A thermal conductive and wave absorbing integrated material and its preparation method

Abstract

The invention discloses a kind of heat-conducting wave-absorbing integrated material and its preparation method, belong to the field of materials, preparation method comprises: step one, mixing saturated sodium chloride solution with the nitrate of magnetic metal, adjusting pH to alkaline generation magnetic metal hydroxide, adding organic solvent to precipitate micron-sized sodium chloride crystals containing magnetic metal hydroxide; step two, adding tetraethyl orthosilicate and reacting to wrap silica, washing and removing sodium chloride, obtaining magnetic metal hydroxide doped hollow cubic silica shell; step three, surface synthesis carbon source, obtaining precursor; step four, calcining at 1250-1400℃ after insulation at 400-650℃, then etching with strong alkaline solution, empty firing to obtain magnetic metal doped hollow cubic silicon carbide; step five, carbonizing and filling the magnetic metal doped hollow cube into liquid silicone rubber, applying magnetic field, solidifying to form heat-conducting wave-absorbing silicone rubber. The present invention has the advantages of controllable morphology, excellent electromagnetic wave absorption performance, good thermal conductivity, etc.

Description

Technical Field

[0001] The present invention belongs to the field of material technology and relates to a heat-conducting and wave-absorbing material, and in particular to a heat-conducting and wave-absorbing integrated material and a preparation method thereof. Background Art

[0002] Microwave absorbing materials have been extensively researched to address electromagnetic interference and contamination caused by the integration and miniaturization of electronic devices. Silicon carbide (SiC) is renowned for its unique properties in electromagnetic wave absorption. SiC is a dielectric absorber with inherent electric dipole polarization. Furthermore, due to its low thermal expansion, good thermal shock resistance, excellent thermal conductivity, high strength, and good chemical inertness, it can be used in harsh operating environments, exhibiting excellent electromagnetic absorption and thermal conductivity. There is considerable research on the specific morphologies and ideal structures of SiC absorbers that can enhance EM wave absorption, such as wires, whiskers, fibers, tubes, and porous SiC.

[0003] As a dielectric material, SiC has good thermal and chemical resistance in high temperatures and / or harsh operating environments, making it an attractive candidate for ideal electromagnetic wave absorption. However, due to its single intrinsic electric dipole, its dielectric loss is relatively low and its electrical conductivity is low, which limits its potential for wider application. This weakness can be partially addressed by tailoring the morphology, phase, or structural features of raw silicon carbide to enhance the polarization and multiple reflections of its incident electromagnetic waves. For example, this can be achieved by inducing a greater number of dipoles and increasing the specific internal surface area, respectively.

[0004] When using SiC as an absorber, the effect of the special structure on the absorption efficiency is usually considered. In recent years, the hollow structure of the absorber has become a research focus. However, the research on hollow absorber particles mainly focuses on ferrite, carbon black, etc. At present, there is little research on hollow silicon carbide absorbers because the synthesis conditions of SiC are difficult and it is difficult to ensure the integrity of the morphology during the synthesis process. Therefore, exploring a stable new preparation method for hollow silicon carbide is of great significance for broadening the application field of silicon carbide and developing lightweight absorbers with high absorption efficiency suitable for high temperature environments. Summary of the Invention

[0005] The present invention provides a heat-conducting and wave-absorbing integrated material and a preparation method thereof, so as to overcome the defects of the prior art.

[0006] To achieve the above object, the present invention provides a method for preparing a thermal conductive and wave absorbing integrated material, which has the following characteristics:

[0007] Step 1: mixing a saturated sodium chloride solution with a nitrate of a magnetic metal, adjusting the pH to alkaline to generate a magnetic metal hydroxide, and then adding an organic solvent to precipitate micron-sized sodium chloride crystals containing the magnetic metal hydroxide;

[0008] Step 2: adding ethyl orthosilicate and reacting to coat micron-sized sodium chloride crystals containing magnetic metal hydroxide with silica, and removing the sodium chloride by water washing to obtain a magnetic metal hydroxide-doped hollow cubic silica shell;

