硼砂与尿素合成六方氮化硼的机理

Synthetic mechanism of h-BN with borax and urea

研究了N_2气氛下硼砂与尿素反应生成六方氮化硼以及主要副产物产生和变化的过程,采用热重-差示扫描量热法(TG-DSC)、X射线衍射(XRD)、扫描电子显微镜(SEM)等检测手段对反应产物和氮化硼样品进行了分析.研究结果表明,氮化硼在700℃左右完全生成,随焙烧温度的提高其结晶度不断提高.反应副产物偏硼酸钠的生成是导致氮化硼产率较低的主要原因,在高温焙烧过程中偏硼酸钠的存在有利于六方氮化硼的结晶过程.研究结果可为硼砂-尿素法六方氮化硼制备工艺的优化和改进提供理论基础.

The experiments for synthesis of h-BN were carried out under N_2 atmosphere using borax and urea as reactants.The production and evolution process of h-BN and the main byproduct were studied.Samples were analyzed by TG-DSC,XRD and SEM.The results indicate that the synthesis reaction of h-BN is finished at about 700℃and the crystallinity of h-BN improves with the temperature increasing.The production of NaBO_2 by-product is the main reason for the low yield of h-BN.However,the NaBO_2 by-product can improve the crystallinity of h-BN during the roasting process at high temperature.These results may provide theoretical basis for the optimization and improvement of h-BN preparation process by borax-urea method.