Method for realizing wide-range humidity low friction by self-assembled nano-silver layer on carbon film surface

Abstract

The application relates to a method for realizing wide-range humidity low friction by self-assembling a nano-silver layer on a carbon film surface. A silver (Ag) element with low surface energy is selected as a doping element to prepare an Ag-doped graphite-like carbon (GLC) film on a substrate surface, and then the escape characteristics of silver are utilized to form a nano-silver layer on the amorphous carbon film surface through self-assembly. Compared with the prior art, the application is not simply prepared with an Ag / GLC composite film, but a carbon film capable of self-assembling an Ag / GLC structure is designed, so that the low friction performance of the carbon film in a wide-range humidity range is realized.

Description

Technical Field

[0001] This article relates to the field of solid lubricating thin film materials, and in particular to a functional carbon-based thin film material that can stably achieve a low coefficient of friction under a wide range of humidity conditions, as well as its preparation method and application. Background Technology

[0002] In high-end equipment fields such as aerospace, precision instruments, medical devices, and new energy, solid lubrication technology has become a research hotspot due to the limitations of traditional lubrication technologies (lubricating oils and greases) under harsh operating conditions (such as extreme temperatures, high vacuum, and strong radiation). Carbon-based thin films, with their unique amorphous structure, high hardness, and good chemical stability, are considered one of the most promising solid lubricant coatings. However, existing carbon-based thin films such as GLC exhibit a significant increase in friction coefficient under high humidity conditions (>40% RH). This is because water molecules adsorb and bind to dangling bonds on the carbon film surface, leading to increased friction coefficients. 2 The inertness of carbon is disrupted, leading to the formation of hydrogen bond networks at the friction interface, increasing adhesion and severely degrading tribological properties. Therefore, the "humidity sensitivity" of GLC films has become a technical bottleneck restricting their wider application. Achieving a low coefficient of friction for GLC films across a wide humidity range will significantly improve the reliability and durability of moving parts in complex operating conditions during practical applications. This will drive technological advancements in high-end manufacturing and has significant engineering value and strategic importance for achieving high-reliability, long-life operation of high-end equipment.

[0003] The prior art discloses a method to achieve ultra-low friction under high load conditions by constructing a two-dimensional heterostructure by dropping two-dimensional materials onto the surface of a carbon thin film (CN113843125B). This technology is mainly aimed at application scenarios with high load conditions across environments. Summary of the Invention

[0004] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of protection of this application.

[0005] To address the shortcomings of existing technologies, this application provides a method for achieving low friction over a wide range of humidity by self-assembling a nano-Ag layer on the surface of a carbon thin film. By escaping Ag nanoparticles from the Ag-doped carbon thin film, a nano-Ag layer is self-assembled on the surface of the carbon thin film, thereby achieving low friction over a wide range of humidity. This solves the potential problems of high friction coefficient of GLC thin films in humid environments, which may lead to friction failure, mechanical equipment malfunction, and other issues.

[0006] The first aspect of this application provides a method for self-assembling a nano-Ag layer on the surface of a carbon thin film. By selecting silver, which has a low surface energy, as a doping element, an Ag nanoparticle-doped GLC thin film is prepared on the substrate surface. Then, by utilizing the escape characteristics of Ag, a nano-Ag layer is formed on the surface of an amorphous carbon thin film through self-assembly, that is, a carbon thin film with an Ag / GLC composite structure.

[0007] In one exemplary embodiment, the method first prepares a GLC thin film with a high Ag doping content on the surface of a substrate using magnetron sputtering technology, and then further drives the internally doped Ag to escape outward, ultimately forming a continuous nano Ag layer on the surface of the GLC carbon thin film through self-assembly.

[0008] In one exemplary embodiment, the method includes the following steps: 1) Pretreatment of the substrate; 2) An Ag-doped GLC thin film was prepared on the substrate by magnetron sputtering. 3) The Ag-doped GLC film is placed in an oven and heated to promote the migration of Ag ions to the surface. Under the constraint of the amorphous carbon network, Ag nanoparticles self-assemble into a continuous nano-Ag layer on the surface of the GLC film, forming a carbon film with an Ag / GLC composite structure.

