Low-resistance dendritic flaky silver-coated copper powder and its preparation method and application

Abstract

The present invention discloses a low-resistance dendritic flaky silver-coated copper powder. The copper powder is dendritic and flaky, with a silver layer uniformly coated on the surface of the dendritic flaky copper powder. The silver layer is coated on the surface of the silver layer with a chelate layer, wherein the chelate layer comprises cysteine and glutathione. The present invention also discloses a method for preparing the low-resistance dendritic flaky silver-coated copper powder, comprising the following steps: plating silver on the surface of the dendritic flaky copper powder to obtain an intermediate; washing the intermediate with an aminothiol solution, drying it, and then adding it to a mixture containing cysteine and glutathione to carry out a chelate reaction to obtain the low-resistance dendritic flaky silver-coated copper powder. The present invention also discloses the use of the low-resistance dendritic flaky silver-coated copper powder in a coating. The present invention also discloses a coating comprising a film-forming substance and the low-resistance dendritic flaky silver-coated copper powder. The low-resistance dendritic flaky silver-coated copper powder of the present invention has good dispersibility, oxidation resistance, and conductivity in the coating, and can improve the adhesion of the coating.

Description

Technical Field

[0001] The invention relates to the technical field of silver-coated copper powder, in particular to low-resistance dendritic flaky silver-coated copper powder and a preparation method and application thereof. Background Art

[0002] Since the 20th century, science and technology have made significant progress, resulting in the emergence of numerous high-performance non-metallic materials, which have seen rapid development and application in the industrial coatings industry. However, while most non-metallic materials possess numerous excellent properties, they also possess inherent properties that must be mitigated during their application in various applications. Currently, the primary challenge is overcoming static electricity generation. To mitigate this, the addition of conductive fillers is often employed during the production process. Among the commonly used conductive fillers on the market, copper powder offers the advantage of low price, but its poor stability and susceptibility to oxidation during production and processing have limited its application prospects. Silver powder offers high conductivity but is expensive and can cause silver migration during use, making its application prospects uncertain. Consequently, conductive silver-coated copper powder, made by coating copper powder with a silver layer, offers the same high conductivity and stability as silver at a relatively low price, making it widely used in conductive self-adhesive paints. However, existing silver-coated copper powders still suffer from insufficient oxidation resistance, low conductivity, easy agglomeration and uneven dispersion in the paint, and poor coating adhesion. Summary of the Invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a low-resistance dendritic flaky silver-coated copper powder and its preparation method and application. The low-resistance dendritic flaky silver-coated copper powder of the present invention has good dispersibility, antioxidant properties, and conductivity in the coating, and can improve the adhesion of the coating.

[0004] The invention provides a low-resistance dendritic flaky silver-coated copper powder. The copper powder is in dendritic flaky form, the surface of which is uniformly coated with a silver layer, and the surface of the silver layer is coated with a chelate layer, wherein the chelate layer comprises cysteine and glutathione.

[0005] Preferably, the dendritic flake copper powder is obtained by processing dendritic copper powder into flakes.

[0006] Preferably, the particle size of the dendritic flaky copper powder is 8-20 μm; the thickness of the dendritic flaky copper powder is 0.4-2 μm.

[0007] The present invention also provides a method for preparing the low-resistance dendritic flaky silver-coated copper powder, comprising the following steps: plating silver on the surface of the dendritic flaky copper powder to obtain an intermediate; washing the intermediate with an aminothiol solution, drying it, and then adding it to a mixed solution containing cysteine and glutathione to carry out a chelating reaction to obtain the low-resistance dendritic flaky silver-coated copper powder.

[0008] Preferably, the solute of the aminothiol solution is at least one of cysteamine and acetylcysteine.

[0009] Preferably, the drying step comprises: keeping the mixture at 35-45°C for 0.4-0.6h, keeping the mixture at 55-65°C for 1.5-2.5h, and then naturally cooling the mixture to 20-25°C in a vacuum environment.

