Flexible wave-absorbing ceramic fiber cloth, preparation method and application thereof

Abstract

The application discloses a flexible wave-absorbing ceramic fiber cloth and a preparation method and application thereof, and belongs to the technical field of wave-absorbing functional materials. The flexible wave-absorbing ceramic fiber cloth is obtained by multiple times of spraying water-based wave-absorbing paint on a ceramic fiber cloth and then ultraviolet light curing and forming. The ceramic fiber cloth is woven by ceramic fibers with a certain resistance. The water-based wave-absorbing paint comprises a water-based ultraviolet light curing resin and a wave-absorbing agent of carbon-coated magnetic nano-particles. The flexible wave-absorbing ceramic fiber cloth not only has a wide-band electromagnetic wave absorption effect in the microwave band, but also can maintain the characteristics of good flexibility, light weight, high strength, and can be sewn and pasted. The flexible wave-absorbing ceramic fiber cloth can be particularly used in intelligent bags or backpacks to ensure that important electronic devices loaded therein are not detected by enemy electromagnetic instruments and information leakage is avoided.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing functional materials technology, specifically to a flexible microwave absorbing ceramic fiber cloth, its preparation method, and its application. Background Technology

[0002] Important electronic devices such as chip modules, data storage devices, signal converters, and wireless identification cards often require dedicated bags or backpacks. This is primarily because the specific dimensions of these bags or backpacks better protect the electronic devices from physical damage. With the increasing sophistication and protection levels of electronic devices, such as requirements for electromagnetic detection and to prevent information leakage, bags and backpacks need to have electromagnetic detection resistance. For example, patent ZL201620554995.0 discloses a bag designed to prevent data card information theft. It utilizes a shielding material to create a shielded cavity, which shields externally emitted electromagnetic signals, thus preventing the reading and theft of bank cards and other card information within the storage cavity. Patent ZL200920058626.2 discloses a bag that can shield electromagnetic radiation. It has an electromagnetic shielding layer between the outer and inner lining layers, which shields or reduces electromagnetic radiation from electronic products inside and outside the bag. However, electromagnetic shielding methods cannot eliminate electromagnetic wave absorption; therefore, materials with wave-absorbing properties are needed.

[0003] Considering its suitability for applications in bags, backpacks, and other related products, flexible fiber fabric with wave-absorbing properties is the optimal choice. Patent CN108252114A discloses a silicon carbide fiber fabric-reinforced polyimide resin-based wave-absorbing material and its preparation method. This involves uniformly mixing a nano-transition metal sulfide absorber with a polyamic acid solution, coating it onto dried silicon carbide fiber fabric, and then baking it for a period of time to obtain the silicon carbide fiber fabric-reinforced polyimide resin-based wave-absorbing material. However, silicon carbide fiber fabric is expensive, and the resulting product lacks flexibility. To further reduce costs and improve flexibility, patent CN115323766A discloses a cobalt tetroxide / carbon cloth flexible wave-absorbing material and its preparation method. This flexible wave-absorbing material consists of a carbon cloth base with a cobalt tetroxide array loaded on its surface, forming a blanket-like structure. While satisfying flexibility requirements, it also possesses wave-absorbing functionality. Although the preparation method is simple in principle, it cannot be industrialized, and due to the low resistivity and poor electromagnetic impedance matching of carbon cloth, it cannot achieve broadband electromagnetic wave absorption. Furthermore, patent CN114149272A discloses a high-temperature broadband absorbing Al2O3f reinforced ceramic matrix composite material and its integrated preparation method. This method optimizes the design of absorbing structural units in an Al2O3f fiber preform using HFSS software, prepares conductive carbon fibers with a certain periodic structure on the Al2O3f fiber cloth using a manual sewing process, and then prepares a ceramic matrix in the periodically structured Al2O3f fiber preform using a precursor impregnation pyrolysis method, resulting in a broadband absorbing Al2O3f / SiOC composite material. The absorption performance of this composite material is closely related to the periodic structure and its content. Although no absorbing agent is used, its performance stability is poor. Moreover, the preparation method involves manual sewing and high-temperature pyrolysis processes, which are not only inefficient but also unsuitable for industrial production. Furthermore, the disclosed absorption intensity is weak (narrow bandwidth with reflection loss better than -10dB). Therefore, proposing a flexible broadband absorbing fiber cloth applicable to bags and luggage is of significant value and importance. Summary of the Invention

[0004] In view of the above-mentioned shortcomings, the present invention provides a flexible microwave absorbing ceramic fiber cloth, its preparation method and application. The flexible microwave absorbing ceramic fiber cloth provided by the present invention not only has a broadband electromagnetic wave absorption effect in the microwave band, but also maintains the good flexibility, light weight, high strength and sewing and pasting characteristics of the fiber cloth. It can be used in particular for smart bags or backpacks to ensure that important electronic devices inside are not detected by enemy electromagnetic instruments and to avoid information leakage.

