Method for preparing high-uniformity nano copper powder on large scale

Abstract

The invention discloses a method for preparing high-uniformity nano copper powder on a large scale, which comprises the following steps of: 1, dissolving copper salt in deionized water to obtain a clear solution; 2, adding a viscosity regulator into the clarified solution to obtain a mixed solution A; 3, adding a short-chain amine solution into the mixed solution A to obtain a mixed solution B; 4, performing water bath on the mixed solution B and adding a reducing agent to obtain a mixed solution C; 5, the mixed solution C is rapidly cooled; and 6, centrifugation, washing and vacuum drying are carried out, and the nano copper powder with the particle size being 200-250 nm is obtained. The obtained nano-copper powder is uniform in particle size distribution, good in dispersity, smooth in surface and excellent in conductivity, the particle size of the nano-copper powder is regulated and controlled by changing parameters, the technical limitation that existing copper powder needs to use a surfactant, agglomeration is serious, particle size distribution is not uniform, and large-scale preparation is difficult is broken through, and the nano-copper powder is suitable for large-scale preparation. And the process is simple, operability is high, repeatability is good, and large-scale preparation of the nano copper powder is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of metal nanomaterials, and particularly relates to a method for large-scale preparation of highly uniform nano copper powder. Background Art

[0002] Nano-metal copper powders, due to their unique thermal and electrical conductivity, lubrication, antimicrobial, and catalytic properties, are widely used in new electronic pastes, lubricant modifiers, antimicrobial materials, and industrial catalysts. In particular, due to their outstanding electrical conductivity and low cost, nano-copper powders can replace precious metals like silver as conductive fillers in the production of green, environmentally friendly, and highly efficient conductive adhesives and coatings.

[0003] Currently, methods for producing nano-copper powder can be broadly categorized into physical and chemical methods. Physical methods primarily include physical vapor deposition (PVD), high-energy ball milling, and electric explosion. Mechanical ball milling produces nano-copper powder by grinding a copper block or coarse powder in a ball mill for a long period of time. While simple to operate, it is prone to introducing impurities and results in a wide particle size distribution. Electric explosion produces nanopowders by applying a high DC voltage along the axis of a metal wire, creating a high current density within the wire and causing it to explode. Physical vapor deposition (PVD) vaporizes copper at high temperatures and then deposits it to form nano-copper powder. This method is the predominant method for commercially producing nano-copper powders. The resulting nano-copper powders are of high purity and can precisely control their particle size and distribution. However, these methods are associated with expensive equipment, low yields, and high production costs. Compared to physical methods, chemical liquid phase methods are the most commonly used method for the controlled synthesis of nanomaterials. These methods involve reacting a solution of a metal compound with a reducing agent under specific conditions, resulting in the reduction of metal ions to metal, producing the corresponding metal powder. This method has a simple process and low cost. It can control the morphology and size of nanomaterials in a simple liquid-phase reaction process and is most likely to be applied to the industrial production of nano-copper powder.

[0004] Researchers have conducted extensive laboratory research on the preparation of nano-copper powders using liquid-phase chemical reduction. Pham et al. reported synthesizing nano-copper with a particle size of approximately 56 nm in a mixed solution of PVP and CTAB using argon as a protective gas. Abdulla-Al-Mamun et al. synthesized nano-copper with a particle size of less than 100 nm using acetonitrile as a solvent and nitrogen as a buffer. Kobayashi et al. obtained nano-copper particles with a diameter of 71 nm by heating a mixed solution of citric acid and copper sulfate with nitrogen as a protective gas. Wen et al. used CuSO₄ as a copper source, oleic acid as a protective agent, NaH₂PO₂ as a reducing agent, and EDTA as a chelating agent. Using a two-step method to control the nucleation process, they obtained nano-copper powders with a particle size of 20-40 nm and good dispersion. Huang Junsheng et al. prepared nano-copper particles with a particle size of 30-50 nm using CuSO₄ as a copper source, KBH₄ as a reducing agent, KOH, EDTA as a chelating agent, and PVP as a dispersant. Zhang et al. synthesized antioxidant nanocopper powders with a particle size of 135 ± 30 nm using slightly soluble Cu(OH)₂ as a copper source, PEG-2000 as a protective agent, C₆H₂O₂ as a reducing agent, and ethylene glycol as a solvent. Although this method has been extensively studied, the liquid-phase chemical reduction method for preparing nanocopper powders still presents several challenges. First, to prevent oxidation of the nanocopper, an inert gas is typically introduced into the reaction system to minimize the effects of air on the product. Second, the resulting nanocopper powders are relatively small in size. To prevent product agglomeration, a large amount of surfactant is added. Surfactants are typically long-chain organic compounds that coat the copper powder surface, making them difficult to clean and significantly affecting its conductive properties. Third, during the nanocopper powder preparation process, organic reagents are often used as reaction solvents to regulate the reduction reaction rate and obtain nanocopper powders with a uniform particle size distribution. However, the use of large amounts of organic compounds can cause significant environmental pollution.

