The Preparation And Application Of Metal And Metal Oxide Nanowires Synthesized By Oxalic Acid Salt Templates

Compared to other nanomaterials, nanowires can find potential applications in many areas due to their intrinsic chemical and physical properties. Up to now, metal and metal oxide nanowires has been widely applied in magnetic materials, gas-sensitive elements, electrode materials, electrochemical capacitors, functional ceramics, photoelectric devices, electrochromic materials and special coating etc. However, it remains a great challenge to find a simple method for large-scale synthesis of metal and metal oxide nanowires.In this thesis, we propose a microemulsion method to synthesize oxalic acid salt nanowires which can act as as sacrifice templates for the synthesis of metal and metal oxide nanowires via calcinations. The magnetic and Li-ion battery properties of the as-synthesized metal oxide and metal nanowires have been investigated. Main achievements are displayed as follows:(1) A microemulsion-based method has been developed to synthesize NiC2O4 nanowires, which can be transformed into porous nickel oxide nanorods via calcinations. The morphology and structure of the products have been characterized by transmission electron microscopy, high-resolution transmission electron microscopy, field emission scanning electron microscopy, X-ray powder diffraction and Fourier transform infrared spectroscopy. It is indicated that the as-synthesized nickel oxide nanorods are poly crystalline and consisted of numerous nanoparticles, whose diameters can be tuned by the annealing temperatures. Moreover, the magnetic properties of the nickel oxide nanorods have also been investigated.(2) Hematite (α-Fe2O3) and magnetite (Fe3O4) nanowires with the diameter of about 100 nm and the length of tens of micrometers have been selectively synthesized by a microemulsion-based method in combination of the calcinations under different atmosphere. The effects of the sacrifice templates, annealing temperature and atmosphere on the morphology and the structure of the products have been investigated.(3) CoC2O4 nanowires were synthesized by a similar microemulsion-based method. Ultralong and uniform Co3O4 and Co nanowires could be selectively fabricated by annealing of CoC2O4 nanowires under different temperatures and atmospheres.(4) CoFe2(C2O4)3 nanowires were synthesized by a similar microemulsion-based method, which can be transformed into porous CoFe2O4 and FeCo nanowires under different atmosphere. The effects of the sacrifice templates, annealing temperature and atmosphere on the morphology and the structure of the products have been investigated.(5) A simple microemulsion-based method has been developed to synthesize ZnCo2(C2O4)3 nanowires which can be transformed into porous ZnCo2O4 nanowires via calcinations. The morphology of porous ZnCo2O4 nanowires can be tuned by the initial ZnCo2(C2O4)3 nanowires and the annealing temperatures. The as-synthesized porous ZnCo2O4 nanowires have been applied as anode materials of Li-ion batteries, which show superior capacity and cycling performance. The porous 1D nanostructures and large surface area are responsible for the superior performance. Moreover, it is indicated that porous ZnCo2O4 nanowires synthesized at low annealing temperature (500℃) show larger capacity and better cycling performance than that prepared at high annealing temperature (700℃) due to their higher porosity and larger surface area.