Metal Graphene Nanocomposites Research Articles

Agglomeration and interphase-influenced effective elastic properties of Metal/Graphene nanocomposites: A developed mean-field model

The strength of metallic nanocomposites structures can be greatly improved by adding nanofillers to the matrix. However, there is a discrepancy between the conventional theories and the experimental evidence on the effect of nanofiller loading on the strength of the nanocomposite. The conventional theories predict that the strength increases with the nanofiller loading, but the experimental evidence shows that there is an optimal nanofiller loading beyond which the strength does not improve much. This discrepancy, especially at high filler loadings, is due to the neglect of the agglomeration and the interphase region formation in the composite structure modeling. In this paper, we propose a new micromechanical model based on mean-field theory to examine how the agglomeration and the interphase region influence the elastic modulus of metal/graphene nanocomposites (MGNs). We also explore how other factors, such as interphase region thickness and strength, graphene size, and metallic matrix elastic modulus, influence the elastic modulus of MGNs. We present a mathematical model that describes how the thickness and modulus of the interphase layer of graphene nanoplatelets change due to agglomeration. This model allows us to reproduce the parabolic behavior of the elastic modulus of the composite, which is more consistent with the experimental results.

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.

One-step synthesis of structural-controlled metal-graphene nanocomposites via flash atomization and plasma-assisted reactions of electrical explosion

Metal-graphene nanocomposites are highly attractive for a wide range of structural and functional applications. One promising approach for their “one-step” synthesis is through electrical explosion, which utilizes high-electric-power pulses to achieve ultrafast heating/quenching rates (dT/dt ∼ 10^10 K/s) of current-carrying conductors. By performing electrical explosion of metallic wire in a graphite-powder-containing tube, hundreds of Joules can be instantaneously confined in 7-cm3 space, leading to intense plasma-material interactions. Our research has yielded two distinct metal-graphene assembly routes: the first involves the graphite nanosheets decorated with metallic nanoparticles (<100 nm-diameter), while the second concerns the nanometal core coated by graphene shell (<10 layers) along with onion-like carbon. Explosion-induced shockwave and its reflection exfoliate graphite powders and initiate turbulent-mixing of the flow field, allowing the atomized metal to quench on graphite nanosheets. Further increasing explosion energy to achieve oscillating-discharge for reaction, strong radiation and kinetic energy of plasmas will sublimate the graphite, cooling to core@shell structures.

The role of carbon allotropes on the radiation resistance of Cu-based nanocomposites: An atomistic, energetic, and thermodynamic perspective

Carbon allotropes can be considered as an excellent radiation resistance enhancer in metal-Graphene nanocomposites (NCs). Many research groups studied the radiationresistanceand interface stability of metal-Graphene NCs and revealed that Graphene can improve the radiation resistance of NCs under irradiation. Other allotropes of carbon have not been studied up to now. Therefore, in this work, four Cu-based NCs such as Cu-Graphene, Cu-Graphyne, Cu-Graphdiyne, and Cu-Graphane were studied by molecular dynamics (MD) to understand the role of carbon allotropes on the radiation resistance of Cu-based NCs. Compared with pure copper; four Cu-based NCs have fewer residual defects in the bulk region after irradiation. The results demonstrated that the interface of these NCs acts as a sink for radiation-induced defects, and preferentially traps interstitials over vacancies. The results of energetic calculations indicate the defect formation energy is reduced in the vicinity of interface regions. Compared with Cu-Graphyne and Cu-Graphdiyne, Cu-Graphene and Cu-Graphane have low segregation energy for interstitial emission mechanism to annihilate vacancies. Also, Cu/Graphane/Cu interface has a higher strength of interaction and attraction with vacancies due to the low value of vacancy formation energy (Evac). Thermodynamic and structural analyses reveal that Graphdiyne plane isn’t a stable plane during collision cascades. The results of this study can provide a fundamental perspective on the radiation resistance of Cu-based NCs including different carbon allotropes to select the best allotrope to improve the radiation resistance of NC for using in extreme radiation environments.

Transfer of dislocation slip through grain boundaries in metal-graphene nanocomposites

A model is suggested that describes the onset of plastic deformation in metal-graphene nanocomposites. Within the model, the plastic deformation of a deformed metal-graphene nanocomposite is realized through the generation of perfect or partial dislocation loops. These loops nucleate at grain boundaries (GBs) of the metallic matrix and expand across grains. The expanded dislocation loops promote the nucleation and expansion of secondary dislocation loops in adjacent grains, thereby realizing dislocation transmission across GBs. Within the model, we have calculated the critical stresses, τc1 and τc2, for the generation of a secondary perfect or partial dislocation loop and for the bypass of the graphene inclusion by the secondary loop. The critical stress τc2 increases with an increase in the graphene concentration and with a decrease in the thickness of the inclusion. This implies that the addition of graphene can raise the critical stress for the expansion of the secondary dislocation loops and thus increase the yield strength of metals.

