1077 results about "Electromagnetic wave absorption" patented technology

The invention provides a modified basalt fiber, a basalt fiber shielding material and a preparation method, and relates to the technical field of fiber composites.The modified basalt fiber comprises an activated basalt fiber, an adhesion layer and an electromagnetic shielding layer, and the surface of the activated basalt fiber is sequentially coated with the adhesion layer and the electromagnetic shielding layer; the adhesion layer comprises polydopamine; the electromagnetic shielding layer comprises magnetic Fe3O4 nano particles and a graphene nano sheet; the mass ratio of the activated basalt fibers to the polydopamine to the magnetic Fe3O4 nanoparticles to the graphene nanosheets is 1 to (0.4 to 0.5) to (0.6 to 1) to (0.1 to 0.25). According to the basalt fiber shielding material provided by the invention, the conductive particles and the magnetic particles are combined, and by optimizing the material components and proportion, a very good electromagnetic wave absorption and shielding effect can be achieved, a wider frequency band shielding effect can be provided, and electromagnetic radiation in various frequency ranges can be effectively covered.

The invention discloses a polypyrrole / cobalt / nitrogen-doped carbon composite material with a coaxial hollow structure and a preparation method thereof, and belongs to the technical field of advanced functional composite materials. The method comprises the following steps: firstly, synthesizing a hollow polypyrrole nanotube by a soft template method; secondly, cobalt / nitrogen-doped carbon is synthesized by adopting a template guiding method; and finally, secondarily coating the outer surface of the cobalt / nitrogen-doped carbon with a polypyrrole layer by adopting an in-situ oxidative polymerization method to construct the polypyrrole / cobalt / nitrogen-doped carbon composite material with a coaxial hollow heterostructure, and the polypyrrole / cobalt / nitrogen-doped carbon composite material has a coaxial sandwich structure: the inner core is a nitrogen-doped carbon hollow tube, the middle layer is a nitrogen-doped porous carbon matrix embedded with cobalt nanoparticles, and the outer surface of the cobalt / nitrogen-doped carbon composite material is a porous carbon matrix embedded with cobalt nanoparticles. And the outer layer is a conductive polypyrrole coating layer. The preparation method provided by the invention can successfully realize in-situ confinement growth and stable combination of ZIF-67, and has the advantages of high repetition rate, high yield and simple method; by adjusting the proportion of polypyrrole in the composite material, good impedance matching and large dielectric loss can be realized, and excellent electromagnetic wave absorption performance can be obtained.

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 belongs to the technical field of electromagnetic wave absorption, and particularly discloses a three-dimensional structure wave-absorbing metamaterial which comprises a first three-dimensional structure layer, a second three-dimensional structure layer and a metal backboard which are sequentially arranged from top to bottom, the first three-dimensional structure layer comprises a first top layer and a first three-dimensional absorption enhancing framework arranged on the lower surface of the first top layer, and the second three-dimensional structure layer comprises a second top layer and a second three-dimensional absorption enhancing framework arranged on the lower surface of the second top layer. A first high-impedance metasurface and a second high-impedance metasurface are loaded on the lower surface of the first three-dimensional absorption enhancement skeleton at intervals; the second three-dimensional structure layer comprises a second top layer and a second three-dimensional absorption enhancement skeleton arranged on the lower surface of the second top layer, and a third high-impedance metasurface is loaded on the top surface of the second top layer. By adopting the three-dimensional structure wave-absorbing metamaterial, ultra-wideband absorption and large-angle stability can be achieved under the condition that the thickness is small, light and thin wideband application of a wave-absorbing body is facilitated, and the three-dimensional structure wave-absorbing metamaterial has great practical value in the field of electromagnetic compatibility.

