Abstract
A positron lifetime study was performed on nickel to investigate the detection of hydrogen in nanovoids. The introduction of hydrogen into well-annealed nickel by electrochemical hydrogen charging increased the positron lifetime by inducing the formation of vacancy-type defects. Hydrogen was released from 323 K to 423 K and the defects introduced disappeared at 573 K. The Vickers hardness recovered at 323 K with the escape of interstitial hydrogen atoms. The size and number of hydrogen atoms in voids were estimated through calculations. The positron lifetimes in quenched and neutron-irradiated Ni were shortened after electrochemical hydrogen charging due to the trapping of hydrogen in vacancy clusters. The hydrogen in nanovoids escaped during annealing at 373 K.
