Silver-plated copper powder and preparation method thereof

Abstract

The invention discloses a silver-plated copper powder and a preparation method thereof. The preparation method first adds a dispersant and a reducing agent to a copper ion solution for reduction to prepare the copper powder. The function of the dispersant is to control the morphology of the prepared copper powder. The purpose of adjusting the pH is to control the reduction rate, thereby controlling the morphology and particle size of the prepared copper powder. The purpose of adding the reducing agent is to reduce the copper ions to obtain the copper powder. The prepared copper powder is directly cleaned and dispersed to avoid oxidation of the copper powder, thereby eliminating the surface treatment process of the copper powder. A complexing agent is added to the copper dispersion, and a silver ammonia solution is added. An alcohol solution is directly used as a reducing agent. The silver ammonia solution can be reduced to obtain silver through a hydrothermal reaction. At the same time, under the action of the complexing agent, the silver atoms are attached to the surface of the copper powder. The hydrothermal process can slow down the reaction rate, make the reaction uniform, and achieve a good silver plating effect.

Description

Technical Field

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

[0002] Silver-plated copper powder composite powder is a composite powder with excellent conductivity formed by covering the surface of micron-sized copper powder with a layer of silver. The preparation of this powder not only maintains the excellent properties of copper powder and silver powder and improves the conductivity of copper powder, but also reduces the high cost of using pure silver powder. Therefore, it can be greatly studied and promoted and can be widely used in the fields of electromagnetic shielding, conductive adhesive, conductive rubber, polymer slurry, conductive, static conductive coating, and various microelectronic technology fields with conductive and static conductive needs, as well as surface modification of non-conductive materials.

[0003] At present, the preparation methods of silver-plated copper powder mainly include mechanical mixing method, atomized droplet deposition method and chemical reduction method. Among them, the mechanical mixing method is to use mechanical force to plastically deform the surface of the silver powder to thin the silver powder and extend it on the surface of the coated copper powder, so as to achieve the coating of the copper powder, but this method consumes a large amount of silver and has high cost. The atomized droplet deposition method is to melt the silver powder and atomize it through an atomizing nozzle, and the silver droplets are dispersed on the surface of the copper particles, and the fluidization of cold and hot air is carried out. The silver droplets are deposited on the surface of the copper powder or agglomerated and crystallized on the surface of the copper powder for coating. The disadvantages of this method are complicated process, high equipment requirements and high cost.

[0004] Chemical reduction is currently the most widely used method, with low equipment requirements and low cost in the preparation process. However, the currently used chemical plating method requires the copper powder to be surface treated first, and the resulting silver-plated layer may have a dotted coating on the surface due to uneven reaction, which in turn leads to poor performance of the silver-plated copper powder in terms of oxidation resistance and electrical conductivity. Summary of the invention

[0005] The invention provides a silver-plated copper powder and a preparation method thereof, which are used to overcome the defects of the silver-plated copper powder in the prior art, such as poor oxidation resistance and electrical conductivity.

[0006] To achieve the above object, the present invention provides a method for preparing silver-plated copper powder, comprising the following steps:

[0007] S1: dissolving a copper source in water to obtain a copper ion solution;

[0008] S2: adding a dispersant to the copper ion solution, stirring to dissolve, and adjusting the pH of the solution to 8-10 to obtain a reaction solution;

[0009] S3: dissolving the reducing agent in water to obtain a reducing agent solution;

[0010] S4: adding the reducing agent solution to the reaction solution under heating conditions while stirring, continuing heating and stirring, washing, filtering, transferring the filtered filter cake to an alcohol solution for dispersion, adding a dispersant and a complexing agent, stirring and dissolving, and obtaining a copper dispersion;

[0011] S5: dissolving silver nitrate in water, and adding ammonia water until the precipitate completely disappears to obtain a silver ammonia solution;

[0012] S6: adding the silver ammonia solution to the copper dispersion, mixing, heating in a reaction kettle for reaction, standing and cooling to room temperature, washing, filtering, and drying to obtain silver-plated copper powder.

