229results about How to "Excellent electromagnetic wave absorption performance" patented technology

The invention relates to a method for preparing multi-layer graphene, and belongs to the technical field of carbon materials. The multi-layer graphene is prepared from expanded graphite serving as a raw material through ultrasonic dispersion, solid-liquid separation and drying. The thickness of the multi-layer graphene prepared by the method is between 1 and 10nm; the number of layers is between 2 and 20 layers; and the aperture is mainly between 6 and 50nm. The multi-layer graphene has the characteristics of high electrical conductivity, high heat conductivity, high electromagnetic wave absorptivity, wear resistance and the like. The method has the advantages of simpleness, convenient operation and low production cost, capability of reducing production energy consumption, no three wastes emission, environmental friendliness and convenient popularization and application. The multi-layer graphene prepared by the method can be used as the electrode materials of batteries and super capacitors, can also be used as the conductive agents of high molecular materials, ceramic materials, silicate materials and the like, and can also be used as the conductive agents of lithium batteries, alkaline batteries and nickel-metal hydride batteries.

The invention relates to the field of aerogel and electromagnetic absorbing materials, in particular to a preparation method of MXene/cellulose composite aerogel. The preparation method includes the steps that firstly, MAX phase ceramic powder is added into a mixed water solution of lithium fluoride, hydrochloric acid and hydrofluoric acid in a certain proportion for etching to obtain MXene nano-powder; a cellulose sol method is adopted, cellulose powder is added into a mixed water solution of sodium hydroxide and urea in a certain proportion, and a transparent cellulose mixed solution is prepared by cooling the mixture to -12 DEG C; the temperature is maintained, the MXene nano-powder is added into the cellulose mixed solution, and then the appropriate amount of epichlorohydrin is added to the mixture and the mixture is stirred thoroughly for chemical crosslinking; the temperature is raised, and the obtained homogeneous mixture is subjected to a gel reaction; and a gel product is frozen directionally and then freeze-dried to obtain the MXene/cellulose composite aerogel. The composite aerogel has the characteristics of low density, high porosity, good absorbing performance, wide absorbing frequency band and the like, and is convenient to use and suitable for large-scale application in the aerospace field.

The invention relates to a preparation method of a carbon-cladding Fe3O4 microsphere wave-absorbing material, and relates to a preparation method of a wave-absorbing material. The preparation method aims to solve the problem of poor electromagnet wave absorption because impedance match is difficult to realize due to lower dielectric constant of Fe3O4 at present. The method comprises the following steps of: 1, preparing a Fe3O4 microsphere; 2, preparing a phenolic resin-cladding Fe3O4 microsphere; 3, preparing a carbon-cladding Fe3O4 microsphere. The carbon and Fe3O4 core-shell structure wave-absorbing material prepared through the method disclosed by the invention achieves the real part of a dielectric constant more than 18 and the imaginary part of the dielectric constant mainly about 0 at low frequency, thereby being favorable to realizing the impedance match and enhancing the wave-absorbing property; the carbon and Fe3O4 core-shell structure composite material prepared through the method disclosed by the invention can be used for the field of electromagnet wave absorption.

An electromagnetic wave absorber is formed by injection-molding a thermoplastic resin blended with approximately 20-60% by volume of soft magnetic material powder, and blended with a molding assistant and a kneading assistant. The electromagnetic wave absorber includes a unit cell having a bore extending from a top face to a bottom face. A portion of the bore located more adjacently to the bottom face than to the top face has a smaller cross-sectional area than the bore at the top face, and a height of the unit cell from the bottom face to the top face is approximately at least 1.2 times and approximately at most 10 times as large as the maximum width of the bore at the top face of the unit cell.

