GO-coated Cu composite material and preparation method thereof

Abstract

The invention belongs to the field of composite materials, and discloses a preparation method of a GO-coated Cu composite material, which comprises the following steps: step 1, adding a composite solution containing graphene oxide, copper powder and a conductive agent into an electrolytic bath, and carrying out self-assembly on the graphene oxide and the copper powder under the action of an electric field to form a self-assembly material in which the copper powder is wrapped by the graphene oxide; and 2, the self-assembly material is subjected to impurity removal and then calcined in the reducing atmosphere, and the RGO-coated Cu composite material is obtained. The composite material prepared by the method can show more excellent conductivity. Meanwhile, the invention further discloses the composite material prepared on the basis of the method.

Description

Technical Field

[0001] The present invention relates to the field of new materials, and specifically to a GO@Cu composite material and a preparation method thereof. Background Art

[0002] Copper is a very important metal among many metals and is widely used in fields such as electronics and chemical industry. With the development of technology, it is used in fields such as printed circuit boards, enameled wires, conductive coatings, coatings, cosmetics, etc. Spherical copper powder has become an ideal material for applications in various fields due to its high specific surface area and good fluidity. However, its poor mechanical properties limit its application scope, and it is of great significance to prepare copper-based composites (CMCs) with high mechanical strain / stress and high electrical conductivity.

[0003] One of the effective methods for preparing CMCs is to introduce a strengthening phase into the system. Among them, graphene oxide (GO) has received extensive attention due to its high strength, Young's modulus, high electrical conductivity, and ultra-high thermal conductivity. The following figure is the structural diagram of graphene oxide. The structure of GO contains a large number of functional groups such as carboxyl, hydroxyl, and epoxy groups, and it is negatively charged when dispersed in water. The unique structure of GO endows it with high stability, corrosion resistance, toughness, and mechanical strength, which also makes GO widely used in modern materials and especially attracts the attention of many materials researchers.

[0004] However, due to the strong van der Waals force between GO nanosheets, GO is prone to agglomeration itself, and the low density of GO makes it difficult to achieve uniform dispersion in the copper matrix with a relatively large density. In addition, the solubility of carbon in copper is only 0.005 at%, the diffusion coefficient is almost zero, and carbon does not react chemically with copper or form compounds. Therefore, GO is unevenly dispersed in the GO@Cu composite material prepared by traditional powder metallurgy methods, resulting in a low interfacial strength of the composite phase of GO and spherical Cu particles, and then poor electrical properties of the composite material. The invention patent CN117070792A discloses a high-conductivity graphene / copper alloy material and a preparation method thereof. Through multiple mixing, filtration, and drying, powder forming is finally carried out in a vacuum hot press furnace to obtain a high-conductivity graphene / copper alloy material composite; however, the preparation process of this patent is complex and requires two times of mixing, filtration, drying, and vacuum hot pressing for forming, which is not conducive to large-scale production; in addition, the composite material obtained by this patent does not form a stable three-dimensional network of RGO on the outer surface of Cu particles, nor does it retain the excellent effects of the high specific surface area and good fluidity of spherical Cu powder.

[0005] At the same time, for the electrochemical assembly method of elemental metal particles and graphene, the following documents can also be seen:

[0006] "Research on the Electroplating Preparation Process and Antibacterial Properties of Graphene Oxide Modified Nickel Coatings", a master's thesis by Lou Guibin from Nanjing University of Aeronautics and Astronautics. Section 3.4 records the preparation of the composite electroplating solution, specifically disclosing the use of a "Watts" nickel plating solution to disperse nickel particles and graphene for electroplating, and Section 2.3 presents the composite deposition theory, which is divided into five steps, specifically: (1) After the particles enter the solution, metal ions will immediately form a charged adsorption layer on their surface; (2) The particles move with the fluid to the boundary of the diffusion layer; (3) The particles reach the cathode surface through the diffusion layer by diffusion and weakly adsorb to it; (4) The metal ions adsorbed on the particle surface are reduced; (5) When the reduction reaction of the metal ions on the particle proceeds to a certain extent, the particles are fixed into the metal deposition layer.

