HDPE/TiB_2-CB导电复合材料组织与性能研究

采用熔体共混法制备了高密度聚乙烯/二硼化钛-炭黑导电复合材料。研究了少量CB（炭黑）对HDPE/TiB2-CB复合材料室温电阻率、正温度系数（PTC）、负温度系数（NTC）效应和热循环稳定性的影响,并对HDPE/TiB2-CB复合材料的PTC效应随CB含量的变化原因进行了探讨。结果表明,加入少量CB明显降低了TiB2的填充量,由50%降为30%（质量分数,下同）。HDPE/TiB2-CB复合材料中CB含量为3%、TiB2含量为27%时复合材料的PTC强度达7,室温电阻率仅为1.25Ω.m,经过多次热循环后PTC效应仍然稳定。当CB含量超过6%时,室温电阻率稍有降低,但PTC强度迅速降到3.5以下。SEM分析表明CB对TiB2及CB在基体中形成导电通道影响明显。     

富镍导电涂层在模拟海水中的耐蚀性能研究

在高黏度的丙烯酸树脂中加入镍粉、消泡剂及其它助剂制备出具有导电功能的防腐涂料并涂覆在作为船舶材料的20#碳钢上。通过测试涂层的表面接触电阻来表征涂层的导电性,研究发现镍粉含量越高,涂层的导电性越好。用电化学阻抗谱研究了不同镍粉含量的导电涂层在模拟海水中的耐蚀性,并用扫描电镜(SEM)观察了浸泡90 d后涂层的表面形貌。结果表明,随浸泡时间的延长,镍粉的含量越高,涂层的容抗弧、阻抗、相位角、|Z|0.05越小;且下降的越快;从Tafel极化曲线可知,镍粉含量越高,涂层的腐蚀电流越大;从涂层表面的SEM像可知,镍粉含量越高,涂层表面腐蚀越严重。在所研究的体系中,镍粉的含量约在20%(质量分数)时,具有较好的导电性能和耐蚀性能。     

掺杂碳化硅对纳米炭黑导电和吸波性能的影响

在纳米炭黑中添加微米碳化硅制备了一种新型的复合吸收剂,并进行形貌表征、导电性能和微波吸收性能的测试.测试结果表明:加入碳化硅使得炭黑/环氧树脂复合涂层体电阻率和渗流阈值降低;炭黑含量较小时,加入碳化硅能有效提高涂层的反射衰减率.在5%(质量分数,后同)的炭黑中添加50%的碳化硅制备厚度为2 mm的涂层,反射衰减率在7.5～13.5 GHz宽频范围内均优于-10 dB,吸收峰最大值达-40 dB.     

镁合金表面有机防腐导电涂层的制备及性能研究

目的通过在AZ31镁合金表面微弧氧化陶瓷层上制备有机导电涂层,实现其既防腐又导电的功能。方法加入无机导电炭黑制备涂料体系,在前期制备的微弧氧化层表面,应用刮涂法制备不同配比的有机防腐导电涂层。采用场发射电子显微镜观察涂层的微观形貌,用电化学方法测试涂层耐蚀性,用双电侧四探针测试仪测量涂层电阻值。结果有机物中添加无机导电炭黑颗粒,对材料形貌有较大影响,随导电颗粒的添加,涂层表面质量下降,出现较多裂纹。与只有微弧氧化涂层的材料相比,其腐蚀电位提高了0.6～0.68 V。导电炭黑能有效地改善涂层的导电性,当炭黑添加量为10%时,涂层的平均电阻仅为70?。结论有机涂层由于封孔和惰性反应作用,能进一步提高微弧氧化涂层的耐蚀性,由于导电炭黑颗粒的隧道效应及导电网络作用,使得涂层导电性大幅提高。     

固化工艺对树脂基导电胶电性能的影响

本文以微米银片为导电填料制备了环氧树脂基各向异性导电胶,研究了固化工艺对导电胶电性能的影响。研究结果表明,固化工艺对银粉填量为55 wt％的导电胶影响较大。当固化温度是180 0C时,体积电阻率是5.2×10-2 Ω.cm,当固化温度是250 0C时,体积电阻率下降到4.5×10-3 Ω.cm. 然而,固化温度对高银粉填量的导电胶的影响较小。原位监测65 wt％的各向异性导电胶的固化过程中的电性能,发现固化27 分钟后体系温度是180 0C, 此时的电阻是1.99×106 Ω,40 分钟后的电阻是1.39 ×103 Ω,60 分钟后的电阻是18.8 Ω.冷却时,导电胶的电阻几乎不变化。采用扫描电阻显微镜分析了银粉在树脂基体中的分布,进而讨论了固化温度对体积电阻率的影响机制。     

