A cobalt-modified silver-clad copper composite material and preparation method thereof

Abstract

The present invention discloses a cobalt-modified silver-coated copper composite material and a preparation method thereof, and belongs to the technical field of composite materials. The preparation method comprises pre-treating copper powder, and then adding the treated copper powder to a dispersant solution to obtain a copper powder suspension; adding the copper powder suspension to a chemical plating solution and adjusting the pH value to 4-6, and then adding a first reducing agent solution to react, washing to obtain cobalt-modified copper powder; adding the cobalt-modified copper powder to a dispersant solution and stirring, and then adding a silver-ammine complex solution and a second reducing agent solution to stir, and then reacting at 50-60°C for 30-120min to obtain a cobalt-modified silver-coated copper composite material; the chemical plating solution is a mixed aqueous solution of a cobalt salt and a complexing agent A. The present invention obtains a cobalt-modified silver-coated copper composite material with strong antioxidant properties, corrosion resistance and high silver reduction rate by regulating the chemical plating solution, reducing agent and acidity and alkalinity in the cobalt plating modification process.

Description

Technical Field

[0001] The invention belongs to the technical field of composite materials, and particularly relates to a cobalt-modified silver-clad copper composite material and a preparation method thereof. Background Art

[0002] Precious metal silver has good antioxidant properties, high electrical conductivity and mobility, but its high price makes it limited in terms of cost and mass production. Base metal copper is cheap, has good electrical conductivity and low mobility, but is easily oxidized to CuO and Cu in the air. 2 O, resulting in the reduction of its performance in all aspects. Silver-coated copper powder, as a composite powder material with a core-shell structure, has good crystal properties, array structure and mechanical properties. It has broad application prospects in various industries and is often used as conductive slurry, electrode material, high-efficiency catalyst and antibacterial material.

[0003] However, in the preparation of silver-coated copper powder by chemical plating, the copper powder has high surface energy and is easy to agglomerate, so silver cannot be completely coated, which reduces the oxidation resistance of the powder. In addition, general silver-coated copper powder begins to oxidize at around 150-230°C and has poor corrosion resistance. Transition metal coatings, such as cobalt and nickel, have good oxidation resistance and corrosion resistance. They can be first introduced to modify the copper powder to improve the oxidation resistance and corrosion resistance of the composite powder. Patent CN105598567A provides a method for preparing silver-coated nickel-coated copper conductive composite powder, but its thermogravimetric test shows that the powder still gains more than 18% weight at 0-800°C, and its oxidation resistance is slightly poor. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides a cobalt-modified silver-clad copper composite material and a preparation method thereof.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A method for preparing a cobalt-modified silver-clad copper composite material comprises the following steps:

[0007] S1: pretreating copper powder in an alkaline aqueous solution, and then adding the pretreated copper powder into a dispersant solution to obtain a copper powder suspension;

[0008] S2: adding the copper powder suspension to the chemical plating solution to form a mixed solution, adjusting the pH value of the mixed solution to 4-6 and stirring at 45-90° C., then adding the first reducing agent solution to react for 15-30 minutes, and washing to neutrality to obtain cobalt-modified copper powder;

[0009] S3: adding cobalt-modified copper powder to a dispersant solution and stirring, then adding a silver-ammine complex solution and a second reducing agent solution and stirring, and then reacting at 50-60° C. for 30-120 min, washing and drying to obtain a cobalt-modified silver-coated copper composite material;

[0010] In S2, the chemical plating solution is a mixed aqueous solution of cobalt salt and complexing agent A.

[0011] As a preferred embodiment of the present invention, in step S2, the pH value of the mixed solution is adjusted to 5-6.

[0012] As a preferred embodiment of the present invention, in step S2, the first reducing agent is at least one of sodium hypophosphite, sodium borohydride, aminoborane, hydrazine and formaldehyde, and the concentration of the first reducing agent in the first reducing agent solution is 0.034-0.204 mol / L.

[0013] As a preferred embodiment of the present invention, the first reducing agent solution is added dropwise at a dropping speed of 2.5-12.5 ml / min.

[0014] As a preferred embodiment of the present invention, in S1 and S3, the dispersant is at least one of cetyltrimethylammonium bromide, Tween 80, sodium stearate, polyvinyl pyrrolidone, polyethylene glycol, polypropylene alcohol, polyester, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate.

[0015] As a preferred embodiment of the present invention, in S1 and S3, the concentration of the dispersant in the dispersant solution is 3.45×10 -5 -20.70×10 -5 mol / L.

[0016] As a preferred embodiment of the present invention, the cobalt salt is one of cobalt chloride, cobalt sulfate, cobalt carbonate and cobalt oxalate; and the complexing agent A is one of sodium citrate, sodium succinate, potassium sodium tartrate and sodium pyrophosphate.

[0017] As a preferred embodiment of the present invention, the concentration of the complexing agent A in the chemical plating solution is 0.010-0.185 mol / L.

