X-band Region Research Articles

Immobilization of Cerium(IV) Oxide onto Reduced Graphene Oxide in Epoxy Resin Matrix as Radar Absorbing Composite for X-band Region

The rGO/CeO2/epoxy composite has been successfully prepared as radar absorbing material (RAM) for the X-band (8–12 GHz) region. The reduced graphene oxide (rGO) originated from pencil graphite oxide (GiO) was synthesized through the modified Hummer method. The synthesis of rGO/CeO2/epoxy was conducted by immobilization of cerium(IV) oxide into rGO (rGO/CeO2) via hydrothermal method and followed by composited the rGO/CeO2 with epoxy resin matrix. Morphological analysis by SEM-EDX indicates that the rGO/CeO2 structure appears to be a tangled layer of edges randomly aggregated, and CeO2 is uniformly anchored on the rGO surface. From the diffractogram result of the XRD instrument, rGO exhibits changes in crystallinity, indicating a transformation of the interlayer structure from multilayer GiO to a single layer of rGO. The presence of Ce–O was indicated at wavenumber 553 cm−1 of rGO/CeO2 by FTIR. The microwave absorbing performance of rGO/CeO2/epoxy conducted by vector network analyzer (VNA) showed that the RL value of the composite was −3.22 dB (47% of electromagnetic wave absorption) at a frequency of 9.25 GHz at the thickness of 1 mm composite. The composite has the promising prospect of being developed as a captivating candidate for the new type of microwave absorptive materials.

Role of Pb(Zr0.52Ti0.48)O3 on Electric, Dielectric, Electromagnetic Wave Absorption Characteristics of Multiferroic Nanocomposites for Magnetoelectric Devices

Multiferroic composites of ferrite and ferroelcectric phases with systematically varying concentration (100-x)Mg0.48Cu0.12Zn0.4Fe2O4 + x Pb(Zr0.52Ti0.48)O3 (MCZPZT) ( where, x mol% = 0, 20, 40, 50, 60, 80, 100) were prepared by mechanical alloying and sintering methods. The dc resistivity and dielectric constant of the samples as a function of temperature were studied in detail and obtained results are reported. The magnetoelectric effect was investigated for the composites. The sample with 80% ferroelectric phase (MP5), shows largest magnetoelectric output voltage coefficient (dE/dH) H value of 880 μVcm.Oe at 2000 Oe magnetic field. Electromagnetic interference shielding properties of transmission loss and attenuation constant were determined for the composites. Skin depth decreases with frequency from 0.29 to 0.2 cm in the range 8–12 GHz for all composites. The composite MP5 with 80% PZT shows lowest α value between 282 dB m−1 and 414 dB m−1 throughout X-band frequencies. The present results proved that the current magnetoelectric materials of all concentrations exhibit strong magnetoelectric coupling with excellent microwave absorbing performance in X-band region and are appropriate for EMI shielding and novel device applications.

Influence of SWCNT on shielding and tensile properties of polyurethane nanocomposites

ABSTRACT The effect of single-walled carbon nanotubes (SWCNTs) as fillers in polyurethane matrix composites on the efficiency of attenuating electromagnetic waves in the X-band region (8–12 GHz) was studied in the current work. To meet the present-day challenges, the composites were tested using a tensile system. The inclusion of SWCNT in the polyurethane matrix proved the enhancement of electromagnetic interference shielding performance along with the improved mechanical properties. The composites were characterised by FTIR and FESEM. The dielectric properties were investigated in X-band frequencies. The shielding performance of the samples was found to be 28 dB for 1 wt% filler at 10 GHz. The effect of CNT on the mechanical performance of polyurethane composites was studied. The maximum tensile strength achieved was 2.87 MPa for 3 wt% CNT. The results showed that the synthesised sample materials found more shielding applications with favourable tensile properties.

