Preparation method of silver-coated copper powder

Abstract

The invention discloses a preparation method of silver-coated copper powder. The preparation method comprises the following steps: reacting copper-containing complexing mother liquor, a silver source and a reducing agent; the copper-containing complexing mother liquor is prepared from the following raw materials: copper powder, a chelating agent, a dispersing agent and a modification additive; the modification additive comprises at least one of ethylenediamine, ammonium carbonate, ammonia water, tetraethylenepentamine, polyethylene polyamine, imidazole, pyridazine, pyrimidine and pyrazine. According to the preparation method of the silver-coated copper powder, the silver coating layer of the prepared silver-coated copper powder is uniform and compact, and controllable preparation of the silver-coated copper powder with different appearances is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of conductive material preparation technology, and in particular relates to a method for preparing silver-coated copper powder. Background Art

[0002] Micron-sized silver-coated copper powder is a new type of composite material in which silver powder is coated on the surface of copper powder. It has the advantages of good conductivity, high oxidation resistance, and excellent ductility of silver powder, as well as the advantages of low price and good conductivity of copper powder. At present, silver-coated copper powder is evenly used in electronics, coatings, photovoltaic slurries and other fields. With the advancement of silver-coated copper powder technology, the market demand for silver-coated copper powder in various fields will be greatly increased. At present, the process of chemical synthesis of silver-coated copper powder is relatively complicated, and the structure of the prepared silver-coated copper powder is mostly spherical silver-coated copper powder with a smooth surface and a single structural morphology.

[0003] Therefore, there is an urgent need for a preparation method that can controllably prepare silver-coated copper powders with different structures and morphologies. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a method for preparing silver-coated copper powder, wherein the silver coating layer of the prepared silver-coated copper powder is uniform and dense, and the silver-coated copper powder with different appearances can be prepared in a controllable manner.

[0005] According to one aspect of the present invention, a method for preparing silver-coated copper powder is provided, comprising: reacting a copper-containing complex mother solution, a silver source and a reducing agent;

[0006] The raw materials for preparing the copper-containing complex mother solution include: copper powder, chelating agent, dispersant and modification additive;

[0007] The modification additive comprises at least one of ethylenediamine, ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium bisulfate, ammonia water, tetraethylenepentamine, polyethylenepolyamine, imidazole, pyridazine, pyrimidine and pyrazine.

[0008] The embodiments according to the first aspect of the present invention have at least the following beneficial effects:

[0009] In the preparation process of conductive powder, the surface of copper powder must be evenly coated with a layer of silver to ensure the stability and consistency of conductive performance. If copper ions are precipitated in the solution, they may undergo a substitution reaction with silver ions, resulting in uneven silver deposition or local failure, thereby affecting the quality and performance of the final product. The chelating agent in the present invention has a high complex stability constant for copper ions, and the chelating agent is used to prevent silver ions from undergoing a substitution reaction with metallic copper, thereby preventing copper ions from re-precipitating. In the copper-containing complex mother liquor, the adjustment of pH value affects the complexing efficiency and stability of the complexing agent and copper ions, preventing copper ions from precipitating in the solution or undergoing unnecessary reactions, thereby maintaining the stability and uniform distribution of copper ions in the solution. The alkaline nitrogen-containing compound in the above-mentioned modification additive can be used as a complex silver ion and also as a pH buffer to adjust the pH value. The addition of the modification additive makes the silver deposition on the surface of the copper powder more uniform and the morphology controllable, which not only improves the conductive performance and stability of the conductive powder, but also realizes the diversified morphology of the silver-coated copper powder to meet different application requirements.

[0010] In some embodiments of the present invention, the chelating agent comprises at least one of ethylenediaminetetraacetic acid, iminodiacetic acid, diethylenetriamine, triethylenediamine, citric acid, tartaric acid, ethylenediamine and soluble salts thereof.

[0011] In some embodiments of the present invention, the dispersant includes at least one of polyethylene glycol, polyvinyl pyrrolidone, sodium dodecyl sulfonate, sodium dodecyl sulfate, polyoxyethylene fatty alcohol ether, octylphenol polyoxyethylene ether and alkylphenol polyoxyethylene ether.

[0012] The above dispersants reduce the surface tension and weaken the interaction between particles, thereby effectively dispersing the particles in the solution and preventing them from agglomerating and precipitating.

