Three-dimensional Graphene Network Research Articles

Improving thermal conductivity of phthalonitrile composite through constructing three-dimensional graphene networks and interfacial engineering

Achieving high thermal conductivity for polymer composite with low filler loading is still a challenge. Here, phthalonitrile (APN)/few-layer graphene (FLG) composite with high thermal conductivity was successfully prepared by constructing three dimensional (3D) thermally conductive pathways. Such 3D structure was formed by hot compressing APN@FLG core-shell structures. The results showed that the thermal conductivity of APN@FLG composites with only 30 wt% of FLG was up to 11.4Wm−1K−1, which was 57 times to that of the pristine resin (0.2 Wm−1K−1). Such high thermal conductivity was attributed to the 3D connected thermally conductive networks. Furthermore, benefited from the high thermal stability of APN matrix, the as-prepared composite also showed high T5 (temperature of mass losing 5 %) of higher than 500 °C. The composite with both high thermal conductivity and heat resistance are expected to be an idea candidate for high temperature thermal management applications.

Overcoming strength-ductility trade-off in bimodal metal matrix composite with 3D graphene-strengthened hetero-interface

Strength-ductility synergy has long been a challenge in the development of advanced metallic materials. In this study, we fabricated a novel bimodal-structured nickel matrix composite, which features in-situ synthesized three-dimensional graphene networks (3DGN) strengthening the hetero-interfaces between coarse-grained and fine-grained zones (CGZ and FGZ). Compared to the bimodal matrix, this 3DGN-reinforced composite exhibits remarkable enhancements of 30 % in yield strength, 40 % in ultimate tensile strength, and 40 % in uniform elongation, respectively, representing the highest comprehensive performance among nickel matrix composites and pure nickel obtained through cold rolling, severe plastic deformation, and dynamic plastic deformation as reported in the previous literature. The superior strength-ductility combination originates from the incorporation of 3DGN, which enables multiple strengthening and toughening mechanisms. Specially, the strength and strain hardening capability have been enhanced through improved dislocation storage capacity, a stronger hetero-deformation induced (HDI) hardening effect, and the activation of numerous stacking fault ribbons. Moreover, high-density dispersed microcracks in the FGZ relieve strain/stress concentrations while being constrained within the CGZ, further enhancing tensile ductility. This study provides new insights into addressing the inherent strength-ductility paradox in metal matrix composites.

Ultrafast reaction kinetic of polyaniline in flexible hydrogel electrodes facilitated by graphene ribbons

Abstract By loading energy storage active materials on hydrogel which is inherently flexible, the flexibility of electrode materials can be simply realized, thereby achieving the flexibility of energy storage devices. However, the polymer network that constructs the three-dimensional skeleton of the hydrogel is not conductive, which inhibits the redox ability of the active material. If a high speed conductive structure can be added to the colloidal phase, the performance of the flexible electrode material can be greatly improved. Here, we introduce redox graphene ribbons into the polyvinyl alcohol hydrogel loaded with polyaniline. The in situ three-dimensional conductive graphene network greatly enhanced the conductivity of the hydrogel electrode, thus increasing the specific capacitance to as high as 1117 F g−1 at 2 mg cm−2 mass loading, with a retention ratio of 66.96% from 0.5 A g−1 to 20 A g−1. These highlighted properties enable the PRP hydrogel as an electrode for flexible supercapacitors, which provides a promising possibility for the practical application of wearable electronics.

Laser-Scribed Battery Electrodes for Ultrafast Zinc-Ion Energy Storage.

Aqueous Zn batteries are promising for large-scale energy storage but are plagued by the lack of high-performance cathode materials that enable high specific capacity, ultrafast charging, and outstanding cycling stability. Here, a laser-scribed nano-vanadium oxide (LNVO) cathode is designed that can simultaneously achieve these properties. The material stores charge through Faradaic redox reactions on/near the surface at fast rates owing to the small grain size of vanadium oxide and interpenetrating 3D graphene network, displaying a surface-controlled capacity contribution (90%-98%). Multiple characterization techniques unambiguously reveal that zinc and hydronium ions co-insert with minimal lattice change upon cycling. It is demonstrated that a high specific capacity of 553 mAh g-1 is achieved at 0.1 A g-1, and an impressive 264 mAh g-1 capacity is retained at 100 A g-1 within 10 s, showing excellent rate capability. The LNVO/Zn can also reach >90% capacity retention after 3000 cycles at a high rate of 30 A g-1, as well as achieving both high energy (369 Wh kg-1) and power densities (56306 W kg-1). Moreover, the LNVO cathode retains its excellent cycling performance when integrated into quasi-solid-state pouch cells, further demonstrating mechanical stability and its potential for practical application in wearable and grid-scale applications.

