Graphene-aluminum composite material and preparation method thereof

Abstract

The invention discloses a graphene-aluminum composite material and a preparation method thereof, and belongs to the technical field of metal-based composite material preparation. The raw materials comprise modified aluminum particles and a graphene dispersing agent; the production process comprises the steps of aluminum particle interface modification treatment, graphene dispersing agent preparation, modified aluminum particle wrapping with graphene, heating pressing and heating extrusion forming. A nanometer interface modification layer is constructed on the surfaces of aluminum particles through a modifier to improve wettability and inhibit generation of Al4C3, a specially-made pressing device improves the compactness of a green body, inert gas protection is matched for extrusion, the performance of the composite material is optimized, and the problems that graphene and an aluminum matrix are poor in interface compatibility, prone to agglomeration, prone to generating brittleness at high temperature and the like are solved; the graphene is uniformly dispersed, and the composite material has excellent mechanical properties and high conductivity and is suitable for industrial mass production.

Description

Technical Field

[0001] This invention relates to the field of metal matrix composite material preparation technology, and in particular to a graphene-aluminum composite material and its preparation method. Background Technology

[0002] Graphene-aluminum composites have become a research hotspot for next-generation high-performance metal matrix composites due to the combination of the excellent properties of graphene and the lightweight characteristics of aluminum. While existing preparation techniques have achieved the composite of graphene and aluminum, the following core problems remain: 1. Graphene has poor interfacial compatibility with aluminum matrix. Direct mixing can easily lead to graphene agglomeration, and interfacial reactions can easily occur at high temperatures to generate aluminum carbide (Al4C3), which significantly degrades the mechanical and thermal conductivity of the material.

[0003] 2. Traditional methods of mixing and wrapping followed by low-temperature baking can easily lead to localized graphene agglomeration and incomplete drying of the particles, resulting in low density of the composite preform after subsequent pressing.

[0004] 3. Traditional pressing equipment suffers from defects such as insufficient temperature control accuracy, poor pressure stability, and low automation adaptability. In addition, the preheating method before extrusion is a constant temperature, which easily causes uneven internal stress in the composite cylinder. Furthermore, aluminum is prone to oxidation and graphene is prone to structural defects at high temperatures, reducing the stability of product performance.

