An L10-type FeNi ordered alloy and its preparation method

Abstract

This invention discloses an L10-type FeNi ordered alloy and its preparation method. The method utilizes a one-step ultrasonic spray thermal decomposition and reduction process to prepare spherical FeNi disordered alloys filled with a pore-forming agent. The pore-forming agent is then removed by alcohol washing to obtain spherical porous FeNi disordered alloys. Following this, high-pressure nitriding and denitrification treatments are performed to finally obtain the L10-type FeNi ordered alloy. This invention offers controllable morphology and size, improving oxidation resistance. The preparation process is simpler, more economical, and has faster nitriding efficiency, facilitating industrialization and promoting the production of high-performance L10-type FeNi ordered alloy magnetic powder.

Description

Technical Field

[0001] This invention belongs to the field of metallic magnetic material preparation technology, and relates to an L10 type-FeNi ordered alloy and its preparation method. Background Technology

[0002] As a rare-earth element-free magnet, L10-type FeNi ordered alloys have attracted widespread attention. The L10-type ordered structure is based on a face-centered cubic lattice, with Fe and Ni arranged in layers along the (001) direction. Such structures are common in alloys such as FePt and FePd. Disordered alloys are typically subjected to temperatures below the order-disorder transition temperature T. λ The following heat treatment is performed to promote diffusion and obtain an ordered structure.

[0003] However, the transformation temperature T for obtaining L10-type FeNi ordered alloys is... λ At a temperature of 320℃, diffusion is extremely slow, making synthesis difficult through heat treatment alone. Therefore, various attempts have been made to synthesize L10-type FeNi ordered alloys. In 2017, the inventors proposed CN106796838A, which describes the formation of L10-type FeNi ordered alloys by preparing a melt containing one or more elements including Fe, Ni, Ti, V, Al, B, and C, subjecting it to intense plastic deformation and annealing for hours to months at a chemically ordered temperature. This method suffers from drawbacks such as uncontrollable powder morphology, long annealing cycles, and low L10-type FeNi ordered alloy content. Another patent, CN110505313A, discloses the purchase of nanoscale FeNi disordered alloys obtained using thermal plasma methods, co-precipitation methods, and spray thermal decomposition methods, followed by reduction-nitriding-denitrification processes to ultimately form L10-type FeNi ordered alloys. However, the powders obtained by this method are prone to oxidation, have low nitriding efficiency, and require long nitriding cycles. In addition, the inventors proposed CN110651337B in 2023, which also employs a reduction-nitriding-denitrification process. After forming an ordered L10-type FeNi phase, it undergoes electrochemical treatment involving borying, carburizing, and nitriding to complete the doping of light elements, thereby forming L10-type FeNi alloy powder with high coercivity and high saturation magnetization. This method suffers from problems such as long electrochemical treatment cycles and low borying and carburizing efficiencies. Meanwhile, patent CN115852204A discloses that nitriding efficiency decreases due to the thermal decomposition of nitrides generated during the nitriding process. Therefore, using a sulfur-containing FeNi alloy as a raw material can achieve high nitriding efficiency. However, when adding sulfur, the sulfur content needs to be precisely controlled, as excessive sulfur will lead to a decrease in saturation magnetization.

[0004] In summary, there is an urgent need to propose an L10-type FeNi ordered alloy with simpler processing, higher nitriding efficiency, and excellent magnetic properties, as well as its preparation method. Summary of the Invention

[0005] The first objective of this invention is to address the shortcomings of existing technologies by proposing a method for preparing L10-type FeNi ordered alloys. This method directly synthesizes spherical FeNi disordered alloys via a one-step spray thermal decomposition and reduction process, and then converts them into near-spherical micro / nano-sized L10-type FeNi ordered alloys with antioxidant properties through high-pressure nitriding-denitrification. This allows for the control of alloy powder particle size to be within the range of 0.1–2 μm without subsequent crushing.

