•MnO nanoparticles anchored on continuous carbon nanosheets was fabricated.•MnO nanoparticles enabled fast transfer of Li ion in insertion/extraction process.•Carbon nanosheets constructed a continuous electron-conducting system.•Carbon nanosheets can prevent the volume expansion of MnO effectively.We fabricated a nanostructure of MnO nanoparticles anchored on continuous carbon nanosheets (MN@CCN) based on an in-situ template method. During the synthesis, the MnO particles were confined in nano-scale by soluble salt templates and embedded in the continuous carbon nanosheets, which can facilitate the lithium ion diffusion in electrode reaction. Such specific nanostructures further construct a 3D network for enhancing the electron conducting efficiency. Meanwhile, the carbon layers cover on the surface of MnO particles, which can hinder the volume expansion of MnO during lithium insert process. As the anode of lithium ion battery, MN@CCN exhibits high specific capacitance (782 mAh g−1) and long-life cycle performance (800 cycles) at a high rate (2 A g−1).

•A simple synthesis method was proposed to form Li2S@porous carbon composites.•Graphite-Li2S full-cells were constructed in DME-based electrolyte.•A novel method was proposed to activate the full cells.Lithium-sulfur (Li-S) batteries have been recognized as one of the promising next-generation energy storage devices owing to their high energy density, low cost and eco-friendliness. As for cathode’s performance, the main challenges for developing highly-efficient and long-life Li-S batteries are to retard the polysulfides diffusion into electrolyte and the reaction with metallic lithium (Li). Especially, the safety issues, derived from metallic Li in anode, must be overcome. Herein, we fabricated lithium sulfide@porous carbon composites (Li2S@PC) by an in-situ reaction between the lithium sulfate (Li2SO4) and the pyrolytic carbon from glucose. The nanosized Li2S particles were uniformly distributed in the carbon matrix, which not only significantly improve electronic conductivity of the electrode but also effectively trap the dissolved polysulfides. Furthermore, on the basis of the graphite’s electrochemical features in ether-based electrolyte, we assembled graphite-Li2S@PC full cells using the obtained Li2S@PC composites as the cathode, graphite as the anode and the DOL/DME with LiNO3 additive as the electrolyte. A unique strategy was proposed to activate the full-cells in descending order using constant voltage and current to charge the cut-off voltage. This Li-S full cell exhibits stable cycling performance at 0.5 C over 100 cycles. Because graphite-Li2S batteries are suitable to the lithium-ion batteries industry, our preliminary results here will shed a new light on the cell design and industrial production.A facile method is proposed to prepare lithium sulfide@porous carbon composites (Li2S@PC) by in-situ reaction of lithium sulfate (Li2SO4) and the pyrolytic carbon from glucose. We assembled graphite-Li2S@PC full-cells using the obtained Li2S@PC composites as the cathode, graphite as the anode and DOL/DME with LiNO3 additive as the electrolyte.Download high-res image (272KB)Download full-size image

•Fe3O4/rebar graphene (FRG) composite was synthesized through a solvothermal route.•FRG was performed as binder and carbon black free anode for lithium ion batteries.•The capacity of FRG anode achieves 1038 mAh g−1 after 100 cycles at 0.1 A g−1.A free-standing Fe3O4/rebar graphene (FRG) composite film was obtained through solvothermal method. The microstructure, phases, electrochemical performance of the composite used as anode in lithium ion battery have been characterized by SEM, TEM, XRD, Raman, FT-IR and electrochemical measurements. In rebar graphene (RG), the single-wall carbon nanotubes (SWCNTs) and graphene are interconnected via π–π stacking and covalent bonding. SWCNTs can keep the graphene in RG from fracture and maintain the integrity of the composite electrodes during lithiation/delithiation. The absence of additive and conductive agent can enhance electrochemical performance of FRG composite by losing redundant weight. The FRG composite exhibits an outstanding rate capability with an excellent cycling performance (1038 mAh g−1 after 100 cycles at 100 mA g−1).

