Preparation method of high-entropy magnetic nano-powder wave-absorbing agent

Abstract

The invention discloses a preparation method of a high-entropy magnetic nano-powder wave-absorbing agent, and belongs to the field of preparation of wave-absorbing materials. The method comprises the following steps: mixing nickel salt, ferric salt, cobalt salt, molybdenum salt, copper salt, ammonium nitrate and fuel according to a molar ratio of 1: (0.1-5): (0.1-5): (0.1-5): (0.1-5): (0-15): (1-30) to prepare an aqueous solution, heating and evaporating until the solution is in a viscous gel state, and continuously heating to enable-3-valence and + 5-valence N ions in the system to be subjected to an oxidation-reduction reaction to obtain a metal oxide composite precursor substance; and grinding and crushing the precursor, and carrying out reduction reaction for a period of time in a hydrogen atmosphere to obtain the high-entropy magnetic nano-powder wave-absorbing agent. The average particle size of the prepared powder wave-absorbing agent is 10-100 nm, and elements such as nickel, iron, cobalt, molybdenum and copper are uniformly dispersed in fine nano-particles in a solid solution manner; the oxygen content of the powdery wave-absorbing agent is as low as 0.17-0.52 wt%, the powdery wave-absorbing agent has good wave-absorbing performance at 1-18 GHz, and the effective absorption bandwidth is greater than or equal to 2 GHz.

Description

Technical Field

[0001] The invention relates to the field of preparation of wave-absorbing materials, and in particular to a method for preparing a high-entropy magnetic nano powder wave-absorbing agent. Background Art

[0002] When electromagnetic waves are incident on absorbing materials, three situations will occur: reflection, absorption, and transmission. This process strictly follows the law of conservation of energy in physics. Most of the incident part of the material will be absorbed by the absorber in the material and converted into heat or other forms of energy for loss. The electromagnetic waves formed by the mutual coupling of electric and magnetic fields, the absorbing material interacts with either or both of the electric or magnetic fields in the incident electromagnetic waves. This interaction relationship conforms to the Maxwell equations in the physical principle. The disturbance caused by the interaction between any field and the absorbing material medium will cause the response change of the other field, thereby achieving the purpose of dissipating the entire electromagnetic wave. At present, the material mainly uses reflection loss (RL for short) as an effective means to most intuitively express the absorbing performance of the material in a quantitative way. When RL = -10 dB, the loss of electromagnetic wave energy reaches 90%, and when RL = -20 dB, the loss of electromagnetic wave energy reaches 99%. In actual use, the frequency bandwidth of RL≤-10 dB is defined as the effective absorption bandwidth (EAB). The thinner the material is, the smaller the reflection loss RL value is and the wider the effective absorption bandwidth EAB is, indicating that the material has better wave absorption performance.

[0003] With the application and development of absorbing materials in military stealth technology, higher requirements are put forward for their performance. The development of absorbing materials that meet the requirements of "thin, light, wide, strong" and strong environmental adaptability has become a hot topic in current research. The unique multi-principal component and high-concentration composition of high-entropy alloys give them a natural advantage in becoming absorbing materials. Their excellent comprehensive properties such as soft magnetic properties, corrosion resistance, and oxidation resistance provide a research basis for the development of new absorbing materials. High-entropy alloy absorbing materials can improve their absorbing performance through various control methods such as adjusting the type and concentration of the principal component, adding trace elements, and compounding with other materials. The absorbing performance of high-entropy alloy absorbing materials is highly controllable, and its absorbing performance can be improved by controlling the morphology structure, regulating the composition of the material, changing the amount of raw materials, and adjusting the process. The alloying composition of high-entropy alloy multi-principal components has significant advantages in the application field of absorbing materials. The unique alloy design concept and significant high mixed entropy effect of high-entropy alloys provide a new direction for the development and development of new absorbing materials.

