Materials Transactions Online

Materials Transactions, Vol.43 No.7 (2002) pp.1494-1497
Special Issue on Grain Boundaries, Interfaces, Defects and Localized Quantum Structure in Ceramics
© 2002 The Japan Institute of Metals

Recovery of Hydrogen Induced Defects and Thermal Desorption of Residual Hydrogen in LaNi5

Kouji Sakaki1,*, Hideki Araki1,2 and Yasuharu Shirai1,2

1Department of Materials Science and Engineering, Osaka University, Suita 565-0871, Japan
2Frontier Research Center, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan

Lattice defects induced by initial hydriding and their effect on residual hydrogen content in LaNi5 have been studied by means of positron lifetime spectroscopy and hydrogen thermal desorption measurement. Component analyses of positron lifetime spectra show that surprising amount of vacancies together with dislocations are generated by the initial hydriding. Vacancy migration in LaNi5 after hydrogen desorption at room temperature is observed around 423-673 K, while dislocations in LaNi5 are much more stable. Hydrogen thermal desorption measurement shows that the release of residual hydrogen occurs mainly in the temperature range from 450 to 650 K, and it ceases at about 800 K. The release temperature of residual hydrogen closely corresponds with the temperature of vacancy migration and annihilation in LaNi5. Residual hydrogen in LaNi5 is most likely trapped by vacancies and vacancy clusters, which are induced by hydriding.

(Received June 3, 2002; Accepted June 12, 2002)

Keywords: positron annihilation, LaNi5, hydrogen-storage alloy, lattice defect, vacancy, dislocation, residual hydrogen, temperature programmed desorption


*Graduate Student, Osaka University.

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