Preparation method and application of carbon nanofiber surface uniformly coated with silver metal

Abstract

The application discloses a preparation method of carbon nanofiber surface uniformly coated with metal silver and application, and relates to the powder metallurgy technical field.The application provides a preparation method of carbon nanofiber surface uniformly coated with metal silver, which comprises the following steps: adding graphene oxide and polyvinylpyrrolidone into a solvent, and performing ultrasonic treatment to obtain a graphene oxide dispersion solution; adding a carbon source and silver nitrate into the graphene oxide dispersion solution and stirring to obtain a precursor solution; electrospinning the precursor solution to obtain a precursor film; placing the precursor film in an air atmosphere to perform pre-oxidation and obtaining a pre-oxidation film; placing the pre-oxidation film in an inert atmosphere to perform calcination and obtaining a silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material.The silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material prepared by the application can be used in the powder metallurgy field, and the performance of a silver-based composite material is improved.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, specifically to a method for preparing and applying a uniform coating of metallic silver on the surface of carbon nanofibers. Background Technology

[0002] Carbon nanofibers are nanoscale fibrous materials composed of carbon atoms, typically consisting of single or multiple layers of graphite formed by the arrangement of carbon atoms, exhibiting a tubular or fibrous structure. Carbon nanofibers generally have a high aspect ratio (diameter ranging from tens to hundreds of nanometers, with lengths reaching the micrometer scale). They exhibit a structure similar to carbon nanotubes, containing multiple layers of graphite rings within a single fiber, which gives them excellent mechanical and electrical properties; simultaneously, their graphitized structure provides good electrical conductivity. Carbon nanofibers can achieve a Young's modulus of up to 800 GPa, demonstrating exceptional mechanical properties, and their outstanding thermal stability allows them to maintain their mechanical properties and stability even at high temperatures. There are various methods for preparing carbon nanofibers, including template synthesis, catalytic chemical vapor deposition, and stretching methods. Among these, electrospinning, as a method for directly and continuously preparing polymer fibers, has been widely used in recent years.

[0003] Electrospinning metal nanoparticles onto the surface of carbon nanofibers can improve the wettability and interfacial bonding between the carbon nanofibers and the matrix, forming a continuous, high-strength interface. This is beneficial for improving the strength, hardness, conductivity, corrosion resistance, and wear resistance of the composite material. Despite the numerous advantages of metal-coated carbon nanofibers, the process still faces technical challenges. Due to the large surface curvature and poor dispersibility of carbon nanofibers, coupled with their low surface reactivity, ensuring successful and uniform metal coating is difficult, resulting in limited research on this type of nanoscale material. Traditional chemical plating methods often struggle to address the dispersion of metal particles when applied to carbon nanofibers, failing to achieve the desired coating effect. Therefore, existing methods for metal coating on carbon nanofibers suffer from uneven coating and weak interfacial bonding, significantly limiting the application of this technology. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing and applying a uniform coating of metallic silver on the surface of carbon nanofibers, thereby solving the following technical problems: Existing methods for coating metals onto the surface of carbon nanofibers suffer from problems such as uneven coating and weak interfacial bonding.

[0005] The objective of this invention can be achieved through the following technical solutions: A method for preparing a uniform coating of metallic silver on the surface of carbon nanofibers, comprising at least the following steps: Graphene oxide and polyvinylpyrrolidone were added to a solvent and ultrasonically treated to obtain a graphene oxide dispersion. A carbon source and silver nitrate were added to the graphene oxide dispersion and stirred to obtain a precursor solution. The precursor solution is electrospun to obtain a precursor film; The precursor film was placed in an air atmosphere for pre-oxidation to obtain a pre-oxidized film. The pre-oxidized film was calcined in an inert atmosphere to obtain a silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material.

[0006] As a further aspect of the present invention: the carbon source is polyacrylonitrile, and the solvent is N,N-dimethylformamide.

[0007] As a further aspect of the present invention: the mass fraction of the carbon source in the precursor solution is 5%-10%, the mass fraction of the silver nitrate is 1%-5%, and the mass fraction of the graphene oxide is 0.5%-2%.

[0008] As a further aspect of the present invention, the mass ratio of the polyvinylpyrrolidone to the multi-walled carbon nanotubes is 0.5-2:1.

