Preparation method of nickel-coated graphene and application of nickel-coated graphene in aluminum matrix composite

Abstract

The application belongs to the technical field of composite materials, and discloses a preparation method of nickel-coated graphene and application of the nickel-coated graphene in aluminum-based composite materials. The preparation method comprises the following steps: obtaining graphene nanosheets by pretreating natural graphite; forming a nickel catalytic seed layer through stannous chloride sensitization and sodium borohydride activation; and performing chemical plating in a plating solution containing nickel sulfate hexahydrate, sodium citrate, ammonium chloride and sodium hypophosphite monohydrate to obtain nickel-coated graphene with a 3-10 nm continuous nickel shell layer on the surface. The nickel-coated graphene is mixed with aluminum-silicon-magnesium alloy powder and ball milled, and then subjected to low-temperature reaction at 350-450 DEG C to generate Al3Ni phase, high-temperature hot pressing densification at 600-650 DEG C to obtain aluminum-based composite materials. The method can effectively control Al-C interface reaction, inhibit the generation of Al4C3, improve the mechanical properties and electrical conductivity of the composite materials, and is suitable for large-scale application.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a method for preparing nickel-coated graphene and its application in aluminum-based composite materials. Background Technology

[0002] Graphene possesses extremely high specific strength, electrical conductivity, and thermal conductivity, making it one of the ideal reinforcing phases for developing lightweight, high-performance aluminum-based composites. Introducing graphene into the aluminum matrix can significantly improve the mechanical, electrical, and thermal conductivity of the material while maintaining ductility, achieving structural and functional integration. However, existing graphene-reinforced aluminum-based composites still face two major technical challenges: first, graphene tends to agglomerate in aluminum powder due to strong van der Waals forces, resulting in poor dispersion uniformity; second, the high activity of the Al-C interface easily leads to the formation of a brittle Al4C3 phase, severely affecting the material's strength and environmental stability.

[0003] To overcome the above problems, CN117399639B proposes a method of vacuum ball milling graphene and Al-12Si powder followed by laser melting deposition, which can improve the dispersibility and density of graphene. The composite material prepared by this method has good hardness and wear resistance, but it cannot effectively suppress the interfacial reaction of Al4C3, and the material still faces the risk of degradation under service conditions. CN120330523A uses chemical copper plating to modify the surface of aluminum powder and then combines it with graphene oxide through electrostatic self-assembly, which can block the Al-C interfacial reaction to a certain extent. However, the copper coating easily dissolves in the aluminum matrix to form a brittle phase, lacking selective control over the interfacial reaction. In summary, existing technologies still have significant shortcomings in graphene dispersion, interfacial reaction regulation, and composite structure stability. A preparation method that can achieve controllable construction of the interfacial structure through in-situ induction and fundamentally solve the problems of graphene agglomeration and Al4C3 formation is still lacking. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a method for preparing nickel-coated graphene and its application in aluminum-based composite materials. This method constructs a continuous and uniform nanoscale nickel shell layer on the graphene surface through a three-step process of sensitization, activation, and chemical plating. Then, during the composite process with aluminum alloy powder, a stable Al3Ni intermediate phase is induced to form, effectively blocking the formation of the Al4C3 brittle phase and achieving in-situ controllable regulation of the interface structure. The resulting composite material has excellent mechanical and electrical properties.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing nickel-coated graphene includes the following steps: (1) Pretreatment of natural graphite to obtain graphene nanosheets; (2) Sensitize the graphene nanosheets; (3) Activation treatment of sensitized graphene nanosheets: disperse them in nickel salt solution, add sodium borohydride solution to carry out reduction reaction, and form nickel catalytic seed layer on the surface of graphene nanosheets; (4) The activated graphene nanosheets were placed in a plating solution containing a nickel source, complexing agent, buffer and hypophosphite reducing agent for chemical nickel plating reaction. After washing and drying, nickel-coated graphene was obtained. The nickel-coated graphene forms a continuous nano-nickel shell on its surface, which is used to induce the formation of an Al3Ni intermetallic compound layer in the preparation of aluminum-based composite materials.

