Conductive silver paste doped with graphene powder and preparation method thereof

Abstract

The invention discloses conductive silver paste doped with graphene powder and a preparation method of the conductive silver paste, and relates to the technical field of conductive silver paste. The method comprises the following steps: performing nitrogen doping on graphene by using plasma, introducing nitrogen atoms into graphene crystal lattices to form nitrogen-doped graphene, and introducing oxygen-containing functional groups on the surface of the graphene through a plasma surface modification technology to further improve the conductivity. The preparation method comprises the following steps: mixing an aniline monomer and an aminobenzoic acid monomer, carrying out in-situ polymerization on the surface of nitrogen-doped graphene to generate a polyaniline-aminobenzoic acid copolymer, and compounding a graphene-polyaniline material obtained by in-situ polymerization with carbon nanotubes to construct a three-dimensional conductive network. Secondly, the prepared three-dimensional filler is added into conductive silver paste, carboxyl in aminobenzoic acid is adsorbed and combined with silver particles through Van der Waals force, a stable interface structure is formed, the interface resistance is reduced, and the connectivity of a conductive network is enhanced. The prepared conductive silver paste has the effect of high conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive silver pastes, and specifically to a conductive silver paste doped with graphene powder and a preparation method thereof. Background Art

[0002] With the rapid development of electronic technology, the demand for high-performance conductive materials is increasing day by day. As an important electronic material, conductive silver paste is widely used in fields such as electronic circuits, electrode materials, and sensors. However, traditional conductive silver pastes are mainly composed of silver powder and organic binders, and have problems such as high cost, limited conductivity, and insufficient flexibility.

[0003] Firstly, the dispersion problem of graphene is one of the main technical bottlenecks. Due to its high specific surface area and strong van der Waals forces, graphene is prone to agglomeration, resulting in uneven dispersion in the silver paste, which in turn affects the overall conductivity and stability of the conductive silver paste. Although mechanical stirring or ultrasonic dispersion methods commonly used in the prior art can improve the dispersion to a certain extent, the effect is limited, and it is easy to introduce defects and reduce the conductive performance of graphene.

[0004] Secondly, the insufficient interfacial binding force between graphene and silver particles is also a key problem. The interfacial binding between graphene and silver particles mainly depends on physical adsorption or weak chemical interactions, and this binding method is prone to failure under high-temperature or high-humidity environments, resulting in poor long-term stability of the conductive silver paste. In addition, although the addition of graphene can improve the conductivity, due to the high interfacial resistance between it and silver particles, the improvement effect of the overall conductive performance is limited. Summary of the Invention

[0005] The purpose of the present invention is to provide a conductive silver paste doped with graphene powder and a preparation method thereof to solve the problems existing in the prior art.

[0006] To solve the above technical problems, the present invention provides the following technical solution: A conductive silver paste doped with graphene powder, wherein the graphene filler in the conductive silver paste is a three-dimensional structure filler, and the preparation steps include:

[0007] (1) Evenly spread 1.0 g of dried graphene powder on the sample stage, introduce nitrogen, with a nitrogen flow rate of 50 - 200 sccm, a chamber pressure of 4 - 10 Pa, and start plasma treatment for 10 min to complete nitrogen doping; then close the nitrogen, introduce oxygen, with an oxygen flow rate of 20 - 100 sccm, a chamber pressure of 6 - 10 Pa, start plasma treatment for 3 - 5 min for surface modification, and finally turn off the equipment and take out the double-plasma-treated graphene;

[0008] (2) Disperse 0.5 - 3 g of double - plasma - treated graphene in 50 mL of hydrochloric acid, and perform ultrasonic treatment for 30 min with an ultrasonic power of 200 - 400 W; then add 5.0 - 10.0 mL of aniline monomer and 0.3 - 0.5 g of aminobenzoic acid, and magnetically stir for 30 min to enable the monomers to be evenly adsorbed on the surface of graphene. The stirring speed is 120 rpm. Dissolve 0.2 - 1.0 g of ammonium persulfate in 10 mL of deionized water and slowly add it dropwise to the mixed solution, control the reaction temperature at 0 - 5 °C, and stir - react for 6 h. After the reaction, filter and wash with deionized water until the filtrate is neutral. Finally, place the product in a vacuum drying oven at 60 °C and dry for 12 h to obtain a graphene - polyaniline composite material;

