Graphite film, metal part comprising graphite film and preparation method of metal part

Abstract

The invention relates to a graphite film, a metal part comprising the graphite film and a preparation method of the graphite film, in particular to a method for rapid in-situ growth of the graphite film on the metal surface based on laser. According to the method, laser serves as a heat source, a solid carbon source serves as a raw material, and rapid in-situ growth of the graphite film on the metal surface can be achieved in an open environment. The grown graphite film has a uniformly stacked carbon atom layered structure, the number of layers of carbon atoms is greater than or equal to 10, and the thickness of the graphite film is 0.01-100 [mu] m. The graphite film and the metal part comprising the graphite film have wide application prospects in the engineering fields of friction reduction, abrasion reduction, corrosion resistance protection, refractory materials and the like.

Description

Technical Field

[0001] The present application belongs to the field of laser processing technology, and specifically relates to a graphite film, a metal part containing a graphite film, and a preparation method thereof, specifically a method for rapid in-situ growth of a graphite film on a metal surface based on laser. Background Art

[0002] Graphite film is composed of numerous layers of carbon atoms arranged in a hexagonal lattice, stacked together by van der Waals forces. This three-dimensional arrangement of carbon atoms, from points, lines, surfaces, to volumes, offers numerous excellent properties, including high electrical and thermal conductivity, wear resistance, lubricity, mechanical strength, and chemical stability. Compared to single-layer or few-layer graphene, graphite film, due to its multilayer structure, generally possesses superior mechanical strength and toughness, better dissipating external forces and impacts, and reducing the risk of material fracture. The interactions between the layers of graphite film provide more conductive pathways, resulting in more stable conductivity on a macroscopic scale. In applications requiring both heat conduction and heat diffusion, graphite film can conduct heat both in-plane and out-of-plane, resulting in superior overall thermal management performance. Furthermore, due to the weak van der Waals forces between the layers of graphite film, the outer carbon atoms act as a sacrificial layer in the event of chemical corrosion or mechanical wear, protecting the inner carbon layers and enhancing the overall stability of the material. Graphite film, due to its performance stability brought by its multi-layer structure, has shown broad application prospects and potential in the fields of thermal management, refractory materials, corrosion protection, solid lubrication, electrode materials, etc.

[0003] However, there is currently a lack of technical means to grow graphite films in situ on metal surfaces. Although there are many studies on the growth or preparation of single-layer or few-layer graphene, none of them are suitable for the growth and preparation of graphite films. Recently, a study used a heating furnace to achieve the growth of graphite on the surface of a metal substrate (Nature Nanotechnology, 2022(17), 1258–1264), but the growth rate is slow and needs to be carried out in a high-temperature, gas-protected environment, and the metal substrate must be heated as a whole. These conditions limit the high-efficiency and large-scale preparation of graphite films to a certain extent.

[0004] Laser beams have the characteristics of good monochromaticity, high energy density and processing precision. When interacting with materials, they can induce photochemical and photothermal effects and have been widely used in the field of material processing and preparation. Many studies have applied laser processing technology to the preparation of carbon materials and developed a variety of technical methods, but they mainly focus on graphene, including pulsed laser exfoliation of highly oriented pyrolytic graphite (HOPG), laser reduction of graphene oxide (RGO), laser opening of carbon nanotubes (CNT), laser-assisted epitaxial growth, laser-assisted chemical vapor deposition (LCVD), laser direct induced graphene (LIG), etc. (Advanced Functional Materials, 2022, 32(42), 2203164). However, the above-mentioned laser preparation of graphene technical methods, the product morphology of which is mainly a few-layer graphene film or three-dimensional porous graphene, cannot obtain high-quality graphite film, especially the controllable preparation of thick-layer graphite film in an open environment has not yet been achieved, which makes it difficult to meet the application needs of the engineering field. For the controllable preparation of graphite films, especially the rapid in-situ growth of graphite films on metal surfaces, effective technical means still need to be developed. Summary of the Invention

[0005] In response to the problems existing in the prior art, the present application provides a graphite film, a metal part containing the graphite film, and a preparation method thereof.

[0006] The method of the present application uses laser as a heat source and a solid carbon source as a raw material, and can realize the rapid in-situ growth of graphite film on the metal surface in an open environment. By setting the laser process parameters, scanning range, scanning path, etc., large-area and patterned preparation of graphite film can be conveniently achieved. The graphite film is grown in situ on the target metal substrate, and does not require a film transfer process, and also avoids the film damage and contamination problems caused by the transfer process; at the same time, the in-situ grown graphite film naturally forms a strong metallurgical bond with the substrate, which greatly reduces the impact of interface defects and can enhance the energy transfer between the graphite film and the metal substrate, which is of great value for practical engineering applications. Compared with single-layer or few-layer graphene, the graphite film prepared by the method of the present application can better meet the requirements of engineering fields such as friction reduction, corrosion protection, and refractory materials for the service stability and service life of functional films.

[0007] Specifically, this application involves the following aspects:

[0008] 1. A metal part comprising a metal substrate and a graphite film formed on a surface of the metal substrate, wherein the graphite film has a thickness of 0.01-100 μm.

[0009] 2. The metal part according to item 1, wherein the graphite film has a uniformly stacked carbon atom layer structure in a cross section perpendicular to the metal substrate, and the number of carbon atom layers is greater than or equal to 10.

[0010] 3. The metal part according to item 1 or 2, wherein the 2D peak intensity in the Raman spectrum of the graphite film is significantly weaker than the G peak.

[0011] 4. The metal part according to any one of items 1 to 3, wherein the material of the metal substrate is selected from one or more of nickel, iron / nickel alloy, and nickel / copper alloy.

