40results about How to "Improve absorbing performance" patented technology

This invention relates to a flame retardant with both microwave absorption and smoke suppression functions. The flame retardant is a hierarchical porous metal-organic framework material with a three-dimensional polygonal structure, a size of 1-3 μm, and a pore size distribution between 1.0-50.0 nm. It carries nano-transition metal oxides internally and on its surface, with the nano-transition metal oxides accounting for 25%-65% of the total mass. The flame retardant provided by this invention possesses microwave absorption, flame retardancy, and smoke suppression properties. Its initial decomposition temperature is 442℃±10℃, with significant mass loss in the temperature range of 450-700℃. At 800℃, the residue content is as high as 50% or more, exhibiting excellent thermal stability and meeting the processing requirements for flame retardants in polyurea, epoxy resin, and polycarbonate.

This invention belongs to the field of functional ceramics technology and discloses a garnet-type microwave absorbing dielectric ceramic and its preparation method. The general chemical formula of the garnet-type microwave absorbing dielectric ceramic is Y3Al. 5‑x Fe x O 12 Through a two-step atmosphere sintering method, firstly, high-temperature sintering is carried out in a reducing atmosphere, introducing a specific proportion of Fe. 2+ The introduction of ions, thereby introducing free charge carriers and lattice defects, significantly enhances conductivity loss and interfacial polarization loss; subsequently, medium-temperature annealing in an oxidizing atmosphere stabilizes the crystal structure, allowing Fe to... 2+ with Fe 3+ The molar ratio is controlled within a certain range to prevent over-reduction and optimize magnetic loss. At the same time, it achieves effective synergy between conductivity loss and magnetic loss in the 2-18GHz frequency band, and has the advantages of strong absorption, wide bandwidth, good high temperature stability and high repeatability.

The application provides a polyvinylidene fluoride matrix wave-absorbing magnetic composite fiber membrane, and a preparation method of the fiber membrane.The fiber membrane is formed by a fiber composite material of Fe3O4 particles with a diameter of 10-500 nm, carbon black particles with a diameter of 20-800 nm and polyvinylidene fluoride (PVDF).It is found that, with the addition of the Fe3O4 particles and the carbon black particles, the polyvinylidene fluoride (PVDF) is endowed with excellent wave-absorbing performance without significantly increasing the volume weight of the fiber material.

This invention belongs to the field of electromagnetic wave absorbing materials technology, specifically relating to an absorbing material, its preparation method, and its application. This invention uses multi-walled carbon nanotubes (MWCNTs), potassium permanganate (KMnO4), and divalent manganese as raw materials, based on Mn... 2+ With MnO4 ‑ The redox reaction between the two components allows for in-situ uniform loading of MnO2 nanoparticles onto the MWCNT surface through simple stirring in a room-temperature liquid environment, resulting in microwave absorption performance superior to most similar absorbing materials. Compared to traditional methods for preparing absorbing materials, the technical route of this invention offers significant advantages, including simple preparation process, no pollutant emissions, energy-saving and environmentally friendly process, adjustable and controllable material structure, excellent microwave absorption performance, and scalability. This method effectively overcomes the technical limitations in the preparation of absorbing materials, providing a scalable new paradigm for the green and large-scale production of high-performance absorbing materials.

This invention relates to the field of composite material technology, specifically to an aramid honeycomb based on magnetic microwave absorbing prepreg and its preparation method. The aramid honeycomb includes an aramid honeycomb core and a magnetic microwave absorbing prepreg layer covering the surface of the honeycomb core. The magnetic microwave absorbing prepreg, by mass percentage, contains 25%-30% magnetic microwave absorbing component, 40%-45% resin matrix, 20%-25% reinforcing fiber, 5%-8% dispersant (based on the magnetic microwave absorbing component), and a curing agent with a mass ratio of 1:1.2 to the resin matrix. The magnetic microwave absorbing component is selected from one or more of coated Fe3O4@SiO2 nanoparticles, nickel-doped MXene (Ni-Ti3C2), and ultrafine Fe-Si-Cr alloy powder, mixed in any proportion. The resin matrix is ​​E-51 modified epoxy resin with a glass transition temperature Tg ≥ 120℃; the reinforcing fiber is para-aramid fiber cloth (Kevlar49) with a length of 0.15 micrometers to 0.5 millimeters; the dispersant is polyetherimide (PEI); and the curing agent is methyltetrahydrophthalic anhydride (MeTHPA).

