Reflection Loss Value Research Articles

Hollow silicon carbide microspheres for excellent and lightweight electromagnetic wave absorber

Developing semiconductor ceramic materials with lightweight, outstanding stability, and high-performance electromagnetic wave (EMW) absorption are attractive for harsh environments. Due to thermal and chemical stability, designable microstructure, and tunable dielectric property, microstructured silicon carbide (SiC) ceramics offer promising potential as excellent EMW absorbers while limited by the scarce fabricating methods. Here, a simple coaxial electrospinning technology and the high-temperature calcination process are developed for the first time to fabricate hollow SiC microspheres (HSCMs) for EMW absorbers. Owing to the sizeable SiC-free space interface in the shell and internal void, the inner hollow structure also endows HSCMs with excellent EMW absorbing properties. By comparing with the composite of 40 wt% solid SiC microspheres (SSCMs)/paraffine, it is found that the 40 wt% HSCMs/paraffin composite exhibits superior dielectric properties and a minimum reflection loss (RL) value of − 61.6 dB at 7.7 GHz and 3.4 mm thickness, associated with the most considerable adequate absorption bandwidth of 4.9 GHz (from 12.6 to 17.5 GHz) at 1.9 mm thickness. This work gives rise to a handy method for fabricating hollow SiC with lightweight and high-efficiency EMW absorption. It will potentially boost the development of next-generation EMW absorbers for harsh environment applications.

Synthesis and microwave absorption performance of heat-treated RF/SiO2 aerogels

The well-designed composite with satisfactory electromagnetic microwave absorption at high temperatures remains a serious challenge. Herein, we fabricated a resorcinol-formaldehyde/silica dioxide composite aerogel (RF/SiO2) with a three-dimensional network structure using sol-gel, atmospheric pressure drying technique as well as heat-treated processes to achieve enhanced microwave absorption capabilities in the low frequency range. The pristine RF/SiO2 aerogel presented a typical micropores structure with a surface area, porous volume, and density of 146.82 m2/g, 62.40%, and 0.28 cm3/g, respectively. Remarkably, the RF/SiO2 aerogel showed an effective absorption bandwidth of 3.56 GHz and a minimum reflection loss value of −46.10 dB at 2.25 mm after being heat-treated at 1500 °C, while the maximum effective absorption bandwidth was 3.60 GHz at 2.30 mm. The intricate three-dimensional networks possessed remarkable impedance matching, multiple attenuation mechanisms, interfacial polarization, and dielectric loss, which were attributed to the exceptional ability to absorb electromagnetic microwaves. It offered a fresh approach to creating adaptable and effective microwave absorption materials in military defense.

MOF-derived flower-like CoFe@C composites for enhanced electromagnetic wave absorption

Metal-organic frameworks (MOFs) display immense potential for the advancement of novel materials that can absorb electromagnetic (EM) waves. This potential stems from their tailored structures, high porosity, and large specific surface areas. However, it is still a challenge to enhance the EM wave absorption performance of magnetic carbon-based absorbers obtained from MOFs by reasonably regulating the structure. Herein, CoFe-MOF-derived CoFe@C composites with flower-like structure are successfully obtained by solvothermal method and high temperature carbonization. The Co/Fe molar ratio can be adjusted to easily tune the microstructure and electromagnetic parameters of CoFe@C. Due to the synergistic effect between components and microstructure of CoFe@C, the best EM absorption characteristics can be obtained. Specifically, Co0.5Fe0.5@C displays the optimal reflection loss (RL) value of −54.0 dB at 1.8 mm when the Co/Fe molar ratio is 0.5:0.5. The EAB can reach 5.8 GHz at a matching thickness of 2.1 mm. The remarkable absorption performance of Co0.5Fe0.5@C is assigned to the synergistic effect of different loss mechanisms, such as interface polarization, conductive loss and magnetic loss, together with the strong attenuation capacity and good impedance matching. The study offers a reference for designing and fabricating flower-like structure magnetic carbon-based composites with remarkable EM wave absorption capabilities.

