Preparation method of graphene-coated copper powder composite

Abstract

The application discloses a preparation method of a graphene-coated copper powder composite material. The method uses sugar alcohol or aliphatic polyhydric alcohol as an organic carbon source, uniformly loads the organic carbon source on the surface of copper powder through hydrothermal treatment, and then performs carbonization treatment on the copper powder in a low-temperature reducing atmosphere through a rotary furnace, so that in-situ growth and uniform coating of graphene are realized. The obtained composite material has excellent conductivity and oxidation resistance, and has high coating completeness, and can be directly used as a precursor to prepare super copper bulk material through pressure sintering, so that high-strength and high-conductivity comprehensive performance is obtained. The method has remarkable synergistic effect, and has good industrialization prospect.

Description

Technical Field

[0001] This invention belongs to the field of graphene super copper materials, specifically relating to a method for preparing a graphene-coated copper powder composite material. Background Technology

[0002] Copper-based materials are widely used in electronic packaging, electrical contacts, and high-end equipment manufacturing due to their excellent electrical and thermal conductivity. However, as the requirements for the comprehensive performance of materials in these fields continue to increase, traditional copper-based materials are insufficient in terms of strength, hardness, and wear resistance. Furthermore, they are prone to oxidation under high temperature or complex service environments, leading to performance degradation and making it difficult to meet the application requirements of high strength, high electrical conductivity, and high thermal conductivity.

[0003] Graphene possesses excellent mechanical, electrical, and thermal properties, and its introduction as a reinforcing phase into a copper matrix helps to mitigate the shortcomings of the aforementioned copper-based materials. To effectively integrate graphene into the copper matrix, it is typically necessary to first prepare a graphene-coated copper powder composite material. This graphene-coated copper powder composite material can then be used as a precursor for subsequent pressing, sintering, and molding processes to prepare super copper. Therefore, the coating state of graphene on the copper powder surface and the interfacial bonding between graphene and copper powder directly affect the subsequent molding applicability of this composite material.

[0004] Existing methods for preparing graphene-coated copper powder composites generally suffer from problems such as insufficient uniformity of graphene coating on the copper powder surface, weak interfacial bonding, and susceptibility to graphene structural damage. For example, Chinese patent CN120940641A discloses a method for preparing graphene-coated copper powder using hydrothermal treatment combined with in-situ pyrolysis. However, its carbonization process uses a static tube furnace, which leads to localized sintering and agglomeration of the copper powder at high temperatures, resulting in an uneven coating layer. Furthermore, its carbon sources are mainly limited to glucose, sucrose, and ascorbic acid, limiting its ability to control the coating quality. In addition, existing technologies do not cover the complete process chain from coated powder to dense bulk material, leaving the subsequent molding adaptability unclear.

[0005] Therefore, there is an urgent need to develop a coating layer that can achieve high quality and uniform distribution of graphene on the surface of copper powder, while also being beneficial as a precursor for subsequent densification molding. Summary of the Invention

[0006] To address the problems in the aforementioned technologies, this invention provides a method for preparing graphene-coated copper powder composite materials. This method involves loading a liquid-phase organic carbon source precursor onto the surface of copper powder through hydrothermal treatment, followed by carbonization in a rotary furnace. This reduces the high-temperature sintering tendency of the copper powder matrix while achieving in-situ growth and uniform coating of graphene on the copper powder surface, thereby improving the interfacial bonding between graphene and copper powder. The resulting graphene-coated copper powder composite material can be further used as a precursor for subsequent densification molding, for the preparation of super copper.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0008] A method for preparing a graphene-coated copper powder composite material includes the following steps:

[0009] S1. Preparation of organic carbon source aqueous solution: Dissolve the organic carbon source in water according to the set mass fraction to prepare an organic carbon source aqueous solution; the organic carbon source is selected from one or more sugar alcohols and / or aliphatic polyols;

[0010] S2. Solid-liquid mixing and precursor preparation: Copper powder is added to the organic carbon source aqueous solution obtained in step S1 according to the set mass ratio. After stirring evenly, a mixed slurry is formed. Then, it is transferred to a reaction vessel for hydrothermal reaction. After the hydrothermal reaction is completed, the obtained product is filtered and dried to obtain a copper powder precursor with organic carbon source attached to its surface.

