Wave-absorbing material, preparation method therefor, and use thereof

Abstract

The present application belongs to the technical field of wave-absorbing materials, and specifically relates to a wave-absorbing material, a preparation method therefor, and a use thereof. The preparation method for the wave-absorbing material provided in the present application comprises the following steps: sequentially performing ball milling, magnetic separation, and heat treatment on magnetite powder to obtain the wave-absorbing material, wherein the magnetite powder is magnetite powder recovered from waste residues, and the average particle size of the product obtained by means of ball milling is 0.5-20 μm. In the present application, the simple treatment on the magnetite powder recovered from waste residues can greatly improve the wave-absorbing performance of waste residue-derived Fe3O4 crystals, and the effective wave-absorbing frequency band thereof can be regulated and controlled within the frequency band range of 2-18 GHz, and said crystals can be made into an Fe3O4-based wave-absorbing agent for industrial production and application. The method provided in the present application for converting waste residue-derived Fe3O4 crystals into a wave-absorbing material having excellent wave-absorbing properties can facilitate large-scale production at low costs, and expand the application range of the magnetite powder recovered from waste residues.

Description

Wave-absorbing material, preparation method and application thereof

[0001] The present application claims priority to the Chinese patent application No. CN202411274004.9, filed on September 12, 2024, and entitled "Wave-absorbing material, preparation method and application thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application belongs to the technical field of wave-absorbing materials, and particularly relates to a wave-absorbing material, a preparation method and application thereof. BACKGROUND

[0003] The exploitation of nickel and copper mines produces a large amount of iron-nickel-copper-rich slag. A large amount of waste slag not only occupies land, but also pollutes the environment, and will also cause a huge waste of resources. The total iron (TFe) content in the iron-nickel-copper-rich slag is more than 40% on average. If it can be recycled and reused, not only can a large amount of waste slag be disposed of, but also a huge economic value will be created. At present, the iron in the iron-nickel-copper-rich slag is mainly extracted in the form of magnetite by the method of smelting oxidation, but how to economically and efficiently reuse the magnetite powder extracted and recovered has become a bottleneck problem in the recycling of waste slag resources. The conventional treatment method is to apply the extracted magnetite powder as iron concentrate to steel smelting, but the impurity content of the recovered magnetite powder is relatively high. If it is to be applied in steel smelting, it still needs to be treated to remove impurities, resulting in rising costs and poor economic efficiency, and it is difficult to be industrialized and popularized.

[0004] It is a technical problem to be solved to explore a new application of the magnetite powder recovered from the iron-nickel-copper-rich slag. SUMMARY

[0005] Therefore, the present application provides a wave-absorbing material, a preparation method and application thereof. The wave-absorbing performance of the magnetite powder recovered from the iron-nickel-copper-rich slag is improved after treatment, and the magnetite powder can be used as a Fe3O4-based wave-absorbing agent.

[0006] In order to solve the above technical problems, the present application provides a preparation method of a wave-absorbing material, comprising the following steps:

[0007] The magnetite powder is sequentially subjected to ball milling, magnetic separation and heat treatment to obtain the wave-absorbing material. The magnetite powder is a magnetite powder recovered from waste slag, and the average particle size of the product obtained by ball milling is 0.5-20 μm.

[0008] Preferably, the ball milling is wet ball milling, and the dispersing agent of the wet ball milling comprises ethanol. The rotation speed of the ball milling is 200-300 r / min, and the ball milling time is 3-15 h.

[0009] Preferably, the grinding balls for the ball milling are large grinding balls, medium grinding balls and small grinding balls; the diameter of the large grinding balls is 8-12 mm, the diameter of the medium grinding balls is 5-7 mm, and the diameter of the small grinding balls is 2-4 mm; the mass ratio of the large grinding balls, the medium grinding balls and the small grinding balls is 1:9-11:18-22; and the ratio of the material to the balls in the ball milling is 1:10-30.

[0010] Preferably, the strength of the magnetic separation is 50-300 mT.

[0011] The method further comprises, before the magnetic separation, dispersing the product obtained by the ball milling in water to obtain a dispersion liquid.

[0012] Preferably, the magnetic separation can be repeated for 2-6 times.

[0013] Preferably, before the heat treatment, the product obtained by the magnetic separation is dried at a temperature of 75-85℃ for 8-16 h.

