Interaction of Hydrogen with Vanadium Layers Preadsorbed on Tungsten Field Emitter Tip

Abstract

Interaction of hydrogen with vanadium layers preadsorbed on a thermally cleaned tungsten field emitter was studied at room temperature and 78 K through measurements of the total work function changes. An increase in the work function followed by its slight decrease at higher exposure can be understood taking into account the possibility of negatively (β -) and positively (β+) polarized adspecies formation on thin vanadium layer. This process leads to vanadium hydride formation. The work function results suggest that hydrogen diffusion into the vanadium layer is meaningful at room temperature. Thermal desorption of hydrogen adsorbate carried out within the temperature range 409-461 K from thin va^iadium layer (θv = 40) provided a value of 127 ± 6 kJ/mol for the activation energy for desorption.

Kinetics of hydrogen desorption from the powders of metal hydrides

“…We emphasize that this set provides a satisfactory fitting of the experimental data for the various heating rates. Furthermore, we note a reasonably good agreement between our data and the value of the activation energy of H desorption from the vanadium hydride, 127 kJ/mol, reported in [9]. Some discrepancy in the data can be caused by the fact that the samples were studied in different forms, as powders (this work) or as thin films as in [9].…”