Diamond-like carbon coating and preparation method thereof

Abstract

The invention relates to a diamond-like carbon coating and a preparation method thereof, and belongs to the technical field of coatings. The preparation is carried out in a closed field unbalanced magnetron sputtering system, and the system is at least provided with a titanium target, a graphite target and a linear ion source; the preparation method comprises the following steps: pretreating a base material, removing surface moisture, transferring the base material into a vacuum chamber, and carrying out ion cleaning and activation; adjusting bias voltage, then turning on a titanium target power supply, cleaning a target surface, depositing a gradient layer, turning off the titanium target power supply, turning on a graphite target power supply to carry out hydrogen-free deposition, and after deposition is finished, carrying out furnace cooling in a vacuum environment. According to the diamond-like carbon coating provided by the invention, the graphite target material is adopted, under the condition that hydrogen-containing gas and a metal transition layer are not introduced, a closed field unbalanced magnetron sputtering technology is combined with linear ion source auxiliary deposition, the DLC coating with excellent biocompatibility is prepared, and the problem of biotoxicity caused by element dissolution is greatly reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of coating and relates to a diamond-like carbon coating and a preparation method thereof. BACKGROUND

[0002] The diamond-like carbon coating, also called DLC coating, is an amorphous functional material composed of carbon elements, which is prepared on the surface of a substrate mainly through physical vapor deposition or chemical vapor deposition process, can form an extremely thin but extremely strong protective film on the surface of various materials such as metals, ceramics and polymers, and has extremely wide application, including the medical field.

[0003] In the medical field, the application of the diamond-like carbon coating extends from early surgical tools to various implantable medical devices and dental equipment, but there are still obvious limitations in actual application. First, the diamond-like carbon coating is not a pure substance with a single composition, but a large family of materials. In order to obtain better performance, other elements are usually doped or a metal transition layer is used in the production process. These doped elements and metal intermediate layers may corrode and ion elute in the complex body fluid of the human body for a long time, thereby causing biological toxicity. Therefore, although the diamond-like carbon coating shows great application potential, its biocompatibility problem still needs to be further solved. SUMMARY

[0004] The purpose of the application is to provide a diamond-like carbon coating and a preparation method thereof. The application provides a diamond-like carbon coating prepared by using a graphite target without introducing hydrogen-containing gas and a metal transition layer, using closed field unbalanced magnetron sputtering technology combined with linear ion source assisted deposition, to prepare a DLC coating with excellent biocompatibility, thereby greatly reducing the biological toxicity problem caused by element elution.

[0005] The purpose of the application can be achieved by the following technical solutions. A preparation method of a diamond-like carbon coating, wherein the preparation of the diamond-like carbon coating is carried out in a closed field unbalanced magnetron sputtering system, and the system is at least provided with a titanium target, a graphite target and a linear ion source; The preparation method of the diamond-like carbon coating comprises the following steps: A1, pretreating a substrate and removing surface moisture to obtain a workpiece; A2, transferring the workpiece to a vacuum chamber for ion cleaning and activation; A3, turning on the titanium target power supply after adjusting the bias voltage, cleaning the target surface and depositing a gradient layer; A4, turning off the titanium target power supply, turning on the graphite target power supply for hydrogen-free deposition, and cooling in a vacuum environment after deposition.

[0006] Further, the pre-treatment in step A1 refers to polishing the surface of the substrate with diamond polishing paste until the surface roughness Ra is less than or equal to 0.05 microns, and then ultrasonic cleaning in acetone and anhydrous ethanol for 10-20 minutes.

[0007] Further, the ultrasonic cleaning refers to setting the ultrasonic frequency to 30-50 kHz and the ultrasonic temperature to 45-55 DEG C.

[0008] Further, the vacuum degree in the vacuum chamber in step A2 is less than or equal to 5*10 -3 Pa.

[0009] Further, the ion cleaning and activation in step A2 refers to introducing high-purity argon into the vacuum chamber, stabilizing the working pressure at 0.25-0.35 Pa, then turning on the workpiece holder bias power supply, applying pulsed direct current bias with a voltage of -780 to -820 V, and simultaneously starting the linear ion source with an anode voltage of 180-220 V and an anode current of 2.5-3.5 A, and processing for 15-25 minutes.

