Silver-tungsten composite electric contact material and preparation method and application thereof

Abstract

The invention discloses a silver-tungsten composite electric contact material and a preparation method and application thereof. The silver-tungsten composite contact material is obtained by directly curing nano tungsten-silver powder with a core-shell structure at high temperature through an electric spark plasma sintering technology, wherein the silver-tungsten composite contact material is composed of nanoscale tungsten and silver particles; the preparation method comprises the following steps: introducing a silver nanoparticle metal shell layer on the surface of a nano tungsten particle through a two-step chemical plating means to obtain nano tungsten-silver powder, and then directly curing the nano tungsten-silver powder at high temperature by adopting an electric spark plasma sintering technology under a vacuum condition. The silver-tungsten composite contact material provided by the invention has excellent physical properties and excellent arc erosion resistance, and has a uniform and compact microstructure.

Description

Technical Field

[0001] The present invention belongs to the field of low-voltage electrical contact and relates to a silver-tungsten composite electrical contact material and a preparation method and application thereof. Background Art

[0002] Electrical contact refers to the state of contact between current-carrying components in electrical / electronic equipment, ensuring circuit continuity and enabling the flow of current. In modern civilization, all power transmission, distribution, control processes, and information exchange rely on the exchange of electrical signals and the occurrence of at least one electrical contact event. Therefore, electrical contacts, as key current-carrying components in the electrical contact process, play a crucial role in controlling the flow of current and bearing loads in circuits. They are widely used in power transmission, electronic equipment, aerospace, 5G communications, high-speed rail, integrated circuits, micro-electromechanical systems, semiconductor manufacturing, and other fields. As the core of electrical contacts, the performance and stability of electrical contact materials determine the operational reliability and safety of electronic / circuit systems. Failure to do so can lead to electrical contact failures, resulting in serious consequences such as urban power outages, communication system failures, and even aircraft and spacecraft crashes. Therefore, the development and application of safe and reliable electrical contact materials are of great significance to the development of my country's basic power infrastructure and high-end intelligent manufacturing.

[0003] For applications in the field of electrical and electronic devices, tungsten phase-reinforced metal matrix composites as electrical contacts need to have excellent comprehensive properties, such as arc resistance, anti-welding, high electrical conductivity, high thermal conductivity, high hardness, and high strength. The metal matrix (silver or copper) provides excellent electrical and thermal conductivity, and the reinforcing phase tungsten provides excellent mechanical properties, arc erosion resistance, and anti-welding performance. However, the silver-tungsten composite electrical contact materials prepared by the traditional infiltration method have the following two practical problems: (1) The physical properties of the two components of silver and tungsten are very different, resulting in poor uniformity of the material structure during processing; (2) During the high-temperature arc erosion process, the external tungsten skeleton is easily oxidized, resulting in increased contact resistance on the contact surface and shortened service life. Based on the above two practical application problems, in order to improve the comprehensive performance of tungsten phase-reinforced metal composites, a large number of studies have focused on the optimization of microstructure, composition, and interface structure, but it is difficult to achieve a balance between various physical properties and arc performance to achieve excellent comprehensive performance.

[0004] Therefore, the prior art lacks a new type of silver-tungsten composite point contact material with synergistically enhanced physical properties and arc erosion resistance and its corresponding preparation process. Summary of the Invention

[0005] In order to solve the problems existing in the background technology, the main purpose of the present invention is to provide a silver-tungsten composite electrical contact material, a preparation method and an application, in the hope of improving the above-mentioned problems existing in the silver-tungsten composite electrical contact material, and having excellent physical properties and excellent anti-arc erosion performance.

[0006] The present invention develops a new type of silver-tungsten composite point contact material with synergistically enhanced physical properties and arc erosion resistance and its corresponding preparation process, which is of great significance for saving precious metal resources, improving the service stability and service life of electrical contacts, and maintaining efficient and stable operation of power transmission and electronic circuit systems.

[0007] To this end, the above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0008] 1. A silver-tungsten composite electrical contact material:

[0009] The silver-tungsten composite contact material is mainly composed of nano-scale tungsten and silver particles / powders and has a uniform and dense microstructure.

