Method for efficiently reducing and purifying carbonyl iron powder

Abstract

The invention belongs to the technical field of soft magnetic materials, and discloses a method for efficiently reducing and purifying carbonyl iron powder. The method comprises the following steps: S1, coating the surface of carbonyl iron powder to be purified with a silicon dioxide prefabricated layer by adopting a sol-gel method; the silicon dioxide prefabricated layer contains occupied particles; s2, removing occupying particles in the silicon dioxide prefabricated layer to obtain a silicon dioxide protective layer; a hole structure is distributed in the silicon dioxide protection layer; and S3, the carbonyl iron powder treated in the step S2 is reduced under reducing gas, and purified carbonyl iron powder is obtained. According to the method, the silicon dioxide protection layer distributed with a large number of penetrating holes is provided to ensure that the temperature of reducing and purifying the carbonyl iron powder is increased to 750 DEG C without the problems of caking, agglomeration and the like, so that the rapidness and high efficiency of the reducing and purifying process of the carbonyl iron powder are realized to the greatest extent; and the method has the advantages of simple process, low cost, mass production and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of soft magnetic materials, and particularly relates to a method for efficiently reducing and purifying carbonyl iron powder. BACKGROUND

[0002] A series of transition elements (iron, cobalt, nickel, etc.) in the periodic table of elements can react with carbon monoxide to generate carbonyl metal compounds, and after thermal decomposition, fine-grained, high-activity, and non-harmful impurity-free carbonyl metal powder can be obtained. Carbonyl iron powder is the most common and widely used carbonyl metal powder at present. It has the characteristics of fine particle size, good spherical appearance, good forming performance, high surface activity, excellent electromagnetic performance, etc. In particular, it has high magnetic flux rate at high frequency and ultra-high frequency, and is therefore widely used in the manufacture of magnetic materials, especially in the manufacture of high-frequency iron powder cores, and plays an irreplaceable role.

[0003] Carbonyl iron powder is obtained by high-temperature decomposition. Generally, the obtained carbonyl iron powder has high oxygen and carbon content in the form of iron oxides, carbides, and free oxygen and carbon impurities. Research results have shown that iron carbide, free carbon, and oxygen seriously affect the magnetic properties and sintering properties of carbonyl iron powder, thereby seriously limiting the application and development of carbonyl iron powder.

[0004] Patent No. CN104475760A discloses a method for producing carbonyl iron powder. The method proposes using a mixed gas composed of carbonyl iron vapor and carbon monoxide gas and a multi-stage decomposition method to successfully control the carbon content of the carbonyl iron powder product to 0.7-0.9%. However, this method cannot solve the problem of high content of other impurities including oxygen.

[0005] In order to meet different application requirements, the commonly used method at present is to reduce and purify the obtained carbonyl iron powder in a reducing gas at a certain temperature to reduce the content of impurity elements, especially oxygen and carbon, so as to obtain carbonyl iron powder with required purity. Moreover, the reduction process at high temperature can also reduce the hardness of carbonyl iron powder, which is beneficial to further subsequent processing. In the reduction and purification process of carbonyl iron powder, theoretically, the higher the reduction temperature, the faster the reduction speed of carbonyl iron powder, thereby improving production efficiency and capacity. Generally, when the reduction temperature is higher than 350℃, the reduction speed begins to significantly accelerate. However, when the temperature is higher than 350℃, especially close to 400℃, the carbonyl iron powder will produce block-shaped particle aggregation and obvious adhesion. Although this problem can be solved to some extent through the later crushing and grinding process, the structure and shape of the particles will be significantly affected, resulting in reduced electromagnetic performance. Therefore, at present, the reduction and purification of carbonyl iron powder can only be carried out below 400℃ by prolonging the reduction time to meet the production requirements.

[0006] Therefore, how to improve the reduction temperature, make the reduction and purification process of the carbonyl iron powder faster and more efficient on the basis of maintaining or optimizing the electromagnetic performance, is still a technical problem to be solved in the art. SUMMARY

[0007] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the purpose of the present application is to provide a method for efficiently reducing and purifying carbonyl iron powder. The method of the present application can raise the reduction temperature to 750℃ without problems such as caking and agglomeration, and make the reduction and purification process of the carbonyl iron powder faster and more efficient on the basis of maintaining or optimizing the electromagnetic performance, and the oxygen, carbon and nitrogen content in the purified carbonyl iron powder is significantly reduced.

[0008] In a first aspect, the present application provides a method for efficiently reducing and purifying carbonyl iron powder, comprising the following steps: S1, using a sol-gel method to coat a silica preformed layer on the surface of the carbonyl iron powder to be purified; the silica preformed layer contains occupation particles; S2, removing the occupation particles in the silica preformed layer to obtain a silica protective layer; the silica protective layer has a pore structure distributed therein; S3, reducing the carbonyl iron powder treated in step S2 under a reducing gas to obtain purified carbonyl iron powder.

[0009] Specifically, when the reduction and purification of the carbonyl iron powder is carried out at high temperature using a reducing gas, the thicker the protective film on the surface of the carbonyl iron powder, the better the protection effect of preventing the adhesion of carbonyl iron powder particles. However, the protective film, while solving the problem of powder adhesion at high temperature, also brings the problem of blocking the contact between the reducing gas and the carbonyl iron powder to remove impurities such as oxygen and carbon, especially the structure of the protective film is generally very dense (traditional processes all pursue the denseness and uniformity of the protective film), which easily leads to the problem that the reducing gas is difficult or reduced to contact with the carbonyl iron powder, i.e. the difficulty of impurity removal is increased. Although a higher temperature and a longer reduction treatment time can improve the effect of the reducing gas in removing impurities such as oxygen and carbon, it will result in a decrease in the efficiency of this process and a significant increase in the processing cost, which cannot achieve the purpose of efficient reduction and purification.

[0010] The present application adopts the above technical scheme, by uniformly distributing the space-occupying particles forming the holes in the sol forming the silica protective layer, removing the space-occupying particles during or after the sol film forming process, thus forming a silica protective layer with a large number of (through) holes on the surface of the carbonyl iron powder, which can simultaneously play the roles of the silica high-temperature resistant protection (preventing the contact and adhesion between the carbonyl iron powders) and the hole structure ensuring the reduction gas to enter and fully contact with the carbonyl iron powder, achieving the purpose of quickly and efficiently reducing and purifying the carbonyl iron powder at a high temperature, which can ensure that the temperature of the reduced and purified carbonyl iron powder is increased to 750 DEG C without problems such as caking and agglomeration, and on the basis of maintaining or optimizing the electromagnetic performance, the reduction and purification process of the carbonyl iron powder is more rapid and efficient. Moreover, the method provided by the present application also has the advantages of simple process, low cost and large-scale production.

