Controlled synthesis of core-shell iron-silica nanoparticles and their magneto-dielectric properties in polymer composites

Low loss core-shell iron-silica nanocomposites with improved magneto-dielectric properties at radio frequencies (1 MHz-1 GHz) were successfully fabricated. A new simple method was developed to synthesize metallic iron (Fe) nanoparticles with uniform size distribution in an aqueous environment at room temperature. Citric acid and oleic acid served as surface-capping agents to control the particle size of the synthesized Fe nanoparticles. Smaller Fe nanoparticles with narrower particle size distribution were obtained as the concentration ratio of iron ions to carboxylic acid groups decreased. The Fe nanoparticles were subsequently coated with silica (SiO(2)) layers to prevent the iron cores oxidizing. Polymer composites were prepared by incorporating Fe@SiO(2) nanoparticles with polydimethylsiloxane (PDMS) elastomers. Experimental results showed that the dielectric permittivity (ε) and magnetic permeability (μ) of the polymer composite increased with increasing amount of Fe@SiO(2) nanoparticle doping. The dielectric loss (tanδ) was near 0.020 at a frequency of 1 GHz.     

Reinforcing polymer composites with epoxide-grafted carbon nanotubes

An in situ functionalization method was used to graft epoxide onto single-walled carbon nanotubes (SWNTs) and improve the integration of SWNTs into epoxy polymer. The characterization results of Raman, FT-IR and transmission electron microscopy (TEM) validated the successful functionalization with epoxide. These functionalized SWNTs were used to fabricate nanocomposites, resulting in uniform dispersion and strong interfacial bonding. The mechanical test demonstrated that, with only 1?wt% loading of functionalized SWNTs, the tensile strength of nanocomposites was improved by 40%, and Young's modulus by 60%.These results suggested that efficient load transfer has been achieved through epoxide-grafting. This investigation provided an efficient way to improve the interfacial bonding of multifunctional high-performance nanocomposites for lightweight structure material applications.     

Controlled diffraction liquid-crystal structures with a photoalignment polymer

The characteristics of electric-field-controlled diffraction elements based on a nematic liquid crystal and a new photoalignment polymer have been studied. The photocross-linking of this polymer allows periodic oriented structures and liquid crystal phase gratings with a 30% diffraction efficiency in the first order to be formed.     

Thermo-protective properties of polymer composites with nano-titanium dioxide

International Journal of Mechanics and Materials in Design - The present work investigates the ablative and thermal properties of an epoxy resin which was modified with titanium dioxide...     

凹凸棒/聚合物复合材料研究进展

本文综述了国内外凹凸棒/聚合物复合材料研究进展,指出了存在的问题,展望了凹凸棒/聚合物复合材料应用前景,并分析了以后需要深入研究的方向.     

Enhanced thermal conductivity in polymer composites with aligned graphene nanosheets

We developed highly aligned graphene nanosheets (GNSs) in epoxy composites with incorporating magnetic GNS–Fe₃O₄ hybrids under a magnetic field with the aim to take full advantage of the high inplane thermal conductivity of graphene. GNS–Fe₃O₄ hybrids were fabricated by a simple coprecipitation method, and their morphology, chemistry, and structure were characterized. GNS–Fe₃O₄ hybrids were found to be homogenously dispersed and well aligned through the direction of the magnetic field in the epoxy matrix, as confirmed by SEM observation and Raman spectra analysis. The resulting epoxy/GNS–Fe₃O₄ composites possessed high thermal conductivity in a parallel magnetic-alignment direction at low GNS–Fe₃O₄ loadings, which greatly outperformed the composites with randomly dispersed bare GNSs. The obtained results indicated that the magnetic alignment of magnetic-functionalized GNSs is an effective way for greatly improving the thermal conductivity of the graphene-based composites.     

甲基丙烯酸缩水甘油酯改善木塑复合材料性能

选用甲基丙烯酸缩水甘油酯(GMA)作为偶联剂,探索了对杨木/塑料复合材料的力学性能和耐久性的改善;并利用SEM和FTIR分析了GMA加入苯乙烯单体(St)前后,高聚物与木材的界面复合效果与反应机制。SEM和FTIR的分析结果表明：GMA借助其自身的环氧基团,实现了与木材细胞壁上羟基的化学键合,且通过自身的双键实现了与单体St的共聚合,最终使高聚物与木材细胞壁较充分地实现了化学键联;高聚物以立体交联的形式填充于细胞腔中,与细胞壁紧密接触,无明显缝隙,复合效果良好。综合性能测试结果表明：GMA的加入,使改性木塑复合材料的静曲强度(MOR)、弹性模量(MOE)、顺纹抗压强度和硬度较未改性前分别提高45%、52%、71%和141%;尺寸稳定性较未改性前提高3倍;耐腐性较未改性前提高8.56倍。     

Thermal conductivity of polymer composites with a disperse filler

Institute of Low-Temperature Engineering and Power, Odessa. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 62, No. 3, pp. 453–458, March, 1992.     

