Free-template synthesis and magnetic properties of Ni micro-chains

Nickel micro-chains assembled with submicrometer-sized flowers were synthesized through a mild hydrothermal method without any template and surfactant. The resulting chains superstructures were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. A self-assembly mechanism is responsible for the formation of hierarchical superstructures. It was found that reaction time played a key role in determining both the morphology and the further self-assembly process of nickel superstructures. This first synthesis of such hierarchical structures implies a simple and inexpensive way to prepare transition metal superstructures on a large scale. Magnetic measurements by SQUID were also carried out to explore their magnetic properties; an the micro-magnetic simulation result showed good agreement with the characters of our samples.