立方氮化硼的低压合成及其相变机理的研究

Cubic boron nitride, which can be only synthesized by the high-temperature and high-pressure method at present, is a kind of superhard material with many important uses. Since cubic boron nitride prophesied in theory to be stable phase in normal pressure, the study for the synthesis of cubic boron nitride in low pressure has become popular in material fields, but the pressure hasn't dropped obviously. The best report result was cubic boron nitride synthesized in 0.5GPa when we began this work. This project is about the study of the synthesis of cubic boron nitride in low pressure and its mechanism of phase conversion. The main achievements are that:1).Cooperation with Shandong University, cBN is synthesized by the raw materials of Li3N and BBr3, and the solvent of benzene, and under the condition of less than 480℃ and the pressure less than 2MPa. After the experimental results are published, Nature, international famous magazine, has also reported them.2) Nano-hBN and nano-cBN are obtained by the raw materials of KBH4, NH4Cl and Li3N under the condition of 650℃ and 7MPa of nitrogen pressure, which has been the lowest pressure condition for the synthesis of cubic boron nitride in this method up to now.3)The cubic boron nitride is synthesized by (C2H5)2O·BF3 as solvent and providing boron, and NaNH2.providing nitrogen. The reaction pressure is less than 2MPa, and the temperature is about 480℃.4)The cubic boron nitride is synthesized by(C2H5)2O·BF3 as solvent, (C2H5)2O·BF3 and NH4BF4 providing boron, and NaNH2 providing nitrogen. Its reaction pressure is less than 2MPa, and the temperature is about 300℃.5).The cubic boron nitride is synthesized by NaNH2 providing nitrogen, NH4BF4 and NaBF4 providing boron, and lithium nitride as catalyst. The pressure is estimated to be less than 2MPa, and the temperature is 450℃. The experimental results of 3), 4) and 5) , with the advantages of little oxicity or non-poison of raw materials, and convenient operation, haven't been eported internal and external.For the moment, the project has achieved the best research results about cubic boron nitride's synthesis in low pressure. What's more, nano-boron nitride synthesized by the methods related above will have many practical prospects..

立方氮化硼目前是用高温高压方法合成的，实现立方氮化硼的低压合成将显著地降低其合成成本，若能实现立方氮化硼的常压合成将使磨削材料领域发生根本性变革。本项目将研究立方氮化硼在催化剂作用下的合成机理，研制适于低压合成立方氮化硼的催化剂、原料和合成工艺，实现一万压力以下的低压合成，并争取实现常压合成。