[0010] Preferably, the chelation reaction temperature is 50-80° C. and the time is 2-8 hours.

[0011] The present invention also proposes the application of the low-resistance dendritic flaky silver-coated copper powder in coatings.

[0012] The present invention also provides a coating comprising: a film-forming substance and the low-resistance dendritic flaky silver-coated copper powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is the SEM image of dendritic flaky copper powder.

[0014] Figure 2 These are SEM images of the dispersed state of silver-coated copper powder in the coating before and after chelation modification, where A is before chelation modification and B is after chelation modification. DETAILED DESCRIPTION

[0015] The invention provides a low-resistance dendritic flaky silver-coated copper powder. The copper powder is in dendritic flaky form, the surface of which is uniformly coated with a silver layer, and the surface of the silver layer is coated with a chelate layer, wherein the chelate layer comprises cysteine and glutathione.

[0016] Preferably, the dendritic flake copper powder is obtained by processing dendritic copper powder into flakes.

[0017] The above-mentioned dendritic copper powder can be purchased from the market.

[0018] The dendritic copper powder is processed into dendritic flake copper powder by ball milling.

[0019] The edges of the dendritic flaky copper powder are irregular, with multiple protrusions and notches.

[0020] The ball milling process comprises the following steps: uniformly mixing the dendritic copper powder with the auxiliary agent, and performing ball milling, wherein zirconia balls and steel balls are used in combination for the ball milling.

[0021] Preferably, the ball-to-material ratio is 3:1 based on the dendritic copper powder.

[0022] The weight ratio of the zirconia balls to the steel balls is preferably 2:1.

[0023] Preferably, the diameters of the zirconia balls are 1.0 mm and 3.0 mm, and the weight ratio of the zirconia balls with diameters of 1.0 mm and 3.0 mm is 1:3.

[0024] Preferably, the diameters of the steel balls are 0.8 mm and 3.0 mm, and the weight ratio of the steel balls with diameters of 0.8 mm and 3.0 mm is 1:3.

[0025] Preferably, the auxiliary agent is at least one of stearic acid and oleic acid; and preferably, the weight ratio of copper powder to auxiliary agent is 1:0.001-0.02.

[0026] According to the present invention, stearic acid, oleic acid and other additives are added during the ball milling process, so that the thickness of the dendritic flakes can be kept uniform during the process of grinding the dendritic copper powder into dendritic flaky copper powder, the particle size span can be made smaller, and the particle size distribution can be kept uniform. Furthermore, the copper powder can be evenly dispersed during the ball milling process, and agglomeration of the copper powder during the ball milling process can be avoided, thereby improving the uniform dispersibility of the dendritic flaky copper powder after ball milling.

[0027] The ball milling process is as follows: ball milling at a speed of 40 r / min for 4 hours, during which time an insulation jacket is added to the ball mill and a 50°C heat-conducting medium (such as at least one of water and heat-conducting oil) is introduced; then ball milling at a speed of 15 r / min for 2 hours, during which time a 30°C heat-conducting medium (such as at least one of water and heat-conducting oil) is introduced.

[0028] The present invention addresses the problem of high copper powder hardness by adjusting the type of grinding balls, grinding ball diameter, ball-to-material ratio, ball milling process, additives, etc., while ensuring ball milling efficiency, effectively improving the dendritic flaky structure after ball milling, preventing it from breaking and having a higher specific surface area, thereby helping to increase the conduction capacity.

[0029] In addition, the irregular edges of the dendritic flaky copper powder can increase the contact points between the copper powders, further increasing the conductivity and reducing the resistance.

[0030] The specific surface area of the dendritic flaky copper powder is 180-220 m 2 / kg, more preferably 202 m 2 / kg.

[0031] Preferably, the particle size of the dendritic flaky copper powder is 8-20 μm; the thickness of the dendritic flaky copper powder is 0.4-2 μm.

