Preparation method of silver-nickel graphene alloy material with good electrical conductivity

Abstract

The application provides a preparation method of a silver-nickel graphene alloy material with good conductive performance, and comprises the following steps: S1. mixing an oxidized graphene dispersion liquid, a metal salt solution containing silver and nickel and a dispersing agent to form a mixed slurry; S2. performing spray drying on the mixed slurry to obtain a composite powder; and S3. performing reduction, shaping and sintering treatment on the composite powder to obtain the silver-nickel graphene alloy material. The graphene precursor and the metal salt are uniformly mixed at the molecular / nanoscale in a solution state, the enhanced phase precursor is "distributed" to each base particle through spray drying, the original uniform distribution of the oxidized graphene in the macroscopic composite material is achieved, in the subsequent reduction and sintering step, the in-situ reduction and reaction of the metal nanoparticles and the graphene are formed, a strong interface combination is formed, and the strength and the conductive performance of the material are improved.

Description

Technical Field

[0001] This invention relates to the field of alloy materials technology, specifically to a method for preparing a silver-nickel-graphene alloy material with good electrical conductivity. Background Technology

[0002] AgNi materials possess excellent electrical and thermal conductivity, machinability, and resistance to arc burn-off, making them widely used in various switches, controllers, voltage regulators, circuit breakers, automotive electrical components, and magnetic starters. However, AgNi materials exhibit relatively poor resistance to welding, limiting their application under high-current conditions.

[0003] To improve the weldability of AgNi materials, introducing a second-phase reinforcement is an effective approach. Graphene, as a single-layer carbon atom material, possesses extremely high strength, electrical conductivity, and thermal stability, making it an ideal nano-reinforcement. Chinese patent CN105679560A discloses a method for plating nickel onto the surface of graphene using magnetron sputtering, followed by ball milling to combine it with atomized AgNi alloy powder. Although this method uses a nano-reinforcement, it still has significant shortcomings: the subsequent high-energy ball milling process may destroy the integrity of the graphene structure and the plating; and it cannot solve the problem of agglomeration of nanomaterials in micron-sized metal powders.

[0004] As can be seen from the above analysis, the mainstream methods for preparing graphene-reinforced silver-nickel composite materials in the existing technology all adopt discrete processes of "stepwise preparation of reinforcement" and "mechanical mixing", which have problems such as complex process flow, uneven dispersion of reinforcement, unsatisfactory interfacial bonding strength, high cost and poor conductivity. Summary of the Invention

[0005] To address the above problems, this invention provides a method for preparing a silver-nickel-graphene alloy material with good electrical conductivity, comprising the following steps: S1. Mix the graphene oxide dispersion, the silver and nickel metal salt solution, and the dispersant to form a mixed slurry; S2. Spray dry the mixed slurry to obtain composite powder; S3. The composite powder is reduced and then sintered to obtain a silver-nickel graphene alloy material.

[0006] Preferably, the concentration of the graphene oxide dispersion is 2 mg / mL.

[0007] Preferably, the metal salt solution comprises silver nitrate and nickel nitrate, and the ratio of the total number of metal moles to the number of carbon moles of graphene oxide is (0.1-0.5):1.

[0008] Preferably, the dispersant is polyvinylpyrrolidone, and its addition amount is 20%-50% of the mass of graphene oxide.

[0009] Preferably, the process parameters for spray drying are: inlet temperature 180-200℃, outlet temperature 80-100℃, droplet size 50-150μm, and atomizing gas nitrogen or air.

[0010] Preferably, step S3 includes: S31. Introduce a mixture of argon and hydrogen, wherein the volume fraction of hydrogen is 30-50%, heat to 260-280℃, heating rate is 2-5℃ / min, time is 90-120 minutes, to obtain a mixture composed of graphene oxide, silver and nickel. The composite powder obtained from S32.S2 is placed in a hydraulic device at a pressure of 300MPa to form a skeleton compact. Then, a mixture of argon and hydrogen is introduced, with the hydrogen volume fraction being 5-10%. The temperature is then raised to 550-620℃ at a rate of 5-8℃ / min and held for 90-150 minutes to obtain a graphite-dispersed silver-nickel alloy. The composite powder obtained from S33.S2 is placed in a hydraulic apparatus at a pressure of 300MPa to form a skeleton compact. Argon gas is introduced, and the temperature is raised to 720-750℃ at a rate of 8-10℃ / min and held for 10-30 minutes. The temperature is then lowered to 350-450℃ at a rate of 3-5℃ / min and annealed for 1-3 hours. Finally, the material is allowed to cool naturally to room temperature to obtain a silver-nickel graphene alloy material.

[0011] Rapid densification at 720-750℃ and 40-50 MPa pressure yields alloy materials with densities close to theoretical densities.

