Enhanced electromagnetic wave dissipation features of magnetic Ni microspheres by developing core-double shells structure

Readily oxidization of magnetic particles is a common drawback of these type of materials which reduce their electromagnetic wave dissipation performance. In this study, the magnetic core-double shells structured (Ni/SiO₂/Polyaniline) composite has been developed for protection of the core from oxidation and in consequent improvement the complex permittivity. Solvothermal and in-situ polymerization methods were utilized for decorating Ni micro-particles with SiO₂ and conductive polyaniline polymer respectively. All physico-chemical, magnetic and electromagnetic features were evaluated via XRD, FTIR, XPS, FESEM, VSM and VNA analysis. The double shells composite possesses significant performance in terms of reflection loss and effective absorption bandwidth. The results reveal that the maximum dissipation capacity of the double shells composite is – 32.5 dB at 16.5 GHz with 4.5 GHz effective absorption bandwidth and 1.5 mm thickness. Enhancement in microwave dissipation features are arises from synergistic influence of various phenomena such as interfacial polarization, multiple Debye relaxation, natural ferromagnetic resonance and proper impedance matching characteristic. Overall, developing double shells structure on magnetic Ni microsphere particles had a meaningful effect on tuning the microwave absorption performance.     

Fabrication of hierarchical PANI@W-type barium hexaferrite composites for highly efficient microwave absorption

Hexagonal barium ferries is a promising and efficient microwave (MW) absorbing material, but the low dielectric loss and poor conductivity have limited their extensive applications. In this work, a simple tactic of coating conductive polymer PANI on hexaferrite BaCo₂Fe₁₆O₂₇ is presented, wherein the dielectric properties are customized, and more significantly, the electromagnetic loss is greatly enhanced. As displayed from structural characterizations, PANI were coated equably on the surface of hexaferrite grains by an in-situ polymerization process. The outcomes exhibit the as-prepared PANI@hexaferrite composite has remarkable electromagnetic wave absorption capacity. When the thickness is 6.0 mm, the minimal RL of ?40.4 dB was achieved at 2.9 GHz. The effective absorption bandwidth (RL < ?20 dB) of 0.65 GHz, 0.53 GHz, 0.65 GHz, 0.52 GHz, 0.46 GHz and 0.39 GHz was achieved separately when the thickness ranges from 4 to 9 mm. The highly efficient MW absorbing performance of PANI@hexaferrite composite were the consequence of multiple loss mechanisms and perfect impedance matching. It is demonstrated that the PANI@hexaferrite composite with excellent MW absorption performance is expected to be potential MW absorbers for extensive applications.     

Rational construction of wideband electromagnetic wave absorber using hybrid FeWO4-based nanocomposite structures and tested by the free-space method

In this research, we developed a wideband electromagnetic wave absorber suitable for the X-band frequency by using a unique hybrid nanocomposite structure made of FeWO₄ embellished with Ag₃PO₄ nanopowders. Simple chemical hydrothermal and microwave-aided hydrothermal procedures were used to successfully produce single-phase spherical-like FeWO4 and FeWO4@Ag3PO4 nanocomposite powders. Using XRD, FTIR, VSM, FESEM, and VNA methods, the phase constituents, morphological, magnetic, and electromagnetic properties of the produced nanocomposite materials were assessed. The resin-based nanocomposite absorber sample allows to obtain a maximum reflection loss of ?21 dB with a matching thickness of 1.8 mm at the ferromagnetic resonance of 10.4 GHz with a 3.8 GHz effective absorption bandwidth, which is evaluated using the waveguide technique, when the filler loading percentage reaches 40 wt percent (S40). S40 had superior impedance matching capabilities, a wide effective absorption bandwidth, and a high absorption capacity when compared to other produced absorber samples. The best sample is prepared for free-space testing with the dimension of 200 × 200 mm and an optimum thickness of 1.8 mm, and the results demonstrate a good agreement between the waveguide and free-space technique results. This absorber sample's wideband absorption capacity was attained by adjusting the magneto-electric composition and enhancing the interfacial characteristics brought on by the core-shell construction. In this study, a design approach for efficient microwave absorbers based on a magneto-electric hybrid nanocomposite structure is presented, using waveguide and free-space experimental methods in two different ways.     

