An AgWCGr contact material and its preparation method

Abstract

This invention discloses an AgWCGr contact material and its preparation method. First, graphene is added to a silver nitrate solution. Then, ultrasonic cavitation is used to reduce graphene agglomeration. Subsequently, Ag is used to coat WC and graphene in a WC-graphene-silver nitrate mixed solution using a solvothermal method, improving the interfacial bonding between the components and the silver matrix. After coating, silver powder is added, and the components are uniformly mixed in the solution under mechanical stirring. The dried mixed powder is then repressed and sintered to obtain the AgWCGr contact material. This invention uses a combination of ultrasonic dispersion, chemical coating, and wet mixing to prepare AgWCGr mixed powder, which, after sintering, yields the AgWCGr contact material. This achieves a dispersed distribution of each component, improves the interfacial bonding between components, helps reduce arc erosion of the contact material, enhances the anti-welding performance of the contact material, and exhibits low and stable contact resistance and good machinability.

Description

Technical Field

[0001] This invention belongs to the field of low-voltage contact material technology, specifically relating to an AgWCGr contact material and its preparation method. Background Technology

[0002] Silver-based contacts, as core components of low-voltage electrical appliances, are responsible for carrying and breaking current, and their performance directly affects the lifespan and reliability of electrical equipment. With the increasing load capacity, miniaturization, and multi-functionality of electrical appliances, existing silver-based contact materials are insufficient to meet these demands. For example, AgSnO2 contact materials experience increased contact resistance, higher temperatures, and poor machinability during service; AgNi contact materials exhibit poor resistance to welding under high-current conditions; and AgG (graphite) contact materials suffer from poor resistance to arc erosion. These problems significantly impact the stability, reliability, and lifespan of electrical equipment. Tungsten carbide (WC) possesses a high melting point and high hardness. However, WC has weak oxidation resistance, and under high-temperature arc conditions, non-conductive tungsten oxide and silver tungstate easily form on the surface of AgWC contacts, leading to increased contact resistance and higher temperatures. Graphene (Gr) possesses a unique two-dimensional structure that endows it with excellent electrical and thermal conductivity, mechanical properties, and wear resistance, making it an ideal reinforcement for silver-based contact materials. It holds promise for improving problems such as reduced mechanical properties, severe material loss, and unstable contact resistance caused by arc erosion during closing and breaking processes. Furthermore, graphene as a component in silver-based contact materials can enhance their machinability. However, commonly used powder mixing methods struggle to achieve uniform dispersion of the components, and the poor affinity between Ag, WC, and Gr makes it difficult to obtain good interfacial bonding, significantly impacting the material's physical, mechanical, and electrical properties. Therefore, developing a high-performance AgWCGr contact material and its preparation method has significant engineering and practical value. Summary of the Invention

[0003] The purpose of this invention is to provide an AgWCGr contact material, which has excellent resistance to arc erosion and welding, low and stable contact resistance, good mechanical properties and machinability.

[0004] Another objective of this invention is to provide a method for preparing AgWCGr contact material, which achieves the diffuse distribution of WC and Gr in the matrix and good bonding with the silver matrix, thereby obtaining AgWCGr contact material with uniform structure and good interfacial bonding, while effectively avoiding the introduction of impurities.

[0005] To address the problems in the existing technology, the technical solution adopted by this invention is as follows:

[0006] An AgWCGr contact material is composed of the following components by mass percentage: Ag 87.5%-91.9%, WC 8%-12%, and graphene (Gr) 0.1%-0.5%, with the sum of the mass percentages of the above components being 100%.

[0007] The preparation method of the above-mentioned AgWCGr contact material includes the following steps:

[0008] Step 1: Weigh the following materials according to their mass percentages: Ag powder 85%-90%, WC powder 8%-12%, and graphene 0.1%-0.5%;

[0009] Step 2: Prepare a silver nitrate solution according to the following mass fractions: 1% AgNO3, 0.5% ammonia, 0.1% PVP, 0.1% gum arabic, and 98.3% deionized water.

[0010] Step 3: Add the graphene weighed in Step 1 to the silver nitrate solution prepared in Step 2 and stir until homogeneous. Then place it in an ultrasonic machine for ultrasonic treatment for 60 min-200 min. After ultrasonic treatment, a graphene suspension is obtained.

[0011] Step 4: Add the WC powder weighed in Step 1 to the graphene suspension obtained in Step 3, perform mechanical stirring and oil bath heating, and add ethylene glycol as a reducing agent. After reacting for 30-60 minutes, add the Ag powder weighed in Step 1, continue mechanical stirring at 500 rpm for 4-6 hours. After stirring, let stand for 20-30 minutes, discard the supernatant, and wash with deionized water and anhydrous ethanol in sequence. Repeat the washing operation 3-5 times until the pH of the mixed solution is 7. Place the washed mixed powder in a 60℃ oven to dry for 6-8 hours.

