Method for realizing macroscopic super-lubricity and low abrasion of carbon film in methanol under assistance of nickel chloride

Abstract

The invention discloses a method for realizing macroscopic super-lubricity and low wear of a nickel chloride-assisted carbon film in methanol, which comprises the following steps: preparing a silicon-doped carbon-based composite film with the thickness of 1-2 microns on the surface of a substrate by using a magnetron sputtering technology, and then preparing a nickel chloride methanol solution with the mass concentration of 5-20%; and finally, dispensing the nickel chloride methanol solution on the surface of the silicon-doped carbon film or infiltrating the silicon-doped carbon film in the nickel chloride methanol solution to realize macroscopic super-lubricity and low abrasion in methanol. In the friction process, Si on the surface of the carbon film can form a Si-O-Si network to serve as a barrier for preventing the film from being further abraded, then generated hydroxyl groups are combined with strong adsorption sites provided by nickel ions to generate two-dimensional layered nickel hydroxide with low interlayer shear force so as to achieve super-lubricity and low abrasion, the friction coefficient is 0.002, and the abrasion rate is 1.291 * 10 <-9 > mm < 3 > / N.m.

Description

Technical Field

[0001] The invention belongs to the technical field of tribology and relates to a method for achieving macroscopic super-lubricity and low wear of a nickel chloride-assisted carbon film in methanol. Background Art

[0002] According to the report of the International Energy Agency (IEA), automobiles consume 30% of the world's petroleum energy, and automobiles emit up to 21% of carbon dioxide (CO2). Therefore, the use of new fuel vehicles is very important to reduce energy consumption and carbon dioxide emissions, such as fuel cell vehicles, pure electric vehicles, pure methanol fuel vehicles and hydrogen fuel vehicles. Among them, methanol fuel has the advantages of high power density, low emissions, green cycle, good economy, etc. At the same time, my country's methanol production capacity is in excess, and methanol vehicles are the most competitive. However, the wear of the dynamic kits such as the engine piston rings and fuel injectors of methanol vehicles seriously reduces the life of methanol vehicles, thereby limiting and hindering the widespread application of pure methanol fuel vehicles.

[0003] In order to avoid the wear of the relevant transmission mechanical parts in the methanol engine, it is very useful to deposit a solid lubricating film on the surface of the mechanical parts. So far, nitride films, carbide films, diamond-like carbon (DLC) films, nitriding materials, etc. have been widely used. However, during the friction process, formic acid, formaldehyde and other substances produced by the decomposition of methanol still have high corrosion and wear on these films, which greatly reduces the service life and stability of the friction pair, resulting in the failure to realize the advantages of the methanol engine.

[0004] Therefore, in order to achieve the industrial development of methanol vehicles in the "Guiding Opinions on the Application of Methanol Vehicles in Some Regions" jointly issued by the Ministry of Industry and Information Technology, the Ministry of Science and Technology and other eight ministries in 2019, it is necessary to improve the tribological properties of friction pairs in methanol environments. In recent years, pure carbon film (aC) has been widely studied. Under the premise that the film group is a friction pair, it is found that by adding NiCl2 to methanol and doping Si in the carbon film, superlubricity can be better achieved and the tribological properties of the carbon film can be improved. Summary of the invention

[0005] The purpose of the present invention is to provide a method for achieving macroscopic superlubricity and low wear of a carbon film in methanol by using nickel chloride to assist the carbon film. By adding nickel chloride to methanol and doping silicon into the carbon film, the wear and corrosion of the carbon film in a methanol environment is effectively reduced, thereby achieving macroscopic superlubricity.

[0006] To achieve the above object, the present invention adopts the following technical solution: A method for achieving macroscopic super-slip and low-wear of a nickel chloride-assisted carbon film in methanol, firstly using magnetron sputtering technology to prepare a silicon-doped carbon-based composite film with a thickness of 1 to 2 microns on the surface of a substrate, then preparing a nickel chloride methanol solution with a mass concentration of 5% to 20%, and finally dripping the nickel chloride methanol solution on the surface of the silicon-doped carbon film or immersing the silicon-doped carbon film in the nickel chloride methanol solution, so as to achieve macroscopic super-slip and low-wear in methanol.

