Tungsten-doped graphene reinforced copper tellurium alloy and preparation method thereof

Abstract

The invention discloses a preparation method of tungsten-doped graphene reinforced copper tellurium alloy, and belongs to the field of electrical materials. According to the method, a tellurium-copper intermediate alloy and tungsten-doped graphene powder are put into a copper melt through a vacuum induction melting-rapid solidification process, and the high-performance alloy is prepared through stirring and pouring. The tungsten-doped graphene is prepared by loading 10-50 nm nano tungsten particles on the surface of graphene, the tungsten content is 30-50 wt%, the density matching performance and interface wettability of the tungsten-doped graphene and copper melt can be improved, and graphene agglomeration is avoided. The oxygen content of the obtained alloy is lt; the high-reliability electric contact material prepared by the method has the advantages of low cost, low cost, large scale and suitability for high-reliability electric contact materials such as high-voltage direct-current relay contacts of new energy automobiles, and the density is greater than or equal to 99.8%, the conductivity is 88-92% IACS (International Annealed Copper Standard), and the tensile strength is 350-400 MPa.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrical materials and metal matrix composites, and particularly relates to a tungsten-doped graphene reinforced copper-tellurium alloy and a preparation method thereof. BACKGROUND

[0002] Tungsten-doped graphene reinforced copper-tellurium alloy and a preparation method thereof.

[0003] With the rapid development of new energy vehicles towards 800 V and above high-voltage platforms, the working environment of contact materials is becoming increasingly severe: higher current density, stronger arc impact, and more stringent requirements for the anti-welding performance of materials. However, the traditional Cu-Te alloy has the inherent defect of low strength, and its tensile strength is usually lower than 250 MPa, which is prone to contact welding or surface ablation during high-current breaking, resulting in a significant decrease in device reliability and difficulty in adapting to the use requirements of high-voltage platforms.

[0004] Graphene, as a new type of material with excellent performance, has ultra-high strength (~130 GPa), excellent electrical conductivity and large specific surface area, and is recognized as an ideal reinforcing phase for copper-based composites. However, in practical applications, the density difference between graphene and copper melt is very large (graphene density is about 2.2 g / cm³, copper melt density is about 8.9 g / cm³), which leads to serious floating and aggregation of graphene in copper melt; at the same time, the interface wettability between the two is poor, and graphene is easily oxidized and decomposed at high temperatures, which seriously restricts its application effect.

[0005] The existing methods for preparing graphene / copper composites (such as powder metallurgy and CVD) have many defects: powder metallurgy has high cost, insufficient density of the prepared material, and high oxygen content (usually > 100 ppm); CVD process is complex and difficult to realize large-scale production. The composite materials prepared by these methods are difficult to meet the dual requirements of high conductivity (>85% IACS) and high reliability of high-voltage electrical contact materials, therefore, it is of great practical significance to develop a low-cost, high-density, low-oxygen and large-scale production method for preparing reinforced copper-tellurium alloy. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a preparation method of tungsten-doped graphene reinforced copper-tellurium alloy. The present application improves the density matching and interface wettability of graphene and copper melt by introducing high-density tungsten elements into graphene, realizes the uniform dispersion and stable existence of graphene in the copper-tellurium alloy melt, and finally obtains a contact material with high strength, high conductivity and excellent anti-melting and welding performance, while meeting the industrial needs of low cost, high density, low oxygen and scalable production.

[0007] The technical scheme adopted by the present application is as follows: a preparation method of tungsten-doped graphene reinforced copper-tellurium alloy, comprising the following steps:

[0008] S1: electrolytic copper with a purity of ≥99.99% is loaded into a smelting crucible, and tellurium-copper intermediate alloy and tungsten-doped graphene powder are uniformly mixed and loaded into a vacuum sealed secondary feeding bin for standby, wherein the tellurium content in the tellurium-copper intermediate alloy is 10-12 wt%, and the addition amount accounts for 0.3-0.7 wt% of the total mass of the final alloy; the tungsten content in the tungsten-doped graphene powder is 30-50 wt%;

