Metal coated RGO composite material and preparation process and application thereof

Abstract

The invention belongs to the field of new materials, and discloses a preparation process for co-depositing a metal (at) RGO composite material under the action of an electric field, which comprises the following steps: step 1, adding an electroplating solution containing graphene oxide and soluble metal salt into an electrolytic bath for electroplating deposition, and intermittently collecting sediments; metal ions in the soluble metal salt can be reduced under the action of an electric field; 2, the sediment is cleaned and then smashed; and (3) calcining the product crushed in the step (2) in a reducing atmosphere to obtain the metal (at) RGO composite material consisting of a metal simple substance and graphene. According to the process, an electrochemical deposition method is combined with a proper crushing method, and graphene oxide is reduced, so that the friction material meeting the requirements can be obtained. Meanwhile, the invention also provides related application of the material.

Description

Technical Field

[0001] The present invention relates to the field of new materials, and in particular to a metal@RGO composite material and a preparation process and application thereof. Background Art

[0002] Friction materials are important supporting materials for high-end equipment such as wind power generation, agricultural machinery, high-speed trains, aircraft and military vehicles. They play the role of transmission, braking and parking in friction transmission devices and brake devices, and are of great significance for the safe, reliable and stable operation of machinery and equipment. Among them, copper-based friction materials are widely used in the fields of brake linings of high-end equipment such as wind power generation, high-speed trains, and aircraft due to their high stability of friction coefficient, good anti-adhesion and anti-seizure properties, and good corrosion resistance.

[0003] The components of copper-based friction materials usually include a copper matrix, a friction-reducing phase, and a reinforcing phase (wear-resistant phase). According to the requirements of the friction environment, the friction-reducing phase and reinforcing phase in the copper-based friction material not only play a role in reducing friction resistance, but also play a role in improving the strength of the matrix. Therefore, the selection of appropriate friction-reducing phases and reinforcing phases plays a key role in copper-based friction materials. Among the many friction-reducing and wear-resistant phases, graphene has received widespread attention due to its high strength, Young's modulus and ultra-high thermal conductivity. Through the principle of particle reinforcement, copper / graphene composites have high stability, corrosion resistance, toughness and mechanical strength, which also makes graphene widely used in the field of friction materials, especially attracting the attention of many material researchers.

[0004] Most existing methods use chemical deposition methods, such as the patent application with publication number CN118703816A, which is about a graphene-reinforced copper alloy composite material and its preparation method. The preparation process of this patent is complicated, and a large amount of chemical additives are required to avoid graphene agglomeration and improve the wear resistance and friction reduction of the matrix. Overall, the patent implementation process is not conducive to large-scale production and has high production costs.

[0005] The preparation of graphene / copper alloy can also be prepared by electrochemical method, such as the patent application with publication number CN116623244A, which is a method for preparing a copper-based graphene composite material. It is prepared by electrochemical method, and its main purpose is to prepare a copper alloy-based graphene composite material with excellent electrical conductivity, thermal conductivity and wear resistance. However, in the production of friction materials, this method has some limitations, such as it cannot prepare friction products that meet the requirements, and it can only obtain a coating with acceptable friction resistance.

[0006] Therefore, there are still many application problems to be solved from the preparation of copper / RGO to the preparation of friction materials. Summary of the invention

[0007] The object of the present invention is to provide a preparation process of a metal@RGO composite material, which adopts an electrochemical deposition method combined with a suitable pulverization method and reduces graphene oxide to obtain a friction material that meets the requirements.

[0008] At the same time, the invention also discloses a composite material prepared based on the method.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A preparation process of a metal@RGO composite material by co-deposition under an electric field comprises the following steps:

[0011] Step 1: adding an electroplating solution containing graphene oxide and a soluble metal salt into an electrolytic cell for electroplating deposition and intermittently collecting the sediment; the metal ions in the soluble metal salt can be reduced under the action of an electric field;

[0012] Step 2: Clean and crush the sediment;

[0013] Step 3: The product crushed in step 2 is calcined in a reducing atmosphere to obtain a metal@RGO composite material composed of a metal element and graphene.