[0032] Preferably, the silver layer has a thickness of 20-120 nm.

[0033] The present invention also provides a method for preparing the low-resistance dendritic flaky silver-coated copper powder, comprising the following steps: plating silver on the surface of the dendritic flaky copper powder to obtain an intermediate; washing the intermediate with an aminothiol solution, drying it, and then adding it to a mixed solution containing cysteine and glutathione to carry out a chelating reaction to obtain the low-resistance dendritic flaky silver-coated copper powder.

[0034] Before silver plating, the dendritic flaky copper powder must be cleaned to remove oil and oxide layers. The specific cleaning steps include: first using an alkaline solution (such as sodium hydroxide aqueous solution, etc.) to remove oil, and then using an acidic solution (such as dilute sulfuric acid, etc.) to remove the oxide layer on the surface of the copper powder to obtain pure copper powder.

[0035] The silver plating step comprises: mixing dendritic flaky copper powder with a silver plating solution, performing a silver plating process, and obtaining an intermediate.

[0036] The silver plating solution includes: 40-170g / L of silver nitrate, 50-250g / L of reducing agent, and the solvent is water.

[0037] The silver plating solution also contains a pH adjuster so that the pH of the silver plating solution is 10.2-10.6.

[0038] Stir and silver plate at 40-60°C for 0.5-4h.

[0039] The reducing agent may be formaldehyde, ethylene glycol, etc., and the pH adjusting agent may be ethylenediamine, ammonium carbonate, etc.

[0040] The invention selects a suitable silver plating solution and process and adjusts a suitable pH value, thereby controlling the silver deposition rate and the uniformity of the silver layer and improving the adhesion of the silver layer.

[0041] In the above intermediate, the thickness of the silver layer is 20-120 nm, and the silver content is 5-40 wt%.

[0042] Preferably, the solute of the aminothiol solution is at least one of cysteamine and acetylcysteine.

[0043] In the aminothiol solution, the solute concentration is 0.08-0.15 mol / L, preferably 0.1 mol / L.

[0044] The aminothiol solution is used to ultrasonically clean the intermediate; preferably, the ultrasonic frequency is 35-45 kHz, more preferably 30 kHz.

[0045] The present invention has been found through research that after silver plating, the surface of the intermediate adsorbs complex, and there are still free impurity metal ions (such as Fe 2+ Cr 3+ The intermediate is ultrasonically cleaned with aminothiol solution. Aminothiol can chelate with free impurity metal ions and be removed from the surface of the intermediate by ultrasound. In addition, the thiol group in aminothiol can reduce the silver ammonia complex ion to generate silver element and attach to the surface of the intermediate, thereby achieving removal. complex to prepare for the subsequent chelation reaction; and select the appropriate type of aminothiol, which has a low activation energy and will not chelate with the intermediate.

[0046] Preferably, the drying step comprises: keeping the mixture at 35-45°C for 0.4-0.6h, keeping the mixture at 55-65°C for 1.5-2.5h, and then naturally cooling the mixture to 20-25°C in a vacuum environment.

[0047] The preferred vacuum environment pressure is -0.06~-1 kPa.

[0048] The present invention adopts a vacuum gradient drying process, which can avoid the agglomeration of intermediate powders and at the same time retain the active sites on the surface of the intermediates to prepare for the subsequent chelating reaction.

[0049] The vacuum gradient drying process of the present invention follows Fick's second law. By regulating the temperature gradient (ΔT=20°C) and the pressure gradient (ΔP=80 kPa), the moisture diffusion coefficient is increased so that the moisture diffusion coefficient is greater than the Hamaker constant of the dendritic flaky silver-coated copper powder. This can avoid the agglomeration of the dendritic flaky silver-coated copper powder caused by van der Waals forces while retaining the active sites on the surface of the intermediate.

[0050] Preferably, the chelation reaction temperature is 50-80° C. and the time is 2-8 hours.

