Microwave Plasma Generator Design
I searched the site for Microwave + Plasma and got no hits - if this has been mentioned elsewhere please merge the topic.
Here is the design and details of operation of a MW Plasma generator from:
Brooks & Douthwaite, 'Microwave-induced plasma reactor based on a domestic microwave oven for bulk solid state chemistry' (2004) 75(12) Rev. Sci.
Instrum. 5277 [http://www.york.ac.uk/res/redgroup/redsite/files/no25.pdf]
I am off to work at the moment so I haven't got a whole lot of time. However, this appears to be seriously interesting for a whole range of reactions
which have been considered to be beyond the capacity of amateur chemists
[EDIT]
The interesting reactions of which I speak include the preparation of Nitrogen Monoxide from Nitrogen + Oxygen =Plasma + Tungsten Oxide=>Nitrogen
Monoxide. Also Phosphorus from Phosphoric Acid and Carbon with plasma (use B4N as the heat adsorber). Teflon coating of substrates using plasma and
gaseous PTFE (made by heating PTFE waste to 450C+ and passing it in with the inert gas).
Also of interest would be the reduction of Silicon from silicon dioxide using carbon (silicon carbide requires a lot more carbon and a massive
increase in heat of plasma), the possibility of producing magnesium from magnesium oxide using the silicon. The preparation of boron from boric acid
and magnesium, the preparation of magnesium diboride from magnesium and boron using microwaves... etc.
Microwaves have also been suggested as a means of sintering both a & b-alumina (which had been slipcast into various shapes). It would also be
interesting to try microwave heating of aluminium in a current of nitrogen and also the same metal in a current of dry chlorine to prepare both
aluminium nitride and aluminium chloride. Similarly, boron and silicon could be heated with a current of dry chlorine/bromine to prepare the
respective halides. Finally, by heating silicon dioxide with carbon and powdered PTFE scrap it is possible to prepare sub-micrometer SiC powder at a
much lower temperature than usual (this is useful for slipcasting crucibles - use a phenolic resin, hold at 200-300C for several hours to convert the
resin to carbon and coat the lot with alkyl alkoxy silane resin (sold as sealant for concrete/stone) to form a silicon carbide crucible).
Magnesium diboride is apparently a source of borohydride (although the yeilds are abysmal), boron can be heated with nitrogen to form boron nitrides
(transparent to MW & a good heat adsorbent). Ferrosilicon can be made with silicon and iron powder, this is used by the military in mobile
generators, which generate high pressure hydrogen for weather balloons.
This looks like a seriously useful bit of kit and I would like to see how it goes. Any suggestions on how to improve the design or alternatively,
whether various parts of the design could be modified to suit other, less easily controlled microwave ovens.
[Edited on 26-1-2008 by LSD25]
Whhhoooppps, that sure didn't work
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