Carbon nanotube composite superconducting copper-based material and preparation method thereof

Abstract

The invention provides a carbon nanotube composite superconducting copper-based material and a preparation method thereof, and belongs to the technical field of metallurgy, and the preparation method comprises the following steps: firstly mixing carbon nanotube powder, copper powder and wax powder, then carrying out press forming and sintering, and finally forging and pressing to obtain a finished product. The copper-carbon composite superconducting material is prepared by mixing the micron-sized copper powder and the carbon nanotube powder through a powder metallurgy process, dealloying of a copper matrix and the growth process of graphene are not needed, and only dispersion and mixing of the copper powder and the carbon nanotube powder are needed, so that the production and preparation process is greatly simplified, a large amount of time and energy are saved, and the production cost is reduced. The production efficiency is improved, and the method is suitable for industrial large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a carbon nanotube composite superconducting copper-based material and a preparation method thereof. Background Art

[0002] In recent years, with the increasingly severe energy and environmental problems and the development of high-tech, higher requirements have been placed on the conductivity of copper-based materials. The development of ultra-high conductive copper-based materials has important economic value and practical significance.

[0003] Therefore, the research on introducing carbon materials into metal matrices has gradually emerged. The high strength (tensile strength ~ 130GPa), high modulus (elastic modulus ~ 1TPa), and high conductivity (electron mobility ~ 2×105cm2 / Vs) characteristics given by the unique structure of carbon materials provide the possibility for copper-based composite materials to achieve high strength (≥550MPa), high modulus (≥140GPa) and high conductivity (≥90%IACS) performance. For example, the Chinese invention patent with publication number CN108149046A discloses a high-strength, high-conductivity graphene / copper composite material and its preparation method and application. Although the material and preparation method have improved to a certain extent in terms of conductivity, there are still problems of complicated and cumbersome production process in the actual application process. Both electrochemical etching and de-alloying and the growth of graphene require a lot of time and energy, and the production cost is relatively high, and the production efficiency is relatively low, which is not suitable for industrial large-scale production. Summary of the invention

[0004] Based on the above problems in the prior art, the present invention provides a method for preparing a carbon nanotube composite superconducting copper-based material, which comprises mixing carbon nanotube powder, copper powder and wax powder, pressing and forming the mixture, sintering the mixture, and finally forging the mixture to obtain a finished product.

[0005] The method of mixing the carbon nanotube powder, copper powder and wax powder includes one or more of the following methods: Wet mixing, adding carbon nanotube powder, copper powder and wax powder into a solvent and dispersing them to form a mixed suspension; Dry mixing, mixing carbon nanotube powder, copper powder and wax powder to form mixed powder; and Layered mixing: carbon nanotube powder, copper powder and wax powder are spread into powder layers separately or mixed together, and multiple powder layers are stacked vertically.

[0006] Wherein, the wet mixing includes the following detailed steps: Step S1-1: copper powder and fatty alcohol polyoxyethylene ether are weighed at a mass ratio of copper powder: fatty alcohol polyoxyethylene ether = 100: (4-8), and the copper powder and fatty alcohol polyoxyethylene ether are successively added to a solvent for mechanical dispersion to prepare a copper powder suspension; Step S1-2: Weigh carbon nanotube powder and octylphenol polyoxyethylene ether according to the mass ratio of copper powder: carbon nanotube powder: octylphenol polyoxyethylene ether = 100: (0.5 - 15): (4 - 8), and successively add the carbon nanotube powder and octylphenol polyoxyethylene ether to a solvent for mechanical dispersion to make a carbon nanotube suspension; Step S1-3: Mix the copper powder suspension and the carbon nanotube suspension to obtain a mixed suspension, add wax powder to the mixed suspension according to 1% - 2% of the mass of the copper powder, then perform ultrasonic dispersion, drain to obtain a mixed wet powder, and perform pressing.

[0007] Among them, the ultrasonic dispersion is to perform two ultrasonic treatments after adding wax powder to the mixed suspension. The treatment conditions for the first time are: the frequency is 20 - 40 kHz, the power is 3500 - 4000 W, pulse treatment for 30 min, and the pulse treatment is to cycle ultrasonic treatment for 2 s and pause for 2 s; the treatment conditions for the second time are: the frequency is 40 - 100 kHz, the power is 3000 - 3500 W, and continuous treatment for 30 min.

