RESUMO
The excellent performance of electromagnetic wave absorbers primarily depends on the coordination among components and the rational design of the structure. In this study, a series of porous fibers with carbon nanotubes uniformly distributed in the shape of pine leaves are prepared through electrospinning technique, one-pot hydrothermal synthesis, and high-temperature catalysis method. The impedance matching of the nanofibers with a porous structure is optimized by incorporating melamine into the spinning solution, as it undergoes gas decomposition during high-temperature calcination. Moreover, the electronic structure can be modulated by controlling the NH4F content in the hydrothermal synthesis process. Ultimately, the Ni/Co/CrN/CNTs-CF specimen (P3C NiCrN12) exhibited superior performance, while achieving a minimum reflection loss (RLmin) of -56.18 dB at a thickness of 2.2 mm and a maximum absorption bandwidth (EABmax) of 5.76 GHz at a thickness of 2.1 mm. This study presents an innovative approach to fabricating lightweight, thin materials with exceptional absorption properties and wide bandwidth by optimizing the three key factors influencing electromagnetic wave absorption performance.
RESUMO
Currently, facing electromagnetic protection requirement under complex aqueous environments, the bacterial reproduction and organic dye corrosion may affect the composition and micro-structures of absorbers to weaken their electromagnetic properties. To address such problems, herein, a series of CoFe2O4@BCNPs (cobalt ferrite @ bio-carbon nanoparticles) composites are synthesized via co-hydrothermal and calcining process. The coupling of magnetic cobalt ferrite and dielectric bio-carbon derived from Apium can endow the composite multiple absorption mechanisms and matched impedance for effective microwave absorption, attaining a bandwidth of 8.12 GHz at 2.36 mm and an intensity of -49.85 dB at 3.0 mm. Due to the ROS (reactive oxygen species) stimulation ability and heavy metal ions of cobalt ferrite, the composite realizes an excellent antibacterial efficiency of 99% against Gram negative bacteria of Escherichia coli. Moreover, the loose porous layer of surface stacked bio-carbon can promote the adsorption of methylene blue for subsequent eliminating, a high removal rate of 90.37% for organic dye can be also achieved. This paper offers a new insight for rational design of composite's component and micro-structure to construct multi-functional microwave absorber for satisfying the electromagnetic protection demand in complicated environments.
RESUMO
Developing multifunctional materials which could simultaneously possess anti-bacterial ability and electromagnetic (EM) absorption ability during medical care is quite essential since the EM waves radiation and antibiotic-resistant bacteria are threatening people's health. In this work, the multifunctional carbon fiber/Ti3C2Tx MXene (CM) were synthesized through repeated dip-coating and following in-situ growth method. The as-fabricated CF/MXene displayed outstanding EM wave absorption and highly efficient photothermal converting ability. The minimum reflection loss (RL) of -57.07 dB and ultra-broad absorption of 7.74 GHz could be achieved for CM composites. By growth of CoNi-layered double hydroxides (LDHs) sheets onto MXene, the absorption bandwidth for carbon fiber/Ti3C2Tx MXene layered double hydroxides (CML) could be reach 5.44 GHz, which could cover the whole Ku band. The excellent photothermal effect endow the CM composites with excellent antibacterial performance. The antibacterials tests indicated that nearly 100 % bactericidal efficiency against E. acoil and S. aureus was obtained for the CM composite after exposure to near-infrared region (NIR) irradiation. This work provides a promising candidate to combat medical device-related infections and EM pollution.
RESUMO
Layered double hydroxides (LDHs) with unique layered structure and atomic composition are limited in the field of electromagnetic wave absorption (EMA) due to their poor electrical conductivity and lack of dielectric properties. In this study, the EMA performance and anticorrosion of hollow derived LDH composites are improved by temperature control and composition design using ZIF-8 as a sacrifice template. Diverse regulation modes result in different mechanisms for EMA. In the temperature control process, chemical reactions tune the composition of the products and construct a refined structure to optimize the LDHs conductivity loss. Additionally, the different phase interfaces generated by the control components optimize the impedance matching and enhance the interfacial polarization. The results show that the prepared NCZ (Ni3ZnC0.7/Co3ZnC@C) has a minimum reflection loss (RLmin ) of -58.92 dB with a thickness of 2.4 mm and a maximum effective absorption bandwidth (EABmax ) of 7.36 GHz with a thickness of 2.4 mm. Finally, due to its special structure and composition, the sample exhibits excellent anticorrosion properties. This work offers essential knowledge for designing engineering materials derived from metal organic framework (MOF) with cutting-edge components and nanostructures.
