High-temperature-resistant polyimide modified silver-plated aluminum powder as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of conductive filler, and particularly relates to high-temperature-resistant polyimide-modified silver-plated aluminum powder and a preparation method and application thereof.The preparation method comprises the steps that coupling modification treatment is conducted on aluminum powder, then polyimide coating modification treatment is conducted on the coupling-modified aluminum powder, and the high-temperature-resistant polyimide-modified silver-plated aluminum powder is obtained; and finally, carrying out chemical silver plating treatment on the polyimide coated and modified aluminum powder to obtain the silver-plated aluminum powder with stable high-temperature environment resistance. The surface of the aluminum powder is firstly coated with a layer of polyimide protective film, and then chemical silver plating is performed, so that the composite conductive powder which is light in weight, excellent in conductivity and stable in high-temperature environment resistance is obtained, the thermal stability of the silver-plated aluminum powder is greatly improved, and the problem that the existing silver-plated aluminum powder is unstable in performance in a high-temperature environment is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of conductive fillers, and in particular relates to a high-temperature resistant polyimide-modified silver-plated aluminum powder, a preparation method and an application thereof. Background Art

[0002] Silver-plated aluminum powder is a new type of conductive filler with excellent performance developed in recent years. The main base material of this product is spherical aluminum powder. A silver layer is evenly plated on the surface of the aluminum powder, which makes the product light, conductive and high in strength. After special treatment, it is very easy to disperse in organic materials such as resin and rubber.

[0003] With the vigorous development of electromagnetic shielding materials, the requirements for the environmental adaptability of materials are getting higher and higher. The existing silver-plated aluminum powder has poor high-temperature resistance due to the active nature of aluminum itself. Even after the surface is coated with a silver layer, the high-temperature resistance is still not ideal, which greatly shortens the service life of the silver-plated aluminum powder in a high-temperature environment, limiting its use.

[0004] In view of this, the present inventor provides a high temperature resistant polyimide modified silver-plated aluminum powder and a preparation method and application thereof to solve the above technical problems. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art, and propose a high-temperature resistant polyimide-modified silver-plated aluminum powder and its preparation method and application, and select polyimide to coat the modified aluminum powder for modification, and then chemically silver-plated to provide good conductivity for the coated modified aluminum powder, thereby ensuring that the silver-plated aluminum powder with stable performance in high-temperature environment is obtained.

[0006] Polyimide (Pl) is a polymer material with excellent thermal stability and mechanical properties. Polyimide can maintain its physical and chemical properties over a wide temperature range. It can usually be used for a long time at a temperature of 250°C to 400°C, and can even withstand higher temperatures in the short term. Even in high temperature environments, polyimide can maintain high strength and toughness. It has good resistance to most solvents, acids and alkalis, which can make it more stable during chemical silver plating.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] On the one hand, the present invention provides a method for preparing high-temperature resistant polyimide-modified silver-plated aluminum powder, comprising first performing coupling modification treatment on the aluminum powder, then performing polyimide coating modification treatment on the coupling-modified aluminum powder, and finally performing chemical silver plating treatment on the polyimide-coated modified aluminum powder to obtain silver-plated aluminum powder with stable high-temperature environment resistance performance.

[0009] Further, the process of the coupling modification treatment is as follows:

[0010] A silane coupling agent is weighed and added to an ethanol aqueous solution for hydrolysis to obtain a silane coupling agent solution, and then aluminum powder is added to the silane coupling agent solution for coupling modification. After the reaction is completed, the powder is separated by suction filtration and dried to obtain coupling-modified aluminum powder.

[0011] Furthermore, the mass ratio of the silane coupling agent to the ethanol aqueous solution is 1 to 5:100;

[0012] The volume ratio of ethanol to water in the ethanol aqueous solution is 90:5-10;

[0013] The ratio of the aluminum powder to the silane coupling agent solution is 5g-10g:100ml;

[0014] The hydrolysis process is carried out by mechanical stirring at a rate of 100 to 200 r / min, a time of 5 to 10 min, and a temperature of 20 to 30° C.

