•RGO/CoFe2O4 was synthesized via combining hydrothermal with co-precipitation ways.•CoFe2O4 nanoparticles with a diameter of 10–20 nm were anchored on graphene.•The quarter-wavelength mechanism is used to explain EM wave absorption properties.The reduced graphene oxide (RGO)/CoFe2O4 magnetical nanocomposites have been successfully fabricated via a facile method combining co-precipitation and hydrothermal process. The TEM results show that the CoFe2O4 nanoparticles with diameters about 10–20 nm are well dispersed on the entire graphene nanosheets without aggregation. In this work, the CoFe2O4 nanoparticles were used to bring magnetic loss ability, while the graphene nanosheets were designed to bring dielectric loss ability. It could enhance impedance matching characteristic, further improving the electromagnetic (EM) wave absorption performance. Therefore, the as-prepared RGO/CoFe2O4 nanocomposites exhibit excellent EM wave absorption properties in terms of both the maximum reflection loss and the absorption bandwidth. The maximum reflection loss of RGO/CoFe2O4 nanocomposites is −53.6 dB at 11.4 GHz with the thickness of 2.5 mm and the maximum absorption bandwidth with the reflection loss below −10 dB is up to 5.0 GHz (from 12.2 to 17.2 GHz) with the thickness of 2.0 mm. And also the absorption bandwidth with the reflection loss below −10 dB is up to 13.5 GHz (from 4.5 to 18.0 GHz) with a thickness in the range of 1.5–5.0 mm. The above results all suggest that the RGO/CoFe2O4 nanocomposites can serve as an ideal candidate for an efficient broad band EM wave absorber.

•Researched Nitrogen and sulfur co-doped graphene for lithium-ion batteries.•The ZnFe2O4/NSG has a unique interconnected network structure.•The ZnFe2O4/NSG exhibits enhanced electrochemical property and high rate stability.Nitrogen and sulfur co-doped graphene supported hollow ZnFe2O4 nanosphere composites have been successfully synthesized via a facile, two-step hydrothermal method. The obtained ZnFe2O4/NSG samples show interconnected hollow sphere nanostructure with a size of ∼250 nm. The product demonstrated a high initial discharge capacity of 2478.6 mAhg−1 at a rate of 300 mAg−1. After 100 cycles, it delivered a high reversible capacity of 729.06 mAhg−1 and coulombic efficiency of 99.36%, while at high rate capability of 1800 mAg−1, the rate capacity stabilize at 650.1 mAhg−1. It is believed that the composite with good rate capability and stability can be a competitive anode for lithium-ion batteries.

In this work, The NiCo2O4/NiO electrode materials are successfully synthesized via hydrothermal and following calcination approach. Due to the distinctive porous nanosheets assembled structure through controlling effectively the feeding amount of HMT, the NiCo2O4/NiO electrode possesses excellent specific surface area and reasonable pore size distribution, which hence minimizes the intrinsic electrode resistance and improves the morphology and structure stability. Therefore, the NiCo2O4/NiO electrode delivers a superior specific capacitance (Csp) (992.85 F g−1 at the current density of 1 A g−1), good rate capability (79.14% Csp retention even at 10 A g−1) and considerable cycle life (79.82% Csp retention at 10 A g−1 after 5000 times). Furthermore, the asymmetric supercapacitor is successfully assembled by NCN-0.1 as positive electrode and activated carbon (AC) as negative electrode. The NCN-0.1//AC device delivers a relatively excellent energy density of 47.43 kW kg−1 at a power density of 0.389 W h kg−1. Consequently, the outstanding performance and stability of the ASC device shows great potential for future energy storage application.Download high-res image (95KB)Download full-size image

•The application of biologic carbon matrix for rechargeable batteries is reviewed.•Biologic microporous carbon matrix is created by using waste shaddock wadding.•The matrix has a coexisting structure with high specific surface (1637.3 m2 g−1).•Excellent electrochemical properties were measured.•The initial discharge capacity is as high as 1050 and 599 mAh g−1 after 200 cycles.In this work, a microporous and high surface area carbon material with excellent electron conductivity is synthesized through carbonizing and activation processes using waste shaddock wadding. Because of the unique multi-hole, thin sheets cluster and irregular wrinkled surface coexisting structure, the shaddock wadding carbon-sulfur (SWD-S) composite can be used as a kind of cathode material for rechargeable lithium-sulfur batteries by loading element sulfur into the shaddock wadding activated carbon via simple heat treatments. Because of the high specific surface area of SWD (1637.3 m2 g−1), the SWD-S composite has a sulfur content about 73.7 wt%, and delivers a high initial discharge capacity of 1050 mAh g−1 at a rate of 0.2C. Moreover, SWD-S composite exhibits a good rate capacity and excellent cycle ability. Over 200 cycles it achieves with a high columbic efficiency around 95%. After 200 cycles at 0.2C, it still remains a capacity of 599 mAh g−1.

The ternary hybrids composed of a CoNi inner unit along with SiO2 and graphene outer units (CoNi@SiO2@RGO) are synthesized via a facile solvothermal/sol–gel/hydrothermal strategy. The structures, chemical composition and morphologies of CoNi, CoNi@SiO2 and CoNi@SiO2@RGO are analyzed in detail. Besides, the electromagnetic (EM) wave absorption performances of the as-prepared products are invested on the basis of transmission lines theory. The results indicate that the ternary CoNi@SiO2@RGO composites display enhanced microwave-absorbing characteristics in terms of both the maximum reflection loss and the absorption bandwidth, compared with the pristine CoNi alloy and CoNi@SiO2 microparticles. The maximum RL of CoNi@SiO2@RGO reaches as high as −50.3 dB at 6.8 GHz, and the absorption bandwidth below −10 dB is up to 4.0 GHz with a thickness of 4 mm. A possible mechanism of microwave absorption is explained, drawing a conclusion that the improvement of absorption property is mainly ascribed to the synergic effect of combining magnetic and dielectric components, and the interface interactions of multi-component hierarchical structure.

•3D GN-CNT hybrids are investigated as a novel Na storage anode for the first time.•Pyrolysis temperature showed an important effect on yield of CNTs.•The GN-CNT hybrid pyrolysized at 900 °C exhibit a best electrical property.A novel graphene/carbon nanotube (GN-CNT) hybrid was synthesized by thermal pyrolysis of urea on the surface of graphene at 800, 900 and 1000 °C. The effects of pyrolysis temperature on yield of carbon nanotubes and electrochemical properties of the GN-CNT hybrid were investigated carefully. The production rate of pyrolysis gas was increased as temperature rising. The GN-CNT hybrid reached the largest surface area and the generation of a mass of pores at the pyrolysis temperature of 900 °C due to the carbon nanotubes cracking during pyrolysis at 1000 °C. The properties of favorable 3D architecture, the generation of a mass of pores during the release of carbon nitride gases and outstanding mechanical flexibility, showed pronounced effects on the fast and steady transfer of electrons and sodium-ion. Consequently, the GN-CNT hybrid pyrolysized at 900 °C exhibit a very high reversible capacity of up to 269.14 mAh g−1 after 100 cycles at a current density of 300 mA g−1. Even up to 5 A g−1, a rate capacity of 195.37 mA h g−1 can be obtained after 700 cycles.

Well-designed hierarchical nanostructured composites consisting of one dimensional cobalt fibers and thin tin disulfide nanosheets were successfully synthesized for the first time through a hydrothermal method. The SnS2 nanosheets were uniformly grown onto the Co fibers and were almost perpendicular to the Co fibers. The composites as one kind anode materials exhibited more remarkable lithium ion storage properties than SnS2 nanosheets. The composites exhibited a capacity of 500.5 mA h/g after 100 cycles even at 1000 mA/g. The improved electrochemical performance could be assigned to the Co fiber substrate support, which could provide short lithium ion and electron pathways, alleviate large volume expansion, contribute to the capacity, and offer mechanical stability for the anode electrode. This special designing perhaps could lay a foundation for the preparation of high performance lithium ion battery anode materials.Download high-res image (133KB)Download full-size image

•Hollow Si-Ni3Sn2 @ graphene composites are firstly fabricated as anodes for LIBs.•The porous surface and hollow structure are expected to alleviate internal stress during electrochemical process.•The graphene layers helps to maintain the electrically conductive network as it leads to better cycling performance.In this paper, we report the original synthesis of hollow Si-Ni3Sn2 @ graphene composite and its high reversible capacity as lithium-ion battery anodes. To build the new architecture, three strategies of hollow architectures, porous surface and specific composition of graphene are attempted to develop lithium storage with far greater energy density and outstand rate performance. The results show that as-designed hollow Si-Ni3Sn2@graphene composites exhibit outstanding reversible capacity of 855.7 mAh g−1 during the first cycle, and 576.6 mAh g−1 can be maintained during a cycling test of 50 cycles at 300 mA g−1. The rate capability is also enhanced, delivering reversible capacity of 449.8, 420.4, 392.7 and 377.1 mAh g−1 at current densities of 600, 800, 1200 and 1800 mA h g−1, thus exhibiting great potential as an anode material for lithium-ion batteries.

