A copper-based composite material based on carbon nanotubes and its preparation method and application

Abstract

The present invention relates to a copper-based composite material based on carbon nanotubes, its preparation method, and application, and belongs to the technical field of copper-based composite materials. The preparation method of the present invention comprises the following steps: stirring and mixing an aqueous solution of copper powder and a dispersion of carbon nanotubes, allowing the mixture to stand, separating the layers, stirring again, allowing the mixture to stand, separating the solid and the liquid, and then mixing the mixture in a planetary ball mill to obtain a CNT / Cu composite powder. The CNT / Cu composite powder is then subjected to cold pressing and hot pressing sintering to obtain the copper-based composite material based on carbon nanotubes. The present invention effectively improves the problem of poor wettability at the interface between carbon nanotubes and copper, and has broad application prospects in the field of friction materials requiring high friction stability and high wear resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of copper-based composite materials, and in particular to a copper-based composite material based on carbon nanotubes, and a preparation method and application thereof. Background Art

[0002] Copper-based composites, due to their excellent workability and thermal conductivity, are used in brake materials for vehicles such as aircraft, automobiles, and high-speed trains. These materials are typically reinforced with ceramic particles, ceramics, or carbon fibers. This ensures that the copper matrix maintains its excellent thermal conductivity and machinability while also effectively improving its mechanical properties, resulting in copper-based composites with high hardness, strength, and wear resistance.

[0003] Carbon nanotubes (CNTs) possess a unique hollow, one-dimensional nanostructure and exceptionally high overall performance, demonstrated by ultra-high elastic modulus (~1.8 TPa), ultra-high strength (~150 GPa), high thermal conductivity, and high electrical conductivity. Furthermore, CNTs possess a large specific surface area. However, existing technologies suffer from issues such as the tendency of CNTs to agglomerate, making uniform dispersion and homogenization difficult, and poor wettability between the Cu matrix and CNTs, resulting in low interfacial bonding strength.

[0004] Therefore, there is an urgent need to provide a method that can improve the mechanical and friction and wear resistance of copper-based composite materials and solve the problem of poor interface bonding between carbon nanotubes and copper. Summary of the Invention

[0005] To address the above-mentioned technical problems, the present invention provides a carbon nanotube-based copper-based composite material, its preparation method, and its application. By adsorbing carbon nanotubes onto the copper-based surface to enhance the copper-based composite material's mechanical and friction and wear resistance, the present invention significantly improves the composite material's mechanical and friction and wear resistance. Furthermore, the present method for preparing the carbon nanotube-based copper-based composite material is simple and easy to produce, and it addresses the issue of poor interfacial bonding between carbon nanotubes and copper.

[0006] The present invention is achieved through the following technical solutions:

[0007] The first object of the present invention is to provide a method for preparing a copper-based composite material based on carbon nanotubes, comprising the following steps:

[0008] (1) preparing an aqueous solution of copper powder and a dispersion of carbon nanotubes;

[0009] (2) stirring and mixing the aqueous solution of copper powder obtained in step (1) and the dispersion of carbon nanotubes, allowing to stand, collecting the solid phase after solid-liquid separation, drying, and ball milling the mixture to obtain CNT / Cu composite powder;

[0010] (3) The CNT / Cu composite powder is subjected to cold pressing and hot pressing sintering to obtain the copper-based composite material.

[0011] In one embodiment of the present invention, in step (1), the size of the copper powder is 4 μm to 7 μm; and the outer diameter of the carbon nanotube is 20 nm to 30 nm.

[0012] In one embodiment of the present invention, in step (1), the content ratio of the copper powder to deionized water is (9.9 g): (100 mL).

[0013] In one embodiment of the present invention, in step (1), the content ratio of the carbon nanotubes to deionized water is (0.1 g): (100 mL).

[0014] In one embodiment of the present invention, in step (1), the carbon nanotubes are obtained by acidification:

[0015] The carbon nanotubes are prepared by reacting the carbon nanotubes with a mixed acid solution at 45° C. to 55° C. for 9 h to 11 h.

