Preparation method of silver-coated copper powder

Abstract

The invention discloses a preparation method of silver-coated copper powder, which comprises the following steps: mixing copper powder with a hydrogen salt solution, and pretreating to obtain pretreated copper powder; preparing a solution A and a solution C; the solution A comprises a reducing agent, and the solution C comprises silver salt and a complexing agent I; mixing the solution A, a dispersing agent, a complexing agent II and the pretreated copper powder to obtain a solution B; and the solution C is dropwise added into the solution B for a reduction reaction, and the silver-coated copper powder is obtained. Hydrogen ions dissociated by hydrosalt are combined with hydroxyl on the surface of the copper powder to generate water, and an oxide layer of the copper powder is removed, so that the silver-coated copper powder has good oxidation resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal powder preparation, and particularly relates to a method for preparing uniformly coated silver-coated copper powder with high antioxidant property. Background Art

[0002] In recent years, ultrafine metal powders have been widely used in many fields such as aerospace, medical equipment, integrated circuits, and electronic pastes due to their excellent mechanical properties, optical properties, antibacterial properties, and electrical conductivity. Ultrafine silver powder has been widely developed due to its excellent electrical conductivity. However, as one of the precious metal materials, its high cost limits its application. Developing a material with comparable performance to silver powder but greatly reduced cost has become the research and development focus in the field of electronic materials.

[0003] Copper has similar electrical conductivity to silver and is widely used. However, its nature is active, and its outer surface is easily oxidized to form non-conductive oxides at room temperature, resulting in a significant reduction in its practicality. After coating the copper powder with metallic silver, a core-shell composite structure with a copper powder core and a silver-covered outer surface is formed. This structure enables the internal copper powder to be wrapped by silver, reducing direct contact with air, thereby significantly improving the antioxidant ability and overall stability of the copper powder, and at the same time, the production cost can be reduced.

[0004] Currently, the commonly used methods for preparing silver-coated copper powder mainly include melting atomization method, mechanical ball milling method, and electroless plating method, etc. Although the melting atomization method and the mechanical ball milling method are easy to achieve large-scale production, they have disadvantages such as high cost, cumbersome process, and weak bonding of the silver shell. In contrast, the electroless plating method is widely used due to its advantages such as simple operation, low production cost, and stable silver-copper bonding. However, the silver-coated copper powder prepared by the electroless plating reaction has weak antioxidant property, resulting in poor performance and limited application scenarios. Therefore, it is urgent to improve the antioxidant property of silver-coated copper powder. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art to a certain extent. For this reason, the present invention provides a method for preparing silver-coated copper powder, and the silver-coated copper powder obtained by the preparation method of the present invention has excellent antioxidant property.

[0006] Therefore, in the first aspect of the present invention, the present invention proposes a method for preparing silver-coated copper powder, including the following steps: mixing copper powder with a hydrogen salt, performing pretreatment to obtain pretreated copper powder; preparing solution A and solution C; solution A includes a reducing agent, and solution C includes a silver salt and complexing agent I; mixing solution A, a dispersant, complexing agent II, and the pretreated copper powder to obtain solution B; dropping solution C into solution B to perform a reduction reaction to obtain silver-coated copper powder.

[0007] In some embodiments, the hydrogen salt includes pyrrolidone hydrotribromide.

[0008] In some embodiments, the mass percentage concentration of the hydrogen salt is 0.5% to 1.5%.

[0009] In some embodiments, the mass of the hydrogen salt accounts for 10% to 30% of the mass of the copper powder.

[0010] In some embodiments, the preparation method satisfies at least one of the following: (1) the reducing agent includes at least one of ascorbic acid, glucose, and sodium potassium tartrate; (2) the silver salt includes silver nitrate; (3) the complexing agent I includes ammonia water.

[0011] In some embodiments, the dispersant includes at least one of PVP-k30, PVP-58k, PVP-360k, and gum arabic.

[0012] In some embodiments, the complexing agent II includes at least one of ethylenediaminetetraacetic acid and ethylenediaminetetraacetate.

[0013] In some embodiments, the mass ratio of the dispersant to the pretreated copper powder is (0.05 to 0.10):1; the mass ratio of the complexing agent II to the pretreated copper powder is (0.02 to 0.08):1.

[0014] In some embodiments, in the step of dropping solution C into solution B for the reduction reaction, the dropping rate of solution C is 1 mL / min to 10 mL / min; and / or, the temperature of the reduction reaction is 20°C to 50°C, and the reaction time is 20 min to 60 min.