Interatomic potentials for graphene reinforced metal composites: Optimal choice

Graphene reinforced metal matrix composites represent a promising class of materials for high-strength surface coatings because of their high strength and ductility. This study reports the application of different interatomic potentials to correctly describe the interaction between graphene and metals (Al, Cu, Ni, and Ti) by molecular dynamics. Both simple pair potentials, such as Lennard-Jones and Morse, and many-body potentials, such as bond order potential are applied for the simulation of a graphene/metal system at room temperature. Three different structures are considered: (i) graphene interacting with one metal atom; (ii) graphene interacting with a metal nanoparticle, and (iii) three-dimensional graphene network filled with metal nanoparticles. We first determine the potential energy that any graphene/metal system can reach during exposure at 300 K; then, we analyze the interaction dynamics for all considered systems and all potentials. A considerable difference in the interaction between metal nanoparticles with planar and folded graphene was found. For graphene/Ni, graphene/Cu, and graphene/Ti, the Lennard-Jones and Morse potentials provide accurate energetic and structural properties of the studied structures; they also describe interaction in the graphene/metal system in a similar way, at variance with bond-order potential. For graphene/Al, the Tersoff and Morse potentials describe the interaction better than Lennard-Jones. For the simulation of graphene/Me system, the optimal choice of the potential for different structures is of crucial importance. The presented analysis of the interatomic potentials appears to be promising for realistic and accurate simulations of graphene reinforced metal composites.

Achieving excellent physico-mechanical properties of Cu matrix composites by incorporating a low content of a three-dimensional graphene network

In-depth investigation of the distribution form of the reinforcement and associated mechanisms has great significance for fabricating highly strengthened and conductive Cu matrix composites. The three-dimensional graphene (3DG) network can withstand more strain due to its large specific surface area, and provides interlinked high-speed conductive paths within the composites. In this study, we propose a feasible method to fabricate 3DG-reinforced Cu matrix composites; here, the Cu foam serves as the initial substrate during the chemical vapour deposition (CVD) process and as the matrix of the composites. Through constructing an ideal 3DG network, the graphene content is approximately 0.28 vol%, and a remarkable 230 % improvement in the ultimate tensile strength (418 MPa) with a high electrical conductivity (97.02 %IACS) is obtained in the composite. The continuous high-quality 3DG network is conducive for achieving excellent physico-mechanical properties of the composites, and the enhanced efficiency is superior. A new concept of fabricating Cu matrix composites was proposed for future research.

Achieving high strength and pseudo-ductility in Bf/Cu composite enabled by 3D-Gr@B4C interface-modified layer

Improving wettability, interfacial mechanical and thermal compatibility between reinforced boron fiber and Cu are strongly desirable for developing continuous boron fiber reinforced Cu matrix (Bf/Cu) composite, which shows great potential for application in nuclear fusion reactor as a promising high-strength heat-sink material. Herein, a three-dimensional graphene network hybrid B4C (3D-Gr@B4C) coating was fabricated on B fiber by single filament chemical vapor deposition as the interface-modified layer of Bf/Cu composite. It is revealed that the 3D-Gr in 3D-Gr@B4C interface-modified layer can not only supply diffusion channel to Cu for enhancing interfacial thickness and strength, but also serve as high-thermal-conductivity network to increase TC of Bf/Cu composite from 322.3 W/m·K to 343.9 W/m·K. Meanwhile, modulus of 3D-Gr@B4C interface-modified layer lying between Cu and B can also improve the interfacial mechanical compatibility of composite. Accordingly, interface modification on B fiber using 3D-Gr@B4C layer enables tensile strength up to 1016 MPa at RT and 620 MPa at 300 °C, which are ∼1.3 and ∼1.5 times higher than the corresponding values of Bf/Cu composite, respectively. Furthermore, introducing 3D-Gr@B4C layer inhibits abrupt failure of Bf/Cu composite at small tensile strain and opens up fiber pull-outs and shearing of Cu matrix at large tensile strain, producing pseudo-ductile fracture.

