Method of making an electrical contact material and electrical contact

Abstract

The application discloses a preparation method of an electric contact material and an electric contact, and the preparation method comprises the following steps: adding a graphene oxide dispersion solution into a target dispersion solution to uniformly disperse, so as to obtain a graphene composite material; the target dispersion solution comprises nano copper oxide powder, nano lanthanum oxide powder and a surfactant; the graphene composite material is subjected to removal and reduction treatment, so as to remove the surfactant in the graphene composite material, and a reduced metal composite material is obtained; the metal composite material comprises graphene, copper, copper oxide and lanthanum oxide; the metal composite material is subjected to ball milling treatment, so as to obtain an electric contact composite material containing lanthanum oxide and graphene. According to the embodiment of the application, the lanthanum oxide and the graphene can be uniformly dispersed, so that the electric conductivity and the anti-welding performance of the electric contact material are effectively improved.

Description

Technical Field

[0001] This application relates to the technical field of electrical contact composite materials, specifically to a method for preparing an electrical contact material and an electrical contact. Background Technology

[0002] Graphene is a type of poly(phosphorus) 2 A novel material, graphene, is a single-layer two-dimensional honeycomb lattice structure formed by the close packing of hybridized carbon atoms. This structure endows graphene with many properties, such as a near-zero bandgap, extremely high carrier mobility, large specific surface area, excellent electrical and thermal conductivity, superior mechanical properties, and Young's modulus and fracture strength comparable to carbon nanotubes. These properties make graphene a promising material for many applications.

[0003] Electrical contacts are one of the core components of electrical switches and instruments, primarily responsible for breaking and connecting circuits and handling load current. The requirements for contact materials are multifaceted, demanding good electrical and thermal conductivity, low and stable contact resistance, high corrosion resistance, weldability, and good mechanical strength. Traditional copper-based composite materials primarily use ceramic particles and carbon materials such as silicon carbide, alumina, graphite, and diamond as reinforcements.

[0004] In related technologies, graphene powder and copper powder are often mixed by ball milling to prepare graphene-copper composite powder. However, due to the significant density difference between graphene powder and copper powder, and the tendency of graphene powder to agglomerate, graphene is difficult to disperse uniformly in the copper matrix, resulting in poor conductivity of the prepared electrical contacts. Alternatively, graphene can be synthesized in situ on the surface of copper powder using an organic solution impregnation process. However, this method has the problem that the graphene coating layer obtained by organic solution impregnation and subsequent in-situ synthesis is often too thick, leading to graphene stacking and resembling graphite, ultimately resulting in poor conductivity of the prepared electrical contacts.

[0005] Currently, rare earth elements are also added to electrical contact materials to improve their resistance to welding, such as lanthanum oxide. However, the addition of rare earth elements is also done by mixing them using conventional ball milling, which also results in uneven mixing and thus limited improvement in their resistance to welding. Summary of the Invention

[0006] This invention provides a method for preparing an electrical contact material and an electrical contact, in order to solve the technical problem of uneven mixing caused by the incorporation of graphene into the electrical contact material.

[0007] To address the above problems, in a first aspect, the present invention provides a method for preparing an electrical contact material, the method comprising the following steps:

[0008] A graphene oxide dispersion solution is added to a target dispersion solution and uniformly dispersed to obtain a graphene composite material. The target dispersion solution includes nano-copper oxide powder, nano-lanthanum oxide powder, and a surfactant.

[0009] The graphene composite material is subjected to a reduction treatment to obtain a metal composite material, which includes graphene, copper, and lanthanum oxide.

[0010] The metal composite material was subjected to ball milling to obtain an electrical contact composite material containing lanthanum oxide and graphene.

[0011] In the method for preparing an electrical contact material provided in this embodiment of the invention, the surfactant includes sodium citrate, sodium alkyl sulfonate, sodium alkyl aryl sulfonate, and sodium alkyl sulfate.

[0012] In the method for preparing an electrical contact material provided in this embodiment of the invention, the surfactant is sodium citrate. Before the step of uniformly dispersing the graphene oxide dispersion solution in the target dispersion solution, the method for preparing the electrical contact material further includes:

[0013] Nano copper oxide powder and nano lanthanum oxide powder were added to water and dispersed by ultrasonication to obtain the first mixture.

[0014] Sodium citrate was added to the first mixture and dispersed by ultrasonication to obtain the target dispersion solution.