[0009] Step 3: synthesizing a carbon source on the surface of a hollow cubic silica shell doped with a magnetic metal hydroxide to obtain a precursor;

[0010] Step 4: The precursor is kept at 400-650°C and then calcined at 1250-1400°C, then etched with a strong alkaline solution, and then air-fired to obtain magnetic metal-doped hollow cubic silicon carbide; the precursor is carbonized at 400-650°C and then reacted at 1250-1400°C to form silicon carbide, while the magnetic metal hydroxide is reduced to magnetic metal particles;

[0011] Step 5: After the magnetic metal-doped hollow cubes are carbonized and filled into the liquid silicone rubber, an external magnetic field is applied to arrange the magnetic metal-doped hollow cubes of silicon carbide in the silicone rubber in sequence and connect them tightly until they are completely cured to form a heat-conducting and wave-absorbing silicone rubber.

[0012] Furthermore, the present invention provides a method for preparing an integrated thermal conductive and wave absorbing material, which may also have the following characteristics: wherein, in step 1, the magnetic metal nitrate is one or more of cobalt nitrate, nickel nitrate, and iron nitrate; the ratio of the magnetic metal nitrate to the saturated sodium chloride solution is 0.1-1g:100ml; the organic solvent is an alcohol organic solvent; and the volume ratio of the saturated sodium chloride solution to the organic solvent is 1:1-4.

[0013] Furthermore, the present invention provides a method for preparing an integrated thermal conductive and wave absorbing material, which may also have the following characteristics: wherein, in step 1, the precipitation time of micron-sized sodium chloride crystals does not exceed 30 minutes.

[0014] Furthermore, the present invention provides a method for preparing an integrated thermal conductive and wave absorbing material, which may also have the following characteristics: wherein, the specific method of step 2 is: adding ethyl orthosilicate dropwise to the suspension mixed with micron-sized sodium chloride crystals containing magnetic metal hydroxide obtained in step 1, stirring evenly and reacting for 30 minutes, then centrifuging, washing with water, and drying to obtain a hollow cubic silica shell doped with magnetic metal hydroxide; the ratio of ethyl orthosilicate to the precipitated micron-sized sodium chloride crystals containing magnetic metal hydroxide is 0.25-0.5 ml: 1 g.

[0015] Furthermore, the present invention provides a method for preparing an integrated thermal conductive and wave absorbing material, which may also have the following characteristics: wherein, in step three, the synthesized carbon source is phenolic, polyaniline or polyurethane.

[0016] Furthermore, the present invention provides a method for preparing an integrated thermal conductive and wave absorbing material, which may also have the following characteristics: wherein, the specific method of step three is: adding a magnetic metal hydroxide-doped hollow cubic silica shell to a mixed solution of ethanol, water, and ammonia water, ultrasonically stirring to uniformly disperse it, then adding formaldehyde and resorcinol to the suspension to allow it to self-polymerize on the surface of the magnetic metal hydroxide-doped hollow cubic silica shell to form a phenolic layer as a carbon source, continuously stirring the reaction for 24 hours, and then centrifuging and drying to obtain a precursor; the volume ratio of ethanol, water, and ammonia water is 50:7:3, and the concentration of ammonia water is 20-40wt%; the amount ratio of the magnetic metal hydroxide-doped hollow cubic silica shell, formaldehyde, and resorcinol is 2.5g:2ml:1g.

[0017] Furthermore, the present invention provides a method for preparing an integrated thermal conductive and wave absorbing material, which may also have the following characteristics: wherein, in step 4, the precursor is mixed with ferric nitrate, and the mixture is kept warm and calcined together; the ferric nitrate accounts for 0.5-3% of the total mass.

