A method for preparing a copper-based composite material with a multi-level heat transfer microstructure

Abstract

This invention discloses a method for preparing a copper-based composite material with a multi-level heat transfer microstructure. The method includes: 1. dispersing carbon fibers in ethanol to form a carbon fiber suspension; 2. adding copper powder and graphite flakes to the carbon fiber suspension and stirring to obtain a semi-solid powder; 3. filling a mold with the semi-solid powder and inserting thin copper foil sheets at intervals; 4. applying pressure and vacuuming to obtain a preform; 5. subjecting the preform to high orientation and densification sintering sequentially. This invention uses a combination of one-dimensional and two-dimensional thermally conductive reinforcements to form a multi-level heat transfer microstructure in the copper matrix, promoting an increase in the number of heat conduction channels and improving their continuity. The intermittent insertion of copper foil facilitates the high orientation distribution of graphite flakes and carbon fibers. Combined with high orientation and densification sintering, the graphite flakes and carbon fibers are preferentially oriented in the in-plane direction, improving the thermal conductivity of the copper-based composite material, which is suitable for the development of thermal management materials for electronic devices.

Description

Technical Field

[0001] This invention belongs to the field of thermal management materials technology, specifically relating to a method for preparing a copper-based composite material with a multi-level heat transfer microstructure. Background Technology

[0002] With the rapid development of modern microelectronics technology, the integration of chips in electronic devices is becoming increasingly higher, leading to ever-increasing power density. This poses a severe challenge to the performance, lifespan, and reliability of electronic devices. Therefore, the development of novel high thermal conductivity thermal management materials is crucial for effectively dissipating heat. Metal matrix composites, which combine the excellent thermal conductivity of the metal matrix with the low coefficient of thermal expansion of the reinforcement, are a class of thermal management materials with enormous application potential, such as graphite / copper composites.

[0003] Graphite flakes exhibit significant anisotropy in thermal conductivity. To utilize their ultra-high planar thermal conductivity, their distribution within the matrix often requires orientation treatment. Previous research (Journal of Alloys and Compounds, 2020, 815:152425) has reported that while a significant increase in graphite flake content (20-60%) does improve in-plane thermal conductivity, the improvement efficiency is low, far below theoretical expectations. This is because the microscopic heat transfer structure of the parallel, discrete distribution of graphite flakes within the copper matrix remains essentially unchanged; the graphite flakes remain isolated within the copper matrix, making it difficult to form a continuous heat transfer network, thus limiting the effective improvement in heat transfer efficiency. Therefore, significantly improving the thermal conductivity of copper-based composites with the same or even lower graphite flake content is a key challenge currently facing this type of material. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method for preparing a copper-based composite material with a multi-level heat transfer microstructure. This method utilizes a combination of one-dimensional and two-dimensional thermally conductive reinforcements to form a multi-level heat transfer microstructure within the copper matrix, including graphite flakes, carbon fibers, and graphite-carbon fiber composites, creating a continuous heat transfer network. This increases the number and improves the continuity of heat transfer channels. The intermittent insertion of copper foil as filler facilitates the high orientation distribution of graphite flakes and carbon fibers. Combined with high orientation and densification sintering, the graphite flakes and carbon fibers are preferentially oriented in the in-plane direction, thus fully utilizing their high thermal conductivity in the in-plane or axial direction. This shortens the heat transfer path, significantly improves the thermal conductivity of the copper-based composite material, reduces the amount of graphite filler, and solves the problem of difficulty in improving the thermal conductivity of copper-based composite materials.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing a copper-based composite material with a multi-level heat transfer microstructure, characterized in that the method includes the following steps:

[0006] Step 1: Ultrasonically disperse carbon fibers with a one-dimensional structure in ethanol to form a carbon fiber suspension;

[0007] Step 2: Add copper powder and graphite sheets with a two-dimensional structure to the carbon fiber suspension obtained in Step 1 and stir mechanically until homogeneous to obtain a uniform semi-solid powder.

