Nanoscale superfine copper powder and preparation method thereof

Abstract

The invention provides nanoscale superfine copper powder and a preparation method thereof, and belongs to the technical field of metal powder, the preparation method comprises the following steps: dispersing copper salt and a complexing agent in deionized water to obtain a copper salt solution; dispersing a reducing agent and a dispersing agent in deionized water to obtain a reducing solution; dispersing sodium hydroxide in deionized water to obtain a sodium hydroxide solution; the method comprises the following steps: heating a copper salt solution, a reduction solution and a sodium hydroxide solution to 45-80 DEG C, adding the reduction solution into the copper salt solution under a stirring condition, then adding the sodium hydroxide solution to obtain a mixed solution, and reacting for 2-3 hours; and after the reaction is finished, a suspension containing copper powder is obtained, and after solid-liquid separation, washing and drying are conducted, the nanoscale superfine copper powder is obtained. The method is simple in technological process, does not need special equipment and is suitable for industrial production. And the prepared nano copper powder is good in dispersing performance, uniform in particle size distribution, high in purity and suitable for being applied to the field of microelectronic components.

Description

Technical Field

[0001] This invention relates to the field of metal powder technology, specifically to a nanoscale ultrafine copper powder and its preparation method. Background Technology

[0002] Nanoscale ultrafine copper powder has become a research hotspot in materials science due to its unique physicochemical properties (such as high specific surface area, excellent electrical conductivity, catalytic activity, and low-temperature sintering characteristics), showing broad application prospects in fields such as electronic packaging, catalysts, biomedicine, and conductive inks. For example, in the electronics field, its high electrical and thermal conductivity and low-temperature sintering characteristics make it suitable for preparing electronic pastes, making it an ideal material for packaging interconnects and printed electronics. It can also replace precious metals as internal electrodes in multilayer ceramic capacitors, reducing costs. In the catalysis field, its high surface activity allows it to be used in coupling reactions, hydrogenation reactions, etc., exhibiting excellent catalytic activity.

[0003] Currently, methods for preparing nanoscale ultrafine copper powder, such as physical pulverization and gas-phase methods, often suffer from problems such as uneven particle size distribution, high energy consumption, and low yield, making it difficult to meet the market demand for high-quality nanoscale copper powder. Chemical methods, as an emerging preparation technology, mainly include microemulsion methods, electrochemical methods, and liquid-phase reduction methods. Among them, the liquid-phase reduction method is a technique that uses a chemical reducing agent in a metal cation solution to achieve the reduction and nucleation growth of metal ions, thereby preparing micron or nano-sized metal particles. This method has mild reaction conditions, controllable process parameters, and low equipment investment, showing good prospects for large-scale preparation of nanoscale ultrafine copper powder. Nevertheless, this method still has significant limitations in application, mainly including difficulties in precisely controlling the reaction rate and nucleation process, low solid-liquid separation efficiency, difficulty in controlling the impurity content of the product, and an excessively wide particle size distribution range. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a nanoscale ultrafine copper powder and its preparation method, aiming to solve the technical problems of existing liquid phase reduction methods, such as difficulty in accurately controlling the reaction rate and nucleation process, low solid-liquid separation efficiency, difficulty in controlling the impurity content of the product, and excessively wide particle size distribution range.

[0005] In a first aspect, embodiments of this application provide a nanoscale ultrafine copper powder and a method for preparing the same, comprising the following steps: S1. Disperse the copper salt and complexing agent in deionized water to obtain a copper salt solution; The reducing agent and dispersant are dispersed in deionized water to obtain a reduced solution; Sodium hydroxide is dispersed in deionized water to obtain a sodium hydroxide solution; S2. Heat the copper salt solution, reducing solution and sodium hydroxide solution to 45~80℃. Under stirring, add the reducing solution to the copper salt solution, and then add the sodium hydroxide solution to obtain a mixed solution. React for 2~3 hours. S3. After the reaction is complete, a copper powder suspension is obtained. After solid-liquid separation, washing and drying, nano-sized ultrafine copper powder is obtained.

[0006] Secondly, this application provides a nano-scale ultrafine copper powder, which is prepared by the above-described method, and the particle size of the nano-scale ultrafine copper powder is 200~1000nm.

