Graphene copper-chromium composite material and preparation method thereof

Abstract

The application discloses a graphene copper-chromium composite material and a preparation method thereof, and belongs to the technical field of electrical materials, and overcomes the defects of low mechanical properties and electrical properties of a contact material in the prior art.The preparation method of the graphene copper-chromium composite material comprises the following steps: step 1, mixing chromium powder and graphene to obtain a mixture; step 2, compression molding the mixture; step 3, sintering the product of step 2; and step 4, vacuum infiltrating copper into the product of step 3 to obtain the graphene copper-chromium composite material; and the chromium powder comprises nanoscale chromium powder and microscale chromium powder.The graphene copper-chromium composite material prepared by the application has improved mechanical properties and electrical conductivity.

Description

Technical Field

[0001] This invention belongs to the field of electrical materials technology, specifically relating to a graphene-copper-chromium composite material and its preparation method. Background Technology

[0002] Traditional copper-chromium alloys possess good mechanical and electrical properties, generally meeting the switching requirements of conventional power transmission projects. However, with the construction of ultra-high voltage (UHV) projects, capacitors used for reactive power compensation require frequent operation of high-voltage circuit breakers, placing higher demands on the mechanical properties of the circuit breaker's moving and stationary arcing contacts. Current modification approaches involve strengthening the alloy by incorporating a third phase, such as graphene, which possesses excellent comprehensive mechanical and electrical properties, to enhance the overall performance of the copper-chromium alloy.

[0003] However, when graphene is used as a reinforcing phase, its low content cannot solve the problem of large porosity, making high-density sintering difficult and limiting its effect on improving density. If the amount of graphene added is too high, graphene agglomeration is likely to occur, thereby affecting the electromechanical properties of the alloy. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of low mechanical and electrical properties of contact materials in the prior art, thereby providing a graphene copper-chromium composite material and its preparation method.

[0005] To this end, the present invention provides the following technical solution.

[0006] In a first aspect, the present invention provides a method for preparing a graphene-copper-chromium composite material, comprising the following steps:

[0007] Step 1: Mix chromium powder and graphene to obtain a mixture;

[0008] Step 2: Press the mixture into shape;

[0009] Step 3: Sinter the product from Step 2;

[0010] Step 4: Vacuum infiltration of copper into the product of step 3 to obtain graphene copper-chromium composite material.

[0011] The chromium powder includes nano-sized chromium powder and micron-sized chromium powder.

[0012] Furthermore, the mass ratio of nano-sized chromium powder to micron-sized chromium powder is (1-30):(20-49), preferably (1-20):(30-49), and more preferably (15-20):(30-35).

[0013] Furthermore, the graphene copper-chromium composite material was prepared, comprising, by mass percentage, 48.5–52.5% Cu, 0.05%–0.2% graphene, with the balance being chromium and unavoidable impurities.

[0014] Furthermore, the average particle size of the nano-sized chromium powder is 150–250 nm.

[0015] Furthermore, the average particle size of the micron-sized chromium powder is 4-8 μm.

[0016] Furthermore, step 1 includes:

[0017] Step 101: Mix nano-sized chromium powder and micron-sized chromium powder to obtain powder mixture A;

[0018] Step 102: Add graphene to the powder mixture A and grind to obtain powder mixture B.

[0019] Further, step 101 includes: adding micron-sized chromium powder to a dispersion medium, ultrasonicating and stirring for 10–60 min; then adding nano-sized chromium powder under ultrasonic stirring conditions, continuing ultrasonication and stirring for 0.5–2 h to obtain powder mixture A. Stirring is continuous during the ultrasonication process.

[0020] Preferably, the mass ratio of the dispersion medium to the chromium powder is 1:(1-2);

[0021] Preferably, the dispersion medium comprises anhydrous ethanol or ultrapure water;

[0022] More preferably, the dispersion medium further includes a binder, wherein the content of the binder in the dispersion medium is 0.5 to 2 wt%.

[0023] Optionally, the adhesive is paraffin wax.

[0024] Furthermore, in step 1, graphene is added in the form of a graphene / copper composite material;

[0025] Preferably, the mass ratio of graphene to copper in the graphene / copper composite material is (3-5):(3-5).

[0026] Furthermore, in step 102, the grinding is ball milling;

[0027] Preferably, the ball mill satisfies at least one of the following conditions:

[0028] (1) Ball milling was performed using a chromium carbide pot and chromium carbide balls;

[0029] (2) The ball-to-powder ratio is (9-11:1); the ball-to-powder ratio refers to the mass ratio of chromium carbide balls to powder mixture B;

[0030] (3) Ball milling time: 2–6 hours;

[0031] (4) The rotation speed is 1000 to 3000 rpm.

[0032] Furthermore, in step 2, the pressing pressure is 400-500 MPa.