[0007] The steps for preparing the silicon-doped carbon-based composite film are as follows: 1) Substrate cleaning: The substrate was ultrasonically cleaned with ethanol and deionized water for 30-45 min respectively, then dried with nitrogen, placed in the vacuum chamber of the coating equipment, and evacuated to 1.0×10 -3 Pa; 2) Substrate surface bombardment pretreatment: The substrate surface is bombarded with argon plasma to achieve micro-nano cleaning and surface activation of the substrate surface to improve the film-substrate bonding strength; the argon plasma bombardment conditions are: argon gas flow rate 200 sccm, gas pressure 2.0 Pa, bias voltage -1000 V, duty cycle 60%, frequency 1000 Hz, bombardment 20-30 min; 3) Deposition of metal intermediate layer: high-power micro-pulse magnetron sputtering technology is used to deposit a metal intermediate layer on the surface of the substrate as a bearing layer; the process conditions are as follows: the metal target material is Ti or Cr, argon gas is introduced at 100 sccm, the gas pressure is adjusted to 0.9~1.1 Pa, the current is 1.0~1.2 A, the bias voltage is -300 V, and the deposition time is 15~20 min; the thickness of the bearing layer is 800~1200 nm; 4) Deposition of silicon-doped carbon composite film: A high-power micro-pulse magnetron sputtering graphite target was used to obtain a carbon-based composite film on the surface of the carrier layer; the process conditions were as follows: the graphite target was turned on, the argon flow rate remained unchanged, 200 sccm of silane was introduced, the gas pressure was maintained at 0.9-1.1 Pa, the current was 1.0-1.2 A, the bias voltage was -100 V, and the deposition was 80-100 min. The total thickness of the silicon-doped carbon composite film was 1-2 µm.

[0008] The nickel chloride methanol solution is prepared by grinding nickel chloride with a purity of 99.9% to 1-5 microns, drying the nickel chloride at 120-150° C. for 4-6 hours, and then ultrasonically dispersing the nickel chloride in methanol.

[0009] A CSM friction tester was selected to perform a rotational friction test in an atmospheric environment at room temperature using ethanol ultrasonically cleaned silicon nitride with a diameter of 4 mm as a dual ball, the silicon-doped carbon composite film as a friction plane, and the nickel chloride methanol solution as a friction medium to obtain a CSM friction curve ( Figure 1). The wear scar is scanned by the step profiler to obtain the wear contour line and wear rate ( Figure 2 ).from Figure 1 It can be seen that the nickel chloride methanol solution obtained by the present invention can achieve super-slip on the carbon film surface for many times, and the friction coefficient during super-slip is 0.004-0.009. This is because the nickel chloride on the friction pair surface gradually absorbs hydroxyl groups to form two-dimensional layered nickel hydroxide during the friction process. This type of material has low interlayer shear force and plays a lubricating role. Figure 2 It can be seen that the wear scar depth is about 20 nm and the wear rate is 1.291×10 -9 mm 3 / N·m, this is because during the friction process, a Si-O-Si network is formed on the surface of the Si-doped film to serve as a barrier against wear.

[0010] In summary, during the friction process, the friction coefficient is relatively large during the running-in period, and a Si-O-Si protective layer and layered nickel hydroxide are gradually formed in situ at the friction interface, which enables the system to achieve low wear and super-lubricity. The specific friction mechanism is as follows: Figure 3 As shown. In the initial state, there are Ni ions and methanol molecules between the interface of silicon nitride ball and silicon-doped carbon film. As the friction progresses, methanol molecules react with oxidized Si on the surface of silicon-doped carbon film to form Si-O-CH3 terminated with methoxy group and release an OH group, which further combines with Ni ion to form nickel hydroxide. By repeating this process repeatedly, layered nickel hydroxide and Si-O-Si network terminated with methoxy group are finally formed at the friction interface.

