Copper powder and method for producing the same

Abstract

The application discloses copper powder and a preparation method thereof. The preparation method of the copper powder comprises the following steps: dissolving copper sulfate pentahydrate in deionized water to prepare a copper sulfate solution with a concentration of 0.1-1.0 mol / L; adding an alkali solution drop by drop into the copper sulfate solution under stirring to adjust the pH value to 6-8, and obtaining a basic copper sulfate precipitate; separating and collecting the basic copper sulfate precipitate, dispersing the basic copper sulfate precipitate in deionized water after washing to obtain a basic copper sulfate suspension with a concentration of 0.5-1 mol / L in terms of copper element; and mixing a polyvinylpyrrolidone solution and a graphene oxide solution to prepare a composite dispersion solution. The copper ion plays a good dispersion role in the reduction process, so that the uniformity of the particle size of the final copper powder is ensured.

Description

Technical Field

[0001] This invention generally relates to the field of metallic materials, and more particularly to a copper powder and its preparation method. Background Technology

[0002] Currently, commonly used methods for preparing copper powder include physical methods and chemical reduction methods. Among them, liquid-phase reduction using copper sulfate as the copper source and green reducing agents such as ascorbic acid (VC) is a research hotspot.

[0003] However, in existing technologies, the reduction reaction is often too violent, resulting in uncontrollable nucleation and growth processes and a wide product particle size distribution; moreover, there is a lack of effective in-situ antioxidant protection, and the product has a short shelf life, making it difficult to meet the needs of industrial applications. Summary of the Invention

[0004] In view of the above-mentioned defects or deficiencies in the prior art, it is desirable to provide a copper powder and a method for preparing the same.

[0005] In a first aspect, the method for preparing copper powder according to the present invention includes the following steps: Dissolve copper sulfate pentahydrate in deionized water to prepare a copper sulfate solution with a concentration of 0.1~1.0 mol / L; add alkali solution dropwise to the copper sulfate solution while stirring to adjust the pH value to 6~8, and obtain basic copper sulfate precipitate; The basic copper sulfate precipitate was separated and collected, washed with deionized water, and then dispersed with deionized water to obtain a basic copper sulfate suspension with a concentration of 0.5~1 mol / L based on copper element. A composite dispersion was prepared by mixing a polyvinylpyrrolidone solution with a graphene oxide solution; the composite dispersion was then added to a basic copper sulfate suspension and stirred until homogeneous to obtain a precursor solution; wherein the amount of polyvinylpyrrolidone added was 1% to 20% of the mass of the copper element in the feed, and the amount of graphene oxide added was 0.01% to 0.05% of the mass of the copper element in the feed. Prepare an ascorbic acid solution with a concentration of 1~2.0 mol / L, and adjust the pH of the ascorbic acid solution to 8~10 with alkaline solution; under stirring and inert atmosphere protection, add the ascorbic acid solution to the precursor solution, and react at 60~90℃ for 30~90 min to obtain reduced graphene oxide coated copper powder precipitate. The copper powder precipitate was separated and washed; the washed copper powder precipitate was redispersed in an ethanol solution containing 0.1%~1.0% fatty acid by mass, and the copper powder precipitate was surface coated. The coated copper powder precipitate is dried to obtain copper powder.

[0006] Secondly, the copper powder of the present invention is prepared according to the method for preparing copper powder.

[0007] According to the technical solution provided in the embodiments of this application, a technical route is adopted to precipitate copper sulfate into basic copper sulfate, use graphene oxide and PVP for dispersion, and simultaneously reduce GO and Cu2+ in situ. Compared with the direct reduction of copper ammonium complex ions or free copper ions, using basic copper sulfate solid as a precursor, whose surface has been uniformly modified by PVP, GO, or PVP@GO, allows copper ions to play a good dispersing role in the reduction process, thereby ensuring the uniformity of the final copper powder particle size.