An integrated in-situ reaction and forming method for microwave-absorbing materials encapsulated in a microwave-transparent composite material is disclosed, relating to a method for preparing microwave-absorbing materials. The purpose of this invention is to solve the problems of existing methods in preparing microwave-absorbing composite structures, such as easy detachment of the microwave-absorbing functional layer, complex preparation processes, unstable bonding between the microwave-absorbing material and the composite matrix, and the inability to simultaneously meet the requirements of high temperature resistance, microwave transmission protection, microwave absorption attenuation, and structural load-bearing. The method includes: 1. Pretreatment of the substrate; 2. Preparation of a cobalt / manganese-ZIFs microwave-absorbing material precursor; 3. Laying up the microwave-absorbing material precursor; 4. Lamination and preform assembly; 5. Simultaneous in-situ reaction and isothermal hot pressing; 6. Cooling and demolding. This invention uses a high-temperature resistant microwave-transparent composite material thin plate as the outer substrate, enabling incident electromagnetic waves to pass through the substrate into the intermediate microwave-absorbing functional layer, while simultaneously providing protection and load-bearing for the microwave-absorbing layer, reducing problems such as microwave-absorbing powder shedding, moisture absorption, oxidation, and erosion wear.

This invention belongs to the field of metamaterials technology, specifically relating to an adjustable integrated absorption and reflection metamaterial structure. It includes several basic units arranged in a periodic array. Each basic unit comprises a resonant unit, a dielectric layer, and a reflector layer stacked sequentially. The dielectric layer is deformable to create a cavity between itself and the reflector layer or to fit tightly against it. The resonant unit includes four sequentially connected arc-shaped segments arranged centrally symmetrically. The ends of adjacent arc-shaped segments connect to form sharp corners extending towards the center of the resonant unit, with a gap between opposing sharp corners. This invention offers good reconfigurability, high flexibility, and deformability, allowing for easy adjustment of the state and switching of operating modes according to actual usage needs, achieving broadband absorption or complete reflection functions from 4.9 GHz to 16.3 GHz.

The invention provides a solid waste-based high-temperature heat storage material and a gradient coating-multi-field synergistic microwave uniform sintering method thereof, and belongs to the technical field of preparation of high-temperature heat storage materials. The method comprises the following steps: adding a polyvinyl alcohol pore-forming agent into a solid waste matrix, carrying out vacuum drying after ball milling, and pressing to obtain a green body; carrying out heat treatment on the green body in a holding furnace through an in-situ reaction synthesis method, and naturally cooling to room temperature to prepare a pre-sintered material; carrying out modification treatment on the surface of the pre-sintered material by adopting Ar / O2 mixed gas plasma, and forming a plasma modified functional layer on the surface of the pre-sintered material; carrying out gradient coating on the surface of the plasma modified functional layer to form an MgO / SiC coating layer; and carrying out microwave sintering treatment on the gradient coated material to obtain the solid-waste-based high-temperature heat storage material. Through the gradient coating layer structural design and in combination with multi-mode microwave field dynamic regulation and control and a temperature-power closed-loop control system, not only is the wave absorbing performance of the material optimized, but also the matching of the microwave penetration depth and the thermal diffusion rate is ensured.

The application discloses a pulse joule heat method for lithium-zinc ferrite post-treatment and wave absorption application, and the pulse joule heat method comprises the following steps: a pre-sintered lithium-zinc ferrite material is prepared by using a sintering furnace method; the pre-sintered lithium-zinc ferrite material is wrapped with carbon cloth and clamped between two electrodes of a joule heating device, then direct current is inputted to generate joule heat; in a vacuum environment, the heating temperature is controlled by adjusting the current parameters, and the heating time is controlled by adjusting the current time, so that the lithium-zinc ferrite material is rapidly post-treated. By introducing the pulse joule heating method, the lithium-zinc ferrite material can be rapidly heat-treated in a very short time, the effective regulation of the defect concentration and the electronic structure is realized, and thus the inherent parameters of the lithium-zinc ferrite are effectively improved and the wave absorption performance is improved.

