Water splitting to produce hydrogen using abundantly available solar energy and water is a process of utmost importance and urgently required due to exponentially increasing global energy requirement, over-consumption and drying up of fossil fuels, as well as economic and environmental issues. Although first water splitting experiment with UV light was demonstrated on n-type TiO2 anode and Pt cathode in a photoelectrochemical cell on 1972 by Fujishima and Honda, there is no breakthrough results reported yet in terms of quantum efficiency more than 10% in visible light and sustainable activity without any sacrificial agent. Especially, catalysts that work with visible light and high efficiency are scarce, although many materials work efficiently in UV light. Nonetheless, there is some progress in this area in the last ten years, after the discovery of anion doping in semiconductor oxides. Especially, solid solution between an oxide and either nitride are emerging as promising materials. Present mini review is restricted to the above class of materials, which show electronic structural changes play a significant role in reducing the band gap to induce visible light absorption. Above solid solutions also demonstrate significant visible light driven photocatalytic activity and exhibiting high potential towards that.
Color filters have been used for a variety of applications such as liquid crystal displays (LCDs). Conventional color filters produce color by absorbing unnecessary wavelengths, which cause energy loss. Additionally, as an important optical element in the LCDs, polarization filters are required since liquid crystals have polarization dependency. We propose hybrid plasmonic-dielectric subwavelength grating (SWG) filters, which have both functions of wavelength- and polarization- selectivities in one filter. The SWG filter consists of a three-layered one-dimensional SWG, in which a plasmonic layer, a buffer layer, and a dielectric layer are stacked on a substrate. Using rigorous coupled-wave analysis, three kinds of the SWG filters with periods of 300, 380, and 500 nm are designed to produce blue, green, and red colors, respectively. For transverse-magnetic polarized light, each SWG filter shows high transmittance in each color region with good wavelength selectivity, which functions as a color filter. Maximum transmittances of 72.4%, 72.6%, and 73.5% are obtained at wavelengths of 445, 540, and 650 nm for the blue, green, and red filters, respectively. For transverse-electric polarized light, each SWG filter shows high reflectance in the whole visible region, which functions as a broadband band-stop filter.
A subwavelength hole array, which consists of a thin metallic film and a dielectric, enables to transmit a certain wavelength caused by surface plasmon polaritons (SPPs). SPPs exist at the interface between the metal and the dielectric, which means that the transmission spectrum strongly depends on the propagation of SPPs across the material interface. SPPs propagation is influenced by the array periodicity and hole shape. The relationship between the periodicity and the transmission spectra can be obtained from a band diagram of the energy and wavenumber of the SPPs. However, determining the hole shape that will provide a desired transmission spectra is difficult. For the systematic design of hole shape, a level set method based on topological optimization can be used to perform an accurate electromagnetic analysis. In the level set method, the material interface is clearly defined using a finite element mesh. Therefore, the physical properties of the boundary interface can be calculated precisely. By comparing experimental and simulated results, we confirmed that the proposed method is effective for the systematic design of hole shape.
We develop an extended cluster expansion (CE) technique, continuous-spin basis variable-lattice cluster expansion (CS-VLCE), enabling complete description of strain effects on alloy configurational energetics for single as well as multiple lattices. In the proposed CS-VLCE, spin variable ω on a virtual lattice is introduced, which specifies the strain of a given cell from the base cell. Basis functions constructed from ωs and those used in the CE satisfy completeness and orthonormality for any atomic arrangement in any strained cell. As an example, combination of the CS-VLCE with first-principles calculation is applied to estimate superlattice formation energy along the  direction for Cu-Au binary alloys. We successfully demonstrate that the CS-VLCE can accurately handle strain effects on total energy, which cannot be achieved by the current CE.
Molecular dynamics simulation (MD) has been performed to investigate the partial dynamical structure factors Sξη(k, ω) of the superionic phases for (AgxCu1-x)Br of x = 0.1, which contains two kinds of mobile cations, Ag+ and Cu+. From the obtained Sξη(k,ω), the longitudinal acoustic (LA), the longitudinal optical (LO), and the transverse acoustic (TA) modes have been observed. All these modes are propagated mainly by Br ions. The interaction between ions is also discussed using the model based on the plasma frequency.
Using non-equilibrium molecular dynamics, we study the thermal transport properties of conical carbon nanofibers, comparing with single-walled carbon nanotubes and graphene nanoribbons. Our results predict that the conical nanofibers have at least a two-order of magnitude smaller thermal conductivity. We then predict the potential applicability of conical-helix carbon nanofibers to nanoscale thermoelectric devices.
