Method of production of fluorinated carbon nanostructures
A method for the production of fluorinated carbon nanostructures such as carbon black is disclosed, wherein a plasma is generated in a plasma chamber and a fluorocarbon, or a fluorocarbon containing mixture, is supplied to the plasma to convert at least some of the fluorocarbon into a fluorinated carbon material. Direct pyrolysis of a fluorocarbon, or a mixture containing this, provides a one-step method for producing fluorinated carbon nanostructures with a formula CF x , where 0.06<x<0.15, the particles having a relatively narrow spread of diameters, and exhibiting excellent hydrophobicity.
1. A process for producing a fluorinated carbon material comprising the steps of:
generating a plasma in a plasma chamber; and
supplying a fluorocarbon or a fluorocarbon containing mixture to the plasma whereby at least some of the fluorocarbon transforms by direct pyrolysis to a fluorinated carbon material which comprises or consists of fluorinated carbon black (FCB having the general formula CF x , where x is ≧0.8 and is in the form of nanometer sized particles and/or agglomerates thereof.
2. A process as claimed in claim 1 , in which the step of generating a plasma comprises:
supplying a plasma-forming fluid to an input of the plasma chamber;
flowing the plasma-forming fluid to a plasma region of the plasma chamber; and
supplying electromagnetic energy to the plasma chamber so as to maintain the said plasma from the plasma-forming fluid, in the said plasma region.
3. A process as claimed in claim 2 , in which the step of generating a plasma further comprises concentrating the electromagnetic energy so as to establish the plasma.
4. A process as claimed in claim 2 , in which the step of flowing the plasma forming fluid to the plasma region comprises passing the plasma-forming fluid through a fluid manifold, which manifold is adapted to introduce vortical motion into the plasma-forming fluid downstream of the plasma chamber input.
5. A process as claimed in claim 2 , wherein the plasma-forming fluid comprises or consists of an inert gas.
6. A process as claimed in claim 5 , wherein the plasma-forming fluid comprises or consists of helium and/or argon.
7. A process as claimed in claim 2 , wherein the plasma-forming fluid comprises or consists of nitrogen or a nitrogen-containing gas.
8. A process as claimed in claim 2 , wherein the electromagnetic energy has a frequency in the RF or microwave range, and wherein the output power is between 2.5 and 3.5 kW.
9. A process as claimed in claim 2 , wherein the plasma forming fluid is supplied at a rate of between 20 and 40 liters/minute.
10. A process as claimed in claim 1 , further comprising mixing the supplied fluorocarbon or fluorocarbon-containing mixture with the plasma in a mixing chamber forming a part of the plasma chamber.
11. A process as claimed in claim 1 , wherein the fluorocarbon is perfluorinated or partially fluorinated.
12. A process as claimed in claim 11 , wherein the fluorocarbon consists of or the fluorocarbon containing mixture comprises 1,1,1,2-tetrafluoroethane (HFC-134a), hexafluorobenzene (C 6 F 6 ) or perfluoromethylcyclohexane (C 7 F 14 ), including mixtures of two or more thereof.
13. A process as claimed in claim 1 , wherein the plasma is maintained at a pressure which is substantially at or above atmospheric pressure.
14. A process as claimed in claim 1 , wherein x is between 0.05 and 0.30.
15. A process as claimed in claim 14 , wherein x is between 0.06 and 0.15.
16. A process as claimed in claim 1 , wherein the fluorinated carbon material also includes a dopant selected from one or more of chlorine, nitrogen and oxygen.