[0008] Step 3: Fill the mixed semi-solid powder obtained in Step 2 into a cemented carbide mold, and insert thin copper foils at intervals in the filling process to separate the filling powder into multiple individual structures.

[0009] Step 4: Place the cemented carbide mold filled in Step 3 into a plasma sintering furnace, apply pressure at room temperature, and use a mechanical pump and a molecular pump to evacuate to a vacuum level of 1×10⁻⁶. -4 Pa, to obtain a preform with a microporous structure;

[0010] Step 5: The preform obtained in Step 4 is sintered using a two-stage sintering method involving high orientation and densification. The specific process is as follows:

[0011] Step 501, High Orientation Sintering: The preform is kept at a temperature of 300℃~400℃ and a pressure of 300MPa~500MPa.

[0012] Step 502, densification sintering: After the high orientation sintering in step 501 is completed, the temperature is further increased to 500℃~600℃, and the pressure is reduced to 100MPa~200MPa for heat preservation and pressure holding to obtain a copper-based composite material with a multi-level heat transfer microstructure.

[0013] This invention first employs an ultrasonic dispersion method to suspend and disperse one-dimensional carbon fibers in ethanol, forming a carbon fiber suspension. Then, copper powder and two-dimensional graphite flakes are added to the carbon fiber suspension and mechanically stirred until homogeneous. The surface tension of ethanol is utilized to achieve uniform mixing of various powders with significant differences in density and shape, while preventing structural damage during mixing. This results in a semi-solid powder containing multiple powders, thus uniformly dispersing the thermally conductive reinforcements—one-dimensional carbon fibers and two-dimensional graphite flakes—within the copper powder. This effectively avoids the problem of powder separation and inability to mix uniformly caused by the large density and shape differences between carbon fibers and copper powder in conventional ball milling processes. Furthermore, by using one-dimensional and two-dimensional thermally conductive reinforcements in combination, this invention forms a multi-level heat transfer microstructure within the copper matrix, including graphite flakes, carbon fibers, and graphite flake-carbon fiber layers. The carbon fibers act as links between the different graphite flakes, thereby forming a continuous heat transfer micronetwork. The increased number and improved continuity of the heat conduction channels in this multi-level heat transfer microstructure are beneficial for significantly improving the thermal conductivity of copper-based composite materials under conditions of equal or even less graphite sheets.

[0014] Then, a semi-solid powder, uniformly mixed with copper powder, graphite flakes, and carbon fibers, is filled into a cemented carbide mold. During the filling process, a thin copper foil is inserted after each certain amount of powder is filled, effectively isolating the powder into multiple individual structures. The thermally conductive reinforcement with one-dimensional and two-dimensional structures is limited by the copper foil in the thickness direction, which helps improve the orientation distribution of the carbon fibers and graphite flakes. This allows for full utilization of the high thermal conductivity of graphite flakes and carbon fibers in the in-plane or axial directions. Simultaneously, the highly oriented distribution of the thermally conductive reinforcement in the in-plane direction shortens the heat transfer path. Therefore, this filling method is beneficial for improving the thermal conductivity of copper-based composite materials. Furthermore, under high vacuum pressure, ethanol diffuses outward through the microporous structure in the preform, thus being completely removed without altering the position of the powder already uniformly distributed in the pressed preform.

[0015] Next, the present invention sequentially performs high orientation and densification sintering on a preform with a microporous structure. In the high orientation sintering stage, the force couple driving effect formed by the two-dimensional graphite sheets under high sintering pressure is utilized to cause the graphite sheets to rotate toward a plane perpendicular to the pressure. At the same time, the rotation of the graphite sheets causes the carbon fibers to rotate as well, so that the graphite sheets and carbon fibers are preferentially oriented in the in-plane direction, thereby making full use of the high thermal conductivity of the graphite sheets and carbon fibers in the in-plane or axial direction. In the densification sintering stage, by using a temperature much lower than that of conventional sintering, the interfacial stress and strain caused by the difference in thermal expansion between the copper matrix and the thermally conductive reinforcement graphite sheets and carbon fibers are significantly reduced, effectively reducing or even overcoming the interfacial defect problem. Thus, a good interfacial bonding state can still be obtained without an interfacial modification layer, resulting in a high thermal conductivity copper matrix composite material with multi-level heat transfer microstructure and synergistic thermal conductivity enhancement of graphite sheets and carbon fibers.

