A method for preparing W surface-modified graphene nanosheets using a molten salt method

Abstract

This invention relates to a method for preparing W-surface-modified graphene nanosheets using a molten salt method. The invention aims to address the problem of poor interfacial interaction between graphene and the matrix in metal-based composite materials. The method comprises: 1. Functionalizing the graphene surface; 2. Preparing a mixed salt; 3. Mechanically mixing WO3 particles with the surface-functionalized graphene until homogeneous; spreading the mixed powder evenly at the bottom of a crucible and covering the surface with the mixed salt; 4. Placing the crucible in a heat treatment furnace for graphene surface modification; 5. Removing the reactants from the crucible, rinsing with distilled water and filtering, separating the W-surface-modified graphene, and drying it to complete the preparation of W-surface-modified graphene nanosheets using the molten salt method. This method is simple and provides good surface modification. Taking titanium-based composite materials as an example, surface modification effectively suppresses severe interfacial reactions between graphene and the titanium matrix, allowing graphene to be retained.

Description

Technical Field

[0001] This invention relates to a method for preparing W surface-modified graphene nanosheets using a molten salt method. Background Technology

[0002] With the continuous development of modern materials science and technology, the demand for high-performance materials is increasing. Metal matrix composites, due to their combination of the toughness of a metal matrix and the unique properties of other reinforcing phases, have become one of the hot topics in materials research. Among them, graphene nanosheets, with their unique structure, exhibit outstanding performance and have attracted much attention in the research and development of high-performance metal matrix composites.

[0003] Graphene possesses significant advantages in mechanical properties, with its strength and modulus leading among numerous materials. For example, its tensile strength can reach approximately 130 GPa, and its Young's modulus is about 1 TPa. These outstanding mechanical properties make it an ideal candidate material for enhancing the mechanical properties of metal matrix composites. Simultaneously, graphene also exhibits remarkable thermal and electrical conductivity. Its thermal conductivity can reach several kilowatts per (m·Kelvin) at room temperature, and its electrical conductivity is close to that of metallic copper. This means it has the potential to significantly improve the thermal and electrical properties of metal matrix composites, expanding its application range in numerous fields such as electronics, aerospace, and automotive.

[0004] However, numerous technical challenges have been encountered in the practice of combining graphene with metal matrices to prepare high-performance metal matrix composites, the most prominent of which is the interface problem between graphene and the matrix. When graphene is combined with commonly used metals such as copper and nickel, poor wettability becomes a key factor restricting interfacial bonding. From a microscopic perspective, wettability mainly depends on the surface energy of the material. The high interfacial energy between graphene and metals like copper makes it difficult for graphene to form a tight bonding interface on the metal surface during contact. For example, in traditional composite processes, even after simply mixing graphene and copper powder and pressing and sintering, poor wettability leads to numerous voids and defects at the interface, resulting in interfacial bonding relying solely on weak physical adsorption forces and lacking strong interactions such as chemical bonding. This weak interfacial bonding severely hinders the effective transfer of graphene's mechanical properties. Under external loads, stress concentration easily occurs at the interface, preventing graphene from fully utilizing its high strength and high modulus properties and failing to provide adequate reinforcement to the metal matrix, thus limiting the overall improvement in the mechanical properties of the composite material. In terms of thermal and electrical conductivity, the loose interfacial bonding greatly hinders the transmission of electrons and phonons at the interface, making it difficult for the composite material to achieve the expected thermal and electrical conductivity, and thus failing to fully utilize the excellent physical properties of graphene.

[0005] On the other hand, when graphene is combined with metals such as titanium, the problem of excessive interfacial reaction arises. Titanium is a highly chemically reactive metal, and under certain temperature and environmental conditions, it undergoes a violent chemical reaction with graphene to form metal carbides, such as TiC. This interfacial reaction fundamentally alters the structure of graphene. For example, during the high-temperature sintering preparation of graphene-reinforced titanium-based composites, the interfacial reaction gradually intensifies with increasing temperature, causing the special structure of graphene to gradually disintegrate, and its originally excellent mechanical, thermal, and electrical properties to decrease significantly. This destruction of the graphene structure due to interfacial reaction also prevents graphene from effectively reinforcing titanium-based composites, severely limiting the improvement of the performance and application expansion of such metal-based composites.