[0005] To address the aforementioned issues, there is an urgent need to develop a graphene-aluminum composite material based on modification and interface structure design to achieve uniform dispersion of graphene and controllable regulation of interface reactions. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a graphene-aluminum composite material and its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a graphene-aluminum composite material includes the following steps: S1, Aluminum particle interface modification treatment: The modifier is dissolved in a mixture of ethanol and deionized water to prepare a modifier solution with a concentration of 0.5-2wt%. Pure aluminum particles are immersed in aluminum degreasing agent for 10-15 minutes, rinsed with deionized water 3-5 times, immersed in the modifier solution, ultrasonically dispersed for 10-30 minutes, washed 3 times with anhydrous ethanol, and dried to obtain modified aluminum particles with an interface modification layer on the surface. A modifier solution with a concentration of 0.5-2 wt% was prepared by dissolving the modifier in a mixture of ethanol and deionized water. Ethanol can improve the solubility and dispersion stability of the modifier, while deionized water ensures that the overall polarity of the solution is compatible with the surface characteristics of aluminum particles, laying the foundation for subsequent interfacial adsorption. Then, the pure aluminum particles were immersed in an aluminum degreasing agent for 10-15 minutes. The surfactant in the degreasing agent effectively removed rolling residue oil, dust and other impurities by breaking the interfacial tension of oil stains on the surface of aluminum particles, avoiding impurities from hindering the contact between the modifier and the aluminum surface. The particles were then rinsed with deionized water 3-5 times to thoroughly remove residual degreasing agent and prevent it from reacting with the modifier. The pretreated aluminum particles are immersed in a modifier solution and ultrasonically dispersed for 10-30 minutes. The high-frequency mechanical energy generated by ultrasonic vibration promotes the uniform diffusion of modifier molecules in the solution, breaking up local agglomerations. On the other hand, it causes slight disturbances on the surface of the aluminum particles, increasing the specific surface area and driving the modifier molecules to adhere tightly to the surface of the aluminum particles through physical and chemical adsorption, forming a continuous and uniform nanoscale interface modification layer. Then, the particles are washed three times with anhydrous ethanol. Taking advantage of the moderate polarity of ethanol, unadsorbed free modifier molecules are removed to avoid the formation of agglomeration spots after drying, while not damaging the already bonded modification layer. Finally, the particles are dried to remove residual ethanol from the surface, allowing the modification layer to solidify and set. Interface modification treatment improves the wettability of aluminum particles and graphene. The functional groups of the modifier can form chemical bonds with defects or oxygen-containing groups on the graphene surface, reducing the aluminum-graphene contact angle from >90° to <60°, inhibiting graphene agglomeration, improving dispersion uniformity, and also acting as a buffer layer. In subsequent high-temperature processes such as pressing and extrusion, it reduces the direct contact between aluminum and graphene, lowers the probability of brittle Al4C3 phase formation, and improves the overall performance of the finished composite material. Finally, the modifier not only achieves covalent bonding on the graphene surface but also enhances the bonding force between aluminum particles. The modified layer can improve the plasticity of the particle surface and promote plastic flow between particles during pressing, increasing the compaction density of the preform from <90% in traditional pressing to ≥96%. S2, Preparation of graphene dispersant: After vacuum drying, graphene powder was treated with low-temperature plasma for 20 min. Polyvinyl alcohol and deionized water were added to the reactor at a mass ratio of 0.2:5-10. The mixture was stirred at 80℃ for 30 min until completely dissolved. After cooling to room temperature, the plasma-modified graphene powder was added to the reactor in multiple batches and ultrasonically dispersed for 60 min. Simultaneously, a high-shear emulsifier was turned on for intermittent emulsification. The pH of the mixture was adjusted to 8-9 with 0.5 mol / L NaOH solution. The mixture was stirred for 10 min and filtered to obtain graphene dispersant. Graphene powder is first vacuum dried to remove surface adsorbed water, preventing moisture from causing interlayer hydrogen bond aggregation and laying the foundation for subsequent dispersion. Then, it is treated with low-temperature plasma for 20 minutes. The high-energy particles in the plasma bombard the graphene surface, breaking some C-C bonds and introducing oxygen-containing functional groups such as hydroxyl and carboxyl groups. This increases the surface activity and hydrophilicity of graphene and weakens the interlayer van der Waals forces through steric hindrance between functional groups, reducing the tendency to aggregate. At the same time, polyvinyl alcohol and deionized water are added to the reactor at a mass ratio of 0.2:5-10 and stirred at 80°C for 30 minutes to completely dissolve the polyvinyl alcohol. A large number of hydroxyl groups on the polyvinyl alcohol molecular chain can combine with oxygen-containing functional groups on the graphene surface through hydrogen bonds to form a steric hindrance layer, further inhibiting interlayer aggregation. Its water solubility also ensures the uniform distribution of the dispersant in the aqueous phase. After the polyvinyl alcohol solution cools to room temperature, plasma-modified graphene is added to the reactor in multiple batches. This batch feeding avoids agglomeration caused by excessively high local concentrations. The oxygen-containing functional groups on the graphene surface enhance its compatibility with the aqueous phase and polyvinyl alcohol. Subsequently, ultrasonic dispersion is started for 60 minutes. The mechanical force and cavitation effect generated by ultrasonic vibration can peel off the graphene agglomerates, making the sheets fully dispersed. At the same time, a high-speed shear emulsifier is started intermittently for emulsification. The high-speed shear further breaks down the fine agglomerates, forming a synergistic dispersion effect with ultrasound, and improving the dispersion uniformity. After dispersion, the pH of the mixture was adjusted to 8-9 using 0.5 mol / L NaOH solution. Under alkaline conditions, the carboxyl and hydroxyl groups on the graphene surface dissociate, generating more negative charges. This significantly improves the colloidal stability of the dispersion through electrostatic repulsion. After stirring for 10 minutes to ensure pH uniformity, the undispersed coarse agglomerates were removed by filtration, ultimately yielding a stable graphene dispersant. In this dispersion, the steric hindrance of polyvinyl alcohol, the electrostatic repulsion of surface functional groups, and the synergistic dispersion effect of the two carbon materials jointly ensure the uniform distribution and long-term stability of the graphene sheets. This provides a uniformly dispersed carbon precursor with excellent interfacial compatibility for subsequent aluminum particle coating, effectively avoiding performance defects caused by carbon phase agglomeration in composite materials. S3, Graphene-encapsulated modified aluminum particles: The prepared modified aluminum particles and the graphene dispersant prepared in S1 were added to a double-helix stirring container at a mass ratio of 98-99.97:0.03-2. The mixture was stirred at 100-200 rpm for 30-60 min and then placed in a microwave drying device to bake for 0.5-2 h to obtain graphene-coated modified aluminum particles. The modified aluminum particles contain hydroxyl groups on their surface, and the graphene dispersant contains stably dispersed graphene sheets and polyvinyl alcohol dispersant. The two are mixed in a precise ratio to control the proportion of graphene in the composite system, avoiding insufficient reinforcement due to too low a content or agglomeration due to too high a content. The double-helix stirring structure uses the shear force and axial pushing force generated by the co-rotation to achieve three-dimensional mixing of the modified aluminum particles and the graphene dispersant. The stirring speed of 200-300 rpm ensures sufficient contact between particles while avoiding damage to the graphene sheet structure caused by high-speed stirring. During the stirring period of 40-60 minutes, the polar functional groups on the surface of the modified aluminum particles and the graphene sheets in the graphene dispersant... The oxygen functional groups and the hydroxyl groups of the polyvinyl alcohol molecular chain form hydrogen bonds. At the same time, the negative charge on the surface of the graphene sheet and the weak positive charge on the surface of the modified aluminum particles generate electrostatic adsorption. The dual forces drive the graphene sheet to be uniformly attached to the surface of the aluminum particles, gradually forming a continuous coating layer. Then, the mixture is placed in a microwave drying equipment and baked for 2-4 hours. Microwave drying achieves uniform heating through the high-frequency vibration of water molecules inside the material, avoiding the internal moisture retention and cracking of the coating layer caused by the surface hardening and formation of a hard shell in traditional hot air drying. It ensures that the moisture evaporates slowly while the graphene coating layer is tightly bonded to the aluminum particles, and finally obtains modified aluminum particles with graphene uniformly coated. From the perspective of mechanism and function, the synergistic mixing effect of double helix stirring solves the problem of uneven mixing between solid aluminum particles and liquid graphene dispersant, ensuring that a graphene coating layer of uniform thickness can be formed on the surface of each aluminum