Zairyo-to-Kankyo
Online ISSN : 1881-9664
Print ISSN : 0917-0480
ISSN-L : 0917-0480
Volume 58 , Issue 5
Showing 1-4 articles out of 4 articles from the selected issue
Commentary
Review
Research Paper
  • Akira Honda, Kaoru Masuda, Tsuyoshi Imakita, Osamu Kato, Tsutomu Nishi ...
    2009 Volume 58 Issue 5 Pages 182-189
    Published: 2009
    Released: October 16, 2009
    JOURNALS FREE ACCESS
    Interaction between carbon steel and nitrate was modeled using the mixed potential concept. Carbon steel was selected as an example of metal components in the repository of radioactive wastes. The nitrate reduction accompanied with the corrosion of carbon steel was modeled as a reaction series of NO3 → NO2 → NH3. The sum of the current of the reaction series of NO3 → NO2 → NH3 and that of water reduction was assumed to be balanced with the oxidation current of carbon steel. The input parameters for this kinetic model were determined by electrochemical measurements and immersion tests. The results of the immersion tests can be interpreted by the analyses of the model.
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  • Michiko Yoshihara, Yu Tanaka, Saburo Katayama
    2009 Volume 58 Issue 5 Pages 190-196
    Published: 2009
    Released: October 16, 2009
    JOURNALS FREE ACCESS
    The binary TiAl alloys and TiAl-based alloys were isothermally oxidized in air, and the oxidation behavior and scale spallation have been investigated. The mass gain due to oxidation of the TiAl-based alloys containing Nb, W or Ta is smaller than that of binary TiAl alloys, because of the suppression of TiO2 growth by the so-called doping effect. The TiAl-based alloys show better scale adhesion than binary TiAl alloys. Although the scales formed on the alloys have similar structure regardless of the alloy composition, the scale/alloy interface of the TiAl-based alloys seems to have good contact compared with that of the binary alloys. The densities of the oxide scales formed on the alloys estimated from the mass gain and the scale thickness are found to be about a half value of the expected one for the completely densified oxides. This is attributable to the formation of the large amount of cavities and pores in the scale. The coefficient of the thermal expansion (CTE) of the alloys decreases with increase of the content of additional elements in the alloy. The better scale adhesion of the TiAl-based alloys may result from the structure of scale/alloy interface and low CTE value of the alloys.
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