242 results about "Absorption bandwidth" patented technology

The invention discloses a silicon carbide / graphene composite material and a preparation method thereof, the composite material is of a three-dimensional network structure generated through in-situ reaction of multilayer graphene and silicon powder, silicon carbide nanowires in the structure are distributed on graphene sheets, the length of the silicon carbide nanowires is 1-5 microns, the diameter of the silicon carbide nanowires is 50-100 nm, and the silicon carbide nanowires are in a beta-SiC crystal form. The material is prepared through a carbon thermal reduction method, specifically, silicon carbide nanowires grow on the surface of graphene in situ, so that electromagnetic parameters and impedance matching characteristics of the material are optimized. The prepared composite material has the characteristics of light weight, high specific surface area, good dielectric loss and the like, and shows good broadband wave-absorbing performance in the frequency band of 2-18 GHz, the minimum reflection loss can reach-23.535 dB, and the effective absorption bandwidth reaches 1.498 GHz. The method is simple in process, low in energy consumption and suitable for large-scale production, and has wide application prospects in the fields of stealth technology, electromagnetic shielding and the like.

The invention provides N-O doped flower-like porous carbon microspheres as well as a preparation method and application thereof, and belongs to the technical field of electromagnetic wave absorbing materials. According to the invention, microspheres are coated by using a simple soap-free emulsion polymerization method, a complex multi-layer heterogeneous interface structure is realized, N and O atoms are introduced, and heteroatom doping is realized so as to improve the wave-absorbing performance; a unique flower-shaped structure is grown on the surface of the microsphere through a self-assembly process, and an exquisite flower-shaped porous carbon microsphere can be obtained through carbonization, so that an ingenious structure beneficial to multiple reflection and scattering generation is realized. Under the conditions that the mass ratio of the flower-like porous carbon microspheres to the paraffin is 1: 5 and the matching thickness is 2.5-3mm, the minimum reflection loss of the flower-like porous carbon microspheres is-40.8 to-48.0 dB, the optimal effective absorption bandwidth is 4.40 GHz, and the flower-like porous carbon microspheres have excellent electromagnetic wave absorption performance.

The invention relates to the technical field of electromagnetic functional materials, in particular to a nested hexagonal resonant structure wave-absorbing metamaterial and a preparation method and application thereof. The wave-absorbing metamaterial with the nested hexagonal resonant structure sequentially comprises a metal resonant layer, a homogeneous wave-absorbing coating and a metal matrix layer, the metal resonance layer is formed by periodically arranging a plurality of metal resonance units on the surface of the homogeneous wave-absorbing coating in an array manner; each metal resonance unit is of a nested hexagonal structure formed by arranging a plurality of structural units, and each structural unit is a hollow hexagonal metal patch. Through the combination of the homogeneous wave-absorbing coating and the metal resonance layer, the wave-absorbing metamaterial with the nested hexagonal resonance structure not only can realize effective absorption of an S wave band under the sub-wavelength scale, but also is beneficial to widening the effective absorption bandwidth and improving the absorption efficiency, simplifies the complex layered stacking framework of a traditional broadband wave absorber from the structural design, and has the advantages of simple structure and low cost. The method has the engineering application advantages of high process adaptability, high preparation feasibility and the like.

The invention belongs to the field of protective materials, and particularly relates to a 3D printing high-performance porous silicon carbide ceramic wave-absorbing material and a preparation method and application thereof. The extrusion type 3D printing technology is combined with the reaction sintering and impregnation technology, the complex structure forming and the high-performance wave absorbing effect are achieved, the material prepared through the method has excellent mechanical performance and wave absorbing performance at the same time (the bending strength is larger than 15 MPa, the reflection loss minimum value at the frequency band of 2-18 GHz is larger than-25 dB, and the absorption bandwidth is larger than 3 GHz), and the material has the good application prospect. The method is suitable for military stealth engineering and other fields.