[0009] As a further aspect of the present invention: the ultrasonic treatment power is 200-400W and the time is 1-2h, and the stirring time is 10-20h.

[0010] As a further aspect of the present invention, the technical parameters of the electrospinning are as follows: the rotation speed of the metal collector is 400-600 r / min, the humidity is 40-70%, the ambient temperature is 20-30℃, the spinning voltage is 10-20kV, and the liquid feeding speed is 0.0012-0.0017mm / s.

[0011] As a further aspect of the present invention: the pre-oxidation temperature is 130-300℃, the heating rate is 2-5℃ / min, and the time is 1-3h.

[0012] As a further aspect of the present invention: the calcination temperature is 500-700℃, the heating rate is 2-5℃ / min, and the time is 1-3h; the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0013] Application of a method for preparing carbon nanofibers uniformly coated with metallic silver as described above in the field of powder metallurgy.

[0014] The beneficial effects of this invention are: The present invention provides a method for preparing a uniform silver coating on the surface of carbon nanofibers. A precursor solution is prepared by adding polyacrylonitrile, silver nitrate, graphene oxide, and polyvinylpyrrolidone to N,N-dimethylformamide. A thin film is then formed using electrospinning technology. Finally, a silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material is obtained through pre-oxidation and calcination treatment. The carbon nanofibers formed by the polyacrylonitrile constitute a continuous fiber skeleton. Graphene oxide is partially reduced to reduced graphene oxide, which is wound, attached, or embedded on the surface of the carbon nanofibers. Silver nitrate is reduced to fine silver nanoparticles that uniformly coat the graphene oxide, reduced graphene oxide, and carbon nanofibers. The present invention provides a method for preparing carbon nanofibers with uniform metal coating on the surface through one-step blending spinning and in-situ synchronous reduction based on electrospinning technology. The preparation process is simple, safe and reliable, and ensures the uniformity and stability of the structure. The silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material prepared by the present invention has high conductivity, large specific surface area and excellent mechanical properties. When used in silver-based composite materials in powder metallurgy, it can significantly improve the wear resistance of electronic contacts and the catalytic activity of electrodes, and expand its application in high-end fields such as flexible electronics and energy storage.

[0015] This invention coats carbon nanofibers with metallic silver. Metal nanoparticles possess excellent catalytic, conductive, and optical properties, while carbon nanofibers exhibit good electrical conductivity. Combining the metal particles with a polymer to form a metal / polymer composite nanomaterial effectively prevents metal particle aggregation and significantly enhances the polymer's ability to participate in electron transfer and transport, thereby improving the material's conductivity. Simultaneously, the nanofibers obtained through electrospinning technology possess excellent specific surface area and mechanical properties; the combination of these two elements greatly enhances the material's mechanical properties. Furthermore, this invention introduces simultaneous electrospinning of graphene oxide. Graphene oxide, as an ideal two-dimensional flexible mesophase, combines with carbon nanotubes through a large contact area and interacts strongly with silver particles through its functional groups, improving interfacial stability, further preventing metal particle aggregation, and improving distribution uniformity. Moreover, the graphene oxide is partially reduced to reduced graphene oxide in the subsequent calcination step, further enhancing conductivity. Graphene oxide itself already possesses excellent hydrophilicity and dispersibility. This invention further introduces polyvinylpyrrolidone as a dispersant and structure-directing agent to further enhance the compatibility of graphene oxide with the polymer matrix and to more precisely control the nucleation sites of silver. This invention forms a highly efficient three-dimensional conductive and thermally conductive pathway by interlocking one-dimensional and two-dimensional materials and synergizing with highly conductive silver particles. When used in powder metallurgy as a reinforcement in silver-based powders, this composite material simultaneously leverages the bridging and toughening effects of one-dimensional fibers and the crack deflection and inhibition effects of two-dimensional sheets, resulting in a significant and simultaneous improvement in the strength, hardness, and toughness of the bulk composite material. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0017] Figure 1 It is the TEM image of the carbon nanofibers with uniformly coated silver on the surface obtained in Example 6 of the present invention; Figure 2 It is the EDS-Mapping image of the carbon nanofibers with uniformly coated silver on the surface obtained in Example 6 of the present invention; Figure 3 It is the hardness statistical chart of the bulk silver-based materials prepared in Application Examples 1, 2 and Comparative Examples 1, 2 of the present invention; Figure 4 It is the stress-strain curve of the bulk silver-based materials prepared in Application Examples 1, 2 and Comparative Examples 1, 2 of the present invention. Detailed implementation manners

