27 results about "Electromagnetic absorbers" patented technology

The invention belongs to the technical field of electromagnetic wave-absorbing materials, and particularly relates to a zero-power absorption type adjustable metasurface composite material and a preparation method thereof. Comprising a panel, a square-ring-shaped metal layer, a cross-shaped metal layer, an electric control metamaterial, a resistive film and a reflecting back plate from top to bottom in sequence, a core layer is arranged among the square metal layer, the cross curve metal layer, the electric control metamaterial, the resistive film and the reflecting back plate; the electric control metamaterial comprises second structure units which are periodically arranged along x and y directions and contain PIN diodes, and the PIN diodes are embedded into the structure; the cross curve metal layer and the square metal layer respectively comprise a third structure unit and a fourth structure unit which are periodically arranged along the x direction and the y direction. Through a cascade structure formed by the electric control metamaterial, the cross-shaped metal layer and the square ring-shaped metal layer, when the PIN diode is switched off, the wave absorbing state is presented, when the PIN diode is switched on, the reflecting state is presented, and electromagnetic waves are absorbed under the condition that bias voltage is not applied.

The invention belongs to the field of electromagnetic wave absorbing materials, and particularly relates to a thin broadband composite wave absorber based on a frequency selective surface. According to the invention, the wave-transparent layer is added in the middle of the multi-layer magnetic material, the mindset of simply stacking the same type of materials in the traditional multi-layer wave-absorbing structure is broken, and the wave-transparent layer is introduced to change the original characteristic that the impedance gradually changes in sequence; meanwhile, a magnetic wave-absorbing material, a frequency selection surface and a medium matching layer are subjected to composite design, the frequency selection surface generates an electromagnetic coupling effect at high frequency, phase and impedance conversion of electromagnetic waves in a multi-layer structure is controlled, and efficient impedance matching and electromagnetic wave energy dissipation in a broadband are achieved through electromagnetic absorption and interference cancellation; and an excellent wave absorbing effect is achieved. The total thickness of the composite wave absorber ranges from 0.064 lambda to 0.1 lambda, the-10 dB absorption bandwidth ranges from 3.3 GHz to 18 GHz, and the relative bandwidth reaches 138%; and meanwhile, the wave absorber has a wide angular domain characteristic under oblique incidence, and a novel thin broadband composite wave absorber scheme is provided.

The invention discloses a multifunctional broadband electromagnetic wave-absorbing composite material based on a bionic periodic unit and a multistage core-shell filler and a preparation method thereof.The multistage core-shell filler is used as a raw material, an impregnation technology is adopted, and the bionic periodic unit is impregnated by preparing high-loss paint and impedance matching paint with different concentrations; the electromagnetic wave-absorbing composite material is obtained. Accurate gradient distribution and better impedance matching of electromagnetic parameters in a three-dimensional space are achieved, the density is lower than 6 kg / m under the thickness of 15-20 mm, the plane compression strength is 2 MPa, and the effective absorption bandwidth (RLlt;-10 dB) covers 8-18 GHz. The invention solves the contradiction between the bandwidth, thickness, weight and single function of the traditional wave-absorbing material, and is suitable for the fields of advanced stealth equipment and electromagnetic protection. The material opens up a new direction for the development of electromagnetic wave-absorbing materials, and is expected to be widely applied to many fields such as national defense, communication, electronics and the like.

The invention discloses a Ni3Al-PPy composite wave-absorbing material as well as a preparation method and application thereof, and belongs to the technical field of electromagnetic wave-absorbing materials. The Ni3Al-PPy composite wave-absorbing material with a core-shell structure is successfully synthesized by combining a thermit reaction with a chemical oxidation polymerization method and hydrochloric acid modification. By regulating and controlling the addition amount of the pyrrole monomer in the range of 0.25-0.75 mL, the continuous regulation and control of the thickness of the PPy shell layer from 0.22 [mu] m to 0.31 [mu] m is realized. When the thickness of a PPy shell layer is 0.27 mu m and the matching thickness of the composite wave-absorbing material is 3.0 mm, the minimum reflection loss and absorptivity gt of-40.0 dB are obtained at 9.27 GHz; and when the matching thickness is 2.0 mm, the effective absorption bandwidth reaches 3.02 GHz. According to the invention, the effect of the shell layer thickness in regulating and controlling the performance of the wave-absorbing material with the core-shell structure is illustrated, and a feasible strategy is provided for designing a high-performance light-weight wave-absorbing material with adjustable electromagnetic parameters and enhanced durability.