The invention provides a wave-absorbing material and a preparation method thereof. The wave-absorbing material is prepared from the following raw materials in parts by mass: 5-15 parts of thermosetting elastomer, 60-80 parts of flaky wave-absorbing agent, 0.1-2 parts of curing agent, 0.1-0.5 part of accelerator and 20-30 parts of solvent. The preparation method comprises the following steps: (1) dissolving a matrix; (2) mixing the matrix with the wave-absorbing agent; (3) scraping the base material; and (4) flattening the surface by a double-roller calender, and passing through a tunnel furnace to perform high-temperature curing, thereby obtaining the product. The method prevents the calendering from crushing the flaky wave-absorbing agent, and maintains the completeness of the flaky wave-absorbing agent particles. The magnetic poles are added to well orient the flaky wave-absorbing agent, thereby avoiding unordered arrangement of the particles in the high-polymer matrix due to calendering. The wave-absorbing material has the advantages of very high magnetic permeability and favorable electromagnetic wave absorption property, and can be prepared into a material of which the minimum thickness is 0.03mm.

The invention discloses an anti-electromagnetic radiation building and belongs to the building field. The outer surface of the side wall of the anti-electromagnetic radiation building is provided with an electromagnetic wave absorbing layer; the electromagnetic wave absorbing layer includes an electric conduction layer and an absorbing wave mortar layer which are distributed from inside to outside, wherein the electric conduction layer is connected with ground through metal. With the anti-electromagnetic radiation building of the invention adopted, electromagnetic waves can be effectively prevented from radiating to an indoor environment.

The invention discloses a double-shell-structure carbonyl iron powder composite wave-absorbing material and a preparation method thereof, wherein the composite wave-absorbing material is of a double shell layer core-shell structure, the core is carbonyl iron powder, the inner layer of the double-shell layer is an insulating layer, and the outer layer of the double-shell layer is a magnetic layer;the thickness of the insulating layer is 1 nm-1 [mu] m; and the thickness of the magnetic layer is 1nm-5 [mu] m; the preparation method comprises the following steps: coating the surface of the carbonyl iron powder with the insulating layer and coating the surface of a core-shell structure precursor by a chemical coprecipitation method. The surface of the carbonyl iron powder is coated with the double-shell layer by the chemical coprecipitation method. The impedance matching characteristic of the material is greatly improved, meanwhile, a large amount of nano-interface heterojunction is formedat the interfaces of the inner core and the double-shell layer, so that interface polarization is effectively induced, the scattering effect is formed for electron migration, and electromagnetic waveloss mechanisms such as multi-reflection absorption, strong ] ferromagnetic resonance and eddy current loss and the like of the material are greatly improved, so that the wave absorbing performance of the material is remarkably improved; the composite wave-absorbing material is simple in preparation method, is uniform and compact in coating and controllable in coating layer thickness and particlesize.

The invention relates to the technical field of optical protection films, and especially relates to an electromagnetic-radiation-resistant protection film and a preparation method thereof. The preparation method comprises the following steps: step 1, preparing light-cure paint with electromagnetic radiation resistant function; step 2, coating a PET base material with the light-cured paint by using a slight-concave roller, and controlling the coating thickness of the light-cured paint to be 3-10 mu m, the diameter of the slight-concave roller to be 30-50 mm and the line screen of the slight-concave roller to be 40-400; step 3, curing the paint to obtain a film; and step 4, preparing the electromagnetic-radiation-resistant protection film. The electromagnetic-radiation-resistant protection film is good in electromagnetic-radiation-resistant effect, the technology is simple and manure and beneficial for popularization and application. When the electromagnetic-radiation-resistant protection film is used, the electromagnetic-radiation-resistant protection film can be attached to a handset or a display screen by tearing a PET protection film. Compared with electromagnetic-radiation-resistant equipment at home and abroad, such as radiation-proof clothes, electromagnetic-wave protection helmets and the like, the electromagnetic-radiation-resistant protection film is simple and convenient to use and easy to popularize.

