Microwave Absorption Applications Research Articles

MnFe2O4/Fe3O4/PANI/rGO heterogeneous nanocomposites: Outstanding dual-broadband nano-coating microwave absorbers

In this study, MnFe2O4/Fe3O4/PANI nanocomposites were synthesized via hydrothermal and coprecipitation methods and decorated on reduced graphene oxide (rGO) sheets with three weight ratios (1:1), (2:1), and (3:1) for MnFe2O4/Fe3O4/PANI versus rGO. FESEM images indicate a random distribution of MnFe2O4/Fe3O4 and PANI components on the rGO sheets. The designed superparamagnetic nanocomposites, MnFe2O4/Fe3O4/PANI/rGO, exhibit multi-reflections, strong interfacial polarizations, scattering of incident microwaves, and multiple magnetic resonances, which results in superior absorption performance. This is due to the structural design and distribution of different components providing various interfaces, high specific surface area, and different magnetic and dielectric components. The microwave absorption properties are evaluated in the frequency range of 1–18 GHz (L, S, C, X, and Ku bands), from electromagnetic parameters according to transmission line theory. Our results show that (MnFe2O4/Fe3O4/PANI)/rGO (1:1) presents the highest reflection loss, −108.71 dB, at 17.8 GHz with a thickness of 4.2 mm and bandwidth of 3.2 GHz. Interestingly, (MnFe2O4/Fe3O4/PANI)/rGO (3:1) shows a broad absorption bandwidth of 5.6 GHz for a thickness of only 2.2 mm, having a remarkable reflection loss of −95.52 dB at 17.8 GHz. Our study introduces a novel approach for the successful design and preparation of multi-dimensional graphene-based quaternary nanocomposites compromised from lightweight microwave absorbers, with numerous heterogeneous interfaces and defects resulting from interfacial engineering that have promising potential applications in broadband microwave absorption.

Synergistic effects of Li-based ferrite and graphene oxide in microwave absorption applications

The successful fabrication of composites consisting of ferrites with a composition of Li0.4Mg0.25Zn0.25Fe2.2O4 and Graphene oxide was carried out using the ultra-sonication technique. The current study examined the impact of graphene oxide in spinel ferrite employing X-ray diffraction, dielectric, and magnetic susceptibility studies. The X-ray diffraction investigation confirmed the spinel phase formation in ferrite and graphene oxide synthesis. The measured range for the size of crystallites was found to be between 48.43 and 30.07 nm. The DC resistivity of cubic ferrite at room temperature was determined to be 1.715 ×1010 ohm-cm by a two-probe approach. Furthermore, it was observed that the resistivity fell significantly as the content of graphene oxide increased. The dielectric constant exhibited behavior consistency with the Maxwell-Wagner phenomenon of interfacial polarization. The rise in graphene oxide content in ferrite results in high AC conductivity of composites due to the relatively large value of conductivity of graphene oxide and the improved charge hopping mechanism. The magnetic susceptibility of all the samples demonstrated a progressive decline as the temperature increased, which can be attributed to the disruption of spin alignment at the Curie temperature. The observed Curie temperature of all samples was 413–473 K. Integrating spinel ferrite with Graphene oxide has significantly improved the magneto-electrical characteristics, indicating potential applications in supercapacitors, high-frequency electromagnetic devices, and microwave absorption.

Study of structural, spectral and dielectric properties of Dy substituted Sr2Co2Fe12-xDyxO22 Y-type hexaferrites via sol-gel auto-combustion method for microwave absorption application