[0015] In the method for preparing an electrical contact material provided in this embodiment of the invention, the step of uniformly dispersing a graphene oxide dispersion solution in a target dispersion solution to obtain a graphene composite material includes:

[0016] Graphene oxide powder was added to water and dispersed by ultrasound to obtain a graphene oxide dispersion solution.

[0017] The graphene oxide dispersion solution is added to the target dispersion solution, and the mixture is ultrasonically dispersed to obtain a second mixture.

[0018] The second mixture was placed in a reaction vessel for reaction, and then freeze-dried after the reaction to obtain a graphene composite material.

[0019] In the method for preparing an electrical contact material provided in this embodiment of the invention, the step of reducing the graphene composite material to obtain a metal composite material includes:

[0020] Under the protection of an inert gas, sodium citrate in the graphene composite material is thermally decomposed to convert sodium citrate into sodium carbonate.

[0021] Remove the sodium carbonate;

[0022] In a first environment, some of the copper oxide in the graphene composite material is reduced by hydrogen gas to obtain a composite material containing graphene oxide, copper, copper oxide and lanthanum oxide.

[0023] In a second environment, an inert gas is used for protection and the graphene oxide in the composite material is reduced to obtain a metal composite material containing graphene, copper, copper oxide, and lanthanum oxide.

[0024] In the method for preparing an electrical contact material provided in this embodiment of the invention, the mass ratio of the nano copper oxide powder to the nano lanthanum oxide powder is 1:0.01 to 1:0.03, 1 liter of the water contains 3 to 5 grams of the nano copper oxide powder and 9 to 10 grams of the sodium citrate, the concentration of the graphene oxide dispersion solution is 5 to 6 grams per liter, and the ultrasonic dispersion time is 25 to 30 minutes.

[0025] In the method for preparing an electrical contact material provided in this embodiment of the invention, the step of placing the second mixture into a reaction vessel for reaction includes:

[0026] The second mixture is placed in a reaction vessel and reacted at a constant temperature of 178°C to 182°C for 4 to 6 hours, then cooled to room temperature.

[0027] In the method for preparing an electrical contact material provided in this embodiment of the invention, the inert gas includes nitrogen, the temperature of the thermal decomposition treatment is 250 degrees Celsius to 300 degrees Celsius, and in the reduction treatment, under a first environment, the flow rate of hydrogen is 0.2 liters / minute to 0.25 liters / minute, the flow rate of nitrogen is 0.5 liters / minute to 0.55 liters / minute, and the temperature of the reduction treatment is 900 degrees Celsius to 1000 degrees Celsius.

[0028] In the second environment, the temperature is 1200 to 1300 degrees Celsius and the pressure is 16 to 17 MPa.

[0029] In the method for preparing an electrical contact material provided in this embodiment of the invention, the ball milling process involves feeding the metal composite material into a ball mill for ball milling. The ball milling time is 4 to 5 hours, the ball-to-material ratio is 2:1 to 3:1, and the rotation speed of the ball mill is 250 rpm to 300 rpm.

[0030] Secondly, the present invention provides an electrical contact, the electrical contact comprising an electrical contact material, the electrical contact material being prepared by the aforementioned method for preparing electrical contact materials.

[0031] Beneficial Effects: This invention provides a method for preparing an electrical contact material and an electrical contact. In this method, a graphene oxide dispersion solution is first added to a target dispersion solution containing nano-copper oxide powder, nano-lanthanum oxide powder, and a surfactant, and uniformly dispersed to obtain a graphene composite material in which graphene oxide and lanthanum oxide are uniformly dispersed. Subsequently, the graphene composite material is subjected to a reduction treatment to obtain a metal composite material containing graphene, copper, and lanthanum oxide. By ball milling the metal composite material, an electrical contact composite material containing uniformly dispersed lanthanum oxide and graphene can be obtained, effectively improving the conductivity and anti-welding performance of the electrical contact material and solving the technical problem of uneven mixing caused by the incorporation of graphene into the electrical contact material. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a schematic flowchart of a method for preparing an electrical contact material provided in an embodiment of the present invention.

[0034] Figure 2 This is another schematic flowchart of a method for preparing an electrical contact material provided in an embodiment of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0036] It should be understood that the steps described in the method embodiments of this disclosure may be performed in different orders and / or in parallel. Furthermore, the method embodiments may include additional steps and / or omit the steps shown. The scope of this disclosure is not limited in this respect.

[0037] The term "comprising" and its variations as used herein are open-ended inclusions, meaning "including but not limited to". The term "based on" means "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". Definitions of other terms will be given in the description below.