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0019] Example 1 The preparation method for uniformly coating silver on the surface of carbon nanofibers includes the following steps: Add 20 mg of graphene oxide and 20 mg of polyvinylpyrrolidone to 3 mL of the solvent N,N-dimethylformamide, and perform ultrasonic treatment for 2 h at a power of 300 W to obtain a graphene oxide dispersion; Add 43 mg of silver nitrate and 0.3 g of polyacrylonitrile (PAN, Mw = 150000) to the above graphene oxide dispersion, and stir at room temperature for 12 h; obtain a precursor solution; Extract the above precursor solution into a 5 ml syringe, set the spinning voltage to 13 KV, the liquid supply speed to 0.0012 mm / s, the rotation speed of the metal collector to 500 r / min, the humidity to 65%, and the temperature to 25 °C. After spinning, obtain a uniform precursor film; Place the above precursor film in a tube furnace, heat it to 180 °C at a heating rate of 5 °C / min in an air atmosphere, keep it warm for 2 h, and cool it to room temperature to obtain a pre-oxidized film; The above pre-oxidized film was further carbonized in a tubular furnace. It was heated to 550 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, held for 2 h, and then cooled to room temperature to obtain a silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material.

[0020] Example 2 The preparation method for uniformly coating silver on the surface of carbon nanofibers includes the following steps: 20 mg of graphene oxide and 20 mg of polyvinylpyrrolidone were added to​​​​​​​​​​​​​​​​​​​​The above pre-oxidized film was further carbonized in a tubular furnace. It was heated to 650 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, held for 2 h, and then cooled to room temperature to obtain a silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material.

[0022] Example 4 The preparation method of uniformly coating silver on the surface of carbon nanofibers includes the following steps: 20 mg of graphene oxide and 20 mg of polyvinylpyrrolidone were added to 3 mL of the solvent N,N-dimethylformamide, and ultrasonic treatment was carried out for 2 h at a power of 300 W to obtain a graphene oxide dispersion; 43 mg of silver nitrate and 0.3 g of polyacrylonitrile (PAN, Mw = 150000) were added to the above graphene oxide dispersion, and stirred at room temperature for 12 h; a precursor solution was obtained; The above precursor solution was drawn into a 5 mL syringe, the spinning voltage was set at 13 KV, the liquid supply speed was 0.0012 mm / s, the rotation speed of the metal collector was 500 r / min, the humidity was 65%, and the temperature was 25 °C. After spinning, a uniform precursor film was obtained; The above precursor film was placed in a tubular furnace, heated to 240 °C at a heating rate of 5 °C / min in an air atmosphere, held for 2 h, and cooled to room temperature to obtain a pre-oxidized film; The above pre-oxidized film was further carbonized in a tubular furnace. It was heated to 650 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, held for 2 h, and then cooled to room temperature to obtain a silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material.

[0023] Example 5 The preparation method of uniformly coating silver on the surface of carbon nanofibers includes the following steps: 40 mg of graphene oxide and 40 mg of polyvinylpyrrolidone were added to 3 mL of the solvent N,N-dimethylformamide, and ultrasonic treatment was carried out for 2 h at a power of 300 W to obtain a graphene oxide dispersion; 85 mg of silver nitrate and 0.3 g of polyacrylonitrile (PAN, Mw = 15,0000) were added to the above graphene oxide dispersion, and stirred at room temperature for 12 h; a precursor solution was obtained; The above precursor solution was drawn into a 5 mL syringe, the spinning voltage was set at 13 KV, the liquid supply speed was 0.0012 mm / s, the rotation speed of the metal collector was 500 r / min, the humidity was 65%, and the temperature was 25 °C. After spinning, a uniform precursor film was obtained; The above precursor film was placed in a tubular furnace, heated to 240 °C at a heating rate of 5 °C / min in an air atmosphere, held for 2 h, and cooled to room temperature to obtain a pre-oxidized film; The above pre-oxidized film was further carbonized in a tube furnace. It was heated to 550 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, held for 2 h, and then cooled to room temperature to obtain a silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material.

