A method for preparing a highly ductile, hierarchical SnO2-reinforced modified silver-based composite material

Abstract

The application discloses a preparation method of a high-plasticity hierarchical structure SnO2 reinforced modified silver-based composite material. The application quantitatively and stably prepares SnO2 reinforced phase powder with a sandwiched three-layer structure type and a hierarchical structure characteristic by using a crystal type transformation regulation and control new strategy, and combines a cumulative cold drawing process to prepare a new type of Ag / SnO2 composite material with high plasticity, solves the industry bottleneck problems of poor plasticity and high processing difficulty of a traditional Ag / SnO2 composite material, and promotes the industrialization process of the Ag / SnO2 composite material.

Description

Technical Field

[0001] This invention relates to a new technology for designing reinforced phase structures and preparing Ag / SnO2 composite materials, particularly a method for preparing highly ductile, hierarchical SnO2-reinforced silver-based composite materials applicable to fields such as nano-electrical contacts and low-voltage switching devices for new energy applications. Technical Background

[0002] Tin dioxide (SnO2) is a wide-bandgap metal oxide semiconductor, widely used in lithium batteries, gas sensors, and electrical alloys due to its excellent physicochemical properties. Currently, SnO2 has made some progress in the field of electrical alloys as an important reinforcing phase material in silver-based composite (Ag / MeO) systems. The comprehensive performance of Ag / SnO2 composites is closely related to the microstructure, volume fraction, particle size, and distribution of the reinforcing phase SnO2 in the silver matrix. Researchers have studied the particle size, content, dispersion, preparation process, and morphology (rod-like) of the reinforcing phase SnO2. 、 Porous 、 Numerous studies have been reported on nanowires and other related fields. Among them, Cosovic et al. employed a template method to improve the dispersion of SnO2 nanoparticles as the reinforcing phase in Ag / SnO2 composites. The Ag / SnO2 samples prepared by the template method exhibited better dispersibility than conventionally prepared Ag-SnO2 samples. After sintering and forging, these samples were found to have higher hardness, density, and lower porosity. Choi et al. atomized AgSn alloy powder and prepared core-(silver)-shell (SnO2) structured composite powders using a combined oxidation-ball milling process. Ball milling significantly increased the electrical conductivity of the Ag / SnO2 material, leading to the peeling and crushing of the SnO2 surface layer. After high-voltage magnetic pulse compression, SnO2 was uniformly distributed in a layered structure within the Ag matrix. Zhang Miao et al. elucidated the influence of SnO2 particle size on the electrical properties and corrosion behavior of Ag-4wt.%SnO2 contact materials. It was found that fine 300nm SnO2 particles help improve density and hardness, but reduce conductivity. With decreasing SnO2 particle size, the arc time of Ag-4%AgSnO2 contact materials decreases, mass loss decreases, arc erosion area increases, and pits become shallower and more dispersed. These studies indicate that existing literature mainly focuses on hardness, density, and resistivity, while reports on its tensile mechanical properties are scarce.

[0003] Generally speaking, compared to hot working processes, cold working processes have advantages such as simpler mold design, easier operation, and lower energy consumption. Moreover, among cold working processes, cold drawing is a lower-cost and lower-energy manufacturing method that silver-based composite material manufacturers particularly desire compared to cold forging. However, traditional Ag / SnO2 materials, composed of tin dioxide reinforcement, suffer from poor plasticity and machinability, resulting in poor deformation capacity and a high susceptibility to fracture during cold working. This reduces the material's yield and prevents a complete breakthrough in this low-cost processing method, significantly limiting the mass production of Ag / SnO2 materials at low cost, and consequently hindering its further expansion in the electrical alloy field. Summary of the Invention

[0004] The technical problem this invention aims to solve is to provide a hierarchical SnO2-reinforced phase structure design concept and propose a method for preparing highly plastic hierarchical SnO2-reinforced modified silver-based composite materials. This method, based solely on the SnO2-reinforced phase structure design concept, constructs a novel SnO2-reinforced phase structure with hierarchical characteristics, significantly improving the mechanical properties of Ag / SnO2 composite materials. It effectively solves the industry bottlenecks of poor plasticity and high processability difficulty in traditional Ag / SnO2 composite materials, providing manufacturers with a novel synthesis strategy for mass production of Ag / SnO2 composite materials with excellent mechanical properties at room temperature using only cold drawing processes (without cold forging processes).

