Superior Microwave Absorption Performance Research Articles

Ni doped carbon-based composites derived from waste cigarette polypropylene filter rod with electromagnetic wave absorption performance

Abstract Polypropylene is widely used in the plastics industry, especially in the tobacco industry, served as cigarette filters to reduce tar and harm. However, it’s difficult to degrade these polypropylene plastics and suitable methods for recycling and reuse is urgent. This research proposes an efficient method for the reuse of polypropylene cigarette filters by mixing waste polypropylene filters with nickel source in different proportions, followed by a facile calcination treatment to prepare nickel-modified carbon-based composite materials with excellent microwave absorption properties. Morphology and magnetic properties of as-prepared samples were analyzed via XRD, SEM, and VSM, exhibiting an increase in carbon content with raising nickel content. Nickel ion anchored on polypropylene fiber may facilitate better fixation of carbon chains during the polypropylene decomposition process. Among the as-prepared samples, CN2 exhibited superior microwave absorption performance, with an optimal absorption peak of -26.76 dB at 7.97 GHz when matched with a given thickness of 4.3 mm, and an effective absorption bandwidth of 3.64 GHz (8.04 GHz to 11.68 GHz) with a matching thickness of 3.5 mm, covering the X band. Therefore, the as-prepared microwave absorbers provides a feasible solution for the recycling and reuse of polypropylene filters, aligning with the tobacco industry requirements for green and sustainable development.

Coupled multiple heterogeneous interfaces lychee-like FeSiAl@C@SiO2@BTA for self-healing corrosion protection and enhanced microwave absorption

Corrosion-resistant ferromagnetic absorbers (FMAs) with self-healing properties are crucial for enhancing their durability under harsh conditions. Herein, we fabricated lychee-like FeSiAl (FSA)@C@SiO2@1H-Benzotriazol (BTA) coupled with multiple heterogeneous interfaces by coating FSA with a C@SiO2@BTA layer using sol-gel, thermal reduction, and molecular encapsulation techniques. The FSA@C@SiO2@BTA showed superior microwave absorption (MA) performance than FSA, with a widest absorption bandwidth of 10.44 GHz at 1.98 mm and a maximum reflection loss of −57.81 dB at 2.98 mm. The enhanced MA performance was due to the better impedance matching and the synergistic effects of interfacial and dipole polarization induced by the C@SiO2@BTA layer. Moreover, the FSA@C@SiO2@BTA exhibited a remarkable corrosion resistance, with a corrosion rate of 3.28 × 10−10 m/s, which was two orders of magnitude lower than that of FSA, and a corrosion protection efficiency of 99.0 %. The epoxy resin coating containing FSA@C@SiO2@BTA also demonstrated a self-healing ability within 5 min after being damaged mechanically. This study presents a novel model that integrates MA, corrosion resistance, and self-healing, heralding new avenues for developing corrosion-resistant FMAs in marine applications.

Exquisite regulation of LZ-BaM/PPy composites for compatible absorption across centimeter-wave and millimeter-wave bands

The increasing complexity of the electromagnetic environment necessitates materials to exhibit superior microwave absorption performance for multitudinous bands. However, reaching satisfactory compatibility for absorption across centimeter-wave and millimeter-wave bands still remains a formidable challenge. In this work, a composite composed of Polypyrrole (PPy) and La3+-Zr4+ co-doped barium ferrite (LZ-BaM) is elaborately designed to address the issue facing us today. By exquisitely regulating the chemical composition, absorption peaks ascribed to different integral orders of interference can appear simultaneously in millimeter-wave and centimeter-wave bands. Ultimately, the as-prepared LZ-BaM/PPy composite reveals an efficient absorption (RL < −5 dB, absorptivity of 68.37 %), covering the centimeter-wave band of 8∼17 GHz and millimeter-wave band of 27∼40+ GHz concurrently under a matching thickness of 2.4 mm. This study thus offers valuable insights for the development of high-efficient absorbers across multiple frequency bands.

