Modifications of Properties of Benzene-Derived Fibers by Intercalation and Implantation. Final Report, August 1, 1983-July 31, 1985

摘要

A major effort was devoted to studying the damage process associated with ion implantation of graphite and its subsequent regrowth using high resolution transmission electron microscopy. Graphite fibers were used. Previous studies of thermal transport in graphite and graphite intercalation compounds were extended to single fibers, leading to more controlled transport measurements and the discovery of new transport phenomena. Measurements on pristine graphite fibers confirmed the Bright model for the negative magnetoresistance of pregraphitic fibers at low magnetic fields (less than or equal to 1.4 Tesla); at higher magnetic fields, the ionized impurity scattering mechanism was introduced to explain deviations from the Bright model. Thermal conductivity measurements over a wide temperature range on vapor-grown carbon fibers annealed at various temperatures showed a direct correlation between the defect-limited phonon mean free path L/sub phi/ and the correlation length L/sub a/ measured by Raman scattering. The favorable geometry of the benzene-derived fibers permitted fiber exfoliation with large increases. Ion implantation could be used to modify the near-surface properties of graphite fibers to enhance their adhesion to epoxies, which could be of significant use in the preparation of carbon-carbon composites. New research areas included the preparation and subsequent studies of hydrogenated graphite intercalation compounds KH/sub x/-GICs, including the stabilization of the superconducting transition temperature of the first stage KHg-GICs through hydrogenation. (ERA citation 11:005823)