Impedance gradient wave-absorbing material and preparation method thereof

Abstract

The invention discloses an impedance gradient wave-absorbing material and a preparation method thereof, and belongs to the field of electromagnetic wave-absorbing materials. The impedance gradient wave-absorbing material is prepared by using a thermoplastic wave-absorbing material and adopting a 3D printing technology, on the basis of an existing structural wave-absorbing material, the material concentration gradient is increased, the impedance matching characteristic is improved, and the wave-absorbing performance is further improved; the concentration-adjustable thermoplastic wave-absorbing material is prepared by regulating and controlling the 3D printing preparation process, and impedance gradual change of the structure is achieved; the technology is simple in process, convenient to operate and high in safety, preparation can be simply and rapidly completed after parameters are determined, the reflection loss of the prepared impedance gradient wave-absorbing material in a 4-8 GHz electromagnetic wave frequency band reaches-10 dB, and the reflection loss in a 8-18 GHz electromagnetic wave frequency band reaches-15 dB.

Description

Technical Field

[0001] The present invention relates to the field of wave absorbing materials, and in particular to a wave absorbing material with a gradient impedance and a preparation method thereof. Background Art

[0002] In recent years, the design and preparation of broadband high-efficiency absorbing materials has received extensive attention from scholars at home and abroad. Studies have shown that the dielectric constant frequency response characteristics of homogeneous carbon composite materials are difficult to meet the impedance matching requirements for broadband strong absorption. Appropriate structural design can effectively broaden the absorption band and increase the absorption intensity, thereby greatly improving its broadband absorbing performance. In the prior art, in order to broaden the absorption band and increase the absorption intensity, the impedance gradient of the material is achieved by adopting a multi-layer stepped structure or a pointed cone structure. Combining the electromagnetic parameter control of the absorber and the optimized design of the absorbing structure to achieve the wave impedance gradient of the absorbing material, good broadband impedance matching can be obtained, so that the absorption band can be broadened.

[0003] 3D printing technology has been widely used in the rapid preparation of structural absorbing materials in recent years due to its advantages such as strong technical flexibility and high dimensional accuracy. 3D printing technology is a technology that manufactures solid parts by gradually accumulating materials. The bottom-up, layer-by-layer accumulation process characteristics give it obvious advantages in molding complex structures. Light-curing 3D printing is a widely used preparation process for preparing metamaterial absorbing structures.

[0004] In view of this, the present invention provides an impedance gradient absorbing material which has good absorbing performance and can achieve different absorbing performances by adjusting the concentration of its own material, which is prepared by adopting 3D printing technology. Summary of the invention

[0005] In order to solve the problems of the prior art, the main purpose of the present invention is to provide an impedance gradient absorbing material and a preparation method thereof. Based on the existing structural absorbing materials, the present invention uses 3D printing preparation technology to design the composition and concentration of each layer of absorbing materials, improve the impedance matching characteristics, and further improve the absorbing performance. The preparation method is simple and the adjustment method is controllable. The prepared impedance gradient absorbing material has a reflection loss of -10dB in the 4-8GHz electromagnetic wave band and a reflection loss of -15dB in the 8-18GHz electromagnetic wave band.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: A method for preparing an impedance gradient absorbing material comprises the following steps: S1. Obtain 3D printing filaments: blend the absorbent and the resin through a twin-screw extruder and extrude them. The prepared 3D printing filaments of different concentrations have a diameter of 1.75 mm. The filaments are rolled up and set aside for use; S2. Feed the 3D printing filament into the nozzle of the 3D printer, import the printed digital model into the 3D printer, slice the structure, set the printing process, set the printing filling rate of each layer of the gradient absorbing material in turn, or alternately print the absorbing materials of each nozzle when printing the same layer to adjust the proportion of different absorbing materials, and then print to obtain the impedance gradient absorbing material.

[0007] In the above technical solution, by selecting a single-nozzle, double-nozzle or triple-nozzle 3D printer, thermoplastic absorbing materials with different concentrations in each layer are prepared to achieve a variety of concentration gradients in any structure.

[0008] Optionally, in step S1, the concentration of the absorbent in the 3D printing filament is 2% to 60%wt.

