Graphene Polymer Research Articles

Graphene-based Coatings - A Corrosion Inhibiting Comrade

Corrosion has been an intense problem the industry has faced since the industrial revolution in the 18th century. As a result, the protection of the machine body from corrosion-causing environmental factors has been a crucial topic of interest of various researchers for many decades. To improve the machine’s service life by inhibiting corrosion, graphene emerged as a revolutionary discovery. The main focus of this paper is concerned with anticorrosive coating derived from graphene and its derivatives. Graphene became evident as a revolutionary material because of its excellent properties. It has been observed that graphene coating has a more excellent corrosion inhibiting effect than a conventional coating. We have briefly discussed various manufacturing methods of graphene and graphene oxide. Industrial manufacturing of graphene is done by chemical vapor deposition. Recent studies reveal that graphene has turned out to be acceptable material for the preparation of polymer composites. Graphene-based polymer composite coatings have superior properties to regular graphene coatings and better corrosion inhibiting performance. These intriguing properties have inspired the research on hybrid graphene polymer composite materials.

Tailoring of Textural Properties of 3D Reduced Graphene Oxide Composite Monoliths by Using Highly Crosslinked Polymer Particles toward Improved CO2 Sorption.

The main constraint on developing a full potential for CO2 adsorption of 3D composite monoliths made of reduced graphene oxide (rGO) and polymer materials is the lack of control of their textural properties, along with the diffusional limitation to the CO2 adsorption due to the pronounced polymers' microporosity. In this work, the textural properties of the composites were altered by employing highly crosslinked polymer particles, synthesized by emulsion polymerization in aqueous media. For that aim, waterborne methyl methacrylate (MMA) particles were prepared, in which the crosslinking was induced by using different quantities of divinyl benzene (DVB). Afterward, these particles were combined with rGO platelets and subjected to the reduction-induced self-assembly process. The resulting 3D monolithic porous materials certainly presented improved textural properties, in which the porosity and BET surface area were increased up to 100% with respect to noncrosslinked composites. The crosslinked density of MMA polymer particles was a key parameter controlling the porous properties of the composites. Consequently, higher CO2 uptake than that of neat GO structures and composites made of noncrosslinked MMA polymer particles was attained. This work demonstrates that a proper control of the microstructure of the polymer particles and their facile introduction within rGO self-assembly 3D structures is a powerful tool to tailor the textural properties of the composites toward improved CO2 capture performance.

Analysis of graphene coated optical fiber for visible range refractive index sensing

In this work, graphene coated optical fiber structure has been exploited theoretically for refractive index sensing within visible operating region. A high refractive index polymer layer is also considered as a matching layer between graphene and the fiber core to generate lossy mode resonances in the desired spectrum. It is observed that multilayer graphene coating supports much sharper and narrower resonances than the graphene monolayer. Sensing characteristics with variation in number of graphene layers and polymer layer thickness are investigated with different polarizations of light. Calibration curves indicating change in resonant wavelength corresponding to the refractive index variation of sensing medium are also presented. It is observed that polymer layer act as the catalyst in enabling the structure to support resonances and shifting the operating region in visible spectrum. A maximum sensitivity of 300 nm/RIU for RI range of 1.33–1.40 is reported for p-polarization of light. It is believed that visible range operation of the proposed structure will make it cost effective and highly suitable for the development of bio-chemical sensors.

Some Electrical and Photoelectrical Properties of Conducting Polymer Graphene Composite /n-Silicon Heterojunction Diode

In this study, polythiophene-graphene (PTh-G) composite thin film was prepared on the n-type silicon (n-Si) semiconductor wafer by the spin coating method. Subsequently, the current-voltage (I-V) measurements were made on the fabricated Au/PTh-G/n-Si/Al device to ascertain the impact of the PTh-G interfacial layer on the device performance. The main device parameters such as ideality factor (n), barrier height (b), series resistance (Rs) were calculated by using the thermionic emission (TE) and Norde functions, and then, the obtained results were discussed in detail. Additionally, the capacitance-voltage (C-V) characteristic of the device was examined as a function of the frequency, and the device parameters such as diffusion potential (Vd), Fermi energy level (Ef), carrier concentration (Nd), b were detemined. Finally, the light intensity-dependent I-V measurements were taken to obtain information about the photoelectrical characteristics of the fabricated device. The obtained results have shown that the prepared composite material has a good potential to be used in optoelectronic applications such as photodiode, and photodetector.

