Silver-clad magnetic metal fillers with magnetic field shielding effectiveness, their preparation methods and applications

Abstract

This invention discloses a silver-coated magnetic metal filler with magnetic field shielding effectiveness, its preparation method, and its application, relating to the field of electromagnetic shielding materials technology. The method includes: acid washing of magnetic metal powder to obtain acidified magnetic metal powder; adding the acidified magnetic metal powder to a silver nitrate solution, adding grease, and stirring to obtain activated magnetic metal powder; uniformly mixing the activated magnetic metal powder, reducing solution, and silver ammonia solution, adding grease again, and stirring to obtain the silver-coated magnetic metal filler with magnetic field shielding effectiveness. This invention utilizes lightweight, inert grease to avoid oxidation during the magnetic metal displacement activation or chemical silver plating process, significantly enhancing the electromagnetic exchange between the magnetic core and the conductive shell, further improving its shielding effectiveness.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic shielding materials technology, specifically to a silver-clad magnetic metal filler with magnetic field shielding effectiveness, its preparation method, and its application. Background Technology

[0002] With the continuous development of electronic technology and the increasing popularity of electronic devices, the electromagnetic environment of modern society is becoming increasingly complex. The frequencies of electromagnetic waves generated by various electronic devices can range from several kilohertz to tens of gigahertz, severely interfering with the normal operation of electronic and electrical equipment. Therefore, electromagnetic shielding materials are needed to shield electromagnetic waves. Existing electromagnetic shielding materials mainly consist of electromagnetic shielding rubber, electromagnetic shielding coatings, and other composite materials. These composite materials are primarily composed of electromagnetic shielding fillers and a matrix, and their shielding performance is determined by the electromagnetic shielding filler. Existing commercial electromagnetic shielding composite materials use various conductive fillers, such as silver powder, graphite powder, carbon nanotubes, and silver-coated copper. These materials have good shielding performance against plane waves in the megahertz and gigahertz bands. When the source distance r > λ / 2Π, electromagnetic radiation is far-field radiation, and the electromagnetic wave exhibits a uniform plane wave behavior. In this case, electromagnetic shielding can be achieved by dissipating either the electric or magnetic field. Magnetic materials have a low natural resonant frequency and low impedance within the plane wave range, resulting in weak dissipation capability for electromagnetic waves. The skin depth of conductive materials decreases with increasing frequency, while their dissipation capability increases with increasing frequency. In summary, using conductive materials to shield plane waves is the most effective approach. When the source distance r < λ / 2Π, electromagnetic radiation is near-field radiation, and the electromagnetic wave exhibits quasi-static field characteristics. Therefore, the design of electromagnetic shielding materials must consider both electric and magnetic field shielding. For magnetic fields, conductive materials, due to the weakened skin effect and reduced wave impedance, cannot provide good shielding. Magnetic materials, however, can achieve magnetic field shielding through magnetic shunt effects and eddy current losses. However, for electromagnetic shielding composite materials, the distribution of the magnetic filler determines its limited conductivity and low eddy current losses, often resulting in limited magnetic shielding effectiveness. In conclusion, magnetic field shielding is the key and challenging aspect of electromagnetic shielding; single conductive or magnetically permeable electromagnetic shielding composite materials are insufficient to meet the electromagnetic shielding requirements for low-frequency magnetic fields.

[0003] Improving the eddy current loss of electromagnetic shielding fillers is key to enhancing their low-frequency magnetic shielding effectiveness. In recent years, many studies and inventions have improved the eddy current loss of electromagnetic shielding fillers by combining magnetically conductive and electrically conductive materials. Existing technology discloses a silver-plated Fe3O4 powder. However, this powder has low permeability, and Fe3O4 itself is not conductive, making it difficult to form a conductive path with the silver shell and thus enhance eddy current loss. Existing technology also discloses electromagnetic shielding fillers composed of nickel and expanded graphite, which exhibit high shielding effectiveness in the 300kHz-1.5MHz range. However, the limited permeability and conductivity of nickel and expanded graphite restrict further improvement in their electromagnetic shielding effectiveness. Therefore, there is an urgent need to develop an electromagnetically composite electromagnetic shielding filler that can achieve good low-frequency magnetic field shielding. Summary of the Invention

[0004] To address the shortcomings of the aforementioned background technology, this invention primarily solves the problem of difficulty in controlling the preparation and oxidation degree of silver-coated magnetic metal powder used for broadband electromagnetic shielding in existing technologies. This invention provides a silver-coated magnetic metal filler with magnetic field shielding effectiveness, its preparation method, and its application. This method utilizes a displacement reaction to uniformly activate the surface of the magnetic metal, further achieving uniform silver coating. Silver and magnetic metals have excellent electrical conductivity; the prepared silver-coated magnetic metal can form a good conductive network, and the magnetic core can improve the material's permeability, thereby increasing the eddy current loss of the electromagnetic shielding filler and ultimately achieving high shielding effectiveness under low-frequency magnetic fields.

[0005] The first objective of this invention is to provide a method for preparing a silver-coated magnetic metal filler with magnetic field shielding effectiveness, comprising the following steps:

[0006] The magnetic metal powder is acid-washed to obtain acidified magnetic metal powder;

[0007] The acidified magnetic metal powder was added to a silver nitrate solution, and then grease was added. After stirring and reacting, activated magnetic metal powder was obtained.

[0008] The activated magnetic metal powder, reducing solution and silver ammonia solution are mixed evenly, and then oil is added. After stirring and reacting, silver-coated magnetic metal filler with magnetic field shielding effect is obtained.

[0009] The reducing solution is prepared from a certain amount of dispersant, reducing agent and deionized water.

[0010] Preferably, the magnetic metal powder is one or more of the following: iron-silicon-aluminum alloy, iron-silicon-chromium alloy, iron-silicon alloy, carbonyl iron, carbonyl nickel, iron-aluminum-boron alloy, iron-boron-phosphorus alloy, iron-nickel-molybdenum alloy, iron-chromium-nickel alloy, iron-nickel alloy, iron-cobalt-chromium alloy, and iron-cobalt-nickel-chromium alloy.

[0011] The magnetic metal powder has a spherical or flake-like morphology and a particle size of 4~42μm.

[0012] Preferably, the silver nitrate solution is prepared by dissolving silver nitrate in an aqueous solvent;

[0013] The concentration of the silver nitrate solution is 0.5~10 g / L;

[0014] The mass ratio of the acidified magnetic metal powder to silver nitrate is 10:0.1~3.

[0015] Preferably, the activated magnetic metal powder is prepared at a reaction temperature of 30-45°C for a reaction time of 0.5-3 hours.

[0016] Preferably, the oil is one or more of cocoa butter, coconut oil, kerosene, and paraffin oil.

[0017] Preferably, the dispersant is one or more of gelatin, polymethylpyrrolidone, OP-10, and sodium dodecylbenzenesulfonate; the reducing agent is one or more of glucose, formaldehyde solution, hydrazine hydrate, and potassium sodium tartrate.

[0018] Preferably, the silver ammonia solution is prepared by dispersing silver nitrate and ammonia in an aqueous solvent, wherein the concentration of the silver ammonia solution is 0.5~20 g / L, and the molar ratio of silver nitrate to ammonia in the silver ammonia solution is 1:1.05~2.