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a highly ductile, hierarchical SnO2-reinforced modified silver-based composite material, comprising the following steps:

[0007] (I) Synthesis of Hierarchical SnO2 Reinforced Phase Powder

[0008] (1) Weigh out tin dichloride raw material and dissolve it in deionized water, while adding dilute HCl solution to inhibit Sn. 2+ The ions undergo hydrolysis; then, under vigorous stirring (200–400 rpm), a 0.1–0.4 mol / L SnCl₂·2H₂O solution is formed and reacted continuously for 20–120 min (labeled as solution A). Excessive reaction time leads to excessive growth of reactant nuclei in solution A, resulting in excessively large crystal sizes in the subsequent hydrothermal reaction product, making it difficult to obtain SnO₂ with a disc-like hierarchical structure. Conversely, insufficient reaction time results in a low nucleation rate in the solution system, and the nuclei do not yet form a disc-like morphology, leading to a granular product after subsequent hydrothermal treatment, rather than a hierarchical structure.

[0009] (2) Add the alkaline reaction solution to solution A under vigorous stirring (200-400 rpm) until the pH of the solution is 7-9.5 to obtain the precursor solution. The alkaline reaction solution is one of ammonium hydroxide aqueous solution, sodium bicarbonate, or hexamethylenetetramine.

[0010] (3) Then, the precursor solution obtained after the above reaction is introduced into a polytetrafluoroethylene-lined high-pressure reactor under stirring, and the reactor is placed in a constant temperature oven at 80-200℃ for hydrothermal reaction for 10-48 hours.

[0011] (4) The hydrothermal reaction product was washed with deionized water and anhydrous ethanol to obtain a black powder, which was then dried at 100℃ for 8 hours. Subsequently, the dried product was calcined at a sintering temperature of 300–1200℃ and an oxygen partial pressure of 0.1–0.5 MPa for 6–12 hours to finally prepare a SnO2-reinforced phase powder with a hierarchical structure (labeled as l-SnO2). The number of layers in the SnO2 hierarchical structure can be changed by adjusting the sintering temperature.

[0012] (II) Preparation of hierarchical SnO2-reinforced modified silver-based composite materials

[0013] (1) Ag and SnO2 powders with a mass ratio of (88-80):(12-20) were mixed and ball-milled in a planetary ball mill for 4-8 hours at a milling speed of 80-120 rpm and a ball-to-powder ratio of (3-10):1. An agate jar with a diameter of 70 mm and a height of 70 mm and agate balls with a diameter of 10 mm were used. Anhydrous ethanol (AR, ≥99.7%, SCR) was added as a process control agent, with the amount of anhydrous ethanol accounting for 15-35 wt.% of the total Ag and SnO2 powders to ensure that the entire ball-milled material was in a fluid slurry state. Finally, after the ball milling reaction, Ag / l-SnO2 composite powder was obtained.

[0014] (2) The prepared Ag / l-SnO2 composite powder was loaded into a cylindrical stainless steel mold with a diameter of 40 mm and a height of 100 mm, and pressed under a hydraulic pressure of 7-25 MPa for 20-60 s. The obtained Ag / l-SnO2 ingot was placed in a vacuum tube furnace and continuously reacted and sintered at 860-920℃ for 6-18 h.

[0015] (3) The obtained Ag / l-SnO2 sintered block was used to prepare Ag / l-SnO2 extruded wire with a diameter of 3.2 mm by hot extrusion under a hydraulic pressure of 10 MPa, with a corresponding hot extrusion temperature of 450~700℃.

[0016] (4) The Ag / l-SnO2 extruded wire is subjected to a cumulative cold drawing process of 9 passes to prepare the Ag / l-SnO2 electrical contact material. The deformation of the first to sixth passes is 10%, and stress-relief annealing is performed in each pass during this period: annealing temperature 540-780℃, annealing time 30-120min; the deformation of the seventh to ninth passes is 5%, during which the stress-relief annealing temperature of the seventh and eighth passes is 540-780℃, annealing time 30-120min, while the stress-relief annealing temperature of the ninth pass is 300-450℃, annealing time 4h-8h.

