电磁屏蔽用聚合物基碳纳米复合材料的构筑

随着通信技术和电子设备的迅速发展,电磁污染已经影响到电子设备正常运行和人类生命安全.因此,开发电磁屏蔽材料具有重大的科学意义.近几年,聚合物基碳纳米复合材料在电磁屏蔽领域迅猛发展,表现出诸多优异的性能,引起学术界的广泛关注.基于本课题组在电磁屏蔽领域的认识和研究,简要介绍了电磁屏蔽原理和聚合物基碳纳米复合材料的制备方法...     

Polymer/carbon based composites as electromagnetic interference (EMI) shielding materials

The extensive development of electronic systems and telecommunications has lead to major concerns regarding electromagnetic pollution. Motivated by environmental questions and by a wide variety of applications, the quest for materials with high efficiency to mitigate electromagnetic interferences (EMI) pollution has become a mainstream field of research. This paper reviews the state-of-the-art research in the design and characterization of polymer/carbon based composites as EMI shielding materials. After a brief introduction, in Section 1, the electromagnetic theory will be briefly discussed in Section 2 setting the foundations of the strategies to be employed to design efficient EMI shielding materials. These materials will be classified in the next section by the type of carbon fillers, involving carbon black, carbon fiber, carbon nanotubes and graphene. The importance of the dispersion method into the polymer matrix (melt-blending, solution processing, etc.) on the final material properties will be discussed. The combination of carbon fillers with other constituents such as metallic nanoparticles or conductive polymers will be the topic of Section 4. The final section will address advanced complex architectures that are currently studied to improve the performances of EMI materials and, in some cases, to impart additional properties such as thermal management and mechanical resistance. In all these studies, we will discuss the efficiency of the composites/devices to absorb and/or reflect the EMI radiation.     

Novel carbon nanotube-polystyrene foam composites for electromagnetic interference shielding

A novel carbon nanotube-polystyrene foam composite has been fabricated successfully. The electromagnetic interference (EMI) shielding effectiveness measurements indicated that such foam composites can be used as very effective, lightweight shielding materials. The correlation between the shielding effectiveness and electrical conductivity and the EMI shielding mechanism of such foam composites are also discussed.     

Recycled carbon fibre reinforced polymer composite for electromagnetic interference shielding

This paper describes the development of an electromagnetic interference shielding material using recycled carbon fibre. Fibre recycled from a fluidised bed process was transformed into a non-woven veil and was moulded into a glass-fibre reinforced polymer plaque to provide shielding. Factors affecting shielding performance were established using a virgin fibre and the result was compared with veil made of the recycled fibre. Shielding performance increased with veil areal densities. The influence of fibre length on shielding seemed insignificant provided the fibre was distributed evenly. Sandwiching the plaque between fibre veils enhanced the shielding performance. A shielding value of 40 dB was attained from a layer of 80 g/m² recycled fibre veil and it was increased to 70 dB when the plaque was sandwiched between two layers of 30 g/m² recycled fibre veil. The correlation between veil formation and shielding effectiveness was established and found that shielding effectiveness increased with the degree of fibre dispersion.     

Multi-walled carbon nanotubes (MWCNTs)-reinforced ceramic nanocomposites for aerospace applications: a review

Journal of Materials Science - Advances in the nanotechnology have been actively applied to the field of aerospace engineering where there is a constant necessity of high durable material with low...     

屏蔽电磁干扰高分子磁性复合材料的研究

与铁氧化比较，二茂铁高分子磁性材料（OPM）在100MHz以下，其频率－磁导率（f-μ′）及温度－磁导率（T－μ′）变化不大，研究了金属纤维及碳纤维填充的OPM复合材料及其配位金属（Cu,Co,Ni)类型，屏蔽形式对屏蔽效果（SE）的影响。     

3D打印制备碳纳米管/环氧树脂电磁屏蔽复合材料

采用3D打印技术制备具有连续通孔的环氧树脂基体,利用浸渍工艺将碳纳米管（CNTs）附着于环氧树脂基体孔壁,获得具有优异电性能和电磁屏蔽功能的CNTs/环氧树脂复合材料。研究结果表明,CNTs含量仅为2.86vol%时,CNTs/环氧树脂复合材料电导率高达35 S/m,总电磁屏蔽效能高达39.2 dB（厚度为2.0 mm）。研究表明,CNTs/环氧树脂复合材料对进入其内部电磁波的吸收占总屏蔽效能的98%,表现出吸收屏蔽为主导的电磁屏蔽机制。CNTs/环氧树脂复合材料的弯曲强度和弯曲模量相比环氧树脂基体也有一定的提高。该研究为具有优异电磁屏蔽性能的高分子基复合材料制备提供了新思路和方法。      

