Ferrite composite multi-walled carbon nanotube wave-absorbing material and preparation method thereof

Abstract

The invention relates to the technical field of wave-absorbing materials. Specifically, the invention relates to a ferrite composite multi-walled carbon nanotube wave-absorbing material and a preparation method thereof. The invention also relates to electronic equipment containing the ferrite composite multi-walled carbon nanotube wave-absorbing material. The ferrite composite multi-walled carbon nanotube wave-absorbing material prepared by the invention comprises a ferrite magnetic material with magnetic loss and a multi-walled carbon nanotube material with electrical loss, and the composite material introduces multiple electromagnetic energy loss modes through unique structural design and component synergy, so that the wave-absorbing performance of the material is enhanced. In addition, the preparation method disclosed by the invention is simple in process, low in requirement on equipment, green and environment-friendly, and free from any toxic and harmful by-products.

Description

Technical Field

[0001] The present invention relates to the technical field of microwave absorbing materials. Specifically, the present invention relates to a ferrite composite multi-walled carbon nanotube microwave absorbing material and a preparation method thereof. The present invention also relates to an electronic device comprising the ferrite composite multi-walled carbon nanotube microwave absorbing material. Background Art

[0002] Among multiple modules of an existing laptop motherboard, such as GPU, DDR, SSD, etc., different intensities of noise may be generated. Some of these noises work in the WLAN frequency band, thus affecting the WLAN performance. Therefore, microwave absorbing materials are usually required to absorb electromagnetic waves generated by electronic products and reduce the interference of these electromagnetic waves on the surrounding environment. This is particularly important for ensuring the normal operation of electronic devices and improving signal quality. In an environment where multiple devices coexist, the electromagnetic compatibility of electronic products becomes crucial.

[0003] Microwave absorbing materials help reduce electromagnetic interference between devices, thereby improving the stability and reliability of the entire system. Some sensitive components inside electronic products, such as chips and circuit boards, may have degraded performance or be damaged due to electromagnetic interference. By reducing electromagnetic interference, microwave absorbing materials help improve the overall performance of electronic products, including communication speed, data processing ability, and energy efficiency.

[0004] However, the microwave absorbing materials currently used in electronic products are all prepared from metal particle-containing materials with only a single magnetic loss mode. They not only have problems such as high density and heavy mass, but also have disadvantages such as narrow effective absorption bandwidth.

[0005] According to electromagnetic theory, for a material to have excellent microwave absorption performance, it generally needs to meet two conditions: good impedance matching and strong electromagnetic attenuation. Therefore, it is promising to obtain an electromagnetic wave absorbing material with high absorption and wide bandwidth by compounding dielectric loss-type carbon black with magnetic materials. After the two materials are compounded, it is expected to have both dielectric loss and magnetic loss, which is beneficial to adjusting the impedance matching of the microwave absorbing material and enhancing the attenuation of incident electromagnetic waves.

[0006] Existing preparation methods of microwave absorbing materials have problems such as complex preparation methods, cumbersome preparation processes, and high requirements for equipment conditions. Moreover, the densities of existing microwave absorbing materials are relatively high, which limits the practical use of microwave absorbing materials.

[0007] Ferrite is a kind of metal oxide magnetic material with excellent performance. Its main components are iron and oxygen, and it has characteristics such as good chemical stability, thermal stability, and ferromagnetism. In the field of microwave absorption materials, ferrite has received extensive attention due to its unique electromagnetic properties. Ferrite microwave absorption materials can effectively absorb and attenuate electromagnetic waves, thereby reducing the impact of electromagnetic waves on the surrounding environment. However, single ferrite has impedance mismatch, weak electromagnetic wave absorption ability, and large density, which to a certain extent limits the application of ferrite in the field of microwave absorption.