[0017] Based on previous research, this invention utilizes a novel strategy for regulating crystal transformation to quantitatively and stably prepare SnO2-reinforced phase powders with hierarchical structural characteristics, which are composed of regularly arranged micro-nano sheets in a "sandwich structure". Combined with a cumulative cold drawing process, a novel Ag / SnO2 composite material with high plasticity is prepared, which solves the industry bottleneck problems of poor plasticity and high processability of traditional Ag / SnO2 composite materials.

[0018] The beneficial effects of this invention are as follows:

[0019] (1) This invention proposes a new strategy for the synthesis of hierarchical SnO2-reinforced phase powder with crystal transformation regulation. This strategy does not require the introduction of additional dopant components. It promotes the transformation of SnO to SnO2 phase structure through a combination of hydrothermal and heat treatment, and achieves precise regulation of the hierarchical structure of SnO2-reinforced phase. It prepares SnO2-reinforced phase powder with a "sandwich structure" composed of regular micro-nano sheets, which can achieve large-scale stable and controllable production, save the raw material cost caused by the introduction of additional dopant components, and achieve the dual effect of cost reduction and efficiency improvement.

[0020] (2) This invention can produce SnO2 modified silver-based contact composite materials with excellent mechanical properties in batches using a simple cold drawing process at room temperature. It solves the problems of poor plasticity and poor processability of traditional Ag / SnO2 composite materials, and provides application value for production enterprises to promote the industrialization of high plasticity Ag / SnO2 composite materials. Attached Figure Description

[0021] Figure 1 SEM (a, b) and XRD patterns (c) of SnO2-reinforced phase powder with hierarchical structure (Example 3).

[0022] Figure 2 Mechanical property curves and toughness fracture morphology of Ag / SnO2 electrical contact material (Example 3). Detailed Implementation

[0023] The implementation of the present invention will be described in detail below with reference to specific embodiments.

[0024] Example 1:

[0025] (I) Synthesis of Hierarchical SnO2 Reinforced Phase Powder

[0026] (1) Weigh a certain amount of tin dichloride raw material and dissolve it in 100 mL of deionized water. At the same time, add 10 mL of dilute HCl solution (concentration of 0.1 mol / L) to inhibit Sn. 2+ Hydrolysis of ions; then, under vigorous stirring (200 rpm), a 0.1 mol / L SnCl2·2H2O solution is formed and the reaction is continued for 20 min (labeled as solution A).

[0027] (2) The prepared alkaline reaction solution (0.1 mol / L) was added to solution A under vigorous stirring (200 rpm) until the pH of the reaction solution was 9.5, thus obtaining the precursor solution. The alkaline reaction solution was an aqueous solution of ammonium hydroxide.

[0028] (3) Then, the precursor solution obtained after the above reaction is quickly introduced into a polytetrafluoroethylene-lined high-pressure reactor, and the reactor is placed in a 200°C constant temperature oven for hydrothermal reaction for 10 hours.

[0029] (4) The hydrothermal reaction product was washed with deionized water and anhydrous ethanol to obtain a black powder, which was then dried at 100°C for 8 hours. Subsequently, the dried product was calcined at 300°C and 0.5 MPa for 6 hours to finally prepare a SnO2-reinforced phase powder with adjustable layer number and hierarchical structure (labeled as l-SnO2).

[0030] (II) Preparation of hierarchical SnO2 modified silver-based composite materials

[0031] (1) Ag and SnO2 powders with a mass ratio of 88:12 were mixed and ball-milled in a planetary ball mill for 4 hours at a ball milling speed of 120 rpm and a ball-to-powder ratio of 3:1. An agate jar with a diameter of 70 mm and a height of 70 mm and agate balls with a diameter of 10 mm were used, and anhydrous ethanol (AR, ≥99.7%, SCR) (35 wt.% of the total Ag and SnO2 powders) was added as a process control agent. After the ball milling reaction was completed, the corresponding Ag / l-SnO2 composite powder was obtained.

