Polarization insensitive wave-absorbing honeycomb and preparation method thereof
Polarized insensitive absorbing honeycombs are prepared by one-step microwave foaming method, and the absorbent core material with a three-dimensional conductive network structure is formed using melamine precursors and multiple absorbents, and the absorbent core material is filled into the honeycomb cell, which solves the problem of the differences in performance of traditional absorbing honeycombs in different polarization directions, and achieves omnidirectional high-efficiency absorbing performance and the feasibility of industrial large-scale production.
Patent Information
- Application Number
- CN202411828043.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-12
- Publication Date
- 2025-04-04
AI Technical Summary
There are significant differences in the absorbing performance of traditional impregnated wave absorbing honeycombs in the horizontal polarization and vertical polarization directions of electromagnetic waves, which cannot meet various usage needs, resulting in reduced equipment safety.
Polarized insensitive absorbing honeycombs are prepared by one-step microwave foaming method. By using raw materials such as melamine precursor, carbon black, carbon nanotubes and chopped carbon fibers, an absorbent core material with a three-dimensional conductive network structure is formed and filled into the honeycomb cell.
It significantly reduces the performance differences of honeycombs in different electromagnetic wave polarization directions, improves the omnidirectional absorption performance of the material, ensures efficient absorption performance in the 2GHz to 18GHz frequency band, and reduces the performance differences under the conditions of heterogeneous polarization.
Smart Images
Figure CN119764866A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for preparing a polarization insensitive wave-absorbing honeycomb machine, and belongs to the technical field of wave-absorbing materials. Background Art
[0002] With the rapid development of communication, detection and other related technologies, electromagnetic waves have contributed tremendous power, but at the same time they have also brought huge threats to human health and the safe use of equipment. In particular, as more and more types of electromagnetic waves are used, the potential threats they pose have also increased exponentially. Therefore, whether it is to maintain human health and eliminate electromagnetic radiation, or to increase the life of equipment and protect human health, it is necessary to develop a type of absorbing material that can efficiently absorb multiple types of electromagnetic waves at the same time.
[0003] As a typical structural and functional integrated absorbing material, the absorbing honeycomb has been widely used in many fields. However, the traditional impregnated absorbing honeycomb is limited by various structures such as "hexagon", "I-shaped" and "quadrilateral", and often has significant differences in the absorbing performance in the horizontal polarization and vertical polarization directions of electromagnetic waves, resulting in the above materials often only meeting some usage requirements, thus posing potential risks to equipment and other protected objects. Although many scholars have developed a variety of high-performance absorbers to improve the efficiency of converting electromagnetic energy into thermal energy in the hope of solving the above problems, they have not been able to fundamentally eliminate the performance differences caused by the anisotropy of the honeycomb macrostructure. Therefore, the two-dimensional absorbing layer attached to the surface of the honeycomb substrate is converted into a polygonal three-dimensional columnar absorber filled in the honeycomb. At the same time, the structural design and distribution control of the absorber in the absorber can further reduce the difference in absorbing performance of the absorbing honeycomb under horizontal polarization and vertical polarization, and further meet the usage needs of various fields. Summary of the invention
[0004] Purpose of the present invention: The present invention provides a polarization-insensitive absorbing honeycomb and a preparation method thereof. Melamine precursor, carbon nanotubes, chopped carbon fibers and carbon black are used as raw materials. Through one-step microwave foaming molding, an absorbing core material with a three-dimensional conductive network structure formed by zero-dimensional absorbing material carbon black and one-dimensional absorbing material carbon nanotubes and chopped carbon fibers is obtained. The core material is cut into absorbing core strips of a certain size according to the size and height of the honeycomb cells and filled into the honeycomb cells to obtain a polarization-insensitive absorbing honeycomb. The present invention fills the absorbing core material into the cells of the wave-transmitting honeycomb substrate, and at the same time combines the structural design and distribution control of the absorbent in the absorber to reduce the difference in absorbing performance of the absorbing honeycomb under horizontal polarization and vertical polarization, and fundamentally eliminates the performance difference caused by the anisotropy of the honeycomb macrostructure. The preparation method of the polarization-insensitive absorbing honeycomb provided by the present invention has the characteristics of simple preparation process, low cost, and suitable for industrial large-scale production.
