Reflection Loss Peak Research Articles

Hierarchical manganese sillenite Bi12MnO20 microparticles assembled by nanocubes with microwave absorption enhancement

Pure manganese sillenite (Bi12MnO20) microparticles with average sizes of 11.5–16.8 μm were prepared via an oxidation-precipitation method assisted by microwave-heating. Their microstructures are characterized by the shapes of single or multiple intersecting tetrahedrons and the massive nanocubes in ordered arrays on each tetrahedron surface. Such hierarchical Bi12MnO20 microparticles have not been reported so far, while their growth mechanisms may include the formation of active centers, the selective nucleation on active center surfaces and the growth of nanocubes along certain orientations. In electromagnetic determination, noticeable resonances both in permittivity and permeability were revealed beyond relaxations. A cone-like reflection loss peak was obtained with the minimum value of −39.1 dB and a broad effective microwave absorption bandwidth covering 12.7–14.6 GHz. Moreover, the reflection loss peak stagnates at the same frequency regardless of the absorbent thickness variations, suggesting a high performance in microwave attenuation.

Bi-phase metallic cobalt with efficient broadband absorption in X and Ku bands

Broadband and lightweight microwave absorbers have gained considerable research interest in overcoming electromagnetic interference pollution. Here, mixture of two phase (fcc and hcp) metallic cobalt powders with broadband absorption was synthesized through solvothermal method using ethylene glycol as the reducing agent. The effect of NaOH content on the structure and morphology of the prepared Co powders is investigated by X-ray diffraction and field-emission scanning electron microscopy. Ring samples of 7.00/3.04 mm of out/inner diameter were prepared with paraffin for microwave absorption testing by vector network analyzer. It was observed that the increase of NaOH content caused a relative higher generation of hcp-Co phase and formation of irregular microspheres. The reflection loss (RL) peak and effective absorbing bandwidth (EABW, RL ≤ − 10 dB) shifted towards lower frequency when the sample thickness increased from 1.00 to 3.00 mm with EABW covering almost all the C, X and Ku bands (4–18 GHz). The bi-phase Co prepared in a low base solution exhibited enhanced microwave absorption properties. The width of largest EABW has reached 6.33 GHz covering partial Ku band and almost all the X band with optimal RL of − 56.95 dB at a sample thickness of only 1.85 mm, which is superior to EABW of Co crystals reported earlier. We proposed that such a wide EABW is due to the fact of Z values closed to 1.0 (0.8 ≤ |Z| ≤ 1.2) at almost the whole frequency range. This indicates that the prepared bi-phase Co powders are excellent microwave absorbers with large bandwidth, have good prospects.

Electromagnetic Wave Absorption Properties of La-Doped Strontium M-Type Hexagonal Ferrite in a 18–40 GHz Frequency Range

This article examines the performance of the M-type lanthanum-doped strontium hexaferrite with general formula Sr1–yLayFe12O19 (y = 0.00, 0.10, 0.15, 0.20 and 0.25) as microwave absorbing materials in a 18–40 GHz frequency range. All the synthesized ferrites exhibited minimum reflection loss (RL) peaks with absorption greater than 90%. The multi-resonance imaginary part of complex permittivity (ɛ′′) and complex permeability (μ′′) contributed to a minimum RL peak with enhancement in the −10-dB bandwidth. Minimum RL of −22 dB, −27.14 dB, −27 dB and −30 dB with a −10-dB absorption bandwidth of 2.2 GHz, 2.3 GHz, 1.4 GHz and 2 GHz was obtained for composition y = 0.10, y = 0.15, y = 0.20 and y = 0.25, respectively, in the K-band. The absorption bandwidth (−10 dB) was further enhanced to 3.43 GHz, 2.62 GHz, 3.93 GHz and 2.3 GHz for these compositions, respectively, in the Ka-band. The synthesized ferrites have a high potential to be used as efficient microwave absorbers.

