An ultrasmooth carbon film and a preparation method and application thereof

Abstract

The application relates to a super-smooth carbon film and a preparation method and application thereof, the super-smooth carbon film comprising a Cr primer layer, a CrC transition layer and a working layer arranged on a substrate in sequence; wherein the working layer is a GLC film doped with metal; in the working layer, the doped metal is selected from metal elements with the characteristics of unfilled d electron orbit, and is optionally any one of Ag, Cu, Ni, Co, Au and the like. The super-smooth carbon film prepared by using the closed field non-equilibrium magnetron sputtering technology has good bonding force on various substrate materials, the doped metal silver nanoparticles in the working layer can be uniformly distributed under room temperature conditions, and the super-smooth carbon film has excellent tribological properties; the super-smooth carbon films with different metal contents can realize macro-scale super-smoothness in a nitrogen atmosphere, and the friction coefficient is as low as 0.006.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of super-slippery and mechanical parts friction and wear, and particularly relates to a super-slippery carbon film and a preparation method and application thereof. BACKGROUND

[0002] Tribology accompanies the origin of human life and the development of society. Nowadays, tribology exists behind almost all super projects. The high precision, high reliability and long service life of mechanical systems are limited by the friction and wear performance of lubricating materials, and many major accidents are caused by friction and wear. The satellite in-orbit failure analysis shows that from 1957 to 2007, 37% of the 272 satellite failures at home and abroad belong to the lubrication failure of the attitude and orbit control subsystem, and more than 50% of the attitude and orbit control subsystem failures are caused by the wear of space moving parts such as gyroscopes and momentum wheels. For example, in 1986, the right rocket booster connecting O-shaped sealing ring of the “Challenger” spacecraft failed due to friction, causing the fuel tank structure to fail, and the spacecraft was torn apart layer by layer by the fierce air friction at the 73rd second of the launch; the “Galileo” spacecraft launched by NASA in 1992 failed to transmit signals normally due to high friction, and the antenna was not opened; in 2006, the right front wheel of the “Courage” had “arthritis”, and the task failed due to insufficient lubrication. Lubricating materials and technologies run through the design, test, manufacture and service of mechanical systems of high-end equipment throughout the life cycle. Therefore, the low friction, high stability, long life and high reliability of space moving parts are the key to solving the above problems, and the development of new low-friction materials and the design of stable matching pair system are one of the effective ways to solve the above problems.

[0003] At present, super-slippery technology is an ideal state of pursuing low friction, that is, to realize the friction coefficient in the order of 0.001. In theory, when the above conditions such as no impurities in the friction interface, surface defects or dangling bonds of the matching pair are saturated, and layer-by-layer slip contact without deformation is met, super-slippery can be easily realized. However, it is difficult to meet all the above conditions at the same time at the macro scale, so the large-scale application of super-slippery is still a challenge. SUMMARY

[0004] The following is a summary of the subject matter described in detail in this document. This summary is not intended to limit the scope of protection of the present application.

[0005] The technical problem to be solved by the present application is to provide a super-slippery carbon film and a preparation method and application thereof.

[0006] Another technical problem to be solved by the present application is to provide a friction pair super-slip system design comprising the super-slip carbon film. In the super-slip carbon film, the amount of metal doping in the working layer can be controlled in the range of 0% to 90% in atomic percentage, and the super-slip state can be realized on the macro scale with the amorphous hydrogen-containing carbon pair ball.

[0007] To solve the above problems, the present application provides the following technical solutions:

[0008] The first aspect of the present application provides a super-slip carbon film, comprising a Cr primer layer, a CrC transition layer and a working layer arranged in sequence on a substrate; the working layer is a metal-doped graphite-like carbon (GLC) film, and the GLC film is a hydrogen-free graphite-like carbon film; in the working layer, the doped metal is selected from metal elements having the characteristic of unfilled d electron orbit, and is optionally any one of Ag, Cu, Ni, Co, Au, etc.

[0009] In an exemplary embodiment, the sum of the thicknesses of the Cr primer layer and the CrC transition layer is 600-650 nm, and the thickness of the working layer is 900-1600 nm.