[0015] The coupling modification process is set at a temperature of 20°C to 30°C and a time of 1h to 2h;

[0016] During the drying process, the drying temperature is set at 80° C. to 120° C. and the drying time is set at 4 h to 8 h.

[0017] Furthermore, the silane coupling agent is an aminosilane coupling agent.

[0018] Optionally, the aminosilane coupling agent is any one of N-(2-aminoethyl) 3-aminopropyltrimethoxysilane, Y-aminopropyltrimethoxysilane, and 3-aminopropyltrihexyloxysilane.

[0019] Furthermore, the process of the polyimide coating modification treatment is as follows:

[0020] (1) Weighing a diamine compound and adding it to a solvent, stirring it once to fully dissolve it, then adding the coupling-modified aluminum powder and stirring it twice, and then adding a dianhydride compound and stirring it three times after mixing it evenly to obtain a precursor mixed solution, and stirring the precursor mixed solution for 3 hours to 6 hours;

[0021] (2) The precursor mixture after stirring is filtered and dried, and then calcined in sequence according to the temperature curve of 100℃ / 1h, 150℃ / 1h, 200℃ / 1h, 250℃ / 1h, and 300℃ / 1h to obtain polyimide-coated modified aluminum powder. Specifically, the use of progressive graded heat treatment can ensure uniform conversion and performance optimization of the material, promote gradual imidization, prevent excessive temperature from causing violent reactions, side reactions or incomplete conversion; and under this temperature curve, it can reduce internal stress, control the release of volatiles, and greatly improve the thermal stability and mechanical properties of the polyimide coating.

[0022] Furthermore, in step (1), the mass ratio of the diamine compound to the solvent is 1:10 to 20;

[0023] The mass ratio of the dianhydride compound to the diamine compound is 1:1-2.

[0024] Specifically, the dianhydride compound and the diamine compound are used as raw materials for synthesizing polyimide. After being dissolved in a set amount of solvent, a uniform polyimide intermediate is formed on the surface of the aluminum powder by controlling the condensation reaction of the dianhydride compound and the diamine compound, and then a uniform polyimide coating layer is formed by heat treatment, curing and imidization. The usage ratio of the coupled modified aluminum powder and the precursor mixed solution is 5g-10g:200ml;

[0025] Furthermore, in step (1), the diamine compound is any one of p-phenylenediamine, tetrafluoro-phenylenediamine, and cyclohexanediamine;

[0026] The solvent is N,N-dimethylacetamide or N-methylpyrrolidone;

[0027] The dianhydride compound is any one of free biphenyl tetracarboxylic dianhydride, pyromellitic acid dianhydride and pyromellitic anhydride.

[0028] Further, in step (1), the first stirring is mechanical stirring, stirring at 10°C to 20°C for 1h to 2h, and the stirring speed is 100r / min to 200r / min; the second stirring is mechanical stirring, stirring at 10°C to 20°C for 10min to 30min, and the stirring speed is 100r / min to 200r / min; the third stirring is mechanical stirring, stirring at 10°C to 20°C for 4h to 8h, and the stirring speed is 100r / min to 200r / min;

[0029] In step (1), the whole process is carried out under nitrogen protection. Nitrogen protection can effectively prevent certain diamine compound monomers and polyamic acid, an intermediate of polyimide, from undergoing oxidation reaction with oxygen in the air, thereby affecting the purity performance of the final polyimide coating.

[0030] In step (2), the drying temperature is set to 80° C. to 120° C. and the drying time is set to 4 h to 8 h.