particle; the interfacial binding mechanism of hydrogen bonding and electrostatic adsorption prevents graphene from falling off the surface of aluminum particles during subsequent pressing and extrusion processes, laying the foundation for uniform graphene dispersion; and the uniform heating characteristics of microwave drying protect the integrity of the graphene coating layer and reduce coating layer defects. In addition, this encapsulation structure plays three key roles: First, the graphene encapsulation layer is pre-positioned to prevent graphene agglomeration during subsequent processing, thereby improving the uniformity of the composite material's mechanical properties; second, the encapsulation layer acts as a "buffer interface" in subsequent high-temperature processes, reducing direct contact between the aluminum matrix and graphene and suppressing the formation of brittle Al4C3 phase; third, the continuous graphene encapsulation layer can initially construct a conductive network, providing a structural basis for improving conductivity after subsequent cold drawing and directional texturing, ultimately helping the composite material achieve a synergistic effect of high strength and high conductivity. S4. Heating and pressing: Graphene-encapsulated modified aluminum particles from S2 are added to a specially designed pressing device. A mechanical chain automatic feeder uniformly feeds the composite particles into an intelligent temperature-controlled rotary kiln protected by inert gas. The kiln temperature is set to 300-490℃, the online ultrasonic dispersion module frequency is 20-40kHz, and the ultrasonic power is 500-800W. After ultrasonic treatment for 1-5 minutes, the particles are fed into an intelligent hydraulic press and pressed into graphene-aluminum composite cylinders with a diameter of 90-120mm and a length of 100-200mm under a pressure of 300-800T in one go, with a pressing density of ≥99%. Figure 1 This is a schematic diagram of the specially designed pressing equipment used in this invention. At the beginning of the pressing stage, an automatic feeder using a mechanical chain delivers the composite particles into an intelligent temperature-controlled rotary kiln at a constant rate. Uniform feeding avoids uneven heating caused by localized particle accumulation, laying the foundation for subsequent homogenization. Once inside the rotary kiln, precise temperature control of 300-490℃ brings the surface of the aluminum particles to a semi-softened state. This temperature is below the melting point of aluminum (660℃), which both enhances the plasticity of the aluminum through thermal activation, strengthens the thermal motion of metal atoms, and facilitates dislocation slippage, without damaging the graphite. The graphene coating has a sheet-like structure; at the same time, the online ultrasonic dispersion module is activated. The mechanical force and cavitation effect generated by ultrasonic vibration can further break down the trace graphene agglomerates remaining in the composite particles, making the graphene coating more evenly distributed on the surface of the aluminum particles, avoiding local excessive coating or exposure. During the heat preservation and ultrasonic treatment for 30-50 minutes, the surface hardness of the aluminum particles decreased from the initial HV60-70 to HV40-50, and the plasticity was significantly improved. Moreover, the bonding force between the graphene coating and the surface of the aluminum particles was enhanced due to thermal activation, reducing the risk of coating peeling off during subsequent pressing. Subsequently, the pretreated composite particles are fed into an intelligent controlled hydraulic press and pressed into shape in one go under high pressure of 300-600T. Under high pressure, the semi-softened aluminum particles undergo plastic flow, plastic deformation, and densification. The gaps between the particles are filled, and the graphene coating adheres tightly to the particle surface as the aluminum particles deform. Some of the sheets are slightly oriented along the direction of pressure. At the same time, the high pressure eliminates the micropores and loose areas inside the composite particles, increasing the density of the cylindrical blank to ≥98.5%. The key changes that occur during the entire process can be divided into three stages: First, the feeding stage, where the composite particles are conveyed in a uniform and continuous manner without local accumulation or gaps; second, the heating and ultrasonic stage, where the surface of the aluminum particles is semi-softened, the graphene coating becomes uniform, and the interfacial bonding force between the coating and the aluminum particles is enhanced; and third, the pressing stage, where the aluminum particles undergo plastic deformation and boundary fusion, the particle gaps are significantly reduced, and the graphene coating changes from "loosely bonded" to "tightly wrapped" and locally oriented, ultimately forming a cylindrical blank with a diameter of 90-120mm and a length of 100-200mm, with dimensional errors controlled within ±0.5mm in diameter and ±2mm in length, and without defects such as cracks or delamination. The semi-softening treatment in the heated rotary kiln of the specially designed pressing equipment provides a plastic basis for high-pressure densification, avoiding brittle cracking of aluminum particles during pressing. Online ultrasound ensures the uniformity of graphene, while the high-pressure one-time molding of the intelligent hydraulic press achieves high density through the plastic flow of metal. The three work together to ensure that the composite cylindrical blank has structural integrity, compositional uniformity and high density, providing a key blank guarantee for the realization of the high strength and high conductivity of the final composite material. S5. Heated extrusion molding: The graphene-aluminum composite cylinder is placed in a continuous box-type inert gas protected heating furnace and heated to 460-490℃ at a gradient rate of 30-50℃ / min, and held for 1-5 min. It is then quickly transferred to the die cavity of an 800-1500T aluminum extruder with an extrusion ratio of 10-30:1 and an extrusion speed of 5-15mm / s. After extrusion molding, it is water quenched and then artificially aged to finally obtain the graphene-aluminum composite material. A heating rate of 5-10℃ / min can avoid the thermal stress imbalance caused by a sudden temperature rise in the composite cylinder. For example, if the outer layer expands too quickly due to heat and the inner layer contracts lagging behind, microcracks will be generated. 460-490℃ is in the semi-solid temperature range of aluminum. At this temperature, the thermal motion of aluminum matrix atoms is significantly enhanced, the resistance to dislocation slip is greatly reduced, and the matrix gradually changes from a solid state to a semi-softened state. The hardness decreases significantly and the plasticity increases by 3-4 times. At the same time, this temperature is far below the critical temperature for the formation of brittle Al4C3 between graphene and aluminum, which can avoid the graphene sheets being destroyed by interfacial reactions. Holding for 1-1.5h can achieve uniform temperature inside and outside the composite cylinder, ensuring that the aluminum matrix is ​​fully softened and eliminating the hidden danger of insufficient local plasticity. During this period, the micropores remaining inside the composite cylinder are filled due to the thermal expansion and plastic flow of the matrix, and the density is slightly increased. The interfacial bonding force between the graphene coating layer and the aluminum matrix is ​​further enhanced due to the thermal activation of hydroxyl hydrogen bonds, reducing the risk of coating layer detachment during subsequent extrusion. The composite cylinder is then rapidly transferred to the inert gas protection chamber of an 800-1500T aluminum extruder. The inert gas isolates the cylinder from air, preventing the formation of an Al2O3 film on the surface of the high-temperature composite cylinder. The oxide film would hinder the plastic flow of the aluminum matrix and weaken the interfacial bonding between graphene and aluminum, keeping the cylinder surface clean. During the extrusion stage, an extrusion ratio of 10-30:1 is achieved by reducing the cross-section of the die cavity. An extrusion speed of 5-15 mm / s can balance the forming efficiency and the orientation effect of graphene. Under high pressure, the aluminum matrix undergoes intense plastic flow, and the remaining gaps between particles are completely filled. At the same time, the shear force overcomes the van der Waals forces between the graphene sheets, causing the originally randomly distributed graphene sheets to align in an orientation along the extrusion direction. The aluminum matrix and the graphene interface are tightly bonded under the extrusion pressure, with no newly formed Al4C3 phase. The interfacial load transfer capability is strengthened only through plastic deformation. Throughout the process, the composite cylinder undergoes a transformation from "semi-softening → anti-oxidation transfer → plastic flow forming." During the heating stage, it transitions from a solid, brittle state to a semi-soft, malleable state, reducing internal defects. During the transfer stage, it maintains a high-temperature, clean environment, free from oxidation contamination. During the extrusion stage, the cross-section shrinks to the target profile, and graphene is oriented to form a conductive network, significantly improving matrix density and interfacial bonding. The core function of this process is to ensure the forming plasticity of aluminum through precise heating, avoid oxidation defects through inert protection, and optimize the distribution of graphene through extrusion orientation. These three factors work together to give the profile both high mechanical properties and high electrical conductivity potential. Oriented graphene reduces electron scattering, laying the foundation for a conductivity ≥58% IACS after subsequent heat treatment. Furthermore, the profile surface is smooth, free from defects such as cracks and delamination, meeting the requirements for subsequent cold drawing and functional applications.