[0005] Technical Solution
[0006] A polarization-insensitive absorbing honeycomb, the absorbing honeycomb is composed of an absorbing core material and a transparent honeycomb substrate, the absorbing core material is filled in the pores of the transparent honeycomb substrate, wherein the absorbing core material is obtained by one-step microwave foaming of multiple absorbents, and the obtained absorbing core material has a three-dimensional network structure.
[0007] Furthermore, types of wave-transmitting honeycomb substrates include aramid honeycomb and glass cloth honeycomb, the cell side length of the wave-transmitting honeycomb substrate includes but is not limited to 2.7 mm to 10 mm, and the thickness of the wave-transmitting honeycomb substrate includes but is not limited to 10 mm to 500 mm.
[0008] Furthermore, the raw materials for preparing the absorbing core material include a melamine precursor and an absorbent, and the absorbent includes carbon black, carbon nanotubes, and chopped carbon fibers. After the above raw materials are processed, the absorbing core material is formed by a one-step foaming method.
[0009] A method for preparing the polarization-insensitive absorbing honeycomb comprises the following steps: controlling the viscosity of a melamine precursor through an aqueous phase; subjecting carbon black, carbon nanotubes and chopped carbon fibers to plasma surface activation treatment; mixing the absorbent and the melamine precursor evenly; obtaining an absorbing foam core material for filling honeycomb cells by controlling the power and duration of microwave bubbling; then cutting the absorbing foam core material according to a certain interference fit based on the size of the honeycomb cells, and filling the honeycomb to obtain a polarization-insensitive absorbing honeycomb.
[0010] Furthermore, the preparation method comprises the following steps:
[0011] (1) Raw materials for preparing the absorbing core material: including melamine precursor, carbon black, carbon nanotubes, and chopped carbon fibers, and plasma surface activation treatment is performed on the carbon black, carbon nanotubes, and chopped carbon fibers respectively; the plasma surface activation treatment can effectively increase the active functional groups on the surfaces of the three types of absorbents, namely, carbon black, carbon nanotubes, and chopped carbon fibers, which is beneficial to the subsequent dispersion of the absorbent in the melamine precursor and the compounding with the resin.
[0012] (2) adding an appropriate amount of water to the melamine precursor to ensure that the viscosity of the melamine precursor is maintained in the range of 10s to 20s;
[0013] (3) adding the carbon black, carbon nanotubes and chopped carbon fibers that have been subjected to plasma surface activation treatment to a melamine precursor in the order of carbon black, carbon nanotubes and chopped carbon fibers to perform dispersion treatment to obtain a wave-absorbing adhesive to be foamed; the dispersion process can ensure that absorbents with various microstructures can obtain a good dispersion effect in the melamine precursor and can maintain long-term suspension characteristics;
[0014] (4) performing microwave foaming on the microwave absorbing adhesive liquid;
[0015] (5) Cutting and filling of absorbing core materials: When the thickness of the honeycomb substrate is 300 mm or less, the side length of the foam core material used to fill the honeycomb cells is 110% to 120% of the honeycomb side length. When the thickness of the honeycomb substrate is more than 300 mm, the side length of the foam core material used to fill the honeycomb cells is 100% to 109% of the honeycomb side length. A mold is used to complete the filling of the absorbing core material in the honeycomb cells.
[0016] Furthermore, in step (1), the treatment time of carbon black and carbon nanotubes is maintained in the range of 10s to 40s, and the treatment time of chopped carbon fibers is maintained in the range of 60s to 120s.
[0017] Furthermore, in step (2), the viscosity of the melamine precursor is measured by a 4-cup coating method.
[0018] Furthermore, in step (3), a homogenizer is used for dispersion treatment, the speed of the homogenizer is between 1000 r / min and 15000 r / min, and the dispersion time of carbon black, carbon nanotubes, and chopped carbon fibers is not less than 30 minutes.