Construction of chiral magnetic structure with enhancement in magnetic coupling for efficient Low-Frequency microwave absorption

Construction of chiral magnetic structure is considered as a promising strategy to achieve efficient low frequency microwave absorption. However, it is not clear that how the magnetic loss is enhanced by the chiral morphology. Herein, a novel chiral magnetic structure containing FeCo2O4-FeCo nanosheets has been constructed by using helical carbon nanocoils (CNCs) as the chiral template. For comparison, the FeCo2O4-FeCo nanosheets are also combined with the linear carbon nanofibers (CNFs). The enhanced magnetic coupling between FeCo2O4-FeCo nanosheets and the magnetic anisotropy induced by the chiral structure are confirmed by the off-axis electron holography and the micro-magnetic simulation. Due to the synergistic effect between chirality, magnetism, and dielectricity, the chiral magnetic structure exhibits superior microwave absorption performance than the linear one with a wide effective bandwidth of 7.1 GHz at an ultra-low filling ratio of 8 %. Meanwhile, the minimum RL value of −60.7 dB is achieved at low frequency (6 GHz). This study provides further evidence of the special mechanisms of the chiral structure for microwave absorption.

Construction of ZIF/CS and ZIF/CS-derivatives with high-efficiency adsorption for dyes/antibiotics and strong microwave absorption performance

Bimetallic Zn/Co-ZIF was in situ loaded onto the surface of chitosan (CS) to form ZIF/CS composites with high-efficiency adsorption of antibiotics (tetracycline (TC)) and dyes (Congo Red (CR), Malachite Green (MG)). The particle size and surface roughness of Zn/Co-ZIF can be effectively adjusted by changing the mass ratio of Zn and Co in ZIF, which helps to regulate the adsorption active sites on the surface of the composites. Meanwhile, the introduction of CS changes the pore structure of the composites, making the molecules of TC, CR and MG easily enter into the pores of ZIF/CS. When the mass ratio of Zn to Co is 1:1, the ZIF/CS composite has the optimal adsorption performance with the ultra-high adsorption capacity qm of 781.3, 1644.2 and 3243.6 mg g−1 for TC, CR and MG, respectively. Impressively, the ZIF/CS-derivative (ZC3–700) from sample ZC3 after calcination at 700 °C under N2 atmosphere owns a good conductive network, which results in its superior microwave absorption performance. Herein, at 30 wt% filler loading, the effective absorption bandwidth and RLmin of ZC3–700 reach 5.28 GHz at 1.90 mm and −68.92 dB at 1.83 mm, respectively. Analyses on microwave absorption mechanism point out the synergistic effect of conduction loss, dipolar polarization and interfacial polarization and magnetic loss on the attenuation of electromagnetic wave. Therefore, ZIF/CS composites and ZIF/CS-derivatives exhibit superior performance on the removal of water pollutants and the absorption of electromagnetic wave, which essentially reveals a multifunctional application of the ZIF/CS composites in the field of environmental protect.

Biomimetic artificial nacre-like microfiber of Co/C modified cellulose nanofiber/Ti3C2Tx MXene with efficient microwave absorption

Although considerable efforts have been made in the fabrication of MXene-based composites for microwave absorption (MA), there is a great challenge to assemble MXene into regularly arranged microfibers prepared by wet-spinning technique for application in the field of MA due to insufficient interlayer interactions between Ti3C2Tx flakes. Heterogeneous interface design by optimizing material components to construct ingenious microstructure is crucial for efficient microwave absorbers. Herein, artificial nacre-like supramolecular microfibers of Co/C modified cellulose nanofiber/Ti3C2Tx MXene (Co/C/CNF/Ti3C2Tx) with plenty of heterogeneous interfaces were prepared by a simple wet-spinning technology through a self-assembly process induced by hydrogen bonding interactions between CNF and Ti3C2Tx. The artificial nacre-like microfibers with layered structure possess abundant heterogeneous interfaces, which facilitate multiple reflections/scattering of electromagnetic waves (EMW) between these interfaces, and at the same time promote interfacial and dipole polarization. The introduction of magnetic Co/C nanoparticles not only offer additional magnetic loss ability and improved impedance matching, but also enhance conductivity loss and polarization loss. Benefiting from these advantages, Co/C/CNF/Ti3C2Tx (1:1:1) fiber exhibits superior MA performance with a minimum reflection loss (RLmin) of up to −62.32 dB (>99.9999 % energy absorption) and a broad effective absorption bandwidth (EAB) of 5.86 GHz. The work provides a promising method for the preparation of biomimetic artificial nacre-like MXene-based microfibers with efficient MA performance, which is expected to be applied in the field of flexible wearable electromagnetic protection.

Ultralight Three-Layer Gradient-Structured MXene/ Reduced Graphene Oxide Composite Aerogels with Broadband Microwave Absorption and Dynamic Infrared Camouflage.

