Preparation method of ultra-wideband radar stealth material coating

Abstract

The present application relates to a kind of preparation methods of ultra-wideband radar stealth material coating, based on the principle that three-dimensional ordered nanostructured material produces diffuse reflection to radar wave, adopt the thorn ball nano nickel powder formed by needle-like nano nickel, strengthen its microstructure with SiO2 Sol, as primary particle structure;Due to the easy agglomeration of nano particles, combined as thorn ball nano nickel powder agglomerate to form secondary ordered structure;Mixed evenly with silicone adhesive to make stealth material coating, so that thorn ball nano nickel powder is evenly distributed in the stealth material coating with a thickness of about 2mm, forming three-dimensional ordered structure;Equivalent to a statistically all-around reflection macroscopic planar structure composed of countless small, different direction reflection particles, diffuse scattering to radar microwave to attenuate radar echo signal intensity, realize ultra-wideband radar microwave stealth.

Description

Technical Field

[0001] This invention relates to a method for preparing an ultra-wideband radar stealth material coating, which falls under the category of functional materials technology. Technical Background

[0002] Radar stealth for stealth aircraft, warships, and cruise missiles involves reducing, suppressing, absorbing, and deflecting the radar echo intensity of a target, thereby lowering its RCS value and making it difficult for enemy radar to identify and detect within a certain range. This can be categorized into electromagnetic cancellation technology, special shaping technology for the target's surface, stealth composite material technology, and plasma stealth technology. Electromagnetic cancellation technology has been theoretically studied abroad for a considerable period, but there are few reports of its practical application to date, and given the rapid development of current radar detection technology, it has virtually no practical value. Special shaping technology for the target's surface is also ineffective against multistatic radar and has a significant impact on aircraft aerodynamics. Plasma technology requires a large amount of electrical energy and cannot be fully implemented on aircraft, warships, and cruise missiles; at most, it can only be used for partial stealth. Current stealth aircraft primarily utilize radar-absorbing materials.

[0003] Existing radar-absorbing materials mainly involve adding high-temperature resistant metal-based magnetic micron particles, rare earth components, or conductive oxides to improve their effectiveness. By absorbing radar waves, they generate magnetic and electrical losses, thereby reducing the vertical radar echo intensity of the target and achieving radar stealth. Since both magnetic and electrical losses have quantum energy level characteristics, they exhibit absorption peaks in specific microwave frequency bands. If the frequency band jumps out of the corresponding "quantum energy level," the absorption becomes very weak. This is why current stealth aircraft do not have stealth effects against frequency-hopping radar or in the C-band, S-band, L-band, and VHF bands.

[0004] Countries are expanding the bandwidth of absorbing materials in hopes of achieving broadband and ultra-wideband stealth. However, due to the "quantum energy level" characteristics of magnetic and electrical loss materials, it is difficult to achieve broadband absorption. The main absorption frequency band is in the X-band, and the absorption bandwidth is at most 6.5 to 7.5 GHz.

[0005] The existing radar microwave stealth coatings in China are similar to those used on the US F-35 and F-22 stealth fighters. They are mainly composite powders made of magnetic loss materials such as ferrite, carbon-based iron powder and electrical loss materials such as conductive oxides. Due to the oxidation of the radar-absorbing materials, their stealth performance is reduced, requiring frequent maintenance and recoating. There has been no disruptive or breakthrough progress.

[0006] Because absorbing materials composed of electrical and magnetic loss materials have quantum energy level characteristics, the expansion of the absorption bandwidth is limited; therefore, only by breaking through the stealth mechanism of absorbing materials can ultra-wideband stealth be achieved; in order to achieve ultra-wideband radar stealth, this invention was completed. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing an ultra-wideband radar stealth material coating, based on the principle of diffuse reflection of radar waves by three-dimensional ordered nanostructured materials. It utilizes needle-like nano-nickel nanoparticles to form spiky-spherical nickel powder as the primary particle structure, which is reinforced by SiO2 sol. Due to the easy aggregation of nanoparticles, they combine to form spiky-spherical nickel powder agglomerates, creating a secondary ordered structure. This agglomerates are then uniformly mixed with an organosilicon adhesive to form a stealth material coating. The spiky-spherical nickel powder is evenly distributed in the stealth material coating, which is approximately 2 mm thick, forming a three-dimensional ordered structure. This is equivalent to countless tiny, differently oriented reflective particles constituting a statistically omnidirectional macroscopic planar structure, which diffusely scatters radar microwaves to attenuate the radar echo signal intensity, thus achieving ultra-wideband radar microwave stealth.

