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In view of the problem of heavy weight of the low-frequency band metamaterial absorber, the weight of the metamaterial absorber is mainly concentrated in the medium dielectric substrate. Different from the previous metamaterial absorbers based on continuous dielectric substrate, a new lightweight metamaterial absorber based on discontinuous dielectric medium is proposed and verified in the L-band (1–2 GHz). Compared with metamaterial absorber based on the continuous dielectric substrate, the weight of the metamaterial absorber designed based on discontinuous media is reduced by 42.58%. The dual-peak reflection losses of −17.29 dB and −15.99 dB are obtained at 1.23 GHz and 1.72 GHz, respectively. Our work provides a new method for constructing light dual-peak metamaterial absorbers in the L-band. [ABSTRACT FROM AUTHOR]

A novel single-layer graphene-based structure is designed in this article. This structure consists of two graphene strips and two graphene blocks. The components of this structure generate two bright modes and one dark mode in the terahertz region, and these three modes undergo destructive interference, leading to the phenomenon of double plasmonic induced transparency. The graphene of this structure has continuity, and the Fermi level can be adjusted by adjusting the bias voltage applied to the structure. Compared with those discontinuous structures, it is easier to achieve tuning function. The structure uses the finite-difference time-domain for data simulation, uses the coupled mode theory for theoretic calculation, and compares the transmission spectra obtained by the two methods. Through observation, it can be found that the frequency positions of the peaks and dips of the simulated transmission spectrum increase with the increase of the Fermi level, showing a perfect linear relationship, which indicates that this structure has great prospects in the modulator. In addition, the structure has achieved good results in the slow light effect, and after measurement, the peak values of group index and group delay can reach up to 380 and 0.241 ps, respectively. By utilizing these advantages, this structure can provide more possibilities for the development and research of slow light fields. [ABSTRACT FROM AUTHOR]

With vitamin A acetate as raw material, ethylenediamine retinyl Schiff base salts coordinated with rare earth ion La3+, Ce3+ were synthesized, and the structure of the products was characterized by FT-IR and Raman spectra. The electromagnetic parameters in the frequency range of 2-18 GHz were measured by microwave vector network analyzer, its reflectivity was calculated, and the main factors and mechanism that affect the wave-absorbing performance of rare retinyl Schiff base salts were discussed. The results show that the coordination bond is formed by the rare earth ions and Schiff base. The reflectivity of Schiff base coordinated with La3+ ion is –16 dB at 12.9 GHz (bandwidth with reflectivity better than –10 dB is 3.1 GHz), the reflectivity of Schiff base coordinated with Ce3+ ion is –18.8 dB at 12.7 GHz (bandwidth with reflectivity better than –10 dB is 3.4 GHz). Microwave absorption performances of the both are superior to the wave-absorbing performance of Schiff base coordinated with non-rare earth ions.

A chaos patterned metasurface absorber (CPMA) with three strong absorption peaks and a wide bandwidth has been designed. This CPMA presents a single-layer sandwich structure, which not only enables easy optimization by adjusting the surface pattern and model size but also contributes to the continuous effective bandwidth (EBW, with an absorptivity larger than 90%) from the multiple adjacent absorption peaks. The continuous EBW is from 4.28 to 9.56 GHz with a bandwidth of 76.3%. Meanwhile, analyses on the distributions of the surface current, electric field, and power loss density illustrate that the absorption mechanisms are mainly magnetic coupling resonance and dielectric loss. The experimental results confirm the good absorption performance with multi-peak and wide bandwidth for the fabricated CPMA sample, which shows potential applications in the field of anti-electromagnetic interference. [ABSTRACT FROM AUTHOR]

The complementary-modeled Rossler chaotic metamaterial (CRCM) with FR-4 dielectric layer is proposed to design metamaterial absorber with multi-resonance peaks. Under "master-slave" boundary condition in high-frequency structure simulator (HFSS) software, the electric field between adjacent boundaries presents phase difference which can simulate an infinite array. The research results show that the CRCM demonstrates multi-resonant peaks from 4 GHz to 10 GHz, and the area of metal patterned-layer can obviously regulate the resonant peaks. The CRCM presents a linear polarization conversion peak around 5.80 GHz, its polarization conversion ratio (PCR) is near 100%. The PCR is also larger than 80% from 5.56 GHz to 5.95 GHz. Through the surface current density distribution and the comparison between the CRCM and complementary-modeled double ring metamaterial (CDRM), the main factors generating polarization conversion are the asymmetry of metal pattern layer and magnetic resonance caused by reverse current. The CRCM also has two strong absorption peaks located at 6.31 and 9.37 GHz, respectively. Dielectric loss and ohmic loss are the main microwave loss mechanisms proved by volume and surface power loss density distribution. The resonant frequencies derived from L – C resonant circuit are well consistent with the simulation data and measurement results. [ABSTRACT FROM AUTHOR]

