The concept from an iconic Star Trek scene is working its way to commercial use, with innumerable military applications. In Star Trek IV: The Voyage Home, Scotty barters for materials by offering up the formula for “transparent aluminum.” The U.S. Naval Research Laboratory (NRL) is making that concept a reality.
The lab is working to improve transparent bulletproof armor for vehicles and face shields, as well as lighter weight bulletproof windows, with the development of a new, moldable material. The material, spinel, which is more durable than glass, could significantly improve military defenses as it is produced for various uses, the NRL said..
“Spinel is actually a mineral; it’s magnesium aluminate,” said Dr. Jas Sanghera, the researcher leading the project. “The advantage is it’s so much tougher, stronger, and harder than glass. It provides better protection in more hostile environments—so it can withstand sand and rain erosion. For weight-sensitive platforms-UAVs, head-mounted face shields—it’s a game-changing technology.”
The NRL developed a method to make spinel, a gemstone that can be mined in a variety of colors, transparent and produce it in sheets. The low-temperature process, called sintering, uses a hot press to mold the material. The technology is scalable, limited only by the size and shape of the press. Using shaped presses, such as a ball-and-socket press, the spinel can be made in to multiple shapes, such as a wing for an unmanned aerial vehicle. At the NRL, pieces were made 8 inches in diameter, but an outside company was able to use the technology to create much larger plates, so far up to 30 inches.
“You put the powder in [a hot press], you press it under vacuum, squash this powder together—and if you can do that right, then you can get rid of all the entrapped air, and all of a sudden it comes out of there clear-looking,” Sanghera said.
Other researchers have attempted sintering spinel, but the method did not yield clear, usable sheets. NRL reworked the process with more pure chemicals and a more uniformly mixed powder and the spinel produced is clear. The spinel made by the NRL is polycrystalline, which means a lot of crystal particles are pressed together to create the material. This is significant because, while it might chip, it will not crack the way glass does. It can be also be developed as a camera lens that can hold up in a sandstorm or used to protect infrared and other cameras.
Spinel can be ground and polished, like gems, to increase optic quality. And, spinel allows infrared light to pass through it, which makes it optimal for military imaging systems. Glass does not transmit infrared light, so the NRL has been developing new optical materials to replace the soft and fragile optics used today.
The NRL is investigating additional uses for spinel, including laser applications and use on space satellites. Researchers said the ultimate goal is to hand the technology over to industry. But, the laboratory is also looking to reduce the finishing cost so it can be affordable to both the Department of Defense (DoD) and private industry.