[0010] 2. A method for preparing a silver-tungsten composite electrical contact material, the method comprising the following steps:

[0011] S1. A small amount of silver nanoparticle seeds are first introduced onto the surface of the nano-tungsten powder by performing chemical plating in an aqueous solution system under mild conditions;

[0012] The silver nanoparticle seed crystals account for about 5% of the mass of the nano-tungsten powder.

[0013] Then, silver nanoparticles are grown around the silver nanoparticle seed crystals to further obtain nano-tungsten powder coated with silver nanoparticles;

[0014] S2. Sintering the nano-tungsten powder by electric spark plasma, sintering and solidifying the nano-tungsten powder under high temperature, high pressure and vacuum conditions to obtain a silver-tungsten composite electrical contact material.

[0015] Before step S1, the nano-tungsten powder is subjected to immersion sensitization treatment using hydrochloric acid and stannous chloride dihydrate aqueous solution.

[0016] The nano tungsten powder is obtained by crushing tungsten metal into nano-scale particle powder, specifically about 220nm.

[0017] In step S1, a small amount of silver nanoparticle seeds are introduced by adding silver nitrate as a silver source, ammonia water as a complexing agent, polyvinyl pyrrolidone as a dispersant, sodium hydroxide aqueous solution as a pH regulator, and glucose as a reducing agent into an aqueous solution for reaction modification, thereby introducing silver nanoparticle seeds on the surface of the nano-tungsten powder.

[0018] The amount of silver nitrate used is 0.85-1.7 g, the amount of ammonia water used is 2-4 mL, the amount of polyvinyl pyrrolidone used is 0.1-0.2 g, the amount of glucose used is 0.35-0.7 g, the mass of nano-tungsten powder is 2-10 g, the pH value of the solution is adjusted to between 11 and 11.5 using sodium hydroxide aqueous solution, and the aqueous solution is placed in a water bath environment and magnetically stirred. The reaction water bath temperature is 40° C. and the magnetic stirring speed is 500 rpm.

[0019] In step S1, silver nanoparticles are grown around the silver nanoparticle seed crystals. Specifically, silver nitrate is used as a silver source, ammonia water is used as a complexing agent, polyvinyl pyrrolidone is used as a dispersant, sodium hydroxide aqueous solution is used as a pH adjuster, glucose is used as a reducing agent, and anhydrous ethanol is used as a dispersant, and the silver nanoparticles are coated on the surface of the silver nanoparticle seed crystals of the nano-tungsten powder.

[0020] The mass of the nano-tungsten powder introduced with the silver nanoparticle seed crystal is 4-15 g, the amount of silver nitrate is 4.2-5.1 g, the amount of ammonia water is 10-15 mL, the amount of polyvinyl pyrrolidone is 0.3-0.8 g, and the amount of glucose is 2.2-3.2 g. The pH value of the solution is adjusted to between 11 and 11.5 using a sodium hydroxide aqueous solution, and the aqueous solution is placed in a water bath environment and magnetically stirred. The reaction water bath temperature is 40° C. and the magnetic stirring speed is 500 rpm.

[0021] As a preferred technical solution of the present invention: after step S1 and before step S2, after the surface of the nano-tungsten powder into which the silver nano-particle seeds are introduced is coated with silver nano-particles, the powder is filtered, washed with water, and vacuum dried in sequence. The vacuum drying temperature is 40° C., and the vacuum drying time is 12 hours.

[0022] In step S2, a graphite mold with an inner diameter of 20 mm is used, and the sintering is carried out in an electric spark plasma sintering furnace under high temperature and high pressure vacuum conditions of 900°C and 100 MPa, and the sintering holding time is 10 minutes.

[0023] The silver-tungsten composite electrical contact material is used to make electrical contacts.

[0024] The present invention provides a preparation method of a silver-tungsten composite electrical contact material, an electrical contact material, and an application of an electrical contact. The method adopts a grain refinement strategy and coats silver nanoparticles on the surface of nano-tungsten powder by a two-step chemical plating method, or introduces a silver nanoparticle metal shell layer on the surface of the nano-tungsten particles to obtain a silver-tungsten composite powder / nano-tungsten-silver powder. The obtained silver-tungsten composite powder / nano-tungsten-silver powder is then sintered and solidified at high temperature by an electric spark plasma sintering technology to obtain a silver-tungsten composite electrical contact material.