In this research work, the dysprosium (Dy) substituted cobalt (Co) Y-type hexagonal ferrites having composition Sr2Co2Fe12-xDyxO22 (x = 0.00, 0.03, 0.06, 0.09, 0.12) were synthesized at temperature 1150 °C using sol-gel Auto combustion method. The research aims to enhance the dielectric, physical, and spectral characteristics of cobalt Y-type hexaferrite. This is achieved by changing the Fe-concentration through dysprosium substitution. XRD spectroscopy results confirmed the manufactured samples' developed pure-phase Y-type hexagonal structure and the successful substitution of Dy. The doping of dysprosium ions led to an overall rise in lattice parameters. FTIR was used to investigate the existence of bonds in the prepared sample. FTIR spectra presented two intrinsic vibrational bands (υ2) and (υ1) in a range of 400−600 cm−1 due to the octahedral and tetrahedral stretching vibrations. It also confirmed the incorporation of dopants, which was also studied in the XRD results. The broadening of Raman peaks of prepared samples displays that the Dy3+ ions are successfully incorporated in Sr2Co2Fe12O22 without disturbing the structure. X-ray photoelectron spectroscopy shows that all metal ions are in the necessary valence states. Magnetic properties such as saturation, remanence, and coercivity of the Dy-doped Sr Y type hexagonal ferrites are also evaluated. Dielectric characterization has revealed better dielectric properties. The dielectric characteristics were analyzed from 0.001 MHz to 6 GHz frequency range. The effect of the grain boundaries and grains on the dielectric behavior was studied from the complex impedance analysis. At x = 0.12, Dy substituted Co Y type hexaferrite sample show minimum reflection losses of −45.27 dB at 2.19 GHz. Therefore, the prepared samples are suitable candidates for microwave absorption applications.

Constructing and optimizing epoxy resin-based carbon Nanotube/Barium ferrite microwave absorbing coating system

High-performance microwave absorbing coatings are highly indispensable for protecting human health and enhancing military strength. A single- and double-layer wave-absorbing coating system that employs complex microwave absorbers composed of the helical carbon nanotubes/doped barium ferrite composite with epoxy resin as the matrix was developed. The concentration and thickness of the coating were optimized by the numerical simulation and the adaptive genetic algorithm. The developed helical carbon nanotubes/doped barium ferrite wave-absorbing composites have a porous reticular structure, with abundant microscopic cavities and an adequately conductive network. The coatings are characterized by a flat surface, good uniformity, and high density. The reflectivity measured by the arch method is similar to that obtained through the finite element simulation, where the absorption bands of all the developed coatings are distributed in the range of 10–18 GHz. The optimized wave-absorbing coating exhibits the most uniform scattering pattern, the largest radar cross section (RCS) reduction, the smallest input reflection coefficient, and the highest absorptivity. Thus, it exhibits the best comprehensive microwave-absorption performance with a minimum reflection loss of −17.22 dB at 16.66 GHz. In particular, the absorption bandwidth of the coating can reach 9.16 GHz, which is attributable to its multiple synergistic electromagnetic attenuation mechanisms and its excellent characteristics of interference-cancellation and impedance-matching characteristics. Generally, helical carbon nanotubes/doped barium ferrite wave-absorbing coatings are promising candidates for applications in Ku-band microwave absorption.

Microwave reflective properties of core-shell FeNX@C/Fe4N composite

Abstract To improve the electromagnetic properties of iron nitride, the core-shell FeNX@C/Fe4N composite material was designed by microwave plasma technique. Within the frequency range of 2-18 GHz, the microwave reflective characteristics of the novel composites mixed with 50% wax were examined. The composition of the core-shell FeNX@C was analyzed by XRD, Raman, and TEM, and the complex permeability and complex permittivity with frequency change were discussed. The results show that the RLmin value (RLmin=-55.1 dB) of FeNx@C/Fe4N composite appears at 17.8 GHz with a thickness of 1.5 mm, and the RLmin value reaches -42.1 dB at the thickness of 3.5 mm corresponding to 6.6 GHz. This work demonstrates the potential prospects for the application of microwave absorbers in the range of 2-18 GHz.

