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Carbon-doped ZnCo 2 O 4 (ZnCo 2 O 4 /C) yolk-shell microspheres are synthesized by a method of thermally decomposing precursor and then successfully compounded with magnetic graphene (MG) via co-precipitation in combination with a reduction pathway. The fabrication processes and characterizations (XRD, XPS, TEM, EDS and SEM) are described and explained in detail. It is confirmed that amorphous carbon (in situ decomposition from PVP) is uniformly doped into ZnCo 2 O 4 yolk-shell microspheres. In addition, the reflection loss (RL) and electromagnetic (EM) wave absorption mechanisms of as-prepared ZnCo 2 O 4 /C/MG composites are calculated and analyzed exhaustively. The results show that absorption bandwidth with RL exceeding −10 dB reaches up to 4.48 GHz with a matching thickness of 3.5 mm while the maximum RL is up to −52.9 dB at 7.52 GHz with a matching thickness of 3.9 mm. Enhanced EM wave absorption performance can be attributed to good dielectric and magnetic loss, excellent impedance matching, diverse interfacial polarization and multiple reflections caused by special structures. [ABSTRACT FROM AUTHOR]

Abstract In this work, an eco-friendly and convenient microwave-assisted synthesis technique was applied in the entire experiment course. The first obtained graphene-Ni composite possess an unsatisfactory microwave absorption capacity due to unbalanced matching nature. Then a sulfurization process was tried at different temperatures to convert Ni into NiS/Ni 3 S 2 , and an innovative graphene-NiS/Ni 3 S 2 composite with a hierarchical architecture was fabricated under the condition of microwave irradiation. The investigation into microwave absorbing performances manifests that the absorption property of graphene-Ni can be obviously improved by sulfurization method. The results show, compared with graphene-Ni, the hierarchical-architecture graphene-NiS/Ni 3 S 2 composites generated at 150 ℃ (S-150) possess excellent absorbing ability with a maximum RL as strong as − 55.1 dB at 6.0 GHz with a thickness of 2.7 mm, and the effective bandwidth covers 8.6 GHz from 2.8 to 11.4 GHz with thickness varies in 1.5–4.5 mm range. The enhanced performances for S-150 mainly derive from the synergy of superior impedance matching character, high attenuation, dielectric loss and plenteous interface polarizations. [ABSTRACT FROM AUTHOR]

Flower-like ZnO–NiO mesoporous architectures were synthesized through annealing the zinc hydroxide carbonate–nickel hydroxide carbonate composite precursor, which was prepared via a one-pot hydrothermal route. More importantly, we successfully prepared flower-like porous ZnO–NiO/graphene composites by introducing flexible graphene into the flower-like porous ZnO–NiO. In addition, we explore the application of the 3D flower-like ZnO–NiO composite mesoporous architectures and flower-like porous ZnO–NiO/graphene composites as anode materials for lithium ion battery. Electrochemical study presented that the as-prepared flower-like porous ZnO–NiO/graphene composites demonstrate excellent electrochemical performance and cycling stability. The first discharge capacity is 1205.7 mA h/g at a high current density of 300 mA/g. After 50 cycles, the reversible capacity is 452.7 mA h/g at a current density of 300 mA/g and the coulomb efficiency reaches at 99%.The improved electrochemical performances are mainly attributed to its morphological characteristics of mesoporous, nanosheet self-assembling architectures, as well as the addition of graphene. These results suggest that such 3D flower-like porous ZnO–NiO/graphene composites are promising materials for lithium ion battery. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) graphene@CNTs@MnO 2 (GCM) nanocomposites materials have been fabricated by a facile two-step method. The structure, morphology and electrochemical properties of the 3D nanocomposites were investigated by XRD, TG, Raman, SEM, TEM and electrochemical measurements. The 3D forest-like rGO@CNTs (GC) serves as both the backbone and ideal electron pathway for MnO 2 . With this sophisticated configuration, the 3D GCM nanocomposites exhibit a specific capacitance of 245 F g −1 at 0.5 A g −1 , excellent cycling stability (91.4% retention after 2000 cycles at 1 A g −1 ) and high rate capability. These excellent capacitive performances may make the as-prepared nanocomposites as promising electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

Graphene supported porous Si@C ternary composites had been synthesized by various routes and their structural, morphological and electrochemical properties were investigated. Porous Si spheres coated with carbon layer and supported by graphene have been designed to form a 3D carbon conductive network. Used as anode materials for lithium ion batteries, graphene supported porous Si@C ternary composites demonstrate excellent electrochemical performance and cycling stability. The first discharge capacity is 2184.7 mA h/g at a high current density of 300 mA/g. After 50 cycles, the reversible capacity is 652.4 mA h/g at a current density of 300 mA/g and the coulomb efficiency reaches at 98.7%. Due to their excellent electrochemical properties, graphene supported porous Si@C ternary composites can be a kind of promising anode materials for lithium ion batteries. [ABSTRACT FROM AUTHOR]

Abstract: The GNS/Li2SnO3/PPY ternary composites were synthesized by a deoxidation technique. The soft polymer matrix and flexible graphene provide a dual buffering structure for Li2SnO3 which synergistic leads to improved stability, enhanced electric conductivity and better electrochemical performance. The GNS/Li2SnO3/PPY composites tested as anode materials for lithium ion batteries exhibit a high reversible capacity of 699.4mAh/g over 30 cycles, which is much better than that of pure Li2SnO3, PPY/Li2SnO3 and GNS/Li2SnO3 composites. [Copyright &y& Elsevier]

Abstract: The carbon-doped Li2SnO3/graphene composites for lithium-ion batteries were synthesized by the hydrothermal route. The structure, morphology and electrochemical properties of the composites were detected by means of XRD, SEM, TEM, Raman, TGA and electrochemical measurements. The Li2SnO3 nanoparticles are surrounded by graphene sheets (GNS) and amorphous carbon layers. The carbon-doped Li2SnO3/graphene materials exhibit good electrochemical performance with high capacity and good cycling stability (736.3mAh/g after 50 cycles at 60mA/g).The presence of graphene sheets and carbon layer can alleviate the effects of volume changes, keep the structure stable and increase the conductivity. Conclusively, The C/Li2SnO3/GNS composites exhibit better electrochemical properties than GNS/Li2SnO3 and Li2SnO3. [Copyright &y& Elsevier]