[0018] Furthermore, the present invention provides a method for preparing an integrated thermal conductive and wave absorbing material, which may also have the following characteristics: wherein, the specific method of step four is: after mixing the precursor with ferric nitrate, placing it in a nitrogen-protected tubular furnace, heating it to 400-650°C at a heating rate of 2-6°C / min, keeping it warm for 1-3 hours, and then heating it to 1250-1400°C again at a heating rate of 2-6°C / min and keeping it warm for 2-5 hours. After cooling to room temperature, the calcined product is immersed in a strong alkaline solution and etched at 80°C for 72 hours, centrifuged, washed to neutrality, and then dried. It is calcined at 450-650°C for 1-3 hours to obtain magnetic metal-doped hollow cubic silicon carbide; the strong alkaline solution is sodium hydroxide solution, potassium hydroxide solution, hydrofluoric acid solution or a mixed solution of hydrofluoric acid and hydrochloric acid, and the concentration of the strong alkaline solution is 5-12 mol / L.

[0019] Furthermore, the present invention provides a method for preparing an integrated thermal conductive and wave absorbing material, which may also have the following characteristics: wherein, in step five, the magnetic flux of the external magnetic field is 0.15-0.5T.

[0020] The present invention also provides a heat-conducting and wave-absorbing integrated material prepared by the above preparation method.

[0021] The beneficial effects of the present invention are as follows: the present invention provides a thermally conductive and wave-absorbing integrated material and its preparation method, wherein a cubic silica shell is prepared using a template, coated with a carbon source, and then carbonized to obtain a hollow cubic silicon carbide. After being filled with silicone rubber, an external magnetic field is applied to arrange the shell in sequence and tightly connect it, ultimately obtaining a thermally conductive and wave-absorbing silicone rubber. The prepared hollow cubic silicon carbide material has a controllable morphology, excellent electromagnetic wave absorption performance, and good thermal conductivity. Specifically, by controlling the precipitation time and adjusting the size of the precipitated salt crystals, the particle size of the generated hollow cubic silicon carbide can be regulated. At the same time, by adjusting the reaction temperature to control the morphological changes of the hollow silicon carbide, the surface defects of the hollow cubic silicon carbide can be effectively adjusted, and the polarization loss can be enhanced. The hollow structure extends the attenuation path of the electromagnetic wave. The magnetic metal particles retained in the silicon carbide increase the microwave attenuation path of the silicon carbide, increase the heterogeneous interface polarization of the silicon carbide, and have a beneficial effect on the microwave absorption capacity of the silicon carbide.

[0022] The silicon carbide prepared by the present invention not only has the characteristic of being hollow, but also has a special cubic structure. By performing magnetic orientation treatment on the silicon carbide, the cubic silicon carbide is tightly connected to each other, thereby greatly improving the thermal conductivity of the silicon carbide. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a diagram of the preparation mechanism of magnetic metal-doped hollow cubic silicon carbide;

[0024] Figure 2 is an SEM image of the magnetic metal-doped hollow cubic silicon carbide prepared in Example 1-3;

[0025] Figure 3 1 is a graph showing the electromagnetic wave absorption performance of the magnetic metal-doped hollow cubic silicon carbide prepared in Example 1;

[0026] Figure 4 This is the arrangement diagram of magnetic metal-doped hollow cubic silicon carbide after magnetic orientation treatment. DETAILED DESCRIPTION

[0027] The present invention will be further described below with reference to specific embodiments.

[0028] Example 1

[0029] This embodiment provides a thermal conductive and wave absorbing integrated material, the preparation method of which includes the following steps:

[0030] Step 1: Sodium chloride is dissolved in 50ml of deionized water and stirred to form a saturated sodium chloride solution. 0.2g of cobalt nitrate hexahydrate is then added to the saturated sodium chloride solution and stirred continuously to form a mixed solution of sodium chloride / cobalt nitrate. 5ml of ammonia water is added to the mixed solution and stirred for 3min to adjust the pH value of the mixed solution to 10 to generate a magnetic metal hydroxide. 200ml of ethanol is then added to the mixed solution to precipitate micron-sized sodium chloride crystals containing cobalt hydroxide to form a mixed suspension, and ultrasonic stirring is continued for 10min.