[0004] In order to meet the demand for high-performance absorbing materials in the development of science and technology, the preparation of fine-grained, ultrafine-grained or even nanocrystalline high-entropy alloy absorbing materials is an inevitable development trend. At present, the main methods for preparing high-entropy magnetic nanopowder absorbers are mechanical alloying and spray drying. The mechanical alloying method usually includes high-energy grinding and mixing methods, which have many disadvantages such as long preparation time, low preparation efficiency, uneven powder composition, poor powder purity control due to powder oxidation and impurity doping, and obvious agglomeration of powder particles during ball milling. The spray drying method is heavily dependent on the spray dryer and is affected by many equipment parameters. However, the machinery and equipment are complex and have high power loss, occupy a large area, have high requirements for the separation of gas-solid mixtures (generally two-stage dust removal is required), low thermal efficiency of the equipment, and high thermal energy consumption. These factors seriously affect the quality of high-entropy magnetic nanopowder absorbers prepared by spray drying. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a high entropy magnetic nano powder absorber. The prepared high entropy magnetic nano powder absorber has the characteristics of fine particles, uniform particle size and element distribution, and the method is simple and easy to implement, has strong controllability, a short preparation process, and is easy to implement.

[0006] The present invention adopts the following technical solution:

[0007] In one aspect, the present invention provides a method for preparing a high entropy magnetic nano powder absorber, comprising:

[0008] S1. Mix nickel salt, iron salt, cobalt salt, molybdenum salt, copper salt, ammonium nitrate, fuel and deionized water in a set ratio to prepare a corresponding aqueous solution, heat and stir to evaporate the aqueous solution until the solution becomes a viscous gel state, and continue to heat to perform a combustion synthesis reaction to obtain a metal oxide composite precursor;

[0009] S2. Grind and crush the composite precursor prepared in step S1, and perform a reduction reaction under a hydrogen atmosphere to obtain the high entropy magnetic nanopowder absorber.

[0010] Any of the possible implementations described above further provides an implementation, in step S1, the metal oxide composite precursor includes NiO and Ni 2 O 3 At least one of FeO, Fe 2 O 3 and Fe 3 O 4 At least one of CoO, Co 2 O 3 and Co 3 O 4At least one of MoO 2 、MoO 3 、NiMoO 4 , Fe 2 Mo 3 O 12 、CoMoO 4 and CuMoO 4 At least one of CuO and Cu 2 O, and NiFe 2 O 4 、CoFe 2 O 4 ,CuFe 2 O 4 、NiCo 2 O 4 、FeCo 2 O 4 、CuCo 2 O 4 Any one of .

[0011] Any possible implementation as described above, further provides an implementation, in which in step S1, the molar ratio of nickel salt, iron salt, cobalt salt, molybdenum salt, copper salt, ammonium nitrate and fuel is 1: (0.1~5): (0.1~5): (0.1~5): (0.1~5): (0~15): (1~30).

[0012] Any possible implementation as described above further provides an implementation, in step S1, the nickel salt is any one of nickel nitrate, nickel chloride, nickel sulfate and nickel carbonate.

[0013] Any possible implementation as described above further provides an implementation, in which in step S1, the iron salt is any one of ferric nitrate, ferric chloride, ferric sulfate, polyferric sulfate and polyferric chloride.

[0014] Any possible implementation as described above further provides an implementation, in step S1, the cobalt salt is any one of cobalt nitrate, cobalt chloride, cobalt sulfate and cobalt carbonate.

[0015] Any possible implementation as described above further provides an implementation, in which in step S1, the molybdenum salt is any one of molybdenum acid, molybdenum sulfate and molybdenum chloride.

[0016] Any possible implementation as described above further provides an implementation, in which in step S1, the copper salt is any one of copper nitrate, copper sulfate, copper chloride and copper carbonate.

[0017] Any possible implementation as described above further provides an implementation, in which in step S1, the fuel is one or more of glycine, citric acid, and urea.

[0018] As any possible implementation described above, a further implementation is provided, in step S1, the conditions of the combustion synthesis reaction are: heating temperature 200-500° C., heating time 10-60 min.

[0019] Any possible implementation as described above, further provides an implementation, in step S2, a reduction reaction is carried out in a tubular furnace under a hydrogen atmosphere, and the reaction conditions are: a heating rate of 2 to 10 ° C / min, a reaction temperature of 300 to 650 ° C, a holding time of 1 to 3 h, and a hydrogen flow rate of 500 to 2000 mL / min.

[0020] On the other hand, the present invention also provides a high entropy magnetic nanopowder absorber, which is prepared by the above method. The high entropy magnetic nanopowder is characterized by having good absorbing performance at 1 to 18 GHz, an average particle size of 10 to 100 nm, uniform particle size, and elements such as nickel, iron, cobalt, molybdenum, and copper are uniformly dissolved and dispersed in fine nanoparticles. The effective absorption bandwidth of this high entropy magnetic nanopowder absorber is ≥2 GHz, and the powder oxygen content is as low as 0.17 to 0.52 wt%.

