Free-standing flexible graphene-based aerogel film with high energy density as an electrode for supercapacitors

Two-dimensional graphene film exhibits sluggish ion diffusivity while three-dimensional(3D)graphene aerogel has low packing density and poor mechanical flexibility.Consequently,there is an urgent need for graphenebased film with both mechanical robustness and high specific capacitance.Here,we present an easy and scalable strategy for fabricating a free-standing flexible graphene-based aerogel film electrode with a two-layered structure,in which the top layer is an interconnected macroporous reduced graphene oxide/carbon nanotube(RGO/CNT)aerogel,and the bottom layer is a flexible electrospun polyacrylonitrile(PAN)nanofiber membrane.The porous 3D structure of the aerogel provides fast transport of electrolyte ions and electrons,while the nanofiber membrane provides both strong support for the aerogel and mechanical flexibility.Polypyrrole(PPy)can be uniformly loaded on RGO/CNT/PAN(RCP)composite aerogel film to provide pseudocapacitance,and nitrogen-doped RGO/CNT/carbon nanofiber(NRCC)aerogel film can be obtained by further pyrolysis.The resultant RCP@PPy-0.05//NRCC based asymmetric supercapacitor can have a maximum voltage of 1.7 V and a maximum energy density of 60.6 W h kg^-1at 850.2 W kg^-1.This indicates that free-standing graphene-based aerogel film can be used in flexible supercapacitors.     

取向碳纳米管/环氧树脂复合薄膜制备及结构与性能表征

碳纳米管(Carbon nanotube, CNT)/环氧树脂(Epoxy resin, EP)纳米复合材料中树脂含量、分布、CNT取向及其与树脂间界面结合是制备高性能纳米复合材料的关键因素。为了探究树脂分布和CNT/EP复合材料性能之间的关系,采用浮动催化化学气相沉积法制备的CNT薄膜和EP为原料,通过浸渍、牵伸、清洗和热压固化工艺制备CNT/EP复合薄膜。利用聚焦离子束结合扫描电子显微镜定性表征树脂在复合膜中的分布状态。结果表明,随着树脂含量增加,树脂在复合薄膜表面富集程度增加。在最优工艺条件下制备的纳米复合材料中CNT含量为66.14wt%, 拉伸强度和拉伸模量达到1405 MPa和46.7 GPa。      

CNT改性连续纤维增强树脂基复合材料研究进展

碳纳米管(CNT)改性连续纤维增强树脂基复合材料是实现复合材料高性能化的重要途径.本文从CNT改性纤维和复合材料层间CNT改性两个方面,论述了CNT改性连续纤维增强树脂基复合材料的改性效果,讨论了该领域的研究现状.     

不同还原温度制备RGO/MnO_2复合材料对电容增效的影响(英文)

将氧化石墨烯GO(Graphene oxide)进行热还原得到RGO(Reduced graphene oxide),通过液相法原位合成出RGO/M n O2电极复合材料。采用扫描电镜(SEM)、X射线衍射(XRD)、傅里叶红外(FT-IR)、四探针法和循环伏安测试表征分析复合材料的表面形貌、微观结构、电导率和比电容。结果表明,相较于纯Mn O2和GO/Mn O2电极材料,RGO/Mn O2复合材料比电容得到提高。热还原温度为600℃时比电容最高,为321 F·g-1。这可能是GO的加入显著降低了Mn O2的团聚程度,增大了Mn O2参与赝电容反应的活性面积。热还原得到的RGO有效提高了复合材料的电导率,其残留的含氧官能团提供了一定的赝电容。     

纳米碳管

纳米碳管 (Carbon nanotube)是 1 991年才被发现的一种碳结构。理想纳米碳管是由碳原子形成的石墨烯片层卷成的无缝、中空的管体。石墨烯的片层一般可以从一层到上百层 ,含有一层石墨烯片层的称为单壁纳米碳管 (Singlewalled carbon nanotube,SWNT) ,多于一层的则称为多壁纳米碳管 (Multi- walled carbon nanotube,MWNT)。SWNT的直径一般为 1 nm～ 6nm,最小直径大约为 0 .5nm,与 C36分子的直径相当 ,但 SWNT的直径大于 6nm以后特别不稳定 ,会发生 SWNT的塌陷 ,长度则可达几百纳米到几个微米。因为 SWNT的最小直径与富勒烯分子类…     

