FACILITATING THE PHASE TRANSFORMATIONS OF BORON NITRIDE NANOPARTICLES AT MILD CONDITIONS BY SOLVOTHERMAL HOT-PRESS ROUTE

摘要

Generally, pressure (＞ 11-12 GPa) and temperature (～2000 °C) are required to achieve the formation of wurtzite and cubic boron nitride (wBN and cBN) from hexagonal boron nitride (hBN). For preparing sp~3-bonded boron nitride (wBN, cBN) under moderate conditions, here we developed a solvothemal hot-press method, by which the phase transformation in boron nitride (BN) nanoparticles was realized at quite low temperature (250～310°C) and pressure (60～150MPa). The results reveal that, this transformation can be promoted by increasing both the temperature and pressure, and chlorobenzene possesses stronger effect in facilitating the transformation of aBN/rBN→cBN. Additionally, the decrease of particle size and crystallinity as well as the existence of structural defects play great roles on the phase transformations of sp~3-bonded BN from sp~2-bonded phase. On the basis of analyzing the experimental results, we proposed a simple model used for explaining the phase transformation process. The authors acknowledge National Natural Science Foundation of China (Contract No. 51372230) for financial support.