[0021] The beneficial effects of the present invention are:

[0022] 1. The preparation method of the high entropy magnetic nano powder absorber provided by the present invention can be selectively prepared by controlling parameters such as the type and ratio of the raw materials, heating rate, hydrogen reduction temperature and time, and then controlling the performance of the synthesized high entropy magnetic nano powder absorber to achieve multi-field application.

[0023] 2. The liquid combustion synthesis in the preparation method provided by the present invention can achieve uniform mixing and dispersion of the metal elements of each component at the molecular level, and the large amount of gas released during the combustion reaction can effectively prevent the agglomeration of nanoparticles, which is conducive to the final formation of a high-entropy magnetic nanopowder absorber with uniform loading and high dispersion of each metal component particle.

[0024] 3. The composite metal powder prepared by the solution combustion synthesis + hydrogen reduction method of the present invention has a low oxygen content, the particle size of the high entropy magnetic nanopowder absorber is uniform, and elements such as nickel, iron, cobalt, molybdenum, and copper are uniformly dissolved and dispersed in fine nanoparticles, laying the foundation for the preparation of high-performance high entropy magnetic nanopowder absorbers.

[0025] 4. The raw materials of the present invention are cheap and easily available, the equipment is simple, the process is fast, the controllability is strong, it is suitable for large-scale industrial production, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The figure is a schematic flow chart of a method for preparing a high entropy magnetic nano powder absorber according to an embodiment of the present invention.

[0027] Figure 2 Shown is a scanning electron microscope image of the morphology of the high entropy magnetic nanopowder absorber prepared in Example 1. DETAILED DESCRIPTION

[0028] The specific embodiments of the present invention will be described in detail below in conjunction with specific drawings. It should be noted that the technical features or combinations of technical features described in the following embodiments should not be considered isolated, and they can be combined with each other to achieve better technical effects.

[0029] like Figure 1 As shown, a method for preparing a high entropy magnetic nano powder absorber according to an embodiment of the present invention comprises:

[0030] S1. Mix nickel salt, iron salt, cobalt salt, molybdenum salt, copper salt, ammonium nitrate, fuel and deionized water in a set ratio to prepare a corresponding aqueous solution, heat and stir to evaporate the aqueous solution until the solution becomes a viscous gel state, and continue to heat to perform a combustion synthesis reaction to obtain a metal oxide composite precursor;

[0031] S2. Grind and crush the composite precursor prepared in step S1, and perform a reduction reaction under a hydrogen atmosphere to obtain the high entropy magnetic nanopowder absorber.

[0032] In a specific embodiment, in step S1, the metal oxide composite precursor comprises NiO and Ni 2 O 3 At least one of FeO, Fe 2 O 3 and Fe 3 O 4 At least one of CoO, Co 2 O 3 and Co 3 O 4 At least one of MoO 2 、MoO 3 、NiMoO 4 , Fe 2 Mo 3 O 12 、CoMoO 4 and CuMoO 4 At least one of CuO and Cu 2 O, and NiFe 2 O 4 、CoFe2 O 4 ,CuFe 2 O 4 、NiCo 2 O 4 、FeCo 2 O 4 、CuCo 2 O 4 Any one of .

[0033] In a specific embodiment, in step S1, the molar ratio of nickel salt, iron salt, cobalt salt, molybdenum salt, copper salt, ammonium nitrate and fuel is 1: (0.1-5): (0.1-5): (0.1-5): (0.1-5): (0.1-5): (0-15): (1-30).

[0034] In a specific embodiment, in step S1, the nickel salt is any one of nickel nitrate, nickel chloride, nickel sulfate and nickel carbonate.

[0035] In a specific embodiment, in step S1, the iron salt is any one of ferric nitrate, ferric chloride, ferric sulfate, polyferric sulfate and polyferric chloride.

[0036] In a specific embodiment, in step S1, the cobalt salt is any one of cobalt nitrate, cobalt chloride, cobalt sulfate and cobalt carbonate.

[0037] In a specific embodiment, in step S1, the molybdenum salt is any one of molybdenum acid, molybdenum sulfate and molybdenum chloride.