[0009] (3) Disperse 0.5 - 1.5 g of the graphene - polyaniline composite material in 50 mL of N - methylpyrrolidone, perform ultrasonic treatment for 30 min with an ultrasonic power of 200 - 400 W, add 0.3 - 0.6 g of carbon nanotubes and continue ultrasonic treatment for 30 min to ensure uniform dispersion. Magnetically stir the mixed solution for 12 h to promote the formation of a three - dimensional network structure; after the stirring ends, filter and wash with ethanol 3 times to remove the residual solvent. Finally, place the product in a vacuum drying oven at 80 °C and dry for 12 h to obtain a three - dimensional structure filler.

[0010] Furthermore, a preparation method of a conductive silver paste doped with graphene powder includes the following preparation steps:

[0011] S1. Disperse 5 - 10 g of silver powder in 10 mL of ethylene glycol, and perform ultrasonic treatment for 30 min with an ultrasonic power of 200 - 400 W; add 0.1 - 0.3 g of the three - dimensional filler and continue ultrasonic treatment for 30 min to ensure uniform mixing of the filler and silver powder. Add 1.5 - 2.5 g of epoxy resin and magnetically stir for 2 - 4 h to form a homogeneous slurry. The stirring speed is 120 rpm. Grind the slurry 3 times through a three - roll mill to improve the dispersion uniformity and obtain a conductive silver paste doped with graphene powder.

[0012] Furthermore, the preparation method of graphene after drying in the step (1) is as follows: Disperse graphene powder in deionized water with a solid - liquid ratio of 1:20, use ultrasonic treatment with a power of 200 - 400 W and a time of 30 - 60 min to ensure uniform dispersion of graphene; centrifuge the washed graphene dispersion at a rotation speed of 5000 - 10000 rpm for 5 - 10 min, collect the solid after completion, and dry at 50 °C for 3 h.

[0013] Furthermore, in the step (1), the power of the two - plasma treatment equipment is 100 - 200 W, the frequency is 13.56 MHz, and the pressure in the vacuum chamber ≤ 10 -3 Pa.

[0014] Further, the concentration of hydrochloric acid in step (2) is 1.0 M.

[0015] Further, the magnetic stirring speed in step (3) is 60 rpm.

[0016] Further, the particle size of the silver powder in step S1 is 1 - 5 μm.

[0017] Further, the distance between the grinding rollers in step S1 is 0.05 mm.

[0018] Further, the particle size of the slurry after grinding in step S1 is 3 - 5 μm.

[0019] Further, the vacuum degree of the vacuum drying is 0.5 Pa.

[0020] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0021] The present invention uses dual plasma treatment to polymerize aniline - aminobenzoic acid copolymer on the surface of graphene, forms a three - dimensional filler with carbon nanotubes and adds it into the conductive silver paste to achieve the effect of high conductivity.

[0022] First, nitrogen - doped graphene is formed by nitrogen doping of graphene using plasma, introducing nitrogen atoms into the graphene lattice. Nitrogen doping can not only adjust the electronic structure of graphene, improve its conductivity, but also increase the surface active sites, providing a basis for subsequent surface modification and polymerization reactions. Then, through plasma surface modification technology, oxygen - containing functional groups are introduced on the surface of graphene to further enhance its surface activity and compatibility with other materials. This dual plasma treatment endows graphene with excellent conductivity and interfacial binding ability. The aniline monomer and aminobenzoic acid monomer are mixed and in - situ polymerized on the surface of nitrogen - doped graphene to generate polyaniline - aminobenzoic acid copolymer. The graphene - polyaniline material obtained by in - situ polymerization is compounded with carbon nanotubes to construct a three - dimensional conductive network. The high aspect ratio and excellent conductivity of carbon nanotubes can form a synergistic effect with graphene - polyaniline, further optimizing the conductivity and mechanical properties of the material.