Research and development about maturing of liquor has been investigated. The heat pump defrosting system at snowy and cold regions was applied to the maturing of sake. The system controls temperature and humidity automatically without any humidifier. This system can be also applied to cold storage for maturing of vegetables and fruit. The developed system can increase productivity and create added value the stored products.
Woodceramics (WCMs) are the new functional carbon materials fabricated by sintering woody materials impregnated with phenolic resin. The fabrication process, properties and application of WCMs are introduced. The properties of WCMs depend on the sintering condition. WCMs have been studied as humidity and gas sensors, electrode for polymer electrolyte fuel cell (PEFC) and electromagnetic wave absorber. Electrical impedance of WCMs changes as humidity and ammonia gas concentration vary. The generated power of the PEFC with WCMs electrodes is almost the same as that of the PEFC with carbon paper electrodes. The shielding and loss properties of the electromagnetic wave absorber made from WCMs denote the same tendency of that of commercially-used electromagnetic wave absorber.
Soluble wool keratin was prepared by derivatization of disulfide (SS) bonds of cysteine residue to carboxymethylalanyl disulfide (CMAD) groups. The solubilization reaction was carried out in 0.2 M thioglycolic acid aqueous solution under alkaline conditions (pH 13.0 and 13.5). The solubilization reaction was performed by derivatization reaction including reduction and oxidation reaction. Carboxymethylalanyl disulfide keratin (CMADK) with desirable molar mass can be obtained by changing reaction conditions. Part of CMADK molecules showed helical structure. To investigate the prevention of hair damage by bleaching and permanent waving treatments, CMADK with low molar mass was prepared at pH 13.5 and 60°C for 3h. It was added to permanent waving agent and the bleaching and permanent waving treatments were carried out. The treated hair was hardly damaged even if the treatment was repeated for 3 times. CMADK is effective for prevention of hair damage.
The concept of greening is well understood and is now widely applied to commercial facilities and office buildings. However, greening requires the use of specific waterproof materials and construction methods, which makes it costly. Therefore, greening is seldom used in general residential houses. In this study, flower mats made of garden greening fabric were used to study the effects of roof and wall greening on two mimic houses. The material was obtained by recycling discarded cloth used for school uniforms and was effective for garden greening. The temperature in a mimic house to which greening was applied was approximately 1ºC lower than in a similar house without greening; i.e., greening had an insulating effect. Therefore, greening is predicted to shorten the time required for running air conditioners. A polyvinyl alcohol (PVA) sponge was added to half of the greening mats placed on the roof and water (2 ℓ per m2 of the roof area) was sprayed on all the greening mats once a day. The sponges improved moisture retention and the plants grown with these sponges showed stronger growth than plants grown without the sponges. The greening of buildings can be easily achieved at low cost by using flower mats made of garden greening fabric. The mats are lightweight, so the load of the flower mats on the building is small and greening can be accomplished without large-scale installation requirements. Flower mats therefore appear to be quite useful for greening of conventional residential houses.
The purpose of this research is to develop the recycling methods of the uniform material, which is the mixture of wool and polyester and had been abandoned up to now because the way of reuse had not been developed. As a basic research, we repeated the experiment to make uniform materials compound by soaking them in the mixture of PVA(polyvinyl alcohol) of the high polymerization degree and biomass oil (i.e. Hiba Japanese cypress oil and wood vinegar oil) in various densities. As a result it turned out that the characteristic changes variously by the difference of PVA consistency and biomass anti-bacterial oil, and that it brings the positive multiplier effect to the qualities of uniform material
Rice hull silica (RHS) carbon material is manufactured by introducing a phenol resin into the naturally porous rice hull structure, then carbonizing in a nitrogen gas atmosphere at high temperature. Several methods has been posed for RHS carbon quality control. One method is improving the production process, because natural resources are used as raw materials. In this paper, variation in rice hull components by cultivation region and rice brand has been investigated, compared and evaluated. Rice produced in Japan has less variation in shape than rice produced abroad, and its structures and composition are largely unaffected by weather conditions such as a rainfall or daylight hours. However, soil type had a large effect on composition of rice, these differences are eliminated by carbonization, because, regardless of cultivation region and brand, the major organic and inorganic components are C and Si, respectively.
