Hosokawa Powder Technology Foundation ANNUAL REPORT
Online ISSN : 2189-4663
ISSN-L : 2189-4663
Volume 12
Showing 1-44 articles out of 44 articles from the selected issue
Preliminaries
Research Grant Report
  • Yukichi Umakoshi, Hiroyuki Yasuda, Wataru Fujitani
    2004 Volume 12 Pages 15-19
    Published: 2004
    Released: June 25, 2019
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    Porous hydroxyapatite (HAp)/α-tricalcium phosphate (α-TCP) composites were prepared by a colloidal process. After the colloidal process, polymethyl methacrylate (PMMA) was added to the slurry, followed by dehydration. Numerous spherical pores were introduced in the composites by mixing PMMA, which was burned out during sintering. The shape, size and volume fraction of pores could be controlled by those of PMMA added to the composites. Calcium-deficient hydroxyapatite (DAp) was synthesized by hydrolysis of α-TCP at different pH. Ca/P ratio of DAp increased with increasing pH during the hydrolysis. Bone-like crystals were formed on DAp which soaked in SBF in vitro. The adhesion of MC3T3-E1 osteoblast-like cells was also influence by pH. High solubility and negative charge of DAp, especially synthesized at lower pH resulted in the fast formation and the good adhesion.

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  • Tatsushi Matsuyama, Hideo Yamamoto
    2004 Volume 12 Pages 20-26
    Published: 2004
    Released: June 25, 2019
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    A CO2 fixation system in which a photocatalysis in a light stage is separated from a biocatalysis in a dark stage can be expected to perform highly selective production through the use of light-energy without denaturation of enzyme due to light irradiation.

    To realize the concept as particle design, an electron-transfer system which combines semiconductor photocatalyst particles (TiO2) with two biocatalysts was proposed. In this study, formate dehydrogenase (FDH) was used as a catalyst of CO2 fixation. Methyl viologen (MV), NAD+ and diaphorase were used to mediate electron-transfer from TiO2 to FDH.

    To confirm the feasibility of the electron-transfer system, the kinetics of the photocatalytic reaction side of the system was studied with time course of the reduction of MV2+ by TiO2 particles under UV-irradiation. It was found that MV+ production depends on the concentrations of MV2+ and TiO2, and the initial rates can be described by Langmuir-Hinshelwood expression.

    Experiments in a batch operation showed that the total system works, and both concentrations of MV and NADH affected the rate of CO2 fixation. In the new photo-bioreactor system with a ceramic membrane inserted between TiO2 particles and the two enzymes, it was shown that the CO2 fixation progressed although the intensity of light is high enough to degrade enzyme's activities. From these results, it was indicated that the proposed system works without denaturation of enzyme due to light irradiation. Next, to immobilize the biocatalytic reaction side of the system, NAD+ -bonded gel beads with entrapped FDH and DAH were prepared by allowing droplets of sodium-alginate solution containing FDH, DAH and polymerized NAD+ fall into a CaCl2 solution. Activity of the beads was confirmed as the internal electron-transfer from formate to MV2+. Therefore, it was found that the coupled reaction of FDH and DAH was successfully immobilized in the gel beads.

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  • Kazuya Kurokawa, Kenichi Oosasa
    2004 Volume 12 Pages 27-31
    Published: 2004
    Released: June 25, 2019
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    Silicides are receiving much attention as high-temperature materials having extremely-high oxidation resistance based on the formation of a protective silica scale. However, they are limited in application because of their brittleness. Therefore, the use of them as coatings on refractory metals, which have poor oxidation resistance, is strongly desired.

    Spark plasma sintering is well known as a useful and simple sintering method. However, the effect of spark between particles on sintering has not been clarified yet. In the present study, sintering behavior of electrically-conductive materials (some metal silicides such as MoSi2, FeSi2, CoSi2, CrSi2, and VSi2) was studied. Based on the results, it was concluded that with sintering of the conductive materials the spark effect was exhibited. In addition, fabrication of dense disilicides can be easily achieved by the application of spark plasma sintering method.

