A silver-nickel composite tin oxide electrical contact material and its preparation method

Abstract

This invention provides a silver-nickel composite tin oxide electrical contact material and its preparation method. The method involves forming a zinc oxide shell on the surface of tin oxide to prepare a core-shell structured composite tin oxide, preventing contact between tin oxide and nickel. This fundamentally avoids the redox reaction between nickel and tin oxide under high-temperature conditions, significantly improving the material's conductivity and arc erosion resistance. Through a rapid discharge plasma sintering process, high-energy particles generated by the discharge impact the contact areas between particles, causing the material to evaporate and purify and activate, greatly improving the sintering density of the ingot. By adding high-melting-point oxide additives, the material's resistance to welding and burn-off is improved, and the coordinated plastic deformation of silver and nickel during extrusion and subsequent drawing processes is blocked, resulting in a more uniform and granular distribution of nickel in the longitudinal direction. This further enhances the material's resistance to welding and burn-off, giving the prepared electrical contact material excellent electrical properties.

Description

Technical Field

[0001] This invention relates to the field of electrical contact materials, specifically a silver-nickel composite tin oxide electrical contact material and its preparation method. This electrical contact material is mainly used in high-power relays and small contactors. Background Technology

[0002] With the development of new energy technologies, intelligent energy consumption patterns are gaining acceptance, such as smart homes, white goods, and the emergence of new energy sources. Existing household power relays not only need to withstand resistive loads but also need to meet the stringent conditions of inductive loads or capacitive loads with large surges, such as cold light sources like LED lights. This results in continuous arc corrosion of the contacts during service or a sudden surge of hundreds of amperes during service. Moreover, with the integration of control circuits, the current carried by some electrical appliances has also increased significantly, from the original 5A and 10A to 16A, 25A, and even higher. Under 5A and 10A resistive load conditions, AgNi materials prepared by conventional processes can fully meet the lifespan requirements. However, with the increase in load type and current level, AgNi10, AgNi15, AgNi20, and AgNi30 prepared by conventional processes can no longer meet the electrical performance requirements. They are prone to bonding or rapid burning under surge current, resulting in non-conductivity or poor product withstand voltage. While AgMeO (silver metal oxide) has good anti-welding properties, when working under plastic encapsulation conditions, silver precipitates easily on the contact surface, causing mechanical bonding and adhesion of the contacts during closing and opening, and continuous arcing due to excessively short gaps. This can lead to product bonding failure or even the risk of burning other structures.

[0003] To further improve the anti-adhesion and anti-burning properties of contact materials under molding and high current conditions, and to meet the service requirements under higher currents, scholars at home and abroad have conducted a great deal of research.

[0004] Patent CN 110802224 describes a method for preparing silver-nickel-tin oxide composite powder and silver-nickel-tin oxide electrical contact materials. The method first mixes tin dioxide powder and nickel powder in an inert gas atmosphere, then mixes the powder with a silver ammonia solution. The resulting mixture is then chemically deposited using a reducing agent to prepare the silver-nickel-tin oxide composite powder. Finally, the silver-nickel-tin oxide composite powder is sequentially shaped and sintered to obtain the silver-nickel-tin oxide electrical contact material. While this method can improve the uneven microstructure and reduced service life of the contact material, the design of nickel and auxiliary metal elements, both of which have lower standard electrode potentials than metallic tin, leads to a redox reaction between nickel and SnO2 at high temperatures during sintering and subsequent use. This results in the formation of a NiO oxide shell around the nickel particles, significantly increasing the material's volume resistivity. During use, this easily causes excessively high temperature rise in the contact material and further leads to the accumulation of oxides on the surface of the silver-nickel-tin oxide electrical contact material, resulting in poor arc erosion resistance.