[0008] To achieve the above objectives, the present invention employs the following steps:

[0009] 1. A method for preparing an ultra-wideband radar stealth material coating, comprising mixing, brushing, and drying spiky spherical nickel nanopowder with a microstructure reinforced by SiO2 sol and a base adhesive, wherein the base adhesive is an organosilicon adhesive; the mass ratio of the two is between 30-60:70-40, wherein the spiky spherical nickel nanopowder includes the weight of the SiO2 sol particles that reinforce the microstructure.

[0010] 2. Before preparing the ultra-wideband radar stealth material coating, spiky spherical nickel nanopowder is slowly stirred with SiO2 sol at a concentration of 1-3% (wt%) until uniformly mixed; the ratio of spiky spherical nickel nanopowder to the total solid content of SiO2 in the spiky spherical nickel nanopowder and SiO2 sol is controlled to be 85-95% (wt%); then it is allowed to stand for 6-12 hours to allow the SiO2 sol particles to adsorb and adhere to the spiky spherical nickel nanopowder; after filtration, it is vacuum dried at 100-110℃ to obtain microstructure-enhanced spiky spherical nickel nanopowder aggregates;

[0011] 3. Mix the microstructure-enhanced spiky nickel nanopowder with silicone adhesive evenly. If the viscosity is too high and not conducive to the construction process, a small amount of organic solvent can be added for dilution. Apply by brushing or spraying to form a coating of about 2 mm. After drying, it forms an ultra-wideband radar stealth material coating. The optimal range is 1.8 to 2.2 mm. Alternatively, it can be brushed onto fiberglass cloth. After drying, it forms an ultra-wideband radar stealth material roll, which is convenient for immediate bonding and repair during wartime.

[0012] Advantages of this invention:

[0013] 1. Using silicone adhesive as the base adhesive can improve the weather resistance and high and low temperature resistance of ultra-wideband radar stealth materials, and extend the service life of coatings or roll materials;

[0014] 2. SiO2 sol particles are adsorbed and solidified onto the spiky nickel nanopowder, which strengthens its microstructure and prevents the internal tension generated during the drying process of the coating base adhesive from destroying the microstructure of the spiky nickel nanopowder and causing it to lose its diffuse scattering function. Attached Figure Description

[0015] Figure 1 shows the field emission electron scanning image of the self-made spiky spherical nickel nanopowder used in Example 1 of the present invention to verify the mechanism of the ultra-wideband radar stealth material coating to diffusely scatter radar microwaves and attenuate the radar echo signal intensity. The reflectivity test curve of the ultra-wideband radar stealth material coating is shown in Figure 1(b).

[0016] Figure 2 is a comparative sample 2 used in Example 1 of the present invention to verify the mechanism of the ultra-wideband radar stealth material coating to diffusely scatter radar microwaves and attenuate the radar echo signal intensity. The field emission electron scanning image of the imported INCO carbonyl nickel powder used is shown in Figure 2(a); and the reflectivity test curve of the coating is shown in Figure 2(b).

[0017] Figure 3 is a comparative sample 3 used in Embodiment 1 of the present invention to verify the mechanism of the ultra-wideband radar stealth material coating to diffusely scatter radar microwaves and attenuate the radar echo signal intensity. The field emission electron scanning image of the carbonyl nickel powder used is shown in Figure 3(a); and the reflectivity test curve of the coating is shown in Figure 3(b).

[0018] Figure 4 is a comparative sample 4 of the mechanism by which the ultra-wideband radar stealth material coating of the present invention generates diffuse scattering of radar microwaves to attenuate the radar echo signal intensity. The field emission electron scanning image of the self-made spiked spherical nickel nanopowder reinforced by SiO2 sol after ball milling is shown in Figure 4(a); and the reflectivity test curve of the coating is shown in Figure 4(b).

