A method for self-repairing growth of graphene on the surface of a nickel-based metal substrate

Abstract

The present invention relates to a method for self-repairing growth of graphene on the surface of a nickel-based metal substrate. A continuous laser is used to irradiate a pure nickel plate pre-set with a graphite layer. After laser irradiation, graphene is grown in situ in the irradiated area, and the graphene is first-grown graphene. Sandpaper is used to remove the first-grown graphene to simulate the friction damage of graphene. The nickel substrate with the graphene removed from the surface is heat-treated. After the heat treatment, second-grown graphene is formed on the damaged nickel-based surface, thereby realizing self-repairing growth of graphene on the surface of the nickel-based metal substrate. The present invention uses a large amount of carbon source remaining in the metal substrate when preparing first-grown graphene by laser method as the parent material, and adopts heat treatment means to form second-grown graphene on the nickel substrate, thereby completing the self-repairing growth of graphene on the nickel-based surface. The method of the present invention is simple and easy to operate, and provides a new solution for providing long-term and stable protection for graphene in the field of metal protection.

Description

Technical Field

[0001] The invention belongs to the technical field of friction materials, and in particular relates to a method for self-repairing growth of graphene on the surface of a nickel-based metal substrate. Background Art

[0002] The economic losses caused by friction and wear in today's society are very huge. According to statistics, nearly 30% of the energy generated today is consumed by transportation vehicles, of which about one-third is lost in the friction and wear of the many moving parts of cars, buses and trucks. The use of lubricating and friction-resistant materials can reduce friction losses and save about 500 million pounds each year.

[0003] Zheng Quanshui and others from Tsinghua University found that graphene-based two-dimensional layered materials have "zero" friction, which opened up the application of graphene in the field of metal anti-friction. Wu et al. prepared a large-area graphene film based on the Marangoni effect, and transferred the graphene film to the surface of the ball-disk friction pair, and realized the relative sliding of graphene relative to graphene at a macroscopic scale, and obtained a minimum friction coefficient of 0.05. Bao et al. added graphene oxide to the lubricating oil, which greatly improved the lubrication performance, reduced the friction coefficient by 54%, and reduced the wear rate by 60%. The above work all reflects the superiority of graphene as a lubricating material. However, adding it only as an additive to the original lubricating oil and grease system fails to fully exert the "super lubrication" characteristics of graphene. Therefore, it is necessary to develop a material system with graphene as a surface coating to give full play to the superior anti-friction performance of graphene.

[0004] The main method for preparing large-area graphene films is chemical vapor deposition (CVD), which is to put Cu foil or Ni foil into a tube furnace, and then introduce argon, hydrogen and methane to obtain a carbon source by high-temperature decomposition of methane gas molecules, which is deposited on the substrate to form graphene; then the graphene-covered Cu foil is pressed between two rollers, and a thin polymer support film is added, and then the Cu substrate is removed by etching the groove, and the graphene is released from the polymer onto the flexible substrate, which can achieve large-scale growth. Another method for growing surface film layers is segregation growth, which relies on the energy difference between carbon atoms in the metal phase and the energy in graphene to form segregation power. When the temperature is lowered, carbon atoms will exist on the surface in the form of single-layer graphene. The number of graphene layers can be controlled by controlling the carbon doping concentration and temperature, or by changing the size of the segregation energy through the alloy method. Both of the above methods involve high temperature, long time, and other flammable and explosive emissions. Ye et al. developed a room temperature, environmentally friendly, and efficient large-area graphene growth method, which uses a laser method to prepare a fully covered graphene surface film on the surface of nickel, 45# steel, and copper. The results show that the graphene grown in situ by the laser method has excellent corrosion resistance and strong film-base bonding. However, the graphene film is only nanometer-level thick and easily disappears under the action of the friction pair. After disappearing, it cannot grow again and cannot protect the metal substrate for a long time. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a method for self-repairing growth of graphene on the surface of a nickel-based metal substrate, using a large amount of carbon source remaining in the metal substrate when preparing graphene by laser as the parent material, and adopting heat treatment means to form secondary growth graphene on the nickel substrate to complete the self-repairing growth of graphene on the nickel-based surface. The method of the present invention is simple and easy to operate, can realize the self-repairing growth of graphene, and provides a new solution for providing long-term and stable protection for graphene in the field of metal protection.