Thermal transport in a defective pillared graphene network: insights from equilibrium molecular dynamics simulation.

Graphene-based hybrid nanostructures have great potential to be ideal candidates for developing tailored thermal transport materials. In this study, we perform equilibrium molecular dynamics simulations employing the Green-Kubo method to investigate the influence of topological defects in three-dimensional pillared graphene networks. Similar to single-layer graphene and carbon nanotubes, the thermal conductivity (k) of pillared graphene systems exhibits a strong correlation with the system size (L), following a power-law relation k ∼ Lα, where α ranges from 0.12 to 0.15. Our results indicate that the vacancy defects significantly reduce thermal conductivity in pillared graphene systems compared to Stone-Wales defects. We observe that, beyond defect concentration, the location of the defects also plays a crucial role in determining thermal conductivity. We further analyze the phonon vibrational spectrum and the phonon participation ratio to obtain more insight into the thermal transport in the defective pillared graphene network. In most scenarios, longitudinal and flexural acoustic phonons experience significant localization within the 15-45 THz frequency range in the defective pillared graphene system.

Anchoring Ultrasmall Pt Nanocrystals onto Carbon Nanohorn-Decorated 3D Graphene Networks to Boost Methanol Oxidation Reaction

The successful commercialization of the direct methanol fuel cell (DMFC) is inseparable from the development of advanced Pt-based anode catalysts with high electrocatalytic activity and acceptable manufacturing cost. Here, we present a robust bottom-up strategy to anchor ultrasmall Pt nanocrystals with an average diameter of only 2.3 nm onto carbon nanohorn-decorated three-dimensional (3D) graphene networks (Pt/CNH-G) through a controllable self-assembly process. The as-derived 3D Pt/CNH-G catalysts manifest a series of distinctive architectural advantages, such as interconnected porous frameworks, large accessible surface areas, plentiful active cones, highly dispersed Pt nanoparticles, and good electron conductivity. Consequently, the optimized Pt/CNH-G catalyst is endowed with exceptional methanol oxidation properties with a large electrochemical active surface area of 128.6 m2 g-1, a high mass activity of 1626.0 mA mg-1, and excellent long-term stability, which are significantly superior to those of conventional Pt catalysts supported by carbon black, carbon nanotube, carbon nanohorn, and graphene matrices.

Spall characteristics of three-dimensional graphene networks with embedded copper: A molecular dynamics study

The phenomenon of shock-induced spallation has garnered significant interest in both scientific and industrial circles. Laminated graphene embedded in graphene-reinforced metal-matrix composites have been shown to improve mechanical properties. This study systematically investigates the dynamic response and spall failure of a three-dimensional graphene network (3DGN) with embedded copper composites (3DGCu) and its dependence on the grain sizes (D). Firstly, increasing the wt% of graphene results in significant increase of shock wave speed due to the intrinsic high modulus of graphene, whilst leading to a reduction in shock pressure. Spallation of 3DGCu at low shock velocity is observed, which is dominated by the bonded interaction at the graphene-metal interface. However, the 3DGCu with higher graphene content (smaller D) exhibits both low density and superior spall resistance. In particular, in the sample with 60 wt% graphene, the complete spallation has never occurred and still maintains a relatively high spall strength within the impact velocity of 3.0 km/s. This is due to the remarkable capacity for 3DGN to absorb the kinetic energy during tension. In addition, during shock loading, the graphene component is responsible to the tension loading, whereas the copper metal matrix undergoes compression, leading to a stable post-shock length. These findings offer a novel approach for tailoring the dynamic properties of advanced graphene-based nano-composites with potential applications in extreme environments.