[0032] (2) The prepared Ag / l-SnO2 composite powder was loaded into a cylindrical stainless steel mold with a diameter of 40 mm and a height of 100 mm, and pressed under a hydraulic pressure of 7 MPa for 60 s. The resulting Ag / l-SnO2 ingot was placed in a vacuum tube furnace and continuously reacted and sintered at 860 °C for 18 h.

[0033] (3) The obtained Ag / l-SnO2 sintered block was used to prepare Ag / l-SnO2 extruded wire with a diameter of 3.2 mm by hot extrusion under a hydraulic pressure of 10 MPa and the corresponding hot extrusion temperature was 450℃.

[0034] (4) Ag / l-SnO2 extruded wire was subjected to a cumulative cold drawing process of 9 passes to prepare the Ag / l-SnO2 composite material. The deformation of the first to sixth passes was 10%, and stress-relief annealing was performed in each pass during this period: annealing temperature 540℃, annealing time 120min; the deformation of the seventh to ninth passes was 5%, during which the stress-relief annealing temperature of the seventh and eighth passes was 540℃, annealing time 120min, and the stress-relief annealing temperature of the ninth pass was 300℃, annealing time 4h.

[0035] The electrical and mechanical properties of the final Ag / l-SnO2 electrical contact material were characterized.

[0036] Example 2:

[0037] (I) Synthesis of Hierarchical SnO2 Reinforced Phase Powder

[0038] (1) Weigh a certain amount of tin dichloride raw material and dissolve it in 100 mL of deionized water. At the same time, add 50 mL of dilute HCl solution (concentration of 0.1 mol / L) to inhibit Sn. 2+ Hydrolysis of ions; then, under vigorous stirring, a 0.4 mol / L SnCl2·2H2O solution is formed and the reaction continues for 120 min (labeled as solution A).

[0039] (2) The prepared alkaline reaction solution (0.8 mol / L) was added to solution A under vigorous stirring until the pH of the reaction solution was 7, thus obtaining the precursor solution. The alkaline reaction solution was sodium bicarbonate.

[0040] (3) Then, the precursor solution obtained after the above reaction is quickly introduced into a polytetrafluoroethylene-lined high-pressure reactor, and the reactor is placed in a 200°C constant temperature oven for hydrothermal reaction for 10 hours.

[0041] (4) The hydrothermal reaction product was washed with deionized water and anhydrous ethanol to obtain a black powder, which was then dried at 100°C for 8 hours. Subsequently, the dried product was calcined at 1200°C and 0.1 MPa oxygen partial pressure for 12 hours to finally prepare a SnO2-reinforced phase powder with adjustable layer number and hierarchical structure (labeled as l-SnO2).

[0042] (II) Preparation of hierarchical SnO2 modified silver-based composite materials

[0043] (1) Ag and SnO2 powders with a mass ratio of 82:18 were mixed and ball-milled in a planetary ball mill for 8 hours at a ball milling speed of 80 rpm and a ball-to-powder ratio of 5:1. An agate jar with a diameter of 70 mm and a height of 70 mm and agate balls with a diameter of 10 mm were used, and anhydrous ethanol (AR, ≥99.7%, SCR) (30 wt.% of the total Ag and SnO2 powders) was added as a process control agent. After the ball milling reaction was completed, the corresponding Ag / l-SnO2 composite powder was obtained.

[0044] (2) The prepared Ag / l-SnO2 composite powder was loaded into a cylindrical stainless steel mold with a diameter of 40 mm and a height of 100 mm, and pressed under a hydraulic pressure of 25 MPa for 20 s. The obtained Ag / l-SnO2 ingot was placed in a vacuum tube furnace and continuously reacted and sintered at 920 °C for 6 h.

[0045] (3) The obtained Ag / l-SnO2 sintered block was used to prepare Ag / l-SnO2 extruded wire with a diameter of 3.2 mm by hot extrusion under a hydraulic pressure of 10 MPa and the corresponding hot extrusion temperature was 700℃.

[0046] (4) Ag / l-SnO2 extruded wire was subjected to a cumulative cold drawing process of 9 passes to prepare the Ag / l-SnO2 composite material. The deformation of the first to sixth passes was 10%, and stress-relief annealing was performed in each pass during this period: annealing temperature 780℃, annealing time 30min; the deformation of the seventh to ninth passes was 5%, during which the stress-relief annealing temperature of the seventh and eighth passes was 780℃, annealing time 30min, and the stress-relief annealing temperature of the ninth pass was 450℃, annealing time 4h.

