Effects of Conductive Carbon Black on Thermal and Electrical Properties of Barium Titanate/Polyvinylidene Fluoride Composites for Road Application

In the field of roads,due to the effect of vehicle loads,piezoelectric materials under the road surface can convert mechanical vibration into electrical energy,which can be further used in road facilities such as traffic signals and street lamps.The barium titanate/polyvinylidene fluoride(BaTiO_(3)/PVDF)composite,the most common hybrid ceramic-polymer system,was widely used in various fields because the composite combines the good dielectric property of ceramic materials with the good flexibility of PVDF material.Previous studies have found that conductive particles can further improve the dielectric and piezoelectric properties of other composites.However,few studies have investigated the effect of conductive carbon black on the dielectric and piezoelectric properties of BaTiO_(3)/PVDF composites.In this study,BaTiO_(3)/PVDF/conductive carbon black composites were prepared with various conductive carbon black contents based on the optimum ratio of BaTiO_(3)to PVDF.The effects of conductive carbon black content on the morphologies,thermal performance,conductivities,dielectric properties,and piezoelectric properties of the BaTiO_(3)/PVDF/conductive carbon black composites were then investigated.The addition of conductive carbon black greatly enhances the conductivities,dielectric properties,and piezoelectric properties of the BaTiO_(3)/PVDF/conductive carbon black composites,especially when the carbon black content is 0.8%by weight of PVDF.Additionally,the conductive carbon black does not have an obvious effect on the morphologies and thermal stabilities of BaTiO_(3)/PVDF/conductive carbon black composites.

Flexible Polydimethylsiloxane Composite with Multi-Scale Conductive Network for Ultra-Strong Electromagnetic Interference Protection

Highly conductive polymer composites(CPCs) with excellent mechanical flexibility are ideal materials for designing excellent electromagnetic interference(EMI) shielding materials,which can be used for the electromagnetic interference protection of flexible electronic devices.It is extremely urgent to fabricate ultra-strong EMI shielding CPCs with efficient conductive networks.In this paper,a novel silver-plated polylactide short fiber(Ag@PL ASF,AAF) was fabricated and was integrated with carbon nanotubes(CNT) to construct a multi-scale conductive network in polydimethylsiloxane(PDMS) matrix.The multi-scale conductive network endowed the flexible PDMS/AAF/CNT composite with excellent electrical conductivity of 440 S m-1and ultra-strong EMI shielding effectiveness(EMI SE) of up to 113 dB,containing only 5.0 vol% of AAF and 3.0 vol% of CNT(11.1wt% conductive filler content).Due to its excellent flexibility,the composite still showed 94% and 90% retention rates of EMI SE even after subjected to a simulated aging strategy(60℃ for 7 days) and 10,000 bending-releasing cycles.This strategy provides an important guidance for designing excellent EMI shielding materials to protect the workspace,environment and sensitive circuits against radiation for flexible electronic devices.

Influence of Water Content on Conductivity and Piezoresistivity of Cement-based Material with both Carbon Fiber and Carbon Black

The influence of water content on the conductivity and piezoresistivity of cement-based material with carbon fiber （CF） and carbon black （CB） was investigated. The piezoresistivity of cement-based material with both CF and CB was compared with that of cement-based material with CF only, and the changes in electrical resistivity of cement-based material with both CF and CB under static and loading conditions in different drying and soaking time were studied. It is found that the piezoresistivity of cement-based material with both CF and CB has better repeatability and linearity than that of cement-based material with CF only. The conductivity and the sensitivity of piezoresistive cement-based material with both CF and CB are enhanced as the water content in piezoresistive cement-based material increases.