Efficient catalyst layer with ultra-low Pt loading for proton exchange membrane fuel cell

Developing rational structure of catalyst layer with high stability and efficient mass transport to maximize the utilization of Pt is critical to fabricate proton exchange membrane fuel cells (PEMFCs) with ultra-low Pt loading down to <100 µg cm−2. Herein, a newly designed catalyst layer with ultra-low Pt loading for PEMFC was developed using a three-dimensional graphene network (3D-GN). In the process, 3D-GN was directly grown onto an Al foil by arc discharge method, and then Pt nanoparticles were deposited by via electron beam evaporation, after the impregnation of Nafion solution and non-destructive transfer onto Nafion membrane, the electrode with Pt/3D-GN was finally fabricated. The 3D-GN possesses unique characteristics of self-supporting structure of graphene nanosheets with 3–7 layers of graphitic lattices, a high macro-porous pore volume of 19.93 mL g−1 and graphitic degree up to 74.9 %, which can provide a stable framework to support Pt nanoparticles and efficient mass transport pathways. The Pt/3D-GN as the cathode can achieve a high cell performance at ultra-low Pt loading, compared to the conventional carbon nanosphere-based electrode (CN). The maximum power density of Pt/3D-GN with 50.8 μgPt cm−2 is 1.31 W cm−2 (H2/O2, 150 kPa) and 0.64 W cm−2 (H2/Air, 150 kPa), higher than that of commercial Pt/C electrode with 100 µgPt cm−2 1.25 W cm−2 and 0.55 W cm−2 respectively. Meanwhile, the Pt/3D-GN also demonstrates excellent stability with 32 % lose after 30 k cycles (0.6 V and 0.95 V) and only 8 % decay after 5 k cycles (1.0 V–1.5 V vs RHE). The outstanding properties of 3D GN-based electrode with high activity and stability provides a new flexible platform for developing high-performance ultra-low Pt loading PEMFCs.

From date syrup to three-dimensional graphene network

As a three-dimensional nano-material, graphene foam is regarded as an ideal choice for a wide array of critical applications due to its porous structure and high surface area. In this study, the main objective is a synthesis of graphene foam via a simple, low-cost, and eco-friendly approach. Graphene foam is synthesized from date syrup (DS), which is used as a carbon-enriched source using potassium chloride KCl particles as a scaffold on which graphene layers are built via dehydration and graphitization processes. Characteristic analyses have revealed that the Date-Derived-Graphene-Foam (DDGF) is indeed graphene material with G and D bands at 1598 cm−1 and 1350 cm−1, respectively, with a layered and porous structure. The lateral size of the obtained DDGF is determined as ∼6 nm. This quick, simple, and eco-friendly approach can be considered as having good potential in the high-yield production of graphene foam.

Double redox-active quinone molecules functionalized a three-dimensional graphene network for high-performance supercapacitor

As a well-known two-dimensional material, graphene is widely used as an electrode material in energy storage devices. However, the tendency of the agglomeration or restacking of graphene sheets limit the properties. To overcome this issue, redox-active molecules can be introduced that inhibit the stacking of graphene sheets and impart excellent pseudocapacitance properties. In this study, we design a three-dimensional (3D) graphene network anchored with redox-active 2,5-(di-p-phenylenediamine)-1,4-benzoquinone (DBP) and hydroquinone (HQ) (DFGN) using a facile one-step hydrothermal process. The covalent binding and absorption between redox-active molecules and graphene sheets reduce restacking and enable promising pseudocapacitance through reversible faradic reactions of quinone and aniline structures. Among all the samples, DFGN-1 shows the best specific capacitance (667.3 F/g at 1 A/g), high-rate capability (89.2 % even up to 50 A/g), and good cycling stability. Furthermore, DFGN-1 is also employed as an electrode material to construct flexible solid-state supercapacitors (FSSCs), which exhibit great specific capacitance (441 F/g at 0.5 A/g), excellent cycling stability (90.6 % after 10,000 cycles at 10 A/g) and high-energy density of 9.29 Wh/kg at a power density of 96.22 W/kg. Interestingly, FSSCs also display great mechanical flexibility in bending and twisting states and extraordinary mechanical durability even after being bent 5000 times. Overall, double redox-active quinone molecules functionalized 3D graphene network provides a novel tactic to construct promising potential electrodes in energy storage applications.

