Lengths of carbon fibers grown from iron catalyst particles in natural gas
Abstract
Carbon fibers produced by pyrolysis of hydrocarbons require submicron-sized metallic particles which act as catalytic nuclei for fiber growth. We have investigated the carbon fiber length distributions produced by particles from five different types of iron-containing catalyst materials. The average particle diameters among these five materials ranged from 12 to 71 nm. Under the lengthening conditions selected for this experiment (6.25% natural gas at 1054°C for 30 min), the distribution of fiber lengths obtained from each catalyst were statistically indistinguishable. A detailed analysis of the aggregate data set of all fibers longer than 0.3 mm showed that the distribution of fiber lengths is an exponential function in which the number of fibers n having a given length l is proportional to exp( - cl). The constant c depends on the conditions under which the fibers grow. The above length distribution allows easy calculation of several important parameters which characterize fiber growth. The distribution is consistent with a mechanism in which filaments grow linearly with time until the cessation of growth, and the probability per unit time of growth cessation is a constant independent of the duration of growth.
- Publication:
-
Journal of Crystal Growth
- Pub Date:
- December 1985
- DOI:
- 10.1016/0022-0248(85)90005-3
- Bibcode:
- 1985JCrGr..73..431T