Assume that the CH4 is using as a hydrocarbon in CCVD process and maximum temperature can be reached by CVD chamber is 900°C, consideraing that the decompositio temperature for CH4 is almost 1200°C, what are your suggestions in order to decompose the CH4 in lower temperature? Do you think this can be done by partial pressure manipulation?
Hi Roham,
Try a plasma chamber to create active CH3+, CH2+ etc particles. This is a non-equilibrium method and you can run the gas through the plasma at room temperature. This idea is used in PECVD (plasma enhanced chemical vapour deposition) and there is a lot of literature on this subject.
Hi Peter,
Thank you so much for your advice, but actually I am trying to find another way instead of using Plasma enhanced CVD, that is a challenging part , maybe not for a specialist but at least for me.
If you don't want to use plasma's there might be active surfaces or katalysing surfaces (Pt, Re, TiO2) which might help to decompose CH4 at lower temperatures.
As Peter has rightly suggested methane can be decomposed at much lower temperature using the catalysts. I would suggest Pd or Pt as the catalyst which is very effective for this purpose. Although Pd and Pt are quite expensive but they can be used for long without deterioration and no other complications.
Hi Basu,
I would like to appreciate time and your suggestion,
I am working with CoMoCat Cobalt-Molybdenum, I actually in the middle of a project which has started with a defined catalyst configuration of Co-Mo , therefore I can not again change the catalyst, as you said, that is right, Pt is always really promissing but it is not to be honest really right choise when we want to talk about cost through the mass production, that is why i began with this catalyst system, it was actually quite good up to now, but recently I starting to use another hydrocarbon(CH4) and it seems like due to high decomposition temerature, not sufficient carbon can accomulate on the the built nanoparticles and costruct CNTs. But I will once more thank you very much that you took your time and answer.
at the moment I am trying to find some relations between partial pressure and temperature
eg; lets assume you can change the boiling point of the water by changing the concetration of pure water when you add salt. That also may be fallowed in CVD process! or at least I am hoping.
Hi Roham,
I understand that you have finalized the catalyst system in your project. otherwise I would have suggested you Cu catalyst which is economic and easy to deposit enough carbon atoms ( in the nano form on CNT. We have used Cu thin films ( by e-beam evaporation) deposited on oxidized silicon substrate for graphene nano thin film formation by CH4 decomposition and obtained good results.
The volume ratio of methane and the carrier gas ( argon or nitrogen) may be optimized to control the partial pressure of methane in the CVD reactor for optimum carbon deposition (by methane cracking).
Hi Mr. Basu,
I really appreciate your time and consideration, and I will appreciate your answer.
Hello Roham,
Very interesting question and discussions! I could maybe provide some of my insights. I perform CVD of graphene on copper at 1000 C but haven't tried to go to lower temperatures.
It's interesting to know that by using catalysts one can reduce the decomposition temperature of methane. However, since it is known that Pt and Pd can be used as CVD graphene growth substrates. In this regard, it would be curious to know if the catalytic effect of the substrate is affected once it is covered with layer/s of CVD graphene on it. Albeit, the latter holds only for a non-oxidizing environment.
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