Surface Area Studies of High Vacuum Evaporated Nickel Films

Duthie, David T (1963) Surface Area Studies of High Vacuum Evaporated Nickel Films. PhD thesis, University of Glasgow.

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Abstract

The adsorption isotherms of krypton on high vacuum evaporated nickel films and nickel films which have chemisorbed oxygen have been studied. The oxygenation of the clean nickel films was effected either by admitting pure oxygen to the surface directly or by allowing nitrous oxide to catalytically decompose on the surface. It has been shown that the decrease in the krypton monolayer value, which was calculated from the B.E.T. equation,was comparable for the chemisorption of oxygen by both methods of oxygenation, and that it cannot be satisfactorily explained by the mechanisms of thermal sintering, induced sintering, or pore blocking. It has been shown that the percentage decrease in the krypton monolayer value brought about by oxygen chemisorption was different from the percentage change in the xenon monolayer value, and it has been inferred that changes in the krypton monolayer value do not necessarily reflect a change in surface area. It has been suggested that this decrease in the krypton monolayer value might be explained by a surface dipole effect whereby the chemisorbed oxygen causes enhanced polarisation of the krypton atoms which would lead to increased lateral repulsion between the krypton atoms and hence to a decrease in the monolayer value. The adsorption isotherms of chemisorbed layers of various types on nickel have been studied, viz. hydrogen, hydrogen and oxygen, ethylene, ethylene and oxygen, mercury, and caesium. These investigations revealed that the effect on the krypton monolayer value was independent of the direction of the induced dipole as would be expected if lateral repulsion were the cause of the Vm changes. Further it has been shown that when krypton is adsorbedon a surface which has chemisorbed two species one which has adsorbed positively and one which has adsorbed negatively, the polarising effect of these chemisorbed species tended to cancel, resulting in decreased lateral repulsion between the krypton atoms subsequently physically adsorbed. The relationship between the coverage of a nickel surface with a chemisorbed species and the change in the krypton monolayer value has been studied using mercury and it has been shown that this relationship is linear until all available nickel sites are occupied.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Applied physics, Condensed matter physics, Inorganic chemistry
Date of Award: 1963
Depositing User: Enlighten Team
Unique ID: glathesis:1963-79497
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 09:02
Last Modified: 05 Mar 2020 09:02
URI: http://theses.gla.ac.uk/id/eprint/79497

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