A silver-graphene composite coating and its preparation method and application

Abstract

A silver-graphene composite coating and a preparation method and application thereof belong to the technical field of electrical materials, and overcome the defects of high contact resistance, poor corrosion resistance, heat dissipation and wear resistance in the prior art. The silver-graphene composite coating of the present invention comprises a first nanosilver layer, a silver-graphene layer and a second nanosilver layer sequentially arranged on a substrate. The thermal conductivity of the silver-graphene composite coating provided by the present invention is ≥330W / m·K; the hardness is ≥80HV; the surface contact resistance is <20μΩ; the dynamic friction coefficient of the coating is ≤0.25; the environmental corrosion resistance of the coating satisfies the anti-sulfur test in 1% Na2S solution within 5h without discoloration, and the anti-sulfur test in 5% Na2S solution is 1h without discoloration.

Description

Technical Field

[0001] The invention belongs to the technical field of electrical materials, and specifically relates to a silver-graphene composite coating and a preparation method and application thereof. Background Art

[0002] At present, my country's power grid is developing towards ultra-high voltage and intelligence. However, the overheating problem of conductive connections in my country's power transmission and transformation system has always been a difficulty, especially in outdoor high-voltage disconnectors. The exposed contact parts are the most prone to failure of disconnectors. They often overheat due to corrosion and wear of electrical contact materials, which in turn causes failures.

[0003] According to data from the State Grid Corporation of China, 43.2% of outdoor high-voltage disconnectors fail due to heat, mainly because outdoor high-voltage disconnectors are generally directly exposed to the atmosphere during use and are greatly affected by harsh environments and climates. Dust, rain, snow, sulfides, etc. in the atmosphere adhere to the surface of the disconnector, corroding the electrical contact material of the disconnector, resulting in increased contact resistance, which causes the electrical contact material to overheat and fail. On the other hand, high-voltage disconnectors are oxidized in the atmosphere, causing the coating to wear and fall off when the switch is opened and closed, which will also increase the contact resistance of the electrical contact material and cause the material to heat up, and there is an urgent need for technical iteration and upgrading. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of high contact resistance, poor corrosion resistance, heat dissipation and wear resistance in the prior art, thereby providing a silver-graphene composite coating and a preparation method and application thereof.

[0005] To this end, the present invention provides the following technical solutions:

[0006] A silver-graphene composite coating comprises a first nano-silver layer, a silver-graphene layer and a second nano-silver layer which are sequentially arranged on a substrate.

[0007] Furthermore, the thickness of the first nanosilver layer is 1 μm to 5 μm, the thickness of the silver-graphene layer is 1 μm to 20 μm, and the thickness of the second nanosilver layer is 1 μm to 5 μm.

[0008] A method for preparing a silver-graphene composite coating comprises the following steps:

[0009] Step 1, preparing a nano silver plating solution and a silver-graphene plating solution, and pretreating the substrate;

[0010] Step 2, plating a first nano silver layer on the substrate by using a vacuum nano ion plating method;

[0011] Step 3, depositing a silver-graphene layer on the first nanosilver layer using a vacuum composite electrodeposition method;

[0012] Step 4: Plating a second nano silver layer on the silver-graphene layer using a vacuum nano ion plating method.

[0013] Furthermore, in step 1, preparing the nano silver plating solution includes: mixing the protective agent and AgNO3 in an aqueous solution at a mass ratio of 1:1 to 4:1, adjusting the pH to 7 to 12, then adding a reducing agent, and heating for reaction;

[0014] The reaction temperature is 80-150°C, the reaction time is 20-60 min, and the stirring speed is 400-800 r / min.

[0015] Furthermore, at least one of the following conditions is met:

[0016] (1) The protective agent is one or more of polyvinyl pyrrolidone, polyethylene glycol, and sodium naphthalene formaldehyde sulfonate;

[0017] (2) The reducing agent is one or more of NaBH4, sodium citrate, polyethyleneimine, ethylene glycol, and propylene glycol;

[0018] (3) The amount of the reducing agent added is 5 g / L to 80 g / L.