[0008] Among them, the dry mixing includes Step S2. Weigh copper powder, carbon nanotube powder and wax powder according to the mass ratio of copper powder: carbon nanotube powder: wax powder = 100: (0.5 - 15): (1 - 2), and successively add them to a ball mill for ball milling dispersion; the ball-to-material ratio of the ball milling dispersion is 3 - 8:1 and copper balls are used, the rotation speed is 250 - 400 rpm, the dispersion time is 3 - 5 hours, and the inner cavity of the barrel of the ball mill is a copper inner cavity. Obtain a mixed powder, take out the mixed powder and perform pressing.

[0009] Among them, a variety of mixed wet powders or mixed powders containing different proportions of carbon nanotube powder are made, and then the various mixed wet powders or mixed powders are respectively laid in a vertical stack in a pressing die to form corresponding powder layers, and the laying order is to lay them in descending order of the proportion of carbon nanotube powder.

[0010] Among them, the layer mixing includes Step S3-1: Weigh copper powder, carbon nanotube powder and wax powder according to the mass ratio of copper powder: carbon nanotube powder: wax powder = 100: (0.5 - 15): (1 - 2). Take the copper powder and wax powder and mix them by ball milling dispersion to obtain a premixed powder; Step S3-21: Divide the carbon nanotube powder into N equal parts on average, divide the premixed powder into N + 1 equal parts on average. In the pressing die, lay the first portion of the premixed powder to form the first powder layer, lay the first portion of the carbon nanotube powder on the first powder layer to form the second powder layer, and repeat laying the premixed powder and the carbon nanotube powder alternately to form the corresponding powder layers until the last portion of the premixed powder is laid to form the topmost powder layer, and then perform pressing; Alternatively, directly execute S3-22 after step S3-1. Divide the carbon nanotube powder unevenly into N portions, and divide the premixed powder evenly into N + 1 portions. In the pressing die, spread the first portion of the premixed powder into the first powder layer, and spread the largest portion of the carbon nanotube powder on the first powder layer to form the second powder layer. Repeat the alternating laying of the premixed powder and the carbon nanotube powder to form the corresponding powder layers until the last portion of the premixed powder is laid into the topmost powder layer. The carbon nanotube powder is laid in order from more to less by weight, and then pressing is carried out.

[0011] Among them, in the steps S3-21 and S3-22, except for the premixed powder on the top layer, embossing treatment is carried out once after laying each layer of the premixed powder. The embossing treatment is to press concave and convex patterns on the upper surface of the powder layer. When laying the carbon nanotube powder, the concave and convex patterns are completely covered to form a carbon nanotube powder layer with a flat upper surface.

[0012] Among them, the press forming is to press the mixture into a specific shape by using a pressing die. The specific shapes include cylindrical and prismatic. The pressing pressure is 800-1000 Mpa. After press forming, it is heated to 60-80 °C in a vacuum or protective gas environment and dried for 10-15 h; the sintering temperature is 500-1000 °C, the pressure is 30-100 Mpa, and the time is 60-240 min; the forging is to carry out multiple rollings by using a rolling wheel. The rolling temperature decreases equidistantly from 900 °C to 600 °C in turn, and the rolling pressure is 60-180 MPa for equal-pressure rolling; both the sintering and the rolling are carried out in a protective gas environment.

[0013] The present invention also provides a carbon nanotube composite superconducting copper-based material, which is made by the preparation method as described above.

[0014] The beneficial effects of the present invention are as follows: 1. A copper-carbon composite superconducting material is made by mixing micron-sized copper powder and carbon nanotube powder and through powder metallurgy process. There is no need to carry out dealloying of the copper matrix and the growth process of graphene. Only the dispersion and mixing of the copper powder and the carbon nanotube powder are required, which greatly simplifies the production and preparation process, saves a large amount of time and energy, improves the production efficiency, and is suitable for large-scale industrial production.

