Silver alloy material for electrical contact based on a lamination composite process

Abstract

This invention relates to the field of electrical contact alloy materials technology, and discloses a silver alloy material for electrical contacts based on a lamination composite process. The preparation method includes the following steps: mixing composite silver powder, nickel powder, and tungsten powder, ball milling to obtain a mixture; pressing and sintering the mixture to obtain a silver-based alloy layer; laminating the silver-based alloy layer, an intermediate copper foil layer, and a welding layer iron foil from top to bottom; performing a first cold rolling followed by annealing heat treatment; cooling to room temperature; and then performing a second cold rolling to obtain the silver alloy material. The silver-based alloy layer serves as the working layer, the copper foil as the intermediate layer, and the welding layer iron foil are laminated from top to bottom. The resulting silver alloy material, after cold rolling and annealing heat treatment, exhibits high mechanical strength, high-temperature resistance, and arc erosion resistance, solving the problems of low strength, poor arc erosion resistance, and short electrical life inherent in silver alloy materials for electrical contacts.

Description

Technical Field

[0001] This invention relates to the field of electrical contact alloy materials technology, specifically to a silver alloy material for electrical contacts based on a lamination composite process. Background Technology

[0002] Electrical contact materials refer to materials used in electrical equipment to transmit, distribute, and control electrical energy. These include components such as conductors, contacts, and styluses. They are key materials used in electrical equipment such as switches and circuit breakers to control the connection and disconnection of current. Their performance directly affects the working performance and service life of electrical equipment. Silver-based electrical contact materials are usually made into components such as electrical contacts, brushes, commutators, and connectors for use in electrical conversion devices such as contactors, potentiometers, and relays, where they play the roles of conducting, cutting off, shunting, and isolating current.

[0003] Silver alloy materials for electrical contacts possess properties such as conductivity, wear resistance, and high temperature resistance. They have evolved from pure metals to composite materials and are widely used in equipment such as switches, relays, and new energy vehicles. However, silver alloy materials for electrical contacts suffer from problems such as low strength, poor resistance to arc erosion, and short electrical life. Summary of the Invention

[0004] This invention provides a silver alloy material for electrical contacts based on a lamination composite process, which solves the problems of low strength, poor resistance to arc erosion, and short electrical life of silver alloy materials for electrical contacts.

[0005] The technical solution of the present invention:

[0006] A method for preparing a silver alloy material for electrical contacts based on a lamination composite process includes the following steps:

[0007] S1. The composite silver powder, nickel powder and tungsten powder are mixed and ball-milled to obtain a mixture. The mixture is then pressed and sintered to obtain a silver-based alloy layer.

[0008] S2. The silver-based alloy layer, the intermediate copper foil layer, and the welding layer iron foil are bonded together from top to bottom. After one cold rolling, the material is subjected to annealing heat treatment, cooled to room temperature, and then subjected to a second cold rolling to obtain the silver alloy material.

[0009] The composite silver powder is obtained by coating the surface of modified silver powder with pyrogallol-modified lignin and then mixing it with carbon fiber.

[0010] The modified silver powder is obtained by synthesizing nitrogen-doped porous carbon on the surface of silver powder, and then reacting it with tin chloride pentahydrate and ammonia.

[0011] Further, in step S1, the mass ratio of the composite silver powder, nickel powder, and tungsten powder is 1:(0.2-0.3):(0.4-0.6).

[0012] Further, in step S1, the ball milling is carried out using a ball mill, the ball material is tungsten carbide with a diameter of 5-10 mm, the ball-to-material ratio in the ball mill is (5-10):1, the rotation speed is 1000-1200 r / min, and the ball milling time is 2-3 h.

[0013] Furthermore, in step S1, the pressing pressure is 300-400 MPa, and the pressing time is 4-5 min.

[0014] Further, in step S1, the sintering specifically involves: heating to 400-450℃ at a rate of 4-6℃ / min and holding for 1-1.5h, then continuing to heat to 800-850℃ at a rate of 7-9℃ / min and holding for 1.5-2.5h.

[0015] Further, in step S2, the rolling speed of the first cold rolling is 3-5 m / min, and the reduction rate is 40-50%; the rolling speed of the second cold rolling is 45-55 m / min, and the reduction rate is 50-60%.

[0016] Further, in step S2, the annealing heat treatment specifically involves: an annealing temperature of 400-450℃, an annealing atmosphere of argon, and an argon flow rate of 0.4-0.6 m³ / s. 3 / h.

[0017] Further, in step S2, the thickness of the welding layer iron foil is 0.6-1.8 mm; the thickness of the intermediate layer copper foil is 3-4.2 mm; and the thickness of the silver-based alloy layer is 1.5-2.4 mm.

[0018] Furthermore, the composite silver powder is prepared by the following steps:

[0019] A1. Mix chitin nanocrystal aqueous solution and urea evenly, add hydrochloric acid to adjust pH, stir, let stand at room temperature to separate into layers, take the lower layer solution, dry, and obtain chitin nanocrystal / urea composite; add silver powder to sodium carboxymethyl cellulose aqueous solution, sonicate, take out, dry, and obtain pretreated silver powder; mix the pretreated silver powder with chitin nanocrystal / urea composite, stir, add potassium hydroxide, stir, treat at 600-700℃ under nitrogen protection for 4-6 h, and obtain silver powder loaded with nitrogen-doped porous carbon layer;

[0020] A2. Mix silver powder loaded with nitrogen-doped porous carbon layer, tin chloride pentahydrate and deionized water, stir evenly, add ammonia water, stir at 70-80℃ for 30-40 min, filter, place in sintering furnace, sinter at 500-600℃ for 3-4 h, cool to room temperature to obtain modified silver powder.

[0021] A3. Add modified silver powder and pyrogallol-modified lignin to deionized water, stir evenly, add hydrochloric acid to adjust the pH, stir and react at 80-90℃ for 20-30 min, filter, wash and dry to obtain functionalized modified silver powder.