Robust ZTO-reinforced Ag nanowire hybrid transparent conductive thin films with absorption-enhanced electromagnetic interference shielding property

Technological advances have accelerated the pursuit of transparent conducting thin films (TCFs) with superior mechanical properties, durability, efficient optoelectrical performance and substrate compatibility as a pivotal focus in the realm of flexible transparent electronics. Against this background, this work investigates the fabrication of multilayer silver nanowire (AgNW) thin films reinforced by zinc tin oxide (ZTO) thin film encapsulation on polycarbonate substrates by a combination of sputtering and spin-coating techniques. An investigation of the influence of AgNW percolation networks on the optoelectrical properties of ZTO/AgNW/ZTO hybrid thin films was carried out. The impact of ZTO protective layers on the enhancement of electrical properties, adhesivity, flexibility and environmental stability of the multilayer TCF was elucidated. Additionally, to explore the compatibility of the fabricated TCF in integrated device and stealth applications, its electromagnetic interference shielding properties were investigated. The hybrid TCF showed 99.47% EMI shielding efficiency with an absorption-dominant EMI shielding effectiveness of 22.7 dB in the x-band region.

The Impact of Al3+ ion substitution on microwave absorption of hexaferrite compound Ba0.6Sr0.4Fe12−xAlxO19 (x = 0.25, 0.50, 0.75, and 1.00)

This paper discusses the impact of Al3+ ion substitution on Fe3+ ions in the hexaferrite compound Ba0.6Sr0.4Fe12−xAlxO19 on the reflection loss value and bandwidth in absorbing microwaves. Hexaferrite Ba0.6Sr0.4Fe12−xAlxO19 (x = 0.25, 0.50, 0.75, and 1.00) was synthesized by high-energy ball milling (HEBM) for forty hours, followed by sintering at 1000 °C in the air for five hours. Then, the crystal structure, formed phase, surface morphology, magnetization, and ability to absorb microwaves in the X-band region were successively characterized. All samples (x = 0.25, 0.50, 0.75, and 1.00) had a single phase with a hexagonal crystal structure. The particle size remained heterogeneous, ranging from 200 to 300 nm, with a platelet-like shape. The maximum amount of magnetic energy that could be absorbed by the material (Ms) increases from x = 0.25 to 0.75 and then decreases slightly for x = 1.00. The maximum value of reflection loss (RLmax) decreases as x increases. For x = 0.25, RLmax is − 16.17 dB (f = 11.06 GHz) with a bandwidth of 3.56 GHz, whereas for x = 1.0, RLmax is −13.94 dB (f = 11.14 GHz) with a bandwidth of 1.68 GHz.

Improvement in the structural, magnetic and electromagnetic behaviour of barium hexaferrites with yttrium doping for EMI shielding

Electromagnetic interference (EMI) shielding is critical for protecting electronic devices from interference generated by various sources such as power lines, radio waves, microwaves, and electronic devices. In this current study, we present a thorough investigation of the structural, magnetic, and electromagnetic properties of Y3+ doped M-type barium nano hexaferrites. Polycrystalline BaFe12−xYxO19 (x = 0.0, 0.3, 0.5, 0.7, and 0.9) hexaferrites are prepared using the citrate precursor method. The results of X-ray diffraction (XRD), Rietveld refinement and Raman spectroscopy confirmed that all samples have a single-phase, and pure hexagonal crystalline structure with space group P69/mmc. This result is consistent for all the prepared compositions. The structure and dopant materials in different chemical states of the sample are determined based on the X-ray photoelectron spectroscopy (XPS) spectrum. Field emission scanning electron microscopy (FESEM) analysis showed that the particles had a distinct hexagonal morphology. The chemical composition of the prepared hexaferrites is investigated using energy dispersive X-ray analysis (EDAX). UV spectroscopy showed an inverse relationship between the molar ratio of yttrium and the band gap. Vibrating sample magnetometer (VSM) results showed a decrease in saturation magnetization (Ms) and coercivity (Hc) with increasing fraction of yttrium ions. The shielding efficiency (SE) of the synthesized hexa materials against EMI is evaluated using a vector network analyser (VNA). In particular, effective EMI shielding was observed in the frequency spectra of 8–12 GHz (X-band region). Among the tested compositions, BaFe12–0.7Y0.7O19 with a thickness of 3 mm exhibited highest SE of 80.07 dB in the X-band region. The proposed yttrium-substituted barium M-type hexagonal ferrites exhibit significant reflection loss with enhanced absorption spectrum even when applied to an extremely thin 3 mm material, making it a possible preference as the radar-absorbed compound for EMI attenuators for weather monitoring, radar tracking, air traffic management, and gigahertz antennas. Furthermore, commercial applications including long-term magnetic media for recording, storing information, etc. are possible uses of the synthesised magnetic yttrium-doped barium M-type hexagonal ferrites.

