Greatly enhanced corrosion/wear resistances of epoxy coating for Mg alloy through a synergistic effect between functionalized graphene and insulated blocking layer

The poor corrosion and wear resistances of Mg alloys seriously limit their potential applications in various industries.The conventional epoxy coating easily forms many intrinsic defects during the solidification process,which cannot provide sufficient protection.In the current study,we design a double-layer epoxy composite coating on Mg alloy with enhanced anti-corrosion/wear properties,via the spin-assisted assembly technique.The outer layer is functionalized graphene(FG)in waterborne epoxy resin(WEP)and the inner layer is Ce-based conversion(Ce)film.The FG sheets can be homogeneously dispersed within the epoxy matrix to fill the intrinsic defects and improve the barrier capability.The Ce film connects the outer layer with the substrate,showing the transition effect.The corrosion rate of Ce/WEP/FG composite coating is 2131 times lower than that of bare Mg alloy,and the wear rate is decreased by~90%.The improved corrosion resistance is attributed to the labyrinth effect(hindering the penetration of corrosive medium)and the obstruction of galvanic coupling behavior.The synergistic effect derived from the FG sheet and blocking layer exhibits great potential in realizing the improvement of multi-functional integration,which will open up a new avenue for the development of novel composite protection coatings of Mg alloys.

A“bricks-and-mortar”structured graphene oxide/polyvinyl alcohol coating:Enhanced water interfacial lubrication and durability

Coatings serve as ideal protective films for mechanical systems,providing dependable as well as efficient lubrication because of their unique structure along with outstanding tribological characteristics.Inspired by the“bricks-and-mortar”structure,we prepared layered graphene oxide(GO)composite finishes strengthened with polyvinyl alcohol(PVA)and borax.Our study demonstrates that the tribological properties of the GO-based coating on 304 stainless steel(SS304)are potentially greatly affected through PVA,GO,and annealing.By optimizing the composition,we achieved the PVA_(40 wt%)/GO_(0.01 wt%)/borax composite coating,which exhibited the lowest average coefficient of friction(COF)of 0.021±0.003(a 97.86%reduction compared to control SS304)with minimal wear and abrasion even in a water environment.We found that the enhanced mechanical characteristics as well as elastic recovery within the coating were attributed to the hydrogen bonds and cross-linking between PVA and borax,which led to stress distribution.Reduced friction was further aided by the formation of a hydrated layer at the friction interface.As a result,the coating demonstrated remarkable durability,maintaining a low COF during long sliding distances(576 m,28,800 cycles,significantly longer than previously reported)without breaking.

Graphene-calcium carbonate coating to improve the degradation resistance and mechanical integrity of a biodegradable implant

Biodegradable implants are critical for regenerative orthopaedic procedures,but they may suffer from too fast corrosion in human-body environment.This necessitates the synthesis of a suitable coating that may improve the corrosion resistance of these implants without compromising their mechanical integrity.In this study,an AZ91 magnesium alloy,as a representative for a biodegradable Mg implant material,was modified with a thin reduced graphene oxide(RGO)-calcium carbonate(CaCO_(3))composite coating.Detailed analytical and in-vitro electrochemical characterization reveals that this coating significantly improves the corrosion resistance and mechanical integrity,and thus has the potential to greatly extend the related application field.

Microstructure Regulation and Combustion Performance Optimization of PVDF/Al Composite Powder by Non-covalent Functionalized Graphenes

Graphene prepared by non-covalent modification of sulfonated poly(ether-ether-ketone)(SPG)was combined with polyvinylidene fluoride(PVDF)/Al to improve the PVDF/Al thermal conductivity while reducing the effect of the thermal resistance at the graphene-polymer interface.The regulation rule of SPG with different contents on the energy release of fluorine-containing system was studied.When the content of SPG is 4%,the peak pressure and rise rate of SPG/PVDF/Al composite powder during ignition reach the maximum of 4845.28 kPa and 8683.58 kPa/s.When the content of SPG is 5%,the PVDF/Al composite powder is completely coated by SPG,and the calorific value of the material reachs the maximum of 29.094 kJ/g.Through the design and micro-control of the composite powder,the calorific value of the material can be effectively improved,but the improvement of the mass release rate still depends on the graphene content and surface modification state.