[0023] Secondly, the three - dimensional filler prepared above is added to the conductive silver paste. The carboxyl group in aminobenzoic acid is exposed on the surface of the polymer chain during the polymerization process and adsorbs and binds with silver particles through van der Waals force to form a stable interfacial structure. This binding method can not only improve the dispersion of silver particles, but also reduce the interfacial resistance and enhance the connectivity of the conductive network. At the same time, the introduction of polyaniline provides an additional conductive channel for the conductive silver paste, further improving the overall conductivity. Specific embodiments

[0024] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0025] To more clearly illustrate the method provided by the present invention, the following embodiments are used for detailed description. The test methods for each index of a conductive silver paste of doped graphene powder prepared in the following embodiments are as follows:

[0026] Conductivity: Take the conductive silver paste obtained in the examples and comparative examples. After printing and coating, it is cured at 100°C for 30 min to prepare specimens. Detect and record the test results of their properties respectively: the screen mesh number of the brush is 100 meshes, the substrate is a PET film, and the size of the cured specimen is 2 mm × 2 mm; Use a four-probe tester to conduct conductivity tests, and take the sheet resistance of the specimen as the experimental index;

[0027] Example 1

[0028] (1) Disperse graphene powder in deionized water with a solid-liquid ratio of 1:20. Use ultrasonic treatment with a power of 200 W and a time of 30 min to ensure uniform dispersion of graphene; Centrifuge the cleaned graphene dispersion at a rotation speed of 5000 rpm for 5 min. After completion, collect the solid and dry it at 50°C for 3 h; Uniformly spread 1.0 g of the dried graphene powder on the sample stage, introduce nitrogen with a nitrogen flow rate of 50 sccm and a chamber pressure of 4 Pa, and start plasma treatment for 10 min to complete nitrogen doping. The power of the plasma treatment equipment is 100 W, the frequency is 13.56 MHz, and the pressure in the vacuum chamber is ≤10-3 Pa; Subsequently, turn off the nitrogen, introduce oxygen with an oxygen flow rate of 20 sccm and a chamber pressure of 6 Pa, and start plasma treatment for 3 min for surface modification. The power of the plasma treatment equipment is 100 W, the frequency is 13.56 MHz, and the pressure in the vacuum chamber is ≤10-3 Pa. Finally, turn off the equipment and take out the double-plasma-treated graphene;

[0029] (2) Disperse 0.5 g of double plasma-treated graphene in 50 mL of hydrochloric acid with a concentration of 1.0 M, and ultrasonically treat it for 30 min with an ultrasonic power of 200 W; then add 5.0 mL of aniline monomer and 0.3 g of aminobenzoic acid, and magnetically stir for 30 min to uniformly adsorb the monomer on the surface of graphene. The stirring speed is 120 rpm. Dissolve 0.2 g of ammonium persulfate in 10 mL of deionized water and slowly add it dropwise to the mixed solution. Control the reaction temperature at 0 °C and stir and react for 6 h. After the reaction is completed, filter and wash with deionized water until the filtrate is neutral. Finally, place the product in a vacuum drying oven at 60 °C and dry it for 12 h with a vacuum degree of 0.5 Pa to obtain a graphene-polyaniline composite material;

[0030] (3) Disperse 0.5 g of the graphene-polyaniline composite material in 50 mL of N-methylpyrrolidone, ultrasonically treat it for 30 min with an ultrasonic power of 200 W, add 0.3 g of carbon nanotubes and continue ultrasonically treating for 30 min to ensure uniform dispersion. Magnetically stir the mixed solution for 12 h to promote the formation of a three-dimensional network structure. The stirring speed is 60 rpm; after the stirring is completed, filter and wash with ethanol 3 times to remove the residual solvent. Finally, place the product in a vacuum drying oven at 80 °C and dry it for 12 h with a vacuum degree of 0.5 Pa to obtain a three-dimensional structure filler;

[0031] (4) Disperse 5 g of silver powder with a particle size of 1 μm in 10 mL of ethylene glycol, ultrasonically treat it for 30 min with an ultrasonic power of 200 W; add 0.1 g of the three-dimensional filler and continue ultrasonically treating for 30 min to ensure uniform mixing of the filler and silver powder. Add 1.5 g of epoxy resin and magnetically stir for 2 h to form a homogeneous slurry. The stirring speed is 120 rpm. Grind the slurry 3 times through a three-roll mill with a roll spacing of 0.05 mm and a particle size of 3 μm to improve the dispersion uniformity and prepare a conductive silver paste doped with a graphene composite.