Hybrid hollow urchin-like cobalt and copper silicate constructed by nanotubes encapsulated in graphene nanosheets composites were successfully prepared using graphene oxide as carrier and silica spheres as template, which were done through a well-known Stȍber process and a hydrothermal method. In fact, the synthesis of hybrid urchin-like silicate constructed by nanotubes through onestep hydrothermal reaction has rarely been reported.The electrochemical performances of the composites as lithium-ion battery anode materials were studiedfor the first time. As novel anode materials of Li-ion batteries, the special hollow urchin-like structure not only could facilitate the Li+ diffusion and electron transport but alsocouldaccommodate the volume variation during the conversion reactions. In addition, the introduction of graphene can make the electrical conductivity better. Graphene wrapped hollow urchin-like silicate compositespossesses superior electrochemical cycling properties. The first discharge capacity is1955.2mAh/g with a current density of 300 mA/g. The unique well-designed configuration presents a beneficial method to synthesize efficient and high performance electrode materials for advanced power applications.

In this work, the polyaniline nanorods/graphene sheets composites with covalent bond were synthesized through in-situ polymerization of aniline in the presence of amino-functionalized graphene sheets (AFG), in which polyaniline (PANI) polymerization is initiated by those amino groups on graphene. The chemical bonding between graphene and PANI is confirmed by several analytical techniques, including Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM) and thermogravimetric analysis (TGA). The microwave-absorbing properties of the composites were measured by a vector network analyzer. The electromagnetic data demonstrates that the maximum reflection loss of covalently bonded PANI-AFG can reach −51.5 dB at 11.2 GHz, and the absorption bandwidths exceeding −10 dB are 4 GHz with thickness of 2.5 mm. The results indicate that the hybrid composites with enhanced microwave absorption properties and lightweight have a promising future in decreasing electromagnetic wave irradiation.

With the advent of flexible electronics, flexible secondary rechargeable batteries have attracted considerable attentions as a promising power source in the new generation of flexible electronics such as roll-up displays, smart electronics, and implantable medical devices. In this work, we report the fabrication of 3D NiCo2O4 arrays on carbon cloth as a binder-free anode for sodium/lithium ion storage. Amorphous carbon layer is used to modify the surface of NiCo2O4 arrays by physical vapor deposition (PVD). The electrochemical performance measurements demonstrate that the amorphous carbon layer can improve the electrochemical stability of NiCo2O4. The NiCo2O4@ C/carbon cloth electrode exhibits a high reversible capacity of 749.9 mAh g−1, stable cycling with more than 535.47 mAh g−1 at 500 mA g−1 over 100 cycles and impressive rate capability (318 mAh g−1 at 5 A g−1 over 700 cycles) for SIBs and excellent electrochemical performance for LIBs (reversible capacity of 807.63 mAh g−1 were observed for 100 cycles).Download high-res image (668KB)Download full-size image

Magnetic materials of FeCo alloy with different morphologies (nanocube, nanoplate and flower-like structure) have been synthesized by controlling the molar ratio of Fe2+ to Co2+, concentrations of cyclohexane and PEG-400. The structure and morphology were characterized by several analytical techniques, including XRD, SEM, TEM, XPS and VSM. The microwave-absorbing properties were measured by a vector network analyzer. The SEM and TEM photographs reveal that the edge length of FeCo nanocube is about 215 nm, the diameter and thickness of the nanoplate is 100 and 15 nm, respectively. The average diameter of flower-like FeCo is about 1.5 μm. The investigation of the electromagnetic wave absorbability revealed that flower-like FeCo exhibited excellent electromagnetic wave absorption properties compared with FeCo nanocube and FeCo nanoplate due to the special structure. The maximum reflection loss of flower-like FeCo was up to −43 dB at 13.1 GHz and the absorption bandwidth with the reflection loss below −10 dB was 5.8 GHz (from 2.7 to 5.4 GHz and from 12 to 15.1 GHz) with a thickness of 3.4 mm. Furthermore, this work offers a simple solvothermal route to fabricate shape and size-controlled FeCo alloy, which can be used as an attractive candidate for new type of electromagnetic wave absorbers.

A two-step strategy combining in situ polymerization and a hydrothermal process has been developed for coupling polyaniline (PANI) with porous TiO2 anchored on magnetic graphene. The microstructure and morphology of magnetic graphene@PANI@porous TiO2 were characterized by FETEM, FESEM, XRD, XPS and VSM in detail. The results indicated that magnetic graphene@PANI was completely covered by porous TiO2 with random orientations and the saturation magnetization value of the composite was 19.2 emu g−1. PANI was used to decrease the absorber thickness, while the porous TiO2 with a large surface area was designed to enhance the interaction between the electromagnetic (EM) wave and the absorber through multiple reflections, thus enhancing EM wave absorption properties. As an EM wave absorber, the maximum reflection loss of the composite was up to −45.4 dB due to the better normalized characteristic impedance (close to 1) at a thickness of only 1.5 mm and the absorption bandwidths exceeding −10 dB were 11.5 GHz when the thickness ranged from 1 to 3.5 mm. The excellent EM wave absorption performance was ascribed to the combined contribution from the enhanced dielectric relaxation processes, the unique porous nanostructures, the quarter-wave length matching model and the well-matched normalized characteristic impedance. Consequently, it is believed that the composite could be used as an excellent EM wave absorption material and the two-step strategy offered an effective way to design a high-performance EM wave absorber with a relatively thin thickness.

Hybrid nanocomposites with enhanced microwave absorption properties have been designed by growing CuS nanoflakes on magnetically decorated graphene, and the effect of special nanostructures on microwave absorption properties has been investigated. The structure of the nanocomposites was characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), N2 adsorption–desorption, and vibrating sample magnetometer (VSM). The influence of cetyltrimethylammonium bromide (CTAB) on the morphology of CuS nanoflakes was also investigated. A possible formation process of the nanocomposites and the mechanism of microwave absorption were explained in detail. As an absorber, the nanocomposites with a filler loading of 20 wt % exhibited enhanced microwave absorption properties due to the special nanostructures, extra void space, and synergistic effect. The maximum reflection loss can reach −54.5 dB at 11.4 GHz, and the absorption bandwidths exceeding −10 dB are 4.5 GHz with a thickness of 2.5 mm, which can be adjusted by the thickness. The results indicate that the hybrid nanocomposites with enhanced microwave absorption properties and lightweight have a promising future in decreasing electromagnetic wave irradiation.Keywords: CuS nanoflakes; graphene; lightweight absorber; microwave absorption properties; three-dimensional nanostructures

•FeNi3@RGO/MoS2 was prepared by two-step of hydrothermal reaction.•The microstructure and microwave absorption properties were investigated.•Microwave absorption properties with different filler loadings in wax were studied.High-performance electromagnetic wave absorption materials with strong absorption intensity, broad bandwidth, low density and thin thickness can be widely applied in the civil and military areas. In this paper, FeNi3 nanoalloy decorated on 3D architecture composite of reduced graphene oxide/molybdenum disulfide (FeNi3@RGO/MoS2) was prepared by two-step of hydrothermal reaction. RGO/MoS2 composite was synthesized by a hydrothermal process and then FeNi3 nanoalloy was decorated on the RGO/MoS2 nanosheets via the second hydrothermal process. Electromagnetic wave absorption performances of FeNi3@RGO/MoS2 composite with different filler loadings in paraffin matrix were investigated for the first time and it improves significantly with the increase of filler loading. The maximum absorption bandwidth is 4.72 GHz with the thickness of 2.0 mm and the corresponding reflection loss value is −30.39 dB when the filler loading of FeNi3@RGO/MoS2 is 40%. The ternary composite possesses dielectric loss and magnetic loss in the testing frequency region, magnetic loss plays an important role in low-frequency region and dielectric loss occupies the main part in the high-frequency area.