[0016] In one embodiment of the present invention, the mixed acid is selected from concentrated sulfuric acid and concentrated nitric acid; the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 1:3 to 1:4.

[0017] In one embodiment of the present invention, in step (2), the aqueous solution of copper powder obtained in step (1) is stirred and mixed with the dispersion of carbon nanotubes, allowed to stand, and stirred again after layering, allowed to stand, and after solid-liquid separation, placed in a planetary ball mill for mixing to obtain CNT / Cu composite powder.

[0018] In one embodiment of the present invention, the stirring time is 15 min to 25 min, and the stirring time after standing and stratification is 5 min to 15 min.

[0019] In one embodiment of the present invention, in step (2), the ball milling mixture is performed using a planetary ball mill with a rotation speed of 180 rpm to 220 rpm;

[0020] In one embodiment of the present invention, in step (2), the mixing time is 1.5 hours to 2.5 hours, and the mass ratio of the steel balls in the ball mill to the powder is 10:1.

[0021] In one embodiment of the present invention, in step (3), the cold pressing forming conditions are: the cold pressing pressure is 20 MPa to 30 MPa, and the holding time is 8 min to 12 min.

[0022] In one embodiment of the present invention, in step (3), the hot pressing sintering conditions are: the vacuum degree in the vacuum hot pressing furnace is 10 -2Under Pa conditions, pressurize to 45MPa~55MPa, then heat to 550℃~650℃ and keep warm for 8min~12min.

[0023] The second object of the present invention is to provide a copper-based composite material based on carbon nanotubes prepared by the preparation method.

[0024] In one embodiment of the present invention, the mass fraction of carbon nanotubes in the copper-based composite material is 0.8% to 1.2%.

[0025] The third object of the present invention is to provide the application of the copper-based composite material based on carbon nanotubes in brake materials.

[0026] The present invention acidifies carbon nanotubes, introduces oxygen-containing functional groups to improve the interfacial capacity between CNTs and copper and makes the CNTs negatively charged. The electrostatic repulsion between CNTs will weaken the original van der Waals force of the CNTs, so that the CNTs are dispersed and better adsorbed on the copper surface, reducing agglomeration; and adopts a wet mixing adsorption low-energy ball milling method to adsorb the acidified carbon nanotubes on the copper surface, and uses a rapid hot pressing sintering furnace to sinter the carbon nanotube-based copper-based composite material.

[0027] The above technical solution of the present invention has the following advantages over the prior art:

[0028] (1) The present invention provides a copper-based composite material based on carbon nanotubes, which gives full play to the characteristics of carbon nanotubes such as ultra-high strength, high thermal conductivity and high electrical conductivity. Compared with traditional copper-based composite materials, the copper-based composite material based on carbon nanotubes has a greatly increased number of interfaces between the reinforcing phase and the copper matrix, and the load-bearing effect of the reinforcing phase on the copper matrix is ​​gradually increased, which significantly improves the load-bearing efficiency of the reinforcing phase; at the same time, carbon nanotubes have good self-lubrication and high-temperature stability, and can play a good role in reducing wear. Carbon nanotubes can play a role in load transfer and lubrication in the copper matrix, which significantly improves the mechanical and friction and wear resistance of the copper-based composite material.

[0029] (2) The present invention provides a method for preparing a copper-based composite material based on carbon nanotubes, which has a simple process and is easy to produce. During the preparation process, the carbon nanotubes are acidified to introduce oxygen-containing functional groups to improve the interface ability between CNTs and copper and make the CNTs negatively charged. The electrostatic repulsion between the CNTs will weaken the original van der Waals force of the CNTs, so that the CNTs are dispersed and can be better adsorbed on the copper surface, reducing agglomeration, and effectively improving the problem of poor wettability of the interface between carbon nanotubes and copper. The method has broad application prospects in the field of friction materials requiring high friction stability and high wear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

[0031] Figure 1 This is the SEM morphology of the carbon nanotube reinforced copper-based composite material prepared in Example 2;

[0032] Figure 2 This is a metallographic photograph of the composite material after rapid hot pressing sintering in Example 2;

