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 62, Issue 4
April
Displaying 1-17 of 17 articles from this issue
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Paper
Review
  • Syntheses of Silicate Phosphors by Aqueous Solution Techniques using Water-Dispersible Inorganic Si Cluster
    Yasushi SATO, Hideki KATO, Makoto KOBAYASHI, Jihae KIM, Masato KAKIHAN ...
    2015 Volume 62 Issue 4 Pages 127-133
    Published: April 15, 2015
    Released on J-STAGE: May 01, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.127
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    ABSTRACT

    In this paper, we demonstrated the synthesis of silicate-based phosphors by solution techniques using glycol-modified silane (GMS) as a Si source. GMS is a water-dispersible inorganic Si cluster, which is vitally involatile and nonflammable compounds, compared to volatile and flammable Si-alkoxides such as tetraethoxysilane (TEOS). Therefore, GMS has allowed the silicon containing compounds to be synthesized through various solution processes for ceramic compounds such as polymerizable complex (PC) and amorphous metal complex (AMC) methods. This paper provides examples of synthesis of new silicate-based phosphors such as NaAlSiO4:Eu2+, BaZrSi3O9:Eu2+, and CaSrSiO4:Eu2+. In addition, other examples of improvement of emission for conventional silicate-based phosphors, Y2SiO5:Ce3+-Tb3+ and Zn2SiO4:Mn2+, prepared by the above solution techniques including homogeneous precipitation using GMS are also given in this paper.
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Paper
  • Al2O3-Compositional Dependence of Mechanical Properties of ZrO2 Based Ceramics Fabricated from ZrO2(Y2O3)-Al2O3 Solid Solution Powders
    Ken HIROTA, Kenta YAMAMOTO, Koki SASAI, Masaki KATO, Hideki TAGUCHI, H ...
    2015 Volume 62 Issue 4 Pages 134-143
    Published: April 15, 2015
    Released on J-STAGE: May 01, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.134
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    ABSTRACT

    ZrO2 composite ceramics containing 10~30 mol% Al2O3 and 1.5 mol% Y2O3, i.e., 90~70 mol% ZrO2(1.5 mol% Y2O3)-10~30 mol% Al2O3 ceramics, have been fabricated by sintering cubic ZrO2 solid solution (ss) nano-powders prepared via the neutralization co-precipitation method. The sintering was performed using a pulsed electric-current pressure sintering (PECPS) at 1598 K for 10 min under 50~60 MPa in Ar. Dense tetragonal-ZrO2 (ss) ceramics containing α-Al2O3 were composed of 277-130 nm grains. FE-SEM observation revealed that their microstructures, that is the grain sizes of both t-ZrO2 (ss) and α-Al2O3, and the distribution of α-Al2O3 particles, were much influenced by the content of α-Al2O3. The best mechanical properties of extreme high bending strength (σb ≥ 1 GPa) and high fracture toughness (KIC ≥ 15 MPa • m1/2) simultaneously were obtained at the composition of 25 mol% Al2O3 with a high relative density 99.9 %, as the same composition reported for the HIP sintered ZrO2(2~3 mol% Y2O3)-Al2O3 composite ceramics.
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  • Pressureless Sintered Titanium Carbonitride based ceramics and their Properties
    Atsushi ARUGA, Hiroaki KISHIMURA, Yoichi OKAMOTO, Hitoshi MATSUMOTO
    2015 Volume 62 Issue 4 Pages 144-151
    Published: April 15, 2015
    Released on J-STAGE: May 01, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.144
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    ABSTRACT

    The densification of titanium carbonitride Ti(C0.3N0.7) ceramics were checked by sintering. Several oxides (Al2O3, Nb2O5, TiO2, WO3, Y2O3, ZrO2) as a sintering aid were looked for. Then Nb2O5 added Ti(C0.3N0.7) ceramics were prepared by pressureless sintering at 2073 to 2473 K for 2h in Ar atmosphere. 5-10 vol% Nb2O5 added Ti(C0.3N0.7) based ceramics fired at 2473 K gave the sintering density over 5.1 g/cm3. And their best Vickers hardness reached 15.7 GPa. The color of polished samples was orangey light brown with metallic luster. It was recommended that polished samples could be utilizes for ornament.
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  • Preparation of CuWO4 by Dissolution of Tungsten
    Nana SUZUKI, Osami SERI
    2015 Volume 62 Issue 4 Pages 152-157
    Published: April 15, 2015
    Released on J-STAGE: May 01, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.152
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    ABSTRACT

