Composite wave-absorbing material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of communication materials, and particularly relates to a composite wave-absorbing material and a preparation method and application thereof. The composite wave-absorbing material comprises a porous carbon material with a layered structure, wherein a material with a core-shell structure is inserted into the layered structure of the porous carbon material; the core in the material with the core-shell structure comprises metal particles; a shell layer in the material with the core-shell structure comprises a carbon layer and an alloy layer, and the alloy layer is coated with the carbon layer. The composite wave-absorbing material has a three-layer core-shell structure, an intercalation structure and a porous structure which are indispensable, and the three-layer core-shell structure, the intercalation structure and the porous structure jointly act to obtain a three-dimensional network structure, so that the composite wave-absorbing material has good electromagnetic absorption performance.

Description

Technical Field

[0001] This invention belongs to the field of communication materials technology, and specifically relates to a composite absorbing material, its preparation method, and its application. Background Technology

[0002] In recent years, with the rapid development of emerging technologies such as 5G communication, artificial intelligence, and the Internet of Things, high-frequency electromagnetic waves (such as the GHz band), as the core medium for information transmission, have been widely used in many fields such as military, science and technology, and people's livelihood, marking the full arrival of the era of the Internet of Everything and human-computer interaction. However, the widespread application of high-frequency electromagnetic waves has also caused many problems, among which electromagnetic radiation and electromagnetic interference (EMI) are particularly prominent, becoming the fifth largest environmental problem after air pollution, water pollution, solid waste pollution, and noise pollution. Electromagnetic radiation not only interferes with the normal operation of communication equipment, leading to signal distortion and information leakage, but may also pose potential harm to human health, such as causing nervous system disorders and decreased immune function.

[0003] To effectively reduce electromagnetic radiation and interference, and to safeguard information security and human health, the research and application of electromagnetic loss materials has become a cutting-edge and popular field internationally. According to electromagnetic absorption theory, the loss mechanisms of materials to electromagnetic waves are mainly divided into two categories: electrical loss and magnetic loss. Traditional methods typically involve simply adding electrical or magnetic loss materials to a substrate (such as plastics or adhesives), imparting electromagnetic loss characteristics to the substrate through physical mixing. However, this simple mixing method is insufficient to fully utilize the electromagnetic loss performance of the material and cannot meet the ever-increasing demand for high-performance electromagnetic shielding and absorption.

[0004] To maximize the absorption performance of electromagnetic loss materials, researchers have focused on constructing highly efficient electromagnetic absorption structures through innovations in structural design and fabrication processes. Studies have found that three-dimensional conductive network structures and rich heterogeneous interface designs are key factors in achieving high-performance electromagnetic loss materials. By optimizing the microstructure and interface properties of the materials, the loss material can be more effectively filled in space, forming a synergistic absorption mechanism, thereby significantly improving the absorption efficiency of electromagnetic waves and driving the development of electromagnetic loss materials towards higher performance. However, most of these materials have overly complex structures, and their electromagnetic absorption performance needs further improvement. Furthermore, the fabrication process often involves delicate operations, cumbersome processes, or expensive equipment, which is detrimental to practical applications.

[0005] Therefore, it is of great significance to provide a composite absorbing material that has good absorption capacity for electromagnetic waves and is simple to prepare. Summary of the Invention

[0006] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial solution. Specifically, the present invention provides a composite absorbing material that can achieve good absorption of electromagnetic waves under low filling conditions, and has a simple preparation process, making it easy for industrial application.

[0007] The inventive concept of this invention is as follows: The composite absorbing material of this invention comprises a porous carbon material with a layered structure, wherein a core-shell structured material is interspersed within the layered structure of the porous carbon material; the core of the core-shell structured material comprises metal particles; the shell of the core-shell structured material comprises a carbon layer and an alloy layer, with the carbon layer covering the alloy layer. This invention forms a carbon layer on the alloy surface and a metal elemental core inside the alloy, obtaining a three-layer core-shell structured material, forming multiple heterogeneous interfaces, which is beneficial for obtaining good magnetic loss and interface loss performance; simultaneously, this core-shell structured material interspersed within the layered structure of the porous carbon material forms a conductive path connecting the upper and lower layers of the porous carbon material, strengthening the construction of the three-dimensional conductive network, achieving high electrical loss performance under low filling conditions, and exhibiting good absorption capability for electromagnetic waves.