[0019] Preferably, when the magnetic metal powder is acid-washed, the process includes:

[0020] Mix the magnetic metal powder with dilute sulfuric acid and stir for 2-6 minutes. Then, use a magnet to adsorb the magnetic metal powder to the bottom of the container and pour off the supernatant. Wash the precipitate with deionized water until the pH of the supernatant is 6.5-7.5.

[0021] The concentration of the dilute sulfuric acid is 4-6 wt%.

[0022] The second objective of this invention is to provide a silver-clad magnetic metal filler with magnetic field shielding effectiveness.

[0023] The third objective of this invention is to provide an application of silver-clad magnetic metal filler with magnetic field shielding effectiveness in electromagnetic shielding.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] This invention provides a silver-coated magnetic metal filler with magnetic field shielding effectiveness, its preparation method, and its application. Targeting the chemical properties of magnetic metals, this invention utilizes a displacement reaction to uniformly activate the surface of the magnetic metal, further achieving uniform silver coating. Silver and magnetic metals have excellent electrical conductivity, allowing the prepared silver-coated magnetic metal to form a good conductive network. The magnetic core enhances the material's permeability, thereby improving the eddy current loss of the electromagnetic shielding filler and ultimately achieving high shielding effectiveness under low-frequency magnetic fields. The use of lightweight, inert grease avoids oxidation during the magnetic metal displacement activation or chemical silver plating process, significantly enhancing the electromagnetic exchange between the magnetic core and the conductive shell, further improving its shielding effectiveness. Attached Figure Description

[0026] Figure 1 The images show the time and photographs at which a large number of bubbles appeared in each of the embodiments and comparative samples.

[0027] Figure 2 The surface conductivity of Examples 1-2 and Comparative Examples 1-2 is given. Detailed Implementation

[0028] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0029] The purpose of this invention is to provide an electromagnetically composite electromagnetic shielding filler that can achieve good low-frequency magnetic field shielding.

[0030] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a silver-clad magnetic metal filler with magnetic field shielding effectiveness, comprising the following steps:

[0031] The magnetic metal powder is acid-washed to obtain acidified magnetic metal powder;

[0032] The acidified magnetic metal powder was added to a silver nitrate solution, and then grease was added. After stirring and reacting, activated magnetic metal powder was obtained.

[0033] The activated magnetic metal powder, reducing solution and silver ammonia solution are mixed evenly, and then oil is added. After stirring and reacting, silver-coated magnetic metal filler with magnetic field shielding effect is obtained.

[0034] The reducing solution is prepared from a certain amount of dispersant, reducing agent and deionized water.

[0035] This invention is based on the fact that the original magnetic metal powder has an oxide layer on its surface. This oxide layer affects the adhesion of subsequent plating layers and weakens the electromagnetic coupling between the magnetic core and the shell. The oxide layer on the surface of the magnetic metal powder can be effectively removed by acid washing. Silver nitrate will undergo a displacement reaction with the acidified magnetic metal powder to generate several to tens of nanometer-sized silver clusters or silver particles on the surface of the magnetic metal, so that the silver layer in the subsequent chemical plating process can be placed on its surface. Finally, through chemical plating, the silver nanoshell is prepared in situ on the surface of the magnetic metal by utilizing the reduction reaction between silver ammonia solution and reducing solution, thereby obtaining silver-coated magnetic metal powder.

[0036] The magnetic metal powder is one or more of the following: iron-silicon-aluminum alloy, iron-silicon-chromium alloy, iron-silicon alloy, carbonyl iron, carbonyl nickel, iron-aluminum-boron alloy, iron-boron-phosphorus alloy, iron-nickel-molybdenum alloy, iron-chromium-nickel alloy, iron-nickel alloy, iron-cobalt-chromium alloy, and iron-cobalt-nickel-chromium alloy.

[0037] The magnetic metal powder has a spherical or flake-like morphology and a particle size of 4~42μm.

[0038] The silver nitrate solution is prepared by dissolving silver nitrate in an aqueous solvent.

[0039] The concentration of the silver nitrate solution is 0.5~10 g / L;

[0040] The mass ratio of the acidified magnetic metal powder to silver nitrate is 10:0.1~3.

[0041] During the preparation of the activated magnetic metal powder, the reaction temperature is 30~45℃ and the reaction time is 0.5~3h.

[0042] The oil is one or more of cocoa butter, coconut oil, kerosene, and paraffin oil.

[0043] The dispersant is one or more of gelatin, polymethylpyrrolidone, OP-10, and sodium dodecylbenzenesulfonate; the reducing agent is one or more of glucose, formaldehyde solution, hydrazine hydrate, and sodium potassium tartrate.

[0044] The silver ammonia solution is prepared by dispersing silver nitrate and ammonia in an aqueous solvent, wherein the concentration of the silver ammonia solution is 0.5~20 g / L, and the molar ratio of silver nitrate to ammonia in the silver ammonia solution is 1:1.05~2.

[0045] When magnetic metal powder is acid-washed, the following steps are included:

[0046] Mix the magnetic metal powder with dilute sulfuric acid and stir for 2-6 minutes. Then, use a magnet to adsorb the magnetic metal powder to the bottom of the container and pour off the supernatant. Wash the precipitate with deionized water until the pH of the supernatant is 6.5-7.5.

[0047] The concentration of the dilute sulfuric acid is 4-6 wt%.

[0048] In one embodiment, a method for preparing a silver-coated magnetic metal filler with magnetic field shielding effectiveness includes:

[0049] (1) Pickling: Mix magnetic metal powder with dilute sulfuric acid and stir continuously with a rotary stirrer. After stirring for a certain period of time, use a magnet to adsorb the magnetic metal powder to the bottom of the container and pour off the supernatant. Wash the precipitate with deionized water until the pH of the supernatant is 7.

[0050] (2) Displacement activation: Mix magnetic metal powder with a certain amount of silver nitrate solution and add a certain amount of oil. Stir the reaction at a certain temperature. After the reaction has been going on for a while, pour off the supernatant. In this step, the mass ratio of silver nitrate solution to oil is 5~20:1.

[0051] (3) Chemical silver plating: A certain amount of dispersant, reducing agent and deionized water are prepared into a reducing solution. Metal powder, reducing solution and silver ammonia solution are mixed in a certain way and a certain amount of grease is added. The mixture is stirred and reacted at a certain temperature. When there are no residual silver particles in the solution, it is filtered, washed and vacuum dried to obtain silver-coated magnetic metal filler. In this step, the mass ratio of silver ammonia solution to grease is 2.5~15:1.

[0052] The magnetic metal powder has a spherical or flake-like morphology, and the equivalent average particle size of the magnetic metal powder is 4~42μm.

[0053] The pickling time is 2-4 minutes. For magnetic metal powders that are high passivation alloys, the pickling time can be extended to 6 minutes.

[0054] In the displacement activation step, the mass ratio of magnetic metal powder to silver nitrate is 10:0.1~3, and the concentration of silver nitrate solution is 0.5~10g / L.

[0055] The displacement activation temperature is 30~45℃, and the reaction time is 0.5~3h.

[0056] The stirring speed in the displacement activation and chemical silver plating steps is 80~150 rpm.

[0057] The magnetic metal powder, reducing solution, and silver ammonia solution are mixed by dispersing the magnetic metal powder in the silver ammonia solution, and then adding or pouring the reducing solution into it.