[0022] A4. Functionalized silver powder and carbon fiber are added to deionized water, ultrasonically treated, and hydrochloric acid is added to adjust the pH. The mixture is stirred at 70-80℃ for 30-40 minutes, filtered, washed, and dried to obtain composite silver powder.

[0023] Furthermore, in the A1 reaction process described above, sodium carboxymethyl cellulose acts as a binder that can adhere to the surface of silver powder, and the chitin nanocrystal / urea composite can also adhere to the surface of silver powder. Chitin nanocrystals serve as a carbon source, and urea serves as a nitrogen source. After high-temperature carbonization, the chitin nanocrystals decompose upon heating to form a dense carbon layer. The nitrogen element produced by the decomposition of urea is embedded in the carbon layer. Potassium hydroxide solution acts as an activator that can form channels on the surface of the dense carbon layer, thereby achieving the synthesis of a nitrogen-doped porous carbon layer on the surface of silver powder.

[0024] Furthermore, in the A2 reaction process described above, the porous structure on the surface of the silver powder loaded with nitrogen-doped porous carbon layer has high adsorption performance, serving as a synthesis site for tin dioxide. Tin ions in tin chloride pentahydrate can be adsorbed into the pores on the surface of the silver powder, and then combine with hydroxide ions provided by ammonia water to form metal hydroxides. After high-temperature calcination, the metal hydroxides decompose to form tin dioxide, thus realizing the synthesis of tin dioxide in the pores on the surface of the silver powder loaded with nitrogen-doped porous carbon layer, and obtaining modified silver powder.

[0025] Furthermore, during the A3 reaction process described above, the pyrogallol-modified lignin contains a large number of phenolic hydroxyl groups, which allows the pyrogallol-modified lignin to coat the surface of the modified silver powder, providing a large number of active functional groups for the modified silver powder, thus obtaining functionalized modified silver powder.

[0026] Furthermore, in the A4 reaction process described above, the functionalized modified silver powder contains a large number of phenolic hydroxyl groups, which, as crosslinking agents, can combine with the hydroxyl groups on the surface of carbon fibers through hydrogen bonds, thereby forming a crosslinked network structure of carbon fibers. This allows the carbon fibers to be coated on the surface of the functionalized modified silver powder in the form of a crosslinked network structure, resulting in composite silver powder.

[0027] Further, in step A1, the mass ratio of the chitin nanocrystal aqueous solution to urea is (35-40):(0.08-0.1).

[0028] Further, in step A1, the mass ratio of the silver powder to the sodium carboxymethyl cellulose aqueous solution is 1:(80-100).

[0029] Further, in step A1, the mass ratio of the pretreated silver powder, chitosan nanocrystals / urea composite, and potassium hydroxide is 1:(0.1-0.2):(0.06-0.1).

[0030] Further, in step A2, the mass ratio of the silver powder, tin chloride pentahydrate, deionized water, and ammonia water supporting the nitrogen-doped porous carbon layer is 1:(4.8-5):(50-60):(2.5-2.7).

[0031] Further, in step A3, the mass ratio of the modified silver powder, pyrogallol-modified lignin, and deionized water is 1:(0.1-0.2):(50-60).

[0032] Further, in step A4, the mass ratio of the functionalized modified silver powder, carbon fiber, and deionized water is 1:(0.1-0.2):(50-60).

[0033] The present invention has the following beneficial effects:

[0034] (1) In the technical solution of the present invention, the nitrogen-doped porous carbon layer synthesized on the surface of silver powder has the following characteristics: First, the synthesized nitrogen-doped porous carbon layer contains a uniformly distributed pore structure, which serves as a synthesis site for tin dioxide. It can synthesize a large amount of uniformly distributed tin dioxide on the surface of silver powder. Moreover, the synthesized nitrogen-doped porous carbon layer has high adsorption performance, which can adsorb and fix tin dioxide, thus preventing tin dioxide from agglomerating in the silver alloy material and affecting the arc erosion resistance of the silver alloy material. Second, the synthesized nitrogen-doped porous carbon layer has high conductivity, which can reduce the resistivity of the silver alloy material. In addition, the nitrogen-doped porous carbon layer has excellent high temperature resistance, which significantly improves the arc erosion resistance of the silver alloy material.

[0035] (2) In the technical solution of the present invention, tin dioxide is synthesized in the pores on the surface of the silver powder loaded with nitrogen-doped porous carbon layer, which can improve the arc erosion resistance of the silver alloy material. The complex network structure of the nitrogen-doped porous carbon layer can adsorb and weaken the stress generated by external force, thereby improving the mechanical properties of the silver alloy material. The pyrogallol-modified lignin can coat the surface of the modified silver powder, giving the modified silver powder a large number of phenolic hydroxyl groups, which is conducive to forming a cross-linked network structure of carbon fibers on the surface of the modified silver powder, increasing the contact area with the raw materials required for the silver alloy material, improving the density of the silver alloy material, and thus enhancing the mechanical strength and arc erosion resistance of the silver alloy material.

[0036] (3) In the technical solution of the present invention, carbon fibers are coated on the surface of functionalized modified silver powder in the form of cross-linked structure. On the one hand, the cross-linked network structure of carbon fibers can increase the contact area between silver powder and the raw materials required for silver alloy materials, improve the density of silver alloy materials, and the cross-linked network structure of carbon fibers can absorb and weaken the stress generated by external forces, thereby improving the mechanical strength of silver alloy materials. On the other hand, the addition of carbon fibers to silver alloy materials can improve the mechanical strength, anti-arc erosion performance and cycle stability of silver alloy materials. In addition, the thermal decomposition of pyrogallol-modified lignin provides a large amount of carbon elements dispersed at the grain boundaries of silver alloy materials, improving the density of silver alloy materials, thereby improving the mechanical strength and anti-arc erosion performance of silver alloy materials.

