Microwave Heating of Metals

The lack of penetratin of electromagnetic waves into metals has been
classically well known for over a century.

There is a "skin depth" related to the conductivity of the metal and to
the frequency of the electromagnetic wave. Both high frequency and high
electrical conductivity limit the penetration of electromagnetic waves
in metals to small depth.

That is why metals reflect electromagnetic waves.

At 10 Ghz, for example, the skin depths of good metallic conductors like
Al, Au, Ag, Cu conductors are a little less than 1 micron.

http://www.ipm.virginia.edu/process/...4/chapter2.pdf

Jim

Jack Ferman wrote:
It seems to me that what happens depends on the conductivity of the metal.
A metal is a lattice of ions swimming in a sea of electrons, so when you
impose a microwave (electric vector in rotary motion) the photon-electron
interactivity coefficient (frequency dependent) the electron will be put
into motion (ie, electric current). Given the resistivity (reciprocal of
the conductivity) there will be an I-squared R loss. This energy term via
the metals heat capacity would generate some temperature rise. I do not
have the numeric databases available so can't estimate the temperature
increase.

On the other hand, I once accidently put a ceramic dinner plate that had a
decorative gold rim into the microwave. The sparking was impressive and
the grub on the plate never warmed up at all. I expect the mobility of the
gold rims electrons sucked up all the microwave energy. Someone else told
me that was a good way to burn out a microwave.

Do not induction furnaces operate at much lower frequencies.


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(sanman) wrote in message . com...
Here's something I just read about:

http://www.e4engineering.com/story.a...d-a7bd9b6a4258


So I'm wondering if this microwave heating of metals can be used for
making of glassy metals. Glassy metals are based on rapid cooling of
molten metal, causing the glassy molecular structure. From what I've
read so far, this has entailed formulating metal alloys with very low
melt points. But why can't a glassy metal be made with a very high
melt-point, by microwaving an alloy formulation to be molten at very
high temp, and quickly chilling it below a melt-point that would
itself also be quite high?

This microwave heating of metals sounds like an efficient and
controllable way to get metals to very high temperatures very quickly.
It also seems like you could cut off that microwave heating very
quickly, to facilitate the quick-chilling necessary for glassy metal
formation.

Comments?

Read the material more carefully.
It is the crucible that is heated, not the metal itself.
The coatings on the crucibles are designed to absorb the microwave
radiation, the metal itself does not.
Pragmatist.

pragmatist wrote:

(sanman) wrote in message . com...

Here's something I just read about:

http://www.e4engineering.com/story.a...d-a7bd9b6a4258


So I'm wondering if this microwave heating of metals can be used for
making of glassy metals. Glassy metals are based on rapid cooling of
molten metal, causing the glassy molecular structure. From what I've
read so far, this has entailed formulating metal alloys with very low
melt points. But why can't a glassy metal be made with a very high
melt-point, by microwaving an alloy formulation to be molten at very
high temp, and quickly chilling it below a melt-point that would
itself also be quite high?

This microwave heating of metals sounds like an efficient and
controllable way to get metals to very high temperatures very quickly.
It also seems like you could cut off that microwave heating very
quickly, to facilitate the quick-chilling necessary for glassy metal
formation.

Comments?


Read the material more carefully.
It is the crucible that is heated, not the metal itself.
The coatings on the crucibles are designed to absorb the microwave
radiation, the metal itself does not.
Pragmatist.


It seems that Uncle Al had a good observation.

Samnam does type faster than he thinks.

But, for nanotech, perhaps that isn't all bad, or else we could run out
of hype for the otherwise valuable topic.

Jim

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Builds strong minds 12 ways.
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- courteous money back
- keep bonus gifts

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