[0007] This process requires the conductive agent to be a nickel-based conductive agent, and its essence is to achieve the deposition of the composite material through the weak adsorption and reduction processes. If the electroplating process is considered separately, it can be regarded as two independent processes: the combination of nickel particles and graphene based on electrostatic adsorption (the second point in Section 3.4), and the co-deposition during the reduction process (the composite deposition model in Section 3.5.4); it can be considered that the electrostatic adsorption model has no relation with the electric field.

[0008] It can be seen that in the prior art, in the relevant cases of combining metal particles and graphene, it must be accompanied by the electrochemical reduction process of metal particles.

[0009] At the same time, in the patent application with the publication number CN110093529A and the theme of graphene-reinforced copper-based composite materials for pantograph sliders and their preparation methods, it uses copper powder and graphene to produce composite materials based on the solution self-assembly method. Through experiments, it is confirmed that compared with the copper matrix prepared from copper powder, its conductivity only decreases by 2-9%, and its conductivity is estimated by us to be only about 90% IACS.

[0010] After research, we believe that by producing through the solution self-assembly method and preparing composite materials based on the adsorption effect between metal particles and graphene, its coating uniformity and conductivity can be further improved.

[0011] The technical problem solved by this case is: how to prepare graphene / copper composite materials with better performance. Summary of the Invention

[0012] The object of the present invention is to provide a preparation method of GO@Cu composite material. This method utilizes the electric field constructed in the electrolytic cell to make the metal particles with positive surface charges concentrate near the cathode based on weak adsorption, and then slowly and evenly adsorb on the surface of the metal particles through the adsorption of negatively charged graphene oxide. When the graphene oxide uniformly wraps the metal particles, it will show insulation in the electroplating solution and be dispersed into the fluid in a uniform state, which is beneficial to the continuous assembly of the remaining uncoated copper particles. Through the above weak adsorption and electrostatic adsorption mechanisms, the preparation of a composite material of graphene-coated copper particles with better uniformity is realized, which can exhibit better conductivity.

[0013] Meanwhile, the present invention also discloses a composite material prepared based on this method.

[0014] To achieve the above object, the present invention provides the following technical solutions:

[0015] A preparation method of GO@Cu composite material, comprising the following steps:

[0016] Step 1: Add a composite solution containing graphene oxide, copper powder, and a conductive agent into an electrolytic cell. Under the action of an electric field, the graphene oxide and copper powder perform self-assembly to form a self-assembled material with graphene oxide wrapping copper powder; the cations in the conductive agent are not reduced in the electrolytic cell.

[0017] Step 2: Remove impurities from the self-assembled material and then calcine it in a reducing atmosphere to obtain the GO@Cu composite material.

[0018] The present invention is different from the traditional electrolysis / electroplating method. The present invention does not involve the reduction of metal particles. Only the enrichment of copper particles is achieved through the electric field, and the assembly is completed at the position where the copper particles are enriched through the electrostatic adsorption characteristics of graphene oxide. The composite material prepared based on the weak adsorption principle of the electrode and the electrostatic adsorption principle of graphene has a uniform three-dimensional network structure. Through the three-dimensional network and void channels, it can be used for the transfer of electrons, further increasing the conductivity of the material.

[0019] The conductivity of the composite material obtained by the method of the present invention is far superior to that of the composite material obtained by the solution self-assembly method in the prior art.

[0020] In the above preparation method, the D50 particle size of the graphene oxide is d GO , and the D50 particle size of the copper powder is d Cu , and the size relationship between the graphene oxide and the copper powder satisfies Equation 1;

[0021]

[0022] k is 20 - 60;

[0023] d Cu <200 microns, d GO <800 nm.

[0024] Preferably, k is 20.4 to 44.7; d Cu Preferably 50 to 200 microns; d GO Preferably 100 to 480 nm.

[0025] In production, the control of the sheet diameter of graphene oxide is carried out through the following process:

[0026] After graphene oxide is crushed, it is placed in a grinding machine, and the grinding balls used for grinding are zirconia beads; the sheet diameter is controlled by controlling the grinding time; continuously sample and analyze the D50 sheet diameter; discharge the material when the requirements are met. The particle size of the zirconia beads can be selected within the range of 0.5 to 1.5 μm.

[0027] The k value has relatively important significance in the present invention. After many experiments, it is found that better coating uniformity and three-dimensional network are not only related to the above-mentioned weak adsorption and graphene electrostatic adsorption models, but through reasonable particle size planning, the network uniformity can be further improved;

[0028] When k > 60, the surface area of GO is too small and the diameter of copper particles is too large, and it is impossible to achieve complete coating of spherical Cu particles; when k < 20, the surface area of GO is too large and agglomerates on the surface of spherical Cu particles.