[0006] Currently, the metal surface-modified graphene nanosheets prepared mainly use elements such as Ni and Ag. Although these can improve the interface between graphene and the metal matrix in composite materials to some extent, they still suffer from the problem that Ni and Ag readily react with other metals to form brittle intermetallic compounds, leading to a decrease in the plasticity of the composite material. W is chosen as the surface-modifying element because it can be dissolved in most metals, ensuring effective interfacial bonding without causing severe interfacial reactions with the metal matrix to form brittle intermetallic compounds. Furthermore, W atoms dissolved in the metal matrix are beneficial for improving the high-temperature performance of the matrix. However, current methods for surface modification of graphene mainly involve wet modification techniques such as hydrothermal methods, which are complex, have low yields and low outputs, and are not suitable for W. Therefore, there is an urgent need to develop a more efficient W surface modification process. In summary, existing technologies for preparing metal matrix composites suffer from poor interfacial properties between graphene and the matrix. Whether it is poor wettability or excessive interfacial reaction, these issues severely restrict the full utilization of graphene's excellent properties in metal matrix composites. There is an urgent need to develop new technologies and methods to improve the interfacial bonding between graphene and the metal matrix in order to achieve the preparation of high-performance metal matrix composites. Summary of the Invention

[0007] The present invention aims to solve the problem of poor interface between graphene and matrix in metal matrix composites, and provides a method for preparing W surface modified graphene nanosheets by molten salt method.

[0008] A method for preparing W-surface modified graphene nanosheets using a molten salt method is specifically carried out according to the following steps:

[0009] 1. Graphene nanosheets are washed with distilled water and dried, then placed in hydrofluoric acid solution for ultrasonic dispersion to functionalize the graphene surface. After ultrasonication, the nanosheets are washed with distilled water and dried again to obtain graphene with functionalized surface.

[0010] 2. Mix NaCl and KCl mechanically until homogeneous to obtain a mixed salt;

[0011] 3. Mechanically mix WO3 particles with surface-functionalized graphene to obtain a mixed powder; spread the mixed powder evenly on the bottom of the crucible and cover the surface of the mixed powder with mixed salt to obtain a crucible containing mixed salt and mixed powder.

[0012] 4. Place the crucible containing the mixed salt and mixed powder into a heat treatment furnace and perform surface modification of graphene under an argon atmosphere; after the reaction is completed, cool the furnace to below 100°C under an argon atmosphere and remove the crucible.

[0013] 5. Remove the reactants from the crucible, rinse with distilled water and filter with filter paper to separate and dry the W-element surface-modified graphene, thus completing the preparation of W-element surface-modified graphene nanosheets by the molten salt method.

[0014] The beneficial effects of this invention are: the method is simple, the surface modification effect is good, and it solves the problem of poor interface between graphene and the matrix in metal matrix composites. Taking titanium-based composites as an example, after surface modification, the severe interfacial reaction between graphene and the titanium matrix is ​​effectively suppressed, allowing graphene to be retained. Attached Figure Description

[0015] Figure 1 SEM image of W-element surface-modified graphene nanosheets prepared for the example;

[0016] Figure 2 for Figure 1 The corresponding distribution diagram of W elements;

[0017] Figure 3 The image shows a comparison of engineering stress-strain between pure titanium and the W-element surface-modified graphene nanosheet-reinforced Ti-based composite material prepared according to the examples. Detailed Implementation

[0018] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0019] Specific Implementation Method 1: This implementation method for preparing W surface-modified graphene nanosheets using the molten salt method is specifically carried out according to the following steps:

[0020] 1. Graphene nanosheets are washed with distilled water and dried, then placed in hydrofluoric acid solution for ultrasonic dispersion to functionalize the graphene surface. After ultrasonication, the nanosheets are washed with distilled water and dried again to obtain graphene with functionalized surface.

[0021] 2. Mix NaCl and KCl mechanically until homogeneous to obtain a mixed salt;

[0022] 3. Mechanically mix WO3 particles with surface-functionalized graphene to obtain a mixed powder; spread the mixed powder evenly on the bottom of the crucible and cover the surface of the mixed powder with mixed salt to obtain a crucible containing mixed salt and mixed powder.

[0023] 4. Place the crucible containing the mixed salt and mixed powder into a heat treatment furnace and perform surface modification of graphene under an argon atmosphere; after the reaction is completed, cool the furnace to below 100°C under an argon atmosphere and remove the crucible.