[0006] More preferably, the pretreatment in step (1) is performed in sequence as follows: preparation of colloidal suspension, shear emulsification, sand milling, high-pressure micro-jet stripping, centrifugal separation, vacuum freeze drying and oxygen plasma treatment; The parameters for oxygen plasma treatment are as follows: oxygen purity not less than 99.99%, oxygen flow rate of 50-100 sccm, plasma power of 50-100 W, treatment time of 30-60 s, and the increase in oxygen content of graphene nanosheets after treatment is less than 1.5 wt%.

[0007] More preferably, the sensitization treatment in step (2) includes: immersing graphene nanosheets in a stannous chloride solution with a concentration of 10 g / L and a pH adjusted to about 1, keeping it at 25-30°C for 30 minutes, and then washing it with deionized water until the filtrate is neutral.

[0008] More preferably, the activation treatment in step (3) includes: dispersing the sensitized graphene nanosheets in a nickel chloride solution with a concentration of 0.1-1 g / L and stirring for 5-15 min, and slowly adding a sodium borohydride solution with a concentration of 1-5 g / L while continuously stirring to carry out a reduction reaction; After the reaction was completed, the graphene nanosheets with a nickel catalytic seed layer formed on the surface were obtained by washing and filtering.

[0009] More preferably, the plating solution in step (4) includes: a) Nickel source: nickel sulfate hexahydrate (NiSO4·6H2O); b) Complexing agent: sodium citrate; c) Buffer: ammonium chloride; d) Reducing agent: sodium hypophosphite monohydrate (NaH2PO2·H2O); The conditions for the electroless nickel plating reaction are: pH value of the plating solution is 8.75±0.25, reaction temperature is 85±2℃, and reaction time is 20 to 40 minutes; After the reaction is completed, the nickel-coated graphene is vacuum dried at 60°C for 12 hours, and a continuous nickel shell layer with a thickness of 3 to 10 nm is formed on the surface of the obtained nickel-coated graphene, covering a surface area of ​​not less than 99% of the graphene.

[0010] A nickel-coated graphene comprises graphene nanosheets and a continuous nano-nickel shell formed on their surface.

[0011] A method for preparing an aluminum-based composite material includes the following steps: S101. Nickel-coated graphene is mixed with aluminum-silicon-magnesium alloy AlSi10Mg powder, and grinding aid is added before ball milling to obtain composite powder; S102. The composite powder is subjected to a low-temperature reaction treatment to initiate the reaction between aluminum and nickel and generate the Al3Ni phase; S103. The composite powder that has undergone low-temperature reaction treatment is subjected to high-temperature hot pressing treatment to densify it and obtain an aluminum-based composite material.

[0012] More preferably, the amount of nickel-coated graphene added in step S101 is 0.1-0.5 wt%; the grinding aid is stearic acid, and the amount added is 1-2 wt%; the ball milling process is carried out under a nitrogen atmosphere, the ball milling speed is 300 rpm, and the ball milling time is 3-5 hours.

[0013] More preferably, the low-temperature heat treatment in step S102 is carried out under an argon atmosphere, with a treatment temperature of 350–450°C and a holding time of 50–70 minutes; the conditions for the high-temperature hot pressing treatment in step S103 are: a pressure of 1.0 GPa, a temperature of 600–650°C, and a holding time of 80–100 minutes.

[0014] An aluminum-based composite material comprising an aluminum-silicon-magnesium alloy AlSi10Mg matrix and a nickel-coated graphene reinforcing phase dispersed in the matrix, wherein a continuous Al3Ni intermetallic compound layer is formed at the interface of the composite material and is substantially free of detectable Al4C3 phase.

