Electromagnetic Microwave Absorption Properties Research Articles

Investigation of the Effect of Alloying Element Equilibrium Relationship on the Electromagnetic Microwave Absorption Properties of Nano FeNi Magnetic Particles

AbstractIn order to effectively comprehend the impact of alloying element equilibrium relationship of binary nano‐magnetic particles on their electromagnetic wave absorption performance, four sets of binary nano FeNi magnetic particles with Fe:Ni alloy ratios of 2:8, 4:6, 6:4, and 8:2 were prepared with liquid‐phase reduction and the microstructure, static magnetic properties, and electromagnetic wave absorption performance of the particles were studied. The results show that the nano FeNi magnetic particles exhibit a spherical geometric structure, with a decrease in crystallinity as the Fe:Ni alloy ratio increases. The remanence and coercivity initially increase and then decrease with the increased Fe:Ni alloy ratio, with a 270 % decrease in saturation magnetization intensity as the alloy ratio changes from 2:8 to 8:2. With the increase in the Fe:Ni alloy ratio, the real and imaginary parts of the complex permittivity exhibit a decreasing trend, while the real part of the magnetic permeability decreases with increasing frequency. Aside from the 8:2 Fe:Ni alloy ratio, significant polarization relaxation losses were observed in the prepared magnetic particles, with eddy current losses was not the main mechanism of magnetic losses. The attenuation constant shows a peak at high frequencies, and the impedance matching performance increases with the increase in the Fe:Ni alloy ratio. When the Fe:Ni alloy ratio changes from 2:8 to 8:2, the minimum reflection loss decreased by 3340 %, and at a thickness of 2.1 mm and a frequency of 12 GHz, the FeNi alloy particles with a ratio of 2:8 exhibited a minimum reflection loss of −17.2 dB with an effective absorption bandwidth of 1.92 GHz.

Dual-modified catalytic core-shell structure biomass carbon cotton fiber extends broadband electromagnetic waves absorption applications

Using vacuum impregnation method, the biomass carbon cotton fiber material was modified with polymer-derived SiCN ceramics and different Ni sources to successfully prepare the composite material. The electromagnetic microwave absorption properties of the material in the range of 2–18 GHz and the catalytic effect of different nickel sources were studied. The material modified by nickel nitrate hexahydrate forms a carbon fiber coated structure, improves impedance matching, enriches heterostructures, and increases electromagnetic synergistic loss, effectively enhancing the effective absorption bandwidth (EAB) reaches 4.72 GHz, the minimum reflection loss (RLmin) is −47.79 dB, and the thickness is only 1.32 mm. The results of CST show that the radar cross section of CFPN-2 material is −36.86 dB m2, and it has obvious effect of optimizing impedance matching.

Organosilane waste-derived SiCnws/SiOC composites with enhanced electromagnetic wave absorption performance

SiCnws/SiOC nanowires composites with a 3D network structure, exhibiting enhanced electromagnetic microwave absorption properties, were synthesized using carbothermal reduction. The solid precursor, organosilane waste, was employed, enabling cost-effective and environmentally friendly production. The structure and morphology of SiCnws/SiOC nanowires composites were extensively investigated by XRD, SEM, TEM, XPS spectra, and Raman spectra. Moreover, the composite demonstrated superior electromagnetic wave absorbing properties, including wide effective absorption bandwidth (EAB) of 2.73 GHz, strong minimum reflection loss (RLmin) of −52.66 dB, and thin thickness of 2.40 mm. These excellent electromagnetic wave attenuation properties stem from the synergistic strategy of dielectric and conductive losses, resulting from the unique 3D network heterostructural architecture. This work not only offers improved EMW absorption solutions but also contributes to waste recycling and resource recovery.

