Spherical copper powder and preparation method and application thereof
By combining a two-step step-phase reduction method with dispersants and halogen compounds, the particle size and morphology of copper powder are controlled, solving the problem of copper powder instability in existing technologies. This enables the preparation of high-purity and highly dispersible copper powder, which is suitable for applications such as conductive adhesives and catalysts.
Patent Information
- Application Number
- CN202511413382.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-29
- Publication Date
- 2025-11-14
AI Technical Summary
Existing methods for preparing copper powder suffer from problems such as high energy consumption, high cost, uneven particle size distribution, irregular morphology, poor dispersibility, and low purity. In particular, the instability of cuprous ions in the two-step liquid-phase reduction method leads to a decrease in particle size uniformity.
A two-step step-phase reduction method is adopted. By controlling the reaction pH, temperature and reducing agent concentration, combined with the use of dispersants and halogen compounds, an antioxidant film is formed, which precisely controls the particle size and morphology of copper powder, prevents agglomeration, and improves the stability and purity of copper powder.
This technology achieves good particle size uniformity, good dispersibility, and high purity of copper powder, significantly reducing production costs and making it suitable for applications such as conductive adhesives and catalysts.
Smart Images
Figure CN120940636A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of metal powder technology, and in particular to a spherical copper powder, its preparation method and application. Background Technology
[0002] Copper powder is a fundamental and crucial functional metal powder with excellent electrical conductivity, thermal conductivity, ductility, and unique antibacterial properties. It plays an indispensable role in many cutting-edge industries, deeply penetrating fields such as electronic information technology (e.g., conductive pastes, printed circuit boards), new energy (e.g., battery electrode materials), high-end equipment manufacturing, chemical catalysis (catalyst carriers), additive manufacturing (3D printing of metal components), powder metallurgy (forming complex parts), biomedicine (antibacterial materials), and friction materials (brake pads, clutch discs).
[0003] Currently, methods for preparing copper powder include electrolysis, atomization, one-step liquid-phase reduction, and two-step liquid-phase reduction. While electrolysis can yield high-purity copper powder, it consumes enormous amounts of energy, resulting in extremely high production costs. The morphology of the product is difficult to precisely control, and it easily generates irregular dendrites, leading to an excessively wide particle size distribution, which fails to meet the stringent requirements for particle size uniformity in high-end applications. Atomization requires expensive equipment, consumes a large amount of energy, and results in significant performance fluctuations between different batches of products, while also generating substantial amounts of wastewater. One-step liquid-phase reduction involves a violent and difficult-to-control reaction process, easily leading to severe copper particle agglomeration, resulting in an excessively wide particle size distribution, irregular morphology, poor dispersibility, and unstable performance. Compared to electrolysis, atomization, and one-step liquid-phase reduction, two-step liquid-phase reduction offers a gentler reaction process, allows for more precise control of copper powder particle size and morphology, significantly reduces agglomeration, provides better particle size uniformity and dispersibility, and achieves higher purity, thus substantially reducing production costs.
[0004] The existing technical solutions mentioned above have the following drawbacks: when producing copper powder using the two-step liquid-phase reduction method, cuprous ions are extremely unstable, which leads to a decrease in particle size uniformity, loss of morphology control, reduced dispersibility, and a decrease in the purity of copper powder. Summary of the Invention
[0005] To improve the stability of cuprous ions, this application provides a spherical copper powder, its preparation method, and its application.
[0006] The primary objective of this application is to provide a method for preparing spherical copper powder, employing the following technical solution: A method for preparing spherical copper powder, comprising: S1. Prepare copper source solution, reducing solution A, reducing solution B, dispersion solution and antioxidant solution; S2. Add a halogen compound to the copper source solution, mix well to form mixed solution A, and adjust the pH of mixed solution A to 8-14; S3. Heat the mixed solution A to a first preset temperature, add reducing solution A to the mixed solution A to obtain suspension A; treat suspension A to obtain cuprous oxide; S4. Disperse cuprous oxide in an antioxidant solution, mix well to form a mixed solution B, heat the mixed solution B to a second preset temperature to obtain a suspension B; treat the suspension B to obtain antioxidant cuprous oxide. S5. Prepare a cuprous oxide aqueous dispersion using antioxidant cuprous oxide, adjust the pH of the cuprous oxide aqueous dispersion to 8-14, add the dispersion solution to the cuprous oxide aqueous dispersion, and mix well to form a mixed solution C. S6. Heat the mixed solution C to the second preset temperature, add the reducing solution B to the mixed solution C, mix well to form a suspension C; process the suspension C to obtain spherical copper powder.