[0033] Furthermore, step 3 includes: heating the product from step 2 to 850–950°C in an inert atmosphere, holding it at that temperature for 0.5–1.5 hours, and then cooling it in the furnace.

[0034] Preferably, the inert atmosphere is argon;

[0035] Preferably, the heating is performed in stages; specifically, it includes: first heating to 400-500°C, holding at that temperature for 5-10 minutes, and then continuing to heat to 850-950°C.

[0036] Preferably, the heating rate is 5–15 °C / min, such as 10 °C / min.

[0037] Furthermore, step 4 includes infiltrating copper into the product of step 3 and copper powder at a vacuum environment of 1100-1200°C for 1.5-3 hours.

[0038] Furthermore, the preparation method of graphene copper-chromium composite material also includes step 5, annealing: the product of step 4 is directly annealed in a copper-infiltrating vacuum furnace at 850-950°C for 1-2 hours.

[0039] The vacuum level of the vacuum environment is 10. -2 ~10 -6 MPa.

[0040] Secondly, the present invention provides a graphene-copper-chromium composite material prepared according to the above method.

[0041] The technical solution of this invention has the following advantages:

[0042] 1. The preparation method of the graphene copper-chromium composite material of the present invention includes the following steps: Step 1, mixing chromium powder and graphene to obtain a mixture; Step 2, pressing the mixture into shape; Step 3, sintering the product of Step 2; Step 4, vacuum melting and infiltrating copper into the product of Step 3 to obtain the graphene copper-chromium composite material; wherein the chromium powder includes nano-sized chromium powder and micron-sized chromium powder.

[0043] In the melt infiltration process, the performance of the chromium skeleton directly affects the overall performance of copper-chromium composite materials. Traditional chromium skeletons use precursor powders with relatively large particles, resulting in numerous pores, uneven matrix structure, low density, and poor mechanical properties. This invention adds nano-sized chromium powder to micron-sized chromium powder. This fills irregular pores, improving the density and uniformity of the chromium skeleton and expanding the sintering neck area of ​​Cr-Cr. It also increases the capillary force within the pores, facilitating uniform and dense copper infiltration. Because the powder particles are not tightly bound and contain some porosity, the increased density further reduces porosity, allowing copper to form a copper network throughout the system, resulting in a more uniform microstructure and enhanced electrical conductivity. During sintering, the higher surface energy and surface area of ​​the nano-sized chromium powder, exhibiting the size effect unique to nanomaterials, aids in the bonding between sintering and the powder. It can also act as an activator, lowering the sintering temperature and improving sintering efficiency.

[0044] The graphene-copper-chromium composite material prepared by this invention improves both mechanical properties and electrical conductivity. Compared with materials obtained using chromium powder of conventional particle size, this graphene-copper-chromium composite material fully leverages the advantages of nano-sized chromium powder in terms of density, improving the density and hardness of the composite material while maintaining high electrical conductivity and resistance to arc erosion. Arc erosion mainly consists of wear and arc ablation. Increased hardness enhances wear resistance, and the more uniform the copper and chromium phases are, the better the arc dispersion, which helps improve the uniformity of contact ablation.

[0045] 2. The mass ratio of nano-sized chromium powder to micron-sized chromium powder is (1-30):(20-49). Nano-sized chromium powder has a high surface energy; too much will easily agglomerate, making it difficult to compact and causing the particle size to grow unevenly during sintering. Too little will result in insufficient filling of pores. Therefore, the mass ratio of nano-sized chromium powder to micron-sized chromium powder is limited to (1-30):(20-49). Preferably, it is (1-20):(30-49), and more preferably (15-20):(30-35). This invention optimizes the chromium powder ratio of different particle sizes by adding nano-sized chromium powder to micron-sized chromium powder, followed by uniform grinding, pressing and pre-sintering, and copper infiltration, thus developing a graphene copper-chromium composite material with significantly improved mechanical and electrical properties.

[0046] 3. Step 1 includes: Step 101, mixing nano-sized chromium powder and micron-sized chromium powder to obtain mixture A; Step 102, adding graphene to mixture A and grinding to obtain powder mixture B. Mixing nano-sized chromium powder and micron-sized chromium powder before adding graphene and grinding can reduce the grinding time of graphene while ensuring uniform dispersion, which helps to maintain the structural integrity of graphene.

[0047] 4. Step 101 includes: adding micron-sized chromium powder to a dispersion medium, sonicating and stirring for 10–60 min; then adding nano-sized chromium powder under ultrasonic stirring conditions, continuing ultrasonic stirring for 0.5–2 h to obtain mixture A. Dispersing the micron-sized chromium powder first, followed by adding the nano-sized chromium powder, makes the nano-sized chromium powder easier to disperse evenly.

[0048] 5. In step 1, graphene is added in the form of a graphene / copper composite material to prevent graphene agglomeration.

