Preparation method of copper-graphene composite material and electric contact

Abstract

The application discloses a preparation method of copper-graphene composite material and an electric contact. The preparation method comprises the following steps: step S1: adding graphene quantum dots and spherical copper powder into water, and performing ultrasonic dispersion to obtain a dispersion liquid; step S2: performing stirring operation on the dispersion liquid to obtain a stirring mixed liquid, the stirring operation comprises a plurality of continuously performed stirring procedures, any stirring procedure comprises a first stage and a second stage which are performed in sequence, the stirring speed of the first stage is greater than that of the second stage, and in two adjacent stirring procedures, the stirring speed of the second stage of the previous stirring procedure is less than that of the first stage of the following stirring procedure; step S3: filtering the stirring mixed liquid to obtain solid particles; and step S4: sintering the solid particles to obtain the copper-graphene composite material. The copper-graphene composite material prepared by the method has relatively optimal electric conductivity.

Description

Technical Field

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

[0002] 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.

[0003] Graphene is a type of poly(phosphorus) 2 A new 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, very 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 an ideal reinforcement in electrical contact materials.

[0004] Currently, graphene-copper composite powders are typically prepared by ball milling graphene powder and copper powder together. However, due to the significant density difference between graphene and copper powders, and the tendency of graphene powder to agglomerate, graphene is difficult to disperse uniformly within the copper matrix, resulting in poor conductivity of the prepared electrical contacts. Alternatively, a solution impregnation process can be used to synthesize graphene in situ on the surface of copper powder. Then, by ball milling the graphene-coated electrolytic copper powder, the graphene trapped between the copper powder dendrites can be milled into the interior of the copper powder. Only a portion of the copper powder surface is coated with graphene. However, because the copper powder is irregularly dendritic, the specific surface area of ​​each particle varies greatly. This results in significant differences in the amount of graphene synthesized in situ on the surface of each copper powder particle after the subsequent solution impregnation process, limiting the improvement in the conductivity of the electrical contacts. Furthermore, the aforementioned method still requires ball milling to extend the graphene-coated copper powder into sheets. During ball milling, the graphene layer is prone to detachment. This detached graphene not only further increases the difference in graphene content between individual copper powder particles but also causes the detached graphene to stack up and turn into graphite, leading to a decrease in conductivity. Therefore, it is necessary to develop a new preparation process to improve the conductivity of graphene-copper composite materials. Summary of the Invention

[0005] This invention provides a method for preparing a copper-graphene composite material and an electrical contact, such that the prepared copper-graphene composite material has excellent electrical conductivity.

[0006] To address the above problems, in a first aspect, the present invention provides a method for preparing a copper-graphene composite material, the method comprising the following steps:

[0007] Step S1: Add graphene quantum dots and spherical copper powder to water and disperse them by ultrasonication to obtain a dispersion.

[0008] Step S2: The dispersion is stirred to obtain a stirred mixture. The stirring operation includes multiple consecutive stirring programs. Each stirring program includes a first stage and a second stage. The stirring speed of the first stage is greater than the stirring speed of the second stage. In two adjacent stirring programs, the stirring speed of the second stage of the previous stirring program is less than the stirring speed of the first stage of the subsequent stirring program.

[0009] Step S3: Filter the stirred mixture to obtain solid particles;

[0010] Step S4: Sinter the solid particles to obtain the copper-graphene composite material.

[0011] In the preparation method of a copper-graphene composite material provided in the embodiment of the present invention, in step S2, in the multiple stirring programs carried out in succession, the stirring speed of each first stage decreases sequentially.

[0012] In the preparation method of a copper-graphene composite material provided in the embodiments of the present invention, the stirring speed in the first stage is 700 r / min-900 r / min, and the stirring speed in the last stage is 50 r / min-150 r / min.

[0013] In the preparation method of a copper-graphene composite material provided in the embodiments of the present invention, the stirring speed of each second stage is equal in the multiple stirring processes carried out in succession.

[0014] In the preparation method of a copper-graphene composite material provided in the embodiments of the present invention, in step S1, the graphene quantum dots are carboxyl functionalized graphene quantum dots.

