Three-dimensional graphene network is a promising structure for improving both the mechanical properties and functional capabilities of reinforced polymer and ceramic matrix composites. However, ...direct application in a metal matrix remains difficult due to the reason that wetting is usually unfavorable in the carbon/metal system. Here we report a powder-metallurgy based strategy to construct a three-dimensional continuous graphene network architecture in a copper matrix through thermal-stress-induced welding between graphene-like nanosheets grown on the surface of copper powders. The interpenetrating structural feature of the as-obtained composites not only promotes the interfacial shear stress to a high level and thus results in significantly enhanced load transfer strengthening and crack-bridging toughening simultaneously, but also constructs additional three-dimensional hyperchannels for electrical and thermal conductivity. Our approach offers a general way for manufacturing metal matrix composites with high overall performance.
Copper nanoparticles coated graphene nanoplates reinforced Al (Cu-GNPs/Al) matrix composites were fabricated by the combination of low temperature ball milling (LTBM) and subsequent hot extrusion ...process. The as-obtained composite with 2.5 wt% Cu-GNPs showed excellent comprehensive properties, i.e. the tensile strength (402 MPa) is 130% higher than that of monolithic Al, meanwhile, the fracture elongation over 10% was maintained. It was found that compared with room temperature ball milling, the LTBM processing could improve the dispersion of graphene in the matrix remarkably and thus enhance the strength of the composites substantially. The introduction of Cu-GNPs weakened the fiber texture of the Al matrix but refined grains as well as reduced the thermal expansion coefficient of the composites. The coated Cu on the GNPs enriched at the interface and inhibited the severe interfacial reaction, which would enable the structural integrity retention of GNPs and improved the interfacial bonding strength and thus be very favorable for the load transfer between GNPs and Al matrix. In addition, two sizes of GNPs were found in the composites due to the ball milling processing, the larger-sized GNPs contributed a lot to the load transfer while the smaller ones contributed more to the Orowan strengthening.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Nanometal materials play very important roles in solar‐to‐chemical energy conversion due to their unique catalytic and optical characteristics. They have found wide applications from semiconductor ...photocatalysis to rapidly growing surface plasmon‐mediated heterogeneous catalysis. The recent research achievements of nanometals are reviewed here, with regard to applications in semiconductor photocatalysis, plasmonic photocatalysis, and plasmonic photo‐thermocatalysis. As the first important topic discussed here, the latest progress in the design of nanometal cocatalysts and their applications in semiconductor photocatalysis are introduced. Then, plasmonic photocatalysis and plasmonic photo‐thermocatalysis are discussed. A better understanding of electron‐driven and temperature‐driven catalytic behaviors over plasmonic nanometals is helpful to bridge the present gap between the communities of photocatalysis and conventional catalysis controlled by temperature. The objective here is to provide instructive information on how to take the advantages of the unique functions of nanometals in different types of catalytic processes to improve the efficiency of solar‐energy utilization for more practical artificial photosynthesis.
Nanometal materials play very important roles in solar‐to‐chemical energy conversion due to their unique catalytic and optical characteristics. Recent research achievements of nanometals regarding applications in semiconductor photocatalysis, plasmonic photocatalysis, and plasmonic photo‐thermocatalysis are presented. Instructive information on how to take the advantage of nanometals in these catalytic processes for efficient artificial photosynthesis is provided.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The rapidly increasing severity of the energy crisis and environmental degradation are stimulating the rapid development of photocatalysts and rechargeable lithium/sodium ion batteries. In ...particular, MoS2/TiO2 based nanocomposites show great potential and have been widely studied in the areas of both photocatalysis and rechargeable lithium/sodium ion batteries due to their superior combination properties. In addition to the low-cost, abundance, and high chemical stability of both MoS2 and TiO2, MoS2/TiO2 composites also show complementary advantages. These include the strong optical absorption of TiO2vs. the high catalytic activity of MoS2, which is promising for photocatalysis; and excellent safety and superior structural stability of TiO2vs. the high theoretic specific capacity and unique layered structure of MoS2, thus, these composites are exciting as anode materials. In this review, we first summarize the recent progress in MoS2/TiO2-based nanomaterials for applications in photocatalysis and rechargeable batteries. We highlight the synthesis, structure and mechanism of MoS2/TiO2-based nanomaterials. Then, advancements and strategies for improving the performance of these composites in photocatalytic degradation, hydrogen evolution, CO2 reduction, LIBs and SIBs are critically discussed. Finally, perspectives on existing challenges and probable opportunities for future exploration of MoS2/TiO2-based composites towards photocatalysis and rechargeable batteries are presented. We believe the present review would provide enriched information for a deeper understanding of MoS2/TiO2 composites and open avenues for the rational design of MoS2/TiO2 based composites for energy and environment-related applications.
In the past few decades, great effort has been made toward the preparation and development of advanced transition metal dichalcogenide (TMD) materials for anodes of alkali metal ion batteries ...(AMIBs). However, their electrochemical performance is still severely impaired by structural aggregation and fracture during the conversion reaction. To address these issues, various methodologies for the fabrication of hierarchical and hybrid nanostructures, with optimization of materials and electrodes, have been fully investigated and reviewed. As regards tuning the TMD-based materials, extensive efforts have been undertaken toward optimization of their intrinsic structure at the atomic level, including surface defects, interlayer spacing expansion, phase control, alloying, and heteroatom doping. However, the design strategies and methods to manipulate the intrinsic structures and electrochemical mechanisms in AMIBs have not been fully summarized. This review provides a well-timed and critical appraisal of recent advances in the engineering of TMDs at the atomic level for AMIBs, by combining computational and experimental approaches. The correlation between these strategies and electrochemical performance is highlighted. The challenges and opportunities in this research field are also outlined. We expect that this review would be beneficial for improving the overall knowledge on the charge storage mechanisms in TMDs and for pointing out the importance of intrinsic structure engineering for enhancing the performance of TMDs in energy storage.
