Effect of iron oxide on vulcanization kinetics and electrical conductance of butyl rubber composites

This paper investigates the effect of iron oxide concentration on the vulcanization process, electrical conductance during swelling in kerosene, and sheds some light on the possible mechanism of vulcanization kinetics. The rate and degree of crosslinking have been evaluated as a function of Fe₂O₃ concentration. It was found that the characteristic time constant during vulcanization decreases as the Fe₂O₃ concentration increases. The activation energy of the crosslinking reaction is calculated. An abrupt decrease in electrical conductance appears after a characteristic time of swelling. A modified model is suggested to calculate the separation distance in the conductive rubber matrix. The effect of microwave irradiation on electrical conductance and separation distance between conductive aggregate of butyl rubber (IIR) composites is also studied. Fe₂O₃ inhibits the degradation of IIR composites and microwave irradiation enhances the texturing microstructure of rubber matrix. © 2000 Society of Chemical Industry     

Preparation and characterization of conductive and magnetic PPy/Fe3O4/Ag nanocomposites

In this article, conductive and magnetic nanocomposites composed of polypyrrole (PPy), magnetite (Fe₃O₄) nanoparticles (NPs), silver (Ag) NPs, have been successfully synthesized with a two step process. First, the PPy/Fe₃O₄ was prepared by the ultrasonic in situ polymerization. Next, the PPy/Fe₃O₄/Ag was synthesized through the electrostatic adsorption. The products were characterized by fourier‐transform infrared (FTIR) spectroscopy, Scanning electron microscopy (SEM), Thermogravimetric (TG), conductivity and magnetization analysis, and the results showed that the Ag NPs with the good conductivity coated uniformly on the surface of PPy/Fe₃O₄ and improved the conductivity of PPy/Fe₃O₄/Ag composites. In addition, as compared with PPy/Fe₃O₄, PPy/Fe₃O₄/Ag composites also have the excellent electro‐magnetic property and enhanced thermostability. POLYM. COMPOS., 35:450–455, 2014. © 2013 Society of Plastics Engineers     

Negative Permittivity of Polyaniline–Fe3O4 Nanocomposite

Polyaniline–Fe₃O₄ nanocomposite with and without ionic liquid were successfully synthesized via in situ polymerization using cetyl trimethylammonium bromide (CTAB) as surfactant. Both TG analysis and FT-IR measurements proved the presence of organic layer on the surface of Fe₃O₄ nanoparticles. The influence of 1-butyl-3-methyl-imidazolium bromide (BMIMBr) as ionic liquid on the structure, conductivity, and magnetic property of PANI–Fe₃O₄–CTAB nanocomposite were studied in detail. The results show that imidazolium-based ionic liquids BMIMBr acts as an anchor agent during the formation of PANI–Fe₃O₄–CTAB nanocomposite. Ionic liquid significantly deteriorated nanocomposite’s magnetic properties, and contributed to non-saturated M–H curve due to the disappearance of antiferromagnetic interactions. It has also an improving effect on AC and DC conductivities. The most important effect of IL is observed in real part of permittivity of PANI–Fe₃O₄–CTAB that it has negative high values at low frequency low temperature region. Due to the negative dielectric constant, material exhibits uncommon properties in electromagnetic waves scattering and attraction between similar charges. This possibility provokes research on these composites as high T superconductors, negative index materials and microwave absorbers.     

Electromagnetic properties of electrospun Fe3O4/carbon composite nanofibers

In order to develop multifunctional nanofibers, the electrical conductivity and magnetic properties of Fe₃O₄/carbon composite nanofibers have been examined. Polyacrylonitrile (PAN) is used as a matrix to produce magnetic composite nanofibers containing different amounts of magnetite (Fe₃O₄) nanoparticles. Electrospun composite nanofibers were thermally treated to produce electrically conductive and magnetically permeable composite carbon nanofibers. The composite nanofibers were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), Raman spectroscopy, four-point probe and Superconducting Quantum Interference Device (SQUID). Uniform nanofibers were obtained with successful transferring of magnetic properties of Fe₃O₄ into the as-spun composite nanofibers. The electromagnetic properties were tuned by adjusting the amount of Fe₃O₄ in the matrix and carbonization process. The electrical conductivity, magnetic moment and also magnetic hysteresis rise up by adding Fe₃O₄ and increasing carbonization temperature. The high surface area provided by the ultrafine fibrous structures, the flexibility and tuneable electromagnetic properties are expected to enable the expansion of the design options for a wide rage of electronic devices.     