[0031] Further, the process of the chemical silver plating treatment is as follows:

[0032] (1) weighing a reducing agent, a surfactant, and a stabilizer in proportion and dissolving them in deionized water to prepare a reducing solution, and weighing a silver salt in proportion and dissolving it in deionized water to prepare a silver ammonia solution;

[0033] Wherein, the ratio of the reducing agent to deionized water is 8-10 g / L, the ratio of the surfactant to deionized water is 1.5-3 g / L, and the ratio of the stabilizer to deionized water is 40-60 g / L;

[0034] The ratio of the silver salt to deionized water is 10-15 g / L;

[0035] (2) adding the polyimide-coated modified aluminum powder to the reducing solution and stirring evenly, then adding the silver ammonia solution to obtain a mixed solution, heating the mixed solution in a water bath at 40°C to 55°C and stirring for 1.5h to 3h, washing with water to neutrality after the reaction is completed, and drying at 80°C to 120°C for 4h to 8h to obtain silver-plated aluminum powder with stable high temperature environment resistance.

[0036] Furthermore, the volume ratio of the reducing solution to the silver ammonia solution is 0.8 to 1.2:1.

[0037] Furthermore, the mass ratio of the silver element to the aluminum element is 15-40:100.

[0038] Optionally, the reducing agent is any one of formaldehyde, glucose, tartaric acid, and potassium sodium tartrate;

[0039] Optionally, the surfactant is polyethylene glycol, polyvinyl pyrrolidone, OP-10, sodium dodecylbenzene sulfonate or gelatin.

[0040] Optionally, the stabilizer is ethanol, methanol or ethylene glycol.

[0041] Preferably, the stabilizer is ethanol.

[0042] Furthermore, the silver salt is silver nitrate.

[0043] Specifically, the configuration method of the silver ammonia solution is as follows:

[0044] Take silver nitrate and dissolve it in deionized water. When it is completely dissolved, start adding concentrated ammonia water while stirring. The solution will become turbid at first. Continue adding. Stop adding when the solution becomes clear. You will get a silver ammonia solution.

[0045] On the other hand, the present invention provides a high temperature resistant polyimide modified silver-plated aluminum powder, which is prepared based on the preparation method described above.

[0046] In another aspect, the present invention provides a use of the high temperature resistant polyimide modified silver-plated aluminum powder as described above in electromagnetic shielding materials.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The present invention provides a method for preparing a high-temperature resistant polyimide-modified silver-plated aluminum powder, which first performs a coupling modification treatment on the aluminum powder so that the surface of the aluminum powder is conducive to combining with polyimide; then performs a polyimide coating modification treatment to give the aluminum powder excellent high-temperature resistance; and finally performs chemical silver plating to provide the aluminum powder with good electrical conductivity, thereby obtaining a composite conductive powder with light weight, excellent electrical conductivity, and stable high-temperature environment resistance. The present invention first coats a layer of polyimide protective film on the surface of the aluminum powder and then performs chemical silver plating, which can greatly improve the thermal stability of the silver-plated aluminum powder and solves the problem of unstable performance of the existing silver-plated aluminum powder in a high-temperature environment. DETAILED DESCRIPTION

[0049] Here, exemplary embodiments will be described in detail, and the embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are only examples consistent with some aspects of the present invention described in detail in the appended claims.

[0050] Example 1

[0051] On the one hand, this embodiment provides a method for preparing a high temperature resistant polyimide modified silver-plated aluminum powder, comprising the following steps:

[0052] Step 1, weighing Y-aminopropyltrimethoxysilane and adding it to an ethanol aqueous solution, using mechanical stirring, the stirring rate is 100r / min, the temperature is 20°C, and hydrolysis is performed for 5min to obtain a silane coupling agent solution;

[0053] The mass ratio of the Y-aminopropyltrimethoxysilane to the ethanol aqueous solution is 1:100, and the volume ratio of ethanol to water in the ethanol aqueous solution is 90:5;

[0054] Step 2, adding aluminum powder to the silane coupling agent solution obtained in step 1, the temperature is 20° C., and coupling modification is performed for 1 hour. After the reaction is completed, the powder is separated by suction filtration, and dried at 80° C. for 4 hours to obtain coupling-modified aluminum powder;