    The mechanism of oxidation of silicides has not been clarified. In other words, it is not well-known that a protective silica scale is formed in what kind of silicides. This review focuses on the classification of oxidation behavior in silicides.

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  • Mikio Konno, Yoshio Kobayashi
    2004 Volume 12 Pages 32-35
    Published: 2004
    Released: June 25, 2019
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    Barium titanate nanoparticles were synthesized by the hydrolysis of complex alkoxide precursor that was prepared in a reflux of metallic barium and tetraethylorthotitanate in solvent. The hydrolysis was performed by the addition of water/ethanol solution to the precursor solution. As reflux time increased, particle sizes, which were measured with transmittance electromicroscopy, became smaller followed by sharpening of size distribution. As water concentration and benzene content in the hydrolysis increased, the particle size increased with crystallite size that was determined with X-ray diffractometry. No significant difference was observed between the particle and crystallite sizes up to 30 nm. Over the size of 30 nm, the particle size was larger than the crystallite size because of generation of polycrystallites. Annealing treatments in air at 400 and 1000℃ also increased both the particle and crystallite sizes. The crystallite sizes estimated from the (111) peaks were smaller than those from (110) peaks in a range of sizes larger than 40 nm, which indicated that the critical crystallite size of transformation from cubic to tetragonal structures was approximately 40 nm.

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  • Aishi Yamamoto
    2004 Volume 12 Pages 36-41
    Published: 2004
    Released: June 25, 2019
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    Recently, optical properties of wide band-gap semiconductors have been attracted much attention because they have potential applications for future optoelectronic devises in blue-UV wavelength region. Zinc-oxide (ZnO) is one of the wide band-gap semiconductors, and it is an environmentally friendly material. Furthremore, it has rather large exciton binding energy (60 meV). Due to the large exciton binding energy, the exciton states are stable even at room temperature. Therefore, it is a desirable material for future exciton-related optoelectronic devices. Recently, many researchers have studied on fabrication and optical properties of ZnO nanostructures since optically excited laser action was reported in 1997.

    Because the exciton states are stable in ZnO, it provides to study exciton state confined in nanometer space. We have fabricated ZnO nanocrystals dispersed in glass films and studied their optical properties. The samples were fabricated by a sol-gel method. Using this method we can vary nanocrystal density very easily. By optimizing the fabrication conditions, we were able to construct transparent glass films enough to be used in optical measurements. Clear excitonic absorption peaks were observed in absorption spectra at 20 K. The observed absorption peaks were due to the A, B and C excitons in wurtzite ZnO nanocrystals, and C exciton absorption was the strongest due to the largest oscillator strength. Three PL peaks were observed in band-edge region at 20 K. These PL peaks seemed to be due to bound excitons and their phonon replicas. However, the temperature dependence of these PL peaks was different in each other. Furthermore, when we decrease the nanocrystal density in glass films, only one PL peak remained. These experimental results suggest that the remained PL is due to an excited state in independent individual nanocrystals whereas the vanished PL peaks are due to excited states in the aggregated nanocrystals.

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  • Noriaki Sano
    2004 Volume 12 Pages 42-47
    Published: 2004
    Released: June 25, 2019
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    Multi-walled fullurene-like particles and nanotubes of carbon were synthesized using arc discharge in water. Here the gas bubble formed from the hot arc plasma in the cold liquid successfully provides reaction field to rapidly quench the carbon vapor to produce such carbon nano materials. Using the presented method, not only nanocarbons but also we can produce fullurene-like materials from other lamellar structural materials, such as MoS2 and WS2. These materials should have excellent tribological properties.

