A high permeability flexible self-supporting Fe-Si-Al electromagnetic shielding sheet and a preparation method thereof

Abstract

The application provides a high magnetic permeability flexible self-supporting FeSiAl electromagnetic shielding sheet and a preparation method thereof. The shielding sheet comprises at least the following components: flaky FeSiAl alloy powder, glyceryl trioleate, polyvinyl butyral, dibutyl phthalate, a toughening agent and a defoaming agent. The flaky FeSiAl powder with a large diameter-thickness ratio is successfully prepared through a segmented ball milling process, which is beneficial to inhibit high-frequency eddy current and enhance a shape anisotropic field. The water-soluble film is used as a substrate, and the defoaming agent is added dropwise in the flow casting slurry, so that the problems of the film and the substrate not being easy to peel off and the film being easy to have air holes are solved. The flow casting is carried out under an applied magnetic field, and the roll pressing treatment after the flow casting forming is beneficial to fully utilize the shape anisotropy of the flaky alloy powder, make the flaky powder parallel to the film and improve the film density, so that the magnetic permeability of the electromagnetic shielding sheet can be effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of soft magnetic materials technology, specifically relating to a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet and its preparation method. Background Technology

[0002] With the advancement of technology, the operating frequency of electronic devices has gradually increased. However, the resulting electromagnetic interference and electromagnetic pollution problems in the high-frequency range have become increasingly serious. Flexible electromagnetic shielding sheets, characterized by their flexibility, ultra-thinness, wide application frequency range, ease of cutting and installation, and low secondary radiation, can effectively reduce crosstalk between circuits, reduce electromagnetic induction coupling of connected circuits, reduce electromagnetic radiation, attenuate interference from radio frequency circuits, and isolate magnetic fields, thus attracting widespread attention.

[0003] Among numerous materials, iron-silicon-aluminum alloys possess advantages such as high saturation magnetization, excellent thermal stability, high permeability, low coercivity, and low cost, making them an important material for electromagnetic shielding sheets. However, the permeability of commonly used iron-silicon-aluminum electromagnetic shielding sheets on the market is still relatively low, with the real part of permeability ranging from 120 to 220. Increasing the sheet thickness to improve electromagnetic shielding effectiveness cannot meet the current trend of miniaturization and high integration in electronic products.

[0004] Studies have shown that using sheet-like iron-silicon-aluminum powder as raw material to prepare electromagnetic shielding sheets helps to suppress eddy currents within particles and enhance shape anisotropy. However, due to the high brittleness, poor processing performance, and small aspect ratio of iron-silicon-aluminum alloy powder, as well as the difficulty in peeling the cast film from the substrate, problems such as unevenness, defects, and low density of the film are caused, which limit the improvement of magnetic permeability and thus affect the final shielding effect. Summary of the Invention

[0005] This invention proposes a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet and its preparation method. It can prepare sheet-like iron-silicon-aluminum alloy powder with a large aspect ratio and obtain a cast film with good in-plane orientation consistency and high density of sheet-like powder, thereby effectively improving the high-frequency permeability of the prepared shielding sheet.

[0006] This invention is achieved through the following technical solution:

[0007] This invention proposes a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet, which includes at least the following components: sheet-like iron-silicon-aluminum alloy powder, trioleic acid glyceride, polyvinyl butyral, toughening agent, dibutyl phthalate, and defoamer.

[0008] In one embodiment of the present invention, the defoamer includes one or more of the following: a mixture of glycerol and ethylene oxide, dimethyl silicone oil, polyether-modified silicone, or higher alcohols.

[0009] This invention also proposes a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet and its preparation method, which includes at least the following steps:

[0010] Irregularly shaped iron-silicon-aluminum alloy powder, along with ZrO2 grinding balls, ethanol, and trioleic acid glyceride, were added to a ball mill for segmented ball milling to obtain flake-shaped iron-silicon-aluminum alloy powder.