[0018] More preferably, the concentration of the complexing agent A in the chemical plating solution is 0.025-0.062 mol / L.

[0019] As a preferred embodiment of the present invention, in step S2, the mass ratio of cobalt element to copper element in the mixed solution is 1:1-8.

[0020] More preferably, in step S2, the mass ratio of cobalt element to copper element in the mixed solution is 1:4-8.

[0021] As a preferred embodiment of the present invention, the silver-ammine complex solution is prepared by silver salt and complexing agent B; the silver salt is one of silver nitrate, silver sulfate, silver bromide, and silver iodide; the complexing agent B is one of triethanolamine, polyethylene polyamine, triethylenetetramine, diethylenetriamine, ammonia water, ethylenediamine, ethylenediaminetetraacetic acid, and ethylenediaminetetraacetate; the concentration of the silver-ammine complex solution is 0.10-0.60 mol / L.

[0022] As a preferred embodiment of the present invention, the second reducing agent is one of glucose, sodium borohydride, hydrazine, formaldehyde, potassium sodium tartrate, sodium sulfite, and sodium thiosulfate, and the concentration of the second reducing agent in the second reducing agent solution is 0.20-0.90 mol / L.

[0023] As a preferred embodiment of the present invention, the silver-ammine complex solution and the second reducing agent solution are added dropwise at a dropping speed of 2.5-12.5 ml / min.

[0024] As a preferred embodiment of the present invention, in S1, the pretreatment includes: washing the copper powder with an alkaline aqueous solution with a concentration of 0.44-1.74 mol / L for 0.5-3 h, and then repeatedly washing with deionized water for multiple times until the supernatant is neutral; the alkaline aqueous solution is an aqueous solution of ammonia, sodium hydroxide or sodium citrate.

[0025] As a preferred embodiment of the present invention, in S1, the particle size of the copper powder is 80 nm-100 μm.

[0026] As a preferred embodiment of the present invention, in S3, the drying temperature is 50-80°C and the drying time is 4-8 hours.

[0027] More preferably, in S3, the drying temperature is 50-70° C. and the drying time is 3-5 hours.

[0028] The present invention also claims to protect the cobalt-modified silver-clad copper composite material prepared by the preparation method of the cobalt-modified silver-clad copper composite material.

[0029] The cobalt-modified silver-clad copper composite material of the present invention is a powdery material.

[0030] Compared with the prior art, the invention has the following beneficial effects: the preparation method of the cobalt-modified silver-coated copper composite material of the invention adopts the acidic cobalt plating modification method to greatly improve the silver reduction rate, and at the same time, by regulating the chemical plating solution and reducing agent of the cobalt plating modification, a cobalt-modified silver-coated copper composite material with strong oxidation resistance, corrosion resistance, high silver reduction rate, dense silver layer and complete wrapping is obtained. In addition, the preparation method of the invention is simple and cost-saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1The nitrogen adsorption-desorption isotherms and pore size distribution diagrams of the copper powder, the cobalt-modified copper powder prepared in Example 1 and Comparative Example 1, wherein (a) is the nitrogen adsorption-desorption isotherms, and (b) is the pore size distribution diagram.

[0032] Figure 2 It is a thermogravimetric comparison diagram of copper powder, cobalt-modified copper powder prepared in Example 1 and Comparative Example 1.

[0033] Figure 3 The Tafel curves of copper powder, cobalt-modified copper powder prepared in Example 1 and Comparative Example 1 are shown.

[0034] Figure 4 This is a SEM image of the cross section of the cobalt-modified copper powder prepared in Example 1.

[0035] Figure 5 SEM-EDS images of the unmodified silver-coated copper powder of Comparative Example 5, the cobalt-modified silver-coated copper composite material obtained in Example 1, and the cobalt-modified silver-coated copper composite material obtained in Comparative Example 1, wherein (a) is the unmodified silver-coated copper powder, (b) is the cobalt-modified silver-coated copper composite material obtained in Example 1, and (c) is the cobalt-modified silver-coated copper composite material obtained in Comparative Example 1.

[0036] Figure 6 The figures are the apparent color change diagrams of the unmodified silver-coated copper powder of Comparative Example 5, the cobalt-modified silver-coated copper composite material obtained in Example 1, and the cobalt-modified silver-coated copper composite material obtained in Comparative Example 1 after high-temperature calcination, wherein (a) is the unmodified silver-coated copper powder, (b) is the cobalt-modified silver-coated copper composite material obtained in Example 1, and (c) is the cobalt-modified silver-coated copper composite material obtained in Comparative Example 1.

[0037] Figure 7 This is the TG diagram of copper powder.

[0038] Figure 8 This is the TG diagram of the unmodified silver-coated copper powder of Comparative Example 5.

[0039] Fig. 9 This is the TG graph of the cobalt-modified silver-clad copper composite material obtained in Example 1 of the present invention.