[0031] Step 2: 3 ml of TEOS was added dropwise to the mixed suspension, stirred evenly and reacted for 30 minutes, then centrifuged, washed with water to remove sodium chloride, and dried to obtain a cobalt hydroxide-doped hollow cubic silica shell.

[0032] Step 3: Add 1 g of cobalt hydroxide-doped hollow cubic silica shell to a mixed solution of 50 ml of ethanol, 7 ml of deionized water, and 3 ml of ammonia water (the concentration of ammonia water is 30 wt%) and stir ultrasonically to make it evenly dispersed. Then add 0.8 ml of formaldehyde and 0.4 g of resorcinol to the suspension so that it self-polymerizes on the surface of the cobalt hydroxide-doped hollow cubic silica shell to form a phenolic layer as a carbon source. After continuous stirring and reacting for 24 hours, the product is collected by centrifugation and drying to obtain a precursor.

[0033] Step 4: 5g of the precursor was mixed with 0.05g of ferric nitrate and placed in a nitrogen-protected tube furnace. The mixture was heated to 600°C at a heating rate of 2-6°C / min and kept warm for 2 hours. The mixture was then heated to 1350°C at a heating rate of 2-6°C / min and kept warm for 3 hours. After cooling to room temperature, the calcined product was immersed in a 5mol / L sodium hydroxide solution and heated to 80°C. The product was etched for 72 hours, centrifuged, washed until neutral, and then dried. The powder was calcined at 500°C for 2 hours to obtain cobalt-doped hollow cubic silicon carbide.

[0034] Step 5: After filling the liquid silicone rubber with cobalt-doped hollow cubic silicon carbide at a mass ratio of 10%, a 0.3T external magnetic field is applied to arrange the cubic silicon carbide in the silicone rubber in sequence and connect them closely until it is completely cured to form a thermally conductive and wave-absorbing silicone rubber.

[0035] Example 2

[0036] This embodiment provides a thermal conductive and wave absorbing integrated material, the preparation method of which includes the following steps:

[0037] Step 1: Sodium chloride is dissolved in 50ml of deionized water and stirred to form a saturated sodium chloride solution. 0.2g of cobalt nitrate hexahydrate is then added to the saturated sodium chloride solution and stirred continuously to form a mixed solution of sodium chloride / cobalt nitrate. 5ml of ammonia water is added to the mixed solution and stirred for 3min to adjust the pH value of the mixed solution to 10 to generate a magnetic metal hydroxide. 200ml of ethanol is then added to the mixed solution to precipitate micron-sized sodium chloride crystals containing cobalt hydroxide to form a mixed suspension, and ultrasonic stirring is continued for 10min.

[0038] Step 2: 3 ml of TEOS was added dropwise to the mixed suspension, stirred evenly and reacted for 30 minutes, then centrifuged, washed with water to remove sodium chloride, and dried to obtain a cobalt hydroxide-doped hollow cubic silica shell.

[0039] Step 3: Add 1 g of cobalt hydroxide-doped hollow cubic silica shell to a mixed solution of 50 ml of ethanol, 7 ml of deionized water, and 3 ml of ammonia water (the concentration of ammonia water is 30 wt%) and stir ultrasonically to make it evenly dispersed. Then add 0.8 ml of formaldehyde and 0.4 g of resorcinol to the suspension so that it self-polymerizes on the surface of the cobalt hydroxide-doped hollow cubic silica shell to form a phenolic layer as a carbon source. After continuous stirring and reacting for 24 hours, the product is collected by centrifugation and drying to obtain a precursor.

[0040] Step 4: 5g of the precursor was mixed with 0.05g of ferric nitrate and placed in a nitrogen-protected tube furnace. The mixture was heated to 600°C at a heating rate of 2-6°C / min and kept warm for 2 hours. The mixture was then heated to 1375°C at a heating rate of 2-6°C / min and kept warm for 3 hours. After cooling to room temperature, the calcined product was immersed in a 5mol / L sodium hydroxide solution and heated to 80°C. The product was etched for 72 hours, centrifuged, washed until neutral, and then dried. The powder was calcined at 500°C for 2 hours to obtain cobalt-doped hollow cubic silicon carbide.