The invention relates to the field of structural wave absorption, in particular to an electromagnetic wave-absorbing material and a preparation method thereof. The electromagnetic wave-absorbing material comprises: a) a honeycomb substrate having a plurality of honeycomb holes penetrating along the thickness direction; the honeycomb holes are filled with the wave-absorbing medium; wherein the wave-absorbing medium is a condensate formed by cooling after paraffin and an absorbent are uniformly dispersed in a molten state; the absorbent has magnetic loss and / or dielectric loss properties. Impedance is adjusted through paraffin, loss is provided through the absorbent, a propagation path is prolonged through the honeycomb structure, and the electromagnetic wave-absorbing material which is reduced in interface reflection, improved in absorption efficiency, good in structural stability and adjustable in absorption performance is achieved.

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

The present application belongs to the cross technical field of electromagnetic wave absorbing material and radiation cooling material, and specifically provides a cellulose-coated radiation cooling wave absorber and a preparation method thereof, to solve the problem that the existing wave absorber is easy to absorb excessive solar radiation in an outdoor environment, causing device temperature rise and unstable operation. The present application uses PEDOT aerogel as the base body and introduces cellulose aerogel as the surface coating layer. On the one hand, high reflectivity is achieved in the visible light band to reduce solar radiation absorption, and on the other hand, high emissivity is achieved in the near-infrared band to release heat energy and suppress temperature rise, even achieving radiation cooling effect. At the same time, the cellulose aerogel is used as a perfect impedance matching layer to make the incident electromagnetic wave completely enter the material inside, improving the absorption efficiency. Furthermore, the PEDOT and cellulose are compounded to form an upper and lower structure network, so that the incident electromagnetic wave is reflected and scattered multiple times between the layers, prolonging the electromagnetic wave propagation path and further improving the absorption efficiency.

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 relates to the technical field of wave-absorbing materials, in particular to a preparation method of a core-shell structure wave-absorbing agent taking hollow ceramic micropearls as cores. The preparation method of the core-shell structure wave-absorbing agent taking hollow ceramic micropearls as cores has the advantages of low density, simple preparation process, low cost and the like, meets the requirements of light weight and high absorption characteristics, and can be widely applied to the field of electromagnetic wave-absorbing materials.

The invention provides a thin-layer strong-absorption mechanical adjustable three-dimensional wave-absorbing structure comprising a bottom plate which is provided with a plurality of basic structure units arranged in a periodic array. Each basic structure unit comprises a hollow frame installed on the bottom plate, a three-dimensional resistive frequency selection substructure arranged on the outer surface of the hollow frame and a nested height-adjustable metal reflection three-dimensional substructure located in the hollow frame and installed on the bottom plate. The invention has the following beneficial effects: through a simple and unique three-dimensional wave-absorbing structure design, the absorption performance with a reflection coefficient lower than-20dB in a range of 8-18GHz is realized, and good oblique incidence stability is achieved; the adjustable reflection coefficient under any incident angle in a broadband range is realized, so that the current requirements of a novel electromagnetic wave-absorbing material which is thin in layer, small in surface density, strong in absorption, adjustable in wave-absorbing performance, simple in structure and good in oblique incidence stability are met.

The application discloses a kind of composite electromagnetic wave-absorbing materials and preparation method thereof.By coating glass, SiO2 and other materials on the outside of graphene, the coating layer has wave-transparent characteristics and can be used to adjust the impedance matching of the composite material, and can also play the role of thermal barrier layer to protect the internal graphene from being oxidized at high temperature.Specifically, a kind of composite electromagnetic wave-absorbing material with special glass / graphene coating structure is prepared by liquid sodium silicate foaming method, thereby relieving the high impedance matching characteristics of reduced graphene oxide itself and improving the electromagnetic absorption performance of the composite electromagnetic wave-absorbing material.Further, by adjusting the heat treatment temperature, the shear stress generated by thermal stress on the graphene sheet is controlled to adjust the particle size of the coating structure, and thus the adjustment of the wave-absorbing performance is realized.The preparation method of the application is simple, green and efficient, and does not have high requirements for related equipment, and a large amount of high-temperature wave-absorbing materials can be prepared in a short time.