The invention discloses a broadband wide-angle polarization insensitive metamaterial wave absorber, which comprises three layers of structures, namely a microstructure unit layer, an FR-4 substrate layer and a metal bottom plate layer which are sequentially superposed from top to bottom, the whole microstructure unit layer is in axial symmetry and comprises four layers of structures, the four layers of structures sequentially comprise a rectangular metal resonance piece, four fan-shaped metal resonance pieces, a first opening metal resonance ring and a second opening metal resonance ring from inside to outside, the first opening metal resonance ring and the second opening metal resonance ring are concentric opening circular rings, and the circle centers of the first opening metal resonance ring and the second opening metal resonance ring are the centers of the rectangular metal resonance pieces. The circle centers of the four fan-shaped metal resonance sheets are located at the four corners of the rectangular metal resonance sheet respectively, the arc angles of the four fan-shaped metal resonance sheets are 90 degrees, and the edges of the four fan-shaped metal resonance sheets are located on the extension lines of the edges of the rectangular metal resonance sheet respectively. The first opening metal resonance ring and the second opening metal resonance ring are respectively provided with two openings along the transverse axis and the longitudinal axis, and the width of the openings is equal to the side length of the rectangular metal resonance piece. The wave-absorbing material has wider wave-absorbing bandwidth and better absorbing performance.

The invention belongs to the technical field of preparation of wave-absorbing materials, and particularly relates to a cobalt-based nitrogen-doped carbon nano composite material with a hollow cubic structure as well as a preparation method and application thereof. Comprising the following steps: taking ZnCo-ZIF with a nano cubic structure as a core, coating ZnCo-ZIF with polydopamine by adopting a precipitation method to form a precursor with a core-shell structure, and carbonizing the precursor at 800-900 DEG C to obtain the cobalt-based nitrogen-doped carbon nano composite material with the hollow cubic structure. According to the invention, the dielectric loss capability can be enhanced by using the conductivity and interface polarization effect of the coated carbon layer, and the Co particles introduce strong magnetic loss; meanwhile, due to interface polarization caused by abundant heterogeneous interfaces existing between the Co particles and the coating carbon layer, between the magnetic particles and the carbon nanotubes and between the carbon matrix and the carbon nanotubes in the composite material, the impedance matching characteristic can be improved, and high reflection loss and wide effective absorption bandwidth can be achieved under the low matching thickness.

The invention discloses a preparation method of a Fe3O4 modified phosphorus-doped carbon-based porous wave-absorbing material constructed on the basis of a multi-component strategy. The preparation method comprises the following steps: firstly, preparing a phosphorus-doped carbon-based porous nano material through a freeze-drying method and a sacrificial template method, then obtaining a Fe3O4 intermediate through oil bath, and finally reducing for 6 hours in an Ar atmosphere to obtain the Fe3O4-modified phosphorus-doped carbon-based porous wave-absorbing material, namely Fe3O4 (at) P-NCP. Based on a good magnetic loss mechanism of the material, a synergistic effect of dielectric loss and magnetic loss is provided for electromagnetic wave absorption. And meanwhile, the porous structure ensures that incident electromagnetic waves can form multiple reflections in the porous structure. The material has the advantages of good microwave absorption performance, thin matching thickness, wide effective absorption frequency band and the like. A good foundation is provided for development of porous materials, and a good design thought is provided for preparation of electromagnetic wave absorbing materials. The good microwave absorption performance of the material can play a good role in electromagnetic radiation and pollution, and the material has a wide application prospect.

The invention discloses a carbonyl iron powder-graphite electromagnetic wave absorption composite material and a preparation method thereof. The carbonyl iron powder-graphite electromagnetic wave absorption composite material is composed of superfine spherical carbonyl iron powder and flake graphite. According to the method for preparing the carbonyl iron powder-graphite electromagnetic wave absorbing composite material, a room-temperature dry ball milling technology is utilized, various carbonyl iron powder-carbon composite wave absorbing materials can be flexibly prepared, the preparation process is simple, the condition is mild, consumed time is short, use of a large amount of solvent is avoided, and the method is economical and environmentally friendly. According to the method for preparing the carbonyl iron powder-graphite electromagnetic wave absorption composite material, cheap carbonyl iron powder and flake graphite are adopted as raw materials, the raw materials are cheap and easy to obtain, and the method is suitable for actual industrial application. The carbonyl iron powder-graphite electromagnetic wave absorption composite material provided by the invention has large reflection loss and absorption bandwidth under the condition of low thickness, and can effectively absorb electromagnetic waves.

