Copper-graphene Composites Research Articles

The effects of crystal orientation and common coal impurities on electronic conductivity in copper–carbon composites

The electronic conduction properties of copper–graphene composite materials including common coal impurities are studied. Exploring the transport properties for three crystallographic orientations [(111), (110), and (100)] of copper in copper–graphene composites, a strong orientational dependence on electronic conductivity is shown. Graphene exhibits near-ideal registries for (111) and (110) orientations, forming a connected network between grains that enables efficient carrier transport. The influence of non-carbon elements: nitrogen (N), oxygen (O), and sulfur (S) in graphene, representing possible structures in coal-based graphene are investigated. N, O, and S in graphene negatively impact the composite’s electronic conductivity relative to pristine graphene. A new method is introduced for visualizing the spatial distribution of electrical conduction activity in materials using the square of the electronic charge density near the Fermi level, based on the work of Mott. We call this technique the N2 method.

Synthesis and characterization of graphene on copper foil via atmospheric pressure chemical vapor deposition method and its impact on electrical properties

Copper, prized for its exceptional electrical conductivity, thermal conductivity, and mechanical strength, is a staple in electronic applications. The ongoing quest for enhanced performance in miniaturized technologies has led to exploring copper-graphene composites, particularly those integrating bilayer graphene (BLG). This study investigates the enhancement of electrical conductivity in copper through the incorporation of BLG via atmospheric pressure chemical vapor deposition (APCVD). The research highlights the APCVD method's ability to grow high-quality BLG on high-purity oxygen-free copper foil, demonstrating significant improvements in electrical properties. Detailed characterization reveal that the graphene growth process induces structural changes in the copper, promoting ideal crystallographic orientations and larger grain sizes. This process achieves nearly complete graphene coverage and results in a copper/graphene (Cu/GR) composite with minimal defects. The electrical conductivity of the Cu/GR composite significantly increased to 59.32 × 10⁶ S·m⁻1, a 7.83 % improvement over the pristine copper foil. This enhancement is attributed to the increased carrier density and mobility within the composite. These advancements suggest the potential of APCVD-grown graphene for various high-performance electronic applications, providing a promising pathway for further development and optimization of graphene-copper composites.

Investigation of microstructure, mechanical, and tribological properties of MoSi2-reinforced copper-graphene composites

The MoSi2-reinforced copper-graphene composites (Cu-MoSi2-GNS) were prepared using mechanical ball milling and spark plasma sintering techniques. The effects of MoSi2 content on the microstructure, electrical conductivity, mechanical performance, and tribological properties were systematically investigated. Results indicate that the addition of MoSi2 significantly enhanced strength and hardness, although slightly reducing electrical conductivity. When the MoSi2 content does not exceed 5 wt%, MoSi2 is uniformly dispersed, refining copper matrix grains and improving GNS dispersion. Optimal MoSi2 addition facilitates the formation of a stable subsurface structure with complete mechanical mixture layer, improving wear resistance and self-lubricating properties. The main wear mechanism shifts from adhesive to abrasive wear. At 5 wt% MoSi2, the Cu-MoSi2-GNS composites exhibits superior mechanical properties, electrical conductivity, and tribological performance.

Copper-Graphene Composite (CGC) Conductors: Synthesis, Microstructure, and Electrical Performance.

Improving the electrical performance of copper, the most widely used electrical conductor in the world is of vital importance to the progress of key technologies, including electric vehicles, portable devices, renewable energy, and power grids. Copper-graphene composite (CGC) stands out as the most promising candidate for high-performance electrical conductor applications. This can be attributed to the superior properties of graphene fillers embedded in CGC, including excellent electrical and thermal conductivity, corrosion resistance, and high mechanical strength. This review highlights the recent progress of CGC conductors, including their fabrication processes, electrical performances, mechanisms of copper-graphene interplay, and potential applications.