Synthesis and characterization of alkali‐soluble photosensitive polysiloxane urethane acrylate

A new negative temperature coefficient of resistor (NTCR) thermistors based on nitrile butadiene rubber/magnetite (NBR/Fe₃O₄) nanocomposites were successfully fabricated by conventional roll milling technique. X‐ray diffraction and transmission (TEM) analysis showed that the product is mainly magnetite nanoparticles with diameter of 10‐13 nm. The microstructure of (NBR/Fe₃O₄) nanocomposites were examined by scanning electron microscopy (SEM) and FTIR spectroscopy. The dispersion of magnetite nanoparticles in the NBR rubber matrix and interfacial bonding between them were rather good. The thermal stability of nanocomposites was also obviously improved with the inclusion of the magnetite nanoparticles. The thermal conductivity, thermal diffusivity and specific heat of nanocomposites were investigated. The electrical conductivity of the NBR/Fe₃O₄ increases with the rise in temperature exhibiting a typical negative temperature coefficient of resistance (NTCR) behavior like a semiconductor. The nature of the temperature variation of electrical conductivity and values of activation and hopping energy, suggest that the transport conduction process is controlled by hopping mechanism. Values of characteristics parameters of the thermistors like thermistor constant, thermistor sensitivity and thermistor stability is quite good for practical application as NTCR devices at high temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Influence of iron (III) acetylacetonate on structure and electrical conductivity of Fe3O4/carbon composite nanofibers

Fe₃O₄/carbon composite nanofibers were prepared by electrospinning polyacrylonitrile (PAN), iron (III) acetylacetonate (AAI) and dimethyl formamide (DMF) compound solutions, followed by stabilization and carbonization processes. Emphasis was put on the influence of AAI on reactions during stabilization and carbonization. The effect of Fe₃O₄ on catalytic graphitization and electrical conductivity was also studied. Experimental results show that AAI has participated in the reactions and structural changes of PAN during stabilization and carbonization, and is evidenced to promote the processes. Fe₃O₄ nanoparticles exhibit catalytic effect on carbonization process that promote graphitization by a catalytic effect at low AAI content and inhibit the formation of graphitized layers when AAI content is excessive. Therefore, there exists an optimum AAI content (C_o) where composite nanofibers show the maximum graphitization degree and electrical conductivity. With proper amount of AAI addition, Fe₃O₄/carbon composite nanofibers showing high graphite degree and electrical conductivity could be achieved.     

Flash Sintering of (La,Sr)(Co,Fe)O3–Gd‐Doped CeO2 Composite

Sintering of composites constituted by two nonstoichiometric phases (La_0.6Sr_0.4)(Co_0.2Fe_0.8)O₃ (LSCF) and Gd_0.1Ce_0.9O₂ (GDC) under constant electric field in constant heating rate experiment is studied in this work. The requirements of field and temperature for composite systematically increase with GDC amounts this indicating the importance of material conductivity. Sintering/grain growth rate is higher in the composite compared to pure LSCF phase. Flash‐sintering phenomenon in the composite is explained on the basis of three factors: (1) large and continuous increase in conductivity of LSCF acts as source of defects, (2) maintenance of sufficient local temperature because of GDC during continuous conductivity increase facilitates the cationic diffusion, and (3) reduction reactions of LSCF, during polaron hopping conduction, and of GDC phase at higher temperature activate the sintering process.     