[0019] Furthermore, in step 1, preparing the silver-graphene plating solution comprises: adding AgNO3, a ligand, graphene, and a graphene dispersant into distilled water, stirring at 800 to 1500 r / min for 1 to 2 h at room temperature, and then ultrasonically dispersing for 10 to 20 minutes after stirring evenly;

[0020] The silver-graphene plating solution includes AgNO330 ~ 60 g / L, a complexing agent 300 ~ 600 g / L, graphene 0 ~ 90 g / L, and a graphene dispersant 0 ~ 18 g / L.

[0021] Furthermore, the complexing agent is one or more of thiosulfate, succinimide, and potassium iodide.

[0022] Furthermore, step 2 and / or step 4 comprises: placing the nanosilver plating solution into a vacuum chamber, wherein the vacuum degree of the vacuum chamber is 1×10 -4 Pa~1×10 -2 Pa, vacuum nano-ion plating method was used for coating for 3 to 30 min.

[0023] Furthermore, in step 3, the vacuum composite electrodeposition method comprises: placing the pre-silver-plated sample into a silver-graphene plating solution for silver-graphene vacuum composite electroplating;

[0024] During the composite electroplating process, the silver-graphene plating solution was continuously stirred at a speed of 500-1000 r / min and a current density of 0.3-0.6 A / dm 2 , temperature is 20-30℃, plating time is 1-2 h, vacuum degree is 1×10 -4 Pa~1×10 -2 Pa.

[0025] Application of a silver-graphene composite coating or a silver-graphene composite coating prepared according to the above preparation method in a disconnector contact.

[0026] The substrate pretreatment in step 1 includes the steps of grinding, degreasing and pickling the substrate.

[0027] Exemplarily, the substrate is copper.

[0028] Specifically, the grinding is sandpaper grinding: first, rough grinding is performed to remove insoluble substances and oxide scale on the surface of the substrate, and then fine grinding is performed to increase the smoothness and flatness of the substrate surface.

[0029] The degreasing method is strong alkaline chemical degreasing: at room temperature, use 50~100 g / L sodium hydroxide solution to dissolve the grease adsorbed on the substrate, so that the substrate is completely exposed, soak for 0.5~2 h, and rinse with distilled water.

[0030] Pickling: Soak in 200 ~ 400 g / L nitric acid solution for 10 ~ 60 seconds and then take it out. Pickling is mainly to neutralize the adsorbed alkaline solution and play the role of brightening the matrix.

[0031] Pretreatment of the substrate can remove the oxide scale, corrosion marks, and incompatible materials adhering to the surface of the substrate, and can make the surface of the substrate smoother and flatter, which is beneficial to improving the bonding strength between the substrate and the coating.

[0032] The present invention aims to study a high heat dissipation, high wear resistance and high corrosion resistance electric contact plating material for outdoor high-voltage disconnectors. Aiming at the problems of abnormal heating and sticking of electric contacts caused by the service conditions and natural environment of outdoor high-voltage disconnectors, the composition formula of the silver-graphene composite plating is designed, and the material is prepared by vacuum electrodeposition technology and vacuum nano-ion electroplating process. The high-performance disconnector electric contact plating material is optimized, the development and application of electric contacts based on graphene composite silver plating layer are realized, and the safe and reliable operation level of outdoor high-voltage disconnectors during the whole life cycle is improved.

[0033] The technical solution of the present invention has the following advantages:

[0034] 1. The silver-graphene composite coating provided by the present invention comprises a first nanosilver layer, a silver-graphene layer and a second nanosilver layer which are sequentially arranged on a substrate.

[0035] Graphene is a typical two-dimensional nanomaterial with outstanding mechanical properties, such as high strength and high modulus. Its tensile strength is as high as 125GPa, its elastic modulus is 1.1TPa, and its hardness is higher than diamond with Mohs hardness level 10. It also has good toughness and excellent ductility and can be bent. The thermal conductivity of graphene can reach 5000 W / (mK). When combined with metal materials, it can not only obtain good thermal conductivity, but also greatly reduce the size of the reinforcement and obtain a strengthening and toughening effect. The theoretical specific surface area of ​​graphene is 2630 m 2 / g, and its high specific surface area makes it more stable and dispersible in the matrix, thus having a higher enhancement efficiency. The present invention utilizes the outstanding characteristics of graphene to effectively improve the corrosion resistance and sulfurization resistance of electrical contact materials used in existing high-voltage disconnectors.