[0015] In the second aspect of the present invention, the present invention provides a silver-coated copper powder, which includes the silver-coated copper powder obtained by the preparation method of the first aspect.

[0016] Compared with the prior art, the beneficial technical effects achieved by the present invention are as follows:

[0017] In the present invention, pyrrolidinone hydrobromide is used to deoxidize copper powder and remove the oxide layer on the surface of copper powder. Pyrrolidinone hydrobromide decomposes to produce pyrrolidinone molecules, hydrogen ions, and bromide ions. Among them, pyrrolidinone molecules combine with the copper surface to form a complex to prevent further oxidation of copper. When it is added to the reducing solution containing PVP, it can not only prevent agglomeration but also enable further adsorption of PVP molecules to prevent the surface of the silver-coated copper powder from being oxidized; hydrogen ions combine with the hydroxyl groups on the copper surface to generate water, removing the oxide layer and impurities on the copper powder, playing an antioxidant role; bromide ions are adsorbed on the silver surface, controlling the arrangement and growth of silver nanocrystals to form a (111) crystal plane, further enhancing the antioxidant ability.

[0018] The additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of embodiments in conjunction with the accompanying drawings, in which:

[0020] Figure 1 XRD pattern of the silver-coated copper powder of Example 1 of the present invention;

[0021] Figure 2 SEM image of the silver-coated copper powder of Example 1 of the present invention;

[0022] Figure 3 Cross-sectional SEM image of the silver-coated copper powder of Example 1 of the present invention;

[0023] Figure 4 SEM image of the silver-coated copper powder of Example 2 of the present invention;

[0024] Figure 5 SEM image of the silver-coated copper powder of Example 3 of the present invention;

[0025] Figure 6 TG curve of the silver-coated copper powder of Example 1 of the present invention;

[0026] Figure 7 Schematic diagram of the chemical reaction in the preparation process of the silver-coated copper powder of the present invention;

[0027] Figure 8 TG curve of the silver-coated copper powder of Comparative Example 1 of the present invention. Detailed Description of the Invention

[0028] Embodiments of the present invention will be described in detail below. The following described embodiments are exemplary and are only used to explain the present invention, and should not be construed as a limitation to the present invention.

[0029] It should be noted that the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Further, in the description of the present invention, unless otherwise stated, "a plurality of" means two or more.

[0030] The endpoints and any values disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0031] In this text, the term "comprising" or "including" is an open expression, that is, it includes the content specified in the present invention, but does not exclude other aspects of the content.

[0032] In the first aspect of the embodiments of the present invention, a method for preparing silver-coated copper powder is proposed, which includes the following steps: mixing copper powder with a hydrogen salt and performing pretreatment to obtain pretreated copper powder; preparing solution A and solution C; solution A includes a reducing agent, and solution C includes a silver salt and complexing agent I; mixing solution A, a dispersant, complexing agent II and the pretreated copper powder to obtain solution B; dropping solution C into solution B for a reduction reaction to obtain silver-coated copper powder.

[0033] The process of the method for preparing silver-coated copper powder provided in the embodiments of the present invention is simple, with low production cost and strong practicability. Mixing the copper powder with the hydrogen salt enables the hydrogen ions dissociated from the hydrogen salt to combine with the hydroxyl groups on the copper surface to form water, removing the oxide layer and impurities on the copper powder and playing an antioxidant role.

[0034] In solution B, it includes a reducing agent, a dispersant, complexing agent II and the pretreated copper powder. Among them, after complexing agent II undergoes a complexation reaction with copper ions to form a stable complex, the concentration of free copper ions in the solution decreases, which can slow down the reaction rate of copper ions in the subsequent reduction reaction, thereby effectively controlling the size of the generated copper particles; the reducing agent reduces complexed copper, and its reaction rate is relatively slow, which is beneficial to controlling the reaction process; the dispersant plays a role in dispersing the copper powder during the reaction, preventing the aggregation of copper powder particles, ensuring that silver ions can be evenly deposited on the surface of the copper powder, and being beneficial to improving the uniformity of particle coating. In addition, the dispersant is compounded with complexing agent II. The copper powder is dispersed through the steric hindrance effect of the dispersant, and at the same time, the silver ions are chelated into complex ions through the chelation effect of complexing agent II, reducing the release rate and chemical activity of silver ions. Therefore, through the synergistic effect of the steric hindrance effect and the chelation effect, the silver plating rate is slowed down, and uniform and dense coating of silver ions on the copper powder is achieved.

