Preparation method of high-uniformity molybdenum-rhenium alloy powder

Abstract

The invention belongs to the technical field of powder metallurgy, and particularly relates to a preparation method of high-uniformity molybdenum-rhenium alloy powder. In the prior art, no matter a dry method or a wet method is adopted for preparing molybdenum-rhenium alloy powder, the problem that metal rhenium is unevenly distributed in the molybdenum-rhenium alloy powder generally exists, and the performance of molybdenum-rhenium alloy is directly affected. The invention discloses a preparation method of high-uniformity molybdenum-rhenium alloy powder. The preparation method comprises the following steps: firstly, adding ammonium molybdate, ammonium perrhenate and a dispersing agent into deionized water, heating and dissolving to obtain a suspension; then, the suspension is subjected to spray drying in a spray drying tower, and dry powder is obtained; and finally, the dry powder is subjected to roasting and two-step reduction in a tubular furnace, and the high-uniformity molybdenum-rhenium alloy powder is obtained. According to the preparation method, the dispersing agent is added in the dissolving process, the problem that ammonium molybdate or ammonium perrhenate is non-uniformly crystallized and separated out when water is removed in the spray drying process is solved, the uniformity of the molybdenum-rhenium alloy powder is improved, and the quality of the molybdenum-rhenium alloy powder is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy, and in particular relates to a method for preparing molybdenum-rhenium alloy powder with high uniformity. Background Art

[0002] Molybdenum metal is a refractory metal with a melting point of up to 2622°C. Molybdenum metal also has a small expansion coefficient, high electrical conductivity and excellent high-temperature performance. Molybdenum metal components are prone to brittle failure during processing and use. Generally, a certain amount of rhenium metal is added to molybdenum metal to form a molybdenum-rhenium alloy to improve the plasticity and strength of molybdenum metal. That is, the so-called "rhenium" effect is used to improve the plasticity, strength and performance of molybdenum metal.

[0003] The methods for preparing molybdenum-rhenium alloy powder mainly include "dry method" and "wet method". The so-called "dry method" is simply to mechanically grind and mix molybdenum powder and rhenium powder directly to obtain molybdenum-rhenium alloy powder. The so-called "wet method" is simply to dissolve molybdenum salt and rhenium salt in water, and obtain a mixed solid of molybdenum salt and rhenium salt after the solution is dried, and the mixed solid is further reduced to obtain molybdenum-rhenium alloy powder. Among them, the molybdenum-rhenium alloy powder prepared by the "dry method" is prone to uneven metal rhenium content, which directly affects the performance of the subsequent molybdenum-rhenium alloy. The molybdenum-rhenium alloy powder prepared by the "wet method" is more uniform than that prepared by the dry method, but the problem of uneven precipitation of molybdenum salt or rhenium salt is prone to occur during the drying process, which will also lead to the problem of uneven metal rhenium content in the molybdenum-rhenium alloy powder.

[0004] In 2019, "CN 111020330 A" disclosed a method for preparing a molybdenum-rhenium alloy profile. It includes: a step of preparing a molybdenum-rhenium alloy powder: mixing molybdenum powder and ammonium rhenate evenly according to the required composition ratio, and performing a reduction treatment to obtain a molybdenum-rhenium alloy powder; a pressing step: loading the molybdenum-rhenium alloy powder into a pressing mold for pressing and molding to obtain a pressed green sheet; a sintering step: sintering the pressed green sheet to obtain a sintered green sheet; a hot isostatic pressing step: performing a hot isostatic pressing treatment on the sintered green sheet to obtain a completely dense molybdenum-rhenium alloy profile. Due to the great difference in the properties of molybdenum powder and ammonium rhenate, uneven mixing is prone to occur, which affects the uniformity of the molybdenum-rhenium alloy powder and the quality of the final molybdenum-rhenium alloy profile.

[0005] In 2023, "CN 117802377 A" disclosed a method for preparing a molybdenum-rhenium alloy. The preparation method includes: step S10, mixing metal molybdenum powder and metal rhenium powder in proportion to obtain a mixed powder; step S20, ball milling the mixed powder to mechanically alloy the mixed powder to obtain an alloy powder; step S30, reducing the alloy powder; step S40, spark plasma sintering the alloy powder after reduction to obtain a molybdenum-rhenium alloy. The preparation method is prone to uneven mixing during the ball milling mixing process, which affects the uniformity of the final molybdenum-rhenium alloy powder.

