°C with 5°C/min of heating rate. By the results of thermogravimetry, it was found that single phase Li₄TiO₄ can absorb CO₂ in the temperature range of 300°C to 856°C, and the maximum absorption is 42 mass% at 856°C. From the results of XRD, LiTiO_x and Li₂CO₃ phases were found in the Li₄TiO₄ sample after complete CO₂ absorption. Therefore, it is supposed that following reaction occurs in the reaction process between Li₄TiO₄ and CO₂. 42 mass% of the maximum absorption could be predicted on the basis of the reaction. Li₄TiO₄(s)+1.5CO₂(g)↔LiTiO_x(s)+1.5Li₂CO₃(s)+(2.5-x)/2 O₂(g) x=2~2.5

抄録全体を表示

In this study, the leucite contents in the sintered porcelain and hydrothermally-derived powders were determined by the quantitative XRD analysis using internal standard. The leucite powders were prepared at 800°C-1200°C. The dental porcelain was sintered at 850°C from the mixture of 20 mass% leucite prepared at 1100°C and 80 mass% low temperature frit. The four standards for quantitative XRD analysis were established by mixing the low temperature frit (as a balance material), the copper (as an internal standard) and different weight content of pure leucite synthesized by molten method. They were X-rayed over the 2θ ranges from 14.5° to 17.5°, 26.5° to 28.5° and 42.5° to 44.5° for measuring the integrated area of leucite (211), (400) peaks and copper (111) peak. The area of leucite (211) and (400) peaks was divided by the area of copper (111) peak respectively and two calibration curves were plotted from these data. Before measuring the leucite content in the synthetic leucite, 40 mass% synthetic leucite was mixed with 60 mass% frit, whereas the leucite content in the sintered porcelain was determined by the method directly. The result of quantitative XRD analysis showed that the leucite content in the synthesized powders and dental porcelain correlated very well with the treating temperature and image analysis of SEM picture. The standards set in the study may be useful for measuring the leucite content in other systems.

抄録全体を表示

SiN_x thin film grown by plasma-enhanced chemical vapor deposition (PECVD) has conventionally been used as an antireflection layer of the silicon solar cell. In this work, a porous silicon (PS) layer formed by electrochemical etching was shaped on the surface of a crystalline silicon wafer for a simple alternative of anti-reflection coating (ARC). The etching solution was prepared by mixing HF and ethanol for efficient bubble elimination on the silicon surface during the etching process. The anodization of the silicon surface was performed under a constant current, and the process parameters, such as current density and etching time including volume fraction of HF to ethanol in the solution, were carefully tuned to minimize the surface reflectance of the CZ silicon wafer with sheet resistance of 35-40 Ω/□. The PS layer as an anti-reflection coating in the solar cell was compared with conventional PECVD SiN_x thin film by measuring the surface reflectance of the cell. Also, Photovoltaic I-V properties and the quantum efficiencies of the cells with PS layers were measured.

抄録全体を表示

Particulate coatings of In₂O₃ with 50-70% transmittance in the visible light were prepared by heat-treating In(OH)₃ deposited from aqueous solutions of In³⁺ and H₂O₂. The In₂O₃ coatings consisted of fine particles 500-800 nm in size. Doping the In₂O₃ with Sn⁴⁺ was conducted by immersing In(OH)₃ layers in a SnCl₄ solution prior to a heat-treatment in a flow of N₂. By incorporating Sn⁴⁺, the electrical resistivity was lowered from 1.02×10⁰ to 1.76×10^-2 Ωm.

抄録全体を表示

We obtained near-infrared (NIR) emissions by applying an electric field to a ZnO thin film containing Er ions. The sample construction was indium tin oxide (ITO) film/Er-doped ZnO film/ITO film on a SiO₂ glass substrate. By applying a suitable alternative voltage to the sample, a broad luminescence in the NIR wavelength range was observed. The intensity of the luminescence increased with applied voltage. The luminescence induced by the electric field had a wavelength of 1.5 μm, which suggests that the light emission is related to the intrashell transition of Er³⁺.

抄録全体を表示

C-axis-oriented aluminum nitride (AlN) thin films were prepared on Inconel substrates by the rf magnetron sputtering technique. The full-width at half-maximum (FWHM) of the X-ray rocking curve of the AlN films was 5.7°, and the piezoelectric constant d₃₃ was 2.4 pC/N. The deviation from the linearity of charges with pressures for the AlN films were 0.2% of a full scale at 0.4 MPa, which indicated a good linearity. Furthermore the AlN films was evaluated under combustion pressures in a single-piston 90 cc engine rotating up to 4000 rpm. The waveforms of the AlN films were similar to those of a commercial sensor. It is demonstrated that the AlN films have a good possibility as combustion pressure sensor elements.

抄録全体を表示