[0011] In some embodiments of the present application, the space-occupying particles include at least one of ammonium bicarbonate, methyl methacrylate resin, polyvinyl chloride, polyformaldehyde, polyvinylidene chloride, polyacrylonitrile, zinc carbonate, metallic zinc, ammonium chloride and magnesium carbonate. The space-occupying particles are preferably at least one of ammonium bicarbonate, zinc carbonate and metallic zinc.

[0012] In some embodiments of the present application, the addition amount of the space-occupying particles accounts for 1-5% of the mass of the carbonyl iron powder to be purified.

[0013] In some embodiments of the present application, the space-occupying particles are nano-level space-occupying particles with an average particle size of 50-200 nm.

[0014] In some embodiments of the present application, the average particle size of the carbonyl iron powder to be purified is 1-20 µm.

[0015] In some embodiments of the present application, the thickness of the silica protective layer is 10-200 nm.

[0016] In some embodiments of the present application, the porosity of the silica protective layer is 10-50%.

[0017] In some embodiments of the present application, the pore size of the hole structure is 50-200 nm.

[0018] In some embodiments of the present application, the step S1 specifically includes the following steps: S1.1, mixing an organosilicon compound, a solvent, space-occupying particles and ammonia water to obtain a mixed solution; S1.2, mixing the mixed solution with the carbonyl iron powder to be purified and stirring to coat a silica preformed layer on the surface of the carbonyl iron powder to be purified.

[0019] In some embodiments of the present application, the organic silicon compound comprises a silane coupling agent and / or a silicate.

[0020] In some embodiments of the present application, the amount of the organic silicon compound added accounts for 1-3% of the mass of the carbonyl iron powder to be purified.

[0021] In some embodiments of the present application, the silane coupling agent comprises at least one of A-1160, A187, KH550, KH560 and KH570.

[0022] In some embodiments of the present application, the silane coupling agent accounts for 1-3% of the mass of the carbonyl iron powder to be purified.

[0023] In some embodiments of the present application, the silicate comprises at least one of methyl orthosilicate, ethyl orthosilicate and propyl orthosilicate. The silicate is preferably ethyl orthosilicate, or preferably a mixture of ethyl orthosilicate and methyl orthosilicate, or preferably a mixture of ethyl orthosilicate and propyl orthosilicate, or preferably a mixture of methyl orthosilicate, ethyl orthosilicate and propyl orthosilicate; the mass content of ethyl orthosilicate in the mixture is ≥50%.

[0024] In some embodiments of the present application, the silicate accounts for 1-3% of the mass of the carbonyl iron powder to be purified.

[0025] In some embodiments of the present application, the solvent comprises anhydrous ethanol.

[0026] In some embodiments of the present application, the amount of the solvent added accounts for 3-10% of the mass of the carbonyl iron powder to be purified.

[0027] In some embodiments of the present application, the mass concentration of the ammonia water is 15-30%.

[0028] In some embodiments of the present application, the amount of the ammonia water added accounts for 0.5-1% of the mass of the carbonyl iron powder to be purified.

[0029] In some embodiments of the present application, in the step S1.1, the space-occupying particles are pre-milled with ceramic balls under the protection of anhydrous ethanol for 1-8h. By controlling the milling time, space-occupying particles of corresponding particle size are obtained, so that the pore structure obtained by removing the space-occupying particles in the step S2 will not cause the carbonyl iron powder to be adhered when reduced in the step S3.

[0030] In some embodiments of the present application, in step S1.2, the mixing is adding the mixed solution into the carbonyl iron powder to be purified, and the adding mode includes gradually adding in the form of drops, pouring, dripping or spraying, and the adding speed of the mixed solution is 0.1-1 L / min to 10 kg of the carbonyl iron powder to be purified.

[0031] In some embodiments of the present application, in step S1.2, the carbonyl iron powder to be purified is sequentially cleaned by anhydrous ethanol and water in advance.

[0032] In some embodiments of the present application, step S2 is removing the occupying particles in the silica preform layer by heating.

[0033] In some embodiments of the present application, the heating includes normal pressure heating, the temperature of the normal pressure heating is 50-120℃, and the time of the normal pressure heating is 0.5-2 h. When ammonium bicarbonate is selected as the occupying particles, the decomposition temperature of ammonium bicarbonate is relatively low (40-60℃), and the normal pressure heating can be used to decompose the ammonium bicarbonate to form pores in the process of forming the film from the gel, thereby reducing the production process and the material cost and time cost.

[0034] In some embodiments of the present application, the normal pressure heating is further followed by vacuum heating, the temperature of the vacuum heating is 170-320℃, the pressure of the vacuum heating is ≤5.0 Kpa, and the time of the vacuum heating is 0.5-2 h. When methacrylic acid resin, polyvinyl chloride, polyformaldehyde, polyvinylidene chloride, polyacrylonitrile, zinc carbonate, metallic zinc, ammonium chloride and magnesium carbonate are selected as the occupying particles, the temperature for forming pores needs to be 170-320℃, and a vacuum heating process can be added at the front end of the reduction and purification production line, which does not increase the production process and the material cost and time cost. The pressure of the vacuum heating is preferably 0.1-5.0 Kpa.

[0035] In some embodiments of the present application, in step S3, the temperature of the reduction is 500-750℃, the pressure of the reducing gas is 0.5-110 Kpa, and the time of the reduction is 0.5-4 h. The temperature of the reduction is preferably 550-750℃, and further preferably 700-750℃. The pressure of the reducing gas is preferably 0.5-2.5 Kpa. The time of the reduction is preferably 2-4 h.

[0036] In some embodiments of the present application, in step S3, the reducing gas includes ammonia and / or hydrogen.

[0037] In the second aspect of the present application, a carbonyl iron powder is provided, which is purified by the method for efficiently reducing and purifying carbonyl iron powder according to the first aspect of the present application.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention is a highly efficient and controllable sol-gel + removal of site-occupying particles + reduction under high-temperature reducing gas composite method designed for the efficient purification and reduction of carbonyl iron powder. This method allows the growth of a controllable thickness of silica protective layer on the surface of carbonyl iron powder particles, containing a number and size of controllable through-holes. The silica protective layer obtained by this method effectively prevents contact between carbonyl iron powder particles, while the numerous pores provide channels for the reducing gas to contact the surface of the carbonyl iron powder (achieving deoxygenation, decarbonization, etc.) and for efficient reaction. This ensures that the reduction and purification temperature can be raised to 750℃ without problems such as agglomeration (the reduction temperature using this method can be further increased, but considering the potential for grain growth within the carbonyl iron powder, the maximum reduction temperature is set at 750℃), thus making the reduction and purification process of carbonyl iron powder more efficient while preserving the original electromagnetic properties of the soft magnetic particles to the greatest extent. Furthermore, this invention has the advantages of simple operation, low cost, and the ability to be mass-produced. Moreover, the method of the present invention produces no wastewater, waste residue, or polluting gases, and is environmentally friendly.

