Method for realizing macroscopic super-slip and low wear in methanol by nickel chloride assisted carbon thin film

Abstract

The application discloses a method for realizing macroscopic super-slip and low abrasion of a nickel chloride assisted carbon film in methanol, which comprises the following steps: firstly, preparing a silicon doped carbon base composite film with a thickness of 1-2 microns on the surface of a substrate by using a magnetron sputtering technology; secondly, configuring a nickel chloride methanol solution with a mass concentration of 5-20%; and finally, dropping and coating 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 that the macroscopic super-slip and low abrasion in the methanol can be realized. In the friction process, the Si on the surface of the carbon film can form a Si-O-Si network as a barrier for preventing further abrasion of the film, and then the produced hydroxyl groups are combined with strong adsorption sites provided by nickel ions to produce two-dimensional layered nickel hydroxide with low interlayer shear force, so that the super-slip and low abrasion can be realized, the friction coefficient is 0.002, and the abrasion rate is 1.291*10 ‑9 mm 3 / N·m.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of tribology, and relates to a method for realizing macroscopic superlubricity and low wear of a nickel chloride assisted carbon film in methanol. BACKGROUND

[0002] According to a report of the International Energy Agency (IEA), automobiles consume 30% of global petroleum energy, and the automobile emission of carbon dioxide (CO2) is as high as 21%. Therefore, it is very important to use new fuel automobiles, such as fuel cell automobiles, pure electric automobiles, pure methanol fuel automobiles and hydrogen fuel automobiles, to reduce energy consumption and CO2 emission. Among them, methanol fuel has the advantages of high power density, low emission, green cycle and good economy, and meanwhile, China has an overcapacity of methanol production, so methanol automobiles are the most competitive. However, the wear of dynamic kits such as engine piston rings and fuel injectors of methanol automobiles seriously reduces the service life of the methanol automobiles, thereby limiting and hindering the wide application of pure methanol fuel automobiles.

[0003] In order to avoid the wear of related transmission mechanical parts in a 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 and nitriding materials have been widely used. However, in the friction process, substances such as formic acid and formaldehyde generated by the decomposition of methanol still have high corrosion and wear on these films, thereby greatly reducing the service time and stability of the friction pair, resulting in that the advantages of the methanol engine cannot be realized.

[0004] Therefore, in order to realize the industrialization development of methanol automobiles in the Guidance Opinion on the Development of Methanol Automobiles in Some Areas jointly issued by the Ministry of Industry and Information Technology and the Ministry of Science and Technology and other eight ministries and commissions in 2019, it is necessary to improve the tribological performance of the friction pair in the methanol environment. In recent years, pure carbon films (a-C) have been widely studied, and under the premise that the film group is a friction pair, it is found that by adding NiCl2 in methanol and doping Si in the carbon film, the superlubricity can be better realized, and the tribological performance of the carbon film can be improved. SUMMARY

[0005] The application aims to provide a method for realizing macroscopic superlubricity and low wear of a nickel chloride assisted carbon film in methanol, which effectively reduces the corrosion and wear of the carbon film in the methanol environment by adding nickel chloride in methanol and doping silicon in the carbon film, and realizes macroscopic superlubricity.

[0006] To achieve the above purpose, the application adopts the following technical scheme:

[0007] The application discloses a method for realizing macroscopic superlubricity and low abrasion in methanol by using a nickel chloride auxiliary carbon film, which comprises the following steps: first, preparing a silicon-doped carbon-based composite film with a thickness of 1-2 microns on the surface of a substrate by using a magnetron sputtering technology; then, configuring a nickel chloride methanol solution with a mass concentration of 5%-20%; and finally, dropping 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.

[0008] The preparation steps of the silicon-doped carbon-based composite film are as follows:

[0009] 1) substrate cleaning: the substrate is cleaned with ethanol and deionized water respectively for 30-45 min, then dried with nitrogen, and placed in a vacuum chamber of a film coating device, and vacuumized to 1.0*10 -3 Pa;

[0010] 2) substrate surface bombardment pretreatment: the surface of the substrate is subjected to bombardment treatment by using argon plasma, so as to realize micro-nano level cleaning and surface activation of the substrate surface, and improve the film-substrate bonding strength; wherein the argon plasma bombardment conditions are as follows: argon gas flow is 200 sccm, gas pressure is 2.0 Pa, bias voltage is -1000 V, duty cycle is 60 %, frequency is 1000 Hz, and the bombardment time is 20-30 min;

[0011] 3) metal intermediate layer deposition: a metal intermediate layer is deposited on the surface of the substrate as a bearing layer by using a high-power micro-pulse magnetron sputtering technology; the process conditions are as follows: a Ti or Cr metal target is selected, 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;

[0012] 4) silicon-doped carbon composite film deposition: a carbon-based composite film is obtained on the surface of the bearing layer by using a high-power micro-pulse magnetron sputtering graphite target; the process conditions are as follows: the graphite target is opened, the argon gas flow is kept unchanged, 200 sccm of silane is introduced, the gas pressure is kept at 0.9-1.1 Pa, the current is 1.0-1.2 A, the bias voltage is -100 V, and the deposition time is 80-100 min. The total thickness of the silicon-doped carbon composite film is 1-2 microns.