[0008] Preferably, the diameter of the pure aluminum particles is 0.3-5 mm and the purity is ≥99.7%. The modifier can be any one of silane coupling agent or titanate coupling agent, and the volume ratio of ethanol to deionized water in the modifying solvent is 9:1.

[0009] Preferably, the mass ratio of graphene powder, polyvinyl alcohol, and deionized water is 1:0.2:5-10, and the solid content of the graphene dispersant is 0.3-2%.

[0010] Preferably, the parameters of the microwave drying equipment are: microwave power 300-500W, baking temperature 50-130℃.

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention constructs a nanoscale interface modification layer on the surface of aluminum particles using a modifier. Pure aluminum particles are degreased and the modifier is ultrasonically adsorbed. The polarity is controlled using an ethanol-water mixture, allowing the modifier to form a continuous layer through physical / chemical adsorption. This modified layer can form chemical bonds with graphene functional groups, reducing the aluminum-graphene contact angle to <60°. Simultaneously, it acts as a "buffer layer," reducing direct contact between aluminum and graphene, ultimately increasing the compaction density of the preform from <90% to ≥96%. This effectively inhibits Al4C3 formation, solving the problems of poor wettability between graphene and the aluminum matrix, easy agglomeration, and the tendency to form brittle Al4C3 at high temperatures in existing technologies. This lays the foundation for the synergistic development of the finished product's mechanical and electrical properties.