•Sandwich structures of GN@Fe3O4@PANI decorated with TiO2 nanosheets were synthesized.•The nanocomposites have a superparamagnetic behavior.•The maximum RL of the nanocomposites is −41.8 dB with a thickness of 1.6 mm.•The absorption bandwidth of RL < −10 dB is almost up to 3.5 GHz.The novel sandwich structures of graphene@Fe3O4@PANI decorated with TiO2 nanosheets were firstly successfully prepared by simple hydrothermal method and in situ polymerization. VSM results reveal that the nanocomposites have a superparamagnetic behavior. Structure and morphology were characterized by X-ray diffraction, transmission electron microscopy, and field-emission scanning electron microscopy. Electron microscopy images show that TiO2 nanosheets are mostly grown upright on the top of graphene@Fe3O4@PANI support with a random orientation, and form hierarchical structures. Electromagnetic (EM) wave absorption properties of graphene@Fe3O4@PANI@TiO2 nanosheets containing 50wt% paraffin were investigated in the frequency region of 2–18 GHz. The maximum reflection loss of the nanocomposites is up to −41.8 dB at 14.4 GHz with a thickness of 1.6 mm, and the absorption bandwidth of RL < −10 dB is almost up to 3.5 GHz. Thus, the enhanced EM wave absorption properties of graphene@Fe3O4@PANI@TiO2 nanosheets can be used as promising EM wave absorbers.

The ternary nanocomposites of rGO–PANI–FeNi3 were successfully synthesized by combining polymerization with hydrothermal reduction reaction. Graphene and polyaniline unite with FeNi3 to form ternary composite for the first time and the paraffin composite containing 20 wt% rGO–PANI–FeNi3 exhibit excellent electromagnetic wave absorption properties. The maximum reflection loss of −43.17 dB is obtained at 6.2 GHz and the absorption bandwidth (<−10 dB) of the reflection loss value can be obtained in the whole frequency range (2.96–18 GHz) with the sample thickness varying from 2.0 to 6.0 mm. The results demonstrate that rGO–PANI–FeNi3 nanocomposites containing magnetic loss and dielectric loss materials have potential applications in the electromagnetic wave absorbing area and can be widely used in developing electromagnetic wave absorption materials.

A Sn-based intermetallic compound (hollow Si–Ni–Sn nanospheres) with a porous and hollow microspheric structure was fabricated via a versatile template synthesis approach followed by an in situ chemical reaction, and directly used as an anode material for lithium-ion batteries (LIBs). The hollow Si–Ni–Sn nanosphere anode with a unique architecture exhibits high initial discharge capacity and excellent cycling stability. The reversible capacity of hollow Si–Ni–Sn nanospheres is 1065 mA h g−1 and is maintained at 402 mA h g−1 after 50 cycles, which is much higher than that of hollow SiO2@Ni@SnO2 nanospheres. The unique configuration of the Sn-based intermetallic compound presents a beneficial approach to create efficient and practical electrodes for energy storage applications.

•The RGO-CPs-NiFe2O4 composites are synthesized via a simple two-step method.•The average diameter of NiFe2O4 particles is in the range of 5–20 nm.•The maximum reflection loss of RGO-PANI-NiFe2O4 is −49.7 dB at 12.4 GHz.•The maximum reflection loss of RGO-PPy-NiFe2O4 is −44.8 dB at 14.9 GHz.•The maximum reflection loss of RGO-PEDOT-NiFe2O4 is −45.4 dB at 15.6 GHz.In this work, conducting polymers (polyaniline, polypyrrole and poly (3,4-ethylenedioxythiophene)) and NiFe2O4 coated on Reduced Graphene Oxide Sheets were successfully fabricated by a two-step method. The structure and morphology were characterized by several analytical techniques, including XRD, XPS, Raman, TEM and VSM. The microwave-absorbing properties of the composites were measured by a vector network analyzer. TEM photographs reveal that many NiFe2O4 nanoparticles with the sizes in the range of 5–20 nm firmly attached on the surface of RGO-CPs. The ternary composites have superparamagnetic character due to the presence of NiFe2O4 nanoparticles. The electromagnetic data demonstrates that the combination of graphene with conducting polymers and NiFe2O4 nanoparticles can improve the impedance matching, the 2D-structure RGO with large specific surface area improve the dielectric loss, the presence of CPs coating layer enhances the Debye dipole and dipole polarization enhances the dielectric loss. The maximum reflection loss of RGO-PANI-NiFe2O4, RGO-PPy-NiFe2O4 and RGO-PEDOT-NiFe2O4 are −49.7 dB, −44.8 dB and −45.4 dB, the absorption bandwidths with the reflection losses below −10 dB are 5.3 GHz, 5.3 GHz and 3.7 GHz with a thickness of 2.4 mm, 1.7 mm and 2.0 mm, respectively. Such excellent microwave absorption composites could be used as a new kind of candidate for the new types of microwave absorbing materials.

Graphene sheets (GNs) have high conductivity, but they exhibit weak electromagnetic (EM) wave absorption performance. Here, poly (3,4-ethylenedioxythiophene) (PEDOT) nanofibers were decorated on the surface of GNs in which the residual defects and groups act as the active sites and therefore are beneficial for the deposition of PEDOT nanofibers. The SEM images display that PEDOT nanofibers are successfully decorated on the surface of GNs through in situ polymerization. The diameter of the PEDOT nanofibers were ranged from 15 to 50 nm with hundreds of nanometers in length. The EM wave absorption properties of graphene, PEDOT, and GNs-PEDOT were also investigated. Compared to pure graphene and PEDOT, the EM wave absorption properties of GNs-PEDOT improved significantly. The maximum value of RL was up to −48.1 dB at 10.5 GHz with a thickness of only 2 mm. Meanwhile, the absorption bandwidth of RL values below −10 dB was 9.4 GHz (5.8–12.3, 12.9–15.8 GHz) in the thickness of 1.5–3 mm. The enhancement is attributed to the modification of PEDOT and the unique structure of nanofibers. On one hand, the deposition of PEDOT nanofibers on the surface of GNs decreases the conductivity of graphene, and makes impedance match better. On the other hand, the unique structure of PEDOT nanofibers results in relatively large specific surfaces areas, providing more active sites for reflection and scattering of EM waves. Therefore, our findings demonstrate that the deposition of conducting polymers on GNs by non-covalent bond is an efficient way to fabricate strong EM wave absorbers.

Functional graphene nanoflakes/cyanate/epoxy (FGNs/CE/EP) nanocomposites were prepared with solution insertion method. The functional graphene nanoflakes (FGNs) were added to CE/EP copolymer to improve the integrated properties of the FGNs/CE/EP nanocomposites. The non-isothermal behavior of the FGNs/CE/EP nanocomposites was investigated using differential scanning calorimetry at different heating rates. The result clearly indicated that the functional graphene nanoflakes (FGNs) acted as a catalyst over the whole curing process and shortened the curing time. The mechanical, dielectric and thermal properties were characterized via mechanical, dielectric and thermogravimetric analysis (TGA) techniques, respectively. The results showed that the mechanical properties of the nanocomposites, enhanced with 2.0 wt% FGNs, not only because the flexural strength reached the optimum value, but also because the impact strength acquired the best value. When compared with the dielectric properties of the CE/EP copolymer, the dielectric constant and dielectric loss factor of the FGNs/CE/EP nanocomposites with 2.0 wt% of FGNs slightly increased. The TGA of the nanocomposites was thoroughly recorded, which indicated that the thermal properties of the FGNs/CE/EP nanocomposites increased as well. Therefore, the FGNs acted as a catalyst as well as a reinforcing agent in the FGNs/CE/EP nanocomposites.

•Researched self-assembled graphene /sulfur composite for lithium-sulfur batteries.•Sulfur content up to 80% is loaded in hydriodic acid reduced graphene oxide.•The composite shows high specific capacity and enhanced rate capability.•Both stacked structure and the conductive RGO support enable high-rate capability.Hydriodic acid and self-assembly approach are used to fabricate graphene wrapped sulfur composite. The self-assembly process of the relative “large” graphene sheet and “small” sulfur is quite controllable, and the sulfur particles are completely enfolded by RGO sheets with a unique stacked structure .The RGO/S composite with 80 wt.% sulfur shows an initial discharge capacity of 865.1 mAh g−1 at 0.5 mA/cm2. A high specific capacity of 720 mAh g−1 with a coulombic efficiency of 95% is achieved after 50 cycles of charge/discharge. The material also delivered a capacity of more than 580 mAh g−1 at 2 mA/cm2 and can be recovered to 736 mAh g−1 when the rate is returned to 0.2 mA/cm2, representing a promising cathode material for high current discharge lithium-sulfur batteries.

A novel three-dimensional graphene@carbon nanotube (CNTs) composite has been prepared using a facile one-pot pyrolysis strategy using urea as the carbon source, in which the density and length of CNTs on graphene are rationally tuned by adding an appropriate amount of urea to a precursor mixture. Correspondingly, the density and length of CNTs on graphene have a significant effect on the microwave absorption properties of graphene@CNTs. When most of the graphene surface is clearly covered by the CNTs whose length ranges from 300 to 600 nm, the graphene@CNT composite exhibits excellent microwave absorption properties. The maximum reflection loss value can reach −44.6 dB at 8.6 GHz and the absorption bandwidth with a reflection loss below −10 dB ranges from 7.1 to 10.4 GHz with an addition amount of only 5 wt% graphene@CNTs composite in the paraffin matrix.

