A MXene / graphene oxide-Fe3O4 composite PVA hydrogel membrane and its preparation method

Abstract

The application relates to the technical field of electromagnetic shielding materials, in particular to a MXene / graphene oxide-Fe3O4 composite PVA hydrogel film and a preparation method thereof. 3+ Ions are adsorbed on the surface of MXene under alkaline conditions, and are in-situ converted into Fe3O4 magnetic nanoparticles through a hydrothermal reaction, so that a conductive-magnetic synergistic composite structure is constructed. The material is prepared through a one-pot hydrothermal method, and then a stable hydrogel network is formed through freezing-melting circulation. The obtained composite hydrogel has good flexibility, conductivity and magnetism, and exhibits excellent electromagnetic shielding performance in the 8.2-12.4 GHz frequency band, and has light weight, flexibility, multifunction and wide-frequency electromagnetic shielding capacity, and has the potential to be applied to the fields of flexible electronic devices, electromagnetic shielding materials and wearable electronic equipment.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic shielding materials technology, and in particular to an MXene / graphene oxide-Fe3O4 composite PVA hydrogel material and its preparation method, and to the application of this material in broadband electromagnetic wave shielding. Background Technology

[0002] With the rapid development of electronic information technology, the number of various electronic devices used has increased rapidly, leading to increasingly serious electromagnetic radiation pollution problems. Electromagnetic interference not only affects the normal operation of electronic devices but may also pose potential hazards to human health. Therefore, the development of high-performance electromagnetic shielding materials is of great significance. Traditional electromagnetic shielding materials are mostly metallic materials, such as copper, aluminum, and nickel. Although metallic materials have excellent electrical conductivity and high electromagnetic shielding capabilities, they also have disadvantages such as high density, poor flexibility, and susceptibility to corrosion, which are not conducive to their application in flexible electronic devices and wearable devices.

[0003] In recent years, two-dimensional materials such as MXene and graphene have attracted widespread attention due to their excellent electrical conductivity and large specific surface area. These materials can be used to construct highly efficient conductive networks, thereby enhancing the reflection and absorption of electromagnetic waves. On the other hand, magnetic materials such as Fe3O4 can absorb electromagnetic waves through magnetic loss mechanisms. However, single magnetic materials typically have poor conductivity, making it difficult to form highly efficient electromagnetic shielding structures.

[0004] Hydrogels are a class of three-dimensional network materials formed by cross-linking hydrophilic polymers, exhibiting excellent flexibility and processability. Introducing conductive and magnetic materials into hydrogel systems can create composite structures with both conductive and magnetic losses, thereby achieving efficient electromagnetic wave absorption. However, current research on constructing flexible hydrogel electromagnetic shielding materials using MXene, graphene, and magnetic nanoparticles simultaneously remains limited.

[0005] Therefore, it is of great significance to develop a composite hydrogel material that combines conductivity, magnetism, and flexibility. Summary of the Invention

[0006] This invention provides an MXene / graphene oxide-Fe3O4 composite PVA hydrogel and its preparation method, which offers a new approach for shielding wideband electromagnetic waves, fills the research gap in low-frequency electromagnetic wave shielding materials for long-wave communication, and provides a simple, convenient, and easy-to-implement one-pot hydrothermal preparation method.

[0007] The purpose of this invention is to provide an MXene / graphene oxide-Fe3O4 composite PVA hydrogel that achieves efficient electromagnetic wave shielding by constructing a conductive-magnetic synergistic structure, while maintaining the flexibility and stability of the material.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: An MXene / graphene oxide-Fe3O4 composite PVA hydrogel comprises: MXene two-dimensional nanosheets, graphene oxide, Fe3O4 magnetic nanoparticles, polyvinyl alcohol, and water. The Fe3O4 magnetic nanoparticles are in situ loaded on the surface of the MXene two-dimensional nanosheets and, together with the graphene oxide, form a three-dimensional conductive network structure. This three-dimensional conductive network structure is dispersed within a three-dimensional hydrogel network formed by polyvinyl alcohol.

[0009] Furthermore, the mass ratio of MXene two-dimensional nanosheets to graphene oxide is 2:8 to 8:2.

[0010] Furthermore, the total mass of MXene two-dimensional nanosheets and graphene oxide is 200 mg to 600 mg.