[0010] In an exemplary embodiment, in the working layer, the doping amount of metal is 0%-90% in atomic percentage, and the doping amount does not include 0%; for example, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or a range value between any two of them as end point value, but not limited to the listed values, and other unlisted values in the range are also applicable. Here, "atomic percentage" means that the number of atoms of a certain element on the surface of a material accounts for a percentage of the total number of atoms of all elements.

[0011] In an exemplary embodiment, in the working layer, the doped metal is Ag, and the doping amount of metal in the working layer is 18%-90% in atomic percentage; under this doping condition, the super-slip state can be realized, and the friction coefficient is <0.01.

[0012] In an exemplary embodiment, in the working layer, the doped metal is Ag, and the doping amount of metal in the working layer is 18%, 43% or 90% in atomic percentage.

[0013] In an exemplary embodiment, the substrate is selected from a silicon wafer or a metal substrate; optionally, the metal substrate is selected from any one of bearing steel, high-temperature alloy, stainless steel, copper, etc.

[0014] The second aspect of the present application provides a method for preparing the above-mentioned super-smooth carbon film, which is prepared by means of a closed field four-cathode magnetron sputtering device and unbalanced closed magnetic field, and comprises the following steps:

[0015] 1) pretreatment of the substrate;

[0016] 2) deposition of a Cr base layer and a CrC transition layer;

[0017] 3) deposition of a working layer of the metal-doped GLC film.

[0018] In an exemplary embodiment, in step 1), the pretreatment of the substrate comprises polishing and polishing the substrate, and then ultrasonic cleaning, and then plasma cleaning of the substrate.

[0019] In an exemplary embodiment, in step 1), the step of ultrasonic cleaning comprises: ultrasonic treatment of the substrate in alcohol and acetone solutions for 15 ~ 30 min (such as 15 min, 20 min, 25 min, 30 min, etc. or any two values between the end point values as a range value, but not limited to the listed values, other values not listed in the value range are also applicable), wherein the cleaning times are 2 times of alcohol cleaning and 2 times of acetone cleaning, and then drying for standby.

[0020] In an exemplary embodiment, in step 1), the step of plasma cleaning comprises: placing the cleaned and dried substrate into a coating cavity, and vacuumizing to less than 1 × 10 -4 Pa, starting ion source cleaning, current is 1 ~ 2 A, high-energy plasma bombarding the substrate in argon atmosphere, bombarding for 20 ~ 30 min (such as 20 min, 25 min, 30 min, etc. or any two values between the end point values as a range value, but not limited to the listed values, other values not listed in the value range are also applicable) under the conditions of working voltage of 400 ~ 500 V (such as 400 V, 450 V, 500 V, etc. or any two values between the end point values as a range value, but not limited to the listed values, other values not listed in the value range are also applicable) and gas pressure of 2 ~ 3 Pa.

[0021] In an exemplary embodiment, in the plasma cleaning of step 1), the current is 1.5 A and the gas pressure is 2.5 Pa.

[0022] In an exemplary embodiment, in step 2), the step of depositing the Cr primer layer and the CrC transition layer comprises: maintaining the ion source current at 1 ~ 2 A and the gas pressure at 2 ~ 3 Pa; turning on the chromium target to first deposit the Cr primer layer, the current being 6.0 ~ 7.5 A (such as 6.0 A, 6.5 A, 7.0 A, 7.5 A, or a range between any two of the values as the end point values, but not limited to the listed values, and other values not listed in the range are also applicable), and the deposition time being 25 ~ 35 min; then turning on the carbon target and the chromium target simultaneously to prepare the CrC transition layer, the current of the chromium target being 6.0 ~ 7.5 A, the current of the carbon target being 1.0 ~ 2.5 A (such as 1.0 A, 1.5 A, 2.0 A, 2.5 A, or a range between any two of the values as the end point values, but not limited to the listed values, and other values not listed in the range are also applicable), and the deposition time being 25 ~ 35 min, and the working voltage of the chromium target and the carbon target being controlled at 300 ~ 500 V (such as 300 V, 350 V, 400 V, 450 V, 500 V, or a range between any two of the values as the end point values, but not limited to the listed values, and other values not listed in the range are also applicable) during the deposition process.

[0023] In an exemplary embodiment, in step 2), the ion source current is maintained at 1.5 A, the gas pressure is 2.5 Pa, the deposition time of the Cr primer layer is 30 min, and the deposition time of the CrC transition layer is 30 min.

