Hosokawa Powder Technology Foundation ANNUAL REPORT
Online ISSN : 2189-4663
ISSN-L : 2189-4663
Volume 18
Showing 1-27 articles out of 27 articles from the selected issue
Preliminaries
Research Grant Report
  • Nobuyasu Adachi
    2010 Volume 18 Pages 11-15
    Published: 2010
    Released: December 29, 2017
    RESEARCH REPORT / TECHNICAL REPORT FREE ACCESS

    Porous NixZn1-xFe2O4 and BaFe12-x(Tix,Mnx)O19 ferrite materials were synthesized from wood and paper templates infiltrated ferrite slurry nitrates for the application of high frequency electromagnetic shielding. The nickel, zinc, barium and iron(III) nitrate aqueous precursor solution was infiltrated into the cedar wood specimens and were sintered at the temperature between 800 ℃ and 1400℃. From the XRD analysis, the ferrite crystallizations were recognized for the all sintered specimens, however, the secondary phase of γ-Fe2O3 were observed for the specimens sintered below 1000℃. From the SEM micrographs, 1-dimensional (1D) porous structure of the wood was remained in all specimens although the volume was decreased with increasing the sintered temperature. For the NixZn1-xFe2O4, the magnetic hysteresis loops showed the magnetic easy axis lies along the 1D pore, which evidence of the magnetic anisotropy depending on the 1D porous structure. At the present stage, the magnetic anisotropy is considered to come from the magnetic shape anisotropy like thin film structure. The real part of the complex permeability was measure up to 2 GHz and the values for the case of the 1D pore along to the magnetic field indicates larger than the case of the 1D pore perpendicular to the field and 3D porous structure. The BaFe12O19 porous ferrite sintered at 800℃ showed the large coercive force Hc and (B-H)max and the Hc decreased with increasing the sintered temperature. The ferromagnetic resonance (FMR) at 9 GHz appeared at the BaFe12-x(Tix,Mnx)O19 (x=3,4,5) specimens, which is the effect of the reduced anisotropy magnetic field. The FMR spectrum of the multilayered sintered BaFe12-x(Tix, Mnx)O19 (x=4,5) showed the superposed spectrum of those of BaFe8(Ti4,Mn4)O19 and BaFe7(Ti5,Mn5)O19. This result indicates that the multilayered BaFe12-x(Tix,Mnx)O19 can be expected for the broad band electromagnetic shields in GHz region.

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  • Hiroyuki Muto
    2010 Volume 18 Pages 16-20
    Published: 2010
    Released: December 29, 2017
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    In the conventional processing technique for fabricating nanocomposites, mechanical mixing of raw powders in a ball mill has often been conducted. However, this technique might be insufficient to fabricate nanocomposites with homogeneous microstructures due to the aggregation of nano-sized raw powder. In order to overcome these issues, novel processing technique was successfully developed to fabricate integrated composite powders by present author. The fabrication of integrated composite powder involves the sequential adsorption of oppositely charged polyelectrolytes, i.e., PSS (Poly(sodium 4-styrene sulfonate)) and PDDA (poly(diallyldimethylanm oniumchloride)) on surface of matrix and additive grains, respectively in order to produce electrically charged particles. And then, the integrated composite particles, i.e., large-sized-particles coated with nanoparticles were successively obtained by the mixing with oppositely charged particles in the solvent. The proposed technique was one of the simplest and the most versatile processing techniques for fabricating integrated composite particles for nanocomposite materials. It was concluded that the proposed technique examined in this study provides an efficient tool for fabricating the microstructural controlled nanocomposite.

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  • Satoshi Watanabe
    2010 Volume 18 Pages 21-25
    Published: 2010
    Released: December 29, 2017
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    Bottom-up self-organization approaches are promising for fabricating higher-order patterned surfaces composed of submicron particles. Thus far, several techniques have been reported to fabricate complex particulate films such as stripes, rings, and circular domain arrays. We have been studying an evaporation-induced self-assembly technique, and reported the stripe pattern formation on a completely hydrophilic substrate. By using this technique, a stripe pattern was produced simply by suspending a substrate in a fairly dilute suspension, without any complicated procedure; the stripes spontaneously aligned parallel to the contact line. In the present study, we examined the effects of salt concentration on the morphology of resultant particulate films. We found out that, under a specific condition, a Sierpinski gasket pattern formed in an ion concentration region around 10-3 M. The requirement for the Sierpinski gasket formation was found out to be the use of a mica substrate and lithium or sodium ion. In this concentration region, alkali ions with a firm hydration layer would play a role as a lubricant between particles and a mica substrate which has an ion-exchange capacity to help the cations adsorbed on the substrate.