[0006] The method of this invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing L10-type FeNi ordered alloys, specifically:

[0008] A one-step spray thermal decomposition and reduction method was used to directly prepare spherical FeNi disordered alloys with intercalated Fe and Ni elements and filled with a pore-forming agent. The pore-forming agent was removed by alcohol washing under an inert atmosphere, yielding spherical porous FeNi disordered alloys. These spherical porous FeNi disordered alloys were then placed in a closed high-pressure reactor and nitrided at 200–400 °C for at least 10 hours under an ammonia-containing atmosphere to form FeNiN alloys. The FeNiN alloys were then subjected to a denitrification reaction to form L10-type FeNi alloys.

[0009] Preferably, the FeNi disordered alloy is prepared by a one-step ultrasonic spray thermal decomposition and reduction method, specifically:

[0010] Iron salts, nickel salts, and pore-forming agents are mixed and dissolved in water to form a spray precursor solution;

[0011] Using the principle of ultrasonic spraying, the spray precursor solution is placed in an ultrasonic atomizer, which turns the mixed solution of iron salt, nickel salt and pore-forming agent into a mist, and then transported to a preheated tube furnace under the action of a carrier gas.

[0012] The atomized precursor solution undergoes evaporation and dehydration, saline-thermal reaction, and reduction reaction in succession under the high temperature of the tube furnace, finally forming a disordered FeNi alloy, which is then transported by the carrier gas to a collector located at the end of the tube furnace.

[0013] Preferably, the pore-forming agent in the atomizing precursor solution is a soluble metal salt such as KCl or NaCl; the molar ratio of the pore-forming agent to the iron salt is 0.33-3:1.

[0014] Preferably, the FeNi disordered alloy has a size of 0.1 to 2 μm and consists of spherical porous particles in which Fe and Ni are interlocked.

[0015] Preferably, the reducing atmosphere is a mixture of hydrogen and an inert gas with a volume ratio of 1:1 to 1:3, wherein the inert gas is argon or helium; the flow rate of the reducing atmosphere is 1-3 L / min.

[0016] Preferably, the molar ratio of Fe to Ni in the FeNi disordered alloy is 1:1.

[0017] Preferably, the atmosphere containing ammonia during nitriding is ammonia gas or a mixture of ammonia and argon gas, to ensure that the gas pressure inside the high-pressure furnace is above 1 MPa.

[0018] Preferably, the denitrification reaction conditions are 200-400℃, and the FeNiN alloy denitrification reaction is carried out for more than 1 hour in a hydrogen atmosphere, with a hydrogen flow rate of 0.1-2 L / min.

[0019] Preferably, FeNiN alloys do not require crushing after denitrification treatment.

[0020] Secondly, the present invention provides an L10-type FeNi ordered alloy with near-spherical micro-nano size and a particle size of 0.1-2 μm, which is prepared by the above method.

[0021] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0022] (1) The present invention directly obtains spherical FeNi disordered alloys through a one-step spray thermal decomposition and reduction method, without the need for intermediate reduction steps, thus shortening the process cycle and allowing for controllable particle size.

[0023] (2) A porous FeNi disordered alloy was obtained by using a pore-forming agent, which increased the specific surface area of ​​the FeNi disordered alloy and increased the contact area between the alloy and the reaction gas during the nitriding process, which is beneficial to improving the nitriding efficiency.

[0024] (3) Nitriding porous FeNi disordered alloy under high pressure increases the kinetic trend of nitriding, reduces the nitriding time, and also increases the nitriding efficiency.

[0025] (4) The near-spherical L10-FeNi ordered alloy with micro-nano size can be directly prepared without ball milling through the nitriding-denitrification heat treatment process, so that the morphology and size of the final product can be controlled and the oxidation resistance of L10-FeNi ordered alloy is improved. Attached Figure Description

[0026] Figure 1 The images show SEM images of the disordered FeNi alloys after the one-step spray thermal decomposition and reduction process in Examples 1-4.

