An oriented multilayer thermal conductive absorber and its preparation method

Abstract

The present invention discloses an oriented multilayer thermal conductive absorber and a preparation method. The preparation method comprises: mixing a thermal conductor, a binder, a solvent, and a curing agent to obtain a mixture; placing the mixture in a magnetic field perpendicular to the horizontal plane so that the thermal conductor aligns along the magnetic field; and heating and curing the mixture to form a magnetron thermal conductive layer; mixing a binder, a wave absorber, a solvent, and a curing agent to obtain a mixture; pouring the mixture onto the magnetron thermal conductive layer; placing the mixture in a rotating magnetic field parallel to the horizontal plane so that the wave absorber aligns along the magnetic field; and heating and curing the mixture to form a magnetron thermal conductive absorber layer; and mixing a binder, a wave absorber, a solvent, and a curing agent to obtain a mixture; pouring the mixture onto the magnetron thermal conductive absorber layer; and placing the mixture in a magnetic field perpendicular to the magnetic conductive absorber layer so that the wave absorber aligns along the magnetic field; and heating and curing the mixture to form a magnetron matching layer. The preparation method of the oriented multilayer thermal conductive absorber proposed by the present invention is simple and controllable, and the resulting absorber has excellent thermal conductivity and wave absorption properties.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave absorption, and in particular to an oriented multilayer heat-conducting absorber and a preparation method thereof. Background Art

[0002] With the rapid development of electronic and electrical technologies such as aerospace weapons and equipment, high-precision intelligent control systems, and fifth-generation mobile communication technology terminals and base stations, the heat generated by electronic and electrical equipment and components during operation has rapidly accumulated, inevitably leading to local overheating problems in electronic products and their components, affecting the operating performance, lifespan, and reliability of electronic equipment and their components. The resulting electromagnetic radiation also interferes with the normal operation of surrounding equipment and components, posing a threat to the health of surrounding personnel (especially operators) and causing significant electromagnetic wave pollution to the outside world. Therefore, the design and development of integrated thermal conductive / electromagnetic shielding polymer composites is imperative to solve these thermal conductive / electromagnetic pollution problems.

[0003] The general solution now is to combine materials with different functions to achieve dual performance improvements in heat conduction and wave absorption. For example, the Chinese patent application document with publication number CN114395310A proposed a GO / Fe / Fe3O4 / epoxy resin thermal conductive and wave absorbing integrated coating and its preparation method. The patent uses graphene oxide (GO) combined with Fe, Fe3O4 nanoparticles and epoxy resin to blend into a thermal conductive and wave absorbing material; the Chinese patent application document with publication number CN108659535A proposed a thermal conductive and wave absorbing material for ETC devices. The patent uses graphene and iron hydroxide blended as fillers and organic silicon to mix evenly to make a thermal conductive and wave absorbing material; the Chinese patent application document with publication number CN114133740A proposed a thermal conductive and wave absorbing silicone rubber composite material and its preparation method, the patent uses flaky graphene loaded with nickel-zinc ferrite particles and boron nitride nanosheets loaded with nickel-zinc ferrite particles to form a thermal conductive and absorbing material; the Chinese patent application document with publication number CN113929963A proposes a thermal conductive and absorbing sheet and its preparation method, the patent uses graphene-coated ferrite system particles and silicone rubber mixed and filled in porous elastic foam to make a thermal conductive and absorbing material; the Chinese patent application document with publication number CN216359814U proposes a three-dimensional thermal conductive and absorbing enhanced composite film, the patent uses a graphene layer connected to a MXene layer, and opens through holes to fill diamond particles and graphene film to make a thermal conductive and absorbing material; the Chinese patent application document with publication number C The Chinese patent application document No. N111031776A proposes a heat-conducting absorbing gasket, which stacks two heat-conducting absorbing layers and at least one conductive flexible layer into a heat-conducting absorbing material by conductive glue or heated rolling; the Chinese patent application document No. CN112519347A proposes a high-heat-conducting absorbing shielding gasket and its production process, which uses a double-roll calender to calender a heat-conducting absorbing base material, a release film and a metal layer to form a five-layer structure of heat-conducting absorbing material; the Chinese patent application document No. CN112194903A proposes a preparation method for a heat-conducting absorbing silicone composite material, which mixes boron nitride nanosheets, heat-conducting powder and M Xene nanosheets are composited to form a thermally conductive and absorbing material. Chinese patent application publication number CN110964480A proposes a graphene oxide / ferroferric oxide / zinc oxide composite material and its preparation method. This material is obtained by compounding ferroferric oxide and zinc oxide on the surface of graphene oxide and further coating the surface with an inorganic nanomaterial with a high thermal conductivity coefficient. Chinese patent application publication number CN115246994A proposes an integrated thermally conductive and absorbing flexible material, its preparation method, and application. This patent fills graphene, polypyrrole, and a thermally conductive filler into a silicone oil matrix and uses a release paper sheeting and curing film-forming process to prepare the thermally conductive and absorbing material.