[0014] Preferably, the heat treatment is performed at a temperature of 500-900℃ for 1-3 h, and the temperature is raised to the heat treatment temperature at a rate of 4-6℃ / min.

[0015] Preferably, the magnetite powder comprises the following components in the following mass percentages:

[0016] The application also provides a wave-absorbing material prepared by the preparation method, which comprises a magnetite phase and an augite phase; the mass percentage of the magnetite phase in the wave-absorbing material is 70-85%.

[0017] The average particle size of the wave-absorbing material is 0.5-20 μm.

[0018] The application also provides an application of the wave-absorbing material as a Fe3O4-based wave-absorbing agent in a composite wave-absorbing material.

[0019] The application provides a preparation method of a wave-absorbing material, comprising the following steps: sequentially subjecting magnetite powder to ball milling, magnetic separation and heat treatment to obtain the wave-absorbing material; the magnetite powder is recovered from waste residue, and the average particle size of the product obtained by ball milling is 0.5-20 μm. The wave-absorbing performance of the Fe3O4 crystal derived from waste residue can be greatly improved by simple treatment of the magnetite powder recovered from waste residue, and the effective wave-absorbing frequency band thereof can be regulated in the frequency band range of 2-18 GHz, so that the Fe3O4-based wave-absorbing agent can be prepared for industrial production and application. The method for converting the Fe3O4 crystal derived from waste residue into the wave-absorbing material with excellent wave-absorbing performance can be produced in large quantities and at low cost, expands the application range of the magnetite powder recovered from waste residue, and can better realize resource recycling of solid waste residue. DETAILED DESCRIPTION

[0020] The application provides a preparation method of a wave-absorbing material, comprising the following steps:

[0021] The magnetite powder is sequentially subjected to ball milling, magnetic separation and heat treatment to obtain the wave-absorbing material.

[0022] In the application, the magnetite powder is recovered from waste residue. The magnetite powder is preferably recovered from fire nickel smelting waste residue by a melting oxidation process. In the application, the average particle size of the magnetite powder is preferably < 74 μm.

[0023] In the application, the magnetite powder preferably comprises the following mass percentage of components in the form of oxides of elements: 45-60% FeO, 10-25% SiO2, 3-7% MgO, 3-7% CaO and 1-2% impurities. In the application, the impurities preferably comprise one or more of Ni, Co, Cu and Al. In the application, the magnetite powder preferably comprises a magnetite phase (Fe3O4), an augite phase (CaMgSi2O6) and an impurity phase; the mass percentage of the magnetite phase in the magnetite powder is preferably 50-65%, more preferably 55-60%; the mass percentage of the augite phase in the magnetite powder is preferably 30-45%, more preferably 35-40%.

[0024] In the present application, the ball milling is preferably wet ball milling, the dispersant of the wet ball milling is preferably ethanol, and the ethanol is preferably analytical pure. In the present application, the rotation speed of the ball milling is preferably 200-300 r / min, and more preferably 250-280 r / min; the ball milling time is preferably 3-15 h, and more preferably 6-12 h. In the present application, the ball milling balls are preferably zirconium balls, and the ball milling balls are preferably large balls, medium balls and small balls; the diameter of the large balls is preferably 8-12 mm, and more preferably 10 mm; the diameter of the medium balls is preferably 5-7 mm, and more preferably 6 mm; the diameter of the small balls is preferably 2-4 mm, and more preferably 3 mm; the mass ratio of the large balls, medium balls and small balls is preferably 1:9-11:18-22, and more preferably 1:10:20; the ratio of the ball milling balls to the product is preferably 1:10-30, and more preferably 1:15-25, and more preferably 1:20.

[0025] In the present application, the ball milling is preferably carried out in a planetary ball mill. In the present application, the average particle size of the product obtained by the ball milling is 0.5-20 μm, preferably 1-10 μm, and more preferably 3-6 μm. The present application realizes effective separation of the magnetite phase and the pyroxene phase by limiting the ratio of the ball milling balls to the product and the ball milling time, so as to facilitate subsequent magnetic separation to make the mass percentage content of the magnetite phase in the wave-absorbing material reach 70-85%, thereby improving the wave-absorbing performance of the wave-absorbing material.