Tetris-Style Stacking Process to Tailor the Orientation of Carbon Fiber Scaffolds for Efficient Heat Dissipation

As the miniaturization of electronic devices and complication of electronic packaging,there are growing demands for thermal interfacial materials with enhanced thermal conductivity and the capability to direct the heat toward heat sink for highly efficient heat dissipation.Pitch-based carbon fiber(CF)with ultrahigh axial thermal conductivity and aspect ratios exhibits great potential for developing thermally conductive composites as TIMs.However,it is still hard to fabricate composites with aligned carbon fiber in a general approach to fully utilize its excellent axial thermal conductivity in specific direction.Here,three types of CF scaffolds with different oriented structure were developed via magnetic field-assisted Tetris-style stacking and carbonization process.By regulating the magnetic field direction and initial stacking density,the self-supporting CF scaffolds with horizontally aligned(HCS),diagonally aligned and vertically aligned(VCS)fibers were constructed.After embedding the polydimethylsiloxane(PDMS),the three composites exhibited unique heat transfer properties,and the HCS/PDMS and VCS/PDMS composites presented a high thermal conductivity of 42.18 and 45.01 W m^(−1)K^(−1)in fiber alignment direction,respectively,which were about 209 and 224 times higher than that of PDMS.The excellent thermal conductivity is mainly ascribed that the oriented CF scaffolds construct effective phonon transport pathway in the matrix.In addition,fishbone-shaped CF scaffold was also produced by multiple stacking and carbonization process,and the prepared composites exhibited a controlled heat transfer path,which can allow more versatility in the design of thermal management system.

The Smart Behavior of Cement-based Composite Containing Carbon Fibers under Three-point-bending Load

The influences of the fiber volume fraction on the electrical conductivity and the fraction change of electrical resistance under three-point-bending test were discussed.It is found that the relationship beween the electrical conductivity of composites and the fiber volume fraction can be explained by the percolation theory and the change of electrical resistance of specimens reflects to the process of loading.The sensitivity and the response of the change of electrical resistance to the load for specimens with different fiber volume fractions are quite different.which provide an important guide for the manufacture of conductive and intrinsically smart carbon fiber composite.

Optimization of mixing speed and time to disperse the composite conductive agent composed of carbon black and graphene in lithium-ion battery slurry

This paper proposed an optimal approach to disperse the composite conductive agent which is composed of carbon black(CB)and graphene(Gr)within lithium-ion battery(LIB)slurry with different mixing speeds and mixing times.The internal structures of LIB slurry are characterized by Electrochemical Impedance Spectroscopy,Scanning Electron Microscopy,and Raman experiment.Initially,a composite conductive solution is prepared by mixing the composite conductive agent with NMP solvent under the conditions of five different mixing speeds n_(1)(n_(1)=1000,1100,1200,1300,1400 rpm)in the case of mixing time t_(1)=10 min.Subsequently,LIB slurry is prepared by blending the composite conductive solution,LiCoO_(2)and PVDF-NMP solution under the conditions of five different mixing speeds n_(2)(n_(2)=1000±280,1100±280,1200±280,1300±280,1400±280 rpm)in the case of mixing time t_(2)=6 min.By analyzing the internal structure of different LIB slurries,it shows that in the case of n_(1)=n_(2)=1200 rpm,a conductive network structure is well formed within LIB slurry.Additionally,in order to determine the optimal time to prepare the composite conductive solution for LIB slurry,nine different t_(1)(t_(1)=0,10,20,30,40,50,60,70,80 min)are selected.By analyzing the internal structure of different LIB slurries,a well-formed conductive network structure and a uniformly distributed composite conductive agent are deduced in LIB slurry when t_(1)=50 min.Therefore,it can be concluded that the composite conductive agent composed of CB and Gr is able to be uniformly dispersed in LIB slurry by establishing a well-formed conductive network structure under the optimal mixing speed n_(1)=n_(2)=1200 rpm and the optimal mixing time t_(1)=50 min,t_(2)=6 min.This kind of the internal structure has the potential to be used to further analyze the dispersion characterizations of LIB slurry under different composite conductive agent and CB/Gr ratios with the aim of improving the final performance of LIB.

Thermo-physical Properties of Continuous Carbon Fiber Reinforced Copper Matrix Composites

Continuous carbon fiber reinforced copper matrix composites with 70%(volume fraction) of carbon fibers prepared by squeeze casting technique have been used for investigation of the coefficient of thermal expansion(CTE) and thermal conductivity.Thermo-physical properties have been measured in both,longitudinal and transversal directions to the fiber orientation.The results showed that Cf/Cu composites may be a suitable candidate for heat sinks because of its good thermo-physical properties e.g.the low CTE(4.18×10-6/K) in longitudinal orientation and(14.98×10-6/K) in transversal orientation at the range of 20-50℃,a good thermal conductivity(87.2 W/m·K) in longitudinal orientation and(58.2 W/m·K) in transversal orientation.Measured CTE and thermal conductivity values are compared with those predicted by several well-known models.Eshelby model gave better results for prediction of the CTE and thermal conductivity of the unidirectional composites.