[0035] In solution C, the silver ions in the silver salt undergo a complexation reaction with complexing agent I to form a stable complex solution, which can ensure that the silver ions are evenly deposited on the surface of the copper powder during the reaction, being beneficial to improving the uniformity and compactness of particle coating.

[0036] Finally, solution C is dropped into solution B for a reduction reaction. By means of dropping, the reaction rate between the complexed silver ion solution and the reducing solution can be slowed down, further controlling the nucleation and growth rate of silver particles, enabling the silver layer to be evenly deposited on the surface of the copper powder, contributing to the formation of a dense and continuous silver coating layer, and improving the conductivity and antioxidant property of the silver-coated copper powder.

[0037] Thus, the preparation method of the present invention can effectively improve the antioxidant property and coating uniformity of the silver-coated copper powder.

[0038] In some embodiments of the present invention, the hydrogen salt includes pyrrolidone hydrobromide.

[0039] The pyrrolidone hydrobromide provided by the embodiments of the present invention can dissociate into pyrrolidone molecules, and can also dissociate into hydrogen ions and bromide ions. The chemical reaction between pyrrolidone hydrobromide and copper is as Figure 7 shown. It can be seen from Figure 7 that the pyrrolidone dissociated from pyrrolidone hydrobromide forms an adsorption layer on the surface of copper powder, which can briefly isolate air and slow down the oxidation of copper nuclei; the hydrogen ions combine with the hydroxyl groups on the copper surface to form water, removing the oxide layer and impurities on the copper powder and playing an antioxidant role; the bromide ions can adsorb on the silver surface to control the arrangement and growth of silver nanocrystals to form a (111) crystal plane. The (111) crystal plane of silver is the most closely packed crystal plane in the face-centered cubic (FCC) structure, with closely arranged atoms and fewer defects. This dense structure can reduce the penetration paths of corrosion media such as oxygen and water, thereby delaying the oxidation of copper nuclei and enhancing the antioxidant ability of silver-coated copper powder.

[0040] In some embodiments of the present invention, the mass percentage concentration of the hydrogen salt is 0.5% - 1%.

[0041] When the hydrogen salt provided by the embodiments of the present invention meets the above conditions, it can effectively remove the oxide layer and impurities on the copper powder, while avoiding corrosion of the copper powder itself and causing damage to the surface of the copper powder.

[0042] As an example, the mass percentage concentration of the hydrogen salt is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, etc.

[0043] In some embodiments of the present invention, the mass of the hydrogen salt accounts for 10% - 30% of the mass of the copper powder. Thereby, the antioxidant performance of the silver-coated copper powder can be further improved.

[0044] As an example, the mass of the hydrogen salt accounts for 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, etc. of the mass of the copper powder.

[0045] In some embodiments of the present invention, the preparation method satisfies at least one of the following: (1) the reducing agent includes at least one of ascorbic acid, glucose, and sodium potassium tartrate; (2) the silver salt includes silver nitrate; (3) the complexing agent I includes ammonia water.

[0046] When the preparation method of the embodiments of the present invention meets the above conditions, silver-coated copper powder with uniform size, dense structure, and antioxidant property can be effectively obtained.

[0047] In some embodiments of the present invention, the molar ratio of the reducing agent to the silver ions of the silver salt is (1 - 2)∶1.

[0048] When the preparation method provided by the embodiments of the present invention meets the above ratio, it is conducive to the full progress of the reaction and obtains silver-coated copper powder with excellent performance. Therefore, the preparation method of the present invention can effectively improve the density and oxidation resistance of the silver-coated copper powder.

[0049] In some embodiments of the present invention, the mass ratio of silver ions of the silver salt to the pretreated copper powder is (0.15 - 0.3):1.

[0050] When the preparation method provided by the embodiments of the present invention meets the above ratio, it is conducive to generating silver-coated copper powder with uniform coating and dense structure.

[0051] As an example, the mass ratio of silver ions to the pretreated copper powder is 0.15:1, 0.18:1, 0.2:1, 0.22:1, 0.25:1, 0.28:1, 0.3:1, etc.

[0052] In some embodiments of the present invention, the dispersant includes at least one of PVP-k30, PVP-58k, PVP-360k, and gum arabic.