[0037] (4) In the technical solution of the present invention, the composite silver powder, nickel powder and tungsten powder are mixed, and the silver-based alloy layer formed by ball milling, pressing and sintering is used as the working layer, and the copper foil is used as the intermediate layer. The copper foil is bonded to the welding layer iron foil from top to bottom. After cold rolling and annealing heat treatment, the silver alloy material prepared has high mechanical strength, high temperature resistance and arc erosion resistance, which solves the problems of low strength, poor arc erosion resistance and short electrical life of silver alloy materials for electrical contact. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] The raw materials used in the embodiments of this invention are shown below, and all reagents used are analytical grade.

[0040] The silver powder has a particle size of 15μm and a purity of 99.99%, and was purchased from Shanghai Kaitai Instrument Co., Ltd.

[0041] The nickel powder with a particle size of 1.0 μm and the product number ST-M-007-2, and the tungsten powder with a particle size of 1 μm and the product number ST-M-008-2, were both purchased from Shanghai Shuitian Materials Technology Co., Ltd.

[0042] Chitosan nanocrystals are prepared by the following steps:

[0043] 10g of chitin was added to 300mL of 3mol / L hydrochloric acid and stirred at 124℃ for 1.5h. After stirring, the mixture was centrifuged at 8000r / min for 10min, washed three times with deionized water, and centrifuged again at 8000r / min until the pH of the solution was 4. The solution was then added to 100mL of deionized water and dialyzed in a dialysis bag (molecular weight cutoff of 10000) for three days. The solution was then removed and freeze-dried at -20℃ for 24h to obtain chitin nanocrystals.

[0044] Carbon fiber is obtained through the following steps:

[0045] 0.5g of TC-35 carbon fiber was placed in a heating furnace and heat-treated at 475℃ for 1 hour. After cooling to room temperature, it was soaked in 30mL of acetone solution for 1 hour. After removal, it was rinsed three times with water and dried in an oven at 70℃ for 10 minutes. Then, it was placed in 30mL of 98% nitric acid and soaked at 88℃ for 1 hour. The pH was adjusted to 7 by adding 0.2mol / L sodium hydroxide solution. After rinsing three times with water, it was dried in an oven at 70℃ for 10 minutes to obtain carbon fiber.

[0046] TC-35 carbon fiber has a single filament diameter of 5μm, a tensile strength of 3.8GPa, an elastic modulus of 235GPa, and a density of 1.76g / cm³. 3 Elongation after fracture: 1.6%.

[0047] Sodium carboxymethyl cellulose, USP grade, viscosity 2000 mPa·s, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0048] Pyrogallol-modified lignin is prepared by the following steps:

[0049] Enzymatically hydrolyzed lignin and pyrogallol were added to a 65% (w / w) lithium chloride aqueous solution, stirred until homogeneous, and the pH was adjusted to 3.5 with 2.4 mol / L hydrochloric acid. The reaction was carried out at 110℃ for 2 h, cooled to room temperature, and the solid was collected by filtration. The solid was washed with ethanol to remove unreacted pyrogallol and dried at 40℃ for 48 h to obtain pyrogallol-modified lignin. The mass ratio of enzymatically hydrolyzed lignin, pyrogallol and lithium chloride aqueous solution was 2.5:0.8:50.

[0050] The enzymatically hydrolyzed lignin was purchased from Shandong Longli Biotechnology Co., Ltd.

[0051] Example 1

[0052] A silver alloy material for electrical contacts based on a lamination composite process is prepared by the following steps:

[0053] S1. Composite silver powder, nickel powder, and tungsten powder are mixed in a mass ratio of 1:0.2:0.4 and ball-milled to obtain a mixture. The mixture is then pressed and sintered to obtain a silver-based alloy layer. The ball milling process uses a ball mill with tungsten carbide balls of 5mm diameter. The ball-to-material ratio in the ball mill is 5:1, the rotation speed is 1000 r / min, and the milling time is 2 hours. The pressing pressure is 300 MPa, and the pressing time is 4 minutes. The sintering process involves heating to 400℃ at a rate of 4℃ / min and holding for 1 hour, then further heating to 800℃ at a rate of 7℃ / min and holding for 1.5 hours.

[0054] S2. The silver-based alloy layer, the intermediate copper foil layer, and the welding layer iron foil are bonded together from top to bottom. After a first cold rolling, an annealing heat treatment is performed, followed by cooling to room temperature and a second cold rolling to obtain the silver alloy material. The rolling speed of the first cold rolling is 3 m / min, with a reduction rate of 40%; the rolling speed of the second cold rolling is 45 m / min, with a reduction rate of 50%. The annealing heat treatment is specifically as follows: annealing temperature is 400℃, annealing atmosphere is argon, and argon flow rate is 0.4 m³ / min. 3 / h;

[0055] The thickness of the welding layer iron foil is 0.6 mm; the thickness of the intermediate layer copper foil is 3 mm; and the thickness of the silver-based alloy layer is 1.5 mm.

[0056] The composite silver powder is prepared by the following steps:

[0057] A1. Mix a 3% (w / w) aqueous solution of chitin nanocrystals with urea, adjust the pH to 5 with 0.1 mol / L hydrochloric acid, stir at 300 rpm for 45 min, let stand at room temperature for 3 days to separate the layers, take the lower layer solution, and dry it in an oven at 35℃ and 30% humidity for 5 days to obtain a chitin nanocrystal / urea composite; the mass ratio of chitin nanocrystal aqueous solution to urea is 35:0.08.

[0058] Silver powder was added to a 1% sodium carboxymethyl cellulose aqueous solution, ultrasonicated at 300W for 5 min, removed, and dried in an oven at 70℃ for 10 min to obtain pretreated silver powder; the mass ratio of silver powder to sodium carboxymethyl cellulose aqueous solution was 1:80.

