A femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material and a preparation method thereof

Abstract

The present application relates to the technical field of electromagnetic shielding material preparation, and particularly relates to a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material and a preparation method thereof, the preparation method comprising the following steps: setting femtosecond laser parameters and a defocusing distance, designing a laser scanning path by using computer-aided SCA software, and using the femtosecond laser to scan polyimide paper attached with a mixed solution to obtain the composite electromagnetic shielding material. The present application utilizes the local photo-thermal effect of the laser to form an LIG array on the polyimide surface in situ, and simultaneously reduces five doped metal salts into FeCoNiCrCu HEO NPs and loads them in the porous structure of the LIG, which can further increase the electromagnetic absorption capacity of the LIG. By combining the laser scribing technology and the salt solution dripping technology, the one-step in-situ synthesis of high-entropy oxide nanoparticles and graphene is realized, and the electromagnetic shielding absorption efficiency and the total electromagnetic shielding efficiency of the composite electromagnetic shielding material are improved.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic shielding materials technology, and in particular to a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material and its preparation method. Background Technology

[0002] With the rapid development of various electronic devices, the electromagnetic interference (EMI) generated by these devices has adversely affected device performance, human health, and the surrounding environment. Traditional metals have been used as the preferred material for EMI shielding; however, due to their high density, susceptibility to corrosion, and lack of flexibility, metallic materials are not ideal for applications in aerospace and next-generation smart electronics. Therefore, obtaining high-performance electromagnetic interference shielding materials with ultra-low density, flexibility, and excellent mechanical properties is crucial for applications in aerospace, portable, and wearable electronic devices.

[0003] To obtain lightweight, flexible, and high-strength EMI shielding materials, various materials have been developed, such as graphene, carbon nanotubes, transition metal carbides (MXenes), and metal nanowires. Graphene, due to its low density, stable chemical properties, and excellent mechanical properties, is considered the most promising candidate to replace metals in achieving lightweight and high-performance EMI shielding materials. Currently, traditional methods for graphene preparation include mechanical exfoliation, chemical vapor deposition (CVD), oxide reduction, liquid phase exfoliation, and silicon carbide template methods. These methods are complex and costly, making them unsuitable for large-scale production.

[0004] In addition, graphene, due to its excellent conductivity, is an electromagnetic shielding material primarily based on reflection. To avoid secondary pollution, composite structures need to be created based on graphene's electromagnetic wave reflection capabilities to enhance its electromagnetic absorption capacity. Currently, most methods to significantly improve the electromagnetic absorption capacity of carbon-based materials involve coating the surface with a metal layer or metal oxide, or using electrochemical deposition to adhere magnetic nanoparticles to the LIG pore walls. However, surface coating methods suffer from poor adhesion between the surface layer and the carbon-based material, and the surface metal layer is easily damaged, resulting in poor durability. While electrochemical deposition can bind magnetic nanoparticles to a carbon substrate, it cannot achieve one-step synthesis, is complex, and incurs high manufacturing costs and time.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material and its preparation method, aiming to solve the problems of poor adhesion, poor durability and high cost of existing electromagnetic shielding material preparation methods.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material includes the following steps:

[0009] Metal salts corresponding to Fe, Co, Ni, Cr, and Cu are mixed with organic solvents to obtain iron salt solutions, cobalt salt solutions, nickel salt solutions, chromium salt solutions, and copper salt solutions, respectively.

[0010] The iron salt solution, the cobalt salt solution, the nickel salt solution, the chromium salt solution, and the copper salt solution are mixed to obtain a mixed solution;

[0011] The mixed solution is applied to the surface of the polyimide paper, and the polyimide paper with the mixed solution applied is placed on a vacuum adsorption stage;

[0012] By setting femtosecond laser parameters and defocus distance, designing the laser scanning path using computer-aided SCA software, and scanning the polyimide paper with the mixed solution attached using the femtosecond laser, a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material is obtained.

[0013] The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material, wherein the molar concentrations of the iron salt solution, the cobalt salt solution, the nickel salt solution, the chromium salt solution, and the copper salt solution are equal and the molar concentrations are between 0.01 and 0.05 M.

[0014] The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material, wherein the metal salts corresponding to Fe, Co, Ni, Cr, and Cu are FeCl3·6H2O, CoCl2·6H2O, NiCl2·6H2O, CrCl3·6H2O, and CuCl2·6H2O, respectively.