[0011] Furthermore, the molecular weight of polyvinyl alcohol is 80,000 to 150,000.

[0012] This invention also provides a method for preparing the above-mentioned MXene / graphene oxide-Fe3O4 composite PVA hydrogel, comprising the following steps: S1: Preparation of MXene two-dimensional nanosheet dispersion; S2: Mix the MXene two-dimensional nanosheet dispersion with graphene oxide to obtain a conductive filler dispersion; S3: Add Fe to the conductive filler dispersion 3+ Source, and adjust the pH of the system to alkaline, stirring to make Fe 3+ Full adsorption; S4: Add polyvinyl alcohol to the system obtained in step S3 to form a homogeneous mixed solution; S5: The homogeneous mixed solution is subjected to a hydrothermal reaction to allow Fe to react. 3+ In situ, it is transformed into Fe3O4 magnetic nanoparticles, forming a composite system; S6: The composite system is subjected to a freeze-thaw cycle to form an MXene / graphene oxide-Fe3O4 composite PVA hydrogel.

[0013] Further, the method for preparing the MXene two-dimensional nanosheet dispersion in step S1 is as follows: LiF is added to hydrochloric acid solution and heated to dissolve, and then Ti3AlC2MAX phase powder is slowly added to carry out the etching reaction; after the reaction is completed, the supernatant is centrifuged and washed until the pH of the supernatant is neutral, and ultrasonic exfoliation is carried out under nitrogen protection in an ice-water bath, and then the dark green monolayer MXene dispersion is collected by centrifugation again.

[0014] Furthermore, in step S3, Fe 3+The source was FeCl3, and the amount added was 5 mmol to 9 mmol; the pH of the system was adjusted to 10 to 12.

[0015] Furthermore, in step S5, the temperature of the hydrothermal reaction is 140℃~180℃, and the time of the hydrothermal reaction is 10h~14h.

[0016] Furthermore, in step S6, the freeze-thaw cycle is repeated 2 to 5 times; each freezing temperature is -20℃ to -30℃, the freezing time is 1h to 3h, and the thawing time at room temperature is 0.5h to 2h.

[0017] This invention also provides the application of the above-mentioned MXene / graphene oxide-Fe3O4 composite PVA hydrogel in electromagnetic shielding materials.

[0018] Compared with the prior art, the present invention has the following advantages: 1. This invention employs a method combining solution mixing, hydrothermal reaction, and freeze-thaw crosslinking to prepare composite hydrogel materials. The entire preparation process is primarily completed in an aqueous system, eliminating the need for complex multi-step chemical modification or high-temperature sintering. Compared to the chemical vapor deposition, high-temperature heat treatment, or multi-stage composite processes commonly used in the preparation of traditional electromagnetic shielding materials, this invention offers a simpler operation and milder reaction conditions, significantly reducing the difficulty of preparation.

[0019] 2. By combining MXene with graphene oxide, two two-dimensional materials form a stable dispersion structure in an aqueous solution system, and a continuous conductive network is constructed during the subsequent hydrogel formation process. This method can effectively avoid the aggregation problem of single conductive fillers in the polymer matrix, improve the utilization efficiency of conductive fillers, and make the conductive network more stable and uniform.

[0020] 3. Adsorption of Fe on the MXene surface 3+ Ions are ionized and, under hydrothermal reaction conditions, are transformed in situ into Fe3O4 magnetic nanoparticles, thereby achieving uniform loading of magnetic particles on the surface of a two-dimensional material. Compared with the traditional method of directly adding magnetic powder, this in-situ growth strategy can effectively avoid the agglomeration of magnetic particles, making the Fe3O4 nanoparticles more uniformly distributed in the composite system, thus improving the structural stability and functional consistency of the material.

