A method for preparing a patterned copper-plated wave-absorbing honeycomb

Abstract

The application relates to a preparation method of a patterned copper-plated wave-absorbing honeycomb, and belongs to the field of microwave absorbing materials. The method solves the problems of high weight increase, low printing precision, low design freedom and poor electromagnetic adjustment capability of the existing printed honeycomb. The method comprises the following steps: one, printing; two, glue coating; three, laminating and bonding; four, cutting and stretching; five, copper plating; and six, glue dipping and curing. The application is used for the preparation of the patterned copper-plated wave-absorbing honeycomb.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials. Background Technology

[0002] Aramid honeycomb is a novel high-performance composite material characterized by its light weight, impact resistance, high strength, and aging resistance, and is widely used in advanced equipment such as aircraft. Currently, aramid honeycomb continues to develop towards functionalization while maintaining its load-bearing capabilities. Load-bearing and stealth integrated aramid honeycomb (hereinafter referred to as radar-absorbing honeycomb) can replace the traditional metal skin + radar-absorbing coating structure of aircraft, effectively reducing aircraft weight, improving maneuverability, and reducing fuel consumption. According to published literature and patent reports, aramid radar-absorbing honeycomb mainly consists of the following types: ① Impregnated honeycomb: Before the honeycomb is cured, a radar-absorbing agent, usually conductive or magnetic powder, is added to the structural resin. The doped resin gives the honeycomb the ability to absorb radar waves of specific frequency bands; ② Filled honeycomb: A radar-absorbing agent, usually a low-density material such as graphene aerogel, is filled into the honeycomb lattice; ③ Printed honeycomb: Before the honeycomb is laminated, a conductive layer is printed on the surface of aramid paper. The inner wall of the honeycomb lattice prepared by printing aramid paper is a three-dimensional frequency-selective or metamaterial structure, and the honeycomb as a whole has radar-absorbing capabilities. The microwave absorption capacity of impregnated honeycomb relies on the amount and dispersibility of the microwave absorbing agent added to the resin, resulting in a trade-off between weight gain and microwave absorption performance. The preparation process of aerogels used to fill honeycomb is complex and difficult to adjust in terms of microwave absorption performance. Compared to the previous two types of honeycomb, printed honeycomb's main advantages are its low weight and strong electromagnetic performance adjustment capability. Patent CN117341288 discloses a three-dimensional microwave absorbing frequency-selective material and its manufacturing method. Its structure is a honeycomb of aramid paper with staggered bonding of two-dimensional metamaterial units printed on it. The microwave absorption performance of the honeycomb is adjusted through the printed metamaterial structure. The conductive printing material is nano-carbon powder, nano-graphene, or various nano-metal powders, and the printed patterns are circular rings, elliptical rings, or regular polygonal patterns. While the above inventions have achieved certain results in terms of lightweight and broadband microwave absorption, they still suffer from high weight gain, low printing precision, limited design freedom, and poor electromagnetic adjustment capability, restricting the application of microwave absorbing honeycomb in lightweight and broadband microwave absorption. In terms of weight gain, the thickness of the screen-printed layer is typically above 50 micrometers, with a silver coating (density 10.5 g / cm³). 3 For example, the density of 50-micron thick aramid paper is 0.72 g / cm³. 3The weight gain after printing is around 1500%. If calculated using the 1mm thick printing layer in the aforementioned invention, the weight gain per unit area can reach 30,000%. Regarding printing precision, aramid paper has good wettability to most organic solvents; therefore, inks from traditional screen printing processes will bleed across the aramid paper surface, significantly reducing the accuracy of the printed pattern. In terms of design freedom, the honeycomb structure prepared by the aforementioned invention uses single-sided printing of aramid paper, resulting in half of the honeycomb cells lacking conductive patterns, limiting the design space for the honeycomb's electromagnetic properties. Furthermore, screen printing is a plate-based process, requiring re-plate making for each change of the printed pattern, making the process cumbersome. Therefore, how to provide a lightweight, stealth-integrated, heat-absorbing honeycomb structure with low weight gain, high printing precision, and high design freedom to meet the lightweight and stealth requirements of aircraft is currently a key research focus and challenge. Summary of the Invention

[0003] This invention aims to address the problems of high weight gain, low printing accuracy, low design freedom, and poor electromagnetic adjustment capability in existing printed honeycomb structures, and provides a method for preparing patterned copper-plated absorbing honeycomb structures.

