Hosokawa Powder Technology Foundation ANNUAL REPORT
Online ISSN : 2189-4663
ISSN-L : 2189-4663
Volume 17
Showing 1-41 articles out of 41 articles from the selected issue
Preliminaries
Research Grant Report
  • Kazuto Tokumitsu
    2009 Volume 17 Pages 11-16
    Published: 2009
    Released: December 29, 2017
    RESEARCH REPORT / TECHNICAL REPORT FREE ACCESS

    The cavitation damage is known in a field of hydromechanics, e.g., propeller and water plane are damaged when they are moving in a fluid at a high speed. This damage is usually caused by the shock wave which is generated by the collapse of cavities, and has been regarded as the negative phenomena. But the new development of cavitation has been beginning in these days, i.e., the positive applications of its mechanical and thermal effects. Mechanism of cavitation is as, quick decompression of fluid -> generation and growth of cavity -> turn to contraction -> collapse and vanish -> rebounding, and shock temperature of several thousands of degree are generated for micro- or picoseconds at the last stage, therefore these two significant features of shock wave and shock temp. would be considered to industrial applications.

    Shock wave by cavitation, in particular, can be appropriated to pulverize powder, where powder is self-fractured by shock wave, so it is called as “Media-less & Contamination-free Method”. We report the application of this method to powder handling.

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  • Takashi Tatsumi
    2009 Volume 17 Pages 17-20
    Published: 2009
    Released: December 29, 2017
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    We have developed the method for synthesizing mesoporous silica having helical channels by using anionic surfactants based on amino acids. During this research, we have established a simple and novel liquid-phase method for preparing uniform-sized silica nanospheres (SNSs) 8-400 nm in size. The SNSs were synthesized through hydrolysis and condensation reactions of TEOS in the emulsion system containing TEOS, water and basic amino acids such as lysine and arginine under weakly basic conditions (pH 9-10). After the reaction, uniform-sized SNSs were stably dispersed in homogeneous solutions without any precipitation. Interestingly, the arrangement of these SNSs into a cubic closed packed (ccp) structure was achieved simply by solvent evaporation. Thus formed SNSs can be categorized into well-ordered mesoporous silicas because they have three-dimensional, interparticle voids with high uniformity.

    The size of the product silica spheres was affected by two factors, the proportion of the seed-solution and the ethanol / water ratio of the solvent. Thus uniform-sized silica nanospheres with the diameter ranging from 8 to 400 nm were successfully obtained. By adding a surfactant to the reactant solution, silica spheres with mesopores inside were also synthesized. Carbon replicas with well-ordered mesostructure were synthesized by using the array of silica nanospheres of diverse sizes as a template. The pore size of the carbon structure was easily regulated by varying the size of silica spheres. The pores were uniform in size and spherical; each of the spherical pores was also three-dimensionally interconnected to neighboring pores through small holes, which were attributed to the contact points between closely-packed silica spheres. Furthermore, by using the porous carbon replica as a template, transition metal oxides having three-dimensional mesopores were prepared. Some of the metal oxides were crystallized with the mesoporous structure retained.

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  • Masato Tominaga
    2009 Volume 17 Pages 21-25
    Published: 2009
    Released: December 29, 2017
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    Bilirubin oxidase (BOD) contains multi active center copper sites (type 1, 2 and 3) and catalyzes the oxidation of bilirubin to biliverdin (at the type 1 site) with the concomitant four-electron reduction of dioxygen to water (at type 2-3 sites). BOD electron transfer reaction investigations at carbon electrodes are attractive studies, not only from the point of view for the basic understanding of multi-copper protein reactions, but also for the application of dioxygen biocathodes for biofuel cells operating near neutral pH solutions. Several studies on the mediated electrochemistry of BOD using monomeric and redox polymer mediators have been reported. Recently, the direct electron transfer reaction of BOD at carbon electrodes under anaerobic and aerobic conditions has been reported. In the present study, we investigated electrode reactions of BOD adsorbed on carbon black (CB). CB has an advantage for large surface area-to-volume ratios. Heterogeneous electron transfer rate constants (k°) between BOD and CB were evaluated by analyzing steady-state catalytic voltammograms under aerobic conditions. We found that k° values improved with the use of UV-ozone treated CB.

