Fabrication, Characterization And The Property Investigation Of Electrospun One-dimensional Multiple Oxide Nanostructures

In recent years, one dimensional (1D) functional nanomaterials with various morphologies, have attracted much increased attention due to their large specific surface area, high aspect ratio and unique shape anisotropy. Considering their distinctive physical and chemical properties from their bulk and nanoparticle counterpartes,1D nanomaterials can be used in various potential applications. Lead zirconate titanate (PZT) is widely used as ferroelectric materials in sensor, actuators, non-volatile ferroelectric memory devices, micro-electromechanical systems (MEMS), because of its highest electromechanical coupling coefficient, large remnant polarization, and high dielectric, pyroelectric, and electro-optic coefficients.1D PZT nano structures are expected to have more attractive properties than those of their bulk counterparts due to their reduced sizes and large surface-to-volume ratios, and fibrous PZT has great potential for utilization in high performance hydrophones and ultrasonic transducer applications. Recently, nanoscale spinel ferrites have also attracted much attention due to their unique magnetic and electrical properties. Since nickel ferrite has the low coercivity, low eddy current loss, and chemical stability, its diverse potential applications include high-density magnetic recording, magnetic sensor, micro/nano devices, spin-electron device, etc.In the last decade, many synthesis methods, including template preparation, hydrothermal routs, polymer-assisted co-precipitation method, magnetic-field-induced assembly and electrospinning process have been developed to fabricate ID micro/nanomaterials. Among these methods, electrospinning technique is a simple, low cost, versatile and effective technology for fabricating nanofibers in large scale. It has been utilized to synthesize size-controlled1D nanostructural material with various morphologies and the diameter ranging from tens to hundreds of nanometers. By virtue of the collection facilities to align fibers uniaxial, electrospinning has also been considered as a promising way to assemble ordered magnetic circuits instead of using expensive electron-beam lithography.In this dissertation, we combined electrospinning technique with sol-gel method and heat treatment process to synthesis size-controlled, morphology tunable1D nanostructures. The relevant characterization and property investigation of1D nano structures for ferroelectric PZT and ferromagnetic NiFe2O4materials have also been carried out. The main work and innovative results are as follows:1. Size-tunable piezoelectric polymer PVDF nanofibers have been fabricated via electrospinning technique. We discussed the influences of the precursor solution’s physical parameters (solution concentration/viscosity and solvent ratio) and electrospinning process parameters (voltage, flow rate, collect distance) on the fiber morphology and diameter distribution, and realized the PVDF fiber diameter tuned from200nm to1.6μm.2. Size-controlled single-crystal-like lead zirconate titanate (PbZr0.52Ti0.48O3, PZT) ceramic nanofibers have been successfully prepared by sol-gel based electrospinning and subsequent calcination process. The fiber diameter can be precisely controlled from～50to540nm by varying the PVP concentration and electrospinning process parameters. The crystal structure of the nanofibers pyrolyzed at400℃for0.5h and calcined at650℃for2h is proved to be single-crystal-like tetragonal perovskite phase. A formation mechanism is also discussed based on the thermal decomposition process, effect of the calcination and pyrolysis procedure. It is found that the pyrolysis procedure is a critical factor for the fabrication of single-crystal-like structure PZT nanofibers using electrospinning.3. Size-controlled single-crystal-like lead zirconate titanate (PbZr0.52Ti0.48O3, PZT) ceramic nanotubes have been successfully prepared by sol-gel based co-axial electrospinning and subsequent calcination process. We discussed the influences of the inner and outer solutions’physical parameters (solution concentration/viscosity and molar concentration) and electrospinning process parameters (inner/outer flow rate ratio) on the fiber morphology, diameter and wall thickness. The outer diameter of PZT nanotubes can be tuned from100nm to1.3μm and their wall thickness is varied from～50to200nm. After pyrolyzed at400℃for0.5h and calcined at650℃for2h, the obtained PZT nanotubes are tetragonal perovskite phase and single-crystal-like.4. We report a facile way to fabricate NiFe2O4multiparticle-chain to single-particle chain via sol-gel-based electrospinning and calcination. NiFe2O4nanofibers with tunable morphology can be obtained by virtue of different calcination temperature. The NiFe2O4single-particle-chain nanofibers exhibit the highest saturated magnetization (Ms) and coercivity (Hc) at room temperature compared to multiparticle-chain. This provides a unique model system for the fundamental investigation into the size-dependent magnetism of NiFe2O4nanofibers from multiparticle-chain to singleparticle-chain, and the magnetization reversal mechanism with the quasi-1D nanostructure.