[0005] As the application areas of nano-copper powder materials continue to expand, their preparation methods will also continue to develop. The development trend will focus on chemical liquid phase methods, developing green and environmentally friendly technologies and processes to reduce environmental factors affecting the crystal growth process. Preparation technologies will develop in the direction of low cost, low consumption, and low pollution. The prepared nano-copper powder materials must be easy to wash and handle, meet industrial production needs, and achieve industrial production. Summary of the Invention

[0006] The present invention aims to address the shortcomings of the prior art by providing a method for the large-scale preparation of highly uniform nano-copper powder. This method involves uniformly mixing a copper salt solution with a viscosity modifier using ultrasonic stirring. The pH of the mixed solution is then adjusted using a short-chain amine. A certain amount of a reducing agent is then added to react, and the product is rapidly cooled. Ultimately, nano-copper powder with a controllable particle size within the range of 200 nm to 250 nm is obtained.

[0007] To solve the above technical problems, the technical solution adopted by the present invention is: a method for large-scale preparation of highly uniform nano copper powder, characterized in that the method comprises the following steps: Step 1: Dissolve copper salt in deionized water and stir evenly to obtain a blue clear solution; Step 2: adding a viscosity regulator solution to the blue clear solution obtained in step 1, followed by stirring and ultrasonication to obtain a blue mixed solution A; Step 3: Add the short-chain amine solution to the blue mixed solution A obtained in step 2, and then stir for 30 minutes to 60 minutes to obtain a mixed solution B; Step 4: Place the mixed solution B obtained in step 3 in a water bath at 90°C to 100°C, add a reducing agent thereto, and stir to react for 30min to 50min to obtain a purple-red mixed solution C; Step 5: quickly pouring the purple-red mixed solution C obtained in step 4 into a bucket containing a large amount of ice cubes to rapidly cool the purple-red mixed solution C to obtain a cooled purple-red mixed solution C; Step 6: Centrifuge the cooled purple-red mixed solution C obtained in step 5 to obtain a purple-red product, which is then washed with deionized water and anhydrous ethanol in sequence, and vacuum-dried to obtain nano-copper powder with a particle size of 200 nm to 250 nm.

[0008] The above-mentioned method for large-scale preparation of highly uniform nano-copper powder is characterized in that the copper salt described in step 1 is copper glycinate, copper gluconate, or sodium copper ethylenediaminetetraacetate, and the mass ratio of the copper salt to deionized water is 1:10-50. The present invention uses a bonded coordination copper salt, which inherently has high steric hindrance and can effectively reduce the conversion rate of copper ions. By controlling the mass ratio of the copper salt to deionized water, the concentration of the copper salt is controlled, thereby controlling the overall reaction process, facilitating the large-scale preparation of highly uniform nano-copper powder.

[0009] The above-mentioned method for large-scale preparation of highly uniform nano-copper powder is characterized in that the viscosity regulator solution in step 2 is prepared by using one or more of gum arabic, guar gum, agar, β-cyclodextrin, and carrageenan with a mass fraction of 30% to 50%, and the mass ratio of the solute of the viscosity regulator solution to the copper salt in the mixed solution A is 1:80 to 150. The present invention adjusts the viscosity of the solution by controlling the mass fraction and solute components of the viscosity regulator solution and the added mass to obtain the optimal solution viscosity, effectively slowing the rate of the reduction reaction, thereby replacing the coating effect of the long-chain surfactant on the copper ions, facilitating the large-scale preparation of highly uniform nano-copper powder, and preventing the solute content from being too low and not playing its due role, and the solute content from being too high and not being conducive to the subsequent washing process.

[0010] The above-mentioned method for large-scale preparation of highly uniform nano-copper powder is characterized in that the stirring and ultrasonication process in step 2 is: stirring for 10 minutes to 30 minutes and then ultrasonicating for 10 minutes to 30 minutes, alternating the operations 2 to 4 times in total. The present invention, through repeated stirring and ultrasonication, fully disperses the copper ions in the solution, which is conducive to the uniform formation of crystal nuclei.

