A diamond-like coating and a method of making the same

Abstract

This invention relates to a diamond-like carbon (DLC) coating and its preparation method, belonging to the field of coating technology. The preparation 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 includes: first, pretreating the substrate to remove surface moisture, then transferring it to a vacuum chamber for ion cleaning and activation; adjusting the bias voltage and turning on the titanium target power supply to clean the target surface and deposit a gradient layer; turning off the titanium target power supply and turning on the graphite target power supply for hydrogen-free deposition; and finally, cooling the substrate in a vacuum environment to obtain the final product. This invention provides a diamond-like carbon coating using a graphite target. Without introducing hydrogen-containing gas and a metal transition layer, it utilizes closed-field unbalanced magnetron sputtering technology combined with a linear ion source to prepare a DLC coating with excellent biocompatibility, greatly reducing the biotoxicity problem caused by element leaching.

Description

Technical Field

[0001] This invention belongs to the field of coating technology and relates to a diamond-like coating and its preparation method. Background Technology

[0002] Diamond-like carbon (DLC) coating, also known as DLC coating, is an amorphous functional material composed of carbon. It is mainly prepared on the surface of a substrate through processes such as physical vapor deposition or chemical vapor deposition. It can form an extremely thin but extremely strong protective film on the surface of various materials such as metals, ceramics, and polymers, and has a wide range of applications, including the medical field.

[0003] In the medical field, the application of diamond-like carbon (DLC) coatings has expanded from early surgical tools to various implantable medical devices and dental equipment. However, significant limitations still exist in practical applications. Firstly, DLC is not a single, pure substance, but rather a large family of materials. To achieve superior performance, other elements are often added or a metallic transition layer is used during the production process. These dopants and metallic interlayers, when present in the complex bodily fluids, can lead to corrosion, ion dissolution, and other issues, resulting in biotoxicity. Therefore, despite the enormous application potential of DLC coatings, their biocompatibility remains a significant challenge. Summary of the Invention

[0004] The purpose of this invention is to provide a diamond-like carbon (DLC) coating and its preparation method. This invention provides a DLC coating using a graphite target. Without introducing hydrogen-containing gas and a metal transition layer, a closed-field non-equilibrium magnetron sputtering technique combined with a linear ion source-assisted deposition is used to prepare a DLC coating with excellent biocompatibility, which greatly reduces the biotoxicity problem caused by element leaching.

[0005] The objective of this invention can be achieved through the following technical solutions: 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, the system being equipped with at least a titanium target, a graphite target and a 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.

[0006] Further, the pretreatment mentioned in step A1 refers to polishing the surface of the substrate 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.

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

[0008] Furthermore, the vacuum level in the vacuum chamber described in step A2 is ≤5×10⁻⁶. -3 Pa.

[0009] Further, 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, 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.

[0010] Furthermore, step A3, which refers to adjusting the bias voltage, means adjusting the bias voltage to -95 to -105V.

[0011] Furthermore, 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.

[0012] Further, 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.

[0013] Further, 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, 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.

[0014] The beneficial effects of this invention are: (1) The present invention provides a diamond-like coating using a graphite target. Without introducing hydrogen-containing gas and a metal transition layer, a DLC coating with excellent biocompatibility is prepared by using closed-field non-equilibrium magnetron sputtering technology combined with linear ion source assisted deposition, which greatly reduces the biotoxicity problem caused by element leaching.

[0015] (2) The present invention provides a diamond-like coating. During the deposition of the gradient layer, as the carbon flow rate increases and the titanium flow rate decreases, the composition of the deposited layer transitions from TiN to TiNC, then to carbon-rich TiC, and finally to an almost pure carbon layer, replacing the traditional metal transition layer. This eliminates the risk of metal ion dissolution and greatly alleviates the problem of coating peeling caused by stress concentration. Detailed Implementation

[0016] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0017] Example 1 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, the system being equipped with at least a titanium target, a graphite target and a 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.

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

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

[0020] The vacuum level in the vacuum chamber described in step A2 is 5 × 10⁻⁶. -3 Pa.

[0021] 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 Pa, turning on the workpiece holder bias power supply, applying a pulsed DC bias voltage of -780V, and simultaneously starting the linear ion source, setting the anode voltage to 180V, the anode current to 2.5A, and the processing time to 15 minutes.

[0022] Step A3 refers to adjusting the bias voltage to -95V.

