Reaction of Atomic Oxygen with Carbon

Abstract

RECENT reports^1–3 have indicated that the reaction of atomic oxygen with carbonaceous materials proceeds rapidly at room temperature and that the reaction has a zero activation energy. Investigations in this laboratory using several carbons have not confirmed these previous results. In the work recorded here, atomic oxygen was formed in a flow system (335 cm³ h⁻¹ S.T.P., 0.13 mm mercury pressure) by the action of a high-frequency (28 Mc/s) electrode-less discharge. The oxygen gas was of British Oxygen Co. medical quality and was used without further purification. During the discharge the plasma was found to extend considerable distances down-stream from the generator coil. The extent of spread of the plasma could be limited by wrapping the glass tubing on either side of the generator coil with earthed aluminium foil. The concentration of atomic oxygen at the position of the carbon specimen was about 10 per cent. This concentration was measured calorimetrically using the method described by Schiff⁴. The carbon was contained in a silica boat and suspended in a silica reaction vessel. Facilities were available for outgassing the carbon at 900° C to pressures less than 10⁻⁵ mm mercury before reaction. The carbons used included purified Ticonderoga graphite crystals⁵, pyrolytic graphite, and various pure amorphous carbons.