合成后的触媒组织结构对立方氮化硼单晶合成效果的影响

Effects of the structure of synthesized lithium-based catalyst on synthetic quality of cBN single crystal

以氮化锂(Li_3N)为触媒和六方氮化硼(hBN)为原料,在静态高温高压条件下加入籽晶批量合成出了≥50目的立方氮化硼(cBN)单晶。通过X射线衍射仪(XRD)和红外线光谱仪(FTIR)对合成后的触媒层内物相组成进行了分层表征;采用K值法、绝热法和RIR值等理论方法,计算出了触媒层内各物相的质量分数,分析了各物相在触媒层中的变化规律。采用扫描电子显微镜(SEM)对cBN单晶形貌和cBN单晶/触媒的界面形貌进行了观察,分析了触媒层的形貌对cBN单晶合成效果的影响。结果表明,触媒层内主要存在不规则的cBN微晶、hBN和Li3BN2等物相。触媒层的中间层是hBN发生固相直接转变生成cBN微晶的主要区域,触媒层中Li3BN2和cBN微晶的含量直接影响cBN单晶的合成效果。

Cubic boron nitride（cBN）single crystals（≥50 mesh） were synthesized through adding seed crystals under high temperature and high pressure,using Li3N as catalyst and hBN as raw materials.In this paper,the compositions of phases were identified with the X-ray diffraction experiment in catalyst layer.The phase structures were examined by FTIR.The mass fractions of phases were calculated to analyse change rule of phases by the method of K-value,RIR-value and the adiabatic method in catalyst layer.The morphologies of catalyst layer near the band-edge of catalyst layer and cBN single crystal surfaces were characterized to analyze the effect of morphology of synthesized lithium–based catalyst on synthetic quality of cBN single crystals by SEM.The results show that the catalyst layer mainly contains hBN,irregular cBN crystallite and Li3BN2 by XRD.The middle layer of catalyst layer is the main area of synthesized cBN single crystals which is transformed directly from hBN structure.The mass fractions of cBN crystallite and Li3BN2 influence directly the synthetic quality of the cBN single crystal in the catalyst layer.