Conductive silver paste doped with graphene powder and preparation method thereof

Abstract

The application discloses a kind of doped graphene powder conductive silver paste and preparation method thereof, it is related to conductive silver paste technical field.The application is first using plasma to carry out nitrogen doping to graphene, nitrogen atom is introduced in graphene lattice, and nitrogen-doped graphene is formed, then through plasma surface modification technology, oxygen-containing functional group is introduced on the surface of graphene, and further mention conductivity.Aniline monomer and amino benzoic acid monomer are mixed, and in-situ polymerization is carried out on the surface of nitrogen-doped graphene, and polyaniline-amino benzoic acid copolymer is generated, graphene-polyaniline material obtained by in-situ polymerization is compounded with carbon nanotube, and three-dimensional conductive network is constructed.Secondly, the three-dimensional filler prepared above is added to the conductive silver paste, the carboxyl group in amino benzoic acid is combined by van der waals force between silver particles, and stable interface structure is formed, the interface resistance is reduced, and the connectivity of conductive network is enhanced.The conductive silver paste prepared by the application has the effect of high conductivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of conductive silver paste, in particular to a conductive silver paste doped with graphene powder and a preparation method thereof. BACKGROUND

[0002] With the rapid development of electronic technology, the demand for high-performance conductive materials is increasing. As an important electronic material, conductive silver paste is widely used in electronic circuits, electrode materials, sensors and other fields. However, the traditional conductive silver paste is mainly composed of silver powder and organic binder, which has the problems of 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 force, graphene is prone to agglomeration, resulting in uneven dispersion in the silver paste, which further affects the overall conductivity and stability of the conductive silver paste. Although the mechanical stirring or ultrasonic dispersion method commonly used in the prior art can improve the dispersion to some extent, the effect is limited, and defects are easily introduced, which reduces the conductivity of graphene.

[0004] Secondly, the insufficient interfacial bonding force between graphene and silver particles is also a key problem. The interfacial bonding between graphene and silver particles mainly depends on physical adsorption or weak chemical action, which is easy to fail in high temperature or high humidity environment, resulting in poor long-term stability of the conductive silver paste. In addition, although the addition of graphene can improve the conductivity, the overall conductivity is limited due to the high interfacial resistance between graphene and silver particles. SUMMARY

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

[0006] In order to solve the above technical problems, the present application provides the following technical scheme: a conductive silver paste doped with graphene powder, the graphene filler in the conductive silver paste is a three-dimensional structure filler, comprising the following preparation steps:

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

[0008] (2) 0.5-3 g of double plasma treated graphene was dispersed in 50 mL of hydrochloric acid and ultrasonically treated for 30 min at an ultrasonic power of 200-400 W; then 5.0-10.0 mL of aniline monomer and 0.3-0.5 g of amino benzoic acid were added, and the monomer was uniformly adsorbed on the surface of graphene by magnetic stirring for 30 min at a stirring speed of 120 rpm, 0.2-1.0 g of ammonium persulfate was dissolved in 10 mL of deionized water and slowly added to the mixture, the reaction temperature was controlled at 0-5°C, and the reaction was stirred for 6 h, after the reaction was completed, the product was filtered and washed with deionized water until the filtrate was neutral, and finally the product was dried in a vacuum drying oven at 60°C for 12 h to obtain a graphene-polyaniline composite material;

[0009] (3) 0.5-1.5 g of graphene-polyaniline composite material was dispersed in 50 mL of N-methylpyrrolidone, ultrasonically treated for 30 min at an ultrasonic power of 200-400 W, 0.3-0.6 g of carbon nanotubes was added and ultrasonically treated for another 30 min to ensure uniform dispersion, the mixture was magnetically stirred for 12 h to promote the formation of a three-dimensional network structure; after stirring, the product was filtered and washed with ethanol three times to remove residual solvents, and finally the product was dried in a vacuum drying oven at 80°C for 12 h to obtain a three-dimensional structure filler.

[0010] Further, a preparation method of a graphene powder doped conductive silver paste comprises the following preparation steps:

[0011] S1. 5-10 g of silver powder was dispersed in 10 mL of ethylene glycol and ultrasonically treated for 30 min at an ultrasonic power of 200-400 W; 0.1-0.3 g of three-dimensional filler was added and ultrasonically treated for another 30 min to ensure uniform mixing of the filler and silver powder, 1.5-2.5 g of epoxy resin was added and magnetically stirred for 2-4 h to form a homogeneous paste, and the stirring speed was 120 rpm; the paste was ground three times by a three-roll grinder to improve the dispersion uniformity, and a graphene powder doped conductive silver paste was prepared.