The utility model relates to a kind of wave-absorbing assembly and electromagnetic darkroom, belong to the technical field of electromagnetic compatibility test.It solves electromagnetic darkroom wave-absorbing efficiency and maintenance problem by grid-shaped arrangement modular unit;Specifically, each absorbing unit adopts split design: the first wave-absorbing part is fixed on the substrate, and the replaceable second wave-absorbing part with wedge shape is connected vertically above the first wave-absorbing part through interference fit convex-concave structure;Annular wave-absorbing cavity with built-in concave-convex surface is formed between adjacent units, forcing multi-path reflection attenuation of gap electromagnetic wave.The utility model is combined with the grid substrate of shielding wall integrated molding and configures absorbing unit on the substrate, realizes efficient absorption of electromagnetic wave and local replacement of wedge body, significantly reduces secondary reflection and maintenance cost.

The application discloses an amorphous carbon-based material with quasi-continuous sp 2 domains, which is prepared by a metal salt-assisted bubble method to induce carbon atoms to rearrange under the curvature of a nano-bubble interface, successfully constructing short-range ordered quasi-continuous sp 2 domains around nanopores, and having long-range electronic transmission channels and rich conjugated / non-conjugated heterogeneous interfaces, which can synergistically enhance conductive loss and interface polarization loss. The method can anchor single-atom metals on the carbon-based body and form M-Nx structures by selecting appropriate metal precursors, and provide strong dipole polarization. The material can effectively absorb an effective absorption bandwidth of 8.0 GHz under a low filling amount of 7 wt%, and the preparation method has strong universality and is suitable for various metals and carbon precursors, thereby providing a new strategy for light-weight wide-band electromagnetic wave absorbing materials.

The application relates to a broadband electromagnetic stealth device based on a plasma array and a radar wave absorbing material, which comprises a metal plate, the bottom of which is connected to the surface of a military equipment shell; a radar wave absorbing material, which is coated on the surface of the metal plate or the military equipment shell, and the coating thickness is 2 mm; and a plasma array, which is covered on the radar wave absorbing material; the plasma array forms a combined plasma layer after being excited; and the plasma frequency in the plasma layer presents high-low alternating distribution. The electromagnetic stealth device is jointly formed by a tubular closed low-pressure plasma generator and a carbon-based radar wave absorbing material; the tubular closed cavity is made of a black glass tube, which can effectively block visible light generated by the plasma from diffusing to the outside of the cavity; the new composite wave absorbing material formed by combining the plasma and the wave absorbing material exhibits extremely excellent wave absorbing performance, and can absorb radar waves in a wide frequency band.

The application discloses a preparation method of a bichiral polyaniline / biomass carbon composite wave-absorbing material. Biomass with natural helical structure chiral characteristics is subjected to high-temperature carbonization activation treatment to obtain a micron-level chiral biomass carbon precursor. Aniline monomers are in-situ oxidatively polymerized on the surface of the chiral biomass carbon precursor under the joint action of chiral complexing inducers and initiators to obtain nanometer-level polyaniline with chiral characteristics, namely the bichiral polyaniline / biomass carbon composite wave-absorbing material. The preparation process is simple, controllable and green. The composite wave-absorbing material has the double chiral characteristics of the micron-level chiral biomass carbon precursor and the nanometer-level chiral polyaniline and the synergistic effect of the complex three-dimensional conductive network structure formed by the chiral biomass carbon precursors supporting each other, and thus the wave-absorbing performance of the composite wave-absorbing material is greatly improved. The composite wave-absorbing material can fully meet the increasingly harsh wave-absorbing performance requirements in actual applications and is convenient for industrial promotion.