Revealing electrostatic-manipulated self-assembly mechanism helps to readily design enhanced MOF-derived microwave absorbers

The controllable self-assembly of Metal Organic Frameworks (MOFs) crystals plays a vital role in modulating the performance for microwave absorbers. However, most current strategies require colloidal or intricate chemical modifications of nanoparticles, thereby increasing the complexity of structural construction and impeding the broader application of microwave absorbers. To resolve this tough issue, we herein innovatively propose a more easily achievable electrostatic-manipulated self-assembly strategy. By readily manipulating the electrostatic adsorption and repulsion between particles, the aggregation and growth sites of initial MOF crystals are anchored, hence facilitating to the construction of solid-core/shell and hollow porous microstructures for absorbers. The substantial improvement depending on electrostatic effects is clearly observed in experimental results. It demonstrates that the Co@hollow N-doped carbon spheres (Co@HNCSs) absorber, induced by electrostatic repulsion, shows the best overall absorption performance, with a strong absorption of −65.4 dB at a thickness of 1.9 mm and an effective absorption bandwidth (EAB) of 5.4 GHz at a thickness of 1.6 mm, covering almost the entire Ku band. The influence of these strategies on the electromagnetic response mechanisms is further comprehensively discussed. Accordingly, we believe this strategy offers new insights for the MOFs’ structural absorbers via electrostatic-manipulated self-assembly strategy.

Laser‐induced self‐propagating synthesis and electromagnetic wave absorption properties of MoAlB powders

AbstractMoAlB powders with a purity of 96 wt.% were successfully fabricated by a laser‐induced self‐propagating method using molybdenum boride (MoB) and aluminum powders as starting materials under the conditions of an n(MoB): n(Al) ratio of 1.0:1.4 and the laser linear energy density (El) of 0.9 J/mm, and the effect of raw material composition and El on the phase composition and microstructure of the resultant MoAlB powders were investigated. The minimum reflection loss (RLmin) value and effective absorption bandwidth (EAB) of the as‐prepared MoAlB absorber with a thickness of 5.0 mm were only determined as −12.5 dB (at 16.9 GHz) and 0.9 GHz (16.4–17.3 GHz) in the frequency of 1–18 GHz, respectively. Nevertheless, the RLmin and EAB of as‐prepared MoAlB powders oxidized after 3 h at 773 K increased to −18.59 dB (at 15.82 GHz) and 2.13 GHz (15.22–17.35 GHz), respectively, demonstrating that the as‐prepared MoAlB powders are potential candidates for high‐temperature microwave absorption applications. This study proposes a new efficient strategy for the preparation of boron‐based ternary compounds for high‐temperature electromagnetic wave absorption application.

Unveiling ball size heterogeneity effect on microwave absorption properties of cobalt

Recent advances in material science have led to impressive microwave absorbing materials, yet their practical applications are hindered by complex synthesis processes. This study explores a cost-effective alternative, emphasizing modifying material morphology using ball size heterogeneity. Unlike using same-sized balls, employing different-sized balls maximizes collision energy, yielding finer particles. In this study, the effect of ball size heterogeneity on microwave absorption performance has been investigated for the first time. An attempt has been made to explore how using ball size heterogeneity changes structural, magnetic, and dielectric properties of cobalt (Co) and how these modifications affect material's absorption properties. Results show that by using ball size heterogeneity, the particle size distribution in 0.1–1 μm range has been increased, yielding much finer particles. The relative permittivity value also increases due to changes in average particle size and surface area. Microwave absorption characteristics of Co milled with different-sized balls showed a significant change. A 15 h milled Co sample using different-sized balls achieved an effective bandwidth of 9.65 GHz (4.75–14.4), contrasting with no absorption bandwidth when using same-sized balls, with a 2 mm coating thickness. This work provides new insights into preparing materials for microwave absorption applications using ball milling method.

