Three-dimensional carbon aerogel composite material based on aramid nanofiber as well as preparation method and application of three-dimensional carbon aerogel composite material

Abstract

The invention discloses a three-dimensional carbon aerogel composite material based on aramid nanofibers as well as a preparation method and application of the three-dimensional carbon aerogel composite material, and belongs to the technical field of electromagnetic wave absorbing materials. The three-dimensional carbon aerogel composite material comprises aramid nanofiber aerogel, nickel cobaltate, a cobalt metal simple substance, a nickel metal simple substance and a carbon nanotube, the nickel cobaltate, the cobalt metal elementary substance, the nickel metal elementary substance and the carbon nano tube are loaded on the aramid nanofiber aerogel. By doping magnetic and dielectric materials into the aramid nanofiber aerogel, a magnetic-dielectric synergistic effect is effectively constructed, impedance matching is improved, and thus absorption of incident electromagnetic waves is improved. The prepared three-dimensional carbon aerogel composite material based on the aramid nanofibers achieves excellent wave absorbing performance under the synergistic effect of appropriate impedance matching and multiple loss mechanisms, and also shows good thermal management capability.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic wave absorbing materials, and in particular relates to a three-dimensional carbon aerogel composite material based on aramid nanofibers, and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] With the rapid development of cutting-edge communication technology, 5G electromagnetic wave spectrum has been widely used in the electronics field, but problems related to electromagnetic wave radiation and pollution have become increasingly prominent. Moreover, due to the complex requirements of the actual application environment, absorbents need to be coated on the surface of the device, and it is necessary to further improve the thermal insulation capacity of the material to reduce the impact of temperature on the device. Therefore, it is crucial to develop aerogel materials with efficient EMW absorption, lightweight performance and excellent thermal insulation performance.

[0004] Carbon aerogel has the advantages of high porosity, multifunctionality and high specific surface area, and shows extraordinary potential in both structural materials and functional materials. The high specific surface area can produce multiple scattering and reflection of electromagnetic waves, which is very beneficial to the application of carbon aerogel in multifunctional absorption materials. Among the various materials used to prepare carbon aerogel, aramid nanofibers stand out due to their excellent dispersion stability and flame retardancy. The electrostatic repulsion between molecular chains can enhance the interfacial interaction with other matrices and promote the loading of nanoparticles. The carbonized aramid nanofiber aerogel can effectively maintain the porous network framework, and the N atoms present in itself can promote dielectric loss. However, the impedance mismatch and single loss mechanism caused by the inherent high conductivity of aramid nanofiber aerogel hinder its application in electromagnetic wave absorption. At present, the main improvement methods include heteroatom doping and the introduction of a second substance. For example, patent CN116456707A provides a method for preparing a cobalt-nickel / graphite phase carbon nitride / reduced graphene oxide composite aerogel absorber, but the electromagnetic wave absorption and lightweight performance of the resulting hydrogel still need to be improved. Summary of the invention

[0005] In order to address the deficiencies of the prior art, the purpose of the present invention is to provide a three-dimensional carbon aerogel composite material based on aramid nanofibers, and a preparation method and application thereof. The three-dimensional carbon aerogel composite material provided by the present invention achieves excellent wave absorbing performance under the synergistic effect of suitable impedance matching and multiple loss mechanisms, and also exhibits good thermal management capabilities.

[0006] In order to achieve the above object, the technical solution of the present invention is:

[0007] The first aspect of the present invention provides a three-dimensional carbon aerogel composite material based on aramid nanofibers, comprising aramid nanofiber aerogel, nickel cobaltate, cobalt metal element and nickel metal element, and carbon nanotubes;

[0008] The nickel cobaltate, cobalt metal element, nickel metal element and carbon nanotubes are loaded on the aramid nanofiber aerogel.

[0009] The second aspect of the present invention provides a method for preparing the three-dimensional carbon aerogel composite material based on aramid nanofibers, comprising the following steps:

[0010] dissolving a nickel source, a cobalt source and urea in water to obtain a precursor solution;

[0011] The aramid nanofiber aerogel and the precursor solution are mixed and subjected to a hydrothermal reaction to obtain an aerogel loaded with a cobalt-nickel precursor;

[0012] By heating in a gaseous carbon source and a reducing gas atmosphere, a three-dimensional carbon aerogel composite material based on aramid nanofibers is obtained.