The invention belongs to the field of wave-absorbing materials and electromagnetic protection materials, and particularly relates to a perovskite material with microwave absorption and radiation heat dissipation functions and a preparation method and application thereof. The perovskite material provided by the invention has a chemical formula shown as the following: Sr < x > Co < y > M < z > On, m is one or more of La, Ce, Sm, Gd, Er and Lu; 0.2 < = x < = 1.2; 0.2 < = y < = 1.0; z is 0 < = z < = 0.2; 1 < = n < = 3. The perovskite material disclosed by the invention has an adjustable strong absorption characteristic in a microwave frequency band of 1-18GHz, the spectral emissivity of the perovskite material in an infrared band of 1.5-25mu m at room temperature is greater than 90%, the perovskite material shows the characteristics of high infrared emissivity and low microwave reflection loss, and the perovskite material can still keep stable performance at high temperature; the material has wide application prospects in thermal management and electromagnetic protection materials of mobile communication base stations and wave-absorbing materials of aerospace crafts.

The application belongs to the technical field of inorganic nano functional materials, and discloses a worm-like / whisker-like composite beta-SiC nano material for wave absorption and a preparation method thereof. Amorphous silicon dioxide and carbon black are used as raw materials, a platinum-rhodium metal mixture is used as a catalyst, and high-temperature reaction is carried out at 2000-2200 DEG C under inert gas protection for 5-20 hours. The process is controllable. By accurately controlling the reaction time and utilizing the evolution of the VSL growth mechanism, the composite beta-SiC nano material with adjustable worm-like and whisker-like proportion can be prepared. The prepared composite nano material has good impedance matching and strong dielectric loss capacity, and has moderate resistivity. In particular, it is especially suitable as a wave absorption material for a wave absorption coating with high requirements for weather resistance and temperature resistance, can realize wide-band, strong-absorption radar stealth effect, and has important application value in the fields of aerospace and high-end electronic equipment electromagnetic compatibility.

This invention discloses a dielectric-magnetic synergistic loss type electromagnetic wave absorbing material, its preparation method, and its application. The dielectric-magnetic synergistic loss type electromagnetic wave absorbing material of this invention comprises rGO aerogel and Ni distributed in the rGO aerogel. x Co 1‑x Fe2O4 magnetic nanoparticles x The range of values ​​for is 0≤ x ≤1. The preparation method of the dielectric-magnetic synergistic loss type electromagnetic wave absorbing material of the present invention includes the following steps: mixing graphene oxide and Ni x Co 1‑x Fe2O4 magnetic nanoparticles are dispersed in water, then subjected to a hydrothermal reaction, followed by freeze-drying. The dielectric-magnetic synergistic loss-type electromagnetic wave absorbing material of this invention possesses advantages such as low density, small matching thickness, wide absorption bandwidth, high absorption intensity, and flexible adjustment of composition and properties, making it a promising candidate for applications in radar stealth and electromagnetic protection.

This invention discloses an asphalt concrete that combines ice-breaking and noise reduction with its manufacturing method, comprising the following raw materials by weight: 100-120 parts aggregate, 5-8 parts thermally conductive asphalt, 2-8 parts mineral powder, and 3-5 parts noise-reducing filler. The aggregate, noise-reducing filler, and mineral powder are stirred for 20 seconds, then the thermally conductive asphalt is added, mixed, and shaped to obtain the asphalt concrete that combines ice-breaking and noise reduction. Modified silicon carbide is introduced into the thermally conductive asphalt, with carbon nanotubes as the carbon source, silicon powder and silicon dioxide as the silicon source, and cobalt acetate as the cobalt source. Modified silicon carbide is prepared by solid-state sintering, in which cobalt atoms enter the silicon carbide lattice to prepare cobalt-doped silicon carbide. While silicon carbide itself has excellent thermal conductivity, the introduction of cobalt gives the modified silicon carbide magnetism and improves its microwave absorption performance. Under microwave action, it can quickly melt snow and break ice, and also improves the thermal conductivity of the asphalt, further improving the ice-breaking performance.

