Magnetic metal nanoparticle-carbon nanotube composite wave-absorbing material and preparation method thereof

Abstract

The application discloses a kind of magnetic metal nanoparticles-carbon nanotube composite wave-absorbing materials and preparation method.The method first dissolves cobalt salt and 2-amino pyrazine in the mixed solution of ethanol and water, then mixed with the aqueous solution of tetracyanatoniobate at room temperature, after solid-liquid separation and constant temperature drying, obtain ZJU-75 precursor powder;Finally, the ZJU-75 precursor powder is placed in joule heating equipment, and in inert atmosphere protection, ultrafast transient high temperature heat treatment is carried out, so that the precursor is in situ converted into magnetic metal nanoparticles-carbon nanotube composite wave-absorbing material.The application breaks through the bottleneck of long preparation process cycle and metal easy to agglomerate, realizes the instantaneous conversion of precursor by using ultrafast joule heat technology;The prepared composite material has extremely small metal particle size and rich heterogeneous interface structure, and shows excellent comprehensive wave-absorbing performance, and has wide application prospect in electromagnetic interference protection and other fields.

Description

Technical Field

[0001] This invention relates to the field of functional materials and electromagnetic wave absorbing materials, specifically to a magnetic metal nanoparticle-carbon nanotube composite wave absorbing material and its preparation method. Background Technology

[0002] In recent years, with the rapid development of wireless communication, radar detection, and high-frequency electronic equipment, electromagnetic interference (EMI) has become an increasingly serious problem. Developing high-performance microwave absorbing materials with the characteristics of being "thin, light, wide, and strong" has become a hot topic in the field of electromagnetic protection.

[0003] Among numerous candidate materials, metal / carbon-based composite microwave absorbing materials have attracted much attention due to their strong structural designability and rich loss mechanisms. However, traditional single-component materials have obvious drawbacks: although magnetic metal particles have excellent magnetic loss capabilities, they are dense, prone to agglomeration, and have poor corrosion resistance; although carbon-based materials (such as carbon nanotubes) are lightweight and have excellent conductivity, their loss mechanisms are simple and easily lead to impedance mismatch, causing electromagnetic waves to be reflected at the surface.

[0004] Combining magnetic metals with carbon materials is an effective strategy to integrate the synergistic effects of dielectric loss and magnetic loss. However, existing preparation processes still face the following technical bottlenecks: (1) The preparation process is cumbersome and complex, which is not conducive to large-scale production. (2) Metal nanoparticles are prone to severe agglomeration on the carbon matrix, resulting in insufficient number of effective heterojunctions and limiting the improvement of microwave absorption performance. (3) The long-term stability of the material in complex environments is poor.

[0005] Therefore, developing a magnetic metal nanoparticle / carbon nanotube composite material with a simple and efficient preparation process, highly controllable structure, uniform magnetic component dispersion, and stable interfacial bonding is of great significance for achieving lightweight, wide-bandwidth, and high-efficiency microwave absorption. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, one objective of this invention is to provide a method for preparing a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material. This method is not only simple in process, short in production cycle, and low in cost, but also produces a composite material with fine-sized metal particles and abundant heterogeneous interfaces, exhibiting excellent microwave absorption performance.

[0007] To achieve the above objectives, the present invention employs the following technical solution: a method for preparing a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material, comprising the following steps: S1. Add cobalt salt and 2-aminopyrazine to a mixed solvent of ethanol and water, stir until fully dissolved to obtain precursor solution A; dissolve tetracyanidate in deionized water to obtain precursor solution B; S2. Under room temperature and stirring conditions, add precursor solution B to precursor solution A and mix while stirring. After the reaction is complete, collect the solid precipitate, dry and grind it under constant temperature conditions to obtain ZJU-75 precursor powder. S3. The obtained ZJU-75 precursor powder is placed in a Joule heating device, a protective gas is introduced into the heating chamber, and transient high-temperature calcination is performed at 700 ℃~1200 ℃ for 10 s~60 s to transform it in situ into a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material.

[0008] Further improvements to the preparation method of magnetic metal nanoparticle-carbon nanotube composite microwave absorbing materials: Preferably, in step S1, the molar ratio of cobalt salt, 2-aminopyrazine and tetracyanonitrile is 1:(1~4):1.