[0010] Further, the bias adjustment in step A3 refers to adjusting the bias to -95 to -105 V.

[0011] Further, the cleaning of the target surface in step A3 refers to using a direct current magnetron sputtering mode, setting the current to 4.5-5.5 A, and pre-sputtering the titanium target in an argon atmosphere for 1.5-2.5 minutes.

[0012] Further, the deposition of the gradient layer in step A3 refers to continuously sputtering the titanium target while introducing nitrogen at a rate of 8-12 seem / min for 12-18 minutes, and simultaneously introducing argon at a rate of 13-17 seem / min while opening the graphite target power supply, and linearly reducing the titanium target current from 4.5-5.5 A to 0 A and linearly increasing the graphite target current from 1 A to 7.5-8.5 A within 15-25 minutes.

[0013] Further, the hydrogen-free deposition in step A4 refers to closing the titanium target and nitrogen gas path, using a direct current magnetron sputtering mode, setting the current to 7.5-8.5 A, stabilizing the argon flow at 48-52 seem, setting the workpiece bias to -75 to -85 V, simultaneously starting the linear ion source with an anode voltage of 245-255 V and an anode current of 3.5-4.5 A, and depositing for 1.8-2.2 hours.

[0014] The beneficial effects of the present application are as follows: (1) The application provides a diamond-like carbon coating, which is prepared by using a graphite target, without introducing hydrogen-containing gas and a metal transition layer, and by using a closed field unbalanced magnetron sputtering technology combined with a linear ion source assisted deposition, so that a DLC coating with excellent biocompatibility is prepared, and the biological toxicity problem caused by element elution is greatly reduced.

[0015] (2) The application provides a diamond-like carbon coating, in the process of depositing a gradient layer, with the increase of carbon flow and the decrease of titanium flow, the composition of the deposited layer is changed from TiN to TiNC, then to carbon-rich TiC, and finally to almost pure carbon layer, which replaces the traditional metal transition layer, so as to eliminate the risk of metal ion elution and greatly alleviate the problem of coating peeling caused by stress concentration. DETAILED DESCRIPTION

[0016] In order to further illustrate the technical means and effects adopted by the application to achieve the predetermined application purpose, the specific embodiments, structures, features and effects according to the application are described in detail below.

[0017] Embodiment 1 A preparation method of a diamond-like carbon coating, wherein the preparation of the diamond-like carbon coating is carried out in a closed field unbalanced magnetron sputtering system, which is equipped with at least one titanium target, one graphite target and one linear ion source; The preparation method of the diamond-like carbon coating comprises the following steps: A1, pretreating the substrate and removing the surface moisture to obtain a workpiece; A2, transferring the workpiece to a vacuum chamber for ion cleaning and activation; A3, adjusting the bias voltage, turning on the titanium target power, cleaning the target surface and depositing a gradient layer; A4, turning off the titanium target power, turning on the graphite target power for hydrogen-free deposition, and cooling in a vacuum environment after deposition.

[0018] The pretreatment in step A1 refers to polishing the surface of the substrate with diamond polishing paste until the surface roughness Ra is 0.05 microns, and then ultrasonic cleaning in acetone and anhydrous ethanol for 10 minutes respectively.

[0019] The ultrasonic cleaning refers to setting the ultrasonic frequency to 30 kHz and the ultrasonic temperature to 45 DEG C.

[0020] The vacuum degree in the vacuum chamber in step A2 is 5*10 -3 Pa.

[0021] The ion cleaning and activation in step A2 refers to introducing high-purity argon into the vacuum chamber, stabilizing the working pressure at 0.25 Pa, then turning on the workpiece holder bias power supply, applying pulsed direct current bias with a voltage of -780 V, and simultaneously starting the linear ion source with an anode voltage of 180 V and an anode current of 2.5 A, and the processing time is 15 min.

[0022] The bias adjustment in step A3 refers to adjusting the bias to -95 V.

[0023] The cleaning of the target surface in step A3 refers to pre-sputtering the titanium target in an argon atmosphere for 1.5 min in a direct current magnetron sputtering mode with a current of 4.5 A.

