Journal
JOURNAL OF ALLOYS AND COMPOUNDS
Volume 864, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2021.158876
Keywords
Hydrogen storage; TiFe alloy; Laves phase; Activation
Categories
Funding
- Korea Institute of Science and Technology (KIST) Flagship Program [2E30201]
- Technology Development Program to Solve Climate Changes of the National Research Foundation (NRF) - Ministry of Science, ICT & Future Planning [2020M1A2A2080881]
- National Research Foundation of Korea [2020M1A2A2080881] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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TiFe-based alloys with a secondary AB(2) phase can address the activation issue, leading to improved practical application potential. Adjusting the Cr concentration in the Ti-Fe-Cr alloys can enable activation at room temperature and optimize reversible capacity.
TiFe-based alloys are solid-state hydrogen storage materials operated at room temperature (RT). The current study presents a systematic approach for solving the activation issue (difficulty in the first hydrogenation), one of the major obstacles to the practical application of TiFe alloys, via the use of a secondary AB(2) phase. Based on the Ti-Fe-Cr ternary phase diagram, Ti-Fe-Cr alloys containing 80 at% Ti(Fe,Cr) (AB phase) and 20 at% Ti(Fe,Cr)(2) (AB(2) phase) were designed; the Cr concentrations in the AB and AB(2) phase were systematically varied while maintaining fixed phase fractions. Activation at RT was achieved when the overall Cr concentration was higher than 9.7 at%. Analysis of the activation characteristics of the individual phases revealed that the AB(2) phase readily absorbed hydrogen, thereby initiating activation of AB + AB(2) alloys. Notably, higher Cr concentrations enable the AB phase to absorb hydrogen at RT during the activation process, although the kinetics are much slower than that of the co-existing AB(2) phase. The equilibrium hydrogen pressures from the pressure-composition isotherms decrease as the Cr concentration increases, indicating that Cr stabilizes hydrides. Increased hydride stability may also promote the kinetics of the initial hydride formation in both the AB and AB(2) phases. An optimal composition for Ti-Fe-Cr alloys can be designed given the conditions of easy activation at RT and maximum reversible capacity within an operating pressure range. (C) 2021 Published by Elsevier B.V.
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