SnO2@Ni / carbon fiber composite wave-absorbing material and preparation method thereof

Abstract

The application discloses a SnO2@Ni / carbon fiber composite wave-absorbing material and a preparation method thereof, and belongs to the field of wave-absorbing materials. The wave-absorbing material comprises the following preparation process: step 1, SnO2 hydrogel is prepared through a sol-gel method, and then SnO2 aerogel microspheres are prepared through freeze drying; step 2, SnO2@Ni composite aerogel material coated with nano Ni metal is prepared through an in-situ precipitation reaction; and step 3, the SnO2@Ni composite aerogel material is mixed with polyacrylonitrile according to a certain proportion, and then hydrothermal reaction is carried out, and then the SnO2@Ni / carbon fiber composite wave-absorbing material is prepared through an electrostatic spinning process. The composite wave-absorbing material can combine dielectric loss and magnetic loss, and can obtain excellent wave-absorbing performance through the synergistic effect of conductivity loss, interface polarization, dipole polarization and multiple resonance behavior, and can be widely applied to the field of electromagnetic shielding.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electromagnetic wave absorbing materials, and particularly relates to a SnO2@Ni / carbon fiber composite wave absorbing material and a preparation method thereof. BACKGROUND

[0002] With the rapid development of modern electronic information technology, the wide application of various electronic devices has caused serious electromagnetic pollution to the environment, which not only affects normal human activities, but also interferes with the normal operation of precision electronic devices. In addition, in the military field, the anti-stealth radar technology is becoming more and more advanced, and aircrafts have higher requirements for stealth technology. Therefore, the research on wave absorbing materials has been widely valued in both civilian and military fields. An ideal wave absorbing material should have high wave absorbing performance and absorption bandwidth at a low filling rate. In order to meet the increasingly strict requirements, a large number of MA materials have emerged, such as polymer nanocomposites, two-dimensional MXene, carbon-based nanomaterials, and ferrite, which are widely used in the field of wave absorbing materials. However, a single material cannot meet the performance requirements of "light, thin, wide, and strong" at the same time. For example, magnetic wave absorbing materials such as Fe, Co, and Ni have high saturation magnetization and magnetic permeability, and strong magnetic loss capacity, but their wide application is limited due to their disadvantages such as easy oxidation, high density, and poor high-temperature resistance.

[0003] Composite materials are a kind of materials that can absorb and dissipate electromagnetic waves through impedance matching and attenuation matching. By combining metal materials with magnetic loss and carbon materials with dielectric loss, a composite wave absorbing material is prepared, and the synergistic effect of magnetic loss and dielectric loss and the multiple polarization effect enhance the attenuation ability of the material to electromagnetic waves. It is a material with wide application prospect. Carbon fiber is a conventional dielectric loss electromagnetic wave absorber. When electromagnetic waves are incident on the surface of carbon fiber, electronic and interfacial polarization effects occur inside the medium, generating induced current. The change of alternating magnetic field and electric field produces eddy current, so that the electromagnetic wave is converted into internal energy, thereby reducing the reflectivity of electromagnetic wave. However, single carbon fiber cannot meet the impedance matching requirement, and needs to be combined with metal materials to improve dielectric loss and magnetic loss.

[0004] Nanometer metal material has quantum effect, macroscopic quantum tunnel effect, small size effect and interface effect and other characteristics, when the electronic energy level of nanometer particle is split, it can produce strong absorption to electromagnetic wave. In addition, nanometer metal material has large specific surface area and high proportion of surface atoms, under electromagnetic radiation, high concentration of grain boundary and special structure of grain boundary atoms lead to free movement of atoms and electrons, so that electromagnetic energy is converted into heat energy, and the absorption capacity of electromagnetic wave is enhanced, therefore, nanometer metal material is widely concerned in the field of electromagnetic wave absorption. Nanometer tin dioxide (SnO2) is a kind of semiconductor metal compound with excellent performance, which has good chemical stability and thermal stability, low cost, wide band gap and dielectric loss and other characteristics. However, single SnO2 has poor wave absorption effect when used as electromagnetic wave absorbing material, because it has problems of large density, weak absorption intensity, narrow absorption frequency band and the like. In order to improve the electromagnetic wave absorption performance of nanometer SnO2 wave absorbing agent, it is necessary to adjust the impedance matching and enhance the electric conduction loss and multiple polarization relaxation loss so as to significantly improve the electromagnetic wave attenuation capacity. Doping magnetic metal can also improve the electromagnetic wave absorption performance of the material, especially doping semiconductor (ZnO, TiO2, SnO2) with magnetic metal (Fe, Co, Ni) can significantly improve the electromagnetic wave absorption performance of the material, therefore, in order to improve the electromagnetic wave absorption performance of SnO2, SnO2, magnetic Ni metal and carbon fiber can be compounded to construct SnO2@Ni / carbon fiber composite wave absorbing material. SUMMARY