[0051] In the mixed solution containing cysteine and glutathione, the concentration of cysteine is 0.03-0.08 mol / L, and the concentration of glutathione is 0.04-0.10 mol / L.

[0052] The present invention found that although both cysteine and glutathione contain sulfhydryl and carboxyl groups, their coordination behaviors are different:

[0053] 1. The adsorption energy of the carboxyl group in cysteine to Ag is weak, significantly weaker than that of the thiol group. The HOMO (highest occupied molecular orbital) in cysteine is mainly localized on the S atom, matching the energy level of the LUMO (lowest unoccupied molecular orbital) of Ag, promoting electron transfer from S to Ag. The thiol group in cysteine is most stable when it is perpendicularly coordinated to the Ag surface.

[0054] 2. The thiol group in glutathione has a low adsorption energy when coordinated with Cu, while the carboxyl and amino groups in glutathione coordinate synergistically with Cu, which can reduce the total energy of the system and form a stable five-membered ring configuration. The HOMO in glutathione is distributed on the carboxylic acid O and amino N atoms. The LUMO energy level difference between them and Cu is significantly smaller than the LUMO energy level difference between the thiol group (SH) and Cu, indicating that the carboxylic acid / amino group coordination is more favorable. The bidentate chelation of the carboxyl and amino groups to the Cu atom is the most stable configuration.

[0055] 3. Steric hindrance effect

[0056] The tripeptide skeleton of glutathione (γ-Glu-Cys-Gly) produces significant steric hindrance on the Ag surface, resulting in a reduced probability of contact between the thiol group and Ag; on the Cu surface, the flexible chain segment of glutathione allows the carboxylic acid and amino groups to adjust their conformation to form a low-strain chelate ring.

[0057] 4. According to Pearson's hard and soft acid-base theory (HSAB), silver It is a soft acid and has a strong coordination tendency with the thiol soft base of cysteine, while copper As a junction acid, it can form stable chelates with the carboxyl and amino groups of glutathione.

[0058] In summary, cysteine and glutathione achieve performance improvement by constructing a dual-ligand organic-inorganic hybrid interface based on the principles of coordination chemistry and colloidal stability. Cysteine preferentially forms a covalent bond with Ag due to its small molecular size and high HOMO energy level of the thiol group. Glutathione synergistically reduces the strain energy of the chelate ring through multiple functional groups, driving the coordination of carboxylic acid and amino groups with Cu. Steric hindrance and orbital matching jointly determine the coordination selectivity.

[0059] The present invention also proposes the application of the low-resistance dendritic flaky silver-coated copper powder in coatings.

[0060] The present invention also provides a coating comprising: a film-forming substance and the low-resistance dendritic flaky silver-coated copper powder.

[0061] The above-mentioned film-forming material can be acrylic resin, epoxy resin, epoxy-acrylic composite resin, etc.

[0062] In the above coating, the volume fraction of the low-resistance dendritic flaky silver-coated copper powder may be 40-80 vol%.

[0063] The above coating may further include: antioxidant, dispersant, flame retardant, filler and the like.

[0064] The double-layer repulsion potential energy of the chelated silver-coated copper powder after chelation modification is significantly higher than the van der Waals attraction potential energy, which can greatly improve the colloidal stability parameters and effectively inhibit agglomeration. This shows that the chelated silver-coated copper powder after chelation modification (i.e., the low-resistance dendritic flaky silver-coated copper powder) has good dispersion stability and can be evenly dispersed in the coating.

[0065] In addition, the amino groups in the chelating layer can form a hydrogen bond network with the resin matrix, and when the resin matrix contains benzene rings, it can also form a hydrogen bond network with the benzene ring structure. The stacking effect and the synergy of the two increase the interfacial bonding energy between the dendritic flaky silver-coated copper powder and the resin by 40%, thereby improving the adhesion of the entire coating.