The invention discloses an aerogel metamaterial capable of switching electromagnetic wave absorption and deflection reflection wave beam and a preparation method thereof, and the preparation method is characterized in that a metamaterial unit with a loose structure is arranged and comprises a first layer of rectangular pyramid, a second layer of quadrangular frustum pyramid, a third layer of quadrangular frustum pyramid and an internal pyramid cavity; the first layer of rectangular pyramid, the second layer of quadrangular frustum pyramid, the third layer of quadrangular frustum pyramid and the internal pyramid cavity are on the same center line; the bottom surface of the internal pyramid cavity is close to the bottom surface of the third-time quadrangular frustum pyramid, and the vertex of the internal pyramid cavity is close to the vertex of the first-layer quadrangular pyramid; the preparation method comprises the following steps: pouring mixed dispersion liquid containing conductive / magnetic functional components and cellulose microfibers into a mold manufactured according to a set structure, freezing, and then freeze-drying to obtain the metamaterial unit. The obtained aerogel metamaterial solves the problems that the effective absorption bandwidth of aerogel with adjustable electromagnetic wave absorption performance is difficult to substantially break through, and the aerogel cannot have both electromagnetic wave absorption performance and deflection reflection beam performance at the same time.

The invention discloses a preparation method of a magnetic doped nanofiber derived carbon aerogel wave-absorbing material with a gradient pore structure and application of carbon aerogel, and belongs to the field of microwave wave-absorbing materials. The aerogel microstructure is controlled by regulating and controlling the parameters of the arched ice template and the content of the magnetic material precursor, and the lightweight carbon aerogel material is obtained through arched ice template freezing, freeze drying and carbonization. The gradient pore structure of the carbon aerogel improves impedance matching and promotes microwave reflection and scattering; the nano cellulose, the aramid nano fiber and the metal organic framework cooperatively optimize the polarization loss and magnetic loss performance by constructing a multi-element heterogeneous interface. Due to the characteristics, the carbon aerogel has excellent wave absorbing performance. According to the present invention, the carbon aerogel has the optimal reflection loss value of-57.03 dB when the frequency is 2-18 GHz and the thickness is 2.8 mm, and the effective absorption bandwidth (RL < =-10 dB) of the microwave absorption is 6.76 GHz, such that the carbon aerogel has the good application prospect in the electromagnetic wave field, and can simultaneously achieve the broadband and the strong absorption of the microwave under the low thickness.

The invention provides a broadband absorption and transmission integrated frequency selective surface with a high selection characteristic, which comprises a first loss layer, a second loss layer and a frequency selection layer, and is characterized in that the first loss layer and the second loss layer realize a transmission band with the high selection characteristic and the broadband characteristic at the same time by using dual-order resonance; the second loss layer and the frequency selection layer are cascaded to realize the absorption and transmission integrated characteristic, and the first loss layer is used for improving the low-frequency and high-frequency wave absorption characteristics and expanding the wave absorption bandwidth. Under the combined action of the first loss layer, the second loss layer and the frequency selection layer, wave transmission within the frequency band of 7.72-11.89 GHz and wave absorption within the frequency band of 1.96-7.12 GHz and the frequency band of 12.95-17.33 GHz are achieved. The antenna has high selection characteristics and broadband characteristics, can effectively suppress interference of external electromagnetic waves of other frequency bands or electromagnetic waves of a frequency band close to a communication frequency band on communication, can reduce the radar cross section of a target, and facilitates target stealth.

