Dispersion Of Graphene Research Articles

Fabrication of Conductive Tissue Engineering Nanocomposite Films Based on Chitosan and Surfactant-Stabilized Graphene Dispersions.

Chitosan (CS)/graphene nanocomposite films with tunable biomechanics, electroconductivity and biocompatibility using polyvinylpyrrolidone (PVP) and Pluronic F108 (Plu) as emulsion stabilizers for the purpose of conductive tissue engineering were successfully obtained. In order to obtain a composite solution, aqueous dispersions of multilayered graphene stabilized with Plu/PVP were supplied with CS at a ratio of CS to stabilizers of 2:1, respectively. Electroconductive films were obtained by the solution casting method. The electrical conductivity, mechanical properties and in vitro and in vivo biocompatibility of the resulting films were assessed in relation to the graphene concentration and stabilizer type and they were close to that of smooth muscle tissue. According to the results of the in vitro cytotoxicity analysis, the films did not release soluble cytotoxic components into the cell culture medium. The high adhesion of murine fibroblasts to the films indicated the absence of contact cytotoxicity. In subcutaneous implantation in Wistar rats, we found that stabilizers reduced the brittleness of the chitosan films and the inflammatory response.

Plasma-bioresource-derived multifunctional porous NGQD/AuNP nanocomposites for water monitoring and purification

Multifunctional metal–organic composites with controlled structures and properties are attractive for smart optoelectronic, drug delivery, cancer therapy, clean energy, and environmental applications. Here we develop lightweight, porous metal-graphene composites with uniformly dispersed nitrogen-doped graphene quantum dots (NGQDs) and gold nanoparticles (AuNPs) using reactive non-thermal microplasmas under ambient conditions. Synergy of NGQDs and AuNPs accelerates the polymer cross-linking during synthesis and ensures the requisite properties for simultaneous water monitoring and purification including reliable photoluminescence for heavy metal detection, as well as high adsorption capacity and fast catalytic degradation of organic pollutants. Large-area hierarchical composites with tunable porosity and self-healing ability can be fabricated by the fast and scalable plasma process avoiding toxic chemicals and high temperatures. The composite achieves 120 g g−1 water purification within 60 min at 0.13 mM 4-nitrophenol concentration and is able to monitor the water quality against Hg2+ with the detection limit of 2.2 μM, producing 2880 L kg−1 freshwater per day. Besides, almost 100 % of recalcitrant dye, remazol brilliant blue R, with the concentration of 20 ppm can be adsorbed by the composite in 120 min. Our work provides new insights into design and production of high-performance graphene-metal composites for emerging applications.

Fabrication of Graphene-Modified Styrene–Acrylic Emulsion by In Situ Aqueous Polymerization

With the aim of developing green coatings, styrene–acrylic emulsion has been widely used in architectural coatings due to its excellent environmental protection and energy conservation. Nevertheless, the lack of water and oxygen resistance of water-based styrofoam coatings has promoted various nanomaterials being studied for modification. To improve the performance of waterborne styrofoam coating, we introduced the graphene nanopowder and expected to enable it with the function of electromagnetic interference (EMI) shielding to reduce the damage of electromagnetic radiation. In this paper, the problem of poor interface compatibility between graphene and polymer resin was successfully addressed by in situ polymerization. In the process of pre-polymerization of styrene–acrylic emulsion monomer, graphene-modified styrene–acrylic emulsion was obtained by introducing graphene aqueous dispersion. The results showed that the styrene–acrylic emulsion with 4 wt% aqueous graphene dispersions exhibited the best dispersion stability, improved water and oxygen resistance, and the conductivity reached 1.89 × 10−2 S/cm. Then, the graphene-modified coating for building was prepared by using graphene-modified styrofoam emulsion. All the performance indexes of the coating are in line with the industry standards, and it still showed benign EMI shielding effect even when the graphene content was low. It is demonstrated that in situ polymerization technology and the application of graphene in resin coatings modification will promote the development of green coatings.