[0039] (2) By controlling parameters such as the amount of organosilicon compound added, the size of the occupier particles (ball milling) and the amount added, and the reaction temperature, the present invention can effectively increase the processing temperature of carbonyl iron powder reduction and purification, which not only prevents carbonyl iron powder particles from sticking together, but also significantly shortens the processing time of reduction and purification (improves efficiency), and maintains and improves the magnetic properties of carbonyl iron powder particles. Attached Figure Description

[0040] Figure 1 This is a surface morphology image of the uncoated, unpurified carbonyl iron powder used in this invention. Figure 2 This is a surface morphology diagram of carbonyl iron powder with a silica protective layer obtained in Example 1 of the present invention; Figure 3 This is a schematic diagram of the carbonyl iron powder coated with a silica protective layer having a through-hole structure according to the present invention; Figure 4 The images are actual photos of the particles after cleaning in step (1) of the present invention after being heat-treated at 380°C, 390°C and 400°C for 1 hour, respectively. Figure 5 This is a surface morphology diagram of carbonyl iron powder with a silicon dioxide protective layer obtained in Comparative Example 1 of the present invention. Figure 6 This is a surface morphology diagram of carbonyl iron powder with a silicon dioxide protective layer obtained in Example 2 of the present invention; Figure 7 This is a cross-sectional image of carbonyl iron powder with a silicon dioxide protective layer obtained in Example 2 of the present invention after being cut by ion beam. Figure 8 This is a surface morphology diagram of carbonyl iron powder with a silicon dioxide protective layer obtained in Example 3 of the present invention; Figure 9 This is a surface morphology diagram of carbonyl iron powder with a silicon dioxide protective layer obtained in Example 4 of the present invention; Figure 10 This is a surface morphology diagram of carbonyl iron powder with a silicon dioxide protective layer obtained in Example 5 of the present invention; Figure 11 This is a surface morphology diagram of carbonyl iron powder with a silicon dioxide protective layer obtained in Example 6 of the present invention; Figure 12 This is a surface morphology diagram of carbonyl iron powder with a silicon dioxide protective layer obtained in Example 7 of the present invention; Figure 13 This is a surface morphology diagram of carbonyl iron powder with a silicon dioxide protective layer obtained in Example 8 of the present invention; Figure 14 This is a surface morphology diagram of carbonyl iron powder with a silicon dioxide protective layer obtained in Example 9 of the present invention; Figure 15 This is a surface morphology diagram of carbonyl iron powder with a silicon dioxide protective layer obtained in Example 10 of the present invention. Detailed Implementation

[0041] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0042] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0043] In this invention, room temperature refers to 25±2℃.

[0044] Example 1 A method for efficiently reducing and purifying carbonyl iron powder includes the following steps: (1) Take 101 kg of carbonyl iron powder particles (Guangdong Jinhong New Materials Co., Ltd.) with an average particle size of 3.6 μm to be purified. After ultrasonic cleaning with anhydrous ethanol solution for 0.5 h, ultrasonic cleaning with deionized water three times for 0.5 h. After filtering out the deionized water, it is ready for use. (2) Mix tetraethyl orthosilicate (1 kg), propyl orthosilicate (0.3 kg) and anhydrous ethanol (4 kg), then add ammonium bicarbonate (2 kg) with an average particle size of 150 nm and ammonia water with a mass concentration of 25% (0.5 kg) to obtain a mixed solution for surface coating; spray the mixed solution into carbonyl iron powder (100 kg) at a rate of 1 L / min and stir continuously for 60 minutes, while controlling the temperature of the container holding the carbonyl iron powder at 20°C to obtain carbonyl iron powder with a silica pre-coated surface; then, stop stirring, heat the carbonyl iron powder with the silica pre-coated surface to 100°C at atmospheric pressure and dry for 2 hours to remove ammonium bicarbonate from the silica pre-coated surface, stop heating, and cool to room temperature to obtain carbonyl iron powder with a silica protective layer; the silica protective layer has a porous structure with a porosity of 30% (measured using Image J software and Image-Pro Plus 6.0 software).

[0045] (3) The carbonyl iron powder coated with a silicon dioxide protective layer is subjected to reduction and purification treatment to obtain purified carbonyl iron powder.

[0046] The surface morphology of carbonyl iron powder before and after coating was observed using a Crossbeam 350 scanning electron microscope from CARL-ZEISS, Germany. The results are as follows: Figure 1 and Figure 2 As shown. From Figure 1 As can be seen, the surface of the uncoated carbonyl iron powder particles to be purified in step (1) is smooth and clean. Figure 2 As can be seen, the carbonyl iron powder with a silicon dioxide protective layer on its surface obtained in step (2) has basically no change in shape and size, but the surface becomes very rough and has a large number of pores with a size of 100-200nm.

[0047] A schematic diagram of the carbonyl iron powder with a surface coated with a silica protective layer obtained by this invention is shown below. Figure 3 As shown, carbonyl iron powder 100 serves as the core, and silicon dioxide protective layer 200 serves as the outer shell. The silicon dioxide protective layer 200 has two typical through-hole structures 201 and 202.

[0048] Take 1 kg of carbonyl iron powder particles after cleaning in step (1), and heat-treat them at 380℃, 390℃ and 400℃ for 1 hour under nitrogen protection. Agglomeration of the carbonyl iron powder particles was observed in all cases (e.g., ...). Figure 4 As shown in the figure, the powder treated at 400℃ has very high agglomeration strength.

[0049] The carbon content in carbonyl iron powder before and after reduction treatment was tested using a domestically produced NCS-CS2800 high-frequency infrared carbon-sulfur analyzer, and the oxygen and nitrogen content in the carbonyl iron powder before and after reduction treatment was tested using a domestically produced NCS-ON3000 oxygen-nitrogen analyzer. The inductance value of the carbonyl iron powder before and after reduction treatment was measured using a TH2826 (LCR) tester. The test results are shown in Table 1.