Fabrication and Characterization of Flexible Solid Polymers Electrolytes for Supercapacitor Application.

In this work, solid flexible polymer blend electrolytes (PBE) composed of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) with different amounts of sodium thiocyanate (NaSCN) salt mixed in double-distilled water (solvent) are prepared via solution casting method. The obtained films are characterized using several techniques. The study of the surface morphology of the polymer blend salt complex films via the POM technique reveals the presence of amorphous regions due to the NaSCN effect. FTIR spectra studies confirm the complex formation between PVA, PVP, and NaSCN. The addition of 20 wt% NaSCN salt in the composition PVA: PVP (50:50 wt%) polymer blend matrix leads to an increase in the number of charge carriers and thus improves the ionic conductivity. The ionic conductivity of each polymer blend electrolyte was studied using the electrochemical impedance spectroscopy (EIS) method. The highest room temperature ionic conductivity of 8.1 × 10−5 S/cm S cm−1 is obtained for the composition of PVA: PVP (50:50 wt%) with 20 wt% NaSCN. LSV test shows the optimized ion-conducting polymer blend electrolyte is electrochemically stable up to 1.5 V. TNM analysis reveals that 99% of ions contribute for the conductivity against 1% of electrons only in the highly conductive polymer electrolyte PVA: PVP (50:50 wt%) + 20 wt% NaSCN. A supercapacitor device was fabricated using the optimized ion-conducting polymer blend film and graphene oxide (GO) coated electrodes. The GCD curve clearly reveals the behavior of an ideal capacitor with less Faradic process and low ESR value. The columbic efficiency of the GO-based system is found to be 100%, the GO-based electrode exhibits a specific capacitance of 12.15 F/g and the system delivers the charge for a long duration. The specific capacitance of the solid-state supercapacitor cell was found to be 13.28 F/g via the CV approach close to 14.25 F/g obtained with EIS data at low frequency.

Modeling of Electrical Conductivity for Graphene-Filled Products Assuming Interphase, Tunneling Effect, and Filler Agglomeration Optimizing Breast Cancer Biosensors.

In this study, the percolation inception, actual filler amount, and concentration of nets are expressed using the filler size and agglomeration, interphase depth, and tunneling size. A modified form of the power-law model is recommended for the conductivity of graphene–polymer products using the mentioned characteristics. The modified model is used to plot and evaluate the conductivity at dissimilar ranges of factors. In addition, the prediction results of the model are compared with the experimented values of several samples. A low percolation inception and high-volume portion of nets that improve the conductivity of nanoparticles are achieved at a low agglomeration extent, thick interphase, large aspect ratio of the nanosheets, and large tunnels. The developed equation for percolation inception accurately predicts the results assuming tunneling and interphase parts. The innovative model predicts the conductivity for the samples, demonstrating good agreement with the experimented values. This model is appropriate to improve breast cancer biosensors, because conductivity plays a key role in sensing.

Preparation and Application of Graphene and Derived Carbon Materials in Supercapacitors: A Review

Graphene has recently attracted a wide range of research interests due to its rigorous two-dimensional structure and extraordinary electrical, thermal and mechanical properties. As a conductive agent, an activated carbon supercapacitor can obtain better performance. This paper summarizes the latest research progress, mainly from two aspects: (1) the preparation of an activated carbon base for a supercapacitor based on waste sugar solution and the relationship between pore structure and activation parameters, and (2) the application of the two-dimensional materials graphene and its composite materials in electric double-layer capacitors, graphene–polymer composite tantalum capacitors, graphene–transition metal oxide composite tantalum capacitors, and asymmetric super capacitors. The studies found that graphene and its composite materials have obvious advantages in improving the cycle efficiency, conversion rate, and energy density of supercapacitors, the overall energy efficiency of mechanical systems, and the chemical properties of nanoelectronics. Therefore, it is urgent to summarize these works in order to promote the next development. Graphene is expected to be effectively and environmentally quantified in the near future, and its application in supercapacitors will be further expanded and matured.