Crumpled graphene epoxy nanocomposites modified with polydopamine for advanced semiconductor packaging applications

Graphene-based epoxy nanocomposites are effective TIMs due to the unique properties of graphene – extraordinarily high thermal conductivity and large specific surface area. However, graphene easily aggregates due to strong van der Waals interactions and has poor interfacial connections due to a smooth surface. In this work, a facile method fabricates highly crumpled graphene nanosheets. The crumpled architecture prevents graphene nanosheets from restacking and maintaining the high specific surface area. Polydopamine (PDA) is used to promote uniform dispersion of graphene through π−π bonds, reducing the thermal interface resistance. Additionally, it enhances the thermal transport between as a TIM as proved by experimentation and modeling. The resultant 2.5 wt% filler loading epoxy nanocomposites present a high through-plane thermal conductivity of 1.02 W/mK. They also have a low CTE, low viscosity, low moisture absorption, high electric resistivity, and high adhesion strength. These results provide insights into the design of graphene-based epoxy nanocomposites to meet TIMs requirements in high density 3D electronic packaging.

Chemical resistance of synthesized graphene-modified cement paste containing natural pozzolans to acid attack

This research aims to evaluate the impact of pumice and zeolite as natural pozzolans in cement paste prepared by water-dispersed graphene synthesized from graphite and surfactant against an acid attack. Firstly, the optimal amount of dispersed graphene was derived. Then, several tests such as compressive strength, sorptivity, and microstructural examination such as X-ray diffraction (XRD), scanning electron microscope (SEM), and mercury intrusion porosimetry (MIP) were applied to investigate the single and synergic influence of supplementary cementitious materials (SCMs) at various age of curing. Finally, the chemical resistance of different mixtures under H2SO4 and HNO3 attack was evaluated by weight loss and loss of compressive strength, followed by a visual and microstructural examination of the degradation at different immersion times up to 22 weeks. According to the results, in graphene-containing mixtures, pumice and zeolite decreased compressive strength by 15.5% and 20.4% at an early age, respectively. However, based on the MIP and XRD results, this reduction was mitigated by improving pozzolanic reaction in the long term. Regarding weight loss and compressive strength loss from acid attack results, zeolite reduced these characteristics by 251.72 % and 239.4% compared to the reference paste, respectively.

Simulation of Figures of Merit for Barristor Based on Graphene/Insulator Junction.

We investigated the tunneling of graphene/insulator/metal heterojunctions by revising the Tsu–Esaki model of Fowler–Nordheim tunneling and direct tunneling current. Notably, the revised equations for both tunneling currents are proportional to V3, which originates from the linear dispersion of graphene. We developed a simulation tool by adopting revised tunneling equations using MATLAB. Thereafter, we optimized the device performance of the field-emission barristor by engineering the barrier height and thickness to improve the delay time, cut-off frequency, and power-delay product.

Synthesis of Nano Ceramic Epoxy Hybrid Composite Coating on Metallic Substrate for Corrosion Protection

In this study, the corrosion protection behavior of fumed SiO2 reinforced epoxy composite coatings applied on steel substrates was evaluated and compared to graphene-epoxy nano-composite coatings. Graphene-epoxy nano-composite coatings provide excellent corrosion protection but the uniform dispersion of graphene in polymer solvent is a challenge. So, the fumed silica was chosen as the reinforcement rather than graphene. Fumed silica was treated with stearic acid and used with epoxy to get hydrophobic and corrosion resistant coatings. The partial carburization of epoxy was carried out to get carbon layer on steel substrate. The epoxy was cured at various temperatures (200, 250 and 300 °C) to see its effect on hydrophobicity and corrosion behavior of the composite coatings. Presence of different functional groups of modified silica and epoxy was confirmed by FTIR ATR. Coating prepared from this material was evaluated microscopically with respect to structure, uniformity and interface with optical microscope. Polarization effect of coatings was studied by potentiodynamic polarization method. Coating thickness was measured by an Elcometer gauge, and these were checked by the micrographs at 50, 200 and 1000x. E250 (60% epoxy + 6% Silica) showed corrosion rate of 0.017mpy much lower than uncoated steel substrate (2.612mpy). Contact angles for npc200 (neat partially carburized epoxy cured at 200°), 4Si70 (60% epoxy+4% Silica cured at 70°), 6Si300 (60% epoxy+6% Silica cured at 300°) and 6Si250 (60% epoxy+6% Silica cured at 250°) were 90°, 89.5°, 72.5° , 97.5° respectively. So, it was proved that partially carburized epoxy coating with 6% modified silica cured at 250 °C was more corrosion resistant and hydrophobic in nature.