[0016] The method for preparing a copper-based composite material with a multi-level heat transfer microstructure, as described above, is characterized in that the carbon fiber in step one has a diameter of 10 μm and a length not exceeding 1 mm; the copper powder in step two has a particle size of 5 μm to 20 μm, and the graphite sheet has a diameter of 500 μm to 1700 μm. This invention, by limiting the diameter of the reinforcing graphite sheet, avoids excessively small sheet diameters that would lead to too many interfaces in the copper-based composite material, which is detrimental to the material's thermal conductivity. Simultaneously, it avoids excessively large sheet diameters that would hinder uniform dispersion in the matrix and the rotation of the sheets under the action of force couples during sintering, which would also negatively impact the composite material's thermal conductivity. Furthermore, by limiting the particle size of the matrix raw material copper powder, this invention avoids excessively small copper powder particles that are prone to oxidation, and also avoids excessively large copper powder particles that would hinder uniform dispersion in the composite material.

[0017] The method for preparing a copper-based composite material with a multi-level heat transfer microstructure, as described above, is characterized in that the mechanical stirring speed in step two is 60 r / min to 120 r / min, and the stirring time is 30 min to 60 min. Since graphite sheets are formed by graphite layers bonded together by van der Waals forces, this invention, by limiting the mechanical stirring speed and stirring time, avoids situations where the speed is too low or the time is too short, thus failing to ensure uniform mixing of the graphite sheets and copper powder. Simultaneously, it avoids situations where increasing the speed or time too long can easily damage the structure of the graphite sheets.

[0018] The method for preparing a copper-based composite material with a multi-level heat transfer microstructure, as described above, is characterized in that the volume fraction of graphite flakes in the mixed semi-solid powder in step two is 40%–50%, and the volume fraction of carbon fibers is 5%–15%. In this invention, the graphite flakes in the copper-based composite material serve as the main heat conduction channels, while the carbon fibers act as bridges connecting the graphite flakes. Compared to graphite flakes, the diameter of the carbon fibers is very small. By limiting the volume fractions of the graphite flakes and carbon fibers, an excessively high carbon fiber volume fraction is avoided, which would lead to a significant increase in the number of interfaces and negatively impact the thermal conductivity of the copper-based composite material. This ensures that the copper-based composite material contains a large amount of graphite flakes for primary heat conduction and a small amount of carbon fibers for connecting purposes.

[0019] The method for preparing a copper-based composite material with a multi-level heat transfer microstructure described above is characterized in that the thickness of the thin copper foil in step three is 25 μm to 100 μm. This invention introduces a thin copper foil to form a limited space that restricts the orientation of the graphite sheets. By controlling the thickness of the thin copper foil, the purpose of this orientation restriction is ensured, while avoiding excessively thick copper foil that would reduce the volume fraction of the reinforcement in the matrix and negatively impact the thermal conductivity of the copper-based composite material.

[0020] The method for preparing a copper-based composite material with a multi-level heat transfer microstructure, as described above, is characterized in that the height of the powder filling between adjacent thin copper foils in step three is 0.5 mm to 2 mm, calculated based on the sintered copper-based composite material. By limiting the height of the powder filling between adjacent thin copper foils to be approximately equivalent to the diameter of the graphite sheets (500 μm to 1700 μm), the limited space formed by the adjacent thin copper foils in the vertical direction effectively confines the graphite sheet substrate in the horizontal direction, improving the orientation of the graphite sheets in the horizontal direction, thereby benefiting the in-plane heat conduction of the copper-based composite material.

