Synthesis And Characterization Of Nanomaterials By Hydrothermal Methods

The present thesis is focused on exploring mild and simple methods to synthesize some important inorganic functional nanomaterilas via designing novel hydrothermal systems and processes. It is aimed at improving purity, reducing the costs, minishing pollutions and controlling its morphology and dimension. Furthermore, many modern techniques including powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), scan electron microscope (SEM), UV-Vis absorption spectra (UV-Vis), room temperature fluorescence spectra (RTPL), Fourier transform infrared spectroscopy (FTIR),Raman spectroscopy (Raman), Vibrating Sample Magnetometer (VSM), and so on, were used to characterize the as-synthesized products, and their possible formation mechanisms were also proposed. The main works completed are summed up as following:1. The mild preparation of submicron Cu₂O and CuO crystallites from a solid metallorganic molecular precursor (copper acetylacetonate, Cu-(ACAC)₂) has been achieved via two simple steps: firstly, the Cu-(ACAC)₂ precursor was precipitated from the reaction of copper acetate and acetyl acetone in distilled water under the ambient condition; then, cubic phase Cu₂O submicrocrystals with the size of mostly 80-260 nm could be produced by hydrothermal treatment of the Cu-(ACAC)₂ in distilled water at 180 oC for 12 h, while monoclinic structure CuO submicrocrystals with the size of about 130-470 nm could be obtained by thermolysis of the Cu-(ACAC)₂ in air at 300 oC for 5 h. The structure, morphology, size and composition of the as-synthesized products were characterized by XRD, FTIR, SEM and XPS, and their possible formation mechanisms were tentatively proposed.2. The controllable synthesis of pure hematite (α-Fe₂O₃), maghemite (γ-Fe₂O₃) and magnetite (Fe₃O₄) nanocrystals from a solid air-stable metallorganic molecular precursor (ferric acetylacetonate: Fe-(ACAC)₃) has been achieved by two simple steps: firstly, Fe-(ACAC)₃ was prepared through the room temperature precipitation reaction of ferric chloride, acetylacetone and sodium acetate in distilled water under atmospheric pressure; secondly,α-Fe₂O₃ and Fe₃O₄ nanocrystals free of organic contaminants could be produced via low temperature (80-180 oC) hydrothermal treatment of the Fe-(ACAC)₃ in distilled water and 20 vol.% hydrazine hydrate aqueous solution, respectively; while pureγ-Fe₂O₃ andα-Fe₂O₃ nanocrystals were synthesized by direct thermolysis of the Fe-(ACAC)₃ in air at 300 oC and 500 oC, respectively. The effects of the solvents, reaction temperatures and reaction times on the phase, shape and size of the resultant products during hydrothermal processing were investigated. The structure, composition, morphology, size and magnetic properties of the obtained products were characterized by XRD, TEM, FTIR, Raman, VSM, and their possible formation mechanisms were tentatively proposed.3. A kind of green hydrothermal method has been developed to prepare nanocrystalline CuCl and CuBr powders. Cubic phase CuCl powders were obtained by using the reaction of CuCl₂ and D-glucose in distilled water in an autoclave at 120 oC for 24 h, while cubic phase CuBr powders were produced by using the reactions of CuSO₄·5H₂O, KBr and D-glucose in distilled water in an autoclave at 100-120 oC for 12-48 h. The structure, morphology, size, composition and optical properties of the resultant CuCl and CuBr nanocrystals were characterized by XRD, SEM, TEM, XPS, UV-Vis, RTPL, and their possible formation mechanisms were also proposed.