CN109551757B - Preparation method of flexible terahertz wave-absorbing material - Google Patents
Preparation method of flexible terahertz wave-absorbing material Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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Abstract
The invention discloses a preparation method of a flexible terahertz wave-absorbing material, which comprises the following steps: step 1, preparing rubber-tin powder mixture wires with different addition ratios by taking tin powder or tin alloy powder with low melting point and rubber particles as raw materials, wherein the addition ratios of the tin powder and the rubber are completed according to the interpolation of a conductive characteristic curve; step 2, respectively taking pure rubber wires and the rubber-tin powder mixture wires prepared in the step 1 as raw materials, and preparing a double-layer flexible film by adopting a three-dimensional forming machine; step 3, carving a structure with patterns in the flexible film by using a laser carving machine to prepare the flexible terahertz wave-absorbing material; wherein, the design of the material is completed by adopting simulation and theoretical calculation. The material prepared by the invention has the characteristics of good flexibility, light weight, convenient design and easy assembly of absorption frequency and the like, can be applied to the scaling electromagnetic scattering test of a large target, has the advantages of good oxidation resistance, corrosion resistance and the like, and is a complex electromagnetic material with better application prospect.
Description
Technical Field
The invention relates to design and manufacture of a flexible terahertz wave-absorbing material, and the prepared product aims at terahertz microwave devices, large-scale target terahertz wave band measurement and the like, can realize the electromagnetic interference of the microwave devices under the terahertz wave band and the reflection and transmission characteristics of targets on electromagnetic waves under the terahertz wave band scale test condition, and is suitable for various military and civilian targets.
Background
Terahertz (THz) is an electromagnetic wave whose frequency lies between the microwave and infrared spectral regions. With the development of the photoelectronic technology and the low-scale semiconductor technology, terahertz electromagnetic waves are extensively and deeply studied in various countries and research institutes thereof. The terahertz electromagnetic wave has good development prospects in the fields of disease detection, environmental protection, drug suppression and counter terrorism, security inspection, national defense, space exploration, interplanetary communication and the like. The terahertz wave absorbing material is developed while the application research of the terahertz wave is developed. The terahertz wave-absorbing material absorbs and converts most of energy of electromagnetic waves incident to the surface of the terahertz wave-absorbing material, and reflects little. According to different loss mechanisms of materials, the absorbed electromagnetic waves are converted into heat energy or energy in other forms, and the function of energy loss is realized.
At present, terahertz wave-absorbing materials mainly comprise two types: conventional particles and a binder, and a metamaterial based on a micro-nano structure. The terahertz wave-absorbing material of the mixture can adopt thermoplastic polyurethane, epoxy resin, rubber and the like as adhesives, and various materials such as carbon fiber, carbon black, polyaniline, glass beads and aluminum powder are used as absorbents, and then the composite coating with the multilayer structure is prepared on the basis. For the metamaterial type, its wave-absorbing properties do not depend on the fundamental physical properties of its structural components, but on the shape and distribution of the particular pattern contained within the structure. The internal size of the terahertz wave band is required to be smaller than the wavelength of electromagnetic waves, the wavelength of the electromagnetic waves in the terahertz wave band is usually in the micron order, so that the preparation of the metamaterial in the terahertz wave band is required to depend on a micro-nano processing technology, parameters are required to be strictly controlled, and the preparation of the wave-absorbing material meeting the reflectivity requirement is difficult.