[0011] S3. Low-temperature in-situ carbonization: The copper powder precursor obtained in step S2 is ground and transferred to a rotary furnace; a reducing gas is introduced, and heat treatment is carried out under the set heating rate, rotation rate and low-temperature conditions; after the heat treatment is completed, the furnace is cooled and sieved to obtain the graphene-coated copper powder composite material.

[0012] Furthermore, the sugar alcohol is selected from one or more of sorbitol, xylitol, or maltitol; the aliphatic polyol is a straight-chain aliphatic polyol with 2 to 4 carbon atoms, specifically selected from one or more of ethylene glycol, propylene glycol, 1,2-butanediol, or glycerol.

[0013] Further, in step S1, the mass fraction of the organic carbon source in the organic carbon source aqueous solution is 10%~80%.

[0014] Further, in step S2, the copper powder has a mesh size of 60-400 mesh; the mass ratio of the copper powder to the organic carbon source is (0.5-5.0):1.

[0015] Furthermore, in step S2, the temperature of the hydrothermal reaction is 120~200°C. oC, the time is 4~24 h; the drying method is selected from rotary drying and vacuum drying; wherein, the temperature of rotary drying is 40~100℃. o C, time is 0.5~4 h; the vacuum drying temperature is 60~150℃. o C, the time is 4~24 hours.

[0016] Further, in step S3, the reducing gas is pure hydrogen or a mixture of hydrogen and an inert gas (argon or nitrogen); when it is a mixture, the volume fraction of hydrogen is 2% to 10%.

[0017] Furthermore, in step S3, the temperature of the in-situ heat treatment is 300~600℃. o C, holding time is 0.5~6 h, heating rate is 1~10 o C / min; the rotational speed of the rotary furnace is 1~15 r / min.

[0018] Further explanation includes step S4: pressing and sintering the graphene-coated copper powder composite material obtained in step S3 to obtain a super copper block.

[0019] To further explain, the pressure sintering in step S4 is carried out using a spark plasma sintering system or a hot press furnace, and the sintering parameters are: heating rate 50~100℃ / min, sintering temperature 600~800℃, holding time 5~20 min, pressure 30~80MPa, and vacuum degree <10 Pa.

[0020] The present invention also provides a graphene-coated copper powder composite material, which is prepared by the preparation method described above.

[0021] The present invention also provides a super copper bulk material, which is prepared by the preparation method described above.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention effectively avoids localized sintering and adhesion between copper powder particles under static heating conditions by continuously rotating the copper powder precursor during carbonization, achieving uniform coating of graphene on the surface of individual copper powder particles with a coating integrity rate far exceeding that of static tube furnaces. The research team discovered that using alcoholic carbon sources containing multiple hydroxyl groups, such as sorbitol and maltitol, can form a good bonding state with the copper powder surface under hydrothermal conditions. The resulting graphene has fewer defects and higher conductivity than conventional carbon sources such as glucose and sucrose. The prepared graphene-coated copper powder exhibits excellent molding adaptability. The super copper formed after spark plasma sintering can achieve an electrical conductivity of over 95% IACS and a tensile strength 2-3 times that of pure copper. Simultaneously, the graphene coating layer forms a dense physical barrier on the copper powder surface, and the resulting composite material retains an electrical conductivity of over 98% after long-term storage in air at room temperature. The combination of hydrothermal treatment and low-temperature in-situ carbonization promotes the adhesion and uniform distribution of organic carbon sources on the copper powder surface, resulting in a more stable and uniformly distributed graphene coating. The resulting graphene-coated copper powder composite material exhibits good electrical conductivity and oxidation resistance, and the interfacial bonding between graphene and copper powder is significantly improved. This composite material can be directly used as a precursor for subsequent densification molding in the preparation of super copper, demonstrating significant application value. Attached Figure Description

[0024] Figure 1 Physical images of pure copper powder (a), graphene-coated copper powder obtained in Example 3 of the present invention (b), and comparative example 4 (c).

[0025] Figure 2 XRD patterns of pure copper powder and graphene-coated copper powder obtained in Example 3 of this invention.

[0026] Figure 3 SEM images of pure copper powder (a) and graphene-coated copper powder (b) obtained in Example 3 of this invention.