[0012] Further, the graphene preparation method after drying in step (1) is: graphene powder is dispersed in deionized water with a solid-liquid ratio of 1:20, ultrasonic treatment is used, the power is 200-400 W, and the time is 30-60 min to ensure uniform dispersion of graphene; the washed graphene dispersion liquid is centrifuged at a speed of 5000-10000 rpm for 5-10 min, and the solid is collected after the end, and dried at 50°C for 3 h.

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

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

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

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

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

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

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

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The present application utilizes double plasma treatment to make the surface of graphene polymerize aniline-amino benzoic acid copolymer, and form a three-dimensional filler with carbon nanotubes added into conductive silver paste to achieve high conductivity.

[0022] Firstly, the graphene is nitrogen-doped by plasma to introduce 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 to provide a basis for subsequent surface modification and polymerization; then, oxygen-containing functional groups are introduced on the surface of graphene by plasma surface modification technology to further enhance the surface activity and compatibility with other materials; this double plasma treatment makes the graphene have excellent conductivity and interface bonding capacity; aniline monomers and amino benzoic acid monomers are mixed and in-situ polymerized on the surface of nitrogen-doped graphene to generate polyaniline-amino benzoic 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 to further optimize 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 groups in amino benzoic acid are exposed on the surface of the polymer chain during polymerization and are adsorbed and combined with silver particles through van der Waals force to form a stable interface structure; this combination mode can not only improve the dispersibility of silver particles, but also reduce the interface resistance and enhance the connectivity of the conductive network; at the same time, the introduction of polyaniline provides additional conductive channels for the conductive silver paste, further improving the overall conductivity. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work are within the protection scope of the present application.

[0025] In order to more clearly illustrate the method provided by the present application, the following embodiments are described in detail. In the following embodiments, the test methods of various indexes of the doped graphene powder conductive silver paste are as follows:

[0026] Conductivity: the conductive silver paste obtained in the examples and comparative examples is printed and coated, and then placed at 100℃ for curing for 30 min to obtain a sample. The performance of the sample is detected and the detection results are recorded. The brush screen mesh number is 100 meshes, the substrate is a PET film, and the size of the cured sample is 2mmx2mm. A four-probe tester is used for conductivity test, and the square resistance of the sample is used as the experimental index.

[0027] Example 1

[0028] (1) The graphene powder is dispersed in deionized water, and the solid-liquid ratio is 1:20. Ultrasonic treatment is used, the power is 200W, and the time is 30min to ensure uniform dispersion of the graphene. The cleaned graphene dispersion is centrifuged at a speed of 5000rpm for 5min. After centrifugation, the solid is collected and dried at 50℃ for 3h. 1.0g of dried graphene powder is uniformly spread on a sample table. Nitrogen is introduced at a flow rate of 50sccm, and the chamber pressure is 4Pa. Nitrogen doping is completed by turning on the plasma treatment for 10min. The plasma treatment equipment power is 100W, the frequency is 13.56MHz, and the vacuum chamber pressure is ≤10-3Pa. Then the nitrogen is turned off, and oxygen is introduced at a flow rate of 20sccm, and the chamber pressure is 6Pa. Surface modification is performed by turning on the plasma treatment for 3min. The plasma treatment equipment power is 100W, the frequency is 13.56MHz, and the vacuum chamber pressure is ≤10-3Pa. Finally, the double-plasma-treated graphene is taken out.

[0029] (2) 0.5 g of double plasma treated graphene was dispersed in 50 mL of 1.0 M hydrochloric acid and ultrasonically treated for 30 min at an ultrasonic power of 200 W. Then 5.0 mL of aniline monomer and 0.3 g of amino benzoic acid were added, and the monomers were uniformly adsorbed on the surface of the graphene by magnetic stirring for 30 min at a stirring speed of 120 rpm. 0.2 g of ammonium persulfate was dissolved in 10 mL of deionized water and slowly added to the mixture, and the reaction temperature was controlled at 0°C. The reaction was stirred for 6 h, and after the reaction was completed, the product was filtered and washed with deionized water until the filtrate was neutral. Finally, the product was dried in a vacuum drying oven at 60°C for 12 h at a vacuum degree of 0.5 Pa to obtain a graphene-polyaniline composite material;