[0038] In a specific embodiment, in step S1, the copper salt is any one of copper nitrate, copper sulfate, copper chloride and copper carbonate.

[0039] In a specific embodiment, in step S1, the fuel is one or more of glycine, citric acid, and urea.

[0040] In a specific embodiment, in step S1, the conditions of the combustion synthesis reaction are: heating temperature 200-500° C., heating time 10-60 min.

[0041] In a specific embodiment, in step S2, a reduction reaction is carried out in a tubular furnace under a hydrogen atmosphere, and the reaction conditions are: a heating rate of 2 to 10 °C / min, a reaction temperature of 300 to 650 °C, a holding time of 1 to 3 h, and a hydrogen flow rate of 500 to 2000 mL / min.

[0042] The embodiment of the present invention provides a high entropy magnetic nano powder absorber, which is prepared by the above method. The high entropy magnetic nano powder is characterized by having good absorbing performance at 1 to 18 GHz, an average particle size of 10 to 100 nm, uniform particle size, and elements such as nickel, iron, cobalt, molybdenum, and copper are uniformly dissolved and dispersed in fine nano particles. The effective absorption bandwidth of the high entropy magnetic nano powder absorber is ≥2 GHz, and the oxygen content of the powder is as low as 0.17 to 0.52 wt%.

[0043] Example 1

[0044] Nickel nitrate, iron nitrate, cobalt nitrate, molybdenum acid, copper nitrate, ammonium nitrate and glycine were weighed in a molar ratio of 1:1:1:0.15:1:0:4, dissolved in a small amount of deionized water, and stirred thoroughly with a glass rod until completely dissolved into an aqueous solution. The mixed solution was placed on a temperature-controlled resistance furnace and heated to gradually evaporate the water until the solution turned into a brown gel state, and then kept at 500 °C for 25 min to produce a violent combustion synthesis reaction. The product after the reaction was fully ground to obtain a precursor powder. The prepared precursor powder was placed in a tubular furnace and subjected to a reduction reaction using a hydrogen atmosphere, and the temperature was raised to 500 °C at a rate of 5 °C / min. After keeping the temperature for 1 h, it was cooled with the furnace, and the hydrogen flow rate was 800 mL / min.

[0045] The prepared high-entropy magnetic nanopowder has an average particle size of 32 nm and uniform particle size. Elements such as nickel, iron, cobalt, molybdenum, and copper are evenly dissolved and dispersed in the fine nanoparticles. The effective absorption bandwidth is 5 to 9 GHz (2.5 mm). The powder has a low oxygen content (0.27 wt%) and a specific surface area of ​​7.15 m 2 / g.

[0046] Example 2

[0047] Nickel chloride, ferric chloride, cobalt sulfate, molybdenum chloride, copper sulfate, ammonium nitrate and glycine were weighed in a molar ratio of 1:2:3.3:1.9:5:5:7, dissolved in a small amount of deionized water, and stirred thoroughly with a glass rod until completely dissolved into an aqueous solution. The mixed solution was placed on a temperature-controlled resistance furnace and heated to gradually evaporate the water until the solution turned into a brown gel state. It was kept at 400 °C for 45 min to undergo a violent combustion synthesis reaction. The product after the reaction was fully ground to obtain a precursor powder. The prepared precursor powder was placed in a tubular furnace and subjected to a reduction reaction using a hydrogen atmosphere. The temperature was raised to 350 °C at a heating rate of 2 °C / min, and then cooled with the furnace after being kept for 3 h. The hydrogen flow rate was 1000 mL / min.

[0048] The prepared high-entropy magnetic nanopowder has an average particle size of 15 nm and uniform particle size. Elements such as nickel, iron, cobalt, molybdenum, and copper are evenly dissolved and dispersed in the fine nanoparticles. The effective absorption bandwidth is 5.5-8 GHz (1.5 mm). The powder has a low oxygen content (0.27 wt%) and a specific surface area of ​​10.02 m 2 / g.