The invention discloses a layered cobalt aluminum oxide / copper sulfide wave-absorbing material and a preparation method thereof, and belongs to the technical field of novel wave-absorbing materials, the wave-absorbing material is prepared through a two-step hydrothermal method, lamellar cobalt aluminum hydroxide is prepared through the hydrothermal method, then the lamellar cobalt aluminum oxide subjected to heat treatment is used as a substrate, and the lamellar cobalt aluminum oxide / copper sulfide wave-absorbing material is prepared through the two-step hydrothermal method. The preparation method comprises the following steps: growing nano flaky copper sulfide on the cobalt-aluminum oxide / copper sulfide composite material by adopting a hydrothermal method to form a layered cobalt-aluminum oxide / copper sulfide heterostructure, and adjusting the wave-absorbing property of the composite material by adjusting the content of the copper sulfide in the composite material. According to the layered cobalt aluminum oxide / copper sulfide wave-absorbing material and the preparation method thereof, the layered cobalt aluminum oxide / copper sulfide wave-absorbing material has the advantages that the density is relatively low, the effective absorption frequency band is relatively wide, the electromagnetic wave absorption performance is relatively high, the preparation method is simple, the morphology of the composite material can be regulated and controlled, and the like.

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 relates to a lightweight porous nickel ferrite composite electromagnetic absorbing material and a preparation method thereof, and belongs to the field of electromagnetic wave absorbing materials, and the lightweight porous nickel ferrite composite electromagnetic absorbing material is a porous electromagnetic absorbing material prepared by high-temperature annealing of a mixture containing ferric salt, nickel salt, an acetic acid solution and chitosan. The lightweight and porous nickel ferrite composite electromagnetic absorbing material has both lightweight and electromagnetic absorbing properties.

The invention relates to the technical field of solid waste recycling and functional building materials, in particular to a wave-absorbing wall material based on a waste glass fiber wind power blade and a preparation method of the wave-absorbing wall material. The wave-absorbing wall material based on the waste glass fiber wind power blade is mainly prepared from the following raw materials in parts by mass: 60-68 parts of waste glass fiber wind power blade granules, 30-35 parts of silicon-aluminum solid wastes, 2-5 parts of a wave-absorbing reinforcing agent and 6-10 parts of water. According to the invention, waste wind power blades and silicon-aluminum solid wastes are used as raw materials, a high-strength porous carbon skeleton structure is formed in the material through a vacuum pugging molding and vacuum sintering process, and meanwhile, a ferrite wave-absorbing reinforcing agent is mixed to form a composite wave-absorbing electromagnetic structure of a carbon aggregate-dielectric loss material and a ferrite particle-magnetic loss material; collaborative optimization of the electromagnetic wave absorption performance and the material mechanical property is achieved, and good ecological value and economic benefits are achieved.

The invention provides a multi-element graded composite hollow microsphere wave-absorbing agent as well as a preparation method and application thereof. The multi-element graded composite hollow microsphere is composed of a hollow core and a composite spherical shell, wherein the hollow inner core is an air cavity, and the composite spherical shell is composed of porous amorphous carbon serving as a continuous phase and carbon nanohorn and magnetic metal composite particles serving as a dispersed phase. According to the scheme, the hollow core of the multi-element graded composite hollow microsphere is the air cavity, the density is low, and electromagnetic waves can be induced to enter the hollow cavity for multi-reflection; the composite spherical shell is composed of porous amorphous carbon serving as a continuous phase and carbon nanohorn-magnetic metal composite particles serving as a dispersed phase, tiny pores in the amorphous carbon can provide more interface polarization, and meanwhile, the amorphous carbon and the carbon nanohorn-magnetic metal composite particles can form a multi-element heterogeneous interface on the surface of the composite spherical shell; through a multi-interface effect and a multi-loss mechanism among the carbon nanohorn, the magnetic metal and the amorphous carbon, the electromagnetic wave loss is effectively enhanced and increased, and the electromagnetic wave absorption capability is enhanced.