[0006] In summary, in the process of preparing molybdenum-rhenium alloy powder in the prior art, the problem of uneven distribution of metallic rhenium in metallic molybdenum easily occurs, which affects the quality of the molybdenum-rhenium alloy powder. Summary of the invention

[0007] In view of the above technical problems, the present invention aims to provide a method for preparing a molybdenum-rhenium alloy powder with high uniformity, which specifically comprises the following steps:

[0008] (1) adding ammonium molybdate, ammonium perrhenate and a dispersant into deionized water and heating and dissolving them to obtain a suspension;

[0009] (2) spray drying the suspension in a spray drying tower to obtain a dry powder;

[0010] (3) The dry powder is calcined and reduced in a tube furnace to obtain a molybdenum-rhenium alloy powder with high uniformity.

[0011] The present invention uses ammonium molybdate and ammonium perrhenate as molybdenum sources and rhenium sources to prepare molybdenum-rhenium alloy powder by a wet method. Compared with the dry method, the wet method for preparing molybdenum-rhenium alloy powder is easier to ensure the uniformity of metal molybdenum and metal rhenium on the macroscopic and microscopic scales, and can ensure the use performance of the molybdenum-rhenium alloy. However, the prior art has the following problems in the process of preparing molybdenum-rhenium alloy powder by a wet method: the problem of uneven crystallization precipitation will occur in the process of removing solvent water, that is, in the process of removing water, as the amount of solvent water decreases, salts with low solubility will be precipitated first, resulting in the inability to evenly mix the molybdenum salt and the rhenium salt in the precursor, which will seriously affect the use performance of the final molybdenum-rhenium alloy powder. In response to this problem, the present invention creatively adds a dispersant in the process of dissolving ammonium molybdate and ammonium perrhenate to overcome the problem of uneven crystallization precipitation in the process of removing solvent water. The present invention dissolves ammonium molybdate, ammonium perrhenate and a dispersant in deionized water to obtain a suspension, and the suspension is spray-dried in a spray drying tower to obtain a dry powder. The spray drying process can make the water in the suspension dry quickly in seconds, overcoming the problem of uneven crystallization of ammonium molybdate or ammonium perrhenate. The dispersant in the suspension has three main functions: 1. Increase the viscosity of the suspension to avoid the aggregation of tiny ammonium molybdate or ammonium perrhenate crystals during the removal of solvent water; 2. In the process of removing solvent water, it is used as a wall material to wrap the outer surface of tiny ammonium molybdate or tiny ammonium perrhenate crystals to form a dry powder with a microcapsule structure; 3. Form a carbon source during the roasting process, which serves as a reducing agent for the first step of carbon powder reduction. The dry powder is roasted in a tube furnace in an air-tight manner, and the dispersant therein forms micron or even nanometer-level carbon powder uniformly dispersed around the molybdenum oxide and rhenium oxide, which is more conducive to the first step of carbon powder reduction reaction. After the first step of carbon powder reduction process, making full use of the carbon source formed by the dispersant can reduce the load of the second step of hydrogen reduction process. After the second step of hydrogen reduction process, a highly uniform molybdenum-rhenium alloy powder is formed.

[0012] The above is the basic technical solution of the present invention. To facilitate those skilled in the art to understand and implement the technical solution of the present invention, the present invention also includes the following additional technical features:

[0013] In the preferred technical solution, in step (1), the content of the dispersant in the suspension is 1.0-5.0%; the dispersant is selected from at least one of dextrin, cyclodextrin, modified starch, gum arabic, and gelatin. Dextrin, cyclodextrin, and modified starch are all derivatives formed by structural modification and / or selective hydrolysis of starch as raw materials, have a certain solubility in water, and their polyhydroxy structure can wrap metal ions to form a colloidal structure. In particular, modified starch has excellent film-forming properties and can be used as a wall material for microcapsules to tightly wrap metal ions and avoid the occurrence of uneven crystallization precipitation problems. Gum arabic and gelatin have better film-forming properties than modified starch and can also avoid the occurrence of uneven crystallization precipitation problems. Among the above dispersants, dextrin and cyclodextrin are cheap, but their effects are not as good as modified starch, gum arabic, and gelatin with film-forming properties. When using modified starch, it is necessary to consider the influence of sodium ions that it may carry. Usually, the pH value of the system is controlled during the preparation of modified starch to avoid the introduction of sodium ions. OSA starch esters are preferably used as dispersants rather than OSA starch sodium to achieve the best overall effect. When using gum arabic and gelatin, it is necessary to consider the adverse effects of nitrogen and sulfur elements that may exist in them on molybdenum-rhenium alloy powder.

