Superfine copper powder and preparation method thereof

Abstract

The invention discloses superfine copper powder and a preparation method thereof, and relates to the technical field of copper powder preparation. The method comprises the following steps: preparing a copper-containing compound into a solution, and adding a pH regulator to obtain a system A; and adding an additive and a reducing agent to obtain a system B, reacting at 50-90 DEG C, filtering, washing and drying to obtain the superfine copper powder. The invention provides a low-temperature normal-pressure liquid-phase reduction preparation technology for the superfine copper powder, the method is simple, the cost is low, and the morphology and size of the micro-nano copper powder can be effectively controlled by adjusting the types, the content and the reaction conditions of all the reaction raw materials. The problems that in the prior art, the copper powder preparation process is complex, and the conductivity of a product is poor are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of copper powder preparation, and in particular to ultrafine copper powder and a preparation method thereof. Background Art

[0002] Ultrafine copper powder has a large specific surface area, strong chemical activity, good electrical and thermal conductivity, and strong catalytic properties, making it widely used in lubrication, catalysis, and electrical conductivity. Furthermore, its price is significantly lower than that of precious metals such as gold, silver, and palladium, making it a superior alternative in many fields.

[0003] Currently, the main methods for preparing copper powder include gas phase, solid phase, and liquid phase methods. Gas phase methods, such as PVD and CVD, are the main technologies for the industrial production of ultrafine copper powder. However, they are subject to high preparation costs, complex equipment requirements, and wide product particle size distribution, which have limited their further development. Solid phase methods, such as mechanical ball milling, have the disadvantages of high energy consumption, long preparation time, and low product purity, making it difficult to obtain small, uniformly dispersed ultrafine powders. Liquid phase reduction is the most widely studied method for preparing nano- and micron-sized particles in laboratories. Its advantages are low cost, readily available raw materials, and simple operation. By adjusting parameters such as reactant concentration, reaction time, and temperature, the particle size, morphology, and dispersion of nanoparticles can be controlled.

[0004] However, the liquid phase reduction method also has some important problems that need to be solved before it can truly move towards large-scale industrial application. The reducing agents currently used in the liquid phase method mainly include hydrazine hydrate, sodium hypophosphite, sodium borohydride, potassium borohydride, formaldehyde, sodium dithionite and other reducing agents with strong reducing ability. Due to factors such as severe toxicity and cost, more suitable reducing agents and reduction processes still need to be developed. In addition, the liquid phase method has the problems of uneven morphology and particle size of copper powder, relatively complex process, easy agglomeration of the obtained micro-nano copper particles, poor antioxidant performance, etc., which will have a serious impact on the conductivity and other properties of the product. Therefore, it is urgent to develop new technologies for preparing ultrafine copper powder. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide an ultrafine copper powder and a preparation method thereof, so as to solve the problems of complex copper powder preparation process and poor product conductivity in the prior art.

[0006] The present invention solves the above technical problems with the following technical solution: a method for preparing ultrafine copper powder is provided, comprising the following steps: (1) Prepare a solution of a copper-containing compound and add a pH regulator to obtain system A; (2) Adding an aqueous solution containing an additive and a reducing agent to the system A prepared in step (1) to obtain a system B, and then reacting at 50-90°C, centrifuging, washing and drying to obtain ultrafine copper powder.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows: Furthermore, in step (1), the copper-containing compound is at least one of copper sulfate, copper nitrate, copper acetate, copper oxalate, copper tartrate, copper citrate, copper gluconate, basic copper sulfate, basic copper carbonate, copper chloride, cuprous chloride, copper oxide, cuprous oxide and copper hydroxide.

[0008] Furthermore, in step (1), the copper-containing compound may also be a hydrate of the copper-containing compound.

[0009] Furthermore, in step (1), the pH adjuster is at least one of ammonia water, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, ammonia water, sodium oxide, potassium oxide, calcium oxide, barium oxide, sodium peroxide, potassium peroxide, calcium peroxide, barium peroxide, sodium carbonate, sodium bicarbonate and urea.

