Hostname: page-component-7bb8b95d7b-lvwk9 Total loading time: 0 Render date: 2024-09-18T00:45:12.741Z Has data issue: false hasContentIssue false
  • English
  • Français

The theory of the structure and formation of a certain type of immobile adsorbed film with an application to the adsorption of oxygen on tungsten

Published online by Cambridge University Press:  24 October 2008

J. K. Roberts
Get access Rights & Permissions [Opens in a new window]

Extract

The theory is given of the structure and behaviour of immobile adsorbed films on a simple quadratic lattice in which each particle is so large that it occupies more than one site and makes it impossible for adsorption to occur on sites which are neighbours to that on which it is adsorbed. The results are obtained partly by statistical methods and partly by the use of a model of the film.

The final or complete film of this type is not homogeneous and has gaps in it. The sites on the surface can be divided into two groups, the gaps occurring where regions of the surface occupied by particles adsorbed on one group and those occupied by particles on the other group meet. The number of these gaps or “boundary sites” is determined, and the possible configurations of particles in the boundary regions are discussed in detail.

The results are considered in connexion with some experiments on the adsorption of oxygen on tungsten. In this case a second layer is formed over the boundary sites and the amount that can be so adsorbed or the number of “second layer sites” to which the boundary sites give rise is obtained. It is shown that numerically the experimental results for oxygen are in better agreement with the view that the first or very stable layer is a molecular layer of the above type than with the view that it is atomic.

Type
Research Article
Information
Mathematical Proceedings of the Cambridge Philosophical Society , Volume 36 , Issue 1 , January 1940 , pp. 53 - 68
Copyright
Copyright © Cambridge Philosophical Society 1940

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

* Morrison, and Roberts, , Proc. Roy. Soc. A (in course of publication).Google Scholar

* For a discussion of this see Roberts, , Some problems in adsorption, p. 28, Cambridge Physical Tracts (Cambridge, 1939).Google Scholar

* See Roberts, , Proc. Cambridge Phil. Soc. 34 (1938), 406.Google Scholar

* Roberts, , Proc. Roy. Soc. A, 152 (1935), 473.Google Scholar

* It is evident that this last probability is only an approximation to what we really require, but consideration of more than nine sites in detail would be extremely laborious.

* The remark made in the footnote in § 4 applies, of course, to probabilities like P IV.

* The diameter of the oxygen molecule is 3.64 × 10−8 cm. and the spacing in the simple quadratic lattice in the 100 plane of tungsten is 3.15 × 10−8 cm. Thus, if the oxygen is adsorbed without dissociation, the spacing of the adsorbed particles on the surface would probably be that considered in this paper.

* Roberts, , Some problems in adsorption, Cambridge Physical Tracts, p. 90 (Cambridge, 1940).Google Scholar

* The same remark as to the independence of the sites tried applies as in the paper by Morrison and the author.