Asymmetric layered pdms electromagnetic shielding material and preparation method thereof

Abstract

The application discloses a preparation method of an asymmetric layered PDMS electromagnetic shielding material, and specifically comprises the following steps f -Ni, AgNPs@GO powder, AgNPs@GO precursor, AgNWs, f -Ni@GO precursor; through f -Ni@GO precursor and AgNPs@GO precursor to obtain an asymmetric layered aerogel; in combination with AgNWs / PDMS conductive paste, an asymmetric three-layer structure is obtained; vacuum-assisted impregnation of PDMS and thermal curing are performed, and the asymmetric layered PDMS electromagnetic shielding material is obtained. The application further discloses the asymmetric layered PDMS electromagnetic shielding material, and solves the problem that polymer-based electromagnetic shielding composite materials in the prior art are difficult to simultaneously consider high electromagnetic shielding efficiency, low reflection characteristics and absorption-dominant shielding effect under the condition of low filler content.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic shielding material technology, specifically relating to a method for preparing asymmetric layered PDMS electromagnetic shielding material, and also relating to asymmetric layered PDMS electromagnetic shielding material. Background Technology

[0002] With the rapid development of electronic information technology, wireless communication technology, and highly integrated electronic devices, electromagnetic interference (EMI) has become increasingly prominent. It not only affects the normal operation of electronic equipment and the quality of signal transmission, but may also cause device malfunctions, system failures, and information leaks. Therefore, developing polymer-based electromagnetic shielding materials that combine high electromagnetic shielding effectiveness with low reflection characteristics is of great significance.

[0003] Currently, polymer-based electromagnetic shielding composites typically construct conductive or magnetic networks by introducing functional fillers such as graphene, metal particles, metal nanowires, and magnetic particles to achieve the reflection, absorption, and attenuation of electromagnetic waves. However, most existing materials are prepared using random blending or simple lamination methods, resulting in disordered dispersion of functional fillers within the polymer matrix, making it difficult to form efficient and continuous conductive / magnetic pathways at low filler contents.

[0004] To improve electromagnetic shielding effectiveness, it is often necessary to increase the filler content. However, high filler content can easily lead to problems such as decreased material processing performance, deterioration of mechanical properties, and increased costs. Numerous studies have shown that introducing magnetic components into electromagnetic shielding composite materials to enhance magnetic loss and constructing three-dimensional porous or layered structures are effective strategies for improving impedance matching, reducing interface reflection, and enhancing absorption and dissipation capabilities. Among these, the three-dimensional porous graphene framework, with its low density, large specific surface area, and abundant interfaces, can effectively extend the propagation path of electromagnetic waves within the material, enhancing multiple reflections, scattering, and interface polarization. The layered structure facilitates the orderly distribution of magnetic and conductive components along the thickness direction, further optimizing the transmission and dissipation process of electromagnetic waves within the material. Nickel, silver nanoparticles, silver nanowires, and graphene are all common electromagnetic shielding functional components. However, research on asymmetric layered polymer-based electromagnetic shielding composite materials that combine magnetic loss layers, conductive loss layers, and highly conductive barrier layers is still limited. It is difficult to simultaneously achieve high electromagnetic shielding effectiveness, low reflection characteristics, and absorption-dominant shielding effects; their structural design and shielding mechanisms still require further optimization.

[0005] Therefore, developing an asymmetric layered magneto-electric synergistic electromagnetic shielding composite material based on a three-dimensional porous framework is of great significance for solving the problems of insufficient shielding efficiency, excessive reflection, and simple structural design in existing electromagnetic shielding materials. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing asymmetric layered PDMS electromagnetic shielding material, which solves the problem in the prior art that polymer-based electromagnetic shielding composite materials are difficult to simultaneously achieve high electromagnetic shielding effectiveness, low reflection characteristics, and absorption-dominant shielding effect under low filler content conditions.

[0007] Another objective of this invention is to provide an asymmetric layered PDMS electromagnetic shielding material.

[0008] The technical solution adopted in this invention is a method for preparing asymmetric layered PDMS electromagnetic shielding material, which is implemented according to the following steps; Step 1, Preparation f -Ni; Step 2, prepare AgNPs@GO powder; Step 3: Prepare AgNPs@GO precursor; Step 4, prepare AgNWs; Step 5, Preparation f -Ni@GO precursor; Step 6, f -Ni@GO precursor and AgNPs@GO precursor were used to construct a layered aerogel precursor, and heat treatment was performed to obtain an asymmetric layered aerogel. Step 7: AgNWs and PDMS are mixed to form AgNWs / PDMS conductive paste, which is then combined with asymmetric layered aerogel to obtain an asymmetric three-layer structure. Step 8: Vacuum-assisted impregnation of PDMS followed by thermosetting yields the final product.

[0009] The invention is further characterized by: The specific process of step 1 is as follows: Step 1.1: Add Ni, ammonium persulfate and deionized water to a three-necked flask, and perform ultrasonic and mechanical stirring under ice-water bath conditions for 0.5 h to 2 h to obtain Ni suspension; Step 1.2: Slowly add acrylic acid solution dropwise to the Ni suspension obtained in Step 1.1, and continue ultrasonic and mechanical stirring at 60℃~80℃ for 2h~5h to cause grafting modification on the Ni surface; Step 1.3: After removing the supernatant by magnetic separation, deionized water is added to the system and the temperature is raised to 60℃~80℃. Ethylenediamine is added dropwise, and ultrasonic and mechanical stirring is continued for 2h~5h to perform amination functional modification on Ni particles. Step 1.4: After magnetic separation, the product obtained in Step 1.3 is washed 2 to 5 times with deionized water until the supernatant is neutral. Then, it is vacuum dried for 6 to 24 hours to obtain amination-modified Ni particles. f -Ni.

[0010] The specific process of step 2 is as follows; Step 2.1: Disperse GO in a mixed solution of deionized water and ethanol, and sonicate for 0.5 h to 2 h to obtain a stable GO dispersion; Step 2.2: Add AgNO3 to the GO dispersion obtained in Step 2.1 and continue sonicating for 0.5h~2h to promote Ag + The mixture is adsorbed and bound to the GO surface to obtain a mixed solution, which is then heated to 60℃~90℃ and stirred for 0.5h~2h. Step 2.3: Add a reducing agent to the mixture obtained in Step 2.2, and keep it at the temperature for 1 to 4 hours. Use the in-situ reduction method to load AgNPs onto the GO surface, so that AgNPs grow in situ on the GO surface. The reducing agent used is ascorbic acid. Step 2.4: Cool the reaction mixture to room temperature, centrifuge and wash it 2 to 5 times with deionized water and anhydrous ethanol respectively, and then freeze-dry it under vacuum for 24 to 72 hours to obtain AgNPs@GO powder.

