Hollow nickel-based composite wave-absorbing coating, preparation method and application

Abstract

The invention discloses a hollow nickel-based composite wave-absorbing coating as well as a preparation method and application thereof. The wave-absorbing coating is prepared from a main body composite material and an organic carrier, wherein the main composite material comprises hollow nickel-based particles and an auxiliary material; the main body composite material accounts for 2-40wt% of the hollow nickel-based composite wave-absorbing coating; the organic carrier accounts for 60-98 wt% of the hollow nickel-based composite wave-absorbing coating; the proportion of the hollow nickel-based particles in the main body composite material is 20-90wt%; and the auxiliary material accounts for 10-80 wt% of the main body composite material. The components and the structure of the hollow nickel-based particles in the composite wave-absorbing coating can be adjusted by adjusting template parameters, and the composite material coating is endowed with good dielectric loss and magnetic loss characteristics, so that the composite material coating has good electromagnetic wave absorption performance in a wide frequency range.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave absorbing coatings, and more specifically to a hollow nickel-based composite microwave absorbing coating, a preparation method and application thereof. Background Art

[0002] The booming electronic communication technology is a double-edged sword. While it brings convenience to mankind, it also produces serious electromagnetic pollution [Peng Qinggang. Preparation and functionalization research of biomass-based electromagnetic shielding and absorbing materials [D]. Qilu University of Technology, 2024.]. These pollutions not only affect the normal use of electronic products, but also endanger human health [Zhang Mengxin. Research on the construction strategy and shielding effectiveness of flexible absorbing textiles [D]. Zhongyuan University of Technology, 2024.]. Therefore, it is of great significance to develop new high-performance absorbing materials.

[0003] Absorbing materials can convert incident electromagnetic energy into heat and dissipate it, thereby absorbing the incident electromagnetic waves and preventing secondary contamination of electromagnetic waves. In order to obtain higher absorbing capacity, absorbing materials need to meet two conditions: (1) the incident electromagnetic waves can enter the absorbing material to the maximum extent, that is, the absorbing material should have good impedance matching characteristics; (2) the electromagnetic waves entering the material can be lost to the maximum extent, that is, the absorbing material has a strong attenuation ability [Han Guangbing, Li Hui, Gao Chengyong, et al.Fe 3 O 4 Research progress of electromagnetic wave absorbing materials based on nanostructured carbon nanotubes[J]. Physical Experiment, 2024, 44(12): 1-12.].

[0004] In the field of microwave absorption, Yin et al. used NaCl as a template and phenolic resin as a carbon source to prepare micron-sized hollow cubic carbon, achieving the best reflection loss of -43.99 dB at a matching thickness of 1.5 mm [Yin X, Zhang Z, Zhang F, et al. Preparation and absorbing properties of ultra-light and large size hollow cubic carbon materials [J]. Journal of Materials Science: Materials in Electronics, 2024, 35, 1114.]. Xiao et al. designed and constructed necklace-like hollow PAN / carbon nanofibers using a continuous electrospinning-carbonization-etching route, achieving the strongest reflection loss of -44.73 dB [Xiao JX, Zhan BB, He MK, et al. Interfacial polarization loss improvement induced by the hollow engineering of necklace-like PAN / carbon nanofibers for boosted microwave absorption [J], Advanced Functional Materials, 2024, 35, 2316722.].

[0005] However, due to their single attenuation mechanism and weak stability, current absorbing materials have insurmountable shortcomings such as complex preparation methods, weak reflection loss intensity, and poor impedance matching characteristics. Therefore, how to design the composition and structure of absorbing materials to optimize electromagnetic protection performance is still a hot topic of research. Summary of the invention

[0006] The first technical problem to be solved by the present invention is to provide a hollow nickel-based composite absorbing coating. The hollow nickel-based particles in the composite absorbing coating can adjust the composition and structure by adjusting the template parameters, and give the composite coating better dielectric and magnetic loss properties, so that it has good electromagnetic wave absorption performance in a wider frequency range.

[0007] The second technical problem to be solved by the present invention is to provide a method for preparing a hollow nickel-based composite absorbing coating; the preparation method solves the problems of complex preparation process of absorbing materials, high energy consumption, poor absorbing performance and impedance matching.