[0025] The silver-tungsten composite contact material of the present invention is obtained by directly high-temperature solidifying nano-tungsten-silver powder with a core-shell structure through electric spark plasma sintering technology, wherein the silver-tungsten composite contact material is composed of nano-scale tungsten and silver particles and has a uniform and dense microstructure.

[0026] The beneficial effects of the present invention are:

[0027] The silver-tungsten composite electrical contact material provided by the present invention has a uniform structure and achieves synergistic enhancement of physical properties and arc erosion resistance, such as excellent conductivity, high Vickers hardness, good compressive resistance and excellent arc erosion resistance.

[0028] The silver nanoparticles on the outside of the nano-tungsten particles of the present invention form a continuous three-dimensional conductive silver network after crystallization and solidification under high temperature conditions, thereby ensuring the excellent conductive performance of the material; the nano-tungsten particles uniformly dispersed in the silver matrix provide the material with high Vickers hardness; under the action of load, the increase in dislocation density inside the tungsten particles and the emergence of a silver twin stress buffer layer provide beneficial conditions for the compressive strength and fracture toughness of the material; during the arc erosion process, the nano-tungsten particles uniformly deposited and dispersed in the silver molten pool play an important role in increasing the viscosity of the silver molten pool, increasing its flow resistance and reducing the flow splashing loss of the silver molten pool. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The particle size distribution diagrams of the two tungsten powders used in the present invention are as follows: (a) is the particle size distribution diagram of micron-sized tungsten powder (CG W), and (b) is the particle size distribution diagram of nano-sized tungsten powder (UFG W).

[0030] Figure 2 Field emission scanning electron micrographs of the silver nanoparticle-coated tungsten powder prepared in the present invention, (a, b) are micron-sized tungsten powders with silver nanoparticle seeds introduced (CG W-Ag-seed), (c, d) are micron-sized tungsten powders with silver nanoparticle seeds introduced (CG W@30Ag), (e, f) are nanoscale tungsten powders with silver nanoparticle seeds introduced (UFG W-Ag-seed), (g, h) (i, j) (k, l) are nanoscale tungsten powders UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag, respectively.

[0031] Figure 3 (a) is the XRD pattern of CG W@30Ag, UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag powders prepared in the present invention, and (b) is the silver content in CG W@30Ag, UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag powders detected by ICP-OES.

[0032] Figure 4 Field emission scanning electron microscope photos of the silver-tungsten composite electrical contact materials prepared in the present invention, (a, b), (c, d), (e, f), and (g, h) are CG W@30Ag, UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag composite electrical contact materials, respectively.

[0033] Figure 5 The electron backscattered diffraction (EBSD) test results of the UFG W@30Ag composite electrical contact material prepared in the present invention, (a) is the element surface distribution map, (b) is the inverse pole figure, (c) is the phase distribution map, and (d) is the grain size distribution map.

[0034] Figure 6 (a) is the XRD pattern of the CG W@30Ag, UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag composite electrical contact materials prepared in the present invention, (b) is the microhardness test results of the CG W@30Ag, UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag composite electrical contact materials prepared in the present invention, (c) is the conductivity test results of the CG W@30Ag, UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag composite electrical contact materials prepared in the present invention, (d) is the uniaxial compression test results of the CG W@30Ag, UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag composite electrical contact materials prepared in the present invention.

[0035] Figure 7 Arc erosion results of the CG W@30Ag, UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag composite electrical contact materials prepared in the present invention, (a) is the mass loss and mass loss rate of the cathode contact, (b) is the number of effective operations, (c) is the XRD pattern of the corroded surface of the electrical contact after arc erosion, and (d) is the mass loss of the anode contact. DETAILED DESCRIPTION

[0036] The present invention will be further described below with reference to the accompanying drawings and specific implementations.

[0037] According to the solution of the present invention, the preparation method of the silver-tungsten composite electrical contact material of the embodiment is to conduct a test experiment by the following steps:

[0038] 1) In an aqueous solution, polyvinyl pyrrolidone, silver nitrate, and ammonia water (AR) are dissolved in deionized water, respectively. Subsequently, the silver ammonia solution is slowly added to the glucose aqueous solution containing nano-tungsten powder while stirring under heating conditions in a water bath. The reaction is carried out for about 30 minutes. After standing for a period of time, vacuum filtration, washing, and vacuum drying are performed to obtain nano-scale tungsten powder (UFG W-Ag-seed) introduced with silver nanoparticle seeds.

