The diffusion of carbon in single crystal graphite

Abstract

A novel method is described by which the etch decoration technique and electron microscopy are applied to the measurement of self-diffusion in graphite. Natural graphite single crystals have been “labelled” on their outer surfaces by a 14CO exchange method. The 14C was diffused into the crystals at temperatures from 2000 °C to 2 600 °C, and they were set aside to allow a few 14°C atoms to decay to 14N and thus create lattice vacancies. After cleaving the crystals, vacancies were expanded by oxidation and decorated with gold so that they could be counted. Self diffusion constants for diffusion parallel and perpendicular to the basal plane were 2.9 × 10 −13 cm 2/sec and 2.5 × 10 −14 cm 2/sec respectively at 2,200 °C.