[0049] 6. When sintering the product from step 2, segmented heating is used, which helps to better control the heating process and avoid problems such as thermal stress and deformation of the product. Detailed Implementation

[0050] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0051] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0052] The nano-sized chromium powder used in the examples is high-purity chromium powder with a purity ≥99.95 and an average particle size of 200nm; the micron-sized chromium powder is high-purity chromium powder with a purity ≥99.9 and an average particle size of 5um.

[0053] Example 1

[0054] This embodiment provides a method for preparing graphene-copper-chromium composite material, including the following steps:

[0055] Step 1: Weigh out 50g of Cu powder, 5g of nano-grade chromium powder, 0.2g of graphene / copper composite material (where the mass ratio of graphene to copper is 1:1), and 45g of micron-grade chromium powder.

[0056] Micron-sized chromium powder was added to 32 ml of dispersion medium and ultrasonically stirred for 30 min. Nano-sized chromium powder was then added under ultrasonic stirring conditions, and ultrasonic stirring was continued for 1 h to ensure uniform dispersion of chromium powder of different particle sizes, resulting in mixture A. The dispersion medium was an anhydrous ethanol solution containing paraffin wax (1 wt%) as a binder.

[0057] Step 2: Add graphene / copper composite material to mixture A, and ball mill the mixture using a chromium carbide can and chromium carbide balls. The ball-to-powder ratio is 10:1, the ball milling time is 4 hours, and the rotation speed is 2000 rpm to obtain powder mixture B.

[0058] Step 3: Place the powder mixture B in a steel mold and press it into shape under a pressure of 450 MPa.

[0059] Step 4: In an argon atmosphere, heat the pressed billet obtained in Step 3 to 500℃ at a heating rate of 10℃ / min, hold for 5 min, then continue heating at a rate of 10℃ / min to 950℃, hold for 1 h, and cool with the furnace; add 50g of copper powder, adjust the melting and infiltration environment, and adjust the ambient vacuum to 10. -2 MPa, melting infiltration temperature of 1150℃, time of 2h.

[0060] Step 5: Cool the furnace to 900°C in a vacuum environment and anneal for 2 hours.

[0061] Example 2

[0062] This embodiment is basically the same as Embodiment 1, except that in step 1, 50g of Cu powder, 10g of nano-grade chromium powder, 0.2g of graphene / copper composite material (where the mass ratio of graphene to copper is 1:1), and 40g of micron-grade chromium powder are weighed.

[0063] Example 3

[0064] This embodiment is basically the same as Embodiment 1, except that in step 1, 50g of Cu powder, 15g of nano-grade chromium powder, 0.2g of graphene / copper composite material (where the mass ratio of graphene to copper is 1:1), and 35g of micron-grade chromium powder are weighed.

[0065] Example 4

[0066] This embodiment is basically the same as Embodiment 1, except that in step 1, 50g of Cu powder, 20g of nano-grade chromium powder, 0.2g of graphene / copper composite material (where the mass ratio of graphene to copper is 1:1), and 30g of micron-grade chromium powder are weighed.

[0067] Example 5

[0068] This embodiment provides a method for preparing graphene-copper-chromium composite material, including the following steps:

[0069] Step 1: Weigh out 50g of Cu powder, 1g of nano-grade chromium powder, 0.1g of graphene / copper composite material (where the mass ratio of graphene to copper is 1:1), and 49g of micron-grade chromium powder.

[0070] Micron-sized chromium powder was added to 52 ml of dispersion medium, and the mixture was sonicated and stirred for 30 min. Nano-sized chromium powder was then added under ultrasonic stirring conditions, and the mixture was sonicated and stirred for another 1 h to ensure uniform dispersion of chromium powder of different particle sizes, resulting in mixture A. The dispersion medium was an anhydrous ethanol solution containing paraffin wax (1 wt%) as a binder.

[0071] Step 2: Add graphene / copper composite material to mixture A, and ball mill the mixture using a chromium carbide can and chromium carbide balls. The ball-to-powder ratio is 10:1, the ball milling time is 2 hours, and the rotation speed is 1000 rpm to obtain powder mixture B.

[0072] Step 3: Place the powder mixture B in a steel mold and press it into shape under a pressure of 400 MPa.

[0073] Step 4: Place the obtained compact in an argon atmosphere, raise the temperature to 500℃ at a rate of 10℃ / min, hold for 5 min, continue raising the temperature to 950℃ at a rate of 10℃ / min, hold for 1 h, and allow to cool naturally; add copper powder, adjust the melting and infiltration environment, and adjust the ambient vacuum to 10. -2 MPa, melting infiltration temperature of 1200℃, time of 2h.

[0074] Step 5: Cool the furnace to 850°C in a vacuum environment and anneal for 2 hours.