Recently, new porous carbon materials have been developed utilizing the natural porous structures of some plant matters. The carbon materials are manufactured by mixing with the phenol resin, pressure forming, drying, and then carbonizing at 900℃. The authors have been studying the carbon material made from the defatted rice bran (RB carbon: RBC). However, the RBC includes some deliquescent components, and therefore has large hygroscopic expansion and large reduction of the mechanical strengths under wet and aquatic conditions. The low water resistance is associated with the inorganic components of P and K in the rice bran. In contrast, the rice hull does not include such inorganic components. In this study, the authors proposed the production of the seawater-resistant rice-hull silica carbon (RHS carbon: RHSC) from the rice hull and the RBC. After immersing the RHSC in seawater, the decrease of the compressive strength and the precipitation of the mineral ingredients were not observed, and the strain was 0.25%. Therefore, the RHSC is a material which has the stable water-resistance in seawater.
Bleaching and permanent waving (B&P) treatments were carried out up to 3 times on Japanese woman virgin hair. B&P in the presence of water soluble wool keratin (carboxymethylalanyl disulfide keratin, CMADK) (BPW) was also carried out. CMADK prepared at pH 13.5 and 60°C for 3h was dissolved in the permanent waving agent and used to treat human hair. The surface of B&P treated hair was gradually damaged with increase of treatment times. BPW treated hair had less damage compared to B&P treated hair. The disulfide bonds changed to cysteic acid with treatment times. Elastic modulus and stress at yield point of treated hair were smaller than those of untreated hair. However, the decrease was smaller in BPW hair than that in B&P hair. The hair permed in the presence of CMADK had solid wave compared to B&P treated hair. All the results suggested the efficiency of CMADK to reduce hair damage caused by bleaching and permanent waving treatments.
In this study, we demonstrate a facile method for the synthesis of mesoporous Au/silica composite particles. TEM images clearly reveal that the solvent evaporation of ethanol solution of F127, Au colloid particles, TEOS and HCl results in the synthesis of highly-ordered mesoporous composite particles. Diffuse reflectance UV-vis absorption spectrum of the obtained composite particles shows that Au colloid particles of the size of around 10 nm are present in the silica frameworks of the obtained composite particles. These results demonstrate that the particles obtained through a solvent evaporation process are mesoporous Au/silica composite particles with Au colloid particles incorporated in the silica frameworks.
The LiMn2O4 films for Li secondary batteries have been prepared by a RF magnetron sputtering method. In this research, we have prepared films by varying sputtering parameters. The dependence of film thickness on the sputtering parameters was evaluated. The relationship between film thickness and sputtering parameters was clarified. The film composition was identified by X-ray diffraction and gravimetric method. The surface morphology was observed by a scanning electron microscopy.
Li2MnO3 powder with a monoclinic cell related to the space group of C2/m was synthesized by a simplified coprecipitation method, followed by a combustion technique. Its electrode properties as a lithium-battery cathode were investigated in the charge-discharge potential ranges of 2.0 – 4.6, 2.0 – 4.8, and 2.0 – 5.0 V. In all the potential ranges, the electrochemical capacities gradually increased during cycling, and the increased capacities significantly depended on the potential ranges. Compared to the discharge capacities for the potential ranges of 2.0 – 4.6 and 2.0 – 5.0 V, the former merely increased from 12.5 to 22.5 mAhg-1 between the 1st and 99th cycles, whereas the latter increased from 20.0 to 110.2 mAhg-1 during the same cycling. The structural variation in Li2MnO3, which is induced by the cycling, also shows a fluctuation depending on the potential range, and conversion to the rhombohedral phase is detected during cycling in the potential range of 2.0 – 5.0 V.
The porous ceramic substrate repelling Si melt was developed for the growth of high quality spherical Si crystals with slow cooling of Si melt on the substrate. For the characterization of the developed porous ceramic substrate, high temperature in-situ observation of Si melt on the substrate was carried out using the original furnace. Contact angle between Si melt and the substrate was measured for the porous substrates composed of Si3N4 and SiO2 at a weight ratio 4:1 with different size of pore (2, 5, 10 and 20 μm). Developed porous ceramic substrate shows excellent repellency against Si melt and the maximum measured contact angle is 160°. The contact angle of Si was affected by the pore size of the porous substrate and the substrate with pore size 2-5 μm is preferable for the growth of spherical Si crystals on the substrate. Grown spherical Si crystals are single or twin crystals and meet the impurity specifications of Si for solar cells.