[0004] Based on the above-mentioned patent introductions and related papers on thermal conductivity and wave absorption, we can find that in the process of compounding thermal conductive / wave absorbing materials: 1) the vast majority adopt a multi-phase (wave absorbing phase, heat conductive phase) composite method; 2) the vast majority adopt a two-phase mixing method in a matrix, with a small number using a layered stacking method. As a result, the resulting absorber is difficult to achieve dual high-efficiency thermal conductivity and wave absorption performance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an oriented multilayer thermal conductive absorber and a preparation method thereof. The preparation method is simple and controllable, and the obtained absorber has excellent thermal conductivity and wave absorbing performance.

[0006] The present invention solves the above technical problems through the following technical means:

[0007] A method for preparing an oriented multilayer thermally conductive absorber comprises the following steps:

[0008] S1. Evenly mixing a thermal conductor, a binder, a solvent, and a curing agent to obtain a mixture, placing the mixture in a magnetic field perpendicular to a horizontal plane so that the thermal conductor is aligned along the magnetic field, and heating and curing the mixture to form a magnetically controlled thermal conductive layer;

[0009] S2. Mixing a binder, a wave absorbing agent, a solvent, and a curing agent to obtain a mixture, pouring the mixture onto the magnetron thermal conductive layer prepared in S1, allowing the mixture to stand in a rotating magnetic field parallel to the horizontal plane so that the wave absorbing agent is aligned along the magnetic field direction, and heating and curing the mixture to form the magnetron thermal conductive wave absorbing layer;

[0010] S3. Evenly mix a binder, an absorber, a solvent, and a curing agent to obtain a mixture, and pour the mixture onto the magnetron thermal conductive absorbing layer formed in S2. Then, the mixture is allowed to stand in a magnetic field perpendicular to the magnetic conductive absorbing layer so that the absorber is aligned along the magnetic field. After heating and curing, the magnetron matching layer is formed to obtain the oriented multilayer thermal conductive absorbing body.

[0011] Preferably, in S1, in the mixture, the weight percentage of the thermal conductor is 3-10%, the weight percentage of the binder and the curing agent is 35-67%, the mass ratio of the binder and the curing agent is between 1:1 and 1:2, and the weight percentage of the solvent is 30-55%.

[0012] Preferably, in S1 and S3, the intensity of the magnetic field is 850-2000 Gs, the standing temperature is room temperature, and the standing time is 3 hours.

[0013] Preferably, in S2, in the mixture, the weight percentage of the absorber is 3-10%, the weight percentage of the binder and the curing agent is 35-67%, the mass ratio of the binder to the curing agent is between 1:1 and 1:2, and the weight percentage of the solvent is 30-55%.

[0014] Preferably, in S2, the intensity of the magnetic field is 850-2000 Gauss, and the rotation speed is 3-15 rpm.

[0015] Preferably, in S3, in the mixture, the weight percentage of the absorber is 3-10%, the weight percentage of the binder and the curing agent is 35-67%, the mass ratio of the binder to the curing agent is between 1:1 and 1:2, and the weight percentage of the solvent is 30-55%.

[0016] Preferably, in S1, the thermal conductor includes one of graphite sheets, graphene, or a composite of one of graphite sheets, graphene and magnetic particles; in S1, S2 and S3, the binder is epoxy resin, the curing agent includes a combination of one or more of aniline formaldehyde resin, phenolic resin, furan resin, polyamide resin, polyester resin, polysulfide rubber, polyurethane, and tung oil anhydride resin, and the solvent includes a mixture of one or more of N-methylpyrrolidone, anhydrous ethanol, and deionized water; in S2 and S3, the absorber includes a mixture of one or more of biomass carbon sheets, graphite sheets, and graphene.

