粉煤灰漂珠@BaTiO_3@PAn的制备及其电流变性能

聚苯胺(PAn)作为电流变材料具有响应快、屈服应力大的特点,但因其良好的导电性能导致漏电击穿现象发生,为了进一步增加PAn的悬浮稳定性,引入了粉煤灰漂珠(FAFB),BaTiO_3作为经典的电介质材料也引入其中以进一步提高材料的介电性能。采用逐层包覆的思路,利用溶胶-凝胶法在漂珠表面包覆BaTiO_3,获得FAFB@BaTiO_3,再利用原位聚合法制备以FAFB@BaTiO_3为核、PAn为壳的结构复合材料即FAFB@BaTiO_3@PAn。利用FTIR、XRD和SEM对材料的结构与形貌进行分析,借助四探针技术和LCR数字电桥对材料的导电与介电性能进行分析,利用自组装电流变仪进行了电流变特性测试,考察了7d内的悬浮稳定性能。结果表明:BaTiO_3、PAn确实发生了逐层包覆,且电导率、介电常数、介电损耗和剪切应力均符合复合效应规律,介于PAn与FAFB@BaTiO_3之间,其中,剪切应力可达675Pa(电场强度为3.0kV/mm);漏电现象得到缓解,击穿电压提高了20%;比较悬浮稳定性发现,7d后FAFB@BaTiO_3@PAn悬浮率仍为82%。     

核壳结构SiCNWs@SiO2/PVDF复合材料的制备与介电储能特性

为了加速新能源电子器件向微型化和集成化的方向发展，提高电子器件内部介电复合材料的性能至为重要，介电复合材料的介电性能和储能性能直接影响电子器件的质量，如何提高介电复合材料的介电性能和储能性能等引起了研究者们的广泛关注。以聚偏氟乙烯(PVDF)为基体，碳化硅纳米线(SiCNWs)和核壳结构碳化硅纳米线@二氧化硅(SiCNWs@SiO₂)为填料，通过溶液共混相转换法及热压工艺制备出一系列的SiCNWs/PVDF二元复合材料和SiCNWs@SiO₂/PVDF复合材料。探究介电纳米填料的表面修饰对PVDF基复合材料的微观结构、宏观介电性能和储能性能等的影响。实验结果表明，硅烷偶联剂KH550成功改性SiCNWs；通过一步法热氧化工艺成功制备出具有典型核壳结构的SiCNWs@SiO₂纳米线，SiO₂壳层的厚度随着SiCNWs热氧化时间的延长而增大，当SiCNWs热氧化时间为10 h,SiO₂壳层的厚度为6.5 nm；采用相转换法和热压处理成功制备一系列的SiCNWs/PVDF二元复合材料...     

聚苯胺@季铵盐阳离子改性粉煤灰漂珠的制备与电流变性能

选用3种不同链长的烷基季铵盐阳离子表面活性剂即十二烷基三甲基溴化铵（DTAB）、十四烷基三甲基溴化铵（TTAB）和十六烷基三甲基溴化铵（CTAB）对粉煤灰漂珠（FAFB）进行改性,并将改性产物与苯胺（An）共混进行乳液聚合,制备聚苯胺@有机改性粉煤灰漂珠（PAn@OFAFB）复合材料。采用化学元素分析、FTIR、XRD、SEM、TGA、数字四探针测试仪、LCR数字电桥和旋转流变仪对复合材料进行结构表征以及电流变性能分析。结果表明:改性剂的碳链长度越长,改性效果越好,CTAB吸附在FAFB表面的量最多,且表面吸附率为1.91wt%,PAn和OFAFB 复合程度越明显,FAFB表面包覆的PAn越多;聚苯胺@十六烷基三甲基溴化铵改性粉煤灰漂珠（PAn@FAFB-CTAB）的电导率最大为0.06 S·cm-1;将其作分散相制成的电流变液比PAn-十二烷基苯磺酸（PAn-DBSA）具有更好的电流变效应,抗击穿能力较纯PAn提高了0.5 kV/mm;将FAFB作为PAn的载体能够提高复合材料的悬浮稳定性;引入FAFB-CTAB可以显著改善复合材料的热稳定性,且PAn的相对包覆量为28.07wt%。      