[0049] Example 3

[0050] Nickel nitrate, iron sulfate, cobalt chloride, molybdenum sulfate, copper carbonate, ammonium nitrate and glycine + citric acid were weighed in a molar ratio of 1:5:4.5:3.2:2.7:15:10+5.5, dissolved in a small amount of deionized water, and stirred thoroughly with a glass rod until completely dissolved into an aqueous solution. The mixed solution was placed on a temperature-controlled resistance furnace and heated to gradually evaporate the water until the solution turned into a brown gel state, and then kept at 450 °C for 30 min to produce a violent combustion synthesis reaction. The product after the reaction was fully ground to obtain a precursor powder. The prepared precursor powder was placed in a tubular furnace and subjected to a reduction reaction using a hydrogen atmosphere, and the temperature was raised to 250 °C at a heating rate of 9 °C / min, and then cooled with the furnace after being kept for 3 hours. The hydrogen flow rate was 2000 mL / min.

[0051] The prepared high-entropy magnetic nanopowder has an average particle size of 10 nm and uniform particle size. Elements such as nickel, iron, cobalt, molybdenum, and copper are evenly dissolved and dispersed in the fine nanoparticles. The effective absorption bandwidth is 3.5-6 GHz (2 mm). The powder has a low oxygen content (0.27 wt%) and a specific surface area of ​​12.16 m 2 / g.

[0052] Example 4

[0053] Nickel sulfate, polyferric sulfate, cobalt chloride, molybdenum acid, copper chloride, ammonium nitrate and urea were weighed in a molar ratio of 1:3.5:5:5:3.2:8:12, dissolved in a small amount of deionized water, and stirred thoroughly with a glass rod until completely dissolved into an aqueous solution. The mixed solution was placed on a temperature-controlled resistance furnace and heated to gradually evaporate the water until the solution turned into a brown gel state. It was kept at 250 °C for 60 min to undergo a violent combustion synthesis reaction. The product after the reaction was fully ground to obtain a precursor powder. The prepared precursor powder was placed in a tubular furnace and subjected to a reduction reaction using a hydrogen atmosphere. The temperature was raised to 650 °C at a heating rate of 10 °C / min, and then cooled with the furnace after being kept for 2 h. The hydrogen flow rate was 500 mL / min.

[0054] The prepared high-entropy magnetic nanopowder has an average particle size of 90 nm and uniform particle size. Elements such as nickel, iron, cobalt, molybdenum, and copper are evenly dissolved and dispersed in the fine nanoparticles. The effective absorption bandwidth is 8.7-12.5 GHz (2.2 mm). The powder has a low oxygen content (0.27 wt%) and a specific surface area of ​​5.16 m 2 / g.

[0055] Example 5

[0056] Nickel nitrate, polyferric chloride, cobalt nitrate, molybdenum chloride, copper nitrate, ammonium nitrate and glycine + urea were weighed in a molar ratio of 1:0.2:0.5:1.5:0.3:12:9+5, dissolved in a small amount of deionized water, and stirred thoroughly with a glass rod until completely dissolved into an aqueous solution. The mixed solution was placed on a temperature-controlled resistance furnace and heated to gradually evaporate the water until the solution turned into a brown gel state, and then kept at 300 °C for 50 min to produce a violent combustion synthesis reaction. The product after the reaction was fully ground to obtain a precursor powder. The prepared precursor powder was placed in a tubular furnace and subjected to a reduction reaction using a hydrogen atmosphere, and the temperature was raised to 550 °C at a rate of 10 °C / min. After being kept for 3 h, it was cooled with the furnace, and the hydrogen flow rate was 1200 mL / min.

[0057] The prepared high-entropy magnetic nanopowder has an average particle size of 59 nm and uniform particle size. Elements such as nickel, iron, cobalt, molybdenum, and copper are evenly dissolved and dispersed in the fine nanoparticles. The effective absorption bandwidth is 6.7-10.9 GHz (2.2 mm). The powder has a low oxygen content (0.27 wt%) and a specific surface area of ​​6.19 m 2 / g.

[0058] The present invention uses a solution combustion synthesis (SCS) method to prepare a high-entropy magnetic nanopowder absorber. Compared with a mechanical alloying method and a spray drying method, the SCS method has some unprecedented advantages. It can utilize the exothermic reaction between ammonium nitrate and metal salts (acting as oxidants in the reaction system) including nitrates, sulfates, carbonates, chlorides, etc. and fuels (acting as reducing agents in the reaction system) such as glycine, citric acid, urea, etc. The heat generated enables the entire reaction system to continuously maintain the redox reaction. The gas generated by the reaction can obtain a sufficiently fluffy and fine metal oxide precursor, which provides a basis for the subsequent hydrogen reduction to prepare nanocomposite powders. The method for preparing nanopowders of the present invention is simple, fast, low in energy consumption, and easy to mass produce. In addition, the method can achieve uniform mixing between metal elements such as nickel, iron, cobalt, molybdenum, copper, etc. at the molecular level, with high purity, fine grain size, and easy control of the composition ratio of nickel, iron, cobalt, molybdenum, and copper, laying a foundation for the preparation of high-performance high-entropy magnetic nanopowder absorbers.