[0013] The nickel chloride methanol solution is prepared by the following steps: grinding nickel chloride with a purity of 99.9 % to 1-5 microns, drying at 120-150 °C for 4-6 h, and then ultrasonic dispersion in methanol.

[0014] The CSM friction tester is selected, the silicon nitride with a diameter of 4 mm cleaned by ethanol ultrasonic is used as a pair of ball, the silicon doped carbon composite film is used as a friction plane, and the methanol solution of nickel chloride is used as a friction medium to carry out the atmospheric environment rotating friction test at room temperature to obtain the CSM friction curve (Fig. 1) Figure 1 . The wear profile and wear rate (Fig. 2) Figure 2 are obtained by scanning the wear scar with a step meter. Figure 1 As can be seen from Figure 2 , the methanol solution of nickel chloride obtained by the application can realize super-slip on the surface of the carbon film for many times, and the friction coefficient during super-slip is 0.004-0.009. This is because the surface of the friction pair gradually absorbs hydroxyl to form two-dimensional nickel hydroxide during the friction process, and such substances have low interlayer shear force and play a lubricating role. Figure 2 As can be seen from , the wear scar depth is about 20 nm, and the wear rate is 1.291*10 -9 mm 3 / N·m, because the Si doped film surface forms a Si-O-Si network as a barrier to resist wear during the friction process.

[0015] Figure 3 In summary, during the friction process, the friction coefficient in the running-in period is relatively large, the Si-O-Si protective layer and the layered nickel hydroxide are gradually formed in situ at the friction interface, which promotes the system to realize low wear and super-slip, and the specific friction mechanism is shown in . In the initial state, there are Ni ions and methanol molecules between the interface of the silicon nitride ball and the silicon doped carbon film, with the friction, the methanol molecules react with the oxidized Si on the surface of the silicon doped carbon film to form Si-O-CH3 terminated with methoxy and release an OH group, the OH further combines with the Ni ions to form nickel hydroxide, through repeated repetition of this process, the layered nickel hydroxide and the Si-O-Si network terminated with methoxy are finally formed at the friction interface.

[0016] The application has the following advantages compared with the prior art:

[0017] 1. The Si doped carbon film is prepared by a magnetron sputtering method, the hardness of the carbon film is 12-16 GPa, and the Si content is 40 at%;

[0018] 2. The NiCl2 powder used in the application refers to the nickel chloride powder with a purity of 99.9% ground to 1-5 microns. Since the nickel chloride powder absorbs a small amount of water molecules, it is hydrated, so it needs to be dried at a temperature greater than or equal to 120℃ for 4 hours, and then immediately dissolved in methanol to avoid rehydration, so as to ensure that there are the least water molecules in the pure methanol solution;

[0019] 3、The ultrasonic dispersion time of the nickel chloride powder in the methanol solution is 1-2 h, and long-time ultrasonic dispersion can improve the solubility of the nickel chloride in the methanol, so that sufficient dissolution is achieved.

[0020] 4、The nickel chloride methanol solution cooperated with the silicon-doped carbon film can realize super-slip in the methanol liquid, and the super-slip is caused by the synergistic effect of the methoxy terminal Si-O-Si network and the layered nickel hydroxide generated on the surface in the friction process. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The friction coefficient curve of the method for realizing macro-super-slip and low wear of the nickel chloride auxiliary carbon film in methanol.

[0022] Figure 2 The wear profile line and wear rate of the method for realizing macro-super-slip and low wear of the nickel chloride auxiliary carbon film in methanol.

[0023] Figure 3 The friction and wear mechanism of the method for realizing macro-super-slip and low wear of the nickel chloride auxiliary carbon film in methanol. DETAILED DESCRIPTION

[0024] The application will be further explained and described below in combination with examples.

[0025] Example 1

[0026] First, a silicon-doped carbon-based composite film with a thickness of 1.5 microns is prepared, and 100 mL of pure methanol liquid with a purity of 99.9% is prepared; then 10 g of nickel chloride powder accounting for 10% of the mass of the methanol is weighed and placed in a mortar for grinding to about 5 micron particles, and then placed at 120 DEG C for drying for 4 hours, the dried nickel chloride powder is poured into the methanol liquid for ultrasonic dispersion for 80 minutes, and finally the methanol liquid after ultrasonic dispersion is added dropwise on the surface of the carbon film for friction.

[0027] The silicon-doped carbon-based composite film is prepared by a reaction magnetron sputtering method, and the specific process is as follows:

[0028] 1) The 440c stainless steel cleaned by ultrasonic ethanol for 30 min is placed in the vacuum chamber of the coating equipment, and vacuumized to 1.0*10 -3 Pa;

[0029] 2) 200 sccm of argon gas is introduced, the gas pressure is 2.0 Pa, the bias voltage is -1000 V, and the sample is cleaned for 30 min to remove impurities on the surface of the substrate.

