Electrospinning Preparation And Applications Of Bismuth Ferrite And Ferroelectric Polymer Fibers

Because of its novel microstructure, unique physical and chemical properties important values in basic research and MEMS field, one dimensional nanostructure materials have been a hot topic in recent years. Bismuth ferrite ?BiFeO₃? is one of the few single-phase multiferroic materials which simultaneously show ordered spin and polarization at room temperature, and it has great potential application in memories?MRAM, multi-state memory?, magnetoelectric coupling sensors and MEMS. Compared with other inorganic piezoelectric materials, ferroelectric copolymer P?VDF-TrFE? is more flexible, transparent and easier for processing, so P?VDF-TrFE? has wide application in flexible sensor, energy harvester and wearable devices.In the last decade, various synthesis methods were used to prepare 1-D micro/nano structure materials, such as hydrothermal method, sol-gel method, template method and high voltage electrospinning. Among these methods, electrospinning is a simple, low cost and useful technology for fabricating nanofibers with various morphologies. In this article, multiferroic BiFeO₃ and ferroelectric polymer P?VDF-TrFE? were prepared with improved electrospinning methods. The relevant characterization and property investigation of those two nanofibers were also carried out. The main research contents and results are as follows:1. One dimensional BiFeO₃ nanofiber was prepared by electrospinning based on sol-gel. The heat treatment process, nanostructure and multiferroic property were tested and characterized by DSC, TG, XRD, SEM and FTIR. The crystallization processes of BiFeO₃ fibers were investigated in detail. The fabricated BiFeO₃ nanofibers show certain ferroelectricity and ferromagnetism at room temperature. Compared with bulks, BiFeO₃ nanofiber has a high specific surface area, so the long-period spin modulated spiral reverse ferromagnetic ordered structure on the surface is destroyed, then the unsaturated spin has greater contribution on the magnetic moment, which causes the enhancement of magnetism of BiFeO₃ nanofiber.2. BiFe?1-x?CoxO₃ ?x=0,0.05,0.1? nannofibers were successfully synthesized by electrospinning. The effects of Co2+ doping on lattice structure, nanofiber morphology and multiferroic properties were investigated. XRD showed that all Co2+ doping BFO nanofibers are polar R3c Perovskite structure. SEM image showed the morphology of fibers did not change after doping. The introduction of Co element greatly improved the magnetic properties of BiFeO₃ nanofibers, the saturation magnetization of BFO,BFC-land BFC-2 were 0.86 emu/g,2.32 emu/g,3.98 emu/g, respectively; and the corresponding coercive magnetic fields were 150 Oe,1146 Oe,1288 Oe. This is because Co doping destroys the BFO space spiral magnetic structure.3. The P ?VDF-TrFE? nanofibers were successfully prepared by electrospinning. The influences of different parameters on the morphology and diameter of P?VDF-TrFE? have been studied, including the concentration of precursor solution, the proportion of flux, the voltage and the rotation speed. We also discussed the impaction of rotation speed on the alignment of nanofiber. The experiment results showed that the optimum parameters for the preparation of P?VDF-TrFE? nanofibers are:the solution concentration is 15%, the ratio of DMF and acetone is 7:3, the applied voltage is about 15 kv, the curing distance is 15 cm and the feeding speed is 0.3 ml/h. we got highly ordered nanofiber when the speed of the drum is faster than 2000 rpm.4. Aligned P?VDF-TrFE? nanofibers were successfully fabricated by electrospinning with parallel electrode and rotating drum collector. The flexible copper parallel electrode is fabricated by standard lithography process and wet etching method. SEM images show that the nanofiber is highly ordered with smooth surface and uniform diameter. XRD and FTIR test indicates that the fiber contains a lot of ? phase. In addition, We present a P?VDF-TrFE? nanogenerator based on the in-situ poled aligned fiber. The nanogenerator exhibits good electric performance with output peak-peak voltage about 2V and peak -peak short circuit current about 120nA.These works show the potential application of aligned P?VDF-TrFE? nanofibers on self-powered and wearable devices.