[0008] Therefore, a first aspect of the present invention provides a composite absorbing material.

[0009] Specifically, the composite absorbing material includes a porous carbon material with a layered structure, wherein a material with a core-shell structure is interspersed in the layered structure of the porous carbon material; The core of the material with a core-shell structure includes metal particles; The shell layer of the material with a core-shell structure includes a carbon layer and an alloy layer, wherein the carbon layer covers the alloy layer.

[0010] Specifically, the core-shell structure consists of metal particles, an alloy layer, and a carbon layer, arranged from the inside out.

[0011] Preferably, the porous carbon material includes any one of two-dimensional porous carbon and three-dimensional porous carbon.

[0012] Preferably, the pore size of the porous carbon material is 20-2000 nm; more preferably, the pore size of the porous carbon material is 50-200 nm.

[0013] Preferably, the metal particles include any one of iron, copper, cobalt, chromium, molybdenum, tungsten, and titanium.

[0014] Preferably, the alloy material in the alloy layer includes at least one of iron, copper, cobalt, chromium, molybdenum, tungsten, and titanium.

[0015] Preferably, the alloy material in the alloy layer includes a magnetic alloy material.

[0016] Preferably, the thickness of the carbon layer is 1-50 nm; more preferably, the thickness of the carbon layer is 2-20 nm.

[0017] Preferably, the thickness of the alloy layer is 20-2000 nm; more preferably, the thickness of the alloy layer is 50-200 nm.

[0018] Preferably, the particle size of the metal particles is 1-50 nm.

[0019] A second aspect of the present invention provides a method for preparing the composite microwave absorbing material described in the first aspect of the present invention.

[0020] Specifically, the preparation method of the composite absorbing material includes the following steps: The composite microwave absorbing material is obtained by heat-treating a mixture containing phase change alloy material and carbon-containing material.

[0021] Preferably, the heat treatment temperature is ≥600℃; more preferably, the heat treatment temperature is 600-1300℃.

[0022] Preferably, the heat treatment time is 0.1-5 hours; more preferably, the heat treatment time is 0.2-2 hours.

[0023] Preferably, the carbon-containing material includes at least one of graphite-structured carbon materials and fibers.

[0024] Specifically, the carbon-containing material has a two-dimensional or three-dimensional network structure.

[0025] Preferably, the phase change alloy material includes at least one of iron, copper, cobalt, chromium, molybdenum, tungsten, and titanium.

[0026] Specifically, the phase change alloy material is a high-temperature phase change alloy.

[0027] Preferably, the heat treatment is carried out in a reducing gas atmosphere.

[0028] Preferably, the composite microwave absorbing material is obtained by cooling after the heat treatment.

[0029] Specifically, during the heat treatment process, the carbon-containing material is thermally reduced and carbonized in a reducing gas atmosphere. Due to the thermal instability of the alloy phase, metal atoms gradually precipitate within the phase change alloy material, forming a metallic elemental core. Simultaneously, utilizing the carbon dissolution and exudation mechanism of the phase change alloy material at high temperatures—that is, the phase change alloy material has higher solubility for carbon atoms at high temperatures than at room temperature—the phase change alloy material dissolves the carbon atoms in the contacting carbon-containing material during heating, causing the carbon-containing material to form pores, resulting in a porous carbon material. During the cooling process after heat treatment, these carbon atoms precipitate on the alloy surface, forming a carbon layer. This invention prepares a composite microwave absorbing material with a three-dimensional conductive network structure of porous carbon material and metallic elemental@alloy@carbon, along with a three-layer core-shell structure, through a one-step heat treatment process.

