The use of partial-pressure mass spectrometry in the study of the thermal desorption and oxidation of carbon and graphite

Abstract

A partial-pressure mass-spectrometer system is described for measuring thermally desorbed species from solid surfaces. The system evaluates not only the ratio of masses present in the gaseous phase but also relates the specific mass (mg g^–1 of solid) desorbed or decomposed during thermal treatment. The extension of the method to include oxidation studies is also described.

A study has been made of the initial evolution of gases from graphitic and non-graphitic carbons. These range in properties from a ground graphite of specific surface 103 m² g^–1 to a nuclear-type graphite of 0·6 m² g^–1. A study of a non-graphitic carbon, saran charcoal, of molecular-sieve type is also included.

The formation of surface oxide on a clean surface at low pressures is evaluated together with the resultant thermal decomposition of the surface oxide. The results from this paper together with other published work on graphites are reviewed and used to illustrate the application of the results of thermal desorption to oxidation studies on carbons and graphites.