[0024] In an exemplary embodiment, in step 3), the working layer is obtained by co-sputtering a metal target and a carbon target, including the following steps: controlling the ion source current to be 2-3 A, the working voltage to be 50-70 V, and keeping the gas pressure unchanged; simultaneously turning on the metal target and the carbon target, the working voltage of the carbon target being 400-450 V (such as 400 V, 410 V, 420 V, 430 V, 440 V, 450 V, or a range value between any two of the above values as the end point value, but not limited to the listed values, and other values not listed in the range are also applicable), the working current of the carbon target being 7.0-8.0 A (such as 7.0 A, 7.5 A, 8.0 A, or a range value between any two of the above values as the end point value, but not limited to the listed values, and other values not listed in the range are also applicable); the working voltage of the metal target being 300-450 V (such as 300 V, 350 V, 400 V, 450 V, or a range value between any two of the above values as the end point value, but not limited to the listed values, and other values not listed in the range are also applicable), the working current of the metal target being 0-1.2 A, excluding 0 A, to control the amount of metal doped in the carbon-based film; keeping other gas pressure conditions unchanged, and depositing for 6-8 h (such as 6 h, 6.5 h, 7 h, 7.5 h, 8 h, or a range value between any two of the above values as the end point value, but not limited to the listed values, and other values not listed in the range are also applicable), thereby obtaining a GLC film with different amounts of metal doping.

[0025] In an exemplary embodiment, in step 3), the ion source current is controlled to be 2.5 A, the working voltage is 60 V, and the gas pressure is 2.5 Pa.

[0026] In an exemplary embodiment, the method includes the following steps:

[0027] 1) A silicon wafer is used as a deposition substrate, and is ultrasonically treated in alcohol and acetone solutions for 15 min, respectively, wherein the cleaning times are 2 times of alcohol cleaning and 2 times of acetone cleaning, and then the silicon wafer is dried for standby;

[0028] 2) The cleaned and dried substrate sample is placed in a coating cavity, and the vacuum degree is extracted to be less than 1×10 -4 Pa, ion source cleaning is started, the current is 1.5 A, the substrate is bombarded by high-energy plasma in an argon atmosphere, the working voltage is 430 V, and the gas pressure is 2.5 Pa, and the bombardment time is 25 min;

[0029] 3) Depositing Cr undercoat layer and CrC transition layer: keeping ion source current at 1.5 A and gas pressure at 2.5 Pa, turn on the chromium target to first deposit the Cr undercoat layer with a current of 7.5 A for 30 min; then turn on the carbon target and the chromium target simultaneously to prepare the CrC transition layer, the current of the chromium target is 7.5 A and the current of the carbon target is 2.5 A for 30 min, the working voltage of the chromium target and the carbon target is controlled at 400 V during the whole deposition process;

[0030] 4) Depositing the working layer of silver-doped GLC film: control the ion source current at 2.5 A and the working voltage at 60 V; turn on the silver target and the carbon target simultaneously, the working voltage of the carbon target is 420 V and the current is 7.5 A; the working voltage of the silver target is 410 V and the current is 0.20 A; keep other gas pressure conditions unchanged, deposit for 7 h to obtain the GLC film with silver content of 18%.

[0031] In an example embodiment, the method comprises the following steps:

[0032] 1) Take a silicon wafer as the deposition substrate, and ultrasonically treat it in alcohol and acetone solution respectively for 15 min, wherein the cleaning times are 2 times of alcohol cleaning and 2 times of acetone cleaning, and then dry the silicon wafer for standby use;

[0033] 2) Put the cleaned and dried substrate sample into the coating cavity, and vacuumize to less than 1×10 -4 Pa, start ion source cleaning, the current is 1.5 A, and the substrate is bombarded by high-energy plasma in an argon atmosphere, the working voltage is 480 V, and the gas pressure is 2.5 Pa for 25 min;

[0034] 3) Depositing Cr undercoat layer and CrC transition layer: keeping ion source current at 1.5 A and gas pressure at 2.5 Pa, turn on the chromium target to first deposit the Cr undercoat layer with a current of 7.0 A for 30 min; then turn on the carbon target and the chromium target simultaneously to prepare the CrC transition layer, the current of the chromium target is 7.0 A and the current of the carbon target is 2.5 A for 30 min, the working voltage of the chromium target and the carbon target is controlled at 350 V during the whole deposition process;

[0035] 4) Depositing the working layer of silver-doped GLC film: control the ion source current at 2.5 A and the working voltage at 60 V; turn on the silver target and the carbon target simultaneously, the working voltage of the carbon target is 400 V and the current is 8.0 A; the working voltage of the silver target is 380 V and the current is 0.55 A; keep other gas pressure conditions unchanged, deposit for 6 h to obtain the GLC film with silver content of 43%.

