A method for preparing a microwave absorbing functional fabric based on a three-phase electromagnetic filler coating

Abstract

The present application relates to the technical field of wave-absorbing textiles, and discloses a preparation method of a wave-absorbing functional fabric based on a three-phase electromagnetic filler coating, comprising the following steps: adding nickel chloride hexahydrate and iron chloride hexahydrate into water to obtain a first solution; adding cobalt nitrate hexahydrate into water to obtain a second solution; adding carboxylated carbon nanotubes into the first solution, and then mixing the carboxylated carbon nanotubes with the second solution after reaction and ultrasonic treatment, and then performing a second hydrothermal reaction to obtain a composite material; grinding the composite material and the carboxylated carbon nanotubes respectively with sodium dodecyl benzene sulfonate to obtain a third solution and a fourth solution; blending the third solution and the fourth solution with water-based polyurethane respectively to obtain a front wave-absorbing coating treatment agent and a back wave-absorbing coating treatment agent; and coating the front wave-absorbing coating treatment agent and the back wave-absorbing coating treatment agent on the front and back of roughened polyester non-woven fabric to obtain the wave-absorbing functional fabric. In the present application, the wave-absorbing material has multiple loss mechanisms, which greatly optimizes the impedance matching characteristics and wave-absorbing performance of the functional fabric.

Description

Technical Field

[0001] This invention belongs to the technical field of microwave absorbing textiles, and more specifically relates to a method for preparing a microwave absorbing functional fabric based on a three-phase electromagnetic filler coating. Background Technology

[0002] With the development of human industry and the progress of science and technology, various electronic products have been invented, such as televisions, computers, and smartphones. However, these products usually emit electromagnetic radiation, which necessitates the invention and creation of wave-absorbing materials and their products.

[0003] Traditional microwave absorbing materials often fail to simultaneously achieve the four key objectives of thinness, lightness, wide bandwidth, and strong absorption. This limits their application in everyday life. Consequently, the development of microwave absorbing materials that are more suitable for combat environments and more readily adaptable to human life has become increasingly urgent. Recent research on microwave absorbing materials has primarily focused on the field of stealth metamaterials. Summary of the Invention

[0004] The main objective of this invention is to address the aforementioned problems by providing a method for preparing a wave-absorbing functional fabric based on a three-phase electromagnetic filler coating. This invention draws on the structural characteristics of metamaterials, namely impedance matching layer-absorbing layer-reflective layer, to modify the wave-absorbing structure of the material, thereby enabling the product to simultaneously achieve the four characteristics of "thin, light, wide, and strong".

[0005] In order to achieve a wide absorption bandwidth and high absorption intensity, this invention breaks through the limitations of traditional single-component or dual-component microwave absorbing materials. It introduces three types of electromagnetic materials into the matrix, utilizes the greater loss mechanism between these three types of materials, and obtains the optimal ratio to achieve the goal of "wide and strong". At the same time, this invention is based on microwave absorbing functional fabrics prepared on textiles, combined with adhesives such as water-based polyurethane that give the fabric softness, to achieve the goal of "thin and light".

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0007] A method for preparing a microwave absorbing functional fabric based on a three-phase electromagnetic filler coating includes the following steps:

[0008] (1) Add nickel chloride hexahydrate and ferric chloride hexahydrate to water and adjust the pH to 9.5-10.5 to obtain the first solution;

[0009] (2) Add carboxylated carbon nanotubes to the first solution, and perform a first hydrothermal reaction after sonication to obtain COOH@MWCNTs / NiFe2O4 composite material;

[0010] (3) Add cobalt nitrate hexahydrate to water, stir to dissolve, and then add NaOH to obtain a second solution;

[0011] (4) The COOH@MWCNTs / NiFe2O4 composite material was mixed with the second solution, and after sonication, a second hydrothermal reaction was carried out to obtain the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material.

[0012] (5) Grind the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material with sodium dodecylbenzenesulfonate, add water and sonicate to obtain the third solution;

[0013] (6) Carboxylated carbon nanotubes and sodium dodecylbenzene sulfonate were ground together, added to water and ultrasonically treated to obtain the fourth solution;

[0014] (7) The third solution and the fourth solution are mixed with water-based polyurethane, defoamer, leveling agent and dispersant respectively to obtain the front microwave absorbing coating agent and the back microwave absorbing coating agent respectively. They are then applied to the front and back of the roughened polyester nonwoven fabric to obtain microwave absorbing functional fabric.

[0015] The Co3O4 / COOH@MWCNTs / NiFe2O4 composite material (functional nanoparticles) prepared through a two-step hydrothermal process exhibits well-developed, small, and uniformly distributed grains after repeated dissolution and recrystallization processes, with minimal particle aggregation. Carbon nanotubes serve as the framework, with Co3O4 and NiFe2O4 adhering to the carbon nanotubes to form connections. The overlapping of carbon nanotubes creates a multi-layered network structure. The carboxylated carbon nanotubes undergo hydrothermal reduction with iron, nickel, and cobalt salts, resulting in functional nanoparticles possessing multiple loss mechanisms, such as magnetic loss, dielectric loss, and polarization loss. Through these different loss mechanisms of the powders and the various polarization phenomena among them, the electromagnetic parameters of the material are optimized after combining with carbon nanotubes, achieving better impedance matching with free space. Furthermore, the extremely large specific surface area of ​​carbon nanotubes causes multiple reflections of electromagnetic waves when incident on the absorbing material, enhancing its absorption performance.