[0012] 5. A method for preparing a graphite film, comprising the following steps:

[0013] applying a slurry containing a solid carbon source on a surface of a metal substrate and drying the slurry to form a solid carbon source coating;

[0014] The solid carbon source coating is laser treated in the presence of a protective gas to form a graphite film on the surface of the metal substrate.

[0015] 6. The preparation method according to item 5, wherein the power density of the laser used in the laser treatment is 1×10 3 -1×10 6 W / cm 2 , preferably 3.5×10 3 -8×10 4 W / cm 2 .

[0016] 7. The preparation method according to item 5 or 6, wherein the power of the laser used in the laser treatment is 10-10000W.

[0017] 8. The preparation method according to any one of items 5 to 7, wherein the duty cycle of the laser used in the laser treatment is 10% to 100%.

[0018] 9. The preparation method according to any one of items 5 to 8, wherein the defocus amount of the laser used in the laser treatment is -20 to +20 mm.

[0019] 10. The preparation method according to any one of items 5 to 9, wherein the shape of the laser spot used in the laser treatment is circular, rectangular or linear.

[0020] 11. The preparation method according to item 10, wherein the diameter of the circular light spot is 0.1-10 mm, and the side length of the rectangular or linear light spot is 0.1-20 mm.

[0021] 12. According to the preparation method described in item 10, the movement speed of the circular, rectangular or linear light spot relative to the surface of the metal substrate during the laser processing is 0.1-1000 mm / s.

[0022] 13. The preparation method according to any one of items 5 to 12, wherein the protective gas is selected from one or more of nitrogen, argon, and helium.

[0023] 14. The preparation method according to any one of items 5 to 13, wherein the flow rate of the protective gas is 1-100 L / min, preferably 20-40 L / min.

[0024] 15. The preparation method according to any one of items 5 to 14, wherein the material of the metal substrate is selected from one or more of nickel, iron / nickel alloy, and nickel / copper alloy.

[0025] 16. The preparation method according to any one of items 5 to 15, wherein the nickel content in the iron / nickel alloy or nickel / copper alloy is 20% or more.

[0026] 17. The preparation method according to any one of items 5 to 16, wherein the solid carbon source is selected from one or more of graphite powder, carbon black, activated carbon, and carbon nanotubes.

[0027] 18. The preparation method according to any one of items 5 to 17, wherein the thickness of the solid carbon source coating layer is 1 to 200 μm.

[0028] 19. A graphite film obtained by the preparation method described in any one of items 5 to 18.

[0029] 20. A metal part comprising a metal substrate and a graphite film formed on the surface of the metal substrate by the preparation method described in any one of items 5 to 18.

[0030] 21. A device comprising the metal part according to any one of items 1 to 4, or the metal part according to item 20.

[0031] Compared with the prior art, this application has the following beneficial effects:

[0032] 1. The present application uses laser as a heat source to grow graphite film, and can realize in-situ growth of graphite film in the desired area on the surface of the metal substrate in an open environment. There is no need to perform high-temperature treatment on the metal substrate as a whole, nor is there a need for high pressure, vacuum, special gas and other conditions. Thus, the restrictions on the shape and size of the sample to be processed by the heating furnace or chamber are avoided during the preparation process, which has significant advantages in engineering applications. In addition, the heating and cooling speeds in the laser action area are extremely fast, which greatly improves the dissolution / precipitation efficiency of carbon atoms in the metal substrate, and its graphite film growth rate is more than several thousand times that of the currently reported furnace heating method. In the present application, the metal substrate is only heated locally for a short time at the laser action position, and the heat-affected zone is narrow and concentrated on the surface of the sample, which avoids the degradation of the physical and chemical properties of the substrate caused by the long-term heating of the sample as a whole in the furnace heating method. The present application can perform laser direct writing processing according to the trajectory set in the software, which is convenient for realizing the automated control of graphite film preparation, and a patterned graphite film can be obtained without any mask plate. The laser processing head in this application is equipped with a spot shape and energy distribution form adjustment module, which can flexibly switch the shape, size and energy distribution form of the spot, and can achieve large-area and high-efficiency preparation of graphite films.

[0033] 2. This application uses a solid carbon source as the raw material for growing graphite film. Compared with gaseous carbon sources, solid carbon sources have lower storage costs and higher safety, and can get rid of the need for a sealed chamber and can be used in an open environment. By adjusting the parameters such as the rotation speed and spin coating time of the spin coater, the thickness of the solid carbon source coating can be flexibly controlled. The solid carbon source is directly spread on the surface of the substrate. Under the action of the laser heat source, it eliminates the cracking and adsorption elementary reaction process experienced by the gaseous carbon source, thereby improving the efficiency of carbon atoms dissolving into the substrate.

[0034] 3. This application achieves structural and functional integration of the processed specimen by in-situ growth of graphite films on target metal substrates. Compared to graphite films coated or transferred to the substrate surface, in-situ grown graphite films exhibit stronger adhesion to the substrate, significantly reducing the impact of interface defects and enhancing energy transfer between the graphite film and the metal substrate. Furthermore, it provides more comprehensive and precise coverage of the substrate surface and better control over the graphite's flake orientation and crystal quality.

[0035] 4. This application is applicable to a wide range of metal substrate materials and forms, including pure nickel, iron / nickel alloys, nickel / copper alloys, and other metal materials. Substrate forms include metal blocks, metal sheets, metal foils, metal meshes, and metal films. The nickel element in the substrate catalyzes the growth of graphite thin films. The substrate surface morphology applicable to this application can be flat or curved, enabling in-situ production of graphite thin films on non-standard shaped parts.

