Preparation Of Metal And Oxid Nanomaterials In Liquid Ammonia And Investigation Of Their Properties

In this dissertation, various metals and metal oxides nanomaterials were prepared by reduction of metal salts in liquid ammonia at the present of sodium metal. Their morphologies and structures were characterized. The optical and magnetism properties of the as-synthesized particles were investigated. Meanwhile, the formation mechanism of nanomaterials prepared in liquid ammonia at the present of alkali metal was proposed. The main work of this dissertation includes the following parts:1. Preparation and Optical Properties of ZnO Nanoparticles in Liquid Ammonia.ZnO nanoparticles were prepared by reduction of zinc nitrate hexahydrate in liquid ammonia at the present of sodium metal. It was found that sodium dodecyl sulfonate (SDS) had an obvious effect on the morphology and size distribution of as-prepared ZnO nanoparticles. Morphologies, structure and thermal properties of ZnO nanoparticles were characterized by means of X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), UV–Visible (UV-vis), Fluorescence (PL) spectroscopy, thermogravimetry (TG) and differential thermal analyzer (DTA). The results show that SDS modified ZnO nanoparticles exhibit uniform size distribution and show rod-like shape, the width of the rods is estimated to 7 nm, and the length of rods is 18 nm, The room temperature PL spectrum was performed on a SPEX F212 ?uorescence spectrophotometer with a Xe lamp upon excitation at 325 nm. It was found that the ZnO and SDS modified ZnO nanoparticles prepared in liquid ammonia are no UV emission. This phenomenon is rarely reported.2. Preparation and Magnetic Properties of Fe₃O₄ Nanomaterials in Liquid Ammonia.Magnetite (Fe₃O₄) nanoparticles with a size range of 8-17 nm were prepared by reduction of anhydrous FeCl3in liquid ammonia at the present of sodium metal, the structure and morphologies of as-prepared Fe₃O₄ nanoparticles were characterized by means of XRD, TEM, FT-IR. The results show that quadrangle and hexagon shape and well-dispersed Fe₃O₄ nanoparticles were syntheized when polyvinylpyrrolidone (PVP) was chosen as the surface modification agent to. the average particles'size was 12 nm with a narrow distribution ranging from 8 to 17 nm. The magnetic properties of Fe₃O₄ nanoparticles were evaluated on a MPMS XL-7 superconductivity quantum interference device (SQUID) at room temperature. The results show that the as-synthesized Fe₃O₄ nanoparticles exhibit superparamagnetic behavior and have a high saturation magnetization (Ms) which slightly below that of bulk Fe₃O₄ (92 emu/g)3. Synthesis and Characterization of Pb Nanotapes in Liquid Ammonia.Lead nanotapes were synthesized in liquid ammonia solvent in the presence of sodium metal at low temperature. The process was template free. TEM, oXRD and Energy-dispersive X-ray spectroscopy (EDX) characterizations revealed that the as-prepared Pb nanotapes have average diameters in the range of 40-50 nm, and lengths up to several hundred nanometers, and exhibit cubic crystal structures. FT-IR investigation indicate that the there are plenty of amino and hydroxyl residums on the surface of as-synthesized Pb nanotapes. The formation mechansim of Pb one-dimension nanostructures without template was proposed.4. Synthesis and Characterization of Sn NanoparticlesStearate modified Sn nanoparticles were synthesized from liquid ammonia in the presence of sodium metal with sodium stearate (St) as a modification agent. The morphology, structure and thermal properties of as-prepared nanoparticles were characterized by means of XRD, TEM, FT-IR and TG. The tribological properties of the as-synthesized nanoparticles used as additives in liquid paraffin (LP) were evaluated on a four-ball test machine. The results show that the surface modified Sn nanoparticles exhibit tetragonal crystal structure. The mean size of the particles is 20 nm. The effect of syntheis method on the tribological preoperties was invesitated.