Al composite foams reinforced by in-situ generated MgAl2O4 spinel whiskers were fabricated via sintering and dissolution processes, using sodium chloride particles as a space holder material. The MgAl2O4 spinel whiskers with diameters ranging from 50 to 300 nm were uniformly distributed in the composite foams and formed well-bonded interface with the Al matrix. The mean pore sizes and the average thickness of the cell wall are about 450 μm and 20 μm, respectively, while the relative density is 0.3. Compressive tests verified that the plateau stress is in the range of 5.4–18.7 MPa at the pore size of 0.45 mm, while the relative density increases from 0.2 to 0.5. Especially, the composite foams showed superior plateau stress (18.7 MPa) and energy absorption capacity (17.5 MJ/m3) by adding 10 wt% Mg powder in starting materials.

In-situ synthesized carbon nanotubes (CNTs) reinforced aluminum–copper (Al–Cu) composites have been prepared by powder metallurgy. The strengthening effect of CNTs reinforcement and precipitation hardening of Al–Cu matrix has been investigated. CNTs and Cu nanoparticles are homogeneously embedded into Al powders through the process of in-situ preparation and ball milling. XRD results show that Cu elemental phase is converted to Al2Cu phase during the procedure of sintering. Raman spectra indicate that CNTs could maintain its structural integrity during powder metallurgy. In T6 heat treatment, the aging time of peak hardness has been reduced from 9 h to 3 h, demonstrating accelerated aging of the composite. Besides, the ultimate tensile strength of CNTs/Al–Cu composites have a 33.9% increase compared with that of Al–Cu alloy, and a further increase could be achieved (20.3%) after T6 heat treatment. The strengthening mechanism of CNTs/Al–Cu composites combines two synergistic factors: CNTs reinforcement and precipitation hardening of Al–Cu alloy.

Nanostructured spinel LiMn1.5Ni0.5O4, layered Li1.5Mn0.75Ni0.25O2.5 and layered-spinel hybrid particles have been successfully synthesized by hydrothermal methods. It is found that the nanostructured hybrid cathode contains both spinel and layered components, which could be expressed as Li1.13Mn0.75Ni0.25O2.32. Diffraction-contrast bright-field (BF) and dark-field (DF) images illustrate that the hybrid cathode has well dispersed spinel component. Electrochemical measurements reveal that the first-cycle efficiency of the layered-spinel hybrid cathode is greatly improved (up to 90%) compared with that of the layered material (71%) by integrating spinel component. Our investigation demonstrates that the spinel containing hybrid material delivers a high capacity of 240 mAh g–1 with good cycling stability between 2.0 and 4.8 V at a current rate of 0.1 C.Keywords: hydrothermal synthesis; layered-spinel hybrid cathode; lithium-ion battery;

The reduced graphene oxide (r-GO) coated with Fe3O4 composite was synthesized through a facile method involving decomposition of Fe(OH)3 in argon atmosphere and reduction in hydrogen and argon mixture atmosphere. The Fe3O4 particles evenly distributed on r-GO, with the diameters from 10 nm to 40 nm, are monocrystalline. The composite demonstrates a reflection loss below −10 dB in 14.3–18 GHz range, and the maximum absorption of −22.2 dB at 17.3 GHz. The microwave absorption of r-GO/Fe3O4 nanocomposites is attributed to relaxation and polarization of the residual groups and defect of graphene and polarization attributed to the presence of Fe2+ ions in Fe3O4.Highlights► The reduced graphene oxide (r-GO) coated with Fe3O4 composite was synthesized. ► The Fe3O4 particles are evenly distributed on r-GO. ► The composite has a reflection loss below −10 dB at 14.3–18 GHz.

The electrochemical hydrogen storage of expanded graphite (EG) decorated with TiO2 nanoparticles (NPs) calcined at different temperatures has been investigated with the galvanostatic charge and discharge method. The TiO2 NPs are deposited on and between the graphene-like nanosheets of EG by a sol-gel method. The morphology, structure, composition, and specific surface area of the samples were characterized. The electrochemical measurement reveals that the EG decorated with TiO2 NPs calcined at 500 °C has a discharge capacity of 373.5 mAh/g which is 20 times higher than that of pure EG and quite appealing for the battery applications. The mechanism of enhancement of the electrochemical activity for the TiO2-decorated EG could be attributed to the preferable redox ability and photocatalytic property of TiO2 NPs.Highlights► Deposited TiO2 NPs on and between the graphene-like nanosheets of EG. ► EG decorated with TiO2 NPs has a discharge capacity of 373.5 mAh/g. ► The discharge capacity is 20 times higher than that of pure EG. ► Electrochemical activity is mainly due to the preferable redox ability of TiO2 NPs.

