Preparation method of Ce-based rare earth soft magnetic wave-absorbing magnetic powder

Abstract

The invention belongs to the technical field of electromagnetic wave-absorbing materials, and discloses a preparation method of Ce-based rare earth soft magnetic wave-absorbing magnetic powder. The method comprises the steps that cerium and iron are prepared according to the mass ratio of 30.88: 9.12, the cerium is 1-5% excessive, and Ce2Fe17 alloy is prepared through smelting; after being crushed, the magnetic powder is sieved through a 200-500-mesh sieve, and magnetic powder with the preset particle size is obtained; carrying out nitriding treatment for 2-8 hours at the temperature of 480-500 DEG C in a nitrogen atmosphere; then carrying out ball-milling refinement in an organic medium and a protective atmosphere; and finally, drying in a protective atmosphere to obtain the magnetic powder. Through combination of precursor particle size control, low-temperature medium-pressure nitriding and protective ball milling, the performance goals that the nitrogen content of the magnetic powder is larger than 2.5% and the oxygen content of the magnetic powder is lower than 0.3% are achieved, the process is simple, and the method is suitable for large-scale production.

Description

Technical Field

[0001] This application belongs to the field of electromagnetic absorbing materials technology, specifically relating to a method for preparing Ce-based rare earth soft magnetic absorbing powder. Background Technology

[0002] High-frequency soft magnetic materials, as fundamental functional materials in modern electronic information technology, play a crucial role in mobile communications, precision instruments, and high-frequency microwave devices. With the rapid development of electronic devices towards higher frequencies, miniaturization, and integration, higher demands are placed on the high-frequency permeability and natural resonant frequency of soft magnetic materials. Traditional ferrite soft magnetic materials are limited by their intrinsic magnetic properties; an inherent constraint exists between permeability and resonant frequency, making it difficult to simultaneously maintain high permeability and good frequency characteristics under high-frequency conditions. This has become a technical bottleneck restricting further performance improvements in high-frequency devices.

[0003] To overcome the aforementioned limitations, rare-earth-iron-nitrogen (Re-Fe-N) soft magnetic alloys have attracted widespread attention in recent years. These materials exhibit significant easy-faceted magnetic anisotropy, with the product of their high-frequency permeability and natural resonant frequency being an order of magnitude higher than that of traditional ferrite materials. They also possess higher Curie temperatures, demonstrating excellent high-temperature stability and application potential. Among the many rare-earth elements, cerium (Ce) is considered a highly promising microwave absorbing material system due to its abundant resources, low cost, and the superior high-frequency soft magnetic properties exhibited by Ce-Fe-N alloys.

[0004] However, existing Ce-Fe-N magnetic powder preparation technologies still face many challenges. For example, patent document CN116900322A discloses a method for achieving highly flake-like iron-silicon-aluminum powder by controlling ball milling parameters. This method includes steps such as material selection, primary ball milling, drying, primary sieving, secondary ball milling, annealing, and secondary sieving. By controlling the ball milling parameters, it achieves flake-like formation and high magnetic permeability of the iron-silicon-aluminum powder, but its applicable frequency range is limited, making it difficult to meet the application requirements of higher frequency bands. Another patent, CN115966395A, uses plasma ball milling to prepare ultrafine rare-earth soft magnetic materials. This method obtains ultrafine magnetic powder through plasma ball milling and optimizes parameters such as ball milling speed, ball milling time, and discharge frequency. This method obtains excellent soft magnetic properties by controlling particle size and reducing magnetic loss by reducing particle size, but it has high equipment requirements, complex processes, and is not suitable for the large-scale preparation of microwave absorbing magnetic powder. Furthermore, patent CN118547235A proposes a nitriding method for samarium iron alloys using organic compounds as nitrogen sources. This method employs carbonyl diamine, melamine, dicyandiamide, adenine, guanine, cytosine, and thymine as carbon and nitrogen sources, obtaining SmFeN magnetic powder through reduction diffusion. This method involves a complex heat treatment process, achieving nitriding of the magnetic powder through multiple heat treatment steps. It is suitable for the preparation of free-axis permanent magnet alloys, effectively avoiding breakage and inhomogeneity of the magnetic powder during mechanical crushing. However, soft magnetic absorbing materials require controllable non-uniform structures to regulate magnetic loss and absorption performance.

