A thin-film coated carbonyl iron powder particle and its preparation method

Abstract

This invention discloses a thin-film coated carbonyl iron powder particle and its preparation method, belonging to the field of metal powder surface protection and modification technology. The method includes the following steps: S1: placing carbonyl iron powder particles in a powder coating device and circulating the carbonyl iron powder particles within the powder coating device; S2: coating the circulating carbonyl iron powder particles within the powder coating device using physical vapor deposition; S3: after the carbonyl iron powder particles have circulated within the powder coating device for a certain period of time, turning off the power and cooling to room temperature to obtain the coated carbonyl iron powder particles. The prepared carbonyl iron powder particles have a dense coating layer on their surface. This invention deposits a thin film on the surface of carbonyl iron powder particles using physical vapor deposition, solving the problems of circulation and easy loss of (ultra)fine metal powders under vacuum conditions, while forming a uniformly coated and densely structured thin film on the surface of carbonyl iron powder.

Description

Technical Field

[0001] This invention relates to the field of metal powder surface protection and modification technology, specifically to a thin film-coated carbonyl iron powder particle and its preparation method. Background Technology

[0002] Carbonyl iron powder is a metallic powder prepared by carbonyl powder metallurgy. It has good radar absorption properties, and its electromagnetic parameters can be controlled by changing the particle size, making it widely used in mobile phones, computers, and high-frequency wireless transceivers. However, due to its small particle size and large specific surface area, carbonyl iron powder is prone to agglomeration, has poor chemical stability, and its complex permittivity is much higher than its magnetic permeability, resulting in poor impedance matching, spectral characteristics, and low-frequency absorption performance, which limits the further application of carbonyl iron powder (in the field of radar absorption).

[0003] In existing technologies, powder coating modification can solve the above problems. The principle of powder coating modification is to uniformly introduce one or more other components onto the surface of powder particles, forming an adsorption layer or monolayer of a certain thickness through chemical reaction or physical adsorption, thereby changing the surface properties of the powder or endowing it with new properties. Numerous research results have also demonstrated that surface coating modification of metal micropowders can effectively improve their oxidation resistance and corrosion resistance, solve their agglomeration problem, and simultaneously reduce the complex dielectric constant and improve electromagnetic wave absorption properties such as impedance matching.

[0004] Generally, applying an organic or inorganic modification layer to the surface of carbonyl iron powder particles can improve its protective properties while reducing the polarization of the material system. This can lower the dielectric constant with almost no impact on the magnetic permeability of the carbonyl iron powder, thereby improving impedance matching, enhancing microwave absorption performance, and broadening the absorption bandwidth. Existing methods for organic coating of carbonyl iron powder particles include: ① surface modification with organic resins; ② coating treatment using silane coupling agents. Inorganic coating methods include: ① SiO2 coating treatment; ② deposition of a dense oxide layer on the surface through acidification treatment; ③ deposition of a high-temperature resistant and corrosion-resistant metal and its oxides, such as Co, ZnO, and MgO. Post-treatment processes such as annealing, high temperature treatment, and external magnetic field application can also be used to further improve the material's corrosion resistance and high-temperature resistance. However, there are few reports in existing patents on the use of nanofilms with quantum size effects to control the electromagnetic parameters of carbonyl iron powder.

[0005] Existing metal powder coating modification technologies mainly fall into two categories: liquid phase methods and gas phase methods. The former includes methods such as mechanochemical methods, liquid phase precipitation methods, sol-gel methods, and chemical plating, while the latter mainly refers to physical vapor deposition and chemical vapor deposition methods.

[0006] Mechanochemical methods utilize strong mechanical stirring, impact, shearing, and grinding to activate powder and surface-coating modifiers, causing the particles to interact with the modifiers and thus coat the powder particles. Furthermore, this method can change carbonyl iron powder from a spherical shape to a flake shape, effectively improving its magnetic properties. Existing invention patents such as "A method for preparing carbonyl iron powder absorbent for low-frequency electromagnetic wave absorbing materials" (201510727290.4), "A method for modifying the electromagnetic parameters of carbonyl iron powder" (201510955959.5), "A method for preparing coated flake carbonyl iron powder" (201811653367.8), and "A method for preparing carbonyl powder" (201811653368.2) all employ this method to obtain coated and modified flake carbonyl iron powder. This method has advantages such as short processing time, easy process control, and continuous batch production. However, it also has disadvantages such as the destruction of the crystal form of inorganic particles and uneven coating during mechanical processing.

[0007] Liquid phase deposition, also known as precipitation, is a method that utilizes the tendency of modifiers in a supersaturated liquid system to deposit and precipitate on the surface of the modified particles, thereby forming a coating on the powder particles. The invention patent "A method for preparing coated carbonyl iron powder" (201210564634.0) uses this method to obtain a phosphate and magnesium oxide coating layer on the surface of carbonyl iron, enabling the carbonyl iron powder to withstand heat treatment at temperatures above 550℃ without damage. The invention patent "A double-shell structure carbonyl iron powder composite microwave absorbing material and its preparation method" (20181104988 3.X) uses this method to obtain a core-shell structure composite material with a carbonyl iron powder core and a double-shell structure including an insulating layer and a magnetic layer, which not only significantly improves the impedance matching characteristics of the material but also significantly enhances its microwave absorption performance. Precipitation is widely used due to its good process controllability and uniform coating, and is particularly suitable for inorganic coating of ultrafine powders. Its drawback is that it requires a very low concentration of the added particles to be coated, otherwise agglomeration is likely to occur. Moreover, traditional liquid-phase coating methods suffer from problems such as high energy consumption, high material loss, and easy particle aggregation and growth during liquid-solid separation and drying.