Stretchable and Self-Healable Graphene-Polymer Conductive Composite for Wearable EMG Sensor.

In bioelectronics, stretchable and self-healable electrodes can reliably measure electrophysiological signals from the human body because they have good modulus matching with tissue and high durability. In particular, the polymer–graphene composite has advantages when it is used as an electrode for bioelectronic sensor devices. However, it has previously been reported that external stimuli such as heat or light are required for the self-healing process of polymer/graphene composites. In this study, we optimized a conducting composite by mixing a self-healing polymer (SHP) and graphene. The composite materials can not only self-heal without external stimulation but also have rapid electrical recovery from repeated mechanical damage such as scratches. In addition, they had stable electrical endurance even when the cyclic test was performed over 200 cycles at 50% strain, so they can be useful for a bioelectronic sensor device with high durability. Finally, we measured the electromyogram signals caused by the movement of arm muscles using our composite, and the measured data were transmitted to a microcontroller to successfully control the movement of the robot’s hand.

The Effect of Carbon/Oxygen Ratio upon Structure-Property Relationships in Polymer/Graphene Nanocomposites

The oxygen functional group limits the performance of graphene oxide (GO). By raising the Carbon/Oxygen (C/O) ratio, reducing the oxygen functional group may enhance thermal stability. The effects of the (C/O) ratio of graphene derivatives on the structure-properties relationship in metallocene linear low-density polyethylene (PE), homo polypropylene (PP), and blends thereof were investigated in this research. Using reduced graphene oxide (rGO) and pristine graphene (G), the oxygen functional groups were reduced. The effect of raising the C/O ratio of GO, rGO, and G blending with PE and PP synthesized by solution blending is discussed. Solvent processing was used to synthesise these nanocomposites, with dimethylformamide) DMF (and o-xylene served as the solvents for graphene flakes and polymers, respectively, before the two components were combined to form a well-mixed initial state. Wide-angle X-ray diffraction was used to investigate the crystallisation of the nanocomposites (WAXD). X-ray photoelectron spectroscopy (XPS), ultraviolet visible spectroscopy (UVVS), and Raman spectroscopy were used to characterise the chemical structures, with the latter being used to calculate the intensity ratio of D and G band (ID/IG) value for pure graphene specimens. The C/O ratio was calculated as , 4.9 and 2.2 for the G, rGO and GO respectively. While the (ID/IG (increased with increasing the C/O ratio, the ID/IG values were calculated as 0.285, 1.137 and 1.726 for pure GO, rGO and G samples. Differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) were used to determine the melting temperature ( ), crystallization temperature ( ) as well as a range of degradation temperatures.

Bioactive NAD+ Regeneration Promoted by Multimetallic Nanoparticles Based on Graphene-Polymer Nanolayers.

The concentration of nicotinamide adenine dinucleotide oxidized form (NAD+) changes during aging, and the production of NAD+ can significantly affect both health span and life span. However, it is still of great challenge to regenerate NAD+ from its precursors. Herein, we introduce a method to prepare multimetallic nanoparticles (including Au, Pt, Cu, and MgO) that can efficiently promote the conversion of NADH to NAD+. The nanoparticles are made by mixing reduced graphene oxide-polyethyleneimine-polyacrylic acid nano-films with metallic salts, where four different metal ions are reduced and grow at the surface of the nanolayers. The morphology, size, and growth rate of nanoparticles can be controlled by adding surfactants, applying an electric field, and so forth. Our multimetallic nanoparticles exhibit excellent catalytic performance that a complete conversion of NADH to NAD+ can be finished in 3 min without introducing additional oxygen. This work presents a way for the preparation of multimetallic nanoparticles to promote NAD+ regeneration, which shows great promise for the future design of high-performance materials for antiaging.