The invention discloses a carbon-based metamaterial electromagnetic wave absorber and a preparation method and application thereof. The wave absorbing body adopts a three-layer composite structure, wherein the bottom layer is a copper plate reflecting layer; the lower layer is of a honeycomb-like structure and is formed by periodically arranging regular octagons and square hollow quadrangular prisms externally connected with the regular octagons, and the adjustable wave absorbing frequency band is achieved by adjusting and controlling the width and height of the hollow cores; the upper layer is of a pointed cone structure, and the impedance matching characteristic is enhanced by optimizing the vertex angle of the regular rectangular pyramid. The wave absorber is made of photosensitive resin, based on the photocuring 3D printing technology, honeycomb-like and pointed cone structures are printed step by step and bonded and combined, and high-precision forming is achieved in combination with parameterized regulation and control. The wave absorber has the advantages of light weight, broadband absorption and adjustable mechanical performance, can be applied to the fields of EMI shielding of electronic equipment, military radar stealth, high-frequency communication protection, electromagnetic environment protection and the like, and remarkably improves the electromagnetic wave absorption and shielding effectiveness through the metamaterial structure design and a multi-component cooperative loss mechanism.

The invention provides a wave-absorbing material, and belongs to the technical field of electromagnetic wave absorption. The wave-absorbing material comprises a metal reflection bottom layer, a wave-absorbing middle layer and a scattering upper layer, the wave-absorbing middle layer is made of a ferroferric oxide loaded reduced graphene oxide and epoxy resin (Fe3O4 (at) RGO / EP) composite material and used for absorbing electromagnetic wave energy, and the scattering upper layer is of a patterned metasurface structure made of chopped carbon fiber reinforced epoxy resin (SCF / EP). And a phase-regulated two-dimensional periodic array is formed. By arranging a three-layer structure of the metal reflecting layer, the Fe3O4 (at) RGO / epoxy composite wave-absorbing layer and the chopped carbon fiber scattering layer, broadband absorption and directional scattering control of electromagnetic waves within the range of 2-18 GHz are achieved, a stealth function composite material system with dissipation and deflection dual-mechanism cooperative work is formed, the structure utilizes the patterning design of the scattering layer, and the structure has the advantages that the structure is simple, the structure is compact, and the application range is wide. On the basis of the generalized Snell's law, engineering regulation and control of the radar wave reflection direction are achieved by regulating and controlling the reflection phase difference between pattern units, reflection energy is effectively deviated from the main lobe direction of a radar receiver, and therefore the reflection signal intensity of a target in a radar detection system is reduced.

The invention relates to a high-temperature electromagnetic functional composite coating and a preparation method thereof, belongs to the technical field of high-temperature electromagnetic functional materials, and solves the problems of narrow absorption frequency band, low absorption loss, poor temperature resistance, poor corrosion resistance, poor environmental medium resistance and poor mechanical property of the existing high-temperature electromagnetic functional coating. From the surface of the substrate from inside to outside, the high-temperature electromagnetic functional composite coating comprises a bonding layer, a protective layer, a functional layer and a surface layer, and the functional layer is made of a thermal spraying composite ceramic material; the multi-layer structure of each layer of the composite coating is mutually coordinated and matched, so that the temperature resistance, the corrosion resistance and the environmental medium resistance of the coating are improved, the electromagnetic wave absorption efficiency is improved, and the service life is prolonged; in addition, the composite ceramic material forming the functional layer has multiple loss mechanisms, the electromagnetic wave absorption frequency band is further widened, and the absorption loss is improved.

The invention discloses a preparation method of an electromagnetic shielding high-strength supersulfate cement-based material, which comprises the following steps: (1) uniformly mixing a powder material with an electromagnetic wave absorption function with saturated lime water, then adding basalt fibers, reacting under a heat preservation condition, then separating out the basalt fibers, and drying to obtain modified fibers; and (2) carbonizing the coal gangue particles, mixing the carbonized coal gangue particles with a saturated aqueous solution of a magnesium source, and mixing the coal gangue particles with alkali liquor after sufficient absorption. After standing, placing the coal gangue particles in saturated lime water for reaction, and then calcining the coal gangue particles to obtain the modified coal gangue fine aggregate. And (2) taking granulated blast furnace slag powder, coarse aggregate, the modified coal gangue fine aggregate, the modified fiber, paraffin particles and the like as raw materials, and uniformly stirring with water to obtain the super sulfate cement-based material. The process not only solves the problem that the mechanical property of the material is reduced due to the addition of the electromagnetic shielding component, but also reduces the possibility that the cement-based material is detected by infrared.

