Preparation, Characterization And Property Of Several Oxides Nano/Micromaterials

Recently, nano/micromaterials have received extensive interests due to their excellent performance in catalysis, optics, and electronics, etc. The controlled growth of nano/micromaterials was very important in current nanoscience and nanotechnology, as the morphology, size and crystal structure of the nano/micromaterials can greatly influence the physical and chemical properties. In this dissertation, we had prepared several oxides nano/micromaterials with different morphologies by hydrothermal process or microwave-assisted hydrothermal process and studied their photocatalytic properties. The main results can be summarized as follows:1 Flower-like Bi2WO6 microstructures were prepared via a simple, rapid, microwave-assisted solution-phase process using Bi(NO3)3, Na2WO4, and hexamethylene tetramine as the reactants. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), field emission scanning electron microscopy (FE-SEM) and high resolution transmission electron microscopy (HRTEM) were employed to characterize the phases and morphologies of the products. The high temperature is found to be favorable for the formation of the flower-like microstructures. The amounts of the hexamethylene tetramine and HNO3 can greatly influence the morphologies of the products. The time-dependent experiments showed an Ostwald ripening mechanism in the crystal growth process. The flower-like morphologies had a good thermal stability. The as-prepared Bi2WO6 was able to efficiently degrade Rhodamine B (RhB) under visible light irradiation. The morphologies of the products could strongly influence the photocatalytic efficiency. Calcination was found to decrease the photocatalytic performance of flower-like Bi2WO6 and the higher calcined temperature corresponds to the lower activity.2 (1) Self-assembled persimmon-like (BiO)2CO3 microstructures were prepared via a simple hydrothermal process employing Bi(NO3)3, trisodium citrate, polyacrylamide, and urea as the reactants. XRD, EDS, FE-SEM, selected area electron diffraction (SAED) and HRTEM were employed to characterize the phases and morphologies of the products. The reactants could greatly influence the phases and morphologies of the final products. Firstly, the suitable amount of trisodium citrate was a necessary condition to prepare the assembled microstructures. Secondly, polyacrylamide can influence the assembly process of the final products. Thirdly, the carbonate ion could preferentially come from the decomposition of the urea via the hydrolysis reaction under hydrothermal conditions. The growth process of the persimmon-like (BiO)2CO3 microstructures has been investigated. The persimmon-like (BiO)2CO3 could be utilized as the sacrificial templates to synthesize Bi2S3, Bi2Te3 and bismuth microstructures by a chemical transformation process. The as-prepared (BiO)2CO3 was able to efficiently degrade RhB and eosin sodium salt under simulated solar irradiation and had a good stability and repeatability after three recycles.(2) (BiO)2CO3 single crystal nanoplates were prepared via a simple microwave-assisted hydrothermal process using Bi(NO3)3, and urea as the reactants. XRD, EDS, FE-SEM, SAED and HRTEM were employed to characterize the phases and morphologies of the products. The controlled experiments were operated to study the influence of the experimental parameters to the morphologies of the final products. The (BiO)2CO3 single crystal nanoplates was able to efficiently degrade RhB under simulated solar irradiation. Under the same photocatalytic conditions, the rate constant of the (BiO)2CO3 single crystal nanoplates was 5 times higher than the above persimmon-like (BiO)2CO3 microstructures prepared via the hrdrothermal process.3 Zn3(OH)2V2O7-2H2O nanodisks were prepared by a simple CTAB-assisted hydrothermal route employing the reaction of zinc nitrate, vanadium pentoxide and sodium hydroxide. The phases and morphologies of the products were characterized by powder XRD, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), Fourier transform infrared spectroscopy (FTIR), HRTEM, EDS and FE-SEM. The results showed that the amount of the CTAB played a key role in controlling the morphology, the size and the self-assembly process of the products. The controlled experiments showed that the high temperature is favorable for the formation of the layer-by-layer self-assembled structures. The crystal growth behavior and the self-assembly process were also investigated by the time evolution experiments.4 CuO nano/micromaterials with three morphologies were prepared via a simple, rapid, microwave-assisted solution-phase process employing Cu(NO3)2 as the copper source, NaOH, urea, and ammonia as the alkali source, respectively. XRD, EDS, FE-SEM HRTEM and SAED were employed to characterize the phases and morphologies of the products. The time-dependent experiments were operated to investigate the crystal growth processes of the products prepared with different alkali source, respectively. The intermediate monoclinic phase Cu2(OH)3NO3 were found in crystal growth processes of three products with different morphologies.