[0008] The sol-gel method first dissolves the modifier precursor in water or an organic solvent to form a homogeneous solution. The solute and solvent undergo hydrolysis or alcoholysis to obtain a sol of the modifier or its precursor. Then, pre-treated coated particles are uniformly mixed with the sol to ensure uniform dispersion of the particles. The sol is then processed to transform into a gel, and finally, the gel is calcined at high temperature to obtain a powder coated with the modifier. The invention patent "A method for preparing an aluminum phosphate-coated carbonyl iron anti-oxidation microwave absorbing material" (201710650050.8) uses this method to obtain aluminum phosphate-coated carbonyl iron particles, solving the problems of high activity and easy oxidation reaction of carbonyl iron metal particles with oxygen in the air. The powder prepared by this method has high purity and good chemical homogeneity, but the process is relatively complex and often requires calcination, which can easily alter the powder's crystal form and internal structure.

[0009] The application of chemical plating in powder surface coating modification utilizes the reduction of metal ions in the plating solution to metal particles by a reducing agent under catalysis, forming a deposition layer on the powder surface. The powder is then separated from the plating solution and dried. Wei Meiling et al. (Bulletin of the Chinese Ceramic Society, 2003(5): 17-20) used chemical plating to coat carbonyl iron powder with a nickel-phosphorus alloy layer, which significantly reduced the infrared emissivity of the carbonyl iron powder. This method is relatively mature and produces a relatively uniform coating thickness, but it also has problems such as difficulty in controlling the coating reaction, some adhesion between coated particles (caused by magnetic stirring), easy decomposition of the plating solution and the need for waste treatment, and the uniform coating of the powder being controlled by its dispersion effect.

[0010] Vapor deposition (CVD) is a process that deposits coating materials or components containing coating materials onto the surface of powder in gaseous form through physical or chemical reactions. This produces dense, uniform films with controllable composition, offering significant advantages such as simple processing, good coating uniformity, and strong controllability. Furthermore, CVD eliminates the post-processing steps of liquid-phase methods, including filtration, washing, and drying, making it environmentally friendly and energy-efficient. It also overcomes the drawbacks of particle agglomeration and growth, making it a promising area for development in powder coating applications. However, physical vapor deposition (PVD) requires a high vacuum environment, leading to potential powder loss and low efficiency. Chemical vapor deposition (CVD) requires high temperatures and faces challenges in maintaining the powder in a suitable fluidized state during coating. These issues have resulted in a scarcity of CVD in existing patents for carbonyl iron powder coating modification technologies, particularly the use of PVD for carbonyl iron powder coating. Summary of the Invention

[0011] In view of this, the present invention provides a method for preparing carbonyl iron powder particles coated with a thin film. This method can solve the problems of flow and loss control of (ultra)fine metal powder under vacuum conditions, and can obtain metal carbide and nitride layers that are difficult to obtain by other methods. Moreover, the carbonyl iron powder particles prepared have uniform coating, good corrosion resistance and high temperature resistance, and good electromagnetic property control capability.

[0012] This invention is achieved through the following technical solutions:

[0013] A method for preparing thin-film coated carbonyl iron powder particles includes the following steps:

[0014] S1: Place carbonyl iron powder particles in a powder coating device and circulate the carbonyl iron powder particles within the powder coating device;

[0015] S2: The carbonyl iron powder particles circulating in the powder coating device are coated using physical vapor deposition.

[0016] S3: After the carbonyl iron powder particles circulate in the powder coating device for a certain period of time, the power is turned off and the powder is cooled to room temperature to obtain carbonyl iron powder particles coated with a thin film after coating treatment; the coating material on the surface of the carbonyl iron powder particles is one or more composite materials selected from elemental metals, alloys, metal carbides, metal nitrides, and metal oxides.

[0017] Compared with existing technologies, this invention forms a thin film on the surface of carbonyl iron powder particles through physical vapor deposition and uses a powder coating device to realize the circulation of carbonyl iron powder particles, solving the problems of circulation and easy loss of (ultra)fine metal powder under vacuum conditions. At the same time, a uniformly coated and dense thin film is formed on the surface of carbonyl iron powder, which can obtain metal carbide and nitride layers.

[0018] Furthermore, in step S1, the circulating flow rate of the carbonyl iron powder particles is 0.01-50 g / s.

[0019] Furthermore, in step S1, after the carbonyl iron powder particles have stabilized and circulated, a working gas is introduced into the powder processing chamber.

[0020] Further, the working gas is argon, or a mixture of argon and one of acetylene, methane, nitrogen, and oxygen. The working gas enters the vacuum chamber through two controlled channels; when the working gas is a mixture of argon and one of acetylene, methane, nitrogen, and oxygen, the argon enters through the inlet ports arranged around the target or arc source, while the acetylene, methane, nitrogen, and oxygen enter through the processing chamber, serving not only as carrier gases for the carbonyl iron powder particles but also facilitating their reaction with the incident metal and ions to form carbides, nitrides, or oxides on the surface of the carbonyl iron powder particles; when the working gas is only argon, part of the gas enters through the inlet ports arranged around the emission source, and part enters through the processing chamber as carrier gases for the carbonyl iron powder particles.

[0021] Furthermore, in step S2, the physical vapor deposition method is magnetron sputtering or arc ion plating.

[0022] Furthermore, in step S2, the coating treatment temperature is 30-500℃, and the coating treatment time is 1-200min.

