Preparation method of composite fiber layer reinforced sandwich structure silver tin oxide contact material

Abstract

The present invention discloses a method for preparing a composite fiber layer-reinforced sandwich structure silver tin oxide contact material, comprising the following steps: 1. preparing a tin salt solution to obtain a precursor solution; 2. performing electrospinning to obtain a nanofiber film; 3. performing cold pressing to obtain a cold-pressed sample block; 4. preparing a sandwich structure preform; 5. utilizing a plasma hot pressing sintering method to prepare the composite fiber layer-reinforced sandwich structure silver tin oxide contact material, placing the sandwich structure preform into a graphite mold, and then placing the graphite mold into an SPS sintering furnace; evacuating the material and entering a sintering process; running the process and waiting for the sintering to complete, thereby producing the composite fiber layer-reinforced sandwich structure silver tin oxide contact material. The method of the present invention significantly delays the surface segregation process caused by repeated arc erosion, enhances the electrical conductivity, thermal conductivity, mechanical properties, and arc erosion resistance of the contact, and prolongs the life of the silver tin oxide contact.

Description

Technical Field

[0001] The invention belongs to the technical field of electric contact material preparation, and relates to a method for preparing a composite fiber layer reinforced sandwich structure silver tin oxide contact material. Background Art

[0002] Contact materials, as key contact components in electrical and electronic products, are essential for the efficient and stable operation of intelligent equipment in various power environments. They bridge the gap between advanced material design and preparation and power electronics technology, and are a crucial support for modern industry and national defense. Silver tin oxide (Ag-SnO2), a non-toxic and environmentally friendly material, is widely used in contact materials due to its excellent electrical contact properties.

[0003] However, in silver tin oxide contacts produced by traditional powder metallurgy and smelting methods, the second phase in their structure is mostly randomly distributed in the silver matrix in a discrete or skeletal structure. When the second phase content is high, more interfaces are generated, which seriously reduces the electrical, thermal, and mechanical properties of the contacts. In particular, after multiple interruptions, repeated arc erosion causes significant segregation on the contact surface, seriously reducing the service life of the contacts and restricting their application as electrical contact materials in medium and low voltage circuit breakers. Therefore, it is urgent to develop a new preparation method to prepare composite fiber layer reinforced sandwich structure silver tin oxide contact materials with better performance. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a composite fiber layer reinforced sandwich structure silver tin oxide contact material, which solves the problems of imperfect process settings of the existing preparation methods, insufficient performance reliability of the obtained finished products during use, and short service life.

[0005] The technical solution adopted by the present invention is a method for preparing a composite fiber layer reinforced sandwich structure silver tin oxide contact material, which is implemented according to the following steps:

[0006] Step 1: prepare tin salt solution.

[0007] Stirring tin salt powder and anhydrous ethanol evenly; then adding NN-dimethylformamide solution and stirring evenly to obtain a tin salt solution; resetting the stirring parameters and adding polyvinyl pyrrolidone powder while stirring to obtain a precursor solution;

[0008] Step 2: electrospinning.

[0009] Place aluminum foil in the electrospinning machine, draw the precursor solution into two syringes and fix them in the corresponding position on the pump, set the spinning parameters, and start spinning to obtain a nanofiber film.

[0010] Step 3: cold press forming.

[0011] The nanofiber film obtained by electrospinning is cut into circular films, and the circular films are stacked to form multiple fiber layers; then silver powder is weighed, and the silver powder and multiple fiber layers are stacked layer by layer, and then laid flat in a cold pressing mold; the cold pressing mold is then placed in a press, and the parameters of the cold pressing molding are set to obtain a cold pressed sample block after cold pressing molding;

[0012] Step 4: Prepare a sandwich structure preform.

[0013] The cold pressed sample block is placed in a tube furnace, sintering parameters are set, and the cold pressed sample block is sintered to obtain a sandwich structure preform;

[0014] Step 5: Prepare a composite fiber layer reinforced sandwich structure silver tin oxide contact material using plasma hot pressing sintering (SPS).

[0015] The sandwich structure preform is placed in a graphite mold, and then the graphite mold is placed in an SPS sintering furnace; vacuum is applied and the sintering process is input; the process is run and the sintering is completed to obtain a composite fiber layer reinforced sandwich structure silver tin oxide contact material.