[0016] Furthermore, by modifying the surface of sodium dodecylbenzenesulfonate using a non-covalent functionalization method, the hydrophilicity of the functional nanoparticle surface is improved, thereby effectively enhancing the interfacial bonding force between the functional nanoparticles and the waterborne polyurethane matrix. This facilitates the uniform distribution of the material in the waterborne polyurethane, making it less prone to particle agglomeration after coating, thus affecting the microwave absorption performance of the material.

[0017] After applying a microwave-absorbing coating to polyester fabric, the fabric is divided into three layers: an impedance-matching absorption layer on the front, a plain fabric layer without electromagnetic properties in the middle, and an impedance-mismatch reflection layer on the back. The carbon nanotubes in the impedance-mismatch reflection layer on the back act as fillers, increasing the coating's conductivity. Without being bonded to magnetic materials, their impedance differs significantly from that of free space, preventing electromagnetic waves from entering the coating. Therefore, the electromagnetic waves are reflected back to the impedance-matching absorption layer for reabsorption. When electromagnetic waves are incident from the front, the impedance-matching characteristics of the material surface allow them to easily penetrate the material. The multi-layered structure causes interfacial polarization of various functional nanoparticles at the microscopic level, and macroscopic interfacial polarization due to the influence of different functional layers, further absorbing electromagnetic waves. The construction of the impedance-mismatch reflection layer on the back also causes continuous reflection of electromagnetic waves within the material. Finally, the absorption layer dissipates the energy of these reflections as heat.

[0018] More preferably, in step (1), the molar ratio of nickel chloride hexahydrate to ferric chloride hexahydrate is 1:2; and the mass ratio of nickel chloride hexahydrate to water is 0.3-0.6:50.

[0019] More preferably, in step (2), the mass ratio of the first solution to carboxylated carbon nanotubes is 100:1-3; the ultrasonic time is 5-10 min; the time of the first hydrothermal reaction is 20-28 h, and the hydrothermal temperature is 120-180℃.

[0020] More preferably, the carboxylated carbon nanotubes are prepared as follows: a certain amount of multi-walled carbon nanotubes are placed in a mixed solution of concentrated nitric acid and concentrated sulfuric acid, stirred for a period of time, and then filtered to obtain carboxylated carbon nanotubes; the ratio of multi-walled carbon nanotubes to the mixed solution is 1-3g:100mL; the mass ratio of concentrated sulfuric acid to concentrated nitric acid is 2-3:0.8-1; and the stirring time is 0.5-1h.

[0021] After being subjected to intense oxidation by a mixture of concentrated sulfuric acid and concentrated nitric acid for a period of time, multi-walled carbon nanotubes develop carboxyl functional groups on their surface. This modification significantly improves the dispersibility of carbon nanotubes in aqueous solutions, facilitating subsequent blending of carbon nanotubes with aqueous polyurethane emulsions.

[0022] More preferably, in step (3), the mass ratio of cobalt nitrate hexahydrate to water is 5-10:100; and the molar ratio of cobalt nitrate hexahydrate to NaOH is 2-4:1.

[0023] More preferably, in step (4), the mass ratio of the COOH@MWCNTs / NiFe2O4 composite material to the second solution is 1:100; the ultrasonic time is 5-10 min; the time of the second hydrothermal reaction is 20-28 h, and the hydrothermal temperature is 120-180℃.

[0024] More preferably, in step (5), the mass ratio of the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material, sodium dodecylbenzenesulfonate, and water is 2.8-3.2:1.5-2.3:28-35; and the ultrasound time is 1.5-2.5h.

[0025] More preferably, in step (6), the mass ratio of the carboxylated carbon nanotubes, sodium dodecylbenzenesulfonate, and water is 0.7-1.1:1.5-2.3:30-35; and the ultrasound time is 1.5-2.5 h.

[0026] More preferably, in step (7), the mass ratio of the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material to waterborne polyurethane in the front-side microwave absorbing coating agent is 0.8-1.2:8-10, the defoamer accounts for 0.01-0.06% of the total mass of the coating agent, the leveling agent accounts for 0.01-0.2% of the total mass of the coating agent, and the mass ratio of the dispersant to the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material is 0.0015-0.003:2.8-3.2.

[0027] More preferably, in step (7), the mass ratio of carboxylated carbon nanotubes to waterborne polyurethane in the reverse microwave absorbing coating agent is 2.8-3.2:25-30, the defoamer accounts for 0.01-0.06% of the total mass of the coating agent, the leveling agent accounts for 0.01-0.2% of the total mass of the coating agent, and the mass ratio of dispersant to carboxylated carbon nanotubes is 0.0005-0.001:0.8-1.2.

[0028] More preferably, in step (7), the roughened polyester nonwoven fabric is prepared by immersing the polyester nonwoven fabric in a NaOH aqueous solution and heating it to obtain the roughened polyester nonwoven fabric.