[0030] Preferably, the phase change alloy material accounts for ≥20% of the mass of the mixture; more preferably, the phase change alloy material accounts for 20-80% of the mass of the mixture.

[0031] Specifically, the proportion of alloy material needs to be controlled within a reasonable range. For example, too much alloy material will lead to severe particle agglomeration, while too little will result in insufficient porosity, both of which will affect electromagnetic wave absorption performance. Furthermore, alloys exhibit high-temperature instability; selecting the aforementioned phase change alloy material can ensure the alloy's stability at high temperatures as much as possible. In addition, alloy particles that are too small (too small grains) will result in poor magnetism, while alloy particles that are too large will have poor dispersibility, also affecting magnetism. Therefore, the particle size of the alloy must be reasonable, meaning the thickness of the alloy layer and the size of the metal particles must be appropriately limited.

[0032] Preferably, the mixture containing phase change alloy material and carbon-containing material can be obtained by in-situ synthesis, or by thoroughly mixing the dispersion of phase change alloy material and the dispersion of carbon-containing material and then freeze-drying them.

[0033] A third aspect of the present invention provides an electromagnetic absorbing material or an electromagnetic absorbing device.

[0034] Specifically, the electromagnetic absorbing material or electromagnetic absorbing device includes the composite absorbing material described in the first aspect of this invention.

[0035] The composite absorbing material of the present invention can be added to a substrate as a filler, and can impart good electromagnetic absorption performance to the substrate with a low filling amount. The equipment for preparing the composite absorbing material of the present invention as a filler can be used to reduce or eliminate the damage of 5G communication electromagnetic waves to the outside world.

[0036] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows: (1) The present invention forms a carbon layer on the surface of the alloy and a metal elemental core inside to obtain a three-layer core-shell structure material, forming multiple heterogeneous interfaces, which is beneficial to obtaining good magnetic loss and interface loss performance; at the same time, this core-shell structure material is interspersed in the layered structure of porous carbon material to form a conductive path connecting the upper and lower layers of porous carbon material, strengthening the construction of the three-dimensional conductive network, and finally obtaining a unique composite microwave absorbing material with a three-layer core-shell structure, intercalation structure and porous structure. It can achieve high electrical loss performance under low filling conditions (filling amount is 2%), has good absorption ability for electromagnetic waves, and has good application potential and prospects.

[0037] (2) This invention innovatively utilizes heat treatment to thermally reduce and carbonize carbon-containing materials in a reducing gas atmosphere. Due to the thermal instability of the alloy phase, metal atoms gradually precipitate inside the alloy material, forming a metallic elemental core. Simultaneously, taking advantage of the higher solubility of carbon atoms in the alloy material at high temperatures compared to room temperature, the alloy dissolves the carbon atoms in the contacted carbon-containing material during the heating process, causing the carbon-containing material to form pores, resulting in a porous carbon material. During the cooling process after heat treatment, these carbon atoms precipitate on the alloy surface, forming a carbon layer. Through a one-step heat treatment process, a composite microwave absorbing material with high microwave absorption performance, consisting of a three-dimensional conductive network structure of porous carbon material and metallic elemental@alloy@carbon and a three-layer core-shell structure, is obtained.

[0038] (3) The preparation method of the composite absorbing material of the present invention is simple and quick, and is easy to realize large-scale production and application. Attached Figure Description

