Silver-based electrical contact containing carbon nanotubes and preparation process thereof

Abstract

The invention discloses a silver-based electrical contact containing a carbon nano tube and a preparation process thereof, and the silver-based electrical contact containing the carbon nano tube comprises the following raw materials in parts by weight: 0.14-0.23 part of Ag-coated CNTs and 100 parts of silver-based powder, the preparation process of the Ag-coated CNTs comprises the following steps: modifying CNTs by using a carboxylic acid derivative of pyrene, and preparing the Ag-coated CNTs by using a liquid-phase atomization method; the modification treatment of the CNTs by using the carboxylic acid derivative of pyrene comprises the following steps: carrying out non-covalent bond modification treatment on the carbon nanotubes by using 1-pyrene butyric acid to obtain surface functionalized carbon nanotubes, carrying out non-covalent functionalization on the carbon nanotubes by using the carboxylic acid derivative of pyrene, and then preparing the Ag-coated CNTs by using a liquid phase atomization method. Uniform nucleation and growth of silver are forcibly realized in a micro-scale reaction space, coating uniformity and binding force are synchronously improved, and finally synergistic improvement of conductivity, welding resistance and arc resistance of the silver-based electrical contact is realized.

Description

Technical Field

[0001] This application relates to electrical contact materials, and more particularly to a silver-based electrical contact containing carbon nanotubes and its preparation process. Background Technology

[0002] Silver-based electrical contact materials are core components of electrical equipment, and their performance directly affects the reliability of circuits and the lifespan of equipment. While pure silver possesses excellent electrical and thermal conductivity, its strength and arc resistance are insufficient. Therefore, reinforcing phases (such as Ag / CdO and Ag / SnO2 metal oxides) are often added to improve performance. However, these ceramic phases have weak bonding with the silver matrix and are prone to surface enrichment under arcing, leading to increased contact resistance and reduced lifespan. Furthermore, their fabrication processes (such as internal oxidation) can easily cause silver volatilization and reinforcing phase agglomeration, affecting performance stability. To seek breakthroughs, carbon nanotubes (CNTs) are considered a highly promising new reinforcing material due to their superior strength, electrical conductivity, and thermal conductivity. Theoretically, CNTs can effectively disperse arc energy and stabilize the molten pool, thereby significantly improving the contact's resistance to arc erosion and its service life.

[0003] However, introducing CNTs directly as a reinforcing phase into a silver matrix faces two core technical challenges that are difficult to resolve simultaneously: Dispersion is a significant challenge. CNTs possess extremely high specific surface area and strong van der Waals forces, making them prone to entanglement and aggregation, thus hindering uniform dispersion in a silver matrix. While mechanical mixing methods such as high-energy ball milling can improve dispersion to some extent, they easily lead to CNT fracture, disrupting their perfect structure and impairing their intrinsic excellent properties. Interfacial bonding is another challenge. CNTs have high surface chemical inertness and poor wettability with silver, resulting in weak interfacial bonding. This weak interfacial bonding prevents effective load transfer, hindering the full realization of CNTs' reinforcing potential. Under harsh conditions such as arc erosion, the interface easily becomes a crack initiation point, leading to material failure.

[0004] Therefore, there is an urgent need for a novel material system that can synergistically resolve the contradiction between uniform dispersion and strong interfacial bonding of carbon nanotubes in a silver matrix, and a matching, efficient and industrially scalable preparation method. Summary of the Invention

[0005] To further improve the performance of carbon nanotube-containing silver substrates in the field of electrical contacts, a carbon nanotube-containing silver-based electrical contact and its preparation process are provided.

[0006] The first inventive objective of this invention is achieved through the following technical solution: A silver-based electrical contact containing carbon nanotubes comprises the following raw materials in parts by weight: Ag@CNTs 0.14-0.23 parts, 100 parts of silver-based powder; The preparation process of Ag@CNTs includes: Ag@CNTs were prepared by modification with pyrene carboxylic acid derivatives and liquid-phase atomization. The modification of CNTs with pyrene carboxylic acid derivatives includes: non-covalent modification of carbon nanotubes with pyrene carboxylic acid derivatives to obtain surface-functionalized carbon nanotubes.

[0007] By adopting the above technical solution, carbon nanotubes are non-covalently functionalized using pyrene carboxylic acid derivatives. The molecule is firmly anchored to the surface of CNTs through strong π-π interactions with its pyrene group, while the exposed carboxyl group provides a large number of active sites for the uniform adsorption of silver ions. Thus, the stable dispersion of CNTs in the aqueous phase is achieved in advance at the molecular level, and an ideal silver deposition interface is constructed. Subsequently, the precursor solution was atomized into micron-sized droplets and pyrolyzed instantaneously using liquid-phase atomization. Each droplet became an independent microreactor, forcing the silver precursor to be reduced and crystallized in situ and uniformly on the surface of the functionalized CNTs, ultimately forming a well-structured "silver shell" coating layer. When the "silver shell" is subsequently combined with silver-based powder and sintered, because it has the same composition as the matrix, the weak physical contact between CNTs and the silver matrix is ​​transformed into a strong and tough chemical / metallurgical bonding interface. The modification of pyrene derivatives significantly improves the dispersibility of CNTs without damaging their intrinsic structure; the liquid-phase atomization method forces uniform nucleation and growth of silver in the microscale reaction space, simultaneously improving the coating uniformity and binding force. The combination of these two factors allows low-dosage CNTs to form an efficient strengthening and conductive network in the silver matrix, ultimately achieving a synergistic improvement in the conductivity, anti-welding properties, and anti-arc performance of silver-based electrical contacts.

