Large-scale fabrication of re duce d graphene oxide-sulfur composite films for flexible lithium-sulfur batteries

The rapid development of flexible electronic devices requires the design of flexible energy-storage devices. Lithium-sulfur(Li-S) batteries are attracting much interest due to their high energy density. Therefore, flexible Li-S batteries with high areal capacity are desired. Herein, we fabricated freestanding reduced graphene oxide-sulfur(RGO@S) composite films with a cross-linked structure using a blade coating technique, followed by a subsequent chemical reduction. The porous cross-linked structure endows the composite films with excellent electrochemical performance. The batteries based on RGO@S composite films could exhibit a high discharge capacity of 1381 m Ah/g at 0.1 C and excellent cycle stability. Furthermore, the freestanding composite film possesses excellent conductivity and high mechanical strength. Therefore, they can be used as the cathodes of flexible Li-S batteries. As a proof of concept, soft-packaged Li-S batteries were assembled and remained stable electrochemical performance under different bending states.

Recent progress on thermal conductivity of graphene filled epoxy composites

With the rapid development of the electronic industry, the requirements for packaging materials with high thermal conductivity(TC) are getting higher and higher. Epoxy is widely used as package material for electronic package applications. But it’s intrinsic TC can’t meets the increasing demands. Adding high TC graphene into epoxy matrix is a proper way to reinforce epoxy composites. This review focuses on the filler modification,preparation process and thermal properties of graphene-filled epoxy resin composites. Different ways of covalent and non-covalent modification methods are discussed. The various kinds of graphene coating layer are also summarized. Then we analysis the hybrid filler system in epoxy composite. We hope this review will provide guidance for the development and application of graphene-filled epoxy resin composites.

Enhancing the Mechanical Strength for a Microwave Absorption Composite Based on Graphene Nanoplatelet/Epoxy with Carbon Fibers

Microwave absorption (MWA) materials such as graphene nanoplatelet (GNP)/epoxy are mostly used as coatings on existing structures without considering mechanical properties. In this work, we aim to enhance the mechanical strength of the composite for multifunctional potentials. We used carbon fiber (four layers) to reinforce GNP/epoxy composite (2 mm thick) and investigated their multifunctional properties with GNP loading from 3 to 7 wt%. We measured the tensile strength, hardness, and MW absorption (26.5 - 40 GHz) of composite samples. Our results showed an increase in tensile strength to 109.1 ± 7.9 MPa with 7 wt% GNP in the composite from 15.3 MPa for pure epoxy. The hardness of the composites was also substantially enhanced with GNP loading up to 7 wt%. A MW absorption ratio of 72% was attained for the sample with 7 wt% GNP loading near 40 GHz. The homogenous dispersion of GNPs in the matrix reduces the stress concentration and minimizes the influence of the defects. The high MW absorption and large transmission loss together with enhanced mechanical strength provides a novel multifunctional material for potential applications.

The Reinforcing Effect of Graphene on the Mechanical Properties of Carbon-Epoxy Composites

Graphene nanoplatelets (GNPs) are novel nanofillers holding attractive characteristics, including vigorous compatibility with majority polymers, outstanding mechanical, thermal, and electrical properties. In this study, the outstanding GNPs filler was reinforced to the epoxy matrix and carbon fabric/epoxy hybrid composite slabs to enrich their mechanical properties. Graphene nanoplatelets of 0.5, 1, 1.5 and 2 weight percentages were integrated into the epoxy and the physico-mechanical (microstructure, density, tensile, flexural and impact strength) properties were investigated. Furthermore, the mechanical properties of unfilled and 1 wt% GNPs filled carbon fabric/epoxy hybrid composite slabs were investigated. Subsequently, noteworthy improvement in the mechanical properties was conquered for the carbon fabric/epoxy hybrid composites.