The invention discloses a method for preparing wave-absorbing integrated SiC / Si3N4 composite ceramic with high strength and toughness in a short period. Silicon nitride, silicon carbide, a sintering aid and other powder are mixed and dispersed for a short time through high-strength mechanical vibration, and the high-strength and high-toughness wave-absorbing composite ceramic is prepared after direct sintering. According to the preparation process, the preparation steps of ball milling, drying, sieving and the like are avoided, the preparation process period of the SiC / Si3N4 composite ceramic can be shortened from 1 week to 1 day, and the labor intensity is reduced; according to the preparation process, an organic solvent and a grinding medium do not need to be introduced, and pollution to samples and the environment is avoided; more importantly, the preparation process can effectively disperse the nano-powder and the whiskers, avoids the damage of a grinding medium to the powder such as particles and the whiskers, and enhances the strength and toughness of the ceramic material. The bending strength of the prepared SiC / Si3N4 composite ceramic can reach up to 1007 MPa, the fracture toughness reaches 11.63 MPa.m < 1 / 2 >, the minimum reflection loss of electromagnetic waves is-27 dB, and the wave absorbing bandwidth is 2.28 GHz.

The invention discloses an ultra-wideband three-dimensional metamaterial wave absorber with large angular domain stability, which comprises M * N wave absorber units, and is characterized in that M is more than or equal to 10 rows, N is more than or equal to 10 columns, and each wave absorber unit sequentially comprises an upper-layer three-dimensional vertical resistive film patch cylindrical structure, a bottom square resistive film structure or a metal bottom plate II from top to bottom, a lower-layer three-dimensional vertical resistive film patch cylindrical structure and a lower-layer square resistive film patch cylindrical structure from top to bottom. And the cylindrical structure of the upper-layer three-dimensional vertical resistive film patch is adhered to the bottom square resistive film structure through optical cement or adhered to the metal bottom plate II. According to the invention, the effects of ultra-wide absorption bandwidth, large angular domain stability and polarization insensitivity can be realized.

The invention relates to the technical field of aerogel materials, in particular to a carbon-rich SiC-coated Si3N4 double-network aerogel and a preparation method thereof. The double-network aerogel comprises an inner framework and an outer framework, the inner framework is a SiC network, the outer framework is a Si3N4 network, the double-network aerogel is formed by interweaving the SiC network and the Si3N4 network, the SiC network and the Si3N4 network are rich in in-situ carbon, and the content of the in-situ carbon in the Si3N4 network is far smaller than that of the in-situ carbon in the SiC network. The aerogel disclosed by the invention successfully integrates multiple key properties, wherein high porosity and low thermal conductivity ensure excellent thermal insulation capability; the reflection loss reaches-60dB to the minimum, and the effective absorption bandwidth reaches 5GHz, so that the excellent broadband wave-absorbing performance is proved; the compressive strength of the material can reach 14 MPa or above, excellent mechanical reliability is shown, and an ideal solution is provided for electromagnetic protection and thermal management of high-end equipment.

The invention relates to an ablation-resistant, heat-insulation and wave-absorbing integrated fiber-reinforced silicon resin composite material, which belongs to the technical field of wave-absorbing materials, and comprises a heat-insulation area and a wave-absorbing area which are sequentially arranged from top to bottom, the wave absorbing area comprises a magnetic modified fiber single sheet and / or an electric modified fiber single sheet; each electrically-modified fiber single sheet comprises electrically-modified fibers and matrix resin, wherein the peripheries of the electrically-modified fibers are coated with electrically-coated modified layers, and gaps of the electrically-modified fibers are filled with the matrix resin; each magnetic modified fiber single sheet comprises a magnetic modified fiber and matrix resin, wherein the periphery of the magnetic modified fiber is coated with a magnetic coating modified layer, and gaps of the magnetic modified fiber are filled with the matrix resin. The modified layer is coated on the periphery of the fiber to form regular and ordered wave-absorbing areas, regular and ordered refraction and reflection areas are formed in gaps among the fibers, interfaces with different absorptivity are formed between the wave-absorbing areas and the refraction and reflection areas due to different materials, the absorption effect is improved, the absorptivity and the absorption bandwidth are improved, and the service life of the fiber is prolonged. And meanwhile, the problems of poor dispersion uniformity and low production efficiency of the wave-absorbing material are solved.