[0008] Optionally, the carboxylic acid derivative of pyrene is 1-pyrenebutyric acid.

[0009] By adopting the above technical solution, the molecular structure of 1-pyrenebutyric acid has a planar large π bond pyrene group at one end, which can be firmly adsorbed onto the graphene surface of carbon nanotubes through strong π-π stacking forces; the other end is a carboxyl group, which can dissociate H⁺ in aqueous solution, making the CNT surface negatively charged. Through electrostatic repulsion, it effectively prevents CNTs from agglomerating, greatly improving its dispersion stability in solution. More importantly, its uniformly distributed carboxyl groups become the preferred adsorption and coordination sites for silver ions, providing precise "anchor points" for the subsequent uniform and dense deposition of silver. Compared to other derivatives, 1-pyrenebutyric acid has an alkyl chain of appropriate length between the pyrene and carboxyl groups. On the one hand, the alkyl chain provides moderate spatial flexibility, allowing the pyrene group to better adapt to the curvature changes of the CNT surface and achieve tighter and more stable adsorption. On the other hand, it ensures that the carboxyl functional group can be fully exposed in the solution to maintain high reactivity, while avoiding poor adsorption due to excessively short molecules or steric hindrance due to excessively long molecules, resulting in more stable material properties.

[0010] Optionally, the liquid-phase atomization method for preparing Ag@CNTs specifically involves: mixing a silver salt composite liquid with a carbon nanotube dispersion, atomizing the mixture using an ultrasonic atomizer, and then introducing it into a tubular furnace reaction zone at 650-750℃. After a thermal decomposition and reduction reaction, the Ag@CNTs precursor powder is collected by electrostatic adsorption.

[0011] By adopting the above technical solution, the precursor solution is broken into micron-sized droplets, making each droplet an independent "microreactor". This allows for the instantaneous and uniform thermal decomposition and reduction reaction of the silver precursor on the surface of the dispersed functionalized carbon nanotubes within the upper spatial limit, thus achieving in-situ, uniform, and complete coating of silver on each CNT.

[0012] Optional: The silver salt composite solution is a mixture of silver nitrate and silver oxalate.

[0013] By adopting the above technical solution, silver nitrate has a lower decomposition temperature and silver oxalate has a higher decomposition temperature. By utilizing the different thermal decomposition kinetics of the two silver salts, "gradient deposition" is achieved during the atomization pyrolysis process. Silver nitrate decomposes preferentially during the heating stage, rapidly forming a uniform and dense silver nanocrystal "seed layer" on the surface of the functionalized carbon nanotubes. Meanwhile, the decomposition process of silver oxalate mainly occurs in the higher temperature range. At this time, the released silver atoms will grow epitaxially with the existing "seed layer" as the core, thereby effectively "thickening" and "densifying" the silver coating layer on the basis of the established uniform structure. The sequential reaction path essentially transforms the silver deposition process from a one-step random nucleation and growth to a two-step controllable "seed-guided" growth. Compared to traditional single silver salt precursors, which are difficult to balance nucleation density and growth quality during instantaneous pyrolysis, leading to discontinuous coating layers or coarse silver particles. The specific combination of silver nitrate and silver oxalate, in the instantaneous high temperature and microreactor environment provided by the liquid phase atomization method, ingeniously constructs a deposition sequence that first ensures uniformity and then enhances integrity. This results in a silver shell layer that has excellent continuity, density, and bonding strength with the CNT substrate. The resulting material has better electrical conductivity, thermal conductivity, arc resistance, anti-welding properties, and stability.

[0014] Optional: The molar ratio of silver nitrate to silver oxalate is 1:3.2, and the total silver ion concentration is 0.65 mol / L.

[0015] By adopting the above technical solution, the total silver ion concentration ensures sufficient silver source to achieve effective coating thickness while avoiding excessively high solution viscosity that could affect atomization uniformity. The 1:3.2 molar ratio ensures that during the programmed temperature pyrolysis process, silver nitrate, which decomposes at a lower temperature, can provide a suitable amount of uniform silver crystal nuclei as "seeds," while silver oxalate, which decomposes at a higher temperature, can provide sufficient silver atoms for adequate epitaxial growth and filling on the formed seeds. This kinetically promotes the formation of a continuous, dense, and moderately thick ideal silver coating layer, ensuring batch-to-batch consistency and high-performance reliability of the Ag@CNTs enhancement phase.

