Hosokawa Powder Technology Foundation ANNUAL REPORT
Online ISSN : 2189-4663
ISSN-L : 2189-4663
Volume 23
Showing 1-44 articles out of 44 articles from the selected issue
Preliminaries
Research Grant Report
  • Masaki AZUMA
    2015 Volume 23 Pages 18-22
    Published: 2015
    Released: February 03, 2017
    RESEARCH REPORT / TECHNICAL REPORT FREE ACCESS

    Thermal expansion causes problems in semiconductor industry and optical communications where precise positioning is required. There are a few materials that show negative thermal expansion (NTE). It was recently found that perovskite Bi1–xLaxNiO3 show giant NTE around room temperature. In this study, BiNi0.85Fe0.15O3 powders were prepared by high-pressure synthesis at 6 GPa and 1000°C and were dispersed in a epoxy resin as filler. TheCTE of BiNi0.85Fe0.15O3 reaches 187 ppm K–1 and it is demonstrated that 18 vol. % addition of the present compound compensates for the thermal expansion of epoxy resin.

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  • Kenji IIMURA
    2015 Volume 23 Pages 23-27
    Published: 2015
    Released: February 03, 2017
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    Room temperature synthesis of metal oxides is quite attractive for not only researchers but industry. However, that is quite difficult due to the low energy level of room temperature. This work proposes the potential of ozone which is known to be strong oxidizer to via synthesis of zinc oxide. As a result, room temperature synthesis of zinc oxide was possible with ozone assist. With ozone assist, the properties of product were different form that by elevation of temperature. From the XRD analysis, it was clarified that crystallinity of zinc oxide was higher as for ozone assist system. And, it was also clarified that ozone could reduce the amount of oxygen defects and loading of impurities.

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  • Teruyuki IKEDA
    2015 Volume 23 Pages 28-32
    Published: 2015
    Released: February 03, 2017
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    Nanostructuring thermoelectric materials has been attempted to enhance thermoelectric figure of merit, zT. Nanostructuring is expected to lead to the reduction of lattice thermal conductivity or the extension of solubility of dopants, either of which could lead to improvement of zT. A nonequilibrium ball milling process has been employed to fabricate forced solid solutions of silicon with supersaturated antimony or boron, or magnesium silicide with supersaturated bismuth. The power obtained in the ball milling process was consolidated by the spark plasma sintering technique, which resulted in nanoprecipitation. In the silicon-antimony system, the carrier concentration is found to be higher than the equilibrium solubility. In the magnesium silicide-bismuth system, we observed the reduction of lattice thermal conductivity from the nanostructuring.

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  • Hironori IZAWA
    2015 Volume 23 Pages 33-37
    Published: 2015
    Released: February 03, 2017
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    The host-guest interaction of cyclodextrin (CD) involved in a polymeric network would be controlled by an ultrasound because the energy from the ultrasound can be transferred though the polymeric network. In this study, we examined preparation of a nano-particle with the network polymeric structure containing CD in response to the ultrasound. The nano-particle was prepared by crosslinking of a chitosan by using a tri-substituted caroboxymethyl β-CD. The mean diameter estimated by a DLS analysis was ca 122.5 nm, which is suitable for the DDS. A particle composed of β-CD-grafted chitosan and tripolyphosphate was prepared as a comparison sample to clarify the importance of the network structure. The release experiment with rhodamine 6G revealed that the nano-particle having the CD-containing polymeric network showed a sustained release by the exposure to the ultrasound, which was 4 folds delayed. Such behavior was not shown in the case of the comparison sample. Furthermore, the results of adsorption experiments under the ultrasound were consistent with the results of the release experiment. These results indicate the inclusion complexes in the CD-containing polymeric network were stabilized by the ultrasound.

