Broad Effective Absorption Bandwidth Research Articles

Construction of urchin-like multiple core-shelled Co/CoS2@NC@MoS2 composites for effective microwave absorption

Designing nanocomposite with multi-level interfaces is an effective approach to improving the microwave absorbing capability of materials. In this study, the urchin-like multiple core-shelled Co/CoS2@NC@MoS2 composites (CCM) are designed and fabricated by high-temperature pyrolysis and solvothermal process, where the structure and phase composition are affected by the migration of Co. Abundant interfaces in the multiple core-shelled structures favor the polarization relaxation loss, defects of MoS2 and nitrogen doping carbon (NC) matrix induce the dipole orientation polarization loss. The CCM composite exhibits excellent microwave absorption with the strongest reflection loss (RL) of − 43.9 dB. Meanwhile, the broadest effective absorption bandwidth (EAB, RL<−10 dB) is 4.4 GHz with a thickness of 1.5 mm. Besides, with the thickness of 1.0–3.5 mm, all peaks of RLmin< −20 dB (99 % absorptivity). It is believed that this work can provide an effective strategy for the design of tunable multi-interface nanostructures to regulate microwave absorption.

A Novel Hierarchically Lightweight Porous Carbon Derived from Egg White for Strong Microwave Absorption

Egg custard is a common dish on the dining table and exhibits a uniform porous structure after freeze-drying. The protein within egg custard is a rich source of carbon and nitrogen, and the custard’s unique microstructure and adjustable electrical properties make it a potential porous carbon precursor. Herein, nitrogen in situ doped porous carbons (NPCs) and potassium-carbonate-modified NPCs (PNPCs) are obtained through a simple gelation and carbonization process using egg white as the raw material. The unique morphologies of the porous carbon are inherited from the protein and include fibrous clusters, honeycomb holes, and a grooved skeleton. Their excellent impedance matching and effective internal loss make the obtained porous carbons good candidates for lightweight electromagnetic (EM) wave absorbers without the need to dope with metal elements. As a representative porous carbon, PNPC10-700 has multiple structures, including fibrous clusters, honeycomb holes, and a porous skeleton. Moreover, it achieves a maximum reflection loss value of −66.15 dB (with a thickness of 3.77 mm) and a broad effective absorption bandwidth of 5.82 GHz (from 12.18 to 18.00 GHz, with a thickness of 2.5 mm), which surpasses the reported values in most of the literature. Thus, gelation combined with the further carbonization of egg white (protein) is a new method for designing the morphology and EM properties of porous carbon absorbers.

Metal-organic framework (MOF) derived porous NiCo2O4 and ZnCo2O4 spinels with high microwave absorption performance for environmentally friendly EMI shielding applications

Sheet-like NiCo2O4 and ZnCo2O4 spinels were prepared by metal-organic framework (MOF) as sacrificial template to derive into porous microwave absorber materials. The NiCo and ZnCo MOFs obtained by using 2-methylimidazole linker were decomposed to the sheet-like NiCo2O4 and ZnCo2O4 powders, respectively, with the similar specific surface area of 75 m2/g and the pore volume of 0.31 cm3/g. However, the NiCo2O4 and ZnCo2O4 absorbers had the distinct microwave absorption performance on account of their various physicochemical properties caused by the nature of Ni and Zn elements. From the practical viewpoint, the MOF-derived NiCo2O4 sample had the broader effective absorption bandwidth (>3 GHz) at smaller thicknesses (<3 mm) in the Ku and X bands, whereas a significant fraction of C2, C1, and S bands could be absorbed by the MOF-derived ZnCo2O4 sample.

Ultralight and Resilient Bicontinuous Si3N4/SiC Nanowire Network for Tunable and Highly Efficient Electromagnetic Wave Absorption in Extreme Conditions

AbstractDeveloping tunable and highly efficient electromagnetic wave (EMW) absorbers with low density is crucial for the development of wireless telecommunications devices in extreme conditions. SiC ceramic has received much attention because of its dielectric tenability, low density, and chemical stability. However, the present SiC‐based materials usually show limited EMW absorbing performance than they are expected. Herein, an ultralight and resilient bicontinuous Si3N4/SiC network (8 mg cm−3) composed of EMW‐transparent Si3N4 microbelts and EMW‐absorption SiC nanowires is designed and prepared to achieve improved impedance matching and EMW attenuation capacity. The optimized bicontinuous network exhibits a broad effective absorption bandwidth of 8.62 GHz and a strong RLmin of −52.31 dB. Furthermore, the resulting bicontinuous Si3N4/SiC network, with thickness of 6 mm, shows a tunable absorption bandwidth ranging from 5.36 to 18 GHz by resilient action. It also exhibits excellent thermal stability (up to 1000 °C), thermal shock resistance (from −196 to 900 °C), and thermal insulation performance (32 Mw m−1 K−1), enabling it to be an ideal candidate for EMW absorption in extreme environments.