[0026] In the present application, the magnetic separation preferably further comprises: dispersing the product obtained by the ball milling in water to obtain a dispersion liquid. In the present application, the product obtained by the ball milling is preferably washed with water before the dispersing. The ethanol dispersant in the ball milling process can be removed by the water washing. In the present application, the dispersing is preferably carried out under ultrasonic conditions, the power of the ultrasonic is preferably 100-150 W, and more preferably 110-120 W; the ultrasonic time is preferably 20-40 min, and more preferably 25-30 min. The dispersing avoids agglomeration of the product (powder) obtained by the ball milling, and facilitates subsequent magnetic separation.

[0027] In the present application, the magnetic separation is preferably carried out in a wet magnetic separator, and the dispersion liquid is preferably fed into the wet magnetic separator, and the flow rate of the feeding is preferably 300-500 mL / min, and more preferably 350-450 mL / min. In the present application, the magnetic separation strength is preferably 50-300 mT, and more preferably 150-200 mT.

[0028] In the present application, the magnetic separation is preferably repeated, and the number of repetitions is preferably 2-6, more preferably 3-5. The purpose of repeating the magnetic separation in the present application is to more fully separate the magnetite from silicate gangue, and to obtain recycled magnetite powder with a higher Fe3O4 grade.

[0029] In the present application, the product obtained by magnetic separation is preferably dried before heat treatment. In the present application, the drying temperature is preferably 75-85℃, more preferably 80℃; and the drying time is preferably 8-16h, more preferably 10-12h.

[0030] In the present application, the heat treatment temperature is preferably 500-900℃, more preferably 600-800℃; and the heat treatment holding time is preferably 1-3h, more preferably 2h. In the present application, the temperature rising rate to the heat treatment temperature is preferably 4-6℃ / min, more preferably 5℃ / min. In the present application, the heat treatment is preferably carried out in a protective atmosphere, which is preferably nitrogen. In the present application, the heat treatment is preferably carried out in a tube furnace. In the present application, the heat treatment does not change the phase composition of the product, but only eliminates crystal defects.

[0031] In the present application, the product after heat treatment is preferably cooled. In the present application, the temperature after cooling is preferably room temperature, and the room temperature is preferably 20-35℃, more preferably 25-30℃. The present application does not have special requirements for the cooling method, as long as the desired temperature can be achieved.

[0032] In the embodiments of the present application, magnetite powder is recovered by a smelting oxidation process from pyrometallurgical nickel smelting slag (iron-nickel-rich slag), and the magnetite crystals in the magnetite powder are inlaid and interlaced with dielectric silicate substances, and are wrapped with each other. The present application adjusts the ratio between the magnetic components and the dielectric components in the magnetite powder by grinding and magnetic separation, and repairs and eliminates the crystal microstructure (crystal defects, intergranular stress, etc.) by a heat treatment process, so that the electromagnetic matching in the material is optimized, the wave absorption performance is improved, and the material has wave absorption ability in different microwave frequency bands.

[0033] The present application also provides a wave absorption material prepared by the preparation method described in the above technical solution, which comprises a magnetite phase and an augite phase; and the mass percentage of the magnetite phase in the wave absorption material is 70-85%, preferably 75-80%. In the present application, the average particle size of the wave absorption material is 0.5-20μm, preferably 0.8-10μm. In the present application, the wave absorption material has good wave absorption performance in the C band, the X band and the Ku band.

[0034] The application further provides application of the wave-absorbing material in the above technical solution as a Fe3O4-based wave-absorbing agent in a composite wave-absorbing material. In the application, the composite wave-absorbing material preferably comprises a rubber wave-absorbing sheet or a wave-absorbing coating.

[0035] In order to further illustrate the application, the technical solutions provided by the application are described in detail below in combination with examples, but they should not be understood as limiting the protection scope of the application.

[0036] Example 1

[0037] 10 g of nickel slag derived magnetite powder (recovered from fire nickel smelting waste slag by a melting oxidation process) was placed in a ball mill tank of a planetary ball mill, and large, medium and small zirconium ball grading with a mass ratio of 1:10:20 was used as the grinding ball, the diameters of the large, medium and small zirconium balls were 10 mm, 6 mm and 3 mm respectively, the ratio of material to ball was 1:20, and analytical pure ethanol was used as the dispersant, and the ball milling was performed at a speed of 300 r / min for 6 h; the material with an average particle size of 3 μm after ball milling was washed with water, and then mixed with water to obtain a dispersion liquid under ultrasonic oscillation at a power of 120 W for 30 min;

[0038] The dispersion liquid was fed into a wet magnetic separator at a flow rate of 400 mL / min, and magnetic separation was performed at a magnetic field strength of 150 mT, the magnetic powder recovered by magnetic separation was repeatedly subjected to magnetic separation for 5 times after adding water, and then was dried at 80℃ in a vacuum drying oven for 8 h to obtain an intermediate, marked as S1.