[0040] Fig.10 This is the TG graph of the cobalt-modified silver-clad copper composite material obtained in Comparative Example 1 of the present invention.

[0041] Fig.11 It is a thermogravimetric fitting curve diagram of copper powder, unmodified silver-coated copper powder of Comparative Example 5 and the cobalt-modified silver-coated copper composite material obtained in Example 1.

[0042] Fig.12 The Tafel curves are of the unmodified silver-coated copper powder of Comparative Example 5, the cobalt-modified silver-coated copper composite material obtained in Example 1, and the cobalt-modified silver-coated copper composite material obtained in Comparative Example 1.

[0043] In the figure, Cu is copper powder; Cu@Co (Example 1) is the cobalt-modified copper powder prepared in Example 1; Cu@Co (Comparative Example 1) is the cobalt-modified copper powder prepared in Comparative Example 1; Cu@Ag (Example 1) is the cobalt-modified silver-clad copper composite material prepared in Example 1; Cu@Ag (Comparative Example 1) is the cobalt-modified silver-clad copper composite material prepared in Comparative Example 1; unmodified Cu@Ag is the unmodified silver-clad copper powder of Comparative Example 5. DETAILED DESCRIPTION

[0044] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0045] Example 1

[0046] The preparation method of the cobalt-modified silver-clad copper composite material described in this embodiment comprises the following steps:

[0047] S1: Place copper powder with a particle size of 0.8-1 μm in 20 mL of 0.87 mol / L sodium citrate solution and stir for 10 minutes to remove the oxide layer on the surface of the copper powder, then wash it with deionized water three to four times until the aqueous solution is neutral to obtain the pretreated copper powder; then add the pretreated copper powder to 6.90×10 -5 mol / LPVP solution was ultrasonically stirred for 30 min to obtain a copper powder suspension;

[0048] S2: Add the copper powder suspension to the chemical plating solution to form a mixed solution, adjust the pH value of the mixed solution to 5, stir at 70°C for 15 minutes, then add 0.1 mol / L sodium hypophosphite solution at a rate of 8.0 ml / min and ultrasonically stir for 30 minutes, wait until the powder is cooled to room temperature and wash to neutrality to obtain cobalt-modified copper powder; the chemical plating solution is a mixed aqueous solution of cobalt chloride and sodium succinate, the concentration of sodium succinate in the chemical plating solution is 0.062 mol / L; the mass ratio of cobalt to copper in the mixed solution is 1:4;

[0049] S3: Add cobalt-modified copper powder to a concentration of 6.90×10 -5 mol / LPVP solution with ultrasonic stirring for 30 minutes, then adding silver ammonia complex solution with a concentration of 0.36 mol / L and glucose solution with a concentration of 0.42 mol / L at a rate of 8.0 ml / min and stirring for 30 minutes, then reacting at 50°C for 60 minutes, washing to neutrality and drying in a 50°C oven for 8 hours to obtain a cobalt-modified silver-coated copper composite material; the silver ammonia complex solution is prepared by silver nitrate and ethylenediaminetetraacetic acid in water.

[0050] Example 2

[0051] The preparation method of the cobalt-modified silver-clad copper composite material described in this embodiment comprises the following steps:

[0052] S1: Place copper powder with a particle size of 80-100 nm in 20 mL of 1.74 mol / L sodium citrate solution and stir for 3 hours to remove the oxide layer on the surface of the copper powder, then wash it with deionized water three to four times until the aqueous solution is neutral to obtain the pretreated copper powder; then add the pretreated copper powder to 2.07×10 -4 mol / LPVP solution was ultrasonically stirred for 30 min to obtain a copper powder suspension;

[0053] S2: Add the copper powder suspension into the chemical plating solution to form a mixed solution, adjust the pH value of the mixed solution to 4, stir at 45°C for 15 minutes, then add 0.034 mol / L sodium hypophosphite solution at a rate of 2.5 ml / min and ultrasonically stir for 30 minutes, wait until it cools to room temperature to wash the powder to neutrality, and obtain cobalt-modified copper powder; the chemical plating solution is a mixed aqueous solution of cobalt chloride and sodium succinate, and the concentration of sodium succinate in the chemical plating solution is 0.010 mol / L; the mass ratio of cobalt to copper in the mixed solution is 1:1;

[0054] S3: Add cobalt-modified copper powder to a concentration of 6.90×10 -5 mol / LPVP solution with ultrasonic stirring for 30 minutes, then adding silver ammonia complex solution with a concentration of 0.10 mol / L and glucose solution with a concentration of 0.60 mol / L at a speed of 12.5 ml / min and stirring for 30 minutes, then reacting at 60°C for 120 minutes, washing to neutrality and drying in an oven at 70°C for 3 hours to obtain a cobalt-modified silver-clad copper composite material; the silver ammonia complex solution is prepared by silver nitrate and ethylenediaminetetraacetic acid in water.