[0012] Technical effects: The graphene precursor and metal salt are uniformly mixed at the molecular / nanoscale in solution. The reinforcing phase precursor is then "distributed" to each matrix particle through spray drying, achieving an intrinsic and uniform distribution of graphene oxide in the macroscopic composite material. In the subsequent reduction sintering step, the metal nanoparticles and graphene are reduced and reacted in situ, forming a strong interfacial bond, which improves the strength and conductivity of the material.

[0013] S31. Introduce a mixture of argon and hydrogen, wherein the volume fraction of hydrogen is 30-50%, heat to 260-280℃, heating rate is 2-5℃ / min, time is 90-120 minutes, to obtain a mixture composed of graphene oxide, silver and nickel. The composite powder obtained from S32.S2 is placed in a hydraulic device at a pressure of 300MPa to form a skeleton compact. Then, a mixture of argon and hydrogen is introduced, with the hydrogen volume fraction being 5-10%. The temperature is then raised to 550-620℃ at a rate of 5-8℃ / min and held for 90-150 minutes to obtain a graphite-dispersed silver-nickel alloy. The composite powder obtained from S33.S2 is placed in a hydraulic apparatus at a pressure of 300MPa to form a skeleton compact. Argon gas is introduced, and the temperature is raised to 720-750℃ at a rate of 8-10℃ / min and held for 10-30 minutes. The temperature is then lowered to 350-450℃ at a rate of 3-5℃ / min and annealed for 1-3 hours. Finally, the material is allowed to cool naturally to room temperature to obtain a silver-nickel graphene alloy material. Attached Figure Description

[0014] Figure 1 A schematic flowchart illustrating a method for preparing a silver-nickel-graphene alloy material with good electrical conductivity, provided by this invention. Figure 2 A microstructure diagram of the product prepared in Example 1; Figure 3 Another microstructure diagram of the product prepared in Example 1. Detailed Implementation

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] like Figure 1 As shown, this invention provides a method for preparing a silver-nickel-graphene alloy material with good electrical conductivity, comprising the following steps: S1. Mix the graphene oxide dispersion, the silver and nickel metal salt solution, and the dispersant to form a mixed slurry; S2. Spray dry the mixed slurry to obtain composite powder; S3. The composite powder is reduced, shaped and sintered to obtain a silver-nickel graphene alloy material.

[0017] The graphene precursor and metal salt are uniformly mixed at the molecular / nanoscale in solution. The reinforcing phase precursor is then "distributed" to each matrix particle through spray drying, achieving an intrinsic and uniform distribution of graphene oxide in the macroscopic composite material. In the subsequent reduction sintering step, the metal nanoparticles and graphene are reduced and reacted in situ, forming a strong interfacial bond, which improves the strength and conductivity of the material.

[0018] Preferably, the concentration of the graphene oxide dispersion is 2-5 mg / mL, more preferably 2 mg / mL. At this concentration, there is sufficient water molecule barrier between the graphene oxide sheets, allowing for thorough exfoliation and dispersion by ultrasound and shear force.

[0019] Preferably, the metal salt solution comprises silver nitrate and nickel nitrate, with the ratio of the total molar number of metals to the molar number of carbon atoms in the graphene oxide being (0.1-0.5):1, preferably 0.1:1. This ratio ensures that the active sites on the graphene oxide sheets are fully occupied, forming a uniform and dense metal nanoparticle modification layer after reduction. If the ratio is too low, the metal coverage is insufficient, resulting in a weak interface strengthening effect; if the ratio is too high, excessive metal nanoparticles are prone to self-aggregation, failing to be effectively loaded onto the graphene.

[0020] Preferably, the dispersant is polyvinylpyrrolidone (PVP), and its addition amount is 20%-50% of the mass of graphene oxide. The addition of PVP significantly improves the stability of the slurry and prevents sedimentation or agglomeration before spray drying. An appropriate amount of PVP can also serve as a carbon source in subsequent heat treatment, assisting the reduction process and partially converting into amorphous carbon, thus buffering interfacial stress. Long-chain PVP molecules can adsorb onto graphene oxide sheets and metal ions, maintaining dispersion stability through steric hindrance.

[0021] Preferably, the spray drying process parameters are: inlet temperature 180-200℃, outlet temperature 80-100℃, droplet size 50-150μm, and atomizing gas nitrogen or air. By controlling the droplet size within this range, spherical precursor powder with good flowability and uniform particle size can be obtained, and each powder particle achieves microscopic uniform composite of graphene oxide and metal salt precursor.

