Body armor isn’t just for superheroes. From the steel armor of medieval knights who didn’t want to get gouged while jousting to the silk vests Genghis Khan’s horsemen wore under their leather and iron armor as an extra arrow shield, body armor has been saving lives for centuries. However, ammo has long since advanced from arrows, and the strongest bulletproof material available until recently was boron carbide—a synthetic called “black diamond”—but even that would crack under pressure.
Turns out that chemistry could transform this flawed material into something (almost) worthy of a Wakandan prince.
“Boron carbide is widely used in body armor and other engineering applications because of its light weight and high hardness [but] consolidated boron carbide loses its strength and toughness when subjected to high-velocity threats,” said Texas A&M assistant professor Kelvin Xie, who recently published a study in Science Advances.
Boron carbide is second to another synthetic, cubic boron nitride, in hardness, but the thing is that boron carbide is harder and lighter than that or silicon carbide or any other material used for protective gear. Never mind it’s much easier to produce on a large scale. The only downsize is amorphization, which is when the crystalline structure of molecules breaks down and makes the substance amorphous. This will happen to boron carbide momentarily when a projectile zooming faster than a certain speed hits the material. Afterward, it will undergo a phase change that could mean its demise. Nothing on this planet can absorb unreal amounts of force like Wakandan vibranium.
The phase change that happens in boron carbide is the same type of phenomenon you see when ice melts to water, except in this case the boron carbide turns into a glassy material that fractures easily. Atoms that were ordered in its crystalline state will end up arranged haphazardly, which weakens boron carbide at the point of contact. This is the problem that Xie and his team were faced with.
“The ability to control and mitigate amorphization could guide the design of boron carbide–based armor materials with improved ballistic performance,” Xie and colleagues said.
Adding silicon turned out to be the answer. Silicon on its own is brittle, but after computer simulations suggested that introducing another element would strengthen the boron carbide and make it less prone to cracking when hit with anything approaching at that break threshold of about 3,000 feet per second. Just a minimal amount of silicon worked wonders. To test the strength of the new alloy, Xie’s team used an ultrafine diamond tip to dent boron carbide samples and then examined the aftermath under an electron microscope. It only showed about a third of the phase transformation it had before.
Now that silicon has proved to be a strengthening agent, Xie wants to experiment with adding other elements. Aluminum and lithium are likely candidates. Whether more than one element will be added to boron carbide in the final version, or whether the alloy of boron carbide and silicon will still prove the strongest, is unknown. This is still incredible news for the military, government investigators from the FBI and CIA, police, firefighters, first responders and anyone else whose career puts them at enough risk to need body armor. The alloy has radiation absorption properties that mean it could even act as a nuclear shield.
By the way, even Vibranium was made into an alloy with Proto-Adamantium for Captain America’s shield, which proves science still needs to exist even in the most outrageous of fictional worlds.
(via Texas A&M University)
Article source: syfy.com