[0016] The present invention has the beneficial effects of controlling the SnO2 content and sandwich structure thickness in the contact material compared to existing technologies, forming a continuous silver conductive path within the contact matrix. Furthermore, the SnO2 fiber composite layer within the sandwich structure significantly delays surface segregation caused by repeated arc erosion, enhancing the electrical, thermal, mechanical, and arc erosion resistance of the contact, extending the service life of the silver tin oxide contact, while also conserving silver and reducing emissions, thereby lowering product production costs. Furthermore, the composite fiber layer-reinforced sandwich structure silver tin oxide contact material prepared by the present invention, while maintaining service performance, exhibits advantages such as uniform heating, rapid temperature rise, low sintering temperature, short sintering time, and high production efficiency during its preparation process, enabling mass production and providing significant guidance for practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a simplified flow chart of the preparation method of the present invention. DETAILED DESCRIPTION

[0018] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Reference Figure 1 The preparation method of the present invention is used to prepare a composite fiber layer reinforced sandwich structure silver tin oxide contact material, which is implemented according to the following steps:

[0020] Step 1: prepare tin salt solution.

[0021] Tin salt powder and anhydrous ethanol were added to a beaker and stirred for 20 minutes, and then NN-dimethylformamide (DMF) solution was added and stirred evenly to obtain a tin salt solution; the stirring parameters (including stirring temperature, stirring speed, and stirring time) were reset, and polyvinyl pyrrolidone (PVP) powder was added while stirring to obtain a precursor solution for electrospinning;

[0022] The tin salt powder is selected from stannous chloride, stannous sulfate, and stannous nitrate;

[0023] The mass ratio of tin salt powder to anhydrous ethanol is 1:2, the mass ratio of NN-dimethylformamide (DMF) solution to tin salt is 1:2, and the mass ratio of polyvinylpyrrolidone (PVP) powder to tin salt is 3:2.

[0024] Step 2: electrospinning.

[0025] Aluminum foil was laid in the electrospinning machine, two syringes were filled with precursor solution and fixed to the corresponding position on the pump, and the spinning parameters (including propulsion speed, syringe volume, and positive and negative pressure) were set; spinning was started to obtain a nanofiber film. After spinning, the nanofiber film was collected and bagged for later use;

[0026] The spinning parameters were set as follows: propulsion speed of 0.5-1.3 mL / h, syringe capacity of 10-20 mL; the negative pressure required for spinning was 3-5 kV, and the positive pressure was 12-18 kV.

[0027] Step 3: cold press forming.

[0028] The nanofiber film obtained by electrospinning was cut into circular films using a cutter, and 10-20 layers of circular films were stacked to form a multilayer fiber layer; then silver powder was weighed, and silver powder and multilayer fiber layers were stacked layer by layer, respectively, for a total of 10 layers of silver powder and 10 layers of multilayer fiber layers, and then flattened in a cold pressing mold with a diameter of 18 mm; the cold pressing mold was then placed in a press, and the molding pressure was set to 20 MPa and maintained for 10 minutes, and a cold pressed sample block was obtained after cold pressing;

[0029] The weight of silver powder in each layer is 0.5g-1.5g, and each multi-layer fiber layer is composed of 10-20 layers of circular films stacked together;

[0030] Step 4: Prepare a sandwich structure preform.

[0031] The cold pressed sample block is placed in a tube furnace, and the sintering parameters are set (sintering temperature is 650-850°C, holding time is 0.5-5h), and the cold pressed sample block is sintered to obtain a sandwich structure preform;

[0032] Step 5: Prepare composite fiber layer reinforced sandwich structure silver tin oxide contact material by plasma hot pressing sintering method.

[0033] The sandwich structure preform was placed in a graphite mold with a diameter of 20 mm, and then the graphite mold was placed in an SPS sintering furnace; vacuum was applied and the sintering process was input, and the sintering pressure, sintering temperature, heating rate, and holding time were set respectively (parameter settings: SPS sintering pressure 40-90 MPa, sintering temperature 750-950°C, heating rate 20-60°C / min, and holding time 15-60 min); the process was run and the sintering was completed, thereby obtaining a composite fiber layer reinforced sandwich structure silver tin oxide contact material.

[0034] Example 1

[0035] (1) Prepare a tin salt solution by adding 3 g of anhydrous ethanol and 1.5 g of stannous chloride into a beaker and stirring for 20 min. Then, add 3 g of DMF solution and stir evenly to obtain a tin salt solution. Set the stirring temperature to 45 °C and the stirring speed to 2100 r / min. Add 2.25 g of polyvinyl pyrrolidone (PVP) powder while stirring and stir for 12 h to obtain an electrospinning precursor solution.