Reduced graphene oxide deposited carbon fiber reinforced polymer composites for electromagnetic interference shielding

Reduced graphene oxide deposited carbon fiber (rGO-CF) was prepared by introducing GO onto CF surface through electrophoretic deposition method, following by reducing the GO sheets on CF with NaBH₄ solution. The rGO-CF was found to be more effective than CF to improve the electromagnetic interference (EMI) shielding property of unsaturated polyester (UP) based composites. With 0.75% mass fraction of rGO-CF, the shielding effectiveness of the composite reached 37.8 dB at the frequency range of 8.2–12.4 GHz (x-band), which had 16.3% increase than that of CF/UP composite (32.5 dB) in the same fiber mass fraction. The results suggest that rGO-CF is a good candidate for the use as a light-weight EMI shielding material.     

Metal-containing amorphous carbon (a-C:Ag) and AlN (AlN:Ag) metallo-dielectric nanocomposites

In this work we study the structure of Pulsed Laser Deposited silver-containing amorphous carbon a-C:Ag and AlN:Ag composites. The films have the form of a dielectric matrix (a-C or AlN) incorporating metal nanoclusters of 3-10 nm diameters. The composition of the films and the crystal structure of the inclusions have been determined by in-situ Auger Electron Spectroscopy and transmission electron microscopy, respectively. We show that the incorporation of the metal nanoparticles may severely alter the structure and properties of the matrix and a simple rule of mixture does not apply. The interactions of the possible matrix-nanoparticle interfaces were investigated using ab-initio calculations.     

Biodegradable PLA/CNTs/Ti3C2Tx MXene nanocomposites for efficient electromagnetic interference shielding

Environment friendly electromagnetic interference (EMI) shielding materials with excellent EMI-shielding efficiency (SE) are urgently required to deal with the increasing electromagnetic wave and environmental pollution. In this work, biodegradable poly(lactic acid) (PLA)/carbon nanotubes (CNTs)/Ti₃C₂T_x MXene nanocomposites are prepared via co-coagulation and compression molding techniques. The distribution state of Ti₃C₂T_x MXene or CNTs, the excellent conductivity and EMI-shielding properties of the nanocomposites are confirmed by scanning electron microscopy (SEM), four-probe conductivity tester and vector network analyzer, respectively. The PLA/CNTs/Ti₃C₂T_x nanocomposites show efficient EMI SE of 24.4 dB for 7 wt% CNTs/8 wt% Ti₃C₂T_x at the thickness of 0.5 mm. By increasing the thickness of the film, the EMI SE of PLA/CNTs/Ti₃C₂T_x nanocomposites can be increased to 39.6 dB at 1.9 mm, nearly 99.989% of electromagnetic wave is shielded. The EM wave reflection is the main shielding mechanism of the PLA/CNTs/Ti₃C₂T_x nanocomposites. Considering future environmental issues, this work provides a novel way for fabricating MXene-based biodegradable EMI shielding materials.

     

Conducting nanocomposites of poly(N-vinylcarbazole) with single-walled carbon nanotubes

The in situ solid-state polymerization of N-vinylcarbazole (NVC) at an elevated temperature in the presence of single-walled carbon nanotubes (SWCNTs) leads to the formation of new types of composite materials, the morphology and properties of which were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and electrical property measurements. FTIR spectroscopy and XPS studies confirmed the ability of SWCNTs to initiate the in situ polymerization of NVC monomers. FE-SEM and TEM results showed the coating of the outer surfaces of SWCNTs by the PNVC hompolymer with separation of individual SWCNTs from the bundles. Thermogravimetric analysis revealed a moderate improvement in the thermal stability of the nanocomposites at a higher temperature region relative to the base polymer. The electrical conductivity of neat polymer dramatically improved in the presence of SWCNTs. For example, dc electrical conductivity increased from 10(-16)-10(-12) S x cm(-1) for neat PNVC to approximately 10(-6) S x cm(-1) for nanocomposite containing 9 wt% SWCNTs.     