P-doped in the shell of Ni@WO3-δ nanocomposites induced electronic structure change for improving microwave absorption performance

In this work, we reported P-doped WO3-δ coated Ni (Ni@P-WO3-δ) nanocomposites prepared by the arc discharge method with a subsequent phosphorylation treatment, where the Ni@P-WO3-δ nanocomposites exhibited a tunable electromagnetic wave absorption (EMA) performances by the doping P into the surface shell WO3-δ compared with the Ni@WO3-δ. The experimental evidence combined with the theory calculation results based on First-principles revealed that the doping P into the WO3-δ endowed improvable electrical conductivity, resulting in higher conduction loss for the Ni@P-WO3-δ nanocomposites. Meanwhile, P doping causes more defects and distorted lattice for the WO3-δ shell, which enhances defect-induced polarization loss. As a result, enhanced conduction loss and polarization relaxation loss of the Ni@P-WO3-δ nanocomposites are dominant for improving EMA performance. Further, the study found that the EMA properties of the Ni@P-WO3-δ nanocomposites are related to P doping content and can be tailored efficiently by controlling the amount of P dopant source. Thus, the Ni@P-WO3-δ nanocomposites with appropriate P doping can optimize their balance between impedance matching and dielectric loss, achieving excellent microwave absorption performance. The minimum reflection loss (RL) value of the Ni@P-WO3-δ nanocomposites was − 55.62 dB, and the efficient absorption bandwidth achieved in 12.58 GHz, with a thickness rang of 1.61–5.00 mm. Therefore, this work confirms that doping engineering has a significant application for the design and synthesis of dielectric-typed microwave absorbers.

Facile constructing Ti3C2Tx/TiO2@C heterostructures for excellent microwave absorption properties

Optimizing and enhancing the performance of electromagnetic wave (EMW) absorption materials relies on the modification of their composition and structure through heterogeneous interface engineering. Ti3C2Tx’s high conductivity results in an impedance mismatch, which hinders efficient EMW absorption. Herein, a one–step catalytic chemical vapor deposition (CCVD) method is used to construct the Ti3C2Tx/TiO2@C heterogeneous structure. Upon annealing at 500 °C, amorphous carbon is uniformly deposited on the Ti3C2Tx surface, thereby incorporating the scale–like TiO2 generated during the process. The inclusion of the amorphous carbon layer and TiO2 reduces the substrate’s conductivity, achieving optimized impedance matching. Additionally, building heterogeneous interfaces between Ti3C2Tx, TiO2, and C enriches multiple loss mechanisms involving dipole and interfacial polarization, ultimately enabling optimal EMW absorption performance. The minimum reflection loss (RLmin) value of Ti3C2Tx/TiO2@C–500 is –53.12 dB when its thickness and frequency are 1.15 mm and 13.80 GHz, respectively. Moreover, thermal infrared imaging confirms that coatings fabricated using Ti3C2Tx/TiO2@C–500 demonstrate a favorable heat dissipation rate, validating its effectiveness in addressing the challenge of efficient heat dissipation in electronic devices. This study significantly contributes to the progress of two–dimensional (2D) materials, enabling high–performance EMW absorption and expanding their applications in complex scenarios.

Enhancement of microwave absorption performance of FeSiCr magnetic powder by dielectric polarization modulation

The Fe3O4@C@FeSiCr composite was successfully prepared by compounding flaky FeSiCr magnetic powder with an organo-metallic frameworks (MIL-88(Fe)), and then subjecting to carbonization heat treatment. The dielectric polarization characteristics is regulated by adjusting the heat treatment temperature. The absorbing performance is optimum when the carbonization heat treatment temperature is 700 °C, the minimum value of reflection loss (RLmin) is −35.71 dB at 5.68 GHz. The effective absorption bandwidth (RL ≤ −10 dB) of the composite material covers 4–16 GHz when the coating thickness is from 1.0 to 3.0 mm. This work provides an important value for the application of FeSi-based soft magnetic materials in the field of microwave absorption.