[0013] By heating in a gaseous carbon source and reducing gas atmosphere, the cobalt-nickel precursor supported on the aerogel is reduced to a nickel cobaltate derivative, and the gaseous carbon source grows carbon nanotubes on the aerogel through chemical vapor deposition to obtain a three-dimensional carbon aerogel composite material based on aramid nanofibers.

[0014] In some embodiments of the present invention, the aramid nanofiber aerogel is prepared by the following method:

[0015] dispersing aramid nanofibers and potassium hydroxide in dimethyl sulfoxide to obtain a dispersion;

[0016] The dispersion is mixed with water to obtain a hydrogel, which is then frozen and dried to obtain an aramid nanofiber aerogel.

[0017] In some embodiments of the present invention, the mass ratio of the aramid nanofiber to potassium hydroxide is 1-2:1.5-3.

[0018] In some embodiments of the present invention, the molar ratio of the cobalt source, the nickel source and the urea is (1-4):(0.5-2):(3-12);

[0019] Preferably, the cobalt source includes cobalt nitrate, cobalt chloride or cobalt sulfate;

[0020] Preferably, the nickel source includes nickel nitrate, nickel chloride or nickel sulfate.

[0021] In some embodiments of the present invention, the temperature of the hydrothermal reaction is 120-130° C., and the reaction time is 10-14 h.

[0022] In some embodiments of the present invention, the gaseous carbon source includes one of ethylene, acetylene, propylene or propyne, preferably acetylene;

[0023] The reducing gas is selected from hydrogen or carbon monoxide, preferably hydrogen;

[0024] The flow rate of the gaseous carbon source and the reducing gas is 0.13-0.17 L / min.

[0025] In some embodiments of the present invention, the heating is specifically:

[0026] Raise the temperature to 550-750°C at 3-7°C / min and maintain for 20-40 min.

[0027] The third aspect of the present invention provides an application of the three-dimensional carbon aerogel composite material or the three-dimensional carbon aerogel composite material prepared by the preparation method in electromagnetic wave absorption.

[0028] A fourth aspect of the present invention provides a carbon aerogel composite absorbing material, which is composed of the three-dimensional carbon aerogel composite material based on aramid nanofibers or the three-dimensional carbon aerogel composite material based on aramid nanofibers prepared by the preparation method, and paraffin;

[0029] Wherein, in the carbon aerogel composite absorbing material, the content of the three-dimensional carbon aerogel composite material based on aramid nanofibers is 14-22wt%.

[0030] In some embodiments of the present invention, in the carbon aerogel composite absorbing material, the content of the three-dimensional carbon aerogel composite material based on aramid nanofibers is 16-22 wt %.

[0031] In some embodiments of the present invention, in the carbon aerogel composite absorbing material, the content of the three-dimensional carbon aerogel composite material based on aramid nanofibers is 19 wt %.

[0032] The beneficial effects of the present invention are:

[0033] The present invention provides a three-dimensional carbon aerogel composite material based on aramid nanofibers. By adding magnetic and dielectric materials into the aramid nanofiber aerogel, a magnetic-dielectric synergistic effect is effectively constructed, impedance matching is improved, and thus the absorption of incident electromagnetic waves is enhanced.

[0034] The present invention also provides a method for preparing a three-dimensional carbon aerogel composite material based on aramid nanofibers. The unidirectional aramid nanofiber aerogel can be prepared by using an ice template method, and the electrostatic repulsion between molecular chains and the transition metal are hydrothermally formed into a metal precursor. Subsequently, a transition metal derivative having metal atoms and metal oxides is formed by chemical vapor deposition, and the metal atoms are conducive to the catalytic growth of bamboo-shaped carbon nanotubes. The obtained three-dimensional carbon aerogel composite material based on aramid nanofibers achieves excellent wave absorption performance under the synergistic effect of suitable impedance matching and multiple loss mechanisms, and also shows good thermal management capabilities.

