124 results about "Electromagnetic wave absorber" patented technology

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.

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 present invention provides: a powder which is capable of forming an electromagnetic wave absorption layer that has electromagnetic wave absorption characteristics in a wider frequency region than ever before and is suppressed in performance variation, and which can be electrostatically adhered or heat fixed to a support body; and an electromagnetic wave absorber which comprises a melt molded body of the powder as an electromagnetic wave absorption layer. The present invention provides: a powder which is capable of forming an electromagnetic wave absorption layer that has electromagnetic wave absorption characteristics in a wider frequency region than ever before and is suppressed in performance variation, and which can be electrostatically adhered or heat fixed to a support body; and an electromagnetic wave absorber which comprises a melt molded body of the powder as an electromagnetic wave absorption layer.

An electromagnetic-wave absorber and reflector includes a base material, and a plurality of unit patterns made of conductive material disposed at even intervals on a surface of the base material. In the electromagnetic-wave absorber and reflector, a portion of each of the plurality of unit patterns overlaps with a portion of adjacent one of the plurality of unit patterns in a stacking direction of the base material, and the portion of each of the plurality of unit patterns and the portion of adjacent one of the plurality of unit patterns have a dielectric layer interposed in between.

A ferrite powder comprising, as a main component compound, a magnetoplumbite-type hexagonal ferrite having a composition represented by the formula Sr(FexAlyZrz)12O19+δ (where x, y, z, and δ satisfy 0.400≤x<1.000, 0.030≤y≤0.350, 0.001≤z≤0.040, 0.750≤x+y+z<1.000, and -5.00≤δ≤-0.200), and having a volume resistance of 1.0×109 Ω·cm or less. A ferrite resin composite material, ferrite resin composite, and electromagnetic wave absorber containing said ferrite powder.

An assembly and method of use are herein disclosed. The assembly comprises a passive guide, an antenna, and an electromagnetic absorber. The passive waveguide has a cross-section dimension, and carries an electromagnetic wave having data encoded within a carrier frequency in a range of 500 GHz to 10 THz wherein the electromagnetic wave having a wavelength. The cross-section dimension of the passive waveguide is in a range of at least 4 wavelengths to 50 wavelengths of the electromagnetic wave. The antenna receives energy from the electromagnetic wave carried by the passive waveguide. And, the electromagnetic absorber is disposed around the antenna so as to avoid interference between the electromagnetic wave and the antenna.

The invention belongs to the technical field of hydrophobic electromagnetic shielding materials, and particularly relates to an asymmetric electromagnetic shielding composite film and a preparation method and application thereof. The PNTs are polypyrrole nanotubes, after Na2MoO4. 2H2O and CH4N2S are added and subjected to a high-temperature reaction, a MoS2 flower-shaped shell structure can grow on the PNTs, the layered structure and the high specific surface area of MoS2 contribute to enhancing scattering and absorption of electromagnetic waves, and rich defect sites can induce dielectric polarization to achieve dielectric loss. Introducing the PNTs (at) MoS2 core-shell nanowire as an electromagnetic wave absorbent into a polylactic acid / dichloromethane system, then putting the system into a culture container in which a conductive filler is pre-paved, and standing and volatilizing at room temperature by adopting an ethanol solution as a volatile agent to finally obtain a three-layer asymmetric electromagnetic shielding composite film comprising the conductive filler, the PNTs (at) MoS2 structure and a polylactic acid matrix from bottom to top. And an asymmetric conductive gradient network is constructed, and the EMI shielding performance which mainly focuses on absorption is remarkably improved, so that the secondary radiation problem of electromagnetic waves is reduced.

To provide an electromagnetic wave absorber having a high electromagnetic wave absorption characteristic, and a wide absorption band width.SOLUTION: An electromagnetic wave absorber includes a structure that a first dielectric body and a second dielectric body are laminated, and in which a complex dielectric constant in a maximum absorption frequency of the first and second dielectric bodies satisfies the following formulas (1) and (2): 8≤ε1'-ε2'≤40...(1), and 5.5≤ε1"-ε2"≤25...(2) (In formula (1), ε1' is a real part of the complex dielectric constant of the first dielectric body, and ε2' is a real part of the complex dielectric constant of the second dielectric body. In formula (2), ε1" is an imaginary part of the complex dielectric constant of the first dielectric body, and ε2" is an imaginary part of the complex dielectric constant of the second dielectric body.)SELECTED DRAWING: None