[0036] (2) Perform electrospinning. Lay aluminum foil in the electrospinning machine, draw 5 mL of precursor solution into each of two syringes and fix them on the pump. Set the propulsion speed to 1 mL / h, the syringe capacity to 10 mL, and the negative pressure required for spinning to -5 kV and the positive pressure to 14 kV. Then, perform spinning. After the spinning is completed, collect the nanofiber film and bag it for later use.

[0037] (3) Prepare a cold-pressed sample block. Use a cutter to cut the nanofiber film obtained by electrospinning into circular films, and stack 10 layers of circular films to form a multilayer fiber layer. Then, weigh 0.6 g of silver powder for each layer, stack the silver powder and the multilayer fiber layer layer by layer, and stack a total of 10 layers of silver powder and 10 layers of multilayer fiber layers. Then, lay them flat in a cold-pressing mold with a diameter of 18 mm. Place the cold-pressing mold in a press, set the molding pressure to 20 MPa, and maintain the pressure for 10 minutes. After cold-pressing, a cold-pressed sample block is obtained.

[0038] (4) Preparing a sandwich structure preform, placing the cold-pressed sample block in a tube furnace, setting the sintering temperature to 650°C, holding time for 5 hours, and sintering the cold-pressed sample block to obtain a sandwich structure preform;

[0039] (5) A composite fiber layer reinforced sandwich structure silver tin oxide contact material was prepared using plasma hot pressing sintering (SPS). The sandwich structure preform was placed in a graphite mold with a diameter of 20 mm, and the graphite mold was placed in an SPS sintering furnace. Vacuum was evacuated and the sintering process was input. The sintering pressure was set to 60 MPa, the sintering temperature was set to 850 °C, the heating rate was set to 30 °C / min, and the holding time was set to 30 min. The process was run and the sintering was completed, and a composite fiber layer reinforced sandwich structure silver tin oxide contact material was obtained.

[0040] The product prepared in this example has a density of 9.68 g / cm 3 , conductivity is 74% IACS, hardness is 98HV, which fully meets the technical requirements.

[0041] Example 2: Comparison of the results of selecting tin salt varieties during the preparation of tin salt solutions.

[0042] (1) Preparation of tin salt solution 1:

[0043] Weigh 3 g of anhydrous ethanol and 1.5 g of stannous chloride into a beaker and stir. After stirring for 20 min, add 3 g of DMF solution. Set the stirring temperature to 45 ° C and the stirring speed to 2100 r / min. Add 2.25 g of polyvinyl pyrrolidone (PVP) powder while stirring. After stirring for 12 h, the precursor solution for electrospinning was obtained.

[0044] (2) Preparation of tin salt solution 2:

[0045] Tin salt solution 2 was prepared by replacing stannous chloride in tin salt solution 1 with stannous sulfate and following the same other steps.

[0046] (3) Preparation of tin salt solution 3:

[0047] Tin salt solution 3 was prepared by replacing stannous chloride in tin salt solution 1 with stannous nitrate and following the same other steps.

[0048] (4) The other steps were the same as those in Example 1. By observing and comparing the tin salt solutions prepared respectively, a small amount of precipitate was found in both tin salt solution 2 and tin salt solution 3, while no precipitate was found in tin salt solution 1. This indicates that stannous chloride has the best solubility in anhydrous ethanol. Therefore, stannous chloride is preferably used to prepare the tin salt solution.

[0049] Example 3: Comparison of different syringe advancement speeds during electrospinning.

[0050] (1) Setting of propulsion speed 1:

[0051] Aluminum foil was placed in the electrospinning machine. Two syringes were loaded with 5 mL of precursor solution each and fixed to the pump. The propulsion speed was set to 0.8 mL / h, the syringe capacity was 10 mL, and the negative pressure required for spinning was set to -5 kV and the positive pressure to 14 kV. Spinning was carried out and the nanofiber film was collected after the spinning was completed.

[0052] (2) Setting of propulsion speed 2:

[0053] Replace 0.8 mL / h in the propulsion speed 1 with 1 mL / h. The other steps remain the same.

[0054] (3) Setting of propulsion speed 3:

[0055] Replace 0.8 mL / h in propulsion speed 1 with 1.2 mL / h. Other steps remain the same.