[0007] By employing the above technical solution, copper ions are first reduced to cuprous oxide under specific conditions. Then, under specific conditions, cuprous oxide is reduced to copper. During the reduction process, the inherent crystal structure of cuprous oxide crystals tends to undergo a spheroidization transformation. The dispersant is adsorbed on the particle surface to prevent particle agglomeration. The two-step step-phase reduction method for producing copper powder is relatively mild. Combined with the dispersing effect of the dispersant, and by precisely controlling key parameters such as reaction pH, temperature, and reducing agent concentration, the generation and growth process of copper crystal nuclei can be effectively regulated. This allows for more precise control of the particle size and morphology of the copper powder, significantly reducing agglomeration, resulting in better particle size uniformity, better copper powder dispersibility, and higher copper powder purity, which can significantly reduce production costs. A halogen compound is added before the copper ions are reduced to cuprous oxide. Halogen ions form soluble complexes with cuprous ions, significantly improving the stability of cuprous ions and inhibiting their disproportionation or oxidation. This greatly reduces the formation of the byproduct copper oxide, which helps ensure the particle size uniformity, morphology, dispersibility, and purity of the copper powder. Before cuprous oxide is reduced to copper, an antioxidant film forms on its surface. This film acts as a physical barrier against oxygen, effectively preventing the oxidation of cuprous ions and improving their stability, further ensuring the particle size uniformity, morphology, dispersibility, and purity of the copper powder. In subsequent reactions, the antioxidant film partially or completely transfers to the surface of the copper powder, greatly enhancing the antioxidant stability of the spherical copper powder.
[0008] This application further specifies the following steps: In step S1, copper salt is dissolved in deionized water to prepare a copper source solution with a concentration of 0.1-2 mol / L; reducing agent A is dissolved in deionized water to prepare a reducing solution A with a concentration of 0.5-4.5 mol / L; reducing agent B is dissolved in deionized water to prepare a reducing solution B with a concentration of 0.5-5 mol / L; dispersant is dissolved in deionized water to prepare a dispersion solution with a concentration of 5-50 mmol / L; and antioxidant coating agent is dissolved in ethanol to prepare an antioxidant solution with a concentration of 0.1-1 g / L. In step S2, the concentration of halogen compounds in mixed solution A is 0.2-1.5 mol / L. In step S4, the concentration of cuprous oxide in mixed solution B is 200-1000 g / L. In step S5, the concentration of cuprous oxide in the cuprous oxide aqueous dispersion is 20-200 g / L.
[0009] By adopting the above technical solution, and controlling the concentrations of reducing solution A and reducing solution B, the reduction rate is prevented from being too high or too low, thereby avoiding an excessively high or low nucleus count, which in turn helps to control the particle size of the copper powder. Furthermore, controlling the concentration of the dispersion solution prevents the copper powder from agglomerating.
[0010] This application further specifies that: the copper salt is copper sulfate pentahydrate, copper nitrate hydrate, copper chloride hydrate, or basic copper carbonate; reducing agent A is ascorbic acid, glucose, sodium hypophosphite, sodium borohydride, triethanolamine, hydrazine hydrate, or formaldehyde; reducing agent B is ascorbic acid, glucose, sodium hypophosphite, sodium borohydride, triethanolamine, hydrazine hydrate, or formaldehyde; and the dispersant is gelatin, Tween, gum arabic, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, hexadecyltrimethylammonium bromide, or sodium dodecylbenzenesulfonate. Sodium dodecyl sulfate, sodium stearate, or sodium oleate; the antioxidant coating agent is imidazole, 2-undecylimidazolium, benzotriazole, stearic acid, oleic acid, hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid, silane coupling agent, or polyaniline; the halogen compound is sodium chloride, potassium chloride, sodium bromide, or sodium iodide; the reagent used to adjust the pH of mixed solution A is lithium hydroxide, sodium hydroxide, potassium hydroxide, or ammonia; the reagent used to adjust the pH of the cuprous oxide aqueous dispersion is lithium hydroxide, sodium hydroxide, potassium hydroxide, or ammonia.
[0011] This application further specifies that: in step S3, the mixed solution A is heated to 40-80℃, the stirring speed is 200-400 r / min, and the reaction time is 0.5-5 h; in step S4, the mixed solution B is heated to 30-55℃, the stirring speed is 200-400 r / min, and the reaction time is 0.5-5 h; in step S6, the mixed solution C is heated to 40-80℃, the stirring speed is 200-400 r / min, and the reaction time is 0.5-5 h.