[0011] The sheet-like iron-silicon-aluminum alloy powder was placed in a nitrogen atmosphere and annealed at 700°C for 12 hours.

[0012] The annealed sheet-like iron-silicon-aluminum alloy powder is mixed evenly with polyvinyl butyral, anhydrous ethanol, dibutyl phthalate and toughening agent to obtain a casting slurry.

[0013] The casting slurry is heated and stirred to remove the solvent. Then, a defoamer is added to the casting slurry, and the casting slurry is subjected to vacuum treatment.

[0014] The vacuum-treated casting paste is coated onto a water-soluble thin film substrate. A movable strong magnetic field is applied below the substrate. After the casting paste solidifies, the magnetic field is removed to obtain a thin film.

[0015] The film is subjected to roll pressing, and the rolled film is placed in water to completely dissolve the substrate. The film is then removed and placed in a drying oven at 60℃~80℃ for 1h~2h to obtain an iron-silicon-aluminum electromagnetic shielding sheet.

[0016] In one embodiment of the present invention, the mass ratio of the irregularly shaped iron-silicon-aluminum alloy powder added to the ball mill to ZrO2 grinding balls, ethanol and trioleic acid glyceride is 0.5:10:1:0.01, and the particle size of the irregularly shaped iron-silicon-aluminum alloy powder is -40 mesh to +80 mesh.

[0017] In one embodiment of the present invention, the aspect ratio of the sheet-like iron-silicon-aluminum alloy powder is (300-400):1.

[0018] In one embodiment of the present invention, the segmented ball milling process includes a first ball milling process and a second ball milling process, wherein the first ball milling speed is 400 r / min to 600 r / min and the first ball milling time is 120 min to 210 min, the second ball milling speed is 100 r / min to 300 r / min and the second ball milling time is 360 min to 540 min.

[0019] In one embodiment of the present invention, in the step of obtaining the cast slurry, the mass ratio of the annealed sheet-like iron-silicon-aluminum alloy powder, polyvinyl butyral, anhydrous ethanol, dibutyl phthalate and toughening agent is 12:2:21:1:0.2.

[0020] In one embodiment of the present invention, in the step of heating and stirring the cast slurry, the heating temperature is 80℃~100℃, the stirring time is 45min~60min, and the viscosity of the cast slurry is 3000mPa·s.

[0021] In one embodiment of the present invention, the mass percentage of defoamer in the cast slurry is 1wt% to 8wt%, and the number of vacuum treatments is 2 to 5.

[0022] In one embodiment of the present invention, in the step of rolling the film, the number of rolling processes is 1 to 5, and the standing time of the film after rolling is 30s to 150s in water.

[0023] This invention proposes a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet and its preparation method. It can prepare sheet-like iron-silicon-aluminum alloy powder with a large aspect ratio, thereby enhancing the shape anisotropy of the iron-silicon-aluminum alloy; it can effectively reduce porosity in the film and effectively avoid the problem of difficulty in peeling the film from the substrate, thus improving the quality of the electromagnetic shielding sheet, increasing the yield, and reducing production costs; it can effectively improve the in-plane orientation consistency of the sheet-like iron-silicon-aluminum alloy powder and the density of the electromagnetic shielding sheet, thereby effectively improving the permeability of the iron-silicon-aluminum electromagnetic shielding sheet. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a flowchart of a method for preparing an iron-silicon-aluminum electromagnetic shielding sheet according to an embodiment of the present invention.

[0026] Figure 2 This is a scanning electron microscope image of an irregularly shaped iron-silicon-aluminum alloy powder according to an embodiment of the present invention.

[0027] Figure 3 Scanning electron microscope (SEM) image of the sheet-like iron-silicon-aluminum alloy powder prepared in Example 1.

[0028] Figure 4 Scanning electron microscope (SEM) image of the sheet-like iron-silicon-aluminum alloy powder prepared in Example 2.