[0008] Using ascorbic acid as a reducing agent, the reaction conditions are mild and environmentally friendly. Through in-situ protection by PVP and dual protection by reduced graphene oxide, a dense protective layer is formed on the surface of the copper powder, exhibiting excellent stability in air and significantly extending the product's shelf life. Attached Figure Description

[0009] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 Here is a scanning electron microscope image of the copper powder obtained in Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the copper powder obtained in Example 2 of the present invention; Figure 3 Here is a scanning electron microscope image of the copper powder obtained in Example 3 of the present invention; Figure 4 A scanning electron microscope image of the copper powder obtained in Comparative Example 1 of the present invention; Figure 5 A scanning electron microscope image of the copper powder obtained in Comparative Example 2 of the present invention; Figure 6 This is a scanning electron microscope image of the copper powder obtained in Comparative Example 3 of the present invention. Detailed Implementation

[0010] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0011] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0012] This application discloses a method for preparing copper powder, comprising the following steps: dissolving copper sulfate pentahydrate in deionized water to prepare a copper sulfate solution with a concentration of 0.1~1.0 mol / L; adding alkaline solution dropwise to the copper sulfate solution under stirring to adjust the pH value to 6~8, thereby obtaining a basic copper sulfate precipitate; separating and collecting the basic copper sulfate precipitate, washing it with deionized water, and then dispersing it with deionized water to obtain a basic copper sulfate suspension with a concentration of 0.5~1 mol / L based on copper element; mixing a polyvinylpyrrolidone solution with a graphene oxide solution to prepare a composite dispersion; adding the composite dispersion to the basic copper sulfate suspension and stirring evenly to obtain a precursor solution; wherein the amount of polyvinylpyrrolidone (PVP) added is equal to the amount of copper added. The amount of graphene oxide (GO) added is 0.01% to 0.05% of the mass of copper in the feed, while the amount of graphene oxide (GO) added is 1% to 20% of the mass of the element. An ascorbic acid solution with a concentration of 1 to 2.0 mol / L is prepared, and the pH of the ascorbic acid solution is adjusted to 8 to 10 with an alkaline solution. Under stirring and an inert atmosphere, the ascorbic acid solution is added to the precursor solution, and the reaction is carried out at 60 to 90 °C for 30 to 90 min to obtain reduced graphene oxide-coated copper powder precipitate. The copper powder precipitate is separated and washed. The washed copper powder precipitate is redispersed in an ethanol solution containing 0.1% to 1.0% fatty acid by mass to perform surface coating treatment on the copper powder precipitate. The coated copper powder precipitate is dried to obtain copper powder.

[0013] In embodiments of the present invention, copper sulfate is precipitated into basic copper sulfate, and graphene oxide and PVP are used for dispersion, while GO and Cu are simultaneously reduced in situ. 2+ The technical approach is as follows. Compared to the direct reduction of copper ammonia complex ions or free copper ions, using basic copper sulfate solid as a precursor, whose surface has been uniformly modified with PVP, GO, or PVP@GO, allows copper ions to play a good dispersing role in the reduction process, thus ensuring the uniformity of the final copper powder particle size.

[0014] The PVP added to the reaction system serves two purposes: firstly, as a dispersant to prevent particle agglomeration; secondly, the carbonyl groups on its molecular chain coordinate with the surface of the newly formed copper to form an initial protective layer, preventing the copper particles from undergoing immediate oxidation during the reaction and washing process.

[0015] The introduction of graphene oxide enables the formation of a stable coordination polymer film on the copper surface. This film is dense and hydrophobic, effectively isolating oxygen and moisture from the air, significantly improving the long-term storage stability of the copper powder. Tests showed that the copper powder obtained by this invention, when placed at 25°C and 60% relative humidity for different periods, exhibited significantly reduced long-term oxidative weight gain compared to copper powder without the two-component coating.

[0016] Uniform particle size distribution: The obtained copper powder consists of near-spherical particles with a narrow particle size distribution and a D50 range of 0.5~2.0μm. There are no coarse particles or obvious agglomeration, making it suitable for high-precision electronic pastes.

[0017] Excellent antioxidant properties: Through in-situ protection by PVP and dual protection by reduced graphene oxide, a dense protective layer is formed on the surface of copper powder, which has excellent stability in air and greatly extends the shelf life of the product.