At present, serial researches are carried out on a design and manufacturing method of a terahertz wave absorbing material, and patent CN200910216064.4 discloses a terahertz wave plane absorbing material, wherein a continuous metal reflecting layer is firstly prepared on the surface of a substrate, then a dielectric layer is prepared, and then an artificial electromagnetic medium layer is prepared on the dielectric layer, the absorbing material has 2 strong absorption frequency bands, the size of the absorbing material reaches micron level, a micro-nano preparation process is required, and the cost is high. The patent CN201710488566.7 discloses a method for preparing a terahertz wave absorbing body and its application, where the terahertz wave absorbing body includes an antenna array, a dielectric layer and a metal layer arranged in sequence from top to bottom, the antenna array includes antenna units, four antenna structures are rotationally symmetric, the antenna structures are unsealed in a concave structure, the dielectric layer makes the phase difference between the electromagnetic wave reflected by the antenna layer and the electromagnetic wave reflected by the metal layer 180 °, so as to achieve the microwave loss, and the prepared antenna unit has a complex structure, a small size and a high preparation precision. Patent CN201710407421.X discloses a design method of a terahertz broadband absorption metamaterial, which adopts a plurality of circular truncated cones and media which are alternately stacked together to form a unit period, simulates S parameters of a periodic structure by CST software according to an effective medium theory, calculates an impedance value, and realizes broadband absorption of the material by changing the unit period size and the sizes of a metal film and a medium material. Patent CN201410294724.1 discloses a broadband high-performance artificial terahertz wave-absorbing material and a design method thereof, the material is composed of a plurality of units, each material unit comprises chromium and photoresist SU-8, the two units are stacked in a crossed manner, wherein, a chromium square array has 5 layers, the thickness of each layer is 200nm, the side length is in a gradual change state, the thickness of the photoresist is 4 microns, the unit period is 95 microns, the preparation process of the structure is complex, the precision requirement is high, and the efficiency is low. Patent CN201310477713.2 discloses an absorption bandwidth developments adjustable terahertz wave absorption body in succession, every wave absorption body unit is by the silicon substrate, the silicon nitride layer, electrode layer and polycrystalline silicon pattern layer are constituteed, be equipped with the hole that a plurality of confession anchor point passed through on the electrode layer, polycrystalline silicon pattern layer is fixed in on the silicon nitride layer through the anchor point, polycrystalline silicon pattern layer is including the square support block that is located same horizontal plane, interior square support ring and foreign side shape support ring, including L type shell fragment between the interior outside direction support ring, dynamic adjustment has been realized, this type of material structure is complicated, small in size, it is big to make the degree of difficulty. Patent CN201310483331.0 proposes a method for manufacturing a terahertz narrow-band wave absorber with dynamically adjustable absorption peak position, which mainly includes processes of multilayer thin film deposition, photolithography, dry etching, wet etching and the like on a silicon substrate. The wave absorber is an array structure, the center of each unit contains a micro-reflector which can rotate around a shaft under the action of electrostatic force, the center of the surface is provided with an I-shaped metal resonator which is used for generating resonance absorption, the wave absorber can realize dynamic adjustment of an absorption peak, but the structure is still complex, and the adjustment condition of the reflector is easily interfered by the outside. The U.S. patent US 5260513 reports a wedge-shaped silicon rubber terahertz wave-absorbing material, the groove angle of the wave-absorbing material wedge-shaped structure is 22.5 degrees, iron oxide is used as an absorbent, and the absorption of terahertz waves of 0.3 THz-3.0 THz is larger than-60 dB. The reflectivity of the wedge-shaped Microwave absorbing materials RIRAM-500 and TERASORB-500 of the university of Massachusellahol and the reflectivity of the pyramid-shaped Microwave absorbing material Eccosorb VFX-NRL-2 of Emerson and Cuming Microwave company of Belgium to terahertz waves of 0.31THz can reach about-40 dB, however, the material is generally thicker and is not suitable for the design of a scaling stealth coating.
In a word, various terahertz wave-absorbing materials are researched at present, micro-nano manufacturing is needed for metamaterial, various filling type wave-absorbing materials are mainly focused on low-thickness narrow frequency bands or high-thickness wide frequency bands, the design and preparation methods are single, and the cost is high.
Disclosure of Invention
The invention aims to overcome the defects of complex process, low efficiency, complex structure of prepared material, high requirement on precision, high preparation difficulty, high cost and the like in the prior art, provides design and preparation of a flexible terahertz wave-absorbing material, introduces an integrated concept of material and structure into the design and preparation, establishes an electric continuous network through a mixture extrusion process on the basis of particle mixing (tin powder is mixed in hot melt rubber in rubber heating, the tin powder is also changed from solid into liquid after being heated, and the tin particles are changed into fibers in a cooling process, and the fibers are uniformly distributed in the rubber to form a conductive network), constructs a template by using a three-dimensional molding process, and completes the construction of a metamaterial by using a laser engraving mode. The material prepared by the invention has the characteristics of light weight, good absorption, flexibility, easy assembly and the like, can be applied to the scaling electromagnetic scattering test of a large target, and is an electromagnetic material with application prospect.