[0036] Graphene is free in the internal defects of the material and builds a continuous conductive network, which greatly reduces the internal micro defects. Graphene has ultra-high electron mobility and a conductivity of 6000 S / cm, which can effectively reduce the resistance of the coating. Silver has extremely high electrical and thermal conductivity. The second nanosilver layer has small particles and can be filled in the surface defects of the silver-graphene layer. It has high bonding force and is not easy to fall off and wear. Nanosilver can reduce defects in the nanosilver layer and improve the uniformity of the coating structure. The second nanosilver layer has a dense microstructure, which effectively isolates water molecules, corrosive media, sulfides and other substances from entering the coating, preventing the coating from failing, and effectively improving the coating performance.

[0037] The silver-graphene composite coating provided by the present invention has a thermal conductivity of ≥330 W / m·K; a hardness of ≥80 HV; a surface contact resistance of <20 μΩ; a coating dynamic friction coefficient of ≤0.25; and an environmental corrosion resistance of the coating that satisfies the requirement of not changing color within 5 hours of an anti-sulfur test in a 1% Na2S solution, and not changing color within 1 hour of an anti-sulfur test in a 5% Na2S solution.

[0038] 2. The preparation method of the silver-graphene composite coating provided by the present invention comprises the following steps: step 1, preparing a nano-silver plating solution and a silver-graphene plating solution, and pre-treating a substrate; step 2, plating a first nano-silver layer on the substrate by a vacuum nano-ion electroplating method; step 3, depositing a silver-graphene layer on the first nano-silver layer by a vacuum composite electrodeposition method; step 4, plating a second nano-silver layer on the silver-graphene layer by a vacuum nano-ion electroplating method.

[0039] The vacuum nano-ion plating method is used to prepare the first nano-silver layer and the second nano-silver layer, which can improve the density of the plating layer, thereby improving the corrosion resistance; and can improve the bonding degree, thereby reducing the contact resistance.

[0040] The silver-graphene layer is deposited on the first nanosilver layer by vacuum composite electrodeposition. In the vacuum composite electrodeposition method, solid particles are evenly dispersed in the electroplating solution, the substrate is used as the cathode, the electroplated metal is used as the anode, and the metal and solid particles are deposited together on the substrate surface to form a coating under the condition of an external current. This method has the advantages of low cost, easy operation and environmental protection. In the vacuum nano-ion electroplating method, nano-silver ions are infiltrated into the substrate through a high-energy beam under vacuum conditions. This method can enhance the density, adhesion, conductivity and oxidation resistance of the coating material.

[0041] The present invention is based on the electrical contact materials and key application indicators of outdoor high-voltage disconnectors, and adopts vacuum composite electrodeposition and vacuum nano-ion electroplating to prepare a high-performance silver-graphene composite coating. The prepared composite coating has excellent electrical conductivity and mechanical properties, and its preparation process is efficient and pollution-free. DETAILED DESCRIPTION

[0042] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the present invention with the features of other prior arts shall fall within the protection scope of the present invention.

[0043] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be purchased commercially.

[0044] Example 1

[0045] This embodiment provides a method for preparing a silver-graphene composite coating, comprising the following steps:

[0046] Step 1, prepare nanosilver plating solution: weigh 4 g protective agent polyvinyl pyrrolidone and 1 g AgNO3 (mass ratio is 4:1), mix them in 1L aqueous solution, adjust the pH to 11, add 10 g sodium citrate reducing agent, heat the magnetic stirrer, the reaction temperature is 85 ° C, the reaction time is 30 min, and the stirring speed is 600 r / min to obtain the desired nanosilver plating solution.

[0047] Prepare silver-graphene plating solution: AgNO3 content 50 g / L, complexing agent succinimide content 400 g / L, graphene content 50 g / L, graphene dispersant 9 g / L, magnetic stirrer in distilled water at room temperature, stirring speed 1000 r / min, stirring time 2 h, stirring evenly and ultrasonic dispersion for 20 minutes.