[0007] The advantages of this application, which differ from existing technical solutions, include: 1. This invention provides a method for preparing nano-sized ultrafine copper powder using a chemical reduction method. The process is simple, requires no special equipment, and is suitable for industrial production. The prepared nano-copper powder exhibits good dispersion, uniform particle size distribution, and high purity, making it suitable for application in the field of microelectronic components.

[0008] 2. This invention can control the reduction reaction rate by adjusting different parameters, such as reaction temperature, molar ratio of copper salt to reducing agent, pH of reaction solution, and amount of complexing agent used, thereby controlling the generation and growth of nano-copper powder nuclei and preparing nano-copper particles with average particle sizes of 300nm, 500nm and 800nm.

[0009] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0010] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0011] Figure 1 This is a SEM image of the nanoscale ultrafine copper powder prepared in Example 1.

[0012] Figure 2 This is a SEM image of the nanoscale ultrafine copper powder prepared in Example 2.

[0013] Figure 3 This is a SEM image of the nanoscale ultrafine copper powder prepared in Example 3. Detailed Implementation

[0014] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0015] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0016] Liquid-phase reduction is a technique that uses chemical reducing agents in a metal cation solution to achieve the reduction and nucleation growth of metal ions, thereby preparing micron or nano-sized metal particles. This method offers mild reaction conditions, controllable process parameters, and low equipment investment, showing promising prospects for large-scale preparation of nanoscale ultrafine copper powder. However, this method still has significant limitations in application, mainly including difficulties in precisely controlling the reaction rate and nucleation process, low solid-liquid separation efficiency, difficulty in controlling the impurity content of the product, and an excessively wide particle size distribution range.

[0017] To address the technical challenges of precise control over reaction rate and nucleation process, low solid-liquid separation efficiency, difficulty in controlling product impurity content, and excessively wide particle size distribution in existing liquid-phase reduction methods, this application provides a nanoscale ultrafine copper powder and its preparation method. The process of this invention is simple, requires no special equipment, and is suitable for industrial production. The prepared nanoscale copper powder exhibits good dispersion properties, uniform particle size distribution, and high purity, making it suitable for application in the field of microelectronic components.

[0018] In a first aspect, embodiments of this application provide a nanoscale ultrafine copper powder and a method for preparing the same, comprising the following steps: S1. Disperse the copper salt and complexing agent in deionized water to obtain a copper salt solution; The reducing agent and dispersant are dispersed in deionized water to obtain a reduced solution; Sodium hydroxide is dispersed in deionized water to obtain a sodium hydroxide solution; S2. Heat the copper salt solution, reducing solution and sodium hydroxide solution to 45~80℃. Under stirring, add the reducing solution to the copper salt solution, and then add the sodium hydroxide solution to obtain a mixed solution. React for 2~3 hours. S3. After the reaction is complete, a copper powder suspension is obtained. The solid product is obtained by filtration. The solid product is washed with deionized water and ethanol until the conductivity of the filtrate is less than or equal to 20 uS / cm. Then, it is placed in a vacuum drying oven for drying at 60℃ for 6 hours to obtain nano-scale ultrafine copper powder.

[0019] In the technical solution of this application embodiment, the technical principle of the present invention is to use a reducing agent in a strongly alkaline environment to reduce the complexed copper ions into zero-valent copper atoms, and to use a dispersant to control the nucleation and growth of copper atoms, and finally obtain nanoscale copper powder.

[0020] In this invention, a complexing agent is first used with Cu 2+ Complexation forms a stable precursor, preventing precipitation and controlling the reduction rate. Then, a reducing solution containing a dispersant is added, followed by the addition of NaOH solution to create a strongly alkaline environment, enhancing the reducing agent's ability and initiating rapid and uniform nucleation.

[0021] In some embodiments, the copper salt includes at least one of copper chloride, copper sulfate, copper nitrate, and copper acetate.

[0022] In some embodiments, the complexing agent includes at least one of sodium citrate, sodium tartrate, and potassium sodium tartrate.

[0023] In the technical solution of this application embodiment, the complexing agent can tightly "bind" copper ions to form a stable, soluble complex. It has the following effects: 1. Preventing precipitation: When adding strong base sodium hydroxide later, without a complexing agent such as sodium citrate, copper ions will directly react with hydroxide ions to form copper hydroxide precipitate. Complexing increases the stability of copper ions, preventing premature precipitation under alkaline conditions and ensuring the uniformity of the reaction.