[0011] The above-mentioned method for large-scale preparation of highly uniform nano-copper powder is characterized in that the short-chain amine solution in step 3 is prepared by mixing a short-chain amine and ethanol in a mass ratio of 1:2-4, wherein the short-chain amine is diethanolamine, triethylamine, or tripropylamine; and the mass ratio of the short-chain amine to the copper salt is 1:30-50. The present invention controls the pH value by adding the short-chain amine solution and combines it with a viscosity modifier to replace the coating effect of the long-chain surfactant on the copper ions, thereby facilitating the large-scale preparation of highly uniform nano-copper powder. The mass ratio of triethylamine or tripropylamine to copper salt is adjusted to form a certain degree of coordination with the copper ions.

[0012] The aforementioned method for large-scale preparation of highly uniform nano-copper powder is characterized in that the reducing agent in step 4 is sodium borohydride, lithium aluminum hydride, or potassium borohydride, and the molar ratio of the reducing agent to the copper salt is 2 to 4:1. By using a strong reducing agent, the present invention enables a rapid reaction at high temperature, achieving crystal nucleation and growth. By adjusting the molar ratio of the copper salt, the particle size of the nano-copper powder can be controlled.

[0013] The above-mentioned method for large-scale preparation of highly uniform nano-copper powder is characterized in that the ice cubes in step 5 are prepared from deionized water. The present invention uses ice cubes prepared from deionized water to prevent the introduction of hypochlorite ions in tap water and prevent their impact on the nano-copper powder.

[0014] The above-mentioned method for preparing nano copper powder with high uniformity on a large scale is characterized in that the temperature of the vacuum drying in step 6 is 50° C. to 80° C. The present invention fully removes residual detergent by controlling the temperature of the vacuum drying.

[0015] Compared with the prior art, the present invention has the following advantages: 1. The present invention uniformly mixes a copper salt solution and a viscosity regulator by ultrasonic stirring, then adjusts the pH value of the mixed solution by using a short-chain amine, then adds a certain amount of a reducing agent to react, and rapidly cools the product to finally obtain nano-copper powder with an adjustable particle size within the range of 200nm to 250nm.

[0016] 2. The present invention controls the crystal nucleation and growth rate by controlling the viscosity of the reaction system solution, replacing the use of organic long-chain surfactants, which can effectively reduce the retention of organic matter on the surface of nano-copper particles and improve the optical, electrical, and magnetic properties of nano-copper powders.

[0017] 3. The present invention can regulate the pH value of the solution by adding short-chain amine substances. On the other hand, the nitrogen on the amine group can combine with copper ions to a certain extent, which can also regulate the speed of crystal growth.

[0018] 4. The present invention adds a strong reducing agent to the hot solution to make the reaction occur quickly and cool it down quickly to prepare nano copper powder with a particle size of 200nm~250nm. The obtained nano copper powder has good dispersibility, smooth surface, uniform particle size distribution and excellent conductivity.

[0019] 5. The present invention addresses the problems that surfactants are often used in the current preparation process of nano-copper powder, which causes a large amount of long-chain organic matter to be coated on the surface of the nanoparticles, making it difficult to clean and affecting the optical, electrical, magnetic and other properties of the nano-copper powder. In addition, the use of a liquid phase reduction method to prepare nano-copper powder also has problems such as uneven product particle size distribution, severe agglomeration, and difficulty in large-scale preparation. The present invention develops a method that does not require the participation of surfactants, is easy to prepare highly uniform nano-copper powder on a large scale, is simple to operate, and has a controllable reaction, which can realize the large-scale preparation of nano-copper powder.

[0020] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a high-magnification SEM image of the nano-copper powder prepared in Example 1 of the present invention.

[0022] Figure 2 This is a low-magnification SEM image of the nano-copper powder prepared in Example 1 of the present invention.

[0023] Figure 3 3 is a SEM image of the nano copper powder prepared in Example 2 of the present invention.

[0024] Figure 4 This is a SEM image of the nano copper powder prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0025] Example 1 This embodiment includes the following steps: Step 1: Take 500g of copper glycinate, add 5L of deionized water, dissolve and stir to obtain a blue clear solution; Step 2: Add 20.83 g of gum arabic solution (30% solute content) to the blue clear solution obtained in step 1, stir for 10 minutes, and then ultrasonicate for 10 minutes. Repeat this operation 4 times to obtain a blue mixed solution A. Step 3: Add 10 g of a short-chain amine solution prepared by 2 g of diethanolamine and the remainder of ethanol to the blue mixed solution A obtained in step 2, and then stir for 30 minutes to obtain a mixed solution B; Step 4: Place the mixed solution B obtained in step 3 in a 90° C. water bath, add 4.73 mol of sodium borohydride, and stir to react for 30 minutes to obtain a purple-red mixed solution C; Step 5: quickly pouring the purple-red mixed solution C obtained in step 4 into a bucket containing a large amount of ice cubes made of deionized water to rapidly cool the purple-red mixed solution C to obtain a cooled purple-red mixed solution C; Step 6: Centrifuge the cooled purple-red mixed solution C obtained in step 5 to obtain a purple-red product, then wash it 4 times with deionized water and 2 times with anhydrous ethanol, and dry the product in a vacuum drying oven at 50° C. for 10 hours to obtain nano copper powder.