Three-dimensional bamboo-like amorphous N/S co-doped carbon nanotubes encapsulated with Cu nanoparticles/carbon fiber heterostructures for boosting electromagnetic wave absorbing properties

Highly efficient and multifunctional electromagnetic wave (EMW) absorbers which can be easily processed are desirably required. Herein, cupric ammonia is creatively adopted as the catalyst precursor of the in-situ growth of carbon nanotubes (CNTs) onto carbon fiber (CF) during chemical vapor deposition. Typically, when prepared at 750 °C, N/S co-doped bamboo-like amorphous CNTs/CF was successfully synthesized, while some Cu nanoparticles were remained in CNT forests. The sample obtains an excellent absorption toward EMWs, demonstrating a minimal reflection loss of −59.28 dB at 14.1 GHz with an ultrathin thickness of 1.42 mm. Concurrently, it is over a relatively broad effective absorption bandwidth (EAB) of 3.3 GHz (12.3–15.6 GHz) with 31% loading in the paraffin matrix. And the EAB value of CA-700 reaches 3.7 GHz (14.3–18 GHz) at merely 1.45 mm. The satisfying attenuation performance mainly originates from the synergistic effects of continuous three-dimensional conducting networks, abundant interfaces, sufficient defects, and the well impedance matching. Moreover, all as-prepared samples could be potentially used as reinforcements of resin matrix composites with high strength. Therefore, a facile route is provided to produce thin, lightweight, superior and high-strength EMW absorbing materials based on CF and CNTs.

Multi-hierarchy heterostructure assembling on MnO2 nanowires for optimized electromagnetic response

One-dimensional (1D) nanomaterials allow reflection of electromagnetic (EM) waves due to large anisotropy and aspect ratio. It is still a challenge to optimize the impedance matching characteristic for strong EM dissipation of 1D nanomaterials. Herein, we propose a strategy of incorporating two-dimensional (2D) layered double hydroxides (LDHs) sheets with 1D nanowires to reinforce interactions with EM waves. Wherein, 1D MnO2 nanowires are used to support the LDH nanosheets, which facilitates the EM waves capture and impedance matching characteristics. Moreover, the heterogeneous interfaces and vacancies contributes to the polarization loss as well. As a consequence, the minimum reflection loss (RLmin) of MnO2@ZnCoNi-LDHs demonstrates −56.3 dB at 2.4 mm and the broad effective absorption bandwidth (fE) reaches 4.56 GHz at 2.1 mm. This heterogeneous structure assembly strategy can be served as a reference for refining the absorption performance of 1D EM absorbers.

Honeycomb-like SnS2/graphene oxide composites for enhanced microwave absorption

Achieving the broad effective absorption bandwidth (EAB), strong absorption capacity and thin matching thickness are still a huge challenge for the dielectric loss-type microwave absorbers. Here, the honeycomb-like SnS 2 / graphene oxide (GO) composites are fabricated via a facile chemical bath deposition method to optimize the microwave absorption performances. The 2D SnS 2 nanosheets are uniformly and vertically grown on the GO sheets, forming a highly open hierarchical network, which can be beneficial to enhance the multiple scatterings and reflections of incident electromagnetic wave. Meanwhile, the impedance matching (Z) and attenuation constant (α) of composites are well-tuned by changing the SnS 2 content in the composites. When the GO sheets are just completely coated by SnS 2 nanosheets, the SnS 2 /GO composite exhibits excellent microwave absorption ability with the minimum reflection loss (RL min ) of − 59.2 dB and EAB of 5.4 GHz (12.3–17.7 GHz) at the thickness of only 1.45 mm, which is mainly ascribed to the strong interfacial polarization and good impedance matching. This work provides a significant guidance to achieve excellent absorption performance with broad EAB and strong absorption for dielectric loss-type absorbers. • Honeycomb-like SnS 2 /GO composites are fabricated via chemical bath deposition. • Abundant SnS 2 -GO interfaces are constructed, resulting in strong polarization. • Excellent EMW absorption performances are obtained by adjusting SnS 2 content. • The RL min and EAB of SG2 reach − 59.2 dB and 5.4 GHz at 1.45 mm, respectively .