[0008] The third technical problem to be solved by the present invention is to provide an application of the above-mentioned hollow nickel-based composite absorbing coating.

[0009] To solve the above-mentioned first technical problem, the technical solution adopted by the present invention is as follows:

[0010] A hollow nickel-based composite absorbing coating is prepared from a main composite material and an organic carrier; wherein:

[0011] The main composite material includes hollow nickel-based particles and auxiliary materials;

[0012] The main composite material accounts for 2-40wt% in the hollow nickel-based composite absorbing coating;

[0013] The organic carrier accounts for 60-98wt% in the hollow nickel-based composite microwave absorbing coating;

[0014] The hollow nickel-based particles account for 20-90wt% of the main composite material;

[0015] The auxiliary material accounts for 10-80wt% in the main composite material.

[0016] Preferably, the organic carrier is selected from one or more of epoxy resin, phenolic resin, polyurethane resin, polyvinyl butyral, polydimethylsiloxane, urea-formaldehyde resin, hydrogenated cyanobutyl rubber, silicone resin and acrylic resin.

[0017] Preferably, the auxiliary material is selected from one or more of graphene, silver, silicon carbide, carbon nanotubes, polypyrrole, polyaniline, polydopamine, polythiophene, ferrosoferric oxide, and Mxene.

[0018] To solve the above second technical problem, the technical solution adopted by the present invention is as follows:

[0019] A method for preparing a hollow nickel-based composite microwave absorbing coating comprises the following steps:

[0020] S1, preparing a sodium sulfate template ethanol dispersion;

[0021] S2, adding nickel salt and surfactant to the template dispersion obtained in S1 to carry out coating reaction, centrifugally washing after the reaction to obtain an intermediate; dispersing the obtained intermediate in anhydrous ethanol, adding sodium borohydride to carry out reduction reaction, and centrifugally washing and drying for a second time after the reduction reaction to obtain hollow nickel-based particles;

[0022] S3, adding the hollow nickel-based particles and the auxiliary materials into a solvent for mixing, separating and drying, and obtaining a main composite material;

[0023] S4, taking the main composite material obtained in step S3 and the organic carrier and stirring and mixing them thoroughly to obtain a hollow nickel-based composite microwave absorbing coating.

[0024] Preferably, in step S1, the specific step of preparing the sodium sulfate template ethanol dispersion is: adding a saturated sodium sulfate aqueous solution dropwise into anhydrous ethanol to obtain a sodium sulfate ethanol dispersion, wherein the volume ratio of the saturated sodium sulfate aqueous solution to the anhydrous ethanol is 1:4-1:100, and the temperature of the anhydrous ethanol is -30-60°C.

[0025] Preferably, in step S2, the nickel salt is selected from one or more of the following substances: nickel acetate tetrahydrate, nickel chloride hexahydrate, nickel nitrate hexahydrate, nickel acetylacetonate, nickel bromide, and nickel iodide.

[0026] Preferably, in step S2, the coating reaction temperature is -30 to 60°C, and the time is 12 to 48 hours; the reduction reaction temperature is -10 to 50°C, and the time is 2 to 24 hours.

[0027] Preferably, in step S2, the surfactant is selected from one or more of the following substances: sodium dodecylbenzene sulfonate, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, polyacrylic acid, polyvinyl pyrrolidone, polyethylene glycol, silane coupling agent, Tween 80, and Triton X-100.

[0028] Preferably, in step S2, the mass ratio of the nickel salt to the surfactant is 1:0.1-1:10.

[0029] Preferably, in step S2, the morphology of the hollow nickel-based particles is one or more of the following shapes: cuboid, hexahedron, octahedron, sphere, rod, cylinder.

[0030] Preferably, in step S3, the auxiliary material is selected from one or more of graphene, silver, silicon carbide, carbon nanotubes, polypyrrole, polyaniline, polydopamine, polythiophene, ferrosoferric oxide, and Mxene.

[0031] Preferably, in step S3, the solvent is selected from one or more of the following materials: deionized water, ethanol, ethylene glycol, methanol, glycerol, acetone, dichloromethane, N,N-dimethylformamide, and acetonitrile.

