A common material found on starships in the Star Trek Universe. Transparent aluminum is as strong as aluminum, yet you can see right through it, unlike conventional aluminum. Thus, it makes a good material for starship windows.

This is a material that humanity could really make good use of. Even the strongest polycarbonates are no match for one atmosphere of air pressure if the window is of any decent size. Making it very thick would work, but the optical properties will make looking through such a window an irritating experience. Something similar to transparent aluminum would also help out in deep sea diving, where portholes tend to be very small due to the massive pressure being exerted on them.

Well, move over sci-fi. News flash: it's been done.

Before the purists jump on me, no, technically it isn't a metal. It's better. It's a ceramic. However, it's nothing more than carefully-treated and maybe doped aluminum oxide (Al2O3, Professor Pi informs me. Thanks!). It is, however, still aluminum, even if not in the 'pure' form.It's under this title because this is how they're referring to it in the press.

German materials science gurus at the Fraunhofer Institute for Ceramics Technologies (I believe) announced the week of 2/11/02 that they have successfully manufactured transparent aluminum (or aluminium for the rest of the world) tiles. The tiles are made, in the roughest possible description, by taking microfine particles of aluminum oxide* and baking them at around 1200 degrees Celsius during a fairly tightly-controlled process. The end result is a transparent but slightly white-tinted (milky) substance. The announcement press release showed a photo of a hand lighting a candle with a match behind a tile of the stuff; everything was clearly visible, and the colors were slightly paler but easily recognizable.

There was a story on Slashdot, you can search there if you need confirmation. It will point you to the following Der Spiegel article:

http://www.spiegel.de/wissenschaft/0,1518,183008,00.html

...which will require you to either read German or use a translator.

The characteristics of the material are such, the team reported, that a 1-cm thick tile (not-so-coincidentally, the thickness required by Chief Engineer Montgomery Scott in Star Trek IV: The Voyage Home) would have a tensile strength or pressure rating approximately three times as great as an equivalent thickness of steel plate, and would weigh around 1/3 as much.

The Pentagon, naturally, is interested; applications there alone are endless- helmet visors, armored vehicle vision blocks, lightly armored vehicle windows, aircraft canopies, etc. etc. We won't be seeing clear tanks, though (for more info on why, see this or that or the other). Other interested parties include civil vehicle manufacturers, civil engineers (now that is a substance that I wish Frank Lloyd Wright had access to...on the other hand, Frank Gehry probably will! Woohoo!), tool manufacturers, optical fiber types, and more. Personally, I look forward to no longer worrying about cracking the touchscreen on my PDA or cell phone.

I just love it when reality takes its cues from science fiction; you can't tell me at least a few of those working on this hadn't first been tickled by the Star Trek mention of the stuff. Of course, Star Trek can't have everything; Germany sure ain't San Francisco, which is where Scott and McCoy handed over the formula to an American firm.

Huzzah for materials science! Now if I could only have my spidersilk bulletproof sportsjacket, please...?

Update:
Apparently, the U.S. Military (never one to shy away from spending money) has been busy in this field as well. Using a variant of this called aluminum oxynitride (ALONtm), the Army Research Laboratory at the Aberdeen Proving Grounds in conjunction with the Air Force Research Laboratory and the University of Dayton Research Institute have created a layered transparent armor to replace current glass-based solutions. This armor consists of outer 'strike plates' of polished ALONtm with central glass cores for mass, and apparently offers more than double the penetration resistance of similar thickness and mass of glass alone.

Glass armor, although it sounds oxymoronic, is necessary for use in direct vision ports ("vision blocks") of armored vehicles. The new material, although more expensive to produce, resists damage from larger and more energetic projectiles and hence should require replacement less often - as well as (more importantly) offering better protection to vehicle occupants. For more information on this application, see:

http://www.af.mil/news/story.asp?id=123012131

1. Powdered aluminum oxide is called Alumina in materials science circles, Jethro Bodine tells me. Thanks!

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