[0016] Optionally: The thermal decomposition and reduction reaction atmosphere in the tubular furnace reaction zone contains CO2.

[0017] By adopting the above technical solution, a reactive atmosphere containing CO2 is introduced. At high temperatures, CO2 can selectively vaporize carbon atoms such as amorphous carbon and structural defects on the surface of carbon nanotubes, achieving "in-situ cleaning and activation" of the CNT surface. This exposes more clean and regular graphite crystal faces, providing an ideal substrate for the subsequent uniform heterogeneous nucleation of silver. Secondly, as a gaseous adsorbate, CO2 molecules can competitively adsorb on specific crystal faces of CNTs or initial silver nuclei, dynamically changing the local interfacial energy. This regulates the surface mobility and adhesion tendency of silver atoms, inhibits their three-dimensional island-like agglomeration growth, and guides them to spread into a more uniform and continuous two-dimensional thin film mode. Finally, CO, a byproduct of the gasification reaction, is a mild reducing gas that can further reduce any incompletely decomposed silver precursor intermediates at the gas phase or interface, playing a role in "secondary reduction and purification" to ensure that silver is deposited in a high-purity metallic state.

[0018] Optional: The thermal decomposition and reduction reaction atmosphere is adjusted to three stages according to the heating process. The low-temperature stage is from room temperature to 500℃, and the thermal decomposition and reduction reaction atmosphere is 20% CO2 and 80% Ar. The temperature range of 500℃-650℃ is the intermediate temperature deposition stage, and the thermal decomposition and reduction reaction atmosphere is 5% CO2 and 95% Ar. The high-temperature insulation stage is from 650℃ to 750℃, during which pure Ar is switched.

[0019] By employing the above technical solution, combining programmed temperature control with gradient regulation of CO2 partial pressure, targeted optimization of the dominant physicochemical processes within three temperature ranges is achieved: In the low-temperature stage, a high-concentration CO2 atmosphere is used, primarily utilizing its selective vaporization reaction with active carbon atoms on the CNT surface to efficiently complete the "in-situ deep cleaning and activation" of CNTs, preparing an atomically clean substrate surface for subsequent deposition. This stage is strictly controlled below the significant decomposition temperature of silver salts to avoid interference; Entering the intermediate-temperature deposition stage, the CO2 concentration is significantly reduced to the controlled level, at which point the precursor decomposes rapidly, and trace amounts of CO2 are released. By preferentially occupying specific high-energy crystal planes through competitive adsorption mechanisms, the surface diffusion barrier and adhesion tendency of silver atoms are subtly altered, effectively suppressing three-dimensional island growth and guiding silver to spread and thicken on the clean CNT surface in a more uniform and continuous two-dimensional pattern, thus achieving "micro-manipulation control" of deposition dynamics. Finally, during the high-temperature holding stage, a pure Ar inert atmosphere is switched to completely eliminate any potential carbon etching reaction risks, providing a stable high-temperature environment for the formed silver coating layer, promoting full diffusion of silver atoms and grain boundary migration, completing the final crystallization and densification, and ensuring that the silver layer has good crystallinity and low internal stress. This ensures that the prepared Ag@CNTs reinforced phase has unparalleled interface cleanliness, coating uniformity, and structural integrity, providing the most reliable raw material guarantee for achieving the ultimate performance of electrical contact materials.

[0020] The second objective of this invention is achieved through the following technical solution: The fabrication process of the above-mentioned silver-based electrical contact containing carbon nanotubes includes the following steps: S1: Carbon nanotube pretreatment; S2: Preparation of Ag@CNTs composite powder; S3: 0.14-0.23 parts by weight of the Ag@CNTs composite powder obtained in step S2 are mechanically mixed with 100 parts by weight of silver-based powder to ensure uniform dispersion; S4: Press the uniformly mixed powder obtained in step S3 into a green contact blank; then sinter the green blank under a protective atmosphere to obtain a dense carbon nanotube silver-based electrical contact material.

[0021] By adopting the above technical solution, the nucleation-growth kinetics of silver are precisely controlled, and a uniformly coated and clean Ag@CNTs core-shell reinforcing phase is synthesized in situ. Finally, through optimized powder metallurgy technology, the high-performance reinforcing phase is ensured to be uniformly dispersed in the silver matrix and form a strong and tough metallurgical bond, thereby transferring and solidifying the structural advantages at the nanoscale into the superior performance of the macroscopic bulk material without damage.

[0022] In summary, this application has at least the following beneficial effects: 1. By combining "non-covalent functionalization of pyrene derivatives" and "liquid phase atomization gradient deposition", uniform dispersion of carbon nanotubes in a silver matrix was achieved without damaging the intrinsic structure of carbon nanotubes. Furthermore, a strong and tough metallurgical bond with the matrix was achieved through an in-situ formed silver coating layer. The prepared silver-based electrical contact material maintains the excellent conductivity of silver while significantly improving its mechanical strength, hardness, resistance to arc erosion, and resistance to welding. 2. A low amount of Ag@CNTs can efficiently construct a reinforcing and conductive network, achieving a perfect balance of high strength, high conductivity and long lifespan. This improves product performance while controlling raw material costs, resulting in good economic efficiency. Detailed Implementation

[0023] raw material CNTs, carbon nanotubes, commercially available products, with parameters and specifications of 10nm diameter and 5μm length; 1-Pyrenebutyric acid, 1-Pyrenecarboxylic acid, acetic acid, silver nitrate, and ammonium oxalate were all commercially available analytical grade products.