A cross-band multistage adjustable radar wave-absorbing structure, a design method and a preparation method belong to the technical field of electromagnetic wave regulation and control. The cross-band multistage adjustable radar wave-absorbing structure is prepared by using a photoetching process and a magnetron sputtering process, can realize absorption of a specific wave band under S / C / X wave bands, and sequentially comprises a patterned microwave absorbing layer, a chalcogenide phase change material layer, a heat bearing layer, a metal electrode layer and a flexible dielectric layer. The metal-insulating state conversion of the chalcogenide phase change material is realized by controlling the conductivity of the chalcogenide phase change material, the Fermi level of the chalcogenide phase change material is adjusted by controlling the chalcogenide phase change material, multi-band absorption adjustment is realized, perfect absorption is realized at multiple specific frequency points, and a certain angle insensitivity characteristic is possessed. Meanwhile, the structure of the chalcogenide phase change material layer is simple, mass production and processing requirements are met, the application of the phase change material in the GHz field is expanded, and the design is flexible, electrically adjustable, and widely applied.

The application belongs to the technical field of wave-absorbing material coating, and particularly relates to an integrated wave-absorbing surface preparation method based on ultrafast laser processing, which realizes integrated preparation of nano wave-absorbing materials by introducing an ultrafast laser micro-nano processing technology. The application uses a spatially shaped femtosecond laser to process and modify a metal base in a liquid precursor environment, so that the ultrafast laser reduces the liquid precursor while processing and modifying the surface of the metal base, can effectively make the metal surface produce a closely combined nano structure layer containing magnetism without loss of surface mechanical properties, thereby improving the magnetic loss of the metal surface for microwaves, improving the wave-absorbing performance, and solving the problem of poor combination of the existing wave-absorbing coating and the base, which affects the wave-absorbing performance.

The application discloses a preparation method of high-entropy carbon nanofiber aerogel, which comprises the following steps: mixing perfluorohexanoic acid, DMF, polyacrylonitrile and metal salts of at least five different metal elements to obtain a precursor solution, directly taking the precursor solution as a spinning solution to obtain a fluffy fiber three-dimensional network structure through electrostatic spinning, and converting the fluffy fiber three-dimensional network structure into high-entropy carbon nanofiber aerogel through pre-oxidation and high-temperature carbonization, so that the aerogel structure is self-constructed, the dielectric loss, the magnetic loss and the interface polarization are simultaneously enhanced, and a broadband, strong-absorption and lightweight composite wave-absorbing material is obtained. The application does not need the complex processes, such as ice template directional assembly, freezing forming and freeze drying, which are necessary for traditional aerogel preparation, so that the process flow is greatly shortened, the energy consumption and the cost are reduced, and the large-scale preparation is easy.

The present application relates to wave-absorbing material technical field, specifically to a kind of flame-retardant wave-absorbing material based on polystyrene foam and preparation method thereof.The present application uses one-dimensional magnetic sepiolite fiber and two-dimensional modified graphene oxide as raw material, three-dimensional directional porous structure composite aerogel is prepared by freeze drying, composite aerogel, flame retardant, film forming agent, dispersing agent, defoaming agent and deionized water are obtained to obtain wave-absorbing coating;Foamed polystyrene beads are put into wave-absorbing coating, and after stirring evenly, drying, molding, the flame-retardant wave-absorbing material based on polystyrene foam is obtained.The flame-retardant wave-absorbing material based on polystyrene foam prepared by the present application not only has excellent wave-absorbing performance, but also has excellent flame-retardant performance and mechanical properties.

The application belongs to the technical field of high-temperature wave-absorbing coating materials, and particularly relates to a high-temperature radar stealth coating for repairing, a preparation method and application, especially application to a radar stealth coating for repairing a damaged surface of weapon equipment at a working temperature of 900 DEG C to 1000 DEG C. The coating is composed of glass powder A, glass powder B, ceramic radar absorber and diluent, and the mass ratio is (1-2):(0.5-1.5):(0.5-1):(1-2). The coating has good radar stealth performance and wave-absorbing performance, and when applied to preparation of the high-temperature radar stealth coating, the coating preparation period is short, the damaged coating can be quickly repaired in the field environment, and the problems of equipment transportation, assembly and debugging difficulty and long coating preparation period in plasma spraying preparation of the high-temperature stealth coating are solved.

