聚乙烯复合导电塑料世

采用高密度聚乙烯、SEBS、导电炭黑和炭纤维等经过混合、造粒、注塑成型等工艺过程,制备了聚乙烯复合导电塑料,测试了其物理化学性能。同时设计了复合导电塑料的检漏方法和耐电化学腐蚀的实验方法。结果表明,聚乙烯复合导电塑料的体积电阻率达到0．2Ω·cm,拉伸强度为47．6MPa,断裂伸长率1．6％,同时具有不渗液、耐腐蚀等特性,SEM观察表明,聚乙烯复合导电塑料中形成了导电网络,适合用作钒电池的集流体。     

交流阻抗谱在聚乙烯/碳黑导电复合材料导电机理研究中的应用

用交流阻抗谱论证了聚乙烯/碳黑(PE/CB)导电复合材料的网络导电机理,分析了热处理过程对复合材料电性能的影响。通过在不同频率和低电压下测定热处理前后及不同长度的导电复合材料样品的导电能力(A)、导电方式(B)和电阻值(Ra Rc),证明了材料内部存在着直通碳链、小间隙的碳链和大间隙的碳链,呈现三维网络导电结构。     

聚乙烯/碳黑导电复合材料的导电性能

提出并验证了聚乙烯/碳黑(PE/CB)导电复合材料的网络导电性能和产生正温度系数(PTC)特性的原因,分析了加工过程、温度和辐射交联等后处理过程对其导电性能的影响.     

聚乙烯/聚并苯复合材料室温电阻率变化规律研究

以新型导电材料聚并苯替代碳黑作为导电填料制备聚乙烯/聚并苯复合物.确定了复合物渗流转变区,并解释渗流转变现象的产生机理.从聚并苯含量和热处理过程,对聚乙烯/聚并苯复合物室温电阻率变化规律进行讨论.结果表明,聚并苯质量分数在20%～40%之间是聚乙烯/聚并苯复合物渗流转变区;热处理有利于聚乙烯晶区完善排列,也有利于导电链形成;以聚并苯作为导电填料所制备的复合物具有较高的PTC强度;辐射交联可以提高聚乙烯/聚并苯复合物PTC强度,抑制NTC效应.     

多壁碳纳米管/聚乙烯复合材料的制备及其导电行为

多壁碳纳米管/聚乙烯复合材料的制备及其导电行为;碳纳米管;高密度聚乙烯;渗流阈值;导电行为;V-PTC特性     

HDPE/EPDM/CB复合物的PTC效应

聚合物正温度系数 (PTC)材料 ,是由聚合物基体与炭黑、碳纤维、金属粉末等导电填料共混而成的一种功能导电复合材料 ,其特点是 :当温度升高时 ,在聚合物结晶熔点附近 ,材料的电阻率随温度升高急剧增加 ,可发生几个数量级的突跃 .聚合物 PTC材料可用作自限温加热器、过电流保护器、传感器等 ,有广阔的发展前景 .目前对聚合物 PTC材料的研究主要以聚乙烯 [1～ 5]、乙烯 -醋酸乙烯酯共聚物[6] 、偏氟乙烯 [7] 等单一组分聚合物作为基体材料 .本文研究了以高密度聚乙烯 (HDPE) /三元乙丙胶(EPDM)共混物为基体材料的炭黑 (CB)导电复合材…     

聚乙烯/炭黑复合材料导电体系的结构形态

将导电填料（例如炭黑）加入绝缘的聚合物基体即得到导电复合材料,两组混全物的电阻率随导电填料体积分数的变化而改变,电阻率与导电填料体积分数的关系称为渗流曲线,可分为三个主要区域：低导电填料含量区域,复合材料的电阻率很大,聚合物的电阻率占主导;渗流区域,导电填料含量少量的增加会引起复合材料电阻率很大的提高;高导电填料区域,复合材料电阻率很大的提高;高导电填料区域,复合材料电阻率主要由导电填料的电阻率决定,对于导电复合材料已有大量的实验和理论工作来解释导电复合材料已有大量的实验和理论工作来解释导电填料含量和复合材料各组分的形貌对电性能的影响,其中有效介质普适方程（GEM方程）已经对大量的渗流曲线进行了精确的拟合。聚乙烯／炭黑复合材料中由于炭黑的大量分布很难观测其微观形貌,本文对不同辐照交联程度和不同环境温度下聚乙烯／炭黑复合材料的渗流曲线进行分析,试图找出GEM方程各参数与复合材料各组分形貌的关系,为导电复合材料的设计和制备提供理论基础。     

X射线光电子能谱测定固体粉末样品的制备方法比较

样品制备方法对X射线光电子能谱测试结果具有较大影响,以导电样品锂电材料和不导电样品奶粉为测试对象,探讨了不同制样方法对两者测试效果的影响.试验结果表明,导电样品锂电材料使用导电胶铜片制样效果较好,而不导电样品奶粉使用导电胶压片或3M胶带压片效果较好.     