[0015] In the preparation method of a copper-graphene composite material provided in the embodiment of the present invention, in step S1, the particle size of the spherical copper powder is 0.300mm-0.355mm.

[0016] In the preparation method of a copper-graphene composite material provided in the embodiments of the present invention, in step S1, the mass ratio of the graphene quantum dots to the spherical copper powder is 8:1000000-15:1000000.

[0017] In the preparation method of a copper-graphene composite material provided in this embodiment of the invention, the relative molecular mass of the graphene quantum dots is greater than 1500.

[0018] In the method for preparing a copper-graphene composite material provided in this embodiment of the invention, step S4, the step of sintering the solid particles, includes:

[0019] The solid particles are placed in a sintering furnace and reacted for 50-60 minutes under a pressure of 15-20 MPa, a temperature of 1200-1500°C, and an inert atmosphere. The inert atmosphere is then maintained while the temperature is reduced to 950-980°C, and the pressure is released to atmospheric pressure for 1-1.5 hours.

[0020] Secondly, the present invention provides an electrical contact comprising a copper-graphene composite material, wherein the copper-graphene composite material is prepared by the aforementioned method for preparing copper-graphene composite materials.

[0021] Beneficial Effects: This invention provides a method for preparing a copper-graphene composite material and an electrical contact. In this preparation method, graphene quantum dots and spherical copper powder are first added to water and dispersed uniformly by ultrasonication. During this process, under the action of ultrasonic vibration, the graphene quantum dots and spherical copper powder are uniformly dispersed in the water. Then, stirring is performed, thereby making the graphene quantum dots uniformly coat the surface of the spherical copper powder. Specifically, the stirring operation includes multiple consecutive stirring programs. Each stirring program includes a first stage and a second stage performed sequentially. The stirring speed of the first stage is greater than the stirring speed of the second stage, and in two adjacent stirring programs, the stirring speed of the first second stage is less than that of the second first stage. The stirring speed is adjusted in each stage. The first stage is a high-speed stirring stage, which allows the spherical copper powder that has settled at the bottom to redistribute evenly in the system. The second stage is a low-speed stirring stage, which allows graphene quantum dots to be adsorbed onto the surface of the spherical copper powder. Repeating this stirring process multiple times helps to maximize and evenly adsorb graphene quantum dots onto the surface of the spherical copper powder, thus resulting in a copper-graphene composite material with superior conductivity. In addition, the copper powder used is specifically spherical copper powder, which results in high uniformity of specific surface area among different copper powders, and thus high uniformity of the content of graphene quantum dots coated on the surface of different copper powders, which is beneficial to further improving the conductivity of the prepared copper-graphene composite material. Attached Figure Description

[0022] 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.

[0023] Figure 1 This is a schematic flowchart of a method for preparing a copper-graphene composite material according to an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of the stirring speed in a method for preparing a copper-graphene composite material according to an embodiment of the present invention. Detailed Implementation

[0025] 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.

[0026] This invention provides a method for preparing a copper-graphene composite material. Please refer to [link / reference]. Figure 1 The preparation method includes the following steps:

[0027] Step S1: Add graphene quantum dots and spherical copper powder to water and disperse them by ultrasonication to obtain a dispersion.

[0028] In this step, the water used is usually deionized water, the ultrasonic time is usually 5-20 minutes, the mixing ratio of spherical copper powder to water is 50g / L-200g / L, and the addition ratio of spherical copper powder to graphene quantum dots is detailed in the following examples. During this ultrasonic dispersion process, due to the large ultrasonic force, the graphene quantum dots and spherical copper powder are basically not attracted to each other due to electrostatics, but are simply uniformly dispersed in the water.

[0029] Step S2: The dispersion is stirred to obtain a stirred mixture. The stirring operation includes multiple consecutive stirring programs. Each stirring program includes a first stage and a second stage performed sequentially. The stirring speed of the first stage is greater than the stirring speed of the second stage. In two adjacent stirring programs, the stirring speed of the second stage of the previous stirring program is less than the stirring speed of the first stage of the subsequent stirring program.

