Nickdul - 22-12-2013 at 04:15
I'm not sure if this is a novel idea or is it viable at all, but I just discovered a quick and dirty way to get carbon filaments and succeeded in
making simple heating elements using it.
I had some broken carbon fishing rods and extracted the carbon fibers by chucking them in a coal fire to burn out the bonding agents and get to the
delaminated layers of carbon cloth in them. I ended up with long thin strips that I intend to use for another project, but at first I checked
resistivity and connected them to a variable DC source. I could easily get 5-8 inch strands to heat up to red hot without breaking. Wrapped around a
test tube with no insulation, 12V@1.5-2Amps, they quickly boiled water.
I haven gotten around to weaving them into some fiberglass cloth for a DIY mantle/hotplate, but I don't see why it would be impossible to do. The
result should be a thin, nonmagnetic heating cloth that could be used with magnetic stirrers or wrapped around RBFs. I'm thinking of either a
low-volatge, high current setup with parallel connections, or get the fibers wired up in series and use a variac, dimmer switch to control the power.
It's a fairly simple idea and I couldn't find any similar projects on the web, so I though I'd share.
Mesa - 22-12-2013 at 17:56
http://scholar.lib.vt.edu/theses/available/etd-03282006-1011...
Ignoring, for a second, the fact that this author is using some polymer resin/carbon fibre composite(and therefore is restricted to temps below 200*C)
the sheer detail and amount of useful information in that link is pretty impressive.
Nickdul - 23-12-2013 at 04:04
Thanks for referencing to that document. I currently am up to my neck in university application work, but I'll make sure to examine it and do some
actual testing. I feel that the idea is worth considering, especially because carbon fibers are flexible and it seems easy to make mantles and heating
pads without having to wind meters of nichrome wire.
Nickdul - 29-12-2013 at 15:55
Proof-of-concept tests were carried out. Carbon fiber strands of fixed length and varying cross section area were tested with DC voltage between 5 and
12v. It has become clear that proper contact between the carbon fibre strips and conducting copper wire/plates is essential.
The material handles high temperatures well and begins to lose weight after prolonged heating above 350C. Strands of cross section between 1 and 4
mm^2 were tested and all were found capable of handling up to 4.5W/cm over a period of at least 12h without variations in resistance or weight.
A very crude hotplate was improvised on a ceramic tile 10cmX10cm wide. Woven 300g/m^2 fiberglass cloth was cut to size and 6 10cm strips of carbon
fiber were stapled to it and connected in parallel with bare copper wire, once again using regular paper staples as a means of attachment. This was
laid on the tile, covered with a thin fiberglass layer and a 2mm thick aluminum plate. Power at 12V - 120W (approx. 45% of tested possible capacity) ,
holding steady for about 10min. However, the method of attachment caused improper contact between the carbon elements and the copper wire, so that
needs to be sorted next.
[Edited on 29-12-2013 by Nickdul]
*FWOOSH* - 30-12-2013 at 23:14
Very interesting, keep up the good work!