Journal of the Society of Powder Technology, Japan
Online ISSN : 1883-7239
Print ISSN : 0386-6157
ISSN-L : 0386-6157
Volume 50, Issue 12
Special Issue of 2013 Spring Annual Meeting
Displaying 1-5 of 5 articles from this issue
Original Paper
  • Megumi Mizutani, Koichi Takeda, Masatoshi Yasuda, Shuji Matsusaka
    2013 Volume 50 Issue 12 Pages 832-839
    Published: December 10, 2013
    Released on J-STAGE: December 27, 2013
    JOURNAL FREE ACCESS
    A new method for characterizing particles triboelectrically charged through repeated contact with a wall has been studied both theoretically and experimentally. A two-stage system consisting of inclined vibrating plates with electrodes was used in this experiment. The first stage possessed functions to control the initial charge and flow rate of the particles. Particle tribocharging was characterized in the second stage. Three types of particles with diameters of less than 100μm were examined, and each particle charge profile as a function of distance travelled on the second vibrating plate was obtained under various experimental conditions. It was found that the pattern of the charge profiles agreed with the theoretical one, which is determined by two parameters related to equilibrium and relaxation. It was also found that particle tribocharging is well-characterized by the two parameters obtained by external electric fields.
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  • Masato Oka, Hiroyuki Asano, Michiro Kitahara, Satoru Nakata, Michiko I ...
    2013 Volume 50 Issue 12 Pages 840-844
    Published: December 10, 2013
    Released on J-STAGE: December 27, 2013
    JOURNAL FREE ACCESS
    Titanium dioxide (TiO2) nanoparticles have been used in sunscreen cosmetics for ultraviolet (UV) light protection. However, nanoparticles of TiO2 tend to form aggregates in aqueous dispersions because of their high surface energy. Therefore, it is important to stably disperse TiO2 nanoparticles in the aqueous solutions in order to enhance the efficient UV protection properties of TiO2. In this study, we tried to prepare aqueous dispersions of TiO2 nanoparticles by using plasma on liqid surface which is generated by applying high voltage between the tip of a needle electrode in the gas phase and the liquid surface.The decreases of average particle size of TiO2 in the dispersions with the plasma treatments in air and Ar atmosphere were confirmed by dynamic light scattering measurements. With the plasma treatment, isotropic point for TiO2 particles increased from 5.4 (without plasma treatment) to 9.3 (with plasma treatment in air) and 8.0 (with plasma treatment in Ar atmosphere). Futhermore, these fine dispersions showed higher UV protection properties compared to the dispersions prepared by only sonication.These facts suggest that the application of plasma on liquid surface is a new method for preparing stable nanoparticle dispersions.
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  • Tadao Akashi, Masayuki Imba, Tatsushi Matsuyama, Junichi Ida, Hideo Ya ...
    2013 Volume 50 Issue 12 Pages 845-850
    Published: December 10, 2013
    Released on J-STAGE: December 27, 2013
    JOURNAL FREE ACCESS
    This paper reports a new development of an apparatus to evaluate the accumulation process of electrostatic charge of bulk powder (or multiple particles). In a metal cubic container installed on an oscillator, a certain number (1-100) of spherical polymer particles of a single size, in the range of 2-4 mm in diameter, were loaded after neutralization, and they were shaken. After the shake, all the particles were poured into a Faraday-cage, and the total charge was measured. The maximum charge per particle decreased with an increase of particle number loaded. The experimental results were well explained with a modified new model of particle charging originally proposed by the authors, in which the space charge effect was involved as a function of particle size and volume fraction of particles in the capsule and capsule size.
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  • Michinori Yamamoto, Shingo Ishihara, Junya Kano
    2013 Volume 50 Issue 12 Pages 851-856
    Published: December 10, 2013
    Released on J-STAGE: December 27, 2013
    JOURNAL FREE ACCESS
    The mixing behavior of particles in an agitating mixer was simulated by Discrete Element Method (DEM) in order to discuss the particle mixing mechanism. First of all, mixing behavior of alumina and SUS particles in the agitating mixer with a wedge-shaped blade was experimentally observed. Most of the alumina particles existed around the rotational center of the blade, and most of SUS particles were near the mixer wall. The segregation of alumina and SUS particles was obviously observed. The similar mixing behavior of particles was also observed in the DEM simulation, and it was confirmed that DEM simulation has high reliability. Two different types of blades, which are comb-shaped and twisted rectangular prism, were prepared in order to investigate the effect of the blades geometry on the particle mixing phenomena via DEM simulation. The DEM simulation indicated that the mixing state is strongly influenced by the blade geometry. In case of comb-shaped blade, most of SUS particles are at the bottom in the mixer, and most of alumina particles are on and near the surface of particle bed. On the other hand, SUS and alumina particles are uniformly mixed in the mixer with twisted rectangular prism blade promptly. This would be due to reciprocating motion of particles in the depth and the radial direction.
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Review
  • Ryoko Otomo
    2013 Volume 50 Issue 12 Pages 857-865
    Published: December 10, 2013
    Released on J-STAGE: July 03, 2014
    JOURNAL RESTRICTED ACCESS
    A number of expressions for fluid permeability of particulate bed have been suggested in literatures. While common formulae, e.g. Kozeny-Carman equation, describe the permeability by macroscopic characteristics of particulate bed such as particle volume fraction and particle size distribution, the permeability also depends on local inhomogeneity in flow channel which is formed by microscopic configuration of the particles. On the assumption of Stokes flow, this article mentions that hydrodynamic effect by the presence of multiple particles on the flow field is affected by the positional relationship between individual particles. Some theoretical and numerical results for the particulate bed with different particle configurations are presented. Furthermore, this article reports the results of authors recent study which shows the dependence of the permeability of polydisperse particulate bed on spatial distribution of particles with different radii. The mechanism of fluid permeation in particulate bed with arbitrary nonuniform structures is discussed.
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