[0009] Preferably, the molar ratio of the cobalt salt, 2-aminopyrazine, and tetracyanonitrile is 1:1:1.

[0010] Preferably, in step S1, the concentration of the cobalt salt in the mixed solvent is 0.01 mol / L to 0.25 mol / L, and the volume ratio of ethanol to water in the mixed solvent is (0.5~2):1; the concentration of tetracyanonitrile in the precursor solution B is 0.01 mol / L to 0.25 mol / L.

[0011] Preferably, in step S1, the concentration of the cobalt salt in the mixed solvent is 0.05 mol / L, and the volume ratio of ethanol to water in the mixed solvent is 1:1; the concentration of tetracyanonitrile in the precursor solution B is 0.25 mol / L; and in step S3, the mixture is subjected to transient high-temperature calcination at 900 °C for 10 s.

[0012] Preferably, in step S1, the cobalt salt is cobalt nitrate; and the tetracyanonitrile is potassium tetracyanonitrile.

[0013] Preferably, in step S2, the temperature for constant temperature drying is 60 ℃~100 ℃.

[0014] Preferably, in step S2, the temperature for constant temperature drying is 80 °C.

[0015] Preferably, in step S3, the temperature of the transient high-temperature calcination treatment is 900 °C and the time is 10 s.

[0016] Preferably, in step S3, the transient high-temperature calcination treatment is carried out under an inert protective gas with a flow rate of 10 mL / min to 500 mL / min.

[0017] Preferably, in step S3, the transient high-temperature calcination treatment is carried out under a high-purity argon atmosphere with an argon flow rate of 100 mL / min.

[0018] The second objective of this invention is to provide a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material prepared by any of the above-described preparation methods.

[0019] The advantages of this invention compared to the prior art are as follows: (1) The present invention provides a method for preparing a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material, comprising four steps: preparation of precursor solution, mixing and precipitation reaction, solid-liquid separation and drying, and ultrafast Joule heat treatment, wherein each step cooperates with each other to form a whole.

[0020] The raw materials selected are cobalt salt, 2-aminopyrazine, and tetracyanonate nickelate. 2-Aminopyrazine forms a stable coordination structure with cobalt ions, while tetracyanonate nickelate provides the nickel source. Together, these three components construct the ZJU-75 precursor, with Co, Ni, and C uniformly distributed at the molecular level. Mixing the two precursor solutions at room temperature rapidly generates the ZJU-75 precipitate through a coordination reaction, requiring no heating and simplifying the process.

[0021] Ultrafast Joule heat treatment is key: processing at 700–1200℃ for 10–60 seconds achieves in-situ conversion of precursors. Compared with traditional tube furnaces, millisecond-level heating and extremely short holding times effectively suppress metal agglomeration, controlling the metal particle size to 20–80 nm. During heat treatment, metal ions are reduced to CoNi alloy, organic ligands undergo pyrolysis and carbonization, and carbon nanotubes are grown in situ under metal catalysis, forming an integrated "metal particle-carbon nanotube" structure, protected by an inert atmosphere to prevent oxidation.

[0022] In summary, the liquid-phase precursor ensures uniform elemental distribution, while Joule heat treatment enables rapid nucleation and limited growth. The combination of these two methods yields fine metal particles, in-situ carbon nanotubes, and abundant interfaces. The entire preparation cycle takes only a few hours, far shorter than the several days of traditional methods. It requires no expensive equipment or complex post-processing, making it suitable for large-scale production and solving the problems of cumbersome processes, metal agglomeration, and insufficient microwave absorption performance.

[0023] (2) The magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material of the present invention is composed of carbon nanotubes and CoNi alloy nanoparticles. The carbon nanotubes form a conductive network framework, and the metal particles are uniformly attached to their surface or ends, forming a large number of closely contacting heterogeneous interfaces. Functionally, the carbon nanotubes provide dielectric loss, and the metal particles provide magnetic loss. The two work synergistically, while enriching the interface to excite polarization effects and enhance electromagnetic wave attenuation. Example verification: minimum reflection loss -51.36 dB, effective absorption bandwidth 8.84 GHz, matching thickness 3.1 mm, metal particle size 20–50 nm. The product performs excellently in terms of "thin, light, wide, and strong", overcoming the problems of easy metal agglomeration and insufficient interface.