固化工艺对树脂基导电胶电性能的影响（英文）

以微米银片为导电填料制备了环氧树脂基各向异性导电胶,研究了固化工艺对导电胶电性能的影响。研究结果表明,固化工艺对银粉填量为55%(质量分数)的导电胶影响较大。当固化温度为180oC时,体积电阻率是5.2×10~(-2)?·cm,当固化温度为250oC时,体积电阻率下降到4.5×10~(-3)?·cm.然而,固化温度对高银粉填量的导电胶的影响较小。原位监测65%的各向异性导电胶的固化过程中的电性能,发现固化27 min后体系温度是180oC,此时的电阻是1.99×10~6?,40 min后的电阻是1.39×10~3?,60 min后的电阻是18.8?,冷却时,导电胶的电阻几乎不变化。采用扫描电阻显微镜分析了银粉在树脂基体中的分布,进而讨论了固化温度对体积电阻率的影响机制。     

基于场致发射和量子隧道效应的镍粉填充压敏复合材料

通过测试不同种类、不同掺量镍粉复合水泥基材料的电阻率和受力时的电阻率变化规律,并结合镍粉颗粒状态和表面形貌的扫描电镜观察,探讨了镍粉水泥基复合材料的导电机理和压敏性产生机理。研究结果表明:刺球状镍粉掺量(体积分数)为15%、20%和25%的水泥基复合材料的导电性和压敏性依次提高;链状镍粉复合水泥基材料的导电性优于球状镍粉水泥基复合材料;刺球状镍粉复合水泥基材料的导电性优于表面光滑的球状镍粉水泥基复合材料。由此可见,镍粉水泥基复合材料的导电性和压敏性与镍粉的颗粒状态、表面形貌和掺量密切相关,刺球状镍粉水泥基复合材料具有良好导电性和压敏性是由场致发射效应和量子隧道效应所致。     

石墨烯/生漆复合抗静电涂层的制备与性能

分别以碳系材料石墨烯、炭黑、石墨为导电填料,生漆复合物为基材制备生漆复合抗静电涂层,讨论了导电填料含量对涂层导电性与力学性能的影响,并用扫描电镜(SEM)和热重分析仪(TGA)对涂层进行分析。结果表明:当导电填料石墨烯、炭黑、石墨的添加量分别为0.6%、15%、15%时,涂层具备抗静电能力。石墨烯复合涂层的附着力为0级、柔韧性1mm、耐冲击性50cm,优于未加填料的涂层以及添加石墨、炭黑为导电填料的复合涂层。同时,石墨烯复合涂层的耐介质性能以及耐热性能均表现优异。     

添加纳米银粉对导电胶体积电阻率的影响

将3种银粉,即:片状银粉、片状银粉加入5%纳米银粉的混合粉、片状银粉加入10%纳米银粉的混合粉,加入双酚F环氧树脂中配制导电胶。通过在玻璃基片上印刷导电胶条,固化后测量其长、宽、厚和电阻,利用公式ρ=Rs/l计算体积电阻率。结果表明,当纳米银粉添加量为5%时,体积电阻率出现明显下降,混合银粉含量为75%时的体积电阻率能达到1.6×10-4?·cm。在接近"穿流阈值"时,加入纳米银粉可以增大颗粒间的接触面积,形成更多的导电通路,能降低导电胶的体积电阻率。     

一维银线制备及其在导电胶中的应用

用不锈钢辅助醇热法高浓度、大规模制得低长径比(约为10～20)的一维银线,AgNO3浓度可达0.65 mol/L;该一维银线可作为导电胶的导电填料使用;一定范围内降低AgNO3浓度生成的一维银线其长度几乎保持不变,但平均直径略有减小;采用反应活性较低的不锈钢,提高初始反应温度对一维银线的形成有不利的影响。一维银线经球磨可制得类似带状的银粉;采用带状银粉制备的导电胶体积电阻率较一维银线更低,渗流阈值可以降至20%(质量分数)。     

From conductive polymer composites with controlled morphology to smart materials

Conductive polymer composites (CPC) based on insulating matrix with conductive dispersed fillers are extensively studied since many years. A specific feature of such materials is a value of the filler content corresponding to the percolation threshold where a sharp transition insulating/conductive state occurs. The objective of this work is first the study of percolation phenomena in composites based on polypropylene (PP), on copolymers of polyamides (CPA) and polymer blends PP/CPA filled with dispersed iron (Fe) related to their structure but also to pay attention to their specific behaviour in temperature so-called PTC effect which can be controlled according the composition and the structure in the heterogeneous polymer matrix of the composites to elaborate intelligent/smart materials.     