[0014] The core innovations of the present invention are two:

[0015] 1. The metal@RGO composite material was obtained by electrochemical deposition and reduction method;

[0016] Compared with the traditional chemical deposition method, the metal element particle size obtained by the electrochemical deposition method is nanometer-level, and the structure of the composite material is metal element coated with graphene. The traditional chemical deposition method uses metal powder, which can only achieve graphene-coated metal powder or cross-coating of metal powder and graphene. The coating form of all its particles is not consistent, which leads to the weakening of the wear resistance of the material.

[0017] 2. Collect and crush the sediment intermittently during the electroplating deposition to reduce the difficulty of crushing and avoid excessive crushing in pursuit of too small particle size or uniform particle size, which may damage the integrity of the coating and make it easy to be oxidized.

[0018] Through the above two improvements, the obtained composite material has the advantages of complete structure, small particle size and controllable material quality, and the performance of the wear-resistant material prepared therefrom can be significantly improved.

[0019] Preferably, the crushing time of step 2 is 30 to 45 seconds, and the rotor speed during crushing is 30,000 to 40,000 rpm; in step 1, the collection time interval of the sediment does not exceed 15 minutes, preferably, the collection time interval of the sediment is 5 to 10 minutes.

[0020] Friction materials have certain requirements for the particle size of composite materials, so the composite materials must be crushed. However, if the crushing time is too short or the crushing speed is too slow, the satisfactory particle size requirements cannot be achieved. If the crushing time is too long or the crushing speed is too fast, the graphene and copper elements will be oxidized faster.

[0021] When preparing the sediment, the present invention timely removes the sediment on the electrode, and the sediment is in a relatively loose state. In the subsequent crushing process, the relatively loose state can be maintained, so that the crushed product can be crushed into a particle size that meets the requirements in a relatively short time, while reducing the degree of oxidation.

[0022] In the above-mentioned preparation process, the concentration of graphene oxide in the electroplating solution is 1-5 g / L, and the concentration of soluble metal salt is 20-100 g / L;

[0023] The D50 flake diameter of the graphene oxide is 0.5 to 1 micron; the metal ions in the soluble metal salt are copper ions and / or silver ions; the particle size specification of the product after crushing in step 2 is: 1 to 5 microns.

[0024] In production, the diameter of graphene oxide flakes is controlled by the following process:

[0025] After the graphene oxide is crushed, it is placed in a grinder. The grinding balls used for grinding are zirconium oxide beads. The sheet diameter is controlled by controlling the grinding time. The D50 sheet diameter is continuously sampled and analyzed. When the requirements are met, the material is discharged. The particle size of the zirconium oxide beads is optional in the range of 0.5 to 1.5 μm.

[0026] In the above-mentioned preparation process, the electrode plates in the electrolytic cell are composed of an inert cathode plate and an inert anode plate; the inert cathode plate and the inert anode plate are arranged horizontally; the inert cathode plate is located below the inert anode plate; the inert cathode plate is equipped with a scraper for scraping off the sediment deposited on the inert cathode plate.

[0027] During the production process, the electrode plates can be arranged vertically or horizontally, with horizontal arrangement being more preferred. The horizontal arrangement can achieve uniform adhesion of copper to the electrode surface during copper precipitation based on the dead weight of the reduced copper particles, thereby avoiding the influence of different degrees of adhesion on electroplating uniformity.

[0028] In the above preparation process, at least one flow channel structure in the electrolytic cell is a Tesla valve structure or a flow channel similar to the Tesla valve structure; both ends of the electrolytic cell are a liquid inlet and a liquid outlet; the liquid inlet and the liquid outlet are used to realize the liquid circulation in the electrolytic cell through a pump; the liquid inlet is used to input the electroplating solution into the inlet of the flow channel; the electroplating solution discharged from the outlet of the flow channel is discharged through the liquid outlet; the flow channel is composed of a main flow channel and a secondary flow channel, most of the liquid in the electroplating solution flows through the main flow channel, and a small part of the liquid in the electroplating solution flows through the secondary flow channel; the inert cathode plate and the inert anode plate are arranged in the secondary flow channel;

[0029] The flow channel is composed of a plurality of first guide plates, second guide plates, and third guide plates; the second guide plate and the third guide plate constitute the secondary flow channel; the first guide plate is located on one side of the second guide plate and the third guide plate; the first guide plate and the second guide plate, and the first guide plate and the third guide plate constitute the main flow channel.