[0027] Figure 4 Raman diagrams of pure copper powder and graphene-coated copper powder obtained in Example 3 of this invention. Detailed Implementation

[0028] The specific embodiments are described in detail below with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise specified, the raw materials and reagents used in the embodiments are commercially available.

[0029] Example 1

[0030] This embodiment provides a method for preparing graphene-coated copper powder composite material, and the specific operation steps are as follows:

[0031] S1. Preparation of organic carbon source aqueous solution: Weigh 20 g of sorbitol and dissolve it in 80 g of water to prepare a 20% sorbitol aqueous solution for later use.

[0032] S2. Solid-liquid mixing and precursor preparation: 30 g of 60-mesh pure copper powder was weighed and added to the organic carbon source aqueous solution obtained in step S1 according to the set ratio of copper powder to organic carbon source of 1.5:1. After stirring evenly, a mixed slurry was formed. The mixture was then transferred to a reaction vessel and subjected to hydrothermal reaction at 120 °C for 24 h. After the hydrothermal reaction was completed, the product was filtered and then placed in a rotary evaporator and dried at 40 °C for 4 h to obtain a copper powder precursor with organic carbon source attached to its surface.

[0033] S3. Low-temperature in-situ carbonization: The copper powder precursor obtained in step S2 is ground and transferred to a rotary furnace; a mixture of hydrogen and argon gas (with a hydrogen volume fraction of 2%) is introduced, and the mixture is heat-treated at a heating rate of 1 °C / min, a rotation rate of 1 r / min, and a holding temperature of 300 °C for 6 h; after the heat treatment, the mixture is cooled with the furnace and passed through a 60-mesh sieve to obtain the graphene-coated copper powder composite material.

[0034] Example 2

[0035] This embodiment provides a method for preparing graphene-coated copper powder composite material, and the specific operation steps are as follows:

[0036] S1. Preparation of organic carbon source aqueous solution: Weigh 30 g xylitol and 10 g sorbitol and dissolve them in 60 g water to prepare a 40% xylitol / sorbitol composite aqueous solution for later use.

[0037] S2. Solid-liquid mixing and precursor preparation: 100 g of 400-mesh pure copper powder was weighed and added to the organic carbon source aqueous solution obtained in step S1 according to the set ratio of copper powder to organic carbon source of 2.5:1. After stirring evenly, a mixed slurry was formed. The mixture was then transferred to a reaction vessel and subjected to hydrothermal reaction at 200 °C for 4 h. After the hydrothermal reaction was completed, the product was filtered and then placed in a vacuum drying oven and vacuum dried at 150 °C for 4 h to obtain a copper powder precursor with organic carbon source attached to its surface.

[0038] S3. Low-temperature in-situ carbonization: The copper powder precursor obtained in step S2 is ground and transferred to a rotary furnace; pure hydrogen is introduced, and heat treatment is carried out at a heating rate of 10 °C / min, a rotation rate of 15 r / min, and a holding temperature of 600 °C for 0.5 h; after the heat treatment is completed, the mixture is cooled with the furnace and passed through a 400-mesh sieve to obtain the graphene-coated copper powder composite material.

[0039] Example 3

[0040] This embodiment provides a method for preparing graphene-coated copper powder composite material, and the specific operation steps are as follows:

[0041] S1. Preparation of organic carbon source aqueous solution: Weigh 50 g of maltitol and dissolve it in 50 g of water to prepare a 50% (w / w) aqueous solution for later use.

[0042] S2. Solid-liquid mixing and precursor preparation: 150g of 200-mesh pure copper powder was weighed and added to the organic carbon source aqueous solution obtained in step S1 according to the set ratio of copper powder to organic carbon source of 3:1. After stirring evenly, a mixed slurry was formed. The mixture was then transferred to a reaction vessel and subjected to hydrothermal reaction at 160 °C for 12 h. After the hydrothermal reaction was completed, the product was filtered and then placed in a vacuum drying oven and vacuum dried at 60 °C for 24 h to obtain a copper powder precursor with organic carbon source attached to its surface.

[0043] S3. Low-temperature in-situ carbonization: The copper powder precursor obtained in step S2 is ground and transferred to a rotary furnace; a mixture of hydrogen and nitrogen gas (with a hydrogen volume fraction of 5%) is introduced, and the mixture is heat-treated at a heating rate of 5 °C / min, a rotation rate of 8 r / min, and a holding temperature of 450 °C for 3 h; after the heat treatment, the mixture is cooled with the furnace and passed through a 200-mesh sieve to obtain the graphene-coated copper powder composite material.