[0004] A method for preparing patterned copper-plated absorbing honeycomb, comprising the following steps:

[0005] 1. Printing:

[0006] Precursor patterns are printed on both sides of aramid paper using a metal particle solution to obtain aramid paper coated with precursor patterns.

[0007] II. Applying adhesive:

[0008] A nodule adhesive is coated onto aramid paper with a precursor pattern and the solvent is dried to obtain coated aramid paper.

[0009] III. Overlapping and bonding:

[0010] The aramid paper with adhesive is stacked and pressed together to cure, resulting in a laminated and bonded aramid paper.

[0011] IV. Cutting and stretching:

[0012] The aramid paper, which is laminated and bonded together, is cut into honeycomb paper stacks and stretched to obtain a honeycomb structure.

[0013] In the honeycomb structure, each surface of the inner wall of the honeycomb pores is provided with a precursor pattern;

[0014] V. Copper plating:

[0015] While under tension, the honeycomb structure is immersed in copper plating solution and copper plating is performed at a temperature of 30℃~60℃ for 30min~120min. Finally, it is cleaned to obtain the honeycomb structure grown by chemical copper plating of the precursor.

[0016] The copper plating solution is composed of agent A, agent B, and solvent; agent A is composed of CuSO4·5H2O, NaOH, potassium sodium tartrate, pH adjuster, and water; agent B is an aqueous solution of HCNO.

[0017] VI. Impregnation and curing:

[0018] While under tension, the honeycomb structure grown by chemical copper plating of the precursor is immersed in phenolic resin containing diluent, then removed and cured to obtain patterned copper-plated microwave absorbing honeycomb.

[0019] The beneficial effects of this invention are:

[0020] Addressing the need for lightweight aircraft, the patterned copper-plated honeycomb conductive layer provided by this invention is only 1 to 2 micrometers thick, which can control the weight increase to within 5% without sacrificing the original mechanical properties of the honeycomb. Compared with other types of wave-absorbing honeycombs, which have a weight increase of tens of times that of the honeycomb itself, the lightweight design of this invention is significantly superior.

[0021] To address the stealth design requirements of aircraft, this invention provides a copper-plated honeycomb structure and its fabrication method, offering high design freedom: First, a precursor pattern is precisely aligned and printed on both sides of aramid paper with a printing accuracy of up to 0.1 mm, supporting 256 grayscale levels from 0 to 255 (i.e., black to white). After applying adhesive, the positional accuracy of the adhesive nodes reaches 0.1 mm. Then, after immersion in a copper plating solution, the precursor undergoes chemical copper plating to grow into a copper-plated layer. Different grayscale precursors result in different grayscale values ​​in the copper layer after plating. Based on this technology, the local electromagnetic properties of individual honeycomb cells can be precisely designed and controlled. Furthermore, the copper-plated honeycomb processing technology is simple and reliable, can be scaled up to assembly line production, and has broad application prospects.

[0022] This invention relates to a method for preparing patterned copper-plated absorbing honeycomb. Attached Figure Description

[0023] Figure 1 The image shows the physical specimen of the fully coated patterned copper-plated aramid honeycomb prepared in step six of Example 1.

[0024] Figure 2 This is a schematic diagram of the honeycomb structure of the precursor after chemical copper plating growth in step five of Example 1;

[0025] Figure 3 This is a schematic diagram of the honeycomb structure after the precursor is grown by chemical copper plating in step five of Example 2;

[0026] Figure 4 This is a schematic diagram of the honeycomb structure of the precursor after chemical copper plating growth in step five of Example 3;

[0027] Figure 5This is a schematic diagram of the honeycomb structure after the precursor is grown by chemical copper plating in step five of Example 4;

[0028] Figure 6 This is a schematic diagram of the honeycomb structure after the precursor is grown by chemical copper plating in step five of Example 5;

[0029] Figure 7 This is a precision test diagram of the printing precursor pattern in step one of Example 3;

[0030] Figure 8 This is a precision test diagram of the joint adhesive coating in step two of Example 3;

[0031] Figure 9 The images are physical images of the precursor patterns. a is a physical image of the precursor patterns with different gray levels achieved by printing using the printing method in step one of Example 1. b is a physical image of the copper patterns deposited on the precursor patterns with different gray levels by using the chemical copper plating method in step five of Example 1.

