Knowledge of the concentration of hydrogen dissolved in materials is essential for the safe design of the components of hydrogen utilization equipment and will help clarify the mechanisms of hydrogen embrittlement. Here, we present a procedure for evaluating the hydrogen concentration in a perfect lattice under practical gaseous hydrogen environments using density functional theory. We employed the condition of chemical potential equilibrium between gaseous hydrogen and dissolved hydrogen in metal as the base equation and evaluated the vibrational energy and entropy at a finite temperature using the small displacement method. The hydrogen concentrations for aluminum and alpha iron obtained by our purely computational approach agree well with experimental data.
We propose the concurrent, hybrid molecular dynamics (MD) and coarse-grained particle (CGP) method for the simulation of problems such as crack growth in which nonlinear and atomistic phenomena occur at a certain confined region while linear elastic field spreads over the surrounding region of material and affects significantly the confined region. In the hybrid method, the MD is applied to the confined region and the CGP is applied to surrounding region. Extra atoms and particles are placed beyond the interface of the MD and CGP regions to connect the two regions with out artificial forces and artificial reflection based on the Langevin equation. The present method allows us the simulation at finite temperatures by adding thermal fluctuation to the total system. We performed the simulation of fracture of a suspended graphene sheet by indentation using the present hybrid method. The results obtained by the present hybrid method agree well with those by the fully atomistic simulation even at high temperatures.
The preparation of electrically conductive silicon nitride (Si3N4) ceramics by dispersing carbon nanotubes (CNTs) has been studied in the recent years. However, the density and strength of Si3N4 ceramics was found to deteriorate and the CNTs disappeared after firing at high temperatures because CNTs prevent Si3N4 from densification and there is a possibility that the CNTs reacted with the Si3N4 or SiO2. To prevent the CNTs from reacting and disappearing, low temperature densification is required. In this study, HfO2 was added to a Si3N4-Y2O3-Al2O3-AlN system to fabricate CNT-dispersed Si3N4 ceramics at low temperatures. As a result, a sample to which HfO2 had been added and which was fired at lower temperatures showed higher electrical conductivity and higher bending strength. It was also observed that the mechanical and electrical properties of the ceramics depended on the quantity of added CNTs.
Carbon nano tubes (CNT) have peculiar thermal properties and some applications with these properties are researched. In this research, we applied to improve heat radiation of silicon grease and investigated CNT diameter dependence of performance of improvement. In this research, we doped multi-walled CNTs (MWCNTs) which have two different diameters into silicon grease by 0.2wt% and 1.0wt% ratio. These samples were applied between an aluminum cube and an aluminum heat sink. Aluminum cubes were heated to 100°C and measured temperatures by the thermo tracer while cooling down. According to results, 0.2wt% CNT-containing grease was not able to improve heat radiation of silicon grease. It is thought that MWCNT which was doped in silicon grease by lower containing ratio could not conduct heat to neighbor CNT efficiently, and it could not improve the heat radiation. On the other hand, 1.0wt% CNT-containing grease had improved heat radiation. Additionally, MWCNT which had smaller diameter improved more effectively than lager one. It is thought that, interlayer bond of MWCNT impede the heat conduction by lattice vibration in the direction of length of CNT.
Preparation of layered double hydroxide (LDH) by substituting Zn in the structure was attempted to create an environmentally friendly photocatalyst with anion adsorption capacities. Zn-Al-substituted LDH with different Zn/Al molar ratios of 2, 3, and 4 were synthesized. The behavior of each synthetic Zn-Al LDH in photo-induced degradation of an anionic dye, sulforhodamine B, in aqueous solution was evaluated by determining the ultraviolet-visible absorption spectra under ultraviolet light irradiation. Zn-Al-substituted LDH showed photocatalytic activity toward sulforhodamine B, and degradation of sulforhodamine B was accelerated without stabilization under ultraviolet irradiation. Furthermore, the results suggested that Zn-Al LDH with a high charge density was more effective for continuous photo-induced degradation of sulforhodamine B in aqueous solution compared with Zn-Al LDH with a low layer charge. Zn-Al-substituted LDH should be useful as efficient photocatalysts for harmful organic anions.
As a phenomenon accompanied by device degradation of OLEDs (organic light emitting diode), our studies confirmed that the ITO (indium-tin oxide) component is diffused into the organic layer by a direct current voltage. This study discusses the pulse driving conditions under which this phenomenon is less likely to occur, aiming to improve the OLED performance. We studied interfacial changes under each set of driving conditions using XPS (X-Ray Photoelectron Spectroscopy). In addition, we measured the device temperature and brightness. As a result, we found that compared to direct current driving, pulse driving causes less damage to the device interface. In particular, when the pulse frequency is 60 Hz and the duty ratio is 50%, when the pulse frequency is 180 Hz and the duty ratio is 50% and when the pulse frequency is 300 Hz and the duty ratio is 75%, no interfacial changes occur and the brightness is stable. We also found that compared to direct current driving and other driving methods, with pulse driving, the device temperature is lower, enabling reduced energy dissipation into heat.
