Preparation method of graphene-aluminum high-conductivity composite material

Abstract

The application provides a preparation method of a graphene aluminum high-conductivity composite material, and relates to the technical field of metal matrix composite material preparation, and comprises the following steps: preparing a naphthyl reactive dispersant+silane coupling agent composite pretreatment liquid, adding graphene into the composite pretreatment liquid, and performing ultrasonic dispersion and mechanical stirring cooperative treatment to obtain a graphene dispersion liquid; adding cerium oxide powder into the graphene dispersion liquid to perform coating modification, and obtaining cerium oxide coated modified graphene; the naphthyl reactive dispersant+silane coupling agent composite pretreatment system is adopted in the application, the limitation of traditional single dispersant is broken through, the naphthyl reactive dispersant produces strong interaction with graphene through a condensed ring structure, efficiently dissociates graphene agglomerates, active groups of the naphthyl reactive dispersant react with the silane coupling agent, one end of the silane coupling agent is combined with the surface hydroxyl group of aluminum powder, a graphene-dispersant-aluminum powder bridging structure is formed, and uniform adsorption and stable dispersion of the graphene are realized.

Description

Technical Field

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

[0002] Graphene, a two-dimensional nanomaterial with ultra-high conductivity and excellent mechanical properties, can be combined with aluminum and aluminum alloys to prepare graphene-aluminum composites. This significantly improves the conductivity, mechanical properties, and wear resistance of the aluminum matrix, expanding the application range of aluminum materials in high-end electronics, aerospace, and other fields, making it one of the current research hotspots in the field of metal matrix composites. Currently, the main methods for preparing graphene-aluminum composites include powder metallurgy, melt casting, and electroplating. Among these, powder metallurgy is one of the most widely used methods due to its simple process, strong controllability, and ability to effectively control the dispersion of graphene. In existing technologies, the core steps in preparing graphene-aluminum composite materials by powder metallurgy typically include the dispersion and mixing of graphene and aluminum powder, molding, and sintering. To improve the dispersion effect of graphene in aluminum powder, a single surfactant is often used as a dispersant to achieve the dissociation and dispersion of graphene through physical adsorption. At the same time, to enhance the interfacial bonding ability between graphene and the aluminum matrix, graphene is subjected to simple oxidation modification or coupling agent modification, and then conventional resistance sintering, hot pressing sintering, and other methods are used to complete the preparation of the composite material.

[0003] However, existing preparation techniques suffer from several drawbacks: poor graphene dispersion, with traditional single dispersants only able to dissociate graphene aggregates through physical adsorption, resulting in poor dispersion stability, a tendency for secondary agglomeration, and high dispersant residues that severely damage the conductive network of the composite material, preventing the full realization of graphene's high conductivity. Furthermore, insufficient interfacial bonding leads to poor wettability between graphene and the aluminum matrix, and direct addition easily generates the brittle Al4C3 phase, causing a decline in the composite material's mechanical properties. Traditional modification methods also fail to form stable interfacial bridging structures, hindering the synergistic effect between graphene and the aluminum matrix. Additionally, unreasonable sintering processes, with conventional high temperatures and long times, not only damage the graphene structure, leading to a decrease in its conductivity, but also reduce the density of the composite material, failing to achieve a balanced optimization of conductivity and mechanical properties. Moreover, low sintering efficiency hinders industrial-scale mass production. Therefore, this invention proposes a method for preparing a graphene-aluminum high-conductivity composite material to address the problems existing in the prior art. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a method for preparing a graphene-aluminum high-conductivity composite material. This method employs a pretreatment system combining a naphthyl reactive dispersant and a silane coupling agent, overcoming the limitations of traditional single dispersants. The naphthyl reactive dispersant, through its fused ring structure, generates strong π-π interactions with graphene, efficiently dissociating graphene aggregates. Its active groups react with the silane coupling agent, and the other end of the silane coupling agent binds to the hydroxyl groups on the aluminum powder surface, forming a graphene-dispersant-aluminum powder bridging structure. This achieves uniform adsorption and stable dispersion of graphene, improving dispersion stability and increasing graphene concentration. Furthermore, the dispersant can participate in interfacial reactions, avoiding the negative impact of residues on conductivity, ensuring that graphene fully utilizes its high conductivity properties to form a continuous three-dimensional conductive network.

