A method for preparing high-performance structured nano-carbon / aluminum composite material

Abstract

The present invention discloses a method for preparing a high-performance structured nanocarbon / aluminum composite material, belonging to the technical field of composite material preparation. The method combines structured carbon nanomaterials and aluminum powder by variable-speed ball milling, followed by sintering, hot extrusion, and subsequent heat treatment to produce a highly dense, strongly bonded structured nanocarbon / aluminum composite material. The structured nanocarbon / aluminum composite material exhibits high strengthening efficiency and excellent strength-ductility synergy.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material preparation, and in particular relates to a method for preparing a high-performance structured nano-carbon / aluminum composite material. Background Art

[0002] Aluminum metal is widely used in aerospace, automotive and other fields due to its low density, high strength and good corrosion resistance. However, due to the low melting point and poor high-temperature heat resistance of pure aluminum and its alloys, it is gradually unable to meet the increasing performance requirements of aluminum in modern industrial society. Compared with traditional aluminum alloys, aluminum-based composites fully combine the respective advantages of the reinforcement phase and the matrix to achieve complementary performance, thereby exhibiting excellent comprehensive properties such as high specific strength / stiffness, thermal stability, wear resistance, and radiation resistance. At present, aluminum-based composites have been regarded as a strong competitor for the next generation of advanced structural materials. When preparing aluminum-based composites, the intrinsic properties (size, dimension, structure, specific surface area, etc.), distribution characteristics, and interface structure of the reinforcement phase are crucial to the mechanical properties (strength and ductility) of the composite material. A large number of studies have shown that the improvement of the strength of composite materials always comes at the expense of ductility. Therefore, how to give full play to the intrinsic strengthening effect of the reinforcement phase and break the strength-ductility contradiction of composite materials has long been the focus of researchers.

[0003] Patent CN109161709B discloses a method for preparing a cracked carbon nanotube-reinforced copper-based composite material. The method comprises preparing a precursor of cracked carbon nanotubes and copper acetate, and then filtering, drying, annealing, SPS sintering, hot extrusion and annealing to obtain the cracked carbon nanotube-reinforced copper-based composite material. The method improves the strength of the composite material while taking into account the plasticity of the material, so that the composite material obtains good comprehensive mechanical properties. However, the chemical reduction method used in the patent to prepare the cracked carbon nanotube / copper composite powder process has complex process, high cost, long cycle, and is not suitable for large-scale production of composite powder. In addition, the cracked carbon nanotube / copper composite material reinforcement phase obtained by the patent is only a single strengthening phase, which has limited effect on improving the performance of the composite material. In addition, the cracked carbon nanotubes are easily distributed at the grain boundaries and will not be able to fully interact with dislocations, resulting in limited work hardening ability of the composite material. At the same time, the composite interface is only a covalently modified interface, which cannot fully guarantee strong interfacial bonding. Summary of the Invention

[0004] In view of the shortcomings of the above-mentioned prior art, the present invention proposes a method for preparing a high-performance structured nano-carbon / aluminum composite material. The present invention adopts a variable speed ball milling method to prepare structured nano-carbon / aluminum powder, which has the characteristics of simple process, low cost, short cycle, etc., and is suitable for large-scale production of composite powders. In addition, the structured nano-carbon of the present invention reacts with the aluminum matrix to form two types of nano-sized aluminum carbide (Al4C3) in situ, intracrystalline and interfacial, which not only greatly improves the interface bonding, but also the nano-carbon and the in-situ Al4C3 composite reinforcement show a synergistic strengthening effect.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing a high-performance structured nano-carbon / aluminum composite material comprises the following steps:

[0006] (1) performing variable speed ball milling on the structured carbon nanomaterial, aluminum powder, and stearic acid to obtain a composite powder;

[0007] (2) When the structured carbon nanomaterial is a GNR material, the composite powder is sequentially subjected to cold pressing, pressureless sintering, and hot extrusion to obtain a high-performance structured nanocarbon / aluminum composite material;

[0008] When the structured carbon nanomaterial is a CNT-GNR hybrid material, the composite powder is sequentially subjected to cold pressing, spark plasma sintering, hot extrusion, and heat treatment to obtain a high-performance structured nanocarbon / aluminum composite material;

[0009] The heating rate of the heat treatment is 10°C / min; the heat treatment time is 10 to 50 minutes; and the heat treatment temperature is 550 to 650°C.

[0010] As a preferred embodiment of the present invention, the structured carbon nanomaterial is a CNT-GNR hybrid material or a GNR material.