[0012] By adopting the above technical solution and controlling the reduction reaction temperature, the rate of the reduction reaction can be effectively controlled, avoiding excessively high or low nuclei, which in turn helps control the particle size of copper powder. By controlling the antioxidant coating temperature, a uniform antioxidant film layer is formed on the surface of cuprous oxide.
[0013] This application further specifies that: in step S3, the suspension A is allowed to stand for 0.5-5 hours, the supernatant is removed, and cuprous oxide is obtained.
[0014] This application further specifies that: in step S4, the suspension B is transferred to a filter press, washed with ethanol and dried to obtain antioxidant cuprous oxide.
[0015] The present application further specifies that: in step S6, the suspension C is transferred to a filter press, washed with deionized water and dried to obtain spherical copper powder.
[0016] The second objective of this application is to provide a spherical copper powder, employing the following technical solution: A spherical copper powder is prepared using the above-described method.
[0017] This application further specifies that the spherical copper powder is spherical with a particle size of 1-6 μm and a tap density of 4.0-4.5 g / cm³. 3 The loose bulk density is 2.5-3 g / cm³. 3 .
[0018] The third objective of this application is to provide an application of spherical copper powder, employing the following technical solution: Spherical copper powder prepared according to the above preparation method or its application in the preparation of conductive adhesive.
[0019] In summary, the beneficial technical effects of this application are as follows: A two-step, stepwise liquid-phase reduction method is employed to produce copper powder. This method features a relatively mild reaction process. Combined with the dispersing effect of a dispersant, precise control of key parameters such as pH, temperature, and reducing agent concentration effectively regulates the formation and growth of copper crystal nuclei. This allows for more precise control of the particle size and morphology of the copper powder, significantly reducing agglomeration, resulting in better particle size uniformity, better dispersibility, and higher purity, thus substantially reducing production costs. Before copper ions are reduced to cuprous oxide, a halogen compound is added. The halide ions form a soluble complex with the cuprous ions, significantly improving the stability of the cuprous ions and inhibiting their disproportionation or oxidation. This greatly reduces the formation of the byproduct copper oxide, ensuring the uniformity, morphology, dispersibility, and purity of the copper powder. Before the cuprous oxide is reduced to copper, an anti-oxidation film is formed on the surface of the cuprous oxide. This film acts as a physical barrier against oxygen, effectively preventing the oxidation of cuprous ions and improving their stability, further ensuring the uniformity, morphology, dispersibility, and purity of the copper powder. In subsequent reactions, the antioxidant film layer will be partially or completely transferred to the surface of the copper powder, which greatly enhances the antioxidant stability of the spherical copper powder. Attached Figure Description
[0020] Figure 1 This is a flowchart of the preparation method for spherical copper powder; Figure 2 This is an electron microscope image of the spherical copper powder obtained in Example 1; Figure 3 This is an electron microscope image of the spherical copper powder obtained in Example 2; Figure 4 This is an electron microscope image of the spherical copper powder obtained in Example 3; Figure 5 This is an electron microscope image of the spherical copper powder obtained in Example 4; Figure 6 This is an electron microscope image of the copper powder prepared in Comparative Example 1; Figure 7 This is an electron microscope image of the copper powder prepared in Comparative Example 2. Detailed Implementation
[0021] The following is in conjunction with the appendix Figure 1-7 This application will be described in further detail.
[0022] Reference Figure 1 This application discloses a method for preparing spherical copper powder, comprising: S1. Prepare copper source solution, reducing solution A, reducing solution B, dispersion solution and antioxidant solution.
[0023] The embodiments of this application do not particularly limit the preparation steps of the copper source solution, reducing solution A, reducing solution B, dispersion solution, and antioxidant solution. Any known preparation steps can be used in this application without departing from the concept of this application. These are merely illustrative examples and not intended to limit the scope of protection. For example, copper salts can be dissolved in deionized water to prepare copper source solutions with concentrations of 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, or 2.0 mol / L. Reducing agent A can be dissolved in deionized water to prepare reducing solutions A with concentrations of 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L, or 4.5 mol / L. Similarly, reducing agent B can be dissolved in deionized water to prepare reducing solutions B with concentrations of 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, 4.0 mol / L, 4.5 mol / L, or 5.0 mol / L. Dispersants can be dissolved in deionized water to prepare dispersions with concentrations of 5 mmol / L, 10 mmol / L, 15 mmol / L, 20 mmol / L, 25 mmol / L, 30 mmol / L, 35 mmol / L, 40 mmol / L, 45 mmol / L, or 50 mmol / L. Antioxidant coatings can be dissolved in ethanol to prepare antioxidant solutions with concentrations of 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, or 1.0 g / L.