[0036] 5. The product of this application is a thick graphite film, composed of tens to tens of thousands of layers of carbon atoms arranged in a hexagonal lattice. It has a uniform layered structure and an overall thickness of over 1 μm. The thickness of the graphite film can be regulated by adjusting the thickness of the solid carbon source coating and laser process parameters. Thick graphite films have excellent performance stability and show broad application prospects and potential in engineering fields such as friction reduction, corrosion protection, and refractory materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the rapid in-situ growth of graphite film on a metal surface based on laser in this application;

[0038] Figure 2 (a) Optical micrograph and (b) SEM image of the surface morphology of the graphite film prepared in Example 1;

[0039] Figure 3 The atomic force microscope test results of the surface morphology of the graphite film prepared in Example 1;

[0040] Figure 4 Raman spectra of the graphite film prepared in Example 1: (a) Raman spectrum of the original solid carbon source coating (without laser treatment), (b) Raman spectrum of the laser in-situ grown graphite film on a pure nickel substrate;

[0041] Figure 5 The scanning electron microscope image of the cross section of the graphite film prepared in Example 1 and the thickness measurement results are shown;

[0042] Figure 6 High-resolution transmission electron microscopy images of different regions of the cross-section of the graphite film prepared in Example 1: (a) a high-resolution transmission electron microscopy image of the pure nickel substrate / graphite layer interface region, and (b) a high-resolution transmission electron microscopy image of the graphite layer region farther from the pure nickel substrate;

[0043] Figure 7 This is a scanning electron microscope image of the surface morphology of the graphite film prepared in Example 2;

[0044] Figure 8 This is the Raman spectrum of the graphite film prepared in Example 2;

[0045] Figure 9 This is an optical microscope photograph of the surface morphology of the graphite film prepared in Example 3;

[0046] Figure 10 This is an optical microscope photograph of the surface morphology of the graphite film prepared in Example 4;

[0047] Figure 11 This is an optical microscope photograph of the surface morphology of the graphite film prepared in Example 5;

[0048] Figure 12 This is an optical microscope photograph of the laser-treated surface in Comparative Example 1;

[0049] Figure 13 This is an optical microscope photograph of the laser-treated surface in Comparative Example 2;

[0050] Figure 14 This is an optical microscope photograph of the laser-treated surface in Comparative Example 3;

[0051] Figure 15 This is an optical microscope photograph of the laser-treated surface in Comparative Example 4;

[0052] Figure 16 This is an optical microscope photograph of the laser-treated surface in Comparative Example 5. DETAILED DESCRIPTION

[0053] The present application is further described below with reference to examples. It should be understood that the examples are only used to further illustrate and explain the present application and are not intended to limit the present application.

[0054] Unless otherwise defined, technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art. Although methods and materials similar or identical to those described herein may be used in experiments or practical applications, the materials and methods are described herein below. In the event of a conflict, the present specification, including definitions, will prevail. In addition, the materials, methods, and examples are provided for illustrative purposes only and are not intended to be limiting. The present application is further described below with reference to specific examples, which are not intended to limit the scope of this application.

[0055] Based on the problems existing in the prior art, the present application provides a metal part, comprising a metal substrate and a graphite film formed on the surface of the metal substrate, wherein the thickness of the graphite film is 0.01-100 μm.

[0056] Wherein, as required, the graphite film can be partially, patterned or completely covered on the surface of the metal substrate.

[0057] In some specific embodiments, the graphite film has a uniformly stacked carbon atom layer structure in a cross section perpendicular to the metal substrate, such as Figure 6 As shown, the number of carbon atom layers is greater than or equal to 10, for example, it can be 10, 20, 50, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 10000, 20000, 50000, 100000, etc.

[0058] The layered structure can be observed by methods known in the art, for example, by high-resolution transmission electron microscopy.

[0059] Assuming that the graphite has a uniform layered structure and interlayer spacing (single carbon atomic layer thickness) as determined by high-resolution transmission electron microscopy, the number of carbon atomic layers can be obtained by dividing the measured thickness of the graphite film by the thickness of the single carbon atomic layer. The thickness of the graphite film can be measured by methods known in the art, such as transmission electron microscopy or scanning electron microscopy.

[0060] In some specific embodiments, the 2D peak intensity in the Raman spectrum of the graphene film is significantly weaker than the G peak.

[0061] In some specific embodiments, the material of the metal substrate is selected from one or more of nickel, iron / nickel alloy, and nickel / copper alloy.

[0062] The metal substrate may be in various forms, including metal blocks, metal sheets, metal foils, metal meshes, metal films, and the like.

[0063] The surface of the metal substrate can be flat or curved, and its specific size can be selected according to actual needs.

[0064] In some specific embodiments, the metal part includes a metal substrate and a graphite film formed on the surface of the metal substrate, wherein the thickness of the graphite film is 0.01-100 μm, the graphite film has a uniformly stacked carbon atom layer structure in a cross-section perpendicular to the metal substrate, the number of carbon atom layers is greater than or equal to 10, the 2D peak intensity in the Raman spectrum of the graphite film is significantly weaker than the G peak, and the material of the metal substrate is selected from one or more of nickel, iron / nickel alloy, and nickel / copper alloy.

[0065] The present application provides a method for preparing a graphite film, comprising the following steps:

[0066] S1: applying a slurry containing a solid carbon source on a surface of a metal substrate and drying the slurry to form a solid carbon source coating;

[0067] S2: In the presence of a protective gas, the solid carbon source coating is laser treated to form a graphite film on the surface of the metal substrate.

[0068] Wherein, in step S1, the solid carbon source can be selected from one or more of graphite powder, carbon black, activated carbon, and carbon nanotubes.

[0069] The slurry containing the solid carbon source can be a mixed slurry obtained by mixing the solid carbon source with an organic solvent, wherein the organic solvent may include anhydrous ethanol, methanol, isopropanol, acetone, ether, etc.