[0005] The purpose of the present application is to provide a SnO2@Ni / carbon fiber composite wave absorbing material and a preparation method thereof, characterized in that it comprises a carbon fiber matrix and SnO2@Ni aerogel microspheres, and the SnO2@Ni aerogel microspheres are loaded on the carbon fiber matrix.

[0006] The SnO2@Ni / carbon fiber composite wave absorbing material provided by the present application comprises the following preparation process:

[0007] Step 1, preparation of SnO2 aerogel microspheres: SnCl2·2H2O is dissolved in a mixed solution of anhydrous ethanol and deionized water, and stirred at room temperature for 2h-3h to obtain a uniform mixed solution, then tetraethyl orthosilicate (TEOS) is slowly added to the mixed solution to form a gel, the gel is first aged at room temperature for 24h, and then aged at 70℃ for 48h, then the aged gel is heated to 50℃ and soaked in n-hexane for 24h to obtain a wet gel, then 2mol / L NaOH solution is added to the wet gel and stirred for 30min, then filtered and washed, then freeze-dried at-20℃ to-60℃ for 6h-12h, and finally calcined at 550℃ for 2h to obtain nanometer SnO2 aerogel microspheres;

[0008] Step 2, preparation of SnO2@Ni aerogel microspheres: take Ni(NO3)2·6H2O, ethylenediaminetetraacetic acid disodium salt and sodium tartrate into deionized water, stir at 50℃ until completely dissolved, cool to room temperature, adjust the solution pH to 12.5 with 2mol / L NaOH, add the SnO2 aerogel microspheres prepared in step 1 to the solution, add formaldehyde and stir for 1h, filter, wash, dry, and finally calcine at 500℃ for 4h to obtain SnO2@Ni / aerogel microspheres;

[0009] Step 3, preparation of SnO2@Ni / carbon fiber composite wave-absorbing material: disperse the SnO2@Ni aerogel microspheres into N,N-dimethylformamide solution, add polyacrylonitrile, obtain an electrospinning solution after thermal reaction, prepare fibers from the electrospinning solution by electrospinning technology, and collect the fibers by copper mesh to obtain SnO2@Ni / carbon fiber film, and perform pre-oxidation and carbonization treatment on the fiber film to obtain SnO2@Ni / carbon fiber composite wave-absorbing material.

[0010] Preferably, the volume ratio of anhydrous ethanol to deionized water in step 1 is 1:(1-5).

[0011] Preferably, the mass ratio of Ni(NO3)2·6H2O to SnO2 aerogel microspheres in step 2 is 1:(1-4).

[0012] Preferably, the mass ratio of SnO2@Ni aerogel microspheres to polyacrylonitrile in step 3 is 1:(5-20).

[0013] Preferably, the mass fraction of polyacrylonitrile in the solution in step 3 is 20%-30%.

[0014] Preferably, the thermal reaction in step 3 is mechanical stirring under nitrogen protection, the temperature is 40-70℃, and the reaction time is 4-8h.

[0015] Preferably, the voltage of electrospinning in step 3 is 8-13KV, the flow rate is 0.2-0.6mL / h, and the distance between the spinneret and the receiving screen is 9-18cm.

[0016] Preferably, the pre-oxidation condition in step 3 is: in an air atmosphere, the ambient temperature is increased to 200-300℃ at a heating rate of 1-3℃ / min, and then held for 2-3h.

[0017] Preferably, the carbonization condition in step 3 is: in a nitrogen atmosphere, the ambient temperature is increased to 700-1000℃ at a heating rate of 5℃ / min, and then held for 3-10h.

[0018] The technical effect of the present application is self-evident, the magnetic Ni metal is coated on the surface of the nano SnO2 aerogel, then is added into a polyacrylonitrile mixed solution, a SnO2@Ni loaded carbon fiber composite wave absorbing material is prepared, the impedance matching and the attenuation matching of the material are well realized, the attenuation ability of the material to electromagnetic waves is enhanced through the synergistic effect of magnetic loss and dielectric loss and multiple polarization effect.

