DESORPTION OF OXIDES AT THE SURFACES OF SYNTHETIC GRAPHITES

The decomposition of surface oxides formed on artificial graphite during combustion at low oxygen pressure (less than 10/sup -1/ mm of Hg) was studied under various experimental conditions. By progressive elevation of the temperatures to 950 deg C, the volatilization of most of the surface oxides is caused. The calculation made from the quantity of gas collected shows that these oxides cover only about 1/20 of the total surface of the graphite sample. Because of the high sensitivity of the experimental method, the desorption of the surface oxides can be followed at the combustion temperature after evacuation of all the oxygen from the apparatus. At a certain stage during the static desorption, CO and CO/sub 2/ are collected in a ratio equal to the coefficient of the relationship found between the formation velocities of CO and CO/sub 2/ during combustion. The total quantities desorbed (either as CO or CO/sub 2/) as a function of time obey the Elovich law. These results, as well as other observations, have led to the suggestion of a mechanism for the combustion of graphite where the formations of CO and CO/sub 2/ are not independent. (tr-auth)