[0015] 2. The micron-sized copper powder and carbon nanotube powder have partial flow characteristics of a fluid to a certain extent, and the density of the copper powder is much greater than that of the carbon nanotube powder. During the pressing process, under the action of external force, the copper powder will "flow" downward faster relative to the carbon nanotube powder, forcing the carbon nanotube powder at the bottom to "float" upward. Therefore, in the layered mixing, the design that the content of carbon nanotubes in the upper layer is less than that in the lower layer can realize the parallel distribution of carbon nanotubes in the superconducting material through the "upward floating" of the carbon nanotube powder during the pressing process, making the distribution of carbon nanotubes more uniform, which is beneficial to improving the superconducting performance of the superconducting material.

[0016] 3. The combination of two dispersants, fatty alcohol polyoxyethylene ether (AEO) and octylphenol polyoxyethylene ether (OP-10), will play a synergistic role of mutual promotion, which can improve the dispersion degree of copper powder and carbon nanotube powder, so that the mixed distribution of copper powder and carbon nanotube powder is more uniform, and is beneficial to improving the superconducting performance of superconducting materials. Description of the Drawings

[0017] Figure 1 It is a schematic flow chart of the preparation method of Example 1.

[0018] Figure 2 It is a schematic flow chart of the preparation method of Example 2.

[0019] Figure 3 It is a schematic diagram of layered mixing of Example 1 and Example 2.

[0020] Figure 4 It is a schematic flow chart of the preparation method of Example 3.

[0021] Figure 5 It is a schematic diagram of layered mixing of Example 3.

[0022] Figure 6 It is a schematic diagram of layered mixing of Example 4. Detailed Embodiments

[0023] The present invention will be described in detail below with reference to the drawings and specific embodiments.

[0024] Example 1: A preparation method of carbon nanotube composite superconducting copper-based material based on wet mixing and layered mixing.

[0025] As shown in the attached Figure 1 and 3 A preparation method of a carbon nanotube composite superconducting copper-based material, which first adopts a wet mixing method to add carbon nanotube powder, 200-mesh copper powder and wax powder to the corresponding solvent and disperse them to make a variety of mixed suspensions containing different proportions of carbon nanotube powder, drain to obtain a variety of mixed wet powders containing different proportions of carbon nanotube powder, and then lay the corresponding powder layers vertically and laminated in a pressing mold for the various mixed wet powders. The laying order is to lay them in sequence from high to low according to the proportion of carbon nanotube powder, and then press and form and sinter, and finally obtain the finished product through forging, specifically including the following steps: Step S1-1: Weigh copper powder and fatty alcohol polyoxyethylene ether (AEO) according to the mass ratio of copper powder: fatty alcohol polyoxyethylene ether (AEO) = 100:6, and add copper powder and fatty alcohol polyoxyethylene ether (AEO) to an appropriate amount of pure water successively, and use a ball mill for mechanical dispersion to make three copper powder suspensions; Step S1-2: Based on the copper content of one portion of the copper powder suspension in Step S1-1, weigh three portions of carbon nanotube powder and three portions of octylphenol polyoxyethylene ether (OP-10) according to the mass ratio of copper powder: carbon nanotube powder: octylphenol polyoxyethylene ether (OP-10) = 100: (6 / 8 / 10): 5. Add the three portions of carbon nanotube powder and the three portions of octylphenol polyoxyethylene ether (OP-10) into three appropriate amounts of absolute ethanol one by one, and use a ball mill for mechanical dispersion to prepare three carbon nanotube suspensions with different carbon nanotube powder contents; Step S1-3: Mix the three portions of copper powder suspension with the three carbon nanotube suspensions respectively to obtain three mixed suspensions. Add wax powder to the three mixed suspensions according to 1.5% of the copper powder mass, and then perform ultrasonic treatment twice. The treatment conditions for the first time are: the frequency is 30 kHz, the power is 4000 W, pulse treatment for 30 min, and the pulse treatment is to cycle ultrasonic treatment for 2 s and pause for 2 s; the treatment conditions for the second time are: the frequency is 70 kHz, the power is 3300 W, continuous treatment for 30 min, and drain to obtain three mixed wet powders. The three mixed wet powders are low-carbon wet powder with a copper-carbon ratio of 100:6, medium-carbon wet powder with a copper-carbon ratio of 100:8, and high-carbon wet powder with a copper-carbon ratio of 100:10. First, evenly lay the high-carbon wet powder into the first powder layer in the pressing mold, then lay the medium-carbon wet powder on the upper surface of the first powder layer in the pressing mold to form the second powder layer, and finally lay the low-carbon wet powder on the upper surface of the second powder layer in the pressing mold to form the third powder layer. After the three powder layers are all laid, use a hydraulic press and the pressing mold to press the mixture composed of the three powder layers into a quadrangular prism shape. The pressing pressure is 900 Mpa. After pressing and forming, demold and transfer the quadrangular prism-shaped pressing product to a protective gas environment and heat it to 70 °C for drying for 12 h.