[0032] Figure 10 The image shows the surface morphology of the aramid paper coated with the precursor pattern prepared in step one of Example 1. a represents the macroscopic, b represents the mesoscopic, and c represents the microscopic.

[0033] Figure 11 The image shows the surface morphology of the honeycomb structure after the precursor prepared in step five of Example 1 is grown by chemical copper plating. a is macroscopic, b is mesoscopic, and c is microscopic.

[0034] Figure 12 EDS surface analysis of the aramid paper coated with the precursor pattern prepared in step one of Example 1.

[0035] Figure 13 The results of EDS surface analysis of the honeycomb structure surface after the precursor prepared in step five of Example 1 was grown by chemical copper plating;

[0036] Figure 14 This is a scanning electron microscope image of the copper layer in the honeycomb structure after the precursor prepared in step five of Example 1 is grown by chemical copper plating.

[0037] Figure 15 The reflection loss curves of the geometric gradient 2 prepared in Example 3 and the grayscale gradient 2 prepared in Example 5 are compared in the X-band and Ku-band. Detailed Implementation

[0038] Specific Implementation Method 1: This implementation method describes a method for preparing a patterned copper-plated absorbing honeycomb, which is carried out according to the following steps:

[0039] 1. Printing:

[0040] Precursor patterns are printed on both sides of aramid paper using a metal particle solution to obtain aramid paper coated with precursor patterns.

[0041] II. Applying adhesive:

[0042] A nodule adhesive is coated onto aramid paper with a precursor pattern and the solvent is dried to obtain coated aramid paper.

[0043] III. Overlapping and bonding:

[0044] The aramid paper with adhesive is stacked and pressed together to cure, resulting in a laminated and bonded aramid paper.

[0045] IV. Cutting and stretching:

[0046] The aramid paper, which is laminated and bonded together, is cut into honeycomb paper stacks and stretched to obtain a honeycomb structure.

[0047] In the honeycomb structure, each surface of the inner wall of the honeycomb pores is provided with a precursor pattern;

[0048] V. Copper plating:

[0049] While under tension, the honeycomb structure is immersed in copper plating solution and copper plating is performed at a temperature of 30℃~60℃ for 30min~120min. Finally, it is cleaned to obtain the honeycomb structure grown by chemical copper plating of the precursor.

[0050] The copper plating solution is composed of agent A, agent B, and solvent; agent A is composed of CuSO4·5H2O, NaOH, potassium sodium tartrate, pH adjuster, and water; agent B is an aqueous solution of HCNO.

[0051] VI. Impregnation and curing:

[0052] While under tension, the honeycomb structure grown by chemical copper plating of the precursor is immersed in phenolic resin containing diluent, then removed and cured to obtain patterned copper-plated microwave absorbing honeycomb.

[0053] The beneficial effects of this specific implementation method are:

[0054] Addressing the need for lightweight aircraft, the patterned copper-plated honeycomb conductive layer provided in this specific embodiment is only 1 to 2 micrometers thick, which can control the weight increase to within 5% without sacrificing the original mechanical properties of the honeycomb. Compared with other types of absorbing honeycombs, which have a weight increase of tens of times that of the honeycomb itself, the lightweight design of this specific embodiment is significantly superior.

[0055] To address the stealth design requirements of aircraft, the copper-plated honeycomb and its fabrication method provided in this specific embodiment offer high design freedom: First, the precursor pattern is precisely aligned and printed on both sides of aramid paper with a printing accuracy of up to 0.1 mm, supporting 256 levels of grayscale adjustment from 0 to 255 (i.e., black to white). After applying adhesive, the positional accuracy of the adhesive nodes can reach 0.1 mm. Then, after immersion in a copper plating solution, the precursor undergoes chemical copper plating to grow into a copper-plated layer. Different grayscale precursors result in different grayscale values ​​in the copper layer after plating. Based on this technology, the local electromagnetic properties of individual honeycomb cells can be precisely designed and controlled. Furthermore, the copper-plated honeycomb processing technology is simple and reliable, can be scaled up to assembly line production, and has broad application prospects.

