High-thermal-conductivity wave-absorbing composite material with flexibility and preparation method thereof

Abstract

This invention discloses a flexible, high thermal conductivity microwave absorbing composite material and its preparation method, relating to the field of composite material technology. The composite material comprises a flexible polymer matrix, high thermal conductivity carbon-based microspheres, magnetic microwave absorbing nanoparticles, and flexible thermal conductivity microwave absorbing fibers. Through a special material combination and structural design, the flexible polymer matrix and flexible thermal conductivity microwave absorbing fibers endow the composite material with excellent bendability and tensile strength, enabling it to adapt to various complex deformation requirements. Regarding high thermal conductivity, the high thermal conductivity carbon-based microspheres and the high thermal conductivity metal core layer in the flexible thermal conductivity microwave absorbing fibers work together to construct an efficient heat conduction network, which can rapidly dissipate heat, effectively reducing the internal temperature of the material and avoiding performance degradation caused by heat accumulation.

Description

Technical Field

[0001] This invention relates to the field of composite material technology, specifically to a flexible, highly thermally conductive, microwave-absorbing composite material and its preparation method. Background Technology

[0002] With the rapid development of modern technology, the integration level of electronic devices is increasing day by day. The problems of electromagnetic radiation and heat accumulation generated during operation are becoming more and more prominent. Furthermore, electromagnetic interference can also affect the normal operation of the equipment itself, leading to signal transmission errors, performance degradation, or even system failures, which can have adverse effects on other electronic devices in the surrounding area and seriously restrict the reliability and stability of electronic devices.

[0003] However, existing microwave absorbing materials often struggle to balance flexibility and high thermal conductivity. Traditional rigid microwave absorbing materials, lacking flexibility, are severely limited in applications requiring bending, folding, or complex shapes. On the other hand, flexible materials tend to have relatively poor thermal conductivity, making it difficult to quickly and effectively conduct heat away. This leads to heat accumulation within the material, affecting microwave absorption performance and overall material stability. Furthermore, issues such as the uniform dispersion of high thermal conductivity and microwave absorbing phases in composite materials and their interfacial bonding with the matrix can easily lead to phase separation and agglomeration, significantly reducing the overall performance of the composite material.

[0004] In summary, existing materials cannot simultaneously meet the requirements of high thermal conductivity, strong wave absorption, and good flexibility, which limits their widespread application in modern high-tech fields. Therefore, there is an urgent need to develop a new type of flexible, high thermal conductivity, wave-absorbing composite material to overcome the shortcomings of existing technologies and meet the growing demand for multi-field applications. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a flexible, high thermal conductivity, and microwave absorbing composite material and its preparation method. This invention achieves an effective combination of flexibility, high thermal conductivity, and excellent microwave absorption performance by using silicone rubber as a flexible polymer matrix, combining the uniform dispersion of high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles, and introducing flexible thermal conductivity and microwave absorbing fibers. This composite material not only has excellent heat dissipation performance, which can quickly conduct away the heat generated by electronic devices, reduce the device temperature, and improve the stability and service life of the device, but also has a strong microwave absorption capability, which can effectively absorb and shield electromagnetic radiation, protecting the surrounding environment.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: On one hand, a flexible, highly thermally conductive, microwave-absorbing composite material, which is composed of a flexible polymer matrix, highly thermally conductive carbon-based microspheres, magnetic microwave-absorbing nanoparticles, and flexible thermally conductive, microwave-absorbing fibers, specifically:

[0007] The flexible polymer matrix uses silicone rubber as the matrix, accounting for 30%-50% of the total mass of the composite material. The flexible polymer matrix contains surface-modified high thermal conductivity carbon-based microspheres and magnetic wave-absorbing nanoparticles.

[0008] The high thermal conductivity carbon-based microspheres are composed of graphene microspheres and carbon nanotube microspheres, accounting for 15%-25% of the total mass of the composite material;

[0009] The magnetic absorbing nanoparticles account for 10%-20% of the total mass of the composite material;

[0010] The flexible thermally conductive and microwave-absorbing fiber is composed of a coaxial structure, which includes a core layer, an intermediate layer and an outer layer. The core layer is a high thermal conductivity metal wire, copper wire, which transfers heat to both ends of the fiber. The intermediate layer is a microwave-absorbing material layer, which is selected from silicon carbide and boron nitride. The outer layer is a flexible polymer sheath layer, including polyimide and polyester.

[0011] Furthermore, the volume fraction of the flexible thermally conductive and microwave-absorbing fiber in the composite material is 5%-20%.