Rietveld refined structural, elastic, XPS, and dielectric evaluations of Zn-doped Cd–Mg spinel ferrites for high-frequency applications

Sol-gel auto ignition route was utilized to synthesize a series of Zn-doped Cd–Mg spinel ferrites with composition Cd0.5-xMg0.5ZnxFe2O4 (x = 0.0, 0.1, 0.2, and 0.3). All of the prepared nanomaterials that were annealed for 4 h at 900 °C had a cubic structure and were spinel, according to X-ray diffraction studies. The lattice constant decreased as the Zn concentration increased. This is because of the substituent's lower radii. The W–H plot, Size strain plot, and Sherrer Formula were used to calculate the crystallite size, which was in the range of a nanometer. Vibrational spectroscopy studies have also shown that M − O bonds are present in every processed sample and that a spinel cubic structure has formed. Additionally, the cationic distribution and cubic spinel structure were validated by Rietveld refinement of the XRD data. The analysis using X-ray photoelectron spectroscopy (XPS) has confirmed the presence of all metal ions in their respective electronic states. The dielectric characteristics in the 1 MHz-6 GHz range of frequencies were ascertained using an impedance analyzer. Jonscher's power law validated the conduction mechanism in the synthesized ferrite samples. The relaxation time constant calculated from impedance Cole-Cole plots shows that the conduction in all the synthesized nanomaterials was due to the grains rather than the grain boundaries. The minimum reflection loss of −36.54 dB was achieved for Zn-doped Cd–Mg ferrites at x = 0.3. The prepared Zn-doped Cd–Mg spinel ferrites would be an excellent material for high-frequency microwave absorption applications.

Optimization of Electrospinning Parameters for Lower Molecular Weight Polymers: A Case Study on Polyvinylpyrrolidone.

Polyvinylpyrrolidone (PVP) is a synthetic polymer that holds significance in various fields such as biomedical, medical, and electronics, due to its biocompatibility and exceptional dielectric properties. Electrospinning is the most commonly used tool to fabricate fibers because of its convenience and the wide choice of parameter optimization. Various parameters, including solution molarity, flow rate, voltage, needle gauge, and needle-to-collector distance, can be optimized to obtain the desired morphology of the fibers. Although PVP is commercially available in various molecular weights, PVP with a molecular weight of 130,000 g/mol is generally considered to be the easiest PVP to fabricate fibers with minimal challenges. However, the fiber diameter in this case is usually in the micron regime, which limits the utilization of PVP fibers in fields that require fiber diameters in the nano regime. Generally, PVP with a lower molecular weight, such as 10,000 g/mol and 55,000 g/mol, is known to present challenges in fiber preparation. In the current study, parameter optimization for PVP possessing molecular weights of 10,000 g/mol and 55,000 g/mol was carried out to obtain nanofibers. The electrospinning technique was utilized for fiber fabrication by optimizing the above-mentioned parameters. SEM analysis was performed to analyze the fiber morphology, and quantitative analysis was performed to correlate the effect of parameters on the fiber morphology. This research study will lead to various applications, such as drug encapsulation for sustained drug release and nanoparticles/nanotubes encapsulation for microwave absorption applications.

Superparamagnetic nanocubes of Co and Cu co-doped Mn-based ferrites as microwave absorbing material

The requirement in resolving electromagnetic (EM) problems in stealth warhead technologies are excellent absorption ability, lightweight, and thin dimensions. In this direction, this study provides a straightforward hydrothermal one-pot method to synthesize superparamagnetic Mn-based ferrite co-doped with Co and Cu (MCCF), and the article presents its microwave absorption properties. Using cutting-edge techniques, the MCCF nanocomposite phase structure, morphological, superparamagnetic, and microwave absorption properties were measured and analyzed. MCCF-822 ferrite shows superparamagnetic properties simultaneously with a high Ms value 71.4 emu/g. Vector network analysis of MCCF-822 with 70 wt% loading demonstrates an effective absorption bandwidth (EAB) of 5.2 GHz with a maximum reflection loss (RLmax) of −19.2 dB at 2 mm thickness, and it spans almost 92.77 % frequency region (3.3–18 GHz range with RL < −10 dB) by varying thickness 1.7 mm–6 mm. At 60 wt% loading, it covers the whole X & Ku band with a thickness range from 2 to 9 mm with a good EAB of 4.3 GHz at 2.5 mm thickness with RLmax of −16 dB. The dual absorption bands are also present in MCCF-613, which increases the EAB with RLmax −52.99 dB at 9 mm, fulfilling the superparamagnetic properties. Thus, MCCF-822 is proposed as a cost-effective superior ferrite nanocomposite for microwave absorption applications.