[0029] After being soaked in NaOH aqueous solution at high temperature, the fibers on the surface of polyester fabric will become rougher than the usually smooth surface of chemical fibers. This makes it easier for functional nanoparticles to adhere to the fabric surface with the adhesive during subsequent coating experiments, forming a conductive network or constructing a wave-absorbing structure.

[0030] More preferably, the molar concentration of the NaOH aqueous solution is 0.5-1 mol / L; the ratio of the polyester nonwoven fabric to the NaOH aqueous solution is 0.5-1.5 g: 125 mL; the heating temperature is 70-100℃, and the soaking time is 0.5-1.5 h.

[0031] More preferably, the front coating thickness of the roughened polyester nonwoven fabric is 0.3-0.6 mm, and the back coating thickness is 0.05-0.25 mm.

[0032] Compared with existing technologies, this invention has the following advantages: This invention uses a two-step hydrothermal method to prepare Co3O4 / COOH@MWCNTs / NiFe2O4 composite materials. The resulting functional nanoparticles have multiple loss mechanisms and more interfacial polarization states, which greatly optimizes the impedance matching characteristics and microwave absorption performance of the material. At the same time, waterborne polyurethane is used as an adhesive to encapsulate the prepared functional nanoparticles onto polyester fabric, so that the prepared functional fabric has both microwave absorption function and is also relatively soft, thus making it suitable for a wide range of applications. Attached Figure Description

[0033] Figure 1 The graph shows the reflection loss as a function of frequency in Experiment Example 1.

[0034] Figure 2 The graph shows the reflection loss as a function of frequency in Experiment Example 2.

[0035] Figure 3 The graph shows the reflection loss as a function of frequency in Experiment Example 3.

[0036] Figure 4 The graph shows the reflection loss as a function of frequency in Comparative Example 1.

[0037] Figure 5 The graph shows the reflection loss as a function of frequency in Comparative Example 2.

[0038] Figure 6 The graph shows the variation of reflection loss as a function of frequency in Comparative Example 3.

[0039] Figure 7 The graph shows the variation of reflection loss with frequency in Comparative Example 4.

[0040] Figure 8 The graph shows the reflection loss as a function of frequency in Comparative Example 5. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to the embodiments, and the technical content and effects thereof are not limited thereto.

[0042] Example 1

[0043] (1) Cut a piece of polyester nonwoven fabric with a size of 180*180mm and a weight of 8g, put it into 1L of 1mol / L NaOH aqueous solution, heat it to 90℃, soak it for 1h, and obtain the roughened polyester nonwoven fabric.

[0044] (2) Take 2g of multi-walled carbon nanotubes and place them in 100mL of a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a mass ratio of 3:1. Stir for 30min and then filter to obtain carboxylated carbon nanotubes.

[0045] (3) Add 0.4064g of nickel chloride hexahydrate and 0.5548g of ferric chloride hexahydrate to 50mL of water, stir to dissolve, and then add ammonia to adjust the pH to 10 to obtain the first solution;

[0046] (4) Add 0.8g of carboxylated carbon nanotubes to the first solution, sonicate for 5min using an ultrasonic cell disruptor, place the mixed solution in a hydrothermal reactor, hydrothermally heat at 140℃ for 24h, centrifuge, dry, grind, and obtain COOH@MWCNTs / NiFe2O4 composite material.

[0047] (5) Add 8.73g of cobalt nitrate hexahydrate to 100mL of water, stir to dissolve, and then add 0.6g of NaOH to obtain the second solution;

[0048] (6) The COOH@MWCNTs / NiFe2O4 composite material was mixed with the second solution at a mass ratio of 1:100. After sonicating for 5 minutes with an ultrasonic cell disruptor, the mixed solution was placed in a hydrothermal reactor and hydrothermally heated at 180℃ for 24 hours. After centrifugation, drying, and grinding, the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material was obtained.

[0049] (7) Grind 3g of Co3O4 / COOH@MWCNTs / NiFe2O4 composite material with 2g of sodium dodecylbenzenesulfonate (SDBS), add 30mL of water and sonicate to obtain the third solution;

[0050] (8) Grind 1g of carboxylated carbon nanotubes with 2g of sodium dodecylbenzenesulfonate, add them to 30mL of water and sonicate to obtain the fourth solution;

[0051] (9) The third solution was blended with 27g of waterborne polyurethane, and 0.015g of defoamer OS-5201 (Guangzhou Guanzhi New Material Technology Co., Ltd.), 0.03g of leveling agent OS-1411 (Guangzhou Guanzhi New Material Technology Co., Ltd.), and 0.003g of dispersant OS-5040 (Guangzhou Guanzhi New Material Technology Co., Ltd.) (the same applies to the additives below) were added to obtain the front-side microwave absorbing coating agent; the fourth solution was blended with 9g of waterborne polyurethane, and 0.005g of defoamer, 0.01g of leveling agent, and 0.001g of dispersant were added to obtain the back-side microwave absorbing coating agent. The front-side microwave absorbing coating agent was applied to the front side of the roughened polyester nonwoven fabric with a coating thickness of 0.5mm, and the back-side microwave absorbing coating agent was applied to the back side of the roughened polyester nonwoven fabric with a coating thickness of 0.15mm to obtain the microwave absorbing polyester fabric.