[0055] The ratio of the aluminum powder to the silane coupling agent solution is 5 g:100 ml;

[0056] Step 3, weigh p-phenylenediamine and add it to N, N-dimethylacetamide, use mechanical stirring, stir at 10°C for 2h, stirring speed is 100r / min, make it fully dissolved, then add the coupling modified aluminum powder obtained in step 2, stir at 10°C for 30min, stirring speed is 100r / min, mix well, then add free biphenyl tetracarboxylic dianhydride, stir at 10°C for 8h, stirring speed is 100r / min, mix well, obtain a precursor mixture, and stir the precursor mixture for 3h;

[0057] Wherein, in step 3, the whole process is carried out under nitrogen protection;

[0058] The mass ratio of p-phenylenediamine to N, N-dimethylacetamide is 1:10, the mass ratio of free biphenyl tetracarboxylic dianhydride to p-phenylenediamine is 1:1, and the ratio of the coupled modified aluminum powder to the precursor mixed solution is 5g:200ml;

[0059] Step 4, the precursor mixture after stirring is filtered to obtain powder, and dried at 80°C for 4 hours, and then calcined in sequence according to the temperature curve of 100°C / 1h, 150°C / 1h, 200°C / 1h, 250°C / 1h, and 300°C / 1h to obtain polyimide-coated modified aluminum powder;

[0060] Step 5, weighing formaldehyde, polyethylene glycol, and ethanol in proportion and dissolving them in deionized water to prepare a reducing solution, and weighing silver nitrate in proportion and dissolving it in deionized water to prepare a silver ammonia solution;

[0061] In this embodiment, the ratio of formaldehyde to deionized water is 8 g / L, the ratio of polyethylene glycol to deionized water is 1.5 g / L, the ratio of ethanol to deionized water is 40 g / L; the ratio of silver nitrate to deionized water is 10 g / L;

[0062] Step 6, adding the polyimide-coated modified aluminum powder obtained in step 4 to the reducing solution prepared in step 5, and stirring evenly, then adding the silver ammonia solution prepared in step 5 to obtain a mixed solution, heating the mixed solution in a water bath at 40° C. and stirring for 1.5 hours, washing with water to neutrality after the reaction is completed, and drying at 80° C. for 4 hours to obtain a silver-plated aluminum powder with stable high temperature environment performance;

[0063] The volume ratio of the reducing solution to the silver ammonia solution is 0.8:1, and the mass ratio of the silver element to the aluminum element is 15:100.

[0064] Among them, the configuration method of silver ammonia solution is as follows:

[0065] Take silver nitrate and dissolve it in deionized water. When it is completely dissolved, start adding concentrated ammonia water while stirring. The solution will become turbid at first. Continue adding. Stop adding when the solution becomes clear. You will get a silver ammonia solution.

[0066] On the other hand, this embodiment provides a high temperature resistant polyimide modified silver-plated aluminum powder, which is prepared by the preparation method as described above.

[0067] In another aspect, the present embodiment provides an application of the high temperature resistant polyimide modified silver-plated aluminum powder as described above in electromagnetic shielding materials.

[0068] Example 2

[0069] On the one hand, this embodiment provides a method for preparing a high temperature resistant polyimide modified silver-plated aluminum powder, comprising the following steps:

[0070] Step 1, weighing N-(2-aminoethyl) 3-aminopropyltrimethoxysilane and adding it to an ethanol aqueous solution, using mechanical stirring, the stirring rate is 150r / min, the temperature is 25°C, and hydrolysis is performed for 8min to obtain a silane coupling agent solution;

[0071] The mass ratio of N-(2-aminoethyl) 3-aminopropyltrimethoxysilane to the ethanol aqueous solution is 3:100, and the volume ratio of ethanol to water in the ethanol aqueous solution is 90:8.