[0008] Carbon materials are a class of materials containing carbon elements, mainly including graphite, diamond, fullerene, carbon nanotubes, and graphene, etc. These materials have unique physical and chemical properties, such as high specific surface area, good electrical conductivity, and thermal stability, etc. The application of carbon materials as microwave absorption materials is very extensive, including military, aerospace, electronic communication and other fields. For example, materials such as carbon nanotubes and graphene can be used to manufacture high-performance microwave absorption materials for stealth technology and electromagnetic interference protection. However, the application of single carbon materials in the field of electromagnetic wave absorption is limited and it is difficult to meet the requirements of commercial applications (reflection loss value is lower than about -10 dB).

[0009] Therefore, how to composite carbon materials with ferrite to construct hybrid materials to obtain a kind of lightweight, high-efficiency, and low-thickness electromagnetic wave absorption material is an urgent problem to be solved in this field. Summary of the Invention

[0010] Object of the Invention

[0011] In view of the problems existing in the prior art described in the above Background Art section, the object of the present invention is to provide a ferrite composite multi-walled carbon nanotube microwave absorption material and its preparation method; the object of the present invention is also to provide an electronic device comprising the ferrite composite multi-walled carbon nanotube microwave absorption material.

[0012] Technical Solution

[0013] In order to achieve the above object, the present invention adopts the following technical solutions:

[0014] Solution 1: A method for preparing a ferrite composite multi-walled carbon nanotube microwave absorption material, wherein the method comprises the following steps:

[0015] Step 1: Mix an aqueous solution or dispersion of acidified multi-walled carbon nanotubes with iron nitrate and nitrate of non-ferrous metal X uniformly to obtain a mixed solution, and preferably continue to ultrasonicate and / or stir the mixed solution for about 0.5 to about 2.5 hours. In the mixed solution, the non-ferrous metal X ions account for about 33.1 mol% to about 33.5 mol%, preferably about 33.3 mol% of the total molar amount of iron ions and non-ferrous metal X ions; and based on each millimole of the iron nitrate, the weight of the acidified multi-walled carbon nanotubes is about 13 to about 17 mg, preferably about 15 mg;

[0016] Step 2: Adjust the pH of the obtained mixed solution to neutral to alkaline;

[0017] Step 3: Carry out a hydrothermal reaction on the mixed solution obtained from Step 2 at a temperature of about 140 to about 180 °C, preferably about 160 °C for about 8 to about 36 hours, and obtain a solid reaction product after cooling;

[0018] Step 4: Wash and dry the solid reaction product obtained from Step 3 to obtain the ferrite composite multi-walled carbon nanotube microwave absorption material.

[0019] Scheme 2: According to the preparation method described in Scheme 1 above, wherein the multi-walled carbon nanotubes have an average length of about 10 to about 30 μm; an outer diameter of about 10 to about 20 nm and an inner diameter of about 5 to about 10 nm.

[0020] Scheme 3: According to the preparation method described in Scheme 1 or 2 above, wherein the concentration of the aqueous solution or dispersion of the acidified multi-walled carbon nanotubes is in the range of about 0.375 to about 20 mg / mL.

[0021] Scheme 4: According to the preparation method described in any one of Schemes 1 to 3 above, wherein the iron nitrate is in the form of iron(III) nitrate nonahydrate.

[0022] Scheme 5: According to the preparation method described in any one of Schemes 1 to 4 above, wherein the nitrate of the non-ferrous metal X includes one or more of zinc nitrate, manganese nitrate, nickel nitrate, cobalt nitrate, magnesium nitrate and copper nitrate.

[0023] Scheme 6: According to the preparation method described in any one of Schemes 1 to 5 above, wherein the pH value of the mixed solution is adjusted to 7 to 9 in Step 2.

[0024] Scheme 7: According to the preparation method described in Scheme 6 above, wherein the pH value of the mixed solution is adjusted by dropwise adding an aqueous sodium hydroxide solution under stirring in Step 2.

[0025] Scheme 8: According to the preparation method described in any one of Schemes 1 to 7 above, wherein Step 4 includes washing the solid reaction product with deionized water or ethanol until neutral before drying.