[0026] After drying, transfer the quadrangular prism-shaped mixture to a sintering furnace, fill it with a protective gas until the furnace pressure reaches 60 Mpa and heat it to 800 °C for sintering. The sintering time is 120 min.

[0027] After sintering, transfer the quadrangular prism-shaped mixture to a rolling furnace, fill it with a protective gas and heat it to 900 °C for the first rolling, then cool it to 800 °C for the second rolling, then cool it to 700 °C for the third rolling, and finally cool it to 600 °C for the fourth rolling. The pressure for the four rollings is 120 MPa, and anneal to obtain the finished product.

[0028] Example 2: A preparation method of a carbon nanotube composite superconducting copper-based material based on dry mixing and layer mixing.

[0029] The difference between this example and Example 1 is that the carbon nanotube powder, copper powder and wax powder are mixed by dry mixing, as shown in the appendix Figure 2 and3 A preparation method of a carbon nanotube composite superconducting copper-based material as shown, without using a solvent, directly mixing carbon nanotube powder, 250-mesh copper powder and wax powder, and then laying the mixed powders in a vertical laminated manner in a pressing mold to form corresponding powder layers. The laying order is to lay them in descending order of the proportion of carbon nanotube powder, and then press and form and sinter, and finally obtain the finished product through forging, specifically including the following steps: Step S2, weigh three portions of copper powder, carbon nanotube powder and wax powder respectively according to the mass ratio of copper powder:carbon nanotube powder:wax powder = 100:(6 / 8 / 10):2, and divide them into three groups one by one. Each group contains the same mass of copper powder and wax powder. The mass ratios of carbon nanotube powder to copper powder in the three groups are copper powder:carbon nanotube powder = 100:6, 100:8 and 100:10 respectively; independently add the copper powder, carbon nanotube powder and wax powder into a ball mill in sequence for ball milling and dispersion; the ball-to-material ratio of the ball milling and dispersion is 4:1 and copper balls are used, the rotation speed is 300 rpm, and the dispersion time is 4 hours to obtain three kinds of mixed powders. The inner cavity of the barrel of the ball mill is a copper inner cavity, which can be made by covering the inner wall of the barrel with a copper plate or directly using a copper ball mill barrel. The design of the copper barrel and copper balls can reduce impurities formed due to equipment wear. The three kinds of mixed powders are low-carbon powder with a copper-carbon ratio of 100:6, medium-carbon powder with a copper-carbon ratio of 100:8 and high-carbon powder with a copper-carbon ratio of 100:10. First, evenly lay the high-carbon powder in the pressing mold to form the first powder layer, then lay the medium-carbon powder on the upper surface of the first powder layer in the pressing mold to form the second powder layer, and finally lay the low-carbon powder on the upper surface of the second powder layer in the pressing mold to form the third powder layer. After all three powder layers are laid, use a hydraulic press in cooperation with the pressing mold to press the mixture composed of the three powder layers into a quadrangular prism shape. The pressing pressure is 850 Mpa. After pressing and forming, demold and transfer the quadrangular prism-shaped pressing product to a protective gas environment and heat it to 65°C for drying for 14 h.