[0030] 3) Open the Ti target, introduce 100 sccm argon, adjust the pressure to 1.0 Pa, the arc current is 1.5 A, the bias voltage is 300 V, and deposit for 15 minutes.

[0031] 4) Close the Ti target, open the graphite target, keep the argon unchanged, introduce 150 sccm silane, the current is 1.5 A, the bias voltage is 150 V, and deposit for 100 minutes.

[0032] Turn off the coating equipment, take out the silicon-doped carbon film, place the film on the clamp of the CSM, drop 1 mL of nickel chloride methanol solution on the surface of the carbon film in sequence, use a 4 mm diameter silicon nitride coupling ball to rub, the rubbing parameters are: load 3 N, rotation speed 200 rpm, rotation radius 4 mm, and rubbing time 1800 s, which can realize macroscopic superlubricity and low wear, and the friction coefficient is 0.006. However, the rubbing time is too short to measure the wear.

[0033] Example 2

[0034] First, prepare a silicon-doped carbon-based composite film with a thickness of 1.5 microns, prepare 100 mL of pure methanol liquid with a purity of 99.9 %; then weigh 20 g of nickel chloride powder of the mass of methanol, and grind it in a mortar to about 3 microns of particles, then dry it at 120 °C for 4 hours, then pour the nickel chloride powder into the methanol liquid for ultrasonic dispersion for 120 minutes, and finally drop the ultrasonically dispersed methanol liquid on the surface of the pure carbon film for rubbing.

[0035] The silicon-doped carbon-based composite film is prepared by a reaction magnetron sputtering method, and the specific process is as follows:

[0036] 1) Put the GCr15 steel sheet cleaned by ultrasonic ethanol for 30 min into the vacuum chamber of the coating equipment, and vacuumize to 1.0×10 -3 Pa.

[0037] 2) Introduce 200 sccm argon, the pressure is 2.0 Pa, the bias voltage is -1000 V, and clean the sample for 30 min to remove the impurities on the surface of the silicon wafer and energize the surface of the silicon wafer.

[0038] 3) Open the Cr target, introduce 100 sccm argon, adjust the pressure to 1.0 Pa, the current is 1.2 A, the bias voltage is 300 V, and deposit for 15 minutes.

[0039] 4) Close the Cr target, open the graphite arc target, keep the argon unchanged, introduce 200 sccm silane, the current is 1.0 A, the bias voltage is -100 V, and deposit for 100 minutes.

[0040] The coating equipment is closed, and the silicon-doped carbon-based composite film is taken out. The prepared film is placed on the clamp of the CSM, and then immersed in the prepared nickel chloride methanol solution. A silicon nitride coupling ball with a diameter of 4 mm is used for friction, and the friction parameters are as follows: a load of 5 N, a rotation speed of 200 rpm, a rotation radius of 4 mm, and a friction time of 10000 min. Macroscopic super-slip is realized, and the friction coefficient is 0.002. The wear profile and wear rate obtained by scanning the wear trace by means of a step meter are shown in Figure 2 .

Claims

1. A method of achieving macroscopic super-slip and low wear in methanol by chlorinated nickel assisted carbon thin film, characterized in that, First, a silicon-doped carbon-based composite film with a thickness of 1-2 μm is prepared on the substrate surface using magnetron sputtering technology. Then, a nickel chloride methanol solution with a mass concentration of 5-20% is prepared. Finally, the nickel chloride methanol solution is drop-coated onto the surface of the silicon-doped carbon film or the silicon-doped carbon film is immersed in the nickel chloride methanol solution, thereby achieving macroscopic super-lubricity and low wear in methanol.

2. A method of achieving macroscopic super-slip and low wear in methanol using nickel chloride assisted carbon thin film as claimed in claim 1, wherein, The preparation steps of the silicon-doped carbon-based composite thin film are as follows: ​ 1) Substrate cleaning: The substrate was cleaned with ethanol and deionized water for 30-45 min, respectively, and then dried with nitrogen. The substrate was placed in the vacuum chamber of the coating equipment and vacuumized to 1.0x10 -3 Pa; 2) Substrate surface bombardment pretreatment: Argon plasma is used to bombard the substrate surface to achieve micro-nano-level cleaning and surface activation to improve the film-substrate bonding strength. The argon plasma bombardment conditions are: argon flow rate 200 sccm, gas pressure 2.0 Pa, bias voltage -1000 V, duty cycle 60%, frequency 1000 Hz, bombardment 10~20 min. 3) Metal Intermediate Layer Deposition: High-power micro-pulse magnetron sputtering technology is used to deposit a metal intermediate layer on the substrate surface as a carrier layer. The process conditions are as follows: Ti or Cr target is selected as the metal 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 time is 15~20 min. 4) Silicon-doped carbon composite film deposition: 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 was kept constant, 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 time was 80~100 min.

3. A method of achieving macroscopic super-slip and low wear in methanol using nickel chloride assisted carbon thin film as claimed in claim 1, wherein, The nickel chloride methanol solution is prepared by grinding nickel chloride with a purity of 99.9% to 1-5 micrometers, drying it at 120-150 ℃ for 4-6 h, and then ultrasonically dispersing it in methanol. ​

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