Effect of filler loading and thickness parameters on the microwave absorption characteristic of double-layered absorber based on MWCNT/BaTiO3/pitted carbonyl iron composite

In this work, single- and double-layer electromagnetic wave absorbers were prepared by as-prepared MWCNTs/BaTiO₃/pitted carbonyl iron composites. MWCNT/BaTiO₃ (MW/BTO) was prepared via sol-gel method whereas the carbonyl iron particles (CI) were corroded via pitting corrosion method. The structural, microstructural, magnetic and microwave absorption properties of the composites were evaluated via X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM) and vector network analyzer (VNA) methods. CST studio software was employed to simulate the microwave absorption characteristics of double-layer absorbers. Moreover, the effects of changing matching and absorbing layer thickness (3 mm in total) and filler loading (10, 20 and 30 wt%) of the as-prepared composite on the microwave absorption properties were investigated. According to the results, maximum RL value for single layer absorber with 20 wt% filler loading can reach ?11.5 dB at 9.7 GHz with 3 mm thickness and 0.4 GHz bandwidth. In contrast, double-layered absorber using 10 wt% of the composite in the upper layer (as matching layer) and 30 wt% of the composite in lower layer (as absorbing layer) can increase the reflection loss and absorption bandwidth values to ?15.5 dB and 1 GHz respectively. Improving in absorption characteristics can be attributed to coupling interactions, impedance matching and multiple scattering. The main advantages of the prepared double layer absorber than single layer absorber are tuning the intensity and effective absorption bandwidth by adjusting the layer order, thickness and filler loading of each layer which shown good potential for practical application.     

Synergistic effect of polyindole decoration on bismuth neodymium ferrite powder for achieving wideband microwave absorber

Recently, composite materials with outstanding absorption properties, like extraordinary absorbing capability, light weight, and thin in size, are required to solve the challenges of electromagnetic pollution. In addition, most of the work is based on the optimization of absorber material structure, and microstructure. In the current work, we improved the reflection loss feature of Bi_0.5Nd_0.5FeO₃ nanopowders via decoration with polyindole polymer by tuning the filler loading of the nanocomposite in the matrix. XRD, UV–Vis, XPS, and FESEM were used to determine the physicochemical features of the as-prepared nanocomposite. The minimum RL was lowered further with the increasing filler loading at 25 wt%. The lower RL of ?22 dB was noticed for 2.2 mm thickness at 11.5 GHz. The maximum value of the SE_R for a 25 wt% sample was 5.5, whereas 19 dB and 24.5 dB values were recorded for SE_A and SET, respectively. The resonance peak above 11.5 GHz demonstrated the better outcome of the absorber at high frequency. Good impedance matching characteristics, conductive features, dielectrics, and magnetic losses were all credited with the excellent reflection loss and electromagnetic interference shielding efficiency. The as-prepared nanocomposite materials that have been proven are interesting prospects for electromagnetic reflection loss and interference shielding that is lightweight, flexible, and extremely effective.     

Optimized impedance matching and enhanced attenuation by heteroatoms doping of yolk-shell CoFe2O4@HCN as highly efficient microwave absorbers

Microwave absorbing (MA) materials with yolk-shell structures have been extensively studied in impedance matching. However, the impedance matching achieved by the complementary effect of the core and the shell does not determine the reflection of the microwaves upon the occurrence at the first incidence. The interaction between the outer layer of materials and the electromagnetic waves significantly impacts the MA properties of materials. In this study, the impedance matching improvement method of the shell structure was further explored by preparing CoFe₂O₄@HCN (honeycomb carbon with N-doping) through the hydrothermal method followed by hydrolysis, polymerization, etching, and annealing. The resulting structure with heteroatoms doping provided the novel CoFe₂O₄@HCN with excellent impedance matching and multiple loss mechanisms contributing to MA process. The absorber with a filler loading of 40% exhibited an RL_min of −68.03 dB with a matching thickness of 2.5 mm. The efficient absorbing bandwidth reached 5.92 GHz (a change from 11.92 to 17.84 GHz) at 1.99 mm thickness. Interestingly, these findings look promising for future synthesis and application of yolk-shell structure microwave absorbers.     