[0039] Figure 1 These are scanning electron microscope (SEM) images of the materials before and after heat treatment in Example 1 of the present invention; Figure 2 This is a transmission electron microscope image of the cobalt@iron-cobalt alloy@carbon obtained by ultrasonic water washing of the composite absorbing material in Example 1 of the present invention; Figure 3 The X-ray diffraction patterns of the materials before and after heat treatment in Embodiment 1 of the present invention are shown below. Figure 4 This is a scanning electron microscope image of the composite absorbing material in Embodiment 2 of the present invention; Figure 5 This is a transmission electron microscope image of the composite absorbing material in Embodiment 2 of the present invention; Figure 6 The graph shows the electromagnetic absorption test results of the graphene oxide-iron-cobalt alloy prepared in Example 1 of this invention. Figure 7 The graph shows the electromagnetic absorption test results of the graphene-cobalt@iron-cobalt alloy@carbon prepared in Example 1 of this invention. Figure 8The graph shows the electromagnetic absorption test results of the cotton fiber-copper-tin alloy prepared in Example 2 of this invention. Figure 9 The graph shows the electromagnetic absorption test results of the carbon-copper@copper-tin alloy@carbon prepared in Example 2 of this invention. Figure 10 The graph shows the electromagnetic absorption test results of the cobalt@iron-cobalt alloy prepared in Comparative Example 1 of this invention. Figure 11 This is a graph showing the electromagnetic absorption test results of the carbon-carbon material prepared in Comparative Example 2 of this invention; Figure 12 The graph shows the electromagnetic absorption test results of the graphene-carbon@cobalt material prepared in Comparative Example 3 of this invention. Detailed Implementation

[0040] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0041] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0042] Example 1 A composite microwave absorbing material includes porous graphene with a layered structure, wherein a core-shell structured material is interspersed within the layered structure of the porous graphene; the core of the core-shell structured material is a cobalt metal particle; the shell of the core-shell structured material is composed of a carbon layer and an iron-cobalt alloy layer, wherein the carbon layer coats the iron-cobalt alloy layer.

[0043] A method for preparing a composite microwave absorbing material includes the following steps: (1) 1.000 g of graphene oxide, 1.784 g of cobalt chloride hexahydrate and 0.497 g of ferrous chloride tetrahydrate were dissolved in 100 mL of ethylene glycol and the mixture was stirred for 20 min. Then, the mixture was heated to 85 °C and 15 g of sodium hydroxide was added. After 20 min, 10 mL of N2H4·H2O was added. All synthesis steps were carried out under nitrogen protection. After the reaction was carried out for 1 h, the product was collected by magnetic separation. Then, it was washed 4 times with acetonitrile and 4 times with deionized water. The mixture was filtered and freeze-dried to obtain graphene oxide-cobalt alloy.

[0044] (2) The dried graphene oxide-cobalt alloy powder obtained in step (1) is added to a tube furnace for heat treatment. In a hydrogen atmosphere, the temperature is raised to 900°C at a rate of 10°C / min, held for 1 hour, and then cooled to room temperature naturally to obtain the composite microwave absorbing material (graphene-cobalt@cobalt alloy@carbon).

[0045] The materials before and after heat treatment were observed using scanning electron microscopy (SEM), and the SEM images are shown below. Figure 1 As shown. Among them, Figure 1 Figure (a) shows a scanning electron microscope image of the graphene oxide-iron-cobalt alloy before heat treatment. Figure 1 Figure (b) is a scanning electron microscope image of the composite absorbing material after heat treatment.

[0046] Depend on Figure 1 It can be seen that before heat treatment, the graphene oxide is a layered structure. After heat treatment, the graphene oxide is reduced to graphene, and a porous structure appears on the surface of the layered graphene. This proves that an intercalated porous structure (i.e., with core-shell structure, porous structure and intercalation structure; material with core-shell structure is inserted between the layered structure of porous graphene) is formed after heat treatment, which confirms the successful construction of the three-dimensional conductive network structure.

[0047] The composite microwave absorbing material obtained after heat treatment was ultrasonically washed with water. The cobalt@ironcobalt alloy@carbon in the graphene-cobalt@ironcobalt alloy@carbon composite material separated from the layered porous graphene. Transmission electron microscopy (TEM) was performed on the cobalt@ironcobalt alloy@carbon, and the TEM image is shown below. Figure 2 As shown. Among them, Figure 2 Figure (a) shows a transmission electron microscope (TEM) image of a cobalt@iron-cobalt alloy@carbon obtained by ultrasonically washing the composite absorbing material. Figure 2 Figure (b) is a magnified view of the area within the red box in Figure (a).

