A wave-absorbing and heat-conducting dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam as well as a preparation method and application thereof

Abstract

The present application relates to the field of functional polymer composites formed by high polymer compound composition, and particularly relates to a wave-absorbing and heat-conducting dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam as well as a preparation method and application thereof; specifically, graphene oxide dispersion liquid is dispersed into PVA aqueous solution through ultrasonic auxiliary means, silicon carbide nanowires are added into the dispersion liquid, a silicon carbide nanowire / graphene oxide / PVA dispersion system is obtained through mechanical stirring and ultrasonic, then a silicon carbide nanowire / graphene oxide / PVA composite foam is prepared by using directional freezing combined with freeze-drying, finally, the obtained composite foam is reduced in a reducing agent solution and freeze-dried to obtain a dual-functional composite foam. The dual-functional composite foam can be used to prepare a composite material with excellent heat-conducting performance and wave-absorbing performance after being combined with a polymer matrix. The preparation method disclosed by the present application is stable and reliable, and the raw materials are environmentally friendly and non-polluting.

Description

Technical Field

[0001] This invention relates to the field of functional polymer composite materials formed by the composition of polymer compounds, specifically to a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam with both microwave absorption and thermal conductivity, its preparation method, and its application. Background Technology

[0002] Modern high-density integrated electronic devices (such as mobile phones, base stations, and radar) generate strong electromagnetic interference (EMI) during operation, affecting not only their own accuracy and reliability but also posing hazards to human health and the environment. Furthermore, the rapid development of radar detection technology has placed higher demands on electromagnetic stealth capabilities. The widespread application of microwave absorbing materials largely meets the needs of controlling electromagnetic pollution and achieving electromagnetic stealth. However, microwave absorbing materials are functional materials that convert incident electromagnetic wave energy into other forms of energy (mainly heat). Under high-power microwave irradiation, they produce significant thermal effects. Excessive heat accumulation can lead to decreased device performance, shortened lifespan, or even failure; therefore, efficient heat dissipation (thermal conductivity) is also crucial. Traditional single-function materials cannot simultaneously meet both requirements. Excellent microwave absorbing materials (such as certain ceramics and ferrites) are often poor conductors of heat (low thermal conductivity), and excessive heat accumulation can damage them. Excellent thermally conductive materials (such as copper and aluminum) are good conductors of electromagnetic waves, reflecting rather than absorbing them, thus failing to achieve stealth and electromagnetic interference resistance.

[0003] Therefore, the research on dual-functional materials for absorbing electromagnetic radiation and conducting heat is an inevitable choice to address the dual challenges of electromagnetic pollution and thermal management in modern high-tech fields. It is a key support for the development of next-generation communications and an important marker of the advancement of materials science itself, moving towards a more advanced stage of multifunctionality and intelligence. The research results will directly translate into technological advantages and market competitiveness, possessing enormous economic value and social benefits. Summary of the Invention

[0004] This invention overcomes the shortcomings of the prior art and provides a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam that combines wave absorption and thermal conductivity.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam that has both microwave absorption and thermal conductivity, wherein the composite foam uses PVA (i.e., polyvinyl alcohol) as the structural framework and silicon carbide nanowires and reduced graphene oxide as functional fillers.

[0006] This invention also provides a method for preparing a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam that combines microwave absorption and thermal conductivity, comprising the following steps:

[0007] S1. Preparation of silicon carbide nanowire / graphene oxide / PVA dispersion:

[0008] A PVA aqueous solution was prepared, boric acid was added, and the mixture was reacted at a constant temperature to obtain a dispersion. The dispersion was mixed with a graphene oxide dispersion and ultrasonically treated to obtain a stable graphene oxide / PVA dispersion system. Then, silicon carbide nanowires were added to the graphene oxide / PVA dispersion system and ultrasonically dispersed to obtain a silicon carbide nanowire / graphene oxide / PVA dispersion.

[0009] S2. Preparation of silicon carbide nanowire / graphene oxide / PVA composite foam:

[0010] The silicon carbide nanowire / graphene oxide / PVA dispersion obtained in step S1 was injected into a polytetrafluoroethylene mold with a copper cold stage and placed in liquid nitrogen for directional freezing. After directional freezing, the sample was taken out and placed in a freeze dryer for vacuum freeze drying to obtain silicon carbide nanowire / graphene oxide / PVA composite foam.