[0030] In this step, a variable speed stirring method is used. During the stirring process, the stirring speed is switched back and forth between high speed and low speed, so that the graphene quantum dots are more completely and uniformly adsorbed on the surface of the spherical copper powder.

[0031] Understandably, in a single stirring speed method, if the stirring speed is high and uniform, the excessive stirring force makes it difficult for graphene quantum dots to adsorb onto the surface of spherical copper powder. If the stirring speed is low and uniform, the insufficient stirring force causes the spherical copper powder to easily settle, resulting in a large accumulation of spherical copper powder at the bottom of the reaction vessel. This uneven distribution of spherical copper powder in the water further prevents graphene quantum dots from adsorbing evenly onto the surface of the spherical copper powder. Therefore, this step uses variable speed stirring. During low-speed stirring, graphene quantum dots adsorb onto the surface of the spherical copper powder. During high-speed stirring, the spherical copper powder that has settled to the bottom of the reaction vessel is stirred back to the top of the bottom of the reaction vessel, resulting in a uniform distribution of spherical copper powder in the water. This process is repeated to ensure that the graphene quantum dots adsorb onto the surface of the spherical copper powder more completely and evenly.

[0032] Step S3: Filter the stirred mixture to obtain solid particles;

[0033] Specifically, after stirring is stopped, the spherical copper powder with graphene quantum dots adsorbed on its surface settles to the bottom of the reaction vessel and is obtained after filtration.

[0034] Step S4: Sinter the solid particles to obtain the copper-graphene composite material.

[0035] This step typically involves sintering under high temperature and high pressure to remove oxygen-containing groups from the graphene.

[0036] In the preparation method of the copper-graphene composite material provided in this embodiment of the invention, graphene quantum dots and spherical copper powder are first added to water and dispersed uniformly by ultrasonication. During this process, under the action of ultrasonic vibration, the graphene quantum dots and spherical copper powder are uniformly dispersed in the water. Then, stirring is performed, so that the graphene quantum dots are uniformly coated on the surface of the spherical copper powder. Specifically, the stirring operation includes multiple consecutive stirring programs. Each stirring program includes a first stage and a second stage performed sequentially. The stirring speed of the first stage is greater than the stirring speed of the second stage, and in two adjacent stirring programs, the stirring speed of the preceding second stage is less than the stirring speed of the following first stage. In each stirring process, the first stage is a high-speed stirring stage, which allows the spherical copper powder that has settled at the bottom to be redistributed evenly in the system. The second stage is a low-speed stirring stage, which allows graphene quantum dots to be adsorbed onto the surface of the spherical copper powder. This stirring process is repeated multiple times to maximize and evenly adsorb the graphene quantum dots onto the surface of the spherical copper powder, thereby resulting in a copper-graphene composite material with superior conductivity. In addition, the copper powder used is specifically spherical copper powder, which results in high uniformity of specific surface area among different copper powders, and thus high uniformity of the content of graphene quantum dots coated on the surface of different copper powders, which is beneficial to further improve the conductivity of the prepared copper-graphene composite material.

[0037] It should be noted that the preparation method provided in this embodiment of the invention eliminates the ball milling process compared to existing conventional preparation methods. This avoids the problem that graphene quantum dots may fall off the surface of spherical copper powder during ball milling, thereby stacking to form graphite and reducing conductivity.

[0038] In addition, during the preparation process, only the raw materials graphene quantum dots and spherical copper powder are added to water, without adding any other materials. That is, no other impurities are introduced during the preparation process, thus avoiding the problem of reduced conductivity due to the introduction of impurities.

[0039] In some embodiments, please refer to Figure 2 In step S2, the stirring operation includes multiple consecutive stirring programs P. The figure exemplarily shows five stirring programs P. Each stirring program P includes a first stage P1 and a second stage P2 performed sequentially. The stirring speed of the first stage P1 is greater than the stirring speed of the second stage P2. In the multiple consecutive stirring programs P, the stirring speed of each first stage P1 decreases sequentially. That is, the maximum stirring speed after each speed increase is less than the stirring speed after the previous speed increase. This reduces the probability of graphene quantum dots adsorbed on the surface of spherical copper powder falling off, which is beneficial for making the graphene quantum dots more completely and uniformly adsorbed on the surface of spherical copper powder, thereby further improving the conductivity of the prepared copper-graphene composite material.