[0011] Compared with the prior art, the present invention has the following advantages: 1. The present invention prepares Si-doped carbon films by magnetron sputtering. The hardness of the carbon films is 12-16 GPa, and the Si content is 40 at%; 2. The NiCl2 powder used in the present invention refers to nickel chloride powder with a purity of 99.9% which is ground to 1-5 microns. Since the nickel chloride powder absorbs a small amount of water molecules and is hydrated, it is necessary to dry it at a temperature greater than or equal to 120°C for 4 hours and then immediately dissolve it in methanol to avoid rehydration, thereby ensuring that there are minimal water molecules in the pure methanol solution; 3. The ultrasonic dispersion time of the nickel chloride powder in the methanol solution of the present invention is 1-2 h. Long-term ultrasonic dispersion can improve the solubility of nickel chloride in methanol and achieve full dissolution.

[0012] 4. The nickel chloride methanol solution of the present invention combined with the silicon-doped carbon film can achieve super-lubricity in methanol liquid, and its super-lubricity comes from the synergistic effect of the methoxy-terminated Si-O-Si network and layered nickel hydroxide generated on the surface during the friction process. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The present invention provides a friction coefficient curve of a method for realizing macroscopic super-lubricity and low wear of a nickel chloride-assisted carbon film in methanol.

[0014] Figure 2 The present invention discloses a wear profile and a wear rate of a method for realizing macroscopic super-lubricity and low wear of a nickel chloride-assisted carbon film in methanol.

[0015] Figure 3 The invention discloses a friction and wear mechanism of a method for realizing macroscopic super-lubricity and low wear of a nickel chloride-assisted carbon film in methanol. DETAILED DESCRIPTION

[0016] The present invention will be further explained below in conjunction with the embodiments.

[0017] Example 1 First, a silicon-doped carbon-based composite film with a thickness of 1.5 microns was prepared, and 100 mL of pure methanol liquid with a purity of 99.9% was prepared; then, 10 g of nickel chloride powder accounting for the mass of methanol was weighed and placed in a mortar and fully ground into particles of about 5 microns, and then dried at 120°C for 4 hours. The dried nickel chloride powder was poured into methanol liquid for ultrasonic dispersion for 80 minutes, and finally the methanol liquid after ultrasonication was dripped on the surface of the carbon film for friction.

[0018] The silicon-doped carbon-based composite film is prepared by reactive magnetron sputtering, and the specific process is as follows: 1) Place the 440c stainless steel after ultrasonic cleaning with ethanol for 30 min into the vacuum chamber of the coating equipment and evacuate to 1.0×10 -3 Pa; 2) Introduce 200 sccm argon gas at a pressure of 2.0 Pa and a bias voltage of -1000 V to clean the sample for 30 min to remove impurities on the substrate surface.

[0019] 3) Open the Ti target, introduce 100 sccm argon, adjust the gas pressure to 1.0 Pa, the arc current to 1.5 A, the bias voltage to 300 V, and deposit for 15 minutes.

[0020] 4) Turn off the Ti target and turn on the graphite target. Keep the argon gas constant and introduce 150 sccm of silane. The current is 1.5 A and the bias voltage is 150 V. Deposition takes place for 100 minutes.

[0021] Turn off the coating equipment, take out the silicon-doped carbon film, place the film on the fixture of the CSM, drip 1 mL of nickel chloride methanol solution on the surface of the carbon film, and use a silicon nitride partner ball with a diameter of 4 mm for friction. The friction parameters are: load 3N, rotation speed 200 rpm, rotation radius 4 mm, and friction time 1800 s. Macroscopic super-slip and low wear can be achieved, and the friction coefficient is 0.006. However, the friction time is too short to measure wear.

[0022] Example 2 First, a silicon-doped carbon-based composite film with a thickness of 1.5 microns was prepared, and 100 mL of pure methanol liquid with a purity of 99.9% was prepared; then 20 g of nickel chloride powder per mass of methanol was weighed, and placed in a mortar and ground into particles of about 3 microns, and then dried at 120 °C for 4 hours, and then the nickel chloride powder was poured into the methanol liquid for ultrasonic dispersion for 120 minutes, and finally the methanol liquid after ultrasonication was dripped on the surface of the pure carbon film for friction.

