92 results about "Electromagnetic wave absorber" patented technology

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.

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.

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.

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 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

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

The invention discloses a periodic embedded multilayer composite frustum electromagnetic wave absorber, which belongs to the technical field of electromagnetic wave absorption and stealth, and comprises a metal plate and a wave absorbing structure, the wave-absorbing structure comprises a substrate layer and a plurality of multi-layer frustum wave-absorbing units. The substrate layer covers the metal plate; the multi-layer frustum wave absorbing unit is arranged on the substrate layer; the multi-layer frustum wave-absorbing unit is of a frustum structure formed by nesting a plurality of wave-absorbing layers from outside to inside; the substrate layer and each wave absorbing layer of the multi-layer frustum wave absorbing unit are made of electromagnetic wave absorbing materials, and the electromagnetic wave absorbing materials comprise a wave absorbing agent and a base material; in the multi-layer frustum wave-absorbing unit, the impedance of the plurality of wave-absorbing layers is gradually reduced in a gradient manner from outside to inside. The electromagnetic wave absorber has the characteristics that the structure is simple, structural parameters are easy to regulate and control, electromagnetic wave absorption is broadband and efficient, and polarization and polarization are insensitive.

This invention relates to a non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber and its preparation method. The technical solution is as follows: fumaric acid is added to deionized water, ultrasonically dispersed, and stirred to obtain solution A; an iron salt is added to deionized water and stirred to obtain solution B. Solutions A and B are mixed to obtain solution C; solution C is subjected to a hydrothermal reaction to obtain MIL-88A template powder. A metal salt is added to N,N-dimethylformamide, stirred, and filtered to obtain a mixed solution; the MIL-88A template powder is added to the mixed solution and stirred to obtain solution D. Polyvinyl alcohol is added to solution D, heated and stirred to obtain solution E. Solution E is electrospun, and the precursor fibers are collected using a collecting roller. The precursor fibers are subjected to thermal oxidation stabilization and carbothermal reduction reactions in an oven to obtain the non-magnetic metal-doped Fe3C / carbon fiber electromagnetic wave absorber. The product manufactured by this invention has the characteristics of strong versatility, excellent performance, high efficiency in absorbing electromagnetic waves, and a wide absorption frequency band.

An electromagnetic wave absorber includes multiple resonator units, each of which has SIW resonators, each of which has: a front surface conductor layer formed with a coupling slot into which an electromagnetic wave is introduced; a rear surface conductor layer which is placed opposite to the front surface conductor layer; and a penetration conductor to electrically connect the front surface conductor layer and the rear surface conductor layer, the SIW resonators being different in resonance frequency from each other, and disposed in a multistage form in a lateral direction of the coupling slot, and the multiple resonator units are disposed in a planar form in such a way that the longitudinal direction of the coupling slots belonging to each of the multiple resonator units is oriented in two or more directions.

The application discloses a preparation method of a rhombic dodecahedron cavity structure electromagnetic wave absorber Fe / ZnO@C, and belongs to the technical field of composite materials, and comprises the following steps: firstly, synthesizing magnetic Fe3O4 particles; then, preparing a precursor Fe3O4@ZIF-8; coating the surface of the Fe3O4@ZIF-8 with polydopamine to obtain Fe3O4@ZIF-8@PDA; and finally, obtaining a rhombic carbon shell coated zinc-iron alloy through high-temperature carbonization treatment. The Fe / ZnO@C composite with a rhombic dodecahedron cavity structure is prepared by using a three-step method, and has excellent electromagnetic wave absorption performance. The preparation process is simple, and the method is suitable for large-scale production; and the material structure is novel, the density is relatively small, and the product has excellent performance.

The invention discloses an electromagnetic wave absorbent based on CeFe-PBA and a preparation method thereof, and belongs to the technical field of electromagnetic wave absorbents. The preparation method comprises the following steps: 1) adding polyvinylpyrrolidone into a cerium salt aqueous solution, uniformly mixing, and then sequentially mixing with ethanol and a potassium ferricyanide aqueous solution to prepare CeFe-PBA precursor powder; (2) the precursor powder is subjected to a carbon thermal reduction reaction, and Fe-CeO2 powder is obtained; (3) the Fe-CeO2 powder is dissolved in a Tris dilute solution, then dopamine hydrochloride is added, and Fe-CeO2 (at) PDA powder is prepared; 4, the Fe-CeO2 (at) PDA powder is subjected to a carbon thermal reduction reaction in the N2 atmosphere, and the CeO2 / Fe3C (at) C electromagnetic wave absorbent is prepared. The method is simple in technological operation, controllable in condition, stable in hollow structure, high in conversion rate and good in repeatability, and the obtained absorbent has excellent microwave absorption performance and has industrial application prospects.

