Journal of the Japan Society of Powder and Powder Metallurgy
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
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Volume 59, Issue 6
June
Displaying 1-15 of 15 articles from this issue
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Paper
Paper
  • Development of High-Porosity Porous Sintered Metal with Low Pressure Drop
    Kenji Date, Takashi Mukai, Tomohisa Ogata, Toshitaka Ishizawa, Kenichi ...
    2012 Volume 59 Issue 6 Pages 297-306
    Published: June 15, 2012
    Released on J-STAGE: September 08, 2012
    DOIhttps://doi.org/10.2497/jjspm.59.297
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    We found that the gas of a decomposed binder can be exhausted from a green body smoothly by means of extracting Space holder (SH) by the solvent before heating for debinding in the case that the volume fraction of SH in the green body is over 70 %, where total volume fraction of SH and the metal powder is 100 %. As a result, we could obtain the porous metal with porosity exceeding 90 % by the SH. This porous metal consists of the voids formed by extracting SH and the skeleton with the pores originated from the space among the metal particles. The porosity and the interconnecting frequency and the area between the voids became larger by increasing the volume fraction, the diameter of SH, the frequency and the area of the contact between SHs in the green body. Furthermore, the pore diameter in the skeleton became larger by adding the small SH of several times the diameter of the metal particle. These effects improved the air permeability and lowered the pressure drop.
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  • Preparation of Flake Alumina by Corrosion of Aluminum in Methanol
    Osami Seri, Ryo Kamazawa
    2012 Volume 59 Issue 6 Pages 307-310
    Published: June 15, 2012
    Released on J-STAGE: September 08, 2012
    DOIhttps://doi.org/10.2497/jjspm.59.307
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    Attempts have been made to synthesize flake alumina from corrosion products of aluminum in methanol solution. The aluminum hydroxide of the corrosion product with additives was sintered at about 1473 K. The micron-sized alumina flake has been identified by the XRD analysis and SEM observations. As an example of the corrosion synthesis methods, the process was electrochemically considered in the view of corrosion of aluminum.
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Special Issue: Anisotropic Crystal Growth and Microstructure Observation of Single Phase SnO2 Nano-sheet Assemblies
Summarization
Review
  • Ceramic Thin Film Processing in Aqueous Solutions
    Hidero Unuma, Yuta Matsushima
    2012 Volume 59 Issue 6 Pages 313-319
    Published: June 15, 2017
    Released on J-STAGE: December 27, 2023
    DOIhttps://doi.org/10.2497/jjspm.59.313
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    This article reviews the techniques of the deposition of ceramic thin films from aqueous solutions and the development of the water-based starting solution for the dip-coating deposition of ceramic thin films. As a solid-precipitation reaction proceeds at an appropriate rate in an aqueous solution in contact with a substrate, heterogeneous nucleation takes place followed by crystal growth to form a ceramic thin film. The precipitation reaction is designed depending on the kind of the metal ion comprised in the ceramic film. In the present article, the following advantages unique to the aqueous solution-based thin film deposition are outlined. It is easy to scale-up the film deposition process, and the film thickness is homogeneous throughout the film. The nano-scale microstructure can be imprinted by using surfactant templates which should extend the application of the films. Calcium phosphate thin films deposited with the mediation of an enzyme were found to promote bone formation by in vivo tests. A homogeneous precursor solution of barium titanate was prepared. The solution may be advantageous over conventional alkoxide-based solutions or sol suspensions in terms of long-term stability and precise composition control.
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Review
  • Development of Flexible Porous Materials from Organotrialkoxysilanes
    Kazuyoshi Kanamori, Gen Hayase, Kazuki Nakanishi
    2012 Volume 59 Issue 6 Pages 320-325
    Published: June 15, 2012
    Released on J-STAGE: September 08, 2012
    DOIhttps://doi.org/10.2497/jjspm.59.320
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    Organosiloxane (RnSiO(4-n)/2) gels can be prepared from organoalkoxysilanes using the sol-gel process. In general, however, formation of uniform networks from these precursors is strongly inhibited due to cyclization reactions. In addition, phase separation of hydrophobic condensates from polar solvent leads to inhomogeneous gels in these systems. A careful control of the hydrolysis and polycondensation reactions is therefore required to obtain a monolithic gel with desired properties. We have been trying to control the sol-gel reactions as well as phase separation in these systems to obtain unique porous materials particularly from methyltrimethoxysilane (MTMS) and dimethyldimethoxysilane (DMDMS). Flexible aerogels and xerogels based on the methylsiloxane networks are discussed.