[0058] Specifically, the magnetic metals used are iron-silicon-aluminum alloy, iron-silicon-chromium alloy, iron-silicon alloy, carbonyl iron, carbonyl nickel, iron-nickel-molybdenum alloy, iron-chromium-nickel alloy, iron-nickel alloy, iron-cobalt-chromium alloy, and iron-cobalt-nickel-chromium alloy, all of which are products of Ganzhou Blue Ocean New Materials Co., Ltd.

[0059] Silver nitrate is a transparent crystalline powder, and the product used is from Shanghai Husheng Laboratory Equipment Co., Ltd.

[0060] The dispersant is one or more of gelatin, PVP, OP-10, and SDBS, wherein gelatin is a white powder, PVP is a fine white powder, OP-10 is a white and milky white paste, and SDBS is a pale yellow powder, all of which are products of Shanghai Roche Pharmaceuticals Co., Ltd.

[0061] The oil is one of cocoa butter, coconut oil, kerosene, or paraffin oil. Cocoa butter is a pale yellow, viscous liquid, coconut oil is a white, viscous liquid, kerosene is a pale yellow, oily liquid, and paraffin oil is a pale yellow, oily liquid. All of these are produced using Jiangsu Saipahan Energy Technology.

[0062] The reducing agents are glucose, formaldehyde solution, hydrazine hydrate, and potassium sodium tartrate. Glucose is a white powder, one or more of these, the formaldehyde solution has a concentration of 50 wt.%, is a colorless solution with a pungent odor, hydrazine hydrate is a colorless fuming liquid, and potassium sodium tartrate is a transparent crystalline powder. All of these are products of Sinopharm Chemical Reagent Co., Ltd.

[0063] A second aspect of the present invention provides a silver-clad magnetic metal filler with magnetic field shielding effectiveness.

[0064] The third aspect of this invention provides the application of a silver-clad magnetic metal filler with magnetic field shielding effectiveness in electromagnetic shielding.

[0065] It should be noted that, unless otherwise specified, the experimental methods used in this invention are all conventional methods; and the reagents and materials used, unless otherwise specified, are all commercially available.

[0066] Example 1

[0067] Add 200 mL of 5 wt% dilute sulfuric acid to 10 g of nickel carbonyl powder, stir mechanically for 8 min, after acidification, pour in a large amount of deionized water to dilute to pH=7 neutral, filter to obtain acidified nickel carbonyl powder;

[0068] Weigh 1g AgNO3 and dissolve it in 150mL of water, then add 1g PVP and the obtained acidified nickel carbonyl powder. After dispersing all the reactants evenly, pour in 20g kerosene and mechanically stir at 120rpm. The water bath temperature is 40℃ and the reaction is carried out for 30 minutes. After the displacement reaction is completed, pour off the upper turbid liquid to obtain the activated nickel carbonyl powder.

[0069] Weigh 6.35 g of glucose and dissolve it in 350 mL of deionized water, then add 1 g of PVP to obtain the reducing solution;

[0070] Weigh 6g of AgNO3 and dissolve it in 300mL of deionized water. Add ammonia water dropwise until the solution is clear to prepare a silver ammonia solution.

[0071] The activated carbonyl nickel powder was mixed with silver ammonia solution, and 20g of kerosene was added. The mixture was placed in a 40℃ water bath and mechanically stirred at 120rpm. The reducing solution was added dropwise to the reaction system at a rate of 100mL / h using a syringe pump. During the addition, the end of the delivery tube should be fixed below the grease layer. After the injection was completed, the reaction was allowed to continue for 30min. Then, the presence of silver particles in the supernatant was checked using sodium chloride solution. If any were found, the reaction was continued until the silver particles in the supernatant were completely reacted. The supernatant was then discarded, and the mixture was washed with deionized water until neutral. After vacuum drying, silver-coated nickel powder was obtained.

[0072] Example 2

[0073] Add 200 mL of 5 wt% dilute sulfuric acid to 10 g of iron-silicon-chromium powder and stir mechanically for 4 min. After acidification, dilute with a large amount of deionized water until neutral, filter, and obtain the acidified iron-silicon-chromium powder.

[0074] Weigh 0.8g AgNO3 and dissolve it in 120mL of water, then add 1g OP-10 and the obtained acidified iron-silicon-chromium powder. After dispersing all the reactants evenly, pour in 20g coconut oil and mechanically stir at 120rpm. The water bath temperature is 40℃, and the reaction is carried out for 40 minutes. After the displacement reaction is completed, the supernatant is discarded to obtain the activated iron-silicon-chromium powder.

[0075] Weigh 20 mL of formaldehyde solution and dissolve it in 300 mL of deionized water, then add 1 g of OP-10 to obtain the reducing solution;

[0076] Weigh 5g of AgNO3 and dissolve it in 260mL of deionized water. Add ammonia water dropwise until the solution is clear to prepare a silver ammonia solution.

[0077] The activated iron-silicon-chromium powder was mixed with silver ammonia solution, and 20g of kerosene was added. The mixture was placed in a 40℃ water bath and mechanically stirred at 120rpm. The reducing solution was added dropwise to the reaction system at a rate of 100mL / h using a syringe pump. During the addition, the end of the delivery tube should be fixed below the grease layer. After the injection was completed, the reaction was allowed to continue for 30min. Then, the presence of silver particles in the supernatant was checked using sodium chloride solution. If any were found, the reaction was continued until the silver particles in the supernatant were completely reacted. The supernatant was then discarded, and the mixture was washed with deionized water until neutral. After vacuum drying, the silver-coated iron-silicon-chromium powder was obtained.

[0078] Example 3

[0079] Add 200 mL of 5 wt% dilute sulfuric acid to 10 g of iron-silicon-aluminum powder and stir mechanically for 3 min. After acidification, dilute with a large amount of deionized water until neutral, filter, and obtain the acidified iron-silicon-aluminum powder.

[0080] Weigh 1.0g AgNO3 and dissolve it in 200mL of water. Then add 1g gelatin and the acidified iron-silicon-aluminum powder. After dispersing all the reactants evenly, pour in 20g cocoa butter and mechanically stir at 100rpm. The water bath temperature is 40℃ and the reaction is carried out for 40 minutes. After the displacement reaction is completed, pour off the upper turbid liquid to obtain the ignited iron-silicon-aluminum powder.

[0081] Weigh 7.5g of glucose and 0.75g of potassium sodium tartrate, dissolve them in 420mL of deionized water, and add 1g of gelatin to obtain a reducing solution;

[0082] Weigh 6g of AgNO3 and dissolve it in 340mL of deionized water. Add ammonia water dropwise until the solution is clear to prepare a silver ammonia solution.

[0083] The activated iron-silicon-aluminum powder was mixed with silver ammonia solution, and 20g of kerosene was added. The mixture was placed in a 40℃ water bath and mechanically stirred at 100rpm. The reducing solution was added dropwise to the reaction system at a rate of 100mL / h using a syringe pump. During the addition, the end of the delivery tube should be fixed below the grease layer. After the injection was completed, the reaction was allowed to continue for 30min. Then, the presence of silver particles in the supernatant was checked using sodium chloride solution. If any were found, the reaction was continued until the silver particles in the supernatant were completely reacted. The supernatant was then discarded, and the mixture was washed with deionized water until neutral. After vacuum drying, the silver-coated iron-silicon-aluminum powder was obtained.

[0084] Example 4

[0085] Add 200 mL of 5 wt% dilute sulfuric acid to 10 g of carbonyl iron powder and stir mechanically for 3 min. After acidification, dilute with a large amount of deionized water until neutral, filter, and obtain the acidified carbonyl iron powder.