[0024] The deposition of the gradient layer in step A3 refers to continuously sputtering the titanium target while introducing nitrogen at a rate of 8 seem / min for 12 min, and while continuing to introduce nitrogen, turning on the graphite target power supply, introducing argon at a rate of 13 seem / min, and simultaneously linearly reducing the titanium target current from 4.5 A to 0 A and linearly increasing the graphite target current from 1 A to 7.5 A within 15 min.

[0025] The hydrogen-free deposition in step A4 refers to closing the titanium target and nitrogen gas path, using a direct current magnetron sputtering mode with a current of 7.5 A, stabilizing the argon flow at 48 seem, setting the workpiece bias to -75 V, simultaneously starting the linear ion source with an anode voltage of 245 V and an anode current of 3.5 A, and depositing for 1.8 h.

[0026] Example 2 A method for preparing a diamond-like coating, wherein the preparation of the diamond-like coating is carried out in a closed-field unbalanced magnetron sputtering system equipped with at least one titanium target, one graphite target, and one linear ion source; The method for preparing the diamond-like coating comprises the following steps: A1. Pre-treating the substrate and removing surface moisture to obtain a workpiece; A2. Transferring the workpiece to a vacuum chamber for ion cleaning and activation; A3. Adjusting the bias, then turning on the titanium target power supply, cleaning the target surface, and depositing a gradient layer; A4. Closing the titanium target power supply, turning on the graphite target power supply for hydrogen-free deposition, and then cooling in a vacuum environment after deposition.

[0027] The pre-treatment in step A1 refers to polishing the surface of the substrate using diamond polishing paste until the surface roughness Ra is 0.05 μm, and then ultrasonic cleaning in acetone and anhydrous ethanol for 12 min, respectively.

[0028] The ultrasonic cleaning refers to setting the ultrasonic frequency to 35 kHz and the ultrasonic temperature to 48℃.

[0029] The vacuum degree in the vacuum chamber in step A2 is 5x10 -3 Pa.

[0030] The ion cleaning and activation in step A2 refers to introducing high-purity argon into the vacuum chamber, stabilizing the working pressure at 0.25 Pa, then turning on the workpiece holder bias power supply, applying pulsed direct current bias with a voltage of -790 V, and starting the linear ion source with an anode voltage of 190 V and an anode current of 2.5 A for 18 min.

[0031] The bias adjustment in step A3 refers to adjusting the bias to -95 V.

[0032] The target surface cleaning in step A3 refers to pre-sputtering the titanium target in an argon atmosphere for 1.5 min in a direct current magnetron sputtering mode with a current setting of 4.5 A.

[0033] The gradient layer deposition in step A3 refers to continuously sputtering the titanium target while introducing nitrogen at a rate of 9 sccm / min for 14 min, continuing to introduce nitrogen while turning on the graphite target power supply, introducing argon at a rate of 14 sccm / min, and simultaneously linearly reducing the titanium target current from 4.5 A to 0 A and linearly increasing the graphite target current from 1 A to 7.5 A within 18 min.

[0034] The hydrogen-free deposition in step A4 refers to closing the titanium target and nitrogen gas path, adopting a direct current magnetron sputtering mode with a current setting of 7.5 A, stabilizing the argon flow at 49 sccm, setting the workpiece bias to -75 V, starting the linear ion source with an anode voltage of 245 V and an anode current of 3.5 A, and depositing for 1.9 h.

[0035] Example 3 A method for preparing a diamond-like coating, wherein the preparation of the diamond-like coating is carried out in a closed-field unbalanced magnetron sputtering system equipped with at least one titanium target, one graphite target, and one linear ion source; The method for preparing the diamond-like coating comprises the following steps: A1, pretreating the substrate and removing surface moisture to obtain a workpiece; A2, transferring the workpiece to a vacuum chamber for ion cleaning and activation; A3, adjusting the bias, then turning on the titanium target power supply, cleaning the target surface, and depositing a gradient layer; A4, closing the titanium target power supply, turning on the graphite target power supply for hydrogen-free deposition, and then cooling in a vacuum environment after deposition.

[0036] The pre-treatment in step A1 refers to polishing the surface of the substrate using diamond polishing paste until the surface roughness Ra is 0.05 μm, and then ultrasonic cleaning in acetone and anhydrous ethanol for 15 min respectively.

[0037] The ultrasonic cleaning refers to setting the ultrasonic frequency to 40 kHz and the ultrasonic temperature to 50℃.