[0014] In the preferred technical solution, in step (1), the mass ratio of the element molybdenum in the ammonium molybdate to the element rhenium in the ammonium perrhenate is 1-99:1. The object of the present invention is to provide a method for preparing a highly uniform molybdenum-rhenium alloy powder, wherein the content of metallic rhenium in the molybdenum-rhenium alloy is ≤50%. In the batching process of step (1), the feeding amount of ammonium molybdate and ammonium perrhenate needs to be back-calculated according to the content of metallic rhenium in the target molybdenum-rhenium alloy powder based on the content of ammonium molybdate and ammonium perrhenate, so that a molybdenum-rhenium alloy powder with a metallic rhenium content within the target content range can be prepared.

[0015] In the preferred technical solution, in step (1), the solid content of the suspension is 15-45%. When the molybdenum-rhenium alloy precursor powder is prepared by spray drying, the solid content of the suspension affects the energy consumption of preparing the molybdenum-rhenium alloy on the one hand, and affects the uniform distribution of metal rhenium in the molybdenum-rhenium alloy powder on the other hand. When a low solid content is used, the amount of insoluble matter in the suspension is small; when a high solid content is used, the amount of insoluble matter in the suspension is large. The dispersant can fully and evenly disperse the insoluble matter in the system. If an extremely low solid content is used, a suspension will not be formed at this time, but a solution will be formed. Even with the presence of a dispersant during the spray drying process, the occurrence of uneven crystallization precipitation cannot be completely avoided, and the energy consumption of the spray drying process is increased.

[0016] In a preferred technical solution, in step (1), the temperature of the heating and dissolving process is 40-60° C. This temperature range is conducive to the rapid dispersion of ammonium molybdate, ammonium perrhenate and the dispersant to form a stable suspension system.

[0017] In the preferred technical solution, the suspension is further homogenized before the spray drying process in step (2); the pressure of the homogenization process is controlled to be 35-50 MPa. Homogenizing the suspension by a homogenizer can maximize the uniformity of the suspension, and a good effect can be achieved by using a pressure of 35-50 MPa in the homogenization process. The homogenized suspension will not settle even if it is placed at room temperature for 4 hours.

[0018] In the preferred technical solution, in step (2), the moisture content of the dry powder is ≤ 5%. The moisture content of the dry powder in step (2) in the basic technical solution has a significant effect on the uniform distribution of metallic rhenium in the final molybdenum-rhenium alloy powder. When the moisture content in the dry powder is too high, the drying and removal of moisture first occurs during the subsequent roasting process. This process is not as fast as the removal of moisture during the spray drying process, which will cause uneven crystallization of ammonium molybdate or ammonium perrhenate, affecting the uniform distribution of metallic rhenium in the final molybdenum-rhenium alloy powder. When the moisture content in the dry powder is less than 5%, there is basically no free water in the dry powder, and the loss of bound water will not cause uneven crystallization of ammonium molybdate or ammonium perrhenate, and will not affect the uniform distribution of metallic rhenium in the final molybdenum-rhenium alloy powder.

[0019] In a preferred technical solution, in step (3), the temperature of the tube furnace is controlled to be 150-300° C. during the calcination process. The purpose of calcination here is to convert ammonium molybdate into molybdenum oxide, ammonium perrhenate into rhenium oxide, and the dispersant into carbon powder. The calcination temperature should not be too high, and the calcination speed should not be too fast, so that the formed carbon powder can be evenly distributed among the molybdenum oxide and / or rhenium oxide.

[0020] In the preferred technical solution, in step (3), the two-step reduction process consists of carbon powder reduction and hydrogen reduction; the temperature of the carbon powder reduction process is 400-500°C; the temperature of the hydrogen reduction process is 500-800°C. After calcination, the substances in the system are mainly carbon powder, metal molybdenum oxide, and metal rhenium oxide. The oxidation state of metal molybdenum oxide and metal rhenium oxide is reduced by the reduction of carbon powder, thereby reducing the load of subsequent hydrogen reduction.