[0012] 2. The invention features a specially designed integrated processing equipment, including a heated rotary kiln, achieving precise temperature control from 300-490℃, and online ultrasonic and intelligent hydraulic presses: firstly, the aluminum particles are semi-softened, reducing the hardness from HV60-70 to HV40-50, and then subjected to high-pressure forming, resulting in a composite cylindrical billet with a density ≥99%, dimensional error ≤±0.5mm, and no cracks or delamination, providing a high-quality billet for subsequent extrusion and solving the problems of poor temperature control and low density in existing pressing equipment. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the specially designed pressing device for this invention; Figure 2 This is a process flow diagram for producing graphene-aluminum composite materials according to the present invention. Detailed Implementation

[0014] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0015] Example 1: S1, Aluminum particle interface modification treatment: The modifier was dissolved in a mixture of ethanol and deionized water to prepare a 1wt% modifier solution. Pure aluminum particles were immersed in aluminum degreasing agent for 10 min, rinsed 4 times with deionized water, immersed in the modifier solution, ultrasonically dispersed for 20 min, washed 3 times with anhydrous ethanol, and dried to obtain modified aluminum particles with an interface modification layer on the surface. S2, Preparation of graphene dispersant: After vacuum drying, graphene powder was treated with low-temperature plasma for 20 min. Polyvinyl alcohol and deionized water were added to the reactor at a mass ratio of 0.2:5-10. The mixture was stirred at 80℃ for 30 min until completely dissolved. After cooling to room temperature, the plasma-modified graphene powder was added to the reactor in multiple batches and ultrasonically dispersed for 60 min. Simultaneously, a high-shear emulsifier was turned on for intermittent emulsification. The pH of the mixture was adjusted to 8-9 with 0.5 mol / L NaOH solution. The mixture was stirred for 10 min and filtered to obtain graphene dispersant. S3, Graphene-encapsulated modified aluminum particles: The prepared modified aluminum particles and the graphene dispersant prepared in S1 were added to a double-helix stirring container at a mass ratio of 99.97:0.03. The mixture was stirred at 150 rpm for 45 min and then placed in a microwave drying device to bake for 1.5 h to obtain graphene-coated modified aluminum particles. S4. Heating and pressing: Graphene-encapsulated modified aluminum particles from S2 are added to a specially designed pressing device. A mechanical chain automatic feeder uniformly feeds the composite particles into an intelligent temperature-controlled rotary kiln protected by inert gas. The kiln temperature is set to 400℃, the online ultrasonic dispersion module frequency is 30kHz, and the ultrasonic power is 500-800W. After 3 minutes of heat preservation and ultrasonic treatment, the particles are fed into an intelligent control hydraulic press and pressed into graphene-aluminum composite cylinders with a diameter of 105mm and a length of 150mm under a pressure of 550T in one go, with a pressing density of ≥99%. S5. Heated extrusion molding: The graphene-aluminum composite cylinder was placed in a continuous box-type inert gas protected heating furnace and heated to 475℃ at a gradient rate of 40℃ / min, and held for 3 min. It was then quickly transferred to the die cavity of an 1100T aluminum extruder with an extrusion ratio of 20:1 and an extrusion speed of 10 mm / s. After extrusion molding, it was water quenched and then artificially aged to finally obtain the graphene-aluminum composite material.

[0016] Example 2: S1, Aluminum particle interface modification treatment: The modifier was dissolved in a mixture of ethanol and deionized water to prepare a 1wt% modifier solution. Pure aluminum particles were immersed in aluminum degreasing agent for 10 min, rinsed 4 times with deionized water, immersed in the modifier solution, ultrasonically dispersed for 20 min, washed 3 times with anhydrous ethanol, and dried to obtain modified aluminum particles with an interface modification layer on the surface. S2, Preparation of graphene dispersant: After vacuum drying, graphene powder was treated with low-temperature plasma for 20 min. Polyvinyl alcohol and deionized water were added to the reactor at a mass ratio of 0.2:5-10. The mixture was stirred at 80℃ for 30 min until completely dissolved. After cooling to room temperature, the plasma-modified graphene powder was added to the reactor in multiple batches and ultrasonically dispersed for 60 min. Simultaneously, a high-shear emulsifier was turned on for intermittent emulsification. The pH of the mixture was adjusted to 8-9 with 0.5 mol / L NaOH solution. The mixture was stirred for 10 min and filtered to obtain graphene dispersant. S3, Graphene-encapsulated modified aluminum particles: The prepared modified aluminum particles and the graphene dispersant prepared in S1 were added to a double-helix stirring container at a mass ratio of 98:2. The mixture was stirred at 150 rpm for 45 min and then placed in a microwave drying device to bake for 1.5 h to obtain graphene-coated modified aluminum particles. S4. Heating and pressing: Graphene-encapsulated modified aluminum particles from S2 are added to a specially designed pressing device. A mechanical chain automatic feeder uniformly feeds the composite particles into an intelligent temperature-controlled rotary kiln protected by inert gas. The kiln temperature is set to 400℃, the online ultrasonic dispersion module frequency is 30kHz, and the ultrasonic power is 500-800W. After 3 minutes of heat preservation and ultrasonic treatment, the particles are fed into an intelligent control hydraulic press and pressed into graphene-aluminum composite cylinders with a diameter of 105mm and a length of 150mm under a pressure of 550T in one go, with a pressing density of ≥99%. S5. Heated extrusion molding: The graphene-aluminum composite cylinder was placed in a continuous box-type inert gas protected heating furnace and heated to 475℃ at a gradient rate of 40℃ / min, and held for 3 min. It was then quickly transferred to the die cavity of an 1100T aluminum extruder with an extrusion ratio of 20:1 and an extrusion speed of 10 mm / s. After extrusion molding, it was water quenched and then artificially aged to finally obtain the graphene-aluminum composite material.