[0075] Example 6

[0076] This embodiment is basically the same as Embodiment 1, except that in step 1, 50g of Cu powder, 30g of nano-grade chromium powder, 0.2g of graphene / copper composite material (where the mass ratio of graphene to copper is 1:1), and 20g of micron-grade chromium powder are weighed.

[0077] Comparative Example 1

[0078] This comparative example is basically the same as Example 1, except that in step 1, 50g of Cu powder, 0.2g of graphene / copper composite material (where the mass ratio of graphene to copper is 1:1), and 50g of micron-sized chromium powder are weighed.

[0079] This comparative example did not contain nano-sized chromium powder.

[0080] Table 1. Parameters of raw materials and composite materials in the examples and comparative examples.

[0081] Example 1 5：45 0.1％ Example 2 10：40 0.1％ Example 3 15：35 0.1％ Example 4 20：30 0.1％ Example 5 1：49 0.05％ Example 6 30：20 0.1％ Comparative Example 1 - 0.1％

[0082] Test case

[0083] The properties of the composite materials in the examples and comparative examples were tested.

[0084] The test methods for hardness, actual density, and conductivity are based on JB / T 5351-2014 Test Methods for Basic Properties of Vacuum Switch Contact Materials.

[0085] Density = Actual density / Theoretical density * 100%. The theoretical density of an alloy is calculated based on the alloy's mass percentage, ρ0 = 1 / (X Cu / ρ Cu +X Cr / ρ Cr ), where ρ0 is the theoretical density of the alloy, X Cu X represents the mass percentage of Cu in the alloy. Cr ρ represents the mass percentage of Cr in the alloy. Cu ρ is the theoretical density of Cu. Cr This represents the theoretical density of Cr.

[0086] The test results are shown in Table 2.

[0087] Table 2 Performance parameters of composite materials

[0088] Example 1 88 97.4 17.5 Example 2 96 97.9 18.1 Example 3 108 98.6 18.9 Example 4 115 99.3 19.2 Example 5 84 97.1 16.1 Example 6 107 98.8 18.4 Comparative Example 1 82 96.8 15.9

[0089] As shown in Table 2, this invention prepares a mixture of nano-sized and micron-sized chromium powders and adjusts the composition ratio of the nano-sized chromium powders. After pressing and firing, a dense chromium skeleton is obtained. Through melt infiltration, a graphene copper-chromium composite material is obtained. This improves the density and hardness of the material while maintaining a steady increase in conductivity.

[0090] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a graphene copper chromium composite material, characterized in that, Includes the following steps: Step 1: Mix chromium powder and graphene to obtain a mixture; Step 2: Press the mixture into shape; Step 3: Sinter the product from Step 2; Step 4: Vacuum infiltration of copper into the product of step 3 to obtain graphene copper-chromium composite material. The chromium powder includes nano-sized chromium powder and micron-sized chromium powder; The mass ratio of nano-sized chromium powder to micron-sized chromium powder is (15~30):(20~35).

2. The method for preparing the graphene-copper-chromium composite material according to claim 1, characterized in that, The graphene-copper-chromium composite material obtained by means of mass percentage includes 48.5%~52.5% Cu, 0.05%~0.2% graphene, and the balance being chromium and unavoidable impurities.

3. The method for preparing the graphene-copper-chromium composite material according to claim 1, characterized in that, The average particle size of the nano-sized chromium powder is 150~250nm; And / or, The average particle size of the micron-sized chromium powder is 4-8 micrometers.

4. The method for preparing the graphene-copper-chromium composite material according to any one of claims 1-3, characterized in that, Step 1 includes: Step 101: Mix nano-sized chromium powder and micron-sized chromium powder to obtain mixture A; Step 102: Add graphene to the mixture A and grind it to obtain powder mixture B.

5. The method for preparing the graphene-copper-chromium composite material according to any one of claims 1-3, characterized in that, In step 2, the pressing pressure is 400~500MPa.

6. The method for preparing the graphene-copper-chromium composite material according to any one of claims 1-3, characterized in that, Step 3 includes: heating the product from step 2 to 850~950℃ in a protective atmosphere, holding it at that temperature for 0.5~1.5h, and then cooling it in the furnace.

7. The method for preparing the graphene-copper-chromium composite material according to any one of claims 1-3, characterized in that, Step 4 includes infiltrating copper into the product from step 3 and copper powder at a vacuum environment of 1100~1200℃ for 1.5~3 hours.

8. The method for preparing the graphene-copper-chromium composite material according to any one of claims 1-3, characterized in that, The preparation method of graphene copper-chromium composite material also includes step 5, annealing: the product of step 4 is cooled to 850~950℃ and annealed for 1~2 hours.

9. A graphene-copper-chromium composite material prepared by the method according to any one of claims 1-8.