Influence of different BFO filler content on microwave absorption performances in BiFeO3/epoxy resin composites

Multiferroic BiFeO3 (BFO) has garnered interest in recent years due to its magneto-electric coupling between ferroelectric and magnetic ordering. This unique property offers some advantages when applied as electromagnetic (EM) wave absorbers. In work reported here, the microwave absorption properties of multiferroic BFO/epoxy resin composites with different weight percentage (wt%) of BFO fillers of various thicknesses were investigated. The BFO powders were synthesized using high energy ball milling (HEBM) and sintered at 775 °C in a furnace with an ambient air condition. The sintered BFO powders with different weight ratios (50 wt%, 60 wt% and 70 wt%) were mixed with epoxy resin as a matrix to form a composite with thicknesses of 1, 2 and 3 mm. Phase identification, grain size and morphology, magnetic and microwave absorption properties of prepared samples were characterized. The absorption performances of samples were measured in the frequency range of 8–18 GHz. As a result, the compressed BFO powders and BFO/epoxy resin composites with 50–70 wt% BFO filler showed dual-band microwave absorption resonance behavior. The best performances were demonstrated by a 3 mm thick BFO70 composite sample which exhibited a primary reflection loss (RL1) of −26.0 dB at 9.1 GHz and a secondary reflection loss (RL2) of −40.5 dB at 11.3 GHz, along with an associated −10 dB bandwidth of 1.31 GHz. The minimum reflection loss (RL) peaks were shifted to a lower frequency as the thicknesses were increased due to the λ4 condition. Theoretical studies on the absorbing wave mechanism reveal a unique combination of dielectric loss relaxations and antiferromagnetic resonance effects in the BFO absorbers.

Compressible Fe3O4/MWCNTs-coated polymer foams for high-performance and tunable electromagnetic microwave absorption

High-performance microwave absorption materials (MAMs) over gigahertz (2∼18 GHz) with tunable microwave absorption (MA) abilities have become indispensable to fight complex and changeable electromagnetic (EM) environments. Herein, Fe3O4/multiwalled carbon nanotube (MWCNTs)-coated polymer foams with high-performance and tunable MA properties were prepared using a simple dip and centrifuge method. The morphologies of the samples impregnated with resin showed that Fe3O4/MWCNTs were coated uniformly on the porous polyurethane foams skeleton. Moreover, the polymer foams had superior MA properties, especially the samples with 20 vol% Fe3O4 and 14 vol% MWCNTs possessed 5 GHz effective absorption area (reflection loss (RL) < −10 dB) at 16 mm thickness, which was attributed to the simultaneous effect of impedance characteristic, dielectric loss, magnetic loss, and porous structures. The EM characteristics and RL properties of the prepared polymer foams could be simply tuned by mechanically compressing, and the results indicated that the RL peak value moved towards the high frequency as the compressibility increased.

Microwave absorption properties of easy-plane anisotropy Fe–Si powders with surface modification in the frequency range of 0.1–4 GHz

To satisfy impedance matching at low frequencies and obtain high microwave absorption performance, easy-plane anisotropy Fe–Si powders coated with SiO2 were produced by a ball milling technique and a chemical deposition method. Then, a scanning electron microscope, a transmission electron microscope, an X-ray photoelectron spectrometer, an X-ray diffractometer, a Mossbauer spectrometer, a vibrating sample magnetometer, and a vector network analyzer were used to characterize the samples. Compared to easy-plane anisotropy Fe–Si powders without surface modification, the dielectric constant of easy-plane anisotropy Fe–Si powders with SiO2 coating decreased dramatically and the microwave absorption performance was improved significantly. The reflection loss peak reached − 10 dB when the thickness was 1.4 mm and even reached − 34 dB when the thickness was 4.5 mm, exhibiting great potential for application in thin absorbers working in the frequency range of 0.1–4 GHz. In addition, the microwave absorption performance at oblique incidence was also investigated. A reflection loss peak of − 30 dB was obtained when the incident angle was 30°, and a reflection loss peak of more than − 10 dB can still be obtained even when the incident angle was 80°. The results show that the easy-plane anisotropy Fe–Si powders with SiO2 coating still possess high microwave absorption performance at oblique incidence.

Interference effects on microwave absorbing properties of W-type BaZn2Fe16O27 prepared by solid method

The W-type BaZn2Fe16O27 was prepared by solid method, using zinc oxide, iron oxide and barium carbonate as raw materials. The phase composition and elemental composition were characterized using X-ray diffraction, electronic differential system. The morphology and microscopic structure were characterized using scanning electron microscopy, transmission electron microscope. The electromagnetic properties were analyzed by a vector network analyzer. The hexagonal ferrite with pure phase composition and uniform size distribution of 5–10 µm was prepared by the solid method for the best preparation condition of calcination temperature of 1300 °C, holding time of 3 h. The absorbing of microwave for as-prepared W-type ferrite is consisted of magnetic loss and dielectric loss, thus the magnetic loss is the main, and they reached the maximum 0.17 and 0.51 at 16.90 GHz and 8.14 GHz respectively. The reflection loss (RL) of W-type BaZn2Fe16O27 coating with 3.5 mm thicknesses reaches the minimum value of − 17.02 dB at 9.04 GHz, and the bandwidth of RL values exceeding − 10 dB ranges from 7.28 GHz to 11.44 GHz. The frequency position of the RL peak depends on the λ/4 (quarter wavelength) interference models.