[0086] Weigh 1.5g AgNO3 and dissolve it in 300mL of water. Then add 1g SDBS and the acidified carbonyl iron powder. After dispersing all the reactants evenly, pour in 20g cocoa butter and mechanically stir at 150rpm. The water bath temperature is 40℃ and the reaction is carried out for 40 minutes. After the displacement reaction is completed, pour off the upper turbid liquid to obtain the activated carbonyl iron powder.

[0087] Weigh 7.5g of glucose and 0.75g of potassium sodium tartrate, dissolve them in 420mL of deionized water, and add 1g of gelatin to obtain a reducing solution;

[0088] Weigh 6g of AgNO3 and dissolve it in 340mL of deionized water. Add ammonia water dropwise until the solution is clear to prepare a silver ammonia solution.

[0089] The activated carbonyl iron powder was mixed with silver ammonia solution, and 20g of kerosene was added. The mixture was placed in a 42℃ water bath and mechanically stirred at 150rpm. The reducing solution was added dropwise to the reaction system at a rate of 100mL / h using a syringe pump. During the addition, the end of the delivery tube should be fixed below the grease layer. After the injection was completed, the reaction was allowed to continue for 30min. Then, the presence of silver particles in the supernatant was checked using sodium chloride solution. If any were found, the reaction was continued until the silver particles in the supernatant were completely reacted. The supernatant was then discarded, and the mixture was washed with deionized water until neutral. After vacuum drying, silver-coated carbonyl iron powder was obtained.

[0090] Example 5

[0091] Add 200 mL of 5 wt% dilute sulfuric acid to 10 g of iron-nickel-molybdenum powder and stir mechanically for 6 min. After acidification, dilute with a large amount of deionized water until neutral, filter, and obtain the acidified iron-nickel-molybdenum powder.

[0092] Weigh 1.2g AgNO3 and dissolve it in 120mL of water. Then add 1g OP-10 and the obtained acidified carbonyl nickel powder. After dispersing all the reactants evenly, pour in 20g cocoa butter and mechanically stir at 150rpm. The water bath temperature is 42℃ and the reaction is carried out for 90 min. After the displacement reaction is completed, pour off the upper turbid liquid and obtain the activated iron-nickel-molybdenum powder.

[0093] Weigh 3g of hydrazine hydrate and dissolve it in 350mL of deionized water, then add 1g of OP-10 to obtain a reducing solution;

[0094] Weigh 5.4g of AgNO3 and dissolve it in 270mL of deionized water. Add ammonia water dropwise until the solution is clear to prepare a silver ammonia solution.

[0095] The activated iron-nickel-molybdenum powder was mixed with silver ammonia solution, and 20g of kerosene was added. The mixture was placed in a 42℃ water bath and mechanically stirred at 150rpm. The reducing solution was added dropwise to the reaction system at a rate of 100mL / h using a syringe pump. During the addition, the end of the delivery tube should be fixed below the grease layer. After the injection was completed, the reaction was allowed to continue for 30min. Then, the presence of silver particles in the supernatant was checked using sodium chloride solution. If any were found, the reaction was continued until the silver particles in the supernatant were completely reacted. The supernatant was then discarded, and the mixture was washed with deionized water until neutral. After vacuum drying, silver-coated iron-nickel-molybdenum powder was obtained.

[0096] Example 6

[0097] Add 200 mL of 5 wt% dilute sulfuric acid to 10 g of iron-silicon alloy powder and stir mechanically for 3 min. After acidification, dilute with a large amount of deionized water until neutral, filter, and obtain the acidified iron-silicon alloy powder.

[0098] Weigh 1g AgNO3 and dissolve it in 150mL of water. Then add 1g PVP and the acidified iron-silicon alloy powder. After dispersing all the reactants evenly, pour in 20g coconut oil and mechanically stir at 90rpm. The water bath temperature is 38℃. The reaction is carried out for 90 minutes. After the displacement reaction is completed, pour off the upper turbid liquid to obtain the activated iron-silicon alloy powder.

[0099] Weigh 9.53g of glucose and dissolve it in 350mL of deionized water, then add 1g of PVP to obtain the reducing solution;

[0100] Weigh 5g of AgNO3 and dissolve it in 300mL of deionized water. Add ammonia water dropwise until the solution is clear to prepare a silver ammonia solution.

[0101] The activated iron-silicon alloy powder was mixed with silver ammonia solution, and 20g of coconut oil was added. The mixture was placed in a 38℃ water bath and mechanically stirred at 90rpm. The reducing solution was added dropwise to the reaction system at a rate of 200mL / h using a syringe pump. During the addition, the end of the delivery tube should be fixed below the oil layer. After the injection was completed, the reaction was allowed to continue for 30min. Then, the presence of silver particles in the supernatant was checked using sodium chloride solution. If any were found, the reaction was continued until the silver particles in the supernatant were completely reacted. The supernatant was then discarded, and the mixture was washed with deionized water until neutral. After vacuum drying, the silver-coated iron-silicon alloy powder was obtained.

[0102] Example 7

[0103] Add 200 mL of 5 wt% dilute sulfuric acid to 10 g of iron-chromium-nickel alloy powder and stir mechanically for 6 min. After acidification, dilute with a large amount of deionized water until neutral, filter, and obtain the acidified iron-chromium-nickel alloy powder.

[0104] Weigh 1g AgNO3 and dissolve it in 150mL of water. Then add 1g PVP and the acidified iron-chromium-nickel alloy powder. After dispersing all the reactants evenly, pour in 20g coconut oil and mechanically stir at 90rpm. The water bath temperature is 38℃ and the reaction is carried out for 90 minutes. After the displacement reaction is completed, pour off the upper turbid liquid to obtain the activated iron-chromium-nickel alloy powder.

[0105] Weigh 9.53g of glucose and dissolve it in 350mL of deionized water, then add 1g of PVP to obtain the reducing solution;

[0106] Weigh 5g of AgNO3 and dissolve it in 300mL of deionized water. Add ammonia water dropwise until the solution is clear to prepare a silver ammonia solution.

[0107] The activated iron-chromium-nickel alloy powder was mixed with silver ammonia solution, and 20g of coconut oil was added. The mixture was placed in a 38℃ water bath and mechanically stirred at 90rpm. The reducing solution was added dropwise to the reaction system at a rate of 200mL / h using a syringe pump. During the addition, the end of the delivery tube should be fixed below the oil layer. After the injection was completed, the reaction was allowed to continue for 30min. Then, the presence of silver particles in the supernatant was checked using sodium chloride solution. If any were found, the reaction was continued until the silver particles in the supernatant were completely reacted. The supernatant was then discarded, and the mixture was washed with deionized water until neutral. After vacuum drying, the silver-coated iron-chromium-nickel alloy powder was obtained.

[0108] Example 8

[0109] Add 200 mL of 5 wt% dilute sulfuric acid to 10 g of iron-cobalt-chromium alloy powder and stir mechanically for 6 min. After acidification, dilute with a large amount of deionized water until neutral, filter, and obtain the acidified iron-cobalt-chromium alloy powder.

[0110] Weigh 1.2g AgNO3 and dissolve it in 210mL of water, then add 0.8g PVP and the obtained acidified iron-cobalt-chromium alloy powder. After dispersing all the reactants evenly, pour in 20g paraffin oil and mechanically stir at 110rpm. The water bath temperature is 40℃, and the reaction is carried out for 180 min. After the displacement reaction is completed, pour off the upper turbid liquid and the activated iron-cobalt-chromium alloy powder is obtained.

