313results about How to "Improve absorbing performance" patented technology

The invention belongs to the technical field of preparation of wave-absorbing materials, and particularly relates to an epoxy resin wave-absorbing prepreg with strong low-frequency wave-absorbing performance and a preparation method of the epoxy resin wave-absorbing prepreg. The method comprises the following steps: mixing an epoxy resin matrix and a flexibilizer to obtain an epoxy resin system; the preparation method comprises the following steps: putting an epoxy resin system and flaky absorbents with different particle sizes into an internal mixer for internal mixing and coarse mixing, performing fine mixing by using an open mill after coarse mixing, and adding a curing agent in the fine mixing process to obtain a low-frequency wave-absorbing resin blank; putting the low-frequency wave-absorbing resin blank into a precision calender, and carrying out wave-absorbing adhesive film calendering, so as to obtain a wave-absorbing resin film after calendering; and thermally compounding the wave-absorbing resin film and the wave-transparent fiber prepreg to obtain the epoxy resin-based wave-absorbing prepreg. The wave-absorbing prepreg prepared by the invention is excellent in mechanical property after being cured, high in low-frequency wave-absorbing property and relatively high in reliability.

The invention discloses an ultra-wideband carbon / boron doped high-entropy alloy wave-absorbing material which is prepared by adjusting Fe and Ni elements, adding Si and Al elements and doping a small amount of C or B. The specific component of the wave-absorbing material is (FeaCobSicAldNie) 100-xMx. In addition, the invention also discloses a preparation method of the wave-absorbing material, and the preparation method comprises the following steps: 1, high-entropy alloy smelting; 2, preparing high-entropy alloy spherical powder; 3, carrying out flaky treatment; and 4, stress relief annealing. On the basis of FeCoNi medium-entropy alloy, the content of the Fe element with low cost is increased, the content of the Ni element with high cost is reduced, the Si element and the Al element are added at the same time, then a small amount of non-metal C and B elements are doped to serve as interstitial atoms, lattice distortion is increased, the wave-absorbing performance and corrosion resistance are improved, and the ultra-wideband carbon / boron doped high-entropy alloy wave-absorbing material is obtained.

The invention belongs to the technical field of foam materials, and discloses wave-absorbing PVC (polyvinyl chloride) structural foam and a preparation method thereof, and the wave-absorbing PVC structural foam comprises the following raw material components in parts by weight: 400-600 parts of PVC resin, 300-550 parts of isocyanate, 10-50 parts of a curing agent, 30-80 parts of a foaming agent, 0.1-10 parts of a cross-linking agent, 5-30 parts of a plasticizer and 30-90 parts of an electromagnetic wave absorbent. Modified carbon nanotubes with carboxyl or hydroxyl functional groups and conductive carbon black are added into a PVC structural foam system, the conductive carbon black is coated by utilizing intermolecular force between the modified carbon nanotubes and the conductive carbon black, the dispersity is improved, and a conductive network is formed, so that the problems that the conductive carbon black is poor in dispersity in the PVC structural foam system, and the conductivity of the PVC structural foam system is poor are solved. The problem that the wave-absorbing performance is reduced after the carbon nanotubes are modified is solved, and the forming performance, the mechanical performance and the wave-absorbing performance of the wave-absorbing PVC structural foam are greatly improved.

The invention discloses a self-repairing wave-absorbing composite material as well as a preparation method and application thereof. The self-repairing wave-absorbing composite material provided by the invention comprises the following components in percentage by mass: 30-80% of a polyurethane matrix; 20%-70% of composite wave absorbing powder; the composite wave-absorbing powder is prepared by performing plasma ball milling on graphene oxide and soft magnetic metal powder. The preparation method of the self-repairing wave-absorbing composite material comprises the following steps: 1) preparing a polyurethane prepolymer solution; and 2) dispersing the composite wave-absorbing powder in a polyurethane prepolymer solution, injecting the solution into a mold, and carrying out curing molding to obtain the self-repairing wave-absorbing composite material. The self-repairing wave-absorbing composite material disclosed by the invention is excellent in wave-absorbing property and mechanical property, the material can realize quick self-repairing, the stability of the wave-absorbing property and the mechanical property is ensured, and the composite material is suitable for the fields of 5G communication, new energy automobiles, national defense and military industry and the like.