[0011] The CNT-GNR hybrid material is a mixture of CNT material and GNR material.

[0012] The CNT material is carbon nanotube, and the GNR material is graphene nanoribbon.

[0013] More preferably, the CNT-GNR hybrid material is a mixed material of quasi-one-dimensional "leaf-shaped" CNT material and GNR material.

[0014] As a preferred embodiment of the present invention, the preparation method of the structured carbon nanomaterial includes: placing the CNT material in a mixed solution of concentrated sulfuric acid and concentrated phosphoric acid and ultrasonicating it, then adding potassium permanganate under ice bath conditions, then heating it to 50-90°C for reaction, and finally centrifuging, washing, and thermally reducing it to obtain the structured carbon nanomaterial.

[0015] As a preferred embodiment of the present invention, the CNT material is multi-walled carbon nanotubes with a purity of more than 95%.

[0016] As a preferred embodiment of the present invention, the volume ratio of concentrated sulfuric acid to concentrated phosphoric acid is 5:1 to 9:1; the mass volume concentration of CNTs in the mixed solution of concentrated sulfuric acid and concentrated phosphoric acid is 1 to 4 g / L; and the mass ratio of potassium permanganate to CNTs is 3:1 to 7:1.

[0017] As a preferred embodiment of the present invention, when the mass ratio of potassium permanganate to CNT is 3:1 to 5:1, a CNT-GNR hybrid material is generated; when the mass ratio of potassium permanganate to CNT is 6:1 to 7:1, a GNR material is generated.

[0018] As a preferred embodiment of the present invention, the product after the reaction with potassium permanganate is placed in ice containing 5 vol.% H2O2 and cooled; the cooled reaction product is centrifuged and washed, the supernatant is removed by centrifugation, and it is diluted with 1 mol / L dilute HCl and then centrifuged and washed again, and this cycle is repeated until the sulfate ions are completely removed. After sufficient freeze-drying and thermal reduction, a structured carbon nanomaterial is obtained.

[0019] As a preferred embodiment of the present invention, the centrifugal speed is 6000-10000 r / min, the thermal reduction temperature is 350-600°C, the heating rate is 0-10°C / min, the thermal reduction time is 0.5-2h, and the thermal reduction gas is a mixture of argon and hydrogen.

[0020] As a preferred embodiment of the present invention, the average particle diameter of the aluminum powder is 1 to 20 μm, and the volume fraction of the structured carbon nanomaterial is 1.5%.

[0021] As a preferred embodiment of the present invention, the stearic acid accounts for 0.4% to 1% of the total weight of the structured carbon nanomaterial, aluminum powder and stearic acid.

[0022] As a preferred embodiment of the present invention, the variable speed ball milling process has a low speed ball milling stage with a rotation speed of 200-250 rpm and a time of 6-10 hours, and a high speed ball milling stage with a rotation speed of 400-500 rpm and a time of 0.5-1 hour. Variable speed ball milling can not only fully ensure the uniform dispersion of the structured nanocarbon, but also the lower ball milling energy can avoid serious damage to the structure of the structured nanocarbon. First, low energy ball milling grinds the spherical Al powder into flaky powder and promotes the initial dispersion of nanocarbon on the surface of the flaky Al powder; high energy ball milling further promotes the micro-cold welding of the flaky aluminum powder into large particles stacked in layers, ultimately achieving uniform dispersion of nanocarbon.

[0023] As a preferred embodiment of the present invention, during the variable speed ball milling, the ball-to-material ratio is 15:1-20:1, the mass ratio of large balls to small balls is 1:2, the diameter of the large balls is 8-12 mm, and the diameter of the small balls is 4-6 mm, and the variable speed ball milling is carried out under argon.

[0024] As a preferred embodiment of the present invention, the ball-milled composite powder is placed in a steel mold with a diameter of 20 mm and cold-pressed at a pressure of 600 MPa for a holding time of 3 minutes to obtain a green body of a structured nano-carbon / aluminum composite material.

[0025] As a preferred embodiment of the present invention, the sintering method is pressureless or spark plasma sintering; the spark plasma sintering temperature is 450-550°C, the vacuum degree is lower than 5 Pa, the heating rate is 10-100°C / min, and the holding time is controlled to be 20-60min; the pressureless sintering is carried out in an argon atmosphere, and during sintering, the heating rate is 10°C / min, the sintering temperature is 530-580°C, and the sintering time is 1h.