[0038] In related technologies, graphene powder and copper powder are often mixed by ball milling to prepare graphene-copper composite powder. However, due to the significant density difference between graphene powder and copper powder, and the tendency of graphene powder to agglomerate, graphene is difficult to disperse uniformly in the copper matrix, resulting in poor conductivity of the prepared electrical contacts. Alternatively, graphene can be synthesized in situ on the surface of copper powder using an organic solution impregnation process. However, this method has the problem that the graphene coating layer obtained by organic solution impregnation and subsequent in-situ synthesis is often too thick, leading to graphene stacking and resembling graphite, ultimately resulting in poor conductivity of the prepared electrical contacts.

[0039] Currently, rare earth elements are also added to electrical contact materials to improve their resistance to welding, such as lanthanum oxide. However, the addition of rare earth elements is also done by mixing them using conventional ball milling, which also results in uneven mixing and thus limited improvement in their resistance to welding.

[0040] To address the technical problems existing in related technologies, embodiments of the present invention provide a method for preparing an electrical contact material. Please refer to [link to relevant documentation]. Figure 1 , Figure 1 This is a schematic flowchart of a method for preparing an electrical contact material according to an embodiment of the present invention, wherein the method for preparing the electrical contact material includes steps S101 to S103.

[0041] Step S101: Add the graphene oxide dispersion solution to the target dispersion solution and disperse it uniformly to obtain the graphene composite material.

[0042] The target dispersion solution includes nano-copper oxide powder, nano-lanthanum oxide powder, and a surfactant.

[0043] In this embodiment, a graphene oxide dispersion solution is added to a target dispersion solution containing nano-copper oxide powder, nano-lanthanum oxide powder, and a surfactant. The surfactant acts as an intermediate to connect the graphene oxide and the nano-oxygen-containing metal particles (i.e., nano-copper oxide powder and nano-lanthanum oxide powder) through chemical bonds, thereby making the connection between the graphene oxide and the nano-oxygen-containing metal particles more stable.

[0044] Optionally, the surfactant provided in this embodiment includes dispersing agents such as sodium citrate, sodium alkyl sulfonate, sodium alkyl aryl sulfonate, and sodium alkyl sulfate. Since sodium citrate not only has the best dispersing effect but is also relatively easy to remove later, it can avoid affecting the final conductivity and anti-welding properties of the composite material due to the presence of surfactants. Therefore, the surfactant provided in this embodiment is mainly sodium citrate, and subsequent embodiments of this invention will also use sodium citrate as the surfactant for detailed explanation.

[0045] It should be noted that pure nano-lanthanum oxide is highly reactive and readily reacts with water and carbon dioxide in the air, forming lanthanum carbonate on the surface of the nano-lanthanum oxide powder. Therefore, commercially available nano-lanthanum oxide powder generally has a lanthanum carbonate layer on its surface. Lanthanum carbonate is poorly soluble in water, so commercially available nano-lanthanum oxide powder is difficult to react with water after being placed in it due to the presence of the outer lanthanum carbonate layer. To induce a reaction between nano-lanthanum oxide and water, commercially available nano-lanthanum oxide powder typically undergoes a high-temperature calcination process at around 900 degrees Celsius to restore its hydrolysis reactivity. However, while nano-lanthanum oxide powder that has undergone this high-temperature calcination process will react rapidly with water after being placed in it, it will form lanthanum hydroxide.

[0046] Therefore, in order to avoid the reaction between the nano-lanthanum oxide powder and water, this embodiment does not subject the nano-lanthanum oxide powder to high-temperature calcination before adding it to water.

[0047] Optionally, to further prevent the nano-lanthanum oxide powder from reacting with water, this embodiment can also purchase commercially available nano-lanthanum oxide powder and then lay it flat in the air for a period of time to allow a lanthanum carbonate coating layer to fully form on the surface of the nano-lanthanum oxide powder. In this way, the reaction between the nano-lanthanum oxide powder and water can be effectively prevented.

[0048] As an optional embodiment, this embodiment mainly involves adding the graphene oxide dispersion solution to the target dispersion solution for mixing, followed by ultrasonic dispersion for 25 to 35 minutes, and then placing it in a reaction vessel for hydrothermal reaction at any temperature between 178 and 182 degrees Celsius for 4 to 6 hours. After the reaction, the graphene composite material is obtained by freeze drying.

[0049] In some embodiments, the ultrasonic dispersion time can be 25 minutes, 30 minutes, or 35 minutes. Using any ultrasonic dispersion time provided in this embodiment can achieve a good dispersion effect.