[0050] Table 1

[0051] As shown in Table 1, the content of impurity elements carbon, nitrogen, and oxygen in carbonyl iron powder gradually decreases with increasing reduction temperature. At lower temperatures, the reduction effect is not particularly significant. The longer the reduction time of carbonyl iron powder in the heating zone (380℃), the lower the content of carbon, nitrogen, and oxygen impurities in the carbonyl iron powder. When the reduction time is relatively short, the impurity element content is higher, and the reduction effect is also more significant. When the impurity content is low, the reduction rate slows down. Furthermore, the carbon and oxygen content in carbonyl iron powder decreases significantly with increasing reduction pressure. In summary, when the reduction time is 2 hours, the carbon, nitrogen, and oxygen content in carbonyl iron powder can remain at a relatively low level, and the overall impurity element content is low. Extending the reduction time will further reduce the impurity element content, but the effect is not significant, and this will also greatly increase production costs and reduce reduction efficiency.

[0052] Comparative Example 1 (using only silicone grease, without spacer particles) A method for reducing and purifying carbonyl iron powder includes the following steps: (1) Take 100 kg of carbonyl iron powder particles with an average particle size of 3.6 μm to be purified, ultrasonically clean them with anhydrous ethanol solution for 0.5 h, then ultrasonically clean them three times with deionized water for 0.5 h, filter out the deionized water and set aside for use. (2) Mix tetraethyl orthosilicate (1 kg), propyl orthosilicate (0.3 kg) and anhydrous ethanol (4 kg), and then add 25% ammonia water (0.5 kg) to obtain a mixed solution for surface coating; spray the mixed solution into the carbonyl iron powder to be used at a rate of 1 L / min and stir continuously for 60 minutes, and control the temperature of the container holding the carbonyl iron powder at 20°C to obtain carbonyl iron powder with a silica pre-coated surface; then, stop stirring, heat the carbonyl iron powder with a silica pre-coated surface to 100°C at normal pressure and dry for 2 hours, stop heating, and cool to room temperature to obtain carbonyl iron powder with a silica protective layer. (3) The carbonyl iron powder coated with a silicon dioxide protective layer is subjected to reduction and purification treatment to obtain purified carbonyl iron powder.

[0053] The surface morphology of the carbonyl iron powder after coating was observed using the same testing instruments as in Example 1, and the results are as follows: Figure 5 As shown. FromFigure 5 As can be seen, compared to uncoated carbonyl iron powder ( Figure 1 The shape and size of the powder remained largely unchanged after coating. A uniform and dense silica coating layer was deposited on the surface of the powder. The coating layer was composed of tightly connected nano-sized fine particles and was relatively dense, with no pores found.

[0054] The oxygen, carbon, and nitrogen content, as well as the inductance value, in carbonyl iron powder before and after reduction treatment were tested using the same testing instruments as in Example 1. The test results are shown in Table 2.

[0055] Table 2

[0056] As can be seen from the data in Table 2, the oxygen, carbon, and nitrogen content in carbonyl iron powder gradually decreases with the extension of reduction treatment time.

[0057] Comparing Table 2 with the results in Table 1 of Example 1, it can be seen that under the same reduction and purification conditions, the oxygen, carbon, and nitrogen contents of the carbonyl iron powder treated for 10 hours in Comparative Example 1 are close to the results of the reduction treatment for 4 hours in Example 1. However, the impurity content is still higher than that in Example 1. This indicates that the pores formed by the occupiers in the silica protective layer significantly improve the reduction and purification speed (efficiency) of the carbonyl iron powder.

[0058] Example 1 demonstrates that coating carbonyl iron powder with a porous silica protective layer significantly improves the rate of oxygen, carbon, and nitrogen removal compared to silica-coated carbonyl iron powder without a porous structure. Furthermore, increasing the reduction purification temperature and gas pressure further enhances the removal rate of oxygen, carbon, and nitrogen. Specifically, in Example 1, increasing the reduction temperature to 700°C and reducing the carbonyl iron powder for 2 hours reduced the oxygen, carbon, and nitrogen content to a very low level. Simultaneously, the inductance of the carbonyl iron powder after reduction purification significantly improved from 3.1 μH to 3.64 μH. The improvement rate of the carbonyl iron powder coated with a porous silica protective layer at higher temperatures was significantly higher than that of the carbonyl iron powder coated with a non-porous silica structure.

[0059] Example 2 A method for efficiently reducing and purifying carbonyl iron powder includes the following steps: (1) Take 100 kg of carbonyl iron powder particles (Guangdong Jinhong New Materials Co., Ltd.) with an average particle size of 3.6 μm to be purified, ultrasonically clean them with anhydrous ethanol solution for 0.5 h, then ultrasonically clean them with deionized water 3 times for 0.5 h, filter out the deionized water and set aside for use. (2) Mix silane coupling agent (KH550, 1.33 kg), tetraethyl orthosilicate (1.67 kg), and anhydrous ethanol (4 kg), then add zinc powder (2 kg) with an average particle size of 50 nm obtained by ball milling for 7.5 h and ammonia water with a mass concentration of 25% (0.6 kg) to obtain a mixed solution for surface coating; spray the mixed solution into the carbonyl iron powder to be used at a rate of 1 L / min and stir continuously for 60 minutes, and control the temperature of the container holding the carbonyl iron powder at 20°C. The carbonyl iron powder with a silica pre-coated surface was obtained at ℃; then, stirring was stopped, and the carbonyl iron powder with the silica pre-coated surface was heated to 100℃ under normal pressure and dried for 2 hours; then it was placed in a vacuum furnace and heated for 1 hour at a temperature of 300℃ and a pressure of 2.5 kPa to remove zinc powder from the silica pre-coated surface. Heating was stopped, and the powder was cooled to room temperature to obtain carbonyl iron powder with a silica protective layer; the silica protective layer has a porous structure with a porosity of 25%.

[0060] (3) The carbonyl iron powder coated with a silicon dioxide protective layer is subjected to reduction and purification treatment to obtain purified carbonyl iron powder.

[0061] The surface morphology of the carbonyl iron powder after coating was observed using the same testing instruments as in Example 1, and the results are as follows: Figure 6 As shown. From Figure 6 As can be seen, compared to uncoated carbonyl iron powder ( Figure 1 After being coated with a silica protective layer, the shape and size of the powder remained largely unchanged, but the powder surface became rough, with pores averaging 50 nm in size. Furthermore, focused ion beam scanning electron microscopy (FIB-SEM) was used to in-situ cut dense areas of the powder surface with an ion beam and observe the cross-sectional morphology (e.g., ...). Figure 7 As shown in the figure, the carbonyl iron powder has a protective layer with a thickness of about 60 nm on its surface, and protrusions and pores with a size of about 50 nm are distributed on the protective layer.

[0062] The oxygen, carbon, and nitrogen contents in carbonyl iron powder before and after reduction treatment were tested using the same testing instruments as in Example 1. The test results are shown in Table 3.