[0044] Example 4

[0045] This embodiment provides a method for preparing graphene-coated copper powder composite material, and the specific operation steps are as follows:

[0046] S1. Preparation of organic carbon source aqueous solution: Weigh 80 g of glycerol and dissolve it in 20 g of water to prepare an 80% (w / w) aqueous solution for later use.

[0047] S2. Solid-liquid mixing and precursor preparation: 40 g of 200-mesh pure copper powder was weighed and added to the organic carbon source aqueous solution obtained in step S1 according to the set ratio of copper powder to organic carbon source of 0.5:1. The mixture was stirred and mixed to form a slurry. The slurry was transferred to a reaction vessel and subjected to hydrothermal reaction at 180 °C for 18 h. After the hydrothermal reaction was completed, the product was filtered and then placed in a rotary evaporator and dried at 100 °C for 0.5 h to obtain a copper powder precursor with organic carbon source attached to its surface.

[0048] S3. Low-temperature in-situ carbonization: The copper powder precursor obtained in step S2 is ground and transferred to a rotary furnace; a mixture of hydrogen and argon gas (with a hydrogen volume fraction of 10%) is introduced, and the mixture is heat-treated at a heating rate of 8 °C / min, a rotation rate of 12 r / min, and a holding temperature of 550 °C for 5 h; after the heat treatment, the mixture is cooled with the furnace and passed through a 200-mesh sieve to obtain the graphene-coated copper powder composite material.

[0049] Example 5

[0050] This embodiment provides a method for preparing graphene-coated copper powder composite material, and the specific operation steps are as follows:

[0051] S1. Preparation of organic carbon source aqueous solution: Weigh 45 g of ethylene glycol and dissolve it in 55 g of water to prepare an aqueous solution with an organic carbon source mass fraction of 45%.

[0052] S2. Solid-liquid mixing and precursor preparation: 112.5 g of pure copper powder with a mesh size of 200 was weighed and added to the organic carbon source aqueous solution obtained in step S1 according to the set ratio of copper powder to organic carbon source of 2.5:1. After stirring evenly, a uniform slurry was formed. The mixture was then transferred to a reaction vessel and subjected to hydrothermal reaction at 150 °C for 20 h. After the hydrothermal reaction was completed, the product was filtered and then placed in a vacuum drying oven and vacuum dried at 120 °C for 16 h to obtain a copper powder precursor with organic carbon source attached to its surface.

[0053] S3. Low-temperature in-situ carbonization: The copper powder precursor obtained in step S2 is ground and transferred to a rotary furnace; a mixture of hydrogen and argon gas (with a hydrogen volume fraction of 5%) is introduced, and the mixture is heat-treated at a heating rate of 2 °C / min, a rotation rate of 5 r / min, and a holding temperature of 430 °C for 4 h; after the heat treatment, the mixture is cooled with the furnace and then passed through a 200-mesh sieve to obtain the graphene-coated copper powder composite material.

[0054] Example 6

[0055] Take 5 g of the graphene-coated copper powder composite material obtained in Example 3, put it into a φ20 mm graphite mold, and place it in a spark plasma sintering system for pressure sintering: heating rate 80 ℃ / min, sintering temperature 700 ℃, holding time 10 min, pressure 50 MPa, vacuum degree 5×10 -3 Pa. Cooling in the furnace yields a denser super copper block.

[0056] Comparative Example 1

[0057] This comparative example provides a method for preparing a graphene-coated copper powder composite material. In step S2, no hydrothermal reaction is performed. The copper powder is stirred with a maltitol aqueous solution at room temperature for 12 h and then directly filtered and dried. The remaining operations are exactly the same as in Example 3.

[0058] Comparative Example 2

[0059] This comparative example provides a method for preparing a graphene-coated copper powder composite material. After the hydrothermal reaction and filtration in S2, the wet filter cake is directly carbonized in S3 without drying. All other operations are exactly the same as in Example 3.

[0060] Comparative Example 3

[0061] Referring to Example 1 of CN120940641B: using glucose as a carbon source, hydrothermal drying at 200 ℃ for 12 h, freeze drying, and static tube furnace pyrolysis at 450 ℃ for 4 h.

