🚀 go-pugleaf

===========================
 sundermm@columbia.dsu.edu (MARC SUNDERMEYER) writes:
>
>	I have always heard of and seen the chemical structures of the new 
>Buckminster Fullerenes, but hat does the actual substance look like if you 
>were to have a handfull of it?  (Any of the types, not just C60.)

 Fullerenes have very interesting (crystal) structures.

 Buckminsterfullerene (C60) looks yellow as a film. In solution it 
 is lilac (beautiful to watch :) ). Different temperature/pressure
 treatments make the appearance of solid C60 change. 
 I have not seen a big C60 crystal, first hand. But, I am told that
 small crystals, made using sublimation and annealing, show hexagonal
 faces; but not the truncated icosahedron.

 Other fullerenes have been difficult to prepare in large quantities.
 C70 can be made in large quantities - atleast here at MIT. It appears
 (dark) red in solution. The solid film is redish pink (a friend of
 mine says - com'on, its pink, can't you see; well, pink is her favorite
 color.) The solid seems to form amorphous form much more easily. There 
 are reports of crystalline forms.

 Bucky tubes, as synthesized, look like broken tree stem. With hard/dark 
 bark outside and tubes packed in - not much orientation tho.

 Latest are bucky onions. See latest Nature for more.

T.Y.
----
tyadav@athena.mit.edu

 sundermm@columbia.dsu.edu (MARC SUNDERMEYER) writes:
>
>	I have always heard of and seen the chemical structures of the new 
>Buckminster Fullerenes, but hat does the actual substance look like if you 
>were to have a handfull of it?  (Any of the types, not just C60.)

There's an article on C60 crystals in the latest Journal of Crystal
Growth (Agafonov et al, volume 123, pages 366-372):  C60 grown
from n-hexane forms decagonal (10-sided) columns with hollow centers.

-- Dr. Mary L. Johnson
mjohnson@alumni.cco.caltech.edu

In article <351@snll-arpagw.llnl.gov> dlmedli@snll-arpagw.llnl.gov (medlin douglas l) writes:

>[...] and below 90K the
>symmetry changes to a rhombohedral structure.

Van Tendaloo proposed a new structure for C60 , below 90K simple
cubic structure (Pa3 I believe) transforms into the rhombohedral str, with
the doubling of the unit cell. According to very extensive research
done at the University of Pennsylvania (using the Synchrotron Radiation
at the Brookhaven Nat. LAb, TGA-DSC, FTIR, 13C NMR and EPR) this second
phase transition is due to impurities picked up by the C60 - paper
will be published soon (sort of nail to the coffin).

>
>Apparently, the same type of transformations alsokjjoccur in C70
>as the "footballs" stop spinning: Descending frot high temperatures 
>there is a continuous transformation from FCC to rhombohedral; at
>337 K there is a shear transformation to HCP; at 276 K there is
>a transformation to another Hexagonal phase; and then at some
>lower temperature the balls stop rotating entirely and the
>structure distorts to a monoclinic phase.

Again shear tranformation rhombohedral->hcp is due to impurities.

Fullerenes , after the column are usually in form of the black (sometimes
shiny) powder. However, I saw a brown powder once!





-- 

Krzysztof Kniaz, Penn |If only God would give me some clear sign! 
LRSM ,                |Like making a large deposit in my name at a Swiss bank.
Phila, PA, 19104, USA |               Woody Allen

dlmedli@snll-arpagw.llnl.gov (medlin douglas l) writes:
>[stuff deleted]
>Also at this talk Dr. Tendaloo presented some SEM pictures and electron
>diffraction patterns of crystals of what they called conical graphite-
>these were crystals that looked like little cones- and are formed
>by the graphite sheet having a defect of a pentagonal (rather than
>hexagonal) carbon ring that causes the graphite sheet to distort into
>a cone.

	Check out an article from one of the latest issues of _Nature_
(sorry, I can't tell you the exact issue - one of my fellow employees has
snagged it from the library).  Some recent studies suggest that those
pentagonal rings you called "defects" are in fact a necessary stabilizing
factor in carbon crystalization - when there are not other compounds
present to bind the "loose ends" of planar graphite sheets.

	Another netter just recently mentioned this same article.  It 
discusses the "bucky onions" which will probably be a hot topic soon.

>Doug Medlin
>dlmedli@snll-arpagw.llnl.gov 


-- 
== John J. Ladasky II ("ii") ========================= ladasky@netcom.COM ==
"Great composers do not borrow -	     "Talking about music is like
 they steal."  - John Ladasky	      ~ -     dancing about architecture."
(quote stolen from Stravinsky, who    o o     - Elvis Costello?  Laurie
 stole it from a statement made by     >        Anderson?  Frank Zappa?
 Pablo Picasso about painting, who    \_/    -------------------------------
 stole it from...)			     "Property is theft." - Groucho
============================================================================

It seems like I read awhile back that a solution of BF's is yellowish,
that was how the experimenters figured out what they had.
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