[0024] 2. Controlling the reduction rate: The complexing agent reduces the concentration of free copper ions, making the reduction reaction of copper ions by ascorbic acid relatively mild and slow. This is key to generating small and uniform nanoparticles. If the reduction is too fast, a large number of crystal nuclei will be generated instantly, leading to particle agglomeration or the formation of large precipitates.

[0025] In some embodiments, the concentration of copper salt in the copper salt solution is 0.5~3.5 mol / L, and the concentration of complexing agent is 0.1~1.5 mol / L.

[0026] In some embodiments, the molar ratio of reducing agent to copper salt is 1:(1.2~2.0).

[0027] In some embodiments, the dispersant is at least one selected from polyvinylpyrrolidone, gelatin, polyethylene glycol, sodium dodecyl sulfate, sodium metaphosphate, and sodium tripolyphosphate.

[0028] In the technical solution of this application embodiment, the dispersant can prevent copper powder grains from agglomerating and growing into macroscopic copper powder, while controlling the morphology of the copper powder.

[0029] In some embodiments, the mass ratio of dispersant to copper salt is (1~10):100.

[0030] In some embodiments, the concentration of sodium hydroxide solution is 1.0~6.0 mol / L.

[0031] In some embodiments, the pH of the mixture in step S2 is 10.0 to 13.0.

[0032] In the technical solution of this application embodiment, a strongly alkaline environment greatly enhances the reducing power of ascorbic acid, enabling the reduction reaction to proceed smoothly. Simultaneously, a high pH value and OH- - Ion concentration helps copper ions to be reduced quickly and uniformly, forming a large number of tiny crystal nuclei (nucleation process). The number of crystal nuclei directly determines the final size of the nanoparticles; the more crystal nuclei, the smaller the average particle size.

[0033] An excessively high pH level will lead to a significant increase in the amount of sodium hydroxide required, resulting in higher costs.

[0034] In some embodiments, the stirring rate in step S2 is 300~600 rad / min.

[0035] Secondly, this application provides a nano-scale ultrafine copper powder, which is prepared by the above-described method, and the particle size of the nano-scale ultrafine copper powder is 200~1000nm.

[0036] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0037] I. Preparation Method Example 1 A method for preparing nanoscale ultrafine copper powder, the specific steps of which are as follows: S1: Weigh 300g of copper chloride and dissolve it in 1000mL of deionized water, then add 103g of sodium citrate and stir well; then dissolve 616g of ascorbic acid and 5g of polyvinylpyrrolidone in 1200mL of water; finally, prepare an appropriate amount of 3mol / L sodium hydroxide solution for later use.

[0038] S2: Heat the three solutions in a water bath to 60°C. After the temperature stabilizes, add the reducing solution to the copper salt solution with stirring to obtain a white turbid liquid. Continue to add 3750 mL of 3 mol / L sodium hydroxide solution until the pH of the solution reaches 12.0, and continue the reaction for 3 hours.

[0039] S3: After the reaction is complete, a copper powder suspension is obtained. Solid-liquid separation is performed on the suspension, and the suspension is washed multiple times with deionized water and ethanol before drying to obtain nano-scale ultrafine copper powder.

[0040] SEM image of the nano-copper powder prepared according to Example 1 is shown below. Figure 1 As shown in the figure, the nano-copper powder is spherical with an average particle size of about 280 nm. The particle size distribution is uniform and there is no obvious agglomeration.

[0041] Example 2 A method for preparing nanoscale ultrafine copper powder, the specific steps of which are as follows: S1: Weigh 300g of copper chloride and dissolve it in 1000mL of deionized water, then add 103g of sodium citrate and stir well; then dissolve 370g of ascorbic acid and 5g of polyvinylpyrrolidone in 1200mL of water; finally, prepare an appropriate amount of 3mol / L sodium hydroxide solution for later use.

[0042] S2: Place the three solutions in a water bath and heat to 75°C. After the temperature stabilizes, add the reducing solution to the copper salt solution with stirring to obtain a white turbid liquid. Continue to add 2900 mL of 3 mol / L sodium hydroxide solution until the pH of the solution reaches 12.0, and continue the reaction for 2 hours.

[0043] S3: After the reaction is complete, a copper powder suspension is obtained. Solid-liquid separation is performed on the suspension, and the suspension is washed multiple times with deionized water and ethanol before drying to obtain nano-scale ultrafine copper powder.

