Ti-Al-V-doped Cr₂O₃ green pigments could present a higher near-infrared (NIR) reflectance compared to pure Cr₂O₃. The amount of Ti and V introduced in the Cr₂O₃ matrix has been systematically varied respectively, in order to evaluate the effects of Ti and V contents on the NIR properties of the doped Cr₂O₃. For comparison, experimental reflectance measurements and mean-NIR reflectance (780–2000 nm) of samples are given. The results reveal significant variations in the NIR region as a function of nominal composition for both Ti-doped Cr₂O₃ and V-doped Cr₂O₃. Moreover, the NIR reflectance of a Ti-Al-V-doped Cr₂O₃ pigment sample was measured. It has been found that it exhibits lower NIR reflectance compared to that reported in previous study. The correlations between electronic structural and spectroscopic features are discussed. For the Ti-doped Cr₂O₃ samples, the decrease of free carriers and the electronic transitions between defect energy levels within the band gap and the conduction band, could be responsible for the variable NIR reflectance. However, for V-doped Cr₂O₃, apart from light absorptions of free carriers, there are new light absorption peaks range from 1190 to 2000 nm, resulting in the variations of the NIR reflectance.

抄録全体を表示

Nanocomposite thin films composed of oriented Co₅₀Pt₄₄Cu₆ nanoparticles embedded in a MgO matrix has been synthesized by rf-magnetron co-sputtering onto NaCl(001) substrates kept at 620 K. As the sputtering power increases, (001) orientation is improved and atomic ordering is also promoted. However, superlattice reflections are quite weak and the ordered region is limited in local area of the nanoparticles, indicating low degree of order. Electron diffraction and elemental mapping revealed that additive Cu is alloyed with CoPt. We have also fabricated (Co₂₆Fe₂₀)Pt₄₄–Ag₁₀–SiO₂ nanocomposite thin films at 675 K for comparison. Atomic ordering is promoted by Fe and Ag addition as well as higher substrate temperature; however, it was found that ternary element (Cu, Ag, Fe) addition into CoPt alloy is not so effective to promote atomic ordering. Origin of the slow ordering kinetics is discussed using thermodynamical parameters.

抄録全体を表示

The physical and optical properties of newly synthesized, environmentally friendly, highly reflective green–black (HRGB) pigments (CoO)_x(MgO)_1−x·n{(Al₂O₃)_y(Fe₂O₃)_1−y} (x = 0.5, y = 0.75, and n = 1) calcined at various temperatures were studied. The pigments were prepared from Fe₂O₃, Al(OH)₃, Mg(OH)₂, and CoCO₃ by a novel modified solid solution method. The synthesis was performed at a reduced calcination temperature with lower energy consumption than the standard methods. The physical and optical properties (lower magnetization and higher total solar reflectance) of the HRGB pigments were superior to those of related pigments with the same chemical structure. Dependence of physical and spectroscopic properties of the HRGB pigments on the calcination temperature was also studied. Mixed with TiO₂, a highly reflective black pigment, synthesized similarly to the HRGB pigment and possessing similar physical properties, exhibited 80% higher reflectivity than a standard black pigment similarly mixed with TiO₂.

抄録全体を表示

Highly dense binderless WC was obtained by hot press sintering (HP) and then treated by hot isostatic pressing (HIP). Compositional and phase analyses of the products were carried out using field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The mechanical properties were evaluated, and the location of the inhibitors was studied by transmission electron microscopy (TEM). The sub-micron (0.53 µm) powders of WC (doped with 0.33 wt % VC and 0.54 wt % Cr₃C₂) were HP sintered at 1800, 1900, and 2000°C. WC with a relative density of 97.9% and a grain size of approximately 0.73 µm was obtained after sintering at 2000°C for 30 min under a pressure of 28 MPa. The Vickers hardness and fracture toughness were 24.15 ± 0.33 GPa and 4.40 ± 0.10 MPa·m^1/2, respectively. After treatment by HIP at 1750°C for 120 min under a pressure of 150 MPa, the relative density of the samples was increased to 99.4%, the hardness was over 26.00 GPa, and the grain size was 0.75–0.81 µm. The grain growth inhibitors were also characterised by TEM and energy dispersive X-ray spectroscopy (EDX); the results show that the grain growth was effectively suppressed by the inhibitors of VC and Cr₃C₂ as a result of the segregation of the inhibitors at the grain boundaries.

抄録全体を表示

A mixture of B₂O₃ and amorphous B with the mole ratio of 1:14 is shown to react and form B₆O ceramic under in-situ spark plasma sintering (SPS) conditions. The optimum SPS temperature and time to obtain phase B₆O are 1250°C and 30 min, respectively, and Rietveld refinement of the XRD patterns indicates that the oxygen occupancy of B₆O_x is reasonably high at x = 0.89(99). However, to reach high density above 98%, SPS temperatures of 1700–1800°C are necessary and a one-step two-temperature in-situ reactive SPS was designed and applied. As-prepared B₆O dense ceramic has Vickers hardness (36.7 ± 1.2 GPa) and fracture toughness (K_1c = 4.2 ± 0.15 MPa.m^1/2) comparable with the highest values reported in literature for the bulks obtained by processing routes of already reacted B₆O powders (ex-situ routes).