[0023] Further, the elemental metal is one of chromium, nickel, titanium, copper, aluminum, zirconium, niobium, gold, silver, platinum, vanadium, and hafnium; the alloy is an alloy of two or more of chromium, nickel, titanium, copper, aluminum, zirconium, niobium, gold, silver, platinum, vanadium, and hafnium; the metal carbide is one or more of carbides of chromium, titanium, aluminum, zirconium, and niobium; the metal nitride is one or more of nitrides of chromium, titanium, aluminum, zirconium, and niobium; and the metal oxide is one or more of oxides of chromium, titanium, aluminum, zirconium, and niobium.

[0024] Further, in step S1, the powder coating device includes a vacuum chamber and a control system. The vacuum chamber includes a powder processing chamber, a powder chamber, and an emission source. The bottom of the powder processing chamber is detachably connected to the top of the powder chamber, and the top of the powder processing chamber and the bottom of the powder chamber are connected through a powder circulation pipeline. A circulation pump is installed on the powder circulation pipeline. The emission source is installed on the inner wall of the vacuum chamber. A window is opened on the side wall of the powder processing chamber to allow the emission source particle flow to pass through. A movable baffle is installed at the window. The control system is electrically connected to the circulation pump, the emission source, and the movable baffle. The carbonyl iron powder particles are placed in the powder chamber, and the circulation pump is turned on to control the carbonyl iron powder particles to circulate between the powder processing chamber and the powder chamber.

[0025] Furthermore, in step S2, the coating material is fixed to the side wall of the vacuum chamber, and a bias voltage is applied to the powder processing chamber. After a stable plasma is formed, the window is opened to allow the coating material particle stream to be injected into the powder processing chamber. This not only prevents the powder from being sucked away but also achieves the coating treatment of carbonyl iron powder particles. Another object of the present invention is to provide a thin film-coated carbonyl iron powder particle, wherein the surface of the carbonyl iron powder particle is covered with a coating layer.

[0026] The present invention has the following beneficial effects:

[0027] This invention addresses the shortcomings of carbonyl iron powder in terms of corrosion resistance and high-temperature resistance by uniformly depositing pure metal, alloy, metal carbide, nitride, oxide film or composite film of the above products with a thickness of 20-2000 nm on the surface of carbonyl iron powder with an average particle size of 1.0-10.0 μm. Furthermore, it improves the spectral characteristics and microwave absorption performance of carbonyl iron powder by optimizing impedance matching through adjusting the dielectric constant.

[0028] In addition, by adjusting the composition of the coating material and performing subsequent heat treatment, the present invention can also form an alloy layer at the interface between the metal coating layer and the carbonyl iron powder. This not only improves the original metal powder's corrosion resistance (including acid and alkali resistance) and high temperature resistance, but also further enhances the ability to control the electromagnetic properties of the metal powder surface. Attached Figure Description

[0029] Figure 1 A schematic diagram of the powder coating device provided by the present invention; wherein, 1, vacuum chamber; 11, powder processing chamber; 12, powder chamber; 13, heater; 14, powder distributor; 15, emission source; 16, powder circulation pipeline; 17, circulation pump; 18, control valve; 111, window.

[0030] Figure 2 This is a morphology diagram of the carbonyl iron powder to be treated selected in this invention.

[0031] Figure 3 This is an overall morphology diagram of carbonyl iron powder after a Cr thin film is deposited on the surface by magnetron sputtering in Example 1.

[0032] Figure 4 This is a surface morphology diagram of carbonyl iron powder after a Cr thin film was deposited on the surface by magnetron sputtering in Example 1.

[0033] Figure 5 This is a cross-sectional morphology diagram of carbonyl iron powder after a Cr thin film was deposited on the surface by magnetron sputtering in Example 1.

[0034] Figure 6 The image shows the EDS energy spectrum of the carbonyl iron powder cross-section edge after a Cr thin film was deposited on the surface by magnetron sputtering in Example 1.

[0035] Figure 7 This is a surface morphology diagram of carbonyl iron powder deposited on the surface using arc ion plating in Example 2.

[0036] Figure 8 This is a cross-sectional morphology diagram (magnified 5000 times) of carbonyl iron powder deposited on the surface using arc ion plating in Example 2.

[0037] Figure 9 This is a cross-sectional morphology diagram (40,000x magnification) of carbonyl iron powder deposited on the surface using arc ion plating in Example 2.

[0038] Figure 10 This is an EDS spectrum near the edge of the carbonyl iron powder cross-section after TiN thin film was deposited on the surface by arc ion plating in Example 2.

[0039] Figure 11 This is a comparison chart of the real part of the dielectric constant of carbonyl iron powder before and after surface deposition of Al-AlN thin film by magnetron sputtering in Example 3.

[0040] Figure 12 This is a comparison of the imaginary part of the dielectric constant of carbonyl iron powder before and after surface deposition of Al-AlN thin films by magnetron sputtering in Example 3.

[0041] Figure 13 This is a comparison of the real part of the magnetic permeability of carbonyl iron powder before and after magnetron sputtering to deposit an Al-AlN thin film on the surface (20 min) in Example 3.

[0042] Figure 14 This is a comparison of the imaginary part of the magnetic permeability of carbonyl iron powder before and after magnetron sputtering to deposit an Al-AlN thin film on the surface (20 min) in Example 3.

[0043] Figure 15 This is a comparison chart of the real part of the dielectric constant of carbonyl iron powder before and after the deposition of TiC thin film by arc ion plating in Example 4.

[0044] Figure 16 This is a comparison chart of the imaginary part of the dielectric constant of carbonyl iron powder before and after the deposition of TiC thin film by arc ion plating in Example 4.

[0045] Figure 17 This is a comparison of the real part of the magnetic permeability of carbonyl iron powder before and after the deposition of TiC thin film by arc ion plating (10 min) in Example 4.

