Synthesis And Investigation Of Magnetic Metal Fe, Ni Nanoparticles-composite Nanostructures

Magnetic nano materials have wide applications in the fields such as magneticresonance imaging, optical nano device, targeted drug delivery, data storage, catalysisand so on, due to their unique electricity, optics, magnetics and excellent chemicalproperties. The preparation of small size and uniform size distribution magneticnanoparticles has been an active research area in the field of functional magneticnanomaterials. This dissertation intended to explore the effect of surfactant, metalprecursor, and synthesis method on crystal structures and morphology ofnanoparticles through the preparation of magnetic metal (Fe, Ni) nanoparticles anddifferent crystal phases magnetic nickel phosphides using high-temperature organicsolution method. High crystallinity, uniform size distribution, morphologycontrollable magnetic metal nanoparticles and their composite materials weresynthesized though controlling size, crystallinity and morphology of nanoparticles.First of all, three methods were used to prepare magnetic metal Fe NPs. In thefirst method, the amorphous Fe NPs were prepared by rapid-injection method usingthe thermal decomposition of iron pentacarbonyl at high temperature, and in thepresence of hexadecylammonium chloride (HAD·HCl) can obtain bcc-Fe NPs. In thesecond method, the quadrilateral Fe NPs were synthesized using ferrous stearic acidas an iron precursor by aging method at high temperature with adding sodium oleate(Na-oleate), which controls the morphology of Fe NPs. In the third method, thespherical and highly crystalline Fe NPs were prepared by reducing acetylacetonateiron at high temperature, with trioetylphosphine (TOP) as a surfactant, and to explorethe influence of continuous-injection method for Fe NPs crystal phases. Comparedwith the three methods show that the different precursors, reaction temperature andsurfactants play an important role on the formation of Fe NPs. The magnetic metalFe@nobel metal Au core-shell nanoparticles was very difficult to be synthesized dueto the large lattice mismatch between Au and Fe by a one-pot reaction. In this thesis, atwo-pot reaction was adopted and a stable triphenylphosphine chlorine gold as a goldprecursor was used to generate Au monomers to coat the as-prepared Fe NPs which ismade by thermal decomposition iron pentacarbonyl. The key point of this synthesislies in the kinetic parameters such as temperature fluctuation rapidly affects the formation of Fe@Au core-shell structure.The above preparation of Fe NPs, have been synthesized by rapid-injections andcontinuous-injections, but it has more advantages for continuous-injections in theaspect of controling of nanoparticles morphology. Furthermore, the different crystalphases of the amorphous Ni NPs and Ni3C@Ni core-shell structure were synthesizedusing the continuous-injection method, with TOP as a surfactant, which was added inthe different reaction steps. Catalytic properties studies have shown that they havemuch lower activation energy, and their catalytic activity was much better than thoseof bulk nickel. Ni/NiO core-shell nanostructure was obtaind after the annealing.Studies of their electrochemical performance have found that they all have highcharge and discharge capacity for the first time, and reversible cycle performance isquite stable. Finally, different crystal phases nickel phosphides nanoparticles wereprepared using different nickle precursors and methods. Hexagon nickel phosphides(Ni2P) NPs have been synthesized by a one-pot method using nickel acetylacetonateas a precursor. Repeated injection method was developed to prepare tetragonal nickelphosphides (Ni12P5) NPs with nickel acetate as a precursor. After annealing, the studyof the electrochemical properties have found they also have good charge anddischarge capacity for the first time, and reversible cycle performance is high.Based-on this, Ni/NiO composite materials and nickel phosphides can be used as ideallithium ion battery anode materials.