[0006] The present invention is specifically implemented by the following technical scheme. According to a method for self-repairing growth of graphene on the surface of a nickel-based metal substrate proposed by the present invention, the method specifically comprises the following steps:

[0007] (1) using a continuous laser to irradiate a pure nickel plate pre-deposited with a graphite layer, and after laser irradiation, in-situ growing graphene in the irradiated area, and this graphene is the graphene grown once;

[0008] (2) The primary grown graphene is removed by sandpaper to simulate the friction damage of graphene, and the nickel substrate with the graphene removed from the surface is heat treated. After the heat treatment, secondary grown graphene is formed on the damaged nickel-based surface, thereby realizing the self-repairing growth of graphene on the surface of the nickel-based metal substrate.

[0009] The aforementioned method for self-repairing growth of graphene on the surface of a nickel-based metal substrate, wherein the power of the laser irradiation in step (1) is 4500-5500W.

[0010] In the aforementioned method for self-repairing growth of graphene on the surface of a nickel-based metal substrate, the power of the laser irradiation in step (1) is 5000 W and the scanning speed is 6 mm / s.

[0011] In the aforementioned method for self-repairing growth of graphene on the surface of a nickel-based metal substrate, the spot size of the laser irradiation in step (1) is 10×1 mm 2 , graphene growth area is 12×30mm 2 .

[0012] In the aforementioned method for self-repairing growth of graphene on the surface of a nickel-based metal substrate, the thickness of the graphite layer in step (1) is 20 μm.

[0013] The aforementioned method for self-repairing growth of graphene on the surface of a nickel-based metal substrate, wherein in step (2), a tubular quartz furnace is used to heat treat the nickel substrate from which the graphene has been removed.

[0014] In the aforementioned method for self-repairing growth of graphene on the surface of a nickel-based metal substrate, the heat treatment in step (2) is carried out at 700° C. for 5 minutes.

[0015] In the aforementioned method for self-repairing growth of graphene on the surface of a nickel-based metal substrate, the friction coefficient of the pure nickel plate in step (1) is 0.169, and the friction coefficient of the once grown graphene sample is 0.093.

[0016] In the aforementioned method for self-repairing growth of graphene on the surface of a nickel-based metal substrate, the friction coefficient of the secondary grown graphene sample in step (2) is 0.056.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] (1) The present invention provides a method for self-repairing growth of graphene on the surface of a nickel-based metal substrate, wherein a nickel substrate pre-set with a graphite layer is irradiated with continuous laser, and primary grown graphene is formed on the nickel substrate after irradiation. After the primary grown graphene is worn, a large amount of carbon source remaining in the metal substrate when the primary grown graphene is prepared by laser method is used as the base material, and a tubular quartz furnace is used to heat treat the nickel substrate with the graphene removed from the surface, so as to form secondary grown graphene on the nickel substrate, thereby completing the self-repairing growth of graphene on the nickel-based surface. The regrown graphene has a 67% improved wear resistance compared to the original nickel substrate.

[0019] (2) The method of the present invention can not only realize the self-repairing growth of graphene, but also the regrown graphene has a lower friction coefficient than pure nickel and once grown graphene. The friction coefficient of the nickel substrate on which the graphene film is grown remains basically stable as the friction time increases, which plays a good protective role on the nickel substrate, indicating that graphene can provide long-term, effective and stable wear resistance, lubrication and protection effects for metal surfaces.

