炭黑-环氧树脂导电复合材料力-电性能研究

研究了填充炭黑的环氧树脂即导电复合材料的导电机理,不同炭黑掺量复合材料在一次加载及反复加卸载下的压阻效应.结果表明,炭黑掺量为20%试件的压阻效应明显且稳定;各掺量试件卸载后均存在较大的残余电阻,经多次加卸载后,电阻变化率逐渐减小并趋于一不变值;卸载后电阻的恢复率不断增加,最终可完全恢复.     

用于电子墨水的纳米炭黑颗粒表面电荷改性

采用硅烷偶联剂KH550和浓硫酸分别对色素炭黑纳米颗粒进行了表面处理。透射电子显微镜、紫外-可见分光光度计分析表明改性前后炭黑纳米颗粒的粒径和色纯度变化非常小。炭黑电泳显示实验表明原本导电的色素炭黑经过处理后均具有较高的介电性,表面分别带了正电荷和负电荷,在施加较低的电压下,改性纳米炭黑颗粒表现出了良好的电场响应和可逆移动特性。     

石墨/炭黑/改性树脂导电复合材料的电学性能研究

以改性环氧树脂为基体、石墨\炭黑为混合导电填料制备了导电复合材料。分析了材料的导电机理,研究导电填料含量与电阻率之间的关系。结果表明:当石墨为15%、炭黑20%时制备的复合材料具有良好的导电性,电阻率为16.4Ω.cm。同时测试了复合材料的伏安特性曲线,发现其呈现非线性欧姆关系,具有正温度系数效应(PTC)。     

炭黑-聚酯复合型导电高分子材料的电热性能研究

研究了炭黑 -聚酯复合型导电高分子材料的电阻率随炭黑填充率及加工成型工艺变化的关系及其伏安特性和力学性能。实验结果表明 ,材料的电导率较高 ,具有非线性伏安特性和负温度系数效应 ,主要用作导电材料和电阻材料。     

负温下炭黑/树脂复合材料温度敏感特性

对纳米炭黑填充的树脂基导电复合材料负温下的温度响应进行了试验研究。试验发现,该导电复合材料在负温下具有正温度系数(PTC)特性,电阻值随温度的降低而降低,随温度的升高而升高。炭黑含量对其温度敏感性的影响是明显的,35%配方的温度灵敏度最好,随着炭黑含量增大,灵敏度逐渐降低。分析认为,树脂基材料的热胀冷缩是导致该复合材料热敏性的主要原因;炭黑含量越高,材料内部的导电网络越稳定,温度变化对电阻的影响越小。     

炭黑分散状态对炭黑/环氧树脂导电复合材料电阻率和力电性能的影响

通过实验研究了搅拌时间和炭黑表面改性对炭黑/环氧树脂导电复合材料电阻率和力电性能的影响。实验结果表明,随着搅拌时间的延长,炭黑在环氧树脂中的分散性提高,炭黑在环氧树脂中形成的一些导电链被破坏,从而导致复合材料的电阻率提高,电阻率变异系数减小及同批试件的电阻随应变的变化率趋于一致。但进一步延长搅拌时间并不能提高分散性,炭黑仍是以较大聚附体的形式存在。炭黑经偶联剂表面改性后,在环氧树脂中的分散性得到进一步的提高。改性后炭黑以小的聚附体甚至单颗粒的形式分散于环氧中,从而减小了复合材料中分布于炭黑颗粒间环氧树脂间隙的宽度,使复合材料的电阻率和电阻随应变的变化率减小。     

炭黑填充高密度聚乙烯开关材料

炭黑填充高密度聚乙烯复合导导材料具有良好的开关效应，其电阻随温度及电压在某一范围内变化时会发生急剧性变化。本文简述了炭黑填充高密度聚乙烯复合体系的导电机理，电阻－温度关系，电流－电压特性，以及交联对其电阻率ρ－温度Ｔ曲线的影响和如何得到良好的ＰＴＣ强度。     

乙炔炭黑水泥基复合材料的压敏性

为探讨乙炔炭黑水泥基复合材料的压敏性 , 验证了利用基于埋入式环状电极的四电极法测试复合材料电阻的可行性; 研究了一次加载至破坏时乙炔炭黑水泥基复合材料的电阻率变化规律 , 并通过在弹性阶段的加载考察了乙炔炭黑水泥基复合材料压敏性的重现性 ; 分析了测试电流和试件偏压对压敏性的影响。研究结果表明 ,基于埋入式环状电极的四电极法测试压敏水泥基材料的电阻误差小于 10 % , 用于复合材料电阻的测试是可行的。掺量 15 vol %的乙炔炭黑水泥基复合材料一次加载至破坏 , 电阻率变化率最大可达 55 % , 弹性阶段电阻率变化率可达 35 %以上 , 且其压敏性基本不受测试电流和试件偏压的影响。乙炔炭黑是制备具有高感知灵敏度的压敏水泥基材料的一种有效功能组分。     