Template-free route to PEDOT nanofibers for 3D electrodes with ultrahigh capacitance and excellent cycling stability

The rapid growth of the electronics industry has increased the demand for electrochemical capacitors with a combination of high capacitance, high energy and power density, and long cycling stability. To achieve this, a rational design of electrode materials with high surface area, suitable porosity, and excellent electronic and ionic conductivity is required. Herein, high aspect ratio poly(3,4-ethylenedioxythiophene) (PEDOT) nano and microfibers with increased accessible surface area and porosity are grown on a three-dimensional laser-scribed graphene (LSG) network through a facile vapor phase polymerization process. The resultant electrode showed an outstanding areal capacitance of 1463 mF cm−2. To the best of our knowledge, this is the highest value reported so far for a vapor phase polymerized PEDOT/LSG supercapacitor. It also displayed an impressive capacitance retention of over 89.7% after 10,000 cycles at a current density of 30 mA cm−2 with a potential window of 1.0 V. Furthermore, the capacitive current contribution is a remarkable 96% with a maximum energy and power density of 75.21 µWh cm−2 and 136 mW cm−2, respectively. This binderless nanofiber composite electrode offers the advantages of better adhesion, improved specific surface area, suitable porosity, and enhanced electronic and ionic conductivity.

Achieving excellent thermal stability in continuous three-dimensional graphene network reinforced copper matrix composites

The stabilization of ultrafine crystalline grains is a tough issue for developing high-performance copper (Cu) matrix composites towards the application in the electronic industries. In order to solve this problem, here we introduced the construction of a three-dimensional graphene network (3DGN) in the Cu matrix to boost the stabilization of both the bi-crystal grain boundaries and the triple junctions. Mechanical properties tests demonstrated that 3DGN/Cu possessed an excellent thermal stability up to 0.9Tm and high-temperature Vickers hardness, which are much higher than those of pure Cu and composites reinforced by two-dimensional (2D) reduced graphene oxides nanosheets. Microstructure characterization revealed that during the hot-rolling (HR) deformation, 3DGN had a strong pinning effect on the recrystallized Cu grains with high-angle grain boundaries and improved the intragranular dislocation density as well as the fractions of the low-angle grain boundaries thus resulting in retaining the equiaxed grain shape and ultrafine grain size. The experimental and molecular dynamics (MD) simulation results both indicated that the key point of attaining the high stability of the graphene/Cu composites lied in the effective restriction of the grain boundary triple junctions migration. These findings may provide guidance for promoting the thermomechanical properties of 2D nanomaterials/Cu composites.

Simultaneous Detection of Naphthol Isomers with a 3D-Graphene-Nanostructure-Based Electrochemical Microsensor

Naphthol is a widely used chemical and medical detection biomarker, but it is harmful to human health and the environment. Therefore, a highly sensitive detection method for naphthol is urgently required. Herein, an electrochemical microsensor for the simultaneous detection of naphthol isomers was fabricated by the in situ growth of a three-dimensional graphene network (3DGN) on screen-printed electrodes. The microsensor exhibited good electrochemical sensing responses to typical isomers of naphthol (1-NAP and 2-NAP). Using the differential pulse voltammetry (DPV) method, the microsensor successfully realized the electrochemical detection of 1-NAP, 2-NAP, and naphthol isomer mixtures. Whether detecting naphthol isomers individually or simultaneously, the microsensor exhibited a good linear relationship for 1-NAP and 2-NAP in a wide range of concentrations. For the simultaneous detection of naphthol isomers, the limit of detection (LOD) of the microsensor to 1-NAP reached 10 nM, and the LOD for 2-NAP was about 20 nM. The microsensor also showed good selectivity, reproducibility, and stability. The simultaneous quantitative detection of 1-NAP and 2-NAP was also successfully achieved in synthetic urine samples.

Mechanical Property and Corrosion Behavior of Powder-Metallurgy-Processed 3D Graphene-Networks-Reinforced Al Matrix Composites

Three-dimensional graphene networks (3DGN) have the potential to be used as a reinforcement for aluminum matrix composites due to their unique wrinkled structure and cost-effectiveness. In this work, the mechanical properties and corrosion resistance of 3DGN in Al matrix were systematically investigated. 3DGN/Al composites with weight ratios of 0, 0.075, 0.150, 0.225, and 0.300 3DGN were prepared by powder metallurgy following by ball mill and spark plasma sintering. Results revealed that the densification of 3DGN/Al composites slightly decreases with the increase of 3DGN content. Increased hardness without loss of ductility was recorded compared to the pure aluminum sample prepared under the same experimental conditions. 3DGN/Al composites exhibit higher corrosion currents density than that of pure aluminum, which shows that the addition of 3DGN reinforcement aggravates the corrosion of aluminum. This study can be used as a reference for future research on the effect of graphene on the various properties of graphene-reinforced aluminum matrix composites.