Preparation and Characterization of Co_(3)O_(4)/Graphene/Cellulose Nanofiber Composite Films

Nanocellulose has served as an eye-catching nanomaterial for constructing advanced functional devices with renewability,light weight,flexibility,and environmental friendliness.In this study,Co_(3)O_(4)/graphene/cellulose nanofiber(CNF)flexible composite films,in which the CNF acted as a spacer for the graphene,were prepared via a facile and scalable vacuum filtration method.The effects of the CNF on the microstructure,hydrophilicity,thermal stability,tensile strength,surface resistance,and electrochemical performance of the Co_(3)O_(4)/graphene/CNF composite films were systematically investigated.The results showed that the synergistic interaction of the CNF and graphene substantially improved the overall properties of the Co_(3)O_(4)/graphene/CNF composite films,particularly their hydrophilicity and tensile strength.Meanwhile,Co_(3)O_(4)/graphene/CNF composite films with a CNF content of 4%appeared to have the optimal electrochemical performance,with an area specific capacitance of 56 mF/cm^(2) and prominent capacitance retention of 95.6%at a current density of 1 A/g after 1000 cycles.This work demonstrated that the prepared Co_(3)O_(4)/graphene/CNF flexible composite films have great application potential in the field of flexible energy storage devices.

Reinforcing Effect of Graphene in Epoxy Adhesives: Review

Due to its great strength, hardness, and chemical resistance, epoxy adhesives are becoming more and more used. They continue to have drawbacks, nevertheless, such as poor thermal stability, and poor electrical conductivity. Two-dimensional graphene is a wonderful substance with exceptional qualities including high strength, high electrical conductivity, and large surface area. Because of these characteristics, graphene has been thoroughly researched for its prospective uses in a variety of industries, including electronics, energy storage, and biomedical engineering. The use of graphene as an additive in epoxy adhesives to enhance the characteristics of such materials is one of its promising uses. This paper reviewed the latest findings about graphene’s effects on epoxy adhesives. The various methods to produce graphene-epoxy composites and their improvements are discussed. This research additionally discusses the challenges associated with the production and processing of graphene-epoxy composites, as well as the mechanisms behind the improvements in mechanical, electrical, and thermal characteristics. The final section of this review discusses the challenges and prospective uses of graphene in epoxy adhesives in the future.

3D Lamellar-Structured Graphene Aerogels for Thermal Interface Composites with High Through-Plane Thermal Conductivity and Fracture Toughness

Although thermally conductive graphene sheets are efficient in enhancing in-plane thermal conductivities of polymers,the resulting nanocomposites usually exhibit low through-plane thermal conductivities,limiting their application as thermal interface materials.Herein,lamellarstructured polyamic acid salt/graphene oxide(PAAS/GO)hybrid aerogels are constructed by bidirectional freezing of PAAS/GO suspension followed by lyophilization.Subsequently,PAAS monomers are polymerized to polyimide(PI),while GO is converted to thermally reduced graphene oxide(RGO)during thermal annealing at 300℃.Final graphitization at 2800℃ converts PI to graphitized carbon with the inductive effect of RGO,and simultaneously,RGO is thermally reduced and healed to high-quality graphene.Consequently,lamellar-structured graphene aerogels with superior through-plane thermal conduction capacity are fabricated for the first time,and its superior through-plane thermal conduction capacity results from its vertically aligned and closely stacked high-quality graphene lamellae.After vacuum-assisted impregnation with epoxy,the resultant epoxy composite with 2.30 vol% of graphene exhibits an outstanding through-plane thermal conductivity of as high as 20.0 W m^−1 K^−1,100 times of that of epoxy,with a record-high specific thermal conductivity enhancement of 4310%.Furthermore,the lamellar-structured graphene aerogel endows epoxy with a high fracture toughness,~1.71 times of that of epoxy.

Electrical and optical properties of indium tin oxide/epoxy composite film

The electrical and optical properties of the indium tin oxide （ITO）/epoxy composite exhibit dramatic variations as functions of the ITO composition and ITO particle size. Sharp increases in the conductivity in the vicinity of a critical volume fraction have been found within the framework of percolation theory. A conductive and insulating transition model is extracted by the ITO particle network in the SEM image, and verified by the resistivity dependence on the temperature. The dependence of the optical transmittance on the particle size was studied. Further decreasing the ITO particle size could further improve the percolation threshold and light transparency of the composite film.