无溶剂环氧导静电涂料的性能研究

以4种导静电填料为研究对象,对涂层采用表面电阻率测试、扫描电镜、X射线衍射法和傅里叶红外分析等检测方法,分析了导静电填料的种类、形状、尺寸、添加比例和分散状态等因素对环氧无溶剂导静电涂料性能的影响.结果表明,导静电填料的添加量越大,导静电性能越好,但涂层的其它性能会有所损失;导电填料的尺寸越小,导电性能越好.试验确定了...     

填料增强先驱体转化法制备陶瓷涂层的研究进展

先驱体转化陶瓷法是一种原位制备陶瓷涂层的新型方法.在先驱体转化陶瓷法制备陶瓷涂层时,选择陶瓷产率较高的先驱体和添加填料是降低陶瓷涂层气孔率和收缩率的重要途径.填料在先驱体转化陶瓷法制备陶瓷涂层中起着重要作用,通过添加填料,可进一步提高陶瓷涂层的性能并扩展其功能特性.填料主要包括惰性填料、活性填料、熔融型填料和牺牲型填料4种.对比了4种填料的类型和特点,介绍了填料增强陶瓷涂层的作用机制和选取原则,综述了填料增强先驱体转化陶瓷法制备陶瓷涂层的研究现状.在裂解过程中,惰性填料的质量和体积均保持不变,可加入较高体积分数的惰性填料制备厚涂层;活性填料可与先驱体、裂解产生的小分子气体、保护气氛等反应,实现陶瓷涂层的近净成形;熔融型填料熔融后,填充到涂层空隙中,可提高涂层的致密化程度,消除基体和陶瓷涂层以及填料和先驱体之间由于热膨胀系数不匹配产生的应力;牺牲型填料分解后,形成孔状涂层,可控制陶瓷涂层中的应力,降低陶瓷涂层的有效弹性模量,增强陶瓷涂层的应变强度.针对陶瓷涂层的服役工况,选择合适的填料类型,确定填料的临界体积分数,揭示填料对陶瓷涂层组成、晶界结构、涂层致密化、裂纹缺陷及裂解反应过程的影响规律,研发新型裂解技术和工艺以控制先驱体转化为陶瓷涂层过程中产生的应力,是后续研究中需要重点关注的问题.     

Application of face centred cubic TiB powder as conductive filler for electrically conductive adhesives

Face centred cubic (FCC) TiB ceramic powder synthesized by Ti-boronizing method was used as conductive filler to make ceramic electrically conductive adhesives (ECAs) with the polymer matrix. Electrically conductive properties of the ceramic ECAs were studied. The bulk electrical resistivity varied with the powder content of the FCC-TiB in ECAs. The FCC-TiB filled ECAs also showed the percolation behavior that usually occurred for the metal-filled ECAs, the percolation threshold was located at the content of 60% FCC-TiB. A minimum value of 0.1 Ω·cm was obtained at a content of 75% FCC-TiB. In order to check the reliability of mechanical property, tensile test was done to measure the shear strength, and the shear strength dropped with increasing the content of FCC-TiB powders. It is about 12.26 MPa at the content of 70% TiB powders. The Cu filled ECAs were also prepared for comparison. The properties of the oxidation resistance of the two ECAs were evaluated. The results show that the ceramic ECAs have excellent oxidation resistance and better stability compared with the Cu filled ECAs.     

