A conductive copper-based nanocarbon composite material and a preparation method thereof

Abstract

The present invention provides a conductive copper-based nanocarbon composite material and a preparation method thereof, belonging to the technical field of composite materials. In the present invention, pre-prepared flaky copper powder is used. The flaky copper powder has a large specific surface area, a small thickness, strong electrostatic adsorption and many adsorption sites, and is compatible with flaky GO in structure, which is beneficial to the adsorption of GO. GO is used as a nanocarbon precursor, and its rich hydrophilic effect and negative charge characteristics are utilized to achieve spontaneous dispersion and adsorption, avoiding agglomeration. The surfactant is beneficial to the further uniform adsorption of GO on the copper sheet surface. The surface of the RGO after high-temperature hydrogen reduction is rich in defects, and a strong electrostatic interaction is generated with the Cu surface, which not only increases the interfacial energy and is conducive to promoting its embedding into the crystal, but also avoids the slip and accumulation of the reinforcement during the subsequent ball milling process.

Description

Technical Field

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

[0002] Metal materials have excellent mechanical properties (strength, plasticity) and good functional properties (electrical conductivity, thermal conductivity), and are widely used in high-tech fields such as machinery, electronics, aerospace, and national defense. However, the development of metal materials is still full of challenges, and there is often a "compromise" relationship between their various physical properties, that is, the improvement of one property is at the expense of other properties. For example, grain refinement as a universal means can significantly improve the strength of metals, but its plasticity, thermal stability and conductivity often decrease. Based on the difficulties and bottlenecks brought about by this "compromise" relationship, by adding a reinforcing phase with special properties to the metal matrix to form a metal-based composite material, this problem can be well solved and a significant improvement in the comprehensive performance of metal materials can be achieved. Among them, carbon materials, as a reinforcing phase with a wide source and low cost, have been widely used in the field of metal materials in recent years due to their excellent mechanical properties and good functional properties, providing the possibility of improving the comprehensive performance of metal materials and integrating structural functions.

[0003] However, existing carbon-reinforced metal-based composite materials still have problems such as carbon dispersion in the matrix and interface bonding. For example, carbon materials are prone to spontaneous agglomeration, which reduces the volume fraction of the reinforcement / matrix interface and weakens the reinforcement effect; the carbon reinforcement phase located at the matrix grain boundary is prone to cause stress concentration at the interface during deformation, resulting in the generation and rapid expansion of cracks. The patent document with announcement number CN110560698A discloses a method for preparing a carbon nanotube-reinforced copper-based composite material, attempting to sensitize and activate the carbon nanotubes by surface nickel plating to prevent the agglomeration of the carbon nanotubes and improve their dispersibility. However, the degree of dispersion is limited, the reinforcement effect is not obvious, and the absolute strength is only about 300MPa. The patent document with announcement number CN110468441A discloses a method for preparing a copper-based modified graphene oxide composite material with high thermal conductivity by electrophoresis, and the interface bonding gap between the modified graphene oxide and the copper alloy matrix is significantly reduced, but it is still not completely eliminated. In addition, most carbon reinforcement phases are difficult to disperse into metal crystals, especially nanocrystals, and cannot play a greater role in strengthening and toughening, as well as taking into account electrical conductivity and thermal stability. The patent document with announcement number CN110408969A discloses a method for preparing a high thermal conductivity copper-based graphene composite material by electrodeposition. From its TEM image, no graphene reinforcement was found to be distributed in the crystal, and the effect of improving tensile strength and thermal conductivity was not significant enough.

[0004] Therefore, to solve the above problems and invent a new method for preparing carbon-reinforced metal matrix composites, enabling the composites to balance strength, plasticity, electrical conductivity, and thermal stability, is of positive significance to the field of metal material development and preparation. Summary of the Invention

[0005] The purpose of the present invention is to provide a conductive copper-based nano-carbon composite material and a preparation method thereof for the above-mentioned urgent problems to be solved.