[0005] To achieve the objectives of this invention, the following technical solution is provided: a method for preparing a graphene-aluminum high-conductivity composite material, comprising the following steps:

[0006] S1: Prepare a composite pretreatment solution of naphthyl reactive dispersant + silane coupling agent. Add graphene to the composite pretreatment solution and treat it by ultrasonic dispersion and mechanical stirring to obtain a graphene dispersion.

[0007] S2: Cerium oxide powder is added to the graphene dispersion for coating modification to obtain cerium oxide coated modified graphene, and then chemically aluminized to obtain chemically aluminized modified graphene.

[0008] S3: Chemically aluminized modified graphene, aluminum powder and magnesium powder are mixed, dispersed in anhydrous ethanol and then vacuum dried to obtain a uniformly mixed graphene-aluminum powder-magnesium powder mixture.

[0009] S4: After the mixture is pressed into shape, it is placed in a microwave sintering furnace and sintered at low temperature using a dynamic power gradient process. The magnesium powder reduces the oxide layer on the surface of the aluminum powder, and the graphene is simultaneously fixed in the aluminum matrix to obtain a graphene aluminum composite green body.

[0010] S5: Using the composite material preform as the surface and bottom skeleton, a high-purity semi-molten aluminum matrix layer is cast in layers to construct a sandwich structure. After cooling, it is polished to obtain a graphene-based aluminum high conductivity composite material.

[0011] A further improvement is made in that: in S1, the mass ratio of naphthyl reactive dispersant HSiOND to silane coupling agent in the composite pretreatment solution is 1:0.8-1.5, and the concentration of the composite pretreatment solution is 5-15 g / L; the silane coupling agent is one or more of KH550, KH560, KH570 or KH590.

[0012] Further improvements are made in the following aspects: In S1, the ultrasonic dispersion power is 300-500W and the ultrasonic time is 30-60min; the mechanical stirring speed is 500-800r / min and the stirring time is 60-120min; the ultrasonic dispersion and mechanical stirring are carried out simultaneously to ensure that the graphene is fully dissociated and dispersed.

[0013] Further improvements are made in the following aspects: In S2, the mass ratio of cerium oxide powder to graphene is 0.3-0.8:1; the pH value of the system is adjusted to 8-10 during coating modification; the reaction temperature is 50-70℃; and the reaction time is 2-4 hours. The cerium oxide coating thickness is controlled at 5-15 nm, and the coating thickness is calculated using the following formula:

[0014] ,

[0015] Where: d is the cerium oxide coating thickness (nm). The mass (g) of cerium oxide powder. Density of cerium oxide SG is the specific surface area of ​​graphene. It was obtained by measuring using the BET method.

[0016] A further improvement is made in that: in step S2, the aluminum ion concentration in the electroless aluminum plating solution is 10-20 g / L, and the electroless aluminum plating temperature is... The reaction time is 1-2 hours. During the electroless aluminum plating process, trace amounts of rare earth elements La or Nd are added, with the amount being 0.1-0.3% of the total mass of the electroless aluminum plating solution, to further improve wettability.

[0017] Further improvements are made in the following aspects: In step S3, the mass ratio of chemically plated aluminum-modified graphene to aluminum powder is 1-5:100; the particle size of the aluminum powder is 10-50μm, and it is pure aluminum powder or aluminum alloy powder; the ultrasonic dispersion power is 200-400W, the ultrasonic time is 20-40min, the mechanical stirring speed is 400-700r / min, and the stirring time is 40-80min; the vacuum drying temperature is 60-80℃, and the drying time is 2-4h.

[0018] A further improvement is made in the following: In step S4, the pressing pressure is 50-70 MPa; the microwave sintering temperature is... The power is 800-1000W, and the sintering time is 5-10 minutes. Argon gas is introduced as a protective gas during the microwave sintering process to prevent graphene oxidation.

[0019] A further improvement is made in S4, where the dynamic power gradient process is as follows: during the initial sintering stage (0-2 min), the surface microwave power is 1000W and the internal microwave power is 800W; during the middle sintering stage (2-8 min), both the surface and internal microwave powers remain at 900W; and during the final sintering stage (8-10 min), the surface microwave power decreases to 800W while the internal microwave power remains at 800W. The difference between the surface and internal microwave powers satisfies the following formula:

[0020] ,

[0021] in: The power difference (W) The surface microwave power is (W). Internal microwave power (W).

