Li_3N在KBH_4和NH_4Cl合成BN反应中的作用

Function of Li_3N in the Synthesis of BN with KBH_4 and NH_4Cl

采用氮气加压加温方法 ,以KBH4和NH4Cl为原料 ,通过在相同的温度、压力条件下 ,向反应体系中添加和不添加少量Li3 N的对比实验 ,研究Li3 N在KBH4和NH4Cl生成BN反应中的作用。反应产物中有无hBN和cBN生成是依据反应产物的X射线衍射图谱 (XRD)和傅立叶变换红外光谱 (FTIR)中有无hBN和cBN物相出现确认的。谢乐公式被用于估算生成的BN的粒径。结果表明 ,在 6 5 0℃、7MPa的反应条件下 ,以KBH4和NH4Cl为原料没有生成BN的反应发生。但当在原料中加入Li3 N后 ,反应产物中有大量hBN和少量cBN生成 ,其中hBN的平均颗粒尺寸约为 14nm。分析确认 ,Li3 N在上述由KBH4和NH4Cl合成hBN和cBN的反应中起催化作用。而且加入Li3 N后 ,由KBH4和NH4Cl合成BN的反应压力和时间都明显低于Hu等人的相关报道结果。

To find out the function of Li 3N in forming BN with KBH 4 and NH 4Cl,the control experiments with or without Li 3N additive were conducted through exerting pressure with nitrogen gas and heating the materials with electricity,KBH 4 and NH 4Cl used as raw materials.Whether hBN and cBN can be formed in the reaction products was identified by whether there were phases of hBN and cBN in XRD and FTIR patterns. Meanwhile,the particle sizes of BN were calculated by means of Scherrer equation.It turned out that under 650℃ and 7MPa but without Li 3N,no BN was made from KBH 4 and NH 4Cl. However,there was massive hBN with average particle size of 14nm,and certain cBN after Li 3N was added in the materials.Analysis showed that Li 3N served as a catalyst in synthesizing hBN and cBN from the reaction of KBH 4 and NH 4Cl.Furthermore,after Li 3N was added into the reaction,pressure and time were apparently less than those having been reported by Hu etc.concerning this subject.