Nano-diamond reinforced silver-based composite electrical contact coating material and preparation method thereof

Abstract

The present invention discloses a nano-diamond reinforced silver-based composite electrical contact coating material and a preparation method thereof, and relates to the technical field of metal surface composite coatings. The present invention deposits a silver-based composite coating on a metal surface by a multi-component rotary spraying method, and adds a second-phase nano-diamond, which can effectively enhance the mechanical properties of the pure silver coating and increase the nucleation sites in the spray deposition process of the silver coating. During the rotary spraying process, the nano-diamond impacts the deposited coating with hard particles, which has an effect similar to "shot peening" and strengthens the coating; in addition, second-phase particle reinforcement is an effective way to improve the comprehensive mechanical properties of the material, and can improve the strength and hardness of the silver coating, thereby achieving a silver-based composite electrical contact coating with good electrical conductivity, high hardness and excellent wear resistance, solving the problem of low hardness and easy wear of the pure silver coating, expanding the scope of application of the silver-based composite coating, and improving the service life of the coating.

Description

Technical Field

[0001] The invention relates to the technical field of composite coatings, and in particular to a nano-diamond reinforced silver-based composite electric contact coating material and a preparation method thereof. Background Art

[0002] With the development of science and technology, the application environment has increasingly stringent requirements for material properties. As an important component of electronic circuits, electrical contact materials are likely to suffer from arc erosion, high-temperature oxidation, melt splashing, heat concentration effects, and stress from repeated motion during operation. Ag has excellent electrical conductivity and oxidation resistance, and is a key consideration for electrical contact materials. However, it has weak resistance to arc erosion and splashing, low hardness, and poor wear resistance in circuits. It cannot meet the requirements for long-term and stable operation of circuits. Nanodiamonds have the dual characteristics of nanomaterials and superhard materials, with high hardness, good thermal conductivity, high temperature resistance, and corrosion resistance. These properties give them obvious advantages as material reinforcement particles. Composite coatings containing nanodiamonds show excellent performance in wear resistance, friction reduction, corrosion resistance, and electrical contact.

[0003] Previously, powder metallurgy and electroplating were mostly used to prepare nano-diamond composite materials. However, powder metallurgy is used to prepare bulk materials, while electroplating is only applicable to cases where the substrate is a conductive material. Composite plating is not only simple to operate, but also has no special requirements for the substrate and will not cause damage to the substrate. Therefore, composite plating is considered to be a very promising method for solving the current problems of high-temperature corrosion resistance, high-temperature strength, and special wear of materials. In the method of Chinese patent application CN110344039A "A method for preparing a silver / nano-diamond composite conductive coating on a plastic surface", a method for preparing a composite conductive coating in which nano-diamonds are mixed into a reducing agent solution and spray-deposited is disclosed. The corrosion resistance of the coating prepared by this method is excellent, but the hardness and wear resistance of the coating material are insufficient. Summary of the Invention

[0004] In view of the shortcomings of the above-mentioned technology, the present invention aims to provide a nano-diamond reinforced silver-based composite electrical contact coating material and a preparation method thereof, so as to solve the problems of low hardness, poor wear resistance and short service life of electrical contact materials.

[0005] To solve the above technical deficiencies, the present invention is achieved through the following technical solutions.

[0006] A method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material comprises the following steps:

[0007] (1) Surface pretreatment of metal substrate;

[0008] (2) preparing a silver salt solution, a reducing agent, and a second phase additive; wherein the second phase additive is a nanodiamond additive;

[0009] (3) The three groups of solutions in step (2) are respectively loaded into three spray guns and simultaneously deposited on the metal surface through an atomizer to obtain a nano-diamond reinforced silver-based composite electrical contact coating material.

[0010] Preferably, in step (2), the second phase additive consists of nanodiamonds, triethanolamine and deionized water, wherein the concentration of the nanodiamonds is 1 to 50 g / L.

[0011] Preferably, in step (3), the three spray guns are set up independently, the angle between each spray gun and the sample substrate is in the range of 10° to 170°, the distance between the nozzle and the substrate is 3 to 15 cm, and the spacing between the three nozzles is 2 to 10 cm; the flow rate of the three spray guns is 5 to 50 mL / min, the time is 10 to 50 min, the spraying volume is 200 to 1000 mL respectively, and the sample base rotation speed is 50 to 150 r / min.