The invention provides an electromagnetic wave absorption structure and electronic equipment, which can be applied to the technical field of communication. The electromagnetic wave absorption structure comprises a first dielectric layer; the first modulation structure is arranged on the first surface of the first dielectric layer and can construct an oscillation circuit so as to absorb electromagnetic waves of a target frequency band; wherein the dielectric constant of the first dielectric layer can be regulated and controlled so as to change the frequency band of the absorbed electromagnetic wave.

The invention belongs to the technical field of nano materials, and relates to a carbon thermal reduction driven high-entropy oxide metastable-state material and a preparation method and application thereof.The preparation method comprises the steps that S1, carbon and soluble metal salt are dissolved in a solvent for ultrasonic treatment, and a metal salt solution and a carbon suspension are obtained; s2, adding a metal salt solution into the carbon suspension, adding strong base, and stirring to obtain a coprecipitation polymer; s3, re-dispersing the coprecipitation polymer in the solvent, adding extra ferric salt and urea, mixing and stirring, and freeze-drying the mixed solution to obtain precursor powder; s4, performing staged annealing treatment on the precursor powder under low oxygen partial pressure to obtain a carbon-loaded high-entropy oxide metastable-state material; the prepared high-entropy oxide metastable-state material is of an alloy phase and high-entropy oxide double-phase coupling structure, the polarization loss of electromagnetic waves is enhanced through a heterogeneous interface, and the high-entropy oxide metastable-state material has the advantages of being excellent in impedance matching and wide in electromagnetic wave absorbing bandwidth and can be widely applied to the fields of industrial electronics, medical communication and military stealth.

The invention discloses an amorphous wire stress-electromagnetic coupling effect modeling method based on a micro-magnetism theory, and belongs to the technical field of magnetic materials and electromagnetic property regulation and control. According to the method, an amorphous wire micro-magnetic three-dimensional simulation model is constructed, solving is conducted through a finite element method, cross-scale simulation of magnetic domain structure evolution of the amorphous wire under the action of external stress is achieved, the change of effective magnetic conductivity of the amorphous wire under the action of different stress fields is further calculated, the skin effect and the magneto-impedance theory are fused, and the magnetic conductivity of the amorphous wire is calculated. And establishing an amorphous wire electromagnetic impedance spectrum model. According to the method, a quantitative mapping relation among the effective magnetic conductivity, the electromagnetic impedance characteristic and the external stress is established, a magnetic domain structure under the action of different stress fields can be deduced, and key parameters such as the effective magnetic conductivity and the electromagnetic impedance spectrum are output; theoretical guidance is provided for wide application of the amorphous wire in the fields of high-sensitivity stress sensing device design, broadband adjustable electromagnetic wave absorption / shielding, self-sensing composite material structure health monitoring and the like.

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.

An electromagnetic wave- and magnetic field-absorbing-and-shielding sheet according to an exemplary embodiment of the present invention is implemented by comprising: an electromagnetic wave- and magnetic field-absorbing-and-shielding unit having a plurality of magnetic layers stacked to shield electromagnetic waves and magnetic fields; and an electromagnetic wave-absorbing adhesive member, which is arranged between the adjacent magnetic layers to absorb electromagnetic waves that have transmitted the magnetic layers or are reflected from the magnetic layers, and fixes the adjacent magnetic layers. Accordingly, together with an electromagnetic wave- and magnetic field-shielding function, the present invention has a function of enabling most of the electromagnetic waves reflected during shielding to be absorbed to minimize influence on surrounding electronic components, electronic devices, or a user of the electronic devices, caused by electromagnetic waves reflected during shielding and the magnetic field shielding, and thus can be widely applied to various electronic devices and the like.