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  • Kiyoshi Kanie
    2009 Volume 17 Pages 26-30
    Published: 2009
    Released: December 29, 2017
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  • Akito Masuhara
    2009 Volume 17 Pages 31-36
    Published: 2009
    Released: December 29, 2017
    RESEARCH REPORT / TECHNICAL REPORT FREE ACCESS

    The preparation of fullerene fine crystals with uniform size and shape would permit the control of their specific electronic energy levels and the fabrication of materials with completely new properties. To this end, we have successfully fabricated, for the first time, shape- and size controlled C60 nanocrystals using a reprecipitation method developed in our laboratory. The C60 nanocrystals obtained were clearly monodisperse and came in an interesting diversity of shapes such as spherical, rodlike, fibrous, disk, and octahedral. We were able to selectively control these sizes and shapes by simply changing the combination of solvents used and the reprecipitation conditions.

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  • Yoshihiko Ninomiya
    2009 Volume 17 Pages 37-42
    Published: 2009
    Released: December 29, 2017
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    This paper aims to evaluate the nanosized additives to coal on the emission/reduction of particulate matter (PM) during coal combustion. Five pulverized coals with different mineralogical properties were investigated. Each of them was mixed with Ca-based, Mg-based and calcium acetate based additives, and combusted at 1450℃ in a lab-scale drop tube furnace (DTF). The results indicate that the additives tested here has a pronounced impact on particle size distribution of PM and the morphologies of individual ash particles. For all of the coals tested here, the addition of the additives increased the coarse ash fraction and substantially reduced the amount of ash particles smaller than 2.5μm (PM2.5). This is because the Ca- based and Mg-based additives are able to reduce the slag viscosity, which promote the coalescence among sub-micrometer mineral particles. The effect of the additives on PM2.5 reduction also depends upon the properties of the original minerals present in the coal. The particle size distributions and concentrations of PM10 were also compared to that predicted by an advanced coalescence and fragmentation model developed here. The comparisons indicate that the model can satisfactorily predict ash formation and properties, taking into account both coalescence of included minerals and fragmentation of excluded minerals at high temperature.

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  • Akira Nakajima
    2009 Volume 17 Pages 43-50
    Published: 2009
    Released: December 29, 2017
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    Effects of TiO2 powder addition on sonochemical destruction of 1,4-dioxane in water were investigated through comparison of SiO2 powders with similar specific surface area. Addition of TiO2 is more effective for decomposition of 1,4-dioxane in water than is SiO2. Contribution of photocatalytic destruction through sonoluminescence is not dominant to the effectiveness of TiO2 for acceleration of sonochemical reactions. Temperature changes of water or suspension during sonolysis suggest that an endothermic process exists in the TiO2-added water. Regarding sonication of TiO2-added water in the present study, thermally excited holes will be generated. Intrinsic oxygen vacancy in TiO2 surface also plays an important role for high decomposition efficiency by producing cavitations. Both ultrasonication energy consumed in water and destruction efficiency of 1,4-dioxane were increased by the addition of reduced TiO2 powder.