[0023] The target cleaning mentioned in step A3 refers to pre-sputtering the titanium target for 1.5 minutes in an argon atmosphere using a DC magnetron sputtering mode with a current set to 4.5A.

[0024] 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 sccm / min for 12 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 sccm / min. At the same time, the titanium target current is linearly reduced from 4.5A to 0A and the graphite target current is linearly increased from 1A to 7.5A within 15 min.

[0025] 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 7.5A, stabilizing the argon flow rate at 48 sccm, setting the workpiece bias voltage to -75V, and simultaneously starting the linear ion source, setting the anode voltage to 245V, the anode current to 3.5A, and depositing for 1.8 hours.

[0026] Example 2 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, the system being equipped with at least a titanium target, a graphite target and a 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.

[0027] The pretreatment mentioned in step A1 refers to polishing the surface of the substrate with diamond polishing paste until the surface roughness Ra is 0.05μm, and then ultrasonically cleaning it in acetone and anhydrous ethanol for 12 minutes respectively.

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

[0029] The vacuum level in the vacuum chamber described in step A2 is 5 × 10⁻⁶. -3 Pa.

[0030] 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 Pa, turning on the workpiece holder bias power supply, applying a pulsed DC bias voltage of -790V, and simultaneously starting the linear ion source, setting the anode voltage to 190V, the anode current to 2.5A, and the processing time to 18 minutes.

[0031] Step A3 refers to adjusting the bias voltage to -95V.

[0032] The target cleaning mentioned in step A3 refers to pre-sputtering the titanium target for 1.5 minutes in an argon atmosphere using a DC magnetron sputtering mode with a current set to 4.5A.

[0033] 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 9 sccm / min for 14 min. While continuing to introduce nitrogen gas, the graphite target power supply is turned on, and argon gas is introduced at a rate of 14 sccm / min. At the same time, the titanium target current is linearly reduced from 4.5A to 0A and the graphite target current is linearly increased from 1A to 7.5A within 18 min.

[0034] 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 7.5A, stabilizing the argon flow rate at 49 sccm, setting the workpiece bias voltage to -75V, and simultaneously starting the linear ion source, setting the anode voltage to 245V, the anode current to 3.5A, and depositing for 1.9 hours.

[0035] Example 3 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, the system being equipped with at least a titanium target, a graphite target and a 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.

[0036] The pretreatment mentioned in step A1 refers to polishing the surface of the substrate with diamond polishing paste until the surface roughness Ra is 0.05μm, and then ultrasonically cleaning it in acetone and anhydrous ethanol for 15min respectively.

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

[0038] The vacuum level in the vacuum chamber described in step A2 is 5 × 10⁻⁶. -3 Pa.

[0039] Step A2, ion cleaning and activation, refers to introducing high-purity argon gas into the vacuum chamber, stabilizing the working pressure at 0.3 Pa, turning on the workpiece holder bias power supply, applying a pulsed DC bias voltage of -800V, simultaneously starting the linear ion source, setting the anode voltage to 200V, the anode current to 3A, and the processing time to 20 minutes.

[0040] Step A3 refers to adjusting the bias voltage to -100V.

[0041] The target cleaning mentioned in step A3 refers to pre-sputtering a titanium target for 2 minutes in an argon atmosphere using a DC magnetron sputtering mode with a current set to 5A.

[0042] The deposition gradient layer mentioned in step A3 refers to the process of introducing nitrogen gas at a rate of 10 sccm / min for 15 min while maintaining titanium target sputtering, and then turning on the graphite target power supply while continuing to introduce nitrogen gas and introducing argon gas at a rate of 15 sccm / min. At the same time, the titanium target current is linearly reduced from 5A to 0A and the graphite target current is linearly increased from 1A to 8A within 20 min.

[0043] 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 8A, stabilizing the argon flow rate at 50 sccm, setting the workpiece bias voltage to -80V, and simultaneously starting the linear ion source, setting the anode voltage to 250V, the anode current to 4A, and depositing for 2 hours.

[0044] Example 4 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, the system being equipped with at least a titanium target, a graphite target and a 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.

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

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

[0047] The vacuum level in the vacuum chamber described in step A2 is 5 × 10⁻⁶. -3 Pa.

[0048] 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 0.35 Pa, turning on the workpiece holder bias power supply, applying a pulsed DC bias voltage of -810V, and simultaneously starting the linear ion source, setting the anode voltage to 210V, the anode current to 3.5A, and the processing time to 22 minutes.

[0049] Step A3 refers to adjusting the bias voltage to -105V.