Structural, Optical, and Electromagnetic Microwave Absorption Properties of Bael Leaves: A Simple Approach to Investigate Microwave Absorption Properties with 3D Printed PLA Tubes

Structural, Optical, and Electromagnetic Microwave Absorption Properties of Bael Leaves: A Simple Approach to Investigate Microwave Absorption Properties with 3D Printed PLA Tubes

Enhanced electromagnetic microwave absorption properties of SiCN(Fe) ceramics produced by additive manufacturing via in-situ reaction of ferrocene

SiCN(Fe) ceramics with excellent electromagnetic wave (EMW) absorption performance were successfully prepared from a preceramic polymer doped with ferrocene. Additive manufacturing (Digital Light Processing), providing enhanced structural design ability, was employed to fabricate samples with complex architectures. During pyrolysis, ferrocene catalyzed the in-situ formation of a large amount of turbostratic carbon, graphite and SiC nanosized phases, which formed carrier channels in the electromagnetic field and increased the conductivity loss. Meanwhile, it also increased the dipole polarization, interface polarization and the dielectric properties of the material, which finally enhanced the EMW absorption capacity of SiCN(Fe) ceramics. When containing 0.5 wt% ferrocene, the material showed good performance with EAB 4.57 GHz at 1.30 mm, and RLmin −61.34 dB at 2.22 mm. The RLmin of 3D-SiCN-0.5 ceramics was −6 dB, and the RL of the X-band was lower than −4 dB at 2 mm.

Preparation of polyaniline/sludge fly ash with improved electromagnetic microwave absorption performance

Transforming solid waste into a functional material is a vital technology that protects the environment and gets high value-added products. The polyaniline (PANI) and sludge fly ash (SFA) composites were fabricated by a facile interfacial polymerization in this study. The structure, composition and morphology of PANI/SFA were investigated in detail. The results showed that with increasing the content of SFA, the electromagnetic microwave absorption properties of PANI/SFA composites first increase then decrease, and it almost stays the same in the end. When the content of SFA is 0.4 g, the composite has an optimal reflection loss of −54.11 dB (thickness of 2.82 mm) at 10.00 GHz and a broad effective absorption bandwidth of 4.08 GHz (RL < −10 dB). The excellent electromagnetic microwave absorption properties are attributed to the synergistic effect of dielectric loss and magnetic loss. These electromagnetic microwave absorbers have potential application prospects.

A facile fabrication and high-performance electromagnetic microwave absorption of ZnO nanoparticles

Abstract Electromagnetic microwave absorption materials are highly desired in electronics application in recent years. Herein, ZnO nanoparticles were successfully fabricated via sonochemical process using zinc acetate dihydrate (Zn(CH3COO)2·2H2O) and ammonia water as raw materials. The as-prepared ZnO nanoparticles annealed at 120 °C for 8 h had significantly enhanced electromagnetic microwave absorption properties. This could be attributed to dielectric loss originating from interface polarization, and dipole polarization due to oxygen vacancy defects. The minimum reflection coefficient reached −37.7 dB at 8.96 GHz with a small thickness of 2.1 mm. This work provides a new idea of preparing electromagnetic microwave absorption materials (MAMs) with strong absorbing properties.

One-Pot Synthesis of Doped-Polypyrrole/Fe₃O₄ Nanosphere Composites and Their Microwave Absorption Performance.

Doped-polypyrrole/Fe₃O₄ (D-PPy/Fe₃O₄) nanospheres were successfully synthesized via a onepot process. In this process, polyvinyl alcohol (PVA) plays an important role in the construction of polypyrrole nanoparticles, and Fe3+ ions were the oxidant and the only raw resource of Fe₃O₄. The morphology, magnetic properties, and electromagnetic microwave absorption properties of D-PPy/Fe₃O₄ composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), a vibrating sample magnetometer (VSM) and a vector network analyser (VNA). The results indicate that D-PPy/Fe₃O₄ nanospheres become more disperse and regular due to the addition of PVA. The influence of the mass ratio of PVA to pyrrole on the microwave absorption performance of the D-PPy/Fe₃O₄ composites was also investigated. When the mass ratio of PVA/pyrrole was 0.75:1, the minimum reflection loss (RLmin) value of the D-PPy/Fe₃O₄ composites reached -41.3 dB at 7.7 GHz with a thickness of 3.0 mm. The microwave interference cancellation of interface reflection, nature resonance loss and current loss are the main reasons for the loss of electromagnetic microwaves for the as-prepared D-PPy/Fe₃O₄ composites.

