From: Eugene Leitl (Eugene.Leitl@lrz.uni-muenchen.de)
Date: Sun Mar 02 1997 - 11:55:45 MST
On Sat, 1 Mar 1997, Carl Feynman/Forrest Bishop wrote:
[...]
> >"Graphite Fiber")
>
> It's a fiber consisting of pure graphite, i.e. carbon. How is this a misnomer?
>
> [[As I understand it, Carbon Fiber come in different grades, and is made by pyrolyzing
> various polymeric hydrocarbons, like rayon or nylon. The resulting fiber is (*I think*)
> a mixed up conglomeration of sp2 and sp3 hybrid bonds. Maybe it is mostly graphitic-
> I’ll put that aside aside.]]
It is difficult to denote a boundary between all the carbon allotropes.
Diamond is easy, as is graphite: the sheets are planar. The most perfect
graphite brand is HOPG (highly ordered pyro graphite, used as SPM
standard substrate, and in xray monochromators), whereas the carbon
in soot has a semimorphous, turbostratic order of graphite sheets.
Buckyballs are easy to spot, but what are buckytubes? I don't think
one can call them graphite, since curvature of the concentric sheets is
quite large.
Btw carbon fibre production, they first used PAN (polyacrylnitrile)
fiber, baked in an oven under tensile load/inert atmosphere. Afair best
carbon fibre grade is now spun from coal tar (I know how this sounds...).
I don't know how the bucky tubes are produced. At a guess, grown from
gas phase, using transition metal (nickel?) catalysis?
ciao,
'gene
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