The role of graphene coating on cordierite-supported Pd monolithic catalysts for low-temperature combustion of toluene

In the present work,a Pd/graphene/cordierite(Pd/Gr/Cor)composite was prepared as a monolithic catalyst for low-temperature combustion of toluene.We mainly focused on understanding the role of graphene coating through investigation of catalytic performance and adsorption behavior of the composite.Compared with the traditional Pd/Cor catalyst without graphene coating,Pd/Gr/Cor catalyst delivered much higher activity and stability for toluene catalytic combustion in both dry and moist conditions.Transmission electron microscopy(TEM)and hydrophobic characterizations indicated that graphene coating can considerably improve the dispersity of Pd nanoparticles and enhance the hydrophobicity of the cordierite support.The adsorption behavior of the above two catalysts,including adsorption isothermal,adsorption kinetics,and adsorption thermodynamics were carefully investigated.The simulation results indicated that a large amount of toluene was adsorbed on graphene surface through relatively weak interaction,whereas only a relatively small amount of toluene was adsorbed on Pd surface with strong affinity.The adsorption thermal calculation indicated that the adsorption of toluene on graphene was a process with reduced entropy,indicating highly-ordered assembly of toluene molecular on graphene.It is the significant concentration and affinity gap between graphene and Pd that ensures a simultaneously and rapid transfer of toluene during the reaction process.

Scalable and fast fabrication of graphene integrated micro-supercapacitors with remarkable volumetric capacitance and flexibility through continuous centrifugal coating

Microscale electrochemical energy storage devices,e.g., micro-supercapacitors(MSCs),possessing tailored performance and diversified form factors of lightweight,miniaturization,flexibility and exceptional integration are highly necessary for the smart power sources-unitized electronics.Despite the great progress,the fabrication of MSCs combining high integration with high volumetric performance remains largely unsolved.Herein,we develop a simple,fast and scalable strategy to fabricate graphene based highly integrated MSCs by a new effective continuous centrifugal coating technique.Notably,the resulting highly conductive graphene films can act as not only patterned microelectrodes but also metal-free current collectors and interconnects,endowing modular MSCs with high integrity,remarkable flexibility,tailored voltage and capacitance output,and outstanding performance uniformity.More importantly,the strong centrifugal force and shear force generated in continuous centrifugal coating process lead to graphene films with high alignment,compactness and packing density,contributing to excellent volumetric capacitance of ~31.8 F cm^(-3) and volumetric energy density of ~2.8 mWh cm^(-3),exceeding most reported integrated MSCs.Therefore,our work paves a novel way for simple and scalable fabrication of integrated MSCs and offers promising opportunities as standalone microscale power sources for new-generation electronics.

One-step electrodeposition to fabricate robust superhydrophobic silver/graphene coatings with excellent stability

A facile method was proposed to prepare stretchable silver-based composite coatings with excellent conductivity and stability for flexible electronics.Silver coating was firstly deposited on thermoplastic polyurethane(TPU)elastomer rubber surface via two-component spraying technique,then the superhydrophobic surface was obtained by one-step electrodeposition of cerium compounds(CeM)and graphene nanosheets(GNS)to produce Ag/CeM/GNS composite coatings.The obtained Ag/CeM/GNS composite coatings maintained high conductivity after experiencing bending cycles and stretching cycles.Furthermore,the as-prepared Ag/CeM/GNS composite coatings showed excellent self-cleaning and anti-fouling properties,and the corrosion resistance has improved significantly compared to the original Ag coating.In addition,the Ag/CeM/GNS composite coatings could drive the circuit normally in the states of tensile,bending and twisting deformation,showing excellent mechanical stability and applicability.As a result,it is believed that the prepared Ag/CeM/GNS composite coatings with excellent conductivity and stability have promising applications for flexible electronics in harsh conditions.

