A method for preparing ultrapure nano copper powder

Abstract

The invention provides a method for preparing ultrapure nano copper powder. The method adopts a metal copper salt as a precursor, polyvinyl pyrrolidone (PVP) as a morphology control reagent, ethylenediaminetetraacetic acid (EDTA) and hexamethylenetetramine as modifiers, and dialysis as a method for removing ions to prepare ultrapure nano copper powder. The nano copper powder obtained by the method has uniform size and high purity, and its highest purity can reach 99.998%. The method uses dialysis and modifiers together to improve the purity of nano copper powder; the method provided by the invention is green, efficient and low-cost.

Description

Technical Field

[0001] The invention belongs to the field of metal nano material preparation, and in particular relates to a method for preparing an ultrapure nano copper powder material. Background Art

[0002] Nano copper powder has important application prospects in many fields, such as electronics, catalysis, and lubricants. There are many methods for preparing nano copper powder, such as physical method, chemical method, and chemical vapor deposition method. The wet chemical method has the characteristics of low cost, simple preparation, and high efficiency, and has been widely studied. Due to its high specific surface energy and small size, nano copper powder is particularly easy to oxidize. Although the use of modifiers to protect the surface can avoid copper oxidation, the surface modifiers will cause the conductivity of copper to decrease, affecting its application in electronics and catalysis. One method to avoid the oxidation of nano copper is to prepare high-purity nano copper powder. Since there is usually a small amount of metal salt in nano copper powder, under the action of water in the air, the metal salt forms an electrolyte with water, thereby forming a primary battery with copper, causing the nano copper powder to be particularly easy to oxidize.

[0003] High-purity nano copper powder can only be obtained by raw materials with higher purity. However, the wet chemical method inevitably introduces metal salts, so the co-growth of salts should be avoided in the lattice growth of copper. Therefore, even if high-purity raw materials are used to prepare high-purity nano copper powder, there is considerable difficulty. The object of the present invention is to solve the problem of residual metal salts in copper crystals during the preparation of high-purity nano copper powder. Summary of the invention

[0004] The invention relates to a method for preparing ultrapure nano copper powder, which is prepared by a method combining dialysis with a modifier; wherein the modifier is ethylenediaminetetraacetic acid and hexamethylenetetramine.

[0005] The invention relates to a method for preparing ultrapure nano copper powder. The method adopts metal copper salt as a precursor, polyvinyl pyrrolidone (PVP) as a morphology control reagent, ethylenediaminetetraacetic acid (EDTA) and hexamethylenetetramine as modifiers, and dialysis as a method for removing ions to prepare the ultrapure nano copper powder.

[0006] A method for preparing ultrapure nano copper powder comprises the following steps:

[0007] (1) Use a metal copper salt with a purity of 6N or above, dissolve it in ultrapure water, add polyvinyl pyrrolidone (PVP) with a purity of 6N or above, ethylenediaminetetraacetic acid (EDTA) and hexamethylenetetramine, use a sodium hydroxide aqueous solution with a purity of 6N or above to adjust the pH to 11-13 (for example, the pH can be adjusted to 11-13 in a mass ratio range of 0.5%-10%), put the solution after pH adjustment into a dialysis bag with a molecular weight of 500-8000, and dialyze for 12-48 hours;

[0008] (2) The dialysate obtained is transferred into a reaction bottle, ethylene glycol is added, the temperature is raised to above 180°C, and reduced for 3-12 hours under an inert gas atmosphere. The reduced nano-copper is treated by a dialysis membrane with a molecular weight of 14000-50000, and the nano-copper that passes through is centrifuged to obtain ultra-high purity nano-copper powder.

[0009] Furthermore, the types of metal copper salts include one or more of copper chloride, copper nitrate, copper sulfate, and copper acetate.

[0010] Furthermore, the mass ratio of polyvinyl pyrrolidone (PVP) to copper is in the range of 3:1-15:1.