[0036] In an example embodiment, the method comprises the following steps:

[0037] 1) Take silicon wafer as deposition substrate, ultrasonic treatment in alcohol and acetone solution for 15 min respectively, wherein, the cleaning times are 2 times of alcohol cleaning and 2 times of acetone cleaning, and then it is dried for standby;

[0038] 2) Put the cleaned and dried substrate sample into the plating cavity, and vacuumize to less than 1*10 -4 Pa, start ion source cleaning, the current is 1.5 A, high-energy plasma bombards the substrate in argon atmosphere, the working voltage is 500 V, and the pressure is 2.5 Pa for 20 min;

[0039] 3) Deposition of Cr primer layer and CrC transition layer: keep the ion source current at 1.5 A and the pressure at 2.5 Pa, open the chromium target to first deposit the Cr primer layer, the current is 7.5 A, the deposition time is 30 min; then open the carbon target and the chromium target at the same time to prepare the CrC transition layer, the chromium target current is 7.5 A, the carbon target current is 2.0 A, the deposition time is 30 min, and the working voltage of the chromium target and the carbon target is controlled at 500 V during the whole deposition process;

[0040] 4) Deposition of silver-doped GLC film working layer: control the ion source current to be 2.5 A and the working voltage to be 60 V; open the silver target and the carbon target at the same time, the working voltage of the carbon target is 450 V, the current is 8.0 A; the working voltage of the silver target is 450 V, the working current is 1.20 A; keep other pressure conditions unchanged, and deposit for 8 h to obtain the GLC film with 90% silver content.

[0041] The third aspect of the application provides an ultra-smooth carbon film prepared by the above method.

[0042] The fourth aspect of the application provides a method for realizing ultra-smoothness by using the above ultra-smooth carbon film.

[0043] In an exemplary embodiment, the method comprises forming a friction pair with the above ultra-smooth carbon film and an amorphous hydrogen-containing carbon film, and realizing ultra-smoothness in a nitrogen atmosphere.

[0044] In an exemplary embodiment, the amorphous hydrogen-containing carbon film refers to a Φ6 mm steel ball coated with an amorphous hydrogen-containing carbon film.

[0045] Compared with the prior art, the application has the following advantages:

[0046] 1. The application modulates the target GLC film by means of unbalanced magnetron sputtering, and the process parameters are designed to make the metal nanoparticles have good dispersity and uniformity in the amorphous carbon network.

[0047] 2、 The application designs appropriate tooling in the process of preparing the thin film, so that the conformal plating can be realized while ensuring that the working layer thin film is uniform and has high bonding force.

[0048] 3、 The application selects, at will, from metal elements having the characteristics of unfilled d electron orbitals.

[0049] 4、 The metal-doped GLC thin film prepared by the application exhibits excellent robust super-slip state. In particular, the silver-doped graphite-like super-slip carbon thin film and the amorphous hydrogen-containing carbon film pair are subjected to tribological performance testing on an Anton Paar friction tester. The results show that the dispersed silver nanoparticles in the amorphous carbon network can induce the surrounding amorphous carbon network to graphitize and tend to be ordered during the friction process, generating a graphene-like structure. The hydrogen-containing carbon film on the pair of balls can synergistically reduce the interfacial shear force. Under the combined action of the silver-doped GLC thin film and the amorphous hydrogen-containing carbon pair, the super-slip range of the carbon thin film is widened on a macro scale, and the friction coefficient is further reduced (friction coefficient < 0.01).

[0050] Other features and advantages of the application will be set forth in the following description, or will be apparent from the description, or can be learned by practice of the application. Other advantages of the application can be realized and obtained by the embodiments described in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0051] The accompanying drawings are included to provide a further understanding of the technical scheme of the application, and constitute a part of the specification, and are used together with the embodiments of the application to explain the technical scheme of the application, and do not constitute a limitation on the technical scheme of the application.