[0026] As a preferred embodiment of the present invention, the hot extrusion temperature is 350-550° C., the extrusion ratio is 10:1-16:1, and the hot extrusion pressure is 400-600 MPa.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention uses a structured carbon nanomaterial to composite with aluminum powder. On the one hand, the structured carbon nanomaterial has high chemical activity and a large number of active carbon atoms at its edges, which allows for mutual diffusion and in-situ interface reaction with the matrix, thereby improving the interface bonding strength of the composite material. On the other hand, the structured carbon nanomaterial has a large specific surface area, which improves the grain refinement and load transfer capacity of the composite material, thereby improving the strengthening efficiency of the reinforcement. The structured carbon nanomaterial with a large specific surface area is conducive to improving the storage of dislocations and introducing an external toughening effect, thereby improving the ductility of the composite material.

[0029] (2) The present invention adopts the method of variable speed ball milling to achieve uniform dispersion of the reinforcing phase, thereby ensuring the structural integrity of the structured carbon nanomaterial. At the same time, different processes are adopted for different structured carbon materials to regulate the interface reaction of the composite material, so that the interface of the composite material has a high number density of nano-sized Al4C3, which effectively improves the interface bonding strength and interface plastic stability, improves the strengthening efficiency of the reinforcing phase and ensures the strength-ductility synergy of the composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1The SEM morphology image (left) of the structured carbon nanophase / aluminum composite powder prepared in Example 1 of the present invention after low-energy ball milling, the low-magnification SEM morphology image (middle) and the high-magnification SEM morphology image (right) after high-energy ball milling.

[0031] Figure 2 TEM image of the high-performance structured nano-carbon / aluminum composite material prepared in Example 1 of the present invention (the arrow in the left image is Al4C3) and the Al4C3 size statistics diagram (right image).

[0032] Figure 3 TEM image of the high-performance structured nano-carbon / aluminum composite material prepared in Example 4 of the present invention (the arrow in the left image is Al4C3) and the Al4C3 size statistics diagram (right image).

[0033] Figure 4 TEM image of the structured nano-carbon (left picture) and the structured nano-carbon / aluminum composite material (right picture) prepared in Comparative Example 1 of the present invention.

[0034] Figure 5 This is a TEM image of the carbon nanotube / aluminum composite material prepared in Comparative Example 2 of the present invention, where the marked area is Al4C3. DETAILED DESCRIPTION

[0035] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0036] Example 1

[0037] A method for preparing a high-performance structured nano-carbon / aluminum composite material, comprising the following steps:

[0038] (1) 0.5 g of graphitized CNTs were placed in 134 ml of a concentrated H2SO4 / H3PO4 (volume ratio 9:1) mixed solution and ultrasonically dispersed for 1 h. The concentration of graphitized CNTs was 3.7 g / L.

[0039] (2) The solution in step (1) was placed in a constant temperature magnetic stirring water bath and ice bathed for 15 minutes, with continuous magnetic stirring during the ice bath. After the ice bath was completed, 1.5 g of oxidant KMnO4 was slowly added. By controlling the temperature and time in the water bath, the graphitized CNTs were subjected to oxidative exfoliation reaction. The reaction product was placed in 240 ml of ice containing 5 vol.% H2O2 and cooled. The cooled reaction product was then centrifuged at 8000 rpm for 8 minutes. After the centrifugation was completed, the supernatant was skimmed off and diluted with 1 mol / L dilute HCl, and then centrifuged again. This cycle was repeated 7 times until the sulfate ions were completely removed. After sufficient freeze drying and thermal reduction, the structured carbon nanomaterial was obtained. The thermal reduction was carried out in an Ar-5 vol% H2 atmosphere at 500°C, with a heating rate of 10°C / min and a reduction time of 1 hour.

[0040] (3) 0.154 g of the structured nanocarbon material prepared in step (2) was mixed with 12 g of spherical aluminum powder (average particle diameter of about 20 μm) and placed in a 250 ml ball mill. Subsequently, 240 g of mixed steel balls (large ball diameter: 10 mm, small ball diameter: 6 mm, mass ratio of 1:2) were added to the ball mill as a ball milling medium, i.e., a ball-to-material ratio of 20:1. 0.048 g of stearic acid was added as a process control agent (mass fraction of about 0.4%). Argon was then filled into the ball mill as a protective gas and the ball mill was sealed. The sealed ball mill was subjected to low-speed ball milling at a ball milling speed of 200 rpm for 8 h; then to high-speed ball milling at a high-speed ball milling speed of 400 rpm for 1 h. The ball-milled composite powder was placed in a steel mold with a diameter of 20 mm and cold-pressed at a pressure of 600 MPa for a holding time of 3 minutes to obtain a green body of a structured carbon nanophase / aluminum composite material.