[0032] Example 2

[0033] (1) Disperse graphene powder in deionized water with a solid-liquid ratio of 1:20. Use ultrasonic treatment with a power of 300 W for 45 min to ensure uniform dispersion of graphene. Centrifuge the cleaned graphene dispersion at a speed of 7500 rpm for 7.5 min. After that, collect the solid and dry it at 50 °C for 3 h. Evenly spread 1.0 g of the dried graphene powder on the sample stage, introduce nitrogen with a flow rate of 125 sccm, a chamber pressure of 7 Pa, and start plasma treatment for 10 min to complete nitrogen doping. The power of the plasma treatment equipment is 150 W, the frequency is 13.56 MHz, and the pressure in the vacuum chamber is ≤10⁻³ Pa. Then, turn off the nitrogen, introduce oxygen with a flow rate of 60 sccm, a chamber pressure of 8 Pa, and start plasma treatment for 4 min for surface modification. The power of the plasma treatment equipment is 150 W, the frequency is 13.56 MHz, and the pressure in the vacuum chamber is ≤10⁻³ Pa. Finally, turn off the equipment and take out the double plasma-treated graphene;

[0034] (2) Disperse 1.75 g of the double plasma-treated graphene in 50 mL of 1.0 M hydrochloric acid and perform ultrasonic treatment for 30 min with an ultrasonic power of 300 W. Then add 7.5 mL of aniline monomer and 0.4 g of aminobenzoic acid, and magnetically stir for 30 min to ensure uniform adsorption of the monomers on the graphene surface with a stirring speed of 120 rpm. Dissolve 0.6 g of ammonium persulfate in 10 mL of deionized water and slowly add it dropwise to the mixed solution, control the reaction temperature at 2.5 °C, and stir and react for 6 h. After the reaction, filter and wash with deionized water until the filtrate is neutral. Finally, place the product in a vacuum drying oven at 60 °C for 12 h with a vacuum degree of 0.5 Pa to obtain the graphene-polyaniline composite material;

[0035] (3) Disperse 1.0 g of the graphene-polyaniline composite material in 50 mL of N-methylpyrrolidone and perform ultrasonic treatment for 30 min with an ultrasonic power of 300 W. Add 0.45 g of carbon nanotubes and continue ultrasonic treatment for 30 min to ensure uniform dispersion. Magnetically stir the mixed solution for 12 h to promote the formation of a three-dimensional network structure with a stirring speed of 60 rpm. After stirring, filter and wash with ethanol three times to remove the residual solvent. Finally, place the product in a vacuum drying oven at 80 °C for 12 h with a vacuum degree of 0.5 Pa to obtain the three-dimensional structure filler;

[0036] (4) Disperse 7.5 g of silver powder with a particle size of 3 μm in 10 mL of ethylene glycol, and perform ultrasonic treatment for 30 min with an ultrasonic power of 300 W; add 0.2 g of three-dimensional filler and continue ultrasonic treatment for 30 min to ensure uniform mixing of the filler and silver powder, add 2.0 g of epoxy resin and magnetically stir for 3 h to form a homogeneous slurry with a stirring speed of 120 rpm. Grind the slurry 3 times through a three-roll mill with a roll spacing of 0.05 mm and a particle size of 4 μm to improve the dispersion uniformity, and obtain a conductive silver paste doped with graphene composite.