[0032] Preferably, in step S4, the organic carrier is selected from one or more of the following materials: epoxy resin, phenolic resin, polyurethane resin, polyvinyl butyral, polydimethylsiloxane, urea-formaldehyde resin, hydrogenated cyanobutyl rubber, silicone resin, acrylic resin.

[0033] To solve the third technical problem, the technical solution adopted by the present invention is as follows:

[0034] An application of the above hollow nickel-based composite absorbing coating in electromagnetic protection.

[0035] Any range described in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0036] Unless otherwise specified, all raw materials in the present invention can be purchased from the market, and the equipment used in the present invention can adopt conventional equipment in the relevant field or refer to the existing technology in the relevant field.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1) The template used in the present invention can be removed by washing, which is green and environmentally friendly, and the size of the outer shell can be adjusted by adjusting the size of the template;

[0039] 2) The present invention can achieve efficient electromagnetic wave absorption performance or electromagnetic shielding performance by adjusting the size of the hollow nickel-based particles;

[0040] 3) The composite material formed by the hollow nickel-based particles of the present invention and other different auxiliary materials has different electromagnetic wave loss mechanisms;

[0041] 4) The present invention can achieve absorption of electromagnetic waves of different frequencies by adjusting the coating thickness, and is expected to be applied to various equipment and products requiring electromagnetic protection in the civil and military fields, such as medical instruments, communication equipment, aerospace equipment, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0043] Figure 1 is a scanning electron microscope image of the hollow nickel / nickel oxide prepared in Example 1;

[0044] Figure 2 is a scanning electron microscope image of the sodium sulfate template prepared in Example 2;

[0045] Figure 3 is a scanning electron microscope image of the sodium sulfate template prepared in Example 3;

[0046] Figure 4 is a scanning electron microscope image of the hollow nickel / nickel oxide@silver prepared in Example 4;

[0047] Figure 5 is a scanning electron microscope image of the hollow nickel / nickel oxide@polypyrrole prepared in Example 5;

[0048] Figure 6 is a graph of the microwave absorption performance of the coating prepared in Example 8;

[0049] Figure 7 The scanning electron microscope image of the hollow nickel / nickel oxide particles prepared in Comparative Example 2;

[0050] Figure 8 The scanning electron microscope image of the hollow nickel / nickel oxide particles prepared in Comparative Example 4;

[0051] Fig. 9 This is the wave absorption performance diagram of the pure epoxy resin prepared in Blank Example 1. DETAILED DESCRIPTION

[0052] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0053] Various cross-sectional views of the embodiments disclosed in the present invention are shown in the accompanying drawings. These drawings are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the drawings and the relative sizes and positional relationships between them are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0054] As one aspect of the present invention, a hollow nickel-based composite absorbing coating is prepared from a main composite material and an organic carrier; wherein:

[0055] The main composite material includes hollow nickel-based particles and auxiliary materials;

[0056] The main composite material accounts for 2-40wt% in the hollow nickel-based composite absorbing coating;

[0057] The organic carrier accounts for 60-98wt% in the hollow nickel-based composite microwave absorbing coating;

[0058] The hollow nickel-based particles account for 20-90wt% of the main composite material;

[0059] The auxiliary material accounts for 10-80wt% in the main composite material.

[0060] According to some embodiments of the present invention, the organic carrier is selected from one or more of epoxy resin, phenolic resin, polyurethane resin, polyvinyl butyral, polydimethylsiloxane, urea-formaldehyde resin, hydrogenated cyanobutyl rubber, silicone resin, and acrylic resin.

[0061] According to some embodiments of the present invention, the auxiliary material is selected from one or more of graphene, silver, silicon carbide, carbon nanotubes, polypyrrole, polyaniline, polydopamine, polythiophene, ferrosoferric oxide, and Mxene.

[0062] As another aspect of the present invention, a method for preparing a hollow nickel-based composite microwave absorbing coating comprises the following steps:

[0063] S1, preparing a sodium sulfate template ethanol dispersion;

[0064] S2, adding nickel salt and surfactant to the template dispersion obtained in S1 to carry out coating reaction, centrifugally washing after the reaction to obtain an intermediate; dispersing the obtained intermediate in anhydrous ethanol, adding sodium borohydride to carry out reduction reaction, and centrifugally washing and drying for a second time after the reduction reaction to obtain hollow nickel-based particles;

[0065] S3, adding the hollow nickel-based particles and the auxiliary materials into a solvent for mixing, separating and drying, and obtaining a main composite material;

[0066] S4, taking the main composite material obtained in step S3 and the organic carrier and stirring and mixing them thoroughly to obtain a hollow nickel-based composite microwave absorbing coating.