[0012] Step 5: The completely dried mixed powder is loaded into a steel mold for pressing and then sintered in a tube furnace under an argon atmosphere. The initial pressure is 200MPa-300MPa, the holding time is 1min-2min, the sintering temperature is 800℃-900℃, and the holding time is 2h-3h. The secondary pressure is 900MPa-1200MPa, the holding time is 3min-5min, the sintering temperature is 600℃-700℃, and the holding time is 1h-2h. The furnace is then cooled to room temperature to obtain the AgWCGr contact material.

[0013] As an improvement, in step 1, the Ag powder has a particle size of 1μm-10μm and a morphology of near-spherical, the WC powder has a particle size of 1μm-10μm and a morphology of irregular polyhedron, the graphene has a thickness of 2nm and a sheet diameter of 2μm-3μm, and the purity of the raw materials is greater than 99.9%.

[0014] As an improvement, the mass ratio of silver nitrate solution to WC powder in step 1 in step 2 is 20-40:1.

[0015] As an improvement, the mass ratio of silver nitrate solution to ethylene glycol in step 4 is 1:2-4.

[0016] As an improvement, the mechanical stirring speed and oil bath temperature in step 4 are 100rpm-200rpm and 120℃-150℃, respectively. Beneficial effects

[0017] Compared with existing technologies, this invention provides a high-performance AgWCGr contact material and its preparation method. First, graphene is added to a silver nitrate solution, and then ultrasonic cavitation is used to reduce graphene agglomeration. Subsequently, Ag is used to coat WC and graphene in a WC-graphene-silver nitrate mixed solution using a solvothermal method, improving the interfacial bonding between the components and the silver matrix. After coating, silver powder is added, and the components are uniformly mixed in the solution under mechanical stirring. The dried mixed powder is then repressed and sintered to obtain the AgWCGr contact material. This invention uses a combination of ultrasonic dispersion, chemical coating, and wet mixing to prepare AgWCGr mixed powder, which is then sintered to obtain the AgWCGr contact material. This preparation method not only achieves the dispersed distribution of each component but also improves the interfacial bonding between each component and the silver matrix. The present invention provides an AgWCGr contact material with excellent comprehensive performance. The dispersed distribution of WC and graphene helps to reduce the erosion of the contact material by electric arc, enhances the anti-welding performance of the contact material, and the contact material has low and stable contact resistance and good machinability. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of a method for preparing an AgWCGr contact material according to the present invention;

[0019] Figure 2 This is a scanning electron microscope image of the mixed powder of WC and Gr coated with Ag prepared in Example 1 of this invention;

[0020] Figure 3 This is a metallographic photograph of the AgWCGr contact material prepared using 2μm WC in Example 2 of this invention;

[0021] Figure 4 This is the anodic morphology of the AgWCGr contact material prepared using 10μm WC in Example 1 of the present invention after 5000 electrical contacts at 36V / 16A;

[0022] Figure 5 This is the cathode morphology of the AgWCGr contact material prepared using 10μm WC in Example 1 of the present invention after 5000 electrical contacts at 36V / 16A. Detailed Implementation

[0023] An AgWCGr contact material is composed of the following components by mass percentage: Ag 87.5%-91.9%, WC 8%-12%, and graphene (Gr) 0.1%-0.5%, with the sum of the mass percentages of the above components being 100%.

[0024] The process flow diagram of the above-mentioned AgWCGr contact material preparation method is as follows: Figure 1 As shown, the specific steps are as follows:

[0025] Step 1: Weigh the following materials according to their mass percentages: 85%-90% Ag powder, 8%-12% WC powder, and 0.1%-0.5% graphene. The Ag powder has a particle size of 1μm-10μm and a spherical morphology, the WC powder has a particle size of 1μm-10μm and an irregular polyhedral morphology, and the graphene has a thickness of approximately 2nm and a sheet diameter of 2μm-3μm. The purity of all raw materials is greater than 99.9%.

[0026] Step 2: Prepare a silver nitrate solution with a mass fraction of 1% AgNO3, 0.5% ammonia, 0.1% PVP, 0.1% gum arabic, and 98.3% deionized water. The mass ratio of the silver nitrate solution to the WC powder in Step 1 is 20-40:1.

[0027] Step 3: Add the graphene weighed in Step 1 to the silver nitrate solution prepared in Step 2 and stir until homogeneous. Then place it in an ultrasonic machine for ultrasonic treatment for 60-200 minutes. After ultrasonic treatment, a graphene suspension is obtained.