[0055] Example 3

[0056] The preparation method of the cobalt-modified silver-clad copper composite material described in this embodiment comprises the following steps:

[0057] S1: Place copper powder with a particle size of 80-100 μm in 20 mL of 0.44 mol / L sodium citrate solution and stir for 0.5 hours to remove the oxide layer on the surface of the copper powder, then wash it with deionized water three to four times until the aqueous solution is neutral to obtain the pretreated copper powder; then add 3.45×10 -5 mol / L hexadecyltrimethylammonium bromide solution was ultrasonically stirred for 30 min to obtain a copper powder suspension;

[0058] S2: Add the copper powder suspension to the chemical plating solution to form a mixed solution, adjust the pH value of the mixed solution to 6, stir at 90°C for 15 minutes, then add 0.204 mol / L sodium hypophosphite solution at a rate of 12.5 ml / min and ultrasonically stir for 30 minutes, wait until it cools to room temperature to wash the powder to neutrality, and obtain cobalt-modified copper powder; the chemical plating solution is a mixed aqueous solution of cobalt chloride and sodium succinate, and the concentration of sodium succinate in the chemical plating solution is 0.185 mol / L; the mass ratio of cobalt to copper in the mixed solution is 1:8;

[0059] S3: Add cobalt-modified copper powder to a concentration of 6.90×10 -5 mol / L sodium dodecyl sulfonate solution with ultrasonic stirring for 30 minutes, then adding 0.90mol / L silver ammonia complex solution and 0.20mol / L sodium borohydride solution at a speed of 2.5ml / min and stirring for 30 minutes, then reacting at 50℃ for 30 minutes, washing to neutrality and drying in an oven at 80℃ for 5 hours to obtain a cobalt-modified silver-clad copper composite material; the silver ammonia complex solution is prepared by silver nitrate and triethanolamine in water.

[0060] Comparative Example 1

[0061] The preparation method of the cobalt-modified silver-clad copper composite material described in this comparative example comprises the following steps:

[0062] S1: Place copper powder with a particle size of 0.8-1 μm in 20 mL of 0.87 mol / L sodium citrate solution and stir for 10 minutes to remove the oxide layer on the surface of the copper powder, then wash it with deionized water three to four times until the aqueous solution is neutral to obtain the pretreated copper powder; then add the pretreated copper powder to 6.90×10 -5 mol / LPVP solution was ultrasonically stirred for 30 min to obtain a copper powder suspension;

[0063] S2: Add the copper powder suspension to the chemical plating solution to form a mixed solution, adjust the pH value of the mixed solution to 9, stir at 65°C for 15 minutes, then add 0.1 mol / L sodium hypophosphite solution at a rate of 8.0 ml / min and ultrasonically stir for 30 minutes, wait until it cools to room temperature to wash the powder to neutrality, and obtain cobalt-modified copper powder; the chemical plating solution is a mixed aqueous solution of cobalt sulfate, sodium citrate and ammonium chloride, the concentration of sodium citrate in the chemical plating solution is 0.017 mol / L, and the concentration of ammonium chloride is 0.075 mol / L; the mass ratio of cobalt to copper in the mixed solution is 1:2;

[0064] S3: Add cobalt-modified copper powder to a concentration of 6.90×10 -5mol / LPVP solution with ultrasonic stirring for 30 minutes, then adding silver ammonia complex solution with a concentration of 0.36 mol / L and glucose solution with a concentration of 0.42 mol / L at a rate of 8.0 ml / min and stirring for 30 minutes, then reacting at 50°C for 60 minutes, washing to neutrality and drying in a 50°C oven for 8 hours to obtain a cobalt-modified silver-coated copper composite material; the silver ammonia complex solution is prepared by silver nitrate and ethylenediaminetetraacetic acid in water.

[0065] Comparative Example 2

[0066] The preparation method of the cobalt-modified silver-clad copper composite material described in this comparative example comprises the following steps:

[0067] S1: Place copper powder with a particle size of 0.8-1 μm in 20 mL of 1.74 mol / L sodium citrate solution and stir for 10 minutes to remove the oxide layer on the surface of the copper powder, then wash it with deionized water three to four times until the aqueous solution is neutral to obtain the pretreated copper powder; then add the pretreated copper powder to 6.90×10 -5 mol / LPVP solution was ultrasonically stirred for 30 min to obtain a copper powder suspension;

[0068] S2: Add the copper powder suspension to a chemical plating solution at 80°C to form a mixed solution, adjust the pH value of the mixed solution to 9.2, stir at 80°C for 15 minutes, then uniformly add a dimethylaminoborane solution with a concentration of 4g / L and ultrasonically stir for 15 minutes within 20 minutes, wash the powder to neutrality after cooling to room temperature, and obtain cobalt-modified copper powder after drying; the chemical plating solution is a mixed aqueous solution of cobalt sulfate, sodium citrate, ammonium chloride and sodium hypophosphite, the concentration of sodium citrate in the chemical plating solution is 0.017mol / L, the concentration of ammonium chloride is 0.075mol / L, and the concentration of sodium hypophosphite is 0.1mol / L; the mass ratio of cobalt to copper in the mixed solution is 1:4;