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  • Hiraku Onishi
    2010 Volume 18 Pages 26-32
    Published: 2010
    Released: December 29, 2017
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    In this work, chitosan-based nanoparticles were applied to enhance efficacy of the immunostimulating agents. Lactoferrin (LF) and fucoidan (FUC) were chosen as immunostimulating agents. As to LF, chitosan/alginate/calcium complex microparticles were prepared as its drug carrier. The microparticles had a size of 1 – 2 μm, and showed relatively high LF content. The LF content and release rate were depended on the concentration of the chitosan solution used for the treatment of microparticles. Efficacy was investigated by the pre-treatment with oral administration to rats with carrageenan-induced edema. The microparticles exhibited better efficacy than LF solution. In addition, chitosan-based nanoparticles containing FUC were prepared and evaluated on the usefulness. From the particle characteristics, N-trimethylchitosan(TMC)/FUC nanoparticles were considered to be possibly useful nanoparticles, rather than chitosan/FUC nanoparticles. TMC/FUC nanoparticles had a size of 320 nm and contained FUC at 47% (w/w). Efficacy was examined by the pre-treatment or post-treatment with oral administration using mice with sarcoma-180 solid tumor. In both treatments, TMC/FUC nanoparticles exhibited better suppression of tumor growth than FUC solution. The nanoparticles were considered to enhance the antitumor efficacy due to the promotion of immune induction etc. These results suggested the chitosan-based micro- or nanoparticles should be available for the enhancement of the functions of immunomostimulating agents.

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  • Hideki Kanda
    2010 Volume 18 Pages 33-37
    Published: 2010
    Released: December 29, 2017
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    The authors previously proposed a clean up method for PCB-polluted sediment by the use of liquefied DME (dimethyl ether) gas. In a laboratory-scale experiment, 99% of PCB and water could be simultaneously removed from the sediment by solvent extraction using liquefied dimethyl ether. The energy consumed by this method was a half of latent heat of water; thus, this method using liquefied DME was confirmed to be effective and energy efficient. However, from a practical application standpoint, not only scale-up procedure but also basic microscopic consideration for clean up mechanism of PCB-polluted sediment particles are indispensable. In this study, we examined coexistence phenomena of binary Lennard-Jones liquid phases adsorbed on sediment particle by molecular dynamics simulation. The simulation results showed that surface coverage of PCB-like phase increased in proportion to PCB concentration in the bulk liquefied DME phase. Based on the results, this method was experimentally tested on oil-polluted soil by using a bench-scale experiment. The bench-scale experiment is successful in simultaneously removing both water and oil from soil powder. One application of this technology is expected to be the recovery of PCBs that leak into the urban rivers and other parts of the environment and from transformers that have been contaminated by oil containing PCBs. We would like to investigate the properties of PCBs in liquefied DME extracted from the sludge obtained from urban rivers etc. that contains PCBs and expand the range of materials to which the DME dewatering and deoiling technologies are applicable.

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  • Atsushi Nishikawa
    2010 Volume 18 Pages 38-44
    Published: 2010
    Released: December 29, 2017
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    We have succeeded in the growth of europium (Eu)-doped GaN layer grown by organometallic vapor-phase epitaxy (OMVPE) and demonstrated the first low-voltage operation of current-injected red emission from a p-type/Eu-doped/n-type GaN light-emitting diode (LED) at room temperature. In order to clarify the growth characteristics, we investigated the growth temperature dependence of luminescence properties. The dominant photoluminescence (PL) peak intensity at 621 nm, due to the intra-4f shell transitions of 5D0-7F2 in Eu3+ ions, became the highest when the sample was grown at 1000℃. Above 1000℃, the PL peak intensity decreased because of the lower Eu concentration associated with the surface desorption of Eu3+ ions. On the other hand, although the Eu concentration of the layer grown at 900℃ was only half of the layer grown at 1000℃ , the pronounced decline in the PL peak intensity was observed with decreasing growth temperature from 1000 to 900℃, which results from the modification of the local structure around Eu3+ ions. These results indicate that the growth temperature strongly influences the Eu concentration and the local structure around Eu3+ ions. Therefore, an optimized growth temperature exists for strong Eu-related luminescence from Eu-doped GaN layer grown by OMVPE. As for an electronic device, the bright red emission was obtained with an applied voltage as low as 3V under normal lighting conditions. At a d.c. current of 20 mA, the output power, integrated over the 5D0-7F2 transition of Eu3+ ions (around 621 nm), was 1.3 μW. This result suggests a novel way to realize GaN-based red LEDs and monolithic devices comprising red, green and blue GaN-based LEDs.

