Facile synthesis of hollow and porous nickel microspheres by low temperature molecular self-assembly

Hollow and porous nickel microspheres with potential applications as catalysts, magnetic materials, and adsorbing materials were synthesized by self-assembly in an aqueous medium in which hydrazine hydrate acted as the reducing agent. The crystal structure, phase, particle size and magnetic performance of the hollow nickel microspheres were characterized and the effects of the template, pH value, temperature, and reaction time were evaluated. Uniform hollow nickel spheres with porous structures could be obtained at 75 °C and pH of 9–10 with a heating time of 30 min. The average diameter of the spheres was 1.4 μm and mean thickness of the sphere wall was 120 nm. Polyvinyl pyrrolidone (PK40) played an important role in the formation of the spherical template which controlled the formation of hollow spheres. Magnetic measurements indicated that the hollow nickel spheres are soft-magnetic materials with much lower coercivity and much higher saturation magnetization compared to the nickel crystals with irregular shapes.

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