Determination of binder oxidation rates in a matrix graphites by means of C14 - labelling

In order to study the contribution to chemical reactivity toward H2O-vapour of the binder materials in a matrix graphite, specimens have been prepared with a binder component which has been labelled with C14. In blank experiments it has been shown that no significant exchange of C14 between binder and graphite matrix occurs at the relatively low carbonisation temperatures (800 to 19000C) at which these matrix graphites were prepared. By measuring the amount of 14CO in the reaction gas the contribution of the binder to total matrix oxidation rate has been evaluated. It has been shown that the binder reactivity decreases considerably as the final heat treatment temperature (HTT) during manufacture of the matrix graphite is raised from 800 to 19000C. But even after a final heat treatment at 20000C the binder reactivity is significantly higher than would be expected from its weight contribution so that a preferential oxidation attack on the binder constituent, decreasing with increasing HTT, has to be postulated for this particular low density matrix graphite. (author)