Nanostructured MnFe2O4 anchored on graphene oxide and reduced graphene oxide sheets for effective regulation of microwave absorption performance

Herein, the composites of MnFe 2 O 4 -graphene oxide (MFO@GO) and MnFe 2 O 4 -reduced graphene oxide (MFO@rGO) were investigated for their structural and microwave absorption properties. The X-ray photoelectron spectroscopy confirmed the presence of C, O, Fe, and Mn elements, as well as the dominance of Fe 3+ over Fe 2+ and Mn 2+ over Mn 3+ oxidation states of Fe and Mn, respectively. The microwave absorption characteristics of composites were discussed in terms of filler loading, dielectric/magnetic loss mechanisms, effective absorption bandwidth (EAB), reflection loss (RL), skin depth, and impedance matching (Smith charts) criteria. The MFO@rGO composites exhibited the best microwave absorption properties (>90% absorption efficiency) over the entire frequency range examined (1–13.5 GHz) among the others. The MFO@rGO composite with 70 wt% filler loading achieved a minimum RL of −38.71 dB at 10.98 GHz and EAB (RL≤10 dB) of 3.40 GHz (9.48–12.88 GHz) for a thickness of 1.8 mm within the vicinity of impedance matching criteria. • A lightweight GO/rGO-MFO microwave absorber with broad EAB was fabricated • Incorporation of rGO in MFO improved impedance matching and widened the EAB. • Defect dipole polarization in rGO-MFO played a key role in microwave attenuation. • Minimum RL of −38.71 dB with EAB of 3.40 GHz was achieved for 1.8 mm thickness. • Results are superior to many reported composites based on GO and rGO.

Ultrabroad Microwave Absorption Ability and Infrared Stealth Property of Nano-Micro CuS@rGO Lightweight Aerogels

HighlightsThe CuS@rGO composite aerogel can achieve the broad effective absorption bandwidth (EAB) of 8.44 GHz with the filler content of 6 wt%.The RLmin of CuS@rGO composite aerogel is -55.1 dB and EAB is 7.2 GHz with the filler content of 2 wt% by ascorbic acid thermal reduction. The radar cross-section reduction value of CuS@rGO composite aerogel can reach 53.3 dB m2.The CuS@rGO composite aerogels possess lightweight, compression and recovery, radar-infrared compatible stealth properties.

Design of polyaniline encapsulated greigite(Fe3S4) microparticles for excellent microwave absorption performance with broad bandwidth and ultrahigh reflection loss

Exploring microwave absorption materials with the advantages of wide effective absorption bandwidth, thin thickness, strong absorption capacity and light weight is significant to solving the problems of electromagnetic (EM) irradiation in both military and civil areas. Herein, to make up for the weaknesses of single component Fe3S4 or polyaniline in microwave absorption performance, the composites with extraordinary microwave absorption performance composed of Fe3S4 encapsulated in polyaniline was elaborately designed. The successful synthesis and the microwave absorption mechanisms of Fe3S4@PANI composites were demonstrated by several characterizations. The results indicated that the dielectric constant of the composites can easily be adjusted by the content of PANI in favor of the impedance matching within the frequency range. Therefore, the sample F–P-2 presented the optimum performance, the minimum reflection loss (RLmin) value and broadest effective absorption bandwidth (EAB) respectively reach −63.8 dB at 7.68 GHz and 5.04 GHz (ranging from 12.88 to 17.92 GHz) under 40 wt% loading. Such good performance could be dependent on multiple loss mechanisms, such as the interface and dipole polarization, conduction loss as well as the multiple reflection and scattering. Based on the excellent properties and simple preparation methods, the Fe3S4@PANI composites can be a potential candidate in military and civil microwave absorption field.