[0035] The present invention provides an advanced strategy for using aramid to prepare absorbing materials with magneto-dielectric loss effect and heterogeneous structure, which can have broad prospects in electromagnetic protection and thermal management devices. By rationally adjusting the aramid content, the concentration of metal ions and the chemical vapor deposition temperature, nickel cobaltate was successfully coated on the aerogel after hydrothermal treatment. Subsequently, a carbon aerogel with rich bamboo-like carbon nanotubes and magnetic components was prepared by chemical vapor deposition. The product obtained excellent impedance matching and magneto-dielectric synergistic effect with dual loss capability for electromagnetic waves. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0037] Figure 1 is a scanning electron microscope image of the three-dimensional carbon aerogel composite material based on aramid nanofibers obtained in Example 1 of the present invention;

[0038] Figure 2 This is a scanning electron microscope image of the three-dimensional carbon aerogel composite material based on aramid nanofibers obtained in Example 2 of the present invention;

[0039] Figure 3 This is a scanning electron microscope image of the three-dimensional carbon aerogel composite material based on aramid nanofibers obtained in Example 3 of the present invention. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0041] Example 1

[0042] The preparation method of the three-dimensional carbon aerogel composite material based on aramid nanofibers comprises the following steps:

[0043] Step 1: 1500 mg KOH was placed in 90 mL DMSO solution, followed by 1000 mg Kevlar fiber (ANF), and magnetic stirring was performed for 6 days to obtain an ANF / DMSO mixed solution;

[0044] Step 2: Mix the obtained mixed solution with 400 mL of deionized water to obtain ANFs hydrogel;

[0045] Step 3: Place the ANFs hydrogel in a copper template for directional freezing, freeze at -70 °C for 12 h, and then vacuum dry for 48 h to obtain the ANFs aerogel;

[0046] Step 4: Put 1mmol of Ni(NO3)2·6H2O, 2mmol of Co(NO3)2·6H2O and 6mmol of CO(NH2)2 into 70mL of deionized water and mix well to obtain a mixed precursor solution;

[0047] Step 5: placing the ANFs aerogel obtained in step 3 and the mixed precursor solution obtained in step 4 into polytetrafluoroethylene for hydrothermal reaction, and keeping the temperature at 130° C. for 12 h to obtain an aerogel loaded with a cobalt-nickel precursor;

[0048] Step 6: Place the aerogel loaded with cobalt-nickel precursor obtained in step 5 into an oven and dry at 60° C. overnight;

[0049] Step 7: Place the aerogel obtained in step 6 into a quartz boat, push it into a tubular furnace, introduce N2 to maintain an inert atmosphere in the tube, heat to 650°C at a heating rate of 5°C / min, introduce C2H2 and H2 at a rate of 0.15L / min, keep the temperature at 650°C for 30min, perform catalyst reduction and chemical vapor deposition to grow carbon nanotubes, then cool to room temperature in a N2 atmosphere, and take out the three-dimensional carbon aerogel;

[0050] Step 8: Mix the three-dimensional carbon aerogel obtained in step 7 with paraffin to prepare a three-dimensional carbon aerogel / paraffin composite material (named CoNi / ANFs1-650), in which the content of the three-dimensional carbon aerogel is 19wt.%, which is used for electromagnetic wave absorption.

[0051] For the measurement, the electromagnetic parameters of the three-dimensional carbon aerogel / paraffin composite material were characterized by a vector network analyzer (Agilent Technologies N5244A) in the range of 2-18 GHz to calculate the microwave absorption performance.

[0052] The minimum reflection loss of CoNi / ANFs1-650 was measured to be -86.01dB at 2.31mm, and when the thickness was reduced to 1.80mm, the effective bandwidth reached 5.4GHz. The minimum reflection loss of pure carbon aerogel was -1.33dB (3mm), with no effective absorption bandwidth.

[0053] Figure 1 This is a scanning electron microscope image of a three-dimensional carbon aerogel composite material based on aramid nanofibers obtained in Example 1 of the present invention.

[0054] Example 2

[0055] The preparation method of the three-dimensional carbon aerogel composite material based on aramid nanofibers comprises the following steps:

[0056] Step 1: 2250 mg KOH was added to 90 mL DMSO solution, followed by 1500 mg Kevlar fiber, and magnetic stirring was performed for 6 days to obtain an ANF / DMSO mixed solution;

[0057] Step 2: Mix the obtained mixed solution with 400 mL of deionized water to obtain ANFs hydrogel;

[0058] Step 3: Place the ANFs hydrogel in a copper template for directional freezing, freeze at -70 °C for 12 h, and then vacuum dry for 48 h to obtain the ANFs aerogel;

[0059] Step 4: Put 1mmol of Ni(NO3)2·6H2O, 2mmol of Co(NO3)2·6H2O and 6mmol of CO(NH2)2 into 70mL of deionized water and mix well to obtain a mixed precursor solution;