[0005] To achieve the above objectives, the present invention provides a flexible microwave absorbing ceramic fiber cloth, which is obtained by repeatedly spraying a ceramic fiber cloth with a water-based microwave absorbing coating and then curing it under ultraviolet light; the ceramic fiber cloth is woven from ceramic fibers with a certain resistance; the water-based microwave absorbing coating contains a water-based ultraviolet-cured resin and a microwave absorbing agent with carbon-coated magnetic nanoparticles.

[0006] According to one aspect of the present invention, the ceramic fiber cloth includes one or more of alumina fiber cloth, high silica fiber cloth, and mullite fiber cloth, and has a thickness of 0.2 to 1.0 mm.

[0007] According to one aspect of the present invention, the waterborne UV-curable resin comprises one or more of waterborne unsaturated polyester, waterborne polyester acrylate, waterborne polyether acrylate, waterborne polyurethane acrylate, and waterborne epoxy resin acrylate, accounting for 60-80% of the total mass of the waterborne microwave absorbing coating.

[0008] According to one aspect of the present invention, the microwave absorbing agent of the carbon-coated magnetic nanoparticles is one or both of carbon-coated magnetic nickel nanoparticles and carbon nanotubes coated with magnetic nickel nanoparticles, accounting for 10-30% of the total mass of the water-based microwave absorbing coating.

[0009] Based on the same inventive concept, the present invention also provides a method for preparing the above-mentioned flexible microwave absorbing ceramic fiber cloth, comprising the following steps:

[0010] Step 1: Add the carbon-coated magnetic nanoparticle absorbing agent to the water-based UV-curable resin in a certain proportion, then add the water-based photoinitiator and deionized water to adjust the viscosity, and disperse evenly by mechanical stirring to obtain the water-based absorbing coating.

[0011] Step 2: After cutting the ceramic fiber cloth of a certain thickness into specific sizes and shapes, sew the edges of the cut ceramic fiber cloth to obtain pre-treated ceramic fiber cloth;

[0012] Step 3: After uniformly spraying the water-based microwave absorbing coating onto both sides of the pretreated ceramic fiber cloth, it is then cured into a film by ultraviolet light;

[0013] Step 4: Repeat step 3 until the required weight and thickness are achieved to obtain a flexible microwave absorbing ceramic fiber cloth with microwave absorbing function.

[0014] According to one aspect of the present invention, in step 2, the edge sewing is performed using an automated sewing machine, and the thread used in the edge sewing is ceramic fiber thread of the same material as the ceramic fiber cloth.

[0015] According to one aspect of the present invention, in steps 3 and 4, the ultraviolet light curing film formation is completed using an ultraviolet light curing device, wherein the wavelength of the light source of the ultraviolet light curing device is 280-420nm, the distance between the light source and the ceramic fiber cloth is 10-15cm, and the ultraviolet light irradiation curing time is 5-10s.

[0016] Based on the same inventive concept, this invention also discloses an application of a flexible microwave absorbing ceramic fiber cloth prepared by any of the above-described flexible microwave absorbing ceramic fiber cloths or by any of the above-described flexible microwave absorbing ceramic fiber cloths preparation methods, wherein the flexible microwave absorbing ceramic fiber cloth is applied to smart bags or backpacks.

[0017] According to one aspect of the present invention, the application of the flexible microwave-absorbing ceramic fiber cloth to a smart bag or backpack specifically involves: attaching or sewing the flexible microwave-absorbing ceramic fiber cloth into the interlayer of the smart bag or backpack.

[0018] The beneficial effects of this invention are:

[0019] (1) Due to the centimeter-scale pore structure of the ceramic fiber cloth, which facilitates the scattering of incident electromagnetic waves, and the multiple dielectric, magnetic, and conductivity loss mechanisms possessed by the carbon-coated magnetic nanoparticles, compared to the existing technical solutions that only employ periodic absorption structures, the product of this invention has multiple electromagnetic wave loss pathways, achieving a wide-bandwidth and strong absorption effect. (See attached...) Figure 3 As shown, the flexible absorbing ceramic fiber cloth with a thickness of 1.0 mm exhibits a reflection loss value better than -10 dB (absorption rate of over 90%) in the 5.25-18 GHz frequency band.