Damage Location Monitoring of Graphene/Conducting Polymer Composites Film Based on Self-Sensing.

Conductive graphene polymer composites are considered promising functional materials in gas detection, strain detection, metal corrosion prevention, and electromagnetic wave absorption, owing to their good flexibility, lightweight, and adjustable conductivity. The internal defects or external damages of composite films will seriously affect the electrical and functional properties of the materials. Based on the conductive network inside the conductive polymer film and the self-inductance to ultrasonic wave, the defect self-monitoring system of the conductive polymer film is designed and optimized in this work. The self-damage detection system is composed of an electrode array, excitation source, resistance signal acquisition and processing circuit, and damage display. Aiming at different scenarios, the improved interdigital structure transducer for sensors and damage detection device for coating film with a large area are presented and optimized respectively. Meanwhile, the damage location algorithm based on time difference measurement and kernel density estimation algorithm is also optimized. The multiple damage detection is realized by a device with a 4 × 8 electrode array, and the relative error of damage area with 1 mm × 1 mm is less than 5%, and the lower detection limits of damage size are 0.3 mm × 0.3 mm.

Polymeric graphene oxide (GO) dispersions for improved carbon capture and utilization in oil recovery

This work aims to explore the use of stable graphene oxide (GO) dispersions for enhanced carbon capture and oil recovery. The objective of the study was to explore novel GO dispersions for effective carbon utilization. Initially, the GO particles were synthesized via the modified Hummers method and dispersed in a 1000 ppm PAM solution. These solutions (0.1 and 0.3 wt% GO) were observed visually and using a particle size analyzer in which they did not show any instability of agglomeration for 28 days. Given their superior stability, the GO dispersions were then used for CO2 solvation in which the amount of CO2 solvated in the solution (molality) was ascertained using the well-established pressure depletion method. Increasing temperature was found to reduce the CO2 uptake while increasing pressure and GO concentration increased CO2 uptake. The GO dispersions were also able to resist CO2 escape from the system for over 200 h. Finally, the carbonated GO dispersions were used for EOR and were able to mobilize up to 61% of original oil in place (OOIP) from a sand-pack. The presented approach has potential for the development of a highly efficient CO2-based enhanced oil recovery method for sandstone reservoirs.

Polarization switching in nanoscale ferroelectric composites containing PVDF polymer film and graphene layers

Modeling and computer study of a composite nanostructure containing a ferroelectric PVDF polymer and graphene layers were carried out in this work by molecular dynamic simulation and semiempirical quantum PM3 RHF method using the HyperChem software. It is shown here that the inclusion of graphene layers into the PVDF ferroelectric polymer increases the coercive field and decreases the polarization switching time of this composite structure. It is possible due to decrease in the damping coefficient of the Landau-Khalatnikov kinetic equation of the Landau-Ginzburg-Devonshire theory for two-dimensional ferroelectrics. Heterostructures with adjustable polarization switching times can be constructed based on such approach.

Chemical Vapour Deposition Graphene-PMMA Nanolaminates for Flexible Gas Barrier.

Successful ways of fully exploiting the excellent structural and multifunctional performance of graphene and related materials are of great scientific and technological interest. New opportunities are provided by the fabrication of a novel class of nanocomposites with a nanolaminate architecture. In this work, by using the iterative lift-off/float-on process combined with wet depositions, we incorporated cm-size graphene monolayers produced via Chemical Vapour Deposition into a poly (methyl methacrylate) (PMMA) matrix with a controlled, alternate-layered structure. The produced nanolaminate shows a significant improvement in mechanical properties, with enhanced stiffness, strength and toughness, with the addition of only 0.06 vol% of graphene. Furthermore, oxygen and carbon dioxide permeability measurements performed at different relative humidity levels, reveal that the addition of graphene leads to significant reduction of permeability, compared to neat PMMA. Overall, we demonstrate that the produced graphene–PMMA nanolaminate surpasses, in terms of gas barrier properties, the traditional discontinuous graphene–particle composites with a similar filler content. Moreover, we found that the gas permeability through the nanocomposites departs from a monotonic decrease as a function of relative humidity, which is instead evident in the case of the pure PMMA nanolaminate. This work suggests the possible use of Chemical Vapour Deposition graphene–polymer nanolaminates as a flexible gas barrier, thus enlarging the spectrum of applications for this novel material.