[0027] Figure 2 This is a schematic diagram illustrating the effects of the entire experimental process. Detailed Implementation

[0028] As mentioned above, in view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention, the main basis of which includes at least the following:

[0029] (1) The present invention directly obtains spherical FeNi disordered alloy filled with pore-forming agent through a one-step spray thermal decomposition and reduction method. Then the pore-forming agent is removed, eliminating the need for intermediate reduction reaction and subsequent ball milling process, thus shortening the process cycle. Then, L10 type-FeNi ordered alloy is obtained through high pressure nitriding-denitrification heat treatment process, so that the morphology and size of the final product can be controlled, and the oxidation resistance of the powder is improved.

[0030] (2) Traditional processes often involve first generating iron-nickel oxide and then reducing it in two steps. This results in larger powder particles that are easily sintered into blocks, making it difficult to control the proportion. However, the one-step spray thermal decomposition and reduction method of this invention enables controllable particle size.

[0031] (3) In this invention, different amounts of pore-forming substances such as NaCl or KCl are added to the spray solution, and then FeNi disordered alloy is washed with alcohol to form a porous spherical FeNi disordered alloy, which increases the specific surface area. Under the same magnetic properties, the porous alloy has a shorter nitriding time than the non-porous alloy, thus improving the subsequent nitriding efficiency.

[0032] (4) This invention uses salts such as nickel nitrate and ferric nitrate as raw materials, avoiding the use of smelting and spinning methods, and uses high-purity iron and nickel as direct raw materials, resulting in low raw material costs;

[0033] (5) The present invention uses high-pressure nitriding in the nitriding process, which is more conducive to the forward reaction and improves the nitriding efficiency compared with atmospheric pressure nitriding.

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0035] This invention provides a method for preparing L10-type FeNi ordered alloys. Figure 2 The specific implementation plan is as follows:

[0036] Step 1: Mix and dissolve water-soluble iron salts, water-soluble nickel salts, and pore-forming agents in water to form an atomization precursor solution;

[0037] In this embodiment of the invention, the water-soluble iron salt is a water-soluble trivalent iron salt or a water-soluble divalent iron salt, preferably one or more combinations of ferric chloride, ferric nitrate, ferric sulfate, ferrous chloride, ferrous nitrate, and ferrous sulfate.

[0038] In this embodiment of the invention, the water-soluble nickel salt is a water-soluble divalent nickel salt, preferably one or a combination of nickel chloride, nickel nitrate, and nickel sulfate.

[0039] In this embodiment of the invention, the pore-forming agent is a metal salt such as KCl or NaCl, and the molar ratio of the pore-forming agent to the iron salt is 0.33-3:1.

[0040] Step 2: Place the atomized precursor solution in an ultrasonic atomizer, adjust the atomizer frequency to 0.5-10MHz, and use the ultrasonic spray principle to atomize the precursor solution. Then, under the action of the carrier gas, deliver it to a tube furnace with three temperature zones at a certain flow rate. The three temperature zones are set to 300℃, 800℃, and 800℃ respectively, with a heating efficiency of 10℃ / min.

[0041] Step 3: The atomized precursor solution undergoes evaporation, dehydration, salt thermal decomposition, and reduction reactions within a tube furnace, ultimately forming spherical FeNi disordered alloys. These alloys are then transported by a carrier gas to a collector located at the end of the tube furnace. The collected material is then washed with alcohol under an inert atmosphere to remove the pore-forming agent, yielding spherical porous FeNi disordered alloys.

[0042] In this embodiment of the invention, the carrier gas in steps two and three is a mixture of reducing gas and inert gas, wherein the inert gas includes one or both of argon or helium. To prevent metallic iron from being nitrided at high temperatures, nitrogen cannot be used as the carrier gas, and hydrogen is used as the reducing gas. The flow rate of the carrier gas is 1-3 L / min, and the ratio is 1:1-1:3. Before spraying begins, inert gas needs to be passed through for a certain period of time to ensure that there is no air residue in the tube to avoid explosion. The size of the target product is 0.1-2 μm.

