A high voltage contact material and preparation method thereof

Abstract

The present invention discloses a high voltage-resistant contact material in the technical field of alloys and a preparation method thereof. In the preparation process of conventional copper-tungsten alloy, graphene-modified tungsten fibers are doped. The addition of tungsten fibers can enhance the mechanical properties and thermal shock resistance of the contact material. Graphene has good electrical and thermal conductivity, can improve the breakdown strength of the contact material, is beneficial to increase the service life of electrical contacts in a high voltage working environment, and improves the stability of the power system.

Description

Technical Field

[0001] The invention belongs to the technical field of alloys, and specifically refers to a high-voltage contact material and a preparation method thereof. Background Art

[0002] Ultra-high voltage transmission and high voltage transmission have the characteristics of large transmission capacity and can realize long-distance transmission of electricity. In the power transmission system, high-voltage circuit breakers, as control circuit system equipment, have complex structures. One of their core components is the electrical contact, which has the functions of disconnecting / connecting circuits, cutting off overload currents or fault circuits, etc. The performance of the electrical contact affects the safety of the power system operation. When the high-voltage circuit breaker is working, during the opening and closing process of the copper-based contacts, the electrode gap breaks down under the action of high voltage to generate an arc. The high-energy arc plasma erodes the copper-based contacts, which can make the surface temperature of the contact material exceed the phase change temperature of the material in a short time, causing phase change and ablation, resulting in the melting of the copper-based contact surface and metal evaporation, further intensifying the physical or chemical reaction of the contact, causing changes in the surface morphology of the contact, and ultimately reducing the service life of the electrical contact, making it difficult to ensure the safety and stability of the high-voltage power transmission system. Ideal electrical contacts should meet the following requirements: 1. The material of the electrical contact should be When it has a high melting point, boiling point, electrical conductivity and electron work function; 2. The electrical contact material is not easy to form oxides or carbides under high temperature and aerobic conditions, and has high chemical stability; 3. It has strong resistance to arc erosion; It is not easy to meet the above requirements using a single metal. In the prior art, the electrical contact material is often a copper-based or silver-based alloy. Silver-based alloy contacts are generally used in low-voltage electrical circuits, and copper-based alloys are commonly used in medium and high voltage environments. Common copper-based alloy contact materials include CuW and CuCr; CuCr alloy contact materials have high mechanical strength and conductivity, but CuCr alloy is an immiscible alloy. During the solidification process, pores are likely to appear in the Cr phase, resulting in a decrease in the alloy density; the proportion of tungsten in the CuW alloy is relatively large. During the arc ablation process of the alloy contact material, the thermal conductivity of the W phase is poor. When breakdown occurs, the temperature cannot be quickly reduced, which makes it easier for electrons in the material to escape and breakdown occurs, resulting in a continuous increase in temperature, melting of the W phase skeleton, and ultimately damage to the contact. Summary of the invention

[0003] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a high voltage-resistant contact material and a preparation method thereof. In order to solve the problem of poor arc erosion resistance of the contact material, the present invention dopes graphene-modified tungsten fibers in the preparation process of conventional copper-tungsten alloy. The addition of tungsten fibers can enhance the mechanical properties and thermal shock resistance of the contact material. Graphene has good electrical and thermal conductivity, can improve the breakdown strength of the contact material, is beneficial to increase the service life of the electrical contact in a high voltage working environment, and improve the stability of the power system.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is as follows: The present invention proposes a method for preparing a high-voltage contact material, which specifically includes the following steps:

[0005] S1. Dispersing graphene oxide in deionized water, adding a surfactant, performing ultrasonic treatment at 300-500W for 30-60min, adding a polyvinyl alcohol aqueous solution, and mixing well to obtain a graphene oxide colloidal solution;

[0006] Preferably, in step S1, the mass concentration of graphene oxide in deionized water is 0.01-0.02 g / mL;

[0007] Preferably, in step S1, the surfactant is at least one of sodium dodecylbenzene sulfonate, sodium lauryl sulfonate and sodium dodecyl sulfate, and the mass ratio of the surfactant to graphene oxide is 1:2-5;

[0008] Preferably, in step S1, the mass concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 15-20 mg / mL, and the added volume of the polyvinyl alcohol aqueous solution is 2-4 mL;

[0009] Graphene has a special phonon vibration heat transfer method, so graphene materials have good electrical and thermal conductivity. Graphene can produce reducing gas under the action of arc, thereby preventing or reducing the oxidation of metals, thereby improving the ability to resist arc erosion;