[0062] Comparative Example 4

[0063] This comparative example provides a method for preparing a graphene-coated copper powder composite material. In S1, 50g of glucose is used instead of maltitol, and the remaining operations are exactly the same as in Example 3.

[0064] Comparative Example 5

[0065] This comparative example provides a method for preparing graphene-coated copper powder composite material. In S3, a static tube furnace (without rotation) is used instead of a rotary furnace, and the remaining operations are exactly the same as in Example 3.

[0066] Comparative Example 6

[0067] This comparative example provides a method for preparing a graphene-coated copper powder composite material. In S1, 50g of ethylene glycol is used instead of maltitol, and the remaining operations are exactly the same as in Example 3.

[0068] Comparative Example 7

[0069] This comparative example provides a method for preparing a graphene-coated copper powder composite material. In step S3, the carbonization temperature is adjusted to 650°C, and the remaining operations are exactly the same as in Example 3.

[0070] Comparative Example 8

[0071] This comparative example provides a method for preparing a graphene-coated copper powder composite material. In step S3, the carbonization temperature is adjusted to 250°C, and the remaining operations are exactly the same as in Example 3.

[0072] Comparative Example 9

[0073] This comparative example provides a method for preparing a graphene-coated copper powder composite material. In step S3, the rotation speed is adjusted to 25 r / min, and the remaining operations are exactly the same as in Example 3.

[0074] Comparative Example 10

[0075] This comparative example provides a method for preparing a graphene-coated copper powder composite material. In step S3, the rotation speed is adjusted to 1 r / min, and the remaining operations are exactly the same as in Example 3.

[0076] Comparative Example 11

[0077] This comparative example provides a method for preparing a graphene-coated copper powder composite material. In S1, maltitol is directly used as the organic carbon source (mass fraction of 100%), and no water is added. All other operations are exactly the same as in Example 3.

[0078] The performance of the products prepared above was tested using the following methods: the powder conductivity was measured using an ST2722-SZ semiconductor powder resistivity meter (four-probe method) and converted to IACS percentage; the defect degree of graphene was analyzed using Raman spectroscopy (excitation wavelength 532 nm). D / I G Antioxidant tests were conducted using a forced-air drying oven (color change was observed after 10 min in an air environment at 140 ℃); the powder was stored in room temperature air for 180 days, and the conductivity was retested to calculate the retention rate; after preparing bulk materials using a spark plasma sintering system, the relative density was determined using Archimedes' water displacement method, the conductivity was determined using a four-terminal resistance meter, and the tensile strength and elongation were tested using a universal testing machine. The relevant test results are summarized in Tables 1 to 3.

[0079] Table 1. Effects of graphene on the conductivity of copper powder under different conditions and key performance indicators

[0080]

[0081] Note: Graphene-coated copper powder is reddish-brown. A positive "percentage (%)" indicates an increase in conductivity, while a negative value indicates a decrease.

[0082] As can be seen from the data in Table 1, Examples 1-5 of the present invention (using sugar alcohols or aliphatic polyols as carbon sources, combined with rotary furnace carbonization treatment) all achieved powder conductivity far higher than that of the comparative examples. Among them, maltitol (Example 3) increased by 149.51%, ethylene glycol (Example 5) increased by 207.52%, and the corresponding I D / I GThe values ​​were as low as 0.26~0.31, indicating that the formed graphene had few defects and was of high quality. In the oxidation test at 140 °C, the color of these samples only changed to light reddish-brown or orange-reddish-brown, and the surface still retained a metallic luster, indicating that the coating layer was dense and had strong oxidation resistance. In contrast, Comparative Example 4 (glucose + rotary furnace), although also using a rotary furnace, had a conductivity of only 574 S / m. D / I G The conductivity was as high as 0.62, and after oxidation, a large area turned black; in contrast, Example 5 (maltitol + static furnace) had a conductivity of 346 S / m, and black spots appeared after oxidation. This fully demonstrates that there is a significant synergistic effect between sugar alcohol carbon sources and rotary furnaces, and neither can be dispensed with. Comparative Examples 7-10 further revealed the criticality of process parameters: when the carbonization temperature deviated from 300-550 ℃ (e.g., 250 ℃ or 650 ℃) or the rotation speed deviated from 5-15 r / min (e.g., 1 or 25 r / min), the conductivity decreased significantly (as low as only 68 S / m). D / I G The oxidation temperature and rate increase significantly (up to 1.42), and the color changes to dark red, brownish-black, or even sintering after oxidation. This indicates that the temperature and rate window defined in this invention is not a conventional optimization, but a process window determined based on the matching relationship between the decomposition of organic carbon source and graphene growth kinetics.