[0111] Weigh 7.62g of potassium sodium tartrate and dissolve it in 340mL of deionized water, then add 0.8g of PVP to obtain the reducing solution;

[0112] Weigh 5g of AgNO3 and dissolve it in 300mL of deionized water. Add ammonia water dropwise until the solution is clear to prepare a silver ammonia solution.

[0113] The activated iron-cobalt-chromium alloy powder was mixed with silver ammonia solution, and 20g of paraffin oil was added. The mixture was placed in a 40℃ water bath and mechanically stirred at 110rpm. Then, the reducing solution was poured in, and a funnel was used to guide the flow. The lower end of the funnel should be submerged below the oil layer. The reaction continued for 30 minutes. Then, sodium chloride solution was used to check whether there were any silver particles remaining in the supernatant. If so, the reaction continued until the silver particles in the supernatant were completely reacted. The supernatant was then discarded, and the mixture was washed with deionized water until neutral. After vacuum drying, the silver-coated iron-cobalt-chromium alloy powder was obtained.

[0114] Example 9

[0115] Add 200 mL of diluted sulfuric acid (7 wt%) to 10 g of iron-cobalt-nickel-chromium alloy powder and stir mechanically for 6 min. After acidification, dilute with a large amount of deionized water until neutral, filter, and obtain the acidified iron-cobalt-nickel-chromium alloy powder.

[0116] Weigh 1g AgNO3 and dissolve it in 150mL of water, then add 1.0g PVP and the obtained acidified iron-cobalt-nickel-chromium alloy powder. After dispersing all the reactants evenly, pour in 20g kerosene and mechanically stir at 130rpm. The water bath temperature is 40℃ and the reaction is carried out for 180 min. After the displacement reaction is completed, pour off the upper turbid liquid to obtain the activated iron-cobalt-nickel-chromium alloy powder.

[0117] Weigh 8.5g of glucose and dissolve it in 340mL of deionized water, then add 1.0g of PVP to obtain the reducing solution;

[0118] Weigh 6.35g of AgNO3 and dissolve it in 270mL of deionized water. Add ammonia water dropwise until the solution is clear to prepare a silver ammonia solution.

[0119] The activated iron-cobalt-nickel-chromium alloy powder was mixed with silver ammonia solution, and 20g of kerosene was added. The mixture was placed in a 40℃ water bath and mechanically stirred at 130rpm. Then, the reducing solution was poured in, and a funnel was used to guide the flow. The lower end of the funnel should be submerged below the grease layer. The reaction continued for 30 minutes. Then, sodium chloride solution was used to check whether there were silver particles remaining in the supernatant. If so, the reaction continued until the silver particles in the supernatant were completely reacted. The supernatant was then discarded, and the mixture was washed with deionized water until neutral. After vacuum drying, silver-coated iron-cobalt-nickel-chromium powder was obtained.

[0120] Example 10

[0121] Add 200 mL of 5 wt% dilute sulfuric acid to 10 g of iron-nickel alloy powder and stir mechanically for 6 min. After acidification, dilute with a large amount of deionized water until neutral, filter, and obtain the acidified iron-nickel alloy powder.

[0122] Weigh 0.5g AgNO3 and dissolve it in 150mL of water, then add 1.0g PVP and the obtained acidified iron-nickel alloy powder. After dispersing all the reactants evenly, pour in 20g paraffin oil and mechanically stir at 100rpm. The water bath temperature is 40℃ and the reaction is carried out for 120 min. After the displacement reaction is completed, pour off the upper turbid liquid to obtain the activated iron-nickel alloy powder.

[0123] Weigh 12.10g of glucose and dissolve it in 450mL of deionized water, then add 1.0g of PVP to obtain the reducing solution;

[0124] Weigh 5.8g of AgNO3 and dissolve it in 410mL of deionized water. Add ammonia water dropwise until the solution is clear to prepare a silver ammonia solution.

[0125] The activated iron-nickel alloy powder was mixed with silver ammonia solution, and 20g of paraffin oil was added. The mixture was placed in a 40℃ water bath and mechanically stirred at 100rpm. Then the reducing solution was poured in, and a funnel was used to guide the flow. The lower end of the funnel should be submerged below the oil layer. The reaction continued for 30 minutes. Then, sodium chloride solution was used to check whether there were silver particles remaining in the supernatant. If so, the reaction continued until the silver particles in the supernatant were completely reacted. The supernatant was then discarded, and the mixture was washed with deionized water until neutral. After vacuum drying, silver-coated iron-nickel alloy powder was obtained.

[0126] To illustrate the performance of the silver-coated magnetic metal powder, the silver-coated magnetic metal powder prepared in each embodiment was mixed with organosilicon resin to prepare a coating, and the corresponding coating was prepared using compressed air spraying technology. The specific method is as follows:

[0127] 70 parts of silver-coated magnetic metal powder, 25 parts of silicone resin, and 5 parts of polyamide curing agent were dispersed at 3000 rpm for 15 min using a stirring disperser. Then, a certain amount of xylene was added to adjust the viscosity of the coating to 20-25 mPa·s, and the mixture was stirred at 3000 rpm for another 15 min to obtain the electromagnetic shielding coating.

[0128] The silicone resin is a transparent, viscous liquid and is a product of Hubei Xin Sihai Chemical Co., Ltd.

[0129] The polyamide curing agent is a medium-viscosity brownish-yellow liquid, and is a product of Hubei Xin Sihai Chemical Co., Ltd.

[0130] The xylene is a colorless, transparent liquid with a distinctive aromatic hydrocarbon odor, and is a product of Nanjing Hecheng Chemical Co., Ltd.

[0131] Subsequently, an electromagnetic shielding coating with a thickness of 1 mm was prepared by compressed air spraying. The specific method is as follows: the coating was poured into a W-71 spray gun, the spraying pressure was adjusted to 0.5 MPa, the spraying distance was 15-20 cm, and the spray gun moving speed was 30-40 cm / s. The coating was sprayed evenly on the substrate surface in an S-shaped path. After each 0.1 mm coating was sprayed, the sample was dried at room temperature for 10-15 minutes. Then, the sample was placed in an oven and kept at 80°C for 12 hours to allow the coating on the substrate surface to cure. This preparation process was repeated until the thickness of the pre-formed layer reached 1.5 mm.

[0132] To further illustrate the protective effect of the lightweight inert grease layer on the magnetic core during the material preparation process, two comparative examples are used for demonstration.

[0133] Comparative Example 1

[0134] Comparative Example 1 was prepared using the same method as Example 1, but without the addition of a light, inert grease for protection. The specific preparation method is as follows: 200 mL of 5 wt% dilute sulfuric acid was added to 10 g of nickel carbonyl powder, and the mixture was mechanically stirred for 8 minutes. After acidification, a large amount of deionized water was added to dilute it to neutral, and the solution was filtered to obtain the acidified nickel carbonyl powder.

[0135] Weigh 1g AgNO3 and dissolve it in 150mL of water, then add 1g PVP and the obtained acidified nickel carbonyl powder. After dispersing all the reactants evenly, mechanically stir at 120rpm. The water bath temperature is 40℃ and the reaction is carried out for 30 min. After the displacement reaction is completed, the upper turbid liquid is poured off to obtain the activated nickel carbonyl powder.