柔性PDMS基介电复合材料的电场及击穿损伤形貌演变规律研究

与其它储能设备相比,由介电复合材料制得的介质电容器在快速充放电能力与高功率密度方面极具优势,如何提高介电复合材料能量密度与优化其击穿性能已成为当前研究热点之一。为进一步调控并兼顾介电常数与击穿性能,本工作基于DBM(DielectricBreakdownModel,介电击穿模型),采用有限元数值模拟,研究了无机填料的分布对柔性聚二甲硅氧烷(PDMS)基介电复合材料体系的电场与发生介电击穿时击穿损伤形貌演变的具体影响。研究结果表明:填料与基体边界处存在较大的介电差异,可以使用较大介电常数的聚合物基体或较小介电常数的无机填料来减小其界面处的高电场区域,继而提高复合材料的耐击穿能力；同时发现当无机填料分散更均匀时,其树状损伤通道更容易产生分支,此种情况将使介电击穿的树状损伤通道的损伤位点增多,延缓其损伤速度,继而提高复合材料的耐击穿性能。该研究结果将为开发高储能密度且具有优异击穿性能的有机-无机复合电介质材料提供坚实的理论依据。     

表面修饰对纳米Fe3O4/导电聚苯胺复合材料结构和电磁性能的影响

主要研究了一种具有雷达波吸收能力的核-壳结构导电、导磁材料,该材料以磁性Fe3O4作为内核,以十二烷基苯磺酸(DBSA)掺杂的聚苯胺包覆在核外形成导电外壳,通过TEM、FTIR、TG和介电常数及磁导率的测量比较了分别用PEG和FeCl3将纳米Fe3O4表面修饰后,其复合材料结构和电磁性能的变化.结果表明:表面改性后的纳米Fe3O4/聚苯胺复合材料的颗粒分散度和热稳定性都得到了提高,其中FeCl3修饰的纳米粒子由于Fe3 的同粒子作用,平均粒径只有60-80nm,热分解温度达到了410℃;同时,经表面修饰后的纳米Fe3O4/聚苯胺复合材料的初始介电常数和磁导率都有大幅度的增加,但其频散效应明显,因此在低频段的电磁损耗相对较大,较表面未改性的纳米复合材料具有更强的吸波性能.     

核-双壳BT@TiO_(2)@PDA纳米粒子的制备及其复合薄膜的介电性能EI北大核心CSCD

为改善聚酰亚胺(PI)基复合薄膜界面相容性,达到提高其介电性能的目的,利用钛酸正丁酯的水解反应在钛酸钡纳米粒子(BT)表面包覆水合TiO_(2)。采用聚多巴胺(PDA)进一步包覆改性粒子,制备出具有核-双壳结构的钛酸钡纳米粒子(BT@TiO_(2)@PDA)。利用核-双壳结构形成双重梯度缓冲层,减小高介电钛酸钡纳米粒子和低介电聚合物之间由于介电常数差异造成的电场畸变。通过溶液流延法制备一系列含有不同质量分数的改性钛酸钡/聚酰亚胺复合薄膜(BT@TiO_(2)@PDA/PI)。结果表明:核-双壳结构可以改善钛酸钡纳米粒子在聚酰亚胺基体中的分散性及二者的界面相容性。当填料质量分数为40%时,BT@TiO_(2)@PDA/PI复合薄膜的介电常数κ提高到8.8(1 kHz),约为纯聚酰亚胺的2.7倍,为钛酸钡/聚酰亚胺复合薄膜(BT/PI)的1.4倍。介电-温度和介电-频率测试证实,BT@TiO_(2)@PDA/PI复合薄膜具有良好的温度和频率稳定性。在100 kHz的频率范围内,复合薄膜的介电损耗均小于0.010;当填料的质量分数低于40%时,温度从25℃增加到160℃,复合薄膜介电常数的降低数值均不超过0.6(1 kHz)。     

活性碳纤维/树脂复合吸波材料的设计

研究了长度为1—2mm的活性碳纤维的介电特性。发现随频率的增大，介电常数的实部减小，虚部增大，具有频响效应。介电常数的实部和虚部均随复合材料中纤维质量百分含量的升高而增大。依据纤维的介电常数，通过阻抗匹配设计方法，优化设计两层和四层活性碳纤维吸波复合材料。根据优化结果制备了含有四个结构层的吸波复合材料，材料-10dB以下的频带宽度为8GHz，最大反射衰减-39．3dB。     