[0010] S2, immersing the tungsten fiber in a mixed acid solution and performing a roughening treatment at room temperature for 40-50 minutes to obtain a pretreated tungsten fiber;

[0011] Preferably, in step S2, the mixed acid solution is concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:2;

[0012] S3, immersing the pretreated tungsten fiber prepared in step S2 in the graphene oxide colloidal solution prepared in step S1, performing ultrasonic treatment at 500-600W, filtering, removing the filtrate, drying the tungsten fiber at 60-80°C, performing sintering treatment, and obtaining modified tungsten fiber after the system is naturally cooled to room temperature;

[0013] Preferably, in step S3, the parameters of the sintering treatment are: raising the temperature to 300-350°C at 10°C / min, keeping the temperature for 20-30min, and continuing to raise the temperature to 600-700°C, keeping the temperature for 1.5-2.5h;

[0014] S4, mixing the copper powder and the tungsten powder, adding grinding balls and anhydrous ethanol for mixed ball milling to obtain alloy mixed powder;

[0015] Preferably, in step S4, the mass ratio between the copper powder and the tungsten powder is 2-3:7-8;

[0016] Preferably, in step S4, during the ball milling process, the grinding balls are composed of zirconia grinding balls with diameters of 4 mm and 8 mm in a mass ratio of 1:2, the ball-to-material ratio is 5:1, the ball milling speed is 400-500 rpm, and the ball milling time is 7-9 h;

[0017] S5, placing the modified tungsten fiber prepared in step S3 and the alloy powder prepared in step S4 in a mixer and mixing them thoroughly for 1-2 hours, drying them, pressing them in a mold at 300-400 MPa to form a green body, loading them into an ark, transferring them to a tubular furnace under an argon atmosphere, performing infiltration sintering, naturally cooling them to room temperature, and then grinding and polishing them to obtain a contact material;

[0018] Preferably, in step S5, the added mass of the modified tungsten fiber is 5%-10% of the alloy powder;

[0019] Preferably, in step S5, the parameters of the infiltration sintering treatment are: heating to 1200-1300° C. at 10° C. / min and keeping the temperature for 1.5-2 h.

[0020] The invention also provides a high voltage-resistant contact material prepared according to the method.

[0021] The beneficial effects achieved by the present invention are as follows:

[0022] The present invention provides a high-voltage contact material and a preparation method thereof. In the preparation process of conventional copper-tungsten alloy, graphene-modified tungsten fibers are doped. The addition of tungsten fibers can enhance the mechanical properties and thermal shock resistance of the contact material. Graphene has good electrical and thermal conductivity, can enhance the breakdown strength of the contact material, is beneficial to increase the service life of the electrical contact in a high-voltage working environment, and improves the stability of the power system. In the present invention, a tungsten fiber structure is added to a copper / tungsten alloy mixed powder, can uniformly grow grains on the tungsten fibers during the infiltration and sintering process, improve the continuity of the W skeleton network, and the tungsten fibers can also enhance the mechanical strength of the W skeleton, avoiding the collapse of the contact material structure caused by the melting of the W skeleton under continuous high temperature. Graphene has high electrical conductivity and thermal conductivity, and its electronic work function is high. The discharge voltage required for the ionization of graphene electrons is lower, which can extend the arc time of the contact material and reduce the damage of the contact material to arc erosion. Due to the high thermal conductivity of graphene, the high temperature generated by arc erosion can be quickly conducted through the mutual conduction network composed of graphene-extended tungsten fibers, which is beneficial to the improvement of the breakdown strength of the contact material. During the infiltration and sintering process, the C in the graphene can form a carbide ceramic phase with the W phase. Under high voltage, the contact material forms a molten pool under arc breakdown. Graphene and tungsten carbide can increase the viscosity of the copper liquid, stabilize the molten pool, inhibit the flow and splashing of the copper liquid, and improve the resistance of the contact material to arc erosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 XRD images of the contact materials prepared in Example 1 and Comparative Examples 1 and 2;

[0024] Figure 2 The conductivity results of the contact materials prepared in Examples 1-3 and Comparative Examples 1 and 2 are shown;

[0025] Figure 3 The result diagram of the voltage resistance strength of the contact materials prepared in the examples and comparative examples;

[0026] Figure 4 The diagram shows the arc ablation diameter and ablation depth of the contact materials prepared in the examples and comparative examples at a discharge voltage of 10 kV.