[0009] S2: the smelting chamber is vacuumed to ≤10 -1 Pa, the electrolytic copper is completely melted by high-frequency induction heating to 1100-1200 ℃ to form a copper melt;

[0010] S3: after the copper melt is kept for 5-10 minutes, the tellurium-copper intermediate alloy and tungsten-doped graphene powder in the secondary feeding bin are put into the copper melt at one time, a water-cooled ceramic stirring rod is used to stir at a speed of 120-480 rpm for 1-3 minutes to promote the complete dissolution of the tellurium element and ensure the uniform dispersion of the tungsten-doped graphene in the copper melt;

[0011] S4: the uniformly stirred melt is poured into a water-cooled copper mold to realize rapid solidification at a cooling rate of >10 3 K / s to obtain an ingot.

[0012] Further, the tungsten-doped graphene is prepared by a chemical vapor deposition method or a liquid deposition method, and nano-tungsten particles are loaded on the surface of the graphene, and the particle size of the nano-tungsten particles is 10-50 nm.

[0013] Further, the specific surface area of the tungsten-doped graphene is ≥100 m² / g, and the number of layers of the graphene is ≤5 layers.

[0014] Further, the material of the water-cooled ceramic stirring rod is Al2O3 or ZrO2.

[0015] Further, the vacuum degree in step S2 is 5×10 -2 Pa.

[0016] Furthermore, the method described above also includes a step of plastic processing of the ingot, wherein the plastic processing is at least one of hot rolling, cold drawing or aging treatment; wherein the hot rolling temperature is 700-800 ℃, the aging treatment temperature is 400-500 ℃ and the holding time is 1-2 h.

[0017] This invention also provides a tungsten-doped graphene-reinforced copper-tellurium alloy prepared by the method described above. The resulting alloy has an oxygen content of less than 10 ppm, a density ≥99.8%, an electrical conductivity ≥88% IACS, and a tensile strength ≥350 MPa. This alloy is particularly suitable for high-reliability electrical contact materials such as high-voltage DC relay contacts in new energy vehicles, and can meet the stringent performance requirements of 800V and above high-voltage platforms for contact materials.

[0018] The present invention also provides the application of a tungsten-doped graphene-reinforced copper-tellurium alloy as described above in the electrical contact material of a high-voltage DC relay or contactor for new energy vehicles.

[0019] Advantages and beneficial effects of the present invention:

[0020] 1. The method of this invention employs a "tungsten-doped graphene" reinforced phase design to solve the core dispersion problem:

[0021] Density matching optimization: Tungsten has a density as high as 19.3 g / cm³. By loading nano-tungsten particles on the surface of graphene, the effective density of tungsten-doped graphene composite particles is increased to 6-8 g / cm³, which is close to the density of copper melt (8.9 g / cm³). This greatly suppresses the floating or settling phenomenon of graphene during the melting process and ensures the uniform distribution of the reinforcing phase.

[0022] Improved interfacial wettability: Tungsten and copper have good interfacial wettability, which can effectively promote the stable retention of graphene during the solidification process of the copper matrix, avoid graphene agglomeration, and significantly improve the bonding strength between the reinforcing phase and the matrix.

[0023] 2. Combining vacuum induction melting with rapid casting technology achieves the following advantages:

[0024] Low oxygen content: The entire process is carried out under vacuum (≤0.1 Pa), which effectively isolates the air and avoids material oxidation, resulting in an oxygen content of less than 10 ppm in the final alloy.

[0025] High density: The rapid solidification process (cooling rate > 10³ K / s) suppresses the generation of defects such as porosity and looseness during casting, making the casting structure close to the theoretical density, with a density ≥ 99.8%;

[0026] Low cost advantage: Compared with traditional powder metallurgy or CVD methods, this method adopts a one-step melting + rapid casting process, which eliminates complex processes such as pressing and sintering, has simple equipment requirements, is suitable for continuous large-scale production, and significantly reduces production costs.