The invention provides an optical transparent flexible electromagnetic wave-absorbing metamaterial, and relates to the technical field of wave-absorbing materials, the electromagnetic wave-absorbing metamaterial comprises a plurality of wave-absorbing units arranged periodically, and the wave-absorbing units are made of optical transparent materials; each wave absorbing unit comprises a dielectric compensation layer, a first resonance layer, a first dielectric layer, a second resonance layer, a second dielectric layer and a reflecting layer which are sequentially arranged from top to bottom; the dielectric compensation layer is used for expanding an absorption frequency band and improving the stability of an incident angle; the first resonance layer is used for adjusting a first resonance frequency point of a reflectivity curve; the second resonance layer is used for adjusting a second resonance frequency point of the reflectivity curve; the first dielectric layer and the second dielectric layer are used for consuming electromagnetic energy; and the reflecting layer is used for reflecting redundant electromagnetic energy back to the electromagnetic wave-absorbing metamaterial for loss again. The light-transparent flexible electromagnetic wave-absorbing metamaterial provided by the invention has the advantages of flexibility, high light transmittance, good broadband wave-absorbing performance and oblique incidence angle stability.

The invention discloses a high-temperature-resistant spliced nested honeycomb pyramid wave-absorbing material as well as a preparation method and application thereof. The high-temperature-resistant spliced nested honeycomb pyramid wave-absorbing material is formed by splicing a plurality of hollow honeycomb pyramid unit arrays and a bottom honeycomb plate, the outer part of each hollow honeycomb pyramid unit is formed by splicing four triangular or trapezoidal honeycomb sheets with saw-toothed edges, and a hollow honeycomb pyramid with a smaller size can be nested in each hollow honeycomb pyramid unit and is wholly impregnated with wave-absorbing slurry. A wave-absorbing agent in the wave-absorbing slurry is one or more of conductive carbon black, conductive carbon fiber, conductive graphite, multi-walled carbon nanotubes, graphene, carbonyl polycrystalline iron fiber, cobalt-based amorphous wires or iron-based amorphous powder. The wave-absorbing performance of the material can be improved, high temperature resistance is achieved, heat concentration is reduced, the use amount of raw materials is reduced by adopting the spliced and nested hollow structure, the cost is low, the structural stability is improved, the service life is prolonged, meanwhile, light weight is achieved, high design flexibility is achieved, and the preparation difficulty and the later maintenance difficulty are reduced.

The invention belongs to the field of glue barrel instruments and the technical field of preparation of wave-absorbing materials, and relates to a layered joint mixture for repairing gaps of wave-absorbing laminates as well as a preparation method and an extrusion device of the layered joint mixture. The extrusion device comprises a glue nozzle, a glue barrel and a glue pushing device; the glue nozzle is fixedly connected with the glue barrel, and the glue pushing device is assembled in the glue barrel; a plurality of partition plates are arranged in the glue nozzle and the glue barrel, and inner cavities of the glue nozzle and the glue barrel are divided into a plurality of runners; the glue pushing device comprises a plurality of glue pushing rods, a plurality of glue pushing plates and a pushed plate, and each glue pushing plate corresponds to one runner. When the pushed plate of the extrusion device is pushed, the pushed plate pushes the glue pushing rod and the glue pushing plate to extrude out the joint mixture in the runner along the glue outlet in the glue nozzle, so that a layered repairing material is formed. The joint mixture is composed of a matrix, an absorbent and a curing agent. The extrusion device disclosed by the invention can extrude the wave-absorbing joint mixture according to a fixed thickness ratio, and a layered structure is formed on the surface of a reflecting layer, so that better wave-absorbing performance is achieved.

