Kinetics of the desorption of hydrogen from a massive-nickel surface modified by plasma and thermal treatments

The kinetics of the desorption of firmly adsorbed hydrogen from the surface of massive foamed nickel was studied over a temperature range of 453 to 753 K. The effects of plasmochemical (in oxygen and hydrogen plasmas) and thermal (annealing and quenching) treatments on the kinetic characteristic of hydrogen desorption were examined. It was found that the values of the activation energy and preexponential factor of the desorption rate constant differ for the temperature ranges below and above the Curie and Curie-Weiss points. It was discovered that the treatment of foamed nickel samples in the plasma of a hydrogen high-frequency discharge produced a more significant effect on the characteristics of hydrogen desorption than the treatment in the plasma of an oxygen glow discharge. Thermal treatments of the samples also affect the characteristics of hydrogen desorption. The experimental results were explained by changes in the magnetization of Ni, which, according to the theory of s-d-electron exchange interaction, affects the electron work function, and by the formation of additional point defects at the surface and in the subsurface layer of the metal during plasma treatment. Copyright © 2005 by Pleiades Publishing, Inc.