Method for efficiently reducing and purifying carbonyl iron powder

Abstract

The application 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, a sol-gel method is used 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, the occupation particles in the silica preformed layer are removed to obtain a silica protective layer; the silica protective layer is distributed with hole structures; S3, the carbonyl iron powder treated in step S2 is reduced in a reducing gas to obtain purified carbonyl iron powder. The silica protective layer distributed with a large number of penetrating holes ensures that the temperature of the reduced and purified carbonyl iron powder is raised to 750 DEG C without problems such as caking and agglomeration, and the rapid and efficient reduction and purification process of the carbonyl iron powder is maximally realized. Moreover, the method has the advantages of simple process, low cost and large-batch production.

Description

Technical Field

[0001] This invention belongs to the field of soft magnetic materials technology, and specifically relates to a method for efficiently reducing and purifying carbonyl iron powder. Background Technology

[0002] A series of transition elements in the periodic table (iron, cobalt, nickel, etc.) can react with carbon monoxide to form carbonyl metal compounds. After thermal decomposition, carbonyl metal powder with fine particle size, high activity, and no harmful impurities can be obtained. Carbonyl iron powder is currently the most common and widely used carbonyl metal powder. It appears as grayish-black spherical particles with an onion-like layered structure. It features fine particle size, good spherical appearance, good formability, high surface activity, and excellent electromagnetic properties. In particular, it exhibits high magnetic flux at high and ultra-high frequencies, thus it is widely used in the manufacture of magnetic materials, playing an irreplaceable role, especially in the production of high-frequency iron powder cores.

[0003] Carbonyl iron powder is obtained through high-temperature decomposition. Generally, the resulting carbonyl iron powder has a high oxygen and carbon content, existing as iron oxides, carbides, and impurities such as free oxygen and carbon. Existing research indicates that iron carbides, free carbon, and oxygen significantly affect the magnetic properties and sintering performance of carbonyl iron powder, thus severely limiting its application and development.

[0004] Patent CN104475760A discloses a method for producing carbonyl iron powder, which proposes a method of using a mixture of carbonyl iron vapor and carbon monoxide gas to form a multi-stage decomposition process, which can 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] To meet diverse application requirements, the commonly used method is to purify the raw carbonyl iron powder obtained during production by reducing it in a reducing gas at a specific temperature. This reduces the content of impurities, particularly oxygen and carbon, thereby achieving the required purity. Furthermore, the high-temperature reduction process also lowers the hardness of the carbonyl iron powder, facilitating further processing. Theoretically, in the reduction and purification process of carbonyl iron powder, the higher the reduction temperature, the faster the reduction rate, thus improving production efficiency and capacity. Generally, during the reduction and purification of carbonyl iron powder, the reduction rate begins to accelerate significantly above 350℃. However, above 350℃, especially approaching 400℃, the carbonyl iron powder will exhibit lumpy particle aggregation and significant agglomeration. Although this problem can be mitigated to some extent by subsequent crushing and ball milling processes, this significantly affects the particle structure and shape, leading to a decrease in electromagnetic properties. Therefore, currently, the reduction and purification process is generally limited to below 400℃, by extending the reduction time to meet production requirements.

[0006] Therefore, how to increase the reduction temperature and make the reduction and purification process of carbonyl iron powder faster and more efficient while maintaining or optimizing electromagnetic properties remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] The present invention aims to at least solve one of the technical problems existing in the prior art. Therefore, the object of the present invention is to provide a method for the efficient reduction and purification of carbonyl iron powder. The method of the present invention can raise the reduction temperature to 750°C without problems such as agglomeration, and while maintaining or optimizing electromagnetic properties, makes the reduction and purification process of carbonyl iron powder faster and more efficient, significantly reducing the oxygen, carbon, and nitrogen content in the purified carbonyl iron powder.

[0008] In a first aspect, the present invention provides a method for efficiently reducing and purifying carbonyl iron powder, comprising the following steps: S1. A silica pre-coated layer is applied to the surface of the carbonyl iron powder to be purified using the sol-gel method; the silica pre-coated layer contains spacer particles. S2. Remove the occupying particles from the silicon dioxide preform layer to obtain a silicon dioxide protective layer; the silicon dioxide protective layer has a porous structure distributed in it. S3. The carbonyl iron powder treated in step S2 is reduced under a reducing gas to obtain purified carbonyl iron powder.