[0024] In the embodiments of this application, the copper salt is copper sulfate pentahydrate, copper nitrate hydrate, copper chloride hydrate, or basic copper carbonate. Reducing agent A is ascorbic acid, glucose, sodium hypophosphite, sodium borohydride, triethanolamine, hydrazine hydrate, or formaldehyde. Reducing agent B is ascorbic acid, glucose, sodium hypophosphite, sodium borohydride, triethanolamine, hydrazine hydrate, or formaldehyde. Dispersant is gelatin, Tween, gum arabic, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium stearate, or sodium oleate. Antioxidant coating agent is imidazole, 2-undecylimidazole, benzotriazole, stearic acid, oleic acid, hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid, silane coupling agent, or polyaniline.
[0025] Preferably, the copper salt is copper sulfate pentahydrate. Reducing agent A is ascorbic acid; its mild reducing properties ensure uniform formation of cuprous oxide particles, providing a uniformly sized precursor for subsequent reactions. Reducing agent B is sodium hypophosphite; sodium hypophosphite can completely reduce cuprous oxide to copper, and due to the uniformity of the precursor, copper powder with uniform particle size is ultimately obtained. The dispersant is gelatin; gelatin can effectively adsorb onto the surface of cuprous oxide crystal nuclei, preventing excessive growth and aggregation. The antioxidant coating agent is benzotriazole; the nitrogen atoms in its molecule can chemically adsorb onto the surface of cuprous oxide, forming a dense protective film. This film effectively blocks contact between cuprous oxide / copper and moisture / oxygen, thereby significantly improving the antioxidant capacity of cuprous oxide / copper powder.
[0026] S2. Add a halogen compound to the copper source solution, mix well to form a mixed solution A, and adjust the pH of mixed solution A to 8-14.
[0027] In the embodiments of this application, the halogen compound is sodium chloride, potassium chloride, sodium bromide, or sodium iodide.
[0028] In the embodiments of this application, the concentration of halogen compounds in mixed solution A is 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, or 1.5 mol / L.
[0029] In the embodiments of this application, the reagents used to adjust the pH of mixed solution A are lithium hydroxide, sodium hydroxide, potassium hydroxide, or ammonia.
[0030] In this embodiment, the pH of the mixed solution A is adjusted to 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5 or 14.
[0031] Preferably, the halogen compound is sodium chloride, and the reagent used to adjust the pH of mixed solution A is sodium hydroxide. The pH of mixed solution A is adjusted to 12.
[0032] S3. Heat the mixed solution A to a first preset temperature, add reducing solution A to the mixed solution A to obtain suspension A. Treat suspension A to obtain cuprous oxide.
[0033] In this embodiment, the mixed solution A is heated to 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C using a water bath. The reducing solution A is then added to the mixed solution A while continuously stirring at a speed of 200 r / min, 210 r / min, 220 r / min, 230 r / min, 240 r / min, 250 r / min, 260 r / min, 270 r / min, 280 r / min, 290 r / min, 300 r / min, 310 r / min, 320 r / min, 330 r / min, 340 r / min, 350 r / min, 360 r / min, 370 r / min, 380 r / min, 390 r / min, or 400 r / min. Suspension A is prepared by reacting for 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h.
[0034] In the embodiments of this application, suspension A is allowed to stand for 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, and then the supernatant is removed to obtain cuprous oxide precipitate.
[0035] Preferably, the ratio of the number of moles of reducing agent A in reducing solution A to the number of moles of copper salt in mixed solution A is 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or 2.0:1.
[0036] S4. Disperse cuprous oxide in an antioxidant solution, mix well to form a mixed solution B, heat mixed solution B to a second preset temperature to obtain suspension B. Treat suspension B to obtain antioxidant cuprous oxide.
[0037] In the embodiments of this application, the concentration of cuprous oxide in mixed solution B is 200 g / L, 250 g / L, 300 g / L, 350 g / L, 400 g / L, 450 g / L, 500 g / L, 550 g / L, 600 g / L, 650 g / L, 700 g / L, 750 g / L, 800 g / L, 850 g / L, 900 g / L, 950 g / L, or 1000 g / L.