[0022] A further improvement is made in S5, where the temperature for layered casting is... This allows the aluminum to be in a semi-molten state, with a casting speed of 5-10 mL / s. In the sandwich structure, the top and bottom layers are graphene-enriched layers, with microwave-sintered green blanks as the skeleton, and the middle layer is a high-purity semi-molten aluminum matrix layer. The thickness ratio of the top, middle, and bottom layers is 1:3:1-3:4:3. The aluminum purity of the high-purity semi-molten aluminum matrix layer is ≥99.9%.

[0023] The further improvement is as follows: In S1, a trace amount of aminosilane coupling agent KH550 is introduced into the composite pretreatment liquid as a graphene surface modifier, and the amount added is 0.5-1.0% of the total mass of the composite pretreatment liquid; In S3, 0.1-0.5% of magnesium powder is added to the mixture as a reducing agent, and the particle size of the magnesium powder is 5-10μm and the purity is ≥99.5%.

[0024] The beneficial effects of this invention are as follows:

[0025] 1. This invention employs a composite pretreatment system of naphthyl reactive dispersant and silane coupling agent, overcoming the limitations of traditional single dispersants. The naphthyl reactive dispersant reacts strongly with graphene through its fused ring structure. Through interaction, graphene aggregates are efficiently dissociated. The active groups react with the silane coupling agent, and the other end of the silane coupling agent combines with the hydroxyl groups on the surface of aluminum powder to form a graphene-dispersant-aluminum powder bridging structure, achieving uniform adsorption and stable dispersion of graphene. This improves dispersion stability, increases the graphene dispersion concentration, and the dispersant can participate in interfacial reactions, avoiding the negative impact of residues on conductivity. This ensures that graphene fully utilizes its high conductivity properties to form a continuous three-dimensional conductive network.

[0026] 2. This invention modifies graphene by coating it with cerium oxide, utilizing the reactive wetting and displacement reactions between rare earth oxides and the aluminum matrix. This improves the interfacial bonding between graphene and aluminum while generating nano-sized... The metamorphic effect of rare earth element Ce can refine the grain size of the aluminum matrix; combined with electroless aluminum plating to pre-deposit a metallic aluminum layer on the surface of modified graphene, the wettability of graphene and molten aluminum is further improved. Then, a sandwich structure is constructed by layered casting, which effectively solves the defects of graphene agglomeration and floating in the aluminum matrix, achieves multidimensional uniform distribution of graphene, and avoids the formation of brittle phases that are easily generated when graphene is directly added. The problem is to improve the mechanical properties of composite materials.

[0027] 3. This invention employs a microwave-assisted low-temperature sintering process, adding magnesium powder as a reducing agent to the mixture. The microwave field selectively heats both aluminum and magnesium powder, simultaneously achieving in-situ reduction of the aluminum powder surface oxide layer and graphene fixation, shortening the sintering time, reducing the graphene damage rate to <5%, and achieving a composite material density of 99.5%. By dynamically adjusting the microwave power gradient, graphene is enriched on the material surface to form a continuous conductive network, while the interior is a high-purity aluminum matrix, forming a conductivity-strength gradient structure. Ultimately, the conductivity of the composite material is increased to 85% IACS, and the tensile strength is increased by 15%, balancing high conductivity with excellent mechanical properties. At the same time, low-temperature rapid sintering reduces energy consumption and improves the feasibility of industrial mass production. Attached Figure Description

[0028] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0029] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0030] Example 1

[0031] according to Figure 1 As shown in the figure, this embodiment proposes a method for preparing a graphene-aluminum high-conductivity composite material, including the following steps:

[0032] Composite dispersion of graphene - pretreatment

[0033] A composite pretreatment solution of "naphthyl reactive dispersant (HSiOND) + silane coupling agent (KH560)" was prepared, wherein the mass ratio of naphthyl reactive dispersant to silane coupling agent was 1:0.8, and the concentration of the composite pretreatment solution was 5 g / L. 10 g of graphene was added to 1000 mL of the composite pretreatment solution, and an ultrasonic disperser (power 300 W) was turned on for 30 min, while a mechanical stirrer (speed 500 r / min) was turned on for 60 min. The synergistic effect of ultrasonication and stirring enabled the graphene to be fully dissociated and dispersed, resulting in a uniformly dispersed graphene dispersion.