[0043] Step 4: Place the obtained porous FeNi disordered alloy in a high-pressure atmosphere reactor, heat it to 200-400℃, introduce a mixture of ammonia and argon gas, and nitrid for more than 10 hours, ensuring the pressure inside the furnace is above 1 MPa. At this time, the nitriding reaction forms FeNiN alloy. Then, a denitrification reaction is carried out. The FeNiN alloy is introduced into the reactor at 200-400℃ with hydrogen gas at a flow rate of 0.1-2 L / min for more than 1 hour to finally obtain L10 type-FeNi alloy.

[0044] The iron and nickel salts mentioned in step one above are different types. When preparing the spray precursor solution, the spray thermal decomposition principles of chlorides and nitrates differ. The actual Fe and Ni content in the solution should be determined based on the type of salt. When preparing the L10-FeNi target product (Fe to Ni molar ratio of 1:1), chlorides obtain oxides through hydrolysis followed by decomposition. Different ions have different hydrolysis capabilities, often leading to deviations in the final ion ratio. Fe ions are more easily hydrolyzed than Ni ions; therefore, when using chlorides to prepare the spray precursor solution, the actual Fe ion ratio should be 15% lower than the Ni ion ratio. Nitrates, on the other hand, directly decompose to obtain oxides. Iron nitrate and nickel nitrate have similar decomposition temperatures, meaning they have similar decomposition capabilities, resulting in an actual Fe to Ni ion ratio of 1:1. The purpose of adding a pore-forming agent is to utilize the high melting point of KCl or NaCl to ensure no reaction with other substances at high temperatures. After the reaction, alcohol washing is used to form spherical porous materials, further increasing the specific surface area and improving subsequent nitriding efficiency.

[0045] The evaporation-dehydration, salt thermal decomposition, and reduction reactions mentioned in step three above refer to the process where the spray precursor solution is atomized by an ultrasonic atomizer and transported to a tube furnace by a carrier gas. In the tube furnace with a temperature gradient, the aqueous solution first evaporates and dehydrates, then undergoes thermal decomposition, oxidizing to form spherical iron-nickel composite oxides. After reaching a certain temperature, these oxides undergo a reduction reaction with hydrogen. The evaporation-dehydration, salt thermal decomposition, and reduction reactions are carried out in a tube furnace, which is divided into three heating stages. The evaporation zone temperature is set at approximately 100-300℃, and the decomposition and phase formation zones are set at 600-900℃. The carrier gas is hydrogen and argon or helium (volume ratio of 1:1 to 1:3), with a flow rate of 1-3 L / min. The effectiveness of hydrogen reduction depends on the hydrogen flow rate, reduction temperature, and time. Higher hydrogen flow rates, higher reduction temperatures, or longer reduction times result in more complete reduction of the iron-nickel oxides. Insufficient reduction will affect the subsequent nitriding effect. The reduction process is more suitable for an argon atmosphere because iron reacts with nitrogen at high temperatures.

[0046] The nitriding-denitrification treatment mentioned in step four above involves processing the porous spherical FeNi disordered phase alloy formed after reduction to form an L10-type FeNi alloy. Due to surface oxidation during the collection of the FeNi disordered alloy, a reduction treatment is required to improve nitriding efficiency. Before nitriding, reduction is performed for 0.2–2 hours at a temperature of 300–450°C to remove surface oxides, increase the contact area with ammonia, and improve the nitriding effect. Reduction below 300°C requires a longer reaction time, while reduction above 450°C easily leads to surface sintering, resulting in decreased nitriding efficiency. After surface treatment, nitriding begins. Ammonia and argon are used as the reaction atmosphere, the nitriding temperature is 200–400°C, the nitriding time is over 10 hours, and the pressure is over 1 MPa, yielding FeNiN compounds. The nitriding effect is mainly related to the nitriding time, nitriding temperature, and reaction pressure. The nitriding time is closely related to the content of the final L10-FeNi phase. Theoretically, the longer the time, the more L10-FeNi alloy phase is formed. The nitriding time, or nitriding efficiency, is closely related to the morphology of the powder. By adding a certain amount of KCl or NaCl to the precursor solution, the spherical FeNi disordered alloy obtained by spray collection becomes porous after alcohol washing, increasing the specific surface area and the contact area with ammonia gas. This reduces the nitriding time required to achieve the same magnetic properties, thus improving nitriding efficiency. Theoretically, a higher nitriding temperature requires a shorter nitriding time; however, higher temperatures and finer powders are more prone to oxidation during the reaction. Within a certain range, increasing the reaction pressure is beneficial for the forward thermal reaction. The denitrification effect is related to the hydrogen flow rate, denitrification temperature, and denitrification time. A higher hydrogen flow rate, higher denitrification temperature, or longer denitrification time results in a better denitrification effect. Insufficient denitrification will affect the final L10-FeNi alloy properties. All sample handling processes were completed in a glove box.