[0050] The target cleaning mentioned in step A3 refers to pre-sputtering the titanium target for 2.5 minutes in an argon atmosphere using a DC magnetron sputtering mode with a current set to 5.5A.

[0051] The deposition gradient layer mentioned in step A3 refers to the process of introducing nitrogen gas at a rate of 11 sccm / min for 17 min while maintaining titanium target sputtering. While continuing to introduce nitrogen gas, the graphite target power supply is turned on and argon gas is introduced at a rate of 16 sccm / min. At the same time, the titanium target current is linearly reduced from 5.5A to 0A and the graphite target current is linearly increased from 1A to 8.5A within 22 min.

[0052] 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 8.5A, stabilizing the argon flow rate at 51 sccm, setting the workpiece bias voltage to -85V, and simultaneously starting the linear ion source, setting the anode voltage to 255V, the anode current to 4.5A, and depositing for 2.1 hours.

[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, the system being equipped with at least a titanium target, a graphite target and a 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.

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

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

[0056] The vacuum level in the vacuum chamber described in step A2 is 5 × 10⁻⁶. -3 Pa.

[0057] 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 0.35 Pa, turning on the workpiece holder bias power supply, applying a pulsed DC bias voltage of -820V, and simultaneously starting the linear ion source, setting the anode voltage to 220V, the anode current to 3.5A, and the processing time to 25 minutes.

[0058] Step A3 refers to adjusting the bias voltage to -105V.

[0059] The target cleaning mentioned in step A3 refers to pre-sputtering the titanium target for 2.5 minutes in an argon atmosphere using a DC magnetron sputtering mode with a current set to 5.5A.

[0060] The deposition gradient layer mentioned in step A3 refers to the process of introducing nitrogen gas at a rate of 12 sccm / min for 18 min while maintaining titanium target sputtering, and then turning on the graphite target power supply while continuing to introduce nitrogen gas and introducing argon gas at a rate of 17 sccm / min. At the same time, the titanium target current is linearly reduced from 5.5A to 0A and the graphite target current is linearly increased from 1A to 8.5A within 25 min.

[0061] 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 8.5A, stabilizing the argon gas flow rate at 52 sccm, setting the workpiece bias voltage to -85V, and simultaneously starting the linear ion source, setting the anode voltage to 255V, the anode current to 4.5A, and depositing for 2.2 hours.

[0062] The diamond-like carbon coating was applied to a 304 bar (Φ10cm) according to the diamond-like carbon coating preparation method in Example 3. The coating thickness was 0.5mm. The final sample was used as the test sample, and the potential cytotoxicity of the test sample was tested. The negative control was high-density polyethylene, sourced from Hatano Research Institute, Food and Drug Safety Center, batch number C-221; Positive controls were ZDBC and ZDEC. ZDBC (0.25% ZDBC polyurethane sheets) was sourced from Hatano Research Institute, Food and Drug Safety Center, batch number B-223K, and ZDEC (0.1% ZDEC polyurethane sheets) was sourced from Hatano Research Institute, Food and Drug Safety Center, batch number A-201K. The composition of MEM medium is: 88% MEM, 10% fetal bovine serum, 1% antibiotics (100 U / mL penicillin, 100 μg / mL streptomycin), and 1% sodium pyruvate; The extraction solution was 10% fetal bovine serum in MEM medium. Among them, MEM is branded by Gibco (batch number 6124013); FBS is branded by WISENT (batch number 086150069); Penicillin and streptomycin are branded by Gibco (batch number 2585644); and MTT (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide) is branded by SICMA-ALDRICH (batch number J2106160). The ATCC number of L-929 mouse fibroblasts is CC-1, and the Lot Number is 7008726.

[0063] According to standard GB / T 16886.5-2017, the sample, negative control and positive control were placed in MEM medium containing 10% fetal bovine serum and extracted at 37°C for 24 hours. Then the sample extract was diluted to concentrations of 100%, 50%, 25% and 12.5%, respectively. L-929 mouse fibroblasts were cultured in MEM medium containing 10% fetal bovine serum and antibiotics (penicillin 100 U / mL, streptomycin ug / mL) and placed in a 37°C, 5% CO2 incubator to obtain L-929 fibroblast monolayer cells. The original culture medium was aspirated, and different concentrations of extract and dilution were added and 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 changes of the extract during the extraction process are 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 refining the vigorous cells cultured for 48-72 hours, prepare a solution with a density of 1.0 × 10⁴ cells per well and seed it into a 96-well plate. Once the cells have grown into a monolayer, remove the original culture medium and add 100 μL of each of the following: 100%, 50%, 25%, 12.5% ​​extract, blank control extract, positive control (100%, 50%, 25%, 12.5%), and negative control (100%). Each group has 3 replicates. The blank control extract is added to the 2nd and 11th vertical rows of the 96-well plate. After adding the samples, incubate the 96-well plate at 37°C with 5% CO₂ for 24 hours.