[0052] Figure 1 A structural schematic diagram of the super-slip carbon thin film prepared by the application, wherein 1 is a substrate, 2 is a Cr primer layer, 3 is a CrC transition layer, and 4 is a working layer.

[0053] Figure 2 A friction coefficient curve obtained by the super-slip carbon thin film constructed by the application and the amorphous hydrogen-containing pair of balls. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical scheme and advantages of the application more clear and apparent, the embodiments of the application will be described in detail in the following. It should be noted that the embodiments in the application and the features in the embodiments can be combined with each other at will without conflict.

[0055] The application will be further described in detail below in combination with specific embodiments, but the embodiments should not be understood as a limitation on the application.

[0056]

Tribological performance testing

[0057] The application forms a friction pair with a super-smooth carbon film and a 6 mm diameter amorphous hydrogen-containing carbon film counter-pair. The friction test is carried out on an Anton Paar friction and wear tester under the conditions of a load of 3-5 N, a frequency of 5 Hz, an amplitude of 5 mm, a nitrogen atmosphere, friction for 6-15 min, and room temperature. The friction pair is placed in a dry nitrogen environment by repeatedly charging and discharging nitrogen gas in the cavity, and a friction coefficient-time curve is obtained. The results show that, compared with the GLC film without silver, the GLC film doped with different amounts of silver (i.e. the silver-doped GLC film prepared under different sputtering currents) can achieve super-smoothness, and the friction coefficient changes between 0.006 and 0.009, having macroscopic super-smoothness in the atmospheric environment (see Figure 2 ).

[0058] Example 1

[0059] As shown in Figure 1 , a silver target is sputtered to prepare a super-smooth carbon film. The film refers to a silver-doped GLC film deposited on the surface of a silicon substrate with a silver target sputtering current of 0.2 A. The content of silver is 18% in terms of atomic percentage.

[0060] The preparation method of the super-smooth carbon film comprises the following steps:

[0061] (1) A silicon wafer is used as a deposition substrate and is ultrasonically treated in alcohol and acetone solutions for 15 min, respectively. The cleaning times are 2 times of alcohol cleaning and 2 times of acetone cleaning, and then the substrate is dried for standby;

[0062] (2) The cleaned and dried substrate sample is placed in a plating cavity, and the vacuum degree is extracted to less than 1×10 -4 Pa. Ion source cleaning is started with a current of 1.5 A. The substrate is bombarded by high-energy plasma in an argon atmosphere at a working voltage of 430 V and a gas pressure of 2.5 Pa for 25 min;

[0063] (3) Depositing a Cr primer layer and a CrC transition layer: maintaining the ion source current at 1.5 A and the gas pressure at 2.5 Pa, a Cr primer layer is first deposited by opening the chromium target with a current of 7.5 A for 30 min. Then, the CrC transition layer is prepared by simultaneously opening the carbon target and the chromium target with a chromium target current of 7.5 A and a carbon target current of 2.5 A for 30 min. The working voltage of the chromium target and the carbon target is controlled at 400 V during the entire deposition process;

[0064] (4) Depositing silver-doped GLC film working layer: control the ion source current to be 2.5 A and the working voltage to be 60 V; simultaneously, turn on the silver target and the carbon target, the working voltage of the carbon target is 420 V and the current is 7.5 A; the voltage of the silver target is 410 V and the working current is 0.20 A; keep other gas pressure conditions unchanged, and deposit for 7 h to obtain the GLC film with a silver content of 18%.

[0065] The friction pair system of the super-smooth carbon film:

[0066] The super-smooth carbon film prepared above and an amorphous hydrogen-containing carbon film pair ball with a diameter of 6 mm are used as a pair, an Anton Paar friction and wear tester is used to perform a friction test under the conditions of a load of 5 N, a frequency of 5 Hz, an amplitude of 5 mm, a nitrogen atmosphere and room temperature, and the friction is performed for 15 min. The friction pair is in a dry nitrogen environment through multiple nitrogen charging and discharging operations of the cavity, and a friction coefficient-time curve is obtained. The results show that when the silver content is 18%, the system friction coefficient is 0.006, and macroscopic super-smoothness is achieved (for details, see Figure 2 ).