[0050] In other embodiments, the temperature for the hydrothermal reaction in the reactor can be 178 degrees Celsius, 180 degrees Celsius, and 182 degrees Celsius, and the reaction time can be 4 hours, 5 hours, and 6 hours. Specifically, the hydrothermal reaction provided in this embodiment can be carried out using any of the hydrothermal reaction temperatures and times provided in this embodiment.

[0051] It should be noted that during the hydrothermal reaction, some of the oxygen-containing functional groups in graphene oxide are reduced (carboxyl groups (-COOH) are not reduced hydrothermally, while hydroxyl groups (-OH) are). After the oxygen-containing functional groups are partially reduced, the C / O ratio of graphene oxide increases, which in turn increases the van der Waals forces between graphene oxide particles. This causes the graphene oxide to curl up, ultimately achieving the purpose of encapsulating nano-oxygen-containing metal particles (i.e., nano-copper oxide powder and nano-lanthanum oxide powder).

[0052] Since sodium citrate is used as a surfactant in this embodiment, and sodium citrate can effectively inhibit the accumulation of graphene and improve the dispersion of graphene, the addition of sodium citrate can increase the dispersibility of graphene and reduce the number of graphene coating layers. Therefore, by first dispersing nano-copper oxide powder and nano-lanthanum oxide powder uniformly in an aqueous solution and then adding sodium citrate, this embodiment enables graphene to coat the nano-oxygen-containing metal particles (i.e., nano-copper oxide powder and nano-lanthanum oxide powder), which is beneficial for the uniform dispersion of lanthanum oxide in the metal composite material, and ultimately improves the weldability of the electrical contact material.

[0053] Step S102: The graphene composite material is subjected to reduction treatment to obtain a metal composite material.

[0054] The metal composite material includes graphene, copper, copper oxide, and lanthanum oxide.

[0055] In this embodiment, the step of reducing the graphene composite material to obtain a metal composite material specifically includes: thermally decomposing sodium citrate in the graphene composite material under the protection of an inert gas to thermally decompose the sodium citrate into sodium carbonate; removing the sodium carbonate; reducing some of the copper oxide in the graphene composite material with hydrogen in a first environment to obtain a composite material containing graphene oxide, copper, copper oxide, and lanthanum oxide; and in a second environment, using an inert gas for protection and reducing the graphene oxide in the composite material to obtain a metal composite material containing graphene, copper, copper oxide, and lanthanum oxide.

[0056] Sodium citrate not only has the best dispersion effect but is also easy to remove, thus avoiding the impact of sodium citrate on the final electrical conductivity and anti-welding properties of the composite material. Therefore, this embodiment can remove sodium citrate from the graphene composite material by introducing an inert gas. Specifically, in this embodiment, an inert gas (i.e., nitrogen) is first introduced into the graphene composite material, then the sodium citrate is thermally decomposed into sodium carbonate, and subsequently the sodium carbonate is removed by washing with water, thereby achieving the purpose of removing sodium citrate.

[0057] After removing the sodium citrate, hydrogen and nitrogen are introduced in a first environment to partially reduce copper oxide. Then, the hydrogen flow is stopped, and an inert gas (nitrogen) is introduced to reduce graphene oxide in a second environment. Finally, a metal composite material containing graphene, copper, copper oxide, and lanthanum oxide is obtained. Since only copper oxide is partially reduced, the metal composite material also contains copper oxide. Because copper oxide also has anti-welding properties, the unreduced copper oxide in the metal composite material can play an anti-welding role, further improving the anti-welding properties of the electrical contact material.

[0058] The first environment is a high-temperature environment, and the second environment is a high-temperature and high-pressure environment. Specifically, the temperature of the first environment is 900 to 1000 degrees Celsius, the temperature of the second environment is 1200 to 1300 degrees Celsius, and the pressure is 16 to 17 MPa. The reduction treatment time in the first environment is 80 to 120 minutes, and the reduction treatment time in the second environment is 60 ± 5 minutes.

[0059] In some embodiments, the temperature of the first environment can be 900 degrees Celsius, 950 degrees Celsius, or 1000 degrees Celsius. Using any temperature as the first environment can achieve the purpose of partially reducing copper oxide when hydrogen and nitrogen are introduced.

[0060] In other embodiments, the temperature of the second environment can be 1200 degrees Celsius, 1250 degrees Celsius, and 1300 degrees Celsius, and the pressure can be 16 MPa, 16.5 MPa, and 17 MPa. Using any temperature and pressure as the second environment, the purpose of reducing graphene oxide can be achieved by introducing an inert gas (i.e., nitrogen).