[0019] The present application has the advantages of simple preparation process, low cost, light weight, thin thickness, stable wave absorbing performance, environmental friendliness, strong practicability, and wide application prospect in the field of electromagnetic wave protection. DETAILED DESCRIPTION

[0020] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the specific embodiments will be briefly introduced below, and obviously, the embodiments described below are some embodiments of the present application, and other embodiments can also be obtained by those skilled in the art without creative labor on the basis of these embodiments.

[0021] Embodiment 1

[0022] The SnO2@Ni / carbon fiber composite wave absorbing material includes the following preparation process:

[0023] Step 1, preparation of SnO2 aerogel microspheres: 20g of SnCl2·2H2O is dissolved in 500ml of a mixed solution of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol and deionized water is 1:1, and the mixed solution is stirred at room temperature for 2h to obtain a uniform mixed solution, 200ml of tetraethyl orthosilicate (TEOS) is slowly added to the mixed solution and stirred to form a gel, the gel is first aged at room temperature for 24h, and then aged at 70℃ for 48h, the aged gel is heated to 50℃ and then soaked in n-hexane for 24h to obtain a wet gel, 250ml of 2mol / L NaOH solution is added to the wet gel and stirred for 30min, then filtered, washed, freeze-dried at-20℃ for 2h, and finally calcined at 550℃ for 2h to obtain nano SnO2 aerogel microspheres.

[0024] Step 2, preparation of SnO2@Ni aerogel microspheres: 5g of Ni(NO3)2·6H2O, 10g of ethylenediaminetetraacetic acid disodium salt and 10g of sodium tartrate are added to 120ml of deionized water, and the solution is stirred at 50℃ to form a solution, the pH of the solution is adjusted to 12.5 at room temperature with 2mol / L NaOH, 5g of SnO2 aerogel microspheres prepared in step 1 is added to the solution, 100ml of formaldehyde is added and stirred for 1h, then filtered, washed, dried, and finally calcined at 500℃ for 4h to obtain SnO2@Ni aerogel microspheres.

[0025] Step 3, preparation of SnO2@Ni / carbon fiber composite wave-absorbing material: 4g of the SnO2@Ni aerogel microspheres were dispersed into 60ml of N,N-dimethylformamide solution, 20g of polyacrylonitrile was added, mechanical stirring was carried out under nitrogen protection, the temperature was 40℃, the reaction time was 8h, the electrospinning solution was obtained after stirring until complete dissolution, the electrospinning solution was prepared into fibers by electrospinning technology, and the fibers were collected by copper mesh, wherein the voltage of electrospinning was 8KV, the flow rate was 0.2mL / h, the distance between the spinneret and the receiving screen was 9cm, the spinning obtained SnO2@Ni / carbon fiber film, the fiber film was subjected to pre-oxidation treatment, the pre-oxidation treatment conditions were that the ambient temperature was increased to 200℃ at a heating rate of 1℃ / min in air atmosphere and then held for 3h. Then carbonization treatment was carried out, the carbonization treatment conditions were that the ambient temperature was increased to 700℃ at a heating rate of 5℃ / min in nitrogen atmosphere and then held for 10h, thereby obtaining the SnO2@Ni / carbon fiber composite wave-absorbing material.

[0026] Example 2

[0027] The SnO2@Ni / carbon fiber composite wave-absorbing material comprises the following preparation process:

[0028] Step 1, preparation of SnO2 aerogel microspheres: 20g of SnCl2·2H2O was dissolved in 500ml of a mixed solution of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol to deionized water was 1:5, a uniform mixed solution was obtained by stirring at room temperature for 3h, 200ml of tetraethyl orthosilicate (TEOS) was slowly added to the mixed solution and stirred to form a gel, the gel was first aged at room temperature for 24h and then aged at 70℃ for another 48h, the aged gel was heated to 50℃ and then soaked in n-hexane for 24h to obtain a wet gel, 250ml of 2mol / L NaOH solution was added to the wet gel and stirred for 30min, then filtered, washed, freeze-dried at-40℃ for 8h, and finally calcined at 550℃ for 2h to obtain nano SnO2 aerogel microspheres.