[0034] Graphene coating modification and electroless aluminum plating

[0035] Add 3g of cerium oxide powder (cerium oxide to graphene mass ratio of 0.3:1) to the obtained graphene dispersion, adjust the pH of the system to 8 with ammonia, and raise the system temperature to [temperature missing]. The reaction was stirred for 2 hours to complete the coating modification of graphene with cerium oxide; the modified graphene was then filtered through vacuum filtration, washed three times with deionized water, and placed in a vacuum drying oven. Cerium oxide-coated modified graphene was obtained by drying under certain conditions for 2 hours. The dried modified graphene was then placed in 1000 mL of electroless aluminum plating solution (aluminum ion concentration of 10 g / L), and the system temperature was raised to [temperature missing]. After a 1-hour heat treatment, a layer of aluminum metal is pre-deposited on the surface of the modified graphene. After filtration, washing, and drying, chemically plated aluminum-modified graphene is obtained.

[0036] Preparation of mixtures

[0037] Take 1g of electroless aluminum-modified graphene, 100g of aluminum powder (particle size 10μm), and 0.1g of magnesium powder (particle size... Mix the ingredients (99.5% purity) with 200 mL of anhydrous ethanol as the dispersion medium. Use an ultrasonic disperser (200W) for 20 minutes, simultaneously stirring with a mechanical stirrer (400 rpm) for 40 minutes. After dispersion, place the mixture in a vacuum drying oven. The mixture was dried for 2 hours under the specified conditions to remove anhydrous ethanol, resulting in a uniformly mixed graphene-aluminum-magnesium powder mixture.

[0038] Microwave-assisted low-temperature in-situ reduction sintering

[0039] The obtained mixture was placed in a graphite mold and pressed into shape using a press at a pressure of 50 MPa to obtain a green body with a diameter of 50 mm and a thickness of 10 mm. The green body was then placed in a microwave sintering furnace, with argon gas introduced as a protective gas. A dynamic power gradient microwave sintering process was adopted: in the initial stage of sintering (0-2 min), the microwave power of the surface layer was 1000 W and the microwave power of the interior layer was 800 W; in the middle stage of sintering (2-8 min), the microwave power of both the surface layer and the interior layer was maintained at 900 W; in the final stage of sintering (8-10 min), the microwave power of the surface layer was reduced to 800 W while the microwave power of the interior layer remained at 800 W. The overall sintering temperature was controlled at [temperature range missing]. The sintering time is 10 min. The graphene is fixed simultaneously by reducing the oxide layer on the surface of aluminum powder with magnesium powder, thus obtaining a green blank of graphene-aluminum composite material.

[0040] Layered casting and post-treatment

[0041] The obtained graphene-aluminum composite green body was placed in a high-temperature resistant casting mold, and a "sandwich" structure was constructed using a layered casting process. The top and bottom layers were graphene-enriched layers (with a microwave-sintered green body as the skeleton, 2 mm thick), and the middle layer was a high-purity semi-molten aluminum matrix layer (99.9% aluminum purity, 6 mm thick). The casting temperature was [temperature missing]. The casting speed is 5 mL / s; after casting, it is naturally cooled to room temperature, the surface of the blank is sanded with sandpaper, and then polished with a polishing machine to obtain a graphene-aluminum high conductivity composite material.

[0042] The performance of the composite material prepared in this embodiment was tested, and the results are as follows: the graphene dispersion was good and there was no obvious agglomeration; the density of the composite material was 99.2% and the graphene damage rate was 4.8%; the conductivity was 82% IACS (35% higher than that of pure aluminum), and the tensile strength was 168 MPa (12% higher than that of pure aluminum); the dispersion stability was improved by 40% compared with the traditional single dispersant system, and the graphene dispersion concentration was increased by 30%.

[0043] Example 2

[0044] according to Figure 1 As shown in the figure, this embodiment proposes a method for preparing a graphene-aluminum high-conductivity composite material, including the following steps:

[0045] Composite dispersion of graphene - pretreatment

[0046] A composite pretreatment solution of "naphthyl reactive dispersant (HSiOND) + silane coupling agent (KH570)" was prepared, wherein the mass ratio of naphthyl reactive dispersant to silane coupling agent was 1:1.2, and the concentration of the composite pretreatment solution was 10 g / L. 15 g of graphene was added to 1000 mL of the composite pretreatment solution, and the ultrasonic disperser (power 400 W) was turned on for 45 min, while the mechanical stirrer (speed 650 r / min) was turned on for 90 min. The synergistic effect of ultrasonication and stirring made the graphene fully dissociate and disperse, and a uniformly dispersed graphene dispersion was obtained.