[0017] Preferably, the epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol glycidyl ether epoxy resin, glycidyl ester epoxy resin, and epoxidized olefin compound epoxy resin.

[0018] Preferably, the single layer thickness of the magnetron heat conducting layer, the magnetron heat conducting absorbing layer and the magnetron matching layer is 1-2 mm.

[0019] The present invention also provides an oriented multilayer heat-conducting absorber, which is prepared by using the preparation method of the oriented multilayer heat-conducting absorber.

[0020] The advantages of the present invention are:

[0021] 1) Simplifying from a multi-phase material to a single-phase material: Most existing thermal conductors and absorbers rely on a composite of a thermally conductive and absorbing material. Due to the limited filler ratio in the matrix, achieving both efficient thermal conductivity and absorption is difficult. Furthermore, the manufacturing process is complex and prone to the introduction of other impurities. This invention leverages the carbon-based sheet's unique combination of strong microwave absorption and high thermal conductivity, using a single carbon-based material as the functional medium.

[0022] 2) From simple composite to optimized three-layer structure: Traditional thermally conductive and absorbing materials are typically formed by adding a thermal conductor and an absorber to a polymer matrix. However, the amount of filler added to the polymer matrix has a maximum limit, making it difficult to achieve synergistic improvements in both thermal conductivity and absorption. This invention achieves efficient synergy in thermal conductivity and absorption at a low filler ratio by designing and stacking the absorber and thermally conductive thin layers.

[0023] 3) Ordered Sheet Preparation: Conventional methods for preparing thermally conductive and absorbing materials result in a haphazard distribution within the matrix, making it difficult to evenly mix the various fillers. This results in unstable thermal conductivity and absorption properties. The present invention utilizes directional and rotational magnetic control alignment to produce highly oriented thermal conductors and absorbers. The resulting thin layers exhibit high thermal conductivity and absorption orientation, avoiding disordered thermal conductivity and absorption losses, reducing the card-bridging structure of the sheet, and improving the overall thermal conductivity and absorption performance of the product, meeting application requirements. The magnetic control alignment method is simple, contactless, and allows for comprehensive control of filler orientation, layering the alignment of absorbers and thermal conductors to produce high-performance, oriented, multilayered thermally conductive and absorbing materials. This method provides a clean, low-cost method for preparing thermally conductive and absorbing materials.

[0024] 4) Multilayer Structure Design: Each layer performs its own function and cooperates with each other. The magnetron matching layer / magnetic thermal absorber layer is responsible for absorbing microwaves. The magnetron matching layer is a microwave matching layer. Its vertical orientation facilitates the channeling of incident microwaves into the material, reducing reflection losses. The magnetron thermal absorber layer is a functional absorbing layer. Its horizontal orientation facilitates multiple microwave reflections (increasing absorption paths) and the establishment of conductive channels (increasing conductivity / dielectric losses). The combination of the magnetron matching layer / magnetic thermal absorber layer improves absorption performance. The magnetron thermal absorber layer / magnetic absorber layer is responsible for heat conduction. The magnetron absorber layer is a longitudinal heat transfer layer. Its vertical orientation facilitates the transfer of heat from attached devices to the thermal absorber. The magnetron thermal absorber layer is a transverse heat transfer layer. Its horizontal orientation facilitates the transfer of heat laterally to heat sinks, preventing heat accumulation. The combination of the magnetron thermal absorber layer / magnetic absorber layer improves thermal conductivity. The present invention adopts magnetic fields of different configurations and a rotating preparation device to obtain sheet layer combinations with different orientations, thereby realizing a multi-layer heat-conducting absorber with high thermal conductivity, strong absorption and wide bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the overall structure of the oriented multilayer thermal conductive absorber in Example 1 of the present invention (left) and a diagram of the preparation method of each layer (right);

[0026] Description of the drawings: 1. Magnetron matching layer; 2. Magnetron thermal conductive wave absorbing layer; 3. Magnetron thermal conductive layer; 4. Wave absorbing agent; 5. Thermal conductive agent;

[0027] Figure 2 Schematic diagram comparing the wave absorbing performance of the absorbers prepared in Example 1 of the present invention and Comparative Example 1;

[0028] Figure 3 Schematic diagram comparing the thermal conductivity of the absorbers prepared in Example 1 of the present invention and Comparative Example 1;