The invention provides a ligand defect type Ti-MOF (Ti-Metal-Organic Framework) derived nitrogen-carbon doped TiO2 wave-absorbing material, a preparation method of which comprises the following steps: mixing dihydrolevo-glucose ketene, N, N-dimethylformamide and methanol to obtain a mixed solvent; the preparation method comprises the following steps: dissolving an organic ligand in a mixed solvent, adding acetic acid, uniformly stirring, dropwise adding titanium salt, stirring for a period of time, and slowly dropwise adding trifluoroacetic acid to obtain a mixture; carrying out hydrothermal reaction on the mixture, and separating a solid after the reaction is completed, so as to obtain a precursor Ti-MOF; and carbonizing the precursor Ti-MOF in an inert atmosphere at a high temperature to obtain the wave-absorbing material. The invention also provides application of the wave-absorbing material in the field of microwave absorption. The material prepared by the preparation method disclosed by the invention shows excellent performance in the aspects of absorption strength and bandwidth. The method is simple in process and controllable in condition, and the obtained material is high in purity and suitable for large-scale preparation and has wide application prospects in the fields of electromagnetic protection, communication devices, aircraft stealth and the like.

A gradient impedance-gradient multi-fiber hybrid broadband absorbing structure is provided, comprising a multi-fiber preform and a low-loss matrix. The low-loss matrix fills within the multi-fiber preform and covers it, with a covering thickness of <0.2 mm. The multi-fiber preform is formed by weaving together high-loss, medium-loss, and low-loss fibers. The multi-fiber preform includes an impedance matching layer formed by low-loss fiber weaving, an impedance transition layer formed by mixing low-loss and medium-loss fibers, and an absorption attenuation layer formed by mixing medium-loss and high-loss fibers. The impedance matching layer, impedance transition layer, and absorption attenuation layer are stacked sequentially to form a three-dimensional structure. This invention can effectively control its microwave electromagnetic characteristics, achieve a reasonable impedance gradient change, and significantly improve broadband absorption performance.

This invention discloses a method for depositing carbon nanofiber composite materials using lotus leaves as a substrate, its preparation, and its application. The method includes the following steps: Cleaned lotus leaves are placed in a catalyst aqueous solution and ultrasonically treated for 20-40 minutes. The solution is then poured into a polytetrafluoroethylene-lined reactor. The catalyst aqueous solution is a mixture of nickel nitrate and thiourea, with a molar ratio of 1:10-15. The total concentration of metal ions in the catalyst aqueous solution is 0.01-0.04 mol / L. The reactor is heated at 170-190℃ for 20-30 hours. After the reaction is complete, the solution is cooled, filtered, and the resulting solid is dried to obtain powder. The powder is placed in a quartz boat, the air is replaced with nitrogen, hydrogen is introduced, and the solution is heated to 430-470℃ for 5-15 minutes to reduce the catalyst. Subsequently, the solution is heated to 600-700℃ for reaction growth, with a single introduction of carbon nanofibers. 2 H 2 and H 2 and control N 2 C 2 H 2 and H 2 The flow rate ratio is 5-7:2-4:2-4. After growing for 20-40 minutes, the target product is obtained. The target product is then cooled.

The application provides a magnetic metal powder / porous carbon composite material, a preparation method and application thereof. The preparation method comprises the following steps: step S1, performing surface oxidation reaction on a magnetic carbonyl metal powder to form pretreated metal powder; step S2, dissolving a copolymer PS n -b-PEO m in a first solvent, adding a mixed solution of ethanol and water into the first solvent to obtain a milk emulsion; step S3, adding the pretreated metal powder, pyrrole and FeCl3 into the milk emulsion to perform in-situ polymerization reaction, so as to form a precursor and obtain a precursor solution; step S4, removing the spherical PS n -b-PEO m micelles in the precursor by a solvothermal method, and then drying to obtain a porous precursor; and step S5, calcining the porous precursor under an inert atmosphere to obtain the magnetic metal powder / porous carbon composite material. The magnetic metal powder / porous carbon composite material prepared by the application has better wave absorption performance in a low frequency band.