[0041] (4) The green body prepared in step (3) is subjected to spark plasma sintering. During sintering, the heating rate is set to 50°C / min, the sintering temperature is 550°C, the sintering time is 20 min, and the vacuum degree during sintering is less than 5 Pa; then, the sintered composite material is subjected to hot extrusion, the hot extrusion temperature is set to 550°C, and the extrusion ratio is 16:1.

[0042] (5) The composite material extruded in step (4) was subsequently heat treated, and the interface structure of the composite material was further regulated by using a heat treatment process. The heat treatment was carried out in a box furnace with specific process parameters: heat treatment temperature of 600°C, heat treatment time of 30 min, and heating rate of 10°C / min, and finally a structured nano-carbon / aluminum composite material was obtained.

[0043] The morphology of the structured carbon nanophase / aluminum composite powder prepared by the variable speed ball milling method in this embodiment is as follows: Figure 1As shown in the figure, after low-speed ball milling, the powder turns into flaky Al powder, and the carbon nanophase is evenly distributed on the surface of the flaky Al powder; after the high-speed ball milling stage, the composite powder undergoes micro-cold welding under the strong impact of the steel ball, and the flaky Al powder is continuously assembled and stacked with each other, so that the thickness and diameter of the composite powder continue to increase, and it is transformed into irregular granular Al powder with a size of about 100μm, which is conducive to the subsequent powder densification. The microstructure of the structured nanocarbon / aluminum-based composite material is shown in the figure. Figure 2 As shown in the figure, it can be seen that the configured carbon nanomaterial is a semi-open "leaf-shaped" CNT-GNR hybrid structure, and a high-density nanorod-like Al4C3 phase (average length of about 53nm) is found at the interface of the composite material. At the same time, the CNT "midrib" part of the CNT in the CNT-GNR is well maintained, and the interfacial reaction does not seriously damage the integrity of the nanocarbon structure. A good coherent / semi-coherent interface is formed between Al4C3 and the Al matrix, further improving the interfacial bonding strength and interfacial plastic stability. Mechanical property tests show that under this process condition, the yield strength of the CNT-GNR / Al composite material is 237MPa, the tensile strength is 284MPa, the elongation at break is 13.8%, and the nanocarbon strengthening efficiency is 50.

[0044] Example 2

[0045] A method for preparing a high-performance structured nano-carbon / aluminum composite material, comprising the following steps:

[0046] (1) 0.5 g of graphitized CNTs were placed in 200 ml of a concentrated H2SO4 / H3PO4 (volume ratio 5:1) mixed solution and ultrasonically dispersed for 2 h. The concentration of graphitized CNTs was 1 g / L.

[0047] (2) The solution in step (1) was placed in a constant temperature magnetic stirring water bath and ice bathed for 15 minutes, with continuous magnetic stirring during the ice bath. After the ice bath was completed, 2.5g of oxidant KMnO4 was slowly added. By controlling the temperature and time in the water bath, the graphitized CNTs were subjected to oxidative exfoliation reaction. The reaction product was placed in 240ml of ice containing 5vol% H2O2 and cooled. The cooled reaction product was then centrifuged and washed at a speed of 6000rpm for 8 minutes. After the centrifugation was completed, the supernatant was skimmed off and diluted with 1mol / L dilute HCl, and then centrifuged and washed again. This cycle was repeated 7 times until the sulfate ions were completely removed. After sufficient freeze drying and thermal reduction, the structured carbon nanomaterial was obtained. The thermal reduction was carried out in an Ar-5vol% H2 atmosphere at 350℃, with a heating rate of 10℃ / min and a reduction time of 2h.

[0048] (3) 0.154 g of the structured nanocarbon material prepared in step (2) was mixed with 12 g of spherical aluminum powder (average particle diameter of about 20 μm) and placed in a 250 ml ball mill, wherein the volume fraction of the structured nanocarbon was 1.5%. Subsequently, 240 g of mixed steel balls (large ball diameter: 10 mm, small ball diameter: 6 mm, mass ratio of 1:2) were added to the spherical ink tank as a ball milling medium, i.e., a ball-to-material ratio of 20:1, and 0.048 g of stearic acid was added as a process control agent (mass fraction of about 0.4%). Argon was then filled into the ball mill as a protective gas and the ball mill was sealed. The sealed ball mill was subjected to low-speed ball milling at a ball milling speed of 250 rpm for 6 h; then to high-speed ball milling at a high-speed ball milling speed of 500 rpm for 0.5 h. The ball-milled composite powder was placed in a steel mold with a diameter of 20 mm and cold-pressed at a pressure of 600 MPa for a holding time of 3 minutes to obtain a green body of a structured nano-carbon / aluminum composite material.