[0046] Figure 18 This is a comparison of the imaginary part of the magnetic permeability of carbonyl iron powder before and after arc ion plating deposition of TiC thin film (10 min) in Example 4.

[0047] Figure 19This is an image showing the overall morphology of carbonyl iron powder after surface deposition of a TiO2 thin film by magnetron sputtering (5 min) in Example 5.

[0048] Figure 20 This is a cross-sectional morphology diagram of carbonyl iron powder after surface deposition of TiO2 film by magnetron sputtering (5 min) in Example 5.

[0049] Figure 21 This is a cross-sectional morphology diagram of a single carbonyl iron powder particle after surface deposition of a TiO2 thin film by magnetron sputtering (5 min) in Example 5.

[0050] Figure 22 The image shows the EDS spectrum near the edge of the carbonyl iron powder cross-section after TiO2 thin film deposition by magnetron sputtering (5 min) in Example 5.

[0051] Figure 23 This is a comparison of the real part of the dielectric constant of carbonyl iron powder before and after TiO2 film deposition on the surface by magnetron sputtering in Example 5.

[0052] Figure 24 This is a comparison of the imaginary part of the dielectric constant of carbonyl iron powder before and after TiO2 film deposition on the surface using magnetron sputtering in Example 5. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same reference numerals in different drawings denote the same or similar elements. Obviously, the described embodiments are only a part of the embodiments disclosed in this invention, and not all of them; they are merely examples consistent with some aspects of the invention as detailed in the appended claims. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without inventive effort are within the scope of protection of this invention.

[0054] This invention utilizes a powder coating apparatus that deposits a protective and modified thin film on the surface of carbonyl iron powder using a physical vapor deposition method, thereby completing the thin film coating of carbonyl iron powder particles; please refer to [link to related documentation]. Figure 1The powder coating device includes a vacuum chamber 1 and a control system. Inside the vacuum chamber 1, a powder processing chamber 11 and a powder chamber 12 are vertically arranged. The powder processing chamber 11 is detachably connected to the top of the powder chamber 12, and the top of the powder processing chamber 11 and the bottom of the powder chamber 12 are connected through a powder circulation pipeline 16. A circulation pump 17 is installed on the powder circulation pipeline 16, and control valves 18 are respectively installed on the powder circulation pipeline 16 on both sides of the circulation pump 17. An emission source 15 is installed on the inner wall of the vacuum chamber 1. A window 111 is installed on the side wall of the powder processing chamber 11 at a position corresponding to the emission source 15 in a straight line. An openable movable cover is installed on the window 111. The control system is electrically connected to the circulation pump 17, the movable cover, and the emission source 15 to control the opening and closing of the circulation pump 17, the movable cover, and the emission source 15. During the vacuuming process, the device controls the movable baffle to close window 111 to reduce powder loss. After the vacuuming is completed, the circulation pump 17 is turned on to transport the powder to the top of the powder processing chamber 11. Then the powder falls from the top of the powder processing chamber 11 in the form of free fall. Subsequently, the movable baffle is opened. During the fall, the powder passes through window 111. Particles emitted by the emission source 15 pass through window 111 and irradiate the powder, completing the powder cleaning and thin film material deposition.

[0055] Multiple emission sources 15 are arranged at different horizontal heights on the inner wall of the vacuum chamber 1. Six emission sources 15 are arranged on the same horizontal plane and are evenly distributed on the inner wall of the vacuum chamber 1 with the axis of the vacuum chamber 1 as the center. The size of the window 111 on the side wall of the powder processing chamber 11 is determined according to the size of the configured emission sources 15 and the distance between the emission sources 15 and the window 111, ensuring that the particle stream emitted by the emission sources 15 can cover the window 111, and the horizontal height of the window 111 is not higher than the horizontal height of the emission sources 15 on the inner wall of the vacuum chamber 1. At the same time, the direction of the particle stream emitted by the emission sources 15 is inclined downward at an angle of 5°-85° with the normal of the wall of the vacuum chamber 1, ensuring that the particle stream emitted by the emission sources 15 irradiates the powder surface as much as possible.

[0056] In addition, a powder distributor 14 is provided on the top of the powder processing chamber 11. After being processed by the powder distributor 14, the powder to be processed falls evenly from the top of the powder processing chamber 11.

[0057] The following examples demonstrate the use of this powder coating device to deposit different thin film coatings on the surface of carbonyl iron powder.

[0058] Example 1

[0059] In this embodiment, based on the powder coating device described above, the emission source 15 is selected as a Cr target, and the carbonyl iron powder is selected from Guangdong Jinhong New Materials Co., Ltd., with an average particle size of 3-5 μm and a morphology as shown in the figure. Figure 2As shown; furthermore, this embodiment uses a DC magnetron sputtering system to prepare thin film-coated carbonyl iron powder particles, and the preparation process is as follows:

[0060] (1) Vacuuming: Open vacuum chamber 1, install the Cr target, disconnect the connection between powder chamber 12 and powder processing chamber 11, put 500g of carbonyl iron powder into powder chamber 12, then restore the connection between powder chamber 12 and powder processing chamber 11, and confirm that the top of powder processing chamber 11 and the bottom of powder chamber 12 are sealed to the powder circulation pipeline 16; close window 111, turn on circulation pump 17 and control valve 18, and control the powder to be processed to circulate in powder processing chamber 11-powder chamber 12 at a speed of 0.01g / s; close vacuum chamber 1, turn on the vacuum system, and wait for vacuum chamber 1 to be evacuated to 2×10 -3 Pa.