[0030] In order to further improve the coating uniformity, we adopted a flow channel with a Tesla valve structure or a structure similar to the Tesla valve structure. Most of the electroplating solution flows through the main flow channel, and a small part of the electroplating solution flows through the secondary flow channel. The flow rate of the liquid in the secondary flow channel is lower than that of the main flow channel, and the cathode plate and the anode plate are in the secondary flow channel, which is more conducive to the uniform coating and assembly of graphene oxide and copper.

[0031] In the above preparation process, in step 1, the electroplating deposition process parameters are: voltage range 3.5 - 4.5V, current range 15 - 35A, electroplating time 30 - 60min;

[0032] In step 3, the reduction process parameters are: heating the product crushed in step 2 from room temperature to 200 - 400°C at a rate of 4 - 6°C / min, and maintaining it at this temperature for 30 - 60min; then heating it to 700 - 900°C at a rate of 8 - 12°C / min, and then thermally insulating it at this temperature for 1 - 2h; finally, naturally cooling it to room temperature. The reduction atmosphere is a reducing gas or a mixed gas of a reducing gas and an inert protective gas. The reducing gas includes at least one of the following gases: H2, CO, CH4, and the inert protective gas includes at least one of Ar and N2, and the volume ratio of the two gases is 4:6.

[0033] Meanwhile, the present invention also discloses a metal@RGO composite material prepared by using any one of the above preparation processes.

[0034] In the above composite material, the metal@RGO composite material is a metal@RGO composite material composed of copper and graphene.

[0035] In addition, the present invention also discloses the use of the composite material as described above in preparing a friction material.

[0036] Finally, a friction material containing the composite material as described above is also disclosed.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] The present invention uses an electrochemical deposition method and a reduction method to obtain a metal@RGO composite material, and intermittently collects and crushes the deposits during electroplating deposition, reducing the crushing difficulty and avoiding damage to the coating integrity and easy oxidation caused by excessive crushing in order to pursue too small and uniform particle sizes. Through the above two improvements, the obtained composite material has the advantages of complete structure, small particle size, and controllable material quality, and the performance of the wear-resistant material prepared therefrom can be significantly improved. Description of the Drawings

[0039] Figure 1 is a top view of the electrolytic cell of the equipment embodiment;

[0040] Figure 2 is a front view of the electrolytic cell of the equipment embodiment;

[0041] Figure 3 is a front view of the scraper and the cathode plate in cooperation in the equipment embodiment;

[0042] Figure 4 is a top view of the electrolytic cell used in Example 13. Detailed Embodiments

[0043] Next, the technical solutions of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0044] The structure of the electrolytic cell used in the present invention is as shown in the equipment embodiment below.

[0045] Equipment Embodiment

[0046] Reference Figures 1 to 3 , an electrolytic cell, which is provided with 2 flow channels 1 with a flow channel structure of a Tesla valve structure or a structure similar to a Tesla valve structure; both ends of the electrolytic cell are a liquid inlet 2 and a liquid outlet 3; the liquid inlet 2 and the liquid outlet 3 realize the liquid circulation in the electrolytic cell through a pump 4; the electroplating solution in the electrolytic cell is always in a flowing state; the liquid inlet 2 is used to input the electroplating solution to the inlet of the flow channel 1; the electroplating solution discharged from the outlet of the flow channel 1 is discharged through the liquid outlet 3.

[0047] The flow channel 1 is composed of a main flow channel 5 and a secondary flow channel 6. Most of the liquid in the electroplating solution flows through the main flow channel 5, and a small part of the liquid in the electroplating solution flows through the secondary flow channel 6. The cathode plate 10 and the anode plate 11 in the fluid are arranged in the secondary flow channel 6.

[0048] In order to further improve the coating uniformity, we adopt a flow channel 1 with a Tesla valve structure or a structure similar to the Tesla valve structure. Most of the liquid flows through the main flow channel 5, and a small part of the liquid flows through the secondary flow channel 6. The flow velocity of the liquid in the secondary flow channel 6 is lower than that of the main flow channel 5, and the cathode plate 10 and the anode plate 11 are located in the secondary flow channel 6, which is more conducive to the uniform coating and assembly of graphene oxide and elemental copper.