Infrared and radar detectors posed substantial challenges to weapon equipment and personnel due to their continuous surveillance and reconnaissance capabilities. Traditional single-band stealth devices are insufficient for dual-band detection in both infrared and microwave bands. To overcome this limitation, a gradient-structured MXene/reduced graphene oxide (rGO) composite aerogel (GMXrGA) is fabricated through a two-step bidirectional freeze casting process, followed by freeze-drying and thermal annealing. GMXrGAexhibits a distinct three-layered structure, with each layer playing a crucial role in microwave absorption. This deliberate design amplifies both the efficiency of microwave absorption and the material's effectiveness in dynamic infrared camouflage. GMXrGA displays an ultralow density of 5.2 mg∙cm-3 and demonstrates exceptional resistance to compression, enduring 200 cycles at a maximum strain of 80%. Moreover, it shows superior microwave absorption performance, with a minimum reflection loss (RLmin) of -60.1dB at a broad effective absorption bandwidth (EAB) of 14.1GHz (3.9-18.0GHz). Additionally, the aerogel exhibits low thermal conductivity (≈26 mW∙m-1∙K-1) and displays dynamic infrared camouflage capabilities within the temperature range of 50-120°C, achieving rapid concealment within 30 s. Consequently, they hold great potential for diverse applications, including intelligent buildings, wearable electronics, and weapon equipment.

NiCo2O4 NANOCHAINS SYNTHESIS WITH EFFECTIVE MICROWAVE ABSORPTION CHARACTERISTICS

Nanochains-like NiCo2O4 material was synthesized via the hydrothermal method utilizing D-glucose template to facilitate microwave absorption across the frequency range of 2 - 18 GHz. Comprehensive characterization employing various analytical techniques was employed to investigate the structural, microstructural, magnetic, and electromagnetic properties. Leveraging the presence of Oxalic acid and D-Glucose, a nanochain morphology comprising spherical nanoparticles (400 - 600 nm) was achieved. The resultant NiCo2O4 demonstrated a single-phase structure and exhibited the reflection loss (RL) value lower than -20 dB was up to 5.9 GHz within the Ku (12 - 18 GHz) frequency band, at a matching thickness of 2.0 mm. Remarkably, the optimal reflection loss reached -52.5 dB at 15 GHz for samples with a thickness of 2.0 mm, while the widest effective bandwidth extended up to 14.1 GHz for samples with a thickness of 5.0 mm. The superior microwave absorption performance of the chains-like NiCo2O4 powders was attributed to the synergistic interplay between their dielectric and magnetic properties, facilitating excellent impedance matching. These results indicate that NiCo2O4 chains-like powders have great promise as a material for microwave absorption.

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.

Large Microsphere Structure of a Co/C Composite Derived from Co-MOF with Excellent Wideband Electromagnetic Microwave Absorption Performance.

In the field of electromagnetic wave (EMW) absorption, carbon matrix materials based on metal-organic frameworks (MOFs) have drawn more interest as a result of their outstanding advantages, such as porous structure, lightweight, controlled morphology, etc. However, how to broaden the effective absorption bandwidth [EAB; reflection loss (RL) ≤ -10 dB] is still a challenge. In this paper, large microsphere structures of a Co/C composite composed of small particle clusters were successfully prepared by the solvothermal method and annealing treatment. At a filling ratio of 40 wt %, the Co/C composite shows attractive microwave absorption (MA) performance after being annealed at 600 °C in an atmosphere of argon. With an EAB of 6.32 GHz (9.92-16.24 GHz) and a thickness of just 2.57 mm, the minimum RL can be attained at -54.55 dB. Most importantly, the EAB can attain 7.12 GHz (10.88-18.0 GHz) when the thickness is 2.38 mm, which is larger than that of the majority of MOF-derived composites. The superior MA performance is strongly related to excellent impedance matching and a higher attenuation constant. This study provides a simple strategy for synthesizing a MOF-derived Co/C composite with a wide EAB.