The invention belongs to the field of composite materials, and particularly relates to a ceramic-based composite high-temperature wave-absorbing material and a preparation method and application thereof. The composite material provided by the invention comprises the following components: a fiber preform, a multi-layer interface, a wave-absorbing phase and a ceramic matrix, the fiber preform is a structural bearing part made of a composite material; the multi-layer interface is deposited on the surface of the fiber preform and comprises a PyC interface, a BN interface and a SiC interface; the wave-absorbing phase is dispersed in the fiber preform and is a bismuth layered structure ceramic phase; the ceramic matrix is filled in the fiber preform and the inner part and the surface of the multi-layer interface, and the components of the ceramic matrix are one or more of SiC, Si3N4 and SiCN. The composite material provided by the invention can keep relatively good wave-absorbing performance at high temperature, has excellent mechanical properties and thermal stability, and has wide application prospects in the fields of heat-resistant protection, aerospace, radar wave-absorbing, stealth technology, electronic warfare, communication shielding and the like.

The invention discloses a liquid metal-manganese oxide-MXene wave-absorbing phase change composite particle as well as a preparation method and application thereof. The liquid metal-manganese oxide-MXene wave-absorbing phase-change composite particle comprises a liquid metal inner core, a manganese oxide middle shell layer and an MXene outer coating layer. The preparation method comprises the following steps: 1) preparing the liquid metal-manganese oxide composite particle; 2) preparing surface modified liquid metal-manganese oxide composite particles; and 3) electrostatic adsorption coating of MXene on the surfaces of the surface modified liquid metal-manganese oxide composite particles. The liquid metal-manganese oxide-MXene wave-absorbing phase-change composite particle has excellent electromagnetic wave absorption performance, also has phase-change heat absorption and cooling functions, is small in matching thickness and simple and convenient in preparation method, and is suitable for the fields of 5G communication, consumer electronics, national defense and military industry and the like.

The invention provides a preparation method of carbon-loaded MOF (Metal Organic Framework) derivative aerogel. The preparation method comprises the following steps: S1, preparing ZIF-67 with a rhombic dodecahedron structure; s2, preparing cellulose aerogel; s3, preparing a ZIF-67 at cellulose compound by using the ZIF-67 with the rhombic dodecahedron structure and the cellulose aerogel; s4, the ZIF-67 at cellulose compound is carbonized, and the carbon-loaded MOF derivative aerogel is obtained. The problems that in the prior art, a wave-absorbing material is poor in performance, does not have good heat insulation performance, and is high in raw material cost are solved.

The invention discloses a metasurface based on multi-unit periodic array distribution, the metasurface is mainly formed by periodically arranging a plurality of microstructure units, each microstructure unit comprises a subunit A1, a subunit B1, a subunit A2 and a subunit B2, the subunit A1 and the subunit A2 are in a central symmetry structure, and the subunit B1 and the subunit B2 are arranged in parallel. The subunit B1 and the subunit B2 are of a central symmetry structure, the wave absorber formed by the super-structure surface comprises a plurality of wave absorbing units which are arranged periodically, each wave absorbing unit comprises a conductive reflecting layer, a dielectric interlayer, a microstructure unit layer and a dielectric top layer which are sequentially attached from bottom to top, the electromagnetic wave absorption rate can reach 90% or above on the frequency band of 8.31-41.75 GHz, and the wave absorbing efficiency can reach 90% or above. The microwave absorber has the advantages of being flexible, easy to prepare, good in wave absorbing effect and beneficial to integration, and is suitable for being used in the technical fields of electromagnetic shielding, microwave imaging and the like, and most of electromagnetic wave energy entering the inside of the microwave absorber is lost under the action of dielectric loss and ohmic loss, and the microwave absorber has the advantages of being flexible, easy to prepare, good in wave absorbing effect and beneficial to integration.