[0026] Embodiment 9: The preparation method according to any one of Embodiments 1 to 8 above, wherein the drying in Step 4 includes vacuum freeze-drying the solid reaction product.

[0027] Embodiment 10: The preparation method according to Embodiment 9 above, characterized in that the vacuum freeze-drying in Step 4 includes freeze-drying for about 24 to about 36 hours at a pressure of about 0.1 to about 100 Pa and a temperature of about -10°C to about -50°C.

[0028] Embodiment 11: A ferrite composite multi-walled carbon nanotube microwave absorbing material prepared by the preparation method according to any one of Embodiments 1 to 10 above, wherein a coaxial ring sample with an outer diameter of about 7.00 mm, an inner diameter of about 3.04 mm, and a thickness of about 2.0 mm obtained from the microwave absorbing material and paraffin according to a mass ratio of about 3:7 can have a minimum reflection loss of up to about -49.1 dB and a maximum effective absorption bandwidth of up to about 4.7 GHz.

[0029] Embodiment 12: An electronic device, which includes the ferrite composite multi-walled carbon nanotube microwave absorbing material according to Embodiment 11 above.

[0030] Technical Effects

[0031] The present invention prepares a ferrite composite multi-walled carbon nanotube microwave absorbing material by a one-step hydrothermal method. The preparation process is simple, the requirements for equipment are low, and the preparation method is green and environmentally friendly without any toxic by-products.

[0032] The ferrite composite multi-walled carbon nanotube microwave absorbing material prepared by the present invention includes a ferrite magnetic material with magnetic loss and a multi-walled carbon nanotube material with electrical loss. Through unique structural design and component synergy, this composite material simultaneously introduces multiple electromagnetic energy loss modes, enhancing the microwave absorption performance of the material.

[0033] The composite material prepared by the method of the present invention has the advantages of strong absorption, controllable electromagnetic wave absorption frequency band, and wide frequency band. By changing the matching thickness of the composite material, effective absorption of electromagnetic waves in different frequency bands can be achieved, and it has important application value in the fields of electromagnetic absorption and electromagnetic shielding.

[0034] Specifically, compared with the traditional microwave absorbing materials in the prior art, the composite material of the present invention has the following advantages:

[0035] (1) The preparation method of the composite microwave absorbing material of the present invention is simple, green and environmentally friendly, and pollution-free;

[0036] (2) The composite material prepared by the composite of multi-walled carbon nanotubes and ferrite in the present invention simultaneously has dielectric loss and magnetic loss, which can enhance the impedance matching ability and improve the performance of the electromagnetic wave absorbing material;

[0037] (3) The composite wave-absorbing material of the present invention has a variety of loss mechanisms. In addition, a heterogeneous interface is formed between the composites, enhancing the dipole polarization.

[0038] (4) The minimum reflection loss that can be obtained from the composite wave-absorbing material of the present invention can reach about -49.1 dB, and the maximum effective absorption bandwidth can reach about 4.7 GHz. Detailed implementation manners

[0039] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention. The process parameters without specific conditions noted in the following embodiments are usually in accordance with conventional conditions.

[0040] In the present invention, the endpoints and any values within the disclosed ranges are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. The term "about" used in the present invention means that the modified number can fluctuate within ±20%, ±15%, ±10%, ±5% or ±2% of the number. For numerical ranges, the endpoints of each range, between the endpoints of each range and a single point value, and between single point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in the present invention.

[0041] In the first aspect of the present invention, the present invention provides a method for preparing a ferrite composite multi-walled carbon nanotube wave-absorbing material. The method includes the following steps 1 to 4.

[0042] Step 1 includes mixing an aqueous solution or dispersion of acidified multi-walled carbon nanotubes with iron nitrate and nitrate of non-ferrous metal X uniformly to obtain a mixed solution.