Evaluating the microwave absorbing performance of polymer-free thin Fe3O4−MWCNT NCs in X-band region

In the past decade, hierarchical structure formation of magnetic (Fe3O4) and carbon based electrically conducting nanocomposites (NCs) has been widely used in microwave shielding applications due to the presence of lightweight, huge surface area, heterogenous interface surface etc. Current research is focused on reducing the thickness of the shielding material without compromising its performance. Herein, the fabrication of a 500 μm thick, polymer-free, stand-alone electromagnetic interference (EMI) shielding pellets of Fe3O4 - amine functionalized multiwalled carbon nanotube (MWCNT) NCs is reported with an average shielding efficiency of 60.7 dB for 8 to 12 GHz. The amine-functionalized MWCNT has superior electric conductivity due to the presence of reduced surface oxidation groups and superior charge carrying by free electrons in the amine groups. The structural and magnetic properties of all the materials were confirmed by XRD, Raman, FESEM, HRTEM, VSM and VNA techniques. The chemical interaction of Fe3O4−MWCNT was confirmed by the presence of the Fe–O–C bond from the O 1s spectrum from XPS analysis. The Fe3O4 nanoparticles (NPs) are homogeneously incorporated on the MWCNT surface, forming composite structures, which improve interface polarization, electron charge carrying, and impedance matching due to the presence of chemical interaction.

Highly stable, ultra-thin Au embedded zinc tin oxide multilayer transparent conductive thin films

Transparent conducting thin films (TCFs) with excellent stability and good mechanical properties, room temperature processing, as well as owing high transparency and conductivity, have become an essential requirement in numerous applications. Here, we report the fabrication of room temperature processed Au-embedded zinc tin oxide (ZTO) multilayer transparent conducting thin films on glass and polycarbonate substrates by radio frequency magnetron sputtering. A detailed investigation on the correlation of optical and electrical properties of the ZTO/Au/ZTO (ZGZ) multilayer thin films, with the thickness of individual layers was carried out. The ZGZ thin films showed excellent performance under various stability tests. To evaluate the commercial application capabilities in aircraft canopies and other optoelectronic devices, the fabricated ZGZ multilayer TCFs was subjected to electromagnetic interference (EMI) shielding studies. The ZGZ thin film exhibited EMI shielding effectiveness of 24.75 dB in the X-band region, yielding 99.66% power attenuation.

Electromagnetic Interference Shielding Performances of Carbon-Fiber-Reinforced PA11/PLA Composites in the X-Band Frequency Range.

To solve the problem of increasing electromagnetic pollution, it is crucial to develop electromagnetic interference (EMI) shielding materials. Using lightweight, inexpensive polymeric composites instead of currently used metal shielding materials is promising. Therefore, bio-based polyamide 11/poly(lactic acid) composites with various carbon fiber (CF) amounts were prepared using commercial extrusion and injection/compression molding methods. The prepared composites' morphological, thermal, electrical conductivity, dielectric, and EMI shielding characteristics were investigated. The strong adhesion between the matrix and CF is confirmed by scanning electron microscopy. The addition of CF led to an increase in thermal stability. As CFs formed a conductive network in the matrix, direct current (DC) and alternative current (AC) conductivities of the matrix increased. Dielectric spectroscopy measurements showed an increase in the dielectric permittivity/energy-storage capability of the composites. Thus, the EMI shielding effectiveness (EMI SE) has also increased with the inclusion of CF. The EMI SE of the matrix increased to 15, 23, and 28 dB, respectively, with the addition of 10-20-30 wt % CF at 10 GHz, and these values are comparable or higher than other CF-reinforced polymer composites. Further analysis revealed that shielding was primarily accomplished by the reflection mechanism similar to the literature data. As a result, an EMI shielding material has been developed that can be used in commercially practical applications in the X-band region.