The fabrication of novel hierarchical graphene@Fe3O4 nanocluster@carbon@MnO2 nanosheet array composites has been successfully carried out for the first time. The fabrication process involves the deposition of Fe3O4 nanoclusters on graphene's surface using a simple in situ hydrothermal method, subsequent introduction of carbon on the surface of graphene@Fe3O4 nanoclusters by combining the hydrothermal reaction and thermal treatment process, and finally formation of the hierarchical composites via a simple in situ redox replacement reaction between potassium permanganate (KMnO4) and carbon on the surface of graphene@Fe3O4 nanoclusters. Moreover, the microwave absorption properties of both graphene@Fe3O4 nanoclusters and hierarchical graphene@Fe3O4 nanocluster@carbon@MnO2 nanosheet array composites were investigated between 2 and 18 GHz microwave frequency bands. The electromagnetic data demonstrate that graphene@Fe3O4 nanocluster@carbon@MnO2 nanosheet array hierarchical composites exhibit significantly enhanced microwave absorption properties compared with graphene@Fe3O4 nanoclusters, which probably originate from the unique hierarchical structure and larger surface area.

ZnFe2O4, a type of mixed transition metal oxide, is considered as one of the most attractive potential anode materials for LIBs due to its high reversible capacity and satisfactory structural stability. However, the low conductivity and the serious volume exchange during the electrochemical process are still two main issues for ZnFe2O4. In this study, we first designed conductive PANI layer coated hollow ZnFe2O4 nanospheres by micro emulsion polymerization. Two strategies of hollow structure and PANI coating were attempted to relieve expansion and increase conductivity. The results show that the as-designed hollow ZnFe2O4@PANI composites exhibited a large initial specific capacity of 1489.38 mA h g−1 with the first discharge that is maintained at over 607.3 mA h g−1 even after 50 charge–discharge cycles.

FeNi3 nanocrystals encapsulated in carbon nanospheres/reduced graphene oxide (FeNi3@C@rGO) composites have been synthesized through liquid-phase reduction reaction and then two-step hydrothermal processes followed by a pyrolysis process. The FeNi3@C and FeNi3@C@rGO composites were characterized by XRD, SEM, TEM, Raman spectroscopy. SEM shows the FeNi3 nanocrystals are sphere-like with a rough surface and the average diameter of the particles is about 100 nm. TEM reveals that FeNi3@C composites with core–shell structures are well distributed on the rGO nanosheets. The paraffin–FeNi3@C@rGO composite containing only 10 wt% of FeNi3@C@rGO exhibits excellent electromagnetic wave absorption properties. The maximum RL value of −47.6 dB is obtained at 10.2 GHz with a layer thickness of 2.6 mm and the absorption bandwidth (RL < −10 dB) is about 3.12 GHz in the range of 7.28–10.40 GHz for a layer of 3.0 mm thickness. It is believed that FeNi3@C@rGO can serve as light-weight electromagnetic wave absorbent and can be widely used in practice.

•We synthesized GN/PEDOT/CoFe2O4 by a facile two-step method.•The GN/PEDOT/CoFe2O4 nanocomposites had a ferromagnetic behavior.•The average diameter of CoFe2O4 nanoparticles was in the range of 10–20 nm.•The GN/PEDOT/CoFe2O4 exhibited excellent microwave absorption properties.In this work, a novel ternary nanocomposites consisting of graphene, poly (3,4-ethylenedioxythiophene) and CoFe2O4 nanoparticles (GN/PEDOT/CoFe2O4) had been prepared by a facile two-step method. The obtained ternary nanocomposites were characterized by XRD, TEM, XPS, TG and VSM. The results indicated that the ternary nanocomposites had a ferromagnetic behavior and the average diameter of CoFe2O4 nanoparticles was in the range of 10–20 nm. The investigation of the microwave absorbability indicated that GN/PEDOT/CoFe2O4 exhibited enhanced microwave absorption properties compared with GN/PEDOT and GN/CoFe2O4. The maximum reflection loss of the ternary nanocomposites was up to − 43.2 dB at 9.4 GHz and the absorption bandwidths exceeding − 10 dB were 3.1 GHz with a coating layer thickness of 2.4 mm. Furthermore, our development strategies expanded the scope of microwave absorbing materials and confirmed that the ternary nanocomposites had a promising future in microwave absorbing materials.

•The RGO–Ni0.5Zn0.5Fe2O4 composite was synthesized by a facile route.•RGO is well loaded by Ni0.5Zn0.5Fe2O4 Nps with diameters about 10–20 nm.•The composite shows a large reflection loss (−47.8 dB at 10.7 GHz).•The composite shows a wide absorption band.The reduced graphene oxide (RGO)–Ni0.5Zn0.5Fe2O4 composite was synthesized by a facile route. The morphology, microstructure and microwave electromagnetic properties of the composite were detected by means of TEM, SEM, XRD, XPS and vector network analyzer. The maximum reflection loss (RL) of the RGO–Ni0.5Zn0.5Fe2O4 reaches −47.8 dB at 10.7 GHz with the thickness of 2.8 mm, and the absorption bandwidth with RL below −10 dB is up to 11.4 GHz (from 6.6 to 18.0 GHz) with the thickness in the range of 2.0–4.0 mm. It is believed that such composite will be applied widely in microwave absorbing area.

•Sandwich-structured graphene@Fe3O4@carbon nanocomposites were fabricated.•The reflection loss of the sandwich-structured nanocomposites was below −10 dB in 12.1–17.5 GHz.•The maximum absorption of the sandwich-structured nanocomposites is −30.1 dB at 14.8 GHz.Sandwich-structured graphene@Fe3O4@carbon nanocomposites were prepared by a rational route. Transmission electron microscopy measurements show that an amorphous carbon layer is covered on the surface of graphene@Fe3O4 and the sandwich-structured graphene@Fe3O4@carbon is formed, and the TGA results indicate that the carbon content is 42.4 wt%. Compared with graphene@Fe3O4, the as-prepared graphene@Fe3O4@carbon nanocomposites exhibit enhanced microwave absorption properties in terms of both the maximum reflection loss value and the absorption bandwidth. The maximum reflection loss of graphene@Fe3O4@carbon is −30.1 dB at 14.8 GHz with a thickness of only 1.8 mm, and the absorption bandwidths with a reflection loss below −10 dB ranges from 12.1 to 17.5 GHz.

•Graphene@Ni@C has been synthesized via a dopamine-assisted one-pot synthesis.•The sandwich-structured composites have a ferromagnetic behavior.•The diameter of Ni particles is in the range of 20–50 nm.•The maximum reflection loss of the composites is −34.2 dB at 13.9 GHz.•The absorption bandwidths exceeding −10 dB are 3.2 GHz with a thickness of 1.6 mm.A novel sandwich-structured composites of graphene@Ni@C have been successfully synthesized via a facile one-pot method by using dopamine as reducing agent and carbon source. TEM and SEM images reveal that the average diameter of Ni particles ranges from 20 to 50 nm and these Ni particles anchored on grephene sheets are completely covered by N-doped carbon coatings. The investigation of the microwave absorbability reveals that the composites exhibit enhanced microwave absorption properties in terms of both the maximum reflection loss and the absorption bandwidths compared with graphene@C. The maximum reflection loss of graphene@Ni@C is −34.2 dB at 13.9 GHz and the absorption bandwidths below −10 dB is 3.2 GHz with a thickness of only 1.6 mm, which makes the composites can be used as lightweight microwave absorption materials. Furthermore, our strategy paves a facile method to design the sandwich-structured nanostructures in microwave absorbing area.

•ZnO/CuO flowers@ graphene have been fabricated via a simple hydrothermal method.•XRD, SEM, TEM were used to examine the structure of the prepared samples.•As anode materials, the electrochemical properties were examined in detail.•The composites showed substantially higher reversible capacity and good stability.Flower-like ZnO/CuO microstructures have been fabricated on Cu substrate via a simple hydrothermal method. The as-prepared ZnO/CuO flowers/graphene (GNS) composites had distributed the ZnO/CuO flowers on the graphene sheets. As anode materials for lithium ion batteries (LIBs), the ZnO/CuO flowers/GNS composites showed substantially higher reversible capacity and better cycling stability compared to ZnO/CuO flowers, which has been attributed to the improvement of structure stability and electrical contact by GNS. The method may be readily extended to synthesize other classes of hybrids based on graphene sheets for technological applications.