[0049] (4) The green body prepared in step (3) is subjected to spark plasma sintering. During sintering, the heating rate is set to 10°C / min, the sintering temperature is 450°C, the sintering time is 60 min, and the vacuum degree during sintering is less than 5 Pa; then, the sintered composite material is subjected to hot extrusion, the hot extrusion temperature is set to 550°C, the extrusion ratio is 10:1, and the hot extrusion pressure is 400 MPa.

[0050] (5) The composite material extruded in step (4) was subsequently heat treated, and the interface structure of the composite material was further regulated by using a heat treatment process. The heat treatment was carried out in a box furnace with specific process parameters as follows: heat treatment temperature of 600°C, heat treatment time of 10 min, and heating rate of 10°C / min, and finally a structured nano-carbon / aluminum composite material was obtained.

[0051] Microstructural analysis of the structured nanocarbon / aluminum composite material prepared in this example shows that the structured carbon nanomaterial still has a semi-open "leaf-like" CNT-GNR hybrid structure, and a nanorod-like Al4C3 phase exists at the interface of the composite material, similar to Example 1. Mechanical property tests show that under this process condition, the CNT-GNR / Al composite material has a yield strength of 232 MPa, a tensile strength of 289 MPa, an elongation at break of 13.6%, and a nanocarbon strengthening efficiency of 48.

[0052] Example 3

[0053] A method for preparing a high-performance structured nano-carbon / aluminum composite material, comprising the following steps:

[0054] (1) 0.5 g of graphitized CNTs were placed in 125 ml of a concentrated H2SO4 / H3PO4 (volume ratio 9:1) mixed solution and ultrasonically dispersed for 0.5 h. The graphitized CNT concentration was 4 g / L.

[0055] (2) The solution in step (1) was placed in a constant temperature magnetic stirring water bath and ice bathed for 15 minutes, with continuous magnetic stirring during the ice bath. After the ice bath was completed, 1.5g of oxidant KMnO4 was slowly added. By controlling the temperature and time in the water bath, the graphitized CNTs were subjected to oxidative exfoliation reaction. The reaction product was placed in 240ml of ice containing 5vol% H2O2 and cooled. The cooled reaction product was then centrifuged and washed at a speed of 10000rpm for 8 minutes. After the centrifugation was completed, the supernatant was skimmed off and diluted with 1mol / L dilute HCl, and then centrifuged and washed again. This cycle was repeated 7 times until the sulfate ions were completely removed. After sufficient freeze drying and thermal reduction, the structured carbon nanomaterial was obtained. The thermal reduction was carried out in an Ar-5vol% H2 atmosphere at 600℃, with a heating rate of 10℃ / min and a reduction time of 0.5h.

[0056] (3) 0.154 g of the structured nanocarbon material prepared in step (2) was mixed with 12 g of spherical aluminum powder (average particle diameter of about 10 μm) and placed in a 250 ml ball mill, wherein the volume fraction of the structured nanocarbon was 1.5%. Subsequently, 240 g of mixed steel balls (large ball diameter: 10 mm, small ball diameter: 5 mm, mass ratio of 1:2) were added to the spherical ink tank as a ball milling medium, i.e., a ball-to-material ratio of 18:1, and 0.12 g of stearic acid was added as a process control agent (mass fraction of about 1%). The volume fraction of the structured nanocarbon was 1.5%. Argon was then filled into the ball mill as a protective gas and sealed. The sealed ball mill was subjected to low-speed ball milling at a ball milling speed of 200 rpm for 10 h; then high-speed ball milling was performed at a high-speed ball milling speed of 500 rpm for 1 h. The ball-milled composite powder was placed in a steel mold with a diameter of 20 mm and cold-pressed at a pressure of 600 MPa for a holding time of 3 minutes to obtain a green body of a structured nano-carbon / aluminum composite material.

[0057] (4) The green body obtained in step (3) is subjected to hot pressing sintering. During sintering, the heating rate is set to 100°C / min, the sintering temperature is 550°C, the sintering time is 20 min, the vacuum degree is less than 5 Pa, and the sintering pressure is 100 MPa; then, the sintered composite material is subjected to hot extrusion, the hot extrusion temperature is set to 500°C, the extrusion ratio is 16:1, and the hot extrusion pressure is 600 MPa.