[0023] The silicon-doped carbon-based composite film is prepared by reactive magnetron sputtering, and the specific process is as follows: 1) Place the GCr15 steel sheet after ultrasonic cleaning with ethanol for 30 min into the vacuum chamber of the coating equipment and evacuate to 1.0×10 -3 Pa.

[0024] 2) Introduce 200 sccm argon gas with a gas pressure of 2.0 Pa and a bias voltage of -1000 V, and clean the sample for 30 min to remove impurities on the surface of the silicon wafer and energize the surface of the silicon wafer.

[0025] 3) Open the Cr target, introduce 100 sccm argon gas, adjust the gas pressure to 1.0 Pa, the current to 1.2 A, the bias to 300 V, and deposit for 15 minutes.

[0026] 4) Turn off the Cr target and turn on the graphite arc target. Keep the argon gas constant and introduce 200 sccm silane. The current is 1.0 A and the bias voltage is -100 V. Deposition takes 100 minutes.

[0027] Turn off the coating equipment and take out the silicon-doped carbon-based composite film. Place the prepared film on the CSM fixture and immerse it in the dissolved nickel chloride methanol solution. Use a silicon nitride partner ball with a diameter of 4 mm for friction. The friction parameters are: load 5 N, rotation speed 200 rpm, rotation radius 4 mm, and friction time 10000 min. Macroscopic super-slip can be achieved, and the friction coefficient is 0.002. Scan the wear scar with a step profiler, and the wear contour line and wear rate are as follows: Figure 2 shown.

Claims

1. A method for achieving macroscopic super-lubricity and low wear of a nickel chloride-assisted carbon film in methanol, characterized in that: Firstly, a silicon-doped carbon-based composite film with a thickness of 1-2 μm is prepared on the surface of the substrate by magnetron sputtering technology, and then a nickel chloride methanol solution with a mass concentration of 5-20% is prepared. Finally, the nickel chloride methanol solution is drop-coated on the surface of the silicon-doped carbon film or the silicon-doped carbon film is immersed in the nickel chloride methanol solution. Macroscopic super-lubricity and low wear can be achieved in methanol.

2. A method for achieving macroscopic super-lubricity and low wear of a nickel chloride-assisted carbon film in methanol as claimed in claim 1, characterized in that: The steps for preparing the silicon-doped carbon-based composite film are as follows: 1) Substrate cleaning: The substrate was ultrasonically cleaned with ethanol and deionized water for 30-45 min respectively, then dried with nitrogen, placed in the vacuum chamber of the coating equipment, and evacuated to 1.0×10 -3 Pa; 2) Substrate surface bombardment pretreatment: The substrate surface is bombarded with argon plasma to achieve micro-nano cleaning and surface activation of the substrate surface to improve the film-substrate bonding strength; the argon plasma bombardment conditions are: argon gas flow rate 200sccm, gas pressure 2.0 Pa, bias voltage -1000 V, duty cycle 60%, frequency 1000 Hz, bombardment 10-20 min; 3) Deposition of metal intermediate layer: high-power micro-pulse magnetron sputtering technology is used to deposit a metal intermediate layer on the surface of the substrate as a bearing layer; the process conditions are as follows: the metal target material is a Ti target or a Cr target, argon gas is introduced at 100 sccm, the gas pressure is adjusted to 0.9-1.1 Pa, the current is 1.0-1.2 A, the bias voltage is -300 V, and the deposition is 15-20 min; 4) Deposition of silicon-doped carbon composite film: A high-power micro-pulse magnetron sputtering graphite target was used to obtain a carbon-based composite film on the surface of the carrier layer; the process conditions were as follows: the graphite target was turned on, the argon flow rate remained unchanged, 200 sccm of silane was introduced, the gas pressure was maintained at 0.9~1.1 Pa, the current was 1.0-1.2 A, the bias was -100 V, and the deposition was 80~100 min.

3. A method for achieving macroscopic super-lubricity and low wear of a nickel chloride-assisted carbon film in methanol as claimed in claim 1, characterized in that: The nickel chloride methanol solution is prepared by grinding nickel chloride with a purity of 99.9% to 1-5 microns, drying it at 120-150° C. for 4-6 hours, and then ultrasonically dispersing it in methanol.

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