Enhancement of the microwave absorption properties of PyC-SiCf/SiC composites by electrophoretic deposition of SiC nanowires on SiC fibers

The employment of coating technique on the silicon carbide fibers plays a pivotal role in preparing SiC fiber-reinforced SiC composites (SiC_f/SiC) toward electromagnetic wave absorption applications. In this work, SiC nanowires (SiCNWs) are successfully deposited onto the pyrolytic carbon (PyC) coated SiC fibers by an electrophoretic deposition method, and subsequently densified by chemical vapor infiltration to obtain SiCNWs/PyC-SiC_f/SiC composites. The results reveal that the introduction of SiCNWs could markedly enhance the microwave absorption properties of PyC-SiC_f/SiC composites. Owing to the increasing of SiCNWs loading, the minimum reflection loss of composites raises up to −58.5 dB in the SiCNWs/PyC-SiC_f/SiC composites with an effective absorption bandwidth (reflection loss ≤ −10 dB) of 6.13 GHz. The remarkable enhancement of electromagnetic wave absorption performances is mainly attributed to the improved dielectric loss ability, impedance matching and multiple reflections. This work provides a novel strategy in preparing SiC_f/SiC composites with excellent electromagnetic wave absorption properties.     

Bridged polysilsesquioxane-derived SiOCN ceramic aerogels for microwave absorption

The development of high-performance microwave absorption materials in harsh environment is highly desirable but challenging. Herein, lightweight silicon oxycarbonitride (SiOCN) ceramic aerogels were fabricated by the pyrolysis of bridged polysilsesquioxane aerogels, which was presynthesized by a sol–gel method followed by vacuum drying. The structural order and content of free carbon phase determined by pyrolysis temperature play a critical role in modulating the impedance matching and attenuation capacity. The as-prepared SiOCN aerogel pyrolyzed at 1000°C achieves a minimal reflection loss of −64.2 dB at 8.96 GHz and a broad bandwidth of 5.4 GHz at a low thickness of 2.15 mm. The hierarchical pore structure, abundant heterogeneous amorphous SiOCN/free carbon interfaces, and conductive free carbon phase benefit the superior absorption performance by forming good impedance matching, multiple scattering, interface polarization, and conduction losses. This work provides an insight for the rational design of polymer-derived ceramic aerogel-based microwave absorption materials for potential application under extreme conditions such as high-temperature and oxidation environments.     

Fabrication of microwave absorbing CoFe2O4 coatings with robust superhydrophobicity on natural wood surfaces

A superhydrophobic wood surface with microwave absorption property was prepared based on the formation of CoFe₂O₄ nanoparticles and subsequent hydrophobization using fluorinated alkylsilane (FAS). Meanwhile, sticky epoxy resin was worked as a caking agent by adhering abundant of CoFe₂O₄ nanoparticles to wood surface. The as-prepared superhydrophobic coatings on wood maintain stable superhydrophobicity after suffering a significant abrasion. Moreover, the complex permeability and permittivity of the coated wood composites were measured in the frequency range of 2–18 GHz by vector network analysis. The microwave absorption properties were elucidated by the traditional coaxial line method. The results show that the as-prepared wood composites have excellent microwave absorption properties at the frequency of 16 GHz, and the minimum reflection loss can reach −12.3 dB. The approach presented may provide further routes for designing outdoor wood wave absorbers with a specified absorption frequency.     

Preparation of carbon fibers@NiS/Ni3S4@MoS2 with core-sheath structure for high efficiency and wide-bandwidth microwave absorption

Numerous studies have focused on the preparation of carbon fibers (CFs)-based high-efficiency microwave absorbers with reasonable structural design and surface morphology control, which simultaneously meet the required impedance matching and loss ability. Here, CFs@NiS/Ni₃S₄@MoS₂ (CNNM) with core-sheath structure was prepared through several simple hydrothermal reactions. The morphology of the as-prepared CNNM nanocomposite is controlled by the amount of added sodium molybdate dihydrate, which causes the difference in minimum reflection loss (RL) and effective attenuation bandwidth among the samples. For the microwave absorbing performance, the minimum RL is ?18 dB and the effective attenuation bandwidth is 8.7 GHz, which appear at the thickness of 2.8 mm and cover most of the X- and Ku-bands. The excellent absorbing performance is attributed to optimized impedance matching and enhanced polarization loss. These results originate from the transition metal sulfides, which not only effectively prevent the skin effect by decreasing the conductivity of CFs but also increase interfaces and flaws, leading to interface polarization and dipole polarization losses.     