[0033] Figure 3 This is the SEM morphology of the carbon nanotube reinforced copper-based composite material prepared in Comparative Example 1;

[0034] Figure 4 This is a metallographic photograph of the composite material after rapid hot pressing sintering in Comparative Example 1;

[0035] Figure 5 This is the SEM morphology of the carbon nanotube reinforced copper-based composite material prepared in Comparative Example 2;

[0036] Figure 6 This is a metallographic photograph of the composite material after rapid hot pressing sintering in comparative example 2. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0038] The present invention provides a copper-based composite material based on carbon nanotubes, the components and mass fractions of which are as follows:

[0039] The mass fraction of the carbon nanotubes is 0.8% to 1.2%, and the balance is electrolytic copper powder.

[0040] The outer diameter of the carbon nanotubes is 20nm to 30nm.

[0041] The present invention also provides a method for preparing a copper-based composite material based on carbon nanotubes, comprising the following steps:

[0042] (1) Acidification: Add carbon nanotubes to a mixed acid solution, place the beaker containing CNTs and the mixed acid in a water bath and stir to react. After the reaction is completed, use a vacuum pump to filter, rinse with deionized water several times until neutral, and finally dry for use. The mixed acid is a mixture of concentrated sulfuric acid and concentrated nitric acid, the volume ratio of the two is 1:3, the content ratio of the mixed acid to CNTs is (40mL): (0.5g), the water bath temperature is 50℃, and the stirring reaction time is 10h to obtain acidified CNTs.

[0043] (2) Mixing: Weigh the Cu powder according to the mass fraction and pour it into a beaker filled with deionized water, and stir it magnetically; wherein, the content ratio of the copper powder to deionized water is (9.9g): (100mL), and the magnetic stirring time is 30min. Weigh the acidified CNTs according to the mass fraction and pour it into a beaker filled with deionized water, and disperse it ultrasonically; wherein, the content ratio of the carbon nanotubes to deionized water is (0.1g): (100mL), and the ultrasonic dispersion time is 1h. Slowly pour the ultrasonically dispersed CNTs solution into the beaker filled with copper powder, and then stir it magnetically. After stirring, let it stand, let it stand for stratification, stir it magnetically again, and then let it stand; wherein, the magnetic stirring time is 20min, and the magnetic stirring time after standing for stratification is 10min. After standing for stratification, use a vacuum pump to filter to obtain CNT / Cu composite powder 1; use a vacuum drying oven to dry the filtered powder; wherein, the drying temperature is 50℃ and the drying time is 24h. The CNT / Cu composite powder 1 was placed in a ball mill, and the ball mill was placed in a planetary ball mill for mixing to obtain a CNT / Cu composite powder 2; wherein the rotation speed of the planetary ball mill was 200 rpm, the mixing time was 2 h, and the ball-to-material ratio was 10:1.

[0044] (3) Cold Pressing: The CNT / Cu composite powder 2 is placed in a steel mold and cold pressed using a hydraulic press. The cold pressing pressure is 20 MPa to 30 MPa, and the holding time is 10 minutes. A blank is obtained after cold pressing.

[0045] (4) Hot pressing sintering: The cold pressed blank is placed into a graphite mold and sintered in a rapid hot pressing furnace. The vacuum degree in the vacuum hot pressing furnace is 10 -2 After applying pressure to 50 MPa at 100°C / min, the temperature in the furnace was raised to 600°C and held for 10 minutes. After the holding time, the power was turned off, the pressure was released, and after the temperature in the furnace dropped below 100°C, the hot-pressed part was removed from the vacuum hot-pressing furnace and the mold was removed to obtain the carbon nanotube-reinforced copper-based composite material.

[0046] Example 1

[0047] This embodiment provides a method for preparing a copper-based composite material based on carbon nanotubes, and the specific steps are as follows:

[0048] (1) Take 0.24 g of carbon nanotubes (OD 20 nm to 30 nm) and pour into 12 mL of a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid at a volume ratio of 1:3. Place the beaker containing the CNTs and the mixed acid in a water bath and stir at 50°C for 10 h. After the reaction is complete, filter using a vacuum pump and rinse with deionized water several times until neutral. Finally, obtain the acidified CNTs and dry them for later use.