[0039] In the above step 1), the amount of deionized water solvent in the silver ammonia solution is 200-400 mL, the amount of silver nitrate is 0.85-1.7 g, the amount of polyvinyl pyrrolidone is 0.1-0.2 g, and the amount of ammonia water is 2-4 mL; the mass of tungsten powder added to the glucose solution is 2-10 g; the amount of deionized water solvent in the glucose solution is 300-600 mL, the amount of glucose is 0.35-0.7 g, and the pH value of the solution is between 11-11.5; the specific time for slowly adding the silver ammonia solution is 2-10 minutes; the specific conditions of the reaction are that the water bath temperature is 40°C and the speed of magnetic stirring is 500 rpm; the filter residue is washed with deionized water 3 times in the vacuum filtration step; the vacuum drying temperature is 40°C and the drying is carried out for 12 hours.

[0040] 2) In an aqueous solution, polyvinyl pyrrolidone, silver nitrate, and ammonia (AR) were dissolved in deionized water. The silver ammonia solution was then slowly added to the glucose water and ethanol solutions containing UFG W-Ag-seed while stirring in a water bath. The reaction lasted approximately 30 minutes. The mixture was allowed to stand for a period of time, and then vacuum filtered, washed, and dried to obtain nanoscale tungsten powders coated with silver nanoparticles at different contents (UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag). UFG represents ultrafine grains, and W@20Ag indicates that the tungsten particles are coated with 20% silver particles by mass.

[0041] In the above step 2), the amount of deionized water solvent in the silver ammonia solution is 200-400 mL, the amount of silver nitrate is 4.2-5.1 g, the amount of polyvinyl pyrrolidone is 0.3-0.8 g, and the amount of ammonia water is 10-15 mL; the mass of tungsten powder added to the glucose solution is 4-15 g; the amount of deionized water solvent in the glucose solution is 300-600 mL, the amount of anhydrous ethanol solvent is 100-200 mL, the amount of glucose is 2.2-3.2 g, and the pH value of the solution is between 11-11.5; the specific time for slowly adding the silver ammonia solution is 2-10 minutes; the specific conditions of the reaction are that the water bath temperature is 40°C and the speed of magnetic stirring is 500 rpm; the filter residue is washed with deionized water 3 times in the vacuum filtration step; the vacuum drying temperature is 40°C and the drying is carried out for 12 hours.

[0042] 3) The nano-tungsten powders in steps 1) and 2) were replaced with micron-sized tungsten powder. Using the same technical route and parameters, a micron-sized tungsten powder seeded with silver nanoparticles (CG W-Ag-seed, intermediate product) was prepared. Furthermore, a micron-sized tungsten powder coated with silver nanoparticles (CG W@30Ag) was obtained, which serves as the control group. CG represents coarse grains.

[0043] 4) The silver metal nanoparticle-coated tungsten powder prepared by the electroless plating method in steps 1), 2), and 3) is placed in a graphite mold, and the CG W@30Ag, UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag powders are cured at high temperature using an electric spark plasma sintering method to obtain a series of silver-tungsten composite electrical contact materials (CG W@30Ag-ECMs, UFG W@20Ag-ECMs, UFG W@30Ag-ECMs, and UFG W@40Ag-ECMs). -ECMs represents electrical contact materials.

[0044] In the above step 4), the inner diameter of the graphite mold is 20 mm; the processing temperature is 900° C., the applied pressure is 100 MPa; and the holding time is 10 minutes.

[0045] The embodiments of the present invention are as follows:

[0046] Example 1:

[0047] In an aqueous solution system, 0.1g (0.2g / L) of polyvinyl pyrrolidone (K60), 0.85g (1.7g / L) of silver nitrate, and 2mL (4ml / L) of ammonia were added to a beaker containing 200mL of deionized water to prepare a silver-ammonia solution. To a round-bottom flask containing 300mL of deionized water, 0.35g (0.7g / L) of glucose and 10g of nano-tungsten powder were added and ultrasonicated for 10 minutes. Then, 200mL of the silver-ammonia solution was slowly added in a 40°C water bath at 500rpm (addition completed within 5 minutes). After approximately 30 minutes of reaction, the mixture was allowed to stand for a period of time. The mixture was then vacuum filtered, washed, and dried to obtain nanoscale tungsten powder (UFG W-Ag-seed) incorporating silver nanoparticle seeds. The nano-tungsten powder was replaced with micron-sized tungsten powder and the above experimental process was repeated to obtain micron-sized tungsten powder (CG W-Ag-seed) incorporating silver nanoparticle seeds.