[0059] Pretreated silver powder was mixed with chitin nanocrystals / urea composite and stirred at 300 rpm for 30 min. 1 mol / L potassium hydroxide was added and stirred until homogeneous. The mixture was then treated at 600 °C under nitrogen protection for 4 h to obtain silver powder loaded with a nitrogen-doped porous carbon layer. The mass ratio of pretreated silver powder, chitin nanocrystals / urea composite, and potassium hydroxide was 1:0.1:0.06.

[0060] A2. Mix silver powder with nitrogen-doped porous carbon layer, tin chloride pentahydrate, and deionized water, stir evenly, add 10% ammonia water, stir at 70℃ for 30 min, filter, place in a sintering furnace, sinter at 500℃ for 3 h, cool to room temperature, and obtain modified silver powder; the mass ratio of silver powder with nitrogen-doped porous carbon layer, tin chloride pentahydrate, deionized water, and ammonia water is 1:4.8:50:2.5;

[0061] A3. Modified silver powder and pyrogallol-modified lignin were added to deionized water and stirred until homogeneous. The pH was adjusted to 3 with 0.1 mol / L hydrochloric acid. The mixture was stirred and reacted at 80°C for 20 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 70°C for 10 min to obtain functionalized modified silver powder. The mass ratio of modified silver powder, pyrogallol-modified lignin, and deionized water was 1:0.1:50.

[0062] A4. Functionalized modified silver powder and carbon fiber were added to deionized water and ultrasonically treated at 300W for 5 min. Hydrochloric acid with a concentration of 0.1 mol / L was added to adjust the pH to 3. The mixture was stirred and reacted at 70℃ for 30 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 90℃ for 10 min to obtain composite silver powder. The mass ratio of functionalized modified silver powder, carbon fiber and deionized water was 1:0.1:50.

[0063] Example 2

[0064] A silver alloy material for electrical contacts based on a lamination composite process is prepared by the following steps:

[0065] S1. Composite silver powder, nickel powder, and tungsten powder are mixed in a mass ratio of 1:0.25:0.5 and ball-milled to obtain a mixture. The mixture is then pressed and sintered to obtain a silver-based alloy layer. The ball milling process uses a ball mill with tungsten carbide balls of 8mm diameter. The ball-to-material ratio in the ball mill is 8:1, the rotation speed is 1100 r / min, and the milling time is 2.5 h. The pressing pressure is 350 MPa, and the pressing time is 4.5 min. The sintering process involves heating to 430℃ at a rate of 5℃ / min and holding for 1.3 h, followed by heating to 830℃ at a rate of 8℃ / min and holding for 2 h.

[0066] S2. The silver-based alloy layer, the intermediate copper foil layer, and the welding layer iron foil are bonded together from top to bottom. After a first cold rolling, an annealing heat treatment is performed, followed by cooling to room temperature and a second cold rolling to obtain the silver alloy material. The rolling speed of the first cold rolling is 4 m / min, with a reduction rate of 45%; the rolling speed of the second cold rolling is 50 m / min, with a reduction rate of 55%. The annealing heat treatment is specifically as follows: annealing temperature is 430℃, annealing atmosphere is argon, and argon flow rate is 0.5 m³ / min. 3 / h;

[0067] The thickness of the welding layer iron foil is 1mm; the thickness of the intermediate layer copper foil is 4mm; and the thickness of the silver-based alloy layer is 2mm.

[0068] The composite silver powder is prepared by the following steps:

[0069] A1. Mix a 3% (w / w) aqueous solution of chitin nanocrystals with urea, adjust the pH to 5 with 0.1 mol / L hydrochloric acid, stir at 300 rpm for 45 min, let stand at room temperature for 3 days to separate the layers, take the lower layer solution, and dry it in an oven at 35℃ and 30% humidity for 5 days to obtain a chitin nanocrystal / urea composite; the mass ratio of chitin nanocrystal aqueous solution to urea is 38:0.09.

[0070] Silver powder was added to a 1% sodium carboxymethyl cellulose aqueous solution, ultrasonicated at 300W for 5 min, removed, and dried in an oven at 70℃ for 10 min to obtain pretreated silver powder; the mass ratio of silver powder to sodium carboxymethyl cellulose aqueous solution was 1:90.

[0071] Pretreated silver powder was mixed with chitin nanocrystals / urea composite and stirred at 300 rpm for 30 min. 1 mol / L potassium hydroxide was added and stirred until homogeneous. The mixture was then treated at 650 °C under nitrogen protection for 5 h to obtain silver powder loaded with a nitrogen-doped porous carbon layer. The mass ratio of pretreated silver powder, chitin nanocrystals / urea composite, and potassium hydroxide was 1:0.15:0.08.

[0072] A2. Mix silver powder with nitrogen-doped porous carbon layer, tin chloride pentahydrate, and deionized water, stir evenly, add 10% ammonia water, stir at 75℃ for 35 min, filter, place in a sintering furnace, sinter at 550℃ for 3.5 h, cool to room temperature, and obtain modified silver powder; the mass ratio of silver powder with nitrogen-doped porous carbon layer, tin chloride pentahydrate, deionized water, and ammonia water is 1:4.9:55:2.6.

[0073] A3. Modified silver powder and pyrogallol-modified lignin were added to deionized water and stirred until homogeneous. The pH was adjusted to 3 with 0.1 mol / L hydrochloric acid. The mixture was stirred at 85°C for 25 min, filtered, washed three times with deionized water, and dried in a 70°C oven for 10 min to obtain functionalized modified silver powder. The mass ratio of modified silver powder, pyrogallol-modified lignin, and deionized water was 1:0.15:55.

[0074] A4. Functionalized modified silver powder and carbon fiber were added to deionized water and ultrasonically treated at 300W for 5 min. Hydrochloric acid with a concentration of 0.1 mol / L was added to adjust the pH to 3. The mixture was stirred and reacted at 75℃ for 35 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 90℃ for 10 min to obtain composite silver powder. The mass ratio of functionalized modified silver powder, carbon fiber and deionized water was 1:0.15:55.