[0012] Further preferably, in step (3), the three spray guns are set up independently, the angle between each spray gun and the sample substrate is in the range of 90° to 120°, and the distance between the nozzle and the substrate is 3 to 10 cm; the flow rate of the three spray guns is 10 to 50 mL / min, and the sample base rotation speed is 100 to 150 r / min.

[0013] Preferably, in step (3), the coating deposition time is 10 min to 50 min, and the deposition temperature is 10° C. to 50° C., and more preferably, the deposition temperature is 25° C. to 50° C.

[0014] Preferably, in step (2), the nanodiamond particle size is 10 to 500 nm. The nanodiamond additive needs to be ultrasonicated for at least 1 hour to prevent sedimentation.

[0015] Preferably, in step (2), the silver salt solution is an aqueous solution of silver nitrate, silver chloride or other soluble silver salts, and ammonia is added to form a transparent complex silver salt solution, wherein Ag + The concentration is 1 to 50 g / L; the reducing agent is an aqueous solution of glyoxal, formaldehyde or other substances containing aldehyde groups and triethanolamine, wherein the concentration of the substance containing aldehyde groups is 0.1 to 50 g / L.

[0016] Preferably, to enhance the bonding between the substrate and the coating, the metal surface to be processed undergoes a three-step treatment: sanding with 600# to 1500# sandpaper to remove surface impurities and oxide film, followed by rinsing with deionized water and drying. The pre-plated surface is then immersed in an etching solution with the surface facing upward to increase the surface roughness of the metal sheet and improve the bonding between the coating and the substrate. After etching, ultrasonic cleaning in deionized water is performed to remove any residual etching solution. The surface can then be soaked in anhydrous ethanol to prevent further surface oxidation, removed, and dried before use.

[0017] Preferably, the metal matrix material is any one of copper, iron, nickel, aluminum, magnesium, or an alloy thereof.

[0018] Conduct current-carrying friction and wear experiments under different parameters for metal coatings with different parameters;

[0019] A ball-disc reciprocating friction was used, and the H6 brass ball was selected for the grinding pair. When the load was 2N, the current range was 0A to 10A, the frequency was kept constant at 1Hz, and the friction was continued for 10 to 60 minutes. When the load was changed to 5N, the above experiment was repeated.

[0020] A nano-diamond reinforced silver-based composite electrical contact coating material prepared by any of the preparation methods described above.

[0021] The present invention deposits a silver-based composite coating on a metal substrate through a three-component rotary spraying method. The addition of second-phase nanodiamonds effectively enhances the mechanical properties of the pure silver coating and increases the number of nucleation sites during the spray deposition of the silver coating. During the rotary spraying process, the nanodiamonds impact the depositing coating with hard particles, creating a similar "shot peening" effect and strengthening the coating. Furthermore, second-phase particle reinforcement is an effective way to improve the overall mechanical properties of the material, enhancing the strength and hardness of the silver coating. This results in a silver-based composite electrical contact coating with good electrical conductivity, high hardness, and excellent wear resistance. This addresses the low hardness and easy wear of pure silver coatings, expands the application range of the silver-based composite coating, and increases the coating's service life.

[0022] Compared with the prior art, the present invention has the following beneficial effects and advantages:

[0023] The present invention obtains better mechanical properties by plating a silver-based composite coating on the metal surface, effectively expanding its scope of application. At the same time, the addition of nanodiamonds is conducive to the refinement of the silver coating particles. The grain refinement makes the coating more compact as a whole, further optimizing the mechanical properties. During the current-carrying friction test, the synergistic effect of force and current causes the grains to be subjected to shear stress at the microscopic level, resulting in a large number of dislocations, stacking faults, twins, etc., which further affect the coating performance. The overall process is simple and easy to operate, and a multifunctional composite coating with excellent electrical conductivity, high hardness, and good wear resistance can be obtained, which better meets the current use requirements in the field of electronic components. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. 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 these drawings without creative work.

