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A series of highly uniform one-dimensional Ni nanochains, with diameters ranging from 20 to 200 nm, have been synthesized by a facile, template-free, wet chemical method at diverse temperature and magnetic field. Our results indicate that the crystallite size, diameter and length of the prepared nanochains depend critically on the reaction temperature. The characteristic thermodynamic cohesive energies, ΔEDand ΔEL, are obtained for the formation of the Ni nanochains. In addition, the chain length also depends on the applied field because of the Zeeman energy of the magnetic Ni nanoparticles. For the morphology control, an external field is required in order to obtain axially aligned rather than dendritic nanochains. The size-dependent magnetic properties are studied systematically. The saturation magnetization is shown to reduce inversely with the chain diameter, attributable to a core−shell structure. The thickness of the shell which encloses the ferromagnetic Ni core is determined to be about 2.3−3.4 nm.

One-dimensional (1D) chainlike arrays of hollow magnetic Fe3O4spheres have been prepared by simply aging magnetically preassembled Fe nanoparticles in aqueous solution at room temperature. The diameter of the 1D nanomaterials is about 100−200 nm, and the length is up to 1−3 μm, observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The structure and magnetic properties of the Fe3O4hollow chains were characterized by X-ray powder diffraction (XRD) and via a superconducting quantum interference device (SQUID) magnetometer. Mechanism investigations on the time dependent process reveal these hollow nanostructures were formed based on the nanoscale Kirkendall effect. Besides the aqueous microenvironment, the partial pressure of oxygen is of great importance in the formation of 1D chainlike Fe3O4hollow nanostructures.

Nickel nanochains assembled with submicrometer-sized hollow spheres were synthesized through a mild polyol reduction method by using PVP as the soft template. The resulting fiberlike superstructures were characterized by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy. A self-assembly mechanism of PVP-assisted bubble templating is responsible for the formation of hierarchical superstructures. It was found that PVP concentration plays a key role in determining both the morphology and the further self-assembly process of nickel hollow fibers. 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; the micromagnetic simulation result by OOMMF code showed good agreement with the characters of our samples.