[0011] The specific process of step 3 is as follows; Step 3.1: Disperse egg white protein powder in deionized water to prepare a protein solution with a mass fraction of 5wt%~15wt%; Step 3.2: Add the AgNPs@GO powder obtained in Step 2 to the protein solution obtained in Step 3.1, and mix and disperse evenly; Step 3.3: The mixture obtained in step 3.2 is subjected to high-speed stirring and foaming for 2 min to 20 min to form AgNPs@GO complex. The AgNPs@GO complex with a stable three-dimensional porous structure serves as the second porous precursor.

[0012] The specific process of step 4 is as follows; Step 4.1: Dissolve AgNO3 in ethylene glycol to obtain solution A; Step 4.2: Dissolve FeCl3·6H2O and polyvinylpyrrolidone in another portion of ethylene glycol to obtain solution B; Step 4.3: Slowly add solution A to solution B over a period of 5 to 30 minutes to obtain mixed solution C; Step 4.4: Transfer the mixed solution C obtained in step 4.3 to the reaction vessel and react at 140℃~180℃ for 2h~8h; Step 4.5: After washing the reaction product by centrifugation with acetone and anhydrous ethanol 2 to 5 times, the product is dried under vacuum at 40℃ to 80℃ for 6 to 24 hours to obtain AgNWs, which serve as functional components of the highly conductive barrier layer.

[0013] Step 5 Preparation fThe specific process of the Ni@GO precursor is as follows: Step 5.1, take the result from Step 1 f -Ni is mixed with an aqueous solution of GO and subjected to ultrasonic treatment for 0.5 h to 2 h to obtain f -Ni@GO suspension; Step 5.2, apply the solution obtained in step 5.1 f - Egg white protein powder was added to the Ni@GO suspension; Step 5.3: The mixture obtained in step 5.2 is subjected to high-speed stirring and foaming for 2 to 20 minutes to form... f -Ni@GO complex, possessing a stable three-dimensional porous structure f -Ni@GO complex serves as the first layer of porous precursor.

[0014] The specific process of step 6 is as follows; Step 6.1: Cast the AgNPs@GO precursor from step 3 into the preset mold; Step 6.2: After the surface of the mold used in Step 6.1 is smooth, pour the material from Step 5 onto it. f -Ni@GO precursor; Step 6.3, Control f The thickness ratio of the Ni@GO layer to the AgNPs@GO layer is 1:2 to 2:1. After freeze-drying for 24 to 72 hours, a layered structure is obtained. f -Ni@GO|AgNPs@GO) aerogel; Step 6.4: Place the aerogel obtained in Step 6.3 under a protective atmosphere and perform programmed temperature heat treatment. First, heat to 150℃~250℃ to remove moisture, then heat to 500℃~700℃ to remove the protein template, and finally heat to 700℃~900℃ for thermal reduction to obtain a symmetrical layered aerogel. f -Ni@PrGO|AgNPs@PrGO) aerogel.

[0015] Step 7 is as follows: Step 7.1: Mix AgNWs with PDMS to prepare AgNWs / PDMS conductive paste; Step 7.2, the layered structure obtained in step 6 ( f One side of the Ni@PrGO|AgNPs@PrGO aerogel is uniformly impregnated or coated with AgNWs / PDMS conductive paste. Step 7.3: Dry the sample obtained in step 7.2 at 40℃~80℃ for 1h~12h to form a bottom AgNWs conductive layer with a thickness of 0.1mm~1.0mm.

[0016] Step 8 is as follows: Step 8.1: Place the three-layer structure obtained in step 7 in a vacuum environment and use a vacuum-assisted impregnation process to fully impregnate the PDMS into the porous skeleton. The vacuum degree is 0.01MPa~0.1MPa and the impregnation time is 0.5h~12h. Step 8.2: Perform heat curing treatment on the sample obtained in step 8.1. The curing temperature is 50℃~100℃ and the curing time is 1h~24h.

[0017] Another technical solution adopted in this invention is an asymmetric layered PDMS electromagnetic shielding material, which is prepared by the above-mentioned preparation method.

[0018] The beneficial effects of this invention are as follows: The preparation method of the asymmetric layered PDMS electromagnetic shielding material of this invention constructs an asymmetric "magnetic-electrical-electrical" layered structure, in which the magnetic loss layer, conductive loss layer and highly conductive barrier layer are arranged in an orderly manner in the thickness direction, and combined with a three-dimensional porous graphene framework, effectively improving the impedance matching between the material and free space, enhancing the multiple reflections, scattering, interface polarization and magnetic-electrical synergistic loss effect of electromagnetic waves inside the material, thereby achieving a balance between high electromagnetic shielding effectiveness and low reflection characteristics under low filler content conditions; at the same time, the preparation method of this invention is simple in process, highly operable, and has good repeatability and application prospects. Attached Figure Description

[0019] Figure 1 This is a cross-sectional morphology diagram of the asymmetric layered PDMS electromagnetic shielding material prepared in Example 1 of the present invention; Figure 2 This is an electromagnetic shielding effectiveness diagram of the asymmetric layered PDMS electromagnetic shielding material prepared in Examples 2-6 of this invention; Figure 3 This is a power coefficient diagram of the asymmetric layered PDMS electromagnetic shielding material prepared in Examples 3-4 of this invention. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] Example 1 The preparation method of the asymmetric layered PDMS electromagnetic shielding material of the present invention is carried out according to the following steps; Step 1: Obtain Ni particles, perform surface modification treatment on the Ni particles, and prepare amination-modified Ni particles. f -Ni; The specific process of step 1 is as follows: Step 1.1: Add Ni, ammonium persulfate and deionized water to a three-necked flask, and perform ultrasonic and mechanical stirring under ice-water bath conditions for 0.5 h to 2 h to obtain Ni suspension; Step 1.2: Slowly add acrylic acid solution dropwise to the Ni suspension obtained in Step 1.1, and continue ultrasonic and mechanical stirring at 60℃~80℃ for 2h~5h to cause grafting modification on the Ni surface; Step 1.3: After removing the supernatant by magnetic separation, deionized water is added to the system and the temperature is raised to 60℃~80℃. Ethylenediamine is added dropwise, and ultrasonic and mechanical stirring is continued for 2h~5h to perform amination functional modification on Ni particles. Step 1.4: After magnetic separation, the product obtained in Step 1.3 is washed 2 to 5 times with deionized water until the supernatant is neutral. Then, it is vacuum dried for 6 to 24 hours to obtain amination-modified Ni particles. f -Ni.