Investigation of mechanical properties of Copper-Graphene composites in terms of production methods and additive ratios: A review

Investigation of mechanical properties of Copper-Graphene composites in terms of production methods and additive ratios: A review

Unprecedented electrical performance of friction-extruded copper-graphene composites

Copper-graphene composites show remarkable electrical performance surpassing traditional copper conductors albeit at a micron scale; there are several challenges in demonstrating similar performance at the bulk scale. In this study, we used shear assisted processing and extrusion (ShAPE) to synthesize macro-scale copper-graphene composites with a simultaneously lower temperature coefficient of resistance (TCR) and improved electrical conductivity over copper-only samples. We showed that the addition of 18 ppm of graphene decreased the TCR of C11000 alloy by nearly 11 %. A suite of characterization tools involving scanning and transmission electron microscopy along with atom probe tomography were used to characterize the grain size, crystallographic orientation, structure, and composition of copper grains and graphene additives in the feedstock and processed samples. We posit that the shear extrusion process may have transformed some of the feedstock graphene additives into higher defect-density agglomerates while retaining the structure of others as mono-to-tri-layer flakes with lower defect density. The combination of these additives with heterogeneous structures may have been responsible for the simultaneous decrease in TCR and enhanced electrical conductivity of the copper-graphene ShAPE composites.

Crystal plasticity modeling for the strengthening effect of multilayered copper–graphene nanocomposites

The paper explores plastic deformation mechanisms in metal–graphene nanocomposites, illustrating their material strengthening effects through a crystal plasticity finite element (CPFE) model. This model is compared with published experimental results, which have previously shown that the two-dimensional shape of graphene effectively controls dislocation motion and significantly enhances the strength of metals. Simulated nanopillar compression tests, using a physics-based CP model that incorporates surface nucleation and single-arm source dislocation mechanisms, help us understand dislocation motions at submicron length scales. The crystal plasticity models are applied to nanolayered composites with copper grain layers and monolayer graphene, featuring repeat layer spacings of 200 nm, 125 nm, and 70 nm, respectively. This study quantifies the accumulation of dislocations at the graphene interfaces, contributing to the ultra-high strength of copper–graphene composites. Moreover, a Hall–Petch-like correlation is established between yield strength and the number of embedded graphene layers.

Interaction of pristine and novel graphene allotropes with copper nanoparticles: Coupled density functional and molecular dynamics study

We combined the density functional theory and classical molecular dynamics to study the time evolution and thermal stability of copper nanoparticles wrapped in graphene flakes. We observed a strong attraction between nanoparticles and flakes, which was underestimated in many previous simulations. We found that the two-parameter Lennard-Jones potential with parameters ε = 0.074 eV and r0 = 3.310 Å reproduces DFT data better than other empirical potentials. We confirmed that a nanoparticle could be held reliable inside a graphene flake. The graphene-coated copper system remains stable over the temperature range of 300–1000 K. In addition to pristine graphene, we considered several strained allotropes containing pentagons, as well as heptagons, octagons, and nanometer-sized pores. Strained allotropes interact with copper nanoparticles approximately twice more strongly as compared to pristine graphene. Molecular dynamics revealed nanoparticle flattening due to strong interaction with graphene allotropes at elevated temperatures. The wettability of graphene with respect to copper strongly depends on the sheet structure and can vary significantly for different allotropes. The results may be useful for further research on copper-graphene composites, which are suitable for catalytic and biomedical applications.

Tribological properties of copper-graphene (CuG) composite fabricated by accumulative roll bonding

The main aim of this study is to clarify the effect of the number of accumulative roll bonding (ARB) cycles on the tribological properties of the copper-graphene composite. To conduct the wear test, the pin-on-disk method was utilized at an average normal force of 20 N and a sliding distance of 1000 m. Field emission scanning electron microscopy (FE-SEM) was used to investigate the worn surface resulting from the wear test and determine the wear mechanism. The results showed that the wear rate increased in the rolled copper sheet and copper-graphene composite as a result of increasing the number of cycles. The increase in wear rate and weight reduction in the composite were less than rolled copper sheet. SEM micrography and EDS analysis showed that adhesive, oxidation, and delamination wear mechanisms were active on the wear surfaces. With increasing the ARB cycles, the dominant wear mechanisms in the copper-graphene composite and copper sheet were delamination, which was associated with severe galling and cracking in high cycles and more accentuated in copper sheet samples.

