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kkeerroo
Experienced Roboteer
Joined: 17 Jun 2004
Posts: 1459
Location: Brisbane
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Since there are apparently some well known people who have seen this effect I thought I would try searching for it on google but was unable to find anything.
So I searched for some info on why certain materials are trnaparent and others arn't. Here's a good website
http://science.howstuffworks.com/question404.htm:
For those who only want to read the good bits here's a cut and paste job:
"Another factor happens at the sub-atomic level. The atoms that bind together to make the molecules of any particular substance have electrons, usually lots of them. When photons come in contact with these electrons, the following can occur:
* An electron absorbs the energy of the photon and transforms it (usually into heat)
* An electron absorbs the energy of the photon and stores it (this can result in luminescence, which is called fluorescence if the electron stores the energy for a short time and phosphorescence if it stores it for long time)
* An electron absorbs the energy of the photon and sends it back out the way it came in (reflection)
* An electron cannot absorb the energy of the photon, in which case the photon continues on its path (transmitted)
Most of the time, it is a combination of the above that happens to the light that hits an object. The electrons in different materials vary in the range of energy that they can absorb. A lot of glass, for example, blocks out ultraviolet (UV) light. What happens is the electrons in the glass absorb the energy of the photons in the UV range while ignoring the weaker energy of photons in the visible light spectrum. If the electrons absorb the energy of any portion of the visible spectrum, the light that transmits through will appeared colored according to the portion of the spectrum absorbed. In fact, the color of any object is a direct result of what levels of energy the electrons in the substance will absorb! "
So for metal to become transparent when it is heated a change would need to take place within the atomic structure of the metal to stop the electrons from absorbing the incoming photons. Since to do this you would need to remove
all
of the free electrons from the metal it doesn't sound possible to me. The removal of the free electrons would also stop the metal from glowing but isn't that part of the story?
Strange, didn't I read that someone was arguing that it was the free electrons causing the metal to become transparent?
I also deceided that since the concept seems so apealing then someone somewhere would be getting paid to research it. Here is what I found in the way of "clear" metals:
The U.S. Air Force has spent billions of dollars researching transparent armour for their aircraft. The latest stuff they are playing with is aluminum oxynitride (ALONtm). It is a clear aluminium based ceramic that can stop a .50cal armour piercing round but since it is a ceramic it doesn't count.
http://www.scienceblog.com/cms/air_force_testing_new_transparent_armor_9113
A German university has also been looking into clear Aluminium oxide panels but again this a cermic not a metal.
A very common clear "metal" is that used in ESD safe bags (the silver bags electronic componants come in). But looking at Descos Material Safety DataSheet for their ESD bags you can see that it is actualy a metallized polyester and therfor a plastic.
http://desco.com/pdf/tb-7024.pdf
The best transparent metal I could find is a aluminium foam. The theory is if you can create enough "bubbles" in the metal then you should be able to see through it. To me this sounds like trying to look through a foam mattress.
But Star Trek fans are convinced that clear aluminium is possible because they saw it on TV. _________________ Get Some!!!
Secretary of the Queensland Robotics Sports Club inc.
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Thu Nov 10, 2005 7:25 pm |
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