[0037] Example 3

[0038] (1) Disperse graphene powder in deionized water with a solid-liquid ratio of 1:20, and use ultrasonic treatment with a power of 400 W for 60 min to ensure uniform dispersion of graphene; centrifuge the cleaned graphene dispersion at a speed of 10000 rpm for 10 min, collect the solid after completion, and dry it at 50 °C for 3 h; evenly spread 1.0 g of the dried graphene powder on the sample stage, introduce nitrogen with a nitrogen flow rate of 200 sccm and a chamber pressure of 10 Pa, and start plasma treatment for 10 min to complete nitrogen doping. The power of the plasma treatment equipment is 200 W, the frequency is 13.56 MHz, and the pressure in the vacuum chamber is ≤10-3 Pa; then close the nitrogen, introduce oxygen with an oxygen flow rate of 100 sccm and a chamber pressure of 10 Pa, and start plasma treatment for 5 min for surface modification. The power of the plasma treatment equipment is 200 W, the frequency is 13.56 MHz, and the pressure in the vacuum chamber is ≤10-3 Pa. Finally, turn off the equipment and take out the double-plasma-treated graphene;

[0039] (2) Disperse 3 g of double-plasma-treated graphene in 50 mL of hydrochloric acid with a concentration of 1.0 M, and perform ultrasonic treatment for 30 min with an ultrasonic power of 400 W; then add 10.0 mL of aniline monomer and 0.5 g of aminobenzoic acid, and magnetically stir for 30 min to uniformly adsorb the monomer on the surface of graphene with a stirring speed of 120 rpm. Dissolve 1.0 g of ammonium persulfate in 10 mL of deionized water and slowly add it to the mixed solution, control the reaction temperature at 5 °C, and stir and react for 6 h. After the reaction is completed, filter and wash with deionized water until the filtrate is neutral. Finally, place the product in a vacuum drying oven at 60 °C and dry for 12 h with a vacuum degree of 0.5 Pa to obtain a graphene-polyaniline composite;

[0040] (3) Disperse 1.5 g of graphene-polyaniline composite in 50 mL of N-methylpyrrolidone, ultrasonically treat for 30 min with an ultrasonic power of 400 W, add 0.6 g of carbon nanotubes and continue ultrasonically treating for 30 min to ensure uniform dispersion. Magnetically stir the mixture for 12 h to promote the formation of a three-dimensional network structure at a stirring speed of 60 rpm. After stirring, filter and wash with ethanol three times to remove residual solvents. Finally, place the product in a vacuum drying oven at 80 °C and dry for 12 h with a vacuum degree of 0.5 Pa to obtain a three-dimensional structure filler.

[0041] (4) Disperse 10 g of silver powder with a particle size of 5 μm in 10 mL of ethylene glycol, ultrasonically treat for 30 min with an ultrasonic power of 400 W. Add 0.3 g of three-dimensional filler and continue ultrasonically treating for 30 min to ensure uniform mixing of the filler and silver powder. Add 2.5 g of epoxy resin and magnetically stir for 4 h to form a homogeneous slurry at a stirring speed of 120 rpm. Grind the slurry three times through a three-roll mill with a roll spacing of 0.05 mm and a particle size of 5 μm to improve the dispersion uniformity and obtain a conductive silver paste doped with graphene composite.

[0042] Comparative Example 1

[0043] The difference between Comparative Example 1 and Example 2 lies in steps (1) and (2). Modify steps (1) and (2) as follows: (1) Disperse graphene powder in deionized water with a solid-liquid ratio of 1:20, use ultrasonic treatment with a power of 300 W and a time of 45 min to ensure uniform dispersion of graphene. Centrifuge the washed graphene dispersion at a rotation speed of 7500 rpm for 7.5 min. After completion, collect the solid and dry it at 50 °C for 3 h. Uniformly spread 1.0 g of the dried graphene powder on the sample stage, introduce nitrogen with a nitrogen flow rate of 125 sccm and a chamber pressure of 7 Pa, and start plasma treatment for 10 min to complete nitrogen doping. The power of the plasma treatment equipment is 150 W, the frequency is 13.56 MHz, and the pressure in the vacuum chamber is ≤10-3 Pa. Finally, turn off the equipment and take out the plasma-treated graphene.