[0063] Table 3

[0064] As can be seen from the data in Table 3, in Example 2, the carbonyl iron powder coated with a silica protective layer containing numerous pores exhibited a significantly higher rate of oxygen, carbon, and nitrogen removal through reduction compared to carbonyl iron powder coated with silica without a porous structure. Furthermore, increasing the reduction purification treatment temperature and gas pressure was beneficial for improving the rate of oxygen, carbon, and nitrogen removal. Specifically, in Example 2, increasing the reduction temperature to 700℃ and reducing the carbonyl iron powder for 2 hours reduced the oxygen, carbon, and nitrogen content to a very low level.

[0065] Example 3 A method for efficiently reducing and purifying carbonyl iron powder includes the following steps: (1) Take 100 kg of carbonyl iron powder particles (Guangdong Jinhong New Materials Co., Ltd.) with an average particle size of 3.6 μm to be purified, ultrasonically clean them with anhydrous ethanol solution for 0.5 h, then ultrasonically clean them with deionized water 3 times for 0.5 h, filter out the deionized water and set aside for use. (2) Mix silane coupling agent (KH550, 1.50 kg) and anhydrous ethanol (4 kg), then add methacrylic acid resin (2.1 kg) with an average particle size of 60 nm obtained by ball milling for 7.5 h and ammonia water with a mass concentration of 25% (0.5 kg) to obtain a mixed solution for surface coating; spray the mixed solution into the carbonyl iron powder to be used at a rate of 1 L / min and stir continuously for 60 minutes, while controlling the temperature of the container holding the carbonyl iron powder at 20℃ to obtain the surface coating. Carbonyl iron powder coated with a silica preform layer was prepared. Then, stirring was stopped, and the carbonyl iron powder with the silica preform layer was heated to 100°C under normal pressure and dried for 2 hours. Then, it was placed in a vacuum furnace and heated for 1 hour at a temperature of 235°C and a pressure of 2.5 kPa to remove the methacrylic resin in the silica preform layer. Heating was stopped, and the powder was cooled to room temperature to obtain carbonyl iron powder with a silica protective layer. The silica protective layer has a porous structure with a porosity of 28%.

[0066] (3) The carbonyl iron powder coated with a silicon dioxide protective layer is subjected to reduction and purification treatment to obtain purified carbonyl iron powder.

[0067] The surface morphology of the carbonyl iron powder after coating was observed using the same testing instruments as in Example 1, and the results are as follows: Figure 8 As shown. From Figure 8 As can be seen, compared to uncoated carbonyl iron powder ( Figure 1 After being coated with a silica protective layer, the shape and size of the powder remained basically unchanged, but the powder surface became rough, with protrusions and pores with an average size of 60 nm.

[0068] The oxygen, carbon, and nitrogen contents in carbonyl iron powder before and after reduction treatment were tested using the same testing instruments as in Example 1. The test results are shown in Table 4.

[0069] Table 4

[0070] As can be seen from the data in Table 4, in Example 3, the carbonyl iron powder coated with a silica protective layer containing numerous pores exhibited a significantly higher rate of oxygen, carbon, and nitrogen removal through reduction compared to carbonyl iron powder coated with silica without a porous structure. Furthermore, increasing the reduction purification treatment temperature and gas pressure was beneficial for improving the rate of oxygen, carbon, and nitrogen removal. Specifically, in Example 3, increasing the reduction temperature to 750°C and reducing the carbonyl iron powder for 2 hours reduced the oxygen, carbon, and nitrogen content to a very low level.

[0071] Example 4 A method for efficiently reducing and purifying carbonyl iron powder includes the following steps: (1) Take 99.5 kg of carbonyl iron powder particles (Guangdong Jinhong New Materials Co., Ltd.) with an average particle size of 3.6 μm to be purified. After ultrasonic cleaning with anhydrous ethanol solution for 1 h, ultrasonic cleaning with deionized water three times for 0.5 h. After filtering out the deionized water, it is ready for use. (2) Mix silane coupling agent (KH550, 1.33 kg), tetraethyl orthosilicate (0.67 kg), methyl orthosilicate (0.16 kg), and anhydrous ethanol (4 kg), then add polyvinyl chloride (2.1 kg) with an average particle size of 60 nm obtained by ball milling for 5.5 h and ammonia water with a mass concentration of 25% (0.52 kg) to obtain a mixed solution for surface coating; spray the mixed solution into the carbonyl iron powder to be used at a rate of 1 L / min and stir continuously for 60 minutes, and the volume of carbonyl iron powder is increased. The temperature was controlled at 20℃ to obtain carbonyl iron powder with a silica pre-coated surface. Then, stirring was stopped, and the carbonyl iron powder with the silica pre-coated surface was heated to 100℃ under normal pressure and dried for 2 hours. It was then placed in a vacuum furnace and heated for 1.5 hours at a temperature of 230℃ and a pressure of 2 kPa to remove the polyvinyl chloride from the silica pre-coated layer. Heating was then stopped, and the powder was cooled to room temperature to obtain carbonyl iron powder with a silica protective layer. The silica protective layer has a porous structure with a porosity of 27%. (3) The carbonyl iron powder coated with a silicon dioxide protective layer is subjected to reduction and purification treatment to obtain purified carbonyl iron powder.

[0072] The surface morphology of the carbonyl iron powder after coating was observed using the same testing instruments as in Example 1, and the results are as follows: Figure 9 As shown. From Figure 9 As can be seen, compared to uncoated carbonyl iron powder ( Figure 1 After being coated with a silica protective layer, the shape and size of the powder remain basically unchanged, but the powder surface becomes rough, with protrusions and pores of an average size of about 60 nm.

[0073] The oxygen, carbon, and nitrogen contents in carbonyl iron powder before and after reduction treatment were tested using the same testing instruments as in Example 1. The test results are shown in Table 5.

[0074] Table 5

[0075] As can be seen from the data in Table 5, in Example 4, the carbonyl iron powder coated with a silica protective layer containing numerous pores exhibited a significantly higher rate of oxygen, carbon, and nitrogen removal through reduction compared to carbonyl iron powder coated with silica without a porous structure. Furthermore, increasing the reduction purification treatment temperature and gas pressure was beneficial for improving the rate of oxygen, carbon, and nitrogen removal. Specifically, in Example 4, increasing the reduction temperature to 700℃ and reducing the carbonyl iron powder for 2 hours reduced the oxygen, carbon, and nitrogen content to a very low level.

