A comparative study of structure and electromagnetic interference shielding performance for silver nanostructure hybrid polyimide foams

Comparison of structure and electromagnetic interference shielding performance for silver nanostructures hybrid polyimide foams.

Fe3O4 nanopearl decorated carbon nanotubes stemming from carbon onions with self-cleaning and microwave absorption properties

A water shedding carbon onion/carbon nanotube@Fe₃O₄ nanocomposite film prepared using a flame strategy possesses self-cleaning and microwave absorption properties.

Highly efficient electromagnetic interference shielding using graphite nanoplatelet/poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonate) composites with enhanced thermal conductivity

We address the ongoing quest for high efficiency, lightweight and thermally conducting electromagnetic interference shields. GNP/PEDOT:PSS composites are used to achieve an extremely high shielding effectiveness with enhanced thermal conductivity.

Single wall carbon nanohorn (SWCNH)/graphene nanoplate/poly(methyl methacrylate) nanocomposites: a promising material for electromagnetic interference shielding applications

Single wall carbon nanohorn (SWCNH)/graphene nanoplates (GNP)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared through addition of GNP/PMMA bead into the SWCNH dispersed PMMA matrix during its polymerization.

Facile, green and affordable strategy for structuring natural graphite/polymer composite with efficient electromagnetic interference shielding

The mechanical mixing and hot compaction method was firstly used to fabricate graphite/polymer segregated composite for efficient electromagnetic interference shielding.

Polymer nanocomposite foam filled with carbon nanomaterials as an efficient electromagnetic interference shielding material

Among different carbon nanomaterial foam-filled polymer composites, graphene-based foam gives superior specific shielding effectiveness when compared to typical metals.

Barium ferrite decorated reduced graphene oxide nanocomposite for effective electromagnetic interference shielding

There is an increased interest in the development of high performance microwave shielding materials against electromagnetic pollution in recent years. Barium ferrite decorated reduced graphene oxide (BaFe12O19@RGO) nanocomposite was synthesized by a high energy ball milling technique and its electromagnetic properties were investigated in the frequency range of 12.4-18 GHz (Ku band). The results showed that barium ferrite (BaFe12O19) nanoparticles with an average particle size of 20-30 nm were well distributed and firmly anchored onto the surface of the reduced graphene oxide sheets. The obtained nanocomposite exhibited a saturation magnetization of 18.1 emu g(-1) at room temperature. The presence of BaFe12O19 nanoparticles in the nanocomposite enhances the space charge polarization, natural resonance, multiple scattering and the effective anisotropy energy leading to a high electromagnetic interference shielding effectiveness of 32 dB (∼99.9% attenuation) at a critical thickness of 3 mm. The results suggested that the as-prepared BaFe12O19@RGO nanocomposite showed great potential as an effective candidate for a new type of microwave absorbing material.

Lightweight polypropylene/stainless-steel fiber composite foams with low percolation for efficient electromagnetic interference shielding

Lightweight polypropylene/stainless-steel fiber (PP-SSF) composites with 15-35% density reduction were fabricated using foam injection molding. The electrical percolation threshold, through-plane electrical conductivity, and electromagnetic interference (EMI) shielding effectiveness (SE) of the PP-SSF composite foams were characterized and compared against the solid counterparts. With 3 wt % CO2 dissolved in PP as a temporary plasticizer and lubricant, the fiber breakage was significantly decreased during injection molding, and well-dispersed fibers with unprecedentedly large aspect ratios of over 100 were achieved. The percolation threshold was dramatically decreased from 0.85 to 0.21 vol %, accounting for 75% reduction, which is highly superior, compared to 28% reduction of the previous PP-carbon fiber composite foam.1 Unlike the case of carbon fiber,1 SSFs were much longer than the cell size, and the percolation threshold reduction of PP-SSF composite foams was thus primarily governed by the decreased fiber breakage instead of fiber orientation. The specific EMI SE was also significantly enhanced. A maximum specific EMI SE of 75 dB·g(-1)·cm(3) was achieved in PP-1.1 vol % SSF composite foams, which was much higher than that of the solid counterpart. Also, the relationships between the microstructure and properties were discussed. The mechanism of EMI shielding enhancement was also studied.