[0047] The electrical and mechanical properties of the final Ag / l-SnO2 electrical contact material were characterized.

[0048] Example 3:

[0049] (I) Synthesis of Hierarchical SnO2 Reinforced Phase Powder

[0050] (1) Weigh a certain amount of tin dichloride raw material and dissolve it in 100 mL of deionized water. At the same time, add 20 mL of dilute HCl solution (concentration of 0.1 mol / L) to inhibit Sn. 2+ Hydrolysis of ions; then, under vigorous stirring, a 0.2 mol / L SnCl2·2H2O solution is formed and the reaction continues for 60 min (labeled as solution A).

[0051] (2) The prepared alkaline reaction solution (0.35 mol / L) was added to solution A under vigorous stirring until the pH of the reaction solution was 8, thus obtaining the precursor solution. The alkaline reaction solution was hexamethylenetetramine.

[0052] (3) Then, the precursor solution obtained after the above reaction is quickly introduced into a polytetrafluoroethylene-lined high-pressure reactor, and the reactor is placed in a 90°C constant temperature oven for hydrothermal reaction for 30 hours.

[0053] (4) The hydrothermal reaction product was washed with deionized water and anhydrous ethanol to obtain a black powder, which was then dried at 100°C for 8 hours. Subsequently, the dried product was calcined at 800°C and 0.2 MPa for 8 hours to finally prepare a SnO2-reinforced phase powder with adjustable layer number and hierarchical structure (labeled as l-SnO2).

[0054] (II) Preparation of hierarchical SnO2 modified silver-based composite materials

[0055] (1) Ag and SnO2 powders with a mass ratio of 84:16 were mixed and ball-milled in a planetary ball mill for 7 hours at a milling speed of 100 rpm and a ball-to-powder ratio of 7:1. An agate jar with a diameter of 70 mm and a height of 70 mm and agate balls with a diameter of 10 mm were used, and anhydrous ethanol (AR, ≥99.7%, SCR) (25 wt.% of the total Ag and SnO2 powders) was added as a process control agent. After the ball milling reaction was completed, the corresponding Ag / l-SnO2 composite powder was obtained.

[0056] (2) The prepared Ag / l-SnO2 composite powder was loaded into a cylindrical stainless steel mold with a diameter of 40 mm and a height of 100 mm, and pressed under a large hydraulic pressure of 12 MPa for 40 s. The resulting Ag / l-SnO2 ingot was placed in a vacuum tube furnace and continuously reacted and sintered at 880 °C for 10 h.

[0057] (3) The obtained Ag / l-SnO2 sintered block was used to prepare Ag / l-SnO2 extruded wire with a diameter of 3.2 mm by hot extrusion under a large hydraulic pressure of 10 MPa, with a corresponding hot extrusion temperature of 550℃.

[0058] (4) Ag / l-SnO2 extruded wire was subjected to a cumulative cold drawing process of 9 passes to prepare the Ag / l-SnO2 composite material. The deformation of the first to sixth passes was 10%, and stress-relief annealing was performed in each pass during this period: annealing temperature 680℃, annealing time 90min; the deformation of the seventh to ninth passes was 5%, during which the stress-relief annealing temperature of the seventh and eighth passes was 680℃, annealing time 90min, and the stress-relief annealing temperature of the ninth pass was 350℃, annealing time 5h.

[0059] The electrical and mechanical properties of the final Ag / l-SnO2 electrical contact material were characterized.

[0060] Example 4:

[0061] (I) Synthesis of Hierarchical SnO2 Reinforced Phase Powder

[0062] (1) Weigh a certain amount of tin dichloride raw material and dissolve it in 100 mL of deionized water. At the same time, add 30 mL of dilute HCl solution (concentration of 0.1 mol / L) to inhibit Sn. 2+ Hydrolysis of ions; then, under vigorous stirring, a 0.35 mol / L SnCl2·2H2O solution is formed and the reaction continues for 100 min (labeled as solution A).