[0021] 4. Utilizing the physical cross-linking properties of PVA, a three-dimensional hydrogel network structure is constructed through a freeze-thaw cycle method. This method does not require the introduction of additional chemical cross-linking agents and does not produce complex side reactions. Attached Figure Description

[0022] Figure 1 This is a flowchart of the hydrogel preparation method of the present invention; Figure 2The X-ray powder diffraction patterns of the MXene / graphene oxide-Fe3O4 composite PVA hydrogel of Example 4 of the present invention and the Fe3O4 synthesized by hydrothermal method in Comparative Example 1 are shown. Figure 3 Infrared spectral images of the MXene / graphene oxide-Fe3O4 composite PVA hydrogels of Examples 4, 6, and 7 of this invention and the pure polyvinyl alcohol gel of Comparative Example 2. Figure 4 This is a scanning electron microscope image of the MXene / graphene oxide-Fe3O4 composite PVA hydrogel of Example 6 of the present invention; Figure 5 The image shows the X-ray energy dispersive spectroscopy (EDS) image of the MXene / graphene oxide-Fe3O4 composite PVA hydrogel of Example 6. Detailed Implementation

[0023] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0024] like Figures 1 to 5 As shown, an MXene / graphene oxide-Fe3O4 composite PVA hydrogel comprises: MXene two-dimensional nanosheets, graphene oxide, Fe3O4 magnetic nanoparticles, polyvinyl alcohol, and water. The Fe3O4 magnetic nanoparticles are in situ loaded on the surface of the MXene two-dimensional nanosheets and, together with the graphene oxide, form a three-dimensional conductive network structure. This three-dimensional conductive network structure is dispersed within a three-dimensional hydrogel network formed by polyvinyl alcohol.

[0025] Furthermore, the mass ratio of MXene two-dimensional nanosheets to graphene oxide is 2:8 to 8:2.

[0026] Furthermore, the total mass of MXene two-dimensional nanosheets and graphene oxide is 200 mg to 600 mg.

[0027] Furthermore, the molecular weight of polyvinyl alcohol is 80,000 to 150,000.

[0028] This invention also provides a method for preparing the above-mentioned MXene / graphene oxide-Fe3O4 composite PVA hydrogel, comprising the following steps: S1: Preparation of MXene two-dimensional nanosheet dispersion; S2: Mix the MXene two-dimensional nanosheet dispersion with graphene oxide to obtain a conductive filler dispersion; S3: Add Fe to the conductive filler dispersion 3+ Source, and adjust the pH of the system to alkaline, stirring to make Fe 3+ Full adsorption; S4: Add polyvinyl alcohol to the system obtained in step S3 to form a homogeneous mixed solution; S5: The homogeneous mixed solution is subjected to a hydrothermal reaction to allow Fe to react. 3+ In situ, it is transformed into Fe3O4 magnetic nanoparticles, forming a composite system; S6: The composite system is subjected to a freeze-thaw cycle to form an MXene / graphene oxide-Fe3O4 composite PVA hydrogel.

[0029] Further, the method for preparing the MXene two-dimensional nanosheet dispersion in step S1 is as follows: LiF is added to hydrochloric acid solution and heated to dissolve, and then Ti3AlC2MAX phase powder is slowly added to carry out the etching reaction; after the reaction is completed, the supernatant is centrifuged and washed until the pH of the supernatant is neutral, and ultrasonic exfoliation is carried out under nitrogen protection in an ice-water bath, and then the dark green monolayer MXene dispersion is collected by centrifugation again.

[0030] Furthermore, in step S3, Fe 3+ The source was FeCl3, and the amount added was 5 mmol to 9 mmol; the pH of the system was adjusted to 10 to 12.

[0031] Furthermore, in step S5, the temperature of the hydrothermal reaction is 140℃~180℃, and the time of the hydrothermal reaction is 10h~14h.

[0032] Furthermore, in step S6, the freeze-thaw cycle is repeated 2 to 5 times; each freezing temperature is -20℃ to -30℃, the freezing time is 1h to 3h, and the thawing time at room temperature is 0.5h to 2h.

[0033] This invention also provides the application of the above-mentioned MXene / graphene oxide-Fe3O4 composite PVA hydrogel in electromagnetic shielding materials.

[0034] Figure 2 The X-ray powder diffraction patterns are those of the MXene / graphene oxide-Fe3O4 composite PVA hydrogel from Example 4 of this invention and the Fe3O4 synthesized by hydrothermal method in Comparative Example 1. Figure 2 It can be seen that when the composite conductive filler in the gel is extracted and subjected to X-ray powder diffraction, strong diffraction peaks of Fe3O4 (200), (311), (400), (422), (511), and (440) are all present, which proves the formation of Fe3O4 in the conductive filler. Moreover, since Fe3O4 is loaded on the MXene surface, the increase in the interlayer spacing of MXene will further shift its (002) peak to the left to 2θ < 5°.