[0047] Graphene coating modification and electroless aluminum plating

[0048] Add 9g of cerium oxide powder (cerium oxide to graphene mass ratio of 0.6:1) to the obtained graphene dispersion, adjust the pH of the system to 9 with sodium hydroxide solution, and raise the system temperature to [temperature missing]. The reaction was stirred for 3 hours to complete the coating modification of graphene with cerium oxide; the modified graphene was then filtered through vacuum filtration, washed four times with deionized water, and placed in a vacuum drying oven. Cerium oxide-coated modified graphene was obtained by drying under certain conditions for 3 hours. The dried modified graphene was then placed in 1000 mL of electroless aluminum plating solution (aluminum ion concentration of 15 g / L), and the system temperature was raised to [temperature missing]. After a 1.5-hour heat treatment, a layer of aluminum metal is pre-deposited on the surface of the modified graphene. After filtration, washing, and drying, chemically aluminized modified graphene is obtained.

[0049] Preparation of mixtures

[0050] Take 3g of electroless aluminum-modified graphene, 100g of aluminum powder (particle size 30μm), and 0.3g of magnesium powder (particle size... Mix the ingredients (99.5% purity) with 300 mL of anhydrous ethanol as the dispersion medium. Use an ultrasonic disperser (300W) for 30 minutes, simultaneously stirring with a mechanical stirrer (550 rpm) for 60 minutes. After dispersion, place the mixture in a vacuum drying oven. The mixture was dried for 3 hours under the specified conditions to remove anhydrous ethanol, resulting in a uniformly mixed graphene-aluminum-magnesium powder mixture.

[0051] Microwave-assisted low-temperature in-situ reduction sintering

[0052] The obtained mixture was placed in a graphite mold and pressed into shape using a press at a pressure of 60 MPa to obtain a green body with a diameter of 50 mm and a thickness of 10 mm. The green body was then placed in a microwave sintering furnace, and argon gas was introduced as a protective gas. A dynamic power gradient microwave sintering process was adopted: in the initial stage of sintering (0-2 min), the microwave power of the surface layer was 1000 W and the microwave power of the interior layer was 800 W; in the middle stage of sintering (2-8 min), the microwave power of both the surface layer and the interior layer was maintained at 900 W; in the final stage of sintering (8-10 min), the microwave power of the surface layer was reduced to 800 W and the microwave power of the interior layer was maintained at 800 W. The overall sintering temperature was controlled at 180℃ and the sintering time was 8 min. The graphene was simultaneously fixed by reducing the oxide layer on the surface of the aluminum powder with magnesium powder, thus obtaining a green body of graphene-aluminum composite material.

[0053] Layered casting and post-treatment

[0054] The obtained graphene-aluminum composite green body was placed in a high-temperature resistant casting mold, and a "sandwich" structure was constructed using a layered casting process. The top and bottom layers were graphene-enriched layers (with microwave-sintered green bodies as the skeleton, 2.5 mm thick), and the middle layer was a high-purity semi-molten aluminum matrix layer (99.9% aluminum purity, 5 mm thick). The casting temperature was 655℃ and the casting speed was 8 mL / s. After casting, the green body was naturally cooled to room temperature, the surface of the green body was sanded with sandpaper, and then polished with a polishing machine to obtain a graphene-aluminum high conductivity composite material.

[0055] The performance of the composite material prepared in this embodiment was tested, and the results are as follows: the graphene dispersion was excellent and there was no agglomeration; the density of the composite material was 99.6% and the graphene damage rate was 3.2%; the conductivity was 85% IACS (38% higher than that of pure aluminum), and the tensile strength was 172.5 MPa (15% higher than that of pure aluminum); the dispersion stability was improved by 45% compared with the traditional single dispersant system, and the graphene dispersion concentration was increased by 32%.