纳米碳/水泥基复合材料研究进展

纳米碳材料以其独特的结构及微观形貌,优异的力学、电学特性等,在信息、材料、能源、生物制药等领域引发了革命性创新。近年来,纳米碳材料以极低的掺量,表现出对水泥基复合材料微观结构、宏观力学性能的改善,同时赋予传统水泥基材料导电性、压阻性等功能特性。本文结合纳米碳材料自身形貌及表面化学特性等,综述了近年来纳米碳材料对水泥水化及微观结构的影响,纳米碳/水泥基复合材料的力学性能及压阻性等,并指出当前存在的问题及未来可能的研究方向。     

柔性纳米复合材料压阻式应变传感器的研究进展

柔性纳米复合材料,由于其优异的传感性能、良好的延展性,在压阻式应变传感器方面,受到研究者们不断的关注,主要应用于智能可穿戴,结构健康监测等领域.本文主要从结构设计、制备方法、应用前景三方面,综述了近年来国内外对复合材料压阻式应变传感器在材料选取及结构设计下传感器性能的研究成果及研究进展.首先分析了压阻式传感器的性能参数...     

SiC纤维表面碳涂层及其SiCf/SiC复合材料性能研究

采用先驱体转化法(PIP)以酚醛和沥青为先驱体在SiC纤维表面涂覆碳层,并制备SiCf/SiC复合材料;优化了两种碳涂层制备工艺;分析了涂层后纤维的表面形貌并测试涂层厚度;研究了两种碳涂层对两种SiC纤维(普通和含铝)及复合材料力学性能的影响.     

利用维生素C和茶多酚还原氧化石墨烯及其表征

采用改进的Hummers法制备氧化石墨烯(Graphene oxide,GO),以环境友好和具有较强还原能力的茶多酚和维生素C为还原剂还原GO制备还原氧化石墨烯(Reduced graphene oxide,RGO).傅里叶变换红外光谱(FT-IR)测得还原后的RGO的含氧官能团吸收峰明显降低,在X射线衍射图谱(XRD)中观察到还原后的RGO的吸收峰位置的变化,原子力显微镜(AFM)观察到样品的厚度.这些表征数据表明实验采用的两种还原剂成功还原了GO制备出RGO.     

碳纳米管-玻璃纤维/环氧层板双真空灌注工艺及性能

针对碳纳米管(CNT)-玻璃纤维/环氧树脂体系, 采用传统的真空灌注工艺(VARIM)和双真空灌注工艺(DVARIM)制备复合材料层板, 分析了不同工艺方法下层板缺陷状况, 测试了层板的弯曲性能和层间剪切性能, 并结合树脂性能和纤维/树脂界面粘结状况观察, 探讨了DVARIM对CNT分布的影响及碳管的增强机制。结果表明: 与传统的VARIM相比, DVARIM能增加纤维的间距, 提高树脂对纤维的浸润能力, 减小纤维束内的孔隙缺陷; 添加质量分数为0.05％的酸化CNT后层板性能提高, 而且采用DVARIM性能提高更明显; 不同灌注工艺对CNT的分布产生影响, 从而改变了CNT对纤维/树脂界面粘接的影响, 同时这种影响与织物结构的紧密程度有关。      

An assessment of the science and technology of carbon nanotube-based fibers and composites

This paper examines the recent advancements in the science and technology of carbon nanotube (CNT)-based fibers and composites. The assessment is made according to the hierarchical structural levels of CNTs used in composites, ranging from 1-D to 2-D to 3-D. At the 1-D level, fibers composed of pure CNTs or CNTs embedded in a polymeric matrix produced by various techniques are reviewed. At the 2-D level, the focuses are on CNT-modified advanced fibers, CNT-modified interlaminar surfaces and highly oriented CNTs in planar form. At the 3-D level, we examine the mechanical and physical properties CNT/polymer composites, CNT-based damage sensing, and textile assemblies of CNTs. The opportunities and challenges in basic research at these hierarchical levels have been discussed.     