[0058] (5) The composite material extruded in step (4) was subsequently heat treated, and the interface structure of the composite material was further regulated by using a heat treatment process. The heat treatment was carried out in a box furnace with specific process parameters: heat treatment temperature of 630°C, heat treatment time of 50 min, and heating rate of 10°C / min, and finally a structured nano-carbon / aluminum composite material was obtained.

[0059] In the structured carbon / aluminum composite material in the present embodiment, the carbon nanomaterial is still a semi-open "leaf-shaped" CNT-GNR hybrid structure, but as the heat treatment temperature increases, the nanorod-like Al4C3 phase size at the composite interface further increases, and its average length is about 81nm, and the Al4C3 length is still within the nanoscale range. However, because relatively coarse Al4C3 is formed in the sample at a higher temperature, this reduces the mechanical properties of the composite material. Mechanical property tests show that under this process condition, the yield strength of the CNT-GNR / Al composite material is 217MPa, the tensile strength is 258MPa, the elongation at break is 13.3%, and the nano-carbon strengthening efficiency is 46.

[0060] Example 4

[0061] The preparation method of the structured nano-carbon / aluminum composite material in this embodiment is different from that in Example 1 in that:

[0062] The amount of KMnO4 added in step (2) is 3.5 g;

[0063] The average particle diameter of the aluminum powder in step (3) is 1 μm;

[0064] The sintering process of the green body prepared in step (4) is adjusted as follows: pressureless sintering is performed in an argon atmosphere, the heating rate is set to 10°C / min, the sintering temperature is 600°C, and the sintering time is 1h;

[0065] The subsequent heat treatment process of step (5) was not adopted.

[0066] In this embodiment, the microstructure of the prepared structured nano-carbon / aluminum composite material was observed by TEM. Figure 3 As shown in the figure, GNR and Al also undergo an interfacial reaction, generating a large number of nano-sized rod-shaped Al4C3 phases (average length: 64nm) at the edges of the GNR, which in turn pin the composite interface to improve its bonding strength. Mechanical property tests show that the "ribbon-like" GNR / Al composite material prepared in this example has a yield strength of 330MPa, a tensile strength of 354MPa, an elongation at break of 12.0%, and a nano-carbon reinforcement efficiency of 66.6.

[0067] Example 5

[0068] The preparation method of the structured nano-carbon / aluminum composite material in this embodiment is different from that in Example 4 in that:

[0069] During the pressureless sintering in step (4), the sintering temperature is adjusted to 580°C.

[0070] In the structured nanocarbon / aluminum composite prepared in this embodiment, the structured nanocarbon is a "ribbon-shaped" GNR. In the resulting GNR / Al composite, the GNR and Al undergo a slight interfacial reaction, generating a large number of nano-sized rod-shaped Al4C3 phases (average length: 33nm) at the edges of the GNR, thereby pinning the composite interface to improve its bonding strength. Mechanical property tests show that the "ribbon-shaped" GNR / Al composite prepared in this embodiment has a yield strength of 318MPa, a tensile strength of 346MPa, an elongation at break of 11.9%, and a nanocarbon strengthening efficiency of 63.5.

[0071] Comparative Example 1

[0072] The only difference between the preparation method of the high-performance structured nano-carbon / aluminum composite material described in this comparative example and that of Example 1 is that the subsequent heat treatment process of step (5) is not performed, and the high-performance structured nano-carbon / aluminum composite material is obtained after hot extrusion.

[0073] The microstructure of the structured carbon nanomaterial / aluminum-based composite material prepared in this comparative example was observed by TEM. Figure 4 As shown in the figure, it can be seen that the structured carbon nanomaterial is a semi-open "leaf-shaped" CNT-GNR hybrid structure. In the obtained CNT-GNR / Al composite material, the CNT-GNR structure is well maintained, and the highly chemically active GNR edge will promote the mutual diffusion of Al-C, thereby forming an interface to ensure the bonding strength. However, the interface reaction product Al4C3 phase is not obviously observed at the interface, and higher comprehensive mechanical properties cannot be obtained. Mechanical property tests show that the yield strength of the CNT-GNR / Al composite material obtained in this comparative example is 199MPa, the tensile strength is 246MPa, the uniform elongation is 6.8%, the elongation at break is 12.9%, and the nano-carbon strengthening efficiency is about 43.