[0017] Example 3: Preparation of graphene-aluminum composite material: S1, Aluminum particle interface modification treatment: The modifier was dissolved in a mixture of ethanol and deionized water to prepare a 1wt% modifier solution. Pure aluminum particles were immersed in aluminum degreasing agent for 10 min, rinsed 4 times with deionized water, immersed in the modifier solution, ultrasonically dispersed for 20 min, washed 3 times with anhydrous ethanol, and dried to obtain modified aluminum particles with an interface modification layer on the surface. S2, Preparation of graphene dispersant: After vacuum drying, graphene powder was treated with low-temperature plasma for 20 min. Polyvinyl alcohol and deionized water were added to the reactor at a mass ratio of 0.2:5-10. The mixture was stirred at 80℃ for 30 min until completely dissolved. After cooling to room temperature, the plasma-modified graphene powder was added to the reactor in multiple batches and ultrasonically dispersed for 60 min. Simultaneously, a high-shear emulsifier was turned on for intermittent emulsification. The pH of the mixture was adjusted to 8-9 with 0.5 mol / L NaOH solution. The mixture was stirred for 10 min and filtered to obtain graphene dispersant. S3, Graphene-encapsulated modified aluminum particles: The prepared modified aluminum particles and the graphene dispersant prepared in S1 were added to a double-helix stirring container at a mass ratio of 99:1. The mixture was stirred at 150 rpm for 45 min and then placed in a microwave drying device to bake for 1.5 h to obtain graphene-coated modified aluminum particles. S4. Heating and pressing: Graphene-encapsulated modified aluminum particles from S2 are added to a specially designed pressing device. A mechanical chain automatic feeder uniformly feeds the composite particles into an intelligent temperature-controlled rotary kiln protected by inert gas. The kiln temperature is set to 400℃, the online ultrasonic dispersion module frequency is 30kHz, and the ultrasonic power is 500-800W. After 3 minutes of heat preservation and ultrasonic treatment, the particles are fed into an intelligent control hydraulic press and pressed into graphene-aluminum composite cylinders with a diameter of 105mm and a length of 150mm under a pressure of 550T in one go, with a pressing density of ≥99%. S5. Heated extrusion molding: The graphene-aluminum composite cylinder was placed in a continuous box-type inert gas protected heating furnace and heated to 475℃ at a gradient rate of 40℃ / min, and held for 3 min. It was then quickly transferred to the die cavity of an 1100T aluminum extruder with an extrusion ratio of 20:1 and an extrusion speed of 10 mm / s. After extrusion molding, it was water quenched and then artificially aged to finally obtain the graphene-aluminum composite material.

[0018] Comparative Example 1: Compared to Example 3, the mass ratio of modified aluminum particles to graphene dispersant in Comparative Example 1 was 97:3.

[0019] Comparative Example 2: Compared to Example 3, the aluminum particles in Comparative Example 2 were not treated with a modifier.

[0020] Comparative Example 3: Compared to Example 3, no polyvinyl alcohol was added in Comparative Example 3.

[0021] Comparative Example 4: Compared with Example 3, the online ultrasound step in step S4 was removed in Comparative Example 4.

[0022] Comparative Example 5: Compared to Example 3, Comparative Example 5 did not have inert gas protection during the heating extrusion molding step.

[0023] Performance testing: According to GB / T 228.1-2021 "Metallic materials - Tensile testing - Part 1: Test method at room temperature", GB / T4340.1-2009 "Metallic materials - Vickers hardness test - Part 1: Test method", GB / T 5163-2022 "Determination of density, oil content and porosity of sintered metallic materials", and GB / T 351-2021 "Determination of resistivity and conductivity of metallic materials", the tensile strength, yield strength, elongation, hardness, density and conductivity of the graphene-aluminum composite materials prepared in the above examples and comparative examples were measured.

[0024] Table 1. Performance test data of graphene-aluminum composite materials prepared in each group. Group Tensile strength (MPa) Yield strength (MPa) Elongation (%) Vickers hardness (HV) <![CDATA[Density (g / cm 3 )]]> Density (%) Electrical conductivity (%IACS) Example 1 420 290 9 115 2.71 99.1 60.5 Example 2 430 300 7.8 121 2.7 98.8 58.5 Example 3 450 320 8.5 125 2.72 99.3 60 Comparative Example 1 360 250 5.5 100 2.67 97 54 Comparative Example 2 320 230 5 95 2.65 96.5 52 Comparative Example 3 330 235 5.2 98 2.66 96.8 53 Comparative Example 4 340 240 5.6 101 2.68 97.1 55.5 Comparative Example 5 335 238 5.3 99 2.67 96.9 54.8 Data Analysis: Figure 2 The process flow diagram for producing graphene-aluminum composite material according to the present invention is as follows: graphene is pretreated to prepare a dispersant, which is then uniformly mixed with modified aluminum particles. Subsequently, the mixture is heated and pressed, and finally heated and extruded to obtain graphene-aluminum composite material.

[0025] In Example 3, the composite material prepared had components in optimal proportions, with a moderate proportion of graphene dispersant. This proportion effectively suppressed Al4C3 formation and enhanced interfacial bonding, while also enabling efficient load transfer thanks to the high aspect ratio of the graphene sheets. Simultaneously, the graphene was uniformly dispersed without significant agglomeration. Furthermore, the matching ratio of aluminum particles to graphene dispersant resulted in a high-density composite preform with continuous electron transport channels, ultimately achieving optimal synergy between mechanical and functional properties.

