Highly efficient conductors are strongly desired because they can lead to higher working performance and less energy consumption in their wide range applications. However, the improvements on the electrical conductivities of conventional conductors are limited, such as purification and growing single crystal of metals. Here, by embedding graphene in metals (Cu, Al, and Ag), the trade-off between carrier mobility and carrier density is surmount in graphene, and realize high electron mobility and high electron density simultaneously through elaborate interface design and morphology control. As a result, a maximum electrical conductivity three orders of magnitude higher than the highest on record (more than 3,000 times higher than that of Cu) is obtained in such embedded graphene. As a result, using the graphene as reinforcement, an electrical conductivity as high as ≈117% of the International Annealed Copper Standard and significantly higher than that of Ag is achieved in bulk graphene/Cu composites with an extremely low graphene volume fraction of only 0.008%. The results are of significance when enhancing efficiency and saving energy in electrical and electronic applications of metals, and also of interest for fundamental researches on electron behaviors in graphene.
Metals can be strengthened by adding hard reinforcements, but such strategy usually compromises ductility and toughness. Natural nacre consists of hard and soft phases organized in a regular "brick-and-mortar" structure and exhibits a superior combination of mechanical strength and toughness, which is an attractive model for strengthening and toughening artificial composites, but such bioinspired metal matrix composite has yet to be made. Here we prepared nacre-like reduced graphene oxide (RGrO) reinforced Cu matrix composite based on a preform impregnation process, by which two-dimensional RGrO was used as "brick" and inserted into "□-and-mortar" ordered porous Cu preform (the symbol "□" means the absence of "brick"), followed by compacting. This process realized uniform dispersion and alignment of RGrO in Cu matrix simultaneously. The RGrO-and-Cu artificial nacres exhibited simultaneous enhancement on yield strength and ductility as well as increased modulus, attributed to RGrO strengthening, effective crack deflection and a possible combined failure mode of RGrO. The artificial nacres also showed significantly higher strengthening efficiency than other conventional Cu matrix composites, which might be related to the alignment of RGrO.
applications to enhance its mechanical strength, but alloying is detrimental for high electrical conductivity because of more electron scattering centers. [3,4] Therefore, achieving electrical conductivity at a level beyond that of pure aluminum in practical applications is a major challenge.Composite fabrication by incorporating ultrahigh conductive reinforcement with a metal matrix is considered a possible approach to improve the electrical conductivity of metals. [5] Graphene has excellent intrinsic electrical properties and is one of the most promising candidates for such purposes. [6,7] An electron mobility (µ) of ≈2.0 × 10 5 cm 2 V −1 s −1 was measured in a suspended graphene with a carrier density (n) of ≈10 12 cm --2 at room temperature, [8,9] exceeding the record of ≈7.7 × 10 4 cm 2 V −1 s −1 reported for InSb. [10] According to the equation σ = enµ (e is the electron charge, ≈1.6021766209 × 10 −19 C), the electrical conductivity (σ) of the graphene is calculated to be 96 × 10 6 S m −1 , [11] which is ≈170% higher than that of aluminum. Therefore, it is possible to improve the electrical conductivity of aluminum by incorporating graphene.However, such improvement is not easy to achieve in practical graphene/aluminum matrix composites. [12,13] The challenges lie in the following factors. First, the forementioned intrinsically high electrical conductivity of a single graphene layer strongly depends on its fabrication method, structural integrity, [14][15][16] intrinsic defects, [17][18][19][20] chemical contamination, [21][22][23][24] and the substrates used to support graphene. [25][26][27][28][29] Second, to exert the intrinsic electrical properties of graphene at macroscopic level (such as in bulk graphene/aluminum matrix composites), fabrication methods have to be developed for achieving homogenous dispersion of graphene in metals without damage and good electrical contact between graphene and metals. Because of these complex prerequisites, the electrical conductivity of almost all the reported graphene/metal matrix composites does not exceed that of the pure matrix. As an exception, Pan et al. [30] reported conductivity enhancement in graphene/copper matrix composites based on highquality graphene. The quality of reduced graphene oxide (GO) was improved by heat treatment at high temperature and high pressure, and then high-quality graphene was incorporated in a copper matrix by a ball-milling process. As a result, an Graphene is considered a promising reinforcement to improve the electrical conductivity of metals because of its excellent intrinsic electrical conductivity. However, graphene/Al matrix composites with enhanced electrical conductivity have not yet been reported. In this work, it is attempted to understand the factors influencing the electrical conductivity of graphene embedded in an Al matrix by adjusting the interfacial structure and composition. By sandwiching graphene (Gr) or graphene oxide (GO) with either pristine or passivated Al foils, three kinds of typical composite interfaces ar...
By using CuO/graphene-oxide/CuO sandwich-like nanosheets as the building blocks, bulk nacre-inspired copper matrix nano-laminated composite reinforced by molecular-level dispersed and ordered reduced graphene oxide (rGO) with content as high as ∼45 vol% was fabricated via a combined process of assembly, reduction and consolidation. Thanks to nanoconfinement effect, reinforcing effect, as well as architecture effect, the nanocomposite shows increased specific strength and at least one order of magnitude greater recoverable deformation ability as compared with monolithic Cu matrix.
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