The invention discloses a dielectric and magnetic loss coupling type multi-frequency high-absorption composite wave-absorbing material. The chemical formula of the composite wave-absorbing material is (FeCoNiCraMn) x. (BaTiO3) y, the invention also discloses a preparation method of the composite wave-absorbing material, which comprises the following steps: step 1, mixing iron, cobalt, nickel, chromium and manganese, and carrying out suspension smelting, vacuum gas atomization and sieving to obtain high-entropy alloy spherical powder; secondly, the flaky high-entropy alloy is obtained after ball milling; thirdly, the flaky high-entropy alloy is naturally cooled and then dried; and fourthly, the dried flaky high-entropy alloy is mixed with barium titanate powder, and ball milling is carried out. According to the composite wave-absorbing material, the FeCoNiCrMn series high-entropy alloy provides magnetic loss capacity, barium titanate provides dielectric loss capacity, the synergistic effect of multiple loss mechanisms is achieved, and the composite wave-absorbing material is suitable for the technical field of wave-absorbing materials.

The invention discloses a sulfur-doped carbon-based composite wave-absorbing material as well as a preparation method and application thereof. Sulfonated resin is used as a carbon source, is impregnated with a salt solution of iron, nickel, cobalt and other metals, and then is subjected to high-temperature carbonization in an inert atmosphere, so that the sulfur-doped carbon-based composite wave-absorbing material is prepared. The content of the magnetic components in the composite wave-absorbing material can be adjusted by adjusting the concentration of the metal salt solution, and the electromagnetic wave absorption performance can be further adjusted and controlled in a wide range. The raw material components are stable, the cost is low, and the preparation method is simple and suitable for industrial production; sulfur-containing sulfonated resin is used, after heat treatment, a defect and a functional group introduced by sulfur doping serve as a dipole center, dipole polarization is induced under a high-frequency electromagnetic field, and the dielectric loss capacity of the material can be improved; the composite wave-absorbing material has multiple electromagnetic loss mechanisms, and is wide in effective absorption frequency band, light in weight, thin in thickness and high in wave-absorbing performance.

The invention belongs to the technical field of fabric coatings, and particularly relates to a self-cleaning sensing type composite coating for fabric and a preparation method of the self-cleaning sensing type composite coating. The self-cleaning sensing type composite coating comprises a polypyrrole coating, a ferroferric oxide coating and a hydrophobic polyurea modified coating. The self-cleaning sensing type composite coating has good self-cleaning performance, sensing performance, wave absorbing performance and hydrophobic performance.

The invention provides an intrinsic magnetic MXene material and a preparation method and application thereof, the preparation method comprises the following steps: S1, mixing an aqueous solution of MXene with an alkaline reagent, and carrying out ultrasonic dispersion to obtain a mixed dispersion liquid; freezing the mixed dispersion liquid into a solid by liquid nitrogen; the alkaline reagent is potassium hydroxide or sodium hydroxide; s2, the obtained solid is subjected to freeze drying, and the Archimedes screw type MXene aerogel is obtained; s3, the Archimedes spiral type MXene aerogel is subjected to heat treatment under the protection of inert gas, and the intrinsic magnetic MXene material is obtained. The invention designs and develops a single-component pure MXene electromagnetic wave absorbing material on the premise of not introducing magnetic nanoparticles.

The invention relates to a Ti3SiC2-containing SiC fiber and a preparation method thereof, and belongs to the technical field of ceramic fibers. The invention discloses a SiC fiber containing Ti3SiC2. The SiC fiber containing Ti3SiC2 is prepared by performing spinning, non-melting and high-temperature firing on a spinning precursor comprising a polycarbosilane precursor, a titanium source and an auxiliary agent. The Ti3SiC2 structure is introduced into the SiC fiber, so that the conductivity and the wave-absorbing property of the SiC fiber are improved.

The invention provides a composite wave-absorbing material as well as a preparation method and application thereof, and relates to the technical field of wave-absorbing materials. The composite wave-absorbing material provided by the invention has high-entropy ferrite with a spinel structure and high-entropy iron alloy with a body-centered cubic structure, the chemical formula of the high-entropy ferrite is (CoxNiyCuzMnaZnbMgcCrd) Fe2O4, x + y + z + a + b + c + d = 1, x, y and z are real numbers greater than 0 and less than 1, a, b, c and d are real numbers greater than or equal to 0 and less than 1, and two or three of a, b, c and d are equal to 0. The composite wave-absorbing material provided by the invention has the advantages of thin matching thickness, strong wave-absorbing performance and wide absorption frequency band.