[0029] Step 2, preparation of SnO2@Ni aerogel microspheres: 5g of Ni(NO3)2·6H2O, 10g of ethylenediaminetetraacetic acid disodium salt and 10g of sodium tartrate were added to 100ml of deionized water, a solution was formed by stirring at 50℃, then the pH of the solution was adjusted to 12.5 with 2mol / L NaOH at room temperature, then 10g of SnO2 aerogel microspheres prepared in step 1 were added to the solution, 100ml of formaldehyde was added and stirred for 1h, then filtered, washed, dried, and finally calcined at 500℃ for 4h to obtain SnO2@Ni aerogel microspheres.

[0030] Step 3, preparation of SnO2@Ni / carbon fiber composite wave-absorbing material: 4g of the SnO2@Ni aerogel microspheres is dispersed into 200ml of N,N-dimethylformamide solution, 80g of polyacrylonitrile is added, mechanical stirring is carried out under nitrogen protection, the temperature is 55℃, the reaction time is 6h, the electrospinning solution is obtained after stirring until complete dissolution, the electrospinning solution is prepared into fibers by electrospinning technology, and the fibers are collected by copper mesh, wherein the electrospinning voltage is 13KV, the flow rate is 0.6mL / h, the distance between the spinneret and the receiving screen is 18cm, the spinning obtains SnO2@Ni / carbon fiber film, and the fiber film is subjected to pre-oxidation treatment, the pre-oxidation treatment conditions are that the ambient temperature is increased to 300℃ at a heating rate of 3℃ / min in an air atmosphere, and then the temperature is kept for 3h. Then carbonization treatment is carried out, the carbonization treatment conditions are that the ambient temperature is increased to 1000℃ at a heating rate of 5℃ / min in a nitrogen atmosphere, and then the temperature is kept for 3h, thereby obtaining the SnO2@Ni / carbon fiber composite wave-absorbing material.

[0031] Example 3

[0032] The SnO2@Ni / carbon fiber composite wave-absorbing material comprises the following preparation process:

[0033] Step 1, preparation of SnO2 aerogel microspheres: 20g of SnCl2·2H2O is dissolved in 500ml of a mixed solution of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol to deionized water is 1:3, a uniform mixed solution is obtained by stirring at room temperature for 3h, then 200ml of tetraethyl orthosilicate (TEOS) is slowly added to the mixed solution and stirred to form a gel, the gel is first aged at room temperature for 24h, then aged at 70℃ for another 48h, the aged gel is heated to 50℃ and then soaked in n-hexane for 24h to obtain a wet gel, 250ml of 2mol / L NaOH solution is added to the wet gel and stirred for 30min, then filtered, washed, freeze-dried at-60℃ for 6h, and finally calcined at 550℃ for 2h to obtain nano SnO2 aerogel microspheres.

[0034] Step 2, preparation of SnO2@Ni aerogel microspheres: 5g of Ni(NO3)2·6H2O, 10g of ethylenediaminetetraacetic acid disodium salt and 10g of sodium tartrate are added to 100ml of deionized water, a solution is formed by stirring at 50℃, then the pH of the solution is adjusted to 12.5 with 2mol / L NaOH at room temperature, then 20g of SnO2 aerogel microspheres prepared in step 1 is added to the solution, 150ml of formaldehyde is added and stirred for 1h, then filtered, washed, dried, and finally calcined at 500℃ for 4h to obtain SnO2@Ni aerogel microspheres.

[0035] Step 3, preparation of SnO2@Ni / carbon fiber composite wave-absorbing material: 4g of the SnO2@Ni aerogel microspheres were dispersed into 150ml of N,N-dimethylformamide solution, 60g of polyacrylonitrile was added, mechanical stirring was carried out under nitrogen protection, the temperature was 70℃, the reaction time was 4h, the electrospinning solution was obtained after stirring until complete dissolution, the electrospinning solution was prepared into fibers by electrospinning technology, and the fibers were collected by copper mesh, wherein the voltage of electrospinning was 13KV, the flow rate was 0.4mL / h, the distance between the spinneret and the receiving screen was 16cm, the spinning obtained SnO2@Ni / carbon fiber film, the fiber film was subjected to pre-oxidation treatment, the pre-oxidation treatment conditions were that the ambient temperature was increased to 200℃ at a heating rate of 2℃ / min in air atmosphere and then held for 2h. Then carbonization treatment was carried out, the carbonization treatment conditions were that the ambient temperature was increased to 900℃ at a heating rate of 5℃ / min in nitrogen atmosphere and then held for 7h, thereby obtaining the SnO2@Ni / carbon fiber composite wave-absorbing material.