The invention belongs to the field of electromagnetic wave absorbing materials, and particularly relates to a thin broadband composite wave absorber based on a frequency selective surface. According to the invention, the wave-transparent layer is added in the middle of the multi-layer magnetic material, the mindset of simply stacking the same type of materials in the traditional multi-layer wave-absorbing structure is broken, and the wave-transparent layer is introduced to change the original characteristic that the impedance gradually changes in sequence; meanwhile, a magnetic wave-absorbing material, a frequency selection surface and a medium matching layer are subjected to composite design, the frequency selection surface generates an electromagnetic coupling effect at high frequency, phase and impedance conversion of electromagnetic waves in a multi-layer structure is controlled, and efficient impedance matching and electromagnetic wave energy dissipation in a broadband are achieved through electromagnetic absorption and interference cancellation; and an excellent wave absorbing effect is achieved. The total thickness of the composite wave absorber ranges from 0.064 lambda to 0.1 lambda, the-10 dB absorption bandwidth ranges from 3.3 GHz to 18 GHz, and the relative bandwidth reaches 138%; and meanwhile, the wave absorber has a wide angular domain characteristic under oblique incidence, and a novel thin broadband composite wave absorber scheme is provided.

The present invention belongs to the field of electromagnetic wave absorbing materials, and specifically provides a multifunctional terahertz wave absorbing fabric based on MXenes materials and a preparation method thereof, aiming to solve the problems of narrow absorption bandwidth, single function, and easy oxidation existing in MXenes absorbing materials; based on the fiber microstructure in the matrix, combining the conductance loss and Ohmic loss of MXenes materials, waterborne polyurethane (WPU) is sprayed on the surface of the absorbing fabric for modification to realize a multifunctional terahertz absorbing material. The absorption efficiency can reach 100% under electromagnetic waves of 0.3 - 1.2 THz. At the same time, the water contact angle and rolling angle reach 151.3° and 0° respectively, with good self-cleaning performance, and the absorption performance of the fabric remains above 99% after self-cleaning. In addition, it has excellent acid and alkali resistance and environmental adaptability.

The invention relates to the technical field of coatings for absorbing electromagnetic waves, and discloses a preparation method of an NZSP wave-absorbing coating with a three-dimensional periodic structure, and the preparation method comprises the following steps: step 1, obtaining NZSP spherical powder; step 2, spraying NZSP spherical powder on the substrate to obtain a first coating; 3, determining the shape of the periodic unit; the plurality of periodic units are arranged into a periodic structure according to a regular space array; step 4, performing laser sintering on the NZSP spherical powder spread on the first coating; 5, laying powder layer by layer, and carrying out accumulative sintering until a preset height is reached, so as to obtain a second coating; and 6, forming the NZSP wave-absorbing coating with a three-dimensional periodic structure by the first coating and the second coating. The first coating and the second coating are manufactured on the basis of the NZSP spherical powder, and the method has outstanding advantages in weight reduction application; the absorption bandwidth of the NZSP wave-absorbing coating is expanded through the macroscopic design of the periodic structure, the wave-absorbing performance is improved, and the NZSP wave-absorbing coating is suitable for the field of aerospace.