[0018] The process is green and controllable: Ascorbic acid is used as a reducing agent, the reaction conditions are mild and environmentally friendly; the process parameters are highly controllable throughout the process, making it easy to achieve industrial-scale production.

[0019] Furthermore, the basic copper sulfate precipitate is washed with deionized water until the conductivity of the filtrate is <20 μS / cm, and then dispersed with deionized water.

[0020] Furthermore, a polyvinylpyrrolidone solution was prepared by dispersing polyvinylpyrrolidone in deionized water and ultrasonically stirring for 45 min; a graphene oxide solution was prepared by dispersing graphene oxide in deionized water and ultrasonically stirring for 45 min; the graphene oxide solution was added to the polyvinylpyrrolidone solution and ultrasonically stirred for another 45 min to obtain a composite dispersion.

[0021] Further, the composite dispersion was added to the basic copper sulfate suspension and stirred for another 30 minutes.

[0022] Furthermore, adding ascorbic acid solution to the precursor solution includes placing ascorbic acid solution in a constant pressure dropping funnel and adding the ascorbic acid solution dropwise to the precursor solution at a dropping rate of 100 mL / min.

[0023] Furthermore, the copper powder precipitate was centrifuged. After the copper powder precipitate was separated, it was washed with deionized water and anhydrous ethanol in sequence until the conductivity of the final cleaning solution was less than 10 μS / cm.

[0024] Furthermore, the fatty acid is stearic acid, and the coating treatment is carried out at 50°C with stirring for 30 minutes.

[0025] Furthermore, the copper powder precipitate was placed in a vacuum drying oven and dried at 50°C for 8 hours to obtain copper powder.

[0026] Furthermore, the alkaline solution used to adjust the pH in each step is a sodium hydroxide solution.

[0027] This application discloses a copper powder prepared according to a copper powder preparation method.

[0028] Example 1 (1) Weigh 25.0g of copper sulfate pentahydrate (0.1mol) and dissolve it in 500mL of deionized water to prepare a 0.2mol / L copper sulfate solution. Under stirring at room temperature, slowly add 2mol / L NaOH solution to adjust the pH to 6, and a blue-green basic copper sulfate precipitate will be formed.

[0029] (2) The basic copper sulfate precipitate was washed with deionized water until the conductivity of the washing water was less than 20 μS / cm, and finally a 0.5 mol / L copper suspension was prepared. (3) Weigh 0.636g PVP (K30) and disperse it in 100mL of pure water and ultrasonically stir for 45min to prepare PVP solution; weigh 1.6mg graphene oxide and disperse it in 100mL of pure water and ultrasonically stir for 45min to prepare GO solution; add GO solution to PVP solution and continue ultrasonic stirring for 45min; then add it to basic copper sulfate suspension and continue stirring for 30min.

[0030] (4) Weigh 65g of ascorbic acid (0.369mol) and dissolve it in 150mL of deionized water. Adjust the pH to 9 with NaOH solution and add water to adjust the concentration to 1mol / L. Place the prepared ascorbic acid solution in a constant pressure dropping funnel.

[0031] (5) Heat the basic copper sulfate suspension from step (2) to 80°C. Under nitrogen protection and vigorous stirring, add the solution at a rate of 100 mL / min. After the addition is complete, continue to keep the solution warm for 60 min until the solution turns completely brownish-red.

[0032] (6) After the reaction is complete, cool to room temperature, centrifuge, and wash the precipitate with deionized water and anhydrous ethanol until the conductivity of the washing water is less than 10 μS / cm.

[0033] (7) The washed wet copper powder is redispersed in 10 mL of ethanol solution containing 0.5% stearic acid and stirred at 50 °C for 30 min.

[0034] (8) Place the copper powder in a vacuum drying oven and dry it at 50°C for 8 hours to obtain brownish-red copper powder (e.g. Figure 1 (As shown).

[0035] Figure 1 The image shown is a scanning electron microscope image of the copper powder prepared in Example 1. It can be seen that the particles are spherical and coated with a layer of reduced graphene oxide.