[0030] (3) 0.5 g of graphene-polyaniline composite material was dispersed in 50 mL of N-methyl pyrrolidone and ultrasonically treated for 30 min at an ultrasonic power of 200 W. 0.3 g of carbon nanotubes was added and ultrasonically treated for another 30 min to ensure uniform dispersion. The mixture was magnetically stirred for 12 h to promote the formation of a three-dimensional network structure at a stirring speed of 60 rpm. After stirring, the product was filtered and washed with ethanol three times to remove residual solvents. Finally, the product was dried in a vacuum drying oven at 80°C for 12 h at a vacuum degree of 0.5 Pa to obtain a three-dimensional structure filler.

[0031] (4) 5 g of silver powder with a particle size of 1 μm was dispersed in 10 mL of ethylene glycol and ultrasonically treated for 30 min at an ultrasonic power of 200 W. 0.1 g of three-dimensional filler was added and ultrasonically treated for another 30 min to ensure uniform mixing of the filler and silver powder. 1.5 g of epoxy resin was added and magnetically stirred for 2 h to form a homogeneous slurry at a stirring speed of 120 rpm. The slurry was ground three times by a three-roll grinder with a roll spacing of 0.05 mm and a particle size of 3 μm to improve dispersion uniformity, and a conductive silver paste doped with a graphene composite was prepared.

[0032] Example 2

[0033] (1) Disperse the 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, collect the solid after the end, and dry at 50°C for 3 h; evenly spread 1.0 g of dried graphene powder on the sample table, introduce nitrogen gas with a flow rate of 125 sccm and a chamber pressure of 7 Pa, turn on the plasma treatment for 10 min to complete nitrogen doping, the plasma treatment equipment power is 150 W, the frequency is 13.56 MHz, and the vacuum chamber pressure is ≤10-3 Pa; then turn off the nitrogen and introduce oxygen with a flow rate of 60 sccm and a chamber pressure of 8 Pa, turn on the plasma treatment for 4 min for surface modification, the plasma treatment equipment power is 150 W, the frequency is 13.56 MHz, and the vacuum chamber pressure is ≤10-3 Pa, finally turn off the equipment and take out the double-plasma-treated graphene;

[0034] (2) Disperse 1.75 g of double-plasma-treated graphene in 50 mL of 1.0 M hydrochloric acid, 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 amino benzoic acid, magnetically stir for 30 min to make the monomer uniformly adsorbed on the surface of graphene, the stirring speed is 120 rpm, dissolve 0.6 g of ammonium persulfate in 10 mL of deionized water and slowly add it to the mixture, control the reaction temperature at 2.5°C, stir for 6 h, after the reaction is completed, filter and wash with deionized water until the filtrate is neutral, finally dry the product in a vacuum drying oven at 60°C for 12 h, the vacuum degree is 0.5 Pa, to obtain graphene-polyaniline composite material;

[0035] (3) Disperse 1.0 g of graphene-polyaniline composite material in 50 mL of N-methyl pyrrolidone, 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 mixture for 12 h to promote the formation of three-dimensional network structure, the stirring speed is 60 rpm; after stirring, filter and wash with ethanol for 3 times to remove residual solvent, finally dry the product in a vacuum drying oven at 80°C for 12 h, the vacuum degree is 0.5 Pa, to obtain a three-dimensional structure filler;

[0036] (4) 7.5 g of silver powder with a particle size of 3 μm was dispersed in 10 mL of ethylene glycol, and ultrasonic treatment was performed for 30 min at an ultrasonic power of 300 W; 0.2 g of three-dimensional filler was added and ultrasonic treatment was continued for 30 min to ensure uniform mixing of the filler and silver powder, 2.0 g of epoxy resin was added and magnetic stirring was performed for 3 h at a stirring speed of 120 rpm to form a homogeneous slurry, the slurry was ground by a three-roll grinder for 3 times at a roll spacing of 0.05 mm and a particle size of 4 μm to improve the dispersion uniformity, and a conductive silver paste doped with a graphene composite was prepared.