The Effect of Graphene Addition on the Microstructure and Properties of Graphene/Copper Composites for Sustainable Energy Materials

Graphene is a single thin layer (mono layer) of a hexagon-bound carbon atom and is an allotropic carbon in the form of a hybrid atomic plane, with a molecular bond length of 0.142 nm. Graphene is the thinnest and lightest material with 0.77 mg square meters, which exhibited excellent electricity and heat conductor. However, the perfect uniform microstructure, strength and optimum thermal properties of copper-graphene composites cannot be achieved because the amount of graphene does not reach the optimum level. In order to solve this problem, copper-graphene composites were produced by metal injection molding method (MIM) with various percentage of graphene, specifically 0.5%, 1.0% and 1.5% in the composite, to compare the physical and mechanical properties of these samples. MIM process involves the preparation of feed materials, pre-mixing process, mixing process, mold injection process, binding process and sintering processes. Feeding materials were used are copper and graphene, which have the powder loading of 62% with a mix of binder comprising 73% polyethylene glycol (PEG), 25% polymethyl methacrylate (PMMA), and 2% stearic acid (SA). Densification and tensile test were conducted to determine the mechanical properties. Scanning electron microstructure (SEM) was performed to obtain the microstructure of the composites. From the research, the result revealed that the 0.5% graphene content had the optimum parameter, which the hardness and tensile stress values were at 94.2 HRL and 205.22 MPa.

Application of machine learning to mechanical properties of copper-graphene composites

Copper-graphene (Cu/Gr) composites have been promising materials due to their theoretically high strength and conductivity; however, their design has been hampered by the large number of variables affecting their properties. We applied four different machine learning (ML) models to manually collected datasets compiling the yield strength and ultimate tensile strength of graphene-reinforced copper composites processed with powder metallurgy techniques. Our results indicate that ML models can predict the mechanical properties of Cu/Gr composites with satisfactory accuracy. Feature analysis provided new insights into the most important factors that affect these properties.

Electronic transport in copper–graphene composites

We investigate electronic transport properties of copper–graphene (Cu–G) composites using a density-functional theory (DFT) framework. Conduction in composites is studied by varying the interfacial distance of copper/graphene/copper (Cu/G/Cu) interface models. Electronic conductivity of the models computed using the Kubo–Greenwood formula shows that the conductivity increases with decreasing Cu–G distance and saturates below a threshold Cu–G distance. The DFT-based Bader charge analysis indicates increasing charge transfer between Cu atoms at the interfacial layers and the graphene with decreasing Cu–G distance. The electronic density of states reveals increasing contributions from both copper and carbon atoms near the Fermi level with decreasing Cu–G interfacial distance. By computing the space-projected conductivity of the Cu/G/Cu models, we show that the graphene forms a bridge to the electronic conduction at small Cu–G distances, thereby enhancing the conductivity.

Experimental investigation of mechanical behavior at the microstructure of copper-graphene thin films

Graphene reinforcements in the metal matrix cause improvement in mechanical properties. The interaction of graphene depends on the microstructure and deformation of the metal matrix. At the nano and micro scale, metal graphene composites are mainly evaluated by indirect techniques like nanoindentation, which only induces specific deformation and failure mechanisms. In this work, nanolayered copper–graphene composites are fabricated to study the impact of graphene particles’ reinforcements on the mechanical behavior during uniaxial tensile loading. The stress required for film cracking increases in the ten-layer copper films (channel cracks) by 50% and the four-layer copper films (microcracks) by 121% with graphene reinforcement. Electron microscopy reveals that the graphene particles’ presence at the interfaces causes deflections in the crack paths leading to improved mechanical performance. The graphene particles also affect the grain boundary sliding (cause of microcracks) in the four-layer samples, increasing the crack onset strain from 1.3% to 2.4%. Comparing the energy release rate ratio of deflection and penetration to the fracture toughness ratio of the copper–graphene interface and graphene particle shows that crack deflection is expected. Molecular dynamics simulations also show that the deflection of cracks is due to graphene stopping the growth of plastic zones, which leads to delaminations at the interface.