[0047] The present invention will be further described below with reference to specific embodiments, but the methods and technical parameters involved in the solution should not be construed as limitations on the present invention.

[0048] Example 1:

[0049] (1) Preparation of precursor solution: Weigh 250 ml of 0.3 mol / L Fe(NO3)3 solution and 250 ml of 0.3 mol / L Ni(NO3)2 solution, mix them, and add 250 ml of 0.6 mol / L KCl solution and stir thoroughly. The tube furnace is heated in three stages, with the three temperature zones being 300℃, 800℃, and 800℃ respectively, at a heating rate of 10℃ / min. Argon gas is introduced to purge the air in the furnace, and the flow rate is controlled at 0.4 L / min. When the set temperature is reached, the precursor solution is poured into the ultrasonic nebulizer, and then the nebulizer is turned on. The frequency of the ultrasonic nebulizer is 10 MHz. The main valve of the hydrogen cylinder is loosened and the pressure reducing valve is tightened. The gas flow rate is controlled at 0.2 L / min by the gas flow meter. The carrier gas transports the atomized droplets into the tube furnace. After 5 hours of atomization, the ultrasonic nebulizer is turned off, and the powder is collected in the collection device at the end of the tube.

[0050] (2) The collected powder was washed with alcohol to remove KCl under an inert atmosphere to obtain spherical porous FeNi disordered alloy. The particle size of the powder was measured, and the results are shown in Table 1. Then, the spherical porous FeNi disordered alloy powder was nitrided in a closed high-pressure furnace at 300℃ for 30h. During the nitriding process, the gas pressure of the high-pressure furnace was kept at 1MPa, and the atmosphere of the tubular furnace was a mixture of ammonia and argon. After the reaction was completed, a sample was taken using a glove box to obtain the nitrided sample powder.

[0051] (3) The FeNiN alloy powder obtained after nitriding was denitrified in a tube furnace at 300℃ for 4 hours. The atmosphere of the tube furnace was a mixture of hydrogen and argon. After the reaction was completed, a sample was taken using a glove box. The obtained powder was subjected to phase analysis by X-ray diffraction (XRD) and magnetic properties were tested by vibrating sample magnetometer (VSM). Finally, the composition of the powder was determined to be L10 type-FeNi ordered alloy.

[0052] Examples 2-4:

[0053] The procedure was carried out according to the steps listed in Example 1, wherein 250 ml of 0.1 mol / L KCl solution, 250 ml of 0.3 mol / L KCl solution, and 250 ml of 0.9 mol / L KCl solution were added when preparing the precursor solution, and other conditions were the same as in Example 1.

[0054] The morphology of the FeNi disordered alloy directly obtained by the one-step spray thermal decomposition and reduction method was observed using SEM. Figure 1 Microstructure images of FeNi disordered alloys obtained by adding different amounts of KCl in Examples 1-4.

[0055] Examples 5-7:

[0056] The procedure was carried out according to the steps listed in Example 1, wherein the gas pressure in the high-pressure furnace was ensured to be 0.5 MPa, 5 MPa, and 10 MPa during the nitriding process, and other conditions were the same as in Example 1.