Composition manipulation of heat-resistant iron-based cores@graphitic carbon@amorphous carbon derived from urea-modulated MOFs for high-efficient microwave absorption

Designing multifunctional microwave absorption materials is crucial in practical application. Herein, the iron-based cores@graphitic carbon@amorphous carbon composites with diverse phase compositions were annealed from urea-modulated metal organic frameworks (MOFs), MIL-88A, as precursors. By simply varying the mass ratio of urea and MIL-88A, the chemical compositions of as-prepared samples were well adjusted, which brought the variation of interfacial polarization, dipole polarization, and magnetic response. Meanwhile, the structure with outer-layered amorphous carbon and inner-layered graphitic carbon enhanced impedance matching. Therefore, with stronger microwave attenuation brought by polarization loss and better impedance matching, the high-efficient microwave absorption performance with a minimum reflection loss (R_L) of ?67.81 dB at 12.5 GHz and an effective absorption bandwidth of 5.76 GHz was obtained with S-05 (Fe/Fe₃C/Fe_15.1C@graphitic carbon@amorphous carbon), which was prepared with the weight ratio of MIL-88A and urea at 2:1. Meanwhile, the iron-based cores@graphitic carbon@amorphous carbon composites possess good heat-resistant properties due to the existence of protecting carbon layers. Thus, urea-assisted treatment paves a way for acquiring multifunctional absorbers derived from MOFs with enhanced microwave absorption performance.     

Role of exchange coupling between the hard and soft magnetic phases on the absorption of microwaves by SrFe10Al2O19/Co0.6Zn0.4Fe2O4 nanocomposite

(1-x)SrFe₁₀Al₂O₁₉/(x)Co_0.6Zn_0.4Fe₂O₄-(SFAO/CZFO) hard/soft nanocomposite ferrite materials were synthesized by ‘one-pot’ self-propagating combustion route. The co-existence of the two magnetic phases were confirmed by XRD, FESEM, EDS and VSM. The prepared nanocomposite samples were also characterized by TGA/DSC, Raman spectroscopy and VNA. Exchange coupling between the hard and the soft magnetic grains was observed by determining the switching field distribution (SFD) curve. As a result of the competing effects of exchange interaction and dipolar interaction, magnetic parameters were observed to be sensitive to the incorporation of soft magnetic phase into the nanocomposite. Results showed that with the inclusion of soft magnetic phase, exchange coupling behaviour between the hard and the soft ferrite phases had significant influence on the microwave absorption capacity of the samples. Related electromagnetic parameters and impedance matching ratio of the nanocomposite system were discussed. A minimum reflection loss of ?42.9 dB with an absorber thickness of 2.5 mm was attained by the nanocomposite (90 wt%)SrFe₁₀Al₂O₁₉/(10 wt %)Co_0.6Zn_0.4Fe₂O₄ at a matching frequency of 11.45 GHz. This assured the candidacy of SrFe₁₀Al₂O₁₉/Co_0.6Zn_0.4Fe₂O₄ nanocomposite as a promising microwave absorption material in the X-band (8–12 GHz).     

Construction of Si3N4/SiO2/SiC–Y2Si2O7 composite ceramics with gradual impedance matching structure for high-temperature electromagnetic wave absorption

Good impedance matching is vital in upgrading the performance of electromagnetic (EM) wave-absorbing materials. In this study, Si₃N₄/SiO₂/SiC–Y₂Si₂O₇ composite ceramics were synthesized by sintering and chemical vapor infiltration (CVI) technology with gradual impedance matching. The relationship between the microstructure of the as-prepared composite ceramics and EM wave absorption characteristics was thoroughly explored. It was found that the amorphous Si₃N₄, SiO₂, and SiC layers were constructed with a gradual impedance matching structure, which not only improved impedance matching but also increased the number of nano interfaces. More importantly, SiC nanocrystals effectively increased the conduction loss, and the presence of defects and nanoscale heterogeneous interfaces further increased the polarization loss. Consequently, the as-prepared composite ceramics displayed enhanced EM wave absorption properties, with a minimum reflection coefficient (RC_min) value of less than ?20 dB over a temperature range of 25 °C (RT)-300 °C, and an effective absorption bandwidth (EAB) maintained at 4.2 GHz with the thickness range of 3.75–4.75 mm. These results demonstrated the practical significance of high-performance EM wave absorption materials that can be applied in high-temperature and water vapor environments.     