Radar retroreflective (R3) devices including an electromagnetic absorber are provided. The electromagnetic absorber is disposed on selected areas of the device to reduce specular reflection without substantially reducing retroreflection of the device.

The application provides a thin-layer strong-absorption mechanically adjustable three-dimensional wave-absorbing structure, which comprises a bottom plate, a plurality of basic structure units arranged in a periodic array are arranged on the bottom plate, the basic structure unit comprises a hollow frame installed on the bottom plate, a three-dimensional resistive frequency selection substructure arranged on the outer surface of the hollow frame and a nested height-adjustable metal reflection three-dimensional substructure located in the hollow frame and installed on the bottom plate; the application has the following beneficial effects: the application realizes the absorption performance of a reflection coefficient lower than -20 dB in the range of 8-18 GHz through a simple and unique three-dimensional wave-absorbing structure design, and has good oblique incidence stability; further combined with the nested height-adjustable metal reflection three-dimensional substructure, the application realizes the adjustable reflection coefficient in a wide-band range and at any incident angle, thereby meeting the demand for a new type of electromagnetic wave-absorbing material with thin layers, small area density, strong absorption, adjustable wave-absorbing performance, simple structure and good oblique incidence stability.

The utility model provides an intelligent energy-saving high-power automatic absorbing and discharging electromagnetic iron remover, which comprises a metal detector, an electromagnetic absorber, a moving system and a control system, the metal detector and the moving system are sequentially arranged on the same conveying belt front and back, and the electromagnetic absorber is arranged on a moving device; a metal detector is arranged in front of the conveying direction of a conveying belt, when the metal detector detects that materials on the conveying belt are mixed with iron substances, the metal detector sends an action signal to a control system, the control system further controls a moving device to move, the moving device drives an electromagnetic attraction to move to the position above the conveying belt, and the iron substances are conveyed to the conveying belt. And after the iron is attracted, the iron is automatically moved to the outside of the conveying belt within a set time, and the iron is unloaded. As the electromagnetic attractor stops outside the conveying belt during standby at ordinary times, the electromagnetic attractor is electrified to move when iron substances are detected, and the electromagnetic attractor is not electrified when iron substances do not exist, so that the effects of saving energy and prolonging the service life are achieved.

This invention belongs to the field of electromagnetic absorbing materials technology. It relates to a layered high-entropy MBene material, its preparation method, and its applications. This invention utilizes high-temperature Joule heating to prepare the layered high-entropy MBene material. This layered high-entropy MBene material possesses many significant advantages, such as abundant defect density, good conductivity loss, high specific surface area, a large number of exposed surface atoms, and excellent mechanical and electronic properties. It can effectively control electromagnetic parameters and achieve excellent electromagnetic absorption performance. Furthermore, it exhibits nanoscale effects, which can induce lattice distortion, defects, and microstrain, significantly optimizing impedance matching and enhancing dipole polarization and conductivity loss, thus demonstrating outstanding microwave absorption performance. The high-temperature Joule heating synthesis strategy proposed in this invention provides a new approach for the development of advanced high-entropy electromagnetic absorbing materials and offers a general method for the development of other layered materials with tunable structures.

An apparatus for testing electronic devices comprises: a base platform; a cover plate disposed on the base platform, and defining with the base platform an array of test chambers and at least one gap separating the test chambers from each other, wherein the cover plate has at each of the test chambers a top opening for placing an electronic device within the test chamber and a side wall around the opening; an array of test boards each being disposed under one of the array of test chambers, wherein each test board includes a socket connectable with the electronic device placed within the test chamber for testing; and an electromagnetic absorber material disposed within the at least one gap and attached onto the cover plate to absorb electromagnetic interferences between adjacent electronic devices when they are placed within the array of test chambers for testing.

Aspects of the disclosure provide a semiconductor package and a method for preparing the same. The disclosed semiconductor package includes a die disposed over and conductively coupled to a laminate; and a member (e.g., a lid) attached to the laminate via one or more conducting materials. The member includes a structure (e.g., an electromagnetic absorber structure) configured to absorb electromagnetic radiation. In one or more embodiments, a wireless device may include the semiconductor package produced via the method as disclosed herein.