RESUMO
This paper considers the aperiodic intermittent control (AIC) for linear time-varying systems (LTVSs), where the occurrence instants are determined by an event triggering mechanism based on Lyapunov functions. For LTVSs, most of the existing results are demanded that the feedback controls are exerted all the time. In fact, in many practical applications, the applied controls are unnecessary/impossible to be imposed all the time. Therefore, the event-triggered AIC is introduced in this paper for LTVSs, and the uniformly stability, globally asymptotic stability and finite-time stability are proposed for LTVSs with event-triggered AIC, respectively. In addition, by using the piecewise constant feedback control method, effective intermittent controllers are designed for LTVSs. Finally, we present two numerical examples to illustrate the efficacy of the derived results.
RESUMO
Electromagnetic wave (EMW) absorbing materials have an irreplaceable position in the field of military stealth as well as in the field of electromagnetic pollution control. And in order to cope with the complex electromagnetic environment, the design of multifunctional and multiband high efficiency EMW absorbers remains a tremendous challenge. In this work, we designed a three-dimensional porous structure via the salt melt synthesis strategy to optimize the impedance matching of the absorber. Also, through interfacial engineering, a molybdenum carbide transition layer was introduced between the molybdenum selenide nanoparticles and the three-dimensional porous carbon matrix to improve the absorption behavior of the absorber. The analysis indicates that the number and components of the heterogeneous interfaces have a significant impact on the EMW absorption performance of the absorber due to mechanisms such as interfacial polarization and conduction loss introduced by interfacial engineering. Wherein, the prepared MoSe2/MoC/PNC composites showed excellent EMW absorption performance in C, X, and Ku bands, especially exhibiting a reflection loss of - 59.09 dB and an effective absorption bandwidth of 6.96 GHz at 1.9 mm. The coordination between structure and components endows the absorber with strong absorption, broad bandwidth, thin thickness, and multi-frequency absorption characteristics. Remarkably, it can effectively reinforce the marine anticorrosion property of the epoxy resin coating on Q235 steel substrate. This study contributes to a deeper understanding of the relationship between interfacial engineering and the performance of EMW absorbers, and provides a reference for the design of multifunctional, multiband EMW absorption materials.
RESUMO
Reasonable composition design and controllable structure are effective strategies for harmonic electromagnetic wave (EMW) adsorption of multi-component composites. On this basis, the hybrid MoS2 /CoS2 /VN multilayer structure with the triple heterogeneous interface is prepared by simple stirring hydrothermal, which can satisfy the synergistic interaction between different components and obtain excellent EMW absorption performance. Due to the presence of multiple heterogeneous interfaces, MoS2 /CoS2 /VN composites will produce strong interfacial polarization, while the defects in the sample will become the center of polarization, resulting in dipole polarization. Due to the excellent structural design of MoS2 /CoS2 /VN composite material, MoS2 /CoS2 /VN composite material not only has good conductive loss and polarization loss, but also can maintain excellent stability in simulated seawater, and enhance corrosion resistance. The MoS2 /CoS2 /VN composite with dual functions of corrosion resistant and microwave absorption achieves a minimum reflection loss (RL) of -50.48 dB and an effective absorption bandwidth of up to 5.76 GHz, covering both the X-band and Ku-band. Finally, this study provides a strong reference for the development of EMW absorption materials based on transition metal nitrides.
RESUMO
The development of wearable multifunctional electromagnetic protective fabrics with multifunctional, low cost, and high efficiency remains a challenge. Here, inspired by the unique flower branch shape of "Thunberg's meadowsweet" in nature, a nanofibrous composite membrane with hierarchical structure was constructed. Integrating sophisticated 0D@2D@1D hierarchical structures with multiple heterointerfaces can fully unleash the multifunctional application potential of composite membrane. The targeted induction method was used to precisely regulate the formation site and morphology of the metal-organic framework precursor, and intelligently integrate multiple heterostructures to enhance dielectric polarization, which improves the impedance matching and loss mechanisms of the electromagnetic wave absorbing materials. Due to the synergistic enhancement of electrospinning-derived carbon nanofiber "stems", MOF-derived carbon nanosheet "petals" and transition metal selenide nano-particle "stamens", the CoxSey/NiSe@CNSs@CNFs (CNCC) composite membrane obtains a minimum reflection loss value (RLmin) of -68.40 dB at 2.6 mm and a maximum effective absorption bandwidth (EAB) of 8.88 GHz at a thin thickness of 2.0 mm with a filling amount of only 5 wt%. In addition, the multi-component and hierarchical heterostructure endow the fibrous membrane with excellent flexibility, water resistance, thermal management, and other multifunctional properties. This work provides unique perspectives for the precise design and rational application of multifunctional fabrics.