[0057] Examples 8-10:

[0058] The steps listed in Example 1 were carried out, with the temperatures of the spray thermal decomposition and reduction stage in Example 1 set sequentially to 300, 600, 600℃; 300, 700, 700℃; and 300, 900, 900℃, while other conditions remained the same as in Example 1.

[0059] Examples 11-14: (

[0060] The procedure was carried out according to the steps listed in Example 1, wherein the temperature of the nitriding stage in Example 1 was set sequentially to 200, 250, 350, and 400°C, and other conditions were the same as in Example 1.

[0061] Compare with Example 1

[0062] In Example 1, KCl solution was not added when preparing the precursor solution, but other procedures and experimental parameters were the same, and finally, L10-type FeNi ordered alloy was obtained.

[0063] Compare with Example 2

[0064] During the nitriding process in Example 1, the gas pressure in the high-pressure furnace was kept at atmospheric pressure, and other processes and experimental parameters were kept consistent, finally yielding L10-type FeNi ordered alloy.

[0065] Compare with Example 3

[0066] First, iron-nickel oxide is prepared by spray thermal decomposition, in which only air is passed through and no hydrogen is passed through. Then, the iron-nickel oxide is further reduced. The specific steps are as follows:

[0067] (1) Preparation of precursor solution: Weigh 250 ml of 0.3 mol / L Fe(NO3)3 solution and 250 ml of 0.3 mol / L Ni(NO3)2 solution, mix them, and add 250 ml of 0.6 mol / L KCl solution and stir thoroughly. The tube furnace is heated in three stages, with the three temperature zones being 300℃, 800℃, and 800℃ respectively, and the heating rate being 10℃ / min. When the set temperature is reached, the precursor solution is poured into the ultrasonic nebulizer, and then the nebulizer is turned on. The frequency of the ultrasonic nebulizer is 10 MHz. Air is introduced, and the gas flow rate is controlled at 0.4 L / min by a gas flow meter. The carrier gas transports the atomized droplets into the tube furnace. After 5 hours of atomization, the ultrasonic nebulizer is turned off, and the powder is collected in the collection device at the end of the tube.

[0068] (2) The collected powder was placed in a tube furnace and reduced at 300℃ for 5 hours with hydrogen. After cooling, the collected powder was washed with alcohol to remove KCl under an inert atmosphere to obtain spherical porous FeNi disordered alloy. The particle size of the powder was measured, and the results are shown in Table 1. Then, the FeNi disordered alloy powder obtained by reduction was nitrided in a closed high-pressure furnace at 300℃ for 30 hours. During the nitriding process, the gas pressure of the high-pressure furnace was kept at 1 MPa, and the atmosphere of the tube furnace was a mixture of ammonia and argon. After the reaction was completed, a sample was taken using a glove box to obtain the nitrided sample powder.

[0069] (3) The FeNiN alloy powder obtained after nitriding was denitrified in a tube furnace at 300℃ for 4 hours. The atmosphere of the tube furnace was a mixture of hydrogen and argon. After the reaction was completed, a sample was taken using a glove box. The obtained powder was subjected to phase analysis by X-ray diffraction (XRD) and magnetic properties were tested by vibrating sample magnetometer (VSM). Finally, the composition of the powder was determined to be L10 type-FeNi ordered alloy.

[0070] Table 1. Performance comparison of the final L10-FeNi alloy products from Examples 1-14 and Control Groups 1-3

[0071]