[0070] In some embodiments, the mass of the solid carbon source is 1-100g, the volume of the organic solvent is 1-2000ml, and the solid carbon source and the organic solvent are stirred and mixed, and then ultrasonically dispersed for 1-600s to obtain a mixed slurry, that is, a slurry containing the solid carbon source. The ratio of the solid carbon source to the organic solvent affects the fluidity of the mixed slurry, which in turn affects the subsequent spreading effect of the solid carbon source on the surface of the metal substrate. When the mixed slurry is thin, it has strong fluidity and is difficult to adhere to the substrate surface; when the mixed slurry is thick, it has poor fluidity, which easily causes uneven spreading of the solid carbon source. Both of the above situations are not conducive to the growth of graphite.

[0071] The material of the metal substrate may be selected from one or more of nickel, iron / nickel alloy, and nickel / copper alloy.

[0072] The nickel element in the metal substrate catalyzes the growth of the graphite film. In some embodiments, the nickel content in the iron / nickel alloy and the nickel / copper alloy is greater than or equal to 20% to better exert the catalytic effect of nickel in the graphite growth process. The nickel content in the iron / nickel alloy and the nickel / copper alloy is greater than or equal to 20%, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc.

[0073] The metal substrate can take various forms, including metal blocks, metal sheets, metal foils, metal meshes, and metal films. The surface of the metal substrate can be flat or curved, enabling in-situ deposition of graphite films on non-standard shaped parts. The specific dimensions of the metal substrate can be selected based on actual needs.

[0074] When coating the solid carbon source on the surface of the metal substrate, methods known in the art can be used as long as the solid carbon source can be evenly coated on the surface of the metal substrate. For example, a slurry containing the solid carbon source can be coated on the surface of the metal substrate by manual coating, spin coating, spraying or brushing.

[0075] In some specific embodiments, the coating is performed using a spin coater with a rotation speed of 100-5000 rpm and a spin coating time of 10-300 s.

[0076] When the slurry containing the solid carbon source coated on the surface of the metal substrate is dried, it can be dried naturally or dried on a constant temperature heating table to volatilize the organic solvent.

[0077] In some specific embodiments, a constant temperature heating platform is used for drying, the temperature of the constant temperature heating platform is set to 20-200° C., and the drying time is 1-60 min.

[0078] In some specific embodiments, the thickness of the solid carbon source coating is 1-200 μm, for example, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, etc. If the coating is thin, the carbon source supply is insufficient, and a thick layer of graphite cannot be grown. If the coating is too thick, the carbon source supply exceeds the carbon solubility of the metal substrate, resulting in residual solid carbon source on the surface. This residual carbon source hinders the growth of the graphite film. Both of the above situations are not conducive to the growth of graphite film.

[0079] In step S2, the protective gas may be selected from one or more of nitrogen, argon, and helium.

[0080] In some specific embodiments, the flow rate of the shielding gas is 1-100 L / min, for example, 1 L / min, 5 L / min, 10 L / min, 15 L / min, 20 L / min, 21 L / min, 22 L / min, 23 L / min, 24 L / min, 25 L / min, 26 L / min, 27 L / min, 28 L / min, 29 L / min, 30 L / min, 31 L / min, 32 L / min, 33 L / min, 34 L / min, 35 L / min, 36 L / min, 37 L / min, 38 L / min, 39 L / min, 40 L / min, 50 L / min, 60 L / min, 70 L / min, 80 L / min, 90 L / min, 100 L / min, etc. When the shielding gas flow rate is low, oxidation of the nickel surface will hinder the precipitation of carbon atoms; when the shielding gas flow rate is too high, the solid carbon source coating on the surface will be stripped off.

[0081] In some specific embodiments, the flow rate of the protective gas is 20-40 L / min.

[0082] When performing laser processing, laser equipment known in the art may be used.

[0083] In some specific embodiments, the power of the laser is 10-10000 W, for example, it can be 10W, 50W, 100W, 200W, 500W, 1000W, 1500W, 2000W, 2500W, 3000W, 3500W, 4000W, 4500W, 5000W, 5500W, 6000W, 6500W, 7000W, 7500W, 8000W, 8500W, 9000W, 9500W, 10000W, etc.

[0084] In some embodiments, the power density of the laser is 1×10 3 -1×10 6 W / cm 2 , for example, it can be 3.5×10 3 W / cm 2 , 5×10 3 W / cm 2 , 8×10 3 W / cm 2 , 1×10 4 W / cm 2 , 1.5×10 4 W / cm 2 , 2×10 4 W / cm 2 , 2.5×10 4 W / cm 2 , 3×10 4 W / cm 2 , 3.5×10 4 W / cm 2 , 4×10 4 W / cm 2 , 4.5×10 4 W / cm 2 , 5×10 4 W / cm 2 , 5.5×10 4 W / cm 2 , 6×10 4 W / cm 2 , 6.5×10 4 W / cm 2 , 7×10 4 W / cm 2 , 7.5×10 4 W / cm 2 , 8×10 4 W / cm 2 When the laser power density is too low, an effective molten pool cannot be formed on the substrate surface to dissolve the solid carbon source. When the laser power density is too high, on the one hand, the solid carbon source will be burned, and on the other hand, a narrow and deep molten pool will be formed on the substrate surface. The carbon atoms dissolved in the molten pool will be difficult to precipitate and reconstruct to the surface.

[0085] In some embodiments, the power density of the laser is 3.5×10 3 -8×10 4 W / cm 2 .

[0086] In some specific embodiments, the duty cycle of the laser is 10%-100%, for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 100%, etc.

[0087] In some specific embodiments, the defocus amount of the laser is -20-+20 mm, for example, it can be -20 mm, -18 mm, -16 mm, -14 mm, -12 mm, -10 mm, -8 mm, -6 mm, -4 mm, -2 mm, 0 mm, 2 mm, 4 mm, 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, etc.