硫化聚合物锂离子电池正极材料的研究进展

用单质硫对聚合物进行硫化,可以制备具有电化学活性的导电高分子材料.这些材料用作锂离子电池正极活性材料,可获得较高的比容量.综述了聚二乙基硅氧烷、聚乙烯、聚乙炔、聚苯乙烯、聚丙烯腈等聚合物通过单质硫在200～360℃下硫化所制得的导电高分子材料的电化学特性.     

导电环氧树脂消除扫描电子显微镜图像荷电问题的原理与实践

荷电问题常造成扫描电子显微镜(SEM)图像上产生亮度不均、条纹等伪影.提出一种利用导电环氧树脂镶嵌样品以消除SEM图像荷电的方法,并与传统导电胶粘贴制样方法对1 000℃高温混凝土、瓷土与河南双槐树考古土三种样品的适应性进行了对比研究.结果表明,利用铜粉与环氧树脂混合制备导电环氧树脂并将样品镶嵌其中所制备样品的SEM图像基本无荷电问题,而传统导电胶粘贴方法所制备样品的SEM图像存在较严重的荷电问题,通过增加导电层厚度并不能对此进行改善,且易造成微纳结构被掩盖.最后对传统制样方法导致荷电问题的原因与导电环氧树脂对荷电问题的改善原理进行了分析.     

Metallic single-walled carbon nanotubes for conductive nanocomposites

This article reports an unambiguous demonstration that bulk-separated metallic single-walled carbon nanotubes offer superior performance (consistently and substantially better than the as-produced nanotube sample) in conductive composites with poly(3-hexylthiophene) and also in transparent conductive coatings based on PEDOT:PSS. The results serve as a validation on the widely held view that the carbon nanotubes are competitive in various technologies currently dominated by conductive inorganic materials (such as indium tin oxide).     

Preparation, microstructure, and electrochemical properties of Sn-Co-C anode materials using composited carbon sources

Sn-Co-C alloy as a promising anode material was prepared via a facile carbothermal reduction method, using both graphite and sucrose as the composited carbon sources. The effect of the combination pattern of graphite and sucrose on the microstructure and electrochemical performances of the alloys was investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and galvanostatic cycling tests. Compared with the Sn-Co-C samples using only graphite or sucrose as the carbon sources, the sample using the composited carbon sources has a relative higher reversible capacity and better rate capability, which is probably related to the continuous and stable conductive network formed by graphite and amorphous carbon originated from the thermal decomposition of sucrose, as well as the small particle size and uniform distribution in the conductive network.     

制样方法对固体粉末X射线光电子能谱测试结果的影响

为了得到准确且分辨率高的X射线光电子能谱(XPS)数据,采用不同制样方法对不同类型的导电、不导电和混合粉末的测试结果进行了研究. 从图谱半峰宽、是否有荷电、真实性、制样效率和数据处理等方面阐述不同制样方法对测试结果的影响. 试验结果表明,对于导电和不导电粉末,粘取制样略优于铟片制样,其中使用碳导电胶带制样效果更好. 对于混合样品,Scotch双面胶带粘样后的测试结果优于其他3种制样方式. 此外,铟片制样可作为数据处理时荷电校正的参考方法.     

Resistivity-Temperature Behavior of CB-Filled HDPE Foaming Composites

High-density polyethylene/carbon black foaming conductive composites were prepared from acetylene black（ACEY） and super conductive carbon black（HG-1P） as conductive filler, low-density polyethylene（LDPE） as the second component, ethylene-vinyl acetate（EVA） and ethylene propylene rubber（EPR） as the third component, azobisformamide（AC） as foamer, and dicumyl peroxide（DCP） as cross-linker. The structure and resistivity-temperature behavior of high-density polyethylene（HDPE）/CB foaming conductive composites were investigated. Influences of carbon black, LDPE, EVA, EPR, AC, and DCP on the foaming performance and resistivity-temperature behavior of HDPE/CB foaming conductive composites were also studied. The results reveal that HDPE/CB foaming conductive composite exhibits better switching characteristic; ACET-filled HDPE foaming conductive composite displays better positive temperature coefficient（PYC） effect; whereas super conductive carbon black（HG-1P）-filled HDPE foaming conductive composite shows better negative temperature coefficient（NTC） effect.     