[0010] Furthermore, in step (1), the copper-containing compound is prepared into a solution using water.

[0011] Furthermore, in step (1), a pH adjuster is added and stirred to obtain system A.

[0012] Further, stirring was continued at 60-90°C for 0.5 h.

[0013] Furthermore, in step (2), the concentration of the copper compound in system B is 0.001-2 mol / L, and the concentration of hydroxide ions is 10 -9 -2mol / L.

[0014] Furthermore, in step (2), the concentration of the copper-containing compound in system B is 0.011-0.05 mol / L, and the concentration of hydroxide ions is 0.65-1.48 mol / L.

[0015] Furthermore, in step (2), the concentration of the copper-containing compound in system B is 0.023 mol / L, and the concentration of hydroxide ions is 0.74 mol / L.

[0016] Furthermore, in step (2), the molar ratio of the copper-containing compound, the additive and the reducing agent is 1:0.0001-100:0.1-100.

[0017] Furthermore, in step (2), the molar ratio of the copper-containing compound, the additive and the reducing agent is 1:1.375-49.5:1.31-4.875.

[0018] Furthermore, in step (2), the molar ratio of the copper-containing compound, the additive and the reducing agent is 1:3.97:4.875.

[0019] Furthermore, in step (2), the additives are dispersants, complexing agents and morphology control agents.

[0020] Furthermore, the dispersant is at least one of ethanolamine, diethanolamine, triethanolamine, acetylethanolamine, diethylenetriamine, triethylenediamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, diethylenetriamine pentacarboxylate, sodium ethylenediaminetetramethylenephosphate, diethylenetriaminepenta(methylenephosphonate), ammonium chloride, ethylenediamine, ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, dipotassium ethylenediaminetetraacetate, sodium nitrilotriacetate, formamide, benzamide and polyacrylamide.

[0021] Furthermore, the complexing agent is at least one of a compound containing a -SH functional group structure, a compound containing a -SS- functional group structure, and a compound containing a -OS(=S)(=O)-O- functional group structure.

[0022] Furthermore, the complexing agent is at least one of thioglycolic acid, mercaptosuccinic acid, mercaptopropionic acid, sodium hydrosulfide, dimercaptoacetic acid, dimethyl disulfide, thiosulfuric acid, sodium thiosulfate, potassium thiosulfate, copper thiosulfate, nickel thiosulfate and palladium thiosulfate.

[0023] Furthermore, the morphology control agent is at least one of pyrophosphate, tripolyphosphate, tetraphosphate, phosphorous acid and hexaphosphate such as sodium tripolyphosphate, sodium pyrophosphate, sodium metaphosphate and sodium hexametaphosphate.

[0024] Furthermore, in step (2), the reducing agent is at least one of an organic acid and an organic acid derivative.

[0025] Furthermore, the organic acid is at least one of formic acid, methyl formate, ethyl formate, propyl formate, citric acid, citral, sodium citrate, potassium citrate, zinc citrate, potassium sodium citrate, ascorbic acid, sodium ascorbate, potassium ascorbate, erythorbic acid and sodium erythorbate.

[0026] Furthermore, in step (2), the reaction time is 0.01-10 h.

[0027] Furthermore, in step (2), the particle size of the ultrafine copper powder is 60-2250 nm.

[0028] The present invention also provides ultrafine copper powder prepared by the method.

[0029] The present invention also provides applications of the ultrafine copper powder in lubricant preparation, catalyst preparation and electrical conduction.

[0030] The present invention also provides application of the ultrafine copper powder in the preparation of multilayer ceramic capacitors.