[0074] Comparative Example 2

[0075] A method for preparing a nano-carbon / aluminum composite material, comprising the following steps:

[0076] (1) 0.154 g of graphitized CNTs and 12 g of spherical aluminum powder (average particle diameter of approximately 20 μm) were mixed and placed in a 250 ml ball mill, wherein the volume fraction of graphitized CNTs was 1.5%. Subsequently, 240 g of mixed steel balls (large ball diameter: 8 mm, small ball diameter: 4 mm, mass ratio of 1:2) were added to the spherical graphite mill as a ball milling medium, i.e., a ball-to-material ratio of 20:1, and 0.048 g of stearic acid was added as a process control agent (mass fraction of approximately 0.4%). The volume fraction of graphitized CNTs was 1.5%. Argon was then filled into the ball mill as a protective gas and the mill was sealed. The sealed ball mill was subjected to low-speed ball milling at a speed of 200 rpm for 8 h; then to high-speed ball milling at a speed of 400 rpm for 1 h. The ball-milled composite powder was placed in a steel mold with a diameter of 20 mm and cold-pressed at a pressure of 600 MPa for a holding time of 3 minutes to obtain a green body of a structured nano-carbon / aluminum composite material.

[0077] (2) The green body prepared in step (1) is subjected to spark plasma sintering. During sintering, the heating rate is set to 50°C / min, the sintering temperature is 550°C, the sintering time is 20 min, and the vacuum degree during sintering is less than 5 Pa; then, the sintered composite material is hot extruded, the hot extrusion temperature is set to 550°C, and the extrusion ratio is 16:1.

[0078] (3) The composite material extruded in step (2) was subsequently heat treated, and the interface structure of the composite material was further regulated by using a heat treatment process. The heat treatment was carried out in a box furnace with specific process parameters: heat treatment temperature of 600°C, heat treatment time of 30 min, and heating rate of 10°C / min, and finally a nano-carbon / aluminum composite material was obtained.

[0079] In this embodiment, the carbon nanomaterial is a CNT structure, such as Figure 5 As shown. A small amount of large-sized Al4C3 exists at the grain boundaries of the composite material. In addition, groove-shaped morphological defects are observed at the edge of Al4C3. In the CNT / Al composite material, the defects of Al4C3 further increase the brittleness of Al4C3, which is not conducive to improving the CNT-Al interface bonding strength. Mechanical property tests show that under this process condition, the composite material has a yield strength of 157MPa, a tensile strength of 215MPa, an elongation at break of 13.4%, and a nanocarbon strengthening efficiency of 28.

[0080] Comparative Example 3

[0081] The preparation method of the structured nano-carbon / aluminum composite material in this embodiment is different from that in Example 6 in that:

[0082] During the pressureless sintering in step (4), the sintering temperature is adjusted to 630°C.

[0083] In this embodiment, the structured nanocarbon prepared was a "ribbon-shaped" GNR. In the resulting GNR / Al composite, a severe interfacial reaction between the GNR and Al occurred, generating a dense, relatively large, rod-shaped Al4C3 phase (average length: 96 nm) at the edges of the GNR. This Al4C3 phase exhibited some brittle characteristics. Mechanical property tests showed that the "ribbon-shaped" GNR / Al composite prepared in this embodiment had a yield strength of 293 MPa, a tensile strength of 319 MPa, an elongation at break of 8.0%, and a nanocarbon strengthening efficiency of 32.

[0084] Comparative Example 4

[0085] The preparation method of the structured nano-carbon / aluminum composite material in this comparative example is different from that in Example 1 in that:

[0086] The amount of KMnO4 added in step (2) is 2.5 g;

[0087] The sintering process of the green body prepared in step (4) is adjusted as follows: pressureless sintering is performed in an argon atmosphere, the heating rate is set to 10°C / min, the sintering temperature is 600°C, and the sintering time is 1h;

[0088] The subsequent heat treatment process of step (5) was not adopted.

[0089] In this embodiment, the structured nanocarbon prepared is a "leaf-shaped" CNT-GNR hybrid material. The CNT-GNR and Al in the obtained CNT-GNR / Al composite material undergo a severe interfacial reaction, and a dense, relatively large-sized rod-shaped Al4C3 phase (average length: 135nm) is generated at the edge of the GNR. The Al4C3 phase of this size has shown obvious brittle characteristics. Mechanical property tests show that the CNT-GNR / Al composite material prepared in this embodiment has a yield strength of 203MPa, a tensile strength of 241MPa, an elongation at break of 9.9%, and a nanocarbon strengthening efficiency of 43.

[0090] Comparative Example 5

[0091] The preparation method of the structured nano-carbon / aluminum composite material in this comparative example is different from that in Example 1 in that:

[0092] The amount of KMnO4 added in step (2) is 3.0 g.