The invention provides a natural rubber composite with an electromagnetic shielding property. The composite comprises natural rubber, a short carbon fiber and a compounding agent, wherein the diameter of the short carbon fiber is 3-10 mu m, the length of the short carbon fiber is 1-5 mm, and the weight ratio of the natural rubber to the short carbon fiber at room temperature is 100:(0.5-11). Because the physical and mechanical properties of the natural rubber and the short carbon fiber are fully used for preparing the composite with the electromagnetic shielding property, the composite has the good electromagnetic wave absorption property of the short carbon fiber and the good physical and mechanical properties of the rubber material, and can be adaptive to the requirement on various environments. The composite has the advantages that the electromagnetic shielding property is high, the preparation method is simple, the preparation cost is low, and the energy consumption is reduced.

The invention relates to an iron-carbon nano composite electromagnetic wave absorption material and a preparation method thereof. Carbonyl iron, methane and acetylene serving as main raw materials are directly synthesized into the iron-carbon nano composite material in a gas-phase reaction device at the temperature of between 300 and 1,000 DEG C. The nano composite material has good stability and uniformity. The iron-carbon nano composite material is wrapped outside iron nano granules by nano-scale C to form a C film; and the iron-carbon nano composite material has the characteristics of good electromagnetic wave absorption performance, wide absorption coverage frequency range, strong corrosion and oxidation resistance and low cost, and is applicable to electromagnetic shielding in a radio communication system, electromagnetic radiation and leakage of equipment of high frequency prevention, microwave heating and the like, construction of microwave darkrooms and hiding technology.

The invention relates to a three-dimensional porous sheet ferroferric oxide/carbon nanometer electromagnetic wave absorption material and a preparing method thereof. Carbon in the electromagnetic waveabsorption material forms a three-dimensional framework of a flower-shaped structure, and ferroferric oxide particles wrapped by carbon are evenly distributed on a carbon base body. The preparing method includes the steps of firstly, making trivalent inorganic ferrite and urea as precursors for synthesizing ferroferric oxide dissolved together with a surface active agent in a solvent according toa certain mass ratio to have a reaction under closed conditions, washing and drying a product after the reaction is completed to prepare hydroxyl ferric oxide, and calcinating the prepared hydroxyl ferric oxide to obtain ferric oxide powder; secondly, mixing the ferric oxide powder in the first step with a carbon source to have a reaction under closed conditions to obtain the three-dimensional porous sheet ferroferric oxide/carbon nanometer electromagnetic wave absorption material. The electromagnetic wave absorption material is high in saturated magnetic susceptibility, large in coercivity,light in weight, strong in oxidization resistance and excellent in electromagnetic wave absorption performance.

The invention relates to a magnetic porous cobalt hollow ball electromagnetic wave absorption material, a preparation method and application of the material. The magnetic porous cobalt hollow ball electromagnetic wave absorption material is composed of monodispersed porous hollow balls, wherein the external diameter of each porous hollow ball is 2-6 microns, and the thickness of each ball shell is 100-200nm. The hollow balls are formed by cobalt particles, wherein the diameter of each cobalt particle is 60-200nm, and 10-100nm air voids exist among the cobalt particles. The preparation method includes the steps of using precursors like cobaltous acetate and precipitants like urea, and polyving akohol or polymethyl methacrylate or polyvinylpyrrolidone as surfactants, enabling the surfactants to be dissolved in ethyl alcohol solvents or methanol solvents to obtain cobaltous hydroxides through reaction, and enabling the cobaltous hydroxides and potassium borohydride to be reacted in water or ethanol solutions to obtain the monodispersed porous cobalt hollow balls. The prepared porous cobalt hollow ball material is good in evenness and dispersity, small in density, strong in magnetism and good in electromagnetic wave absorption performance and can be used as the electromagnetic wave absorption material.

An electromagnetic wave absorber comprising (a) soft ferrite having its surface treated with a silane compound having no functional group, (c) magnetite and (d) silicone, or comprising (a) soft ferrite having its surface treated with a silane compound having no functional group, (b) flat soft magnetic metal powder, (c) magnetite and (d) silicone, which electromagnetic wave absorber excels in electromagnetic wave absorption, heat conduction and flame resistance, exhibiting less temperature dependence, and which electromagnetic wave absorber is soft, excelling in adhesion strength and further excelling in high resistance high insulation properties and in energy conversion efficiency being stable in MHz to 10GHz broadband frequency. There is further provided a laminated electromagnetic wave absorber comprising the above electromagnetic wave absorber overlaid with a reflection layer of conductor, which laminated electromagnetic wave absorber can be closely stuck onto an unwanted electromagnetic wave emission source such as a high-speed operating device, having such an adhesive strength that even when stuck to a horizontal glassy-surface ceiling face of resin-made cage, would not fall.