[0028] Step 4: Add the WC powder weighed in Step 1 to the graphene suspension obtained in Step 3, and then mechanically stir and heat in an oil bath at 100-200 rpm and 120-150℃. Simultaneously add the reducing agent ethylene glycol, with a silver nitrate solution to ethylene glycol mass ratio of 1:2-4. After reacting for 30-60 minutes, add the Ag powder weighed in Step 1, and continue mechanical stirring at 500 rpm for 4-6 hours. After stirring, let stand for 20-30 minutes, discard the supernatant, and wash 3-5 times with deionized water and anhydrous ethanol until the pH of the mixed solution reaches 7. Place the washed mixed powder in a 60℃ oven and dry for 6-8 hours.

[0029] Step 5: The completely dried mixed powder is loaded into a steel mold for pressing and then sintered in a tube furnace under an argon atmosphere. The initial pressure is 200MPa-300MPa, the holding time is 1min-2min, the sintering temperature is 800℃-900℃, and the holding time is 2h-3h. The secondary pressure is 900MPa-1200MPa, the holding time is 3min-5min, the sintering temperature is 600℃-700℃, and the holding time is 1h-2h. The furnace is then cooled to room temperature to obtain the AgWCGr contact material.

[0030] The present invention will now be described in detail with reference to specific embodiments. Example 1

[0031] Step 1: Weigh out 86% Ag powder, 12% WC powder, and 0.1% graphene by mass percentage. The Ag powder has a particle size of 1μm-10μm and a spherical morphology, the WC powder has a particle size of 10μm and an irregular polyhedral morphology, and the graphene has a thickness of approximately 2nm and a sheet diameter of 2nm-3μm. The purity of all raw materials is greater than 99.9%.

[0032] Step 2: Prepare a silver nitrate solution with a mass fraction of 1% AgNO3, 0.5% ammonia, 0.1% PVP, 0.1% gum arabic, and 98.3% deionized water. The mass ratio of the silver nitrate solution to the WC powder in Step 1 is 20:1.

[0033] Step 3: Add the graphene weighed in Step 1 to the silver nitrate solution prepared in Step 2 and stir until homogeneous. Then place it in an ultrasonic machine for ultrasonic treatment for 120 minutes. After ultrasonic treatment, a graphene suspension is obtained.

[0034] Step 4: Add the WC powder weighed in Step 1 to the graphene suspension obtained in Step 3, then mechanically stir and heat in an oil bath at 100 rpm and 150°C. Simultaneously add ethylene glycol as a reducing agent; the mass ratio of silver nitrate solution to ethylene glycol is 1:2. After reacting for 30 minutes, add the Ag powder weighed in Step 1, and continue mechanical stirring at 500 rpm for 4 hours. After stirring, let stand for 30 minutes, discard the supernatant, and wash three times with deionized water and anhydrous ethanol until the pH of the mixed solution reaches 7. Place the washed mixed powder in a 60°C oven and dry for 8 hours.

[0035] Step 5: The completely dried mixed powder is loaded into a steel mold for pressing and then sintered in a tube furnace under an argon atmosphere. The initial pressure is 200 MPa, the holding time is 2 min, the sintering temperature is 900℃, and the holding time is 3 h. The secondary pressure is 1200 MPa, the holding time is 5 min, the sintering temperature is 600℃, and the holding time is 1 h. The furnace is then cooled to room temperature to obtain the AgWCGr contact material. Example 2

[0036] Step 1: Weigh out 85% Ag powder, 12% WC powder, and 0.1% graphene by mass percentage. The Ag powder has a particle size of 1μm-10μm and a spherical morphology, the WC powder has a particle size of 2μm and an irregular polyhedral morphology, and the graphene has a thickness of approximately 2nm and a sheet diameter of 2μm-3μm. The purity of all raw materials is greater than 99.9%.

[0037] Step 2: Prepare a silver nitrate solution with a mass fraction of 1% AgNO3, 0.5% ammonia, 0.1% PVP, 0.1% gum arabic, and 98.3% deionized water. The mass ratio of the silver nitrate solution to the WC powder in Step 1 is 30:1.

[0038] Step 3: Add the graphene weighed in Step 1 to the silver nitrate solution prepared in Step 2 and stir until homogeneous. Then place it in an ultrasonic machine for ultrasonic treatment for 120 minutes. After ultrasonic treatment, a graphene suspension is obtained.