[0052] Example 2

[0053] (1) Cut a piece of polyester nonwoven fabric with a size of 180*180mm and a weight of 8g, put it into 1L of 1mol / L NaOH aqueous solution, heat it to 90℃, soak it for 1h, and obtain the roughened polyester nonwoven fabric.

[0054] (2) Take 2g of multi-walled carbon nanotubes and place them in 100mL of a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a mass ratio of 3:1. Stir for 30min and then filter to obtain carboxylated carbon nanotubes.

[0055] (3) Add 0.508g of nickel chloride hexahydrate and 0.6935g of ferric chloride hexahydrate to 50mL of water, stir to dissolve, and then add ammonia to adjust the pH to 10 to obtain the first solution;

[0056] (4) Add 1g of carboxylated carbon nanotubes to the first solution, sonicate for 5min using an ultrasonic cell disruptor, place the mixed solution in a hydrothermal reactor, hydrotherm at 140℃ for 24h, centrifuge, dry, grind, and obtain COOH@MWCNTs / NiFe2O4 composite material.

[0057] (5) Add 7.275g of cobalt nitrate hexahydrate to 100mL of water, stir to dissolve, and then add 0.5g of NaOH to obtain the second solution;

[0058] (6) The COOH@MWCNTs / NiFe2O4 composite material was mixed with the second solution at a mass ratio of 1:100. After sonicating for 5 minutes with an ultrasonic cell disruptor, the mixed solution was placed in a hydrothermal reactor and hydrothermally heated at 180℃ for 24 hours. After centrifugation, drying, and grinding, the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material was obtained.

[0059] (7) Grind 3g of Co3O4 / COOH@MWCNTs / NiFe2O4 composite material with 2g of sodium dodecylbenzenesulfonate (SDBS), add 30mL of water and sonicate to obtain the third solution;

[0060] (8) Grind 1g of carboxylated carbon nanotubes with 2g of sodium dodecylbenzenesulfonate, add them to 30mL of water and sonicate to obtain the fourth solution;

[0061] (9) The third solution was blended with 27g of waterborne polyurethane, and 0.015g of defoamer, 0.03g of leveling agent and 0.003g of dispersant were added to obtain the front-side microwave absorbing coating agent; the fourth solution was blended with 9g of waterborne polyurethane, and 0.005g of defoamer, 0.01g of leveling agent and 0.001g of dispersant were added to obtain the back-side microwave absorbing coating agent. The front-side microwave absorbing coating agent was applied to the front side of the roughened polyester nonwoven fabric with a coating thickness of 0.5mm, and the back-side microwave absorbing coating agent was applied to the back side of the roughened polyester nonwoven fabric with a coating thickness of 0.15mm to obtain microwave absorbing polyester fabric.

[0062] Example 3

[0063] (1) Cut a piece of polyester nonwoven fabric with a size of 180*180mm and a weight of 8g, put it into 1L of 1mol / L NaOH aqueous solution, heat it to 90℃, soak it for 1h, and obtain the roughened polyester nonwoven fabric.

[0064] (2) Take 2.5g of multi-walled carbon nanotubes and place them in 100mL of a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a mass ratio of 3:1. Stir for 30min and then filter to obtain carboxylated carbon nanotubes.

[0065] (3) Add 0.508g of nickel chloride hexahydrate and 0.6935g of ferric chloride hexahydrate to 50mL of water, stir to dissolve, and then add ammonia to adjust the pH to 10 to obtain the first solution;

[0066] (4) Add 1.5g of carboxylated carbon nanotubes to the first solution, sonicate for 5min using an ultrasonic cell disruptor, place the mixed solution in a hydrothermal reactor, hydrothermally heat at 140℃ for 24h, centrifuge, dry, grind, and obtain COOH@MWCNTs / NiFe2O4 composite material.

[0067] (5) Add 3.6375g of cobalt nitrate hexahydrate to 100mL of water, stir to dissolve, and then add 0.25g of NaOH to obtain the second solution;

[0068] (6) The COOH@MWCNTs / NiFe2O4 composite material was mixed with the second solution at a mass ratio of 1:100. After sonicating for 5 minutes with an ultrasonic cell disruptor, the mixed solution was placed in a hydrothermal reactor and hydrothermally heated at 180℃ for 24 hours. After centrifugation, drying, and grinding, the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material was obtained.

[0069] (7) Grind 3g of Co3O4 / COOH@MWCNTs / NiFe2O4 composite material with 2g of sodium dodecylbenzenesulfonate (SDBS), add 30mL of water and sonicate to obtain the third solution;

[0070] (8) Grind 1g of carboxylated carbon nanotubes with 2g of sodium dodecylbenzenesulfonate, add them to 30mL of water and sonicate to obtain the fourth solution;

[0071] (9) The third solution was blended with 27g of waterborne polyurethane, and 0.015g of defoamer, 0.03g of leveling agent and 0.003g of dispersant were added to obtain the front-side microwave absorbing coating agent; the fourth solution was blended with 9g of waterborne polyurethane, and 0.005g of defoamer, 0.01g of leveling agent and 0.001g of dispersant were added to obtain the back-side microwave absorbing coating agent. The front-side microwave absorbing coating agent was applied to the front side of the roughened polyester nonwoven fabric with a coating thickness of 0.5mm, and the back-side microwave absorbing coating agent was applied to the back side of the roughened polyester nonwoven fabric with a coating thickness of 0.15mm to obtain microwave absorbing polyester fabric.