[0006] To achieve the above purpose, the present invention can be realized through the following solutions:

[0007] The present invention provides a preparation method of a conductive copper-based nano-carbon composite material, and the preparation method includes the following steps:

[0008] S1. Add flaky copper powder into a solvent for dispersion to obtain a Cu dispersion liquid, and add a surfactant into the Cu dispersion liquid for modification to obtain a modified Cu dispersion liquid;

[0009] S2. Add GO into a solvent for dispersion to obtain a GO dispersion liquid, and add a surfactant into the GO dispersion liquid for modification to obtain a modified GO dispersion liquid;

[0010] S3. Add the modified GO dispersion liquid in step S2 into the modified Cu dispersion liquid in step S1, mix and stir to make the surface of the copper powder adsorb GO, filter and dry to obtain GO-Cu composite flaky powder;

[0011] S4. Place the GO-Cu composite flaky powder in a heater to raise the temperature for a reduction reaction, keep the temperature during the reaction, and after the reaction ends, wait for the temperature to drop to room temperature, turn off the gas and discharge the material to obtain RGO-Cu composite powder of reduced graphene oxide and copper flakes;

[0012] S5. Perform ball milling treatment and densification treatment on the RGO-Cu composite powder to obtain the conductive copper-based nano-carbon composite material.

[0013] The preparation steps of the flaky copper powder in step S1 are as follows:

[0014] Put spherical copper powder with a particle size of 1-10 μm into a ball milling tank, and add absolute ethanol as a process control agent for ball milling; wherein, the ball-to-material ratio is 20:1, the ball milling speed is 200-400 rpm, and the ball milling time is 4-8 h.

[0015] Further, step S1 is specifically as follows: Stir and disperse flaky copper powder in an aqueous solution, add dodecyl trimethyl ammonium bromide as a cationic surfactant for modification, and stir for 2 - 3 h to prepare a modified Cu dispersion; wherein the mass ratio of Cu, water, and dodecyl trimethyl ammonium bromide is 200 - 300:1000 - 1200:15 - 20.

[0016] Step S2 is specifically as follows: Ultrasonically disperse GO with a sheet diameter of 0.5 - 1 μm in an aqueous solution under an ice bath, add sodium dodecyl benzene sulfonate as an anionic surfactant for modification, and ultrasonically modify for 2 - 3 h. The mass ratio of GO, water, and sodium dodecyl benzene sulfonate is 1 - 2:500:1 - 5.

[0017] Step S4 is specifically as follows: Place the GO-Cu composite flaky powder in a tubular furnace, introduce a hydrogen-argon mixed gas into the furnace, with a mixed gas flow rate of 40 - 50 mL / min and a hydrogen ratio of 20 - 30 vol.%, until all the air in the furnace is replaced, then raise the temperature to 400 - 450 °C, hold the temperature for reaction for 1 - 2 h. After the reaction is completed, wait for the temperature to drop to room temperature, turn off the gas and discharge the material to obtain the RGO-Cu composite powder.

[0018] Step S5 is specifically as follows: Put the RGO-Cu composite powder into a ball milling tank for ball milling, with a ball-to-material ratio of 10:1, a ball milling speed of 200 - 400 rpm, and a ball milling time of 4 - 8 h; put the ball-milled RGO-Cu composite powder into a compact and cold press it into shape under an argon atmosphere, with a pressure of 100 - 300 MPa to obtain an RGO-Cu cold-pressed compact; further vacuum and hot press the RGO-Cu cold-pressed compact at 300 - 500 °C, with a hot press pressure of 500 - 600 Mpa, and hold the pressure for 1 - 2 h to obtain the conductive copper-based nanocarbon composite material.

[0019] The conductive copper-based nanocarbon composite material prepared by the above method also belongs to the protection scope of the present invention.

