Researches Of One Dimensional Nano-Materials On Diameter-Controlled Synthesis, Growth Mechanisms And Physical Properties

With the development and advanced research in nano-science and technology, one-dimensional (1-D) nano-materials have attract widely interesting due to their unique property and broad foreground in application. However, there are still many technique problems needed to be overcame in order to use them in nano-devices and practical application. Thereinto, diameter-controlled synthesis method is needed to obtain homogeneous 1-D nanomaterials system, and it is also a quite important and available route for the further research in their property and potential application.In the present work, metal nanocrystalline materials is electro-deposited on a metal substrate using periodic reverse (P.R.) pulse plating and it is used as the catalysts to synthesis the 1-D carbon and metal oxide nano-materials in diffuse flames and thermal oxidation method, respectively. The grain size of the nanocrystalline materials could be controlled by adjusting the plating parameters such as the output pulse frequency (f) and the duty cycle (r), therefore, the diameter-controlled synthesis of 1-D nano-materials is realized in this method. At the same time, the physical property and growth mechanisms of the 1-D nanomaterials are also discussed, and it provide the possibility for the further research and application of the 1-D nano-materials.This dissertation consists of eleven chapters. Chapter one is the introduction, in which the origin and supporter of the project, significance and the major author's work are introduced briefly. The development and present research situation in the world in the areas are reviewed and the trend of the further development is also discussed, such as 1-D nanomaterials, 1-D metal oxide nanomaterials, 1-D carbon nanomaterials and 1-D carbon nanomaterials synthesized in flames.Pulse electro-deposition technique and nano-science and technology are two different branches of science subjects. The task of the present work is to synthesize metal nanocrystalline materials by pulse electro-deposition technique in chapter two, and they are used as the catalysts to synthesize the 1-D nanomaterials. On order to reflect this combination, the fundamental knowledge of pulse electro-deposition technique is introduced briefly. At the same time, the development and present research situation in the world about the metal nanocrystalline materials synthesized by pulse electro-deposition technique are reviewed and the trend of the further development is also discussed.Synthesis of the metal nanocrystalline materials is the important basis of successful synthesis of the diameter-controlled 1-D nano-materials. In chapter three, the electro-deposition techniques of some kinds of the metal nanocrystalline materials and the experimental project of synthesis of the 1-D nanomaterials are introduced in detail.In chapter four, liquid-fuel flames method is successful used in the synthesis of some kinds of 1-D carbon nanomaterials on different substrate materials for the first time, including: multi-walled carbon nanotubes (MWCNTs), carbon nanofibers (CNFs), well-aligned carbon nanotubes arrays and helical carbon nanofibers. It is also found that different kinds of substrates materials have different influence on the morphologies and microstructures of the 1-D carbon nanomaterials: Ni element is inclined to catalyzed grow"hollow-center"carbon nanotubes, while the Fe element is inclined to catalyzed grow"solid-core"carbon nanofibers, and the corresponding growth mechanisms is put forward to be"hollow-center"and"solid-core"growth model. The graphite degree of order and graphite structure of the 1-D carbon nanomaterials with different structure in flames are investigated by laser-Raman spectra and their fluorescence phenomena are firstly found in the side of high Raman shift range, which is induced by the defects or impurities in the 1-D carbon nano-materials synthesized in this method.Diameter-controlled synthesis of the carbon nanotubes and nanofibers is realized in flames for the first time, which is introduced in chapter five and chapter six, respectively. Pulse electro-deposition technique is firstly used to synthesize a layer of Ni or Fe nanocrystalline materials on the surface of the substrates, and which is used as the catalysts to grow homogeneous-sized CNTs or CNFs in ethanol flames, respectively. The morphology and grain size of the nanocrystalline materials could be controlled by adjusting the plating parameters such as the output pulse frequency (f) and the duty cycle (r), then, the diameter-controlled synthesis of 1-D nano-materials is realized in this method. And a"base-growth"model in this method is also introduced. In chapter six, it is also found that straight or helical solid-cored CNFs are synthesized by adding different additives, respectively, which is due to the change of the crystal structure of the plated Fe nanocrystalline materials.1-D metal oxide nanoneedles materials (CuO, ZnO,γ-Fe2O3) is synthesized by thermal oxidation of the corresponding plated nanocrystalline materials in air, which is introduced in detail in chapter seven, chapter eight and chapter nine, respectively. The influence parameters on the synthesis and morphology of the 1-D metal oxide nanoneedles materials is discussed systematically, such as the effect of the pulse electro-deposition, thermal oxidation temperature and reaction atmosphere. In chapter seven, it is found that the formation of Cu2O form is quite important to the growth of the 1-D CuO nanoneedles materials. The filed emission property of the single CuO nanoneedles is firstly measured by"in-situ"transmission electron microscope (TEM) observation, and the filed emission property and the performance of the dye-sensitized solar cells of the 1-D CuO nanoneedles film are also investigated. In chapter nine, the filed emission property of the 1-D ZnO nanoneedles film is studied. In chapter seven, modulated structure of the 1-Dγ-Fe2O3 nanoneedles materials is found in their middle and top part, which is caused by the growth method in this method. And the carbon-coated nanoneedles composite materials are synthesized with the catalysis of the 1-Dγ-Fe2O3 nanoneedles materials in ethanol flames.In chapter ten, the influence of the oxidation effect on the synthesis of 1-D metal oxidation nanoneedles materials and their growth and nucleation model are discussed. At the same time, a"base growth"model with electric field assisted oxidation in this method is put forward fisrtly.Chapter eleven is the conclusions of all the research work mentioned in this dissertation. The last part of the dissertation lists author's research projects and published papers finished during the doctorate study period.