[0005] In summary, although existing technologies provide various preparation routes for soft magnetic materials, there is still a lack of a nitriding process and preparation method that can balance high nitrogen content, low oxygen pollution, simple process, low equipment requirements, and suitability for large-scale production in the preparation of Ce-based rare earth soft magnetic powder for high-frequency microwave absorption applications. Summary of the Invention

[0006] To address the problems of complex processes, high equipment requirements, and difficulty in achieving both high nitrogen content and low oxygen pollution under simplified process conditions in existing technologies, this application provides a nitriding process and preparation method for Ce-based rare earth soft magnetic wave-absorbing powder. This method aims to obtain soft magnetic wave-absorbing powder with a nitrogen content greater than 2.5% and an oxygen content less than 0.3% by optimizing alloy composition and controlling the particle size of nitriding precursors, combined with specific nitriding and ball milling processes.

[0007] In one aspect of this application, a method for preparing Ce-based rare-earth soft magnetic absorbing powder is provided, comprising the following steps: 1) Smelting: Iron and cerium metals are mixed in a mass ratio of 30.88:9.12, with cerium metal in excess of 1-5%, and smelted to produce Ce2Fe. 17 alloy; 2) Crushing and sieving: The Ce2Fe 17After the alloy is crushed, it is sieved through a 200-500 mesh sieve to obtain magnetic powder with a predetermined particle size. 3) Nitriding: The sieved magnetic powder is nitrided at 480-500℃ for 2-8 hours under a nitrogen atmosphere; 4) Ball milling: The nitrided magnetic powder is ball-milled and refined under an organic medium and a protective atmosphere; 5) Drying: Dry the ball-milled magnetic powder under a protective atmosphere.

[0008] In one embodiment, the smelting is carried out in a vacuum rapid solidification furnace to produce Ce2Fe. 17 Quick-setting tablets.

[0009] In one embodiment, the nitriding treatment specifically involves: first, evacuating the furnace body to a vacuum level of 1×10⁻⁶. -3 Below Pa, the temperature is increased to 480-500℃ at a heating rate of 8-12℃ / min. Then, high-purity nitrogen is introduced and the gas pressure inside the furnace is maintained at 0.02-0.04MPa. After the heat preservation is completed, the furnace is cooled to room temperature by air.

[0010] In one embodiment, the ball mill is a planetary ball mill, and the grinding jar and grinding balls are made of stainless steel.

[0011] In one embodiment, the organic medium is selected from at least one of n-hexane, n-heptane, isopropanol, or ethanol, and contains oleic acid and a silane coupling agent.

[0012] In one embodiment, the ball mill rotates at a speed of 360-420 r / min and the milling time is 2-4 hours.

[0013] In one embodiment, the heat treatment holding time for the nitriding process is 6 hours.

[0014] In one embodiment, the sieving step uses a 300-mesh sieve.

[0015] In one embodiment, the protective atmosphere is a nitrogen atmosphere.

[0016] In another aspect of this application, a Ce-based rare-earth soft magnetic wave-absorbing powder is provided, wherein the Ce-based rare-earth soft magnetic wave-absorbing powder is prepared by the above-mentioned method for preparing Ce-based rare-earth soft magnetic wave-absorbing powder.

[0017] The beneficial effects of this application are as follows: 1) By employing a specific Ce / Fe mass ratio and controlling the excess rare earth element addition range, combined with particle size classification of the nitriding precursor using a 200-500 mesh sieve, a foundation was laid for subsequent controllable nitriding. This pretreatment method effectively avoided the problem of accelerated oxidation caused by excessively fine powder, while ensuring that the nitriding reaction had sufficient specific surface area and activity.

[0018] 2) A low-temperature (480-500℃) medium-pressure (0.02-0.04 MPa) nitriding process, combined with specific vacuum levels, heating rates, and holding times, enables efficient nitrogen infiltration under relatively mild conditions. This process results in a final magnetic powder with a nitrogen content consistently above 2.5%, while successfully controlling the oxygen content below 0.3%, significantly improving the soft magnetic properties and high-frequency stability of the magnetic powder.

[0019] 3) The optimized ball milling process, using a specific combination of organic media and additives, is conducted under nitrogen protection, effectively preventing secondary oxidation of the powder during the refining process. This optimizes powder particle size while ensuring the integrity of the magnetic powder particle morphology and the stability of its composition.