[0031] The present invention has the following beneficial effects: 1. The present invention provides a low-temperature, atmospheric-pressure, liquid-phase reduction technology for preparing ultrafine copper powder. This method is simple and low-cost. By adjusting the types and contents of the various reaction raw materials and the reaction conditions, the morphology and size of the micro-nano copper powder can be effectively controlled. The impurity content of the resulting copper powder can be controlled to below 1%, and the resulting copper powder can be sintered at a temperature below 600°C.

[0032] 2. In the reaction step, in a reaction solution containing at least a water-soluble copper salt, a reducing agent, a pH regulator, a dispersant, a complexing agent, a morphology regulator, and water, a copper salt (a copper ion or a copper coordination ion) is reduced with at least one reducing agent selected from organic acids and their derivatives, thereby reducing the copper salt (a copper ion or a copper coordination ion) in the form of a powder to metallic copper through an oxidation-reduction reaction. If ascorbic acid is used as the reducing agent, the reaction principle can be described by equations (1) to (3).

[0033] Reduction reaction: Formula (1) Oxidation reaction: Formula (2) From this calculation, the standard potential of the reaction can be obtained as: Formula (3) 3. The copper salt used in the present invention is not particularly limited as long as it is a water-soluble copper salt that is readily soluble in water; the reaction principle of the reducing agent is as shown in the aforementioned reaction formula (2). The stronger the alkalinity of the reaction solution, the stronger the reducing ability of the reducing agent, which is an organic acid and its derivative (see the aforementioned reaction formula (2)). The pH adjuster of the present invention is used to increase the alkalinity.

[0034] The present invention prepares micro-nano copper powder by adding a reducing agent to a mixed solution. During this step, the copper ions in the solution are reduced to metallic copper in powder form by the reducing agent. The dispersant molecules of the present invention adsorb on the surface of the metallic copper powder, which enhances the repulsive force between each copper powder particle and other particles, preventing the metallic copper particles from agglomerating. This promotes uniform growth of the metallic copper particles, resulting in a metallic copper powder with low coagulation and good dispersibility.

[0035] The copper ions in the solution of the present invention form a complex with the complexing agent molecules, which reduces the free copper ions in the solution, thereby controlling the release rate of the copper ions during the reduction reaction, preventing the excessive formation of metallic copper during the reduction reaction, which would otherwise make the morphology and particle size of the micro-nano copper powder difficult to control. This facilitates the uniform growth of metallic copper particles.

[0036] The copper ions in the solution of the present invention are reduced to metallic copper in the form of powder by a reducing agent, and the morphology regulator molecules are adsorbed on the surface of the metallic copper particles, thereby controlling the nucleation and growth process of the metallic copper, thereby obtaining micro-nano copper powder with a spherical morphology. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the SEM image of the sample obtained in Example 1; Figure 2 This is the SEM image of the sample obtained in Example 2; Figure 3 This is the SEM image of the sample obtained in Example 3; Figure 4 This is the SEM image of the sample obtained in Example 4; Figure 5 This is the SEM image of the sample obtained in Example 5; Figure 6 This is the SEM image of the sample obtained in Comparative Example 1; Figure 7 This is the XRD pattern of the sample obtained in Example 3. DETAILED DESCRIPTION

[0038] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not intended to limit the scope of the invention. In the embodiments, if specific conditions are not specified, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0039] Copper sulfate is copper sulfate pentahydrate.

[0040] Example 1: An ultrafine copper powder, the preparation method of which comprises the following steps: (1) Weigh 1 g of copper sulfate (0.004 mol) and dissolve it in 200 mL of water to prepare a solution. Under strong stirring, add 10 g of sodium hydroxide (0.25 mol) and continue stirring at 60 °C for 0.5 h to obtain system A. (2) Weigh 1 mL of diethanolamine (0.01 mol), 1 g of sodium hydrosulfide (0.18 mol), 5 g of sodium hexametaphosphate (0.008 mol), and 2 g of ascorbic acid (0.011 mol) and dissolve them in 150 mL of water. Add them to system A to obtain system B. Keep system B at 65 °C for 4 h, stop the reaction, centrifuge the reactants, wash them repeatedly, and finally dry them in a vacuum drying oven to obtain sample - copper powder A.