[0027] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0029] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to those described herein may be applied to the present invention. The preferred implementation methods and materials described herein are for demonstration purposes only and are not intended to limit the content of this application.

[0030] The experimental methods in the following examples are conventional methods unless otherwise specified; the experimental materials used in the following examples are purchased from commercial channels unless otherwise specified.

[0031] Example 1

[0032] This embodiment provides a method for preparing a high withstand voltage contact material, which specifically includes the following steps:

[0033] S1. Accurately weigh 75 mg of graphene oxide in a beaker, add 7.5 mL of deionized water to disperse the graphene oxide, add 25 mg of sodium dodecylbenzene sulfonate, mix well, and obtain a uniform graphene oxide dispersion. Prepare a 20 mg / mL polyvinyl alcohol aqueous solution, accurately pipette 2.5 mL into the graphene oxide dispersion, and mix well to obtain a graphene oxide colloidal solution;

[0034] S2. Prepare a mixed acid solution with concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:2, completely immerse the tungsten fiber in the mixed acid solution for 40 minutes to perform a roughening treatment, and after the roughening treatment, clean the acidic liquid on the surface of the tungsten fiber with deionized water, transfer the cleaned tungsten fiber to an ultrasonic cleaner, perform ultrasonic cleaning with anhydrous ethanol and acetone for 10 minutes in turn, and dry it under vacuum conditions to obtain a pretreated tungsten fiber;

[0035] S3, placing the pretreated tungsten fiber prepared in step S2 in a beaker, adding the graphene oxide colloidal solution prepared in step S1, placing the beaker in an ultrasonic machine, treating at 500W ultrasonic power for 1 hour, filtering, removing the filtrate, transferring the tungsten fiber to a vacuum oven, drying at 70°C for 3 hours, transferring to a high-temperature tube furnace, raising the temperature to 300°C at 10°C / min, keeping the temperature for 30 minutes, and then continuing to raise the temperature to 700°C at the above rate, keeping the temperature for 1.5 hours, completing the sintering treatment, and after the system is naturally cooled to room temperature, a modified tungsten fiber is obtained;

[0036] S4, accurately weigh 0.5 g of copper powder and 2 g of tungsten powder, put them into a planetary ball mill, add 4.17 g of zirconia grinding balls with a diameter of 4 mm and 8.33 g of zirconia grinding balls with a diameter of 8 mm, add 10 mL of anhydrous ethanol, and perform ball milling at a ball milling speed of 500 rpm for 8 h to obtain alloy mixed powder;

[0037] S5. Weigh 0.25 g of the modified tungsten fiber prepared in step S1, add it and the alloy mixed powder prepared in step S4 into a mixer and mix them for 1 hour. After fully mixing, transfer it to a vacuum drying oven for drying, fill it into a mold, and press it into a green body at a pressure of 300 MPa. After loading it into an ark, heat it to 1200°C at 10°C / min under the protection of a high-purity argon atmosphere flowing at a speed of 1 L / h, keep it warm for 2 hours, and carry out infiltration sintering. After completion, the reaction system is naturally cooled to room temperature, placed on a grinder for further grinding and polishing to obtain a contact material.

[0038] This embodiment also provides a high voltage-resistant contact material prepared according to the above preparation method.

[0039] Example 2

[0040] This embodiment provides a method for preparing a high withstand voltage contact material, which specifically includes the following steps:

[0041] S1. Accurately weigh 0.16 g of graphene oxide in a beaker, add 8 mL of deionized water to disperse the graphene oxide, add 16 mg of sodium lauryl sulfate, mix well, and obtain a uniform graphene oxide dispersion, prepare a 20 mg / mL polyvinyl alcohol aqueous solution, accurately pipette 2 mL into the graphene oxide dispersion, and mix well to obtain a graphene oxide colloidal solution;

[0042] S2. Prepare a mixed acid solution with concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:2, completely immerse the tungsten fiber in the mixed acid solution for 50 minutes, and perform a roughening treatment. After the roughening treatment, clean the acidic liquid on the surface of the tungsten fiber with deionized water, transfer the cleaned tungsten fiber to an ultrasonic cleaner, perform ultrasonic cleaning with anhydrous ethanol and acetone for 10 minutes in turn, and dry it under vacuum conditions to obtain a pretreated tungsten fiber;