[0024] Silver-based powder, 99.9% pure silver powder.

[0025] Preparation Example 1 The preparation process of Ag@CNTs composite powder is as follows: Weigh 1.0g of CNTs and add 100mL of deionized water and 0.1g of 1-pyrenebutyric acid. Stir the mixture for 1 minute with a mechanical stirrer to initially wet and mix the CNTs and 1-pyrenebutyric acid powder. Place the container of the mixture in an ice-water bath and then perform ultrasonic treatment. The ultrasonic power is 300W, and the intermittent ultrasonic mode is used - ultrasonic work for 2 seconds, intermittent for 1 second, for a total of 30 minutes. After ultrasonic treatment, remove the container and let it stand at room temperature for 1 hour. Observe the state of the dispersion. The qualified standard is that there is no obvious sedimentation, stratification or coarse particles after standing. The whole is a uniform black colloidal state. After standing and stabilizing, a uniform black functionalized CNTs dispersion is obtained. Silver nitrate was dissolved in deionized water to obtain a 1.30 mol / L silver nitrate solution, and ammonium oxalate was dissolved in deionized water to obtain a 0.5625 mol / L ammonium oxalate solution. Under continuous stirring at 1000 rpm, 100 ml of oxalate solution was slowly added to 100 ml of silver nitrate solution. After the addition and reaction were completed, the volume was balanced to 200 ml to obtain a silver salt composite solution. The silver salt composite solution was a suspension in which silver nitrate and silver oxalate were dissolved in the liquid phase, and silver oxalate was suspended in the solid phase. Functionalized CNTs dispersion and silver salt composite solution were mixed at a volume ratio of 1:1 and atomized into micron-sized droplets (droplet diameter 8±4μm) using an ultrasonic atomizer (frequency 1.7MHz). The atomized droplets were then introduced into the reaction zone of a tube furnace, and the temperature of the reaction zone was controlled by the following program: Low-temperature stage (room temperature to 500℃): The atmosphere is 20% CO2 and 80% Ar, and the flow rate is 1 L / min, which allows the amorphous carbon on the surface of CNTs to be vaporized and cleaned. Intermediate-temperature deposition stage (500℃ to 650℃): The atmosphere is switched to 5% CO2 and 95% Ar, with a flow rate of 1 L / min. Silver salts undergo thermal decomposition and reduction, resulting in uniform deposition of silver atoms on the CNT surface. High temperature holding stage (650℃ to 750℃): The atmosphere is switched to pure Ar, the flow rate is 1L / min, and the holding time is 10min to make the silver layer crystallize and become dense. The reaction products were collected by an electrostatic adsorption device to obtain Ag@CNTs precursor powder.

[0026] Preparation Example 2 The Ag@CNTs composite powder differs from Preparation Example 1 in that it uses an equimolar amount of 1-pyrenecarboxylic acid instead of 1-pyrenebutyric acid.

[0027] Preparation Example 3 The Ag@CNTs composite powder differs from that in Preparation Example 1 in that the temperature of the reaction zone is controlled by a program as follows: Low-temperature stage (room temperature to 200°C): The atmosphere is 20% CO2 and 80% Ar, and the flow rate is 1 L / min, which allows the amorphous carbon on the surface of CNTs to be vaporized and cleaned. Intermediate-temperature deposition stage (200℃ to 350℃): The atmosphere is switched to 5% CO2 and 95% Ar, with a flow rate of 1 L / min. Silver salts undergo thermal decomposition and reduction, resulting in uniform deposition of silver atoms on the CNT surface. High temperature holding stage (350℃ to 450℃): The atmosphere is switched to pure Ar, the flow rate is 1L / min, and the holding time is 10min to make the silver layer crystallize and densify. The reaction products were collected by an electrostatic adsorption device to obtain Ag@CNTs precursor powder.

[0028] Preparation Example 4 The Ag@CNTs composite powder differs from that in Preparation Example 1 in that the silver salt composite solution is a 0.65 mol / L nitrate solution.

[0029] Preparation Example 5 The Ag@CNTs composite powder differs from that in Preparation Example 1 in that the silver salt composite solution is a 0.325 mol / L silver oxalate suspension.

[0030] Preparation Example 6 The Ag@CNTs composite powder differs from that in Preparation Example 1 in that the silver salt composite solution is prepared as follows: Silver nitrate was dissolved in deionized water to obtain a 0.8 mol / L silver nitrate solution, and ammonium oxalate was dissolved in deionized water to obtain a 0.346 mol / L ammonium oxalate solution. Under continuous stirring at 1000 rpm, 100 ml of oxalate solution was slowly added to 100 ml of silver nitrate solution. After the addition and reaction were completed, the volume was balanced to 200 ml to obtain a silver salt composite solution.