[0066] After 24 hours of culture, the 96-well plates were removed for cell morphology observation, but cytotoxicity was not assessed. The original culture medium was then aspirated, and 50 μL of MTT (1 mg / mL) was added to each well. The plates were cultured for another 2 hours. Afterward, the supernatant was aspirated, and 100 μL of 99.5% pure isopropanol was added to dissolve the crystals. The absorbance was measured using a microplate reader with 570 nm as the primary absorption wavelength and 650 nm as the reference wavelength. Cell status was examined using a microscope, and the results of the experimental group were qualitatively evaluated. Changes in cell morphology caused by the cytotoxic effects of the sample extract were recorded. The evaluation criteria are shown in Table 3.

[0067] Microscopic observation showed that no more than 50% of the cells in the undiluted (100%) sample were shrunken, without intracytoplasmic granules, and without extensive cell lysis; no more than 50% of the cells showed growth inhibition, and the undiluted (100%) sample group showed no tendency for cytotoxicity (grade 2).

[0068] The MTT assay was used to quantitatively evaluate cytotoxicity. The MTT assay quantitatively measured cell viability and cell proliferation after cells were exposed to extracts or solutions. Metabolically active cells reduced yellow tetrazolium salt MTT (3-(4,5-dimethylthiazol-2)-2,5-diphenyltetrazolium bromide) to water-insoluble blue-purple crystal formazan through the action of succinate dehydrogenase in the mitochondria of living cells, which was then deposited in the cells. The change from yellow to purple could be quantitatively analyzed by spectrophotometric measurement. Among them, an absorbance value lower than that of blank control cells indicates a decrease in cell activity, while an increase in absorbance value indicates an increase in cell activity; the reduction in the number of live cells in the sample also caused a decrease in cell metabolic activity, which was directly related to the amount of blue-purple formazan detected at a wavelength of 570 nm. Cell viability percentage is the ratio of the measured value of the sample cells to that of the control cells, calculated using the following formula: Cell viability percentage = (100 × OD570) e ) / OD570 rc OD570 e This is the average absorbance of the sample or control after blank well correction, OD570. rc It is the average absorbance of the blank control after blank well correction; The effectiveness of the test results should meet the following requirements: cell observation under an inverted microscope to rule out cell seeding errors; review of the test process to rule out other human errors; the average absorbance value of the blank control should be ≥0.2, and the difference in the average absorbance value between the left blank control (vertical row 2) and the right blank control (vertical row 11) should not exceed 15%; if cytotoxicity is indicated, the 50% sample extract should have at least the same or higher cell viability than 100%, with lower cell viability percentages indicating higher potential cytotoxicity. If the cell viability percentage of the sample extract is less than 70%, it is determined to have cytotoxicity; the specific test results are recorded in Table 4 below.

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

[0070] Referring to the experimental method of Example 3, the diamond-like carbon coating preparation methods of Examples 1, 2, 4, and 5 were used to apply the diamond-like carbon coating to a 304 rod (Φ10cm) with a coating thickness of 0.5mm. The resulting sample was used as the test sample. The potential cytotoxicity of the sample was tested. The final results were as follows: under microscopic observation, no more than 50% of the cells in the undiluted (100%) sample were rounded, without intracytoplasmic particles, and without large-scale cell lysis; no more than 50% of the cells showed cell growth inhibition; the undiluted (100%) sample group showed no tendency for cytotoxicity (grade 2); in the quantitative evaluation, the cell activity of the 100% concentration extract of the sample was greater than 70%, and the sample extract had no potential cytotoxicity to L-929 mouse fibroblasts.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method of producing a diamond-like coating, characterized by: 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 the deposition is completed, cool the furnace in a vacuum environment to obtain the final product. In step A3, the deposition gradient layer refers to the process of introducing nitrogen gas at a rate of 8-12 sccm / min for 12-18 min while maintaining titanium target sputtering. Simultaneously, 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. 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.

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 degree in the vacuum chamber described in step A2 is ≦ 5 x 10 -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.

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