Investigation Of Metal Nanoparticles Synthesized By Hydrothermal Method

Owing to the small size effect, surface effect, quantum size effect, quanta tunnel effect and coulomb blockade effects, metal nanoparticles exhibit unique and superior properties that are significantly different from those of corresponding bulk solid state in such aspects as optics, electronics, magnetism and catalysis and thus can be applied to various fields such as photoelectron apparatus, wave-absorption materials, catalyst, lubricants, activation and sintering materials, etc.Hydrothermal method possesses such merits as high temperature and high pressure, even distribution of energy as well as no-sintering process. At the same time, Hydrothermal system has high vapor pressure, low intensity and low surface tension. All this creates a perfect physical and chemical environment for the preparation of metal nanoparticles.In the present thesis, silver and copper nanoparticles are prepared respectively with Hydrothermal method. Since aggregation frequently takes place during the process of preparing metal nanoparticles so as to affect the properties of nanoparticles, the present author first arrives at a systematic summary of how experiment parameters affect properties of nanoparticles. Then in the experiments, less aggregation is achieved in preparation of nanoparticles by adjusting experiment parameters.First, through Hydrothermal method, well-dispersed Ag nanoparticles are prepared with Sodium dodecyl sulfate(SDS) and Polyvinylpyrrolid-one(PVP) as surface active agents and with Hydrazine hydrate(N2H4·H2O) and no-water ethanol as the reductive agents. Then their grain sizes, lattice structure, morphology, property of dispersion and absorption spectrum property are characterized by X-ray Diffraction (XRD), Transmission Electron Microcopy (TEM),High Resolution Transmission Electron Microcopy (HRTEM) and UV-Vis. Besides, the grain sizes of Ag nanoparticles are worked out with the help of Scherrer Formula. Finally, the process mechanism of Ag nanoparticles and the function of the surface active agents are discussed. Then, the lattice structures of Ag nanoparticles prepared by Hydrothermal method are measured and calculated from two aspects. On one hand, the lattice parameters of samples with different grain sizes are calculated and analyzed. Then the results of one group of samples are picked out and discussed in detail. On the other hand, the relation between the grain sizes and lattice parameters of different samples is studied. At the same time, the impact of the average grain sizes of Ag nanoparticles on the values of lattice distortion is discussed. The result shows that lattice expansion takes place in the lattice structure of Ag nanoparticles prepared by Hydrothermal method. Finally, the above phenomena are illustrated based on the theory of thermodynamics and the theory of entropy.Finally, Cu nanoparticles are prepared on the condition that the values of PH range from 9 to 11 and with Hydrazine hydrate(N2H4·H2O) as the reductive agent. Then the impacts of ion contents of the precursor, the PH values of the reaction solution and the temperatures of heat treatment on the morphology, lattice types and particle sizes of Cu nanoparticles are examined, using a variety of approaches.