[0009] In one exemplary embodiment, the substrate is a silicon wafer or a metal; optionally, the metal is selected from any one of bearing steel, high-temperature alloy, stainless steel, and copper, for example, GCr15 steel sheet.

[0010] In one exemplary embodiment, in step 2), the silver-doped graphite-like carbon film has a silver doping amount of 50%-60% by atomic percentage.

[0011] In one exemplary embodiment, in step 2), the thickness of the Ag-doped GLC film is 1.4-1.8 μm, for example, 1.4 μm or 1.8 μm.

[0012] In one exemplary embodiment, in step 2), the GLC film is a hydrogen-free graphite-like carbon film.

[0013] In an exemplary embodiment, in step 2), a transition layer may be provided between the Ag-doped GLC film and the substrate.

[0014] In one exemplary embodiment, step 3) includes: placing the Ag-doped GLC film in an oven at 40-60 °C and heating it for 1.5-3.5 h, continuously heating for 2-4 days, 1-2 times a day, to promote the migration of Ag ions through the amorphous carbon network to the surface layer, so that the Ag nanoparticles self-assemble into a continuous nano Ag layer on the surface of the GLC film.

[0015] In one exemplary embodiment, the heating conditions in step 3) are: heating in a 50 ℃ oven for 2 h, continuously for 3 days, once a day.

[0016] In one exemplary embodiment, in step 3), the thickness of the self-assembled nano-Ag layer is 280-500 nm, for example, 280 nm or 300 nm.

[0017] In one exemplary embodiment, step 1) includes: grinding and polishing the substrate, then performing ultrasonic cleaning, and then placing the substrate in a vacuum chamber for plasma cleaning.

[0018] In one exemplary embodiment, the ultrasonic cleaning step includes: ultrasonically treating the substrate in alcohol and acetone solutions for 15-30 minutes respectively; wherein the cleaning is performed twice with alcohol and twice with acetone, and then drying is performed for later use.

[0019] The second aspect of this application provides a carbon thin film with an Ag / GLC composite structure that is self-assembled by the above method.

[0020] The third aspect of this application provides a method for achieving low friction over a wide range of humidity by self-assembling a nano-Ag layer on the surface of a carbon thin film, comprising: preparing the aforementioned carbon thin film with an Ag / GLC composite structure on at least one of the two contact surfaces of a friction pair, and achieving low friction in an atmospheric environment with a wide range of humidity.

[0021] In one exemplary embodiment, the tribological performance test is performed using a ball-disc friction and wear tester.

[0022] In one exemplary embodiment, the carbon film is located on at least one of the two contact surfaces of the friction pair.

[0023] In one exemplary embodiment, the friction test conditions of the method are: humidity RH 10%-70%, load 1-10 N, frequency 1-5 Hz, amplitude 4-5 mm, in an ambient temperature environment, to obtain a low coefficient of friction on the contact surface of the friction pair.

[0024] In one exemplary embodiment, the friction test conditions of the method are: load 5 N, frequency 5 Hz, amplitude 4 mm, humidity RH 10%-50%, and friction for 15 min.

[0025] In one exemplary embodiment, the friction coefficient is 0.009-0.095.

[0026] The fourth aspect of this application provides an application of the above-mentioned method in high-end equipment.

[0027] In one exemplary embodiment, the high-end equipment is an aerospace, precision instrument, medical device, or new energy equipment, etc.

[0028] This application does not simply prepare a carbon thin film with an Ag / GLC composite structure, but rather designs a carbon thin film capable of self-assembling to form an Ag / GLC structure, achieving low friction performance over a wide humidity range. The self-assembly process involves: first, preparing an Ag-doped carbon thin film; then, driven by thermodynamics (surface energy difference) and kinetics (defect channel diffusion), the Ag nanoparticles escape to the surface of an amorphous carbon network and self-assemble to form a continuous nano-Ag layer (coverage >70%, i.e., an Ag / GLC composite structure). The self-assembled Ag / GLC composite structure exhibits stability: during friction, a transfer film with a layered, easily sheared structure forms at the friction interface, suppressing hydrogen bonding on the GLC film surface, thereby achieving a low coefficient of friction over a wide humidity range.