Poly(adipic acid-hexamethylene diamine)-functionalized multi-walled carbon nanotube nanocomposites

Poly(adipic acid-hexamethylene diamine) (PA66)-functionalized multi-walled carbon nanotubes (PACNT) were fabricated using amino multi-walled carbon nanotubes (AMWNT), adipic acid-hexamethylene diamine salt as reactants at 260–270 °C. The solubility of AMWNT in formic acid is improved after PA66 functionalization. PA66 was successfully grafted onto the surface of AMWNT to form a core–shell nanostructure. AMWNT are surrounded by PA66 chains with an average thickness of 3 nm. The length of PA66 chains on the surface of AMWNT decreases, with the content of AMWNT increasing. The thermal decomposition temperature of the composite is lower than that of PA66 functionalized carboxylic multi-walled carbon nanotubes. The storage modulus of PACNT containing 5 wt% AMWNT is 2.8-fold that of PA66; and it increases as the content of AMWNT increases.     

The effect of geometric factor of carbon nanofillers on the electrical conductivity and electromagnetic interference shielding properties of poly(trimethylene terephthalate) composites: a comparative study

In this study, the effects of filler geometry on the electrical conductivity and electromagnetic interference (EMI) shielding properties of poly(trimethylene terephthalate) (PTT) composites filled with graphene nanosheets (GNSs), carbon nanotubes (CNTs), and GNS–CNT hybrid nanofillers have been investigated. The GNSs, CNTs, and hybrid GNS–CNT were well dispersed in the PTT matrix using a simple coagulation process. GNSs were prepared from graphene oxide (GO) through hydrazine reduction, and thermal reduction of GO at two different temperatures of 1050 and 1500 °C. PTT filled with different aspect ratios and oxygen functional groups of GNS were also prepared in order to compare the electrical conductivity and EMI shielding properties. The aspect ratios of GNSs and CNTs were estimated by using an ellipsoid model. Percolation scaling laws were applied to the magnitudes of conductivity to reveal the percolation network and filler dispersion. The percolation exponent of the PTT/GNS composites was larger than that of the PTT/CNT composites. The percolated filler–filler network at which the percolation exponent changed was correlated with the filler geometric structure. GNS–CNT hybrid nanofillers formed a complex double brush structure in the PTT/GNS–CNT composites. The geometric structure, aspect ratio, and intrinsic conductivity of carbon nanofillers affected the electrical percolation threshold and EMI shielding efficiency of the composites.     

Morphological,electrical, electromagnetic interference (EMI) shielding,and tribological properties of functionalized multi-walled carbon nanotube/poly methyl methacrylate (PMMA) composites

The functionalized multi-walled carbon nanotubes (MWCNTs) had been prepared via Friedel–Crafts acylation with maleic anhydride. X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) confirmed the functionalization of MWCNTs. The composites with maleic anhydride modified MWCNTs (Mah-g-MWCNTs) and poly (methyl methacrylate) were then prepared by the in situ and ex situ solution polymerization system. The Electromagnetic Interference (EMI) shielding effectiveness (SE) of Mah-g-MWCNTs/PMMA composites increased with the increasing of the Mah-g-MWCNTs content, and the in situ system shows higher EMI SE value. The wear resistance was enhanced while the loading of the Mah-g-MWCNTs was above the percolation threshold, and the in situ system provides higher efficiency than that of ex situ system.     

Poly(ethylene-co-vinyl alcohol) functionalized single-walled carbon nanotubes and related nanocomposites

Single-walled carbon nanotubes (SWNTs) were functionalized by poly(ethylene-co-vinyl alcohol) (EVOH) copolymer under carbodiimide-activated esterification reaction conditions. Similar to the parent EVOH copolymer, the EVOH-functionalized carbon nanotubes are soluble in highly polar solvent systems such as DMSO and hot ethanol-water mixtures. The soluble EVOH-SWNT sample was characterized by various techniques, including optical absorption, Raman, NMR, electron microscopy, and thermogravimetric analysis. The common solubility of EVOH and EVOH-SWNT allowed their intimate mixing in solution, and thus the fabrication of nanocomposites in which the SWNTs are homogeneously dispersed in the polymer matrix.     