[0041] Step 5: After filling the liquid silicone rubber with cobalt-doped hollow cubic silicon carbide at a mass ratio of 10%, a 0.3T external magnetic field is applied to arrange the cubic silicon carbide in the silicone rubber in sequence and connect them closely until it is completely cured to form a thermally conductive and wave-absorbing silicone rubber.

[0042] Example 3

[0043] This embodiment provides a thermal conductive and wave absorbing integrated material, the preparation method of which includes the following steps:

[0044] Step 1: Sodium chloride is dissolved in 50ml of deionized water and stirred to form a saturated sodium chloride solution. 0.2g of cobalt nitrate hexahydrate is then added to the saturated sodium chloride solution and stirred continuously to form a mixed solution of sodium chloride / cobalt nitrate. 5ml of ammonia water is added to the mixed solution and stirred for 3min to adjust the pH value of the mixed solution to 10 to generate a magnetic metal hydroxide. 200ml of ethanol is then added to the mixed solution to precipitate micron-sized sodium chloride crystals containing cobalt hydroxide to form a mixed suspension, and ultrasonic stirring is continued for 10min.

[0045] Step 2: 3 ml of TEOS was added dropwise to the mixed suspension, stirred evenly and reacted for 30 minutes, then centrifuged, washed with water to remove sodium chloride, and dried to obtain a cobalt hydroxide-doped hollow cubic silica shell.

[0046] Step 3: Add 1 g of cobalt hydroxide-doped hollow cubic silica shell to a mixed solution of 50 ml of ethanol, 7 ml of deionized water, and 3 ml of ammonia water (the concentration of ammonia water is 30 wt%) and stir ultrasonically to make it evenly dispersed. Then add 0.8 ml of formaldehyde and 0.4 g of resorcinol to the suspension so that it self-polymerizes on the surface of the cobalt hydroxide-doped hollow cubic silica shell to form a phenolic layer as a carbon source. After continuous stirring and reacting for 24 hours, the product is collected by centrifugation and drying to obtain a precursor.

[0047] Step 4: 5g of the precursor was mixed with 0.05g of ferric nitrate and placed in a nitrogen-protected tube furnace. The mixture was heated to 600°C at a heating rate of 2-6°C / min and kept warm for 2 hours. The mixture was then heated to 1400°C at a heating rate of 2-6°C / min and kept warm for 3 hours. After cooling to room temperature, the calcined product was immersed in a 5mol / L sodium hydroxide solution, heated to 80°C, and etched for 72 hours. The mixture was centrifuged, washed until neutral, and then dried. The powder was calcined at 500°C for 2 hours to obtain cobalt-doped hollow cubic silicon carbide.

[0048] Step 5: After filling the liquid silicone rubber with cobalt-doped hollow cubic silicon carbide at a mass ratio of 10%, a 0.3T external magnetic field is applied to arrange the cubic silicon carbide in the silicone rubber in sequence and connect them closely until it is completely cured to form a thermally conductive and wave-absorbing silicone rubber.

[0049] Figure 2 The following are SEM images of cobalt-doped hollow cubic silicon carbide obtained in Examples 1-3. (a) and (d) are obtained by calcining at 1350°C in Example 1, (b) and (e) are obtained by calcining at 1375°C in Example 2, and (c) and (f) are obtained by calcining at 1400°C in Example 3. Figure 2It can be seen that as the reaction temperature increases, the morphology of the silicon carbide becomes increasingly unstable, with a large number of silicon carbide fibers gradually forming on the surface and extending outward. The hollow cubes obtained in Example 1 have a clear structure and the smoothest surface, while Examples 2 and 3 exhibit a large number of silicon carbide whiskers on their surfaces. The damaged areas in Figures (e) and (f) also indicate that the prepared cobalt-doped hollow cubes of silicon carbide are indeed hollow structures.