[0056] Example 3

[0057] according to Figure 1 As shown in the figure, this embodiment proposes a method for preparing a graphene-aluminum high-conductivity composite material, including the following steps:

[0058] Composite dispersion of graphene - pretreatment

[0059] A composite pretreatment solution of "naphthyl reactive dispersant (HSiOND) + silane coupling agent (KH590)" was prepared, wherein the mass ratio of naphthyl reactive dispersant to silane coupling agent was 1:1.5, and the concentration of the composite pretreatment solution was 15 g / L. 20 g of graphene was added to 1000 mL of the composite pretreatment solution, and the ultrasonic disperser (power 500 W) was turned on for 60 min, while the mechanical stirrer (speed 800 r / min) was turned on for 120 min. The synergistic effect of ultrasonication and stirring made the graphene fully dissociate and disperse, and a uniformly dispersed graphene dispersion was obtained.

[0060] Graphene coating modification and electroless aluminum plating

[0061] Add 16g of cerium oxide powder (cerium oxide to graphene mass ratio of 0.8:1) to the obtained graphene dispersion, adjust the pH of the system to 10 with ammonia, and raise the system temperature to [temperature missing]. The reaction was stirred for 4 hours to complete the coating modification of graphene with cerium oxide; the modified graphene was then filtered through vacuum filtration, washed five times with deionized water, and placed in a vacuum drying oven. Cerium oxide-coated modified graphene was obtained by drying under certain conditions for 4 hours. The dried modified graphene was then placed in 1000 mL of electroless aluminum plating solution (aluminum ion concentration of 20 g / L), and the system temperature was raised to [temperature missing]. After a 2-hour heat treatment, a layer of aluminum metal is pre-deposited on the surface of the modified graphene. After filtration, washing, and drying, chemically aluminized modified graphene is obtained.

[0062] Preparation of mixtures

[0063] Take 5g of chemically aluminized modified graphene and 100g of aluminum powder (particle size... ) and 0.5g magnesium powder (particle size) Mix the ingredients (99.5% purity) with 400 mL of anhydrous ethanol as the dispersion medium. Use an ultrasonic disperser (400W) for 40 minutes, simultaneously stirring with a mechanical stirrer (700 rpm) for 80 minutes. After dispersion, place the mixture in a vacuum drying oven. The mixture was dried for 4 hours under the specified conditions to remove anhydrous ethanol, resulting in a uniformly mixed graphene-aluminum-magnesium powder mixture.

[0064] Microwave-assisted low-temperature in-situ reduction sintering

[0065] The obtained mixture was placed in a graphite mold and pressed into shape using a press at a pressure of 70 MPa to obtain a green body with a diameter of 50 mm and a thickness of 10 mm. The green body was then placed in a microwave sintering furnace, with argon gas introduced as a protective gas. A dynamic power gradient microwave sintering process was adopted: in the initial stage of sintering (0-2 min), the microwave power of the surface layer was 1000 W and the microwave power of the interior layer was 800 W; in the middle stage of sintering (2-8 min), the microwave power of both the surface layer and the interior layer was maintained at 900 W; in the final stage of sintering (8-10 min), the microwave power of the surface layer was reduced to 800 W while the microwave power of the interior layer remained at 800 W. The overall sintering temperature was controlled at [temperature range missing]. The sintering time is 5 minutes. The graphene is fixed simultaneously by reducing the oxide layer on the surface of aluminum powder with magnesium powder, thus obtaining a green blank of graphene-aluminum composite material.

[0066] Layered casting and post-treatment

[0067] The obtained graphene-aluminum composite green body was placed in a high-temperature resistant casting mold, and a "sandwich" structure was constructed using a layered casting process. The top and bottom layers were graphene-enriched layers (with a microwave-sintered green body as the skeleton, 3 mm thick), and the middle layer was a high-purity semi-molten aluminum matrix layer (99.9% aluminum purity, 4 mm thick). The casting temperature was [temperature missing]. The casting speed is 10 mL / s; after casting, it is naturally cooled to room temperature, the surface of the blank is sanded with sandpaper, and then polished with a polishing machine to obtain a graphene-aluminum high conductivity composite material.

[0068] The performance of the composite material prepared in this embodiment was tested, and the results are as follows: the graphene was uniformly dispersed without obvious agglomeration; the density of the composite material was 99.4%, and the graphene damage rate was 4.1%; the conductivity was 84% ​​IACS (37% higher than that of pure aluminum), and the tensile strength was 170 MPa (13.3% higher than that of pure aluminum); the dispersion stability was improved by 48% compared with the traditional single dispersant system, and the graphene dispersion concentration was increased by 35%.