[0022] Step 2, f -Ni was combined with graphene oxide (GO) to prepare AgNPs@GO powder; The specific process of step 2 is as follows; Step 2.1: Disperse GO in a mixed solution of deionized water and ethanol, and sonicate for 0.5 h to 2 h to obtain a stable GO dispersion; Step 2.2: Add AgNO3 to the GO dispersion obtained in Step 2.1 and continue sonicating for 0.5h~2h to promote Ag + The mixture is adsorbed and bound to the GO surface to obtain a mixed solution, which is then heated to 60℃~90℃ and stirred for 0.5h~2h. Step 2.3: Add a reducing agent to the mixture obtained in Step 2.2, and keep it at the temperature for 1 to 4 hours. Use the in-situ reduction method to load AgNPs onto the GO surface, so that AgNPs grow in situ on the GO surface. The reducing agent used is ascorbic acid. Step 2.4: Cool the reaction mixture to room temperature, centrifuge and wash it 2 to 5 times with deionized water and anhydrous ethanol respectively, and then freeze-dry it under vacuum for 24 to 72 hours to obtain AgNPs@GO powder.

[0023] Step 3: Prepare AgNPs@GO precursor using the protein foaming method; The specific process of step 3 is as follows; Step 3.1: Disperse egg white protein powder in deionized water to prepare a protein solution with a mass fraction of 5wt%~15wt%; Step 3.2: Add the AgNPs@GO powder obtained in Step 2 to the protein solution obtained in Step 3.1, and mix and disperse evenly; Step 3.3: The mixture obtained in step 3.2 is subjected to high-speed stirring and foaming for 2 min to 20 min to form an AgNPs@GO complex with a stable three-dimensional porous structure, which serves as the second-layer precursor.

[0024] Step 4: Prepare AgNWs using the polyol method; The specific process of step 4 is as follows; Step 4.1: Dissolve AgNO3 in ethylene glycol to obtain solution A; Step 4.2: Dissolve FeCl3·6H2O and polyvinylpyrrolidone in another portion of ethylene glycol to obtain solution B; Step 4.3: Slowly add solution A to solution B over a period of 5 to 30 minutes to obtain mixed solution C; Step 4.4: Transfer the mixed solution C obtained in step 4.3 to the reaction vessel and react at 140℃~180℃ for 2h~8h; Step 4.5: After washing the reaction product by centrifugation with acetone and anhydrous ethanol 2 to 5 times, the product is dried under vacuum at 40℃ to 80℃ for 6 to 24 hours to obtain AgNWs, which serve as functional components of the highly conductive barrier layer.

[0025] Step 5, Preparation f -Ni@GO precursor; Step 5 Preparation f The specific process of the Ni@GO precursor is as follows: Step 5.1, take the result from Step 1 f -Ni is mixed with an aqueous solution of GO and subjected to ultrasonic treatment for 0.5 h to 2 h to obtain f -Ni@GO suspension; Step 5.2, apply the solution obtained in step 5.1 f - Egg white protein powder was added to the Ni@GO suspension; Step 5.3: The mixture obtained in step 5.2 is subjected to high-speed stirring and foaming for 2 to 20 minutes to form... f -Ni@GO complex, possessing a stable three-dimensional porous structure f -Ni@GO complex serves as the first layer of porous precursor.

[0026] Step 6, the mixture prepared in step 5 f -Ni@GO precursor and AgNPs@GO precursor prepared in step 3 were used to construct a bilayer precursor by layer casting. After freeze-drying, a layered aerogel precursor was obtained. The layered aerogel precursor was then heat-treated in a hydrogen-containing reducing atmosphere to remove the protein template and achieve thermal reduction of the GO backbone, resulting in an asymmetric layered aerogel. f-Ni@PrGO|AgNPs@PrGO) aerogel; The specific process of step 6 is as follows; Step 6.1: Cast the AgNPs@GO precursor from step 3 into the preset mold; Step 6.2: After the surface of the mold used in Step 6.1 is smooth, pour the material from Step 5 onto it. f -Ni@GO precursor; Step 6.3, Control f The thickness ratio of the Ni@GO layer to the AgNPs@GO layer is 1:2 to 2:1. After freeze-drying for 24 to 72 hours, a layered structure is obtained. f -Ni@GO|AgNPs@GO) aerogel; Step 6.4: Place the aerogel obtained in Step 6.3 under a protective atmosphere and perform programmed temperature heat treatment. First, heat to 150℃~250℃ to remove moisture, then heat to 500℃~700℃ to remove the protein template, and finally heat to 700℃~900℃ for thermal reduction to obtain a layered aerogel. f -Ni@PrGO|AgNPs@PrGO) aerogel.

[0027] Step 7: Mix the AgNWs prepared in Step 4 with PDMS to form AgNWs / PDMS conductive paste, and impregnate or coat it on the surface of AgNPs@PrGO layer to obtain an asymmetric three-layer structure, forming the third highly conductive barrier layer. Step 7 is as follows: Step 7.1: Mix AgNWs with PDMS to prepare AgNWs / PDMS conductive paste; Step 7.2, the layered structure obtained in step 6 ( f One side of the Ni@PrGO|AgNPs@PrGO aerogel is uniformly impregnated or coated with AgNWs / PDMS conductive paste. Step 7.3: Dry the sample obtained in step 7.2 at 40℃~80℃ for 1h~12h to form a bottom AgNWs conductive layer with a thickness of 0.1mm~1.0mm.

[0028] Step 8: Vacuum-assisted impregnation with PDMS and thermosetting are performed on the obtained three-layer structure to obtain an asymmetric layered structure. f -Ni@PrGO|AgNPs@PrGO|AgNWs) / PDMS electromagnetic shielding composite material.

[0029] Step 8 is as follows: Step 8.1: Place the three-layer structure obtained in step 7 in a vacuum environment and use a vacuum-assisted impregnation process to fully impregnate the PDMS into the porous skeleton. The vacuum degree is 0.01MPa~0.1MPa and the impregnation time is 0.5h~12h. Step 8.2: The sample obtained in Step 8.1 is subjected to thermosetting treatment at a temperature of 50℃~100℃ for 1h~24h to obtain a layered structure. f -Ni@PrGO|AgNPs@PrGO|AgNWs) / PDMS electromagnetic shielding composite material. The cross-sectional morphology of the prepared L-NGPGW composite material shows a clear layered structure, such as... Figure 1 As shown, this demonstrates the successful preparation of the asymmetric L-NGPGW composite material.

[0030] The mechanism of the preparation method of the asymmetric layered PDMS electromagnetic shielding material of this invention is as follows: by constructing an asymmetric "magnetic-electrical-electrical" layered structure, a magnetic loss layer, a conductive loss layer, and a highly conductive barrier layer are sequentially formed along the thickness direction of the material. When electromagnetic waves are incident, the surface layer... f The magnetic components and three-dimensional porous framework in Ni@PrGO improve impedance matching between the material and free space, allowing more electromagnetic waves to penetrate the material. Subsequently, the AgNPs@PrGO layer enhances conductivity loss, interface polarization, and multiple reflections through a continuous conductive network, rich interfaces, and porous structure, further dissipating electromagnetic wave energy. The bottom AgNWs / PDMS conductive layer acts as a highly conductive barrier layer, blocking residual electromagnetic wave transmission and promoting secondary reflection and dissipation of transmitted waves. Through the synergistic effect of the three-layer structure, the composite material of this invention can achieve high electromagnetic shielding effectiveness with low filler content, while reducing the material's reflection coefficient, exhibiting absorption-dominant electromagnetic shielding characteristics.