[0020] 4) The process is simple, the equipment requirements are low, there is no need for complex multi-step heat treatment or special atmosphere fine control, the error tolerance is high, the production cost is effectively controlled, and it has excellent industrial production potential. Attached Figure Description

[0021] Figure 1 The hysteresis loops of the magnetic powder in Example 8 before nitriding, after nitriding, and after ball milling; Figure 2 The high-frequency magnetoelectric properties of the magnetic powder in Example 8 after ball milling are shown; where a is the real part of the dielectric constant, b is the imaginary part of the dielectric constant, c is the real part of the permeability, and d is the imaginary part of the permeability. Figure 3 The microwave absorption performance of magnetic powder after ball milling in Example 8. Detailed Implementation

[0022] The technical solution of this application will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are only some embodiments of this application, not all embodiments, and are only used to illustrate this application, and should not be regarded as limiting the scope of this application. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] This application addresses the core contradiction in the preparation of CeFeN soft magnetic powder by establishing a process chain of "precursor particle size control - low-temperature nitriding - protective ball milling".

[0024] Specifically, a specific Ce / Fe stoichiometric ratio and a trace amount of rare earth elements are first set during the alloy smelting stage to form the target Ce2Fe. 17The first step provides the basic composition. Then, an innovative 200-500 mesh sieve is used to rigorously classify the crushed alloy powder. This aims to select precursor particles with optimal specific surface area and nitriding activity, avoiding excessive oxidation caused by overly fine powder, while creating structural conditions for subsequent uniform nitriding. In the nitriding process, a relatively low temperature range of 480-500℃ is used, coupled with precisely controlled nitrogen pressure and holding time, to achieve efficient nitrogen infiltration while suppressing excessive powder oxidation. Finally, ball milling is performed in a nitrogen-protected environment containing organic media and additives to ensure optimized powder particle size while effectively isolating oxygen and maintaining the stability of the magnetic powder composition and structure.

[0025] This application, through coordinated control of various process steps, has successfully achieved the technical effect of magnetic powder with a nitrogen content greater than 2.5% and an oxygen content less than 0.3% using a simple process flow and conventional equipment conditions, thus achieving the goals of high performance, low cost, and suitability for large-scale production.

[0026] In one specific embodiment, a method for preparing Ce-based rare-earth soft magnetic absorbing powder is provided, comprising the following steps: 1) Smelting: Iron and cerium metals are mixed in a mass ratio of 30.88:9.12, with cerium metal in excess of 1-5%, and smelted to produce Ce2Fe. 17 alloy.

[0027] Among them, according to the target product Ce2Fe 17 Based on the stoichiometric ratio and combined with process practice, the baseline mass ratio of iron (Fe) to cerium (Ce) metal was determined to be 30.88:9.12.

[0028] In the actual batching process, the amount of cerium (Ce) metal added should be intentionally 1-5% excess, based on the aforementioned baseline ratio. This "excess" means that the actual mass of cerium metal weighed is 1-5% more than the theoretically calculated required mass. The purpose of this excess is to compensate for losses such as burn-off and oxidation volatilization that may occur during the smelting process due to the high reactivity of cerium metal. By actively and controllably ensuring an excess of cerium, it is possible to obtain a Ce2Fe with accurate stoichiometry and a pure phase in the final rapid-setting sheet. 17 Alloys are used to avoid impurities or performance degradation in the alloy phase due to the loss of key rare earth components.

[0029] Specific examples of ingredient preparation and implementation methods are as follows: Determining the baseline mass: Taking the preparation of a batch of alloy as an example, the materials are prepared according to the clearly defined mass ratio of iron metal to cerium metal of 30.88:9.12. Under this ratio, if the amount of iron (Fe) metal added is determined to be 30.88 kg, then the theoretical baseline amount of cerium (Ce) metal added is 9.12 kg.

[0030] Calculating Excess Addition: In actual operation, to achieve the process effect of this invention, the amount of cerium metal added needs to be controlled to be excessive, based on the theoretical baseline feeding amount mentioned above. For example, if 3% is selected as the excess ratio, the additional mass of cerium metal to be added is: 9.12 kg × 3% = 0.2736 kg. Therefore, the actual total mass of cerium metal added should be: baseline mass (9.12 kg) + excess mass (0.2736 kg) = 9.3936 kg.