Effect of graphene wrinkle degree on the interfacial behavior between iron and graphene: Atomic simulation

Graphene has become a research hotspot in the field of materials due to its excellent properties and unique two-dimensional structure. Metal-graphene nanocomposites are usually formed by dispersing metal nanoparticles on graphene surface. Therefore, the wettability of metal on graphene is an important factor affecting the synthesis. In this paper, molecular dynamics simulation methods are used to study the wetting behavior of molten iron on the graphene surface. The changing law of the wettability of molten iron under different wrinkles of graphene was discussed in depth. The similarities and differences of wetting behavior changes are compared from the perspectives of interaction energy, spreading area, contact angle, interface atomic force and cluster analysis. The results show that the change of graphene wrinkle amplitude and wrinkle frequency have different effects on the variation of wettability. The influence of wrinkle amplitude is obviously stronger than that of wrinkle frequency. And the smoother the graphene, the better the wettability of the molten iron. Therefore, if we want to make iron-graphene composite materials, it is necessary to strictly control the flatness of graphene.

On the dynamic effects of evaporation and boiling of drops on inhomogeneous graphene substrates for effective thermal management of energy devices

This research examines thermal performance of metal-graphene nanocomposites for thermal management. Graphene nanoflakes and graphite microparticles were compressed with cooper meshes under different pressures. The prepared samples were characterized using optical microscopy. The fabricated samples of cooper-graphene composites were studied to determine the droplet evaporation rates and contact angles at different temperatures including film boiling.

In-situ growth of single-crystal plasmonic aluminum–lithium-graphene nanosheets with a hexagonal platelet-like morphology using ball-milling

Metal-graphene nanocomposites and plasmonic metal nanoparticles are two nanoscience fields of a rapidly growing interest due to their potential in advanced applications. In this study, we combine both fields by synthesizing plasmonic aluminum-lithium-graphene nanosheets (Al–Li-GNSs) with anisotropic morphologies using a simple ball-milling technique. Structural analysis using SEM and TEM revealed that the Al–Li-GNSs nanoparticles are single-crystals with a hexagonal platelet-like morphology of a ∼300–500 nm diagonal and a ∼60 nm thickness. Electron diffraction analysis indicated that the as-milled platelets have an FCC structure with (111) top and bottom facets and revealed the presence of 1/3(422) and 1/3(220) forbidden reflections. UV–Vis spectroscopy of the hexagonal Al-based nanoplatelets was found to exhibit plasmonic resonance absorption bands in the UV region at a wavelength of 214 nm and 345 nm. In this report, we confirm the feasibility of building epitaxial plasmonic metal-graphene systems inside bulk metal-graphene composites using a simple milling process.

Recent Trends in Design and Development of Nanomaterial-based Aptasensors

The past decade has witnessed extensive research in the field of biosensors, where nanoaptasensors achieved widespread interest. Aptamer, the single-stranded DNA or RNA nucleotide, is extensively employed as a bioreceptor due to its stability, ease in a modification that ensures convenient immobilization strategies, reducing the cost of sensor manufacturing. The detection limit and sensitivity were notably improved when modified with nanomaterials such as metal nanoparticles, carbon nanomaterials, graphene, quantum dots, and other nanocomposites. This paper introduces various design strategies for the fabrication of sensors utilizing aptamers and nanomaterials in ¬developing signal-readout mechanism, focusing mainly on the latest research in food, biomedical and environmental applications. Aptasensors that utilize various signal recognition methods such as electrochemistry, colorimetry, luminescence, and fluorescence are highlighted. This review offers a wide range of outlook for future developments of aptamer bioreceptors employing the unique physicochemical nanomaterials as efficient transducers and amplifiers. Furthermore, this review will also provide an insight into aptamer-aided biosensors' technology over the last three to five years of work.

Strengthening mechanisms of graphene in copper matrix nanocomposites: A molecular dynamics study

To clarify the strengthening mechanism of coated/embedded graphene in metal matrixnanocomposites, nanoindentation responses of graphene-coated/embedded copper nanocomposites are investigated using molecular dynamics simulations, with the consideration of indentation force-displacement relation, stress distribution, evolution of microstructure and dislocation, and elastic recovery. Results show that two mechanisms, graphene layer bearing surface tensile stress disperses the contact stress and blocks the propagation of dislocations, contribute to the enhanced hardness and improved load bearing capacity, but one is often dominant for different nanocomposites. The former dominates in graphene-coated structure while the latter dominates in graphene-embedded structure, and the reinforcement is more obvious in the coated structure. The graphene delays the plastic deformation of matrix, and its elastic recovery is boosted due to the stress homogenization effect. The embedded graphene promotes the stress concentration and accelerates the plastic deformation of up Cu film, weakening its width elastic recovery. The observations will provide a practical guide for the mechanical optimization and design of metal-graphene nanocomposites.

