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Solid State Reaction between Nb<sub>2</sub>O<sub>5</sub> and the Compounds in the System Al<sub>2</sub>O<sub>3</sub>-CaO

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  • HOTTA Noriyasu
    Depatment of Chemical Engineering, Faculty of Engineering, Niigata University
  • SAITO Natsukaze
    Depatment of Chemical Engineering, Faculty of Engineering, Niigata University
  • MATSUO Shigetomo
    Depatment of Chemical Engineering, Faculty of Engineering, Niigata University
  • MATSUSHITA Toru
    Department of Applied Chemistry, Faculty of Engineering, Hokkaido University

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  • Ｎｂ２Ｏ５とＡｌ２Ｏ３‐ＣａＯ系化合物の固相反応
  • Nb2O5 ト Al2O3 CaOケイ カゴウブツ ノ コソウ ハンノウ

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Abstract

Solid state reactions between sintered Nb2O5 and five kinds of Al2O3-CaO compounds (3CaO⋅Al2O3, 12CaO⋅7Al2O3, CaO⋅Al2O3, CaO⋅2Al2O3, CaO⋅6Al2O3) have been studied at the temperature range from 1225°C; to 1300°C; in air. The reaction products formed at the interface of each reaction were examined by using EPMA and X-ray diffraction. In the cases of the reactions between Nb2O5 and three compounds, namely, 3CaO⋅Al2O3, 12CaO⋅7Al2O3 and CaO⋅Al2O3, three kinds of Nb2O5-CaO compounds (CaO⋅Nb2O5, 2CaO⋅Nb2O5, 3CaO⋅Nb2O5) were formed by the one-way diffusion of CaO into the Nb2O5. While, the reactions between Nb2O5 and the other compounds, CaO⋅2Al2O3 or CaO⋅6Al2O3, yielded CaO⋅Nb2O5, 2CaO⋅Nb2O5 and Al2O3⋅Nb2O5 by the one-way diffusion of Nb2O5 into the Al2O3-CaO system. The prismoidal and tabular CaO⋅Nb2O5, the tabular 2CaO⋅Nb2O5 and the spherical Al2O3⋅Nb2O5 having the particle size of 2-3μm, were distributed in the reaction layers. The reaction rate “x” followed the parabolic law “x2=2Dt”. The rate of the reactions of the former compounds (3CaO⋅Al2O3, 12CaO⋅7Al2O3 and CaO⋅Al2O3) were smaller than those of the latter compounds (CaO⋅2Al2O3 and CaO⋅6Al2O3).

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