炭纤维增强水泥基复合材料的导电性研究

通过向水泥基材料中添加炭纤维制备炭纤维增强水泥基复合材料(CFRC),研究了炭纤维掺量、硅粉掺量、养护龄期等因素对其导电性能的影响。结果表明,CFRC复合材料的电阻率随着炭纤维掺量的增加而减小;掺入10%的硅粉能够显著降低CFRC复合材料的电阻率;CFRC复合材料中的炭纤维掺量低于0.6%时,电阻率随着养护龄期的延长而迅速增大,炭纤维掺量高于0.6%时电阻率增加不明显。     

焦炭-水泥基复合材料电磁屏蔽性能的研究

研究了焦炭和碳纤维的掺量,焦炭细度,减水剂,样品厚度对材料电磁屏蔽性能的影响。分别利用两电极法和同轴电缆法测试了材料的电阻和电磁屏蔽效能。研究结果表明,增加焦炭的掺量对水泥基材料导电性能的影响不显著,但增加焦炭细度能明显提高水泥基材料的导电性能;而样品厚度对水泥基材料的电磁屏蔽性能影响不大;焦炭-水泥基材料掺入碳纤维后能使材料的导电性能和电磁屏蔽性能明显提高。     

石墨-水泥基复合材料的制备与性能

为提高水泥基材料的抗电磁干扰性能,制备了石墨-水泥基复合材料,测试了材料的电阻率、电磁屏蔽效能和力学性能.结果表明:对石墨-水泥基复合材料,在一定范围内,随掺入的石墨质量分数(下同)的增加,材料电阻率呈下降趋势.石墨掺入量为5%～10%时复合材料电阻率下降非常明显,超过15%以后,电阻率变化已不太明显;随着石墨掺量的增加,复合材料的电磁屏蔽效能也逐渐增大,石墨掺入量为15%时达到最大值,而抗折强度及抗压强度则随着石墨掺入量的增加有所下降.     

碳系水泥基复合材料的研究进展

本文介绍了国内外水泥基复合材料的研究进展,重点对水泥基导电复合材料、水泥基电磁屏蔽复合材料和水泥基压电机敏复合材料,如导电性能、磁性能、屏蔽性能、压电性能等材料的组成、特性及发展状况进行了综述.     

基于磁控溅射技术的碳基电磁屏蔽材料

利用磁控溅射技术在碳纤维表面沉积铜膜制备了高效的电磁屏蔽材料,并通过调整磁控溅射时间和碳纤维单向布铺层层数,分析了磁控溅射改性方式和铺层层数对碳纤维织物及其复合材料电磁屏蔽性能的影响。结果表明,磁控溅射碳纤维表面铜膜沉积有利于碳纤维电磁屏蔽性能的改善。经磁控溅射改性处理后,碳纤维电磁屏蔽效能最小提高了37.73%,且电磁屏蔽性能随着磁控溅射时间的延长而增强,但碳纤维电磁屏蔽效能增加率则随磁控溅射时间的增加而逐渐减小。增加碳纤维织物铺层层数有利于碳纤维织物集合体电磁屏蔽性能的改善,但织物层间的不连续性对织物集合体电磁屏蔽性能起消极作用。环氧树脂经碳纤维复合后,电磁屏蔽效能显著增强,增加了约30 dB,但由于环氧树脂对碳纤维的包覆性能,影响了复合材料对电磁波的屏蔽效果,不随碳纤维复合材料中碳纤维织物铺层层数的增加和改性碳纤维导电性能的增加而增强。     

具有电磁屏蔽功能聚苯硫醚复合材料的制备与性能研究

本文采用粉末浸渍工艺制得连续玄武岩纤维和不锈钢纤维增强聚苯硫醚预浸料,预浸料的编织物经层压成型制备了聚苯硫醚复合材料,对复合材料的力学和电磁屏蔽性能进行了研究。结果表明:不锈钢纤维/聚苯硫醚预浸料与玄武岩纤维/聚苯硫醚预浸料层压所形成的复合材料其力学性能和电磁屏蔽性能均优于铝箔与玄武岩纤维/聚苯硫醚预浸料层压所形成的复合材料;当电磁波频率小于200 MHz时,复合材料的电磁屏蔽效能较高,不锈钢纤维/聚苯硫醚预浸料中不锈钢纤维质量分数(含量)为30%时,复合材料的电磁屏蔽效果达到较高值,当电磁波频率在200～1 500 MHz范围内,材料的屏蔽效能在20～30dB间波动。     