The invention discloses a Ni3InC0.5 wave-absorbing material and a preparation method thereof, and the preparation method comprises the following steps: (1) dispersing Ni (CH3COO) 2.4 H2O and In (CH3COO) 2.6 H2O into N, N-dimethylformamide (DMF), and magnetically stirring to obtain a liquid A; (2) dispersing terephthalic acid (PTA) and triethylamine (TEA) into DMF, and magnetically stirring to obtain liquid B; (3) pouring the liquid B into the liquid A, and continuously stirring to obtain a Ni3InC0.5 precursor solution; (4) putting the solution obtained in the step (3) into a circulating water suction filter for suction filtration to obtain a gelatinous sample; and (5) taking a sample obtained in the step (4), calcining the sample in a nitrogen atmosphere, and naturally cooling the sample to room temperature to obtain Ni3InC0.5. The method has the characteristics of simple process and low cost, and the material is applied to the field of wave absorption for the first time.

The invention provides a light broadband wave-absorbing structure based on 3D printing and a resistive film and a preparation method thereof.The light broadband wave-absorbing structure comprises a metal bottom layer, a supporting layer, a resistive film layer and a structural wave-absorbing material layer which are sequentially arranged from bottom to top, the structural wave-absorbing material layer is of a 3D printing structure and is made of CNTs doped with ABS, and the supporting layer is made of carbon nanotubes doped with ABS. Periodic units of the 3D printing structure are two kinds of regular hexagonal cylinder periodic units with different sizes. The CNTs-doped ABS 3D printing structure is introduced into the single-layer resistive film wave-absorbing structure, the 3D printing structure, the size and the resistance value of the resistive film are optimized, the wave-absorbing structure small in thickness and weight is obtained, meanwhile, the wave-absorbing structure has excellent wave-absorbing performance, and the reflection loss is smaller than-10 dB within 2.0 GHz to 18 GHz.

The invention relates to a preparation method of a lightweight reduced graphene oxide-silicon dioxide electromagnetic wave absorbing material. The invention belongs to the technical field of electromagnetic wave absorbing materials. The invention solves the problems that the impedance of the existing reduced graphene oxide is mismatched, the density of the modified reduced graphene oxide composite wave-absorbing material is increased and the preparation method is complicated. The method comprises the following steps: performing chemical crosslinking on graphene oxide, silicon dioxide and a silane coupling agent to obtain a precursor; and drying and sintering the precursor. The material prepared in the invention has good impedance matching and abundant interface polarization and relaxation effects, can effectively reduce the reflection loss value of electromagnetic waves and increase the effective absorption bandwidth of the electromagnetic waves, and has excellent electromagnetic wave absorption performance. When the thickness of the material is only 1.5 mm, the RL of the material can reach-54.08 dB, and when the thickness of the material is 1.7 mm, the effective absorption bandwidth of the material can reach 5.12 GHz. In addition, the density of the material is only 0.083 g / cm < 3 >, the process is simple, and stable batch production can be realized.

The present application discloses an integrated wave-absorbing and heat-insulating composite material and a preparation method thereof, and relates to the technical field of wave-absorbing composite materials; the application aims to solve the technical problem that the electromagnetic wave absorption performance and heat-insulating performance of existing composite materials need to be improved; the integrated wave-absorbing and heat-insulating composite material has silicon carbide nanowires as a skeleton, and the surface is modified with nano-magnetic particle materials; wherein the mass ratio of the silicon carbide nanowires to the nano-magnetic particles is 1:0.5-2.