Electrostatic self-assembly synthesis of ZnFe2O4 quantum dots (ZnFe2O4@C) and electromagnetic microwave absorption

Making effective usage of quantum size effect is a foregrounded strategy to design and fabricate excellent electromagnetic microwave absorption materials. In this research, ZnFe2O4 quantum dots were coated by hybrid amorphous carbon to form a sea islands structure by a facile electrostatic self-assembly synthetic technology. Simultaneously, the rejection of heterogeneous charges leads to the formation of quantum dots, by which the quantum size effects on dielectric and magnetic characteristic were investigated. Consequently, multiple hetero-interface and interfacial polarization was originated from polycrystalline feature of ZnFe2O4 with spinel and inverse spinel structures. In particular, the electromagnetic microwave absorption properties of ZnFe2O4 were greatly optimized, as the minimized reflection loss reached −40.68 dB at the frequency 11.44 GHz and thickness 2.5 mm, while the effective bandwidth corresponding was 3.66 GHz (from 9.87 to 13.52 GHz). The largest effective bandwidth was 4.16 GHz (from 8.08 to 12.24 GHz) with a thickness of 3 mm. It is suggested that high performance of microwave absorption of ZnFe2O4 quantum dots was well guided by the optimized impedance matching and attenuation constants.

Laminated microwave absorbers of A-site cation deficiency perovskite La0.8FeO3 doped at hybrid RGO carbon

Laminated hybrid carbon of amorphous carbon and RGO (reduced graphene oxide) perovskite composite, La0.8FeO3/C/RGO-BD, was fabricated by a simple method in one pot. The amorphous carbon was carbonized from d-glucose which also played a role as reducing agent. RGO provided a great condition for the formation of conductive loops. While A-site cation deficiency perovskite La0.8FeO3 doped at carbon nanosheets was induced to adjust the comprehensive microwave absorption properties. The phase and composition characteristics were studied by X-ray diffraction patterns (XRD), Raman and FT-IR spectrums and X-ray photoelectron spectroscopy (XPS), especially the confirmation of the existence of A-site cation deficiency and Oxygen vacancy. The morphology and microstructure of samples were visualized by a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The electromagnetic microwave absorption properties were further studied, as the reflection loss of La0.8FeO3/C/RGO-BD reached −42.69 dB at 8.08 GHz with an effective band 2.72 GHz at 3.15 mm. And the excellent microwave absorption properties were confirmed by impedance matching, one quarter-wavelength theory, Debye relaxation polarization theory and eddy current loss.

Development of Fe/Fe3O4@C composite with excellent electromagnetic absorption performance

In this work, core-shell shaped Fe3O4@C composites have been firstly prepared by in-situ polymerization of phenolic resin on the surface of Fe3O4 and subsequent high-temperature carbonization. The core of Fe3O4 nanoparticles can be partial or totally reduced to metallic Fe in a N2/H2 atmosphere and resulted in Fe3O4-Fe@C and Fe@C products. These as-prepared Fe-Fe3O4@C and Fe@C products are analyzed by X-ray diffraction (XRD), and transmission electron microscopy (TEM). Furthermore, the electromagnetic microwave absorption properties of the core-shell nanocomposites are investigated in terms of the theory of transmission lines. Compared with pristine Fe3O4, Fe3O4@C and Fe@C, the Fe3O4-Fe@C ternary heterostructures exhibit the outstanding microwave absorption properties. The minimum reflection loss (RL) of −29.3 dB can be observed at the frequency of 12.6 GHz with the thickness of 3.9 mm. The bandwidth (RL ≤ −10 dB) can be monitored in the frequency of 3.6–18 GHz with the thickness of 1.5–4.0 mm. The excellent absorption is attributed to the synergistic effect of dielectric and magnetic loss, multiple interfacial polarization resonances, and good impedance match.