[0031] Example 2 The preparation method of the asymmetric layered PDMS electromagnetic shielding material of the present invention is carried out according to the following steps; Step 1, prepare aminated modified Ni ( f -Ni); Step 1.1: Add 2g Ni, 1g ammonium persulfate (APS) and 100mL deionized water to a three-necked flask and perform ultrasonic and mechanical stirring for 1h under ice-water bath conditions; Step 1.2: Slowly add 10 mL of acrylic acid (AA) solution to the Ni suspension, and continue ultrasonic and mechanical stirring at 70 °C for 3 h; Step 1.3: After the reaction is complete, remove the supernatant by magnetic separation, add 100 mL of deionized water and heat to 70 °C, add 20 mL of ethylenediamine (EN) dropwise, and continue sonication and mechanical stirring for 3 h. Step 1.4: After magnetic separation, the obtained product is washed with deionized water until neutral, and then vacuum dried to obtain... f -Ni.

[0032] Step 2, prepare AgNPs@GO powder; Step 2.1: Disperse 0.75g GO in a mixed solution of 100mL deionized water and 100mL ethanol, and sonicate for 1h to obtain a stable GO dispersion; Step 2.2: Add AgNO3 to the GO dispersion, wherein the mass ratio of GO to AgNO3 is 1:0.25, and continue sonication for 1 hour; Step 2.3: Heat the resulting mixture to 80°C and stir for 1 hour; Step 2.4: Gradually add 2g of ascorbic acid (AsA) to the above mixture, keep warm and stir for 2 hours, and let the system change from brown to black before naturally cooling to room temperature. Step 2.5: Wash the product three times by centrifugation with deionized water and anhydrous ethanol, respectively, at speeds of 10,000 rpm and 6,000 rpm. Then freeze-dry it under vacuum to obtain AgNPs@GO powder.

[0033] Step 3: Prepare AgNPs@GO precursor; Step 3.1: Disperse 20g of egg white protein powder in 200mL of deionized water to obtain a protein solution with a mass fraction of 10wt%. Step 3.2: Disperse the AgNPs@GO powder obtained in step 2 in 50 mL of protein solution and mix thoroughly. Step 3.3: The mixture obtained in step 3.2 is subjected to high-speed stirring and foaming for 2 minutes to form an AgNPs@GO complex with a stable three-dimensional porous structure, which serves as the second-layer precursor.

[0034] Step 4, prepare AgNWs; Step 4.1: Dissolve 0.68g AgNO3 in 45mL ethylene glycol to obtain solution A; Step 4.2: Dissolve 0.69 mg FeCl3·6H2O and 0.71 g PVP in 50 mL ethylene glycol to obtain solution B; Step 4.3: Slowly add solution A to solution B over a period of 15 minutes to obtain mixed solution C; Step 4.4: Transfer the mixed solution C to a 100 mL reaction vessel and react at 160 °C for 4 h; Step 4.5: After the reaction is complete, the sample is washed three times by centrifugation with acetone and anhydrous ethanol, and then dried under vacuum at 60°C for 12 hours to obtain AgNWs.

[0035] Step 5, Preparation f -Ni@GO precursor; Step 5.1, quantify f -Ni was mixed with an aqueous solution of GO and ultrasonically dispersed to obtain f -Ni@GO suspension; Step 5.3: The mixture obtained in step 5.2 is subjected to high-speed stirring and foaming for 2 minutes to form a stable three-dimensional porous structure. f -Ni@GO complex, as the first-layer precursor.

[0036] Step 6, prepare the layered structure ( f -Ni@PrGO|AgNPs@PrGO) aerogel; Step 6.1: First, pour the AgNPs@GO layer into the mold, then pour the top layer on top of it. f -Ni@GO layer; Step 6.2, Control f The thickness ratio of the Ni@GO layer to the AgNPs@GO layer is 1:1, and the total thickness of the two layers is 2.5 mm. Step 6.3: After freeze-drying the bilayer precursor for 48 hours, a layered structure is obtained. f -Ni@GO|AgNPs@GO) aerogel; Step 6.4: Place the obtained aerogel in a tube furnace under a 5% H2 / Ar atmosphere. First, raise the temperature to 200℃ at 5℃ / min, then raise it to 600℃ at 1℃ / min, and finally raise it to 800℃ at 5℃ / min and hold for 2 hours to obtain a layered structure. f -Ni@PrGO|AgNPs@PrGO) aerogel.

[0037] Step 7: Prepare an asymmetric layered three-layer composite material; An AgNWs / PDMS solution was uniformly impregnated onto one side of the AgNPs@PrGO layer using an impregnation coating method to form a bottom AgNWs conductive layer with a thickness of 0.5 mm. Step 8: Place the obtained three-layer structure in a vacuum oven for vacuum-assisted impregnation to allow PDMS to fully penetrate into the porous skeleton. After thermosetting, an asymmetric layered structure is obtained. f -Ni@PrGO|AgNPs@PrGO|AgNWs) / PDMS electromagnetic shielding composite material, denoted as L-NGPGW-I.

[0038] The L-NGPGW-I composite material prepared in Example 2 has a total electromagnetic shielding effectiveness of 55 dB in the X-band and an absorption coefficient of 0.58.

[0039] Example 3 The preparation method of the asymmetric layered PDMS electromagnetic shielding material of the present invention is carried out according to the following steps; Step 1, prepare aminated modified Ni ( f -Ni); Step 1.1: Add 2g Ni, 1g ammonium persulfate (APS) and 100mL deionized water to a three-necked flask and perform ultrasonic and mechanical stirring for 1h under ice-water bath conditions; Step 1.2: Slowly add 10 mL of acrylic acid (AA) solution to the above Ni suspension, and continue ultrasonic and mechanical stirring at 70 °C for 3 h; Step 1.3: After the reaction is complete, remove the supernatant by magnetic separation, add 100 mL of deionized water and heat to 70 °C, add 20 mL of ethylenediamine (EN) dropwise, and continue sonication and mechanical stirring for 3 h. Step 1.4: After magnetic separation, the obtained product is washed with deionized water until neutral, and then vacuum dried to obtain... f -Ni.