[0035] Figure 3The images shown are infrared spectra of the MXene / graphene oxide-Fe3O4 composite PVA hydrogels of Examples 4, 6, and 7 of this invention, and the pure polyvinyl alcohol gel of Comparative Example 2. Figure 3 It can be seen that when the content and ratio of conductive filler are consistent, the peak positions of infrared images of FeCl3 gels with different masses added are completely consistent. This proves that Fe... 3+ The addition of [a specific ingredient] and pH=11 under hydrothermal conditions at 160℃ will not destroy the molecular structure of PVA.

[0036] Figure 4 This is a scanning electron microscope (SEM) image of the MXene / graphene oxide-Fe3O4 composite PVA hydrogel from Example 6 of the present invention. Figure 4 It can be seen that the cross-section of the composite hydrogel has a regular pore arrangement.

[0037] Figure 5 The image shown is an X-ray energy dispersive spectroscopy (EDS) image of the MXene / graphene oxide-Fe3O4 composite PVA hydrogel from Example 6. Figure 5 It can be seen that the iron element is uniformly filled in the composite gel.

[0038] Unless otherwise specified, the following test methods and detection methods are all conventional methods; unless otherwise specified, the reagents and raw materials are all commercially available.

[0039] Example 1: A method for preparing an MXene / graphene oxide-Fe3O4 composite PVA hydrogel includes the following steps: S1: Graphene oxide and MXene sheets were mixed at a mass ratio of 8:2, with a total mass of 600 mg. The mixture was stirred for 1 hour to obtain a mixed solution. 5 mmol of ferric chloride was added to the mixed solution, and the mixture was stirred for 2 hours to allow ferric ions to be fully adsorbed onto the MXene surface. The pH was adjusted to 11 with saturated sodium hydroxide solution, and stirring was continued for 1 hour.

[0040] S2: Add 6g of polyvinyl alcohol to the pH-adjusted solution, and adjust the total mass of the solution to 60g with deionized water. Heat and stir at 95℃ for 30min to dissolve the polyvinyl alcohol, then add 1mL of hydrazine hydrate and continue stirring for 10min. Transfer the solution to a 100mL high-pressure reactor and hydrothermally react at 160℃ for 12h.

[0041] S3: After hydrothermal reaction, the product was sonicated for 30 minutes to remove air bubbles, then poured into a silicone mold and frozen at -20°C for 1.5 hours, followed by thawing at room temperature for 1 hour. This process was repeated three times to obtain a gel sample. The gel was then purified by soaking in deionized water for 48 hours, with the deionized water being replaced twice during this period.

[0042] Example 2: A method for preparing an MXene / graphene oxide-Fe3O4 composite PVA hydrogel includes the following steps: S1: Graphene oxide and MXene sheets were mixed at a mass ratio of 6:4, with a total mass of 600 mg. The mixture was stirred for 1 hour to obtain a mixed solution. 5 mmol of ferric chloride was added to the mixed solution, and the mixture was stirred for 2 hours to allow ferric ions to be fully adsorbed onto the MXene surface. The pH was adjusted to 11 with saturated sodium hydroxide solution, and stirring was continued for 1 hour.

[0043] S2: Add 6g of polyvinyl alcohol to the pH-adjusted solution, and adjust the total mass of the solution to 60g with deionized water. Heat and stir at 95℃ for 30min to dissolve the polyvinyl alcohol, then add 1mL of hydrazine hydrate and continue stirring for 10min. Transfer the solution to a 100mL high-pressure reactor and hydrothermally react at 160℃ for 12h.

[0044] S3: After hydrothermal reaction, the product was sonicated for 30 minutes to remove air bubbles, then poured into a silicone mold and frozen at -20°C for 1.5 hours, followed by thawing at room temperature for 1 hour. This process was repeated three times to obtain a gel sample. The gel was then purified by soaking in deionized water for 48 hours, with the deionized water being replaced twice during this period.