[0075] Example 3

[0076] A silver alloy material for electrical contacts based on a lamination composite process is prepared by the following steps:

[0077] S1. Composite silver powder, nickel powder, and tungsten powder are mixed in a mass ratio of 1:0.3:0.6 and ball-milled to obtain a mixture. The mixture is then pressed and sintered to obtain a silver-based alloy layer. The ball milling process uses a ball mill with tungsten carbide balls of 10mm diameter. The ball-to-material ratio in the ball mill is 10:1, the rotation speed is 1200 r / min, and the milling time is 3 hours. The pressing pressure is 400 MPa, and the pressing time is 5 minutes. The sintering process involves heating to 450℃ at a rate of 6℃ / min and holding for 1.5 hours, followed by heating to 850℃ at a rate of 9℃ / min and holding for 2.5 hours.

[0078] S2. The silver-based alloy layer, the intermediate copper foil layer, and the welding layer iron foil are bonded together from top to bottom. After a first cold rolling, an annealing heat treatment is performed, followed by cooling to room temperature and a second cold rolling to obtain the silver alloy material. The rolling speed of the first cold rolling is 5 m / min, with a reduction rate of 50%; the rolling speed of the second cold rolling is 55 m / min, with a reduction rate of 60%. The annealing heat treatment is specifically as follows: annealing temperature is 450℃, annealing atmosphere is argon, and argon flow rate is 0.6 m³ / min. 3 / h;

[0079] The thickness of the welding layer iron foil is 1.8 mm; the thickness of the intermediate layer copper foil is 4.2 mm; and the thickness of the silver-based alloy layer is 2.4 mm.

[0080] The composite silver powder is prepared by the following steps:

[0081] A1. Mix a 3% (w / w) aqueous solution of chitin nanocrystals with urea, adjust the pH to 5 with 0.1 mol / L hydrochloric acid, stir at 300 rpm for 45 min, let stand at room temperature for 3 days to separate the layers, take the lower layer solution, and dry it in an oven at 35℃ and 30% humidity for 5 days to obtain a chitin nanocrystal / urea composite; the mass ratio of chitin nanocrystal aqueous solution to urea is 40:0.1.

[0082] Silver powder was added to a 1% sodium carboxymethyl cellulose aqueous solution, ultrasonicated at 300W for 5 min, removed, and dried in an oven at 70℃ for 10 min to obtain pretreated silver powder; the mass ratio of silver powder to sodium carboxymethyl cellulose aqueous solution was 1:100.

[0083] Pretreated silver powder was mixed with chitin nanocrystals / urea composite and stirred at 300 r / min for 30 min. 1 mol / L potassium hydroxide was added and stirred until homogeneous. The mixture was then treated at 700 °C under nitrogen protection for 6 h to obtain silver powder loaded with a nitrogen-doped porous carbon layer. The mass ratio of pretreated silver powder, chitin nanocrystals / urea composite, and potassium hydroxide was 1:0.2:0.1.

[0084] A2. Mix silver powder with nitrogen-doped porous carbon layer, tin chloride pentahydrate, and deionized water, stir evenly, add 10% ammonia water by mass, stir at 80℃ for 40 min, filter, place in a sintering furnace, sinter at 600℃ for 4 h, cool to room temperature, and obtain modified silver powder; the mass ratio of silver powder with nitrogen-doped porous carbon layer, tin chloride pentahydrate, deionized water, and ammonia water is 1:5:60:2.7;

[0085] A3. Modified silver powder and pyrogallol-modified lignin were added to deionized water and stirred until homogeneous. The pH was adjusted to 3 with 0.1 mol / L hydrochloric acid. The mixture was stirred at 90°C for 30 min, filtered, washed three times with deionized water, and dried in a 70°C oven for 10 min to obtain functionalized modified silver powder. The mass ratio of modified silver powder, pyrogallol-modified lignin, and deionized water was 1:0.2:60.

[0086] A4. Functionalized modified silver powder and carbon fiber were added to deionized water and ultrasonically treated at 300W for 5 min. Hydrochloric acid with a concentration of 0.1 mol / L was added to adjust the pH to 3. The mixture was stirred and reacted at 80℃ for 40 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 90℃ for 10 min to obtain composite silver powder. The mass ratio of functionalized modified silver powder, carbon fiber and deionized water was 1:0.2:60.

[0087] Comparative Example 1

[0088] The only difference between this comparative example and Example 3 is the preparation of the composite silver powder, as detailed below:

[0089] The composite silver powder is prepared by the following steps:

[0090] A1. Add silver powder to a 1% sodium carboxymethyl cellulose aqueous solution, sonicate at 300W for 5 min, remove and dry in an oven at 70℃ for 10 min to obtain pretreated silver powder; the mass ratio of silver powder to sodium carboxymethyl cellulose aqueous solution is 1:100.

[0091] A2. Mix pretreated silver powder, tin chloride pentahydrate, and deionized water, stir evenly, add 10% ammonia water, stir at 80℃ for 40 min, filter, place in a sintering furnace, sinter at 600℃ for 4 h, cool to room temperature, and obtain modified silver powder; the mass ratio of pretreated silver powder, tin chloride pentahydrate, deionized water, and ammonia water is 1:5:60:2.7;

[0092] A3. Modified silver powder and pyrogallol-modified lignin were added to deionized water and stirred until homogeneous. The pH was adjusted to 3 with 0.1 mol / L hydrochloric acid. The mixture was stirred at 90°C for 30 min, filtered, washed three times with deionized water, and dried in a 70°C oven for 10 min to obtain functionalized modified silver powder. The mass ratio of modified silver powder, pyrogallol-modified lignin, and deionized water was 1:0.2:60.

[0093] A4. Functionalized modified silver powder and carbon fiber were added to deionized water and ultrasonically treated at 300W for 5 min. Hydrochloric acid with a concentration of 0.1 mol / L was added to adjust the pH to 3. The mixture was stirred and reacted at 80℃ for 40 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 90℃ for 10 min to obtain composite silver powder. The mass ratio of functionalized modified silver powder, carbon fiber and deionized water was 1:0.2:60.