Immobilization of Metalloporphyrin on Functionalized Magnetic Nanoparticles as a Catalyst in Oxidation of Cyclohexene: Novel Modified Fe3O4 Nanoparticles with Triethoxysilane Agent

Magnetic nanoparticles, Fe₃O₄, have been prepared and functionalized by (N-(3-(triethoxysilyl)propyl)isonicotinamide) and characterized by infrared spectroscopy, thermal analysis (TGA/DTA), X-ray powder diffraction, scanning electron microscopy, elemental analysis and BET surface area measurement. The functionalized Fe₃O₄ nanoparticles were used as a support to anchor metalloporphyrin. Application of immobilized metalloporphyrin as a heterogeneous catalyst in the oxidation of cyclohexene was explored. Effect of various parameters such as solvent and temperature on immobilization process and also various parameters (solvent, time, oxidant and axial group effect) on oxidation of cyclohexene has been investigated. The result showed that the immobilized metalloporphyrin on functionalized magnetic nanoparticles is an efficient and reusable catalyst for oxidation of cyclohexene.     

Crystallinity,conductivity, and magnetic properties of PVDF‐Fe3O4 composite films

The formation of Fe₃O₄ nanoparticles by hydrothermal process has been studied. X‐ray Diffraction measurements were carried out to distinguish between the phases formed during the synthesis. Using the synthesized Fe₃O₄ nanoparticles, poly(vinyledene fluoride)‐Fe₃O₄ composite films were prepared by spin coating method. Scanning electron microscopy of the composite films showed the presence of Fe₃O₄ nanoparticles in the form of aggregates on the surface and inside of the porous polymer matrix. Differential Scanning calorimetry revealed that the crystallinity of PVDF decreased with the addition of Fe₃O₄. The conductitivity of the composite films was strongly influenced by the Fe₃O₄ content; conductivity increased with increase in Fe₃O₄ content. Vibration sample magnetometry results revealed the ferromagnetic behavior of the synthesized iron oxide nanoparticles with a Ms value of 74.50 emu/g. Also the presence of Fe₃O₄ nanoparticles rendered the composite films magnetic. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Magnetically aligning multilayer graphene to enhance thermal conductivity of silicone rubber composites

The increasing demand for packaging materials calls for new technologies to achieve excellent thermal conductivity of polymer composites with low content of thermal conductive filler. This article prepared a kind of magnetically functionalized multilayer graphene (Fe₃O₄@MG) via electrostatic interactions, which efficiently enhanced the thermal conductivity of silicone rubber (SR) composites by the alignment of Fe₃O₄@MG in an external magnetic field. The morphology and structure of the Fe₃O₄@MG together with the thermal conductivity of corresponding Fe₃O₄@MG/SR composites were systematically investigated by SEM, TEM, XRD, elemental mapping, and thermal conductivity tester. The obtained results showed that Fe₃O₄@MG was induced to form chain-like bundles in silicone rubber matrix under the applied magnetic field, which enhanced the MG–MG interaction, and formed effective thermal pathways in the alignment direction. Furthermore, as coating mass ratio of Fe₃O₄@MG increased, the thermal conductivity of randomly oriented Fe₃O₄@MG/silicone rubber composites (R-Fe₃O₄@MG/SR) decreased gradually, whereas the through-plane thermal conductivity of vertically aligned Fe₃O₄@MG/silicone rubber composites (V-Fe₃O₄@MG/SR) increased even filled with same contents of thermal conductive filler. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47951.     

Synthesis and characterization of novel conducting composites of Fe3O4 nanoparticles and sulfonated polyanilines

Surface charged iron oxide (Fe₃O₄) nanoparticles were used for the synthesis of sulfonated polyaniline (SPAN)‐Fe₃O₄ nanocomposites (SPAN/Fe₃O₄‐NCs). 2,5‐diaminobenzenesulfonic acid (DABSA) and 2‐aminobenzenesulfonic acid (ABSA) were independently polymerized with aniline to form SPAN. The structure of the composites was characterized by means of transmission electron microscopy (TEM), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectra, conductivity and magnetic properties. TEM reveals that Fe₃O₄ nanoparticles are “glued” with SPAN in the composite. TGA indicates that SPAN/Fe₃O₄‐NCs are having better thermal stability. The room temperature conductivity of SPAN/Fe₃O₄‐NCs is higher than that of pristine PANI and SPAN. SPAN/Fe₃O₄‐NCs exhibits magnetic behavior. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4127–4134, 2007     