Composites of Co-Ti-Mn substituted M-type barium hexaferrite and CuO: Structural, optical, electromagnetic and X-band absorption for commercial applications

In this research, composites of M-type barium hexaferrite (BaFe12O19) substituted with Co-Ti-Mn and Copper oxide (CuO) have been prepared to mitigate electromagnetic pollution caused by cellphones (0.9–40 GHz) and 4G–5G networking technologies. X-ray diffraction (XRD), FTIR and transmission electron microscopy (TEM) were used to study structural and morphological analysis of synthesized composites. In the XRD analysis, the composite shows a pure phase of BaM hexaferrite and copper oxide, this was further confirmed by FTIR. Characteristic absorption bands of Co-Ti-Mn substituted BaM and CuO were observed at 260.9 cm−1, 265.2 cm−1 and 273.4 cm−1; these peaks suggest the formation of BaM and CuO phase. The optical and magnetic properties of synthesized samples were characterized by UV–visspectroscopy and Vibrating sample magnetometer (VSM). The UV-blue LED application is compatible with the band gap observed by UV–visspectroscopy. Hysteresis loops show that the magnetization (Ms), remnant magnetization (Mr) and coercivity (Hc) decreased with the increase of substitution (x). At room temperature, x = 0.10 (CTMC1) yields maximum values such Ms (35.84 emu/g), Mr ( 11.75 emu/g), and Hc (478.002 Oe). The complex permittivity and permeability were investigated in the X-band (8.2–12.4 GHz) using vector network analyzer (VNA). Composite with x = 0.15 (CTMC2) yielded an optimum value of reflection loss up to −35.79 dB at a matching frequency of 11.49 GHz and more than 90 % absorption bandwidth of 1.5 GHz. The results suggest that the synthesized composites have potential to be used as new generations of electromagnetic shielding materials.

Fabrication of MWCNTs/rGO/PPy ternary composites for excellent electromagnetic absorption

With the development of radar stealth technology and electronic communication technology, electromagnetic (EM) wave absorbing materials with lightweight and broad absorbing bandwidth are widely expected. In this study, the multi-walled carbon nanotubes (MWCNTs)/reduced graphene oxide (rGO)/polypyrrole (PPy) ternary composites were prepared by in-situ polymerization under hydrothermal conditions. The effects of carbon substrate of MWCNTs/rGO and the content of PPy on the microwave absorption (MWA) properties of the ternary composites and the corresponding attenuation mechanism were investigated. The results showed that MWCNTs and rGO nanosheets interweave together to form a relatively uniform micro-network structure with even wrapping of PPy on the surface of MWCNTs/rGO substrate. The adjustable amount of PPy optimizes the impedance matching and EM wave attenuation capacity. The composites achieve effective absorption bandwidth (EAB) of 4.6 GHz at 2.1 mm, and the minimum reflection loss (RLmin) value of −57 dB at 15.8 GHz. The multi-void network structures formed by MWCNTs and lamellar rGO and the interfacial polarization between MWCNTs/rGO composite carbon substrate and PPy can effectively decay EM wave absorption, thus improving the MWA performance of the composites. This work provides an effective reference for the application of multi-component carbon composites in the field of microwave absorption.

Urchin-like Fe3O4@C with core-shell structure modified 2D MXene for high-performance microwave absorption

As a typical two-dimensional material, Ti3C2Tx MXene has been considered a novel potential microwave-absorbing material because of its outstanding metallic-like conductivity and rich surface functional groups. Unfortunately, the microwave absorption performance is constrained by its intrinsic high conductivity and single loss mechanism. Herein, an urchin-like Fe3O4@C hollow sphere with core-shell structure was built by hydrothermal and annealing processes, which was subsequently used to modify MXene via electrostatic self-assembly. The Fe3O4@C/Ti3C2Tx hybrid with 30 wt% Fe3O4@C loading displayed a minimum reflection loss (RLmin) value of –64.0 dB at a thickness of 3.32 mm and a maximum efficient absorption bandwidth (EABmax) of 3.02 GHz at 3.24 mm. The exceptional microwave absorption performance is mainly attributed to the impedance matching brought about by the special urchin-like core-shell structure of Fe3O4@C, as well as the rich interfacial polarization and multiple reflections/scatterings. This work offers a novel idea for the design of efficient MXene-based microwave-absorbing materials.