[0067] According to certain embodiments of the present invention, in step S1, the specific step of preparing the sodium sulfate template ethanol dispersion is: adding a saturated sodium sulfate aqueous solution dropwise into anhydrous ethanol to obtain a sodium sulfate ethanol dispersion, wherein the volume ratio of the saturated sodium sulfate aqueous solution to the anhydrous ethanol is 1:4-1:100, and the temperature of the anhydrous ethanol is -30 to 60°C

[0068] According to some embodiments of the present invention, in step S2, the nickel salt is selected from one or more of the following substances: nickel acetate tetrahydrate, nickel chloride hexahydrate, nickel nitrate hexahydrate, nickel acetylacetonate, nickel bromide, and nickel iodide.

[0069] According to certain embodiments of the present invention, in step S2, the coating reaction temperature is -30 to 60°C, and the time is 12 to 48 hours; the reduction reaction temperature is -10 to 50°C, and the time is 2 to 24 hours.

[0070] According to certain embodiments of the present invention, in step S2, the surfactant is selected from one or more of the following substances: sodium dodecylbenzene sulfonate, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, polyacrylic acid, polyvinyl pyrrolidone, polyethylene glycol, silane coupling agent, Tween 80, and Triton X-100.

[0071] According to some embodiments of the present invention, in step S2, the mass ratio of the nickel salt to the surfactant is 1:0.1-1:10.

[0072] According to some embodiments of the present invention, in step S2, the morphology of the hollow nickel-based particles is one or more of the following shapes: cuboid, hexahedron, octahedron, sphere, rod, or cylinder.

[0073] According to some embodiments of the present invention, in step S3, the auxiliary material is selected from one or more of graphene, silver, silicon carbide, carbon nanotubes, polypyrrole, polyaniline, polydopamine, polythiophene, ferrosoferric oxide, and Mxene.

[0074] According to some embodiments of the present invention, in step S3, the solvent is selected from one or more of the following materials: deionized water, ethanol, ethylene glycol, methanol, glycerol, acetone, dichloromethane, N,N-dimethylformamide, acetonitrile

[0075] According to some embodiments of the present invention, in step S4, the organic carrier is selected from one or more of the following materials: epoxy resin, phenolic resin, polyurethane resin, polyvinyl butyral, polydimethylsiloxane, urea-formaldehyde resin, hydrogenated cyanobutyl rubber, silicone resin, acrylic resin

[0076] As another aspect of the present invention, the present invention provides an application of the above-mentioned hollow nickel-based composite absorbing coating in electromagnetic protection.

[0077] Example 1

[0078] A method for preparing rectangular hollow nickel / nickel oxide particles comprises the following steps:

[0079] 10 mL of a saturated aqueous solution of sodium sulfate was added dropwise into 200 mL of anhydrous ethanol (-10°C) to obtain a sodium sulfate dispersion; 3 g of nickel nitrate hexahydrate and 1.2 g of polyvinyl pyrrolidone were added to the above dispersion, mechanically stirred for 24 hours, and then centrifuged and washed; the collected intermediate was dispersed in 150 mL of anhydrous ethanol, reduced with 1.6 g of sodium borohydride (dispersed in 50 mL of anhydrous ethanol) for 12 hours (-30°C), and then centrifuged and washed again to obtain rectangular hollow nickel / nickel oxide particles.

[0080] Figure 1 This is a scanning electron microscope image of the hollow nickel / nickel oxide particles prepared in this example.

[0081] Example 2

[0082] A method for preparing spherical hollow nickel / nickel oxide particles comprises the following steps:

[0083] 5 mL of a saturated aqueous solution of sodium sulfate was added dropwise into 100 mL of anhydrous ethanol (-10°C) to obtain a sodium sulfate dispersion; 2 g of nickel acetylacetonate and 0.6 g of hexadecyltrimethylammonium bromide were added to the above dispersion, mechanically stirred for 18 hours, and then centrifuged and washed; the collected intermediate was dispersed in 150 mL of anhydrous ethanol, reduced with 0.8 g of sodium borohydride (dispersed in 50 mL of anhydrous ethanol) for 6 hours (-10°C), and then centrifuged and washed again to obtain a spherical hollow nickel / nickel oxide.