Preparation and Thermal Characterization of Nanographene- Enhanced Fatty Acid-Based Solid-Liquid Organic Phase Change Material Composites for Thermal Energy Storage

In this research work, nano-phase change material (NPCM) composites were prepared by adding 1 %, 2 %, and 3 % mass fractions of highly conductive carbon-based graphene nanoparticles into the base phase change material (PCM). The existence and uniform graphene dispersion in the PCM was confirmed through Raman spectrometer and scanning electron microscope (SEM) analysis. The Fourier transform infrared (FTIR) and x-Ray diffraction (XRD) results showed that all three NPCM composites were chemically stable, and their crystallinity was similar to the base PCM. For the sample with 3 % graphene, the solid-state thermal conductivity was increased by 219.89 %, and liquid-state thermal conductivity was increased by 161.65 %, with a 3.52 % drop in latent heat capacity was revealed from differential scanning calorimetry (DSC) analysis. All NPCM composites have onset and peak melting temperatures closer to the base PCM. Hence, the NPCM composites can be employed for thermal energy storage (TES) integrated solar water heater (SWH) applications.

High yields of graphene nanoplatelets by liquid phase exfoliation using graphene oxide as a stabilizer

The exfoliation of graphene nanoplatelets (GNP) in aqueous media is challenging due to their restacking tendency. The sheets need to overcome the van der Waals attractive forces as well as the π−π interactions to form stable dispersions. The use of surfactants can resolve this issue but compromises the properties of GNP and therefore requires additional processing steps. In this work, we utilize graphene oxide as a dispersing agent in the liquid phase exfoliation of GNP from raw graphite. We first analyze the exfoliation process and determine that the relevant process parameters are graphene oxide and graphite concentration, graphite sheet size, dynamic viscosity of the dispersion, shear rate, and exfoliation time. Applying dimensional reasoning reduces the problem to four non-dimensional groups. A set of experiments, guided by a factorial design, is undertaken to analyze the exfoliated content using UV–Vis spectroscopy. We achieve a high GNP concentration of 8.6 mg ml−1, corresponding to a yield of 23 wt%, after a relatively-short exfoliation time of around 3 h. This is a considerably better performance compared to other liquid phase exfoliation processes. Experimental results are used to derive a functional correlation between the dimensional groups, which can be used for optimization. Additionally, we use exfoliated graphene dispersions to synthesize graphene hydrogels as electrode material for flexible aqueous supercapacitors. We measure a capacitance of 206 F g−1 and 143 F g−1 at a current density of 1 A g−1 and 10 A g −1, respectively. The supercapacitor retains 87% of the initial capacitance over 1000 charge and discharge cycles at a current density of 10 A g −1.

Effects of Preparation Methods on the Microstructure and Mechanical Properties of Graphene-Reinforced Alumina Matrix Composites.

Recent years have witnessed a growing research interest in graphene-reinforced alumina matrix composites (Al2O3-G). In this paper, to better achieve the dispersion of graphene in composites, a ball milling method for adding raw materials step by step, called stepwise feeding ball milling, was proposed. The Al2O3-1.0 wt % graphene composites were prepared by this stepwise feeding ball milling and hot pressing. Then, the effects of sintering temperature and sintering pressure on the microstructure and mechanical properties of composites were studied. Results showed that the bending strength, fracture toughness and Vickers hardness of composites increased firstly and then decreased with increasing sintering temperature. The mechanical properties of composites were all at their maximum with the sintering temperature of 1550 °C. For example, the bending strength of composites reached 754.20 MPa, which was much bigger than 478.03 MPa at 1500 °C and 364.01 MPa at 1600 °C. Analysis suggested that the strength of composites was mainly related to the grain size, microflaw size and porosity.

Achieving high strength and modulus in graphene reinforced Mg matrix composites via an in-situ process

Magnesium matrix composites reinforced with graphene have attracted great attention because of their fascinating properties. However, it is still challenging to realize the effective addition and dispersion of graphene in the Mg matrix. In this work, a novel in-situ liquid metallurgical process that converts CO2 to graphene is developed to fabricate Mg matrix composites. Firstly, graphene coated with MgO nanoparticles could be produced during the in-situ process, promoting the uniform dispersion of graphene and strong interfacial bonding simultaneously. Furthermore, the fine grain size and dynamic precipitates were formed in the as-extruded composites. Finally, the in-situ formed graphene in the composites shows much higher strengthening efficiency than reinforcements prepared by conventional methods reported so far. This preparation strategy is both efficient and environmentally friendly, and it is suitable for expanding the industrial production of Mg matrix composites.

