A multifunctional MC / G composite coating, its preparation method and application

Abstract

This invention relates to a multifunctional M-C / G composite coating, its preparation method, and its applications. A multi-point co-sputtering method is used to first prepare an M-C (M refers to metals such as Cr, Ti, and Nb) mixed coating on a metal substrate surface. Then, a thin, flat G (G refers to noble metals such as Au, Pd, and Pt) nano-coating is prepared on the M-C coating surface using a negative bias sputtering method, forming an M-C / G composite coating. The M-C / G composite coating prepared by this method exhibits multifunctional characteristics, including excellent corrosion resistance, excellent electrical conductivity, and hydrophobic properties, meeting the DOE technical specifications set by the U.S. Department of Energy. It can serve as a commercially viable surface modification solution for metal bipolar plates.

Description

Technical Field

[0001] This invention pertains to composite coatings and their preparation methods, specifically a multifunctional MC / G composite coating, its preparation method, and its applications. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs), as a novel power generation device, possess advantages such as high energy conversion efficiency, environmental friendliness, low noise, large operating current, simple assembly, and wide application range, and have broad application prospects. Bipolar plates (BBPs) are one of the most important components in PEMFCs, playing a role in supporting the cell, distributing oxidant and reductant, collecting and conducting electrons, and discharging product water. Currently, commonly used bipolar plates are generally made of metal, with common materials including Ti alloys, aluminum alloys, 316L, and 304 stainless steel. Metal materials themselves have excellent electrical and thermal conductivity, good gas barrier properties, and excellent machinability. However, metal bipolar plates still have many shortcomings that need improvement. The most significant problem is that metal materials are prone to electrochemical corrosion in the acidic operating environment of PEMFCs, resulting in a reduced service life. Secondly, during the corrosion process, metal materials undergo passivation, forming an oxide film on the surface. Increased corrosion and passivation will increase the contact resistance between the plate and the diffusion layer, affecting the efficiency of PEMFCs.

[0003] To address the poor corrosion resistance and hydrophobicity of metal bipolar plates, current solutions primarily involve surface modification of the metal material, with surface coating being the most effective method. Surface coatings for metal bipolar plates mainly include noble metal coatings (Au, Pt, etc.), polymer coatings (polyaniline, polypyrrole, etc.), amorphous carbon coatings, and metal compound coatings (carbides or nitrides of elements such as Cr and Ti). Noble metal coatings offer both good corrosion resistance and conductivity; however, these coatings require a certain thickness to fully meet the technical specifications set by the U.S. Department of Energy (DOE), resulting in excessively high costs and making them unsuitable for commercial applications. Compared to expensive noble metals, metal compound coatings are relatively inexpensive and readily available, but the reported performance of metal compound coatings still falls short of the DOE technical specifications. Furthermore, currently reported metal compound coatings exhibit low water contact angles, demonstrating poor hydrophobic properties.

[0004] To improve the corrosion resistance and hydrophobic properties of metal bipolar plates while maintaining good electrical conductivity, this invention innovatively proposes a multi-point co-sputtering method to first prepare a mixed MC (Cr, Ti, Nb, etc.) coating on the surface of a 316L stainless steel substrate. Then, an ultrathin, flat G (Au, Pd, Pt, etc.) nano-coating is prepared on the MC coating surface using negative bias sputtering, forming an MC / G composite coating. The MC / G composite coating prepared by this method possesses multifunctional characteristics, exhibiting not only excellent corrosion resistance but also superior electrical conductivity and hydrophobic properties, meeting the DOE technical specifications set by the U.S. Department of Energy. This method can serve as a commercially viable surface modification solution for metal bipolar plates. Summary of the Invention

[0005] Technical problems to be solved

[0006] To avoid the shortcomings of existing technologies, this invention proposes a multifunctional MC / G composite coating, its preparation method, and its application. The technical problem it solves is to provide a surface coating preparation process that addresses issues such as poor corrosion resistance, easy passivation after long-term operation, high contact resistance, and poor hydrophobicity of metal bipolar plates.

[0007] The equipment required for this process is easy to operate, the raw materials are readily available, the cost is low, and the process has good repeatability. This MC / G composite coating has a smooth surface, very low contact resistance, low corrosion current density in acidic media, and exhibits significant hydrophobic properties. This provides a reference surface coating modification scheme for the commercial application of stainless steel bipolar plates.

[0008] Technical solution

[0009] A method for preparing a multifunctional MC / G composite coating, characterized by the following steps:

[0010] The target material is installed on the target position connected to the radio frequency power source, and the metal substrate is fixed on the sample holder in the vacuum chamber. The MC hybrid coating (M refers to metals such as Cr, Ti, and Nb) is prepared on the surface of the metal substrate by multi-point co-sputtering.