[0009] Optionally, in step S1, the absorbent is a carbon-based or magnetic absorbent, including at least one of carbon nanotubes, graphene, carbon fiber, carbon black, carbonyl iron powder, alloy powder, and ferrite.

[0010] Optionally, in step S1, the resin includes at least one of acrylonitrile butadiene styrene (ABS), polyamide (PA), polyphthalamide, thermoplastic polyurethane, and polylactic acid.

[0011] Optionally, in step S2, the temperature of the printing platform for 3D printing is 90° C.-110° C., the printing speed is 20 mm / s-60 mm / s, and the filling rate is 25%-100%.

[0012] In the above technical solution, by adjusting the printing process and the printing filling density of each layer of absorbing material, the volume proportion of each layer of absorbing material can be controlled, thereby controlling the concentration of each layer of material and preparing a structural absorbing material with a concentration gradient.

[0013] Optionally, the impedance gradient absorbing material structure is any one of a pointed cone type, a honeycomb type or a flat plate type.

[0014] Optionally, the number of stacked layers of the impedance gradient absorbing material is 3-15 layers.

[0015] The present invention also provides an impedance gradient absorbing material prepared by the above preparation method.

[0016] According to the above technical solution, the reflection loss of the impedance gradient absorbing material obtained by the present invention reaches -10dB in the 4-8GHz electromagnetic wave band, and the reflection loss reaches -15dB in the 8-18GHz electromagnetic wave band.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. Based on the existing structural absorbing materials, the present invention adopts 3D printing preparation technology to increase the material concentration gradient, improve the impedance matching characteristics, and further improve the absorbing performance. The reflection loss of the absorbing material in the 4-8GHz electromagnetic wave band reaches -10dB, and the reflection loss in the 8-18GHz electromagnetic wave band reaches -15dB; the impedance gradient absorbing material with different absorbing performances is achieved by adjusting the printing process.

[0018] 2. The present invention adopts a single material and 3D printing technology. By adopting a single-nozzle, double-nozzle or triple-nozzle 3D printer, the printing filling rate of each layer of absorbing material can realize the concentration control of each layer. Thermoplastic absorbing materials of any concentration can be prepared to achieve a variety of concentration gradients of the structure.

[0019] 3. The present invention adopts a variety of materials and 3D printing technology. Through a dual-nozzle or triple-nozzle 3D printer, each nozzle is used alternately to adjust the printing path of each layer of absorbing material printing nozzle, and the volume proportion of various absorbing materials can be adjusted to achieve concentration and composition control of each layer. Thermoplastic absorbing materials with adjustable concentration and composition can be prepared to achieve impedance gradient; and the technical process is simple, easy to operate, and highly safe. After the parameters are determined, the preparation can be completed simply and quickly. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below in conjunction with the accompanying drawings: Figure 1 1 is a schematic structural diagram of the impedance gradient absorbing material prepared in Example 1 of the present invention; Figure 2 3D printing process schematic diagram of the impedance gradient absorbing material prepared in Example 1 of the present invention; Figure 3 3D printing process schematic diagram of the impedance gradient absorbing material prepared in Example 2 of the present invention; Figure 4 is the electromagnetic wave reflectivity curve of the impedance gradient absorbing material prepared in Example 1 of the present invention at 1-18 GHz; Figure 5 is the electromagnetic wave reflectivity curve of the impedance gradient absorbing material prepared in Example 2 of the present invention at 1-18 GHz; Figure 6 This is the electromagnetic wave reflectivity curve of the impedance gradient absorbing material prepared in Example 3 of the present invention at 1-18 GHz. DETAILED DESCRIPTION

[0021] Embodiment 1: like Figure 1As shown, this embodiment provides an impedance gradient absorbing material, which is a pointed cone structure with a height of 15 mm, 3 layers, each layer is 5 mm high, and the concentration of the absorbing material decreases from bottom to top; the absorbing material includes carbon nanotubes and acrylonitrile-butadiene-styrene (ABS).