[0043] To make the obtained mixed solution fully uniform, the mixing process of the aqueous solution or dispersion of acidified multi-walled carbon nanotubes with iron nitrate and nitrate of non-ferrous metal X is preferably carried out under simultaneous ultrasonic and stirring, and further preferably, after the mixing operation is completed, the obtained mixed solution is continuously ultrasonicated and / or stirred for about 0.5 to about 2.5 hours.

[0044] In the step 1, in the obtained mixed solution, the non-ferrous metal X ions account for about 33.1 mol% to about 33.5 mol%, preferably about 33.3 mol% of the total molar amount of the ferric ions and the non-ferrous metal X ions. Here, the molar ratio of the ferric ions to the non-ferrous metal X ions should be around about 2:1 to conform to the ratio of the formed ferrite molecular formula.

[0045] In addition, based on each millimole of the ferric nitrate, the weight of the acidified multi-walled carbon nanotubes ranges from about 13 to about 17 mg, such as about 14 mg, about 15 mg or about 16 mg. Here, based on each millimole of the ferric nitrate, the weight of the acidified multi-walled carbon nanotubes should not be outside the range of about 13 to about 17 mg, otherwise the wave absorption performance of the obtained ferrite composite multi-walled carbon nanotube wave absorption material may be reduced.

[0046] In addition, the concentration of the aqueous solution or dispersion of the acidified multi-walled carbon nanotubes is not particularly limited, but in some exemplary embodiments of the present invention, the concentration of the aqueous solution or dispersion of the acidified multi-walled carbon nanotubes can be set within the range of about 0.375 to about 20 mg / mL. Such as about 1 mg / mL, about 2 mg / mL, about 5 mg / mL, about 10 mg / mL or about 15 mg / mL.

[0047] In addition, the type of the nitrate of the non-ferrous metal X is not particularly limited as long as it can form a ferrite with the ferric nitrate. For example, in some preferred embodiments of the present invention, the nitrate of the non-ferrous metal X may include one or more of zinc nitrate, manganese nitrate, nickel nitrate, cobalt nitrate, magnesium nitrate and copper nitrate.

[0048] In addition, the ferric nitrate and the nitrate of the non-ferrous metal X used in the step 1 may optionally be in the form of their hydrates. For example, the ferric nitrate used in the step 1 may be in the form of ferric nitrate nonahydrate.

[0049] The step 2 includes adjusting the pH of the mixed solution obtained from the above step 1 to the neutral to alkaline range.

[0050] In the step 2, since the ferrite needs to be formed in a neutral to alkaline environment, generally the pH value of the mixed solution can be adjusted to the range of about 7 to about 9.

[0051] In addition, in the step 2, the pH value of the mixed solution can be adjusted by dropwise adding an aqueous sodium hydroxide solution under stirring.

[0052] The step 3 includes subjecting the mixed solution from the above step 2 to a hydrothermal reaction and obtaining a solid reaction product after cooling.

[0053] In an exemplary embodiment of the present invention, the hydrothermal reaction of the mixed solution is carried out at a temperature of about 140 to about 180 °C (such as about 150 °C, about 160 °C or about 170 °C). Here, the temperature of the hydrothermal reaction should be within the defined range, otherwise the wave absorption performance of the obtained ferrite composite multi-walled carbon nanotube wave-absorbing material may not meet the requirements.

[0054] In addition, those skilled in the art can also make the hydrothermal reaction last for the required time according to the actual situation. For example, in some exemplary embodiments of the present invention, the hydrothermal reaction in step 3 is preferably carried out for about 8 to about 36 hours, such as about 12 hours, about 16 hours, about 20 hours, about 24 hours, about 28 hours or about 32 hours.

[0055] Step 4 includes drying the solid reaction product obtained from the above step 3 after washing to obtain the ferrite composite multi-walled carbon nanotube wave-absorbing material.

[0056] In a preferred embodiment of the present invention, before drying the solid reaction product in the above step 4, it is washed with deionized water or ethanol until neutral.

