Body armor can come in many forms, with different materials offering different strengths and weaknesses. One engineers often turn to is boron carbide, also known as "black diamond" for the incredible hardness and lightness that makes it highly suitable for ballistic vests. Scientists at Texas A&M University have figured out a way to supercharge its already impressive abilities, adding a little silicon to the mix so that it can withstand bullets traveling at even higher speeds.
“Boron carbide is really good at stopping bullets traveling below 900 meters per second (2,953 ft/s), and so it can block bullets from most handguns quite effectively,” says Kelvin Xie, assistant professor in the Department of Materials Science and Engineering. “But above this critical speed, boron carbide suddenly loses its ballistic performance and is not as effective.”
When armor made from boron carbide encounters high-velocity projectiles, it leads to what scientists call phase transformation. This reshapes the internal makeup of the material, turning neatly arranged crystalline structures into a glass-like phase where atoms are instead all over the place.
“When boron carbide undergoes phase transformation, the glassy phase creates a highway for cracks to propagate,” Xie says. “So, any local damage caused by the impact of a bullet easily travels throughout the material and causes progressively more damage.”
Earlier studies had indicated that adding a small amount of another element may address this shortcoming in boron carbide armors, so Xie and his team put this theory to test using silicon. They produced boron carbide with just a tiny amount of the element, and then conducted some experiments to see how it fared.
The team used diamond tips to simulate the impacts of a high-speed bullet, punching dents in the material and then using a high-powered electron microscope to assess the damage. Even with this small amount of silicon, the material withstood the blows much more effectively, with the scientists observing a 30-percent reduction in phase transformation and less overall damage as a result.
“Just as in cooking where a small sprinkle of spices can greatly boost flavor, by using a small amount of silicon we can dramatically improve the properties of boron carbide and consequently find novel applications for these ultra-hard materials,” Xie says.
From here, the team hopes to conduct further experiments to see if other elements such as lithium or aluminum could also be introduced to boost the performance of the armor.
The research was published in the journal Science Advances.
Source: Texas A&M University