[0029] Compared with the prior art, this application has the following technical effects: 1) This application selects Ag with low surface energy and uses thermodynamic drive to enable Ag nanoparticles to migrate to the surface of carbon film. The position is adjusted on the carbon film surface by electrostatic-van der Waals forces to form a closely packed quasi-continuous layer, which self-assembles to form a nano Ag layer with a thickness of about 280-500 nm. 2) In terms of preparation method, magnetron sputtering is selected, which can control the particle size of Ag nanoparticles in the original film to a certain extent, which is more conducive to the subsequent diffusion and self-assembly to the surface. 3) The silver content in the Ag-doped GLC thin film is 50%-60%; 4) Ag nanoparticles diffuse to the surface and self-assemble to form a hard-soft composite structure in which the Ag nanolayer is supported by a relatively high-hardness GLC film, which effectively prevents plastic deformation during the friction process, while the soft Ag nanolayer dissipates energy through shear deformation. 5) The carbon thin film of this application self-assembles on the surface to form an Ag / GLC composite structure, which can release energy through GLC during friction. sp 2 C The fragments and Ag together form a carbon-silver hybrid transfer film, which enhances lubrication performance; 6) Using a ball-disc friction and wear tester, a carbon film with an Ag / GLC structure is self-assembled on the surface and formed into a friction pair with a steel ball or a steel ball with the same coating. This can achieve a low coefficient of friction on the surface under a wide range of humidity (10%-70% RH).

[0030] Other features and advantages of this application will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the application. Other advantages of this application can be realized and obtained by means of the embodiments described in the description and the accompanying drawings. Attached Figure Description

[0031] The accompanying drawings are used to provide an understanding of the technical solutions of this application and constitute a part of the specification. They are used together with the embodiments of this application to explain the technical solutions of this application and do not constitute a limitation on the technical solutions of this application.

[0032] Figure 1 This is a schematic diagram of the cross-sectional structure of the Ag-doped GLC thin film prepared in this application; Figure 2 This is a schematic diagram of the cross-sectional structure of the Ag nanolayer formed by self-assembly in this application; Figure 3 It is the coefficient of friction of the carbon thin film with Ag / GLC composite structure prepared in the embodiments and comparative examples of this application under a wide range of humidity environments. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in detail below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be arbitrarily combined with each other.

[0034] In the following specific embodiments, operations without specified conditions are performed under standard conditions or conditions recommended by the manufacturer. Raw materials without specified manufacturers and specifications are all commercially available products.

[0035] In the following embodiments, the prepared self-assembled silver-doped solid lubricating carbon film was combined with a pair of steel balls with the same coating to form a friction pair. Tribological experiments were conducted using a ball-disc tribological tester under the conditions of load 5 N, frequency 5 Hz, amplitude 4 mm, and humidity 10%-50% RH for 15 min.

[0036] Example 1 This embodiment uses a magnetron sputtering method to prepare a silver-doped carbon thin film, including the following steps: 1) Pretreatment of substrate: Using silicon wafer as substrate, the substrate is ground and polished, and then ultrasonically treated in alcohol and acetone solutions for 15 min each; wherein, the cleaning is performed twice with alcohol and twice with acetone, and then dried for later use. 2) An Ag-doped GLC film with an Ag content of 60% was prepared on the substrate by magnetron sputtering, and the thickness of the Ag-doped GLC film was 1.8 μm. 3) The prepared Ag-doped GLC film was placed in a 50℃ oven and heated for 2 h. The heating was repeated for 3 days, once a day, to promote the migration of Ag ions in the doped film to the surface. Under the constraint of the amorphous carbon network, a continuous nano Ag layer with a thickness of 300 nm was self-assembled on the surface of the GLC carbon film.