Curing Kinetics, Mechanical Properties and Thermal Stability of Epoxy/Graphene Nanoplatelets(GNPs) Powder Coatings

Epoxy/graphene nanoplatelets（GNPs） powder coatings were fabricated using ultrasonic predispersion of GNPs and melt-blend extrusion method. The isothermal curing kinetics of epoxy/GNPs powder coating were monitored by means of real-time Fourier transform infrared spectroscopy（FT-IR） with a heating cell. The mechanical properties of the epoxy/GNPs cured coatings had been investigated, by evaluating their fracture surfaces with field-emission scanning electron microscopy（FE-SEM） after three-point-bending tests. The thermal stability of the epoxy/GNPs cured coatings was studied by thermo-gravimetric analysis（TGA）. The isothermal curing kinetics result showed that the GNPs would not affect the autocatalytic reaction mechanism, but the loading of GNPs below 1.0 wt % additive played a prompting role in the curing of the epoxy/GNPs powder coatings. The fracture strain, fracture toughness and impact resistance of the epoxy/GNPs cured coatings increased dramatically at low levels of GNPs loading（1 wt %）, indicating that the GNPs could improve the toughness of the epoxy/GNPs powder coatings. Furthermore, from FE-SEM studies of the fracture surfaces, the possible toughening mechanisms of the epoxy/GNPs cured coatings were proposed. TGA result showed that the incorporation of GNPs improved the thermal stability of the cured coatings. Hence, the GNPs modified epoxy can be an efficient approach to toughen epoxy powder coating along with improving their thermal stability.

Influence of graphene on the anti-corrosion performance of epoxy-based coatings

In this work, graphene-modified epoxy-based anti-corrosion coatings were prepared and the influence of graphene on the anti-corrosion performance of the epoxy-based coatings was investigated with water contact angle test ,chemical solution immersion test, and electrochemical test. The water contact angle and chemical solution resistance of the epoxy-based coatings were improved with an increase in graphene content from 0 to 0.4%. These results prove that addition of graphene can significantly improve the hydrophobicity and impermeability of epoxy- based coatings. However, when the graphene content was increased to 0.5%, the performance of the epoxy-based coatings decreased because of graphene aggregation. Tafel polarization results show that graphene addition can significantly reduce the corrosion current density and corrosion potential of epoxy-based coatings, which enhance their anti-corrosion performance.

Effect of Dip Coating Process on the Performance of Graphene/Spandex Yarn Strain Sensor

This study presented the effect of the concentration of graphene in the dispersion,the type of polyvinyl alcohol(PVA)and the surfactant on the sensing properties of dip-coated graphene/spandex yarns as resistance strain sensors.Experimental results showed that the addition of styrene-acrylic emulsion surfactant facilitates the dispersion of graphene and then improves the conductivity and sensing performance,and the sensitivity is up to 91.The conductivity and sensing properties of graphene/spandex yarns at 2%graphene dispersion are better than those at 1%graphene dispersion.When the conductive yarn treated by 2%graphene dispersion is stretched to 50%,the sensitivity is up to 29,the repeatability is good,and the hysteresis is low.In terms of the binding agent,PVA as a high alcoholysis and large polymerization decreases the sensitivity,repeatability as well as the hysteresis.

Anticorrosive Coatings Based on Few-Layer Graphene

In this paper the anticorrosive properties of the few-layer graphene nanostructures were investigated. On the surface ofcopper and nickel plates the few-layer graphene nanostructures were formed using the CVD （chemical vapor deposition） method.After that, these plates were exposed to the temperature in the air atmosphere. The results of elemental analysis, performed by theEDS （energy dispersive spectroscopy） method showed that the few-layer graphene coated metal plates proved to be more resistant tooxidation than bare metal plates. In addition, we presented computer models and theoretical calculations of the studied systems,performed by the DFT （density functional theory） and MD （molecular dynamics） methods. These results combined with experimentaldata show the high effectiveness of the protective action of the few-layer graphene against metal corrosion.