[0012] Furthermore, the surface of the high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles is modified into a composite layer of siloxane and metal oxide, and the mass ratio of the high thermal conductivity carbon-based microspheres to the magnetic microwave absorbing nanoparticles is 3:1-1:3.

[0013] Furthermore, the magnetic absorbing nanoparticles include ferrite nanoparticles and carbonyl iron powder nanoparticles.

[0014] On the other hand, a method for preparing a flexible, highly thermally conductive, microwave-absorbing composite material includes the following specific steps:

[0015] Surface modification of S100, high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles: High thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles were placed in a mixed solution containing silane coupling agent and metal alkoxide for surface modification. The modification reaction temperature was controlled at 40-60℃ and the reaction time was 3-6 hours to obtain surface-modified high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles.

[0016] Preparation of S200 flexible thermally conductive and microwave-absorbing fiber: A microwave-absorbing material layer is deposited on the surface of a high thermal conductivity metal wire as the core material. The deposition temperature is controlled at 300-500℃, the pressure is 1-5kPa, and the deposition rate is 0.1-0.5μm / min. The deposited microwave-absorbing material layer is then impregnated and coated with a flexible polymer sheath layer. The polymer solution concentration is controlled at 10%-30%, and the impregnation time is 10-30 seconds.

[0017] Preparation of S300 composite material: The surface-modified high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles in S100 are uniformly dispersed in a flexible polymer matrix solution, wherein the mass ratio of high thermal conductivity carbon-based microspheres to magnetic microwave absorbing nanoparticles is 3:1-1:3. The dispersion process is carried out by ultrasonic and high-speed stirring in combination, with ultrasonic power of 300-500W and stirring speed of 1000-1500rpm.

[0018] S400, Dispersion and Mixing: The flexible thermally conductive and microwave-absorbing fiber obtained by S200 is added to the dispersion system of S300 at a volume fraction of 5%-20%, and the blend is obtained by twin-screw extrusion process. The temperature of each zone of the twin screw is set to 150-250℃, and the screw speed is 80-120rpm.

[0019] S500, Stepwise Curing: The blend is cured according to a stepwise curing process, which includes preliminary curing, vacuum degassing and secondary curing, to obtain a flexible, highly thermally conductive, microwave-absorbing composite material.

[0020] Furthermore, in the S100 mixture of silane coupling agent and metal alkoxide, the mass ratio of silane coupling agent to metal alkoxide is 1:2-2:1.

[0021] Furthermore, in the S300 process, when ultrasound and high-speed stirring are used in synergistic treatment, ultrasound treatment is performed for 10-20 minutes first, followed by high-speed stirring for 20-30 minutes, and this process is repeated 2-3 times.

[0022] Furthermore, the S500 is initially cured at 60-80℃ for 1-2 hours, so that the highly thermally conductive carbon-based microspheres and magnetic microwave-absorbing nanoparticles are initially fixed in the matrix.

[0023] Furthermore, the S500 vacuum degassing process involves vacuum degassing between pre-curing and secondary curing, achieving a vacuum level of 0.01-0.1 Pa and a degassing time of 30-60 minutes.

[0024] Furthermore, the S500 secondary curing is carried out at 120-150℃ for 2-4 hours.

[0025] Compared with existing technologies, this flexible, highly thermally conductive microwave absorbing composite material and its preparation method have the following advantages:

[0026] I. The flexible, high thermal conductivity microwave absorbing composite material of the present invention, through a special material combination and structural design, endows the composite material with good bendability and tensile strength through its flexible polymer matrix and flexible thermally conductive microwave absorbing fibers, enabling it to adapt to various complex deformation requirements. In terms of high thermal conductivity, the high thermal conductivity carbon-based microspheres and the high thermal conductivity metal core layer in the flexible thermally conductive microwave absorbing fibers work together to construct an efficient heat conduction network, which can quickly dissipate heat, effectively reduce the internal temperature of the material, and avoid performance degradation caused by heat accumulation. As for microwave absorption performance, the magnetic microwave absorbing nanoparticles and the microwave absorbing material layer in the flexible thermally conductive microwave absorbing fibers work synergistically to efficiently absorb electromagnetic waves in a wide frequency band, reduce the impact of electromagnetic interference on the surrounding environment and equipment, and ensure the stable operation of electronic equipment.

[0027] II. The composite material preparation method of the present invention adopts a stepwise curing process combined with vacuum degassing, which effectively solves the problems of dispersion of high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles in flexible polymer matrix and the interfacial bonding with the matrix. In the stepwise curing process, pre-curing is performed first to fix the particles initially, then vacuum degassing is performed to remove air bubbles, and finally secondary curing is performed to strengthen the bonding, so that the particles are uniformly and stably dispersed in the matrix, avoiding agglomeration and phase separation, and ensuring the consistency and stability of the composite material properties.