    Attempts have been made to obtain copper tungstate (CuWO4) powders by application of corrosion synthesis. The well-stirred solution with WO42− ions which has been obtained by the dissolution of W in a hydrogen peroxide solution poured into the solution with Cu2+ ions by the dissolution of Cu in a nitric acid solution. The mixed solution was then dried and fired at temperature higher than 773 K. The XRD analysis of the fired powder obtained showed CuWO4 particles with mean diameter of 0.7 μm. The synthesis of the CuWO4 by dissolution and mixture of W and Cu is considered from electrochemical point of view.
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  • Effects of Boron Content on Properties of High Corrosion and Wear Resistant Ni-Cr-Mo-B Alloy with High Corrosion Resistant Matrix Consolidated by HIP
    Toshiyuki SAWADA
    2015 Volume 62 Issue 4 Pages 158-166
    Published: April 15, 2015
    Released on J-STAGE: May 01, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.158
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    ABSTRACT

    The effects of B content on the properties of Ni-Cr-Mo-B P/M material with Ni-22mass%Cr-Xmass%Mo-Ymass%B compositions ((X,Y) = (23,1.0), (26,1.6), (30,2.1), (33,2.6)) were investigated. Raw material powders were produced by gas atomization, followed by sieving under 500 μm in the particle size. And then, these powders were consolidated by HIP. HIP process was carried out at 1423 K in the temperature, at 147 MPa in the pressure and for 5 h in the holding time. All specimens consisted of γNi matrix with the composition of almost Ni-23%Cr-16%Mo and tetragonal M3B2 type complex boride.
    Rockwell hardness increased and Charpy impact value decreased with increasing B content. The variation in bending strength as a function of B content showed the local maximum at 1.6%B. It is considered that this variation is caused by the both effects of hardening and embrittling with increasing B content. Wear resistance by Ohgoshi-type abrasion test improved with increasing B content. Compared with Co-C-Cr-W P/M material, even if Rockwell hardness of Ni-Cr-Mo-B is equivalent to that of Co-C-Cr-W, Ni-Cr-Mo-B shows higher wear resistance than Co-C-Cr-W. As a result of immersion test in HF aqueous solution, all Ni-Cr-Mo-B P/M materials showed higher corrosion resistance than C-276 alloy.
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Special Issue: Thermoelectric Conversion Materials
Summarization
Review
  • Thermal Conductance Analysis of Sintered Nanostructures from the Viewpoint of Phonon Transport
    Takuma HORI, Junichiro SHIOMI
    2015 Volume 62 Issue 4 Pages 169-174
    Published: April 15, 2015
    Released on J-STAGE: May 01, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.169
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    ABSTRACT

    Over the last decade, there has been a great enhancement in efficiency of bulk thermoelectric materials by reducing lattice thermal conductivity with internal nanostructures. This includes sintered nanostructures, which has merit in applicability and scalability. While the material development so far has been rather empirical, for further improvement of the bulk nanostructured materials, the need for material design based on prediction of lattice thermal conductivity is growing. This paper reviews recently developed multiscale method to calculate lattice thermal conductivity of bulk crystalline nanostructures. The method seamlessly combines first-principles calculations of interatomic force constants, lattice dynamics calculations of intrinsic phonon transport properties, and Monte Carlo simulation of phonon Boltzmann transport through nanostructures. The method can handle phonon transport through a large system with randomly placed and shaped nanostructures, and thus it is sufficient to quantify how reduction of thermal conductivity of polycrystalline nanostructures depends on mean size and distribution of nano-grains. The results for sintered polycrystalline silicon nanostructure are presented.
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Paper
  • Preparation and Characterization of Ca3(Co,M)4O9+δ Type Thermoelectric Materials Using the Electrostatic Spray Deposition Method
    Kenjiro FUJIMOTO, Takuto ISA, Haruka SAKURAI, Yuki YAMAGUCHI, Keishi N ...
    2015 Volume 62 Issue 4 Pages 175-184
    Published: April 15, 2015
    Released on J-STAGE: May 01, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.175
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    ABSTRACT

