407 results about "Electromagnetic wave absorption" patented technology

The invention discloses supercritical fluid foaming polyimide wave-absorbing foam and a preparation method thereof.The thermoplastic polyimide is prepared by the steps that aromatic dianhydride, aromatic diamine and aliphatic diamine serve as comonomers, polyimide acid is generated through solution polymerization, and then high-temperature cyclization is conducted; wherein the mole number of the aliphatic diamine accounts for 10-50% of the total mole number of the diamine, and the free volume and glass transition temperature of a molecular chain are effectively regulated and controlled by introduction of the aliphatic diamine; the wave-absorbing foam is prepared by taking polyimide as a matrix, doping 1-20wt% of wave-absorbing filler, and foaming for 1-3 hours in a supercritical carbon dioxide or nitrogen environment at the temperature of 180-220 DEG C and the pressure of 9-25MPa, through molecular structure design, the adsorption capacity and impact resistance of polyimide to carbon dioxide are remarkably improved, and the prepared foam has the advantages of light weight, high porosity, uniform foam structure and excellent heat resistance, can realize effective electromagnetic wave absorption in an X wave band, and is suitable for the fields of aerospace stealth and electromagnetic compatibility protection.

The invention relates to the technical field of high-entropy ceramic powder, in particular to diboride high-entropy ceramic powder and a preparation method thereof.The preparation method comprises the following steps that five transition metal oxides, boron powder and fused salt serve as raw materials, are evenly mixed through a mixer and then are dried at the temperature of 60-200 DEG C, and a mixture is obtained; then, the mixture is put into a corundum crucible, and heat preservation is conducted for 1-20 h at the temperature interval of 700-1600 DEG C and under the protective atmosphere; and after the reaction is completed, cooling, washing, carrying out suction filtration, and drying at 60-200 DEG C to finally prepare the diboride high-entropy ceramic powder. The method has the advantages of low synthesis temperature, small product particle size, uniform element distribution, environment friendliness and the like, and the prepared diboride high-entropy ceramic powder shows excellent electromagnetic wave absorption performance.

The invention relates to a preparation method and application of a two-dimensional ultrathin porous nitrogen-doped carbon composite material. According to the invention, a metal salt nitrate ion mediation method is adopted, and the ultrathin porous carbon nanosheet loaded with metal single atoms and metal nanoparticles is successfully prepared through decomposition of a prepolymerized dopamine-metal salt precursor. By changing the type of metal salt ligand anions, accurate regulation and control between a non-porous structure and a porous structure can be realized. Endogenous multi-scale pore defects are introduced into the surface of the carbon nanosheet, so that the impedance matching of the prepared carbon nanosheet system is effectively improved, and meanwhile, high conductivity is kept. According to the prepared material, the dielectric constant is improved by introducing a porous structure, impedance matching is optimized, and the electromagnetic wave absorption capacity is improved.

The invention discloses an electromagnetic wave absorbing material CoFe2O4 / ZnO-RGO with a ternary heterostructure as well as a preparation method and application of the electromagnetic wave absorbing material CoFe2O4 / ZnO-RGO, and belongs to the technical field of electromagnetic wave absorption. According to the material, a novel heterostructure with a multi-scale interface and a three-dimensional conductive network is constructed by compounding magnetic loss type CoFe2O4, dielectric loss type ZnO nanorods and resistance loss type RGO. Wherein the ZnO nanorod not only serves as a dielectric loss body, but also effectively enhances the structural anisotropy and the interface polarization effect of the material, and cooperates with the magnetic loss of CoFe2O4 and the resistance loss of RGO to jointly optimize impedance matching and improve the electromagnetic attenuation capability, so that the material shows excellent wave-absorbing performance under various thickness and even ultrathin conditions. The material source is wide, the cost is low, the preparation process is green, simple and convenient, the material is suitable for large-scale production, and an effective material solution is provided for electromagnetic wave absorption application in the national defense and civil fields.