[0049] (2) Weigh 29.76g of copper powder and pour it into a beaker filled with 300mL of deionized water, and stir it magnetically for 30min; pour 0.24g of acidified CNTs into a beaker filled with 150mL of deionized water and disperse it ultrasonically for 1h; slowly pour the CNTs solution obtained after ultrasonic dispersion into the beaker filled with copper powder, and then stir it magnetically for 20min, let it stand after stirring, let it stand for stratification, stir it magnetically again and let it stand for 10min; after standing for stratification, use a vacuum pump to filter, and the obtained powder is dried at 50℃ for 24h to obtain CNT / Cu composite powder 1; put the CNT / Cu composite powder 1 into a ball mill, and put the ball mill into a planetary ball mill for mixing, wherein the planetary ball mill rotates at 200rpm, the mixing time is 2h, and the ball-to-material ratio is 10:1 to obtain CNT / Cu composite powder 2.

[0050] (3) The CNT / Cu composite powder 2 was placed in a steel mold with an inner diameter of 30 mm and cold-pressed using a hydraulic press. The cold-pressing pressure was 20 MPa and the holding time was 10 min. A blank was obtained after cold-pressing.

[0051] (4) The cold-pressed blank is placed into a Φ30mm graphite mold and sintered in a rapid hot pressing furnace. The vacuum degree in the vacuum hot pressing furnace is 10 -2 After applying pressure to 50 MPa at 100°C / min, the temperature in the furnace was raised to 600°C and held for 10 minutes. After the holding time, the power was turned off, the pressure was released, and when the temperature in the furnace dropped below 100°C, the hot-pressed part was removed from the vacuum hot-pressing furnace and the mold was removed to obtain a copper-based composite material based on carbon nanotubes.

[0052] Example 2

[0053] This embodiment provides a method for preparing a copper-based composite material based on carbon nanotubes, and the specific steps are as follows:

[0054] (1) Take 0.3 g of carbon nanotubes (OD 20 nm to 30 nm) and pour into 24 mL of a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid at a volume ratio of 1:3. Place the beaker containing the CNTs and the mixed acid in a water bath and stir at 50°C for 10 h. After the reaction is complete, filter using a vacuum pump and rinse with deionized water several times until neutral. Finally, obtain the acidified CNTs and dry them for later use.

[0055] (2) Weigh 29.7 g of copper powder and pour it into a beaker filled with 300 mL of deionized water, and stir it magnetically for 30 minutes; pour 0.3 g of acidified carbon nanotubes into a beaker filled with 300 mL of deionized water and disperse it ultrasonically for 1 hour; slowly pour the ultrasonically dispersed CNTs solution into the beaker filled with copper powder, and then stir it magnetically for 20 minutes, let it stand after stirring, let it stand for stratification, stir it magnetically again, and let it stand for 10 minutes; after standing for stratification, use a vacuum pump to filter, and the resulting powder is dried at 50°C for 24 hours to obtain CNT / Cu composite powder 1; put the CNT / Cu composite powder 1 into a ball mill, and put the ball mill into a planetary ball mill for mixing, wherein the planetary ball mill rotates at 200 rpm, the mixing time is 2 hours, and the ball-to-material ratio is 10:1 to obtain CNT / Cu composite powder 2.

[0056] (3) The CNT / Cu composite powder 2 was placed in a steel mold with an inner diameter of 30 mm and cold-pressed using a hydraulic press. The cold-pressing pressure was 20 MPa and the holding time was 10 min. A blank was obtained after cold-pressing.

[0057] (4) The cold-pressed blank is placed into a Φ30mm graphite mold and sintered in a rapid hot pressing furnace. The vacuum degree in the vacuum hot pressing furnace is 10 -2 After applying pressure to 50 MPa at 100°C / min, the temperature in the furnace was raised to 600°C and held for 10 minutes. After the holding time, the power was turned off, the pressure was released, and when the temperature in the furnace dropped below 100°C, the hot-pressed part was removed from the vacuum hot-pressing furnace and the mold was removed to obtain a copper-based composite material based on carbon nanotubes.