Epoxy resin addition on the microstructure, thermal stability and microwave absorption properties of core-shell carbonyl iron@epoxy composites

Abstract In this study, novel CIP@EP composites with a core-shell structure were prepared by using the in-situ polymerization method. The phase structure, morphology and thermal stability were investigated by FTIR, XRD, SEM, TEM and TG. The results indicated that EP were densely covered on the surface of CIP particles, and with the increase of EP contents, the EP shell became thicker, which effectively strengthened the thermal stability of the materials. The magnetic and electromagnetic properties of the composites were systematically investigated. It was found that the content of EP played an important role in improving the magnetic and dielectric properties. High EP content can effectively improve the impedance matching between the dielectric and magnetic loss of the absorbers and enhance the EM wave absorption ability of the composites. This study proves that the CIP@30%EP exhibits an excellent EM wave absorption ability, which has higher value of RL and wider absorption width than other CIP@EP composites. The CIP@30%EP has a strong reflection loss peak of −16.1 dB and wide effective absorption bandwidths of 5.4 GHz at the thickness of 2.2 mm. Furthermore, the method utilized to synthesis the CIP@EP composites can be a suitable and efficient way to prepare other spherical microwave absorption materials.

Amorphous Bimetallic Nanowires with High-Performance Microwave Absorption: A Case for FeCo Nanowires

Amorphous FeCo nanowires (NWs) with the average diameter of 120[Formula: see text]nm were successfully prepared with a magnetic-field-assisted (MFA) hydrothermal method. Rapid reaction time was adopted to obtain amorphous FeCo NWs, being checked by XRD and TEM. Tuning the stoichiometric ratio of Fe/Co content meets the optimal impedance matching under different absorption frequency, making both improved intensities and frequency ranges of microwave absorption. For example, under 3[Formula: see text]mm coating thickness, the reflection loss (RL) peaks of Fe3Co7, Fe5Co5 and Fe7Co3 NWs are [Formula: see text]25.88[Formula: see text]dB at 4[Formula: see text]GHz, [Formula: see text]19.06[Formula: see text]dB at 4.24[Formula: see text]GHz and [Formula: see text]21.98[Formula: see text]dB at 5.44[Formula: see text]GHz. The related efficient absorption bandwidths ([Formula: see text]10 dB) of Fe3Co7 NWs, Fe5Co5 NWs and Fe7Co3 NWs are 5.40[Formula: see text]GHz, 3.52[Formula: see text]GHz and 4.91[Formula: see text]GHz, respectively. It is ascribed to integrating enhanced dielectric/conductive losses, negligible damages from eddy current effect and good impedance matching for high-performance FeCo NWs absorbers. This work paves a new path on synthesizing bimetallic wire-like nanostructures for microwave absorption demands.

A superior microwave absorption material: Ni2+-Zr4+ Co-Doped barium ferrite ceramics with large reflection loss and broad bandwidth

Large reflection loss and wide bandwidth are significant targets, determining the microwave absorption ability. However, it is still a challenge to simultaneously satisfy the two conditions. As a multifunctional material, BaFe12O19 possess excellent electromagnetic properties in the microwave frequency band. Due to the natural resonance phenomenon of the material, BaFe12O19 can produce a large magnetic loss which correlates with Fe3+ content, and the microwave absorption characteristics of barium ferrite can be modulated by ion doping. As a typical magnetic metal, Ni coupled with high-valence state Zr4+ doping helps to produce double resonance peaks. In this work, Ni2+-Zr4+ co-doping M-type barium ferrites (BaFe12-2xNixZrxO19, BNZFO-x, x = 0–0.8) were prepared conveniently by solid-state reaction method. Several necessary measurements to characterize its microwave absorption property have been operated such as morphology, magnetic performance and electromagnetic parameters. The results show that reflection loss and bandwidth can be simply tuned by tailoring Ni2+-Zr4+ content. The reflection loss peak drifts from 18 GHz to 9.76 GHz, which involves a half of the studied frequency range. The maximum reflection loss achieves −60.6 dB and the corresponding bandwidth over −10 dB is 7.68 GHz for BNZFO-0.6 ceramic with only 2.1 mm thickness. Thus, the doping of Ni2+-Zr4+ ion pairs is beneficial to improve the absorbing properties of the material, and the superior microwave absorption property may originate from its inner double natural resonance in micro-scale. The excellent microwave absorption properties suggest that BNZFO-x is a promising candidate applied for designing electromagnetic shielding devices.

