The US Naval Research Laboratory has developed a superior ceramic nano-crystalline spinel, highly transparent and strong, with ambitions to improve armor windows for military vehicles. Using an enhanced high pressure sintering (EHPS) technique, NRL scientists increased spinel hardness by 50% over what is currently used in military armour windows. "The EHPS approach uses high pressures (up to 6GPa) to retard bulk diffusion rates, break powder agglomerates, and reposition nano-particles very close to each other to help eliminate porosity in the sintered ceramic," said an NRL press release. "NRL researchers then can exploit the increased surface potential of nano-particles for surface-energy-driven densification without coarsening." The new technique did not decrease density or fracture resistance, as had been previously observed because of residual porosity in nano-crystalline spinel. The spinel also retained high transparency, a must for optical equipment on military vehicles.
