Investigation of hydrogen absorption kinetics on intermetallic compounds Hf2Ni, Hf2Co and Hf2Fe

Abstract

Polycrystalline intermetallics Hf2Ni, Hf2Co and Hf2Fe are investigated as the hydrogen absorbers in the temperature range 348 to 823 K, under the constant hydrogen pressure of 1 bar. The absorption process was carried out in typical volumetric apparatus and H/M mole ratios together with rate constants and activation energies for hydrogen absorption reaction were determined. Achieved hydrogen absorption capacities at 573 K are: 0.60, 0.90 and 1.48 and rate constants at 573 K are: 0.38×10-3, 0.55×10-3 and 4.72×10-3 s-1 for Hf2Ni, Hf2Co and Hf2Fe respectively. Determined activation energies are: for Hf2Ni, 38.44 kJ/mol, for Hf2Co, 19.62 kJ/mol and 2.74 kJ/mol for Hf2Fe. From the obtained experimental results, it was concluded that Hf2Fe has the best hydrogen absorption ability among the examined intermetallics.

Keywords

• Hf
• intermetallics
• activation energy
• rate constant
• hydriding capacity
• hydriding isotherm