[0056] (4) The other steps are the same as those in Example 1. The nanofiber films obtained at various propulsion speeds are observed and compared. The nanofiber films obtained at propulsion speed 2 are evenly distributed and have a diameter of about 700 nm, which meets the requirements. However, at propulsion speeds 1 and 3, droplets flow out of the needle during the electrospinning process, affecting the spinning quality. Therefore, propulsion speed 2 is preferred for electrospinning operations.

[0057] Example 4: Comparison of positive pressure applied during electrospinning.

[0058] (1) Setting of applied voltage 1:

[0059] Aspirate 5 mL of precursor solution into each of the two syringes and fix them on the electrospinning pump. Set the propulsion speed to 1 mL / h and the syringe capacity to 10 mL. Start the roller, move the syringe pump left and right, set the negative pressure of spinning to -5 kV and the positive pressure to 12 kV, and start spinning.

[0060] (2) Setting of applied voltage 2:

[0061] The positive voltage 12 kV in the applied voltage 1 was replaced by 14 kV, and the other steps were the same.

[0062] (3) Setting of applied voltage 3:

[0063] The positive voltage 12 kV in the applied voltage 1 was replaced by 16 kV, and the other steps were the same.

[0064] (4) The other steps are the same as those in Example 1. The experimental process is observed and the nanofiber films obtained are compared. In the experiment of applying voltage 1, it is found that the nanofiber film cannot be filamented. The fiber diameter distribution of the experiment of applying voltage 3 is uneven. The morphology and diameter of the nanofiber film obtained by applying voltage 2 meet the experimental requirements. Therefore, applying voltage 2 is preferred for electrospinning operation.

[0065] Example 5: Comparison of silver powder and fiber layup quality during cold pressing.

[0066] (1) Setting of stacking scheme 1:

[0067] First, evenly spread a layer of 0.6g of silver powder in a cold pressing mold with a diameter of 18mm, then evenly spread 10 layers of multi-layer fiber layers, and then evenly spread 0.6g of silver powder, and so on, stacking a total of 10 silver powder layers and 10 multi-layer fiber layers.

[0068] (2) Setting of stacking scheme 2:

[0069] Each 0.6g layer was replaced with a 1.2g layer of silver powder, which was evenly spread in a cold-pressing mold with a diameter of 18mm. The other steps were the same as those in stacking scheme 1.

[0070] (3) Setting of stacking scheme 3:

[0071] Each 0.6g layer was replaced with a 1.5g layer of silver powder, which was evenly spread in a cold-pressing mold with a diameter of 18mm. The other steps were the same as those in stacking scheme 1.

[0072] (4) The other steps are the same as those in Example 1. Experiments have shown that the contacts made by stacking scheme 2 have significantly higher arc erosion resistance than the other two schemes. Therefore, stacking scheme 2 is preferred for actual operation.

[0073] Example 6: Comparison of temperature settings during tube furnace sintering.

[0074] (1) Setting of temperature selection 1:

[0075] Place the cold pressed sample block into the tube furnace, turn on the power switch, adjust the experimental time, adjust the experimental temperature to 650°C, and start the experiment.

[0076] (2) Setting of temperature selection 2:

[0077] The temperature of 650°C in temperature selection 1 is replaced by the temperature of 750°C, and the other steps are the same.

[0078] (3) Setting of temperature selection 3:

[0079] The temperature of 650°C in temperature selection 1 is replaced by the temperature of 850°C, and the other steps are the same.

[0080] (4) The other steps in the above three cases are the same as those in Example 1. The products after sintering in the tube furnace are analyzed. In addition to the tin dioxide fibers, there are also some tin dioxide particles in the products of temperature selection 2 and temperature selection 3, while the product of temperature selection 1 is basically tin dioxide fibers. Therefore, it is preferred to perform tube furnace sintering at 650°C.

[0081] Example 7: Comparison of temperature settings during SPS sintering.

[0082] (1) Setting of temperature selection 1:

[0083] The mold and the finished product obtained in step 4) were placed in an SPS sintering furnace, the process was input, the sintering temperature was set to 750°C, the process was run, and the experiment was started.

[0084] (2) Setting of temperature selection 2:

[0085] The temperature 750°C in temperature selection 1 is replaced by the temperature 850°C, and the other steps are the same.

[0086] (3) Setting of temperature selection 3:

[0087] The temperature 750°C in temperature selection 1 is replaced by the temperature 950°C, and the other steps are the same.