[0076] Example 5 A method for efficiently reducing and purifying carbonyl iron powder includes the following steps: (1) Take 100 kg of carbonyl iron powder particles (Guangdong Jinhong New Materials Co., Ltd.) with an average particle size of 3.6 μm to be purified, ultrasonically clean them with anhydrous ethanol solution for 0.5 h, then ultrasonically clean them with deionized water 3 times for 0.5 h, filter out the deionized water and set aside for use. (2) Mix silane coupling agent (KH560, 2.00 kg) and anhydrous ethanol (4 kg), then add polyoxymethylene (2.0 kg) with an average particle size of 60 nm obtained by ball milling for 3.5 h and ammonia water with a mass concentration of 25% (0.8 kg) to obtain a mixed solution for surface coating; spray the mixed solution into the carbonyl iron powder to be used at a rate of 1 L / min and stir continuously for 60 minutes, while controlling the temperature of the container holding the carbonyl iron powder at 20℃ to obtain the surface coating. Carbonyl iron powder coated with a silica preform layer was prepared. Then, stirring was stopped, and the carbonyl iron powder coated with the silica preform layer was heated to 100°C under normal pressure and dried for 2 hours. It was then placed in a vacuum furnace and heated for 1 hour at a temperature of 220°C and a pressure of 2.5 kPa to remove the polyoxymethylene in the silica preform layer. Heating was then stopped, and the powder was cooled to room temperature to obtain carbonyl iron powder coated with a silica protective layer. The silica protective layer has a porous structure with a porosity of 31%.

[0077] (3) The carbonyl iron powder coated with a silicon dioxide protective layer is subjected to reduction and purification treatment to obtain purified carbonyl iron powder.

[0078] The surface morphology of the carbonyl iron powder after coating was observed using the same testing instruments as in Example 1, and the results are as follows: Figure 10 As shown. From Figure 10 As can be seen, compared to uncoated carbonyl iron powder ( Figure 1 After being coated with a silica protective layer, the shape and size of the powder remained basically unchanged, but the powder surface became rough, with fluffy protrusions and pores with an average size of 60 nm.

[0079] The oxygen, carbon, and nitrogen contents in carbonyl iron powder before and after reduction treatment were tested using the same testing instruments as in Example 1. The test results are shown in Table 6.

[0080] Table 6

[0081] As can be seen from the data in Table 6, in Example 5, the carbonyl iron powder coated with a silica protective layer containing numerous pores exhibited a significantly higher rate of oxygen, carbon, and nitrogen removal through reduction compared to carbonyl iron powder coated with silica without a porous structure. Furthermore, increasing the reduction purification treatment temperature and gas pressure was beneficial for improving the rate of oxygen, carbon, and nitrogen removal. Specifically, in Example 5, increasing the reduction temperature to 700°C and reducing the carbonyl iron powder for 2 hours reduced the oxygen, carbon, and nitrogen content to a very low level.

[0082] Example 6 A method for efficiently reducing and purifying carbonyl iron powder includes the following steps: (1) Take 100 kg of carbonyl iron powder particles (Guangdong Jinhong New Materials Co., Ltd.) with an average particle size of 3.6 μm to be purified, ultrasonically clean them with anhydrous ethanol solution for 0.5 h, then ultrasonically clean them with deionized water 3 times for 0.5 h, filter out the deionized water and set aside for use. (2) Mix silane coupling agent (KH570, 2.50 kg) and anhydrous ethanol (5 kg), then add polyvinylidene chloride (1.8 kg) with an average particle size of 50 nm obtained by ball milling for 6.5 h and ammonia water with a mass concentration of 25% (1.0 kg) to obtain a mixed solution for surface coating; spray the mixed solution into the carbonyl iron powder to be used at a rate of 1 L / min and stir continuously for 60 minutes, while controlling the temperature of the container holding the carbonyl iron powder at 20℃ to obtain the surface coating solution. Carbonyl iron powder with a silica pre-coated layer was prepared. Then, stirring was stopped, and the carbonyl iron powder with the silica pre-coated layer was heated to 100°C under normal pressure and dried for 2 hours. Then, it was placed in a vacuum furnace and heated for 1 hour at a temperature of 260°C and a pressure of 2.5 kPa to remove the polyoxymethylene in the silica pre-coated layer. Heating was stopped, and the powder was cooled to room temperature to obtain carbonyl iron powder with a silica protective layer. The silica protective layer has a porous structure with a porosity of 26%.

[0083] (3) The carbonyl iron powder coated with a silicon dioxide protective layer is subjected to reduction and purification treatment to obtain purified carbonyl iron powder.

[0084] The surface morphology of the carbonyl iron powder after coating was observed using the same testing instruments as in Example 1, and the results are as follows: Figure 11 As shown. From Figure 11 As can be seen, compared to uncoated carbonyl iron powder ( Figure 1After being coated with a silica protective layer, the shape and size of the powder remained basically unchanged, but the powder surface became rough and had protruding pores with an average size of 50 nm.

[0085] The oxygen, carbon, and nitrogen contents in carbonyl iron powder before and after reduction treatment were tested using the same testing instruments as in Example 1. The test results are shown in Table 7.

[0086] Table 7

[0087] As can be seen from the data in Table 7, Example 6, which uses a silica protective layer with numerous pores to coat carbonyl iron powder, exhibits a significantly higher rate of oxygen, carbon, and nitrogen removal through reduction compared to silica-coated carbonyl iron powder without a porous structure. Furthermore, increasing the reduction purification temperature and gas pressure further enhances the rate of oxygen, carbon, and nitrogen removal. Specifically, in Example 6, increasing the reduction temperature to 700°C and reducing the carbonyl iron powder for 2 hours effectively reduced the oxygen, carbon, and nitrogen content to a very low level.

[0088] Example 7 A method for efficiently reducing and purifying carbonyl iron powder includes the following steps: (1) Take 100 kg of carbonyl iron powder particles (Guangdong Jinhong New Materials Co., Ltd.) with an average particle size of 3.6 μm to be purified, ultrasonically clean them with anhydrous ethanol solution for 0.5 h, then ultrasonically clean them with deionized water 3 times for 0.5 h, filter out the deionized water and set aside for use. (2) Mix silane coupling agent (A-1160, 1.50 kg) and anhydrous ethanol (3.5 kg), then add polyacrylonitrile (1.9 kg) with an average particle size of 70 nm obtained by ball milling for 6.5 h and ammonia water with a mass concentration of 25% (0.5 kg) to obtain a mixed solution for surface coating; spray the mixed solution into the carbonyl iron powder to be used at a rate of 1 L / min and stir continuously for 60 minutes, while controlling the temperature of the container holding the carbonyl iron powder at 20℃ to obtain the surface coating solution. Carbonyl iron powder with a silica pre-coated layer was prepared. Then, stirring was stopped, and the carbonyl iron powder with the silica pre-coated layer was heated to 100°C under normal pressure and dried for 2 hours. Then, it was placed in a vacuum furnace and heated for 1 hour at a temperature of 270°C and a pressure of 2.5 kPa to remove the polyacrylonitrile in the silica pre-coated layer. Heating was stopped, and the powder was cooled to room temperature to obtain carbonyl iron powder with a silica protective layer. The silica protective layer has a porous structure with a porosity of 39%.