Composite bilayer films with organic compound-triggered bending properties

Organic compounds are widely used in both industry and daily life,and composite bilayer films with organic compound-triggered bending properties are promising for applications of transducers,soft robotics,and so on.Here,a universal and straightforward strategy to generate composite bilayer films with organic compoundtriggered bending properties is demonstrated.The composite bilayer films with organic compound-triggered bending properties are designed with bilayer structures,in which one layer is a porous polymeric membrane with appropriate solubility parameter that matches the value of organic solvents in order to produce prominent affinity to the solvent molecules,and the other layer is reduced graphene oxide membrane stacked on the porous polymeric membrane as an inert layer for restraining the swelling of the polymeric membrane on one side.Guided by matching the solubility parameters between solvent and polymer,a significant bending curvature of 27.3 cm-1 is obtained in acetone vapor.The results in this study will provide valuable guidance for designing and developing functional composite materials with significant organic compound-triggered bending properties.

A graphene-enhanced high-barrier and fast-curing film for deep in situ condition preserved coring in coal seams

Scientific research on deep in situ resources is highly important to the theory and technology system construction for deep in-situ resource exploitation.To obtain high-condition preserved core samples,it is vital to maintain the original material,humidity and luminous flux information inside the core.Therefore,this study proposes a research and development strategy for a high-toughness and highbarrier sealing film based on the molecular structure design and filler synergistic enhancement via a deep solid-state sealing film using in situ substance preservation(ISP),in situ moisture preservation(IMP)and in situ light preservation(ILP)coring principles.A graphene/epoxy composite sealing film with a high barrier,high strength and high toughness was developed.The oxygen permeability of the film was 0.23 cm^(3)/(m^(2)·d),the water vapor permeability was 1.26 g/(m^(2)·d),and the light transmittance was 0.The tensile strength reached 15.4 MPa,and the toughness was 5242.9 kJ/m^(3).The results from the film substance and moisture preservation performance verification experiments showed that the sealing film had an excellent sealing effect on small molecules,such as water,alkanes and even ions,which further verified that the sealing film greatly contributed to the maintenance and preservation of deep in-situ resource reserves and abundance.

Reduction Band Gap Energy of TiO₂Assembled with Graphene Oxide Nanosheets

This research work aims to reduce the band gap of thin layers of titanium oxide by the incorporation of graphene oxide sheets. Thin layers of the TiO2-GO composites were prepared on a glass substrate by the spin-coating technique from GO and an aqueous solution of TiO2. A significant decrease in optical band gap was observed at the TiO2-GO compound compared to that of pure TiO2. Samples as prepared were characterized using XRD, SEM and UV-visible spectra. XRD analysis revealed the amorphous nature of the deposited layers. Scanning electron microscope reveals the dispersion of graphene nanofiles among titanium oxide nanoparticles distributed at the surface with an almost uniform size distribution. The band gap has been calculated and is around 2 eV after incorporation of Graphene oxide. The chemical bond C-Ti between the titanium oxide and graphene sheets is at the origin of this reduction.

基于MAPbI_(3)/Graphene/Si复合结构的高灵敏宽带太赫兹调制器

高性能硅基太赫兹调制器是构建超宽带太赫兹-光纤混合通信系统的关键器件之一.提出了一种基于钙钛矿/石墨烯/硅(MAPbI_(3)/Graphene/Si)复合结构的近红外光驱动的超宽带大调制深度太赫兹调制器.实验结果表明,石墨烯薄膜和钙钛矿空穴传输层在近红外光驱动下可有效地促进界面电荷分离,增大载流子复合寿命,显著增强器件的表面电导率,进一步调控太赫兹波的传输幅度,实现光控型太赫兹波调制器的功能.通过波长808 nm的近红外调制激励源,对器件在0.2—2.5 THz超宽频率范围的太赫兹透射特性进行表征,实验用6.1 mW/mm^(2)的低功率密度近红外光驱动下实现了高达88.3%的大调制深度,远高于裸硅基底的调制深度(约14.0%),具有高灵敏、宽带和大调制深度等显著优势,并且建立了相应的半解析器件模型,仿真验证了实验结果.所提出的MAPbI_(3)/Graphene复合薄膜在增强硅基调制器性能方面效果显著,为未来实现硅基太赫兹调制器在近红外太赫兹-光纤混合通信系统的集成提供了一种新策略.