The invention relates to the technical field of electromagnetic shielding materials, and particularly discloses an electromagnetic shielding composite material with active and passive infrared stealth functions and a preparation method thereof. The composite material comprises an electromagnetic wave reflecting layer and a plurality of electromagnetic wave absorbing layers. The electromagnetic wave reflecting layer is made of silver-plated bacterial cellulose, and efficient reflection of electromagnetic waves is achieved through high conductivity of the silver-plated bacterial cellulose. The electromagnetic wave absorbing layer is formed by compounding bacterial cellulose, multi-walled carbon nanotubes and core-shell magnetic nanoparticles, and the content of the multi-walled carbon nanotubes is gradually decreased and the content of the core-shell magnetic nanoparticles is gradually increased from the position close to the electromagnetic wave reflecting layer to the outside, so that a gradient structure is formed; the gradient design can improve surface impedance matching, promote electromagnetic waves to enter the material, and enhance electromagnetic loss through an interlayer multiple reflection-absorption process. The material disclosed by the invention has the functions of efficient electromagnetic shielding and active and passive infrared stealth.

The invention relates to a preparation method of an infrared stealth and wave-absorbing material and the infrared stealth and wave-absorbing material.The preparation method of the infrared stealth and wave-absorbing material comprises the steps that PMMA microspheres are coated with Ti < 3 > C < 2 > T < x >, and PMMA-coated Ti < 3 > C < 2 > T < x > is obtained; the PMMA microspheres in the PMMA coated Ti < 3 > C < 2 > T < x > are removed, and hollow Ti < 3 > C < 2 > T < x > is obtained; growing ZnO on the hollow Ti < 3 > C < 2 > T < x > to obtain a first substance; the first substance is dispersed in a cellulose nanofiber suspension with the concentration of 5 mg / mL, vacuum filtration and drying are carried out, the infrared stealth and wave-absorbing material is obtained, and 0.5 g to 1 g of the first substance corresponds to 20 mL of the cellulose nanofiber suspension. The infrared stealth and wave-absorbing material prepared by the method has excellent electromagnetic wave absorption performance and good infrared stealth performance.

The application provides a hollow carbon / Co efficient electromagnetic wave absorbing material and a preparation method and application thereof, and comprises the following steps: step 1, dissolving cobalt nitrate hexahydrate, tetradecyl trimethyl ammonium bromide, 2-methyl imidazole and zinc nitrate hexahydrate in water, stirring and reacting to obtain solution C; step 2, washing solution C, separating and drying a solid product to obtain a hollow ZIF-8 / ZIF-67 precursor; and step 3, carbonizing the hollow ZIF-8 / ZIF-67 precursor under an inert atmosphere to obtain the hollow carbon / Co efficient electromagnetic wave absorbing material. The preparation process is simple, the material can be prepared on a large scale, and the prepared composite material has excellent electromagnetic wave absorbing performance.

A composite electromagnetic wave-absorbing material and preparation method therefor are provided. The composite electromagnetic wave-absorbing material includes following raw materials: magnetite powder, nickel powder, copper powder, samarium oxide, gadolinium oxide, cerium oxide, carbon black powder, graphite powder, epoxy resin, barium titanate powder, antioxidant, curing agent, diluent and leveling agent. Ferrite wave-absorbing materials are used as matrixes to be compounded with nickel powder, copper powder, graphite powder, carbon black and barium titanate, and doped with mixed rare earth oxides through combination of samarium oxide, gadolinium oxide and cerium oxide to thereby obtain the composite electromagnetic wave-absorbing material which combines magnetic loss characteristics of magnetite powder, ferromagnetic behavior of nickel powder and conductivity of copper powder, helping to achieve good electromagnetic wave-absorbing performance. By introducing graphite powder, carbon black powder and barium titanate powder as fillers and doping rare earth, wave-absorbing characteristics of the composite electromagnetic wave-absorbing material are improved.

