Nucleation and Growth of Carbon Filaments and Vapor-Grown Carbon Fibers

Abstract

Fifty years of research on the growth of carbon filaments has elucidated many aspects of filament production and worked out mechanisms that provide guidance for experiment and invention. The role of the catalytic particles has been investigated in many ways. It is known that the particle must dissolve carbon, and that any carbide phases formed should be of low stability, so as to minimize competition with the filament growth process. The particle must also become highly supersaturated in carbon in order that filament nucleation can occur. A useful growth procedure must optimize the chances of growing filaments of the proper length, diameter and morphology. The catalytic particle must become highly supersaturated in carbon in order that filament nucleation can occur. Since filaments are only one of a variety of structures that may be precipitated by the catalytic particle to relieve its supersaturation, the growing conditions must be carefully optimized. Encouraging filament growth requires that small diameter catalyst particles be protected from aggregation.

Cessation of filament growth may be due to the deposition of a passivating layer of carbon from the vapor phase or to a simple phase change in the catalytic particle.