抄録全体を表示

Highly ion-conductive thin films in the pseudobinary system Li₄GeS₄–Li₃PS₄ were prepared by pulsed laser deposition (PLD). Raman spectra showed that the obtained thin films were mainly composed of Li⁺, (PS₄)³⁻, (GeS₄)⁴⁻ and (GeS_1/2S₃)³⁻ ions. The 33Li₄GeS₄·67Li₃PS₄ (mol %) thin film showed glass transition phenomenon at about 160°C, suggesting that the obtained amorphous thin film was in a glassy state. The thin film exhibited higher ionic conductivity than the Li₄GeS₄ and Li₃PS₄ thin films because of the so-called “mixed anion effect”. Furthermore, the structural rearrangement and crystallization after heat treatment for the thin film increased ionic conductivity from 1.1 × 10⁻⁴ to 1.8 × 10⁻³ S cm⁻¹ at 25°C, and decreased activation energy from 42 to 28 kJ mol⁻¹. Highly lithium-ion conductive thin films prepared in this study are promising for the application to bulk-type all-solid-state lithium secondary batteries.

抄録全体を表示

First-principles electronic-structure calculations have been performed to examine electronic properties of hexagonal boron nitride (h-BN) monolayers. The dispersion of the energy bands and the width of the band gaps are calculated under biaxial strains. It is found that the band gap decreases as the tensile strain increases, whereas the band gap increases and then it decreases as the compressive strain increases. The relationship between the energy-band structures and the applied strains is reported to clarify the unique behaviors of the band gaps induced by biaxial strains.

抄録全体を表示

The preparation technique to obtain purely inorganic silica doped titania fibers using electrospinning together with sol–gel method was proposed. For the system without silicon doping, fibers were too brittle to form long fiber. And it was clarified that small amount of doped silicon could modify the flexibility of fibers drastically and long fibers with appropriate mechanical property could be obtained. After calcination at 500°C for 2 h anatase phase was appeared and the specific surface area of fibers with composition of [Ti]/[Si] = 6 showed highest value 71.9 m²/g among all the samples tested, which is even higher than typical fine particles. The result of decomposition experiment of Rhodamine B dye solution showed that the silica doped titania fiber has adequate photocatalytic activity to decompose organic matters.

抄録全体を表示

A vanadium oxide based precursor fine powder was prepared by the reaction of vanadium metal and W-IPA H₂O₂ aqueous solution, and non-doped VO₂ or W-doped VO₂ fine powder was obtained by heat-treatment of the precursor powder at 650°C in an H₂/Ar atmosphere. Composite films were fabricated using the non-doped or W doped VO₂ fine powder and transparent urethane resin. The resulting composite films showed a reversible thermochromic property. The transition temperature of the composite using non-doped VO₂ powder was 68.9°C, and that of the composite using 1% W doped VO₂ powder was 46.3°C.

抄録全体を表示

The silicalite membrane, which is a type of zeolite membrane, has the highest hydrophobicity. An improvement in membrane selectivity would enhance the energy efficiency of the separation process. An enhancement in the hydrophobicity of silicalite membranes is possible by surface modification. Tubular silicalite membranes were hydrophobized by silylation, and their pervaporation (PV) performance for the separation of ethanol from a dilute ethanol-water mixture was investigated. The tubular silicate membranes were prepared by the secondary growth method, which consists of seeding by electrophoretic deposition and hydrothermal synthesis. Trimethylchlorosilane (TMCS), methyltrichlorosilane, propyltrichlorosilane, and 3,3,3-trifluoropropyltrichlorosilane were examined as the silylation reagents. The desired improvement in hydrophobicity and membrane performance were achieved only in case of TMCS. The contact angle increased from 20 to 130° and the PV performance improved after the silylation. A permeate EtOH concentration of 85.9 vol % with a total flux of 0.31 kg/m²·h from a 5 vol % EtOH aqueous solution at 30°C was obtained.

抄録全体を表示

Cu₂O is a p-type semiconductor with a direct band gap of ~2.1 eV, and is expected for solar cell applications etc. Since monovalent Cu is necessary, compositional control is a key step for Cu₂O processing. Electrospray is a phenomenon generating ultrafine droplets, when a high voltage is applied to the surface of liquid. In this study, Cu₂O thin films with unique ring-shaped 2-D network structure have been prepared by using electrospray pyrolysis method. Copper (II) acetate monohydrate, (CH₃COO)₂Cu·H₂O was used as a raw material, and D(+) glucose was used as a reducing agent for the reaction from Cu²⁺ to Cu⁺. At the substrate temperature of 300°C, only Cu₂O was obtained as a crystalline phase. Microstructure, sheet resistance and some optical properties will be discussed.

抄録全体を表示