Core-shell PCIP/NiFe2O4/PANI composite: Preparation, characterization, and applications in microwave absorption

Narrow absorption bandwidth is a common problem faced by current electromagnetic wave absorbing materials. Herein, a porous carbonyl iron/NiFe2O4/polyaniline-based wave absorbing composite material with wideband microwave absorption performance was designed by metal pitting technique, co-precipitation and in-situ polymerization. The results of SEM, XPD and XPS show that PCIP/NiFe2O4/PANI nanostructures were successfully synthesized. It is found that NiFe2O4/PANI agglomeration on the PCIP surface significantly enhances the electric loss capability of the composites. When the amount of PANI is 0.7 mL, the composite exhibits broad and strong absorbing properties, and a minimum reflection loss of −45.45 dB is obtained at 2.0 mm. The effective absorption bandwidth reaches 7.5 GHz when the matching thickness is only 2.0 mm. The synergistic effect of multiple absorbing mechanisms such as dipole polarization, interface polarization, conduction loss, natural resonance, exchange resonance and eddy current loss enables it to exhibit good wave absorption performance.

CoNi/MXene@CoNi/MXene microsphere/silicone rubber multilayered composites for ultra-broadband microwave absorption

2D transition metal carbide/nitride (MXene) nanomaterials have prospective applications in high-performance microwave absorption (MA). However, the excessively high permittivity, absence of magnetic loss, and susceptible oxidizability of MXene severely hinder the enhancement of its MA properties. Here, we used a facile organic solution–phase thermal decomposition method to prepare dielectric–magnetic MXene@CoNi nanocomposites with heterojunctions, which can effectively prevent the oxidation of MXene. Subsequently, the MXene@CoNi nanocomposites were integrated with magnetic CoNi alloys, MXene microspheres (MXene MPs), and a silicon rubber (SR) matrix to construct multilayered CoNi/MXene@CoNi/MXene MPs/SR composites by casting and curing. Benefiting from the multilayered structure and complementary effects of the dielectric and magnetic components, the multilayered CoNi/MXene@CoNi/MXene MPs/SR composites composed of matching, absorbing, and reflective layers showed a remarkable minimum reflection loss of −53.3 dB and an ultra-broad effective absorption bandwidth up to 11.12 GHz at a thickness of 2.96 mm. These results demonstrated the developed multilayered composites are promising candidates for high-performance MA. Our study provides new insights into the development of ultra-broadband MXene-based absorbent materials.

Estimation of reflection loss of lossy dielectric powders using coaxial line based guided wave technique for conventional cement based microwave absorber applications

Coaxial transmission line technique to determine Plane Wave Reflection Loss of dielectric powders is proposed. The technique provides rapid determination of suitability of powders as conductive filler for Microwave Absorbers, specifically cement based Absorber. Ash by-product from steel industry including Argon Oxygen Decarburization (AOD), Acid Recovery Station (ARS) and Electric Arc Furnace (EAF) are considered over frequency range 1–12 GHz. Scattering parameters (S-matrix) of ash filled coaxial lines are measured. Short-Open technique is adopted. Formulation to compute reflection loss from measured S11 is presented. Teflon, with known reflection loss, is considered for validation. A 10 % error in computed results is observed in range 1–4 GHz, and 10–15 % in range 4–12 GHz. Broadband MAM characterization employing Free Space Methods involve enormous material requirement, frequency dependent prototype dimensions and anechoic chambers. The error percentage notwithstanding, the technique provides rapid estimates, enabling smart selection of conductive fillers, providing cost and time reduction.