Novel electrically conductive and ferromagnetic composites of poly(aniline‐co‐aminonaphthalenesulfonic acid) with iron oxide nanoparticles: Synthesis and characterization

Nanocomposites of iron oxide (Fe₃O₄) with a sulfonated polyaniline, poly(aniline‐co‐aminonaphthalenesulfonic acid) [SPAN(ANSA)], were synthesized through chemical oxidative copolymerization of aniline and 5‐amino‐2‐naphthalenesulfonic acid/1‐amino‐5‐naphthalenesulfonic acid in the presence of Fe₃O₄ nanoparticles. The nanocomposites [Fe₃O₄/SPAN(ANSA)‐NCs] were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, elemental analysis, UV–visible spectroscopy, thermogravimetric analysis (TGA), superconductor quantum interference device (SQUID), and electrical conductivity measurements. The TEM images reveal that nanocrystalline Fe₃O₄ particles were homogeneously incorporated within the polymer matrix with the sizes in the range of 10–15 nm. XRD pattern reveals that pure Fe₃O₄ particles are having spinel structure, and nanocomposites are more crystalline in comparison to pristine polymers. Differential thermogravimetric (DTG) curves obtained through TGA informs that polymer chains in the composites have better thermal stability than that of the pristine copolymers. FTIR spectra provide information on the structure of the composites. The conductivity of the nanocomposites (～ 0.5 S cm^?1) is higher than that of pristine PANI (～ 10^?3 S cm^?1). The charge transport behavior of the composites is explained through temperature difference of conductivity. The temperature dependence of conductivity fits with the quasi‐1D variable range hopping (quasi‐1D VRH) model. SQUID analysis reveals that the composites show ferromagnetic behavior at room temperature. The maximum saturation magnetization of the composite is 9.7 emu g^?1. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Electro-Magnetic Polyfuran/Fe3O4 Nanocomposite: Synthesis,Characterization, Antioxidant Activity,and Its Application as a Biosensor

Herein, the authors report the synthesis of electro-magnetic polyfuran/Fe₃O₄ nanocomposites using Fe₃O₄ magnetic nanoparticles of different content as nucleation sites via in situ chemical oxidation polymerization method. Surface, structural, morphological, thermal, electrical and magnetic properties of the nanocomposites were studied by FT-IR, UV-visible spectroscopies, XRD, FESEM, TGA, four probe, and VSM, respectively. The effect of Fe₃O₄ nanoparticles content on the electrical conductivity and magnetization of nanocomposites was studied. The obtained polyfuran and polyfuran/Fe₃O₄ nanocomposites were analyzed for their antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. In addition, polyfuran/Fe₃O₄ nanocomposites have been investigated for application as electrochemical biosensor.     

Magnetic and conducting Fe3O4–polypyrrole nanoparticles with core‐shell structure

Magnetic and conducting Fe₃O₄–polypyrrole nanoparticles with core‐shell structure were prepared in the presence of Fe₃O₄ magnetic fluid in aqueous solution containing sodium dodecylbenzenesulfonate (NaDS) as a surfactant and dopant. Both the conductivity and magnetization of the composites depend strongly on the Fe₃O₄ content and the doping degree. With increase of Fe₃O₄ content in the composite, the conductivity at room temperature decreases, but the saturated magnetization and coercive force increase. Transmission electron microscopy (TEM) images of Fe₃O₄ and Fe₃O₄–polypyrrole particles show almost spherical particles with diameters ranging from 20 to 30 and 30 to 40 nm, respectively. The thermal stability of Fe₃O₄–polypyrrole composites is higher than that of pure polypyrrole. Studies of IR, UV–visible and X‐ray photoelectron spectroscopy (XPS) spectra suggest that the increased thermal stability may be due to interactions between Fe₃O₄ particles and polypyrrole backbone. Copyright © 2003 Society of Chemical Industry     

Activation and deactivation of the commercial-type CuO–Cr2O3–Fe2O3 high temperature shift catalyst

