Fabrication Of Composite Nanofibers By Electrospinning And Its Application

Electrospinning is a simple and versatile technique for generating continuous nanofibers. Nanofiber possesses features of excellent mechanical property, very high specific surface area and aspect ratios, which assure its promising applications in various areas, such as catalysts, gas sensing, reinforcing materials, tissue engineering scaffolds, and photoelectric materials. This thesis research work includes the following aspects:(1) TiO₂/ZnO composite nanofibers with diameter in the range of 85-200 nm were fabricated via the electrospinning technique. After treated with 0.1 mol/L NaOH solution, TiO₂/ZnAc/CA composite nanofibers were transformed into Ti02/Zn(OH)2/cellulose composite nanofibers. TiO₂/ZnO composite nanofibers were obtained by calcinating the hydrolyzed composite fibers at 500 and 700℃for 5h. With the blending of ZnO into TiO₂, a new crystallite ZnTiO3 was formed in addition to the ZnO and TiO₂ crystallites, and the ultraviolet light absorption efficiency was enhanced according to the UV-vis diffuse reflectance spectroscopy (DRS). Almost 100% Rhodamine B (RhB) and 85% phenol were decomposed in the presence of TiO₂/ZnO composite nanofibers under mild conditions. The results demonstrated that the blending of ZnO in the composite nanofibers increased the photocatalytic efficiency, whereas the optimum ZnO content was 15.76 wt% to reach the most efficient photocatalytic activity.(2) The mesoporous ZnO/SnO₂ composite nanofibers with pore size less than 15 nm were prepared via the electrospinning technique. Transmission electron microscopy (TEM) images showed that the mesoporous ZnO/SnO₂ composite nanofibers were composed of grain-like nanoparticles. The nanoparticles size increased with the increasing of the calcination temperature from 500℃to 900℃. Moreover, the crystal phases, grain sizes, and band gap energy of the mesoporous ZnO/SnO₂ composite nanofibers were influenced by the molar ratio of Zn:Sn and the calcination temperatures. It was found that the photocatalytic activity of the mesoporous ZnO/SnO₂ composite nanofibers was dependant on their surface areas, light utilization efficiency, and the separation of photogenerated electron/hole pairs. The maximum photocatalytic activity was shown for composite nanofibers with the molar ratio of Zn:Sn=2:1 and calcination at 500℃for 5 h. A mechanism of the charge separation and photocatalytic reaction for the mesoporous ZnO/SnO₂ composite nanofibers was also presented.(3) Sea-island polyurethane (PU)/polycarbonate (PC) composite nanofibers were obtained through electrospinning of partially miscible PU and PC in 3:7 (v/v) N,N-dimethylformamide (DMF) and tetrahydrofuran (THF) mixture solvent. The structures and morphologies of the nanofibers were influenced by composition ratio in the binary mixtures. The pure PC nanofiber was brittle and easy to break. With increasing the PU content in the PU/PC composite nanofibers, PU component not only facilitated the electrospinning of PC, but improved the mechanical properties of PU/PC nanofibrous mats. In a series of nanofibrous mats with varied PU/PC composition ratios, PU/PC 70/30 showed excellent tensile strength of 9.60 Mpa and Young's modulus of 55 Mpa. After selective removal of PC component in PU/PC composite nanofibers by washing with acetone, the residual PU maintained fiber morphology. However, the residual PU nanofiber became irregular and contained elongated indents and ridges along the fiber surface. PU/PC composite fibers showed sea-island nanofiber structure due to phase separation in the spinning solution and in the course of electrospinning.