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  • Hiroshi Nishikawa
    2009 Volume 17 Pages 51-54
    Published: 2009
    Released: December 29, 2017
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    Electrical conductive adhesives (ECAs) are being investigated for the use in microelectronics packaging as a lead-free solder substitute due to their advantages such as low bonding temperature and simple process. However, high resistivity and poor mechanical behavior may be the limiting factors for the development of ECAs. Conventional ECAs are composed of micro-sized filler metal and polymer matrix. Currently the conductivity of the ECA is considered to be generated by small contacts formed among the micro-sized particles during the curing process and by the tunneling effect. In this study, a new class of ECA, composed of nano-particles and micro-particles in epoxy resin, was designed and developed. Especially, the effect of the addition of nano-particles on the electrical resistivity of ECA was investigated and the configuration of nano-particles and micro-particles was observed by using scanning electron microscopy. As a result, it was found that, when nano-particles were added into the ECA filled with micro-particles, the addition of a small amount of nano-particles helps to get lower electrical resistivity of ECA. Namely, some nano-particles were aggregated and acted as bridges between micro-particles. Then the contact points between micro-particles and electrical path were increased and the electrical resistivity of ECA was eventually decreased.

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  • Junko Umeda
    2009 Volume 17 Pages 55-60
    Published: 2009
    Released: December 29, 2017
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    In this study, the advanced coating process of un-bundled CNTs on metal powders has been established by using surfactant solutions containing CNTs. When applying the process to sponge titanium powders to prepare the CNT-Ti composite ones, the extruded titanium composite reinforced with CNTs and in-situ formed TiC nano-particles showed extremely high tensile strength and reasonable ductility.

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  • Katsuya Teshima
    2009 Volume 17 Pages 61-66
    Published: 2009
    Released: December 29, 2017
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    Highly crystalline, NaYF4 and NaYF4:Ln (Ln=Yb, Er, Tm) crystals with upconversion fluorescence were successfully grown by the cooling of the solo NaF at a growth temperature of 1100 ℃. The basic forms of NaYF4 and NaYF4:Ln crystals were a sphere and hexagonal cube, respectively. The crystal system, form and size were affected by cooling rate. In addition, the upconversion fluorescence property of the grown NaYF4:Ln crystals was also dependent on the cooling rate, that is, the crystal system, and type of dopant. The red, green and blue upconversion fluorescence of NaYF4:Ln crystals were clearly observed under 980 nm laser irradiation by a two- or three-photon upconversion process. The upconversion fluorescence of NaYF4:Ln crystals was successfully controlled by changing the cooling rate and type of dopant. Furthermore, the NaYF4:Yb,Er crystals were successfully grown using a mixed NaF-KF flux cooling method at a growth temperature of 800 ℃.

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  • Takayuki Suehiro
    2009 Volume 17 Pages 67-70
    Published: 2009
    Released: December 29, 2017
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    In the last few years, highly covalent Si3N4-based oxynitrides (SiAlONs) have been developed as an important family of phosphor host materials due to their great potentials for white LED applications. Generally, SiAlON-based nitride phosphors are synthesized by the reaction sintering of Si3N4, AlN, and other constituent metal oxide or nitride raw powders under pressured N2 atmosphere at ~1600–2000oC, followed by the postsynthesis grinding step to pulverize crude reaction products. This obvious low manufacturability is a major obstacle to their widespread use in LED applications, triggering the intense investigations for developing more sophisticated processing techniques.

    In this regard, the present authors have developed the gas-reduction–nitridation (GRN) method, which enables direct synthesis of fine SiAlON powders from the multicomponent oxide system by using an NH3–CH4 gas mixture as a reduction–nitridation agent. The Ca-α-SiAlON powder produced by the GRN is characterized by high phase purity, nonaggregated fine particle morphology, and very low impurity absorption throughout emissive regions, all of which meet the demands for phosphor applications.

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  • Hiroaki Sasai, Shinobu Takizawa
    2009 Volume 17 Pages 71-78
    Published: 2009
    Released: December 29, 2017
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    Immobilization of asymmetric catalysts has been achieved utilizing the spherical nano-particles that function like dendrimer. Asymmetric catalysts such as Al-Li-bis(binaphthoxide), Ga-Na-bis(binaphthoxide) and μ-oxodititanium complexes were successfully introduced on the surface of either micelle-derived polymer (MDP) or monolayer-protected metal cluster (MPC). In addition, utilizing metal-bridged polymers, a simple and efficient method for the immobilization of catalyst without the need for a polymer support has also been realized. The Immobilized catalysts thus obtained displayed high activity affording the corresponding products with high enantiomeric excesses.