Interfacial engineering of carbon nanofiber-graphene-carbon nanofiber heterojunctions in flexible lightweight electromagnetic shielding networks

Lightweight carbon materials of effective electromagnetic interference (EMI) shielding have attracted increasing interest because of rapid development of smart communication devices. To meet the requirement in portable electronic devices, flexible shielding materials with ultrathin characteristic have been pursued for this purpose. In this work, we demonstrated a facile strategy for scalable fabrication of flexible all-carbon networks, where the insulting polymeric frames and interfaces have been well eliminated. Microscopically, a novel carbon nanofiber-graphene nanosheet-carbon nanofiber (CNF-GN-CNF) heterojunction, which plays the dominant role as the interfacial modifier, has been observed in the as-fabricated networks. With the presence of CNF-GN-CNF heterojunctions, the all-carbon networks exhibit much increased electrical properties, resulting in the great enhancement of EMI shielding performance. The related mechanism for engineering the CNF interfaces based on the CNF-GN-CNF heterojunctions has been discussed. Implication of the results suggests that the lightweight all-carbon networks, whose thickness and density are much smaller than other graphene/polymer composites, present more promising potential as thin shielding materials in flexible portable electronics.

Lightweight and flexible reduced graphene oxide/water-borne polyurethane composites with high electrical conductivity and excellent electromagnetic interference shielding performance

In this study, we developed a simple and powerful method to fabricate flexible and lightweight graphene-based composites that provide high electromagnetic interference (EMI) shielding performance. Electrospun waterborne polyurethane (WPU) that featured sulfonate functional groups was used as the polymer matrix, which was light and flexible. First, graphene oxide (GO)/WPU composites were prepared through layer-by-layer (L-b-L) assembly of two oppositely charged suspensions of GO, the cationic surfactant (didodecyldimethylammonium bromide, DDAB)-adsorbed GO and intrinsic negatively charged GO, depositing on the negatively charged WPU fibers. After the L-b-L assembly cycles, the GO bilayers wrapped the WPU fiber matrix completely and revealed fine connections guided by the electrospun WPU fibers. Then, we used hydroiodic acid (HI) to obtain highly reduced GO (r-GO)/WPU composites, which exhibited substantially enhanced electrical conductivity (approximately 16.8 S/m) and, moreover, showed a high EMI-shielding effectiveness (approximately 34 dB) over the frequency range from 8.2 to 12.4 GHz.

Fabrication of lightweight, flexible polyetherimide/nickel composite foam with electromagnetic interference shielding effectiveness reaching 103 dB

The preparation of lightweight materials with electromagnetic interference-shielding effectiveness higher than 30 dB is critical for most industrial and consumer applications. Compounding polymer resin with conductive filler can generate excellent electromagnetic interference-shielding effectiveness but usually leads to a high-sample density, while the foaming of polymer composite suffers from the significant-reduced electromagnetic interference-shielding effectiveness. In this study, polyetherimide composite foams with loading of 10–80 phr (parts per hundred of resins) nickel particles were fabricated to meet the gap. The polyetherimide/nickel composite foams possessed uniform cell structure and low-sample density such as 0.86 g/cm3 at 70 phr nickel. The coupling effects of gravity settlement and cell-structure solidification led to the formation of gradient distribution of nickel particles across the foams. The formed novel structure facilitated the enhancement of multi-reflection and multi-scattering among nickel particles and cells. As a consequence, polyetherimide/nickel foam with 70 phr nickel (PEIN70) possessed a high-electromagnetic interference shielding effectiveness of 86.7–106.5 dB over a frequency range of 50–3000 MHz. When the sample density was considered, the specific electromagnetic interference shielding effectiveness of PEIN70 foam was as high as 121.3 dB/(g/cm3) at 1 GHz, which was higher than the reported electromagnetic interference-shielding materials. The excellent electromagnetic interference-shielding properties, lightweight, well-defined resin properties ensure polyetherimide/nickel composite foams useful in many advanced applications.