Tetramethylsilane was decomposed in the microwave discharge flow of Ar to produce emission spectra of the CH(A2Δ-X2П) and Si(4s-3p) transitions. The mechanisms of the production of the excited states were studied by the combined analysis of the laser-induced fluorescence (LIF) spectroscopy of the 3P0 metastable state of Ar and electrostatic-probe measurements. The pressure of Ar was varied in the range of 0.2-0.4 Torr; the density of Ar(3P0), nM, and the density, ne, and temperature, Te, of free electrons were varied. By comparing the Ar-pressure dependencies of the emission intensities, nM, ne, and Te with the support of a kinetic analysis, the production processes of CH(A2Δ) and Si(4s) states were found predominantly to be the energy transfer from the metastable state of Ar atoms.
FeSix films were deposited on Si(100) substrates at room temperature and at temperatures in the range of 100-300°C using RF-sputtering method with an FeSi3 target. After deposition, FeSix films were annealed at 400-900°C for 10 min in Ar gas. The crystal quality of the films was analyzed by X-ray diffraction (XRD) measurements, the surface of β-FeSi2 films was observed by an optical microscope and the film thickness was measured by surface step-measuring microscope. For the films deposited at 300°C and annealed over 800°C, Si(111) peak at 28.4° was superimposed on the β-FeSi2 (202/220) peak, which indicates that the films contained silicon crystals. On the other hand, for the films deposited at room temperature, Si(111) peak at 28.4° was not observed. No cracks were observed after annealing on the surface of the films deposited at 300°C although the films deposited at room temperature had cracks on the surfaces after annealing over 700°C. The major factor of cracks is considered to be the difference of the expansion coefficients between β-FeSi2 and silicon. For the film deposited at 300°C, a layer containing silicon crystals was formed near Si substrates. This layer served as a buffer between β-FeSi2 and silicon.
LaNbO4: Eu3+, Dy3+ phosphors prepared by a solid-state reaction were characterized by X-ray diffraction (XRD) and photoluminescence spectra. The XRD patterns of LaNbO4 doped with Eu3+ and Dy3+ essentially agreed with those of LaNbO4, indicating that the doping of Eu3+ and Dy3+ ions does not change the host crystal structure. From the strong emission peak at 615 nm corresponding to 5D0→7F2, Eu3+ was thought to occupy the sites with lower symmetry. In addition to the usual emission transitions from 5D0, the emission transitions from the higher 5D1 and 5D2 levels were observed. The transitions from the higher levels were explained by the reduced multi-phonon relaxation from the 5D1 and 5D2 to the lowest excited level 5D0 due to the lower vibrational energy of NbO43-. The relative emission intensity of the 5D0→7F2 transition decreased with an increase in the amount of Dy3+. This was attributed to energy transfer to the Dy3+ ions.
In this study, the synthesis of an indolo[3,2-b]carbazole (INC) derivative containing an octyl group and a p-vinylbenzyl group at N-positions was carried out as a monomer compound to obtain copolymers with methyl methacrylate (MMA) by a radical polymerization. These copolymers showed the amorphous state and exhibited the higher thermal stability as INC content increased, which maintained the high emission property of INC moiety. Furthermore, the spin-coating and casting films could be prepared form the copolymer solutions. Then, it was found that the strong photoluminescence was observed for these polymer films, the INC content of which was ca. 5 mol%.
Built-in potential maps of metal-oxide-semiconductor field effect transistors (MOSFETs) with gate lengths of 30 and 150 nm were measured on cross sectional Si(110) surfaces covered with ultra-thin oxide. The maps were obtained by measuring the contact potential difference (CPD) using multimode scanning probe microscopy (MSPM) with a vibrating probe in the constant force mode. The improved spatial resolution and the sensitivity to the electrostatic potential were achieved for an optimal probe-sample gap (～1 nm) and vibration amplitude of 0.2 nm. The capability and challenges of the measurement method are discussed by comparing measured CPD maps with device simulation results.
