ADSORPTION AND ABSORPTION OF DIATOMIC GASES BY ZIRCONIUM - STUDIES OF THE DISSOCIATION AND DIFFUSION OF CO, NO, N-2, O-2 AND D-2

Journal article

The adsorption of D2, CO, N2, NO and O2 on polycrystalline Zr has been studied at 300 K. The behaviour of D2 differs in every respect from that of the other gases: continuous absorption occurs at 300 K apparently with some charge transfer to the metal from the deuterium. Work function, electron impact, Auger, and diffusion data indicate that adsorption of CO, N2, NO and O2 is almost entirely dissociative at 300 K; heating of these adsorbed phases leads to rapid surface → bulk diffusion and very little desorption. Coadsorption experiments tend to support the view that these adsorbates do not exist as simple overlayers at 300 K, but form instead a rather complex selvedge at the solid-vacuum interface in which adatoms penetrate and become intimately mixed with the metal lattice. Nitrogen seems to form an underlayer. Diffusion coefficients for surface → bulk transport of C, N and O are obtained over a range of temperatures, with the following results: D(C) = 3.6 × 10-16 exp( -64000 RT) m2 s-1; D(N) = 2.2 × 10-16exp( 57000 RT) m2 s-1; D(O) = 7.4 × 10-16exp( -50400 RT) m2 s-1 with the activation energies quoted in joules. Very marked relative attenuation effects are observed in the valence band Zr Auger spectra upon adsorption of CO, N2, NO and O2. These effects cannot be accounted for in terms of conventional escape depth arguments: they are ascribed to extensive metal → adsorbate charge transfer which has its origins in the very electropositive nature of Zr. © 1980.

Authors: Foord, J; Goddard, P; Lambert, R

• Publication status: Published
• Journal: SURFACE SCIENCE
• Volume: 94
• Issue: 2-3
• Pages: 339-354
• Publication date: 1980-01-01
• DOI: 10.1016/0039-6028(80)90011-4
• ISSN: 0039-6028
• Language: English