[0019] Figure 5 The laser particle size distribution curve of the spiky spherical nickel nanopowder used in Embodiment 1 of this invention to verify the mechanism by which the ultra-wideband radar stealth material coating diffusely scatters radar microwaves to attenuate the intensity of radar echo signals is shown.

[0020] Figure 6 shows the field emission electron scanning images of the self-made spiky spherical nickel nanopowder before and after ultrasonic treatment, used in Example 1 of this invention to verify the mechanism of the ultra-wideband radar stealth material coating to diffusely scatter radar microwaves and attenuate the radar echo signal intensity. Figure 6(a) is a photo of the self-made spiky spherical nickel nanopowder before ultrasonic treatment, and Figure 6(b) is a scanning image of the self-made spiky spherical nickel nanopowder after ultrasonic dispersion in anhydrous ethanol for 2 minutes.

[0021] Figure 7 shows the field emission electron scanning image and microwave reflectivity test curve of the self-made spiky spherical nickel nanopowder used in the preparation of the ultra-wideband radar stealth material coating in Example 2 of the present invention; Figure 7(a) and 7(b) are field emission electron scanning images of the self-made spiky spherical nickel nanopowder used in Example 2 at magnification of 80,000x and 4,000x, respectively; Figure 7(c) is the microwave reflectivity test curve of the ultra-wideband radar stealth material coating prepared in Example 2.

[0022] Figure 8 shows a field emission electron scanning image of the self-made spiky spherical nickel nanopowder reinforced with SiO2 sol used in the preparation of the ultra-wideband radar stealth material coating in Example 3 of the present invention, as shown in Figure 8(a); and a reflectivity test curve of the ultra-wideband radar stealth material roll, as shown in Figure 8(b).

[0023] Appendix Explanation

[0024] Appendix 1: Relevant test parameters and test results for each embodiment. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments:

[0026] Example 1

[0027] I. SiO2 Sol-Strengthening Treatment of Nickel Powder

[0028] 400g of self-made spiky spherical nickel nanopowder was weighed and added to 2000g of SiO2 nanosol with a solid content of 1.5% (wt%) and an average particle size of 20nm. The mixture was slowly stirred for 60min, allowed to stand for 10 hours, and filtered to remove the SiO2 sol that was not adsorbed on the nickel nanopowder. The mixture was then vacuum dried at 100℃ for 2 hours and weighed to 396g. Some nickel nanopowder was lost during filtration. The 396g of processed spiky spherical nickel nanopowder was divided into two portions of 198. One portion was used as test sample 1, and the other portion was ball-milled for 5 minutes as control sample 4.

[0029] 200g each of imported INCO carbonyl nickel powder and Jinchuan carbonyl nickel powder were weighed and added to 1000g of SiO2 nanosol with a solid content of 1.5% (wt%) and an average particle size of 20nm. The mixture was stirred slowly for 60min, allowed to stand for 10 hours, and filtered to remove the SiO2 sol that was not adsorbed on the nano-nickel powder. The mixture was then vacuum dried at 100℃ for 2 hours. The treated INCO carbonyl nickel powder was weighed to be 203g and the treated Jinchuan carbonyl nickel powder to be 204g, which were reserved as control sample 2 and control sample 3, respectively.

[0030] II. Preparation of Absorbing Coatings for Verifying the Mechanism of Diffuse Reflection Attenuation of Radar Echoes

[0031] 60g each of the following nano-nickel powders were weighed: self-made spiky spherical nano-nickel powder (SiO2 sol-reinforced), imported INCO carbonyl nickel powder (SiO2 sol-reinforced), Jinchuan carbonyl nickel powder (SiO2 sol-reinforced), and self-made spiky spherical nano-nickel powder (ball-milled). Each was placed in one of four clean 500mL beakers, and 60mL of xylene was added to each. The mixture was stirred to adjust the viscosity of the coating. 60g each of commercially available Giant Arrow 988 silicone adhesive was added to each beaker, and the mixture was stirred. Both samples were then evenly brushed onto a 5mm thick 200mm x 200mm 7075 aluminum alloy plate to create coating samples. After drying, the adhesive residue along the vertical edges of the aluminum alloy plate was scraped off with a scraper. The samples were weighed to determine the areal density of the coating samples. The vertical reflectance of the coating samples was then tested using the bow method.