[0061] (2) Cleaning of powder to be treated: Argon gas is introduced into vacuum chamber 1 and the gas pressure in vacuum chamber 1 is maintained at 2.0 Pa. The circulation speed of the powder to be treated is adjusted to 5 g / s. The negative terminal of the power supply is connected to the Cr target and grounded, and the positive terminal is connected to the shell of vacuum chamber 1 and powder treatment chamber 11. The current is selected as 2A and the voltage as 300V. After a stable glow plasma is formed, the movable baffle of the side wall window of powder treatment chamber 11 is opened, and the carbonyl iron powder is glow-cleaned for 5 minutes.

[0062] (3) Heating temperature adjustment: Turn on heater 13 and set the temperature to 200℃.

[0063] (4) Protective and modified film deposition: Close the movable baffle of the side wall window of powder treatment chamber 11, adjust the pressure of vacuum chamber 1 to 0.3 Pa, then adjust the current to 3.5 A and the voltage to 400 V. After the parameters stabilize, open the movable baffle of the side wall window of powder treatment chamber 11 and deposit Cr film for 30 minutes.

[0064] (5) After completing the protective and modified film deposition of the powder to be treated, close the side wall window 111 of the powder treatment chamber, turn off the Cr target sputtering power supply, heater 13, air pressure and circulation pump 17, continue to evacuate for 1 hour, and finally turn off the vacuum system, open the vacuum chamber 1, disconnect the connection between the powder chamber 12 and the powder treatment chamber 11, and take out the treated carbonyl iron powder.

[0065] The treated carbonyl iron powder was characterized, and its structure is as follows: Figure 3-6 As shown in the figure. The cross-sectional morphology is the result of grinding and polishing the powder after metallographic mounting; the composition of the cross-section edge is the result of electron probe microanalysis. It can be seen that a dense Cr film with a thickness of about 130 nm is uniformly deposited on the surface of the carbonyl iron powder.

[0066] A 5g powder sample was spread evenly on a plastic plate and placed in a salt spray test chamber. Its corrosion resistance was tested under 25℃ and 3.5% NaCl solution spray. The results showed that the Cr film improved the salt spray corrosion resistance of the carbonyl iron powder, increasing the time for visible red rust to appear from 4 hours (original carbonyl iron powder) to 48 hours.

[0067] Example 2

[0068] In this embodiment, based on the powder coating device described above, the emission source 15 is a Ti arc source, and the carbonyl iron powder is carbonyl iron powder from Guangdong Jinhong New Materials Co., Ltd., with an average particle size of 3-5 μm and a morphology as shown in the figure. Figure 2 As shown; furthermore, this embodiment uses an arc ion plating system to prepare thin-film coated carbonyl iron powder particles, and the preparation process is as follows:

[0069] (1) Vacuuming: Open vacuum chamber 1, install the Ti arc source, disconnect the connection between powder chamber 12 and powder processing chamber 11, put 1000g of carbonyl iron powder into powder chamber 12, then restore the connection between powder chamber 12 and powder processing chamber 11, and confirm that the top of powder processing chamber 11 and the bottom of powder chamber 12 are sealed to the powder circulation pipeline 16; close window 111, turn on circulation pump 17 and control valve 18, and control the powder to be processed to circulate in powder processing chamber 11-powder chamber 12 at a speed of 0.01g / s; close vacuum chamber 1, turn on the vacuum system, and wait for the vacuum chamber to be evacuated to 3×10 -3 Pa.

[0070] (2) Cleaning of powder to be treated: Argon gas is introduced into vacuum chamber 1 and the gas pressure in the vacuum chamber is maintained at 2.0 Pa. The circulation speed of the powder to be treated is adjusted to 7.5 g / s. Under the condition of negative bias voltage -800V (duty cycle adjusted to 0), the glow discharge cleaning state is entered. Then the movable baffle at window 111 is opened and the carbonyl iron powder is glow discharged for 5 minutes.

[0071] (3) Heating temperature adjustment: Turn on heater 13 and set the temperature to 300℃.

[0072] (4) Protective and modified film deposition; close the movable baffle of window 111, adjust the argon flow rate to the pressure in vacuum chamber 1 to 0.6 Pa, turn on the Ti arc power supply, control the current to 70 A (corresponding voltage to 21 V), open the baffle to continue arc cleaning of carbonyl iron powder for 5 minutes, and then close the baffle; introduce nitrogen and control the flow rate ratio with argon to 2:1, maintain the pressure in vacuum chamber 1 to 0.6 Pa, adjust the bias voltage to -400 V (duty cycle adjusted to 40%), adjust the target power supply current to 58 A (corresponding voltage to 17.2 V), after the parameters stabilize, open the movable baffle of window 111, and deposit TiN film for 10 minutes.

[0073] (5) After completing the protection and modification film deposition of the powder to be treated, close window 111, Ti arc power supply, bias power supply, heater 13, circulation pump 17 and air pressure. The vacuum system continues to work for 30 minutes. Finally, close the vacuum system, open the vacuum chamber 1, disconnect the connection between the powder chamber 12 and the powder treatment chamber 11, and take out the treated carbonyl iron powder.

[0074] The treated carbonyl iron powder was characterized, and its structure is as follows: Figure 7-10 As shown in the figure. The cross-sectional morphology is the result of grinding and polishing the powder after metallographic mounting; the composition of the cross-sectional edge is the result of electron probe microanalysis. It can be seen that a dense TiN film with a thickness of about 60 nm is uniformly deposited on the surface of the carbonyl iron powder.