[0039] Step 4: Add the WC powder weighed in Step 1 to the graphene suspension obtained in Step 3, and then mechanically stir and heat in an oil bath at 100 rpm and 150℃. Simultaneously add the reducing agent ethylene glycol, with a silver nitrate solution to ethylene glycol mass ratio of 1:3. After reacting for 45 min, add the Ag powder weighed in Step 1, and continue mechanical stirring at 500 rpm for 4 h. After stirring, let stand for 30 min, discard the supernatant, and wash five times with deionized water and anhydrous ethanol until the pH of the mixed solution reaches 7. Place the washed mixed powder in a 60℃ oven to dry for 8 h.

[0040] Step 5: The completely dried mixed powder is loaded into a steel mold for pressing and then sintered in a tube furnace under an argon atmosphere. The initial pressure is 200 MPa, the holding time is 2 min, the sintering temperature is 900℃, and the holding time is 3 h. The secondary pressure is 1200 MPa, the holding time is 5 min, the sintering temperature is 600℃, and the holding time is 1 h. The furnace is then cooled to room temperature to obtain the AgWCGr contact material. Example 3

[0041] Step 1: Weigh out 85% Ag powder, 12% WC powder, and 0.5% graphene by mass percentage. The Ag powder has a particle size of 1μm-10μm and a spherical morphology, the WC powder has a particle size of 2μm and an irregular polyhedral morphology, and the graphene has a thickness of approximately 2nm and a sheet diameter of 2μm-3μm. The purity of all raw materials is greater than 99.9%.

[0042] Step 2: Prepare a silver nitrate solution with a mass fraction of 1% AgNO3, 0.5% ammonia, 0.1% PVP, 0.1% gum arabic, and 98.3% deionized water. The mass ratio of the silver nitrate solution to the WC powder in Step 1 is 25:1.

[0043] Step 3: Add the graphene weighed in Step 1 to the silver nitrate solution prepared in Step 2 and stir until homogeneous. Then place it in an ultrasonic machine for ultrasonic treatment for 180 minutes. After ultrasonic treatment, a graphene suspension is obtained.

[0044] Step 4: Add the WC powder weighed in Step 1 to the graphene suspension obtained in Step 3, then mechanically stir and heat in an oil bath at 100 rpm and 150°C. Simultaneously add ethylene glycol as a reducing agent; the mass ratio of silver nitrate solution to ethylene glycol is 1:3. After reacting for 45 minutes, add the Ag powder weighed in Step 1, and continue mechanical stirring at 500 rpm for 4 hours. After stirring, let stand for 30 minutes, discard the supernatant, and wash five times with deionized water and anhydrous ethanol until the pH of the mixed solution reaches 7. Place the washed mixed powder in a 60°C oven and dry for 8 hours.

[0045] Step 5: The dried mixed powder is loaded into a steel mold for pressing and then sintered in a tube furnace under an argon atmosphere. The initial pressure is 200 MPa, the holding time is 2 min, the sintering temperature is 900℃, and the holding time is 3 h. The secondary pressure is 1200 MPa, the holding time is 5 min, the sintering temperature is 600℃, and the holding time is 1 h. The furnace is then cooled to room temperature to obtain the AgWCGr contact material.

[0046] Figure 2 The image shows a scanning electron microscope (SEM) image of the mixed powder of WC and Gr prepared in step 3 of Example 1 of this invention after being coated with Ag. It can be seen that the Ag coating effect is good.

[0047] Figure 3 This is a metallographic photograph of the AgWCGr contact material prepared using 2μm WC in Example 2 of this invention. It can be seen that WC and graphene are diffusely distributed in the silver matrix.

[0048] Figure 4 and Figure 5 The images show the anode and cathode morphologies of the AgWCGr contact material prepared using 10μm WC in Example 1 of this invention after 5000 electrical contacts at 36V / 16A. It can be seen that shallow pits are formed on the anode of the contact material after arc erosion, while small protrusions are formed on the cathode, indicating that the arc erosion of the anode and cathode of the contact material is low.

[0049] The AgWCGr contact material prepared according to the embodiments of the present invention was tested using the following methods:

[0050] Conductivity testing: The conductivity σ (unit: S / m) of the material was measured using a Sigma2008 digital eddy current metal conductivity meter and converted to the international standard unit for annealed copper (%IACS) according to formula (1). The sample surface should be flat and smooth, and free from interference such as oxide scale. After calibration with a standard sample, the measurement was performed. Each sample was tested 10 times on both sides and the average value was taken.