Atomistic understanding of extreme strain shear deformation of Copper-Graphene composites

Copper-Graphene (Cu-Gr) composites demonstrate high strength, lubricity, and enhanced electrical and thermal conductivity compared to pure copper. A homogeneous dispersion of graphene/graphitic domains in Cu is highly desirable, which can be achieved by solid-state shear-assisted processing. A detailed understanding of structure evolution of Cu-Gr under deformation is needed. Here we subjected Gr coated Cu foils to high strain shear deformation using a tribometer to observe the distribution and reallocation of Gr in Cu matrix. A rupture and smearing of Gr layer into Cu were observed reducing the Cu grain size from 67 ± 14 μm to <10 nm, in maximum shear region close to surface. While a gradual strain accumulation further below resulted in grain rotations and dynamic recrystallization. During deformation, the Gr film was first observed to fracture into flakes and then embed into the Cu matrix. Graphitic domains observed in the Cu evinced the metastable composite microstructure with a sandwich layer of Cu2O on the interface. The local conductance, measured by conductive atomic force microscopy, shows a fivefold increase in Cu-Gr composite region compared to pure Cu. Our study shows the feasibility of shear processing to create fine-grained Cu-Gr composites with enhanced conductivity.

New Graphene Composites for Power Engineering.

Intensive research is underway worldwide to develop new conductive materials for applications in the power industry. Such tests aim to increase the electrical conductivity of materials for conductors and cables, thus increasing the current carrying capacity of the line and reducing the loss of electricity transmission. The scientific discovery of recent years, graphene, one of the allotropic types of carbon with very high electrical and thermal conductivity and mechanical strength, creates great opportunities for designing and producing new materials with above-standard operational properties. This project concentrates on developing technology for manufacturing aluminum-graphene and copper-graphene composites intended to be used to produce a new generation of power engineering conductors. In particular, we present the results of the research on the mechanical synthesis of aluminum-graphene and copper -graphene composites, as well as the results of the electric, mechanical, and structural properties of rods obtained after the extrusion process and wires after the drawing process.

Atomistic Understanding of Extreme Strain Shear Deformation of Copper Graphene Composites

Atomistic Understanding of Extreme Strain Shear Deformation of Copper Graphene Composites

Macro copper-graphene composites with enhanced electrical conductivity

Composites demonstrating enhanced electrical conductivity compared to copper have been highly sought after for their advantages in efficient energy transport behavior. While such conductors have been demonstrated in 1D (nanowires) and 2D (films) samples, achieving similar behavior in 3D has been challenging owing to the limitations of the synthesis techniques used. In this paper, novel macro-scale 3D copper conductors were demonstrated with increased electrical conductivity through the addition of graphene. Hot extrusion was used to manufacture 12 AWG copper-graphene composite wires with varying graphene content and defect density. Graphene defect density was measured using Raman spectroscopy. Results showed that the electrical conductivity of composites with low defect density graphene increased as a function of graphene content. Comparatively composites with high defect density graphene demonstrated lower electrical conductivity. This study provides first-of-its-kind evidence of 3D metal composites whose bulk electrical performance has been enhanced using graphene additive in minute quantities (15 ppm). Further developments in this area are essential to achieve high performance composite conductors that can improve energy transport efficiency and pave way for industrial adoption of such materials in the future.