Simultaneous global and local strain sensing in SWCNT-epoxy composites by Raman and impedance spectroscopy

Polymer composites can be benefited in many ways through the addition of carbon nanotubes (CNT). For instance, CNT can build up a percolated network within the polymer matrix, which results in a composite material with electrical conductivity and piezoresistive characteristics. This has very important implications for the realization of self-stress sensing structural composites. Moreover, the remarkable optical and transport properties of CNT permit to obtain information about the stress state of the composite at different scales. In the present work, the local and global stress response of SWCNT-epoxy composites is characterised by simultaneous Raman spectroscopic and electrical measurements on nanocomposite specimens submitted to different levels of surface strain. Both the Raman G′-band resonance frequency and the electrical resistance of the composite are found to change monotonically with strain until an inflection point is reached at ∼1.5% strain. Increased sensitivity of the piezoresistive network and lower load transfer efficiency occur beyond this strain level, and are considered to be the result of CNT slippage from the polymer. The reversibility of the stress sensitivity of the composites is verified by performing cyclic loading tests. Hysteresis loop are found to develop earlier on the Raman curves as in the resistance curves, which indicates that even at low strain levels, permanent damage is induced in the vicinity of carbon nanotubes. The use of Raman spectroscopy in combination with electrical methods provides a further insight on the stress sensing capabilities of CNT and the factors which affect the sensitivity and reproducibility of this behaviour.     

Composites get smart

Intrinsically smart structural composites are multifunctional structural materials which can perform functions such as sensing strain, stress, damage or temperature; thermoelectric energy generation; EMI shielding; electric current rectification; and vibration reduction. These capabilities are rendered by the use of materials science concepts to enhance functionality without compromising structural properties. They are not achieved by the embedding of devices in the structure. Intrinsically smart structural composites have been attained in cement-matrix composites containing short electrically conducting fibers and in polymer-matrix composites with continuous carbon fibers. Cement-matrix composites are important for infrastructure, while polymer-matrix composites are useful for lightweight structures.Smart structures are important because of their relevance to hazard mitigation, structural vibration control, structural health monitoring, transportation engineering, thermal control, and energy saving. Research on smart structures has emphasized the incorporation of various devices in a structure for providing sensing, energy dissipation, actuation, control or other functions. Work on smart composites has focused on the incorporation of a functional material or device in a matrix material for enhancing the smartness or durability, while that on smart materials has studied materials (e.g. piezoelectric) used for making relevant devices. However, relatively little attention has been given to the development of structural materials (e.g. concrete and composites) that are inherently able to provide some of the smart functions, so that the need for embedded or attached devices is reduced or eliminated, thereby lowering cost, enhancing durability, increasing the smart volume, and minimizing mechanical property degradation (which usually occurs in the case of embedded devices).     

Carbon fiber/epoxy composite property enhancement through incorporation of carbon nanotubes at the fiber–matrix interphase – Part I: The development of carbon nanotube coated carbon fibers and the evaluation of their adhesion

A new method to realize the uniform coating of carbon nanotubes (CNTs) to carbon fibers (CFs) has been developed, which enables the scalable fabrication of CNT containing CF/epoxy composites. In this method, CNTs are treated by cationic polymers, then, the CNTs are coated to CFs by immersion into a CNT/water suspension. Good dispersion is achieved by repulsive force between positively charged CNTs and uniform coating of the CNTs is achieved by attractive forces between positively charged CNTs and negatively charged CFs. It is found that the use of specific cationic polymers including polyethyleneimine (PEI) results in stable CNT/water suspensions, and uniform coating of the CNTs. Single fiber fragmentation tests of the CF/epoxy composites were conducted to evaluate the strength of interface and interphase under shear loading. The results show that the combination of epoxy resin sizing and PEI treated CNT coating to CFs results in high interfacial shear strength.     

Effect of carbon nanotubes on the interfacial shear strength of T650 carbon fiber in an epoxy matrix

The interfacial shear strength of carbon nanotube coated carbon fibers in epoxy was studied using the single-fiber composite fragmentation test. The carbon fibers were coated with carbon nanotubes (CNT) on the fiber surface using thermal chemical vapor deposition (CVD). The CVD process was adjusted to produce two CNT morphologies for the study: radially aligned and randomly oriented. The purpose of the CNT coating was to potentially produce a multifunctional structural composite. Results of the single-fiber fragmentation tests indicate an improvement in interfacial shear strength with the addition of a nanotube coating. This improvement can most likely be attributed to an increase in the interphase yield strength as well as an improvement in interfacial adhesion due to the presence of the nanotubes.     