[0025] Figure 1 This is a surface SEM image of the composite silver coating of Example 1 of the present invention;

[0026] Figure 2 is a cross-sectional microhardness diagram of the composite silver coating of Example 1 of the present invention;

[0027] Figure 3 : is the friction coefficient curve of the composite silver coating in Example 1 of the present invention during the current-carrying friction process;

[0028] Figure 4 This is a cross-sectional microhardness diagram of the composite silver coating of Example 2 of the present invention;

[0029] Figure 5 : is the friction coefficient curve of the composite silver coating in Example 2 of the present invention during the current-carrying friction process;

[0030] Figure 6 is a surface SEM image of the composite silver coating of Example 3 of the present invention;

[0031] Figure 7 is a cross-sectional microhardness diagram of the composite silver coating of Example 3 of the present invention;

[0032] Figure 8 This is a friction coefficient curve of the composite silver coating in Example 3 of the present invention during the current-carrying friction process. DETAILED DESCRIPTION

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0034] Example 1

[0035] A method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material comprises the following steps:

[0036] Step 1: Metal substrate surface pretreatment

[0037] Surface cleaning: Sand the surface of an industrial pure copper sheet of 20mm×20mm×2mm with sandpaper of 600#~1500#, then clean and dry it.

[0038] Surface Etching: Clean a beaker and fill it with 20 mL of deionized water. Add 3.75 g of ferric chloride hexahydrate, 2.5 mL of HCl, and the remaining volume up to 50 mL of deionized water. Stir until completely dissolved. Immerse the substrate in the etchant, with the primary pre-plated surface facing up, for 4 hours. After etching, ultrasonically rinse with deionized water and dry.

[0039] Step 2: preparing silver ammonia solution, reducing agent and nanodiamond additive;

[0040] Silver ammonia solution: Weigh 4 g of silver nitrate and dissolve it in deionized water to obtain a 16 g / L silver nitrate solution. Then, add 2% ammonia water dropwise to the solution until it becomes clear to obtain a silver ammonia solution.

[0041] Reducing agent: total volume 250 mL, of which the concentration of glyoxal is 50 mL / L, and the volume ratio of glyoxal to triethanolamine is 5:1;

[0042] Second phase additives: total volume 150 mL, of which nanodiamond concentration is 1 g / L, triethanolamine concentration is 10 mL / L, and the rest is deionized water. Ultrasonication is performed for 1 hour during preparation.

[0043] Step 3: Connect and adjust the spray equipment

[0044] Three spray guns were used for spraying. The spray gun angles of each component were adjusted so that the three components were 120° apart. The nozzle height was 3 cm from the sample surface. The spray flow rate of the silver ammonia solution and the reducing agent was 15 mL / min, the spray flow rate of the nano-diamond additive was 10 mL / min, and the rotation speed of the sample base was about 100 r / min.

[0045] Step 4: Preparation of nanodiamond reinforced silver-based composite electrical contact coating

[0046] The pre-treated metal sheet was placed on a rotating base. After turning on the rotating button, the engine controlling the air valve connected to the nozzle was turned on, and sample preparation began through atomized spray deposition. The sample preparation time was 50 minutes and the deposition temperature was 25°C.

[0047] Step 5: Using ball-disc reciprocating friction, select H6 brass ball as the friction pair, connect the coating prepared in step 4 to direct current, set the load to 2N, no current, friction frequency to 1Hz, friction time to 30min, load to 2N, current to 1A, voltage to 5V, friction frequency to 1Hz, friction time to 30min, and load to 5N, no current, friction frequency to 1Hz, friction time to 30min.

[0048] The prepared coating was tested as follows:

[0049] 1) SEM images of coating surface Figure 1 As shown, it is observed that the surface coating of the composite coating has a certain degree of roughness, and Ag eventually grows into particles, which are densely and evenly arranged as a whole.

[0050] 2) If Figure 2 As shown, the average coating thickness is about 60 to 70 μm.

[0051] 3) If Figure 2 As shown, the cross-sectional hardness is 184.1 HV, and the overall cross-sectional hardness ranges from about 150 to 180 HV.

[0052] 4) If Figure 3 As shown, the friction coefficient curve ranges from 0.1 to 0.2.

[0053] Example 2

[0054] A method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material comprises the following steps:

[0055] Step 1: Metal substrate surface pretreatment

[0056] Surface cleaning: Sand the surface of an industrial pure copper sheet of 20mm×20mm×2mm with sandpaper of 600#~1500#, then clean and dry it.