The invention discloses a preparation method of an acacia melanoxylon veneer MWCNT multilayer electromagnetic wave absorbing material, and belongs to the technical field of novel electromagnetic wave absorbing materials.The method comprises the steps that carboxylated carbon nanotubes, polyvinylpyrrolidone, N, N-dimethylformamide and ethylene glycol are evenly mixed and subjected to ultrasonic dispersion, and a solution A is obtained; the method comprises the following steps: weighing ferrous sulfate heptahydrate (FeSO4. 7H2O) and cobaltous sulfate heptahydrate (CoSO4. 7H2O), and dissolving the ferrous sulfate heptahydrate and the cobaltous sulfate heptahydrate into deionized water to obtain a metal ion solution; mixing the solution A with a metal ion solution; a reaction product is obtained after reaction treatment; dipping GFM in the reaction product, taking out and drying to form a GFM layer; and preparing the novel acacia melanoxylon electromagnetic wave absorbing material from the GFM layer and the acacia melanoxylon board in a staggered lamination manner. The preparation method disclosed by the invention has the advantages of simple process, capability of realizing enterprise production, low requirements on synthesis equipment and the like, and the prepared material has excellent broadband wave-absorbing property and excellent mechanical property.

The invention discloses an MgO-C nano chain, a preparation method thereof and application of the MgO-C nano chain as a wave-absorbing material, a horizontal tube furnace is adopted for preparation, and an evaporation area and a reduction area are arranged at the two ends of a furnace body respectively; taking Mg (acac) 2 as a precursor, and placing the precursor in an evaporation area; placing a substrate for collecting products in a reduction area; inert gas is adopted as carrier gas and reaction atmosphere, a vacuum pump system is used for maintaining the internal pressure intensity of the system, reaction is conducted, and the MgO-C nano chain is collected on the substrate. In the MgO-C nano chain, the nano MgO particles are connected into a three-dimensional structure through carbon, the wave-absorbing effects such as interface polarization and multiple scattering reflection are enhanced by means of the unique structure, the wave-absorbing performance is greatly improved, and the frequency band is widened. The material has good microwave absorption performance, and has a very good application prospect in the fields of stealth technology and electromagnetic shielding.

The invention discloses a rain-erosion-resistant ceramic-based composite material as well as a preparation method and application thereof, and belongs to the technical field of wave-bearing and wave-absorbing ceramic-based composite materials. According to the preparation method, a BN interface layer is deposited on the surface or in internal gaps of an Al2O3 fiber preform or a SiC fiber preform through a chemical vapor infiltration process, and then a reinforced matrix is introduced into the fiber preform with the BN interface layer through the chemical vapor infiltration process and a polymer impregnation and cracking process. The ceramic-based composite material prepared in the invention has good wave-absorbing performance, mechanical performance and rain erosion resistance; the method can be applied to preparation of aircraft hot end components.

The present invention provides a FeNiHo / carbon nanofiber composite absorber and a preparation method thereof, an absorbent material and a preparation method thereof, and belongs to the technical field of electromagnetic wave absorbing materials. The present invention first mixes iron salt, nickel salt, holmium salt and polyvinyl pyrrolidone in a mixed solvent, and electrostatically spins the obtained spinning precursor solution to obtain a nanofiber membrane; the nanofiber membrane is sequentially subjected to pre-oxidation treatment and carbonization treatment to obtain a FeNiHo / carbon nanofiber composite absorber. The FeNiHo / carbon nanofiber composite absorber, paraffin and petroleum ether are mixed, and then pressed and irradiated with ultraviolet light to obtain an absorbing material. The FeNiHo alloy nanoparticles in the composite absorber improve the impedance matching performance and electromagnetic wave attenuation ability of the carbon nanofiber. The obtained absorbing material can achieve the purpose of real-time adjustment of the absorption frequency by irradiation with ultraviolet light.

The invention relates to the technical field of wave-absorbing metamaterials, in particular to a lattice element sequential wave-absorbing metamaterial and a preparation method thereof.The wave-absorbing metamaterial comprises a substrate and a lattice structure layer, and the lattice structure layer is formed by arranging a plurality of structure units on the surface of the substrate in a periodic array mode; each structural unit is formed by arranging a plurality of dot matrix elements; the dot matrix elements are sheet-shaped magnetic dot matrix elements. The wave absorbing crest of the dot matrix superstructure moves towards high frequency, and RLlt; and the effective absorption bandwidth of-10dB is improved. The wave-absorbing strength and bandwidth are improved, and the problem that an existing homogeneous wave-absorbing coating is difficult to have the characteristics of small thickness and light weight while the bandwidth is improved is solved.