[0032] III. SEM Analysis of Powder Samples

[0033] Powder samples were placed on the conductive adhesive on the sample stage for field emission electron scanning electron microscopy analysis.

[0034] One sample of spiky nickel nanoparticles was dispersed in anhydrous ethanol, sonicated for 2 minutes, and then compared with an untreated sample to observe the microstructural strength of the spiky nickel nanoparticles.

[0035] IV. Laser particle size testing of spiky nickel nanoparticles

[0036] The spiky spherical nickel nanoparticles of test sample 1 were taken and their particle size distribution was analyzed using a BT-2300ST laser particle size analyzer and compared with the SEM analysis results.

[0037] Example 2

[0038] I. SiO2 Sol-Reinforced Treatment of Spiky Spherical Nickel Nanopowder

[0039] Weigh 200g of the self-made spiky nano-nickel powder and add it to 1150g of SiO2 nanosol with a solid content of 3.0% (wt%) and an average particle size of 15nm. Stir slowly for 60min, let stand for 6 hours, filter to remove the SiO2 sol that is not adsorbed on the nano-nickel powder; vacuum dry at 110℃ for 2 hours, take it out and weigh it, which is 202g, of which a small amount of nano-nickel powder was lost during filtration.

[0040] A small amount of self-made spiky nano-nickel powder was also taken and analyzed by SEM.

[0041] II. Preparation of Absorbing Coatings for Diffuse Reflection Attenuation of Radar Echoes

[0042] Weigh 36g of self-made spiky nano-nickel powder that has been strengthened by SiO2 sol and place it in a clean 500mL beaker. Add 65mL of xylene and stir well to adjust the viscosity of the coating. Add 84g of commercially available Sibao 998 organosilicon weather-resistant sealant and stir well. Then, brush the sealant evenly onto a 5mm thick 200mm x 200mm 7075 aluminum alloy plate to make a coating sample. After drying, scrape off the adhesive on the vertical edge of the aluminum alloy plate with a scraper and weigh it to determine the areal density of the coating sample. Then, use the bow method to test the vertical reflectance of the coating sample.

[0043] Example 3

[0044] I. SiO2 Sol-Reinforced Treatment of Spiky Spherical Nickel Nanopowder

[0045] Weigh 200g of the self-made spiky nano-nickel powder and add it to 1000g of SiO2 nanosol with a solid content of 1.15% (wt%) and an average particle size of 15nm. Stir slowly for 60min, let stand for 12 hours, filter to remove the SiO2 sol that is not adsorbed on the nano-nickel powder, vacuum dry at 110℃ for 2 hours, and weigh it to 201g. A small amount of nano-nickel powder was lost during filtration.

[0046] A small amount of spiky nickel nanoparticles treated with SiO2 sol were taken and analyzed by SEM.

[0047] II. Preparation of Absorbing Coatings for Diffuse Reflection Attenuation of Radar Echoes

[0048] Weigh 112g of self-made spiky nano-nickel powder reinforced with SiO2 sol, place it in a clean 500mL beaker, add 70mL of xylene, and stir well to adjust the viscosity of the coating; add 75g of commercially available Sibao 998 organosilicon weather-resistant sealant, stir well, and then brush it evenly onto a 1mm thick 250mm x 250mm high-silica fiberglass cloth to make a roll sample; after drying, cut out 200mm x 200mm samples, weigh them, and determine the areal density of the coating by comparing the weight of the 200mm x 200mm sample with that of the 200mm x 200mm high-silica fiberglass cloth; use a 200mm x 200mm 5mm thick 7075 aluminum alloy plate as a good conductor metal plate for microwave vertical reflectivity testing, and use the bow method to test the reflectivity of the roll.

[0049] Table 1. Relevant test parameters and test results for each embodiment*

[0050]

[0051] *Note: The weight of the nickel powder treated with SiO2 sol-reinforced in Examples 1-3 is 200g.