[0024] (3) The composite absorbing material of the present invention exhibits excellent absorbing performance. Example 2 shows a minimum reflection loss of -51.36 dB in the 2–18 GHz range, with an effective bandwidth of 8.84 GHz, covering the X-band and part of the Ku-band, meeting various radar stealth requirements. This composite absorbing material has a low density and a matching thickness of only 3.1 mm, far lower than traditional ferrites (usually more than 5 mm), making it suitable for applications where weight and thickness are sensitive, such as UAVs, missiles, and portable devices. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The images show the XRD patterns of the composite absorbing materials prepared in Examples 1-5 and the comparative examples of this invention.

[0027] Figure 2 The images shown are FESEM images of the intermediate and final products of Examples 1-5 and the comparative examples; wherein (a) is an FESEM image of the ZJU-75 precursor powder prepared in Example 1 at a magnification of 100k; (b), (c), (d), (e), and (f) are FESEM images of the composite absorbing materials prepared in Examples 1, 2, 3, 4, and 5 at a magnification of 100k, respectively; (g) is an FESEM image of the composite absorbing material prepared in Example 5 at a magnification of 20k; and (h) is an FESEM image of the composite absorbing material prepared in the comparative example at a magnification of 100k.

[0028] Figure 3The images show the absorption performance of the composite absorbing materials prepared in Examples 1-5 and the comparative examples; (a), (b), (c), (d), (e), and (f) are the absorption performance diagrams obtained by testing and calculating the electromagnetic parameters of the composite absorbing materials prepared in Examples 1-5 and the comparative examples of the present invention using a network vector analyzer. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0030] The preparation method of a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material provided by the present invention will be described in detail below. Contents not described in detail in the embodiments of the present invention are prior art known to those skilled in the art.

[0031] Example 1 This embodiment provides a method for preparing a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material, the specific steps of which are as follows: Step S1: Preparation of precursor solution Accurately weigh 0.5 mmol of cobalt nitrate hexahydrate Co(NO3)2·6H2O and 0.5 mmol of 2-aminopyrazine, and add them together to 10 mL of a mixed solvent of ethanol and deionized water (volume ratio 1:1). Stir at room temperature until completely dissolved to obtain precursor solution A.

[0032] Another 0.5 mmol of potassium tetracyanide nickelate hydrate (K2[Ni(CN)4]·H2O) was dissolved in 2 mL of deionized water to obtain precursor solution B.

[0033] Step S2, Precipitation reaction and precursor preparation

[0034] Under room temperature (approximately 25 °C) and magnetic stirring conditions, precursor solution B was slowly added to precursor solution A, and stirring was continued at a constant temperature until the reaction was complete. After the reaction, the mixture was filtered, and the resulting solid precipitate was collected, dried at a constant temperature of 80 °C to constant weight, and then ground to obtain a uniform ZJU-75 precursor powder.

[0035] Step S3, Ultrafast Joule Heat Treatment

[0036] The ZJU-75 precursor powder was placed on a graphite boat in a Joule heating apparatus. The heating chamber was sealed, and high-purity argon gas (flow rate 100 mL / min) was introduced to purge the air. The Joule heating was then activated, instantly raising the powder temperature to 700 ℃. After holding at this temperature for 10 s, the power was quickly cut off, and the powder was allowed to cool naturally to room temperature under argon protection. Through ultrafast thermal shock, the precursor underwent in-situ pyrolysis and catalytic growth, yielding a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material with uniform morphology and excellent microwave absorption properties.

[0037] Example 2 This embodiment provides a method for preparing a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material. The specific steps are the same as in Example 1, except that in step S3, the powder temperature is instantly raised to 900 ℃, held at that temperature for 10 s, and then the power is quickly cut off. The magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material is finally obtained.

[0038] Example 3 This embodiment provides a method for preparing a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material. The specific steps are the same as in Example 1, except that in step S3, the powder temperature is instantly raised to 1100 ℃, held at that temperature for 10 s, and then the power is quickly cut off. The magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material is finally obtained.