[0020] (2) The present invention uses a water-based resin system to design a microwave absorbing coating. After spraying, the coating film can be cured by ultraviolet light. The preparation method is not only easy to automate continuous production and highly efficient, but also has good environmental protection of raw materials and processes, and has greater practical application and promotion value.

[0021] (3) Water-based UV-curable resin has good wettability with ceramic fiber cloth, fast curing speed and small shrinkage of the paint film, simple and efficient construction, and is safe and environmentally friendly.

[0022] (4) The product of the present invention has good flexibility and can be integrated into targets of various sizes and shapes by means of adhesion or sewing, which is especially suitable for practical applications of bags or backpacks. Attached Figure Description

[0023] Figure 1 This is a TEM image of the spherical carbon-coated magnetic nickel nanoparticles used in Example 1 of the present invention;

[0024] Figure 2 This is a TEM image of carbon nanotube-coated magnetic nickel nanoparticles used in Example 2 of the present invention.

[0025] Figure 3 The graph shows the reflection loss curves of the flexible absorbing ceramic fiber cloth obtained in Examples 1-3 of the present invention in the 1GHz-18GHz frequency band. Detailed Implementation

[0026] To make the present invention easier to understand, specific embodiments are described below to further illustrate the invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art; unless otherwise specified, the raw materials and reagents involved herein can be purchased commercially or obtained by known methods.

[0027] Example 1

[0028] In this embodiment, the flexible microwave absorbing ceramic fiber cloth is a cloth woven from alumina fibers with a thickness of 1.0 mm. The water-based ultraviolet curable resin is water-based polyester acrylate, and the carbon-coated magnetic nanoparticle microwave absorbing agent is carbon-coated nano-magnetic nickel particles.

[0029] The preparation method of the flexible microwave absorbing ceramic fiber cloth includes the following steps:

[0030] (1) Add 30g of spherical carbon-coated magnetic nano nickel particles and 160g of waterborne polyurethane acrylate emulsion to a container, then add 15g of waterborne photoinitiator and 20g of deionized water, and disperse evenly by mechanical stirring for 30min to obtain waterborne microwave absorbing coating.

[0031] (2) Cut the 1.0mm thick flexible alumina ceramic fiber cloth into pieces with a width and length of 180mm, and sew the four sides of the alumina fiber cloth with alumina fiber thread.

[0032] (3) After the water-based microwave absorbing coating prepared in (1) is evenly sprayed onto the upper and lower surfaces of the flexible ceramic fiber through a spraying process, it is then irradiated for 5 seconds under an ultraviolet lamp with a light source wavelength of 280-420nm and a distance of 10cm between the light source and the fiber cloth to achieve the curing of the coating on the ceramic fiber cloth into a film.

[0033] (4) Repeat step (3) to perform three spraying and UV curing processes until the entire ceramic fiber cloth increases in weight by 40g, thus obtaining the flexible ceramic fiber cloth with wave absorption function in this embodiment.

[0034] The spherical carbon-coated magnetic nickel nanoparticles in Example 1 were subjected to TEM detection, and the results are as follows: Figure 1 As shown, from Figure 1It can be seen that the surface of the nickel nanoparticles is coated with a uniform carbon layer, forming a core-shell microstructure. The spherical carbon-coated nickel nanoparticles contain both dielectric carbon and magnetic nickel materials, and the core-shell structure generates a large number of heterogeneous interfaces, which is conducive to obtaining strong and multiple dielectric, magnetic and conductivity loss mechanisms.

[0035] The reflection loss value of the flexible absorbing ceramic fiber cloth obtained in Example 1 of this invention in the 1GHz-18GHz frequency band was tested using a bow-shaped method test system built with an Agilent N5230A-based vector network analyzer. The results are as follows: Figure 3 As shown, by Figure 3 It can be seen that the flexible absorbing ceramic fiber cloth of Example 1 has a reflection loss value better than -10dB (absorption rate greater than 90%) in the 5.25-18GHz frequency band, that is, the effective absorption bandwidth is as high as 12.75GHz.

[0036] Example 2:

[0037] In this embodiment, the flexible microwave absorbing ceramic fiber cloth is a cloth woven from high silica fibers with a thickness of 1.0 mm. The water-based ultraviolet curable resin is water-based epoxy resin acrylate, and the carbon-coated magnetic nanoparticle microwave absorbing agent is one-dimensional carbon nanotubes coated with nano-magnetic nickel particles.