[0021] The method for preparing a copper-based composite material with a multi-level heat transfer microstructure, as described above, is characterized in that the pressure in step four is 30 MPa to 60 MPa. This invention controls the pressure range to ensure the formation of a preform with a microporous structure. Then, under high vacuum pressure, ethanol diffuses outward through the microporous structure in the preform and is completely removed without altering the position of the powder already uniformly distributed in the pressed preform. This overcomes the problem of powder separation and inability to mix due to significant differences in density and shape between the carbon reinforcement and copper powder. It also avoids situations where the pressure is too low, potentially causing changes in the position of the previously uniformly dispersed powder under high vacuum, while simultaneously avoiding situations where the pressure is too high, preventing the formation of a porous structure and resulting in incomplete ethanol removal.

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

[0023] 1. This invention incorporates one-dimensional carbon fibers and two-dimensional graphite sheets into copper-based composite materials. By combining one-dimensional and two-dimensional thermally conductive reinforcements, a microstructure with multi-level heat transfer, including graphite sheets, carbon fibers, and graphite-carbon fiber structures, is formed in the copper matrix. The carbon fibers link different graphite sheets, which is beneficial for forming a continuous heat transfer network. This allows the synergistic reinforcement effect of the multi-dimensional thermally conductive reinforcements to be utilized, promoting an increase in the number of thermally conductive channels and improving the continuity of these channels. This significantly improves the thermal conductivity of the copper-based composite material while also reducing the amount of graphite sheets required.

[0024] 2. The present invention employs a powder filling method that involves inserting thin copper foil sheets at intervals into the powder filling material to isolate the powder filling material into multiple individual structures. This restricts the one-dimensional and two-dimensional thermally conductive reinforcements by the thin copper foil sheets in the thickness direction, which is conducive to their high orientation distribution. This allows full utilization of the high thermal conductivity of graphite sheets and carbon fibers in the in-plane or axial directions. At the same time, the high orientation distribution of the in-plane thermally conductive reinforcements shortens the heat transfer path, which is beneficial to improving the thermal conductivity of copper-based composite materials.

[0025] 3. This invention employs a wet powder mixing process to ensure uniform mixing of carbon reinforcement and copper powder. It first obtains a preform with a microporous structure within a relatively small pressure range. Under high vacuum pressure, ethanol diffuses outward through the microporous structure in the preform and is completely removed without changing the position of the powder that is already uniformly distributed in the pressed preform. This overcomes the problem of powder separation and inability to mix evenly caused by the large difference in density and shape between carbon reinforcement and copper powder in conventional ball milling powder mixing processes.

[0026] 4. In the high-orientation sintering stage of the preform, the present invention uses pressure far exceeding that of conventional powder metallurgy sintering processes to make the graphite sheets rotate under the action of a force couple and drive the carbon fibers to rotate. This results in the graphite sheets and carbon fibers being preferentially oriented in the in-plane direction, thereby making full use of the high thermal conductivity of the graphite sheets and carbon fibers in the in-plane or axial direction. In addition, the high orientation distribution of the thermally conductive reinforcement also shortens the heat transfer path and improves the thermal conductivity of the copper-based composite material.

[0027] 5. In the densification sintering stage, this invention uses a temperature much lower than that of conventional copper-based composite powder metallurgy sintering, which significantly reduces the total amount of strain accumulation caused by the significant difference in thermal expansion between the copper matrix (copper's thermal expansion coefficient is 17ppm / K) and the thermally conductive reinforcement (graphite's in-plane thermal expansion coefficient is -1ppm / K, and out-of-plane thermal expansion coefficient is 28ppm / K). This reduces interfacial stress, effectively reduces or even overcomes the problem of defects caused by stress concentration at the interface, and still achieves a good interfacial bonding state without an interface modification layer. It completely avoids the harmful effects of low intrinsic thermal conductivity interface layers on the thermal conductivity of composite materials, which is beneficial to improving the thermal conductivity of copper-based composite materials.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] Figure 1 This is a cross-sectional morphology diagram of the copper-based composite material with a multi-level heat transfer microstructure prepared in Example 1 of this invention.

