OVERPOTENTIAL EFFECTS IN FORMATION OF GRAPHITE NITRATES

As in many other solid state transformations, excess chemical potential must be built up to start the change from the crystal packing of graphite to the crystal packing of an intercalate compound. In the conversion of graphite to graphite nitrate by nitric acid vapour, thresholds of the excess potential needed can be measured conveniently and sensitively. The degree of perfection of various graphites can be correlated with the intercalation thresholds observed. Using nitration thresholds and starting with near-ideal graphite, effects of progressive exposure to fast neutron irradiation can be followed down to exposures of less than 2 × 1014 ncm-2. Since dislocations must be free to move to permit intercalation, this high degree of sensitiveness to radiation damage gives a measure of effects due to the creation of dislocation pins. Saturation effects are apparent for doses of the order 2 × 1015ncm-2. © 1969.