[0049] More specifically, the flow channel 1 is composed of a number of first guide plates 7, second guide plates 8, and third guide plates 9. The second guide plate 8 and the third guide plate 9 constitute the secondary flow channel 6. The first guide plate 7 is located on one side of the second guide plate 8 and the third guide plate 9. The first guide plate 7 and the second guide plate 8, and the first guide plate 7 and the third guide plate 9 constitute the main flow channel 5.

[0050] The first guide plates 7 are arranged in two columns in a fishbone form, and there is also fluid flow between the two columns of first guide plates 7. Therefore, comprehensively Figure 1 It can be seen that the fluid flow form of the present invention is generally divided into the flow of the flow channel 1 based on the Tesla valve structure and the fluid flow between the two columns of first guide plates 7. Among them, in these two flow forms, there is a part of the liquid that enters between the two columns of first guide plates 7 from the flow channel 1 with the Tesla valve structure, and enters the flow channel 1 with the Tesla valve structure from between the two columns of first guide plates 7. However, the overall flow mode is still mainly based on the flow channel 1 with the Tesla valve structure.

[0051] The present invention has multiple groups of cathode plates 10 and anode plates 11.

[0052] Both the cathode plate 10 and the anode plate 11 are inert electrode plates, specifically titanium alloy plates with a ruthenium-iridium alloy coating. The cathode plate 10 and the anode plate 11 are both arranged horizontally, with the cathode plate 10 below and the anode plate 11 above.

[0053] There is also a scraper 12 beside the cathode plate 10. The scraper 12 is connected to an external shaft in a sealed manner, and the shaft is driven by an additional drive module to regularly scrape off the deposits on the cathode plate 10 obtained by the electrochemical deposition method; the deposits can be filtered and removed before entering the circulation pump 4 with the liquid, and then sent to subsequent cleaning, drying, and pulverizing processes. More preferably, there is a buffer tank 13 outside the above electrolytic cell. The electroplating solution flows out of the electrolytic cell and enters the buffer tank 13, and then flows back to the electrolytic cell. By controlling the material concentration in the buffer tank 13 within an acceptable concentration range, the smoothness of production operations is ensured. If the buffer tank 13 is set, no filter is set. Through the natural sedimentation in the buffer tank, the particles that have been plated to the appropriate thickness are sedimented, and the graphene without a coating or the graphene oxide with an insufficient coating will float on the upper layer of the solution and return to the electrolytic cell through circulation for further electroplating treatment.

[0054] More specifically, in the embodiments described below, the electrolytic cell of the present invention used has the following specific design parameters (in actual applications, relevant parameters can be adjusted according to factors such as production scale, and the actual protection scope is not limited to the following specific structural parameters):

[0055] Electrolytic cell: length: 56 cm; width: 45 cm; height: 16 cm;

[0056] First baffle 7: 9 cm;

[0057] Second baffle 8: 5 cm

[0058] Third baffle 9: 16 cm

[0059] The distance between the second baffle 8 and the third baffle 9 is: 5 cm

[0060] The distance between the anode and the cathode is: 3 - 4 cm

[0061] The volume of the electroplating solution accommodated in the electrolytic cell is: 30000 cm 3 ;

[0062] The circulation volume of the pump 4 during operation is: 8 - 12 L / h.

[0063] Example 1

[0064] Example: Co - deposition preparation of Cu@GO composite material

[0065] S1: Preparation of CuSO4 solution: Weigh a part of copper sulfate pentahydrate crystal powder, add it to deionized water, stir ultrasonically for 2 - 5 h, add a small amount of dilute sulfuric acid, and keep the pH at 3.0 - 3.5 to prepare a CuSO4 solution and store it at room temperature;

[0066] S2: Preparation of GO dispersion: Weigh a certain amount of GO, add it to deionized water, and perform ultrasonic treatment for 4 h to form a uniform and stable GO dispersion; the D50 particle size of flaky GO is 1 micron;

[0067] S3: Preparation of electroplating reaction solution: Add the above-mentioned GO dispersion and CuSO4 solution to deionized water respectively, stir evenly and perform ultrasonic dispersion to obtain a uniformly mixed electroplating solution, and then pour it into an electrolytic cell. The mass concentration of GO in the electroplating solution is 2 g / L and the mass concentration of CuSO4 is 50 g / L; the ultrasonic time is 1 h; the ultrasonic power is 200 w; the ultrasonic frequency is 10,000 Hz;

[0068] S4: Preparation of GO@Cu composite material: Turn on the feed pump of the electrolytic cell (as in the equipment embodiment) for 45 min.