Silica films were prepared on stainless steel substrates by dip coating in a perhydropolysilazane (PHPS)/polydimethylsilazane (PDMS) solution. The effect of thermal treatment on the conversion from PDMS/PHPS to silica was investigated in detail with SEM and FTIR. A crack-free silica film was obtained with solutions containing PDMS. The mechanical properties of silica films were examined by performing the pencil hardness test and the Vickers hardness test. Silica films made from solutions containing PDMS were flexible. The corrosion resistance properties were investigated using a combined cyclic corrosion test instrument. Silica film is not adhered the rust even if PDMS was added.
Formation behavior of wear-induced layer in Fe-Ni alloys is investigated. The wear-induced layer i s observed just below worn surface and it has very fine microstructure. Moreover, reverse transformation occurs around worn surface, and volume fraction of austenite (γ) phase increases. As a result, microstructure and hardness of the wear-induced layer become the same regardless of initial microstructure. From these results, it is found that both microstructural refinement and reverse transformation occur during wear. These phenomena are induced by large shear strain and frictional heat due to wear. Based on these obtained results, formation behavior of the wear-induced layer in stainless steel (SUS304) is also investigated. As well as Fe-Ni alloys, the wear-induced layer with fine microstructure is formed just below worn surface of SUS304. However, strain-induced martensitic transformation occurs without reverse transformation. This is because that amount shear strain induced by wear is not enough to cause reverse transformation. Finally, it is concluded that phase transformation induced by wear is controlled by both the amount of shear strain and the frictional heat.
Photonic crystal is a new type of optical material in which a refractive index or dielectric constant is periodically changed. It is easy to fabricate 3-D periodic structures using textile technology. The main goal of our study has been, therefore, to fabricate the flexible photonic crystals by using high-dielectric-constant fibrous material. For this purpose, in this study, the high-dielectric-constant fiber was fabricated by coating of TiO2 particles onto the cotton-yarn by irradiation of ultraviolet light (UV), since the TiO2 is a photocatalytic material.
Softening behavior of eutectic and hyper-eutectic Al-Si-Cu-Mg-(Ni, Fe, Mn) cast billets produced by the new vertical semi-continuous casting process using an adiabatic and rapid cooling mold was examined. Ductile fracture manner fully covered on fracture surface of the specimens fatigued at 523 K, and was responsible for the low fatigue strength. Hyper-eutectic casts containing coarse Si crystals exhibited higher hardness than eutectic ones. However the hyper-eutectic alloys remarkably showed softening behavior above 523 K. The additions of Fe and Mn were effective to increase hardness of the Al-Si-Cu-Mg alloys at high temperature. Coarsening of Al-Cu-Mg compounds and precipitation of acicular compounds enriched Mg-Si-Cu were detected in the matrix of the hyper-eutectic alloy annealed at 523 K, and those may result in the softening behavior.
We have developed the ways to utilize a large amount of abandoned uniform materials. We found out that through the PVA soaking process, uniform materials are strengthened and get the new functions, such as water permeability, moisture absorption and durability against ultraviolet rays. These are the suitable functions of materials for agriculture and for the garden greening, and it is possible to divert it to the multi sheet for agriculture, because of its durability. Moreover, by making use of scrapped materials, we have devised the flower mat which is light , easy to handle
Various by-products of food growing and processing industries were evaluated for use in animal feeds. The by-products studied were tofu by-products (TF), brewers wet grains (BWG), soy sauce cake (SSC), apple juice pulp (AJP), mushroom bed (MRB), buckwheat hulls (BWH), rice husk (RH), saw dust (SD), and wheat straw (WS). Tofu by-products were further made into silage (TFS), or treated with enzyme (TFE). Chemical analysis alone can not predict the true value of these by-products. Degradation in the rumen of cattle (in situ method) provides better evaluation of these by-products for use as animal feed. Dry matter disappearance of more than 90% was observed in SSC, AJP, TFF, and MRB. Disappearance of 60-90% DM were observed in TFS, BWG, TFE, and WS. BWH, RH, and SD were very poorly degraded in the rumen. Among the tofu materials, silage showed faster degradation in the rumen. Addition of enzyme in the tofu silage helped it to slow the degradation which might be beneficial for use in cattle feed. Higher DM degradation of MRB relative to BWG indication that it can be used in cattle feed at low inclusion rate.
