First off, spinel is not exactly glass. It’s ceramic.
It’s been mined as a gemstone for commercial uses. And it’s tough as armor. Sand won’t scratch it, rain won’t erode it, and a bullet won’t shatter it.
The mineral that makes up spinel is magnesium aluminate. Bulletproof glass, by contrast, is usually made of acrylic or polycarbonate, a type of plastic (3).
Because the Navy often finds itself in hostile environments, they needed something a bit more resistant to force than bulletproof glass.
They needed something they could use in autonomous vehicles (4), head-mounted face shields, and other types of common military equipment so that the materials of war can be made more durable. Through a process called sintering, Naval Research Laboratory (NRL) invented a way to make spinel transparent so that it looks like glass.
Another benefit to sintering is the Navy can shape the material to conform to common prototypes, such as airplane windshields. Spinel is tougher, stronger, harder, and more durable than ordinary glass (even bulletproof glass), and you can see through it. Plus, there’s the added benefit that it allows infrared (IR) light to pass through, which glass doesn’t do (5).
How the Navy Will Use Spinel
There are all sorts of uses for spinel, military and commercial. In fact, according to NRL researcher Dr. Jas Sanghera, the Navy plans to hand over its spinel glass technology to the commercial sector.
In order to scale the material for mass use, they licensed it to a private sector company to make 30-inch wide plates.
One method of working with crystals is to use a high-temperature process called crucible. That didn’t work for the Navy and that’s why they turned to sintering.
What the Navy wants to do is equip military vehicles with transparent armor. That could include Army tanks, Air Force airplanes, and Navy submarines. Another use is for face shields.
SCUBA tanks, aviator helmets, combat goggles, and all sorts of other military equipment can be fitted with transparent armor to protect military personnel better. Rather than use thick and heavy bulletproof glass, which wouldn’t be practical for nighttime goggles, for instance, the cost and weight of the goggles can be reduced with spinel.
Another use could be to make better infrared cameras that are used on military vehicles like planes and some of the Army’s combat systems. The military’s current optical gear uses soft, fragile materials in place of glass because, remember, glass doesn’t transmit IR light.
Even NASA can use spinel on its space satellites, which NRL is currently testing.
Laser weapons also use optics where spinel can replace the current material. There are active and passive optics on such systems and both types of optics have their own unique applications. NRL is working on using spinel to replace the current materials for both applications.
Commercial Applications for Spinel
It’s important when working with transparent materials that the material maintain a certain type of purity as well as quality. Think of diamonds, which are often rated according to a purity scale. In jeweler’s terms, it’s called clarity (6).
Any impurities in glass or other transparent materials could block light from passing through, so it’s important that spinel have a huge purity rating. When it does, it has a lot of practical use commercially and militarily.
Imagine a watch with an unbreakable face, or a cell phone that doesn’t crack when it’s dropped. What if your car windshield was replaced with spinel and didn’t crack when a rock flew up from the vehicle in front of it? These are just a few of the ways spinel can be used in the commercial market.
Any way you look at it, the Navy is on the cutting edge of transparent technology. Glass isn’t all that anymore.
References & Image Credits:
(2) Naval Research Laboratory
(3) Explain That Stuff!
(4) The US Defense Department Plans for Unmanned Aerial Vehicles
(6) Gemological Institute of America
(8) Navy: Hotpress image