[0048] Pretreatment of the substrate: grinding, degreasing and pickling pretreatment procedures are performed on the copper substrate.

[0049] Step 2: Use vacuum nano-ion plating to plate the first nano-silver layer on the substrate: Place the nano-silver plating solution into a vacuum chamber with a vacuum degree of 5×10 -4 Pa, vacuum nano-ion plating method was used to coat the pretreated copper substrate specimen for 15 min.

[0050] Step 3: Deposit a silver-graphene layer on the first nanosilver layer by vacuum composite electrodeposition: the electroplating anode plate is a 99.99% mass fraction special silver plate for electroplating, and the silver-plated sample is placed in a silver-graphite plating solution for silver-graphene vacuum composite plating to obtain a silver-graphene layer. The speed of the magnetic stirrer is set to 1000 r / min, and the current density is 0.4 A / dm 2 , temperature was 25 °C, plating time was 1.5 h, vacuum degree was 1×10 -3 Pa.

[0051] Step 4: Use vacuum nano-ion plating to plate a second nano-silver layer on the silver-graphene layer: Place the nano-silver in a vacuum chamber with a vacuum degree of 5×10 -4 Pa, and the silver-graphite composite coating was coated on the surface by vacuum nano-ion plating for 15 min.

[0052] The thickness of the first nanosilver layer is 2 μm, the thickness of the silver-graphene layer is 16 μm, and the thickness of the second nanosilver layer is 2 μm.

[0053] Example 2

[0054] This embodiment provides a method for preparing a silver-graphene composite coating, comprising the following steps:

[0055] Step 1, prepare nanosilver plating solution: weigh 4 g protective agent polyvinyl pyrrolidone and 2 g AgNO3 (mass ratio is 2:1), mix them in 1L aqueous solution, adjust the pH to 9, add 10 g sodium citrate reducing agent, heat the magnetic stirrer, reaction temperature is 85 ° C, reaction time is 30 min, stirring speed is 600 r / min, and the desired nanosilver plating solution is obtained.

[0056] Prepare silver-graphene plating solution: AgNO3 content is 30 g / L, complexing agent sodium thiosulfate content is 300 g / L, graphene content is 10 g / L, graphene dispersant is 9 g / L, and a magnetic stirrer is used in distilled water at room temperature. The stirring speed is 1000 r / min, the stirring time is 2 h, and after stirring evenly, ultrasonic dispersion is performed for 20 minutes.

[0057] Pretreatment of the substrate: grinding, degreasing and pickling pretreatment procedures are performed on the copper substrate.

[0058] Step 2: Use vacuum nano-ion plating to plate the first nano-silver layer on the substrate: Place the nano-silver plating solution into a vacuum chamber with a vacuum degree of 5×10 -4 Pa, vacuum nano-ion plating method was used to coat the pretreated copper substrate specimen for 5 minutes.

[0059] Step 3: Deposit a silver-graphene layer on the first nanosilver layer by vacuum composite electrodeposition: the electroplating anode plate is a 99.99% mass fraction special silver plate for electroplating, and the silver-plated sample is placed in a silver-graphite plating solution for silver-graphene vacuum composite plating to obtain a silver-graphene layer. The speed of the magnetic stirrer is set to 1000 r / min, and the current density is 0.4 A / dm 2 , temperature was 25℃, plating time was 2 h, vacuum degree was 1×10 -3 Pa.

[0060] Step 4: Use vacuum nano-ion plating to plate a second nano-silver layer on the silver-graphene layer: Place the nano-silver in a vacuum chamber with a vacuum degree of 5×10 -4 Pa, and the silver-graphite composite coating was coated on the surface by vacuum nano-ion plating for 5 min.

[0061] The thickness of the first nanosilver layer is 1 μm, the thickness of the silver-graphene layer is 18 μm, and the thickness of the second nanosilver layer is 1 μm.

[0062] Example 3

[0063] This embodiment provides a method for preparing a silver-graphene composite coating, comprising the following steps:

[0064] Step 1, prepare nanosilver plating solution: weigh 4 g protective agent polyethylene glycol and 4 g AgNO3 (mass ratio is 1:1), mix them in 1L aqueous solution, adjust the pH to 8, add 10 g ethylene glycol reducing agent, heat the magnetic stirrer, reaction temperature is 120 ° C, reaction time is 40 min, stirring speed is 400 r / min, and the desired nanosilver plating solution is obtained.