The invention discloses a multi-component alloy / carbon black composite wave-absorbing material. The molecular formula of the composite wave-absorbing material is (Fe50Co20SiaAlbNic)-xC, the invention also discloses a preparation method of the composite wave-absorbing material. The preparation method comprises the following steps: step 1, preparing the multi-component alloy spherical powder; 2, ball milling and powder mixing; step 3, spray granulation; step 4, carrying out primary flaking; step 5, dry grinding; and step 6, carrying out second-time flaking. The composite wave-absorbing material is obtained by compounding the multi-component alloy mainly containing magnetic loss and the carbon material mainly containing conductive loss, so that the problems that the reflection loss is low and the absorption frequency band is narrow when the multi-component alloy is singly used and the effective absorption frequency band is narrow and the oxidation resistance is poor when the carbon black is singly used can be solved; the combination of the two can improve the impedance matching of the material, and is suitable for the technical field of electromagnetic shielding wave-absorbing materials.

The invention provides a preparation method and application of a Fe-coated Si3N4 heat-conducting wave-absorbing material, and the method comprises the following steps: taking ZrOCl2. 8H2O as a raw material, forming a ZrO2 coating layer on the surface of reduced iron powder on the surface of Si powder, then taking the coated Si powder as a raw material, and coating the surface of the reduced iron powder with a Si3N4 layer. According to the invention, the surface of the reduced iron powder is coated with a Si3N4 layer to prepare the novel Fe-coated Si3N4 heat-conducting wave-absorbing material, the shell layer Si3N4 has high heat conductivity and good dielectric loss, the core layer reduced iron powder has high magnetic loss capability, and the material is an electromagnetic wave absorbing material with high heat conductivity, strong absorption and good filling performance.

The invention provides a middle and far infrared broadband metamaterial absorber and a design method thereof. The middle and far infrared broadband metamaterial absorber comprises metamaterial absorption units which are arranged in a periodic array mode. The whole metamaterial absorption unit is square and comprises a top metal layer, a dielectric layer and a bottom metal layer from top to bottom in sequence. The top metal layer is attached to the upper surface of the dielectric layer and is formed by arranging eight metal sheets according to a certain arrangement mode, namely a circular metal sheet which is arranged at the central position of the upper surface of the dielectric layer, and the center of the circular metal sheet is aligned with the center of the upper surface of the dielectric layer; three annular metal sheets concentric with the circular metal sheet surround the periphery of the circular metal sheet, and gaps exist between the circular metal sheet and the annular metal sheet on the innermost layer and between the annular metal sheets on the adjacent layers from inside to outside. And the four metal square sheets with the same size are respectively arranged at four corners of the upper surface of the dielectric layer. The absorption bandwidth is greatly prolonged, and perfect absorption of a target wave band can be infinitely approached by adjusting geometric parameters of the absorber.

The invention belongs to the technical field of electromagnetic functional materials, and particularly relates to a hexagonal element sequential wave-absorbing metamaterial and a preparation method and application thereof. Superstructure design is carried out on the surface of the wave-absorbing coating with intrinsic electromagnetic loss, a superstructure wave-absorbing coating for carrying out structural loss on electromagnetic waves is obtained, the superstructure wave-absorbing coating is attached to the metal matrix layer, and the hexagonal element sequential wave-absorbing metamaterial is obtained. The hexagonal primitive sequential wave-absorbing metamaterial breaks through the Rogov limit, solves the problem that a traditional homogeneous wave-absorbing material is limited in the aspects of increasing the bandwidth and reducing the thickness, breaks through the limitation that the thickness and the bandwidth cannot be met at the same time, achieves efficient wave-absorbing and stealth compatibility under the deep sub-wavelength size, and improves the wave-absorbing efficiency. And the thickness of the super-structure wave-absorbing coating is reduced to 2mm, so that practical engineering application is facilitated, and the super-structure wave-absorbing coating can be applied to the fields of communication and national defense.