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  • Satoshi Tanaka, Keizo Uematsu
    2009 Volume 17 Pages 79-84
    Published: 2009
    Released: December 29, 2017
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    We have applied a high magnetic field to fabricate functional ceramics with textured structure. Bismuth titanate ceramics families, which are candidate for piezoelectric materials, were prepared through well-dispersed slurry preparation, orientation in a high magnetic field, and subsequent reaction sintering. a- and b- axis oriented bismuth titanate ceramics Bi4Ti3O12 had been prepared by a high magnetic field. In this study, the crystal oriented bismuth titanate families MBi4Ti4O15 (M=Ca, Sr, Ba) ceramics was fabricated by using oriented Bi4Ti3O12 particle and reaction sintering. The MBi4Ti4O15 (M=Ca, Sr, Ba), which has high coercive electric field and high piezoelectric properties, has been expected for application use. Bismuth titanate particles with about 1μm were used as host material. Reacted additives were perovskite titanate materials MTiO3 (M=Ca, Sr, Ba). Well-dispersed slurry was prepared by mixing bismuth titanate powders and other titanate powders. The slurry was poured into a mold and set in a magnetic field 10Tesla until drying. Bismuth titanate particles in the slurry were highly oriented in a magnetic field, that is, the dried powder compact was consist of highly oriented bismuth titanate particle Bi4Ti3O12 and random MTiO3 (M=Ca, Sr, Ba) particles. The crystal oriented MBi4Ti4O15 (M=Ca, Sr, Ba) ceramics with a,b-axis orientation were successfully produced after sintering. We examined the reaction sintering process between oriented bismuth titanate particle Bi4Ti3O12 and random MTiO3 (M=Ca, Sr, Ba) particle. Influence of particle size ratio of Bi4Ti3O12 and MTiO3 was discussed on the reaction and microstructure of MBi4Ti4O15 (M=Ca, Sr, Ba) ceramics.

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  • Tsutomu Nakazato
    2009 Volume 17 Pages 85-90
    Published: 2009
    Released: December 29, 2017
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    High-temperature fluidized-bed coating on alumina balls of 300-μm was carried out to produce particles covered with Ni-calcium hydroxyapatite (Ni-HAp) catalyst layer for partial oxidation of methane. The attrition durability of the catalyst-coated particles was investigated by a cold-model fluidization method. The catalytic partial oxidation of methane (POM) was demonstrated at 1073K in a fluidized bed reactor, where the catalyst-coated particles were fluidized by the reactant gas mixture. The effect of Ni loading (2.5wt.% and 12.4wt.% of the catalyst layer), superficial gas velocity on the CH4 conversion and H2 yield was investigated. The results clarified that the coating efficiency was improved by decreasing the superficial gas velocity. The catalyst particles produced in the present work had fair attrition durability, showing 5wt% loss of catalyst layer after 48h fluidization at 0.60m/s. The CH4 conversion increased with decreasing superficial gas velocity, reaching more than 95% at 0.18m/s irrespective of Ni loading of Ni-HAp catalyst used in the present work. An optimum superficial gas velocity was found, at which the CO selectivity and the H2 selectivity were both high.