[0069] Validation data:

[0070] The graphene-aluminum high-conductivity composite material prepared in this invention was tested through three embodiments. Combined with a comparison with existing technologies, the core performance data are summarized in the table below. The performance of pure aluminum is used as a benchmark, and the existing technology is a graphene-aluminum composite material prepared by conventional powder metallurgy.

[0071]

[0072] As can be seen from the above data, the graphene-aluminum high conductivity composite material prepared by this invention is significantly superior to the prior art in terms of core properties such as conductivity, tensile strength, and density. At the same time, it greatly reduces the graphene damage rate, improves the dispersion stability and graphene dispersion concentration, and shortens the sintering time, achieving a dual improvement in performance and preparation efficiency, and solving the core bottleneck of the prior art.

[0073] This method for preparing graphene-aluminum high-conductivity composite materials employs a composite pretreatment system of naphthyl reactive dispersant and silane coupling agent, overcoming the limitations of traditional single dispersants. The naphthyl reactive dispersant reacts strongly with graphene through its fused ring structure. Through interaction, graphene aggregates are efficiently dissociated. The active groups react with the silane coupling agent, and the other end of the silane coupling agent binds to the hydroxyl groups on the aluminum powder surface, forming a graphene-dispersant-aluminum powder bridging structure. This achieves uniform adsorption and stable dispersion of graphene, improving dispersion stability and increasing graphene concentration. Furthermore, the dispersant can participate in interfacial reactions, avoiding the negative impact of residues on conductivity, ensuring that graphene fully utilizes its high conductivity properties to form a continuous three-dimensional conductive network. This invention modifies graphene by coating it with cerium oxide, utilizing the reactive wetting and displacement reactions between rare earth oxides and the aluminum matrix. While improving the bonding between graphene and aluminum, the generated nanoparticles... The metamorphic effect of rare earth element Ce can refine the grain size of the aluminum matrix; combined with electroless aluminum plating to pre-deposit a metallic aluminum layer on the surface of modified graphene, the wettability of graphene and molten aluminum is further improved. Then, a sandwich structure is constructed by layered casting, which effectively solves the defects of graphene agglomeration and floating in the aluminum matrix, achieves multidimensional uniform distribution of graphene, and avoids the formation of brittle phases that are easily generated when graphene is directly added. This invention addresses the problem of improving the mechanical properties of composite materials. It employs a microwave-assisted low-temperature sintering process, adding magnesium powder as a reducing agent to the mixture. The microwave field selectively heats both aluminum and magnesium powders, simultaneously achieving in-situ reduction of the aluminum powder surface oxide layer and fixation of graphene, shortening the sintering time by 70% (to approximately 8 minutes). The graphene damage rate is <5%, and the composite material density reaches 99.5%. By dynamically adjusting the microwave power gradient, graphene is enriched on the material surface to form a continuous conductive network (thickness...). The interior is a high-purity aluminum matrix, forming a conductivity-strength gradient structure, which ultimately increases the conductivity of the composite material to 85% IACS (38% higher than pure aluminum) and the tensile strength to 15% (150 MPa for pure aluminum). It balances high conductivity and excellent mechanical properties. At the same time, low-temperature rapid sintering reduces energy consumption and improves the feasibility of industrial mass production.

[0074] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a graphene-aluminum high-conductivity composite material, characterized in that, Includes the following steps: S1: Prepare a composite pretreatment solution of naphthyl reactive dispersant + silane coupling agent. Add graphene to the composite pretreatment solution and treat it by ultrasonic dispersion and mechanical stirring to obtain a graphene dispersion. S2: Cerium oxide powder is added to the graphene dispersion for coating modification to obtain cerium oxide coated modified graphene, and then chemically aluminized to obtain chemically aluminized modified graphene. S3: Chemically aluminized modified graphene, aluminum powder and magnesium powder are mixed, dispersed in anhydrous ethanol and then vacuum dried to obtain a uniformly mixed graphene-aluminum powder-magnesium powder mixture. S4: After the mixture is pressed into shape, it is placed in a microwave sintering furnace and sintered at low temperature using a dynamic power gradient process. The magnesium powder reduces the oxide layer on the surface of the aluminum powder, and the graphene is simultaneously fixed in the aluminum matrix to obtain a graphene aluminum composite green body. S5: Using the composite material preform as the surface and bottom skeleton, a high-purity semi-molten aluminum matrix layer is cast in layers to construct a sandwich structure. After cooling, it is polished to obtain a graphene-based aluminum high conductivity composite material.