In order to achieve the purpose, the invention provides a preparation method of a flexible terahertz wave-absorbing material, which comprises the following steps:
step 1, preparing rubber-tin powder mixture wires with different addition ratios by taking tin powder or tin alloy powder with low melting point and rubber particles as raw materials, wherein the addition ratios of the tin powder and the rubber are completed according to the interpolation of a conductive characteristic curve; designing a terahertz wave-absorbing material, determining a leakage threshold value of the tin-rubber composite material and a structure of the wave-absorbing material, and determining the proportion of a rubber-tin powder mixture wire in the wave-absorbing material according to the leakage threshold value; the low melting point is within a melting point range of 210-230 ℃, the low melting point is a key for realizing the melting of the tin powder in the hot-melt rubber, if the melting point of the hot-melt rubber is too low, the tin powder is difficult to melt in the rubber and still distributed in a spherical powder form, a conductive network is difficult to form, and the conductivity is low.
step 3, carving a structure with patterns in the flexible film by using a laser carving machine according to the structural design of the terahertz wave-absorbing material to prepare the flexible terahertz wave-absorbing material;
the design of the terahertz wave-absorbing material is completed by adopting simulation and theoretical calculation; the terahertz wave-absorbing material comprises the following design steps: determining a leakage threshold value of the tin-rubber composite material and designing a structure of the wave-absorbing material; wherein the tin-rubber composite leakage threshold is determined by a leakage threshold curve; the structural design comprises the thickness of the wave-absorbing material, the carving pattern, the pattern size and the unit size.
The simulation and theoretical calculation are completed under a CST software platform, the calculation method is a time domain finite integration method, the data needing to be input comprises a unit structure model of the material, material parameters (including conductivity and dielectric constant), and the result of the simulation calculation is mainly the reflectivity of the material.
Preferably, in the step 1, the rubber is TPU, and the particle size of the rubber is 1 mm-5 mm; the particle size of the tin powder or the tin alloy powder is 200-500 meshes, and the weight ratio of the tin powder to the tin alloy powder is 10-70%.
Preferably, in the step 1, a screw extruder is used for preparing the rubber-tin powder mixture wire, wherein the diameter of a screw of the screw extruder is 30-45 mm, the length-diameter ratio of the screw is 10-25, the extrusion section of the screw extruder adopts a die heating mode, the die heating temperature is 160-200 ℃, and the diameter of the extruded wire is 3 mm.
Preferably, the step 2 comprises:
step 2.1, preparing a first thin film layer by using a three-dimensional forming machine by using a pure rubber wire as a raw material;
and 2.2, preparing a second thin film layer on the first thin film layer by using the rubber-tin powder mixture wire prepared in the step 1 as a raw material and adopting a three-dimensional forming machine, wherein the first thin film layer and the second thin film layer form a double-layer flexible thin film.
Preferably, the design of the terahertz wave-absorbing material comprises: determining a leakage threshold value of the tin-rubber composite material and designing a material structure; wherein, the leakage threshold value of the tin-rubber composite material is determined by a leakage threshold value curve, and the leakage threshold value curve is completed by adopting an experimental method; the structural design includes the thickness of the material, the engraved pattern, the pattern size and the cell size.
Preferably, the experimental method is that the conductive property of the material is determined according to the wire rods with different addition ratios prepared in the step 1, and on the basis of testing the conductive property, a relation curve among a leakage threshold value, the conductive property and a filling ratio can be obtained, wherein the addition ratios are 10%, 20%, 30%, 40%, 50% and 60% by mass.
Preferably, the thickness of the material is 0.05-0.1 mm, the pattern is cross-shaped or double-ring-shaped, and the unit size is 5-10 mm.
Preferably, the cruciform pattern has a width of 0.2mm and an overall length of 0.8mm, and the double annular pattern has a width of 0.2mm and a radius of 0.3 mm.
