Comments on: Transparent Aluminum

By: russell s

russell s — Fri, 28 Jul 2006 07:42:09 +0000

tranparent aluminium=Si6O12Al2
i may not be a trekie
but i made transparent aluminium in my lab
it is strong and light waight…
after it is heated …cool it with O2 gas
to cause the SiO2 to bond in a crystal matricswith the Al..
beware the cooling is some what expolsive.
but the results are great.

By: JediBear

JediBear — Tue, 10 Jan 2006 11:55:19 +0000

Pay attention to what the guy actually said.

“The substance itself is light-years ahead of glass,â€

He’s not using light-years as a measure of distance or time but /technological progress/.

There aren’t any units for that, or any firm measure for it, but in modernistic thought, we tend to think that technology gets better as time goes on — thus “years” might be an acceptable measure of progress — being a measure of time.

What doesn’t fit is light-years. I can’t imagine any way to measure technological progress in terms of distance.

There’s also the fact that what he said, with the word ‘light’ removed drops to the level of the fundamentally obvious — of /course/ it’s more advanced than glass. Glass has been in use for hundreds of years.

A better sound bite might have been “This material is years ahead of even the most modern applications of glass.” Which would at least have left the poor guy sounding a little more educated.

As an aside, I /have/ read a book in less than two hundred miles — I was on a car trip at the time.

By: Matt Opitz

Matt Opitz — Wed, 04 Jan 2006 16:43:23 +0000

Space shuttle tiles (we had one we used for “show and tell” when I was at Penn State) are basically chunks of compressed glass foam. Now that doesn’t mean it’s “foamy” like soap, just that it’s more air than solid. The particulate part of the foam was very very fine, like chalk dust almost. We did a demonstration where one of us would stand with a space shuttle tile in our hand while another person blowtorched the opposite side for minutes at a time. You could feel the heat radiating from the top side of the tile and yet the bottom, where your hand was, would still be room temperature. Pretty cool stuff. But to answer the question, AlON armor is absolutely nothing at all like space shuttle tiles.

By: Wayne VanWeerthuizen

Wayne VanWeerthuizen — Wed, 04 Jan 2006 06:05:14 +0000

An loose analogy may help to explain how some substances are transparent. When the aluminum has its “hands” free, it can catch passing photons; but when it is holding on to adjacent oxygen atoms, it no longer has a free “hand” to catch the passing photon with.

By “hand”, I rather mean available energy levels for its electrons. The molecule needs to have a particular energy level available to it in order to “catch” a particular frequency range of light. The formation of chemical bonds affects the energy levels that are available to each atom.

Of course, reality is more complicated than this, but this should be enough to get the basic idea across. If you investigate it much deeper, you are likely to find yourself studying a subject called Quantum Electrodynamics, or QED.

By: Irishman

Irishman — Tue, 03 Jan 2006 22:26:12 +0000

Tim G Said:
>I wonder how this material compares to what is used on the space shuttle.

I imagine not very well. You’re thinking the durability and it being a ceramic, right? I think it’ probably still fairly heavy in comparison to shuttle tiles. About half the weight of glass for this new stuff? I’m not certain on the details, but glass is pretty heavy stuff, and shuttle tile material is interspersed with air to help with the weight and thermal mass issues.

By: Irishman

Irishman — Tue, 03 Jan 2006 22:22:29 +0000

Pssst, Phil, I think the guy’s name is Lt. La Monica.

By: Matt Opitz

Matt Opitz — Tue, 03 Jan 2006 14:22:31 +0000

OK, I’m a materials engineer, specifically a ceramic engineer, and this whole “transparent aluminum” thing really irks me for some reason. Aluminum is a metal. Aluminum oxynitride is a ceramic. They are nothing at all alike or even “similar”. Saying that this armor material is transparent aluminum is like saying that rust, which is iron oxide, is merely “red steel”, or that the pigment they use for white paint (titanium dioxide) is actually “white titanium”. They’re completely different things! You will never have “transparent aluminum” because the metallic bonds in aluminum (and other metals) allow enough free electrons (well, free enough) in the structure to absorb any incoming photons due to resonance of the electrons with the incident electromagnetic fields. This is why metals are completely opaque. You CAN, however, have transparent ALUMINA (the common name for aluminum oxide, or sapphire) or aluminum oxynitride, which is what they talk about in the article. The ionic bonds in AlON not only don’t result in any free electrons that would resonate with the incoming light photons’ frequencies, but are also arranged such that they (the bonded ion pairs themselves) don’t resonate at those frequencies, either, making the material transparent at visible light frequencies for large single crystals of the materal or when the crystallite size is large enough for a polycrystalline version of the material (grain boundaries in polycrystalline ceramics act as scattering sites due to lattice mismatches at the boundaries).

Oh and one more nitpicky thing, alumina is Al2O3, not AlO3…