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 60, Issue 7
July
Displaying 1-7 of 7 articles from this issue
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Paper
Paper
  • Novel Colossal Magnetoresistance in Sodium Chromium Oxide
    Hiroya SAKURAI, Taras KOLODIAZHNYI, Yuichi MICHIUE, Eiji TAKAYAMA-MURO ...
    2013 Volume 60 Issue 7 Pages 313-318
    Published: July 15, 2013
    Released on J-STAGE: September 05, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.313
    JOURNAL OPEN ACCESS
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    Recently, a new calcium-ferrite type chromium oxide, NaCr2O4, was synthesized under high pressure of 7 GPa, and was found to show the unconventional colossal magnetoresistance (CMR) effect below the canted-antiferromagnetic transition temperature of TN = 125 K. In this paper, in addition to crystal structure data and magnetic properties, we show the temperature dependence of the electrical resistivity under 0, 3, and 9 T and the field dependence of magnetoresistance ratio at 45, 60, and 80 K. These clearly support the unconventional nature of the CMR effect. We discuss the existence of holes on oxygen ions, and propose a possible mechanism of CMR in NaCr2O4, in which the spin frustration and the holes play an important role. A guide to find new CMR compounds is also presented.
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  • Preparation of NiAl2O4 Spinel by Corrosion Synthesis
    Osami SERI, Tetsuhiro SUZUKI, Daichi SASAKI
    2013 Volume 60 Issue 7 Pages 319-324
    Published: July 15, 2013
    Released on J-STAGE: September 05, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.319
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    NiAl2O4 was tried to make by metallic corrosion with chloride as a catalyst in ethanol. As synthesis of NiAl2O4, two ways were carried out: ①nickel was corroded with addition of aluminum chloride, and ②aluminum was corroded with nickel chloride. The corrosion products obtained by two methods were hydrolyzed, adjusted pH and then fired. It was found that the powder fired at 1073 K and over by two methods was of NiAl2O4 spinel whose diameter was 0.4 to 30 µm. The above results were considered as electrochemical and corrosion phenomena.
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  • Preparation of Zinc Aluminate Spinel ZnAl2O4 by Corrosion Synthesis in Ethanol
    Daichi SASAKI, Osami SERI
    2013 Volume 60 Issue 7 Pages 325-329
    Published: July 15, 2013
    Released on J-STAGE: September 05, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.325
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    ZnAl2O4 was obtained by corrosion synthesis which produced mixtures of zinc alkoxide by metallic zinc dissolution in ethanol and aluminum ions by addition of aluminum chloride as a catalyst. The corrosion product became ZnAl2O4 when the mixtures were hydrolyzed, pH-adjusted, and fired at temperature higher than 873 K. It is shown that the ZnAl2O4 powder has the particle size distribution of 0.4 to 10 µm. It is considered that the corrosion synthesis of a ZnAl2O4 production has some features of fast reaction in ethanol and well blending circumstances in ion size level condition.
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  • Preparation of SrTiO3 by Dissolution Reaction of Titanium
    Mitsutomo ＨＩＲＯＴＡ, Taro KASHIWAI, Daichi SASAKI, Tsutomu SAITO, Osami ...
    2013 Volume 60 Issue 7 Pages 330-333
    Published: July 15, 2013
    Released on J-STAGE: September 05, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.330
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    Attempts have been made to obtain SrTiO3 powder by applying dissolution reaction of titanium in solution with mixture of hydrogen peroxide and ammonium hydroxide. The reaction product obtained was peroxotitanium anion containing strontium chloride. The product was filtered and sintered at 873 K～1473 K for 7.2 ks. The XRD analysis proves that the powders were identified as SrTiO3. Average size of the particle was around 0.08～30 µm and it shape is almost polygon lump by the FE-SEM observations.
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  • Direct Reduction of Copper Oxide to Metallic Copper by using Metal Ion Reducing Bacteria “Shewanella algae”
    Masaru YOKOTA, Koshiroh TAMAOKI, Norizoh SAITOH, Toshio SABURI, Tak ...
    2013 Volume 60 Issue 7 Pages 334-340
    Published: July 15, 2013
    Released on J-STAGE: September 05, 2013
    DOIhttps://doi.org/10.2497/jjspm.60.334
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    Metal ion reducing bacteria “Shewanella algae” were used in this experiment to directly reduce copper oxide powder to Cu(0) powder. The liquid medium used for culturing Shewanella algae contained sodium lactate as the electron donor and iron(III) citrate as the electron acceptor.
    Results obtained are as follows:
    (1)When Cu2O powder was added in the liquid medium, the population of Shewanella algae grew exponentially in two stages. The first exponential growth occurred about 20 hours after the experiment began, and the second growth occurred about 200 hours after the experiment began. No growth of bacteria occurred when CuO powder was added in the liquid medium.
    (2)When Cu2O powder was added in the liquid medium, Cu concentration in the liquid medium maintained 0.01 mg/m3 during the first inductive phase and maintained 7 mg/m3 during the second inductive phase. Cu concentration decreased drastically during the second exponential growth phase. When the bacterial culture reached the stationary phase, Cu concentration still decreased slightly and dropped to approximately 0.07 mg/m3 at the end of the experiment.
    (3) Three different types of reduced Cu(0) particles were observed: ultra fine particles on the surface of Shewanella algae cells; spherical, triangular and hexagonal particles of sub-micron size obtained from the liquid medium; and many particles which are similar in shape and size to raw Cu2O powder.
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