Preferably, the three-dimensional forming machine is provided with double printing nozzles, wherein one printing nozzle is used for printing the conductive tin rubber material, and the other printing nozzle is used for printing the pure rubber material; the temperature of the double printing nozzles is set between 190 ℃ and 230 ℃, the temperature of the hot bed is kept between 50 ℃ and 60 ℃, and the printing speed is 15 mm/s to 25 mm/s. The hot bed is a part of a three-dimensional forming machine and is used for supporting a printed model and can better keep the fixed state of the model after being heated to a certain temperature.
Preferably, the laser engraving machine uses He-Ne as indicating light, the resonant cavity is a symmetrical flat cavity, the diameter of a machine focusing light spot is 0.1 mm-0.8 mm, a focusing head with a focal length of 100mm is adopted, a processing film is placed 0.05 mm-0.2 mm below a focal point (namely, the vertical distance between the film and the focusing point), and engraving of the material is completed through computer program control.
The invention provides a method for manufacturing a terahertz wave-absorbing material by adopting a three-dimensional forming and laser engraving process on the basis of preparing a conductive flexible wave-absorbing wire, and the design of the material is finished by adopting simulation and theoretical calculation. The method comprises the steps of taking tin powder (or alloy powder of tin) with a low melting point and rubber particles as raw materials, preparing a mixture wire of rubber and the tin powder by using a screw extruder, wherein the adding proportion of the tin powder and the rubber is completed according to the interpolation of a conductive characteristic curve, analyzing a terahertz wave absorbing frequency band by using electromagnetic simulation software, preparing a flexible film by using a three-dimensional forming machine for the prepared mixture wire, and finally engraving a structure with a pattern in the flexible film by using a laser engraving machine, thereby preparing the flexible terahertz wave absorbing material. The input data analyzed by the electromagnetic simulation software are a unit structure model of the material, and parameters of conductivity and dielectric constant. The output result mainly comprises the reflectivity of the material and the determined wave-absorbing frequency band. The frequency band is used for preparing a scaling material and carrying out a scaling test.
The design and manufacture of the flexible terahertz wave-absorbing material provided by the invention can realize that a microwave device avoids electromagnetic interference phenomenon under a terahertz waveband, and can also be applied to keeping the reflection and transmission characteristics of a target under the irradiation of electromagnetic waves under the condition of terahertz waveband scaling test. Different from the forming mode of other conventional terahertz wave-absorbing materials, the terahertz wave-absorbing material is manufactured by combining three-dimensional forming and laser engraving so as to meet the expected electromagnetic property requirement. Compared with the prior art, the invention has the following advantages:
(1) the invention can realize the manufacture of a complex wave-absorbing structure by utilizing a three-dimensional forming process, and has high forming efficiency and low cost.
(2) According to the invention, the micro structure of the terahertz wave-absorbing material is constructed by laser engraving, the structural size of the terahertz metamaterial is larger than the micro-nano scale, the unit area of the sample piece is large when the required wave-absorbing performance is realized, and the processing efficiency is high.
Drawings
FIG. 1 is a flow chart of the preparation of the flexible terahertz wave-absorbing material.
FIG. 2 is a structural diagram of the flexible terahertz wave-absorbing material.
FIG. 3 is a reflectivity curve of the terahertz wave-absorbing material of the invention.
Detailed Description
The technical solution of the present invention is further described below with reference to the following embodiments and the accompanying drawings.
As shown in fig. 1, the design and preparation method of the flexible terahertz wave-absorbing material provided by the invention comprises the following steps:
step 1 (S1), flexible conductive wire preparation
The preparation method of the flexible conductive wire rod takes flexible thermoplastic elastomer polyurethane (also called TPU) and tin powder or tin alloy powder as raw materials, wherein the size of tin powder particles is 200-500 meshes, the particle size of the TPU powder is 1-5 mm, the two powders are mixed, and the weight ratio of the two powders is 20-70%. A special single-screw extruder is adopted for mixing materials, the diameter of a screw is 30-45 mm, and the length-diameter ratio of the screw is 10-25. The machine barrel is designed in four sections, namely a feeding section, two compression sections and a metering section. Rectangular grooves are formed in the inner wall of a machine barrel of the extruder from the feeding section to the tail end of the compression section so as to prevent materials from slipping, and pressure is established through the feeding section in the preparation process so as to push the materials to advance. The extrusion section adopts a die heating mode, the die heating temperature is 160-200 ℃, and the diameter of the extruded wire is 3 mm. And finally, collecting the extruded wires to obtain the three-dimensional formed wires.