[0065] Prepare silver-graphene plating solution: AgNO3 content is 30 g / L, complexing agent potassium iodide content is 300 g / L, graphene content is 10 g / L, graphene dispersant is 9 g / L, and a magnetic stirrer is used in distilled water at room temperature. The stirring speed is 1500 r / min, the stirring time is 1 h, and after stirring evenly, ultrasonic dispersion is performed for 10 minutes.

[0066] Pretreatment of the substrate: grinding, degreasing and pickling pretreatment procedures are performed on the copper substrate.

[0067] Step 2: Use vacuum nano-ion plating to plate the first nano-silver layer on the substrate: Place the nano-silver plating solution into a vacuum chamber with a vacuum degree of 1×10 -3 Pa, vacuum nano-ion plating method was used to coat the pretreated copper substrate specimen for 20 min.

[0068] Step 3: Deposit a silver-graphene layer on the first nanosilver layer by vacuum composite electrodeposition: the electroplating anode plate is a 99.99% mass fraction special silver plate for electroplating, and the silver-plated sample is placed in a silver-graphite plating solution for silver-graphene vacuum composite plating to obtain a silver-graphene layer. The magnetic stirrer speed is set to 500 r / min, and the current density is 0.6 A / dm 2 , temperature was 30℃, plating time was 1 h, vacuum degree was 5×10 -3 Pa.

[0069] Step 4: Use vacuum nano-ion plating to plate a second nano-silver layer on the silver-graphene layer: Place the nano-silver in a vacuum chamber with a vacuum degree of 1×10 -3 Pa, and the silver-graphite composite coating was coated on the surface by vacuum nano-ion plating for 20 min.

[0070] The thickness of the first nanosilver layer is 5 μm, the thickness of the silver-graphene layer is 10 μm, and the thickness of the second nanosilver layer is 5 μm.

[0071] Comparative Example 1

[0072] This comparative example provides a method for preparing a composite coating, comprising the following steps:

[0073] Step 1, prepare nano silver plating solution: weigh 4 g protective agent polyvinyl pyrrolidone and 1 g AgNO3, mix them in an aqueous solution at a mass ratio of 4:1, adjust the pH to 9, add 300 ml sodium citrate reducing agent, heat with a magnetic stirrer, reaction temperature 85 ° C, reaction time 30 min, stirring speed 600 r / min, to obtain the desired nano silver ions.

[0074] Silver-graphene plating solution: AgNO3 content is 30 g / L, complexing agent content is 300 g / L, graphene content is 0 g / L, magnetic stirrer is used in distilled water at room temperature, the stirring speed is 1000 r / min, the stirring time is 2 h, and after stirring evenly, ultrasonic dispersion is performed for 20 minutes.

[0075] Pretreatment: The copper substrate is subjected to grinding, degreasing and pickling pretreatment processes.

[0076] Step 2: Pre-silvering with vacuum nano-ions: Place nano-silver in a vacuum chamber with a vacuum degree of 5×10 - 4 Pa, vacuum nano-ion plating method was used to coat the pretreated copper substrate specimen for 15 min.

[0077] Step 3, vacuum composite electrodeposition method: the electroplating anode plate is a 99.99% mass fraction of special silver plate for electroplating. The silver-plated sample is placed in the plating tank for vacuum electroplating to obtain a composite coating. The magnetic stirrer speed is set to 1000 r / min and the current density is 0.4 A / dm 2 , temperature is 25℃, and electroplating time is 1.5 h.

[0078] Step 4: Vacuum nano-ion surface silver plating: Place nano-silver into a vacuum chamber with a vacuum degree of 5×10 -4 Pa, and the silver-graphite composite coating was coated on the surface by vacuum nano-ion plating for 15 min.

[0079] Comparative Example 2

[0080] This comparative example is substantially the same as Example 1, except that step 4 is not performed in this comparative example.