[0038] The preparation method of the flexible microwave absorbing ceramic fiber cloth includes the following steps:

[0039] (1) Add 20g of carbon nanotube-coated nano-magnetic nickel particle powder and 170g of waterborne epoxy resin acrylate emulsion into a container, then add 15g of waterborne photoinitiator and 10g of deionized water, and disperse evenly by mechanical stirring for 30min to obtain waterborne microwave absorbing coating.

[0040] (2) Cut a 1.0mm thick flexible high-silica fiber cloth into pieces with a width and length of 180mm, and sew the four sides of the high-silica fiber cloth with high-silica fiber thread.

[0041] (3) After the water-based microwave absorbing coating prepared in (1) is uniformly sprayed onto the upper and lower surfaces of the flexible high-silica ceramic fiber through a spraying process, it is then irradiated for 10 seconds under an ultraviolet lamp with a light source wavelength of 280-420nm and a distance of 15cm between the light source and the fiber cloth to achieve the curing of the coating on the ceramic fiber cloth into a film.

[0042] (4) Repeat step (3) to perform three spraying and UV curing processes until the entire ceramic fiber cloth increases in weight by 30g, thus obtaining the flexible ceramic fiber cloth with wave absorption function in this embodiment.

[0043] The carbon nanotube-coated magnetic nickel nanoparticles in Example 2 were subjected to TEM detection, and the results are as follows: Figure 1 As shown, from Figure 2 It can be seen that the nickel nanoparticles coated at the ends of the carbon nanotubes also form a core-shell microstructure and have dielectric anisotropy. The carbon nanotubes coated with the magnetic nickel nanoparticles contain both dielectric carbon and magnetic nickel materials. The core-shell structure generates a large number of heterogeneous interfaces and dielectric anisotropy, which is conducive to the formation of conductive networks. Therefore, strong and multiple dielectric, magnetic and conductivity loss mechanisms can be obtained.

[0044] The reflection loss value of the flexible absorbing ceramic fiber cloth obtained in Example 2 of this invention in the 1GHz-18GHz frequency band was tested using a bow-shaped method test system built with an Agilent N5230A-based vector network analyzer. The results are as follows: Figure 3 As shown, by Figure 3 It can be seen that the flexible absorbing ceramic fiber cloth of Example 2 has a reflection loss value better than -10dB in the 7.51-18GHz frequency band, that is, the effective absorption bandwidth reaches 10.49GHz, and the absorption peak reaches -20.2dB at 11.45GHz (absorption rate is greater than 99%).

[0045] Example 3:

[0046] In this embodiment, the flexible microwave absorbing ceramic fiber cloth is a cloth woven from mullite fibers with a thickness of 0.8 mm. The water-based ultraviolet curable resin is water-based polyester acrylate. The carbon-coated magnetic nanoparticle microwave absorbing agent is a mixture of carbon-coated magnetic nickel nanoparticles and carbon nanotube-coated magnetic nickel nanoparticles.

[0047] The preparation method of the flexible microwave absorbing ceramic fiber cloth includes the following steps:

[0048] (1) Add the mixed powder consisting of 20g of spherical carbon-coated magnetic nickel nanoparticles and 10g of carbon nanotube-coated magnetic nickel nanoparticles, 160g of waterborne polyurethane acrylate emulsion to a container, then add 15g of waterborne photoinitiator and 20g of deionized water, and disperse evenly by mechanical stirring for 40min to obtain waterborne microwave absorbing coating.

[0049] (2) Cut a 1.0mm thick flexible mullite ceramic fiber cloth into pieces with a width and length of 180mm, and sew the four sides of the mullite fiber cloth with mullite fiber thread.

[0050] (3) After the water-based microwave absorbing coating prepared in (1) is evenly sprayed onto the upper and lower surfaces of the flexible mullite ceramic fiber through a spraying process, it is then irradiated for 10 seconds under an ultraviolet lamp with a light source wavelength of 280-420nm and a distance of 15cm between the light source and the fiber cloth to achieve the curing of the coating on the ceramic fiber cloth.

[0051] (4) Repeat (3) to perform three spraying and UV curing processes until the entire ceramic fiber cloth increases in weight by 30g, thus obtaining the flexible ceramic fiber cloth with wave absorption function in this embodiment.

[0052] The reflection loss value of the flexible absorbing ceramic fiber cloth obtained in Example 3 of this invention in the 1GHz-18GHz frequency band was tested using a bow-shaped method test system built with an Agilent N5230A-based vector network analyzer. The results are as follows: Figure 3 As shown, by Figure 3 It can be seen that the flexible absorbing ceramic fiber cloth of Example 3 has a reflection loss value better than -10dB in the 7.12-18GHz frequency band, that is, the effective absorption bandwidth reaches 10.88GHz.