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  • Hiroyuki Shinto
    2010 Volume 18 Pages 45-49
    Published: 2010
    Released: December 29, 2017
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    A direct numerical method, based on statistical mechanics and fluid mechanics, is proposed to simulate the solid particles suspended in immiscible oil/water mixtures. Our simulation method successfully reproduces (i) the Laplace pressure of oil droplets in water, and (ii) oil droplets on the solid surfaces with various wettabilities in water. Our method allows us to represent not only the hydrodynamics of the particles, but the arbitrary wettability of the particles for the two liquids (e.g., the hydrophobic, hydrophilic, and surface-active particles).

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  • Takami Kai
    2010 Volume 18 Pages 50-55
    Published: 2010
    Released: December 29, 2017
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    Catalysts for methanol steam reforming were prepared from the glassy-metal powder produced by gas atomizing method. The basic components of the alloys were cupper and zirconium, and a small amount of platinum was added to the key components. The alloy powdereasilymelted and fused together to form agglomerate at relatively low temperature in pretreatment process. Consequently, the surface area of the powder decreased and the catalytic activity was very low. Coating the powder by silicasuccessfully prevented the sintering of the alloys. The coated alloy powder was used as a catalyst for methanol steam reforming after pretreatment of oxidation in the air and reduction with hydrogen. The catalytic activity was one order higher than that of the catalyst prepared from the amorphous alloys producedby using single-roll quenching method. Since the reaction temperature could be decreased by 100 K because of the high activity, the deactivation of the catalytic activity was reduced. Although the amorphous alloy by using single-roll quenching methodwithout platinum did not show the activity, the powder alloy without platinum formed an active catalyst for the reaction. However, the concentration of carbon monoxide in the product gas was about 0.1%. This value is still high for the practical use as the catalyst for methanol steam reforming.

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  • Hisashi Imai
    2010 Volume 18 Pages 56-61
    Published: 2010
    Released: December 29, 2017
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    Characteristics of pure metal matrix composites reinforced with carbon nanotubes (CNTs) have been investigated. Pure Cu powders coated with un-bundled CNTs were prepared by using the surfactant (surface active agent) solution, containing both hydrophobic and hydrophilic groups, via wet process. The microstructural and mechanical properties of CNT-Cu composites were particularly investigated in detail. Cu powder with a mean particle size of 130μm and multi-wall CNTs with 20 nm in diameter were used as matrix material and reinforcements, respectively. After dipping Cu powder into the solution with CNTs, the composite Cu powders coated with CNTs were served to heat treatment in hydrogen gas atmosphere to thermally resolve the surfactant films of the powder surface. The suitable temperature for heat treatment was determined by differential thermal analysis on the composite Cu powder. The extruded Cu composite including CNTs indicated an increase of 30% in hardness and 17% in yield strength, compared to pure Cu without CNTs. The thermal conductivity of CNT-Cu composites by using wet process steadily decreased with increasing the CNT contents.

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  • Kungen Teii
    2010 Volume 18 Pages 62-66
    Published: 2010
    Released: December 29, 2017
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    There is an increasing interest in applications of wide-gap materials to high-temperature and high-power electronics. It is necessary to radiate extra heat efficiently through an aluminum heat sink coated with a heat-resistant material with high thermal conductivity. Diamond has the highest thermal conductivity in all materials, which at room-temperature is above 1000 W/mK. However, at high temperatures, diamond films show low adhesion to aluminum substrates due to a large difference in thermal expansion coefficient between diamond and aluminum.

