纳米无机粒子/聚合物复合材料界面结构的研究

纳米粒子具有许多特性,聚合物中加入纳米粒子可以制备得到性能更加优异的复合材料,其中纳米粒子和聚合物基体间的界面对决定纳米复合材料的性能起着重要作用.本文综述了近些年来表征纳米无机颗粒/聚合物复合材料中界面结构的研究手段,如红外光谱(FTIR)、热重(TGA)、电子显微镜、小角中子散射(SANS)及小角X射线散射(SAXS)等,及界面结构与复合材料力学性能和热稳定性关系的研究进展.同时也介绍了纳米粒子对复合材料的渗透、光催化、阻燃、介电及导电性能的影响.最后对这一领域的研究进行了展望.     

Ag负载KTa1-xNbxO3-BaTiO3颗粒掺杂P(VDF-TrFE-CTFE)复合材料的制备及介电性能

通过光照还原法制备了银颗粒负载的铌钽酸钾-钛酸钡复合粉体（Ag/KTN-BT）,并将其与聚偏氟乙烯-三氟乙烯-三氟氯乙烯（P（VDF-TrFE-CTFE））聚合物复合,获得Ag/KTN-BT聚合物基复合材料。研究发现,Ag/KTN-BT填料颗粒在聚合物基体中分散均匀,复合材料结构致密,无明显气孔和裂纹,且具有较好的柔韧性。银纳米颗粒的负载,一方面在复合材料中引入了额外的界面,导致界面极化作用增强,明显提高复合材料的介电常数;另一方面银纳米颗粒的量子尺寸效应和库伦阻塞效应使得复合材料保持较低的介电损耗。当填充体积分数为20%的Ag/KTN-BT颗粒时,聚合物基复合材料的介电常数大幅提升,从聚合物的37提升到125（100 Hz）,介电损耗仅为0.12。与KTN-BT基复合材料对比,Ag/KTN-BT基复合材料也显示出较好的介电性能。     

不同应变速率下纳米橡胶颗粒对环氧树脂的增韧特性与机理分析

为了解释不同应变速率下纳米橡胶颗粒对环氧树脂基体的增韧机理,制备了质量分数为6%的纳米橡胶颗粒/环氧树脂复合材料,分别测试了该材料在3种低应变速率(5×10-4s-1,1×10-1s-1,2.5×10-1s-1)和高应变速率下(90 s-1)的I型平面断裂韧性.结果表明,纳米橡胶颗粒在3种低应变速率下可以显著提高环氧树脂的断裂韧性,提高幅度分别为158%,283%和309%.在高应变速率下,纯环氧树脂的断裂韧性由于动态效应而显著升高,然而纳米橡胶颗粒对环氧基体的增韧效果却不明显,增韧幅度仅为2%.由光学显微镜照片可知,随着应变速率的提高,纳米橡胶颗粒/环氧树脂复合材料断口表面的应力发白区域逐渐较少,甚至在高应变速率(90 s-1)下消失.偏光显微镜照片表明,纯环氧树脂与纳米橡胶颗粒/环氧树脂复合材料的裂纹尖端塑性形变尺寸随着应变速率的升高而减小.通过扫描电子显微镜对断口形貌进行分析可知,不同应变速率下纳米橡胶颗粒在环氧基体中空穴增长程度不同,进而导致纳米橡胶颗粒对环氧基体的增韧效果的不同.     

LSMO/SiO2复合材料变温微波吸收特性研究

通过固相反应法制备了LSMO/SiO2复合材料, 测试了LSMO材料500 MHz～18 GHz介电特性和LSMO/SiO2复合材料样品不同温度下X波段介电常数和微波吸收特性. 测试结果表明, 在12 GHz附近复合材料样品有明显的介电损耗特征峰, 随着温度的升高材料的介电常数虚部明显升高, tgδ变大;吸收特性测试表明, 随着温度升高, 吸收峰升高, 吸收峰略微往低频移动.     

基于介孔分子筛MCM-41“有机-无机”互穿结构纳米复合材料体系研究

采用硅烷偶联剂KH550对介孔分子筛MCM-41内、外表面进行改性,并利用氮气吸附-脱附,傅里叶红外光谱以及小角X衍射等进行表征,其结果显示KH550分子被引入MCM-41纳米孔道中,且—NH_2基团成功嫁接到MCM-41纳米颗粒表面.凝胶液相色谱实验结果证实本文中采用的双酚A型环氧树脂为低分子量环氧.随后,采用原位聚合的方法制备不同MCM-41含量环氧树脂纳米复合材料.最后,利用正电子湮没寿命谱测量复合材料自由体积孔洞;利用透射电镜,动态热机械分析和交流击穿对复合材料宏观性能进行研究.复合材料超薄切片TEM观察结果显示,在低MCM-41添加含量时,MCM-41颗粒可在复合材料中良好分散.同时,环氧分子在外施作用力和硅烷偶联剂功能作用下引入纳米孔道,形成"有机-无机"互穿结构复合材料体系,增强MCM-41和环氧树脂间相互作用力,在低MCM-41添加含量下提高复合材料玻璃化温度(15.1%↑)和击穿电压(22.6%↑).     

