I am trying to prepare expanded graphite. During literature review, I came across heat treatment, ultrasonic irradiation and microwave irradiation as methods of expansion after intercalation. Due to lack of appropriate equipment, I was wondering if I could substitute microwave irradiation with heat treatment using a muffle furnace?
Also, I realize this might come off as a very unintelligent question, but I'd be glad if I could get any help here!
Expansion is more efficient if the chemicals intercalated between the carbon layers turn to gas very quickly, thereby producing the separation of the graphite flakes and hence the expected increase of volume. Therefore, temperature alone is not enough. The risk in a muffle furnace is that the heating is not fast, producing a quite low expansion, if not negligible. Alternatively, if you suddenly introduce the intercalated graphite in the muffle furnace already hot, the corresponding movement of air will make the resultant "black snow" hover in air, and it will be very difficult to recover the particles. Moreover, their rather long residence time in the furnace is not good either, as the particles will start to oxidize. Finally, the sulfuric acid thus released will attack the resistances of your furnace !
So, definitely, I would not use of muffle furnace. If you are not suitably equipped, I recommend the good, old method: passing the graphite intercalation compound throughout a hot flame. The thermal shock will be correct for a good expansion, and the residence time will be quite short. A Bunsen heater, or better a Mecker heater (more powerful), fed by ordinary gas (methane or propane) will do it.
Alain
Expansion is more efficient if the chemicals intercalated between the carbon layers turn to gas very quickly, thereby producing the separation of the graphite flakes and hence the expected increase of volume. Therefore, temperature alone is not enough. The risk in a muffle furnace is that the heating is not fast, producing a quite low expansion, if not negligible. Alternatively, if you suddenly introduce the intercalated graphite in the muffle furnace already hot, the corresponding movement of air will make the resultant "black snow" hover in air, and it will be very difficult to recover the particles. Moreover, their rather long residence time in the furnace is not good either, as the particles will start to oxidize. Finally, the sulfuric acid thus released will attack the resistances of your furnace !
So, definitely, I would not use of muffle furnace. If you are not suitably equipped, I recommend the good, old method: passing the graphite intercalation compound throughout a hot flame. The thermal shock will be correct for a good expansion, and the residence time will be quite short. A Bunsen heater, or better a Mecker heater (more powerful), fed by ordinary gas (methane or propane) will do it.
Alain
Thank you so much Alain! I had absolutely no idea we could pass graphite over a flame. This would make things much easier for me. Really appreciate the help!
Just be careful about the very corrosive vapours that you'll generate, and think about a box for recovering the expanded graphite particles that we fly everywhere ... Not that easy in practice !
Alain
Dear Vidisha,
I highly recomend you to check Robert Murray-Smith work. He comes from the UK. I am following his work for the last two years and it is really interesting.
Dear Alain,
Would it be possible to do it with a big fresnel lens?. They are really powerful. Maybe too much. Here I would also recommend Dan Rojas work, from USA, master of fresnel lenses.
Thanks!
https://www.youtube.com/channel/UC4AkVj-qnJxNtKuz3rkq16A
https://www.youtube.com/channel/UCQ9e0JHba7ApNz_-HL-p_6A
To Miguel: I confirm that exfoliated graphite was successfully prepared in a solar furnace in France (at Odeillo) by concentrating solar power on GIC samples. But it is really not a device that is easily available !!! Better trying to find a MW oven !!
Alain
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