The invention belongs to the technical field of electromagnetic wave absorbing materials, and discloses a composite coating with electromagnetic protection and explosion-proof functions as well as a preparation method and application of the composite coating. The coating comprises 40 to 60 parts of polycarbodiimide modified diphenylmethane diisocyanate, 40 to 60 parts of a semi-prepolymer which is synthesized from polycarbonate diol with the equivalent weight of 1000 and has the NCO content of 10 to 20 percent, 73 to 100 parts of a polyether amine curing agent, 15 to 20 parts of diethyl toluenediamine or dimethyl thio toluenediamine, 0.5 to 2 parts of calcium carbonate and 3 to 6 parts of magnetic powder. And the two components are quickly reacted and molded through a spraying process. According to the invention, the polyurea elastomer is used as a matrix, so that the coating is endowed with excellent impact resistance, explosion-proof characteristics, water impermeability, oil resistance, low temperature resistance and other environmental tolerance; meanwhile, an adjustable electromagnetic wave absorption function is realized by doping specific magnetic powder. The coating is simple in preparation process and excellent in comprehensive performance, and is particularly suitable for equipment surfaces with high requirements on stealth and survival protection, such as oil storage equipment.

The invention relates to the technical field of electromagnetic wave absorbing materials, in particular to a composite material and a preparation method and application thereof. The composite material is prepared from magnetic microspheres, modified SiO2 aerogel and Mxene, wherein the magnetic microsphere comprises an inner core and a coating layer, the inner core comprises Fe3O4, the surface of the inner core is at least partially coated with the coating layer, and the coating layer comprises SiO2; a modified group of the modified SiO2 aerogel comprises at least one of amino, hydroxyl and carboxyl; the magnetic microspheres are positioned on the two-dimensional surface of the MXene. According to the composite material, through the synergistic effect of the magnetic microspheres, the modified SiO2 aerogel and the MXene, impedance matching between the composite material aerogel and air is remarkably enhanced, and the electromagnetic wave absorption performance of the composite material is promoted.

The application discloses a multi-dimensional structure silicon carbide-silicon nitride composite material and a preparation method thereof. S As the core of the multi-dimensional structure, the prepared silicon carbide-silicon nitride composite material not only solves the long-term technical problems of'single dimension' and 'incomplete carbonization and nitridation', but also realizes the structural and functional integration of'mechanical strength and toughness' and 'electromagnetic wave absorption function', has the advantages of high purity, excellent mechanical properties, good electromagnetic wave absorption effect, low raw material cost, industrializable process and the like, and has a wide industrialization prospect.

The invention relates to a preparation method and application of a CoNi alloy nanoparticle doped double-shell hollow carbon material, and belongs to the field of nano material preparation technology and electromagnetic wave absorption application. 3-aminophenol and formaldehyde are subjected to a condensation polymerization reaction to synthesize phenolic resin balls, the phenolic resin balls are placed in 3-aminophenol and formaldehyde again to react, and the double-shell hollow phenolic structure is obtained. And adding the double-shell hollow phenolic aldehyde structure into cobalt nitrate hexahydrate (Co (NO3) 2.6 H2O) and 2-methylimidazole for low-temperature reaction, then adding a solution of (Ni (NO3) 2.6 H2O) for reaction at high temperature and high pressure, and drying to obtain the CoNi alloy nanoparticle doped double-shell hollow carbon material. According to the preparation method disclosed by the invention, the double-shell structure is taken as a main template, and the CoNi alloy nanoparticles are used as active components to be doped in the double-shell hollow structure in situ, so that the cascade synthesis of the microstructure of the nano material is greatly enriched, and the obtained CoNi alloy nanoparticle doped double-shell hollow carbon material has excellent electromagnetic wave absorption performance.

The invention provides a ZrO2 (at) SiC (at) NiCo2O4 / NiO composite material with high temperature tolerance and a preparation method and application thereof, the composite material takes ZrO2 (at) SiC fibers as a three-dimensional conductive network framework, and NiCo2O4 / NiO nanosheets are anchored on the surfaces of the ZrO2 (at) SiC fibers. The composite material shows excellent electromagnetic wave absorption performance in a high-temperature environment.