RESUMO
In the field of electromagnetic (EM) wave absorption, intrinsic conductive polymers with conjugated long-chain structures, such as polyaniline (PANI) and polypyrrole (PPy), have gained widespread use due to their remarkable electrical conductivity and loss ability. However, current research in this area is limited to macroscopic descriptions of the absorption properties of these materials and the contribution of various components to the absorption effect. There has been insufficient exploration of the impact mechanisms of polymer aggregation states on the material's absorption performance and mechanism. To address this, a series of flexible PANI sponge absorbers with different molecular weights and aggregation states were prepared. By carefully controlling the crystallinity and other aggregation characteristics of PANI through the adjustment of its preparation conditions, we were able to influence its electrical conductivity and electromagnetic parameters, thereby achieving control over the material's absorption properties. The resulting PANI sponge absorbers exhibited an effective absorption bandwidth (EAB) that covered the entire X-band at a thickness of 3.2 mm. This study comprehensively explores the absorption mechanisms of conductive polymer absorbers, starting from the microstructure of PANI, and providing a more complete theoretical support for the research and promotion of polymer absorbers.
RESUMO
The design of metal-organic frameworks (MOF) derived composites with multiple loss mechanisms and multi-scale micro/nano structures is an important research direction of microwave absorbing materials. Herein, multi-scale bayberry-like Ni-MOF@N-doped carbon composites (Ni-MOF@NC) are obtained by a MOF assisted strategy. By utilizing the special structure of MOF and regulating its composition, the effective improvement of Ni-MOF@NC's microwave absorption performance has been achieved. The nanostructure on the surface of core-shell Ni-MOF@NC can be regulated and N doping on carbon skeleton by adjusting the annealing temperature. The optimal reflection loss of Ni-MOF@NC is -69.6 dB at 3 mm, and the widest effective absorption bandwidth is 6.8 GHz. This excellent performance can be attributed to the strong interface polarization caused by multiple core-shell structures, the defect and dipole polarization caused by N doping, and the magnetic loss caused by Ni. Meanwhile, the coupling of magnetic and dielectric properties enhances the impedance matching of Ni-MOF@NC. The work proposes a particular idea of designing and synthesizing an applicable microwave absorption material that possesses excellent microwave absorption performance and promising application potential.
RESUMO
The combination of carbon materials and magnetic elements is considered as an effective strategy to obtain high-performance electromagnetic wave (EMW) absorption materials. However, using nanoscale regulation to the optimization of composite material dielectric properties and enhanced magnetic loss properties is facing significant challenges. Here, the dielectric constant and magnetic loss capability of the carbon skeleton loaded with Cr compound particles are further tuned to enhance the EMW absorption performance. After 700 °C thermal resuscitation of the Cr3-polyvinyl pyrrolidone composite material, the chromium compound is represented as a needle-shaped structure of nanoparticles, which is fixed on the carbon skeleton derived from the polymer. The size-optimized CrN@PC composites are obtained after the substitution of more electronegative nitrogen elements using an anion-exchange strategy. The minimum reflection loss value of the composite is -105.9 dB at a CrN particle size of 5 nm, and the effective absorption bandwidth is 7.68 GHz (complete Ku-band coverage) at 3.0 mm. This work overcomes the limitations of impedance matching imbalance and magnetic loss deficiency in carbon-based materials through size tuning, and opens a new way to obtain carbon-based composites with ultra-high attenuation capability.