[0036] Example 2: (1) Weigh 25.0g of copper sulfate pentahydrate (0.1mol) and dissolve it in 1000mL of deionized water to prepare a 0.1mol / L copper sulfate solution. Under stirring at room temperature, slowly add 2mol / L NaOH solution to adjust the pH to 6, and a blue-green basic copper sulfate precipitate will be formed.

[0037] (2) The basic copper sulfate precipitate was washed with deionized water until the conductivity of the washing water was less than 20 μS / cm, and finally a 0.5 mol / L copper suspension was prepared. (3) Weigh 65 mg PVP (K30) and disperse it in 100 mL of pure water and sonicate for 45 min to prepare PVP solution; weigh 0.64 mg graphene oxide and disperse it in 100 mL of pure water and sonicate for 45 min to prepare GO solution; add GO solution to PVP solution and continue sonicating for 45 min; then add it to basic copper sulfate suspension and continue stirring for 30 min.

[0038] (4) Weigh 65g of ascorbic acid (0.369mol) and dissolve it in 150mL of deionized water. Adjust the pH to 8 with NaOH solution and add water to adjust the concentration to 1mol / L. Place the prepared ascorbic acid solution in a constant pressure dropping funnel.

[0039] (5) Heat the basic copper sulfate suspension from step (2) to 80°C. Under nitrogen protection and vigorous stirring, add the solution at a rate of 100 mL / min. After the addition is complete, continue to keep the solution warm for 60 min until the solution turns completely brownish-red.

[0040] (6) After the reaction is complete, cool to room temperature, centrifuge, and wash the precipitate with deionized water and anhydrous ethanol until the conductivity of the washing water is less than 10 μS / cm.

[0041] (7) The washed wet copper powder is redispersed in 10 mL of ethanol solution containing 0.5% stearic acid and stirred at 50 °C for 30 min.

[0042] (8) Place the copper powder in a vacuum drying oven and dry it at 50°C for 8 hours to obtain brownish-red copper powder (e.g. Figure 2 (As shown).

[0043] Figure 2 The image shown is a scanning electron microscope image of the copper powder prepared in Example 2. Due to the reduced amount of graphene oxide added, only a small amount of reduced graphene oxide coating is visible on the surface of the copper powder.

[0044] Example 3: (1) Weigh 25.0g of copper sulfate pentahydrate (0.1mol) and dissolve it in 100mL of deionized water to prepare a 1mol / L copper sulfate solution. Under stirring at room temperature, slowly add 2mol / L NaOH solution to adjust the pH to 6, and a blue-green basic copper sulfate precipitate is formed.

[0045] (2) The basic copper sulfate precipitate was washed with deionized water until the conductivity of the washing water was less than 20 μS / cm, and finally a 1 mol / L copper suspension was prepared. (3) Weigh 1.26g PVP (K30) and disperse it in 100mL of pure water and ultrasonically stir for 45min to prepare PVP solution; weigh 3.2mg graphene oxide and disperse it in 100mL of pure water and ultrasonically stir for 45min to prepare GO solution; add GO solution to PVP solution and continue ultrasonic stirring for 45min; then add it to basic copper sulfate suspension and continue stirring for 30min.

[0046] (4) Weigh 65g of ascorbic acid (0.369mol) and dissolve it in 50mL of deionized water. Adjust the pH to 10 with NaOH solution and add water to adjust the concentration to 2mol / L. Place the prepared ascorbic acid solution in a constant pressure dropping funnel.

[0047] (5) Heat the basic copper sulfate suspension from step (2) to 80°C. Under nitrogen protection and vigorous stirring, add the solution at a rate of 100 mL / min. After the addition is complete, continue to keep the solution warm for 60 min until the solution turns completely brownish-red.

[0048] (6) After the reaction is complete, cool to room temperature, centrifuge, and wash the precipitate with deionized water and anhydrous ethanol until the conductivity of the washing water is less than 10 μS / cm.

