I just became familiar with the existence of pyrolytic graphite and its diamagnetic properties. Magnetic suspension without power has long been an interest of mine so i was disappointed to find out that pyrolytic graphite is so hard to produce. As I understand it, it is usually produced by cracking methane on a hot ~1000C catalytic surface at low pressure. I was wondering though. Wouldn't benzene or maybe a PAH be more suitable since it would naturally by closer to the final desired structure. Each deposition event would transfer 6 times the carbon, and I would hope that the Pi orbitals would tend to align the molecule with the substrate. Does anybody know if this has been tried? A brief google search didn't turn up anything for me.
The field of pyrolytic graphite is at least 50 years old.
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> Pyrolytic graphite is not really new since its discovery dates back to Thomas Edison, however, this class of refractory materials has been rediscovered recently because it possesses certain desirable properties at extremely high operating temperatures, including a high strength to weight ratio, low oxidation rate, and a low transverse coefficient of thermal conductivity. =========================
In that time, a lot of things have been tried, probably what you suggested with benzene but benzene vapor is fraught with health hazards- more so than methane.
On the other hand, the thought of depositing single carbons from methane has the opportunity to produce more perfect "graphitic" alignments than adding as many as six carbons all at once. These hypothetical "carbon clumps" may or may not lead to massive planar deposits instead of more disorganized deposits.
A paper indicates that benzene based aerosols might be good new sources for nanotubes via pyrolysis.
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I found this in a patent from the 1980's
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Any hydrocarbon gas which typically yields pyrolytic carbon and/or pyrolytic graphite upon heating or cracking, may be used to make the pyrolytic carbon and pyrolytic graphite, respectively. Typical hydrocarbon gases which may be used in the process of the invention, include methane, ethane, propane, butane, acetylene, benzene, toluene and the like. The gases may be purified and/or dried in any conventional manner as desired by any method well known in the prior art. Auxiliary gases such as hydrogen, oxygen and the like; mixtures of hydrocarbon gases; and diluent inert gases, such as argon, nitrogen and the like, can be used in the process of the present invention as long as the heated gas or gases can form a pyrolytic carbon which penetrates the foam and covers the surface of the foam, and as long as the gas or gases can form a pyrolytic graphite which can be deposited upon the pyrolytic carbon-covered-and-penetrated foam material. The preferred hydrocarbon gas is methane. Although the preferred embodiments utilize the same hydrocarbon gas for forming the pyrolytic carbon and for forming the pyrolytic graphite, it is possible in accordance with the present invention to utilize one gas or mixture of gases for forming and depositing the pyrolytic carbon and a different gas or mixture of gases for forming and depositing the pyrolytic graphite. Thus, for example, propane gas may be used to form the pyrolytic carbon, and methane gas may be used to form the pyrolytic graphite.
> Pyrolytic graphite is not really new since its discovery dates back
I did, but I assumed the nanotube production wasn't necessarily a good generalization for mass quantities of pyrolytic graphite and also it seemed to be a cya patent rather than a real study of optimization techniques.
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