[0039] Example 4 This embodiment provides a method for preparing a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material, the specific steps of which are as follows: Step S1: Preparation of precursor solution Accurately weigh 0.5 mmol of cobalt nitrate hexahydrate Co(NO3)2·6H2O and 0.5 mmol of 2-aminopyrazine, and add them together to 15 mL of a mixed solvent of ethanol and deionized water (volume ratio 0.5:1). Stir at room temperature until completely dissolved to obtain precursor solution A.

[0040] Another 0.5 mmol of potassium tetracyanide nickelate hydrate (K2[Ni(CN)4]·H2O) was dissolved in 2 mL of deionized water to obtain precursor solution B.

[0041] Step S2, Precipitation reaction and precursor preparation Under room temperature (approximately 25 °C) and magnetic stirring conditions, precursor solution B was slowly added to precursor solution A, and stirring was continued at a constant temperature until the reaction was complete. After the reaction, the mixture was filtered, and the resulting solid precipitate was collected, dried at 100 °C to constant weight, and then ground to obtain a uniform ZJU-75 precursor powder.

[0042] Step S3: Place the ZJU-75 precursor powder on a graphite boat in a Joule heating apparatus, seal the heating chamber, and purge the air with high-purity argon gas (flow rate 10 mL / min). Power on the Joule heating to instantly raise the powder temperature to 1200 ℃, hold for 60 s, and then quickly de-energize. Allow the powder to cool naturally to room temperature under argon protection. Through ultrafast thermal shock, the precursor undergoes in-situ pyrolysis and catalytic growth, yielding a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material with uniform morphology and excellent microwave absorption performance.

[0043] Example 5 This embodiment provides a method for preparing a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material, the specific steps of which are as follows: Step S1: Preparation of precursor solution Accurately weigh 0.5 mmol of cobalt nitrate hexahydrate Co(NO3)2·6H2O and 2 mmol of 2-aminopyrazine, add them together to 10 mL of a mixed solvent of ethanol and deionized water (volume ratio 1:1), stir at room temperature until completely dissolved to obtain precursor solution A.

[0044] Another 0.5 mmol of potassium tetracyanide nickelate hydrate (K2[Ni(CN)4]·H2O) was dissolved in 2 mL of deionized water to obtain precursor solution B.

[0045] Step S2, Precipitation reaction and precursor preparation Under room temperature (approximately 25 °C) and magnetic stirring conditions, precursor solution B was slowly added to precursor solution A, and stirring was continued at a constant temperature until the reaction was complete. After the reaction, the mixture was filtered, and the resulting solid precipitate was collected, dried at a constant temperature of 60 °C to constant weight, and then ground to obtain a uniform ZJU-75 precursor powder.

[0046] Step S3, Ultrafast Joule Heat Treatment The ZJU-75 precursor powder was placed on a graphite boat in a Joule heating apparatus. The heating chamber was sealed, and high-purity argon gas (flow rate 500 mL / min) was introduced to purge the air. The Joule heating was then activated, instantly raising the powder temperature to 1000℃. After holding at this temperature for 30 seconds, the power was quickly cut off, and the powder was allowed to cool naturally to room temperature under argon protection. Through ultrafast thermal shock, the precursor underwent in-situ pyrolysis and catalytic growth, resulting in a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material with uniform morphology and excellent microwave absorption properties.

[0047] Comparative Example This embodiment provides a method for preparing a magnetic metal nanoparticle-carbon composite microwave absorbing material. The specific steps are the same as in Embodiment 1, except that step S3 involves tube furnace heat treatment. The specific steps are as follows: The ZJU-75 precursor powder is placed in a quartz boat in a tube furnace, and high-purity argon gas (flow rate 100 mL / min) is introduced to purge the air inside the tube. Under argon protection, the powder sample is heated to 900 °C and calcined for 1 h, then naturally cooled to room temperature to obtain the magnetic metal nanoparticle-carbon composite microwave absorbing material.