[0049] (7) The washed wet copper powder is redispersed in 10 mL of ethanol solution containing 0.5% stearic acid and stirred at 50 °C for 30 min.

[0050] (8) Place the copper powder in a vacuum drying oven and dry it at 50°C for 8 hours to obtain brownish-red copper powder (e.g. Figure 3 (As shown).

[0051] Figure 3 The image shown is a scanning electron microscope image of the copper powder prepared in Example 3. It can be seen that the particles are spherical and uniformly coated with a layer of reduced graphene oxide.

[0052] To verify the individual roles and synergistic effects of PVP and graphene oxide, three comparative examples were set up: Comparative Example 1: Only PVP was added, without graphene oxide, to verify the anti-oxidation effect of graphene oxide coating; Comparative Example 2: Only graphene oxide was added, without PVP, to verify the dispersion and in-situ protection effect of PVP; Comparative Example 3: No PVP or graphene oxide was added, serving as a blank control group.

[0053] Comparative Example 1 (1) Weigh 25.0g of copper sulfate pentahydrate (0.1mol) and dissolve it in 500mL of deionized water to prepare a 0.2mol / L copper sulfate solution. Under stirring at room temperature, slowly add 2mol / L NaOH solution to adjust the pH to 6, and a blue-green basic copper sulfate precipitate will be formed.

[0054] (2) The basic copper sulfate precipitate was washed three times with 500 mL of deionized water. The final cleaning solution had a conductivity of 15 μS / cm. Water was added to prepare a 0.5 mol / L copper suspension. (3) Take 5 mL of PVP (K30) aqueous solution with a mass fraction of 15.0%, stir ultrasonically for 45 min, add it to the basic copper sulfate suspension, and continue stirring for 30 min.

[0055] (4) Weigh 65g of ascorbic acid (0.369mol) and dissolve it in 150mL of deionized water. Adjust the pH to 9 with NaOH solution and add water to adjust the concentration to 1mol / L. Place the prepared ascorbic acid solution in a constant pressure dropping funnel.

[0056] (5) Heat the basic copper sulfate suspension from step (2) to 80°C. Under nitrogen protection and vigorous stirring, add the solution at a rate of 100 mL / min. After the addition is complete, continue to keep the solution warm for 60 min until the solution turns completely brownish-red.

[0057] (6) After the reaction is complete, cool to room temperature, centrifuge, and wash the precipitate with deionized water and anhydrous ethanol until the conductivity of the washing water is less than 10 μS / cm.

[0058] (7) The washed wet copper powder is redispersed in 10 mL of ethanol solution containing 0.5% stearic acid and stirred at 50 °C for 30 min.

[0059] (8) Place the copper powder in a vacuum drying oven and dry it at 50°C for 8 hours to obtain brownish-red copper powder (e.g. Figure 4 (As shown).

[0060] Figure 4 The image shown is a scanning electron microscope image of copper powder prepared for Comparative Example 1. This group did not add graphene oxide, and the copper powder surface had no reduced graphene oxide coating layer.

[0061] Comparative Example 2: (1) Weigh 25.0g of copper sulfate pentahydrate (0.1mol) and dissolve it in 500mL of deionized water to prepare a 0.2mol / L copper sulfate solution. Under stirring at room temperature, slowly add 2mol / L NaOH solution to adjust the pH to 6, and a blue-green basic copper sulfate precipitate will be formed.

[0062] (2) The basic copper sulfate precipitate was washed three times with 500 mL of deionized water. The final cleaning solution had a conductivity of 15 μS / cm. Water was added to prepare a 0.5 mol / L copper suspension. (3) Weigh 0.32 mg GO, disperse it in 100 mL of pure water, sonicate and stir for 45 min, add it to the basic copper sulfate suspension, and continue stirring for 30 min.

[0063] (4) Weigh 65g of ascorbic acid (0.369mol) and dissolve it in 150mL of deionized water. Adjust the pH to 9 with NaOH solution and add water to adjust the concentration to 1mol / L. Place the prepared ascorbic acid solution in a constant pressure dropping funnel.

