212 results about "Absorption bandwidth" patented technology

A graphene/magnetic particle/polyaniline composite porous wave-absorbing material and a preparing method thereof are disclosed. The composite porous wave-absorbing material comprises, by mass, 5-30 wt% of graphene, 5-20 wt% of magnetic particles, 45-90 wt% of polyaniline and 1-5 wt% of a foaming agent. The composite porous wave-absorbing material is prepared by loading the graphene sheet surfaces with the magnetic particles by a solvothermal method, cladding the graphene sheet surfaces loaded with the magnetic particles with the polyaniline through an in-situ polymerization process, performing heating and foaming by using the foaming agent, and performing high-temperature carbonization. The material has characteristics of a low cost, a simple preparing process, high electromagnetic wave absorption capability, a wide absorption bandwidth, and the like, and has a wide application prospect in sensing techniques, electromagnetic shielding, radar absorption, and other wave-absorbing fields.

The invention discloses a China Mobile 4G full band absorbing material, and a preparation method and application thereof. A composite auxiliary agent of a silane coupling agent and a stearate surfactant is added to a carbonyl iron powder, and a high-energy ball milling process is carried out to prepare a sheet-shape carbonyl iron powder absorbing material with excellent impedance matching performance. The material can meet the following requirements: in the frequency range from 1 to 18 GHz, an absorbing coating has thickness of less than or equal to 2mm; the absorbing material has -8dB absorption bandwidth reaching 1.5GHz (1.3-2.8GHz), which completely covers the whole band of China Mobile 4G (1.8GHz-2.8GHz); the proportion of the silane coupling agent and stearate can be adjusted to obtain proper sheet structure and size, thus changing the relationship between the complex permittivity and complex permeability to reach impedance matching, and then adjusting the absorption peak position. The material achieves the purpose of selecting absorption interference noise at three arbitrary main frequencies of China Mobile 4G and improving the signal-to-noise ratio of the base station and mobile terminal.

The invention discloses a broadband micro-perforated board sound absorber, a sound absorber performance prediction method and a sound absorber structure design method. The sound absorber comprises a surface micro-perforated board and a back chamber with unequal periodicity depth, and the back chamber is used for expanding sound absorption bandwidth of the sound absorber. The performance prediction method is used for predicting a sound absorption coefficient frequency spectrum of the sound absorber, through finite element simulation and experiment measurement verification, the performance prediction method is accurate and reliable; the structure design method used for effectively realizing the broadband micro-perforated board sound absorber comprises steps that (1), a depth matrix of the periodic back chamber is designed on the basis of the secondary residual sequence combination arrangement theory; and (2), evaluation is realized on the basis of the performance prediction method, combination of parameters of the sound absorber are sequentially determined, including total sound absorber width of the periodic back chamber, depth of each sub back chamber, board thickness of the micro-perforated board, aperture and perforated percentage. Through the sound absorber performance prediction method and the sound absorber structure design method, the micro-perforated board sound absorber having the broadband sound absorption performance can be accurately, reliably and simply designed.

The invention discloses a passive mode-locked laser device which comprises a pumping light source, a pumping coupling device and a resonant cavity which are arranged along a light path in sequence, wherein the resonant cavity comprises a light input cavity mirror, a gain medium as well as a first saturable absorber mirror and a second saturable absorber mirror which form oscillating light in the resonant cavity; the first saturable absorber mirror is a reflective saturable absorber mirror which takes graphdiyne as a saturable absorption body; the second saturable absorber mirror which takes the graphdiyne as the saturable absorption body serves as a light output cavity mirror. According to the laser device, stable oscillation of light beams in the cavity is realized and maintained through the first saturable absorber mirror and the second saturable absorber mirror to obtain a continuous mode-locked pulse; the graphdiyne is taken as the saturable absorption body of the saturable absorber mirror, light can be selectively absorbed within a relatively wide wavelength range due to the light absorption bandwidth of the graphdiyne, and the wavelength range of an output pulse of the passive mode-locked laser device can be extended.