[0005] Patent CN 110576192 describes a method for preparing an improved silver-nickel-tin oxide electrical contact material. The method involves ball milling tin dioxide in a high-energy ball mill to obtain tin dioxide powder. Then, the tin dioxide powder, nickel powder, and auxiliary element powder are added to a silver ammonia solution and mixed evenly. A reducing agent and a chemical deposition method are used to prepare a silver-nickel-tin oxide composite powder. Finally, the composite powder is sequentially shaped and sintered to obtain the silver-nickel-tin oxide electrical contact material. This method aims to improve the anti-adhesion and burn-off resistance of traditional AgNi materials by adding certain high-melting-point oxide additives. However, since the design components, nickel and auxiliary metal elements, are all elemental metals with a standard electrode potential lower than that of metallic tin, nickel and auxiliary metal elements and SnO2 undergo redox reactions at high temperatures during the sintering process and subsequent use. Some Ni and auxiliary metal elements are oxidized to form oxides, while SnO2 is reduced to form SnO. The generated NiO has poor wettability with the Ag matrix. Under the high temperature of the electric arc, Ni and SnO2 are prone to accumulate on the surface of the silver-nickel-tin oxide electrical contact material, resulting in a high temperature rise and poor arc erosion resistance of the electrical contact material.

[0006] The processes employed in the aforementioned patents all aim to address the problem of reduced conductivity and decreased arc erosion resistance in silver-nickel-tin oxide materials during high-temperature sintering due to the redox reaction between nickel and tin oxide. However, due to issues with process design or additive selection, it is impossible to fundamentally prevent the redox reaction between nickel or additives and tin oxide at high temperatures. Therefore, eliminating the redox reaction between nickel and tin oxide at high temperatures and avoiding the resulting reduction in conductivity and arc erosion resistance remains a challenge in the preparation of silver-nickel-tin oxide electrical contact materials, necessitating improvements. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology, and to provide a silver-nickel composite tin oxide electrical contact material and its preparation method. The technical solution adopted by this invention is as follows:

[0008] Step 1. A layer of metallic zinc is coated onto the surface of tin oxide particles using a chemical plating method, followed by cleaning and drying to obtain coated powder I;

[0009] Step 2. A layer of silver is further coated onto coated powder I using a chemical coating process, followed by cleaning and drying to obtain coated powder II;

[0010] Step 3. Perform a powder oxidation process on the coated powder II to oxidize the intermediate zinc plating layer and form a zinc oxide shell;

[0011] Step 4. Mix the composite oxide powder prepared in step 3 with silver powder in a high-speed powder mixer until uniform, and finally obtain a uniform composite powder.

[0012] Step 5. The composite powder with uniform composition obtained in Step 4 is rapidly sintered by spark plasma to obtain a dense silver-nickel composite tin oxide ingot.

[0013] Step 6. The spindle prepared in step 5 is hot-extruded into filaments, and finally drawn into finished filaments of the required specifications.

[0014] Furthermore, the components and contents of the prepared silver-nickel composite tin oxide electrical contact material are as follows: nickel content is 3%~10% (wt%), composite tin oxide content is 8%~15% (wt%), zinc oxide content is 0.8~1.5% (wt%), and the balance is silver.

[0015] Furthermore, in step 1, the average tin oxide content in the composite zinc oxide powder coated with zinc by chemical plating is 70%~90% (wt%), the average zinc content is 10%~30% (wt%), and the average particle size of the tin oxide powder is 2~4μm; the reason for choosing zinc plating is that the standard electrode potential of elemental zinc is smaller than that of elemental nickel.

[0016] Furthermore, in step 2, the average silver content in the powder coated with silver using the chemical coating process must be <25% (wt%).

[0017] Furthermore, the powder oxidation process described in step 3 is a low-temperature high-pressure powder oxidation process, with specific oxidation parameters as follows: oxidation temperature 300~420℃, oxidation pressure 0.5~0.9Mpa, and oxidation time 24~48h;

[0018] Furthermore, the high-speed powder mixing process described in step 4 is as follows: mixing speed 750~1500 r / min, mixing time 60~120 min, and single mixing weight 10~30 kg; the silver powder is 200~500 mesh atomized silver powder, and the nickel powder is 3~8 μm carbonyl nickel powder.

[0019] Furthermore, the rapid spark plasma sintering process described in step 5 is as follows: the inner diameter of the graphite mold containing the powder is 80cm~120cm, the pressure is 20~30Mpa, the sintering temperature is 850~920℃, and the time is 10min~15min.