[0088] The shape of the laser spot used in the laser processing is circular, rectangular or linear.

[0089] In some specific embodiments, when a circular spot is used, laser processing is performed by multi-pass scanning overlap, and the overlap rate is 5%-95%, for example, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc.; the scanning speed is 0.1-1000 mm / s, for example, 0.1 mm / s, 1 mm / s, 1 0mm / s, 50mm / s, 100mm / s, 150mm / s, 200mm / s, 250mm / s, 300mm / s, 350mm / s, 400mm / s, 450mm / s, 500mm / s, 550mm / s, 600mm / s, 650mm / s, 700mm / s, 750mm / s, 800mm / s, 850mm / s, 900mm / s, 950mm / s, 1000mm / s, etc. The overlap rate primarily affects the quality of graphite growth at the edges of each scanning pass. When the overlap rate is too low, the edges of each pass are insufficiently heated, resulting in a high amount of residual carbon source. When the overlap rate is too high, the subsequent laser pass will damage the graphite film grown in the previous pass during scanning.

[0090] In some specific embodiments, the diameter of the circular spot is 0.1-10 mm, for example, it can be 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 5 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc.

[0091] In some specific embodiments, the side length of the rectangular or linear light spot is 0.1-20 mm, for example, it can be 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, 10 mm, 10.5 mm, 11 mm, 11.5 mm, 12 mm, 12.5 mm, 13 mm, 13.5 mm, 14 mm, 14.5 mm, 15 mm, 15.5 mm, 16 mm, 16.5 mm, 17 mm, 17.5 mm, 18 mm, 18.5 mm, 19 mm, 19.5 mm, 20 mm, etc.

[0092] In some specific embodiments, the moving speed (i.e., scanning speed) of the circular, rectangular or linear spot relative to the surface of the metal substrate during laser processing is 0.1-1000 mm / s, for example, 0.1 mm / s, 1 mm / s, 2 mm / s, 3 mm / s, 4 mm / s, 5 mm / s, 6 mm / s, 7 mm / s, 8 mm / s, 9 mm / s, 10 mm / s, 15 mm / s, 20 mm / s, 25 mm / s, 30 mm / s, 35 mm / s, 40 mm / s, 45 mm / s, 50 mm / s, mm / s, 60mm / s, 70mm / s, 80mm / s, 90mm / s, 100mm / s, 150mm / s, 200mm / s, 250mm / s, 300mm / s, 350mm / s, 400mm / s, 450m m / s, 500mm / s, 550mm / s, 600mm / s, 650mm / s, 700mm / s, 750mm / s, 800mm / s, 850mm / s, 900mm / s, 950mm / s, 1000mm / s, etc.

[0093] In some specific embodiments, the method for preparing a graphite film comprises the following steps:

[0094] S1: applying a slurry containing a solid carbon source on a surface of a metal substrate and drying the slurry to form a solid carbon source coating, wherein the material of the metal substrate is selected from one or more of nickel, iron / nickel alloy, and nickel / copper alloy, and the solid carbon source is selected from one or more of graphite powder, carbon black, activated carbon, and carbon nanotubes, and the thickness of the solid carbon source coating is 1-200 μm;

[0095] S2: In the presence of a protective gas, the solid carbon source coating is subjected to laser treatment to form a graphite film on the metal substrate, wherein the laser power used in the laser treatment is 10-10000 W and the power density is 1×10 3 -1×106 W / cm 2 , the laser duty cycle is 10%-100%, the laser defocus is -20-+20mm, the scanning speed is 0.1-1000mm / s, and the flow rate of the protective gas is 1-100L / min.

[0096] In some specific embodiments, the method for preparing a graphite film comprises the following steps:

[0097] S1: applying a slurry containing a solid carbon source on a surface of a metal substrate and drying the slurry to form a solid carbon source coating, wherein the material of the metal substrate is selected from one or more of nickel, an iron / nickel alloy, and a nickel / copper alloy, the solid carbon source is selected from one or more of graphite powder, carbon black, activated carbon, and carbon nanotubes, the solid carbon source coating has a thickness of 1-200 μm, and the nickel content of the iron / nickel alloy or the nickel / copper alloy is greater than 20%;

[0098] S2: In the presence of a protective gas, the solid carbon source coating is subjected to laser treatment to form a graphite film on the metal substrate, wherein the laser power used in the laser treatment is 10-10000 W and the power density is 3.5×10 3 -1×10 5 W / cm 2 , the laser duty cycle is 10%-100%, the laser defocus is -20-+20mm, the scanning speed is 0.1-1000mm / s, and the flow rate of the protective gas is 20-40L / min.

[0099] Before step S1, the metal substrate may be treated, for example, by grinding or polishing the metal substrate to make the surface flat and smooth, and ultrasonic cleaning to remove contaminants attached to the surface. The cleaned sample is dried with compressed air, nitrogen, argon, or helium.

[0100] Existing technologies for preparing graphite thin films utilize furnace heating. However, furnace heating places high demands on the substrate and requires stringent temperature control during heating to achieve the necessary reconstruction of carbon atoms between and within the layers, making it difficult to meet the needs of engineering applications. Furthermore, furnace heating heats the entire part, which can adversely affect its microstructure and performance.

[0101] The graphite film preparation method disclosed herein uses a laser as a heat source to grow graphite film. This allows for in-situ growth of graphite film on the desired area of a metal substrate surface in an open environment, eliminating the need for high-temperature treatment of the entire metal substrate, high pressure, vacuum, or special gas conditions, and thus avoiding the limitations imposed by furnaces or chambers on the shape and size of the sample being processed. This offers significant advantages in engineering applications. Furthermore, while furnace-based heating methods often require several hours to grow graphite film, using a laser as a heat source allows for growth in just seconds, significantly improving the efficiency of graphite film preparation.