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  • Tomoya Konishi
    2009 Volume 17 Pages 91-96
    Published: 2009
    Released: December 29, 2017
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    Fluorescence bioimaging is a technique to visualize biological phenomena both in vivo and in vitro by specific adsorption of fluorescence probes to target organic tissues. One of the most serious problems in the fluorescence bioimaging is the limitation of observation time due to color-fading of the organic fluorescence probes and damages on the bio system, both of which are caused by the excitation of ultraviolet irradiation. This problem will be solved by using upconversion emission of rare-earth doped inorganic nanophosphors under infrared excitation. For the practical application of inorganic phosphors by using upconversion emission of doped rare earth, it is essential to choose an appropriate matrix with a low maximum phonon energy for efficient emissions and practical chemical durability. It is also important to prepare the phosphors in small particle-sizes with nanometer-order to probe micrometer-order cells. Lanthanum oxyhalides (LaOCl), as an intermediate host between oxides and halides, have both moderate phonon energy and chemical durability. LaOCl nanoparticles containing trivalent erbium ions (Er3+) are prepared through a self-hydrolysis process of hydrated chlorides of lanthanum (LaCl3) and erbium. However, this process costs much time ~12h to dry LaCl3 aqueous solution. In this study, the acceleration of this process was demonstrated by using a spray dryer. The powder prepared by spray drying of Er3+ doped LaCl3 aqueous solution was calcined at 700 ℃ in air and nitrogen (N2) atmospheres. The samples after calcination were evaluated by fluorescence emission, X-ray diffraction, and dynamic laser scattering. X-ray diffraction measurement showed that the sample after calcination in a N2 atmosphere contained LaOCl nanoparticles in LaCl3 matrix. Dynamic laser scattering measurement showed that the average particle size of LaOCl was about 600 nm. The Er3+ doped LaOCl nanoparticles showed visible upconversion emission around 500 and 660 nm after calcination under excitation at 980 nm. It was shown that rare-earth doped LaOCl nano phosphor was prepared by spray drying followed by calcination in a N2 atmosphere.

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  • Syuji Fujii
    2009 Volume 17 Pages 97-102
    Published: 2009
    Released: December 29, 2017
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    A series of colloidally stable near-monodisperse polyacrylonitrile (PAN) latex particles with a submicrometer diameter were synthesized by either dispersion or emulsion polymerization and examined for their performance in the preparation of highly stable latex foams. Poly(N-vinylpyrrolidone) was used as a colloidal stabilizer, which adsorbed at PAN particle surface. The PAN particles were extensively characterized using scanning electron microscopy, fourier transform infrared spectroscopy, and dynamic light scattering method. Submicrometer-sized PAN latex particles were invariably adsorbed at air-water interface and stabilized foams generated by simple hand-shaking or using a foam column, with no additives (e.g., surfactant, salt, or cosolvent) being required to induce latex destabilization. The foams stabilized with the PAN particles could keep their 3 dimensional porous structures even after drying. Scanning electron microscopy studies indicate near close-packed PAN particles within the dried foam, which suggests high colloid stability for the PAN particles prior to their adsorption at the air-water interface. Annealing the particulate foams up to 1000℃ under nitrogen atmosphere led to black-colored materials. Thermogravimetry and fourier transform infrared spectroscopy studies and scanning electron microscopy observation confirmed that porous carbon materials were successfully synthesized from the PAN latex-stabilized particulate foam. This particulate foam-based method should be advantageous because only particles, water and air are required, and production on an industrial scale is much more likely compared to a template-based synthetic route. Potential applications for these porous carbon materials include catalyst supports and novel electronic and optical devices.

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  • Toshihiro Nakamura
    2009 Volume 17 Pages 103-109
    Published: 2009
    Released: December 29, 2017
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    The effects of thermal oxidation on the photoluminescence (PL) properties of powdered porous silicon (PSi) are studied using X-ray photoelectron spectroscopy (XPS). It is found that the PL intensity is steeply quenched after annealing at ~ 300℃ and recovered at above ~ 700℃. The XPS intensity of oxides formed on the PSi surface is also found to strongly depend on the annealing temperature. The comparison between the annealing temperature dependence of PL intensity and that of the oxide XPS intensity suggests that the formation of thin disordered SiO2 layer accompanies the quenching of the PL intensity, and that the formation of thick high-quality SiO2 layer results in the PL intensity recovery. These results indicate that the thickness and quality of SiO2 layer play a crucial role in the PL properties of thermally oxidized PSi.

