krfkeith
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Location: Utah, United States
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Making Glassy Carbon?
So I've been trying to figure out a way to make glassy carbon to make a crucible out of it for some experiments that would otherwise require things
like platinum or iridium crucibles. Obviously, either of those are far too expensive, but then so is glassy carbon! Nevertheless, it is at least
conceivable one could make glassy carbon themselves, whereas figuring out how to transmute something into platinum is, well, shall we say, a bit out
of reach for the amateur  .
2spi materials sells glassy carbon crucibles and is to my knowledge, the only place online that sells them that lists the price and doesn't require
you to request a quote (or, in other words, make up a price on the spot to see what they can gouge out of you). The problem is, these are still very,
very expensive. I was able to find a 0.3 mL crucible on their site somewhere for $18, but they have a minimum order of $50, so that does no good.
This thread: http://www.sciencemadness.org/talk/viewthread.php?tid=17370 made mention of it, but it didn't mention if anyone had any success, or their methods.
I found a few patents and articles, but all require the use of phenol-formaldehyde resin. It's nearly impossible to find, none of the articles specify
what type is needed anyway, and making it from scratch is off the table.
Please help! I'm at my wits end. Any suggestions are most appreciated.
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WGTR
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The synthesis of glassy carbon requires phenol, formaldehyde, and concentrated ammonia.
http://onlinelibrary.wiley.com/doi/10.1002/masy.200900127/pd...
It doesn't sound that hard, really.
In the first step Bakelite is produced. At 80°C, 15g of phenol is stirred with 49mL of formaldehyde and 9mL of 38% ammonia until an opaque solution
is obtained.
The solution is allowed to cool down, and the liquid discarded from above the thick layer left at the bottom. The bottom layer then is heated at
60°C for 30 minutes.
Once the color changes to a thick, clear, yellow syrup; this is transferred quickly to a glass mold, where it is heated at 75°C for 24 hours.
From there the glassy carbon is made. In the article they did this under nitrogen flow in a furnace. During the heating process there is
off-gassing from the material,
and the nitrogen flushes it away. There are probably other ways to accomplish the same thing. The most important thing probably is that an inert
atmosphere is needed,
and allowance needs to be made for the gasses to escape. Perhaps doing this in a covered crucible, with charcoal over the top of the resin, would
work.
The most significant part of this process is the heating time. This isn't something that you do with a propane torch in a few minutes of time. The
process releases gasses.
If you want a solid piece of glassy carbon, heating needs to be done very, very, slowly. The heating rate used by the authors was 1°C per minute,
with hold times at
various temperatures. The temperature was ramped from 25-200°C, held at 200°C for 3hours, ramped from 200-600°C, held at 600°C for 24 hours,
ramped from
600-1000°C, held at 1000°C for 2 hours.
The thinner your piece of bakelite, the easier it is to degas successfully.
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macckone
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Bisphenol resins should be usable. But given the reqired temperature scheme, it is going to be easier to buy unless you need a large crucible.
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macckone
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Dang duplicate post. Some epoxy bisphenol resins are high molecular weight and will yield a high carbon item.
[Edited on 1-4-2014 by macckone]
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wg48temp9
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I have frequently made charcoal by heating a closed (except for a small hole) tin can of saw dust to redness in a garden fire. When I open the can
there is frequently a shiny thin (<0.1mm) black coating on parts of the inside of the can. My last batch also had some similar looking flakes
on the top of the charcoal that I suspect flaked off the top of the can. The can was an empty food can that has a plastic coating on the inside which
may be the source of the metallic looking material. It could also be deposited from the decomposition products of the wood. I wounder if its glassy
carbon. I will reuse a can and see if the metallic material forms again.
The pic below shows some of the charcoal left and some of the metallic flakes with charcoal on the right. it was difficult to make electrical contact
with metallic flakes to measure the resistance but I eventually succeeded by placing a flake between two drops of salt solution. About 2 Megohm and
about 3 Megohm for a charcoal flake. Give the charcoal was much thicker I conclude they have similar resistance.
Pic to follow problems with down loading it.
I am wg48 but not on my usual pc hence the temp handle.
Thank goodness for Fleming and the fungi.
Old codger' lives matters, wear a mask and help save them.
Be aware of demagoguery, keep your frontal lobes fully engaged.
I don't know who invented mRNA vaccines but they should get a fancy medal and I hope they made a shed load of money from it.
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