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Paper
  • Synthesis and Characterization of Highly Crystallized TiO2(B) Nanofibers via the Hydrothermal Treatment in Supercritical Fluid
    Noritsugu Taniguchi, Masaki Kato, Ken Hirota
    2012 Volume 59 Issue 6 Pages 326-332
    Published: June 15, 2012
    Released on J-STAGE: September 08, 2012
    DOIhttps://doi.org/10.2497/jjspm.59.326
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    Single-crystal TiO2(B) nanofibers were synthesized by the hydrothermal treatment in supercritical fluid at c.a. 375∼425°C under 23∼37 MPa using 10 mol·L-1 NaOH aq. followed by ion-exchange of Na to H in dilute HCl aq. and post-heating at 400°C in air. Thus prepared TiO2(B) nanofibers were characterized by XRD analysis, SEM/TEM observations, DTA/TG and BET surface area measurements. Electrical conductivity of the nanofibers and thermal conductivity of the nanofiber-compacts were also evaluated using "Nano-probe" and an Xenon flash measurement systems, respectively. Compared to the conventional TiO2(B) fibers prepared from the normal hydrothermal treatment at c.a.185°C for 8 h, the present TiO2(B) with several microns in length and 300∼400 nm in diameter, revealed higher thermal stability; TiO2(B) phase was stable even after heating at 800°C for 5 h in air, and an extreme high electrical conductivity of 1.2∼1.3 S·m-1 in addition to high thermal conductivity; the former and the latter were higher 1011 and 1.5 times than those of anatase TiO2 and normal TiO2(B).
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  • Fabrication of Tungsten Oxide Nanoparticles by Thermal Decomposition of Complex Powder
    Yoko Yamashita, Tomohiro Harada, Teruhisa Makino
    2012 Volume 59 Issue 6 Pages 333-336
    Published: June 15, 2012
    Released on J-STAGE: September 08, 2012
    DOIhttps://doi.org/10.2497/jjspm.59.333
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    In recent years tungsten oxide (WO3) has been attracting attention as a visible light response type photocatalyst. The particle size of WO3 particles is preferably less than 100 nm in order to improve the catalytic performance and ensure transparency of base material after coating. WO3 nanoparticles have been fabricated by thermal decomposition at 793 K of the tungsten complex powder which was prepared of Ammonium paratungstate, citric acid and ammonia solution. The effect of the chemical composition of the tungsten complexes on particle size was examined.
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  • Preparation of Nano Mn-Zn Ferrite Powders by Ultrasonic Spray Pyrolysis Method and Their Magnetic Properties
    Sho Tominaga, Kenji Kamishima, Koichi Kakizaki, Yoshihiro Ishimaru, N ...
    2012 Volume 59 Issue 6 Pages 337-341
    Published: June 15, 2012
    Released on J-STAGE: September 08, 2012
    DOIhttps://doi.org/10.2497/jjspm.59.337
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    Nano-crystalline Mn-Zn ferrite powders (Mn1-xZnxFe2O4, x=0∼1.0) have been prepared by ultrasonic spray pyrolysis method. Mn-Zn ferrite samples sintered at 700°C had the single phase of spinel-type for all of the compositions. The lattice constant decreased with increasing Zn content and followed Vegard's law. Curie temperature linearly decreased from that of MnFe2O4 (x=0) with increasing Zn substitution rate. These results indicate that the Mn-Zn ferrite formed solid solution. The Mn-Zn ferrite particles were found to be in nano-size of 20∼30 nm by scanning electron microscopy. And their crystalline diameters were 15∼30 nm, determined by the use of Scherrer equation for X-ray diffraction peak broadening. Mn0.6Zn0.4Fe2O4 sample had a magnetization value of 48 emu/g, which was lower than that of bulk sample (80 emu/g). This is possibly caused by the existence of a disordered surface region on the nanoparticles, where the crystallographic and magnetic structures are disordered due to the nearly random distribution of cations and the canted spin arrangement.
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  • Anisotropic Crystal Growth and Microstructure Observation of Single Phase SnO2 Nano-sheet Assemblies
    Yoshitake Masuda, Tatsuki Ohji, Kazumi Kato
    2012 Volume 59 Issue 6 Pages 342-346
    Published: June 15, 2012
    Released on J-STAGE: September 08, 2012
    DOIhttps://doi.org/10.2497/jjspm.59.342
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    SnO2 nano-sheet assemblies were prepared in aqueous solutions containing SnF2 at 90°C for 30 min. A transmission electron microscope and a field emission scanning electron microscope observation revealed that they were assembly of nano-sheets of about 50-100 nm in size and 5-10 nm thickness. Electron diffraction patterns from the nano-sheets were assigned to tin dioxide (SnO2) that had tetragonal system and rutile-type crystalline structure. X-ray diffraction pattern of the particles also indicated that they were single phase of tin dioxide (SnO2). SnO2 particles that had unique nano-sheet assembled structure were candidate materials for dye-sensitized solar cells and high sensitive sensors.
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