Effect of thermal annealing on the electrical conductivity of high-strength bicomponent polymer tapes containing carbon nanofillers

A new concept is described that creates highly oriented multifunctional polymer nanocomposite tapes (or fibres) that combine high stiffness and strength with good electrical properties and a low percolation threshold of conductive nanofillers. The concept is based on a bicomponent construction consisting of a highly oriented polymer core together with conductive polymer composite skins based on a polymer with lower melting temperature than the core. This construction allows for a thermal annealing process that can be applied selectively to the skins to improve their conductivity through a kinetic re-aggregation process while retaining the mechanical properties of the core and hence those of the overall tape or fibre. In the current study this generic concept was applied to bicomponent tapes based on a polypropylene homopolymer core and a multi-wall carbon nanotube or carbon black filled polypropylene copolymer skin. The conductivity of the bicomponent tape containing 5.3 wt.% of MWNTs in its outer skins increased from 1.3E?6 to 1.5 S/cm after annealing while the percolation threshold in the copolymer skins of highly drawn bicomponent tapes could be decreased from 5.3 to 1.1 wt.%. To the best of the authors’ knowledge this is the lowest percolation threshold reported in literature for highly drawn polymer nanocomposites fibres or tapes. In fact, the percolation threshold is as low as 0.1 wt.% when considered on the overall tape as the conductive skins account for only 10% of the total volume of these bicomponent tapes.     

Preparation and characterization of graphite-nickel composite coatings by automatic brush plating

Composite coatings of nickel with G particles were produced on AISI 1045 carbon steel substrate by using a newly developed automatic brush plating system. Pure nickel coating was also prepared for comparative study. The volume percent incorporation of G powder in the composite coatings was investigated with respect to its concentration in bath and relative anode to cathode speed. It was shown that the volume percentage of G was strongly affected by these parameters. The G particle distribution in the composite coatings was uniform across the coating at low concentration of G in bath and agglomerated on the surface at high concentrations. The wear and friction properties of G-Ni composite coatings containing different amounts of G particles were studied. The results revealed that hardness, wear resistance and friction coefficient are dependent on volume percentage of G in composite coating. In this study, it was shown that G-Ni composite coating with 15% G possessed the best wear-resistance property.     

Conductivity and mechanical properties of conductive adhesive with silver nanowires

The aim of this study was to develop conductive adhesive using silver nanowires prepared via solvothermal method as conductive fillers and epoxymodified organosilicone resin as matrix resin. Effect of the addition of silver nanowires/flakes on the conductive adhesive's electrical and mechanical properties was investigated. Compared with conventional conductive adhesive with silver flakes fillers, the percolation threshold of conductive adhesive with silver nanowires fillers is 10 % lower approximately. However, further rise of the content of silver nanowires has no obvious influence on improvement of the electrical conductivity of conductive adhesive. Both conductive and mechanical properties of conductive adhesive can be compatible by adding silver nanowires, which traditional silver conductive adhesives cannot reach.     

碳纤维含量对导电涂层雷达波反射特性的影响研究

目的获得不同碳纤维含量导电涂层对雷达波反射特性的影响规律,实现假目标雷达波反射特性控制。方法选择碳纤维粉为导电功能填料,丙烯酸聚氨酯树脂为粘结剂,制得碳纤维质量分数为0%~20%的导电涂料。研究碳纤维含量对涂层试板雷达波反射特性、涂层表面电阻率的影响,并在聚氨酯泡沫圆锥体构件模型上进行了试验验证。结果碳纤维质量分数从0%增加4%时,涂层表面电阻率从2.40×10~(11)?迅速降低至1.80×10~3?,雷达散射截面积(RCS)从-3.07 dBsm急剧增大至10.54 dBsm;增大到10%时,涂层表面电阻率呈波动缓慢下降的趋势,RCS缓慢增大至11.05 dBsm;继续增至20%时,涂层表面电阻率和RCS均变化很小。构件模型雷达波反射特性测试表明,碳纤维质量分数达10%时,聚氨酯泡沫圆锥体模型的表面电阻率为6.29×10~2?,0°~360°RCS达-7.12 dBsm,与贴铝膜诱饵的RCS(-6.48 dBsm)接近。结论碳纤维含量对涂层表面电阻率和雷达波反射特性的影响显著,在4%~10%为宜,在此范围内,涂层表面电阻率明显降低,呈现明显的金属化特征,雷达波反射特性与金属材料接近。     

耐火填料急热膨胀值与涂层高温抗裂性的关系

通过对耐火填料和砂基底的急热膨胀值的测定，证实了耐火填料与砂基底之间的膨胀值是否相匹配决定了涂料层在高温下开裂的程度。根据此法选出的耐火材料所组成的涂料在高温急热时不开裂，浇注出的铸件表面无缺陷，表面粗糙度达１８－Ｓ。