[0072] Step 2: adding the silane coupling agent solution obtained in step 1 to the aluminum powder at a temperature of 25° C. for coupling modification for 1.5 hours. After the reaction is completed, the powder is separated by suction filtration and dried at 100° C. for 6 hours to obtain the coupled modified aluminum powder;

[0073] The ratio of the aluminum powder to the silane coupling agent solution is 8 g:100 ml;

[0074] Step 3, weigh tetrafluoro-phenylenediamine and add it to N-methylpyrrolidone, use mechanical stirring, stir at 15°C for 1.5 hours, stirring speed is 150r / min, make it fully dissolved, then add the coupling modified aluminum powder obtained in step 2, stir at 15°C for 15 minutes, stirring speed is 150r / min, mix well, then add pyromelitic dianhydride, stir at 15°C for 6 hours, stirring speed is 150r / min, mix well, obtain a precursor mixture, and stir the precursor mixture for 5 hours;

[0075] Wherein, in step 3, the whole process is carried out under nitrogen protection;

[0076] The mass ratio of tetrafluoro-phenylenediamine to N-methylpyrrolidone is 1:15, the mass ratio of pyromelitic acid dianhydride to tetrafluoro-phenylenediamine is 1:1.5, and the ratio of the coupled modified aluminum powder to the precursor mixed solution is 8g:200ml;

[0077] Step 4: Filter the precursor mixture after stirring to obtain powder, dry it at 100°C for 6 hours, and then calcine it according to the temperature curve of 100°C / 1h, 150°C / 1h, 200°C / 1h, 250°C / 1h, and 300°C / 1h to obtain polyimide-coated modified aluminum powder;

[0078] Step 5, weigh glucose, polyvinyl pyrrolidone, and methanol in proportion and dissolve them in deionized water to prepare a reducing solution, and weigh silver nitrate in proportion and dissolve it in deionized water to prepare a silver ammonia solution;

[0079] Among them, the ratio of glucose to deionized water is 9 g / L, the ratio of polyvinyl pyrrolidone to deionized water is 2.3 g / L, the ratio of methanol to deionized water is 50 g / L; the ratio of silver nitrate to deionized water is 13 g / L;

[0080] Step 6, adding the polyimide-coated modified aluminum powder obtained in step 4 to the reducing solution prepared in step 5, and stirring evenly, then adding the silver ammonia solution prepared in step 5 to obtain a mixed solution, heating the mixed solution in a water bath at 50° C. and stirring for 2 hours, washing with water to neutrality after the reaction is completed, and drying at 100° C. for 6 hours to obtain a silver-plated aluminum powder with stable high temperature environment performance;

[0081] The volume ratio of the reducing solution to the silver ammonia solution is 1:1, and the mass ratio of the silver element to the aluminum element is 25:100.

[0082] Among them, the configuration method of silver ammonia solution is as follows:

[0083] Take silver nitrate and dissolve it in deionized water. When it is completely dissolved, start adding concentrated ammonia water while stirring. The solution will become turbid at first. Continue adding. Stop adding when the solution becomes clear. You will get a silver ammonia solution.

[0084] On the other hand, this embodiment provides a high temperature resistant polyimide modified silver-plated aluminum powder, which is prepared by the preparation method as described above.

[0085] In another aspect, the present embodiment provides an application of the high temperature resistant polyimide modified silver-plated aluminum powder as described above in electromagnetic shielding materials.

[0086] Example 3

[0087] On the one hand, this embodiment provides a method for preparing a high temperature resistant polyimide modified silver-plated aluminum powder, comprising the following steps:

[0088] Step 1, weigh 3-aminopropyltrihexyloxysilane and add it to an ethanol aqueous solution, use mechanical stirring, the stirring rate is 200r / min, the temperature is 30°C, and hydrolysis is carried out for 10min to obtain a silane coupling agent solution;

[0089] The mass ratio of 3-aminopropyltrihexyloxysilane to the ethanol aqueous solution is 5:100, and the volume ratio of ethanol to water in the ethanol aqueous solution is 90:10.