[0084] Figure 2 This is a scanning electron microscope image of the sodium sulfate template prepared in this example.

[0085] Example 3

[0086] A method for preparing spherical hollow nickel / nickel oxide particles comprises the following steps:

[0087] 5 mL of a saturated aqueous solution of sodium sulfate was added dropwise into 100 mL of anhydrous ethanol (50° C.) to obtain a sodium sulfate dispersion; 2 g of nickel chloride hexahydrate and 0.6 g of hexadecyltrimethylammonium bromide were added to the above dispersion, mechanically stirred for 18 hours, and then centrifuged and washed; the collected intermediate was dispersed in 150 mL of anhydrous ethanol, reduced with 1 g of sodium borohydride (dispersed in 50 mL of anhydrous ethanol) (50° C.), and then centrifuged and washed again to obtain a spherical hollow nickel / nickel oxide.

[0088] Figure 3 This is a scanning electron microscope image of the sodium sulfate template prepared in this example.

[0089] Example 4

[0090] A method for preparing a hollow nickel / nickel oxide@silver composite material comprises the following steps:

[0091] Take 0.3 g of the dried hollow nickel / nickel oxide in Example 1 and disperse it in 150 mL of anhydrous ethanol. -1 The silver nitrate ethanol solution was added into the above ethanol, and after mechanical stirring for 1 hour, the hollow nickel / nickel oxide@silver composite material was obtained after separation and drying.

[0092] Figure 4 This is a scanning electron microscope image of the hollow nickel / nickel oxide@silver composite material prepared in this example.

[0093] Example 5

[0094] A method for preparing a hollow nickel / nickel oxide@polypyrrole composite material comprises the following steps:

[0095] 0.3 g of the dried hollow nickel / nickel oxide in Example 1 and 0.3 g of pyrrole were dispersed in 150 mL of deionized water, 50 mL of ammonium persulfate aqueous solution was added to the mixed dispersion, and after mechanical stirring at 0-5° C. for 12 h, the hollow nickel / nickel oxide@polypyrrole composite material was obtained after separation and drying.

[0096] Figure 5 This is a scanning electron microscope image of the hollow nickel / nickel oxide@polypyrrole composite material prepared in this example.

[0097] Example 6

[0098] A method for preparing a hollow nickel / nickel oxide and carbon nanotube composite material comprises the following steps:

[0099] 0.3 g of the dried hollow nickel / nickel oxide in Example 1 and 0.05 g of carbon nanotubes were dispersed in 150 mL of deionized water, and mechanically stirred for 6 h, followed by separation and drying to obtain a composite material of hollow nickel / nickel oxide and carbon nanotubes.

[0100] Example 7

[0101] A method for preparing a hollow nickel-based composite microwave absorbing coating comprises the following steps:

[0102] The composite material in Example 5 was added to the polyurethane resin and stirred evenly to prepare an electromagnetic protection coating, wherein the composite material accounted for 40wt% and the polyurethane resin accounted for 60wt%.

[0103] Example 8

[0104] A method for preparing a hollow nickel-based composite microwave absorbing coating comprises the following steps:

[0105] The composite material in Example 6 was added into epoxy resin and stirred evenly to prepare an electromagnetic protection coating, wherein the mass proportion of the composite material was 10 wt % and the mass proportion of the epoxy resin was 90 wt %.

[0106] Figure 6 This is a graph showing the microwave absorption performance of the coating prepared in this embodiment.

[0107] Comparative Example 1

[0108] Example 1 was repeated, except that 1 mL of a saturated aqueous solution of sodium sulfate was added dropwise into 200 mL of anhydrous ethanol (-10° C.) to obtain a sodium sulfate dispersion.

[0109] The results show that the sodium sulfate template in this comparative example is severely damaged. This is because when the solvent ratio is too low, too many particles are nucleated, many particles are not fully grown, and the surface is damaged.