[0024] Example 6 A preparation method for uniformly coating silver on the surface of carbon nanofibers includes the following steps: 85 mg of graphene oxide and 85 mg of polyvinylpyrrolidone were added to 3 mL of the solvent N,N-dimethylformamide, and ultrasonic treatment was carried out for 2 h at a power of 300 W to obtain a graphene oxide dispersion; 170 mg of silver nitrate and 0.3 g of polyacrylonitrile (PAN, Mw = 150000) were added to the above graphene oxide dispersion, and stirred at room temperature for 12 h to obtain a precursor solution; The above precursor solution was drawn into a 5 mL syringe. The spinning voltage was set to 13 KV, the liquid supply speed was 0.0012 mm / s, the rotation speed of the metal collector was 500 r / min, the humidity was 65%, and the temperature was 25 °C. After spinning, a uniform precursor film was obtained; The above precursor film was placed in a tube furnace, heated to 180 °C at a heating rate of 5 °C / min in an air atmosphere, held for 2 h, and cooled to room temperature to obtain a pre-oxidized film; The above pre-oxidized film was further carbonized in a tube furnace. It was heated to 550 °C at a heating rate of 5 °C / min under a nitrogen atmosphere, held for 2 h, and then cooled to room temperature to obtain a silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material.

[0025] Application Example 1 The application of uniformly coating silver on the surface of carbon nanofibers in powder metallurgy at least includes the following steps: <B The silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material obtained in Example 6 was mixed with Ag 92.5 Cu7Sb 0.5 alloy powder with a powder particle size of 25 - 75 μm in a volume ratio of 1:99 and ground for 10 min. Subsequently, it was added to absolute ethanol and ultrasonicated for 30 min, and dried in a blast drying oven at 60 °C to obtain a composite matrix powder material.

[0026] The above obtained composite matrix powder material was hot-pressed and sintered by a Harten Technology FHP-808 rapid hot-pressing furnace under the conditions of a sintering temperature of 973 K, a heating rate of 293 K / min, a pressure of 50 MPa during sintering, and a holding time of 30 min to obtain a bulk silver-based material C.

[0027] Application Example 2 The application of uniformly coating silver on the surface of carbon nanofibers in powder metallurgy at least includes the following steps: The silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material obtained in Example 6 was mixed with Ag powder having a particle size of 25 - 75 μm 92.5 Cu 6.5 and Sb1 series alloy powder in a volume ratio of 1:99 and ground for 10 min. Subsequently, it was added to absolute ethanol, ultrasonicated for 30 min, and dried in a blast drying oven at 60 °C to obtain a composite matrix powder material.

[0028] The obtained composite matrix powder material was hot - pressed and sintered by a Harten Technology FHP - 808 rapid hot - press furnace under the conditions of a sintering temperature of 973 K, a heating rate of 293 K / min, a pressure during sintering of 50 MPa, and a holding time of 30 min to obtain a bulk silver - based material D.

[0029] Comparative Example 1 Ag powder with a particle size of 25 - 75 μm 92.5 Cu7Sb 0.5 series alloy powder was hot - pressed and sintered by a Harten Technology FHP - 808 rapid hot - press furnace under the conditions of a sintering temperature of 973 K, a heating rate of 293 K / min, a pressure during sintering of 50 MPa, and a holding time of 30 min to obtain a bulk silver - based material A.

[0030] Comparative Example 2 Ag powder with a particle size of 25 - 75 μm 92.5 Cu 6.5 and Sb1 series alloy powder was hot - pressed and sintered by a Harten Technology FHP - 808 rapid hot - press furnace under the conditions of a sintering temperature of 973 K, a heating rate of 293 K / min, a pressure during sintering of 50 MPa, and a holding time of 30 min to obtain a bulk silver - based material B.

[0031] Performance testing The silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material obtained in Example 6 was observed and tested, and the test results are as Figure 1 and Figure 2 ; The bulk silver - based materials obtained in Application Example 1, Application Example 2, Comparative Example 1 and Comparative Example 2 were observed and tested, and the results are as Figure 3 and Figure 4 .