[0036] Comparative Example 1

[0037] The SnO2@Ni aerogel microspheres loaded with Ni metal particles in this comparative example were prepared as follows:

[0038] Step 1, preparation of SnO2 aerogel microspheres: 20g of SnCl2·2H2O was dissolved in 500ml of a mixed solution of anhydrous ethanol and deionized water, wherein the volume ratio of anhydrous ethanol to deionized water was 1:3, stirring was carried out at room temperature for 3h to obtain a uniform mixed solution, then 200ml of tetraethyl orthosilicate (TEOS) was slowly added to the mixed solution and stirring was carried out to form a gel, the gel was first aged at room temperature for 24h, then aged at 70℃ for another 48h, the aged gel was heated to 50℃ and then soaked in n-hexane for 24h to obtain a wet gel, 250ml of 2mol / L NaOH solution was added to the wet gel and stirred for 30min, then filtered, washed, freeze-dried at-60℃ for 6h, and finally calcined at 550℃ for 2h to obtain nano SnO2 aerogel microspheres.

[0039] Step 2, preparation of SnO2@Ni aerogel microspheres: 5g of Ni(NO3)2·6H2O, 10g of ethylenediaminetetraacetic acid disodium salt and 10g of sodium tartrate were added to 500ml of deionized water, stirring was carried out at 50℃ to form a solution, the pH of the solution was adjusted to 12.5 at room temperature with 2mol / L NaOH, then 20g of SnO2 aerogel microspheres prepared in step 1 were added to the solution, 400ml of formaldehyde was added and stirred for 1h, then filtered, washed, dried, and finally calcined at 500℃ for 4h to obtain SnO2@Ni aerogel microspheres.

[0040] Comparative Example 2

[0041] The comparative example is a carbon fiber, and the preparation process is as follows:

[0042] 60 g of polyacrylonitrile is dispersed into 150 ml of N,N-dimethylformamide solution, and mechanical stirring is carried out under nitrogen protection at 70 DEG C. After the polyacrylonitrile is dissolved, an electrospinning solution is obtained. The electrospinning solution is prepared into fibers by an electrospinning technology, and the fibers are collected by a copper mesh. The electrospinning voltage is 13 KV, the flow rate is 0.4 mL / h, and the distance between the spinneret and the receiving screen is 16 cm. SnO2@Ni / carbon fiber film is obtained by spinning. The fiber film is subjected to pre-oxidation treatment. The pre-oxidation treatment conditions are as follows: the ambient temperature is increased to 200 DEG C at a heating rate of 2 DEG C / min in an air atmosphere, and then the ambient temperature is kept for 2 h. Then, carbonization treatment is carried out. The carbonization treatment conditions are as follows: the ambient temperature is increased to 900 DEG C at a heating rate of 5 DEG C / min in a nitrogen atmosphere, and then the ambient temperature is kept for 7 h. Thus, a carbon fiber material is obtained.

[0043] The sample is ground into powder in a mortar, and then the sample is blended with paraffin. After water bath heating, the sample is fully stirred until it is uniformly mixed. Then, the sample is poured into a mold in a heated state. After cooling and solidification, the sample is demolded. Thus, a concentric ring test sample with an outer diameter of 7 mm, an inner diameter of 3.04 mm, and a thickness of 2 mm is obtained. The electromagnetic parameters in a frequency range of 2 GHz-18 GHz are tested by using an Agilent-N5244A vector network analyzer. The test results are shown in the following table.

[0044] Absorption peak (GHz) Reflectivity (dB) RL <-10 dB wideband (GHz) Example 1 14.65 -21.36 8.87 Example 2 12.36 -19.57 5.63 Example 3 9.53 -15.44 7.62 Comparative Example 1 6.28 -10.55 2.54 Comparative Example 2 7.16 -2.79 -

[0045] According to the data in the table, the sample prepared in Example 1 has excellent electromagnetic wave absorption characteristics. The optimal wave absorption reflection effect is obtained at 14.65 GHz, and the reflectivity is -21.36 dB. The effective wave absorption bandwidth is 8.87 GHz. It is indicated that the composite wave absorption material of the application well realizes the mutual synergistic effect of impedance matching and attenuation matching. The synergistic effect of magnetic loss and dielectric loss and the multiple polarization effect enhance the electromagnetic wave attenuation capacity of the material.

[0046] The above examples are preferred embodiments of the application, but the embodiments of the application are not limited by the above examples. Any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the application shall be equivalent replacement modes, and shall be included in the protection scope of the application.

