Nickel-based Phosphide Nanostructures: Synthesis, Assembly, And Magnetic Properties

Increasing attention had been paid to the new styles of nanoscale structures with various application in the field of chemistry, physics and material, due to the unique properties and considerable potencial of the hollow nanostructures and core-shell nanostructures. On the basis of current nanoscale magnetic phenomena, the design and preparation of various new-style magnetic nanostructures with potential new nanomagnetic effect and properties would make it possible to further improve the capacity of magnetic information. In this thesis, the synthesis, assembly, and magnetic properties of the nickel-based phosphide nanoparticles with hollow and core-shell nanostructures were investigated.Ni2P hollow nanoparticles with tunable void sizes were obtained by one-pot synthetic technique using triphenylphosphine as a lower-price phosphorus source in a mild temperature organic solution. It was found that the Ni2P hollow nanoparticles were formed by the reaction of as-formed Ni nanoparticles with the surface triphenylphosphine and the outward-diffusion of Ni core via Kirkendall bridges. Varied triphenylphosphine concentrations were used to prepare nanoparticles with void sizes tunable from about 5 to 60 nm in diameter, showing that the lower-price phosphorus source triphenylphosphine can serve a reactive surfactant to tune and heighten the void capacity for potentia applications.Ni/Ni2P core-shell nanoparticles with tunable core-shell sizes were synthesized through surface phosphatizing Ni nanoparticles using triphenylphosphine as phosphorus source in a mild temperature organic solution. It was found that increasing phosphatizing time would lead to thickening of the Ni2P shell, with the Ni core diminishing. Overphosphatizing the particles would make Ni2P nanoparticles form with almost no Ni remaining. And after adjusting the core-shell proportion by reaction time, annealing the Ni/Ni2P core-shell nanoparticles would lead the formation of new-style phosphide Ni3P, through the chemical combination of Ni2P shell with inner Ni during annealing.The magnetic properties of as-synthesized nickel-based phosphide nanoparticles were studied at and below the room temperature. It was found that the Ni/Ni2P core-shell nanoparticles have a magnetic transforming from ferromagnetism to superparamagnetism as warming from 10 K to the room temperature. However, the Ni2P nanoparticles are paramagnetic. As a result, the surface magnetic modification of Ni core by the Ni2P shell was enhanced as the increase of phosphatizing time. And the magnetic thermal stability of the nanoparticles with redued ferromagnetic Ni core was inproved through the enhanced influence of magnetic surface anisotropy after surface magnetic modification, which makes it possible to further improve the information capacity via size.The magnetization-temperature memory effect up to room-temperature was observed in the self-assembly of Ni/Ni2P core-shell nanomagnetic particles under low-filed direct-current magnetization process. It was found that the self-assembly of nanoparticels with higher magnetic thermal stability can highen the temperature-rang for memory effect, and lowering interparticle spacing can further improve the temperature-rang. However, heightening applied magnetic field can suppress the memory effect with decreasing temperature-range. Moreover, a new mode to read-write magnetic coding was realized based on temperature using the memory effect, indicating a new way to further heighten the information capacity via temperature.