[0029] From another perspective, even if k is lower than 20 or exceeds 60, it can also form a composite material based on the electrostatic adsorption theory, but the coating uniformity and integrity of the composite material will be damaged, thereby causing a certain degree of weakening of the electrical conductivity of the composite material.

[0030] In the above preparation method, the copper powder is pre-reacted with an acid solution to remove the oxide layer on the surface of the copper powder.

[0031] While removing the oxide layer, the surface of the copper powder can be made to carry metal copper ions. When the copper powder enters the solution, the copper ions carried on its surface will adhere to the surface of the copper powder. At the same time, the cations in the conductive agent in the solution also tend to be distributed around the copper powder, making it easier for the copper powder to combine with negatively charged graphene oxide.

[0032] In the above preparation method, the composite solution includes the following components:

[0033] The GO concentration is controlled at 1 to 5 g / L, and the copper powder concentration is controlled at 50 to 150 g / L;

[0034] In the above preparation method, the conductive agent is one or more of potassium salts, sodium salts, calcium salts, magnesium salts, and aluminum salts; the conductive agent is a soluble salt; specifically, it can be sodium sulfate, potassium sulfate, sodium chloride, potassium chloride, etc., and sulfates are preferred because if chlorides are used during the electrolysis process, chlorine may be generated during electrolysis and hydrated to produce hypochlorous acid, which will have a certain impact on the stability of the system and environmental protection. The concentration of the conductive agent in the composite solution is 50 - 125 g / L.

[0035] In the above preparation method, in step 1, both the cathode and anode in the electrolytic cell are inert electrodes;

[0036] The voltage range is 3.5 - 4.5 V, the current range is 15 - 35 A, and the electroplating time is 30 - 60 min.

[0037] In the above preparation method, 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 composite solution into the inlet of the flow channel; the composite 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 composite solution flows through the main flow channel, and a small part of the liquid in the composite solution flows through the secondary flow channel; the cathode and anode in the fluid are arranged in the secondary flow channel.

[0038] In order to further improve the coating uniformity, we adopted a flow channel with a Tesla valve structure or a flow channel similar to the Tesla valve structure. Most of the liquid flows through the main flow channel, and a small part of the liquid 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 and anode are located in the secondary flow channel, which is more conducive to the uniform coating and assembly of graphene oxide and copper particles.

[0039] In the above preparation method, the flow channel is composed of several first guide plates, second guide plates, and third guide plates; the second guide plate and the third guide plate form 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 form the main flow channel;

[0040] An aeration module is provided below the cathode and anode; the aeration module is used to provide an inert gas to the composite solution flowing through the cathode and anode.

[0041] The aeration module can improve the suspension performance of copper powder, increase the contact probability between copper powder and graphene oxide, improve the coating uniformity, and avoid the problem of reduced coating uniformity caused by deposition due to the excessive density of copper powder.

[0042] In the above preparation method, step 2 is specifically as follows: After cleaning and drying the self-assembled material, it is heated from room temperature to 200 - 400 °C at a rate of 3 - 7 °C / min and maintained at this temperature for 30 - 60 min; then it is heated to 700 - 900 °C at a rate of 8 - 12 °C / min and reduced at this temperature for 1 - 2 h.

[0043] The reducing atmosphere is a reducing gas or a mixed gas of a reducing gas and an inert protective gas. The reducing gas at least includes one of the following gases: H2, CO, CH4, and the inert protective gas at least includes one of Ar and N2.

[0044] Finally, the present invention also discloses a GO@Cu composite material prepared by using any one of the above methods.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] The present invention utilizes an electrolytic cell to construct an electric field, so that metal particles with a positive surface charge are concentrated near the cathode based on weak adsorption, and then are slowly and uniformly adsorbed on the surface of the metal particles through the adsorption of negatively charged graphene oxide. When the graphene oxide uniformly wraps the metal particles, it will show insulation in the electroplating solution and be dispersed into the fluid in a uniform state, which is conducive to the continued assembly of the remaining uncoated copper particles; through the above weak adsorption and electrostatic adsorption mechanisms, a composite material of graphene-coated copper particles with better uniformity is prepared, which can exhibit better conductivity. Description of the Drawings

[0047] Figure 1 is the electron micrograph of the composite material in Example 3 of the present invention;

[0048] Figure 2 is the structural schematic diagram of the electrolytic cell of the present invention;

[0049] Figure 3 is the assembly principle diagram of graphene oxide and copper powder of the present invention. Detailed Embodiments

[0050] 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0051] The structure of the electrolytic cell used in the present invention is as shown in the following equipment embodiment.