[0060] Step 5: placing the ANFs aerogel obtained in step 3 and the mixed precursor solution obtained in step 4 into polytetrafluoroethylene for hydrothermal reaction, and keeping the temperature at 130° C. for 12 h to obtain an aerogel loaded with a cobalt-nickel precursor;

[0061] Step 6: Place the aerogel loaded with cobalt-nickel precursor obtained in step 5 into an oven and dry at 60° C. overnight;

[0062] Step 7: Place the aerogel obtained in step 6 into a quartz boat, push it into a tube furnace, introduce N2 to maintain an inert atmosphere in the tube, heat to 600°C at a heating rate of 5°C / min, introduce C2H2 and H2 at a rate of 0.15L / min, keep the temperature at 600°C for 30min, perform catalyst reduction and chemical vapor deposition to grow carbon nanotubes, then cool to room temperature in a N2 atmosphere and take out the sample;

[0063] Step 8: Mix the sample obtained in step 7 with paraffin to prepare a three-dimensional carbon aerogel / paraffin composite material (named CoNi / ANFs2-600), in which the content of the three-dimensional carbon aerogel is 19wt.%, which is used for electromagnetic wave absorption.

[0064] For the measurement, the electromagnetic parameters of the three-dimensional carbon aerogel / paraffin composite material were characterized by a vector network analyzer (Agilent Technologies N5244A) in the range of 2-18 GHz to calculate the microwave absorption performance.

[0065] The minimum reflection loss of CoNi / ANFs2-600 was measured to be -24.49dB at 2.12mm, and the effective absorption bandwidth reached 6.1GHz (2.29mm). The minimum reflection loss of pure carbon aerogel was -1.33dB (3mm), and there was no effective absorption bandwidth.

[0066] Figure 2 This is a scanning electron microscope image of a three-dimensional carbon aerogel composite material based on aramid nanofibers obtained in Example 2 of the present invention.

[0067] Example 3

[0068] The preparation method of the three-dimensional carbon aerogel composite material based on aramid nanofibers comprises the following steps:

[0069] Step 1: 3000 mg KOH was added to 100 mL DMSO solution, followed by 2000 mg Kevlar fiber, and magnetic stirring was performed for 6 days to obtain an ANF / DMSO mixed solution;

[0070] Step 2: Mix the obtained mixed solution with 400 mL of deionized water to obtain ANFs hydrogel;

[0071] Step 3: Place the ANFs hydrogel in a copper template for directional freezing, freeze at -70 °C for 12 h, and then vacuum dry for 48 h to obtain the ANFs aerogel;

[0072] Step 4: Put 1mmol of Ni(NO3)2·6H2O, 2mmol of Co(NO3)2·6H2O and 6mmol of CO(NH2)2 into 70mL of deionized water and mix well to obtain a mixed precursor solution;

[0073] Step 5: placing the ANFs aerogel obtained in step 3 and the mixed precursor solution obtained in step 4 into polytetrafluoroethylene for hydrothermal reaction, and keeping the temperature at 130° C. for 12 h to obtain an aerogel loaded with a cobalt-nickel precursor;

[0074] Step 6: Place the aerogel loaded with cobalt-nickel precursor obtained in step 5 into an oven and dry at 60° C. overnight;

[0075] Step 7: Place the aerogel obtained in step 6 into a quartz boat, push it into a tube furnace, introduce N2 to maintain an inert atmosphere in the tube, heat to 600°C at a heating rate of 5°C / min, introduce C2H2 and H2 at a rate of 0.15L / min, keep the temperature at 600°C for 30min, perform catalyst reduction and chemical vapor deposition to grow carbon nanotubes, then cool to room temperature in a N2 atmosphere and take out the sample;

[0076] Step 8: Mix the sample obtained in step 7 with paraffin to prepare a three-dimensional carbon aerogel / paraffin composite material (named CoNi / ANFs3-600), in which the content of the three-dimensional carbon aerogel is 19wt.%, which is used for electromagnetic wave absorption.

[0077] For the measurement, the electromagnetic parameters of the three-dimensional carbon aerogel / paraffin composite material were characterized by a vector network analyzer (Agilent Technologies N5244A) in the range of 2-18 GHz to calculate the microwave absorption performance.

[0078] The minimum reflection loss of CoNi / ANFs3-600 was measured to be -79.76dB at 2.07mm, and the effective absorption bandwidth can reach 6.60GHz (2.29mm). The minimum reflection loss of pure carbon aerogel is -1.33dB (3mm), and there is no effective absorption bandwidth.