[0102] This application uses a solid carbon source as the raw material for growing graphite thin films. Compared to gaseous carbon sources, solid carbon sources have lower storage costs and higher safety. They also eliminate the need for a sealed chamber and can be used in an open environment. The solid carbon source is directly spread on the substrate surface. Under the action of the laser heat source, it eliminates the cracking and adsorption reactions that gaseous carbon sources undergo, thereby improving the efficiency of carbon atoms dissolving into the substrate.

[0103] This application achieves structural and functional integration of the processed specimen by in-situ growth of a graphite film on a target metal substrate. Compared to graphite films coated or transferred to the substrate surface, in-situ grown graphite films exhibit stronger adhesion to the substrate, significantly reducing the impact of interface defects and enhancing energy transfer between the graphite film and the metal substrate. Furthermore, it provides more comprehensive and precise coverage of the substrate surface and better control over the graphite's flake orientation and crystal quality.

[0104] The product obtained by the preparation method of this application is a thick graphite film, composed of dozens to tens of thousands of layers of carbon atoms arranged in a hexagonal lattice, with a uniform layered structure and an overall thickness of 0.01-100 μm. Thick graphite films have excellent performance stability and show broad application prospects and potential in engineering fields such as friction reduction, corrosion protection, and refractory materials.

[0105] The present application also provides a graphite film, which is obtained by the above-mentioned preparation method.

[0106] The present application also provides a metal part, comprising a metal substrate and a graphite film formed on the surface of the metal substrate by the above-mentioned preparation method.

[0107] The present application also provides a device comprising the aforementioned metal part. The aforementioned metal part can be attached or connected to the surface of other metal or non-metal materials in other ways.

[0108] Example

[0109] Example 1: Rapid in-situ growth of graphite film on a pure nickel substrate

[0110] Step 1: A pure nickel block measuring 15 mm x 15 mm and 5 mm thick was ground and polished to a flat and smooth surface. The sample was then ultrasonically cleaned with anhydrous ethanol to remove surface contaminants. In this example, the ultrasonic cleaning time in anhydrous ethanol was 25 minutes. The cleaned sample surface was then blown dry with nitrogen gas. In this example, the nitrogen pressure was 100 bar and the blowing time was 50 seconds.

[0111] Step 2: Use graphite powder as the solid carbon source and anhydrous ethanol as the organic solvent. Weigh 1g of graphite powder using an electronic balance and 10ml of anhydrous ethanol using a graduated cylinder. Pour the two into a beaker and mix. In this example, the graphite powder used has a particle size of 20nm. Mechanically stir the mixed solution with a glass rod for 3 minutes, then place the beaker in an ultrasonic cleaner for 20 seconds for ultrasonic dispersion to obtain a mixed slurry.

[0112] Step 3: Place the nickel block on the vacuum chuck of the spin coater and secure the sample using vacuum suction. Set the spin speed and time on the spin coater's control panel. In this example, the spin speed was 1000 rpm and the spin time was 60 seconds, resulting in a solid carbon source coating with a thickness of 40 μm.

[0113] Step 4: Place the pure nickel block with the solid carbon source coating on a constant temperature heating table for drying to evaporate the anhydrous ethanol. In this embodiment, the constant temperature heating table is set at 65° C. for 5 minutes.

[0114] Step 5: Place the dried sample on the laser processing platform and set the laser processing area, processing trajectory, scanning spacing, and scanning speed on the robotic arm's control panel. In this example, a circular spot multi-pass scanning method with overlapping paths is used to process a large area of the nickel block surface. The spacing between adjacent laser scanning paths is 2.4 mm, the overlap ratio is 20%, and the scanning speed is 1 mm / s.

[0115] Step 6: Set the laser power in the laser control software. In this embodiment, the laser power is 900W and the power density is 1.27×10 4 W / cm 2 The height of the laser processing head is adjusted through the robot operation panel to ensure that the sample surface to be processed has an appropriate defocus distance relative to the laser focus spot. In this embodiment, the defocus distance is -10mm, and the diameter of the circular spot on the sample surface is 3mm.

[0116] Step 7: Use the robotic arm control panel to horizontally move the laser processing head and activate the coaxial shielding gas system. In this example, the shielding gas is argon at a flow rate of 20 L / min. The robotic arm control panel synchronizes the activation of the laser and the robotic arm. The laser emits light, and the robotic arm drives the laser processing head along a pre-set processing trajectory, beginning the laser in-situ graphite thin film growth process.

[0117] Step 8: The robotic arm drives the laser processing head to the processing end point, the laser stops emitting light, the coaxial protective gas device is turned off, and the sample is naturally cooled to room temperature.

[0118] Step 9: Use optical microscope and scanning electron microscope to photograph the graphite film grown by laser in situ on nickel surface. Figure 2 As shown, a bright white continuous film is generated in the laser-activated area on the nickel surface ( Figure 2 a), High-magnification scanning electron microscopy confirmed that the black lines on the film surface are film wrinkles ( Figure 2 b).

[0119] Step 10: Use an atomic force microscope to photograph the microscopic surface morphology of the laser in situ grown graphite film on the nickel surface, and measure the roughness and wrinkle size of the film surface. Figure 3 The white boxes A, B, and C indicate the surface roughness measurement locations. The surface roughness values for areas A, B, and C are 5.68 nm, 4.08 nm, and 6.55 nm, respectively, with an average surface roughness of 5.44 nm. Five wrinkles were randomly selected from the atomic force microscope image for wrinkle height and width measurement. In this example, the average wrinkle height was 76.53 nm, and the average wrinkle width was 406.4 nm.