[0067] Embodiment 2

[0068] As shown in Figure 1 , a silver target is sputtered to prepare a super-smooth carbon film. The film refers to a silver-doped GLC film deposited on the surface of a silicon substrate by sputtering a silver target with a current of 0.55 A. The silver content is 43% in terms of atomic percentage.

[0069] The preparation method of the super-smooth carbon film includes the following steps:

[0070] (1) A silicon wafer is used as a deposition substrate, and is ultrasonically treated in alcohol and acetone solutions for 15 min, respectively. The cleaning times are 2 times of alcohol cleaning and 2 times of acetone cleaning, and then the silicon wafer is dried for standby use.

[0071] (2) The cleaned and dried substrate sample is placed in a plating cavity, and the vacuum degree is extracted to be less than 1×10 -4 Pa. Ion source cleaning is started, the current is 1.5 A, the substrate is bombarded by high-energy plasma in an argon atmosphere, the working voltage is 480 V, and the gas pressure is 2.5 Pa. Bombard for 25 min.

[0072] (3) Depositing Cr bottom layer and CrC transition layer: keep the ion source current to be 1.5 A and the gas pressure to be 2.5 Pa, turn on the chromium target to first deposit the Cr bottom layer, the current is 7.0 A, and the deposition time is 30 min; then turn on the carbon target and the chromium target at the same time to prepare the CrC transition layer, the current of the chromium target is 7.0 A, the current of the carbon target is 2.5 A, the deposition time is 30 min, and the working voltage of the chromium target and the carbon target is controlled to be 350 V during the whole deposition process.

[0073] (4) Depositing the working layer of silver-doped GLC film: control the ion source current to be 2.5 A and the working voltage to be 60 V; simultaneously, turn on the silver target and the carbon target, control the working voltage of the carbon target to be 400 V and the current to be 8.0 A, control the voltage of the silver target to be 380 V and the working current to be 0.55 A; keep other gas pressure conditions unchanged, and deposit for 6 hours to obtain the GLC film with a silver content of 43%.

[0074] The friction pair system of the super-smooth carbon film:

[0075] The prepared super-smooth carbon film and the amorphous hydrogen-containing carbon film pair ball with a diameter of 6 mm are used as a pair, an Anton Paar friction and wear tester is used, a friction test is carried out under the conditions of a load of 3 N, a frequency of 5 Hz, an amplitude of 5 mm, a nitrogen atmosphere and room temperature, and the friction is carried out for 10 minutes. The friction pair is in a dry nitrogen environment through the operation of charging and discharging nitrogen gas in the cavity, and a curve of the friction coefficient changing with time is obtained. The results show that when the silver content is 43%, the friction coefficient of the system is 0.007, and macroscopic super-smoothness is achieved (for details, see Figure 2 ).

[0076] Embodiment 3

[0077] As shown in Figure 1 , a silver target is sputtered to prepare a super-smooth carbon film. The film refers to a silver-doped GLC film deposited on the surface of a silicon substrate by sputtering a silver target with a current of 1.2 A. The silver content is 90% in terms of atomic percentage.

[0078] The preparation method of the super-smooth carbon film comprises the following steps:

[0079] (1) The silicon wafer is used as a deposition substrate, and is ultrasonically treated in alcohol and acetone solutions for 15 minutes, respectively. The cleaning times are 2 times of alcohol cleaning and 2 times of acetone cleaning, and then the silicon wafer is dried for standby use.

[0080] (2) The cleaned and dried substrate sample is placed in a coating cavity, and the vacuum degree is extracted to be less than 1×10 -4 Pa. Ion source cleaning is started, the current is 1.5 A, the substrate is bombarded by high-energy plasma in an argon atmosphere, the working voltage is 500 V, and the gas pressure is 2.5 Pa. Bombard for 20 minutes.

[0081] (3) Depositing Cr primer layer and CrC transition layer: keep the ion source current to be 1.5 A and the gas pressure to be 2.5 Pa, turn on the chromium target to first deposit the Cr primer layer, the current is 7.5 A, and the deposition time is 30 minutes; then turn on the carbon target and the chromium target at the same time to prepare the CrC transition layer, the current of the chromium target is 7.5 A, the current of the carbon target is 2.0 A, the deposition time is 30 minutes, and the working voltage of the chromium target and the carbon target is controlled to be 500 V during the whole deposition process.