[0059] Although the embodiments of the present invention have been given herein, those skilled in the art should understand that the embodiments of the present invention may be modified without departing from the spirit of the present invention. The above embodiments are merely exemplary and should not be used as a limitation on the scope of the present invention.

Claims

1. A method for preparing a high entropy magnetic nano powder absorber, characterized in that: The method comprises: S1. Mix nickel salt, iron salt, cobalt salt, molybdenum salt, copper salt, ammonium nitrate, fuel and deionized water in a set ratio to prepare a corresponding aqueous solution, heat and stir to evaporate the aqueous solution until the solution becomes a viscous gel state, and continue to heat to perform a combustion synthesis reaction to obtain a metal oxide composite precursor; S2. Grind and crush the composite precursor prepared in step S1, and perform a reduction reaction under a hydrogen atmosphere to obtain the high entropy magnetic nanopowder absorber.

2. The method for preparing the high entropy magnetic nano powder absorber according to claim 1, characterized in that: In step S1, the metal oxide composite precursor includes at least one of NiO and Ni2O3, at least one of FeO, Fe2O3 and Fe3O4, at least one of CoO, Co2O3 and Co3O4, MoO2, MoO3, NiMoO4, Fe2Mo3O 12 , at least one of CoMoO4 and CuMoO4, at least one of CuO and Cu2O, and any one of NiFe2O4, CoFe2O4, CuFe2O4, NiCo2O4, FeCo2O4, and CuCo2O4.

3. The method for preparing nano tungsten heavy alloy composite powder according to claim 1, characterized in that: In step S1, the molar ratio of nickel salt, iron salt, cobalt salt, molybdenum salt, copper salt, ammonium nitrate and fuel is 1: (0.1-5): (0.1-5): (0.1-5): (0.1-5): (0.1-5): (0-15): (1-30).

4. The method for preparing the high entropy magnetic nano powder absorber according to claim 1, characterized in that: In step S1, the nickel salt is any one of nickel nitrate, nickel chloride, nickel sulfate and nickel carbonate; the iron salt is any one of iron nitrate, iron chloride, iron sulfate, polyferric sulfate and polyferric chloride; the cobalt salt is any one of cobalt nitrate, cobalt chloride, cobalt sulfate and cobalt carbonate; the molybdenum salt is any one of molybdenum acid, molybdenum sulfate and molybdenum chloride; the copper salt is any one of copper nitrate, copper sulfate, copper chloride and copper carbonate.

5. The method for preparing the high entropy magnetic nano powder absorber according to claim 1, characterized in that: In step S1, the fuel is one or more of glycine, citric acid, and urea.

6. The method for preparing the high entropy magnetic nano powder absorber according to claim 1, characterized in that: In step S1, the conditions of the combustion synthesis reaction are: heating temperature 200-500°C, heating time 10-60 min.

7. The method for preparing the high entropy magnetic nano powder absorber according to claim 1, characterized in that: In step S2, a reduction reaction is carried out in a tubular furnace under a hydrogen atmosphere, and the reaction conditions are: a heating rate of 2 to 10 °C / min, a reaction temperature of 300 to 650 °C, a holding time of 1 to 3 h, and a hydrogen flow rate of 500 to 2000 mL / min.

8. The method for preparing the high entropy magnetic nano powder absorber according to claim 1, characterized in that: The prepared high-entropy magnetic nanopowder has good absorbing performance in the range of 1 to 18 GHz. The average particle size is 10 to 100 nm, the particle size is uniform, and the nickel, iron, cobalt, molybdenum, and copper elements are evenly dissolved and dispersed in the fine nanoparticles. The effective absorption bandwidth of this high-entropy magnetic nanopowder absorber is ≥2 GHz, and the oxygen content of the powder is as low as 0.17 to 0.52 wt%.

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