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 relates to the technical field of wave absorbing materials, and to a preparation method of a flaky carbonyl iron / molybdenum disulfide composite wave absorbing material and corresponding materials, comprising: adding sodium dodecylbenzene sulfonate, sodium molybdate, and thiourea to an ethanol solution according to a ratio and stirring to obtain a precursor solution; placing the precursor solution in a reactor for hydrothermal reaction to obtain a hydrothermal reaction solution, centrifugally washing the hydrothermal reaction solution to obtain a hydrothermal reaction product, vacuum drying the obtained hydrothermal reaction product to obtain a molybdenum disulfide nanomaterial; mixing the molybdenum disulfide nanomaterial with flaky carbonyl iron according to a ratio and grinding to obtain a mixed powder, bonding the mixed powder to obtain a flaky carbonyl iron / molybdenum disulfide composite wave absorbing material. The preparation method of the flaky carbonyl iron / molybdenum disulfide composite wave absorbing material and the corresponding materials of the invention can prepare a wave absorbing material with excellent electromagnetic wave absorption performance and can meet the absorption requirements of different frequency bands.

A unit cell of a metamaterial absorber may be an electromagnetic wave absorber for a 5.8 GHz band or 10 GHz band. The unit cell of the metamaterial absorber may include a first metal layer including at least one concentric circular ring-shaped conductor pattern, a first intermediate layer disposed on the lower surface of the first metal layer and composed of polyimide, a resistive layer disposed on the lower surface of the first intermediate layer, a second intermediate layer disposed on the lower surface of the resistive layer and composed of polyimide, and a second metal layer disposed on the lower surface of the second intermediate layer. The resistive layer may increase the operating bandwidth of an operating frequency. The thickness of the resistive layer may be 0.05 mm to 0.15 mm. The sheet resistance of the resistive layer may be 530 Ω·sq−1 to 550 Ω·sq−1.

The invention belongs to the technical field of electromagnetic wave functional materials, and particularly relates to a nested split ring wave-absorbing metamaterial and a preparation method thereof. The wave-absorbing metamaterial sequentially comprises an FSS metal structure layer, a dielectric layer and a metal matrix layer from top to bottom in the thickness direction, the FSS metal structure layer is formed by distributing structure units in a periodic array mode, each structure unit is composed of a double-opening outer ring shaped like a Chinese character'hui 'and a double-opening inner ring, the double-opening outer ring is a split square, and the double-opening inner ring is a hollow square. The structural units are symmetrically arranged about the diagonal line of the dielectric layer. The FSS metal structure layer designed by the invention has anisotropy, so that the polarization direction of an incident wave can be rotated by 90 degrees in a reflection mode. By means of the design, the two functions of electromagnetic wave absorption and polarization conversion are achieved at the same time, and meanwhile the effect of multiband wave absorption is achieved. Within the frequency band of 4 GHz to 18 GHz, the maximum wave-absorbing strength of the nested wave-absorbing metamaterial is as high as-30 dB, and the effective wave-absorbing bandwidth can reach 7.5 GHz.

The invention discloses an electromagnetic shielding fabric and a preparation method thereof, and relates to the technical field of fabrics. The bismuth ion-doped polyimide is used as an external phase spinning solution, contains a large number of benzene ring structures, has a certain shielding effect on electromagnetism, does not generate radiation crosslinking and chemical degradation reactions after being subjected to high-energy radiation, and has a good electromagnetic shielding effect; then, carboxylated graphene oxide, barium ions and iron ions generate electrostatic adsorption, so that ferrite is loaded on a graphene sheet layer, a synergistic shielding effect is generated, the electromagnetic shielding effect of the fabric is improved, the graphene sheet layer serves as an inner phase, polyimide serves as an outer phase, gel fibers of a core-shell structure are prepared through spinning, a double-layer electromagnetic wave absorption path is constructed, and the electromagnetic shielding effect of the fabric is improved. Then under the reduction action of sodium borohydride, a layer of uniform metal bismuth is formed on the surface of the fiber, the electromagnetic shielding performance of the fabric is improved, then through drying, the gel on the inner layer forms a porous aerogel structure, the pores of the aerogel structure are communicated with the pores of the fiber, and the air permeability of the fabric is improved.