[0028] Other advantages, objectives and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination or study, or may be learned from the practice of the invention. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0030] Figure 1 This is a flowchart of a method for preparing a flexible, highly thermally conductive microwave absorbing composite material. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] A flexible, highly thermally conductive, microwave-absorbing composite material is composed of a flexible polymer matrix, highly thermally conductive carbon-based microspheres, magnetic microwave-absorbing nanoparticles, and flexible thermally conductive, microwave-absorbing fibers. Specifically:

[0033] Regarding the flexible polymer matrix, the selected silicone rubber (accounting for 30%-50% of the total mass of the composite material) has a molecular chain structure that can freely stretch, contract, and bend, effectively buffering external stress. This allows the composite material to withstand repeated stretching, compression, and bending deformation without breaking or losing its properties, providing a stable and elastic basic framework for the entire composite material.

[0034] The high thermal conductivity carbon-based microspheres consist of graphene microspheres (40%-60% of the total mass) and carbon nanotube microspheres (40%-60% of the total mass), together accounting for 15%-25% of the total mass of the composite material. Graphene microspheres can rapidly conduct heat in a plane; carbon nanotube microspheres construct efficient three-dimensional heat conduction channels. The synergistic effect of the two greatly improves the thermal conductivity of the composite material in all directions, promptly and evenly dispersing and conducting heat away, effectively reducing the risk of material performance degradation due to localized overheating.

[0035] The magnetic absorbing nanoparticles comprise ferrite nanoparticles (40%-60% of the total mass of the magnetic absorbing nanoparticles) and carbonyl iron powder nanoparticles (40%-60% of the total mass of the magnetic absorbing nanoparticles), accounting for 10%-20% of the total mass of the composite material. Ferrite nanoparticles effectively absorb electromagnetic waves in specific frequency bands and convert them into heat energy; carbonyl iron powder nanoparticles enhance the magnetic coupling effect on electromagnetic waves. The two work together to broaden the absorption frequency band and absorption intensity of the composite material for electromagnetic waves, significantly reducing electromagnetic wave reflection and transmission, and effectively minimizing the impact of electromagnetic interference on surrounding electronic equipment and systems.

[0036] The flexible thermally conductive and microwave-absorbing fiber is composed of a coaxial structure. The core layer is made of copper wire, the middle layer is made of silicon carbide (40%-60% of the total mass of the microwave-absorbing material layer) and boron nitride (40%-60% of the total mass of the microwave-absorbing material layer), and the outer layer is made of polyimide (40%-60% of the total mass of the flexible polymer sheath) or polyester (40%-60% of the total mass of the flexible polymer sheath), with a volume fraction of 5%-20% in the composite material. The copper wire in the core layer serves as the main heat conduction path, rapidly conducting heat to both ends of the fiber. The middle layer microwave-absorbing material efficiently absorbs and converts electromagnetic waves of specific frequency bands. The outer flexible polymer sheath ensures the flexibility of the fiber while isolating it from external environmental erosion and damage to the internal structure, and promotes good bonding between the fiber and the flexible polymer matrix.

[0037] Example 1

[0038] This embodiment will describe in detail the specific implementation process of a method for preparing a flexible, high thermal conductivity, microwave absorbing composite material, and control the content of different components to present different performance results.

[0039] Surface modification of S100, high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles: Graphene microspheres (60% of the total mass of high thermal conductivity carbon-based microspheres), carbon nanotube microspheres (40%), ferrite nanoparticles (60% of the total mass of magnetic microwave absorbing nanoparticles), and carbonyl iron powder nanoparticles (40%) were respectively placed in a mixed solution containing silane coupling agent and metal alkoxide (the mass ratio of silane coupling agent to metal alkoxide was 1:2) for surface modification. The modification reaction temperature was controlled at 40℃ and the reaction time was 6 hours to obtain surface-modified high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles.

[0040] Preparation of S200 flexible thermally conductive and microwave-absorbing fiber: Copper wire is used as the core material and a microwave-absorbing material layer (silicon carbide accounts for 60% of the total mass of the microwave-absorbing material layer and boron nitride accounts for 40%) is deposited on the surface. The deposition temperature is controlled at 300℃, the pressure is 5kPa, and the deposition rate is 0.1μm / min. A flexible polymer sheath layer (polyimide accounts for 60% of the total mass of the flexible polymer sheath layer and polyester accounts for 40%) is wrapped around the microwave-absorbing material layer by impregnation coating. The polymer solution concentration is controlled at 10%, and the impregnation time is 30 seconds.