Free-standing polymer/multiwalled carbon nanotubes composite thin films for high thermal conductivity and prominent EMI shielding

Lightweight composite materials with efficient thermal conductivity (TC) and high electromagnetic interference (EMI) shielding effectiveness (SE) are of paramount importance for a wide range of applications such as electronics, aerospace, and stealth technology. In this work, lightweight, flexible, and free-standing poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/multiwalled carbon nanotube (MWCNT) composite thin films are fabricated by a single-step, solution casting method. Fabricated PVDF-HFP/MWCNT composite thin films are characterized by many physicochemical techniques such as Raman spectra, Fourier transform infrared spectra, X-ray diffractometer, and high-resolution transmission electron microscope. The resulting composite thin film exhibits a TC of 1.1 Wm−1K−1 at room temperature. Further analysis shows that the TC of the composite film is increased up to 1.8 Wm−1K−1 at 100 °C. As fabricated flexible and free-standing composite thin film (thickness ∼ 150 µm) exhibit an excellent EMI SE of ∼ 36 dB in the X-band region (8.2–12.4 GHz) at just 15 wt. % loading of MWCNT. The outstanding EMI shielding and high TC of PVDF-HFP/MWCNT composite films are attributed to the homogenous distribution and well-connected network of MWCNT within the polymer matrix, forming a conductive network throughout the composite film.

Investigation of dielectric properties of P(VDF-Trfe)-Nafion blended solutions in the microwave frequency region

The dielectric permittivity and dielectric loss were measured using the open-ended coaxial probe technique on P(VDF-TrFE) and Nafion blended solutions between the frequencies of 0.5 GHz–50 GHz at room temperature. The permittivity was decreased as the concentration of Nafion is increased. The dielectric loss was increased with Nafion up to the X-band region and then dropped. The dielectric relaxation peak was shifted to a lower frequency with the rise in Nafion concentration. The dielectric relaxation time was analyzed from the Havriliak-Negami relation. The Cole-Cole plot showed a depressed semicircle and revealed possible molecular interactions between the dipoles.

Cognizing the electromagnetic shielding performance of ultrafine magnetite (Fe3O4) and a few layers of carbon black nanocomposite in the X-band region

In the present work, ultrafine Fe3O4, a few layers of CB and theircomposites are fabricated viathe polyolroute and physicochemical properties are carried out by precision instruments. The chemical interaction of the Fe3O4–CB (1:1) nanocomposite (NC) is confirmed by the presence of the FeOC bond from oxygen core spectra.The dielectric permittivity ofFe3O4–CB (1:2) NC varies around ε′ − j ε′′ = 60.36 − j 91.82 and permeability around μ′ − j μ′′ = 0.23 − j 0.64 as measured by a microwave vector network analyzer. It is found that the typical value of the electrical conductivity at the X band frequency range of Fe3O4–CB (1:2) (50.71 S/m) NC is found to be the maximum among the pristine and otherreported values for these composites.The Fe3O4-CB (1:2) NC with a thickness of 1mm, exhibits a maximum shielding efficiency (SE) of 66.35 dB (blocking the transmittance effectiveness of 99.99997 %) when EMW SE is measured in the range 8-12 GHz. and its a new electromagnetic interference shielding efficiency (EMI SE) achievement in the composite material.

Silver Nanowires Coated Nitrocellulose Paper for High-Efficiency Electromagnetic Interference Shielding.

A thin and conductive coating on an environmentally friendly polymer is imperative for protecting sensitive electronic devices. In this regard, a series of silver nanowires (AgNWs) coated nitrocellulose (NC) papers are fabricated by a simple and fast processed vacuum-assisted filtration method by varying filtrate volume to address electromagnetic interference. Their structural and EMI shielding performance is analyzed. The submicron thick and the lighter paper reveal the conductive AgNWs interwoven on the rough NC surface, making a 2D in-planar structure. Due to a strongly interconnected network, the coated paper displays an exceptional electrical conductivity of 8603 S/m. Despite having a minimum AgNW coating thickness of ∼0.69 μm and an area density of 0.041 mg/cm2, an ultrahigh EMI shielding effectiveness (SE) of about 69.4 dB (a specific EMI SE (SE/t) of 1005797 dB/cm) in the entire X-band (8-12 GHz) region is achieved. The effective material parameters, extracted using plane-wave theory, indicate that AgNWs form closed current loops resulting in magnetic losses. These AgNWs coated NC papers synthesized by a simple procedure are promising EMI shielding materials for current emerging electronic devices.