[0044] (2) Disperse 1.75 g of plasma-treated graphene in 50 mL of hydrochloric acid with a concentration of 1.0 M, ultrasonically treat for 30 min with an ultrasonic power of 300 W. Then add 7.5 mL of aniline monomer and 0.4 g of aminobenzoic acid, magnetically stir for 30 min to ensure uniform adsorption of the monomer on the surface of graphene at a stirring speed of 120 rpm. Dissolve 0.6 g of ammonium persulfate in 10 mL of deionized water and slowly add it dropwise to the mixture, control the reaction temperature at 2.5 °C, stir and react for 6 h. After the reaction, filter and wash with deionized water until the filtrate is neutral. Finally, place the product in a vacuum drying oven at 60 °C and dry for 12 h with a vacuum degree of 0.5 Pa to obtain a graphene-polyaniline composite. The remaining steps are the same as in Example 2.

[0045] Comparative Example 2

[0046] The difference between Comparative Example 2 and Example 2 lies in the differences in steps (1) and (2). Steps (1) and (2) are changed to: (1) Disperse graphene powder in deionized water with a solid-liquid ratio of 1:20. Use ultrasonic treatment with a power of 300 W and a time of 45 min to ensure uniform dispersion of graphene. Centrifuge the washed graphene dispersion at a speed of 7500 rpm for 7.5 min. After completion, collect the solid and dry it at 50 °C for 3 h. Evenly spread 1.0 g of the dried graphene powder on the sample stage, introduce oxygen with an oxygen flow rate of 60 sccm and a chamber pressure of 8 Pa, and start plasma treatment for 4 min for surface modification. The power of the plasma treatment equipment is 150 W, the frequency is 13.56 MHz, and the pressure in the vacuum chamber is ≤10-3 Pa. Finally, turn off the equipment and take out the plasma-treated graphene;

[0047] (2) Disperse 1.75 g of plasma-treated graphene in 50 mL of hydrochloric acid with a concentration of 1.0 M, and perform ultrasonic treatment for 30 min with an ultrasonic power of 300 W. Then add 7.5 mL of aniline monomer and 0.4 g of aminobenzoic acid, and magnetically stir for 30 min to evenly adsorb the monomer on the surface of graphene with a stirring speed of 120 rpm. Dissolve 0.6 g of ammonium persulfate in 10 mL of deionized water and slowly add it dropwise to the mixed solution, control the reaction temperature at 2.5 °C, and stir and react for 6 h. After the reaction is completed, filter and wash with deionized water until the filtrate is neutral. Finally, place the product in a vacuum drying oven at 60 °C and dry it for 12 h with a vacuum degree of 0.5 Pa to obtain a graphene-polyaniline composite material; the remaining steps are the same as those in Example 2.

[0048] Comparative Example 3

[0049] The difference between Comparative Example 3 and Example 2 lies in the difference in step (2). Step (2) is changed to: Disperse 1.75 g of double plasma-treated graphene in 50 mL of hydrochloric acid with a concentration of 1.0 M, and perform ultrasonic treatment for 30 min with an ultrasonic power of 300 W. Then add 7.5 mL of aniline monomer, and magnetically stir for 30 min to evenly adsorb the monomer on the surface of graphene with a stirring speed of 120 rpm. Dissolve 0.6 g of ammonium persulfate in 10 mL of deionized water and slowly add it dropwise to the mixed solution, control the reaction temperature at 2.5 °C, and stir and react for 6 h. After the reaction is completed, filter and wash with deionized water until the filtrate is neutral. Finally, place the product in a vacuum drying oven at 60 °C and dry it for 12 h with a vacuum degree of 0.5 Pa to obtain a graphene-polyaniline composite material; the remaining steps are the same as those in Example 2.