[0038] The vacuum degree in the vacuum chamber in step A2 is 5×10 -3 Pa.

[0039] The ion cleaning and activation in step A2 refers to introducing high-purity argon into the vacuum chamber, stabilizing the working pressure at 0.3 Pa, then turning on the workpiece holder bias power, applying pulsed direct current bias with a voltage of -800 V, starting the linear ion source, setting the anode voltage to 200 V and the anode current to 3 A, and processing for 20 min.

[0040] The bias adjustment in step A3 refers to adjusting the bias to -100 V.

[0041] The cleaning of the target surface in step A3 refers to pre-sputtering the titanium target in an argon atmosphere for 2 min in a direct current magnetron sputtering mode with a current setting of 5 A.

[0042] The deposition of the gradient layer in step A3 refers to continuously sputtering the titanium target while introducing nitrogen at a rate of 10 sccm / min for 15 min, continuing to introduce nitrogen while turning on the graphite target power, introducing argon at a rate of 15 sccm / min, and simultaneously linearly reducing the titanium target current from 5 A to 0 A and linearly increasing the graphite target current from 1 A to 8 A within 20 min.

[0043] The hydrogen-free deposition in step A4 refers to closing the titanium target and nitrogen gas path, adopting a direct current magnetron sputtering mode with a current setting of 8 A, stabilizing the argon flow at 50 sccm, setting the workpiece bias to -80 V, starting the linear ion source, setting the anode voltage to 250 V and the anode current to 4 A, and depositing for 2 h.

[0044] Example 4 A method for preparing a diamond-like coating, wherein the preparation of the diamond-like coating is carried out in a closed-field unbalanced magnetron sputtering system equipped with at least one titanium target, one graphite target, and one linear ion source; The method for preparing the diamond-like coating comprises the following steps: A1, pre-treating and removing surface moisture of the substrate to obtain a workpiece; A2, transferring the workpiece to a vacuum chamber for ion cleaning and activation; A3, open the titanium target power supply after adjusting the bias, clean the target surface, and deposit a gradient layer; A4, close the titanium target power supply, open the graphite target power supply for hydrogen-free deposition, and cool down in a vacuum environment after deposition, thereby obtaining the product.

[0045] The pretreatment in step A1 refers to polishing the surface of the substrate using diamond polishing paste until the surface roughness Ra is 0.05 μm, and then ultrasonic cleaning in acetone and anhydrous ethanol for 17 min, respectively.

[0046] The ultrasonic cleaning refers to setting the ultrasonic frequency to 45 kHz and the ultrasonic temperature to 52℃.

[0047] The vacuum degree in the vacuum chamber in step A2 is 5×10 -3 Pa.

[0048] The ion cleaning and activation in step A2 refer to introducing high-purity argon into the vacuum chamber, stabilizing the working pressure at 0.35 Pa, opening the workpiece holder bias power supply, applying pulsed direct current bias with a voltage of -810 V, starting the linear ion source, setting the anode voltage to 210 V and the anode current to 3.5 A, and processing for 22 min.

[0049] The adjustment of the bias after step A3 refers to adjusting the bias to -105 V.

[0050] The cleaning of the target surface in step A3 refers to pre-sputtering the titanium target in an argon atmosphere for 2.5 min using a direct current magnetron sputtering mode with a current setting of 5.5 A.

[0051] The deposition of the gradient layer in step A3 refers to introducing nitrogen at a rate of 11 sccm / min for 17 min while maintaining titanium target sputtering, introducing argon at a rate of 16 sccm / min while continuing to introduce nitrogen, and opening the graphite target power supply, and linearly reducing the titanium target current from 5.5 A to 0 A and linearly increasing the graphite target current from 1 A to 8.5 A within 22 min.

[0052] The hydrogen-free deposition in step A4 refers to closing the titanium target and nitrogen gas circuit, using a direct current magnetron sputtering mode with a current setting of 8.5 A, stabilizing the argon flow at 51 sccm, setting the workpiece bias to -85 V, starting the linear ion source, setting the anode voltage to 255 V and the anode current to 4.5 A, and depositing for 2.1 h.