[0069] Connect the electroplating electrodes of the electrolytic cell to the positive and negative electrodes of an external power supply respectively, change the voltage, current and electroplating time of the electrodes (voltage: 4.2 V, current: 21 A, electroplating time: 45 min) to synthesize the GO@Cu composite material. During electroplating, the temperature of the electrolytic cell is controlled at 35 °C. Every 10 minutes, scrape the GO@Cu coating co-precipitated on the negative electrode surface into the solution with a scraper, and then continue the electroplating experiment;

[0070] S5: Impurity removal: After electroplating, let the solution obtained after electroplating stand and precipitate to remove the supernatant, and repeatedly perform precipitation washing with deionized water to mainly wash away the Cu 2+ 、SO4 2- attached to the surface of the GO@Cu composite material, and then perform vacuum drying treatment to obtain the GO@Cu composite powder. The vacuum drying temperature is 90 °C, and the drying time is controlled at 20 h.

[0071] S6: Crushing of GO@Cu powder: Crush the dried GO@Cu co-deposited powder with a pulverizer for 35 s. After that, sieve it with a 2500-mesh sieve. The particle size of the crushed powder is less than 5 microns. The material of the pulverizer is 304 stainless steel, the model is BF-3, and the rotation speed is 35,000 rpm.

[0072] S7: Preparation of RGO@Cu: Calcine the GO@Cu powder under a reducing gas. Specifically, it is a H2-N2 gas mixture (volume ratio 6:4). The GO@Cu powder is heated from room temperature to 300 °C at a rate of 5 °C / min and held at this temperature for 30 min; then it is quickly heated to 800 °C (10 °C / min), and then annealed at this temperature for 2 h; finally, the powder is naturally cooled to room temperature to obtain the RGO@Cu composite material.

[0073] Example 2

[0074] Basically the same as Example 1, the differences are as follows:

[0075] In the electroplating solution, the concentration of graphene oxide is 1 g / L, the concentration of CuSO4 is 20 g / L, and the D50 particle size of graphene oxide is 800 nm.

[0076] Example 3

[0077] Basically the same as Example 1, the differences are as follows:

[0078] In the electroplating solution, the concentration of graphene oxide is 5 g / L, the concentration of CuSO4 is 100 g / L, and the D50 particle size of graphene oxide is 500 nm.

[0079] Example 4

[0080] Basically the same as Example 1, the differences are as follows:

[0081] In the electroplating solution, the concentration of graphene oxide is 1 g / L, and the concentration of CuSO4 is 100 g / L.

[0082] Example 5

[0083] Basically the same as Example 1, the differences are as follows:

[0084] In the electroplating solution, the concentration of graphene oxide is 5 g / L, and the concentration of CuSO4 is 20 g / L.

[0085] Example 6

[0086] Basically the same as Example 1, the differences are as follows:

[0087] In the electroplating solution, the concentration of graphene oxide is 0.5 g / L, and the concentration of CuSO4 is 50 g / L.

[0088] Example 7

[0089] In the electroplating solution, the concentration of graphene oxide is 0.1 g / L, and the concentration of CuSO4 is 50 g / L.

[0090] Example 8

[0091] In the electroplating solution, the concentration of graphene oxide is 2 g / L, and the concentration of CuSO4 is 150 g / L.

[0092] Example 9

[0093] In the electroplating solution, the concentration of graphene oxide is 2 g / L, and the concentration of CuSO4 is 10 g / L.

[0094] Example 10

[0095] Basically the same as Example 1, the differences are as follows:

[0096] The scraper scrapes once every 15 minutes; the pulverization duration is extended to 45 seconds, and the rotation speed is 35000 rpm;

[0097] The electroplating process is as follows: voltage: 3.5V, current: 15A, electroplating time: 60 minutes.

[0098] The reduction and calcination steps are as follows:

[0099] Heat from room temperature to 400°C at a rate of 4°C / min and hold at this temperature for 30 minutes; then increase the temperature to 900°C at a rate of 8°C / min, and then perform thermal insulation at this temperature for 1 hour; finally, cool naturally to room temperature.