[0026] Figure 1 This is a high-magnification SEM image of the nano copper powder prepared in this embodiment. Figure 2 This is a low-magnification SEM image of the nano copper powder prepared in this embodiment. Figure 1 and Figure 2 It can be seen that the nano copper powder prepared in this embodiment has a granular structure with a particle size of about 210 nm. In addition to the granular structure, no products with other morphologies appear, indicating that the nano copper powder prepared in this embodiment has high purity and good morphological uniformity, and the nano copper powder has a uniform particle size distribution and is all spherical.

[0027] Example 2 This embodiment includes the following steps: Step 1: Take 500g of sodium copper ethylenediaminetetraacetate, add 5L of deionized water, dissolve and stir to obtain a blue clear solution; Step 2: Add 6.7 g of agar solution with a solute content of 50% to the blue clear solution obtained in step 1, stir for 20 minutes, and then ultrasonicate for 20 minutes. Repeat this operation three times to obtain a blue mixed solution A. Step 3: Add 16.7 g of a short-chain amine solution prepared by 4.175 g of tripropylamine and the remainder of ethanol to the blue mixed solution A obtained in step 2, and then stir for 40 minutes to obtain a mixed solution B; Step 4: Place the mixed solution B obtained in step 3 in a water bath at 100° C., add 4.6 mol of lithium aluminum hydride, and stir to react for 30 minutes to obtain a purple-red mixed solution C; Step 5: quickly pouring the purple-red mixed solution C obtained in step 4 into a bucket containing a large amount of ice cubes made of deionized water to rapidly cool the purple-red mixed solution C to obtain a cooled purple-red mixed solution C; Step 6: Centrifuge the cooled purple-red mixed solution C obtained in step 5 to obtain a purple-red product, then wash it 5 times with deionized water and 5 times with anhydrous ethanol, and dry the product in a vacuum drying oven at 60° C. for 8 hours to obtain nano copper powder.

[0028] Figure 3 This is the SEM image of the nano copper powder prepared in this embodiment. Figure 3 It can be seen that the nano copper powder prepared in this embodiment has a granular structure with a particle size of about 250 nm. In addition to the granular structure, no products with other morphologies appear, indicating that the nano copper powder prepared in this embodiment has high purity and good morphological uniformity, and the nano copper powder has a uniform particle size distribution and is all spherical.

[0029] Example 3 This embodiment includes the following steps: Step 1: Take 600g of copper gluconate, add 10L of deionized water, dissolve and stir to obtain a blue clear solution; Step 2: Add 18 g of carrageenan solution with a solute content of 40% to the blue clear solution obtained in step 1, stir for 30 minutes, and then ultrasonicate for 30 minutes. Repeat the operation twice to obtain a blue mixed solution A. Step 3: Add 20 g of a short-chain amine solution prepared by 5.7 g of triethylamine and the remainder of ethanol to the blue mixed solution A obtained in step 2, and then stir for 50 minutes to obtain a mixed solution B; Step 4: Place the mixed solution B obtained in step 3 in a water bath at 100° C., add 5.3 mol of potassium borohydride, and stir for 30 minutes to obtain a purple-red mixed solution C; Step 5: quickly pouring the purple-red mixed solution C obtained in step 4 into a bucket containing a large amount of ice cubes made of deionized water to rapidly cool the purple-red mixed solution C to obtain a cooled purple-red mixed solution C; Step 6: Centrifuge the cooled purple-red mixed solution C obtained in step 5 to obtain a purple-red product, then wash it 4 times with deionized water and 3 times with anhydrous ethanol, and dry the product in a vacuum drying oven at 80° C. for 4 hours to obtain nano copper powder.

[0030] Figure 4 This is the SEM image of the nano copper powder prepared in this embodiment. Figure 4 It can be seen that the nano copper powder prepared in this embodiment has a granular structure with a particle size of about 200nm~230nm. In addition to the granular structure, no products with other morphologies appear, indicating that the nano copper powder prepared in this embodiment has high purity and good morphological uniformity, and the nano copper powder has a uniform particle size distribution and is a spherical structure.