[0083] Table 2. Effect of graphene-coated copper powder on conductivity after 180 days at room temperature.

[0084] (Conductivity retention rate / % = Conductivity after 180 days at room temperature / Initial conductivity × 100%)

[0085]

[0086] The table above shows the conductivity retention rate after 180 days at room temperature. All embodiments of the present invention exhibit a retention rate above 96%, reaching a maximum of 99.84%, demonstrating the excellent long-term antioxidant stability of the coating layer. In contrast, among the comparative embodiments, except for Comparative Example 1 (85.55%), the retention rate is below 70%, with particularly significant decreases in Comparative Examples 2 (no drying treatment), 3 (no rotational carbonization), 5 (no rotational carbonization), 9 (excessive rotational speed), and 10 (excessive rotational speed). This indicates that the drying step, rotation process, and rotational speed are crucial for forming a stable coating layer. Therefore, the present invention demonstrates its advantage in long-term stability.

[0087] Table 3 Mechanical and electrical properties of super copper blocks after pressure sintering

[0088]

[0089] Table 3 Note: Pure copper powder treated with the same SPS sintering process serves as a control. The super copper block of this invention (Example 6) maintains high conductivity while achieving a tensile strength 1.6 times that of pure copper, and its overall performance is significantly superior to existing technologies and samples not treated in a rotary furnace.

[0090] The table above shows the properties of the super copper bulk material after pressure sintering. The bulk material prepared from the powder of Example 3 (Example 6) has a relative density as high as 99.3%, an electrical conductivity of 98.2% IACS, a tensile strength of 360 MPa (approximately 1.6 times that of pure copper), and an elongation of 10.5%. In contrast, the sintered bulk material from the powder of Comparative Example 5 (maltitol + static furnace) has an electrical conductivity of only 82.5% IACS and a strength of 265 MPa; the bulk material from Comparative Example 3 (prior technology) has an even lower electrical conductivity of 65.4% IACS and a strength of only 180 MPa. This indicates that the present invention not only solves the problem of uniformity of the coated powder, but also ensures the integrity of the graphene structure and good interfacial bonding with the copper matrix during the subsequent densification process, achieving the application goal of high strength and high conductivity.

[0091] To further verify the microstructure and quality of the graphene coating obtained in this invention, typical samples were characterized by XRD, SEM, and Raman spectroscopy. The results are as follows: Figures 1 to 4 As shown.

[0092] Depend on Figure 1 As can be seen from the actual photos, the pure copper powder (a) is uniformly reddish-brown; the coated copper powder (b) obtained in Example 3 of the present invention still maintains a good reddish-brown appearance, without obvious agglomeration or black spots; while the comparative example 4 (glucose + rotary furnace, c) shows large areas of blackening and local caking, indicating that when only the carbon source is replaced with glucose and other conditions are the same, the quality of the coating layer is significantly deteriorated.

[0093] Figure 2 The XRD pattern showed that the diffraction peak positions of the sample in Example 3 were completely consistent with those of pure copper powder. No impurities such as copper oxide (CuO) or copper carbide (Cu2C) were detected, indicating that no harmful byproducts were introduced during the carbonization process. Furthermore, the graphene coating layer was thin and did not change the crystal structure of the copper matrix.

[0094] Figure 3 The SEM images further revealed the differences in sample surface morphology and particle dispersion. The pure copper powder (a) had a smooth and clean surface with no obvious surface coating layer observed; while the sample (b) of Example 3 had a continuous graphene film on its surface, and the boundaries between copper powder particles were clear, without the sintering and adhesion phenomenon commonly seen in static tube furnace carbonization (Comparative Example 5). This indicates that the dynamic tumbling of the rotary furnace effectively suppressed local sintering of particles at high temperatures.

