Vapor-grown carbon fibers: Status and prospects

Abstract

Vapor-grown carbon fibers are produced by exposing a metal catalyst particle (usually Fe) of a few nanometers in diameter to a gas supersaturated in carbon. Under these conditions, the catalyst particles can produce rapidly lengthening carbon filaments of nanometer diameter. Macroscopic fibers may be obtained by vapor deposition of carbon on these filaments. Several different approaches are now being used to exploit this concept. In the first, Fe particles are deposited on a substrate on which the fibers are grown. This method can produce fibers of good uniformity, stiffness of 240 GPa (34 Msi), and tensile strength of 2.9 GPa (420 ksi). It has been researched in Japan, France, and the U.S.A. without the fibers being made available in commercial quantities. In a more recent conception, an organometallic containing iron dissolved in a liquid hydrocarbon is sprayed into a reactor under conditions where filaments can form. The filaments are of smaller diameter and length than the fibers grown on substrates, and their mechanical properties are inferior. However, because this process has a high reactor productivity and can be made continuous, several groups are now attempting to make these fibers commercially available. These fibers could find many applications in composite materials.