Rice-hull and soy-hull are agricultural by-products in Japan, and are required to be reused from a viewpoint of the recycling. The rice-hull and soy-hull carbon (RHC and SHC) powders are manufactured by carbonizing in nitrogen gas atmosphere at high temperature. The RHC and SHC carbon sheets are manufactured by wet papermaking process, in which the RHC and SHC powders, aramid fiber and LDPE (low density polyethylene) fiber are mixed in the water, and then drained the water to make the RHC and SHC carbon sheets. In this study, electrical conductivity, electromagnetic wave shielding and absorption properties of the RHC and SHC carbon sheets were discussed. Especially, the effects of the powder content, test-piece thickness, and the particle size of the RHC and SHC powders were measured. The result showed that the conductivity and the shielding effects were high in the SHC sheets with the large particle size. The absorption property was also high under certain high frequency areas for the RHC and SHC carbon sheets.
Activated carbon was fabricated from rice husks by KOH activation. The effect of the initial cooling rate of activation on the pore structure in the activated carbon fabricated by KOH activation was investigated. The specific surface area of the activated carbon increased from 1813 to 2418 m2/g with increasing the cooling rate from 3 to 32 ºC/min. The micropore diameter in the activated carbons was distributed approximately 0.6 and 1.1 nm. The micropore volume increased from 0.86 to 1.29 cm3/g with increasing initial cooling rate. The proportion of the volume Vmicro to the total pore volume Vtotal was calculated to be in the range from 90 to 96 %. Thus, the micropore structure of the activated carbon was strongly affected on the initial cooling rate on alkali activation.
Polypropylene (PP) is a polymer suitable for research of melt electrospinning. We examined the special properties of micrometer to nanometer order fibers produced through the latest heating-type melt electrospinning device whose amount of extrusion is strictly controlled. We found it necessary to control the extrusion speed of the six-nozzle type head to 0.4-0.6ml/h. This translates into a 1/10 or less decrease of speed in the melt electrospinning process while the extruding speed is 2.0-20ml/h in the melt blowing. When the melt temperature was lowered in melt electrospinning, the fiber diameter thinned. PP fiber spun from the nozzle by the electrospinning is believed to orient the molecular chains most effectively at the temperature of 250 ℃.
Potassium niobate, K(1+x)NbO3 (KN-10000x, 10000x = 0-40), ceramics were fabricated using KHCO3 powder as a starting material to improve their density, microstructure homogeneity and piezoelectric properties. The KN-7.2 ceramic has the highest density ratio of approximately 97% among the KN-10000x ceramics, showing excess K ions are very effective for the densification. The KN-7.2 ceramics also has homogeneous microstructure with small grains with a size of about 1-3 μm. On the other hand, grains of stoichiometric KN-0 are larger than those of the KN-7.2 ceramic. Also, each grain of the KN-0 ceramic has a faceted structure. Therefore, there are many pores between the grains. Our results show the strong effect of excess K on grain growth.
We have investigated the behaviors of domain clamping in Bi-based ferroelectric single crystals of Bi4Ti3O12 (BiT) and (Bi0.5Na0.5)TiO3 (BNT) using piezoresponse force microscopy (PFM). PFM observations reveal that 90° domains are clamped during polarization switching in BiT single crystals. BNT single crystals exhibited a large volume fraction of unswitched 71° domains after applying a high electric field. Electrostatic potential calculations for 90° domain structure indicate that the most stable sites for oxygen vacancies are adjacent to the domain walls with a distance of 0.1 nm. These experimental results and calculations show that an attractive interaction between non-180° domain walls and oxygen vacancies is the main origin of the clamping of non-180° domains in Bi-based ferroelectrics.
The perovskite ferroelectric system AgNbO3 exhibits a successive phase transition. Recent synchrotron X-ray and neutron powder diffraction measurements have revealed a monoclinic phase remains down to low temperature. In the present work we describe a Rietveld analysis of the detailed structure in the wide temperature range. The structure analysis indicated a possibility that a rhombohedral structure exists in a temperature region lower than monoclinic structure. The monoclinic structure can be viewed as a condensation along one of the ＜110＞ direction of the local displacements present in the tetragonal phase. It equally well corresponds to a freezing-out of the local displacements along the ＜100＞ directions recently reported by Noheda et al. for PZT. The monoclinic structure therefore provides a microscopic picture in which one of the locally monoclinic phases in the average rhombohedral or tetragonal structures freezes out, and thus represents a bridge between two phases.
The electronic structures of BiFe0.96Mn0.04O3 and BiFe0.96Co0.04O3 thin films have studied by X-ray absorption spectroscopy and soft-X-ray emission spectroscopy. The BiFe0.96Mn0.04O3 thin film has the mixed valence states of Mn3+ and Mn4+, although the BiFe0.96Co0.04O3 thin film has the valence state of Co3+. The conduction band consists of the Fe 3d state. The valence band is mainly composed of the O 2p state hybridized with the Fe 3d state. The bandwidth of valence band depends on the valence state of doped element. The energy gap of BiFe0.96Mn0.04O3 thin film is smaller than that of BiFe0.96Co0.04O3 thin film. These findings may indicate that the leakage current of thin film is closely related with the electronic structure and energy gap.
