Studies On Electrospinning Preparation And Properties Of Ti-based Ceramic Nanofibers

One-dimensional （1D） nanomaterials and nano-devices have been widely studiedfor their significant properties. These researches have demonstrated the potentialapplications of1D nanostructures in the fields of environmental protection, newenergies, information and so on. In this dissertation, multifunctional ceramic nanofiberswere fabricated by electrospinning. And their unique properties in the area ofphotocatalysis, electrics and optics were explored.TiO₂nanofibers with controllable diameters were fabricated by a facileelectrospinning method. The dependence of fiber diameter and crystal structure on thephotocatalytic properties of TiO₂nanofibers were investigated. It was found that thediameter of the nanofibers, controlled by changing the tetrabutyl titanate content in theprecursor solution, plays an important role on the photocatalytic activity of TiO₂nanofibers. There is an optimal value of diameter on the photocatalytic activity of TiO₂nanofibers, which increases with the increasing of fiber diameter up to about200nmand then decreases. On the other hand, the photocatalytic activity of TiO₂nanofiberswas found to be enhanced when annealed at higher temperatures with amount of anatasephase transformed to rutile, which is due to the more efficient electron-hole separationwith an appropriate amount of rutile phase introduction.Enhanced visible-light-driven photocatalysis of TiO₂nanofibers were prepared bythe electrospinning method combined with a surface nitridation process. Thevisible-light-driven photocatalytic activity of the electrospun TiO₂nanofibers could beenhanced by nitridation in NH3atmosphere. The optimal visible-light photocatalyticactivity of N–TiO₂nanofibers exceeded that of pure TiO₂nanofibers by a factor of morethan12. The nitridation temperature under NH3flow was found to play an importantpart in the performance of N–TiO₂nanofibers, and the optimum temperature is500℃.We synthesized high-quality TiN nanofibers by the combination of electrospinningand ammonification process. The current through nanofibers was remarkably debasedwith the increase of calcination temperature. A single TiN nanofiber showed a linearI-V curve, with the conductivity up to121.1S/cm when annealed at800℃. The TiNnanofiber networks exhibited high electrical conductivity and high optical transmittance. A sheet resistance of15.8Ohm/sq has been achieved at84%transmittance.BaTiO₃nanofibers were prepared by electrospinning. The morphology ofsynthesized BaTiO₃nanofibers was investigated under different heat treatmentconditions. The phase transformations in BaTiO₃nanofibers were monitored usingRaman spectroscopy. It was found that the Curie temperature of BaTiO₃nanofibersincreased to220℃, which is notably higher than the bulk BaTiO₃ceramics. Broadvisible emission at the wavelength range of400⁸00nm was obtained at roomtemperature in amorphous BaTiO₃nanofibers, which were prepared by electrospinningand calcined at low temperatures.Unique Ag/BaTiO₃heterostructured nanofibers was fabricated. It was found thatsmall and homogeneously distributed Ag nano-particles could decrease thecrystallization temperature of BaTiO₃nanofibers to a much lower value compared withbulk BaTiO₃ceramics. The mechanism of the effect of Ag addition on BaTiO₃crystallization is accordingly analyzed and discussed. Besides, the addition of Agsharply increases the conductivity of BaTiO₃nanofiber.