Enhanced Electrochemical Matching between NiCo2O4/Reduced Graphene Oxide and Polymer Cement Electrolyte for Structural Supercapacitor

Electrochemical performance of electrode in structural supercapacitor is much lower than that in common supercapacitor owing to solidification confinement of ions movement. Herein, NiCo2O4/reduced graphene oxide (rGO) nanosheets are firstly assembled with KOH/polyacrylic acid (PAA)/cement, LiOTf/PAA cement, KOH/polyethylene oxide (PEO) cement and LiOTf/PEO cement into four structural supercapacitors through hydration process. As the NiCo2O4 content in NiCo2O4/rGO composite exceeds 13 wt%, the areal capacitance of NiCo2O4/rGO electrode at high current densities decreases. The (13%) NiCo2O4/rGO electrode presents the best electrochemical performances with initial areal capacitance of 3.16 F cm−2 at 0.5 mA cm−2, capacitance retention rate of 61% after current density increasing by 80-fold and retention of 86.1% after 10000 cycles at 10 mA cm−2. The corresponding four structural supercapacitors show superior electrochemical performances with areal capacitances of ∼ 330.4 mF cm−2, coulombic efficiencies of ∼ 100%, power densities of ∼ 2.7 mW cm−2 and energy densities of ∼ 0.64 mWh cm−2. The electrochemical efficiencies of (13%) NiCo2O4/rGO electrodes in four structural supercapacitor devices are in the range of 0.16 ∼ 0.12, which are prominent in high-end structural supercapacitors. Thus NiCo2O4/rGO electrode is demonstrated to enhance the electrochemical matching with polymer cement electrolyte for structural supercapacitor.

Friction and Wear Behavior of Graphene and Graphite Oxide–Reinforced Epoxy Composites

Graphene has gained prominence owing to its excellent mechanical, thermal, and electrical properties. Indeed, polymer–graphene composites have demonstrated superior mechanical properties over monoliths and are well suited for seals and bearings. The objective of this work was to gain a fundamental understanding of the friction and wear mechanics of epoxy reinforced by graphene-based fillers. Epoxy composites were prepared with three commercially available graphene/graphite fillers identified as KS6, synthetic graphite powder; xGNP, graphene platelets; and iGO, industrial graphite oxide and tribologically evaluated in a ball-on-disc configuration at sliding velocities from 0.047 to 1.61 m/s. It was found that only the epoxy +5 wt% iGO demonstrated a lower wear rate among other fillers, with 1 wt% being the best for a range of iGO content. The addition of iGO improved the friction and wear resistance due to functional groups on the surface and the resulting enhanced adhesion; it was the nature of the surface film rather than the bulk polymer that dictated the tribological response. Although further studies are warranted, there are indications that harder particles such as iGO may have limited the rate of detachment and wear by arresting crack propagation in the matrix and filler dispersion. The wrinkled morphology of iGO led to better interlocking with the matrix, thereby limiting the detachment of particles; the filler–matrix interaction between functional groups on the graphene oxide surface may also play an important role. These results have important implications for improving the manufacture of composites with superior tribological and mechanical properties.