[0040] In some embodiments, the stirring speed of the first stage in the initial stage is 700 r / min-900 r / min, for example, it can be 750 r / min, 800 r / min or 850 r / min, etc., and the stirring speed of the first stage in the final stage is 50 r / min-150 r / min, for example, it can be 80 r / min, 100 r / min or 120 r / min, etc., that is, as stirring proceeds, the stirring speed of the first stage in each stirring degree gradually decreases from the initial 700 r / min-900 r / min to 50 r / min-150 r / min;

[0041] Furthermore, in step S2, the number of stirring programs is 4-8, for example, 5, 6 or 7. The number of stirring programs should not be too small, otherwise the improvement of the conductivity of the prepared copper-graphene composite material will be limited. The number of stirring programs should not be too large either, otherwise the preparation process will be too complicated, which is not conducive to large-scale industrial production.

[0042] In some embodiments, the time for each stirring program is typically set to 10-20 minutes, wherein the time for the first stage and the second stage are each set to 5-10 minutes. For example, the time for both the first stage and the second stage is set to 5 minutes.

[0043] In some embodiments, in a plurality of consecutive stirring processes, the stirring speed of each second stage is equal, that is, the stirring speed of each second stage is less than the stirring speed of the last first stage. The stirring speed of the second stage can be set to 40-80 r / min, for example, it can be set to 50 r / min, 60 r / min or 70 r / min.

[0044] In some embodiments, in step S1, the graphene quantum dots are carboxyl-functionalized graphene quantum dots, specifically graphene with carboxyl functional groups connected to its edges, and their chemical formula can be found below:

[0045]

[0046] It should be noted that the number of carbon atoms and carboxyl groups in the above chemical formula is only shown as an example and is only used to illustrate that in this carboxyl-functionalized graphene quantum dot, the carboxyl groups are connected to the edge of the graphene.

[0047] During the preparation process using the aforementioned carboxyl-functionalized graphene quantum dots, the carboxyl-functionalized graphene quantum dots ionize in water to form carboxylate ions, making the edges of the carboxyl-functionalized graphene quantum dots negatively charged. The negatively charged carboxylate ions can form a strong electrostatic adsorption force with the spherical copper powder, which is beneficial to improving the adsorption force between the graphene quantum dots and the spherical copper powder. As a result, during the stirring process, the graphene quantum dots are more easily adsorbed on the surface of the spherical copper powder, which is beneficial to make the graphene quantum dots more completely and uniformly adsorbed on the surface of the spherical copper powder, thereby further improving the conductivity of the prepared copper-graphene composite material.

[0048] Specifically, the carboxyl-functionalized graphene quantum dots can be prepared by the following method:

[0049] Mix glucose and deionized water at a weight-to-volume ratio of 1:10 (g / ml), for example, 1g of glucose with 10ml of deionized water solution, so that the glucose is completely dissolved. Then add 95% concentrated sulfuric acid solution, with a volume ratio of glucose solution to concentrated sulfuric acid solution of 5:1, for example, 5ml of glucose solution with 1ml of concentrated sulfuric acid solution.

[0050] After stirring evenly, the mixed solution is sealed and placed in an oven. The oven temperature is adjusted to 180℃ and kept at a constant temperature for 6 hours. After the reaction is complete, it is allowed to cool naturally to obtain the reaction liquid. Then, 0.1 mol / L sodium hydroxide aqueous solution is added to the reaction liquid to adjust the pH value to neutral, thus initially preparing the graphene quantum dot solution.

[0051] Finally, the preliminarily prepared graphene quantum dot solution was placed in a dialysis bag, the dialysis bag was placed in deionized water and stirred, the deionized water was replaced every 12 hours, and dialysis was performed for a total of 4 days. The retained solution was freeze-dried to obtain the final carboxyl-functionalized graphene quantum dot powder.