[0024] 5. Remove the reactants from the crucible, rinse with distilled water and filter with filter paper to separate and dry the W-element surface-modified graphene, thus completing the preparation of W-element surface-modified graphene nanosheets by the molten salt method.

[0025] This embodiment modifies the surface of graphene incorporated into a metal matrix composite. This enhances the interfacial bonding between graphene and metal matrices such as copper, while simultaneously suppressing severe interfacial reactions between graphene and metal matrices such as titanium. W was chosen as the surface-modifying element because it is readily dissolved in most metals, ensuring effective interfacial bonding without causing severe interfacial reactions that could lead to brittle intermetallic compounds. Furthermore, the W atoms dissolved in the metal matrix contribute to improved high-temperature performance of the matrix.

[0026] This embodiment introduces functional groups to change the graphene surface from being non-wetting to wetting of elemental W to being wetting, allowing the reduced elemental W to nucleate and grow on the graphene surface, thus achieving surface modification of elemental W.

[0027] The molten salt system (NaCl-KCl) in this embodiment is in a molten state at high temperatures. This liquid environment provides an excellent medium for the reaction between WO3 and graphene. The molten salt lowers the activation energy of the reaction, promoting the reduction of W from WO3 particles and its nucleation and growth on the graphene surface, thereby forming a W-modified layer on the graphene surface. When the modified graphene is combined with a metal matrix, the presence of W on its surface avoids direct contact between graphene and the metal matrix, transforming the originally poorly bonded graphene-metal matrix interface into two interfaces: graphene-W and W-metal matrix. Since W nucleates and grows in situ on the graphene surface, its interfacial bonding with graphene is excellent. Simultaneously, W diffuses into the metal matrix through solid solution, also exhibiting good interfacial bonding. That is, by modifying the W surface, the original graphene-metal matrix interface with poor interfacial bonding or severe interfacial reaction is transformed into a graphene-W elemental-metal matrix interface with good bonding and no severe interfacial reaction, thus effectively solving the problem of poor graphene-matrix interface.

[0028] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the graphene nanosheets described in step one have a particle size of 1–5 μm and a thickness of 5–20 nm. Everything else is the same as in Specific Implementation Method One.

[0029] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 in that the volume concentration of the hydrofluoric acid solution in step one is 5-20%. Everything else is the same as in Specific Implementation Method 1.

[0030] Specific Implementation Method Four: This implementation method differs from Specific Implementation Method One in that the ultrasonic dispersion time in step one is 30–60 minutes. Everything else is the same as in Specific Implementation Method One.

[0031] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method One in that the molar ratio of NaCl to KCl in step two is 1:(0.5~2). Everything else is the same as in Specific Implementation Method One.

[0032] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method One in that the particle size of the WO3 particles mentioned in step three is 1-5 μm. Everything else is the same as in Specific Implementation Method One.

[0033] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method One in that the molar ratio of WO3 particles to surface-functionalized graphene in step three is 1:(5-20). Everything else is the same as in Specific Implementation Method One.

[0034] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method One in that the volume ratio of the mixed powder to the mixed salt in step three is 1:(2-4). Everything else is the same as in Specific Implementation Method One.

[0035] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Method One in that the reaction temperature in step four is 950–1100°C, and the holding time is 30–120 minutes. Everything else is the same as in Specific Implementation Method One.

[0036] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Method One in that the number of rinsing cycles in step five is 3 to 5. Everything else is the same as in Specific Implementation Method One.

[0037] The beneficial effects of the present invention are verified by the following embodiments:

[0038] A method for preparing W-surface modified graphene nanosheets using a molten salt method is specifically carried out according to the following steps:

[0039] 1. Graphene nanosheets with a particle size of 1-5 μm and a thickness of 5-20 nm were washed with distilled water and dried. Then, they were placed in a 10% hydrofluoric acid solution and ultrasonically dispersed for 30 min to allow the graphene to be fully dispersed in the solution and to come into full contact with HF to functionalize its surface. After ultrasonication, the graphene was washed with distilled water and dried again to obtain graphene with functionalized surface.

[0040] 2. Mix NaCl and KCl mechanically at a molar ratio of 1:1 until homogeneous to obtain a mixed salt;

[0041] 3. WO3 particles and surface-functionalized graphene are mechanically mixed uniformly at a molar ratio of 1:8 to obtain a mixed powder; the mixed powder is spread evenly on the bottom of a crucible, and mixed salt is covered on the surface of the mixed powder to obtain a crucible containing mixed salt and mixed powder; the volume ratio of mixed powder to mixed salt is 1:2.