[0057] In addition, the drying in the above step 4 preferably includes vacuum freeze-drying. The vacuum freeze-drying preferably includes freeze-drying for about 24 to about 36 hours at a pressure of about 0.1 to about 100 Pa and a temperature of about -10 °C to about -50 °C.

[0058] In the second aspect of the present invention, the present invention relates to a ferrite composite multi-walled carbon nanotube wave-absorbing material prepared by the preparation method according to the first aspect of the present invention described above.

[0059] A coaxial ring specimen with an outer diameter of about 7.00 mm, an inner diameter of about 3.04 mm, and a thickness of about 2.0 mm obtained from the ferrite composite multi-walled carbon nanotube wave-absorbing material described in the second aspect of the present invention and paraffin according to a mass ratio of about 3:7 can have a minimum reflection loss of up to about -49.1 dB and a maximum effective absorption bandwidth of up to about 4.7 GHz.

[0060] The wave absorption mechanism of the ferrite composite multi-walled carbon nanotube wave-absorbing material of the present invention includes: in the composite material prepared in the present invention, the acidified multi-walled carbon nanotubes themselves have dielectric loss, and the oxygen-containing functional groups on their surfaces can generate dipole polarization; the ferrite has magnetic loss ability. After being compounded with the multi-walled carbon nanotubes, it can not only enhance the magnetic loss ability in the system and regulate the impedance matching, but also there is an obvious interface after the two components are compounded, which can enhance the interfacial polarization effect of the system. The multiple loss modes of the ferrite composite multi-walled carbon nanotube wave-absorbing material of the present invention play a synergistic role and can jointly enhance the electromagnetic wave absorption ability of the system.

[0061] In the third aspect of the present invention, the present invention relates to an electronic device comprising a ferrite composite multi-walled carbon nanotube absorbing material prepared by the preparation method according to the first aspect of the present invention described above or a ferrite composite multi-walled carbon nanotube absorbing material according to the second aspect of the present invention described above.

[0062] The present invention will be further described in detail below in conjunction with specific examples and comparative examples.

[0063] The multi-walled carbon nanotubes used in the following examples were obtained from Xianfeng Nano Company, and the multi-walled carbon nanotubes had an average length of 10 to 30 μm, an outer diameter of 10 to 20 nm, and an inner diameter of 5 to 10 nm.

[0064] Other chemical raw materials used in the examples were all analytically pure products that could be commercially obtained.

[0065] The acidification process of the multi-walled carbon nanotubes includes:

[0066] 1. Weigh the multi-walled carbon nanotubes and concentrated nitric acid in a three-necked flask, wherein the volume of concentrated nitric acid used based on each gram of the multi-walled carbon nanotubes is about 300 ml;

[0067] 2. Place the three-necked flask on a stirring constant temperature electric heating mantle and heat it to about 120 °C, and keep it warm at this temperature for about 4 hours;

[0068] 3. Pour the mixture in the three-necked flask into a large beaker and let it stand for about 24 hours;

[0069] 4. Filter the solid product by suction and wash it with deionized water;

[0070] 5. Obtain acidified multi-walled carbon nanotubes after drying the solid product.

[0071] Example 1

[0072] (1) Add about 90 mg of the acidified multi-walled carbon nanotubes as described above to about 60 mL of deionized water while stirring, ultrasonicate for about 1 hour and then continue to stir for about 0.5 hour to prepare a dispersion of acidified multi-walled carbon nanotubes with a concentration of about 1.5 mg / mL.

[0073] (2) Under the condition of vigorous stirring, add about 6 mmol of Fe(NO 3 ) 3 ·9H 2 O and about 3 mmol of Ni(NO 3 ) 2 ·6H 2 O to the dispersion obtained in step (1) respectively, and continue to stir until the nitrates are completely dissolved.