The invention discloses an on-line radiation monitoring and power-off protection MEMS pressure sensor and a preparation method thereof. The sensor can synchronously realize pressure measurement, radiation monitoring and power-off protection functions on a single chip. On the basis of realizing high-precision pressure measurement, the sensor is provided with a platinum film resistor in a specific area and is coated with an electromagnetic wave absorbing material to form a radiation sensing unit, so that the on-line monitoring on the electromagnetic radiation intensity of the environment is realized. The protection circuit closely integrated with the sensor continuously analyzes radiation dose signals, and once it is judged that the dose exceeds a preset safety threshold value, a control signal is generated, a power supply access of the pressure measurement unit is actively cut off, the pressure measurement unit is made to enter a dormant state, and therefore irreversible performance degradation or permanent damage is avoided. According to the invention, the conversion from passive bearing to active protection during the working of the sensor is realized, and the reliability of long-term working in an extreme electromagnetic environment is obviously improved.

The invention discloses a three-dimensional structure electromagnetic regulation and control material and a preparation method thereof, and belongs to the technical field of electromagnetic functional composite materials. In order to solve the problems of narrow band wave absorption and high density of a traditional electromagnetic regulation and control material, spherical carbonyl iron powder, conductive carbon black, graphene, carbon nanotubes, methyl vinyl silicone rubber and hydrophobic fumed silica are used as an electromagnetic regulation and control base material system, and the electromagnetic regulation and control material is prepared through mixing, vulcanization, forming and secondary processing. And the electromagnetic regulation and control material with the three-dimensional periodic tower-shaped microstructure, which has broadband electromagnetic wave absorption and low density and can be flexibly attached, is prepared.

A device (100) for heating by electromagnetic waves comprises: an electrically conductive housing (1); an electromagnetic wave generation unit (10) that generates electromagnetic waves which are linearly polarized waves; a plurality of radiating units (3) that radiate the electromagnetic waves generated by the electromagnetic wave generation unit into the interior of the housing; a directivity control unit (2) that controls the directivity of the electromagnetic waves from the plurality of radiating units; and an electromagnetic wave absorbing unit (5) that is arranged inside the housing in such a way that the electromagnetic wave absorbing unit is aligned with a plane of oscillation of the electromagnetic waves and absorbs electromagnetic waves inside the housing.

The application discloses a graphene quantum dot / indium sulfide electromagnetic wave absorbing material and a preparation method thereof, and comprises the following steps: carrying out a hydrothermal reduction reaction on trinitro-pyrene and an alkaline solution to obtain graphene quantum dot powder rich in hydroxyl functional groups on the surface; and carrying out a hydrothermal reaction on a mixture of indium chloride tetrahydrate and thioacetamide and the graphene quantum dot powder to obtain a graphene quantum dot / indium sulfide heterojunction electromagnetic wave absorbing material with a sulfur vacancy concentration of 3.8% to 5.7%. The addition amount of the sulfur source is controlled by regulating the addition amount of the thioacetamide in the hydrothermal reaction process, the introduced sulfur vacancy concentration is accurately controlled, the In-O covalent bond is formed at the interface between the graphene quantum dot and the indium sulfide, the interface covalent bridging structure is formed, the interface charge transfer efficiency is accelerated, the built-in electric field in the interface is enhanced, stronger interface polarization loss is induced, and the performance of high absorption intensity and wide bandwidth of the composite wave absorbing material is realized.

A system for heat conditioning an area of Earth includes an Earth-orbiting satellite. The satellite includes a power supply, a precursor gas supply, and one or more double helicon plasma beam generators coupled to the power supply and the gas supply and configured to generate a plasma and further configured with a magnetic nozzle to maintain a shape of the beam; therefore, the top surface area of the beam is maximized. The generated plasma provides enhanced electromagnetic waves absorption, reflection, and deflection of incoming solar light and electromagnetic radiation, thereby reducing the heat striking the area of the Earth.

This application discloses an electromagnetic absorber and an electromagnetic wave absorption method. The electromagnetic absorber includes: a reflective phase gradient metasurface array, comprising a first dielectric layer, a first metal backplate layer, and multiple metal resonant units. The first dielectric layer is disposed on the upper surface of the first metal backplate layer, and the multiple metal resonant units are arrayed on the first dielectric layer. Each metal resonant unit includes n metal H-shaped structures of different sizes. The reflective phase gradient metasurface array is used to convert plane waves into surface waves. A surface plasmon polariton coupler is used to converge and absorb the energy of the converted surface waves. This application can achieve effective convergence and absorption of surface wave energy.

