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Translucent Metal

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Adam Munich

Mon Feb 21 2011, 09:24PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
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I was jiggling my jar of mercury and noticed some bubbles. Of course they did not last long, but they lasted long enough for me to notice that they are opaque.

I was wondering, at what thickness do metals become translucent? Or are they opaque, even down to layers one atom thick?

Patrick

Mon Feb 21 2011, 11:05PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Ive been told that the gold on space helmet visors are a few gold atoms think.

"Scotty told Kirk that 1 inch of transparent aluminum could hold back all the ocean water to float a whale"... if that helps?

Proud Mary

Tue Feb 22 2011, 09:29AM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
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"(The) tradeoff between transparency and electrical conductivity limits the range of feasible metal thicknesses to 10â€“20nm. At the low extreme, it can be difficult to maintain film continuity because the metal tends to aggregate into droplets on glass and plastic, while at the high end transparency suffers."

Shtein, Max, Thin metal films as simple transparent conductors, SPIE Newsroom. DOI: 10.1117/2.1200912.1848 28, December 2009

Patrick

Tue Feb 22 2011, 06:03PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

He never said anything about conductivity.

Bored Chemist

Tue Feb 22 2011, 07:38PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
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I suspect they obey the Beer Lambert law for any thickness.

Patrick

Tue Feb 22 2011, 08:09PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Bored Chemist wrote ...

I suspect they obey the Beer Lambert law for any thickness.

Mmmmm...Beer.

So after a search of wiki, I presume you mean that transparency is an inverse funtion of attenuation, and that attenution is approxmately constant relative to thickness (until extinction), thus transparency could be possible in the single or dozens of atomic diameters? Though it would clearly depend on the identity of each metal.

...

Wed Feb 23 2011, 07:51AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

My understanding is that a metal will become opaque when the layer has enough conductivity that it can effectively reflect an incoming electromagnetic wave. At optical frequencies and any metal I can think of the skin depth has to be taken into account, so as long as the metal is on the order of the skin depth at 500THz (middle of the visible spectrum) it will be transparent. The skin depth for gold at 500THz is about 4nm, so we are at least within an order of magnitude of the other answers.

IntraWinding

Wed Feb 23 2011, 09:59AM

Registered Member #2261 Joined: Mon Aug 03 2009, 01:19AM
Location: London, UK
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Gold leaf is apparently transparent and appears green.

I've personally seen a gold (I assume) coated wine glass that appeared green when held up to the light.

Bored Chemist

Thu Feb 24 2011, 08:29PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Gold leaf is transparent to green light and is about 100 nm thick.

The point I was making is that the fraction of light that gets through particular thickness ( at a given wavelength) is constant. That's the Beer Lambert law.
So, if a tenth of the light gets through our 100 nm gold leaf example (the rest being reflected or absorbed) then a hundredth of the light will get through 200 nm and a thousandth through 300 nm. Only 1 photon in 10 billion will get through a micron, but that's still not zero. Of course 1 in 10^20 will even get through two whole microns.
(Actually, I suspect the fraction that gets through gold leaf is rather less than 10% but that's not the point.)

In principle, with a bright enough lamp on one side and a good enough detector on the other side, a steel girder can be shown to let light through.

PresentTeck

Sun Jun 05 2011, 03:19AM

Registered Member #3922 Joined: Thu Jun 02 2011, 06:24AM
Location:
Posts: 23

It's not so much the thickness as the molecular structure that makes it transparent.

glass is made primarily from quarts sand (powder) witch is a white powder, you fire it correctly and it becomes transparent due to the chemical change at that temperature.
but you already know that...

what you didn't know is that if you do the same with aluminum powder it will be transparent too. it's mixed with a few other things (oxygen and nitrogen I believe) witch technically makes it a ceramic, but it's a lot of really strong aluminum thats transparent so close enough.

What it is:

specs from the company:

The process:

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