[0038] In this embodiment, the mixed solution B is heated to 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, 54℃, or 55℃ using a water bath, while stirring at speeds of 200r / min, 210r / min, 220r / min, 230r / min, 240r / min, 250r / min, 260r / min, 270r / min, and 280r / min. Under continuous stirring at speeds of 290 r / min, 300 r / min, 310 r / min, 320 r / min, 330 r / min, 340 r / min, 350 r / min, 360 r / min, 370 r / min, 380 r / min, 390 r / min, or 400 r / min, the reaction is carried out for 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, or 5 h, allowing the antioxidant coating agent to fully coordinate with the surface of cuprous oxide, forming a dense protective film on the surface of cuprous oxide, thus obtaining suspension B.
[0039] In this embodiment, suspension B is transferred to a filter press for filtration, washed with ethanol to remove excess antioxidant coating agent, and dried using a vacuum drying oven to obtain cuprous oxide coated with antioxidant coating agent.
[0040] S5. Prepare a cuprous oxide aqueous dispersion using antioxidant cuprous oxide, adjust the pH of the cuprous oxide aqueous dispersion to 8-14, add the dispersion solution to the cuprous oxide aqueous dispersion, and mix well to form a mixed solution C.
[0041] In the embodiments of this application, the concentration of the antioxidant cuprous oxide in the aqueous dispersion is 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L, 150 g / L, 160 g / L, 170 g / L, 180 g / L, 190 g / L, or 200 g / L.
[0042] The reagents used to adjust the pH of the cuprous oxide aqueous dispersion in this application embodiment are lithium hydroxide, sodium hydroxide, potassium hydroxide, or ammonia.
[0043] In the embodiments of this application, the pH of the cuprous oxide aqueous dispersion is adjusted to 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5 or 14.
[0044] Preferably, sodium hydroxide is used as the reagent to adjust the pH of the cuprous oxide aqueous dispersion. The pH of the cuprous oxide aqueous dispersion is adjusted to 11.
[0045] S6. Heat the mixed solution C to a second preset temperature, add the reducing solution B to the mixed solution C, and mix well to form a suspension C. Treat the suspension C to obtain spherical copper powder.
[0046] In this embodiment, the mixed solution C is heated to 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C using a water bath. The reducing solution B is then added to the mixed solution C while continuously stirring at a speed of 200 r / min, 210 r / min, 220 r / min, 230 r / min, 240 r / min, 250 r / min, 260 r / min, 270 r / min, 280 r / min, 290 r / min, 300 r / min, 310 r / min, 320 r / min, 330 r / min, 340 r / min, 350 r / min, 360 r / min, 370 r / min, 380 r / min, 390 r / min, or 400 r / min. Suspension C was prepared by reacting for 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h.
[0047] In this embodiment, the suspension C is transferred to a filter press for filtration, repeatedly washed with deionized water until the conductivity is less than 20 μS / cm, and then dried in a vacuum drying oven to obtain spherical copper powder.
[0048] Preferably, the drying temperature is 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, and the drying time is 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h or 8h.
[0049] Preferably, the ratio of the number of moles of reducing agent B in reducing solution B to the number of moles of cuprous oxide in mixed solution C is 0.5:1, 1.0:1, 1.5:1, 2.0:1, 2.5:1, 3.0:1, 3.5:1, 4.0:1, 4.5:1 or 5.0:1.
[0050] This application also discloses a spherical copper powder, prepared using the above-described method for preparing spherical copper powder. The spherical copper powder is spherical in shape, with particle sizes of 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, and 3.4 μm. μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4.0μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm m, 4.8μm, 4.9μm, 5.0μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm or 6.0μm. The tap density of spherical copper powder is 4.0g / cm 3 4.1g / cm 3 4.2g / cm 3 4.3g / cm 3 4.4 g / cm 3 Or 4.5g / cm 3 The loose bulk density is 2.5 g / cm³. 3 2.6g / cm 3 2.7g / cm 3 2.8g / cm 3 2.9g / cm 3 Or 3.0g / cm 3 .
[0051] This application also discloses an application of spherical copper powder, which is used to manufacture conductive adhesive. Example
[0052] Example 1 This embodiment provides a method for preparing spherical copper powder, including: S1. Dissolve 400g of copper sulfate pentahydrate in 2L of deionized water to prepare a copper source solution. Dissolve ascorbic acid in deionized water to prepare a reducing solution A with a concentration of 2mol / L. Dissolve sodium hypophosphite in deionized water to prepare a reducing solution B with a concentration of 2mol / L. Dissolve 5g of gelatin in 0.1L of deionized water to prepare a dispersion solution. Dissolve benzotriazole in ethanol to prepare an antioxidant solution with a concentration of 0.5g / L.