[0064] (5) Heat the basic copper sulfate suspension from step (2) to 80°C. Under nitrogen protection and vigorous stirring, add the solution at a rate of 100 mL / min. After the addition is complete, continue to keep the solution warm for 60 min until the solution turns completely brownish-red.

[0065] (6) After the reaction is complete, cool to room temperature, centrifuge, and wash the precipitate with deionized water and anhydrous ethanol until the conductivity of the washing water is less than 10 μS / cm.

[0066] (7) The washed wet copper powder is redispersed in 10 mL of ethanol solution containing 0.5% stearic acid and stirred at 50 °C for 30 min.

[0067] (8) Place the copper powder in a vacuum drying oven and dry it at 50°C for 8 hours to obtain brownish-red copper powder (e.g. Figure 5 (As shown).

[0068] Figure 5 The image shown is a scanning electron microscope image of the copper powder prepared in Comparative Example 2. In this group, no PVP was added, and only a small amount of reduced graphene oxide adhered to the surface of the copper powder, resulting in a significant decrease in particle dispersibility.

[0069] Comparative Example 3: (1) Weigh 25.0g of copper sulfate pentahydrate (0.1mol) and dissolve it in 500mL of deionized water to prepare a 0.2mol / L copper sulfate solution. Under stirring at room temperature, slowly add 2mol / L NaOH solution to adjust the pH to 6, and a blue-green basic copper sulfate precipitate will be formed.

[0070] (2) The basic copper sulfate precipitate was washed three times with 500 mL of deionized water. The final cleaning solution had a conductivity of 15 μS / cm. Water was added to prepare a 0.5 mol / L copper suspension. (3) Weigh 65g of ascorbic acid (0.369mol) and dissolve it in 150mL of deionized water. Adjust the pH to 9 with NaOH solution and add water to adjust the concentration to 1mol / L. Place the prepared ascorbic acid solution in a constant pressure dropping funnel.

[0071] (4) Heat the basic copper sulfate suspension from step (2) to 80°C. Under nitrogen protection and vigorous stirring, add the solution at a rate of 100 mL / min. After the addition is complete, continue to keep the solution warm for 60 min until the solution turns completely brownish-red.

[0072] (5) After the reaction is complete, cool to room temperature, centrifuge, and wash the precipitate with deionized water and anhydrous ethanol until the conductivity of the washing water is less than 10 μS / cm.

[0073] (6) The washed wet copper powder is redispersed in 10 mL of ethanol solution containing 0.5% stearic acid and stirred at 50 °C for 30 min.

[0074] (7) Place the copper powder in a vacuum drying oven and dry it at 50°C for 8 hours to obtain brownish-red copper powder (e.g. Figure 6 (As shown).

[0075] Figure 6 The image shown is a scanning electron microscope image of copper powder prepared in Comparative Example 3. This group did not add PVP or graphene oxide, and the copper powder particles were severely agglomerated and poorly dispersed, with no reduced graphene oxide coating on the surface.

[0076] The copper powders obtained in the above examples and comparative examples were subjected to particle size distribution and antioxidant performance tests: particle size was measured using a laser particle size analyzer; antioxidant performance was characterized by changes in oxygen content over different storage times at 25°C and 60% relative humidity. The test results are shown in the table below: As shown in Table 1, the copper powder prepared in the embodiments of the present invention has a narrower particle size distribution, with D50 ranging from 0.95 to 1.12 μm, all controlled within 1.2 μm, and a maximum D100 of only 4.05 μm, showing no coarse particles or obvious agglomeration. In contrast, the comparative examples lacking PVP or graphene oxide have a maximum D50 of 1.55 μm and a maximum D100 of 5.78 μm, indicating significant particle agglomeration. These results demonstrate that the basic copper sulfate slow-release precursor combined with the two-component synergistic dispersion can effectively regulate the nucleation and growth process of copper powder, significantly improving particle size uniformity.