[0020] Furthermore, step 6 includes the following process: heating the silver-nickel composite tin oxide ingot obtained by rapid sintering by discharge plasma in a nitrogen atmosphere, with heating parameters of 750℃~830℃ and holding time of 2~4h; then hot extruding it into an extruded wire with a diameter of φ5mm~φ8mm, and finally drawing it to the required specifications according to the rivet specifications and processing it into contacts of the required shape and specifications.

[0021] The beneficial effects of this invention are as follows:

[0022] (1) The electrode potential of elemental zinc is smaller than that of metallic nickel, which can avoid the redox reaction between nickel and zinc oxide at high temperature. By preparing core-shell structured composite tin oxide, a zinc oxide shell is formed on the surface of tin oxide, which avoids the contact between tin oxide components and nickel. This fundamentally solves the redox reaction between nickel and tin oxide components under high temperature sintering conditions of silver-nickel tin oxide materials prepared by conventional processes, thereby greatly improving the conductivity and arc erosion resistance of the material.

[0023] (2) Through the rapid sintering process of discharge plasma, high-energy particles generated by discharge collide with the contact parts between particles, causing the material to evaporate and play a role in purification and activation, which ultimately greatly improves the sintering density of the ingot; at the same time, it shortens the material preparation process and has obvious cost advantages.

[0024] (3) By adding high-melting-point oxide additives, the anti-welding and anti-burning properties of the material can be improved on the one hand; on the other hand, the coordinated plastic deformation of silver and nickel in the extrusion and subsequent drawing process can be blocked, so that the longitudinal nickel distribution is more uniform and presents a granular distribution, further improving the anti-welding and anti-burning properties of the material.

[0025] In summary, the silver-nickel composite tin oxide electrical contact material prepared by this invention, when applied to plastic-encapsulated, high-current power relays, effectively mitigates the phenomenon of silver deposits on the contact surface during use. This avoids mechanical sticking or continuous arcing due to excessively short gaps during the closing and opening processes caused by silver deposits, thus preventing product adhesion failure and effectively improving the electrical performance stability of the material. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0027] Figure 1 This is a process flow diagram for the preparation of the silver-nickel composite tin oxide electrical contact material. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0029] Example 1:

[0030] Based on a final product weight percentage of Ag:composite tin oxide:Ni = 85:10:5, this implementation case is carried out according to the following steps:

[0031] Step 1. A layer of zinc is coated onto tin oxide powder with an average particle size of 2.5 micrometers using a chemical plating method, resulting in an average tin oxide content of 91.8% (wt%) and an average zinc content of 8.2% (wt%) in the powder. This embodiment is specifically achieved through the following steps:

[0032] a) Pre-plating dispersion: The effectiveness of oxide particle dispersion directly affects the particle distribution and content in the composite coating, thus influencing the performance of the composite coating. This implementation uses polyethylene glycol 400 as the disperser. Specifically, 200g of tin oxide powder is first soaked in 500ml of anhydrous ethanol. Then, 10g of polyethylene glycol 400 is weighed and dissolved in 1L of deionized water. The tin oxide powder soaked in anhydrous ethanol is slowly added to the deionized water containing polyethylene glycol 400 dispersant. Ultrasonic stirring is initiated, and mechanical stirring is performed to obtain a dispersion.

[0033] b) Electroless zinc plating: The tin oxide dispersion treated above is slowly added to the prepared electroless plating solution for electroplating (the main components of the plating solution are: ZnCl 40g~60g / L, KCl 120g~150g / L, H3BO3 25~35g / L, additives 15~25ml / L), with a current density of 3~4A / dm³. 2 The plating temperature is 45±5℃, and the plating time is 60 minutes. Then rinse with distilled water and dry.

[0034] c) Repeat the above two steps until the required weight of tin oxide-coated powder I is prepared;

[0035] Step 2. Weigh 0.980 kg of tin oxide-coated powder I and disperse it in glucose reducing agent solution. Weigh 0.245 kg of silver oxide acid solution and then add ammonia water to prepare silver ammonia solution (control the pH value 9~11). Slowly add the reducing agent solution containing tin oxide-coated powder to the silver ammonia solution. After the reaction is complete, filter out the precipitate, and wash and dry it in sequence to finally obtain silver-coated composite tin oxide powder II.