[0090] Step 2: adding the silane coupling agent solution obtained in step 1 to the aluminum powder at a temperature of 30° C. for coupling modification for 2 h. After the reaction is completed, the powder is separated by suction filtration and dried at 120° C. for 8 h to obtain coupling-modified aluminum powder;

[0091] Wherein, the ratio of the aluminum powder to the silane coupling agent solution is 10g:100ml;

[0092] Step 3, weigh cyclohexanediamine and add it to N, N-dimethylacetamide, use mechanical stirring, stir at 20°C for 1h, stirring speed is 200r / min, make it fully dissolved, then add the coupling modified aluminum powder obtained in step 2, stir at 20°C for 10min, stirring speed is 200r / min, mix well, then add pyromellitic anhydride, stir at 20°C for 4h, stirring speed is 200r / min, mix well, obtain a precursor mixture, and stir the precursor mixture for 6h;

[0093] Wherein, in step 3, the whole process is carried out under nitrogen protection;

[0094] The mass ratio of cyclohexanediamine to N,N-dimethylacetamide is 1:20, the mass ratio of pyromellitic anhydride to cyclohexanediamine is 1:2, and the ratio of the coupled modified aluminum powder to the precursor mixed solution is 10g:200ml;

[0095] Step 4: Filter the precursor mixture after stirring to obtain powder, dry it at 120°C for 8h, and then calcine it in sequence according to the temperature curve of 100°C / 1h, 150°C / 1h, 200°C / 1h, 250°C / 1h, and 300°C / 1h to obtain polyimide-coated modified aluminum powder;

[0096] Step 5, weigh tartaric acid, OP-10, and ethylene glycol in proportion and dissolve them in deionized water to prepare a reducing solution, and weigh silver nitrate in proportion and dissolve it in deionized water to prepare a silver ammonia solution;

[0097] Among them, the ratio of tartaric acid to deionized water is 10g / L, the ratio of OP-10 to deionized water is 3g / L, the ratio of ethylene glycol to deionized water is 60g / L; the ratio of silver nitrate to deionized water is 15g / L;

[0098] Step 6, adding the polyimide-coated modified aluminum powder obtained in step 4 to the reducing solution prepared in step 5, and stirring evenly, then adding the silver ammonia solution prepared in step 5 to obtain a mixed solution, heating the mixed solution in a water bath at 55° C. and stirring for 3 hours, washing with water to neutrality after the reaction is completed, and drying at 120° C. for 8 hours to obtain a silver-plated aluminum powder with stable high temperature environment performance;

[0099] The volume ratio of the reducing solution to the silver ammonia solution is 1.2:1, and the mass ratio of the silver element to the aluminum element is 40:100.

[0100] Among them, the configuration method of silver ammonia solution is as follows:

[0101] Take silver nitrate and dissolve it in deionized water. When it is completely dissolved, start adding concentrated ammonia water while stirring. The solution will become turbid at first. Continue adding. Stop adding when the solution becomes clear. You will get a silver ammonia solution.

[0102] On the other hand, this embodiment provides a high temperature resistant polyimide modified silver-plated aluminum powder, which is prepared by the preparation method as described above.

[0103] In another aspect, the present embodiment provides an application of the high temperature resistant polyimide modified silver-plated aluminum powder as described above in electromagnetic shielding materials.

[0104] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0105] It should be understood that the present invention is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing high temperature resistant polyimide modified silver-plated aluminum powder, characterized in that: The method comprises the steps of firstly subjecting aluminum powder to coupling modification treatment, then subjecting the coupled modified aluminum powder to polyimide coating modification treatment, and finally subjecting the polyimide coated modified aluminum powder to chemical silver plating treatment to obtain silver-plated aluminum powder with stable high temperature resistant performance.