[0030] After drying, transfer the quadrangular prism-shaped mixture to a sintering furnace, fill it with a protective gas until the pressure in the furnace reaches 40 Mpa and heat it up to 900°C for sintering. The sintering time is 80 min.

[0031] After sintering, transfer the quadrangular prism-shaped mixture to a rolling furnace, fill it with a protective gas and heat it up to 900°C for the first rolling, then cool it down to 800°C for the second rolling, then cool it down to 700°C for the third rolling, and finally cool it down to 600°C for the fourth rolling. The pressure for the four rollings is 120 MPa, and anneal to obtain the finished product.

[0032] Example 3: A preparation method of a carbon nanotube composite superconducting copper-based material based on layered mixing.

[0033] The difference between this embodiment and the first embodiment lies in the different mixing methods of carbon nanotube powder, 150-mesh copper powder and wax powder. Only the layer mixing method is adopted for mixing, as shown in the attached Figure 4 and 5 A method for preparing a carbon nanotube composite superconducting copper-based material, which specifically includes the following steps: Step S3-1: Weigh copper powder, carbon nanotube powder and wax powder according to the mass ratio of copper powder: carbon nanotube powder: wax powder = 100: (0.5-15): 1. Take the copper powder and wax powder and disperse and mix them by ball milling to obtain a premixed powder; Step S3-21: Divide the carbon nanotube powder into 3 equal parts on average, and divide the premixed powder into 4 equal parts on average. In a pressing mold, spread the first portion of the premixed powder into a first powder layer, and spread the first portion of the carbon nanotube powder on the first powder layer to form a second powder layer. Repeat the alternating laying of the premixed powder and the carbon nanotube powder into corresponding powder layers until the last portion of the premixed powder is laid into the topmost powder layer. Except for the premixed powder on the top layer, perform a texturing treatment once after laying each layer of the premixed powder. The texturing treatment is to press concave and convex patterns on the upper surface of the powder layer. When laying the carbon nanotube powder, completely cover the concave and convex patterns and form a carbon nanotube powder layer with a flat upper surface. Use a hydraulic press in cooperation with the pressing mold to press the mixture composed of three powder layers into a quadrangular prism shape. The pressing pressure is 950 Mpa. After pressing and forming, demold and transfer the quadrangular prism-shaped pressed product to a protective gas environment and heat it to 75 °C for drying for 11 h.

[0034] After drying, transfer the quadrangular prism-shaped mixture to a sintering furnace, fill it with a protective gas until the furnace pressure reaches 90 Mpa and heat it up to 600 °C for sintering. The sintering time is 220 min.

[0035] After sintering, transfer the quadrangular prism-shaped mixture to a rolling furnace, fill it with a protective gas and heat it up to 900 °C for the first rolling, then cool it down to 800 °C for the second rolling, then cool it down to 700 °C for the third rolling, and finally cool it down to 600 °C for the fourth rolling. The pressure for the four rollings is 120 MPa, and then anneal to obtain the finished product.

[0036] Example 4: A method for preparing a carbon nanotube composite superconducting copper-based material based on layer mixing.

[0037] The difference between this embodiment and the third embodiment lies in the different contents of each carbon nanotube powder layer. The specific different steps are as follows: After step S3-1, directly execute S3-22. Divide the carbon nanotube powder unevenly into three parts, and the mass ratio of the three parts of carbon nanotube powder is 6:8:10. Divide the premixed powder into four equal parts. In the pressing die, spread the first part of the premixed powder into the first powder layer, and spread the largest part of the carbon nanotube powder on the first powder layer to form the second powder layer. Repeat the process of alternately laying the premixed powder and the carbon nanotube powder to form the corresponding powder layers until the last part of the premixed powder forms the topmost powder layer. The carbon nanotube powder is laid in order from more to less by weight, that is, the part of the carbon nanotube powder corresponding to a mass ratio of 10 is laid first, and the part of the carbon nanotube powder corresponding to a mass ratio of 6 is laid last. As Figure 6 shown, except for the premixed powder on the top layer, after laying each layer of premixed powder, a texturing process is performed. The texturing process is to press concave and convex patterns on the upper surface of the powder layer. When laying the carbon nanotube powder, completely cover the concave and convex patterns and form a carbon nanotube powder layer with a flat upper surface. Use a hydraulic press in cooperation with the pressing die to press the mixture composed of three powder layers into a quadrangular prism shape. The pressing pressure is 1000 Mpa. After pressing and forming, demold and transfer the quadrangular prism-shaped pressed product to a protective gas environment and heat it to 70 °C for drying for 12 h.