[0041] S300, Preparation of composite material: Surface-modified high thermal conductivity carbon-based microspheres and magnetic microwave-absorbing nanoparticles are uniformly dispersed in a silicone rubber matrix solution, wherein the mass ratio of high thermal conductivity carbon-based microspheres to magnetic microwave-absorbing nanoparticles is 3:1. The dispersion process adopts a combination of ultrasonic treatment and high-speed stirring. First, ultrasonic treatment is performed for 10 minutes, followed by high-speed stirring for 30 minutes, and this process is repeated 3 times. The ultrasonic power is 300W and the stirring speed is 1500rpm.

[0042] S400, Dispersion and Mixing: The prepared flexible thermally conductive and microwave-absorbing fibers are added to the dispersion system at a volume fraction of 5%, and the mixture is blended by a twin-screw extrusion process to obtain a blend. The temperature of each zone of the twin screw is set to 150°C, and the screw speed is 120 rpm.

[0043] S500, Stepwise Curing: The blend is first pre-cured at 60℃ for 2 hours to initially fix the high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles in the matrix. Then, vacuum degassing is performed between pre-curing and secondary curing, with a vacuum degree of 0.01 Pa and a degassing time of 60 minutes. Finally, secondary curing is performed at 120℃ for 4 hours to obtain a flexible high thermal conductivity microwave absorbing composite material.

[0044] Performance test results: When the tensile strain reaches 30%, the combined index of microwave absorption performance and thermal conductivity of this composite material decreases by 8%. After repeated folding 800 times, the microwave absorption bandwidth changes by 8% and the thermal conductivity remains at a high level, with a thermal conductivity of 8 W / (m·K). The microwave absorption rate reaches more than 90% in the 8-12 GHz frequency band.

[0045] Example 2

[0046] Surface modification of S100, high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles: Graphene microspheres (50% of the total mass of high thermal conductivity carbon-based microspheres), carbon nanotube microspheres (50%), ferrite nanoparticles (50% of the total mass of magnetic microwave absorbing nanoparticles), and carbonyl iron powder nanoparticles (50%) were respectively placed in a mixed solution containing silane coupling agent and metal alkoxide (the mass ratio of silane coupling agent to metal alkoxide was 1.5:1.5) for surface modification. The modification reaction temperature was controlled at 50℃ and the reaction time was 4.5 hours to obtain surface-modified high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles.

[0047] Preparation of S200 flexible thermally conductive and microwave-absorbing fiber: Copper wire is used as the core material to deposit a microwave-absorbing material layer (silicon carbide accounts for 50% of the total mass of the microwave-absorbing material layer, and boron nitride accounts for 50%) on its surface. The deposition temperature is controlled at 400℃, the pressure is 3kPa, and the deposition rate is 0.3μm / min. Then, a flexible polymer sheath layer (polyimide accounts for 50% of the total mass of the flexible polymer sheath layer, and polyester accounts for 50%) is wrapped around the microwave-absorbing material layer by impregnation coating. The polymer solution concentration is controlled at 20%, and the impregnation time is 20 seconds.

[0048] S300, Preparation of composite material: Surface-modified high thermal conductivity carbon-based microspheres and magnetic microwave-absorbing nanoparticles are uniformly dispersed in a silicone rubber matrix solution, wherein the mass ratio of high thermal conductivity carbon-based microspheres to magnetic microwave-absorbing nanoparticles is 2:1. The dispersion process adopts a combination of ultrasonic treatment and high-speed stirring. First, ultrasonic treatment is performed for 15 minutes, followed by high-speed stirring for 25 minutes, and this process is repeated 2.5 times. The ultrasonic power is 400W and the stirring speed is 1200rpm.

[0049] S400, Dispersion and Mixing: The prepared flexible thermally conductive and microwave-absorbing fibers are added to the dispersion system at a volume fraction of 12%, and the mixture is blended by a twin-screw extrusion process to obtain a blend. The temperature of each zone of the twin screw is set to 200℃, and the screw speed is 100rpm.

[0050] S500, Stepwise Curing: The blend is first pre-cured at 70℃ for 1.5 hours to initially fix the high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles in the matrix. Then, vacuum degassing is performed between pre-curing and secondary curing, with a vacuum degree of 0.05 Pa and a degassing time of 45 minutes. Finally, secondary curing is performed at 135℃ for 3 hours to obtain a flexible high thermal conductivity microwave absorbing composite material.