[0011] Then, a G noble metal nanocoating was prepared on the surface of the MC hybrid coating by negative bias sputtering to obtain the MC / G composite coating;

[0012] When the multi-point co-sputtering method prepares the MC hybrid coating on the surface of a metal substrate, the target material is a series of high-purity metal M sheets uniformly placed within the sputtering ring of a graphite target, forming an MC composite target composed of a graphite target and metal sheets.

[0013] When preparing an ultrathin G nanocoating on the surface of an MC hybrid coating using the negative bias sputtering method, a negative bias is applied, the target material is a high-purity G target, and the deposition time does not exceed 7 minutes.

[0014] The multi-point co-sputtering method for preparing an MC hybrid coating on a metal substrate surface is as follows:

[0015] Vacuuming and cleaning the pipes: Vacuuming is performed to achieve a vacuum level of less than 5 × 10⁻⁶. -4 Pa, turn on the radio frequency power source to preheat for 15-30 minutes; at the same time, control the Ar gas flow rate at 100-150 SCCM and clean the gas pipeline;

[0016] Ignition and pre-sputtering: Turn on the power source to ignite, and after the glow stabilizes, adjust the Ar gas flow rate to stabilize the working pressure at 4.0-6.0 Pa, and the sputtering power at 300-500 W; at this time, keep the shielding disk and baffle closed, and perform pre-sputtering for 15-30 minutes to remove the contaminants adsorbed on the target surface.

[0017] Depositing MC hybrid coating: Open the shielding disk and baffle, the Ar gas flow rate is 75-125 SCCM, the working pressure is 3.0-5.0 Pa, the substrate temperature is room temperature to 300℃, the RF power is 200-400 W, and the deposition time is 30-50 min, so that the MC composite target is sputtered and an MC hybrid coating is obtained on the surface of the metal substrate.

[0018] The vacuuming is performed using a two-stage pumping system consisting of a mechanical pump and a molecular pump.

[0019] The ultrathin G nano-coating was prepared on the surface of the MC hybrid coating using a negative bias sputtering method.

[0020] Vacuuming and cleaning the pipes: Vacuuming ensures the vacuum level in the vacuum chamber is less than 5 × 10⁻⁶. -4 Pa; At the same time, turn on the DC power source to preheat, control the Ar gas flow rate at 100-150 SCCM, and clean the gas pipeline;

[0021] Ignition and pre-sputtering. Turn on the power source to ignite, and after the glow stabilizes, adjust the Ar gas flow rate to stabilize the working pressure at 4.0–6.0 Pa and the DC power at 300–400 W. At this time, keep the shielding disk and baffle closed and perform pre-sputtering for 6–10 minutes to remove contaminants adsorbed on the target surface;

[0022] Deposition of G nano-coating: Open the shielding disk and baffle, Ar gas flow rate is 50-100 SCCM, working pressure is 2.0-4.0 Pa, negative bias voltage is -200-300 V, DC power is 200-300 W, substrate temperature is room temperature, and deposition time is 3-7 min, so that the G target is sputtered and an ultrathin G nano-coating is obtained on the MC coating surface.

[0023] The G target includes precious metals such as Au, Pd, or Pt.

[0024] The vacuuming is performed using a two-stage pumping system consisting of a mechanical pump and a molecular pump.

[0025] Before multi-point co-sputtering, the surface of the metal substrate is pretreated, including substrate polishing and substrate cleaning. The substrate cleaning involves ultrasonically cleaning the polished stainless steel sheet with acetone, anhydrous ethanol, and deionized water for 15-30 minutes, and finally drying the substrate. The substrate polishing involves sequentially polishing the upper and lower surfaces of the stainless steel sheet with 400, 600, 800, 1000, 1500, and 2000 grit sandpaper to remove the oxide layer on the stainless steel surface, increase the roughness of the substrate surface, and make the coating adhesion stronger.

[0026] The multiple metal M-plates are 2 to 10 pieces of 99.999% high-purity metal M-plates.

[0027] The purity of the graphite target and the G target is 99.999%.

[0028] A multifunctional MC / G composite coating obtained by the preparation method described above is characterized in that: the coating is a two-layer composite coating comprising a bottom MC mixed coating and a top G nano coating, and the performance of the MC / G composite coating meets the US DOE standard.

[0029] The MC hybrid coating is a stoichiometric coating composed of sp... 2 elemental C and sp bonds 3 It is composed of various substances, including elemental C, elemental M, carbonized M, and oxide M.

[0030] The G nano-coating is an ultrathin noble metal nano-coating with a dense, smooth surface and a thickness not exceeding 20 nm.

[0031] An application of the aforementioned multifunctional MC / G composite coating is characterized by a modification scheme for enhancing the corrosion resistance, reducing contact resistance, and improving the hydrophobic properties of metal bipolar plates.