[0036] Step 3. The silver-coated composite tin oxide powder II prepared in Step 2 is subjected to a special powder oxidation process, namely a low-temperature high-pressure powder oxidation process. The specific oxidation parameters are: oxidation temperature 380℃, oxidation pressure 0.6Mpa, and oxidation time 28h.

[0037] Step 4. Mix the silver-coated composite oxide powder prepared in Step 3 with 8.255 kg of 350-mesh silver powder and 0.5 kg of carbonyl nickel powder with an average particle size of 3.8 μm in a high-speed powder mixer until homogeneous. The mixing parameters are: mixing speed 1000 r / min and mixing time 80 min. The final homogeneous composite powder should be obtained. The composite powder should be calculated by weight percentage and meet the following requirements: Ag:composite tin oxide:Ni = 85:10:5.

[0038] Step 5. The composite powder with uniform composition prepared in Step 4 is subjected to rapid spark plasma sintering. The spark plasma sintering parameters are set as follows: the inner diameter of the graphite mold holding the powder is 105 cm, the pressure is 25 MPa, the sintering temperature is 880 °C, and the time is 12 min; a dense silver-nickel tin oxide ingot is obtained.

[0039] Step 6. The silver-nickel tin oxide ingots obtained by rapid sintering by spark plasma are heated in a nitrogen atmosphere with the following heating parameters: temperature 800℃ and holding time 2.5h. Then, they are hot-extruded into extruded wires with a diameter of φ5.2mm. Finally, they are drawn to the required specifications according to the rivet specifications and processed into contacts of the required shape and specifications.

[0040] Example 2:

[0041] Based on a final product weight percentage of Ag:composite tin oxide:Ni = 87:10:3, this implementation case is carried out according to the following steps:

[0042] Step 1. A layer of zinc is coated onto tin oxide powder with an average particle size of 2.5 micrometers using a chemical plating method, resulting in an average tin oxide content of 91.8% (wt%) and an average zinc content of 8.2% (wt%) in the powder. This embodiment is specifically achieved through the following steps:

[0043] a) Pre-plating dispersion: The effectiveness of oxide particle dispersion directly affects the particle distribution and content in the composite coating, thus influencing the performance of the composite coating. This implementation uses polyethylene glycol 400 as the disperser. Specifically, 200g of tin oxide powder is first soaked in 500ml of anhydrous ethanol. Then, 10g of polyethylene glycol 400 is weighed and dissolved in 1L of deionized water. The tin oxide powder soaked in anhydrous ethanol is slowly added to the deionized water containing polyethylene glycol 400 dispersant. Ultrasonic stirring is initiated, and mechanical stirring is performed to obtain a dispersion.

[0044] b) Electroless zinc plating: The tin oxide dispersion treated above is slowly added to the prepared electroless plating solution for electroplating (the main components of the plating solution are: ZnCl 40g~60g / L, KCl 120g~150g / L, H3BO3 25~35g / L, additives 15~25ml / L), with a current density of 3~4A / dm³. 2 The plating temperature is 45±5℃, and the plating time is 60 minutes. Then rinse with distilled water and dry.

[0045] c) Repeat the above two steps until the required weight of tin oxide-coated powder I is prepared;

[0046] Step 2. Weigh 0.980 kg of tin oxide-coated powder I and disperse it in glucose reducing agent solution. Weigh 0.245 kg of silver oxide acid solution and then add ammonia water to prepare silver ammonia solution (control the pH value 9~11). Slowly add the reducing agent solution containing tin oxide-coated powder to the silver ammonia solution. After the reaction is complete, filter out the precipitate, and wash and dry it in sequence to finally obtain silver-coated composite tin oxide powder II.

[0047] Step 3. The silver-coated composite tin oxide powder II prepared in Step 2 is subjected to a special powder oxidation process, namely a low-temperature high-pressure powder oxidation process. The specific oxidation parameters are: oxidation temperature 380℃, oxidation pressure 0.6Mpa, and oxidation time 28h.