[0063] (2) The prepared alkaline reaction solution (0.65 mol / L) was added to solution A under vigorous stirring until the pH of the reaction solution reached 8.5, thus obtaining the precursor solution. The alkaline reaction solution was sodium bicarbonate.

[0064] (3) Then, the precursor solution obtained after the above reaction is quickly introduced into a polytetrafluoroethylene-lined high-pressure reactor, and the reactor is placed in a 130°C constant temperature oven for hydrothermal reaction for 40 hours.

[0065] (4) The hydrothermal reaction product was washed with deionized water and anhydrous ethanol to obtain a black powder, which was then dried at 100°C for 8 hours. Subsequently, the dried product was calcined at 860°C and 0.35 MPa for 9 hours to finally prepare a SnO2-reinforced phase powder with adjustable layer number and hierarchical structure (labeled as l-SnO2).

[0066] (II) Preparation of hierarchical SnO2 modified silver-based composite materials

[0067] (1) Ag and SnO2 powders with a mass ratio of 88:12 were mixed and ball-milled in a planetary ball mill for 7 hours at a ball milling speed of 90 rpm and a ball-to-powder ratio of 9:1. An agate jar with a diameter of 70 mm and a height of 70 mm and agate balls with a diameter of 10 mm were used, and anhydrous ethanol (AR, ≥99.7%, SCR) (15 wt.% of the total Ag and SnO2 powders) was added as a process control agent. After the ball milling reaction was completed, the corresponding Ag / l-SnO2 composite powder was obtained.

[0068] (2) The prepared Ag / l-SnO2 composite powder was loaded into a cylindrical stainless steel mold with a diameter of 40 mm and a height of 100 mm, and pressed for 40 s under a large hydraulic pressure of 16 MPa. The obtained Ag / l-SnO2 ingot was placed in a vacuum tube furnace and continuously reacted and sintered at 850 °C for 10 h.

[0069] (3) The obtained Ag / l-SnO2 sintered block was used to prepare Ag / l-SnO2 extruded wire with a diameter of 3.2 mm by hot extrusion under a large hydraulic pressure of 10 MPa, with a corresponding hot extrusion temperature of 650℃.

[0070] (4) Ag / l-SnO2 extruded wire was subjected to a cumulative cold drawing process of 9 passes to prepare the Ag / l-SnO2 composite material. The deformation of the first to sixth passes was 10%, and stress-relief annealing was performed in each pass during this period: annealing temperature 640℃, annealing time 80min; the deformation of the seventh to ninth passes was 5%, during which the stress-relief annealing temperature of the seventh and eighth passes was 680℃, annealing time 70min, and the stress-relief annealing temperature of the ninth pass was 400℃, annealing time 7.5h.

[0071] The electrical and mechanical properties of the final Ag / l-SnO2 electrical contact material were characterized.

[0072] Example 5:

[0073] (I) Synthesis of Hierarchical SnO2 Reinforced Phase Powder

[0074] (1) Weigh a certain amount of tin dichloride raw material and dissolve it in 100 mL of deionized water. At the same time, add 10–50 mL of dilute HCl solution (concentration of 0.1 mol / L) to inhibit Sn. 2+ Hydrolysis of ions; then, under vigorous stirring, a 0.35 mol / L SnCl2·2H2O solution is formed and the reaction continues for 80 min (labeled as solution A).

[0075] (2) The prepared alkaline reaction solution (0.65 mol / L) was added to solution A under vigorous stirring until the pH of the reaction solution was 9, thus obtaining the precursor solution. The alkaline reaction solution was hexamethylenetetramine.

[0076] (3) Then, the precursor solution obtained after the above reaction is quickly introduced into a polytetrafluoroethylene-lined high-pressure reactor, and the reactor is placed in a 150°C constant temperature oven for hydrothermal reaction for 24 hours.

[0077] (4) The hydrothermal reaction product was washed with deionized water and anhydrous ethanol to obtain a black powder, which was then dried at 100°C for 8 hours. Subsequently, the dried product was calcined at 900°C and 0.4 MPa oxygen partial pressure for 9 hours to finally prepare a SnO2-reinforced phase powder with adjustable layer number and hierarchical structure (labeled as l-SnO2).