[0052] Equipment Embodiment

[0053] Reference Figure 2 and Figure 3 An electrolytic cell is provided with two flow channels 1 having a Tesla valve structure or a structure similar to the Tesla valve structure therein; 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 are used to realize the liquid circulation in the electrolytic cell through a pump 4; the liquid in the electrolytic cell is in a flowing state at all times; the liquid inlet 2 is used to input a composite solution into the inlet of the flow channel 1; the composite solution discharged from the outlet of the flow channel 1 is discharged through the liquid outlet 3.

[0054] The flow channel 1 is composed of a main flow channel 12 and a secondary flow channel 11. Most of the liquid in the composite solution flows through the main flow channel 12, and a small part of the liquid in the composite solution flows through the secondary flow channel 11; the cathode 8 and the anode 9 in the fluid are arranged in the secondary flow channel 11.

[0055] In order to further improve the coating uniformity, we adopt a flow channel 1 having a Tesla valve structure or a structure similar to the Tesla valve structure. Most of the liquid flows through the main flow channel 12, and a small part of the liquid flows through the secondary flow channel 11. The flow velocity of the liquid in the secondary flow channel 11 is lower than that of the main flow channel 12, and the cathode 8 and the anode 9 are in the secondary flow channel 11, which is more conducive to the uniform coating and assembly of graphene oxide and copper particles.

[0056] More specifically, the flow channel 1 is composed of a number of first guide plates 5, second guide plates 6, and third guide plates 7; the second guide plates 6 and the third guide plates 7 constitute the secondary flow channel 11; the first guide plates 5 are located on one side of the second guide plates 6 and the third guide plates 7; the first guide plates 5 and the second guide plates 6, and the first guide plates 5 and the third guide plates 7 constitute the main flow channel 12;

[0057] The first guide plates 5 are arranged in two columns in a fishbone form, and there is also fluid flow between the two columns of the first guide plates 5. Therefore, comprehensively Figure 1 It can be seen that the fluid flow form of the present invention is generally divided into the flow based on the flow channel 1 with a Tesla valve structure and the fluid flow between the two columns of the first guide plates 5; among them, in these two flow forms, there is a part of the liquid entering between the two columns of the first guide plates 5 from the flow channel 1 with a Tesla valve structure, and entering the flow channel 1 with a Tesla valve structure from between the two columns of the first guide plates 5; however, the overall flow mode is still mainly based on the flow channel 1 with a Tesla valve structure;

[0058] An aeration module 10 is provided below the cathode 8 and the anode 9; the aeration module 10 is used to provide an inert gas to the composite solution flowing through the cathode 8 and the anode 9.

[0059] The aeration module 10 is a ceramic aeration plate, which is connected to an inert gas supply device; a buffer layer such as a transparent epoxy adhesive layer can be provided at its bottom to prevent the ceramic aeration plate from cracking.

[0060] The aeration module 10 can improve the suspension performance of copper powder, increase the contact probability between copper powder and graphene oxide, improve the coating uniformity, and avoid the problem of reduced coating uniformity caused by deposition due to the excessive density of copper powder.

[0061] 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):

[0062] Electrolytic cell:

[0063] Length: 56 cm; Width: 45 cm; Height: 16 cm;

[0064] First baffle 5: 9 cm

[0065] Second baffle 6: 5 cm

[0066] Third baffle 7: 16 cm

[0067] The distance between the second baffle 6 and the third baffle 7 is: 5 cm; The distance between the main flow channel and the secondary flow channel is similar.

[0068] Both the cathode 8 and the anode 9 are titanium alloy plates with a ruthenium-iridium alloy coating; The distance between the anode 9 and the cathode 8 is: 4 - 5 cm;

[0069] The volume of the composite solution accommodated in the electrolytic cell is: 30000 cm 3 ;

[0070] The circulation volume of the pump 4 during operation is: 8 - 12 L / h.