[0057] Surface etching: First, add 20 mL of deionized water, 3.75 g of ferric chloride hexahydrate, 2.5 mL of HCl, and then add deionized water to 50 mL. Stir until completely dissolved. Immerse the substrate in the etching solution with the primary pre-plated surface facing up for 4 hours. After etching, ultrasonically rinse with deionized water and dry.

[0058] Step 2: Prepare silver ammonia solution, reducing agent and second phase additives

[0059] Silver ammonia solution: Weigh 4 g of silver nitrate and dissolve it in deionized water to obtain a 16 g / L silver nitrate solution. Then, add 2% ammonia water dropwise to the solution until it becomes clear to obtain a silver ammonia solution.

[0060] Reducing agent: total volume 250 mL, of which the concentration of glyoxal is 50 mL / L, and the volume ratio of glyoxal to triethanolamine is 5:1;

[0061] Second phase additives: total volume 150 mL, of which nanodiamond concentration is 10 g / L, triethanolamine concentration is 10 mL / L, and the rest is deionized water. Ultrasonication is performed for 1 hour during preparation.

[0062] Step 3: Connect and adjust the spray equipment

[0063] Three spray guns were used for spraying. The spray gun angles of the three components were 90° to each other. The nozzle height was 5 cm from the sample surface. The spray flow rate of the silver ammonia solution and the reducing agent was 25 mL / min, the spray flow rate of the nanodiamond additive was 15 mL / min, and the rotation speed of the sample base was 120 r / min.

[0064] Step 4: Preparation of nanodiamond reinforced silver-based composite electrical contact coating

[0065] The pre-treated metal sheet was placed on the rotating base. After turning on the rotating button, the engine controlling the air valve connected to the nozzle was turned on, and the sample preparation was started by atomized spray deposition. The sample preparation time was 15 minutes and the deposition temperature was 30°C.

[0066] Step 5: Using ball-disc reciprocating friction, select H6 brass ball as the friction pair, connect the coating prepared in step 4 to direct current, set the load to 2N, no current, friction frequency to 1Hz, friction time to 30min, load to 2N, current to 1A, voltage to 5V, friction frequency to 1Hz, friction time to 30min, and load to 5N, no current, friction frequency to 1Hz, friction time to 30min.

[0067] The prepared coatings were tested as follows:

[0068] 1) By observing the SEM image of the coating surface, it was observed that the surface coating of the composite coating had a certain degree of roughness, and Ag eventually grew into granular form, which was densely and evenly arranged as a whole.

[0069] 2) If Figure 4 As shown, the average coating thickness is about 45 to 55 μm.

[0070] 3) If Figure 4As shown, the cross-sectional hardness is 178.3 HV, and the overall cross-sectional hardness ranges from about 130 to 180 HV.

[0071] 4) If Figure 5 As shown, the friction coefficient curve ranges from 0.1 to 0.2.

[0072] Example 3

[0073] A method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material comprises the following steps:

[0074] Step 1: Pretreatment of the metal substrate surface: Sand the metal surface to remove impurities and oxide layer, clean and dry it, etch it for 4 hours, remove it, ultrasonically clean it, and dry it for later use;

[0075] Surface cleaning: Sand the surface of an industrial pure copper sheet of 20mm×20mm×2mm with sandpaper of 600#~1500#, then clean and dry it.

[0076] Surface etching: Prepare the etching solution as in Example 1, and immerse the substrate in the etching solution with the pre-plated surface facing upward for 4 hours. Afterwards, ultrasonically clean the substrate with deionized water and blow dry.

[0077] Step 2: preparing a silver ammonia solution, a reducing agent and a second phase additive;

[0078] Silver ammonia solution: Weigh 4 g of silver nitrate and dissolve it in deionized water to obtain a 16 g / L silver nitrate solution. Then, add 2% ammonia water dropwise to the solution until it becomes clear.

[0079] Reducing agent solution: total volume 250 mL, of which the concentration of glyoxal is 50 mL / L, and the volume ratio of glyoxal to triethanolamine is 5:1;

[0080] Second phase additives: total volume 150 mL, of which nanodiamond concentration is 50 g / L, triethanolamine concentration is 10 mL / L, and the rest is deionized water, and ultrasonication is performed for 1 hour during preparation.

