Yolk-shell Fe 3 O 4 @N-doped carbon nanochains, intended for application as a novel microwave-absorption material, have been constructed by a three-step method. Magnetic-field-induced distillation-precipitation polymerization was used to synthesize nanochains with a one-dimensional (1D) structure. Then, a polypyrrole shell was uniformly applied to the surface of the nanochains through oxidant-directed vapor-phase polymerization, and finally the pyrolysis process was completed. The obtained products were characterized by X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and thermogravimetric analyses (TGA) to confirm the compositions. The morphology and microstructure were observed using an optical microscope, scanning electron microscope (SEM), and transmission electron microscope (TEM). The N 2 absorption-desorption isotherms indicate a Brunauer-Emmett-Teller (BET) specific surface area of 74 m 2 /g and a pore width of 5-30 nm. Investigations of the microwave absorption performance indicate that paraffin-based composites loaded with 20 wt.% yolk-shell Fe 3 O 4 @N-doped carbon nanochains possess a minimum reflection loss of −63.09 dB (11.91 GHz) and an effective absorption bandwidth of 5.34 GHz at a matching layer thickness of 3.1 mm. In addition, by tailoring the layer thicknesses, the effective absorption frequency bands can be made to cover most of the C, X, and Ku bands. By offering the advantages of stronger absorption, broad absorption bandwidth, low loading, thin layers, and intrinsic light weight, yolk-shell Fe 3 O 4 @N-doped carbon nanochains will be excellent candidates for practical application to microwave absorption. An analysis of the microwave absorption mechanism reveals that the excellent microwave absorption performance can be explained by the quarter-wavelength cancellation theory, good impedance matching, intense conductive loss, multiple reflections and scatterings, dielectric loss, magnetic loss, and microwave plasma loss.
High thermal conductivity graphite nanoplatelets/ultra high molecular weight polyethylene (GNPs/UHMWPE) nanocomposites are fabricated via mechanical ball milling followed by a hot-pressing method.
Constructing heterointerfaces between metals and metal compounds is an attractive strategy for the fabrication of high performance electrocatalysts. However, realizing the high degree of fusion of two different metal components to form heterointerfaces remains a great challenge, since the different metal components tend to grow separately in most cases. Herein, by employing carboxyl-modified carbon nanotubes to stabilize different metal ions, the engineering of abundant Ni|MnO heterointerfaces is achieved in porous carbon nanofibers (Ni|MnO/CNF) during the electrospinning-calcination process. Remarkably, the resulting Ni|MnO/ CNF catalyst exhibits activities that are among the best reported for the catalysis of both the oxygen reduction and oxygen evolution reactions. Moreover, the catalyst also demonstrates high power density and long cycle life in Zn-air batteries. Its superior electrochemical properties are mainly ascribed to the synergy between the engineering of oxygen-deficient Ni|MnO heterointerfaces with a strong Ni/Mn alloying interaction and the 1D porous CNF support. This facile anchoring strategy for the initiation of bimetallic heterointerfaces creates appealing opportunities for the potential use of heteronanomaterials in practical sustainable energy applications.
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