Effect of contact resistance on the electrical conductivity of polymer graphene nanocomposites to optimize the biosensors detecting breast cancer cells

This study focuses on the contact regions among neighboring nanoparticles in polymer graphene nanocomposites by the extension of nanosheets. The resistance of graphene and the contact zones represent the total resistance of the prolonged nanosheets. Furthermore, the graphene size, interphase depth, and tunneling distance express the effective volume portion of graphene, while the onset of percolation affects the fraction of percolated nanosheets. Finally, a model is developed to investigate the conductivity of the samples using the graphene size, interphase depth, and tunneling size. In addition to the roles played by certain factors in conductivity, the experimental conductivity data for several samples confirm the conductivity predictions. Generally, the polymer sheet in tunnels determines the total resistance of the extended nanosheets because graphene ordinarily exhibits negligible resistance. In addition, a large tunnel positively accelerates the onset of percolation, but increases the tunneling resistance and attenuates the conductivity of the nanocomposite. Further, a thicker interphase and lower percolation threshold promote the conductivity of the system. The developed model can be applied to optimize the biosensors detecting the breast cancer cells.

High-Strength Liquid Crystal Polymer-Graphene Oxide Nanocomposites from Water.

We report on the morphology and mechanical properties of nanocomposite films derived from aqueous, hybrid liquid crystalline mixtures of rodlike aggregates of a sulfonated, all-aromatic polyamide, poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) (PBDT), and graphene oxide (GO) platelets. An isothermal step at 200 °C facilitates in situ partial thermal reduction of GO to reduced GO (rGO) in nanocomposite films. X-ray scattering studies reveal that PBDT-rGO nanocomposites exhibit both higher in-plane alignment of PBDT (the order parameter increases from 0.79 to 0.9 at 1.8 vol % rGO) and alignment along the casting direction (from 0.1 to 0.6 at 1.8 vol % rGO). From dynamic mechanical thermal analysis, the interaction between PBDT and rGO causes the β-relaxation activation energy for PBDT to increase with rGO concentration. Modulus mapping of nanocomposites using atomic force microscopy demonstrates enhanced local stiffness, indicating reinforcement. From stress-strain analysis, the average Young's modulus increases from 16 to 37 GPa at 1.8 vol % rGO and the average tensile strength increases from 210 to 640 MPa. Despite polymer alignment along the casting direction, an average transverse tensile strength of 230 MPa is obtained.

Engineered anti-erosion coating for wind turbine blade protection: Computational analysis

The objective of this paper is to explore the potential of structured, reinforced coatings to improve the erosion protection of wind turbine blades and prevent the surface degradation of wind turbine blades over a longer time. A multiscale computational model of the liquid impact of rain droplet on polymer coatings with internal structures is developed. The finite element model-based CEL (Coupled Eulerian-Lagrangian) approach combined with the sub-modeling technique allows the determination of the local stress distribution in the structured coatings. Wave reflection on particle reinforcement in coatings and stress concentration around the voids in the material were investigated in computational experiments. It is demonstrated that both fiber pulp reinforced polymer coatings and graphene particle reinforced coatings reduce stress concentration in the voids/air bubbles available in the polymer, as compared with the non-reinforced polymers. Given that the erosion of coatings is often initiated near the voids, the stress shielding effect on voids, caused by the fiber pulp or disc particles reinforcement, has a great potential to extend the lifetime and performance of anti-erosion coatings.

Advances of Metal Oxide Composite Cathodes for Aqueous Zinc‐Ion Batteries

Aqueous zinc‐ion batteries (AZIBs) lately garner a lot of interest and are viewed as a promising energy storage technology due to their low cost, eco‐friendliness, and exceptional safety. Crystal metal oxide cathode research has advanced significantly in recent years, making AZIBs a viable choice for low‐cost grid storage applications. However, the readily available (Mn‐ and V‐based oxides) electrode materials suffer from instability and low conductivity. As a consequence, extensive study efforts are dedicated into the development and evaluation of high‐performance cathode systems. Herein, advanced composite cathodes with modified structures are reviewed in an attempt to increase capacity and cycle life. The Mn‐ and V‐based composite framework with polymer template, graphene, and MXene induces electric conductivity, improved lattice spacing, and tunable characteristics, as well as possible benefits for overcoming the redox kinetics and stability constraints for AZIBs. As a result, rational modification of the metal oxides as well as the production of composites shows promise in solving problems and improving cathode performance in high‐performance AZIBs.