[0048] Step 4. Mix the silver-coated composite oxide powder prepared in Step 3 with 8.455 kg of 350-mesh silver powder and 0.3 kg of carbonyl nickel powder with an average particle size of 3.8 μm in a high-speed mixer until homogeneous. The mixing parameters are: mixing speed 1000 r / min and mixing time 80 min. The final homogeneous composite powder should be obtained. The composite powder should meet the following weight percentage requirements: Ag:composite tin oxide:Ni = 87:10:3.

[0049] Step 5. The composite powder with uniform composition is rapidly sintered by spark plasma. The spark plasma rapid sintering parameters are set as follows: the inner diameter of the graphite mold holding the powder is 105 cm, the pressure is 25 MPa, the sintering temperature is 880 ℃, and the time is 12 min; a dense silver-nickel tin oxide ingot is obtained.

[0050] Step 6. The silver-nickel tin oxide ingots obtained by rapid sintering by spark plasma are heated in a nitrogen atmosphere with the following heating parameters: temperature 800℃ and holding time 2.5h. Then, they are hot-extruded into extruded wires with a diameter of φ5.2mm. Finally, they are drawn to the required specifications according to the rivet specifications and processed into contacts of the required shape and specifications.

[0051] Example 3:

[0052] Based on a final product weight percentage of Ag:composite tin oxide:Ni = 83:12:5, this implementation case is carried out according to the following steps:

[0053] Step 1. A layer of zinc is coated onto tin oxide powder with an average particle size of 2.5 micrometers using a chemical plating method, resulting in an average tin oxide content of 91.8% (wt%) and an average zinc content of 8.2% (wt%) in the powder. This embodiment is specifically achieved through the following steps:

[0054] a) Pre-plating dispersion: The effectiveness of oxide particle dispersion directly affects the particle distribution and content in the composite coating, thus influencing the performance of the composite coating. This implementation uses polyethylene glycol 400 as the disperser. Specifically, 200g of tin oxide powder is first soaked in 500ml of anhydrous ethanol. Then, 10g of polyethylene glycol 400 is weighed and dissolved in 1L of deionized water. The tin oxide powder soaked in anhydrous ethanol is slowly added to the deionized water containing polyethylene glycol 400 dispersant. Ultrasonic stirring is initiated, and mechanical stirring is performed to obtain a dispersion.

[0055] b) Electroless zinc plating: The tin oxide dispersion treated above is slowly added to the prepared electroless plating solution for electroplating (the main components of the plating solution are: ZnCl 40g~60g / L, KCl 120g~150g / L, H3BO3 25~35g / L, and additives 15~25ml / L), the current density is 3~4A / dm2, the plating temperature is 45±5℃, and the plating time is 60min. Then rinse with distilled water and dry.

[0056] c) Repeat the above two steps until the required weight of tin oxide-coated powder I is prepared;

[0057] Step 2. Weigh 1.176 kg of tin oxide-coated powder I and disperse it in a glucose reducing agent solution. Weigh 0.294 kg of silver oxide acid solution and then add ammonia water to prepare a silver ammonia solution (control the pH value 9~11). Slowly add the reducing agent solution containing tin oxide-coated powder to the silver ammonia solution. After the reaction is complete, filter out the precipitate, and wash and dry it in sequence to finally obtain silver-coated composite tin oxide powder II.

[0058] Step 3. The silver-coated composite tin oxide powder II prepared in Step 2 is subjected to a special powder oxidation process, namely a low-temperature high-pressure powder oxidation process. The specific oxidation parameters are: oxidation temperature 380℃, oxidation pressure 0.6Mpa, and oxidation time 28h.

[0059] Step 4. The silver-coated composite oxide powder prepared in Step 3 is mixed uniformly with 8.006 kg of 350-mesh silver powder and 0.5 kg of carbonyl nickel powder with an average particle size of 3.8 μm in a high-speed powder mixer. The mixing parameters are: mixing speed 1000 r / min and mixing time 80 min. The final uniform composite powder is required. The composite powder is calculated by weight percentage and meets the following conditions: Ag:composite tin oxide:Ni = 83:12:5.