[0013] To achieve the above object, the present invention also provides a silver-plated copper powder prepared by the above-mentioned preparation method; the particle size of the silver-plated copper powder is 0.5-2 μm, and the thickness of the silver-plated layer is 0.01-0.1 μm.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The preparation method of silver-plated copper powder provided by the present invention comprises the following steps: firstly, a dispersant and a reducing agent are added to a copper ion solution to reduce and prepare copper powder, wherein the function of the dispersant is to control the morphology of the prepared copper powder, and the purpose of adjusting the pH is to control the reduction rate, thereby controlling the morphology and particle size of the prepared copper powder. The purpose of adding the reducing agent is to reduce the copper ions to obtain copper powder. The prepared copper powder is directly cleaned and dispersed to avoid oxidation of the copper powder, thereby eliminating the need for surface treatment of the copper powder. A complexing agent is added to the copper dispersion, and a silver ammonia solution is added, and an alcohol solution is directly used as a reducing agent. The silver ammonia solution can be reduced to obtain silver through a hydrothermal reaction, and silver atoms are attached to the surface of the copper powder under the action of the complexing agent. The hydrothermal process can slow down the reaction rate, make the reaction uniform, and achieve a good silver plating effect.

[0016] The invention adopts a chemical reduction method to obtain silver-plated copper powder in two steps, has a simple process route and low equipment requirements; after the copper powder is prepared, it is directly dispersed for surface silver plating, and the copper powder does not need to be surface treated; a hydrothermal method is used for the second step of chemical silver plating, and an alcohol solution is used as a dispersant and a reducing agent at the same time, so that the prepared silver powder has a uniform surface, good coating, and good oxidation resistance and electrical conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0018] Figure 1This is an electron microscope image of the silver-plated copper powder prepared in Example 1.

[0019] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in 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 protection of the present invention.

[0021] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0022] Unless otherwise specified, all drugs / reagents used were commercially available.

[0023] The present invention provides a method for preparing silver-plated copper powder, comprising the following steps:

[0024] S1: Dissolve a copper source in water to obtain a copper ion solution.

[0025] S2: adding a dispersant to the copper ion solution, stirring to dissolve, and adjusting the pH of the solution to 8 to 10 to obtain a reaction solution. The pH is more preferably 8 to 9.

[0026] S3: dissolving the reducing agent in water to obtain a reducing agent solution;

[0027] S4: adding the reducing agent solution to the reaction solution under heating conditions while stirring, continuing heating and stirring, washing, filtering, transferring the filtered filter cake to an alcohol solution for dispersion, adding a dispersant and a complexing agent, stirring and dissolving, and obtaining a copper dispersion;

[0028] S5: dissolving silver nitrate in water, and adding ammonia water until the precipitate completely disappears to obtain a silver ammonia solution;

[0029] S6: adding the silver ammonia solution to the copper dispersion, mixing, heating in a reaction kettle for reaction, standing and cooling to room temperature, washing, filtering, and drying to obtain silver-plated copper powder.

[0030] The preparation method of the present invention directly prepares copper powder, can control the morphology of copper powder, and does not need to perform surface treatment on the copper powder. The silver plating reaction is carried out by a hydrothermal method, which can control the reaction rate, so that the silver plating is uniform and well coated.

[0031] Preferably, in step S1, the copper source is copper chloride or copper sulfate; the concentration of copper ions in the copper ion solution is 0.1-0.5 mol / L. More preferably, it is 0.1-0.3 mol / L. The concentration is controlled to prepare copper powder of a certain concentration and morphology. Too high a concentration will lead to agglomeration, and too low a concentration will reduce the actual production efficiency.

[0032] Preferably, in step S2, the dispersant is at least one of polyvinyl pyrrolidone, polyvinyl alcohol, sodium lauryl sulfate, hexadecyltrimethylammonium bromide and citric acid.

[0033] The function of the dispersant in S2 is to prevent the copper powder obtained by reduction from agglomerating and control the morphology of the copper powder. The function of the dispersant in S4 is to disperse the copper powder and control the formation of silver powder on the surface.

[0034] Preferably, in step S2, the mass fraction of the dispersant in the reaction solution is 10 to 50 wt %, more preferably 10 to 25 wt %.