The core-shell structure of nitrogen-doped carbon coated Fe3O4 decorated MXene for broadband and efficient microwave absorption

In recent years, MXene has gained widespread attention in the field of microwave absorption (MA) due to its unique two-dimensional layered structure, excellent electrical conductivity, and chemically active surface. However, the MA mechanism of MXene is limited to dielectric loss alone, which poses a challenge in meeting the performance requirements of new absorbers. Therefore, to enhance the performance of MXene in MA, this paper successfully prepared Fe3O4/NC@MXene (FNCM) composites by modifying core-shell magnetic nanoparticles of nitrogen-doped carbon coated Fe3O4 (Fe3O4/NC) on MXene. By adjusting the dose of Fe3O4/PDA precursor, the impedance matching is further optimized. FNCM-2 demonstrates superior MA performance with a thickness of 2mm, achieving a minimum reflection loss (RLmin) of −54.41 dB and an effective absorption bandwidth (EAB) of 7.32 GHz. Meanwhile, the RLmin of the FNCM-1 sample at a thickness of 2 mm can reach −55.65 dB. The remarkable improvement in MA performance can be attributed to the synergistic effect of dielectric and magnetic losses, which optimizes impedance matching. This study is expected to provide insights for the development of efficient and broadband MXene-based MA materials.

Linkage Effect Induced by Hierarchical Architecture in Magnetic MXene-based Microwave Absorber.

Hierarchical architecture engineering is desirable in integrating the physical-chemical behaviors and macroscopic properties of materials, which present great potential for developing multifunctional microwave absorption materials. However, the intrinsic mechanisms and correlation conditions among cellular units have not been revealed, which are insufficient to maximize the fusion of superior microwave absorption (MA) and derived multifunctionality. Herein, based on three models (disordered structure, porous structure, lamellar structure) of structural units, a range of MXene-aerogels with variable constructions are fabricated by a top-down ice template method. The aerogel with lamellar structure with a density of only 0.015g cm-3 exhibits the best MA performance (minimum reflection loss: -53.87dB, effective absorption bandwidth:6.84GHz) at a 6wt.% filling ratio, which is preferred over alternative aerogels with variable configurations. This work elucidates the relationship between the hierarchical architecture and the superior MA performance. Further, the MXene/CoNi Composite aerogel with lamellar structure exhibits >90% compression stretch after 1000 cycles, excellent compressive properties, and elasticity, as well as high hydrophobicity and thermal insulation properties, broadening the versatility of MXene-based aerogel applications. In short, through precise microstructure design, this work provides a conceptually novel strategy to realize the integration of electromagnetic stealth, thermal insulation, and load-bearing capability simultaneously.

Surface structural engineering of carbonyl iron powder for enhancing microwave absorption and anti-oxidation performance

Surface structural engineering is desirable in modifying the surface performance of carbonyl iron powder (CIP) to enhance microwave absorption (MA) and anti-oxidation performance. Herein, the surface shape-dependent CIP absorbers are designed via surface coating with zinc oxide (ZnO) nanoparticles and then a thermal annealing treatment. The morphology of ZnO nanoparticles which can be easily regulated by controlling the annealing temperature ultimately affects the MA performance of CIP coating with ZnO nanoparticles (CIP@ZnO). The core-shell CIP@ZnO particles with cubic cone ZnO nanoparticles exhibit excellent MA performance and thermal stability in comparison to the original CIP. Specifically, the CIP@ZnO annealed at 350 °C (CIP@ZnO-350) samples which have the cubic cone ZnO nanoparticles exhibit a minimum reflection loss (RLmin) of –55.35 dB at a thickness of 2.1 mm and a maximum effective absorption bandwidth (EAB) of 7.09 GHz at a thickness of 2.0 mm. In addition, the antioxidant property of the CIP@ZnO composite particles is abruptly enhanced, which breaks the restriction of the application of CIP at high temperatures. The superior MA performance of CIP@ZnO particles with cubic cone ZnO nanoparticles comes from the enhancement in surface shape-dependent multiple microwave scattering, interfacial polarization, and electromagnetic-dielectric synergism between ZnO and CIP.

Constructing honeycomb-like hierarchical foam via electromagnetic cooperation strategy for broadband microwave absorption

The application of wireless electronic devices inevitably leads to electromagnetic pollution. Three-dimensional porous foam structures have been shown to be an effective strategy to construct high-performance microwave absorbers. Herein, the honeycomb-like hierarchical foams were fabricated via melamine-formaldehyde (MF) foam as substrate coupled with flaky carbonyl iron (CI)-MXene lamellae. Inside the synthesized composite foam, flaky CI is interlaced into MXene nanosheets to form hierarchical structures, which effectively alleviates the originally self-stacking phenomenon and provides numerous heterogeneous interfaces, resulting in the optimization of impedance matching. In addition, owing to the construction of consecutive electromagnetic networks, the CI-MXene/MF foams exhibit significant dielectric loss and magnetic loss capability. Moreover, the honeycomb-like structure offers multiple reflections/scattering for electromagnetic waves, which effectively prolongs the transmission paths, further improving the microwave attenuation ability. Hence, the synthesized composite foam exhibits superior microwave absorption performance with a minimum refection loss of −61.4 dB and a maximum effective absorption band of 7.18 GHz. The construction of unique microstructure and regulation of electromagnetic components is demonstrated to be feasible strategies for the design of efficient microwave absorbers in future.