Toughness of aromatic polymer composites reinforced with carbon fibres

This experimental study focuses on the toughness of a thermoplastic composite, namely, poly ether-ether-ketone (PEEK) reinforced with 60% by volume of continous carbon fibres (APC 2). Toughness is assessed using both comparative and intrinsic techniques and a critical discussion of the two approaches is presented.The comparative toughness of cross-ply and quasi-isotropic sheets of APC 2 is studied using a damage tolerance test (compression after impact) and by using an instrumented falling weight impacr test over a range of temperatures. Intrinsic toughness is discussed by applying fracture mechanics techniques to unidirectional laminates. Double cantilever beam and three-point flexure tests are used, the latter being performed in six different crack directions. Fracture toughness results are presented for APC 2 and unreinforced PEEK.An ultrasonic C-scan on impacted specimens and scanning electron microscopy on fracture surfaces are used to explore further the mechanisms of fracture, e.g. delamination, fibre breakage and matrix cracking.     

Piezoelectric relaxation in polymer and ferroelectric composites

Recently, fairly large numbers of studies have been reported on piezoelectric relaxations of polymers. The piezoelectric constants of polymer and ferroelectric composites also show such relaxations. It has been found that both polymer and polymer and ferroelectric composities exhibit typical Debye-type piezoelectric dispersion. Cole-Cole diagrams for the piezoelectric properties of these materials have been drawn and an attempt has been made to interpret the results.     

石墨烯/聚合物复合材料的研究进展

石墨烯是最近几年才发现的炭材料的新成员, 其完美的二维结构和许多奇特的性质, 引起了科学家的极大兴趣。石墨烯和氧化石墨烯的改性以及各种石墨烯/聚合物复合材料的制备成为当前研究的热点之一。与纯的聚合物相比, 石墨烯的加入可赋予复合材料不同的功能性, 不但表现出优异的力学和电学性能, 且具有优良的加工性能, 为复合材料提供了更广阔的应用空间。文中概述了石墨烯/聚合物复合材料的制备方法、结构及性能, 并展望了石墨烯及其聚合物复合材料的研究前景。     

聚合物基石墨烯纳米复合材料的研究进展

综述了聚合物基石墨烯及改性石墨烯纳米复合材料的研究进展.添加少量的石墨烯就可以显著提聚合物材料的各方面性能,因此,近年来石墨烯得到了学术界和工业界的高度关注,石墨烯、氧化石墨烯的改性,以及聚合物基石墨烯纳米复合材料被广泛研究.通过广泛的文献阅读对聚合物基石墨烯纳米复合材料的结构、制备方法以及性能进行了深入探讨.     

Time-dependent damage in carbon fibre-reinforced polymer composites

Time-dependent damage (matrix cracks) evolution in AS4/3501-6 cross-ply laminates was studied using constant strain rate and constant stress tests. First ply failure stress and strain as well as the matrix crack density at a given stress level were found to be strongly dependent on strain rate. Matrix crack density increased with creep time at a constant stress level. The compliance and creep rate of the laminate increased in the presence of these cracks. These results emphasize the importance of the knowledge of time-dependent damage evolution in a lamina/laminate of a polymer composite for reliable prediction of creep and creep rupture.     

Visible tunable lighting system based on polymer composites embedding ZnO and metallic clusters: from colloids to thin films

The development of phosphor devices free of heavy metal or rare earth elements is an important issue for environmental reasons and energy efficiency. Different mixtures of ZnO nanocrystals with Cs₂Mo₆I₈(OOC₂F₅)₆ cluster compound (CMIF) dispersed into polyvinylpyrrolidone matrix have been prepared by very simple and low cost solution chemistry. The resulting solutions have been used to fabricate highly transparent and luminescent films by dip coating free of heavy metal or rare earth elements. The luminescence properties of solution and dip-coated films were investigated. The luminescence of such a system is strongly dependent on the ratios between ZnO and CMIF amounts, the excitation wavelength and the nature of the system. By varying these two parameters (ratio and wavelength), a large variety of colors, from blue to red as well as white, can be achieved. In addition, differences in the luminescence properties have been observed between solutions and thin films as well as changes of CMIF emission band maximum wavelength. This may suggest some possible interactions between the different luminophore centers, such as energy transfer or ligands exchange on the Mo₆ clusters.     

Epoxidised soybean oil polymer composites reinforced with modified microcrystalline cellulose

Microcrystalline cellulose (MCC) grafted with n-octadecyl isocyanate (18C-g-MCC) was introduced as the reinforcing filler in epoxidised soybean oil (ESO) polymer. The wetting characteristics of 18C-g-MCC were evaluated by static contact angle and the results show that the hydrophobicity of MCC was improved by the introduction of nonpolar alkyl groups. The ESO composites were synthesised with different contents of 18C-g-MCC (from 0 to 25 wt%) by a thermally cured method. The reinforcing effects of 18C-g-MCC were evaluated by scanning electron microscopy, mechanical test, dynamic mechanical analysis and thermal stability test. The results show that the tensile strength, the impact strength, Young's modulus, the flexural strength and glass transition temperature of the composites increase gradually with the increase of 18C-g-MCC content, while the elongation at break begins to decrease with 18C-g-MCC content of more than 20 wt%. Contact angle and water absorption analysis of the composites indicate the addition of 18C-g-MCC increases the water absorption of the ESO polymer.