[0100] Example 11

[0101] Basically the same as Example 1, the differences are as follows:

[0102] The scraper scrapes once every 5 minutes; the pulverization duration is 30 seconds, and the rotation speed is 35000 rpm;

[0103] The electroplating process is as follows: voltage: 4.5V, current: 35A, electroplating time: 30 minutes;

[0104] The reduction steps are as follows:

[0105] Heat from room temperature to 200°C at a rate of 6°C / min and hold at this temperature for 60 minutes; then increase the temperature to 800°C at a rate of 12°C / min, and then perform reduction insulation at this temperature for 2 hours.

[0106] Example 12

[0107] Basically the same as Example 1, the differences are in steps S4 and S6:

[0108] In S4, it scrapes once every 20 minutes;

[0109] In S6, in order to meet the synchronous particle size requirements and yield requirements, the duration is extended to 55 seconds, and the rotation speed remains unchanged.

[0110] Example 13

[0111] Basically the same as Example 1, the differences are as follows:

[0112] Set the cathode plate and anode plate in the main flow channel, specifically refer to Figure 4 .

[0113] Example 14

[0114] Basically the same as Example 1, the differences are as follows:

[0115] The cathode plate and the anode plate are arranged vertically in the secondary flow channel, and the plate spacing is the same as that in Example 1. At the same time, a scraper is provided on the cathode plate to scrape off the deposited material at the same time interval.

[0116] Sample preparation

[0117] The powders of the above examples were used to prepare corresponding metal samples by an SPS sintering furnace (process, 1000 °C, 40 MPa). After that, the surface was polished with 1000-mesh sandpaper and tested with an eddy current conductivity meter.

[0118] Friction performance detection:

[0119] Using a pin-on-disc tribometer: Prepare a pin-shaped sample (sample size 4×4×15 mm, sliding speed 100 rpm, wear radius 10 mm, load 15 N, load material stainless steel, test time 30 min) to slide on a rotating disc, suitable for small-sized materials. After the test, clean the sample with an ultrasonic cleaner for 2 - 5 min. According to the mass change of the sample before and after, obtain the wear amount and calculate it using the volume wear rate formula.

[0120]

[0121] In the formula:

[0122] ρ —— The actual density of the specimen, g / cm 3 ;

[0123] V m —— Volume wear rate, mm 3 / N·m;

[0124] Δ m —— Mass loss before and after wear, g

[0125] N —— Experimental load, kg;

[0126] S —— Sliding distance, m;

[0127] ρ V —— Density of the worn material, g / cm;

[0128] The detection results are shown in Table 1 below;

[0129] Table 1 Detection result table

[0130]

[0131]

[0132] Result analysis:

[0133] 1. As can be seen from Examples 1 to 5, there is a positive correlation between the concentration of copper sulfate and the conductivity. The possible reason is that an increase in the concentration of copper sulfate will lead to an increase in the conductivity of the entire electroplating system, accelerating the deposition of the copper layer on the surface of graphene. When the graphene powder stays between the electrodes, a relatively complete coating modification process on the surface of graphene can be completed. There is not much correlation between the friction coefficient and the wear rate and the concentrations of graphene oxide and copper sulfate. However, it should be noted that there is a certain correlation between the wear rate and the concentration of copper sulfate. When the concentration of copper sulfate reaches 100 g / L, its wear rate increases. The possible reason is that the higher conductivity will increase the thickness of the coating on the surface of graphene oxide, which will not only directly change the wear rate but also affect the reducibility of the internal graphene oxide.

[0134] 2. As can be seen from Examples 1, 6 to 9, when the concentration of graphene oxide is too low, the abrasion further increases. The possible reason is the increase in the coating thickness because a lower concentration of graphene will increase the coating thickness of individual graphene sheets, thereby affecting the wear rate and the reducibility of graphene oxide.

[0135] When the concentration of copper sulfate is too high or too low, the comprehensive performance will decrease. Especially when the concentration of copper sulfate is too low, its coating thickness is low, which may cause the composite material to form a ceramic precursor before sintering, resulting in a decrease in the overall strength after sintering and affecting the comprehensive performance.

[0136] 3. As can be seen from Examples 1, 10, 11, 12, scraping the composite material into the solution at an appropriate frequency is a relatively crucial operation, which is related to subsequent pulverization. When too much deposition occurs, phenomena such as adhesion will occur between particles, increasing the difficulty of subsequent pulverization, and excessive pulverization will damage the integrity of the particles, ultimately leading to a deterioration of the overall performance.