Studying the Effect of Process Controlling Agent on the Microstructure, Electrical and Thermal Conductivities of Copper /Graphene Composite Prepared by PM

Copper-graphene composite is prepared with 0.25,0.50,0.75,1.00,1.25 and 1.50 wt.% graphene. Powder metallurgy technique is used for the preparation process. In which copper powder is mechanically milled with graphene nanosheets (GNSs) by 10: 1 ball to powder ratio, and 400 rpm for 12 hr milling time. The mixtures are compacted by a uniaxial press under 700 Mpa pressure. The compacted samples are sintered under a controlled atmosphere at 950 oC for 1.5 hrs. A comparison between methanol & hexane as a process control agent is established. The effect of both on the microstructure, electrical and thermal conductivities of the prepared Cu /graphene nanocomposites is studied. All results indicated that hexane samples have a more homogeneous microstructure with low porosity. For the two groups (Hexane and Methanol group samples), the density was decreased gradually by increasing the graphene percentage. The results indicated that both the electrical and thermal conductivities decrease by increasing graphene content. 1wt. % graphene sample has the most homogenous microstructure, while, 0.25 wt. % graphene is the most one for the methanol group samples. Generally, all results indicated that hexane is the better PCA than methanol.

Direct laser writing of copper-graphene composites for flexible electronics

Copper-graphene composites have potential applications in flexible electronics due to their unique three-dimensional porous structure, high specific surface area, high electrical conductivity and electrochemical properties. Here, a simple room temperature fabrication method for conductive copper-graphene composites on different substrates, such as glass and polycarbonate, using direct laser writing process without pre-synthesis of copper nanomaterials and graphene flakes is presented. This process uses copper ion precursor and laser to generate copper nanoparticles and in-situ join them to form a network structure. Meanwhile, graphene also can be synthesized and coated on copper networks. The as-prepared copper-graphene composites are highly conductive and electrochemically active for thin conductive film and electrodes of supercapacitor. The composite film has a sheet resistance of 0.57Ω sq−1 and the capacitance of as-written copper-graphene all-solid-state flexible micro-supercapacitor is 13.2mF cm−2 at a current density of 0.5mA cm−2. This simple and low temperature process for composite structures will enable the rapid fabrication of flexible devices with low cost.

Copper-graphene composites; developing the MEAM potential and investigating their mechanical properties

Unraveling the deformation mechanisms at the atomistic scale of metal matrix-graphene composites is a key step toward designing and fabricating these materials with exceptional mechanical properties. While these composites can be made by embedding graphene into multiple metallic matrices, it is shown that superior mechanical properties can be obtained by combining copper and graphene. In the past few years, molecular dynamics simulations have been used to investigate the fundamental deformation mechanisms at the nanoscale of Cu-graphene composites to facilitate designing these composites with improved mechanical properties. However, in all of the reported works, Lennard-Jones potential has been used for modeling the interaction between copper and carbon atoms. The complexities in the Cu-C interaction emerges the necessity of utilizing more accurate potentials. In this work, a 2NN MEAM (second nearest-neighbor modified embedded atomic method) potential for the copper and carbon atom interaction is developed. Since crystal structures like B1 or B2 are not experimentally available for the Cu-C system, first-principle calculations are used to determine the reference structure and its elastic constants in this work. It is shown that the B1 and B2 structure of Cu-C has positive formation energy, but B1 is dynamically stable. Accordingly, the B1 crystal structure is used as the reference structure for the Cu-C system to develop the interatomic potential. It is shown that the reported potential agrees reasonably well for phonon dispersion frequencies, stacking fault energies, and the atomic forces with the available experimental data and first-principle calculations. The developed potential is utilized to study the mechanical properties of copper-graphene composites subjected to uniaxial loading. Our results show that adding graphene to a defect-free Cu crystal weakens the metallic matrix’s mechanical properties. However, when the graphene is embedded into a Cu matrix with some defects, e.g., in a polycrystalline Cu, it can significantly improve the mechanical properties.