The application belongs to the technical field of electromagnetic wave absorbing materials, and particularly relates to a co-doped mesoporous carbon sphere wave absorbing material, a preparation method and an application. The preparation method comprises the following steps: aniline is added into a colloidal silica hydrochloric acid solution and uniformly mixed to obtain a mixed solution; then, ammonium persulfate hydrochloric acid solution is added into the mixed solution and uniformly mixed; drying is performed to obtain a precursor; the precursor is calcined under a protective atmosphere to obtain an intermediate; then, the intermediate and a sodium hydroxide solution are mixed, heated, and treated to obtain the co-doped mesoporous carbon sphere wave absorbing material. The calcination method comprises the following steps: the precursor is heated to 250-350 DEG C under a protective atmosphere and then heated to 700-900 DEG C for calcination. The co-doped mesoporous carbon sphere wave absorbing material has excellent wave absorbing performance.

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 relates to a hydrogel with both strength and electromagnetic wave absorption and a preparation method thereof. The preparation method of the hydrogel material comprises the following steps: S1, carrying out amination treatment on Fe3O4; s2, adding Fe3O4-NH2 and GO in the step S1 into deionized water, and carrying out ultrasonic dispersion; s3, adding polyethylene glycol methyl ether acrylate-480 and acryloyl morpholine into the dispersion liquid in the S2, and dissolving the polyethylene glycol methyl ether acrylate-480 and the acryloyl morpholine to obtain a mixed liquid; s4, removing dissolved oxygen in the mixed solution in S3, sealing the container, and stirring under an ice bath condition; s5, adding potassium persulfate and N, N, N ', N'-tetramethylethylenediamine into the mixed solution stirred in the step S4, and closing the container again; s6, the container is subjected to a polymerization reaction at the temperature of 60 DEG C, and hydrogel is obtained. Compared with the prior art, when the thickness of the hydrogel material is 2.07 mm, strong broadband microwave absorption is achieved, RLmin is-57.0 dB, EABmax is 6.4 GHz, meanwhile, excellent flexibility is kept, and the work provides a new view angle for developing a high-flexibility and efficient electromagnetic wave absorber.

The invention discloses a multifunctional rubber film with electromagnetic wave absorption performance and a preparation method thereof, and belongs to the field of microwave absorption. The preparation method comprises the following steps: physically and uniformly mixing N, S co-doped hollow carbon spheres (SNC) with wrinkles on the surface with a rubber solution, and evaporating to remove moisture at 50-60 DEG C to obtain the SNC rubber film. The SNC rubber film prepared by the method has excellent electromagnetic wave absorption performance, the effective absorption broadband is 7.12 GHz, and the SNC rubber film also has the multifunctional characteristics of hydrophobicity, frost prevention, flexibility, stretchability, viscidity and the like.

The invention relates to the technical field of electromagnetic wave absorbing materials, in particular to a neodymium-cobalt co-substituted M-type strontium ferrite dual-band wave absorbing material and a preparation method thereof. The chemical formula of the dual-band wave-absorbing material is Sr < 1-x > Nd < x > Co < 0.2 > Fe < 1. 8 > O < 19 >, wherein x is equal to 0.1 to 0.4. The method comprises the following steps: forming sol from a strontium source, a neodymium source, a cobalt source, an iron source and citric acid monohydrate, adjusting the pH value through ammonia water, heating to form gel, drying, grinding, and carrying out heat treatment at 250 DEG C, 450 DEG C and 1400 DEG C to obtain a target product. After the obtained material is compounded with paraffin, wave-absorbing response can be shown in wave bands of 2-18 GHz and 26.5-40 GHz, and the material can be used as a wave-absorbing filler for an electromagnetic protection material.

