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Registered Member #1084
Joined: Mon Oct 29 2007, 08:58PM
Location:
Posts: 28
i am trying to make a vanadium redox cell, but am stuck for a vital part. i need some 1/4 inch/ 5 mm thick graphite felt. the only response i have had from anyone has a 8 month backlog. i need a couple of pieces around 2 inches square before i can proceed any further. it seems almost impossible to get in the UK. the world production seems to be going to Boeing and Airbus for making aircraft wings and the industry haven't caught up yet.does anyone in the US know where to get any. of course it might all end in tears anyway, but i need the small pieces to even start the process.
Registered Member #1084
Joined: Mon Oct 29 2007, 08:58PM
Location:
Posts: 28
that wouldn't work. the idea is to get as much surface area as possible. graphite blocks used to be used but the surface area was very low. you need as much surface area as possible in contact with the electrolyte. i could use graphite blocks but the energy density would be very low. the reason i want to use graphite felt is that i need to bond it to a sheet of polythene to form 2 sides of each cell. the higher the energy density the less ,very expensive, proton exchange membrane i need to buy. carbon felt might work but is chemically inferior and leaches out into the electrolyte from what i have read. it might do to just test if i can do the process. graphite can be treated to work by boiling it in concentrated H2SO4 for 5 hours then baking at 600 degrees in a inert atmosphere but that is a bit beyond my kitchen sink chemical lab. here is a link to the process i want to use.
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
I don't know anythings about this felt but if the fibres are thhe same diameter as those in the cloth then the area is proprtional to the mass. If that's the case then the same weight of cloth will give you the same area. There might be an issue with diffusion limited current. If you wanted I guess you could get the cloth, unweave it to get fibres then felt them together. The CF cloth is made by baking the precursor at very high temp so it's pretty pure carbon.
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vanadium redox battery
then baking at 600 degrees in a inert atmosphere 
but that is a bit beyond my kitchen sink chemical lab. 