[0081] Step 3: Connect and adjust the spray equipment

[0082] Three spray guns were used for spraying. The spray gun angles of each component were adjusted so that the three components were 120° apart. The nozzle height was 10 cm from the sample surface. The spray flow rate of the silver ammonia solution and the reducing agent was 50 mL / min, the spray flow rate of the second phase additive was 20 mL / min, and the rotation speed of the sample base was 150 r / min.

[0083] Step 4: Preparation of nanodiamond reinforced silver-based composite electrical contact coating The sample preparation time is 10 min and the deposition temperature is 50°C.

[0084] Step 5: Using ball-disc reciprocating friction, select H6 brass ball as the friction pair, connect the coating prepared in step 4 to direct current, set the load to 2N, no current, friction frequency to 1Hz, friction time to 30min, load to 2N, current to 1A, voltage to 5V, friction frequency to 1Hz, friction time to 30min, and load to 5N, no current, friction frequency to 1Hz, friction time to 30min.

[0085] The prepared coatings were tested as follows:

[0086] 1) SEM surface micromorphology of coating surface Figure 6 As shown, it is observed that the surface coating of the composite coating has a certain degree of roughness, and Ag eventually grows into particles, which are densely and evenly arranged as a whole.

[0087] 2) If Figure 7 As shown, the average coating thickness is about 30 to 40 μm.

[0088] 3) If Figure 7 As shown, the cross-sectional hardness is 175.4 HV, and the overall cross-sectional hardness ranges from about 130 to 180 HV.

[0089] 4) If Figure 8 As shown, the friction coefficient curve ranges from 0.1 to 0.2.

[0090] Comparative Example 1

[0091] A method for preparing a silver-based electrical contact coating material comprises the following steps:

[0092] Step 1:

[0093] Surface cleaning: Sand the surface of an industrial pure copper sheet of 20mm×20mm×2mm with sandpaper of 600#~1500#, then clean and dry it.

[0094] Surface Etching: Clean a beaker and fill it with 20 mL of deionized water. Add 3.75 g of ferric chloride hexahydrate, 2.5 mL of HCl, and the remaining volume up to 50 mL of deionized water. Stir until completely dissolved. Immerse the substrate in the etchant, with the primary pre-plated surface facing up, for 4 hours. After etching, ultrasonically rinse with deionized water and dry.

[0095] Step 2: Prepare silver ammonia solution, reducing agent, and second phase additives

[0096] Silver ammonia solution: Weigh 4 g of silver nitrate and dissolve it in deionized water to obtain a 16 g / L silver nitrate solution. Then, add 2% ammonia water dropwise to the solution until it becomes clear to obtain a silver ammonia solution.

[0097] Reducing agent solution: total volume 250 mL, of which the concentration of glyoxal is 50 mL / L, and the volume ratio of glyoxal to triethanolamine is 5:1;

[0098] Second phase additives: total volume 150 mL, of which nanodiamond concentration is 0 g / L, triethanolamine concentration is 10 mL / L, and the rest is deionized water, and ultrasonication is performed for 1 h during preparation.

[0099] Step 3: Connect and adjust the spray equipment

[0100] Three spray guns were used for sample preparation. The spray gun angles of each component were adjusted so that the three components were 120° apart. The nozzle height was 3 cm from the sample surface. The spray flow rates of the silver ammonia solution and the reducing agent were 15 mL / min, the spray flow rate of the nanodiamond additive was 10 mL / min, and the rotation speed of the sample base was 100 r / min.

[0101] Step 4: Place the pre-treated metal sheet on the rotating base. After turning on the rotating button, turn on the engine that controls the nozzle air valve and start sample preparation through atomized spray deposition. The sample preparation time is 50 minutes and the deposition temperature is 25°C.

[0102] Step 5: Use ball-disc reciprocating friction, select H6 brass ball as the friction pair, connect the coating prepared in step 4 to direct current, set the load to 2N, the current to 1A, the voltage to 5V, the friction frequency to 1Hz, and the friction time to 30min.

[0103] The prepared coating was tested as follows:

[0104] 1) According to the SEM image of the coating surface, it was observed that the surface of the coating was a rough surface.

[0105] 2) The average coating thickness is about 35 to 45 μm.