[0037] Example 3

[0038] (1) The graphene powder was dispersed in deionized water at a solid-liquid ratio of 1:20, and ultrasonic treatment was performed at a power of 400 W for 60 min to ensure uniform dispersion of the graphene; the washed graphene dispersion liquid was centrifuged at a speed of 10,000 rpm for 10 min, and the solid was collected after the centrifugation was completed and was dried at 50°C for 3 h; 1.0 g of the dried graphene powder was uniformly laid on a sample table, nitrogen was introduced at a flow rate of 200 sccm, the chamber pressure was 10 Pa, and nitrogen doping was completed by turning on the plasma treatment for 10 min, the plasma treatment device had a power of 200 W, a frequency of 13.56 MHz, and a vacuum chamber pressure of ≤10-3 Pa; then the nitrogen was turned off, oxygen was introduced at a flow rate of 100 sccm, the chamber pressure was 10 Pa, and surface modification was performed by turning on the plasma treatment for 5 min, the plasma treatment device had a power of 200 W, a frequency of 13.56 MHz, and a vacuum chamber pressure of ≤10-3 Pa, and finally the device was turned off and the double-plasma-treated graphene was taken out;

[0039] (2) 3 g of the double-plasma-treated graphene was dispersed in 50 mL of hydrochloric acid with a concentration of 1.0 M, and ultrasonic treatment was performed for 30 min at an ultrasonic power of 400 W; then 10.0 mL of aniline monomer and 0.5 g of amino benzoic acid were added, and magnetic stirring was performed for 30 min to uniformly adsorb the monomers on the surface of the graphene, the stirring speed was 120 rpm, 1.0 g of ammonium persulfate was dissolved in 10 mL of deionized water and was slowly added to the mixed solution, the reaction temperature was controlled at 5°C, and stirring reaction was performed for 6 h, after the reaction was completed, the product was filtered and washed with deionized water until the filtrate was neutral, and finally the product was placed in a vacuum drying oven at 60°C and was dried for 12 h at a vacuum degree of 0.5 Pa to obtain a graphene-polyaniline composite material;

[0040] (3) 1.5 g of graphene-polyaniline composite material was dispersed in 50 mL of N-methylpyrrolidone, ultrasonic treatment for 30 min, ultrasonic power was 400 W, 0.6 g of carbon nanotubes was added and ultrasonic treatment was continued for 30 min to ensure uniform dispersion, the mixture was magnetically stirred for 12 h to promote the formation of three-dimensional network structure, the stirring speed was 60 rpm; after stirring, it was filtered and washed with ethanol for 3 times to remove residual solvent, finally the product was placed in a vacuum drying oven at 80°C for drying for 12 h, the vacuum degree was 0.5 Pa, three-dimensional structure filler was obtained;

[0041] (4) 10 g of silver powder with a particle size of 5 μm was dispersed in 10 mL of ethylene glycol, ultrasonic treatment for 30 min, ultrasonic power was 400 W; 0.3 g of three-dimensional filler was added and ultrasonic treatment was continued for 30 min to ensure uniform mixing of the filler and silver powder, 2.5 g of epoxy resin was added and magnetically stirred for 4 h to form a homogeneous slurry, the stirring speed was 120 rpm, the slurry was ground through a three-roll grinder for 3 times, the roll spacing was 0.05 mm, the particle size was 5 μm, the dispersion uniformity was improved, and the conductive silver paste doped with graphene composite was prepared.

[0042] Comparative Example 1

[0043] The difference between Comparative Example 1 and Example 2 lies in the difference of steps (1) and (2), which are changed to: (1) graphene powder was dispersed in deionized water, the solid-liquid ratio was 1:20, ultrasonic treatment was used, the power was 300 W, and the time was 45 min to ensure uniform dispersion of graphene; the washed graphene dispersion was centrifuged at a speed of 7500 rpm for 7.5 min, after the end, the solid was collected and dried at 50°C for 3 h; 1.0 g of dried graphene powder was uniformly laid on a sample table, nitrogen was introduced, the nitrogen flow was 125 sccm, the chamber pressure was 7 Pa, plasma treatment was started for 10 min to complete nitrogen doping, the plasma treatment equipment power was 150 W, the frequency was 13.56 MHz, and the vacuum chamber pressure was ≤10-3 Pa, finally the plasma treated graphene was taken out;

[0044] (2) 1.75 g of plasma treated graphene was dispersed in 50 mL of 1.0 M hydrochloric acid, ultrasonic treatment for 30 min, ultrasonic power was 300 W; then 7.5 mL of aniline monomer and 0.4 g of amino benzoic acid were added, magnetic stirring for 30 min to make the monomer uniformly adsorbed on the surface of graphene, the stirring speed was 120 rpm, 0.6 g of ammonium persulfate was dissolved in 10 mL of deionized water and slowly added to the mixture, the reaction temperature was controlled at 2.5°C, stirring reaction for 6 h, after the reaction, it was filtered and washed with deionized water until the filtrate was neutral, finally the product was placed in a vacuum drying oven at 60°C for drying for 12 h, the vacuum degree was 0.5 Pa, graphene-polyaniline composite material was obtained; the rest of the steps were the same as Example 2.