[0011] Preparation of S3, silicon carbide nanowire / reduced graphene oxide / PVA composite foam

[0012] The composite foam obtained in step S2 is placed in a reducing agent solution for reduction reaction. After the reaction is completed, the composite foam is freeze-dried to obtain silicon carbide nanowire / reduced graphene oxide / PVA composite foam.

[0013] As a further limitation of the technical solution of the present invention, the mass concentration of the PVA aqueous solution in step S1 is 2~6wt%, and the mass ratio of boric acid to PVA is 1:8~3:8; the temperature of the isothermal reaction in step S1 is 85~95℃, and the reaction time is 3~5h.

[0014] As a further limitation of the technical solution of the present invention, the solid content of the graphene oxide dispersion in step S1 is 1 wt%, and the mass ratio of the graphene oxide dispersion to the PVA aqueous solution is 1:1 to 1:5; the mass ratio of graphene oxide to silicon carbide nanowires in step S1 is 1:0 to 10, and is not 0.

[0015] As a further limitation of the technical solution of the present invention, the vacuum degree of freeze drying in step S2 is -0.09~-0.1MPa and the temperature is -55±2℃.

[0016] As a further limitation of the technical solution of the present invention, the reducing agent in step S3 is at least one of ascorbic acid, citric acid and urea; the mass fraction of the reducing agent solution is 0.2%~0.8%, the reduction reaction temperature is 75~95℃, and the reaction time is 8~14h.

[0017] In addition, the present invention also provides the application of the microwave absorbing and thermally conductive bifunctional silicon carbide nanowire / reduced graphene oxide / PVA composite foam obtained by the above preparation method in the preparation of resin-based composite materials.

[0018] Furthermore, the preparation method of the resin-based composite material includes the following steps:

[0019] (1) Mix the thermosetting resin matrix with the curing agent to obtain a resin solution;

[0020] (2) Place the microwave-absorbing and thermally conductive dual-function silicon carbide nanowires / reduced graphene oxide / PVA composite foam in the resin solution described in step (1) and perform resin infusion in a vacuum oven.

[0021] (3) After the injection is completed, the vacuum oven is heated to the temperature required for resin curing, and the resin is cured under vacuum conditions to obtain the composite material.

[0022] Furthermore, the thermosetting resin matrix mentioned in step (1) is at least one of epoxy resin, polyurethane and silicone rubber.

[0023] Furthermore, the vacuum degree of the vacuum oven mentioned in step (3) is -0.09~-0.085MPa.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. This invention employs a process combining directional freeze-drying and chemical reduction to prepare a composite foam with PVA as the framework and silicon carbide nanowires and reduced graphene oxide as functional fillers. The directional freeze-drying technique allows the one-dimensional silicon carbide nanowires and two-dimensional reduced graphene oxide sheets to form a three-dimensional interpenetrating network structure. This three-dimensional porous network structure achieves excellent impedance matching characteristics, allowing incident electromagnetic waves to penetrate the material's interior to a greater extent. Furthermore, under the influence of electromagnetic waves, the heterogeneous interface between the silicon carbide nanowires and reduced graphene oxide generates significant interfacial polarization, thus attenuating electromagnetic wave energy. Simultaneously, the dangling bonds and lattice defects on the surface of the reduced graphene oxide act as polarization centers, generating dipole polarization and further attenuating electromagnetic wave energy. The synergistic effect of excellent impedance matching characteristics and strong attenuation capabilities endows the composite foam with superior wave absorption performance.

[0026] 2. Both silicon carbide nanowires and reduced graphene oxide are nanofunctional particles with good thermal conductivity. The combination of the two to form an interpenetrating three-dimensional network structure can form a relatively complete thermally conductive network, thus enabling the composite foam to obtain excellent thermal conductivity.

[0027] 3. This invention obtains a composite foam with both excellent microwave absorption and thermal conductivity through a simple, efficient, and environmentally friendly preparation process. Combining this composite foam with thermosetting resins such as epoxy resin can prepare resin-based composite materials with dual functionalities of microwave absorption and thermal conductivity. This provides a new approach for the development of high-efficiency, lightweight, and high-strength functional polymer composite materials. Attached Figure Description

[0028] Figure 1 A digital photograph of the silicon carbide nanowire / reduced graphene oxide / PVA composite foam prepared in Example 1 of this invention.

[0029] Figure 2 The bar chart shows the thermal conductivity of the silicon carbide nanowire / reduced graphene oxide / PVA composite foam / epoxy resin composite materials prepared in Examples 1-4 of this invention.