[0074] (3) Add an aqueous sodium hydroxide solution with a concentration of about 2 mol / L dropwise to the mixed solution obtained from step (2) to adjust the pH to weakly alkaline (pH value in the range of 7 to 9), and continue stirring for about 0.5 hours.

[0075] (4) Transfer the mixed solution obtained from step (3) to a hydrothermal reaction kettle with a volume of 100 mL, and carry out a hydrothermal reaction at a temperature of about 160 °C for about 12 hours, and then cool the reaction solution to room temperature to obtain a solid reaction product.

[0076] (5) Wash the solid reaction product obtained from step (4) with absolute ethanol and deionized water until neutral.

[0077] (6) Dry the washed product obtained from step (5) in a vacuum drying oven at a pressure of about 0.1 to about 100 Pa and a temperature of about -10 °C to about -50 °C for at least about 24 hours to obtain the final ferrite composite multi-walled carbon nanotube microwave absorbing material.

[0078] Comparative Example 1:

[0079] Prepare a ferrite composite multi-walled carbon nanotube microwave absorbing material by a process similar to that of Example 1, except that about 60 mg of the acidified multi-walled carbon nanotubes are added in step (1).

[0080] Comparative Example 2:

[0081] Prepare a ferrite composite multi-walled carbon nanotube microwave absorbing material by a process similar to that of Example 1, except that about 120 mg of the acidified multi-walled carbon nanotubes are added in step (1).

[0082] Respectively, press the ferrite composite multi-walled carbon nanotube microwave absorbing material powder products obtained from Example 1 and Comparative Examples 1 and 2 and paraffin into coaxial ring specimens with an outer diameter of about 7.00 mm, an inner diameter of about 3.04 mm, and a thickness of about 2.0 mm in a special mold, and test their electromagnetic parameters with a vector network analyzer, calculate the microwave absorbing performance, and the test frequency range is about 2 to about 18 GHz.

[0083] Specific test results show that when based on each millimole of the ferric nitrate nonahydrate, the weight of the acidified multi-walled carbon nanotubes is about 10 mg, the minimum reflection loss that can be obtained from the resulting microwave absorbing material can only reach about -19.0 dB, and the maximum effective absorption bandwidth can only reach about 2.6 GHz.

[0084] When based on each millimole of the ferric nitrate nonahydrate, the weight of the acidified multi-walled carbon nanotubes is about 15 mg, the minimum reflection loss that can be obtained from the resulting microwave absorbing material can reach about -49.1 dB, and the maximum effective absorption bandwidth can reach about 4.7 GHz.

[0085] When the weight of the acidified multi-walled carbon nanotubes is about 20 mg based on per millimole of the iron(III) nitrate nonahydrate, the minimum reflection loss obtainable from the resulting microwave absorbing material can only reach about -8.7 dB.

[0086] Thus, it can be seen that the ferrite composite multi-walled carbon nanotube microwave absorbing material obtained in Example 1 of the present invention has a better microwave absorption effect than the microwave absorbing materials obtained in Comparative Examples 1 and 2.

[0087] Comparative Example 3

[0088] A ferrite composite multi-walled carbon nanotube microwave absorbing material was prepared in a process similar to that of Example 1, except that the hydrothermal reaction in step (3) was carried out at a temperature of about 120 °C for about 12 hours.

[0089] Comparative Example 4

[0090] A ferrite composite multi-walled carbon nanotube microwave absorbing material was prepared in a process similar to that of Example 1, except that the hydrothermal reaction in step (3) was carried out at a temperature of about 200 °C for about 12 hours.

[0091] The ferrite composite multi-walled carbon nanotube microwave absorbing material powder products obtained from Comparative Examples 3 and 4 and paraffin were respectively pressed into coaxial ring specimens with an outer diameter of about 7.00 mm, an inner diameter of about 3.04 mm, and a thickness of about 2.0 mm in a special mold according to a mass ratio of about 3:7. The electromagnetic parameters were measured with a vector network analyzer, and the microwave absorption performance was calculated. The test frequency range was about 2 to about 18 GHz.