[0060] Step 5. The composite powder with uniform composition is rapidly sintered by spark plasma. The spark plasma rapid sintering parameters are set as follows: the inner diameter of the graphite mold holding the powder is 105 cm, the pressure is 25 MPa, the sintering temperature is 880 ℃, and the time is 12 min; a dense silver-nickel tin oxide ingot is obtained.

[0061] Step 6. The silver-nickel tin oxide ingots obtained by rapid sintering by spark plasma are heated in a nitrogen atmosphere with the following heating parameters: temperature 800℃ and holding time 2.5h. Then, they are hot-extruded into extruded wires with a diameter of φ5.2mm. Finally, they are drawn to the required specifications according to the rivet specifications and processed into contacts of the required shape and specifications.

[0062] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing a silver-nickel composite tin oxide electrical contact material, characterized in that... Includes the following steps: Step 1. A layer of metallic zinc is coated onto the surface of tin oxide particles using a chemical plating method, followed by cleaning and drying to obtain coated powder I; Step 2. A layer of silver is further coated onto coated powder I using a chemical coating process, followed by cleaning and drying to obtain coated powder II; Step 3. The coated powder II is subjected to a powder oxidation process to oxidize the intermediate zinc plating layer to form a zinc oxide shell, thereby obtaining a composite oxide powder. The powder oxidation process is a low-temperature and high-pressure powder oxidation process, and the specific oxidation parameters are: oxidation temperature 300~420℃, oxidation pressure 0.5~0.9Mpa, and oxidation time 24~48h. Step 4. Mix the composite oxide powder prepared in Step 3 with silver powder and nickel powder at high speed until uniform, and finally obtain a uniform composite powder. Step 5. The uniform composite powder obtained in Step 4 is rapidly sintered by spark plasma to obtain a dense silver-nickel composite tin oxide ingot; Step 6. The ingots prepared in Step 5 are hot-extruded into wires, and finally drawn into finished wires of the required specifications, namely silver-nickel composite tin oxide electrical contact materials.

2. The method for preparing a silver-nickel composite tin oxide electrical contact material according to claim 1, characterized in that, The weight percentages of each component in the prepared silver-nickel composite tin oxide electrical contact material are: nickel 3%~10%, composite tin oxide 8%~15%, zinc oxide 0.8~1.5%, and the balance is silver.

3. The method for preparing a silver-nickel composite tin oxide electrical contact material according to claim 1, characterized in that: In step 1, the weight percentage of tin oxide in the composite tin oxide powder coated with zinc by chemical plating is 70%~90%, and the weight percentage of zinc is 10%~30%. The average particle size of tin oxide powder is 2~4μm.

4. The method for preparing a silver-nickel composite tin oxide electrical contact material according to claim 1, characterized in that: In step 2, the weight percentage of silver in the powder coated with silver using the chemical coating process is less than 25%.

5. The method for preparing a silver-nickel composite tin oxide electrical contact material according to claim 1, characterized in that, The high-speed mixing process in step 4 is as follows: the mixing speed of the high-speed mixer is set to 750~1500 r / min, the mixing time is 60~120 min, and the weight of a single mixing is 10~30 kg; The silver powder is 200-500 mesh atomized silver powder, and the nickel powder is 3-8 μm carbonyl nickel powder.

6. The method for preparing a silver-nickel composite tin oxide electrical contact material according to claim 1, characterized in that, The rapid spark plasma sintering process described in step 5 is as follows: the inner diameter of the graphite mold containing the powder is 80cm~120cm, the pressure is 20~30MPa, the sintering temperature is 850~920℃, and the time is 10min~15min.

7. The method for preparing a silver-nickel composite tin oxide electrical contact material according to claim 1, characterized in that, Step 6 includes the following process: heating the silver-nickel composite tin oxide ingot obtained by rapid electro-plasma sintering in a nitrogen atmosphere with the following heating parameters: temperature 750℃~830℃, holding time 2~4h; then hot extruding it into an extruded wire with a diameter of φ5mm~φ8mm, and finally drawing it to the required specifications according to the rivet specifications and processing it into contacts of the required shape and specifications.

8. The silver-nickel composite tin oxide electrical contact material prepared by the preparation method of the silver-nickel composite tin oxide electrical contact material according to any one of claims 1-7.

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