[0110] Comparative Example 2

[0111] Example 1 was repeated, except that 10 mL of a saturated aqueous solution of sodium sulfate was added dropwise into 200 mL of anhydrous ethanol (-10° C.) to obtain a sodium sulfate dispersion, 3 g of nickel nitrate hexahydrate and 1.2 g of polyvinyl pyrrolidone were added to the dispersion, the mixture was mechanically stirred for 6 h, and then centrifuged for washing.

[0112] The results show that the hollow nickel / nickel oxide particles obtained in this comparative example are severely broken. This is because the coating time is short, the coating layer is not completely formed, and the hollow structure is broken after reduction washing.

[0113] Figure 7 This is a scanning electron microscope image of the hollow nickel / nickel oxide particles prepared in the comparative example.

[0114] Comparative Example 3

[0115] Example 1 was repeated, except that 10 mL of a saturated aqueous solution of sodium sulfate was added dropwise into 200 mL of anhydrous ethanol (-10° C.) to obtain a sodium sulfate dispersion; 3 g of nickel nitrate hexahydrate and 1.2 g of polyvinyl pyrrolidone were added to the dispersion, mechanically stirred for 24 h, and then centrifuged for washing; the collected intermediate was dispersed in 150 mL of anhydrous ethanol, and reduced with 1.6 g of sodium borohydride (dispersed in 50 mL of anhydrous ethanol) for 12 h (-30° C.).

[0116] The results show that the hollow nickel / nickel oxide particles obtained in this comparative example are severely broken. This is because the reduction temperature is low, the reduction reaction cannot be fully carried out, and a complete hollow nickel / nickel oxide shell is not formed. The hollow structure is broken after washing.

[0117] Comparative Example 4

[0118] Example 1 was repeated, except that 10 mL of a saturated aqueous solution of sodium sulfate was added dropwise into 200 mL of anhydrous ethanol (-10°C) to obtain a sodium sulfate dispersion; 3 g of nickel nitrate hexahydrate and 1.2 g of polyvinyl pyrrolidone were added to the dispersion, mechanically stirred for 24 h, and then centrifuged for washing; the collected intermediate was dispersed in 150 mL of anhydrous ethanol and reduced with 1.6 g of sodium borohydride (dispersed in 50 mL of anhydrous ethanol) for 1 h.

[0119] The results show that the hollow nickel / nickel oxide particles obtained in this comparative example are severely broken. This is because the reduction time is short, the hollow nickel / nickel oxide shell is not completely formed, and the hollow structure is broken after washing.

[0120] Figure 8 This is a scanning electron microscope image of the hollow nickel / nickel oxide particles prepared in the comparative example.

[0121] Comparative Example 5

[0122] A composite material of hollow nickel / nickel oxide and nano-iron oxide particles is added to polyurethane resin and stirred evenly to form an electromagnetic protection coating, wherein the composite material accounts for 10wt% and the polyurethane resin accounts for 90wt%.

[0123] The results show that the coating obtained in this comparative example has poor wave absorption performance, which is because the hollow nickel / nickel oxide and the nano-iron oxide particles are both magnetic materials with weak dielectric loss characteristics.

[0124] Comparative Example 6

[0125] The composite material in Example 6 was added into epoxy resin and stirred evenly to prepare an electromagnetic protection coating, wherein the mass proportion of the composite material was 1 wt % and the mass proportion of the epoxy resin was 99 wt %.

[0126] The results show that the coating obtained in this comparative example has poor wave absorption performance, which is because the proportion of the hollow nickel / nickel oxide and carbon nanotube composite material is small, and the dielectric loss and magnetic loss characteristics are weak.

[0127] Blank example 1

[0128] Compared with Example 7, this blank example does not add the hollow nickel-based material composite material, and only contains epoxy resin.

[0129] The results show that the reflection loss value of pure epoxy resin in this blank example does not reach the theoretically available value (less than -10dB). Fig. 9 This is a graph of the microwave absorption performance of pure epoxy resin.