[0038] After drying is completed, transfer the quadrangular prism-shaped mixture to a sintering furnace, fill it with a protective gas until the pressure in the furnace reaches 60 Mpa, and heat it to 800 °C for sintering. The sintering time is 120 min.

[0039] After sintering is completed, transfer the quadrangular prism-shaped mixture to a rolling furnace, fill it with a protective gas and heat it to 900 °C for the first rolling, then cool it to 800 °C for the second rolling, then cool it to 700 °C for the third rolling, and finally cool it to 600 °C for the fourth rolling. The pressure for the four rollings is 120 MPa, and then anneal to obtain the finished product.

[0040] Example Five: Verification of the preparation method disclosed in the present invention.

[0041] Next, the properties of the copper-based materials prepared by using the preparation methods of Examples 1 to 4 and related parallel preparation methods are tested for tensile strength, specified plastic extension strength, actual compressive force, Vickers hardness, and electrical conductivity. Each experimental group and control group are set up with three repetitions, and the average value of the three repetitions of a certain parameter is taken as the value of this parameter for this experimental group or control group. The designs of each experimental group and control group are as follows: 　 Corresponding embodiment And the difference steps of the corresponding embodiment Experimental group 1 1 None Experimental group 2 2 None Experimental group 3 3 None Experimental group 4 4 None Control group 1 1 Use an equal amount of AEO to replace OP-10 as the dispersant of carbon nanotube powder Control group 2 1 Use an equal amount of OP-10 to replace AEO as the dispersant of copper powder Control group 3 1 Do not add AEO and OP-10 Control group 4 1 Do not perform the first ultrasonic treatment and directly perform the second ultrasonic treatment Control group 5 1 Do not perform layered mixing and directly press the mixed wet powder with a copper-carbon ratio of 100:8 Control group 6 2 Do not perform layered mixing and directly press the mixed powder with a copper-carbon ratio of 100:8 Control group 7 3 Do not perform embossing treatment Among them, the test methods for tensile strength Rm and specified plastic extension strength Rp0.2 refer to GB / T228.1-2010; the test method for actual compressive force refers to GB / T 7314-2005; the test method for Vickers hardness HV0.2 refers to 4340.1-2009; the electrical conductivity is detected by the four-probe detection method. The test results are as follows: 　 Tensile strength Rm (MPa) Specified plastic extension strength Rp0.2 (MPa) Actual compression force F (N) Vickers hardness HV0.2 Conductivity (IACS) Experimental group 1 208 75 9968 54.1 116.8% Experimental group 2 208 76 9971 53.8 115.1% Experimental group 3 200 74 9910 51.2 107.3% Experimental group 4 205 74 9976 52.3 107.9% Control group 1 207 73 9983 53.6 110.1% Control group 2 203 72 9923 52.9 108.9% Control group 3 206 73 9943 53.4 105.1% Control group 4 206 73 9998 54.3 112.9% Control group 5 202 71 9903 51.4 101.2% Control group 6 209 74 9985 53.5 109.3% Control group 7 199 72 9899 51.9 106.2% As can be seen from the above results, the copper-based material prepared by the preparation method provided by the present invention has good mechanical properties and high electrical conductivity.