[0035] Preferably, in step S3, the reducing agent is at least one of ascorbic acid, formaldehyde and glucose; and the amount of the reducing agent is 1 to 2 times the amount of the copper source.

[0036] Preferably, in step S4, the heating temperature of the heating condition is 20-50° C. (more preferably 20-30° C.); the alcohol solution is one of ethanol, isopropanol, n-propanol, n-butanol and sec-butanol.

[0037] Preferably, in step S4, the dispersant is one of polyvinyl pyrrolidone, polyethylene glycol, sodium lauryl sulfate and Tween; the mass fraction of the dispersant in the copper dispersion is 50-500wt% (more preferably 50-200wt%); the complexing agent is at least one of ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, triethanolamine, ammonia water and ethylenediamine; the mass fraction of the complexing agent in the copper dispersion is 5-50wt% (more preferably 10-50wt%).

[0038] Preferably, in step S5, the silver ion concentration in the silver ammonia solution is 0.1-0.5 mol / L.

[0039] Preferably, in step S6, the heating reaction is carried out at a temperature of 100 to 200°C (more preferably 150 to 200°C) for 6 to 12 hours.

[0040] The present invention also provides a silver-plated copper powder, which is prepared by the above-mentioned preparation method; the particle size of the silver-plated copper powder is 0.5-2 μm, and the thickness of the silver-plated layer is 0.01-0.1 μm.

[0041] The silver plating effect is determined by the surface state of the copper powder. The surface coating of the copper powder is uniform without any dotted coating.

[0042] Example 1

[0043] This embodiment provides a method for preparing silver-plated copper powder, comprising the following steps:

[0044] Take 30g of copper chloride and add it to 1000g of deionized water, stir and dissolve to obtain a copper ion solution; add 6g of polyvinyl pyrrolidone and stir and dissolve;

[0045] Take ammonia water to adjust the pH of the solution, and use pH monitoring to adjust the pH of the solution to 9-10; take another 48.5g of ascorbic acid and dissolve it in deionized water, stirring to dissolve;

[0046] The ascorbic acid solution is slowly and uniformly added to the copper solution to reduce the copper powder;

[0047] The copper powder was washed several times with deionized water, and after solid-liquid separation, the filter cake was dispersed in 500 ml of ethanol solution;

[0048] 14 g of polyvinyl pyrrolidone was added to fully dissolve, and 1.5 g of disodium ethylenediaminetetraacetate was added, and the solution was ultrasonically dispersed for 20 min to obtain a mixed solution A;

[0049] Weigh 5g of silver nitrate and dissolve it in 100ml of deionized water, add ammonia water until the precipitate is completely dissolved, and obtain silver ammonia solution B. Mix A and B evenly and transfer them to a hydrothermal reactor. Place the reactor in an oven and set the temperature to 150°C. The reaction time is 5h. After the reaction is completed, let the reactor stand and cool to room temperature. Take out the reaction solution, wash it several times, separate the solid and liquid, and dry it to obtain silver-plated copper powder. The silver-plated copper powder is as follows. Figure 1 As shown, the copper powder surface is evenly coated without any dotted coating.

[0050] Example 2

[0051] This embodiment provides a method for preparing silver-plated copper powder, comprising the following steps:

[0052] Take 30g of copper chloride and add it to 1000g of deionized water, stir and dissolve to obtain a copper ion solution; add 3g of sodium dodecyl sulfate and stir and dissolve;

[0053] Take ammonia water to adjust the solution pH, and use pH monitoring to adjust the solution pH to 9-10;

[0054] Take another 48.5 g of ascorbic acid and dissolve it in deionized water, stirring to dissolve;

[0055] The ascorbic acid solution is slowly and uniformly added to the copper solution to reduce the copper powder;

[0056] The copper powder was washed several times with deionized water, and after solid-liquid separation, the filter cake was dispersed in 500 ml of isopropanol solution;

[0057] Add 20 g of sodium dodecyl sulfate to fully dissolve, then add 1.5 g of disodium ethylenediaminetetraacetate, and ultrasonically disperse the solution for 20 min to obtain a mixed solution A;

[0058] Weigh 5g of silver nitrate and dissolve it in 100ml of deionized water. Add ammonia water until the precipitate is completely dissolved to obtain silver ammonia solution B. Mix A and B evenly and transfer them to a hydrothermal reactor. Place the reactor in an oven and set the temperature to 150°C for a reaction time of 5h. After the reaction is completed, let the reactor stand and cool to room temperature. Take out the reaction solution, wash it several times, separate the solid and liquid, and dry it to obtain a surface silver-plated copper powder.