A broadband and wide-angled microwave absorber based on resistive-type metamaterial has been proposed and demonstrated in the low-frequency regime of 2–8 GHz. The minimum reflection loss of the absorption peak located at 5.27 GHz is −51.41 dB. Effective bandwidth better than −10 dB reflection loss is able to achieve 2.70 GHz in the range from 3.81 GHz to 6.51 GHz. The underlying physical mechanisms of electromagnetic wave energy attenuation are illustrated in detail by means of surface current, electromagnetic field and power loss density. Furthermore, the influence of structural dimensions on the attenuation properties of the proposed resistive-type metamaterial absorber is also investigated. More importantly, the designed resistive-type metamaterial absorber could operate well with incident angles changing from 0 ∘ to 60 ∘ under the transverse electric (TE) and transverse magnetic (TM) waves. Research results will be capable of providing guidance for the design and preparation of broadband microwave absorbing materials at low frequencies. [ABSTRACT FROM AUTHOR]

A dual-band microwave metamaterial absorber with single-peak regulation and wide-angle absorption has been proposed and illustrated. The designed metamaterial absorber is consisted of hollow-cross resonators, solid-cross resonators, dielectric substrate and metallic background plane. Strong absorption peak coefficients of 99.92% and 99.55% are achieved at 8.42 and 11.31 GHz, respectively, which is basically consistent with the experimental results. Surface current density and changing material properties are employed to illustrate the absorptive mechanism. More importantly, the proposed dual-band metamaterial absorber has the adjustable property of single absorption peak and could operate well at wide incidence angles for both transverse electric (TE) and transverse magnetic (TM) waves. Research results could provide and enrich instructive guidances for realizing a single-peak-regulation and wide-angle dual-band metamaterial absorber. [ABSTRACT FROM AUTHOR]

An optically transparent metamaterial absorber (MMA) has been demonstrated numerically and experimentally at the S-band. The designed MMA is composed of polymethyl methacrylate (PMMA), indium-tin-oxide (ITO) attached to polyethylene terephthalate (PET) film, and numerically provides effective absorption with reflection loss lower than −10 dB in the frequency range of 1.85–4.65 GHz. Experimental measurement shows the reflection loss of the proposed MMA is better than −10 dB from 2.00 GHz to 4.25 GHz, which agrees pretty well with the simulated results. Distributions of surface current, electromagnetic field and power loss density for the designed MMA are systematically investigated to explain microwave attenuation characteristic and loss mechanisms. More importantly, the prepared sample exhibits an optical transparency above 68% in the whole visible band, thus realizing a wide range of applications, such as optically transparent S-band absorbers. [ABSTRACT FROM AUTHOR]

A high-performance microwave absorption material is highly demanded. Herein, the laminated Ti3C2 Mxene was synthesised via HF etching process, and the flaky carbonyl iron (FCI) particles were prepared by high-energy ball milling. The hybrid Ti3C2/FCI powders with different mass ratios were fabricated by ultrasonic mixing method. Electromagnetic and microwave absorption properties of the single layer Ti3C2/FCI coatings were investigated in 2–18 GHz. A broadened microwave absorption property can be realized by optimizing the Ti3C2 and FCI content. Especially, the coating with 20 wt% Ti3C2 and 40 wt% FCI loading presents the measured absorption bandwidth (RL < − 10 dB) of 8.16 GHz with the thickness of 1.0 mm. The remarkable microwave absorbing performance was attributed to the good impedance matching and moderate attenuation ability. These results indicate that the Ti3C2/FCI composites have great potential to be a broadband microwave absorbent. [ABSTRACT FROM AUTHOR]