[0095] Figure 4 The Raman spectroscopy of the sample in Example 3 provided direct evidence for the presence of graphene. -1 A D peak appeared nearby, at 1580 cm. -1 A G-peak, 2700 cm, appeared nearby. -1 A 2D peak appears nearby, with the D peak having a lower intensity (I D / I G =0.26), indicating a reduced degree of graphene defects and higher quality. In contrast, the D peak in the Raman spectrum of Comparative Example 4 (glucose + rotary furnace) was significantly enhanced (I D / I G =0.62), indicating numerous defects and poor quality.

[0096] In summary, this invention, through synergistic control of the structure type and dosage range of the organic carbon source, hydrothermal high-temperature and high-pressure treatment, precursor drying state, and dynamic heat treatment process under a reducing atmosphere, is beneficial for improving the uniformity of organic carbon source loading and conversion stability on the copper powder surface, as well as improving the powder dispersion state and interfacial bonding state during subsequent sintering, thereby enhancing the overall performance of the obtained composite material. The obtained graphene-coated copper powder composite material can be further used as a precursor for subsequent densification molding in the preparation of super copper.

[0097] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a graphene-coated copper powder composite material, characterized in that, The following steps are included: S1. Preparation of organic carbon source aqueous solution: Dissolve the organic carbon source in water according to the set mass fraction to prepare an organic carbon source aqueous solution; the organic carbon source is selected from one or more sugar alcohols and / or aliphatic polyols; S2. Solid-liquid mixing and precursor preparation: Copper powder is added to the organic carbon source aqueous solution obtained in step S1 according to the set mass ratio. After stirring evenly, a mixed slurry is formed. Then, it is transferred to a reaction vessel for hydrothermal reaction. After the hydrothermal reaction is completed, the obtained product is filtered and dried to obtain a copper powder precursor with organic carbon source attached to its surface. S3. Low-temperature in-situ carbonization: The copper powder precursor obtained in step S2 is ground and transferred to a rotary furnace; A reducing gas is introduced, and heat treatment is carried out under set heating rate, rotation rate, and medium-low temperature conditions. After heat treatment, the material is cooled in the furnace and then sieved to obtain a graphene-coated copper powder composite material.

2. The preparation method according to claim 1, characterized in that, The sugar alcohol is selected from one or more of sorbitol, xylitol, or maltitol; the aliphatic polyol is a straight-chain aliphatic polyol with 2 to 4 carbon atoms, selected from one or more of ethylene glycol, propylene glycol, 1,2-butanediol, or glycerol.

3. The preparation method according to claim 1, characterized in that, In step S1, the organic carbon source aqueous solution has a mass fraction of 10% to 80%. The copper powder has a mesh size of 60 to 400 mesh; the mass ratio of copper powder to organic carbon source is (0.5 to 5.0):

1.

4. The preparation method according to claim 1, characterized in that, In step S2, the temperature of the hydrothermal reaction is 120~200°C. o C, the time is 4~24 h, and the drying method is selected from rotary drying and vacuum drying; wherein, the temperature of rotary drying is 40~100℃. o C, time is 0.5~4 h; the vacuum drying temperature is 60~150℃. o C, the time is 4~24h.

5. The preparation method according to claim 1, characterized in that, In step S3, the reducing gas is pure hydrogen or a mixture of hydrogen and an inert gas; when it is a mixture, the volume fraction of hydrogen is 2% to 10%.

6. The preparation method according to claim 1, characterized in that, In step S3, the temperature of the heat treatment is 300~600℃. o C, holding time is 0.5~6 h, heating rate is 1~10 o C / min; the rotational speed of the rotary furnace is 1~15 r / min.

7. The preparation method according to claim 1, characterized in that, It also includes step S4: pressing and sintering the graphene-coated copper powder composite material obtained in step S3 to obtain a super copper block.

8. The preparation method according to claim 1, characterized in that, The pressure sintering described in step S4 is carried out using a spark plasma sintering system or a hot press furnace. The sintering parameters are: heating rate 50~100 ℃ / min, sintering temperature 600~800 ℃, holding time 5~20 min, pressure 30~80 MPa, and vacuum degree <10 Pa.

9. A graphene-coated copper powder composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 6.

10. A super copper block material, characterized in that, It is prepared by the preparation method described in claim 7 or 8.

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