Tunable electromagnetic wave-absorbing capability achieved in liquid-metal-based nanocomposite

A Galinstan (GaInSn) liquid-metal-(LM-)based composite consisting of polydimethylsiloxane (PDMS) filled with GaInSn nanoparticles is developed for application as a tunable electromagnetic-(EM-)absorbing material. The minimum reflection loss (RL) of the GaInSn/PDMS composite is −19.3 dB at 14.8 GHz at a thickness of 2 mm, and the bandwidth over which the RL is lower than −10.0 dB is 9.9 GHz. The RL peak shifts from 14.8 GHz to 9.7 GHz under elongation by 30% shape deformation. After release, the absorption properties of the previously stretched sample almost returning to their original values suggests an approach to construct a reversibly tunable GaInSn LM-based EM-absorbing system.

Enhanced Microwave Absorption Properties of Absorbing Materials Induced by Complex Coupling Agents

The microstructure and electromagnetic parameters of carbonyl iron powder (CIP) modified by complex coupling agents were studied to analyze the characteristics of absorbing materials. The samples were detected by scanning electron microscope, X-ray diffraction (XRD), Raman scattering spectroscopy, and vibrating sample magnetometer. The electromagnetic parameter was measured by vector network analyzer. The result indicated that the typical flaky-shape was obtained for all samples after milling. In addition, a similar structure was confirmed by XRD and Raman. With the use of the complex coupling agents, the saturation magnetization (Ms) increased and the coercivity (Hc) did not change significantly. According to transmission line theory, the reflection loss (RL) and loss tangent of absorbing material were calculated. When the thickness was 2 mm, the RL peak reached to -15 dB near 2 GHz for CIP modified by ternary coupling agents; the effective absorption bandwidth was 1 GHz (1.6-2.6 GHz) when the RL <; -10 dB. And, the adding of complex coupling agents boosted the magnetic tangent loss of the composites significantly, particularly in the high frequency. Therefore, the proper doping of complex coupling agents can achieve good impedance matching and achieve the purpose of improving the absorbing properties of the absorbing materials. It would lay a good foundation for further engineering application.

Fe3O4/Fe/C composites prepared by a facile thermal decomposition method and their application as microwave absorbers

The Fe3O4/Fe/C composites used as microwave absorbers were synthesized by a facile thermal decomposition method using sodium chloride as a template. The hierarchical flower-like structure was obtained by thermally treating the precursors at 600 °C for 2 h under a nitrogen atmosphere with a heating rate of 5 °C/min. Based on the complex permittivity and permeability results, the Reflection loss (RL) of the Fe3O4/Fe/C composites were calculated. The Fe3O4/Fe/C composites show a RL peak of −51.3 dB for a 2 mm thick positioned at 17.2 GHz frequency. When the absorber thickness was adjusted to 2.3 mm, the effective adsorption bandwidth (RL ≤ −10 dB) is 5.6 GHz (12.4–18 GHz) frequency. Simultaneously, the RL peak of the absorber still reaches −40.8 dB at 14.7 GHz frequency. The RL peak is explained using the quarter-wave cancellation model. The microwave absorption behavior of Fe3O4/Fe/C composites can be attributed to the reasonable impedance matching and the existence of interfaces around the composites. Our findings offer an effective way to design and synthesis the excellent microwave absorber of Fe3O4/Fe/C composite.