Carbonization of Ni@SiC@C nanoparticles reinforced PAN nanofibers for adjustable impedance matching

Achieving a broad bandwidth and efficient absorption of electromagnetic wave absorption materials remains a significant challenge, especially when considering electromagnetic pollution protection. One-dimensional carbon nanofibers with a three-dimensional network structure have been extensively studied to address this need. However, the high permittivity of carbon nanofibers results in a strong impedance mismatch with free space. In this work, we successfully dispersed double-shell Ni@SiC@C nanoparticles into one-dimensional carbon nanofibers (Ni@SiC@C CNFs) using electrospinning and heat treatment. We extensively explored the effect of carbonization temperature on the impedance matching and magnetic-dielectric loss for electromagnetic wave. The presence of rich interfaces from the double-shell nanoparticles and defects from N-doping optimizes the impedance matching of the composites. The exceptional electromagnetic wave absorption properties of the Ni@SiC@C CNFs are attributed to the synergistic effect between the three-dimensional conductive network, the interface electronic engineering induced by the sensibly loaded double-shell nanoparticles, and the multiple reflections, especially at a carbonization temperature of 600 ℃. The achieved minimum reflection loss value has been measured at an outstanding −53.27 dB, coupled with a remarkable absorption bandwidth that spans from 2.53 GHz to 18.00 GHz (15.47 GHz) across various thicknesses. These findings underscore the potential of the meticulously engineered Ni@SiC@C CNFs as highly promising candidates for efficient and broadband electromagnetic wave absorption applications.

3D Honeycomb Fe/MXene Derived from Prussian Blue Microcubes with a Tunable Structure for Efficient Low-Frequency and Flexible Electromagnetic Absorbers.

The unique layered structure and high conductivity of MXene materials make them highly promising for microwave absorption. However, the finite loss mechanism and severe agglomeration present challenging obstacles for ideal microwave absorbers, which could be effectively improved by constructing a three-dimensional (3D) porous structure. This study reports a 3D honeycomb MXene using a straightforward template method. The 3D MXene framework offers ample cavities to anchor the Prussian blue microcubes and their derivatives including Fe microboxes and Fe clusters by a simple annealing process. Based on the superiority of the 3D honeycomb architecture and magnetic-dielectric synergistic effects, the Fe/MXene absorbers demonstrate outstanding microwave absorption capabilities with the optimum reflection loss value of -40.3 dB at 2.00 mm in the low-frequency range from 4.2 to 5.6 GHz. The absorber also manifests superior radar wave attenuation by finite element analysis and exhibits great potential to be a flexible and thermal insulation material in a wide range of temperatures. This work proposes a useful reference for the design of 3D MXene-based porous architectures, and the synergistic magnetic-dielectric strategy further expands the potential of MXene-based absorbers, enabling them to be used as flexible and highly efficient microwave absorbers.