[0032] Beneficial effects

[0033] This invention proposes a multifunctional MC / G composite coating, its preparation method, and its application. A multi-point co-sputtering method is used to first prepare a mixed MC (MC, representing metals such as Cr, Ti, and Nb) coating on a metal substrate surface. Then, a thin, flat G (G, representing noble metals such as Au, Pd, and Pt) nano-coating is prepared on the MC coating surface using negative bias sputtering, forming an MC / G composite coating. The MC / G composite coating prepared by this method exhibits multifunctional characteristics, including excellent corrosion resistance, superior electrical conductivity, and hydrophobic properties, meeting the DOE technical specifications set by the U.S. Department of Energy. It can serve as a commercially viable surface modification solution for metal bipolar plates.

[0034] The main innovation of this invention is:

[0035] (1) Multiple high-purity metal M sheets are uniformly placed within the sputtering ring of the graphite target to form an MC composite target composed of the graphite target and the metal M (as shown in the attached figure). Figure 1 As shown in the figure, a multi-point co-sputtering preparation mode can be effectively realized.

[0036] (2) The equipment used in this method is simple, the process parameters are easy to control, and the process repeatability is good;

[0037] (3) This method can be used to obtain MC hybrid coatings with adjustable stoichiometry, the hybrid coating being composed of sp 2 elemental C and sp bonds 3 The bond is composed of various substances including elemental C, elemental M, carbide M, and oxide M (see appendix). Figure 2 XPS spectra of the MC hybrid coating;

[0038] (4) The noble metal G coating prepared by this method has a dense, smooth surface and an ultrathin nanometer-scale thickness (as shown in the attached figure). Figure 3 Appendix Figure 4 (as shown);

[0039] (5) The composite coating prepared by this method has a fast film formation rate, a dense film and few micropore defects, which solves the problem of many micropore defects and easy formation of corrosion channels in the columnar crystal structure of traditional compound coatings.

[0040] (6) The obtained MC / G composite coating makes up for the problem of poor conductivity of the current compound coating, while avoiding the problem of high cost of thick precious metal coating.

[0041] (7) The performance of 316L stainless steel is significantly improved after the MC / G composite coating is applied to the surface, and the corrosion current density is low, approximately 0.03 μA·cm. -2 The contact resistance is relatively low, approximately 2.33 mΩ·cm. 2The composite coating exhibits hydrophobic properties with a water contact angle of approximately 100.21°. This coating performance meets US DOE standards and solves the current problems faced by metal bipolar plates, such as poor corrosion resistance, high contact resistance, and poor hydrophobicity. Attached Figure Description

[0042] Figure 1 (a) Schematic diagram of MC composite target placement in magnetron sputtering (top view); (b) Schematic diagram of MC composite target and substrate placement in magnetron sputtering (side view).

[0043] Figure 2 XPS fine spectra of Cr 2p(a), C1s(b), and O1s(c) in Cr-C mixed coatings

[0044] Figure 3 SEM surface morphology of Cr-C / Au composite coating

[0045] Figure 4 SEM cross-sectional morphology of Cr-C / Au composite coating Detailed Implementation

[0046] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0047] The preparation method of the MC / G composite coating of the present invention includes the following steps in sequence:

[0048] (1) Grinding the substrate. Use 400, 600, 800, 1000, 1500 and 2000 grit sandpaper to grind the upper and lower surfaces of the stainless steel sheet in sequence. The purpose is to remove the oxide layer on the stainless steel surface and increase the roughness of the substrate surface to make the coating adhesion stronger.

[0049] (2) Cleaning the substrate. The polished stainless steel sheet was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 15-30 minutes respectively. Finally, the substrate was dried and fixed on the sample holder in the vacuum chamber.

[0050] (3) Install the target material. Install the high-purity graphite target (99.999%, δ60mm×5mm) on the target position where the radio frequency power source is turned on, and evenly place 2 to 10 high-purity metal M sheets (99.999%, 8mm×8mm) in the sputtering ring of the graphite target to form an MC composite target composed of graphite target and metal M.

[0051] (4) Evacuate the vacuum chamber and clean the pipes. A two-stage pumping system consisting of a mechanical pump and a molecular pump is used to achieve a vacuum level of less than 5 × 10⁻⁶. -4 Pa; turn on the RF power source and preheat for 15-30 minutes; at the same time, control the Ar gas flow rate at 100-150 SCCM and clean the gas pipeline.

[0052] (5) Ignition and pre-sputtering. Turn on the power source to ignite. After the glow stabilizes, adjust the Ar gas flow rate to stabilize the working pressure at 4.0-6.0 Pa and the sputtering power at 300-500 W. At this time, keep the shielding disk and baffle closed and perform pre-sputtering for 15-30 minutes to remove contaminants adsorbed on the target surface.