Enhanced microwave absorption properties of graphite nanoflakes by coating hexagonal boron nitride nanocrystals

We report herein the synthesis of a novel hexagonal boron nitride nanocrystal/graphite nanoflake (h-BNNC/GNF) composite through a wet-chemistry coating of graphite nanoflakes and subsequent in-situ thermal treatment process. The characterization results of X-ray diffraction, scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectrum, and X-ray photoelectron spectroscopy demonstrate that h-BNNCs with diameter of tens of nanometers are highly crystallized and anchored on the surfaces of graphite nanoflakes without obvious aggregation. The minimum reflection loss (RL) value of the h-BNNC/GNF based absorbers could reach −32.38dB (>99.99% attenuation) with the absorber thickness of 2.0mm. This result is superior to the other graphite based and some dielectric loss microwave absorption materials recently reported. Moreover, the frequency range where the RL is less than −10dB is 3.49–17.28GHz with the corresponding thickness of 5.0–1.5mm. This reveals a better electromagnetic microwave absorption performance of h-BNNC/GNFs from the X-band to the Ku-band. The remarkable enhancement of the electromagnetic microwave absorption properties of h-BNNC/GNFs can be assigned to the increase of multiple scattering, interface polarization as well as the improvement of the electromagnetic impedance matching of graphite nanoflakes after being coated with h-BNNCs.

Electromagnetic microwave absorption properties of carbon nanocoils/tissue

An economic electromagnetic wave absorber with carbon nanocoils (CNCs)/tissue and paraffin has been successfully synthesized and exhibits excellent microwave absorption property. The CNCs/tissue composite was obtained by growing spring-like CNCs on the tissue substrate with Fe2(SO4)3/SnCl2 catalyst in a chemical vapor deposition method. It is found that the absorbers containing 10wt% and 20wt% CNCs/tissue show strong microwave absorption in a frequency range of 2–18GHz. For the composite with 10wt% CNCs/tissue, the maximum reflection loss (RL) of −46.36dB at 14.72GHz and the bandwidths of 7.44 and 5.68GHz respectively corresponding to RL below −10 and −20dB can be obtained. In addition, the composite with 20wt% CNCs/tissue can also gain broad bandwidth corresponding to reflection loss below −10dB, which is as high as 7.52GHz. It is revealed that the composite with 10wt% CNCs/tissue owns suitable real part of permittivity, which helps to obtain better impedance match and lower reflection coefficient to enhance the absorption of electromagnetic wave.

Antioxidation and electromagnetic properties of Co-coated hollow carbonyl iron particles by electroless plating method

Co-coated hollow carbonyl iron particles were prepared by a method combining pitting corrosion and electroless plating. The comparison of morphology from images of SEM, phase composition, magnetic property and apparent density of initial and processed particles before and after heat treatment demonstrated the low density and high antioxidation properties after processing, which proved Co coating acts as a protection layer. The complex permittivity and complex permeability of raw carbonyl iron, hollow carbonyl iron and Co-coated hollow carbonyl iron particles were measured and the mechanisms of varying electromagnetic parameters were analyzed. And the electromagnetic microwave absorption properties of raw carbonyl iron, hollow carbonyl iron and Co-coated hollow carbonyl iron particles were investigated in the frequencies during 2–18 GHz. The band width below −10 dB could reach 4 GHz and the minimum of reflection loss value could reach to −19.5 dB for the Co-coated hollow carbonyl iron particles, which can maintain a good microwave absorption property.

Lanthanum and Neodymium Doped Barium Ferrite-TiO₂/MCNTs/poly(3-methyl thiophene) Composites with Nest Structures: Preparation, Characterization and Electromagnetic Microwave Absorption Properties.