FeCo-BN magnetic composite membrane prepared via an atomized aerosol process for electromagnetic wave absorption and thermal management

Soft magnetic materials with high magnetic flux density and low coercive force exhibit a significant reflection loss, generating effective electromagnetic waves (EMWs) in the S-band to K-band frequency range. However, the limited complex permeabilities of commonly available soft magnetic materials at higher frequencies restrict their EMW absorption bandwidth. Here, we present a new class of thin EMW absorbing composite membrane comprising shape-modulated soft magnetic FeCo and thermally conductive boron nitride (BN) particles. The designed chemical process facilitates a one-step synthesis of composites with diverse structures, including spheres, cubes, and hollows, without requiring any shape-controlling additives. The FeCo/BN composite membrane, which was only 1.5 mm thick, demonstrated enhanced permeability and effective impedance matching, resulting in a high reflection loss value of − 46.4 dB at 11.3 GHz. Furthermore, the incorporation of BN nanoparticles with thermal conductivity enabled the thermal dissipation of the absorbed EMW energy. This study comprehensively investigated the correlation between shape modulation and complex permeability, which can provide valuable insights for the development of advanced EMW-absorbing materials.

Development of high-efficiency tri-layer microwave absorbing materials based on SrMeFe11O19 hexaferrite

Recently, electronic devices have become an essential part of daily life as well as national defense. Along with their use and convenience, the electromagnetic (EM) radiation generated by them is a new pollutant that should be mitigated. SrMeFe11O19 (Me = Fe, Zn, and Co) samples were successfully prepared with the expectation of being high-efficiency microwave absorbers. Samples were crystallized into the M-type hexaferrite phase with an average crystallite size of 24–26 nm and an average grain size in the range of 160–220 nm. The change in doping element also modified static magnetic and EM properties, leading to their differences in microwave absorption properties. SrFeFe11O19 and SrCoFe11O19 samples showed reflection loss (RL) values of –25.7 and –15.9 dB for the same thickness of 5.50 mm, respectively. Meanwhile, the SrZnFe11O19 sample had RL = –25.5 and –28.8 dB for thicknesses of 1.50 mm and 5.00 mm, respectively. The good microwave dissipation features of these samples could be attributed to good impedance matching, excellent attenuation constants, and a large number of dynamic processes of dielectric loss. The tri-layer MAMs fabricated from SrMeFe11O19 samples even showed more impressive microwave absorption performance with higher RL values for lower matching thicknesses. SrFeFe11O19/SrZnFe11O19/SrCoFe11O19 and SrCoFe11O19/SrZnFe11O19/SrFeFe11O19 with layer thicknesses of 2/2/1 (mm) could reach RL values of –39.4 and –48.0 dB, respectively. Meanwhile, tri-layer absorbers of SrFeFe11O19/SrCoFe11O19/SrZnFe11O19 and SrCoFe11O19/SrFeFe11O19/SrZnFe11O19 with layer thicknesses of 1/1/3 (mm) could reach RL values of –44.9 and –46.3 dB, respectively. These excellent RL values could be attributed to the synergistic effects of three layers, which provided an easy approach to improving the microwave absorption performances of as-prepared materials. These results would be beneficial for practical applications, such as covering weapons with different types of microwave-absorbing paint to make them invisible on enemy radars.

Fabrication and electromagnetic wave absorbing properties of the (Hf0.25Zr0.25Nb0.25Ta0.25)C high-entropy ceramics

High-entropy engineering is an effective strategy for developing high properties of the transition-metal carbides, including their mechanical and functional performance, owing to its high-entropy effect, sluggish diffusion effect, sever lattice distortion, and cocktail effect. In this study, a single-phase high-entropy ceramic with a rock-salt crystal structure (Hf0.25Zr0.25Nb0.25Ta0.25)C was fabricated through a solid-phase reaction at 2200 °C. The as-obtained, high-entropy ceramic powder exhibited high efficiency electromagnetic-wave-absorption capability. The minimum reflection loss (RL) value reached approximately − 64.38 dB at 16 GHz with a thickness of 4.43 mm. By tuning the thickness of the sample, the total effective absorption bandwidth (RL ≤ −10 dB) was ∼ 4.46 GHz, almost covering the Ku band. The excellent microwave absorption performance was ascribed to the high-entropy effect of the strong dielectric loss of the material as well as the proper impedance matching degree. Thus, high-entropy engineering is expected to be a promising route for developing microwave absorbers with excellent absorption capability.