[0081] Comparative Example 3

[0082] This comparative example is basically the same as Example 1, except that step 4 of this comparative example is: placing the test piece prepared in step 3 in an aqueous solution of sodium lauroyl sarcosinate with a concentration of 5 g / L and immersing it for 30 minutes, taking it out and drying it, to obtain a silver / silver-graphene coating with sodium lauroyl sarcosinate attached to the surface.

[0083] Table 1 shows the performance test results of the silver-graphene composite coatings prepared in the examples and comparative examples, wherein the coatings were immersed in 1% Na2S solution to test the anti-sulfurization performance.

[0084] Table 1 Performance test results of silver-graphene composite coating

[0085]

[0086] It can be seen from Table 1 that the silver-graphene composite coating of the present invention has excellent comprehensive performance.

[0087] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A silver-graphene composite coating, characterized in that: It includes a first nanosilver layer, a silver-graphene layer and a second nanosilver layer sequentially arranged on a substrate; The preparation method of the silver-graphene composite coating comprises the following steps: Step 1, preparing a nano silver plating solution and a silver-graphene plating solution, and pretreating the substrate; Step 2, plating a first nano silver layer on the substrate by using a vacuum nano ion plating method; Step 3, depositing a silver-graphene layer on the first nanosilver layer using a vacuum composite electrodeposition method; Step 4, plating a second nano silver layer on the silver-graphene layer using a vacuum nano ion plating method; The silver-graphene plating solution is prepared as follows: AgNO3, a complexing agent, graphene, and a graphene dispersant are added into distilled water, stirred at 800 to 1500 r / min for 1 to 2 hours at room temperature, and then ultrasonically dispersed for 10 to 20 minutes after stirring evenly; The silver-graphene plating solution comprises 30-60 g / L of AgNO3, 300-600 g / L of a complexing agent, 50-90 g / L of graphene, and 0-18 g / L of a graphene dispersant.

2. The silver-graphene composite coating according to claim 1, characterized in that: The thickness of the first nanosilver layer is 1 μm to 5 μm, the thickness of the silver-graphene layer is 1 μm to 20 μm, and the thickness of the second nanosilver layer is 1 μm to 5 μm.

3. The silver-graphene composite coating according to claim 1, characterized in that: In step 1, preparing the nano silver plating solution includes: mixing the protective agent and AgNO3 in a mass ratio of 1:1 to 4:1 in an aqueous solution, adjusting the pH to 7 to 12, then adding a reducing agent, and heating for reaction; The reaction temperature is 80-150°C, the reaction time is 20-60min, and the stirring speed is 400-800r / min.

4. The silver-graphene composite coating according to claim 3, characterized in that: At least one of the following conditions is met: (1) The protective agent is one or more of polyvinyl pyrrolidone, polyethylene glycol, and sodium naphthalene formaldehyde sulfonate; (2) The reducing agent is one or more of NaBH4, sodium citrate, polyethyleneimine, ethylene glycol, and propylene glycol; (3) The amount of the reducing agent added is 5 g / L to 80 g / L.

5. The silver-graphene composite coating according to claim 1, characterized in that: The complexing agent is one or more of thiosulfate, succinimide and potassium iodide.

6. The silver-graphene composite coating according to claim 1, characterized in that: The step 2 and / or step 4 comprises: placing the nanosilver plating solution into a vacuum chamber, wherein the vacuum degree of the vacuum chamber is 1×10 -4 Pa~1×10 -2 Pa, vacuum nano-ion plating method was used for coating, and magnetron sputtering was performed for 3 to 30 minutes.

7. The silver-graphene composite coating according to claim 1, characterized in that: In step 3, the vacuum composite electrodeposition method comprises: placing the pre-silver-plated sample into a silver-graphene plating solution for silver-graphene vacuum composite electroplating; The silver-graphene plating solution is continuously stirred during the composite electroplating process, the speed is 500-1000r / min, and the current density is 0.3-0.6A / dm 2 , temperature is 20-30℃, plating time is 1-2h, vacuum degree is 1×10 -4 Pa~1×10 -2 Pa.

8. Use of the silver-graphene composite coating according to any one of claims 1 to 7 in disconnector contacts.

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