To provide an electromagnetic wave shielding material which is lightweight yet has excellent electromagnetic wave absorbing performance.SOLUTION: An electromagnetic wave shielding material includes carbon nanotubes that have been surface-treated with a silane coupling agent. The bulk density of the electromagnetic wave shielding material is 1.23 kg / m3 or less.SELECTED DRAWING: Figure 2

The invention discloses a Ni3Sn2S2-coated FeCoCrNiAl composite powder electromagnetic wave absorbent, which is formed by compounding Ni3Sn2S2 and a FeCoCrNiAl high-entropy alloy, the core is FeCoCrNiAl, and the shell layer is uniformly coated Ni3Sn2S2, and the Ni3Sn2S2-coated FeCoCrNiAl composite powder electromagnetic wave absorbent is formed by compounding Ni3Sn2S2 and FeCoCrNiAl high-entropy alloy. And a core-shell or heterogeneous nano composite structure is formed. The invention also discloses a preparation method of the electromagnetic wave absorbent. The mass fraction of the Ni3Sn2S2 is 10%-40%, and the mass fraction of the FeCoCrNiAl high-entropy alloy is 60%-90%. When the Ni3Sn2S2 and the FeCoCrNiAl high-entropy alloy are compounded, the magnetic dielectric coupling effect generated between the Ni3Sn2S2 and the FeCoCrNiAl high-entropy alloy remarkably improves the overall impedance matching, the reflection loss is reduced, and meanwhile dual energy attenuation is achieved through the magnetic loss brought by the high-entropy alloy and the dielectric dissipation of the Ni3Sn2S2.

This invention relates to a method for preparing a broadband absorption hydrogel. The method comprises the following steps: S1, mixing solvent A (N,N-dimethylformamide or acetonitrile) with deionized water to obtain a mixed solvent; S2, adding polyethylene glycol methyl ether acrylate-480 and acryloylmorpholine to the solvent in S1 and dissolving them to obtain a mixed solution; S3, removing dissolved oxygen from the mixed solution in S2, sealing the container, and stirring under ice bath conditions; S4, adding potassium persulfate and N,N,N',N'-tetramethylethylenediamine to the mixed solution after stirring in S3, and sealing the container again; S5, completing the polymerization reaction in the container at 60 °C to obtain the hydrogel. Compared with the prior art, the hydrogel material provided by this invention has improved reflection loss intensity and effective absorption bandwidth performance, thus providing a new perspective for developing highly flexible and efficient electromagnetic wave absorbers.

An assembly and method of use are herein disclosed. The method comprises coupling an antenna and an electromagnetic wave via a passive waveguide having a cross-section dimension, the passive waveguide carrying the electromagnetic wave having a carrier frequency in a range of 500 GHz to 10 THz, the electromagnetic wave having a wavelength, the cross-section dimension of the passive waveguide in a range of at least 4 wavelengths to 50 wavelengths; and positioning an electromagnetic absorber around the antenna.

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.

To provide an electromagnetic wave absorption body capable of obtaining satisfactory electromagnetic wave absorption characteristics in "Low / Mid bands", a composition for electromagnetic wave absorption body molding for forming the same, and a composite filler for electromagnetic wave absorption body molding.SOLUTION: Disclosed is a composition for electromagnetic wave absorption body molding including: a polymer containing at least an acrylic acid ester copolymer as a main component; and a composite filler comprising a conductive filler which is coated with silicon oxide, consequently, formed with a an insulating membrane, wherein the conductive filler is kneaded in the polymer into a dispersion state and contains at least one kind of carbon material selected from among a carbon micro coil, a carbon nano fiber, a carbon nano tube and active carbon. Further disclosed is an electromagnetic wave absorption body which is made of the composition for electromagnetic wave absorption body molding through molding and hardening in a state where the composite filler is dispersed in the polymer.SELECTED DRAWING: Figure 1

To provide a lightweight electromagnetic wave absorber excellent in electromagnetic wave absorption properties.SOLUTION: The electromagnetic wave absorber 1 includes: a flat base 2; and multiple protrusions 3 that are formed on one surface 1a of the base 2 in a thickness direction. The base 2 and each of the protrusions 3 include a matrix and carbon nanotubes dispersed in the matrix, in which the bulk density is 1.23 kg / m3 or less.SELECTED DRAWING: Figure 1

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

The invention provides a passive broadband non-reciprocal electromagnetic wave absorber and a manufacturing method, and the passive broadband non-reciprocal electromagnetic wave absorber comprises three layers of structures from bottom to top: a bottom layer metal reflection backboard, a ferrite substrate and a metal complementary split ring resonator (CSRR) array. Wherein the bottom metal reflection back plate, the ferrite substrate and the CSRR array are square plate-shaped structures with the same shape, and the ferrite substrate is arranged between the bottom metal reflection back plate and the CSRR array; the ferrite substrate is made of La-doped BaFe12O9, and has an asymmetric magnetic conductivity tensor characteristic; the surface layer of the CSRR array is provided with a metal complementary opening; and the CSRR array is coupled with the non-reciprocal characteristic of the ferrite substrate to form differential absorption of left-hand circularly polarized waves and right-hand circularly polarized waves.