Coupling CoFe2O4 and SnS2 nanoparticles with reduced graphene oxide as a high-performance electromagnetic wave absorber

The reduced graphene oxide (RGO)/CoFe₂O₄/SnS₂ composites have been successfully synthesized by two-step hydrothermal processes. TEM results show that CoFe₂O₄ and SnS₂ nanoparticles with both diameters about 5–10 nm are well dispersed on the surface of graphene. Compared with RGO/CoFe₂O₄ composites, the as-prepared RGO/CoFe₂O₄/SnS₂ composites exhibit excellent electromagnetic (EM) wave absorption properties in terms of both the maximum reflection loss and the absorption bandwidth. The maximum reflection loss of RGO/CoFe₂O₄/SnS₂ composites is −54.4 dB at 16.5 GHz with thickness of only 1.6 mm and the absorption bandwidth with the reflection loss below −10 dB is up to 12.0 GHz (from 6.0 to 18.0 GHz) with a thickness in the range of 1.5–4.0 mm. And especially, they cover the whole X band (8.0–12.0 GHz), which could be used for military radar and direct broadcast satellite (DBS).     

Design of hierarchical core-shell ZnFe2O4@MnO2@RGO composite with heterogeneous interfaces for enhanced microwave absorption

In order to overcome the problems caused by electromagnetic pollution, the design and development of high-performance microwave absorbers is urgently required. In this work, a hierarchical ZnFe₂O₄@MnO₂@RGO composite was successfully fabricated via a facile and rapid hydrothermal method. Its unique core-shell structure and synergistic effect between multiple components are beneficial for electromagnetic wave absorption. The morphology, elemental composition, microstructure and microwave absorption characteristics were systematically studied. With a filler loading of 20 wt%, the composite presents a minimum reflection loss (R_Lmin) of ?46.7 dB and an effective absorption bandwidth (EAB) as wide as 5.2 GHz at a thickness of 2.5 mm. The superior absorption ability profits from a special microstructure, good impedance matching, multiple attenuation features, interfacial polarization, and the synergistic effect of dielectric and magnetic loss. Consequently, this work lays a foundation for the design of high-performance electromagnetic wave absorbers with multicomponent heterogeneous structures.     

A nanocomposite of dual-phase Fe/TiCN wrapped in nitrogen-doped carbon with magnetic and dielectric characters for superior microwave absorption

A careful approach to the optimization of magnetic and dielectric losses in nanomaterials can improve the electromagnetic wave absorption loss performance for certain microwave absorption applications. In this study we prepared dual core (Fe/TiCN) coated with nitrogen (N) doped carbon shell nanocomposite by arc-discharge method under mix atmospheres of working gases and with varying elemental compositions. Among all nanocomposites, (Fe/TiC_0.7N_0.3)@N–C dual-core@ N- doped shell nanocomposite exhibits enhanced microwave absorption. Owing to the novel dual-core@ N-doped shell structure and numerous defects induced by doping N in carbon shells, an improved dielectric relaxation in composite is observed and the minimum reflection loss was reached −44.36 dB at 5.3 GHz for 4.8 mm thickness.     

Confined tailoring of CoFe2O4/MWCNTs hybrid-architectures to tune electromagnetic parameters and microwave absorption with broadened bandwidth

Multi-walled carbon nanotubes (MWCNTs) are highly alluring as an electromagnetic (EM) wave absorber owing to their multi-dimensional structure, high chemical stability, low density, and significant conduction loss, which provide great promises as an excellent EM wave absorber in practical applications. Herein, a simple and controllable solvothermal technique is applied to synthesize cobalt ferrite/MWCNTs (CoFe₂O₄/MWCNTs) hybrid composite. Various analytical techniques were used to investigate the composition, morphological structure, and electromagnetic parameters of the as-prepared hybrid composite. The obtained results revealed that, a strong network of CoFe₂O₄ microspheres interweaved with MWCNTs in the prepared hybrid composite. The resultant CoFe₂O₄/MWCNTs composites achieve a minimum reflection loss (RL_min) of ?50.80 dB at a thickness of 4.2 mm and effective absorption bandwidth (EAB) of 3.36 GHz at a thickness of 1.6 mm exhibiting the superior RL_min compared to the typical magnetic composite derived absorbers. This research advocates the precise development and designing of unique MWCNTs-based composites as a high-efficient and lightweight electromagnetic wave absorber.     