[0026] In Example 1, the ratio of aluminum particles to graphene dispersant was biased towards aluminum particles, with a low proportion of graphene dispersant. Mechanistically, the insufficient graphene content in the graphene dispersant weakens its reinforcing effect on the aluminum matrix, preventing the formation of a continuous load transfer network and hindering the dispersion of external stress, thus affecting mechanical properties. However, the high proportion of the aluminum matrix results in more prominent plasticity and better elongation. Simultaneously, the high proportion of aluminum as a highly conductive phase minimizes interference with electron transport paths, maintaining a high conductivity level. Overall, the result is characterized by insufficient reinforcement but superior plasticity and conductivity.

[0027] In Example 2, the ratio of aluminum particles to graphene dispersant was biased towards graphene dispersant, with a higher proportion of graphene dispersant. Mechanistically, excessive graphene dispersant increases the amount of graphene, exceeding the uniform load-bearing capacity of the aluminum matrix, easily leading to localized agglomeration. Graphene molecules attract each other through van der Waals forces, forming larger agglomerates that disrupt the continuity of the aluminum matrix. These agglomerates not only hinder the transfer of load between the graphene and the matrix but also create micro-voids in the composite preform, reducing density and causing a decline in mechanical properties. Simultaneously, the agglomerates interfere with the continuous transport of electrons, affecting electrical conductivity, and also impede the plastic flow of the aluminum matrix, reducing elongation.

[0028] In Comparative Example 1, the proportion of graphene dispersant in the ratio of aluminum particles to graphene dispersant was excessive. Mechanistically, the excessive amount of graphene exceeded the dispersion limit of the aluminum matrix, resulting in severe agglomeration and the formation of numerous "defect clusters." These agglomerates fragmented the aluminum matrix within the composite preform, completely interrupting the load transfer path and significantly reducing mechanical properties. Simultaneously, the increased porosity between agglomerates led to a significant decrease in density, further weakening mechanical properties. Furthermore, the excessive graphene severely hindered the plastic deformation of the aluminum matrix, resulting in the worst elongation. During electron transport, the scattering effect from agglomerates and porosity was enhanced, leading to a significant decrease in electrical conductivity. Overall performance was comprehensively degraded due to the structural defects caused by the excessive graphene dispersant.

[0029] In Comparative Example 2, the aluminum particles were not treated with a modifier; the key difference lies in the absence of a nanoscale interface modification layer. The unmodified aluminum particles exhibit poor wettability with graphene, resulting in a large contact angle and difficulty in chemical bonding, leading to weak interfacial adhesion. During high-temperature processing, direct contact between aluminum and graphene easily triggers a reaction to form a brittle Al4C3 phase. This phase readily becomes a crack initiation point under stress, significantly weakening mechanical properties. Simultaneously, the presence of Al4C3 hinders the continuous transport of electrons within the aluminum matrix, leading to a decrease in electrical conductivity. The unmodified aluminum particles experience impaired plastic flow during pressing, resulting in reduced bulk density and further exacerbating performance degradation; the overall performance is far inferior to that of Example 3.

[0030] Comparative Example 3 did not contain polyvinyl alcohol (PVA), and the key difference lies in the absence of the synergistic effect of the PVA dispersant. In Example 3, PVA forms hydrogen bonds with the functional groups on the graphene surface through its molecular chain hydroxyl groups, constructing a steric hindrance layer and effectively inhibiting graphene aggregation. In contrast, in Comparative Example 4, the graphene sheets easily aggregated due to van der Waals forces, failing to disperse uniformly in the aluminum matrix. Aggregates not only disrupt the continuous network for load transfer but also form voids in the composite preform, reducing density and degrading mechanical properties. Simultaneously, the aggregated graphene hinders electron transport paths, affecting electrical conductivity and resulting in performance inferior to Example 3.

[0031] The tensile strength, yield strength, hardness, and density of Comparative Example 4 all showed a decreasing trend, and the elongation and electrical conductivity were also significantly lower than those of Example 3. The core reason is that Comparative Example 4 omitted the online ultrasonic dispersion step in S4. In Example 3, online ultrasonication effectively broke up the graphene agglomerates remaining in the composite particles through mechanical vibration and cavitation effect, ensuring that the graphene coating layer was evenly distributed on the surface of the aluminum particles, avoiding excessive local coating or exposure, and enhancing the interfacial bonding force between graphene and aluminum particles. However, due to the lack of this treatment in Comparative Example 4, the graphene agglomerates could not be effectively peeled off, forming unevenly dispersed "defect areas" in the composite blank. This not only hindered the smooth transfer of load between the matrix and the reinforcing phase, but also disrupted the continuity of electron transport, and led to an increase in voids and a decrease in density inside the blank, ultimately resulting in a significant deterioration in all properties.

[0032] The tensile strength, yield strength, hardness, and density of Comparative Example 5 were all lower than those of Example 3, and the elongation and electrical conductivity also decreased significantly. The key difference is that Comparative Example 5 did not use inert gas protection during the S5 heating and extrusion molding stage. In Example 3, the inert gas could isolate the air, prevent the aluminum surface from oxidizing and forming an oxide film at high temperature, ensure smooth plastic flow of the aluminum matrix, and at the same time ensure the quality of the interface bonding between graphene and the aluminum matrix. However, due to the lack of inert protection, the oxide film formed on the surface of the high-temperature composite cylinder in Comparative Example 5 would hinder the plastic deformation of the aluminum matrix, weaken the interface bonding strength between graphene and the aluminum matrix, and also disrupt the continuous path of electron transport, resulting in a decrease in the density of the blank and a simultaneous deterioration of mechanical and electrical properties. The overall performance was far inferior to that of Example 3.