Microwave Absorption Properties of Polyaniline/Titanium Dioxide (PAni/TiO2) Doped with Different Types of Fullerenes

In this work, Polyaniline/titanium dioxide (PAni/TiO2) nanocomposites without and with addition of fullerene such as pristine fullerene (C60) and small gap fullerene (S.G.F) were prepared through template‐free method by using hexanoic acid (HA) as a dopant. FTIR and UV‐Vis spectra confirmed the chemical structure of conjugated PAni and indicated that the resulted PAni is in conducting state. The existence of fillers in PAni nanocomposites were confirmed by the characteristic peaks of TiO2 and fullerene in XRD pattern. Based on FESEM images obtained, nanocomposites formulated with C60 (PAni/HA/TiO2/C60) formed the nanorods/nanotubes and microrods/microtubes with the biggest diameter (240 nm), followed by PAni with S.G.F (PAni/HA/TiO2/S.G.F) and PAni without the addition of fullerene (PAni/HA/TiO2) with diameter of 180 nm and 160 nm, respectively. Besides, PAni/HA/TiO2/C60 also possessed the highest electrical conductivity of 1.708 × 10−1 S/cm as compared to PAni/HA/TiO2/S.G.F and PAni/HA/TiO2 (4.531 × 10−3 S/cm to 1.439 × 10−2 S/cm). Microwave absorption studies of PAni nanocomposites were carried out by using Microwave Vector Network Analyzer (MVNA) in the frequency range of 0.5–18.0 GHz. Among all nanocomposites, PAni/HA/TiO2/C60 exhibited a narrow and the highest reflection loss (RL) peak of −61.3 dB at 9 GHz due to the highest conductivity (1.708 × 10−1 S/cm), dielectric permittivity (0.46) and heterogeneity of PAni (larger amount of nanorods/nanotubes and microrods/microtubes) that have induced more disordered motion of charge carrier along the backbone of PAni. Thus, it eventually enhanced the molecular polarization such as greater space charge relaxation and hopping of confined charges.

Microstructure, electromagnetic and microwave absorbing properties of plate-like LaCeNi powder

La1−xCexNi5 (x = 0, 0.05, 0.10, 0.15) powders were prepared by arc melting and high-energy ball milling method. The structures and morphologies of LaCeNi powders were evaluated by X-ray diffraction and scanning electron microscopy. The saturation magnetization and electromagnetic parameters of the powders were characterized by using vibrating-sample magnetometry and vector network analysis, respectively. The results reveal that the La1−xCexNi5 (x = 0, 0.05, 0.10, 0.15) powders consist of LaNi5 single phase with different Ce contents. With the increase of Ce content, the particle size decreases and the saturation magnetization increases. The reflection-peak frequency shifts to lower frequency region upon Ce concentration. The minimum reflection loss and reflection peak frequency, for the sample with coating thickness of 1.8 mm, are − 19.7 dB and 8.16 GHz, respectively.

Electromagnetic and microwave absorbing properties of cementitious composite for 3D printing containing waste copper solids

The increasing electromagnetic energy and multiple reflections of electromagnetic wave (EMW) produce various negative impact on the human body, equipment, information security and even military defense structures. In this study, a new electromagnetic wave EMW absorbing cementitious composite incorporating copper slag and powder was manufactured to accommodate the rapid development of 3D printing technology. The microscale morphology and chemical compositions of adopted absorbents were examined through scanning electron microscopy (SEM), energy dispersive spectrophotometry (EDS), and X-ray fluorescence (XRF). Electromagnetic parameters for copper slag and powder were measured in the range of 1–18 GHz. Then seven cementitious composites incorporating 0-30 wt% copper slag were manufactured to access and evaluate the printable capability for extrusion-based printing. Five mass ratios (2–10 wt%) of copper powder were thereafter incorporated to the printability-optimized composite for further enhancement of EMW absorption. Based on the printable capacity, reflectivity tests using network analyzer over the 1–18 GHz range showed that the cementitious composite with 25 wt% copper slag and 6 wt% copper powder performed a favorable EMW absorption capacity with a 10.2 dB peak reflection loss value and a 3.48 GHz absorption band. In addition, the influence of macroscale configuration includes surfaces roughness and thickness on the EMW absorption were elaborated. The results provide experimental basis and references for functionalizing and intelligenting the cementitious composite for application in infrastructures.