[0053] S2. Add 150g of sodium chloride to the copper source solution above and mix well to form mixed solution A. Add 700mL of 20% sodium hydroxide solution to mixed solution A, stir at 350rpm, and adjust the pH of mixed solution A to 12.
[0054] S3. Using a water bath, heat the mixed solution A to 50°C. While continuously stirring at 350 r / min, add 800 mL of reducing solution A to the mixed solution A. The reaction time is 2 h to obtain suspension A. Let suspension A stand for 1 h, then remove the supernatant to obtain cuprous oxide precipitate.
[0055] S4. Disperse 350g of cuprous oxide in 1L of antioxidant solution and mix well to form mixed solution B. Heat mixed solution B to 50°C using a water bath and react for 0.5h with continuous stirring at 350r / min to allow the antioxidant coating agent to fully coordinate with the surface of cuprous oxide, forming a dense protective film on the surface of cuprous oxide, thus obtaining suspension B. Transfer suspension B to a filter press for filtration, wash with ethanol to remove excess antioxidant coating agent, and dry in a vacuum drying oven at 50°C for 4h to obtain cuprous oxide with an antioxidant coating.
[0056] S5. Disperse 120g of antioxidant cuprous oxide in 1L of deionized water to prepare a cuprous oxide aqueous dispersion. Add 50mL of 20% sodium hydroxide solution to the cuprous oxide aqueous dispersion, stir at 350rpm, and adjust the pH of the cuprous oxide aqueous dispersion to 11. Add 0.1L of dispersion solution to the cuprous oxide aqueous dispersion and mix well to form mixed solution C.
[0057] S6. Using a water bath, heat the mixed solution C to 70°C. While continuously stirring at 350 r / min, add 400 mL of reducing solution B to the mixed solution C. The reaction time is 2 h to obtain suspension C. Transfer suspension C to a filter press for filtration. Wash repeatedly with deionized water until the conductivity is less than 20 μS / cm. Then dry in a vacuum drying oven at 60°C for 8 h to obtain spherical copper powder.
[0058] Example 2 The difference from Example 1 is that, in step S3, the mixed solution A is heated to 60°C using a water bath. In step S6, the mixed solution C is heated to 80°C using a water bath.
[0059] Example 3 The difference from Example 1 is that, in step S2, the pH of the mixed solution A is adjusted to 11. In step S5, the pH of the cuprous oxide aqueous dispersion is adjusted to 10.
[0060] Example 4 The difference from Example 1 is that, in step S1, ascorbic acid is used to prepare a reducing solution A with a concentration of 4 mol / L. Sodium hypophosphite is used to prepare a reducing solution B with a concentration of 4 mol / L. In step S3, 400 mL of reducing solution A is added to mixed solution A. In step S6, 200 mL of reducing solution B is added to mixed solution C.
[0061] Comparative Example Comparative Example 1 The difference from Example 1 is that, in step S1, ascorbic acid is used to prepare a reducing solution A with a concentration of 6 mol / L. Sodium hypophosphite is used to prepare a reducing solution B with a concentration of 6 mol / L. In step S3, 800 mL of reducing solution A is added to mixed solution A. In step S6, 400 mL of reducing solution B is added to mixed solution C.
[0062] Comparative Example 2 The difference from Example 1 is that, in step S3, the mixed solution A is heated to 90°C using a water bath. In step S6, the mixed solution C is heated to 90°C using a water bath. Step S4 is omitted.
[0063] Performance testing Test 1: The particle size distribution of copper powder prepared in each example and comparative example was tested using a Malvern 2000 particle size analyzer.
[0064] Test 2: The tap density of the copper powder prepared in each example and comparative example was tested using a tap density tester.
[0065] Test 3: The loose packing density of the copper powder prepared in each embodiment and each comparative example was tested using a loose packing density tester.
[0066] Test 4: The morphology of the copper powder prepared in each embodiment and comparative example was tested using a JEOL JSM-7800 scanning electron microscope.
[0067] The test results are shown in Table 1. Electron micrographs of the copper powders prepared in Examples 1, 2, 3, and 4, and Comparative Examples 1 and 2, are provided in the table below. Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 .