[0058] The SEM morphology of the carbon nanotube reinforced copper matrix composite material prepared in this embodiment is shown in FIG. Figure 1 As shown. Figure 1 It can be seen that the strips are carbon nanotubes and the blocks are copper matrix. The carbon nanotubes are evenly distributed on the matrix, which shows that the mixing process of the present invention is reasonable. Figure 2 As shown. Figure 2 It can be seen that the long strip phase is carbon nanotubes, and the carbon nanotubes are evenly distributed in the matrix. It can be seen that the interface between the carbon nanotubes and the copper matrix is ​​well bonded, and there are no obvious pores, which shows that the preparation process of the present invention is reasonable.

[0059] Example 3

[0060] This embodiment provides a method for preparing a copper-based composite material based on carbon nanotubes, and the specific steps are as follows:

[0061] (1) Take 0.36 g of carbon nanotubes (OD 20 nm to 30 nm) and pour into 36 mL of a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid at a volume ratio of 1:3. Place the beaker containing the CNTs and the mixed acid in a water bath and stir at 50°C for 10 h. After the reaction is complete, filter using a vacuum pump and rinse with deionized water several times until neutral. Finally, obtain the acidified CNTs and dry them for later use.

[0062] (2) Weigh 29.55g of copper powder and pour it into a beaker filled with 300mL of deionized water, and stir it magnetically for 30min; pour 0.36g of carbon nanotubes after acidification into a beaker filled with 450mL of deionized water and ultrasonically disperse it for 1h; slowly pour the ultrasonically dispersed CNTs solution into the beaker filled with copper powder, and then magnetically stir it for 20min, let it stand after stirring, let it stand for stratification, stir it magnetically again and let it stand for 10min; after standing for stratification, use a vacuum pump to filter, and the obtained powder is dried at 50℃ for 24h to obtain CNT / Cu composite powder 1; put the CNT / Cu composite powder 1 into a ball mill, and put the ball mill into a planetary ball mill for mixing, wherein the planetary ball mill rotates at 200rpm, the mixing time is 2h, and the ball-to-material ratio is 10:1 to obtain CNT / Cu composite powder 2.

[0063] (3) The CNT / Cu composite powder 2 was placed in a steel mold with an inner diameter of 30 mm and cold-pressed using a hydraulic press. The cold-pressing pressure was 20 MPa and the holding time was 10 min. A blank was obtained after cold-pressing.

[0064] (4) The cold-pressed blank is placed into a Φ30mm graphite mold and sintered in a rapid hot pressing furnace. The vacuum degree in the vacuum hot pressing furnace is 10 -2 After applying pressure to 50 MPa at 100°C / min, the temperature in the furnace was raised to 600°C and held for 10 minutes. After the holding time, the power was turned off, the pressure was released, and when the temperature in the furnace dropped below 100°C, the hot-pressed part was removed from the vacuum hot-pressing furnace and the mold was removed to obtain a copper-based composite material based on carbon nanotubes.

[0065] Comparative Example 1

[0066] This comparative example provides a method for preparing a copper-based composite material based on carbon nanotubes, and the specific steps are as follows:

[0067] (1) Take 0.3 g of carbon nanotubes (OD 20 nm to 30 nm) and pour into 24 mL of a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid at a volume ratio of 1:3. Place the beaker containing the CNTs and the mixed acid in a water bath and stir at 50°C for 10 h. After the reaction is complete, filter using a vacuum pump and rinse with deionized water several times until neutral. Finally, obtain the acidified CNTs and dry them for later use.

[0068] (2) Weigh 29.7 g of copper powder and pour it into a beaker filled with 300 mL of deionized water, and stir it magnetically for 30 minutes; pour 0.3 g of acidified carbon nanotubes into a beaker filled with 300 mL of deionized water and disperse it ultrasonically for 1 hour; slowly pour the ultrasonically dispersed CNTs solution into the beaker filled with copper powder, and then stir it magnetically for 20 minutes. After stirring, let it stand, let it stand for stratification, stir it magnetically again, and let it stand for 10 minutes; after standing for stratification, use a vacuum pump to filter to obtain CNT / Cu composite powder.