[0120] Step 11: Use Raman spectrometer to collect Raman spectra of the original solid carbon source coating without laser treatment and the laser in-situ grown graphite film. Figure 4 As shown in a, after mechanical stirring, ultrasonic dispersion, and spin coating, the Raman signal of the original graphite powder coating is close to that of amorphous carbon, the D peak and the G peak are broadened and connected to each other, and the overall intensity of the Raman signal is weak. Figure 4 As shown in Figure b, the Raman spectrum of the laser-in-situ grown graphite film is close to that of HOPG, with no obvious defect D peak and a sharp G peak, indicating good crystalline quality. Furthermore, the intensity of the 2D peak in the Raman spectrum of the laser-in-situ grown graphite film is significantly weaker than the G peak, indicating that the grown graphite film is multilayered.

[0121] Step 12: In a focused ion beam-scanning electron microscope system, use a focused ion beam to cut grooves in the laser in-situ grown graphite film on the nickel surface, and use a scanning electron microscope to photograph and observe the cross-sectional structure of the graphite film. Figure 5It can be seen intuitively that a thick graphite film is in situ grown on the surface of the metal substrate, and the graphite film is well bonded to the metal substrate without obvious interface defects. According to measurement, the thickness of the graphite film in this embodiment is 1.5 μm, corresponding to more than 4,000 carbon atomic layers.

[0122] Step 13: Use a high-resolution transmission electron microscope to photograph and observe the cross-sectional lattice structure of the thick graphite film. Figure 6 As shown in a, the graphite film grown in situ by laser on the metal substrate has a densely stacked layered structure with uniform interlayer spacing and consistent orientation. The stacking direction of the graphite sheets is normal to the metal substrate, reflecting the epitaxial growth characteristics of the graphite film. Figure 6 As shown in b, the graphite film still has a uniform layered structure in the area far away from the metal substrate, indicating that the overall crystallization quality of the laser in-situ grown graphite film is good. Figure 6 In b, the total thickness of 10 graphite sheets was measured, and the thickness of a single graphite sheet was calculated. In this embodiment, the thickness of a single graphite sheet is 0.34 nm, which meets the standard thickness of a single graphite atomic layer.

[0123] This example uses a continuous fiber laser as a heat source, graphite powder as a solid carbon source, and nickel blocks as metal catalyst substrates to achieve in-situ high-efficiency, high-quality, and controllable preparation of graphite thin films in an open environment. The area expansion rate of the graphite film reaches 1.8 cm 2 The system achieves a layer-thick epitaxial growth rate of 1470 layers / s, without requiring additional film transfer processes. This enables structural and functional integration of the target metal substrate and in-situ grown graphite film. By configuring the laser scanning range and scanning path in the software, large-area, patterned graphite film can be fabricated without any mask, demonstrating exceptional processing flexibility and industrial application value.

[0124] Example 2: Rapid in-situ growth of graphite film on Invar substrate surface

[0125] Step 1: A 15 mm x 15 mm long and wide, 5 mm thick Invar steel block (an iron-based high-nickel alloy with a nickel content of 36%) was ground and polished to a smooth surface. The sample was then ultrasonically cleaned with anhydrous ethanol to remove surface contaminants. In this example, the ultrasonic cleaning time in anhydrous ethanol was 30 minutes. The cleaned sample surface was then blown dry with nitrogen. In this example, the nitrogen pressure was 100 bar, and the blowing time was 60 seconds.

[0126] Step 2: Use graphite powder as the solid carbon source and anhydrous ethanol as the organic solvent. Weigh 1g of graphite powder using an electronic balance and 10ml of anhydrous ethanol using a graduated cylinder. Pour the two into a beaker and mix. In this example, the graphite powder used has a particle size of 20nm. Mechanically stir the mixed solution with a glass rod for 3 minutes, then place the beaker in an ultrasonic cleaner for 20 seconds for ultrasonic dispersion to obtain a mixed slurry.

[0127] Step 3: Place the Invar block on the vacuum chuck of the spin coater and secure the sample using vacuum suction. Set the spin speed and time on the spin coater's control panel. In this example, the spin speed was 1000 rpm and the spin time was 80 seconds, resulting in a solid carbon source coating with a thickness of 35 μm.

[0128] Step 4: Place the invar block with the solid carbon source coating on a constant temperature heating table for drying to evaporate the anhydrous ethanol. In this embodiment, the constant temperature heating table is at 50° C. and the drying time is 3 minutes.

[0129] Step 5: Place the dried sample on the laser processing platform and set the laser processing area, processing trajectory, scanning spacing, and scanning speed on the robotic arm's control panel. In this example, a circular spot multi-pass scanning method with overlapping paths is used to process a large area of the Invar steel surface. The spacing between adjacent laser scanning paths is 2.1 mm, the overlap ratio is 30%, and the scanning speed is 3 mm / s.

[0130] Step 6: Set the laser power in the laser control software. In this embodiment, the laser power is 400W and the power density is 5.6×10 3 W / cm 2 The height of the laser processing head is adjusted through the robot operation panel to ensure that the sample surface to be processed has an appropriate defocus distance relative to the laser focus spot. In this embodiment, the defocus distance is -10mm, and the diameter of the circular spot on the sample surface is 3mm.

[0131] Step 7: Use the robotic arm control panel to horizontally move the laser processing head and activate the coaxial shielding gas system. In this example, the shielding gas is argon at a flow rate of 25 L / min. The robotic arm control panel synchronizes the activation of the laser and the robotic arm. The laser emits light, and the robotic arm drives the laser processing head along a pre-set processing trajectory, beginning the laser in-situ graphite thin film growth process.

[0132] Step 8: The robotic arm drives the laser processing head to the processing end point, the laser stops emitting light, the coaxial protective gas device is turned off, and the sample is naturally cooled to room temperature.