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  • Shigeki Koyanaka, Shigehisa Endoh
    2004 Volume 12 Pages 48-52
    Published: 2004
    Released: June 25, 2019
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    Many industrial processes for manufacturing fine particles face the problem of how to maintain the uniformity of product’s physical properties. Particle-particle separation technology has important potential for improving product quality and uniformity. Separation between micronorder and smaller particles is of particular importance, since no conventional method is able to separate particles of this small size effectively. In our previous study, long-range movement of a particle in a weakly focused Gaussian beam was confirmed to be strongly affected by the particle’s refractive index; any optical separation method is likely to actualized base on differences in particle transport distance under laser radiation pressure. To this end, however, the most important and difficult problem to overcome is how to improve particle throughput.

    In this study, the repetitive scanning of a focused laser beam was applied to increase the throughput of particle separation using laser radiation pressure. The relationship between the scanning conditions, specifically laser output power, scanning distance, scanning frequency, and the characteristics of particle transportation, was investigated using micron-sized polystyrene-latex particles. The improvement of particle throughput by laser scanning was confirmed through a separation experiment using a mixture of micron-sized synthetic diamond and graphite particles. The results showed that the optimized laser beam scan-system enables particle separation throughput to be increased by approximately 70 % compared to the non-scanning state.

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  • Toshiyuki Fujimoto
    2004 Volume 12 Pages 53-57
    Published: 2004
    Released: June 25, 2019
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    The differential mobility analyzer (DMA) is widely used to measure the aerosol size distribution as well as generate mono-dispersed aerosol. Aerosol particles must be electrically charged before the measuring or classifying by DMA because they are classified according to an electrical mobility. The combination probability of ions to nanometer-sized particles is quite small because of small cross sections of meter-sized particles. Furthermore, the charging fraction in bipolar charger, which is widely used in aerosol research, is limited by the neutralizing as a result of combination of ions and charged particles of opposite polarity.

    A numerical simulation code, in which advection-diffusion equations for aerosol particles and ions are combined with computational fluid dynamics code, was developed in this study to optimize the shape of unipolar charger and an electric field in it. The charging frequency of aerosol particles of 5 nm in diameter was predicted to be 7 %, which is improved by a factor of approximately 7 compared with the bipolar charger. We have also experimentally demonstrated the charging efficiency of nanometer-sized particles by the tandem DMA method.

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  • Kazuo Isonishi
    2004 Volume 12 Pages 58-64
    Published: 2004
    Released: June 25, 2019
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    Powder mixture of Fe, Al and mill scale Fe power (24.5 mass% O) was milled for certain period. Powders were mixed to become the composition of Fe-40mol%Al + 0, 2.5, 5.0, 7.5, 10.0 vol% Al2O3 after mechanochemical reaction. Longer time milling over 1080ks, FeAl phase newly formed only by MA. Al acts as a reducing agent for Fe oxide (mill scale powder) and then synthesizes Al2O3. The mill scale powder affected the MA process and phase formation behavior. Almost full density compacts were obtained by vacuum hot pressing under the condition of 1273K-150MPa-3.6ks, and those become FeAl intermetallic compound. Compacts, made with adding high weight percent of mill scale powder, showed higher hardness compared with the case of FeAl monolithic compact. This is presumably resulting from the effect of dispersed Al2O3 introduced by mechanochemical reaction during MA and later consolidation process.

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  • Junpei Yamanaka
    2004 Volume 12 Pages 65-71
    Published: 2004
    Released: June 25, 2019
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    We report a fractionation of colloidal silica particles by using charge-induced phase separation in the binary mixtures of high and low charge colloidal silica particles. Charged colloidal silica dispersions are stabilized by a strong electrostatic interparticle interaction, and undergo liquid to solid (crystal) phase transition with increasing the magnitude of the interaction. We examined the binary mixtures of two kinds of charged silica having nearly the same diameters (110 and 120 nm) and different surface charge densities (0.06 and 0.23 μC/cm2). In one-component dispersion, the less charged sample took liquid state, while the high charge sample formed the colloidal crystal. The binary mixtures were prepared at various mixing ratios (R, a ratio of the low-charge particle concentration to the total concentration), with keeping the total particle concentration constant at 3vol%. Since the lattice spacings of the colloidal crystals were of the order of visible light wavelength (0.3micron), the formation of the crystal phase could be identified by observing iridescent color due to Bragg diffraction of visible light. At R<0.05, the samples were macroscopically uniform and in the crystal state. At 0.05<R<0.5, the solid-liquid phase-separated structure with a well-defined phase boundary was observed. At 0.5 < R, the binary mixture took a liquid one-phase. The particle size distribution in the crystal region under the phase separated condition was determined from TEM images and by applying dynamic light scattering method. The high-charge sample had a bimodal particle size distribution, while the low-charge one was unimodal. The particles size distribution in the crystal phase was much narrower than that for the original one, and nearly unimodal. The present finding suggests a spontaneous fractionation mechanism accompanying with the phase separation process, which resembles to molecular-weight fractionation in polydisperse linear polymer and re-crystallization purification of atomic or molecular materials.