[0041] The morphology of sample copper powder A was observed by scanning electron microscopy. Figure 1 ,from Figure 1 It can be seen that the copper particles in the sample - copper powder A are spherical and have a particle size of 300-900 nm.

[0042] Example 2: An ultrafine copper powder, the preparation method of which comprises the following steps: (1) Weigh 1.8 g of copper chloride (0.013 mol) and dissolve it in 150 mL of water to prepare a solution. Add 8 g of sodium hydroxide (0.2 mol) under vigorous stirring and continue stirring at 90 °C for 0.5 h to obtain system A. (2) Weigh 3 mL of diethanolamine (0.029 mol), 0.1 mL of mercaptopropionic acid (0.001 mol), 2 g of sodium hexametaphosphate (0.003 mol), and 3 g of ascorbic acid (0.017 mol) and dissolve them in 150 mL of water. Add them to system A to obtain system B. Continue the reaction of system B at 90 °C for 5 h, stop the reaction, centrifuge the reactants, wash them repeatedly, and finally dry them in a vacuum drying oven to obtain sample - copper powder B.

[0043] The morphology of sample copper powder B was observed by scanning electron microscopy. Figure 2 ,from Figure 2 It can be seen that the copper particles in the sample - copper powder B are spherical and have a particle size of 60-150 nm.

[0044] Example 3: An ultrafine copper powder, the preparation method of which comprises the following steps: (1) Weigh 2 g of copper sulfate (0.008 mol) and dissolve it in 200 mL of water to prepare a solution. Under strong stirring, add 10 mL of ammonia water (0.26 mol) and continue stirring at 70 °C for 0.5 h to obtain system A. (2) Weigh 3 mL of diethanolamine (0.029 mol), 0.5 g of sodium thiosulfate (0.002 mol), 0.2 g of sodium pyrophosphate (0.00075 mol), and 7 g of ascorbic acid (0.039 mol) and dissolve them in 150 mL of water. Add them to system A to obtain system B. Continue the reaction of system B at 70 °C for 2 h, stop the reaction, centrifuge the reactants, wash them repeatedly, and finally dry them in a vacuum drying oven to obtain sample - copper powder C.

[0045] The morphology of sample copper powder C was observed by scanning electron microscopy. Figure 3 ,from Figure 3 It can be seen that the copper particles in the sample - copper powder C are spherical and have a particle size of 1.0-1.15 μm.

[0046] XRD pattern of copper powder C, see Figure 7 ,from Figure 7 This shows that the sample is pure copper.

[0047] Example 4: An ultrafine copper powder, the preparation method of which comprises the following steps: (1) Weigh 5 g of copper sulfate (0.02 mol) and dissolve it in 200 mL of water to prepare a solution. Under strong stirring, add 10 mL of ammonia water (0.26 mol) and continue stirring at 70 °C for 0.5 h to obtain system A. (2) Weigh 3 mL of triethanolamine (0.02 mol), 0.1 mL of thioglycolic acid (0.0014 mol), 3 g of sodium pyrophosphate (0.01 mol), and 7 g of ascorbic acid (0.039 mol) and dissolve them in 200 mL of water. Add them to system A to obtain system B. Continue the reaction of system B at 70 °C for 3 h, stop the reaction, centrifuge the reactants, wash them repeatedly, and finally dry them in a vacuum drying oven to obtain sample - copper powder D.

[0048] The morphology of sample copper powder D was observed by scanning electron microscopy. Figure 4 ,from Figure 4 It can be seen that the copper particles in the sample - copper powder D are spherical and have a particle size of 1.25-1.4 μm.