[0066] In summary, the present invention uses cysteine and glutathione, both of which have good biocompatibility, as a dual-ligand system. The thiol group of cysteine forms an Ag-S covalent bond with the silver atom, while the carboxylic acid and amino groups of glutathione chelate with the uncoated copper core, forming an organic-inorganic hybrid interface with a double-anchor structure on the surface of the silver-coated copper powder to obtain a chelate layer.

[0067] Compared with the traditional method of modifying silver-coated copper powder with a silane coupling agent, the present invention forms a denser chelate layer through the synergistic effect of dual ligands, thereby increasing its coverage and improving the antioxidant properties of the dendritic flaky silver-coated copper powder. It can also ensure that the dendritic flaky silver-coated copper powder has good dispersion stability, avoids agglomeration, and is evenly dispersed in the coating. In addition, the dendritic flaky silver-coated copper powder can form a three-dimensional conductive network in the coating, thereby reducing the resistivity of the coating and improving the conductivity of the coating.

[0068] The chelating layer also contains amino and thiol groups, which can construct a dynamic disulfide bond network to achieve stress adaptive regulation during the coating curing process, and can also provide a hydrogen bond network with the resin matrix. Conjugation effect increases interfacial binding energy and improves the adhesion of the coating.

[0069] Furthermore, the preparation process of the low-resistance dendritic flaky silver-coated copper powder of the present invention is VOC-free and complies with RoHS environmental standards. This green and efficient preparation method provides new ideas for the development of high-performance conductive coatings.

[0070] Hereinafter, the technical solutions of the present invention will be described in detail through specific embodiments. However, it should be clearly stated that these embodiments are provided for illustration only and are not to be construed as limiting the scope of the present invention.

[0071] The water used in the following examples and comparative examples was deionized water.

[0072] Example 1

[0073] A method for preparing low-resistance dendritic flaky silver-coated copper powder comprises the following steps:

[0074] Ball milling: Take dendritic copper powder with a particle size of 18 μm and mix it with stearic acid in a weight ratio of 1:0.01, transfer it to a ball mill, adjust the ball-to-material ratio to 3:1 based on the dendritic copper powder, and ball mill it at a speed of 40 r / min for 4 h. During this period, add a heat preservation jacket to the ball mill and pass 50°C water. Then, ball mill it at a speed of 15 r / min for 2 h. During this period, pass 30°C water. After the ball milling is completed, take it out and obtain a specific surface area of 202 m 2 / kg of dendritic flaky copper powder (SEM images of dendritic flaky copper powder are as follows Figure 1 As shown in the figure, it can be seen that the edges of the dendritic flaky copper powder are irregular, with multiple protrusions and notches on the edges; the particle size D50 The thickness of the dendritic flaky copper powder is 19.18 μm; the thickness of the dendritic flaky copper powder is 400 nm); wherein, the grinding balls are composed of zirconia balls and steel balls in a weight ratio of 2:1;

[0075] The diameters of the zirconia balls are 1.0 mm and 3.0 mm, and the weight ratio of the zirconia balls with diameters of 1.0 mm and 3.0 mm is 1:3;

[0076] The diameters of the steel balls are 0.8 mm and 3.0 mm, and the weight ratio of the steel balls with diameters of 0.8 mm and 3.0 mm is 1:3;

[0077] Silver plating: The dendritic flaky copper powder was first washed with a sodium hydroxide solution to remove oil stains, and then washed with dilute sulfuric acid. The oxide layer on the surface of the copper powder was removed by the reaction mechanism of sulfuric acid and oxides to obtain pure dendritic flaky copper powder. The powder was then mixed with a silver plating solution (the silver plating solution included: 40g / L silver nitrate, 60g / L ethylene glycol, and ammonium carbonate adjusted to a pH of 10.3, with water as the solvent). The powder was silver-plated at 45°C for 30 minutes with stirring, and then washed with water to obtain an intermediate. The silver layer thickness was determined to be 70nm.