[0051] Performance test results: When the tensile strain reaches 30%, the combined index of microwave absorption performance and thermal conductivity of this composite material decreases by 6%. After repeated folding 800 times, the microwave absorption bandwidth changes by 6% and the thermal conductivity remains at a high level, with a thermal conductivity of 10 W / (m·K). The microwave absorption rate reaches more than 92% in the 6-10 GHz frequency band.

[0052] Example 3

[0053] Surface modification of S100, high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles: Graphene microspheres (40% of the total mass of high thermal conductivity carbon-based microspheres), carbon nanotube microspheres (60%), ferrite nanoparticles (40% of the total mass of magnetic microwave absorbing nanoparticles), and carbonyl iron powder nanoparticles (60%) were respectively placed in a mixed solution containing silane coupling agent and metal alkoxide (the mass ratio of silane coupling agent to metal alkoxide was 2:1) for surface modification. The modification reaction temperature was controlled at 60℃ and the reaction time was 3 hours to obtain surface-modified high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles.

[0054] Preparation of S200 flexible thermally conductive and microwave-absorbing fiber: Copper wire is used as the core material and a microwave-absorbing material layer (silicon carbide accounts for 40% of the total mass of the microwave-absorbing material layer and boron nitride accounts for 60%) is deposited on its surface. The deposition temperature is controlled at 500℃, the pressure is 1kPa, and the deposition rate is 0.5μm / min. Then, a flexible polymer sheath layer (polyimide accounts for 40% of the total mass of the flexible polymer sheath layer and polyester accounts for 60%) is wrapped around the microwave-absorbing material layer by impregnation. The polymer solution concentration is controlled at 30%, and the impregnation time is 10 seconds.

[0055] S300, Preparation of composite material: Surface-modified high thermal conductivity carbon-based microspheres and magnetic microwave-absorbing nanoparticles are uniformly dispersed in a silicone rubber matrix solution, wherein the mass ratio of high thermal conductivity carbon-based microspheres to magnetic microwave-absorbing nanoparticles is 1:1. The dispersion process adopts a combination of ultrasonic treatment and high-speed stirring. First, ultrasonic treatment is performed for 20 minutes, followed by high-speed stirring for 20 minutes, and this process is repeated twice. The ultrasonic power is 500W and the stirring speed is 1000rpm.

[0056] S400, Dispersion and Mixing:

[0057] The prepared flexible thermally conductive and microwave-absorbing fibers were added to the dispersion system at a volume fraction of 20%, and the mixture was blended by a twin-screw extrusion process to obtain a blend. The temperature of each zone of the twin screw was set to 250℃, and the screw speed was 80rpm.

[0058] S500, Stepwise Curing: The blend is first pre-cured at 80℃ for 1 hour to initially fix the high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles in the matrix. Then, vacuum degassing is performed between pre-curing and secondary curing, with a vacuum degree of 0.1 Pa and a degassing time of 30 minutes. Finally, secondary curing is performed at 150℃ for 2 hours to obtain a flexible high thermal conductivity microwave absorbing composite material.

[0059] Performance test results: When the tensile strain reaches 30%, the combined index of microwave absorption performance and thermal conductivity of this composite material decreases by 5%. After repeated folding 800 times, the microwave absorption bandwidth changes by 5% and the thermal conductivity remains at a high level, with a thermal conductivity of 12W / (m·K). The microwave absorption rate reaches more than 95% in the 4-8GHz frequency band.

[0060] Example 4

[0061] Surface modification of S100, high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles: Graphene microspheres (45% of the total mass of high thermal conductivity carbon-based microspheres), carbon nanotube microspheres (55%), ferrite nanoparticles (45% of the total mass of magnetic microwave absorbing nanoparticles), and carbonyl iron powder nanoparticles (55%) were respectively placed in a mixed solution containing silane coupling agent and metal alkoxide (the mass ratio of silane coupling agent to metal alkoxide was 1.8:1.2) for surface modification. The modification reaction temperature was controlled at 45℃ and the reaction time was 5 hours to obtain surface-modified high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles.

[0062] Preparation of S200 flexible thermally conductive and microwave-absorbing fiber: A microwave-absorbing material layer (silicon carbide accounts for 45% of the total mass of the microwave-absorbing material layer and boron nitride accounts for 55%) is deposited on the surface of copper wire as the core material. The deposition temperature is controlled at 350℃, the pressure is 4kPa, and the deposition rate is 0.2μm / min. Then, a flexible polymer sheath layer (polyimide accounts for 45% of the total mass of the flexible polymer sheath layer and polyester accounts for 55%) is wrapped around the microwave-absorbing material layer by impregnation coating. The polymer solution concentration is controlled at 15%, and the impregnation time is 15 seconds.