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  • Naoyuki ISHIDA
    2015 Volume 23 Pages 38-43
    Published: 2015
    Released: February 03, 2017
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    The interaction forces between hydrophobized silica surfaces with no nanobubbles were measured using atomic force microscopy (AFM). To obtain hydrophobic surfaces without nanobubbles, an aqueous solution was introduced between the surfaces following an exchange process involving several solvents. In the obtained approaching force curves, an attractive force was observed from a distance of 10–20 nm, which is an additional attractive force stronger than typical van der Waals attractions. We also conducted the force measurements between the fluorinated silica surfaces in formamide and found an attractive force that is stronger than the van der Waals attraction. This result confirms that the ‘solvophobic attraction’, which is very similar to the hydrophobic attraction, exists in some organic solvents. The interaction forces were also measured between a hydrophobized substrate and an AFM tip, which has the small radius of curvature. The range of the attraction was found to become smaller abruptly when the radius of curvature of the tip is around 100–200 nm, implying that the origin of the force is different depending on the size of the surfaces.

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  • Satoshi INAGAKI
    2015 Volume 23 Pages 44-49
    Published: 2015
    Released: February 03, 2017
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    The catalytic reaction systems into the electric field are much attention as energy-saved catalytic processes, and zeolite catalysts might be potentially used in the system. Therefore, mechanochemical preparation of compounded particles of micro-sized ZSM-5 zeolite and CeO2 nanoparticles was investigated in this research. During the mechanochemical treatment by using a powder composer, the crystallinity of ZSM-5 zeolite was almost retained. Bead-milling treatment of CeO2 agglomerates can be changed into mono-dispersed CeO2 nanoparticles with ca. 30 nm in size, and the following mechanochemical treatment with ZSM-5 can successfully give the compounded particles. In the cross-sectional view of the compounded particles (CeO2(40 wt%)/ZSM-5), the thickness of CeO2 layer was about dozens of nanometers. The compounded particles showed the catalytic activity originating from ZSM-5 zeolite to promote the catalytic cracking reactions of various hydrocarbons.

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  • Shu YIN
    2015 Volume 23 Pages 50-56
    Published: 2015
    Released: February 03, 2017
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    The synthesis, structure, and the multifunctionality, such as conductivity, NIR shielding property and biomedical thermal therapy of the mixed-valence tungsten bronze based materials (MxWO3) were investigated. The environmentally friendly solvothermal process was carried out to synthesize the well-crystallized nanosize materials with controllable morphologies, particle size and chemical constitution. In a typical synthesis process, the mixture of ethanol and desired amount of acetic acid utilized as a reaction media was introduced in a Teflon-lined autoclave and heated at 200°C for desired reaction time. The esterification reaction between ethanol and acetic acid led to the formation of a desired amount of water, which acts an import role on the crystalline growth in the solution. By controlling the amount of the acetic acid, it is possible to control the water molecule formation, and consequently, affect the particle size and the morphologies of the products. The tungsten bronze nanomaterials with homogeneous morphology possess more excellent visible light transparency, electronic conductivity and UV/IR shielding ability than tungsten trioxide and even commercial ITO glass materials, indicating their extremely high-potential applications in transparent conductive thin film, smart window materials, and biomedical materials.

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  • Hiroki UEHARA
    2015 Volume 23 Pages 57-64
    Published: 2015
    Released: February 03, 2017
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    Stereo-complex crystallization of poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) was performed by flowing their blend solution through nano-channels of porous membranes. The spacing restriction within the nano-channels induces the contact between PLLA and PDLA chains. The stereo-complex crystalline structure of the obtained material was confirmed by differential scanning calorimetry and X-ray measure­ments. Morphological observation by scanning electron microscope indicates that the characteristic nano-particles with the diameter corresponding to channel width aggregate each other. Such nano-particles play a role of nucleating agent for matrix crystallization when they are blended with pure PLLA.

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  • Shinjiro UMEZU
    2015 Volume 23 Pages 65-69
    Published: 2015
    Released: February 03, 2017
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    Solar cell is recognized as clean energy. Si type of the solar cell dominated the market of solar cell because of high efficiency. On the other hand, dye-sensitized solar cell (DSC) had good merits those were flexibility, colorful, cost and installation location in spite of the low efficiency. Most researchers focused on materials of DSC and relatively improved the efficiency. We focused on the fabrication process of DSC for improving the efficiency. We applied the micro 3D printer for fabrication of titania layer to control the thickness and porous ratio in the titania layer.

