Creation of Nanostuctures by Extreme Conditions: High- Pressure Synthesis of Ultrahard Nanocrystalline Cubic Boron Nitride

摘要

Nanomaterials in the form of zero-, one-, and two-dimensional nanostructures make a high-impact background for both science and technology. At the same time, the synthesis of bulk nanostructured materials remains the least-explored but challenging domain that allows combination of desired physical, chemical, and mechanical properties and gives rise to nano-electronics, nanomechanics, bandgap engineering, etc. The common methods of soft chemistry allow nanoparticles to be obtained whose direct sintering unavoidably leads to grain growth and loss of nanostructures. Extreme pressure is a parameter of choice to suppress the self-diffusion responsible for high-temperature recrystallization. Here we report the synthesis of high-purity bulk nanostructured cubic boron nitride (cBN) with a unique combination of properties (ultrahardness, high thermal and chemical stability, etc.) by direct phase transformation of graphite-like BN with an "ideal random layer" structure at 20 GPa and 1770 K.