[0043] S3, placing the pretreated tungsten fiber prepared in step S2 in a beaker, adding the graphene oxide colloidal solution prepared in step S1, placing the beaker in an ultrasonic machine, treating at 600W ultrasonic power for 1h, filtering, removing the filtrate, transferring the tungsten fiber to a vacuum oven, drying at 60°C for 3h, transferring to a high-temperature tube furnace, raising the temperature to 300°C at 10°C / min, keeping the temperature for 30min, and then continuing to raise the temperature to 600°C at the above rate, keeping the temperature for 2h, completing the sintering treatment, and after the system is naturally cooled to room temperature, obtaining the modified tungsten fiber;

[0044] S4, accurately weigh 1.5 g of copper powder and 3.5 g of tungsten powder, put them into a planetary ball mill, add 8.33 g of 4 mm diameter zirconium oxide grinding balls, 16.67 g of 8 mm diameter zirconium oxide grinding balls, add 15 mL of anhydrous ethanol, and perform ball milling at a ball milling speed of 400 rpm for 9 hours to obtain alloy mixed powder;

[0045] S5. Weigh 0.5 g of the modified tungsten fiber prepared in step S1, add it and the alloy mixed powder prepared in step S4 into a mixer and mix them for 2 h. After fully mixing, transfer it to a vacuum drying oven for drying, fill it into a mold, and press it into a green body at a pressure of 400 MPa. After loading it into an ark, heat it to 1300 ° C at 10 ° C / min under the protection of a high-purity argon atmosphere flowing at a speed of 1 L / h, and keep it warm for 1.5 h to carry out infiltration sintering. After completion, the reaction system is naturally cooled to room temperature, placed on a grinder for further twisting, grinding and polishing to obtain a contact material.

[0046] This embodiment also provides a high voltage-resistant contact material prepared according to the above preparation method.

[0047] Example 3

[0048] This embodiment provides a method for preparing a high withstand voltage contact material, which specifically includes the following steps:

[0049] S1. Accurately weigh 0.12 g of graphene oxide in a beaker, add 8 mL of deionized water to disperse the graphene oxide, add 25 mg of sodium dodecylbenzene sulfonate, mix well, and obtain a uniform graphene oxide dispersion. Prepare a 15 mg / mL polyvinyl alcohol aqueous solution, accurately pipette 4 mL into the graphene oxide dispersion, and mix well to obtain a graphene oxide colloidal solution;

[0050] S2. Prepare a mixed acid solution with concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:2, completely immerse the tungsten fiber in the mixed acid solution for 40 minutes to perform a roughening treatment, and after the roughening treatment, clean the acidic liquid on the surface of the tungsten fiber with deionized water, transfer the cleaned tungsten fiber to an ultrasonic cleaner, perform ultrasonic cleaning with anhydrous ethanol and acetone for 10 minutes in turn, and dry it under vacuum conditions to obtain a pretreated tungsten fiber;

[0051] S3, placing the pretreated tungsten fiber prepared in step S2 in a beaker, adding the graphene oxide colloidal solution prepared in step S1, placing the beaker in an ultrasonic machine, treating at 500W ultrasonic power for 1 hour, filtering, removing the filtrate, transferring the tungsten fiber to a vacuum oven, drying at 70°C for 3 hours, transferring to a high-temperature tube furnace, raising the temperature to 350°C at 10°C / min, keeping the temperature for 20 minutes, and then continuing to raise the temperature to 600°C at the above rate, keeping the temperature for 2.5 hours, completing the sintering treatment, and after the system is naturally cooled to room temperature, a modified tungsten fiber is obtained;

[0052] S4, accurately weigh 0.5 g of copper powder and 1.5 g of tungsten powder, put them into a planetary ball mill, add 3.33 g of 4 mm diameter zirconium oxide grinding balls, 6.67 g of 8 mm diameter zirconium oxide grinding balls, add 10 mL of anhydrous ethanol, and perform ball milling at a ball milling speed of 500 rpm for 7 h to obtain alloy mixed powder;

[0053] S5. Weigh 0.1 g of the modified tungsten fiber prepared in step S1, add it and the alloy mixed powder prepared in step S4 into a mixer and mix them for 1 hour. After fully mixing, transfer it to a vacuum drying oven for drying, fill it into a mold, and press it into a green body at a pressure of 300 MPa. After loading it into an ark, heat it to 1300°C at 10°C / min under the protection of a high-purity argon atmosphere flowing at a speed of 1 L / h, keep it warm for 2 hours, and carry out infiltration sintering. After completion, the reaction system is naturally cooled to room temperature, placed on a grinder for further grinding and polishing to obtain a contact material.