[0031] Complete the batching: Based on the above calculations, in this specific example, 30.88 kg of ferrous metal and 9.3936 kg of cerium metal (this mass corresponds to an excess of 3% cerium metal) should be accurately weighed together as raw materials for smelting to complete the batching operation in preparation for subsequent smelting.

[0032] In some embodiments, the smelting is carried out in a vacuum rapid solidification furnace to produce Ce2Fe. 17 Quick-setting tablets.

[0033] The cerium and iron metal raw materials, prepared according to the aforementioned ratio, are placed in the crucible of a vacuum rapid solidification furnace. The equipment is then started, and the furnace chamber is evacuated to a high vacuum state to effectively isolate the metal raw materials from air and prevent oxidation during subsequent high-temperature smelting.

[0034] After achieving the required vacuum environment, the metal raw material in the crucible is heated until it completely melts into a homogeneous alloy melt. This molten alloy is then directed to the surface of a high-speed rotating cooling roller. The alloy melt undergoes rapid heat exchange with the cooling roller surface, causing it to solidify instantaneously at an extremely high cooling rate.

[0035] This rapid solidification process causes the melt to form a non-equilibrium microstructure and directly solidify into a thin sheet-like solid, namely "Ce2Fe". 17 "Rapid-setting tablets". Rapid-setting tablets obtained using the "rapid-setting" process are characterized by fine internal grains and low degree of component segregation.

[0036] 2) Crushing and sieving: The Ce2Fe 17 After the alloy is crushed, it is sieved through a 200-500 mesh screen to obtain magnetic powder with a predetermined particle size.

[0037] Firstly, mechanical crushing is used to process Ce2Fe. 17 The brittle precipitated flakes are crushed. Mechanical crushing can be achieved by using a jaw crusher, hammer mill, or similar crushing equipment to break the brittle precipitated flakes into coarse particles of varying sizes.

[0038] The crushed particles are then graded and sieved. Standard sieves are used, with mesh sizes ranging from 200 to 500 mesh. Particles can be sieved through a single mesh size sieve, such as a 300-mesh sieve, to collect the powder that passes through it; alternatively, a combination of two or more sieve stages can be used for sorting, such as using 200-mesh and 300-mesh sieves sequentially to collect intermediate particle sizes that pass through the 200-mesh sieve but not the 300-mesh sieve.

[0039] By controlling the mesh size of the selected sieve, magnetic powder with a predetermined particle size range is obtained. The typical particle size range of the target powder obtained by sieving corresponds to the aperture range defined by the 200-500 mesh sieve used. Specifically, the sieving step can use 200 mesh, 220 mesh, 240 mesh, 260 mesh, 280 mesh, 300 mesh, 320 mesh, 340 mesh, 360 mesh, 380 mesh, 400 mesh, 420 mesh, 440 mesh, 460 mesh, 480 mesh, and 500 mesh sieves. Preferably, a 300 mesh sieve is used in the sieving step.

[0040] 3) Nitriding: The sieved magnetic powder is nitrided at 480-500℃ for 2-8 hours under a nitrogen atmosphere.

[0041] The magnetic powder, obtained by sieving to a predetermined particle size, is uniformly spread in a container suitable for high-temperature processing, such as an alumina crucible or a quartz boat. The container is then transferred to a furnace with atmosphere control, such as a vacuum tube furnace. After closing the furnace, the vacuum system is activated to evacuate the furnace cavity. While maintaining the vacuum, the furnace is heated to the target processing temperature. Once the temperature stabilizes, high-purity nitrogen is introduced into the furnace as a reaction atmosphere, and the nitriding reaction is carried out at a constant temperature for 2-8 hours. After the reaction is complete, heating is stopped, and the material in the furnace is cooled to room temperature using air cooling. Then, avoiding intense contact with air, the nitrided magnetic powder is removed. Through this process, the magnetic powder is transformed into Ce₂Fe. 17 N x The compound has a nitrogen content of over 2.5% while keeping the oxygen content at a low level.

[0042] In some embodiments, the nitriding treatment temperature can be 480°C, 485°C, 490°C, 495°C, or 500°C. The holding time for the nitriding treatment can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours. In a preferred embodiment, the holding time for the nitriding treatment is 6 hours.