Electromagnetic wave absorption properties of Ni0.5Zn0.5Fe2O4–BaTiO3–epoxy composites

Composites consisting of ferrimagnetic spinel ferrite Ni0.5Zn0.5Fe2O4 (ZNF) and ferroelectric BaTiO3 (BT) powders embedded in epoxy (10 wt%) were synthesized and analyzed for their electromagnetic (EM) wave absorption properties. The ZNF and BT powders were combined in weight ratios of 1-x: x, where x = 0, 0.1, 0.2, 0.3, 0.4, and 1.0. With increasing x, the height of the complex permittivity (ε′ and ε″) spectra increased, while the height of the complex permeability (μ′ and μ″) spectra gradually decreased. The reflection loss (RL) value, indicative of EM absorption efficiency, was calculated using measured ε′, ε″, μ′, and μ″ data. Apart from the BT–epoxy sample (x = 1.0), which exhibited no magnetic loss mechanisms, the EM wave absorption characteristics in the NZF-BT-epoxy composites were predominantly influenced by magnetic loss mechanisms, as reflected in the μ″ values. The incorporation of BT modified the impedance matching conditions, causing the frequency at which maximum EM wave absorption indicated by the minimum RL (RLmin) occurs to shift to lower frequencies. The most remarkable EM wave absorption performance was observed for the sample with x = 0.4, where RLmin reached −70 dB. Notably, the samples with x values ranging from 0 to 0.4 demonstrated outstanding EM wave absorption capabilities within the radar frequency range of L and S-bands (1–4 GHz). Furthermore, the EM wave absorption bandwidth (Δf), representing the frequency range where RL < -10 dB, was 8.3 GHz (4.5–12.8 GHz) for the x = 0 sample. However, this bandwidth decreased to 2.6 GHz (5.0–7.6 GHz) for the x = 0.4 sample. Although the addition of BT led to a reduction in the EM wave absorption bandwidth compared to the NZF–epoxy composite (x = 0), it enabled the tuning of the absorption band towards lower frequencies, particularly emphasizing excellent EM wave absorption in the L-band.

A Multifunctional Composites Membrane Aiming at Flexible Sensor and Ultrabroadband Electromagnetic Wave Absorption

A study was conducted on SEBS-based composites granules containing different volume fractions of carbon nanotubes (CNTs) using a twin extruder and hot pressing procedure to produce a SEBS/CNTs membrane. SEM was used to study the membrane s morphology, revealing a 3-D network of CNTs. TGA was utilized to measure the degradation temperature of SEBS polymer and determine the actual volume fraction of CNTs. The mechanical properties, electrical conductivity, and cyclic strain sensing behavior of the SEBS/CNTs were investigated using a tensile testing machine and pico-ammeter. Mathematical models were used to fit the measured data, demonstrating the strain sensing potential of the composites. The composite membrane with 2 wt.% of CNTs exhibited superior electromagnetic wave absorption performance with a minimum reflection loss (RLmin) value. This study provides promising opportunities for the development of advanced materials.

Construction of heterogeneous interfaces on Ti3AlC2 micro-particles via surface dotting liquid metal to enhance electromagnetic wave absorption performance

MAX phase (Ti3AlC2) and its derivative MXene has brought the development of electromagnetic shielding and absorbing materials into a new stage. Herein, the MAX phase was creatively used to prepare microwave absorbing materials. The Ti3AlC2/liquid metal (TLM) hybrid micro-particles with multiple heterogeneous interfaces were prepared by simply liquid metal (LM) dotting on Ti3AlC2 surface and annealing at high temperature. When the mass fraction of liquid metal is 35 wt% and the sample is annealed for 2 h, the reflection loss (RL) value is -36.07 dB, and the maximum effective absorption bandwidth (EAB) is 7.2 GHz at a thickness of 2.5 mm. The electromagnetic wave loss ability of the TLM hybrid micro-particles comes from its special heterostructures, including multiple interfaces and defects caused by liquid metal etching.