[0136] Weigh 6.35 g of glucose and dissolve it in 350 mL of deionized water, then add 1 g of PVP to obtain the reducing solution;

[0137] Weigh 6g of AgNO3 and dissolve it in 300mL of deionized water. Add ammonia water dropwise until the solution is clear to prepare a silver ammonia solution.

[0138] The activated nickel carbonyl powder was mixed with silver ammonia solution and placed in a 40°C water bath with mechanical stirring at 120 rpm. The reducing solution was added dropwise to the reaction system at a rate of 100 mL / h using a syringe pump. During the dropwise addition, the end of the delivery tube should be fixed below the grease layer. After the injection was completed, the reaction was allowed to continue for 30 min. Then, the presence of silver particles in the supernatant was checked using sodium chloride solution. If any were found, the reaction was continued until the silver particles in the supernatant were completely reacted. The supernatant was then discarded, and the mixture was washed with deionized water until neutral. After vacuum drying, silver-coated nickel carbonyl powder was obtained. Subsequently, the silver-coated nickel carbonyl powder provided in Comparative Example 1 was used to prepare an electromagnetic shielding coating using the same preparation process as in Example 1.

[0139] Comparative Example 2

[0140] Comparative Example 2 was prepared using the same method as Example 2, but without the addition of a light, inert grease for protection. The specific preparation method is as follows: 200 mL of 5 wt% dilute sulfuric acid was added to 10 g of iron-silicon-chromium powder, and mechanically stirred for 4 min. After acidification, a large amount of deionized water was added to dilute to neutral, and the mixture was filtered to obtain the acidified iron-silicon-chromium powder.

[0141] Weigh 0.8g AgNO3 and dissolve it in 120mL of water. Then add 1g OP-10 and the acidified iron-silicon-chromium powder. After dispersing all the reactants evenly, pour in 20g coconut oil and mechanically stir at 120rpm. The water bath temperature is 40℃ and the reaction is carried out for 40 minutes. After the displacement reaction is completed, pour off the upper turbid liquid to obtain the activated iron-silicon-chromium powder.

[0142] Weigh 20 mL of formaldehyde solution and dissolve it in 300 mL of deionized water, then add 1 g of OP-10 to obtain the reducing solution;

[0143] Weigh 5g of AgNO3 and dissolve it in 260mL of deionized water. Add ammonia water dropwise until the solution is clear to prepare a silver ammonia solution.

[0144] The activated iron-silicon-chromium powder was mixed with silver ammonia solution and placed in a 40°C water bath with mechanical stirring at 120 rpm. The reducing solution was added dropwise to the reaction system at a rate of 100 mL / h using a syringe pump. During the dropwise addition, the end of the delivery tube should be fixed below the grease layer. After the injection was completed, the reaction was allowed to continue for 30 min. Then, the presence of silver particles in the supernatant was checked using sodium chloride solution. If any were found, the reaction was continued until the silver particles in the supernatant were completely reacted. The supernatant was then discarded, and the mixture was washed with deionized water until neutral. After vacuum drying, silver-coated iron-silicon-chromium powder was obtained. Subsequently, the silver-coated iron-silicon-chromium powder provided in Comparative Example 2 was used to prepare an electromagnetic shielding coating using the same preparation process as in Example 2.

[0145] To illustrate the shielding performance of the silver-clad magnetic metal coating prepared in the embodiments of the present invention, the magnetic shielding performance of the silver-clad magnetic metal coating was tested using a loop antenna and the shielding chamber method in accordance with GB / T 30142-2013 "Test Method for Shielding Effectiveness of Planar Electromagnetic Shielding Materials". The specific results are shown in Table 1 below.

[0146] Table 1. Magnetic shielding effectiveness of each embodiment in the 200kHz-30MHz range.

[0147]

[0148] As shown in Table 1, the silver-coated magnetic metal coating prepared in the embodiments of the present invention has excellent magnetic shielding effect on electromagnetic waves in the 200kHz-30MHz band, and its magnetic shielding effectiveness value is higher than 20dB, which meets the requirements for use of civilian electromagnetic shielding materials.

[0149] To further illustrate the protective effect of the lightweight inert grease layer on the magnetic core during material preparation in this invention, Examples 1-2 and Comparative Examples 1-2 were compared and analyzed. First, the oxidation degree of the silver-coated magnetic metal filler was determined using an acid washing method. The specific method is as follows: 2g of the prepared silver-coated metal filler was placed in a vial, followed by the addition of 20mL of dilute hydrochloric acid (pH=4), and a timer was started. The time it took for a large number of bubbles to appear in the mixture was recorded and photographed. The results are as follows. Figure 1 As shown. The hydrochloric acid solution first reacts with the oxide layer on the surface of the silver-clad metal filler to generate water and metal ions; no bubbles are produced in this process. Once the oxide layer is completely corroded by the hydrochloric acid solution, the internal metal undergoes a displacement reaction with the hydrochloric acid, generating bubbles. Therefore, the higher the degree of oxidation of the sample and the longer the oxide layer, the longer it takes for a large number of bubbles to appear in the hydrochloric acid solution. Figure 1 As shown, the bubble formation time in each comparative example was longer than that in the corresponding example, and most of the filler powder settled at the bottom of the bottle or remained suspended in the bottle, indicating that the reaction was slower and the degree of oxidation was higher.

[0150] Furthermore, the surface conductivity and magnetic shielding effectiveness of each embodiment are as follows: Figure 2 As shown in Table 2, it can be seen that due to the higher degree of oxidation in each comparative example, the contact resistance between the core and shell, and between particles, is higher, the conductivity is lower, the eddy current loss is weaker, and the magnetic shielding effectiveness is weaker. Therefore, it is evident that the silver-coated magnetic metal fillers prepared in this invention have a lower degree of oxidation, a tighter contact between the magnetic core and the conductive shell, and exhibit excellent magnetic shielding effectiveness.

[0151] Table 2. Magnetic shielding effectiveness of Examples 1-2 and Comparative Examples 1-2

[0152]

[0153] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for producing a silver-coated magnetic metal filler having a magnetic field shielding effect, characterized by, The method comprises the following steps: 200 mL of 5 wt% dilute sulfuric acid is added to 10 g of carbonyl nickel powder, mechanically stirred for 8 min, after acidification is completed, diluted to neutral pH by pouring into a large amount of deionized water, and the acidified carbonyl nickel powder is obtained after filtration; 1 g of AgNO3 is weighed and dissolved in 150 mL of water, then 1 g of PVP is added, and the obtained acidified carbonyl nickel powder is added, and after all the reactants are uniformly dispersed, 20 g of kerosene is poured in and mechanically stirred at a speed of 120 rpm, the temperature of the water bath is 40 DEG C, and the reaction is carried out for 30 min, after the displacement reaction is completed, the upper turbid liquid is poured out, and the activated carbonyl nickel powder is obtained; 6.35 g of glucose is weighed and dissolved in 350 mL of deionized water, and 1 g of PVP is added to obtain a reducing solution; 6 g of AgNO3 is weighed and dissolved in 300 mL of deionized water, and ammonia water is added dropwise until it is clear to prepare a silver amine solution; The activated carbonyl nickel powder is mixed with the silver amine solution, 20 g of kerosene is added, and the mixture is placed in a 40 DEG C water bath and mechanically stirred at a speed of 120 rpm; a syringe pump is used to add the reducing solution to the reaction system at a rate of 100 mL / h, and the end of the delivery tube is fixed below the oil layer during the addition; after the injection is completed, the reaction is continued for 30 min, then sodium chloride solution is used to detect whether there are silver particles remaining in the supernatant, if there are, the reaction is continued until the silver particles in the supernatant are completely reacted, the supernatant is poured out, and washed with deionized water until neutral, and then vacuum dried to obtain the silver-coated magnetic metal filler.