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  • Takasi Nisisako
    2009 Volume 17 Pages 110-115
    Published: 2009
    Released: December 29, 2017
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    We report a microfluidic technology for making biphasic emulsion droplets and shape-controlled nonspherical polymer microparticles. Microfluidic channels on a glass chip comprise a Y-junction so as to form a two-phase organic stream of polymerizable and non-polymerizable phases, and a T-junction to produce phase-separated droplets in a cross-flowing aqueous stream. The biphasic droplets at equilibrium formed a Janus configuration consistent with minimizing the interfacial free energies among the three liquid phases, according to the three spreading coefficients. The biphasic Janus droplets were highly monodisperse, e.g., with a mean droplet size of 119 μm and a coefficient of variation (CV) of 1.9%. Subsequent UV-initiated radical polymerization yielded monodisperse particles with controlled convex/concave structures, which were tunable through variation of the ratio of the flow rates between the two organic phases.

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  • Tetsuya Kida, Kengo Shimanoe, Masayoshi Yuasa, Hiroyuki Kurachi
    2009 Volume 17 Pages 116-121
    Published: 2009
    Released: December 29, 2017
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    The deposition of Pd nanoparticles onto thiol-functionalized SnO2 nanoparticles was carried out at the aqueous/organic liquid/liquid interface to prepare high-sensitive gas sensor materials. The method is based on the self-assembly deposition of Pd onto dimercaptosucinic acid (DMSA)-functionalized SnO2 nanoparticles prepared from a reaction of Na2SnO3 with HNO3 at room temperature. Pd nanoparticles of 2-3 nm in toluene were prepared by thermal decomposition of a Pd complex at high temperature (120-150℃). The mixing of the two suspensions containing the SnO2 nanoparticles and the Pd nanoparticles, respectively, produced Pd-loaded SnO2 nanoparticles, as confirmed by TEM observations. Thick film-type device using the prepared Pd-loaded SnO2 nanoparticles was fabricated and tested for its sensing properties. The fabricated sensor using the Pd-loaded SnO2 nanoparticles exhibited high gas sensitivity to hydrogen in air.

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  • Yoshitaka Kitamoto
    2009 Volume 17 Pages 122-128
    Published: 2009
    Released: December 29, 2017
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    Effects of surfactants on synthesis and properties of Fe-Pt nanoparticles were investigated in the present study. Fe-Pt nanoparticles were synthesized by a polyol method using Fe and Pt organic complexes in tetraethylene glycol. Whereas the addition of Poly (diaryldimethylammonium chloride) (PDDA) or poly (N-vinyl-2-pyrrolidone)(PVP) influenced the atomic ordering of Fe-Pt nanoparticles, that of oleic acid/oleylamine did not have an effect on the formation of ordered alloy Fe-Pt nanoparticles. Surfactant-coated silica microspheres were used for the growth of Fe-Pt nanoparticles on their surfaces to investigate preferential sites for nucleation of the Fe-Pt nanoparticles. Fe-Pt nanoparticles were selectively deposited only on surfactant-coated silica microspheres although Fe-Pt nanoparticles were formed in a solution without any surfactants. When Fe-Pt nanoparticles were synthesized with silica microspheres and a surfactant such as PDDA in a reaction solution, few Fe-Pt nanoparticles were observed on the silica microspheres. These results indicate that the nucleation of Fe-Pt nanoparticles commences selectively on surfactants such as PDDA, PVP, and oleic acid/oleylamine. In particular, polymer surfactants such as PDDA and PVP influenced the atomic ordering of Fe and Pt, leading to the formation of ferromagnetic nanoparticles at room temperature even though the particle size is less than 5 nm.