[0072] Comparative Example 1 (The difference from Example 1 is that the composite material does not contain cobalt oxide)

[0073] (1) Cut a piece of polyester nonwoven fabric with a size of 180*180mm and a weight of 8g, put it into 1L of 1mol / L NaOH aqueous solution, heat it to 90℃, soak it for 1h, and obtain the roughened polyester nonwoven fabric.

[0074] (2) Take 3g of multi-walled carbon nanotubes and place them in 100mL of a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a mass ratio of 3:1. Stir for 30min and then filter to obtain carboxylated carbon nanotubes.

[0075] (3) Add 1.016g of nickel chloride hexahydrate and 1.387g of ferric chloride hexahydrate to 100mL of water, stir to dissolve, and then add ammonia to adjust the pH to 10 to obtain the first solution;

[0076] (4) Add 2g of carboxylated carbon nanotubes to the first solution, sonicate for 5min using an ultrasonic cell disruptor, place the mixed solution in a hydrothermal reactor, hydrothermally heat at 140℃ for 24h, centrifuge, dry, grind, and obtain COOH@MWCNTs / NiFe2O4 composite material.

[0077] (5) Grind 3g of COOH@MWCNTs / NiFe2O4 composite material with 2g of sodium dodecylbenzenesulfonate (SDBS), add 30mL of water and sonicate to obtain the third solution;

[0078] (6) Grind 1g of carboxylated carbon nanotubes with 2g of sodium dodecylbenzenesulfonate, add them to 30mL of water and sonicate to obtain the fourth solution;

[0079] (7) The third solution was blended with 27g of waterborne polyurethane, and 0.015g of defoamer, 0.03g of leveling agent and 0.003g of dispersant were added to obtain the front-side microwave absorbing coating agent; the fourth solution was blended with 9g of waterborne polyurethane, and 0.005g of defoamer, 0.01g of leveling agent and 0.001g of dispersant were added to obtain the back-side microwave absorbing coating agent. The front-side microwave absorbing coating agent was applied to the front side of the roughened polyester nonwoven fabric with a coating thickness of 0.5mm, and the back-side microwave absorbing coating agent was applied to the back side of the roughened polyester nonwoven fabric with a coating thickness of 0.15mm to obtain the microwave absorbing polyester fabric.

[0080] Comparative Example 2 (The difference from Example 1 is that the composite material does not contain nickel ferrite)

[0081] (1) Cut a piece of polyester nonwoven fabric with a size of 180*180mm and a weight of 8g, put it into a NaOH aqueous solution with a concentration of 1mol / L and a volume of 1L, heat it to 90℃, soak it for 1h, and obtain the roughened polyester nonwoven fabric.

[0082] (2) Take 2g of multi-walled carbon nanotubes and place them in 100mL of a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a mass ratio of 3:1. Stir for 30min and then filter to obtain carboxylated carbon nanotubes.

[0083] (3) Add 8.73g of cobalt nitrate hexahydrate to water, stir to dissolve, and then add 0.6g of NaOH to obtain the second solution;

[0084] (4) The carboxylated carbon nanotubes were mixed with the second solution at a mass ratio of 1:100. After sonicating for 5 minutes with an ultrasonic cell disruptor, the mixed solution was placed in a hydrothermal reactor and hydrothermally heated at 180°C for 24 hours. After centrifugation, drying, and grinding, the Co3O4 / COOH@MWCNTs composite material was obtained.

[0085] (5) Grind 3g of Co3O4 / COOH@MWCNTs composite material together with 2g of sodium dodecylbenzenesulfonate (SDBS), add 30mL of water and sonicate to obtain the third solution;

[0086] (6) Grind 1g of carboxylated carbon nanotubes with 2g of sodium dodecylbenzenesulfonate, add them to 30mL of water and sonicate to obtain the fourth solution;

[0087] (7) The third solution was blended with 27g of waterborne polyurethane, and 0.015g of defoamer, 0.03g of leveling agent and 0.003g of dispersant were added to obtain the front-side microwave absorbing coating agent; the fourth solution was blended with 9g of waterborne polyurethane, and 0.005g of defoamer, 0.01g of leveling agent and 0.001g of dispersant were added to obtain the back-side microwave absorbing coating agent. The front-side microwave absorbing coating agent was applied to the front side of the roughened polyester nonwoven fabric with a coating thickness of 0.5mm, and the back-side microwave absorbing coating agent was applied to the back side of the roughened polyester nonwoven fabric with a coating thickness of 0.15mm to obtain the microwave absorbing polyester fabric.

[0088] Comparative Example 3 (the difference from Example 1 is that the content of the microwave absorber in the treatment agent is increased)

[0089] (1) Cut a piece of polyester nonwoven fabric with a size of 180*180mm and a weight of 8g, put it into a NaOH aqueous solution with a concentration of 1mol / L and a volume of 1L, heat it to 90℃, soak it for 1h, and obtain the roughened polyester nonwoven fabric.

[0090] (2) Take 3g of multi-walled carbon nanotubes and place them in 100mL of a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a mass ratio of 3:1. Stir for 30min and then filter to obtain carboxylated carbon nanotubes.