Terahertz wave-absorbing material design
The design of the terahertz wave-absorbing material mainly comprises two parts, namely determination of a leakage threshold value of a tin/rubber composite material and material structure design.
The conductive property of the tin/rubber composite material depends on conductive tin fibers in the composite material, and the conductive tin/rubber composite material is different from a conductive mixture prepared by filling powder to a certain extent, because the melting point of rubber in extrusion is higher than that of tin powder, the molten tin powder is easy to form a loose conductive network in the extrusion process, a leakage threshold value curve is completed by adopting an experimental method, namely the conductive property of the material is determined according to various wire rods prepared in the first step, for example, the addition ratio is 10%, 20%, 30%, 40%, 50% and 60%, and on the basis of testing the conductive property, a relation curve among the leakage threshold value, the conductive property and the filling ratio can be obtained.
The design of the terahertz wave-absorbing material further comprises the thickness of the material, the carving pattern, the pattern size and the unit size. The selected unit size is 5-10 mm, the material thickness d = 0.05-0.1 mm, the shape is cross, double ring, I-shaped and the like, wherein the width of the cross is 0.2mm, the total length is 0.8mm, the width of the double ring is 0.2mm, and the radius is 0.3 mm.
Step 2 (S2), three-dimensional forming of the terahertz wave-absorbing film
Establishing a unit model file, introducing a cuboid with the size of 100mm multiplied by 0.15mm into cutting software corresponding to a three-dimensional forming machine, controlling the roughness of the formed surface in the preparation of a sample piece, selecting the controlled element as printing interlayer spacing, and then cutting and analyzing the material to generate a cod file which is stored in a storage medium of the three-dimensional forming machine.
The preparation of the template is carried out by utilizing a three-dimensional forming machine, the printer is of a double-nozzle type, one nozzle is used for printing the conductive tin rubber material, the other nozzle is used for printing the pure rubber material, the thickness of the bottom layer is 0.1mm in actual operation, the pure rubber is adopted for printing, and the subsequent height is adopted for printing by adopting the conductive tin rubber material. In addition, other parameters that require setting of printing include printing temperature and printing speed. The temperature of the printing head is set between 190 ℃ and 230 ℃, the temperature of the hot bed is kept between 50 ℃ and 60 ℃, and the printing speed of the model is 15 mm/s to 25 mm/s. And printing to obtain the three-dimensional flexible film.
Step 3 (S3), laser engraving of the terahertz wave-absorbing material
The laser of the carving machine of the wave-absorbing material adopts He-Ne as indicating light, and the resonant cavity is a symmetrical flat cavity. The output average power of the machine is maximum 450W, the pulse width is adjustable within 0.1-10ms, the frequency is adjustable within 1-1000Hz, the power instability degree is less than 2%, and the diameter of a focusing light spot is 0.8-0.1 mm. A focusing head with a focal length of 100mm is adopted, a processed film is placed below the focal point by 0.05 mm-0.2 mm, and the carving of the material can be completed through computer program control.
Example 1
1. Preparation of flexible conductive wire
The preparation of the flexible conductive wire takes flexible thermoplastic elastomer polyurethane (also called TPU) and tin powder or tin alloy powder as raw materials, wherein the average size of tin powder particles is 400 meshes, the average particle size of TPU powder is 3mm, the two powders are mixed, and the weight ratio of the two powders is 10%, 20%, 25%, 30%, 40%, 50% and 60%. From 10% to 60% were prepared for the samples in order to obtain a relationship between conductivity and addition ratio for determining the leakage threshold. The different ratios are for better interpolation to determine the leakage threshold. A special single-screw extruder is adopted for mixing materials, the diameter of a screw is 30mm, and the length-diameter ratio of the screw is 20. The extrusion section adopts a mode of heating by a die, the heating temperature of the die is 200 ℃, and the diameter of the die is 3 mm. And finally, collecting the extruded wires to obtain the three-dimensional formed wires.