[0029] Figure 4Schematic diagram comparing the wave absorbing performance of the absorbers prepared in Example 3 of the present invention and Comparative Example 2;

[0030] Figure 5 Schematic diagram comparing the thermal conductivity of the absorbers prepared in Example 3 of the present invention and Comparative Example 2. DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0032] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0033] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0034] Example 1

[0035] A method for preparing an oriented multilayer thermally conductive absorber comprises the following steps:

[0036] S1. Disperse 0.9 g of industrial graphite flakes in 50 ml of anhydrous ethanol, ultrasonicate for 2 h, and then dry the mixed solution in an oven at 100°C for 18 h until dry to obtain pretreated graphite flakes, which are used as thermal conductors and absorbers.

[0037] S2. Preparation of a magnetron thermal conductive layer: 0.3 g of pretreated graphite sheet was selected, and the pretreated graphite sheet, bisphenol A epoxy resin adhesive, N-methylpyrrolidone, and aniline formaldehyde resin were mixed uniformly in a mass ratio of 3:33.5:30:33.5 to obtain a mixture. The mixture was then placed in a magnetic field perpendicular to the horizontal plane so that the pretreated graphite sheet was aligned along the magnetic field direction to form a vertically oriented single-layer material. The magnetic field strength was 1000 Gs, the standing temperature was room temperature, and the standing time was 3 hours. The mixture was then placed in an oven at 70° C. and heated for 1 hour to obtain a magnetron thermal conductive layer with a thickness of 1 mm.

[0038] S3, preparation of a magnetron thermal conductive absorbing layer, selecting 0.3 g of pretreated graphite sheet, mixing the pretreated graphite sheet, bisphenol A epoxy resin adhesive, N-methylpyrrolidone, and aniline formaldehyde resin in a mass ratio of 3:33.5:30:33.5, and pouring the mixture onto the magnetron thermal conductive layer prepared in step S2 to obtain a mixture, and allowing the mixture to stand in a rotating magnetic field at 3 rpm with the magnetic field direction parallel to the horizontal plane so that the pretreated graphite sheet is aligned along the magnetic field direction to form a horizontally oriented single-layer material, wherein the magnetic field strength is 1000 Gs, the standing temperature is room temperature, and the standing time is 3 hours, and then placed in an oven at 70°C for 1 hour to heat and cure to form a magnetron thermal conductive absorbing layer with a thickness of 1 mm;

[0039] S4, preparation of magnetron matching layer, select 0.3g pretreated graphite sheet, mix the pretreated graphite sheet, bisphenol A epoxy resin adhesive, N-methyl pyrrolidone, and aniline formaldehyde resin in a mass ratio of 3:33.5:30:33.5, pour it on the magnetron thermal conductive absorber layer formed in step S3, and then place it in a magnetic field of 1000Gs with the magnetic field direction perpendicular to the magnetron thermal conductive absorber layer. Let it stand at room temperature for 3 hours, then place it in an oven at 70℃ for 18 hours to heat and cure it to form a magnetron matching layer with a thickness of 1mm, and obtain an oriented multilayer thermal conductive absorber. The total thickness of the obtained oriented multilayer thermal conductive absorber is 3mm. Figure 1 The overall structure diagram of the oriented multi-layer thermal conductive absorber in Example 1 of the present invention (left) and the preparation method of each layer (right) are shown; the material is then subjected to absorption and thermal conductivity tests.

[0040] Example 2

[0041] A method for preparing an oriented multilayer thermally conductive absorber comprises the following steps:

[0042] S1. Disperse 0.9 g of graphene in 50 ml of anhydrous ethanol, ultrasonicate for 2 h, and then dry the mixed solution in an oven at 100° C. for 18 h to obtain pretreated graphene, which is used as a thermal conductor and absorber.

