铁纳米粒子的结晶形态与表面氧化膜分析

CRYSTAL HABIT AND SURFACE OXIDE FILM ANALYSIS OF Fe NANO-PARTICLES

铁纳米粒子样品系采用气体蒸发法制备,用透射电子显微镜观察其结晶形态和粒径大小,采用X射线衍射、电子衍射、X射线光电子能谱和俄歇电子能谱等多种分析手段详细分析了粒子表面氧化膜的组成、结构和厚度及其稳定性,提出了铁纳米粒子组成和结构模型。结果发现铁纳米粒子本身的晶体结构与普通α-Fe是一致的,为体心立方结构,粒子表面存在约3nm厚的双层氧化膜,外面一层为γ-Fe_2O_3,厚度约为1nm。里面一层为Fe_3O_4,厚度约为2nm,这两种氧化物均为尖晶石型立方结构。结果还表明,用气体蒸发法制备的铁纳米粒子在干燥空气中是相当稳定的,氧化膜虽薄但很致密,对粒子本身具有很好的保护作用。

The crystal habit and size of the Fe nano-particles prepared by an inert gas evaporation method have been observed with transmission electron microscope. The composition, structure and thickness of the surface oxide film on the Fe nano-particles have been analysed in detail by means of several techniques, such as, X-ray diffraction, electron diffraction, X-ray photo-electron spectrum and Auger electron energy spectrum. A model of the composition and structure for these particles has been given. The results show that the crystalline structure of the Fe nano-particles is consistent with the general α-Fe, i.e. bcc structure. On the surface of these particles, there are double layers of the oxide film with about 3 nm thickness, in which the outside is γ-Fe2O3 of about Inm thickness and the inside is Fe3O4 of about 2 nm thickness. The crystal structure of the two kinds of oxide are of cubic spinel-type. The results also indicate that the Fe nano-particles prepared by the gas evaporation method are very stable in dry air. Though the oxide film is thin, it is quite compact and give good protective effect on the particles.