Graphene encapsulated Fe3O4 nanospindles were synthesized by a simple hydrothermal method. From field-emission and transmission electron microscopy results, the Fe3O4 nanospindles with the length of about 260 nm are highly encapsulated in graphene matrix. The reversible Li-cycling properties of graphene encapsulated Fe3O4 nanospindles have been evaluated by galvanostatic discharge-charge cycling and cyclic voltammetry. Results show that graphene encapsulated Fe3O4 nanospindles exhibits a high reversible capacity about 745 mA h g(-1) for the first cycle and a stable capacity of about 558 mA h g(-1) for up to 200th cycle in the voltage range of 0.01-3.0 V at a current density of 100 mA g(-1), indicating excellent cycling stability. The graphene in the composite materials could act not only as lithium storage active materials, but also as an electronically conductive matrix to improve the electrochemical performance of Fe3O4.
A simple catalytic pyrolysis route was developed to prepare one-dimensional Fe3O4@C composites using waste polypropylene as carbon resource, in which the Fe3O4 nanoparticles were self-assembled to necklace-shaped structures. The products were characterized by means of X-ray power diffraction (XRD), Raman spectra, field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The results indicate that the diameter of chains is about 550 nm, the size of Fe3O4 particles is ranging from 200 to 500 nm, and the thickness of carbon shells is about 150 nm. The magnetic measurement at room temperature indicates that the value of saturation magnetization (22.0 emu/g) and coercivity (171.7 Oe) is different from that of bare Fe3O4 nanoparticles and bulk Fe3O4 due to the different carbon content, dipolar interactions, size and morphology of the products.
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