0-3 型压电陶瓷/ 硫铝酸盐水泥复合材料的介电性及压电性

以硫铝酸盐水泥为基体, 铌镁锆钛酸铅(PMN) 陶瓷颗粒为功能体制备了水泥基压电复合材料。重点讨论了复合材料的介电性能和压电性能。结果表明: 水泥基压电复合材料的介电温谱在- 30 ℃～150 ℃范围内较平坦, 表现出优良的介电温度稳定性, 而介电损耗随着温度的升高而增加; 水泥基压电复合材料的压电应变常数和介电常数均随着PMN 含量的增加而增大。      

壳核型聚苯胺/钛酸钡复合电流变材料的制备及表征

采用溶液聚合的方法,在经过硅烷偶联剂表面修饰的钛酸钡微粉表面原位聚合聚苯胺,得到聚苯胺/钛酸钡壳核结构(BaTiO3/PAn)的有机-无机复合粒子.借助SEM、XRD、FT-IR、DSC-TG等分析手段研究了复合粒子的形貌、结构及热性能.利用改装后的旋转粘度计分别对钛酸钡和聚苯胺/钛酸钡复合颗粒的电流变性能进行研究.结果表明利用硅烷偶联剂成功地在钛酸钡粒子表面接枝合成聚苯胺,聚苯胺/钛酸钡复合颗粒电流变液的电流变性能明显比纯钛酸钡的电流变性能有所提高.     

碳化钛/环氧树脂纳米复合材料的介电性能研究

采用溶液混合随后热压的方法制备了TiC/epoxy纳米复合材料.运用渗流阈值理论解释了TiC/epoxy复合材料的介电行为.研究了复合材料介电常数与填料体积百分比含量和测试频率的关系.结果表明:当TiC体积百分比含量为0.192时,复合材料的介电常数高达214(103Hz).复合材料介电常数在高测试频率范围(104～106Hz)不随频率的变化而改变.     

Tailoring of thermal and dielectric properties of LDPE-matrix composites by the volume fraction,density, and surface modification of hollow glass microsphere filler

Hollow glass microsphere (HGM) filled low-density polyethylene (LDPE) composites were prepared, and the effects of density, content, and surface modification of HGM on the thermal and dielectric properties of the composites were investigated. It is found that the thermal conductivity of the composites decreases with increasing HGM content or decreasing HGM density. At the same HGM content and density, the composites filled with suitable amount of silane coupling agent (KH570) modified HGM exhibit higher thermal conductivity than unmodified-HGM filled composites. The dielectric constant at 1 MHz of the composites also decreases with increasing HGM content or decreasing HGM density, but their dielectric loss increases with increasing HGM content or increasing HGM density. By modifying the surface of HGM with suitable amount of KH570, the dielectric constant and loss at 1 MHz of the composites can be decreased at the same time. The results of microwave dielectric properties of the composites indicate that the dielectric constant decreases with increasing HGM content or decreasing HGM density, the quality factor (Q × f) decreases with increasing HGM content or increasing HGM density, but both dielectric constant and quality factor are slightly affected by the surface modification of HGM. Due to lower intrinsic thermal conductivity and dielectric constant but higher dielectric loss of HGM than LDPE, the thermal conductivity and dielectric properties of the composites can be controlled with adding HGM and varying its volume fraction. The surface modification of HGM improves the interface contact between HGM and LDPE in the composites, which is confirmed by the SEM observation, and thus the heat conduction and dielectric properties at low frequency are improved. Based on calculated thermal conductivity and dielectric constant of HGM, the experimental trends of thermal conductivity and dielectric constant at 1 MHz of the composites are analyzed by using different models, including typical models for particles-filled composites and special models developed for hollow microsphere filled composites. The results from suitable models show close correlation with the experimental values.     

多壁碳纳米管/聚偏氟乙烯高介电常数复合材料的制备与性能

为制备具有高介电常数的复合材料,采用注射成型法制备了原始多壁碳纳米管(P-MWCNTs)/聚偏氟乙烯(PVDF)复合材料和石墨化多壁碳纳米管(G-MWCNTs)/PVDF复合材料。然后,对P-MWCNTs和G-MWCNTs进行了Raman光谱表征,对MWCNTs/PVDF复合材料进行了断面形貌、力学性能和电学性能测试。结果表明:G-MWCNTs比P-MWCNTs具有更高的纯度和结晶度,两种不同的MWCNTs都能均匀分散在PVDF基体中,添加MWCNTs会显著影响PVDF的力学行为。MWCNTs/PVDF复合材料的介电性能随MWCNTs含量的增加而提高,与P-MWCNTs相比,G-MWCNTs有效降低了复合材料的渗流阈值。当频率为100 Hz时,纯PVDF的介电常数为7.0;当P-MWCNTs的含量为5wt%时,复合材料的介电常数为23.8;当G-MWCNTs的含量为5wt%时,复合材料的介电常数高达105.0。注射成型法制备的MWCNTs/PVDF复合材料仍保持相对较低的电导率,进而导致复合材料的能量损耗较低,对电荷存储应用具有重要意义。     