•The silver-modified hollow ZnSnO3 boxes composites were obtained.•The electrochemical properties of the hollow ZnSnO3 boxes @Ag were investigated.•The impacts of the Ag content on the electrochemical properties were compared.•The composites with Ag at about 5 wt% showed better electrochemical properties.Silver particles were dispersed on the hollow ZnSnO3 cubes by a thermal decomposition method. With good cycling performance for lithium-ion batteries anode materials, the impacts of the Ag content on the electrochemical properties of the electrodes were compared. The results showed that the silver-modified hollow ZnSnO3 boxes composites exhibit higher specific capacity and better cycling performance than hollow ZnSnO3 boxes. When Ag content reaches at about 5 wt%, the retain capacity is 464.5 mAh/g after 45 cycles at a current density of 300 mA/g, which is higher than that of hollow ZnSnO3 boxes.

•The novel three-component nanocomposites of GN@CoFe2O4@PANI were synthesized.•The nanocomposites had a ferromagnetic behavior.•The maximum reflection loss of GN@CoFe2O4@PANI is −47.7 dB at 14.9 GHz.•The absorption bandwidths exceeding −10 dB and −20 dB are 5.7 GHz and 2.0 GHz.The novel three-component nanocomposites of graphene@CoFe2O4@polyaniline were firstly prepared by a simple hydrothermal process and an in situ polymerization. TEM and FESEM images showed that the incorporation of polyaniline could reduce the agglomeration of CoFe2O4 nanoparticles and VSM result revealed that the three-component nanocomposites had a ferromagnetic behavior. The measured electromagnetic parameters showed that the nanocomposites exhibited excellent electromagnetic wave absorption properties and broad absorption bandwidths due to the better impedance matching. The maximum reflection loss of the nanocomposites was up to −47.7 dB at 14.9 GHz with a thickness of 1.6 mm and the absorption bandwidths with reflection loss lower than −10 dB and −20 dB were 5.7 GHz and 2.0 GHz, respectively. Furthermore, the three-component nanocomposites with excellent electromagnetic wave absorption properties and wide absorption bandwidth can be used as a new kind of candidate for lightweight electromagnetic wave absorption materials.

•Hierarchical structures of graphene@CoFe2O4@SiO2@TiO2 nanosheets were synthesized.•The composites have a ferromagnetic behavior.•The maximum reflection loss of the composites is −62.8 dB at 6.24 GHz.•The RL value below −10 dB could be obtained in the whole frequency range with the sample thickness varied from 2.0 to 6.0 mm.Hierarchical structures of graphene@CoFe2O4@SiO2@TiO2 nanosheets were successfully synthesized by combining the versatile sol–gel process with a hydrothermal reaction. Scanning electron microscopy and transmission electron microscopy observations display that the TiO2 nanosheets are mostly grown upright on the top of graphene@CoFe2O4@SiO2 support with a random orientation. When its microwave absorbing properties were investigated, the results show that the maximum reflection loss of the composites is up to −62.8 dB at 6.24 GHz with a thickness of 4.9 mm, and the RL value below −10 dB could be obtained in the whole frequency range with the sample thickness varying from 2.0 to 6.0 mm. The excellent microwave absorption properties of graphene@CoFe2O4@SiO2@TiO2 nanosheets can be used as an attractive candidate for new type of microwave absorption materials.

Hierarchical structures of graphene@Fe3O4@SiO2@NiO nanosheets were prepared by combining the versatile sol–gel process with a hydrothermal reaction. Graphene@Fe3O4 composites were first synthesized by the reduction reaction between FeCl3 and diethylene glycol (DEG) in the presence of GO. Then, graphene@Fe3O4 was coated with SiO2 to obtain graphene@Fe3O4@SiO2. Finally, NiO nanosheets were grown perpendicularly on the surface of graphene@Fe3O4@SiO2 and graphene@Fe3O4@SiO2@NiO nanosheet hierarchical structures were formed. Moreover, the microwave absorption properties of both graphene@Fe3O4 and graphene@Fe3O4@SiO2@NiO nanosheets were investigated between 2 and 18 GHz microwave frequency bands. The electromagnetic data demonstrate that graphene@Fe3O4@SiO2@NiO nanosheet hierarchical structures exhibit significantly enhanced microwave absorption properties compared with graphene@Fe3O4, which probably originate from the unique hierarchical structure with a large surface area and high porosity.

•N-doped graphene@PANI@Fe3O4 nanoclusters hierarchical structures were fabricated.•The reflection loss of the composites is below −10 dB in 10.4–15.5 GHz.•The maximum absorption of the composites is −40.8 dB at 14.8 GHz.The hierarchical structures of N-doped graphene (NG)@PANI nanorod arrays modified with Fe3O4 nanocluster have been fabricated by a hydrothermal reaction. The as-prepared (NG@PANI@Fe3O4) composites were characterized by XRD, Raman and FTIR spectra, VSM, XPS spectroscopy, TEM and FESEM. The results reveal that the surfaces of NG@PANI nanorod arrays are randomly covered by Fe3O4 nanocluster with an average size of about 40 nm. With Fe3O4 nanoclusters coated on the surfaces of NG@PANI nanorod arrays, the composites exhibit superparamagnetic characteristics at room temperature. Moreover, the microwave absorption properties of both NG@PANI nanorod arrays and NG@PANI@Fe3O4 nanocluster were investigated between 2 and 18 GHz microwave frequency bands. The electromagnetic data demonstrates that NG@PANI@Fe3O4 nanocluster composites exhibit significantly enhanced microwave absorption properties compared with graphene@Fe3O4, which probably originates from improved level of impedance matching and interfacial polarization.

•PPy–BaFe12O19/Ni0.8Zn0.2Fe2O4–graphene nanocomposites were prepared by a deoxidation technique. >PPy–BaFe12O19/Ni0.8Zn0.2Fe2O4 nanoparticles dispersed on the graphene sheets.•With excellent thermal stability and electromagnetic properties.•Potential applications in magnetic materials and microwave absorbers.The polypyrrole(PPy)–BaFe12O19/Ni0.8Zn0.2Fe2O4 was produced by an in situ polymerization, and then PPy–BaFe12O19/Ni0.8Zn0.2Fe2O4–graphene composites were prepared by a deoxidation technique. The structures, morphology and electromagnetic properties of the samples were characterized by various instruments. Results show that PPy–BaFe12O19/Ni0.8Zn0.2Fe2O4 nanoparticles are dispersed on the graphene sheets. The saturation magnetization of the composites decrease from 33.93 to 26.93 emu/g with increasing the contents of graphene. However, the conductivities of the composites increase from 0.33 to 1.32 S/cm. Measurement of electromagnetic parameters indicates the reflection loss of the composites with 10% graphene is below −10 dB at 7.8–11.6 GHz and its maximum loss value is –25.5 dB at 9.8 GHz. The bandwidth corresponding to the reflection loss below –10 dB is 3.8 GHz.

•The composites composed of GN, branching-like PPy and CoFe2O4 were synthesized.•The ternary composites have a ferromagnetic behavior.•The diameter of CoFe2O4 nanoparticles is in the range of 5–15 nm.•The maximum reflection loss of the ternary composites is –50.8 dB at 14.5 GHz.•The absorption bandwidths exceeding –10 dB are 4.2 GHz with a thickness of 1.5 mm.In order to expand the scope of electromagnetic wave absorbers, the ternary composites composed of graphene, branching-like polypyrrole and CoFe2O4 nanoparticles were synthesized. TEM results indicated that polypyrrole on the surface of graphene had a branching-like geometrical morphology and the diameter of CoFe2O4 nanoparticles ranged from 5 to 15 nm. The electromagnetic wave absorbability revealed that the ternary composites exhibited excellent electromagnetic wave absorption properties. The maximum reflection loss was up to −50.8 dB at 14.5 GHz and the absorption bandwidths with the reflection loss exceeding −10 dB were 4.2 GHz with a thickness of only 1.5 mm. Furthermore, our development strategies confirmed that the surface modification of graphene with branching-like polypyrrole and CoFe2O4 nanoparticles could make the ternary composites have a promising future in electromagnetic wave absorption materials.

•N-doped graphene@PANI nanorod arrays hierarchical structures were fabricated.•The reflection loss of the composites is below −10 dB in 6.5–8.8 GHz.•The maximum absorption of the composites is −37.4 dB at 15.1 GHz.N-doped graphene@polyaniline nanorod arrays hierarchical structures were fabricated via in situ growth of polyaniline nanorod arrays on surfaces of N-doped graphene. The electromagnetic data demonstrate that the as-prepared hierarchical structures exhibit significantly enhanced microwave absorption properties compared with N-doped graphene. The enhanced electromagnetic performances would originate from the unique hierarchical structure and N-doping in host graphene.