[0051] (1)

[0052] Hardness testing: The hardness of the silver-based contact material was measured using an HV-1000 micro Vickers hardness tester. Before testing, the sample was rough-ground to remove surface impurities and oxide layers, and then dried before measurement. During measurement, a load of 500g was selected, and the holding time was 15s. After unloading the test force, the lengths of the two diagonals of the indentation were measured, and then the Vickers hardness was calculated according to formula (2). 30 points were measured on both sides of each sample (evenly distributed across the entire sample surface), and the average value was calculated.

[0053] (2)

[0054] Testing of contact resistance, welding force, and mass loss: The prepared AgWCGr contact material was wire-cut into Φ3mm anode and cathode contacts. Testing was conducted using the JF04D electrical contact material testing system. Test parameters were: DC resistive load 36V / 16A, contact frequency 1Hz, electrode spacing 2mm, contact pressure 0.4N, and 5000 cycles. The contact testing system automatically saved the contact resistance and welding force test results, and the average value was calculated. The overall average value directly reflects the magnitude of contact resistance and welding force. A TG382A electronic balance was used to measure the mass change of the contact material before and after the anode and cathode electrical contact tests.

[0055] The test results are shown in Table 1:

[0056] Table 1 Performance data of AgWCGr contact materials prepared in different embodiments of the present invention

[0057]

[0058] Data from Examples 1 and 2 show that as the WC particle size decreases, the conductivity and contact resistance of the AgWCGr contact materials prepared in Examples 1 and 2 decrease, while the hardness, welding force, and mass loss increase. Data from Examples 2 and 3 show that as the graphene content increases, the conductivity and welding force of the AgWCGr contact materials prepared in Examples 2 and 3 decrease, while the contact resistance increases. Among all examples, the AgWCGr contact material prepared in Example 2 exhibits the best overall performance.

[0059] In summary, this invention introduces WC and graphene into a silver matrix to prepare an AgWCGr contact material with excellent overall performance.

Claims

1. An AgWCGr contact material, characterized in that, It is composed of the following components by mass percentage: Ag 87.5%-91.9%, WC 8%-12%, graphene Gr 0.1%-0.5%, and the sum of the mass percentages of the above components is 100%; The preparation method of the AgWCGr contact material includes the following steps: Step 1, weigh the following materials according to the mass percentage: Ag powder 85%-90%, WC powder 8%-12%, and graphene 0.1%-0.5%; Step 2: Prepare a silver nitrate solution according to the following mass fractions: 1% AgNO3, 0.5% dilute ammonia, 0.1% PVP, 0.1% gum arabic, and 98.3% deionized water. Step 3: Add the graphene weighed in Step 1 to the silver nitrate solution prepared in Step 2 and stir until homogeneous. Then place it in an ultrasonic machine for ultrasonic treatment for 60 min-200 min. After ultrasonic treatment, a graphene suspension is obtained. Step 4: Add the WC powder weighed in Step 1 to the graphene suspension obtained in Step 3, perform mechanical stirring and oil bath heating, and add the reducing agent ethylene glycol. After reacting for 30-60 minutes, add the Ag powder weighed in Step 1, continue mechanical stirring at 500 rpm for 4-6 hours. After stirring, let stand for 20-30 minutes, discard the supernatant, and wash with deionized water and anhydrous ethanol in sequence. Repeat the washing operation 3-5 times until the pH of the mixed solution is 7. Place the washed mixed powder in a 60℃ oven to dry for 6-8 hours. Step 5: The completely dried mixed powder is loaded into a mold steel mold for pressing and then sintered in a tube furnace under an argon atmosphere. The initial pressure is 200MPa-300MPa, the holding time is 1min-2min, the sintering temperature is 800℃-900℃, and the holding time is 2h-3h. The secondary pressure is 900MPa-1200MPa, the holding time is 3min-5min, the sintering temperature is 600℃-700℃, and the holding time is 1h-2h. The furnace is then cooled to room temperature to obtain AgWCGr contact material.

2. The AgWCGr contact material according to claim 1, characterized in that, In step 1, the Ag powder has a particle size of 1μm-10μm and a morphology of near-spherical, the WC powder has a particle size of 1μm-10μm and a morphology of irregular polyhedron, the graphene has a thickness of 2nm and a sheet diameter of 2μm-3μm, and the purity of the raw materials is greater than 99.9%.

3. The AgWCGr contact material according to claim 1, characterized in that, In step 2, the mass ratio of silver nitrate solution to WC powder in step 1 is 20-40:

1.

4. The AgWCGr contact material according to claim 1, characterized in that, In step 4, the mass ratio of silver nitrate solution to ethylene glycol is 1:2-4.

5. The AgWCGr contact material according to claim 1, characterized in that, In step 4, the mechanical stirring speed and oil bath temperature are 100rpm-200rpm and 120℃-150℃, respectively.

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