2. A method for producing a silver-coated magnetic metal filler having a magnetic field shielding effect, characterized by, The method comprises the following steps: 200 mL of 5 wt% dilute sulfuric acid is added to 10 g of carbonyl nickel powder, mechanically stirred for 8 min, after acidification is completed, diluted to neutral pH by pouring into a large amount of deionized water, and the acidified carbonyl nickel powder is obtained after filtration; 1 g of AgNO3 is weighed and dissolved in 150 mL of water, then 1 g of PVP is added, and the obtained acidified carbonyl nickel powder is added, and after all the reactants are uniformly dispersed, 20 g of kerosene is poured in and mechanically stirred at a speed of 120 rpm, the temperature of the water bath is 40 DEG C, and the reaction is carried out for 30 min, after the displacement reaction is completed, the upper turbid liquid is poured out, and the activated carbonyl nickel powder is obtained; 6.35 g of glucose is weighed and dissolved in 350 mL of deionized water, and 1 g of PVP is added to obtain a reducing solution; 6 g of AgNO3 is weighed and dissolved in 300 mL of deionized water, and ammonia water is added dropwise until it is clear to prepare a silver amine solution; The activated carbonyl nickel powder is mixed with the silver amine solution, 20 g of kerosene is added, and the mixture is placed in a 40 DEG C water bath and mechanically stirred at a speed of 120 rpm; a syringe pump is used to add the reducing solution to the reaction system at a rate of 100 mL / h, and the end of the delivery tube is fixed below the oil layer during the addition; after the injection is completed, the reaction is continued for 30 min, then sodium chloride solution is used to detect whether there are silver particles remaining in the supernatant, if there are, the reaction is continued until the silver particles in the supernatant are completely reacted, the supernatant is poured out, and washed with deionized water until neutral, and then vacuum dried to obtain the silver-coated magnetic metal filler.

3. A method for producing a silver-coated magnetic metal filler having a magnetic field shielding effect, characterized by, The method comprises the following steps: Take 200 mL of 5 wt% dilute sulfuric acid into 10 g of iron silicon aluminum powder, mechanically stir for 3 min, after acidification is completed, pour into a large amount of deionized water to dilute to neutral, after filtration, the acidified iron silicon aluminum powder is obtained; Take 1.0 g of AgNO3 and dissolve in 200 mL of water, then add 1 g of gelatin, and add the obtained acidified iron silicon aluminum powder, after all the reactants are uniformly dispersed, pour into 20 g of cocoa oil and mechanically stir at a speed of 100 rpm, the temperature of the water bath is 40℃, react for 40 min, after the displacement reaction is completed, pour off the upper turbidity, and the activated iron silicon aluminum powder is obtained; Take 7.5 g of glucose, 0.75 g of potassium sodium tartrate and dissolve in 420 mL of deionized water, and add 1 g of gelatin to obtain a reducing solution; Take 6 g of AgNO3 and dissolve in 340 mL of deionized water, add ammonia water dropwise until clear, and prepare a silver amine solution; Mix the activated iron silicon aluminum powder with the silver amine solution, add 20 g of kerosene, and place it in a 40℃ water bath and mechanically stir at a speed of 100 rpm; use a syringe pump to add the reducing solution to the reaction system at a rate of 100 mL / h, and fix the end of the delivery tube below the oil layer during the dropwise addition; after the injection is completed, continue the reaction for 30 min, then use a sodium chloride solution to detect whether there are silver particles remaining in the supernatant, if there are, continue the reaction until the silver particles in the supernatant are completely reacted, pour off the supernatant, and wash with deionized water until neutral, and then vacuum dry to obtain the silver-coated magnetic metal filler.

4. A method for producing a silver-coated magnetic metal filler having a magnetic field shielding effect, characterized by, The steps include: Take 200 mL of 5 wt% dilute sulfuric acid into 10 g of iron silicon aluminum powder, mechanically stir for 3 min, after acidification is completed, pour into a large amount of deionized water to dilute to neutral, after filtration, the acidified iron silicon aluminum powder is obtained; Take 1.0 g of AgNO3 and dissolve in 200 mL of water, then add 1 g of gelatin, and add the obtained acidified iron silicon aluminum powder, after all the reactants are uniformly dispersed, pour into 20 g of cocoa oil and mechanically stir at a speed of 100 rpm, the temperature of the water bath is 40℃, react for 40 min, after the displacement reaction is completed, pour off the upper turbidity, and the activated iron silicon aluminum powder is obtained; Take 7.5 g of glucose, 0.75 g of potassium sodium tartrate and dissolve in 420 mL of deionized water, and add 1 g of gelatin to obtain a reducing solution; Take 6 g of AgNO3 and dissolve in 340 mL of deionized water, add ammonia water dropwise until clear, and prepare a silver amine solution; Mix the activated iron silicon aluminum powder with the silver amine solution, add 20 g of kerosene, and place it in a 40℃ water bath and mechanically stir at a speed of 100 rpm; use a syringe pump to add the reducing solution to the reaction system at a rate of 100 mL / h, and fix the end of the delivery tube below the oil layer during the dropwise addition; after the injection is completed, continue the reaction for 30 min, then use a sodium chloride solution to detect whether there are silver particles remaining in the supernatant, if there are, continue the reaction until the silver particles in the supernatant are completely reacted, pour off the supernatant, and wash with deionized water until neutral, and then vacuum dry to obtain the silver-coated magnetic metal filler.

5. A method for producing a silver-coated magnetic metal filler having a magnetic field shielding effect, characterized by, The steps include: Take 200 mL of 5 wt% dilute sulfuric acid into 10 g of iron-chromium-nickel alloy powder, mechanically stir for 6 min, after acidification is completed, pour into a large amount of deionized water to dilute to neutral, after filtration, the acidified iron-chromium-nickel alloy powder is obtained; Take 1 g of AgNO3 and dissolve it in 150 mL of water, then add 1 g of PVP, and add the obtained acidified iron-chromium-nickel alloy powder, after all the reactants are uniformly dispersed, pour into 20 g of coconut oil and mechanically stir at a speed of 90 rpm, the temperature of the water bath is 38℃, and the reaction is carried out for 90 min, after the displacement reaction is completed, the upper turbidity is poured out, and the activated iron-chromium-nickel alloy powder is obtained; Take 9.53 g of glucose and dissolve it in 350 mL of deionized water, and add 1 g of PVP to obtain a reducing solution; Take 5 g of AgNO3 and dissolve it in 300 mL of deionized water, add ammonia water dropwise until it is clear, and prepare a silver-ammonia solution; Mix the activated iron-chromium-nickel alloy powder with the silver-ammonia solution, add 20 g of coconut oil, and place it in a 38℃ water bath and mechanically stir at a speed of 90 rpm; use a syringe pump to add the reducing solution to the reaction system at a rate of 200 mL / h, and fix the end of the delivery tube below the oil layer during the dropwise addition; after the injection is completed, continue the reaction for 30 min, then use a sodium chloride solution to detect whether there are silver particles remaining in the supernatant, if there are, continue the reaction until the silver particles in the supernatant are completely reacted, pour out the supernatant, and wash with deionized water until neutral, and then vacuum dry to obtain silver-coated magnetic metal fillers.