[0020] (3) The method of the present invention is simple and easy to operate, and can realize the self-repair growth of graphene, providing a new solution for providing long-term and stable protection for graphene in the field of metal protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of laser in-situ growth of graphene;

[0022] Figure 2 is a schematic diagram of graphene regrowth;

[0023] Figure 3 The morphology of the once grown graphene under different laser processing techniques of Example 1 to Example 5; wherein, Figures (a), (b), (c), (d), and (f) represent the morphology of the once grown graphene prepared in Example 1, Example 2, Example 3, Example 4, and Example 5, respectively;

[0024] Figure 4 is the Raman spectra of graphene grown once under different laser processing techniques in Example 1 to Example 5;

[0025] Figure 5 The surface morphology and cross-sectional morphology of the primary grown graphene of Example 2; wherein (a) represents a surface scanning electron microscope image, (b) represents a cross-sectional scanning electron microscope image, and (c) represents a cross-sectional component distribution image;

[0026] Figure 6 The front and back surfaces, cross-sectional morphology and structure of the secondary grown graphene of Example 2; wherein, (a) represents the surface optical micrograph of the primary grown graphene after mechanical polishing; (b) represents the cross-sectional scanning electron micrograph of the primary grown graphene; (c) represents the surface optical micrograph of the secondary grown graphene; (d) represents the surface scanning electron micrograph of the secondary grown graphene; (e) represents the surface scanning electron micrograph of the secondary grown graphene after magnification; (f) represents the surface Raman spectrum of the secondary grown graphene;

[0027] Figure 7 This is the curve of the friction coefficient of the original nickel substrate, the primary growth and the secondary growth samples changing with time under the test conditions of 500g load and 100r / min. DETAILED DESCRIPTION

[0028] In order to better understand the content of the present invention, the present invention will be further described below in conjunction with the embodiments and drawings. This embodiment is implemented based on the technology of the present invention, and provides detailed implementation methods and operating steps, but the protection scope of the present invention is not limited to the following embodiments.

[0029] The present invention provides a method for self-repairing growth of graphene on the surface of a nickel-based metal substrate, which specifically comprises the following steps:

[0030] (1) Pre-depositing a graphite layer on a pure nickel plate, specifically, mechanically polishing the pure nickel sheet; then mixing graphite nanoparticles with ethanol to form a paste, and evenly coating the paste on the polished nickel substrate through a spin coater to form a 20 μm thick graphite layer.

[0031] (2) A continuous laser (IPG-LDF6000) was used to generate a 20 μm thick graphite layer (D50 = 50 nm) on a pure nickel plate (30 × 30 × 5 mm 3 ) for irradiation, the schematic diagram is as follows Figure 1 The laser irradiation power is 4500-5500W, the scanning speed is 4-10mm / s, and the spot size is 10×1mm 2 , graphene growth area is 12×30mm 2 After laser irradiation, graphene is in-situ grown in the irradiated area, and this graphene is once grown.

[0032] (3) The graphene grown once is removed using 800-grit sandpaper to simulate the friction damage of graphene. The nickel substrate with the graphene removed from the surface is heat treated using a tubular quartz furnace. The schematic diagram is shown in FIG. Figure 2 As shown. The heat treatment is to keep the temperature at 700°C for 5 minutes. After the heat treatment, secondary growth graphene is formed on the damaged nickel-based surface, realizing the self-repair growth of graphene on the surface of the nickel-based metal matrix.

[0033] The following is a detailed description with specific embodiments in conjunction with the accompanying drawings:

[0034] Example 1

[0035] A continuous laser was used to irradiate a pure nickel plate with a 20 μm thick graphite layer pre-set, with a laser power of 4500 W and a scanning speed of 6 mm / s. After laser irradiation, a primary growth of graphene was formed in the irradiated area.