Synthesis and microwave absorption studies on 2D graphitic carbon nitride loaded polyaniline/polyvinyl alcohol nanocomposites

A light weight electromagnetic interference (EMI) shielding and microwave absorbing composite films has been developed by loading varying weight content of graphitic carbon nitride (g-C3N4) nanosheets and polyaniline (PANI) into polyvinyl alcohol (PVA) matrix. The prepared PVA/PANI/g-C3N4 (1%, 3%, 5%) composites has been subjected to FTIR, X-Ray powder diffraction, SEM, Thermal studies, Dielectric studies and electromagnetic shielding effectiveness (EMI SE) analysis. The PVA/PANI/g-C3N4 (1%, 3%, 5%) composites was discovered to have improved electrical conductivity, dielectric loss, and dielectric constant. It is observed from the SEM images that the sheet layers of g-C3N4 are wrapped by the polymer matrix and the morphology to PVA/PANI composite in the g-C3N4 indicates homogeneous blending of PVA/PANI without any phase separation and has porous in it. The PANI/g-C3N4 fractured surfaces present are smooth but irregular in appearance indicating good compatibility between the PVA and PANI matrices. The dielectric properties was found to increase on increasing the concentration of the g-C3N4 nanofiller and reached a maximum of 9.8 × 106 at 1 MHz for 3% g-C3N4 in PVA/PANI. The incorporation of g-C3N4 into PVA/PANI enhanced the conductivity and the 5% g-C3N4 loaded composite film exhibited a conductivity value of 0.043 S/cm at 1 MHz. The PVA/PANI/g-C3N4 (1%, 3%, 5%) composites exhibited potential EMI SE values ranging from 24 to 35 dB at 8.6 GHz and from 42 to 63 dB at 12.4 GHz, for instance the PVA/PANI/g-C3N4 5% composite showed highest value of 63 dB at 12.4 GHz. The PVA/PANI/g-C3N4 5% exhibits the maximum highest reflection loss 8 GHz–12 GHz in which the higher absorption of −36 dB is observed at 10.3 GHz of the X-band region.

Microwave Attenuation Studies of Polypyrrole-SWCNT Nanocomposite Films for Improved EMI Shielding

In the process of finding stable, lightweight, broadband, cost-effective and improved electromagnetic interference (EMI) shielding material, electromagnetic wave attenuation properties of polypyrrole (PPy)—single-walled carbon nanotube (SWCNT) nanocomposite hybrid films were investigated in X-band region (8.2–12.4 GHz) and reported in the present work. The incorporation of SWCNT as a nanofiller in polymer matrix exhibits enhanced EMI shielding performance as compared to pure polymer films. The substantial values of dielectric loss with good impedance matching contribute to improvement in EMI shielding performance. It is found that with an increase of SWCNT loading in polymer matrix from 0 wt% to 5 wt%, nanocomposite films display a gradual increase in AC conductivity and total shielding effectiveness. The maximum total shielding effectiveness of 32.10 dB and minimum reflection loss of −45.54 dB with a wide bandwidth of 3.1 GHz, were obtained for 5 wt% CNT loading. The present results revealed that the prepared nanocomposite films are appropriate materials for lightweight, broadband EMI shields for radar and stealth applications.

CoFe2O4 Nanoparticles Grown within Porous Al2O3 and Immobilized on Graphene Nanosheets: A Hierarchical Nanocomposite for Broadband Microwave Absorption.

Demands to develop efficient microwave-absorbing materials are increasing with the advancement of information technology and the exponential rise in the usage of electromagnetic devices. To reduce electromagnetic interference and to overcome the adverse effects caused by microwave exposure resulting from the excessive usage of electromagnetic devices, microwave absorbers are very necessary. In addition, radar-absorbing materials are essential for stealth technology in military applications. Herein, we report a nanocomposite in which CoFe2O4 (CF) nanoparticles were grown within the porous structure of Al2O3 (PA), and this CoFe2O4-loaded Al2O3 (PA–CF) nanocomposite was immobilized on the surface of nanometer-thin graphene sheets (Gr). Owing to the hierarchical structure created by the constituents, the (60PA-40CF)90-Gr10 nanocomposite exhibited excellent microwave-absorption properties in the X-band region with a reflection loss (RL) value of ∼−30.68 dB (∼99.9% absorption) at 10.71 and 9.04 GHz when thicknesses were 2.0 and 2.3 mm, respectively. This nanocomposite demonstrated its competence as a lightweight, high-performance microwave absorber in the X-band region, which can be utilized in the applications of pioneering stealth technology.