[0130] Obviously, the above embodiments of the present invention are merely examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all implementation methods here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A hollow nickel-based composite microwave absorbing coating, characterized in that: It is prepared from a main composite material and an organic carrier; wherein, The main composite material includes a hollow nickel-based material and an auxiliary material; The main composite material accounts for 2-40wt% in the hollow nickel-based composite absorbing coating; The organic carrier accounts for 60-98wt% in the hollow nickel-based composite microwave absorbing coating; The hollow nickel-based particles account for 20-90wt% of the main composite material; The auxiliary material accounts for 10-80wt% in the main composite material.

2. The hollow nickel-based composite microwave absorbing coating according to claim 1, characterized in that: The organic carrier is selected from one or more of epoxy resin, phenolic resin, polyurethane resin, polyvinyl butyral, polydimethylsiloxane, urea-formaldehyde resin, hydrogenated cyanobutyl rubber, silicone resin and acrylic resin.

3. The hollow nickel-based composite microwave absorbing coating according to claim 1, characterized in that: The auxiliary material is selected from one or more of graphene, silver, silicon carbide, carbon nanotubes, polypyrrole, polyaniline, polydopamine, polythiophene, ferrosoferric oxide, and Mxene.

4. A method for preparing the hollow nickel-based composite microwave absorbing coating according to any one of claims 1 to 3, characterized in that: The steps include: S1, preparing a sodium sulfate template ethanol dispersion; S2, adding nickel salt and surfactant to the template dispersion obtained in S1 to carry out coating reaction, centrifugally washing after the reaction to obtain an intermediate; dispersing the obtained intermediate in anhydrous ethanol, adding sodium borohydride to carry out reduction reaction, and centrifugally washing and drying for a second time after the reduction reaction to obtain hollow nickel-based particles; S3, adding the hollow nickel-based particles and the auxiliary materials into a solvent for mixing, separating and drying, and obtaining a main composite material; S4, taking the main composite material obtained in step S3 and the organic carrier and stirring and mixing them thoroughly to obtain a hollow nickel-based composite microwave absorbing coating.

5. The preparation method according to claim 4, characterized in that: In step S1, the specific steps of preparing the sodium sulfate template ethanol dispersion are: adding a saturated sodium sulfate aqueous solution dropwise into anhydrous ethanol to obtain a sodium sulfate ethanol dispersion, wherein the volume ratio of the saturated sodium sulfate aqueous solution to the anhydrous ethanol is 1:4-1:100, and the temperature of the anhydrous ethanol is -30-60°C.

6. The preparation method according to claim 4, characterized in that: In step S2, the nickel salt is selected from one or more of the following substances: nickel acetate tetrahydrate, nickel chloride hexahydrate, nickel nitrate hexahydrate, nickel acetylacetonate, nickel bromide, and nickel iodide; Preferably, in step S2, the coating reaction temperature is -30 to 60°C, and the time is 12 to 48 hours; the reduction reaction temperature is -10 to 50°C, and the time is 2 to 24 hours.

7. The preparation method according to claim 4, characterized in that: In step S2, the surfactant is selected from one or more of the following substances: sodium dodecylbenzene sulfonate, dodecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, polyacrylic acid, polyvinyl pyrrolidone, polyethylene glycol, silane coupling agent, Tween 80, Triton X-100; Preferably, in step S2, the mass ratio of the nickel salt to the surfactant is 1:0.1-1:10; Preferably, in step S2, the morphology of the hollow nickel-based particles is one or more of the following shapes: cuboid, hexahedron, octahedron, sphere, rod, cylinder.

8. The preparation method according to claim 4, characterized in that: In step S3, the auxiliary material is selected from one or more of graphene, silver, silicon carbide, carbon nanotubes, polypyrrole, polyaniline, polydopamine, polythiophene, ferroferric oxide, and Mxene; Preferably, in step S3, the solvent is selected from one or more of the following materials: deionized water, ethanol, ethylene glycol, methanol, glycerol, acetone, dichloromethane, N,N-dimethylformamide, and acetonitrile.

9. The preparation method according to claim 4, characterized in that: In step S4, the organic carrier is selected from one or more of the following materials: epoxy resin, phenolic resin, polyurethane resin, polyvinyl butyral, polydimethylsiloxane, urea-formaldehyde resin, hydrogenated cyanobutyl rubber, silicone resin, acrylic resin.

10. Application of the hollow nickel-based composite radar absorbing coating as claimed in any one of claims 1 to 3 in electromagnetic protection.

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