The Y-doped BaCeO3 (BaCe0.90Y0.10O3-δ) thin films have prepared on Al2O3(0001) substrates by RF magnetron sputtering. The thin films prepared at the substrate temperature of 300～500°C exhibits (002), (022) and (400) orientations. The thin film consists of grain with a diameter of 60～150 nm and smooth surface, although the grain size depends on substrate temperature. The prepared thin films were transparent. The electrical conductivity of the thin film exhibits thermal activation type behavior in H2O atmosphere of temperature region from 700 to 300°C. The activation energy (EA) of the thin film estimated from the Arrhenius plot is 0.30～0.42 eV. The EA values of the thin films are lower than that of the bulk ceramics.
Sc-doped SrTiO3 (SrTi0.99Sc0.01O3) thin film have prepared on MgO (001) substrate by RF magnetron sputtering using ceramic target. The substitution of Sc3+ ions was confirmed by X-ray absorption spectroscopy. The thin film prepared at the substrate temperature of 700℃ was crystallized by postannealing in O2 atmosphere at 800℃. The thin film exhibited a-axis orientation. The postannealed thin film was transparent The fundamental absorption edge of SrTi0.99Sc0.01O3 thin film shifts to lower wavelength side than that of SrTiO3 thin film. The valence band and conduction band measured by soft-X-ray spectroscopy are in good agreement with the calculated band-DOS. The energy separation between the top of the valence band and the bottom of the conduction band of the thin film is estimated to be ～3.5 eV
We previously reported the bioavailability enhancement of lipophilic Coenzyme Q10 (CoQ10) by complexing with γ-Cyclodextrin (γCD) in spite of poorly-soluble characteristics in water. We recently found the most plausible explanation mechanism which is due to the significant increase of water solubility of CoQ10 with the aid of sodium taurocholate (Na TCA) as a major component of bile acid in small intestine. By adding Na TCA into a water suspension of CoQ10-γCD complex, water soluble Na TCA-γCD complex is formed by the substitution of guest molecule from CoQ10 to Na TCA since Na TCA has higher association constant with γCD than CoQ10. Generally CoQ10 molecule agglutinates in water to form visible particles. But the dissociated CoQ10 from γCD cavity could be significantly solubilized in water captured in the midst of Na TCA micelle. This method could be applied for the other nutra-ceuticals like Curcumin and R-α-Lipoic acid. In the wake of the breakthrough projects using various nutra-ceutical-γCD complexes and Na TCA, we could also establish this new nanotech formulation system in personal care field by the combination of cosme-ceutical-γCD complexes with a cosmetic ingredient, dipotassium glycyrrhizate (GZK2) which has high association constant as well as Na TCA.
(Co, Zr)-substituted Al2Mo3O12-related compounds with various chemical compositions were synthesized by a solid-state reaction. All of the synthesized compounds with a single phase were identified as Al2Mo3O12 or Al2W3O12-related compounds by XRD. High-temperature XRD and DTA analysis clarified that the structural phase-transition temperature of the synthesized Co0.05Zr0.05Al1.9Mo3-yWyO12 (0≦y≦3) decreased with increasing the W content. High temperature XRD also revealed that the synthesized Co0.05Zr0.05Al1.9Mo0.9W2.1O12 had a discontinuous thermal expansion around 333 K. The UV-vis-NIR spectra of the synthesized compound at each temperature of 303 to 373 K were investigated. Although the diffusion-reflectance ratio almost unchanged until 333 K, it began to decrease at 343 K. The spectral change corresponded to the discontinuous thermal expansion of the synthesized Co0.05Zr0.05Al1.9Mo0.9W2.1O12. Furthermore, it was found that the synthesized (Co, Zr)-substituted compounds had the optical property with the ΔL* luminance decreasing in the range of R.T. to 373 K due to its structural phase transition.
The LiMn2O4 films for Li secondary batteries have been prepared by a RF magnetron sputtering method. This research was designed for investigating the deposition condition of the films. The parameters were sputtering time, RF power, sputtering pressure and sputtering atmosphere. The LiMn2O4 films were deposited on the Al substrates, and their film properties were evaluated by X-ray diffraction. The film thickness was estimated by the gravimetry method. It was shown that the film thickness and the deposition rate were proportional to the Ar：O2 ratio as well as the sputtering time and the RF power. It was also shown that the deposition rate decreased as increasing the sputtering pressure.