[0030] Figure 3 The image shows the RL-f curve of the silicon carbide nanowire / reduced graphene oxide / PVA composite foam / epoxy resin composite material prepared in Example 1 of this invention.

[0031] Figure 4 The RL-f curve is shown for the silicon carbide nanowire / reduced graphene oxide / PVA composite foam / epoxy resin composite material prepared in Example 2 of this invention.

[0032] Figure 5 The RL-f curve is shown for the silicon carbide nanowire / reduced graphene oxide / PVA composite foam / epoxy resin composite material prepared in Example 3 of this invention.

[0033] Figure 6 The image shows the RL-f curve of the silicon carbide nanowire / reduced graphene oxide / PVA composite foam / epoxy resin composite material prepared in Example 4 of this invention. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments.

[0035] Example 1

[0036] A method for preparing a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam with both microwave absorption and thermal conductivity includes the following steps:

[0037] (1) Preparation of PVA aqueous solution

[0038] Weigh 8g of PVA and dissolve it in 192g of 95℃ deionized water. After complete dissolution, add 1g of boric acid to the solution. After the boric acid is completely dissolved, place the mixed solution in a constant temperature water bath and react at 95℃ for 4 hours to obtain an aqueous PVA solution.

[0039] (2) Preparation of silicon carbide nanowires / graphene oxide / PVA mixed dispersion

[0040] Weigh 20g of the PVA aqueous solution prepared in step (1) and 20g of graphene oxide dispersion with a solid content of 1wt%, and ultrasonically disperse them for 15min at 200W power to obtain a uniformly dispersed graphene oxide / PVA mixed dispersion.

[0041] 0.6g of silicon carbide nanowires were weighed and dispersed in the above graphene oxide / PVA mixed dispersion under stirring and ultrasonication to obtain the silicon carbide nanowire / graphene oxide / PVA mixed dispersion.

[0042] (3) Preparation of silicon carbide nanowire / graphene oxide / PVA composite foam

[0043] The silicon carbide nanowire / graphene oxide / PVA dispersion obtained in step (2) was poured into a polytetrafluoroethylene mold with a copper cold stage and placed in liquid nitrogen for directional freezing. After directional freezing for 30 minutes, the sample was taken out and placed in a freeze dryer for freeze drying at a vacuum of -0.09 MPa and a temperature of -55°C to obtain silicon carbide nanowire / graphene oxide / PVA composite foam.

[0044] (4) Preparation of silicon carbide nanowires / reduced graphene oxide / PVA composite foam

[0045] The composite foam obtained in step (3) was placed in a 0.4% ascorbic acid solution and reduced at 90°C for 12 hours. After the reaction was completed, the composite foam was freeze-dried under a vacuum of -0.09 MPa and a temperature of -55°C to obtain silicon carbide nanowire / reduced graphene oxide / PVA composite foam.

[0046] The preparation of a silicon carbide nanowire / reduced graphene oxide / PVA composite foam / epoxy resin composite material includes the following steps:

[0047] a. Epoxy resin and curing agent cis-hexahydrophthalic anhydride are mixed at a mass ratio of 1:0.8 to obtain a resin solution;

[0048] b. Place the silicon carbide nanowire / reduced graphene oxide / PVA composite foam described in step a into the resin solution described in step a, and place it in a vacuum oven for resin infusion at a vacuum degree of -0.09MPa;

[0049] After the infusion is completed, the vacuum oven is heated to 120°C to cure the resin under vacuum conditions, thus obtaining the composite material.

[0050] Example 2

[0051] A method for preparing a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam with both microwave absorption and thermal conductivity includes the following steps:

[0052] (1) Preparation of PVA aqueous solution

[0053] Weigh 8g of PVA and dissolve it in 192g of 95℃ deionized water. After complete dissolution, add 1g of boric acid to the solution. After the boric acid is completely dissolved, place the mixed solution in a constant temperature water bath and react at 95℃ for 4 hours to obtain an aqueous PVA solution.

[0054] (2) Preparation of silicon carbide nanowires / graphene oxide / PVA mixed dispersion

[0055] Weigh 20g of the PVA aqueous solution prepared in step (1) and 20g of graphene oxide dispersion with a solid content of 1wt%, and ultrasonically disperse them for 15min at 200W power to obtain a uniformly dispersed graphene oxide / PVA mixed dispersion.

[0056] 1g of silicon carbide nanowires were weighed and dispersed in the graphene oxide / PVA mixed dispersion prepared above under stirring and ultrasonication to obtain the silicon carbide nanowire / graphene oxide / PVA mixed dispersion.