The synthesis of porous carbon material derived from coal liquefied residue and its electromagnetic wave absorption

To solve the problem of electromagnetic radiation pollution, it is necessary to develop an economic and environmentally friendly way of producing efficient electromagnetic wave absorbing materials. Carbon-based materials have attracted much attention but finding suitable precursors and ways of producing defined pore structures are still challenges. This work reported a facile method to produce porous carbon by using coal liquefaction oil residue as carbon source. The produced porous skeletons should be attributed to the generated Na2CO3 templates and CO2 gas during the thermal decomposition process of NaHCO3 templates. It is found that changing the pore structure not only adjusts the impedance matching of the material but also increases the length of the electromagnetic wave transmission path and increases dielectric loss. With the combined effect of multiple electromagnetic loss mechanisms, the material has excellent electromagnetic wave absorption. Specifically, with a filler loading of only 10% and a thickness of 2.03 mm, the obtained carbon material has a reflection loss value of −60.28 dB and an effective absorption bandwidth of 5.36 GHz. This work provides a new approach to developing high-performance carbon-based electromagnetic wave absorbing materials and also offers a new idea for the high value-added use of coal liquefaction oil residue products.

Dielectric, structural and absorption properties of Mg2+ substituted Ba2Zn2X hexa-ferrites for microwave devices and applications

Electromagnetic devices have hazardous effects to the environment in the form of pollution. Materials having higher reflection loss and good absorption properties can overcome this pollution. This study synthesizes the Ba2Zn2-xMgxFe28O46 (x = 0.0, 0.1, 0.2, 0.3, and 0.4) using sol-gel method. The higher value of reflection loss of prepared samples was successfully achieved which can be used for absorption applications. X-ray diffraction patterns show a x-type hexagonal phase with crystallite's size ranged from 18 to 43 nm. All the vibrational bands shifted by changing the substitution in all compositions. Six distinct peaks in Raman spectra are located at positions 62, 174, 332, 408, 525, and 673 because of the molecules' phonon vibrations. The peaks were found in the XPS spectrum mode range of 1350-1 eV. All substitutions had a high dielectric constant, dielectric loss, and tan loss at low frequencies, but this value decreased as the frequency increased. The Cole-Cole plots and complex impedance spectroscopy revealed that grain boundary contributed for most dielectric responses. For these materials, cole-cole plots showed a complete semicircle, demonstrating the grain boundary resistance within the samples. Mg substituted Zn-X ferrite with RL of −69.3, and −62.0 dB are found to have excellent microwave absorption properties. The prepared samples could be used for absorption and super-capacitor applications.

Hierarchical-Bioinspired MOFs Enhanced Electromagnetic Wave Absorption.

Proteins exhibit complex and diverse multi-dimensional structures, along with a wide range of functional groups capable of binding metal ions. By harnessing the unique characteristics of proteins, it is possible to enhance the synthesis of metal-organic frameworks (MOFs) and modify their morphology. Here, the utilization of biomineralized bovine serum albumin (BSA) protein as a template for synthesizing Mil-100 with superior microwave absorption (MA) properties is investigated. The multi-dimensional structure and abundant functional groups of biomineralized BSA protein make it an ideal candidate for guiding the synthesis of Mil-100 with intricate network structures. The BSA@Mil-100 synthesized using this method exhibits exceptional uniformity and monodispersity of nanocrystals. The findings suggest that the BSA protein template significantly influences the regulation of nanocrystal and microstructure formation of Mil-100, resulting in a highly uniform and monodisperse structure. Notably, the synthesized 2-BSA@Mil-100 demonstrates a high reflection loss value of -58dB at 8.85GHz, along with a maximum effective absorption bandwidth value of 6.79GHz, spanning from 6.01 to 12.8GHz. Overall, this study highlights the potential of utilizing BSA protein as a template for MOF synthesis, offering an effective strategy for the design and development of high-performance MA materials.