Fabrication and microwave absorption properties of size-controlled polymer/Fe3O4hybrid microsphere based on aggregation-induced emission active polyarylene ether nitrile

The article fabricated novel polymer/magnetic hybrid microspheres via solvothermal method by using ferroferric oxide (Fe3O4) and aggregation-induced emission (AIE) active polyarylene ether nitrile (PEN) as building components. The PEN was copolymerized through phenolphthalin and AIE-gen (4, 4′-(1, 2-di (4-hydroxyphenyl)-1, 2-diyl) diphenol), wherein AIE-gen endowed the copolymer with AIE effect so that the copolymer could aggregate correspondingly in different solvent/nonsolvent systems and produce fluorescence enhanced. In these experiments, the diameter of Fe3O4/PEN hybrid microspheres was controlled by the volume proportion of nonsolvent (ethylene glycol (EG)) and solvent (N-methyl pyrrolidone (NMP)) in preparation process based on the aggregation behavior of AIE active PEN. Moreover, the resulted hybrid microspheres also had excellent magnetic and electromagnetic absorption performance. Specifically, they all exhibited a strong reflection loss peak both in the low and high frequency range. Meanwhile, with the change of coating thickness, these hybrid microspheres had a wide wave-absorbing frequency from 5 GHz to16 GHz. The results supported that the hybrid microspheres integrated with magnetism and AIE property will have a wide application in the preparation and improvement of size-controlled inorganic organic nanocomposites.

Cobalt nanoparticles embedded nitrogen-doped porous graphitized carbon composites with enhanced microwave absorption performance

For high-efficiency microwave absorption, both of the self loss of materials (dielectric loss and magnetic dissipation) and structural attenuation (multiple scattering, interfacial polarization) play important roles. In addition, the magnetic/dielectric materials combination, and void volume introduction can also contribute to the optimization of impedance matching. Given that, 2D cobalt nanoparticles embedded nitrogen-doped porous graphitized carbon composites (Co@N-C) were fabricated via a simple sacrificial templates method, where the CoAl-layered double hydroxide (CoAl-LDH) nanosheets were prepared to hold ZIF-67 and then decomposed during the sintering process. In this work, strong dielectric attenuation, multiple microwave scattering and dielectric polarization, as well as shortened impedance matching all make for the nice microwave absorption performance. This work not only exhibits the importance in materials selection and structure design, but also demonstrates the close relation between matching thickness and response frequency at maximum reflection loss (RL) peak.

Ferric metal-organic framework for microwave absorption

In this study, we have shown for the first time that ferric metal-organic framework (Fe-MOF) has the ability to attenuate gigahertz-range electromagnetic radiation through means of a novel interference mechanism. A large reflection loss value of −54.2 dB can be obtained, equivalent to over 99.999% absorption efficiency. The microwave absorption performance is largely dependent on the dielectric permittivity and magnetic permeability properties. The electrical loss ratio tgδε increases with the frequency from 0.13 at 1.0 GHz to 0.69 at 18.0 GHz, while the magnetic loss ratio tgδμ is only between 0.05 and 0.14. The conductivity σ increases with the frequency from 0.08 S/m at 1.0 GHz to 5.24 S/m at 18.0 GHz, while the skin-depth δ decreases with the frequency. The thickness (d) of the absorber is inversely proportional to the reflection loss peak value (RLpeak), the reflection loss peak frequency (fpeak), and the critical reflection loss peak width (Δf10). The non-zero magnetic susceptibility (χ) accelerates the shift of fpeak to lower values as d grows bigger; however, it improves the RLpeak value and larger microwave absorption efficiency and reduces the quick narrowing of the critical frequency range. The microwave performance of Fe-MOF is likely related to its microwave conductivity, which may originate from the polar rotations in the interface or defects. A new mechanism is proposed for the large reflection loss based on the interference of the reflected microwave from the front and back surface of the microwave absorber, especially when the thickness matches with the odd integer values of the wavelength.

Effects of Co content on microwave absorbing properties of Dy–Ni powder

Abstract DyNi2- x Co x (x = 0, 0.4, 0.6 and 0.8) absorbing powders were prepared using a non-consumable vacuum melting furnace and a high energy ball milling method. The effects of Co content on the microstructure and the absorbing properties of DyNi2 powders were investigated by X-ray diffraction, scanning electron microscopy and vector network analysis. The absorbing properties of DyNi2 powders were optimized, but did not affect the composition of DyNi2 alloy with increasing Co content. With the addition of Co, the ∊″ formant frequency, μ″ formant frequency and reflection loss peak frequency of the powders shifted to higher values. The minimum reflection loss peak of DyNi1.4Co0.6 powder is about −30.65 dB with a coating thickness of 1.8 mm, and a bandwidth where R &lt; −10 dB is 1.9 GHz.