2. The preparation method of a graphene-aluminum high conductivity composite material according to claim 1, characterized in that: In step S1, the mass ratio of naphthyl reactive dispersant HSiOND to silane coupling agent in the composite pretreatment solution is 1:0.8-1.5, and the concentration of the composite pretreatment solution is 5-15 g / L; the silane coupling agent is one or more of KH550, KH560, KH570 or KH590.

3. The preparation method of a graphene-aluminum high conductivity composite material according to claim 2, characterized in that: In step S1, the ultrasonic dispersion power is 300-500W and the ultrasonic time is 30-60min; the mechanical stirring speed is 500-800r / min and the stirring time is 60-120min; the ultrasonic dispersion and mechanical stirring are carried out simultaneously to ensure that the graphene is fully dissociated and dispersed.

4. The preparation method of a graphene-aluminum high conductivity composite material according to claim 3, characterized in that: In step S2, the mass ratio of cerium oxide powder to graphene is 0.3-0.8:

1. During the coating modification, the pH of the system is adjusted to 8-10, the reaction temperature is 50-70℃, and the reaction time is 2-4 hours. The cerium oxide coating thickness is controlled at 5-15 nm, and the coating thickness is calculated using the following formula: ， Where: d is the cerium oxide coating thickness (nm). The mass (g) of cerium oxide powder. Density of cerium oxide SG is the specific surface area of ​​graphene. It was obtained by measuring using the BET method.

5. The preparation method of a graphene-aluminum high conductivity composite material according to claim 4, characterized in that: In step S2, the aluminum ion concentration in the electroless aluminum plating solution is 10-20 g / L, and the electroless aluminum plating temperature is... The reaction time is 1-2 hours. During the electroless aluminum plating process, trace amounts of rare earth elements La or Nd are added, with the amount being 0.1-0.3% of the total mass of the electroless aluminum plating solution, to further improve wettability.

6. The method for preparing a graphene-aluminum high-conductivity composite material according to claim 5, characterized in that: In step S3, the mass ratio of chemically aluminized modified graphene to aluminum powder is 1-5:100; the particle size of the aluminum powder is... It is pure aluminum powder or aluminum alloy powder; the ultrasonic dispersion power is 200-400W, the ultrasonic time is 20-40min, the mechanical stirring speed is 400-700r / min, and the stirring time is 40-80min; the vacuum drying temperature is... The drying time is 2-4 hours.

7. The method for preparing a graphene-aluminum high-conductivity composite material according to claim 1, characterized in that: In step S4, the pressing pressure is 50-70 MPa; the microwave sintering temperature is... The power is 800-1000W, and the sintering time is 5-10 minutes. Argon gas is introduced as a protective gas during the microwave sintering process to prevent graphene oxidation.

8. The method for preparing a graphene-aluminum high-conductivity composite material according to claim 7, characterized in that: In S4, the dynamic power gradient process is specifically as follows: during the initial sintering stage (0-2 min), the surface microwave power is 1000W and the internal microwave power is 800W; during the middle sintering stage (2-8 min), both the surface and internal microwave powers remain at 900W; and during the final sintering stage (8-10 min), the surface microwave power decreases to 800W while the internal microwave power remains at 800W. The difference between the surface and internal microwave powers satisfies the following formula: ， in: The power difference (W) The surface microwave power is (W). Internal microwave power (W).

9. The preparation method of a graphene-aluminum high conductivity composite material according to claim 1, characterized in that: In S5, the temperature for layered casting is This allows the aluminum to be in a semi-molten state, with a casting speed of 5-10 mL / s. In the sandwich structure, the top and bottom layers are graphene-enriched layers, with microwave-sintered green blanks as the skeleton, and the middle layer is a high-purity semi-molten aluminum matrix layer. The thickness ratio of the top, middle, and bottom layers is 1:3:1-3:4:

3. The aluminum purity of the high-purity semi-molten aluminum matrix layer is ≥99.9%.

10. The method for preparing a graphene-aluminum high-conductivity composite material according to claim 6, characterized in that: In step S1, a trace amount of aminosilane coupling agent KH550 is introduced into the composite pretreatment solution as a graphene surface modifier, with the addition amount being 0.5-1.0% of the total mass of the composite pretreatment solution; in step S3, 0.1-0.5% of magnesium powder is added to the mixture as a reducing agent, the particle size of which is [missing information]. Purity ≥ 99.5%.

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