[0040] Step 2, prepare AgNPs@GO powder; Step 2.1: Disperse 0.75g GO in a mixed solution of 100mL deionized water and 100mL ethanol, and sonicate for 1h to obtain a stable GO dispersion; Step 2.2: Add AgNO3 to the GO dispersion, wherein the mass ratio of GO to AgNO3 is 1:0.5, and continue sonication for 1 hour; Step 2.3: Heat the resulting mixture to 80°C and stir for 1 hour; Step 2.4: Gradually add 2g of ascorbic acid (AsA) to the above mixture, keep warm and stir for 2 hours, and let the system change from brown to black before naturally cooling to room temperature. Step 2.5: Wash the product three times by centrifugation with deionized water and anhydrous ethanol, respectively, at speeds of 10,000 rpm and 6,000 rpm. Then freeze-dry it under vacuum to obtain AgNPs@GO powder.

[0041] Step 3: Prepare AgNPs@GO precursor; Step 3.1: Disperse 20g of egg white protein powder in 200mL of deionized water to obtain a protein solution with a mass fraction of 10 wt%. Step 3.2: Disperse the AgNPs@GO powder obtained in step 2 in 50 mL of protein solution and mix thoroughly. Step 3.3: The mixture obtained in step 3.2 is subjected to high-speed stirring and foaming for 20 minutes to form an AgNPs@GO complex with a stable three-dimensional porous structure, which serves as the second-layer precursor.

[0042] Step 4, prepare AgNWs; Step 4.1: Dissolve 0.68g AgNO3 in 45mL ethylene glycol to obtain solution A; Step 4.2: Dissolve 0.69 mg FeCl3·6H2O and 0.71 g PVP in 50 mL ethylene glycol to obtain solution B; Step 4.3: Slowly add solution A to solution B over a period of 15 minutes to obtain mixed solution C; Step 4.4: Transfer the mixed solution C to a 100 mL reaction vessel and react at 160 °C for 4 h; Step 4.5: After the reaction is complete, the sample is washed three times by centrifugation with acetone and anhydrous ethanol, and then dried under vacuum at 60°C for 12 hours to obtain AgNWs.

[0043] Step 5, Preparation f -Ni@GO precursor; Step 5.1, quantify f -Ni was mixed with an aqueous solution of GO and ultrasonically dispersed to obtain f -Ni@GO suspension; Step 5.2: Add egg white protein powder to the above suspension; Step 5.3: The mixture obtained in step 5.2 is subjected to high-speed stirring and foaming for 20 minutes to form a stable three-dimensional porous structure. f -Ni@GO complex, as the first-layer precursor.

[0044] Step 6, prepare the layered structure ( f -Ni@PrGO|AgNPs@PrGO) aerogel; Step 6.1: First, pour the AgNPs@GO layer into the mold, then pour the top layer on top of it. f -Ni@GO layer; Step 6.2, Control f The thickness ratio of the Ni@GO layer to the AgNPs@GO layer is 2:1, and the total thickness of the two layers is 2.5 mm. Step 6.3: After freeze-drying the bilayer precursor for 48 hours, a layered structure is obtained. f -Ni@GO|AgNPs@GO) aerogel; Step 6.4: Place the obtained aerogel in a tube furnace under a 5% H2 / Ar atmosphere. First, raise the temperature to 200℃ at 5℃ / min, then raise it to 600℃ at 1℃ / min, and finally raise it to 800℃ at 5℃ / min and hold for 2 hours to obtain a layered structure. f -Ni@PrGO|AgNPs@PrGO) aerogel.

[0045] Step 7: Prepare an asymmetric layered three-layer composite material; An AgNWs / PDMS solution was uniformly impregnated onto one side of the AgNPs@PrGO layer using an impregnation coating method to form a bottom AgNWs conductive layer with a thickness of 0.5 mm. Step 8: Place the obtained three-layer structure in a vacuum oven for vacuum-assisted impregnation to allow PDMS to fully penetrate into the porous skeleton. After thermosetting, an asymmetric layered structure is obtained. f -Ni@PrGO|AgNPs@PrGO|AgNWs) / PDMS electromagnetic shielding composite material, denoted as L-NGPGW-II.

[0046] The L-NGPGW-II composite material prepared in Example 3 of this invention has a total electromagnetic shielding effectiveness of 51 dB in the X-band and an absorption coefficient of 0.55.

[0047] Example 4 The preparation method of the asymmetric layered PDMS electromagnetic shielding material of the present invention is carried out according to the following steps; Step 1, prepare aminated modified Ni ( f -Ni); Step 1.1: Add 2g Ni, 1g ammonium persulfate (APS) and 100mL deionized water to a three-necked flask and perform ultrasonic and mechanical stirring for 0.5h under ice-water bath conditions; Step 1.2: Slowly add 10 mL of acrylic acid (AA) solution to the above Ni suspension, and continue ultrasonic and mechanical stirring at 60 °C for 2 h; Step 1.3: After the reaction is complete, remove the supernatant by magnetic separation, add 100 mL of deionized water and heat to 60 °C, add 20 mL of ethylenediamine (EN) dropwise, and continue sonication and mechanical stirring for 2 h. Step 1.4: After magnetic separation, the obtained product is washed with deionized water until neutral, and then vacuum dried to obtain... f -Ni.

[0048] Step 2, prepare AgNPs@GO powder; Step 2.1: Disperse 0.75g GO in a mixed solution of 100mL deionized water and 100mL ethanol, and sonicate for 0.5h to obtain a stable GO dispersion; Step 2.2: Add AgNO3 to the GO dispersion, wherein the mass ratio of GO to AgNO3 is 1:0.75, and continue sonication for 0.5 h; Step 2.3: Heat the resulting mixture to 60°C and stir for 0.5 hours; Step 2.4: Gradually add 2g of ascorbic acid (AsA) to the above mixture, keep warm and stir for 1 hour, and let the system change from brown to black before naturally cooling to room temperature. Step 2.5: Wash twice with deionized water and anhydrous ethanol by centrifugation, with centrifugation speeds of 10,000 rpm and 6,000 rpm respectively, and then freeze-dry under vacuum to obtain AgNPs@GO powder.

[0049] Step 3: Prepare AgNPs@GO precursor; Step 3.1: Disperse 20g of egg white protein powder in 200mL of deionized water to obtain a protein solution with a mass fraction of 5wt%. Step 3.2: Disperse the AgNPs@GO powder obtained in step 2 in 50 mL of protein solution and mix thoroughly. Step 3.3: The mixture obtained in step 3.2 is subjected to high-speed stirring and foaming for 20 minutes to form AgNPs@GO foam precursor.

[0050] Step 4, prepare AgNWs; Step 4.1: Dissolve 0.68g AgNO3 in 45mL ethylene glycol to obtain solution A; Step 4.2: Dissolve 0.69 mg FeCl3·6H2O and 0.71 g PVP in 50 mL ethylene glycol to obtain solution B; Step 4.3: Slowly add solution A to solution B over a period of 5 minutes to obtain mixed solution C; Step 4.4: Transfer the mixed solution C to a 100 mL reaction vessel and react at 140 °C for 2 h; Step 4.5: After the reaction is complete, the sample is washed twice by centrifugation with acetone and anhydrous ethanol, and then dried under vacuum at 40°C for 6 hours to obtain AgNWs.