表面热处理碳纤维及其增强水泥基复合材料的电磁屏蔽性能

在1200℃左右,将短切碳纤维进行化学气相沉积处理后,制成碳纤维增强水泥基复合材料.对处理后的碳纤维表面形貌及复合材料样品的断面进行了扫描电镜观察,利用海军研究实验室弓型反射率测试系统测试了碳纤维质量掺量为0.2%,0.5%,0.6%,1.0%时,复合材料试样在C,X,Ku波段对电磁波的反射率.结果表明:高温热处理改变了碳纤维的表面形貌,增强了纤维与基体之间的界面结合力,改善了复合材料的电磁屏蔽性能.当碳纤维掺量为0.2%时,在上述3个波段均出现最小反射率,复合材料主要吸收电磁波;当碳纤维掺量为0.5%时,复合材料主要反射电磁波.     

电磁屏蔽复合材料包装箱的研究

采用复合材料树脂传递模塑（RTM）工艺，利用一层含不锈钢纤维的导电布为屏蔽材料，制备了具有电磁屏蔽效能的玻璃纤维增强树脂基复合材料包装箱，该包装箱材料在1．0～4．0GHz电磁波范围内，电磁屏蔽效能最高可高达36dB左右，且与未含导电布的相同体系的复合材料相比，力学性能基本保持不变。     

碳基纳米填料增强微孔发泡电磁屏蔽材料的研究进展

航空航天等新兴行业以及电子等领先行业的发展对聚合物特殊性能的要求越来越高,将微孔发泡和具有功能特性的碳基纳米填料结合形成的导电聚合物泡沫具有优异的电子传输特性,有利于在较低渗透阈值下获得均匀的导电网络,提高材料的电导率与介电常数,在电磁屏蔽等领域有广阔的应用前景。介绍了导电复合材料的电磁屏蔽原理以及碳基纳米填料与发泡的协同作用机理,重点论述了不同发泡工艺下碳基微孔材料的电导率、电磁屏蔽效能等电学性能,并对碳基纳米填料增强微孔电磁屏蔽材料的研究和应用前景进行了展望。     

碳纳米管填充聚合物基电磁屏蔽复合材料的研究进展

对碳纳米管填充聚合物基电磁屏蔽复合材料的研究进展进行了综述。在阐述研究电磁屏蔽材料必要性的基础上,介绍了复合材料的电磁屏蔽机理,重点论述了碳纳米管填充量、长径比及管径、屏蔽体的厚度、复合材料的加工方式等对复合材料电磁屏蔽性能的影响。最后对碳纳米管填充聚合物基复合电磁屏蔽材料的研究进行了展望,指出低成本填料与碳纳米管协同作用、可提高碳纳米管分散性的制备工艺的研究以及复合材料电磁屏蔽机理的研究等为未来的研究方向。     

碳纤维增强水泥基复合材料的电磁屏蔽性能

利用弓形法测试了碳纤维质量掺量分别为0.2%、0.4%、0.6%、0.8%和1.0%时,碳纤维增强水泥基复合材料(CFRC)在低频段4~8 GHz和高频段8~18 GHz对电磁波的反射率,讨论了碳纤维质量掺量变化对反射率的影响。结果发现,碳纤维质量掺量相同、低频段时,反射率小于-10 dB,复合材料对电磁波表现出吸收性;高频段时,反射率大于-10 dB,复合材料对电磁波表现出反射性。低频段、碳纤维质量掺量为0.6%时出现最小反射率-15.1 dB;高频段、碳纤维质量掺量为0.4%时,出现最小反射率-19.4 dB。     

Behavior of carbon matrix in carbon fiber reinforced composites (CFRC) synthesized through the film boiling chemical vapor infiltration (FB-CVI) process