[0029] Figure 5 Scanning electron microscope (SEM) image of the sheet-like iron-silicon-aluminum alloy powder prepared in Example 3.

[0030] Figure 6 The image shows a cross-sectional scanning electron microscope image of the iron-silicon-aluminum electromagnetic shielding sheet prepared in Example 2.

[0031] Figure 7 This is a physical image of the iron-silicon-aluminum electromagnetic shielding sheet prepared in Example 2.

[0032] Figure 8 This is a comparison chart showing the density of the iron-silicon-aluminum electromagnetic shielding sheets prepared in Comparative Example 1 and Examples 1-3.

[0033] Figure 9 The frequency spectrum of the real part μ' of the permeability of the iron-silicon-aluminum electromagnetic shielding sheet prepared in Comparative Example 1 and Examples 1-3 is shown. Detailed Implementation

[0034] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0035] It should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Unless otherwise specified, “%” and “parts” as shown in the following embodiments refer to “% by mass” and “parts by mass”, respectively.

[0036] The technical solution of the present invention will be further described in detail below with reference to several embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] This invention proposes a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet, comprising sheet-like iron-silicon-aluminum alloy powder, trioleic acid glyceride, polyvinyl butyral, dibutyl phthalate, toughening agent, and defoamer. The aspect ratio of the sheet-like iron-silicon-aluminum alloy powder is, for example, (300-400):1. The defoamer includes, for example, one or more of a mixture of glycerol and ethylene oxide, dimethyl silicone oil, polyether-modified silicone, or higher alcohols.

[0038] Please see Figure 1 As shown, the present invention also proposes a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet and its preparation method, including but not limited to steps S10-S60.

[0039] Step S10: Add irregularly shaped iron-silicon-aluminum alloy powder, ZrO2 grinding balls, ethanol, and trioleic acid glyceride to a ball mill for segmented ball milling to obtain flake-shaped iron-silicon-aluminum alloy powder.

[0040] Step S20: Place the sheet-like iron-silicon-aluminum alloy powder in a nitrogen atmosphere and anneal it at 700°C for 12 hours.

[0041] Step S30: Mix the annealed sheet iron-silicon-aluminum alloy powder with polyvinyl butyral, anhydrous ethanol, dibutyl phthalate and toughening agent evenly to obtain a casting slurry.

[0042] Step S40: Heat and stir the cast slurry to remove the solvent, then add defoamer to the cast slurry and vacuum the cast slurry.

[0043] Step S50: The vacuum-treated casting paste is coated onto a water-soluble thin film substrate. A movable strong magnetic field is applied below the substrate. After the casting paste has solidified, the magnetic field is removed to obtain the thin film.

[0044] Step S60: Roll the film, place the rolled film in water to completely dissolve the substrate, remove the film, and dry it in a drying oven at 60℃~80℃ for 1h~2h to obtain the iron-silicon-aluminum electromagnetic shielding sheet.

[0045] Please see Figure 1 and Figure 2 As shown, in step S10, in one embodiment of the present invention, by Figure 2It is known that the iron-silicon-aluminum alloy powder used has an irregular shape and a large thickness with a small aspect ratio. In one embodiment of the present invention, the particle size of the irregularly shaped iron-silicon-aluminum alloy powder used is, for example, -40 mesh to +80 mesh. The mass ratio of the irregularly shaped iron-silicon-aluminum alloy powder, ZrO2 grinding balls, ethanol, and trioleic acid glyceride added to the ball mill is, for example, 0.5:10:1:0.01. In one embodiment of the present invention, the ball mill is, for example, a planetary ball mill. After the irregularly shaped iron-silicon-aluminum alloy powder, ZrO2 grinding balls, ethanol, and trioleic acid glyceride are added to the ball mill, a segmented ball milling process is performed. In one embodiment of the present invention, the segmented ball milling process includes, for example, a first-stage ball milling process and a second-stage ball milling process. In the first-stage ball milling process, the first-stage ball milling speed is, for example, 400 r / min to 600 r / min, and the first-stage ball milling time is, for example, 120 min to 210 min. In the second stage of ball milling, the milling speed is, for example, 100 r / min to 300 r / min, and the milling time is, for example, 360 min to 540 min. After two stages of ball milling, the irregularly shaped iron-silicon-aluminum alloy powder is flattened to obtain sheet-like iron-silicon-aluminum alloy powder. The aspect ratio of the sheet-like iron-silicon-aluminum alloy powder reaches, for example, (300-400):1. The sheet-like iron-silicon-aluminum alloy powder has a large aspect ratio, thereby enhancing the shape anisotropy of the iron-silicon-aluminum alloy. Furthermore, using this sheet-like iron-silicon-aluminum alloy powder as raw material to prepare iron-silicon-aluminum electromagnetic shielding sheets can effectively improve the high-frequency permeability of the final prepared shielding sheet.