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  • Takahiko Ban, Ryosuke Sera, Katsuyuki Suzuki
    2009 Volume 17 Pages 129-134
    Published: 2009
    Released: December 29, 2017
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    When an outer electrolyte diffuses into a gel containing an inner electrolyte, rhythmic patterns of precipitate are formed, which is known as the Liesegang phenomenon. The patterns are static and stationary in the sense that the formed precipitation objects stay at the given position. Dynamically changing precipitation patterns can be formed if the complex formation of precipitate is possible. In this study, spontaneous appearance of traveling waves, spiral formation and chemical turbulence of precipitation bands is reported. The formation of spatiotemporal patterns allows us to spontaneous classification of fine particles because size distribution of particles varies with location. We investigated the effect of the inner electrolyte and gel concentrations on morphology of precipitation bands.

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  • Toshihiro Kawaguchi
    2009 Volume 17 Pages 135-140
    Published: 2009
    Released: December 29, 2017
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    DEM (Discrete Element Method) has been employed by many researchers to simulate the motion of granular particles. Additional forces, such as the fluid drag force, van der Waals force, liquid bridge force, electrostatic force, can be introduced easily in the DEM simulation. The DEM simulation has been combined with the CFD (Computational Fluid Dynamics) technique, and the DEM-CFD simulation has been applied to the fluidized bed by many researchers. Some researchers have taken account of the cohesive forces to simulate the small particles, such as A-particles or C-particles in the Geldart's classification. Recently, some research groups reported that the addition of the liquid in the fluidized bed with coarse particles enhances the particle motion. However, the mechanism is not understood yet. In the present study, a liquid transportation model is introduced in the DEM simulation to understand the mechanism of the enhancement of the particle motion in the fluidized bed by adding liquid.

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  • Rie Y. Umetsu, Ryosuke Kainuma, Kouhei Ito
    2009 Volume 17 Pages 141-145
    Published: 2009
    Released: December 29, 2017
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    Ni-Mn-X (X = In, Sn and Sb) based ferromagnetic shape memory alloys have been intensively investigated. Because their martensitic transformation can be controlled not only by temperature but also magnetic field and stress, these alloys are thought to be good candidate for applicable materials. However, the polycrystalline specimens are difficult to use for the application because of the considerable brittleness. One of the methods to improve the brittleness is the powder metallurgy. In the present study, mechanical and magnetic properties of Ni-Co-Mn-Sn specimens fabricated by spark plasma sintering (SPS) were investigated.

    Ni43Co7Mn39Sn11 (at.%) alloy was melted by high frequency induction and powders were obtained with using conventional nitrogen gas atomization. Powders with a diameter between 25 and 63 μm were selected, and specimens were obtained by SPS technique at 1073 or 1173 K for 15 min. The microstructures of the specimens were examined by optical microscopy. The magnetization was measured by a superconducting quantum interference device magnetometer. The mechanical properties were examined by compressive test.

    Microstructural observation revealed that the sintering is hardly proceeded in the specimen sintered at 1073 K, on the other hand, sintering at 1173 K is sufficient to obtain a specimen with high density. From the magnetic measurements, change of the magnetization is observed associated to the martensitic transformation, in addition, the martensitic transformation temperature decreases about 21 K by applying the magnetic field of 7 T. For the stress‒strain curve at room temperature, the fracture occurred at a strain of about 13% and a large plastic deformation of about 7.7% is obtained in the sintered specimen, while the fracture started at a low strain of about 1% for the polycrystalline bulk specimen with same composition. It can be said that the ductility was drastically improved without any large loss in the martensitic and magnetic properties.