[0068] Table 1 Performance Test Results Refer to Table 1. Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 As can be seen, the copper powder obtained in Example 1 consists of regular spherical or near-spherical particles with a smooth surface, excellent dispersibility, and no obvious agglomeration. The particle size is approximately 2.2 μm, and the particle size distribution range is relatively narrow. The copper powder obtained in Example 2 still maintains good spherical morphology and dispersibility, but the particle size is reduced to approximately 1.8 μm. Due to the increased reduction reaction temperature, the reaction rate is increased, and the supersaturation of the system is increased, leading to an increase in the number of nuclei. Therefore, with the total reduction amount remaining unchanged, more particles are generated, and the final size of each particle is smaller. The copper powder obtained in Example 3 still has a spherical morphology and good dispersibility, with a particle size of approximately 3 μm. This indicates that even with a certain degree of reduction in the pH of the reaction system, copper powder with controllable morphology can still be prepared. The copper powder obtained in Example 4 has a particle size of approximately 1.5 μm, with finer particles, but still maintains good sphericity and dispersibility. The higher concentration of reducing agent created a stronger reducing environment, accelerating the reduction rate and significantly increasing the number of nuclei, resulting in finer particles after the reaction. The copper powder obtained in Comparative Example 1 exhibited severe agglomeration and an extremely wide particle size distribution. This indicates that a severe excess of reducing agent leads to the instantaneous generation of a large number of fine cuprous oxide nuclei in the initial stage of the reaction. The reaction system consumes copper ions too quickly, disrupting the controllability of the crystallization process and reducing the uniformity of particle size distribution. Furthermore, the excessive number of nuclei exceeds the coating capacity of the dispersant, causing some small particles to agglomerate. The copper powder obtained in Comparative Example 2 exhibited severe agglomeration, forming large precipitates with an extremely wide particle size distribution and very poor dispersibility. Excessive temperature resulted in a violent and uncontrollable reaction. A large amount of cuprous oxide was rapidly reduced to copper, and the enormous exothermic reaction and extremely high supersaturation led to explosive nucleation and disordered growth. Therefore, selecting appropriate reducing agent concentration and reaction temperature is crucial for achieving stable and controllable reduction and ultimately obtaining highly dispersible copper powder. In addition, the copper powder prepared in Comparative Example 2 turned significantly black after being exposed to air for 7 days due to the lack of antioxidant coating treatment, indicating severe surface oxidation. In contrast, the copper powder prepared in Examples 1-4 and Comparative Example 1 retained its initial brick-red color after being exposed to air for 7 days.
[0069] The implementation principle of this embodiment is as follows: First, under specific conditions, copper ions are reduced to cuprous oxide. Then, under specific conditions, cuprous oxide is reduced to copper. During the reduction process, the inherent crystal structure of cuprous oxide crystals tends to undergo a spheroidization transformation. The dispersant is adsorbed on the particle surface to prevent particle agglomeration. The two-step step-phase reduction method for producing copper powder results in a relatively mild reaction process. Combined with the dispersing effect of the dispersant, and by precisely controlling key parameters such as reaction pH, temperature, and reducing agent concentration, the generation and growth process of copper crystal nuclei can be effectively regulated. This makes it easier to accurately control the particle size and morphology of copper powder, significantly reducing agglomeration, resulting in better particle size uniformity, better copper powder dispersibility, and higher copper powder purity, which can significantly reduce production costs. A halogen compound is added before copper ions are reduced to cuprous oxide. Halogen ions form soluble complexes with cuprous ions, significantly improving the stability of cuprous ions and inhibiting their disproportionation or oxidation. This greatly reduces the formation of the byproduct copper oxide, ensuring the uniformity of copper powder particle size, morphology, dispersibility, and purity. Before cuprous oxide is reduced to copper, an antioxidant film forms on its surface. This film acts as a physical barrier against oxygen, effectively preventing the oxidation of cuprous ions and improving their stability, further ensuring the uniformity of copper powder particle size, morphology, dispersibility, and purity. In subsequent reactions, the antioxidant film partially or completely transfers to the surface of the copper powder, greatly enhancing the antioxidant stability of the spherical copper powder. This makes it suitable for applications such as conductive adhesives, electronic conductive pastes, and catalysts.