In this work, first-principles total energy calculations were performed in order to study the structure and hydrogen storage behavior on Ca-decorated graphene. On the stable structure of Ca-decorated graphene with 3×3−300 reconstruction, the first hydrogen molecule adsorbed is dissociative, with the energy barrier of only 0.05 eV. The electrons of H atoms saturate the electronic states of Ca around the Fermi level and enhance the system stability. Further adsorption of hydrogen molecules on Ca-adsorbed graphene is weak, which indicates Ca-adsorbed graphene does not suit for the hydrogen storage via physical adsorption of hydrogen molecules. On the other hand, hydrogen spillover mechanism could exist on Ca-decorated graphene. On the graphene with one Ca dimer adsorbed, one of the four H atoms adsorbed on the Ca dimer adsorbes chemically on C in graphene more stably by 0.37 eV than on the Ca dimer. With the number of hydrogen atoms adsorbed on Ca-decorated graphene increases, the binding energy of hydrogen atoms tends to increase. Thus, the spillover process is energetically favorable. The hydrogen storage capacity via the spillover mechanism in Ca-adsorbed graphene depends on the Ca content and could approach 7.7 wt.%.Highlights► Dissociation of hydrogen molecules on Ca-decorated graphene is discovered. ► Adsorption of hydrogen molecules on Ca-decorated graphene is weakened. ► The spillover process is energetically favorable on Ca-decorated graphene. ► Ca dimers act as nucleation positions of hydrogen adsorption on graphene.

Single-crystal aluminum borate (Al4B2O9) nanowhiskers with diameters from 20 to 200 nm have been synthesized on the surface of aluminum powder at relatively low temperatures after high energy ball-milling pretreatment. It was found that the reaction temperature plays an important role in determining the diameter and length of the single-crystal Al4B2O9 nanowhiskers. The growth of the nanowhiskers can occur at a low temperature of 650 °C due to the ball-milling pretreatment. The growth mechanism of the nanowhiskers is considered to be the solution–liquid–solid (SLS) growth. Our in-situ growth of nanowhiskers on the aluminum matrix is an effective way to prepare Al4B2O9 nanowhisker/aluminum composite powders with homogenous distribution of the reinforcement.Single-crystal aluminum borate nanowhiskers with diameters from 20 to 200 nm have been synthesized on the surface of aluminum powder at relatively low temperatures after high energy ball-milling pretreatment. It was found that the growth of the nanowhiskers can occur at a low temperature of 650 °C due to the ball-milling pretreatment.Research highlights► Ball-milling pretreatment reduces the growth temperature of the aluminum borate nanowhisker obviously. ► The aluminum borate nanowhiskers could in-situ generate on the aluminum powder surface. ► Reaction temperature plays an important role in determining the size and shape of the Al4B2O9 nanowhiskers.

We studied the magnetic coupling between magnetic atoms at the O-terminated ZnO(0001̅) surface using first-principles total energy calculations. It was found that the substitutional Co and Mn in the O-terminated ZnO(0001̅) surface tend to occupy the outermost cation layer. Different from the magnetic behaviors between substitutional Co and Mn atoms in bulk ZnO, at O-terminated ZnO(0001̅), due to the presence of surface states, the magnetic atoms display ferromagnetic coupling. On the basis of the analysis of electron density of states, n- and p-type doping could enhance the ferromagnetic coupling between Co and Mn atoms at O-terminated ZnO(0001̅), respectively, in good agreement with previous experimental observations. Our results complement the understanding of the origin of ferromagnetism in ZnO-based diluted magnetic semiconductors.