We report herein the synthesis of a novel nest structured electromagnetic composite through in-situ chemical polymerization of 3-methyl thiophene (3MT) in the presence of the BaFe11.92(LaNd)0.04O19-TiO2 (BFTO) nanoparticles and MCNTs. As an absorbing material, the BFTO/MCNTs/P3MT/wax composites were prepared at various loadings of BFTO/MCNTs/P3MT (0.2:0.10:1.0 ~ 0.2:0.30:1.0), and they exhibited strong microwave absorption properties in the range of 1.0–18 GHz. When the loading of BFTO/MCNTs/P3MT is 0.2:0.30:1.0, the composite has a strongest absorbing peak at 11.04 GHz, and achieves a maximum absorbing value of −21.56 dB. The absorbing peak position moves to higher frequencies with the increase of MCNTs content. The mechanism for microwave absorption of these composites has been explained in detail.

Electromagnetic Microwave Absorption Properties of a Fine Structure Formed from the Sm&lt;SUB&gt;&lt;B&gt;2&lt;/B&gt;&lt;/SUB&gt;Fe&lt;SUB&gt;&lt;B&gt;17&lt;/B&gt;&lt;/SUB&gt; Compound after Disproportionation in Air or Nitrogen

It was reported in our previous papers that the disproportionation reaction of the Sm2Fe17 compound in hydrogen can be used to prepare fine, soft-magnetic powders for use in electromagnetic wave absorbers. In this study, the microstructure and electromagnetic wave absorption properties in the GHz frequency range of Sm2Fe17 powders, disproportionated in air or nitrogen atmospheres, were investigated. A fine α-Fe structure, of sub-micron order size, is formed from the Sm2Fe17 compound after disproportionation in either air or nitrogen. In the case of disproportionation in air, the powder treated at 423–573 K was in a α-Fe/SmO two-phase state. While in the case of disproportionation in nitrogen, the powder treated at 923 K showed α-Fe/SmN two-phase state; this powder then had to be heated at 423–523 K in air in order to oxidize the SmN phase. Epoxy-resin composite samples were made from these powders, and their electromagnetic wave absorption properties were measured. It was found that the sample disproportionated at 923 K for 2 hours in a nitrogen gas flow, milled for 30 minutes and oxidized at 523 K for 2 hours in air, exhibited the best absorption properties. The R.L. value was under −20 dB in the frequency range 1.2 to 2.3 GHz, when the absorber thickness was between 7.2 to 4.2 mm. Therefore, compared with a carbonyl-iron/resin composite (which had the same Fe content), the absorber was 30% thinner.

Barium M-type Ferrite as an Electromagnetic Microwave Absorber in the GHz Range

The electromagnetic microwave absorption properties of Barium M-type ferrite, in which Fe3+ was substituted by (Ti0.5Mn0.5)3+, were investigated in the GHz frequency range. The anisotropy field (HA) of Barium M-type ferrite can be changed by varying the Ti0.5Mn0.5 content, which enables the natural resonance frequency (fr) to be controlled, in the range 48 GHz to 8 GHz. BaFe12−x(Ti0.5Mn0.5)xO19 sintered ferrites with compositions x=2.5 to 5 exhibited good microwave absorption properties, with minimum reflection losses (R.L.) less than −20 dB in 1 to 20 GHz frequency range, for matching thicknesses (dm) of 0.5 to 3.8 mm. BaFe12−x(Ti0.5Mn0.5)xO19 ferrite-resin composites with 70 mass% ferrite, exhibited wide bandwidths with R.L.<−20 dB. In particular, the composite samples with compositions x=3 and x=4 had wide bandwidths of 14.1 to ∼20 GHz and 7.4 to 12.0 GHz, for matching thicknesses of 1.6 mm and 2.7 mm, respectively. These matching thicknesses were smaller than for conventional spinel ferrites. It may be concluded that Barium M-type ferrite is a good candidate for a thin electromagnetic microwave absorber in the GHz range. This is the first study to show that it is possible to use the natural resonance of M-type ferrite for the absorption of microwave radiation.