[0051] Step 5, Preparation f -Ni@GO precursor; Step 5.1, quantify f -Ni was mixed with an aqueous solution of GO and ultrasonically dispersed to obtain f -Ni@GO suspension; Step 5.2: Add egg white powder to the above suspension, and stir at high speed to foam, to obtain... f -Ni@GO foam precursor.

[0052] Step 6, prepare the layered structure ( f -Ni@PrGO|AgNPs@PrGO) aerogel; First, pour the AgNPs@GO layer into the mold, then pour the top layer on top of it. f -Ni@GO layer; control f The thickness ratio of the Ni@GO layer to the AgNPs@GO layer is 1:2, and the total thickness of the two layers is 2.5 mm. After freeze-drying the bilayer precursor for 24 h, a layered structure is obtained. f -Ni@GO|AgNPs@GO) aerogel; The obtained aerogel was placed in a tube furnace under a 5% H2 / Ar atmosphere. The temperature was first increased to 150℃ at 5℃ / min, then increased to 500℃ at 1℃ / min, and finally increased to 700℃ at 5℃ / min and held for 2 hours to obtain a layered structure. f -Ni@PrGO|AgNPs@PrGO) aerogel.

[0053] Step 7: Prepare an asymmetric layered three-layer composite material; An AgNWs / PDMS solution was uniformly impregnated onto one side of the AgNPs@PrGO layer using an impregnation coating method to form a bottom AgNWs conductive layer with a thickness of 0.5 mm. Step 8: Place the obtained three-layer structure in a vacuum oven for vacuum-assisted impregnation to allow PDMS to fully penetrate into the porous skeleton. After thermosetting, an asymmetric layered structure is obtained. f The L-NGPGW-III electromagnetic shielding composite material (Ni@PrGO|AgNPs@PrGO|AgNWs) / PDMS is designated as L-NGPGW-III. The L-NGPGW-III composite material prepared in Example 3 of this invention exhibits a total electromagnetic shielding effectiveness of 58 dB in the X-band and an absorption coefficient of 0.60.

[0054] Example 5 This embodiment uses the physically blended homogeneous composite material B-NGPGW-I, and the specific steps are as follows: Step 1, prepare aminated modified Ni ( f -Ni); Step 1.1: Add 2g Ni, 1g ammonium persulfate (APS) and 100mL deionized water to a three-necked flask and perform ultrasonic and mechanical stirring for 1h under ice-water bath conditions; Step 1.2: Slowly add 10 mL of acrylic acid (AA) solution to the above Ni suspension, and continue ultrasonic and mechanical stirring at 80 °C for 5 h; Step 1.3: After the reaction is complete, remove the supernatant by magnetic separation, add 100 mL of deionized water and heat to 80 °C, add 20 mL of ethylenediamine (EN) dropwise, and continue sonication and mechanical stirring for 5 h. Step 1.4: After magnetic separation, the obtained product is washed with deionized water until neutral, and then vacuum dried to obtain... f -Ni.

[0055] Step 2, prepare AgNPs@GO powder; Step 2.1: Disperse 0.75g GO in a mixed solution of 100mL deionized water and 100mL ethanol, and sonicate for 2h to obtain a stable GO dispersion; Step 2.2: Add AgNO3 to the GO dispersion, wherein the mass ratio of GO to AgNO3 is 1:0.25, and continue sonication for 2 hours; Step 2.3: Heat the resulting mixture to 90°C and stir for 2 hours; Step 2.4: Gradually add 2g of ascorbic acid (AsA) to the above mixture, keep warm and stir for 4 hours, and let the system color change from brown to black before naturally cooling to room temperature; Step 2.5: Wash the product five times by centrifugation with deionized water and anhydrous ethanol, respectively, at speeds of 10,000 rpm and 6,000 rpm. Then freeze-dry it under vacuum to obtain AgNPs@GO powder.

[0056] Step 3: Prepare AgNPs@PrGO aerogel powder; Step 3.1: Disperse 20g of egg white protein powder in 200mL of deionized water to obtain a protein solution with a mass fraction of 10%. Step 3.2: Disperse the AgNPs@GO powder obtained in step 2 in 50 mL of protein solution, stir and foam at high speed, and then freeze dry. Step 3.3 involves a thermal reduction treatment to obtain AgNPs@PrGO aerogel; the aerogel is then ground and pulverized to obtain AgNPs@PrGO powder.

[0057] Step 4, prepare AgNWs; Step 4.1: Dissolve 0.68g AgNO3 in 45mL ethylene glycol to obtain solution A; Step 4.2: Dissolve 0.69 mg FeCl3·6H2O and 0.71 g PVP in 50 mL ethylene glycol to obtain solution B; Step 4.3: Slowly add solution A to solution B over a period of 30 minutes to obtain mixed solution C; Step 4.4: Transfer the mixed solution C to a 100 mL reaction vessel and react at 180 °C for 8 h; Step 4.5: After the reaction is complete, the sample is washed five times by centrifugation with acetone and anhydrous ethanol, and then dried under vacuum at 80°C for 24 hours to obtain AgNWs.

[0058] Step 5, Preparation f -Ni@PrGO aerogel powder; Step 5.1, quantify f -Ni was mixed with an aqueous solution of GO and ultrasonically dispersed to obtain f -Ni@GO suspension; Step 5.2: Add the same amount of protein solution as in step 3.1 to the above suspension, stir and foam at high speed, and then freeze dry. Step 5.3: Place the obtained product in a tube furnace under a 5% H2 / Ar atmosphere and perform heat treatment using the same heating program as in Step 3.3 to obtain... f -Ni@PrGO aerogel; the aerogel was ground and pulverized to obtain f -Ni@PrGO powder.

[0059] Step 6, use the same amount as L-NGPGW-I f Ni@PrGO, AgNPs@PrGO, and AgNWs were uniformly dispersed in a PDMS matrix. After mechanical stirring, vacuum degassing, and thermosetting, a physically blended homogeneous composite material, B-NGPGW-I, was obtained. The B-NGPGW-I composite material prepared in Example 5 of this invention has a total electromagnetic shielding effectiveness of 6 dB in the X-band.

[0060] Example 6 This embodiment uses the physically blended homogeneous composite material B-NGPGW-III, and the specific steps are as follows: Step 1, prepare aminated modified Ni ( f -Ni); Step 1.1: Add 2g Ni, 1g ammonium persulfate (APS) and 100mL deionized water to a three-necked flask and perform ultrasonic and mechanical stirring for 1h under ice-water bath conditions; Step 1.2: Slowly add 10 mL of acrylic acid (AA) solution to the above Ni suspension, and continue ultrasonic and mechanical stirring at 70 °C for 3 h; Step 1.3: After the reaction is complete, remove the supernatant by magnetic separation, add 100 mL of deionized water and heat to 70 °C, add 20 mL of ethylenediamine (EN) dropwise, and continue sonication and mechanical stirring for 3 h. Step 1.4: After magnetic separation, the obtained product is washed with deionized water until neutral, and then vacuum dried to obtain... f -Ni.