[0045] Example 3: A method for preparing an MXene / graphene oxide-Fe3O4 composite PVA hydrogel includes the following steps: S1: Graphene oxide and MXene sheets were mixed at a 1:1 mass ratio (600 mg total mass) and stirred for 1 hour to obtain a mixed solution. 5 mmol of ferric chloride was added to the mixed solution, and the mixture was stirred for 2 hours to allow ferric ions to be fully adsorbed onto the MXene surface. The pH was adjusted to 11 with saturated sodium hydroxide solution, and stirring was continued for 1 hour.

[0046] S2: Add 6g of polyvinyl alcohol to the pH-adjusted solution, and adjust the total mass of the solution to 60g with deionized water. Heat and stir at 95℃ for 30min to dissolve the polyvinyl alcohol, then add 1mL of hydrazine hydrate and continue stirring for 10min. Transfer the solution to a 100mL high-pressure reactor and hydrothermally react at 160℃ for 12h.

[0047] S3: After hydrothermal reaction, the product was sonicated for 30 minutes to remove air bubbles, then poured into a silicone mold and frozen at -20°C for 1.5 hours, followed by thawing at room temperature for 1 hour. This process was repeated three times to obtain a gel sample. The gel was then purified by soaking in deionized water for 48 hours, with the deionized water being replaced twice during this period.

[0048] Example 4: A method for preparing an MXene / graphene oxide-Fe3O4 composite PVA hydrogel includes the following steps: S1: Graphene oxide and MXene sheets were mixed at a mass ratio of 4:6, with a total mass of 600 mg. The mixture was stirred for 1 hour to obtain a mixed solution. 5 mmol of ferric chloride was added to the mixed solution, and the mixture was stirred for 2 hours to allow ferric ions to be fully adsorbed onto the MXene surface. The pH was adjusted to 11 with saturated sodium hydroxide solution, and stirring was continued for 1 hour.

[0049] S2: Add 6g of polyvinyl alcohol to the pH-adjusted solution, and adjust the total mass of the solution to 60g with deionized water. Heat and stir at 95℃ for 30min to dissolve the polyvinyl alcohol, then add 1mL of hydrazine hydrate and continue stirring for 10min. Transfer the solution to a 100mL high-pressure reactor and hydrothermally react at 160℃ for 12h.

[0050] S3: After hydrothermal reaction, the product was sonicated for 30 minutes to remove air bubbles, then poured into a silicone mold and frozen at -20°C for 1.5 hours, followed by thawing at room temperature for 1 hour. This process was repeated three times to obtain a gel sample. The gel was then purified by soaking in deionized water for 48 hours, with the deionized water being replaced twice during this period.

[0051] Example 5: A method for preparing an MXene / graphene oxide-Fe3O4 composite PVA hydrogel includes the following steps: S1: Graphene oxide and MXene sheets were mixed at a mass ratio of 2:8, with a total mass of 600 mg. The mixture was stirred for 1 hour to obtain a mixed solution. 5 mmol of ferric chloride was added to the mixed solution, and the mixture was stirred for 2 hours to allow ferric ions to be fully adsorbed onto the MXene surface. The pH was adjusted to 11 with saturated sodium hydroxide solution, and stirring was continued for 1 hour.

[0052] S2: Add 6g of polyvinyl alcohol to the pH-adjusted solution, and adjust the total mass of the solution to 60g with deionized water. Heat and stir at 95℃ for 30min to dissolve the polyvinyl alcohol, then add 1mL of hydrazine hydrate and continue stirring for 10min. Transfer the solution to a 100mL high-pressure reactor and hydrothermally react at 160℃ for 12h.

[0053] S3: After hydrothermal reaction, the product was sonicated for 30 minutes to remove air bubbles, then poured into a silicone mold and frozen at -20°C for 1.5 hours, followed by thawing at room temperature for 1 hour. This process was repeated three times to obtain a gel sample. The gel was then purified by soaking in deionized water for 48 hours, with the deionized water being replaced twice during this period.

[0054] Example 6: A method for preparing an MXene / graphene oxide-Fe3O4 composite PVA hydrogel includes the following steps: S1: Graphene oxide and MXene sheets were mixed at a mass ratio of 4:6, with a total mass of 600 mg. The mixture was stirred for 1 hour to obtain a mixed solution. 7 mmol of ferric chloride was added to the mixed solution, and the mixture was stirred for 2 hours to allow ferric ions to be fully adsorbed onto the MXene surface. The pH was adjusted to 11 with saturated sodium hydroxide solution, and stirring was continued for 1 hour.