[0009] Specifically, when carbonyl iron powder is reduced and purified using reducing gas at high temperatures, the thicker the protective film on its surface, the better the protection against particle adhesion. However, while the protective film solves the problem of powder adhesion at high temperatures, it also hinders the contact between the reducing gas and the carbonyl iron powder to remove impurities such as oxygen and carbon. In particular, the structure of the protective film is generally very dense (traditional processes strive for density and uniformity of the protective film), which makes it difficult or reduces the contact between the reducing gas and the carbonyl iron powder, thus increasing the difficulty of impurity removal. Although higher temperatures and longer reduction times can improve the effect of reducing gas in removing impurities such as oxygen and carbon, this will lead to a decrease in the efficiency of the process and a significant increase in processing costs, making it impossible to achieve the goal of efficient reduction and purification.

[0010] This invention employs the aforementioned technical solution, pre-distributing vacant particles evenly within a sol forming a silica protective layer. These vacant particles are removed during or after the sol film formation process. This results in a silica protective layer with numerous (interconnected) pores on the surface of the carbonyl iron powder. This simultaneously provides high-temperature protection (preventing contact and adhesion between carbonyl iron powder particles) and ensures sufficient contact between reducing gas and the carbonyl iron powder due to the porous structure. This achieves rapid and efficient reduction and purification of carbonyl iron powder at higher temperatures, guaranteeing that the reduction and purification temperature can be raised to 750°C without agglomeration or clumping. Furthermore, it maintains or optimizes electromagnetic properties, making the reduction and purification process of carbonyl iron powder faster and more efficient. Moreover, the method provided by this invention has advantages such as simple process, low cost, and the ability to be mass-produced.

[0011] In some embodiments of the present invention, the spacer particles comprise at least one selected from ammonium bicarbonate, methacrylic acid resin, polyvinyl chloride, polyoxymethylene, polyvinylidene chloride, polyacrylonitrile, zinc carbonate, metallic zinc, ammonium chloride, and magnesium carbonate. Preferably, the spacer particles are at least one selected from ammonium bicarbonate, zinc carbonate, and metallic zinc.

[0012] In some embodiments of the present invention, the amount of the spacer particles added accounts for 1-5% of the mass of the carbonyl iron powder to be purified.

[0013] In some embodiments of the present invention, the occupant particles are selected as nano-sized occupant particles with an average particle size of 50-200 nm.

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

[0015] In some embodiments of the present invention, the thickness of the silicon dioxide protective layer is 10-200 nm.

[0016] In some embodiments of the present invention, the porosity of the silicon dioxide protective layer is 10-50%.

[0017] In some embodiments of the present invention, the aperture of the hole structure is 50-200 nm.

[0018] In some embodiments of the present invention, step S1 specifically includes the following steps: S1.1. Mix the organosilicon compound, solvent, spacer particles and ammonia water to obtain a mixed solution; S1.2. Mix the mixed solution with the carbonyl iron powder to be purified, stir, and coat the surface of the carbonyl iron powder to be purified with a silicon dioxide pre-formed layer.

[0019] In some embodiments of the present invention, the organosilicon compound includes a silane coupling agent and / or a silicate.

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

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

[0022] In some embodiments of the present invention, 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 invention, the silicate ester includes at least one selected from methyl orthosilicate, ethyl orthosilicate, and propyl orthosilicate. The silicate ester is preferably ethyl orthosilicate, or more preferably a mixture of ethyl orthosilicate and methyl orthosilicate, or more preferably a mixture of methyl orthosilicate, ethyl orthosilicate, and propyl orthosilicate; wherein the mass content of ethyl orthosilicate in the mixture is ≥50%.

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

[0025] In some embodiments of the present invention, the solvent includes anhydrous ethanol.

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

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

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

[0029] In some embodiments of the present invention, in step S1.1, the occupant particles are pre-milled with ceramic balls under anhydrous ethanol protection for 1-8 hours. By controlling the milling time to obtain occupant particles of the appropriate particle size, the porous structure obtained by removing the occupant particles in step S2 will not cause the carbonyl iron powder to agglomerate during reduction in step S3.

[0030] In some embodiments of the present invention, in step S1.2, the mixing involves adding the mixed solution to the carbonyl iron powder to be purified. The addition method includes gradually adding the solution by dripping, pouring, sprinkling, or spraying. The mixed solution is added at a rate of 0.1-1 L / min to 10 kg of the carbonyl iron powder to be purified.