    Nanocrystalline diamond films are composed mainly of two carbon phases: the diamond phase in form of nanograins and amorphous carbon at the grain boundaries. The thermal expansion coefficient can also be controlled if the diamond/amorphous carbon ratio in the films can be varied. The author has showed a way of increasing the diamond/amorphous carbon ratio in plasma-enhanced CVD. In this study, we examine the thermal and electrical transport properties of nanocrystalline diamond films.

    The films were deposited on aluminum and silica substrates. The room-temperature thermal conductivity increased when the diamond fraction was increased. Nitrogen addition increased the electrical conductivity, however, the thermal conductivity decreased. This was attributed to an increase in thermal resistance at the grain boundaries due to a decrease in the diamond/amorphous ratio.

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  • Teruoki Tago
    2010 Volume 18 Pages 67-73
    Published: 2010
    Released: December 29, 2017
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    In hydrothermal synthesis of zeolites, organic-structure-directing agents (OSDA) are employed to form zeolite structure, in addition to alkali metals, and Si and Al sources. Recently, there has been growing interest in OSDA-free synthesis of zeolites, such as MFI and MOR. Since formation of zeolite nuclei and crystals proceeds in a strong alkaline solution, however, nucleation/crystallization and resolution of zeolites simultaneously occurs, leading to low yield of zeolite and poor crystallinity due to deposition of amorphous silica. In contrast, we successfully prepared MFI and MOR zeolite nanocrystals via hydrothermal synthesis in a water/surfactant/organic solvent, where the non-ionic surfactants adsorbed on the surface of the zeolite precursors likely induced the formation of zeolite nuclei. Moreover, it is considered that the adsorbed surfactant inhibit the zeolite nuclei and crystal from their resolution. Main objective of this study is development of OSDA-free synthesis of MFI zeolite at high zeolite yield.

    In order to investigate the effect of surfactant properties on the crystallinity, OSDA-free MFI zeolite synthesis is carried out using the surfactants with different oxyethylene-chain length. Addition of surfactant into the synthetic solution is effective in improving the crystallinity of obtained MFI zeolite. Moreover, the HLB (Hydrophile-Lipophile Balance) vales of surfactant affect the amount of N2 adsorbed on micropore. Since zeolites possess hydrophilic-hydrophobic properties on their surface, there exists the affinity between the zeolite surface and surfactant, depending on HLB values. As compared with the sample without surfactant, the yield of MFI zeolite at Si/Al ratio of 12.5 increased from approximately 60% to 90% in OSDA-free synthesis using surfactant O-15. The high yield of zeolite in OSDA-free synthesis is ascribed to the adsorption of surfactant on the zeolite surface, where the resolution of Si and Al atoms in zeolite framework are inhibited.

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  • Mika Eguchi
    2010 Volume 18 Pages 74-80
    Published: 2010
    Released: December 29, 2017
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    In the PEFC catalyst layer, the electron, the ion, and the gas vertically flow to the electrode plane. Therefore, the structure that the catalyst and the electrolyte ionomer and the porosity are vertically connected is preferable1. The catalyst layer based on the organic crystalline whisker in 3M company2 and the catalyst layer based on vertically aligned carbon nanotube(CNT)in the Toyota Motor Corporation3 were researched.

    In this study, we propose a new fabricating process for an ideal catalyst layer structure that the material transfer paths of the ion, the gas and the electron are ensured by using the Pt catalyst support vertically aligned CNTs. The concept of the process is shown in Figure 1.

    The process was examined experimentally. Vertically aligned CNTs of about 10 nm in diameter were obtained by the CVD method on the silicon substrate using published techniqe4. In order to take away the Fe compound catalyst and make bonding sites for Pt atoms, the tip of vertically aligned CNTs were burned by the heat treatment in oxygen5. In this study, the Pt catalyst was supported on the tip of vertically aligned CNT by Pt sputtering, after burning off the tip of CNT. Pt was dispersed on the tip surface of vertically aligned CNT, as shown in Figure 2. The vertically aligned CNT was coated by Nafion ionomer solution, hot-pressed with Nafion membrane, then transcribed on the Nafion membrane by peeling off the Si substrate. Figure 3 shows the cross section of ionomer coated vertically aligned CNT on the Nafion membrane.