[0052] The molecular weight cutoff of the dialysis bag is set according to the required molecular weight of the graphene quantum dots. For example, in this embodiment of the invention, graphene quantum dots with a molecular weight greater than 1500 are used as raw materials. The molecular weight cutoff of the dialysis bag is set to 1500, so the dialysis bag will retain graphene quantum dots with a molecular weight greater than 1500 in the bag.

[0053] Of course, the carboxyl-functionalized graphene used in this invention can also be prepared by other methods, or commercially available finished products can be purchased directly. This invention does not impose any special limitations on this.

[0054] In some embodiments, in step S1, the particle size of the spherical copper powder used is 0.300 mm-0.355 mm. When the particle size of the spherical copper powder is too small, it is prone to agglomeration. When the particle size of the spherical copper powder is too large, the settling speed is too fast, making it difficult to maintain a uniform distribution in the reaction system. Therefore, whether the particle size of the spherical copper powder used is too large or too small, it is not conducive to the mutual adsorption of graphene quantum dots and spherical copper powder. This invention verifies that setting the particle size of the spherical copper powder to 0.300 mm-0.355 mm can make the prepared copper-graphene composite material have better conductivity.

[0055] Specifically, the spherical copper powder can be prepared by the following method:

[0056] Commercially available copper powder is melted and then atomized using an inert gas atomization method to obtain spherical micron-sized copper powder. The obtained spherical copper powder is then sieved, and spherical copper powder with a particle size between 45 mesh and 50 mesh is selected, thus obtaining spherical copper powder with a particle size between 0.300mm and 0.355mm.

[0057] Of course, the spherical copper powder used in this invention can also be prepared by other methods, or commercially available finished products can be purchased directly. This invention does not impose any special limitations on this.

[0058] In some embodiments, in step S1, the mass ratio of the graphene quantum dots to the spherical copper powder is 8:1000000-15:1000000. Under this ratio, the prepared copper-graphene composite material has better electrical conductivity. For details, please refer to the embodiments described later.

[0059] In some embodiments, step S4, the step of sintering the solid particles, includes:

[0060] The solid particles are placed in a sintering furnace and reacted for 50-60 minutes under a pressure of 15-20 MPa, a temperature of 1200-1500°C, and an inert atmosphere. The inert atmosphere is then maintained while the temperature is reduced to 950-980°C, and the pressure is released to atmospheric pressure for 1-1.5 hours.

[0061] Another embodiment of the present invention provides an electrical contact comprising a copper-graphene composite material, wherein the copper-graphene composite material is prepared by the preparation method of the copper-graphene composite material provided in the foregoing embodiment. Specifically, the copper-graphene composite material is heat-insulated and then hot-extruded at 800℃-850℃, and finally cold-rolled to the desired shape.

[0062] The following are specific examples for detailed explanation:

[0063] Preparation Example 1: Preparation of Graphene Quantum Dots

[0064] Glucose and deionized water were mixed at a weight-to-volume ratio of 1:10 (g / ml) to ensure complete dissolution of the glucose. Then, 95% concentrated sulfuric acid solution was added dropwise, with a glucose-to-sulfuric acid solution volume ratio of 5:1. After thorough mixing, the mixture was sealed and placed in an oven at 180℃ for 6 hours. After the reaction was complete, the mixture was allowed to cool naturally, yielding the reacted liquid. A 0.1 mol / L sodium hydroxide solution was then added to the reacted liquid to adjust the pH to neutral, thus preparing a preliminary graphene quantum dot solution. Finally, the preliminarily prepared graphene quantum dot solution was placed in a dialysis bag with a molecular weight cutoff of 1500. The dialysis bag was immersed in deionized water and stirred, with the deionized water replaced every 12 hours for a total of 4 days. The retained solution was then freeze-dried to obtain the final carboxyl-functionalized graphene quantum dot powder for later use.

[0065] Preparation Example 2: Preparation of Spherical Copper Powder

[0066] Commercially available copper powder is melted and then atomized using an inert gas atomization method to obtain spherical, micron-sized copper powder. The resulting spherical copper powder is then sieved, selecting powder that passes through a 45-mesh sieve but not a 50-mesh sieve. The particle size of the obtained spherical copper powder is approximately between 0.300 mm and 0.355 mm, and is set aside for later use.