[0091] (3) Add 0.8128g of nickel chloride hexahydrate and 1.1096g of ferric chloride hexahydrate to 100mL of water, stir to dissolve, and then add ammonia to adjust the pH to 10 to obtain the first solution;

[0092] (4) Add 1.6g of carboxylated carbon nanotubes to the first solution, sonicate for 5min with an ultrasonic cell disruptor, place the mixed solution in a hydrothermal reactor, hydrotherm at 140℃ for 24h, centrifuge, dry, grind to obtain COOH@MWCNTs / NiFe2O4 composite material.

[0093] (5) Add 17.46g of cobalt nitrate hexahydrate to 100mL of water, stir to dissolve, and then add 1.2g of NaOH to obtain the second solution;

[0094] (6) The COOH@MWCNTs / NiFe2O4 composite material was mixed with the second solution at a mass ratio of 1:100. After sonicating for 5 minutes with an ultrasonic cell disruptor, the mixed solution was placed in a hydrothermal reactor and hydrothermally heated at 180℃ for 24 hours. After centrifugation, drying, and grinding, the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material was obtained.

[0095] (7) Grind 6g of Co3O4 / COOH@MWCNTs / NiFe2O4 composite material with 3g of sodium dodecylbenzenesulfonate (SDBS), add 30mL of water and sonicate to obtain the third solution;

[0096] (8) Grind 1g of carboxylated carbon nanotubes with 3g of sodium dodecylbenzenesulfonate, add them to 30mL of water and sonicate to obtain the fourth solution;

[0097] (9) The third solution was blended with 24g of waterborne polyurethane, and 0.015g of defoamer, 0.03g of leveling agent, and 0.006g of dispersant were added to obtain the front-side microwave-absorbing coating agent; the fourth solution was blended with 9g of waterborne polyurethane, and 0.005g of defoamer, 0.01g of leveling agent, and 0.001g of dispersant were added to obtain the back-side microwave-absorbing coating agent. The front-side microwave-absorbing coating agent was applied to the front side of the roughened polyester nonwoven fabric with a coating thickness of 0.5mm, and the back-side microwave-absorbing coating agent was applied to the back side of the roughened polyester nonwoven fabric with a coating thickness of 0.15mm to obtain the microwave-absorbing polyester fabric.

[0098] Comparative Example 4 (The difference from Example 1 is that no impedance mismatch reflection layer is constructed in the absorbing structure)

[0099] (1) Cut a piece of polyester nonwoven fabric with a size of 180*180mm and a weight of 8g, put it into 1L of 1mol / L NaOH aqueous solution, heat it to 90℃, soak it for 1h, and obtain the roughened polyester nonwoven fabric.

[0100] (2) Take 1g of multi-walled carbon nanotubes and place them in 100mL of a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a mass ratio of 3:1. Stir for 30min and then filter to obtain carboxylated carbon nanotubes.

[0101] (3) Add 0.4064g of nickel chloride hexahydrate and 0.5548g of ferric chloride hexahydrate to 50mL of water, stir to dissolve, and then add ammonia to adjust the pH to 10 to obtain the first solution;

[0102] (4) Add 0.8g of carboxylated carbon nanotubes to the first solution, sonicate for 5min using an ultrasonic cell disruptor, place the mixed solution in a hydrothermal reactor, hydrothermally heat at 140℃ for 24h, centrifuge, dry, grind, and obtain COOH@MWCNTs / NiFe2O4 composite material.

[0103] (5) Add 8.73g of cobalt nitrate hexahydrate to 100mL of water, stir to dissolve, and then add 0.6g of NaOH to obtain the second solution;

[0104] (6) The COOH@MWCNTs / NiFe2O4 composite material was mixed with the second solution at a mass ratio of 1:100. After sonicating for 5 minutes with an ultrasonic cell disruptor, the mixed solution was placed in a hydrothermal reactor and hydrothermally heated at 180℃ for 24 hours. After centrifugation, drying, and grinding, the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material was obtained.

[0105] (7) Grind 3g of Co3O4 / COOH@MWCNTs / NiFe2O4 composite material with 1g of sodium dodecylbenzenesulfonate (SDBS), add 30mL of water and sonicate to obtain the third solution;

[0106] (8) The third solution and 27g of waterborne polyurethane were blended, and 0.015g of defoamer, 0.03g of leveling agent, and 0.003g of dispersant were added to obtain a front-side microwave-absorbing coating agent. The front-side microwave-absorbing coating agent was applied to both the front and back sides of the roughened polyester nonwoven fabric. The front-side coating thickness was 0.5mm, and the back-side coating thickness was 0.15mm, resulting in a microwave-absorbing polyester fabric. Comparative Example 5 (the difference from Example 1 is the change in the thickness of the coated fabric).

[0107] (1) Cut a piece of polyester nonwoven fabric with a size of 180*180mm and a weight of 8g, put it into 1L of 1mol / L NaOH aqueous solution, heat it to 90℃, soak it for 1h, and obtain the roughened polyester nonwoven fabric.

[0108] (2) Take 2g of multi-walled carbon nanotubes and place them in 100mL of a mixed solution of concentrated nitric acid and concentrated sulfuric acid in a mass ratio of 3:1. Stir for 30min and then filter to obtain carboxylated carbon nanotubes.