RESUMO
Although multifunctional aerogels are expected to be used in applications such as portable electronic devices, it is still a great challenge to confer multifunctionality to aerogels while maintaining their inherent microstructure. Herein, a simple method is proposed to prepare multifunctional NiCo/C aerogels with excellent electromagnetic wave absorption properties, superhydrophobicity, and self-cleaning by water-induced NiCo-MOF self-assembly. Specifically, the impedance matching of the three-dimensional (3D) structure and the interfacial polarization provided by CoNi/C as well as the defect-induced dipole polarization are the primary contributors to the broadband absorption. As a result, the prepared NiCo/C aerogels have a broadband width of 6.22 GHz at 1.9 mm. Due to the presence of hydrophobic functional groups, CoNi/C aerogels improve the stability in humid environments and obtain hydrophobicity with large contact angles > 140°. This multifunctional aerogel has promising applications in electromagnetic wave absorption, resistance to water or humid environments.
RESUMO
Harvesting largely ignored and wasted electromagnetic (EM) energy released by electronic devices and converting it into direct current (DC) electricity is an attractive strategy not only to reduce EM pollution but also address the ever-increasing energy crisis. Here we report the synthesis of nanoparticle-templated graphene with monodisperse and staggered circular nanopores enabling an EM-heat-DC conversion pathway. We experimentally and theoretically demonstrate that this staggered nanoporous structure alters graphene's electronic and phononic properties by synergistically manipulating its intralayer nanostructures and interlayer interactions. The staggered circular nanoporous graphene exhibits an anomalous combination of properties, which lead to an efficient absorption and conversion of EM waves into heat and in turn an output of DC electricity through the thermoelectric effect. Overall, our results advance the fundamental understanding of the structure-property relationships of ordered nanoporous graphene, providing an effective strategy to reduce EM pollution and generate electric energy.
RESUMO
In order to achieve excellent electromagnetic wave (EMW) absorption properties, the microstructure design and component control of the absorber are critical. In this study, three different structures made of Mo2 C/C hollow spheres are prepared and their microwave absorption behavior is investigated. The Mo2 C/C double-shell hollow spheres consisting of an outer thin shell and an inner rough thick shell with multiple EMW loss mechanisms exhibit good microwave absorption properties. In order to further improve the microwave absorption properties, MoC1-x /C double-shell hollow spheres with different crystalline phases of molybdenum carbide are prepared to further optimize the EMW loss capability of the materials. Finally, MoC1-x /C double-shell hollow spheres with α-phase molybdenum carbide have the best microwave absorption properties. When the filling is 20 wt.%, the minimum reflection loss at 1.8 mm is -50.55 dB and the effective absorption bandwidth at 2 mm is 5.36 GHz, which is expected to be a microwave absorber with the characteristics of "thin, light, wide, and strong".
RESUMO
Tunable designs of polymorphic structured transition metal dichalcogenide (TMDC) demonstrate promising applications in the field of electromagnetic wave absorption (EMW). However, it remains a technical challenge for achieving a balanced relationship between well-matched impedance characteristics and dielectric losses. Therefore, the co-modification strategies of polydopamine coating and wet impregnation are chosen to construct CoS2 magnetic double-shell microspheres with phase component modulation to achieve the optimized performance. Dopamine hydrochloride forms a coating on the surface of CoS2 microspheres by self-polymerization and forms a double-shell structure during the pyrolysis process. Then the different metal is doped to generate heterogeneous components in the process of heat treatment. The results show that the cobalt doped double-shell microspheres have an ultra-high electromagnetic wave absorption absorption capacity with an effective absorption bandwidth of 5.04 GHz (1.98 mm) and a minimum reflection loss value of -48.90 dB. The double-shell layer structure and metal ion hybridization can improve the interfacial polarization and magnetic loss behavior, which provides an explicit inspiration for the development of transition metal dichalcogenide and even transition metal compounds with tunable absorption properties.