[0069] (3) The composite powder was placed in a steel mold with an inner diameter of Φ30 mm and cold pressed using a hydraulic press. The cold pressing pressure was 20 MPa and the holding time was 10 min. A blank was obtained after cold pressing.

[0070] (4) The cold-pressed blank is placed into a Φ30mm graphite mold and sintered in a rapid hot pressing furnace. The vacuum degree in the vacuum hot pressing furnace is 10 -2 After applying pressure to 50 MPa at 100°C / min, the temperature in the furnace was raised to 600°C and held for 10 minutes. After the holding time, the power was turned off, the pressure was released, and when the temperature in the furnace dropped below 100°C, the hot-pressed part was removed from the vacuum hot-pressing furnace and the mold was removed to obtain a copper-based composite material based on carbon nanotubes.

[0071] The SEM morphology of the carbon nanotube reinforced copper matrix composite material prepared in this comparative example is as follows: Figure 3 As shown, the metallographic photograph of the composite material after rapid hot pressing sintering is as follows Figure 4 As shown, it can be seen that the carbon nanotubes are evenly distributed in the matrix, but compared Figure 1 and Figure 3 ,contrast Figure 3 It can be seen that the carbon nanotubes agglomerate, so it can be concluded that the mixing process and preparation process of Comparative Example 1 are not as good as Example 2.

[0072] Comparative Example 2

[0073] This comparative example provides a method for preparing a copper-based composite material based on carbon nanotubes, and the specific steps are as follows:

[0074] (1) Take 0.3 g of carbon nanotubes (OD 20 nm to 30 nm) and pour into 24 mL of a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid at a volume ratio of 1:3. Place the beaker containing the CNTs and the mixed acid in a water bath and stir at 50°C for 10 h. After the reaction is complete, filter using a vacuum pump, rinse with deionized water several times until neutral, and finally dry for use.

[0075] (2) Weigh 29.7 g of copper powder and 0.3 g of acidified carbon nanotubes into a ball mill, and place the ball mill into a planetary ball mill for mixing to obtain a composite powder. The planetary ball mill rotates at a speed of 200 rpm, the mixing time is 2 h, and the ball-to-material ratio is 10:1 to obtain a composite powder.

[0076] (3) The composite powder was placed in a steel mold with an inner diameter of Φ30 mm and cold pressed using a hydraulic press. The cold pressing pressure was 20 MPa and the holding time was 10 min. A blank was obtained after cold pressing.

[0077] (4) The cold-pressed blank is placed into a Φ30mm graphite mold and sintered in a rapid hot pressing furnace. The vacuum degree in the vacuum hot pressing furnace is 10 -2 After applying pressure to 50 MPa at 100°C / min, the temperature in the furnace was raised to 600°C and held for 10 minutes. After the holding time, the power was turned off, the pressure was released, and when the temperature in the furnace dropped below 100°C, the hot-pressed part was removed from the vacuum hot-pressing furnace and the mold was removed to obtain a copper-based composite material based on carbon nanotubes.

[0078] The SEM morphology of the carbon nanotube reinforced copper matrix composite material prepared in this comparative example is as follows: Figure 5 As shown, the metallographic photograph of the composite material after rapid hot pressing sintering is as follows Figure 6 As shown, it can be seen that the carbon nanotubes are evenly distributed in the matrix, but compared Figure 1 and Figure 5 , it can be seen Figure 5 Medium copper only absorbs a small amount of carbon nanotubes, so it can be concluded that the mixing process and preparation process of Comparative Example 2 are not as good as Example 2.

[0079] Comparative Example 3

[0080] This comparative example provides a method for preparing a copper-based composite material based on carbon nanotubes, and the specific steps are as follows:

[0081] (1) Take 0.15g of carbon nanotubes (OD 20nm-30nm) and pour into 12mL of a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid, with the volume ratio of concentrated sulfuric acid to concentrated nitric acid being 1:3. Place the beaker containing the CNTs and the mixed acid in a water bath and stir at 50℃ for 10h. After the reaction is completed, filter with a vacuum pump and rinse with deionized water several times until neutral. Finally, obtain the acidified CNTs and dry them for use.

