Search

Abstract Traditional laminated metal matrix composites are confined to two-component system of pure metal matrix and its reinforcement. To achieve further improvement of the applied mechanical properties, in this work, the soft phase of laminated composites was enhanced by alloying with Cu. The synergistic effect of Cu on phases of both soft and hard including in-situ catalyzing and precipitation hardening was firstly explored. The laminated graphene nanosheets (GNSs) /AlCu composites of 2 vol% GNSs, were fabricated by ball milling and hot-rolling processes with much higher mechanical properties. The multi-pass hot rolling provided the solution-precipitation process of Cu transforming into Al 2 Cu and significantly increased the dislocation density of the original soft Al matrix. In addition, the fracture mechanism and fracture model of the laminated GNSs/AlCu composites were also investigated. [ABSTRACT FROM AUTHOR]

Abstract: Electrochemical reduction of CO2 provides an opportunity to reach a carbon‐neutral energy recycling regime, in which CO2 emissions from fuel use are collected and converted back to fuels. The reduction of CO2 to CO is the first step toward the synthesis of more complex carbon‐based fuels and chemicals. Therefore, understanding this step is crucial for the development of high‐performance electrocatalyst for CO2 conversion to higher order products such as hydrocarbons. Here, atomic iron dispersed on nitrogen‐doped graphene (Fe/NG) is synthesized as an efficient electrocatalyst for CO2 reduction to CO. Fe/NG has a low reduction overpotential with high Faradic efficiency up to 80%. The existence of nitrogen‐confined atomic Fe moieties on the nitrogen‐doped graphene layer is confirmed by aberration‐corrected high‐angle annular dark‐field scanning transmission electron microscopy and X‐ray absorption fine structure analysis. The Fe/NG catalysts provide an ideal platform for comparative studies of the effect of the catalytic center on the electrocatalytic performance. The CO2 reduction reaction mechanism on atomic Fe surrounded by four N atoms (Fe–N4) embedded in nitrogen‐doped graphene is further investigated through density functional theory calculations, revealing a possible promotional effect of nitrogen doping on graphene. [ABSTRACT FROM AUTHOR]

A hybrid of graphene nanoribbons (GNRs) interlacing hollow NiCoO (G-HNCO) nanocages in a size range of 300~500 nm with rough surface is synthesized by a chemical etching CuO templates and followed by GNR interlacing process. The G-HNCO showed high electrochemical performance of oxygen evolution reaction (OER), which exhibited small onset potential of 1.50 V and achieved current densities of 10 mA cm at potentials of 1.62 V. Also, the hybrid delivered high capacitance of 937.8 F g at 1 A g in supercapacitor (SC) tests as well as stable cycling performance in both OER and SC measurements. The approach to synthesize the hybrid is simple and scalable for other graphene nanoribbon-based electrocatalysts. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) reduced graphene oxide (rGO) anchored carbon-coated Fe 2 O 3 core-shell nanoparticles (Fe 2 O 3 @C-rGO) has been developed successfully through a simple one-pot hydrothermal process followed by a further annealing treatment. The 3D Fe 2 O 3 @C-rGO nanocomposite consists of carbon-coated Fe 2 O 3 nanoparticle clusters (Fe 2 O 3 @C) and rGO nanosheets. The homogenously distributed and intercalated Fe 2 O 3 @C nanoparticles between rGO nanosheets form a highly conductive 3D carbon network with rGO, and present a hierarchical pore size structure, enabling fast ion and electron transport, as well as remarkable specific surface area. The electrochemical performance in supercapacitor has been characterized, and the as-prepared Fe 2 O 3 @C-rGO electrode shows a significant high specific capacitance of 211.4 F/g at 0.5 A/g and 177.2 F/g at 20 A/g with no visible performance decay even after 2500 cycles testing. These properties indicate a good potential to achieve high performance electrochemical devices. [ABSTRACT FROM AUTHOR]

Three-dimensional bi-functional modular graphene network (3D bmG) is developed by using metal powder assisted soluble salt templates method. The 3D bmG contains two kinds of modules with different functions: the 3D graphene catalyzed by Ni powder (3D bmG-n) and the 3D graphene grown on NaCl crystals (3D bmG-s). The 3D bmG-n with high crystallization degree ensures the high electrical conductivity and structural stability and protects the 3D bmG-s from etching in electrolyte. The 3D bmG-s with more defects and pores provides high capacity and rate properties. Thus, the synergistic effects of the two modules endow the 3D bmG excellent electrochemical performance as both cathode and anode of lithium-ion capacitors (LICs). The as-prepared "all-carbon" bmG//bmG full LIC with a high voltage window of 4.5 V presents high energy densities of 278 Wh kg−1 and 52.2 Wh kg−1 at power densities of 405 W kg−1 and 16200 W kg−1, respectively, and excellent cycling stability with a capacity retention ratio of 88.57% after 3000 cycles, which is superior compared with LICs reported previously. These properties indicate promising application of 3D bmG in high performance energy storage devices, and the modular design in this work will inspire more designs and types of 3D materials. [Display omitted] • 3D bi-functional modular graphene network was successfully developed. • Two modules with specific structures ensure synergistic improvement of properties. • 4.5 V symmetrical LIC achieved high energy and power density and long cycle life. [ABSTRACT FROM AUTHOR]