Claims

1. A method for preparing a SnO2@Ni / carbon fiber composite microwave absorbing material, characterized in that, The SnO2@Ni / carbon fiber composite microwave absorbing material includes a carbon fiber matrix and SnO2@Ni aerogel microspheres, wherein the SnO2@Ni aerogel microspheres are loaded on the carbon fiber matrix; The preparation method includes: Step 1, Preparation of SnO2 aerogel microspheres: SnCl2·2H2O was dissolved in a mixed solution of anhydrous ethanol and deionized water and stirred at room temperature for 2-3 hours to obtain a homogeneous mixed solution. Tetraethyl orthosilicate (TEOS) was slowly added to the mixed solution and stirred to form a gel. The gel was first aged at room temperature for 24 hours, and then aged at 70°C for 48 hours. The aged gel was heated to 50°C and then soaked in n-hexane for 24 hours to obtain a wet gel. 2 mol / L NaOH solution was added to the wet gel and stirred for 30 minutes. After filtration and washing, the gel was freeze-dried at -20°C to -60°C for 6-12 hours. Finally, it was calcined at 550°C for 2 hours to obtain nano-SnO2 aerogel microspheres. Step 2, preparation of SnO2@Ni aerogel microspheres: Ni(NO3)2·6H2O, disodium ethylenediaminetetraacetate and sodium tartrate were added to deionized water and stirred at 50°C until completely dissolved. After cooling to room temperature, the pH of the solution was adjusted to 12.5 with 2 mol / L NaOH. The SnO2 aerogel microspheres prepared in Step 1 were added to the solution, formaldehyde was added and stirred for 1 h, filtered, washed and dried, and finally calcined at 500°C for 4 h to obtain SnO2@Ni aerogel microspheres; Step 3, Preparation of SnO2@Ni / carbon fiber composite microwave absorbing material: The SnO2@Ni aerogel microspheres are dispersed in an N,N-dimethylformamide solution, polyacrylonitrile is added, and after thermal reaction, an electrospinning solution is obtained. The electrospinning solution is then used to prepare fibers, which are collected through a copper mesh to obtain a SnO2@Ni / carbon fiber film. The fiber film is then subjected to pre-oxidation and carbonization treatment to obtain the SnO2@Ni / carbon fiber composite microwave absorbing material.

2. The preparation method of the SnO2@Ni / carbon fiber composite microwave absorbing material according to claim 1, characterized in that, In step 1, the volume ratio of anhydrous ethanol to deionized water is 1:(1-5).

3. The preparation method of the SnO2@Ni / carbon fiber composite microwave absorbing material according to claim 1, characterized in that, In step 2, the mass ratio of Ni(NO3)2·6H2O to SnO2 aerogel microspheres is 1:(1-4).

4. The preparation method of the SnO2@Ni / carbon fiber composite microwave absorbing material according to claim 1, characterized in that, In step 3, the mass ratio of SnO2@Ni aerogel microspheres to polyacrylonitrile is 1:(5-20).

5. The preparation method of the SnO2@Ni / carbon fiber composite microwave absorbing material according to claim 1, characterized in that, In step 3, the mass fraction of polyacrylonitrile in the solution is 20% to 30%.

6. The preparation method of the SnO2@Ni / carbon fiber composite microwave absorbing material according to claim 1, characterized in that, The thermal reaction is carried out under nitrogen protection with mechanical stirring at a temperature of 40℃~70℃ for a reaction time of 4h~8h.

7. The preparation method of the SnO2@Ni / carbon fiber composite microwave absorbing material according to claim 1, characterized in that, In step 3, the electrospinning voltage is 8KV to 13KV, the flow rate is 0.2mL / h to 0.6mL / h, and the distance between the spinneret and the receiving screen is 9cm to 18cm.

8. The preparation method of the SnO2@Ni / carbon fiber composite microwave absorbing material according to claim 1, characterized in that, The pre-oxidation conditions in step 3 are as follows: in an air atmosphere, the ambient temperature is raised to 200℃~300℃ at a heating rate of 1℃ / min~3℃ / min and then kept at that temperature for 2h~3h.

9. The preparation method of the SnO2@Ni / carbon fiber composite microwave absorbing material according to claim 1, characterized in that, The carbonization conditions in step 3 are as follows: in a nitrogen atmosphere, the ambient temperature is raised to 700℃~1000℃ at a heating rate of 5℃ / min and then kept at that temperature for 3h~10h.