[0061] Step 2, prepare AgNPs@GO powder; Step 2.1: Disperse 0.75g GO in a mixed solution of 100mL deionized water and 100mL ethanol, and sonicate for 1h to obtain a stable GO dispersion; Step 2.2: Add AgNO3 to the GO dispersion, wherein the mass ratio of GO to AgNO3 is 1:0.25, and continue sonication for 1 hour; Step 2.3: Heat the resulting mixture to 80°C and stir for 1 hour; Step 2.4: Gradually add 2g of ascorbic acid (AsA) to the above mixture, keep warm and stir for 2 hours, and let the system change from brown to black before naturally cooling to room temperature. Step 2.5: Wash the product three times by centrifugation with deionized water and anhydrous ethanol, respectively, at speeds of 10,000 rpm and 6,000 rpm. Then freeze-dry it under vacuum to obtain AgNPs@GO powder.

[0062] Step 3: Prepare AgNPs@PrGO aerogel powder; Step 3.1: Disperse 20g of egg white protein powder in 200mL of deionized water to obtain a protein solution with a mass fraction of 10%. Step 3.2: Disperse the AgNPs@GO powder obtained in step 2 in 50 mL of protein solution, stir and foam at high speed, and then freeze dry. Step 3.3 involves a thermal reduction treatment to obtain AgNPs@PrGO aerogel; the aerogel is then ground and pulverized to obtain AgNPs@PrGO powder.

[0063] Step 4, prepare AgNWs; Step 4.1: Dissolve 0.68g AgNO3 in 45mL ethylene glycol to obtain solution A; Step 4.2: Dissolve 0.69 mg FeCl3·6H2O and 0.71 g PVP in 50 mL ethylene glycol to obtain solution B; Step 4.3: Slowly add solution A to solution B over a period of 15 minutes to obtain mixed solution C; Step 4.4: Transfer the mixed solution C to a 100 mL reaction vessel and react at 160 °C for 4 h; Step 4.5: After the reaction is complete, the sample is washed three times by centrifugation with acetone and anhydrous ethanol, and then dried under vacuum at 60°C for 12 hours to obtain AgNWs.

[0064] Step 5, Preparation f -Ni@PrGO aerogel powder; Step 5.1, quantify f -Ni was mixed with an aqueous solution of GO and ultrasonically dispersed to obtain f -Ni@GO suspension; Step 5.2: Add the same amount of protein solution as in step 3.1 to the above suspension, stir and foam at high speed, and then freeze dry. Step 5.3: Place the obtained product in a tube furnace under a 5% H2 / Ar atmosphere and perform heat treatment using the same heating program as in Step 3.3 to obtain... f -Ni@PrGO aerogel; the aerogel was ground and pulverized to obtain f -Ni@PrGO powder.

[0065] Step 6, use the same amount as L-NGPGW-III f Ni@PrGO, AgNPs@PrGO, and AgNWs were uniformly dispersed in a PDMS matrix. After mechanical stirring, vacuum degassing, and thermosetting, a physically blended homogeneous composite material, B-NGPGW-III, was obtained. The B-NGPGW-III composite material prepared in Example 6 of this invention has a total electromagnetic shielding effectiveness of 10 dB in the X-band.

[0066] like Figure 2 and Figure 3 As shown in Embodiments 2-4 of the present invention, f The thickness ratio of the Ni@PrGO layer to the AgNPs@PrGO layer was selected as 1:1, 2:1, or 1:2, resulting in composite materials named L-NGPGW-I, L-NGPGW-II, and L-NGPGW-III, respectively. Using the same amount of AgNPs@PrGO as in the layered composite material, f -Ni@PrGO and AgNWs were uniformly dispersed in a PDMS matrix. Examples 5 and 6 were used as comparisons to prepare physically blended homogeneous composite materials. The physically blended composite material corresponding to L-NGPGW-I was designated B-NGPGW-I, and the physically blended composite material corresponding to L-NGPGW-III was designated B-NGPGW-III. In summary, the electromagnetic shielding performance of the composite materials was significantly improved by adopting an asymmetric layered structure design, and the thickness ratio of different functional layers had a significant regulatory effect on the material properties. With the increase of the thickness of the intermediate AgNPs@PrGO conductive layer, the electromagnetic shielding effectiveness and absorption-dominant characteristics of the composite materials showed an enhancing trend, with the L-NGPGW-III composite material exhibiting the best overall performance. The prepared ( f-Ni@PrGO|AgNPs@PrGO|AgNWs) / PDMS asymmetric layered composite material exhibits excellent electromagnetic shielding performance and high electromagnetic wave absorption capability.

[0067] In the preparation method of the asymmetric layered PDMS electromagnetic shielding material of the present invention, by constructing a "magnetic-electrical-electrical" asymmetric layered composite material, the top layer is utilized... f The magnetic loss effect and moderate conductivity of Ni@PrGO improve the impedance matching of the material surface, making it easier for electromagnetic waves to penetrate the material interior. Furthermore, the three-dimensional conductive network, rich interfaces, and porous structure of the intermediate AgNPs@PrGO layer enhance conductivity loss, dielectric loss, and multiple reflection dissipation. Simultaneously, the highly conductive barrier layer of the underlying AgNWs / PDMS blocks the transmission of residual electromagnetic waves and induces secondary reflection and dissipation, thereby achieving efficient attenuation of incident electromagnetic waves and ultimately obtaining excellent electromagnetic shielding performance. Among these, when... f When the thickness ratio of the Ni@PrGO layer to the AgNPs@PrGO layer is 1:2, the resulting L-NGPGW-III composite material exhibits the best overall performance, with an electromagnetic shielding effectiveness of 58 dB and an absorption coefficient of 0.60, significantly superior to physically blended composite materials. This invention provides a feasible solution for preparing absorption-dominant electromagnetic shielding materials that combine high electromagnetic shielding effectiveness, low reflection characteristics, and high absorption capacity.

Claims

1. A method for preparing asymmetric layered PDMS electromagnetic shielding material, characterized in that, The specific steps are as follows: Step 1, Preparation f -Ni; Step 2, prepare AgNPs@GO powder; Step 3: Prepare AgNPs@GO precursor; Step 4, prepare AgNWs; Step 5, Preparation f -Ni@GO precursor; Step 6, f -Ni@GO precursor and AgNPs@GO precursor were used to construct a layered aerogel precursor, and heat treatment was performed to obtain an asymmetric layered aerogel. Step 7: AgNWs and PDMS are mixed to form AgNWs / PDMS conductive paste, which is then combined with asymmetric layered aerogel to obtain an asymmetric three-layer structure. Step 8: Vacuum-assisted impregnation of PDMS followed by thermosetting yields the final product.