The invention discloses an optical modulation terahertz broadband wave absorber based on doped silicon. A three-layer structure comprises a silicon substrate layer, a metamaterial layer and an opticalpumping source, which are sequentially arranged from bottom to top; the silicon substrate layer and the metamaterial layer are both boron-doped p-type silicon materials; and the metamaterial layer iscomposed of a unit structure array. The unit structure arrays are periodically arranged on the silicon substrate layer in an xoy plane; terahertz waves are incident on the wave absorber; the opticalpumping source is coupled into the wave absorber and excites electromagnetic resonance to realize broadband absorption of terahertz waves; and the optical pumping source generates a pumping light beamwhich is directly incident on the silicon substrate layer and the metamaterial layer to change the carrier concentration of doped silicon and realize the modulation function of the wave absorber on the absorption frequency band and the absorption rate of the terahertz waves. The terahertz wave absorption device is simple in structure, single in material, easy to process, high in terahertz wave absorption rate and wide in absorption bandwidth, has a light modulation function, and can be widely applied to multiple fields of imaging, stealth, communication, terahertz detection and the like.

The invention discloses Ni nanoparticle modified graphene and a preparation method of a wave-absorbing material of Ni nanoparticle modified graphene and belongs to the technical field of preparation of function materials. Firstly, low-defect graphite oxide is prepared with an improved Hummers method and subjected to ultrasonic oscillating, graphene oxide is obtained, and graphene oxide and Ni<2+> are reduced with a reducer in one step, so that Ni nanoparticles are sufficiently adsorbed on the surface of graphene; then, a product is blended with epoxy resin for preparation of a nano wave-absorbing material. Compared with the wave-absorbing performance of the same type of wave-absorbing materials, the wave-absorbing performance of the Ni nanoparticle modified graphene wave-absorbing material is greatly improved, and the Ni nanoparticle modified graphene wave-absorbing material has both electric absorption and magnetic absorption capability and has a higher effective absorption bandwidth. According to the preparation method, the raw materials are low in cost and easy to obtain; the experiment conditions are easy to realize; the preparation method has the advantages of simplicity in operation and small pollution.

The present invention belongs to the sound processing technical field and relates to a low-frequency composite sound absorption device. The device comprises a sound absorbing plate and Helmholtz resonators; sound absorbing holes and unit holes are formed in the sound absorbing plate, wherein a plurality of unit holes are provided; the number of the Helmholtz resonators is equal to the number of the unit holes; and the Helmholtz resonators are in one-to-one corresponding connection with the unit holes; openings are formed in the Helmholtz resonators; and the openings face the front surface side of the sound absorbing plate. When the low-frequency composite sound absorption device is to be used, the low-frequency composite sound absorption device can be mounted on the wall of a building, a ceiling, a door, a window or the like; one part of sound is absorbed by the sound absorbing holes in the sound absorbing plate, and the other part of the sound enters the cavities of the Helmholtz resonators through the unit holes and the openings of the Helmholtz resonators on the sound absorbing plate and moves in the cavities in a reciprocating manner so as to be dissipated; and the sound absorbing plate and the Helmholtz resonators are utilized to broaden absorption bandwidth; and the structure of the low-frequency composite sound absorption device is simple.

The invention relates to the technical field of an acoustic baffle and discloses a porous composite sound absorption structure. The porous composite sound absorption structure comprises a cover plate, side plates and a base plate. The cover plate and the base plate are in opposite arrangement at an interval, and the side plates are respectively closely connected with the cover plate and the base plate to form a sound absorption back cavity; and one or more porous material layers in opposite arrangement with the cover plate is arranged in the sound absorption back cavity, when there are multiple porous material layers, an acoustic baffle or a sound absorption membrane is arranged between two adjacent porous material layers, the cover plate is provided with a plurality of micro sound absorption holes, and each porous material layer is provided with a plurality of openings at intervals. According to the invention, under the condition that the complexity of the sound absorption structure is not increased, the sound absorption bandwidth of the sound absorption structure is enlarged; and the processing is easy, the installation is convenient, and the cost is quite low.

The invention provides a preparation method of an MXene composite fiber reinforced graphene aerogel wave-absorbing material. The preparation method comprises the following steps of: preparing MXene composite fibers; preparing a graphene oxide aqueous dispersion solution; adding the MXene composite fiber into the graphene oxide aqueous dispersion solution, then adding a reducing agent, and carrying out high-speed dispersion to obtain an MXene composite fiber-graphene oxide aqueous dispersion solution; putting the MXene composite fiber-graphene oxide aqueous dispersion solution into a reaction kettle, and obtaining MXene composite fiber reinforced graphene hydrogel through a hydrothermal self-assembly reaction; putting the MXene composite fiber reinforced graphene hydrogel into liquid nitrogen to pre-freeze the hydrogel, then carrying out freeze drying treatment so as to obtain the MXene composite fiber reinforced graphene aerogel wave-absorbing material. The wave-absorbing material provided by the invention gives consideration to impedance matching while improving the electromagnetic wave loss capability, and has stronger wave-absorbing loss and wider effective absorption bandwidth.