[0031] In some embodiments of the present invention, in step S1.2, the carbonyl iron powder to be purified is first ultrasonically cleaned by passing it sequentially through anhydrous ethanol and water.

[0032] In some embodiments of the present invention, step S2 removes the occupant particles in the silicon dioxide preform by heating.

[0033] In some embodiments of the present invention, the heating includes atmospheric pressure heating; the temperature of the atmospheric pressure heating is 50-120°C, and the heating time is 0.5-2 hours. When ammonium bicarbonate is selected as the site-filling particle, its low decomposition temperature (40-60°C) allows it to decompose and form pores during the gelation process under atmospheric pressure heating, thereby reducing production steps and lowering material and time costs.

[0034] In some embodiments of the present invention, vacuum heating is performed after atmospheric pressure 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, polyoxymethylene, polyvinylidene chloride, polyacrylonitrile, zinc carbonate, zinc metal, ammonium chloride, and magnesium carbonate are selected as site-filling particles, considering that the temperature required for pore formation is 170-320℃, a vacuum heating process can be added at the front end of the reduction and purification production line, which basically does not increase the production process, material, or time costs. The preferred pressure of the vacuum heating is 0.1-5.0 kPa.

[0035] In some embodiments of the present invention, in step S3, the reduction temperature is 500-750°C, the reducing gas pressure is 0.5-110 kPa, and the reduction time is 0.5-4 h. The reduction temperature is preferably 550-750°C, more preferably 700-750°C. The reducing gas pressure is preferably 0.5-2.5 kPa. The reduction time is preferably 2-4 h.

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

[0037] In a second aspect, the present invention provides a carbonyl iron powder, which is obtained by the efficient reduction and purification method for carbonyl iron powder described in the first aspect of the present invention.

[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. From Figure 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 during reduction 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 silica without a porous 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 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 220°C and a pressure of 2.5 kPa to remove the polyoxymethylene 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 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, Includes the following steps: S1. A silica pre-coated layer is applied to the surface of the carbonyl iron powder to be purified using the sol-gel method; the silica pre-coated layer contains spacer particles. S2. Remove the occupying particles from the silicon dioxide preform layer to obtain a silicon dioxide protective layer; the silicon dioxide protective layer has a porous structure distributed in it. S3. The carbonyl iron powder treated in step S2 is reduced under a reducing gas to obtain purified carbonyl iron powder. The spacer particles include at least one of ammonium bicarbonate, methacrylic acid resin, polyvinyl chloride, polyoxymethylene, polyvinylidene chloride, polyacrylonitrile, zinc carbonate, metallic zinc, ammonium chloride, and magnesium carbonate. The amount of the spacer particles added is 1-5% of the mass of the carbonyl iron powder to be purified; The average particle size of the occupier particles is 50-200 nm. The porosity of the silica protective layer is 10-50%; The pore size of the hole structure is 50-200 nm; Step S2 removes the occupier particles in the silicon dioxide preform by heating. The heating includes atmospheric pressure heating, the temperature of which is 50-120°C, and the heating time is 0.5-2 hours. After atmospheric pressure heating, vacuum heating is also performed; the temperature of vacuum heating is 170-320℃, the pressure of vacuum heating is ≤5.0KPa, and the time of vacuum heating is 0.5-2h.

2. The process for high efficiency reduction purification of carbonyl iron powder as claimed in claim 1 wherein, Step S1 specifically includes the following steps: S1.

1. Mix the organosilicon compound, solvent, spacer particles and ammonia water to obtain a mixed solution; S1.

2. Mix the mixed solution with the carbonyl iron powder to be purified, stir, and coat the surface of the carbonyl iron powder to be purified with a silicon dioxide pre-formed layer.

3. The process for the efficient reductive purification of carbonyl iron powder according to claim 2, characterized in that, The organosilicon compound includes a silane coupling agent and / or a silicate; and / or, the amount of the organosilicon compound added accounts for 1-3% of the mass of the carbonyl iron powder to be purified.

4. The process for high efficiency reduction purification of carbonyl iron powder as claimed in claim 2 wherein, The ammonia solution has a mass concentration of 15-30%; and / or the amount of ammonia solution added is 0.5-1% of the mass of the carbonyl iron powder to be purified.

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

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