[0109] (3) Add 0.4064g of nickel chloride hexahydrate and 0.5548g of ferric chloride hexahydrate to 50mL of water, stir to dissolve, and then add ammonia to adjust the pH to 10 to obtain the first solution;

[0110] (4) Add 0.8g of carboxylated carbon nanotubes to the first solution, sonicate for 5min using an ultrasonic cell disruptor, place the mixed solution in a hydrothermal reactor, hydrothermally heat at 140℃ for 24h, centrifuge, dry, grind, and obtain COOH@MWCNTs / NiFe2O4 composite material.

[0111] (5) Add 8.73g of cobalt nitrate hexahydrate to 100mL of water, stir to dissolve, and then add 0.6g of NaOH to obtain the second solution;

[0112] (6) The COOH@MWCNTs / NiFe2O4 composite material was mixed with the second solution at a mass ratio of 1:100. After sonicating for 5 minutes with an ultrasonic cell disruptor, the mixed solution was placed in a hydrothermal reactor and hydrothermally heated at 180℃ for 24 hours. After centrifugation, drying, and grinding, the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material was obtained.

[0113] (7) Grind 3g of Co3O4 / COOH@MWCNTs / NiFe2O4 composite material with 2g of sodium dodecylbenzenesulfonate (SDBS), add 30mL of water and sonicate to obtain the third solution;

[0114] (8) Grind 1g of carboxylated carbon nanotubes with 2g of sodium dodecylbenzenesulfonate, add them to 30mL of water and sonicate to obtain the fourth solution;

[0115] (9) The third solution was blended with 27g of waterborne polyurethane, and 0.015g of defoamer, 0.03g of leveling agent and 0.003g of dispersant were added to obtain the front-side microwave-absorbing coating agent; the fourth solution was blended with 9g of waterborne polyurethane, and 0.005g of defoamer, 0.01g of leveling agent and 0.001g of dispersant were added to obtain the back-side microwave-absorbing coating agent. The front-side microwave-absorbing coating agent was applied to the front side of the roughened polyester nonwoven fabric with a coating thickness of 0.3mm, and the back-side microwave-absorbing coating agent was applied to the back side of the roughened polyester nonwoven fabric with a coating thickness of 0.1mm to obtain microwave-absorbing polyester fabric.

[0116] Table 1

[0117]

[0118] The reflectivity of the above eight samples was tested using an arched reflectivity testing system to analyze their effective absorption width (EAB) and reflection loss (RL).

[0119] like Figure 1-3 As shown in Table 1, the test graphs of fabric reflection loss show that when an impedance mismatch reflection layer is present, the absorber composition mass ratio of Co3O4:NFO(NiFe2O4):CNTs = 6:1:2, the absorber concentration is 10%, and the coating thickness is 0.65 mm, the fabric has the best absorption performance, with the maximum reflection loss at 19.26 GHz, a maximum RL value of -22.7 dB, and an effective absorption frequency band of 13.46–20 GHz (bandwidth 6.54 GHz).

[0120] like Figure 4As shown in Comparative Example 1, the absorber filler does not contain cobalt tetroxide, which reduces its maximum reflection loss to -12dB and shifts the effective absorption frequency band to lower frequencies (7.3-10.9dB), with a bandwidth of 3.6GHz.

[0121] like Figure 5 As shown in Comparative Example 2, the absorber component does not contain nickel ferrite, which reduces its maximum reflection loss to -11.73 dB and the effective absorption frequency band to 8.95–11.43 GHz.

[0122] like Figure 6 As shown in Comparative Example 3, the concentration of the absorbing agent increased, and the filler agglomerated severely in the coating, resulting in the impedance matching absorbing layer being unable to achieve effective absorption. The maximum reflection loss was only -2dB, and there was no effective absorption band.

[0123] like Figure 7 As shown, in Comparative Example 4, due to the absence of a reflective layer, the electromagnetic wave cannot undergo multiple reflections when it is incident on the interior of the material. This makes the propagation path of the electromagnetic wave shorter than that of Experimental Example 1, thereby reducing the absorption of the electromagnetic wave and reducing its maximum reflection loss to -14.8dB and the effective absorption bandwidth to 3.38GHz.

[0124] like Figure 8 As shown, in Comparative Example 5, the coating thickness is reduced for the same reason as in Comparative Example 4, which is to reduce the propagation path of electromagnetic waves inside the material, thereby reducing its maximum reflection loss to -9.1dB and eliminating the effective absorption band.

