Synthesis And Characterization Of Perovskite-Typed Nanofibers By Electrospinning Technique

Nanofiber has become a hot studied subject in the field of nano-technology due to its superior optical, acoustic, electrical, magnetic, thermal and mechanical properties. Perovskite-typed rare-earth composite oxide occupied a very important position due to its giant magnetoresistance effect, photocatalytic oxidation activity, sensitivity characteristic and the application in purifying automotive exhaust, arousing great interests of researchers. If the perovskite-typed rare-earth composite oxides can be prepared into nanofibers, the functions of these compounds will be further improved, and their applications will be widen. Consequently, the nanofibers will be of great significance.In this dissertation, sol-gel method was applied to prepare the precursor solution with a certain viscosity using polyvinylalcohol (PVA Mn=80000) and various inorganic salts as starting materials, and the electrospinning technique was used to fabricate PVA/[La(NO₃)₃+Co(CH₃COO)₂], PVA/ [La(NO₃)₃+Fe(NO₃)₃], PVA/[La(NO₃)₃+Mn(CH₃COO)₂], PVA/[La(NO₃)₃+ Cr(NO₃)₃] and PVA/[La(NO₃)₃+Ni(CH₃COO)₂] composite nanofibers. Perovskite-typed LaCoO₃, LaFeO₃, LaMnO₃, LaCrO₃ and LaNiO₃ nanofibers were obtained by calcinations of the above composite nanofibers.The morphology of fibers were discussed by adjusting all the important parameters such as the concentration of PVA, the mass of metallic salts added to the sol, the voltage, the distance between capillary tip and collector, the velocity of raising temperature. As a result, 9wt% is the best PVA concentration. With the increasing in the concentration of PVA, the diameter of composite fibers increased and the morphology changed from beads to regular and then unregular. 3wt% is the best inorgnic salts concentration. Increasing in the concentration of inorgnic salts made the diameter of fibers increase and the morphology to be unregular, and lead to the deliquescence of fibers. 20kV is the best voltage. With the increase of the voltage, the diameter of composite fibers decreased, but the fibers exhibited a broad diameter distribution. 15cm is the best distance between tip of the capillary and collector. With the increase of the distance of collection, the diameter of composite fibers increased, but the morphology became more regular. The fibers were broken when the calcination temperature was raised quickly, so the velocity of the raising temperature should be controlled below 2℃/min. Moreover, room temperature and humidity have effects on the electrospinning process.The samples were characterized by X-ray diffraction (XRD), scanning...