SiC/ZnO nanocomposites were prepared by radio frequency alternate sputtering followed by annealing in N2 ambient. Well-crystallized ZnO matrix was obtained after annealed at 750 °C according to X-ray diffractometer patterns. Transmission electron microscopy analyses indicated that the SiC thin layer aggregated to form SiC nanoclusters with the average size of 7.2 nm when the annealing temperature was 600 °C. When the annealing temperatures increased above 900 °C, some of the SiC nanoclusters changed into SiC nanocrystals and surfacial atoms of the SiC nanoparticles were surrounded by a layer of SiOx (x ≤ 2) according to the Fourier transform infrared spectrums. The SiC/ZnO nanocomposites annealed at 750 °C exhibit strong photoluminescence bands ranging from 250 to 600 nm. UV light originates from the near band edge emission of ZnO and the blue emission peaked at around 465 nm (2.7 eV) may be due to the formation of emission centers caused by the defects in Si–O network, while the green-emission peak at around 550 nm (2.3 eV) may be attributed to the deep level recombination luminescence caused by the vacancies of oxygen and zinc.

We investigated theoretically the adsorption of individual Mg atoms on single-walled carbon nanotubes (SWCNTs) by first-principles method within density functional theory in order to clarify the binding energies and the electronic structures of Mg atoms contact with SWCNTs. Our results suggest that the interaction of Mg atom adsorbed on pristine SWCNTs, which is normally very weak, can be enhanced upon functionalization of SWCNTs by B- or N-doping. Especially, the B-doping increases dramatically the binding energies of Mg-adsorbed on both armchair and zigzag SWCNTs.B-doping increases dramatically the binding energy of single Mg atom on both armchair and zigzag SWCNTs.

Solid carbon nanofibers (CNFs), hollow CNFs, metal-filled carbon nanotubes (CNTs), and carbon onions were synthesized by chemical vapor deposition (CVD) using a novel Ni/Y catalyst supported on Cu at different reaction temperatures. XRD, TEM, and EDS analyses reveal that the structure of the catalyst changes with increasing reaction temperature. The evolution of Y doped in Ni directly influences the morphologies of the products. At relatively low temperature, Y is doped in Ni and causes CNF formation, and when the temperature is increased to above 650 °C, Y separates from Ni as yttria nanoparticles and carbon onions are synthesized. The catalyst evolution and carbon nanostructure growth mechanism are discussed in detail.

Bamboo-shaped carbon nanotubes (CNTs) and herringbone nanofibers were catalytically synthesized by a decomposition of methane over Ni/Al catalyst under N2 at the low temperature (500–600 °C). Transmission electron microscopy (TEM) was used to investigate the bamboo-shaped CNTs and the nanofibers. High-resolution TEM analysis revealed that two species of bamboo-shaped tubes with different morphologies and structures, categorized according to the shape and participation of the encapsulated catalytic nanoparticles, coexist in one sample. It is found that the morphology and structure of the catalytic particles play very important roles during carbon nanomaterial growth. The growth mechanisms for the bamboo-shaped CNTs and nanofibers are proposed in detail, especially the formation process of compartments of the bamboo-shaped CNTs.

•Mo2C submicron layer was coated on diamond particles by a molten salts route.•Mo powder was used as the Mo source for preparing Mo2C coating.•Mo2C coating plays diverse roles on diamond/Cu or diamond/Al composites.•Mo2C coating increases the thermal conductivity of diamond/Cu composites.Mo2C submicron layer coated diamond particles prepared by a molten salts route with Mo powder as the starting material were used as the filler in Cu- and Al- matrix composites. The microstructure and thermal property of the composites prepared by a vacuum pressure infiltration method were investigated. When introducing a 500 nm thick Mo2C layer, the thermal conductivity of the composites with different matrix presented different performance. A high thermal conductivity (657 W m−1 K−1) was obtained in diamond/Cu composites owing to the improved interfacial bonding and lower interfacial thermal resistance, while the thermal conductivity of diamond/Al composites decreased from 553 W m−1 K−1 to 218 W m−1 K−1 when introducing the Mo2C layer, which can be attributed to the formation of harmful granule-phase (Al12Mo) at the interface of diamond and aluminum. This work provides a promising approach to improve performance of diamond reinforced metal matrix composites by selecting carbide as an interface modifier.