[0021] In a preferred technical solution, inert gas is filled in the roasting process and the carbon powder reduction process to isolate the air, and the inert gas is selected from at least one of nitrogen, argon and helium. The dispersant actually undergoes a dry distillation process under the condition of isolating the air, forming water, carbon powder and small molecular organic matter, the water is taken out of the tube furnace by the inert gas, and the carbon powder is evenly distributed between the oxides of metal molybdenum and / or metal rhenium to form a uniform system. Since argon has the highest density, it has the best effect of isolating from the air.

[0022] The method for preparing a highly uniform molybdenum-rhenium alloy powder of the present invention overcomes the problem of uneven distribution of metallic rhenium in the molybdenum-rhenium alloy powder during the preparation of a precursor suspension and the preparation of a precursor dry powder, thereby preparing a highly uniform molybdenum-rhenium alloy powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The SEM image of the molybdenum-rhenium alloy powder with a rhenium content of 26.03% prepared by the method of the present invention. DETAILED DESCRIPTION

[0024] The present invention is described in detail below by way of examples, but the present invention is not limited to these examples.

[0025] Example 1

[0026] (1) Preparation of suspension:

[0027] Add 640g of 55°C deionized water and 28.5g of hydroxypropyl β-cyclodextrin to a 2000ml beaker, and turn on the magnetic stirring rotor to dissolve. After the hydroxypropyl β-cyclodextrin is dissolved, add 180.0g of ammonium molybdate tetrahydrate (content: 99.24%) and 49.8g of ammonium perrhenate (content: 99.45%) to the beaker. Dissolve for 30 minutes to obtain a suspension.

[0028] (2) Spray drying:

[0029] The suspension was transported into a homogenizer by a peristaltic pump for homogenization, and the homogenization pressure was controlled at 40 MPa. The homogenized suspension was dried in a spray drying tower at 180°C to obtain a dry powder. The moisture content of the dry powder was 3.54%.

[0030] (3) Calcination:

[0031] The dry powder was placed in a tubular furnace, the argon flow rate was controlled to 0.2 L / min, the temperature inside the tubular furnace was 250°C, and the powder was fully calcined for 2.0 hours under the protection of argon.

[0032] (4) First step of reduction: After calcination, control the argon flow rate to 0.2 L / min, increase the temperature inside the tubular furnace to 460°C, and perform carbon powder reduction for 2.5 hours.

[0033] (5) Second step of reduction: After the carbon powder reduction is completed, the hydrogen flow rate is controlled to 0.6 / min, the temperature inside the tube furnace is increased to 650°C, and the hydrogen reduction is carried out for 8.0 hours. After the hydrogen reduction is completed, a highly uniform molybdenum-rhenium alloy powder is obtained.

[0034] Uniformity evaluation: After the molybdenum-rhenium alloy powder is evenly mixed, 20 g of the sample is taken and spread into a 4*3 cm rectangular thin layer. Samples are taken at the four corners and the midpoint of the thin layer (samples are taken in the order of upper left, upper right, lower left, lower right, and middle). The rhenium content of the molybdenum-rhenium alloy powder is detected by ICP-OES. The detected contents are: 25.88%, 25.94%, 25.86%, 26.34%, 26.12%, respectively. The average content is: 26.03%, standard deviation (SD): 0.20%, relative standard deviation (RSD): 0.78%.

[0035] Example 2

[0036] The preparation process and process parameters of Example 2 are basically the same as those of Example 1, except that the amount of ammonium perrhenate added is reduced to 1.5 g when preparing the suspension. The water content of the dry powder obtained by spray drying is 3.42%. Uniformity evaluation: After the molybdenum-rhenium alloy powder is evenly mixed, 20 g of the sample is taken and spread into a 4*3 cm rectangular thin layer. Samples are taken at the four corners and the midpoint of the thin layer (sampled in the order of upper left, upper right, lower left, lower right, and middle). The rhenium content of the molybdenum-rhenium alloy powder is detected by ICP-OES. The detected contents are: 0.98%, 0.99%, 1.02%, 1.02%, 1.01%, respectively, and the average content is: 1.00%, standard deviation (SD): 0.02%, relative standard deviation (RSD): 1.81%.