[0046] Please see Figure 1 As shown, in step S20, in one embodiment of the present invention, for example, flake-shaped iron-silicon-aluminum alloy powder is placed in a tube furnace, and nitrogen gas is continuously introduced into the furnace to anneal the flake-shaped iron-silicon-aluminum alloy powder. The annealing temperature is, for example, 700°C, and the annealing time is, for example, 12 hours. After high-temperature annealing, the solvent in the flake-shaped iron-silicon-aluminum alloy powder is fully evaporated, reducing the impurity concentration, improving the purity of the iron-silicon-aluminum alloy, stabilizing the crystal structure of the iron-silicon-aluminum alloy, and further refining the particle size of the iron-silicon-aluminum alloy powder.

[0047] Please see Figure 1 As shown, in step S30, in one embodiment of the present invention, the annealed sheet-like iron-silicon-aluminum alloy powder is mixed uniformly with polyvinyl butyral, anhydrous ethanol, dibutyl phthalate, and a toughening agent, for example, at a mass ratio of 12:2:21:1:0.2, to obtain a casting slurry. In one embodiment of the present invention, the toughening agent is selected, for example, from epoxy resin, polyurethane resin, polyamide resin, acetal resin, nitrile rubber, or polysulfide rubber.

[0048] Please see Figure 1As shown, in step S40, in one embodiment of the present invention, the casting slurry is heated and stirred to remove solvents, such as ethanol, from the casting slurry. The heating temperature is, for example, 80°C to 100°C, and the stirring time is, for example, 45 min to 60 min. At this time, the viscosity of the casting slurry is, for example, 3000 mPa·s. After removing the solvent, a defoamer is added to the casting slurry, and the mass percentage of the defoamer in the casting slurry is, for example, 1 wt% to 8 wt%. In one embodiment of the present invention, the defoamer includes, for example, one or more of a mixture of glycerol and ethylene oxide, dimethyl silicone oil, polyether-modified silicone, or higher alcohols. By adding a defoamer to the casting slurry, the porosity in the subsequent film can be effectively reduced, thereby improving the smoothness of the film. After adding the defoamer, the casting slurry is then subjected to vacuum treatment, and the number of vacuum treatments is, for example, 2 to 5 times.

[0049] Please see Figure 1 As shown, in step S50, in one embodiment of the present invention, the substrate used is a water-soluble thin film substrate. Cleaning completely dissolves the substrate, resulting in a complete and undamaged electromagnetic shielding sheet. This effectively avoids the problem of the film being difficult to peel off from the substrate, improving yield and reducing production costs. In one embodiment of the present invention, for example, a casting machine is used to coat the casting paste onto the water-soluble thin film substrate. When coating the casting paste onto the substrate, a movable strong magnetic field can be applied below the substrate. The applied magnetic field causes the sheet-like iron-silicon-aluminum alloy powder with strong shape anisotropy to align parallel to the substrate direction, effectively improving the in-plane orientation consistency of the sheet-like powder. This effectively avoids the problem of the sheet-like powder springing back after casting, causing unevenness in the electromagnetic shielding sheet, and also helps to increase the density of the electromagnetic shielding sheet.