[0061] Optionally, the reduction treatment time in the first environment can be 80 minutes, 100 minutes, or 120 minutes. Specifically, any of the reduction treatment times can complete the partial reduction of copper oxide.

[0062] Optionally, the reduction treatment time in the second environment can be 55 minutes, 60 minutes, or 65 minutes. Specifically, the reduction of graphene oxide can be completed using any of the reduction treatment times described above.

[0063] As an optional embodiment, since nano-lanthanum oxide powder readily reacts with water and carbon dioxide in the air, a lanthanum carbonate coating layer is easily formed on the surface of the nano-lanthanum oxide powder. Therefore, in this embodiment, when hydrogen and nitrogen are introduced to reduce the graphene composite material, the lanthanum carbonate formed on the surface of the nano-lanthanum oxide powder can also be reduced, causing the lanthanum carbonate to thermally decompose to form lanthanum oxide. This increases the content of lanthanum oxide uniformly dispersed in the metal composite material, further improving the anti-welding properties of the electrical contact material.

[0064] It should be noted that when hydrogen and nitrogen are introduced to reduce the graphene composite material, lanthanum carbonate thermally decomposes to form lanthanum oxide. However, hydrogen cannot reduce lanthanum oxide in this process; it only reduces copper oxide. Since the oxygen-containing functional groups in the graphene oxide of the metal composite material are mostly carboxyl groups, and the conditions for reducing carboxyl groups with hydrogen are quite demanding, graphene oxide can be further reduced under high temperature and high pressure to improve the C / O ratio.

[0065] Step S103: The metal composite material is ball-milled to obtain an electrical contact composite material containing lanthanum oxide and graphene.

[0066] In this embodiment, after obtaining the metal composite material, it needs to be fed into a ball mill for ball milling. Specifically, the ball milling time is 4 to 5 hours, the ball-to-material ratio is 2:1 to 3:1, and the rotation speed of the ball mill is 250 to 300 rpm. After the ball milling is completed, sintering is performed to obtain the electrical contact composite material containing lanthanum oxide and graphene.

[0067] It should be noted that the purpose of ball milling is to partially expose the surfaces of the copper and lanthanum oxide coated with graphene, rather than completely covering them with graphene, thus facilitating the sintering of the materials. Furthermore, the ball milling process also serves to re-mix and homogenize the materials.

[0068] In some embodiments, the ball milling time can be 4 hours, 4.5 hours, or 5 hours; the ball-to-material ratio can be 2:1, 2.5:1, or 3:1; and the ball mill speed can be 250 rpm, 275 rpm, or 300 rpm. Specifically, the ball milling process of the metal composite material can be completed using any ball milling time, ball-to-material ratio, and ball mill speed.

[0069] For a better illustration of the preparation method of the electrical contact material provided in the embodiments of the present invention, please refer to [link to relevant documentation]. Figure 2 , Figure 2 This is another schematic flowchart of the method for preparing electrical contact materials provided in the embodiments of the present invention, wherein the method for preparing electrical contact materials includes steps S201 to S215;

[0070] In step S201, graphite powder and potassium permanganate powder are mixed and concentrated sulfuric acid solution is added to carry out the first reaction treatment to obtain the first solution.

[0071] Step S202: Add the same amount of concentrated sulfuric acid solution to the first solution to carry out a second reaction treatment, and obtain a second solution after cooling.

[0072] In this embodiment, the mass ratio of graphite powder to potassium permanganate powder is 1:5, and 1 gram of graphite powder corresponds to 20 ml of concentrated sulfuric acid solution, wherein the concentrated sulfuric acid solution is 98% concentrated sulfuric acid solution; the first reaction treatment is carried out at a water bath temperature of 80 degrees Celsius for 50 minutes, and the second reaction treatment is carried out at a water bath temperature of 80 degrees Celsius for 30 minutes.

[0073] Step S203: Hydrogen peroxide is added dropwise to the second solution to obtain a graphene oxide synthesis solution.

[0074] In step S204, calcium hydroxide is added to the graphene oxide synthesis solution under stirring to form calcium sulfate precipitate.

[0075] Step S205: The graphene oxide synthesis solution with calcium sulfate precipitate is stirred and carbon tetrachloride solution is added, and then allowed to stand and dry to obtain graphene oxide powder.