Synthesis, electricaland structural characterization of a composite material based on powdered magnetite and high density polyethylene

Garzón Posada A.O., F.E. Fajardo Tolosa, D.A. Landínez Téllez, J. Roa-Rojas, G. Peña Rodríguez. Synthesis, electrical and structural characterization of a composite material based on powdered magnetite and high density polyethylene. Rev. Acad. Colomb. Cienc., 37 (1): 55-59, 2013. ISSN 0370-3908. This work describes the synthesis and characterization of a composite material based on magnetite filled HDPE, which is comrnonly known for its magnetic properties. Composites of this kind are used in different applica­tions such as magnetic and microwave absorption, transducers manufacturing, and biomedical applications like targeted drug delivery, organs tagging, etc. The samples were produced according to different volume ratios of magnetite and HDPE. The samples structure was analyzed through X-ray diffraction tests and the crystallinity degree was calculated. Then, the samples were electrically characterized through volume resistivity measure­ments. The results showed that for ratios less than the 20% of magnetite there is not a substantial reduction in the resistivity ofthe composite compared to the unfilled HDPE. For magnetite ratios above the 30% the com­posite shows a substantial reduction of six orders of magnitude in its electrical resistivity.

EVA copolymer loaded with PAni/CNT/GNP hybrids: A flexible and lightweight material with high microwave absorption

AbstractMicrowave‐absorbing materials are widely used for electromagnetic interference shielding and stealth technology. However, most existing materials are heavy, rigid, and expensive, limiting their practical applications. Therefore, there is a need to develop new materials that are flexible, lightweight, and cost effective. This study aimed to synthesize and characterize a novel ternary composite material based on polyaniline (PAni), carbon nanotubes (CNTs), and graphene nanoplatelets (GNPs) in an ethylene‐vinyl acetate (EVA) copolymer matrix. PAni‐based ternary composites were prepared by in situ polymerization of aniline in toluene dispersion of CNT/GNP hybrids and EVA. The microwave absorption properties were evaluated using a vector network analyzer in the frequency range of 8.2–18 GHz. The presence of as little as 0.8 wt% of CNT/GNP hybrid with appropriate mass ratio increased the conductivity by more than four orders of magnitude compared to the EVA@PAni blend. The minimum reflection loss corresponded to −40.55 dB at 16.31 GHz for the system containing CNT/GNP = 0.3:0.7, whereas those with CNT/GNP = 0.0:1.0 and 0.7:0.3 presented the widest effective absorption bandwidths (RL &lt; −10 dB), covering almost the entire Ku‐band. Due to the excellent flexibility, low weight, and high microwave absorption performance, these composites are potential candidates for microwave absorption applications.

Core-shell designed high entropy alloy CoNiFeCuV-C nanoparticles for enhanced microwave absorption

The widespread interest in high entropy alloy nanostructures stems from their potential utilization in a variety of technological and scientific fields. This study presents an innovative approach employing a one-step metal organic chemical vapor deposition to synthesize quinary high entropy alloy (CoNiFeCuV-C) core-shell nanoparticles designed for microwave absorption applications. Superior microwave absorption performance is attained through the optimization of conduction loss via thermal treatment, coupled with the interfacial polarization across the interfaces between CoNiFeCuV cores and C shell. The paraffin composite filled with an optimal 20% content of CoNiFeCuV-C core-shell nanoparticles demonstrates a minimal reflection loss (RLmin) of −51.8 dB at 13.76 GHz, achieving this performance with a thickness of 2.2 mm. Moreover, the absorbing bandwidth spans 7.44 GHz at a thickness of 2.4 mm. The outstanding accomplishments underscore the potential of utilizing CoNiFeCuV-C core-shell nanoparticles as a promising choice for lightweight, effective microwave absorber material.

