Comparison of electromagnetic shielding with polyaniline nanopowders produced in solvent-limited conditions

Design and Analysis of a Textured Cu-Encapsulated Ni Tube for Low-Reflection Electromagnetic Interference Shielding Material

With the frequent increase and update of electromagnetic interference (EMI) shielding materials, a low-resolution material that can absorb most electromagnetic waves, thereby effectively reducing the secondary pollution, is urgently needed. However, the excellent performance, flexibility, and low cost of these methods are usually incompatible with current reports. To address the above dilemma, we reported a facile solution for fabricating a low-reflection and high-performance EMI shielding composite by means of electroless nickel plating (EP-Ni), electroless copper plating (EP-Cu), annealing, and coating with a polydimethylsiloxane (PDMS) polymer with the structure of a Ni@Cu tube encapsulated with PDMS. The results indicate that the active groups on vegetable wool can act as active sites for the absorption of the Pd catalyst, thereby catalyzing the reduction of Ni2+, Cu2+, and the subsequent deposition on the plant fiber surface. Notably, the Ni@Cu-encapsulated plant fibers decreased during annealing at 100 °C. According to the segregated network and synergistic effect of the porous structure, the as-fabricated EMI shielding material demonstrated high absorption and low reflection, in which the power coefficient of the T value was approximately 0.0001, the R value was about 0.1764 (a decrease of 27.5% compared that of EP-Ni cotton), and the A value was approximately 0.8235.

Hollow Superstructure In Situ Assembled by Single-Layer Janus Nanospheres toward Electromagnetic Shielding Flame-Retardant Polyurea Composites

A dodecahedral superstructure consisting of a single layer of Janus spheres containing ZIF-67 nanodots is prepared by in situ polymerization, with ZIF-67 and bio-based phytic acid (PA) as templates and dopants. It is used to improve the flame retardant, electromagnetic (EMI) shielding, and thermal conductivity properties of polyurea (PUA). By adding 5 wt% polyaniline@cobalt phytate-2.0 (PANI@Co-PA-2.0), the peak of heat release rate and the peak of smoke production rate are reduced by 54.9 and 59.9%, respectively. The peak of CO and CO2 production also decreased by 46.2 and 53.1%, respectively. A decrease in the absorption intensity of aliphatic and aromatic volatiles is also observed. The fire safety of PUA is greatly improved. In addition, PUA/PANI@Co-PA-2.0 exhibits an EMI shielding capability of 22.4 dB with the help of reduced graphene oxide, which confirms the possibility of PUA material application in the field of electromagnetic shielding. The 5 wt% filler increases the tensile strength of the PUA matrix to 6.3 MPa, and the composite material obtains good thermal conductivity. This work provides a viable method for the preparation of a flame-retardant, conductive, and electromagnetic refractory PUA substrate.

Tuning Electro-Magnetic Interference Shielding Efficiency of Customized Polyurethane Composite Foams Taking Advantage of rGO/Fe3O4 Hybrid Nanocomposites

Electromagnetic interference (EMI) has been recognized as a new sort of pollution and can be considered as the direct interference of electromagnetic waves among electronic equipment that frequently affects their typical efficiency. As a result, shielding the electronics from this interfering radiation has been addressed as critical issue of great interest. In this study, different hybrid nanocomposites consisting of magnetite nanoparticles (Fe₃O₄) and reduced graphene oxide (rGO) as (conductive/magnetic) fillers, taking into account different rGO mass ratios, were synthesized and characterized by XRD, Raman spectroscopy, TEM and their magnetic properties were assessed via VSM. The acquired fillers were encapsulated in the polyurethane foam matrix with different loading percentages (wt%) to evaluate their role in EMI shielding. Moreover, their structure, morphology, and thermal stability were investigated by SEM, FTIR, and TGA, respectively. In addition, the impact of filler loading on their final mechanical properties was determined. The obtained results revealed that the Fe₃O₄@rGO composites displayed superparamagnetic behavior and acceptable electrical conductivity value. The performance assessment of the conducting Fe₃O₄@rGO/PU composite foams in EMI shielding efficiency (SE) was investigated at the X-band (8-12) GHz, and interestingly, an optimized value of SE -33 dBw was achieved with Fe₃O₄@rGO at a 80:20 wt% ratio and 35 wt% filler loading in the final effective PU matrix. Thus, this study sheds light on a novel optimization strategy for electromagnetic shielding, taking into account conducting new materials with variable filler loading, composition ratio, and mechanical properties in such a way as to open the door for achieving a remarkable SE.