Freestanding reduced graphene oxide/sodium vanadate composite films for flexible aqueous zinc-ion batteries

With the booming development of portable and wearable electronic devices, flexible energy storage devices have attracted great attention. Among various energy storage devices, aqueous zinc ion batteries(ZIBs) are one of the promising candidates due to their low cost, good safety, high energy and power densities. However, the conventional cathodes of aqueous ZIBs were often prepared by mixing active materials with binders and conductive additives and then coating them onto current collectors. The resultant cathodes often suffer from unsatisfied flexibility. Herein, we fabricated freestanding reduced graphene oxide/NaV_3O_8·1.5H_2O(RGO/NVO) composite films with interlinked multilayered architecture by a vacuum filtrating process. Such composite films exhibit excellent mechanical property and high electronic conductivity. Owing to unique architecture, they display a high capacity of 410 mA h g^(-1) and excellent cycling performance up to 2000 cycles with a high capacity retention of 94%. Moreover, RGO/NVO composite films can directly serve as the cathodes of flexible aqueous ZIBs. As a proof of concept,flexible ZIBs were assembled based on the composite films. Impressively, they exhibit stable performance at different bending states, demonstrating great potential application in flexible energy storage devices.

Fiber-reinforced Three-dimensional Graphene Aerogels for Electrically Conductive Epoxy Composites with Enhanced Mechanical Properties

To enhance the mechanical properties of three-dimensional graphene aerogels with aramid fibers, graphene/organic fiber aerogels are prepared by chemical reduction of graphene oxide in the presence of organic fibers of poly（p-phenylene terephthalamide） （PPTA） and followed by freeze-drying. Thermal annealing of the composite aerogels at 1300℃ is adopted not only to restore the conductivity of the reduced graphene oxide component but also to convert the insulating PPTA organic fibers to conductive carbon fibers by the carbonization. The resultant graphene/carbon fiber aerogels （GCFAs） exhibit high electrical conductivities and enhanced compressive properties, which are highly efficient in improving both mechanical and electrical performances of epoxy composites. Compared to those of neat epoxy, the compressive modulus, compressive strength and energy absorption of the electrically conductive GCFA/epoxy composite are significantly increased by 60%, 59% and 131%, respectively.

Enhanced tribological properties of aligned graphene-epoxy composites

The random distribution of graphene in epoxy matrix hinders the further applications of grapheneepoxy composites in the field of tribology.Hence,in order to fully utilize the anisotropic properties of graphene,highly aligned graphene-epoxy composites(AGEC)with horizontally oriented structure have been fabricated via an improved vacuum filtration freeze-drying method.The frictional tests results indicated that the wear rate of AGEC slowly increased from 5.19x10^(-6)mm^(3)/(N-m)to 2.87x10^(-5)mm^(3)/(N-m)with the increasing of the normal load from 2 to 10 N,whereas the friction coefficient(COF)remained a constant of 0.109.Compared to the neat epoxy and random graphene-epoxy composites(RGEC),the COF of AGEC was reduced by 87.5%and 71.2%,and the reduction of wear rate was 86.6%and 85.4%at most,respectively.Scanning electron microscope(SEM)observations illustrated that a compact graphene self-lubricant film was formed on the worn surface of AGEC,which enables AGEC to possess excellent tribological performance.Finally,in light of the excellent tribological properties of AGEC,this study highlights a pathway to expand the tribological applications of graphene-epoxy composites.