This work elucidates the structural evolution of a commercial-type iron oxide-based high temperature water–gas shift (HT-WGS) catalyst during activation and deactivation stages. The findings highlight the importance of Cu–FeO _x interfaces. Based on the new insights, future improvement of commercial iron-based catalysts should focus on stabilization of the active Cu–FeO _x interface. Much effort has been devoted to understanding the structure, mechanism, and promotion of the commercial-type CuO–Cr₂O₃–Fe₂O₃ catalyst for the high temperature water–gas shift (HT-WGS) reaction. However, structural evolution of the catalyst during the activation and deactivation stages was rarely reported. Herein, catalyst characterization, temperature-programmed studies, and kinetic analysis were conducted on iron oxide-based HT-WGS catalysts. Addition of Cu was found to accelerate both the bulk (Fe₂O₃ → Fe₃O₄) and surface (active FeO _x–Cu interface) transformations during the catalyst activation stage. During catalyst deactivation, Cu accelerated both sintering of the Fe₃O₄ bulk phase and unfavorable encapsulation of the metallic Cu particles with a substantial FeO _x overlayer. The loss of the initial active Cu–FeO _x interfacial sites reversed the promotional effect of Cu.     

Study of polyarylene ether nitrile terminated with phthalonitrile/hybrid Fe3O4 nanospheres composites by orthogonal experiments

A novel series of composites of polyarylene ether nitrile terminated with phthalonitrile (PEN‐t‐Ph) filled with hybrid Fe3O4 nanospheres (h‐Fe₃O₄) was prepared via in situ composition. Based on the cross‐linking interactions between the phthalonitrile at the end of PEN‐t‐Ph molecular chains and the phthalonitrile on the surface of h‐Fe₃O₄ particles to form phthalocyanine ring, it was shown that the PEN‐t‐Ph/h‐Fe₃O₄ system had superior interfacial compatibility and the h‐Fe₃O₄ particles were locked in the matrix resin. These results had been confirmed by scanning electron microscope analysis. By orthogonal experiments and statistic analysis, the optimal conditions of cure temperature, type of h‐Fe₃O₄ and content of h‐Fe₃O₄ had been determined. Meanwhile, the results of range analysis and variance analysis indicated that the cure temperature had great effects on the thermal properties. Thermal studies revealed that the glass transition temperature of PEN‐t‐Ph/h‐Fe₃O₄ cured at 320°C was 214.7°C, increased by about 40°C compared to the PEN‐t‐Ph/h‐Fe₃O₄ without heat treatment, and the temperature corresponding to the weight loss of 5 wt % was increased by about 20°C. Mechanical measurements indicated that PEN‐t‐Ph/h‐Fe₃O₄ cured at 320°C possesses excellent mechanical properties with tensile strength of 93.33 MPa and tensile modulus of 2414.05 MPa, 9.91 MPa, 355.76 MPa higher than pure PEN‐t‐Ph film cured at 320°C, and 13.26 MPa, 397.90 MPa higher than PEN‐t‐Ph/h‐Fe₃O₄ without heat treatment. Most importantly, the presence of h‐Fe₃O₄ particles endows PEN‐t‐Ph/h‐Fe₃O₄ system with good magnetic property. Thus, PEN‐t‐Ph/h‐Fe₃O₄ cured at 320°C may have potential applications in field of magnetic materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40418.     

High dielectric constant and superparamagnetic polymer-based nanocomposites induced by percolation effect

To obtain the high dielectric constant and superparamagnetic composites for application in dielectric energy storage capacitors and other electromagnetic devices, the Fe₃O₄ nanoparticles have been embedded into polyvinylidene fluoride (PVDF) polymer. As expectation, a distinct percolation effect has been found in these composites, because of the good conductivity of Fe₃O₄ nanoparticles. The composites exhibit great increase of the dielectric constants and conductivities near the percolation threshold. The maximum of dielectric constant is up to 5240 at 100 Hz, which is the highest value reported to date among the PVDF based percolative composites. Meanwhile, the dielectric loss is controlled in the range of 0–2.2. These composites also exhibit superparamagnetic with the presence of Fe₃O₄ nanoparticles. The maximum of saturation magnetization is 30.8 emu/g. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Structural,Optical and Electrical Conductivity Studies in Polycarbazole and its Metal Oxide Nano Composites