[0071] Example 1

[0072] S1: Pretreatment of spherical Cu powder: Add spherical Cu powder to a 3 mol / L dilute sulfuric acid solution, soak for 12 h, then wash it with deionized water multiple times, and obtain the pretreated spherical Cu powder after drying;

[0073] S2: Preparation of GO dispersion: Weigh a certain amount of GO, then add it to deionized water and perform ultrasonic treatment for 4 h to obtain a uniform and stable GO dispersion;

[0074] The D50 particle size of Cu powder is about 50 microns; The D50 sheet diameter of GO is about 100 nm; After calculation, k = 22.3;

[0075] In production, the control of the sheet diameter of graphene oxide is carried out through the following process:

[0076] After pulverizing graphene oxide, it is placed in a grinding machine, and the grinding balls used for grinding are zirconia beads; the sheet diameter is controlled by controlling the grinding time; samples are continuously taken for analysis of the D50 sheet diameter; when the requirements are met, the material is discharged. The particle diameter of the zirconia beads can be selected within the range of 0.5 to 1.5 μm.

[0077] S3: Prepare the electroplating reaction solution: respectively add the above-mentioned GO dispersion liquid, a quantitative spherical copper powder, and sodium sulfate into deionized water, stir evenly and perform ultrasonic dispersion to obtain a uniformly mixed electroplating reaction solution A, with the GO concentration controlled at 1 g / L, the copper powder concentration controlled at 100 g / L, and the concentration of sodium sulfate being 100 g / L;

[0078] S4: Prepare the GO@Cu composite material: Connect the electroplating electrodes of the electrolytic cell (refer to the above text) to the positive and negative electrodes of an external power supply respectively, change the voltage, current, and electroplating time of the electrodes (voltage range 4V, current range 20A, electroplating time 40 min) to synthesize the GO@Cu composite material; during the electroplating process, the temperature of the electrolytic cell is controlled at 35 °C; at the same time, keep the pump in working condition to make the liquid in the electrolytic cell keep circulating;

[0079] S5: Impurity removal: After electroplating, let the solution obtained after electroplating stand for precipitation to remove the supernatant, and perform repeated precipitation washing with deionized water to mainly wash away the Na + 、SO4 2- attached to the surface of the GO@Cu composite material, and then perform vacuum drying treatment to obtain the final product GO@Cu composite material. Among them, the vacuum drying temperature is 100 °C, and the drying time is controlled at 20 h.

[0080] S6: Prepare RGO@Cu: Calcine GO@Cu under a reducing gas. Specifically, it is a H2-N2 gas mixture. The GO@Cu powder is heated from room temperature to 300 °C at a rate of 5 °C / min and kept at this temperature for 30 min; then it is quickly heated to 800 °C (10 °C / min), and then reduced at this temperature for 2 h; finally, the powder is naturally cooled to room temperature to obtain the RGO@Cu composite material.

[0081] Example 2

[0082] Generally the same as Example 1, the differences are as follows:

[0083] K = 44.7; at this time, the D50 particle diameter of the Cu powder is about 200 microns; the D50 sheet diameter of the GO is about 100 nanometers.

[0084] Example 3

[0085] Generally the same as Example 1, the differences are as follows:

[0086] K = 20.4; At this time, the D50 particle size of the Cu powder is about 200 microns; the D50 sheet diameter of the GO is about 480 nanometers.

[0087] Example 4

[0088] Generally the same as Example 1, the difference is:

[0089] K = 13.7; At this time, the D50 particle size of the Cu powder is about 150 microns; the D50 sheet diameter of the GO is about 800 nanometers.

[0090] Example 5

[0091] Generally the same as Example 1, the difference is:

[0092] K = 61.6; At this time, the D50 particle size of the Cu powder is about 380 microns; the D50 sheet diameter of the GO is about 100 nanometers.

[0093] Example 6

[0094] Generally the same as Example 1, the difference is in step S3:

[0095] Prepare the electroplating reaction solution: Add the GO dispersion, spherical copper powder, and sodium sulfate to deionized water simultaneously, stir evenly and perform ultrasonic dispersion, where the GO concentration is also controlled at 3 g / L and the copper powder concentration is controlled at 50 g / L.