[0048] The particle size distribution of the two tungsten powders used in the experiment is as follows: Figure 1 As shown, the average particle size of the nano-scale tungsten powder is 226.441nm, and the average particle size of the micron-scale tungsten powder is 8.926μm. The obtained UFG W-Ag-seed and CG W-Ag-seed powders were tested by field emission scanning electron microscopy, and the results are shown in Figure 2. Figure 2 As shown in a, b, e, and f, the surface of the micron-sized tungsten particles in the CG W-Ag-seed powder is uniformly coated with a layer of silver nanoparticles with a particle size of 50-200 nm ( Figure 2 a, b); In the UFG W-Ag-seed powder, tiny silver nanoparticles are evenly distributed on the surface of the nanoscale tungsten particles, and a small amount of silver nanoparticles are also agglomerated around the tungsten particles ( Figure 2 e,f).

[0049] Example 2

[0050] In an aqueous solution system, 0.5 g (0.5 g / L) of polyvinyl pyrrolidone (K60), 4.25 g (4.25 g / L) of silver nitrate, and 12 mL (12 mL / L) of ammonia were added to a beaker containing 400 mL of deionized water to prepare a silver ammonia solution. To a round-bottom flask containing a mixed solvent of 500 mL of deionized water and 100 mL of anhydrous ethanol, 2.25 g (2.25 g / L) of glucose and 7.56 g of UFG W-Ag-seed powder were added and ultrasonicated for 10 minutes. Then, 400 mL of the silver ammonia solution was slowly added in a 40°C water bath at 500 rpm (addition completed within 5 minutes). After reacting for approximately 30 minutes, the mixture was allowed to stand for a period of time, vacuum filtered, washed, and vacuum dried to obtain nanoscale tungsten powder containing 30 wt.% silver nanoparticles (UFG W@30Ag). By varying the amount of UFG W-Ag-seed powder to 13.56g and 4.67g, nanoscale tungsten powders coated with 20wt.% silver nanoparticles (UFG W@20Ag) and 40wt.% silver nanoparticles (UFG W@40Ag) were obtained. Micron-sized tungsten powder coated with 30wt.% silver nanoparticles (CG W@30Ag) was obtained by replacing the nano-tungsten powder with micron-sized tungsten powder and repeating the above experimental process.

[0051] The obtained CG W@30Ag, UFG W@20Ag, UFG W@30Ag and UFG W@40Ag powders were tested by field emission scanning electron microscopy. Figure 2 As shown in c, d, and g1, the micron-sized tungsten particles in CG W@30Ag are uniformly wrapped by silver nanoparticles, and needle-shaped leaf-shaped aggregates formed by stacking silver nanoparticles exist around the tungsten particles ( Figure 2 c, d); in UFGW@20Ag( Figure 2 g,h)、UFG W@30Ag( Figure 2 i,j) and UFG W@40Ag( Figure 2In (k, l), the tungsten nanoparticles are uniformly wrapped by the silver nanoparticles, and as the silver content increases, the silver nanoparticle aggregates around the tungsten particles gradually increase.

[0052] The obtained CG W@30Ag, UFG W@20Ag, UFG W@30Ag and UFG W@40Ag powders were subjected to XRD test. The results are as follows: Figure 3 As shown in (a), CG W@30Ag, UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag powders all contain only characteristic peaks of tungsten and silver, corresponding to standard cards PDF#04-0806 (W, 2θ = 40.264°, 58.274°, 73.195°, and 87.021°) and PDF#04-0783 (Ag, 2θ = 38.116°, 44.277°, 64.426°, and 77.472°), respectively. Furthermore, for the XRD spectra of UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag powders, with the increase of silver content, the intensity of the characteristic peak of tungsten gradually weakens, while the intensity of the characteristic peak of silver gradually increases.

[0053] The obtained CG W@30Ag, UFG W@20Ag, UFG W@30Ag and UFG W@40Ag powders were subjected to ICP-OES test, and the results were as follows: Figure 3 As shown in Figure 2b, the silver contents in CG W@30Ag, UFG W@20Ag, UFG W@30Ag and UFG W@40Ag powders are 29.85wt.%, 19.57wt.%, 29.64wt.% and 40.40wt.%, respectively, which are close to the theoretical values ​​of the feed ratios in Examples 1 and 2.