[0053] Example 5 A method for preparing a diamond-like carbon coating, wherein the preparation of the diamond-like carbon coating is carried out in a closed-field unbalanced magnetron sputtering system equipped with at least one titanium target, one graphite target, and one linear ion source. The preparation method of the diamond-like coating comprises the following steps: A1, pretreating the substrate and removing surface moisture to obtain a workpiece; A2, transferring the workpiece to a vacuum chamber for ion cleaning and activation; A3, adjusting the bias voltage, opening the titanium target power supply, cleaning the target surface, and depositing a gradient layer; A4, closing the titanium target power supply, opening the graphite target power supply for hydrogen-free deposition, and cooling in a vacuum environment after deposition.

[0054] The pretreatment in step A1 refers to polishing the surface of the substrate with diamond polishing paste until the surface roughness Ra is 0.05 μm, and then ultrasonic cleaning in acetone and anhydrous ethanol for 20 min respectively.

[0055] The ultrasonic cleaning refers to setting the ultrasonic frequency to 50 kHz and the ultrasonic temperature to 55℃.

[0056] The vacuum degree in the vacuum chamber in step A2 is 5×10 -3 Pa.

[0057] The ion cleaning and activation in step A2 refers to introducing high-purity argon into the vacuum chamber, stabilizing the working pressure at 0.35 Pa, opening the workpiece holder bias power supply, applying pulsed direct current bias voltage of -820 V, starting the linear ion source, setting the anode voltage to 220 V and the anode current to 3.5 A, and processing for 25 min.

[0058] The adjustment of the bias voltage in step A3 refers to adjusting the bias voltage to -105 V.

[0059] The cleaning of the target surface in step A3 refers to using direct current magnetic control sputtering mode, setting the current to 5.5 A, and pre-sputtering the titanium target in argon atmosphere for 2.5 min.

[0060] The deposition of the gradient layer in step A3 refers to continuously sputtering the titanium target while introducing nitrogen at a rate of 12 sccm / min for 18 min, opening the graphite target power supply while continuing to introduce nitrogen, introducing argon at a rate of 17 sccm / min, and linearly reducing the titanium target current from 5.5 A to 0 A and linearly increasing the graphite target current from 1 A to 8.5 A within 25 min.

[0061] The hydrogen-free deposition in step A4 refers to closing the titanium target and nitrogen gas path, using direct current magnetic control sputtering mode, setting the current to 8.5 A, stabilizing the argon flow to 52 sccm, setting the workpiece holder bias voltage to -85 V, starting the linear ion source, setting the anode voltage to 255 V and the anode current to 4.5 A, and depositing for 2.2 h.

[0062] The diamond-like carbon coating was applied on the 304 bar (Φ10 cm) according to the diamond-like carbon coating preparation method in Example 3, and the coating thickness was 0.5 mm. The final sample was Test Sample 1, and the potential cytotoxicity of the test sample was tested; The negative control was high-density polyethylene, which was obtained from Hatano Research Institute, Food and Drug Safety Center, and the batch number was C-221; The positive control was ZDBC and ZDEC, wherein the ZDBC (0.25% ZDBC polyurethane sheet) was obtained from Hatano Research Institute, Food and Drug Safety Center, and the batch number was B-223K, and the ZDEC (0.1% ZDEC polyurethane sheet) was obtained from Hatano Research Institute, Food and Drug Safety Center, and the batch number was A-201K; The composition of the MEM medium was: 88% MEM, 10% fetal bovine serum, 1% antibiotic (100 U / mL penicillin, 100 μg / mL streptomycin), and 1% sodium pyruvate; The extraction solution was 10% fetal bovine serum MEM medium; Among them, the brand of MEM is Gibco (batch number is 6124013); the brand of FBS is WISENT (batch number is 086150069); the brand of Penicillin, streptomycin is Gibco (batch number is 2585644); the brand of MTT (3- (4, 5-dimethylthiazole-2) -2, 5-diphenyl tetrazolium bromide) is SICMA-ALDRICH (batch number is J2106160); The ATCC Number of L-929 mouse fibroblasts is CC-1, and the Lot Number is 7008726.