The invention provides a method for recycling a carbon fiber material from a waste wind power blade main beam carbon plate, hydrophilic carbon fibers and a wave-absorbing material, and belongs to the technical field of waste recycling and reusing and electromagnetic wave absorbing materials. The wave-absorbing material is prepared by the following steps: recycling a carbon fiber material in a waste wind power blade main beam carbon plate by pyrolyzing the waste wind power blade main beam carbon plate, crushing the carbon fiber material into powder by a ball mill, doping recycled carbon fibers and recycled carbon fiber powder according to a certain proportion, preparing the recycled carbon fibers and the recycled carbon fiber powder into a composite wave-absorbing material sample by using epoxy resin as a matrix through a template method, and preparing the composite wave-absorbing material sample into a sample. Finally, a composite wave-absorbing material product with excellent wave-absorbing performance is obtained. The recycled carbon fiber material can be subjected to surface modification in a pyrolysis oxidation mode, clean hydrophilic carbon fibers are obtained, the treated carbon fiber surface has more oxygen-containing groups, the interfacial compatibility and bonding strength of the carbon fiber and a matrix can be improved, and the carbon fiber material can be suitable for compounding of other various materials.

The invention provides a copper-doped silicon carbide composite material and a preparation method and application thereof, and relates to the technical field of electromagnetic wave absorbing materials. The preparation method of the copper-doped silicon carbide composite material provided by the invention comprises the following steps: performing arc plasma cracking on a precursor containing silicon and carbon to obtain the copper-doped silicon carbide composite material, the precursor containing silicon and carbon comprises organic chlorosilane; an anode adopted by the arc plasma cracking comprises copper. The prepared copper-doped silicon carbide composite material has excellent electromagnetic wave absorption performance and large effective absorption bandwidth.

The invention relates to the technical field of electromagnetic wave absorption, in particular to a composite wave-absorbing heterostructure plate for high-power electronic shelter equipment and a preparation method of the composite wave-absorbing heterostructure plate. The composite wave-absorbing heterostructure plate is of a gradient composite structure, the outer layer is a carbon fiber composite material plate, the middle layer is a composite honeycomb plate filled with carbon nano composite slurry and aerogel, the inner layer is a dielectric material composite plate with a carbon nano composite slurry composite layer on one side, and the carbon fiber composite material plate and the honeycomb plate are connected through a bonding layer. And the cellular board and the dielectric material composite board are connected through a bonding layer. Through the heterostructure design of the carbon nano composite wave-absorbing slurry and the silicon dioxide aerogel, the effective wave-absorbing bandwidth covering 16 GHz with the reflection loss larger than 40 dB and smaller than-15 dB in the ultra-wideband of 2-18 GHz is achieved, the wave-absorbing material is remarkably superior to a traditional wave-absorbing material, and the electromagnetic compatibility requirement of high-power electronic equipment is met.

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 discloses a preparation method of a beaded cobalt-doped Bi25FeO40 / BiFeO3 nanofiber wave-absorbing material, which comprises the following steps: obtaining a precursor by a standing method, and adding the precursor, bismuth nitrate, ferric nitrate and a spinning aid into a mixed solvent compounded by N, N-dimethylformamide and absolute ethyl alcohol to obtain a spinning solution; spinning the spinning solution by adopting an electrostatic spinning technology to obtain a nanofiber membrane; and finally, drying and calcining to obtain the wave-absorbing material. According to the wave-absorbing material, multiple reflection and scattering of electromagnetic waves are increased, the absorption performance of the electromagnetic waves is improved, due to the fact that a heterogeneous interface is generated after two phases are compounded, the interface polarization loss is further increased, when the thickness of the wave-absorbing material is 2.33 mm, the minimum reflection loss reaches-56.01 dB, the effective absorption frequency band width is 6.32 GHz, and the whole Ku wave band is covered.

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 utility model relates to a feed antenna and electronic equipment, the feed antenna comprises a main branch, a parasitic branch and a floor, the main branch is provided with a feed branch, the feed branch is connected with the floor, the parasitic branch is provided with a grounding branch, the grounding branch is connected with the floor, and the main branch and the parasitic branch are at least partially overlapped. According to the feed antenna, the electromagnetic wave absorption ratio of the front end facing the user to the rear end back to the user is low, and the degree of harm to the user is smaller.