[0072] Table 1 compares and analyzes the above examples and control group, showing that adding a pore-forming agent to the precursor solution can refine the powder, form a porous structure, and increase the specific surface area. This increases the contact area between the powder and ammonia or nitrogen during nitriding, thereby improving nitriding efficiency. Within a certain range, the more pore-forming agent added, the better the refining effect. Compared with atmospheric pressure nitriding, high-pressure conditions can promote the forward nitriding reaction. Within a certain range, the higher the pressure, the more obvious the promoting effect. The one-step spray thermal decomposition and reduction method directly obtains FeNi disordered alloys, solving the problem of uncontrollable grain size in traditional asynchronous spray thermal decomposition and reduction methods, effectively... The phenomenon of grain size enlargement was suppressed, thus ensuring the success of nitriding. At the same time, different reduction temperatures in the one-step process also affected the performance of the final product. As the temperature of the reduction stage increased, the conversion rate of the disordered FeNi alloy gradually increased. When the reduction temperature was higher than 800℃, the reduction was complete. However, when the reduction temperature was lower, some unreduced iron oxide and nickel oxide remained, leading to nitriding failure. Different nitriding temperatures affected the nitriding effect. When the nitriding temperature was lower, the reactivity was lower, and a longer nitriding time was required for successful nitriding. When the nitriding temperature was higher, finer powders were more prone to oxidation during the nitriding process, which greatly reduced the nitriding effect and affected the transformation from disorder to order.

Claims

1. A method for producing an LlO-type FeNi ordered alloy, characterized by The method is specifically: Fe and Ni intercalated and filled with pore-forming agent spherical FeNi disordered alloy is directly obtained by spray pyrolysis and reduction one-step method; The spherical FeNi disordered alloy is subjected to alcohol washing to remove the pore-forming agent in an inert atmosphere protection environment to obtain spherical porous FeNi disordered alloy; The spherical porous FeNi disordered alloy is placed in a sealed high-pressure reaction furnace, and is subjected to high-pressure nitriding at 200-400℃ for more than 10h in an atmosphere containing ammonia to form FeNiN alloy; The FeNiN alloy is subjected to denitrogenation reaction to form L10 type-FeNi alloy; The preparation of the spherical FeNi disordered alloy adopts spray pyrolysis and reduction one-step method, and is specifically: Iron salt, nickel salt and pore-forming agent are mixed and dissolved in water to form a spray precursor solution; The spray precursor solution is placed in an ultrasonic atomizer by using ultrasonic spray principle, so that the mixed solution of the iron salt, the nickel salt and the pore-forming agent becomes mist, and then is transported to a preheated tube furnace under the action of carrier gas; The mist-shaped precursor solution is subjected to evaporation dehydration, salt thermal decomposition and reduction reaction under the action of high temperature of the tube furnace, and finally directly forms the spherical FeNi disordered alloy filled with pore-forming agent, which is transported to a collector arranged at the end of the tube furnace by the carrier gas; The evaporation dehydration, salt thermal decomposition and reduction reaction are carried out in the tube furnace, which is divided into three sections for temperature rising, wherein the temperature of the evaporation zone is set to 100-300℃, the temperature of the decomposition zone and the phase formation zone is set to 600-900℃, and the carrier gas is hydrogen and argon or helium.

2. The method of claim 1, wherein, The pore-forming agent in the preparation process of the spherical FeNi disordered alloy is KCl or NaCl, and the molar ratio of the pore-forming agent to the iron salt is 0.33-3:

1.

3. The method of claim 1, wherein, The reducing atmosphere in the preparation process of the spherical FeNi disordered alloy adopts a mixed gas of hydrogen and inert gas, and the flow rate is 1-3L / min.

4. The method of claim 3, wherein, The volume ratio of hydrogen to inert gas in the reducing atmosphere in the preparation process of the spherical FeNi disordered alloy is 1:1-1:

3.

5. The method of claim 1, wherein, The molar ratio of Fe to Ni in the FeNi disordered alloy is 1:

1.

6. The method of claim 1, wherein, The ammonia-containing atmosphere during nitriding adopts ammonia or a mixed gas of ammonia and argon.

7. The method of claim 1 wherein, The gas pressure in the high-pressure furnace during nitriding is above 1Mpa.

8. The method of claim 1, wherein, The denitrogenation reaction conditions are that the FeNiN alloy is subjected to denitrogenation reaction at 200-400℃ under hydrogen atmosphere for more than 1h, and the hydrogen flow rate is 0.1-2L / min.

9. An L10 type-FeNi ordered alloy in near-spherical micro-nano size, which is prepared by the method of any one of claims 1-8.

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