[0054] This embodiment also provides a high voltage-resistant contact material prepared according to the above preparation method.

[0055] Comparative Example 1

[0056] This comparative example provides a contact material, and its preparation method is different from that of Example 1 in that the preparation method of this comparative example does not include steps S1 and S3, and the pretreated tungsten fiber is directly mixed with the alloy mixed powder, pressed into a green body, and then melt infiltration and sintering are performed to obtain the contact material.

[0057] Comparative Example 2

[0058] This comparative example provides a contact material, and its preparation method is different from that of Example 1 in that the preparation method described in this comparative example does not include steps S1, S2 and S3. In step S5, graphene oxide powder is added according to 0.3% of the mass of the alloy mixed powder, and after sufficient mixing, it is pressed into a green body, and subjected to infiltration and sintering treatment to obtain the contact material.

[0059] Experimental Example 1

[0060] In this experimental example, the phase structure analysis of the contact materials prepared in Example 1 and Comparative Examples 1 and 2 was carried out. An X-ray diffractometer was used to measure the phase composition of the contact materials prepared in Example 1 and Comparative Examples 1 and 2 with Cu target Kα rays. The specific parameters included: grazing angle 2°, scanning speed 8° / min, step size 0.02°, working voltage 40kV, working current 40mA, and scanning range 10°-90°.

[0061] Figure 1 1 and 2, wherein image A is the XRD image of the contact material prepared in Example 1, image C is the XRD image of the contact material prepared in Comparative Example 1, and image B is the XRD image of the contact material prepared in Comparative Example 2. It can be seen that the contact material described in Example 1 clearly has diffraction peaks of W phase and Cu phase, and also has carbon diffraction peaks and tungsten carbide diffraction peaks. This is because during the sintering process, C in graphene can react with W to form tungsten carbide; the XRD image of the contact material prepared in Comparative Example 1 does not show diffraction peaks of carbon and tungsten carbide; the XRD image of the contact material prepared in Comparative Example 2 has almost no diffraction peak of C, but has obvious diffraction peaks of tungsten carbide. This is because the activity of graphene powder is relatively high. Under high temperature conditions, it is easy to react with W powder. The degree of graphene reaction is relatively high, resulting in a low carbon content in the contact material and an unclear carbon diffraction peak.

[0062] Experimental Example 2

[0063] In this experimental example, the conductivity of the contact materials prepared in Examples 1-3 and Comparative Examples 1 and 2 is measured. A digital metal conductivity meter is used to measure the conductivity of the contact materials prepared in the Examples and Comparative Examples. The digital metal conductivity meter is turned on and preheated, and the instrument is calibrated with a standard sample after the probe is connected, and then the contact material to be measured is measured.

[0064] Figure 2 The conductivity results of the contact materials prepared in Examples 1-3 and Comparative Examples 1 and 2 are shown in the figure. As shown in the figure, the conductivity of the contact materials prepared in Examples 1-3 is between 47.78 and 48.81, the conductivity of the contact material prepared in Comparative Example 1 is 31.57, and the conductivity of the contact material prepared in Comparative Example 2 is 37.41. Graphene has good conductivity. In Comparative Example 1, the Wu phase component is added, and the conductivity is reduced. In Comparative Example 2, the graphene is converted into a carbide with poor conductivity, resulting in a decrease in the conductivity of the contact material.

[0065] Experimental Example 3

[0066] In this experimental example, the high-energy arc ablation resistance of the contact materials prepared in Examples 1-3 and Comparative Examples 1-2 was tested using a high-voltage discharge power supply platform system, and the vacuum degree was set to 8×10 -3 Pa, the cathode is the contact material to be tested, the anode is a tungsten needle with a diameter of 5mm and a needle tip diameter of 1mm, a voltage is applied between the two electrodes, and the discharge voltage when breakdown occurs is recorded. The withstand voltage strength is calculated according to the following formula:

[0067] ;

[0068] Where E is the withstand voltage strength / V·m -1 ; U is the discharge voltage / V; d is the discharge gap / mm.