•The absorbing properties of the presented ternary composites are not satisfactory.•The ternary composites of GN/PPy/Fe3O4 have never been reported.•The GN/PPy/Fe3O4 composites are synthesized via a co-precipitation method.•The maximum reflection loss of the composites is up to −56.9 dB at 6.6 GHz.•The absorption bandwidths exceeding −10 dB is 15.1 GHz with a thickness of 3–7 mm.The microwave absorption properties of the presented ternary composites are not satisfactory and the microwave absorption properties of the ternary composites composed of graphene, polypyrrole and Fe3O4 have never been reported. Herein, in order to expand the scope of microwave absorbers, the graphene/polypyrrole/Fe3O4 (GN/PPy/Fe3O4) composites were synthesized by a co-precipitation method. The microwave absorbability reveals that GN/PPy/Fe3O4 exhibits excellent microwave absorption properties and broad absorption bandwidths compared with GN, GN/PPy and GN/Fe3O4. The maximum reflection loss of GN/PPy/Fe3O4 is up to −56.9 dB at 6.6 GHz with a thickness of 5.3 mm and the absorption bandwidths exceeding −10 dB are more than 15.1 GHz with a thickness in the range of 3–7 mm. Furthermore, our strategy confirms that GN/PPy/Fe3O4 can be used as an attractive candidate for the new type of microwave absorbers.

•RGO/CoFe2O4 composite was synthesized by a one-pot hydrothermal route.•This method avoids the usage of reducing agent.•GO was reduced well by hydrothermal method.•The composite shows a large RL (−47.9 dB) and a wide absorption band (5.0 GHz).Reduced graphene oxide (RGO)/CoFe2O4 composite was synthesized by a one-pot hydrothermal route, which avoided the usage of chemical reducing agent. The reduction of graphene oxide (GO) and the crystallization of CoFe2O4 crystals happened in a one step process by the hydrothermal method. The RGO/CoFe2O4 composite shows remarkably improved electromagnetic performance in comparison with CoFe2O4 NPs and reported pure RGO. Not only a larger reflection loss (−47.9 dB at 12.4 GHz), but also a wider absorption band (less than −10 dB from 12.4 to 17.4 GHz) has been achieved in the frequency range of 2–18 GHz. It is believed that such composites could be used as a candidate microwave absorber.

The composites of reduced graphene oxide-polyaniline film (RGO-PANI) were synthesized by an in situ polymerization method and the microwave absorption properties of the composites were investigated. FESEM results indicate that RGO is covered with polyaniline film, and some PANI nanoparticles with the diameter in the range of 10–30 nm embed in the film. As PANI film covered on RGO, the microwave adsorption properties of RGO are significantly enhanced. The maximum reflection loss of RGO-PANI is up to −41.4 dB at 13.8 GHz and the bandwidths exceeding −10 and −20 dB are 4.2 GHz (from 11.7 to 15.9 GHz) and 1.5 GHz (from 12.8 to 14.3 GHz) with a coating layer thickness of 2 mm. The excellent microwave absorption properties of the composites may be attributed to the unique structural characteristics and the charge transfer between RGO and PANI film. Thus, the composites can be used as an attractive candidate for the new type of microwave absorption materials.

The ternary composites of poly(3,4-ethylenedioxythiophene)-reduced graphene oxide–Co3O4 (PEDOT–RGO–Co3O4) were synthesized and the electromagnetic absorption property of the composites was investigated. The structure of the composites was characterized with Fourier-transform infrared spectra, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscope. The electromagnetic parameters indicate the enhanced electromagnetic absorption property of the composites was attributed to the better impedance matching. On the basis of the above characterization, an electromagnetic complementary theory was proposed to explain the impedance matching. It can be found that the maximum reflection loss of PEDOT–RGO–Co3O4 can reach −51.1 dB at 10.7 GHz, and the bandwidth exceeding −10 dB is 3.1 GHz with absorber thickness of 2.0 mm. Therefore, the PEDOT–RGO–Co3O4 composites, with such excellent electromagnetic absorption properties and wide absorption bandwidth, can be used as a new kind of candidate for microwave absorbing materials.Keywords: conducting polymers; electromagnetic parameters; graphene; magnetic nanoparticles; microwave absorbing materials;

Three kinds of NiO@SiO2@graphene hierarchical structures, NiO nanoparticles@SiO2@graphene, NiO nanosheets@SiO2@graphene and NiO nanoflowers@SiO2@graphene composites were successfully fabricated by multi-step routes. The measured electromagnetic parameters show that NiO nanosheets@SiO2@graphene composites exhibit enhanced microwave absorption performance with wide absorption bandwidth as compared to NiO nanoparticles@SiO2@graphene and NiO nanoflowers@SiO2@graphene. The maximum reflection loss can reach −43.8 dB at 11.6 GHz with a thickness of 3 mm, and the absorption bandwidth with the reflection loss below −10 dB is 5.8 GHz (from 9.2 to 15 GHz). In addition, the mechanisms for the enhanced absorption performance are also discussed.

Hollow ZnSn(OH)6 boxes were synthesized from solid ZnSn(OH)6 cubes via an alkaline etching method followed by a calcination process. The as-prepared hollow boxes have an edge length ranging from 200 nm to 1 μm. Compared with the solid Zn2SnO4 cubes, hollow Zn2SnO4 boxes show an improved electrochemical performance (540 mA h g−1 at a current density of 300 mA g−1 after 45 cycles) and high rate capability (540, 482, 434, 353 and 300 mA h g−1 at the current densities of 300, 600, 1200 1800 and 2400 mA g−1, respectively). This class of hollow box-like structure may hold great promise for the development of high-performance lithium-ion batteries.

•Ni0.8Zn0.2Ce0.06Fe1.94O4 was prepared by sol–gel method.•Graphene supported Ni0.8Zn0.2Ce0.06Fe1.94O4 nanocomposite was synthesized by a deoxidation technique.•The samples were characterized by XRD, TEM, Raman and TGA.•The microwave absorbing property of Ni0.8Zn0.2Ce0.06Fe1.94O4/GNS is superior to that of Ni0.8Zn0.2Ce0.06Fe1.94O4.The graphene supported Ni0.8Zn0.2Ce0.06Fe1.94O4 nanocomposite was prepared by a deoxidation technique. The structure, morphology and electromagnetic properties of the composites were characterized by various instruments. The Ni0.8Zn0.2Ce0.06Fe1.94O4 powders could be distributed on the graphene sheets (GNS). The as-prepared Ni0.8Zn0.2Ce0.06Fe1.94O4/GNS nanocomposite exhibits a saturated magnetization of 50.42 emu/g. The electromagnetic parameters of Ni0.8Zn0.2Ce0.06Fe1.94O4/GNS nanocomposite were investigated in the 2–18 GHz range. The composite Ni0.8Zn0.2Ce0.06Fe1.94O4/GNS exhibits better microwave absorbing properties than Ni0.8Zn0.2Ce0.06Fe1.94O4. The minimum loss value of Ni0.8Zn0.2Ce0.06Fe1.94O4/GNS nanocomposite is − 37.4 dB at 12.3 GHz and a broad peak with a bandwidth lower than − 10 dB is at 10.7–15.2 GHz. These results show that the introduction of GNS can increase the complex permittivities and has an important effect on the improvement of microwave absorption properties.

Zn2SnO4@PANI composites were synthesized via a micro emulsion polymerization method. The outer surfaces of monodispersed cubes are covered with amorphous aggregated PANI. The addition of PANI can create a buffering structure for Zn2SnO4 cubes. Compared with Zn2SnO4 cubes, Zn2SnO4@PANI composites show an improved electrochemical performance (491.0 mAh g−1 at a current density of 600 mAg−1 after 50 cycles). It is believed that PANI coating is a simple and effective way to improve the cycling performance for lithium batteries.

The traditional synthesis of reduced graphene oxide (RGO) from graphene oxide (GO) involves harmful chemical reducing agents and is undesirable for practical applications. Here, we have demonstrated a green and facile approach to synthesize RGO with Zn powder under acidic condition at room temperature, which results in a substantial removal of oxygen functionalities, and yields a C/O ratio as high as 8.2. The conductivity of RGO is 6.5×102 S/m, which is about 14 times higher than that of NaBH4-reduced-GO. Furthermore, the approach offers a potential for cost-effective, environmentally friendly, and large-scale production of RGO.Highlights► Reduced graphene oxide (RGO) is prepared by Zn power reduction under acidic condition. ► Morphology of RGO signifies that RGO has multilayer structure. ► Conductivity of RGO is 6.5×102 S/m, which is about 14 times higher than that of NaBH4-reduced-GO. ► C/O ratio of RGO is 8.2 after reduction.