[0063] S300, Preparation of composite material: Surface-modified high thermal conductivity carbon-based microspheres and magnetic microwave-absorbing nanoparticles are uniformly dispersed in a silicone rubber matrix solution, wherein the mass ratio of high thermal conductivity carbon-based microspheres to magnetic microwave-absorbing nanoparticles is 1.5:1. The dispersion process adopts a combination of ultrasonic treatment and high-speed stirring. First, ultrasonic treatment is performed for 18 minutes, followed by high-speed stirring for 22 minutes, and this process is repeated 2.2 times. The ultrasonic power is 350W and the stirring speed is 1300rpm.

[0064] S400, Dispersion and Mixing: The prepared flexible thermally conductive and microwave-absorbing fibers are added to the dispersion system at a volume fraction of 15%, and the mixture is blended by a twin-screw extrusion process to obtain a blend. The temperature of each zone of the twin screw is set to 180°C, and the screw speed is 110 rpm.

[0065] S500, Stepwise Curing: The blend is first pre-cured at 65℃ for 1.8 hours to initially fix the high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles in the matrix. Then, vacuum degassing is performed between pre-curing and secondary curing, with a vacuum degree of 0.03 Pa and a degassing time of 50 minutes. Finally, secondary curing is performed at 130℃ for 3.5 hours to obtain a flexible high thermal conductivity microwave absorbing composite material.

[0066] Performance test results: When the tensile strain reaches 30%, the combined index of microwave absorption performance and thermal conductivity of this composite material decreases by 7%. After repeated folding 800 times, the microwave absorption bandwidth changes by 7% and the thermal conductivity remains at a high level, with a thermal conductivity of 9W / (m·K). The microwave absorption rate reaches over 91% in the 7-11GHz frequency band.

[0067] Example 5

[0068] Surface modification of S100, high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles: Graphene microspheres (55% of the total mass of high thermal conductivity carbon-based microspheres), carbon nanotube microspheres (45%), ferrite nanoparticles (55% of the total mass of magnetic microwave absorbing nanoparticles), and carbonyl iron powder nanoparticles (45%) were respectively placed in a mixed solution containing silane coupling agent and metal alkoxide (the mass ratio of silane coupling agent to metal alkoxide was 1.2:1.8) for surface modification. The modification reaction temperature was controlled at 55℃ and the reaction time was 4 hours to obtain surface-modified high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles.

[0069] Preparation of S200 flexible thermally conductive and microwave-absorbing fiber: Copper wire is used as the core material to deposit a microwave-absorbing material layer (silicon carbide accounts for 55% of the total mass of the microwave-absorbing material layer, and boron nitride accounts for 45%) on its surface. The deposition temperature is controlled at 450℃, the pressure is 2kPa, and the deposition rate is 0.4μm / min. Then, a flexible polymer sheath layer (polyimide accounts for 55% of the total mass of the flexible polymer sheath layer, and polyester accounts for 45%) is wrapped around the microwave-absorbing material layer by impregnation coating. The polymer solution concentration is controlled at 25%, and the impregnation time is 25 seconds.

[0070] S300, Preparation of composite material: Surface-modified high thermal conductivity carbon-based microspheres and magnetic microwave-absorbing nanoparticles are uniformly dispersed in a silicone rubber matrix solution, wherein the mass ratio of high thermal conductivity carbon-based microspheres to magnetic microwave-absorbing nanoparticles is 2.5:1. The dispersion process adopts a combination of ultrasonic treatment and high-speed stirring. First, ultrasonic treatment is performed for 12 minutes, followed by high-speed stirring for 28 minutes, and this process is repeated 2.8 times. The ultrasonic power is 450W and the stirring speed is 1100rpm.

[0071] S400, Dispersion and Mixing: The prepared flexible thermally conductive and microwave-absorbing fibers are added to the dispersion system at a volume fraction of 18%, and the mixture is blended by a twin-screw extrusion process to obtain a blend. The temperature of each zone of the twin screw is set to 220°C, and the screw speed is 90 rpm.

[0072] S500, Stepwise Curing: The blend is first pre-cured at 75℃ for 1.2 hours to initially fix the high thermal conductivity carbon-based microspheres and magnetic microwave-absorbing nanoparticles in the matrix. Then, vacuum degassing is performed between the pre-curing and secondary curing, with a vacuum degree of 0.08 Pa and a degassing time of 40 minutes. Finally, secondary curing is performed at 140℃ for 2.5 hours to obtain a flexible high thermal conductivity microwave-absorbing composite material.