[0050] Comparative Example 4

[0051] The difference between Comparative Example 4 and Example 2 is that step (2) is absent, and step (3) is modified as follows: 1.0 g of double-plasma-treated graphene is dispersed in 50 mL of N-methylpyrrolidone, sonicated for 30 min at a sonication power of 300 W, 0.45 g of carbon nanotubes is added and sonication is continued for 30 min to ensure uniform dispersion, the mixture is magnetically stirred for 12 h to promote the formation of a three-dimensional network structure at a stirring speed of 60 rpm; after stirring, it is filtered and washed three times with ethanol to remove residual solvents, and finally the product is dried in a vacuum oven at 80 °C for 12 h with a vacuum degree of 0.5 Pa to obtain a three-dimensional structure filler; the remaining steps are the same as those in Example 2.

[0052] Comparative Example 5

[0053] The difference between Comparative Example 5 and Example 2 is that step (3) is absent, and step (4) is modified as follows: 7.5 g of silver powder with a particle size of 3 μm is dispersed in 10 mL of ethylene glycol, sonicated for 30 min at a sonication power of 300 W; 0.2 g of graphene-polyaniline composite is added and sonication is continued for 30 min to ensure uniform mixing of the filler and silver powder, 2.0 g of epoxy resin is added and magnetically stirred for 3 h to form a homogeneous slurry at a stirring speed of 120 rpm, and the slurry is ground three times through a three-roll mill with a roll spacing of 0.05 mm and a particle size of 4 μm to improve dispersion uniformity, and a conductive silver paste doped with a graphene composite is prepared; the remaining steps are the same as those in Example 2.

[0054] Effect Example

[0055] The following Table 1 gives the performance analysis results of a conductive silver paste of a doped graphene powder using Examples 1 to 3 and Comparative Examples 1 to 5 of the present invention.

[0056] Table 1

[0057] <![CDATA[Resistivity (×10 -5 Ω / cm)]]> Example 1 0.16 Example 2 0.15 Example 3 0.15 Comparative Example 1 0.35 Comparative Example 2 0.28 Comparative Example 3 0.25 Comparative Example 4 0.40 Comparative Example 5 0.20

[0058] From the comparison of the experimental data of the resistivity of the examples and the comparative examples, it can be found that in the present invention, plasma is used to perform nitrogen doping on graphene, introducing nitrogen atoms into the graphene lattice to form nitrogen-doped graphene; nitrogen doping can not only adjust the electronic structure of graphene and improve its conductivity, but also increase the surface active sites, providing a basis for subsequent surface modification and polymerization reactions; then, through plasma surface modification technology, oxygen-containing functional groups are introduced onto the graphene surface to further enhance its surface activity and compatibility with other materials; this dual plasma treatment endows graphene with excellent conductivity and interfacial bonding ability; aniline monomer and aminobenzoic acid monomer are mixed and in-situ polymerization is carried out on the surface of nitrogen-doped graphene to generate polyaniline-aminobenzoic acid copolymer, and the graphene-polyaniline material obtained by in-situ polymerization is compounded with carbon nanotubes to construct a three-dimensional conductive network; the high aspect ratio and excellent conductivity of carbon nanotubes can form a synergistic effect with graphene-polyaniline to further optimize the conductivity and mechanical properties of the material. In the present invention, the three-dimensional filler prepared above is added to the conductive silver paste, and the carboxyl group in aminobenzoic acid is exposed on the surface of the polymer chain during the polymerization process and adsorbs and binds with silver particles through van der Waals force to form a stable interfacial structure. This binding method can not only improve the dispersion of silver particles, but also reduce the interfacial resistance and enhance the connectivity of the conductive network; at the same time, the introduction of polyaniline provides an additional conductive channel for the conductive silver paste, further improving the overall conductivity.

[0059] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed within the present invention. Any reference signs in the claims should not be construed as limiting the claimed claim.

