Formation of Photocatalytically Active TiO₂ Layers on Ti-Nb Alloys by Two-Step Thermal Oxidation (Special Issue on Latest Research and Development of Structural and Functional Titanium-Based Materials) Formation of Photocatalytically Active TiO<sub>2</sub> Layers on Ti–Nb Alloys by Two-Step Thermal Oxidation

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Abstract

<p>A two-step thermal oxidation process was applied to Ti–<i>x</i>Nb binary alloys (<i>x</i> = 0, 1, 10, 15, and 30 at%) to prepare anatase-containing TiO<sub>2</sub> layers, and their photocatalytic activities were evaluated by measuring the water contact angle and decomposition of methylene blue (MB) under UV irradiation. The condition of the first-step treatment was fixed as heating in Ar–1%CO atmosphere at 1073 K for 3.6 ks, and the subsequent second-step treatment was conducted in air at 673–1073 K for 10.8 ks. The reaction layer formed after the two-step thermal oxidation consisted of TiO<sub>2</sub>. The anatase fraction of the TiO<sub>2</sub> layers increased with decreasing second-step temperature and increasing Nb content of the Ti–Nb alloys. In addition, Nb and carbon were introduced into the TiO<sub>2</sub> layers. A water contact angle of around 5° was observed on the TiO<sub>2</sub> layers formed at the second-step temperatures of 673–973 K. The rate constant of MB decomposition showed a maximum for an anatase fraction of 0.6–0.8 at which the recombination of exited electrons and holes are suppressed. The TiO<sub>2</sub> layer formed on the Ti–10 at%Nb alloy exhibited a higher rate constant of MB decomposition compared with Ti–30 at%Nb, in which the TiNb<sub>2</sub>O<sub>7</sub> phase formed. These results indicate that Nb is an effective alloying element for producing a photocatalytically active TiO<sub>2</sub> layer on Ti by the two-step thermal oxidation process. Nevertheless, the presence of an anatase-rich TiO<sub>2</sub> layer and an appropriate Nb content in TiO<sub>2</sub> are required for achieving high photocatalytic activities.</p>

Journal

  • MATERIALS TRANSACTIONS

    MATERIALS TRANSACTIONS 60(9), 1814-1820, 2019

    The Japan Institute of Metals and Materials

Codes

  • NII Article ID (NAID)
    130007695362
  • NII NACSIS-CAT ID (NCID)
    AA1151294X
  • Text Lang
    ENG
  • ISSN
    1345-9678
  • NDL Article ID
    029912114
  • NDL Call No.
    Z53-J286
  • Data Source
    NDL  J-STAGE 
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