Economic and facile approach for synthesis of graphene–titanate nanocomposite for water reclamation

Graphene and its composites with semiconductor materials have been received highly attention in many research areas because of their unique properties. Efficient application of graphene is hindered by the lack of cost-effective synthesis methods. In this work, an economic and facile route for mass production of graphene-titanate nanocomposite has been discussed. Graphene was prepared by exfoliation of graphite powder in 40% ethanol aqueous solution. Titanate nanotubes were grown on graphene sheets by hydrothermal method, where the dispersed graphene sheets were mixed with titanate solution and then placed in autoclave and placed in oven for 16 h at 160 °C. The prepared composite was characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FTIR), thermogravimetric analysis (TGA). All the obtained results confirmed the synthesis of graphene and its composite with titanate in highly uniform and pure form. The adsorption efficiency of the prepared composite was tested using methylene blue (MB) as a model dye. The adsorption isotherm was investigated using Freundlich and Langmuir models. The adsorption capacity of MB was 270.27 mg/g. The obtained correlation coefficients (R2) by Freundlich and Langmuir model were 0.996 and 0.973, respectively. The adsorption kinetics was investigated and discussed using different models. The thermal stability of the developed composite is improved after MB adsorption.

Preparation, corrosion resistance and mechanical properties of electroless Ni-W-P-eGO composite coatings

In this paper, highly dispersed edge graphene oxides (hereinafter referred to as eGO) were successfully applied in the Ni-W-P bath system, and high-performance Ni-W-P-eGO coating was prepared on the surface of N80 carbon steel by an electroless deposition method. By investigating concentration of eGO in solution in the solution, and using XPS, XRD, EDS, and SEM to analyze the crystal properties, electroless composition, micromorphology, and microstructure of the coating in detail,and the hardness, corrosion resistance and wear resistance of the coatings were investigated by microhardness tests, electrochemical corrosion and friction and wear tests. The niversal electrochemical methods determined the corrosion resistance of the coating, and the abrasion resistance of the coating was determined by ageneralduty reciprocating test. The experimental characterization results show that the addition of eGO nanomaterials to the Ni-W-P composite coating significantly improves the corrosion resistance of the coating in 3.5 wt% NaCl solution, improve the mechanical properties of the coating. When eGO content reaches 0.1 g/l, Ni-W-P-eGO coating demonstrated the most excellent corrosion resistance with a corrosion current of 0.9476 μA/cm2, and mechanical properties (the average friction coefficient is 0.173, and the microhardness value is 744.58 HV).

Effects of graphene dispersion in hot pressing UO2-graphene nanosheet ceramic matrix composites

The safe use of nuclear energy is crucial, especially after the Fukushima nuclear disaster. A novel uranium dioxide (UO2)-graphene nanosheet (GN) ceramic matrix composite fuel has been proposed as an accident tolerant fuel (ATF) with excellent thermal-mechanical properties. The UO2-GN pellet system is developed using mechanically mixed and hot pressing (HP) sintering, providing a new idea for the industrial production of UO2-GN pellets. Raman spectroscopy and scanning electron microscopy (SEM) show that most GN survives in composite pellets by HP sintering. Furthermore, we discovered various toughening mechanisms in the composite pellets for the first time. With the further increase of graphene content (1, 3, 5 wt%), the behavior of GN in the matrix changed from anchoring to wrapping. Among different sintering methods, HP sintering has excellent thermal performance. The thermal diffusivity of the composite pellets prepared by HP sintering (HPed) doped with 3 and 5 wt% is 1.300 and 1.423 mm2 s−1 at 973 K, increased by 5.43% and 15.41% compared with the pure pellets, respectively. Furthermore, the thermal conductivities of the HPed doped with 1, 3, and 5 wt% are 4.31, 5.00, and 6.06 W m−1 K−1 at 973 K, which were 3.61%, 20.20%, 45.67% higher than those of the pure pellets, respectively. These results highlight the immense possibilities of HP sintering in fabricating UO2-GN pellets to improve fuel performance.

