The thermal decomposition of surface oxides formed on Graphon

Abstract

The thermal decomposition of surface oxides formed during the low pressure oxidation of Graphon was studied. Oxidation reactions were performed at 525°, 575° and 625°C in a static reactor, using initial O 2 pressures between 10 and 200 mtorr. The amount of surface oxide formed was found to increase with decreasing reaction temperature and increasing initial O 2 pressure. The surface oxides were decomposed by raising the temperature at 3°C per min up to 950°C in a closed system and measuring the partial pressures of the CO and CO 2 produced at frequent intervals. Each graph of accumulated CO against temperature consisted of a series of intersecting linear portions, suggesting that desorption was taking place from a number of discrete types of sites. The accumulated CO 2 measured was found to pass through a maximum at about 700°C, after which the partial pressure decreased due to the reaction of CO 2 with the Graphon surface. The rate of this secondary reaction was found to be strongly dependent on the rate of decomposition of the surface oxide, and it is suggested that decomposition of surface oxide leaves highly reactive ‘nascent’ sites on the Graphon surface at which CO 2 can react.