[0020] The application of the described conductive copper-based nanocarbon composite material in the fields of electricity conduction and heat conduction also belongs to the protection scope of the present invention.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention uses pre-prepared flaky copper powder. The flaky copper powder has a large specific surface area, a small thickness, strong electrostatic adsorption and many adsorption sites, and is compatible with flaky GO in structure, which is beneficial to the adsorption of GO. GO is used as a nano-carbon precursor, and its rich hydrophilic effect and negative charge characteristics are utilized to achieve spontaneous dispersion and adsorption, avoiding agglomeration. The surfactant is beneficial to the further uniform adsorption of GO on the copper sheet surface. The surface of RGO after high-temperature hydrogen reduction is rich in defects, generating strong electrostatic interaction with the Cu surface, which not only increases the interfacial energy and promotes its embedding into the crystal grains, but also avoids the slip and accumulation of the reinforcement during the subsequent ball milling process. In addition, due to the relatively large number of defects in RGO and its relatively low fracture strength, it is easy to fracture and fragment into nano-carbon during the ball milling process and enter the interior of Cu nanocrystals.

[0023] (2) The conductive copper-based nano-carbon composite material provided by the present invention has excellent yield strength (890 ± 21 MPa, 35% higher than that of nanocrystalline pure copper) and tensile plasticity (total tensile elongation is 13.3% ± 0.9%, 111% higher than that of nanocrystalline pure copper); it has excellent thermal stability, and there is no grain coarsening phenomenon at 0.64Tm (T m is the melting point), which is much higher than the recrystallization coarsening temperature of general nanocrystalline pure copper (~0.3T m ); in addition, the composite material has excellent electrical conductivity, and its electrical conductivity (41.8×10 6 S m -1 ) is nearly 40% higher than that of nanocrystalline pure copper (~30×10 6 S m -1 ).

[0024] (3) The method of the present invention has a relatively low cost and a relatively simple process flow, and has a certain universality for the composite of other metal-based materials, and can well achieve the effective dispersion of nano-carbon reinforcement in the interior of nanocrystals, greatly improving the comprehensive performance of metal materials. Brief Description of the Drawings

[0025] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objectives and advantages of the present invention will become more obvious:

[0026] Figure 1 It is the scanning transmission electron microscope image (STEM) of the copper-based nano-carbon composite material obtained in Example 2 of the present invention;

[0027] Figure 2 It is the atom probe tomography image (APT) of the copper-based nano-carbon composite material obtained in Example 2 of the present invention;

[0028] Figure 3 It is the statistical chart of the distribution of nano-carbon reinforcement in Example 2 of the present invention;

[0029] Figure 4 It is a comparison chart of the tensile curves of the materials in Example 1, Example 2 and the comparative example;

[0030] Figure 5 This is the percentage of the area occupied by grains of different scales of the copper-based nanocarbon composite material obtained in Example 2 of the present invention and the materials in the comparative example at different temperatures;

[0031] Table 1 is a statistical table of the electrical conductivities of the materials in Example 2 and the comparative example. Detailed implementation manners

[0032] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. 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. These all belong to the protection scope of the present invention.

[0033] The conductive copper-based nanocarbon composite material and preparation method described in the present invention include the following steps:

[0034] (1) Respectively perform surface modification on flaky copper powder (Cu) and graphene oxide (GO), mix and stir them in an aqueous solution according to a certain ratio, so that GO is uniformly adsorbed on the surface of the copper powder, and after completion, filter and dry to obtain GO-Cu composite flaky powder;

[0035] (2) Place the GO-Cu composite flaky powder in a tubular furnace, introduce a hydrogen-argon mixed gas into the furnace until all the air in the furnace is replaced, then raise the temperature for reduction and hold the reaction, and after the reaction ends, wait for the temperature to drop to room temperature, turn off the gas and discharge the material to obtain a composite powder RGO-Cu of reduced graphene oxide (RGO) and copper flakes;

[0036] (3) Perform ball milling treatment on the above RGO-Cu composite powder and further densification processes such as cold pressing and hot pressing to obtain a conductive copper-based nanocarbon composite material.

[0037] Example 1

[0038] In this example, a (0.4 vol%)-Cu conductive copper-based nanocarbon composite material was prepared, and the preparation method is as follows:

[0039] 1. Put spherical copper powder with a particle size of 1 μm into a ball milling tank, add absolute ethanol as a process control agent for ball milling, the ball-to-material ratio is 20:1, the ball milling speed is 352 rpm, and the ball milling time is 4 h; the flaky copper powder (Cu) obtained after ball milling is recovered after vacuum drying at 60 °C for 24 h.