[0037] test: The carbon film with an Ag / GLC composite structure obtained in step 3) that self-assembles on the surface is used to form a friction pair with a steel ball or a steel ball with the same coating. Using a ball-disc tribology tester, the following tribological experiments were conducted: ① Under the conditions of load 5 N, frequency 5 Hz, amplitude 4 mm, and humidity 10% RH, the friction coefficient was measured to be 0.043 when the paired ball was a steel ball with the same coating, after 15 min of friction; ② Under the conditions of load 5 N, frequency 5 Hz, amplitude 4 mm, and humidity 60% RH, the friction coefficient was measured to be 0.009 when the paired ball was a steel ball with the same coating, indicating superlubricity with a friction coefficient less than 0.01; ③ Under the conditions of load 5 N, frequency 5 Hz, amplitude 4 mm, and humidity 45% RH, the friction coefficient was measured to be 0.067 when the paired ball was a steel ball, after 15 min of friction.

[0038] Example 2 This embodiment uses a magnetron sputtering method to prepare a silver-doped carbon thin film, including the following steps: 1) Pretreatment of substrate: Using silicon wafer as substrate, the substrate is ground and polished, and then ultrasonically treated in alcohol and acetone solutions for 15 min each; wherein, the cleaning is performed twice with alcohol and twice with acetone, and then dried for later use. 2) An Ag-doped GLC film with an Ag content of 50% was prepared on the substrate by magnetron sputtering, and the thickness of the Ag-doped GLC film was 1.4 μm. 3) The prepared Ag-doped GLC film was placed in a 50℃ oven and heated for 2 h. The heating was repeated for 3 days, once a day, to promote the migration of Ag ions in the doped film to the surface. Under the constraint of the amorphous carbon network, a continuous nano Ag layer with a thickness of 280 nm was self-assembled on the surface of the GLC carbon film.

[0039] test: The carbon film with an Ag / GLC composite structure obtained in step 3) that self-assembles on the surface is used to form a friction pair with a steel ball or a steel ball with the same coating. Using a ball-disc tribological tester, ① a tribological experiment was conducted under the conditions of a load of 5 N, a frequency of 5 Hz, an amplitude of 4 mm, and a humidity of 35% RH for 15 min. When the paired ball is a steel ball with the same coating, the friction coefficient was measured to be 0.095 under this humidity environment; ② a tribological experiment was conducted under the conditions of a load of 5 N, a frequency of 5 Hz, an amplitude of 4 mm, and a humidity of 50% RH for 15 min. When the paired ball is a steel ball, the friction coefficient was measured to be 0.091 under this humidity environment.

[0040] Comparative Example 1 This comparative example uses a carbon thin film prepared by magnetron sputtering, and includes the following steps: 1) Pretreatment of substrate: Using silicon wafer as substrate, the substrate is ground and polished, and then ultrasonically treated in alcohol and acetone solutions for 15 min each; wherein, the cleaning is performed twice with alcohol and twice with acetone, and then dried for later use. 2) A GLC thin film with an Ag content of 0% was prepared on the substrate by magnetron sputtering, and the thickness of the carbon thin film was 847 nm. 3) The prepared GLC film was placed in a 50℃ oven and heated for 2 h. The heating was repeated for 3 days, once a day. Under the same conditions, the GLC film with 0% silver content could not self-assemble to form a nano Ag layer on the surface.

[0041] test: The GLC film obtained in step 3) was paired with a steel ball, and a ball-disc tribological tester was used. ① Tribological experiments were conducted under the conditions of 5 N load, 5 Hz frequency, 4 mm amplitude, and 25% RH humidity for 15 min. When the paired ball was a steel ball, the friction coefficient was measured to be 0.160 under this humidity environment. ② Tribological experiments were conducted under the conditions of 5 N load, 5 Hz frequency, 4 mm amplitude, and 65% RH humidity for 15 min. When the paired ball was a steel ball, the friction coefficient was measured to be 0.120 under this humidity environment. ③ Tribological experiments were conducted under the conditions of 5 N load, 5 Hz frequency, 4 mm amplitude, and 65% RH humidity for 15 min. When the paired ball was a steel ball with the same coating, the friction coefficient was measured to be 0.103 under this humidity environment.

