Study On Synthesis Of Large CBN Single Crystal

The synthesis technology of cubic boron nitride (CBN) under high temperature and highpressure (HTHP) is the main method applied in super-hard materials industry so far. Thesynthesis technology of CBN has made great progress over the years. Because of thecomplexity of the crystal growth process, and the difficulty of synthesis process real-timemonitoring, it is hard to make large size (diameter more than0.5) CBN under HTHP atpresent. This paper focuses on studying the synthesis technology of large CBN single crystal,and analyzed its growth mechanism.Using Ca3N2as catalyst and hexagonal boron nitride (HBN) as raw material, by meansof the method of temperature gradient, large CBN has been synthesized with CBN crystalseed. The influence rule of different process parameters on the synthesis of CBN monocrystalhas been investigated.CBN monocrystal growth mechanism are discussed in this paper. By means of SEM. Wehas observed the growth of the stripe with small particles, the growth of the spiral stripes andthe cone particles on the surface of the smooth CBN crystals. According to the experimentresults we figure out that the CBN crystals surface of the particles formed under HTHP, theHBN and catalytic Ca3N2form supersaturated total melt, seed growth with the catalyst andHBN melt wrapped around the seed crystal in low temperature area, in the first place catalystreleasing electronic for B atoms as melt, and the absorption of N atoms near completeconversion of CBN, depositing on seed surface gradually form small particles, and graduallygrow up.We analyzed the principle of formation of CBN monocrystal color by using SEM andEDS. The structure of CBN is unbalanced due to the impurity elements. It affected thetransparency of CBN single crystal and the color deepened.At the same time, We analyzed the growth regularity of large CBN single crystal,We established the regression equation for a simple simulation.