[0040] 2. Stir and disperse 200 g of flaky copper powder Cu (flake diameter about 30 μm, thickness about 0.5 μm) prepared in step 1 in 1000 mL of aqueous solution, add 15 g of dodecyltrimethylammonium bromide as a cationic surfactant for modification, and stir for 2 h to obtain a modified Cu dispersion.

[0041] 3. Ultrasonically disperse 144 mg of GO with a diameter of 0.5 - 1 μm in an ice bath in 500 mL of aqueous solution, add 2 g of sodium dodecylbenzenesulfonate as an anionic surfactant for modification, and ultrasonically modify for 2 h to obtain a modified GO dispersion.

[0042] 4. Add 500 mL of 0.3 mg / mL modified GO aqueous dispersion prepared in step 3 to 1000 mL of 0.2 g / mL modified Cu aqueous dispersion prepared in step 2, mix and stir to make GO uniformly adsorbed on the surface of Cu. The stirring time is 24 h, the rotation speed of the stirring rod is 400 rpm, and after adsorption, vacuum dry at 60 °C for 24 h to obtain GO-Cu composite flaky powder.

[0043] 5. Place the GO-Cu composite flaky powder in a tubular furnace, introduce a hydrogen-argon mixed gas (flow rate 40 mL / min, hydrogen ratio 20 vol.%) into the furnace until all the air in the furnace is replaced, then raise the temperature to 400 °C, keep the temperature for 1 h, and after the reaction is completed, wait for the temperature to drop to room temperature, turn off the gas and discharge the material to obtain RGO-Cu composite powder.

[0044] 6. Put the above RGO-Cu composite powder into a ball mill for ball milling, the ball-to-material ratio is 10:1, the ball milling speed is 300 rpm, and the ball milling time is 8 h; put the ball-milled RGO-Cu composite powder into a 40 mm green compact and cold press it under an argon atmosphere at a pressure of 200 MPa to obtain an RGO-Cu cold-pressed green compact.

[0045] 7. Further hot press the RGO-Cu cold-pressed green compact under vacuum (0.01 Pa) at 300 °C, the hot press pressure is 600 Mpa, and keep the pressure for 1 h to obtain a conductive copper-based nanocarbon composite material (0.4 vol%)-Cu.

[0046] Example 2

[0047] This example prepared a conductive copper-based nanocarbon composite material (0.8 vol%)-Cu, and the preparation method is as follows:

[0048] 1. Put spherical copper powder with a particle size of 1 μm into a ball mill, add absolute ethanol as a process control agent for ball milling, the ball-to-material ratio is 20:1, the ball milling speed is 352 rpm, and the ball milling time is 4 h. The flaky copper powder (Cu) obtained after ball milling is recovered after vacuum drying at 60 °C for 24 h.

[0049] 2. Stir and disperse 200 g of flaky copper powder Cu (flake diameter about 30 μm, thickness about 0.5 μm) prepared in Step 1 in 1000 mL of aqueous solution, add 15 g of dodecyltrimethylammonium bromide as a cationic surfactant for modification, and stir for 2 h to prepare a modified Cu aqueous dispersion.

[0050] 3. Ultrasonically disperse 289 mg of GO with a flake diameter of 0.5 - 1 μm in an ice bath in 500 mL of aqueous solution, add 4 g of sodium dodecylbenzenesulfonate as an anionic surfactant for modification, and ultrasonically modify for 2 h to prepare a GO aqueous dispersion modified with sodium dodecylbenzenesulfonate.

[0051] 4. Add 500 mL of the modified GO aqueous dispersion with a concentration of 0.6 mg / mL prepared in Step 3 to 1000 mL of the modified Cu aqueous dispersion with a concentration of 0.2 g / mL prepared in Step 2, mix and stir to make GO uniformly adsorbed on the surface of Cu. The stirring time is 24 h, the rotation speed of the stirring rod is 400 rpm, and after adsorption, vacuum dry at 60 °C for 24 h to obtain GO-Cu composite flaky powder.