[0075] Example 3

[0076] In this embodiment, based on the powder coating device described above, the emission source 15 is selected as an Al target, and the carbonyl iron powder is selected from Guangdong Jinhong New Materials Co., Ltd., with an average particle size of 3-5 μm and a morphology as shown in the figure. Figure 2 As shown; furthermore, this embodiment uses a medium-frequency magnetron sputtering system to prepare thin-film coated carbonyl iron powder particles, and the preparation process is as follows:

[0077] (1) Vacuuming: Open vacuum chamber 1, install Al target material, disconnect the connection between powder chamber 12 and powder processing chamber 11, put 600g carbonyl iron powder into powder chamber 12, then restore the connection between powder chamber 12 and powder processing chamber 11, and confirm that the top of powder processing chamber 11 and the bottom of powder chamber 12 are sealed to powder circulation pipeline 16; close window 111, turn on circulation pump 17 and control valve 18, and control the powder to be processed to circulate in powder processing chamber 11-powder chamber 12 at a speed of 0.01g / s; close vacuum chamber 1, turn on vacuum system, and wait for vacuum chamber 1 to be evacuated to 2×10 -3 Pa.

[0078] (2) Cleaning of powder to be treated: Argon gas is introduced into vacuum chamber 1 and the gas pressure in the vacuum chamber is maintained at 2.0 Pa. The circulation speed of the powder to be treated is adjusted to 5 g / s. The negative terminal of the power supply is connected to the Al target and grounded, and the positive terminal is connected to the shell of vacuum chamber 1 and the powder treatment chamber. The intermediate frequency power supply is selected with a frequency of 20 kHz, a duty cycle of 30%, a current of 2.5 A, and a voltage of 350 V. After the above parameters are stable, the movable cover of window 111 is opened, and the carbonyl iron powder is glow-cleaned for 5 minutes.

[0079] (3) Heating temperature adjustment: Turn on heater 13 and set the temperature to 240℃.

[0080] (4) Protective and modified film deposition: Close the movable baffle at window 111, introduce nitrogen into vacuum chamber 1 and control the flow ratio of nitrogen to argon to 1:2, adjust the pressure of vacuum chamber 1 to 0.1 Pa, then adjust the current to 3.2 A and the voltage to 350 V. After the parameters stabilize, open the movable baffle at window 111 and deposit Al+AlN films for 10, 20 and 30 minutes respectively.

[0081] (5) After completing the protection and modification film deposition of the powder to be treated, close window 111, turn off the Al target sputtering intermediate frequency power supply, heater 13, air pressure, and circulation pump 17, continue to evacuate for 1 hour, and finally turn off the vacuum system, open the vacuum chamber 1, separate the powder chamber 12 and the powder treatment chamber 11 connection part, and take out the treated carbonyl iron powder.

[0082] The salt spray corrosion resistance of the treated carbonyl iron powder was tested. Its dielectric constant and permeability were measured using a vector network analyzer (Agilent N5244A), and the results are as follows: Figure 11-14 As shown, CIP represents carbonyl iron powder; CIP+Al-AlN-1, 2, and 3 represent the deposition time of Al-AlN films on the surface of carbonyl iron powder for 10, 20, and 30 minutes, respectively. Before measuring electromagnetic parameters, carbonyl iron powder and paraffin were mixed at a mass ratio of 4:1 to form a coaxial ring with an outer diameter of 7 mm, an inner diameter of 3 mm, and a thickness of 2.5 mm. The test frequency range was selected as 2.0–18.0 GHz. It can be seen that as the deposition time of the Al+AlN film increases, the dielectric constant decreases, while the magnetic permeability remains basically unchanged. The spectral characteristics of the electromagnetic parameters of the carbonyl iron powder with the Al+AlN film deposited on the surface are the same as those of the original carbonyl iron powder. 5 g of powder samples were spread evenly on a plastic plate and placed in a salt spray test chamber. The corrosion resistance was tested under 25°C and 3.5% NaCl solution spray. The results show that the Al+AlN film improves the salt spray corrosion resistance of carbonyl iron powder, and the time for the powder to develop visible red rust increased from the original 4 hours (original carbonyl iron powder) to 24 hours, 32 hours, and 36 hours.

[0083] Example 4

[0084] In this embodiment, based on the powder coating device described above, the emission source 15 is a Ti arc source, and the carbonyl iron powder is carbonyl iron powder from Guangdong Jinhong New Materials Co., Ltd., with an average particle size of 3-5 μm and a morphology as shown in the figure. Figure 2 As shown; furthermore, this embodiment uses an arc ion plating system to prepare thin-film coated carbonyl iron powder particles, and the preparation process is as follows:

[0085] (1) Vacuuming: Open vacuum chamber 1, install the Ti arc source, disconnect the connection between powder chamber 12 and powder processing chamber 11, put 800g of carbonyl iron powder into powder chamber 12, then restore the connection between powder chamber 12 and powder processing chamber 11, and confirm that the top of powder processing chamber 11 and the bottom of powder chamber 12 are sealed to the powder circulation pipeline 16; close window 111, turn on circulation pump 17 and control valve 18, and control the powder to be processed to circulate in powder processing chamber 11-powder chamber 12 at a speed of 0.01g / s; close vacuum chamber 1, turn on the vacuum system, and wait for the vacuum chamber to be evacuated to 3×10 -3 Pa.

[0086] (2) Cleaning of powder to be treated: Argon gas is introduced into vacuum chamber 1 and the gas pressure in the vacuum chamber is maintained at 2.0 Pa. The circulation speed of the powder to be treated is adjusted to 7.5 g / s. Under the condition of negative bias voltage -800V (duty cycle adjusted to 0), the glow discharge cleaning state is entered. Then the movable baffle at window 111 is opened and the carbonyl iron powder is glow discharged for 5 minutes.

