模板法掺铁金红石纳米管制备与形成机理

以TiCl4为钛源,针铁矿（α-FeOOH）为模板,采用牺牲模板法制备掺铁金红石纳米管,应用X射线衍射（XRD）、透射电镜（TEM）、扫描透射面扫描（STEM EDX-Mapping）和X射线光电子能谱（XPS）等手段对掺铁金红石纳米管的物相、形貌、微结构和化学组成等进行系统地表征.结果表明,在高温条件下制备的掺铁金红石样品颗粒为管状结构,纳米管的物相为纯金红石相,管壁外表面由许多针状体包裹,管的两端封闭,内孔直径60～80 nm；管壁由纳米颗粒构成,并具有明显的层状结构特征；元素分析结果表明,Fe3+均匀地掺入到了金红石晶格中,且金红石晶格形成大量的位错和面缺陷.结合金红石纳米管的微结构特征探讨形成机理：在低温条件下,金红石先包覆于针铁矿外表面,并构成以金红石为壳,针铁矿为核的核壳结构纳米复合材料；随着反应温度从30 ℃上升到90 ℃,载体针铁矿逐渐溶解,包覆于载体针铁矿外表面的金红石逐渐增加；同时,铁离子经扩散而进入金红石晶格,最终载体针铁矿全部溶解而形成掺铁金红石纳米管.

Preparation and formation mechanism of iron-doped rutile nanotube prepared by template method

Iron doped rutile nanotube was prepared by a template method, using TiCl4 as titania precursor and goethite (α-FeOOH) as a template. The crystal phase, morphology, microstructure and chemical composition of the samples were characterized by X-ray diffraction(XRD), Transmission electron microscopy(TEM), Scanning transmission electron microscopy(STEM) EDX-Mapping and X-ray photoelectron spectroscopy(XPS). The results show the crystal phase of the Iron-doped rutile sample prepared at high temperature is rutile, the morphology of the sample particle is tube-like, with two tips enclosed and an inner diameter of 60～80 nm, and a lot of needle like particles grow on the outer surface of the nanotube wall, which is constituted of small particles. Element analyses of EDX-mapping results show that iron element distributes homogeneously in the nanotube. The microstructure of the nanotube shows that many displaces and regional defects exist in the lattice of rutile. A formation mechanism of rutile nanotube growth was proposed: rutile nanoparticles grow on the outer surface of needle-like goethite particles and wrap around the goethite particles at lower temperature, thus rutile-goethite composite with core shell structure forms, in which rutile as a shell layer and goethite as a core; when the preparation temperature rised from 30 ℃ to 90 ℃, the template, goethite is dissolving gradually; at the same time, more and more rutile nanoparticles precipitate onto the outer surface of goethite particle, and iron cations are entering into the lattice of rutile nanoparticles through diffusion; goethite particle is disappearing at last, thus iron doped rutile nanotube forms．