[0015] The beneficial effects of this invention are: This invention significantly improves the interfacial bonding between graphene and the aluminum matrix by constructing an "interfacial relay mechanism" and introducing a nanoscale continuous nickel coating layer on the graphene surface. Traditional aluminum-carbon interfaces, due to their high thermodynamic activity, readily form a brittle Al4C3 phase, leading to a decline in the mechanical properties and environmental stability of the composite material. However, the introduction of the nickel layer in this invention achieves a synergistic reaction pathway from graphene (C) to nickel (Ni), then to the intermediate phase Al3Ni, and finally to the aluminum matrix (Al), thus forming a stable, continuous, and dense Al3Ni intermetallic compound interfacial layer. This effectively blocks the formation of Al4C3 and constructs a strong and tough interfacial structure, significantly improving load transfer efficiency and interfacial stability. The proposed electroless nickel plating method is simple and highly controllable. By optimizing pH and temperature conditions, a uniform coating of a 3–10 nm continuous nickel shell layer is achieved on the graphene surface, with a nickel shell coverage exceeding 99%, providing a fundamental guarantee for the engineering feasibility of subsequent composite homogeneity and interfacial reactions. In the composite material preparation stage, the formation of the Al3Ni interface phase and the densification of the microstructure are further promoted by the ball milling-low temperature reaction-hot pressing integrated process. Attached Figure Description

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Figure 1 The graph shows a comparison of the tensile strength and tensile strength of the aluminum-based composite materials in Examples 1-3 and Comparative Examples 1-2. Figure 2 The graph shows a comparison of the tensile strength of aluminum-based composite materials in Examples 1-3 and Comparative Examples 1-2. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: This invention verifies that it can still achieve continuous and uniform coating and form an effective Al3Ni interface phase under low dosage, low energy consumption and low reaction intensity, providing a lower limit benchmark for process parameter optimization.

[0020] I. Preparation of Graphene Nanosheets 100 g of natural graphite with a particle size D50 = 8 μm and a purity ≥ 99.5% was weighed and mixed with 79.7 g of deionized water and 0.3 g of sodium deoxycholate dispersant. The dispersant was first stirred at 300 rpm for 10 min until completely dissolved, and then the graphite was slowly added. Stirring was continued for 30 min to obtain a colloidal suspension with a Zeta potential of approximately ±30 mV. This suspension was fed into a high-shear emulsifier and emulsified at 8000 rpm for 20 min. During emulsification, a cold water bath was used to maintain the temperature below 30℃ to obtain a preliminarily dispersed graphite colloidal solution. Subsequently, the emulsified colloidal solution was ground using zirconia beads as the grinding media at 2000 rpm, a grinding chamber pressure of 0.2 MPa, and a circulation flow rate of 10 L / h for 30 min. The ground slurry was then mixed at 8000 rpm for 4 h with continuous nitrogen purging to control the coefficient of variation of dispersion uniformity below 15%. The mixed slurry was then homogenized 30 times at a working pressure of 1500 bar with a feed flow rate of 5 L / h to obtain a graphene slurry with a solid content of approximately 10%. The slurry underwent two-stage centrifugation: the first stage involved centrifugation at 500 rpm for 20 min to remove unpeeled coarse particles, and the second stage involved centrifugation at 2500 rpm for 20 min to obtain graphene nanosheet precipitates. The precipitates were placed in a freeze dryer and dried for 24 h at a cold trap temperature of −50 °C and a vacuum of 10 Pa to obtain graphene nanosheets with a water content of no more than 1% and a specific surface area of ​​approximately 300 m² / g. The dried sample was then placed in an oxygen plasma device and treated for 30 s at an oxygen purity of no less than 99.99%, a flow rate of 50 sccm, and a plasma power of 50 W, ensuring that the increase in graphene oxygen content did not exceed 1.5 wt%.

[0021] II. Preparation of Nickel-Coated Graphene Weigh 0.5 g of the above graphene nanosheets and add them to 50 mL of a 10 g / L stannous chloride solution adjusted to pH 1 for sensitization treatment. After stirring at 25 °C for 30 min, filter and wash with deionized water until the filtrate is neutral. Add the sensitized sample to 50 mL of a 0.1 g / L nickel chloride (NiCl2) solution and stir for 5 min. Then, slowly add 20 mL of a 1 g / L sodium borohydride (NaBH4) solution and continue stirring for 15 min. Wash and filter to obtain graphene with a Ni seed layer on the surface. Prepare a chemical plating solution consisting of 25 g / L nickel sulfate hexahydrate, 15 g / L sodium citrate, and 5 g / L ammonium chloride. Adjust the pH of the solution to 8.5 and heat to 83 °C. Then add a 20 g / L sodium hypophosphite monohydrate reducing agent solution and the above-mentioned activated graphene, and maintain the reaction for 20 min. After the reaction was completed, the system was cooled, filtered under vacuum and washed multiple times with ethanol, and then dried under vacuum at 60°C for 12 h to obtain nickel-coated graphene powder with a continuous nickel shell layer on the surface. The thickness of the nickel shell layer was about 3 nm and the coverage was not less than 99%.

