The difference in the environmental stability of TaCl5-intercalated pitch-based and vapor-grown carbon fibers

Tantalum(V) chloride has been intercalated from the gas phase in commercially available Thornel P-120. Thornel P-100 and Thornel P-75 carbon fibers and also in self-prepared vapor-grown carbon fibers. All fibers are cut into pieces of 1.5 cm length. All pitch-based fibers have approximately the same diameter, but the vapor-grown carbon fibers are thicker. The as-prepared intercalation compounds are exposed to the ambient air. The evolution of (001) reflections of the intercalation compound is monitored by X-ray diffraction. With exposure time to air, a staging disorder takes place in the samples. The stability of TaCl5-intercalated pitch-based fibers depends on the structural perfection of the host material. The deintercalation process in fibers with low structural perfection is slower. The vapor-grown carbon fibers used have the highest structural perfection of all studied fibers. Their environmental stability is more similar to the high environmental stability of TaCl5-intercalated graphite flakes. The important difference between pitch-based fibers and vapor-grown carbon fibers is the different construction scheme. Pitch-based fibers have small particle sizes and large interfaces between guest species and the ambient air. Vapor-grown carbon fibers have large particle sizes and small interfaces to the surrounding air. The particle size and the interface size to the surrounding air are more important for the stability of TaCl5-intercalated carbon fibers than the structural perfection of the host lattice.