[0087] (3) Heating temperature adjustment: Turn on heater 13 and set the temperature to 400℃.

[0088] (4) Protective and modified film deposition; close the movable baffle of window 111, adjust the argon flow rate to the pressure in vacuum chamber 1 to 0.6 Pa, turn on the Ti arc power supply, control the current to 70 A (corresponding voltage to 21 V), open the baffle to continue arc cleaning of carbonyl iron powder for 5 minutes, and then close the baffle; introduce acetylene gas and control the flow ratio with argon gas to 2:1, maintain the pressure in vacuum chamber 1 to 0.6 Pa, adjust the bias voltage to -400 V (duty cycle adjusted to 30%), adjust the target power supply current to 55 A (corresponding voltage to 18.6 V), and after the parameters stabilize, open the movable baffle of window 111 and deposit TiC thin films for 10, 20 and 30 minutes.

[0089] (5) After completing the protection and modified film deposition of the powder to be treated, close the window 111 on the side wall of the powder treatment chamber, Ti arc power supply, bias power supply, heater 13, circulation pump 17 and turn off the air pressure. The vacuum system continues to work for 30 minutes. Finally, turn off the vacuum system, open the vacuum chamber 1, disconnect the connection between the powder chamber 12 and the powder treatment chamber 11, and take out the treated carbonyl iron powder.

[0090] The salt spray corrosion resistance of the treated carbonyl iron powder was tested. Its dielectric constant and permeability were measured using a vector network analyzer (Agilent N5244A), and the results are as follows: Figure 15-18As shown, CIP represents carbonyl iron powder; CIP+TiC-1, 2, and 3 represent the deposition time of TiC films on the surface of carbonyl iron powder for 10, 20, and 30 minutes, respectively. Before measuring electromagnetic parameters, carbonyl iron powder and paraffin were mixed at a mass ratio of 4:1 to form a coaxial ring with an outer diameter of 7 mm, an inner diameter of 3 mm, and a thickness of 2.5 mm. The test frequency range was selected as 2.0–18.0 GHz. It can be seen that, unlike the sample with TiN film deposited on the surface of carbonyl iron powder, due to the better conductivity of TiC, the dielectric constant increases with the increase of TiC film deposition time, while the magnetic permeability remains basically unchanged; the spectral characteristics of electromagnetic parameters of carbonyl iron powder with TiC film deposited on the surface are the same as those of the original carbonyl iron powder.

[0091] A 5g powder sample was spread evenly on a plastic plate and placed in a salt spray test chamber. Its corrosion resistance was tested under 25℃ and 3.5% NaCl solution spray. The results showed that the TiC film improved the salt spray corrosion resistance of carbonyl iron powder, increasing the time for visible red rust to appear from 4 hours (original carbonyl iron powder) to 12 hours, 18 hours, and 24 hours.

[0092] Example 5

[0093] In this embodiment, based on the powder coating device described above, the emission source 15 is selected as a Ti target, and the carbonyl iron powder is selected from Guangdong Jinhong New Materials Co., Ltd., with an average particle size of 3-5 μm and a morphology as shown in the figure. Figure 2 As shown; furthermore, this embodiment uses a medium-frequency magnetron sputtering system to prepare thin-film coated carbonyl iron powder particles, and the preparation process is as follows:

[0094] (1) Vacuuming: Open vacuum chamber 1, install the Ti target, disconnect the connection between powder chamber 12 and powder processing chamber 11, put 750g of carbonyl iron powder into powder chamber 12, then restore the connection between powder chamber 12 and powder processing chamber 11, and confirm that the top of powder processing chamber 11 and the bottom of powder chamber 12 are sealed to the powder circulation pipeline 16; close the movable cover of window 111, turn on circulation pump 17 and control valve 18, and control the powder to be processed to circulate in powder processing chamber 11-powder chamber 12 at a speed of 0.01g / s; close vacuum chamber 1, turn on the vacuum system, and wait for the vacuum chamber to be evacuated to 2×10 -3 Pa.

[0095] (2) Cleaning of powder to be treated: Argon gas is introduced into vacuum chamber 1 and the gas pressure in the vacuum chamber is maintained at 2.0 Pa. The circulation speed of the powder to be treated is adjusted to 5 g / s. The negative terminal of the power supply is connected to the Ti target and grounded, and the positive terminal is connected to the shell of vacuum chamber 1 and powder treatment chamber 11. The intermediate frequency power supply is selected with a frequency of 20 kHz, a duty cycle of 25%, a current of 2.3 A, and a voltage of 340 V. After the above parameters are stable, the movable cover of window 111 is opened, and the carbonyl iron powder is glow-cleaned for 5 minutes.

[0096] (3) Heating temperature adjustment: Turn on heater 13 and set the temperature to 280℃.

[0097] (4) Protective and modified film deposition: Close the movable baffle of window 111, introduce oxygen into vacuum chamber 1 and control the flow ratio of oxygen to argon to 1:1, adjust the pressure of vacuum chamber 1 to 0.1 Pa, then adjust the current to 3.5 A and the voltage to 360 V. After the parameters stabilize, open the movable baffle of window 111 and deposit TiO2 films for 5, 10 and 15 minutes respectively.

[0098] (5) After completing the protective and modified film deposition of the powder to be treated, close the movable baffle of window 111, turn off the Al target sputtering intermediate frequency power supply, heater 13, air pressure, and circulation pump 17, and let the vacuum system continue to work for 1 hour. Finally, turn off the vacuum system, open the vacuum chamber 1, separate the powder chamber 12 and the powder treatment chamber 11 connection, and take out the treated carbonyl iron powder.