A preparation method of nano core-shell microwave absorbing material relates to in-situ obtaining core-shell structure Fe @ C @ Co3O4 nanometer powder by heat treatment of precursor and applying it inmicrowave absorbing field. The invention takes ferricyanide and cobalt salt as raw materials, firstly synthesizes the precursor nano-meter powder with core-shell structure, and secondly heat-treats the precursor to obtain Fe @ C @ Co3O4 nano-meter powder with core-shell structure in situ. The process is not only simple, but also has excellent microwave absorbing properties, especially wide absorption bandwidth, which has a good application prospect.

A ZnFe2O4@SiO2@RGO wave absorbent is obtained by compounding a ZnFe2O4@SiO2@RGO ternary complex and paraffin, wherein the ZnFe2O4@SiO2@RGO ternary complex is obtained by compounding magnetic loss zinc ferrite (ZnFe2O4), conductive and dielectric loss graphene (RGO) and SiO2 with favorable wave transmissivity. The wave absorbent has the minimum reflection loss of -43.9 dB within the range of 2-18 GHz, and the absorption bandwidth of smaller than 10 dB exceeds 6 GHz. The ZnFe2O4@SiO2@RGO wave absorbent is simple in preparation method, mild in preparation condition, pollution-free in preparation process and easy for realizing batch production, and therefore, has a good application prospect in such fields as electromagnetic wave shielding and absorption and stealth materials.

The invention discloses a two-dimensional titanate nanometer material and a preparation method thereof. The two-dimensional titanate nanometer material comprises a modified protonated titanate film which comprises organic groups and a doped Cr element. Through the doped Cr element which facilitates to broadening absorption bandwidth of the two-dimensional titanate nanometer material, the two-dimensional titanate nanometer material can absorb ultraviolet light and visible light, and greatly improves efficiencies of light absorption and photoelectric conversion, thereby improving photocatalytic efficiency. Meanwhile, through doping of the organic groups which are relatively large molecules and are used as a balance medium of nanometer sheets, the prepared two-dimensional titanate nanometer material is not easy to curl and has relatively-stable two-dimensional structure and relatively-large surface area, thereby further improving photocatalytic efficiency.

The invention provides a corrosion-resistant light broadband wave-absorbing coating and a preparation method thereof. The wave-absorbing coating comprises an electromagnetic wave absorbent, resin, a diluent, a curing agent, a filler and an auxiliary agent, wherein the electromagnetic wave absorbent comprises a carbon-based absorbent and a corrosion-resistant iron-based absorbent. According to the wave-absorbing coating, a compound system of the carbon-based absorbent and the corrosion-resistant iron-based absorbent is adopted, the advantages of the carbon-based absorbent and the corrosion-resistant iron-based absorbent are integrated, the wave-absorbing coating with the electrical loss characteristic and the magnetic loss characteristic is prepared, and strong absorption in a wide frequency range is achieved. Experiments show that the absorption peak intensity of a coating with the thickness of 1 mm prepared from the wave-absorbing coating exceeds -20 dB, and the absorption bandwidth smaller than or equal to -4 dB exceeds 7.4 GHz; and experiments show that the wave-absorbing coating prepared from the wave-absorbing coating can tolerate more than 2400 hours in neutral salt mist and can tolerate more than 300 hours in acid salt mist (pH 3.5).

Based on the principle of dual-cavity coupling, the present invention realizes an integrated all-fiber passive Q-switched pulsed fiber laser through in-band pumping, fully utilizes the wide absorption bandwidth and emission bandwidth of the doped gain fiber and there is a considerable overlap between the two range characteristics, the working band of the resonator is reasonably designed, and the dual functions of laser radiation gain and saturation absorption are realized in the doped gain fiber. The radiation laser of the first resonator is used to pump the second resonator, and the coupling cavity is realized. All-fiber integrated passive Q-switched pulsed fiber laser. At the same time, the difference between the core diameter of the second resonant cavity doped gain fiber and the first resonant cavity doped gain fiber is used to increase the energy density of the laser in the second resonant cavity doped gain fiber and improve the passive saturable absorber. Bleach switch ability. The pulsed fiber laser of the present invention has compact structure and stable performance, and truly realizes the all-fiberization of the pulsed fiber laser.

