By David Ponce
Maybe you watched Star Trek IV and thought the idea of having a whale tank made from transparent aluminum to be one of those far fetched sci-fi gimmicks. But would you be surprised to find out that at the time the movie was made, that particular material already existed? Not from the metallic aluminum you know and love, mind you, but from an aluminum-based ceramic called aluminum oxynitride, aka “AlON.” You may be thinking to yourself that this is not the same, but hey, this is still a transparent, aluminum-based material that is capable of stopping a .50 bullet with a plate 1.6 inches in thickness. A 3.7 inch slab of laminate glass not only doesn’t stop this same bullet, but lets it go through with enough speed for it to do some serious damage to a dummy skull on the other side.
Transparent aluminum starts out as a pile of white aluminum oxynitride powder. That powder gets packed into a rubber mold in the rough shape of the desired part, and subjected to a procedure called isostatic pressing, in which the mold is compressed in a tank of hydraulic fluid to 15,000 psi, which mashes the AlON into a grainy “green body.” The grainy structure is then fused together by heating at 2000 °C for several days. The surface of the resulting part is cloudy, and has to be mechanically polished to make it optically clear.
Of course this material is super expensive, and is usually reserved for high-performance military applications. “AlON is manufactured by Massachusetts-based Surmet Corporation for use in armored windows, lenses for battlefield optics, and “seeker domes,” which are the clear round windows covering the sensor heads on the business ends of many missiles.”
VIA [ Make Blog ]