The Preparation Of Fe, Ni, Core/Shell Ni/Au Nanoparticles And Hydrotalcite-like Nanocompounds From Reverse Microemulsion

Fe and Ni nanoparticles possess the merits of magnetic metal fine powders, nanometer metals, and nanometer magnetic materials. As a new kind of nanometer functional composite materials, core/shell Ni/Au nanoparticles have broad applications in biomedical field. However, due to the limitations of the traditional preparation methods, it is difficult to get nanoparticles with uniform diameters, and to control the morphology elaborately. Reverse microemulsion provids a new possible method to resolve these problems.In this work, Fe2+, Ni2+ cations were reduced in the reverse microemulsionsystem to prepare Fe, Ni nanoparticles, and the relations between the Ni nanoparticle diameters and the ratios of Ni2+ solution to emulsifier were investigated. On this basis, core/shell Ni/Au nanoparticles were prepared through a redox-transmetalation method, and the diameters of Ni nanoparticles, the amount of added HAuCl4 which affected the morphology of core/shell Ni/Au nanoparticles was discussed. The morphology was found determined by these factors. The Fe, Ni, and core/shell Ni/Au nanoparticles prepared in this work was pure, without any impurities. For core/shell Ni/Au nanoparticles, the gold shells could effectively slow down the oxidation of the Ni cores. The block temperature of the core/shell Ni/Au nanoparticles decreased from 53K to 16K, with the decreasing of the Ni cores. When the temperature below the block temperature, the sample was ferromagnetic, while above the temperature the sample was superparamagnetic.In addition, Ni-based hydrotalcite-like compounds was synthesized through the reverse microemulsion method, which could be used as catalyst precursor. The type of emulsifiers which could affect the synthesis process was investigated. The mixture of anion emulsifier and cation emulsifier were able to provide a proper system for the syntheis of hydrotalcite-like compounds. Compared with the conventional coprecipitation method, the catalyst obtained from reverse microemulsion exhibited finer Ni crystal grains, higher specific surface, better thermal stability, and uniform dispersion.