[0069] Figure 3 The result diagram of the withstand voltage strength of the contact materials prepared by the embodiment and the comparative example shows that, under the discharge voltage within 10kv, the withstand voltage strength of the embodiment is higher than that of the contact materials prepared by comparative examples 1 and 2. Under the discharge voltage above 10kv, the withstand voltage strength of the contact material prepared by the embodiment is equivalent to that of the comparative example, and is slightly higher than that of the contact materials prepared by comparative examples 1 and 2. The withstand voltage strength of the alloy material is related to the electron work function of the material itself. The doping of graphene leads to the appearance of C phase and WC phase in the copper-tungsten alloy, and its electron work function is lower than that of the Cu phase and the W phase, resulting in the electrons of the C phase and the WC phase reaching the ionization condition first and breaking down. Figure 4 The results of arc ablation diameter and ablation depth of the contact materials prepared in the examples and comparative examples under a discharge voltage of 10 kV are shown. It can be seen that the ablation diameter of the contact material prepared in the example is larger than that of comparative example 1 and smaller than that of comparative example 2. In terms of ablation depth, the contact material prepared in the example is significantly smaller than that of comparative example 1 and comparative example 2, indicating that the contact material prepared in the example has a stronger ability to resist arc ablation.

[0070] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0071] The present invention and its implementation methods are described above, which is not restrictive. The drawings are only one of the implementation methods of the present invention, and the actual application is not limited thereto. In short, if ordinary technicians in the field are inspired by it and design methods and embodiments similar to the technical solution without creativity without departing from the purpose of the invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high withstand voltage contact material, characterized in that: The specific steps include: S1. Dispersing graphene oxide in deionized water, adding a surfactant, performing ultrasonic treatment at 300-500W for 30-60min, adding a polyvinyl alcohol aqueous solution, and mixing well to obtain a graphene oxide colloidal solution; The mass ratio of the surfactant to graphene oxide is 1:2-5; S2, immersing the tungsten fiber in a mixed acid solution, and performing a roughening treatment at room temperature for 40-50 minutes to obtain a pretreated tungsten fiber; the mixed acid solution is concentrated nitric acid and concentrated sulfuric acid in a volume ratio of 1:2; S3, immersing the pretreated tungsten fiber prepared in step S2 in the graphene oxide colloidal solution prepared in step S1, performing ultrasonic treatment at 500-600W, filtering, removing the filtrate, drying the tungsten fiber at 60-80°C, and performing sintering treatment. The sintering treatment parameters are: increasing the temperature to 300-350°C at 10°C / min, keeping the temperature for 20-30min, continuing to increase the temperature to 600-700°C, keeping the temperature for 1.5-2.5h, and after the system is naturally cooled to room temperature, a modified tungsten fiber is obtained; S4, mixing copper powder and tungsten powder, adding grinding balls and anhydrous ethanol to mix and ball mill to obtain alloy mixed powder; the mass ratio between the copper powder and the tungsten powder is 2-3:7-8; S5. Place the modified tungsten fiber prepared in step S3 and the alloy mixed powder prepared in step S4 in a mixer and mix them thoroughly for 1-2 hours. After drying, press them in a mold at 300-400 MPa to form a green body, put them into an ark, transfer them to a tubular furnace under an argon atmosphere, perform infiltration sintering, naturally cool to room temperature, and then grind and polish them to obtain the contact material.

2. The method for preparing a high withstand voltage contact material according to claim 1, characterized in that: In step S1, the mass concentration of the graphene oxide in deionized water is 0.01-0.02 g / mL.

3. The method for preparing a high withstand voltage contact material according to claim 2, characterized in that: In step S1, the surfactant is at least one of sodium dodecylbenzene sulfonate, sodium lauryl sulfonate and sodium dodecyl sulfate.

4. The method for preparing a high withstand voltage contact material according to claim 3, characterized in that: In step S1, the mass concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 15-20 mg / mL, and the added volume of the polyvinyl alcohol aqueous solution is 2-4 mL.

5. The method for preparing a high withstand voltage contact material according to claim 4, characterized in that: In step S4, during the ball milling process, the grinding balls are composed of zirconia grinding balls with diameters of 4 mm and 8 mm in a mass ratio of 1:2, the ball-to-material ratio is 5:1, the ball milling speed is 400-500 rpm, and the ball milling time is 7-9 hours.

6. The method for preparing a high withstand voltage contact material according to claim 5, characterized in that: In step S5, the added mass of the modified tungsten fiber is 5%-10% of the alloy mixed powder.

7. The method for preparing a high withstand voltage contact material according to claim 6, characterized in that: In step S5, the parameters of the infiltration sintering treatment are: heating to 1200-1300°C at 10°C / min and keeping the temperature for 1.5-2h.

8. A high withstand voltage contact material, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 7.

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