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  • Makoto Nanko
    2009 Volume 17 Pages 146-151
    Published: 2009
    Released: December 29, 2017
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    Optimization of the recycling process of Mg alloy scrap chips to obtain superconducting MgB2 via a nano-mixing technology was carried out. In the present process, the an attrition type mechanical milling process without a milling media was used to mix and grind AZ31 scrap chips with commercial B powder. Fine AZ31/B powder mixture can be fabricated via the mechanical milling process in vacuum. The milling process can also reduce the volume of the mixture up to a half of the mixture by the blending in a plastic bottle. An AZ31/boron mixture via the mechanical milling was successfully reacted completely to MgB2 by heating at 700℃ for 3 h in reduced-pressure Ar gas, 50% shorter in reaction time than the mixture by blending in a PE bottle. The powder-in-tube (PIT) technique for producing an MgB2 coil can be conducted by using pulsed electric current sintering (PECS) with the recycled MgB2 powder encapsulated in a stainless steel tube. Dense MgB2 with less MgB4 phase can be obtained by the PIT technique with PECS. The PIT process is also useful to suppress the evaporation of Mg from MgB2 powder during sintering. Any significant reaction between stainless steel and MgB2 was not observed.

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  • Kohei Tahara
    2009 Volume 17 Pages 152-158
    Published: 2009
    Released: December 29, 2017
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    We previously developed modified poly (D, L-lactide-co-glycolide) (PLGA) nanosphere (NS) prepared by an emulsion solvent diffusion (ESD) method as a gene delivery system. In this study, PLGA NS was modified by chitosan (CS) and polysorbate 80 (Tween 80, P80) to improve cellular uptake. We investigated cellular uptake, intracellular distribution and transfection efficiency of P80 modified PLGA NS for a plasmid DNA delivery system in A549 cells. Cellular uptake and transfection efficiency of P80-PLGA NS were greater than CS-PLGA NS. The uptake of unmodifed and CS-PLGA NS was mediated, predominantly, by clathrin-mediated endocytosis. In contrast, specific endocytic pathway could not be determined on cellular uptake of P80-PLGA NS. Intracellular distribution of PLGA NS depended on the surface properties of PLGA NS. P80-PLGA NS did not show cytotoxicity for A549 cells. Thus, P80-PLGA NS could serve as an effective gene delivery system, and the surface properties of PLGA NS are key parameters for optimal intracellular uptake and distribution.

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  • Kensuke Egashira, Kaku Nakano
    2009 Volume 17 Pages 159-164
    Published: 2009
    Released: December 29, 2017
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    Background: The enthusiastic use of currently marketed drug-eluting stents presents a serious safety issue because of the associated increased risk of potentially fatal late thrombosis. Nanoparticle (NP)-mediated drug delivery systems (DDS) are poised to transform the development of innovative therapeutic devices. Therefore, we hypothesized that a bioabsorbable polymeric NP-eluting stent could provide a more safe and efficient DDS.

    Methods and Results: We report the first successful formulation of an NP-eluting stent using a novel cation electrodeposit coating technology. NPs encapsulated with FITC were taken up stably and efficiently by cultured vascular smooth muscle cells. In a porcine coronary artery, FITC was observed in neointimal and medial layers until 4 weeks after implantation. The magnitudes of stent-induced injury, inflammation, endothelial recovery, and neointima formation were comparable between control and NP-eluting stent groups.

    Conclusions: Therefore, this NP-eluting stent is an efficient and safe NP-mediated DDS that holds promise as a platform for innovative nano-devices targeting cardiovascular disease.

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  • Hisanori Yokoyama, Makio Naito
    2009 Volume 17 Pages 165-169
    Published: 2009
    Released: December 29, 2017
    RESEARCH REPORT / TECHNICAL REPORT FREE ACCESS

    Optimization of slurry for nozzle-free ink-jet forming was investigated. 10mass% aqueous slurry of colloidal silica was prepared, and the effect of the slurry characters on the droplet formation process and the printed characters was examined. Surface tension and apparent viscosity of the slurries had the influence on the droplet formation and the printed dot diameter, and the dot diameter decreased as the viscosity increases. Using the slurry with the phosphor powder (mean particle size: 1.8μm), the clear pattern was obtained by nozzle-free ink-jet forming.

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