[0078] Surface modification: The intermediate was added to a 0.1 mol / L cysteamine aqueous solution and ultrasonically cleaned at 40 kHz. The intermediate was then transferred to a vacuum drying oven and the pressure was adjusted to -0.08 kPa to maintain a vacuum environment. The intermediate was kept at 40°C for 0.5 h, then at 60°C for 2 h, and then naturally cooled to 25°C to equilibrate the water content.

[0079] Then, a mixture containing cysteine and glutathione (the concentration of cysteine is 0.05 mol / L, the concentration of glutathione is 0.08 mol / L, and the solvent is water) is added and mixed, and the chelation reaction is stirred at 80°C for 2 hours. The powder is taken out, washed with water and ethanol, and dried to obtain low-resistance dendritic flaky silver-coated copper powder.

[0080] The silver-coated copper powder before chelation modification (i.e., the intermediate of Example 1) and the silver-coated copper powder after chelation modification (i.e., the low-resistance dendritic flaky silver-coated copper powder of Example 1) were used in the same amount in an epoxy-acrylic composite coating (the coating consists of an epoxy / acrylic composite resin containing a benzene ring, a solvent propyl ester, and an additive polyvinyl pyrrolidone in a weight ratio of 30:5:4) for testing. The results are as follows. Figure 2 shown.

[0081] Figure 2 These are SEM images of the dispersed state of silver-coated copper powder in the coating before and after chelation modification, where A is before chelation modification and B is after chelation modification.

[0082] Depend on Figure 2It can be seen that the agglomeration index of the silver-coated copper powder in the coating decreased from 23.7% to 6.5% before and after chelation modification. This is because the surface potential of the silver-coated copper powder was changed after chelation modification. The double-layer repulsion potential energy of the silver-coated copper powder was significantly higher than the van der Waals attraction potential energy, and the van der Waals attraction between the particles was effectively suppressed by electrostatic repulsion.

[0083] More importantly, the surface of the silver-coated copper powder after chelation modification is grafted with amino and thiol groups, which can form a hydrogen bond network with the resin matrix and The conjugation effect (its interfacial binding energy increased by about 40%) increased the peel strength of the coating from 1.2 N / mm to 2.8 N / mm;

[0084] The present invention also found that the silver-coated copper powder after chelation modification forms a three-dimensional conductive network in the coating, and compared with the silver-coated copper powder before chelation modification, its percolation threshold is reduced from 12 vol% to 7.5 vol%.

[0085] When the volume fraction of the chelated silver-coated copper powder in the coating reaches 15 vol%, the volume resistivity of the coating is , the volume resistivity of silver-coated copper powder before chelation modification is reduced by one order of magnitude.

[0086] The chelated silver-coated copper powder was made into a slurry, subjected to 2000h of wet heat aging treatment, and then its conductivity was tested. It was found that it could still maintain 86% of its initial conductivity, showing excellent antioxidant properties, corrosion resistance, and environmental stability.

[0087] Example 2

[0088] A method for preparing low-resistance dendritic flaky silver-coated copper powder comprises the following steps:

[0089] The intermediate of Example 1 was added to a 0.1 mol / L cysteamine aqueous solution and ultrasonically cleaned at an ultrasonic frequency of 40 kHz. The mixture was then transferred to a vacuum drying oven and the pressure was adjusted to -0.06 kPa to maintain a vacuum environment. The mixture was kept at 40°C for 0.5 h, then at 60°C for 2 h, and then naturally cooled to 25°C to equilibrate the water content.

[0090] Then, a mixture containing cysteine and glutathione (the concentration of cysteine is 0.05 mol / L, the concentration of glutathione is 0.04 mol / L, and the solvent is water) is added and mixed, and the chelation reaction is stirred at 75°C for 2.5 hours. The powder is taken out, washed with water and ethanol, and dried to obtain low-resistance dendritic flaky silver-coated copper powder.