2. Terahertz wave-absorbing material design
According to various flexible conductive wires prepared in the step 1, determining the conductive characteristics of the materials according to the relation between the addition ratio and the conductivity, determining the leakage threshold value to be 30%, selecting the addition ratio to be 10%, and the conductivity to be 6 multiplied by 104And (5) S/m. The terahertz wave-absorbing material is designed mainly by the thickness, the carving pattern, the pattern size and the unit size of the material. Specifically, as shown in FIG. 2, the unit has a size of 4mm, a material thickness of 0.1mm, and a cross shape with a width of 0.1mm and a total length of 0.8mAnd m is selected. The reflectivity curve calculated through simulation is shown in figure 3, and it can be seen that the material has good absorptivity within the range of 0.57 THz-0.59 THz, and the lowest reflectivity reaches-14 dB.
3. Three-dimensional forming of terahertz wave-absorbing film
Establishing a unit model file, introducing a cuboid with the size of 100mm multiplied by 0.15mm into cutting software corresponding to a three-dimensional forming machine, controlling the roughness of the formed surface in the preparation of a sample piece, selecting the controlled element as printing interlayer spacing, and then cutting and analyzing the material to generate a cod file which is stored in a storage medium of the three-dimensional forming machine.
And preparing a template by using a three-dimensional forming machine. The preparation of the template is carried out by utilizing a three-dimensional forming machine, the printer is of a double-nozzle type, one nozzle is used for printing the conductive tin rubber material, the other nozzle is used for printing the pure rubber material, the thickness of the bottom layer is 0.1mm in actual operation, the pure rubber material is adopted for printing, and the subsequent height of the bottom layer is 0.05mm, and the conductive tin rubber material is adopted for printing. Print parameters, including print temperature and print speed, need to be set in preparation. Wherein the temperature of the printing head is set at 230 ℃, the temperature of the hot bed is kept at 50 ℃, the printing speed of the model is 25mm/s, and finally the flexible film can be obtained by printing.
4. Terahertz wave-absorbing material laser engraving
The laser of the carving machine of the wave-absorbing material adopts He-Ne as indicating light, and the resonant cavity is a symmetrical flat cavity. The output average power of the machine is 300W, the pulse width is adjustable within 0.1-10ms, the frequency is adjustable within 1-1000Hz, the power instability degree is less than 2%, and the diameter of a focusing light spot is 0.1 mm. A focusing head with the focal length of 100mm is adopted, a processed film is placed 0.05mm below the focal point, and the carving of the material can be completed through the control of a computer program.
In conclusion, on the basis of preparing the conductive flexible wave-absorbing micro powder, the manufacturing of the terahertz wave-absorbing material is completed by adopting a three-dimensional forming and laser engraving process, and the design of the material is completed by adopting simulation and theoretical calculation. The method is characterized in that tin powder (or alloy powder of tin) with a low melting point and rubber particles are used as raw materials, a screw extruder is used for preparing a mixture wire of thermoplastic elastomer polyurethane and the tin powder, wherein the adding proportion of the tin powder and the rubber is completed according to the interpolation of a conductive characteristic curve, a terahertz wave absorption frequency band is completed by adopting electromagnetic simulation software analysis, a three-dimensional forming machine is used for preparing a flexible film for the mixture wire and a pure rubber wire, and finally a laser engraving machine is used for engraving a structure with patterns in the flexible film, so that the flexible terahertz wave absorption material is prepared.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.