•c-NiFe2O4/RGO are synthesized by using PEO as a structure directing reagent.•The diameter of NiFe2O4 clusters is in the range of 40–70 nm.•NiFe2O4 clusters are composed of NiFe2O4 nanoparticles.•The maximum reflection loss is −47.3 dB at 11.9 GHz with a thickness of 2.5 mm.•The absorption bandwidth with the reflection loss below −10 dB is 4.7 GHz.Novel composites composed of NiFe2O4 clusters and reduced graphene oxide were synthesized by using polyethylene oxide as a structure directing reagent and the microwave absorption properties of NiFe2O4 clusters-reduced graphene oxide (c-NiFe2O4/RGO) were investigated. The results indicate that NiFe2O4 clusters with diameters in the range of 40–70 nm are composed of NiFe2O4 nanoparticles with diameters ranging from 3 to 5 nm. The microwave adsorption properties show that the maximum reflection loss of c-NiFe2O4/RGO is up to −47.3 dB at 11.9 GHz and the absorption bandwidth with the reflection loss below −10 dB is 4.7 GHz with a thickness of 2.5 mm. The excellent microwave absorption properties of c-NiFe2O4/RGO can be used as an attractive candidate for the new type of microwave absorptive materials.

Ordered mesoporous carbon-reduced graphene oxide (OMC-RGO) composites are prepared through organic-organic self-assembly method. The conductivity of OMC-RGO (32.5 S m−1) is higher than that of OMC (0.76 S m−1), while the pore structure is reduced and the BET surface area and pore volume of OMC-RGO (361 m2 g−1, 0.23 cm3 g−1) are lower than OMC (670 m2 g−1, 0.40 cm3 g−1). Furthermore, the presence of RGO in OMC-RGO is favorable to load more Ag nanoparticles due to the oxygen-containing groups on the surface of RGO and the Raman signal intensity of OMC-RGO–Ag is greatly increased comparing with OMC–Ag, showing surface-enhanced Raman scattering (SERS) activity.Highlights► Ordered mesoporous carbon-reduced graphene oxide (OMC-RGO) composites are prepared through organic-organic self-assembly method. ► The conductivity of OMC-RGO (32.5 S m−1) is higher than that of OMC (0.76 S m−1). ► The BET surface area and pore volume of OMC-RGO (361 m2 g−1, 0.23 cm3 g−1) are lower than that of OMC (670 m2 g−1, 0.40 cm3 g−1). ► The Raman signal intensity of OMC-RGO–Ag shows surface-enhanced Raman scattering (SERS) activity.

•RGO/Fe3O4 composite was synthesized by a facile one-pot simplified co-precipitation route.•This method avoids the usage of inert gas and any additional chemical agents (such as surfactants), which is a simple and large-scale yield route to RGO/Fe3O4 composite.•The RGO/Fe3O4 composite shows the maximum absorption of −44.6 dB at 6.6 GHz with the thickness of 3.9 mm.The reduced graphene oxide (RGO) coated with Fe3O4 composite was synthesized through a facile one-pot simplified co-precipitation route, which avoided the usage of inert gas and any additional chemical agents (such as surfactants). Given these advantages, the strategy described in this study can be developed as a simple and large-scale yield route to RGO/Fe3O4 composite. The RGO/Fe3O4 composite shows the maximum absorption of −44.6 dB at 6.6 GHz with the thickness of 3.9 mm, and the loss mechanism is mostly dielectric loss. It is believed that such composite will find its wide applications in microwave absorbing area.

•The ternary composite was synthesized through a facile one-pot wet-chemical route.•RGO is well loaded by Cu2O and Cu quantum dot with diameters about 4 nm.•The composite shows a large reflection loss (−51.8 dB at 14.6 GHz).•The composite shows a wide absorption band (4.1 GHz).The new ternary composite composed of RGO, Cu2O and Cu quantum dot was successfully synthesized at room temperature by using NaBH4 as reducing agent under mild wet-chemical conditions. The morphology, structure and microwave electromagnetic properties of the composite were characterized by XRD, XPS, TEM and vector network analyzer. The composite shows a large RL (−51.8 dB at 14.6 GHz) and a wide absorption band (less than −10 dB from 12.1 to 16.2 GHz) with the thickness of only 1.3 mm. The enhanced microwave absorbing properties were also explained, and the loss mechanism is dielectric loss. The ternary composite can act as efficient and lightweight microwave absorbing material.

•PANI-RGO-Co3O4 nanocomposites were firstly synthesized by a three-step method.•The average diameter of Co3O4 nanoparticles onto PANI-RGO is between 5 and 20 nm.•The maximum RL of PANI-RGO-Co3O4 is −32.6 dB at 6.3 GHz with a thickness of 3 mm.•The absorption bandwidth of PANI-RGO-Co3O4 with the RL below −10 dB is 13.5 GHz.A novel kind of three component nanocomposites of polyaniline-reduced graphene oxide-Co3O4 (PANI-RGO-Co3O4) was firstly synthesized by a three-step method. Several analytical techniques indicate that small Co3O4 nanoparticles are anchored on the surface of PANI-RGO and the average diameter of Co3O4 nanoparticles is between 5 and 20 nm. The PANI-RGO-Co3O4 nanocomposites demonstrate that the maximum reflection loss is −32.6 dB at 6.3 GHz with a thickness of 3 mm and the absorption bandwidth with the reflection loss below −10 dB is up to 13.5 GHz (from 3.4 to 11.8 GHz and from 12.9 to 18 GHz) with a thickness in the range of 2–4 mm, suggesting that the microwave absorption properties and the absorption bandwidth are greatly enhanced compared to PANI-RGO. The three component nanocomposites consisting of polyaniline, reduced graphene oxide and Co3O4 nanoparticles could be used as a kind of candidate for the new types of microwave absorptive materials.Polyaniline-reduced graphene oxide-Co3O4 (PANI-RGO-Co3O4) nanocomposites were firstly synthesized by a three-step method. The results demonstrate that the maximum reflection loss of PANI-RGO-Co3O4 is −32.6 dB at 6.3 GHz with a thickness of 3 mm and the absorption bandwidth with the reflection loss below −10 dB is up to 13.5 GHz (from 3.4 to 11.8 GHz and from 12.9 to 18 GHz) with a thickness in the range of 2–4 mm, suggesting that the microwave absorption properties and the absorption bandwidth are greatly enhanced comparing with PANI-RGO.

Reduced graphene oxide has been successfully prepared via chemical reduction of graphene oxide by indole as a previously unreported reducing agent. The obtained single layer reduced graphene oxide, with an average thickness of 1.7 nm, is dispersible in organic solvents such as ethanol, N,N-dimethylformamide, N-methylpyrrolidone, dimethylsulfoxide, tetrahydrofuran and isopropanol. Several analytical techniques including X-ray diffraction, UV/vis spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy have been used to characterize the resulting reduced graphene oxide, which indicates that most of oxygen functionalities are removed and yielding C/O ratio as high as 7.4. We further have demonstrated the subsequent decoration of reduced graphene oxide by direct adsorption of negatively charged Ag nanoparticles. It was found that the average diameter of Ag nanoparticles on the surface of reduced graphene oxide is between 20 and 40 nm. Furthermore, the intensity of Raman signals of reduced graphene oxide-Ag nanoparticles is about 21-fold by decorating with Ag nanoparticles, in comparison with reduced graphene oxide showing surface-enhanced Raman scattering activity.Highlights► Reduced graphene oxide (RGO) and reduced graphene oxide-Ag nanoparticles (RGO-AgNPs) nanocomposites are prepared. ► RGO, with an average thickness of 1.7 nm, has single layer structure and can be dispersible in several organic solvents. ► The C/O ratio of RGO is 7.4 after reduction. ► The average diameter of AgNPs on the surface of RGO is between 20 and 40 nm. ► The Raman signals of RGO-AgNPs is about 21-fold than RGO, showing surface-enhanced Raman scattering (SERS) activity.

•The ternary composite was synthesized through a rational route.•RGO is well loaded by Fe3O4 and Ag Nps with diameters about 25 nm.•The composite shows a large reflection loss (−58.1 dB at 9.0 GHz).•The composite shows a wide absorption band.A novel kind of reduced graphene oxide (RGO)/Fe3O4/Ag composite was firstly synthesized by a rational route. The RGO/Fe3O4/Ag composite shows the maximum absorption of −58.1 dB at 9.0 GHz with the thickness of 2.6 mm, and the absorption bandwidth with the reflection loss below −10 dB is up to 13.4 GHz (from 4.6 to 18.0 GHz) with a thickness in the range of 1.5–4.0 mm, suggesting that the microwave absorption properties and the absorption bandwidth are obviously enhanced by adding Ag NPs. It is believed that such composite could be used as a kind of candidate microwave absorber.

The BaFe12O19 nanocrystalline was prepared via a sol–gel process. The structure, morphology and electrochemical properties of the nanocrystallines were detected by means of XRD, TEM, TGA and electrochemical measurements. This BaFe12O19 is firstly used as anode electrode material for lithium-ion batteries. The mechanism of BaFe12O19 with Li will also be discussed. The reversible specific capacity of BaFe12O19 is 959.5 mAh/g. A capacity of 358.3 mAh/g can be retained after 50 cycles which will have a broad space for improvement with modifying.