[0052] Analysis of the results from Example 1 shows that the nano-nickel powder with a spiky nanostructure (see Figure 1(a)) dispersed in an organosilicon-based coating after SiO2 sol reinforcement can form a good microwave absorption effect (see Figure 1(b)). However, under the same conditions, the coatings prepared by INCO carbonyl nickel powder and Jinchuan carbonyl nickel powder, which do not have this microstructure (see Figures 2(a) and 3(a)), have very poor microwave absorption effects (see Figures 2(b) and 3(b)). For the control sample 4, which has the same microstructure as the test sample, the nano-nickel powder particles after SiO2 sol reinforcement are ground, resulting in the destruction of their microstructure, and the coating prepared also has a poor microwave absorption effect (see Figures 4(a) and 4(b)). Here, the explanation using the concept of microwave absorption effect follows a traditional term for radar microwave attenuation coatings. In fact, this invention utilizes the diffuse reflection phenomenon of radar microwaves formed by the multi-layered micro-ordered structure of spiky nano-nickel powder, which leads to the attenuation of radar vertical echo.

[0053] As can be seen from Table 1, the stealth bandwidth of the test sample has reached 8.5 GHz, exceeding the electrical and magnetic losses of 6.5 to 7.5 GHz.

[0054] from Figure 5 The laser particle size analysis results, compared with the SEM image of the spiky nickel nanoparticles in Figure 1(a), show that the spiky nickel nanoparticles exist in the form of aggregates, forming an ordered microstructure of secondary particles.

[0055] As can be seen from Figures 6(a) and 6(b), after ultrasonic treatment, the spiked structure of the spiky nickel nanopowder is broken and the needle-like particles are fractured. This shows the fragility of the spiked nickel nanopowder structure. It must be strengthened to maintain its microstructure and to diffusely scatter radar microwaves to attenuate the radar echo signal intensity.

[0056] As can be seen from Table 1, the stealth bandwidth of the coating prepared by the spiked nickel nanoparticles in Example 2 only reached 5.8 GHz (see Figures 7(a), 7(b), and 7(c), which seems unsatisfactory). Although it has good primary and secondary microstructures of spiked nickel nanoparticles, the content of spiked nickel nanoparticles in the coating is low, and it failed to form an effective tertiary ordered structure, which may be the main reason. In contrast, Example 3, by increasing the content of spiked nickel nanoparticles in the coating, achieved a stealth bandwidth of 11.8 GHz, covering the C, X, and Ku bands (see Figures 8(a) and 8(b), which far exceeds the performance of conventional stealth materials with electrical loss + magnetic loss. This highlights the stealth advantage of ultra-wideband radar stealth materials in that they diffusely scatter radar microwaves to attenuate the radar echo signal intensity.

[0057] It should be noted that the specific embodiments described above enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the present invention in any way. Therefore, although the present invention has been described in detail with reference to the accompanying drawings and embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention; and all technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention patent.

Claims

1. A method for preparing an ultra-wideband radar stealth material coating, characterized in that... The ultra-wideband radar stealth material coating is made by uniformly mixing spiky spherical nickel nanopowder with a microstructure reinforced by SiO2 sol and a base adhesive, brushing and drying to form a coating with a thickness of 1.8 to 2.2 mm. The mass ratio of spiky spherical nickel nanopowder with a microstructure reinforced by SiO2 sol and the base adhesive is between 30 to 60: 70 to 40. Among them: the weight of the spiky spherical nickel nanopowder includes the SiO2 sol particles that enhance its microstructure. The base adhesive is an organosilicone adhesive.

2. The method for preparing an ultra-wideband radar stealth material coating as described in claim 1, characterized in that... The SiO2 sol-reinforced spiky spherical nickel nanopowder is prepared by slowly stirring and mixing SiO2 sol with spiky spherical nickel nanopowder at a concentration of 1-3 wt%, letting it stand for 6-12 hours, filtering, and vacuum drying at 100-110℃.

3. The method for preparing an ultra-wideband radar stealth material coating as described in claims 1 and 2, characterized in that... In the preparation of SiO2 sol-reinforced spiky nickel nanopowder, the spiky nickel nanopowder accounts for 85-95 wt% of the total solid content of SiO2 in the spiky nickel nanopowder and SiO2 sol.

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