[0022] Preferably, step S3 includes: S31. Introduce a mixture of argon and hydrogen, wherein the volume fraction of hydrogen is 30-50%, and heat to 260-280℃ for 90-120 minutes to obtain a mixture composed of graphene oxide, silver and nickel. S32. Introduce a mixture of argon and hydrogen, wherein the volume fraction of hydrogen is 5-10%, and then heat to 550-620℃ and hold for 90-150 minutes to obtain a graphite-dispersed silver-nickel alloy. S33. Introduce argon gas, heat to 720-750℃, pressure 40-50Mpa, and hold for 10-30 minutes to obtain silver-nickel graphene alloy material.

[0023] Under conditions of 260-280℃ and high hydrogen concentration (30-50%), silver nitrate and nickel nitrate are preferentially and selectively completely reduced to Ag and Ni nanoparticles, which then attach in situ to graphene oxide. During this stage, graphene oxide undergoes only physical dehydration and very slight reduction, thus preserving its carbon framework and reactivity.

[0024] In a low-hydrogen atmosphere at 550-620℃, graphene oxide undergoes deep thermal reduction, transforming into graphene with excellent electrical conductivity. Simultaneously, the already generated active Ni nanoparticles undergo solid-state diffusion and interfacial reactions with the carbon atoms of the newly formed graphene, forming a strong interface dominated by chemical bonding.

[0025] Rapid densification at 720-750℃ and 40-50 MPa pressure yields an alloy material with near-theoretical density. This low-temperature, short-time process maximizes the protection of the graphene nanostructure and the formed reinforced interfaces from high-temperature damage.

[0026] Preferably, in S31, the temperature is increased at a rate of 2-5℃ / min; in S2, the temperature is increased at a rate of 5-8℃ / min; and in S32, the temperature is increased at a rate of 8-10℃ / min.

[0027] Preferably, step S33 further includes: cooling to 350-450 at a rate of 3-5℃ / min and annealing for 1-3 hours; then naturally cooling to room temperature. Example 1

[0028] S1. Preparation of mixed slurry Prepare a graphene oxide dispersion with a concentration of 2 mg / mL; weigh silver nitrate and nickel nitrate hexahydrate separately according to the ratio of total metal (Ag+Ni) moles to carbon moles in graphene oxide of 0.1:1 (where the ratio of Ag to Ni is 1:1), dissolve them in deionized water, and prepare a mixed metal salt solution; prepare polyvinylpyrrolidone with a mass of 20% of graphene oxide; mix the graphene oxide dispersion, metal salt solution and dispersant evenly to obtain a mixed slurry.

[0029] S2. Spray drying to obtain composite powder The above-mentioned mixed slurry was fed into a centrifugal spray dryer, with the inlet temperature set at 180℃ and the outlet temperature at 80℃. The rotation speed of the atomizing disc was adjusted to control the atomized droplet size to approximately 50μm. Nitrogen was used as both the drying medium and the atomizing gas, and the dried composite powder was collected.

[0030] S3. Reduction and Sintering S31: Spread the composite powder evenly in an alumina crucible, place it in a tube furnace, introduce a mixed gas with a volume ratio of 30% H2 / 70% Ar, heat to 260℃ at a heating rate of 2℃ / min, and hold at this temperature for 90 minutes.

[0031] S32: After the heat preservation is completed, switch the atmosphere in the furnace to 5% H2 / 95% Ar, raise the temperature to 550℃ at a rate of 5℃ / min, and keep it at that temperature for 90 minutes.

[0032] S33: Heat to 720℃ at a rate of 8℃ / min, apply axial pressure of 40 MPa, hold for 10 minutes, after sintering, cool to 350℃ at a controlled rate of 3℃ / min, and anneal at this temperature for 1 hour. Then, allow the furnace to cool naturally to room temperature to obtain silver-nickel graphene alloy material (sintered billet). Example 2

[0033] S1. Preparation of mixed slurry A graphene oxide dispersion with a concentration of 3.5 mg / mL was prepared. The metal / carbon molar ratio was 0.3:1. The amount of PVP added was 35% of the mass of graphene oxide.

[0034] S2. Spray drying to obtain composite powder The spray dryer has an inlet temperature of 190℃, controls the droplet size to about 100μm, and uses nitrogen as the atomizing gas.

[0035] S3. Reduction and Sintering S31: Introduce 40% H2 / Ar, raise the temperature to 270℃ at 3.5℃ / min, and hold for 105 minutes. S32: Switch to 7.5% H2 / Ar, raise the temperature to 585℃ at 6.5℃ / min, and hold for 120 minutes.

[0036] S33: Heat to 735℃ at 9℃ / min, apply 45 MPa pressure, and hold for 20 minutes. Cool to 400℃ at 4℃ / min and anneal for 2 hours. Example 3

[0037] S1: Prepare a graphene oxide dispersion with a concentration of 5 mg / mL. The metal / carbon molar ratio is 0.5:1. The PVP addition amount is 50% of the graphene oxide mass.