[0049] Example 5: An ultrafine copper powder, the preparation method of which comprises the following steps: (1) Weigh 2 g of copper sulfate (0.008 mol) and dissolve it in 200 mL of water to prepare a solution. Under strong stirring, add 20 mL of ammonia water (0.52 mol). Stir continuously at 70 °C for 0.5 h to obtain system A. (2) Weigh 1 mL of diethanolamine (0.009 mol), 0.1 g of sodium thiosulfate (0.0004 mol), 0.5 g of sodium pyrophosphate (0.0016 mol), and 6 g of ascorbic acid (0.034 mol) and dissolve them in 150 mL of water. Add them to system A to obtain system B. Continue the reaction of system B at 70 °C for 2 h. Stop the reaction, centrifuge the reactants, wash them repeatedly, and finally dry them in a vacuum drying oven to obtain sample - copper powder E.

[0050] The morphology of sample copper powder E was observed by scanning electron microscopy. Figure 5 ,from Figure 5 It can be seen that the copper particles in the sample copper powder E are spherical and have a particle size of 1.95-2.25 μm.

[0051] Comparative Example 1: A copper powder, the preparation method of which comprises the following steps: (1) Weigh 2 g of copper sulfate (0.008 mol) and dissolve it in 200 mL of water to prepare a solution. Under strong stirring, add 20 mL of ammonia water (0.52 mol) and continue stirring at 70 °C for 0.5 h to obtain system A. (2) Weigh 1 mL of thioglycolic acid (0.014 mol), 2 g of sodium tripolyphosphate (0.0054 mol), and 6 g of ascorbic acid (0.034 mol) and dissolve them in 150 mL of water. Add them to system A to obtain system B. Continue the reaction of system B at 70 °C for 2 h, stop the reaction, centrifuge the reactants, wash them repeatedly, and finally dry them in a vacuum drying oven to obtain sample - copper powder F.

[0052] The morphology of sample copper powder F was observed by scanning electron microscopy. Figure 6 ,from Figure 6 It can be seen that a large number of copper particles in the sample copper powder F are agglomerated.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing ultrafine copper powder, characterized in that: The following steps are involved: (1) Prepare a solution of a copper-containing compound and add a pH regulator to obtain system A; (2) Adding an aqueous solution containing an additive and a reducing agent to the system A prepared in step (1) to obtain a system B, and then reacting at 50-90°C, centrifuging, washing and drying to obtain ultrafine copper powder.

2. The method for preparing ultrafine copper powder according to claim 1, wherein In step (1), the copper-containing compound is at least one of copper sulfate, copper nitrate, copper acetate, copper oxalate, copper tartrate, copper citrate, copper gluconate, basic copper sulfate, basic copper carbonate, copper chloride, cuprous chloride, copper oxide, cuprous oxide and copper hydroxide.

3. The method for preparing ultrafine copper powder according to claim 1, wherein In step (2), the concentration of the copper compound in system B is 0.001-2 mol / L, and the concentration of hydroxide ions is 10 -9 -2mol / L.

4. The method for preparing ultrafine copper powder according to claim 1, wherein In step (2), the molar ratio of the copper-containing compound, the additive and the reducing agent is 1:0.0001-100:0.1-100.

5. The method for preparing ultrafine copper powder according to claim 1, wherein In step (2), the additives are dispersants, complexing agents and morphology regulators.

6. The method for preparing ultrafine copper powder according to claim 1, wherein In step (2), the reducing agent is at least one of an organic acid and an organic acid derivative.

7. The method for preparing ultrafine copper powder according to claim 1, wherein In step (2), the reaction time is 0.01-10h.

8. The method for preparing ultrafine copper powder according to claim 1, wherein In step (2), the particle size of the ultrafine copper powder is 60-2250 nm.

9. Ultrafine copper powder prepared by the method for preparing ultrafine copper powder according to any one of claims 1 to 8.

10. Use of the ultrafine copper powder according to claim 9 in lubricant preparation, catalyst preparation and electrical conductivity.

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