RESUMO
In consideration of the growing electromagnetic wave (EMW) pollution and interference, it is of crucial and imperative significance to develop high-efficiency EMW absorption materials. Herein, hierarchical hybrid network of MoS2@poly (3, 4-ethylenedioxythiophene) (PEDOT)/reduced graphene oxide (rGO) were successfully constructed and fabricated through the combination of oxidative polymerization and microwave-irradiated thermal reduction. The original defects in graphene oxide (GO) could be in situ repaired by introducing carbon source, and the rational regulation of polarization relaxation and conductivity of composites could be achieved. Profiting from the good impedance matching, ameliorated conductivity and enhanced dipole polarization as well as interfacial polarization by introducing GO/defect-recovered rGO and conductive PEDOT, both the MoS2@PEDOT/GO and MoS2@PEDOT/rGO composites exhibited outstanding EMW absorption performances. In details, the minimum reflection loss (RLmin) and effective absorption bandwidth (EAB) of MoS2@PEDOT/GO can reach -48.65 dB at 4.5 mm, and 6.48 GHz (11.52-18 GHz) at 2.2 mm, respectively. And the EAB of MoS2@PEDOT/rGO can reach 7.04 GHz (10.8-17.84 GHz) with an optimized RLmin of -32.41 dB at 2.1 mm under 20 wt% filler loading. Therefore, these composites can be regarded as competitive candidates for lightweight and high-efficient EMW absorbers.
Assuntos
Radiação Eletromagnética , MolibdênioRESUMO
Application of novel radio technologies and equipment inevitably leads to electromagnetic pollution. One-dimensional polymer-based composite membrane structures have been shown to be an effective strategy to obtain high-performance microwave absorbers. Herein, we reported a one-dimensional N-doped carbon nanofibers material which encapsulated the hollow Co3SnC0.7 nanocubes in the fiber lumen by electrospinning. Space charge stacking formed between nanoparticles can be channeled by longitudinal fibrous structures. The dielectric constant of the fibers is highly related to the carbonization temperature, and the great impedance matching can be achieved by synergetic effect between Co3SnC0.7 and carbon network. At 800 °C, the necklace-like Co3SnC0.7/CNF with 5% low load achieves an excellent RL value of - 51.2 dB at 2.3 mm and the effective absorption bandwidth of 7.44 GHz with matching thickness of 2.5 mm. The multiple electromagnetic wave (EMW) reflections and interfacial polarization between the fibers and the fibers internal contribute a major effect to attenuating the EMW. These strategies for regulating electromagnetic performance can be expanded to other electromagnetic functional materials which facilitate the development of emerging absorbers.
RESUMO
Three-dimensional (3D) graphene oxide aerogel (GOA) is one of the best fillers for composites for microwave absorption. However, its further development has been hindered by the poor mechanical properties. Methodology to improve the mechanical properties of the aerogel remains an urgent challenge. Herein, graphene oxide/carbon nanotube/epoxy resin composite aerogel (GCEA) was successfully prepared by a facile method. The results showed that the prepared GCEA with the hierarchical and 3D cross-linked structures exhibited excellent compression performance, structural and thermal stability, high hydrophilicity, and microwave absorption. The prepared GCEA recovered from multiple large strain cycles without significant permanent deformation. The minimum reflection loss (RL) was -39.60 dB and the maximum effective absorption bandwidth (EAB) was 2.48 GHz. The development of the enhanced GO aerogels will offer a new approach to the preparation of 3D microwave-absorbing skeletal materials with good mechanical properties.
RESUMO
Lithium metal batteries (LMBs) are promising next-generation battery technologies with high energy densities. However, lithium dendrite growth during charge/discharge results in severe safety issues and poor cycling performance, which hinders their wide applications. The rational design and application of functional polymer materials in LMBs are of crucial importance to boost their electrochemical performances, especially the cycling stability. In this review, recent advances of advanced polymer materials are examined for boosting the stability and cycle life of LMBs as different components including artificial solid electrolyte interface (SEI) and functional interlayers between the separator and lithium metal anode. Thereafter, the research progress in the design of advanced polymer electrolytes will be analyzed for LMBs. At last, the major challenges and key perspectives will be discussed for the future development of functional polymers in LMBs.
RESUMO
Lithium-metal batteries have attracted extensive research attention because of their high energy densities. Developing appropriate electrolytes compatible with lithium-metal anodes is of great significance to facilitate their practical application. Currently used electrolytes still face challenges of high production costs and unsatisfactory Coulombic efficiencies of lithium plating/stripping. In this research, we have developed a diluted electrolyte which is compatible with both lithium-metal anode and sulfurized polyacrylonitrile cathode. It presents a very high Li plating/stripping Coulombic efficiency of 99.3% over prolonged cycling, and the as-assembled anode-free Li-S battery maintains 71.5% of the initial specific capacity after 200 cycles at 0.1 A g-1. This work could shed light on designing a low-cost and high-performance liquid electrolyte for next-generation high-energy batteries.