[0043] S2, preparation of magnetron thermal conductive layer, select 0.3g pretreated graphene, epoxidized olefin compound type epoxy resin binder, deionized water, and polyurethane according to the mass ratio of 10:11.7:55:23.3, then place it in a magnetic field of 2000Gs, with the magnetic field direction perpendicular to the horizontal plane, and let it stand at room temperature for 3h to align the pretreated graphene along the magnetic field direction to form a vertically oriented single-layer material, and then place it in an oven at 70°C for 1 hour to form a magnetron thermal conductive layer with a thickness of 2mm;

[0044] S3, preparation of magnetic control thermal absorption layer, select 0.3g pretreated graphene, epoxidized olefin compound type epoxy resin binder, deionized water, and polyurethane according to the mass ratio of 10:11.7:55:23.3, pour it on the magnetic control thermal absorption layer prepared in step S2, and then place it in a rotating magnetic field of 2000Gs, 15rpm, and the magnetic field direction is parallel to the horizontal plane. Let it stand at room temperature for 3 hours to align the pretreated graphene along the magnetic field direction to form a horizontally oriented single layer material. After heating and curing in an oven at 70°C for 1 hour, a magnetic control thermal absorption layer with a thickness of 2mm is formed;

[0045] S4. Preparation of a magnetron matching layer: 0.3 g of pretreated graphene was prepared. A mixture of the pretreated graphene, an epoxidized olefin compound-based epoxy resin binder, deionized water, and polyurethane was uniformly mixed in a mass ratio of 10:11.7:55:23.3. The mixture was then poured onto the magnetron thermal conductive absorber layer prepared in step S3. The mixture was then placed in a magnetic field perpendicular to the magnetron thermal conductive absorber layer at 2000 Gs and allowed to stand at room temperature for 3 hours to align the pretreated graphene along the magnetic field, forming a perpendicularly oriented monolayer. The mixture was then oven-cured at 70°C for 18 hours to form a magnetron matching layer with a thickness of 2 mm. This oriented multilayer thermal conductive absorber was obtained. The total thickness of the obtained oriented multilayer thermal conductive absorber was 6 mm. The material was then tested for absorption and thermal conductivity.

[0046] Example 3

[0047] A method for preparing an oriented multilayer thermally conductive absorber comprises the following steps:

[0048] S1. Mix and disperse 0.15g of industrial graphite flakes and 0.15g of Fe3O4 nanoparticles in 50ml of anhydrous ethanol, sonicate for 2h, and then dry the mixed solution in an oven at 100°C for 18h to obtain a graphite flake@Fe3O4 composite material for use as a thermal conductor. Disperse 0.6g of biochar flakes in 50ml of anhydrous ethanol, sonicate for 2h, and then dry the mixed solution in an oven at 100°C for 18h to obtain a pretreated biochar flake for use as a wave absorber.

[0049] S2. Preparation of magnetron thermal conductive layer: 0.3 g of graphite sheet @ Fe3O4 composite material was selected, and the graphite sheet @ Fe3O4 composite material, bisphenol F epoxy resin binder, anhydrous ethanol, and polyester resin were evenly mixed in a mass ratio of 7:22:38:33. The mixture was then placed in a vertical magnetic field of 850 Gs with the magnetic field direction perpendicular to the horizontal plane and allowed to stand at room temperature for 3 hours to allow the graphite sheet @ Fe3O4 composite material to be arranged along the magnetic field direction to form a vertically oriented single layer material. The mixture was heated and cured in an oven at 70°C for 1 hour to form a magnetron thermal conductive layer with a thickness of 1.5 mm.

[0050] S3. Preparation of a magnetron thermal absorption layer: 0.3 g of pretreated biocarbon sheets were selected, and the pretreated biocarbon sheets, bisphenol F epoxy resin binder, anhydrous ethanol, and polyester resin were uniformly mixed in a mass ratio of 7:22:38:33. The mixture was poured onto the magnetron thermal absorption layer prepared in step S2, and then placed in a rotating magnetic field of 850 Gs, 10 rpm, and with the magnetic field direction parallel to the horizontal plane. The mixture was allowed to stand at room temperature for 3 hours to align the pretreated biocarbon sheets along the magnetic field direction to form a horizontally oriented single layer material. The mixture was heated and cured in an oven at 70°C for 1 hour to form a magnetron thermal absorption layer with a thickness of 1.5 mm.

[0051] S4: Preparation of the magnetron matching layer: 0.3 g of pretreated biocarbon sheets were mixed uniformly with a bisphenol F epoxy resin binder, anhydrous ethanol, and a polyester resin in a mass ratio of 7:22:38:33. The mixture was then poured onto the magnetron thermal conductive absorber layer formed in step S3. The material was then placed in a perpendicular magnetic field of 850 Gs, perpendicular to the magnetron thermal conductive absorber layer, at room temperature for 3 hours to align the pretreated biocarbon sheets along the magnetic field, forming a vertically oriented single layer. The material was then oven-cured at 70°C for 18 hours to form a magnetron matching layer with a thickness of 1.5 mm, thus obtaining the oriented multilayer thermal conductive absorber. The resulting oriented multilayer thermal conductive absorber had a total thickness of 4.5 mm. The material was then tested for absorption and thermal conductivity.