A metal-dielectric-metal (MDM) sandwich metamaterial perfect absorber (MPA) with magnetic nickel metal has been designed. An optimal absorption of 99.28% at 404 MHz is achieved for MPA with thickness of 5.54 mm. Resonant absorption is demonstrated to be main mechanism according to analyses on surface current distributions and electromagnetic field distributions. Furthermore, the electromagnetic energy is mainly dissipated in magnetic metal with magnetic loss proportion of 55.43% by comparatively analyzing the wave-absorbing performance of using magnetic metal, non-magnetic metal and perfect electric conductor (PEC) as metallic layers. These results would provide a guidance for the design of quasi-microwave absorbing/shielding materials. [ABSTRACT FROM AUTHOR]

Lead-free magnetoelectric (ME) laminated (80Bi0.5Na0.5TiO3-20Bi0.5K0.5TiO3)/(Ni0.8Zn0.2)Fe2O4 (BNKT/NZFO) composites are prepared via a modified cofiring processing, combining grain refinement and liquid phase sintering with low sintering aid content. The microstructure, dielectric, ferroelectric, magnetic, and magnetoelectric properties are investigated by varying the thickness of NZFO layer. The results show that the coexistence of independent BNKT and NZFO phase and the presence of the morphotopic phase boundary in BNKT phase with high piezoelectric coefficient d33 of 131 pC/N are confirmed. Laminated composites have clear and well-bonded interfaces across the two layers, as well as improved ME properties. The maximum ME voltage coefficient ( αE31) of the laminated composite reach 115.1 mV cm−1 Oe−1 with an optimized BNKT/NZFO layer thickness ratio of 1/2. In addition, a zero-biased ME response was observed in BNKT/NZFO laminated composites. [ABSTRACT FROM AUTHOR]

• The infrared emissivity presents periodical fluctuation phenomenon along edge length. • The peaked frequency is inclined to shift towards lower region with area ratio increased. • There exists intrinsic attenuation which is probably attributed to the diffuse scattering. Composites or structures with adequate infrared reflection and microwave transmission are favorable from practical point of view. In this paper, oriented flaky aluminum filled pyramidal-frustum shaped periodic coatings was developed, and the effect of area of flaky aluminum powder filled coating on the infrared emissivity as well as microwave transmission behavior was intensively studied combined experiments with simulation. Results shown that the increments of oriented flaky aluminum filled coating could effectively reduce infrared emissivity. After spraying flaky aluminum filled periodic structures on the microwave absorbing material, the frequency corresponding to minimal reflection loss is inclined to shift towards lower frequency. Numerical simulation results shown that reflection coefficient gradually increases with increasing in frequency and area ratio of flaky aluminum filled coating. Besides, there exists intrinsic attenuation of flaky aluminum filled pyramidal-frustum shaped periodic coating, which is probably attributed to the diffuse scattering within step edge region. [ABSTRACT FROM AUTHOR]

Highlights • Ti 3 SiC 2 encapsulated by magnetic Ni 0.5 Zn 0.5 Fe 2 O 4 shell were successfully prepared. • Moderated complex permittivity for the Ni 0.5 Zn 0.5 Fe 2 O 4 /Ti 3 SiC 2 was achieved. • Desirable higher complex permeability for the Ni 0.5 Zn 0.5 Fe 2 O 4 /Ti 3 SiC 2 was realized. • The Ni 0.5 Zn 0.5 Fe 2 O 4 /Ti 3 SiC 2 coating with wide bandwidth (RL <-10 dB) of 5.3 GHz. Abstract Ti 3 SiC 2 particles encapsulated by Ni 0.5 Zn 0.5 Fe 2 O 4 shell were in-situ synthesized via a facile sol-gel method. Effects of Ni 0.5 Zn 0.5 Fe 2 O 4 shell on electromagnetic properties of Ti 3 SiC 2 were investigated in 2–18 GHz. Moderated complex permittivity and desirable higher complex permeability presented for the Ni 0.5 Zn 0.5 Fe 2 O 4 /Ti 3 SiC 2 composite, resulting in strong microwave attenuation ability and good impedance matching property. The measured effective absorbing bandwidth (RL < −10 dB) of 5.3 GHz and corresponding maximum RL of −38.6 dB were obtained for the Ni 0.5 Zn 0.5 Fe 2 O 4 /Ti 3 SiC 2 absorbing coating of 1.2 mm thickness. These results indicate that the Ni 0.5 Zn 0.5 Fe 2 O 4 /Ti 3 SiC 2 composite may become a new type of microwave absorbent. [ABSTRACT FROM AUTHOR]