[0070] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A method for preparing spherical copper powder, characterized in that, include: S1. Prepare copper source solution, reducing solution A, reducing solution B, dispersion solution and antioxidant solution; S2. Add a halogen compound to the copper source solution, mix well to form a mixed solution A, and adjust the pH of the mixed solution A to 8-14; S3. Heat the mixed solution A to a first preset temperature, add the reducing solution A to the mixed solution A to obtain suspension A; treat the suspension A to obtain cuprous oxide. S4. Disperse the cuprous oxide in the antioxidant solution, mix well to form a mixed solution B, heat the mixed solution B to a second preset temperature to obtain a suspension B; treat the suspension B to obtain the antioxidant cuprous oxide; S5. Prepare a cuprous oxide aqueous dispersion using the antioxidant cuprous oxide, adjust the pH of the cuprous oxide aqueous dispersion to 8-14, add the dispersion solution to the cuprous oxide aqueous dispersion, and mix well to form a mixed solution C; S6. Heat the mixed solution C to a second preset temperature, add the reducing solution B to the mixed solution C, and mix well to form a suspension C; The suspension C was treated to obtain spherical copper powder.
2. The method for preparing spherical copper powder according to claim 1, characterized in that, In step S1, copper salt is dissolved in deionized water to prepare a copper source solution with a concentration of 0.1-2 mol / L; reducing agent A is dissolved in deionized water to prepare a reducing solution A with a concentration of 0.5-4.5 mol / L; reducing agent B is dissolved in deionized water to prepare a reducing solution B with a concentration of 0.5-5 mol / L; dispersant is dissolved in deionized water to prepare a dispersion solution with a concentration of 5-50 mmol / L; and antioxidant coating agent is dissolved in ethanol to prepare an antioxidant solution with a concentration of 0.1-1 g / L. In step S2, the concentration of the halogen compound in the mixed solution A is 0.2-1.5 mol / L. In step S4, the concentration of cuprous oxide in the mixed solution B is 200-1000 g / L. In step S5, the concentration of cuprous oxide in the cuprous oxide aqueous dispersion is 20-200 g / L.
3. The method for preparing spherical copper powder according to claim 2, characterized in that, The copper salt is copper sulfate pentahydrate, copper nitrate hydrate, copper chloride hydrate, or basic copper carbonate; the reducing agent A is ascorbic acid, glucose, sodium hypophosphite, sodium borohydride, triethanolamine, hydrazine hydrate, or formaldehyde; the reducing agent B is ascorbic acid, glucose, sodium hypophosphite, sodium borohydride, triethanolamine, hydrazine hydrate, or formaldehyde; the dispersant is gelatin, Tween, gum arabic, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, or dodecyl sulfate. Sodium stearate, sodium oleate, or sodium oleate; the antioxidant coating agent is imidazole, 2-undecylimidazolium, benzotriazole, stearic acid, oleic acid, hydroxyethylidene diphosphonic acid, aminotrimethylphosphonic acid, silane coupling agent, or polyaniline; the halogen compound is sodium chloride, potassium chloride, sodium bromide, or sodium iodide; the reagent used to adjust the pH of the mixed solution A is lithium hydroxide, sodium hydroxide, potassium hydroxide, or ammonia; the reagent used to adjust the pH of the cuprous oxide aqueous dispersion is lithium hydroxide, sodium hydroxide, potassium hydroxide, or ammonia.
4. The method for preparing spherical copper powder according to claim 1, characterized in that, In step S3, the mixed solution A is heated to 40-80°C, the stirring speed is 200-400 r / min, and the reaction time is 0.5-5 h; In step S4, the mixed solution B is heated to 30-55°C, the stirring speed is 200-400 r / min, and the reaction time is 0.5-5 h; In step S6, the mixed solution C is heated to 40-80°C, the stirring speed is 200-400 r / min, and the reaction time is 0.5-5 h.
5. The method for preparing spherical copper powder according to claim 1, characterized in that, In step S3, the suspension A is allowed to stand for 0.5-5 hours, and the supernatant is removed to obtain the cuprous oxide.
6. The method for preparing spherical copper powder according to claim 1, characterized in that, In step S4, the suspension B is transferred to a filter press, washed with ethanol and dried to obtain the antioxidant cuprous oxide.
7. The method for preparing spherical copper powder according to claim 1, characterized in that, In step S6, the suspension C is transferred to a filter press, washed with deionized water and dried to obtain the spherical copper powder.
8. A spherical copper powder, characterized in that, It is prepared by the method for preparing spherical copper powder according to any one of claims 1 to 7.
9. The spherical copper powder according to claim 8, characterized in that, The spherical copper powder is spherical with a particle size of 1-6 μm and a tap density of 4.0-4.5 g / cm³. 3 The loose bulk density is 2.5-3 g / cm³. 3 .
10. The spherical copper powder prepared by the method according to any one of claims 1 to 7, or the spherical copper powder according to any one of claims 8 to 9, in the preparation of conductive adhesives.