Crossover from Deformation Twinning to Lattice Dislocation Slip in Metal–Graphene Composites with Bimodal Structures

Theoretical model is suggested, which describes of a new micromechanism of crossover from deformation twinning to lattice dislocation slip in metal–graphene nanocomposite with a bimodal structure. In the framework of the model, the lattice dislocation slip occurs through emission of lattice dislocations from the disclinated grain boundary fragments between a nanocrystalline metal–matrix and large (micrometer-size) grains providing the plastic deformation of bimodal metal–graphene nanocomposite. It is shown that the lattice dislocation emission serves as an effective stress relaxation channel being in competition with nanocrack generation.

The effects of temperature and alignment state of nanofillers on the thermal conductivity of both metal and nonmetal based graphene nanocomposites

Temperature and the alignment state of nanofillers are two important factors that can greatly affect the thermal conductivity of graphene nanocomposites, but the simultaneous influence of these two issues have never been considered in any theoretical treatment. In this work we incorporate the contributions of electron-phonon coupling and phonon-phonon interaction into the diffuse mismatch model to establish the temperature dependence of filler-matrix interfacial thermal resistance and filler-filler contact resistance, both crucial for thermal conduction in graphene nanocomposites. The electron and phonon transport mechanisms, suitable for metal and nonmetal matrices respectively, are both taken into account. Then through an effective-medium approximation based on Maxwell's far-field matching, the temperature-dependent thermal conductivity of both metal and nonmetal-based graphene nanocomposites is derived. By further introducing a confinement angle with respect to the main alignment direction wherein the graphene nanofillers are supposed to be dispersed, the influence of the alignment state of graphene nanofillers is also investigated. We highlight this newly developed theory with direct comparisons to several sets of experimental data, and demonstrate the significant effects of temperature level and alignment state in thermal conductivity of graphene metal and nonmetal nanocomposites.

Effects of reduction of graphene oxide on the hydrogen storage capacities of metal graphene nanocomposite

Light-weight materials such as graphene have attracted a great interest for hydrogen storage applications. In this study, a metal-on graphene nanocomposite was synthesized for hydrogen storage for on-board applications. The graphene used as support was obtained from precursor graphite oxide, which was synthesized using the Improved Tours method and later reduced by L-Ascorbic acid and ammonia. The precursor graphite flakes used in the synthesis of graphite oxide were 100 μm in size. The XRD patterns depicted a low angle shift in GO, 11.3° from graphite 30° proved successful oxidation of graphite. The FTIR and Raman band showed L-Ascorbic reduced the GO better than ammonia through the observed decrease on the functional bands after reduction. The elemental analysis carried out using XRF showed the successful loading of Ca on the graphene matrix and TEM images also confirmed this. The hydrogen storage capacity of the nanocomposite was tested using TGA and TPD equipped with Mass Spectrometer. The Ca/graphene nanocomposite reduced by ammonia exhibited a large hydrogen storage uptake at 4.98 wt. % compared to L-Ascorbic acid.

Palladium nanoparticles immobilized on the magnetic few layer graphene support as a highly efficient catalyst for ligand free Suzuki cross coupling and homo coupling reactions

In this study, we prepared a magnetic metal–graphene nanocomposite for the synthesis of substituted biaryls via Suzuki cross coupling and homo coupling reaction of aryl halides. The magnetic few layer graphene composite was synthesized by using one-step electrochemical exfoliation of graphite foil in aqueous iron (II) ammonium sulfate as electrolyte without using of any additive or corrosive media. Then, Fe2O3@FLG composite was used an efficient support for the immobilization and suitable dispersing of palladium nanoparticles. The obtained Fe2O3@FLG@Pd0 nanocomposite was characterized using FT-IR, SEM, TEM, EDS, XRD, VSM and ICP-AES analysis. Very low loading of this catalyst was displayed high activity in the producing substituted biaryls. It simply recovered from the reaction mixture and reused without any pre-activation in six consecutive runs with no loss of its catalytic activity or the observation of any detectable palladium leaching process.

Direct fabrication of highly porous graphene/TiO2 composite nanofibers by electrospinning for photocatalytic application

We reported the fabrication of highly porous graphene/TiO2 composite nanofibers in the form of a nonwoven mat by electrospinning followed by calcination in air at 450 °C. The graphene can uniformly disperse in highly porous TiO2 nanofibers. The highly porous graphene/TiO2 composite nanofibers exhibited excellent catalytic activities. The new method for producing graphene/TiO2 composite nanofibers is versatile and can be extended to fabricate various types of metal oxide and graphene nanocomposites.