[0015] The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material, wherein the amount of the mixed solution adhering to the surface of the polyimide paper is 0.8-1.2 ml / cm². 2 .

[0016] The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material further includes, in the step of placing the polyimide paper with the mixed solution attached on a vacuum adsorption stage, the step of pressing the four edges of the polyimide paper with a glass slide mold.

[0017] The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material, wherein the femtosecond laser parameters include: laser wavelength, laser pulse frequency, laser power, laser scanning speed, laser pulse, and laser density.

[0018] The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material includes the following: the laser wavelength is 1020-1040 nm; the laser pulse frequency is 555-1111 kHz; the laser power is 0.8-2.4 W; the laser scanning speed is 30-60 mm / s; the laser pulse is 400-500; and the laser density is 55-68.

[0019] The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material, wherein the defocus distance is 0.1-0.3 mm.

[0020] The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material includes a laser scanning path comprising: first moving in a zigzag pattern along the x-direction of the polyimide paper, and then moving in a zigzag pattern along the y-direction of the polyimide paper.

[0021] A femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material is prepared using the same method.

[0022] Beneficial Effects: This invention provides a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material and its preparation method. The preparation method includes the following steps: mixing metal salts corresponding to Fe, Co, Ni, Cr, and Cu with organic solvents to obtain iron salt solutions, cobalt salt solutions, nickel salt solutions, chromium salt solutions, and copper salt solutions; mixing the iron salt solutions, cobalt salt solutions, nickel salt solutions, chromium salt solutions, and copper salt solutions to obtain a mixed solution; attaching the mixed solution to the surface of polyimide paper and placing the polyimide paper with the mixed solution attached on a vacuum adsorption stage; setting femtosecond laser parameters and defocusing distance, designing the laser scanning path using computer-aided SCA software, and scanning the polyimide paper with the mixed solution attached using a femtosecond laser to obtain the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material. This invention utilizes the local photothermal effect of laser to simultaneously form a laser-induced graphene (LIG) array on the surface of polyimide while simultaneously reducing five doped metal salts to FeCoNiCrCu HEO NPs and loading them into the porous structure of LIG, thereby further enhancing the electromagnetic absorption capacity of LIG. By combining laser scribing technology and salt solution dripping technology, a one-step in-situ synthesis of high-entropy oxide nanoparticles and graphene is achieved. Compared with pure LIG, this improves the electromagnetic shielding absorption efficiency (SEA) and total electromagnetic shielding efficiency (SET) of the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the process flow for preparing a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material according to the present invention.

[0024] Figure 2 This is a schematic diagram of a glass slide mold;

[0025] Figure 3 This is a schematic diagram of the defocusing device;

[0026] Figure 4 SEM image of pure LIG;

[0027] Figure 5 The image shows a SEM image of the LIG / FeCoNiCrCu HEO NPs composite electromagnetic shielding material in Example 1.

[0028] Figure 6 The electromagnetic shielding effectiveness diagram for pure LIG;

[0029] Figure 7 The electromagnetic shielding effectiveness diagram of the LIG / FeCoNiCrCu HEO NPs composite electromagnetic shielding material in Example 1 is shown. Detailed Implementation

[0030] This invention provides a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0031] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0032] like Figure 1 As shown, this invention provides a method for preparing a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material, comprising the following steps:

[0033] Step S10: Mix the metal salts corresponding to Fe, Co, Ni, Cr, and Cu with organic solvents respectively to obtain iron salt solution, cobalt salt solution, nickel salt solution, chromium salt solution, and copper salt solution;

[0034] Step S20: Mix the iron salt solution, the cobalt salt solution, the nickel salt solution, the chromium salt solution, and the copper salt solution to obtain a mixed solution;

[0035] Step S30: Adhere the mixed solution to the surface of the polyimide paper, and place the polyimide paper with the mixed solution attached on the vacuum adsorption stage;

[0036] Step S40: Set the femtosecond laser parameters and defocus distance, design the laser scanning path using computer-aided SCA software, and use the femtosecond laser to scan the polyimide paper with the mixed solution attached to it to obtain the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material.