Introduction of magnetism in large-area monolayer graphene has captured much attention in the graphene community, owing to the potential applications in transistors, magnetic memory, spintronic devices, and so on. Here, we use graphene nanoribbons (GNRs) as reinforcing rebar to in situ reinforce large-area graphene, where the edges of graphene nanoribbons are found to be seamlessly welded with graphene sheet. Based on the GNR-reinforced graphene, Fe nanoparticles encapsulated by carbon nano-onions (CNOs) with controllable shell thickness are in situ grown on the surface to introduce efficient ferromagnetic phase to graphene by a facile and scalable method. When core-shell Fe@CNOs with thick shells are anchored, the hybrid film shows a strong p -doping electric behavior and an intriguing ferromagnetic property with remarkable remanence and coercivity in applied magnetic fields. The in situ growth of nanoscale Fe@CNOs on large-area GNR reinforced graphene will provide an additional avenue for the application of graphene-based films in flexible and transparent spintronic or magnetic electronics. Image 1 [ABSTRACT FROM AUTHOR]

A free-standing Fe 3 O 4 /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 ). [ABSTRACT FROM AUTHOR]

Achieving uniform reinforcement dispersion and strong interfacial bonding remains challenging to increase the strengthening efficiency in advanced metal matrix composites (MMCs). In this work, we report the prominent strengthening efficiency in graphene nanosheet reinforced Al matrix (GNS/Al) composites fabricated via hybrid deformation combining hot extrusion and multi-pass hot rolling (MPHR). Results show that most GNS-rich zones in extruded GNS/Al composites were eliminated by MPHR, leading to an even layer-distribution of GNSs aligning along the Al grains, which initiates grain recrystallization and promotes dislocation accumulation for a high strain hardening of the composites. Moreover, the shear stress induced by MPHR was revealed to exfoliate overlapped GNSs to attach with Al and enhance the formation of boundary-like defects/disorders at the edge of GNSs, which promotes Al–C interdiffusion and generates the typically infiltrated Al-GNS interfaces featured by transition zones. Such unique interface structure exhibits a high interfacial shear strength, enabling the effective load transfer between GNSs and Al. It is confirmed that the fine distribution of GNS and robust Al-GNS interfacial cohesion contribute to the remarkable strengthening efficiency of GNSs. The present work paves a new way to disperse GNSs and tune interface structures for enhancing mechanical performance of Al matrix composites. [Display omitted] [ABSTRACT FROM AUTHOR]

Designing heterogeneous structures is a promising pathway for overcoming the trade-off between strength and toughness in metal matrix composites (MMCs). Herein, we report an innovative strategy for fabricating graphene nanosheet-Cu reinforced Al matrix (GNS-Cu/Al) composites with heterogeneous structure. This strategy involves the consolidation of unique composite powders with core-shell grain structure, which are synthesized with the aid of in-situ GNS-Cu hybrids. Results reveal that the fabricated GNS-Cu/Al composite exhibits multiple microstructural heterogeneities, including both heterogeneous grain structure and reinforcement spatial distribution, which endow the composite with a prominent combination of tensile strength of ∼437 MPa, fracture elongation of ∼12.5% and toughness of ∼48.7 MJ m−3. It is confirmed that such microstructural heterogeneities in GNS-Cu/Al composite contribute significant hetero-deformation induced (HDI) stress strengthening and sustained strain hardening, making the key mechanical properties of GNS-Cu/Al considerably outperform the counterpart of Cu/Al composite. Moreover, the coordinated deformation and crack bridging/blunting behaviors are demonstrated to be responsible for the exceptional toughness of GNS-Cu/Al composite. This work offers a promising bottom-up tactic to fabricate Al matrix composites with heterogeneous structures and superior mechanical performances for structural applications. [Display omitted] [ABSTRACT FROM AUTHOR]

The interface bonding was found to be related with the element electronegativity. And the first-principles tensile experiments including the rigid stretching and the relaxed stretching were implemented to simulate the stretching process, then a fitting function was applied to determine the quantitative relationship between the interface bonding and mechanical properties. [Display omitted] • Transition metal (TM) elements doping effects on Gr/Cu interface binding are studied. • Work of separation of the doped interfaces relates to the TM electronegativity. • The rigid and relaxed stretching are used to study the related mechanical properties. • Quantitative relationship between interface binding and mechanical property is explored. The interface doping with transition metal elements (TM = Ti, Cr, Co, Ni) has been experimentally proved to be an effective pathway to improve the weak interface bonding of graphene/copper (Gr/Cu) composites. In this paper, the microscopic influencing mechanism of TM doping on the interface interaction and mechanical properties of Gr/Cu was investigated by the first-principles calculations. The sandwich model with graphene embedded in Cu matrix was adopted here to simulate the TM-doped interfaces. It is revealed that the introduction of TM doping elements can significantly improve the work of separation, which relates to the electronegativity difference between TM and Cu elements based on the analysis of the interface electronic structure. Then, the mechanical properties of the clean and TM-doped interfaces were studied by the rigid stretching and the relaxed stretching. We found that, in rigid case, the theoretical tensile strengths of different interfaces are positively correlated with the work of separation, and the electronegativity is also a main factor affecting the mechanical properties. Furthermore, a fitting function containing the element electronegativity was applied to get the stress–strain relationship curve, and the quantitative relationship between the interface bonding and mechanical properties determined in this work can be served as a favorable support for the experimental design of Gr/Cu composites. [ABSTRACT FROM AUTHOR]