[0096] Example 7

[0097] Generally the same as Example 1, the difference is in step S3:

[0098] Prepare the electroplating reaction solution: Add the GO dispersion, spherical copper powder, and sodium sulfate to deionized water simultaneously, stir evenly and perform ultrasonic dispersion, where the GO concentration is also controlled at 5 g / L and the copper powder concentration is controlled at 150 g / L.

[0099] Example 8

[0100] Generally the same as Example 1, the difference is in step S3:

[0101] Prepare the electroplating reaction solution: Add the GO dispersion, spherical copper powder, and sodium sulfate to deionized water simultaneously, stir evenly and perform ultrasonic dispersion, where the GO concentration is also controlled at 0.5 g / L and the copper powder concentration is controlled at 100 g / L.

[0102] Example 9

[0103] Generally the same as Example 1, the difference is in step S3:

[0104] Preparation of electroplating reaction solution: The GO dispersion, spherical copper powder, and sodium sulfate are respectively added to deionized water, stirred evenly, and ultrasonically dispersed. The concentration of GO is also controlled at 1 g / L, and the concentration of copper powder is controlled at 200 g / L.

[0105] Example 10

[0106] Generally the same as Example 1, the difference is that:

[0107] An aeration module is not provided below the cathode and anode.

[0108] Example 11

[0109] Generally the same as Example 1, the difference is that:

[0110] The cathode and anode are arranged in the main flow channel.

[0111] Comparative Example 1

[0112] Preparation of the composite material by the solution self-assembly method, including the following steps:

[0113] S1: Pretreatment of spherical Cu powder: The spherical Cu powder is added to a 3 mol / L dilute sulfuric acid solution, soaked for 12 h, washed repeatedly with deionized water, and dried to obtain the pretreated spherical Cu powder;

[0114] S2: Preparation of GO dispersion: Weigh a certain amount of GO, and then add it to deionized water, and perform ultrasonic treatment for 4 h to form a uniform and stable GO dispersion;

[0115] The D50 particle size of Cu powder is about 50 microns; the D50 sheet diameter of GO is about 100 nm; after calculation, k = 22.3;

[0116] S3: Preparation of self-assembly solution: The above-mentioned dispersion, spherical copper powder, and sodium sulfate are respectively added to deionized water to obtain a uniformly mixed solution. The concentration of GO is controlled at 1 g / L, the concentration of copper powder is controlled at 100 g / L, and the concentration of sodium sulfate is 100 g / L; it is treated in a high-shear mixing emulsifier at a rotation speed of 1000 - 5000 r / min for 1 h;

[0117] S4: Impurity removal: Standing precipitation is used to remove the supernatant, and deionized water is used to repeat the precipitation cleaning many times, mainly to wash away the Na + 、SO4 2- attached to the surface of the GO@Cu composite material, and then vacuum drying treatment is carried out to obtain the final product GO@Cu composite material. The vacuum drying temperature is 100 °C, and the drying time is controlled at 20 h.

[0118] S5: Preparation of RGO@Cu: GO@Cu is calcined under a reducing gas, specifically, a H2-N2 gas mixture. The GO@Cu powder is heated from room temperature to 300 °C at a rate of 5 °C / min and maintained at this temperature for 30 min. Then, it is rapidly heated to 800 °C (10 °C / min) and then thermally annealed at this temperature for 2 h. Finally, the powder is naturally cooled to room temperature to obtain the RGO@Cu composite material.

[0119] Performance detection:

[0120] 1. Conductivity

[0121] Respectively take 20 - 30 g of the RGO@Cu composite materials obtained in the examples and comparative examples, and perform hot pressing sintering at 950 °C - 1000 °C using a rapid sintering furnace. The sintering time is 30 min, the pressure is 30 MPa, and the mold is a 21 mm graphite mold. After completion, polish its surface with 1000-mesh sandpaper and test it using an eddy current conductivity meter.

[0122] The test results are shown in Table 1 below;

[0123] Table 1 Test result table

[0124] Conductivity Example 1 108% IACS Example 2 97% IACS Example 3 101% IACS Example 4 91% IACS Example 5 87% IACS Example 6 111% IACS Example 7 104% IACS Example 8 96% IACS Example 9 98% IACS Example 10 96% IACS Example 11 92% IACS Comparative Example 1 81% IACS

[0125] Figure 1 It is the electron microscope image of the composite material of Example 3;

[0126] Result analysis:

[0127] 1. It can be seen from Examples 1 to 3 that when k is from 20 to 45, the whole particle coating is relatively uniform and the conductivity is relatively high. It can be seen from Examples 4 and 5 that when K is 13, the surface area of GO is too large and it cannot be fully and effectively coated on the surface of spherical copper particles, affecting the conductivity. When K is 62, the copper particles are too large and their sedimentation rate is too high, resulting in poor contactability between them and graphene oxide at the plate position, which also affects the conductivity.