[0133] Step 9: Use a scanning electron microscope to photograph the graphite film grown by laser in situ on the surface of Invar. Figure 7 As shown, a continuous graphite film is generated in the laser-activated area on the Invar surface.

[0134] Step 10: Use Raman spectrometer to collect Raman spectrum of laser in-situ grown graphite film on Invar surface. Figure 8 As shown in Figure 3, the Raman spectrum of the laser in situ grown graphite film on the surface of Invar is close to that of HOPG, with no obvious defect D peak and a sharp G peak, indicating that its crystallization quality is good.

[0135] Example 3

[0136] The steps for preparing the graphite film in Example 3 refer to steps 1 to 8 of Example 1, with the only difference being the laser power density. In Example 3, the laser power density is 1.1×10 4 W / cm 2 The optical microscope photo of the graphite film obtained in Example 3 is as follows: Figure 9 shown.

[0137] Example 4

[0138] The steps for preparing the graphite film in Example 4 refer to steps 1 to 8 of Example 1, with the only difference being the laser power density. In Example 4, the laser power density is 1.4×10 4 W / cm 2 The optical microscope photo of the graphite film obtained in Example 4 is as follows: Figure 10 shown.

[0139] Example 5

[0140] The preparation steps of the graphite film in Example 5 refer to steps 1 to 8 of Example 1, with the only difference being the flow rate of the protective gas, which is 25 L / min in Example 5. The optical microscope photograph of the graphite film obtained in Example 5 is shown in FIG. Figure 11 shown.

[0141] Comparative Example 1

[0142] The preparation steps of the graphite film in Comparative Example 1 refer to steps 1 to 8 of Example 1, with the only difference being the laser power density. In Comparative Example 1, the laser power density is 8.5×10 4 W / cm 2 The optical microscope photo of the graphite film obtained in Comparative Example 1 is as follows: Figure 12 As shown in the figure, when the laser power density is too high, no graphite film is generated on the surface, and the solidified structure of the substrate is exposed.

[0143] Comparative Example 2

[0144] The preparation steps of the graphite film in Comparative Example 2 refer to steps 1 to 8 of Example 1, with the only difference being the laser power density. In Comparative Example 2, the laser power density is 3×10 3 W / cm 2 The optical microscope photo of the graphite film obtained in Comparative Example 2 is as follows: Figure 13 As shown in the figure, when the laser power density is insufficient, a large amount of undissolved solid carbon source remains on the surface and a continuous graphite film cannot be generated.

[0145] Comparative Example 3

[0146] The preparation steps of the graphite film in Comparative Example 3 refer to steps 1 to 8 of Example 1, with the only difference being the flow rate of the protective gas, wherein the flow rate of the protective gas in Comparative Example 3 is 10 L / min. The optical microscope photograph of the graphite film obtained in Comparative Example 3 is shown in FIG. Figure 14 As shown in the figure, when the protective gas flow rate is too low, the protective effect is insufficient, the substrate is oxidized, and the oxide layer hinders the precipitation of carbon atoms, resulting in no graphite film being generated on the surface.

[0147] Comparative Example 4

[0148] The preparation steps of the graphite film in Comparative Example 4 refer to steps 1 to 8 of Example 1, with the only difference being the flow rate of the protective gas, wherein the flow rate of the protective gas in Comparative Example 4 is 45 L / min. The optical microscope photograph of the graphite film obtained in Comparative Example 4 is shown in FIG. Figure 15 As shown in the figure, when the protective gas flow rate is too large, the solid carbon source layer on the substrate surface is blown off, resulting in no graphite film being generated on the surface.

[0149] Comparative Example 5

[0150] The preparation steps of the graphite film in Comparative Example 5 refer to steps 1 to 8 of Example 1, with the only difference being the type of substrate. The substrate used in Comparative Example 5 is GCr15 bearing steel (nickel content less than 0.3%). Figure 16 As shown in the figure, no graphite film is generated on the surface of the substrate with low nickel content.

[0151] Specifically, the specific conditions of the above examples and comparative examples are shown in Table 1.

[0152] Table 1

[0153]

Claims

1. A metal part comprising a metal substrate and a graphite film formed on a surface of the metal substrate, wherein the graphite film has a thickness of 0.01-100 μm.

2. The metal part according to claim 1, wherein the graphite film has a uniformly stacked carbon atom layer structure in a cross section perpendicular to the metal substrate, and the number of carbon atom layers is greater than or equal to 10. 3 . The metal part according to claim 1 , wherein the 2D peak intensity in the Raman spectrum of the graphite film is significantly weaker than the G peak.

4. The metal part according to any one of claims 1 to 3, wherein the material of the metal substrate is selected from one or more of nickel, iron / nickel alloy, and nickel / copper alloy.

5. A method for preparing a graphite film, comprising the following steps: applying a slurry containing a solid carbon source on a surface of a metal substrate and drying the slurry to form a solid carbon source coating; The solid carbon source coating is laser treated in the presence of a protective gas to form a graphite film on the surface of the metal substrate.

6. The preparation method according to claim 5, wherein the power density of the laser used in the laser treatment is 1×10 3 -1×10 6 W / cm 2 , preferably 3.5×10 3 -8×10 4 W / cm 2 .

7. The preparation method according to claim 5 or 6, wherein the power of the laser used in the laser treatment is 10-10000W.

8. The preparation method according to any one of claims 5 to 7, wherein the duty cycle of the laser used in the laser treatment is 10% to 100%.

9. The preparation method according to any one of claims 5 to 8, wherein the defocusing amount of the laser used in the laser treatment is -20 to +20 mm.

10. The preparation method according to any one of claims 5 to 9, wherein the shape of the laser spot used in the laser treatment is circular, rectangular or linear.

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