[0042] Among them, from the result comparison of experimental group 1, control group 1, control group 2 and control group 3, it can be seen that adding dispersants AEO and OP-10 can both improve the electrical conductivity of the copper-based material, and adding AEO and OP-10 simultaneously can further improve the electrical conductivity. Therefore, AEO and OP-10 play a synergistic and mutually promoting role in the dispersion of copper powder and carbon nanotube powder, making the carbon nanotube powder more evenly distributed in the copper powder, that is, the distribution of carbon in the final copper-based material is more uniform, thereby improving the electrical conductivity. Through research, the fatty alcohol chain of AEO and the phenolic group of OP-10 form a more stable mixed micelle through hydrophobic interaction. When AEO and OP-10 are compounded, the CMC of the mixed system is 30–50% lower than that of a single component, the micelle formation ability is enhanced, and the dispersion efficiency is improved. At the same time, the absolute value of the Zeta potential of the AEO / OP-10 compound system increases by 20% (from -25 mV to -30 mV), indicating that the electrostatic repulsion is enhanced, and the polyoxyethylene chains (EO chains) of the two form a thicker hydration layer, delaying particle sedimentation and improving dispersion stability.

[0043] As can be seen from the result comparison of experimental group 1 and control group 4, performing high-power pulsed ultrasonic treatment can improve the electrical conductivity of the copper-based material. It should be that the high-power pulsed ultrasonic waves break the carbon nanotubes to a certain extent, reduce the influence of the radial insulation of the carbon nanotubes, and make the performance of the carbon nanotubes close to that of graphene.

[0044] As can be seen from the result comparison of experimental group 1 and control group 5, experimental group 2 and control group 6, and experimental group 3 and experimental group 4, in the pressed precursor mixture, increasing the content of the carbon nanotube powder in the lower part can improve the electrical conductivity of the copper-based material. During the pressing process, the carbon nanotube powder in the lower part will automatically rise, making the distribution of the carbon nanotube powder more uniform.

[0045] As can be seen from the result comparison of experimental group 3 and control group 7, performing embossing treatment can improve the electrical conductivity of the copper-based material. The embossing treatment forms grooves on the upper surface of the copper powder layer, increasing the carbon nanotube powder layer with a certain depth in the normal direction, forming a three-dimensional structure of carbon nanotube clusters, thereby improving the electrical conductivity.

[0046] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent for the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention shall be subject to the appended claims.

Claims

1. A preparation method of a carbon nanotube composite superconducting copper-based material, characterized in that, It mixes carbon nanotube powder, copper powder and wax powder, then presses and shapes them and conducts sintering, and finally obtains the finished product through forging and pressing.

2. The preparation method of a carbon nanotube composite superconducting copper-based material according to claim 1, wherein The ways of mixing the carbon nanotube powder, copper powder and wax powder include one or a combination of more than one of the following ways: Wet mixing, adding the carbon nanotube powder, copper powder and wax powder into a solvent and dispersing them to make a mixed suspension; Dry mixing, mixing the carbon nanotube powder, copper powder and wax powder to make a mixed powder; and Layered mixing, laying the carbon nanotube powder, copper powder and wax powder alone or after mixing to form powder layers, and vertically stacking multiple powder layers in combination.

3. The preparation method of a carbon nanotube composite superconducting copper-based material according to claim 2, wherein The wet mixing includes the following detailed steps: Step S1-1: Weigh copper powder and fatty alcohol polyoxyethylene ether according to the mass ratio of copper powder: fatty alcohol polyoxyethylene ether = 100: (4-8), and successively add the copper powder and fatty alcohol polyoxyethylene ether into the solvent for mechanical dispersion to make a copper powder suspension; Step S1-2: Weigh carbon nanotube powder and octylphenol polyoxyethylene ether according to the mass ratio of copper powder: carbon nanotube powder: octylphenol polyoxyethylene ether = 100: (0.5-15): (4-8), and successively add the carbon nanotube powder and octylphenol polyoxyethylene ether into the solvent for mechanical dispersion to make a carbon nanotube suspension; Step S1-3: Mix the copper powder suspension and the carbon nanotube suspension to obtain a mixed suspension, add wax powder to the mixed suspension according to 1%-2% of the copper powder mass, then conduct ultrasonic dispersion, drain to obtain a mixed wet powder, and conduct pressing.