The application discloses a kind of laser thermochemical calcination electromagnetic wave absorber and its preparation method and application, belong to electromagnetic wave absorbing material technical field.The method of the present application includes the following steps: (1) iron source, cobalt source, nickel source are mixed with solvent, obtain iron cobalt nickel mixed solution;Phthalic acid is mixed with solvent, obtain phthalic acid solution;Iron cobalt nickel mixed solution and phthalic acid solution are mixed and reacted, after reaction, separate crude product, obtain multi-metal organic framework material precursor by purification, for standby;(2) in air atmosphere, using laser on the obtained multi-metal organic framework material precursor is carried out thermochemical calcination treatment, obtain electromagnetic wave absorber.The method uses laser thermochemical calcination process, simple and convenient process, lower cost, suitable for industrial large-scale production.The electromagnetic wave absorber prepared has excellent wave-absorbing performance, shows good shielding performance in terahertz wave band, and has good application prospect.

The present application belongs to the cross technical field of electromagnetic wave absorbing material and radiation cooling material, and specifically provides a cellulose-coated radiation cooling wave absorber and a preparation method thereof, to solve the problem that the existing wave absorber is easy to absorb excessive solar radiation in an outdoor environment, causing device temperature rise and unstable operation. The present application uses PEDOT aerogel as the base body and introduces cellulose aerogel as the surface coating layer. On the one hand, high reflectivity is achieved in the visible light band to reduce solar radiation absorption, and on the other hand, high emissivity is achieved in the near-infrared band to release heat energy and suppress temperature rise, even achieving radiation cooling effect. At the same time, the cellulose aerogel is used as a perfect impedance matching layer to make the incident electromagnetic wave completely enter the material inside, improving the absorption efficiency. Furthermore, the PEDOT and cellulose are compounded to form an upper and lower structure network, so that the incident electromagnetic wave is reflected and scattered multiple times between the layers, prolonging the electromagnetic wave propagation path and further improving the absorption efficiency.

The invention belongs to the field of electromagnetic wave-absorbing materials, and particularly relates to a novel power-resistant patterned honeycomb wave-absorbing material. According to the patterned honeycomb structure provided by the invention, while the characteristics of light weight and high specific strength of the honeycomb body are maintained, designable gradient periodic impedance films are introduced into the inner walls of odd layers of honeycombs in the thickness direction of the honeycomb material; according to the setting rule of the periodic impedance film, m absorption peaks are introduced at a high frequency through a resonance effect to correspond to a frequency band required by wave absorption of the whole wave-absorbing honeycomb, and the characteristics of high-frequency broadband absorption and low-frequency high transmission are achieved; the wave-absorbing frequency band can be flexibly designed, and under the condition that the wave-absorbing performance is guaranteed, the remarkable temperature rise suppression advantage is achieved in the aspect of thermal performance. According to the invention, the stealth requirements of the airborne antenna at different frequency bands can be met, and the antenna has higher thermal stability and engineering availability under the irradiation of a high-power antenna, and is suitable for scenes with synchronous requirements on stealth performance and power-resistant characteristics, such as a wing leading edge integrated antenna.

The invention relates to an electromagnetic absorbing structure, in particular to an ultra-wideband composite wave-absorbing honeycomb structure, and belongs to the field of electromagnetic wave-absorbing materials. The invention relates to a composite wave-absorbing honeycomb structure which comprises a honeycomb framework, a multi-layer tower type gradient structure and a wave-absorbing substrate. The multi-layer tower type gradient structure is fixed in the honeycomb framework in an embedded mode, and the wave absorbing substrate is arranged below the structure where the multi-layer tower type gradient structure and the honeycomb framework are embedded. According to the composite wave-absorbing honeycomb structure, the honeycomb framework, the multi-layer tower type gradient structure and the wave-absorbing substrate are subjected to composite design, so that the wave-absorbing bandwidth of the whole wave-absorbing honeycomb is effectively expanded, and the ultra-wideband efficient wave-absorbing characteristic is realized. The prepared composite wave-absorbing honeycomb has an excellent wave-absorbing effect in a frequency band range of 2-18GHz.