A preparation method and application of a flexible iron carbonyl inverted pyramid metamaterial thin film, which relate to the preparation method and application of electromagnetic absorption metamaterials. It is intended to solve the technical problems of the existing metamaterials having fixed functions after processing and narrow absorption frequency bands at a fixed thin thickness. The method includes: adding iron carbonyl powder, dibutyl phthalate, and tributyl phosphate into a PVB binder to prepare a slurry; then casting and drying the slurry on a glass substrate to obtain a cast film; laminating the cast films and engraving periodic units, and then laminating and assembling the periodic units into an inverted pyramid structure to obtain a metamaterial thin film. A film of about 2 mm is directly attached to a metal plate to form an electromagnetic absorption flat component, and its absorption bandwidth covers about 12.4 GHz - 18.5 GHz; the film is bent and covered on the metal plate with an air layer of adjustable thickness, realizing dual-frequency absorption at about 6.8 GHz and 14.5 GHz. This multifunctional thin film can be used in the field of wave absorption.

The utility model discloses a three-dimensional wave absorber and electronic equipment, and relates to the technical field of metamaterial wave absorbers, and the three-dimensional wave absorber comprises a substrate which is provided with a first surface and a second surface which are opposite to each other; the horizontal wave absorbing structure is arranged on the first surface and is provided with a plurality of first wave absorbing units; the bearing plate is fixed on the first surface between the first wave absorbing units; the side wall, perpendicular to the substrate, of the bearing plate is provided with a vertical wave-absorbing structure, and the vertical wave-absorbing structure is provided with a plurality of second wave-absorbing units. The pattern structure of the first wave absorbing unit is different from that of the second wave absorbing unit. According to the technical scheme, the three-dimensional wave absorbing body can be formed based on the horizontal wave absorbing structure and the vertical wave absorbing structure, compared with a two-dimensional wave absorbing body, the three-dimensional wave absorbing body has the wide absorption bandwidth and the high absorption rate, the performance of the three-dimensional wave absorbing body can be optimized by adjusting the graph structure of the wave absorbing unit, the angle stability is improved, and the wave absorbing effect is improved. And wave absorption in a relatively high bandwidth range is realized.

The application discloses a reconfigurable transparent wave absorber based on a miura fold, and relates to a transparent wave absorber. The application aims to solve the problems of a narrow variable absorption bandwidth, a small change amplitude and a small absorption angle of an existing reconfigurable wave absorber. The reconfigurable transparent wave absorber based on the miura fold is composed of a miura fold-shaped wave absorbing layer and a planar reflecting layer from top to bottom; or the reconfigurable transparent wave absorber based on the miura fold is a single miura fold-shaped wave absorbing layer.

The present invention belongs to the technical field of electromagnetic wave absorption, and particularly relates to a deep ultraviolet-visible-near infrared ultra-wideband band absorber and a preparation method thereof. The present invention provides a deep ultraviolet-visible-near infrared ultra-wideband band absorber, which comprises a substrate, a metal thin film reflection layer and a functional layer stacked in sequence from bottom to top; the functional layer comprises a plurality of dielectric absorption layers with decreasing complex refractive index from bottom to top. The present invention utilizes a thin film stack structure, which has the characteristics of polarization insensitivity and angle insensitivity. Moreover, the obtained band absorber has an extremely wide absorption bandwidth, and the band range is from 190 to 1700 nm.

The invention discloses a broadband strong-absorption microwave metamaterial design and preparation method based on impedance control, and belongs to the field of electromagnetic absorption metamaterials. The invention aims to solve the problem that a microwave absorption metamaterial is difficult to realize wide absorption bandwidth and strong absorption intensity at the same time. The method comprises the following steps of: 1, solving an impedance value range of a resistive film layer on the surface of the microwave absorption metamaterial; 2, further extracting the available value ranges of the equivalent resistance and the equivalent capacitance of the resistive film layer; 3, traversing value ranges of the equivalent resistance and the equivalent capacitance, and collecting phase information of electromagnetic waves reflected by the corresponding metamaterial; 4, calculating a reflected electromagnetic wave phase difference; 5, selecting two metamaterial units of which the difference between the average value of the absolute values of the phase differences and the pi is minimum in the target frequency band; and 6, forming a new metamaterial unit through chessboard type distribution and arrangement, and realizing the design of the broadband strong-absorption metamaterial through common regulation and control of amplitude and phase. The method has universality and can be used for efficiently designing other metamaterial microwave absorbers with target performance.