[0022] III. Preparation of Aluminum-Based Composite Materials 0.2 g of nickel-coated graphene was weighed and mixed with 199.8 g of AlSi10Mg alloy powder, and 2 g of stearic acid was added as a grinding aid. The mixture was then placed in a planetary ball mill under a nitrogen atmosphere and milled at 300 rpm for 3 h to obtain a composite powder. The resulting composite powder was placed in an argon atmosphere and held at 350 °C for 50 min to allow aluminum and nickel to react and form the Al3Ni phase. Subsequently, the treated powder was placed into a graphite mold, and a pressure of 1.0 GPa was applied under vacuum. The mixture was then held at 600 °C for 80 min to complete hot pressing sintering. After cooling and demolding, a dense nickel-coated graphene-reinforced aluminum matrix composite material was obtained.

[0023] Example 2: By selecting higher parameter values, the applicability and performance stability of the process of the present invention in enhancing interfacial reaction regulation and material densification are verified, demonstrating its feasibility and expansion potential under high temperature and high load conditions.

[0024] I. Preparation of Graphene Nanosheets 100 g of natural graphite with a particle size D50 of 12 μm and a purity of not less than 99.5% was weighed, and 79.7 g of deionized water and 0.3 g of sodium dodecylbenzenesulfonate dispersant were added. The mixture was stirred at 500 rpm for 20 min to fully dissolve the dispersant. Then, graphite particles were added, and stirring continued for 60 min to form a stable colloidal suspension with an absolute Zeta potential of not less than 30 mV. The resulting suspension was fed into a high-shear emulsifier and processed at 12000 rpm for 40 min, with the system temperature controlled to not exceed 30℃ using a cooling water bath. Subsequently, the emulsified colloidal solution was introduced into a sand mill, using zirconia beads as the grinding media, and ground for 120 min at 3000 rpm, a grinding chamber pressure of 0.4 MPa, and a circulation flow rate of 20 L / h. The ground slurry was transferred to a high-speed mixer and mixed at 8000 rpm for 4 h, with nitrogen continuously introduced to control the coefficient of variation of dispersion uniformity below 15%. The mixed slurry was then fed into a high-pressure microfluidic device and homogenized for 40 cycles at a working pressure of 2000 bar with a feed flow rate of 10 L / h, yielding a graphene slurry with a solid content of approximately 15%. The slurry underwent two-stage centrifugation: the first stage was centrifugation at 500 rpm for 30 min, and the second stage was centrifugation at 2500 rpm for 30 min to obtain graphene nanosheet precipitates. These precipitates were placed in a freeze dryer and dried for 48 h at a cold trap temperature of −40℃ and a vacuum of 20 Pa, yielding graphene nanosheets with a water content not exceeding 1% and a specific surface area of ​​approximately 600 m² / g. The dried sample was then placed in a plasma device and treated for 60 s at an oxygen purity not less than 99.99%, a flow rate of 100 sccm, and a plasma power of 100 W, ensuring that the increase in oxygen content did not exceed 1.5 wt%.