To provide a signal transmitter / receiver capable of achieving both target detection performance and reduction of erroneous detection.SOLUTION: A signal transceiver comprising: a control circuit; an antenna body including an antenna element group that is an assembly of a plurality of antenna elements; and an electromagnetic wave absorber, wherein the electromagnetic wave absorber and the antenna body have all of the following features 1 to 3. Feature 1: An angle φ formed between the electromagnetic wave absorber and the antenna body surface is π / 4 or more and 3 π / 4 or less. Feature 2: An electromagnetic wave absorber is installed toward an electromagnetic wave transmission direction of the antenna body surface. Feature 3: The following expressions 1 and 2 are satisfied, where A (k) is a return loss at a peak top when an electromagnetic wave is incident on the electromagnetic wave absorber from the antenna body at an incident angle k, and θ is an angle formed by a traveling direction of the electromagnetic wave transmitted by the antenna body and a direction of a main side lobe. A (π / 2 - θ)> A (2 π / 3 - θ) Expression 1 A (π / 2 - θ)> A (π / 3 - θ) Expression 2 SELECTED DRAWING: Figure 1

The invention discloses an ultra-wideband high-angle stability electromagnetic composite structure wave absorber which is formed by periodically arranging a plurality of wave absorber units. Each wave absorber unit comprises a metal bottom plate, a first magnetic material layer, a second magnetic material layer, a first resistive film FSS layer, a first foam supporting layer, a second resistive film FSS layer, a second foam supporting layer and a medium matching layer which are cascaded in sequence, and the first magnetic material layer and the second magnetic material layer are different in size; the patterns of the first resistive film FSS layer and the second resistive film FSS layer are different. The electromagnetic wave absorber has the ultra-wide-band wave absorbing characteristic, the reflection loss can be smaller than 10 dB within the frequency band of 1.6-19 GHz, meanwhile, good angle stability is kept, and the electromagnetic wave absorber has important application prospects in the fields of electromagnetic interference resistance, electromagnetic stealth and the like.

The application provides a wave-absorbing film material with electrostatic adsorption function and a preparation method thereof, and belongs to the field of functional film materials.The wave-absorbing film material with electrostatic adsorption function comprises a PVC film and PP films compounded on both sides of the PVC film; the preparation raw materials of the PVC film comprise an electromagnetic wave absorber, PVC resin particles and an additive; the electromagnetic wave absorber comprises a carbon material type electromagnetic wave absorber; the additive comprises a stabilizer and a plasticizer; the preparation raw materials of the PP film comprise PP resin particles, a filler and an additive; and the additive comprises a toughening agent and a lubricant.The PVC film and the PP film with wave-absorbing function are compounded by a co-extrusion technology, and then the compounded film is subjected to corona treatment to obtain the wave-absorbing film material with electrostatic adsorption function, which has good insulation, excellent electrostatic adsorption capacity, high surface energy and excellent wave-absorbing performance, and can meet the requirements of different use environments.

The invention provides an electromagnetic wave absorbent for a high-frequency band and a preparation method thereof. The preparation method comprises the following steps: (1) adding spherical carbonyl iron powder, a grinding aid and a dispersion medium into a stirring ball-milling tank, and carrying out ball-milling treatment to obtain slurry containing flaky carbonyl iron powder; (2) carrying out filter pressing treatment on the slurry, and separating filtrate and a filter cake to obtain wet powder of which most of the liquid medium is removed; and (3) drying the wet powder under a vacuum condition, removing the residual liquid medium to obtain dried flaky carbonyl iron powder, and screening to obtain the high-frequency band electromagnetic wave absorbent. Common carbonyl iron powder is difficult to meet the requirement of wave absorbing performance at high frequency, and after the common carbonyl iron powder is treated through the preparation method, the electromagnetic wave absorbing capacity of the common carbonyl iron powder at the high-frequency wave band is remarkably improved.

The present invention discloses a metamaterial electromagnetic wave absorber with polarization selectivity in the long-wave infrared band, relating to the technical field of metamaterial electromagnetic wave absorbers. The metamaterial electromagnetic wave absorber comprises a unit structure, wherein the unit structure is provided in n groups, and the n groups of unit structures constitute a periodic metamaterial electromagnetic wave absorber; the unit structure comprises a metal grating layer and an MIM structure, wherein the metal grating layer is provided at a central position above the MIM structure. Through the above-mentioned method, the present invention has an average absorption rate of up to 95.7% in the 8-14um band under the incidence of TM electromagnetic waves. When applied to infrared detectors, it can significantly improve the detection capability of long-wave infrared detection. When applied to TE electromagnetic waves, the absorption rate is lower than an average of 1.7%. The selective absorption performance of TM and TE polarized electromagnetic waves enables it to be applied to polarized light detection in the 8-14um band. By introducing a polarization dimension in addition to the intensity dimension, the contrast between different targets can be effectively enhanced. The metamaterial electromagnetic wave absorber is suitable for application scenarios where the temperature difference between targets is small and the polarization difference is obvious.