[0011] Furthermore, the mass ratio of ethylenediaminetetraacetic acid (EDTA) to copper is in the range of 0.5:1-5:1, and more preferably in the range of 1:1-2:1.

[0012] Furthermore, the mass ratio of hexamethylenetetramine to copper is in the range of 0.3:1-3:1, and the preferred range is 0.8:1-2:1.

[0013] Furthermore, the mass ratio of ethylene glycol to copper is in the range of 100:1-500:1.

[0014] Furthermore, the pH value is adjusted to 12 using a sodium hydroxide aqueous solution with a purity of 6N or above.

[0015] The beneficial effect of the present invention is that the impurity metal salt is not easy to grow in the copper lattice by using a method combining dialysis and a modifier. Specifically, the ions in the system and the introduced polymer can be completely removed by dialysis to improve the purity of copper; the modifiers ethylenediaminetetraacetic acid (EDTA) and hexamethylenetetramine can chelate the impurity metal ions and play a role in slow release of the impurity ions, making it difficult for the impurity ions to grow in the lattice. The combined effect of the dialysis method and the modifier can improve the growth environment of copper nanoparticles and improve the purity of copper nanoparticles. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0017] in,

[0018] Attached Figure 1 This is a transmission electron microscope photo of the ultrapure copper nanoparticles obtained in Example 1;

[0019] Attached Figure 2 This is a high-resolution transmission electron microscopy photograph of the ultrapure copper nanoparticles obtained in Example 1;

[0020] Attached Figure 3 The X-ray photoelectron spectrum curve of the ultrapure copper nanoparticles obtained in Example 1;

[0021] Attached Figure 4 This is a transmission electron microscope photo of copper nanoparticles prepared in Comparative Example 1 without modification with EDTA and hexamethylenetetramine;

[0022] Attached Figure 5 This is a transmission electron microscopy photograph of the copper nanoparticles in comparative example 2 that were not dialyzed. DETAILED DESCRIPTION

[0023] To facilitate understanding of the present invention, various exemplary embodiments of the present invention are now described in detail. This detailed description should not be regarded as a specific limitation of the present invention, but should be understood as a more detailed description of certain aspects, features and embodiments of the present invention.

[0024] Example 1

[0025] Prepare 100mL of 1% ultra-high purity copper chloride solution, add 3g of 6N purity PVP, 0.5g of EDTA, 0.8g of hexamethylenetetramine, and 100mL of 6N purity sodium hydroxide solution (4%). Under room temperature stirring, drip the sodium hydroxide solution into the copper chloride mixed solution, adjust the pH to 12, and put the solution after pH adjustment into a dialysis bag with a molecular weight of 500 for dialysis for 36 hours, during which ultrapure water is continuously replaced. The dialyzed solution is transferred to a 500ml three-necked glass flask, 150ml of ethylene glycol is added, and the temperature is gradually raised to 180 degrees under inert atmosphere protection (argon). The color of the solution changes from dark green to reddish brown. After 6 hours of reaction, cool it down, transfer the coolant to a dialysis membrane with a molecular weight of 20,000 for 8 hours, and separate the dialyzed liquid by centrifugation. After drying, ultrapure nano copper powder is obtained.

[0026] The purity of the obtained nano copper powder was determined by laser ablation ICP method. Solid-state ICP can characterize the purity of copper. It was determined that the content of other metals other than copper was less than 50ppm, and its metal-based purity was ≥99.995%. The transmission electron microscope photo of the copper nanoparticles is attached. Figure 1 As shown in the figure, the particle size of copper nanoparticles is very uniform, and no impurities are observed in the electron microscope photos; the high-resolution transmission electron microscope photos are shown in the attached Figure 2 As shown, its lattice spacing is the characteristic spacing of Cu (111); specifically, the lattice spacing of the copper (111) crystal plane is 0.209 nanometers, and the Cu (111) crystal plane can be observed by transmission electron microscopy, indicating that the obtained copper is metallic copper. Figure 3The XPS spectrum curve shown in the figure shows that it is 0 valence, indicating that the surface valence state of the obtained nano copper is 0 valence. Specifically, the XPS of copper can characterize the valence state of copper. The 2p 3 / 2 The binding energy is 932 eV, which is a characteristic signal of metallic copper. Figure 1-3 It shows that the obtained nano copper has the characteristics of metallic copper.