[0013] In some embodiments of the present invention, the silver source includes a silver salt and a complexing agent;

[0014] The complexing agent includes at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, diethylenetriaminepentaacetic acid, pentasodium diethylenetriaminepentaacetate, tetrasodium glutamate diacetate and tetrasodium aspartate diacetate.

[0015] The above-mentioned complexing agent forms a stable complex with the silver ion. The complexing agent combines with the silver ion through a functional group to form a cyclic or polycyclic complex, which effectively stabilizes the silver ion and prevents it from being precipitated or reduced prematurely in the solution.

[0016] In some embodiments of the present invention, the reducing agent includes at least one of formaldehyde, vitamin C, glucose, potassium sodium tartrate, sodium hypophosphite and sodium borohydride.

[0017] In some embodiments of the present invention, the raw materials for preparing the shape-modifying additive include: ethylenediamine and ammonia water;

[0018] The weight ratio of the ethylenediamine to the ammonia water is 1:1.

[0019] In some embodiments of the present invention, the preparation method comprises:

[0020] S1. Add the silver source to the copper-containing complex mother liquor within 30-90 min and react for 10-30 min to obtain a mixed solution;

[0021] S2. Add the reducing agent to the mixed solution for reaction within 20-60 minutes.

[0022] In the present invention, the silver solution and the reducing solution are added in batches to control the reaction rate. Under the above conditions, silver ions can gradually form a stable complex in the complexing mother solution, thereby preventing excessive precipitation of silver or forming an uneven silver coating layer. When adding the reducing solution, the stepwise addition can ensure that the reduction reaction is carried out uniformly, avoiding the possible incomplete reaction or local excessive reduction. The silver-coated copper powder prepared by the double addition reaction has a uniform and dense silver coating layer, and the quality of the silver-coated copper powder with different silver contents can be controlled. The above method can realize the preparation of silver powders with different appearances and morphologies, solving the technical problem that different processes are currently required to prepare copper powders with different morphologies.

[0023] In some embodiments of the present invention, step S1 comprises: adding the silver solution to a copper-containing complex mother solution at 10-60° C. within 30-90 minutes and reacting for 10-30 minutes to obtain a mixed solution.

[0024] In some embodiments of the present invention, the silver source and the reducing agent are added in the form of solutions respectively, and the volume ratio of the copper-containing complex mother solution, the silver source solution and the reducing agent solution is 1-1.5:0.3-1:0.3-1.5.

[0025] In some embodiments of the present invention, in the copper-containing complexing mother liquor, the concentration of the chelating agent is 0.35-0.50 mol / L, the concentration of the dispersant is 10-30 g / L, and the concentration of the modification additive is 0.40-0.60 mol / L; and / or, in the silver source solution, the silver ion concentration is 6-32 g / L, and the concentration of the complexing agent is 200 g-300 g / L; and / or, the concentration of the reducing agent in the reducing solution is 2-3 mol / L.

[0026] Under the above conditions, the addition rate of each component is ensured to be within a suitable range, thereby avoiding the precipitation of nanosilver due to too slow an addition rate, and the appearance of voids or spherical silver-coated copper powder on the surface of the silver-coated copper powder due to too fast an addition rate.

[0027] In some embodiments of the present invention, the copper powder is copper powder after impurities are removed, and the step of removing impurities includes: taking copper powder with an average particle size of 1 to 50 um and washing it with an acidic aqueous solution.

[0028] In some embodiments of the present invention, the mass percentage of the acidic aqueous solution is 1-5%.

[0029] Use an acidic aqueous solution to remove surface copper oxide. Oxides usually cause an uneven surface of the copper powder, affecting the uniformity and quality of the covering layer or coating. Removing oxides can make the copper powder surface smoother and more consistent, help form a more uniform covering layer or coating, and improve the quality and performance of the final product.

[0030] In some embodiments of the present invention, the acidic aqueous solution includes at least one of dilute nitric acid, dilute sulfuric acid, dilute acetic acid, dilute ethylenediaminetetraacetic acid and dilute hydrochloric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0032] Figure 1 This is a SEM image of the silver-coated copper powder prepared in Example 1;

[0033] Figure 2 This is a SEM image of the silver-coated copper powder prepared in Example 1;

[0034] Figure 3 This is a SEM image of the silver-coated copper powder prepared in Example 2;

[0035] Figure 4 This is a SEM image of the silver-coated copper powder prepared in Example 2;

[0036] Figure 5 This is a SEM image of the silver-coated copper powder prepared in Example 11;

[0037] Figure 6 This is the SEM image of the silver-coated copper powder prepared in Comparative Example 1. DETAILED DESCRIPTION

[0038] The words "preferably", "more preferably", etc. in the present invention refer to embodiments of the present invention that may provide certain beneficial effects in certain circumstances. However, other embodiments may also be preferred under the same circumstances or other circumstances. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not applicable, nor is it intended to exclude other embodiments from the scope of the present invention.