[0056] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mass percentage of metal particles in the metal particle solution described in step one is 30%–40%; and the solvent in the metal particle solution described in step one is water, a weakly acidic aqueous solution, or an organic solvent. Everything else is the same as in Specific Implementation Method One.

[0057] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the metal particles in the metal particle solution are nano-silver particles or nano-platinum particles with a particle size of 30nm to 50nm; the weakly acidic aqueous solution is a 10% to 14% (w / w) HCl aqueous solution; and the organic solvent is trimethylol trioxide (1,2-propanediol). Everything else is the same as in Specific Implementation Method One or Two.

[0058] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the grayscale form of the precursor pattern described in Step One is a uniform grayscale, a grayscale gradient, or a grayscale jump. Everything else is the same as in Specific Implementation Methods One to Three.

[0059] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the printing described in step one is performed as follows: ① Place the aramid paper in the working area of ​​the printer head. Then, under the conditions of piezoelectric on-demand ink supply drive, independent drive, nozzle resolution ≥360npi, ink droplet volume ≤13pl, emission frequency ≥45kHz, print width ≥72mm, and grayscale level of 1dpd~8dpd, use a motion platform to control the printer head to reciprocate on one side of the aramid paper to print the precursor pattern. Finally, dry at room temperature for 30min~60min; ② Repeat step ① to print the precursor pattern on the other side of the aramid paper. Everything else is the same as in Specific Implementation Methods One, Two, and Four.

[0060] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the coating method described in step two is dispensing, gravure coating, or screen printing coating; the drying solvent described in step two is specifically dried at a temperature of 50℃~60℃ for 1h~3h. Everything else is the same as Specific Implementation Methods One to Five.

[0061] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the curing described in step three is specifically carried out at a temperature of 120℃ to 140℃ for 1 to 3 hours. Everything else is the same as in Specific Implementation Methods One to Six.

[0062] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the area of ​​the precursor pattern described in step four accounts for 30% to 100% of the area of ​​the inner wall of the honeycomb lattice; the precursor pattern in the honeycomb structure described in step four is a rectangle or an isosceles triangle. Everything else is the same as in Specific Implementation Methods One to Seven.

[0063] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in the following ways: the volume ratio of agent A to agent B in step five is 1:(1.5-3); the volume ratio of agent A to solvent in step five is 1:(2.5-4); the solvent is water; the concentration of CuSO4·5H2O in agent A is 5g / L-8g / L, the concentration of NaOH is 5g / L-8g / L, the concentration of potassium sodium tartrate is 25g / L-30g / L, and the concentration of pH adjuster is 3g / L-6g / L; the pH adjuster is Na2CO3; and the mass percentage of HCHO in agent B is 30%-40%. Everything else is the same as in Specific Implementation Methods One to Eight.

[0064] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: in step six, while maintaining the stretched state, the honeycomb structure grown by chemical copper plating of the precursor is immersed in phenolic resin containing a diluent for 10 to 20 minutes. Then, it is removed and cured first at 70°C to 90°C for 0.5 to 1 hour, then at 110°C to 130°C for 0.5 to 1 hour, then at 140°C to 160°C for 0.5 to 1 hour, and finally at 170°C to 190°C for 1 to 3 hours. The phenolic resin containing the diluent has a mass percentage of 80% to 95%. Everything else is the same as in Specific Implementation Methods One to Nine.

[0065] The beneficial effects of the present invention are verified using the following embodiments:

[0066] Example 1:

[0067] A method for preparing patterned copper-plated absorbing honeycomb, comprising the following steps:

[0068] 1. Printing:

[0069] Precursor patterns are printed on both sides of aramid paper using a metal particle solution to obtain aramid paper coated with precursor patterns.

[0070] The metal particle solution contains 40% metal particles by mass; the solvent in the metal particle solution is trimethylolpropanetriol trimethylolpropane ether.

[0071] The metal particles in the metal particle solution are silver nanoparticles with an average particle size of 50 nm.

[0072] The grayscale value of the precursor pattern is 120, which is light gray.

