Absorbers have been investigated widely so as to eliminate or at least significantly attenuate the hazards of electromagnetic radiation. A porous structure is believed to be beneficial for the high-performance of microwave absorption. Here, an embedded magnetic mesoporous composite (FeNi alloyed porous carbon microspheres, FeNi/CS) is for the first time evaluated as a microwave absorbing material. Upon combining reduced graphene oxide (rGO) with the FeNi/CS composite, a multiple-component absorber of FeNi/CS/rGO is synthesized via hydrothermal and freeze-drying processes. Compared to unmodified FeNi/CS, the FeNi/CS/rGO composite provides an effective component and a more specific structure, which is favorable for translating microwave into thermal energy or other forms of energy. The minimum reflection loss (RL) value of the FeNi/CS/rGO composite reaches −45.2 dB at a thickness of 1.5 mm, and the maximum effective microwave absorption bandwidth (RL < −10 dB) is up to 5.0 GHz at d = 1.5 mm. In virtue of the dielectric loss, magnetic loss, unique heterostructure of the absorber, and impedance matching, the FeNi/CS/rGO composite exhibits overwhelming advantages of low density, small thickness, broad bandwidth, strong absorption and high anti-oxidation capability.

•Porous ZnFe2O4 Nanospheres were synthesized by hydrothermal method followed by calcination.•The as-prepared sample shows excellent cycling stability and rate capability.•The excellent electrochemical performance is benefit from its unique structural framework.Transition metal oxides have attracted considerable attention as anode materials of lithium-ion batteries (LIBs). However, poor electrical conductivity and huge volume change hinder their practical application. Porous nanostructure is vital to attain high-performance lithium-ion batteries. Herein, we have designed and fabricated regularly porous ZnFe2O4 nanospheres consisted of small primary nanoparticles via a facile hydrothermal method followed by calcination. The structural properties and morphology of the sample are characterized by powder X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The composite is then evaluated as anode for Li-ion battery and shows excellent electrochemical properties. The reversible capacity of 868.9 mAh g−1 can be obtained at 200 mA g−1 over 80 cycles. Furthermore, the discharge capacity can still retain 456 mAh g−1 after 600 cycles at a high charge rate of 2 A g−1. Our findings reveal that ZnFe2O4 sample is a promising anode material for LIBs due to its superior rate capability and long cycle life.Download high-res image (438KB)Download full-size image

Magnetic mesoporous FeNi/CS composites (FeNi alloy embedded in a porous carbon sphere) have been synthesized via a facile one-pot hydrothermal carbonization method, using metal nitrates and glucose as magnetic particle precursors and the carbon source, respectively. The properties of FeNi/CS were characterized with X-ray diffraction (XRD), Raman spectroscopy, a scanning electron microscopy (SEM) system, transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA), nitrogen adsorption/desorption isotherms and a magnetic property measurement system (SQUID-VSM). FeNi/CS derived at different pyrolysis temperatures of 500, 700, 900 °C (FeNi/CS-500, FeNi/CS-700, FeNi/CS-900, respectively) could serve as novel magnetic carbonaceous adsorbents for removing trichloroethylene from aqueous media. FeNi/CS produced at 700 °C has the best removal capacity among all, mainly due to its large surface area, a wider range of pore size distribution, and suitable carbonized extent. The pseudo-second order model is well fitted to the kinetic data, indicating that chemisorption is the primary mechanism of TCE adsorption onto FeNi/CS. Moreover, the obtained magnetic porous composites could be easily separated from solution by using a permanent magnet after adsorbing TCE and used as efficient and recyclable adsorbents in the successive removal of TCE from wastewater.

A simple one-pot approach to synthesizing 5-ethyl-2-methylpyridine(EMP) was established using NH4HCO3 and C2H5OH as starting materials and commercial Cu2O as catalyst and oxidant under hydrothermal condition. Different reaction conditions were researched and the optimal ones were achieved by studying the parameters, that could affect the yield of product and by considering the energy and resource saving. The present study provided an eco-friendly way to obtaining EMP with lower volatility using fewer toxic starting materials.

•NiFe2O4 nanooctahedrons were synthesized by a facile hydrothermal process.•A phase formation mechanism was studied by time-dependent experiments.•NiFe2O4 with N-doped carbon shell was fabricated via carbonization of polydopamine.•NiFe2O4@NC20 showed the best rate capability and cycle stability.Combining nanostructure engineering with conductive carbonaceous material is a promising strategy to obtain high-performance lithium ion batteries (LIBs). In this work, spinel NiFe2O4 nanooctahedrons were initially synthesized at a low temperature without further annealing. We investigated the phase formation mechanism by time-dependent experiments. Next, octahedral NiFe2O4 with a nitrogen-doped carbon shell (NiFe2O4@NC) were successfully fabricated via a subsequent carbonization of polydopamine (PDA). We systematically varied the dopamine content in the NiFe2O4/carbon nanocomposites and found that a nanocomposite containing 20% mass fraction of dopamine exhibited enhanced lithium ion battery performance with high reversible cycle capacity and good rate retention performance compared with the pure material. Remarkably, the hybrid nanocomposite delivered a high reversible capacity of 1297 mAh g−1 even after 50 cycles at a current density of 100 mA g−1. Additionally, a high capacity of 1204 mAh g−1 was retained at a high current density of 500 mA g−1 after 300 cycles. This improvement in electrochemical performance is attributed to the enhanced structural stability and electrical conductivity caused by the carbon layer, and is supported by TEM and EIS measurements.NiFe2O4@NCweresuccessfullyfabricatedviaasubsequentcarbonizationofpolydopamine.(*) A nanocomposite containing 20% mass fraction of dopamine exhibited enhanced lithium ion battery performance with high reversible cycle capacity and good rate retention performance.