[0050] Please see Figure 1 As shown, in step S60, in one embodiment of the present invention, the number of times the film is rolled is, for example, 1 to 5. The rolled film is then placed in water until the substrate is completely dissolved, allowing the intact film to be removed and dried in a 60°C drying oven for 2 hours to obtain an iron-silicon-aluminum electromagnetic shielding sheet. By rolling the film, the density of the electromagnetic shielding sheet is further increased, thereby effectively improving the permeability of the iron-silicon-aluminum electromagnetic shielding sheet. The real part of the permeability of the prepared electromagnetic shielding sheet can reach 210 to 290.

[0051] The present invention will be explained in more detail below by referring to embodiments, which should not be construed as limiting. Appropriate modifications can be made within the scope of the present invention, and all such modifications fall within the technical scope of the present invention.

[0052] Example 1

[0053] Step S10: Mix irregularly shaped iron-silicon-aluminum alloy powder of -40 mesh to +80 mesh with ZrO2 grinding balls, ethanol and trioleic acid glyceride in a mass ratio of 0.5:10:1:0.01, add to a planetary ball mill, and mechanically ball mill using a segmented ball milling process. The first segment ball milling speed is 550 r / min and the first segment ball milling time is 150 min. The second segment ball milling speed is 150 r / min and the second segment ball milling time is 480 min, to obtain sheet-like iron-silicon-aluminum alloy powder with a diameter-to-thickness ratio of 360:1.

[0054] Step S20: Place the obtained sheet-like iron-silicon-aluminum alloy powder in a nitrogen atmosphere and anneal at 700°C for 12 hours.

[0055] Step S30: Mix the annealed sheet iron-silicon-aluminum alloy powder with polyvinyl butyral, anhydrous ethanol, dibutyl phthalate and toughening agent in a mass ratio of 12:2:21:1:0.2 to prepare a casting slurry.

[0056] Step S40: Heat and stir the cast slurry at 80°C for 60 minutes to remove the solvent and make the viscosity of the cast slurry reach 3000 mPa·s. Then add 2 wt% dimethyl silicone oil and perform vacuum treatment on the cast slurry twice.

[0057] Step S50: The vacuum-treated casting paste is coated onto a water-soluble thin film substrate using a casting machine. A movable strong magnetic field is applied below the substrate. After the casting paste has solidified, the magnetic field is removed to obtain the thin film.

[0058] Step S60: The film is subjected to rolling treatment twice, and then the film is placed in water for 140 seconds until the water-soluble film substrate is completely dissolved. The film is then removed and placed in a drying oven at 60°C for 2 hours to obtain an iron-silicon-aluminum electromagnetic shielding sheet.

[0059] Please see Figure 3 , Figure 8 and Figure 9 As shown, the obtained flake-shaped iron-silicon-aluminum powder has a large aspect ratio, reaching a maximum of 360:1 (e.g., Figure 3 As shown in the figure, the obtained iron-silicon-aluminum electromagnetic shielding sheet has a high density, reaching 5.48 g / cm³. 3 It also has high permeability and good frequency stability; at a typical frequency of 13.56 MHz, the real part of the permeability μ' is 267 (e.g., Figure 8 and Figure 9 (As shown).

[0060] Example 2

[0061] Step S10: Mix irregularly shaped iron-silicon-aluminum alloy powder of -40 mesh to +80 mesh with ZrO2 grinding balls, ethanol and trioleic acid glyceride in a mass ratio of 0.5:10:1:0.01, add to a planetary ball mill, and mechanically ball mill using a segmented ball milling process. The first segment ball milling speed is 450 r / min and the first segment ball milling time is 180 min. The second segment ball milling speed is 200 r / min and the second segment ball milling time is 400 min, to obtain sheet-like iron-silicon-aluminum alloy powder with a diameter-to-thickness ratio of 400:1.

