Microwave Heating of Metals

Here's something I just read about:
http://www.e4engineering.com/story.aspx?uidL3a6d3e-41d5-434e-9831-7c377b02a891&cuid น6dad81-0ef4-4fcc-9e3d-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.
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sanman wrote:

http://www.e4engineering.com/story.aspx?uidL3a6d3e-41d5-434e-9831-7c377b02a891&cuid น6dad81-0ef4-4fcc-9e3d-a7bd9b6a4258
quickly.
Read carefully, not the metal is heated directly, they create a microwave plasma around the part to heat it. Such a system has no benefits for rapid cooling, compaerd to an induction heater for example. It is just a very uniform heat source without the insulation needs of a conventiunal furnace.
if you want an amorphous alloy that works without crazy cooling rates, read here :
http://mrsec.wisc.edu/edetc/IPSE/educators/amMetal.html
You will not be able to make it at home. Don't try to heat the stuff outside of a vacuum or inert gas furnace or you will get a nice highly toxic firework.
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snipped-for-privacy@yahoo.com (sanman) wrote in message

http://www.e4engineering.com/story.aspx?uidL3a6d3e-41d5-434e-9831-7c377b02a891&cuid น6dad81-0ef4-4fcc-9e3d-a7bd9b6a4258
Microwaves are generally reflected off of metals. I have found google links for microwave sintering of powdered metals. I don't truely understand how microwaves sinter powedered metals. I suspect that it would be a very dangerous thing to attempt without an inert atmosphere.
Now for non-metals, microwaves can facilitate ultra rapid volumetric heating. These guys have some interesting (if not sparse) info about using a gyrotron source for ceramic sintering http://www.gyrotrontech.com /
If you want rapid heating of metals you need an inductance heater. Check this out http://ameritherm.com/videoindex.html
Inductance heaters can utilize a range of operating frequencys. Lower frequencys seem to heat from the inside out, higher frequencys seem to heat the outer surface.
Maybe you could couple a non-conductive coolant to the metal part as it is heated by a low frequency inductance heater.. Just a thought
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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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snipped-for-privacy@ties.k2.mn.us (Jack Ferman) wrote in

A loop of metal in an RF field tends to look like a short circuit. Try it with loosely crumpled aluminum foil. (Actually, don't!) Food seems to be innately higher impedance, and the mass is greater than a thin gold foil so heating is much slower, and less spectacular. It's not nuclear physics, just basic RF electronics.

I think so, but probably still in the RF range.
--Damon
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Damon Hill wrote:
<snip>

Depends on size/power requirements but generally 50/60 Hz for melting several tons, audio frequencies for for small melts (eg dental) going up to ~ 1MHz for welding/surface hardening.
--

regards

jc

LEGAL - I don't believe what I wrote and neither should you. Sobriety and/or
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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/PVD/Pubs/thesis4/chapter2.pdf
Jim
Jack Ferman wrote:

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snipped-for-privacy@yahoo.com (sanman) wrote in message

http://www.e4engineering.com/story.aspx?uidL3a6d3e-41d5-434e-9831-7c377b02a891&cuid น6dad81-0ef4-4fcc-9e3d-a7bd9b6a4258
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.
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pragmatist wrote:

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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