The invention discloses a method for preparing natural-cellulose based magnetic porous carbon. The method comprises the steps: firstly, soaking natural cellulose into a strongly-alkaline solution, carrying out activation for 0.5 to 24 hours, then, carrying out water washing until the activated cellulose is neutral, carrying out filtering, carrying out drying, then, putting the activated cellulose into a metal salt solution with a catalytic action, carrying out stirring for 0.5 to 24 hours, carrying out filtering, and carrying out drying, so as to obtain a cellulose/metal salt mixture precursor; and calcining the obtained cellulose/metal salt mixture precursor for 0.5 to 12 hours at the temperature of 400 DEG C to 1,000 DEG C in a reducing atmosphere, naturally cooling the calcination product to room temperature, thereby obtaining the natural-cellulose based magnetic porous carbon. According to the method, the raw materials are cheap and readily available, the equipment and procedures are simple and are easy in operation, and the method is pollution-free, is low in cost and facilitates industrialized and large-scale production; and the prepared composite material has properties of both magnetic nano-metal materials and porous carbon materials, so that the requirements of wave absorbing materials on electromagnetic wave dissipation capability and impedance matching are excellently met, and the electromagnetic wave absorption property is excellent.

The invention provides a preparation method of an Ni-Co alloy embedded N-doped graphite carbon capsule composite wave-absorbing material, and belongs to the field of synthesis of composite materials. The method is characterized in that Ni(OH)2 particles are designed and synthesized, an Ni(OH)2 methanol solution is prepared, and Ni(OH)2/ZIF-67 is synthesized by adding a certain quantity of the Ni(OH)2 solution during the synthesis of ZIF-67; the Ni(OH)2/ZIF-67 is taken as a template, trishydroxymethylaminomethane is taken as a buffer agent, in situ polymerization of dopamine hydrochloride is carried out on the surface to form Ni(OH)2/ZIF-67@PDA, the ZIF template is subjected to self-etching during dopamine coating, and a hollow dodecahedral capsule is formed; high-temperature calcination and aftertreatment are carried out to prepare the Ni-Co alloy embedded N-doped graphite carbon capsule composite wave-absorbing material (Air@NCs euro Ni-Co). The synthetic method provided by the invention has universality, and N-doped graphite carbon capsule composite wave-absorbing materials embedded with different alloys (Fe-Co, Co-Cu, Co-Zn, FeCoNi, FeCoZn ternary alloy, and the like) can be synthesized. The Ni-Co alloy embedded N-doped graphite carbon capsule composite wave-absorbing material prepared by a three-step method has good wave-absorbing properties.

An electromagnetic wave-absorbing composition is obtained by dispersing in a base polymer a magnetic powder coated with electrically insulating inorganic fines and optionally, a heat conductive powder. The composition has a high breakdown voltage, and can be applied to any adequate site within electronic equipment without a need to pay substantial attention to short-circuits.

The invention provides a double-layer allotype surface cement-based absorption material and a preparation method thereof, which relate to the cross technology field of electromagnetism and material science. Cement is adopted as a matrix, polystyrene foam and pulverized fuel ash are adopted as admixtures, an appropriate microwave absorption agent is compounded, and the obtained double-layer allotype surface cement-based absorption material is low in cost, energy saving and environmentally-friendly; a traditional panel material is subjected to surface shape designs such as a double-layer shape, a triangular shape, a sinusoidal shape, a semicircular shape and a right-angle groove shape, so that a series of double-layer allotype surface cement-based absorption material with a favorable electromagnetic absorption performance is prepared, the density and the thickness are small, the effective absorption bandwidth smaller than -10dB within the range of 1.7 to 18GHz is 13GHz or more, and the minimum reflectance is less than -30dB.