[0044] SEM image of the nano-copper powder prepared according to Example 2. Figure 2 As shown in the figure, the average particle size of the nano-copper powder is about 500 nm, exhibiting a near-spherical shape, with a uniform particle size distribution and no obvious agglomeration. This indicates that increasing the reaction temperature is beneficial for crystal nucleus growth, thereby increasing the particle size of the copper powder.

[0045] Example 3 A method for preparing nanoscale ultrafine copper powder, the specific steps of which are as follows: S1: Weigh 300g of copper chloride and dissolve it in 1000mL of deionized water, then add 103g of sodium citrate and stir well; then dissolve 370g of ascorbic acid and 5g of polyvinylpyrrolidone in 1200mL of water; finally, prepare an appropriate amount of 3mol / L sodium hydroxide solution for later use.

[0046] S2: Place the three solutions in a water bath and heat to 60°C. After the temperature stabilizes, add the reducing solution to the copper salt solution with stirring to obtain a white turbid liquid. Continue to add 2900 mL of 3 mol / L sodium hydroxide solution until the pH of the solution reaches 12.0, and continue the reaction for 3 hours.

[0047] S3: After the reaction is complete, a copper powder suspension is obtained. Solid-liquid separation is performed on the suspension, and the suspension is washed multiple times with deionized water and ethanol before drying to obtain nano-scale ultrafine copper powder.

[0048] SEM images of the nano-copper powder prepared according to Example 3 are shown below. Figure 3 As shown in the figure, the average particle size of the nano copper powder is about 800 nm, which is spherical and has a uniform particle size distribution without obvious agglomeration. This indicates that reducing the amount of reducing agent will reduce the number of crystal nuclei generated, which is beneficial to crystal nuclei growth and increases the particle size of copper powder.

[0049] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing nanoscale ultrafine copper powder, characterized in that, Includes the following steps: S1. Disperse the copper salt and complexing agent in deionized water to obtain a copper salt solution; The reducing agent and dispersant are dispersed in deionized water to obtain a reduced solution; Sodium hydroxide is dispersed in deionized water to obtain a sodium hydroxide solution; S2. Heat the copper salt solution, reducing solution and sodium hydroxide solution to 45~80℃, and under stirring, add the reducing solution to the copper salt solution, followed by the addition of sodium hydroxide solution to obtain a mixed solution, and react for 2~3 hours; S3. After the reaction is complete, a copper powder suspension is obtained. After solid-liquid separation, washing and drying, nano-sized ultrafine copper powder is obtained.

2. The method for preparing nanoscale ultrafine copper powder according to claim 1, characterized in that, The copper salt includes at least one of copper chloride, copper sulfate, copper nitrate, and copper acetate.

3. The method for preparing nanoscale ultrafine copper powder according to claim 1, characterized in that, The complexing agent includes at least one of sodium citrate, sodium tartrate, and potassium sodium tartrate.

4. The method for preparing nanoscale ultrafine copper powder according to claim 1, characterized in that, The concentration of copper salt in the copper salt solution is 0.5~3.5 mol / L, and the concentration of complexing agent is 0.1~1.5 mol / L.

5. The method for preparing nanoscale ultrafine copper powder according to claim 1, characterized in that, The molar ratio of the reducing agent to the copper salt is 1:(1.2~2.0).

6. The method for preparing nanoscale ultrafine copper powder according to claim 1, characterized in that, The dispersant is at least one of polyvinylpyrrolidone, gelatin, polyethylene glycol, sodium dodecyl sulfate, sodium metaphosphate, and sodium tripolyphosphate. The mass ratio of the dispersant to the copper salt is (1~10):

100.

7. The method for preparing nanoscale ultrafine copper powder according to claim 1, characterized in that, The concentration of the sodium hydroxide solution is 1.0~6.0 mol / L.

8. The method for preparing nanoscale ultrafine copper powder according to claim 1, characterized in that, The pH of the mixture in step S2 is 10.0~13.

0.

9. The method for preparing nanoscale ultrafine copper powder according to claim 1, characterized in that, The stirring rate in step S2 is 300~600 rad / min.

10. A nano-scale ultrafine copper powder, characterized in that, The nanoscale ultrafine copper powder is prepared by any one of claims 1 to 9, and the particle size of the powder is 200 to 1000 nm.

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