This review provides enriched information for understanding the charge storage mechanisms of transition metal dichalcogenides (TMDs), as well as the importance of intrinsic structure engineering for enhancing the performance of TMDs in energy storage.
Hybrid materials composed of transition‐metal compounds and nitrogen‐doped carbonaceous supports are promising electrocatalysts for various electrochemical energy conversion devices, whose activity ...enhancements can be attributed to the synergistic effect between metallic sites and N dopants. While the functionality of single‐metal catalysts is relatively well‐understood, the mechanism and synergy of bimetallic systems are less explored. Herein, the design and fabrication of an integrated flexible electrode based on NiCo2S4/graphitic carbon nitride/carbon nanotube (NiCo2S4@g‐C3N4‐CNT) are reported. Comparative studies evidence the electronic transfer from bimetallic Ni/Co active sites to abundant pyridinic‐N in underlying g‐C3N4 and the synergistic effect with coupled conductive CNTs for promoting reversible oxygen electrocatalysis. Theoretical calculations demonstrate the unique coactivation of bimetallic Ni/Co atoms by pyridinic‐N species (a Ni, Co–N2 moiety), which simultaneously downshifts their d‐band center positions and benefits the adsorption/desorption features of oxygen intermediates, accelerating the reaction kinetics. The optimized NiCo2S4@g‐C3N4‐CNT hybrid manifests outstanding bifunctional performance for catalyzing oxygen reduction/evolution reactions, highly efficient for realistic zinc–air batteries featuring low overpotential, high efficiency, and long durability, superior to those of physical mixed counterparts and state‐of‐the‐art noble metal catalysts. The identified bimetallic coactivation mechanism will shed light on the rational design and interfacial engineering of hybrid nanomaterials for diverse applications.
A novel free‐standing NiCo2S4/graphitic carbon nitride (g‐C3N4)/carbon nanotubes (CNTs) hybrid electrode is developed by combining a hydrothermal approach and vacuum filtration. Experimental and theoretical investigations demonstrate the coactivation of bimetallic Co and Ni sites by abundant pyridinic‐N in g‐C3N4 and the synergistic effect with coupled conductive CNTs contributes to substantially enhanced oxygen electrocatalytic activities and discharge/charge behaviors in Zn–air batteries.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A facile and scalable in situ synthesis strategy is developed to fabricate carbon-encapsulated Fe3O4 nanoparticles homogeneously embedded in two-dimensional (2D) porous graphitic carbon nanosheets ...(Fe3O4@C@PGC nanosheets) as a durable high-rate lithium ion battery anode material. With assistance of the surface of NaCl particles, 2D Fe@C@PGC nanosheets can be in situ synthesized by using the Fe(NO3)3·9H2O and C6H12O6 as the metal and carbon precursor, respectively. After annealing under air, the Fe@C@PGC nanosheets can be converted to Fe3O4@C@PGC nanosheets, in which Fe3O4 nanoparticles (∼18.2 nm) coated with conformal and thin onion-like carbon shells are homogeneously embedded in 2D high-conducting carbon nanosheets with a thickness of less than 30 nm. In the constructed architecture, the thin carbon shells can avoid the direct exposure of encapsulated Fe3O4 to the electrolyte and preserve the structural and interfacial stabilization of Fe3O4 nanoparticles. Meanwhile, the flexible and conductive PGC nanosheets can accommodate the mechanical stress induced by the volume change of embedded Fe3O4@C nanoparticles as well as inhibit the aggregation of Fe3O4 nanoparticles and thus maintain the structural and electrical integrity of the Fe3O4@C@PGC electrode during the lithiation/delithiation processes. As a result, this Fe3O4@C@PGC electrode exhibits superhigh rate capability (858, 587, and 311 mAh/g at 5, 10, and 20 C, respectively, 1 C = 1 A/g) and extremely excellent cycling performance at high rates (only 3.47% capacity loss after 350 cycles at a high rate of 10 C), which is the best one ever reported for an Fe3O4-based electrode including various nanostructured Fe3O4 anode materials, composite electrodes, etc.
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IJS, KILJ, NUK, PNG, UL, UM
Simultaneously achieving high strength and ductility is a critical issue for graphene reinforced aluminum matrix composites, which couldn't be resolved by the conventional mechanical milling-powder ...metallurgy technology due to the following reasons. On one hand, the low addition of graphene in the matrix traceable to its poor dispersibility limits the further strength improvement. On the other hand, the introduced graphene tends to distribute into grain boundaries rather than inside grains, which would result in stress concentrations at grain boundaries and localized strains, leading to the poor ductility of graphene/Al composites. In this work, intragranular nano-sized graphene nanoplates with high-content were dispersed in the matrix uniformly by a modified ball milling strategy, which induces that the strength and uniform elongation of the composites were simultaneously enhanced due to the improved work hardenability. Furthermore, the strengthening and toughening mechanisms were also discussed. This work offers a new insight into the fabrication and design of graphene/Al composites with both high strength and ductility.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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