As electronic device dimensions are continuously reduced, new functions based on atomistic considerations can be implemented. Single-dopant transistors have been proposed based on a different mechanism as compared to conventional transistors, by making use of tunneling transport via individual dopant atoms located in nanoscale-channel transistors. However, typical dopants have shallow ground-state levels and thermally-activated transport becomes dominant at high temperatures. It is necessary to find a way to enhance the tunnel barrier height, i.e., to deepen the ground-state level, so that tunneling operation is maintained up to higher temperatures. In this work, as a first step, we use an atomistic simulation to extract information about the properties of dopants in nanostructures, in particular about the importance of channel design. For donors embedded in specifically-shaped channels, dielectric confinement effect is strong enough to ensure an enhancement of the tunnel barrier height. For the experimental study, we fabricated and characterized electrically nanoscale silicon-on-insulator field-effect transistors with ultra-thin stub-shaped channels. It was found that tunneling operation can be maintained even at elevated temperatures (approximately 100 K), which makes single-dopant transistors promising for more practical applications.
Structural and electronic properties of silicon-on-insulator (SOI) nanowires with a cross section area of 20×20 nm2 were investigated with high spatial resolution by multimode scanning probe microscopy (MSPM) in the constant force mode. The position-dependent tunneling current was measured in the interior of the Si nanowires whose surfaces were terminated with hydrogen and with ultrathin thermal oxide. The current value and fluctuations were reduced for Si nanowires terminated with an ultrathin oxide layer (～0.3 nm), indicating the homogeneous surface passivation. The tunneling current decreased within a distance of ~300 nm from the Si pad electrode for both types of surface termination. Calculations of the tunneling current were performed based on the macroscopic conduction model including the conductance contributions of the nanowire volume and the surface states. In the model, the bulk carrier concentration and the surface state density were tuned to fit the experimental data for the small Si nanowires. The results support the length-dependent conductance of thin Si nanowires, demonstrating the ability of the technique for characterization of modern silicon-on-insulator devices.
In order to apply for the magneto-optical (MO) imaging sensor, the preparation method of Bi3(FeGa)5O12 (BIGG) films on glass substrate using metal organic decomposition (MOD) was investigated. Generally, the BIGG system is thermally non-equilibrium and not precipitated from direct annealing treatments on glass substrates. It became possible to crystallize on glass substrate by inserting garnet buffer layer. The (YBi)3Fe5O12 was directly crystallized on glass substrate as polycrystalline buffer layer by annealing treatment. Then, the precursor BIGG films were coated on the buffer layer, then, they were crystallized by annealing treatment. The magneto-optical properties of the BIGG film were inferior to that on the Gd3Ga5O12 single crystal substrate, however, these results indicate the possibility to prepare the magnetic garnet film with huge MO effect without single crystal substrate.
The magnetic flux invasion into the Y-Ba-Cu-O-based high temperature superconducting bulk magnets were precisely evaluated during the pulsed field magnetization processes. Various bulk magnets with different contents of Y2BaCuO5 (Y211) particles were fabricated so as to examine how the Y211 concentrations affect the flux invasion behaviors. The flux motions and the resultant trapped field densities were monitored at the surface of each bulk sample at 30.6 K. As a result, the applied fields at which the magnetic flux began to invade the sample increased with increasing Y211 contents. This means that the pinning centers are promoted with increasing nominal Y211 addition. According to the evolutional profiles during the pulsed-field applications, the flux-penetration ratio gradually promoted with increasing applied fields, whereas the flux-trapping ratio decreased. This implies that the heat generation due to the flux motion seriously affects the field-trapping ability. The anomalous behaviors for the sample, which has displaced position of seed crystal, showed us more effective flux-trapping than usual, exhibiting the higher flux-penetration and flux-trapping ratios at lower applied-field than those of other samples. This suggests a possible high-field activation method with preferential flux invasion due to the different microstructures in the bulk magnet.
The response of chemical vapor deposited (CVD) diamond thin film to focused ionized particle irradiation was investigated in order to evaluate the film's use as a transmission detector for heavy ion hits from azimuthally varying field (AVF) cyclotron at the Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency. A spectroscopic grade Single-Crystalline (SC) CVD diamond film with thickness of 50 μm was prepared and characterized by using an ion beam-induced charge (IBIC) system with a 3 MeV H+ microbeam and a transient ion beam-induced current (TIBIC) system with a 15 MeV O4+ microbeam. The IBIC signals decreased significantly during a short period of microbeam irradiation, whereas the signal responded satisfactorily to the alpha particles from an 241Am radiation source. The peak degradation due to microbeam irradiation was quickly recovered by releasing the bias. These effects can be explained by terms of polarization due to charge capture by defects in the SC-CVD diamond.