[0076] In this embodiment, the graphene oxide powder is synthesized using the Hummers method. Specifically, the synthesis process is as follows: Graphite powder and potassium permanganate solid powder are mixed (5 grams of potassium permanganate are needed for every 1 gram of graphite powder). After thorough mixing, 98% concentrated sulfuric acid solution is added (20 ml of 98% concentrated sulfuric acid solution is needed for every 1 gram of graphite powder). The mixture is reacted in a water bath at 80°C for 50 minutes. Then, the same volume of 98% concentrated sulfuric acid solution is added, and the reaction continues for another 30 minutes at the same temperature. After the reaction liquid cools to room temperature, hydrogen peroxide is added dropwise to the solution to obtain a graphene oxide synthesis solution. Then, calcium hydroxide is added dropwise to the graphene oxide synthesis solution with stirring. Calcium ions and sulfate ions react to form calcium sulfate precipitate. Carbon tetrachloride solution is then added with stirring, and the mixture is allowed to stand and separate into layers. The upper layer is a colorless and transparent aqueous layer, the middle layer is an aqueous layer containing yellow substances, and the lower layer is a carbon tetrachloride layer containing a white emulsion. The water layer containing the yellow substance in the middle layer is taken and dried to obtain the graphene oxide powder.

[0077] Step S206: Add nano copper oxide powder and nano lanthanum oxide powder to water, and disperse by ultrasonication to obtain the first mixture.

[0078] In this embodiment, the mass ratio of the nano-copper oxide powder to the nano-lanthanum oxide powder is 1:0.01 to 1:0.03, and 1 liter of the water contains 3 to 5 grams of the nano-copper oxide.

[0079] Specifically, in this embodiment, 1 liter of water is taken, and then 4 grams of nano copper oxide and 0.08 grams of nano lanthanum oxide are added respectively. Then, ultrasonic dispersion is performed for 10 minutes to obtain the first mixture.

[0080] Step S207: Sodium citrate is added to the first mixture and dispersed by ultrasonication to obtain the target dispersion solution.

[0081] In this embodiment, 9 to 10 grams of sodium citrate are added to 1 liter of the water.

[0082] Specifically, since 1 liter of water was used in this embodiment, 9.5 grams of sodium citrate powder were added to the first mixture and ultrasonically dispersed for 30 minutes to obtain the target dispersion solution.

[0083] The addition of sodium citrate improves the dispersibility of nanoparticles, significantly enhancing their dispersion performance. Furthermore, sodium citrate, as an intermediate, chemically bonds graphene oxide and oxygen-containing metal nanoparticles, resulting in a more stable connection between them. Subsequently, the sodium citrate can be thermally decomposed into sodium carbonate by breaking these chemical bonds and then removed.

[0084] Step S208: Add the graphene oxide powder to water and disperse it by ultrasound to obtain a graphene oxide dispersion solution.

[0085] In this embodiment, the concentration of the graphene oxide dispersion solution is 5 to 6 g / L, and the ultrasonic dispersion treatment time is 25 minutes.

[0086] Step S209: The graphene oxide dispersion solution is added to the target dispersion solution, and the mixture is ultrasonically dispersed to obtain a second mixture.

[0087] In this embodiment, 80 ml of a graphene oxide dispersion solution with a concentration of 5 g / L is added to the target dispersion solution, and the ultrasonic dispersion treatment is performed for 30 minutes to obtain the second mixture.

[0088] Step S210: The second mixture is placed in a reaction vessel for reaction, and then freeze-dried after the reaction to obtain a graphene composite material.

[0089] The step of placing the second mixture into the reaction vessel for reaction specifically involves placing the second mixture into the reaction vessel and reacting it at a constant temperature of 178 degrees Celsius to 182 degrees Celsius for 4 to 6 hours, then cooling it to room temperature.

[0090] Specifically, in this embodiment, the graphene composite material is obtained by reacting at a constant temperature of 180 degrees Celsius for 5 hours, cooling to room temperature, and then freeze-drying.

[0091] Step S211: Under the protection of an inert gas, the sodium citrate in the graphene composite material is subjected to thermal decomposition treatment to thermally decompose the sodium citrate into sodium carbonate.

[0092] Step S212: Remove the sodium carbonate.

[0093] In this embodiment, the temperature of the thermal decomposition treatment is 250 degrees Celsius to 300 degrees Celsius.