[0036] The primary grown graphene was removed by using 800-grit sandpaper to simulate the friction damage of graphene, and the nickel substrate with graphene removed from the surface was heat treated by using a tubular quartz furnace, and the heat treatment was carried out at 700°C for 5 minutes. After the heat treatment, secondary grown graphene was formed on the damaged nickel-based surface, realizing the self-repairing growth of graphene on the surface of the nickel-based metal substrate.

[0037] Example 2

[0038] A continuous laser was used to irradiate a pure nickel plate with a 20 μm thick graphite layer pre-set, with a laser power of 5000 W and a scanning speed of 6 mm / s. After laser irradiation, a primary growth of graphene was formed in the irradiated area.

[0039] The primary grown graphene was removed by using 800-grit sandpaper to simulate the friction damage of graphene, and the nickel substrate with graphene removed from the surface was heat treated by using a tubular quartz furnace, and the heat treatment was carried out at 700°C for 5 minutes. After the heat treatment, secondary grown graphene was formed on the damaged nickel-based surface, realizing the self-repairing growth of graphene on the surface of the nickel-based metal substrate.

[0040] Example 3

[0041] A continuous laser was used to irradiate a pure nickel plate with a 20 μm thick graphite layer pre-set, with a laser power of 5500 W and a scanning speed of 6 mm / s. After laser irradiation, a primary growth of graphene was formed in the irradiated area.

[0042] The primary grown graphene was removed by using 800-grit sandpaper to simulate the friction damage of graphene, and the nickel substrate with graphene removed from the surface was heat treated by using a tubular quartz furnace, and the heat treatment was carried out at 700°C for 5 minutes. After the heat treatment, secondary grown graphene was formed on the damaged nickel-based surface, realizing the self-repairing growth of graphene on the surface of the nickel-based metal substrate.

[0043] Example 4

[0044] A continuous laser was used to irradiate a pure nickel plate with a 20 μm thick graphite layer pre-set, with a laser power of 5000 W and a scanning speed of 10 mm / s. After laser irradiation, a primary growth of graphene was formed in the irradiated area.

[0045] The primary grown graphene was removed by using 800-grit sandpaper to simulate the friction damage of graphene, and the nickel substrate with graphene removed from the surface was heat treated by using a tubular quartz furnace, and the heat treatment was carried out at 700°C for 5 minutes. After the heat treatment, secondary grown graphene was formed on the damaged nickel-based surface, realizing the self-repairing growth of graphene on the surface of the nickel-based metal substrate.

[0046] Example 5

[0047] A continuous laser was used to irradiate a pure nickel plate with a 20 μm thick graphite layer pre-set, with a laser power of 5000 W and a scanning speed of 4 mm / s. After laser irradiation, a primary growth of graphene was formed in the irradiated area.

[0048] The primary grown graphene was removed by using 800-grit sandpaper to simulate the friction damage of graphene, and the nickel substrate with graphene removed from the surface was heat treated by using a tubular quartz furnace, and the heat treatment was carried out at 700°C for 5 minutes. After the heat treatment, secondary grown graphene was formed on the damaged nickel-based surface, realizing the self-repairing growth of graphene on the surface of the nickel-based metal substrate.

[0049] The primary grown graphene, the secondary grown graphene and the pure nickel substrate in the above embodiment were characterized by an optical microscope, a scanning electron microscope (LEO-1530), an energy dispersive spectrometer (EDS) and a Raman spectrometer (Renishaw-inVia).

[0050] Figure 3 The morphology of the graphene grown once under different laser processing techniques in Example 1 to Example 5. It can be seen that at a scanning speed of 6 mm / s, different laser powers have an effect on the morphology of the graphene grown once. When the laser power is too small (4500 W, Figure 3 (a)) The heat input from the laser is insufficient, so carbon remains on the surface of the nickel metal, hindering the formation of graphene. When the laser power is too high (5500W, Figure 3 (c)), resulting in severe oxidation of the metal surface. When the laser power reaches a certain value (5000W, Figure 3 (b)), a large graphene area can be formed.