[0099] The carbonyl iron powder was characterized 5 minutes after the TiO2 film was deposited, and its structure is as follows. Figure 19-22 As shown, the cross-sectional morphology is the result of grinding and polishing the powder after metallographic inlay; the selected cross-sectional composition is the result of electron probe microanalysis. It can be seen that a dense TiO2 film with a thickness of about 45 nm is uniformly deposited on the surface of the carbonyl iron powder.

[0100] Its dielectric constant and permeability were measured using a vector network analyzer (Agilent N5244A). The dielectric constant results are as follows: Figure 23 and Figure 24 As shown; since the values ​​are basically the same, the permeability results are omitted. Wherein, CIP represents carbonyl iron powder; CIP+TiO2-1, 2, and 3 represent 5, 10, and 15 minutes of TiO2 film deposition on the surface of carbonyl iron powder, respectively. Before measuring the electromagnetic parameters, carbonyl iron powder and paraffin were mixed at a mass ratio of 4:1 to form a coaxial ring with an outer diameter of 7 mm, an inner diameter of 3 mm, and a thickness of 2.5 mm. The test frequency range was selected as 2.0–18.0 GHz. It can be seen that the results are basically the same as those for the TiC film sample. With the increase of TiO2 film deposition time, the dielectric constant slightly increases, and the spectral characteristics of the electromagnetic parameters of the carbonyl iron powder with TiO2 film deposited on the surface are the same as those of the original carbonyl iron powder. A 5g powder sample was spread evenly on a plastic plate and placed in a salt spray test chamber. The corrosion resistance was tested under 25℃ and 3.5% NaCl solution spray. The results showed that the TiO2 film improved the salt spray corrosion resistance of carbonyl iron powder, and the time for the powder to develop visible red rust was increased from the original 4 hours (original carbonyl iron powder) to 15 hours, 19 hours and 28 hours.

[0101] In addition, carbonyl iron powder mixed with epoxy resin as a binder was pressed into a magnetic ring in a mold at a pressure of 600 MPa for 60 s, resulting in a magnetic ring with an outer diameter of 10.5 mm, an inner diameter of 5 mm, and a height of 4.5 mm. The magnetic ring was wound with 13 turns of 0.3 mm enameled copper wire to form a toroidal inductor, and its insulation performance was tested at room temperature and 200 °C. The test results are shown in Table 1. The results indicate that the TiO2 film improves the insulation performance of carbonyl iron powder at high temperatures, and the resistivity increases significantly with the increase of the coating thickness.

[0102] Table 1 Insulation performance test results of TiO2 deposition examples

[0103]

[0104]

[0105] The above description is only a part of the embodiments of the present invention, and is not intended to limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content of the present invention specification should be included within the protection scope of the present invention.

Claims

1. A method for preparing thin-film coated carbonyl iron powder particles, characterized in that, Includes the following steps: S1: Place carbonyl iron powder particles in a powder coating device and allow the carbonyl iron powder particles to circulate within the powder coating device; after the carbonyl iron powder particles have stabilized and circulated, introduce working gas into the powder coating device. The powder coating device includes a vacuum chamber and a control system. The vacuum chamber includes a powder processing chamber, a powder chamber, and an emission source. The bottom and top of the powder processing chamber are detachably connected, and the top and bottom of the powder processing chamber are connected by a powder circulation pipeline. A circulation pump is installed on the powder circulation pipeline. The emission sources are evenly distributed on the inner wall of the vacuum chamber with the axis of the vacuum chamber as the center. A window is opened on the side wall of the powder processing chamber to allow the emission source particle stream to pass through. The particle stream emitted by the emission source can cover the window. The direction of the particle stream emitted axially by the emission source is inclined downward at an angle of 5°-85° with the normal of the vacuum chamber wall. A movable baffle is installed at the window. The control system is electrically connected to the circulation pump, the emission source, and the movable baffle. The carbonyl iron powder particles are placed in the powder chamber, and the circulation pump is turned on to control the carbonyl iron powder particles to circulate between the powder processing chamber and the powder chamber. S2: The carbonyl iron powder particles circulating in the powder coating device are coated using physical vapor deposition. The coating material is fixed on the side wall of the vacuum chamber, and a bias voltage is applied to the powder processing chamber. After a stable plasma is formed, the window is opened to allow the particle stream ejected from the coating material to enter the powder processing chamber, thus completing the coating treatment of the carbonyl iron powder particles. The coating treatment temperature is 30-500℃, and the coating treatment time is 1-200 min. The physical vapor deposition method is magnetron sputtering or arc ion plating. S3: After the carbonyl iron powder particles circulate in the powder coating device for a certain period of time, the power is turned off and the powder is cooled to room temperature to obtain carbonyl iron powder particles coated with a thin film after processing; the coating material on the surface of the carbonyl iron powder particles is one or more composite materials selected from elemental metals, alloys, metal carbides, metal nitrides, and metal oxides.

2. The method for preparing film-coated carbonyl iron powder particles according to claim 1, characterized in that, The working gas is argon, or a mixture of argon with one of acetylene, methane, nitrogen, or oxygen.

3. The method for preparing film-coated carbonyl iron powder particles according to claim 1, characterized in that, In step S1, the circulating flow rate of the carbonyl iron powder particles is 0.01-50 g / s.

4. A film-coated carbonyl iron powder particle prepared by the preparation method according to any one of claims 1-3, characterized in that, The carbonyl iron powder particles coated by the film include carbonyl iron powder particles and a coating layer covering their outer surface.

5. The carbonyl iron powder particles according to claim 4, characterized in that, The average particle size of the carbonyl iron powder particles is 1.0-10.0 μm; the thickness of the coating layer is 20-2000 nm.

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