A Novel Method for Preparing Polyurethane Based Conductive Composites with Low Percolation Threshold

A novel method for preparing conductive carbon black fllled polymer composites with low percolation threshold from polyurethane emulsion are reported in this paper. The experimental results indicate that with a rise in carbon black concentration the insulator-conductor transition in the emulsion blended composites occurs at 0.8-1.4vol%. In contrast, the solution blended composites exhibit drastic increase in conductivity at conducting filler fraction as high as 12.3-13.3vol%. It is demonstrated that the composites microstructure rather than chemical structure of the matrix polymer predominantly determines the electrical conduction performance of the composites.

碳纤维/UiO66-NH2环氧复合材料的制备及其性能研究

本文首先合成出锆基MOF材料UiO66-NH_(2),并设计得到PA功能化的MOF材料UiO66-NH_(2)-PA,再将其分散在环氧树脂基体中,制备了性能优异的碳纤维/UiO66-NH_(2)环氧复合材料.随后,通过FT-IR、SEM、XRD对UiO66-NH_(2)以及UiO66-NH_(2)-PA进行了表征,使用万能试验机对碳纤维/UiO66-NH_(2)环氧复合材料的力学性能进行了测试.结果表明,UiO66-NH_(2)-PA被成功制备,且改性后的碳纤维复合材料的抗弯曲和抗剪切强度分别提高了26.54%和29.09%.这是因为UiO66-NH_(2)-PA中氨基和磷基的作用增强了界面强度,既提高了碳纤维/UiO66-NH_(2)环氧复合材料的储能模量,又增强了复合材料的界面结合能力,从而实现了通过共同作用以提高碳纤维、环氧复合材料力学性能的目标.

预氧化碳纤维增强受电弓碳滑板材料的研究

利用预氧化碳纤维(OPF)和沥青、焦炭等为原料,采用热压、焙烧等工艺制备预氧化碳纤维增强受电弓碳滑板;研究不同OPF含量受电弓碳滑板导电导热以及力学性能;利用扫描电镜(SEM)、偏光显微镜(POM)、X射线衍射仪(XRD)等仪器对复合材料内部结构进行观察。结果表明:滑板材料性能的提升与OPF/沥青间的共碳化界面以及界面处与基体中的微晶网络形成有关。OPF质量分数为1.5%的复合材料具有较好的导电导热以及力学性能,电导率和导热系数分别为279.33 S/cm和3.37 W/(m·K),抗压强度和抗折分别为155.00、48.85 MPa,且符合受电弓碳滑板性能要求。

氮掺杂碳层对铜碳纳米管纤维复合材料性能影响及机制初探

用碳纳米管纤维(CNTF)、盐酸多巴胺、五水硫酸铜作为原料,通过浸泡、热处理和电化学沉积等连续工艺合成了高导电性铜-碳纳米管纤维复合材料(Cu@NC@CNTF)。用场发射扫描电子显微镜对复合纤维表面进行形貌表征,用X射线光电子能谱、小角X射线散射站对氮掺杂的碳纳米管纤维(NC@CNTF)表面进行结构分析。结果表明:氮掺杂碳层的界面改性高效调节了CNTF表面浸润性,导致CNTF和Cu之间强的耦合作用;通过界面优化和调控电流密度大小,实现了Cu@NC@CNTF复合纤维的可控制备和性能改善,Cu@NC@CNTF的电导率和比电导率分别达到了3.06×10^(7)S/m和7571.48 S·m^(2)/kg;这种超亲水的Cu@NC@CNTF基复合材料为制造轻质、高导电性的工业级新型供电导线提供了思路。