[0053] The present invention uses PVP as a dispersant to coordinate with silver, which can effectively prevent the aggregation between silver-coated copper particles, avoid uneven coating, and at the same time prevent the surface of the silver-coated copper from being oxidized. In addition, the combined action of the pyrrolidone ring adsorption and the methylene long chain of PVP can play a steric hindrance role; gum arabic is a polyhydroxy polymer, and its branched structure plays a steric hindrance role. The dispersant is compounded with complexing agent II, and the silver plating rate is slowed down through the synergistic effect of steric hindrance and chelation to achieve uniform and dense coating of silver on the copper powder. Thus, silver-coated copper powder with a smooth and dense silver layer, a relatively high tapped density, and excellent oxidation resistance is obtained.

[0054] In some embodiments of the present invention, the mass ratio of the dispersant to the pretreated copper powder is (0.05 - 0.10):1.

[0055] When the preparation method provided by the embodiments of the present invention meets the above ratio, it is conducive to generating silver-coated copper powder with uniform coating and dense structure.

[0056] As an example, the mass ratio of the dispersant to the pretreated copper powder is 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, etc.

[0057] In some embodiments of the present invention, the complexing agent II includes at least one of ethylenediaminetetraacetic acid and ethylenediaminetetraacetate. Therefore, the preparation method of the present invention can effectively improve the oxidation resistance of the silver-coated copper powder.

[0058] In some embodiments of the present invention, the mass ratio of the complexing agent II to the pretreated copper powder is (0.02 - 0.08):1.

[0059] When the preparation method provided by the embodiments of the present invention meets the above ratio, it is beneficial to generate silver-coated copper powder with uniform coating and dense structure.

[0060] As an example, the mass ratio of complexing agent II to pretreated copper powder is 0.02∶1, 0.03∶1, 0.04∶1, 0.05∶1, 0.06∶1, 0.07∶1, 0.08∶1, etc.

[0061] In some embodiments of the present invention, in the step of adding solution C dropwise to solution B for the reduction reaction, the dropping rate of solution C is 1 mL / min to 10 mL / min; and / or, the temperature of the reduction reaction is 20°C to 50°C, and the reaction time is 20 min to 60 min.

[0062] In the present invention, when the dropping rate of solution C is controlled to be 1 mL / min to 10 mL / min, the contact time between the silver solution and the copper particles can be prolonged, enabling silver to grow slowly onto the surface of the copper particles, which is beneficial to improving the uniformity of the coating. At the same time, controlling the temperature of the reduction reaction to be 20°C to 50°C and the reaction time to be 20 min to 60 min is beneficial to the full progress of the reaction, further improving the density and oxidation resistance of the coating.

[0063] As an example, the dropping rate is 1 mL / min, 2 mL / min, 3 mL / min, 4 mL / min, 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min, etc.

[0064] As an example, the temperature of the reduction reaction is 20°C, 30°C, 40°C, 50°C, etc.

[0065] As an example, the reaction time is 20 min, 30 min, 40 min, 50 min, 60 min, etc.

[0066] In some embodiments of the present invention, after the reduction reaction, it further includes centrifugation, washing, and drying; the washing process includes washing the silver-coated copper powder with water and absolute ethanol at least 3 times each; the temperature of the drying process is 55 - 65°C, and the time is 5 - 8 h.

[0067] As an example, the temperature of the drying process is 55°C, 57°C, 59°C, 60°C, 62°C, 64°C, 65°C, etc.

[0068] As an example, the time of the drying process is 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, etc.

[0069] In the second aspect of the present invention, the present invention provides a silver-coated copper powder, which includes the silver-coated copper powder obtained by the preparation method of the first aspect. Thus, the silver-coated copper powder of the present invention has excellent antioxidant properties.

[0070] The solutions of the present invention will be explained below with reference to the examples. Those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be construed as limiting the scope of the present invention. For those not specifically noted in the examples regarding technical or conditions, the techniques or conditions described in the literature in this field or according to the product specifications are followed. For reagents or instruments not indicated with the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0071] Example 1

[0072] (1) Pretreatment of copper powder: Take 1 g of untreated copper powder and add it to 20 mL of a 0.5% pyrrolidone hydrotribromide solution, and ultrasonicate for 3 min to remove the oxygen on the surface of the copper powder;

[0073] (2) Preparation of reducing solution A: Weigh 1.016 g of potassium sodium tartrate and dissolve it in 50 mL of deionized water to obtain a reducing solution A with a concentration of 0.07 mol / L;

[0074] (3) Preparation of reaction solution B: Weigh 0.05 g of gum arabic, 0.03 g of ethylenediaminetetraacetic acid and the product obtained in step (1) and add them to solution A, and stir well to mix evenly to obtain reaction solution B;

[0075] (4) Preparation of silver plating solution C: Weigh 0.315 g of silver nitrate and dissolve it in 30 mL of deionized water, and then dropwise add ammonia water until the solution just becomes clear to obtain a silver ammonia solution C with a concentration of 0.06 mol / L.