The effects of Co 2 O 3 addition on the electromagnetic properties of NiCuZn ferrite were investigated, by considering the variation of complex permeability, complex permittivity and quasi-microwave absorption property in the 1–1000 MHz frequency range. Results show that the introduction of Co 3+ ions in NiCuZn ferrite leads to the marked shifting of magnetic resonance towards high-frequency and a slight increase of the permittivity. These Co-related effects enhance the maximum reflection loss in NiCuZn ferrite to reach −55.1 dB with its absorption bandwidth being tunable in the frequency range 480–1000 MHz, which provides a potential absorber for the anti-electromagnetic interference applications in electronic industry. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the effect of magnetic grain size on magnetoelectric responses of particulate magnetoelectric 0.7(Bi 0.5 Na 0.5 TiO 3 -Bi 0.5 K 0.5 TiO 3 )-0.3(Ni 0.8 Zn 0.2 )Fe 2 O 4 (BNKT-NZFO) composites. The coexistence of two chemically separated phases was confirmed using x-ray diffraction analysis. The composites had homogeneous microstructure with controlled grain size. The magnetoelectric response of the BNKT-NZFO composites sensitively depended on the grain size of the NZFO phase and the magnetoelectric voltage coefficients presented a marked enhancement of 33% in the engineered grain size range. This result indicated that tailoring the magnetic grain size physically will provide a powerful mean of enhancing magnetoelectric coupling in a two-phase particulate composite, with large potential application in area of magnetic field sensor. [ABSTRACT FROM AUTHOR]

Particulate magnetoelectric (ME) ceramics constituted by (1- x )(80Bi 0.5 Na 0.5 TiO 3 -20Bi 0.5 K 0.5 TiO 3 )- x CoFe 2 O 4 [(1- x )BNKT- x CFO] ( x = 0, 0.1, 0.2, 0.3, 0.4 and 1.0) were synthesized by an powder-in-sol precursor hybrid processing method and their structure, magnetic, ferroelectric, magnetodielectric (MD) and ME properties have been investigated. Results showed that the ceramics consisted of only two chemically separated phases and had homogeneous microstructure. The introduction of CFO into BNKT matrix led to the weakening of ferroelectric and dielectric properties whereas the strengthening magnetic and MD properties. The observation of the MD effect revealed the evidence of the strain-induced ME coupling and the MD value is well scaled with M 2 . A maximum value of ME output of 25.07 mV/cm·Oe was achieved for the 0.7BNKT-0.3CFO composite. The improved ME response together with the linear MD effect makes the ceramics promise for use in magnetic field controllable devices or magneto-electric transducers. [ABSTRACT FROM AUTHOR]

The magnetic insulator Fe 3 O 4 -modified flaky Fe 85 Si 9.5 Al 5.5 (FeSiAl) powders with significantly enhanced electromagnetic wave absorption properties in the frequency range of 2–8 GHz were prepared by chemical co-precipitation. X-ray diffraction (XRD) and scanning electron microscopy (SEM) have confirmed the formation of nanoparticles Fe 3 O 4 precipitated on the flake-shaped FeSiAl. The electromagnetic measurements of the modified flakes presents a nearly invariable complex permeability and decreased complex permittivity in the 2–8 GHz, as well as improved impedance matching performance. More importantly, an excellent microwave absorbing performance with the bandwidth (RL <−10 dB) of 5.36 GHz is achieved in modified sample with the thickness of 1.5 mm, which is a promising microwave absorbing material in 2–8 GHz. [ABSTRACT FROM AUTHOR]

The single-phase Bi 1- x Nd x FeO 3 ( x =0, 0.05, 0.10, 0.15, 0.20) were synthesized by the sol-gel method. Their crystal structure and microwave electromagnetic property in the frequency range of 2–18 GHz were investigated. The XRD patterns and Raman spectra showed that structural transition from rhombohedral ( x =0, 0.05, 0.1) to triclinic ( x =0.15) and tetragonal structure ( x =0.20) appeared in the Bi 1- x Nd x FeO 3 . Electromagnetic measurement suggested that both microwave permeability μ′ and magnetic loss tanδ m increased remarkably over 2–18 GHz by doping Nd. Strong dielectric loss peak was observed on the samples of Bi 1- x Nd x FeO 3 ( x =0.15) and Bi 1- x Nd x FeO 3 ( x =0.2). Results show that Nd substitution is an effective way to push BiFeO 3 to become microwave absorbing materials with high performance. [ABSTRACT FROM AUTHOR]