摘要
采用Li3N和hBN为原料,在静态高温高压条件下合成出大颗粒cBN单晶。利用扫描电镜(SEM)、高分辨透射电镜(HRTEM)对合成块断面、大颗粒cBN单晶形貌及其周围物相进行了表征。结果表明:在大颗粒cBN单晶周围主要存在hBN、cBN及Li3BN2等物相。HRTEM在大颗粒单晶周围发现了纳米尺寸的cBN微颗粒,并发现该微颗粒处在Li3BN2物相包裹中。由此可以推测,高温高压状态下,hBN与Li3N发生共熔反应生成Li3BN2,而Li3BN2作为触媒中间相促使cBN的形成。同时结合SEM结果分析表明,一旦cBN微颗粒形成,在随后的生长过程中,cBN在Li3BN2熔体中以扩散的方式进行台阶生长,从而形成宏观可见的cBN单晶。
Cubic boron nitride crystals were synthesized by Li3N as catalyst under high pressure and high temperature.By using scanning electron microscopy（SEM）,the morphology of bulk cross-section and the morphology of cubic boron nitride single crystal were observed,at the same time,the phases around cubic boron nitride crystal were determined by high-resolution transmission electron microscopy（HRTEM）.The results showed that hexagonal boron nitride,cubic boron nitride particles and lithium boron nitride were the main substances around the cBN crystal.By HRTEM experiment,the nanometer-sized cBN was found,and it was encapsulated by Li3BN2 phase.It was conjectured that Li3BN2 can be obtained by hBN and Li3N reaction under high pressure and high temperature,and Li3BN2 as catalyst can convert hBN to cBN in the form of allotropic transformation for their different Gibbs free energy.Combined with SEM results,it can be concluded that cBN can be growing by diffusion method,and Li3BN2 is the melt at here.The growth steps can be observed obviously on（111） crystal face of cBN,by this process,the large single cBN crystal can be obtained.
出处
《人工晶体学报》
EI
CAS
CSCD
北大核心
2012年第6期1538-1542,共5页
Journal of Synthetic Crystals
基金
国家自然科学基金(51272139)
关键词
立方氮化硼
微观结构
HRTEM
高温高压合成
cubic boron nitride
micro-structure
high-resolution transmission electron microscopy
synthesis under high pressure and high temperature