[0082] (2) Weigh 29.85g of copper powder and pour it into a beaker filled with 300mL of deionized water, and stir it magnetically for 30min; pour 0.15g of acidified CNTs into a beaker filled with 150mL of deionized water and disperse it ultrasonically for 1h; slowly pour the CNTs solution obtained after ultrasonic dispersion into the beaker filled with copper powder, and then stir it magnetically for 20min, let it stand after stirring, let it stand for stratification, stir it magnetically again and let it stand for 10min; after standing for stratification, use a vacuum pump to filter, and the obtained powder is dried at 50℃ for 24h to obtain CNT / Cu composite powder 1; put the CNT / Cu composite powder 1 into a ball mill, and put the ball mill into a planetary ball mill for mixing, wherein the planetary ball mill rotates at 200rpm, the mixing time is 2h, and the ball-to-material ratio is 10:1 to obtain CNT / Cu composite powder 2.

[0083] (3) The CNT / Cu composite powder 2 was placed in a steel mold with an inner diameter of 30 mm and cold-pressed using a hydraulic press. The cold-pressing pressure was 20 MPa and the holding time was 10 min. A blank was obtained after cold-pressing.

[0084] (4) The cold-pressed blank is placed into a Φ30mm graphite mold and sintered in a rapid hot pressing furnace. The vacuum degree in the vacuum hot pressing furnace is 10 -2 After applying pressure to 50 MPa at 100°C / min, the temperature in the furnace was raised to 600°C and held for 10 minutes. After the holding time, the power was turned off, the pressure was released, and when the temperature in the furnace dropped below 100°C, the hot-pressed part was removed from the vacuum hot-pressing furnace and the mold was removed to obtain a copper-based composite material based on carbon nanotubes.

[0085] Comparative Example 4

[0086] This comparative example provides a method for preparing a copper-based composite material based on carbon nanotubes, and the specific steps are as follows:

[0087] (1) Take 0.45 g of carbon nanotubes (OD 20 nm to 30 nm) and pour into 36 mL of a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid at a volume ratio of 1:3. Place the beaker containing the CNTs and the mixed acid in a water bath and stir at 50°C for 10 h. After the reaction is complete, filter with a vacuum pump and rinse with deionized water several times until neutral. Finally, obtain the acidified CNTs and dry them for later use.

[0088] (2) Weigh 29.55g of copper powder and pour it into a beaker filled with 300mL of deionized water, and stir it magnetically for 30min; pour 0.45g of carbon nanotubes after acidification into a beaker filled with 450mL of deionized water and ultrasonically disperse it for 1h; slowly pour the ultrasonically dispersed CNTs solution into the beaker filled with copper powder, and then magnetically stir it for 20min, let it stand after stirring, let it stand for stratification, stir it magnetically again and let it stand for 10min; after standing for stratification, use a vacuum pump to filter, and the resulting powder is dried at 50℃ for 24h to obtain CNT / Cu composite powder 1; put the CNT / Cu composite powder 1 into a ball mill, and put the ball mill into a planetary ball mill for mixing, wherein the planetary ball mill rotates at 200rpm, the mixing time is 2h, and the ball-to-material ratio is 10:1 to obtain CNT / Cu composite powder 2.

[0089] (3) The CNT / Cu composite powder 2 was placed in a steel mold with an inner diameter of 30 mm and cold-pressed using a hydraulic press. The cold-pressing pressure was 20 MPa and the holding time was 10 min. A blank was obtained after cold-pressing.

[0090] (4) The cold-pressed blank is placed into a Φ30mm graphite mold and sintered in a rapid hot pressing furnace. The vacuum degree in the vacuum hot pressing furnace is 10 -2 After applying pressure to 50 MPa at 100°C / min, the temperature in the furnace was raised to 600°C and held for 10 minutes. After the holding time, the power was turned off, the pressure was released, and when the temperature in the furnace dropped below 100°C, the hot-pressed part was removed from the vacuum hot-pressing furnace and the mold was removed to obtain a copper-based composite material based on carbon nanotubes.