[0051] Figure 3 (b), (d) and (f) show the surface microscopy images of graphene grown once at the same laser power (5000W) and different scanning speeds. Figure 3 (d), Example 4), the heat generated by the laser is not enough to form a complete molten pool on the nickel surface, and the carbon source on the surface fails to dissolve into the nickel substrate, so that the carbon particles remain on the surface and graphene cannot be formed. At a scanning speed of 4 mm / s ( Figure 3 (f), Example 5), the laser stays on the surface for a long time, and the heat generated by the laser causes the nickel-based surface layer to be overheated, resulting in oxidation of its surface. Figure 3(b), Example 2), the heat generated just forms a stable molten pool, so that the carbon source on the surface can be fully dissolved into the molten pool. When the laser is removed, the surface of the metal nickel cools down. Since carbon has a certain solid solubility in nickel, it can form a supersaturated solid solution. As the temperature decreases, the solubility decreases, and the carbon in the molten pool undergoes surface segregation and precipitation to form a graphene film on the surface.

[0052] Figure 4 The Raman spectra of graphene grown once under different laser processing techniques in Examples 1 to 5 show that typical graphene characteristic peaks can only appear under the conditions of 5000W and 6mm / s (Example 2). In summary, the best laser growth graphene process is 5000W and 6mm / s.

[0053] Figure 5 The surface morphology and cross-sectional morphology of the graphene grown once in Example 2; Figure 5 (a) is a scanning electron microscope image of the once-grown graphene. Obvious wrinkles in the graphene film can be clearly observed, which is caused by the different shrinkage coefficients of nickel and graphene during rapid solidification during laser processing. Figure 5 (b) is a cross-sectional scanning electron microscope image of once-grown graphene. Carbon particles can be clearly seen in the image, which provide the parent material carbon source for the regrowth of graphene. Figure 5 (c) shows Figure 5 (b) The composition distribution of different regions shows that the region ① close to the surface of the nickel substrate has the richest carbon source, with a mass fraction of 8.07%, followed by the carbon source mass fractions in regions ② and ③. This is because after the laser is turned off, the molten pool cools and begins to solidify, and the solubility of the carbon that has been dissolved in the nickel substrate also decreases. At the same time, the supersaturated carbon source begins to precipitate into carbon particles. When the solidification process reaches the terminal stage, a small amount of C in the liquid phase will precipitate to the free surface. These precipitated C will use the superior nucleation conditions of the free surface to eventually grow into a graphene film. From the surface to the depth of the substrate, the concentration of carbon particles decreases. Since the carbon concentration on the surface is higher than that in the bulk phase, this concentration gradient will promote the diffusion of the surface carbon source into the matrix. During the cooling process, the solid solubility of carbon in the metal decreases, and carbon atoms precipitate from the matrix to the surface.