[0128] 2. It can be seen from Examples 1, 6 to 9 that under the condition of appropriate concentrations of graphene oxide and copper powder, good conductivity can be achieved. Further research in the present invention found that when the GO concentration is lower than 1 g / L, its concentration in the solution is too low, resulting in a reduced probability of contact with copper powder, and to a certain extent, reducing the uniformity of the coating layer and thus reducing the conductivity; when the copper powder concentration is too high, in the case of insufficient GO, it is easy to cause damage to the coating uniformity, thereby reducing the conductivity. This shows that the concentrations of GO and copper powder and the value of k are all related to the optimization of product performance.

[0129] 3. As can be seen from Example 10 and Example 11, the positions of aeration and electrode plate setting are also relevant to the product coating uniformity.

[0130] 4. As can be seen from Example 1 and Comparative Example 1, compared with the traditional electrostatic adsorption-based method in solution, the method of the present invention can significantly improve the conductivity.

Claims

1. A preparation method of a GO@Cu composite material, characterized in that, It includes the following steps: Step 1: Add the composite solution containing graphene oxide, copper powder, and conductive agent into the electrolytic cell. Under the action of an electric field, graphene oxide and copper powder undergo self-assembly to form a self-assembled material with graphene oxide wrapping copper powder; the cations in the conductive agent are not reduced in the electrolytic cell. Step 2: Remove impurities from the self-assembled material and then remove oxygen in a reducing atmosphere to obtain the RGO@Cu composite material.

2. The preparation method according to claim 1, wherein The D50 particle size of the graphene oxide is d GO , and the D50 particle size of the copper powder is d Cu . The size relationship between the graphene oxide and the copper powder satisfies Equation 1; k is 20 to 60; d Cu ≤200 microns, d GO ≤800 nanometers.

3. The preparation method according to claim 1, wherein, The copper powder is pre-reacted with an acid solution to remove the oxide layer on the surface of the copper powder.

4. The preparation method according to claim 1, characterized in that, The concentration of GO in the composite solution is controlled at 1 to 5 g / L, and the concentration of copper powder is controlled at 50 to 150 g / L.

5. The preparation method according to claim 4, characterized in that, The conductive agent is one or more of potassium salts, sodium salts, calcium salts, magnesium salts, and aluminum salts; the conductive agent is a soluble salt; the concentration of the conductive agent in the composite solution is 50 to 125 g / L.

6. The preparation method according to claim 1, characterized in that, In Step 1, both the cathode and anode in the electrolytic cell are inert electrodes; The voltage range is 3.5 to 4.5 V, the current range is 15 to 35 A, and the electroplating time is 30 to 60 min.

7. The preparation method according to claim 6, characterized in that, The electrolytic cell is provided with at least one flow channel structure that 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 composite solution into the inlet of the flow channel; the composite solution discharged from the outlet of the flow channel is discharged through the liquid outlet. The flow channel consists of a main flow channel and a secondary flow channel. Most of the liquid in the composite solution flows through the main flow channel, and a small part of the liquid in the composite solution flows through the secondary flow channel; the cathode and anode in the fluid are arranged in the secondary flow channel.

8. The preparation method according to claim 7, characterized in that, The flow channel consists of several first guide plates, second guide plates, and third guide plates; the second guide plate and the third guide plate form 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 form the main flow channel. An aeration module is provided below the cathode and anode; the aeration module is used to supply inert gas to the composite solution flowing through the cathode and anode.

9. The preparation method according to claim 1, wherein, Step 2 is specifically: After cleaning and drying the self-assembled material, heat it from room temperature to 200 to 400 °C at a rate of 3 to 7 °C / min and keep it at this temperature for 30 to 60 min; then heat it to 700 to 900 °C at a rate of 8 to 12 °C / min, and then keep it warm at this temperature for 1 to 2 h.

10. A GO@Cu composite material, characterized in that, It is prepared by using the method according to any one of claims 1 to 9.

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