Film boiling chemical vapor infiltration (FB-CVI) technique is considered as one of the fastest process to manufacture carbon fiber reinforced carbon (CFRC) composite products. In the present work, the characteristics of the carbon matrix deposited through FB-CVI process under deposition and infiltration are investigated. A novel reactor with unique features was developed, to simulate the process conditions. Utilizing the indigenously build reactor, pyrocarbon (PyC) was deposited on graphite substrates. The kinetics of the process is investigated within temperature range of 1100 °C–1150 °C and characteristics of carbon matrix was investigated. The nature of the carbon deposited and effect of graphitization on the microstructure of the deposited PyC was examined. The role of preform architecture on densification through FB-CVI process and characteristics of the composites were further studied. The mechanical behavior of the FB-CVI based CFRC material were investigated through nanoindentation technique. The present study has provided process guidelines for densification of 2D continuous fibers based preform. Structure property relationship is evolved to optimally develop CFRC composite products for aerospace applications.     

碳纤维增强水泥混凝土导电机理的研究

研究了沥青碳纤维掺量及外加剂对碳纤维混凝土复合材料导电性的影响，讨论了碳纤维混凝土复合体的导电机理。结果表明：碳纤维掺量对复合材料的导电性有一个临界值(Vfe)，外加剂能降低复合材料的电导率。     

Thermoelectric percolation phenomena in carbon fiber-reinforced concrete

The measurements of thermoelectric power (TEP) and conductivity on carbon fiber-reinforced concrete (CFRC) containing short polyacrylonitrile-based carbon fibers (0.2–2.0 wt.%) were conducted. Percolation phenomena in CFRC associated with TEP were observed. TEP in CFRC increases, with the content of short carbon fiber increasing from 0.2 to 1.0 wt.%. As the content of carbon fiber reaches 1.2 wt.%, TEP decreases abruptly. In the end, TEP is almost maintained marginally with increasing content of carbon fiber from 1.4 to 2.0 wt.%. Therefore, the threshold is 1.2 wt.%, which is the same as the percolation content associated with conductivity. The results provide an important guide for the manufacture of smart concrete that has the ability for thermal self-diagnosis.     

Dispersion of carbon fibers and conductivity of carbon fiber-reinforced cement-based composites

Dispersion of carbon fibers in the cement matrix remains a hot topic in the preparation of carbon fiber-reinforced cement-based composites (CFRC) because it affects greatly both the mechanical and electrical properties of the composites. In this work, a new dispersant hydroxyethyl cellulose was used with the aids of pre-dispersion by ultrasonic wave to realize the uniform distribution of chopped carbon fibers in the cement matrix. The fracture surface of the prepared CFRC was observed by scanning electron microscopy, the elemental distribution was investigated by energy dispersive spectroscopy, and the components was analyzed by X-ray diffraction. Influences of carbon fiber lengths and contents, water/cement weight ratio, molding process, curing time, and silica fume content over the conductivity of the CFRC composites were studied. The mechanism of conductivity was discussed. Results shown that the electrical resistivity intended to decrease with the increasing of carbon fiber contents. The mass fraction 0.6% of carbon fibers was a turning point. The concentration of hydroxyethyl cellulose between 1.66% and 1.86% was mostly beneficial for the dispersion of carbon fibers. The resistivity was increased first and decreased then with the increase of water/cement ratio. When the CFRC sample was prepared by the vibrating pressing method, the resistivity of the sample was reduced far greatly than that of the sample by the vibrating method. The incorporation of silica fume into the CFRC composites exerted not only a good effect on the dispersion of carbon fibers, but also increased the density of the composites to further influence the conductivity of the CFRC.     

两种表面活性剂对碳纤维的协同分散作用分析

探讨了纤维分散剂与减水分散剂的作用机理,并确定了提高碳纤维水泥石均匀性所需要的两种表面活性剂的合适掺量.研究结果表明:纤维分散剂可以有效地分散纤维,但对胶结料粒子的分散是不利的;减水分散剂可以有效的分散胶结料粒子;二者协同作用可以有效提高整个纤维-水-胶结料粒子体系的均匀性;纤维分散剂的适用掺量为0.3～0.4%,减水分散剂的适用掺量应大于1.2%.     