[0092] From the specific test results, it can be seen that when the hydrothermal reaction is carried out at a temperature of about 120 °C, the resulting microwave absorbing material has almost no microwave absorption effect.

[0093] When the hydrothermal reaction is carried out at a temperature of about 160 °C, the minimum reflection loss obtainable from the resulting microwave absorbing material can reach about -49.1 dB, and the maximum effective absorption bandwidth can reach about 4.7 GHz.

[0094] When the hydrothermal reaction is carried out at a temperature of about 200 °C, the minimum reflection loss obtainable from the resulting microwave absorbing material can only reach about -26.3 dB, and the maximum effective absorption bandwidth can only reach about 1.9 GHz.

[0095] Thus, it can be seen that the ferrite composite multi-walled carbon nanotube microwave absorbing material obtained in Example 1 of the present invention has a better microwave absorption effect than the microwave absorbing materials obtained in Comparative Examples 3 and 4.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions required to be protected by the present invention.

Claims

1. A method for preparing a ferrite composite multi-walled carbon nanotube absorbing material, characterized in that: The method comprises the following steps: Step 1: uniformly mixing an acidified aqueous solution or dispersion of multi-walled carbon nanotubes with ferric nitrate and a nitrate of a non-ferrous metal X to obtain a mixed solution, wherein in the mixed solution, the non-ferrous metal X ions account for 33.1 mol% to 33.5 mol%, preferably 33.3 mol%, of the total molar amount of ferric ions and non-ferrous metal X ions; and the weight of the acidified multi-walled carbon nanotubes is 13 to 17 mg, preferably 15 mg, based on each millimole of the ferric nitrate; Step 2: adjusting the pH of the obtained mixed solution to neutral to alkaline; Step 3: subjecting the mixed solution obtained in step 2 to a hydrothermal reaction at a temperature of 140 to 180° C., preferably 160° C., for 8 to 36 hours, and cooling to obtain a solid reaction product; Step 4: washing and drying the solid reaction product obtained in step 3 to obtain the ferrite composite multi-walled carbon nanotube absorbing material.

2. The preparation method according to claim 1, characterized in that: The multi-walled carbon nanotubes have an average length of 10 to 30 μm; an outer diameter of 10 to 20 nm and an inner diameter of 5 to 10 nm; and / or The concentration of the acidified aqueous solution or dispersion of multi-walled carbon nanotubes is in the range of 0.375 to 20 mg / mL; and / or The ferric nitrate is in the form of ferric nitrate nonahydrate.

3. The preparation method according to claim 1, characterized in that: The nitrate of the non-ferrous metal X comprises one or more of zinc nitrate, manganese nitrate, nickel nitrate, cobalt nitrate, magnesium nitrate and copper nitrate.

4. The preparation method according to claim 1, characterized in that: In step 2, the pH value of the mixed solution is adjusted to 7 to 9.

5. The preparation method according to claim 4, characterized in that: In step 2, the pH value of the mixed solution is adjusted by dropwise adding sodium hydroxide aqueous solution under stirring.

6. The preparation method according to any one of claims 1 to 5, characterized in that The step 4 includes washing the solid reaction product with deionized water or ethanol to neutrality before drying it.

7. The preparation method according to any one of claims 1 to 5, characterized in that The drying in step 4 includes vacuum freeze drying the solid reaction product.

8. The preparation method according to claim 7, characterized in that: The vacuum freeze drying in step 4 comprises freeze drying at a pressure of 0.1 to 100 Pa and a temperature of -10°C to -50°C for 24 to 36 hours. 9 . A ferrite composite multi-walled carbon nanotube absorbing material prepared by the preparation method according to claim 1 .

10. An electronic device, characterized in that: The electronic device comprises the ferrite composite multi-walled carbon nanotube absorbing material according to claim 9.