[0037] Example 3

[0038] The preparation process and process parameters of Example 3 are basically the same as those of Example 1, except that the amount of ammonium perrhenate added is increased to 141.0 g when preparing the suspension. The water content of the dry powder obtained by spray drying is 2.89%. Uniformity evaluation: After the molybdenum-rhenium alloy powder is evenly mixed, 20 g of the sample is taken and spread into a 4*3 cm rectangular thin layer. Samples are taken at the four corners and the midpoint of the thin layer (sampled in the order of upper left, upper right, lower left, lower right, and middle). The rhenium content of the molybdenum-rhenium alloy powder is detected by ICP-OES. The detected contents are: 49.72%, 50.08%, 50.03%, 49.85%, 49.91%, respectively, and the average content is: 49.92%, standard deviation (SD): 0.14%, relative standard deviation (RSD): 0.29%.

[0039] Example 4

[0040] The preparation process and process parameters of Example 4 are basically the same as those of Example 1, except that the amount of hydroxypropyl β-cyclodextrin is reduced to 9.0 g when preparing the suspension. The water content of the dry powder obtained by spray drying is 2.67%. Uniformity evaluation: After the molybdenum-rhenium alloy powder is evenly mixed, 20 g of the sample is taken and spread into a 4*3 cm rectangular thin layer. Samples are taken at the four corners and the midpoint of the thin layer (sampled in the order of upper left, upper right, lower left, lower right, and middle). The rhenium content of the molybdenum-rhenium alloy powder is detected by ICP-OES. The detected contents are: 26.21%, 26.31%, 25.73%, 26.16%, 25.54%, and the average content is: 25.99%, standard deviation (SD): 0.34%, relative standard deviation (RSD): 1.29%.

[0041] Example 5

[0042] The preparation process and process parameters of Example 5 are basically the same as those of Example 1, except that the amount of hydroxypropyl β-cyclodextrin added is increased to 46.0 g when preparing the suspension. The water content of the dry powder obtained by spray drying is 3.58%. Uniformity evaluation: After the molybdenum-rhenium alloy powder is evenly mixed, 20 g of the sample is taken and spread into a 4*3 cm rectangular thin layer. Samples are taken at the four corners and the midpoint of the thin layer (sampled in the order of upper left, upper right, lower left, lower right, and middle). The rhenium content of the molybdenum-rhenium alloy powder is detected by ICP-OES. The detected contents are: 26.01%, 26.12%, 25.97%, 26.14%, 25.89%, and the average content is: 26.03%, standard deviation (SD): 0.10%, and relative standard deviation (RSD): 0.40%.

[0043] Example 6

[0044] The preparation process and process parameters of Example 6 are basically the same as those of Example 1, except that the feed amount of the suspension is reduced during spray drying, and the water content of the dry powder is reduced to 1.35%. Uniformity evaluation: After the molybdenum-rhenium alloy powder is evenly mixed, 20 g of the sample is taken and spread into a 4*3 cm rectangular thin layer. Samples are taken at the four corners and the midpoint of the thin layer (sampled in the order of upper left, upper right, lower left, lower right, and middle). The rhenium content of the molybdenum-rhenium alloy powder is detected by ICP-OES. The detected contents are: 25.87%, 25.91%, 25.95%, 26.12%, 26.15%, and the average content is: 26.00%, standard deviation (SD): 0.13%, relative standard deviation (RSD): 0.49%.

[0045] Example 7

[0046] The preparation process and process parameters of Example 7 are basically the same as those of Example 1, except that the feed amount of the suspension is increased during spray drying, and the water content of the dry powder is increased to 4.98%. Uniformity evaluation: After the molybdenum-rhenium alloy powder is evenly mixed, 20 g of the sample is taken and spread into a 4*3 cm rectangular thin layer. Samples are taken at the four corners and the midpoint of the thin layer (sampled in the order of upper left, upper right, lower left, lower right, and middle). The rhenium content of the molybdenum-rhenium alloy powder is detected by ICP-OES. The detected contents are: 25.88%, 25.79%, 26.22%, 25.89%, 26.26%, and the average content is: 26.01%, standard deviation (SD): 0.22%, relative standard deviation (RSD): 0.83%.