[0054] Test 1:

[0055] 55 g of UFG W@30Ag powder was placed in a graphite mold with an inner diameter of 20 mm. The powder was heated to 900 °C at a heating rate of 100 °C / min under vacuum conditions at a pressure of 100 MPa and kept at this temperature for 10 min. The powder was then cooled to room temperature to obtain a W-30Ag composite material with refined grains, named UFG W@30Ag-ECMs.

[0056] By changing the type of W@Ag powder, UFG W@20Ag, UFG W@40Ag, and CG W@30Ag were treated in the same way as above to obtain UFG W@20Ag-ECMs, UFG W@40Ag-ECMs, and CG W@30Ag-ECMs, respectively.

[0057] The obtained CG W@30Ag-ECMs, UFG W@20Ag-ECMs, UFG W@30Ag-ECMs, and UFG W@40Ag-ECMs were tested by field emission scanning electron microscopy. Figure 4 As shown, the tungsten phase shows a higher contrast due to the larger atomic number of tungsten. Figure 4 The white area in the graph is the silver phase, and the dark gray area is the silver phase. Figure 4 In a, b), the tungsten particles are relatively evenly dispersed in the Ag aggregate, but aggregation of tungsten particles will occur, and there will be a large number of micropores at the interface between the silver phase and the tungsten phase ( Figure 4 b white arrow), but can also form a relatively continuous silver phase three-dimensional network structure; in contrast, UFG W@20Ag-ECMs ( Figure 4 In (c, d), the ultrafine tungsten particles are evenly dispersed in the Ag matrix, the interface between the silver and tungsten phases is obvious and the micropores are very few, but a small amount of tungsten particles will aggregate to form a tungsten-rich area. As the silver content increases to 30wt%, in UFG W@30Ag-ECMs ( Figure 4 In (e, f), the interface between the ultrafine tungsten powder and the Ag phase is clearer and free of voids, but a small amount of silver-rich regions appear, and the size of the silver-rich regions is only a few hundred nanometers, which is much smaller than that in the CG W@30Ag composites. When the silver content is further increased to 40wt%, ... the interface between the ultrafine tungsten powder and the Ag phase is clearer and free of voids, and the interface between the ultrafine tungsten powder and the Ag phase is clearer and free of voids, Figure 4 e, f), the microstructure heterogeneity increases, and more micropores appear ( Figure 4 g,h) Larger areas of tungsten-rich and silver-rich regions.

[0058] The obtained UFG W@30Ag-ECMs were subjected to electron backscatter diffraction (EBSD) test, and the results are as follows: Figure 5 As shown in Figure 2, in UFGW@30Ag-ECMs, the particle size of tungsten particles is maintained between 200-300 nm. Compared with the initial UFGW powder particles, the size of tungsten particles does not increase significantly after rapid sintering, and the average particle size of the grains is 230 nm ( Figure 4 d); and silver and tungsten are evenly distributed in UFGW@30Ag-ECMs ( Figure 4 c), forming a three-dimensional continuous silver conductive network ( Figure 4 a); In addition, the grains in UFGW@30Ag-ECMs have no specific orientation.

[0059] The obtained CG W@30Ag-ECMs, UFG W@20Ag-ECMs, UFG W@30Ag-ECMs and UFG W@40Ag-ECMs were subjected to XRD test. Figure 6As shown in a,

[0060] Test 2:

[0061] The silver-tungsten composite contact material was cut into 5×5×5mm cubes by wire cutting, resin-mounted at 156°C, and polished with 600-grit, 1000-grit, and 2000-grit sandpaper in sequence. It was then polished on a polishing machine with diamond polishing paste. The Vickers hardness of the material was tested using a microhardness tester under a load of 500g for 15 seconds. The electrical conductivity of the material was tested using a metal four-probe resistivity tester at room temperature. The results are shown in Figure 2. Figure 6 As shown in b and c, the hardness of the control group CG W@30Ag-ECMs is 154.98HV; when the silver content increases from 20wt%, 30wt%, and 40wt%, the hardness of UFG W-Ag decreases from 331.69HV, 265.16HV, and 181.58HV, which is mainly attributed to the grain refinement effect of metal tungsten and silver ( Figure 6 b) From Figure 6 As shown in Figure 3, the electrical conductivity of CG W@30Ag-ECMs is 39.37% IACS. When the silver content increases from 20wt%, 30wt%, and 40wt%, the conductivity of UFG W-Ag-ECMs increases from 8.08% IACS, 15.71% IACS, and finally 28.00% IACS. The conductivity variation of UFG W-Ag-ECMs conforms to the general rule that, for composites with the same structure, the conductivity increases with the content of the more conductive component. However, even at a silver content of 40wt%, the conductivity of UFG W@40AgECMs does not exceed that of CG W@30Ag-ECMs with only 30wt%. This is primarily due to the increased grain boundaries after grain refinement, which leads to enhanced interface scattering and increased resistance to the directional movement of free electrons.

[0062] The compression test was carried out on a Φ3×5mm cylinder using an electronic universal testing machine at a compression rate of 0.01mm / min. The results are as follows: Figure 6As shown in Figure d, CG W@30Ag-ECMs exhibited a low compressive strength of 490 MPa and a high fracture deformation rate of 21%, while UFG W@40Ag-ECMs exhibited a low compressive strength of 465 MPa and a high fracture deformation rate of 16.37%. Both exhibited good plastic deformation. UFG W@30Ag-ECMs exhibited a high compressive strength of 892 MPa and a low fracture deformation rate of 5.33%, while UFG W@20Ag-ECMs exhibited a high compressive strength of 723 MPa and a low fracture deformation rate of 4.13%. Both exhibited almost no plastic deformation. The compressive strength of UFG W@30Ag-ECMs was 1.8 times that of CG W@30Ag-ECMs, but their fracture toughness was significantly weakened. This indicates that grain refinement can significantly improve the material's compressive strength while also significantly weakening its fracture toughness, in accordance with the Hall-Petch rule.

[0063] Test 3:

[0064] The arc erosion resistance of the silver-tungsten composite contact material prepared above was investigated. A rivet-shaped composite silver-tungsten composite contact material was obtained through a turning process and welded to a copper sheet. Arc erosion resistance tests were conducted in air using a JF04D electrical contact test system under an AC current mode of 250V, 25A, 1s ON, 1s OFF, with the copper as the moving contact (anode) and the silver-tungsten composite contact material as the static contact (cathode), with a distance of 2mm between the two contacts.

[0065] from Figure 7 The results show that the effective arc erosion times of CG W@30Ag-ECMs, UFG W@20Ag-ECMs, UFG W@30Ag-ECMs and UFGW@40Ag-ECMs are 2378, 1125, 2230 and 2705 respectively. Figure 7 b); the mass losses after arc erosion for their respective effective times were 10.8 mg, 9.8 mg, 7.7 mg and 8.6 mg respectively; the mass loss rates were 0.83%, 0.80%, 0.60% and 0.70% respectively ( Figure 7 a); the average contact resistances were 0.027Ω, 0.051Ω, 0.109Ω and 0.058Ω respectively; and the welding force F during arc erosion welding For UFG W-Ag-ECMs, as the silver content increases, the effective arc erosion times of the material increase, that is, the service life of the contact material is extended; the arc duration and arc energy within the same arc erosion times decrease, and are smaller than those of the control group CG W@30Ag-ECMs. Figure 7Figure c depicts the XRD spectra of the corroded contact surfaces after arc erosion. The corroded surfaces of the CG W@30Ag, UFG W@20Ag, UFG W@30Ag, and UFG W@40Ag composite contact materials all contain silver, tungsten, tungsten oxide, and copper oxide, corresponding to standard cards PDF#04-0786 (Ag), PDF#04-0806 (W), PDF#86-0134 (WO2), and PDF#44-0706 (CuO), respectively. For the UFG W-Ag-ECMs, the intensities of the characteristic peaks corresponding to Ag and WO2 gradually decrease with increasing silver content, indicating a decrease in the degree of oxidation of the tungsten particles on the corroded surfaces of the contact materials.

[0066] At the same time, according to the mass loss characteristics of the cathode and the anode, it can be judged that the arc erosion material transfer direction of the silver-tungsten composite contact material prepared by the present invention is from the cathode to the anode.