[0038] S2. Spray drying to obtain composite powder The spray dryer has an inlet temperature of 200℃, controls the droplet size to 150μm, and uses air as the atomizing gas.

[0039] S3. Reduction and Sintering S31: Introduce 50% H2 / Ar, raise the temperature to 280℃ at 5℃ / min, and hold for 120 minutes.

[0040] S32: Switch to 10% H2 / Ar, heat to 620℃ at 8℃ / min, and hold for 150 minutes.

[0041] S33: Heat to 750℃ at 10℃ / min, apply 50 MPa pressure, and hold for 30 minutes. Cool to 450℃ at 5℃ / min and anneal for 3 hours.

[0042] Comparative Example 1 1. Preparation of nickel-plated graphene: A layer of metallic nickel was deposited on the surface of multilayer graphene (average 5 layers) by DC magnetron sputtering with a sputtering power of 100W, a working gas pressure of 1.0 Pa, and a deposition time of 15 min.

[0043] 2. Preparation of matrix powder: Silver-nickel alloy powder with a nickel content of 10 wt.% was prepared by gas atomization and the powder with a particle size of 15-45 μm was sieved out.

[0044] 3. Mixing: Weigh nickel-plated graphene and Ag-10Ni alloy powder at a graphene mass fraction of 1%, place them in a planetary ball mill jar, and add agate balls at a ball-to-material ratio of 3:1. Under argon protection, ball mill at 250 rpm for 4 hours to mix.

[0045] 4. Molding and Sintering: The mixed powder is cold-pressed under 300 MPa pressure, placed in a hydrogen atmosphere sintering furnace, and heated to 850℃ at 5℃ / min, and held for 2 hours. After sintering, the compact is re-pressed to the calculated thickness, and the finished product is annealed (350℃, held for 0.5H) (in principle, materials that are cold-pressed and sintered from powder will undergo re-pressing + annealing).

[0046] The microstructure of the product prepared in Example 1 was tested, and the results are shown in the figure. Figure 2 and 3 It is evident that its structure is dense and uniform.

[0047] The obtained product was subjected to electrical conductivity and tensile strength tests, and its density and hardness were also tested.

[0048] Conclusion: The process of this invention can stably prepare high-performance materials, and the comprehensive properties of electrical conductivity, tensile strength and hardness are far superior to those of traditional methods.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a silver-nickel-graphene alloy material with good electrical conductivity, characterized in that, Includes the following steps: S1. Mix the graphene oxide dispersion, the silver and nickel metal salt solution, and the dispersant to form a mixed slurry; S2. Spray dry the mixed slurry to obtain composite powder; S3. The composite powder is reduced, shaped and sintered to obtain a silver-nickel graphene alloy material.

2. The preparation method according to claim 1, characterized in that, The concentration of the graphene oxide dispersion is 2 mg / mL.

3. The preparation method according to claim 1, characterized in that, The metal salt solution comprises silver nitrate and nickel nitrate, and the ratio of the total number of metal moles to the number of carbon moles of graphene oxide is 0.1:

1.

4. The preparation method according to claim 1, characterized in that, The dispersant is polyvinylpyrrolidone, and its addition amount is 20%-50% of the mass of graphene oxide.

5. The preparation method according to claim 1, characterized in that, The process parameters for spray drying are: inlet temperature 180-200℃, outlet temperature 80-100℃, droplet size 50-150μm, and atomizing gas nitrogen or air.

6. The preparation method according to claim 1, characterized in that, Step S3 includes: S31. Introduce a mixture of argon and hydrogen, wherein the volume fraction of hydrogen is 30-50%, heat to 260-280℃, heating rate is 2-5℃ / min, time is 90-120 minutes, to obtain a mixture composed of graphene oxide, silver and nickel. The composite powder obtained from S32.S2 is placed in a hydraulic device at a pressure of 300MPa to form a skeleton compact. Then, a mixture of argon and hydrogen is introduced, with the hydrogen volume fraction being 5-10%. The temperature is then raised to 550-620℃ at a rate of 5-8℃ / min and held for 90-150 minutes to obtain a graphite-dispersed silver-nickel alloy. The composite powder obtained from S33.S2 is placed in a hydraulic apparatus at a pressure of 300MPa to form a skeleton compact. Argon gas is introduced, and the temperature is raised to 720-750℃ at a rate of 8-10℃ / min and held for 10-30 minutes. The temperature is then lowered to 350-450℃ at a rate of 3-5℃ / min and annealed for 1-3 hours. Finally, the material is allowed to cool naturally to room temperature to obtain a silver-nickel graphene alloy material.

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