The invention discloses a preparation method of a Fe-Co / Zn-coated NC carbon-based composite material for absorbing high-frequency electromagnetic waves. The invention belongs to the field of preparation of carbon-based composite electromagnetic wave absorbing materials. The method comprises the following steps: uniformly mixing dimethylimidazole, zinc acetate dehydrate, cobalt nitrate hexahydrate and ferric acetylacetonate in deionized water, aging, washing, centrifuging, freeze-drying, and carrying out high-temperature treatment. The introduction of Fe leads the formation of a Fe-Co solid solution so as to drive the whole phase change process, and further mediates a gradual microstructure evolution process, so that Fe-Co / Zn-coated NC achieves compatible components and optimized configuration, and the high-frequency electromagnetic wave absorption performance is remarkably improved. When the doping ratio is 40 wt%, the reflection loss reaches-84.41 dB, and incident electromagnetic waves exceeding 99.999999% can be absorbed; the effective absorption bandwidth of 6.08 GHz can be achieved under the doping ratio of 50 wt%, namely, the frequency band of 11.92-18.00 GHz is covered, and complete absorption of high-frequency electromagnetic waves is achieved.

This invention relates to a method for preparing a broadband absorption hydrogel. The method comprises the following steps: S1, mixing solvent A (N,N-dimethylformamide or acetonitrile) with deionized water to obtain a mixed solvent; S2, adding polyethylene glycol methyl ether acrylate-480 and acryloylmorpholine to the solvent in S1 and dissolving them to obtain a mixed solution; S3, removing dissolved oxygen from the mixed solution in S2, sealing the container, and stirring under ice bath conditions; S4, adding potassium persulfate and N,N,N',N'-tetramethylethylenediamine to the mixed solution after stirring in S3, and sealing the container again; S5, completing the polymerization reaction in the container at 60 °C to obtain the hydrogel. Compared with the prior art, the hydrogel material provided by this invention has improved reflection loss intensity and effective absorption bandwidth performance, thus providing a new perspective for developing highly flexible and efficient electromagnetic wave absorbers.

The invention discloses a multifunctional broadband electromagnetic wave-absorbing composite material based on a bionic periodic unit and a multistage core-shell filler and a preparation method thereof.The multistage core-shell filler is used as a raw material, an impregnation technology is adopted, and the bionic periodic unit is impregnated by preparing high-loss paint and impedance matching paint with different concentrations; the electromagnetic wave-absorbing composite material is obtained. Accurate gradient distribution and better impedance matching of electromagnetic parameters in a three-dimensional space are achieved, the density is lower than 6 kg / m under the thickness of 15-20 mm, the plane compression strength is 2 MPa, and the effective absorption bandwidth (RLlt;-10 dB) covers 8-18 GHz. The invention solves the contradiction between the bandwidth, thickness, weight and single function of the traditional wave-absorbing material, and is suitable for the fields of advanced stealth equipment and electromagnetic protection. The material opens up a new direction for the development of electromagnetic wave-absorbing materials, and is expected to be widely applied to many fields such as national defense, communication, electronics and the like.

The invention discloses a Ni3Al-PPy composite wave-absorbing material as well as a preparation method and application thereof, and belongs to the technical field of electromagnetic wave-absorbing materials. The Ni3Al-PPy composite wave-absorbing material with a core-shell structure is successfully synthesized by combining a thermit reaction with a chemical oxidation polymerization method and hydrochloric acid modification. By regulating and controlling the addition amount of the pyrrole monomer in the range of 0.25-0.75 mL, the continuous regulation and control of the thickness of the PPy shell layer from 0.22 [mu] m to 0.31 [mu] m is realized. When the thickness of a PPy shell layer is 0.27 mu m and the matching thickness of the composite wave-absorbing material is 3.0 mm, the minimum reflection loss and absorptivity gt of-40.0 dB are obtained at 9.27 GHz; and when the matching thickness is 2.0 mm, the effective absorption bandwidth reaches 3.02 GHz. According to the invention, the effect of the shell layer thickness in regulating and controlling the performance of the wave-absorbing material with the core-shell structure is illustrated, and a feasible strategy is provided for designing a high-performance light-weight wave-absorbing material with adjustable electromagnetic parameters and enhanced durability.