[0073] II. Applying adhesive:

[0074] Using a dispensing machine, a nodule adhesive is applied to aramid paper with a precursor pattern, and then dried at 60°C for 2 hours to obtain the coated aramid paper.

[0075] III. Overlapping and bonding:

[0076] The coated aramid paper is stacked and pressed together, and cured at 130℃ for 2 hours to obtain the stacked and bonded aramid paper.

[0077] IV. Cutting and stretching:

[0078] The aramid paper, which is laminated and bonded together, is cut into honeycomb paper stacks and stretched to obtain a honeycomb structure.

[0079] In the honeycomb structure, each surface of the inner wall of the honeycomb lattice is provided with a precursor pattern; the area of ​​the precursor pattern occupies 100% of the area of ​​the inner wall of the honeycomb lattice; the honeycomb lattice in the honeycomb structure is a regular hexagonal lattice with a side length of 2.5mm and a thickness of 10mm; the precursor pattern in the honeycomb structure is rectangular with a size of 2.5mm × 10mm.

[0080] V. Copper plating:

[0081] While under tension, the honeycomb structure was immersed in a copper plating solution and copper plating was performed at a temperature of 30°C for 60 minutes, with a copper plating thickness of approximately 2 micrometers. Finally, it was cleaned to obtain the honeycomb structure grown from the precursor by chemical copper plating.

[0082] The copper plating solution comprises agent A, agent B, and a solvent. Agent A consists of CuSO4·5H2O, NaOH, potassium sodium tartrate, a pH adjuster, and water. Agent B is an aqueous solution of HCNO. The volume ratio of agent A: agent B: water is 1:2:3. The concentrations of CuSO4·5H2O, NaOH, potassium sodium tartrate, and pH adjuster in agent A are 5 g / L, 5 g / L, 25 g / L, and 3.75 g / L, respectively. The pH adjuster is Na2CO3. The mass percentage of HCHO in agent B is 34%.

[0083] VI. Impregnation and curing:

[0084] While under tension, the honeycomb structure grown from the precursor through chemical copper plating is immersed in acetone-diluted phenolic resin for 15 minutes. It is then removed and cured first at 80°C for 0.5 hours, then at 120°C for 0.5 hours, then at 150°C for 0.5 hours, and finally at 180°C for 2 hours to obtain a fully coated patterned copper-plated aramid honeycomb, abbreviated as fully copper-plated. The acetone-diluted phenolic resin contains 95% phenolic resin by mass.

[0085] The aramid paper mentioned in step one is model YT822A with a thickness of 0.05mm.

[0086] The printing described in step one is performed as follows: ① Place the aramid paper in the working area of ​​the printer head, and then, under the conditions of piezoelectric on-demand ink supply drive, independent drive, nozzle resolution of 360npi, ink droplet volume of 13pl, emission frequency of 45kHz, print width of 72mm and gray level of 1dpd, use the motion platform to control the printer head to reciprocate on one side of the aramid paper to print the precursor pattern, and finally dry at room temperature for 30 minutes; ② Repeat step ① to print the precursor pattern on the other side of the aramid paper.

[0087] The node adhesive mentioned in step two is J-71 core strip adhesive produced by Heilongjiang Petrochemical Research Institute; the width of the adhesive strip coated with node adhesive in step two is the side length of the honeycomb cell.

[0088] The phenolic resin mentioned in step six is ​​PR43204 phenolic resin produced by Suzhou Hangyu Composite Materials Co., Ltd.

[0089] Example 2: This example differs from Example 1 in that the precursor pattern in the honeycomb structure described in step four is an isosceles triangle with a base of 2.5 mm and a height of 10 mm, and the width of the isosceles triangle gradually decreases from one side of the honeycomb grid to the other; step six yields a geometrically gradient patterned copper-plated aramid honeycomb 1, abbreviated as Geometric Gradient 1. Everything else is the same as in Example 1.

[0090] The width of the isosceles triangle decreases from the bottom to the top of the honeycomb grid as the positive direction of geometric gradient 1, and the width of the isosceles triangle decreases from the top to the bottom of the honeycomb grid as the negative direction of geometric gradient 1.

