for the Spring 2003 NASA-Missouri Space Grant Consortium Meeting.
Are nano-cones a popular state for galactic carbon?
See our October 20, 2002 ApJ Letters note.
Closeup of a HREM
image of onion core material, showing
evidence both for "edge-on" sheets, and for defect-related
bending of those sheets as well. The latter is
a possible mechanism needed to grow one atom at a time the space-filling
structures that we find in laboratory observations (e.g. by condensation in
a carbon-rich stellar atmosphere).
images of onion core material with simulated
images of hexagonal graphene sheets without defects, and with simulated
images from graphene sheets with one
pentagon per sheet added by Martin Wackenhut here in StL.
HTML version of Dori's 3/21/01 Missouri Space Grant Consortium report.
Image of terrestrial graphite onions found in graphitized carbon annealed
D. Witt's discovery on 5 Oct 2000 of a meteoritic graphite sphere with well-defined core. The darkfield image shows how the intensity of electrons diffracted from 3.4 Angstrom graphite layers drops off abruptly in the particle center. The brightfield image animation shows tilts varying by 15 degrees. Note the spherical symmetry of the core, even though rim symmetry is significantly less.
Abstract on "red giant onions" for the 2000 Meteoritical Society Meeting in Chicago
The study of extraterrestrial dust, both interplanetary dust from the
cloud around our sun, and pre-solar dust extracted from meteorites, has
from time to time called for a careful look at dust on earth. The recent
discovery of novel carbon structures, in the core of carbon blacks
(graphite onions) formed in the outer atmosphere of asymptotic giant
branch stars, mandates a planetwide look at: (i) carbon-based soots, and
at (ii) polycyclic aromatic hydrocarbon solids. We are interested in
those found in nature, as well as in those made by man.
The search has two components, literature and lab, one byproduct of
which will be a "rogue's gallery" of carbon-based soot particles and PAH-related
solids. Of course, fine-grained carbon "soots" are perhaps more often
allies than rogues as far as humans are concerned. For example, they are
likely used to make india ink black, to purify water as activated charcoal,
to help in the blast furnace manufacture of steel in the form of
steel-industry "coke", to support metal-catalysts in the manufacture
of many helpful compounds, to fuel barbecues, as an occasion for the employment
of chimney sweeps, to change the flavor of foods cooked just to the
point of blackening, and as byproducts from carbon arcs including newly
discovered buckminsterfullerines & carbon nano-tubes.
We will try to post the developing results of this search here. For
the moment, we are interested in literature references in the above areas,
and suggestion of specimens to look at by high resolution microscopy. You
can contact us at firstname.lastname@example.org
with these things. Of course, do
not send specimens without prior arrangement.
UM-StL Physics and Astronomy, P. Fraundorf (c) 2000-2005 Mindquilts site
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