[0048] Phase detection, morphology observation and absorption performance testing The products obtained in Examples 1-5 and the comparative examples were subjected to phase analysis and morphological observation, and the following results were obtained: (1) The products obtained in Examples 1-5 and the comparative examples were subjected to phase analysis using an X-ray diffraction analyzer to obtain the following results. Figure 1 The X-ray diffraction pattern shown is from... Figure 1 It can be seen that the main phases of the products obtained in Examples 1-5 and the comparative examples are all consistent with the face-centered cubic structure of metallic Ni. This is mainly because the similar atomic radii and electronegativity of Co and Ni promote the formation of a continuous substitution solid solution. Co atoms successfully entered the fcc lattice of Ni and replaced some Ni atoms without forming an independent new phase. In addition, the products should also contain a large amount of amorphous carbon, but there is no obvious signal in the XRD pattern.

[0049] (2) The morphology of the products prepared in Examples 1-5 and the comparative examples was examined using a scanning electron microscope, and the results were as follows: Figure 2 The following are scanning electron microscope (SEM) images. Among them, (a) is a FESEM image of the ZJU-75 precursor powder prepared in Example 1 at a magnification of 100k; (b), (c), (d), (e), and (f) are FESEM images of the products prepared in Examples 1, 2, 3, 4, and 5, respectively, at a magnification of 100k; (g) is a FESEM image of the product prepared in Example 5 at a magnification of 20k; and (h) is a FESEM image of the product prepared in the comparative example at a magnification of 100k.

[0050] Depend on Figure 2It can be seen that the particle size of the ZJU-75 precursor powder prepared in Example 1 is approximately 50 nm. In the product obtained by Joule heating treatment at 700 °C in Example 1, the CoNi alloy morphology is granular, with a particle size of approximately 20-30 nm. A small amount of carbon forms carbon nanotubes with a diameter of approximately 20-30 nm and a length of approximately 50-100 nm. In the product obtained by Joule heating treatment at 900 °C in Example 2, the CoNi alloy morphology is spherical, with a particle size of approximately 20-50 nm. The carbon portion transforms into carbon nanotubes with a relatively large length-to-diameter ratio of approximately 20-50 nm and a length of approximately 200-300 nm, while some carbon blocks still remain. In the product obtained by Joule heating treatment at 1100 °C in Example 3, the CoNi alloy morphology is spherical, with a particle size of approximately 20-50 nm. The carbon portion transforms into carbon nanotubes with a relatively large length-to-diameter ratio of approximately 20-50 nm and a length of approximately 200-300 nm. At the same Joule heating time, as the Joule heating temperature increases, the size of CoNi alloy nanoparticles increases, the diameter of carbon nanotubes increases, and the length increases significantly.

[0051] In the magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material prepared in Example 4, the metal particles have a diameter of approximately 20-50 nm, and the carbon nanotubes have a diameter of approximately 20-50 nm and a length of approximately 300-500 nm. In the magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material prepared in Example 5, the metal particles have a diameter of approximately 50-80 nm, and the carbon nanotubes have a diameter of approximately 50-80 nm and a length of approximately 2-3 μm. In the comparative product, the CoNi alloy is spherical with a particle size of approximately 20-50 nm. Pyrolytic carbon exists on the particle surface and between the particles, but no carbon nanotubes are formed.

[0052] (3) Electromagnetic parameters of the products obtained in Examples 1-5 and the comparative examples were tested using a network vector analyzer, and the results were obtained by calculation. Figure 3 The absorption performance diagrams shown correspond to the following in sequence. Figure 3 (a), (b), (c), (d), (e), and (f) are from [the provided text]. Figure 3 A comparison of the absorption performance shows that: The magnetic metal nanoparticle-carbon nanotube composite absorbing material prepared in Example 1 exhibits strong absorption performance in the frequency range of 2-18 GHz. It shows the lowest reflection loss at a thickness of 6.3 mm, with a minimum reflection loss of -40.82 dB and an effective absorption bandwidth of 3.42 GHz.

[0053] The magnetic metal nanoparticle-carbon nanotube composite absorbing material prepared in Example 2 also exhibits strong absorbing performance in the 2-18 GHz frequency range. It shows the lowest reflection loss at a thickness of 3.1 mm, with a minimum reflection loss as low as -51.36 dB and an effective absorption bandwidth of 8.84 GHz.

[0054] The magnetic metal nanoparticle-carbon nanotube composite absorbing material prepared in Example 3 also exhibits strong absorption performance in the 2-18 GHz frequency range. It shows the lowest reflection loss at a thickness of 2.4 mm, with a minimum reflection loss of -37.58 dB and an effective absorption bandwidth of 5.41 GHz.