CFGO@PVDF复合纳滤膜的结构调控及截留性能

以聚偏氟乙烯(PVDF)和羧基化氧化石墨烯(CFGO)为原料,制备了高亲水性和高脱盐效能的CFGO@PVDF复合纳滤膜(GONF膜),通过优化制备条件,结合微观结构及形貌表征,获得了GONF膜的最佳制备条件,实现了复合纳滤膜性能的显著提升。结果表明,与传统PVDF纳滤膜(CNF膜)相比,CFGO@PVDF复合纳滤膜展现了更深的孔通道和显著提高的亲水性,其纯水通量可达13.1 L/(m^(2)·h·bar)(1 bar=100 kPa),是CNF膜的2.5倍以上。此外,GONF膜的晶型实现了由α相向β相转化,膜表面的含氧官能团含量增加,大幅提升了对2 g/L不同盐溶液的截留率,其中对Na_(2)SO_(4)和MgSO_(4)的截留率分别高达96%和95%以上,且60 min内未发生明显衰减。研究成功研制了一种高水通量、高效稳定脱盐的CFGO@PVDF复合纳滤膜,为纳滤膜的设计与制备提供了新的思路,也为解决全球水处理问题提供了有效的技术思路。

Two-Dimensional Graphitic Carbon-Nitride(g-C_(3)N_(4))-Coated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) Cathodes for High-Energy-Density and Long-Life Lithium Batteries

High-capacity nickel-rich layered oxides are promising cathode materials for high-energy-density lithium batteries.However,the poor structural stability and severe side reactions at the electrode/electrolyte interface result in unsatisfactory cycle performance.Herein,the thin layer of two-dimensional(2D)graphitic carbon-nitride(g-C_(3)N_(4))is uniformly coated on the LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(denoted as NCM811@CN)using a facile chemical vaporization-assisted synthesis method.As an ideal protective layer,the g-C_(3)N_(4)layer effectively avoids direct contact between the NCM811 cathode and the electrolyte,preventing harmful side reactions and inhibiting secondary crystal cracking.Moreover,the unique nanopore structure and abundant nitrogen vacancy edges in g-C_(3)N_(4)facilitate the adsorption and diffusion of lithium ions,which enhances the lithium deintercalation/intercalation kinetics of the NCM811 cathode.As a result,the NCM811@CN-3wt%cathode exhibits 161.3 mAh g^(−1)and capacity retention of 84.6%at 0.5 C and 55°C after 400 cycles and 95.7 mAh g^(−1)at 10 C,which is greatly superior to the uncoated NCM811(i.e.129.3 mAh g^(−1)and capacity retention of 67.4%at 0.5 C and 55°C after 220 cycles and 28.8 mAh g^(−1)at 10 C).The improved cycle performance of the NCM811@CN-3wt%cathode is also applicable to solid–liquid-hybrid cells composed of PVDF:LLZTO electrolyte membranes,which show 163.8 mAh g^(−1)and the capacity retention of 88.1%at 0.1 C and 30°C after 200 cycles and 95.3 mAh g^(−1)at 1 C.

DCMC/PEI涂层改性PVDF超滤膜的分离和抗污染性能研究

为了减轻膜污染和提高膜的分离性能,采用一步沉积法将双醛羧甲基纤维素(DCMC)和聚乙烯亚胺(PEI)涂覆在聚偏氟乙烯(PVDF)超滤膜的表面.DCMC上的醛基可以和PEI上的氨基在膜表面发生席夫碱反应,形成化学交联.与纯PVDF膜相比,DCMC/PEI涂层改性膜具有更高的亲水性(水接触角<40°)和收缩的孔径(平均孔径≈20.32 nm).以腐殖酸(HA)、牛血清白蛋白(BSA)和海藻酸钠(SA)为代表,研究DCMC/PEI涂层改性膜的分离和抗污染性能.涂层膜对HA、BSA和SA具有超过93%的截留率和通量恢复率(FRR),相比原PVDF膜提升了38%.这种兼具高分离和抗污染性能的纤维素涂层膜,为废水净化提供了新的思路.