[0073] Performance test results: When the tensile strain reaches 30%, the combined index of microwave absorption performance and thermal conductivity of the composite material decreases by 9%. After repeated folding 800 times, the microwave absorption bandwidth changes by 9% and the thermal conductivity remains at a high level, with a thermal conductivity of 11 W / (m·K). The microwave absorption rate reaches more than 93% in the 5-9 GHz frequency band.

[0074] Comparative Example

[0075] This comparative example uses conventional preparation methods, without surface modification of the high thermal conductivity carbon-based microspheres and magnetic microwave absorbing nanoparticles, and without stepwise curing and vacuum degassing treatment during the preparation of the composite material.

[0076] Unmodified graphene microspheres, carbon nanotube microspheres, ferrite nanoparticles, and carbonyl iron powder nanoparticles were simply mixed with a silicone rubber matrix. Meanwhile, flexible thermally conductive and microwave-absorbing fibers, made of copper wire as the core material, silicon carbide and boron nitride as microwave-absorbing material layers, and polyimide or polyester as a flexible polymer sheath layer, were directly added to the mixing system. After ordinary stirring and mixing, the composite material was obtained by curing at 100°C for 6 hours.

[0077] Performance test results: When the tensile strain reaches 20%, the combined index of microwave absorption performance and thermal conductivity of this composite material decreases by more than 20%. After repeated folding 500 times, the microwave absorption frequency band width changes by more than 20% and the thermal conductivity decreases significantly, with a thermal conductivity of only 5 W / (m·K). The highest microwave absorption rate in the 8-12 GHz frequency band is only about 70%.

[0078] In summary, the performance test results of the high thermal conductivity microwave absorbing composite materials prepared in Examples 1, 2, 3, 4, 5, and the comparative example are shown in the table below:

[0079]

[0080] As shown in the table above, it is clear from the data that each embodiment has its own unique characteristics in terms of the performance of the flexible, high thermal conductivity, and microwave absorbing composite material, and all are significantly better than the comparative example. In terms of tensile strain performance, when the tensile strain reaches 30%, the combined microwave absorption and thermal conductivity performance of Examples 1-5 is controlled between 5% and 9%, while the comparative example shows a decrease of more than 20% when the tensile strain is only 20%. This indicates that the preparation method of the present invention effectively improves the performance stability of the material during the deformation process.

[0081] Regarding repeated folding performance, the absorption band width of the embodiments changed by 5%-9% after 800 folds, while the comparative example changed by more than 20% after 500 folds, highlighting the advantages of the present invention in ensuring material flexibility and absorption stability. In terms of thermal conductivity, the embodiments 1-5 can reach 8-12 W / (m·K), which is much higher than the comparative example's 5 W / (m·K), indicating that the material combination and process of the present invention can significantly improve thermal conductivity. In terms of absorption rate, the embodiments can achieve a high absorption rate of more than 90% in their respective specific frequency bands, while the comparative example is only about 70% in the same frequency band, further confirming the excellent effect of the present invention in absorption performance. In summary, the preparation method and material design of the present invention successfully achieve a good combination of flexibility, high thermal conductivity and strong absorption, with significant innovation and practicality, showing great application potential in related material fields.

[0082] In summary, the study of the above embodiments shows that the preparation method of the flexible high thermal conductivity microwave absorbing composite material of the present invention has high flexibility and controllability. By adjusting the composition ratio of high thermal conductivity carbon-based microspheres, magnetic microwave absorbing nanoparticles, and flexible thermal conductivity microwave absorbing fibers, as well as the key parameters in the preparation process, the performance of the composite material can be precisely controlled, demonstrating the technological advancement of the present invention.

[0083] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A high thermal conductive wave-absorbing composite material with flexibility, characterized in that, The composite material is composed of a flexible high polymer matrix, high-thermal-conductivity carbon-based microspheres, magnetic wave-absorbing nanoparticles and flexible thermal-conductivity wave-absorbing fibers, specifically comprising: The flexible high polymer matrix is made of silicone rubber material as the matrix, accounting for 30%-50% of the total mass of the composite material, and the flexible high polymer matrix uniformly disperses the high-thermal-conductivity carbon-based microspheres and the magnetic wave-absorbing nanoparticles which have been surface modified; The high-thermal-conductivity carbon-based microspheres are made of graphene microspheres and carbon nanotube microspheres, accounting for 15%-25% of the total mass of the composite material; The magnetic wave-absorbing nanoparticles account for 10%-20% of the total mass of the composite material; The surface modification of the high-thermal-conductivity carbon-based microspheres and the magnetic wave-absorbing nanoparticles is a siloxane and metal oxide composite layer; The flexible thermal-conductivity wave-absorbing fiber is composed of a coaxial structure, which includes a core layer, an intermediate layer and an outer layer. The core layer is a high-thermal-conductivity metal wire copper wire that transmits heat to both ends of the fiber. The intermediate layer is a wave-absorbing material layer, which is made of silicon carbide and boron nitride. The outer layer is a flexible polymer sheath layer, which includes polyimide and polyester.