[0052] 5. Place the GO-Cu composite flaky powder in a tubular furnace, introduce a hydrogen-argon mixed gas (flow rate 40 mL / min, hydrogen ratio 20 vol.%) into the furnace until all the air in the furnace is replaced, then raise the temperature to 400 °C, keep the temperature for 1 h, wait for the temperature to drop to room temperature after the reaction, turn off the gas and discharge the material to obtain RGO-Cu composite powder.

[0053] 6. Put the above RGO-Cu composite powder into a ball mill for ball milling, the ball-to-material ratio is 10:1, the ball milling rotation speed is 300 rpm, and the ball milling time is 8 h. Put the ball-milled RGO-Cu composite powder into a 40 mm compact and cold press it into shape under an argon atmosphere with a pressure of 200 MPa to obtain an RGO-Cu cold-pressed compact.

[0054] 7. Further hot press the RGO-Cu cold-pressed compact in a vacuum (0.01 Pa) at 300 °C, with a hot pressing pressure of 600 MPa and a holding pressure of 1 h to obtain a conductive copper-based nanocarbon composite material (0.8 vol%)-Cu.

[0055] Comparative Example 1

[0056] A nanocrystalline pure copper material was prepared in this comparative example, and the preparation method is as follows:

[0057] Replace the RGO-Cu composite powder with 1μm spherical copper powder, that is: put 1μm spherical copper powder into the ball mill for ball milling, the ball-to-material ratio is 10:1, the ball milling speed is 300rpm, and the ball milling time is 8h. Put the ball-milled pure copper powder into a 40mm green compact and cold press it into shape under an argon atmosphere with a pressure of 200MPa. Further hot press the pure copper cold-pressed green compact in vacuum (0.01Pa) at 300°C, with a hot press pressure of 600Mpa and a holding pressure of 1h to obtain a nanocrystalline pure copper material (nc-Cu).

[0058] Performance testing

[0059] The high-angle annular dark-field scanning transmission electron micrograph of the conductive copper-based nanocarbon composite material ((0.8vol%)-Cu) described in Example 2 of the present invention. Figure 1 ) shows that the near-spherical nanocarbon particles with a high-density distribution are evenly dispersed inside the Cu nanocrystals. The statistical results Figure 3 ) show that the average particle size of the nanocarbon nanoparticles is 2.6±1.2nm, and about 92% of the particles are located inside the grains. It shows that by using the method of the present invention, the uniform dispersion of the nanocarbon reinforcement phase inside the grains can be effectively achieved. The atom probe tomography image of the copper-based nanocarbon composite material Figure 2 ) further confirms the analysis results of the scanning transmission electron microscope, showing that the average particle size of the nanocarbon nanoparticles is 2.5±1.2nm.

[0060] The tensile test of the high strength and high plasticity performance described in the present invention uses a tensile specimen processed by focused ion beam (FIB) on an in-situ micro / nano mechanical testing machine (Nanoflip, ) to perform a room temperature tensile test. The tensile strain rate is 5×10 -4 s -1 , the tensile width of the tensile specimen is 1.3μm, the tensile length is about 4μm, and the specimen thickness is 1.3μm. Analyze the tensile properties of each material (Example 1, Example 2 and Comparative Example), see Figure 4 . The yield strength of the nanocrystalline pure copper material is 660±28MPa, the tensile strength is 776±21MPa, and the total tensile elongation is 6.3%±0.4%; while the yield strengths of the copper-based composite materials reinforced with 0.4vol.% and 0.8vol.% nanocarbon are 765±32MPa and 890±21MPa respectively, the tensile strengths are 995±11MPa and 1,252±22MPa respectively, and the total tensile elongations are 11.2±0.8% and 13.3%±0.9% respectively; compared with the nanocrystalline pure copper material, the mechanical properties of the copper-based nanocarbon composite material are significantly improved.

[0061] The high thermal stability performance described in the present invention is to heat the copper-based nanocarbon composite material in Example 1 to 0.72T m (T mWhen the melting point) still shows no obvious grain coarsening phenomenon, see Figure 5 . Compared with nanocrystalline pure copper (recrystallization coarsening temperature ~ 0.3T m ), its thermal stability is greatly improved and exceeds the highest reported recrystallization coarsening temperature of nanocrystalline copper, 0.45T m .