[0027] Example 2

[0028] Prepare 100mL of 2% ultra-high purity copper sulfate solution, add 6g of 6N purity PVP, 0.5g of EDTA, 0.8g of hexamethylenetetramine, and 100mL of 6N purity sodium hydroxide solution (4%). Stir at room temperature, drop the sodium hydroxide solution into the copper sulfate mixed solution, adjust the pH to 12, and put the solution after pH adjustment into a dialysis bag with a molecular weight of 2000 for 24 hours, during which ultrapure water is continuously replaced. The dialyzed solution is transferred to a 500ml three-necked glass flask, 250ml of ethylene glycol is added, and the temperature is gradually raised to 180 degrees under the protection of nitrogen atmosphere. The color of the solution changes from dark green to reddish brown. After 8 hours of reaction, cool it down, transfer the coolant to a dialysis membrane with a molecular weight of 40,000 for 8 hours, and separate the dialyzed liquid by centrifugation. After drying, ultrapure nano copper powder is obtained. The purity of the obtained nano copper powder is measured by laser ablation ICP method. It is determined that the content of other metals except copper is less than 30ppm, and the metal base purity is ≥99.997%.

[0029] Example 3

[0030] Prepare 100mL of 1.5% ultra-high purity copper nitrate solution, add 5.0g of 6N purity PVP, 0.5g of EDTA, 0.8g of hexamethylenetetramine, and 100mL of 6N purity sodium hydroxide solution (4%). Stir at room temperature, drop the sodium hydroxide solution into the copper nitrate mixed solution, adjust the pH to 12, and put the solution after pH adjustment into a dialysis bag with a molecular weight of 5000. Dialyze for 12 hours, and constantly change ultrapure water during the period. The dialyzed solution is transferred to a 500ml three-necked glass flask, 250ml of ethylene glycol is added, and the temperature is gradually raised to 180 degrees under the protection of argon atmosphere. The color of the solution changes from dark green to reddish brown. After 8 hours of reaction, cool it down, transfer the coolant to a dialysis membrane with a molecular weight of 40000 for 8 hours, and separate the dialyzed liquid by centrifugation. After drying, ultrapure nano copper powder is obtained. The purity of the obtained nano copper powder is measured by laser ablation ICP method. It is determined that the content of other metals except copper is less than 20ppm, and the metal base purity is ≥99.998%.

[0031] Comparative Example 1

[0032] Prepare 100mL of 1% ultra-high purity copper chloride solution, add 3g of 6N pure PVP, and prepare 100mL (4%) of 6N pure sodium hydroxide solution. Under stirring at room temperature, drip the sodium hydroxide solution into the copper chloride mixed solution, adjust the pH to 12, and put the solution after pH adjustment into a dialysis bag with a molecular weight of 500. Dialyze for 36 hours, and change ultrapure water continuously during the period. The dialyzed solution is transferred to a 500ml three-necked glass flask, and 150ml of ethylene glycol is added. Under the protection of argon atmosphere, the temperature is gradually raised to 180 degrees. The color of the solution changes from dark green to reddish brown. After 6 hours of reaction, cool it down, transfer the coolant to a dialysis membrane with a dialysis molecular weight of 20,000 for 8 hours, and separate the dialyzed liquid by centrifugation. After drying, nano copper powder is obtained. The purity of the obtained nano copper powder is determined by laser ablation ICP method. After determination, the content of other metals other than copper is 3500ppm, and its metal base purity is 99.65%. Its transmission electron microscope photo is as attached Figure 4 As shown in the figure, in addition to copper nanoparticles with small particle sizes, copper nanoparticles with larger particle sizes can also be observed; the electron microscope image is an electron microscope image of copper nanoparticles without modifiers. The copper nanoparticles with larger particle sizes may contain the growth of impurity metal salts, which is not conducive to improving the purity. Due to the lack of the introduction of EDTA and hexamethylenetetramine, the particle size is larger and it is easy to introduce impurity ions. This result shows that EDTA and hexamethylenetetramine can effectively avoid the growth of impurity ions.