[0048] Depend on Figure 2 It can be seen that after heat treatment, cobalt is precipitated inside the iron-cobalt alloy, and a carbon layer appears on the surface of the iron-cobalt alloy, confirming the successful preparation of the three-layer core-shell structure.

[0049] X-ray diffraction analysis was performed on the materials before and after heat treatment. The X-ray diffraction patterns (XRD patterns) are as follows: Figure 3 As shown, graphene oxide-iron-cobalt alloy is the material before heat treatment, graphene-cobalt@iron-cobalt alloy@carbon is the material after heat treatment, JCDPS No. 65-4131 represents the standard card for Co7Fe3, and JCDPS No. 15-0806 represents the standard card for Co.

[0050] Depend on Figure 3 It can be seen that elemental cobalt appears in the material after heat treatment.

[0051] Example 2 A composite microwave absorbing material includes porous carbon with a layered structure, wherein a core-shell structured material is interspersed within the layered structure of the porous carbon; the core of the core-shell structured material is a copper metal particle; the shell of the core-shell structured material consists of a carbon layer and a copper-tin alloy layer, wherein the carbon layer coats the copper-tin alloy layer.

[0052] A method for preparing a composite microwave absorbing material includes the following steps: (1) Dissolve 1.250g copper sulfate pentahydrate and 0.380g tin chloride dihydrate in 100mL ethylene glycol and stir the mixture for 20min. Then heat to 85℃ and add 15g sodium hydroxide. After 20min, add 10mL N2H4·H2O. All synthesis steps are carried out under nitrogen protection. After the reaction is carried out for 1h, the product is collected by magnetic separation. Then wash with acetonitrile 3-5 times and deionized water 3-5 times. Sonicate disperse in 100mL deionized water to obtain copper-tin alloy dispersion. 1g of cotton fiber fragments were soaked in 0.5M NaOH solution, heated and stirred at 80℃ for 1 hour to remove wax and impurities, then treated with an ultrasonic crusher for 30 minutes, washed 4 times with deionized water, and ultrasonically dispersed in 100mL of deionized water to obtain cotton fiber dispersion. After mixing the copper-tin alloy dispersion and the cotton fiber dispersion, the mixture was stirred for 2 hours and then freeze-dried to obtain the cotton fiber-copper-tin alloy. (2) The dried cotton fiber-copper-tin alloy powder obtained in step (1) is placed in a tube furnace and heated to 700°C at a heating rate of 20°C / min under a hydrogen / argon atmosphere. The temperature is held for 3 hours and then naturally cooled to room temperature to obtain the composite microwave absorbing material (carbon-copper@copper-tin alloy@carbon).

[0053] The composite absorbing material after heat treatment in Example 2 was observed by scanning electron microscopy. The scanning electron microscopy image is shown below. Figure 4 As shown. By Figure 4 It can be seen that a porous structure appears on the surface of the layered carbon after heat treatment, proving that an intercalated porous structure (i.e., having a core-shell structure, a porous structure, and an intercalated structure; the material with the core-shell structure is inserted between the layered structures of the porous carbon) was formed after heat treatment, confirming the successful construction of the three-dimensional conductive network structure.

[0054] The composite absorbing material after heat treatment in Example 2 was observed by transmission electron microscopy (TEM). The TEM image is shown below. Figure 5 As shown. By Figure 5 It can be seen that the material exhibits a core-shell structure after heat treatment.