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  • Koichi Nakamura, Yoshitaka Michihiro, Tatsuo Kanashiro
    2004 Volume 12 Pages 72-77
    Published: 2004
    Released: June 25, 2019
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    Lithium transition metal oxides are attractive as the positive electrode of secondary battery. Li+ ionic diffusion plays an important role in the electrode materials. In this study, the internal friction was measured by the phonon echo technique to study the Li+ ionic motion in polycrystalline LiNbO3 powders. The Phonon echo is generated through the non-linear interaction between acoustic waves and lattice vibration. The inverse decay time of the echo, 1/T2 is connected with a magnitude of the internal friction of each particle, which is functional as an acoustic oscillator. The samples were ground and were arranged to be the size of 46 - 53μm in diameter with stainless steel mesh. Phonon echo measurements were carried out at 40 MHz in the temperature range of 300K to 900K. The decay time T2 showed the significant decrease above 800K. The temperature dependence of T2 was explained in terms of a Debye-type relaxation model based on the Li+ ionic motion. It yields the activation energy of about 0.93 eV. This result is in fairly good agreement with those of NMR and ionic conductivity measurements. Further investigation is now in progress, but the present study seems to prove that the phonon echo measurement is useful to elucidate the ionic motion in ionic conductors.

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  • Takakazu Takahashi, Toshinari Yamazaki
    2004 Volume 12 Pages 78-81
    Published: 2004
    Released: June 25, 2019
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    TiO2 films have been deposited onto the surface of the organic powders composed of the fine particles by dc facing targets sputtering in a mixture gas of Ar and O2. During exhaustion in the sputtering chamber, the fine particles were scattered from the vessel vibrated by sound pressure. The sputtering could not be performed for a long time by the unstable discharge due to the scattered particles. To prevent this, the stainless steel mesh plate was placed on the vessel with a distance of 5 mm. AC voltage VA of 60 Hz was applied to the stainless steel mesh plate with mesh size DM varying from 2 to 8 mm. The scattering amount of the fine particles significantly depended on the VA and the DM. The scattering amount of the fine particles steeply decreased from 8 to 1.5g with increasing VA in the range from 50 to 150V, where the DM and the total amount of the fine particles are 2mm and 30g, respectively. With further increase of VA in the range from 150 to 250V, the scattering amount of the fine particles steeply increased. At VA of 150V, the scattering amount of the fine particles has a minimum value. On the other hand, the scattering amount of the fine particles monotonically increased from 1.5 to 15g with increasing DM in the range from 2 to 8mm, where the VA and the total amount of the fine particles are 150V and 30g, respectively. It has found that the larger mesh size is the more scattering amount of the fine particles.