[0037] In this embodiment, the femtosecond pulsed laser, in addition to satisfying the normal photothermal effect generated by traditional continuous-wave lasers, can also induce new photochemical reactions. The interaction between the pulsed laser and the material is a nonlinear process, and nonlinear absorption confines all induced changes within the focal volume, thereby allowing the creation of complex micro / nanostructures. While carbon-based materials exhibit excellent dielectric loss properties, they are inherently nonmagnetic, resulting in poor impedance matching. However, laser-induced graphene, besides possessing excellent conductivity and reflection loss, is rich in porous structures and also has the ability to absorb losses. Therefore, this invention utilizes the local photothermal effect of lasers to form a LIG array in situ on the surface of polyimide (PI), and simultaneously reduces five metal salts to FeCoNiCrCu HEO NPs (high-entropy oxide nanoparticles) and loads them into the porous structure of the LIG, further increasing the electromagnetic absorption capability of the LIG.

[0038] Specifically, when polyimide paper with the aforementioned mixed solution is irradiated by a laser, the irradiated area experiences lattice vibrations, resulting in local temperatures exceeding 2500°C. This causes the instantaneous breakage of the C-C, CO, and CN bonds in the polyimide (PI), leading to the rearrangement of C atoms into graphene. Some atoms escape as gas, forming a porous structure. Simultaneously, metal elements with the same crystal structure dissolve in Fe to maintain their original phase structure: Cr readily dissolves in Fe to form a body-centered cubic (BCC) structure, Cu readily dissolves in Ni to form an FCC structure, and Co exists simultaneously in both the FCC and BCC structures of FeCoNiCrCu HEO NPs. This ultimately yields a femtosecond laser-induced graphene composite electromagnetic shielding material loaded with high-entropy oxides. By combining laser etching technology and salt solution dripping technology, further in-situ synthesis of high-entropy oxide nanoparticles and graphene is achieved. This process is mild and controllable, low-cost, and yield-efficient, suitable for large-scale production. It achieves one-step synthesis while significantly reducing energy and other resource consumption.

[0039] In some implementations, elements such as Fe, Co, Ni, Cr, and Cu can be substituted, but the primary magnetic elements are iron, cobalt, nickel, and chromium, to achieve electromagnetic absorption. The choice of another element involves principles; different elements can be selected based on different principles, such as Mn.

[0040] In some embodiments, before step S10, the method further includes the step of cleaning and drying the polyimide paper to obtain clean polyimide paper; further, specifically, it includes the step of ultrasonically cleaning the polyimide paper for 15 minutes with anhydrous ethanol and deionized water at an ultrasonic power of 100W, and then drying it in a vacuum oven to obtain clean polyimide paper; the drying temperature is 55-65℃, and the drying time is 0.5-2 hours.

[0041] In some embodiments, the molar concentrations of the iron salt solution, the cobalt salt solution, the nickel salt solution, the chromium salt solution, and the copper salt solution are equal, and the molar concentrations are between 0.01 and 0.05 M. Since entropy increases with the addition of new species, it reaches its maximum value when the proportions of all species are equal. Therefore, controlling the molar concentrations of the iron salt solution, the cobalt salt solution, the nickel salt solution, the chromium salt solution, and the copper salt solution to be equal yields a high-entropy oxide. Simultaneously, the concentration of the metal salt plays a decisive role in the synthesis of the material and its electromagnetic shielding effectiveness. Low concentrations of metal salt result in only a slight improvement in the material's electromagnetic absorption capacity; high concentrations of metal salt often destroy the ordered structure of graphene because the simultaneously formed nanoparticles hinder graphene growth. On the other hand, under high loads on the metal salt precursor, the formation of nanoparticles requires more energy, and LIG will over-carbonize under excessively high energy conditions, thus turning into powder.

[0042] In a preferred embodiment, the molar concentrations of the iron salt solution, the cobalt salt solution, the nickel salt solution, the chromium salt solution, and the copper salt solution are all 0.05 M.

[0043] In some embodiments, steps S10-S20 specifically include the following steps: adding equimolar amounts of five elemental metal salts—Fe, Co, Ni, Cr, and Cu—to anhydrous ethanol, stirring with a magnetic stirrer for 30 minutes at room temperature, and after the metal salts are completely dissolved, mixing equal volumes of the five equimolar salt solutions, stirring again for 30 minutes, and obtaining the mixed solution after homogeneous mixing. Traditional metal salts are simultaneously reduced to elemental metals through the carbothermic reaction of the laser and the reducing atmosphere generated during the decomposition of polyimide. However, some more reactive metals, such as Fe, Co, Ni, Cr, and Cu, cannot be photochemically reduced. Specifically, the high flux from the femtosecond laser is insufficient for the photochemical reduction of these metals, and metal oxides are formed, subsequently crystallizing to form pentagonal FeCoNiCrCu HEO NPs, which are then loaded onto the LIG porous structure.