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  • Tsunenobu ONODERA
    2015 Volume 23 Pages 70-74
    Published: 2015
    Released: February 03, 2017
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    In the present study, a useful method to prepare a well-defined metal-organic complex nanoparticles has been developed. Namely, organic ligand was first nanocrystallized by the reprecipitation method, and then metal ion solution was added to the organic ligand nanocrystals dispersion liquid to produce complex nanocrystals. As a result, insoluble fluorescent complexes [Cu(μ-Br)dppb]2 nanoparticles were successfully fabricated. Furthermore, fluorescence properties of [Cu(μ-Br)dppb]2 nanoparticles were investigated. It has become apparent that the fluorescence peak position of the [Cu(μ-Br)dppb]2 nanoparticles was red-shifted compared with the corresponding bulk crystal, and that the fluorescence intensity increased by annealing treatment.

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  • Tetsuya KIDA, Satoshi SUEHIRO
    2015 Volume 23 Pages 75-80
    Published: 2015
    Released: February 03, 2017
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    P-type nanocrystals of copper-based chalcogenides such as CuInSe2 and Cu2ZnSnS4 have attracted increasing attention in photovoltaics because of their prospects for cheap solution-processed solar cells. In this study, copper-antimony-sulfide (CAS) nanocrystals including CuSbS2, Cu3SbS4 and Cu12Sb4S13 were synthesized by a hot-injection method. The crystal phase control was achieved by changing the reaction temperature and starting precursor ratios. Crystal morphologies significantly depended on the crystal phase; CuSbS2 and Cu12Sb4S13 were rod-like crystals while Cu3SbS4 was angulate crystals. Photoemission yield measurements and UV-Vis-NIR spectroscopy revealed differences in the electronic structures of the three phases. Devices coupling CAS particulate films with dense CdS layers exhibited a diode like behavior, suggesting the formation of pn junction between them. Devices based on the structure of ITO/ZnO/CdS/CuSbS2/Au exhibited a PV response with the power conversion efficiency of 0.01% under simulated sunlight, while devices with Cu3SbS4 and Cu12Sb4S13 showed no PV response. Although the obtained efficiency is very low for practical applications, improving the film quality by sintering and optimizing the thickness would further improve the performance.

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  • Kenji KOFU
    2015 Volume 23 Pages 81-87
    Published: 2015
    Released: February 03, 2017
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    The purpose of this research is to control the particles motion in the ultrasonic standing wave. The results of simulation have been compared with experiment in order to examine the possibility of particles motion control in the air. Simulations have corresponded with experiments on acoustic pressure distribution and particle motion. However particle motion control was impossible in this experiment because radiation pressure acting on particle was poor and gravity force dominates. Then, simulation showed that the particle motion is changed if the sound pressure is increased. This means it is possible to control the particles motion by ultrasonic if high acoustic pressure is applied. Additionally particle can be collected by changing vibration mode even though maximum acoustic pressure is not changed.

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  • Chika TAKAI
    2015 Volume 23 Pages 88-95
    Published: 2015
    Released: February 03, 2017
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    The micro-structures and derived physical properties of skeletal nanoparticles were investigated using microscopic, macroscopic techniques. A scattering function of hollow silica nanoparticles from a small angle X-ray scattering (SAXS) indicates that defects among siloxane bonds in silica shell. It can be thought that the defects also exist in the silica frames of the skeletal nanoparticles. The bias observed in the SAXS-derived PDDF represents characteristic silica frame structures such as width, length, window size, etc. From these results, the existing defects in the silica frames could contribute to skeletal particle’s specific functionalities.