[0091] Example 3

[0092] A method for preparing low-resistance dendritic flaky silver-coated copper powder comprises the following steps:

[0093] The intermediate of Example 1 was added to a 0.1 mol / L aqueous solution of acetylcysteine, and ultrasonic cleaning was performed at an ultrasonic frequency of 40 kHz. The mixture was then transferred to a vacuum drying oven and the pressure was adjusted to -0.1 kPa to maintain a vacuum environment. The mixture was kept at 40°C for 0.5 h, then at 60°C for 2 h, and then naturally cooled to 25°C to equilibrate the water content.

[0094] Then, a mixture containing cysteine and glutathione (the concentration of cysteine is 0.03 mol / L, the concentration of glutathione is 0.08 mol / L, and the solvent is water) is added and mixed, and the chelation reaction is stirred at 60°C for 3 hours. The powder is taken out, washed with water and ethanol, and dried to obtain low-resistance dendritic flaky silver-coated copper powder.

[0095] Comparative Example 1

[0096] A method for preparing dendritic flaky silver-coated copper powder comprises the following steps:

[0097] The “mixed solution containing cysteine and glutathione (the concentration of cysteine is 0.05 mol / L, the concentration of glutathione is 0.08 mol / L, and the solvent is water)” is replaced with “a cysteine aqueous solution with a concentration of 0.05 mol / L”, and the rest is the same as in Example 1.

[0098] Comparative Example 2

[0099] A method for preparing dendritic flaky silver-coated copper powder comprises the following steps:

[0100] The “mixed solution containing cysteine and glutathione (the concentration of cysteine is 0.05 mol / L, the concentration of glutathione is 0.08 mol / L, and the solvent is water)” is replaced with “a glutathione aqueous solution with a concentration of 0.08 mol / L”, and the rest is the same as in Example 1.

[0101] Comparative Example 3

[0102] A method for preparing dendritic silver-coated copper powder comprises the following steps:

[0103] The “dendritic flaky copper powder” was replaced with “dendritic copper powder with a particle size of 18 μm”, and dendritic silver-coated copper powder was prepared according to the silver plating and surface modification process of Example 1.

[0104] Comparative Example 4

[0105] A method for preparing low-resistance dendritic flaky silver-coated copper powder comprises the following steps:

[0106] The intermediate of Example 1 was directly added to a mixture containing cysteine and glutathione (the concentration of cysteine was 0.05 mol / L, the concentration of glutathione was 0.08 mol / L, and the solvent was water), mixed, and stirred at 80°C for chelation reaction for 2 hours. The mixture was washed with water and dried to obtain low-resistance dendritic flaky silver-coated copper powder.

[0107] Comparative Example 5

[0108] A method for preparing low-resistance dendritic flaky silver-coated copper powder comprises the following steps:

[0109] The intermediate of Example 1 was added to a 0.1 mol / L cysteamine aqueous solution and ultrasonically cleaned at an ultrasonic frequency of 40 kHz. The mixture was then transferred to a vacuum drying oven, the pressure was adjusted to -0.08 kPa to maintain a vacuum environment, and the mixture was kept at 40° C. for 2 h.

[0110] Then, a mixture containing cysteine and glutathione (the concentration of cysteine is 0.05 mol / L, the concentration of glutathione is 0.08 mol / L, and the solvent is water) is added and mixed, and the chelation reaction is stirred at 80°C for 2 hours. The powder is taken out, washed with water, and dried to obtain low-resistance dendritic flaky silver-coated copper powder.

[0111] The silver-coated copper powders prepared in Examples 1-3 and Comparative Examples 1-5 were mixed with acrylic resin coatings (the acrylic resin coatings consisted of acrylic resin, solvent propyl ester, and additive polyvinyl pyrrolidone in a weight ratio of 30:5:4) to obtain conductive coatings. The volume fraction of the silver-coated copper powder in each group of conductive coatings was 40 vol%.