[0044] In some embodiments, the metal salts corresponding to Fe, Co, Ni, Cr, and Cu are FeCl3·6H2O, CoCl2·6H2O, NiCl2·6H2O, CrCl3·6H2O, and CuCl2·6H2O, respectively. Utilizing the localized photothermal effect of laser, a LIG array can be formed in situ on the polyimide surface, while simultaneously reducing five equimolarly doped chloride salt precursors to FeCoNiCrCu HEONPs and loading them into the porous structure of the LIG, further enhancing the electromagnetic absorption capability of the LIG.

[0045] In some embodiments, the amount of the mixed solution adhering to the surface of the polyimide paper is 0.8-1.2 ml / cm². 2 By controlling the amount of adhesion within this range, an appropriate amount of high-entropy oxides can be loaded onto the laser-induced graphene, thereby forming a laser-induced graphene composite electromagnetic shielding material loaded with high-entropy oxides, achieving the effect of electromagnetic shielding interference.

[0046] In some preferred embodiments, the amount of the mixed solution adhering to the surface of the polyimide paper is 1 ml / cm. 2 .

[0047] In some embodiments, step S30 specifically includes the following steps: using a pipette to drip the mixed solution onto PI paper, so that there is 1 ml of the mixed solution per square centimeter, then slowly evaporating the organic solvent in the mixed solution under natural conditions, and then using a glass slide mold to press the edges of the polyimide paper together, the effect of which is as follows. Figure 2 As shown. Since PI paper is actually porous and breathable, the function of the glass slide mold is to increase the adsorption area. The larger the surface area, the greater the total adsorption. Thus, PI can be adsorbed flatly on the worktable, and the focusing depth at different positions is similar. The repeatability of LIG conductivity prepared by this device is as high as 95%-99%, achieving stable preparation.

[0048] In some embodiments, the femtosecond laser parameters include: laser wavelength, laser pulse frequency, laser power, laser scanning speed, laser pulse burst, and laser density. Femtosecond laser processing is a cold processing method with rapid cooling and short melt duration, allowing liquid metal droplets to grow into nanoscale particles. Photochemical reduction, photothermal decomposition, and the crystallization process of liquid-phase nanoparticles are all influenced by the laser parameters, and the final electromagnetic shielding effectiveness of the composite electromagnetic shielding material depends on the selection of the laser parameters. Furthermore, the high repetition frequency of ultrashort pulses can convert metal salts into metal oxides without damaging the substrate. Simultaneously, by jointly controlling the laser power, laser scanning speed, laser pulse, and laser density, processing speed can be increased, thermal damage and burning to the sensitive substrate can be reduced, and the size and composition distribution of HEO NPs (high-entropy oxide nanoparticles) can be controlled, maximizing the total electromagnetic shielding effectiveness (SET) of the LIG / HEO NPs composite electromagnetic shielding material.

[0049] In some embodiments, the laser wavelength is 1020-1040 nm; the laser pulse frequency is 555-1111 kHz; the laser power is 0.8-2.4 W; the laser scanning speed is 30-60 mm / s; the laser pulse count is 400-500; and the laser density is 55-68. By controlling the femtosecond laser parameters within the above ranges, LIG ​​can be generated.

[0050] In a preferred embodiment, the laser wavelength is 1030 nm; the laser pulse frequency is 1111 kHz; the laser power is 2 W; the laser scanning speed is 60 mm / s; the laser pulse is 500; and the laser density is 57.

[0051] In some embodiments, the defocus distance is 0.1-0.3 mm, which allows for a larger laser spot to result in more uniform illumination of the substrate and more overlapping scans. Figure 3 This is a schematic diagram of the defocusing device.

[0052] In a preferred embodiment, the defocus distance is 0.3 mm.

[0053] In some embodiments, the laser scanning path includes: first moving in a zigzag pattern along the x-direction of the polyimide paper, and then moving in a zigzag pattern along the y-direction of the polyimide paper.

[0054] In some embodiments, the scanning of the polyimide paper with the mixed solution attached using a femtosecond laser in step S50 is performed in an air environment at room temperature.

[0055] In some embodiments, the polyimide may be replaced by, but is not limited to, pine wood, carbon nanotubes, resin, etc.

[0056] In addition, the present invention also provides a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material, which is prepared using the preparation method of the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material.

