Correlation of the reactivity, the active surface area and the total surface area of thin films of pyrolytic carbon

Abstract

Using thin films of pyrolytic carbon the rate of the reaction with oxygen has been measured over the temperature range 625–740°C and at pressures of oxygen from 6–100 torr. The active surface area (ASA) of the films was measured from the total concentration of strongly-bound complexes with oxygen on the surface and the relative total surface area (TSA) was measured by low-temperature adsorption of nitrogen. A maximum in reactivity and in ASA was observed for films of average thickness of about 20 nm with a TSA of about 30 m2 g−1. At the maximum the ASA and TSA were essentially equal. The results are interpreted in terms of the mechanism of formation of pyrolytic carbon in the initial stages.