介电高分子及其纳米复合材料的电容储能应用

静电电容器具有极快的放电速率和超高的功率密度,是先进电力与电子系统中的重要储能元件.介电高分子凭借其高击穿、可自愈、低损耗、低成本等优势成为了广泛使用的电容器电介质材料.然而,介电高分子能量密度偏低、热稳定性较差等问题制约了它们在大功率电力电子和紧凑型功率模块中的应用.为了提高介电高分子的能量密度和满足其在高温环境下的应用需求,我们开展了一系列研究.本文着重介绍了我们近年来在开发高性能聚合物基电介质材料及相关介电现象理论研究方面的进展.主要内容涵盖基于聚偏氟乙烯的铁电聚合物、共聚物、纳米复合材料,以及聚合物基高温介电材料的制备与表征,还包括介电纳米复合材料界面微区特性的研究.最后对介电高分子在电容储能应用领域仍存在的问题进行了总结,并展望了未来可能的研究方向.     

Au@PS纳米颗粒掺杂PDMS/(PVDF-TrFE)复合薄膜的制备及介电-疏水性能

结合乳液聚合和还原法在250 nm的聚苯乙烯(PS)微球表面均匀负载了Au纳米颗粒.通过溶液共混法,使Au@PS纳米颗粒与聚二甲基硅氧烷(PDMS)/聚偏氟乙烯-三氟乙烯[P(VDF-TrFE)](质量比为2∶3)均匀混合,制备出结构致密、Au@PS均匀分布的微突起的复合薄膜.研究了不同Au@PS纳米颗粒掺杂量对复合薄膜的结构、熔融结晶行为和介电疏水特性的影响.研究发现,Au@PS纳米颗粒的引入阻碍了P(VDFTr FE)的β相的产生,但对PDMS/P(VDF-TrFE)复合薄膜的化学健结构没有显著影响;随着Au@PS纳米颗粒含量的增多,复合薄膜结晶温度和玻璃化转化温度升高,熔点略有降低.由于界面极化和微电容效应协同作用,掺杂Au@PS复合薄膜的介电常数有显著提升.PS球表面均匀负载的Au纳米颗粒减少了导电网络的构成,使介电损耗维持在较低值.掺杂5%(质量分数) Au@PS的复合薄膜介电常数达到22(100 Hz),分别为纯PDMS和PDMS/P(VDF-TrFE)的8. 8倍和3. 14倍,同时具有优异的疏水特性,接触角达到112. 31°.     

低介电损耗苯并噁唑复合材料的合成与表征

对介孔二氧化硅SBA-15进行氨基官能团化,制得NH2-SBA-15,通过溶液缩聚合成了一系列具有不同SBA-15质量分数的聚亚苯基苯并二噁唑/SBA-15(PBO/SBA-15)复合材料。利用红外光谱(FT-IR)、扫描电子显微镜(SEM)、热重分析(TG)和矢量网络分析仪(VNA)分别对复合材料的结构、微观形貌、热性能和电磁性能进行了表征与分析,研究了SBA-15对PBO/SBA-15复合材料介电参数的影响。研究表明:经过氨基官能团化之后,SBA-15能够均匀地分散在PBO基体中;当复合材料中SBA-15的质量分数小于8%时,PBO/SBA-15复合材料仍然保持着PBO优异的热稳定性;介孔二氧化硅SBA-15能够有效地降低PBO/SBA-15复合材料的复介电常数和介电损耗角正切,减弱PBO/SBA-15复合材料对电磁波的介电存储和损耗能力,使PBO/SBA-15复合材料表现出低介电损耗的性能。     