Radiation tolerance of nickel–graphene nanocomposite with disordered graphene

Metal–graphene nanocomposites are expected to have excellent radiation tolerance, and may become a candidate structural material for advanced fission reactors. Nevertheless, whether the structural disorder of graphene introduced by preparation or irradiation can strongly affect the radiation tolerance of the composites is still unclear. Here we investigate the radiation tolerance of nickel–graphene nanocomposite by using 300 keV helium-ion irradiation at 823 K. Results showed that the intrinsic crystalline structure of graphene would be continuously disrupted by the elevated temperature and irradiation. However, lesser crystal defects, such as lattice swelling and stacking faults, and smaller helium bubbles are observed in the composite than those in its pure counterpart. The reason may be attributed to graphene's own capability in maintaining two-dimensional structure and inhibiting the formation of large-size defects. Thus, nickel–graphene interfaces can be maintained and their role in healing radiation-induced defects is still able to play. Results of the study highlight the potential of metal–graphene nanocomposites for use as radiation tolerance materials.

Failure mechanisms in pre-cracked Ni-graphene nanocomposites

Graphene is a 2-D material with superior mechanical properties and is highly desirable as a filler in nanocomposite materials. However, the mechanical properties of the resulting nanocomposite are anisotropic, with strengthening or weakening depending on the loading direction. The presence of graphene also introduces new failure mechanisms to the matrix it is embedded within. In addition, the structure of graphene, pristine or polycrystalline, can affect its interfacial properties in the nanocomposite. We use molecular dynamics to predict the failure mechanisms of Ni-graphene nanocomposites for different loading directions with a crack present in the Ni matrix. We observe a variety of failure mechanisms including dislocation nucleation, graphene bond breaking, and delamination. We also compare the yield stress and strain of nanocomposites with either pristine or polycrystalline graphene. We find that graphene of either kind can improve the yield stress of Ni by 27–76% when loaded parallel to the graphene sheet. We also find that, compared to pristine graphene, polycrystalline graphene can improve the yield stress of a Ni-graphene nanocomposite by up to 27%. This is explained by the higher interfacial shear stress of polycrystalline graphene on Ni’s (1 1 1) surface compared to pristine graphene. This is in part related to the wrinkling of graphene sheets, which differs between polycrystalline and pristine sheets. Our research indicates that metal-graphene nanocomposites benefit from graphene’s polycrystalline structure when superior mechanical properties are desired.

Role of graphene layers on the radiation resistance of copper–graphene nanocomposite: Inhibiting the expansion of thermal spike

Metal–graphene nanocomposites are expected to have excellent radiation resistance. The intrinsic role of the graphene layers (GrLs) in their performance has not been fully understood. Five copper–graphene nanocomposite (CGNC) systems were used to investigate the detailed mechanisms underpinning this behaviour by atomistic simulation. Results showed that GrLs can reduce the formation, growth, and intensity of the thermal spike of CGNC; this effect became more evident with the increasing number of layers of graphene. The role of the GrLs can be explained by three mechanisms: first, the ultra-strength C–C bonds of graphene hindered the penetration of high-energy atoms, second, the number of recoiled atoms decreased with the increasing number of layers of graphene, and third, the energy dissipation along the graphene planes also indirectly weakened the damage caused to the entire system. These mechanisms may provide a pathway to prevent material degradation in extreme radiation environments.

Pd Nanoparticles Immobilized on Supported Magnetic GO@PAMPS as an Auspicious Catalyst for Suzuki–Miyaura Coupling Reaction

A novel catalytic system based on palladium nanoparticles (Pd-NPs) immobilized onto the surface of graphene oxide (GO) modified by poly 2-acrylamido-2-methyl-1-propansulfonic acid decorated with magnetic Fe3O4 was designed, prepared and fully characterized. It was successfully examined as a highly efficient heterogeneous catalyst in the Suzuki–Miyaura cross coupling reaction. The results showed excellent catalytic activity for the cross coupling of aryl bromides, alkyl iodides as well as aryl chlorides as the challenging substrates. It was easily separated by an external magnet and reused without any pre-activation at least in seven consecutive runs without any loss in its catalytic activity as well as any detectable Pd leaching. This study demonstrates the great potential of polymeric-functionalized GO as a support owing to its high loading and suitable dispersing of Pd-NPs, for the development of metal–graphene nanocomposites in industrial scale.

Micromechanics of plastic deformation through grain-boundary migration in metal–graphene nanocomposites

A theoretical description of the plastic deformation of metal–graphene nanocomposites through stress-induced migration of grain boundaries is proposed. Within the micromechanical approach developed, the plastic deformation induced by this migration leads to the formation of disclination quadrupoles (intense elastic stress sources). The energy characteristics and critical stress are calculated for the plastic deformation mode under consideration. The influence of graphene nanoinclusions is shown to cause significant hardening of metal–graphene nanocomposites. This conclusion is consistent with the corresponding experimental data.