[0030] Figure 2 This is a schematic diagram of the cross-sectional structure of the copper-based composite material with a multi-level heat transfer microstructure prepared in Example 1 of this invention.

[0031] Figure 3 This is a cross-sectional morphology diagram of the copper-based composite material with a single-stage heat transfer microstructure prepared in Comparative Example 1 of this invention.

[0032] Figure 4 This is a schematic diagram of the cross-sectional structure of the copper-based composite material with a single-stage heat transfer microstructure prepared in Example 1 of this invention. Detailed Implementation

[0033] Example 1

[0034] This embodiment includes the following steps:

[0035] Step 1: Ultrasonically disperse carbon fibers with a one-dimensional structure in ethanol to form a carbon fiber suspension; the carbon fibers have a diameter of 10 μm and a length of no more than 1 mm.

[0036] Step 2: Add copper powder and graphite flakes with a two-dimensional structure to the carbon fiber suspension obtained in Step 1 and mechanically stir until homogeneous to obtain a uniform semi-solid powder. The copper powder has a particle size of 5μm to 20μm, the graphite flakes have a diameter of 1000μm, the mechanical stirring speed is 60r / min, and the stirring time is 30min. The volume fraction of graphite flakes in the uniform semi-solid powder is 50%, and the volume fraction of carbon fiber is 5%.

[0037] Step 3: Fill the mixed semi-solid powder obtained in Step 2 into a cemented carbide mold, and during the filling process, insert thin copper foils at intervals in the filling powder to isolate the filling powder into multiple individual structures; the thickness of the thin copper foils is 25μm; the filling powder height between adjacent thin copper foils is 1mm based on the copper-based composite material of the sintered product;

[0038] Step 4: Place the cemented carbide mold filled in Step 3 into a plasma sintering furnace, apply a pressure of 40 MPa at room temperature, and use a mechanical pump and a molecular pump to evacuate to a vacuum level of 1 × 10⁻⁶ MPa. -4 Pa, to obtain a preform with a microporous structure;

[0039] Step 5: The preform obtained in Step 4 is sintered using a two-stage sintering method involving high orientation and densification. The specific process is as follows:

[0040] Step 501, High Orientation Sintering: The preform is kept at 350℃ and 400MPa for heat and pressure.

[0041] Step 502, densification sintering: After the high orientation sintering in step 501 is completed, the temperature is raised to 550℃ and the pressure is reduced to 150MPa for heat preservation and pressure holding to obtain a copper-based composite material with a multi-level heat transfer microstructure.

[0042] Figure 1 This is a cross-sectional morphology image of the copper-based composite material with a multi-level heat transfer microstructure prepared in this embodiment. Figure 2 This is a schematic diagram of the cross-sectional structure of the copper-based composite material with a multi-level heat transfer microstructure prepared in this embodiment, combined with... Figure 1 and Figure 2 As can be seen, the present invention forms a microstructure with multi-level heat transfer channels in a copper matrix by using a combination of one-dimensional carbon fiber and two-dimensional graphite sheet, and achieves a high orientation distribution of the thermally conductive reinforcement by isolating the powder with copper foil and sintering in stages with high orientation and densification.

[0043] Testing showed that the thermal diffusivity of the copper-based composite material with a multi-level heat transfer microstructure prepared in this embodiment was 281 mm. 2 / s.

[0044] Comparative Example 1

[0045] This embodiment includes the following steps:

[0046] Step 1: Add copper powder and graphite flakes with a two-dimensional structure to ethanol and mechanically stir until homogeneous to obtain a uniform semi-solid powder; the copper powder has a particle size of 5μm to 20μm, the graphite flakes have a diameter of 1000μm, the mechanical stirring speed is 60r / min, and the stirring time is 30min; the volume fraction of graphite flakes in the uniform semi-solid powder is 55%.