[0050] The microwave absorption performance of the cobalt-doped hollow cubic silicon carbide obtained in Example 1 was tested, and the results were as follows: Figure 3 As shown in the figure. Among them, (a) shows the absorption performance of cobalt-doped hollow cubic silicon carbide with a filling ratio of 10% (the mass ratio of cobalt-doped hollow cubic silicon carbide to paraffin wax), with a maximum effective bandwidth of 2.94 GHz at a thickness of 8.7 mm; (b) shows the absorption performance of cobalt-doped hollow cubic silicon carbide with a filling ratio of 20%, with a maximum effective bandwidth of 4.63 GHz at a thickness of 1.7 mm; (c) shows the absorption performance of cobalt-doped hollow cubic silicon carbide with a filling ratio of 30%, with a maximum effective bandwidth of 4.34 GHz at a thickness of 1.2 mm. Overall, the cobalt-doped hollow cubic silicon carbide with a filling ratio of 20% has better electromagnetic wave absorption performance, while the cobalt-doped hollow cubic silicon carbide with a filling ratio of 30% has a lower bandwidth than that of the 20% filling ratio, but it has a thinner thickness.

[0051] The cobalt-doped hollow cubic silicon carbide obtained in Example 1 was subjected to magnetic orientation treatment (0.3T external magnetic field) and then characterized by SEM. The arrangement morphology is as follows: Figure 4 shown.

[0052] The effective absorption bandwidth and thermal conductivity of the heat-conducting and wave-absorbing silicone rubbers prepared in Examples 1-3 were measured, and the results are shown in Table 1.

[0053] Table 1 Wave absorbing and heat conducting properties of the heat-conducting and wave-absorbing silicone rubber prepared in Examples 1-3

[0054] sample Performance indicators Example 1 Example 2 Example 3 Wave absorbing performance Effective absorption bandwidth (GHz) 2.94 4.63 4.34 Thermal conductivity Thermal conductivity (W / (mk)) 0.31 0.47 0.62

[0055] As can be seen from Table 1, as the content of cobalt-doped hollow cubic silicon carbide in the silicone rubber gradually increases, its thermal conductivity also increases. The thermal conductivity of the composite with a 30% filling ratio is more than 100% higher than that of the composite with a 10% filling ratio. It can be inferred that as the cobalt-doped hollow cubic silicon carbide is gradually filled, its thermal conductivity will inevitably increase again.

[0056] The present invention provides an integrated thermal conductive and wave absorbing material and a preparation method thereof. Cubic hollow silicon carbide is prepared by using micron-sized sodium chloride containing a magnetic metal and coating the material with silicon dioxide and a carbon source. The material is then densely arranged under magnetic guidance. This achieves the goals of controllable morphology and stable electromagnetic wave absorption performance of the irregularly shaped hollow silicon carbide, resolves the conflict between thermal conductivity and wave absorption performance, and simultaneously improves both within a foreseeable range. This provides basic information for subsequent research on hollow silicon carbides with other morphologies and has certain guiding significance for the subsequent development and industrial application of hollow silicon carbide.

[0057] In the present invention, unless otherwise specified, the scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. In addition, the reagents, materials and operating procedures used herein are those widely used in the corresponding fields.