[0078] (II) Preparation of hierarchical SnO2 modified silver-based composite materials

[0079] (1) Ag and SnO2 powders with a mass ratio of 86:12 were mixed and ball-milled in a planetary ball mill for 6 hours at a ball milling speed of 90 rpm and a ball-to-powder ratio of 7:1. An agate jar with a diameter of 70 mm and a height of 70 mm and agate balls with a diameter of 10 mm were used, and anhydrous ethanol (AR, ≥99.7%, SCR) (10 wt.% of the total Ag and SnO2 powders) was added as a process control agent. After the ball milling reaction was completed, the corresponding Ag / l-SnO2 composite powder was obtained.

[0080] (2) The prepared Ag / l-SnO2 composite powder was loaded into a cylindrical stainless steel mold with a diameter of 40 mm and a height of 100 mm, and pressed under a hydraulic pressure of 9 MPa for 60 s. The obtained Ag / l-SnO2 ingot was placed in a vacuum tube furnace and continuously reacted and sintered at 920 °C for 6 h.

[0081] (3) The obtained Ag / l-SnO2 sintered block was used to prepare Ag / l-SnO2 extruded wire with a diameter of 3.2 mm by hot extrusion under a hydraulic pressure of 10 MPa, with a corresponding hot extrusion temperature of 580℃.

[0082] (4) Ag / l-SnO2 extruded wire was subjected to a cumulative cold drawing process of 9 passes to prepare the Ag / l-SnO2 composite material. The deformation of the first to sixth passes was 10%, and stress-relief annealing was performed in each pass during this period: annealing temperature 650℃, annealing time 80min; the deformation of the seventh to ninth passes was 5%, during which the stress-relief annealing temperature of the seventh and eighth passes was 580℃, annealing time 100min, and the stress-relief annealing temperature of the ninth pass was 400℃, annealing time 6.5h.

[0083] The electrical and mechanical properties of the final Ag / l-SnO2 electrical contact material were characterized.

[0084] Table 1. Characterization of the electrical and thermal properties of SnO2-modified silver-based contact composite materials with hierarchical structure.

[0085]

[0086] A comparative analysis of the performance of the Ag / l-SnO2 electrical contact materials prepared in Examples 1-5 (see Table 1) shows that this invention can achieve large-scale stable preparation of SnO2 reinforcing phase powder with a hierarchical structure, composed of regularly arranged micro-nano sheets, resembling a "sandwich structure." Combined with a cumulative cold drawing process at room temperature, it can prepare novel Ag / l-SnO2 composite materials with high plasticity, solving the industry bottlenecks of poor plasticity and high processability difficulty of traditional Ag / SnO2 composite materials, and promoting the industrialization of Ag / SnO2 composite materials. In particular, the novel Ag / l-SnO2 composite material prepared in Example 3 exhibits the best mechanical properties. This is mainly due to the synergistic adjustment of hydrothermal reaction parameters, heat treatment temperature, and oxygen partial pressure, which allows for the acquisition of multi-layered SnO2 powder. Then, the Ag / SnO2 composite material composed of multilayer SnO2 is more prone to deformation-induced twinning during the cumulative drawing process, and the multilayer SnO2 structure of the SnO2 reinforcement phase is clearly cut and deformed during the cumulative drawing process. Therefore, the composite material prepared in Example 3 has superior performance.

[0087] like Figure 1 The image shows the SnO2 powder prepared in Example 3, which is made from... Figure 1 As shown in (a) and (b), the SnO2 powder prepared by this invention exhibits a morphological structure of a disc-like "sandwich-like" structure and a multi-layered SnO2 powder with hierarchical arrangement; in terms of phase, it is a single-phase SnO2 with a rutile structure, corresponding to card PDF#41-1445 ( Figure 1 (c) Therefore, SnO2-reinforced phase powder with a hierarchical structure can be prepared based on the method of the present invention.

[0088] like Figure 2 The image shows the Ag / SnO2 electrical contact material prepared in Example 3, which is made from... Figure 2 As shown in (a), the Ag / SnO2 composite material exhibits an elongation after fracture of 15.9% and a tensile strength of 280.97 MPa, demonstrating excellent tensile mechanical properties. Corresponding fracture morphology photographs are shown below. Figure 2 As shown in (b), it can be observed that there are obvious dimple morphology on the tensile fracture surface, which shows a ductile fracture mode.