2. The high thermal conductive and wave absorbing composite material with flexibility according to claim 1, characterized in that, The volume fraction of the flexible thermal-conductivity wave-absorbing fiber in the composite material is 5%-20%.

3. The high thermal conductive and wave absorbing composite material with flexibility according to claim 1, characterized in that, The mass ratio of the high-thermal-conductivity carbon-based microspheres to the magnetic wave-absorbing nanoparticles is 3:1-1:

3.

4. The high thermal and wave absorbing composite material with flexibility according to claim 1, characterized in that, The magnetic wave-absorbing nanoparticles include ferrite nanoparticles and carbonyl iron powder nanoparticles.

5. A method for preparing a flexible high thermal conductive and wave-absorbing composite material, which is suitable for the flexible high thermal conductive and wave-absorbing composite material according to any one of claims 1-4, characterized in that, The specific steps of the preparation method are as follows: S100, surface modification of high-thermal-conductivity carbon-based microspheres and magnetic wave-absorbing nanoparticles: the high-thermal-conductivity carbon-based microspheres and the magnetic wave-absorbing nanoparticles are respectively placed in a mixed solution containing silane coupling agent and metal alkoxide for surface modification, the modification reaction temperature is controlled at 40-60℃, and the reaction time is 3-6 hours, to obtain the surface-modified high-thermal-conductivity carbon-based microspheres and the magnetic wave-absorbing nanoparticles; S200, preparation of flexible thermal-conductivity wave-absorbing fiber: the high-thermal-conductivity metal wire is used as the core material to deposit a wave-absorbing material layer on its surface, the deposition temperature is controlled at 300-500℃, the pressure is 1-5kPa, and the deposition rate is 0.1-0.5μm / min. The wave-absorbing material layer after deposition is immersed and coated with a flexible polymer sheath layer outside the wave-absorbing material layer, and the polymer solution concentration is controlled at 10%-30%, and the immersion time is 10-30 seconds; S300, preparation of the composite material: the surface-modified high-thermal-conductivity carbon-based microspheres and the magnetic wave-absorbing nanoparticles in S100 are uniformly dispersed in the flexible high polymer matrix solution, and the mass ratio of the high-thermal-conductivity carbon-based microspheres to the magnetic wave-absorbing nanoparticles is 3:1-1:

3. The dispersion process adopts ultrasonic and high-speed stirring cooperative treatment, the ultrasonic power is 300-500W, and the stirring speed is 1000-1500rpm; S400, dispersion and mixing: the flexible thermal-conductivity wave-absorbing fiber prepared in S200 is added to the dispersion system of S300 at a volume fraction of 5%-20%, and a blend is obtained through a double-screw extrusion process. The temperature of each zone of the double-screw is set at 150-250℃, and the screw rotation speed is 80-120rpm. S500, curing by steps: the blend is cured by a curing process by steps, which includes preliminary curing, vacuum degassing and secondary curing, to obtain a high-thermal-conductivity wave-absorbing composite material with flexibility.

6. The method of claim 5, wherein the high thermal conductive wave absorbing composite material with flexibility is prepared by the following steps. The mass ratio of the silane coupling agent to the metal alkoxide in the mixed solution of the silane coupling agent and the metal alkoxide in S100 is 1:2-2:

1.

7. The method according to claim 5, wherein the high thermal conductive wave-absorbing composite material has flexibility. In S300, the ultrasonic treatment is performed for 10-20 minutes, and then the high-speed stirring is performed for 20-30 minutes, and the two steps are alternately performed for 2-3 times. 8.The method for preparing a high-thermal-conductivity wave-absorbing composite material with flexibility according to claim 5, characterized in that, In S500, the preliminary curing is pre-curing at 60-80℃ for 1-2 hours, so that the high-thermal-conductivity carbon-based microspheres and the magnetic wave-absorbing nanoparticles are preliminarily fixed in the matrix.

9. The method of claim 5, wherein the high thermal conductive wave absorbing composite material has flexibility. In S500, the vacuum degassing is performed between the pre-curing and the secondary curing, the vacuum degree reaches 0.01-0.1 Pa, and the degassing time is 30-60 minutes. 10.The method for preparing a high-thermal-conductivity wave-absorbing composite material with flexibility according to claim 5, characterized in that, In S500, the secondary curing is performed at 120-150℃ for 2-4 hours.

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