Effect of multilayer graphene/nano-Fe2O3 composite additions on dry sliding wear behavior of titanium matrix composites

The wear tests of titanium matrix composites(TMCs)at the loads of 50,100,120,and 150 N were carried out with an MMW-1 vertical universal friction and wear tester to study the addition of multilayer graphene(MLG)/nano-Fe2O3 composites(0,0.1,0.2,0.3,0.4,and 0.5 g)on the dry sliding wear behavior of TMCs.TMCs presented a marked variation in wear loss as a function of the amount of MLG/Fe2O3 addition,and a significant decrease in the friction coefficient was obtained,reducing this parameter up to 50%.With the rise and fall of wear loss,TMCs underwent a transition from severe wear to mild wear.These phenomena were attributed to the existence of a protective lubricating film,which prevented the surface from coming in direct contact,and the lubricating film was 15-20μm thick and made up of MLG/Fe2O3(1:2)nanocomposites.Its structure was speculated to be similar to a rolling wood.

环氧树脂/石墨烯复合材料的制备及其性能

为提高环氧树脂的导电性能和电磁屏蔽性能,将石墨烯作为导电填料添加到环氧树脂中制备了环氧树脂/石墨烯复合材料,并研究了石墨烯含量对复合材料力学性能及微观形貌的影响。结果表明:添加石墨烯使复合材料的电导率和电磁屏蔽效率显著提高。石墨烯含量为10.0%(w)时,复合材料的电导率和电磁屏蔽效率分别为1.34×10^(-3)S/m,2.95 dB;石墨烯含量为7.5%(w)时,复合材料的冲击强度为1.67 kJ/m^(2),较纯环氧树脂提高了50%。

新型石墨烯复合材料在金属防腐蚀领域的研究进展

介绍了石墨烯复合材料的防腐蚀原理,总结了国内外石墨烯和氧化石墨烯防护膜在金属防腐蚀领域的研究现状及存在的问题。简要介绍了改性石墨烯复合涂层的制备工艺及其效果。从无机纳米氧化物/石墨烯复合材料、聚苯胺/石墨烯复合材料、聚氨酯/石墨烯复合材料和硅烷/石墨烯复合材料等四方面综述了改性石墨烯复合材料在金属防护中的应用,指出目前我国石墨烯复合材料存在的主要问题,并对石墨烯复合材料在金属防腐蚀领域的研究方向进行了展望。

石墨烯增强环氧树脂胶黏剂的研究进展

环氧树脂胶黏剂具有较高的强度、硬度和耐化学腐蚀性,故其应用越来越广泛。但它也存在一些缺点,如热稳定性差、导电性差等。二维石墨烯是一种具有高强度、高导电性、大比表面积等优异性能的材料,在环氧树脂胶黏剂中添加石墨烯可增强其性能。综述了石墨烯-环氧复合材料的制备及石墨烯对环氧胶黏剂的影响,展望了石墨烯-环氧复合材料的应用前景。未来,在石墨烯-环氧复合材料合成与加工过程中还需解决石墨烯的均匀分散、生产的可扩展性、与环氧树脂及固化剂的相容性等问题。

石墨烯/碳纳米管复合电热膜制备过程工艺优化及预测模型

目的本文利用响应面法和神经网络遗传算法对石墨烯/碳纳米管复合电热膜的固化工艺进行优化,并对2种方法的优化结果进行比较,为复合电热膜制备提供了最佳的工艺参数。方法通过单因素实验探讨浆料定量、固化温度和固化时间对复合电热膜体积电阻率的影响,在此基础上进行BB试验设计,在BB试验结果上进行响应面法(RSM)和BP神经网络分析及优化。结果单因素实验结果表示随电热膜定量增加,体积电阻率先下降后上升,随着固化温度的升高或固化时间增加,体积电阻率逐渐下降直至趋于稳定。对BB响应面法和GA-BP遗传神经网络法优化获得的最佳工艺进行实验验证,GA-BP遗传神经网络模型优化的结果相对误差较小为1.06%,因此得出最佳固化工艺参数:定量为0.056 g/cm^(2)、固化温度为85.71℃、固化时间为11.13 h。该研究结果对石墨烯碳纳米管复合电热膜的制备工艺具有参考价值。结论通过响应面方差分析表明,定量、固化温度和固化时间三因素对体积电阻率既有显著的线性影响,也有极其显著的平方影响。BP神经网络预测模型的准确性很好,可用于石墨烯/碳纳米管复合电热膜体积电阻率的预测。