44results about How to "Increased absorption bandwidth" patented technology

A heating apparatus using an electromagnetic wave is disclosed, by which cut-of performance of an electromagnetic wave is enhanced by increasing an electromagnetic wave absorption bandwidth having cut-off performance below −70 dB. The present invention includes a door provided to an open front side of a body to be opened/closed and a choke filter having a panel type choke part arranged by at least one row each along an edge of the door and a filter part arranged by at least one row each along an edge of the choke part and having a plurality of slots, wherein a prescribed choke part is provided to a most inner side among rows of the choke and filter part.

The invention discloses a ceramic whisker/ferromagnetic metal composite wave-absorbing material and a preparation method thereof, relates to a composite material for absorbing electromagnetic waves and a preparation method thereof, and solves the problems that the prior wave-absorbing material has low wave-absorbing efficiency and complex preparation process and is difficult to achieve large-scale industrial production. The ceramic whisker/ferromagnetic metal composite wave-absorbing material is made of ceramic whisker of which the surface is plated with a ferromagnetic metal layer. The preparation method comprises the following steps: thermally treating the ceramic whisker of which the surface is plated with the ferromagnetic metal layer for 60 minutes at a temperature of between 300 and 400 DEG C under the condition that the thermal treatment atmosphere is hydrogen or argon to obtain the ceramic whisker/ferromagnetic metal composite wave-absorbing material. The complex dielectric constants and complex magnetic conductivities of the ceramic whisker/ferromagnetic metal composite wave-absorbing material obtained by the method are remarkably improved; as an electromagnetic wave absorbing coat, the maximum absorption reaches 78dB, and the absorption bandwidth of more than 10dB is as high as 4GHz; and the method is simple and practical, and is suitable for large-scale production.

The invention discloses a foaming type polyurethane wave-absorbing material and a preparation method thereof. The foaming type polyurethane wave-absorbing material is prepared in the way that a wave-absorbing material, a fire retardant and an additive are directly added to semi-rigid foam and rigid foam polyurethane which serve as carriers. The preparation method comprises the steps of: firstly, dividing the polyurethane raw material into a component A and a component B, wherein the component A is diisocyanate or a derivative of diisocyanate, the component B is polyether glycol or polyester polyol; adding the additive into the component B, mixing and stirring uniformly for later use, adding the fire retardant and the wave absorbing material in the component A or B in any proportion, respectively pouring the prepared components A and B which are uniformly mixed into two material tanks of a low-pressure polyurethane pouring machine, then pouring the prepared material into a mould by using the pouring machine, foaming for 6-8min and then opening the mould, taking a product out, curing the product for 0.5-2 days, and finishing to obtain the foaming type polyurethane wave-absorbing material. The foaming type polyurethane wave-absorbing material has the advantages of strong wave absorbing property and stable reflectivity, and is suitable for mass production.

The invention discloses a novel three-dimensional broadband super-light wave-absorbing material and a designing method thereof. The wave-absorbing material comprises a metal baseboard, a three-dimensional rotary support and a periodic array which is constituted by square resistor discs on the upper surface. The three-dimensional rotary support is formed by a square planar resistor disc and four rhombic planar resistor discs which are connected. The four rhombic planar resistor discs are connected with four edges of the square planar resistor disc, respectively, and are folded by a certain angle alpha towards the square center along the edges of the square planar resistor disc. The edges of the square planar resistor disc are equal to those of the rhombic planar resistor discs. The square planar resistor disc, the rhombic planar resistor discs and the square resistor discs are made of resistive films. For the situation of vertical and oblique incidence of electromagnetic wave in the TM polarization manner, especially the situation of large angle of incidence of electromagnetic wave, good broadband wave-absorbing effect is achieved.

The invention discloses a multi-resonance absorption zirconium-doped barium ferrite broadband wave-absorbing material having an expression formula of xBaZr[n]Fe[12-n]O[19]+(1-x)BaZr[m]Fe[12-m]O[19], wherein x is 0.1-0.9, n is 0.1-0.2, m is 0.3-0.5, and m is not equal to n. A preparation process comprises the steps: preparing a BaZr[n]Fe[12-n]O[19] powder; preparing a BaZr[m]Fe[12-m]O[19] powder; and then mixing and grinding the BaZr[n]Fe[12-n]O[19] powder and the BaZr[m]Fe[12-m]O[19] powder. A composite system is formed by the materials having different intrinsic parameter peak values, intrinsic parameters in the formed wave-absorbing system have corresponding different characteristic resonance frequencies, the appearing range of the resonance frequency of the composite material is greater than the appearing ranges of the own resonance frequencies of the compositing single-phase materials. The wave-absorbing material can be widely applied to the corresponding electromagnetic protection and microwave stealth fields.