2. The method for preparing the asymmetric layered PDMS electromagnetic shielding material according to claim 1, characterized in that, The specific process of step 1 is as follows: Step 1.1: Add Ni, ammonium persulfate and deionized water to a three-necked flask, and perform ultrasonic and mechanical stirring under ice-water bath conditions for 0.5 h to 2 h to obtain Ni suspension; Step 1.2: Slowly add acrylic acid solution to the Ni suspension obtained in Step 1.1, and continue ultrasonic and mechanical stirring at 60℃~80℃ for 2h~5h to cause grafting modification on the Ni surface; Step 1.3: After removing the supernatant by magnetic separation, deionized water is added to the system and the temperature is raised to 60℃~80℃. Ethylenediamine is added dropwise, and ultrasonic and mechanical stirring is continued for 2h~5h to perform amination functional modification on Ni particles. Step 1.4: After magnetic separation, the product obtained in Step 1.3 is washed 2 to 5 times with deionized water until the supernatant is neutral. Then, it is vacuum dried for 6 to 24 hours to obtain amination-modified Ni particles. f -Ni.

3. The method for preparing the asymmetric layered PDMS electromagnetic shielding material according to claim 2, characterized in that, The specific process of step 2 is as follows; Step 2.1: Disperse GO in a mixed solution of deionized water and ethanol, and sonicate for 0.5 h to 2 h to obtain a stable GO dispersion; Step 2.2: Add AgNO3 to the GO dispersion obtained in Step 2.1 and continue sonicating for 0.5h~2h to promote Ag + The mixture is adsorbed and bound to the GO surface to obtain a mixed solution, which is then heated to 60℃~90℃ and stirred for 0.5h~2h. Step 2.3: Add a reducing agent to the mixture obtained in Step 2.2, and keep it at the temperature for 1 to 4 hours. Use the in-situ reduction method to load AgNPs onto the GO surface, so that AgNPs grow in situ on the GO surface. The reducing agent used is ascorbic acid. Step 2.4: Cool the reaction mixture to room temperature, centrifuge and wash it 2 to 5 times with deionized water and anhydrous ethanol respectively, and then freeze-dry it under vacuum for 24 to 72 hours to obtain AgNPs@GO powder.

4. The method for preparing the asymmetric layered PDMS electromagnetic shielding material according to claim 3, characterized in that, The specific process of step 3 is as follows; Step 3.1: Disperse egg white protein powder in deionized water to prepare a protein solution with a mass fraction of 5wt%~15wt%; Step 3.2: Add the AgNPs@GO powder obtained in Step 2 to the protein solution obtained in Step 3.1, and mix and disperse evenly; Step 3.3: The mixture obtained in step 3.2 is subjected to high-speed stirring and foaming for 2 min to 20 min to form AgNPs@GO complex. The AgNPs@GO complex with a stable three-dimensional porous structure serves as the second porous precursor.

5. The method for preparing the asymmetric layered PDMS electromagnetic shielding material according to claim 4, characterized in that, The specific process of step 4 is as follows; Step 4.1: Dissolve AgNO3 in ethylene glycol to obtain solution A; Step 4.2: Dissolve FeCl3·6H2O and polyvinylpyrrolidone in another portion of ethylene glycol to obtain solution B; Step 4.3: Slowly add solution A to solution B over a period of 5 to 30 minutes to obtain mixed solution C; Step 4.4: Transfer the mixed solution C obtained in step 4.3 to the reaction vessel and react at 140℃~180℃ for 2h~8h; Step 4.5: After washing the reaction product by centrifugation with acetone and anhydrous ethanol 2 to 5 times, the product is dried under vacuum at 40℃ to 80℃ for 6 to 24 hours to obtain AgNWs, which serve as functional components of the highly conductive barrier layer.

6. The method for preparing the asymmetric layered PDMS electromagnetic shielding material according to claim 5, characterized in that, Step 5 Preparation f The specific process of the Ni@GO precursor is as follows: Step 5.1, take the result from Step 1 f -Ni is mixed with an aqueous solution of GO and subjected to ultrasonic treatment for 0.5 h to 2 h to obtain f -Ni@GO suspension; Step 5.2, apply the solution obtained in step 5.1 f - Egg white protein powder was added to the Ni@GO suspension; Step 5.3: The mixture obtained in step 5.2 is subjected to high-speed stirring and foaming for 2 to 20 minutes to form... f -Ni@GO complex, possessing a stable three-dimensional porous structure f -Ni@GO complex serves as the first layer of porous precursor.

7. The method for preparing the asymmetric layered PDMS electromagnetic shielding material according to claim 6, characterized in that, The specific process of step 6 is as follows; Step 6.1: Cast the AgNPs@GO precursor from step 3 into the preset mold; Step 6.2: After the surface of the mold used in Step 6.1 is smooth, pour the material from Step 5 onto it. f -Ni@GO precursor; Step 6.3, Control f The thickness ratio of the Ni@GO layer to the AgNPs@GO layer is 1:2 to 2:

1. After freeze-drying for 24 to 72 hours, a layered structure is obtained. f -Ni@GO|AgNPs@GO) aerogel; Step 6.4: Place the aerogel obtained in Step 6.3 under a protective atmosphere and perform programmed temperature heat treatment. First, heat to 150℃~250℃ to remove moisture, then heat to 500℃~700℃ to remove the protein template, and finally heat to 700℃~900℃ for thermal reduction to obtain a symmetrical layered aerogel. f -Ni@PrGO|AgNPs@PrGO) aerogel.

8. The method for preparing the asymmetric layered PDMS electromagnetic shielding material according to claim 7, characterized in that, Step 7 is as follows: Step 7.1: Mix AgNWs with PDMS to prepare AgNWs / PDMS conductive paste; Step 7.2, the layered structure obtained in step 6 ( f One side of the Ni@PrGO|AgNPs@PrGO aerogel is uniformly impregnated or coated with AgNWs / PDMS conductive paste. Step 7.3: Dry the sample obtained in step 7.2 at 40℃~80℃ for 1h~12h to form a bottom AgNWs conductive layer with a thickness of 0.1mm~1.0mm.

9. The method for preparing the asymmetric layered PDMS electromagnetic shielding material according to claim 8, characterized in that, Step 8 is as follows: Step 8.1: Place the three-layer structure obtained in step 7 in a vacuum environment and use a vacuum-assisted impregnation process to fully impregnate the PDMS into the porous skeleton. The vacuum degree is 0.01MPa~0.1MPa and the impregnation time is 0.5h~12h. Step 8.2: Perform heat curing treatment on the sample obtained in step 8.

1. The curing temperature is 50℃~100℃ and the curing time is 1h~24h.

10. An asymmetric layered PDMS electromagnetic shielding material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 9.

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