Electromagnetic interference shielding of segregated polymer composite with an ultralow loading of in situ thermally reduced graphene oxide

An in situ thermally reduced graphene/polyethylene conductive composite with a segregated structure was fabricated, which achieved a high electromagnetic interference shielding effectiveness of up to 28.3-32.4 dB at an ultralow graphene loading of 0.660 vol.%. Our work suggests a new way of effectively using graphene.

Interactive oxidation-reduction reaction for the in situ synthesis of graphene-phenol formaldehyde composites with enhanced properties

We report a facile in situ synthesis of reduced graphene oxide (RGO)-phenol formaldehyde (PF) composites with an interactive oxidation-reduction reaction. In this interactive chemical reaction, graphene oxide (GO) was reduced to RGO by phenol, and simultaneously phenol was oxidized to benzoquinone. The noncovalently adsorbed phenol on the RGO surface can not only serve as an effective reductant but also participate in the in situ polymerization and guide the formation of PF on the RGO surface. RGO-PF composites with different RGO contents were prepared successfully and further characterized with fluorescent spectroscopy, scanning electron microscopy, and transmission electron microscopy. The mechanical strength, electrical conductivity, thermal conductivity, and thermal resistance of the created RGO-PF were investigated. The results indicated that the dispersity of RGO in the PF matrix and the interfacial interaction between RGO and PF were improved greatly because of formation of the RGO-PF hybrid in the in situ synthesis. The homogeneous dispersion and in situ polymerization of RGO sheets help to enhance the thermal conductivity of RGO-PF composites from 0.1477 to 0.3769 W m(-1) K(-1) and endow the composites with a good electrical conductivity. In addition, the well-dispersed RGO-PF composites are much more effective in improving their mechanical property and heat resistance.

Facile method to synthesize silver nanoparticles on the surface of hollow glass microspheres and their microwave shielding properties

In this paper, a facile method for the fabrication of hollow glass microspheres–Ag composite particles with core–shell structures is investigated.

Lightweight, multifunctional polyetherimide/graphene@Fe3O4 composite foams for shielding of electromagnetic pollution

Novel high-performance polyetherimide (PEI)/graphene@Fe3O4 (G@Fe3O4) composite foams with flexible character and low density of about 0.28-0.4 g/cm(3) have been developed by using a phase separation method. The obtained PEI/G@Fe3O4 foam with G@Fe3O4 loading of 10 wt % exhibited excellent specific EMI shielding effectiveness (EMI SE) of ~41.5 dB/(g/cm(3)) at 8-12 GHz. Moreover, most the applied microwave was verified to be absorbed rather than being reflected back, resulting from the improved impedance matching, electromagnetic wave attenuation, as well as multiple reflections. Meanwhile, the resulting foams also possessed a superparamagnetic behavior and low thermal conductiviy of 0.042-0.071 W/(m K). This technique is fast, highly reproducible, and scalable, which may facilitate the commercialization of such composite foams and generalize the use of them as EMI shielding materials in the fields of spacecraft and aircraft.

Facile preparation of lightweight microcellular polyetherimide/graphene composite foams for electromagnetic interference shielding

We report a facile approach to produce lightweight microcellular polyetherimide (PEI)/graphene nanocomposite foams with a density of about 0.3 g/cm3 by a phase separation process. It was observed that the strong extensional flow generated during cell growth induced the enrichment and orientation of graphene on cell walls. This action decreased the electrical conductivity percolation from 0.21 vol % for PEI/graphene nanocomposite to 0.18 vol % for PEI/graphene foam. Furthermore, the foaming process significantly increased the specific electromagnetic interference (EMI) shielding effectiveness from 17 to 44 dB/(g/cm3). In addition, PEI/graphene nanocomposite foams possessed low thermal conductivity of 0.065-0.037 W/m·K even at 200 °C and high Young's modulus of 180-290 MPa.