[0022] The method for preparing the above-mentioned impedance gradient absorbing material comprises the following steps: S1. Obtain ABS wave-absorbing wire with 12%wt carbon nanotubes: dry carbon nanotubes and ABS in an electric hot air drying oven at 80°C for 4h, mix them in a ratio of 3:22, add them to a twin-screw extruder, and set the temperatures of each zone of the twin-screw extruder to: 210°C for zone 1, 220°C for zone 2, and 220°C for zone 3, melt extrude, and wind up; S2. Feed the ABS absorbing filament into the nozzle of the 3D printer, import the pointed cone printing digital model, set the printing process parameters, the printing nozzle temperature is 235°C, the printing platform temperature is 100°C, the printing speed is 30mm / s, the lower layer filling rate is 100%, the middle layer filling rate is 75%, and the upper layer filling rate is 25%. Print each layer of absorbing material from bottom to top, and print absorbing materials with concentrations of 12%wt, 8%wt, and 4%wt in turn, so as to prepare a pointed cone absorbing material with impedance gradient.

[0023] Figure 2 Schematic diagram of the 3D printing process of the impedance gradient absorbing material described in this embodiment.

[0024] Figure 4 The reflectivity curve of the tapered absorbing material with impedance gradient prepared above. As can be seen from the figure, the reflection loss of the absorbing material reaches -10dB in the 4-8GHz electromagnetic wave band, and the reflection loss reaches -15dB in the 8-18GHz electromagnetic wave band. The above results show that the tapered absorbing material with impedance gradient has excellent broadband absorbing performance.

[0025] Embodiment 2: This embodiment provides an impedance gradient absorbing material, which is a pointed cone structure with a height of 9 mm and 3 layers, each layer is 3 mm high, and the concentration of the absorbing material decreases from bottom to top; the impedance gradient absorbing material includes carbon nanotubes and polyamide (PA).

[0026] The method for preparing the above-mentioned impedance gradient absorbing material comprises the following steps: S1. Obtain PA wave-absorbing wire with 15%wt carbon nanotubes: dry the carbon nanotubes and PA in an electric hot air drying oven at 80°C for 4h, mix them in a ratio of 3:17, add them into a twin-screw extruder, and set the temperatures of each zone of the twin-screw extruder to: 200°C for zone 1, 210°C for zone 2, and 210°C for zone 3, melt extrude, and wind up; S2. The PA absorbing filament and the pure PA filament are respectively fed into the two nozzles of a 3D printer with dual nozzles, and each layer of absorbing material is printed in sequence from bottom to top. The lower layer is prepared by only using the PA absorbing filament of 15%wt carbon nanotubes. The concentration of the middle and upper absorbing materials is prepared by adjusting the printing ratio of the PA absorbing filament of 15%wt carbon nanotubes and the pure PA filament. The printing nozzle temperature is 210°C, the printing platform temperature is 100°C, the printing speed is 30mm / s, and the printing filling rate is 100%. The printing path of each nozzle is adjusted when printing each layer of material. When printing the same layer of material, the nozzles are used alternately to print the PA absorbing filament and the pure PA filament. The absorbing materials with concentrations of 15wt%, 10%wt, and 5%wt are printed in sequence, thereby preparing a pointed cone-shaped absorbing material with impedance gradient.

[0027] Figure 3 Schematic diagram of the 3D printing process of the impedance gradient absorbing material described in this embodiment.

[0028] Figure 5 The reflectivity curve of the tapered absorbing material with impedance gradient prepared above is shown in the figure. As can be seen from the figure, the reflection loss of the absorbing material reaches -8dB in the 6-18GHz electromagnetic wave band, indicating that the tapered absorbing material with impedance gradient has excellent broadband absorbing performance.

[0029] Embodiment 3: This embodiment provides an impedance gradient absorbing material, which is a flat plate structure with a height of 10 mm and 5 layers, each of which has a height of 2 mm. In the absorbing material, the concentration of carbonyl iron and PA absorbing wire decreases from bottom to top; the impedance gradient absorbing material includes carbon nanotubes, carbonyl iron powder and polyamide (PA).