[0067] The above-mentioned specific implementation methods are used to illustrate the present invention and are only preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit of the present invention and the scope of protection of the claims shall fall within the scope of protection of the present invention.

Claims

1. A silver-tungsten composite electrical contact material, characterized by: The silver-tungsten composite contact material is mainly composed of nano-scale tungsten and silver particles / powder.

2. A method for preparing a silver-tungsten composite electrical contact material, characterized in that: The method comprises the following steps: S1. Electroless plating is performed in an aqueous solution under mild conditions to introduce a small amount of silver nanoparticle seeds onto the surface of the nano-tungsten powder; silver nanoparticles are then grown around the silver nanoparticle seeds to obtain silver nanoparticle-coated nano-tungsten powder; S2. Sintering the nano-tungsten powder by electric spark plasma, sintering and solidifying it under high temperature, high pressure and vacuum conditions to obtain a silver-tungsten composite electrical contact material.

3. The method for preparing a silver-tungsten composite electrical contact material according to claim 1, characterized in that: Before step S1, the nano-tungsten powder is sensitized using hydrochloric acid and stannous chloride dihydrate aqueous solution.

4. The method for preparing a silver-tungsten composite electrical contact material according to claim 1, characterized in that: In step S1, a small amount of silver nanoparticle seeds are introduced by adding silver nitrate as a silver source, ammonia water as a complexing agent, polyvinyl pyrrolidone as a dispersant, sodium hydroxide aqueous solution as a pH regulator, and glucose as a reducing agent into an aqueous solution for reaction modification, thereby introducing silver nanoparticle seeds on the surface of the nano-tungsten powder.

5. The method for preparing a silver-tungsten composite electrical contact material according to claim 4, characterized in that: The amount of silver nitrate used is 0.85-1.7 g, the amount of ammonia water used is 2-4 mL, the amount of polyvinyl pyrrolidone used is 0.1-0.2 g, the amount of glucose used is 0.35-0.7 g, the mass of nano-tungsten powder is 2-10 g, and the pH value of the solution is adjusted to between 11 and 11.5 using sodium hydroxide aqueous solution. The aqueous solution is placed in a water bath environment and magnetically stirred. The water bath temperature is 40° C. and the magnetic stirring speed is 500 rpm.

6. The method for preparing a silver-tungsten composite electrical contact material according to claim 1, characterized in that: In step S1, silver nanoparticles are grown around the silver nanoparticle seed crystals. Specifically, silver nitrate is used as a silver source, ammonia water is used as a complexing agent, polyvinyl pyrrolidone is used as a dispersant, sodium hydroxide aqueous solution is used as a pH adjuster, glucose is used as a reducing agent, and anhydrous ethanol is used as a dispersant, and the silver nanoparticles are coated on the surface of the silver nanoparticle seed crystals of the nano-tungsten powder.

7. The method for preparing a silver-tungsten composite electrical contact material according to claim 6, characterized in that: The mass of the nano-tungsten powder introduced with the silver nanoparticle seed crystal is 4-15 g, the amount of silver nitrate is 4.2-5.1 g, the amount of ammonia water is 10-15 mL, the amount of polyvinyl pyrrolidone is 0.3-0.8 g, and the amount of glucose is 2.2-3.2 g. The pH value of the solution is adjusted to between 11 and 11.5 using a sodium hydroxide aqueous solution, and the aqueous solution is placed in a water bath environment with magnetic stirring. The water bath temperature is 40° C. and the magnetic stirring speed is 500 rpm.

8. The method for preparing a silver-tungsten composite electrical contact material according to claim 1, characterized in that: After step S1 and before step S2, after the surface of the nano-tungsten powder into which the silver nano-particle seeds are introduced is coated with the silver nano-particles, the powder is filtered, washed with water, and vacuum dried in sequence. The vacuum drying temperature is 40° C., and the vacuum drying time is 12 hours.

9. The method for preparing a silver-tungsten composite electrical contact material according to claim 1, characterized in that: In step S2, a graphite mold is used, and the sintering time is 10 minutes under high temperature, high pressure and vacuum conditions with a processing temperature of 900° C. and a pressure of 100 MPa.

10. Use of the silver-tungsten composite electrical contact material according to claim 1 or the silver-tungsten composite electrical contact material prepared by the preparation method according to any one of claims 2 to 9, characterized in that: Application in the production of electrical contacts.

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