[0079] Figure 3 This is a scanning electron microscope image of a three-dimensional carbon aerogel composite material based on aramid nanofibers obtained in Example 3 of the present invention.

[0080] Table 1 shows the Raman spectra of the three-dimensional carbon aerogel composite materials based on aramid nanofibers prepared in Example 1, Example 2 and Example 3. All samples were at 1350 cm -1 Nearby and 1580cm -1 There are two obvious peaks near the graphite, corresponding to the D peak representing graphite defects / lattice distortion and the graphite sp 2 The intensity ratio of the D peak to the G peak in the Raman curve (R = I D / I G ) is higher, indicating that there are more defects and amorphous carbon content in the sample. The R value of pure aramid nanofiber carbon aerogel is 0.91.

[0081] It can be seen from Table 1 that the R values ​​of all samples are greater than the R value of pure aramid nanofiber carbon aerogel, and Example 3> Example 2> Example 1. A good degree of graphitization can effectively improve the conductivity of the material, thereby enhancing the dissipation of electromagnetic wave energy.

[0082] Table 1 Raman spectrum information of materials prepared in Example 1, Example 2 and Example 3

[0083]

[0084] Table 2 shows the X-ray diffraction pattern information of the three-dimensional carbon aerogel composite materials based on aramid nanofibers prepared in Example 1, Example 2 and Example 3 of the present invention.

[0085] As shown in Table 2, all samples have obvious broad diffraction peaks around 2θ≈26°, corresponding to the (002) crystal plane of graphitic carbon, which proves the presence of graphite structure in the samples. In addition, the appearance of diffraction peaks of NiCo2O4 (JCPDS No.02-1074), Co (JCPDS No.05-0727) and Ni (JCPDS No.04-0850) in the samples confirms the successful preparation of NiCo2O4, partial reduction of Co and Ni nanoparticles and the formation of CoNi / CNTs / ANFs heterogeneous interface.

[0086] Table 2 X-ray diffraction pattern information of materials prepared in Example 1, Example 2 and Example 3

[0087]

[0088] Table 3 shows the N2 adsorption-desorption isotherms of the three-dimensional carbon aerogel composite materials based on aramid nanofibers prepared in Examples 1, 2 and 3, and analyzes the specific surface area, pore volume and pore size of different samples. The isotherms of the samples are typical IV type, and the specific surface areas of Examples 1, 2 and 3 are 280.28 m 2 g -1 、238.67m 2 g -1 and 284.28m 2 g -1 , the volume of mesopores is larger than that of micropores, proving that the mesopores account for a large proportion of the sample’s abundant specific surface area and the pore structure provides more surface for microwave transmission, which is beneficial to multiple reflections and scattering of electromagnetic waves.

[0089] Table 3 N2 adsorption-desorption isotherm information of materials prepared in Example 1, Example 2 and Example 3

[0090]

[0091] Table 4 shows the hysteresis loops and coercive force data of the three-dimensional carbon aerogel composite materials based on aramid nanofibers prepared in Example 1, Example 2 and Example 3. Due to the presence of metal and metal oxide, the samples exhibit good ferromagnetism under external magnetic field excitation. As shown in Table 5, the saturation magnetization value of Example 3 is the highest, corresponding to the highest total magnetic material content, indicating that the magnetic loss is the largest, which is beneficial to improving the dissipation capacity of electromagnetic waves.

[0092] Table 4 N2 adsorption-desorption isotherm information of materials prepared in Example 1, Example 2 and Example 3

[0093]

[0094] Table 5 shows the electromagnetic wave absorption performance of the three-dimensional carbon aerogel composite material based on aramid nanofibers prepared in Example 1, Example 2 and Example 3. By calculating their minimum reflection loss (RL min ), effective absorption bandwidth (EAB), corresponding thickness (t), filling amounts, specific minimum reflection loss (SRL=|RL min |÷(Loading×t)) for comparative analysis. The minimum reflection loss of pure carbon aerogel is -1.33dB (3mm), and there is no effective absorption bandwidth. The effective absorption bandwidth of all embodiments can be stably maintained above 5.30GHz under thin thickness and low filling amount, and Examples 1 and 3 also show excellent absorption capacity, which verifies its wide application value. This is inseparable from the establishment of the three-dimensional network structure and the dual loss capacity brought about by the magneto-dielectric synergistic effect.