[0055] S2: Add 6g of polyvinyl alcohol to the pH-adjusted solution, and adjust the total mass of the solution to 60g with deionized water. Heat and stir at 95℃ for 30min to dissolve the polyvinyl alcohol, then add 1mL of hydrazine hydrate and continue stirring for 10min. Transfer the solution to a 100mL high-pressure reactor and hydrothermally react at 160℃ for 12h.

[0056] S3: After hydrothermal reaction, the product was sonicated for 30 minutes to remove air bubbles, then poured into a silicone mold and frozen at -20°C for 1.5 hours, followed by thawing at room temperature for 1 hour. This process was repeated three times to obtain a gel sample. The gel was then purified by soaking in deionized water for 48 hours, with the deionized water being replaced twice during this period.

[0057] Example 7: A method for preparing an MXene / graphene oxide-Fe3O4 composite PVA hydrogel includes the following steps: S1: Graphene oxide and MXene sheets were mixed at a mass ratio of 4:6, with a total mass of 600 mg. The mixture was stirred for 1 hour to obtain a mixed solution. 9 mmol of ferric chloride was added to the mixed solution, and the mixture was stirred for 2 hours to allow ferric ions to be fully adsorbed onto the MXene surface. The pH was adjusted to 11 with saturated sodium hydroxide solution, and stirring was continued for 1 hour.

[0058] S2: Add 6g of polyvinyl alcohol to the pH-adjusted solution, and adjust the total mass of the solution to 60g with deionized water. Heat and stir at 95℃ for 30min to dissolve the polyvinyl alcohol, then add 1mL of hydrazine hydrate and continue stirring for 10min. Transfer the solution to a 100mL high-pressure reactor and hydrothermally react at 160℃ for 12h.

[0059] S3: After hydrothermal reaction, the product was sonicated for 30 minutes to remove air bubbles, then poured into a silicone mold and frozen at -20°C for 1.5 hours, followed by thawing at room temperature for 1 hour. This process was repeated three times to obtain a gel sample. The gel was then purified by soaking in deionized water for 48 hours, with the deionized water being replaced twice during this period.

[0060] The following analysis table is derived from the above embodiments 1-7: Table 1 Comparison of the effects of different graphene oxide / MXene ratios on composite hydrogels; ; Table 2 Different Fe 3 Comparison of the effects of addition amount on composite hydrogels

[0061] • The formulation is adjustable in two dimensions and has strong adaptability. The material properties can be precisely controlled through two independent dimensions: "two-dimensional filler ratio" and "magnetic precursor dosage". Adjusting the ratio of GO to MXene can balance the system's dispersibility and conductivity, and adjusting the amount of FeCl3 can control the magnetic loss intensity. The formulation can be customized for different frequency bands and different shielding requirements.

[0062] The electromagnetic shielding mechanism of conductive-magnetic synergy uses an in-situ hydrothermal method to generate Fe3O4 nanoparticles on the surface of MXene, which are then combined with graphene oxide to construct a three-dimensional conductive network. This achieves a dual shielding mechanism for both conductive and magnetic losses, which has advantages in shielding efficiency and bandwidth compared to single conductive or single magnetic fillers.

[0063] The preparation process is stable and mild. All seven examples adopt a unified "solution mixing-one-pot hydrothermal-freeze-thaw physical crosslinking" process, which does not require chemical crosslinking agents. The reaction conditions (160℃ hydrothermal, room temperature freeze-thaw) are mild and controllable. The PVA molecular structure is not destroyed by the hydrothermal environment, and the process has good repeatability and scalability.

[0064] With excellent microstructure uniformity, under appropriate formulation parameters (such as in Example 6), Fe3O4 is uniformly distributed in the hydrogel matrix without obvious agglomeration; the hydrogel cross-section exhibits a regular pore structure, which not only ensures the flexibility and water absorption rate of the material, but also provides a structural basis for multiple reflections of electromagnetic waves.

[0065] With a clear baseline formulation and well-defined optimization logic, Example 4 serves as a common control group for the two sets of variable experiments. It represents the balance point between "MXene-dominant conductive filler + low-dosage magnetic particles," providing a clear reference baseline for subsequent performance optimization. The variable control is rigorous, and the experimental design logic is complete.