A method for preparing a ferrite solid waste-based electromagnetic wave absorbing material, relating to the field of electromagnetic wave absorbing materials, involves first purifying the ferrite solid waste, then surface-modifying it using a silane coupling agent KH550. Next, MoS2 nanoparticles and the surface-modified ferrite solid waste particles are ball-milled using a high-energy ball mill to obtain a composite electromagnetic wave absorber. The composite electromagnetic wave absorber is then granulated, pressed, and heat-treated to obtain a preform. Finally, the preform is processed to obtain an electromagnetic wave absorbing material of a specific shape. This invention first surface-modifies the purified ferrite solid waste particles, then composites them with molybdenum disulfide through a ball milling process. This preparation process allows for the complementary advantages of the two materials, resulting in an electromagnetic wave absorbing material with higher mechanical properties and superior electromagnetic wave absorption performance.

To provide a resin composition having high absorptivity of electromagnetic waves and having low transmittance and reflectivity of electromagnetic waves, which is a resin composition for an electromagnetic-wave absorber having small difference in reflectivity due to the difference in frequency of electromagnetic waves and an electromagnetic-wave absorber.SOLUTION: There is provided a resin composition for an electromagnetic-wave absorber which comprises 0.1 to 10.0 pts.mass of a carbon nanotube based on 100 pts.mass of a thermoplastic resin, wherein when the resin composition is molded into 150 mm×150 mm×2 mm thickness, the absorptivity determined by the expression (A) in the frequency of 76.5 GHz is 40.0 to 100%, and when the resin composition is molded into 150 mm×150 mm×2 mm thickness, the difference between the highest value and the lowest value of the reflectivity determined by the expression (B) in the frequency of 70 to 80 GHz is 20.0% or less.SELECTED DRAWING: None

The electromagnetic wave absorber comprises a matching impedance layer, a temperature control phase change resonance layer, a magnetic control phase change regulation and control layer and a metal reflection layer which are sequentially stacked, wherein the temperature-control phase-change resonance layer comprises a base body layer, a plurality of temperature-control phase-change units which are periodically arranged on the base body layer, and a heating layer which is attached to the surface of one side of the base body layer; the heating layer is used for adjusting the temperature of the temperature control phase change unit, so that the conductivity of the temperature control phase change resonance layer is changed; the magnetic control phase change regulation and control layer comprises a magnetic control coil and magnetic control phase change units which are periodically arranged; the magnetic control coil is used for applying magnetic fields with different sizes to the magnetic control phase change unit, so that the magnetic conductivity of the magnetic control phase change material structure is changed; and the arrangement period sizes of the temperature control phase change units and the magnetic control phase change units are between nanometer magnitude and millimeter magnitude. According to the electromagnetic wave absorber, the wave absorbing frequency capable of absorbing waves can be switched and adjusted within a larger range, and therefore the requirements of various different application scenes can be better met.

The invention discloses an environment-friendly wave-absorbing phase-change energy-storage temperature-control coating as well as a preparation method and application thereof, and belongs to the technical field of special coatings. The environment-friendly wave-absorbing phase-change energy-storage temperature-control coating comprises the following raw materials in percentage by mass: 28%-32% of a phase-change energy-storage material, 30%-35% of an interior wall paint raw material, 8%-12% of an amphiphilic electromagnetic wave absorbent, 1%-2% of a negative expansion coefficient material, 3%-5% of an emulsifier, 2%-4% of an initiator, 0.2%-0.5% of a pH regulator and 15%-20% of water, and the sum of the mass fractions of all the components is 100%. The phase-change energy storage material comprises at least one phase-change material with the phase-change temperature of 29-45 DEG C and at least one phase-change material with the phase-change temperature of 0-10 DEG C. Heat is absorbed and released through the phase change reaction of the system, indoor temperature balance is automatically regulated and controlled, energy consumption caused by refrigeration in summer and heating in winter is reduced, carbon emission is reduced, intelligent upgrading of buildings is achieved, and green sustainable development is achieved.

