Codex Futurius: Transparent Aluminum

By Eric Wolff | March 25, 2009 7:00 pm

Codex Futurius LogoMichael D. asked, on the Assignment Desk post:

In the most recent issue of Nature, there are two papers…that detail the characteristics of sodium and lithium under extreme pressure. Specifically, these two metals adopt semiconductor-like (even superconductor-like) characteristics if you subject them to giga-pressure (literally, 80-200 gigapascals). The sodium actually becomes optically transparent during this squeeze. Reading this reminded me of a Star Trek [movie] that involved a not-so-scientific explanation of “transparent aluminum” …Is the idea of using transparent metal for windows pure science fiction?

The paper you’re talking about, the one on high pressure sodium, sure did make a lot of noise in the science world, and for good reason. Drs. Yanming Ma and Artem Oganov at SUNY Stonybrook showed that  lithium and sodium do goofy things under pressure — like turn transparent. Normally under really high pressure, elements turn into metals, c.f. hydrogen. The science makes intuitive sense because the atoms are getting smooshed together as the pressure increases. The electrons are freed to become conductors, and the element takes a metal-like structure. But in sodium, it turns out, the electrons line up into columns, one on top of the other. This creates gaps between the atoms, and instead of becoming a conductor, it becomes an insulator, and, conicidentally,  becomes transparent.

All of which is cool, but it doesn’t really answer Michael D’s question, because the sodium is under 200 gigapasacals of pressure, the sort of pressure you find if you were journeying from Jupiter’s surface toward its core, not hanging out on the bridge of the Enterprise.

And yet! That formula Scotty gave for transparent aluminum in Star Trek IV: The Voyage Home very nearly exists in the form of aluminum oxynitride  (known as ALONtm). Harder than diamond, ALONtm is far more shock resistant than even bullet resistant glass. In Air Force tests it has resisted multiple rounds from a .50 caliber sniper rifle. That hardness also prevents wear and tear, since neither sand nor rocks nor shrapnel in the night will scratch the stuff.

In practical use, the ALONtm would be the outer layer for windscreens of cockpit covers. It would be backed by a thin layer of glass and a layer of transparent polymer to prevent shattering. All together the ALONtm windscreen would be thinner and lighter than a traditional bullet-resistant windscreen.What’s unclear from my research is whether it would be strong enough to hold back enough water to make the aquarium for all those humpbacks whales on a captured Klingon spaceship, but it’s a start.

The main downside? It’s wicked expensive. Traditional bullet resistant glass goes for $3 per inch-squared, but ALONtm costs between $10-$15, or it did back in 2005.  I can’t seem to find any more current applications for it, but this is the military, it could be classified.

Anyway Michael D., I hope that answers your question.

CATEGORIZED UNDER: Codex Futurius, Movies, Physics
MORE ABOUT: ALONtm, Scotty, Star Trek, whales

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