[0069] S3: Add cobalt-modified copper powder to a 4 g / L PVP solution and stir ultrasonically for 30 minutes, then add a 0.36 mol / L silver ammonia complex solution and a 0.42 mol / L glucose solution at a uniform rate within 10 minutes and stir for 30 minutes, then react at 50°C for 30 minutes, react at 60°C for 30 minutes, wash to neutrality and dry in a 50°C oven for 8 hours to obtain a cobalt-modified silver-coated copper composite material; the silver ammonia complex solution is prepared by preparing silver nitrate and triethylenetetramine in water.

[0070] Comparative Example 3

[0071] The only difference between the preparation method of the cobalt-modified silver-clad copper composite material described in this comparative example and that in Example 1 is that in step S2, the pH value of the mixed solution is adjusted to 9.0.

[0072] Comparative Example 4

[0073] The only difference between the preparation method of the cobalt-modified silver-clad copper composite material described in this comparative example and that in Example 1 is that: in step S2, the chemical plating solution is replaced with an equal volume of chemical plating solution A; the chemical plating solution A is a mixed aqueous solution of cobalt sulfate, sodium citrate, and ammonium chloride, the concentration of sodium citrate in the chemical plating solution A is 0.017 mol / L, and the concentration of ammonium chloride is 0.075 mol / L; the mass ratio of cobalt to copper in the mixed solution is 1:4.

[0074] Comparative Example 5

[0075] The preparation method of the silver-clad copper composite material of this comparative example comprises the following steps:

[0076] S1: Place copper powder with a particle size of 0.8-1 μm in 20 mL of 0.87 mol / L sodium citrate solution and stir for 10 minutes to remove the oxide layer on the surface of the copper powder, and then wash it with deionized water three to four times until the aqueous solution is neutral to obtain the pretreated copper powder;

[0077] S2: Add the pretreated copper powder to 6.90×10 -5 mol / LPVP solution by ultrasonic stirring for 30 minutes to obtain a copper powder suspension; then a silver ammonia complex solution with a concentration of 0.36 mol / L and a glucose solution with a concentration of 0.42 mol / L are added dropwise at a rate of 8.0 ml / min and stirred for 30 minutes, then reacted at 50°C for 60 minutes, washed to neutrality and dried in a 50°C oven for 8 hours to obtain a silver-coated copper composite material; the silver ammonia complex solution is prepared by preparing silver nitrate and ethylenediaminetetraacetic acid in water.

[0078] Table 1 Comparison of cobalt content in chemical cobalt plating solution of cobalt-modified copper powder

[0079]

[0080]

[0081] Table 1 shows the Co content in the cobalt-modified copper powder plating solution after chemical cobalt plating in Example 1 and Comparative Example 1 using EDTA titration. 2+ The remaining content shows that Co in the plating solution of Example 1 2+ The remaining content is 15.85%, and the Co 2+ The remaining content is 41.41%. The results show that the Co 2+ The reduction effect is better than that of Comparative Example 1.

[0082] according to Figure 1 It can be seen that Figure 1The illustration in (b) is a partial enlarged view of the pore size distribution of the Cu powder, the cobalt-modified copper powder prepared in Example 1 and Comparative Example 1 in the range of 0-12 nm. The average pore sizes of the copper powder, the cobalt-modified copper powder obtained in Example 1 and Comparative Example 1 are 34.0, 21.9 and 26.6 nm, respectively, indicating that the three powders all have mesoporous structures. 2 / g specific surface area, the specific surface area of ​​the cobalt-modified copper powder increased significantly. The specific surface areas of the cobalt-modified copper powders in Example 1 and Comparative Example 1 were 8.0607 and 4.7219 m 2 / g, and the specific surface area obtained in Example 1 is the largest. The results show that the addition of cobalt increases the specific surface area of ​​the powder and provides more active sites for the subsequent plating of the silver layer.

[0083] Figure 2 The middle illustration is an enlarged view of the TG curve of the Cu powder, the cobalt-modified copper powder prepared in Example 1 and Comparative Example 1 in the frame area. Figure 2 It can be seen that the oxidation resistance of copper powder has been significantly improved after cobalt plating. At low temperatures, cobalt-modified copper powders all showed weight loss. The initial oxidation temperatures of the three powders were relatively close. The oxidation temperatures of copper powder and cobalt-modified copper powder of comparative example 1 were about 220°C, and the oxidation temperature of cobalt-modified copper powder of embodiment 1 was about 230°C, and the initial oxidation temperature was increased by 10°C. As the temperature increased, the copper powder was in a state of continuous oxidation. When the temperature was raised to 800°C, the weight gain rate rose to 20.8945%, and there was a trend of continued increase. The weight gain of cobalt-modified copper powder of comparative example 1 began to be significantly higher than that of copper powder at 320°C, and finally at 720°C, the weight gain was lower than that of continuously oxidized copper powder. When the temperature was raised to 800°C, the weight gain rate reached 18.1492%. At the same temperature, the weight gain of cobalt-modified copper powder of embodiment 1 was always lower than that of copper powder, and the weight gain slowed down at about 615°C. When the temperature was raised to 800°C, the weight gain rate was 16.0787%. This indicates that cobalt modification can improve the antioxidant properties of copper powder, and the antioxidant properties of the cobalt-modified copper powder prepared in Example 1 are significantly better than those in Comparative Example 1.