[0025] II. Preparation of Nickel-Coated Graphene Weigh 0.5 g of the above graphene nanosheets and add them to 50 mL of a 10 g / L stannous chloride solution with pH adjusted to approximately 1. Stir at 30 °C for 30 min, filter, and wash with deionized water until the filtrate is neutral. Add the sensitized graphene to 50 mL of a 1 g / L nickel chloride solution and stir for 15 min. Then, slowly add 20 mL of a 5 g / L sodium borohydride solution while stirring continuously, and continue the reaction for 15 min. Filter and wash thoroughly to obtain graphene with a nickel catalytic seed layer formed on its surface. Prepare a chemical plating solution consisting of 25 g / L nickel sulfate hexahydrate, 15 g / L sodium citrate, and 5 g / L ammonium chloride. Adjust the pH of the solution to 9.0 and heat to 87 °C. Then add a 20 g / L sodium hypophosphite monohydrate reducing agent solution and the above-mentioned activated graphene, and maintain the reaction for 40 min. After the reaction was completed, the system was cooled, filtered under vacuum and washed multiple times with ethanol, and then dried under vacuum at 60°C for 12 h to obtain nickel-coated graphene powder with a continuous nickel shell layer on the surface with a thickness of about 10 nm and a coverage of not less than 99%.

[0026] III. Preparation of Aluminum-Based Composite Materials 1.0 g of nickel-coated graphene was weighed and mixed with 199.0 g of AlSi10Mg alloy powder, and 4 g of stearic acid was added as a grinding aid. The mixture was then placed in a planetary ball mill under a nitrogen atmosphere and ball-milled at 300 rpm for 5 h to obtain a composite powder. The resulting composite powder was placed in an argon atmosphere and held at 450 °C for 70 min to allow aluminum and nickel to react and form the Al3Ni phase. Subsequently, the treated powder was loaded into a graphite mold, and hot-pressed sintering was completed by applying a pressure of 1.0 GPa under vacuum and holding at 650 °C for 100 min. After cooling and demolding, a dense nickel-coated graphene-reinforced aluminum matrix composite material was obtained.

[0027] Example 3: Using typical parameter conditions, the stability and repeatability of the material microstructure control and performance optimization of the process of the present invention were verified in actual preparation.

[0028] I. Preparation of Graphene Nanosheets 100 g of natural graphite with a particle size D50 of 10 μm and a purity ≥99.5% was weighed and added to 88.65 g of deionized water and 0.15 g of sodium deoxycholate dispersant. The dispersant was first dissolved by stirring at 400 rpm for 15 min, then the graphite particles were added, and stirring was continued for 45 min to obtain a colloidal suspension with a Zeta potential of |35| mV. This suspension was placed in a high-shear emulsifier, with a rotation speed of 10000 rpm and an emulsification time of 30 min. The system temperature was maintained at ≤30℃ by water bath cooling to obtain a graphite colloidal solution with an average particle size of approximately 8 μm. Subsequently, it was transferred to a sand mill using zirconia beads as the grinding media, with a grinding speed of 2500 rpm, a grinding time of 75 min, a circulation flow rate of 15 L / h, and a grinding chamber pressure of 0.3 MPa. After grinding, the slurry was fed into a high-speed mixer, with a rotation speed of 8000 rpm and a mixing time of 4 h, while nitrogen was continuously introduced. The CV value was controlled at 10%. Next, the sample was treated 35 times at 1750 bar in a high-pressure microfluidic apparatus with a feed rate of 7.5 L / h to obtain a graphene slurry with a solid content of 12.5%. The slurry was then fractionated using a horizontal centrifuge: the first stage was centrifuged at 500 rpm for 25 min; the second stage was centrifuged at 2500 rpm for 25 min, and the graphene nanosheets (GNPs) were collected. The separated sample was then placed in a freeze dryer at a cold trap temperature of -45℃ and a vacuum degree of 15 Pa for 36 h to obtain a dried GNP sample with a specific surface area of ​​450 m² / g and a moisture content ≤1%. This sample was subsequently treated with oxygen plasma (purity ≥99.99%, flow rate 75 sccm), with a plasma power of 75 W and a treatment time of 45 s, resulting in an increase in oxygen content of approximately 1.0 wt%.

