硅热还原法制备球形无定形硼

Preparation of spherical amorphous boron via silicothermic reduction method

在传统硅热还原反应的基础上,向反应体系中引入碱金属硅酸盐,将传统硅热还原反应的副产物SiO_(2)转变为水溶性的碱金属硅酸盐,确立一种无定形硼的制备方法;以Si、Na_(2)B_(4)O_(7)、Na_(4)SiO_(4)为原料,制备球形无定形硼样品,经水洗去除水溶性硅酸钠杂质,冷冻干燥得到无定形硼,并探讨反应温度和钠盐添加量对反应进程的影响;利用X射线衍射仪、傅里叶变换红外光谱仪、场发射扫描电子显微镜、高分辨透射电子显微镜对无定形硼的结构和形貌进行表征。结果表明:制备球形无定形硼的最佳工艺条件为,物质的量比n(Si)∶n(Na_(2)B_(4)O_(7))∶n(Na_(4)SiO_(4))=3∶1∶2,反应温度为900℃,保温时间为3 h,制得的无定形硼的粒径为200~400 nm;含硅酸钠杂质的滤液可以回收利用,实现球形无定形硼的环境友好制备。

The method for the preparation of amorphous boron was developed by introducing alkali metal silicates into the reaction system and converting the by-product SiO_(2) of the conventional silicothermic reduction reaction into water-soluble alkali metal silicate.Spherical amorphous boron was prepared from Si,Na_(2)B_(4)O_(7) and Na_(4)SiO_(4).The spherical amorphous boron sample was washed to remove water-soluble sodium silicate impurities,and then freeze-dried to obtain amorphous boron.The effect of reactant temperature as well as the amount of sodium salt added on the reaction process was also explored,and the structure and morphology of the amorphous boron powder was characterized by using X-ray diffractometer,FTIR spectrometer,field emission scanning electronmicroscope and transmission electron microscope.The results show that when the moles ratio of the raw materials n(Si)∶n(Na_(2)B_(4)O_(7))∶n(Na_(4)SiO_(4))is 3∶1∶2,the reactant temperature is 900℃,and the reaction time is 3 h,the amorphous boron with a particle size of 200~400 nm is obtained.The filtrate containing sodium silicate impurities can be recycled for the environmentally friendly preparation of spherical amorphous boron.