6. A method for producing a silver-coated magnetic metal filler having a magnetic field shielding effect, characterized by, The steps include: Take 200 mL of 5 wt% dilute sulfuric acid into 10 g of iron-chromium-nickel alloy powder, mechanically stir for 6 min, after acidification is completed, pour into a large amount of deionized water to dilute to neutral, after filtration, the acidified iron-chromium-nickel alloy powder is obtained; Take 1.2 g of AgNO3 and dissolve it in 210 mL of water, then add 0.8 g of PVP, and add the obtained acidified iron-chromium-nickel alloy powder, after all the reactants are uniformly dispersed, pour into 20 g of coconut oil and mechanically stir at a speed of 90 rpm, the temperature of the water bath is 38℃, and the reaction is carried out for 90 min, after the displacement reaction is completed, the upper turbidity is poured out, and the activated iron-chromium-nickel alloy powder is obtained; Take 9.53 g of glucose and dissolve it in 350 mL of deionized water, and add 1 g of PVP to obtain a reducing solution; Take 5 g of AgNO3 and dissolve it in 300 mL of deionized water, add ammonia water dropwise until it is clear, and prepare a silver-ammonia solution; Mix the activated iron-chromium-nickel alloy powder with the silver-ammonia solution, add 20 g of coconut oil, and place it in a 38℃ water bath and mechanically stir at a speed of 90 rpm; use a syringe pump to add the reducing solution to the reaction system at a rate of 200 mL / h, and fix the end of the delivery tube below the oil layer during the dropwise addition; after the injection is completed, continue the reaction for 30 min, then use a sodium chloride solution to detect whether there are silver particles remaining in the supernatant, if there are, continue the reaction until the silver particles in the supernatant are completely reacted, pour out the supernatant, and wash with deionized water until neutral, and then vacuum dry to obtain silver-coated magnetic metal fillers.

7. A method for producing a silver-coated magnetic metal filler having a magnetic field shielding effect, characterized by, The steps include: Take 200 mL of 5 wt% dilute sulfuric acid into 10 g of iron-chromium-nickel alloy powder, mechanically stir for 6 min, after acidification is completed, pour into a large amount of deionized water to dilute to neutral, after filtration, the acidified iron-chromium-nickel alloy powder is obtained; Take 1.2 g of AgNO3 and dissolve it in 210 mL of water, then add 0.8 g of PVP, and add the obtained acidified iron-chromium-nickel alloy powder, after all the reactants are uniformly dispersed, pour into 20 g of coconut oil and mechanically stir at a speed of 90 rpm, the temperature of the water bath is 38℃, and the reaction is carried out for 90 min, after the displacement reaction is completed, the upper turbidity is poured out, and the activated iron-chromium-nickel alloy powder is obtained; Take 9.53 g of glucose and dissolve it in 350 mL of deionized water, and add 1 g of PVP to obtain a reducing solution; Take 5 g of AgNO3 and dissolve it in 300 mL of deionized water, add ammonia water dropwise until it is clear, and prepare a silver-ammonia solution; Mix the activated iron-chromium-nickel alloy powder with the silver-ammonia solution, add 20 g of coconut oil, and place it in a 38℃ water bath and mechanically stir at a speed of 90 rpm; use a syringe pump to add the reducing solution to the reaction system at a rate of 200 mL / h, and fix the end of the delivery tube below the oil layer during the dropwise addition; after the injection is completed, continue the reaction for 30 min, then use a sodium chloride solution to detect whether there are silver particles remaining in the supernatant, if there are, continue the reaction until the silver particles in the supernatant are completely reacted, pour out the supernatant, and wash with deionized water until neutral, and then vacuum dry to obtain silver-coated magnetic metal fillers. The steps include: Put 200 mL of 7 wt% dilute sulfuric acid into 10 g of iron-cobalt-nickel-chromium alloy powder, mechanically stir for 6 min, after acidification is completed, pour into a large amount of deionized water to dilute to neutral, after filtration, obtain the acidified iron-cobalt-nickel-chromium alloy powder; Dissolve 1 g of AgNO3 in 150 mL of water, then add 1.0 g of PVP, and add the obtained acidified iron-cobalt-nickel-chromium alloy powder, after all the reactants are uniformly dispersed, pour into 20 g of kerosene and mechanically stir at a speed of 130 rpm, the temperature of the water bath is 40℃, react for 180 min, after the displacement reaction is completed, pour off the upper turbid liquid, obtain the activated iron-cobalt-nickel-chromium alloy powder; Dissolve 8.5 g of glucose in 340 mL of deionized water, and add 1.0 g of PVP to obtain a reducing solution; Dissolve 6.35 g of AgNO3 in 270 mL of deionized water, add ammonia water dropwise until clear, prepare a silver-ammonia solution; Mix the activated iron-cobalt-nickel-chromium alloy powder with the silver-ammonia solution, add 20 g of kerosene, and place it in a 40℃ water bath and mechanically stir at a speed of 130 rpm; then pour the reducing solution into it, use a funnel to guide the flow when pouring, the lower end of the funnel is immersed below the oil layer, continue to react for 30 min, then use a sodium chloride solution to detect whether there are silver particles remaining in the supernatant, if there are, continue to react until the silver particles in the supernatant are completely reacted, pour off the supernatant, and wash with deionized water until neutral, then vacuum dry to obtain the silver-coated magnetic metal filler.

8. A method for producing a silver-coated magnetic metal filler having a magnetic field shielding effect, characterized by, Comprise the following steps: Put 200 mL of 5 wt% dilute sulfuric acid into 10 g of iron-nickel alloy powder, mechanically stir for 6 min, after acidification is completed, pour into a large amount of deionized water to dilute to neutral, after filtration, obtain the acidified iron-nickel alloy powder; Dissolve 0.5 g of AgNO3 in 150 mL of water, then add 1.0 g of PVP, and add the obtained acidified iron-nickel alloy powder, after all the reactants are uniformly dispersed, pour into 20 g of paraffin oil and mechanically stir at a speed of 100 rpm, the temperature of the water bath is 40℃, react for 120 min, after the displacement reaction is completed, pour off the upper turbid liquid, obtain the activated iron-nickel alloy powder; Dissolve 12.10 g of glucose in 450 mL of deionized water, and add 1.0 g of PVP to obtain a reducing solution; Dissolve 5.8 g of AgNO3 in 410 mL of deionized water, add ammonia water dropwise until clear, prepare a silver-ammonia solution; Mix the activated iron-nickel alloy powder with the silver-ammonia solution, add 20 g of paraffin oil, and place it in a 40℃ water bath and mechanically stir at a speed of 100 rpm; then pour the reducing solution into it, use a funnel to guide the flow when pouring, the lower end of the funnel is immersed below the oil layer, continue to react for 30 min, then use a sodium chloride solution to detect whether there are silver particles remaining in the supernatant, if there are, continue to react until the silver particles in the supernatant are completely reacted, pour off the supernatant, and wash with deionized water until neutral, then vacuum dry to obtain the silver-coated magnetic metal filler.

9. A silver-coated magnetic metal filler with magnetic field shielding efficiency prepared by the method of any one of claims 1-8.

10. Use of the silver-coated magnetic metal filler having magnetic field shielding effectiveness according to claim 9 in electromagnetic shielding.

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