MWCNTs改善WS2/三元乙丙橡胶复合材料的非线性电导特性与热导性能

通过在一定量的纳米WS₂中添加极少量的多壁碳纳米管（MWCNTs）,形成MWCNTs-WS₂复配填料,采用双辊开炼机将三元乙丙橡胶（EPDM）与不同配比的复配填料混合制备了不同MWCNTs含量的MWCNTs-WS₂/EPDM复合材料。并研究了极少量的MWCNTs添加对MWCNTs-WS₂/EPDM复合材料非线性电导性能、直流击穿性能和导热性能的影响。结果表明,极少量的MWCNTs对MWCNTs-WS₂/EPDM复合材料在25℃时的非线性电导特性起到明显的增强作用,且随着MWCNTs含量的增加,复合材料非线性电导特征有明显的规律性变化;由于MWCNTs自身的高电导率和电导正温度系数效应,MWCNTs-WS₂/EPDM复合材料电导率随电场强度的变化趋势在80℃时不再表现非线性特征。另外,极少量的MWCNTs对MWCNTs-WS₂/EPDM复合材料的热导率有明显地改善。      

炭黑/聚丙烯-聚(苯乙烯-乙烯/丁烯-苯乙烯)复合材料的介电性能和压阻性能

为了制备柔性较好的聚合物基压阻材料,利用熔融共混法制备了炭黑/聚丙烯-聚(苯乙烯-乙烯/丁烯-苯乙烯)(CB/PP-SEBS)复合材料,并研究了CB含量对CB/PP-SEBS复合材料介电性能和压阻性能的影响。结果表明:随着CB含量的增加,CB/PP-SEBS复合材料的介电常数、介电损耗及电导率均提高;CB/PP-SEBS复合材料发生导电逾渗时,CB的含量为12.2wt%;在CB/PP-SEBS复合材料发生弹性形变时,由于外力破坏了CB的导电网络,复合材料的电阻随着应变的增大而增大;循环压阻测试结果显示,在弹性变形区CB/PP-SEBS复合材料的电阻随着应变呈现周期性变化。研究结果可为制备具有稳定电阻变化的聚合物基压阻材料提供借鉴。     

Electrical properties of polyvinylidene fluoride (PVDF)/multi-walled carbon nanotube (MWCNT) semi-transparent composites: Modelling of DC conductivity

Transparent conductive composites can be achieved from PVDF–MWCNT at very low concentration of MWCNT. These composites show different degree of UV–Visible radiation absorption depending on MWCNT concentration in composites. The composition dependent dielectric properties and AC conductivity were also measured for these composites. Properties like AC conductivity, dielectric constant and loss are increasing with filler concentration. The variations of DC conductivity against composition and temperature are also reported. The electrical hysteresis and electrical set are observed for PVDF–MWCNT composites when subjected to heating–cooling cycle. The validity of different theoretical models depicting percolation threshold with respect to DC conductivity was tested for these composites.     

PAN-based carbon fibers/PMMA composites: thermal, dielectric, and DC electrical properties

The study deals with thermal, dielectric, and DC electrical properties of polyacrylonitrile (PAN)-based carbon fibers/poly(methyl methacrylate) composites. The polymer composites contain 0, 5, 10, 20 and 30 wt.% PAN-based carbon fibers. The thermal conductivity was studied as a function of filler content and temperature. It was found that the thermal conductivity is enhanced by addition of carbon fibers concentration and temperature. The dielectric properties were determined using impedance measurements. The results showed that the dielectric constant and dielectric loss are decreased with frequency, and increased with both temperature and fibers content. The DC electrical conductivity, temperature coefficient of resistance, and activation energy were studied as a function of fibers concentration in the temperature ranges 30–110?°C. It was found that the composites exhibit negative temperature coefficient of resistivity and enhancement of electrical conductivity with increasing temperature and carbon fibers concentration. The observed increase in the DC conductivity was explained according to the approach of conductive paths and connections between the carbon fibers.     