A broadband polarization-independent long-wave infrared absorber plate belongs to infrared absorber devices, overcomes the shortcomings that a conventional infrared absorber cannot draw the absorptivity, the absorption bandwidth and the duty cycle into consideration, and is broadband, polarization-dependent and compact in structure. The broadband polarization-independent long-wave infrared absorber plate sequentially comprises a substrate layer, a bottom metal layer, a dielectric layer and a top metal layer from bottom to top, wherein the top metal layer consists of a plurality of metal graphic groups in periodically array arrangement, the metal graphic groups are the same in structure, each metal graphic group consists of a plurality of metal graphic units in symmetrical arrangement and with approximate sizes, and each metal graphic unit, together with the dielectric layer and the bottom metal layer under vertical projection of the corresponding metal graphic unit, forms a resonant unit. The broadband polarization-independent long-wave infrared absorber plate can realize perfect absorption of electromagnetic waves with specific wavelengths, the resonant units can realize polarization-independent absorption and ultra-wide-band absorption, the structures and the distances of the resonant units are optimized, the structural duty cycle can be improved, and device miniaturization can be realized.

The invention belongs to the field of electromagnetic wave absorption and radiation control, and in particular relates to a design method of a terahertz broadband absorbing metamaterial. According to the effective medium theory, and using CST microwave studio to obtain S parameters through frequency domain simulation, the periodic unit structure is at x Both the and y directions are periodically distributed, and are set as periodic boundary conditions. Combining the parameters S11 and S21 obtained by scanning, the impedance value is calculated. By changing the period of the unit structure and the size of the metal thin film and dielectric material, the corresponding absorption frequency is adjusted, and multiple metal thin films and dielectric materials are cross-stacked in one unit period, so that the absorption lines corresponding to different resonant circular frustums are superimposed. The invention can effectively broaden the absorption spectrum of the terahertz frequency band, so that the frequency band with an absorption rate exceeding 90% can be widened, and meanwhile, a certain high relative absorption bandwidth can be guaranteed. And the first 9 absorption peaks are caused by the interior of the unit structure, so they are not affected by the period.

The invention relates to a magnetic reduction graphene oxide nano composite material and a preparation method and application thereof. The nano composite material comprises reduced graphene oxide andmagnetic nickel ferrite nanocrystalline with the average particle diameter of 6-12 nm uniformly deposited on the surface of the reduced graphene oxide. The method comprises the following steps: uniformly dispersing graphene oxide with deionized water to obtain graphene oxide dispersion liquid; adding divalent nickel salt and trivalent iron salt into the graphene oxide dispersion liquid, and uniformly stirring to obtain a first mixed solution; adding ammonia water into the first mixed solution to adjust the first mixed solution to be alkaline to obtain a second mixed solution; and carrying outhydrothermal treatment on the second mixed solution to obtain the nano composite material. The nano composite material has strong absorption strength, wide absorption bandwidth and double-band microwave absorption performance. The process is simple and convenient, the agglomeration problem of reduced graphene oxide and magnetic small-size nanocrystals can be avoided, and the microwave absorption performance and the effective absorption bandwidth of the composite material are improved.

The invention relates to the technical field of sound absorption plates, and discloses a composite resonance sound absorption structure. The structure comprises a bottom plate, side walls, and a cover plate. The cover plate and the bottom plate are arranged at an interval in an opposite manner. The side walls are respectively in tight connection with the bottom plate and the cover plate, thereby forming a sound absorption back cavity. The cover plate is provided with a plurality of miniature sound absorption holes and a plurality of composite sound absorption holes. Each composite sound absorption hole is provided with one sound absorption diaphragm. The cover plate is provided with the plurality of composite sound absorption holes, and the sound absorption holes are provided with the sound absorption diaphragms in a pasted manner, thereby enlarging the sound absorption bandwidth of the structure. The structure is easy to machine, is low in cost, is convenient to install, and is good in sound absorption effect.

The invention discloses a preparation method for a highly-oriented electromagnetic shielding membrane by assembling graphene and metal layer by layer. The method comprises the following steps of preparing a graphene oxide gel membrane from oversized fragment-free graphene oxide, freezing the graphene oxide gel membrane, and introducing the frozen graphene oxide gel membrane into a high-temperature furnace for high-temperature thermal treatment at 3,000 DEG C, thus acquiring an oriented graphene aerogel membrane with high heat conduction, electrical conduction and ultralight weight; depositing metal on the surface of a graphene sheet layer in the graphene aerogel membrane by chemical electroplating to obtain the electromagnetic shielding membrane taking a graphene membrane as a substrate and formed by stacking the grapheme and metal layer by layer; and pressing the graphene aerogel and metal composite membrane with high pressure to obtain the graphene and metal composite membrane. The graphene and metal composite membrane prepared according to the method has the advantages of high conductivity and wide absorption bandwidth, the thickness and the size both can be adjusted, a microstructure is regular, and the graphene and metal composite membrane has wide application prospect in the field of electromagnetic shielding and wave absorption.

