The Growth of Vapor-Deposited Carbon Fibres

Abstract

As is discussed elsewhere in this book, the formation of microscopic filaments is a source of harmful carbon deposition when carbonaceous gases (carbon monoxide, hydrocarbons...) flow or stay over a metallic surface which does not present the conditions necessary for their thermodynamic stability. The specific conditions in which these filaments have grown to macroscopic dimensions have occasionally been accidentally attained. Thus the “chemical vapor deposition” of carbon fibres was reported as early as 1890 [1] and several other papers older than 1958 were reviewed by HILLERT and LANGE [2]. These last authors observed not only fibres but also filaments (diameters between 10 and 80 nm, length greater than 100 pm) both thinner than fibres and longer than carbon filaments which are commonly obtained from the decomposition of carbonaceous gases; they postulated that these thin filaments were the precursors of thicker fibres. They proposed a two-stage mechanism: first lengthening of these filaments from a catalytic particle (several authors had observed by transmission electron microscopy — TEM -“ a material denser than graphite” inside the fibres and suggested it consisted of catalyst particles), then thickening by direct chemical carbon deposition from the gas phase.