[0042] 4. Place the crucible containing the mixed salt and mixed powder into a heat treatment furnace. The reaction temperature is 1000℃. The surface modification of graphene is carried out under an argon atmosphere for 30 minutes. WO3 particles react with graphene to reduce W element to nucleate and grow on the graphene surface, thus achieving W surface modification. After the reaction is completed, the furnace is cooled to below 100℃ under an argon atmosphere, and the crucible is removed.

[0043] 5. Remove the reactants from the crucible, rinse with distilled water and filter with filter paper to completely remove the salt from the mixed powder. Separate and dry the W-element surface-modified graphene to complete the preparation of W-element surface-modified graphene nanosheets by the molten salt method.

[0044] The room-temperature tensile properties of the hot-pressed sintered composite material prepared using W-modified graphene were tested, and the engineering stress-strain ratio is shown in the figure. The tensile strength of the W-modified graphene-reinforced Ti-based composite material is close to 380 MPa, which is about 20 MPa higher than that of pure titanium, while still retaining a fracture strain of about 0.17. Furthermore, with a graphene content of less than 0.5 wt.%, the thermal conductivity exceeds 19 W / (m·K), which is about 80% higher than that of pure titanium. This demonstrates that W-modified graphene can improve the composite material interface, enhancing strength while also exhibiting extremely high thermal conductivity.

Claims

1. A method of preparing W surface-modified graphene nanoplatelets by a molten salt method, characterized by The method for preparing W-surface modified graphene nanosheets by the molten salt method is specifically carried out according to the following steps:

1. Graphene nanosheets are washed with distilled water and dried, then placed in hydrofluoric acid solution for ultrasonic dispersion to functionalize the graphene surface. After ultrasonication, the nanosheets are washed with distilled water and dried again to obtain graphene with functionalized surface.

2. Mix NaCl and KCl mechanically until homogeneous to obtain a mixed salt; 3. Mechanically mix WO3 particles with surface-functionalized graphene to obtain a mixed powder; spread the mixed powder evenly on the bottom of the crucible and cover the surface of the mixed powder with mixed salt to obtain a crucible containing mixed salt and mixed powder.

4. Place the crucible containing the mixed salt and mixed powder into a heat treatment furnace and perform surface modification of graphene under an argon atmosphere; after the reaction is completed, cool the furnace to below 100°C under an argon atmosphere and remove the crucible.

5. Remove the reactants from the crucible, rinse with distilled water and filter with filter paper. Separate and dry the W-element surface-modified graphene, thus completing the preparation of W-element surface-modified graphene nanosheets by the molten salt method.

2. The method of claim 1, wherein the molten salt method of preparing W surface-modified graphene nanoplatelets is characterized by The graphene nanosheets mentioned in step one have a particle size of 1–5 μm and a thickness of 5–20 nm.

3. The method of claim 1, wherein the molten salt method of preparing W surface-modified graphene nanoplatelets is characterized by The volume concentration of the hydrofluoric acid solution mentioned in step one is 5-20%.

4. The method of claim 1, wherein the molten salt method of preparing W surface-modified graphene nanosheets is characterized by The ultrasonic dispersion time in step one is 30 to 60 minutes.

5. The method of claim 1, wherein the molten salt method of preparing W surface-modified graphene nanosheets is characterized by In step two, the molar ratio of NaCl to KCl is 1:(0.5~2).

6. The method of claim 1, wherein the molten salt method of preparing W surface-modified graphene nanosheets is characterized by The particle size of the WO3 particles mentioned in step three is 1-5 μm.

7. The method of claim 1, wherein the molten salt method of preparing W surface-modified graphene nanosheets is characterized by In step three, the molar ratio of WO3 particles to surface-functionalized graphene is 1:(5-20).

8. The method for preparing W surface-modified graphene nanosheets by molten salt method according to claim 1, characterized in that... In step three, the volume ratio of the mixed powder to the mixed salt is 1:(2-4).

9. The method for preparing W surface-modified graphene nanosheets by molten salt method according to claim 1, characterized in that... The reaction temperature in step four is 950–1100℃, and the holding time is 30–120 min.

10. The method for preparing W surface-modified graphene nanosheets by molten salt method according to claim 1, characterized in that... In step five, the rinsing should be repeated 3 to 5 times.

Images