Naval Research Lab team aims to design better armor through nanoscience

WASHINGTON. A multidisciplinary team of researchers at the U.S. Naval Research Laboratory (NRL) reports that they have pushed grain-size engineering to the limit and as a result recently discovered previously unseen behaviors in nanocrystalline ceramics that could lead to the design of lighter and stronger ceramic armor for the warfighter. The discovery -- recently published in American Chemical Society Nano -- continues NRL research published in 2014.

According to NRL team members, the discovery was made possible by a cutting-edge nanosintering technique, which is the process of essentially bonding nanosized particles together.

"A few years ago, NRL was the first to show that if you decrease the grain size of ceramics to tens of nanometers, the hardness and strength increase," said Dr. James Wollmershauser, a materials research engineer in NRL's Materials Science and Technology Division. "Our current work takes this much further. We decreased the grain size of fully dense ceramics to record-breaking single digits, and analyzed the elasticity, hardness, energy dissipation, and fracture behavior in ceramics with a wide range of nanosize grains." Research team member Dr. Heonjune Ryou, a postdoctoral fellow in NRL's Chemistry Division, characterized the mechanics of the nanocrystalline ceramics and found that they accommodate mechanical energy in a unique way, something that had never been seen before in bulk nanocrystalline ceramics; this aspect of the ceramics may revolutionize the design of ceramic armor.

"NRL was the first to see the increase of energy dissipation in single-digit nanograin ceramics," said Dr. Boris Feygelson, a materials research engineer in NRL's Electronics Science and Technology Division who heads the team's nanosintering efforts. "The better the material can accommodate mechanical energy, the better it can stop an incoming threat."

The key, say team members, to unlocking these materials and their phenomenon is NRL's Environmentally Controlled Pressure Assisted Sintering (EC-PAS) approach, which enabled NRL to break the world record for the smallest grain size in dense ceramics at 3.6 nanometers, or about 30,000 times smaller than the width of a human hair.

As they pushed the boundaries of nanosintering science, NRL researchers showed that it may be possible to one day design a lightweight, nanocrystalline ceramic material that can better dissipate mechanical energy, for example from a sharp projectile, thereby absorbing more damage while retaining its very high hardness. Such a discovery could open the door for higher-performing armor for sailors, Marines, and other troops.