[0019] Furthermore, in step (4), the microwave foaming power of the absorbing glue is controlled between 200W and 600W, and the foaming time is controlled between 3min and 7min. The foaming process parameters are important parameters to ensure the uniformity of the foam. By using the above parameters, absorbing foam with good quality uniformity can be obtained.
[0020] Beneficial Effects
[0021] The present invention prepares a polarization-insensitive absorbing honeycomb by a one-step microwave foaming method. Compared with the current impregnated absorbing honeycomb, the performance difference of the honeycomb in different polarization directions of electromagnetic waves is greatly reduced, and the omnidirectional absorbing performance of the material is effectively improved. The polarization-insensitive absorbing honeycomb with a thickness of 30 mm has an average vertical reflectivity of ≤-15 dB under horizontal polarization and vertical polarization in the 2GHz to 18GHz frequency band, and the difference between the average vertical reflectivity of the honeycomb under horizontal polarization of 2GHz to 18GHz and the average vertical reflectivity under vertical polarization is less than 1.5 dB. While ensuring high-efficiency absorbing performance, the performance difference of the honeycomb under directional polarization conditions is effectively reduced, and the honeycomb is polarization-insensitive. At the same time, the increase in honeycomb density is ≤35 kg / m 3 , taking into account both light weight and broadband high absorption performance. It effectively solves the problem of reduced safety of related equipment due to the anisotropy of the absorption performance of the absorbing material. In addition, the preparation method of the present invention has simple process and low cost, does not require complex synthesis equipment, and can achieve large-scale mass production. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1The flowchart of the preparation of the polarization-insensitive microwave-absorbing honeycomb of the present invention is as follows;
[0023] Figure 2 This is a physical picture of the polarization-insensitive microwave-absorbing honeycomb prepared in Example 1;
[0024] Figure 3 This is a morphology diagram of the absorbing core material prepared in Example 1;
[0025] Figure 4 This is a reflection loss diagram of the polarization-insensitive absorbing honeycomb prepared in Example 1. DETAILED DESCRIPTION
[0026] The technical solution of the present invention is further described below with reference to the accompanying drawings and specific embodiments, but is not intended to limit the protection scope of the claims.
[0027] Example 1
[0028] In this embodiment, the process for preparing the polarization-insensitive microwave-absorbing honeycomb includes the following steps:
[0029] Step 1, performing plasma surface activation treatment on carbon black, carbon nanotubes and chopped carbon fibers respectively, the treatment time of carbon black and carbon nanotubes is 10 seconds, and the treatment time of chopped carbon fibers is 60 seconds;
[0030] Step 2, adding an appropriate amount of water to the melamine precursor to ensure that the viscosity of the melamine precursor (4-cup coating method) is maintained within 15s;
[0031] Step 3, adding the activated absorbents to the melamine precursor in the order of carbon black, carbon nanotubes, and chopped carbon fibers, using a homogenizer at a speed of 5000 r / min, and the dispersion time of each absorbent is 30 min;
[0032] Step 4, the microwave foaming power of the absorbing foam core material is controlled at 300 W, and the foaming time is controlled at 5 minutes;
[0033] Step 5, cutting and filling of absorbing core material: when the thickness of the honeycomb substrate is 300 mm or less, the side length of the foam core material filling the honeycomb cells is 110% of the honeycomb side length; when the thickness of the honeycomb substrate is more than 300 mm, the side length of the foam core material filling the honeycomb cells is 100% of the honeycomb side length. Use a homemade mold to complete the filling of the absorbing core material in the honeycomb cells, and the filling pressure is 1000 Pa.