[0067] Example 1

[0068] Step 1: Take 100g of the spherical copper powder prepared in Preparation Example 2 and 1000ug of the carboxyl functionalized graphene quantum dot powder prepared in Preparation Example 1 and add them to the reaction vessel. Then add 1L of deionized water and sonicate for 10min to make the copper powder and carboxyl functionalized graphene quantum dots uniformly dispersed in the aqueous solution.

[0069] Step 2: After the ultrasound is completed, immediately stir the aqueous dispersion of copper powder and graphene quantum dots. Stir at 800 r / min for 5 minutes, then reduce the stirring speed to 50 r / min for 5 minutes, increase the stirring speed to 600 r / min for 5 minutes, then reduce the stirring speed to 50 r / min for 5 minutes, then increase the stirring speed to 400 r / min for 5 minutes, then reduce the stirring speed to 50 r / min for 5 minutes, then increase the stirring speed to 200 r / min for 5 minutes, then reduce the stirring speed to 50 r / min for 5 minutes, then increase the stirring speed to 100 r / min for 5 minutes, and finally reduce the stirring speed to 50 r / min for 5 minutes before stopping the stirring.

[0070] Step 3: Filter the stirred mixture to obtain solid particles;

[0071] Step 4: Place the filtered solid particles into a sintering furnace and react them at a pressure of 15MPa-20MPa and a temperature of 1200℃-1500℃. During the reaction, inert gases such as nitrogen or helium are introduced. After reacting for 50-60 minutes, the reaction temperature is lowered to 950℃-980℃. While maintaining the inert gas supply, the pressure is released, and sintering continues at atmospheric pressure for 1-1.5 hours to obtain the copper-graphene composite material preform.

[0072] Step 5: The obtained copper-graphene composite material blank is hot-extruded and deformed at a temperature of 800℃-850℃, and finally cold-rolled to obtain the electrical contact 1.

[0073] Example 2

[0074] 100g of spherical copper powder and 500ug of carboxyl-functionalized graphene quantum dot powder were mixed, and other conditions were the same as in Example 1, to finally obtain electrical contact 2.

[0075] Example 3

[0076] 100g of spherical copper powder and 800ug of carboxyl-functionalized graphene quantum dot powder were mixed, and other conditions were the same as in Example 1, to finally obtain electrical contact 3.

[0077] Example 4

[0078] 100g of spherical copper powder and 1500ug of carboxyl-functionalized graphene quantum dot powder were mixed, and other conditions were the same as in Example 1, to finally obtain electrical contact 4.

[0079] Example 5

[0080] 100g of spherical copper powder and 1800ug of carboxyl-functionalized graphene quantum dot powder were mixed, and other conditions were the same as in Example 1, to finally obtain electrical contact 5.

[0081] Example 6

[0082] 100g of spherical copper powder and 2000ug of carboxyl-functionalized graphene quantum dot powder were mixed, and other conditions were the same as in Example 1, to finally obtain electrical contact 6.

[0083] Comparative Example 1

[0084] After the ultrasound was completed, the spherical copper powder and the aqueous solution of carboxyl-functionalized graphene quantum dots were immediately stirred. Specifically, the mixture was stirred at a constant speed of 500 r / min for 50 min, with other conditions the same as in Example 1, and finally the electrical contact 7 was obtained.

[0085] Comparative Example 2

[0086] After the ultrasound was completed, the spherical copper powder and the aqueous solution of carboxyl-functionalized graphene quantum dots were immediately stirred. Specifically, the mixture was stirred at a constant speed of 200 r / min for 50 min, with other conditions the same as in Example 1, and finally the electrical contact 8 was obtained.

[0087] Comparative Example 3

[0088] After the ultrasound was completed, the copper powder and carboxyl-functionalized graphene quantum dot aqueous solution were immediately stirred. Specifically, the mixture was stirred at a constant speed of 20 r / min for 50 min, with other conditions the same as in Example 1, and finally the electrical contact 9 was obtained.