[0063] According to the standard GB / T 16886.5-2017, the test sample, the negative control and the positive control were placed in 10% fetal bovine serum MEM medium, and then extracted at 37℃ for 24h. Then the test sample extract was diluted to 100%, 50%, 25%, and 12.5% concentrations, respectively. L-929 mouse fibroblast cells were cultured in MEM medium containing 10% fetal bovine serum and antibiotics (penicillin 100 U / mL, streptomycin ug / mL) in a 37°C, 5% CO2 incubator to obtain L-929 fibroblast monolayer cells. The original culture solution was removed and different concentrations of the extract and diluent were added, respectively, and the cells were cultured in a 37°C, 5% CO2 incubator.

[0064] The samples, negative control, positive control and blank control were extracted according to the conditions described in Table 1. The extract was continuously shaken during the extraction process. The state of the extract during the extraction process is shown in Table 2. The extract was used immediately after extraction and was not centrifuged, filtered or otherwise treated before being used for testing.

[0065] After the cells were cultured for 48-72 h and grew vigorously, the cells were diluted to a density of 1.0 x 104 cells per well and inoculated in a 96-well plate. After the cells grew into a monolayer, the original culture solution was removed and 100 μL (100%, 50%, 25%, 12.5%) of the extract, the blank control extract, the positive control (100%, 50%, 25%, 12.5%) and the negative control (100%) were added, respectively. Each group had three replicate wells. The blank control extract was added to the second and eleventh vertical rows of the 96-well plate. After the addition was completed, the 96-well plate was placed in a 37°C, 5% CO2 incubator for 24 h.

[0066] After 24 h of culture, the 96-well plate was removed for cell morphology observation, but no cell toxicity evaluation was performed. The original culture solution was then removed and 50 μL of MTT (1 mg / mL) was added to each well. The culture was continued for another 2 h. After the end of the culture, the supernatant was removed and 100 μL of 99.5% pure isopropyl alcohol was added to dissolve the crystals. The absorbance value was measured on an enzyme marker with 570 nm as the main absorption wavelength and 650 nm as the reference wavelength. The cell state was detected using a microscope and the results of the test group were qualitatively evaluated. The morphological changes in the cells caused by the cytotoxicity of the sample extract were recorded and the evaluation criteria are shown in Table 3.

[0067] Under the microscope, no more than 50% of the cells in the undiluted (100%) sample showed rounding, no intracellular granules, and no large-scale cell lysis. Cell growth inhibition was observed in no more than 50% of the cells. The undiluted (100%) sample group showed no tendency of cytotoxicity (level 2).

[0068] The MTT method is used to quantitatively evaluate the cytotoxicity, and the MTT method quantitatively measures the cell viability and cell proliferation after the cells receive the extraction solution or solution. The active cells reduce the yellow tetrazolium salt MTT (3- (4, 5-dimethylthiazole-2) -2, 5-diphenyl tetrazolium bromide) to water-insoluble blue-violet formazan through the action of succinate dehydrogenase in the mitochondria of living cells and deposit in the cells. The change from yellow to purple can be quantitatively analyzed by spectrophotometric measurement; Wherein, the absorbance value lower than the blank control cell indicates the decrease of cell activity, and the higher absorbance value indicates the increase of cell activity; The decrease of the number of living cells in the sample also causes the decrease of cell metabolic activity, and this decrease is directly related to the amount of blue-violet formazan detected at 570 nm wavelength; The percentage of cell viability is the ratio of the measured value of the sample to the control cells, which is calculated according to the following formula: percentage of cell viability = (100 x OD570 e ) / OD570 rc , OD570 e is the average absorbance of the sample or control after correction of the blank well, and OD570 rc is the average absorbance of the blank control after correction of the blank well; The test results should meet the following requirements: observe the cells under the inverted microscope to exclude cell seeding errors; review the test process to exclude other errors; the average absorbance of the blank control should be ≧0.2, and the average absorbance difference between the left blank control (vertical row 2) and the right blank control (vertical row 11) should not be greater than 15%; if cell toxicity is shown, at least 50% of the sample extraction solution has the same or higher cell viability as 100% of the sample extraction solution, wherein the lower the percentage of cell viability, the higher the potential cytotoxicity of the sample; if the percentage of cell viability of the sample extraction solution is less than 70%, it is determined that the sample has cytotoxicity; the specific test results are shown in Table 4.

[0069] As shown in Table 4, during the experiment, the cell activity of the sample 100% concentration extraction solution was greater than 70%, and the sample extraction solution had no potential cytotoxicity to L-929 mouse fibroblasts.

