Carbon Black EM Enclosure
Carbon Black EM Enclosure
(OP)
Is it possible to use "carbon black" or materials containing it to produce an EM enclosure that will act as a cavity resonator? If so, any info on permissible freq ranges?
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RE: Carbon Black EM Enclosure
<nbucska@pcperipherals.com>
RE: Carbon Black EM Enclosure
Second, many electrically conductive polymers and composites are effective EMI shields, thus demonstrating they have electrical properties that emulate metals, and many of these do not contain metal additives.
Third, I am constantly reminded that metals have very low DC resistance, but then at even moderately high frequencies it is the "skin effect" conductance that is important, thus the AC resistance is the factor to be considered.
In conventional metal waveguides the following has been found to be true, "The distribution of current density in the surface of the conductor will vary with depth into the conductor according to an exponential law (Skin depth)."
One might think the conductive bonds in non-metallic conductors act in the same manner. I find that this issue is being studied at the following sites:
http://www.physics.ohio-state.edu/~ppl/shield.html
"Applications of polymers and molecular magnets - low frequency electromagnetic shielding and resonators/absorbers"
and at:
http://www.zipperling.de/Research/Synthmet/Part_A4.html
where they have found, "At high frequencies, by contrast, the measured shielding efficiency tends to increase with frequency earlier than theoretically predicted."
RE: Carbon Black EM Enclosure
I suggest you use a carbon filament or carbon mat material. These, when embedded in a resin still mmaintain their electrrical conductivity properties.
have used carbon tissue and carbon mat for years to make carbon reinforced plastic reflectors and waveguides. I have used the waveguides through 5 Ghz and the reflectors through 40 gHz. I have not tried to use them as waveguide above g5 gHz because I had no need. I see no reason why they would not work.
This should work efficiently as a screening material.
Gene Augustin
TECHNICAL SYSTEMS ASSOCIATES
http://www.tsa-orlando.com
RE: Carbon Black EM Enclosure
It appears that a crude waveguide could be made by "painting" a layer of carbon on a dielectric, and it could be very thin.
Thanks FrankM
RE: Carbon Black EM Enclosure
rgds
Zeit.
RE: Carbon Black EM Enclosure
I you want an inexpensive shielding material, you can buy aluminized mylar film in rolls. It is a vapor deposited film of aluminum on mylar. If you dont crinkle it, it works fine. It becomes relatively transparant if you crinkle it.
Gene Augustin
TECHNICAL SYSTEMS ASSOCIATES
http://www.tsa-orlando.com
RE: Carbon Black EM Enclosure
http://www.marmoset.net/radio/howto/aquadag/
http://www.tpub.com/content/neets/14178/css/14178_89.ht...
Using "carbon paint" in a search identified many product varieties. Thanks 'zeitghost' and Gene Augustin for your help.