[0039] The intermediate was loaded into a corundum magnetic boat, and was placed in a horizontal tube furnace, and was heated to 700℃ at a heating rate of 5℃ / min under a nitrogen protective atmosphere, and was heat-treated for 2 h, and was cooled to room temperature (25℃) at a cooling rate of 5℃ / min, and the sample was taken out to obtain a wave-absorbing material, marked as S2.

[0040] Example 2

[0041] 10 g of nickel slag derived magnetite powder (recovered from fire nickel smelting waste slag by a melting oxidation process) was placed in a ball mill tank of a planetary ball mill, and large, medium and small zirconium ball grading with a mass ratio of 1:10:20 was used as the grinding ball, the diameters of the large, medium and small zirconium balls were 10 mm, 6 mm and 3 mm respectively, the ratio of material to ball was 1:20, and analytical pure ethanol was used as the dispersant, and the ball milling was performed at a speed of 300 r / min for 6 h; the material with an average particle size of 3 μm after ball milling was washed with water, and then mixed with water to obtain a dispersion liquid under ultrasonic oscillation at a power of 120 W for 30 min;

[0042] The dispersion liquid was fed into a wet magnetic separator at a flow rate of 400 mL / min, and magnetic separation was performed at a magnetic field strength of 150 mT, the magnetic powder recovered by magnetic separation was repeatedly subjected to magnetic separation for 5 times after adding water, and then was dried at 80℃ in a vacuum drying oven for 8 h to obtain an intermediate, marked as S1.

[0043] The intermediate was loaded into a corundum magnetic boat, placed in a horizontal tube furnace, and heated to 500°C at a rate of 5°C / min under a nitrogen protective atmosphere, and heat-treated for 3h, and cooled to room temperature (25°C) at a rate of 5°C / min, and the sample was taken out to obtain the wave-absorbing material, denoted as S2.

[0044] Example 3

[0045] 10g of nickel slag derived magnetite powder (recovered from fire nickel smelting waste slag by a molten oxidation process) was placed in a ball mill pot of a planetary ball mill, and large, medium and small zirconium ball grading with a mass ratio of 1:10:20 was used as the grinding ball, the diameters of the large, medium and small zirconium balls were 10mm, 6mm and 3mm respectively, the ratio of material to ball was 1:20, and analytical pure ethanol was used as the dispersant, and the ball milling was carried out at a speed of 300r / min for 12h; the material with an average particle size of 1.5μm after ball milling was washed with water, and then mixed with water to obtain a dispersion liquid under ultrasonic oscillation at a power of 140W for 30min;

[0046] The dispersion liquid was passed into a wet magnetic separator at a flow rate of 500mL / min for magnetic separation at a magnetic field strength of 200mT, the magnetic powder recovered by magnetic separation was repeatedly subjected to magnetic separation 5 times after adding water, and then dried at a constant temperature of 80°C in a vacuum drying oven for 12h to obtain the intermediate, denoted as S1;

[0047] The intermediate was loaded into a corundum magnetic boat, placed in a horizontal tube furnace, and heated to 700°C at a rate of 5°C / min under a nitrogen protective atmosphere, and heat-treated for 1h, and cooled to room temperature (25°C) at a rate of 5°C / min, and the sample was taken out to obtain the wave-absorbing material, denoted as S2.

[0048] Example 4

[0049] 10g of nickel slag derived magnetite powder (recovered from fire nickel smelting waste slag by a molten oxidation process) was placed in a ball mill pot of a planetary ball mill, and large, medium and small zirconium ball grading with a mass ratio of 1:10:20 was used as the grinding ball, the diameters of the large, medium and small zirconium balls were 10mm, 6mm and 3mm respectively, the ratio of material to ball was 1:20, and analytical pure ethanol was used as the dispersant, and the ball milling was carried out at a speed of 300r / min for 15h; the material with an average particle size of 1.5μm after ball milling was washed with water, and then mixed with water to obtain a dispersion liquid under ultrasonic oscillation at a power of 100W for 40min;

[0050] The dispersion liquid was passed into a wet magnetic separator at a flow rate of 500mL / min for magnetic separation at a magnetic field strength of 200mT, the magnetic powder recovered by magnetic separation was repeatedly subjected to magnetic separation 5 times after adding water, and then dried at a constant temperature of 80°C in a vacuum drying oven for 8h to obtain the intermediate, denoted as S1;

[0051] The intermediate was loaded into a corundum magnetic boat, placed in a horizontal tube furnace, and heated to 800℃ at a rate of 5℃ / min under a nitrogen protective atmosphere, and heat-treated for 1h, and cooled to room temperature (25℃) at a rate of 5℃ / min, and the sample was removed to obtain the wave-absorbing material, which is denoted as S2.