Superior quality chemically reduced graphene oxide for high performance EMI shielding materials

The chemical reduction process of graphene oxide combined with a mild and controllable thermal treatment under vacuum at 200 °C for 4 hours provided a cost-effective, scalable, and high-yield route for Reduced Graphene Oxide (RGO) industrial production and became a potential candidate for producing electromagnetic interference (EMI) shielding. We investigated graphite, and RGO using l-ascorbic acid and Sodium borohydride before and after thermal treatment by carefully evaluating the chemical and morphological structures. The thermally treated l-ascorbic Acid reduction route (TCRGOL) conductivity was 2.14 × 10³ S m⁻¹ and total shielding efficiency (SET) based on mass loadings per area of shielding was 94 dB with about one-tenth less graphite weight and surpassing other graphene reduction mechanisms in the frequency range of 8.2–12.4 GHz, i.e., X-band, at room temperature while being tested using the waveguide line technique. The developed treatment represents valuable progress in the path to chemical reduction using a safe reducing agent and offering superior quality RGO rarely achieved with the top-down technique, providing a high EMI shielding performance.

The developed two-step protocol offers a superior reduced graphene oxide TCRGOL quality (7 layers), and its SET was 94 dB over the X-band.

Biomass-Derived, Highly Conductive Aqueous Inks for Superior Electromagnetic Interference Shielding, Joule Heating, and Strain Sensing

Conductive composite inks are widely used in various applications such as flexible electronics. However, grand challenges still remain associated with their relatively low electrical conductivity and require heavy use of organic solvents, which may limit their high performance in broad applications and cause environmental concerns. Here, we report a generalized and eco-friendly strategy to fabricate highly conductive aqueous inks using silver nanowires (AgNWs) and biomass-derived organic salts, including succinic acid-chitosan (SA-chitosan) and sebacic acid-chitosan. SA-chitosan/AgNW composite coatings can be prepared by directly casting conductive aqueous inks on various substrates, followed by subsequently heating for cross-linking. The composite coatings exhibit an ultrahigh electrical conductivity up to 1.4 × 10⁴ S/cm, which are stable after being treated with various organic solvents and/or kept at a high temperature of 150 °C, indicating their high chemical and thermal resistance. The flexibility and performance durability of these composite coatings were demonstrated by a suite of characterization methods, including bending, folding, and adhesion tests. Moreover, a high electromagnetic interference shielding (EMI) effectiveness of 73.3 dB is achieved for SA-chitosan/AgNW composite coatings at a thickness of only 10 μm due to the ultrahigh electrical conductivity. Additionally, we further demonstrated that such conductive composite inks can be used for fabricating functional textiles for a variety of applications with high performance, such as EMI shielding, Joule heating, and strain sensing. The robust and highly conductive inks prepared by this simple and environmental-friendly method hold great promise as important material candidates for the potential large-scale manufacturing of flexible and wearable electronics.

Conducting Polymeric Composites Based on Intrinsically Conducting Polymers as Electromagnetic Interference Shielding/Microwave Absorbing Materials—A Review

The development of sophisticated telecommunication equipment and other electro-electronic devices resulted in a kind of electromagnetic pollution that affects the performance of other equipment as well as the health of human beings. Intrinsically conducting polymers (ICP), mainly polyaniline and polypyrrole, have been considered as promising candidates for applications in efficient electromagnetic interference shielding (EMI) due to their ease of preparation, light weight, good conductivity and corrosion resistance. One of the important advantages of these materials is the capability to interact with the EM radiation through both absorption and reflection mechanisms thus enlarging the field of application. In this context, this review article describes a recent overview of the existing methods to produce intrinsically conducting polymers and their blends for electromagnetic shielding application. Additionally, it highlights the relationship between preparation methods reported in the literature with the structure and properties, such as electrical conductivity, electromagnetic shielding effectiveness (EMI SE), complex permittivity and permeability of these materials. Furthermore, a brief theory related to the electromagnetic mechanism and techniques for measuring the microwave absorbing properties are also discussed.

EMI and microwave absorbing efficiency of polyaniline-functionalized reduced graphene oxide/γ-Fe2O3/epoxy nanocomposite