Recent progress in the modification of carbon materials and their application in composites for electromagnetic interference shielding

With the development in the modern technologies such as telecommunication instruments and scientific electronic devices, large amount of the electromagnetic radiations are produced, which lead to harmful effect on the highly sensitive electronic devices as well as on the health of human beings. To minimize the effect of electromagnetic radiations produced by different technologies, more efficient shielding materials are required which must be cost-effective, lightweight and good corrosion resistive. In this review, we focused on the shielding materials based on composites of carbon nanotubes and graphene. The typical surface modification of carbon nanotubes and graphene to optimize their interactions with polymers matrix has also summarized. It was found that the composites based on these carbon fillers were more efficient for electromagnetic interference shielding due to their unique properties (i.e., superior electrical, mechanical and thermal) together with lightweight, easy processing. Hence, the carbon nanotubes and graphene-based composites are excellent shielding materials against the electromagnetic radiations.     

Segregated poly(vinylidene fluoride)/MWCNTs composites for high-performance electromagnetic interference shielding

Conductive polymer composites (CPCs) that contain a segregated structure have attracted significant attentions because of their promising for fulfilling low filler contents with high electromagnetic interference (EMI) properties. In the present study, segregated poly(vinylidene fluoride) (PVDF)/multi-walled carbon nanotubes (MWCNTs) composites were successfully prepared by mechanical mixing and hot compaction. The PVDF/MWCNTs samples with 7 wt% filler content possess high electrical conductivities and high EMI shielding effectiveness (SE), reaching 0.06 S cm⁻¹ and 30.89 dB (in the X-band frequency region), much higher than lots of reported results for CNT-based composites. And the EMI SE greatly increased across the frequency range as the sample thickness was improved from 0.6 to 3.0 mm. The EMI shielding mechanisms were also investigated and the results demonstrated absorption dominating shielding mechanism in this segregated material. This effective preparation method is simple, low-cost, and environmentally-friendly and has potential industrial applications in the future.     

Thermal fracture interference: a two-dimensional boundary element approach

Thermal loading of fractured structures is associated with the development of differential deformations along crack surfaces which result in the closure of the crack. Inherent non-linearities demand application of numerical procedures to resolve this problem. In this paper, a boundary element procedure is formulated to treat crack surface interference imposed under thermal steady-state or transient loadings. An iterative-incremental procedure is developed to deal with the non-linearity produced by the frictional contact of the crack surfaces. The open, adhesion and slip contact conditions are modeled through the utilization of the multi-domain technique. Two approaches are followed regarding the thermal boundary contact conditions along the crack region. In the first, crack surfaces are assumed to be thermally insulated. This assumption simplifies the formulation significantly. In the second, the crack surfaces are assumed to provide perfect thermal contact. Thermal stress intensity factors are evaluated from traction nodal results that adopt singular elements in the crack tip region. Numerical examples are illustrated, discussed and compared with analytical solutions, where possible. Fracture characteristics are predicted in terms of the involved parameters. As a general conclusion, peak values of thermal stress intensity factors depend on the friction conditions existing between crack faces.*Author for correspondence. (E-mail: nanif@mech.upatras.gr, Phone: +30-2610-997-197, Fax: +30-2610-997-207)     

Processing and characterization of carbon nanotube/poly(styrene-co-butyl acrylate) nanocomposites

Nanocomposite materials were prepared from an amorphouspoly(styrene-co-butyl acrylate) latex as the matrix using an aqueous suspension of carbon nanotubes as the filler. After stirring, the preparations were cast and evaporated. The morphology of the resulting films was examined by scanning electron microscopy and a good dispersion of the filler was observed, except for the 5 wt% filled sample. The electrical conductivity and mechanical behavior in both the linear and non-linear ranges were analyzed. From conductivity measurements, a clear percolation threshold has been observed for a relatively low critical volume fraction around 1.5%. The mechanical characterization displayed a continuous reinforcing effect of the carbon nanotubes without lowering of the elongation at break up to 3 wt%. The thermal stability of the composites was strongly improved by carbon nanotubes loading. For instance, the terminal zone was shifted by 115 K with only 15 wt% of nanotubes.