Polycarbazole (PCz) has been synthesized by chemical oxidation method using APS as an oxidizing agent and PCz/CuO and PCz/Fe₂O₃ nanocomposites by in situ polymerization method for different wt% of CuO and Fe₂O₃ at room temperature. XRD patterns confirmed crystalline nature of samples. FTIR indicated strong interaction between PCz and nano fillers. The morphological and optical absorption studies were carried out using SEM and UV–Vis respectively. Addition of CuO or Fe₂O₃ to PCz decreased its direct and indirect band gaps. However, band gap showed a small change with dopant contents up to 30%. Urbach energy decreased with the addition of dopants. But Urbach energy of the composites increased with increasing dopants content from 10 to 30%. DC conductivity of PCz and its nanocomposites has been measured by following two probe technique in the temperature range 300–423 K. The conductivity of both the nanocomposites is found to be less than the pure PCz and it is found to increase with wt% of CuO or Fe₂O₃ as the case may be. The activation energy has been determined by fitting Arrhenius expression to the dc conductivity data at high temperature. The activation energy of polycarbazole is determined to be less than that of the composites. In both the composites, activation energy decreased and conductivity increased with the increase of dopant content.

     

Synthesis and characterization of (Fe3O4/MWCNTs)/ epoxy nanocomposites

A sonochemical technique is used for in situ coating of iron oxide (Fe₃O₄) nanoparticles on outer surface of MWCNTs. These Fe₃O₄/MWCNTs were characterized using a high‐resolution transmission electron microscope (HRTEM), X‐ray diffraction, and thermogravimetric analysis. The as‐prepared Fe₃O₄/MWCNTs composite nanoparticles were further used as reinforcing fillers in epoxy‐based resin (Epon‐828). The nanocomposites of epoxy were prepared by infusion of (0.5 and 1.0 wt %) pristine MWCNTs and Fe₃O₄/MWCNTs composite nanoparticles. For comparison purposes, the neat epoxy resin was also prepared in the same procedure as the nanocomposites, only without nanoparticles. The thermal, mechanical, and morphological tests were carried out for neat and nanocomposites. The compression test results show that the highest improvements in compressive modulus (38%) and strength (8%) were observed for 0.5 wt % loading of Fe₃O₄/MWCNTs. HRTEM results show the uniform dispersion of Fe₃O₄/MWCNTs nanoparticles in epoxy when compared with the dispersion of MWCNTs. These Fe₃O₄/MWCNTs nanoparticles‐infused epoxy nanocomposite shows an increase in glass transition (T_g) temperature. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Dielectric properties of graphene–iron oxide/polyimide films with oriented graphene

The preparation of high‐dielectric‐constant (k) materials is important in the field of electronics. However, how to effectively use the function of fillers to enhance k is still a challenge. In this study, anisotropic graphene (GNS)–iron oxide (Fe₃O₄)/polyimide (PI) nanocomposite films with oriented GNSs were prepared by the in situ polymerization of 4,4′‐oxydianiline and pyromellitic anhydride in the presence of GNS–Fe₃O₄. Films of the precursors were fabricated, and this was followed by stepwise imidization under a magnetic field at a higher temperature to orient the magnetic sheets. The orientation of GNS–Fe₃O₄ and the relationships of the GNS–Fe₃O₄ content and measurement frequency with the dielectric properties of the GNS–Fe₃O₄/PI films were studied in detail. The dielectric property differences of the GNS–Fe₃O₄/PIs with GNS–Fe₃O₄ parallel or perpendicular to the film surface were not obvious, when the content of GNS–Fe₃O₄ was lower than 5 wt %. However, at the percolation threshold, the k values of GNS–Fe₃O₄/PI films with horizontal GNS–Fe₃O₄ were much higher than those of the other two kinds of films at 10³ Hz; this was derived from the contribution of more effective microcapcitors parallel to the film surface. So, making the GNS–Fe₃O₄ parallel to the film surface greatly enhanced k of GNS–Fe₃O₄. However, switching the charges on the large lateral surface of the parallel GNSs with the electric field also caused a higher dielectric loss and the frequency dependence of k and the dielectric loss at low frequency. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43041.