[0045] Comparative Example 2

[0046] Comparative Example 2 differs from Example 2 in that step (1)(2) is 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 for 45 min to ensure uniform dispersion of graphene; centrifuge the cleaned graphene dispersion at a speed of 7500 rpm for 7.5 min, collect the solid after the end, and dry at 50°C for 3 h; evenly spread 1.0 g of dried graphene powder on the sample table, introduce oxygen, oxygen flow is 60 sccm, chamber pressure is 8 Pa, turn on plasma treatment for 4 min for surface modification, plasma treatment equipment power is 150 W, frequency is 13.56 MHz, vacuum chamber pressure is ≤10-3Pa, 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 1.0 M hydrochloric acid, ultrasonic treatment for 30 min, ultrasonic power is 300 W; then add 7.5 mL of aniline monomer and 0.4 g of amino benzoic acid, magnetically stir for 30 min to make the monomer uniformly adsorbed on the surface of graphene, stirring speed is 120 rpm, dissolve 0.6 g of ammonium persulfate in 10 mL of deionized water and slowly add to the mixture, control the reaction temperature at 2.5°C, stir for 6 h, after the reaction is completed, filter and wash with deionized water until the filtrate is neutral, finally dry the product in a vacuum drying oven at 60°C for 12 h, vacuum degree is 0.5 Pa, to obtain graphene-polyaniline composite material; the rest of the steps are the same as Example 2.

[0048] Comparative Example 3

[0049] Comparative Example 3 differs from Example 2 in that step (2) is changed to: disperse 1.75 g of double plasma treated graphene in 50 mL of 1.0 M hydrochloric acid, ultrasonic treatment for 30 min, ultrasonic power is 300 W; then add 7.5 mL of aniline monomer, magnetically stir for 30 min to make the monomer uniformly adsorbed on the surface of graphene, stirring speed is 120 rpm, dissolve 0.6 g of ammonium persulfate in 10 mL of deionized water and slowly add to the mixture, control the reaction temperature at 2.5°C, stir for 6 h, after the reaction is completed, filter and wash with deionized water until the filtrate is neutral, finally dry the product in a vacuum drying oven at 60°C for 12 h, vacuum degree is 0.5 Pa, to obtain graphene-polyaniline composite material; the rest of the steps are the same as Example 2.

[0050] Comparative Example 4

[0051] Comparative Example 4 differs from Example 2 in that step (2) is omitted, and step (3) is changed to: 1.0 g of double plasma treated graphene is dispersed in 50 mL of N-methylpyrrolidone, ultrasonic treatment for 30 min, ultrasonic power is 300 W, 0.45 g of carbon nanotubes is added and ultrasonic treatment is continued for 30 min to ensure uniform dispersion, the mixture is magnetically stirred for 12 h to promote the formation of three-dimensional network structure, the stirring speed is 60 rpm; after stirring, it is filtered and washed with ethanol for 3 times to remove residual solvent, finally the product is placed in a vacuum drying oven at 80℃ for drying for 12 h, the vacuum degree is 0.5 Pa, to obtain a three-dimensional structure filler; the rest of the steps are the same as Example 2.

[0052] Comparative Example 5

[0053] Comparative Example 5 differs from Example 2 in that step (3) is omitted, and step (4) is changed to: 7.5 g of silver powder with a particle size of 3 μm is dispersed in 10 mL of ethylene glycol, ultrasonic treatment for 30 min, ultrasonic power is 300 W; 0.2 g of graphene-polyaniline composite material is added and ultrasonic treatment is continued for 30 min to ensure that the filler and silver powder are uniformly mixed, 2.0 g of epoxy resin is added and magnetically stirred for 3 h to form a homogeneous slurry, the stirring speed is 120 rpm, the slurry is ground through a three-roll grinder for 3 times, the roll spacing is 0.05 mm, the particle size is 4 μm, to improve the dispersion uniformity, to prepare a conductive silver paste doped with graphene composite; the rest of the steps are the same as Example 2.

