A New Mechanism for the Catalytic Growth of Carbon Filaments and Metal Dusting Phenomenon

Abstract

ABSTRACTRaman scattering and X-ray diffraction were used to study the mechanism of the catalytic crystallization of carbon and metal dusting. The following new mechanism is proposed for metal dusting and the growth of carbon filaments. Carbon cannot crystallize well by deposition from carburizing gases at low temperature without catalytic activation because of its strong C-C bonds and high melting temperature. The poorly crystalline carbon has higher free energy than that of good crystalline carbon. To form good crystalline carbon, carbon atoms have to dissolve, diffuse through metal particles, and crystallize on a proper lattice plane that can act as a template to help the epitaxial growth of carbon crystals. Metal particles are liberated from the pure metal and alloys in this process, which leads to metal dusting attack. The decrease of free energy from highly disordered to well crystalline carbon is the driving force for metal dusting and carbon filament growth through metal particles.