(Invited) Metrology of Solution Processable 2D Materials for Electronic Applications

Two-dimensional materials have attracted intense interest due to their remarkable physical and electronic properties as well as their potential for a diverse range of applications. Many of these envisaged applications (i.e. printed/flexible electronics, energy storage, photovoltaics) require single or few layer flakes of a 2D material that can be dispersed in solution to facilitate deposition onto a substrate, formulation into an ink and/or mixing into a composite. A variety of powders and dispersions claiming to contain 2D materials such as graphene are now becoming available but the variable quality of these materials and lack of standardized protocols for their assessment is hampering the development of applications.Here we will describe ongoing work at the NRC aimed at developing characterization methods and standard protocols to characterize graphene and graphene oxide (GO) powders, dispersions and inks. We employ a variety of experimental techniques including scanned probe microscopies (AFM and STM), vibrational spectroscopy (Raman and FTIR), X-ray diffraction, X-ray photoelectron spectroscopy and dynamic light scattering in order to characterize the structure and chemical composition of in-house and commercially available materials. These methods allow us to measure key parameters to assess material quality such as flake thickness and lateral size, carbon to oxygen ratio and impurity content. Conductivity and work function of ultrathin films produced from various graphene and graphene oxide containing dispersions have been also measured. The performance of these films as transparent conductors can be characterized by a figure of merit based on the optical transmission and conductivity of the film. Performance of films made via reduction of GO will be compared with those based on graphene exfoliated without oxidation.Recently we have begun to extend this work to dispersions of other two-dimensional materials such as the transition metal dichalcogenides (TMDC). Initial characterization of commercially available TMDCs will be presented.

(Digital Presentation) Recovery of Copper from Wastewater By Electrodeposition Onto Nanocarbon Composites