[0088] (4) The other steps in the above three cases are the same as those in Example 1. After the experiment, the samples were analyzed. The density of the sample obtained in the experiment with temperature selection 1 was 9.44 g / cm 3 The density is poor. The sample obtained by temperature selection 3 has obvious segregation. The density of the sample obtained by temperature selection 2 is 9.68g / cm 3 , the electrical conductivity is 74% IACS, the hardness is 98HV, and the performance meets the requirements. Therefore, 850℃ is preferred for SPS sintering.

[0089] In summary, the composite fiber layer reinforced sandwich structure silver tin oxide contact material prepared by the method of the present invention, its SnO2 composite fiber layer and sandwich reinforcement structure can form a through silver conductive path, improve the conductivity of the silver tin oxide contact, enhance the mechanical properties and corrosion resistance of the contact, and extend the service life of the contact material. At the same time, it can save silver and reduce emissions, reduce the cost of silver tin oxide contacts and expand their application range. It can be used in medium and large capacity AC and DC contactors, AC and DC power relays, automotive electrical appliances, etc.

Claims

1. A method for preparing a composite fiber layer reinforced sandwich structure silver tin oxide contact material, characterized in that: Follow these steps to implement: Step 1: prepare tin salt solution. Stirring tin salt powder and anhydrous ethanol evenly, then adding N,N-dimethylformamide solution and stirring evenly to obtain a tin salt solution; resetting the stirring parameters, adding polyvinyl pyrrolidone powder while stirring to obtain a precursor solution; Step 2: electrospinning. Place aluminum foil in the electrospinning machine, draw the precursor solution into two syringes and fix them in the corresponding position on the pump, set the spinning parameters, and start spinning to obtain a nanofiber film. Step 3: cold press forming. The nanofiber film obtained by electrospinning is cut into circular films, and the circular films are stacked to form multiple fiber layers; then silver powder is weighed and stacked in a cycle of one layer of silver powder, one layer of multi-layer fiber layers, another layer of silver powder, and another layer of multi-layer fiber layers, and then laid flat in a cold pressing mold; Then, the cold pressing mold is placed in a press, and the parameters of the cold pressing forming are set, and a cold pressed sample block is obtained after cold pressing forming; Step 4: Prepare a sandwich structure preform. The cold pressed sample block is placed in a tube furnace, sintering parameters are set, and the cold pressed sample block is sintered to obtain a sandwich structure preform; Step 5: Prepare composite fiber layer reinforced sandwich structure silver tin oxide contact material by plasma hot pressing sintering method. Place the sandwich structure preform into a graphite mold, and then place the graphite mold into an SPS sintering furnace; evacuate and enter the sintering process. The sintering process parameters are: sintering pressure of 40-90MPa, sintering temperature of 750-850℃, heating rate of 20-60℃ / min, and holding time of 15-60min; The process is run, and the sintering is completed, to obtain a composite fiber layer reinforced sandwich structure silver tin oxide contact material.

2. The method for preparing the composite fiber layer reinforced sandwich structure silver tin oxide contact material according to claim 1, characterized in that: The tin salt powder is selected from one of stannous chloride, stannous sulfate and stannous nitrate.

3. The method for preparing the composite fiber layer reinforced sandwich structure silver tin oxide contact material according to claim 1, characterized in that: The mass ratio of the tin salt powder to anhydrous ethanol is 1:2, the mass ratio of the N,N-dimethylformamide solution to the tin salt is 1:2, and the mass ratio of the polyvinyl pyrrolidone powder to the tin salt is 3:

2.

4. The method for preparing the composite fiber layer reinforced sandwich structure silver tin oxide contact material according to claim 1, characterized in that: The spinning parameters are: propulsion speed of 0.5-1.3 mL / h, syringe capacity of 10-20 mL; negative pressure required for spinning is 3-5 kV, and positive pressure is 12-18 kV.

5. The method for preparing the composite fiber layer reinforced sandwich structure silver tin oxide contact material according to claim 1, characterized in that: In step 3, the mass of the silver powder in each layer is 0.5-1.5 g, and each multi-layer fiber layer is formed by stacking 10-20 layers of circular films.

6. The method for preparing the composite fiber layer reinforced sandwich structure silver tin oxide contact material according to claim 1, characterized in that: The parameters of the cold pressing molding in step 3 are: a pressure of 20 MPa and holding pressure for 10 minutes.

7. The method for preparing the composite fiber layer reinforced sandwich structure silver tin oxide contact material according to claim 1, characterized in that: The sintering parameters of step 4 are: sintering temperature of 650-850° C., and holding time of 0.5-5 h.

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