[0125] The above embodiments of the present invention are merely illustrative examples and are not intended to limit the implementation of the invention. Those skilled in the art can make other variations and modifications based on the above description. It is impossible to exhaustively list all possible implementations here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a wave-absorbing functional fabric based on a three-phase electromagnetic filler coating, characterized in that, The method comprises the following steps: (1) adding nickel chloride hexahydrate and ferric chloride hexahydrate into water, adjusting pH to 9.5-10.5 to obtain a first solution; (2) adding carboxylated carbon nanotubes into the first solution, performing ultrasonic treatment and then performing a first hydrothermal reaction to obtain a COOH@MWCNTs / NiFe2O4 composite material; (3) adding cobalt nitrate hexahydrate into water, dissolving after stirring, and then adding NaOH to obtain a second solution; (4) mixing the COOH@MWCNTs / NiFe2O4 composite material with the second solution, performing ultrasonic treatment and then performing a second hydrothermal reaction to obtain a Co3O4 / COOH@MWCNTs / NiFe2O4 composite material, wherein the mass ratio of Co3O4:NiFe2O4:CNTs is 6:1:2 or 4:1:2 or 2:1:3; (5) grinding the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material together with sodium dodecylbenzenesulfonate, the mass ratio of the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material, the sodium dodecylbenzenesulfonate and water is 2.8-3.2:1.5-2.3:28-35, adding water and performing ultrasonic treatment to obtain a third solution; (6) grinding carboxylated carbon nanotubes together with sodium dodecylbenzenesulfonate, adding water and performing ultrasonic treatment to obtain a fourth solution; (7) blending the third solution and the fourth solution with water-based polyurethane, defoaming agent, leveling agent and dispersant respectively to obtain a front wave-absorbing coating treatment agent and a back wave-absorbing coating treatment agent respectively, coating the agents on the front and back of roughened polyester non-woven fabric respectively, the coating thickness on the front is 0.3-0.6 mm, and the coating thickness on the back is 0.05-0.25 mm, to obtain a wave-absorbing functional fabric.

2. The method of claim 1, wherein the method of preparing the wave-absorbing functional fabric based on the three-phase electromagnetic filler coating is characterized by, In step (1), the molar ratio of the nickel chloride hexahydrate to the ferric chloride hexahydrate is 1:2, and the mass ratio of the nickel chloride hexahydrate to water is 0.3-0.6:

50.

3. The method of claim 1, wherein the method of preparing the wave-absorbing functional fabric based on the three-phase electromagnetic filler coating is characterized by, In step (2), the mass ratio of the first solution to the carboxylated carbon nanotubes is 100:1-3, the ultrasonic treatment time is 5-10 min, the first hydrothermal reaction time is 20-28 h, and the hydrothermal temperature is 120-180℃.

4. The method of claim 1, wherein the method of preparing the wave-absorbing functional fabric based on the three-phase electromagnetic filler coating is characterized by, In step (3), the mass ratio of the cobalt nitrate hexahydrate to water is 5-10:100, and the molar ratio of the cobalt nitrate hexahydrate to NaOH is 2-4:

1.

5. The method of claim 1, wherein the method of preparing the wave-absorbing functional fabric based on the three-phase electromagnetic filler coating is characterized by, In step (4), the mass ratio of the COOH@MWCNTs / NiFe2O4 composite material to the second solution is 1:100, the ultrasonic treatment time is 5-10 min, the second hydrothermal reaction time is 20-28 h, and the hydrothermal temperature is 120-180℃.

6. The method for preparing wave-absorbing functional fabric based on three-phase electromagnetic filler coating according to any one of claims 1-5, characterized in that, In step (5), the ultrasonic treatment time is 1.5-2.5 h.

7. The method of claim 1, wherein the method of preparing the wave-absorbing functional fabric based on the three-phase electromagnetic filler coating is characterized by, In step (6), the mass ratio of the carboxylated carbon nanotubes, the sodium dodecylbenzenesulfonate and water is 0.7-1.1:1.5-2.3:30-35, and the ultrasonic treatment time is 1.5-2.5 h.

8. The method of claim 1, wherein the method of preparing the wave-absorbing functional fabric based on the three-phase electromagnetic filler coating is characterized by, In step (7), in the front wave-absorbing coating treatment agent, the mass ratio of Co3O4 / COOH@MWCNTs / NiFe2O4 composite material to water-based polyurethane is 2.8-3.2:25-30, the defoaming agent accounts for 0.01-0.06% of the total mass of the coating treatment agent, the leveling agent accounts for 0.01-0.2% of the total mass of the coating treatment agent, and the mass ratio of the dispersing agent to the Co3O4 / COOH@MWCNTs / NiFe2O4 composite material is 0.0015-0.003:2.8-3.

2.

9. The method for preparing the wave-absorbing functional fabric based on the three-phase electromagnetic filler coating according to claim 1 or 8, characterized in that, In step (7), in the back wave-absorbing coating treatment agent, the mass ratio of carboxylated carbon nanotubes to water-based polyurethane is 0.8-1.2:8-10, the defoaming agent accounts for 0.01-0.06% of the total mass of the coating treatment agent, the leveling agent accounts for 0.01-0.2% of the total mass of the coating treatment agent, and the mass ratio of the dispersing agent to the carboxylated carbon nanotubes is 0.0005-0.001:0.8-1.

2.

10. The method for preparing the wave-absorbing functional fabric based on the three-phase electromagnetic filler coating according to claim 1 or 8, characterized in that, In step (7), the preparation of the roughened polyester non-woven fabric is as follows: the polyester non-woven fabric is placed in a NaOH aqueous solution, heated and soaked to obtain a roughened polyester non-woven fabric; the molar concentration of the NaOH aqueous solution is 0.5-1 mol / L; the ratio of the polyester non-woven fabric to the NaOH aqueous solution is 0.5-1.5 g:125 mL; the heating temperature is 70-100℃, and the soaking time is 0.5-1.5 h.

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