[0094] Specifically, in this embodiment, 1 kg of the graphene composite material obtained in the above steps is extracted and placed in a reduction furnace. First, a vacuum is drawn, then nitrogen gas is introduced, and sodium citrate is thermally decomposed at 280 degrees Celsius to form sodium carbonate. Then, the graphene composite material is taken out and washed with deionized water in small amounts several times to remove the sodium carbonate.

[0095] Step S213: In the first environment, a portion of the copper oxide in the graphene composite material is reduced by hydrogen gas to obtain a composite material containing graphene oxide, copper, copper oxide and lanthanum oxide.

[0096] Step S214: In the second environment, an inert gas is used for protection and the graphene oxide in the composite material is reduced to obtain a metal composite material containing graphene, copper, copper oxide and lanthanum oxide.

[0097] In this embodiment, during the reduction process, under a first environment, the flow rate of hydrogen is 0.2 L / min to 0.25 L / min, the flow rate of nitrogen is 0.5 L / min to 0.55 L / min, the temperature of the first environment is 900 degrees Celsius to 1000 degrees Celsius, and the reaction time is 80-120 minutes.

[0098] In the second environment, the temperature is 1200 to 1300 degrees Celsius, the pressure is 16 to 17 MPa, and the reduction treatment time is 60 ± 5 minutes.

[0099] Specifically, after removing the sodium carbonate, the graphene composite material is placed back into the reduction furnace. A mixture of hydrogen and nitrogen gas is introduced at atmospheric pressure, with a hydrogen flow rate of 0.2 L / min and a nitrogen flow rate of 0.5 L / min. Copper oxide is reduced to copper at 950°C for 100 minutes. During this process, lanthanum carbonate is also thermally decomposed to form lanthanum oxide. The hydrogen flow is then stopped, and nitrogen gas is introduced again to increase the reaction pressure to 16 MPa. Graphene oxide is then reduced to graphene at 1200°C for 60 minutes. Finally, a metal composite material containing graphene, copper, copper oxide, and lanthanum oxide is obtained.

[0100] It should be noted that under the initial protection of nitrogen and at a low temperature, sodium citrate thermally decomposes to form sodium carbonate. Sodium carbonate can be removed by washing with water. Then, under normal pressure and high temperature, hydrogen is used to reduce copper oxide to copper. Experimental data shows that 93.3% to 95.1% of copper oxide is reduced to copper. A small portion of copper oxide is not reduced, and the unreduced copper oxide can play a role in preventing welding in metal composite materials.

[0101] It is understandable that, since graphene, copper, copper oxide, and lanthanum oxide are uniformly dispersed in the metal composite material, the metal composite material provided in this embodiment has better electrical conductivity and anti-welding properties compared to metal materials made by simply mixing graphene, copper, copper oxide, and lanthanum oxide.

[0102] Step S215: The metal composite material is ball-milled to obtain an electrical contact composite material containing lanthanum oxide and graphene.

[0103] In this embodiment, after obtaining the metal composite material, it is fed into a ball mill for ball milling. Specifically, the ball milling time is 4 hours, the ball-to-material ratio is 3:1, and the ball mill speed is 250 rpm. After completing the ball milling process, the ball-milled metal composite material is sintered to obtain the electrical contact material.

[0104] Optionally, electrical contacts with strong resistance to welding and high conductivity can be prepared using the aforementioned lanthanum oxide and graphene-containing electrical contact composite material. Experimental results show that the electrical contacts prepared using the method provided in this embodiment of the invention have a conductivity between 95.3% IACS and 96.9% IACS. The resulting electrical contacts have a lifespan exceeding 130,000 cycles under certain current conditions (250V 30A), exhibiting excellent resistance to welding.

[0105] In the method for preparing electrical contact materials provided in this invention, a graphene oxide dispersion solution is first added to a target dispersion solution containing nano-copper oxide powder, nano-lanthanum oxide powder, and sodium citrate, and uniformly dispersed to obtain a graphene composite material in which graphene oxide and lanthanum oxide are uniformly dispersed. Subsequently, the graphene composite material is subjected to removal and reduction treatment to remove sodium citrate from the graphene composite material and obtain a reduced metal composite material containing graphene, copper, and lanthanum oxide. By ball milling the metal composite material, an electrical contact composite material containing uniformly dispersed lanthanum oxide and graphene can be obtained, which effectively improves the conductivity and anti-welding performance of the electrical contact composite material and solves the technical problem of uneven mixing caused by the incorporation of graphene into the electrical contact material.