[0032] As Figure 1 and Figure 2 shown Figure 1TEM (Transmission Electron Microscope) image of the silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite prepared by the preparation method for uniformly coating silver on the surface of carbon nanofibers provided in Example 6. In the figure, the nanocrystals exhibit periodic lattice fringes with a measured spacing of 0.203 nm, corresponding to the (200) crystal plane of Ag; Figure 2 EDS (Energy-dispersive X-ray spectroscopy) image of the silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite prepared in Example 6. It can be seen from Figure 2 that the particles on the surface of the carbon nanofibers are indeed metallic silver.

[0033] As Figure 3 and Figure 4 shown, Figure 3 Hardness of the bulk silver-based materials C prepared in Application Example 1, the bulk silver-based materials D prepared in Application Example 2, the bulk silver-based materials A prepared in Comparative Example 1, and the silver-based bulk material B in Comparative Example 2. It can be seen from the figure that the hardness of the bulk silver-based materials A and B without adding carbon nanofibers are 67.69 and 65.91 respectively, while the hardness of the bulk silver-based materials C and D with the composite prepared in Example 6 added are 70.98 and 69.21 respectively. The hardness of the bulk silver-based composite after adding the composite prepared in Example 6 of the present invention has increased to a certain extent. Figure 4 Stress-strain curves of the bulk silver-based materials C prepared in Application Example 1, the bulk silver-based materials D prepared in Application Example 2, the bulk silver-based materials A prepared in Comparative Example 1, and the silver-based bulk material B in Comparative Example 2. The tensile strength of the bulk silver-based composite after adding the composite prepared in Example 6 of the present invention has increased compared to that without adding the sample, indicating that the mechanical properties of the bulk silver-based materials with the composite prepared in the present invention added have been enhanced.

[0034] In the description of this specification, the descriptions referring to terms such as "one embodiment", "example", "specific example", etc. mean that the specific features, structures, materials or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0035] The above has described an embodiment of the present invention in detail, but the content described is only the preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention shall still fall within the scope covered by the patent of the present invention.

Claims

1. A method for preparing a uniform coating of metallic silver on the surface of carbon nanofibers, characterized in that, At least the following steps are included: Graphene oxide and polyvinylpyrrolidone were added to a solvent and ultrasonically treated to obtain a graphene oxide dispersion. A carbon source and silver nitrate were added to the graphene oxide dispersion and stirred to obtain a precursor solution. The precursor solution is electrospun to obtain a precursor film; The precursor film was placed in an air atmosphere for pre-oxidation to obtain a pre-oxidized film. The pre-oxidized film was calcined in an inert atmosphere to obtain a silver / graphene oxide / reduced graphene oxide / carbon nanofiber composite material. Wherein, the carbon source is polyacrylonitrile, and the solvent is N,N-dimethylformamide; The precursor solution contains 5%-10% carbon source by mass, 1%-5% silver nitrate by mass, and 0.5%-2% graphene oxide by mass. The pre-oxidation temperature is 130-300℃, the heating rate is 2-5℃ / min, and the time is 1-3h; The calcination temperature is 500-700℃, the heating rate is 2-5℃ / min, and the time is 1-3h. The inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

2. The method for preparing a uniform coating of metallic silver on the surface of carbon nanofibers according to claim 1, characterized in that, The mass ratio of the polyvinylpyrrolidone to the graphene oxide is 0.5-2:

1.

3. The method for preparing a uniform coating of metallic silver on the surface of carbon nanofibers according to claim 1, characterized in that, The ultrasonic treatment power is 200-400W and the time is 1-2h, and the stirring time is 10-20h.

4. The method for preparing a uniform coating of metallic silver on the surface of carbon nanofibers according to claim 1, characterized in that, The technical parameters for electrospinning are as follows: the rotation speed of the metal collector is 400-600 r / min, the humidity is 40-70%, the ambient temperature is 20-30℃, the spinning voltage is 10-20kV, and the liquid feeding speed is 0.0012-0.0017mm / s.

5. The application of uniformly coated carbon nanofibers with metallic silver obtained by the preparation method according to any one of claims 1-4 in the field of powder metallurgy.

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