The invention discloses a preparation method of a hollow flower-shaped nitrogen-doped nickel oxide/nickel/carbon composite material, and relates to the technical field of electromagnetic absorption materials. The preparation method comprises the following steps of: S1, sequentially dispersing water-soluble nickel salt, glucose and hexamethylenetetramine into a water solvent, and carrying out hydrothermal reaction at 170-190 DEG C for 20-36 hours to obtain a nickel/carbon compound; and S2, sintering the nickel/carbon compound obtained in the step S1 in a nitrogen atmosphere at 700-900 DEG C for 2-4 hours, then placing the sintered nickel/carbon compound in an air atmosphere, heating the sintered nickel/carbon compound to 250-350 DEG C, and keeping the temperature for 8-15 minutes to obtain the hollow flower-shaped nitrogen-doped nickel oxide/nickel/carbon composite material. A porous carbon/metal composite material is subjected to pyrolysis conversion by adopting a precursor, so that a porous carbon framework beneficial to electromagnetic wave reflection is realized, nano metal particles are uniformly introduced into the framework, a composite interface is increased, impedance matching is favorably improved, and the absorption bandwidth is increased.

The invention provides a wave-absorbing coating and a preparation method thereof. Micron silicon carbide and carbon black are compounded and modified by a silane coupling agent, and then the product is compounded in matrix resin to prepare a wave-absorbing agent with excellent performance. Silicon carbide utilizes dielectric polarization relaxation to lose electromagnetic wave and has poor magnetic properties, while carbon black has good electrical conductivity, light weight and low price, but still has the disadvantages of low absorption peak, narrow absorption bandwidth and the like. The invention combines the advantages of the two, and micron silicon carbide and carbon black are compounded and modified by a silane coupling agent to prepare the wave-absorbing agent with excellent performance. The preparation method provided by the invention is simple and easy to realize industrial production, and can be widely applied to clutter rejection, anti-electromagnetic interference and othertechnical fields of mobile phones, electronic instrument equipment, high frequency equipment, microwave active devices, radar and microwave communication systems.

A heating apparatus using an electromagnetic wave is disclosed, by which a capacity of a cavity is increased and by which cut-off performance of the electromagnetic wave and facilitation of door cleaning can be enhanced. The present invention includes a door provided to an open front side of a body to be opened/closed, a choke filter having a panel type choke part arranged by at least one or more rows along an edge of the door and a filter part having a plurality of slots wherein a prescribed choke part is provided to a most outer side, and a glass panel attached to an inner lateral side of the door and the choke filter.

The invention relates to a metamaterial wave absorber, and the wave absorber comprises a plurality of wave absorbing units. Each wave absorbing unit comprises a metal backboard, a dielectric substrateand a resistive film three-dimensional structure, wherein the metal backboard is arranged on one surface of the dielectric substrate, the resistive film three-dimensional structure is embedded in thedielectric substrate, and the resistive film three-dimensional structure comprises four first resistive films, a first square ring resistive film, four second resistive films and a second square ringresistive film; every two adjacent first resistive films are perpendicularly connected in a crossed mode to form a first #-shaped structure in a three-dimensional space. The first square ring resistive films penetrate through the first #-shaped structure and are connected with the first resistive films in a crossed mode, and the plane where the first square ring resistive films are located is perpendicular to the plane where the first resistive films are located; similarly, a second #-shaped structure is obtained, and the second #-shaped structure is arranged in the wellhead of the first #-shaped structure. The wave absorber disclosed by the invention can realize a good broadband absorption effect, and has good wide incident angle stability and polarization insensitivity.

The invention belongs to the technical field of electromagnetic functional materials, and particularly relates to a three-dimensional broadband wave-absorbing metamaterial integrating multiple absorption mechanisms. The three-dimensional broadband wave-absorbing metamaterial is an array of three-dimensional metamaterial units, each row at least comprises two three-dimensional metamaterial units, and each column at least comprises two three-dimensional metamaterial units; each three-dimensional metamaterial unit comprises an upper-layer dielectric plate, a lower-layer dielectric plate and a metal bottom plate which are sequentially arranged from top to bottom, a high-magnetic-loss material plate is embedded in the center inside the lower-layer dielectric plate, and the lower surfaces of the lower-layer dielectric plate and the high-magnetic-loss material plate are tightly attached to the upper surface of the metal bottom plate; a conductor core is embedded in the center inside the upper dielectric plate, and the lower surfaces of the conductor core and the upper dielectric plate cling to the upper surface of the lower dielectric plate. The conductor core is introduced into an all-dielectric metamaterial, and materials with different loss capacities are used at different parts, so that the prepared wave-absorbing metamaterial simultaneously has the loss mechanisms of a traditional metamaterial and a stepped all-dielectric metamaterial, and the use of high-loss materials can be reduced while the effective absorption bandwidth is expanded.