4. The preparation method of a carbon nanotube composite superconducting copper-based material according to claim 3, characterized in that, The ultrasonic dispersion is to conduct two ultrasonic treatments after adding wax powder to the mixed suspension. The treatment conditions for the first time are: the frequency is 20-40 kHz, the power is 3500-4000 W, pulse treatment for 30 min, and the pulse treatment is to cycle ultrasonic treatment for 2 s and pause for 2 s; the treatment conditions for the second time are: the frequency is 40-100 kHz, the power is 3000-3500 W, and continuous treatment for 30 min.

5. The preparation method of a carbon nanotube composite superconducting copper-based material according to claim 2, characterized in that, The dry mixing includes Step S2, weighing copper powder, carbon nanotube powder and wax powder according to the mass ratio of copper powder: carbon nanotube powder: wax powder = 100: (0.5-15): (1-2), and successively adding them into a ball mill for ball milling and dispersion; the ball-to-material ratio of the ball milling and dispersion is 3-8:1 and copper balls are used, the rotation speed is 250-400 rpm, the dispersion time is 3-5 hours, the inner cavity of the barrel of the ball mill is a copper inner cavity, obtaining a mixed powder, taking out the mixed powder for pressing.

6. The preparation method of a carbon nanotube composite superconducting copper-based material according to any one of claims 3-5, characterized in that, Make multiple mixed wet powders or mixed powders containing different proportions of carbon nanotube powder, and then respectively lay the corresponding powder layers vertically stacked in a pressing mold for the multiple mixed wet powders or mixed powders, and the laying order is to lay them in sequence from high to low according to the proportion of carbon nanotube powder.

7. The preparation method of a carbon nanotube composite superconducting copper-based material according to claim 2, characterized in that, The layered mixing includes Step S3-1: Weigh copper powder, carbon nanotube powder and wax powder according to the mass ratio of copper powder: carbon nanotube powder: wax powder = 100: (0.5-15): (1-2). Take the copper powder and wax powder and disperse and mix them by ball milling to obtain a premixed powder. Step S3-21: Divide the carbon nanotube powder into N equal parts on average, and divide the premixed powder into N + 1 equal parts on average. In a pressing mold, spread the first portion of the premixed powder into a first powder layer, and spread the first portion of the carbon nanotube powder into a second powder layer on the first powder layer. Repeat the alternating laying of the premixed powder and the carbon nanotube powder into corresponding powder layers until the last portion of the premixed powder is laid into the topmost powder layer, and then perform pressing. Alternatively, directly execute S3-22 after step S3-1. Divide the carbon nanotube powder into N unequal parts, and divide the premixed powder into N + 1 equal parts on average. In a pressing mold, spread the first portion of the premixed powder into a first powder layer, and spread the largest portion of the carbon nanotube powder into a second powder layer on the first powder layer. Repeat the alternating laying of the premixed powder and the carbon nanotube powder into corresponding powder layers until the last portion of the premixed powder is laid into the topmost powder layer. The carbon nanotube powder is laid in order from more to less by weight, and then perform pressing.

8. The preparation method of a carbon nanotube composite superconducting copper-based material according to claim 7, characterized in that, In the steps S3-21 and S3-22, except for the topmost premixed powder layer, a texturing treatment is performed once after each layer of the premixed powder is laid. The texturing treatment is to press concave and convex patterns on the upper surface of the powder layer. When laying the carbon nanotube powder, the concave and convex patterns are completely covered to form a carbon nanotube powder layer with a flat upper surface.

9. The preparation method of a carbon nanotube composite superconducting copper-based material according to claim 1, wherein, The pressing and forming is to press the mixture into a specific shape by using a pressing mold. The specific shapes include cylindrical and prismatic. The pressing pressure is 800-1000 Mpa. After pressing and forming, it is heated to 60-80 °C and dried for 10-15 h in a vacuum or protective gas environment. The sintering temperature is 500-1000 °C, the pressure is 30-100 Mpa, and the time is 60-240 min. The forging is to perform multiple rollings by using rolling wheels. The rolling temperature decreases equidistantly from 900 °C to 600 °C in turn, and the rolling pressure is 60-180 MPa for isobaric rolling. Both the sintering and rolling are carried out in a protective gas environment.

10. A carbon nanotube composite superconducting copper-based material, characterized in that, It is made by the preparation method according to any one of claims 1-9.

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