CNT/乙炔黑复合导电剂对LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2)的影响

为解决乙炔黑单一导电剂自身团聚的问题,采用含碳纳米管(CNT)的导电浆料进行改性。复合后,直径80~100 nm的球形乙炔黑颗粒均匀分散在直径20 nm的CNT表面,比表面积提高至107.96 m^(2)/g。与乙炔黑导电剂电池相比,CNT/乙炔黑电池的电化学阻抗更小、CV曲线面积更大,氧化峰和还原峰的电位差较小(0.19 V),以200 mA/g在2.75~4.20 V循环,首次充放电比容量分别为151.8 mAh/g和155.5 mAh/g,首次库仑效率为97.6%。第200次循环的放电比容量为141.9 mAh/g,容量保持率为92.4%。在5.0 C倍率下,CNT/乙炔黑电池的放电比容量为116.9 mAh/g,倍率性能更好。

不同形态回收碳纤维水泥基材料的力学与导电性能

将碳纤维生命周期内产生的预浸料、织物及复合材料废弃物通过切割与粉碎制备短切回收碳纤维(CRCF)、回收碳纤维球(RCFS)及回收碳纤维粉(RCFP),研究不同形态回收碳纤维对水泥基材料力学与导电性能的影响机理和规律。结果表明,CRCF阻裂作用与RCFP填充孔隙作用使水泥基材料抗压强度和抗折强度显著提升,但RCFS的团聚导致其提升效果不显著。CRCF在水泥基材料内部搭接形成导电通路,电阻率随CRCF掺量的增加而降低,下降幅度超过90%,且渗滤阈值的掺量随CRCF长度的增大而显著降低。RCFS掺入基体后以孤立的球状形态分散在基体中,RCFP表面残留的树脂会阻碍导电通路的形成,这两种形态的回收碳纤维水泥基材料的电阻率降低幅度均小于10.7%。将CRCF水泥基材料中的电阻分为纤维通路电阻、纤维接触电阻和隧道传输电阻,建立了导电模型,模型误差为9.24%~40.1%。

新型导电水泥基复合材料导电性能研究

采用炭黑作为主要导电掺料,加入少量碳纳米管和钢纤维构建高效导电网络以提高导电性能,研究其在不同环境中的稳定性以及微观形态下复相导电掺料的协同作用。结果表明:掺5%炭黑、0.3%碳纳米管、0.6%体积掺量钢纤维的导电水泥基复合材料C5P3F6固化28 d电阻率为304Ω·cm,比传统水泥基复合材料降低94.5%;掺5%炭黑、0.9%碳纳米管、0.6%体积掺量钢纤维的导电水泥基复合材料C5P9F6受水泥水化、干燥环境和温度的影响较小,表现出较为优异的稳定性。微观形态下能观察到导电掺料分散性较好,碳纳米管、钢纤维有效地与分散的炭黑协同作用桥接成为导电网络。

Preparation and 3D printing of high-thermal-conductivity continuous mesophase-pitch-based carbon fiber/epoxy composites

To meet the requirements of spacecraft for the thermal conductivity of resins and solve the problem of low thermal conduction efficiency when 3D printing complex parts,we propose a new type of continuous mesophase-pitch-based carbon fiber/thermoplastic polyurethane/epoxy(CMPCF/TPU/epoxy)composite filament and its preparation process in this study.The composite filament is based on the high thermal conductivity of CMPCF,the high elasticity of TPU,and the high-temperature resistance of epoxy.The tensile strength and thermal conductivity of the CMPCF/TPU/epoxy composite filament were tested.The CMPCF/TPU/epoxy composites are formed by 3D printing technology,and the composite filament is laid according to the direction of heat conduction so that the printed part can meet the needs of directional heat conduction.The experimental results show that the thermal conductivity of the printed sample is 40.549 W/(m·K),which is 160 times that of pure epoxy resin(0.254 W/(m·K)).It is also approximately 13 times better than that of polyacrylonitrile carbon fiber/epoxy(PAN-CF/epoxy)composites.This study breaks through the technical bottleneck of poor printability of CMPCF.It provides a new method for achieving directional thermal conductivity printing,which is important for the development of complex high-performance thermal conductivity products.