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  • Tetsuo Uchikoshi, Tohru Suzuki
    2004 Volume 12 Pages 82-88
    Published: 2004
    Released: June 25, 2019
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    Utilization of external vector fields for colloidal processing of ceramics was investigated to fabricate microstructure-controlled ceramics. Electric and magnetic fields were selected as external fields applied to stable colloidal suspensions. The following three sub-themes were set up in this research: (i) Elucidation of various factors which affect deposition characteristics of ceramic particles by electrophoretic deposition in aqueous and non-aqueous media, (ii) Fabrication of crystalline-textured ceramic monoliths by slip casting in a strong magnetic field, (iii) Control of crystalline texture in ceramic laminate composites synthesized by electrophoretic deposition in a strong magnetic field. It was shown the utilization of external field has made great advances of colloidal processing technique. Especially, it was demonstrated that the simultaneous application of the electric and magnetic fields, electrophoretic deposition in a strong magnetic field, enables to fabricate microstructure-controlled ceramics with crystalline texture.

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  • Tomomi Uchiyama
    2004 Volume 12 Pages 89-92
    Published: 2004
    Released: June 25, 2019
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    The particulate jet induced by small solid particles falling from a circular orifice into an unbounded quiescent air is simulated. The three-dimensional vortex method, proposed for the analysis of particle-laden free turbulent flow in a prior study, is employed for the simulation. It is found that the falling particles induce complicated three-dimensional unsteady air flow involving large-scale eddies. The air takes its maximum velocity at the jet centerline, and the velocity profile satisfies the self-similarity around the centerline. The effect of particle diameter on the velocity distribution for the two phases is investigated. The entrained air flow rate is favorably compared with the value predicted by the analytical models.

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  • Norikazu Namiki
    2004 Volume 12 Pages 93-98
    Published: 2004
    Released: June 25, 2019
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    An aerosol tubular reactor system to synthesize nanostructured vanadium doped titanium dioxide particles is described. The resultant particle size distributions, crystal phases, and morphology and distribution of dopant are established as a function of the operating conditions. The addition of the dopant promotes sintering and an increase in the primary particle size. Downstream of the furnace, a corona-soft X-ray reactor is used to demonstrate the effectiveness in degradation of toluene. An improvement in the degradation rates is observed when soft X-ray irradiation is used in conjunction with the corona. Addition of the V-dopant enhanced the photodegradation of toluene.

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  • Takashi Ogihara
    2004 Volume 12 Pages 99-103
    Published: 2004
    Released: June 25, 2019
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    Spherical lithium manganate fine particles were successfully prepared by the aerosol process using metal nitrate solution. As-prepared particles had a porous microstructure and were nonagglomerated, which had an average diameter of about 1μm with narrow size distribution. XRD showed that asprepared powders were well crystallized to spinel structure with Fd3m space group. Chemical analysis revealed that the concentration of as-prepared particles was good agreement with that of the starting solution. As-prepared lithium manganate powders were used as cathode active material for lithium secondary battery and its electrochemical properties were investigated at the range from 3.5 and 4.3 V. The charge/discharge capacity of lithium manganate was 120 mAh/g at the rate of 1C. The discharge capacity of lithium manganate exhibited 30mAh/g at the rate of 9C. The charge/discharge capacity of lithium manganate was higher than that of commercial lithium manganate powders. The cycle performance of lithium manganate obtained from spray pyrolysis was superior to that of commercial lithium manganate powders. The battery module for electric bicycle was also developed. The performance of developed battery module was expected for pure electric vehicle (EV) and hybrid EV.

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  • Hidetaka Konno
    2004 Volume 12 Pages 104-109
    Published: 2004
    Released: June 25, 2019
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    A process to synthesize fine β-SiC particles was developed utilizing microspaces of exfoliated graphite (EG). Two types of low molecular weight silicone and a catalyst were dissolved into a silicone oil and they were impregnated into EG by sorption, and then heated in air to cure the compounds. Formed precursors were black flakes of a few millimeters in diameter. Only by the heat treatment of precursors at 1500℃ for 5 h or at 1550-1600℃ for 1 h in Ar, β-SiC of a few tens to hundreds nanometers in size was obtained. In the present process, EG plays two important roles; one is as reaction spaces and the other is as a reductant that functions at elevated temperatures. Initially the cured silicone is coating the graphite sheets of EG as thin films of less than 1μm, and above 1300℃ they start to decompose and form small particles of a few tens to 100 nm in diameter on the graphite sheets. These intermediate particles are composed of the Si-C-O composites and SiO2 and they spontaneously decompose to β-SiC from around 1400℃, and between 1400 and 1500℃ the reduction of remaining intermediates by graphite sheets occur and form well crystallized fine β-SiC particles. In the present work, further development of the process was made: (1) solventless preparation of precursors was found to be possible, (2) finer particles were obtained by either grinding the precursor prior to the heat treatment or preparing the precursor using shorter chain-type silicone compound, and (c) the yield of β-SiC increased up to 41% by curing silicone compounds at lower temperature and shorter period. The process is simple and raw materials are not expensive so that it is promising for industrial applications.