[0031] Preparation Example 7 The Ag@CNTs composite powder differs from that in Preparation Example 1 in that the silver salt composite solution is prepared as follows: Silver nitrate was dissolved in deionized water to obtain a 1.8 mol / L silver nitrate solution, and ammonium oxalate was dissolved in deionized water to obtain a 0.778 mol / L ammonium oxalate solution. Under continuous stirring at 1000 rpm, 100 ml of oxalate solution was slowly added to 100 ml of silver nitrate solution. After the addition and reaction were completed, the volume was balanced to 200 ml to obtain a silver salt composite solution.

[0032] Preparation Example 8 The Ag@CNTs composite powder differs from that in Preparation Example 1 in that the silver salt composite solution is prepared as follows: Silver nitrate was dissolved in deionized water to obtain a 1.3 mol / L silver nitrate solution, and ammonium oxalate was dissolved in deionized water to obtain a 0.52 mol / L ammonium oxalate solution. Under continuous stirring at 1000 rpm, 100 ml of oxalate solution was slowly added to 100 ml of silver nitrate solution. After the addition and reaction were completed, the volume was balanced to 200 ml to obtain a silver salt composite solution.

[0033] Preparation Example 9 The Ag@CNTs composite powder differs from that in Preparation Example 1 in that the silver salt composite solution is prepared as follows: Silver nitrate was dissolved in deionized water to obtain a 1.3 mol / L silver nitrate solution, and ammonium oxalate was dissolved in deionized water to obtain a 0.578 mol / L ammonium oxalate solution. Under continuous stirring at 1000 rpm, 100 ml of oxalate solution was slowly added to 100 ml of silver nitrate solution. After the addition and reaction were completed, the volume was balanced to 200 ml to obtain a silver salt composite solution.

[0034] Preparation Example 10 The Ag@CNTs composite powder differs from that in Preparation Example 1 in the following ways: Functionalized CNTs dispersion and silver salt composite solution were mixed at a volume ratio of 1:1 and atomized into micron-sized droplets (droplet diameter 8±4μm) using an ultrasonic atomizer (frequency 1.7MHz). The atomized droplets were then introduced into the reaction zone of a tube furnace, and the temperature of the reaction zone was controlled by the following program: Low temperature stage (room temperature to 500℃): atmosphere is 100% Ar, flow rate is 1L / min; Intermediate-temperature deposition stage (500℃ to 650℃): atmosphere is 100% Ar, flow rate is 1L / min; Temperature preservation stage (650℃ to 750℃): atmosphere is 100% Ar, flow rate is 1L / min.

[0035] Preparation Example 11 The Ag@CNTs composite powder differs from that in Preparation Example 1 in the following ways: Functionalized CNTs dispersion and silver salt composite solution were mixed at a volume ratio of 1:1 and atomized into micron-sized droplets (droplet diameter 8±4μm) using an ultrasonic atomizer (frequency 1.7MHz). The atomized droplets were then introduced into the reaction zone of a tube furnace, and the temperature of the reaction zone was controlled by the following program: Low-temperature stage (room temperature to 500℃): atmosphere is 20% CO2, 80% Ar, flow rate is 1 L / min. Intermediate-temperature deposition stage (500℃ to 650℃): atmosphere of 20% CO2, 80% Ar, flow rate of 1 L / min. Temperature preservation stage (650℃ to 750℃): atmosphere is 20% CO2, 80% Ar, flow rate is 1L / min.

[0036] Preparation Example 12 The Ag@CNTs composite powder differs from that in Preparation Example 1 in the following ways: Functionalized CNTs dispersion and silver salt composite solution were mixed at a volume ratio of 1:1 and atomized into micron-sized droplets (droplet diameter 8±4μm) using an ultrasonic atomizer (frequency 1.7MHz). The atomized droplets were then introduced into the reaction zone of a tube furnace, and the temperature of the reaction zone was controlled by the following program: Low-temperature stage (room temperature to 500℃): atmosphere is 5% CO2, 95% Ar, flow rate is 1 L / min. Intermediate-temperature deposition stage (500℃ to 650℃): atmosphere of 5% CO2, 95% Ar, flow rate of 1 L / min. Temperature preservation stage (650℃ to 750℃): atmosphere is 5% CO2, 95% Ar, flow rate is 1L / min.

[0037] Preparation Example 13 The Ag@CNTs composite powder differs from Preparation Example 1 in that it uses acetic acid in an equimolar amount instead of 1-pyrenebutyric acid.

[0038] Example 1 The preparation process of silver-based electrical contact materials containing carbon nanotubes is as follows: Take 0.18g of Ag@CNTs composite powder and 100g of silver-based powder (99.9% pure silver powder) and put them into a planetary ball mill. Mix them mechanically at 200rpm for 2 hours to ensure uniform dispersion.