The application relates to the technical field of electromagnetic shielding materials, and particularly discloses an electromagnetic shielding composite material with active and passive infrared stealth functions and a preparation method thereof. The composite material comprises an electromagnetic wave reflection layer and a multilayer electromagnetic wave absorption layer. The electromagnetic wave reflection layer is silver-plated bacterial cellulose, and high-efficiency electromagnetic wave reflection is realized by utilizing the high conductivity of the silver-plated bacterial cellulose. The electromagnetic wave absorption layer is composed of bacterial cellulose, multi-walled carbon nanotubes and core-shell magnetic nanoparticles, and from the side close to the electromagnetic wave reflection layer to the outside, the content of the multi-walled carbon nanotubes decreases, and the content of the core-shell magnetic nanoparticles increases, so that a gradient structure is formed; the gradient design can improve the surface impedance matching, promote the electromagnetic wave to enter the material interior, and enhance the electromagnetic loss through the interlayer multiple reflection-absorption process. The material has the functions of high-efficiency electromagnetic shielding and active and passive infrared stealth.

This invention discloses a functionalized MXene hollow sphere / MXene-PI composite aerogel and its preparation method. The composite aerogel uses MXene / PI aerogel with a vertically oriented millimeter-scale pore structure as the base layer and magnetic Fe-OH functionalized MXene hollow spheres as the self-supporting functional layer. The base layer and the self-supporting functional layer form a composite aerogel with a gradient structure. This invention obtains MXene hollow spheres using a template method, anchors Fe-OH magnetic particles to the surface of the hollow spheres using in-situ loading, and fabricates a three-dimensional porous aerogel framework base layer of MXene-PI using directional freeze-thermal imidization. Then, the functional layer and the base layer are co-frozen and assembled, followed by thermal imidization to obtain the composite aerogel. This invention achieves integrated electromagnetic wave absorption and thermal management performance by synergistically integrating magnetically functionalized MXene hollow spheres and a conductive PI network, forming a gradient structure.

The electromagnetic wave absorber has a three-dimensional network structure of conductive fibers and is used for absorbing terahertz waves.

The invention provides a cascading flexible metasurface wave-absorbing composite material and a preparation method and application thereof. The composite material sequentially comprises a first flexible dielectric layer, a first coupling type active frequency selection surface layer, a second flexible dielectric layer, a flexible lossy substrate layer, a third flexible dielectric layer, a second coupling type active frequency selection surface layer and a fourth flexible dielectric layer, the unit structure of the frequency selective surface layer is any one of a square ring structure, a square structure, a square split ring structure, a square ring-square nested concentric structure or a T-shaped connection type square ring-square nested concentric structure, a traditional reflecting layer is replaced by the active frequency selective surface layer structure, the quarter-wavelength thickness limitation is broken through, and low-frequency ultra-thin wave absorption is achieved; the frequency selection characteristic of the active frequency selection surface layer is utilized to realize an electromagnetic wave absorption-screening-reabsorption cascade working mechanism, and the composite material has flexibility, thermal stability and conformality, and is suitable for the fields of electronic equipment electromagnetic compatibility management, aircraft radar stealth and the like.

This application relates to the field of electromagnetic wave absorbing materials technology, and discloses a composite aerogel that combines thermal conductivity and tunable effective electromagnetic wave absorption band, its preparation method, and its applications. The composite aerogel consists of composite nanosheets, magnetic nanorods, and a binder; the composite nanosheets form a continuously oriented layered structure through the binder, and the magnetic nanorods are loaded onto the composite nanosheets; the composite nanosheets are composed of Ti3C2T... x The composite aerogel is composed of MXene nanosheets and reduced graphene oxide through hydrogen bonding; the magnetic nanorods are iron oxide nanorods; and the binder is a one-dimensional fiber. The unique layered oriented arrangement of this composite aerogel improves the impedance matching at the aerogel / air interface, reduces electromagnetic wave surface reflection, and allows electromagnetic waves entering the aerogel to be gradually converted into heat energy through multiple reflections and absorption processes. Furthermore, its layered oriented arrangement facilitates directional heat conduction. Through the synergistic effect of its structure and materials, it possesses both electromagnetic wave absorption and high thermal conductivity.