Claims

1. A conductive silver paste doped with graphene powder, characterized in that: The graphene filler in the conductive silver paste is a three-dimensional structure filler, which includes the following preparation steps: (1) 1.0 g of dried graphene powder was evenly spread on the sample table, nitrogen was introduced, the nitrogen flow rate was 50-200 sccm, the chamber pressure was 4-10 Pa, and plasma treatment was started for 10 min to complete nitrogen doping; then nitrogen was turned off, oxygen was introduced, the oxygen flow rate was 20-100 sccm, the chamber pressure was 6-10 Pa, and plasma treatment was started for 3-5 min for surface modification, and finally the equipment was turned off and the dual plasma treated graphene was taken out; (2) Dispersing 0.5-3g of dual plasma treated graphene in 50mL of hydrochloric acid, ultrasonically treating for 30min, with an ultrasonic power of 200-400W; then adding 5.0-10.0mL of aniline monomer and 0.3-0.5g of aminobenzoic acid, magnetically stirring for 30min to allow the monomer to be uniformly adsorbed on the graphene surface, with a stirring speed of 120rpm, dissolving 0.2-1.0g of ammonium persulfate in 10mL of deionized water and slowly dropping it into the mixed solution, controlling the reaction temperature to 0-5°C, stirring the reaction for 6h, filtering after the reaction and washing with deionized water until the filtrate is neutral, and finally drying the product in a 60°C vacuum drying oven for 12h to obtain a graphene-polyaniline composite material; (3) Disperse 0.5-1.5 g of graphene-polyaniline composite material in 50 mL of N-methylpyrrolidone, ultrasonically treat for 30 min at an ultrasonic power of 200-400 W, add 0.3-0.6 g of carbon nanotubes and continue ultrasonically treating for 30 min to ensure uniform dispersion, and magnetically stir the mixture for 12 h to promote the formation of a three-dimensional network structure; after stirring, filter and wash with ethanol three times to remove residual solvent, and finally dry the product in a vacuum drying oven at 80 ° C for 12 h to obtain a three-dimensional structure filler.

2. A method for preparing a conductive silver paste doped with graphene powder, characterized in that: The method comprises the following preparation steps: S1. Disperse 5-10g of silver powder in 10mL of ethylene glycol and ultrasonically treat for 30min at an ultrasonic power of 200-400W; add 0.1-0.3g of three-dimensional filler and continue ultrasonic treatment for 30min to ensure that the filler and silver powder are evenly mixed, add 1.5-2.5g of epoxy resin and magnetically stir for 2-4h to form a homogeneous slurry at a stirring speed of 120rpm, grind the slurry three times with a three-roll grinder to improve the dispersion uniformity, and obtain a conductive silver paste doped with graphene fragments.

3. The method for preparing a conductive silver paste doped with graphene powder according to claim 1, characterized in that: The method for preparing the dried graphene in step (1) is as follows: dispersing graphene powder in deionized water at a solid-liquid ratio of 1:20, using ultrasonic treatment at a power of 200-400 W for 30-60 min to ensure that the graphene is evenly dispersed; centrifuging the washed graphene dispersion at a speed of 5000-10000 rpm for 5-10 min, collecting the solid after the centrifugation, and drying at 50° C. for 3 h.

4. The method for preparing a conductive silver paste doped with graphene powder according to claim 1, characterized in that: The power of the plasma treatment equipment in the step (1) is 100-200W, the frequency is 13.56MHz, and the vacuum chamber pressure is ≤10 -3 Pa.

5. The method for preparing a conductive silver paste doped with graphene powder according to claim 1, characterized in that: The concentration of hydrochloric acid in step (2) is 1.0M.

6. The method for preparing a conductive silver paste doped with graphene powder according to claim 1, characterized in that: The magnetic stirring speed in step (3) is 60 rpm.

7. The method for preparing a conductive silver paste doped with graphene powder according to claim 2, characterized in that: In the step S1, the particle size of the silver powder is 1-5 μm.

8. The method for preparing a conductive silver paste doped with graphene powder according to claim 2, characterized in that: In step S1, the grinding roller spacing is 0.05 mm.

9. The method for preparing a conductive silver paste doped with graphene powder according to claim 2, characterized in that: The particle size of the slurry after grinding in step S1 is 3-5 μm.

10. The method for preparing a conductive silver paste doped with graphene powder according to claim 1, characterized in that: The vacuum degree of the vacuum drying is 0.5 Pa.