[0052] Comparative Example 1

[0053] 0.9g of industrial graphite flakes were dispersed in 50ml of anhydrous ethanol and ultrasonicated for 2h. The mixture was then oven-dried at 100°C for 18h until dry, yielding a pretreated graphite flake for use as a thermal conductor and absorber. The pretreated graphite flakes were then mixed uniformly with bisphenol A epoxy resin adhesive, N-methylpyrrolidone, and aniline formaldehyde resin in a mass ratio of 3:33.5:30:33.5. After standing at room temperature for 3 hours, the mixture was oven-cured at 70°C for 1 hour. The sample was removed and then again stood at room temperature for 3 hours and oven-cured at 70°C for 1 hour. After standing at room temperature for 3 more hours, the mixture was oven-cured at 70°C for 1 hour. Finally, the mixture was oven-cured at 70°C for 18 hours after standing at room temperature for 3 more hours. A 3mm thick single-layer composite material was obtained, which was then tested for wave absorption and thermal conductivity.

[0054] The material prepared in Example 1 is shown in FIG. Figure 2 and Figure 3 The material prepared in Comparative Example 1 is shown in FIG. Figure 2 and Figure 3 In the paper, it is expressed as mixed materials. Figure 2 and Figure 3 As shown in the figure, the electromagnetic wave absorption performance and thermal conductivity of the thermal conductive absorbing material under the layered structure are significantly improved compared with the thermal conductive absorbing material composed of mixed materials; among them, the absorption test of the sample is carried out using the coaxial method; the thermal conductivity test is carried out using the laser flash method.

[0055] Comparative Example 2

[0056] S1. Mix and disperse 0.15g of industrial graphite flakes and 0.15g of Fe3O4 nanoparticles in 50ml of anhydrous ethanol, sonicate for 2h, and then dry the mixed solution in an oven at 100°C for 18h to obtain a graphite flake@Fe3O4 composite material for use as a thermal conductor. Disperse 0.6g of biochar flakes in 50ml of anhydrous ethanol, sonicate for 2h, and then dry the mixed solution in an oven at 100°C for 18h to obtain a pretreated biochar flake for use as a wave absorber.

[0057] S2. Select 0.3 g of graphite sheet @ Fe3O4 composite material, mix the graphite sheet @ Fe3O4 composite material, bisphenol F epoxy resin binder, anhydrous ethanol, and polyester resin in a mass ratio of 7:22:38:33, let it stand at room temperature for 3 hours, and then heat and cure it in an oven at 70°C for 1 hour to obtain a thermal conductive layer with a thickness of 1.5 mm;

[0058] S3. Select 0.3 g of pretreated biochar sheet, mix the pretreated biochar sheet, bisphenol F epoxy resin binder, anhydrous ethanol, and polyester resin in a mass ratio of 7:22:38:33, and pour the mixture onto the thermal conductive layer prepared in step S2. After standing at room temperature for 3 hours, heat and cure in an oven at 70°C for 1 hour to form a thermal conductive and wave absorbing layer with a thickness of 1.5 mm.

[0059] S4. 0.3 g of pretreated biochar was mixed with a bisphenol F epoxy resin binder, anhydrous ethanol, and polyester resin in a mass ratio of 7:22:38:33. The mixture was then poured onto the thermally conductive absorber layer prepared in step S3. The mixture was allowed to stand at room temperature for 3 hours, then oven-cured at 70°C for 18 hours to form a matching layer with a thickness of 1.5 mm. This resulted in a multilayer, high-performance thermally conductive absorber with a total thickness of 4.5 mm. The absorber was then tested for absorption and thermal conductivity.

[0060] The material prepared in Example 3 is shown in FIG. Figure 4 and Figure 5 The material prepared in Comparative Example 2 is shown in the diagram as oriented layered. Figure 4 and Figure 5 In the random stratification, Figure 4 and Figure 5 As shown, the electromagnetic wave absorption performance and thermal conductivity of the multilayer thermal conductive absorbing material prepared by the magnetron orientation method in Example 3 are significantly improved compared with the multilayer thermal conductive absorbing material prepared by the conventional method; the absorption test of the sample is tested using the coaxial method; the thermal conductivity test is tested using the laser flash method.