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  • Shinichi Kikkawa
    2004 Volume 12 Pages 110-113
    Published: 2004
    Released: June 25, 2019
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    Nano-sized crystals were obtained for both (Y0.95Eu0.05)2O3 phosphor and Co2Z ferrite (Ba3Co2Fe24O41) GHz noise absorber by the respective gel-combustion reactions, Nitrate aqueous mixtures were gelated by heating in a presence of glycine. (Y0.95Eu0.05)2O3 phosphor with crystallite size of 43nm was prepared from the glycine gel ignited at 300℃. For Co2Z ferrite preparation, use of Fe(acac)3 as an iron source was effective to obtain its nanocrystals in lower firing temperature of 1000℃ than that in solid state reaction.

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  • Yasumasa Tomita
    2004 Volume 12 Pages 114-117
    Published: 2004
    Released: June 25, 2019
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    Lithium-ion Conductive Solid Electrolytes have attracted the particular interest for possible applications as solid electrolyte of lithium ion secondary batteries and many studies for them have been carried out. In recent years, the crystal structures, the ionic conductivity and the dynamics of component ions for a series of compounds MBr-m' Br3 (M=Li, Cu, Ag ; M'=Al, Ga, In) was investigated and it was found that Li3InBr6 is a good lithium ion conductor with high ionic conductivity, α~10-3 Scm-1, at 330 K. Because this solid electrolyte, Li3InBr6 shows such high conductivity only at high temperature phase, I tried to dope this compound with another element to improve its ionic conductivity in this study. In Li3InBr6 doped with divalent cations (M=Mg, Ca, and Ba), the conductivity decreased with x unfortunately, accompanied by a broadening of the 115In NMR spectra. In Li3-2xSrxInBr6(x ≤ 0.7), the conductivity of high temperature phase also decreased with an increase of x but LiSrInBr6 show almost the same conductivity to Li3InBr6. The conductivity of the low temperature phase in Li3-2xMgxInBr6(x ≤ 0.4) increased with x. On the other hand, in the case of the compounds doped with CI ion, Li3InBr6-xClx, phase transition temperature lowered in the compound of x = 3 and the high ionic conduction phase is stable under the room temperature. Furthermore, the value of the ionic conductivity of the Li3InBr3Cl3 was almost equal to the original Li3InBr6.

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  • Jun Oshitani
    2004 Volume 12 Pages 118-123
    Published: 2004
    Released: June 25, 2019
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     It is generally known that the fluidized bed has liquid-like properties such as apparent density and viscosity. When objects are immersed in a fluidized bed, objects of smaller density than apparent density of the fluidized bed float, while those of larger density sink into the fluidized bed. Different density objects can be separated at the top and bottom of the fluidized bed by controlling the apparent density between the object densities. However, when the particles are fluidized by wet air, it will be difficult to make the particles to fluidize stably because of particles aggregation. In this case, FBMS (fluidized bed medium separation) efficiency will be also reduced. In this study, the particles of different wettability are employed to investigate the fluidization stability against the relative humidity of air. The fluidization of hydrophilic particles becomes unstable and the minimum fluidization velocity becomes large with increasing the relative humidity. This would be because particle aggregation caused by high humidity. On the other hand, in the case of hydrophobic particles, the fluidization is stable and the minimum fluidization velocity keeps constant even if the relative humidity is increased. The apparent density of fluidized bed is evaluated by floating and sinking of different density spheres and by measuring the fluidized bed height at different humidity. The apparent density keeps constant against the relative humidity in the case of hydrophobic particles, although it decreases with increasing the relative humidity in the case of hydrophilic particles. By employing hydrophobic particles, the apparent density is not affected by the relative humidity and it means that the FBMS can be carried out at high humidity.