2. The preparation method according to claim 1, characterized in that: The process of the coupling modification treatment is as follows: A silane coupling agent is weighed and added to an ethanol aqueous solution for hydrolysis to obtain a silane coupling agent solution, and then aluminum powder is added to the silane coupling agent solution for coupling modification. After the reaction is completed, the powder is separated by suction filtration and dried to obtain coupling-modified aluminum powder.

3. The preparation method according to claim 2, characterized in that: The mass ratio of the silane coupling agent to the ethanol aqueous solution is 1 to 5:100; The volume ratio of ethanol to water in the ethanol aqueous solution is 90:5-10; The ratio of the aluminum powder to the silane coupling agent solution is 5g-10g:100ml; During the hydrolysis process, the stirring rate is set to 100r / min-200r / min, the time is set to 5min-10min, and the temperature is set to 20°C-30°C; The coupling modification process is set at a temperature of 20°C to 30°C and a time of 1h to 2h; During the drying process, the drying temperature is set at 80° C. to 120° C. and the drying time is set at 4 h to 8 h.

4. The preparation method according to claim 1, characterized in that: The process of the polyimide coating modification treatment is as follows: (1) Weighing a diamine compound and adding it to a solvent, stirring it once to fully dissolve it, then adding the coupling-modified aluminum powder and stirring it twice, and then adding a dianhydride compound and stirring it three times after mixing it evenly to obtain a precursor mixed solution, and stirring the precursor mixed solution for 3 hours to 6 hours; (2) After the stirring, the precursor mixture is filtered to obtain powder, dried, and then calcined in sequence according to a temperature curve of 100°C / 1h, 150°C / 1h, 200°C / 1h, 250°C / 1h, and 300°C / 1h to obtain polyimide-coated modified aluminum powder.

5. The preparation method according to claim 4, characterized in that: In step (1), the mass ratio of the diamine compound to the solvent is 1:10-20; The mass ratio of the dianhydride compound to the diamine compound is 1:1-2; The ratio of the coupling-modified aluminum powder to the precursor mixed solution is 5g-10g:200ml.

6. The preparation method according to claim 4, characterized in that: In step (1), the diamine compound is any one of p-phenylenediamine, tetrafluoro-phenylenediamine, and cyclohexanediamine; The solvent is N,N-dimethylacetamide or N-methylpyrrolidone; The dianhydride compound is any one of free biphenyl tetracarboxylic dianhydride, pyromellitic acid dianhydride and pyromellitic anhydride.

7. The preparation method according to claim 4, characterized in that: In step (1), the first stirring is carried out at 10°C to 20°C for 1h to 2h, and the stirring speed is 100r / min to 200r / min; the second stirring is carried out at 10°C to 20°C for 10min to 30min, and the stirring speed is 100r / min to 200r / min; the third stirring is carried out at 10°C to 20°C for 4h to 8h, and the stirring speed is 100r / min to 200r / min; In step (1), the whole process is carried out under nitrogen protection; In step (2), the drying temperature is set to 80° C. to 120° C. and the drying time is set to 4 h to 8 h.

8. The preparation method according to claim 1, characterized in that: The process of chemical silver plating is as follows: (1) weighing a reducing agent, a surfactant, and a stabilizer in proportion and dissolving them in deionized water to prepare a reducing solution, and weighing a silver salt in proportion and dissolving it in deionized water to prepare a silver ammonia solution; (2) adding the polyimide-coated modified aluminum powder to the reducing solution and stirring evenly, then adding the silver ammonia solution to obtain a mixed solution, heating the mixed solution to 40°C to 55°C and stirring for 1.5h to 3h, washing with water to neutrality after the reaction is completed, and drying at 80°C to 120°C for 4h to 8h to obtain silver-plated aluminum powder with stable high temperature environment resistance.

9. A high temperature resistant polyimide modified silver-plated aluminum powder, characterized in that: It is prepared based on the preparation method according to any one of claims 1 to 8.

10. Use of the high temperature resistant polyimide modified silver-plated aluminum powder as claimed in claim 9 in electromagnetic shielding materials.