[0043] In some embodiments, the nitriding treatment specifically involves: first evacuating the furnace body to a vacuum of 1×10⁻⁶. -3Below a certain pressure (Pa), most of the residual oxygen, water vapor, and other gaseous components in the furnace are removed. The heating system is controlled to raise the temperature to 480-500℃ at a rate of 8-12℃ / min. After the target temperature stabilizes, high-purity nitrogen is introduced into the furnace as the reaction gas. By adjusting the inlet and outlet pressures, the furnace atmosphere pressure is precisely maintained within the range of 0.02-0.04 MPa. Under stable temperature and pressure conditions, the magnetic powder and nitrogen gas are allowed to come into full contact and react. This holding state needs to be maintained for a set time to complete the nitriding process.

[0044] 4) Ball milling: The nitrided magnetic powder is ball-milled and refined under an organic medium and a protective atmosphere.

[0045] The nitrided magnetic powder is placed in a ball mill and milled in an environment where organic media and a protective atmosphere coexist. The role of the organic media is to disperse the powder, reduce cold welding, and prevent excessive oxidation; the protective atmosphere is used to isolate the powder from air and prevent significant oxidation of the magnetic powder during mechanical activation.

[0046] In some embodiments, the ball mill is a planetary ball mill. High-intensity grinding force is generated by the revolution and rotation of the planetary disk and the jar. Both the grinding jar and the grinding balls are made of stainless steel, a material with sufficient strength and wear resistance to prevent the introduction of non-magnetic impurities during the grinding process, thus ensuring the purity of the magnetic powder.

[0047] In some embodiments, the organic medium is selected from at least one of n-hexane, n-heptane, isopropanol, or ethanol. Oleic acid and a silane coupling agent are also added to the organic medium. Oleic acid, as a surfactant, adsorbs onto the surface of the nascent magnetic powder, reducing its surface energy and effectively inhibiting particle aggregation and excessive growth; the silane coupling agent is used to improve the interfacial compatibility between the magnetic powder and other polymer matrices that may be used subsequently.

[0048] In some embodiments, controlling the ball mill rotation speed within the range of 360-420 r / min and maintaining the ball milling time at 2-4 hours ensures that the magnetic powder receives sufficient mechanical energy, achieving effective particle refinement and morphology control, while avoiding over-processing or lattice damage to the particles due to excessive energy input or prolonged time. Specifically, the ball mill rotation speed can be 360 ​​r / min, 370 r / min, 380 r / min, 390 r / min, 400 r / min, 410 r / min, or 420 r / min.

[0049] In some embodiments, the protective atmosphere is a nitrogen atmosphere. Nitrogen is introduced into the milling jar before the ball milling operation to replace the air inside, and this inert atmosphere is maintained throughout the milling process, thereby providing reliable oxidation protection for the magnetic powder.

[0050] 5) Drying: Dry the ball-milled magnetic powder under a protective atmosphere.

[0051] Example 1 A method for preparing Ce-based rare-earth soft magnetic absorbing powder includes the following steps: 1) Smelting 30.88 kg of metallic iron (Fe) and 9.25 kg of metallic cerium (Ce) were weighed, with the amount of cerium metal in excess by 1.5% relative to the theoretical stoichiometry. The weighed metal raw materials were placed in a vacuum rapid solidification furnace and smelted under vacuum. Ce₂Fe was prepared using a melt-spinning process. 17 Quick-setting tablets.

[0052] 2) Crushing and screening The above Ce2Fe 17 The quick-setting tablets were transferred to a nitrogen-atmospheric glove box and crushed using a mechanical grinder to obtain coarse powder. Subsequently, the crushed powder was graded and sieved using standard sieves: 200-mesh and 300-mesh sieves were used successively to collect intermediate-sized magnetic powder that could pass through the 200-mesh sieve but not the 300-mesh sieve, which was used as a nitriding precursor.

[0053] 3) Nitriding treatment The sieved magnetic powder was evenly spread in an alumina crucible and transferred to a vacuum tube furnace. After closing the furnace, the furnace was evacuated to a vacuum level of 1×10⁻⁶. -3 The pressure was initially below 0.04 MPa, then increased to 480℃ at a heating rate of 10℃ / min. After the temperature stabilized, high-purity nitrogen was introduced into the furnace to maintain the furnace pressure at 0.04 MPa, and the furnace was held at this temperature for 2 hours. After the holding period, heating was stopped, and the material in the furnace was cooled to room temperature using air cooling to obtain nitrided Ce₂Fe. 17 N x Magnetic powder.