Modified zirconia fiber/reduced graphene oxide composite aerogels with exceptional mechanical and microwave absorption properties for harsh-environment applications

The exploration of space is a global endeavor that demands sophisticated technologies and skills to ensure survival in harsh environments. Graphene aerogels have demonstrated great potential for thermal insulation and electromagnetic protection in the aerospace industry because of their low density, porous structure, and high dielectric properties. However, their weak mechanical properties are a severe limitation in harsh environments, hindering their diverse applications such as microwave absorption (MA). To address this issue, we prepared zirconia fiber (ZF)/reduced graphene oxide (rGO) composite aerogels through bidirectional freezing and subsequent thermal annealing. The resultant lamellar structure of the composite aerogels exhibits exceptional mechanical properties, such as high compressive deformation up to 90%, excellent cyclic compressibility, low thermal conductivity of 0.027 W·m−1·K−1, and superior MA performance with a minimum reflection loss (RLmin) of −72.2 dB at a thickness of 2.1 mm and an effective absorption bandwidth (EAB) of 8.4 GHz (9.6–18.0 GHz). Furthermore, the absorbing coatings based on modified ZF/rGO composite aerogels have significantly reduced radar cross-section by 22.94 dBsm. Consequently, the composite aerogels exhibit robust mechanical properties and excellent MA performance after high- and low-temperature treatments, showing high potential for advanced applications in space suits, spacecraft, and probes and so on.

Ambient-drying to construct unidirectional cellulose nanofibers/ carbon nanotubes aerogel with ultra-lightweight, robust, and superior microwave absorption performance

Microwave absorption materials (MAMs) with lightweight wide effective absorption band, superb mechanical performance, and capable of large-scale preparation are highly desirable for dealing with microwave pollution, but it is still a challenge to realize these performances simultaneously on one material. Herein, we report an ambient drying and non-chemical cross-linking way of preparing high-performance microwave absorption aerogels from cellulose nanofibers (CNF) and carbon nanotubes (CNT). Anisotropic aerogel pore walls with excellent mechanical properties can be constructed by unidirectional cycling freeze-thaw to cross-linking CNF and CNT. During this process, a sustainable bioinspired dual-networks interpenetrating strategy is constructed by benefiting from the mono-dispersion of CNF and CNT, thus enabling the creation of hybrid dual-networks of hydrophobic/hydrophilic nanofibers. Impressively, it is found that the dual-networks induced anisotropic aerogel structure and dense pore walls can synergistically result in favorable mechanical properties. In detail, aerogels with tunable ultralow densities (0.0262–0.0296 g cm−3), high mechanical properties (the stress of the sample reaches up to 329.8 kPa at 75% strain) and low shrinkage (∼10%) can be prepared. Besides, the aerogels behave a large-scale production future (diameter of aerogel up to 9.24 cm). The as-prepared aerogel delivers a remarkable minimal reflection loss (RLmin) of −60.22 dB at 13.012 GHz and a wide effective absorption bandwidth (EAB) from 2.163 to 18 GHz (15.84 GHz) at a thin thickness of 7.46 mm, which covers almost all the S, C, X, and Ku bands. This work provides a strategy to prepare lightweight and efficient microwave absorbers, as well as illustrates good impedance matching and moderate dielectric loss capability.

