Study On The Preparation And Properties Of Structured Tin Dioxide Nanofibers

Tin dioxide is an environmentally-friendly N-type, broad band gap (3.6eV) oxide semiconductor. Nowadays, morphology and structure modification of nano-tin dioxide has attracted much attention because they enable the utilization of the unique optical, electronic, and chemical properties of tin dioxide in different applications.In this research, one-step method for the fabrication of tin dioxide solid, hollow and core-shell nanofibers by directly annealing electrospun composite nanofibers were proposed. And their applications in photocatalysis, gas sensor and lithium ion battery were also tested. It is focus on the forming mechanisms of different structures of tin dioxide nanofibers, and the effect of different morphologies on their applications.Tin dioxide hydrosol was deposited on high tenacity polyester fibers by dip-coating method. The photocatalytic properties of samples were analyzed through the degradation of methylene blue. Atmospheric plasma treatment was used as pre-treatment to improve its hydrophilism. The modulus of monofilament was tested using the force-distence curves, the morphologies and mechanical properties of samples were observed as well. The study revealed that the photocatalytic activity of tin dioxide coated high tenacity polyester fibers were enhanced due to the wettability of high tenacity polyester surfaces improved by plasma treatment. After photocatalysis, the morphologies can be hold as pretreated ones; the modulus of monofilament was decrease, strength was increased as well as elongation was decreased.Tin dioxide/polymer vinyl acetate hybrid nanofibers were fabricated by electrospinning, and the photocatalytic properties of samples were analyzed through the degradation of methylene blue. It is revealed that the photocatalytic activity of tin dioxide/polymer vinyl acetate nanofibers were improved by adding more content of tin dioxide. After photocatalysis, the sample was still retained fibrous structure, but the modulus of single nanofiber was decreased while the strength was increased.At the same time, the photocatalytic property was also improved by adding titanium dioxide doping.Two types of tin dioxide nanofibers, one was cobweb-like structure and the other was fibrous structure were prepared by electrospinning and calcination of polyvinyl acetate/stannic chloride pentahydrate and polyvingl pyrrolidone/stannic chloride pentahydrate precursors, respectively. They were applied in the photocatalytic degradation and the lithium-ion battery tests. The transformation process of nanofibers’structure was tracked by transmission electron microscope, thermogravimetric analysis, Fourier transform infrared spectroscopy and others tests. Experiments have shown that the cobweb-like structure of tin dioxide nanofibers showed better cycling performance in lithium-ion battery tests because it had better ability to preserve the integrity of the electrode structure. On the other hand, the fibrous structure of tin dioxide nanofibers exhibited better photocatalytic activity because they provided higher surface area for absorbing and degrading dye. Additionally, high specific surface areas of tin dioxide nanofibers were obtained by adding silicon dioxide doping and then etched it. According to Kirkendall effect, hollow tin dioxide nanofibers and core/shell tin dioxide/titanium dioxide nanofibers were prepared. The forming mechanisms of those nanofibers were analyzed in details. The hollow tin dioxide nanofibers exhibited an excellect gas sensitivity to ethyl acetate.It also has a high response to a low concentration of ethanol. Especially, the speed of response was fast to all of test-gases. For the core/shell tin dioxide/titanium dioxide nanofibers, they have better cycle performance than hollow tin dioxide nanofibers during lithium-ion battery test.In order to improve tin’s cycle performance in the lithium-ion battery test, core/shell tin/carbon nanofibers were prepared by coaxial electrospinning and carbonization. The elelctrospinning parameters, the ratio of active materials and the structure design were adjusted to get better electrochemical properties. Meanwhile, when the different intermediate polymers, i.e. polyvingl pyrrolidone and polymethyl methacrylate used in the core electrospinning solution, the nanofibers were showed different electrochemical properties during lithium-ion battery test. So the relationship among intermediate polymers and the morphologies of nanofibers and the electrochemical properties were discussed in details as well.