[0058] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a thermal conductive and wave absorbing integrated material, characterized in that: The following steps are involved: Step 1: mixing a saturated sodium chloride solution with a magnetic metal nitrate, adjusting the pH to alkaline to generate a magnetic metal hydroxide, and then adding an organic solvent to precipitate micron-sized sodium chloride crystals containing the magnetic metal hydroxide; the magnetic metal nitrate is one or more of cobalt nitrate, nickel nitrate, and iron nitrate; the ratio of the magnetic metal nitrate to the saturated sodium chloride solution is 0.1-1 g:100 ml; the organic solvent is an alcohol; the volume ratio of the saturated sodium chloride solution to the organic solvent is 1:1-4; and the precipitation time of the micron-sized sodium chloride crystals does not exceed 30 minutes; Step 2: adding ethyl orthosilicate and reacting to coat micron-sized sodium chloride crystals containing magnetic metal hydroxide with silica, and removing the sodium chloride by water washing to obtain a magnetic metal hydroxide-doped hollow cubic silica shell; Step 3: synthesizing a carbon source on the surface of a hollow cubic silica shell doped with a magnetic metal hydroxide to obtain a precursor; Step 4: The precursor is kept at 400-650°C and then calcined at 1250-1400°C, then etched with a strong alkaline solution, and then air-fired to obtain magnetic metal-doped hollow cubic silicon carbide; Step 5: After the magnetic metal-doped hollow cubes are carbonized and filled into the liquid silicone rubber, an external magnetic field is applied to arrange the magnetic metal-doped hollow cubes of silicon carbide in the silicone rubber in sequence and connect them tightly until they are completely cured to form a heat-conducting and wave-absorbing silicone rubber.

2. The method for preparing the thermal conductive and wave absorbing integrated material according to claim 1, wherein: in, The specific method of step 2 is: adding ethyl orthosilicate dropwise to the suspension of micron-sized sodium chloride crystals containing magnetic metal hydroxide obtained in step 1, stirring evenly and reacting for 30 minutes, then centrifuging, washing with water, and drying to obtain a hollow cubic silica shell doped with magnetic metal hydroxide; The ratio of ethyl orthosilicate to the precipitated micron-sized sodium chloride crystals containing magnetic metal hydroxide is 0.25-0.5 ml:1 g.

3. The method for preparing the thermal conductive and wave absorbing integrated material according to claim 1, wherein: in, In step 3, the synthesized carbon source is phenolic formaldehyde, polyaniline or polyurethane.

4. The method for preparing the thermal conductive and wave absorbing integrated material according to claim 1, wherein: in, The specific method of step three is: adding the magnetic metal hydroxide-doped hollow cubic silica shell to a mixed solution of ethanol, water, and ammonia, and ultrasonically stirring to uniformly disperse it, then adding formaldehyde and resorcinol to the suspension to allow it to self-polymerize on the surface of the magnetic metal hydroxide-doped hollow cubic silica shell to form a phenolic layer as a carbon source, continuously stirring the reaction for 24 hours, and then centrifuging and drying to obtain a precursor; The volume ratio of ethanol, water and ammonia water is 50:7:3, and the concentration of ammonia water is 20-40 wt%; The amount ratio of the magnetic metal hydroxide-doped hollow cubic silica shell, formaldehyde and resorcinol is 2.5 g:2 ml:1 g.

5. The method for preparing the thermal conductive and wave absorbing integrated material according to claim 1, wherein: in, In step 4, the precursor is mixed with ferric nitrate, and the mixture is kept warm and calcined together; Ferric nitrate accounts for 0.5-3% of the total mass.

6. The method for preparing the thermal conductive and wave absorbing integrated material according to claim 5, wherein: in, The specific method of step 4 is as follows: the precursor is mixed with ferric nitrate and placed in a nitrogen-protected tube furnace, heated to 400-650°C at a heating rate of 2-6°C / min, kept warm for 1-3 hours, and then heated to 1250-1400°C at a heating rate of 2-6°C / min and kept warm for 2-5 hours. After cooling to room temperature, the calcined product is immersed in a strong alkaline solution and etched at 80°C for 72 hours, centrifuged, washed to neutrality, and then dried. It is then calcined at 450-650°C for 1-3 hours to obtain magnetic metal-doped hollow cubic silicon carbide; The strong alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the strong alkaline solution is 5-12 mol / L.

7. The method for preparing the thermal conductive and wave absorbing integrated material according to claim 1, wherein: in, In step five, the magnetic flux of the external magnetic field is 0.15-0.5T.

8. The thermal conductive and wave absorbing integrated material prepared by the preparation method according to any one of claims 1 to 7.

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