The invention discloses a hollow cobalt-based microtube designed based on a skin depth theory and a preparation method and application thereof, relates to the technical field of electromagnetic wave absorbing materials, and aims to solve the problems that an existing microwave absorbing material is insufficient in low-frequency-band magnetic loss, high in filling ratio or large in thickness, so that the system load is too heavy; and the design of the electromagnetic wave absorption microtube structure is lack of theoretical guidance. According to the method, the skin depth of electromagnetic waves in a conductor is converted into a wall thickness design parameter, the Co / rGO composite layer is constructed on the surface of the carbon fiber by electrodeposition for 9.0 minutes at the temperature of 60 DEG C for the first time, then the wall thickness is accurately controlled through gradient heat treatment of 800 DEG C air oxidation and 500 DEG C Ar / H2 reduction, and matching with the skin depth of cobalt at the frequency point of 3 GHz is achieved. The material breaks through the low-frequency absorption limit under the ultralow filling ratio of 0.85 wt%:-37.89 dB minimum reflection loss is obtained at the S wave band when the thickness is 1.0 mm, and the effective absorption bandwidth reaches 5.4 GHz; and when the thickness is 3.0 mm, the bandwidth is expanded to 7.8 GHz to cover multiple frequency bands. And an innovative solution is provided for aerospace stealth equipment and high-frequency electronic equipment.

A method for preparing a MOF-based multiphase composite electromagnetic wave absorbing material is disclosed, which relates to the preparation method and application of electromagnetic wave absorbing materials. The purpose of this invention is to solve the problems of poor attenuation and narrow absorption bandwidth in ABO3-type perovskite electromagnetic wave absorbing materials prepared by existing methods. This invention is based on the metallic Fe in MIL-88A. 3+ Ions were successfully induced to form an oxide perovskite phase in MIL-88A via etching, resulting in a hierarchical hollow nanocomposite material. In this structure, the oxide perovskite, a typical spinel-type p-type semiconductor, is composited with the surrounding elemental Fe phase through an outer graphitized carbon shell. Utilizing the heterojunction effect with metal-semiconductor contacts, an excellent interfacial polarization process is generated, significantly enhancing the dielectric loss performance of the composite material. Simultaneously, by consuming excess Fe metal... 3+ Excellent electromagnetic wave absorption performance was obtained by adjusting the impedance matching of the composite material.

The invention discloses a method for preparing a high-performance wave-absorbing material by in-situ construction of a polar organic coating through cooperation of microwaves and AlCl3-NaCl molten salt, and relates to the technical field of new material synthesis. Cutting, cleaning and drying the waste carbon fiber reinforced resin-based composite material to obtain a clean composite material a; the preparation method comprises the following steps: weighing a composite material a and AlCl3-NaCl molten salt, enabling the AlCl3-NaCl molten salt to be in full contact with the composite material a, carrying out microwave molten salt in-situ pyrolysis in a microwave oven under the protection of a protective atmosphere, and realizing in-situ construction of a polar organic nano coating on the surface of the carbon fiber by utilizing microwave and AlCl3-NaCl molten salt catalysis treatment; and repeatedly washing with deionized water, and carrying out suction filtration and drying to obtain the organic coating / carbon fiber wave-absorbing composite material. When the thickness of the prepared organic coating / carbon fiber composite material is 1.4-4.0 mm, the reflection loss can reach-40.20--69.00 dB, the effective absorption bandwidth is 2.2-4.05 GHz, and the organic coating / carbon fiber composite material has light and thin characteristics and excellent electromagnetic wave absorption, is excellent in electromagnetic wave absorption performance and has a relatively good application prospect.