[0030] The method for preparing the above-mentioned impedance gradient absorbing material comprises the following steps: S1. Obtain PA wave-absorbing wire with 10%wt carbon nanotubes: dry the carbon nanotubes and PA in an electric hot air drying oven at 80°C for 4h, mix them in a ratio of 1:9, add them to a twin-screw extruder, and set the temperatures of each zone of the twin-screw extruder to: 200°C for zone 1, 210°C for zone 2, and 210°C for zone 3, melt extrude, and wind up; Obtain PA wave-absorbing wire with 40%wt carbonyl iron: dry carbonyl iron and PA in an electric hot air drying oven at 80°C for 4h, mix them in a ratio of 2:3, and add them to a twin-screw extruder. The temperatures of each zone of the twin-screw extruder are: 200°C for zone 1, 210°C for zone 2, and 210°C for zone 3. Melt extrusion and winding. S2. Feed the carbon nanotube / PA absorbing wire and the carbonyl iron / PA absorbing wire into the two nozzles of the 3D printer with dual nozzles, import the structure digital model, and print each layer of absorbing material from bottom to top. The lower layer is prepared by only using 40%wt carbonyl iron PA absorbing wire. The composition of the middle and upper absorbing materials is adjusted by adjusting the printing ratio of 20%wt carbon nanotube PA absorbing wire and carbonyl iron / PA absorbing wire to achieve the respective volume proportion control and preparation. The printing platform temperature is 9 0℃, the printing nozzle temperature is 210℃, the printing speed is 30mm / s, the printing filling rate is 100%, 95%, 90%, 85%, 80% respectively, the printing path of each nozzle when printing each layer of material is adjusted, when printing the same layer of material, the nozzle is used alternately to print carbon nanotube / PA absorbing wire and carbonyl iron / PA absorbing wire, and the absorbing materials with carbonyl iron proportion of 100%, 80%, 60%, 40%, 20% are printed in turn, so as to prepare the absorbing material with impedance gradient.

[0031] Figure 6 The reflectivity curve of the flat-plate absorbing material with impedance gradient prepared above. As can be seen from the figure, the reflection loss of the absorbing material reaches -10dB in the 6-18GHz electromagnetic wave band. The above results show that the above-mentioned impedance gradient absorbing material has excellent broadband absorbing performance.

[0032] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A method for preparing an impedance gradient absorbing material, characterized in that: The following steps are involved: S1. Obtain 3D printing filaments: blend the absorbent and the resin through a twin-screw extruder and extrude them to prepare 3D printing filaments with different concentrations. The diameter of the filaments is 1.75 mm, and the filaments are rolled up for standby use; S2. Feed the 3D printing filament into the nozzle of the 3D printer, import the printed digital model into the 3D printer, slice the structure, set the printing process, set the printing filling rate of each layer of the gradient absorbing material in turn, or alternately print the absorbing materials of each nozzle when printing the same layer to adjust the proportion of different absorbing materials, and then print to obtain the impedance gradient absorbing material.

2. The method for preparing a gradient impedance absorbing material according to claim 1, characterized in that: In step S1, the concentration of the absorbent in the 3D printing filament is 2% to 60%wt.

3. The method for preparing a gradient impedance absorbing material according to claim 1, characterized in that: In the step S1, the absorbent is a carbon-based or magnetic absorbent, including at least one of carbon nanotubes, graphene, carbon fiber, carbon black, carbonyl iron powder, alloy powder, and ferrite.

4. The method for preparing a gradient impedance absorbing material according to claim 1, characterized in that: In the step S1, the resin includes at least one of acrylonitrile butadiene styrene (ABS), polyamide (PA), polyphthalamide, thermoplastic polyurethane, and polylactic acid.

5. The method for preparing a gradient impedance absorbing material according to claim 1, characterized in that: In step S2, the printing temperature of 3D printing is 90-110° C., the printing speed is 20 mm / s-60 mm / s, and the filling rate is 25%-100%.

6. The method for preparing a gradient impedance absorbing material according to claim 1, characterized in that: The impedance gradient absorbing material structure is any one of a pointed cone type, a honeycomb type or a flat plate type.

7. The method for preparing a gradient impedance absorbing material according to claim 1, characterized in that: The number of stacked layers of the absorbing material is 3 to 15 layers.

8. The impedance gradient absorbing material obtained by the method for preparing the impedance gradient absorbing material according to any one of claims 1 to 7.

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