[0091] Example 3: This example differs from Example 1 in that: the honeycomb structure described in step four uses regular hexagonal cells with a side length of 2.5mm and a thickness of 20mm; the precursor pattern in the honeycomb structure described in step four is an isosceles triangle with a base of 2.5mm and a height of 20mm, and the width of the isosceles triangle gradually decreases from one side of the honeycomb cell to the other; step six yields a geometrically gradient patterned copper-plated aramid honeycomb 2, abbreviated as Geometric Gradient 2. Everything else is the same as in Example 1.

[0092] The width of the isosceles triangle decreases from the bottom to the top of the honeycomb grid as the positive direction of geometric gradient 2, and the width of the isosceles triangle decreases from the top to the bottom of the honeycomb grid as the negative direction of geometric gradient 2.

[0093] Example 4: This example differs from Example 1 in that: the grayscale form of the precursor pattern described in step 1 is a gradient grayscale, with the grayscale value gradually changing from 120 to 255, i.e., from light gray to white; the grayscale of the precursor pattern in the honeycomb structure described in step 4 gradually decreases from one side of the honeycomb cells to the other; step 6 yields a grayscale gradient patterned copper-plated aramid honeycomb 1, abbreviated as Grayscale Gradient 1. Everything else is the same as in Example 1.

[0094] The grayscale of the foreground pattern gradually decreases from the bottom to the top of the honeycomb grid to a grayscale gradient of 1 in the positive direction, and the width of the isosceles triangle gradually decreases from the top to the bottom of the honeycomb grid to a grayscale gradient of 1 in the negative direction.

[0095] Example 5: This example differs from Example 1 in that: the grayscale form of the precursor pattern described in step 1 is a gradient grayscale, with the grayscale value gradually changing from 120 to 255, i.e., from light gray to white; the honeycomb structure described in step 4 has regular hexagonal cells with a side length of 2.5 mm and a thickness of 20 mm; the grayscale of the precursor pattern in the honeycomb structure described in step 4 gradually decreases from one side of the honeycomb cell to the other; step 6 yields a grayscale gradient patterned copper-plated aramid honeycomb 2, abbreviated as Grayscale Gradient 2. Everything else is the same as in Example 1.

[0096] The grayscale of the forerunner pattern gradually decreases from the bottom to the top of the honeycomb grid to the positive direction of grayscale gradient 2, and the width of the isosceles triangle gradually decreases from the top to the bottom of the honeycomb grid to the negative direction of grayscale gradient 2.

[0097] Comparative experiment: This embodiment differs from Embodiment 1 in that steps one and five are omitted, and step six yields an empty honeycomb. Everything else is the same as in Embodiment 1.

[0098] Table 1:

[0099]

[0100]

[0101] Table 2:

[0102] sample <![CDATA[Average density g / cm 3 > Weight gain compared to empty honeycomb Comparative experiment with empty honeycomb 28.0 0％ Example 1: Full Copper Plating 29.3 4.6％ Example 2: Geometric Gradient 1 28.7 2.5％ Example 3: Geometric Gradient 2 28.9 3.2％ Example 4: Grayscale Gradient 1 28.9 3.2％ Example 5: Grayscale Gradient 2 28.8 2.9％

[0103] Table 3

[0104] sample Planar compressive strength (MPa) L-axis shear strength (MPa) W-axis shear strength (MPa) Comparative test empty honeycomb 1.19 0.87 0.56 Example 1: Full Copper Plating 1.20 0.84 0.59 Example 4: Grayscale Gradient 1 1.16 0.85 0.57 GJB1874-2021A 0.85 0.61 0.42

[0105] As can be seen from Table 1, the patterned copper-plated honeycomb prepared in the examples has wave absorption capability and absorption frequency band adjustment capability in the range of 1-18 GHz.

[0106] As can be seen from Table 2, the weight gain of the patterned copper-plated honeycomb prepared in the examples can be controlled to less than 5% compared with that of the empty honeycomb, making it an ultralight structural and functional integrated composite material.

[0107] As can be seen from Table 3, compared with the mechanical properties of the empty honeycomb and related standards, the patterned copper-plated honeycomb prepared in the examples has the same planar compressive strength and L and W-direction shear strength as the empty honeycomb (L and W directions refer to the provisions in GJB1874-2021A standard), and is higher than the relevant industry standards.