Claims

1. A method for preparing a highly ductile, hierarchical SnO2-reinforced modified silver-based composite material, characterized in that, The steps are as follows: (I) Synthesis of hierarchical SnO2-reinforced phase powder (1-1) Weigh out tin dichloride raw material and dissolve it in deionized water, while adding dilute HCl solution to inhibit Sn. 2+ Hydrolysis of ions; Then, under vigorous stirring, a 0.1~0.4 mol / L SnCl2∙2H2O solution is formed and the reaction continues for 20~120 min to obtain solution A; (1-2) Add the alkaline reaction solution to solution A under vigorous stirring until the pH of the solution is 7~9.5 to obtain the precursor solution; (1-3) Then, the prepared precursor solution is introduced into a polytetrafluoroethylene-lined high-pressure reactor under stirring, and the reactor is placed in a constant temperature box at 80~200℃ for hydrothermal reaction for 10~48h. (1-4) The hydrothermal reaction product obtained in step (1-3) was washed with deionized water and anhydrous ethanol to obtain a black powder, which was then dried at 100°C for 8 hours. Subsequently, the dried product was continuously calcined at a sintering temperature of 300~1200℃ and an oxygen partial pressure of 0.1~0.5MPa for 6~12h to finally prepare SnO2 reinforced phase powder with a hierarchical structure, denoted as l-SnO2. (II) Preparation of hierarchical SnO2 modified silver-based composite materials (2-1) Ag with a mass ratio of (88~80): (12~20) and l-SnO2 powder obtained in step (I) are mixed and ball-milled in a planetary ball mill for 4~8h at a ball milling speed of 80~120rpm and a ball-to-material ratio of (3~10):

1. Anhydrous ethanol is added as a process control agent during the ball milling process. After the ball milling reaction is completed, Ag / l-SnO2 composite powder is obtained. (2-2) The prepared Ag / l-SnO2 composite powder was loaded into a cylindrical stainless steel mold and pressed under a hydraulic pressure of 7~25MPa for 20~60s. The obtained Ag / l-SnO2 ingot was placed in a vacuum tube furnace and continuously reacted and sintered at 860~920℃ for 6~18h to obtain Ag / l-SnO2 sintered block; (2-3) The obtained Ag / l-SnO2 sintered block was used to prepare Ag / l-SnO2 extruded wire with a diameter of 3.2 mm by hot extrusion under a hydraulic pressure of 10 MPa. The hot extrusion temperature was 450~700℃. (2-4) Ag / l-SnO2 extruded wires were subjected to a cumulative cold drawing process of 9 passes to prepare Ag / l-SnO2 electrical contact materials; The stirring speed in steps (1-1) and (1-2) is 200~400 rpm.

2. The method for preparing a highly ductile, hierarchical SnO2-reinforced modified silver-based contact composite material according to claim 1, characterized in that, In steps (1-2), the alkaline reaction solution is one of ammonium hydroxide aqueous solution, sodium bicarbonate, and hexamethylenetetramine.

3. The method for preparing the highly ductile, hierarchical SnO2-reinforced modified silver-based composite material according to claim 1, characterized in that, In step (2-1), the amount of anhydrous ethanol used accounts for 15~35 wt.% of the total amount of Ag and 1-SnO2 powder to ensure that the entire ball-milled material is in a fluid slurry state.

4. The method for preparing the highly ductile, hierarchical SnO2-reinforced modified silver-based composite material according to claim 1, characterized in that, In steps (2-4), the cumulative cold drawing process of 9 passes is specifically performed as follows: The deformation of passes 1 to 6 is 10%, and stress-relieving annealing is performed in each pass during this period: annealing temperature 540~780℃, annealing time 30~120min; The deformation of passes 7 through 9 is 5%, and stress-relief annealing is performed in each pass. The stress-relief annealing temperature for passes 7 and 8 is 540~780℃, and the annealing time is 30~120min. The stress-relief annealing temperature for pass 9 is 300~450℃, and the annealing time is 4h~8h.

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