[0034] Example 2
[0035] In this embodiment, the process for preparing the polarization-insensitive microwave-absorbing honeycomb includes the following steps:
[0036] Step 1, performing plasma surface activation treatment on carbon black, carbon nanotubes and chopped carbon fibers respectively, the treatment time of carbon black and carbon nanotubes is 20 seconds, and the treatment time of chopped carbon fibers is 80 seconds;
[0037] Step 2, adding an appropriate amount of water to the melamine precursor to ensure that the viscosity of the melamine precursor (4-cup coating method) is maintained within 20 seconds;
[0038] Step 3, adding the activated absorbent to the melamine precursor in the order of carbon black, carbon nanotubes, and chopped carbon fibers, using a homogenizer at a speed of 10000 r / min, and the dispersion time of each absorbent is 30 min;
[0039] Step 4, the microwave foaming power of the microwave absorbing foam core material is controlled at 400W, and the foaming time is controlled at 4 minutes;
[0040] Step 5, cutting and filling of absorbing core material: when the thickness of the honeycomb substrate is 300 mm or less, the side length of the foam core material filling the honeycomb cells is 115% of the honeycomb side length; when the thickness of the honeycomb substrate is more than 300 mm, the side length of the foam core material filling the honeycomb cells is 105% of the honeycomb side length. Use a homemade mold to complete the filling of the absorbing core material in the honeycomb cells, and the filling pressure is 2000 Pa.
[0041] Example 3
[0042] In this embodiment, the process for preparing the polarization-insensitive microwave-absorbing honeycomb includes the following steps:
[0043] Step 1, performing plasma surface activation treatment on carbon black, carbon nanotubes and chopped carbon fibers respectively, the treatment time of carbon black and carbon nanotubes is 30 seconds, and the treatment time of chopped carbon fibers is 100 seconds;
[0044] Step 2, adding an appropriate amount of water to the melamine precursor to ensure that the viscosity of the melamine precursor (4-cup coating method) is maintained within the range of 18s;
[0045] Step 3, adding the activated absorbent into the melamine precursor in the order of carbon black, carbon nanotubes, and chopped carbon fibers, using a homogenizer at a speed of 13000 r / min, and the dispersion time of each absorbent is 40 min;
[0046] Step 4, the microwave foaming power of the microwave absorbing foam core material is controlled at 500W, and the foaming time is controlled at 3 minutes;
[0047] Step 5, cutting and filling of absorbing core material: when the thickness of the honeycomb substrate is 300 mm or less, the side length of the foam core material filling the honeycomb cells is 120% of the honeycomb side length; when the thickness of the honeycomb substrate is more than 300 mm, the side length of the foam core material filling the honeycomb cells is 109% of the honeycomb side length. Use a homemade mold to complete the filling of the absorbing core material in the honeycomb cells, and the filling pressure is 3000 Pa.
[0048] Figure 1 This is a flow chart for the preparation of polarization-insensitive absorbing honeycombs. The entire preparation process does not require complex, large-scale equipment, the preparation method is simple, and the materials used are all easily available conventional materials with low cost, which is conducive to the large-scale mass production of polarization-insensitive absorbing honeycombs.
[0049] Figure 2 This is a photo of the polarization-insensitive microwave-absorbing honeycomb obtained in Example 1 of the present invention. Figure 2 It can be seen that the honeycomb cells of the polarization-insensitive microwave-absorbing honeycomb prepared in Example 1 are uniformly filled with the microwave-absorbing core material.
[0050] Figure 3 This is a scanning electron microscope photo of the absorbing core material prepared in Example 1 of the present invention. Figure 3 It can be seen that the absorbing core material has a three-dimensional network structure, and the absorbent is evenly distributed in the three-dimensional network structure.
[0051] Figure 4 This is a reflection loss diagram of the polarization-insensitive absorbing honeycomb prepared in Example 1 of the present invention. It can be seen from this figure that when the thickness of the absorbing honeycomb is 30 mm, the average vertical reflectivity under 2GHz-18.0GHz horizontal polarization and vertical polarization is ≤-15dB. It can be seen that the average vertical reflectivity of the honeycomb under 2GHz-18GHz horizontal polarization is -16.6dB, and the average vertical reflectivity under vertical polarization is -15.8dB. The difference in the average vertical reflectivity under the two polarizations is only 0.8dB, which solves the problem of significant polarization differences while ensuring the efficient absorbing performance of the honeycomb under various polarization modes.