短碳纤维在不同分散剂中的分散性

碳纤维增强水泥基复合材料(CFRC)已成为一种很有潜力的智能材料,其制备的关键是尽可能将碳纤维均匀分散到水泥基体中,这样才能得到性能优良的CFRC复合材料。该研究探讨了制备CFRC前期阶段碳纤维分散这一关键环节中,甲基纤维素(MC)、羧甲基纤维素钠(CMC)、羟乙基纤维素(HEC)3种常用分散剂的质量分数对短碳纤维在其水溶液中分散性的影响;分析了一定温度下分散剂质量分数和溶液黏度的关系;从纤维素结构出发,解释了不同分散剂的分散效果。实验表明,采用超声波对短碳纤维进行预分散,然后加入分散剂继续超声分散,均能提高短碳纤维的分散性。短碳纤维的分散性与分散剂的种类和质量分数有关。一定温度下,分散剂质量分数相同时,分散剂对短碳纤维的分散效果为HEC>CMC>MC,HEC掺量为水泥质量的0.6%~0.8%、其水溶液质量分数为1.56%~1.77%时,短碳纤维在水溶液中呈理想分散态。     

短碳纤维的分散性与CFRC复合材料的力学性能

碳纤维增强水泥基复合材料(CFRC)是新发展起来的一种功能材料,制备CFRC复合材料过程中,碳纤维在水泥基体中的分散性直接影响CFRC复合材料的力学性能。借助超声波和分散剂羟乙基纤维素(HEC),实现了短碳纤维在水泥基体中的均匀分散。对所制备的CFRC复合材料的断口形貌,作了SEM观察和能谱分析;测试了试件的抗压强度和抗折强度。结果发现,水灰质量比为0.44,碳纤维均匀分散,其质量掺量为0.6%时,复合材料的抗压强度可提高20%,抗折强度提高129%。     

碳纤维增强水泥基复合材料的电阻计算模型

根据碳纤维增强水泥基复合材料(carbon fiber reinflorced cement composite,CFRC)导电机理,将CFRC材料内部导电通路分成碳纤维搭接导电与隧道效应导电两种方式.通过假定碳纤维理想搭接,运用定量体视学理论计算碳纤维的搭接电阻.结果表明:随着碳纤维掺量的增加,CFRC材料中网络搭接导电通路所占比例逐渐增加,尤其在渗流区域附近,搭接通路所占比例急剧上升,但是在过渗流区碳纤维掺量对搭接电阻所占比例的影响呈现微弱上升趋势.隧道效应电阻模型计算则依据定态schTodinger方程,通过选取合适参数--电子跃迁的势垒与电子能量的比值U0/E,运用模型得到的计算值与试验值有较好的一致性.在相同的U0/E取值下,隧道效应电阻随着碳纤维掺量的增加而减小;而在同一掺量下,隧道效应电阻计算值随U0/E的增大而增大.     

New hybrid method for simultaneous improvement of tensile and impact properties of carbon fiber reinforced composites

For weight savings of automobiles to improve fuel efficiency, tensile and impact strengths of carbon fiber reinforced composites (CFRC) are important properties required for substitution of metallic or ceramic automotive parts by CFRC parts. Effect of surface treatments of carbon fiber (CF) such as plasma, nitric acid, and liquid nitrogen treatments on interfacial bonding and mechanical properties of CF reinforced thermoplastic composites was investigated and nitric acid treatment was the best method to improve the interfacial affinity between the used CF and thermoplastic polymer matrix since the treatment induced acidic functional groups on the surface and increased surface roughness simultaneously. A new hybrid fabrication method was suggested by applying a bi-component two-layer structure to the film insert molding to improve tensile and impact strengths of CFRC simultaneously. Compared with tensile and impact strengths of the base polymer, those of the new hybrid composites filled with rubber particles and CF were improved by about 41.3% and 105.7%, respectively. In particular, tensile and impact strengths of the composite specimen prepared by the hybrid fabrication method were improved by about 15.0% and 36.0%, respectively when compared with those of the composite specimen prepared by the conventional melt mixing.