模板法掺铁金红石纳米管制备与形成机理

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

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60～80nm;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.

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.