[0027] High conductivity: The low oxygen content and high density material structure, combined with the conductive network formed by graphene, effectively reduces scattering and obstruction during electron transmission, enabling the alloy conductivity to reach 88-92% IACS.

[0028] 3. Enhanced performance to meet the needs of high-voltage scenarios:

[0029] Significantly improved strength: Compared with the traditional Cu-0.5Te alloy, the alloy prepared by this invention has a 40-60% increase in tensile strength, reaching 350-400 MPa, and a 20-30% increase in Vickers hardness, with a hardness value of 110-130 HV;

[0030] Excellent anti-fusion welding performance: In 500 cycles of 1000 A / 1000 V electrical life test, the alloy showed no fusion welding phenomenon, which can effectively cope with the arc impact under high voltage and high current scenarios, and is significantly better than commercial contact materials.

[0031] Synergistic effect of conductivity and strength: While significantly improving strength, it maintains high conductivity of 88-92% IACS, solving the technical contradiction of traditional copper-based materials that are difficult to balance strength and conductivity. Detailed Implementation

[0032] The present invention will be further described in detail below with examples, but the embodiments of the present invention are not limited thereto.

[0033] Example 1

[0034] Raw material ratio: 10 kg of electrolytic copper; 60 g of tellurium copper master alloy (Te content 11%) (Te element accounts for 0.66% of the total mass of the final alloy); 30 g of tungsten-doped graphene powder (accounting for 0.3% of the total mass of the final alloy), the tungsten-doped graphene contains 40 wt% tungsten, has 3-5 graphene layers, and the surface-loaded nano-tungsten particles have a particle size of 10-50 nm.

[0035] The preparation method includes the following steps:

[0036] S1: Electrolytic copper with a purity ≥ 99.99% is loaded into a melting crucible. Tellurium copper master alloy is mixed evenly with tungsten-doped graphene powder and loaded into a vacuum-sealed secondary feeding hopper for later use.

[0037] S2: Evacuate the melting chamber to 5×10 -2Pa, through high-frequency induction heating to 1150 ℃, completely melts the electrolytic copper to form a copper melt;

[0038] S3: After holding the copper melt at a constant temperature for 8 minutes, add the tellurium copper intermediate alloy and tungsten-doped graphene powder from the secondary feeding hopper into the copper melt at once. Stir for 2 minutes at a speed of 300 rpm using a water-cooled ceramic stirring rod to promote the full dissolution of tellurium and ensure that the tungsten-doped graphene is evenly dispersed in the copper melt.

[0039] S4: Pour the well-stirred melt into a Φ50 mm water-cooled copper mold and achieve rapid solidification at a cooling rate of >10³ K / s to obtain an ingot.

[0040] Test results: The density of the obtained ingot was 99.9%; the electrical conductivity (four-probe method test) was 90% IACS; the tensile strength was 385 MPa; the Vickers hardness was 125 HV; after 500 cycles of 1000A / 1000V electrical life test, no welding phenomenon was observed.

[0041] Example 2 (Comparative Experiment: Tungsten-Free Graphene)

[0042] Experimental design: The process parameters were exactly the same as in Example 1, except that the tungsten-doped graphene was replaced with an equal amount of pure graphene (without tungsten particles).

[0043] Test results: During the smelting process, pure graphene floated to the top of the ingot due to its low density, and there was almost no reinforcing phase distribution at the bottom of the ingot; the electrical conductivity fluctuated greatly (70-95% IACS); the tensile strength was only 280 MPa, which was significantly lower than that of Example 1, proving that tungsten doping is crucial for improving the dispersibility of graphene and enhancing the performance of the alloy.

[0044] Example 3 (Comparison of different tungsten contents)

[0045] Experimental design: Keep the other raw material ratios and process parameters the same as in Example 1, only adjust the tungsten content in the tungsten-doped graphene, setting it to 30 wt%, 40 wt%, and 50 wt%, respectively.

[0046] Test results:

[0047] 30 wt% tungsten content: Graphene has good dispersibility, but due to insufficient tungsten content, the strengthening effect is slightly weak, and the tensile strength is 350 MPa;

[0048] With a tungsten content of 40 wt%, the density matching effect is optimal, the graphene is uniformly dispersed, the tensile strength is 385 MPa, and the cost and performance are optimally balanced.