Ultrawide meta-film replication process for the mass production of a flexible microwave absorbing meta-surface.

The manufacturing process for an ultrawide flexible microwave absorbing meta-surface was developed and optimized experimentally. The developed replication process consists of four main steps to demonstrate double-square loop array meta-structures: (1) mechanical machining of a master mold, (2) soft mold replication and patterned film imprinting, (3) conductive ink blade filling, (4) lamination of a base flexible film to meta sheet. Based on experimental optimization of the individual steps, the manufacturing process for a large-area flexible meta-film was established successfully. The feasibility of a developed process has been demonstrated with a 200 mm × 500 mm fabricated meta-film with a focus on microwave absorbing uniformity in the X-band region.

3D printed polylactic acid/graphene nanocomposites with tailored multifunctionality towards superior thermal management and high-efficient electromagnetic interference shielding

The relative lack of printable materials with tailored functionalities limits the development of three-dimensional (3D) printing techniques. Herein, a promising multifunctional filament was fabricated by incorporating graphene nanosheets (GNs) into polylactic matrix via a solution-blending method. With this strategy, the uniform-distributed GNs were obtained in the matrix, even with a high GNs concentration (9.08 vol%). The resultant nanocomposites exhibited desired functionalities, that the thermal conductivity (Tc) was up to 3.22 W/m·k, more than ten times that of pure one (0.25 W/m·k), and the electromagnetic interference shielding (EMI SE) reached 34.9 dB at X-band region, meaning 99.97 % shielding efficiency to EWMs energy. Thereafter, by tapping into the manufacturing potential of 3D printing, a series of ideal parts featuring arbitrarily designated structures and exceptional performance was constructed. Particularly, the 3D-printed heat sinks possessed outstanding behaviors in thermal management, where the corresponding initial dissipating rate achieved a 266 % improvement over that of the pure one. Besides, the 3D-printed shielding module posed high-efficiency EMI SE performance, corresponding to 35.8 dB at a specific Bluetooth-interaction signal (2.4 GHz). Overall, this innovative study not only enriches the printable materials with tailored multifunctionality but also brings the promising potential for applications in the next-generation functional parts.

PANI-SWCNT Blends with PVA Nanocomposite Films: Structural, Morphological and Electrical Properties for Effective EMI Shielding Applications

Hybrids of Polyaniline-Single walled carbon nanotube (PANI-SWCNT) nanocomposites were synthesized by in situ polymerization and are embedded in the polyvinyl alcohol (PVA) matrix to form nanocomposite films. X-ray diffraction technique (XRD), Fourier transform infrared spectroscopy (FTIR), and Field Emission Scanning Electron Microscopy (FESEM) were used to study structural and morphological properties which confirm the phase formation, characteristic infrared spectrum and surface morphology of the prepared films. Electrical, dielectric and electromagnetic properties were analyzed and found to enhance with increase of SWCNT in the films. The 3 wt% SWCNT loading film showed the highest AC conductivity with 18.37 × 10−5 S m−1 and maximum shielding effectiveness of 22.73 dB in X-band (8.2–12.4 GHz) region, among all other samples.

Enhanced electromagnetic interference (EMI) shielding in BiFeO3–graphene oxide nanocomposites over X-band frequency region

BiFeO3–graphene oxide (BFO–GO) nanocomposites were synthesized through ultra-sonication under mild heating, and their electromagnetic interference (EMI) shielding performance was investigated. The nanocomposites preserve the crystalline phase with R3c symmetry as analyzed by Rietveld refinement of x-ray diffraction data. The Raman spectroscopy and x-ray photoelectron spectroscopy studies confirm the formation of structured GO in nanocomposites samples. Magnetic hysteresis curves indicate unsaturated magnetic behavior. The interfacial polarization is dominating in BFO–GO composites as estimated from frequency dependent complex parameters determined in line with the Nicolson–Ross–Weir algorithm. The BFO–GO nanocomposites showed EMI shielding effectiveness of 18 dB (93% attenuation) over the measured frequency range. The oxide composite is a suitable EMI shielding material for techno-commercial applications.