[0082] (4) Depositing the working layer of silver-doped GLC film: control the ion source current to be 2.5 A and the working voltage to be 60 V; simultaneously, turn on the silver target and the carbon target, the working voltage of the carbon target is 450 V and the current is 8.0 A; the voltage of the silver target is 450 V and the working current is 1.20 A; keep other gas pressure conditions unchanged, and deposit for 8 h to obtain the GLC film with a silver content of 90%.

[0083] The friction pair system of the super-smooth carbon film:

[0084] The prepared super-smooth carbon film and the amorphous hydrogen-containing carbon film pair ball with a diameter of 6 mm are used as a friction pair, and the Anton Paar friction and wear testing machine is used to carry out friction test under the conditions of a load of 3 N, a frequency of 5 Hz, an amplitude of 5 mm, a nitrogen atmosphere and room temperature, and the friction is carried out for 15 min. The friction pair is in a dry nitrogen environment through the operation of charging and discharging nitrogen gas in the cavity, and the friction coefficient-time curve is obtained. The results show that when the silver content is 90%, the system has a long running-in period. Under the condition of keeping the subsequent conditions unchanged, the friction experiment is continuously carried out for 6 min in the above wear track, and the friction coefficient is reduced to 0.009, and the macro-scale super-smoothness is realized (for details, see Figure 2 ).

[0085] In the above examples 1 to 3, the silver (Ag) doped nanoparticles can be replaced by other metal elements with the characteristic of d electron orbit not filled, such as Cu, Ni, Co, Au, etc.

[0086] Comparative Example 1

[0087] A silver target is sputtered to prepare a super-smooth carbon film. The film refers to a silver-doped GLC film deposited on the surface of a silicon substrate by sputtering a silver target with a current of 0 A, and the silver content is 0%, that is, there is no metal element doped in the GLC film.

[0088] The preparation method of the super-smooth carbon film comprises the following steps:

[0089] (1) A stainless steel sheet is used as a deposition substrate, and is ultrasonically treated in alcohol and acetone solutions for 30 min, respectively. The cleaning times are 2 times of alcohol cleaning and 2 times of acetone cleaning, and then the substrate is dried for standby;

[0090] (2) The cleaned and dried substrate sample is placed in a coating cavity, and the vacuum degree is extracted to be less than 1×10 -4 Pa, the ion source cleaning is started, the current is 1.5 A, the substrate is bombarded by high-energy plasma in an argon atmosphere, the working voltage is 400 V, and the gas pressure is 2.5 Pa, and the bombardment time is 30 min;

[0091] (3) Depositing Cr primer layer and CrC transition layer: keeping the ion source current at 1.5 A and the gas pressure at 2.5 Pa, the chromium target is turned on to first deposit the Cr primer layer, the current is 6.0 A, and the deposition time is 30 min; then the carbon target and the chromium target are turned on simultaneously to prepare the CrC transition layer, the current of the chromium target is 6.0 A, the current of the carbon target is 1.0 A, and the deposition time is 30 min, and the working voltage of the chromium target and the carbon target is controlled at 300 V during the whole deposition process;

[0092] (4) Depositing GLC film working layer: the ion source current is controlled at 2.5 A, and the working voltage is 60 V; only the carbon target is turned on, the working voltage of the carbon target is 400 V, and the current is 7.0 A. The other gas pressure conditions remain unchanged, and the GLC film with a silver content of 0% is obtained after 6 h of deposition.

[0093] The friction pair system of the super-smooth carbon film:

[0094] The prepared super-smooth carbon film and the amorphous hydrogen-containing carbon film pair ball with a diameter of 6 mm are used as a pair, and the Anton Paar friction and wear tester is used to perform friction test under the conditions of a load of 3 N, a frequency of 5 Hz, an amplitude of 5 mm, a nitrogen atmosphere, and room temperature, and the friction is performed for 15 min. The friction pair is placed in a dry nitrogen environment by repeatedly charging and discharging nitrogen gas in the cavity, and the friction coefficient-time curve is obtained. The results show that when the silver content is 0%, the system cannot achieve super-smoothness.