[0053] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A flexible wave-absorbing ceramic fiber cloth, characterized by, The flexible wave-absorbing ceramic fiber cloth is obtained by multiple spraying of water-based wave-absorbing paint on the ceramic fiber cloth and then ultraviolet curing; the ceramic fiber cloth is woven by ceramic fibers with certain resistance, and includes one or more of alumina fiber cloth, high-silicon oxygen fiber cloth, and mullite fiber cloth, with a thickness of 0.2-1.0 mm; the water-based wave-absorbing paint includes water-based ultraviolet curing resin and wave-absorbing agent of carbon-coated magnetic nanoparticles; the wave-absorbing agent of carbon-coated magnetic nanoparticles is one or both of carbon-coated nano-magnetic nickel particles and carbon nanotube-coated nano-magnetic nickel; the carbon-coated magnetic nanoparticles have a core-shell structure; the wave-absorbing agent of carbon-coated magnetic nanoparticles accounts for 10-30% of the total mass of the water-based wave-absorbing paint. The preparation method of the flexible wave-absorbing ceramic fiber cloth includes the following steps: Step 1: add the wave-absorbing agent of carbon-coated magnetic nanoparticles to the water-based ultraviolet curing resin in a certain proportion, then add water-based photoinitiator and deionized water for viscosity adjustment, and uniformly disperse by mechanical stirring to obtain water-based wave-absorbing paint; Step 2: cut the ceramic fiber cloth with a certain thickness into a specific size and shape, then perform edge sewing treatment on the two edges of the cut ceramic fiber cloth to obtain pretreated ceramic fiber cloth; Step 3: uniformly spray the water-based wave-absorbing paint on both sides of the pretreated ceramic fiber cloth, and then perform ultraviolet curing film formation; Step 4: repeat Step 3 until the required weight and thickness are reached to obtain the flexible wave-absorbing ceramic fiber cloth with wave-absorbing function.

2. The flexible wave-absorbing ceramic fiber cloth according to claim 1, characterized in that, The water-based ultraviolet curing resin includes one or more of water-based unsaturated polyester, water-based polyester acrylate, water-based polyether acrylate, water-based polyurethane acrylate, and water-based epoxy resin acrylate, and accounts for 60-80% of the total mass of the water-based wave-absorbing paint.

3. A method of producing the flexible wave-absorbing ceramic fiber cloth according to any one of claims 1 to 2, characterized by, The preparation method includes the following steps: Step 1: add the wave-absorbing agent of carbon-coated magnetic nanoparticles to the water-based ultraviolet curing resin in a certain proportion, then add water-based photoinitiator and deionized water for viscosity adjustment, and uniformly disperse by mechanical stirring to obtain water-based wave-absorbing paint; Step 2: cut the ceramic fiber cloth with a certain thickness into a specific size and shape, then perform edge sewing treatment on the two edges of the cut ceramic fiber cloth to obtain pretreated ceramic fiber cloth; Step 3: uniformly spray the water-based wave-absorbing paint on both sides of the pretreated ceramic fiber cloth, and then perform ultraviolet curing film formation; Step 4: repeat Step 3 until the required weight and thickness are reached to obtain the flexible wave-absorbing ceramic fiber cloth with wave-absorbing function.

4. The method for preparing the flexible microwave absorbing ceramic fiber cloth according to claim 3, characterized in that, In Step 2, the edge sewing treatment is completed by using an automatic sewing machine, and the thread used for the edge sewing treatment is ceramic fiber thread of the same material as the ceramic fiber cloth.

5. The method for preparing the flexible microwave absorbing ceramic fiber cloth according to claim 3, characterized in that, In Steps 3 and 4, the ultraviolet curing film formation is completed by using an ultraviolet curing device, the wavelength of the light source of the ultraviolet curing device is 280-420 nm, the distance between the light source and the ceramic fiber cloth is 10-15 cm, and the ultraviolet light irradiation curing time is 5-10 s.

6. Use of the flexible wave-absorbing ceramic fiber cloth according to any one of claims 1-2 or the flexible wave-absorbing ceramic fiber cloth prepared by the preparation method according to any one of claims 3-5, characterized in that, The flexible wave-absorbing ceramic fiber cloth is applied to intelligent bags or backpacks.

7. Use according to claim 6, characterized in that, The flexible wave-absorbing ceramic fiber cloth is applied to the smart luggage or backpack, specifically, the flexible wave-absorbing ceramic fiber cloth is pasted or sewn in the interlayer of the smart luggage or backpack.

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