Accordion-like reduced graphene oxide embedded with Fe nanoparticles between layers for tunable and broadband electromagnetic wave absorption

Electromagnetic wave absorbers constructed by reduced graphene oxide (rGO) and magnetic nanoparticles are extremely desirable for enhancing electromagnetic wave absorption performance due to the effective integration of the properties of dielectric and magnetic materials. However, the arrangement of graphene sheets and the growth of magnetic nanoparticles have always been challenging. Herein, an in-situ growth process has been used to successfully prepare accordion-like graphene with homogeneously distributed Fe nanoparticles in the confined structure via ion absorption and pyrolysis. The as-prepared Fe/layered rGO composites show excellent electromagnetic wave absorption performance with thin thickness, low filler loading, and broad effective absorption bandwidth (EAB). The minimum reflection loss of the composites achieves −54.6 dB with 20 wt% filler loading, and the tunable EAB reach 6.8 GHz (2.2 mm with 10 wt% filler loading) and 4.6 GHz (2.8 mm with 30 wt% filler loading), which can cover the entire Ku-band and X-band. The mechanism analysis indicates that the superior absorption performance is attributed to the multi-component loss mechanism, enhanced impedance matching degree and attenuation ability caused by the synergistic effect of layered rGO sheets and magnetic nanoparticles. This work opens up a new avenue for constructing accordion-like graphene-based composites as highly efficient electromagnetic wave absorbers.

Achieving broadband microwave absorption and excellent mechanical properties via constructing 3D reduced graphene oxide networks in glass fiber/epoxy resin composites

The rapid development of electronic information technology makes it more urgent that explore high-efficiency microwave absorption materials to cope with the challenges of electromagnetic pollution for guarding information security and human health. Herein, we prepared functional composites with both broadband microwave absorption and excellent mechanical properties via constructing three-dimensional (3D) reduced graphene oxide (RGO) networks. In these composites, glass fibers (GFs) were uniformly coated by RGO through a straightforwardly feasible repeated dip-coating process and subsequent reduction, which were named (RGO)n@GF (n was dip-coating times). The GFs supported RGO to form 3D networks, which increased the transmission paths and multiple scattering of electromagnetic waves. Meanwhile, the networks improved the electrical conductivity and conduction loss. The results show that the (RGO)10@GF reinforced epoxy resin (EP) composites ((RGO)10@GF/EP) have particularly significant improvement in microwave absorption properties, achieving a broad effective absorption bandwidth of 7.54 GHz and a low reflection loss of −46.02 dB. Compared with GF/EP, the bending strength and modulus of (RGO)10@GF/EP increased by 39% and 45%, respectively. The present work provides an effective solution for developing advanced composites with both broadband absorption and excellent mechanical properties.

Construction of FeNi3 and core–shell structured FeNi3@C microspheres toward broadband electromagnetic wave absorbing

The rational design of electromagnetic wave absorption (EMA) materials featured with broadband and high-efficiency in gigahertz (GHz) is still a great challenge. In this study, we prove fabricating FeNi3 and FeNi3@C core–shell microspheres to solve the challenge. The as-prepared FeNi3 microspheres exhibits extremely broad effective absorption bandwidth (EAB, RL ≥ 10 dB, > 90 % absorbing) of 10.3 GHz (7.7–18.0 GHz) at only 2.0 mm, occupying 64.4 % of the investigated frequency range with a single matching thickness. Such an outstanding EMA performances is credited to strong dielectric loss and magnetic loss. Compared with pristine FeNi3, the delicate design of core–shell structure and tailored synergistic effect of FeNi3 and carbon produce positive reinforcement both in magnetic loss and dielectric loss, endowing FeNi3@C samples with optimized impedance matching and appropriate attenuation ability. As a result, FeNi3@C samples present impressive EMA performances from C to Ku band, especially for FeNi3@C-3, demonstrating its potential of effectively dissipates electromagnetic wave in 6.1–18.0 GHz (RL ≥ 20 dB, > 99 % absorbing) by simply regulating a thickness of 1.5–2.5 mm. FeNi3 and FeNi3@C feature with optional broad bandwidth (completely covering C, X and Ku band), strong absorption, and thin thickness ensure them a superior EMA material.

Sustainable Kapok Fiber-Derived Carbon Microtube as Broadband Microwave Absorbing Material.