[0089] The conductivity of the electrical contacts 1-9 prepared above was tested, and the test structure is shown in Table 1 below:

[0090] Table 1

[0091]

[0092] Comparing the conductivity data of electrical contacts 1-6, it can be seen that within a certain range, the conductivity of the copper-graphene composite material electrical contacts increases with the increase of the graphene quantum dot powder content added during the preparation process. However, comparing the conductivity of electrical contacts 4-6, it can be seen that when the graphene quantum dot powder content increases to a certain extent, further increasing the graphene quantum dot content does not further improve the conductivity. Therefore, considering both conductivity and preparation cost, in some preferred embodiments, the mass ratio of graphene quantum dots to spherical copper powder is set in the range of 8:1000000-15:1000000.

[0093] Comparing the conductivity data of electrical contact 1 and electrical contacts 7-9, it can be seen that the conductivity of the electrical contact prepared by the variable-speed stirring method in this embodiment of the invention is significantly higher than that of the electrical contact prepared by the uniform-speed stirring method in the comparative example. Specifically, in the comparative example, the conductivity of the final electrical contact is relatively low regardless of whether the stirring is at a low speed, medium speed, or high speed. However, by using the preparation method provided by this invention, the stirring speed is switched repeatedly between high and low speeds during the stirring process, which is beneficial for the graphene quantum dots to be more completely and uniformly adsorbed on the surface of the spherical copper powder. This results in the copper-graphene composite material having better conductivity, thereby significantly improving the conductivity of the final electrical contact.

[0094] The foregoing has provided a detailed description of a copper-graphene composite material and an electrical contact provided by the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a copper-graphene composite material, characterized in that, The preparation method includes the following steps: Step S1: Add graphene quantum dots and spherical copper powder to water and disperse them by ultrasonication to obtain a dispersion. Step S2: The dispersion is stirred to obtain a stirred mixture. The stirring operation includes multiple consecutive stirring programs. Each stirring program includes a first stage and a second stage performed sequentially. The stirring speed of the first stage is greater than the stirring speed of the second stage. In two adjacent stirring programs, the stirring speed of the second stage of the previous stirring program is less than the stirring speed of the first stage of the subsequent stirring program. Step S3: Filter the stirred mixture to obtain solid particles; Step S4: Sinter the solid particles to obtain the copper-graphene composite material; In step S2, in the multiple consecutive stirring processes, the stirring speed of each first stage decreases sequentially. In each of the multiple consecutive mixing processes, the mixing speed of each second stage is less than the mixing speed of the last first stage.

2. The method for preparing the copper-graphene composite material according to claim 1, characterized in that, The stirring speed for the first stage in the initial stage is 700 r / min-900 r / min, and the stirring speed for the last stage in the initial stage is 50 r / min-150 r / min.

3. The method for preparing the copper-graphene composite material according to claim 1, characterized in that, In the multiple consecutive stirring processes described, the stirring speed of each second stage is equal.

4. The method for preparing the copper-graphene composite material according to claim 1, characterized in that, In step S1, the graphene quantum dots are carboxyl-functionalized graphene quantum dots.

5. The method for preparing the copper-graphene composite material according to claim 1, characterized in that, In step S1, the particle size of the spherical copper powder is 0.300mm-0.355mm.

6. The method for preparing the copper-graphene composite material according to claim 1, characterized in that, In step S1, the mass ratio of the graphene quantum dots to the spherical copper powder is 8:1000000-15:1000000.

7. The method for preparing the copper-graphene composite material according to claim 6, characterized in that, The graphene quantum dots have a relative molecular mass greater than 1500.

8. The method for preparing the copper-graphene composite material according to claim 1, characterized in that, In step S4, the step of sintering the solid particles includes: The solid particles are placed in a sintering furnace and reacted for 50-60 minutes under a pressure of 15-20 MPa, a temperature of 1200-1500°C, and an inert atmosphere. The inert atmosphere is then maintained while the temperature is reduced to 950-980°C, and the pressure is released to atmospheric pressure for 1-1.5 hours.

9. An electrical contact, characterized in that, The electrical contact comprises a copper-graphene composite material, which is prepared by the method for preparing the copper-graphene composite material according to any one of claims 1-8.

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