[0057] In this embodiment, the composite electromagnetic shielding material prepared by the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material preparation method exhibits a 9 dB improvement in electromagnetic shielding absorption efficiency (SEA) and a high performance of 40.3 dB in total electromagnetic shielding efficiency (SET) compared to pure LIG. Furthermore, this preparation method simplifies the process, saves energy and cost, and allows for the direct synthesis of high-entropy oxides in air, which are then loaded onto a porous LIG substrate to achieve high electromagnetic absorption.

[0058] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention.

[0059] Example 1

[0060] This embodiment provides a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material based on electromagnetic shielding interference. The preparation method specifically includes the following steps:

[0061] (1) Take the size as 40×25mm 2 PI paper with a thickness of about 0.1 mm was ultrasonically cleaned with anhydrous ethanol and deionized water for 15 minutes at an ultrasonic power of 100W, and then dried in a vacuum oven at 60℃ for 2 hours.

[0062] (2) Preparation of metal salt solution:

[0063] Weigh out equimolar amounts of five elemental metal salts: Fe, Co, Ni, Cr, and Cu. Add each salt to 10 ml of anhydrous ethanol and stir with a magnetic stirrer for 30 minutes at room temperature until the metal salts are completely dissolved, resulting in a solution of the five metal salts with a molar concentration of 0.05 M. Mix equal volumes of the five equimolar metal salt solutions and stir again for 30 minutes until homogeneous, resulting in a mixed solution.

[0064] (3) Use a pipette to drip the mixed solution onto PI paper so that there is 1 ml of solution per square centimeter, and then let the organic solvent in the mixed solution evaporate slowly under natural conditions.

[0065] (4) Place the PI paper with the mixed solution dripped on the vacuum adsorption stage, and press the PI paper with a glass slide mold around the edges so that the surface of the PI paper is strictly adsorbed on the work stage.

[0066] (5) The pattern was designed using computer-aided SCA software, so that the scanning path first followed a zigzag pattern along the x-direction and then along the y-direction, ultimately resulting in a 25×14mm pattern. 2 Coral pattern.

[0067] (6) Set the femtosecond laser parameters: laser wavelength is 1030nm, laser pulse frequency is 1111kHz, power = 2W, speed = 60mm / s, burst = 500, density = 57; set the defocus distance to 0.3mm.

[0068] (7) Under the above steps, the PI loaded with the mixed solution was scanned by a femtosecond laser in an air environment at room temperature, and finally the laser-induced graphene composite electromagnetic shielding material loaded with high-entropy oxide (LIG / FeCoNiCrCuHEO NPs composite electromagnetic shielding material) was obtained.

[0069] like Figure 4 and Figure 5 The images shown are scanning electron microscope (SEM) images of pure LIG and the LIG / FeCoNiCrCu HEO NPs composite electromagnetic shielding material in this embodiment, respectively. As can be seen from the images, the pore walls of pure LIG are relatively smooth, while the metal oxide nanoparticles adhere to the pore walls of LIG, and the constituent elements in the nanoparticles are uniformly distributed. Furthermore, even under high loads, the nanoparticles can still adhere to the pore walls, maintaining the integrity of the porous structure without causing pore filling or collapse. This is of great significance for improving the battery interference shielding performance of the composite electromagnetic shielding material.

[0070] The scattering parameters (S11 and S21) of the composite electromagnetic shielding material in this embodiment were measured at room temperature in the frequency range of 8.2–12.4 GHz (x-band) using a vector network analyzer. The equipment was calibrated using the TRL calibration method prior to testing S11 and S21. The electromagnetic interference shielding effectiveness (EMI SE) of the sample was calculated using the following formula:

[0071] R = (S 11 ) 2 (1)

[0072] T = (S 21 ) 2 (2)

[0073] A+R+T=1 (3)

[0074] SER = -10log(1-R) ​​(4)

[0075] SEA = -10log(T / (1-R)) (5)

[0076] SET = -10logT (6)

[0077] Where R, T, and A represent the reflection coefficient, transmission coefficient, and absorption coefficient, respectively. SER, SEA, and SET represent the reflection, absorption, and total shielding effectiveness, respectively. The sample size used for testing was ~22.9 × 10.2 mm. 2 .