Bamboo charcoal/Li2SnO3 composites for lithium-ion batteries were synthesized by a sol–gel route. The structure, morphology, and electrochemical properties of the composites were detected by means of X-ray diffraction, scanning electron microscope, Raman spectroscopy, thermal gravimetric analysis, and electrochemical measurements. The results showed that Li2SnO3 particles were loaded on the surface of bamboo charcoal and some of them entered into the hole. The bamboo charcoal/Li2SnO3 composites exhibited good electrochemical performance with high capacity and good cycling stability (616.5 mAh g−1 after 50 cycles). The composites showed a better electrochemical property than Li2SnO3 and bamboo charcoal.

BaFe12O19–Ni0.8Zn0.2Fe2O4/graphene nanocomposites were prepared by a deoxidation technique. The structure, morphology and electromagnetic properties of the samples were detected by means of X-ray diffraction, scanning electron microscope, transmission electron microscopy, Raman, thermogravimetric analysis. Results show that the BaFe12O19–Ni0.8Zn0.2Fe2O4 nanoparticles dispersed on the graphene sheets. The magnetic properties of the composites decreased with the increasing of graphene contents, However, the electrical conductivity is in the contrary. Measurement of electromagnetic parameters shows that when the mass ratio of BaFe12O19–Ni0.8Zn0.2Fe2O4 to graphene is 5:1, it can be matched well. The microwave absorption property of it is below −10 dB at 6.8–8.2 GHz and the minimum loss value is −19.63 dB at 7.2 GHz. The introduction of graphene can increase the dielectric loss and has an important effect on the microwave absorption properties.

Electroless Ni–Co–P alloys on glass fibers with sodium hypophophite as a reducing agent and sodium citrate as a complexing agent in an alkaline bath was studied. A kind of silane coupling agent was used during its pretreatmeat. Plating rate was determined by measuring the weight of glass fibers after plating. The effect of deposition parameters, such as mole ratios of CoSO4/(CoSO4 + NiSO4) and pH, on the composition and the plating rate of the deposits were examined. The crystallization behavior of Ni–Co–P alloys was studied by using differential scanning colorimetry (DSC) and X-ray diffraction (XRD). It was found that all of the three exothermic peaks in DSC curves alter distinctly as the mole ratios of CoSO4/(CoSO4 + NiSO4) increase. When the concentration of sodium hypophophite is not below 16 g l− 1 in the plating bath, the structure of the as-plated Ni–Co–P alloys plated at all conditions is amorphous. The deposit transformed into Ni5P2 and Ni12P5 phase after heat treatment at 300 °C and 420 °C, but they disappear and stable Ni3P appeared after sintering at 480 °C.

•Novel hierarchical Sn3O4 decorated on graphene nanosheets has been synthesized.•As the anode materials, the composite has not been investigated.•An insight into the common discharging behavior of the composite.•The composite displayed high capacity and good cycling stability.Novel hierarchical flower-like Sn3O4 assembled by thin Sn3O4 nanosheets, as a kind of mixed-valence tin oxide, decorated on two-dimensional graphene nanosheets has been synthesized via a hydrothermal route and a step solution deoxidization technique. More importantly, as the anode materials for lithium ion batteries, the flower-like Sn3O4/graphene composite has not been investigated in detail. Noticeably, the nanosheets stemming from flower-like Sn3O4 and graphene have been linked together to form a specials three dimensional structure, possessing high active surface area and large enough inner spaces, which is benefit to the diffusion of liquid electrolyte into the electrode materials. In addition, the special structure could provide sufficient free volume to buffer the volume expansion appeared in the process of discharging and charging. The as-prepared flowers-like Sn3O4/graphene displayed excellent electrochemical performance with high capacity and good cycling stability as anode materials for lithium ion batteries. The discharge capacity is 1727 mAh/g in the first cycle at the current density of 60 mA/g. The obtained reversible capacity is 631mAh/g with a coulomb efficiency of 97.04% after 50 cycles. With its better electrochemical properties, the as-prepared flowers-like Sn3O4/graphene has the potential to be the next generation materials as an environmentally benign, abundant, cheap anode materials for lithium ion batteries.

•Researched three-dimensional graphene@carbon nanotube interlayer for lithium-sulfur batteries.•An insight into the dual sulfur locking strategy by heat impregnation and interlayer.•Excellent performance with reversible capacities 935.1mAh g-1 at 0.2C and 755.6 mAh g-1 at 1C were achievedThree-dimensional graphene@carbon nanotube (G@CNT) composite was coated on polypropylene separator as an interlayer for high performance of lithium-sulfur batteries. In this study, the novel G@CNT nanotubes coated separator offers not only fast electron pathway for insulating sulfur, but also outstanding restriction of dissolving polysulfides. The heat impregnation of sulfur in carbon black also plays an auxiliary role on the cycling performance of the G@CNT interlayer assisted cathodes. As the dual sulfur locking strategy by heat impregnation and G@CNT interlayer, the prepared Li-S cells exhibited high rate capacity and sustainably enhanced cycling stability. Excellent cycling performance with a high capacity 935.1 mAh g−1 at 0.2C and 755.6 mAh g−1 at 1C after 200 cycles is achieved. Moreover, the cell delivers reversible discharge capacities up to 669.7 mAh g−1 and 555.1 mAh g−1 after 200 cycles even at 2C and 4C.

A two-step strategy combining in situ polymerization and a hydrothermal process has been developed for coupling polyaniline (PANI) with porous TiO2 anchored on magnetic graphene. The microstructure and morphology of magnetic graphene@PANI@porous TiO2 were characterized by FETEM, FESEM, XRD, XPS and VSM in detail. The results indicated that magnetic graphene@PANI was completely covered by porous TiO2 with random orientations and the saturation magnetization value of the composite was 19.2 emu g−1. PANI was used to decrease the absorber thickness, while the porous TiO2 with a large surface area was designed to enhance the interaction between the electromagnetic (EM) wave and the absorber through multiple reflections, thus enhancing EM wave absorption properties. As an EM wave absorber, the maximum reflection loss of the composite was up to −45.4 dB due to the better normalized characteristic impedance (close to 1) at a thickness of only 1.5 mm and the absorption bandwidths exceeding −10 dB were 11.5 GHz when the thickness ranged from 1 to 3.5 mm. The excellent EM wave absorption performance was ascribed to the combined contribution from the enhanced dielectric relaxation processes, the unique porous nanostructures, the quarter-wave length matching model and the well-matched normalized characteristic impedance. Consequently, it is believed that the composite could be used as an excellent EM wave absorption material and the two-step strategy offered an effective way to design a high-performance EM wave absorber with a relatively thin thickness.

The fabrication of novel hierarchical graphene@Fe3O4 nanocluster@carbon@MnO2 nanosheet array composites has been successfully carried out for the first time. The fabrication process involves the deposition of Fe3O4 nanoclusters on graphene's surface using a simple in situ hydrothermal method, subsequent introduction of carbon on the surface of graphene@Fe3O4 nanoclusters by combining the hydrothermal reaction and thermal treatment process, and finally formation of the hierarchical composites via a simple in situ redox replacement reaction between potassium permanganate (KMnO4) and carbon on the surface of graphene@Fe3O4 nanoclusters. Moreover, the microwave absorption properties of both graphene@Fe3O4 nanoclusters and hierarchical graphene@Fe3O4 nanocluster@carbon@MnO2 nanosheet array composites were investigated between 2 and 18 GHz microwave frequency bands. The electromagnetic data demonstrate that graphene@Fe3O4 nanocluster@carbon@MnO2 nanosheet array hierarchical composites exhibit significantly enhanced microwave absorption properties compared with graphene@Fe3O4 nanoclusters, which probably originate from the unique hierarchical structure and larger surface area.

A novel three-dimensional graphene@carbon nanotube (CNTs) composite has been prepared using a facile one-pot pyrolysis strategy using urea as the carbon source, in which the density and length of CNTs on graphene are rationally tuned by adding an appropriate amount of urea to a precursor mixture. Correspondingly, the density and length of CNTs on graphene have a significant effect on the microwave absorption properties of graphene@CNTs. When most of the graphene surface is clearly covered by the CNTs whose length ranges from 300 to 600 nm, the graphene@CNT composite exhibits excellent microwave absorption properties. The maximum reflection loss value can reach −44.6 dB at 8.6 GHz and the absorption bandwidth with a reflection loss below −10 dB ranges from 7.1 to 10.4 GHz with an addition amount of only 5 wt% graphene@CNTs composite in the paraffin matrix.