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  • Sadatsugu TAKAYAMA
    2015 Volume 23 Pages 96-99
    Published: 2015
    Released: February 03, 2017
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    The goal of this study is to rationally prepare partially fluorinated tin oxide (SnO2:F) and synthesis of nanocomposite consisting of SnO2:F and carbon. For this purpose, a mecahnochemical process (MCP) and a microwave irradiation one (MWR) were combined. Physicochemical properties of MCP, MWR products were investigated by measuring X-ray diffraction (XRD) and X-rays photoelectron spectroscopy (XPS).

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  • Kazuo TANAKA
    2015 Volume 23 Pages 100-104
    Published: 2015
    Released: February 03, 2017
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    The synthesis of imidazolium-presenting silica nanoparticles and the role as a heating source under microwave irradiation are described here. The series of modified nanoparticles with various kinds of counter anions were prepared, and their enhancement abilities of heating under microwave irradiation were compared. Finally, it was summarized that the dielectric loss originated from the interaction between imidazolium cation and water molecules should play a crucial role in the heating effect. Next, based on the modified nanoparticles, thermal enzyme deactivation by the imidazolium-presenting silica nanoparticles with the microwave irradiation is presented. The modified nanoparticles were synthesized, and it was observed that the modified nanoparticles can be a heat source in the buffer under the weak-power microwave irradiation. Finally, based on the heat-generating ability of these nanoparticles, deactivation of glutathione reductase and alkaline phosphatase with the modified nanoparticles were demonstrated.

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  • Kenji TANNO
    2015 Volume 23 Pages 105-109
    Published: 2015
    Released: February 03, 2017
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    Particle concentration control technology is important for increasing the load changeability of a coal-fired power plant. In this study, momentum transport and particle dissipation behavior in a mixing layer with and without wake flow. Results show that momentum transport and particle dissipation is enhanced in the region where large-scale eddies are generated in the case of without wake. On the other hand, in the with wake case, particle dissipation is promoted in some region and suppressed in some region.

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  • Takuya TSUJI
    2015 Volume 23 Pages 110-113
    Published: 2015
    Released: February 03, 2017
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    Fluidized bed is widely used in the processes related to heat and mass transfers such as drying, combustion and gasification. It is not trivial to observe these transport phenomena occurring inside of the beds experimentally and the promotion of our understandings on internal transport processes by numerical simulation is important. In the present study, extension of DEM-CFD mesoscopic model to be able to consider heat and mass transfers was conducted. We especially focused on drying process of wet particles in hot fluidized bed. By comparing the results of drying experiment using wet Silica-gel particles and the proposed model, validity of the model was successfully demonstrated; the proposed model enables quantitative prediction of the drying process with acceptable level.

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  • Chiaki TERASHIMA
    2015 Volume 23 Pages 114-118
    Published: 2015
    Released: February 03, 2017
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    Development of photocatalytic system to produce useful fuels and chemicals utilizing pollutant CO2 has attracted much attention as to address the issue of energy demand and global warming. Recently diamond has explored for its excellent photocatalytic behavior. Though diamond has band width of 5.5 eV, it opens the new avenue of diamond research on photocatalytic application. We demonstrate the photocatalytic performance of the nanodiamond (ND) on reduction of CO2 in water. Two types of ND such as ND-A (size: 250 nm) and ND-B (size: 20 nm) have been investigated in the CO2 saturated water under UV light irradiation of 222 nm. The experiments carried out in the airtight photocatalytic cell and the UV light is illuminated through quarts opening. The gas chromatogram analysis of the gaseous product revealed the formation of carbon monoxide. The CO generated by ND-A and ND-B is 10 and 95, μmol/g, respectively. The proof of CO source from CO2 reduction was carried out with 13CO2 isotope experiment. This is first report on diamond particles based photocatalytic process.

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  • Takanari TOGASHI
    2015 Volume 23 Pages 119-122
    Published: 2015
    Released: February 03, 2017
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    In this study, we have synthesized of COOH group displayed metal oxide, Fe3O4 and CeO2 nanoparticles via thermal decomposition of 3,4-dihydroxyhydroxycinnamic acid (DHCA)-metal complex in high temperature and pressure water. The COOH groups useful for binding the protein and nanoparticles were displayed on the synthesized metal oxide nanoparticles. In addition, the synthesized particles have narrow size distribution and water dispersibility. Cytokines such as IL-12 and TNF-a were not produced from the dendritic cells of mice by co-incubation with our synthesized nanoparticles. This indicates that the synthesized nanoparticles had no immune stimulating property for the dendritic cells of the mouse.