[0029] II. Preparation of Nickel-Coated Graphene 0.5 g of graphene nanosheets were dispersed in 50 mL of a 10 g / L SnCl2 solution and stirred at 27 °C for 30 min. The solution was washed until the filtrate was neutral. Then, 50 mL of a 0.5 g / L NiCl2 solution was added, and the mixture was stirred for 10 min. Next, 20 mL of a 3 g / L NaBH4 solution was added dropwise, and the reaction was allowed to proceed for 15 min. After filtration and washing, graphene powder with a Ni seed layer on the surface was obtained. A plating solution (NiSO4·6H2O 25 g / L, sodium citrate 15 g / L, NH4Cl 5 g / L, pH = 8.75) was prepared and heated to 85 °C. Freshly prepared NaH2PO2·H2O solution (20 g / L) was added to the activated graphene powder, and the mixture was reacted under stirring for 30 min. After cooling and filtration, the powder was washed with ethanol and dried under vacuum at 60 °C for 12 h to obtain nickel-coated graphene powder with a shell thickness of approximately 6 nm and a coverage of ≥99%.

[0030] III. Preparation of Aluminum-Based Composite Materials 0.75 g of nickel-coated graphene powder was weighed and mixed with 199.25 g of AlSi10Mg powder. 3 g of stearic acid (1.5 wt%) was added, and the mixture was ball-milled at 300 rpm for 4 h under a nitrogen atmosphere to obtain a composite powder. The powder was placed in a tube furnace and reacted at 400 °C for 60 min under an argon atmosphere to induce the reaction between Al and Ni to form Al3Ni. After the reaction, the powder was placed in a graphite mold, and sintered at 625 °C for 90 min under a vacuum pressure of 1.0 GPa. After cooling and demolding, a dense and uniform nickel-coated graphene-reinforced aluminum matrix composite material sample was obtained.

[0031] Comparative Example 1: Preparation of graphene-reinforced aluminum matrix composite material without nickel coating.

[0032] I. Preparation of Graphene Nanosheets Referring to the method in Example 3, natural graphite (particle size D50=10 μm, purity ≥99.5%) was used as raw material. Graphene nanosheets (GNP) were prepared through steps such as dispersion, shear emulsification, sand milling, high-speed mixing, high-pressure micro-jet exfoliation, and two-stage centrifugation. Finally, GNP powder with a specific surface area of ​​about 450 m² / g and an oxygen content increase of about 1.0 wt% was obtained by freeze drying and oxygen plasma treatment.

[0033] II. Preparation of Aluminum-Based Composite Materials 0.75 g of uncoated GNP powder was weighed and mixed with 199.25 g of AlSi10Mg alloy powder. 3 g of stearic acid was added as a grinding aid, and the mixture was ball-milled at 300 rpm for 4 h under a nitrogen atmosphere to obtain a composite powder. The composite powder was placed in a tube furnace and reacted at 400 °C for 60 min under argon protection. Then, it was transferred to a vacuum environment and hot-pressed and sintered at 625 °C and 1.0 GPa for 90 min. After cooling and demolding, a comparative reinforced aluminum matrix composite material was obtained.

[0034] Comparative Example 2: Preparation method of nickel-coated graphene-reinforced aluminum matrix composite material without low-temperature pre-reaction treatment.

[0035] I. Preparation of Nickel-Coated Graphene Following the procedures outlined in Example 3 for "Preparation of Graphene Nanosheets" and "Preparation of Nickel-Coated Graphene," natural graphite with a particle size D50 of 10 μm and a purity ≥99.5% was selected as the raw material. Through steps such as shear emulsification, high-pressure microfluidic exfoliation, centrifugal drying, and plasma treatment, graphene nanosheets (GNPs) with an oxygen content increased by approximately 1.0 wt% and a specific surface area of ​​approximately 450 m² / g were obtained. Subsequently, through sensitization, activation, and electroless nickel plating processes, nickel-coated graphene powder with a shell thickness of approximately 6 nm and a coverage rate ≥99% was obtained.

[0036] II. Preparation of Aluminum-Based Composite Materials 0.75 g of nickel-coated graphene powder was weighed and mixed with 199.25 g of AlSi10Mg alloy powder. 3 g of stearic acid was added as a process control agent. The mixture was then placed in a planetary ball mill under a nitrogen atmosphere and ball-milled at 300 rpm for 4 h to obtain a uniformly dispersed composite powder. This composite powder was directly loaded into a graphite mold without any intermediate cryogenic treatment and placed under vacuum for direct hot-pressing sintering at 625℃ and 1.0 GPa for 90 min. After cooling and demolding, a comparative aluminum-based composite material was obtained.