[0091] Performance Testing

[0092] The Brinell hardness, tensile strength, friction coefficient and wear loss of the copper-based composite materials prepared in Examples 1-3 and Comparative Examples 1-2 were tested, and the results are shown in Table 1.

[0093] Table 1 Performance of the copper-based composite materials prepared in each embodiment and comparative example

[0094] Brinell hardness (HBW) Tensile strength (MPa) Average friction coefficient <![CDATA[Wear amount (mm 3 )]]> Example 1 49.6 345.7 0.565 0.048 Example 2 51.3 369.5 0.563 0.046 Example 3 50.7 333.6 0.573 0.050 Comparative Example 1 44.9 275.3 0.575 0.072 Comparative Example 2 47.8 306.4 0.730 0.071 Comparative Example 3 39.7 252.9 0.774 0.051 Comparative Example 4 46.6 316.4 0.592 0.088

[0095] As can be seen from Table 1, compared with the copper-based composite materials prepared in Comparative Examples 1-4, the copper-based composite material based on carbon nanotubes prepared in Example 2 has higher Brinell hardness and tensile strength, and has a lower average friction coefficient and lower wear. Therefore, it can be seen that the preparation method of wet mixing adsorption-low energy ball milling can effectively improve the comprehensive performance of the material. This is because the wet mixing adsorption-low energy ball milling process can make the carbon nanotubes more uniformly adsorbed on the copper (Comparative Example 1-4). Figure 1 and Figure 3 、 Figure 5 ), after rapid hot pressing and sintering, the carbon nanotubes are evenly distributed on the substrate (compared to Figure 2 and Figure 4 、 Figure 6 By comparing the properties of the copper-based composite materials obtained in Examples 1 to 3 with those in Comparative Examples 3 and 4, it can be found that the copper-based composite materials with a mass fraction of carbon nanotubes of 0.8% to 1.2% have better properties.

[0096] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a copper-based composite material based on carbon nanotubes, characterized in that: The following steps are involved: (1) preparing an aqueous solution of copper powder and a dispersion of carbon nanotubes; (2) stirring and mixing the aqueous solution of copper powder obtained in step (1) and the dispersion of carbon nanotubes, allowing to stand, collecting the solid phase after solid-liquid separation, drying, and ball milling the mixture to obtain CNT / Cu composite powder; (3) cold pressing and hot pressing the CNT / Cu composite powder to obtain the copper-based composite material; In step (1), the carbon nanotubes are obtained by acidification: The carbon nanotubes were prepared by reacting a mixed acid solution at 45°C to 55°C for 9 h to 11 h. The mixed acid is selected from concentrated sulfuric acid and concentrated nitric acid; the volume ratio of the concentrated sulfuric acid to the concentrated nitric acid is 1:3 to 1:4; In step (2), the ball milling mixture is carried out using a planetary ball mill with a rotation speed of 180 rpm to 220 rpm; The aqueous solution of the copper powder is obtained by pouring the Cu powder into a beaker filled with deionized water and stirring magnetically; In step (3), the hot pressing sintering conditions are: the vacuum degree in the vacuum hot pressing furnace is 10 -2 Under the conditions of Pa, pressurize to 45MPa~55MPa, then heat to 550℃~650℃ and keep warm for 8min~12min; The mass fraction of carbon nanotubes in the copper-based composite material is 0.8% to 1.2%.

2. The preparation method according to claim 1, characterized in that In step (1), the size of the copper powder is 4 μm to 7 μm; the outer diameter of the carbon nanotube is 20 nm to 30 nm.

3. The preparation method according to claim 1, characterized in that In step (3), the cold pressing forming conditions are: the cold pressing pressure is 20 MPa to 30 MPa, and the holding time is 8 min to 12 min.

4. The copper-based composite material based on carbon nanotubes prepared according to the preparation method according to any one of claims 1 to 3.

5. Use of the carbon nanotube-based copper-based composite material according to claim 4 in brake materials.

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