[0061] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing an oriented multilayer thermally conductive absorber, characterized by: The following steps are involved: S1. Evenly mixing a thermal conductor, a binder, a solvent, and a curing agent to obtain a mixture, placing the mixture in a magnetic field perpendicular to a horizontal plane so that the thermal conductor is aligned along the magnetic field, and heating and curing the mixture to form a magnetically controlled thermal conductive layer; the thermal conductor comprises one of graphite sheets and graphene, or a composite of one of graphite sheets and graphene and magnetic particles; S2. Mixing a binder, a wave absorbing agent, a solvent, and a curing agent to obtain a mixture, pouring the mixture onto the magnetron thermal conductive layer prepared in S1, allowing the mixture to stand in a rotating magnetic field parallel to the horizontal plane so that the wave absorbing agent is aligned along the magnetic field direction, and heating and curing the mixture to form the magnetron thermal conductive wave absorbing layer; S3, uniformly mixing a binder, an absorber, a solvent, and a curing agent to obtain a mixture, pouring the mixture onto the magnetron thermal conductive absorbing layer formed in S2, then allowing the mixture to stand in a magnetic field perpendicular to the magnetic conductive absorbing layer so that the absorber is aligned along the magnetic field, and heating and curing the mixture to form a magnetron matching layer to obtain the oriented multilayer thermal conductive absorbing body; In S2 and S3, the absorber includes a mixture of one or more of biomass carbon sheets, graphite sheets, and graphene.

2. The method for preparing an oriented multilayer thermally conductive absorber according to claim 1, wherein: In S1, in the mixture, the weight percentage of the thermal conductor is 3-10%, the weight percentage of the binder and the curing agent is 35-67% of the total weight, the mass ratio of the binder to the curing agent is between 1:1 and 1:2, and the weight percentage of the solvent is 30-55%.

3. The method for preparing an oriented multilayer thermally conductive absorber according to claim 1, wherein: In S1 and S3, the intensity of the magnetic field is 850-2000 Gs, the standing temperature is room temperature, and the standing time is 3 hours.

4. The method for preparing an oriented multilayer thermally conductive absorber according to claim 1, wherein: In S2, in the mixture, the weight percentage of the absorber is 3-10%, the weight percentage of the binder and the curing agent is 35-67%, the mass ratio of the binder to the curing agent is between 1:1 and 1:2, and the weight percentage of the solvent is 30-55%.

5. The method for preparing an oriented multilayer thermally conductive absorber according to claim 1, wherein: In S2, the intensity of the magnetic field is 850-2000 Gauss, and the rotation speed is 3-15 rpm.

6. The method for preparing an oriented multilayer thermally conductive absorber according to claim 1, wherein: In S3, in the mixture, the weight percentage of the absorber is 3-10%, the weight percentage of the binder and the curing agent is 35-67%, the mass ratio of the binder to the curing agent is between 1:1 and 1:2, and the weight percentage of the solvent is 30-55%.

7. The method for preparing an oriented multilayer thermally conductive absorber according to claim 1, wherein: In S1, S2 and S3, the binder is an epoxy resin, the curing agent includes a combination of one or more of aniline formaldehyde resin, phenolic resin, furan resin, polyamide resin, polyester resin, polysulfide rubber, polyurethane, and tung oil anhydride resin, and the solvent includes a mixture of one or more of N-methylpyrrolidone, anhydrous ethanol, and deionized water.

8. The method for preparing an oriented multilayer thermally conductive absorber according to claim 7, wherein: The epoxy resin includes one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol glycidyl ether epoxy resin, glycidyl ester epoxy resin, and epoxidized olefin compound epoxy resin.

9. The method for preparing an oriented multilayer thermally conductive absorber according to any one of claims 1 to 8, wherein: The single layer thickness of the magnetron heat conducting layer, the magnetron heat conducting wave absorbing layer and the magnetron matching layer is 1-2 mm.

10. An oriented multilayer thermally conductive absorber, characterized in that: The oriented multilayer thermal conductive absorber is prepared by the preparation method of any one of claims 1 to 9.

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