The invention relates to an acoustic panel with a unit structure. The acoustic panel comprises an ultramicropore acoustic panel, a side edge plate and an acoustic back plate. The edge part of the ultramicropore acoustic panel is connected with the acoustic back plate through the side edge plate to form a sound absorption resonant cavity. The acoustic panel is characterized in that an sound absorption metal film parallel to the sound absorption resonant cavity or an sound absorption metal film with nano microspheres is arranged in the sound absorption resonant cavity. The acoustic panel not only has the advantages of wide sound absorption bandwidth and good noise reduction effects, but also has the advantages of simple structure and simplicity, convenience and reliability in process manufacture and assembly use. The acoustic panel is suitable for the occasions in various buildings where ceiling hanging and wall decoration are required, and particularly suitable for the occasions where high sound absorption is required.

The invention discloses broadband tunable terahertz wave absorber which comprise a doped semiconductor material substrate, A lay of microstructure array is fabricated on that surface of the substrateof the dope semiconductor material, the microstructure array comprises a plurality of uniformly arranged microstructure units, the microstructure unit is capable of responding to THz waves, A rectangular waveguide structure is also designed in the microstructure unit to increase the absorption bandwidth, A substrate of that dope semiconductor material is a p-type silicon material, the doping concentration is -0.3 *1017/cm<3>, A substrate thickness of that semiconductor material is 250 to 300 [mu]mm, the resistivity is 0.5 omega.cm, the microstructure unit is H-type microstructure unit, Each H-type microstructure unit is symmetrical with respect to the geometrical center, and the thickness of the H-type microstructure unit is 53 [mu]m. The invention also discloses a manufacturing method ofa broadband tunable terahertz wave absorber. The invention solves the problems that the terahertz wave device in the prior art is large in volume and limited in bandwidth.

The invention provides a wide-spectrum superconducting nanowire single photon detector. The wide-spectrum superconducting nanowire single photon detector comprises a substrate, a mirror which is located on the surface of the substrate, and a lamination structure which is located on the surface of the mirror. The lamination structure comprises at least two layers of superconducting nanowires which are arranged up and down. According to the wide-spectrum superconducting nanowire single photon detector provided by the invention, the absorption of two or more layers of superconducting nanowires is realized by arranging the lamination structure which comprises at least two layers of superconducting nanowires arranged at intervals up and down on the mirror; the efficient absorption bandwidth of the wide-spectrum superconducting nanowire single photon detector is expanded; and the absorption efficiency is high.

The invention relates to a low-frequency sound absorption metamaterial, and belongs to the technical field of sound absorption metamaterials. The sound absorption metamaterial disclosed by the invention is mainly based on a circuit control theory of a piezoelectric material, a piezoelectric film and a piezoelectric stack are independently regulated and controlled through a piezoelectric film circuit and a piezoelectric stack circuit, and the matching condition of the acoustic resistance and the acoustic reactance can be greatly improved without changes of the geometric configuration and the size. The sound absorption strength, the sound absorption frequency and the sound absorption bandwidth of the sound absorption metamaterial are regulated and controlled, a wide sound absorption frequency range is achieved for sound waves below 300 Hz, and the sound absorption frequency can be regulated within the wide range. The sound absorption metamaterial is small in structural thickness, small in size and high in sound absorption efficiency, and the limitation of a traditional method and a common metamaterial in low-frequency (smaller than or equal to 300 Hz) sound absorption is broken through.

The invention discloses a terahertz switch and a control method based on a periodic graphene structure absorption characteristic. According to the invention, a multilayer graphene array is adopted, and the multilayer graphene array is provided with different resonance absorption peaks, so that wider absorption bandwidth is obtained; the resonance absorption frequency of the graphene array is adjusted by changing a bias voltage, thereby controlling the on-off of the corresponding frequency of the output wave and realizing the switching function; due to the high electron mobility characteristicof the graphene, the switch has a faster switching speed; the ON/OFF state of the switch is switched by adopting an electric tuning mode, and the switch is simple in operation and low in energy consumption; the switch works in the terahertz frequency band, the application range of the terahertz device is widened; By changing the effective length of the graphene unit of the graphene array, the terahertz switch is suitable for the input wave and the output wave which are terahertz wave, microwave, infrared or visible light.