[0106] 3) The cross-section hardness range is approximately 100 to 120 HV.

[0107] 4) The final range of the friction coefficient curve is between 0.6 and 0.8.

[0108] Comparative Example 2

[0109] A method for preparing a nano-diamond reinforced silver-based composite coating comprises the following steps:

[0110] Step 1: Metal substrate surface pretreatment

[0111] Surface cleaning: Sand the surface of an industrial pure copper sheet of 20mm×20mm×2mm with sandpaper of 600#~1500#, then clean and dry it.

[0112] Surface Etching: Clean a beaker and fill it with 20 mL of deionized water. Weigh 3.75 g of ferric chloride hexahydrate, add 2.5 mL of HCl, and add deionized water to 50 mL. Stir until completely dissolved. Immerse the substrate in the etching solution, with the primary pre-plated surface facing up, for 4 hours. After etching, ultrasonically rinse with deionized water and air dry.

[0113] Step 2: Prepare silver ammonia solution, reducing agent, and nanodiamond additives

[0114] Silver ammonia solution: Weigh 4 g of silver nitrate and dissolve it in deionized water to obtain a 16 g / L silver nitrate solution. Then, add 2% ammonia water dropwise to the solution until it becomes clear to obtain a silver ammonia solution.

[0115] Reducing agent solution: total volume 250 mL, of which the concentration of glyoxal is 50 mL / L, and the volume ratio of glyoxal to triethanolamine is 5:1;

[0116] Second phase additives: total volume 150 mL, of which nanodiamond concentration is 10 g / L, triethanolamine concentration is 10 mL / L, and the rest is deionized water;

[0117] The prepared nanodiamond additive was added to the reducing agent solution and ultrasonicated for 1 h.

[0118] Step 3: Connect and adjust the spray equipment

[0119] Two spray guns were used for spraying. One spray gun was used for the silver ammonia solution alone, and another spray gun was used for the mixed solution of the reducing agent solution and the nano-diamond additive. The spray gun angles of the two components were 180° to each other, and the nozzle height was 5 cm from the sample surface. The spray flow rate of the silver ammonia solution and the reducing agent added as the second phase was 15 mL / min, and the rotation speed of the sample base was 120 r / min.

[0120] Step 4: Preparation of silver-based composite coating with nanodiamond as particle reinforcement phase, sample preparation time is 15 minutes, and deposition temperature is 30°C.

[0121] Step 5: Use ball-disc reciprocating friction, select H6 brass ball as the friction pair, connect the coating prepared in step 4 to direct current, set the load to 2N, the current to 1A, the voltage to 5V, the friction frequency to 1Hz, and the friction time to 30min.

[0122] The prepared coatings were tested as follows:

[0123] 1) According to the SEM image of the coating surface, it was observed that the surface coating of the composite coating was a rough surface.

[0124] 2) The average coating thickness is about 35 to 45 μm.

[0125] 3) The cross-section hardness range is approximately 100 to 120 HV.

[0126] 4) The final range of the friction coefficient curve is between 0.6 and 0.8.

[0127] Comparative Example 3

[0128] A method for preparing a nano-diamond reinforced silver-based composite coating comprises the following steps:

[0129] Step 1: Metal substrate surface pretreatment

[0130] Surface cleaning: Sand the surface of an industrial pure copper sheet of 20mm×20mm×2mm with sandpaper of 600#~1500#, then clean and dry it.

[0131] Surface Etching: Clean a beaker and fill it with 20 mL of deionized water. Weigh 3.75 g of ferric chloride hexahydrate, add 2.5 mL of HCl, and add deionized water to 50 mL. Stir until completely dissolved. Immerse the substrate in the etching solution, with the primary pre-plated surface facing up, for 4 hours. After etching, ultrasonically rinse with deionized water and air dry.

[0132] Step 2: Prepare silver ammonia solution, reducing agent, and second phase additives

[0133] Silver ammonia solution: Weigh 4 g of silver nitrate and dissolve it in deionized water to obtain a 16 g / L silver nitrate solution. Then, add 2% ammonia water dropwise to the solution until it becomes clear.