[0031] Example 4 This embodiment includes the following steps: Step 1: Take 700g of copper gluconate, add 35L of deionized water, dissolve and stir to obtain a blue clear solution; Step 2: Add 7 g of guar gum and 5 g of β-cyclodextrin solution to the blue clear solution obtained in step 1, wherein the solute content is 40%, stir for 10 minutes and then ultrasonicate for 20 minutes, alternating the operation for a total of 3 times to obtain a blue mixed solution A; Step 3: Add 20 g of a short-chain amine solution prepared by 6.8 g of triethylamine and the remainder of ethanol to the blue mixed solution A obtained in step 2, and then stir for 60 minutes to obtain a mixed solution B; Step 4: Place the mixed solution B obtained in step 3 in a water bath at 100° C., add 5.3 mol of potassium borohydride, and stir for 30 minutes to obtain a purple-red mixed solution C; Step 5: quickly pouring the purple-red mixed solution C obtained in step 4 into a bucket containing a large amount of ice cubes made of deionized water to rapidly cool the purple-red mixed solution C to obtain a cooled purple-red mixed solution C; Step 6: Centrifuge the cooled purple-red mixed solution C obtained in step 5 to obtain a purple-red product, then wash it 4 times with deionized water and 3 times with anhydrous ethanol, and dry the product in a vacuum drying oven at 80° C. for 4 hours to obtain nano copper powder.

[0032] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for large-scale preparation of highly uniform nano copper powder, characterized in that: The method comprises the following steps: Step 1: Dissolve copper salt in deionized water and stir evenly to obtain a blue clear solution; Step 2: adding a viscosity regulator solution to the blue clear solution obtained in step 1, followed by stirring and ultrasonication to obtain a blue mixed solution A; Step 3: Add the short-chain amine solution to the blue mixed solution A obtained in step 2, and then stir for 30 minutes to 60 minutes to obtain a mixed solution B; Step 4: Place the mixed solution B obtained in step 3 in a water bath at 90°C to 100°C, add a reducing agent thereto, and stir to react for 30min to 50min to obtain a purple-red mixed solution C; Step 5: quickly pouring the purple-red mixed solution C obtained in step 4 into a bucket containing a large amount of ice cubes to rapidly cool the purple-red mixed solution C to obtain a cooled purple-red mixed solution C; Step 6: Centrifuge the cooled purple-red mixed solution C obtained in step 5 to obtain a purple-red product, which is then washed with deionized water and anhydrous ethanol in sequence, and vacuum-dried to obtain nano-copper powder with a particle size of 200 nm to 250 nm.

2. The method for preparing high-uniformity nano copper powder on a large scale according to claim 1, wherein: The copper salt in step 1 is copper glycinate, copper gluconate or sodium copper ethylenediaminetetraacetate, and the mass ratio of the copper salt to deionized water is 1:10-50.

3. The method for preparing nano copper powder with high uniformity on a large scale according to claim 1, wherein: The viscosity regulator solution in step 2 is prepared by mixing one or more of gum arabic, guar gum, agar, β-cyclodextrin and carrageenan with a mass fraction of 30% to 50%, and the mass ratio of the solute of the viscosity regulator solution to the copper salt in the mixed solution A is 1:80 to 150.

4. The method for large-scale preparation of highly uniform nano copper powder according to claim 1, wherein: The stirring and ultrasonic process in step 2 is as follows: stirring for 10 min to 30 min and then ultrasonicating for 10 min to 30 min, alternating the operations 2 to 4 times in total.

5. The method for large-scale preparation of high-uniformity nano copper powder according to claim 1, characterized in that: The short-chain amine solution in step 3 is prepared by mixing a short-chain amine and ethanol in a mass ratio of 1:2-4, wherein the short-chain amine is diethanolamine, triethylamine or tripropylamine; and the mass ratio of the short-chain amine to the copper salt is 1:30-50.

6. The method for large-scale preparation of highly uniform nano copper powder according to claim 1, characterized in that: The reducing agent in step 4 is sodium borohydride, lithium aluminum hydride or potassium borohydride, and the molar ratio of the reducing agent to the copper salt is 2-4:

1.

7. The method for large-scale preparation of highly uniform nano copper powder according to claim 1, characterized in that: The ice cubes in step 5 are ice cubes prepared from deionized water.

8. The method for large-scale preparation of highly uniform nano copper powder according to claim 1, characterized in that: The vacuum drying temperature in step 6 is 50°C to 80°C.

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