[0049] With a tungsten content of 50 wt%, the density matching effect is the best, and the tensile strength is 395 MPa. However, the cost of tungsten raw materials is relatively high, and the overall cost-effectiveness is lower than that of the 40 wt% content option.

[0050] In summary, this invention has successfully solved the technical problems of insufficient strength and difficulty in graphene dispersion in traditional copper-tellurium alloys by rationally designing the tungsten-doped graphene reinforcing phase and optimizing the preparation process. The prepared alloy has high conductivity, high strength and excellent anti-welding performance, and has low production cost and can be mass-produced. It has broad application prospects in the field of high-voltage DC relay contacts for new energy vehicles.

Claims

1. A method for preparing a tungsten-doped graphene-reinforced copper-tellurium alloy, characterized in that, Includes the following steps: S1: Electrolytic copper with a purity ≥99.99% is loaded into a melting crucible. Tellurium copper master alloy and tungsten-doped graphene powder are mixed evenly and loaded into a vacuum-sealed secondary feeding hopper for later use. The tellurium content in the tellurium copper master alloy is 10-12 wt%, and its addition amount accounts for 0.3-0.7 wt% of the final alloy's total mass. The tungsten content in the tungsten-doped graphene powder is 30-50 wt%. S2: Evacuate the melting chamber to ≤10 -1 Pa, through high-frequency induction heating to 1100-1200 ℃, completely melts the electrolytic copper to form a copper melt; S3: After holding the copper melt at a constant temperature for 5-10 minutes, add the tellurium copper master alloy and tungsten-doped graphene powder from the secondary feeding bin into the copper melt at once. Use a water-cooled ceramic stirring rod to stir at a speed of 120-480 rpm for 1-3 minutes to promote the full dissolution of tellurium and ensure that the tungsten-doped graphene is evenly dispersed in the copper melt. S4: Pour the well-stirred melt into a water-cooled copper mold, with a pressure >10. 3 A cooling rate of K / s enables rapid solidification, resulting in an ingot.

2. The method for preparing a tungsten-doped graphene-reinforced copper-tellurium alloy according to claim 1, characterized in that, The tungsten-doped graphene is prepared by chemical vapor deposition or liquid phase deposition, and tungsten nanoparticles are loaded on the surface of the graphene. The particle size of the tungsten nanoparticles is 10-50 nm.

3. The method for preparing a tungsten-doped graphene-reinforced copper-tellurium alloy according to claim 1, characterized in that, The tungsten-doped graphene has a specific surface area ≥100 m² / g and the number of graphene layers ≤5.

4. The method for preparing a tungsten-doped graphene-reinforced copper-tellurium alloy according to claim 1, characterized in that, The water-cooled ceramic stirring rod is made of Al2O3 or ZrO2.

5. The method for preparing a tungsten-doped graphene-reinforced copper-tellurium alloy according to claim 1, characterized in that, The vacuum level mentioned in step S2 is 5 × 10⁻⁶. -2 Pa.

6. A method for preparing a tungsten-doped graphene-reinforced copper-tellurium alloy according to any one of claims 1-5, characterized in that, The method also includes a step of plastic processing of the ingot, wherein the plastic processing is at least one of hot rolling, cold drawing or aging treatment; wherein the hot rolling temperature is 700-800 ℃, the aging treatment temperature is 400-500 ℃ and the holding time is 1-2 h.

7. A tungsten-doped graphene-reinforced copper-tellurium alloy prepared by the method according to any one of claims 1-5, characterized in that, The resulting alloy has an oxygen content of less than 10 ppm, a density of ≥99.8%, an electrical conductivity of ≥88% IACS, and a tensile strength of ≥350 MPa.

8. The application of the tungsten-doped graphene-reinforced copper-tellurium alloy according to claim 7 in the electrical contact material of high-voltage DC relays or contactors for new energy vehicles.