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  • Yasuaki TOKUDOME
    2015 Volume 23 Pages 123-128
    Published: 2015
    Released: February 03, 2017
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    Adaptive functional materials which exhibit responses to external stimuli, such as temperature, humidity, pH, and light, have been a topic of interest towards applications of sensing, drug delivery, and actuation. In the present study, novel stimuli-responsive microstructures were designed on the surfaces of hybrid bilayered films, and their structural features, as a function of external stimuli, were closely investigated. PNIPAM/hybrid silica and silica/PDMS bilayered films were demonstrated to exhibit thermal and solvent response, allowing the appearance/disappearance of the surface textures (wrinkles and folding). Moreover, the surface wrinkles and foldings were successfully formed on spherical core-shell particles. The morphological features of wrinkles on a spherical surface depends on curvature of the sphere, which is in good agreement with a previously-reported theoretical description. As an application, catch & release of micro-particles has been demonstrated.

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  • Takahiro NAMAZU
    2015 Volume 23 Pages 129-135
    Published: 2015
    Released: February 03, 2017
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    In this study, we focus on developing a fabrication technique for self-propagating exothermic nanoparticles, which are made of biocompatible materials, Si and Ti, used for cancer treatment. Atomized heating method was employed to fabricate porous silica nanoparticles. The influences of heater temperature, nitrogen gas flow rate, polystyrene particle’s diameter and its density in the slurry on the size and shape of the silica nanoparticles were investigated. Then, the fabricated porous silica nanoparticles were deoxidized by molten-salt plasma electrolysis technique, which could reduce oxygen percentage in a particle to 27 at%. Ti was deposited in pores and on the particle by dc magnetron sputtering to make exothermic nanoparticles made of Ti and SiO. By supplying an electric shock, Ti/SiO nanoparticles successfully reacted, and the exothermic reaction gradually propagated. The combination of atomized heating, molten-salt plasma electrolysis, and sputtering techniques enabled us to realize producing self-propagating exothermic nanoparticles made of biocompatible materials.

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  • Yuichi NEGISHI
    2015 Volume 23 Pages 136-141
    Published: 2015
    Released: February 03, 2017
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    In this work, we attempted to synthesize the novel small platinum cluster via common ligand (tetraoctylammonium and phenylethanethiolate) and polyol reduction procedure. Then, some clusters were synthesized size-selectively by modulating the simple parameters, i.e. reaction time. MALDI analysis revealed that minimum phenylethanethiolate protected platinum cluster contained 54–57 platinum atoms and 12–16 sulfur atoms. Finally, we tested catalytic activity of oxygen reduction regarding obtained clusters. The results indicated that the catalytic activity of small cluster is about 1.5 times higher than that of conventional platinum nanoparticle.

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  • Ryuji NOMURA
    2015 Volume 23 Pages 142-147
    Published: 2015
    Released: February 03, 2017
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    Effects of disorder on the dynamics of the first order phase transition are intriguing in the low-temperature limit where thermal fluctuation ceases and novel quantum phenomena would emerge. We have been investigating crystal growth of 4He in silica aerogels visually. Crystallization of 4He in aerogel was revealed to exhibit a dynamical transition in the growth mode. Crystals grow via creeps at high temperatures and via avalanches at low temperatures due to the competition between thermal fluctuation and disorder. It was also found from a crystallization rate and a nucleation probability measurements that crystals grow via thermal activation in the high-temperature creep region and via macroscopic quantum tunneling in the low-temperature avalanche region. In the low-temperature quantum region, avalanche size distribution has a power law which indicates that the system is in a self-organized critical state. Here, we demonstrated that a crystallization on cooling at a constant pressure was possible in aerogels, using a variable volume cell to independently control the pressure and temperature. Crystallization was induced by cooling below a particular temperature, indicating that mass transport occurred from the surrounding bulk crystals into the aerogel below that onset temperature. While a possible explanation for the mass transport would be supersolidity, the onset temperature of the crystallization was lower than the reported supersolid transition temperature. Therefore, the supersolidity was found to be one of the necessary conditions for the crystallization to proceed and the stability of the crystal phase in the aerogel was another important condition that governed the crystallization. This result was the first indication of a strong connection between the crystallization in pores and the supersolidity of the surrounding crystals.