[0039] Compression molding: The mixed powder is compressed under a pressure of 500MPa to obtain a contact blank (diameter 10mm, thickness 2mm).

[0040] Sintering: The green blank is placed in an argon-protected atmosphere sintering furnace, heated to 850℃ at 10℃ / min, held for 1 hour, and cooled with the furnace to obtain a dense carbon nanotube silver-based electrical contact material.

[0041] The Ag@CNTs composite powder was prepared in Preparation Example 1.

[0042] Example 2 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that the Ag@CNTs composite powder was prepared in Preparation Example 2.

[0043] Example 3 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that the Ag@CNTs composite powder was prepared in Preparation Example 3.

[0044] Example 4 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that the Ag@CNTs composite powder was prepared in Preparation Example 4.

[0045] Example 5 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that the Ag@CNTs composite powder was prepared in Preparation Example 5.

[0046] Example 6 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that the Ag@CNTs composite powder was prepared in Preparation Example 6.

[0047] Example 7 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that the Ag@CNTs composite powder was prepared in Preparation Example 7.

[0048] Example 8 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that the Ag@CNTs composite powder was prepared in Preparation Example 8.

[0049] Example 9 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that the Ag@CNTs composite powder was prepared in Preparation Example 9.

[0050] Example 10 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that the Ag@CNTs composite powder was prepared in Preparation Example 10.

[0051] Example 11 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that the Ag@CNTs composite powder was prepared in Preparation Example 11.

[0052] Example 12 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that the Ag@CNTs composite powder was prepared in Preparation Example 12.

[0053] Comparative Example 1 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that it uses CNTs of equal mass instead of Ag@CNTs composite powder.

[0054] Comparative Example 2 The silver-based electrical contact material containing carbon nanotubes differs from that in Example 1 in that the Ag@CNTs composite powder was prepared in Preparation Example 13.

[0055] Conductivity: Contact resistance is tested according to GB / T 14048.1.

[0056] Arc erosion resistance: Electrical life and mass loss rate were tested according to GB / T 14048.4.

[0057] Resistance to fusion welding: The resistance to fusion welding current is tested according to GB / T 14048.1.

[0058] The electrical contact materials obtained in Examples 1-12 and Comparative Examples 1-2 were tested.

[0059] Contact resistance (μΩ) Electrical life (ten thousand cycles) Mass loss rate (mg / 10,000 cycles) Resistance to welding current (A) Example 1 25 12.5 0.8 2850 Example 2 32 10 1.2 2600 Example 3 31 10.2 1.1 2620 Example 4 35 8.5 1.8 2400 Example 5 45 7 2.5 2200 Example 6 30 9.5 1.3 2550 Example 7 38 8 1.7 2450 Example 8 28 11 1 2700 Example 9 26 12 0.9 2800 Example 10 40 7.5 2 2350 Example 11 50 6.5 2.8 2100 Example 12 36 8.8 1.6 2500 Comparative Example 1 85 3 5.5 1800 Comparative Example 2 95 3.5 5 1850 Compared with Comparative Examples 1 and 1-2, the contact resistance of Example 1 is significantly lower than that of Comparative Examples 1 and 2, the electrical life of Example 1 is significantly greater than that of Comparative Examples 1 and 2, the mass loss rate of Example 1 is significantly lower than that of Comparative Examples 1 and 2, and the resistance to welding current of Example 1 is significantly greater than that of Comparative Examples 1 and 2. Therefore, it can be seen that the electrical contact material of Example 1 is significantly better than that of Comparative Examples 1 and 2 in terms of contact resistance, resistance to arc erosion, and resistance to welding.

[0060] Therefore, this application utilizes a pyrene carboxylic acid derivative to non-covalently functionalize carbon nanotubes. This molecule is firmly anchored to the CNT surface through strong π-π interactions with its pyrene group, while the exposed carboxyl groups provide a large number of active sites for the uniform adsorption of silver ions. This achieves stable dispersion of CNTs in the aqueous phase at the molecular level and constructs an ideal silver deposition interface. Subsequently, the precursor solution is atomized into micron-sized droplets and instantaneously pyrolyzed using a liquid-phase atomization method. Each droplet becomes an independent microreactor, forcing the silver precursor to be uniformly reduced and crystallized in situ on the surface of the functionalized CNTs, ultimately forming a well-structured "silver shell" coating layer. When the "silver shell" is subsequently combined with silver-based powder and sintered, because its composition is the same as the matrix, the weak physical contact between CNTs and the silver matrix is ​​transformed into a strong and tough chemical / metallurgical bonding interface. Pyrene derivative modification significantly improves the dispersibility of CNTs with almost no damage to their intrinsic structure; the liquid-phase atomization method forces uniform nucleation and growth of silver within a microscale reaction space, solving the problems of coating uniformity and binding force. The combination of these two methods enables low-dosage CNTs to form a highly efficient reinforcing and conductive network in the silver matrix, ultimately achieving a synergistic improvement in conductivity, weldability, and arc resistance of silver-based electrical contacts.