[0112] The conductive coatings of each group were prepared into coatings according to the respective methods. The coatings were dried at 65° C. for 30 min. The performance of the coatings was tested, and the results are shown in Table 1.

[0113] The corrosion resistance was tested according to the ASTM D2247 humidity and heat cycle test.

[0114] Adhesion is tested in accordance with GB / T9286-2021-1C-1.

[0115]

[0116] It can be seen from Example 1 and Comparative Examples 1-2 that when modified with cysteine or glutathione alone, the corrosion resistance of the dendritic flaky silver-coated copper powder in the coating is lower than that of Example 1 modified with cysteine and glutathione together, and its conductivity is also lower than that of Example 1;

[0117] It can be seen from Example 1 and Comparative Example 3 that the dendritic silver-coated copper powder of Example 1 has better conductivity, adhesion and corrosion resistance than the dendritic silver-coated copper powder of Comparative Example 3;

[0118] It can be seen from Example 1 and Comparative Example 4 that the conductivity and corrosion resistance of the obtained dendritic flaky silver-coated copper powder are lower than those of Example 1 when the chelation modification is performed directly without washing with an aminomercaptan aqueous solution and vacuum gradient drying.

[0119] It can be seen from Example 1 and Comparative Example 5 that the conductivity and corrosion resistance of the dendritic flaky silver-coated copper powder obtained after constant temperature vacuum drying and chelation modification are lower than those in Example 1.

[0120] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A low-resistance dendritic flaky silver-coated copper powder, characterized in that: The copper powder is in the shape of dendrite flakes, a silver layer is evenly coated on the surface of the dendrite flake copper powder, and a chelate layer is coated on the surface of the silver layer, wherein the chelate layer comprises: cysteine and glutathione; The method for preparing the low-resistance dendritic flaky silver-coated copper powder comprises the following steps: plating silver on the surface of the dendritic flaky copper powder to obtain an intermediate; washing the intermediate with an aminothiol solution, drying it, and then adding it to a mixed solution containing cysteine and glutathione to carry out a chelating reaction to obtain the low-resistance dendritic flaky silver-coated copper powder.

2. The low-resistance dendritic flaky silver-coated copper powder according to claim 1, characterized in that: Dendritic flake copper powder is obtained by processing dendritic copper powder into flakes.

3. The low-resistance dendritic flaky silver-coated copper powder according to claim 1, characterized in that: The particle size of the dendritic flake copper powder is 8-20 μm.

4. The low-resistance dendritic flaky silver-coated copper powder according to claim 1, characterized in that: The thickness of the dendritic flake copper powder is 0.4-2 μm.

5. A method for preparing the low-resistance dendritic flaky silver-coated copper powder according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: plating silver on the surface of dendritic flaky copper powder to obtain an intermediate; washing the intermediate with an aminothiol solution, drying, and then adding the intermediate into a mixed solution containing cysteine and glutathione to carry out a chelating reaction to obtain low-resistance dendritic flaky silver-coated copper powder.

6. The method for preparing the low-resistance dendritic flaky silver-coated copper powder according to claim 5, characterized in that: The solute of the aminothiol solution is at least one of cysteamine and acetylcysteine.

7. The method for preparing the low-resistance dendritic flaky silver-coated copper powder according to claim 5, characterized in that: The drying steps include: keeping the temperature at 35-45 DEG C for 0.4-0.6 hours, keeping the temperature at 55-65 DEG C for 1.5-2.5 hours, and then naturally cooling the mixture to 20-25 DEG C in a vacuum environment.

8. The method for preparing the low-resistance dendritic flaky silver-coated copper powder according to claim 5, characterized in that: The chelating reaction temperature is 50-80°C and the time is 2-8 hours.

9. Use of the low-resistance dendritic flaky silver-coated copper powder according to any one of claims 1 to 4 in coatings.

10. A coating, characterized in that: include: A film-forming substance and the low-resistance dendritic flaky silver-coated copper powder as claimed in any one of claims 1 to 4.

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