The connection of carbon nanostructures such as graphene or carbon nanotubes with other materials like metals [1] or polymers [2] is often beneficial. For example, composites consisting of copper and nanocarbon materials have improved electrical [1] and mechanical [3] properties due to the synergy effect. Unfortunately, the integration between copper and nanocarbon is not an easy task because of the “cuprophobic” nature of nanocarbon [4]. Recently, many methods have been developed to accomplish this challenge. Out of all available techniques, physical (casting, spark plasma sintering or metal spinning) and electrochemical [5] gained a considerable share of attention. In particular, electrodeposition is a commonly employed strategy to deposit copper onto nanocarbon electrodes. In this method, nanocarbon surface plays the role of working electrode, onto which copper ions are reduced, thereby creating a Cu coating on the surface.This study demonstrates the recovery of copper from industrial wastewater by thin films based on carbon nanotubes (CNTs). Such a substrate was found as an ideal surface for the electrodeposition of metallic particles. Single/multi-walled CNTs, oxidized CNTs, nitrogen-doped CNTs and graphene were combined to obtain nanocarbon-nanocarbon composite electrodes, which were then used as substrates in Cu electrodeposition [6].To establish the coating process parameters, synthetic solution of CuSO4 was first used as a source of copper ions. Then, wastewater of complex composition was employed directly for the electrodeposition process. Besides the 40 ppm of Cu, the wastewater contained other elements like salts Fe, Mg, Al, Zn and As in much greater amounts. It was discovered that such nanocomposite materials may be an excellent substrate for electrochemical recovery of Cu also from such a problematic waste, while simultaneously giving a product of high added value. Interestingly, the product was free from other metals, and only copper was detected on the nanocarbon surface. After just 1-hour of electrodeposition at -0.1V vs. SCE, a nanocarbon-based composite evenly coated with Cu was manufactured. Thorough investigation of the microstructure, and chemical composition of the nanocomposites correlated with the properties of the Cu coated materials enabled us to deduce critical parameters needed to make the Cu coating process effective [7].[1] C. Arnaud, F. Lecouturier, D. Mesguich, N. Ferreira, G. Chevallier, C. Estournès, A. Weibel, C. Laurent, High strength - High conductivity double-walled carbon nanotube - Copper composite wires, Carbon N. Y. 96 (2016) 212–215. doi:10.1016/j.carbon.2015.09.061.[2] S.N. Beesabathuni, J.G. Stockham, J.H. Kim, H.B. Lee, J.H. Chung, A.Q. Shen, Fabrication of conducting polyaniline microspheres using droplet microfluidics, RSC Adv. 3 (2013) 24423–24429. doi:10.1039/c3ra44808h.[3] R. Jiang, X. Zhou, Q. Fang, Z. Liu, Copper-graphene bulk composites with homogeneous graphene dispersion and enhanced mechanical properties, Mater. Sci. Eng. A. 654 (2016) 124–130. doi:10.1016/j.msea.2015.12.039.[4] D. Janas, B. Liszka, Copper matrix nanocomposites based on carbon nanotubes or graphene, Mater. Chem. Front. 2 (2018) 22–35. doi:10.1039/c7qm00316a.[5] A. Singh, T. Ram Prabhu, A.R. Sanjay, V. Koti, An Overview of Processing and Properties of CU/CNT Nano Composites, Mater. Today Proc. 4 (2017) 3872–3881. doi:10.1016/J.MATPR.2017.02.286.[6] D. Janas, M. Rdest, K.K.K. Koziol, Free-standing films from chirality-controlled carbon nanotubes, Mater. Des. 121 (2017) 119–125. doi:10.1016/j.matdes.2017.02.062.[7] G. Stando, P.-M. Hannula, B. Kumanek, M. Lundström, D. Janas, Copper recovery from industrial wastewater - Synergistic electrodeposition onto nanocarbon materials, Water Resour. Ind. 26 (2021) 100156. doi:10.1016/J.WRI.2021.100156.G.S. and P.S. would like to thank the Ministry of Science and Higher Education of Poland for financial support of research (under Diamond Grant, grant agreement 0036/DIA/201948). G.S. also would like to thank European Union for thanks for financing the costs of the conference (European Social Fund, grant nr POWR.03.05.00-00-Z305) and National Agency for Academic Exchange of Poland (under the Iwanowska program, grant agreement PPN/IWA/2019/1/00017/UO/00001) for financial support during the stay at the University of Pittsburgh in the USA. G.S. and H.L. acknowledge NSF (CBET-2028826) for partial support of this work. G. S. and D.J. acknowledge the National Agency for Academic Exchange of Poland (under the Academic International Partnerships program, grant agreement PPI/APM/2018/1/00004) for supporting training in the Aalto University. G.S, B.K. and D.J. would like to thank the National Centre for Research and Development, Poland (under the Leader program, grant agreement LIDER/0001/L-8/16/NCBR/2017).

A multi-scale analysis on reinforcement origin of static and dynamic mechanics in graphene-elastomer nanocomposites

The graphene reinforced nanocomposites have been attracting considerable attention owing to their excellent mechanical and physical properties. Herein we systematically develop a multiscale scheme of graphene-polyisoprene nanocomposites, in which the effective coarse-grained potentials of polyisoprene (PI), graphene, interface derived from the all-atom models using inverse Boltzmann iteration along with pressure correction, strain energy conservation and energy matching method during graphene pull-out testing respectively. Graphene dispersion, PI entanglement network and PI-graphene network structures are quantitively characterized by the interlayer distance distributions of graphene sheets, conformity of PI chains with the entanglement theory and the conformation of polymer chains adjacent to graphene surfaces respectively. Particularly, there are three regimes of reptation dynamics, chain confinement, sufficient network of PI chains in terms of various graphene loading correspond to the dispersion, percolation and aggregation of graphene. In the rubbery region the initial high reinforcement of shear modulus is caused by trapped conformation at high frequency, while at low frequencies, the gained conformational freedom leads a relatively low reinforcement, which increases exponentially with a reduced weight fraction. Generally, our multi-scale strategy may be readily extended to other kinds of filling models, and this work could guide the rational design and preparation of nanocomposites.

