Diffusion of Carbon Atoms in Natural Graphite Crystals

Abstract

Diffusion in purified natural graphite crystals was studied by two techniques. Crystals with ${\mathrm{C}}^{14}$ atoms on the surface were prepared by heating at 1575°C for thirty minutes in a mixture of radioactive carbon monoxide and helium. These crystals were heated at diffusion temperatures in vacuo, and the ${\mathrm{C}}^{14}$ distribution within the crystals was determined by burning them slowly and measuring the radioactivity in the carbon dioxide produced. Diffusion measurements were carried out for times up to twenty-five hours in the temperature range 1995°-2195°C. The results indicated that simultaneous diffusion into single-crystal regions and into disordered regions occurred.