层状仿生高分子纳米复合材料

自然界中,鲍鱼壳具有有机-无机多级次层状结构以及大量的复合界面作用,力学性能优异。这一独特的层状结构主要由霰石碳酸钙片层构成,并通过体积分数约为5%的生物高分子在层间进行粘合。受鲍鱼壳这一微观结构的启发,我们利用不同的基元材料如纳米蒙脱土、碳纳米管以及氧化石墨烯等构筑仿鲍鱼壳层状结构,并结合多种界面设计,实现不同界面、不同基元材料之间的协同作用,得到了力学性能优异的高分子纳米复合材料。仿生高分子纳米复合材料的成功制备,为今后的研究提供了崭新的思路,拓宽了高分子纳米复合材料的应用前景。     

纳米TiO_2/硅橡胶复合材料的制备及研究

介电弹性体是一种通过在其两端施加电压就能够获得变形的材料。硅橡胶类介电弹性体因变形响应速度快、可自由制备、温度适用范围广等优点而备受关注,但是因介电常数较低、激发电场强度较高、电致变形较小等缺点制约了其发展。针对这些问题,本文以液体硅橡胶为基体,以纳米TiO_2为填料,通过溶液混合法制备了纳米TiO_2/硅橡胶复合材料,并对其介电性能、电致变形性能进行测试。结果表明,通过在聚合物基体中添加纳米TiO_2,提高了其介电常数,降低了介电损耗,能够获得较大的电致变形。     

Conducting polyaniline-rutile TiO2 nanocomposites for the development of high-k dielectric materials

Inorganic dielectrics encapsulated in an organic matrix are showing excellent promise as novel dielectric materials. In this work, firstly highly organized crystalline nanoparticles of rutile TiO₂ were synthesized by acid hydrolysis of titanium isopropoxide at room temperature. Then we developed a novel dielectric material consisting of highly organized rutile TiO₂/polyaniline (PAni) nanocomposites by in-situ chemical oxidative polymerization. The structural, morphological, conducting, and dielectric properties of the rutile TiO₂/PAni nanoparticles have been evaluated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution-transmission emission microscopy (HR-TEM), four-point probe technique, CV (Capacitance versus Voltage), and Impedance analyzer. The nanocomposites show 70 times higher permittivity compared to rutile nanoparticles and much higher compared to anatase/PAni (ES) nanocomposites at 10 MHz. Large interfacial polarizations, nanostructure, and dopant levels are the key factors for the large dielectric constant of the nanocomposites. The rutile/PAni (ES) nanocomposites might see potential uses in super-capacitors, gate dielectric in transistors, and capacitive-type gas sensors.     

Effect of polyaniline as a surface modifier of TiO2 nanoparticles on the properties of polyvinyl chloride/TiO2 nanocomposites

Surface of TiO2 nanoparticles was modified with the in situ chemical oxidative polymerization of aniline. Polyaniline modified TiO2 nanoparticles (PANI-TiO2 ) were characterized with the FT-IR, XRD, SEM and TEM techniques. Results confirmed that PANI was grafted successfully on the surface of TiO2 nanoparticles, therefore agglomeration of nanoparticles decreased dramatically. Polyvinyl chloride nanocomposites filled with 1 wt% 5 wt% of PANI-TiO2 and TiO2 nanoparticles were prepared via the solution blending method. PVC nanocomposites were analyzed with FT-IR, XRD, SEM, TG/DTA, DSC and tensile test techniques. Effect of PANI as surface modifier of nanoparticles was discussed according to the final properties of PVC nanocomposites. Results demonstrated that deposition of PANI on the surface of TiO2 nanoparticles improved the interfacial adhesion between the constituents of nanocomposites, which resulted in better dispersion of nanoparticles in the PVC matrix. Also PVC/PANI-TiO2 nanocomposites showed higher thermal resistance, tensile strength and Young’s modulus compared to those of unfilled PVC and PVC/TiO2 nanocomposites.     

Investigations on the structural,mechanical, thermal,and electrical properties of Ce-doped TiO2/poly(n-butyl methacrylate) nanocomposites

This study focused on the fabrication of poly(n-butyl methacrylate) (PBMA) nanocomposites with various concentrations of cerium-doped titanium dioxide (Ce–TiO₂) nanoparticles via in situ polymerization technique. The structural characterization and the material properties of all the composites were analyzed by UV–visible, FTIR, XRD, SEM, DSC, TG, and tensile strength measurements. The UV–visible and FTIR studies confirmed the effective inclusion of Ce–TiO₂ nanoparticles into the PBMA matrix. The change in amorphous morphology of PBMA to a crystalline structure was observed from the XRD pattern. The SEM morphology revealed the attachment of nanoparticles in the polymer matrix. The inclusion of Ce–TiO₂ nanoparticles enhanced the glass transition temperature, and thermal stability of the PBMA matrix was revealed from DSC and TG, respectively. The tensile strength of PBMA was greatly enhanced by the addition of Ce–TiO₂ nanoparticles. The AC conductivity, dielectric constant, and dielectric loss studies were also performed in the frequency range 10²–10⁶ Hz, and it was observed that addition of Ce–TiO₂ nanoparticles greatly enhanced the electrical properties of PBMA. The change in dielectric constant with the addition of nanoparticles was correlated with a theoretical modeling study. This work also extended to study the role of Ce–TiO₂ nanoparticles in the reinforcing mechanism of the nanocomposite by comparing the actual tensile strength of the composite with different theoretical modeling. The high dielectric constant and tensile strength of composite are beneficial in designing lightweight and highly efficient nanoelectronic materials based on the family of polybutyl acrylates.

