Structure Controlled Low-dimensional Zinc Oxide And The Application Research Of Molten Salts Assisted Technique In The Synthesis Of Nanomaterials

Low-dimensional nanostructured materials have received a worldwide interest because of their unique electronic, optical, and mechanical properties and their potential applications in nanodevices and functional materials. We find that the structure, dimension, shape and size of dimensional nanomaterials have important effects on their performances according to a lot of literatures. In the thesis, structure-controlled products were synthesized using a simple solution method according to the crystals growth behavior or inorganic molten salts as reaction media. The approach required neither complex apparatus and sophisticated procedures nor metal catalysts, templates or regulating surfactants.1. 1D ZnO nanorods were successfully synthesized by a simple chemical precipitation method in aqueous solution at 80℃using ammonia water as precipitant. The method utilized the crystals growth behavior and hexagonal ZnO nanorods with 120 nm in diameter and 800 nm～1μm in length were achieved without subsequent calcinations in oven. The effects of reaction conditions on the morphologies and performances of ZnO nanorods, including reation temperature, ammonia water amount, calcination temperature and so on, were studied. Furthmore, skin-colored ZnO nanorods were obtained with appropriate amounts of ammonia water or in a certain range of calcination temperature. The growth mechanisms and pigmentation mechanisms of ZnO nanorods were finally developed.2. The size-controlled and better-dispersed ZnO nanoparticles were obtained in aqueous solution and water-ethanol mixed solvent using molten salts assisted approach, respectively. Submicron- and nano-sized ZnO were synthesized in aqueous solution below 70℃using ammonia water as precipitant. The effects of reaction conditions on the diameter size of ZnO nanoparticles were studied, and the addition of eutectic could improve the dispersibility of the products. The formation mechanisms of ZnO nanoparticles in aqueous solution were also discussed. ZnO nanoparticles were synthesized in water-ethanol mixed solution. The diameter size and dispersion of the products were easy to control with the addition of low dielectric constant ethanol and subsequently calcination with an appropriate amount of molten salts. And the formation mechanisms in mixed solution and the effect of molten salts were investigated.3. ZnO nanoparticles were grafted by steric acid and silane coupling agent, respectively. The surface of nanosized ZnO changed from hydrophilicity to hydrophobicity after organic modification, and the hydrophobicity was impoved with the increase of agent amount. Surface bonding characteristics and surface characteristics were analyzed. The reaction of steric acid with surface hydroxyl of ZnO was similar to esterification reaction between carboxylic acids and alcohol. And steric acid could bridge with ZnO nanoparticles. KH570 silane coupling agent grafted onto the surface of ZnO nanoparticles in the form of chemical bond.4. Based on the general molten salts assisted technique, the others nanomaterials were also prepared and many novel achievements were developed. Different nanomaterials, such as In₂O₃, ZrO₂, NiO, Al₂O₃, MgO, Mg(OH)₂, TiCN and BP, were successfully prepared with adding molten salts or by-products. Under ambient pressure, the so-called high pressure phase, corundum type In₂O₃ nanocrystals were firstly prepared using ZnCl₂ as additive, the method required neither surfactants nor organic solvents. And the high temperature phase, c-ZrO₂, was also obtained in the presence of KCl-ZnCl₂ eutectic. Furthermore, the decomposition of precursor was adjusted with the addition of molten salts. Finally, the formation mechanisms of molten salts in the synthesis of nanomaterials were investigated in detail.