Polyaniline-decorated reduced graphene oxide/ferrite nanofiller (RGPF) prepared by the solution mixing method in three different ratios (1 : 3, 1 : 1 and 3 : 1) of polyaniline-decorated reduced graphene oxide and ferrite have been studied for microwave absorption properties in defence application. The polyaniline-decorated reduced graphene oxide/ferrite and neat ferrite nano-fillers have been used for the preparation of an epoxy nanocomposite (RGPFE) of 60 wt%. The distribution of the RGPF nanofiller in the epoxy matrix was analyzed by field emission scanning electron microscopy. Further, thermal gravimetric analyses revealed the excellent thermal stability of the nanocomposites. A vibrating sample magnetometer was employed to find out the magnetic behavior of the prepared nanocomposites. The complex permittivity and permeability were investigated to evaluate the principal properties in the frequency range from 2 to 18 GHz. These results show that an epoxy nanocomposite with 60 wt% RGPF filler in the ratio of 3 : 1 has maximum dielectric loss. Finally, these electromagnetic data were used to calculate the reflection loss of the epoxy nanocomposites, and showed good agreement between the calculated and measured data of these nanocomposites. The minimum reflection loss was observed as -10.26 dB in the X band with a thickness of 3.0 mm, and the bandwidth was 8.47 GHz for RL ≤-10 dB. On the basis of the above observations, these nanocomposites could be a good candidate for electromagnetic interference shielding (EMI) and microwave absorption applications.

Organic Thin Paper of Cellulose Nanofiber/Polyaniline Doped with (±)-10-Camphorsulfonic Acid Nanohybrid and Its Application to Electromagnetic Shielding

A superior electrical conductivity of 38.5 S/cm and an electromagnetic shielding (EMS) effectiveness of -30 dB (-545 dB/mm) across a wide frequency range of 0-15 GHz, including the X-band, were achieved with thin organic paper of (55 μm) cellulose nanofiber (CNF)/polyaniline (PANI) doped with (±)-10-camphorsulfonic acid nanohybrid. Both electrical conductivity and EMS effectiveness of the PANI-coated CNF were strongly affected by the amount and type of dopant, which could be tunable after fabrication process via simple in situ oxidative polymerization of aniline. Flexible and free-standing film was obtained, since CNF provides good mechanical property without diminishing the electrical property of PANI.

A Novel Polyaniline-Coated Bagasse Fiber Composite with Core-Shell Heterostructure Provides Effective Electromagnetic Shielding Performance

A facile route was proposed to synthesize polyaniline (PANI) uniformly deposited on bagasse fiber (BF) via a one-step in situ polymerization of aniline in the dispersed system of BF. Correlations between the structural, electrical, and electromagnetic properties were extensively investigated. Scanning electron microscopy images confirm that the PANI was coated dominantly on the BF surface, indicating that the as-prepared BF/PANI composite adopted the natural and inexpensive BF as its core and the PANI as the shell. Fourier transform infrared spectra suggest significant interactions between the BF and PANI shell, and a high degree of doping in the PANI shell was achieved. X-ray diffraction results reveal that the crystallization of the PANI shell was improved. The dielectric behaviors are analyzed with respect to dielectric constant, loss tangent, and Cole-Cole plots. The BF/PANI composite exhibits superior electrical conductivity (2.01 ± 0.29 S·cm^-1), which is higher than that of the pristine PANI with 1.35 ± 0.15 S·cm^-1. The complex permittivity, electromagnetic interference (EMI), shielding effectiveness (SE) values, and attenuation constants of the BF/PANI composite were larger than those of the pristine PANI. The EMI shielding mechanisms of the composite were experimentally and theoretically analyzed. The absorption-dominated total EMI SE of 28.8 dB at a thickness of 0.4 mm indicates the usefulness of the composite for electromagnetic shielding. Moreover, detailed comparison of electrical and EMI shielding properties with respect to the BF/PANI, dedoped BF/PANI composite, and the pristine PANI indicate that the enhancement of electromagnetic properties for the BF/PANI composite was due to the improved conductivity and the core-shell architecture. Thus, the composite has potential commercial applications for high-performance electromagnetic shielding materials and also could be used as a conductive filler to endow polymers with electromagnetic shielding ability.

Bimetallic zeolitic imidazolate frameworks-derived porous carbon-based materials with efficient synergistic microwave absorption properties: the role of calcining temperature

The porous and graphitized carbon-based materials prepared by sacrificing template and in situ reduction show an excellent microwave absorbing performance.

Synthesis, characterization, photophysical, thermal and electrical properties of composite of polyaniline with zinc bis(8-hydroxyquinolate): a potent composite for electronic and optoelectronic use

A novel fluorescent as well as conducting composite of polyaniline with zinc bis(8-hydroxyquinolate) complex, prepared via in situ oxidative polymerization method.