Novel headspace gas chromatographic method for determination of oxalate in oxygen delignification liquor

A novel headspace gas chromatographic (HS-GC) method is demonstrated for an indirect determination of oxalate in oxygen delignification liquors. A small volume (50-100 microL) of liquor sample is introduced into a sampling vial that contains 1.0 mL of 2 mol/L sulfuric acid. After removal of carbon dioxide (generated from carbonate in the acidic medium) by heating, the sample was mixed with a 0.5 mL of 0.02 mol/L potassium permanganate solution in a closed testing vial. At an elevated temperature (70 degrees C), the oxalate in the sample is rapidly converted to carbon dioxide by reacting with permanganate. The carbon dioxide in the headspace can be measured by gas chromatography with a thermal conductive detector. Using a multiple headspace extraction (MHE) measurement technique, the kinetics of formation of the carbon dioxide from the other organic species in the sample can be determined, and thus a correction can be made for minimizing the interferences. The present method is simple, accurate and can be easily automated.     

Segregated network polymer/carbon nanotubes composites

In this work we present the preparation of conductive polyethylene/carbon nanotube composites based on the segregated network concept. Attention has been focused on the effect of decreasing the amount of filler necessary to achieve low resistivity. Using high- and low-grade single-walled carbon nanotube materials we obtained conductive composites with a low percolation threshold of 0.5 wt.% for high-grade nanotubes, about 1 wt% for commercial nanotubes and 1.5 wt% for low-grade material. The higher percolation threshold for low-grade material is related to low effectiveness of other carbon fractions in the network formation. The electrical conductivity was measured as a function of the single-walled carbon nanotubes content in the polymer matrix and as a function of temperature. It was also found that processing parameters significantly influenced the electrical conductivity of the composites. Raman spectroscopy was applied to study single wall nanotubes in the conductive composites.     

Improving Elasticity of Conductive Silicone Rubber by Hollow Carbon Black

Carbon black-based conductive rubber composites have important impacts on electromagnetic interference(EMI) shielding applications. However, an excessive amount of carbon black in the recipes of these conductive rubbers has caused their weak elasticity. Herein, hollow carbon black(HCB) particles were used to tune the elasticity of conductive rubber composites. Unique hollow morphology produced a better compression recovery of HCB than other solid carbon black, such as acetylene black. When the coupling agent was bonded to HCB, their conductive silicone rubber composites were featured by high stretching resilience, a fast compression recovery and excellent conductivity to satisfy the electromagnetic interference shielding requirements. Importantly, the rubber composites with coupling HCB had extremely low variations of mechanical property, conductivity and EMI shielding effectiveness after thermal accelerated aging tests. It is therefore revealed that the elasticity of HCB and its interfacial chemical coupling with rubber chains both play crucial roles in adjusting the elasticity of conductive rubber to sever long-term EMI protection.     

Carbon nanotubes as a conductive additive in LiFePO<Subscript>4</Subscript> cathode material for lithium-ion batteries

The electrochemical properties and cyclic performances of commercial LiFePO₄ cathode material with different ratio of carbon black (CB) and carbon nanotubes (CNTs) as conductive material were tested in this study. Compared with other samples, the sample with 3 wt % CNTs exhibited the best electro-chemical and cyclic performances at various discharging rate at room temperature; and adhesion strength of electrode was improved by adding CNTs. The enhanced electrode performance may due to the unique natures of CNTs and the contact area of CNTs with active material or current collector.     

Carbon Nanostructures Derived through Hypergolic Reaction of Conductive Polymers with Fuming Nitric Acid at Ambient Conditions

Hypergolic systems rely on organic fuel and a powerful oxidizer that spontaneously ignites upon contact without any external ignition source. Although their main utilization pertains to rocket fuels and propellants, it is only recently that hypergolics has been established from our group as a new general method for the synthesis of different morphologies of carbon nanostructures depending on the hypergolic pair (organic fuel-oxidizer). In search of new pairs, the hypergolic mixture described here contains polyaniline as the organic source of carbon and fuming nitric acid as strong oxidizer. Specifically, the two reagents react rapidly and spontaneously upon contact at ambient conditions to afford carbon nanosheets. Further liquid-phase exfoliation of the nanosheets in dimethylformamide results in dispersed single layers exhibiting strong Tyndall effect. The method can be extended to other conductive polymers, such as polythiophene and polypyrrole, leading to the formation of different type carbon nanostructures (e.g., photolumincent carbon dots). Apart from being a new synthesis pathway towards carbon nanomaterials and a new type of reaction for conductive polymers, the present hypergolic pairs also provide a novel set of rocket bipropellants based on conductive polymers.