Preparation And Characterization Of Continuous Long One-dimensional Organic/Inorganic Composite Nanomaterials

Nanostructural materials can be classified into zero dimensional (0D), one dimensional (1D), and two dimensional (2D) structural materials in the light of the definition of nanomaterial. These basic nanostructures become the small units for assembling the nanoscale building. Among three nanostructures, 0D and 2D nanostructures are researched more early. The attention to 1D nanostructures start from 1991, since Iijima who comes from Japanese NEC Company found out carbon nanotubes the preparation and exploitation to quasi-one dimensional or one dimensional nanostructures have been paid much attention. Subsequently, large numbers of methods in preparing variety one dimensional nanostructures emerged continuously. Among variety methods for preparing one dimensional nanomaterials, electrospinning is a simple but versatile process to fabricate one dimensional micro-/nanomaterials. Compared with one dimensional nanomaterials prepared other processes, one dimensional micro-/nanomaterials fabricated using electrospinning are macroscale long in one-dimensional direction. In addition, large-scale production can be obtained using this process. Sol-Gel process has an important position in the preparation of nanostructural materials. Sol-Gel process has been widely used in the preparation of zero dimensional sol nanoparticles, one dimensional ceramic nanowires, two dimensional nanomembranes, and in the coating of nanomaterials. It will be significant to extend the applications of electrospinning technique and Sol-Gel process to incorporate them together to prepare novel one dimensional nanomaterials. This dissertation describes the preparation of one dimensional micro-/nanomaterials by incorporating above-mentioned two processes. According to the different of the preparing routes and the production morphologies, it can be classified into tree categories in this dissertation, i.e., (i) sol particles were assembled into polymer micro-/ nanofibers to form inorganic particles-polymer composite fibers using electrospinning; (ii) ultralong inorganic micro-/nanofibers were prepared by using electrospun polymer fibers as the templates; (iii) inorganic oxides were coated/grown on the fiber surface by using the Sol-Gel coating process; and (iv) hydrolysis in situ the precursors of inorganic/organic composite fibers were hydrolyzed for preparing the inorganic/organic composite fibers. Besides electrostatically assembling the pure micro-/nanofibers, electrospinning can be used for assembling the nanoparticles-polymer composite fibers. Such process can be classified into two steps: (i) preparing the polymer solution with monodispersive particles; (ii) electrospinning above composite solution to form the composite fibers. It is key important to obtain the desirable morphological production that particles can be monodispersive in solution in the first step. The approaches in preparing solution with monodispersive particles can be to dope particles directly into a polymer solution, can also to synthesize particles in situ in polymer solution. Section one and two in Chapter two introduce the preparation solution with monodispersive TiO2 and SiO2 particles by doping directly them into polymer solution. Section three in Chapter two introduces the preparation of PVP solution with monodispersive TiO2 particles by synthesizing in situ them in PVP solution. During the preparation of silica-polymer composite fiber, silica particles with different diameters (45, 95, and 150 nm) were added into different polymer solution with different concentration, respectively. Experimental results showed variety morphologies of silica-polymer fibers could be formed by electrospinning above composite solutions, in which three kinds of structures could be classified: The diameter of particles is far smaller than that of fibers (i); is similar to that of fibers (ii); and is far larger than that of fibers (iii). For preparing the functional composite fibers, TiO2 nanoparticles are incorporated into PAN and PVP fibers. Experimental results showed that the electrospun composite fibers of TiO2 possess the relative abilities of ultraviolet absorption and sterilization. Chapter three introduces the use polymer fibers as the templates to prepare the inorganic micro-/nanofibers. The formation of aim production goes through three steps: (i) preparing the compositesolution of polymer and precursor of inorganic oxides; (ii) electrospinning the composite solution to form the inorganic-organic composite fibers, and (iii) calcining under high temperature these composite fibers in air. This introduced process is employed for fabricating TiO2 and ZnO micro-/nanofibers. Gone through above-mentioned three steps, large-scale TiO2 nanofibers could be prepared. TEM images showed that in fact the fibers were composed of small size TiO2 nanoparticles. The diameter, morphology, and structure of TiO2 nanofibers are decided mainly by the concentration of TiO2 precursor and polymer in solution and electrospinning circumstance parameters. Lower the concentration of TiO2 precursor in solution is, smaller the diameter of formed fibers is. However, the composite fibers with excessive low concentration of TiO2 precursor will fail to form TiO2 fibers, in contrast, will form TiO2 powder. The rule of variations of the diameter and morphology of composite fibers following polymer concentration and electrospinning circumstance parameters abides by that of electrospinning pure polymer solution for preparing pure polymer fibers. The crystalline structures of TiO2 nanofibers will be affected by different experimental conductions. The XRD pattern showed that following the increase of calcined temperature, the crystalline structures of TiO2 will transfer from amorphous to anatase to rutile. In addition, the existence of acetic acid will increase the transition temperature of crystal. ZnO fibers can be prepared by repeating above steps. ZnO fibers are also composed of small ZnO particles. The rule of variation of the diameter and morphology also abides by that of TiO2. Compared with TiO2, whose crystalline structure will transfer following the increase of temperature, the crystalline structure of ZnO is invariant with the crease of calcined temperature. However, with the increase of calcined temperature, small ZnO particles inside fibers will melt and incorporate together to form a single crystalline ZnO fiber. In addition, it is interesting that the fibrous networks of ZnO can be obtained when PVA is used as the template polymer. Chapter four introduces the use of Sol-Gel process to coat/modify the surface of electrospun fibers. The precursors of TiO2 and SiO2 are selected as the coated materials. In the light of the hydrolysis qualities of the precursors of TiO2 and SiO2, three routes were exploited for...