[0047] Comparative Example 1

[0048] The preparation method and process parameters of Comparative Example 1 are basically the same as those of Example 1, except that hydroxypropyl β-cyclodextrin is not added when preparing the suspension. The water content of the dry powder obtained by spray drying is 3.45%. Uniformity evaluation: After the molybdenum-rhenium alloy powder is evenly mixed, 20g of the sample is taken and spread into a 4*3cm rectangular thin layer. Samples are taken at the four corners and the midpoint of the thin layer (sampled in the order of upper left, upper right, lower left, lower right, and middle). The rhenium content of the molybdenum-rhenium alloy powder is detected by ICP-OES. The detected contents are: 25.34%, 26.53%, 26.36%, 25.37%, 26.37%, and the average content is: 25.99%, standard deviation (SD): 0.59%, and relative standard deviation (RSD): 2.26%.

[0049] Comparative Example 2

[0050] The preparation method and process parameters of Comparative Example 2 are basically the same as those of Example 1, except that: hydroxypropyl β-cyclodextrin is not added when preparing the suspension, and the suspension is not homogenized by a homogenizer before spray drying. The water content of the dry powder obtained by spray drying is 3.27%. Uniformity evaluation: After mixing the molybdenum-rhenium alloy powder evenly, 20g of the sample is taken and spread into a rectangular thin layer of 4*3cm. Samples are taken at the four corners and midpoint of the thin layer (sampled in the order of upper left, upper right, lower left, lower right, and middle). The rhenium content of the molybdenum-rhenium alloy powder is detected by ICP-OES. The detected contents are: 25.74%, 26.69%, 26.87%, 25.98%, 27.12%, and the average content is: 26.28%, standard deviation (SD): 0.67%, relative standard deviation (RSD): 2.54%.

[0051] Comparative Example 3

[0052] The preparation method and process parameters of Comparative Example 3 are basically the same as those of Example 1, except that: hydroxypropyl β-cyclodextrin is not added when preparing the suspension, and the amount of deionized water is increased to 1280g, and a transparent dissolved solution is obtained at this time. Spray drying obtains a dry powder moisture content of 3.15%. Uniformity evaluation: After mixing the molybdenum-rhenium alloy powder evenly, 20g of the sample is taken and spread into a 4*3cm rectangular thin layer. Samples are taken at the four corners and midpoint of the thin layer (sampled in the order of upper left, upper right, lower left, lower right, and middle). The rhenium content of the molybdenum-rhenium alloy powder is detected by ICP-OES, and the detected contents are: 26.33%, 27.14%, 27.36%, 24.38%, 25.63%, and the average content is: 26.17%, standard deviation (SD): 1.21%, relative standard deviation (RSD): 4.63%.

[0053] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a highly uniform molybdenum-rhenium alloy powder, characterized in that: The specific steps include: (1) adding ammonium molybdate, ammonium perrhenate and a dispersant into deionized water and heating and dissolving them to obtain a suspension; (2) spray drying the suspension in a spray drying tower to obtain a dry powder; (3) The dry powder is calcined and reduced in a tube furnace to obtain a molybdenum-rhenium alloy powder with high uniformity.

2. The preparation method according to claim 1, characterized in that: In step (1), the content of the dispersant in the suspension is 1.0-5.0%; the dispersant is selected from at least one of dextrin, cyclodextrin, modified starch, gum arabic and gelatin.

3. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of the element molybdenum in the ammonium molybdate to the element rhenium in the ammonium perrhenate is 1-99:

1.

4. The preparation method according to claim 1, characterized in that: In step (1), the solid content of the suspension is 15-45%.

5. The preparation method according to claim 1, characterized in that: In step (1), the temperature of the heating and dissolving process is 40-60°C.

6. The preparation method according to claim 1, characterized in that: Before the spray drying process in step (2), a homogenization process of the suspension is also included; the pressure of the homogenization process is controlled to be 35-50 MPa.

7. The preparation method according to claim 1, characterized in that: In step (2), the moisture content of the dry powder is ≤5%.

8. The preparation method according to claim 1, characterized in that: In step (3), the temperature of the tube furnace is controlled to be 150-300° C. during the roasting process.

9. The preparation method according to claim 1, characterized in that: In step (3), the two-step reduction process consists of carbon powder reduction and hydrogen reduction; the temperature of the carbon powder reduction process is 400-500°C; the temperature of the hydrogen reduction process is 500-800°C.

10. The preparation method according to claim 8 or 9, characterized in that: In the calcination process and the carbon powder reduction process, an inert gas is filled to isolate the air; the inert gas is selected from at least one of nitrogen, argon and helium.

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