The application discloses a kind of catalysts for microwave-driven methanol-water reforming hydrogen production.The catalyst is composite catalyst obtained by CuO / ZnO composite oxide active component being supported on the surface of microwave absorption component, and the microwave absorption component is carbon nanotube or mixture of carbon nanotube and graphite;The mass of microwave absorption component accounts for 10-40wt.% of the mass of the entire catalyst;It is prepared by impregnation loading method.The application uses carbon with appropriate graphitization degree and specific surface area as carrier and as microwave absorption material at the same time, and loading copper-zinc oxide shows excellent wave-absorbing performance and methanol / water reforming reaction performance, and the preparation process is simple, when applied to microwave-driven methanol / water reforming hydrogen production, methanol can be converted to nearly 100% under the condition of using lower molar ratio of methanol / water raw material, and the H2 content in reforming gas product is about 70mol.%, and the CO content is less than 1mol.%.

The application belongs to the field of fabric treatment, and particularly relates to a wave-absorbing yarn and a wave-absorbing fabric. In order to solve the technical problem that the wave-absorbing performance of a composite fiber fabric in the prior art is poor because, after electromagnetic waves enter the composite fiber fabric, the part of the electromagnetic waves that enters the wave-absorbing fiber after being reflected is less, and the part of the electromagnetic waves that reaches the outside after being reflected is more, the application provides a wave-absorbing yarn. The wave-absorbing yarn comprises a wave-transparent base body, a connecting surface is formed on a part of the circumferential surface of the wave-transparent base body in the circumferential direction, the cross section of the connecting surface is parabolic, a reflecting structure is connected to the connecting surface, the reflecting structure has a reflecting surface that is consistent with the connecting surface, and a wave-absorbing body is arranged in the wave-transparent base body and located at the focal point of the reflecting surface. The application further provides a wave-absorbing fabric comprising the wave-absorbing yarn. The parabolic reflecting surface can effectively reflect the electromagnetic waves to the wave-absorbing body, thereby improving the wave-absorbing capacity of the wave-absorbing yarn and the wave-absorbing fabric.

The invention relates to an electromagnetic absorbing structure, in particular to an ultra-wideband composite wave-absorbing honeycomb structure, and belongs to the field of electromagnetic wave-absorbing materials. The invention relates to a composite wave-absorbing honeycomb structure which comprises a honeycomb framework, a multi-layer tower type gradient structure and a wave-absorbing substrate. The multi-layer tower type gradient structure is fixed in the honeycomb framework in an embedded mode, and the wave absorbing substrate is arranged below the structure where the multi-layer tower type gradient structure and the honeycomb framework are embedded. According to the composite wave-absorbing honeycomb structure, the honeycomb framework, the multi-layer tower type gradient structure and the wave-absorbing substrate are subjected to composite design, so that the wave-absorbing bandwidth of the whole wave-absorbing honeycomb is effectively expanded, and the ultra-wideband efficient wave-absorbing characteristic is realized. The prepared composite wave-absorbing honeycomb has an excellent wave-absorbing effect in a frequency band range of 2-18GHz.

The invention discloses a bifunctional catalyst and application thereof in microwave-assisted biodiesel preparation, and belongs to the technical field of catalysis. Cobalt metal is introduced into a ZIF-8 skeleton, when the MOFs derivative is prepared through calcination, a magnetic center can be constructed through introduction of transition metal, and the magnetic loss capacity of a derivative material is adjusted, so that the prepared catalyst has high wave absorbing performance in an industrial microwave field of 2.45 GHz, microwave energy can be effectively absorbed and converted into heat energy, and the catalyst can be used for preparing the MOFs derivative. Therefore, the energy utilization efficiency of a reaction system is improved, the catalytic performance of the catalyst is finally improved, the microwave-assisted biodiesel preparation efficiency is further improved, and the method has good application value and prospect in the technical field of catalysis.