[0070] Referring to the test method of Example 3, the diamond-like carbon coating was applied to a 304 rod (Φ10 cm) by the diamond-like carbon coating preparation method of Example 1, Example 2, Example 4 and Example 5, and the coating thickness was 0.5 mm. The final sample was tested for potential cytotoxicity. The results showed that, by microscopic observation, no more than 50% of the cells in the undiluted (100%) sample were round, had no cytoplasmic granules, and no large-scale cell lysis; no more than 50% of the cells were observed to have growth inhibition, and the undiluted (100%) sample group had no cytotoxicity tendency (grade 2); in the quantitative evaluation, the cell activity of the 100% concentration of the sample extract was greater than 70%, and the sample extract had no potential cytotoxicity to L-929 mouse fibroblasts.

[0071] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, without departing from the technical solution of the present application. Any indirect modification, equivalent change and modification of the above embodiments according to the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A method for preparing a diamond-like carbon coating, characterized in that: The diamond-like coating was prepared in a closed-field unbalanced magnetron sputtering system, which is equipped with at least one titanium target, one graphite target and one linear ion source. The method for preparing the diamond-like carbon coating includes the following steps: A1. Pre-treat the substrate and remove surface moisture to obtain the workpiece; A2. Transfer the workpiece to the vacuum chamber for ion cleaning and activation; A3. After adjusting the bias voltage, turn on the titanium target power supply, clean the target surface, and deposit the gradient layer. A4. Turn off the titanium target power supply and turn on the graphite target power supply to perform hydrogen-free deposition. After deposition, cool the furnace in a vacuum environment to obtain the final product.

2. The method for preparing a diamond-like coating according to claim 1, characterized in that: The pretreatment mentioned in step A1 refers to polishing the substrate surface with diamond polishing paste until the surface roughness Ra≦0.05μm, and then ultrasonically cleaning it in acetone and anhydrous ethanol for 10-20 minutes respectively.

3. The method for preparing a diamond-like coating according to claim 2, characterized in that: The ultrasonic cleaning refers to setting the ultrasonic frequency to 30-50kHz and the ultrasonic temperature to 45-55℃.

4. The method for preparing a diamond-like coating according to claim 1, characterized in that: The vacuum level in the vacuum chamber described in step A2 is ≤5×10⁻⁶. -3 Pa.

5. The method for preparing a diamond-like coating according to claim 1, characterized in that: The ion cleaning and activation described in step A2 refers to introducing high-purity argon gas into the vacuum chamber, stabilizing the working pressure at 0.25-0.35 Pa, turning on the workpiece holder bias power supply, applying a pulsed DC bias voltage of -780 to -820 V, and simultaneously starting the linear ion source, setting the anode voltage to 180-220 V, the anode current to 2.5-3.5 A, and the processing time to 15-25 min.

6. The method for preparing a diamond-like coating according to claim 1, characterized in that: Step A3 refers to adjusting the bias voltage to -95 to -105V.

7. The method for preparing a diamond-like coating according to claim 1, characterized in that: The target cleaning mentioned in step A3 refers to pre-sputtering the titanium target for 1.5-2.5 minutes in an argon atmosphere using a DC magnetron sputtering mode with a current set to 4.5-5.5A.

8. The method for preparing a diamond-like coating according to claim 1, characterized in that: The deposition gradient layer mentioned in step A3 refers to the following steps: while maintaining titanium target sputtering, nitrogen gas is introduced at a rate of 8-12 sccm / min for 12-18 min. While continuing to introduce nitrogen gas, the graphite target power supply is turned on, and argon gas is introduced at a rate of 13-17 sccm / min. At the same time, the titanium target current is linearly reduced from 4.5-5.5A to 0A within 15-25 min, and the graphite target current is linearly increased from 1A to 7.5-8.5A.

9. The method for preparing a diamond-like coating according to claim 1, characterized in that: The hydrogen-free deposition mentioned in step A4 refers to shutting off the titanium target and nitrogen gas path, using DC magnetron sputtering mode, setting the current to 7.5-8.5A, stabilizing the argon flow rate at 48-52 sccm, setting the workpiece bias voltage to -75 to -85V, and simultaneously starting the linear ion source, setting the anode voltage to 245-255V, the anode current to 3.5-4.5A, and depositing for 1.8-2.2 hours.

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