[0061] Comparing Example 1 and Example 2, it can be seen that the electrical life of Example 1 is greater than that of Example 2, the mass loss rate of Example 1 is less than that of Example 2, and the anti-fusion welding current of Example 1 is greater than that of Example 2.

[0062] Therefore, compared with other derivatives, 1-pyrenebutyric acid in this application has an alkyl chain of appropriate length between the pyrene group and the carboxyl group. On the one hand, the alkyl chain provides moderate spatial flexibility, allowing the pyrene group to better adapt to the curvature changes of the CNT surface and achieve tighter and more stable adsorption. On the other hand, it ensures that the carboxyl functional group can be fully exposed in the solution to maintain high reactivity, while avoiding the poor adsorption caused by the molecule being too short or the steric hindrance caused by the molecule being too long, resulting in more stable material properties.

[0063] Comparing Examples 1 and 3, it can be seen that the contact resistance of Example 1 is lower than that of Example 3, the electrical lifetime of Example 1 is greater than that of Example 3, the mass loss rate of Example 1 is lower than that of Example 3, and the anti-welding current of Example 1 is greater than that of Example 3. Therefore, it can be seen that in this application, the precursor solution is broken into micron-sized droplets, making each droplet an independent "microreactor." This forces the silver precursor to undergo instantaneous and uniform thermal decomposition and reduction reactions on the surface of the dispersed functionalized carbon nanotubes within a spatially confined space. This achieves in-situ, uniform, and complete coating of silver on each CNT, thereby obtaining Ag@CNTs with stable performance and excellent dispersion, thus steadily improving the performance of the electrical contact material.

[0064] Comparing Examples 1 and 4-5, it can be seen that the contact resistance of Example 1 is less than that of Example 4-5, the electrical life of Example 1 is greater than that of Example 4-5, the mass loss rate of Example 1 is less than that of Example 4-5, and the anti-fusion welding current of Example 1 is greater than that of Example 4-5.

[0065] Therefore, it can be seen that the silver salt composite solution used in this application is a mixture of silver nitrate and silver oxalate, and the resulting electrical contact material has better performance. The reason is that by utilizing the different thermal decomposition kinetics of the two silver salts, a "gradient deposition" is achieved during the atomization pyrolysis process. Silver nitrate decomposes preferentially during the heating stage, and a uniform and dense silver nanocrystal "seed layer" is rapidly formed on the surface of the functionalized carbon nanotubes. The decomposition process of silver oxalate mainly occurs in a higher temperature range. At this time, the released silver atoms will grow epitaxially with the existing "seed layer" as the core, thereby effectively "thickening" and "densifying" the silver coating layer on the basis of the established uniform structure. The sequential reaction path essentially transforms the silver deposition process from a one-step random nucleation and growth to a two-step controllable "seed-guided" growth. Compared to traditional single silver salt precursors, which are difficult to balance nucleation density and growth quality during instantaneous pyrolysis, leading to discontinuous coating layers or coarse silver particles. The specific combination of silver nitrate and silver oxalate, in the instantaneous high temperature and microreactor environment provided by the liquid phase atomization method, ingeniously constructs a deposition sequence that first ensures uniformity and then enhances integrity. This results in a silver shell layer that has excellent continuity, density, and bonding strength with the CNT substrate. The resulting material has better electrical conductivity, thermal conductivity, arc resistance, anti-welding properties, and stability.

[0066] Comparing Example 1 and Example 6-7, it can be seen that the contact resistance of Example 1 is less than that of Example 6-7, the electrical life of Example 1 is greater than that of Example 6-7, the mass loss rate of Example 1 is less than that of Example 6-7, and the anti-fusion welding current of Example 1 is greater than that of Example 6-7.

[0067] Comparing Example 1 with Examples 8-9, it can be seen that the contact resistance of Example 1 is less than that of Example 8-9, the electrical life of Example 1 is greater than that of Example 8-9, the mass loss rate of Example 1 is less than that of Example 8-9, and the anti-fusion welding current of Example 1 is greater than that of Example 8-9.

[0068] Therefore, it can be seen that when the molar ratio of silver nitrate to silver oxalate in this application is 1:3.2 and the total silver ion concentration is 0.65 mol / L, the resulting electrical contact material has superior performance. The total silver ion concentration ensures sufficient silver source to achieve effective coating thickness while avoiding excessively high solution viscosity that would affect atomization uniformity. The 1:3.2 molar ratio ensures that during the programmed temperature pyrolysis process, silver nitrate, with its lower decomposition temperature, can provide a suitable amount of uniform silver crystal nuclei as "seeds," while silver oxalate, with its higher decomposition temperature, can provide sufficient silver atoms for adequate epitaxial growth and filling on the formed seeds. This kinetically promotes the formation of a continuous, dense, and moderately thick ideal silver coating layer, ensuring batch-to-batch consistency and high-performance reliability of the Ag@CNTs reinforcing phase.

