Rosco Bodine
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" glassy " carbon ????
http://cgi.ebay.com/Large-rod-of-glassy-carbon-100x6-6mm-99-...
Very curious , and costly . Wonder what sort of anode usefulness this might have in a perchlorate cell , directly or as a substrate for lead dioxide
.
Must be something like carbon fiber , but " unspun " ? 
Black , prematurely born diamond ...maybe .
Or maybe just an upwardly mobile graphite stopped
dead in its tracks when it was " movin' on up "
Hypergolic graphite of sorts ? Hmmmm .
[Edited on 13-10-2006 by Rosco Bodine]
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The_Davster
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Yeah, another weird form of carbon out there. There was a thread a while back. I think it can be made by carbonizing phenolic resins, or in other
words, torch some bakelite with a blowtorch. Not sure if specific conditions
are needed.
Another interesting form out there is graphite foil. Completly flexible sheets of graphite. Like tin foil, but more fragile. They are garbage for
electrodes though.
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Rosco Bodine
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There is a fairly dense graphite bushing material used as a fluid seal on the motor shaft in well water pumps , and it is mounted in a spring loaded
rubber sleeve so that it
presses firmly against a flat unglazed ceramic porcelain seat mounted in the pump housing , and polishes a very flat and close tolerance running seal
which is watertight
even to 60psi or more , maybe leaking a single drop every couple of days ....if leaking at all more than what simply evaporates at the edge of the
seal . I wonder if those pump seals are the same sort of material . I did some checking via google and it is likely a sintered carbon / graphite
composite
used for the pump seals .
http://www.azom.com/details.asp?ArticleID=516
They mention an oxidation inhibited phosphate impregnated
carbon/graphite composite , which might have decent performance as an anode or anode substrate .
And thirty years ago there were tobacco smoking pipes made from a high temperature high density graphite
which was said to be a spinoff product from the space program , it was black not gray or silvery , and it would not mark paper or rub off like a
pencil lead but had a
more ceramic nature ...don't know what was its electrical conductivity .
[Edited on 14-10-2006 by Rosco Bodine]
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Waffles
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Curious, very much so! Costly is always a factor of demand and resale. Everything from smart-elements is extravagantly expensive compared to what it
should cost...
\"…\'tis man\'s perdition to be safe, when for the truth he ought to die.\"
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ordenblitz
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I am wondering if a suitable electrode of carbon could be grown from the dehydration of sucrose by sulfuric acid. I have done this experiment a few
times and anyone who has done the same, has noticed the hard, glassy and porous log of carbon that forms. Depending on the shape of your reaction
vessel and the conditions which it is grown, it could be possible to make any shape or density one desires.
Just a thought.
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Rosco Bodine
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I have just downloaded a few patents which I haven't read yet , after a google search related to:
phosphate impregnated carbon graphite
Evidently if a carbon electrode is soaked in soluble phosphates and then carefully dried and fired at high temperature , the result is a high
temperature oxidation resistant electrode having greater life in molten aluminum , for electrolytic cells . It seems logical that
such treatment would also harden a carbon electrode
for use as an anode in a perchlorate cell if the fired
phosphate was insoluble or nearly insoluble , and might
greatly reduce the deterioration of the carbon anode in perchlorate cells . It is something along the lines of the same idea as linseed oil and could
be more effective .
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Fleaker
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Just as an aside: Glassy carbon is used in ultra-high end crucibles for high purity metals analysis. Very expensive, but very nice. I've heard that
metals won't fuse and stick to them, and they're remarkably resistant to oxidation.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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franklyn
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Google for "carbon carbon" with the quotes
this is an engineered material that derives its
structural properties from the pyrolysed composition
of its constituants.
see _
http://en.wikipedia.org/wiki/Reinforced_carbon-carbon
.
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woelen
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From all what I've read, it is not clear to me whether this is a real (new) allotrope of carbon or not. Sometimes I have the feeling that it is just
carbon, with a large amount of impurities, which make it glassy. However, if rods of this are conductive and resistant against oxidation, then of
course they would make great anodes for electrolysis.
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Rosco Bodine
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I found a patent regarding an electrolytic production
of persulfates , where the anode material specified
is glassy carbon ....so evidently this is an oxidation resistant form of carbon suitable for anodes .
US4802959
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The_Davster
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Alfa's catalog has an entire section on glassy carbon. Really expensive stuff.
A quote:
"Advantages over more traditional materials:
resistance to all wet decomposition agents
no memory effects
no contamination of analytical samples
stability to acid and alkaline melts
no wetting effects of metal melts
good resistance to thermal shock
resistive to abrisive wear
good electrical conductivity"
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Hilski
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"Carbon carbide"
I have heard the head metallurgist in the Q.A. lab at the company I work for, refer to a compound he calls "carbon carbide." I've never bothered to
ask him about it, but I wonder if it's anything like "glassy carbon"? Anybody else ever hear of carbon carbide?
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12AX7
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Wouldn't that be diamond? (In analogy to other IV-IV solids such as Si (diamond structure) and SiC (cubic).)
Saying "carbon carbide" suggests an ionic character to the structure, which is impossible with one element.
Maybe a technical ceramic, like carbon-carbon (used on the Space Shuttle) is meant.
Tim
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garage chemist
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I have seen glassy carbon crucibles in catalogues for dental laboratories, for casting (precious) metal alloys, under the trademark name "Sigradur".
It is claimed that they can even be used for melting palladium- containing alloys, which are known to take up carbon from graphite crucibles and
become brittle due to this. Seemingly not the case with glassy carbon.
They look shiny like metal, and yes they are really expensive, to the point where it would be more economic to just buy platinum wire if it's
perchlorates that one is after.
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Texium
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Thread Moved
19-11-2023 at 11:32 |
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