[0066] Table 3 shows the different Fe values. 3+ Comparison table of the effects of addition amount on composite hydrogels:

[0067] With all other parameters remaining constant—a fixed GO to MXene mass ratio of 4:6, a total two-dimensional packing mass of 600 mg, hydrothermal process, freeze-thaw process, etc.—only the FeCl3 addition amount was changed, and the Fe... 3+ The effect of dosage on material structure and properties.

[0068] Although preferred embodiments of this application have been described, those skilled in the art, once they learn the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application. Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if these modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include these modifications and variations.

Claims

1. An MXene / graphene oxide-Fe3O4 composite PVA hydrogel, characterized in that: The composite hydrogel comprises: MXene two-dimensional nanosheets, graphene oxide, Fe3O4 magnetic nanoparticles, polyvinyl alcohol, and water; wherein, the Fe3O4 magnetic nanoparticles are in situ loaded on the surface of the MXene two-dimensional nanosheets and together with the graphene oxide form a three-dimensional conductive network structure, which is dispersed in the three-dimensional hydrogel network formed by the polyvinyl alcohol.

2. The MXene / graphene oxide-Fe3O4 composite PVA hydrogel according to claim 1, characterized in that: The mass ratio of the MXene two-dimensional nanosheets to the graphene oxide is 2:8 to 8:

2.

3. The MXene / graphene oxide-Fe3O4 composite PVA hydrogel according to claim 1, characterized in that: The total mass of the MXene two-dimensional nanosheets and the graphene oxide is 200 mg to 600 mg.

4. The MXene / graphene oxide-Fe3O4 composite PVA hydrogel according to claim 1, characterized in that: The molecular weight of the PVA is 80,000 to 150,000.

5. A method for preparing an MXene / graphene oxide-Fe3O4 composite PVA hydrogel according to any one of claims 1 to 4, characterized in that: The steps include the following: S1: Preparation of MXene two-dimensional nanosheet dispersion; S2: Mix the MXene two-dimensional nanosheet dispersion with graphene oxide to obtain a conductive filler dispersion; S3: Add Fe to the conductive filler dispersion 3+ Source, and adjust the pH of the system to alkaline, stirring to make Fe 3+ Fully adsorbed; S4: Add polyvinyl alcohol to the system obtained in step S3 to form a homogeneous mixed solution; S5: The homogeneous mixed solution is subjected to a hydrothermal reaction to allow Fe to react. 3+ In-situ transformation of Fe3O4 magnetic nanoparticles to form a composite system; S6: Perform a freeze-thaw cycle on the composite system to form the MXene / graphene oxide-Fe3O4 composite PVA hydrogel.

6. The method for preparing an MXene / graphene oxide-Fe3O4 composite PVA hydrogel according to claim 5, characterized in that: The method for preparing the MXene two-dimensional nanosheet dispersion in step S1 is as follows: LiF is added to hydrochloric acid solution and heated to dissolve, and then slowly added... Ti3AlC2MAX phase powder was etched; after the reaction, the supernatant was centrifuged and washed until the pH of the supernatant was neutral, and then ultrasonically exfoliated under nitrogen protection in an ice-water bath. Subsequently, the dark green monolayer MXene dispersion was collected by centrifugation again.

7. The method for preparing an MXene / graphene oxide-Fe3O4 composite PVA hydrogel according to claim 5, characterized in that: Fe in step S3 3+ The source is FeCl3, and the amount added is 5 mmol to 9 mmol; the pH of the system is adjusted to 10 to 12.

8. The method for preparing an MXene / graphene oxide-Fe3O4 composite PVA hydrogel according to claim 5, characterized in that: In step S5, the temperature of the hydrothermal reaction is 140℃~180℃, and the reaction time is 10h~14h.

9. The method for preparing an MXene / graphene oxide-Fe3O4 composite PVA hydrogel according to claim 5, characterized in that: In step S6, the freeze-thaw cycle is repeated 2 to 5 times; each freezing temperature is -20℃ to -30℃, the freezing time is 1h to 3h, and the thawing time at room temperature is 0.5h to 2h.

10. The application of the MXene / graphene oxide-Fe3O4 composite PVA hydrogel as described in any one of claims 1 to 4 in electromagnetic shielding materials.

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