The design of hierarchical structures from biomass has become one of the hottest subjects in the field of microwave absorption due to its low cost, vast availability and sustainability. A kapok-fiber-derived carbon microtube was prepared by facile carbonization, and the relation between the structure and properties of the carbonized kapok fiber (CKF) was systematically investigated. The hollow tubular structures afford the resulting CKF composites with excellent microwave-absorbing performance. The sample with a 30 wt.% loading of CKF in paraffin demonstrates the strongest microwave attenuation capacity, with a minimum reflection loss of −49.46 dB at 16.48 GHz and 2.3 mm, and an optimized effective absorption bandwidth of 7.12 GHz (10.64–17.76 GHz, 2.3 mm) that covers 34% of the X-band and 96% of the Ku-band. Further, more than 90% of the incident electromagnetic wave in the frequency from 4.48 GHz to 18.00 GHz can be attenuated via tuning the thickness of the CKF-based absorber. This study outlines a foundation for the development of lightweight and sustainable microwave absorbers with a high absorption capacity and broad effective absorption bandwidth.

Bimetal-doped core-shell carbon derived from nickel-cobalt dual-ligand metal-organic framework for adjustable strong microwave absorption

Metal-organic framework materials (MOF) have become a new generation of microwave absorption (MA) materials. However, it is still challenging to design an appropriate microstructure that can efficiently adjust the microwave absorbing characteristics. Herein, a novel bimetal-doped core-shell carbon derived from nickel-cobalt dual-ligand MOF has been successfully prepared. By changing the ratio of the second ligand, the morphology can change from sea urchin-like to rod-like and petal-like shapes, thereby regulating the final wave absorption performance of MOF derivatives. The Bi-MOF-1 exhibited strong microwave absorption (up to −70.70 dB), while Bi-MOF-2 presented broad effective absorption bandwidth (5.92 GHz). The analyses indicated that the excellent impedance matching can be attributed to the double-layer magnetic loss and multiple dielectric loss of the core-shell structure. This work provides a feasible approach for the design and preparation of functional composite structures based on MOF derivatives with controllable microwave absorbing properties.

FeNi LDH/Loofah Sponge-Derived Magnetic FeNi Alloy Nanosheet Array/Porous Carbon Hybrids with Efficient Electromagnetic Wave Absorption

Electromagnetic wave (EMW) absorption materials have tremendous potential in protecting national security and human health from harmful electromagnetic irradiation. However, it is still a great challenge to achieve lightweight and broadband high-performance EMW absorption. Integrating layered double hydroxides (LDH) with porous biomass materials is a promising approach to construct magnetic metal/porous carbon composites as highly efficient EMW absorption materials due to their synergy loss, lightweight, and low-cost characteristics. Herein, FeNi alloy nanosheet array/porous carbon (FeNi/PC) hybrids derived from FeNi/loofah sponges have been prepared by hydrothermal and subsequent carbonization processes. As expected, the FeNi/PC hybrids achieve a high reflection loss of −58.3 dB at 2.98 mm and exhibits a broad effective absorption bandwidth (EAB) of 6.72 GHz with 8 wt % filler content. The outstanding EMW absorption performance of the FeNi/PC hybrid provides a new insight into the design of biomass-based composite materials as lightweight and broadband high-performance EMW absorbers.

Optimal electrical conductivity and interfacial polarization induced by loaded nanoparticles on carbon nanotubes for excellent electromagnetic wave absorption performance

Carbon materials have aroused wide attention in the field of electromagnetic wave absorption because of their advantages of good electrical conductivity, low density and adjustable structure. To obtain enhanced performance of electromagnetic wave absorption, the elaborate design of structures for carbon materials has become essential. In this work, the nitrogen-doped and large diameter carbon nanotubes modified with cobalt nanoparticles (M-Co/C-CNTs) composites were successfully prepared by adsorption and carbonization of the gases generated by organic matter pyrolysis. It is concluded that the enhanced conduction loss and polarization loss are attributed to the interfacial electronic engineering induced by the sensibly loaded cobalt nanoparticles and nitrogen doping. As a result, the samples achieved a broad effective absorption bandwidth of 4.56 GHz, and a strong reflection loss of −52.2 dB with a thin thickness of 2.1 mm. This work proposes a tailored way to fabricate the large diameter carbon nanotube composites and enhance electromagnetic wave absorption through novel structural modulation.