[0037] Performance testing 1. Mechanical property testing The hardness of the aluminum matrix composite was tested using a Brinell hardness tester. Tensile strength and elongation were tested using an electronic universal testing machine at room temperature (25℃) with a tensile rate of 1 mm / min, in accordance with GB / T 228 standard. Three-point bending strength was tested according to GB / T 1449 standard, with a span of 20 times the distance between supports and a loading rate of 2 mm / min. Impact toughness was tested using a simply supported beam impact testing machine, conforming to GB / T 229 standard, and the K_IC value was calculated by measuring the energy absorbed at fracture. The results are shown in Table 1 below.

[0038] Table 1 Mechanical performance test results

[0039] As shown in Table 1, the mechanical properties of Examples 1-3 are significantly superior to those of Comparative Examples 1 and 2 in multiple indicators, fully demonstrating the effectiveness of nickel-coated graphene in reinforcing aluminum matrix composites. Example 2 exhibits the best overall performance, with yield strength and tensile strength reaching 355 MPa and 490 MPa, respectively, far exceeding the 250–265 MPa and 360–375 MPa of the comparative examples, indicating that the nickel-coated structure can effectively promote the formation of the reinforcing phase Al3Ni and improve load transfer capability. Furthermore, the increased elongation indicates that the material's ductility and toughness were not significantly sacrificed due to reinforcement. The simultaneous improvement in fracture toughness and three-point bending strength further demonstrates that the nickel-coated interface improves crack propagation resistance and interfacial bonding strength, significantly enhancing the structural reliability of the composite material.

[0040] 2. Thermal performance test Thermal performance testing included the determination of thermal conductivity and coefficient of thermal expansion. Thermal conductivity was measured using the laser flash method according to ASTM E1461. Samples were prepared as Φ10 mm × 2 mm discs, and the thermal diffusivity was measured at room temperature. The thermal conductivity was calculated by combining specific heat capacity and density. The coefficient of thermal expansion was measured using a thermomechanical analyzer. Within a temperature range of 25℃ to 300℃, the change in sample length was measured at a heating rate of 5℃ / min, and the linear coefficient of thermal expansion was calculated. The results are shown in Table 2 below. Table 2 Thermal conductivity and linear thermal expansion coefficient of each sample

[0041] As shown in Table 2, Examples 1–3 of this invention outperform the comparative samples in both thermal conductivity and coefficient of linear expansion, exhibiting significant advantages in thermal performance. Specifically, after introducing nickel-coated graphene, the thermal conductivity increased from 145 W / m·K in Comparative Example 1 and 150 W / m·K in Comparative Example 2 to 162–178 W / m·K in Examples 1–3, with a maximum increase of 22.8%. This indicates that the coated graphene forms a continuous and effective thermally conductive network in the aluminum matrix, significantly improving heat transfer efficiency. Simultaneously, the coefficient of linear expansion increased from 20.8–21.5 × 10⁻⁻⁻⁻⁶ in the comparative samples. 6 / K was reduced to 17.0–19.2 ×10⁻ in the examples. 6 / K effectively alleviates the problem of thermal expansion mismatch and improves thermal stability and dimensional stability.

[0042] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0043] 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 claimed invention.

Claims

1. A method for preparing nickel-coated graphene, characterized in that, Includes the following steps: (1) Pretreatment of natural graphite to obtain graphene nanosheets; (2) Sensitize the graphene nanosheets; (3) Activation treatment of sensitized graphene nanosheets: disperse them in nickel salt solution, add sodium borohydride solution to carry out reduction reaction, and form nickel catalytic seed layer on the surface of graphene nanosheets; (4) The activated graphene nanosheets were placed in a plating solution containing a nickel source, complexing agent, buffer and hypophosphite reducing agent for chemical nickel plating reaction. After washing and drying, nickel-coated graphene was obtained. The nickel-coated graphene forms a continuous nano-nickel shell on its surface, which is used to induce the formation of an Al3Ni intermetallic compound layer in the preparation of aluminum-based composite materials.