[0057] (3) Preparation of silicon carbide nanowire / graphene oxide / PVA composite foam

[0058] The silicon carbide nanowire / graphene oxide / PVA dispersion obtained in step (2) was poured into a polytetrafluoroethylene mold with a copper cold stage and placed in liquid nitrogen for directional freezing. After directional freezing for 30 minutes, the sample was taken out and placed in a freeze dryer to dry at a vacuum of -0.09 MPa and a temperature of -55°C to obtain silicon carbide nanowire / graphene oxide / PVA composite foam.

[0059] (4) Preparation of silicon carbide nanowires / reduced graphene oxide / PVA composite foam

[0060] The composite foam obtained in step (3) was placed in a 0.4% ascorbic acid solution and reduced at 90°C for 12 hours. After the reaction was completed, the composite foam was freeze-dried under a vacuum of -0.09 MPa and a temperature of -55°C to obtain silicon carbide nanowire / reduced graphene oxide / PVA composite foam.

[0061] Preparation of a silicon carbide nanowire / reduced graphene oxide / PVA composite foam / epoxy resin composite material

[0062] a. Epoxy resin and curing agent cis-hexahydrophthalic anhydride are mixed at a mass ratio of 1:0.8 to obtain a resin solution;

[0063] b. Place the silicon carbide nanowire / reduced graphene oxide / PVA composite foam described in step a into the resin solution described in step a, and place it in a vacuum oven for resin infusion at a vacuum degree of -0.09MPa;

[0064] c. After the injection is completed, the vacuum oven is heated to 120°C, and the resin is cured under vacuum conditions to obtain the composite material.

[0065] Example 3

[0066] A method for preparing a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam with both microwave absorption and thermal conductivity includes the following steps:

[0067] (1) Preparation of PVA aqueous solution

[0068] Weigh 8g of PVA and dissolve it in 192g of 95℃ deionized water. After complete dissolution, add 1g of boric acid to the solution. After the boric acid is completely dissolved, place the mixed solution in a constant temperature water bath and react at 95℃ for 4 hours to obtain an aqueous PVA solution.

[0069] (2) Preparation of silicon carbide nanowires / graphene oxide / PVA mixed dispersion

[0070] Weigh 20g of the PVA aqueous solution prepared in step (1) and 20g of graphene oxide dispersion with a solid content of 1wt%, and ultrasonically disperse them for 15min at 200W power to obtain a uniformly dispersed graphene oxide / PVA mixed dispersion.

[0071] 1.4g of silicon carbide nanowires were weighed and dispersed in the graphene oxide / PVA mixed dispersion prepared above under stirring and ultrasonication to obtain the silicon carbide nanowire / graphene oxide / PVA mixed dispersion.

[0072] (3) Preparation of silicon carbide nanowire / graphene oxide / PVA composite foam

[0073] The silicon carbide nanowire / graphene oxide / PVA dispersion obtained in step (2) was poured into a polytetrafluoroethylene mold with a copper cold stage and placed in liquid nitrogen for directional freezing. After directional freezing for 30 minutes, the sample was taken out and placed in a freeze dryer for freeze drying at a vacuum of -0.09 MPa and a temperature of -55°C to obtain silicon carbide nanowire / graphene oxide / PVA composite foam.

[0074] (4) Preparation of silicon carbide nanowires / reduced graphene oxide / PVA composite foam

[0075] The composite foam obtained in step (3) was placed in a 0.4% ascorbic acid solution and reduced at 90°C for 12 hours. After the reaction was completed, the composite foam was freeze-dried under a vacuum of -0.09 MPa and a temperature of -55°C to obtain silicon carbide nanowires / reduced graphene oxide / PVA composite foam.

[0076] Preparation of a silicon carbide nanowire / reduced graphene oxide / PVA composite foam / epoxy resin composite material

[0077] a. Epoxy resin and curing agent cis-hexahydrophthalic anhydride were mixed at a mass ratio of 1:0.8 to obtain a resin adhesive.

[0078] b. Place the silicon carbide nanowire / reduced graphene oxide / PVA composite foam described in step a into the resin solution described in step a, and place it in a vacuum oven for resin infusion at a vacuum degree of -0.09MPa;

[0079] c. After the injection is completed, the vacuum oven is heated to 120°C, and the resin is cured under vacuum conditions to obtain the composite material.