[0093] In this embodiment, the structured nanocarbon prepared is a "ribbon-shaped" GNR. The GNR and Al in the resulting GNR / Al composite undergo a severe interfacial reaction, forming a dense, relatively large rod-shaped Al4C3 phase (average length: 126nm) at the edge of the GNR. This Al4C3 phase exhibits significant brittle characteristics, and the formation of Al4C3 seriously sacrifices the structural integrity of the GNR. Mechanical property tests show that the GNR / Al composite prepared in this embodiment has a yield strength of 209MPa, a tensile strength of 253MPa, an elongation at break of 11.9%, and a nanocarbon strengthening efficiency of 48.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a high-performance structured nano-carbon / aluminum composite material, characterized in that: The steps include: (1) performing variable speed ball milling on the structured carbon nanomaterial, aluminum powder, and stearic acid to obtain a composite powder; (2) When the structured carbon nanomaterial is a GNR material, the composite powder is sequentially subjected to cold pressing, pressureless sintering, and hot extrusion to obtain a high-performance structured nanocarbon / aluminum composite material; When the structured carbon nanomaterial is a CNT-GNR hybrid material, the composite powder is sequentially subjected to cold pressing, spark plasma sintering, hot extrusion, and heat treatment to obtain a high-performance structured nanocarbon / aluminum composite material; The heating rate of the heat treatment is 10°C / min; the heat treatment time is 10 to 50 minutes; Heat treatment temperature is 550~650℃; The preparation method of the structured carbon nanomaterial comprises: placing the CNT material in a mixed solution of concentrated sulfuric acid and concentrated phosphoric acid, ultrasonicating the solution, then adding potassium permanganate under ice bath conditions, heating the solution to 50-90° C. for reaction, and finally centrifugally washing and thermally reducing the solution to obtain the structured carbon nanomaterial.

2. The method for preparing the high-performance structured nano-carbon / aluminum composite material according to claim 1, wherein: The volume ratio of the concentrated sulfuric acid to the concentrated phosphoric acid is 5:1 to 9:1; the mass volume concentration of CNT in the mixed solution of concentrated sulfuric acid and concentrated phosphoric acid is 1 to 4 g / L.

3. The method for preparing the high-performance structured nano-carbon / aluminum composite material according to claim 2, wherein: When the mass ratio of potassium permanganate to CNT is 3:1 to 5:1, a CNT-GNR hybrid material is generated; when the mass ratio of potassium permanganate to CNT is 6:1 to 7:1, a GNR material is generated.

4. The method for preparing the high-performance structured nano-carbon / aluminum composite material according to claim 1, wherein: The centrifugal speed is 6000-10000 r / min, the thermal reduction temperature is 400-600° C., the heating rate is 0-10° C. / min, the thermal reduction time is 0.5-1.5 h, and the thermal reduction gas is a mixed gas of argon and hydrogen.

5. The method for preparing the high-performance structured nano-carbon / aluminum composite material according to claim 1, wherein: The average particle diameter of the aluminum powder is 1-20 μm, the volume fraction of the structured carbon nanomaterial in the composite powder is 1.5%, and the mass of the stearic acid is 0.4-1% of the total weight of the structured carbon nanomaterial, aluminum powder and stearic acid.

6. The method for preparing the high-performance structured nano-carbon / aluminum composite material according to claim 1, wherein: The speed of the variable speed ball mill is 200-250 rpm in the low-speed ball milling stage, and the time is 6-10 hours. The speed of the high-speed ball milling stage is 300-500 rpm, and the time is 0.5-1.5 hours.

7. The method for preparing the high-performance structured nano-carbon / aluminum composite material according to claim 1, wherein: The spark plasma sintering temperature is 450-650°C, the vacuum degree is lower than 5 Pa, the heating rate is 50-150°C / min, and the holding time is controlled to be 20-60 minutes; the pressureless sintering is carried out in an argon atmosphere, the heating rate is 10°C / min, the sintering temperature is 530-580°C, and the sintering time is 1 hour.

8. The method for preparing the high-performance structured nano-carbon / aluminum composite material according to claim 1, wherein: The hot extrusion temperature is 350-550° C., the extrusion ratio is 10:1-16:1, and the hot extrusion pressure is 400-600 MPa.

9. The method for preparing the high-performance structured nano-carbon / aluminum composite material according to claim 1, wherein: The ball-milled composite powder was placed in a steel mold with a diameter of 20 mm and cold-pressed at a pressure of 600 MPa for a holding time of 3 minutes to obtain a green body of a structured nano-carbon / aluminum composite material.

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