Ni/CNTs and carbon coating engineering to synergistically optimize the interfacial behaviors of TiO2 for thermal conductive microwave absorbers

With the coming of 5G era, endowing the microwave absorbers with a light weight and a high thermal conductivity is crucial yet challenging. Combining dielectric/magnetic components with the abundant heterointerfaces has been considered as a promising approach for the development of functional materials with excellent microwave absorption (MA) performances. Herein, we successfully constructed a hierarchical hetero-nanobrush architecture with carbon-coated TiO2 as a backbone decorated by Ni-catalyzed carbon nanotubes (TiO2@C-Ni/CNTs) for excellent MA and thermal management application, and investigated the influence of the Ni/CNTs content on its MA property. CNTs and the well-distributed Ni nanoparticles on top can promote dielectric behaviors and magnetic performances of composites, which is beneficial to the formation of dielectric and magnetic coupling network. Furthermore, the multiple core-shell structures included in TiO2@C-Ni/CNTs composites have the vast heterogeneous interfaces, which can result in multiple relaxation and effective interfacial polarization. Under the synergic action of the conductive loss, interface polarization, and three-dimensional spatial network structure, as-synthesized TiO2@C-Ni/CNTs nanobrushes possess superior MA performances with the minimum reflection loss (RL) of −32.3 dB at 17.3 GHz with a thickness of 1.6 mm and the broadest effective absorption bandwidth (EAB) of 5.5 GHz with a thickness of 1.8 mm. Furthermore, the thermal conductivities and diffusivities of the TiO2@C-Ni/CNTs/nature rubber hybrids are also effectively enhanced. This work provides an idea to design magnetic-dielectric composite nanostructures for MA and thermal management materials.

Oxygen Vacancy‐Induced Dielectric Polarization Prevails in the Electromagnetic Wave‐Absorbing Mechanism for Mn‐Based MOFs‐Derived Composites

AbstractPolymeric metal‐organic framework (MOF)‐derived composites are promising functional materials because of their exceptional chemical homogeneity, designable components, and adjustable pore size. The modulation of oxygen and Mn vacancies via the introduction of heteroatoms and changes in the annealing temperature in MOFs‐derived composites can be a possible solution to investigate the polarization loss mechanism, which facilitates the improvement of electromagnetic loss capacity. Herein, the design of laminate‐stacked sphere‐shaped trimetallic CoNiMn‐MOFs is presented. The derived CoNi/MnO@C composites retain the original topography of the MOFs. The concentration of oxygen vacancies increases with the incorporation of heteroatoms, but decreases with annealing temperature, which prevails in the polarization loss mechanism rather than the contribution of Mn2+ vacancies and heterogeneous interfaces. Therefore, the minimum reflection loss of the CoNi/MnO@C sample demonstrates −55.2 dB at 2.6 mm and the broad effective absorption bandwidth reaches 8.0 GHz at 2.1 mm. This work is expected to provide meaningful insights into the significant effect of ion vacancy modulation on the EM wave‐absorbing performance of Mn‐based MOFs‐derived composites.

Multifunctional interstitial-carbon-doped FeCoNiCu high entropy alloys with excellent electromagnetic-wave absorption performance

Electromagnetic-wave absorbing (EMA) materials that have efficient absorption performances, great mechanical properties and chemical stability are rare and yet essential for communication security and protection. Herein, flaky interstitial-carbon-doped FeCoNiCu high entropy alloys (HEAs) as novel EMA materials were successfully prepared by high-energy ball-milling method. Interstitial-carbon doping as a modulating approach impacted the phase forming, morphology and electromagnetic properties of FeCoNiCu HEAs. Impedance matching was significantly optimized via tuning interstitial carbon contents. The carbon-doped FeCoNiCu HEAs with appropriate carbon contents delivered superior EMA performance compared with other HEAs EMA materials. Strong reflection loss as low as -61.1 dB in the Ku band, broad effective absorption bandwidth of 5.1 GHz was achieved for FeCoNiCuC0.04. Moreover, the carbon-doped FeCoNiCu HEAs exhibited excellent mechanical hardness and chemical stability. This work not only suggests that interstitial-carbon doping is an available approach to tuning electromagnetic properties of HEAs, but also presents carbon-doped FeCoNiCu HEAs as promising EMA materials for civilian and military due to the efficient absorption, broad bandwidth, great durability and stability.