RADIATION DAMAGE IN DIAMOND AND SILICON CARBIDE

Diamond and silicon carbide were irradiated in nuclear reactors and were found to be damaged in a manner similar to that for graphite. Detailed observations were made of the dilatation and increase in energy content and their annealing. Dilatations as great as about 3.7 percent and increases in energy content as great as about 400 cal/g were observed. The dilatations and the energy content (release of stored energy) seemed to anneal in a parallel manner and could be treated kinetically as a distribution of processes in activation energy. The initial distribution for diamond showed a peak at about 1.6 ev and a plateau extending (at about \textonequarter{} the height of the peak at short irradiations and greater proportionately for long irradiations) to activation energies in excess of 3.7 ev. The initial distribution for silicon carbide showed a smaller narrow peak at about 1.6 ev and a very broad larger peak extending from about 2.2 ev to 4.3 ev with a maximum at about 3.4 ev. In many of the samples of irradiated diamond the stored energy exceeded the heat capacity in certain temperature ranges, and catastrophic stored energy release was observed on heating.