[0039] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0040] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of the present invention.

[0041] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0042] Example 1

[0043] This embodiment provides a method for preparing silver-coated copper powder, which is specifically:

[0044] A1. Take 50g of copper powder with a particle size distribution of 3-4um and an average particle size of 3.5um and put it into a 1wt% aqueous solution of dilute sulfuric acid and stir for 10 minutes to remove surface copper oxide;

[0045] A2. 125 g of ethylenediaminetetraacetic acid, 15 g of polyvinylpyrrolidone, and 25 ml of ethylenediamine were added to 1.25 L of deionized water to prepare a copper-containing complex mother solution;

[0046] A3. Take 20g of silver nitrate, 106.8g of ethylenediaminetetraacetic acid, and 59g of ammonium carbonate and dissolve them in 500ml of deionized water to prepare a silver source solution;

[0047] A4. Dissolve 228 g of glucose in 500 ml of deionized water to prepare a reducing agent;

[0048] Steps A1 to A4 are performed in no particular order.

[0049] S1. The deoxidized copper powder was added to the complex mother solution and stirred at a temperature of 40 ° C for 15 minutes to obtain a copper-containing complex mother solution, and then a silver source solution was added to the copper-containing complex mother solution at a rate of 7 ml / min within 30 minutes to react for 20 minutes to obtain a mixed solution;

[0050] S2. Using a double addition method, the reducing agent was added to the mixed solution at a rate of 9.8 ml / min within 20 min;

[0051] S3. After the reaction is completed, the reaction solution is filtered to obtain silver-coated copper powder, which is washed three times with deionized water and ethanol alternately, and dried in an oven at 60°C for 2h to obtain Figure 1 , Figure 2 The polygonal structure of silver-coated copper powder is shown.

[0052] Example 2

[0053] This embodiment provides a method for preparing silver-coated copper powder, which is specifically:

[0054] A1. Take 50g of copper powder with a particle size distribution of 3-4um and an average particle size of 3.5um and put it into a 1wt% aqueous solution of dilute sulfuric acid and stir for 10 minutes to remove surface copper oxide;

[0055] A2. 125 g of ethylenediaminetetraacetic acid, 15 g of polyvinylpyrrolidone, and 25 ml of aqueous ammonia were added to 1.25 L of deionized water to prepare a copper-containing complex mother liquor;

[0056] A3. Take 20g of silver nitrate, 106.8g of ethylenediaminetetraacetic acid, and 59g of ammonium carbonate and dissolve them in 500ml of deionized water to prepare a silver source solution;

[0057] A4. Dissolve 228 g of glucose in 500 ml of deionized water to prepare a reducing agent;

[0058] Steps A1 to A4 are performed in no particular order.

[0059] S1. The deoxidized copper powder was added to the complex mother solution and stirred at a temperature of 40°C for 15 minutes to obtain a copper-containing complex mother solution, and then a silver solution was added to the copper-containing complex mother solution at a rate of 7 ml / min within 30 minutes to react for 20 minutes to obtain a mixed solution;

[0060] S2. Using the double addition method, add reducing agent to the mixed solution at a rate of 9.8 ml / min within 20 minutes.

[0061] S3. After the reaction is completed, the reaction solution is filtered to obtain silver-coated copper powder, which is washed three times with deionized water and ethanol alternately, and dried in an oven at 60°C for 2 hours to obtain a powder with a polyhedral morphology. The results are as follows: Figure 3 , Figure 4 As shown, the contact resistance of the silver-coated copper powder is low.

[0062] Embodiments 3 to 10

[0063] Examples 3 to 10 respectively use ammonium carbonate, tetraethylene pentamine, polyethylene polyamine, imidazole, pyridazine, pyrimidine and pyrazine to replace the ammonia water in Example 2, and the other conditions are the same to prepare the following Figure 3 , Figure 4The polyhedral-like structure of silver-coated copper powder is shown.