[0089] (3) The carbonyl iron powder coated with a silicon dioxide protective layer is subjected to reduction and purification treatment to obtain purified carbonyl iron powder.

[0090] The surface morphology of the carbonyl iron powder after coating was observed using the same testing instruments as in Example 1, and the results are as follows: Figure 12As shown. From Figure 12 As can be seen, compared to uncoated carbonyl iron powder ( Figure 1 After being coated with a silica protective layer, the shape and size of the powder remained basically unchanged, but the powder surface became rough, with protrusions of an average size of 70nm distributed in the middle, interspersed with pores.

[0091] The oxygen, carbon, and nitrogen contents in carbonyl iron powder before and after reduction treatment were tested using the same testing instruments as in Example 1. The test results are shown in Table 8.

[0092] Table 8

[0093] As can be seen from the data in Table 8, in Example 7, the carbonyl iron powder coated with a silica protective layer containing numerous pores exhibited a significantly higher rate of oxygen, carbon, and nitrogen removal through reduction compared to carbonyl iron powder coated with silica without a porous structure. Furthermore, increasing the reduction purification treatment temperature and gas pressure was beneficial for improving the rate of oxygen, carbon, and nitrogen removal. Specifically, in Example 7, increasing the reduction temperature to 700°C and reducing the carbonyl iron powder for 2 hours reduced the oxygen, carbon, and nitrogen content to a very low level.

[0094] Example 8 A method for efficiently reducing and purifying carbonyl iron powder includes the following steps: (1) Take 100 kg of carbonyl iron powder particles (Guangdong Jinhong New Materials Co., Ltd.) with an average particle size of 3.6 μm to be purified, ultrasonically clean them with anhydrous ethanol solution for 0.5 h, then ultrasonically clean them with deionized water 3 times for 0.5 h, filter out the deionized water and set aside for use. (2) Mix silane coupling agent (A187, 1.50 kg) and anhydrous ethanol (4 kg), then add zinc carbonate (2.0 kg) with an average particle size of 60 nm obtained by ball milling for 6.5 h and ammonia water with a mass concentration of 25% (0.5 kg) to obtain a mixed solution for surface coating; spray the mixed solution into the carbonyl iron powder to be used at a rate of 1 L / min and stir continuously for 60 minutes, while controlling the temperature of the container holding the carbonyl iron powder at 20℃ to obtain the surface coating. Carbonyl iron powder with a silica pre-coated layer was prepared. Then, stirring was stopped, and the carbonyl iron powder with the silica pre-coated layer was heated to 100°C under normal pressure and dried for 2 hours. Then, it was placed in a vacuum furnace and heated for 1 hour at a temperature of 300°C and a pressure of 2.5 kPa to remove zinc carbonate from the silica pre-coated layer. Heating was stopped, and the powder was cooled to room temperature to obtain carbonyl iron powder with a silica protective layer. The silica protective layer has a porous structure with a porosity of 33%.

[0095] (3) The carbonyl iron powder coated with a silicon dioxide protective layer is subjected to reduction and purification treatment to obtain purified carbonyl iron powder.

[0096] The surface morphology of the carbonyl iron powder after coating was observed using the same testing instruments as in Example 1, and the results are as follows: Figure 13 As shown. From Figure 13 As can be seen, compared to uncoated carbonyl iron powder ( Figure 1 After being coated with a silica protective layer, the shape and size of the powder remained basically unchanged, but the powder surface became rough, with protrusions of an average size of 60nm distributed in the middle, interspersed with pores.

[0097] The oxygen, carbon, and nitrogen contents in carbonyl iron powder before and after reduction treatment were tested using the same testing instruments as in Example 1. The test results are shown in Table 9.

[0098] Table 9

[0099] As can be seen from the data in Table 9, in Example 8, the carbonyl iron powder coated with a silica protective layer containing numerous pores exhibited a significantly higher rate of oxygen, carbon, and nitrogen removal through reduction compared to carbonyl iron powder coated with silica without a porous structure. Furthermore, increasing the reduction purification treatment temperature and gas pressure was beneficial for improving the rate of oxygen, carbon, and nitrogen removal. Specifically, in Example 8, increasing the reduction temperature to 700°C and reducing the carbonyl iron powder for 2 hours reduced the oxygen, carbon, and nitrogen content to a very low level.

[0100] Example 9 A method for efficiently reducing and purifying carbonyl iron powder includes the following steps: (1) Take 100 kg of carbonyl iron powder particles (Guangdong Jinhong New Materials Co., Ltd.) with an average particle size of 3.6 μm to be purified, ultrasonically clean them with anhydrous ethanol solution for 0.5 h, then ultrasonically clean them with deionized water 3 times for 0.5 h, filter out the deionized water and set aside for use. (2) Mix silane coupling agent (KH550, 1.00 kg and KH570, 0.50 kg) and anhydrous ethanol (6 kg), then add ammonium chloride (2.0 kg) with an average particle size of 70 nm obtained by ball milling for 5.5 h and ammonia water with a mass concentration of 25% (0.5 kg) to obtain a mixed solution for surface coating; spray the mixed solution into the carbonyl iron powder to be used at a rate of 1 L / min and stir continuously for 60 minutes, and control the temperature of the container holding the carbonyl iron powder at 20°C. At ℃, carbonyl iron powder with a silica pre-coated surface was obtained; then, stirring was stopped, and the carbonyl iron powder with the silica pre-coated surface was heated to 100℃ under normal pressure and dried for 2 hours; then it was placed in a vacuum furnace and heated for 1 hour at a temperature of 320℃ and a pressure of 2.5 kPa to remove ammonium chloride from the silica pre-coated surface. Heating was stopped, and the powder was cooled to room temperature to obtain carbonyl iron powder with a silica protective layer; the silica protective layer has a porous structure with a porosity of 41%.

[0101] (3) The carbonyl iron powder coated with a silicon dioxide protective layer is subjected to reduction and purification treatment to obtain purified carbonyl iron powder.

[0102] The surface morphology of the carbonyl iron powder after coating was observed using the same testing instruments as in Example 1, and the results are as follows: Figure 14 As shown. From Figure 14 As can be seen, compared to uncoated carbonyl iron powder ( Figure 1 After being coated with a silica protective layer, the shape and size of the powder remain basically unchanged, but the powder surface becomes rough, with protrusions of an average size of 60-70nm distributed in the middle, interspersed with pores.

[0103] The oxygen, carbon, and nitrogen contents in carbonyl iron powder before and after reduction treatment were tested using the same testing instruments as in Example 1. The test results are shown in Table 10.