Claims
1. A polarization-insensitive microwave absorbing honeycomb, characterized in that: The absorbing honeycomb is composed of an absorbing core material and a transparent honeycomb substrate, wherein the absorbing core material is filled in the pores of the transparent honeycomb substrate, wherein the absorbing core material is obtained by one-step microwave foaming of multiple absorbents, and the obtained absorbing core material has a three-dimensional network structure.
2. The polarization-insensitive microwave absorbing honeycomb according to claim 1, characterized in that: Types of wave-transmitting honeycomb substrates include aramid honeycomb and glass cloth honeycomb. The cell side length of the wave-transmitting honeycomb substrate includes but is not limited to 2.7 mm to 10 mm. The thickness of the wave-transmitting honeycomb substrate includes but is not limited to 10 mm to 500 mm.
3. The polarization-insensitive microwave absorbing honeycomb according to claim 2, characterized in that: The raw materials for preparing the absorbing core material include melamine precursor and absorbent, and the absorbent includes carbon black, carbon nanotubes, and chopped carbon fibers. After the above raw materials are processed, the absorbing core material is formed by a one-step foaming method.
4. A method for preparing the polarization-insensitive microwave-absorbing honeycomb as claimed in claim 3, characterized in that: The viscosity of the melamine precursor is controlled by the water phase, and the carbon black, carbon nanotubes and chopped carbon fibers are treated with plasma surface activation. The absorber and the melamine precursor are evenly mixed, and the absorbing foam core material for filling the honeycomb cells is obtained by controlling the microwave bubbling power and duration. Then, according to the size of the honeycomb cells and a certain interference fit, the absorbing foam core material is cut to fill the honeycomb, thereby obtaining a polarization-insensitive absorbing honeycomb.
5. The preparation method according to claim 4, characterized in that: The preparation method comprises the following steps: (1) Raw materials for preparing the absorbing core material: including melamine precursor, carbon black, carbon nanotubes, and chopped carbon fibers, and plasma surface activation treatment is performed on the carbon black, carbon nanotubes, and chopped carbon fibers respectively; (2) adding an appropriate amount of water to the melamine precursor to ensure that the viscosity of the melamine precursor is maintained in the range of 10s to 20s; (3) adding the carbon black, carbon nanotubes and chopped carbon fibers that have been subjected to plasma surface activation treatment to a melamine precursor in the order of carbon black, carbon nanotubes and chopped carbon fibers, and performing dispersion treatment to obtain a wave-absorbing adhesive to be foamed; (4) performing microwave foaming on the microwave absorbing adhesive liquid; (5) Cutting and filling of absorbing core materials: When the thickness of the honeycomb substrate is 300 mm or less, the side length of the foam core material used to fill the honeycomb cells is 110% to 120% of the honeycomb side length. When the thickness of the honeycomb substrate is more than 300 mm, the side length of the foam core material used to fill the honeycomb cells is 100% to 109% of the honeycomb side length. A mold is used to complete the filling of the absorbing core material in the honeycomb cells.
6. The preparation method according to claim 5, characterized in that: In step (1), the treatment time of carbon black and carbon nanotubes is maintained in the range of 10s to 40s, and the treatment time of chopped carbon fibers is maintained in the range of 60s to 120s.
7. The preparation method according to claim 5, characterized in that: In step (2), the viscosity of the melamine precursor is measured by a 4-cup coating method.
8. The preparation method according to claim 5, characterized in that: In step (3), a homogenizer is used for dispersion treatment, the speed of the homogenizer is between 1000 r / min and 15000 r / min, and the dispersion time of carbon black, carbon nanotubes, and chopped carbon fibers is not less than 30 minutes.
9. The preparation method according to claim 5, characterized in that: In step (4), the microwave foaming power of the absorbing glue is controlled between 200W and 600W, and the foaming time is controlled between 3min and 7min.