Corrosive synthesis and enhanced electromagnetic absorption properties of hollow porous Ni/SnO2 hybrids

In this study, novel porous hollow Ni/SnO2 hybrids were prepared by a facile and flexible two-step approach composed of solution reduction and subsequent reaction-induced acid corrosion. In our protocol, it can be found that the hydrothermal temperature exerts a vital influence on the phase crystal and morphology of Ni/SnO2 hybrids. Notably, the Ni microspheres might be completely corroded in the hydrothermal process at 220 °C. The complex permittivity and permeability of Ni/SnO2 hybrids-paraffin wax composite were measured based on a vector network analyzer in the frequency range of 1-18 GHz. Electromagnetic absorption properties of samples were evaluated by transmission line theory. Ni/SnO2 hybrid composites exhibit superior electromagnetic absorption properties in comparison with pristine Ni microspheres. The outstanding electromagnetic absorption performances can be observed for the hollow porous Ni/SnO2 hybrid prepared at 200 °C. The minimum reflection loss is -36.7 dB at 12.3 GHz, and the effective electromagnetic wave absorption band (RL < -10 dB, 90% microwave attenuation) was in the frequency range of 10.6-14.0 GHz with a thin thickness of 1.7 mm. Excellent electromagnetic absorption properties were assigned to the improved impedance match, more interfacial polarization and unique hollow porous structures, which can result in microwave multi-reflection and scattering. This novel hollow porous hybrid is an attractive candidate for new types of high performance electromagnetic wave-absorbing materials, which satisfies the current requirements of electromagnetic absorbing materials, which include wide-band absorption, high-efficiency absorption capability, thin thickness and light weight.

Morphology-Control Synthesis of a Core-Shell Structured NiCu Alloy with Tunable Electromagnetic-Wave Absorption Capabilities

In this work, dendritelike and rodlike NiCu alloys were prepared by a one-pot hydrothermal process at various reaction temperatures (120, 140, and 160 °C). The structure and morphology were analyzed by scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction, and transmission electron microscopy, which that demonstrate NiCu alloys have core-shell heterostructures with Ni as the shell and Cu as the core. The formation mechanism of the core-shell structures was also discussed. The uniform and perfect dendritelike NiCu alloy obtained at 140 °C shows outstanding electromagnetic-wave absorption properties. The lowest reflection loss (RL) of -31.13 dB was observed at 14.3 GHz, and the effective absorption (below -10 dB, 90% attenuation) bandwidth can be adjusted between 4.4 and 18 GHz with a thin absorber thickness in the range of 1.2-4.0 mm. The outstanding electromagnetic-wave-absorbing properties are ascribed to space-charge polarization arising from the heterogeneous structure of the NiCu alloy, interfacial polarization between the alloy and paraffin, and continuous micronetworks and vibrating microcurrent dissipation originating from the uniform and perfect dendritelike shape of NiCu prepared at 140 °C.

Self assembled polyaniline nanofibers with enhanced electromagnetic shielding properties

Self assembly of PANI nano fibers with enhanced emi shielding.

Investigation of the electromagnetic absorption properties of Ni@TiO2 and Ni@SiO2 composite microspheres with core–shell structure

The core–shell Ni–SiO₂ composite exhibits the best electromagnetic wave absorption in the GHz range with a minimum reflection loss of −40.0 dB, which is superior to those of Ni–TiO₂ and Ni microspheres.

In situ chemical oxidative graft polymerization of aniline from phenylamine end-caped poly(ethylene glycol)-functionalized multi-walled carbon nanotubes

The aim of this study is the in situ chemical oxidative graft polymerization of aniline from phenylamine end-caped poly(ethylene glycol)-functionalized multi-walled carbon nanotubes.

Detection of aniline oligomers on polyaniline-gold interface using resonance Raman scattering

In situ deposited conducting polyaniline films prepared by the oxidation of aniline with ammonium peroxydisulfate in aqueous media of various acidities on gold and silicon supports were characterized by Raman spectroscopy. Enhanced Raman bands were found in the spectra of polyaniline films produced in the solutions of weak acids or in water on gold surface. These bands were weak for the films prepared in solutions of a strong acid on a gold support. The same bands are present in the Raman spectra of the reaction intermediates deposited during aniline oxidation in water or aqueous solutions of weak or strong acids on silicon removed from the reaction mixture at the beginning of the reaction. Such films are formed by aniline oligomers adsorbed on the surface. They were detected on the polyaniline-gold interface using resonance Raman scattering on the final films deposited on gold. The surface resonance Raman spectroscopy of the monolayer of oligomers found in the bulk polyaniline film makes this method advantageous in surface science, with many applications in electrochemistry, catalysis, and biophysical, polymer, or analytical chemistry.

Using organic solvent absorption as a self-assembly method to synthesize three-dimensional (3D) reduced graphene oxide (RGO)/poly(3,4-ethylenedioxythiophene) (PEDOT) architecture and its electromagnetic absorption properties

A novel self-assembling 3D-RGO/PEDOT architecture has been synthesized through organic solvent absorption and gentle heating. It gives a promising application in electromagnetic absorption.