[0054] 4) Ball milling refinement The nitrided magnetic powder was placed in a planetary ball mill jar, with n-hexane added as the organic medium, and oleic acid and silane coupling agent added as dispersants and surface modifiers. Both the mill jar and the grinding balls were made of stainless steel. Nitrogen gas was introduced into the mill jar to replace the air, and this protective atmosphere was maintained throughout the milling process. The milling speed was controlled at 400 r / min, and the milling time was 3 hours to achieve finer grinding and morphological control of the magnetic powder.

[0055] 5) Drying After ball milling, the magnetic powder is separated from the organic medium under a nitrogen protective atmosphere, and then the magnetic powder is transferred to a drying device for drying under a nitrogen atmosphere to obtain the final Ce-based rare earth soft magnetic wave-absorbing magnetic powder product.

[0056] Example 2 The experimental procedure is the same as in Example 1, except that magnetic powder that has passed through a 300-mesh sieve but not a 500-mesh sieve is nitrided.

[0057] Example 3 The experimental procedure is the same as in Example 1, except that magnetic powder passing through a 500-mesh sieve is nitrided.

[0058] Example 4 The experimental procedure is the same as in Example 1, except that the heat preservation time at 480℃ is 4 hours.

[0059] Example 5 The experimental procedure is the same as in Example 2, except that the heat preservation time at 480℃ is 4 hours.

[0060] Example 6 The experimental procedure is the same as in Example 3, except that the heat preservation time at 480℃ is 4 hours.

[0061] Example 7 The experimental procedure is the same as in Example 1, except that the heat preservation time at 480℃ is 6 hours.

[0062] Example 8 The experimental procedure is the same as in Example 2, except that the heat preservation time at 480℃ is 6 hours.

[0063] Example 9 The experimental procedure is the same as in Example 3, except that the heat preservation time at 480℃ is 6 hours.

[0064] Experimental Example 1) Magnetic powder particle size distribution detection 1. Instrument measurement Transfer 0.3-0.5g of magnetic powder sample into the sample cell of the laser particle size analyzer. Set the instrument parameters: Dispersed air pressure 0.4 MPa Measurement range: 0.1-1000 μm Temperature measured: 25±1℃ Start the measurement program, and the instrument will automatically complete the background and sample measurements. Each sample is measured in parallel three times to ensure the repeatability of the results.

[0065] 2. Data Analysis The instrument's software automatically analyzes the scattered light intensity distribution and calculates the sample's particle size distribution data using Mie scattering theory. Characteristic particle size parameters are recorded. D10: The particle size value corresponding to a cumulative distribution percentage of 10%; D16: The particle size value corresponding to a cumulative distribution percentage of 16%; D50: Median particle size, which is the particle size value when the cumulative distribution percentage reaches 50%; D84: The particle size value corresponding to a cumulative distribution percentage of 84%; D90: The particle size value corresponding to a cumulative distribution percentage of 90%.

[0066] 3. Experimental Results The particle size distribution of Examples 1, 2, and 3 is shown in Table 1.

[0067] Table 1. Particle size distribution of Examples 1, 2, and 3

[0068] 2) Detection of oxygen and nitrogen content Oxygen content detection: Oxygen content is determined using the inert gas melting-infrared absorption method. An appropriate amount of magnetic powder sample is weighed and placed in a graphite crucible. The sample is heated at high temperature in a pulse furnace under a helium atmosphere, causing the oxygen in the sample to be released as carbon monoxide. A carrier gas carries the gas into the infrared detection cell. The oxygen content is calculated by measuring the infrared absorption value of carbon monoxide. The instrument is calibrated using a standard steel sample before testing.

[0069] Nitrogen content determination: The nitrogen content was determined using the inert gas melting-thermal conductivity method. The weighed sample was placed in a high-temperature graphite crucible and heated to melt in a helium carrier gas flow. Nitrogen in the sample was released as nitrogen gas, separated by a chromatographic column, and then introduced into a thermal conductivity detector. The nitrogen content was calculated by measuring the change in the thermal conductivity signal and comparing it with a standard sample. The entire analytical process was performed under controlled gas flow and temperature conditions.

[0070] The results are shown in Tables 2 and 3. Smaller powder particle size corresponds to higher oxygen content, and extending the nitriding time has a smaller impact on oxygen content. Refining the particle size or extending the nitriding time helps increase nitrogen content. Considering both oxygen and nitrogen content, Example 8 exhibits the best nitriding effect.