[0055] Comparative Example 1 Comparative Example 1: A cobalt@iron-cobalt alloy was prepared using the following specific method: (1) Dissolve 1.784 g cobalt chloride hexahydrate and 0.497 g ferrous chloride tetrahydrate in 100 mL of ethylene glycol and stir the mixture for 20 min. Then heat it to 85 °C and add 15 g sodium hydroxide. After 20 min, add 10 mL of N2H4·H2O. All synthesis steps are carried out under nitrogen protection. After the reaction is carried out for 1 h, the product is collected by magnetic separation. Then wash it 4 times with acetonitrile and 4 times with deionized water. Filter and freeze dry to obtain iron-cobalt alloy. (2) The dried iron-cobalt alloy powder obtained in step (1) is placed in a tube furnace and heated to 900°C at a heating rate of 10°C / min in a hydrogen atmosphere. The temperature is held for 1 hour and then naturally cooled to room temperature to obtain a cobalt@iron-cobalt alloy with cobalt metal particles coated with iron-cobalt alloy.

[0056] Comparative Example 2 Comparative Example 2 prepared a carbon-carbon material by adding the graphene-cobalt@iron-cobalt alloy@carbon prepared in Example 1 into a 3% hydrochloric acid solution and soaking it for 24 hours to obtain the product.

[0057] Comparative Example 3 Comparative Example 3 prepared a graphene-carbon@cobalt material. The only difference between this material and the composite microwave absorbing material in Example 1 is that it does not contain iron-cobalt alloy, that is, the carbon layer directly coats the cobalt metal particles.

[0058] The preparation method of graphene-carbon@cobalt includes the following steps: (1) 1.000 g of graphene oxide and 2.281 g of cobalt chloride hexahydrate were dispersed in 100 mL of ethylene glycol and the mixture was stirred for 20 min. Then, the mixture was heated to 85 °C and 15 g of sodium hydroxide was added. After 20 min, 10 mL of N2H4·H2O was added. All synthesis steps were carried out under nitrogen protection. After the reaction was carried out for 1 h, the product was collected by magnetic separation. Then, it was washed 4 times with acetonitrile and 4 times with deionized water. The product was filtered and lyophilized to obtain graphene oxide-cobalt. (2) The dried graphene-cobalt powder obtained in step (1) is placed in a tube furnace and heated to 900°C at a heating rate of 10°C / min in a hydrogen atmosphere. The temperature is held for 1 hour and then naturally cooled to room temperature to obtain the composite microwave absorbing material (graphene-cobalt@carbon).

[0059] Electromagnetic absorption tests were performed on the graphene oxide-iron-cobalt alloy and graphene-cobalt@iron-cobalt alloy@carbon prepared in Example 1, the cotton fiber-copper-tin alloy and carbon-copper@copper-tin alloy@carbon prepared in Example 2, the cobalt@iron-cobalt alloy prepared in Comparative Example 1, the carbon-carbon material prepared in Comparative Example 2, and the graphene-carbon@cobalt prepared in Comparative Example 3. The specific testing method was a coaxial method test using a vector network analyzer. The above seven materials were mixed with paraffin wax (each material was added at a 2% filler), heated to 60°C, and then uniformly mixed. After cooling, the mixtures were placed in molds and pressed into coaxial rings with an outer diameter of 7.0 mm, an inner diameter of 3.04 mm, and a thickness of approximately 2.6 mm using a hydraulic press at 5 MPa. Tests were then conducted at 1-18 GHz. The test results for Examples 1 (graphene oxide-iron-cobalt alloy, graphene-cobalt@iron-cobalt alloy@carbon), Examples 2 (cotton fiber-copper-tin alloy, carbon-copper@copper-tin alloy@carbon), Comparative Example 1 (cobalt@iron-cobalt alloy), Comparative Example 2 (carbon-carbon material), and Comparative Example 3 (graphene-carbon@cobalt) are as follows: Figures 6-12 As shown.

[0060] Depend on Figure 6 , 7 As can be seen, in Example 1, the absorption intensity increased significantly after heat treatment, from -8dB (14.2GHz) before heat treatment to -65dB (17.1GHz).

[0061] Depend on Figure 8 , 9 As can be seen, in Example 2, the absorption intensity increased significantly after heat treatment, from -21dB (7.2GHz) before heat treatment to -69dB (14.0GHz).

[0062] Depend on Figure 10 As can be seen, in Comparative Example 1, the cobalt@iron-cobalt alloy has the minimum reflection loss RLmin=-39dB at 13.7GHz.