[0080] Example 4

[0081] A method for preparing a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam with both microwave absorption and thermal conductivity includes the following steps:

[0082] (1) Preparation of PVA aqueous solution

[0083] Weigh 8g of PVA and dissolve it in 192g of 95℃ deionized water. After complete dissolution, add 1g of boric acid to the solution. After the boric acid is completely dissolved, place the mixed solution in a constant temperature water bath and react at 95℃ for 4 hours to obtain an aqueous PVA solution.

[0084] (2) Preparation of silicon carbide nanowires / graphene oxide / PVA mixed dispersion

[0085] Weigh 20g of the PVA aqueous solution prepared in step (1) and 20g of graphene oxide dispersion with a solid content of 1wt%, and ultrasonically disperse them for 15min at 200W power to obtain a uniformly dispersed graphene oxide / PVA mixed dispersion.

[0086] 1.8g of silicon carbide nanowires were weighed and dispersed in the graphene oxide / PVA mixed dispersion prepared above under stirring and ultrasonication to obtain the silicon carbide nanowire / graphene oxide / PVA mixed dispersion.

[0087] (3) Preparation of silicon carbide nanowire / graphene oxide / PVA composite foam

[0088] The silicon carbide nanowire / graphene oxide / PVA dispersion obtained in step (2) was poured into a polytetrafluoroethylene mold with a copper cold stage and placed in liquid nitrogen for directional freezing. After directional freezing for 30 minutes, the sample was taken out and placed in a freeze dryer to dry at a vacuum of -0.09 MPa and a temperature of -55°C to obtain silicon carbide nanowire / graphene oxide / PVA composite foam.

[0089] (4) Preparation of silicon carbide nanowires / reduced graphene oxide / PVA composite foam

[0090] The composite foam obtained in step (3) was placed in a 0.4% ascorbic acid solution and reduced at 90°C for 12 hours. After the reaction was completed, the composite foam was freeze-dried under a vacuum of -0.09 MPa and a temperature of -55°C to obtain silicon carbide nanowire / reduced graphene oxide / PVA composite foam.

[0091] Preparation of a silicon carbide nanowire / reduced graphene oxide / PVA composite foam / epoxy resin composite material

[0092] a. Epoxy resin and curing agent cis-hexahydrophthalic anhydride were mixed at a mass ratio of 1:0.8 to obtain a resin adhesive.

[0093] b. Place the silicon carbide nanowire / reduced graphene oxide / PVA composite foam described in step a into the resin solution described in step a, and place it in a vacuum oven for resin infusion at a vacuum degree of -0.09MPa;

[0094] c. After the injection is completed, the vacuum oven is heated to 120°C, and the resin is cured under vacuum conditions to obtain the composite material.

[0095] The performance testing methods for Examples 1-4 above are as follows:

[0096] (1) Thermal conductivity test of silicon carbide nanowire / reduced graphene oxide / PVA composite foam

[0097] The composite foam was cut into circular pieces with a diameter of 17 mm and its thermal conductivity was tested on a DRE-V thermal conductivity tester.

[0098] (2) Wave absorption performance test of silicon carbide nanowire / reduced graphene oxide / PVA composite foam / epoxy resin composite material

[0099] The silicon carbide nanowire / reduced graphene oxide / PVA composite foam / epoxy resin composite material was processed into a coaxial ring with an inner diameter of 3.04 mm and an outer diameter of 7 mm on a CNC engraving machine, and then its electromagnetic wave absorption performance in the range of 2~18 GHz was tested using a vector network analyzer.

[0100] Depend on Figure 1 As can be seen, the silicon carbide nanowire / reduced graphene oxide / PVA composite foam prepared by this invention is uniformly black and lightweight.

[0101] Depend on Figure 2 It can be seen that the silicon carbide nanowire / reduced graphene oxide / PVA composite foam prepared by the present invention has excellent thermal conductivity, which increases with the increase of the ratio between silicon carbide nanowire and reduced graphene oxide.

