直流碳弧法制备碳包覆铁纳米颗粒机理研究

Study on Growth Mechanism of Carbon-encapsulated Fe Nano-particles Prepared by Direct Current Carbon Arc Plasma

采用直流碳弧等离子体法成功制备了碳包覆铁纳米颗粒，利用透射电子显微镜和高分辨透射电子显微镜、X射线衍射、X射线能谱仪对样品的形貌、物相结构、化学成分和粒度进行表征分析，并对碳包覆纳米金属颗粒的形成机理进行初步探讨。结果表明：直流碳弧等离子体技术制备的碳包覆纳米金属颗粒具有明显的铁核（bcc—Fe）／碳壳（石墨层片）包覆结构，颗粒大多呈球形和椭球形，粒径分布在20-60nm范围，平均粒径为44nm，铁粒子外碳层的厚度为5～8nm。碳包覆铁纳米铁颗粒是通过颗粒内部固态形式的碳自行扩散至颗粒表面和颗粒外部气态形式的碳沉积到颗粒表面形成的。

The carbon encapsulated Fe nano-particles were successfully prepared by direct current carbon arc plasma method. The morphology, microstructure, chemical composition and particle size distribution of the product were investigated using the highesolution transmission electron microscopy （HRTEM）, transmission electron microscopy （TEM）, X-ray diffraction （XRD）, X-ray energy dispersive spectrometry （XEDS）. The formation mechanism of carbon encapsulated Fe nano-particles was discussed. The experiment results showed that the carbon encapsulated Fe nano-particles with clear core-shell structure, consisting of a bcc-Fe core and a graphitic shell. The particles were scattered homogeneously in spherical and ellipsoidal shapes. The particle size distribution was 20-60 nm, with average diameter about 44 nm and the thickness of the cages was about 5-8 nm. The carbon encapsulated Fe nano-particles was formed by free diffuse of internal solid state carbon to the surface and deposition of external gas phase carbon on the outside.