[0062] Step S20: Place the obtained sheet-like iron-silicon-aluminum alloy powder in a nitrogen atmosphere and anneal at 700°C for 12 hours.

[0063] Step S30: Mix the annealed sheet iron-silicon-aluminum alloy powder with polyvinyl butyral, anhydrous ethanol, dibutyl phthalate and toughening agent in a mass ratio of 12:2:21:1:0.2 to prepare a casting slurry.

[0064] Step S40: Heat and stir the cast slurry at 80°C for 60 minutes to remove the solvent and make the viscosity of the cast slurry reach 3000 mPa·s. Then add 3 wt% of a mixture of glycerol and ethylene oxide and perform vacuum treatment on the cast slurry three times.

[0065] Step S50: The vacuum-treated casting paste is coated onto a water-soluble thin film substrate using a casting machine. A movable strong magnetic field is applied below the substrate. After the casting paste has solidified, the magnetic field is removed to obtain the thin film.

[0066] Step S60: The film is subjected to three rolling processes, and then the film is placed in water for 100 seconds until the water-soluble film substrate is completely dissolved. The film is then removed and placed in a 60°C drying oven for 2 hours to obtain an iron-silicon-aluminum electromagnetic shielding sheet.

[0067] Please see Figure 4 , Figure 8 and Figure 9 As shown, the obtained flake-shaped iron-silicon-aluminum powder has a large aspect ratio, reaching a maximum of 400:1 (e.g., Figure 4 As shown in the figure, the obtained iron-silicon-aluminum electromagnetic shielding sheet has a high density, reaching 5.80 g / cm³. 3 It also has high permeability and good frequency stability; at a typical frequency of 13.56 MHz, the real part of the permeability μ' is 287 (e.g., Figure 8 and Figure 9 (As shown).

[0068] Example 3

[0069] Step S10: Mix irregularly shaped iron-silicon-aluminum alloy powder of -40 mesh to +80 mesh with ZrO2 grinding balls, ethanol and trioleic acid glyceride in a mass ratio of 0.5:10:1:0.01, add to a planetary ball mill, and mechanically ball mill using a segmented ball milling process. The first segment ball milling speed is 420 r / min and the first segment ball milling time is 200 min. The second segment ball milling speed is 250 r / min and the second segment ball milling time is 380 min, to obtain sheet-like iron-silicon-aluminum alloy powder with a diameter-to-thickness ratio of 320:1.

[0070] Step S20: Place the obtained sheet-like iron-silicon-aluminum alloy powder in a nitrogen atmosphere and anneal at 700°C for 12 hours.

[0071] Step S30: Mix the annealed sheet iron-silicon-aluminum alloy powder with polyvinyl butyral, anhydrous ethanol, dibutyl phthalate and toughening agent in a mass ratio of 12:2:21:1:0.2 to prepare a casting slurry.

[0072] Step S40: Heat and stir the cast slurry at 80°C for 60 minutes to remove the solvent and make the viscosity of the cast slurry reach 3000 mPa·s. Then add 3 wt% of a mixture of glycerol and ethylene oxide and perform vacuum treatment on the cast slurry three times.

[0073] Step S50: The vacuum-treated casting paste is coated onto a water-soluble thin film substrate using a casting machine. A movable strong magnetic field is applied below the substrate. After the casting paste has solidified, the magnetic field is removed to obtain the thin film.

[0074] Step S60: The film is subjected to rolling treatment 4 times, and then the film is placed in water for 50 seconds until the water-soluble film substrate is completely dissolved. The film is then removed and placed in a drying oven at 60°C for 2 hours to obtain an iron-silicon-aluminum electromagnetic shielding sheet.