[0052] Comparative Example 1

[0053] The wave-absorbing material was prepared according to the method of Example 1, except that the ball milling ratio was 1:8, the ball milling time was 2h, and the average particle size of the material after ball milling was 24μm.

[0054] The intermediate S1 and the wave-absorbing material S2 prepared in Examples 1-4 and Comparative Example 1 were characterized by X-ray diffraction (XRD), vector network analyzer (VNA), and laser particle size analyzer for phase composition, wave-absorbing electromagnetic performance parameters, and particle size distribution. The electromagnetic parameters of the samples were characterized by vector network analyzer, and the wave-absorbing performance parameters were calculated according to the transmission line theory.

[0055] Table 1 Wave-absorbing performance of the wave-absorbing agent S1 and the wave-absorbing agent S2 prepared in Examples 1-4 and Comparative Example 1 at different wave bands Note: The lowest reflection loss is lower than -10dB, indicating that 90% of the electromagnetic wave energy can be absorbed, and the wave-absorbing performance is applicable; the lowest reflection loss is lower than -20dB, indicating that 99% of the electromagnetic wave energy can be absorbed, and the wave-absorbing performance is excellent.

[0056] The intermediate S1 prepared in Example 1 exhibited wave-absorbing performance in the Ku wave band 15-18GHz, with the lowest reflection loss of -40dB at 16.65GHz; the wave-absorbing material S2 prepared in Example 1 exhibited wave-absorbing performance in the C wave band 3-8GHz, the X wave band 8-12GHz, and the Ku wave band 12-18GHz, with the lowest reflection loss of -39dB at 6.9GHz.

[0057] The intermediate S1 prepared in Example 2 exhibited wave-absorbing performance in the Ku wave band 16.5-18GHz, with the lowest reflection loss of -20dB at 17.45GHz; the wave-absorbing material S2 prepared in Example 2 exhibited wave-absorbing performance in the C wave band 4-8GHz, the X wave band 8-10GHz, and the Ku wave band 14-18GHz, with the lowest reflection loss of -23dB at 4.8GHz.

[0058] The intermediate S1 prepared in Example 3 exhibits wave absorption performance in the Ku band of 15-18 GHz, and the lowest reflection loss is -34 dB at 16.60 GHz; the magnetic wave material S2 prepared in Example 3 exhibits wave absorption performance in the C band of 3-8 GHz, the X band of 8-10.5 GHz and the Ku band of 13-18 GHz, and the lowest reflection loss is -30 dB at 6.8 GHz.

[0059] The intermediate S1 prepared in Example 4 exhibits wave absorption performance in the Ku band of 15-18 GHz, and the lowest reflection loss is -31 dB at 16.20 GHz; the magnetic wave material S2 prepared in Example 4 exhibits wave absorption performance in the C band of 3-8 GHz, the X band of 8-12 GHz and the Ku band of 12-18 GHz, and the lowest reflection loss is -18 dB at 15.8 GHz.

[0060] The intermediate S1 prepared in Comparative Example 1 exhibits wave absorption performance in the Ku band of 16.5-18 GHz, and the lowest reflection loss is -12 dB at 17.50 GHz; the magnetic wave material S2 prepared in Comparative Example 1 exhibits wave absorption performance in the C band of 2-8 GHz and the Ku band of 14-18 GHz, and the lowest reflection loss is -13 dB at 5.5 GHz, but does not exhibit wave absorption performance in the X band of 8-12 GHz.

[0061] As can be seen from Table 1, the magnetite powder recovered and treated according to the method provided in the present application has good wave absorption performance and can be used as a wave absorber.