[0104] Table 10

[0105] As can be seen from the data in Table 10, Example 9, which uses a silica protective layer with numerous pores to coat carbonyl iron powder, exhibits a significantly higher rate of oxygen, carbon, and nitrogen removal through reduction compared to silica-coated carbonyl iron powder without a porous structure. Furthermore, increasing the reduction purification temperature and gas pressure is beneficial for improving the rate of oxygen, carbon, and nitrogen removal. Specifically, in Example 9, increasing the reduction temperature to 550°C and reducing the carbonyl iron powder for 2 hours reduced the oxygen, carbon, and nitrogen content to a very low level.

[0106] Example 10 A method for efficiently reducing and purifying carbonyl iron powder includes the following steps: (1) Take 100 kg of carbonyl iron powder particles (Guangdong Jinhong New Materials Co., Ltd.) with an average particle size of 3.6 μm to be purified, ultrasonically clean them with anhydrous ethanol solution for 0.5 h, then ultrasonically clean them with deionized water 3 times for 0.5 h, filter out the deionized water and set aside for use. (2) Mix silane coupling agent (KH550, 1.50 kg) and anhydrous ethanol (6 kg), then add magnesium carbonate (2.0 kg) with an average particle size of 75 nm obtained by ball milling for 6.5 h and ammonia water with a mass concentration of 25% (0.5 kg) to obtain a mixed solution for surface coating; spray the mixed solution into the carbonyl iron powder to be used at a rate of 1 L / min and stir continuously for 60 minutes, while controlling the temperature of the container holding the carbonyl iron powder at 20℃ to obtain the surface coating. Carbonyl iron powder coated with a silica preform layer was prepared. Then, stirring was stopped, and the carbonyl iron powder with the silica preform layer was heated to 100°C under normal pressure and dried for 2 hours. Then, it was placed in a vacuum furnace and heated for 1 hour at a temperature of 320°C and a pressure of 2.5 kPa to remove magnesium carbonate from the silica preform layer. Heating was stopped, and the powder was cooled to room temperature to obtain carbonyl iron powder with a silica protective layer. The silica protective layer has a porous structure with a porosity of 43%.

[0107] (3) The carbonyl iron powder coated with a silicon dioxide protective layer is subjected to reduction and purification treatment to obtain purified carbonyl iron powder.

[0108] The surface morphology of the carbonyl iron powder after coating was observed using the same testing instruments as in Example 1, and the results are as follows: Figure 15 As shown. From Figure 15 As can be seen, compared to uncoated carbonyl iron powder ( Figure 1 After being coated with a silica protective layer, the shape and size of the powder remained basically unchanged, but the powder surface became rough, with protrusions of an average size of 75nm and interspersed with pores.

[0109] The oxygen, carbon, and nitrogen contents in carbonyl iron powder before and after reduction treatment were tested using the same testing instruments as in Example 1. The test results are shown in Table 11.

[0110] Table 11

[0111] As can be seen from the data in Table 11, in Example 10, the carbonyl iron powder coated with a silica protective layer containing numerous pores exhibited a significantly higher rate of oxygen, carbon, and nitrogen removal through reduction compared to carbonyl iron powder coated with silica without a porous structure. Furthermore, increasing the reduction purification treatment temperature and gas pressure was beneficial for improving the rate of oxygen, carbon, and nitrogen removal. Specifically, in Example 10, increasing the reduction temperature to 700°C and reducing the carbonyl iron powder for 2 hours reduced the oxygen, carbon, and nitrogen content to a very low level.

[0112] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A method for efficiently reducing and purifying a carbonyl iron powder, characterized by, The method comprises the following steps: S1, adopting a sol-gel method to coat a silica pre-layer on the surface of the carbonyl iron powder to be purified; the silica pre-layer contains a space-occupying particle; S2, removing the space-occupying particle in the silica pre-layer to obtain a silica protective layer; the silica protective layer has a pore structure distributed therein; S3, reducing the carbonyl iron powder treated in step S2 under a reducing gas to obtain purified carbonyl iron powder.

2. The process for the efficient reductive purification of carbonyl iron powder according to claim 1, characterized in that, The space-occupying particle comprises at least one of ammonium bicarbonate, methacrylic acid resin, polyvinyl chloride, polyformaldehyde, polyvinylidene chloride, polyacrylonitrile, zinc carbonate, metallic zinc, ammonium chloride, and magnesium carbonate; and / or, the addition amount of the space-occupying particle accounts for 1-5% of the mass of the carbonyl iron powder to be purified; and / or, the average particle size of the space-occupying particle is 50-200 nm.

3. The process for the efficient reductive purification of carbonyl iron powder according to claim 1, characterized in that, The step S1 specifically comprises the following steps: S1.1, mixing an organosilicon compound, a solvent, a space-occupying particle, and ammonia water to obtain a mixed solution; S1.2, mixing the mixed solution with the carbonyl iron powder to be purified, stirring, and coating a silica pre-layer on the surface of the carbonyl iron powder to be purified.

4. The process for the efficient reductive purification of carbonyl iron powder according to claim 3, characterized in that, The organosilicon compound comprises a silane coupling agent and / or a silicic acid ester; and / or, the addition amount of the organosilicon compound accounts for 1-3% of the mass of the carbonyl iron powder to be purified.

5. The process for the efficient reductive purification of carbonyl iron powder according to claim 3, characterized in that, The mass concentration of the ammonia water is 15-30%; and / or, the addition amount of the ammonia water accounts for 0.5-1% of the mass of the carbonyl iron powder to be purified.

6. The process for the efficient reductive purification of carbonyl iron powder according to claim 1, characterized in that, The step S2 removes the space-occupying particle in the silica pre-layer by heating.

7. The process for the efficient reductive purification of carbonyl iron powder according to claim 6, characterized in that, The heating comprises normal-pressure heating; the temperature of the normal-pressure heating is 50-120℃, and the time of the normal-pressure heating is 0.5-2 h.

8. The process for the efficient reductive purification of carbonyl iron powder according to claim 7, characterized in that, After the normal-pressure heating, vacuum heating is further performed; the temperature of the vacuum heating is 170-320℃, the pressure of the vacuum heating is ≤5.0 Kpa, and the time of the vacuum heating is 0.5-2 h.

9. The process for the efficient reductive purification of carbonyl iron powder according to claim 1, characterized in that, In the step S3, the temperature of the reduction is 500-750℃, the pressure of the reducing gas is 0.5-110 Kpa, and the time of the reduction is 0.5-4 h.

10. A carbonyl iron powder characterised in that, The purified carbonyl iron powder is obtained by the method for high-efficiency reduction and purification of carbonyl iron powder according to any one of claims 1-9.

Images