3D printed honeycomb bilayer structures based on polylactic acid as lightweight microwave absorbing materials

Abstract3D printed honeycomb structures constituted by neat polylactic acid (PLA) and conductive PLA (PLAc) with different cell sizes and thicknesses were manufactured through 3D printing technology based on material extrusion (MEX). These structures were arranged into bi‐layer honeycomb structures (BHS) for evaluation of the microwave absorbing properties at the X‐band (8.2–12.4 GHz) and Ku‐band (12.4–18 GHz) frequency ranges. The effects of cell size, sample thickness, layer thickness ratio and the nature of the top layer on the electromagnetic attenuation performance of BHS samples were investigated in terms of reflection loss (RL). The components geometric characteristics and the arrangement of the layers exerted great influence on the RL values and effective absorption bandwidth (EAB). Overall the bilayer structures with 5 mm total thickness presented the best EM response in terms of EAB and minimum RL, where the component with the larger cell size (7.7 mm), PLAc (1 mm) as the top layer and PLA (4 mm) as the bottom layer exhibited the best results with RL values of −41 dB and EAB of 9.5 GHz. The BHS system with 7.7 mm cell size was more efficient in Ku band frequency range, whereas that with 3.5 mm cell size gave better response in the X‐band frequency range. Therefore, RL values and EAB can be adjustable by modifying the building strategy of the printed parts, such as thickness of the sample, cell size and thickness distribution of the conductive and non‐conductive layers. The findings in this work show the importance of the building strategy to fabricate components with controllable BHS and improved properties for microwave absorption application.

Hybrid Foams based on Multi‐Walled Carbon Nanotubes and Cellulose Nanocrystals for Anisotropic Electromagnetic Shielding and Heat Transport

AbstractLightweight and mechanically robust hybrid foams based on cellulose nanocrystals (CNC) and multi‐walled carbon nanotubes (MWCNT) with an anisotropic structure are prepared by directional ice‐templating. The anisotropic hybrid CNC‐MWCNT foams displayed a combination of highly anisotropic thermal conductivity and an orientation‐dependent electromagnetic interference (EMI) shielding with a maximum EMI shielding efficiency (EMI‐SE) of 41–48 dB between 8 and 12 GHz for the hybrid foam with 22 wt% MWCNT. The EMI‐SE is dominated by absorption (SEA) which is important for microwave absorber applications. Modelling of the low radial thermal conductivity highlighted the importance of phonon scattering at the heterogeneous CNC‐MWCNT interfaces while the axial thermal conductivity is dominated by the solid conduction along the aligned rod‐like particles. The lightweight CNC‐MWCNT foams combination of an anisotropic thermal conductivity and EMI shielding efficiency is unusual and can be useful for directional heat transport and EMI shielding.

Strong microwave absorption performance of simply grinding FAPbI3/CNTs composite absorbers

The distinctive physical and chemical characteristics of organic-inorganic lead halide perovskite make it a promising candidate for microwave absorption applications. However, the high-efficiency microwave absorption of halide perovskite-based composites is concentrated at high frequencies, while electronic equipment operates at low-frequency bands. Exploring simple and efficient methods to achieve optimal microwave absorption efficiency at low frequencies continues to pose a considerable challenge. Here, FAPbI3 was synthesized by a simple solvent-free hand grinding method and mixed with carbon nanotubes (CNTs) to obtain a series of FAPbI3/CNTs (FC) composites. By modulating the mass ratio of the components, FAPbI3 modulates the absorption bands, CNTs can effectively establish a conductive network to enhance both polarization loss and conductive loss and regulate impedance matching. The lower permittivity of FAPbI3 gives FC an advantage in terms of low-frequency microwave absorption. The FC-4 composite exhibits a minimum reflection loss (RLmin) of −55.67 dB at a low frequency of 6.88 GHz with a thickness of 3.5 mm. Meanwhile, microwave absorption performance can reach 99 % covering almost the entire C band when utilizing a thickness ranging from 3 to 5 mm. Additionally, according to adjusting the load of FAPbI3 in the mixture, the FC-3 composite displays the highest microwave absorption value among the composites based on halide perovskites. With a thickness of 1.4 mm, the reflection loss at 17.4 GHz reaches an impressive minimum value of −71.89 dB. This study represents the first research specifically focused on FAPbI3 perovskite in the domain of microwave absorption. FC composites display remarkable capabilities in absorbing microwaves, indicating their promising prospects for advancement within the realm of microwave absorption. This research may provide valuable insights for the design of low-frequency and high-efficiency microwave absorbers.