[0078] like Figure 6 As shown, the optimal electromagnetic shielding capability of pure LIG is SER = 10.8 dB, SEA = 19.8 dB, and SET = 30.7 dB, while... Figure 7 The SER of the LIG / FeCoNiCrCu HEO NPs composite electromagnetic shielding material remains almost unchanged, while the SEA is significantly improved by 9dB, resulting in a total shielding effectiveness SET of 40.3dB.

[0079] In summary, this invention provides a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material and its preparation method. The preparation method includes the following steps: mixing metal salts corresponding to Fe, Co, Ni, Cr, and Cu with organic solvents to obtain iron salt solutions, cobalt salt solutions, nickel salt solutions, chromium salt solutions, and copper salt solutions; mixing the iron salt solutions, cobalt salt solutions, nickel salt solutions, chromium salt solutions, and copper salt solutions to obtain a mixed solution; attaching the mixed solution to the surface of polyimide paper and placing the polyimide paper with the mixed solution attached on a vacuum adsorption stage; setting femtosecond laser parameters and defocusing distance, designing the laser scanning path using computer-aided SCA software, and scanning the polyimide paper with the mixed solution attached using a femtosecond laser to obtain the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material. This invention utilizes the local photothermal effect of laser to simultaneously form a laser-induced graphene (LIG) array on the surface of polyimide while simultaneously reducing five doped metal salts to FeCoNiCrCu HEO NPs and loading them into the porous structure of LIG, thereby further enhancing the electromagnetic absorption capacity of LIG. By combining laser scribing technology and salt solution dripping technology, a one-step in-situ synthesis of high-entropy oxide nanoparticles and graphene is achieved. Compared with pure LIG, the electromagnetic shielding absorption efficiency (SEA) of the laser-induced graphene / high-entropy oxide composite electromagnetic shielding material is improved by 9 dB, and the total electromagnetic shielding efficiency (SET) reaches a high performance of 40.3 dB.

[0080] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material, characterized in that, Including the following steps: Metal salts corresponding to Fe, Co, Ni, Cr, and Cu are mixed with organic solvents to obtain iron salt solutions, cobalt salt solutions, nickel salt solutions, chromium salt solutions, and copper salt solutions, respectively. The iron salt solution, the cobalt salt solution, the nickel salt solution, the chromium salt solution, and the copper salt solution are mixed to obtain a mixed solution; The mixed solution is applied to the surface of the polyimide paper, and the polyimide paper with the mixed solution applied is placed on a vacuum adsorption stage; By setting femtosecond laser parameters and defocus distance, designing the laser scanning path using computer-aided SCA software, and scanning the polyimide paper with the mixed solution attached using the femtosecond laser, a femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material is obtained.

2. The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material according to claim 1, characterized in that, The iron salt solution, the cobalt salt solution, the nickel salt solution, the chromium salt solution, and the copper salt solution have equal molar concentrations, and the molar concentrations are between 0.01 and 0.05 M.

3. The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material according to claim 1, characterized in that, The metal salts corresponding to Fe, Co, Ni, Cr, and Cu are FeCl3·6H2O, CoCl2·6H2O, NiCl2·6H2O, CrCl3·6H2O, and CuCl2·6H2O, respectively.

4. The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material according to claim 1, characterized in that, The amount of the mixed solution adhering to the surface of the polyimide paper is 0.8-1.2 ml / cm. 2 .

5. The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material according to claim 1, characterized in that, The step of placing the polyimide paper with the mixed solution attached onto the vacuum adsorption stage further includes: pressing the four edges of the polyimide paper with a glass slide mold.

6. The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material according to claim 1, characterized in that, The femtosecond laser parameters include: laser wavelength, laser pulse frequency, laser power, laser scanning speed, laser pulse, and laser density.

7. The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material according to claim 6, characterized in that, The laser wavelength is 1020-1040nm; the laser pulse frequency is 555-1111kHz; the laser power is 0.8-2.4W; the laser scanning speed is 30-60mm / s; the laser pulses are 400-500 times; and the laser density is 55-68 pulses / mm.

8. The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material according to claim 1, characterized in that, The defocus distance is 0.1-0.3mm.

9. The method for preparing the femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material according to claim 1, characterized in that, The laser scanning path includes: first moving in a zigzag pattern along the x-direction of the polyimide paper, and then moving in a zigzag pattern along the y-direction of the polyimide paper.

10. A femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material, characterized in that, The material was prepared using the method described in any one of claims 1-9 for the preparation of femtosecond laser-induced graphene / high-entropy oxide composite electromagnetic shielding material.

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