[0055] The magnetic metal nanoparticle-carbon nanotube composite absorbing material prepared in Example 4 has a minimum reflection loss of -45.15 dB (thickness 4.5 mm) in the range of 2~18 GHz and an effective absorption bandwidth of 5.01 GHz.

[0056] The magnetic metal nanoparticle-carbon nanotube composite absorbing material prepared in Example 5 has a minimum reflection loss of -52.03 dB (thickness 1.8 mm) in the range of 2~18 GHz and an effective absorption bandwidth of 6.77 GHz.

[0057] The magnetic metal nanoparticle-carbon composite absorbing material prepared in the comparative example also exhibits strong absorption performance in the frequency range of 2-18 GHz. It shows the lowest reflection loss at a thickness of 3.1 mm, with a minimum reflection loss of -29.46 dB and an effective absorption bandwidth of 6.61 GHz.

[0058] In summary, the technical solution of this invention can prepare CoNi alloy nanoparticle / carbon nanotube composite materials, and the microstructure of the CoNi alloy nanoparticles and carbon nanotubes can be effectively adjusted by the preparation parameters, thereby further controlling the microwave absorption performance of the composite material. Compared with the composite materials of the comparative examples, the magnetic metal nanoparticle-carbon nanotube composite microwave absorbing materials prepared in Examples 1-5 exhibit superior microwave absorption performance. The composite material of this invention not only has a simple preparation process, short production cycle, and low cost, but also has a low metal particle size and abundant interfaces, exhibiting good microwave absorption performance.

[0059] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material, characterized in that, Includes the following steps: S1. Add cobalt salt and 2-aminopyrazine to a mixed solvent of ethanol and water, stir until fully dissolved to obtain precursor solution A; dissolve tetracyanidate in deionized water to obtain precursor solution B; S2. Under room temperature and stirring conditions, add precursor solution B to precursor solution A and mix while stirring. After the reaction is complete, collect the solid precipitate, dry and grind it under constant temperature conditions to obtain ZJU-75 precursor powder. S3. The obtained ZJU-75 precursor powder is placed in a Joule heating device, a protective gas is introduced into the heating chamber, and transient high-temperature calcination is performed at 700 ℃~1200 ℃ for 10 s~60 s to transform it in situ into a magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material.

2. The preparation method of the magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material according to claim 1, characterized in that, In step S1, the molar ratio of cobalt salt, 2-aminopyrazine and tetracyanonitrile is 1:(1~4):

1.

3. The preparation method of the magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material according to claim 2, characterized in that, The molar ratio of the cobalt salt, 2-aminopyrazine, and tetracyanonitrile is 1:1:

1.

4. The method for preparing the magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material according to claim 1, characterized in that, In step S1, the concentration of the cobalt salt in the mixed solvent is 0.01 mol / L to 0.25 mol / L, and the volume ratio of ethanol to water in the mixed solvent is (0.5~2):1; the concentration of tetracyanonitrile in the precursor solution B is 0.01 mol / L to 0.25 mol / L.

5. The preparation method of the magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material according to claim 4, characterized in that, In step S1, the concentration of the cobalt salt in the mixed solvent is 0.05 mol / L, and the volume ratio of ethanol to water in the mixed solvent is 1:1; the concentration of tetracyanonitrile in the precursor solution B is 0.25 mol / L.

6. The method for preparing the magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material according to claim 1 or 4, characterized in that, In step S1, the cobalt salt is cobalt nitrate; the tetracyanonitrile salt is potassium tetracyanonitrile.

7. The method for preparing the magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material according to claim 1 or 4, characterized in that, In step S2, the temperature for constant temperature drying is 60 ℃~100 ℃.

8. The method for preparing the magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material according to claim 5, characterized in that, In step S3, the transient high-temperature calcination treatment is performed at a temperature of 900 °C for 10 s.

9. The method for preparing the magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material according to claim 1 or 8, characterized in that, In step S3, the transient high-temperature calcination treatment is carried out under an inert protective gas with a flow rate of 10 mL / min to 500 mL / min.

10. A magnetic metal nanoparticle-carbon nanotube composite microwave absorbing material prepared by the preparation method of any one of claims 1-9.

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