[0054] Figure 6 The surface, cross-sectional morphology and structure before and after the secondary growth of graphene in Example 2; before the secondary growth of graphene, the graphene film grown once on the surface of the nickel substrate was polished and removed completely with sandpaper of different meshes to simulate the friction damage of graphene. Then, the carbon source in the substrate was promoted to precipitate to the surface by heat treatment, and a new graphene film (secondary growth of graphene) was regrown. Figure 6 (a) is a nickel substrate on which graphene is grown after mechanical polishing. It can be seen that the surface of the nickel substrate is smooth and there is no graphene film. Figure 6(b) is a longitudinal scanning electron micrograph of the cross section of the nickel substrate after the first growth of graphene, showing a large number of carbon particles precipitated, which provide the necessary conditions for the regrowth of graphene film. Figure 6 (c) and (d) are optical microscopy and scanning electron microscopy images of the secondary growth graphene, respectively. Figure 6 Compared with (a), a very obvious morphological change has occurred, and many carbon particles have appeared on the surface of the nickel substrate. This is because the concentration of carbon particles on the surface of the metal nickel after mechanical polishing is relatively low, while the substrate contains a large amount of carbon source, the concentration is much higher than the surface, forming a concentration difference. After high-temperature heat treatment, the high-concentration carbon source inside the substrate can continue to diffuse to a lower concentration on the surface under the action of heat and the transition from its own supersaturated state to a saturated state. Finally, during the cooling process, the supersaturated carbon atoms meet on the surface and nucleate and grow into graphene. Figure 6 (e) In the enlarged image of the scanning electron microscope, obvious wrinkles can be seen, which is a typical morphology of graphene. The Raman spectrum of the graphene grown under the optimal growth conditions of Example 2 was tested using a Raman spectrometer. Figure 6 As shown in (f), four positions were randomly selected on the surface after secondary growth of graphene, and the characteristic peaks of graphene, G peak and 2D peak, appeared, which is consistent with the structural characteristics of graphene. The defect peak D peak is smaller, indicating that the crystallinity of graphene after secondary growth is better; the intensity of 2D peak is lower than that of G peak, showing the characteristics of multilayer graphene.

[0055] The friction properties of pure nickel, primary grown graphene and secondary grown graphene in Example 2 were studied using a friction and wear testing machine. Figure 7 This is the relationship between the friction coefficient of the original nickel substrate, the once grown graphene and the second grown graphene samples and their changes over time under the test conditions of 500g load and 100r / min. The friction coefficient of the original nickel substrate is about 0.169, the friction coefficient of the sample after the first growth of graphene is about 0.093, and the friction coefficient of the sample after the second growth of graphene is about 0.056. The wear resistance of the sample after the first growth of graphene film is 45% higher than that of the original nickel substrate. The sample obtained by the second growth has a lower friction coefficient, and its wear resistance is 67% higher than that of the original nickel. The nickel substrate on which the graphene film is grown remains basically stable with only a small fluctuation as the friction test time increases, while the friction coefficient of the original nickel substrate fluctuates greatly as time goes by. Due to the presence of graphene film, while reducing the friction coefficient of the nickel-based surface, the stability of the friction coefficient can also be maintained for a long period of time. When the stainless steel ball slides relatively on the graphene film on the surface of the nickel substrate, it is equivalent to sliding on the crystal plane. That is, graphene can provide long-term, effective and stable wear resistance, lubrication and protection effects for the metal surface.

[0056] The above is only an embodiment of the present invention, and does not limit the present invention in any form. The present invention can also have other forms of embodiments according to the above structures and functions, which are not listed one by one. Therefore, any simple modification, equivalent change and modification made by any technician familiar with the profession to the above embodiment according to the technical essence of the present invention without departing from the scope of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for self-repairing growth of graphene on the surface of a nickel-based metal substrate, characterized in that The specific steps include: (1) A continuous laser is used to irradiate a pure nickel plate pre-deposited with a 20 μm thick graphite layer, wherein the laser power is 5000 W and the scanning speed is 6 mm / s. After laser irradiation, graphene is grown in situ in the irradiated area, and the graphene is once grown. The friction coefficient of the pure nickel plate is 0.169, and the friction coefficient of the once grown graphene sample is 0.

093. (2) The above-mentioned primary grown graphene is removed by sandpaper to simulate the friction damage of graphene, and the nickel substrate with the graphene removed from the surface is heat treated by a tubular quartz furnace, and the heat treatment is carried out at 700°C for 5 minutes. After the heat treatment, secondary grown graphene is formed on the damaged nickel-based surface, and the self-repairing growth of graphene on the surface of the nickel-based metal substrate is achieved. The friction coefficient of the secondary grown graphene sample is 0.

056.

2. The method for self-repairing growth of graphene on the surface of a nickel-based metal substrate as claimed in claim 1, characterized in that The spot size of the laser irradiation in step (1) is 10×1 mm 2 , the graphene growth area is 12×302 mm.

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