[0076] (5) Reduction reaction: Under the condition of a 40°C water bath, slowly drop the silver ammonia solution C into the reaction solution B at a dropping rate of 2 min / mL. After the addition of the silver ammonia solution is completed, react for 30 min; after the reaction is completed, wash the powder 3 times with deionized water and anhydrous ethanol respectively, the drying temperature is 60°C, and the drying time is 5 h to obtain the silver-coated copper powder.

[0077] The silver-coated copper powder obtained in Example 1 was subjected to XRD analysis, and the results are shown in Figure 1 . From Figure 1 it can be seen that the diffraction characteristic peaks of copper and silver are included in the spectrum, indicating that silver is deposited on the surface of the copper powder. No other diffraction peaks are shown in the spectrum, proving that there are no other impurities in the prepared product.

[0078] The silver-coated copper powder prepared in Example 1 was observed by electron microscopy, and the results are shown in Figure 2 and Figure 3 . Figure 2It shows that the silver-coated copper powder is highly dispersed, the surface of the silver shell layer is smooth and dense, and there is no exposed copper matrix. As shown in Figure 3 a, the silver-coated copper powder has a core-shell structure, and the silver layer is uniformly and densely coated. Figure 3 b shows that the thickness of the silver layer is about 100 nm, and there is no obvious interface between the copper core and the silver layer, indicating good coating effect.

[0079] Thermogravimetric analysis was carried out on the silver-coated copper powder prepared in Example 1, and the uncoated copper powder was used as a control at the same time. The results are shown in Figure 6 . As shown in Figure 6 , in an air atmosphere, the copper powder begins to be oxidized at 200 °C, and the weight gain phenomenon is obvious, while the initial oxidation temperature of the silver-coated copper powder is 260 °C; when the temperature rises to 300 °C, the weight gain of the silver-coated copper powder is only 0.5%, while the weight gain of the copper powder is 3.7%; as the temperature rises to 600 °C, the difference in the weight gain percentage between the copper powder and the silver-coated copper powder is 5%, indicating that the silver-coated copper powder has excellent antioxidant performance.

[0080] Example 2

[0081] (1) Pretreatment of copper powder: Take 1 g of untreated copper powder and add it to 20 mL of a 1% pyrrolidinium hydrotribromide solution, and ultrasonicate for 3 min to remove the oxygen on the surface of the copper powder;

[0082] (2) Preparation of reducing solution A: Weigh 1.016 g of sodium potassium tartrate and dissolve it in 50 mL of deionized water to obtain a reducing solution A with a concentration of 0.07 mol / L;

[0083] (3) Preparation of reaction solution B: Weigh 0.08 g of PVP-k30, 0.05 g of ethylenediaminetetraacetic acid and the product obtained in step (1) and add them to solution A, stir well and mix evenly to obtain reaction solution B;

[0084] (4) Preparation of silver plating solution C: Weigh 0.477 g of silver nitrate and dissolve it in 30 mL of deionized water, and then drop ammonia water until the solution just becomes clear to obtain a silver ammonia solution C with a concentration of 0.09 mol / L.

[0085] (5) Reduction reaction: Under the condition of a 30 °C water bath, slowly drop the silver ammonia solution C into the reaction solution B at a dropping rate of 5 min / mL. After the addition of the silver ammonia solution is completed, react for 30 min; after the reaction is completed, wash the powder 3 times with deionized water and absolute ethanol respectively, and the drying temperature is 60 °C and the drying time is 5 h to obtain silver-coated copper powder.

[0086] The silver-coated copper powder obtained in Example 2 was observed by electron microscopy. The results are shown in Figure 4 . As can be seen from Figure 4 , the surface of the prepared silver-coated copper powder is smooth, there are a small number of silver particles adsorbed on the shell layer, and there is no exposed copper matrix, indicating that the silver-coated copper powder has excellent antioxidant performance.