[0047] Step 3: The mixed semi-solid powder obtained in Step 2 is loaded into a cemented carbide mold and transferred into a plasma sintering furnace. The pressure is increased to 40 MPa at room temperature, and a vacuum of 1 × 10⁻⁶ is achieved using a mechanical pump and a molecular pump. -4 Pa, to obtain a preform with a microporous structure;

[0048] Step 5: The preform obtained in Step 4 is sintered using a conventional one-step sintering method. The preform is kept at 950℃ and 40MPa to obtain a copper-based composite material with a single-stage heat transfer microstructure.

[0049] Figure 3 This is a cross-sectional morphology image of the copper-based composite material with a single-stage heat transfer microstructure prepared in this comparative example. Figure 4 This is a schematic diagram of the cross-sectional structure of the copper-based composite material with a single-stage heat transfer microstructure prepared in this comparative example. Figure 3 and Figure 4 It is known that conventional methods of adding two-dimensional graphite sheets and one-step sintering only form a microstructure of single-level heat transfer channels within the copper matrix, and the poor orientation of the graphite sheets is detrimental to improving the thermal conductivity of copper-based composite materials.

[0050] Testing showed that the thermal diffusivity of the copper-based composite material with a multi-level heat transfer microstructure prepared in this comparative example was 180 mm. 2 / s, far lower than in Example 1.

[0051] Example 2

[0052] This embodiment includes the following steps:

[0053] Step 1: Ultrasonically disperse carbon fibers with a one-dimensional structure in ethanol to form a carbon fiber suspension; the carbon fibers have a diameter of 10 μm and a length of no more than 1 mm.

[0054] Step 2: Add copper powder and graphite flakes with a two-dimensional structure to the carbon fiber suspension obtained in Step 1 and mechanically stir until homogeneous to obtain a uniform semi-solid powder. The copper powder has a particle size of 5μm to 20μm, the graphite flakes have a diameter of 500μm, the mechanical stirring speed is 90r / min, and the stirring time is 45min. The volume fraction of graphite flakes in the uniform semi-solid powder is 45%, and the volume fraction of carbon fiber is 10%.

[0055] Step 3: Fill the mixed semi-solid powder obtained in Step 2 into a cemented carbide mold, and during the filling process, insert thin copper foil sheets at intervals in the filling powder to separate the filling powder into multiple individual structures; the thickness of the thin copper foil sheets is 50 μm; the filling powder height between adjacent thin copper foil sheets is 0.5 mm based on the copper-based composite material of the sintered product;

[0056] Step 4: Place the cemented carbide mold filled in Step 3 into a plasma sintering furnace, apply a pressure of 30 MPa at room temperature, and use a mechanical pump and a molecular pump to evacuate to a vacuum level of 1 × 10⁻⁶. -4 Pa, to obtain a preform with a microporous structure;

[0057] Step 5: The preform obtained in Step 4 is sintered using a two-stage sintering method involving high orientation and densification. The specific process is as follows:

[0058] Step 501, High Orientation Sintering: The preform is kept at 300℃ and 300MPa for heat and pressure.

[0059] Step 502, densification sintering: After the high orientation sintering in step 501 is completed, the temperature is raised to 500℃ and the pressure is reduced to 100MPa for heat and pressure holding to obtain a copper-based composite material with a multi-level heat transfer microstructure.

[0060] Testing showed that the thermal diffusivity of the copper-based composite material with a multi-level heat transfer microstructure prepared in this embodiment was 230 mm. 2 / s.

[0061] Example 3

[0062] This embodiment includes the following steps:

[0063] Step 1: Ultrasonically disperse carbon fibers with a one-dimensional structure in ethanol to form a carbon fiber suspension; the carbon fibers have a diameter of 10 μm and a length of no more than 1 mm.