Cr颗粒对Ni-Graphene复合沉积层组织结构及性能的优化

目的电沉积技术制备Ni-Cr-Graphene复合沉积层,调查不同Cr颗粒浓度对复合沉积层组织结构及性能的优化影响。方法利用电沉积技术在镍铝青铜(NAB)表面制备出Ni-Cr-Graphene复合沉积层。采用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)与拉曼光谱仪(Raman),对复合沉积层的形貌、成分与组织结构(晶粒大小、结晶形状及结晶织构)进行表征,并采用显微硬度计与电化学工作站分别对沉积层的硬度及耐腐蚀性能进行调查。结果Graphene颗粒使得纯Ni沉积层中的Ni晶粒尺寸由175.3 nm减小到Ni-0Cr-4Graphene沉积层中的Ni晶粒尺寸60.5nm。随着Cr颗粒质量浓度进一步从0g/L增加到100 g/L,Ni-Cr-Graphene复合沉积层中的Cr质量分数从0%增加到23.8%,且Ni晶粒尺寸进一步减小到Ni-100Cr-4Graphene沉积层的29.1nm,Ni[200]结晶织构被消除。Graphene与Cr颗粒显著提高了Ni-CrGraphene复合沉积层的表面硬度,所有复合沉积层的显微硬度均高于纯Ni沉积层(260.1HV0.2),且在100 g/L Cr颗粒浓度下,沉积层平均显微硬度为489.8HV0.2。同时Graphene与Cr颗粒改善了Ni-Cr-Graphene复合沉积层在3.5%NaCl溶液中的耐腐蚀性能,在100 g/L Cr颗粒浓度下,复合沉积层的自腐蚀电位(Ecorr)为-0.21 V,自腐蚀电流密度(Jcorr)为0.25μA/cm^2,其相对纯Ni沉积层Jcorr(7.01μA/cm^2)降低了1个数量级。结论溶液中Cr颗粒浓度的增加引起了Ni-Cr-Graphene复合沉积层中Cr含量的增加,使得更多Cr颗粒与Graphene颗粒共同作为Ni金属结晶形核点,促进了Ni的晶粒细化与织构转变,最终提高了复合沉积层的硬度与耐腐蚀性能。

High-efficiency preparation of multifunctional conjugated electrospun graphene doped PVDF/CF yarns for energy harvesting and human movement monitoring in TENG textile

Portable power is an effective solution to realize self-powered sensors for wearable devices,promoting future sustainable development.Membrane-based triboelectric nanogenerators(M-TENGs)have emerged as a promising technology for harvesting biomechanical energy from human motion owing to their advantages,such as simple structure,lightweight design,and efficient energy conversion.However,the poor durability,low adaptability,and un-washability of two-dimensional membrane materials have largely hindered their application in wearable electronics.In this study,we propose a sheath-core polyvinylidene fluoride(PVDF)/graphene(G)-carbon fiber(CF)yarn fabricated via conjugate electrospinning,comprising a commercial CF core and an electrospun graphene-doped PVDF sheath,which improves the fatigue resistance of electrospun nanofiber films under prolonged friction and keeps a high degree of freedom.The resulting electronic textile,woven with the large-scale electrospun PVDF/G-CF yarn,demonstrates a remarkable power density of 25.5 mW·m^(-2).The tight distribution of PVDF/G nanofibers on the textile surface ensures excellent softness,washability,and durability.Furthermore,the electrospun PVDF/G-CF textile exhibits significant potential in pressure sensing,self-powered operation,and motion detection,making it highly suitable for wearable electronics applications.

A reduced graphene oxide-coated conductive surgical silk suture targeting microresistance sensing changes for wound healing

Conventional sutures used in surgical procedures often lack the capability to effectively monitor physical and chemical activities or the microbial environment of surgical wounds due to their inadequate mechanical properties,insufficient electrical accuracy and unstability.Here,we present a straightforward layer-by-layer coating technique that utilizes 3-glycidoxypropyltrimethoxysilane(CA),graphene oxide(GO),and ascorbic acid(AA)to develop conductive silk-based surgical sutures(CA-rGSFS).The CA-rGSFS feature a continuous reduced graphene oxide(rGO)film on their surface,forming robust hydrogen bonds with silk fibroin.The reduction process of rGO is confirmed through Raman analysis,demonstrating an enhanced D peak to G peak ratio.Notably,the CA-rGSFS exhibit exceptional mechanical properties and efficient electron transmission,with a knot-pull tensile strength of 2089.72±1.20 cN and an electrical conductivity of 130.30±11.34 S/m,respectively,meeting the requirements specified by the United States Pharmacopeia(USP)for 2-0 sutures.These novel CA-rGSFS demonstrate the ability to accurately track resistance changes in various fluid environments with rapid response,including saline,intestinal,and gastric fluids.The suture also retains remarkable stretchablility and stability even after enduring 3000 tensile cycles,highlighting their potential for precise surgical site monitoring during the wound healing process.