碳纳米管对酚醛树脂基复合材料性能的影响

为制备具有隔热、耐烧蚀、电磁屏蔽等多功能集成的结构复合材料,满足武器装备对多功能复合材料的迫切需求,采用超声波分散的工艺将碳纳米管(Carbon Nanotubes,CNTs)在树脂基体中进行分散,并制备CNTs改性国产碳布/酚醛复合材料。经对CNTs改性国产碳布/酚醛复合材料的层间性能检测,当CNTs含量达到1.5%时,其层间剪切强度提高57.4%。对CNTs改性定向国产碳纤维/酚醛树脂复合材料的弯曲性能、层间性能和抗冲击性能都进行检测。检测结果表明,经CNTs改性后,定向国产碳纤维/酚醛复合材料的力学性能和模量均得到了大幅提高。对CNTs改性短切高强玻璃纤维/酚醛树脂基复合材料的导电性能和导热性能进行了研究。研究结果表明:随着CNTs含量的提高,短切高强玻璃纤维/酚醛树脂基复合材料的电阻率呈数量级速度降低,当CNTs含量达到14%时,复合材料的电阻率由10^(10)Ω·m降低到了10^(-2)Ω·m,复合材料由绝缘体转变为导体;当CNTs含量小于6%时,复合材料的导热系数虽有提高,但与复合材料电性能相比提高幅度不大。

高模量碳纤维表面双金属MOFs结构的构筑

经高温热处理制备得到的碳纤维具有高惰性表面结构,导致其与基体之间的润湿性较差。为了改善碳纤维与基体间的界面性能,本研究通过采用阴极电沉积法在高模量碳纤维表面原位生长金属有机框架(MOFs)材料,在纤维表面同时引入两种不同金属元素,研究双金属MOFs的引入机制、形貌及其对性能的影响。结果表明:双金属MOFs材料呈一定取向的绣球状形貌,经退火后演变成疏松多孔结构,该结构可显著提高高模量碳纤维表面粗糙度及界面黏结性;双金属MOFs的成核与生长取决于金属还原性,还原性越强、MOF生长速率更快,且沉积量更高;双金属MOFs结构的引入使得纤维电阻率下降至0.05×10^(−5)Ω∙cm,导电性能提升,独特的三维多孔结构也赋予高模量碳纤维高温环境下优异的热稳定性。

碳纤维增强环氧树脂复合材料的智能性试验研究

监测了碳纤维复合材料试件在拉伸过程中电阻值的变化,对所得数据进行计算和线性拟合,建立了碳纤维复合材料在拉伸过程中电阻率与应变的关系。研究结果表明:在拉伸过程中,碳纤维的电阻率随着应变的增加一直增大;含不同长度碳纤维的复合材料的电阻率随应变变化的灵敏度系数也不同,碳纤维复合材料在拉伸过程中的灵敏度系数随着碳纤维长度的增加而增大;单束碳纤维拉伸试验中,含25 cm碳纤维试件的灵敏度系数最大;串联的方法可以进一步提高碳纤维复合材料在拉伸过程中的灵敏度。

纤维增强碳化硅陶瓷基复合材料高导热性能研究进展

作为一种先进的高温结构及功能材料,高效传热和高温耐热相结合对纤维增强碳化硅陶瓷基复合材料(silicon carbide matrix composites,SiC CMC)在热管理领域(thermal management,TM)中的应用至关重要。常见的纤维增强碳化硅陶瓷基复合材料,如碳纤维增强碳化硅陶瓷基复合材料(C_(f)/SiC或C_(f)/C-SiC)、碳化硅纤维增强碳化硅陶瓷基复合材料(SiC_(f)/SiC)等,增强纤维的石墨化程度较低,难以形成有效的热输运网络。本文综述了纤维增强碳化硅陶瓷基复合材料制备及高导热性能等方面的最新研究进展。可通过引入高导热相、优化界面结构、粗粒化碳化硅晶体、设计预制体结构等方式提高纤维增强碳化硅陶瓷基复合材料的热输运能力。此外,展望了纤维增强碳化硅陶瓷基复合材料发展趋势,即综合考虑影响高导热碳化硅陶瓷基复合材料性能要素,灵活运用复合材料结构与性能的构效关系,以期制备尺寸稳定、性能优异的纤维增强碳化硅陶瓷基复合材料。