磷酸铝-聚醚砜层状复合材料的隔热及介电性能

采用高温煅烧成型工艺在聚醚砜(PES)基体表面复合了AlPO4耐热层,制备得到了AlPO4-PES层状复合材料。利用SEM、激光共聚焦显微镜三维形貌分析(CLSM-3D)、FTIR和TGA等分析技术对AlPO4-PES微观结构、化学成分以及热稳定性进行了表征。研究了AlPO4含量对AlPO4-PES层状复合材料的热导率和介电性能的影响。结果表明:AlPO4层显著地改变了PES基体的微观结构,二者之间通过物理方式紧密结合;随着AlPO4含量的增加,AlPO4-PES层状复合材料的热稳定性明显增强,而热导率却不断降低;AlPO4-PES层状复合材料的介电常数和介电损耗均随着AlPO4含量的增加而减小,并且在0.1~5MHz测试范围内表现出良好的频率稳定性。     

Epoxy Composites Filled with Micro-Sized AlN Particles for Microelectronic Applications

With the rapid development of the electronic information industry, better properties are required for substrate and packaging materials such as high thermal conductivity, low coefficient of thermal expansion, and low dielectric constant. Polymers are ordinarily being used for this purpose due to their high electrical resistivity and low density, but unfortunately they suffer from a disadvantage like low thermal conductivity. To offset this deficiency, adding inorganic conductive particles to polymer is a versatile method. In view of this, the present work aims at developing a class of particulate filled polymer composites with micro-sized aluminum nitride (AlN) particles having an average particle size of 60–80 µm reinforced in epoxy matrix. A set of composites, with filler content ranging from 0 to 25 vol%, have been prepared by the hand-layup technique. Effects of filler percentage on various properties like effective thermal conductivity (k_eff), coefficient of thermal expansion (CTE), glass transition temperature (T_g), and dielectric constant (ε_c) are studied. It is found that the incorporation of AlN in resin increases the k_eff and T_g, whereas CTE of the composite decreases favorably. Though dielectric constant of the matrix increases with filler content yet it remains well within the desirable limit. With modified thermal and dielectric characteristics, these composites can possibly be used for microelectronics applications.     

SrTiO_3/CaCu_3Ti_4O_(12)复合陶瓷材料的介电性能

本文采用固相反应法制备了xSrTiO_3/(1-x)CaCu_3Ti_4O_(12)(x=0,0.2,0.4,0.6,0.8,1)复合陶瓷,研究了复合材料的物相、微观结构和宽温度宽频率范围内的介电性能。结果表明:在1348~1600K的温度范围内烧结能够得到致密性良好的xSrTiO_3/(1-x)CaCu_3Ti_4O_(12)(x=0,0.2,0.4,0.6,0.8,1)复合陶瓷。频率为100kHz时,样品的室温介电常数随SrTiO_3含量的增加而减少,从71358(x=0)单调减少至270(x=1),其变化规律遵循Lichtenecker法则。介电损耗随SrTiO_3含量的增加先增大后减少。当x=0.2时,样品与CaCu_3Ti_4O_(12)陶瓷的介电性能相似,存在低温的介电弛豫和巨介电常数平台。随着SrTiO_3含量的增加,复合陶瓷的低温介电弛豫激活能增大,介电响应被抑制,而高温介电响应由于高温电导的影响而增强,使得CaCu_3Ti_4O_(12)特有的巨介电常数平台随着SrTiO_3的增加逐渐消失,xSrTiO_3/(1-x)CaCu_3Ti_4O_(12)复合材料的温度依赖性增强。     

石英纤维/KH308复合材料的介电性能

为研究石英纤维/聚酰亚胺（KH308）复合材料介电性能与纤维体积分数、频率、温度和吸水率之间的关系,通过热压成型法,制备了4种不同纤维体积含量的石英纤维/KH308复合材料,采用高Q谐腔法分别测试这4种复合材料在不同状态下的介电常数和介电损耗。结果表明：石英纤维/KH308复合材料的介电常数随着纤维体积分数增加而变大,介电损耗随纤维体积分数变化不大;7~18 GHz频率下,复合材料的介电常数和介电损耗基本不随频率变化;25~300℃下,复合材料的介电常数随温度增加变化比较平缓,而介电损耗随温度的增加而降低;复合材料吸水后,介电常数和介电损耗都会增加;复合材料介电常数ε<4,介电损耗tanδ<0.1,能满足导弹天线罩透波材料介电性能的要求。