Core@shell sulfur@polypyrrole nanoparticles sandwiched in graphene sheets as cathode for lithium–sulfur batteries

A nano sulfur-based composite cathode material featured by uniform core@shell-structured sulfur@polypyrrole nanoparticles sandwiched in three-dimensional graphene sheets conductive network（S@PPy/GS） is fabricated via a facile solution-based method. The S@PPy nanoparticles are synthesized by in situ chemical oxidative polymerization of pyrrole on the surface of sulfur particles,and then graphene sheets are covered outside the S@PPy nanoparticles,forming a three-dimensional conductive network. When evaluating the electrochemical performance of S@PPy/GS in a lithium–sulfur battery,it delivers large discharge capacity,excellent cycle stability,and good rate capability. The initial discharge capacity is up to 1040 m Ah/g at 0.1 C,the capacity can remain 537.8 m Ah/g at 0.2 C after 200 cycles,even at a higher rate of 1 C,the specific capacity still reaches 566.5 m Ah/g. The good electrochemical performance is attributed to the unique structure of S@PPy/GS,which can not only provide an excellent transport of lithium and electron ions within the electrodes,but also retard the shuttle effect of soluble lithium polysulfides effectively,thus plays a positive role in building better lithium-sulfur batteries.

Laser-Etched Stretchable Graphene-Polymer Composite Array for Sensitive Strain and Viscosity Sensors

The ability to control surface wettability and liquid spreading on textured surfaces is of interest for extensive applications.Soft materials have prominent advantages for producing the smart coatings with multiple functions for strain sensing.Here,we report a simple method to prepare flexible hydrophobic smart coatings using graphene-polymer films.Arrays of individual patterns in the films were created by laser engraving and controlled the contact angle of small drops by pinning the contact lines in a horizontal tensile range of 0-200%.By means of experiments and model,we demonstrate that the ductility of drops is relied on the height-to-spacing ratio of the individual pattern and the intrinsic contact angle.Moreover,the change of drop size was utilized to measure the applied strain and liquid viscosity,enabling a strain sensitivity as high as 1068μm2/%.The proposed laser-etched stretchable graphene-polymer composite has potential applications in DNA microarrays,biological assays,soft robots,and so on.

基于静电纺丝法原位极化PVDF纳米纤维薄膜构建高效压电纳米发电机

全球化石能源危机和环境污染问题使得高效利用绿色、可再生清洁能源成为大势所趋.机械能因其丰富、易获取和无污染等特点被认为是理想的替代能源之一.压电纳米发电机(PENG)可以将环境中的机械能转化为电能,为电子设备提供动力.然而,传统的压电材料必须通过电极化诱导偶极子排列才能获得压电性能,增加了器件制备的工序和能耗.同时,当去除外加电场时会发生退极化效应,致使压电材料的性能稳定性下降.通过静电纺丝法纺丝过程产生的强电场和机械拉伸使聚偏二氟乙烯(PVDF)纳米纤维晶体中的偶极子定向排列,从而实现原位极化,获得了高电活性β相达78.7%的PVDF纳米纤维薄膜.基于该薄膜构建的PENG实现了机械能向电能的直接转化,其开路输出电压为1.6 V,短路输出电流为0.14μA,分别是旋涂法制备薄膜的4.5和2.6倍.PVDF-PENG通过桥式整流器在人的手指敲打60 s后可将1μF的电容器充电到2 V.在200 MΩ的外加负载下其最大输出功率为0.03μW.PVDF-PENG在连续2000次按压发电后,仍能保持约100%的输出能力,验证了其长期稳定的服役能力.最后PVDF-PENG通过采集手指轻敲的能量可点亮LED灯和驱动电子表,证明了实际应用的能力.