炭黑填充粒子对导电硅橡胶压阻特性的影响

阐述了复合型导电高分子材料的导电机理,分析了4种导电炭黑填充量对导电硅橡胶导电特性的影响,实验分析了相同导电填料、不同质量分数情况下的导电硅橡胶压阻特性,分析了相同质量分数、不同导电填料对复合材料压阻特性的影响。研究表明,随着炭黑填充量的不断增加,复合材料体积电阻率均呈下降趋势;4种炭黑填充的导电硅橡胶渗流阀值较接近;导电硅橡胶的电阻-压力变化规律符合隧道效应理论模型;为保证导电硅橡胶具有良好的压阻特性,应根据原料控制好导电炭黑的添加量。     

导电硅橡胶复合材料压缩敏感性研究

分别对短切碳纤维和炭黑填充的硅橡胶基导电复合材料试样进行了单次与循环压缩试验,研究两种复合材料的压敏特性及可重复性。测试结果表明,两种导电复合材料都具有较好的压缩敏感性;碳纤维填充时,试样的灵敏度较高,达到250左右,且电阻相对值与应变之间基本呈线性关系;炭黑填充时,试样具有较好的可重复性,但灵敏度较差。通过导电机理研究,对两种导电复合材料不同的导电敏感特性进行了分析。     

I–V characteristics and electro-mechanical response of different carbon black/epoxy composites

I–V characteristics and electro-mechanical response of carbon black (CB)/epoxy composites were studied experimentally. Two types of CB were used in the experiment, they were: sprayed CB and conductive CB particles. During the experiment, it was found that the I–V characteristics of the composites and their electro-mechanical response were greatly affected by the particle size of CB as well as their dispersion properties. The epoxy containing sprayed CB with the diameter of 123 nm composites gave predicted relationships, in terms of I–V characteristics and strain/electrical resistivity once they were subjected to a compressive load. The electrical breakdown assumption incorporated in the DC circuit model is proposed in this paper to interpret the response of the composites with different types of CB particles.     

New type of piezo-damping epoxy-matrix composites with multi-walled carbon nanotubes and lead zirconate titanate

A new type of rigid piezo-damping epoxy-matrix composites containing multi-walled carbon nanotubes (CNT) and piezoelectric lead zirconate titanate (PZT) was prepared, and the electrical and the damping properties were investigated. Dynamic mechanical thermal analysis reveals that the loss factors of the composites were improved by incorporation of PZT and CNT under the concentration above a critical electrical percolation. Based on this piezo-damping material, the PZT contributes to the transformation of mechanical noise and vibration energies into electric energy, while the CNT serve in the shorting of the generated electric current to the external circuit. An optimum formulation for the piezo-damping epoxy-based materials can be designed on the basis of the results of this study.     

Nickel particle based electrical resistance heating cementitious composites

In this study, electrical resistance heating cementitious composites are developed by employing nickel particles as conductive fillers and heating elements. The conductive properties of cementitious composites with different types and different content levels of nickel particles are investigated. The electrical resistance heating performance of the composites is studied. Deicing and snow-melting experiments are also performed in refrigerator and outdoor environment, respectively. Experimental results show that the cementitious composites with nickel particles can achieve a temperature increment of about 50 °C within 30 s when the input voltage is 20 V. At an input voltage of 15 V, the cementitious composites with nickel particles (12.0 vol.% and 2.6–3.3 μm diameter) can deice 3 mm of ice in 478 s under an ambient temperature of − 16.0 °C and melt 2 cm of snow in 368 s under an ambient temperature of − 5.3 °C, respectively. These findings indicate that the fabricated cementitious composites with nickel particles have a superior electrical resistance heating performance.     

Micromechanics models for the effective nonlinear electro-mechanical responses of piezoelectric composites

The nonlinear behavior of piezoelectric composites becomes prominent when the composites are subjected to high electric fields, which is often the case in actuator applications. Understanding the nonlinear behavior of piezoelectric composites is crucial in designing structures comprising of these materials. This study presents micromechanics models for predicting nonlinear electro-mechanical responses of polarized piezoelectric composites, comprising of a linear non-piezoelectric homogeneous medium (matrix) reinforced by either nonlinear piezoelectric fibers or particles, subjected to high electric fields. The maximum electric field applied is within the coercive electric field limit. The constitutive relations for the polarized piezoelectric inclusions consist of the third- and fourth-order electro-mechanical coupling tensors and the second- and third-order electric permeability tensors. The Mori–Tanaka micromechanics and simplified unit-cell micromechanics models are formulated to predict the effective nonlinear electro-mechanical responses of piezoelectric fiber reinforced and particle reinforced composites, respectively. Linearized micromechanical relations are first used to provide trial solutions followed by iterative schemes in order to correct errors from linearizing the nonlinear responses. Numerical results are presented to illustrate the performance of each micromechanics model.     