Controllable synthesis of FeSe2/rGO porous composites towards an excellent electromagnetic wave absorption with broadened bandwidth

Due to the escalating demand for electronic dependability and defense security, there has been a surge in research into broadband and lightweight microwave absorbers. Porous composites that are lightweight and plentiful in interfaces have the potential to be high-performance absorbers due to their ability to attenuate waves in a balanced manner and match impedance. “Using a solvothermal technique we generated FeSe₂/rGO composites with a porous topology. By varying the weight of rGO, the electromagnetic properties of FeSe₂/rGO composites may be finely tuned. Impedance matching and attenuation capability are both improved as a direct result of the porous structure and the appropriate electromagnetic parameters. FeSe₂/rGO composites benefit from the tunable composition, porous structure, and strong synergistic effect between FeSe₂ and rGO sheets and display outstanding microwave absorption performance with an ultrabroad bandwidth approaching 5.2 GHz with a thin thickness of 1.6 mm which covers 75% of the studied frequency range. At the same thickness, a significant reflection loss of ?43.7 dB is attained. This work not only enables the tuning of electromagnetic parameters but also expands the use of high-performance microwave absorption devices. Remarkable microwave absorption ability, of the porous composites FeSe₂/rGO can be utilized as a high-performance microwave absorber.”     

Magnetically recoverable CoFe1.9Gd0.1O4 ferrite/polyaniline nanocomposite synthesized via green approach for radar band absorption

The gadolinium substituted cobalt ferrite (CoFe_1.9Gd_0.1O₄) nanoparticles and CoFe_1.9Gd_0.1O₄/Polyaniline (PANI) microwave absorber were synthesized by sol-gel auto combustion technique using lemon juice and in-situ polymerization method respectively. X-ray patterns confirmed the formation of single phase cubic structure. The crystallite size of the synthesized CoFe_1.9Gd_0.1O₄ nanoparticles are within the range of 15–68 nm. The saturation magnetization of CoFe_1.9Gd_0.1O₄ ferrite/Polyaniline (PANI) composite was reduced due to nonmagnetic PANI. The reflection loss for microwave absorbing properties of CoFe_1.9Gd_0.1O₄ ferrite nanoparticles and CoFe_1.9Gd_0.1O₄/PANI nanocomposite were investigated and minimum value of reflection loss was found to be −16.85 dB at 13.52 GHz for nanoparticles of thickness 2.5 mm and −25.59 dB at 11.92 GHz for CoFe_1.9Gd_0.1O₄/PANI nanocomposite of thickness 2.0 mm) respectively. The prepared samples have low density, high surface resistivity and enhanced attenuation constant. The nanocomposite exhibits excellent absorption performance over a broad band range in the radar band.     

Boosted microwave absorption properties of CoFe2O4 with extraordinary 3D morphologies

Due to their strong magnetic dissipation and low cost, ferrites were one of the first generations of microwave absorbers. However, ferrites also have some drawbacks, such as a low natural resonance frequency (f_r), a lack of dielectric loss, and high density. In order to overcome these drawbacks and improve the microwave dissipation features of ferrites, we successfully prepared CoFe₂O₄ samples with flower-like and crochet ball-like morphologies (named as M1 and M2 samples, respectively). Structural and optical properties were studied by XRD, FTIR, and UV–Vis light absorption. The microwave performance of CoFe₂O₄ was significantly improved with the reflection loss (RL) of M2 of ?40 dB. Furthermore, M1 and M2 samples achieved an ultra-wide effective absorption bandwidth (EAB) of 13 and 12.5 GHz, respectively. It is worth noticing that the EAB of M1 was one of the largest EABs for CoFe₂O₄ that has been reported so far. The excellent microwave dissipation of M1 and M2 samples in the 2–18 GHz frequency range was due to the enhancement of ferrite f_r to the high-frequency range and the introduction of dielectric loss to achieve impedance matching. The flower-like and crochet ball-like morphologies with many pores of M1 and M2 also resolved the high-density issue of CoFe₂O₄. With the relatively good values of RL and EAB combined with low filler loading, thin thickness, and low density, M1 and M2 samples could be expected to be promising microwave absorbers for practical applications.