Synthesis Of One-dimensional Inorganic Nanomaterials Using Alumina Membrane As Template

A great deal of attention has been paid to one-dimensional nanomaterials due to their novel electrical, optical, magnetic, thermal and chemical properties. They have significant potential applications in many fields, such as solar energy conversion, chemical sensor, catalysis, absorption and separation. So, research on the preparation and properties of one-dimensional nanomaterials are one of the most exciting areas in materials science. Among the different fabrication methods, using porous alumina as template is one of the most widespread methods to synthesize one-dimensional nanomaterials, because porous alumina membranes have high pore density, thermal stability, good insulating properties and are easy to prepare, and the products formed in it are easy to be separated. The goal of the thesis is to investigate the relationship among the synthesis conditions, structures and properties of one-dimensional nanomaterials obtained by precipitation method using alumina membrane as a nanoreactor. The method provided a simple and convenient way for preparing nanotubes or nanowires at room temperature, also established the base for the preparation of novel functional nanomaterials. Firstly, We tried to prepare BaSO4 nanotubes using porous alumina membrane as the template,Ba²⁺(BaCl₂) and SO₄^2- (Na₂SO₄) would enter the pores of the alumina membranes and form nanotubes. The products were characterized by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), scanning electron microscopy (SEM), and X-ray powder diffraction (XRD). The results indicated that the products were single crystal BaSO₄ nanotubes with outer diameters of 200-350 nm which correspond to the pore diameters of alumina membrane, and length up to 30 μm which correspond to the thickness of the alumina membrane used. Secondly, BaWO₄ nanorods were prepared by reaction of aqueous solutions of BaCl₂ with Na₂WO₄ for 48 h using porous alumna membrane and widened alumina membrane as templates, which were characterized by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer attached to the field emission scanning electron microscopy (EDX), X-ray powder diffraction (XRD) and stimulated Raman scattering (SRS). The diameters of the BaWO₄ nanorods could change from 200-350 nm to 350-450 nm when the pores of alumina membrane were widened by 5 wt% H₃PO₄, which indicated that the diameter of BaWO4 nanorods could be controlled by the pore diameter of alumina membrane. It is noted that the reaction time for the BaWO₄ nanorods formed was 12 h only. Thirdly, We tried to prepare rare earth fluoride nanomaterials with length over 10μm using alumina membrane as a reaction vessel. Ln³⁺ (LnCl₃) and F^-(NaF) would enter the pores of the alumina membranes and form rare earth fluoride nanotubes or nanorods (EuF₃, LaF₃ and TbF₃). The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDX) attached to the field emission scanning electron and high-resolution transmission electron microscopy (HRTEM). It is found that nanorods could be obtained with long reacting time (48 h) or high concentration, while nanotubes were obtained with short reacting time (24 h) or dilute concentration, which suggested that the deposition of the precipitants also started at the pore wall of alumina membrane.