[0071] Table 2 Oxygen content of Examples 1-9

[0072] Table 3 Nitrogen content of Examples 1-9

[0073] 3) Hysteresis loop test Measurements were performed using a vibrating sample magnetometer (VSM) or a BH analyzer. The magnetic powder sample from Example 8 was fixed in a sample rod, and a scanning magnetic field ranging from -15 kOe to +15 kOe was applied at room temperature. The relationship between magnetization and magnetic field was measured to obtain parameters such as coercivity, saturation magnetization, and remanence ratio.

[0074] like Figure 1 As shown, compared with the magnetic powder before nitriding, the saturation magnetization of the magnetic powder after nitriding is significantly improved, reaching 132.20 emu / g. The saturation magnetization of the magnetic powder decreases slightly after ball milling.

[0075] 4) High-frequency magnetoelectric performance testing A vector network analyzer was used in conjunction with a coaxial test fixture. Magnetic powder from Example 8 was mixed with paraffin at a mass ratio of 7:3 to form a ring-shaped sample (outer diameter 7 mm, inner diameter 3 mm, thickness 2 mm). The sample was scanned within a frequency range of 1-18 GHz, and the complex permittivity (real and imaginary parts) and complex permeability (real and imaginary parts) were calculated using S-parameter inversion.

[0076] like Figure 2 As shown, both the real and imaginary parts of the dielectric constant exhibit a fluctuating trend, while the real part of the permeability gradually decreases with increasing frequency, reaching over 1.5 at 2 GHz.

[0077] 5) Wave absorption performance analysis The reflection loss at different thicknesses was calculated based on the results of high-frequency magnetoelectric performance tests. For example... Figure 3 As shown, the minimum reflection loss is -53.12 dB when the thickness is 3.1 mm, and the effective absorption bandwidth (-10 dB) reaches 5.54 GHz when the thickness is 1.7 mm.

[0078] Although the embodiments of this application have been described above in conjunction with the accompanying drawings, this application is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of this application, and these are all within the scope of protection of this application.

Claims

1. A method for preparing Ce-based rare-earth soft magnetic wave-absorbing powder, characterized in that, Includes the following steps: 1) Iron and cerium metals are mixed in a mass ratio of 30.88:9.12, with cerium metal in excess of 1-5%, and smelted to produce Ce2Fe. 17 alloy; 2) The Ce2Fe 17 After the alloy is crushed, it is sieved through a 200-500 mesh sieve to obtain magnetic powder with a predetermined particle size. 3) The sieved magnetic powder is subjected to nitriding treatment at 480-500℃ for 2-8 hours under a nitrogen atmosphere; 4) The nitrided magnetic powder was ball-milled and refined under an organic medium and a protective atmosphere; 5) Dry the ball-milled magnetic powder under a protective atmosphere.

2. The preparation method according to claim 1, characterized in that, The smelting was carried out in a vacuum rapid solidification furnace to produce Ce2Fe. 17 Quick-setting tablets.

3. The preparation method according to claim 1, characterized in that, The nitriding treatment specifically involves: first, evacuating the furnace body to a vacuum level of 1×10⁻⁶. -3 Below Pa, the temperature is increased to 480-500℃ at a heating rate of 8-12℃ / min. Then, high-purity nitrogen is introduced and the gas pressure inside the furnace is maintained at 0.02-0.04 MPa. After the heat preservation is completed, the furnace is cooled to room temperature by air.

4. The preparation method according to claim 1, characterized in that, The ball mill is a planetary ball mill, and the grinding jar and grinding balls are made of stainless steel.

5. The preparation method according to claim 1, characterized in that, The organic medium is selected from at least one of n-hexane, n-heptane, isopropanol or ethanol, and contains oleic acid and silane coupling agent.

6. The preparation method according to claim 1, characterized in that, The ball mill rotates at a speed of 360-420 r / min and the milling time is 2-4 hours.

7. The preparation method according to claim 1, characterized in that, The heat treatment time for nitriding is 6 hours.

8. The preparation method according to claim 1, characterized in that, The sieving step uses a 300-mesh sieve.

9. The preparation method according to claim 1, characterized in that, The protective atmosphere is a nitrogen atmosphere.

10. A Ce-based rare-earth soft magnetic wave-absorbing powder, characterized in that, The Ce-based rare earth soft magnetic wave-absorbing powder is prepared by the preparation method described in any one of claims 1 to 9.

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