Superior electrical conductivity-strength combination of an in-situ fabricated La2O3-doped copper/graphene composite conductor

In the past decade, Cu/graphene composite shows great potential in energy and electric power fields. Unfortunately, the uneven dispersion of graphene and the poor interfacial bonding between the copper and graphene have always been the bottlenecks hindering its development. Furthermore, it is almost impossible to obtain facile and scalable Cu/graphene materials with the combined high electrical conductivity and great strength through traditional ways. Here, we innovatively introduce lanthanum acetate as the carbon source to in-situ grow high-quality graphene and nano-sized La2O3 particles in copper through vacuum hot-press sintering to solve the above problems. The uniformly-distributed three-dimensional (3D) graphene network acts as an electron-transport channel, and the in-situ generated nano-sized La2O3 particles pin the Cu/graphene interface. Both the graphene and the nano-sized particles strengthen the matrix and hinder the matrix to soften at high temperatures. By further optimizing the sintering parameters, the doping content, the cold-drawing process, the La2O3-doped Cu/graphene composite wire with the high electrical conductivity of 95.5% IACS (International Annealed Copper Standard), great tensile strength of 539 MPa, and high softening temperature about 500 °C are obtained. The present work provides a new design idea for interface-strengthening Cu/graphene composites and establishes a suitable method for the large-scale production of high-performance Cu/graphene composites, which can be used at higher temperatures, such as the integrated circuit lead frame and the railway contact line.

Green synthesis of zinc sulfide-reduced graphene oxide composite and its application in sodium-ion batteries

A green chemistry synthesis of a sodium-ion battery (SIB) anode is described. The anode comprises nanometric Sphalerite (ZnS) film, coated uniformly on reduced graphene oxide. Compliance of an energy storage component with sustainability goals requires the following attributes: i) exclusive use of abundant and non-toxic raw materials; ii) energy-minimized processing that uses cheap materials of construction, and involves a minimal waste generation, and no hazardous wastes, and iii) high energy efficiency without compromising power performance. Only low-cost, abundant raw materials are used in this synthesis: zinc acetate, 1 wt% hydrogen peroxide solution, and in-situ generated hydrogen sulfide. The synthesis protocol is based on hydrogen peroxide sol-gel (HPSG) processing, i.e. synthesis of zinc peroxide sol followed by a delicate pH change to deposit the zinc peroxide on dispersed graphene oxide. HPSG is a wet-chemistry process that does not rely on energy-rich hydrothermal/solvothermal steps, water or solvent evaporation, or the use of dispersing organic solvents, and the zinc precursor is fully converted to ZnS. We show film deposition from as low as 1 wt% aqueous hydrogen peroxide solution. The anode exhibits excellent electrochemical characteristics: 550 mAh g −1 at 0.1 A g −1 after 150 cycles between 0 and 2.5 V vs. Na reference, and a high-rate capability of 420 mAh g −1 at 2 A g −1 (ca 5 C rate). Despite being a conversion type anode, ZnS exhibits similar voltage hysteresis (and energy efficiency) to tin sulfide - graphene-oxide composite, a conversion-alloying anode. Despite being a SIB anode, it compares favorably with the Fe 3 O 4 and MnO LIB conversion anodes, commended for their high energy efficiency. SYNOPSIS: A green chemistry synthesis of a sodium ion battery anode based on ZnS-rGO. • A green chemistry synthesis of a sodium ion battery anode based on ZnS-rGO. • ZnS-rGO anode revealed a high specific capacitance of 543 mAh g −1 . • Anodes show lower voltage hysteresis, higher 1st cycle discharging–charging efficiency.

Tribological Performance and Rheological Properties of Engine Oil with Graphene Nano-Additives

Nanoparticles dispersed in lubricants are being studied for their ability to reduce friction and wear. This paper examines SAE 5W-30 oil enhanced with dispersed graphene nanoplates for tribological and rheological properties. Graphene nanoplate (GNs) concentration effects on the rheological and tribological properties of 5W-30 base oil (0.03, 0.06, 0.09, 0.12, and 0.15 wt percent) were tested. Under various loads, a four-ball testing model was used to conduct a tribological analysis (200, 400, 600, and 800 N). Kinematic viscosity is calculated, and base oil and nanofluid-added 5W30 lubricant are compared for thermal conductivity and flashpoint. Wear scar and coefficient of friction improved by 15% and 33% with nano-additives. When related to the base oil, the flashpoint, thermal conductivity, kinematic viscosity, and pour point all increased, by 25.4%, 77.4%, 29.9%, and 35.4%, respectively. The addition of GNs improved the properties of 5W30 engine oil.