Mechanism of Activation of TiFe for Hydrogen Storage by High-Pressure Torsion

2014 Fiscal Year Final Research Report

• Project/Area Number: 25889043
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Single-year Grants
• Research Field: Physical properties of metals/Metal-base materials
• Research Institution: Kyushu University
• Principal Investigator: EDALATI Kaveh 九州大学, カーボンニュートラル・エネルギー国際研究所, 学術研究員 (60709608)
• Project Period (FY): 2013-08-30 – 2015-03-31
• Keywords: Hydrogen Storage / Energy Storage / Severe Deformation / High-Pressure Torsion / Activation / Deactivation / Metal Hydrides / Ultrafine Grains

Outline of Final Research Achievements

TiFe intermetallic, a candidate for hydrogen storage, does not absorb hydrogen easily because of difficult activation, while TiFe processed by HPT absorb hydrogen. We showed that the activation is due to (i) enhanced diffusion, (ii) surface segregation of Fe-rich islands and (iii) formation of grain boundaries.
To investigate the importance of grain boundaries, TiFe was processed by 4 routes. The annealed sample, with micrometer grain sizes, didn't absorb hydrogen. The groove-rolled sample, with submicrometer subgrain sizes, was partially activated. The HPT-processed and ball-milled samples, with nanograins, were fully activated. Therefore, the activation becomes easier when nanograins form.
Mg2Ni intermetallic was also processed by HPT and its hydrogenation was examined. While Mg2Ni after annealing absorbed hydrogen partially, the HPT-processed sample fully absorbed hydrogen at 423 K. It was concluded that the large fractions of grain boundaries are responsible for activation.

Free Research Field

Hydrogen Storage Materials