多壁碳纳米管增强炭黑/聚丙烯导电复合材料导电行为

为了充分利用不同导电粒子的导电作用,在炭黑(CB)/聚丙烯(PP)导电复合体系中引入了多壁碳纳米管(CNTs)。研究发现：引入的CNTs分散在CB粒子间起到“桥梁”作用,使体系的导电性能得到明显改善,并且CB∶CNTs为19∶1时其协同导电效果最好,该复合体系出现逾渗现象,对应的导电填料体积分数明显降低。在导电填料总体积分数为4.76%时,少量CNTs的引入就可使复合体系的体积电阻率从109Ω·cm下降到105Ω·cm;同时少量的CNTs能明显抑制炭黑/聚丙烯导电复合材料的正温度效应(PTC),使PTC强度从6.10降低到1.48,PTC转变峰温度从166℃升高到174℃。少量的 CNTs可以使PP的结晶温度提高12℃,对PP结晶的成核作用比CB更加明显。复合体系力学性能随导电填料体积分数增加而明显降低,但因为体积电阻率一定时CB-CNTs/PP体系所需导电填料体积分数较CB/PP体系明显降低,因此少量CNTs的引入能够使复合体系的力学性能得到更大程度的保持。     

Fabrication and performances of epoxy/multi-walled carbon nanotubes/piezoelectric ceramic composites as rigid piezo-damping materials

Piezo-damping epoxy-based composites containing various amounts of multi-walled carbon nanotubes (CNT) and piezoelectric lead zirconate titanate (PZT) were prepared, and their performances were investigated. The composites exhibited a percolation threshold in the range of 1–1.5 g CNT per 100 g epoxy, in which a continuous electro-conductive network formed. Dynamic mechanical thermal analysis reveals that the loss factors of the composites were improved by incorporation of the PZT and the CNT at above critical electrical percolation loading. Based on this new type rigid piezo-damping material, the PZT contributes to the transformation of mechanical noise and vibration energies into electric energy, while the CNT serve in shorting of the generated electric current to the external circuit. Thermal stability and mechanical properties were also improved by incorporating these two fillers. An optimum formulation for the rigid piezo-damping materials can be designed on the basis of the results of this study.     

Effect of compressive strain on electrical resistivity of carbon black-filled cement-based composites

This paper investigates the strain sensing properties of carbon black (CB)-filled cement-based composites which were prepared with 120 nm CB. A linear relationship between the fractional change in resistivity and compressive strain was observed for cement-based composites containing a large amount of CB, suggesting that this kind of composite was a promising candidate for strain sensors used in concrete structures. Tunneling effect theory and percolation theory are employed to interpret the conductivity and electromechanical properties of CB-filled cement-based composites.     

Microwave absorbing properties of activated carbon-fiber felt dipole array/epoxy resin composites

Microwave absorbing properties of the composites containing activated carbon-fiber felt dipole arrays (ACFFDAs) were investigated. The results show that the absorbing performances of the composites containing ACFFDAs are affected greatly by the dimension parameters of the arrays, the resistance connecting the two arms and the materials of the dipoles. The absorption of the composites containing ACFFDAs presents anisotropy. When the dipoles are parallel to the incident electric field, the composites show better absorbing effect. The absorbing properties rise at first and then fall with increasing the resistance connecting arms or the space between dipoles. In this work, when the dipoles are parallel to the incident electric field, the composite obtains a reflection loss below −10 dB over 12.2 GHz and the minimum value reaches −32 dB. The bandwidth below −10 dB increases with increasing the length of the arms when the dipoles are parallel to the incident electric field. The bandwidth below −10 dB is 13.1 GHz when the length of the arms is 85 mm. Compared with copper plate, the dipole arrays whose arms are made of activated carbon-fiber felt exhibit better absorption properties.     

On the electrical resistance of carbon fiber polymer matrix composites

This paper studies the response of carbon fiber polymer matrix composites subjected to DC electric currents. A new fully automated experimental setup that enables one to measure electric field characteristics (current, voltage, resistance) and temperature at the surface of electrified composites in real time has been developed. The experimental procedure ensured a low contact resistance between the composite and electrodes and low resistance heating. An extensive experimental study on the electrical characterization of AS4/3501-6 and IM7/977-2 carbon fiber polymer composites of different lay-up and thickness has been conducted. The effect of the resistive heating was studied using experimental analysis as well as the finite element modeling.     

有限元法研究填料形貌与介电常数对无机/有机介电复合材料介电性能的影响

为了开发高储能密度的无机/有机介电复合材料,本文采用有限元法分别研究了直径为100 nm的球形填料与基体介电常数的比值（k）、球形填料在复合材料中的排列方式、球形填料尺寸（100~300 nm）、纤维状填料长径比（α）和片状填料的球形度（β）对复合材料介电性能的影响。计算结果表明,当k值大于20时,复合材料的介电常数变化不明显;球形填料沿电场方向成链式排列时,复合材料有较大的介电常数,且材料中球形填料附近处存在较大的电位移和较大的电场,说明这种填料排列方式有利于材料介电常数的提高,但会削弱材料的耐击穿能力;当球形填料随机分布时,颗粒尺寸变化对复合材料介电常数的影响不明显。对于纤维状填料,其长径比α越大且长轴沿电场方向分布时,填料自身及周边会产生较大的电位移,表明这种情况有利于复合材料介电常数的提高。对于片状填料,其球形度β越小,填料与基体界面处高电场区域越小,表明材料的耐击穿能力越高。本研究可为高介高储能材料的实验研究提供理论指导。