[0062] The copper-based nano-carbon composite material described in the present invention has excellent electrical conductivity. The electrical conductivity of the composite material in Example 1 was measured using an eddy current meter (Fischer, SMP10), as shown in Table 1. Its electrical conductivity (41.8 ± 1.7 × 10 6 S m -1 ) is nearly 40% higher than that of nanocrystalline pure copper (27.8 ± 1.2 × 10 6 S m -1 ).

[0063] Table 1

[0064] nc-Cu (0.8 vol.%)-Cu <![CDATA[Conductivity (S m -1 )]]> <![CDATA[27.8±1.2×10 6 > <![CDATA[41.8±1.7×10 6 >

[0065] The results of the examples provided by the present invention show that the copper-based nano-carbon composite material prepared by the method described in the present invention has excellent strength, plasticity, thermal stability and electrical conductivity, and has broad application prospects.

[0066] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A preparation method of a conductive copper-based nano-carbon composite material, characterized in that, The preparation method comprises the following steps: S1. Add flaky copper powder into a solvent for dispersion to obtain a Cu dispersion, and add a surfactant into the Cu dispersion for modification to obtain a modified Cu dispersion; S2. Add GO into a solvent for dispersion to obtain a GO dispersion, and add a surfactant into the GO dispersion for modification to obtain a modified GO dispersion; S3. Add the modified GO dispersion obtained in step S2 into the modified Cu dispersion obtained in step S1, mix and stir to enable GO to be adsorbed on the surface of the copper powder, filter and dry to obtain GO-Cu composite flaky powder; S4. Place the GO-Cu composite flaky powder in a tubular furnace, introduce a hydrogen-argon mixed gas into the furnace, with the mixed gas flow rate of 40-50 mL / min and the hydrogen proportion of 20-30 vol.%, until all the air in the furnace is displaced, then raise the temperature to 400-450 °C, keep the temperature for reaction for 1-2 h, wait for the temperature to drop to room temperature after the reaction ends, turn off the gas and discharge the material to obtain RGO-Cu composite powder; S5. Put the RGO-Cu composite powder into a ball milling tank for ball milling, with the ball-to-material ratio of 10:1, the ball milling rotation speed of 200-400 rpm and the ball milling time of 4-8 h; put the ball-milled RGO-Cu composite powder into a compact and cold press it into shape under an argon atmosphere, with the pressure of 100-300 MPa to obtain an RGO-Cu cold-pressed compact; further vacuumize and hot press the RGO-Cu cold-pressed compact at 300-500 °C, with the hot press pressure of 500-600 Mpa and keep the pressure for 1-2 h to obtain the conductive copper-based nanocarbon composite material; The preparation steps of the flaky copper powder in step S1 are as follows: Put spherical copper powder with a particle size of 1-10 μm into a ball milling tank, and add absolute ethanol as a process control agent for ball milling; wherein, the ball-to-material ratio is 20:1, the ball milling rotation speed is 200-400 rpm, and the ball milling time is 4-8 h.

2. The preparation method according to claim 1, characterized in that, Step S1 specifically is: Stir and disperse the flaky copper powder in an aqueous solution, add dodecyl trimethyl ammonium bromide as a cationic surfactant for modification, and stir for a modification time of 2-3 h to prepare a modified Cu dispersion; wherein the mass ratio of Cu, water and dodecyl trimethyl ammonium bromide is 200-300:1000-1200:15-20.

3. The preparation method according to claim 1, characterized in that, Step S2 specifically is: Ultrasonically disperse GO with a sheet diameter of 0.5-1 μm in an aqueous solution under ice bath, add sodium dodecyl benzene sulfonate as an anionic surfactant for modification, and ultrasonically modify for 2-3 h, wherein the mass ratio of GO, water and sodium dodecyl benzene sulfonate is 1-2:500:1-5.

4. The conductive copper-based nanocarbon composite material prepared by the preparation method according to any one of claims 1-3.

5. The application of the conductive copper-based nanocarbon composite material according to claim 4 in the fields of electricity conduction and heat conduction.

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