Claims (10)
1. A preparation method of a flexible terahertz wave-absorbing material is characterized by comprising the following steps:
step 1, preparing rubber-tin powder mixture wires with different addition ratios by taking low-melting-point tin powder or tin alloy powder and rubber particles as raw materials, designing a terahertz wave-absorbing material, determining a leakage threshold value of a tin-rubber composite material and a structure of the wave-absorbing material, and determining the ratio of the rubber-tin powder mixture wires in the wave-absorbing material according to the leakage threshold value;
step 2, respectively taking a pure rubber wire and a rubber-tin powder mixture wire in a proportion determined by the leakage threshold value as raw materials, and preparing a double-layer flexible film by using a three-dimensional forming process;
step 3, carving a structure with patterns in the flexible film by using a laser carving machine according to the structural design of the terahertz wave-absorbing material to prepare the flexible terahertz wave-absorbing material;
the design of the terahertz wave-absorbing material is completed by adopting simulation and theoretical calculation; the terahertz wave-absorbing material comprises the following design steps: determining a leakage threshold value of the tin-rubber composite material and designing a structure of the wave-absorbing material; wherein the tin-rubber composite leakage threshold is determined by a leakage threshold curve; the structural design comprises the thickness of the wave-absorbing material, the carving pattern, the pattern size and the unit size.
2. The preparation method of the flexible terahertz wave-absorbing material according to claim 1, wherein in the step 1, the rubber is TPU, and the particle size of the rubber is 1mm to 5 mm; the particle size of the tin powder or the tin alloy powder is 200-500 meshes, and the weight ratio of the tin powder or the tin alloy powder is 10-70%.
3. The preparation method of the flexible terahertz wave-absorbing material as claimed in claim 1, wherein in the step 1, a screw extruder is used for preparing the rubber-tin powder mixture wire, wherein the diameter of the screw is 30-45 mm, and the length-diameter ratio of the screw is 10-25; the extrusion section of the screw extruder adopts a die heating mode, the die heating temperature is 160-200 ℃, and the diameter of the extruded wire is 3 mm.
4. The method for preparing the flexible terahertz wave-absorbing material according to claim 1, wherein the step 2 comprises:
step 2.1, preparing a first thin film layer by using a three-dimensional forming machine by using a pure rubber wire as a raw material;
and 2.2, preparing a second thin film layer on the first thin film layer by using the rubber-tin powder mixture wire prepared in the step 1 as a raw material and adopting a three-dimensional forming machine, wherein the first thin film layer and the second thin film layer form a double-layer flexible thin film.
5. The method for preparing the flexible terahertz wave-absorbing material according to claim 4, wherein the three-dimensional forming machine is provided with double printing nozzles, one of the printing nozzles is used for printing the conductive tin rubber material, and the other printing nozzle is used for printing the pure rubber material; the temperature of the double printing nozzles is set to be 190-230 ℃, the temperature of the hot bed is kept to be 50-60 ℃, and the printing speed is 15-25 mm/s.
6. The method for preparing the flexible terahertz wave-absorbing material according to claim 1, wherein the leakage threshold curve is completed by an experimental method.
7. The method for preparing the flexible terahertz wave-absorbing material according to claim 6, wherein the experimental method is that the conductive property of the material is determined according to the wires with different addition ratios prepared in the step 1, and a relation curve among a leakage threshold value, the conductive property and a filling ratio is obtained on the basis of testing the conductive property, wherein the addition ratio of tin powder to rubber is 10-70% by mass.
8. The preparation method of the flexible terahertz wave-absorbing material as claimed in claim 1, wherein the thickness of the material is 0.05-0.1 mm, and the pattern is in a cross shape or a double ring shape.
9. The method for preparing the flexible terahertz wave-absorbing material as claimed in claim 8, wherein the width of the cross-shaped pattern is 0.2mm, the total length is 0.8mm, the width of the double annular pattern is 0.2mm, and the radius is 0.3 mm.
10. The method for preparing the flexible terahertz wave-absorbing material as claimed in claim 1, wherein the laser engraving machine uses He-Ne as indicating light, the resonant cavity is a symmetrical flat cavity, the diameter of a machine focusing light spot is 0.1 mm-0.8 mm, a focusing head with a focal length of 100mm is adopted, a processing film is placed 0.05 mm-0.2 mm below a focal point, and engraving of the material is completed through computer program control.
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| CN111154264B (en) * | 2020-01-06 | 2021-03-19 | 四川大学 | Flexible terahertz dynamic regulation and control material based on stress driving and preparation method thereof |
| CN111896811B (en) * | 2020-08-03 | 2023-03-24 | 北京环境特性研究所 | Method for inhibiting influence of video leakage on scattering measurement |
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