Peapodlike Ni/Ni3S2 chains of about 30 nm in outer diameter, with Ni cores of 10–15 nm, can be synthesized by a sacrificial template route. The Ni3S2 shell exhibits paramagnetic properties with a mass susceptibility of χ ≈ 5 × 10−5 emu (gOe)−1, while the ferromagnetic Ni cores show a superparamagnetic behavior with a blocking temperature of TB ≈ 130 K. The shape anisotropy of the chainlike structure is determined as 5.0 × 104 J·m−3, which is larger than the bulk magnetocrystalline anisotropy by one order of magnitude. The demagnetization factor is determined as ΔN = 0.29. The sample provides an ideal structure for studying the magnetization reversal property by the chain‐of‐sphere model. The observations on the formation of the peapod structure verify a growth mechanism of the nanoscale Kirkendall effect. Based on the preparation of peapod chains, a series of nickel sulfide hollow chains with average diameters of 25, 50, and 100 nm are fabricated. In addition, the phase transition for hollow chains from Ni3S2 to NiS is studied.
One-dimensional (1D) chainlike arrays of hollow magnetic Fe3O4 spheres 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 Fe3O4 hollow 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 Fe3O4 hollow 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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.