     

Glass fiber reinforced bismaleimide/epoxy BaTiO3 nano composites for high voltage applications

BaTiO₃/bismaleimide/epoxy/glass fiber reinforced composites were prepared using E-glass fiber (E-GF) and silane coated E-glass fiber (SC-EGF) separately as reinforcement. BaTiO₃ nanoparticles were prepared by hydrothermal method. Results show that the addition of BaTiO₃ nanoparticles has significant effects on the mechanical and dielectric properties of the composite. Both E-GF and SC-EGF reinforced BaTiO₃/bismaleimide/epoxy composites with 2 wt percentages of BaTiO₃ nanoparticles showed improved tensile strength, flexural strength and dielectric constant and those with 3% showed high dielectric strength indicating this composition is more adaptable for high voltage insulating applications. Dielectric constants and dielectric loss of the fabricated nanocomposites have been obtained at higher frequencies (in GHz) by using Vector Network Analyser at room temperature and was found to be highest for the BMI-Epoxy nanocomposite with 1% weight nanofiller.     

The Primary Origin of Excellent Dielectric Properties of (Co,Nb) Co-Doped TiO2 Ceramics: Electron-Pinned Defect Dipoles vs. Internal Barrier Layer Capacitor Effect

(Co, Nb) co-doped rutile TiO₂ (CoNTO) nanoparticles with low dopant concentrations were prepared using a wet chemistry method. A pure rutile TiO₂ phase with a dense microstructure and homogeneous dispersion of the dopants was obtained. By co-doping rutile TiO₂ with 0.5 at.% (Co, Nb), a very high dielectric permittivity of ε′ ≈ 36,105 and a low loss tangent of tanδ ≈ 0.04 were achieved. The sample–electrode contact and resistive outer-surface layer (surface barrier layer capacitor) have a significant impact on the dielectric response in the CoNTO ceramics. The density functional theory calculation shows that the 2Co atoms are located near the oxygen vacancy, creating a triangle-shaped 2CoV_oTi complex defect. On the other hand, the substitution of TiO₂ with Nb atoms can form a diamond-shaped 2Nb2Ti complex defect. These two types of complex defects are far away from each other. Therefore, the electron-pinned defect dipoles cannot be considered the primary origins of the dielectric response in the CoNTO ceramics. Impedance spectroscopy shows that the CoNTO ceramics are electrically heterogeneous, comprised of insulating and semiconducting regions. Thus, the dielectric properties of the CoNTO ceramics are attributed to the interfacial polarization at the internal insulating layers with very high resistivity, giving rise to a low loss tangent.     

Single-step solvothermal synthesis of mesoporous anatase TiO<Subscript>2</Subscript>-reduced graphene oxide nanocomposites for the abatement of organic pollutants

In the present work, we have fabricated a novel mesoporous TiO₂–rGO nanocomposite by a facile one-step solvothermal method using titanic sulfate as the TiO₂ source. The as-prepared composites were characterized by transmission electron microscopy, X-ray diffraction; UV–Vis diffuse reflectance spectra, X-ray photoelectron spectroscopy and photoluminence spectra. In situ nucleation and anchoring of TiO₂ nanoparticles onto a graphene sheet is favorable fpr forming an intimate interfacial contact, and the chemically bonded TiO₂–rGO nanocomposites commendably enhanced their photocatalytic activity in the photodegradation of rhodamine B and phenol. The high photocatalytic activity of the as-synthesized nanocomposites are primarily ascribed to the mesoporous structure, efficient charge transportation and separation with enhanced visible light absorption, which come from the appealing nanoarchitecture, for instance, ultra-dispersed and ultra-small TiO₂ nanocrystals along with intimate and absolute interfacial contact between the TiO₂ nanocrystals and the graphene sheet.     