[0134] Reducing agent: total volume 250 mL, of which the concentration of glyoxal is 50 mL / L, and the volume ratio of glyoxal to triethanolamine is 5:1;

[0135] Second phase additives: total volume 150 mL, of which nanodiamond concentration is 10 g / L, triethanolamine concentration is 10 mL / L, and the rest is deionized water;

[0136] The prepared nanodiamond additive was added to the silver ammonia solution and ultrasonicated for 1 h.

[0137] Step 3: Connect and adjust the spray equipment

[0138] Two spray guns were used for spraying. The silver ammonia solution and the nanodiamond additive were sprayed using the same spray gun, and the reducing agent was sprayed using another spray gun. The spray gun angles of the two components were 180° to each other, and the nozzle height was 5 cm from the sample surface. The spray flow rate of the silver ammonia solution and the reducing agent added as the second phase was 15 mL / min, and the rotation speed of the sample base was 120 r / min.

[0139] Step 4: Preparation of silver-based composite coating with nanodiamond as particle reinforcement

[0140] The treated metal sheet was placed on a rotating base, and after maintaining a stable rotation speed of about 120 r / min, atomization spray deposition began to prepare the sample. The sample preparation time was 15 min and the deposition temperature was 30°C.

[0141] Step 5: Use ball-disc reciprocating friction, select H6 brass ball as the friction pair, connect the coating prepared in step 4 to direct current, set the load to 2N, the current to 1A, the voltage to 5V, the friction frequency to 1Hz, and the friction time to 30min.

[0142] The prepared coating was tested as follows:

[0143] 1) According to the SEM image of the coating surface, it was observed that the surface coating of the composite coating was a rough surface.

[0144] 2) The average coating thickness is about 45 to 55 μm.

[0145] 3) The cross-section hardness range is approximately 100 to 120 HV.

[0146] 4) The final range of the friction coefficient curve is between 0.6 and 0.8.

Claims

1. A method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material, characterized in that: The steps include: (1) Surface pretreatment of metal substrate; (2) preparing a silver salt solution, a reducing agent, and a second phase additive; the second phase additive comprises nanodiamonds, triethanolamine, and water; (3) The silver salt solution, reducing agent and second phase additive of step (2) are respectively loaded into three spray guns and sprayed onto the pre-treated metal surface through an atomizer to obtain a nano-diamond reinforced silver-based composite electrical contact coating material.

2. The method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material according to claim 1, characterized in that: In step (2), the second phase additive consists of nanodiamonds, triethanolamine and water, wherein the concentration of nanodiamonds is 1-50 g / L.

3. The method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material according to any one of claims 1 to 2, characterized in that: In step (3), the three spray guns are set up independently, the angle between each spray gun and the sample substrate is in the range of 10° to 170°, and the distance between the nozzle and the substrate is 3 to 15 cm.

4. The method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material according to any one of claims 1 to 2, characterized in that: In step (3), the flow rate of the three spray guns is 5~50mL / min, and the rotation speed of the sample base is 50~150r / min.

5. The method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material according to any one of claims 1 to 2, characterized in that: In step (3), the coating deposition time is 10 min to 50 min, and the deposition temperature is 10° C. to 50° C.

6. The method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material according to any one of claims 1-2, characterized in that: In step (2), the particle size of the nanodiamond is 10-500 nm.

7. The method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material according to any one of claims 1-2, characterized in that: In step (2), the silver salt solution is an aqueous solution of silver nitrate, silver chloride or other soluble silver salts, and ammonia water is added to form a transparent complex silver salt solution, wherein Ag + The concentration is 1~50g / L; the reducing agent is an aqueous solution of glyoxal, formaldehyde or other substances containing aldehyde groups and triethanolamine, wherein the concentration of the substance containing aldehyde groups is 0.1~50g / L.

8. The method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material according to any one of claims 1-2, characterized in that: The metal substrate surface pretreatment includes sanding the metal surface to remove surface impurities and oxide layer, ultrasonic cleaning and drying, then independently immersing in etching solution for surface etching, ultrasonic cleaning and drying for standby use.

9. The method for preparing a nano-diamond reinforced silver-based composite electrical contact coating material according to any one of claims 1-2, characterized in that: The metal matrix material is any one of copper, iron, nickel, aluminum, magnesium or an alloy thereof.

10. A nano-diamond reinforced silver-based composite electrical contact coating material prepared by the preparation method according to any one of claims 1 to 9.

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