[0108] Figure 1 The image shows a physical picture of the fully coated patterned copper-plated aramid honeycomb prepared in step six of Example 1; as can be seen from the picture, the copper-plated honeycomb has an orange appearance and a metallic luster.

[0109] Figure 2 This is a schematic diagram of the honeycomb structure of the precursor after chemical copper plating growth in step five of Example 1; Figure 3 This is a schematic diagram of the honeycomb structure after the precursor is grown by chemical copper plating in step five of Example 2; Figure 4 This is a schematic diagram of the honeycomb structure of the precursor after chemical copper plating growth in step five of Example 3; Figure 5 This is a schematic diagram of the honeycomb structure after the precursor is grown by chemical copper plating in step five of Example 4; Figure 6 This is a schematic diagram of the honeycomb structure after the precursor is grown by chemical copper plating in step five of Example 5.

[0110] Figure 7 This is a precision test diagram of the printing precursor pattern in step one of Example 3; Figure 8 This is a precision test diagram of the joint adhesive coating in step two of Example 3; Figure 9 The figures show actual images of the precursor patterns. Image a shows an actual image of a precursor pattern with different gray levels achieved using the printing method in step one of Example 1. Image b shows an actual image of a copper pattern deposited on a precursor pattern with different gray levels using the chemical copper plating method in step five of Example 1. As can be seen from the figures, the printing accuracy can reach 0.1 mm, and it supports 256 levels of copper plating adjustment. The accuracy of the adhesive dotting position can reach 0.1 mm.

[0111] Figure 10 The image shows the surface morphology of the aramid paper coated with the precursor pattern prepared in step one of Example 1. a represents the macroscopic, b represents the mesoscopic, and c represents the microscopic. As can be seen from the image, the nano-silver precursor is evenly distributed on the surface of the aramid paper after printing.

[0112] Figure 11 The image shows the surface morphology of the honeycomb structure of the precursor prepared in step five of Example 1 after chemical copper plating. a represents the macroscopic, b represents the mesoscopic, and c represents the microscopic. After copper plating, a layer of gravelly copper is deposited and grown on the surface of the precursor.

[0113] Figure 12 EDS surface analysis of the aramid paper coated with the precursor pattern prepared in step one of Example 1; as shown in the figure, the precursor component is silver (Jin Feng is gold-plated sample prepared for electron microscopy).

[0114] Figure 13 The figure shows the EDS surface analysis results of the honeycomb structure surface after the precursor prepared in step five of Example 1 was grown by chemical copper plating; as can be seen from the figure, the chemically deposited layer is copper (the gold peak is gold plating prepared for electron microscopy).

[0115] Figure 14 The image shows a scanning electron microscope (SEM) image of the copper layer in the honeycomb structure after the precursor prepared in step five of Example 1 is grown by chemical copper plating. As can be seen from the image, the patterned copper-plated honeycomb conductive layer in Example 1 is only about 2 micrometers thick.

[0116] Figure 15 The figures show the reflection loss comparison curves of the geometric gradient 2 prepared in Example 3 and the grayscale gradient 2 prepared in Example 5 in the X-band and Ku-band. It can be seen from the figure that, under the same honeycomb density (20mm) and similar weight gain, the honeycomb with grayscale gradient copper plating has a stronger wave absorption capacity than the honeycomb with geometric gradient copper plating, which shows the advantage of grayscale gradient printing.

Claims

1. A method for preparing patterned copper-plated absorbing honeycomb, characterized in that... It is done in the following steps:

1. Printing: Precursor patterns are printed on both sides of aramid paper using a metal particle solution to obtain aramid paper coated with precursor patterns. II. Applying adhesive: A nodule adhesive is coated onto aramid paper with a precursor pattern and the solvent is dried to obtain coated aramid paper. III. Overlapping and bonding: The aramid paper with adhesive is stacked and pressed together to cure, resulting in a laminated and bonded aramid paper. IV. Cutting and stretching: The aramid paper, which is laminated and bonded together, is cut into honeycomb paper stacks and stretched to obtain a honeycomb structure. In the honeycomb structure, each surface of the inner wall of the honeycomb pores is provided with a precursor pattern; V. Copper plating: While under tension, the honeycomb structure is immersed in copper plating solution and copper plating is performed at a temperature of 30℃~60℃ for 30min~120min. Finally, it is cleaned to obtain the honeycomb structure grown by chemical copper plating of the precursor. The copper plating solution is composed of agent A, agent B, and solvent; agent A is composed of CuSO4·5H2O, NaOH, potassium sodium tartrate, pH adjuster, and water; agent B is an aqueous solution of HCNO. VI. Impregnation and curing: While under tension, the honeycomb structure grown by chemical copper plating of the precursor is immersed in phenolic resin containing diluent, then removed and cured to obtain patterned copper-plated microwave absorbing honeycomb.

2. The method for preparing a patterned copper-plated absorbing honeycomb according to claim 1, characterized in that... The mass percentage of metal particles in the metal particle solution described in step one is 30% to 40%; the solvent in the metal particle solution described in step one is water, a weakly acidic aqueous solution, or an organic solvent.

3. The method for preparing a patterned copper-plated absorbing honeycomb according to claim 2, characterized in that... The metal particles in the metal particle solution are nano-silver particles or nano-platinum particles with a particle size of 30nm to 50nm; the weakly acidic aqueous solution is an aqueous solution of HCl with a mass percentage of 10% to 14%; and the organic solvent is trimethylol trioxide (1,2-propanediol).

4. The method for preparing a patterned copper-plated absorbing honeycomb according to claim 1, characterized in that... The grayscale form of the precursor pattern described in step one is the same grayscale, grayscale gradient, or grayscale jump.

5. The method for preparing a patterned copper-plated absorbing honeycomb according to claim 1, characterized in that... The printing described in step one is carried out in the following steps: ① Place the aramid paper in the working area of ​​the printer head, and then, under the conditions of piezoelectric on-demand ink supply drive, independent drive, nozzle resolution ≥360npi, ink droplet volume ≤13pl, emission frequency ≥45kHz, print width ≥72mm and gray level 1dpd~8dpd, use the motion platform to control the printer head to reciprocate on one side of the aramid paper to print the precursor pattern, and finally dry at room temperature for 30min~60min; ② Repeat step ① to print the precursor pattern on the other side of the aramid paper.

6. The method for preparing a patterned copper-plated absorbing honeycomb according to claim 1, characterized in that... The coating method described in step two is dispensing, gravure coating, or screen printing coating; the drying solvent described in step two is specifically drying at a temperature of 50℃~60℃ for 1h~3h.

7. The method for preparing a patterned copper-plated absorbing honeycomb according to claim 1, characterized in that... The curing process described in step three specifically involves curing at a temperature of 120℃~140℃ for 1h~3h.

8. The method for preparing a patterned copper-plated absorbing honeycomb according to claim 1, characterized in that... The area of ​​the precursor pattern described in step four accounts for 30% to 100% of the area of ​​the inner wall of the honeycomb lattice; the precursor pattern in the honeycomb structure described in step four is a rectangle or an isosceles triangle.

9. The method for preparing a patterned copper-plated absorbing honeycomb according to claim 1, characterized in that... In step five, the volume ratio of agent A to agent B is 1:(1.5-3); the volume ratio of agent A to solvent in step five is 1:(2.5-4); the solvent is water; the concentration of CuSO4·5H2O in agent A is 5 g / L-8 g / L, the concentration of NaOH is 5 g / L-8 g / L, the concentration of potassium sodium tartrate is 25 g / L-30 g / L, and the concentration of pH adjuster is 3 g / L-6 g / L; the pH adjuster is Na2CO3; and the mass percentage of HCHO in agent B is 30%-40%.

10. The method for preparing a patterned copper-plated absorbing honeycomb according to claim 1, characterized in that... In step six, while maintaining the stretched state, the honeycomb structure grown by chemical copper plating of the precursor is immersed in phenolic resin containing diluent for 10-20 minutes. Then, it is removed and cured first at 70-90°C for 0.5-1 hour, then at 110-130°C for 0.5-1 hour, then at 140-160°C for 0.5-1 hour, and finally at 170-190°C for 1-3 hours. The phenolic resin containing diluent comprises 80%-95% by mass of phenolic resin.

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