Microwave absorption properties and infrared emissivities of ordered mesoporous C-TiO2 nanocomposites with crystalline framework

Ordered mesoporous C-TiO₂ nanocomposites with crystalline framework were prepared by the evaporation-induced triconstituent co-assembly method. The products were characterized by XRD, TEM, N₂ adsorption-desorption and TG. Their microwave absorption properties were investigated by mixing the product and epoxy resin. It is found that the peak with minimum reflection loss value moves to lower frequencies and the ordered mesoporous C-TiO₂ nanocomposite possesses an excellent microwave absorbing property with the maximum reflection loss of −25.4 dB and the bandwidth lower than −10 dB is 6.6 GHz. The attenuation of microwave can be attributed to dielectric loss and their absorption mechanism is discussed in detail. The mesoporous C-TiO₂ nanocomposites also exhibit a lower infrared emissivity in the wavelength from 8 to 14 μm than that of TiO₂-free powder.     

Enhancement of water barrier properties and tribological performance of hybrid glass fiber/epoxy composites with inclusions of carbon and silica nanoparticles

Water barrier properties and tribological performance (hardness and wear behavior) of new hybrid nanocomposites under dry and wet conditions were investigated. The new fabricated hybrid nanocomposite laminates consist of epoxy reinforced with woven and nonwoven tissue glass fibers and two different types of nanoparticles, silica (SiO₂) and carbon black nanoparticles (C). These nanoparticles were incorporated into epoxy resin as a single nanoparticle (either SiO₂ or C) or combining SiO₂ and C nanoparticles simultaneously with different weight fractions. The results showed that addition of carbon nanoparticles with 0.5 and 1 wt% resulted in maximum reduction in water uptake by 28.55% and 21.66%, respectively, as compared with neat glass fiber reinforced epoxy composites. Addition of all studied types and contents of nanoparticles improves hardness in dry and wet conditions over unfilled fiber composites. Under dry conditions, maximum reduction of 47.26% in weight loss was obtained with specimens containing 1 wt% carbon nanoparticles; however, in wet conditions, weight loss was reduced by 17.525% for specimens containing 0.5 wt% carbon nanoparticles as compared with unfilled fiber composites. Diffusion coefficients for different types of the hybrid nanocomposites were computed using Fickian and Langmuir models of diffusion. Copyright © 2017 John Wiley & Sons, Ltd.     

Electrorheological properties of suspensions of hollow globular titanium oxide/polypyrrole particles

Hollow globular clusters of titanium oxide (TiO₂) nanoparticles were synthesized by a simple hydrothermal method. The prepared particles were consequently coated by in situ polymerization of conductive polymer polypyrrole (PPy) to obtain novel core–shell structured particles as a dispersed phase in electrorheological (ER) suspensions. The X-ray diffraction analysis and scanning electron microscopy provided information on particle composition and morphology. It appeared that PPy coating improved the compatibility of dispersed particles with silicone oil which results in higher sedimentation stability compared to that of mere TiO₂ particles-based ER suspension. The ER properties were investigated under both steady and oscillatory shears. It was found that TiO₂/PPy particles-based suspension showed higher ER activity than that of mere TiO₂ hollow globular clusters. These observations were elucidated well in view of their dielectric spectra analysis; a larger dielectric loss enhancement and faster interfacial polarization were responsible for a higher ER activity of core–shell structured TiO₂/PPy-based suspensions. Investigation of changes in ER properties of prepared suspensions as a function of particles concentration, viscosity of silicone oil used as a suspension medium, and electric field strength applied was also performed.     

Probing the magnetoelectric response and energy efficiency in Fe3O4/epoxy nanocomposites

Fe₃O₄/epoxy nanocomposites were manufactured and studied. Structural, morphological, thermomechanical and dielectric characterization was conducted via X-Ray Diffraction, Scanning Electron Microscopy, Differential Scanning Calorimetry, Dynamic Mechanical Analysis, and Broadband Dielectric Spectroscopy. Nanocomposites’ magnetic behaviour was obtained by a Superconducting Quantum Interference Device and their ability to store/harvest energy was investigated by DC charge/discharge tests. Data imply that the incorporation of the nanoparticles has an augmenting influence on the thermomechanical, dielectric and magnetic properties of the systems. Dielectric relaxations recorded in all systems are attributed to interfacial polarization, glass to rubber transition of the polymer matrix, and re-orientation of polar side groups of the polymer chain. Magnetic measurements confirmed the ferrimagnetic nature of the nanocomposites, while induced magnetic properties enhance with filler content. Stored and harvested energies increase with the applied DC field and the coefficient of energy efficiency increases in general with filler content.