[0042] In summary, 1) the Ag-doped GLC thin film prepared in this application utilizes thermodynamically driven migration of doped Ag nanoparticles through an amorphous carbon network to the surface of the carbon thin film, forming a nano-Ag layer with a thickness of approximately 280-300 nm on the carbon film surface through self-assembly; 2) the preparation method chosen is magnetron sputtering; 3) the Ag content in the Ag-doped GLC thin film is 50%-60%; 4) the GLC thin film in this application is a hydrogen-free Ag-doped GLC thin film; 5) after the nano-Ag layer is formed on the surface of the carbon thin film through self-assembly, this application can achieve a low coefficient of friction, or even super-slippery surface, under a wide range of humidity (10%-70% RH) conditions.

[0043] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for self-assembling a nano-silver layer on the surface of a carbon thin film, comprising the following steps: 1) Pretreatment of the substrate; 2) An Ag-doped GLC thin film was prepared on the substrate by magnetron sputtering. 3) The Ag-doped GLC film is placed in an oven and heated. Ag nanoparticles self-assemble into a continuous nano-Ag layer on the surface of the GLC film, forming a carbon film with an Ag / GLC composite structure.

2. The method according to claim 1, wherein, In step 2), the Ag-doped GLC thin film has an Ag doping amount of 50%-60% by atomic percentage; and / or In step 2), the thickness of the Ag-doped GLC film is 1.4-1.8 μm; and / or The GLC film is a hydrogen-free graphite-like carbon film.

3. The method according to claim 1 or 2, wherein, Step 3) includes: placing the Ag-doped GLC film in an oven at 40-60°C and heating for 1.5-3.5 h, continuously heating for 2-4 days, 1-2 times a day, until the Ag nanoparticles self-assemble on the surface of the GLC film to form a continuous nano-Ag layer.

4. The method according to claim 3, wherein, In step 3), the heating conditions are: heating in a 50℃ oven for 2 hours, continuously for 3 days, once a day; and / or In step 3), the thickness of the self-assembled nano-Ag layer is 280-500 nm.

5. The method according to claim 1 or 2, wherein, The substrate is a silicon wafer or metal; Optionally, the metal is selected from any one of bearing steel, high-temperature alloy, stainless steel, and copper.

6. A method according to any one of claims 1 to 5 for self-assembly forming a carbon thin film having an Ag / GLC composite structure.

7. A method for achieving low friction over a wide range of humidity by self-assembling Ag nanolayers on the surface of a carbon thin film, comprising: A carbon thin film with an Ag / GLC composite structure, obtained by any one of claims 1 to 5, or a carbon thin film with an Ag / GLC composite structure as described in claim 6, is prepared on at least one of the two contact surfaces of the friction pair, and low friction is achieved in an atmospheric environment with a wide range of humidity.

8. The method according to claim 7, wherein, The tribological performance was tested using a ball-disc friction and wear testing machine; and / or The friction test conditions of the method are: humidity RH 10%-70%, load 1-10 N, frequency 1-5 Hz, amplitude 4-8 mm, room temperature and atmospheric environment; a low coefficient of friction is obtained on the contact surface of the friction pair.

9. The method according to claim 7 or 8, wherein, The friction test conditions of the method are: load 5 N, frequency 5 Hz, amplitude 4 mm, humidity RH 10%-50%, friction for 15 min; and / or In the method, the coefficient of friction is 0.009-0.

095.

10. The application of the method according to any one of claims 7 to 9 in high-end equipment; Optionally, the high-end equipment may be aerospace, precision instruments, medical devices, or new energy equipment.

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