Germanium decorated on three dimensional graphene networks as binder-free anode for Li-ion batteries

Three-dimensional (3D) graphene networks are successfully fabricated on nickel (Ni) foam by the chemical vapor deposition (CVD) technique. Amorphous Ge layer is then deposited on the 3D graphene supporting skeleton via the facile radio frequency magnetron sputtering (RFMS) method. The Ge decorated on the 3D graphene (3D Ge@Gr) networks deliver improved electrochemical performance when employed as anode for lithium ion batteries (LIBs), which is obvious superior than the two dimensional Ge nanoelectrode directly coated on the bare Ni foam (2D Ge). Significantly enhanced electrochemical cyclability upon 1500 long-term cycles under the higher current density of 1.2 mA cm−2 is accomplished in the optimized 3D Ge@Gr hybrid electrode. The interconnected 3D graphene with enlarge surface area can not only effectively provide enough space to buffer the volume change of the Ge anode during cycling, but also bring improved electrical/ionic conductivity to promote the electrochemical kinetics, thus eventually bring superb stable cyclability.

Rational Construction of C@Sn/NSGr Composites as Enhanced Performance Anodes for Lithium Ion Batteries.

As a potential anode material for lithium-ion batteries (LIBs), metal tin shows a high specific capacity. However, its inherent "volume effect" may easily turn tin-based electrode materials into powder and make them fall off in the cycle process, eventually leading to the reduction of the specific capacity, rate and cycle performance of the batteries. Considering the "volume effect" of tin, this study proposes to construct a carbon coating and three-dimensional graphene network to obtain a "double confinement" of metal tin, so as to improve the cycle and rate performance of the composite. This excellent construction can stabilize the tin and prevent its agglomeration during heat treatment and its pulverization during cycling, improving the electrochemical properties of tin-based composites. When the optimized composite material of C@Sn/NSGr-7.5 was used as an anode material in LIB, it maintained a specific capacity of about 667 mAh g-1 after 150 cycles at the current density of 0.1 A g-1 and exhibited a good cycle performance. It also displayed a good rate performance with a capability of 663 mAh g-1, 516 mAh g-1, 389 mAh g-1, 290 mAh g-1, 209 mAh g-1 and 141 mAh g-1 at 0.1 A g-1, 0.2 A g-1, 0.5 A g-1, 1 A g-1, 2 A g-1 and 5 A g-1, respectively. Furthermore, it delivered certain capacitance characteristics, which could improve the specific capacity of the battery. The above results showed that this is an effective method to obtain high-performance tin-based anode materials, which is of great significance for the development of new anode materials for LIBs.

Three-dimensional Conductive Interconnected Graphene Networks for High-Performance Electromagnetic Interference Shielding

As electronic and information technology advance, it is critical to reduce the electromagnetic pollution caused by electronic devices. Herein, graphene foam (GF) was prepared via chemical vapor deposition and composited with polydimethylsiloxane (PDMS) to prepare GF/PDMS composites with excellent flexibility. It was discovered that the GF/PDMS composites morphologically coupled to each other to create a low-density porous network with excellent electrical conductivity. A comprehensive investigation of the relationship between electromagnetic interference (EMI) shielding performance and 3D graphene foam growth conditions indicated that the thickness of graphene, influencing the continuity and conductivity of 3D foam, has a critical influence in how well GF/PDMS composites perform in terms of EMI. Furthermore, the electromagnetic shielding effectiveness and absolute effectiveness of the GF/PDMS composites in our work can be higher than 52 dB and 2800 dB·cm2/g, respectively, which is better than most carbon-based EMI shielding materials. The comprehensive studies on GF/PDMS composites in this work will benefit the application of electromagnetic shielding materials for next-generation aviation and wearable devices.