[0063] Depend on Figure 11 As can be seen, in Comparative Example 2, the maximum electromagnetic absorption of the carbon-carbon material at 11.2 GHz is -34 dB.

[0064] Depend on Figure 12 As can be seen, in Comparative Example 3, the maximum electromagnetic absorption of graphene-carbon@cobalt at 17.4 GHz is -45 dB.

[0065] Depend on Figures 6-12 It is evident that heat treatment can significantly improve the absorption intensity of the material, i.e., enhance its electromagnetic absorption performance. Furthermore, the absorption intensity of the composite absorbing materials in Examples 1-2 is significantly higher than that in Comparative Examples 1-3. This demonstrates that the combination of the specific three-dimensional mesh structure, three-layer core-shell structure, intercalation structure, and porous structure of this invention is crucial and effective; none can be omitted. Their combined action is essential for the composite absorbing material to possess excellent electromagnetic absorption performance and achieve high absorption intensity.

[0066] In summary, this invention forms a carbon layer on the alloy surface and a metallic elemental core within it through heat treatment, resulting in a three-layer core-shell structure material. This creates multiple heterogeneous interfaces, which is beneficial for achieving excellent magnetic and interfacial loss performance. Simultaneously, this core-shell structure material is intercalated within the layered structure of the porous carbon material, forming conductive pathways connecting the upper and lower layers of the porous carbon material. This strengthens the construction of the three-dimensional conductive network, achieving high electrical loss performance even with low filler content. Consequently, the composite absorbing material exhibits excellent electromagnetic wave absorption capabilities. The three-layer core-shell structure, intercalation structure, and porous structure are all indispensable; their combined action results in a three-dimensional network structure, giving the composite absorbing material excellent electromagnetic absorption performance.

[0067] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A composite microwave absorbing material, characterized in that, The material includes porous carbon materials with a layered structure, wherein materials with a core-shell structure are interspersed within the layered structure of the porous carbon material. The core of the material with a core-shell structure includes metal particles; The shell layer of the material with a core-shell structure includes a carbon layer and an alloy layer, wherein the carbon layer covers the alloy layer.

2. The composite absorbing material according to claim 1, characterized in that, The porous carbon material includes any one of two-dimensional porous carbon and three-dimensional porous carbon.

3. The composite absorbing material according to claim 1, characterized in that, The porous carbon material has a pore size of 20-2000 nm.

4. The composite absorbing material according to claim 3, characterized in that, The metal particles include any one of iron, copper, cobalt, chromium, molybdenum, tungsten, and titanium; and / or, the alloy material in the alloy layer includes at least one of iron, copper, cobalt, chromium, molybdenum, tungsten, and titanium.

5. The composite absorbing material according to claim 4, characterized in that, The alloy material in the alloy layer includes a magnetic alloy material.

6. The composite microwave absorbing material according to any one of claims 1-5, characterized in that, The thickness of the carbon layer is 1-50 nm; and / or the thickness of the alloy layer is 20-2000 nm; and / or the particle size of the metal particles is 1-50 nm.

7. The method for preparing the composite microwave absorbing material according to any one of claims 1-6, characterized in that, Includes the following steps: The composite microwave absorbing material is obtained by heat-treating a mixture containing phase change alloy material and carbon-containing material.

8. The preparation method according to claim 7, characterized in that, The heat treatment temperature is ≥600℃; and / or the heat treatment time is 0.1-5h.

9. The preparation method according to claim 7, characterized in that, The carbon-containing material includes at least one of graphite-structured carbon materials and fibers; and / or, the phase change alloy material includes at least one of iron, copper, cobalt, chromium, molybdenum, tungsten, and titanium; and / or, in the mixture, the mass percentage of the phase change alloy material is ≥20%.

10. An electromagnetic absorbing material or electromagnetic absorbing device, characterized in that, Includes the composite microwave absorbing material as described in any one of claims 1-6.

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