[0106] In addition, embodiments of the present invention also provide an electrical contact, which includes the electrical contact composite material in any of the above embodiments, or an electrical contact composite material prepared by the preparation method of the electrical contact material described in any of the above embodiments. Please refer to the description above for details, which will not be repeated here.

[0107] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0108] The preparation method of an electrical contact material and an electrical contact provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application. Moreover, those skilled in the art can make several improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of this invention.

Claims

1. A method for preparing an electrical contact material, characterized in that, The preparation method includes the following steps: A graphene oxide dispersion solution is added to a target dispersion solution and uniformly dispersed to obtain a graphene composite material. The target dispersion solution includes nano-copper oxide powder, nano-lanthanum oxide powder, and a surfactant. The graphene composite material is subjected to a reduction treatment to obtain a metal composite material, which includes graphene, copper, and lanthanum oxide. The metal composite material was subjected to ball milling to obtain an electrical contact composite material containing lanthanum oxide and graphene.

2. The method for preparing the electrical contact material according to claim 1, characterized in that, The surfactants include sodium citrate, sodium alkyl sulfonate, sodium alkyl aryl sulfonate, and sodium alkyl sulfate.

3. The method for preparing the electrical contact material according to claim 2, characterized in that, The surfactant is sodium citrate. Prior to the step of uniformly dispersing the graphene oxide dispersion solution in the target dispersion solution, the method for preparing the electrical contact material further includes: Nano copper oxide powder and nano lanthanum oxide powder were added to water and dispersed by ultrasonication to obtain the first mixture. Sodium citrate was added to the first mixture and dispersed by ultrasonication to obtain the target dispersion solution.

4. The method for preparing the electrical contact material according to claim 3, characterized in that, The step of uniformly dispersing the graphene oxide dispersion solution in a target dispersion solution to obtain a graphene composite material includes: Graphene oxide powder was added to water and dispersed by ultrasound to obtain a graphene oxide dispersion solution. The graphene oxide dispersion solution is added to the target dispersion solution, and the mixture is ultrasonically dispersed to obtain a second mixture. The second mixture was placed in a reaction vessel for reaction, and then freeze-dried after the reaction to obtain a graphene composite material.

5. The method for preparing the electrical contact material according to claim 3, characterized in that, The reduction treatment of the graphene composite material to obtain a metal composite material includes: Under the protection of an inert gas, sodium citrate in the graphene composite material is thermally decomposed to convert sodium citrate into sodium carbonate. Remove the sodium carbonate; In a first environment, hydrogen and nitrogen are introduced to reduce some of the copper oxide in the graphene composite material, resulting in a composite material containing graphene oxide, copper, copper oxide, and lanthanum oxide. In a second environment, an inert gas is used for protection and the graphene oxide in the composite material is reduced to obtain a metal composite material containing graphene, copper, copper oxide, and lanthanum oxide.

6. The method for preparing the electrical contact material according to claim 3, characterized in that, The mass ratio of the nano-copper oxide powder to the nano-lanthanum oxide powder is 1:0.01 to 1:0.03, 1 liter of the water contains 3 to 5 grams of the nano-copper oxide powder and 9 to 10 grams of the sodium citrate, the concentration of the graphene oxide dispersion solution is 5 to 6 grams per liter, and the ultrasonic dispersion time is 25 to 35 minutes.

7. The method for preparing the electrical contact material according to claim 4, characterized in that, The step of placing the second mixture into a reaction vessel for reaction includes: The second mixture is placed in a reaction vessel and reacted at a constant temperature of 178°C to 182°C for 4 to 6 hours, then cooled to room temperature.

8. The method for preparing the electrical contact material according to claim 5, characterized in that, The inert gas includes nitrogen, the thermal decomposition treatment is performed at a temperature of 250°C to 300°C, and in the reduction treatment, under a first environment, the flow rate of hydrogen is 0.2 L / min to 0.25 L / min, the flow rate of nitrogen is 0.5 L / min to 0.55 L / min, and the temperature of the first environment is 900°C to 1000°C. In the second environment, the temperature is 1200 to 1300 degrees Celsius and the pressure is 16 to 17 MPa.

9. The method for preparing the electrical contact material according to claim 1, characterized in that, The ball milling process involves feeding the metal composite material into a ball mill for ball milling. The ball milling time is 4 to 5 hours, the ball-to-material ratio is 2:1 to 3:1, and the rotation speed of the ball mill is 250 to 300 rpm.

10. An electrical contact, characterized in that, The electrical contact includes an electrical contact material, which is prepared by the method for preparing the electrical contact material according to any one of claims 1-9.

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