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  • Hiroyuki MUTO
    2015 Volume 23 Pages 148-152
    Published: 2015
    Released: February 03, 2017
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    The structures containing 2D ordering of nano/micrometer-sized monodisperse particles have several key applications in materials science and engineering. The study on the geometrical packing/arrangement of such particles has been proposed and developed for fabricating colloidal crystals with 2D or 3D ordered structures. However, localized ordering of particles occurs in limited areas, leading to the aggregate containing spatially partitioned domain structures with anisotropic orientations. In order to overcome such a difficulty, the application of electrical forces to fabricate 2D or 3D close-packed structures was examined in this study.

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  • Shinya YAMANAKA
    2015 Volume 23 Pages 153-157
    Published: 2015
    Released: February 03, 2017
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    We report effective uses for discarded shells as an additive of plywood adhesive because more than 200,000 tons of scallop shells are disposed of annually in Hokkaido alone. In our previous work, we proposed so-called “nano-grinding method” in which nano-sized scallop shells were produced by planetary ball milling under dry condition and subsequent water addition. By mixing the shell nanoparticles with a resin, it was found that the emission of formaldehyde from the resulting plywood could be substantially reduced. Results of formaldehyde emission from plywood will be reported, followed by discussion of the effects of specific surface area of the shell particles within the resin on the emission of formaldehyde.

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  • Daigo YAMAMOTO
    2015 Volume 23 Pages 158-163
    Published: 2015
    Released: February 03, 2017
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    Most catalytic micro/nanomotors that have been developed until now use hydrogen peroxide as fuel. The fuel is difficult to apply because they can cause skin irritation and often form disruptive bubbles. In this paper, we demonstrate a novel catalytic Pt micromotor that does not produce bubbles and is driven by the oxidation of stable and safe primary alcohols and aldehydes. We confirmed that primary alcohols and aldehydes are oxidized to aldehydes and carboxylic acids, respectively, using dissolved oxygen on the Pt surface. This use of organic oxidation mirrors living systems, and lends this new motor essentially the same characteristics, including decreased motility in low oxygen environments and the direct isothermal conversion of chemical energy into mechanical energy. In addition, the exerting power of the produced micromotor is roughly the same as that of a bacterium. These motors work even at fuel concentrations as low as 0.2 vol%, which is roughly equivalent to blood alcohol concentrations resulting from moderate drinking. Interestingly, motile direction is reversed by replacing the reducing fuels with oxidizers like hydrogen peroxide. Therefore, these micromotors not only provide a novel system in nanotechnology, but also help to further reveal the underlining mechanisms of the motion of smaller organisms.

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  • Mikio YOSHIDA
    2015 Volume 23 Pages 164-168
    Published: 2015
    Released: February 03, 2017
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    One of the techniques used to improve particle cohesiveness is the admixing of nano-particle to main particles. However, the mechanism for this improvement in cohesiveness has not been clarified yet. In the present study, we focused on compressed packing as one of the operations that is affected by particle cohesiveness, and we investigated the effects of the main particle diameter on the improvement in the cohesiveness. The main and admixed particles were 397, 1566 nm and 8, 21, 62, 104 nm in diameter, respectively. The main and admixed particles were mixed for various mass ratios, and compressed packing fractions for the mixed particles were measured. SEM images were used to analyze the coverage diameter and the surface coverage ratio of the admixed particles on the main particles. As a result, the improvement in the cohesiveness was obtained easily when the diameter ratio (=main particle/ admixed particle) increased. This was explained by the linking rigid-3-bodies model applying the principle of leverage. Furthermore, the surface coverage ratio showing the most improvement increased with main particle diameter. This was explained by the contact probability of the main particles based on the curvatures in the main particle surface.