[0062] The present application uses the process of ball milling, magnetic separation and heat treatment to deeply process and remanufacture the nickel slag derived magnetite powder, changes the particle size and the Fe3O4-SiO2 ratio of the material powder, improves the degree of crystallization of the crystal in the material, and repairs the crystal defects, so as to greatly improve the wave absorption performance and control the frequency band in the commonly used wave absorption frequency band of 2-18 GHz. The wave absorption performance of the nickel slag derived Fe3O4 wave absorber produced by the present application has reached or even exceeded that of the Fe3O4 wave absorber produced by the pure chemical method, the wave absorption frequency width can cover the frequency band of 3-18 GHz, and the lowest reflection loss can reach -40 dB, and the performance has reached that of the similar products with excellent performance on the market. More importantly, the product is extracted from non-ferrous metallurgical slag, is a solid waste resource recycling, and the remanufacturing process is simple and has great industrialization potential.

[0063] Although the above embodiments have been described in detail, it should be understood that the above embodiments are only some embodiments of the present application, but not all embodiments of the present application, and other embodiments can be obtained by those skilled in the art without creativity on the basis of the above embodiments, and these embodiments all belong to the protection scope of the present application.

Claims

1. A method for preparing a wave-absorbing material, characterized by, The method comprises the following steps: The magnetite powder is sequentially subjected to ball milling, magnetic separation and heat treatment to obtain the wave-absorbing material. The magnetite powder is recovered from waste residue, and the average particle size of the product obtained by ball milling is 0.5-20 μm.

2. The method of claim 1, wherein the wave-absorbing material is prepared by the steps of: The ball milling is wet ball milling, and the dispersant used in the wet ball milling comprises ethanol; the rotation speed of the ball milling is 200-300 r / min, and the ball milling time is 3-15 h. ​ 3. The method of claim 2, wherein the wave-absorbing material is prepared by the steps of: The ball milling uses large balls, medium balls and small balls; the diameter of the large balls is 8-12 mm, the diameter of the medium balls is 5-7 mm, and the diameter of the small balls is 2-4 mm; the mass ratio of the large balls, the medium balls and the small balls is 1:9-11:18-22. ​ 4. The method of claim 2 or 3, wherein the wave-absorbing material is prepared by a method comprising: The ball milling has a ball-to-material ratio of 1:10-30.

5. The method for preparing the microwave absorbing material according to claim 1, characterized in that, Before the magnetic separation, the product obtained by ball milling is dispersed in water to obtain a dispersion liquid.

6. The method of claim 5, wherein the wave-absorbing material is prepared by mixing the metal oxide and the metal powder in a weight ratio of 1 : 1 to 1 :

10. The dispersion is performed under ultrasonic condition, and the power of the ultrasonic is 100-150 W.

7. The method of claim 5, wherein the wave-absorbing material is prepared by mixing the metal oxide and the metal powder in a weight ratio of 1:1 to 1:

3. The magnetic separation is performed in a wet magnetic separator, specifically, the dispersion liquid is fed into the wet magnetic separator for magnetic separation. The feeding flow rate is 300-500 mL / min.

8. The method of claim 7, wherein the wave-absorbing material is prepared by a process comprising: The magnetic separation has a strength of 50-300 mT.

9. The method of claim 1 or 8, wherein the wave-absorbing material is prepared by a method comprising: The magnetic separation is repeated, and the number of repetitions is 2-6. ​ 10. The method of claim 1, wherein the wave-absorbing material is prepared by a process comprising: Before the heat treatment, the product obtained by magnetic separation is dried, the drying temperature is 75-85 ℃, and the drying time is 8-16 h. ​ 11. The method of claim 1 or 10, wherein the wave-absorbing material is prepared by a method comprising: The heat treatment has a temperature of 500-900 ℃, a holding time of 1-3 h, and a heating rate of 4-6 ℃ / min to the temperature of the heat treatment. ​ 12. The method of claim 11, wherein the wave-absorbing material is prepared by a process comprising: The heat treatment is performed in a protective atmosphere.

13. The method of claim 1, wherein the wave-absorbing material is prepared by a method comprising: The magnetite powder comprises the following mass percentages of components, calculated as oxides of the elements: ​ 14. The wave-absorbing material prepared according to the method of any one of claims 1 to 13, characterized in that, The wave-absorbing material comprises magnetite phase and pyroxene phase; the mass percentage of the magnetite phase in the wave-absorbing material is 70-85%; The average particle size of the wave-absorbing material is 0.5-20 μm.

15. The wave-absorbing material of claim 14 as Fe3O4-based wave-absorbing agent in a composite wave-absorbing material.

Images