[0064] Step 2: Add copper powder and graphite flakes with a two-dimensional structure to the carbon fiber suspension obtained in Step 1 and mechanically stir until homogeneous to obtain a uniform semi-solid powder. The copper powder has a particle size of 5μm to 20μm, the graphite flakes have a diameter of 1700μm, the mechanical stirring speed is 120r / min, and the stirring time is 60min. The volume fraction of graphite flakes in the uniform semi-solid powder is 40%, and the volume fraction of carbon fiber is 15%.

[0065] Step 3: Fill the mixed semi-solid powder obtained in Step 2 into a cemented carbide mold, and during the filling process, insert thin copper foils at intervals in the filling powder to separate the filling powder into multiple individual structures; the thickness of the thin copper foils is 100μm; the filling powder height between adjacent thin copper foils is 2mm based on the copper-based composite material of the sintered product;

[0066] Step 4: Place the cemented carbide mold filled in Step 3 into a plasma sintering furnace, apply a pressure of 60 MPa at room temperature, and use a mechanical pump and a molecular pump to evacuate to a vacuum level of 1 × 10⁻⁶ MPa. -4 Pa, to obtain a preform with a microporous structure;

[0067] Step 5: The preform obtained in Step 4 is sintered using a two-stage sintering method involving high orientation and densification. The specific process is as follows:

[0068] Step 501, High Orientation Sintering: The preform is kept at 400℃ and 500MPa for heat and pressure.

[0069] Step 502, densification sintering: After the high orientation sintering in step 501 is completed, the temperature is raised to 600℃ and the pressure is reduced to 200MPa for heat and pressure holding to obtain a copper-based composite material with a multi-level heat transfer microstructure.

[0070] Testing showed that the thermal diffusivity of the copper-based composite material with a multi-level heat transfer microstructure prepared in this embodiment was 238 mm. 2 / s.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method of producing a copper-based composite material having a multi-stage heat transfer microstructure, characterized by, The method comprises the following steps: Step one, ultrasonic dispersion of carbon fibers with one-dimensional structure in ethanol to form a carbon fiber suspension; Step two, adding copper powder and graphite sheets with two-dimensional structure into the carbon fiber suspension obtained in step one and mechanically stirring to obtain a mixed semi-solid powder; the volume fraction of graphite sheets in the mixed semi-solid powder is 40-50%, and the volume fraction of carbon fibers is 5-15%; Step three, loading the mixed semi-solid powder obtained in step two into a hard alloy mold, and inserting a thin copper foil in the middle of the loading powder during the loading process to isolate the loading powder into multiple individual structures; the thickness of the thin copper foil is 25-100 μm, and the height of the loading powder between adjacent thin copper foils is 0.5-2 mm in terms of the copper-based composite material after sintering; Step four, put the hard alloy mold filled in step three into the plasma sintering furnace, load pressure at room temperature, and use mechanical pump and molecular pump to vacuum to 1 x 10 -4 Pa, to obtain a preform with a micro-porous structure; Step five, sintering the preform obtained in step four by using a two-stage sintering method of high orientation and densification in sequence, and the specific process is as follows: Step 501, high orientation sintering: the preform is kept at a temperature of 300-400 ℃ and a pressure of 300-500 MPa; Step 502, densification sintering: after the high orientation sintering in step 501 is completed, the temperature is continuously increased to 500-600 ℃, and the pressure is reduced to 100-200 MPa for keeping, to obtain a copper-based composite material with a multi-stage heat transfer microstructure.

2. The method of claim 1, wherein the copper-based composite material having a multi-stage heat transfer microstructure is prepared by the steps of: In step one, the diameter of the carbon fiber is 10 μm, and the length is not more than 1 mm; in step two, the particle size of the copper powder is 5-20 μm, and the diameter of the graphite sheet is 500-1700 μm.

3. The method of claim 1, wherein the copper-based composite material having a multi-stage heat transfer microstructure is prepared by the steps of: In step two, the rotating speed of the mechanical stirring is 60-120 r / min, and the stirring time is 30-60 min.

4. The method of claim 1, wherein the copper-based composite material having a multi-stage heat transfer microstructure is prepared by the steps of: In step four, the pressure is 30-60 MPa.

Images