[0094] Comparative Example 2

[0095] The only difference between this comparative example and Example 3 is the preparation of the composite silver powder, as detailed below:

[0096] The composite silver powder is prepared by the following steps:

[0097] A1. Mix a 3% (w / w) aqueous solution of chitin nanocrystals with urea, adjust the pH to 5 with 0.1 mol / L hydrochloric acid, stir at 300 rpm for 45 min, let stand at room temperature for 3 days to separate the layers, take the lower layer solution, and dry it in an oven at 35℃ and 30% humidity for 5 days to obtain a chitin nanocrystal / urea composite; the mass ratio of chitin nanocrystal aqueous solution to urea is 40:0.1.

[0098] Silver powder was added to a 1% sodium carboxymethyl cellulose aqueous solution, ultrasonicated at 300W for 5 min, removed, and dried in an oven at 70℃ for 10 min to obtain pretreated silver powder; the mass ratio of silver powder to sodium carboxymethyl cellulose aqueous solution was 1:100.

[0099] Pretreated silver powder was mixed with chitin nanocrystals / urea composite and stirred at 300 r / min for 30 min. 1 mol / L potassium hydroxide was added and stirred until homogeneous. The mixture was then treated at 700 °C under nitrogen protection for 6 h to obtain silver powder loaded with a nitrogen-doped porous carbon layer. The mass ratio of pretreated silver powder, chitin nanocrystals / urea composite, and potassium hydroxide was 1:0.2:0.1.

[0100] A2. Modified silver powder and pyrogallol-modified lignin were added to deionized water and stirred until homogeneous. The pH was adjusted to 3 with 0.1 mol / L hydrochloric acid. The mixture was stirred at 90°C for 30 min, filtered, washed three times with deionized water, and dried in an oven at 70°C for 10 min to obtain silver powder with a functionalized nitrogen-doped porous carbon layer. The mass ratio of modified silver powder, pyrogallol-modified lignin, and deionized water was 1:0.2:60.

[0101] A3. Add functionalized nitrogen-doped porous carbon layer silver powder and carbon fiber to deionized water, sonicate at 300W for 5 min, add 0.1 mol / L hydrochloric acid to adjust pH to 3, stir at 80℃ for 40 min, filter, wash 3 times with deionized water, and dry in 90℃ oven for 10 min to obtain composite silver powder; the mass ratio of functionalized nitrogen-doped porous carbon layer silver powder, carbon fiber and deionized water is 1:0.2:60.

[0102] Comparative Example 3

[0103] The only difference between this comparative example and Example 3 is the preparation of the composite silver powder, as detailed below:

[0104] The composite silver powder is prepared by the following steps:

[0105] A1. Mix a 3% (w / w) aqueous solution of chitin nanocrystals with urea, adjust the pH to 5 with 0.1 mol / L hydrochloric acid, stir at 300 rpm for 45 min, let stand at room temperature for 3 days to separate the layers, take the lower layer solution, and dry it in an oven at 35℃ and 30% humidity for 5 days to obtain a chitin nanocrystal / urea composite; the mass ratio of chitin nanocrystal aqueous solution to urea is 40:0.1.

[0106] Silver powder was added to a 1% sodium carboxymethyl cellulose aqueous solution, ultrasonicated at 300W for 5 min, removed, and dried in an oven at 70℃ for 10 min to obtain pretreated silver powder; the mass ratio of silver powder to sodium carboxymethyl cellulose aqueous solution was 1:100.

[0107] Pretreated silver powder was mixed with chitin nanocrystals / urea composite and stirred at 300 r / min for 30 min. 1 mol / L potassium hydroxide was added and stirred until homogeneous. The mixture was then treated at 700 °C under nitrogen protection for 6 h to obtain silver powder loaded with a nitrogen-doped porous carbon layer. The mass ratio of pretreated silver powder, chitin nanocrystals / urea composite, and potassium hydroxide was 1:0.2:0.1.

[0108] A2. Mix silver powder with nitrogen-doped porous carbon layer, tin chloride pentahydrate, and deionized water, stir evenly, add 10% ammonia water by mass, stir at 80℃ for 40 min, filter, place in a sintering furnace, sinter at 600℃ for 4 h, cool to room temperature, and obtain modified silver powder; the mass ratio of silver powder with nitrogen-doped porous carbon layer, tin chloride pentahydrate, deionized water, and ammonia water is 1:5:60:2.7;

[0109] A3. Modified silver powder and carbon fiber were added to deionized water and ultrasonically treated at 300W for 5 min. Hydrochloric acid with a concentration of 0.1 mol / L was added to adjust the pH to 3. The mixture was stirred and reacted at 80℃ for 40 min. After filtration, the mixture was washed three times with deionized water and dried in an oven at 90℃ for 10 min to obtain composite silver powder. The mass ratio of modified silver powder, carbon fiber and deionized water was 1:0.2:60.

[0110] Comparative Example 4

[0111] The only difference between this comparative example and Example 3 is the preparation of the composite silver powder, as detailed below:

[0112] The composite silver powder is prepared by the following steps:

[0113] A1. Mix a 3% (w / w) aqueous solution of chitin nanocrystals with urea, adjust the pH to 5 with 0.1 mol / L hydrochloric acid, stir at 300 rpm for 45 min, let stand at room temperature for 3 days to separate the layers, take the lower layer solution, and dry it in an oven at 35℃ and 30% humidity for 5 days to obtain a chitin nanocrystal / urea composite; the mass ratio of chitin nanocrystal aqueous solution to urea is 40:0.1.

[0114] Silver powder was added to a 1% sodium carboxymethyl cellulose aqueous solution, ultrasonicated at 300W for 5 min, removed, and dried in an oven at 70℃ for 10 min to obtain pretreated silver powder; the mass ratio of silver powder to sodium carboxymethyl cellulose aqueous solution was 1:100.