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  • Cathy Elizabeth McNAMEE
    2010 Volume 18 Pages 81-91
    Published: 2010
    Released: December 29, 2017
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    In this study, we made monolayers of hydrophilic particles at an air/aqueous interface using TiO2 particles. In order to study the conditions and parameters necessary to obtain a monolayer with a controlled close-packing, we studied the effects of subphase pH, subphase salt concentration, and particle size on the ability to form a monolayer. These factors were chosen as the solution pH controls the charge on the TiO2 surface, the salt concentration can vary the magnitude of electrostatic repulsion and therefore the attractive forces affecting a TiO2 particle, and the size of the particle may affect the magnitude of the flotation and gravitational forces. TiO2 particles with diameters of 300nm , 500nm, 1μm, 5μm, 10μm, and 20μm, solution pH of 2, 6, and 11, and salt concentrations of 0, 100mM, and 500mM have been used in this study.

    We saw that hydrophilic particles could be made to form a monolayer at an air/aqueous solution by tuning the physical parameters of the system, e.g. by pH. This was done in our case for TiO2 particles by spreading them at an air/aqueous interface, when the subphase had a pH < iep of TiO2. The positive charge of the particle and the negative charge of the interface allow the particle to float, due to a charge-induced capillary force.

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  • Takuya Tsuji
    2010 Volume 18 Pages 92-96
    Published: 2010
    Released: December 29, 2017
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    In a number of industrial applications that include flow with dense solid particles, large solid objects are also existing in the flow. The behavior of large objects is complex due to the existence of interactions with surrounding gas/liquid flows, small particles and walls. In the case of fluidized and spouted beds, especially, it is still difficult to predict whether a solid object rises or sinks depending on its size, shape and density. In the present study, we try to develop a numerical model which reproduces the behavior of large solid object in a bubbling fluidized bed. Discrete element method (DEM) - Computational Fluid Dynamics (CFD) mesoscopic model is coupled with immersed boundary method (IBM).

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  • Makoto Ogawa
    2010 Volume 18 Pages 97-102
    Published: 2010
    Released: December 29, 2017
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    Monodispersed spherical particles have been claimed to be promising materials’ morphology for such applications as liquid crystal display spacer, photonic crystal, liquid chromatography stationary phase etc. depending on the size, composition and structure. Since the monodispersed spherical particles of silica and polystyrene in the size range of several hundreds of nm to microns are commercially available and also their syntheses are possible in the laboratory, their syntheses and applications have been published extensively. If the monodispersed porous spherical particles are available, one can extend the applications by means of host-guest chemistry. However, this type of materials is only available on surfactant templated nanoporous silicas. In this study, we examined the syntheses of nanoporous titania spherical particles. Titania possesses unique properties including high refractive index and UV absorption and photocatalytic abilities, therefore, monodispersed spherical particles may find applications where silica based nanoprorous silica spherical particles do not have an access. In the present study, we applied a microfluidic reaction to obtain well-defined titania based particles from titanium alkoxide and octadecylamine. Reactions occurred within micron sized channel have been known to show characteristic features such that temperature and concentration gradient are negligible, having potential to realize uniform reactions which directly correlate with the homogeneity of products. Nanoporous amorphous titanium dioxides with the surface area of 620m2・g-1 and BJH pore size of 2.2 nm was obtained.