[0084] Table 2 Corrosion potential and corrosion current of electrode materials made from copper powder, cobalt-modified copper powder of Examples 1-3 and Comparative Examples 1-4

[0085]

[0086]

[0087] according to Figure 3As shown in Table 2, the corrosion potentials of the electrode materials made of copper powder, Example 1, and cobalt-modified copper powder obtained in Comparative Example 1 are -0.350, -0.326, and -0.083 V, respectively, indicating that cobalt plating can effectively reduce the self-corrosion of copper powder and improve the corrosion resistance of copper powder. In addition, the corrosion current density of the three has a significant change range, showing a gradually decreasing trend, which also shows that cobalt plating can effectively delay the corrosion of copper powder and improve its self-corrosion. Among them, the corrosion current density of the Cu@Co material of Example 1 is the smallest, indicating that the electrode made therefrom dissolves more slowly and has better corrosion resistance.

[0088] According to Table 2, the corrosion resistance of the cobalt-modified copper powder of Examples 1-3 is higher than that of Comparative Examples 1-4. It can be seen from the comparison between Examples 1 and Comparative Examples 1-2 that the cobalt-modified copper powder prepared by the present invention has higher corrosion resistance than other technical solutions. It can be seen from the comparison between Example 1 and Comparative Example 3 that the pH of the cobalt-modified solution is crucial to the corrosion resistance of the cobalt-modified copper powder. The corrosion resistance of the cobalt-modified copper powder finally obtained under acidic conditions is better because when pH=5, H + The concentration is more suitable, and no violent hydrogen evolution reaction will occur, which is conducive to the positive redox reaction. 2+ The reduction deposition can be achieved, but as the pH value continues to increase, it may cause the substrate to be passivated, and at the same time, it will reduce the bonding force, which is not conducive to the deposition of the Co layer. When the chemical plating is completed, the original color of the copper powder is still maintained, and the coating effect is extremely poor; therefore, the pH value should not be selected too large. According to Example 1 and Comparative Example 4, it can be seen that the chemical plating solution has a great influence on the performance of the cobalt-modified copper powder. The chemical plating solution of the present invention has a simple composition, only containing cobalt salt and complexing agent A, which can improve the corrosion resistance of the cobalt-modified copper powder; while the chemical plating solution in Comparative Example 4 contains cobalt salt, complexing agent A and auxiliary complexing agent. Too many types of reagents in the plating solution are prone to complex side reactions, and the generated by-products may reduce the stability of the plating solution and cause the plating solution to decompose. Co 2+ The reduction rate decreases, affecting the overall performance of the composite powder.

[0089] according to Figure 4 and Figure 5 It can be seen that the cobalt-modified silver-coated copper composite material is a core-shell structure, and the surface of Cu is coated with a layer of Ag. No Co was detected during the test scan. This is because the metal activity of cobalt is much greater than that of silver and copper, and its catalytic activity is stronger and its potential is lower than that of silver. While improving the oxidation resistance and corrosion resistance of the powder, cobalt first reacts with [Ag(NH 3 ) 2 ] + Replacement reaction occurs with NH 3 The stable complex Co[(NH 3 ) 6 ] 2+ Dissolved in the plating solution, inhibiting [Cu(NH3 ) 4 ] 2+ Generation, reducing the loss of Cu in the powder and increasing the deposition rate of Ag.

[0090] according to Figure 5 As can be seen from Table 3, the Ag contents in the unmodified silver-coated copper powder of Comparative Example 5, the cobalt-modified silver-coated copper composite material obtained in Example 1, and the cobalt-modified silver-coated copper composite material obtained in Comparative Example 1 are 66.14%, 76.58% and 69.52%, respectively, that is, the Ag content of the cobalt-modified silver-coated copper composite material is significantly higher than that of the unmodified composite powder, and the cobalt-modified silver-coated copper composite material of Example 1 has the highest Ag content, indicating that the acidic cobalt plating performance can greatly improve the reduction rate of silver.