[0115] Pretreated silver powder was mixed with chitin nanocrystals / urea composite and stirred at 300 r / min for 30 min. 1 mol / L potassium hydroxide was added and stirred until homogeneous. The mixture was then treated at 700 °C under nitrogen protection for 6 h to obtain silver powder loaded with a nitrogen-doped porous carbon layer. The mass ratio of pretreated silver powder, chitin nanocrystals / urea composite, and potassium hydroxide was 1:0.2:0.1.

[0116] A2. Mix silver powder with nitrogen-doped porous carbon layer, tin chloride pentahydrate, and deionized water, stir evenly, add 10% ammonia water by mass, stir at 80℃ for 40 min, filter, place in a sintering furnace, sinter at 600℃ for 4 h, cool to room temperature, and obtain modified silver powder; the mass ratio of silver powder with nitrogen-doped porous carbon layer, tin chloride pentahydrate, deionized water, and ammonia water is 1:5:60:2.7;

[0117] A3. Add modified silver powder and pyrogallol-modified lignin to deionized water, stir evenly, add 0.1 mol / L hydrochloric acid to adjust the pH to 3, stir and react at 90℃ for 30 min, filter, wash 3 times with deionized water, and dry in an oven at 70℃ for 10 min to obtain composite silver powder; the mass ratio of modified silver powder, pyrogallol-modified lignin and deionized water is 1:0.2:60.

[0118] The performance of the silver alloy materials prepared in Examples 1-3 and Comparative Examples 1-4 was then tested.

[0119] The silver alloy material prepared above has a size of Φ10mm×10mm.

[0120] Resistivity test: The polished bulk samples were tested using an RTS-11 metal four-probe tester. Each sample was measured in parallel 5 times. The resistivity of the bulk material was then calculated using the formulas p=R·2π S and S=1 / S1+2 / S2-1 / (S1+S3)-1 / (S2+S3).

[0121] Where p refers to resistivity, R refers to resistance, S refers to the average spacing between probes, and S1, S2, and S3 refer to the spacing between two adjacent probes in the four metal probes from one end to the other.

[0122] Arc erosion resistance test: The arc erosion resistance of the silver alloy material prepared above was determined according to the JB / T8632-2011 standard. 10,000 opening and closing operations were carried out in a simulated AC switch test platform (voltage 220V, current 10A), and the contact mass loss (unit: mg / thousand times) was measured.

[0123] Vickers hardness test: The Vickers hardness of the silver alloy material prepared above was determined according to GB / T4340.1-2024 standard. The Vickers hardness tester (load 1kg) was used for measurement, and the unit is HV.

[0124] Cyclic life test: In accordance with GB / T2423.22-2012 standard, thermal cycling test was conducted between -40℃ and 200℃, and the number of cycles before the silver alloy material cracked or its performance deteriorated was recorded.

[0125] As shown in Table 1 below.

[0126] Table 1. Performance testing of silver alloy materials prepared in Examples 1-3 and Comparative Examples 1-4

[0127] project resistivity / Ω·m Arc erosion resistance mg / thousand times Vickers hardness / HV Loop count Example 1 <![CDATA[2.25×10 -8 ]]> 1.0 155 8523 Example 2 <![CDATA[2.22×10 -8 ]]> 0.8 158 8525 Example 3 <![CDATA[2.26×10 -8 ]]> 1.1 154 8520 Comparative Example 1 <![CDATA[3.12×10 -8 ]]> 2.0 112 6578 Comparative Example 2 <![CDATA[2.88×10 -8 ]]> 1.6 144 6887 Comparative Example 3 <![CDATA[2.99×10 -8 ]]> 1.2 122 6599 Comparative Example 4 <![CDATA[3.23×10 -8 ]]> 1.8 105 6352

[0128] As can be seen from the data in Table 1, the silver alloy materials prepared in Examples 1-3 have high mechanical strength and resistance to arc erosion.

[0129] In Comparative Example 1, replacing the silver powder with a nitrogen-doped porous carbon layer with composite silver powder prepared from pretreated silver powder resulted in a decrease in the performance of the silver alloy material. This demonstrates that the nitrogen-doped porous carbon layer synthesized on the silver powder surface contains a uniformly distributed pore structure, which serves as a synthesis site for tin dioxide. This allows for the synthesis of a large amount of uniformly distributed tin dioxide on the silver powder surface. Furthermore, the synthesized nitrogen-doped porous carbon layer exhibits high electrical conductivity, which can reduce the resistivity of the silver alloy material. In addition, the nitrogen-doped porous carbon layer possesses excellent high-temperature resistance and mechanical strength, significantly improving the arc erosion resistance and mechanical properties of the silver alloy material.

[0130] In Comparative Example 2, the composite silver powder prepared by replacing the modified silver powder with silver powder loaded with nitrogen-doped porous carbon layers was used to prepare silver alloy materials, and its performance decreased. This proves that the synthesis of tin dioxide in the pores on the surface of silver powder loaded with nitrogen-doped porous carbon layers can improve the arc erosion resistance of silver alloy materials.

[0131] In Comparative Example 3, replacing the functionalized modified silver powder with composite silver powder prepared from modified silver powder resulted in a decrease in the performance of the silver alloy material. This demonstrates that pyrogallol-modified lignin can coat the surface of the modified silver powder, imparting a large number of phenolic hydroxyl groups. This facilitates the formation of cross-linked network carbon fibers on the surface of the modified silver powder, increasing the contact area with the raw materials required for the silver alloy material, improving the density of the silver alloy material, and thus enhancing its mechanical strength and resistance to arc erosion. Furthermore, the thermal decomposition of pyrogallol-modified lignin provides a large amount of carbon elements dispersed at the grain boundaries of the silver alloy material, increasing its density and further improving its mechanical strength and resistance to arc erosion.