Effect of phenoxy-based coating resin for reinforcing pitch carbon fibers on the interlaminar shear strength of PA6 composites

Carbon fiber-reinforced thermoplastic composites have not been considered as constituent materials for structural parts due to the poor interfacial adhesion between the fiber and the thermoplastic matrix. In this work, polyamide 6 (PA6) composites with pitch carbon fibers (pCF) were fabricated by alternatively stacking PA6 films and pCF fabrics followed by being pressed. In order to improve the interfacial adhesion, phenoxy resin-based materials were coated on the surface of the fiber. The surface analyses of the fiber were carried out by XPS, TGA and dynamic contact angle method. Interlaminar shear strength (ILSS) of the composites was measured to evaluate the effect of the coating materials. The results showed that the composites with the coated pCF had higher ILSS than that with neat pCF by more than 20%. This indicated that a proper coating material can improve mechanical properties of the PA6 composites, which can be applied to the structural parts.     

改性酚醛树脂处理剂对石英纤维增强芳基乙炔复合材料性能的影响

采用改性酚醛树脂作为石英纤维表面处理剂来提高石英纤维增强芳基乙炔复合材料(SF/PAA)界面性能。通过性能测试,研究处理剂对力学性能和介电性能的影响。通过XPS和SEM分析方法,研究了酚醛树脂表面处理剂对复合材料界面官能团变化和微观形貌的影响。性能测试结果表明改性酚醛树脂处理剂可以显著提高PAA复合材料的力学性能和介电性能。XPS分析结果表明酚醛树脂处理后的石英纤维表面与酚醛树脂发生了化学反应,SEM研究表明酚醛树脂处理后的复合材料界面粘结性能得到显著提高。     

A facile method for preparing CNT-grafted carbon fibers and improved tensile strength of their composites

Carbon nanotube (CNT)-grafted carbon fibers (CFs) have emerged as new reinforcements for improving the mechanical properties of CF-reinforced composites but such enhancement in macroscale composites has not been realized. This paper reports a facile method for preparing CNT-grafted CFs and improving the tensile strength of their composites. A CNT/polyacrylonitrile solution was sprayed onto the surface of the CF woven fabrics, and the CNTs were grafted by a thermal treatment at 300 °C. CNT-grafted CF composites were fabricated using the CNT-grafted CF woven fabrics using a vacuum-assisted resin transfer molding process with epoxy resin. The CNT-grafted CF composite exhibited 22% enhancement in the tensile strength compared to that of the pristine CF composite. Fracture surfaces of the CNT-grafted CF composites showed that the grafted CNTs obstructed the propagation of micro-cracks and micro-delamination around the CFs and also yarn boundaries, resulting in improved tensile strength of CNT-grafted CF composites.     

Concept and model of a piezoelectric structural fiber for multifunctional composites

The use of piezoceramic materials for structural sensing and actuation is a fairly well developed practice that has found use in a wide variety of applications. However, just as advanced composites offer numerous benefits over traditional engineering materials for structural design, actuators that utilize the active properties of piezoelectric fibers can improve upon many of the limitations encountered when using monolithic piezoceramic devices. Several new piezoelectric fiber composites have been developed, however almost all studies have implemented these devices such that they are surface-bonded patches used for sensing or actuation. This paper will introduce a novel active piezoelectric structural fiber that can be laid up in a composite material to perform sensing and actuation, in addition to providing load bearing functionality. The sensing and actuation aspects of this multifunctional material will allow composites to be designed with numerous embedded functions including, structural health monitoring, power generation, vibration sensing and control, damping, and shape control through anisotropic actuation. A one-dimensional micromechanics model of the piezoelectric fiber will be developed to characterize the feasibility of constructing structural composite lamina with high piezoelectric coupling. The theoretical model will be validated through finite element (FE) modeling in ABAQUS. The results will show that the electromechanical coupling of a fiber-reinforced polymer composite incorporating the active structural fiber (ASF) could be more than 70% of the active constituent.