[0069] Comparing Example 1 and Example 10, it can be seen that the contact resistance of Example 1 is less than that of Example 10, the electrical life of Example 1 is greater than that of Example 10, the mass loss rate of Example 1 is less than that of Example 10, and the anti-fusion welding current of Example 1 is greater than that of Example 10.

[0070] Furthermore, comparing Example 1 and Example 11-12, it can be seen that the contact resistance of Example 1 is less than that of Example 11-12, the electrical life of Example 1 is greater than that of Example 11-12, the mass loss rate of Example 1 is less than that of Example 11-12, and the anti-fusion welding current of Example 1 is greater than that of Example 11-12.

[0071] Therefore, this application introduces a CO2-containing reactive atmosphere and uses a three-stage temperature control to regulate the proportion of the atmosphere. At high temperatures, CO2 can selectively vaporize with highly reactive carbon atoms such as amorphous carbon and structural defects on the surface of carbon nanotubes, achieving "in-situ cleaning and activation" of the CNT surface. This exposes more clean and regular graphite crystal faces, providing an ideal substrate for the subsequent uniform heterogeneous nucleation of silver. Secondly, CO2 molecules, as a gaseous adsorbate, can competitively adsorb on specific crystal faces of CNTs or initial silver nuclei, dynamically changing the local interfacial energy. This regulates the surface mobility and adhesion tendency of silver atoms, inhibits their three-dimensional island-like agglomeration growth, and guides them to spread into a more uniform and continuous two-dimensional thin film mode. Finally, the vaporization reaction byproduct CO is a mild reducing gas that can further reduce any incompletely decomposed silver precursor intermediates at the gas phase or interface, playing a role in "secondary reduction and purification" to ensure that silver is deposited in a high-purity metallic state. Ultimately, this ensures that the prepared Ag@CNTs reinforced phase has unparalleled interface cleanliness, coating uniformity, and structural integrity, providing the most reliable raw material guarantee for the electrical contact material to achieve its ultimate performance, and further improving the arc resistance and weldability of the obtained electrical contact material.

[0072] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but as long as they are within the scope of protection claimed by the present invention, they are protected by patent law.

Claims

1. A silver-based electrical contact containing carbon nanotubes, characterized in that, Including the following parts by weight of raw materials: Ag@CNTs 0.14-0.23 parts, 100 parts of silver-based powder; The preparation process of Ag@CNTs includes: Ag@CNTs were prepared by modification with pyrene carboxylic acid derivatives and liquid-phase atomization. The modification of CNTs with pyrene carboxylic acid derivatives includes: non-covalent modification of carbon nanotubes with pyrene carboxylic acid derivatives to obtain surface-functionalized carbon nanotubes.

2. The silver-based electrical contact containing carbon nanotubes according to claim 1, characterized in that, The carboxylic acid derivative of pyrene is 1-pyrenebutyric acid.

3. The silver-based electrical contact containing carbon nanotubes according to claim 1, characterized in that, The liquid-phase atomization method for preparing Ag@CNTs specifically involves: mixing a silver salt composite liquid with a carbon nanotube dispersion, atomizing the mixture using an ultrasonic atomizer, and then introducing it into a tubular furnace reaction zone at 650-750℃. After a thermal decomposition and reduction reaction, the Ag@CNTs precursor powder is collected by electrostatic adsorption.

4. A silver-based electrical contact containing carbon nanotubes according to claim 3, characterized in that, The silver salt composite solution is a mixture of silver nitrate and silver oxalate.

5. A silver-based electrical contact containing carbon nanotubes according to claim 4, characterized in that, The molar ratio of silver nitrate to silver oxalate is 1:3.2, and the total silver ion concentration is 0.65 mol / L.

6. A silver-based electrical contact containing carbon nanotubes according to claim 3, characterized in that, The thermal decomposition and reduction reaction atmosphere in the tubular furnace reaction zone contains CO2.

7. A silver-based electrical contact containing carbon nanotubes according to claim 3, characterized in that, The atmosphere for the thermal decomposition and reduction reaction is adjusted in three stages according to the heating process. The low-temperature stage is from room temperature to 500℃, and the thermal decomposition and reduction reaction atmosphere is 20% CO2 and 80% Ar. The temperature range of 500℃-650℃ is the intermediate temperature deposition stage, and the thermal decomposition and reduction reaction atmosphere is 5% CO2 and 95% Ar. The high-temperature insulation stage is from 650℃ to 750℃, during which pure Ar is switched.

8. The preparation process of the silver-based electrical contact containing carbon nanotubes according to any one of claims 1-7, characterized in that, Includes the following steps, S1: Carbon nanotube pretreatment; S2: Preparation of Ag@CNTs composite powder; S3: 0.14-0.23 parts by weight of the Ag@CNTs composite powder obtained in step S2 are mechanically mixed with 100 parts by weight of silver-based powder to ensure uniform dispersion; S4: Press the uniformly mixed powder obtained in step S3 into a green contact blank; then sinter the green blank under a protective atmosphere to obtain a dense carbon nanotube silver-based electrical contact material.