Construction of chiral-magnetic-dielectric trinity composites for efficient microwave absorption with low filling ratio and thin thickness

The combination of carbon nanomaterials and magnetic nanomaterials has been proven to be a promising strategy to fabricate thin and lightweight microwave absorbers with tunable absorption bands and broadened bandwidth, especially the absorption capability in low frequency (2–10 GHz). Herein, a series of CoNi-based magnetic nanomaterials have been synthesized on the surfaces of chiral carbon nanocoils (CNCs) to form a chiral-magnetic-dielectric trinity composite through solvothermal reaction followed by a subsequent annealing method. The well-dispersed CoNi nanostructures enhance the magnetic loss of the composites, giving rise to the strong microwave absorption at low frequency. In addition, the dielectric CNCs with excellent chirality and dispersibility not only provide conduction loss and cross-polarization loss to broaden the absorption bandwidth, but also reduce the filling ratio of the composites. Accordingly, with the synergistic effect of the chiral-magnetic-dielectric components, combined with the good impedance and quarter-wavelength matchings, the trinity composite exhibits superior microwave absorption performance with a wide effective bandwidth of 6.1 GHz at the thickness of 1.85 mm. More importantly, the reflection loss value reaches −42 dB at 4.5 GHz with a low filling ratio of 12 wt%. This study provides a novel chiral-magnetic-dielectric trinity structure for highly efficient microwave absorption.

Hierarchical Carbon Network Composites Derived from ZIF-8 for High-Efficiency Microwave Absorption.

Metal-organic framework (MOF)-derived composites have gained wide attention due to their specific structures and enhanced performance. In this work, we prepared carbon nanotubes with Fe nanoparticles connected to two-dimensional (2D) hierarchical carbon network composites via a low-pressure gas-solid reaction strategy. Specifically, the three-dimensional (3D) networks derived from ZIF-8 exploited the carbon nanotubes with the function of charge modulation. Meanwhile, we utilized the interconnected 2D nanostructures to optimize impedance matching and facilitate multiple scattering, ultimately improving the overall microwave absorption performance. Furthermore, based on the well-designed structures, the composites prepared at 800 °C (Fe-N-C@CNTs-800) achieved the best reflection loss (RL) of -58.5 dB, thereby obtaining superior microwave absorption performance. Overall, this study provides a good groundwork for further investigation into the modification and dimension design of novel hierarchical microwave absorbers.

Synthesis of a one-dimensional carbon nanotube-decorated three-dimensional crucifix carbon architecture embedded with Co7Fe3/Co5.47N nanoparticles for high-performance microwave absorption

Low-dimensional cell-decorated three-dimensional (3D) hierarchical structures are considered excellent candidates for achieving remarkable microwave absorption. In the present work, a one-dimensional (1D) carbon nanotube (CNT)-decorated 3D crucifix carbon framework embedded with Co7Fe3/Co5.47N nanoparticles (NPs) was fabricated by the in-situ pyrolysis of a trimetallic metal–organic framework (MOF) precursor (ZIF-ZnFeCo). Co7Fe3/Co5.47N NPs were uniformly dispersed on the carbon matrix. The 1D CNT nanostructure was well regulated on the 3D crucifix surface by changing the pyrolysis temperature. The synergistic effect of 1D CNT and the 3D crucifix carbon framework increased the conductive loss, and Co7Fe3/Co5.47N NPs induced interfacial polarization and magnetic loss; thus, the composite manifested superior microwave absorption performance. The optimum absorption intensity was −54.0 dB, and the effective absorption frequency bandwidth reached 5.4 GHz at a thickness of 1.65 mm. The findings of this work could provide significant guidance for the fabrication of MOF-derived hybrids for high-performance microwave absorption applications.

Constructing multi-effect synergistic rare-earth doped CoFe2O4/CoFe composites for improved microwave absorption performance

It is an appealing strategy to improving the low reflection loss and narrow microwave absorption band of cobalt ferrite-derived composites by optimizing the various components of the material and building microstructures with complementary properties. In this study, rare-earth doped CoFe2O4/CoFe composites (LCF-2, NCF-2, ECF-2) were synthesized via the sol-gel self-combustion and reduction process, a two-step route. The results show that the effects on the cation vacancies and charge distribution of CoFe2O4 showed differences attributed to the doping of La, Nd, and Eu. While the CoFe introduced by reduction increases the oxygen vacancies and grows on the material surface to form a non-uniform, strongly coupled CoFe2O4–CoFe heterointerface. Benefiting from the multi-effect synergy of rare earth and CoFe on cobalt ferrite, the electromagnetic properties and microwave attenuation of the composites were significantly enhanced. And the potential microwave dissipation mechanism was also explicated. Notably, LCF-2 exhibited superior microwave absorption performance with a minimum reflection loss of −65.2 dB and an effective absorption bandwidth of 5.1 GHz at a thin thickness of 1.6 mm. Our works will provide some reference for the design of efficient and broadband microwave absorbing composites in the future.