[0095] Table 5 Electromagnetic wave absorption properties of the materials prepared in Example 1, Example 2 and Example 3

[0096]

[0097] Table 6 shows the thermal insulation properties of the three-dimensional carbon aerogel composite materials based on aramid nanofibers prepared in Example 1, Example 2 and Example 3. The three-dimensional carbon aerogel composite materials based on aramid nanofibers obtained in the examples were placed on a heating table at 150°C, and the temperature changes on the aerogel surface were recorded using an infrared camera at 120s and 300s, respectively. All aerogels showed good thermal insulation properties.

[0098] Table 6 Thermal insulation properties of materials prepared in Example 1, Example 2 and Example 3

[0099]

[0100]

[0101] Table 7 shows the density of the three-dimensional carbon aerogel composite materials based on aramid nanofibers prepared in Example 1, Example 2 and Example 3.

[0102] Table 7 Density of materials prepared in Example 1, Example 2 and Example 3

[0103] Example <![CDATA[Density (mg / cm 3 )]]> 1 45.74 2 48.87 3 46.29

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A three-dimensional carbon aerogel composite material based on aramid nanofibers, characterized in that: Including aramid nanofiber aerogel, nickel cobalt oxide, cobalt metal and nickel metal, and carbon nanotubes; The nickel cobaltate, cobalt metal element, nickel metal element and carbon nanotubes are loaded on the aramid nanofiber aerogel.

2. A method for preparing a three-dimensional carbon aerogel composite material based on aramid nanofibers according to claim 1, characterized in that: The following steps are involved: dissolving a nickel source, a cobalt source and urea in water to obtain a precursor solution; The aramid nanofiber aerogel and the precursor solution are mixed and subjected to a hydrothermal reaction to obtain an aerogel loaded with a cobalt-nickel precursor; By heating in a gaseous carbon source and a reducing gas atmosphere, a three-dimensional carbon aerogel composite material based on aramid nanofibers is obtained.

3. The preparation method according to claim 2, characterized in that: The aramid nanofiber aerogel is prepared by the following method: dispersing aramid nanofibers and potassium hydroxide in dimethyl sulfoxide to obtain a dispersion; The dispersion is mixed with water to obtain a hydrogel, which is then frozen and dried to obtain an aramid nanofiber aerogel.

4. The preparation method according to claim 3, characterized in that: The mass ratio of the aramid nanofiber to potassium hydroxide is 1-2:1.5-3.

5. The preparation method according to claim 2, characterized in that: The molar ratio of the cobalt source, the nickel source and the urea is (1-4):(0.5-2):(3-12); Preferably, the cobalt source includes cobalt nitrate, cobalt chloride or cobalt sulfate; Preferably, the nickel source includes nickel nitrate, nickel chloride or nickel sulfate.

6. The preparation method according to claim 2, characterized in that: The temperature of the hydrothermal reaction is 120-130° C., and the reaction time is 10-14 hours.

7. The preparation method according to claim 2, characterized in that: The gaseous carbon source comprises one of ethylene, acetylene, propylene or propyne, preferably acetylene; The reducing gas is selected from hydrogen or carbon monoxide, preferably hydrogen; The flow rate of the gaseous carbon source and the reducing gas is 0.13-0.17 L / min.

8. The preparation method according to claim 2, characterized in that: The heating specifically includes: Raise the temperature to 550-750°C at 3-7°C / min and maintain for 20-40 min.

9. Use of the three-dimensional carbon aerogel composite material according to claim 1 or the three-dimensional carbon aerogel composite material prepared by the preparation method according to any one of claims 2 to 8 in electromagnetic wave absorption.

10. A carbon aerogel composite absorbing material, characterized in that: Composed of the aramid nanofiber-based three-dimensional carbon aerogel composite material according to claim 1 or the aramid nanofiber-based three-dimensional carbon aerogel composite material prepared by the preparation method according to any one of claims 2 to 8, and paraffin; Wherein, in the carbon aerogel composite absorbing material, the content of the three-dimensional carbon aerogel composite material based on aramid nanofibers is 14-22wt%; Preferably, in the carbon aerogel composite absorbing material, the content of the three-dimensional carbon aerogel composite material based on aramid nanofibers is 16-22wt%; Further preferably, in the carbon aerogel composite absorbing material, the content of the three-dimensional carbon aerogel composite material based on aramid nanofibers is 19 wt %.

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