We theoretically demonstrate that the temperature (T)-dependence of photo-excited carrier relaxation time (τ) in energy-gapped systems strongly depends on the rate of energy transfer from a longitudinal to transverse acoustic phonon mode. By considering the anharmonic coupling between them, we resolve an ambiguity in how to interpret the T-dependence of τ in alkali-doped C60 superconductors.
Transparent colorless polyimide (C. PI) substrate with good optical transparency and high glass transition temperature was developed. To explore performance and process-ability, IZO (indium zinc oxide) pixel electrode was deposited onto the C. PI and the quality of IZO thin films in terms of sheet resistance and transparency was measured. We next fabricated 3-inch C.PI-based liquid crystal display (LCD) clock by mean of sheet-to-sheet freestanding process and investigated its electro-optic characteristics. The resulting LCD showed good electro-optic characteristics; contrast ratio and response time of on/off operation were 826:1 and 12.0 ms, respectively.
TiO2 nanowires and nanorods were prepared on ITO coated glass substrates by hydrothermal method. TiO2 films were prepared under different preparation conditions. In this paper, effect of growth conditions on the surface morphological and structural properties of anatase and rutile TiO2 films was studied. XRD results showed that the pure rutile TiO2 phase was grown in HCl medium. In contrast, pure anatase TiO2 phase was grown in HNO3 medium. The crystallinity of TiO2 films increased as the reaction temperature was increased from 120 to 160°C. The phase transformation from rutile to anatase was observed when the volume concentration of titanium n-butoxide (TNB) increased from 0.5 to 1.0 ml. Scanning electron microscopy images showed that the morphology of the final product was strongly dependent on the experimental parameters, such as volume of HCl and annealing temperatures. The nanostructured TiO2 films fabricated by hydrothermal method can be used for dye-sensitized solar cell applications.
A scenario of ferroelectric domain formation in BaTiO3 is proposed based on our previous observation of temperature evolution of polarization clusters in paraelectric phase, ferroelectric domains, and relaxation dynamics of the polarizations. How the temporal polarization clusters observed at high temperature phase corrugate into static polarization domains in ferroelectric phase is discussed. Temporal polarization clusters turn out to static ones at 4.5˚C above Currie temperature due to a kind of critical slowing down which take place in polarization clusters. Static polarization clusters work like as super paraelectric dipole moments and dipole interaction among static polarization clusters increase according as power low when the temperature decrease toward Currie temperature. These static polarization clusters order at Currie temperature due to a mean field working among them. Bunches of ordered static polarization clusters evolve into relevant complete ferroelectric domains 6˚C bellow the Currie temperature.
We have determined refractive indices of rubrene crystals in the wavelength regions where their emissions were observed. For this purpose, we grew in a vapor phase the rubrene crystals having both horizontal and vertical pairs of parallel crystal facets. The facets functioned as optical resonators that produced interference fringes in the emission and reflectance spectra. From the fringes in the emission spectrum, we estimated the dispersion of the phase refractive index along the crystal a-axis. The anisotropic group refractive indices were evaluated along the b- and c-axes from the fringes in the reflectance spectra. The experimental indices were compared with those computed from the density functional theory.
Large-scale drop-cast films of π-conjugated polymers such as polythiophene derivatives and polyfluorene-based copolymers have been formed on a liquid-substrate with one-step deposition of Floating-film Transfer Method (FTM). Centimeter-scale uniform cast films could be obtained. Relative sharp vibronic structure was found in the Absorption spectra of FTM films as compared to those in spin-coated ones. FTM provides concentrically oriented films of a polymer having thermotropic liquid crystal characteristics. Comparative study of AFM topography with absorption spectra revealed that the origin of the optical anisotropic absorption was in the uniaxial orientation of nano-scale fibrils. This indicates that the oriented FTM films possess extremely large domains extended over 5 orders from micrometer to 10 centimeter scale. The findings represent that FTM is a simple and effective casting method to provide large-scale and uniform drop-cast films.