[0095] The above examples and comparative examples show that when there is no metal element doped in the carbon-based film, super-smoothness cannot be achieved at the macro scale; when a metal element with the characteristic of unfilled d orbit, such as silver element, is doped into the GLC working layer, robust super-smoothness can be achieved at the macro scale, that is, a super-smooth carbon film is successfully obtained by the method provided in the present application, and super-smooth application can be achieved.

[0096] Although the embodiments of the present application have been shown and described above, it should be understood that the above examples are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above examples within the scope of the present application.

Claims

1. An ultrasmooth carbon film, characterized by, The super-smooth carbon film comprises a Cr undercoat layer, a CrC transition layer and a working layer arranged on a substrate in sequence; wherein the working layer is a GLC film doped with metal; and the metal in the working layer is selected from any one of Ag, Cu, Ni, Co and Au. In the working layer, the doping amount of metal is 18% to 90% in atomic percentage.

2. The ultralow friction carbon film according to claim 1, wherein The sum of the thicknesses of the Cr undercoat layer and the CrC transition layer is 600 to 650 nm, and the thickness of the working layer is 900 to 1600 nm.

3. A method for preparing the ultrasmooth carbon film according to any one of claims 1 to 2, characterized by, The method comprises the following steps: 1) pretreatment of the substrate, including polishing and polishing the substrate, then ultrasonic cleaning, and then plasma cleaning of the substrate; The substrate is selected from a silicon wafer or a metal substrate; The step of plasma cleaning comprises: placing the cleaned and dried substrate into a coating chamber, vacuumizing to less than 1*10 -4 Pa, starting the ion source cleaning, the current being 1 ~ 2 A, bombarding the substrate with high-energy plasma in an argon atmosphere, the working voltage being 400 ~ 500 V, the pressure being 2 ~ 3 Pa, and the bombardment time being 20 ~ 30 min. 2) depositing a Cr undercoat layer and a CrC transition layer, including: keeping the ion source current at 1 to 2 A, controlling the gas pressure at 2 to 3 Pa, opening the chromium target to first deposit the Cr undercoat layer, the current is 6.0 to 7.5 A, the deposition time is 25 to 35 min; then simultaneously open the carbon target and the chromium target to prepare the CrC transition layer, the chromium target current is 6.0 to 7.5 A, the carbon target current is 1.0 to 2.5 A, the deposition time is 25 to 35 min, and the working voltage of the chromium target and the carbon target during the entire deposition process is controlled at 300 to 500 V; 3) depositing a GLC film working layer doped with metal, the working layer is obtained by co-sputtering a metal target and a carbon target, including: controlling the ion source current to be 2 to 3 A, the working voltage to be 50 to 70 V, simultaneously opening the metal target and the carbon target, the carbon target working voltage being 400 to 450 V, and the carbon target working current being 7.0 to 8.0 A; the metal target working voltage is 300 to 450 V, and the metal target working current is 0 to 1.2 A, excluding 0 A; keeping other gas pressure conditions unchanged, depositing for 6 to 8 hours to obtain a GLC film doped with different metal contents.

4. The method of claim 3, wherein, In step 1), the ultrasonic cleaning step includes: ultrasonic treatment of the substrate in alcohol and acetone solutions for 15 to 30 min respectively; wherein the cleaning times are 2 times of alcohol cleaning and 2 times of acetone cleaning, and then drying for standby.

5. The method of claim 3, wherein, In step 1), the metal substrate is selected from any one of bearing steel, high-temperature alloy, stainless steel and copper.

6. The method of claim 3, wherein, In the plasma cleaning of step 1), the current is 1.5 A, and the gas pressure is 2.5 Pa.

7. The method according to any one of claims 3 to 6, characterized in that, In step 2), the ion source current is kept at 1.5 A, and the gas pressure is 2.5 Pa, the deposition time of the Cr undercoat layer is 30 min, and the deposition time of the CrC transition layer is 30 min; In step 3), the ion source current is controlled to be 2.5 A, the working voltage is 60 V, and the gas pressure is 2.5 Pa.

8. A super-smooth carbon film prepared by the method of any one of claims 3 to 7.

9. A method for achieving super-slip using the super-slippery carbon film according to any one of claims 1 to 2 and 8, characterized by, The method comprises forming a friction pair of the super-smooth carbon film and an amorphous hydrogen-containing carbon film, and realizing super-smoothness in a nitrogen atmosphere.

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