To provide an electromagnetic wave absorber capable of improving adhesion between an electromagnetic wave absorption layer and a resin layer.SOLUTION: An electromagnetic wave absorber 100 according to the present invention comprises an electromagnetic wave absorption layer 10 comprising carbon nanotubes, and a resin layer 50 provided on the electromagnetic wave absorption layer 10 and formed by curing a resin composition comprising urethane (meth)acrylate, thiol, and a photopolymerization initiator, wherein the number of (meth)acryloyl groups per monomer in the urethane (meth)acrylate is 3 or more, and a content ratio of thiol in the resin composition is 3 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the urethane (meth)acrylate.SELECTED DRAWING: Figure 1

The application discloses a kind of PEI or PEEK-based 3D printing wave-absorbing materials and preparation method thereof.The 3D printing wave-absorbing material includes the following components by mass fraction: polyetherimide resin or polyether ether ketone resin: 45~65 parts;Electromagnetic wave absorber: 10~50 parts;Impact modifier: 4~12 parts;Flow aid: 2~8 parts;Antioxidant: 0.5~3 parts;Wherein, the electromagnetic wave absorber includes magnetic absorber and carbon-based absorber, the impact modifier and the carbon-based absorber are pre-coated to form the carbon-based absorber coated with the impact modifier on the surface, and the magnetic absorber is surface modified by silane coupling agent.The application significantly improves the mechanical properties and thermal stability of the material by using specific raw material composition and combining specific multi-layer co-extrusion and online heat treatment process.The preparation process is simple and easy to operate, and is suitable for industrial continuous production.

To provide a resin composition that has a high electromagnetic wave absorption rate, a molded body, an electromagnetic wave absorber, and a method for manufacturing the resin composition.SOLUTION: A resin composition contains a polybutylene telephthalate resin, a polystyrene resin, and carbon nanotubes. There are also provided a molded body of the resin composition, and an electromagnetic wave absorber, and a method for manufacturing the resin composition.SELECTED DRAWING: None

To provide an electromagnetic wave absorber that can improve electromagnetic wave absorption performance. [Solution] The electromagnetic wave absorber according to the present invention includes a plurality of sheets comprising glass fibers and a conductive carbon material, the plurality of sheets being laminated, the first sheet of the plurality of sheets being provided on the incident surface side to which electromagnetic waves are incident, and the surface resistivity of the first sheet is higher than that of the second sheet.

The present invention provides a ferrite powder which contains 0.9% by mass to 2.5% by mass of lithium (Li), 1.0% by mass to 8.0% by mass of manganese (Mn), and 58.0% by mass to 69.5% by mass of iron (Fe), and has a crystal phase belonging to the space group P4132 and a crystal phase belonging to the space group Fd-3m. In the X-ray diffraction profile, the half width of the (311) plane of the crystal phase belonging to the space group Fd-3m is 0.09° to 0.22°, and the volume average particle diameter D50 is not less than 1 μm but less than 20 μm.

To provide a resin composition, a pellet, a molding, an electromagnetic wave absorber and a method for producing a resin composition, which have high electromagnetic wave absorption rates.SOLUTION: A resin composition contains, with respect to 100 pts.mass of a polyester resin having intrinsic viscosity of 0.87-2.00 dL / g, 0.1-10.0 pts.mass of a polyamide resin, and carbon nanotube.SELECTED DRAWING: None

Provided is an electromagnetic wave absorber that can be downsized and have a wide response bandwidth while suppressing an increase in manufacturing cost.The electromagnetic wave absorber according to the present technology includes a spiral body having a non-constant spiral diameter.

An electromagnetic wave absorber (1) includes a dielectric layer (10), a resistive layer (20), and an electrically conductive layer (30). The resistive layer (20) is disposed on one principal surface of the dielectric layer (10). The electrically conductive layer (30) is disposed on the other principal surface of the dielectric layer (10) and has a sheet resistance lower than a sheet resistance of the resistive layer (20). The resistive layer (20) has a sheet resistance of 200 to 600Ω / □. When the resistive layer (20) is subjected to an immersion treatment in which the resistive layer (20) is immersed in a 5 weight % aqueous solution of NaOH for 5 minutes, an absolute value of a difference between a sheet resistance of the resistive layer (20) before the immersion treatment and a sheet resistance of the resistive layer (20) after the immersion treatment is less than 100Ω / □.

To provide a resin composition having high absorptivity of electromagnetic waves and having high flame retardancy, and a molded product and an electromagnetic wave absorber.SOLUTION: A resin composition contains thermoplastic resin, carbon nanotubes and a bromine flame retardant. The mass ratio in the content of bromine atoms (Br) between the carbon nanotubes (CNT) and the bromine flame retardant, CNT / Br, is 0.01-0.40.SELECTED DRAWING: None