[0075] Please see Figure 5 , Figure 8 and Figure 9 As shown, the obtained flake-shaped iron-silicon-aluminum powder has a large aspect ratio, reaching a maximum of 320:1 (e.g., Figure 5 As shown in the figure, the obtained iron-silicon-aluminum electromagnetic shielding sheet has a high density, reaching 5.09 g / cm³. 3 It also has high permeability and good frequency stability; at a typical frequency of 13.56 MHz, the real part of the permeability μ' is 238 (e.g., Figure 8 and Figure 9 (As shown).

[0076] Comparative Example 1

[0077] Currently, the density of commercially available conventional sheet-shaped iron-silicon-aluminum electromagnetic shielding sheets does not exceed 5 g / cm³.3 At a typical frequency of 13.56 MHz, the real part of the permeability μ' does not exceed 220.

[0078] Please see Figure 8 and Figure 9 As shown, a typical commercially available high-permeability conventional sheet-shaped iron-silicon-aluminum electromagnetic shielding sheet with a density of 4.78 g / cm³ was selected. 3 The real part of the permeability μ' at a typical frequency of 13.56MHz is 218.

[0079] Please see Figures 2 to 7 As shown, the sheet-like iron-silicon-aluminum alloy powders prepared by the preparation method in this application all have a large aspect ratio, and in Example 2, the aspect ratio can reach a maximum of 400:1 (e.g., Figure 4 As shown). Using the above-mentioned sheet-like iron-silicon-aluminum alloy powder as raw material, the sheet-like iron-silicon-aluminum alloy powder inside the prepared electromagnetic shielding sheet is arranged in an orderly and compact manner (as shown). Figure 6 As shown), the surface is flat and flexible, self-supporting. Even after multiple folds and rolls, the electromagnetic shielding sheet remains wrinkle-free (as shown). Figure 7 (As shown).

[0080] Please see Figure 8 and Figure 9 As shown, the commercially available high-permeability conventional sheet-shaped iron-silicon-aluminum electromagnetic shielding sheet in Comparative Example 1 has a low density of only 4.78 g / cm³. 3 At a typical frequency of 13.56 MHz, the real part of the permeability μ' is only 218. However, the iron-silicon-aluminum electromagnetic shielding sheet prepared by the method described in this application has a higher density and a higher real part of permeability than commercially available high-permeability conventional sheet-shaped iron-silicon-aluminum electromagnetic shielding sheets. Furthermore, in Example 2, the density can reach 5.80 g / cm³. 3 The real part of the permeability μ' can reach 287 at a typical frequency of 13.56MHz.

[0081] In summary, this invention proposes a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet and its preparation method. By improving the segmented ball milling process of irregularly shaped iron-silicon-aluminum alloy powder, sheet-like iron-silicon-aluminum alloy powder with a large aspect ratio is obtained, which is beneficial for suppressing high-frequency eddy currents and enhancing the shape anisotropy of the iron-silicon-aluminum alloy, thereby effectively improving the high-frequency permeability of the prepared shielding sheet. By adding an antifoaming agent to the casting slurry, the porosity in the film is effectively reduced. By selecting a water-soluble film as the substrate of the iron-silicon-aluminum film, the substrate can be completely dissolved after cleaning, resulting in a complete and undamaged electromagnetic shielding sheet, effectively avoiding the problem of the film and substrate being difficult to peel off, improving the yield rate and reducing production costs. During casting and coating, by applying a movable strong magnetic field parallel to the film below the substrate, the strong shape anisotropy of the sheet-like alloy powder can be fully utilized, making the sheet-like powder arranged parallel to the film, thereby effectively improving the in-plane orientation consistency of the sheet-like powder and avoiding the problem of uneven electromagnetic shielding sheet caused by the rebound of the sheet-like powder after casting. The density of the electromagnetic shielding sheet is increased by rolling the thin film, thereby effectively improving the permeability of the iron-silicon-aluminum electromagnetic shielding sheet. The real part of the permeability of the prepared electromagnetic shielding sheet can reach 210-290. The iron-silicon-aluminum electromagnetic shielding sheet preparation method proposed in this invention is simple, efficient, has a high yield, and is low in cost, making it highly valuable for application.