[0087] Example 3

[0088] (1) Pretreatment of copper powder: Take 1 g of untreated copper powder and add it to 20 mL of a 1.5% pyrrolidone hydrotribromide solution, ultrasonicate for 3 min to remove the oxygen on the surface of the copper powder;

[0089] (2) Preparation of reducing solution A: Weigh 1.016 g of potassium sodium tartrate and dissolve it in 50 mL of deionized water to obtain a reducing solution A with a concentration of 0.07 mol / L;

[0090] (3) Preparation of reaction solution B: Weigh 0.08 g of PVP-360k, 0.02 g of ethylenediaminetetraacetic acid and the product obtained in step (1) and add them to solution A, stir well and mix evenly to obtain reaction solution B;

[0091] (4) Preparation of silver-plated solution C: Weigh 0.315 g of silver nitrate and dissolve it in 30 mL of deionized water, then dropwise add ammonia water until the solution becomes just clear to obtain a silver ammonia solution C with a concentration of 0.06 mol / L.

[0092] (5) Reduction reaction: Under the condition of a 30 °C water bath, slowly drop the silver ammonia solution C into the reaction solution B at a dropping rate of 10 min / mL. After the addition of the silver ammonia solution is completed, react for 30 min; after the reaction is completed, wash the powder 3 times with deionized water and anhydrous ethanol respectively, the drying temperature is 60 °C, and the drying time is 5 h to obtain silver-coated copper powder.

[0093] The silver-coated copper powder obtained in Example 3 was observed by electron microscopy, and the results are shown in Figure 5 . From Figure 5 it can be seen that the silver layer of the prepared silver-coated copper powder is tightly coated, the surface is relatively rough, and there is no exposed copper matrix, indicating that the silver-coated copper powder has excellent antioxidant performance.

[0094] Comparative Example 1:

[0095] The difference between Comparative Example 1 and Example 2 is that Comparative Example 1 does not have the pretreatment of copper powder in step (1).

[0096] The silver-coated copper powder prepared in Comparative Example 1 was subjected to thermogravimetric analysis, and at the same time, uncoated copper powder was used as a control. The analysis results are shown in Figure 8 . From Figure 8 it can be seen that in an air atmosphere, when the temperature rises to 300 °C, the copper powder weighs 1.4% more than the silver-coated copper powder; as the temperature rises to 600 °C, the weight gain percentage difference between the copper powder and the silver-coated copper powder is 1.7%, indicating that the silver-coated copper powder in Comparative Example 1 has excellent antioxidant performance. And from the thermogravimetric analysis Figure 6 and Figure 8From the comparison, it can be seen that the untreated silver-coated copper powder in Comparative Example 1 has a higher weight gain percentage and poorer antioxidant performance than the silver-coated copper powder in Example 1 at the same temperature. Thus, it shows that the copper powder treated with hydrogen salt in the present invention can remove the oxide layer and impurities of the copper powder and play an antioxidant role.

[0097] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0098] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing silver-coated copper powder, characterized in that, It includes the following steps: Mix copper powder with a hydro-salt solution and conduct pretreatment to obtain pretreated copper powder; Prepare solution A and solution C; solution A includes a reducing agent, and solution C includes a silver salt and complexing agent I; Mix solution A, a dispersant, complexing agent II and the pretreated copper powder to obtain solution B; Dropwise add solution C to solution B for a reduction reaction to obtain silver-coated copper powder.

2. The preparation method according to claim 1, characterized in that, The hydro-salt includes pyrrolidone hydrotribromide.

3. The preparation method according to claim 1 or 2, characterized in that The mass percentage concentration of the hydro-salt in the hydro-salt solution is 0.5% to 1.5%.

4. The preparation method according to claim 1 or 2, characterized in that, The mass of the hydro-salt accounts for 10% to 30% of the mass of the copper powder.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The preparation method satisfies at least one of the following: (1) The reducing agent includes at least one of ascorbic acid, glucose and sodium potassium tartrate; (2) The silver salt includes silver nitrate; (3) The complexing agent I includes ammonia water.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The dispersant includes at least one of PVP-k30, PVP-58k, PVP-360k and gum arabic.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The complexing agent II includes at least one of ethylenediaminetetraacetic acid and ethylenediaminetetraacetate.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The mass ratio of the dispersant to the pretreated copper powder is (0.05 to 0.10):1; the mass ratio of the complexing agent II to the pretreated copper powder is (0.02 to 0.08):

1.

9. The preparation method according to any one of claims 1 to 8, characterized in that, In the step of dropping solution C into solution B for a reduction reaction, the dropping rate of solution C is 1 mL / min to 10 mL / min; and / or, the temperature of the reduction reaction is 20°C to 50°C, and the reaction time is 20 min to 60 min.

10. A silver-coated copper powder, characterized in that, The silver-coated copper powder includes the silver-coated copper powder obtained by the preparation method according to any one of claims 1 to 9.

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