    Ca3(Co1−xAlx)4O9+δ, Ca3(Co1−yCuy)4O9+δ, Ca3(Co1−x−yAlxCuy)4O9+δ thin-films and sintered bodies were prepared using the electrostatic spray deposition method. Electrical conductivity of Ca3(Co0.95Al0.025Cu0.025)4O9 showed large values compared with Ca9Co12O28. Power factor of Ca3(Co0.95Al0.025Cu0.025)4O9 also showed approximately same values as those of single phase compounds of Ca9Co12O28. It was considered that the phenomenon was due to the increase of hole concentration and its mobility.
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  • Fabrication and Thermoelectric Properties of Perovskite Like La0.3(Ca1−xAx)0.55Cu3Ti4O12 (A = Sr, Mg) Ceramics
    Mikoto OKUMURA, Masaki KATO, Ken HIROTA, Hideki TAGUCHI
    2015 Volume 62 Issue 4 Pages 185-193
    Published: April 15, 2015
    Released on J-STAGE: May 01, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.185
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    ABSTRACT

    The powders of La0.3(Ca1−xAx)0.55Cu3Ti4O12 (A = Sr, 0 ≤ x < 0.8, A = Mg, 0 ≤ x ≤ 0.1) with cubic Perovskite like structure were synthesized at 1323 K in air via a polymerized complex route. Lattice constants a of the dense (≥ 97 %) ceramics, fabricated in air using a hot-pressing (1273 K/3.60 × 103 s/50 MPa), increased and decreased with increasing x for the ceramics (A = Sr) and (A = Mg), respectively, On the other hand, the electrical conductivities σe decreased and increased with increasing x and temperature, respectively. Their negative Seebeck coefficients S had the maximum values of ca. −560 µV·K−1 for the ceramics (A = Sr at x = 0.8: Sr0.8) and −515 µV·K−1 for Mg0.02, showing the behavior that the absolute S values decreased and increased slightly with increasing temperature and x, respectively. Their power factor S2σe had the maximum values at Sr0.2 and Mg0.05. Thermal conductivities λ for the ceramics (x = 0.0, Sr0.2 and Mg0.1) were measured from 300 to 1073 K in air; lower λ were attained for Mg0.1 in comparison with others. Their dimensionless figure of merit ZT reached ~4.0 × 10−3 at 1073 K. These results indicated that La0.3(Ca0.8Mg0.05)0.55Cu3Ti4O12 could be a candidate of the host materials of the new hybrid-type thermoelectric element.
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  • Effect of Codoping on Thermoelectric Properties of Silicon Clathrate
    Hiroaki ANNO, Takahiro UEDA, Hironori SAKUMA
    2015 Volume 62 Issue 4 Pages 194-199
    Published: April 15, 2015
    Released on J-STAGE: May 01, 2015
    DOIhttps://doi.org/10.2497/jjspm.62.194
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    ABSTRACT

    We investigated codoping of Ba8AlySi46−y clathrate system with gallium and phosphorus, nominal composition Ba8Al16GaxSi30−2xPx (x = 0, 0.5, 0.6, 0.75, 1.0, 1.5, 2.0), and their thermoelectric properties. Samples were prepared by combining arc melting and spark plasma sintering methods. The x-ray diffraction, scanning electron microscopy, and energy dispersive analysis of x-ray studies revealed that the total content of Al and Ga increased to 15.66 (at x = 2.0), which was higher than the solubility limit (approximately y~15) of aluminum in Ba8AlySi46−y system. The carrier concentration of samples decreased from ~1 × 1021 cm−3 (y = 15), which was the lowest value in Ba8AlySi46−y system so far, to ~6 × 1020 cm−3. According to the decrease in carrier concentration, the Seebeck coefficient increased while the electrical conductivity decreased. The thermal conductivity decreased monotonically with x. The thermoelectric figure of merit ZT was improved to about 0.47 at 900 K, which was higher than the maximum value for Ba8AlySi46−y system.
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