Superhard transparent polycrystalline cubic boron nitride

Polycrystalline cubic boron nitride (PcBN) has been synthesized at 14GPa and high temperatures of 1300-2000 degrees C in a two-stage multi-anvil cell. Sintered PcBN synthesized at 1700-1800 degrees C and 14GPa with a grain size of similar to 200nm is optically transparent with a transmittance of similar to 70% at wavelengths of 400-1500nm and has the Vickers hardness of similar to 63-69GPa. Analyses with scanning and transmission electron microscopy reveal that PcBN can be strengthened by introducing nanometer-scale grains and microscopic defects at high pressure and temperature. The optical transparency of the bulk PcBN synthesized at high pressure and temperature can be explained by the very thin intergranular films between grains. The present sintered PcBN is the second-hardest transparent material after diamond and can be used for windows in extreme conditions.

Automated summary

Polycrystalline cubic boron nitride (PcBN) synthesized at high pressure and temperature exhibits small grain size, excellent optical transparency, and hardness, making it suitable for windows in extreme conditions.