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  • Satoshi Semboshi, Shuji Hanada, Naoya Masahashi
    2004 Volume 12 Pages 124-130
    Published: 2004
    Released: June 25, 2019
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    The fracture behavior and microstructure changes of pure tantalum (Ta) by hydrogenation have been investigated to elucidate fundamentals for hydrogen pulverization which can be used for producing fine Ta powder with high purity and low cost. Concentric cracks are introduced in recrystallized Ta plate with about 100 mm grains when the Ta plate is annealed at 1473 K and cooled in a hydrogen atmosphere. On the other hand, no crack is observed when the Ta plate is annealed at 1473 K in a hydrogen atmosphere and cooled in an argon atmosphere. It is suggested that the surface activation caused by annealing in a hydrogen atmosphere at 1473 K facilitates hydrogen absorption at lower temperature. After hydrogen-induced cracking, tantalum hydride (Ta2H) with a pseudo-tetragonal structure is formed along the {001} of Ta, suggesting that cracking by hydrogenation arises from the formation of Ta2H in the matrix. The Ta2H lattice has a large misfit to the Ta matrix; and thus the hydride formation brings about strain, large enough to trigger multiple cracks. Hence, the multiple cracking in the Ta plate occurs in the following sequence: (1) hydrogen absorption, (2) strain generation by volume expansion and hydride formation, and (3) crack nucleation and propagation.

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  • Yoshinari Miyamoto, Soshu Kirihara
    2004 Volume 12 Pages 131-135
    Published: 2004
    Released: June 25, 2019
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    Photonic crystal is known as a new functional material with the periodic structure of dielectric media which can form the photonic band gap due to Bragg diffraction and thereby totally reflect electromagnetic waves. Various applications are expected for photonic crystals in communication, information and optical devices. We have tried to fabricate photonic crystals for control electromagnetic waves in THz region. The THz waves can be applied to the next generation communication with high speed and large contents, sensors of surface defects of materials, skin cancer, bacteria in foods, and others. The photonic crystal consisting of epoxy resin including TiO2-SiO2 nano-composite particles with the diamond structure was successfully fabricated by using a CAD/CAM freeforming process of stereolithography. The crystal consists of 1000 unit cells with the lattice constant of 1mm. The diamond photonic crystal showed the band gap in THz range.

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  • Osamu Yamada
    2004 Volume 12 Pages 136-142
    Published: 2004
    Released: June 25, 2019
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    Present research purpose is to develop the efficient concentration and separation system of sea water by using combustion synthesized porous ceramic materials. The inside of the porous ceramic material becomes the skeleton structure with the smooth surface. The capillarity can be generated by this peculiar micro structure. In addition, evaporation rate rapidly increases on the porous material, since it has large specific surface area. The seawater desalination system of the good energy efficiency was constructed.

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  • Motohide Matsuda
    2004 Volume 12 Pages 143-146
    Published: 2004
    Released: June 25, 2019
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    The influence of mechanical milling of the corresponding powder elements on the formation of superconducting MgB2 phase was investigated. Ma and B powders were attrition-milled, and then the milled power mixture was annealed under atmospheric pressure of argon. It was observed that amorphous B powders were embedded in Mg powders by the milling process. The composite layers of B and Mg had a thickness of ca. 1μm on the surface of Mg powders. After relatively low temperature annealing, superconducting MgB2 phase formed from the composite surface layers. MgB2 phase clearly appeared after annealing the 60 min milled powder mixture at 500℃. The results indicate that the Mg and B composite surface layers may be microscopically mixed, and may have a highly disordered crystal structure, which would provide a strong driving force for the formation of MgB2 at lower temperature than can be achieved conventionally. In addition, it became apparent that the 60 min milled mixture led to much larger diamagnetism magnitude at 4 K than that was milled for 5 min. From the above results, it is clear that the mechanical milling of the powder elements can enhance the reactivity for the formation of MgB2.