The invention relates to the technical field of electromagnetic wave-absorbing materials, in particular to a dopamine modified La2CoMnO6 double-perovskite electromagnetic wave-absorbing material and a preparation method thereof. The preparation method comprises the following steps: coating La2CoMnO6 powder with polydopamine, then carrying out carbonization treatment, cooling and grinding to obtain the electromagnetic wave-absorbing material coated with the carbon layer on the outer layer. The polydopamine can be converted into an amorphous carbon layer after low-temperature carbonization, the carbon layer uniformly coats the surfaces of the LCMO particles, a core-shell structure is locally formed, on one hand, a continuous conductive network is constructed, and the conductivity loss is enhanced; on the other hand, a rich heterogeneous interface is formed, interface polarization is promoted, meanwhile, oxygen vacancy introduced in the carbonization process can serve as a dipole center, dipole polarization relaxation is enhanced, and dielectric loss and impedance matching performance are improved.

The invention relates to a flexible electromagnetic metamaterial wave absorber and a preparation method thereof, and belongs to the technical field of electromagnetic wave absorbing metamaterials. The flexible electromagnetic metamaterial wave absorber is composed of a plurality of unit arrays of the same structure, each unit array comprises three layers of structures, namely a resistive film pattern layer, a middle dielectric layer and a metal reflecting layer from top to bottom, and each unit array comprises a circular resistive film pattern layer located in the center of the unit. The wave absorber can be applied to flexible working occasions, has the advantages of being simple in structure, small in thickness, low in cost, convenient to prepare, large in wave absorbing bandwidth and the like, and is an electromagnetic wave absorbing material which is thin, light, wide and strong.

This invention relates to an electromagnetic wave absorbing material in the 600MHz-1GHz frequency band, its preparation method, and its applications. The electromagnetic wave absorbing material comprises a magnetic composite material and carbonyl iron particles, wherein the carbonyl iron particles are aggregates of multiple two-dimensional nano-carbonyl iron particles. The magnetic composite material comprises carbon crystal clusters composed of multiple carbon crystals and tungsten disulfide. At least a portion of the carbon crystals have tungsten disulfide and carbonyl iron particles attached to their surfaces, and at least a portion of the interstices between the carbon crystal clusters are filled with tungsten disulfide and carbonyl iron particles. The carbon crystals are three-dimensional prismatic in shape and have a porous structure, while the tungsten disulfide is plate-like. This electromagnetic wave absorbing material has the advantages of being lightweight and having good thermal stability, and exhibits strong absorption performance for electromagnetic waves in the 600MHz-1GHz frequency band.

The invention relates to the technical field of electromagnetic wave materials, in particular to a preparation method of a wave absorbing agent with hollow glass bead-graphene as a core-shell structure. According to the preparation method of the wave-absorbing agent with the hollow glass bead-graphene as the core-shell structure, the hollow glass beads are ultrasonically dispersed in a sodium hydroxide aqueous solution and continuously stirred, and the hollow glass beads are subjected to surface treatment; carrying out surface amination reaction on the hollow glass microspheres subjected to surface treatment in a silane coupling agent solution; adding the hollow glass microspheres subjected to surface amination into a graphene oxide aqueous solution, and carrying out amidation reaction, so that the hollow glass microspheres are compounded with graphene oxide; hydrazine hydrate is added as a reducing agent, the core-shell structure wave absorbing agent with the hollow glass beads as cores and the surfaces coated with reduced graphene oxide is obtained, and the wave absorbing agent is low in density, simple in preparation process and low in cost, has corrosion resistance, meets the requirements for light weight and high absorption characteristics and can be widely applied to the field of electromagnetic wave absorbing materials.

The invention belongs to the technical field of electromagnetic wave-absorbing materials, and relates to a broadband anti-corrosion double-layer structure wave-absorbing coating and a preparation method and application of a wave-absorbing coating. The wave-absorbing coating comprises a lower-layer coating and an upper-layer coating, wherein the lower-layer coating comprises the following components in parts by mass: 20-30 parts of resin A, 55-70 parts of an absorbent A, 9-14 parts of a diluent A and 1-2 parts of an auxiliary agent A; the upper-layer coating is prepared from the following components in parts by mass: 30 to 40 parts of resin B, 3 to 7 parts of filler, 22 to 31 parts of absorbent B and 25 to 43 parts of diluent B. According to the wave-absorbing coating, the lower-layer paint adopts carbonyl iron powder as an absorbent, so that the wave-absorbing coating has strong electromagnetic wave absorbing performance; the upper-layer coating is a carbon-series wave-absorbing material prepared by ball-milling dispersion, and the lower-layer coating is covered, so that external air is isolated, a corrosion channel is blocked, and the coating has good corrosion resistance and can work for more than 12 months under the salt mist condition.