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  • Takeshi Yanagida
    2010 Volume 18 Pages 103-107
    Published: 2010
    Released: December 29, 2017
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    Metal oxides have recently renewed the interests due to the resistive memory switching phenomena based on the electrically stimulated change of the resistance of a metal-insulator-metal (MIM) memory cell, frequently called resistive switching RAM (ReRAM). The ReRAM devices are expected to be future nonvolatile memory devices used as alternatives to the current flash memory technology. The nonvolatile memory characteristics have been intensively investigated using the thin film forms, and excellent memory characteristics have been demonstrated. However, to achieve high-density memory and improve the performance of the devices, it is crucial to reduce the size of the cells beyond the limitation of current lithographic length scales. In addition, details of resistive memory switching mechanisms, including the switching types (bipolar and/or unipolar), have not been well understood. Thus the scaling down of the cell structures is strongly desired not only for understanding the underlying memory mechanisms within a confined nanoscale but also for improving the device characteristics of ReRAM. The bottom-up approach using self-assembled nanowires is a promising solution for scaling down the size of memory devices. Thus, single crystalline oxide nanowires formed via a self-assembling fashion would be a candidate for overcoming the above issues. However difficulties in both fabricating nanowires composed of metal oxides and evaluating electrically the insulative oxide nanowires have impeded investigation of the resistive memory switching events in oxide nanowires. Here we have demonstrated nonvolatile bipolar resistive memory switching in heterostructured oxide nanowires. The self-assembled oxide nanowires are expected to open up opportunities to explore not only the detailed nanoscale mechanisms in resistive memory switching but also next-generation nanoscale nonvolatile memory devices with the potential for high-density device integration and improved memory characteristics.

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  • Shinsuke Ifuku
    2010 Volume 18 Pages 108-113
    Published: 2010
    Released: December 29, 2017
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    We have prepared silver nanoparticles on the surface of bacterial cellulose (BC) nanofibers. The synthesis of silver nanoparticles incorporates 2,2,6,6-tetramethylpiperidine-1-oxyradical (TEMPO)-mediated oxidation to introduce carboxylate groups on the surface of BC nanofibers. An ion exchange of the sodium to the silver salt was performed in AgNO3 solution, followed by thermal reduction. By using oxidized BC nanofibers as a reaction template, we have prepared stable silver nanoparticles with a narrow size distribution and high density through strong ion interactions between host carboxylate groups and guest silver cations, which have been investigated by scanning electron microscopy, UV-visible spectroscopy, and a small-angle X-ray scattering method.

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  • Shinya Maenosono, Viet Thu Tran
    2010 Volume 18 Pages 114-117
    Published: 2010
    Released: December 29, 2017
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    Al-doped ZnO (AZO) nanoparticles (NPs) have been synthesized via the thermal decomposition of metal acetylacetonate precursors in a nonoxygen and nonpolar solvent. Long-chain alkyl amines have been utilized to terminate the growth of AZO NPs and to stabilize them. The NPs have been characterized by a number of techniques as monocrystalline, exhibiting a hexagonal (wurtzite) structure with sizes from 8 to 13 nm. The composition of Al in the resulting NP is related solely to the composition of the reaction mixture and the size is controllable with the temperature of the reaction. The AZO NP dispersion has been proven to be stable over a 24 h period by dynamic light scattering measurements. The influence of the synthetic conditions, such as temperature, reaction time and the Al doping content, on the properties of NPs have also been investigated. An optically transparent AZO thin film was fabricated using the AZO nanoink by spin casting followed by annealing. The resulting film resistivity was measured to be 5.0 10-3 Ω·cm.

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  • Motohiro Yamada, Tjitra Salim Noviana, Hiromi Nakano, Dickinson E. Mic ...
    2010 Volume 18 Pages 118-126
    Published: 2010
    Released: December 29, 2017
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    This research studied about the bonding mechanism of supersonically accelerated solid ceramic powder material in cold spray process. In order to understand the bonding mechanism of the solid ceramic particles, the structure of feedstock titanium dioxide (TiO2) particles was carefully observed with the scanning electron microscope (SEM) and the high-resolution transmission electron microscope (TEM). The SEM and TEM data clearly reveal the deformation and adhesion mechanism of the sprayed ceramic particles and the substrate. We have discovered three essential factors for solid ceramic bonding and these are related to the structures of feedstock powder. Firstly, powder has to be agglomerated to a size of about 10μm. This is the suitable particle size for high particles acceleration in the supersonic gas stream. Secondly, the powder has to be an agglomerated porous structure with nano-scaled primary particles. It is believed that porosity assists with the breaking down phenomenon of particles occurred during the cold spray process and this phenomenon influences the adhesion of ceramic particles. Finally, the powder must have primary particles that are agglomerated and oriented within a single crystal axes. This particular structure is believed to be responsible for the adhesion between TiO2 particle and substrate. These three unique structures of the feedstock powder material are required to obtain thick and defined coatings of TiO2 via cold spray process.

