1. Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
2. Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan
3. Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
4. Showa Titanium Co., Ltd, 3-1 Nishinomiya-machi, Toyama, Toyama 931-8577, Japan
5. Corporate R&D Center, Showa Denko K. K., 1-1-1 Ohnodai, Midori-ku, Chiba, Chiba, 267-0056, Japan