We investigated the important properties for practical use of (±)-10-camphorsulfonic acid (CSA) doped polyaniline (PANI) films on polyimide substrate as thermoelectric materials. We tested the flexibility and the thermal stability of electrical conductivity and Seebeck coefficient for the CSA-PANI films. The electrical conductivity and the Seebeck coefficient for the CSA-PANI films were almost unchanged after bending of 10,000 times. In addition, the CSA-PANI films were not exfoliated from the substrate after the bending test. The thermal stability of electrical conductivity and Seebeck coefficient for a CSA-PANI film on polyimide substrate was tested by the heat cycles of 30 times in the temperature range of 330-380 K. After the heat cycle test, the Seebeck coefficient slightly increased (approximately 10%) while the electrical conductivity slightly decreased (approximately 5%). The CSA-PANI film on polyimide substrate was found to be mechanically tough, flexible and possess relatively good thermal stability of electrical conductivity and Seebeck coefficient. These results suggest that if the thermoelectric properties are improved, CSA-PANI films are promising for use of the flexible organic thermoelectric devices.
Preparation of organic-inorganic hybrid architectures was accomplished on a copper foil surface immersed in various aqueous solutions of formamide and aniline. Beautiful “flowers” (spherically folded crystals) as well as “buds” and “petals” were observed on the copper surface in an aqueous solution of formamide alone. These crystals were composed of nanosheets of copper hydroxide hydrate, Cu(OH)2・H2O. The petal-like crystals appeared to aggregate, resulting in the flower-like spherical forms, via the bud-like structures. When the copper foils were immersed in aqueous formamide and aniline, spherical particles of polyaniline were deposited on the copper surface. There were no hybrid structures consisting of copper and aniline under the present conditions.
Optical properties of upconversion nanoparticles Y2O3:Er,Yb were investigated. The upconversion nanoparticles were prepared by laser ablation in liquid, which was one of the promising plasma processes to fabricate nanoparticle-dispersed solution. Highly crystalline nanoparticles with particle size of 11±3 nm were observed by electron microscope. Upconversion spectra with an excitation of 980 nm were measured by fluorescence spectrophotometer. Photon-avalanche effect of the nanoparticles, which significantly increased upconversion intensity, was observed. This phenomenon would be due to the increase in population at red emission by cross-relaxation. The ratio of red emission to green one was increased by the increase in the concentration of Yb in phosphor and the decrease in the excitation power.
We propose a structure of integrated micro solution plasmas, in which a number of microplasmas can be generated in a liquid medium, and we can expect efficient plasma-liquid interaction. It consists of a non-isolated porous dielectric material filled with a gas-liquid mixed medium. Since the bubbles in this structure are surrounded with conductive liquid, electrical discharges in the bubbles are not expected if we use liquid with infinite electrical conductivity. However, numerical simulation has revealed that the electric field in the bubbles can be high enough to ignite atmospheric pressure discharge in it if the liquid has finite electrical conductivity, for example 200 uS/cm for typical tap water, and that the concept of the integrated micro solution plasmas is feasible one.
We report the surface morphology of gallium nitride (GaN) films during the argon and nitrogen plasma etching at elevated temperatures up to 800°C. For Ar plasma at high substrate temperatures above 600°C, Ar+ ion bombardment dissociates Ga-N bonds by the preferential removal of nitrogen, which promotes roughness of the GaN surface by the aggregation of gallium atoms. In N2 plasma exposure, the N/Ga remains stoichiometric with higher values above 0.85, and the surface is not significantly roughened, even higher at 600°C. Therefore, the aggregation of metallic Ga induces surface roughening during ion-enhanced etching of GaN with elevated substrate temperatures.
Fe-45 at.% Rh bulk intermetallic compounds with ordered B2 structure were irradiated with 16 MeV Au ions at room temperature. The irradiation-induced phase transformation was examined by means of X-ray diffraction (XRD). By the Au irradiation, the degree of order for B2 structure decreased, instead ordered L10 and disordered A1 structures appeared. The change of crystal structure was considered in terms of the thermal spike and the martensitic transformation induced by the energetic heavy ion irradiation. Also the effect of the Au ion irradiation on hardness of the FeRh intermetallic compound was discussed.
Lignocresol was synthesized from Hinoki cypress (Chamaecyparis obtusa) through the phase-separation treatment with p-cresol and 72% sulfuric acid. Thermal responses of lignocresol were observed around 160°C, which is attributed to existence of unstable sites. Molecular rearrangements associated with the cleavages of benzyl aryl ether linkages improved thermal stabilities of lignocresols. Low molecular weight units formed by the molecular rearrangements work as plasticizer of lignocresol. The grass-transition temperatures (Tg) and solid-liquid transition temperatures of lignocresols were shifted down with increasing ratios of low molecular weight units. The results indicated that low molecular weight units have the function as plasticizer, forming a new application of lignophenol.