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  • Keun-Soo Kim
    2004 Volume 12 Pages 147-149
    Published: 2004
    Released: June 25, 2019
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    In the current work, nano-meter scale Ag particles were analyzed on their sintering properties and on resistivity. The microstructural features on sintering are also examined and the possibility of lowering sintering temperature is discussed. The nano paste composed of 10 nm Ag particles exhibits exothermic reaction both at about 150℃ and at 180℃ depending on the organic medium and the separation of dispersant. Sintering proceeds according to those thermal reactions. For a higher sintering temperature of 250℃ , the electrical resistance and microstructural feature exhibited the best characteristics.

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Report of Overseas Conference Participation
Young Researcher Scholarship Report
  • Satoshi Kimura, Masayuki Horio
    2004 Volume 12 Pages 157-158
    Published: 2004
    Released: June 25, 2019
    RESEARCH REPORT / TECHNICAL REPORT FREE ACCESS
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  • Kazuchika Tamura, Fumio Watari
    2004 Volume 12 Pages 159-161
    Published: 2004
    Released: June 25, 2019
    RESEARCH REPORT / TECHNICAL REPORT FREE ACCESS
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  • Mohammed Saedi Jami, Eiji Iritani
    2004 Volume 12 Pages 162-163
    Published: 2004
    Released: June 25, 2019
    RESEARCH REPORT / TECHNICAL REPORT FREE ACCESS

    This paper presents an experimental investigation of constant rate and constant pressure microfiltration behaviors of sewage secondary effluent, pretreated with polyaluminum chloride (PAC). The microfiltration unit was tubular module with monolithic ceramic membrane. The experimental apparatus designed specially for this work is fully automated, has backwashing capability and was operated in deadend mode. Membrane fouling encountered in the microfiltration of sewage secondary effluent represents serious design and operational concem. The apparatus was designed in such a way that when the pressure drop or flux reaches a pre-set value, backwashing is initiated. Based on the intermediate blocking law, the mathematical model has been developed to explain the pore blocking behavior. This work clearly indicated that constant pressure filtration characteristics of sewage secondary effluent can be derived from the results of constant rate experiment. The energy consumption and net filtrate flux were calculated and compared with the experimentally measured data. The most interesting result of this work is that there exists an optimum pressure increment for each net filtrate volume. However, further assessment of energy consumption and product indicated that when the optimum operational conditions are determined, there should be a trade off between the energy consumption and the effective flux. Furthermore, this work also proved that constant pressure filtration with cyclic backwashing operation is desirable in industrial application. Water quality analysis showed that the filtrate is free from microorganisms and can be used as reclaimed water for toilet flushing, car washing, etc.

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  • Camellia Panatarani, Kikuo Okuyama
    2004 Volume 12 Pages 164-165
    Published: 2004
    Released: June 25, 2019
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  • Hiroyuki Hasegawa, Tetsuya Suzuki
    2004 Volume 12 Pages 166
    Published: 2004
    Released: June 25, 2019
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  • Kentaro Kuratani, Shigehito Deki
    2004 Volume 12 Pages 167
    Published: 2004
    Released: June 25, 2019
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  • Satoshi Watanabe, Ko Higashitani
    2004 Volume 12 Pages 168
    Published: 2004
    Released: June 25, 2019
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  • Shintaro Morisada, Ko Higashitani
    2004 Volume 12 Pages 169-170
    Published: 2004
    Released: June 25, 2019
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  • Takao Sato, Koichi Kameoka
    2004 Volume 12 Pages 171
    Published: 2004
    Released: June 25, 2019
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