[0137] 4. As can be seen from Examples 1, 13 and 14, the electrolytic cell of the present invention has a positive impact on the electroplating process. The position of the electrode plate is crucial, which determines the flow rate of graphene at the electrode plate position, thereby affecting the uniformity and integrity of the electroplating layer. In addition, the arrangement method of the electrode plates is also important. In the present invention, by arranging the electrode plates horizontally and with a smaller flow rate, graphene can settle regularly in the solution, improving the uniformity of coating and the comprehensive performance.

Claims

1. A preparation process of a co-deposited metal@RGO composite material under the action of an electric field, characterized in that, The steps include: Step 1: adding an electroplating solution containing graphene oxide and a soluble metal salt into an electrolytic cell for electroplating deposition and intermittently collecting the sediment; the metal ions in the soluble metal salt can be reduced under the action of an electric field; Step 2: Clean and crush the sediment; Step 3: The product crushed in step 2 is calcined in a reducing atmosphere to obtain a metal@RGO composite material composed of a metal element and graphene.

2. The preparation process according to claim 1, characterized in that, The crushing time of step 2 is 30 to 45 seconds, and the rotation speed of the rotor during crushing is 30,000 to 40,000 rpm; in step 1, the collection time interval of the sediment does not exceed 15 minutes, preferably, the collection time interval of the sediment is 5 to 10 minutes.

3. The preparation process according to claim 1, characterized in that, The concentration of graphene oxide in the electroplating solution is 1 to 5 g / L, and the concentration of the soluble metal salt is 20 to 100 g / L; The D50 sheet diameter of the graphene oxide is 0.5 to 1 micron; the metal ions in the soluble metal salt are copper ions and / or silver ions; and the particle size of the product after pulverization in step 2 is less than 5 microns.

4. The preparation process according to claim 1, characterized in that, The electrode plates in the electrolytic cell are composed of an inert cathode plate and an inert anode plate; the inert cathode plate and the inert anode plate are arranged horizontally; the inert cathode plate is located below the inert anode plate; the inert cathode plate is equipped with a scraper for scraping off the sediment deposited on the inert cathode plate.

5. The preparation process according to claim 4, wherein The electrolytic cell is provided with at least one flow channel structure of a Tesla valve structure or a flow channel similar to a Tesla valve structure; the two ends of the electrolytic cell are a liquid inlet and a liquid outlet; the liquid inlet and the liquid outlet realize liquid circulation in the electrolytic cell through a pump; the liquid inlet is used to input the electroplating liquid into the inlet of the flow channel; the electroplating liquid discharged from the outlet of the flow channel is discharged through the liquid outlet; The flow channel is composed of a main flow channel and a secondary flow channel, most of the liquid in the electroplating solution flows through the main flow channel, and a small part of the liquid in the electroplating solution flows through the secondary flow channel; the inert cathode plate and the inert anode plate are arranged in the secondary flow channel; The flow channel is composed of a plurality of first guide plates, a second guide plate, and a third guide plate; the second guide plate and the third guide plate constitute the secondary flow channel; the first guide plate is located on one side of the second guide plate and the third guide plate; the first guide plate and the second guide plate, the first guide plate and the third guide plate constitute the main flow channel.

6. The preparation process according to claim 1, wherein In step 1, the electroplating deposition process parameters are: voltage range 3.5-4.5V, current range 15-35A, electroplating time 30-60min; In step 3, the process parameters of reduction calcination are as follows: heating the product crushed in step 2 from room temperature to 200-400°C at a rate of 4-6°C / min, and maintaining this temperature for 30-60min; then heating to 700-900°C at a rate of 8-12°C / min, and then heat preservation at this temperature for 1-2h; finally, naturally cooling to room temperature.

7. A metal@RGO composite material, characterized in that, The method is prepared by the preparation process according to any one of claims 1 to 6.

8. The composite material according to claim 7, wherein The metal@RGO composite material is a metal@RGO composite material composed of copper and graphene.

9. Use of the composite material as claimed in claim 8 in preparing friction materials.

10. A friction material, characterized in that, Comprising the composite material as described in claim 8.

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