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  • Kimiaki WASHINO
    2015 Volume 23 Pages 169-172
    Published: 2015
    Released: February 03, 2017
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    In wet granulation, it is important to accurately predict the liquid dispersion for process optimisation and quality assurance. In this work, a new contact dispersion model was developed by taking into account the partial wetting of particle surfaces, which was incorporated into the Discrete Element Method (DEM). In the developed model, individual particle surfaces are sub-divided and the liquid redistribution between these sub-divided surfaces are tracked with time. The proposed model was applied to simulate the liquid dispersion rate in several granulators. It is implied from the obtained results that the conventional contact liquid dispersion models, including the Shi and McCarthy model (Shi D. and McCarthy J. J., 2008), give faster liquid dispersion especially when highly viscous liquid is used and the mobility of liquid is poor.

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  • Satoshi WATANABE
    2015 Volume 23 Pages 173-179
    Published: 2015
    Released: February 03, 2017
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    The present study focused on the synthesis of zeolitic imidazolate framework-8 (ZIF-8) particles, which is a family of porous coordination polymers (PCPs) or metal-organic frameworks (MOFs). We simply mixed a zinc nitrate solution with a 2-methylimidazole solution in a microreactor with high mixing performance. Taking advantage of the rapid and uniform mixing, the microreactor successfully produced ZIF-8 particles with high reproducibility. The synthesis at room temperature resulted in ZIF-8 particles with chamfered cubic shape, while a lower temperature of 5°C produced raspberry-type spherical particles. We then investigated the effect of the ratio of the concentration of 2-methylimidazole to that of zinc nitrate on the particle size, and found that the increase in the ratio decreases the ZIF-8 particle size, and the minimum particle size is 50 nm at the ratio of 200. Further decrease in the particle size to 20 nm was achieved by the addition of n-butylamine molecules. We measured adsorption isotherms of N2 in ZIF-8 particles and found that smaller ZIF-8 nanoparticles show the gate adsorption at higher pressures, demonstrating the possibility in the gate pressure control by particle size.

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  • Hiroaki WATANABE, Wei ZHANG, Masaya MUTO, Toshiaki KITAGAWA
    2015 Volume 23 Pages 180-191
    Published: 2015
    Released: February 03, 2017
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    A numerical investigation of the motion of spherical and non-spherical particles with/without gas blowing-out in a vertical uniform air flow was conducted in this study. A sphere, spheroid and pulverized coal particle were targeted. The shape of coal particle was three-dimensionally modeled by scanning a coal particle using the X-ray CT method. As a first stage of the research, the Arbitrary Lagrangian-Eulerian (ALE) method was validated by comparing with the experiment and the existing equations of drag coefficient, CD. Secondly, the direct numerical simulations of spherical, spheroid and coal particles with or without gas blowing-out in a vertical uniform air flow were performed and discussed in terms of the rotating motion and the variation of CD. The results showed that the particle with the equivalent volume had a similar accelerating motion to that of coal particle than that with the equivalent surface area. In addition, spheroidal particle showed the similar motion to coal particle than spherical particle. The spheroidal particle with the initial angle of 0 degree stayed without rotation in the flow, while that with the initial angle of the other never attain the stable position and kept rotating. The value of CD was fluctuating with varying Reynolds number, Re. It was also found that the probability density function of CD behave as that of sine function. This suggests a possibility to formulate a CD equation with Re and particle’s orientation. It was revealed that the value of CD decreased with the gas-blowing out due to the reduction of friction force on the particle surface. The probability density function for the spheroidal particle with the gas blowing-out could be expressed by the sine function as well. It is also revealed that the motion of coal particle with irregular shape is significantly dependent on its shape, especially with gas blowing-out. A new model in which this complex shape effects can be considered is required to describe the irregular shape particle.

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