2. The method for preparing nickel-coated graphene according to claim 1, characterized in that, The pretreatment in step (1) involves the following operations in sequence: preparation of colloidal suspension, shear emulsification, sand milling, high-pressure micro-jet stripping, centrifugal separation, vacuum freeze drying and oxygen plasma treatment; The parameters for oxygen plasma treatment are as follows: oxygen purity not less than 99.99%, oxygen flow rate of 50-100 sccm, plasma power of 50-100 W, treatment time of 30-60 s, and the increase in oxygen content of graphene nanosheets after treatment is less than 1.5 wt%.

3. The method for preparing nickel-coated graphene according to claim 1, characterized in that, The sensitization treatment in step (2) includes: immersing graphene nanosheets in a stannous chloride solution with a concentration of 10 g / L and a pH adjusted to about 1, keeping it at 25-30°C for 30 minutes, and then washing it with deionized water until the filtrate is neutral.

4. The method for preparing nickel-coated graphene according to claim 1, characterized in that, The activation process in step (3) includes: dispersing the sensitized graphene nanosheets in a nickel chloride solution with a concentration of 0.1-1 g / L and stirring for 5-15 min; slowly adding a sodium borohydride solution with a concentration of 1-5 g / L while continuously stirring to carry out a reduction reaction; and washing and filtering after the reaction to obtain graphene nanosheets with a nickel catalytic seed layer formed on the surface.

5. The method for preparing nickel-coated graphene according to claim 1, characterized in that, The plating solution in step (4) includes: a) Nickel source: nickel sulfate hexahydrate (NiSO4·6H2O); b) Complexing agent: sodium citrate; c) Buffer: ammonium chloride; d) Reducing agent: sodium hypophosphite monohydrate (NaH2PO2·H2O); The conditions for the electroless nickel plating reaction are: pH value of the plating solution is 8.75±0.25, reaction temperature is 85±2℃, and reaction time is 20 to 40 minutes; After the reaction is completed, the nickel-coated graphene is vacuum dried at 60°C for 12 hours, and a continuous nickel shell layer with a thickness of 3 to 10 nm is formed on the surface of the obtained nickel-coated graphene, covering a surface area of ​​not less than 99% of the graphene.

6. A nickel-coated graphene, characterized in that, The nickel-coated graphene is prepared by the preparation method according to any one of claims 1-5, and includes graphene nanosheets and a continuous nano-nickel shell formed on their surface.

7. A method for preparing an aluminum-based composite material, characterized in that, Includes the following steps: S101. The nickel-coated graphene described in claim 6 is mixed with aluminum-silicon-magnesium alloy AlSi10Mg powder, and a grinding aid is added before ball milling to obtain a composite powder. S102. The composite powder is subjected to a low-temperature reaction treatment to initiate the reaction between aluminum and nickel and generate the Al3Ni phase; S103. The composite powder that has undergone low-temperature reaction treatment is subjected to high-temperature hot pressing treatment to densify it and obtain an aluminum-based composite material.

8. The method for preparing the aluminum-based composite material according to claim 7, characterized in that, In step S101, the amount of nickel-coated graphene added is 0.1–0.5 wt%; the grinding aid is stearic acid, and the amount added is 1–2 wt%; the ball milling process is carried out under a nitrogen atmosphere, the ball milling speed is 300 rpm, and the ball milling time is 3–5 hours.

9. The method for preparing the aluminum-based composite material according to claim 7, characterized in that, The low-temperature heat treatment in step S102 is carried out under an argon atmosphere, with a treatment temperature of 350-450℃ and a holding time of 50-70 minutes; the conditions for the high-temperature hot pressing treatment in step S103 are: pressure of 1.0 GPa, temperature of 600-650℃, and holding time of 80-100 minutes.

10. An aluminum-based composite material, characterized in that, The aluminum-based composite material is prepared by any of the preparation methods described in claims 7-9. The composite material comprises an aluminum-silicon-magnesium alloy AlSi10Mg matrix and a nickel-coated graphene reinforcing phase dispersed in the matrix. A continuous Al3Ni intermetallic compound layer is formed at the interface of the composite material, and it is substantially free of detectable Al4C3 phase.

Images