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  • Masaharu Isobe, Jun'ichi Wakou
    2010 Volume 18 Pages 127-131
    Published: 2010
    Released: December 29, 2017
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    We propose a novel approach based on a Langevin equation for fluctuating motion of the center of mass of granular media fluidized by energy injection from a bottom plate. In this framework, the analytical solution of the Langevin equation is used to derive analytic expressions for several macroscopic quantities and the power spectrum for the center of mass. In order to test our theory, we performed event-driven molecular dynamics simulations for one- and two-dimensional systems. Energy is injected from a vibrating bottom plate in the one-dimensional case and from a thermal wall at the bottom in the two-dimensional case. We found that the theoretical predictions are in good agreement with the results of those simulations under the assumption that the fluctuation-dissipation relation holds in the case of nearly elastic collisions between particles. However, as the inelasticity of the interparticle collisions increases, the power spectrum for the center of mass obtained by the simulations gradually deviates from the prediction of theoretical curve. Connection between this deviation and violation of the fluctuation-dissipation relation is discussed.

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  • Kazuyoshi Sato
    2010 Volume 18 Pages 132-137
    Published: 2010
    Released: December 29, 2017
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    Three-dimensionally extended functional interfaces were built using hybrid nanoparticles synthesized by the unique break-down and bottom-up approaches. Here, we report the processes in detail and the applications of the hybrid nanoparticles for high performance solid oxide fuel cells (SOFCs). The first generation NiO/yttria-stabilized zirconia (YSZ) hybrid nanoparticles (~100nm) was fabricated by a dry mechanochemical process without milling media. The nanoparticles provide the uniform three-dimensional networks of Ni, YSZ and pore phases suggesting the formation of large amount of triple phase boundaries (TPBs) in Ni/YSZ anode. The anode showed the performance high enough for the practical applications and good long-term stability at 700℃. More uniform Ni/YSZ anode microstructure and resultant better performance were achieved using the second generation NiO/YSZ hybrid nanoparticles (<100nm) synthesized via a modified co-precipitation of hydroxides. We found that the homogeneous hybrid nanoparticles can be synthesized at pH >13 through this method. For further higher performance of the SOFCs, we newly developed a co-precipitation method of third generation NiO/YSZ and (La0.85Sr0.15)0.98MnO3(LSM)/YSZ hybrid nanocrystals (<10nm) using YSZ nanocrystals of ca. 3nm, perfectly dispersed in aqueous medium, as the seed crystals. The obtained hybrid nanocrystals successfully forms nanostructured electrodes consisting of the homogeneously distributing nanosized grains. The homogeneous nanostructure provides huge amount of the functional interfaces within the electrodes. Finally, SOFC consisting of the nanostructured electrodes showed the very high power density of 0.18, 0.40, 0.70 and 0.86 W·cm-2 at 650, 700, 750 and 800℃, respectively, under the constant cell voltage of 0.7 V.

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Young Researcher Scholarship Report
  • Asep Bayu Dani Nandiyanto, Kikuo Okuyama
    2010 Volume 18 Pages 139-142
    Published: 2010
    Released: December 29, 2017
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    Control of the particle morphology and particle outer diameter (from nano and submicron sizes) has increasingly captured the attention of researchers for decades. The exploration of unique sizes and shapes as they relate to various properties has become a great quest for large field applications. To meet these demands, this study covered our recent developments in an aerosol-assisted self-assembly technique (a spray method) for particle processing. The particle processing of several morphologies (sphere, doughnut, encapsulated, porous, hollow, raspberry, and hairy shapes) was discussed in terms of the selection of material types, the addition of supporting materials, and the change of process conditions. Controllable particle outer diameter was discussed in terms of the adjustment of the droplet size and concentration, and the addition of specific techniques. A theoretical mechanism was also simplified described, especially to describe how particles are designed with various sizes and morphologies. The performance of various particle morphologies was also demonstrated, which was essential for an understanding of the importance that shape could exert on practical use. Because the method outlined here can be broadly applied to the production of various types of functional materials, we believe that this report contributes new information to the field of chemical, material, environmental, and medical engineering.

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  • [in Japanese], [in Japanese]
    2010 Volume 18 Pages 143-145
    Published: 2010
    Released: December 29, 2017
    RESEARCH REPORT / TECHNICAL REPORT FREE ACCESS
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