[0033] Comparative Example 2

[0034] Prepare 100mL of 1% ultra-high purity copper chloride solution, add 3g of 6N pure PVP, 0.5g of EDTA, 0.8g of hexamethylenetetramine, and separately prepare 100mL of 6N pure sodium hydroxide solution (4%). Under stirring at room temperature, drop the sodium hydroxide solution into the copper chloride mixed solution and adjust the pH to 12. The solution is transferred to a 500ml three-necked glass flask, and 150ml of ethylene glycol is added. Under the protection of argon atmosphere, the temperature is gradually raised to 180 degrees. The color of the solution changes from dark green to reddish brown. After reacting for 6 hours, cool it, separate the coolant by high-speed centrifugation, and dry it to obtain nano copper powder. The purity of the obtained nano copper powder is determined by laser ablation ICP method. After determination, the content of other metals other than copper is 5500ppm, and its metal-based purity is 99.45%. The transmission electron microscope photo of copper nanoparticles that have not passed dialysis is shown in the attached figure. Figure 5 As shown in the figure, in addition to copper nanoparticles with small particle sizes, copper nanoparticles with larger particle sizes can also be observed, and a small amount of polymer substances are wrapped around the particles; nano-copper with larger particle sizes is easy to wrap metal salts, and the presence of polymers will also reduce the purity of nano-copper. This result shows that dialysis can not only effectively remove impurity ions in metals, but also effectively remove polymer materials, providing the purity of copper nanoparticles.

[0035] It should be noted and understood that various modifications and improvements can be made to the invention described in detail above without departing from the spirit and scope of the invention as claimed in the claims. Therefore, the scope of the claimed technical solution is not limited by any specific exemplary teaching given.

[0036] The applicant declares that the present invention illustrates the detailed method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed method, that is, it does not mean that the present invention must rely on the above-mentioned detailed method to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing ultrapure nano copper powder, characterized in that: The following steps are involved: (1) Use a metal copper salt with a purity of 6N or above, dissolve it in ultrapure water, add polyvinyl pyrrolidone (PVP), ethylenediaminetetraacetic acid (EDTA) and hexamethylenetetramine with a purity of 6N or above, use a sodium hydroxide aqueous solution with a purity of 6N or above to adjust the pH to 11-13, put the solution after pH adjustment into a dialysis bag with a molecular weight of 500-8000, and dialyze for 12-48 hours; (2) The dialysate obtained is transferred into a reaction bottle, ethylene glycol is added, the temperature is raised to above 180°C, and reduced for 3-12 hours under an inert gas atmosphere. The reduced nano-copper is treated by a dialysis membrane with a molecular weight of 14000-50000, and the nano-copper that passes through is centrifuged to obtain ultra-high purity nano-copper powder.

2. The method for preparing ultrapure nano copper powder according to claim 1, further characterized in that the types of metal copper salts include one or more of copper chloride, copper nitrate, copper sulfate, and copper acetate.

3. The method for preparing ultrapure nano copper powder according to claim 1, further characterized in that the mass ratio of polyvinyl pyrrolidone (PVP) to copper is in the range of 3:1-15:

1.

4. The method for preparing ultrapure nano copper powder according to claim 1, further characterized in that the mass ratio of ethylenediaminetetraacetic acid (EDTA) to copper is in the range of 0.5:1-5:

1.

5. The method for preparing ultrapure nano copper powder according to claim 1, further characterized in that the mass ratio of hexamethylenetetramine to copper is in the range of 0.3:1-3:

1.

6. The method for preparing ultrapure nano copper powder according to claim 1, further characterized in that the pH is adjusted to 12 using a sodium hydroxide aqueous solution with a purity of 6N or above.

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