[0054] Effect Example

[0055] The performance analysis results of the conductive silver paste doped with one kind of graphene powder of Examples 1 to 3 and Comparative Examples 1 to 5 of the present application are given in Table 1 below.

[0056] Table 1

[0057] Resistivity (xlO -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 resistivity of the examples and the comparative examples, it can be found that the nitrogen-doped graphene is prepared by using the plasma to dope nitrogen into the graphene lattice in the application; the nitrogen doping can not only adjust the electronic structure of the graphene and improve the conductivity, but also increase the surface active sites, providing a basis for subsequent surface modification and polymerization; then the oxygen-containing functional groups are introduced on the surface of the graphene by the plasma surface modification technology, further enhancing the surface activity and the compatibility with other materials; the double plasma treatment makes the graphene have excellent conductivity and interface bonding capacity; the aniline monomer and the amino benzoic acid monomer are mixed and in-situ polymerized on the surface of the nitrogen-doped graphene to generate the polyaniline-amino benzoic acid copolymer; the graphene-polyaniline material obtained by in-situ polymerization is compounded with the carbon nanotube to construct a three-dimensional conductive network; the high aspect ratio and excellent conductivity of the carbon nanotube can form a synergistic effect with the graphene-polyaniline to further optimize the conductivity and mechanical properties of the material. The three-dimensional filler prepared above is added to the conductive silver paste, the carboxyl groups in the amino benzoic acid are exposed on the surface of the polymer chain during the polymerization process, and are adsorbed and combined with the silver particles by the van der Waals force to form a stable interface structure; this combination mode can not only improve the dispersibility of the silver particles, but also reduce the interface resistance and enhance the connectivity of the conductive network; at the same time, the introduction of the polyaniline provides an additional conductive channel for the conductive silver paste, further improving the overall conductivity.

[0059] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments but can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. The embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the above description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference signs in the claims should not be construed as limiting the claims.

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, and its preparation includes the following steps: (1) Spread 1.0g of dried graphene powder evenly on the sample stage, introduce nitrogen gas with a flow rate of 50-200 sccm and a chamber pressure of 4-10 Pa, and turn on plasma treatment for 10 min to complete nitrogen doping; then turn off the nitrogen gas, introduce oxygen gas with a flow rate of 20-100 sccm and a chamber pressure of 6-10 Pa, and turn on plasma treatment for 3-5 min to perform surface modification; finally turn off the equipment and take out the double plasma-treated graphene. (2) Disperse 0.5-3g of double plasma-treated graphene in 50mL of hydrochloric acid and sonicate for 30min with an ultrasonic power of 200-400W. Then add 5.0-10.0mL of aniline monomer and 0.3-0.5g of aminobenzoic acid and stir magnetically for 30min to make the monomer uniformly adsorbed on the graphene surface. The stirring speed is 120rpm. Dissolve 0.2-1.0g of ammonium persulfate in 10mL of deionized water and slowly add it to the mixture. Control the reaction temperature at 0-5℃ and stir for 6h. 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℃ and dry for 12h to obtain graphene-polyaniline composite material. (3) Disperse 0.5-1.5g of graphene-polyaniline composite material in 50mL of N-methylpyrrolidone, sonicate for 30min with an ultrasonic power of 200-400W, add 0.3-0.6g of carbon nanotubes and continue sonication for 30min to ensure uniform dispersion. Stir the mixture magnetically for 12h to promote the formation of a three-dimensional network structure. After stirring, filter and wash with ethanol three times to remove residual solvent. Finally, place the product in an 80℃ vacuum drying oven and dry for 12h to obtain a three-dimensional structure filler.

2. The 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: disperse graphene powder in deionized water with a solid-liquid ratio of 1:20, and use ultrasonic treatment with a power of 200-400W for 30-60 minutes to ensure uniform dispersion of graphene; centrifuge the washed graphene dispersion at a speed of 5000-10000rpm for 5-10 minutes, collect the solid after the centrifugation, and dry it at 50℃ for 3 hours.

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

4. The conductive silver paste doped with graphene powder according to claim 1, characterized in that, In step (2), the concentration of hydrochloric acid is 1.0M.

5. The conductive silver paste doped with graphene powder according to claim 1, characterized in that, In step (3), the magnetic stirring speed is 60 rpm.

6. The conductive silver paste doped with graphene powder according to claim 1, characterized in that, The vacuum degree of the vacuum drying process is 0.5 Pa.