[0059] Comparative Example 1

[0060] This comparative example provides a method for preparing silver-plated copper powder, compared with Example 1:

[0061] The copper powder was washed several times with deionized water, and after solid-liquid separation, the filter cake was dispersed into 500 ml of aqueous solution;

[0062] After A and B are evenly mixed, ascorbic acid solution is added for reduction. After the reaction is complete, the solid-liquid separation is performed by washing, and the powder is dried. The other processes are the same as in Example 1.

[0063] The silver-plated copper powders of Examples 1 and 2 and Comparative Example 1 were made into silver-plated copper powder slurries, and the conductive properties of the silver-plated copper powder slurries were compared. The results are shown in Table 1. The conductive properties of the silver-plated copper powder prepared by the preparation method provided by the present invention are significantly better than those of Comparative Example 1.

[0064] Table 1

[0065] Silver coated copper powder Glass powder Organic carrier Square resistance (mΩ / □) Example 1 80％ 5％ 15％ 4.1 Example 2 80％ 5％ 15％ 4.5 Comparative Example 1 80％ 5％ 15％ 10.2

[0066] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing silver-plated copper powder, characterized in that: The following steps are involved: S1: dissolving a copper source in water to obtain a copper ion solution; In step S1, the copper source is copper chloride or copper sulfate; the concentration of copper ions in the copper ion solution is 0.1-0.5 mol / L; S2: adding a dispersant to the copper ion solution, stirring to dissolve, and adjusting the pH of the solution to 8-10 to obtain a reaction solution; S3: dissolving the reducing agent in water to obtain a reducing agent solution; S4: adding the reducing agent solution to the reaction solution under heating conditions while stirring, continuing heating and stirring, washing, filtering, transferring the filtered filter cake to an alcohol solution for dispersion, adding a dispersant and a complexing agent, stirring and dissolving, and obtaining a copper dispersion; In step S4, the heating temperature of the heating condition is 20-50° C.; the alcohol solution is one of ethanol, isopropanol, n-propanol, n-butanol, and sec-butanol; In step S4, the dispersant is one of polyvinyl pyrrolidone, polyethylene glycol, sodium lauryl sulfate and Tween; the mass fraction of the dispersant in the copper dispersion is 50-500wt%; the complexing agent is at least one of ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, triethanolamine, ammonia water and ethylenediamine; the mass fraction of the complexing agent in the copper dispersion is 5-50wt%; S5: dissolving silver nitrate in water, and adding ammonia water until the precipitate completely disappears to obtain a silver ammonia solution; S6: adding the silver ammonia solution to the copper dispersion, mixing, heating in a reaction kettle for reaction, standing and cooling to room temperature, washing, filtering, and drying to obtain silver-plated copper powder.

2. The preparation method according to claim 1, characterized in that In step S2, the dispersant is at least one of polyvinyl pyrrolidone, polyvinyl alcohol, sodium lauryl sulfate, hexadecyltrimethylammonium bromide and citric acid.

3. The preparation method according to claim 1, characterized in that: In step S2, the mass fraction of the dispersant in the reaction solution is 10-50wt%.

4. The preparation method according to claim 1, characterized in that: In step S3, the reducing agent is at least one of ascorbic acid, formaldehyde and glucose; the amount of the reducing agent is 1 to 2 times the amount of the copper source.

5. The preparation method according to claim 1, characterized in that: In step S5, the silver ion concentration in the silver ammonia solution is 0.1-0.5 mol / L.

6. The preparation method according to claim 1, characterized in that: In step S6, the heating reaction is carried out at a temperature of 100-200°C and for a time of 6-12 hours.

7. A silver-plated copper powder, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6; the particle size of the silver-plated copper powder is 0.5 to 2 μm, and the thickness of the silver-plated layer is 0.01 to 0.1 μm.

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