[0091] According to Table 3, the silver content of the composite materials of Examples 1-3 is higher than that of Comparative Examples 1-5. It can be seen from the comparative examples and comparative examples 1-2 that, compared with other technical solutions, the cobalt-modified silver-coated copper composite materials prepared by the present invention have a higher silver content and will not cause waste of silver. It can be seen from the comparative example 1 and comparative example 3 that the pH of the cobalt-modified solution is crucial to the silver content of the composite material. The composite material finally obtained under acidic conditions has a higher silver content because the metal cobalt reduction rate of the cobalt-coated copper powder obtained under acidic conditions is larger, and thus the specific surface area obtained is the largest. The increase in specific surface area provides more active sites for the subsequent plating of the silver layer. According to Example 1 and comparative example 4, it can be seen that the chemical plating solution has a greater influence on the performance of the cobalt-modified silver-coated copper composite material, mainly because in the process of chemical silver plating, the Co content of the cobalt-modified composite powder will affect its catalytic activity in the redox reaction, thereby affecting the silver ion reduction deposition rate. The composition of the plating solution in Example 1 is simple, containing only cobalt salt and complexing agent A sodium succinate. Sodium succinate is complexed with Co 2+ At the same time, it also acts as an accelerator to promote the dehydrogenation of the reducing agent and accelerate the reaction process. In Comparative Example 4, the plating solution has more ingredients, sodium citrate is used as the complexing agent A, and ammonium chloride is used as the auxiliary complexing agent in the plating solution. It is corrosive to copper and can easily destroy the performance of copper powder during the reaction, affecting Co 2+ Reduction deposition.

[0092] Table 3 Comparison of Ag content in cobalt-modified silver-coated copper composites and unmodified silver-coated copper powder

[0093] Ag content (%) Example 1 76.58％ Example 2 70.14％ Example 3 72.36％ Comparative Example 1 69.52％ Comparative Example 2 66.49％ Comparative Example 3 51.47％ Comparative Example 4 60.98％ Comparative Example 5 66.14％

[0094] Depend on Figure 6 (a) It can be seen that when the temperature reaches 300℃, the unmodified silver-coated copper powder changes from silvery white to dark gray, indicating that the powder has begun to oxidize at this time. At 600℃, it has turned into a slightly agglomerated black. When the temperature reaches 800℃, the powder forms a tight, difficult-to-separate black agglomerate, indicating that the powder has been completely oxidized at this time. Figure 6The color of the cobalt-modified silver-clad copper composite material in Example 1 (b) also changes with increasing temperature. At 600°C, the powder turns black. However, during the entire temperature change process, the powder remains fine and dispersed. There is little difference between 600°C and 800°C. At 800°C, there are slightly more fine agglomerates inside the powder than at 600°C. Figure 6 As the temperature rises, the color of the cobalt-modified silver-clad copper composite material of Comparative Example 1 in (c) darkens. At 600°C, the powder turns dark brown and produces small agglomerated particles. At 800°C, the powder forms soft, easily separable large black agglomerates.

[0095] Figure 7-11 It can be seen that the four powders all underwent severe oxidation between 300 and 500°C, the copper powder began to oxidize at 220°C, and was in a continuous oxidation state as the temperature increased. When the temperature was raised to 800°C, the weight gain rate had reached 20.89%, and there was a trend of continuing to rise; the oxidation reaction of the unmodified silver-coated copper powder was basically completed at 510°C, and when the temperature was raised to 800°C, the weight gain rate was 9.89%; when the temperature of the cobalt-modified silver-coated copper composite material obtained in Example 1 was raised to 800°C, the weight gain rate reached 9.18%; the weight gain of the cobalt-modified silver-coated copper composite material obtained in Comparative Example 1 was significantly higher than that of the unmodified silver-coated copper powder after 420°C and until the end of the test, the final weight gain was 10.30%. The results show that the cobalt-modified silver-coated copper composite material obtained in Example 1 has the lowest weight gain and exhibits better antioxidant properties.

[0096] Fig.12 As shown in the results of Table 4, cobalt modification can effectively delay the corrosion of silver-clad copper. The cobalt-modified silver-clad copper electrode material dissolves more slowly and has better corrosion resistance. Among them, the cobalt-modified silver-clad copper electrode material obtained in Example 1 has better corrosion resistance.

[0097] According to Table 4, the corrosion resistance of the composite materials of Examples 1-3 is higher than that of Comparative Examples 1-5. Comparative Examples and Comparative Examples 1-2 show that, compared with other technical solutions, the cobalt-modified silver-coated copper composite material prepared by the present invention has higher corrosion resistance. Comparative Example 1 and Comparative Example 3 show that the pH of the cobalt-modified solution is crucial to the corrosion resistance of the composite material. The composite material finally obtained under acidic conditions has better corrosion resistance because the powder after cobalt modification is chemically silver-plated. At this time, the cobalt-modified composite powder prepared under alkaline conditions damages the copper matrix due to the large pH, resulting in less cobalt deposition, and at the same time, the binding force with the copper matrix is ​​reduced, so that the subsequent silver layer coverage rate decreases and exhibits poor corrosion resistance. According to Example 1 and Comparative Example 4, it can be seen that the chemical plating solution has a greater impact on the performance of the cobalt-modified silver-coated copper composite material, mainly because the plating solution in Comparative Example 4 is a weakly alkaline plating solution with a pH value greater than 7, which will also cause corrosion and dissolution of the matrix copper, reduce the binding force between the matrix and cobalt, and is not conducive to the deposition of cobalt.