[0077] Regarding antioxidant properties, the initial oxygen content of the copper powder in the examples was only 0.21%~0.25%, far lower than the 0.45%~0.51% of the comparative examples, indicating that the in-situ protection system can effectively inhibit the oxidation of copper powder during the preparation process. After 120 days of storage at 25°C and 60% relative humidity, the oxygen content increase of the copper powder in the examples was only 0.09%~0.13%, with a slow oxidation rate, while the oxygen content increase of the copper powder in the comparative examples could reach up to 0.44%, with a significantly faster oxidation rate. These results demonstrate that the composite antioxidant system formed by in-situ coordination protection of PVP and dense coating of reduced graphene oxide can significantly improve the long-term storage stability of copper powder.

[0078] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method for preparing copper powder, characterized in that, Includes the following steps: Dissolve copper sulfate pentahydrate in deionized water to prepare a copper sulfate solution with a concentration of 0.1~1.0 mol / L; add alkali solution dropwise to the copper sulfate solution while stirring to adjust the pH value to 6~8, and obtain basic copper sulfate precipitate; The basic copper sulfate precipitate was separated and collected, washed with deionized water, and then dispersed with deionized water to obtain a basic copper sulfate suspension with a concentration of 0.5~1 mol / L based on copper element. A composite dispersion was prepared by mixing a polyvinylpyrrolidone solution with a graphene oxide solution; the composite dispersion was then added to a basic copper sulfate suspension and stirred until homogeneous to obtain a precursor solution; wherein the amount of polyvinylpyrrolidone added was 1% to 20% of the mass of the copper element in the feed, and the amount of graphene oxide added was 0.01% to 0.05% of the mass of the copper element in the feed. Prepare an ascorbic acid solution with a concentration of 1~2.0 mol / L, and adjust the pH of the ascorbic acid solution to 8~10 with alkaline solution; Under stirring and an inert atmosphere, the ascorbic acid solution was added to the precursor solution and reacted at 60-90°C for 30-90 min to obtain reduced graphene oxide-coated copper powder precipitate. The copper powder precipitate was separated and washed. The washed copper powder precipitate was redispersed in an ethanol solution containing 0.1%~1.0% fatty acid by mass to perform a surface coating treatment on the copper powder precipitate. The coated copper powder precipitate is dried to obtain copper powder.

2. The method for preparing copper powder according to claim 1, characterized in that, The basic copper sulfate precipitate was washed with deionized water until the conductivity of the filtrate was <20 μS / cm, and then dispersed with deionized water.

3. The method for preparing copper powder according to claim 1, characterized in that, A polyvinylpyrrolidone solution was prepared by dispersing polyvinylpyrrolidone in deionized water and ultrasonically stirring for 45 min; a graphene oxide solution was prepared by dispersing graphene oxide in deionized water and ultrasonically stirring for 45 min; the graphene oxide solution was added to the polyvinylpyrrolidone solution and ultrasonically stirred for another 45 min to obtain a composite dispersion.

4. The method for preparing copper powder according to claim 1, characterized in that, The composite dispersion was added to the basic copper sulfate suspension, and the mixture was stirred for another 30 minutes.

5. The method for preparing copper powder according to claim 1, characterized in that, The ascorbic acid solution is added to the precursor solution, comprising: Place the ascorbic acid solution in a constant pressure dropping funnel and add it dropwise to the precursor solution at a dropping rate of 100 mL / min.

6. The method for preparing copper powder according to claim 1, characterized in that, The copper powder precipitate was separated by centrifugation. After the copper powder precipitate was separated, it was washed with deionized water and anhydrous ethanol in sequence until the conductivity of the final washing solution was less than 10 μS / cm.

7. The method for preparing copper powder according to claim 1, characterized in that, The fatty acid is stearic acid, and the coating process is carried out at 50°C with stirring for 30 minutes.

8. The method for preparing copper powder according to claim 1, characterized in that, The copper powder precipitate was placed in a vacuum drying oven and dried at 50°C for 8 hours to obtain copper powder.

9. The method for preparing copper powder according to claim 1, characterized in that, The alkaline solution used to adjust the pH in each step is a sodium hydroxide solution.

10. A copper powder, characterized in that, The copper powder is prepared according to any one of claims 1 to 9.

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