The invention relates to a road asphalt material technology and discloses an electromagnetic wave absorption fiber asphalt mixture for an asphalt pavement and a preparation method of the electromagnetic wave absorption fiber asphalt mixture. The electromagnetic wave absorption fiber asphalt mixture comprises the following components in percentage by weight: 0.1-0.8 percent of a fiber absorbent, 4-6 percent of asphalt, 4.9-7.2 percent of mineral powder and 86-91 percent of gravels. The preparation method of the electromagnetic wave absorption fiber asphalt mixture for the asphalt pavement comprises the following steps of weighing electromagnetic wave absorption fibers, the asphalt, the mineral powder and the gravels according to a ratio for later use; under the stirring temperature of 130-190 DEG C, doping the electromagnetic wave absorption fibers into the mineral powder and the gravels and dry-stirring; and adding the asphalt and stirring to obtain the electromagnetic wave absorption fiber asphalt mixture.

Provided is an electromagnetic wave absorbent material comprising a magnetic film as the main constituent thereof. The magnetic film comprises a titania nanosheet where a 3d magnetic metal element is substituted at the titanium lattice position. The electromagnetic wave absorbent material stably and continuously exhibits electromagnetic wave absorption performance in a range of from 1 to 15 GHz band and is useful as mobile telephones, wireless LANs and other mobile electronic instruments. The absorbent material can be fused with a transparent medium and is applicable to transparent electronic devices such as large-sized liquid crystal TVs, electronic papers, etc.

An electromagnetic wave absorbing material is provided by shaping a resin composition containing 5 to 10 parts by weight of a carbon black and 1 to 10 parts by weight of a gas phase growth carbon fiber in a resin based on 100 parts by weight of the resin.

The invention discloses a method for preparing glucosyl mesoporous carbon-coated ZnFeO used for electromagnetic wave absorbing coating, which belongs to the preparation process of the electromagnetic wave absorbing coating. In the method, a carbon-coated layer is formed on the surface of Zn ferrite by combining a solvothermal method and high-temperature calcination, which cannot only improve the monodispersion and stability of the ferrite and reduce the density of the ferrite, but also increase the effective absorption of electromagnetic wave, be favorable for expanding absorbing frequency range and fulfill the aims of 'thinness, lightness, wideness and rigidness'. The method is widely used for civil and military use and is more practical.

The invention relates to a multi-pore hollow iron nano spherical electromagnetic wave absorption material as well as a preparation method and the application thereof. The electromagnetic wave absorption material is a hollow sphere of which the diameter is 500-600nm. The preparation method comprises the following steps: dissolving a precursor salt such as ferric nitrate and surfactants such as polyvinylpyrrolidone into an alcohol solvent, further adding a small amount of deionized water, performing a thermal reaction on the solvent so as to obtain a precursor, performing calcining treatment, further reducing in the presence of a hydrogen atmosphere, and performing direct reduction at 400-500 DEG C, so as to obtain a multi-pore hollow iron nano sphere. The obtained multi-pore hollow iron nano sphere has the characteristics of good stability and uniformity, good electromagnetic wave absorption performance, wide absorption cover frequency range, small corrosion and low cost, and can be adopted to manufacture an electromagnetic absorber.

An electromagnetic wave absorber is provided which has an outstanding electromagnetic wave absorption property with a return loss of 20 dB or greater in a wide frequency band of 30 MHz to 20 GHz. A combined electromagnetic wave absorber includes a magnetic absorber plate, a crossed electromagnetic wave absorber disposed on the magnetic absorber plate, and a compact electromagnetic wave absorber disposed in a space defined by the dielectric loss plates of the crossed electromagnetic wave absorber on the magnetic absorber plate. When viewed in the direction perpendicular to the magnetic absorber plate, the compact electromagnetic wave absorber is configured in a multilayer structure having a plurality of electromagnetic wave absorbent layers with a low dielectric layer interposed therebetween.