[0082] The above description is merely a preferred embodiment of this application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by replacing the above-mentioned features with technical features with similar functions disclosed in this application (but not limited to) each other.

[0083] Apart from the technical features described in the specification, the other technical features are known to those skilled in the art. To highlight the innovative features of this invention, the other technical features will not be described in detail here.

Claims

1. A method for preparing a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet, characterized in that, At least the following steps are included: Irregularly shaped iron-silicon-aluminum alloy powder, along with ZrO2 grinding balls, ethanol, and trioleic acid glyceride, is added to a ball mill for segmented ball milling to obtain flake-shaped iron-silicon-aluminum alloy powder. The aspect ratio of the flake-shaped iron-silicon-aluminum alloy powder is (300-400):

1. The segmented ball milling process includes a first stage ball milling process and a second stage ball milling process. The ball milling speed in the first stage is 400 r / min to 600 r / min, and the ball milling time in the first stage is 120 min to 210 min. The ball milling speed in the second stage is 100 r / min to 300 r / min, and the ball milling time in the second stage is 360 min to 540 min. The flake-shaped iron-silicon-aluminum alloy powder was placed in a nitrogen atmosphere and annealed at 700°C for 12 hours. The annealed sheet-like iron-silicon-aluminum alloy powder is mixed evenly with polyvinyl butyral, anhydrous ethanol, dibutyl phthalate and toughening agent to obtain a casting slurry. The casting slurry is heated and stirred to remove anhydrous ethanol. Then, a defoamer is added to the casting slurry, and the casting slurry is subjected to vacuum treatment. The defoamer includes one or more of the following: a mixture of glycerol and ethylene oxide, dimethyl silicone oil, polyether modified silicone, or higher alcohols. The vacuum-treated casting paste is coated onto a water-soluble thin film substrate. A movable strong magnetic field is applied below the substrate. After the casting paste solidifies, the magnetic field is removed to obtain a thin film. The film is subjected to roll pressing, and the rolled film is placed in water to completely dissolve the substrate. The film is then removed and placed in a drying oven at 60℃~80℃ for 1h~2h to obtain an iron-silicon-aluminum electromagnetic shielding sheet.

2. The method for preparing a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet according to claim 1, characterized in that, The irregularly shaped iron-silicon-aluminum alloy powder added to the ball mill has a mass ratio of 0.5:10:1:0.01 to ZrO2 grinding balls, ethanol, and trioleic acid glyceride, and the particle size of the irregularly shaped iron-silicon-aluminum alloy powder is -40 mesh to +80 mesh.

3. The method for preparing a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet according to claim 1, characterized in that, In the step of obtaining the cast slurry, the mass ratio of the annealed sheet iron-silicon-aluminum alloy powder to polyvinyl butyral, anhydrous ethanol, dibutyl phthalate and toughening agent is 12:2:21:1:0.

2.

4. The method for preparing a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet according to claim 1, characterized in that, In the step of heating and stirring the cast slurry, the heating temperature is 80℃~100℃, the stirring time is 45min~60min, and the viscosity of the cast slurry is 3000mPa•s.

5. The method for preparing a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet according to claim 1, characterized in that, The defoamer in the cast slurry has a mass percentage of 1wt% to 8wt%, and the vacuum treatment is performed 2 to 5 times.

6. The method for preparing a high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet according to claim 1, characterized in that, In the step of rolling the film, the rolling process is performed 1 to 5 times, and the film after rolling is left to stand in water for 30 to 150 seconds.

7. A high-permeability flexible self-supporting iron-silicon-aluminum electromagnetic shielding sheet obtained by the preparation method according to any one of claims 1-6, characterized in that, It includes at least the following components: flake iron-silicon-aluminum alloy powder, trioleic acid glyceride, polyvinyl butyral, toughening agent, dibutyl phthalate, and defoamer.

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