[0102] Depend on Figures 3-6 As can be seen, the silicon carbide nanowire / reduced graphene oxide / PVA composite foam / epoxy resin composite material prepared in this invention exhibits excellent electromagnetic wave absorption performance. The composite material prepared in Example 1 achieves an RLmin of -15.64 dB when the thickness is 5.5 mm and has an effective absorption bandwidth of 3.66 GHz when the thickness is 3.5 mm. The composite material prepared in Example 2 achieves an RLmin of -18.48 dB when the thickness is 2.5 mm and has an effective absorption bandwidth of 4.18 GHz when the thickness is 3.0 mm. The composite material prepared in Example 3 achieves an RLmin of -39.67 dB when the thickness is 3.5 mm and has an effective absorption bandwidth of 9.26 GHz when the thickness is 3.5 mm. The composite material prepared in Example 4 achieves an RLmin of -31.20 dB when the thickness is 2.0 mm and has an effective absorption bandwidth of 5.5 GHz when the thickness is 2.0 mm.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam that exhibits both microwave absorption and thermal conductivity, characterized in that, Includes the following steps: S1. Preparation of silicon carbide nanowire / graphene oxide / PVA dispersion: A PVA aqueous solution was prepared, boric acid was added, and the mixture was reacted at a constant temperature to obtain a dispersion. The dispersion was mixed with a graphene oxide dispersion and ultrasonically treated to obtain a stable graphene oxide / PVA dispersion system. Then, silicon carbide nanowires were added to the graphene oxide / PVA dispersion system and ultrasonically dispersed to obtain a silicon carbide nanowire / graphene oxide / PVA dispersion. S2. Preparation of silicon carbide nanowire / graphene oxide / PVA composite foam: The silicon carbide nanowire / graphene oxide / PVA dispersion obtained in step S1 was injected into a polytetrafluoroethylene mold with a copper cold stage and placed in liquid nitrogen for directional freezing. After directional freezing, the sample was taken out and placed in a freeze dryer for vacuum freeze drying to obtain silicon carbide nanowire / graphene oxide / PVA composite foam; Preparation of S3, silicon carbide nanowire / reduced graphene oxide / PVA composite foam The composite foam obtained in step S2 is placed in a reducing agent solution for reduction reaction. After the reaction is completed, the composite foam is freeze-dried to obtain silicon carbide nanowire / reduced graphene oxide / PVA composite foam.

2. The method for preparing a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam with both microwave absorption and thermal conductivity according to claim 1, characterized in that, In step S1, the mass concentration of the PVA aqueous solution is 2-6 wt%, and the mass ratio of boric acid to PVA is 1:8-3:8; the temperature of the isothermal reaction in step S1 is 85-95℃, and the reaction time is 3-5 h.

3. The method for preparing a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam with both microwave absorption and thermal conductivity according to claim 1, characterized in that, In step S1, the solid content of the graphene oxide dispersion is 1 wt%, and the mass ratio of the graphene oxide dispersion to the PVA aqueous solution is 1:1 to 1:5; the mass ratio of graphene oxide to silicon carbide nanowires in step S1 is 1:0 to 10, and is not 0.

4. The method for preparing a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam with both microwave absorption and thermal conductivity according to claim 1, characterized in that, In step S2, the vacuum degree of freeze drying is -0.09~-0.1MPa, and the temperature is -55±2℃.

5. The method for preparing a dual-functional silicon carbide nanowire / reduced graphene oxide / PVA composite foam with microwave absorption and thermal conductivity according to claim 1, characterized in that, In step S3, the reducing agent is at least one of ascorbic acid, citric acid, and urea; the mass fraction of the reducing agent solution is 0.2% to 0.8%, the reduction reaction temperature is 75 to 95°C, and the reaction time is 8 to 14 hours.

6. The microwave-absorbing and thermally conductive bifunctional silicon carbide nanowire / reduced graphene oxide / PVA composite foam obtained by the preparation method according to any one of claims 1-5.

7. The application of the microwave-absorbing and thermally conductive bifunctional silicon carbide nanowire / reduced graphene oxide / PVA composite foam obtained by the preparation method according to any one of claims 1-5 in the preparation of resin-based composite materials.

8. The application according to claim 7, characterized in that, The preparation method of resin-based composite materials includes the following steps: (1) Mix the thermosetting resin matrix with the curing agent to obtain a resin solution; (2) Place the microwave-absorbing and thermally conductive dual-function silicon carbide nanowires / reduced graphene oxide / PVA composite foam in the resin solution described in step (1) and perform resin infusion in a vacuum oven. (3) After the injection is completed, the vacuum oven is heated to the temperature required for resin curing, and the resin is cured under vacuum conditions to obtain the composite material.

9. The application according to claim 8, characterized in that, The thermosetting resin matrix mentioned in step (1) is at least one of epoxy resin, polyurethane and silicone rubber.

10. The application according to claim 8, characterized in that, The vacuum degree of the vacuum oven mentioned in step (3) is -0.09~-0.085MPa.

Images