[0132] In Comparative Example 4, the composite silver powder prepared without carbon fiber was used to prepare silver alloy materials, resulting in a decrease in performance. This demonstrates that carbon fiber, in a cross-linked structure, coats the surface of the functionalized modified silver powder. The cross-linked network structure of the carbon fiber increases the contact area between the silver powder and the raw materials required for the silver alloy material, improving the density of the silver alloy material. Furthermore, the cross-linked network structure of the carbon fiber can absorb and weaken stress generated by external forces, improving the mechanical strength of the silver alloy material. In addition, the addition of carbon fiber to the silver alloy material can improve its mechanical strength, arc erosion resistance, and cycle stability.

[0133] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0134] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A silver alloy material for electrical contact based on a lamination composite process, characterized by, Its preparation method includes the following steps: S1. The composite silver powder, nickel powder and tungsten powder are mixed and ball-milled to obtain a mixture. The mixture is then pressed and sintered to obtain a silver-based alloy layer. S2. The silver-based alloy layer, the intermediate copper foil layer, and the welding layer iron foil are bonded together from top to bottom. After one cold rolling, the material is subjected to annealing heat treatment, cooled to room temperature, and then subjected to a second cold rolling to obtain the silver alloy material. The composite silver powder is obtained by coating the surface of modified silver powder with pyrogallol-modified lignin and then mixing it with carbon fiber. The modified silver powder is obtained by synthesizing nitrogen-doped porous carbon on the surface of silver powder, and then reacting it with tin chloride pentahydrate and ammonia.

2. The silver alloy material for electrical contact based on a lamination composite process according to claim 1, characterized in that, The composite silver powder is prepared by the following steps: A1. Mix chitin nanocrystal aqueous solution and urea evenly, add hydrochloric acid to adjust pH, stir, let stand at room temperature to separate into layers, take the lower layer solution, dry to obtain chitin nanocrystal / urea composite; add silver powder to sodium carboxymethyl cellulose aqueous solution, sonicate, take out, dry to obtain pretreated silver powder. Pretreated silver powder was mixed with chitin nanocrystals / urea composite, stirred, potassium hydroxide was added, stirred, and treated at 600-700℃ under nitrogen protection for 4-6 hours to obtain silver powder loaded with nitrogen-doped porous carbon layer. A2. Mix silver powder loaded with nitrogen-doped porous carbon layer, tin chloride pentahydrate and deionized water, stir evenly, add ammonia water, stir at 70-80℃ for 30-40 min, filter, place in sintering furnace, sinter at 500-600℃ for 3-4 h, cool to room temperature to obtain modified silver powder. A3. Add modified silver powder and pyrogallol-modified lignin to deionized water, stir evenly, add hydrochloric acid to adjust the pH, stir and react at 80-90℃ for 20-30 min, filter, wash and dry to obtain functionalized modified silver powder. A4. Functionalized silver powder and carbon fiber are added to deionized water, ultrasonically treated, and hydrochloric acid is added to adjust the pH. The mixture is stirred at 70-80℃ for 30-40 minutes, filtered, washed, and dried to obtain composite silver powder.

3. The silver alloy material for electrical contact based on a lamination composite process according to claim 2, characterized in that, In step A1, the mass ratio of the chitin nanocrystal aqueous solution to urea is (35-40):(0.08-0.1); In step A1, the mass ratio of the silver powder to the sodium carboxymethyl cellulose aqueous solution is 1:(80-100); In step A1, the mass ratio of the pretreated silver powder, chitin nanocrystals / urea composite and potassium hydroxide is 1:(0.1-0.2):(0.06-0.1).

4. The silver alloy material for electrical contact based on a lamination composite process according to claim 2, characterized in that, In step A2, the mass ratio of silver powder, tin chloride pentahydrate, deionized water and ammonia water supporting the nitrogen-doped porous carbon layer is 1:(4.8-5):(50-60):(2.5-2.7).

5. The silver alloy material for electrical contact based on a lamination composite process according to claim 2, characterized in that, In step A3, the mass ratio of the modified silver powder, pyrogallol-modified lignin, and deionized water is 1:(0.1-0.2):(50-60).

6. The silver alloy material for electrical contact based on a lamination composite process according to claim 2, characterized in that, In step A4, the mass ratio of the functionalized modified silver powder, carbon fiber and deionized water is 1:(0.1-0.2):(50-60).

7. The silver alloy material for electrical contact based on a lamination composite process according to claim 1, characterized in that, In step S1, the mass ratio of the composite silver powder, nickel powder, and tungsten powder is 1:(0.2-0.3):(0.4-0.6); In step S1, the ball milling is carried out using a ball mill, the ball material is tungsten carbide with a diameter of 5-10 mm, the ball-to-material ratio in the ball mill is (5-10):1, the rotation speed is 1000-1200 r / min, and the ball milling time is 2-3 h.

8. The silver alloy material for electrical contact based on a lamination composite process according to claim 1, characterized in that, In step S1, the pressing pressure is 300-400 MPa, and the pressing time is 4-5 min; In step S1, the sintering specifically involves: heating to 400-450℃ at a rate of 4-6℃ / min and holding for 1-1.5h, then continuing to heat to 800-850℃ at a rate of 7-9℃ / min and holding for 1.5-2.5h.

9. The silver alloy material for electrical contact based on a lamination composite process according to claim 1, characterized in that, In step S2, the rolling speed of the first cold rolling is 3-5 m / min, and the reduction rate is 40-50%; the rolling speed of the second cold rolling is 45-55 m / min, and the reduction rate is 50-60%. In step S2, the annealing heat treatment is specifically: the annealing temperature is 400-450℃, the annealing atmosphere is argon, the argon flow rate is 0.4-0.6m 3 / h.

10. The silver alloy material for electrical contact based on a lamination composite process according to claim 1, characterized in that, In step S2, the thickness of the welding layer iron foil is 0.6-1.8 mm; the thickness of the intermediate layer copper foil is 3-4.2 mm; and the thickness of the silver-based alloy layer is 1.5-2.4 mm.