[0098] Table 4 Corrosion potential and corrosion current of electrodes made from cobalt-modified silver-coated copper composite materials obtained in Examples 1-3 and Comparative Examples 1-4 and unmodified silver-coated copper powder obtained in Comparative Example 5

[0099] electrode <![CDATA[E corr (V / MSE)]]> <![CDATA[i corr (A / cm 2 )]]> Example 1 -0.389 <![CDATA[1.448×10 -4 ]]> Example 2 -0.397 <![CDATA[2.345×10 -4 ]]> Example 3 -0.400 <![CDATA[2.483×10 -4 ]]> Comparative Example 1 -0.418 <![CDATA[3.192×10 -4 ]]> Comparative Example 2 -0.439 <![CDATA[4.582×10 -4 ]]> Comparative Example 3 -0.747 <![CDATA[6.543×10 -2 ]]> Comparative Example 4 -0.542 <![CDATA[6.826×10 -3 ]]> Comparative Example 5 -0.473 <![CDATA[5.193×10 -4 ]]>

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a cobalt-modified silver-clad copper composite material, It is characterized in that The steps include: S1: pretreating copper powder in an alkaline aqueous solution, and then adding the pretreated copper powder into a dispersant solution to obtain a copper powder suspension; S2: adding the copper powder suspension to the chemical plating solution to form a mixed solution, adjusting the pH value of the mixed solution to 4-6 and stirring at 45-90° C., then adding the first reducing agent solution to react for 15-30 minutes, washing to neutrality to obtain cobalt-modified copper powder; the first reducing agent is at least one of sodium hypophosphite, sodium borohydride, aminoborane, hydrazine and formaldehyde, and the concentration of the first reducing agent in the first reducing agent solution is 0.034-0.204 mol / L; S3: adding cobalt-modified copper powder to a dispersant solution and stirring, then adding a silver-ammine complex solution and a second reducing agent solution and stirring, and then reacting at 50-60° C. for 30-120 min, washing and drying to obtain a cobalt-modified silver-coated copper composite material; the second reducing agent is one of glucose, sodium borohydride, hydrazine, formaldehyde, sodium potassium tartrate, sodium sulfite, and sodium thiosulfate, and the concentration of the second reducing agent in the second reducing agent solution is 0.20-0.60 mol / L; In S2, the chemical plating solution is a mixed aqueous solution of a cobalt salt and a complexing agent A; the complexing agent A is one of sodium citrate, sodium succinate, potassium sodium tartrate and sodium pyrophosphate; the concentration of the complexing agent A in the chemical plating solution is 0.010-0.185 mol / L; The silver-ammine complex solution is prepared from a silver salt and a complexing agent B; the silver salt is one of silver nitrate, silver sulfate, silver bromide and silver iodide; the complexing agent B is one of triethanolamine, polyethylene polyamine, triethylenetetramine, diethylenetriamine, ammonia water, ethylenediamine, ethylenediaminetetraacetic acid and ethylenediaminetetraacetate; the concentration of the silver-ammine complex solution is 0.10-0.90 mol / L.

2. The method for preparing the cobalt-modified silver-clad copper composite material according to claim 1, It is characterized in that In S1 and S3, the dispersant is at least one of cetyltrimethylammonium bromide, Tween 80, sodium stearate, polyvinyl pyrrolidone, polyethylene glycol, polypropylene alcohol, polyester, sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate, and the concentration of the dispersant in the dispersant solution is 3.45×10 -5 -2.07×10 -4 mol / L.

3. The method for preparing the cobalt-modified silver-clad copper composite material according to claim 1, It is characterized in that The cobalt salt is one of cobalt chloride, cobalt sulfate, cobalt carbonate and cobalt oxalate.

4. The method for preparing the cobalt-modified silver-clad copper composite material according to claim 1, It is characterized in that In S2, the mass ratio of cobalt element to copper element in the mixed solution is 1:1-8.

5. The method for preparing the cobalt-modified silver-clad copper composite material according to claim 1, It is characterized in that The first reducing agent solution is added dropwise at a rate of 2.5-12.5 ml / min.

6. The method for preparing the cobalt-modified silver-clad copper composite material according to claim 1, It is characterized in that The silver-ammine complex solution and the second reducing agent solution are added dropwise at a rate of 2.5-12.5 ml / min.

7. A cobalt-modified silver-clad copper composite material prepared by the method for preparing a cobalt-modified silver-clad copper composite material according to any one of claims 1 to 6.

Images