[0064] Embodiment 11

[0065] This embodiment provides a method for preparing silver-coated copper powder. The difference between this embodiment and embodiment 1 is that ethylenediamine is replaced with a mixed solution of ethylenediamine and ammonia water in a mass ratio of 1:1. Figure 5 As shown, the silver-coated copper powder has high activity and good conductivity.

[0066] Embodiments 12 to 15

[0067] This embodiment provides a method for preparing silver-coated copper powder. The difference between this embodiment and embodiment 11 is that the ammonia water is replaced with ammonium carbonate, ammonium bicarbonate, ammonium sulfate and ammonium bisulfate, respectively, and silver-coated copper powder with a multi-layer flaky structure on the surface as shown in 5 can be obtained. The silver-coated copper powder has high activity and good conductivity.

[0068] Comparative Example 1

[0069] This comparative example provides a method for preparing silver-coated copper powder. The difference between this comparative example and Example 1 is that no shape-modifying additive is added, and the other conditions are the same. The results are as follows Figure 6 As shown, only regular spherical silver-coated copper powder can be formed.

[0070] The above content describes the embodiments of the present invention in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A method for preparing silver-coated copper powder, characterized in that: include: reacting a copper-containing complexing mother solution, a silver source, and a reducing agent; The raw materials for preparing the copper-containing complex mother solution include: copper powder, chelating agent, dispersant and modification additive; The modification additive comprises at least one of ethylenediamine, ammonium carbonate, ammonium bicarbonate, ammonium sulfate, ammonium bisulfate, ammonia water, tetraethylenepentamine, polyethylenepolyamine, imidazole, pyridazine, pyrimidine and pyrazine.

2. The preparation method according to claim 1, characterized in that: The chelating agent comprises: at least one of ethylenediaminetetraacetic acid, iminodiacetic acid, diethylenetriamine, triethylenediamine, citric acid, tartaric acid, ethylenediamine and soluble salts thereof.

3. The preparation method according to claim 1, characterized in that: The dispersant includes at least one of polyethylene glycol, polyvinyl pyrrolidone, sodium dodecyl sulfonate, sodium dodecyl sulfate, polyoxyethylene fatty alcohol ether, octylphenol polyoxyethylene ether and alkylphenol polyoxyethylene ether.

4. The preparation method according to claim 1, characterized in that: The silver source includes a silver salt and a complexing agent; The complexing agent includes at least one of ethylenediaminetetraacetic acid, disodium ethylenediaminetetraacetate, tetrasodium ethylenediaminetetraacetate, diethylenetriaminepentaacetic acid, pentasodium diethylenetriaminepentaacetate, tetrasodium glutamate diacetate and tetrasodium aspartate diacetate.

5. The preparation method according to claim 1, characterized in that: The reducing agent includes at least one of formaldehyde, vitamin C, glucose, potassium sodium tartrate, sodium hypophosphite and sodium borohydride.

6. The preparation method according to claim 1, characterized in that: The modification additives include: ethylenediamine and ammonia water; The weight ratio of the ethylenediamine to the ammonia water is 1:

1.

7. The preparation method according to claim 1, characterized in that: The preparation method comprises: S1. Add the silver source to the copper-containing complex mother liquor within 30-90 min and react for 10-30 min to obtain a mixed solution; S2. Add the reducing agent to the mixed solution within 20-60 minutes to react.

8. The preparation method according to claim 7, characterized in that: The silver source and the reducing agent are added in the form of solutions respectively, and the volume ratio of the copper-containing complex mother solution, the silver source solution and the reducing agent solution is 1-1.5:0.3-1:0.3-1.5; and / or, in the copper-containing complex mother solution, the concentration of the chelating agent is 0.35-0.50 mol / L, the concentration of the dispersant is 10-30 g / L, and the concentration of the shape-modifying additive is 0.40-0.60 mol / L; and / or, in the silver source solution, the concentration of silver ions is 6-32 g / L, and the concentration of the complexing agent is 200 g-300 g / L; and / or, the concentration of the reducing agent in the reducing solution is 2-3 mol / L.

9. The preparation method according to claim 1, characterized in that: The copper powder is copper powder after impurities are removed, and the impurity removal step includes: taking copper powder with an average particle size of 1 to 50 um and washing it with an acidic aqueous solution.

10. The preparation method according to claim 9, characterized in that: The mass percentage of the acidic aqueous solution is 1-5%.

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