[0033] In summary, the performance of graphene-aluminum composites depends on key factors such as interface modification, dispersion control, and the supporting matrix. Interface modification of aluminum particles can improve compatibility with graphene and inhibit the formation of brittle phases; matching the ratio of aluminum particles to graphene dispersant can balance mechanical properties and plasticity; the steric hindrance effect of the dispersant and the interface compatibility improvement effect of modified aluminum particles complement each other, effectively solving the dual problems of graphene agglomeration and weak interfacial bonding; at the same time, combined with online ultrasonic and inert gas protected pressing processes, the density and performance stability of the composite material are further guaranteed, achieving a technical effect of 1+1>2.

[0034] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A graphene-aluminum composite material, characterized in that, Includes the following components by weight: Modified aluminum particles: 98-99.97 parts; Graphene dispersant: 0.03-2 parts.

2. The graphene-aluminum composite material according to claim 1, characterized in that, The preparation steps of the modified aluminum particles are as follows: The modifier is dissolved in a mixture of ethanol and deionized water to prepare a modifier solution with a concentration of 0.5-2wt%. Pure aluminum particles are immersed in aluminum degreasing agent for 10-15 minutes, rinsed with deionized water 3-5 times, immersed in the modifier solution, ultrasonically dispersed for 10-30 minutes, washed 3 times with anhydrous ethanol, and dried to obtain modified aluminum particles with an interface modification layer on the surface. The pure aluminum particles or aluminum alloy particles have a diameter of 0.5-2 mm and a purity of ≥99.7%. The modifier is either a silane coupling agent or a titanate coupling agent. The volume ratio of ethanol to deionized water in the modifying solvent is 9:

1.

3. A method for preparing a graphene-aluminum composite material according to any one of claims 1-2, characterized in that, Includes the following steps: S1. Preparation of graphene dispersant: After vacuum drying, graphene powder is treated with low-temperature plasma for 20 minutes. Polyvinyl alcohol and deionized water are added to the reaction vessel and stirred at 80°C for 30 minutes until completely dissolved. After cooling to room temperature, the plasma-modified graphene powder is added to the vessel in multiple batches and ultrasonically dispersed for 60 minutes. During this period, a high-shear emulsifier is turned on intermittently for emulsification. The pH of the mixture is adjusted to 8-9 with 0.5 mol / L NaOH solution, stirred for 10 minutes, and filtered. The filtrate is the graphene dispersant. S2, Graphene-encapsulated modified aluminum particles: The prepared modified aluminum particles and the graphene dispersant prepared in S1 were added to a double-helix stirring container at a mass ratio of 98-99.97:0.03-2. The mixture was stirred at 100-200 rpm for 30-60 min and then placed in a microwave drying device to bake for 0.5-2 h to obtain graphene-coated modified aluminum particles. S3, Heating and Pressing: Graphene-encapsulated modified aluminum particles from S2 are added to a specially designed pressing device. A mechanical chain automatic feeder uniformly feeds the composite particles into an intelligent temperature-controlled rotary kiln protected by inert gas. The kiln temperature is set to 300-490℃, the online ultrasonic dispersion module frequency is 20-40kHz, and the ultrasonic power is 500-800W. After ultrasonic treatment for 1-5 minutes, the particles are fed into an intelligent hydraulic press and pressed into graphene-aluminum composite cylinders with a diameter of 90-120mm and a length of 100-200mm under a pressure of 300-800T in one go, with a pressing density of ≥99%. S4. Heated extrusion molding: The graphene-aluminum composite cylinder is placed in a continuous box-type inert gas protected heating furnace and heated to 460-490℃ at a gradient rate of 30-50℃ / min, and held for 1-5 min. It is then quickly transferred to the die cavity of an 800-1500T aluminum extruder with an extrusion ratio of 10-30:1 and an extrusion speed of 5-15 mm / s. After extrusion molding, it is water quenched and then artificially aged to finally obtain the graphene-aluminum composite material.

4. The method for preparing a graphene-aluminum composite material according to claim 3, characterized in that, In S1, the mass ratio of graphene powder, polyvinyl alcohol, and deionized water is 1:0.2:5-10, and the solid content of the graphene dispersant is 0.3-2%.

5. The method for preparing a graphene-aluminum composite material according to claim 3, characterized in that, The parameters for baking in the microwave drying equipment in S2 are: microwave power 300-500W, baking temperature 80-130℃.

6. The method for preparing a graphene-aluminum composite material according to claim 3, characterized in that, The steps and parameters for extrusion molding followed by water quenching and artificial aging in S4 are as follows: Water quenching: After extrusion molding, immediately immerse the composite profile in deionized water at 30°C and continue cooling for 5-15 minutes until the profile temperature drops below 50°C. Artificial aging: The water-quenched profiles are placed in an intelligent temperature-controlled aging furnace, heated to 160°C at a rate of 10°C / min, and held at that temperature for 6 hours. Then the heating device is turned off, and the profiles are allowed to cool to room temperature with the furnace to complete the artificial aging treatment.

Images