[0053] (6) Deposition of MC hybrid coating. Open the shielding disk and baffle, and use the MC composite target to sputter the MC hybrid coating on the stainless steel surface. The preparation process parameters are: the number of metal M is 2 to 10 pieces, the Ar gas flow rate is 75 to 125 SCCM, the working pressure is 3.0 to 5.0 Pa, the substrate temperature is room temperature to 300℃, the RF power is 200 to 400 W, and the deposition time is 30 to 50 min.

[0054] (7) Replace the target material. Replace the MC composite target with a high-purity precious metal G target (99.999%, φ60mm×5mm).

[0055] (8) Evacuate the vacuum chamber and clean the pipes. A two-stage pumping system consisting of a mechanical pump and a molecular pump is used to achieve a vacuum level of less than 5 × 10⁻⁶. -4 Pa; simultaneously turn on the DC power source to preheat, control the Ar gas flow rate at 100-150 SCCM, and clean the gas pipeline.

[0056] (9) Ignition and pre-sputtering. Turn on the power source to ignite. After the glow stabilizes, adjust the Ar gas flow rate to stabilize the working pressure at 4.0-6.0 Pa and the DC power at 300-400 W. At this time, keep the shielding plate and baffle closed and perform pre-sputtering for 6-10 minutes to remove contaminants adsorbed on the target surface.

[0057] (10) Deposition of G nano-coating. Open the shielding disk and baffle, and use a noble metal G target to sputter the G nano-coating on the MC coating surface. The preparation process parameters are: Ar gas flow rate of 50-100 SCCM, working pressure of 2.0-4.0 Pa, negative bias voltage of -200-300 V, DC power of 200-300 W, substrate temperature of room temperature, and deposition time of 3-7 min.

[0058] (11) After coating is completed, shut down the equipment. Turn off the substrate rotation, power source, substrate heating, and Ar gas cylinder. Increase the Ar gas flow rate to extract the residual gas in the pipeline. After the flow meter shows a flow rate of 0, sequentially close the shut-off valve, gate valve, and flow meter, and decelerate the molecular pump. After the molecular pump speed reaches 0, turn off the mechanical pump.

[0059] Remove the sample. Open the inflation valve. After inflation is complete, open the chamber, remove the prepared coating sample, and place it in a vacuum drying oven for later use.

[0060] Example 1:

[0061] (1) Grinding the substrate. Use 400, 600, 800, 1000, 1500 and 2000 grit sandpaper to grind the upper and lower surfaces of the stainless steel sheet in sequence. The purpose is to remove the oxide layer on the stainless steel surface and increase the roughness of the substrate surface to make the coating adhesion stronger.

[0062] (2) Cleaning the substrate. The polished stainless steel sheet was ultrasonically cleaned for 15 minutes each with acetone, anhydrous ethanol and deionized water. Finally, the substrate was dried and fixed on the sample holder in the vacuum chamber.

[0063] (3) Install the target material. Install the high-purity graphite target (99.999%, δ60mm×5mm) on the target position where the radio frequency power source is turned on, and evenly place two high-purity Cr sheets (99.999%, 8mm×8mm) in the sputtering ring of the graphite target to form a Cr-C composite target composed of the graphite target and the Cr sheets.

[0064] (4) Evacuate the vacuum chamber and clean the pipes. A two-stage pumping system consisting of a mechanical pump and a molecular pump is used to achieve a vacuum level of less than 5 × 10⁻⁶. -4 Pa; turn on the RF power source and preheat for 15 minutes; at the same time, control the Ar gas flow rate at 100 SCCM and clean the gas pipeline.

[0065] (5) Ignition and pre-sputtering. Turn on the power source to ignite. After the glow stabilizes, adjust the Ar gas flow rate to stabilize the working pressure at 4.0 Pa and the sputtering power at 500 W. At this time, keep the shielding disk and baffle closed and perform pre-sputtering for 15 minutes to remove contaminants adsorbed on the target surface.

[0066] (6) Deposition of Cr-C hybrid coating. Open the shielding disk and baffle, and use a Cr-C composite target to sputter a Cr-C hybrid coating on the stainless steel surface. The preparation process parameters are: 2 Cr sheets, Ar gas flow rate of 75 SCCM, working pressure of 3.0 Pa, substrate temperature of room temperature, RF power of 400 W, and deposition time of 50 min.

[0067] (7) Replace the target material. Replace the Cr-C composite target with a high-purity precious metal Au target (99.999%, δ60mm×5mm).

[0068] (8) Evacuate the vacuum chamber and clean the pipes. A two-stage pumping system consisting of a mechanical pump and a molecular pump is used to achieve a vacuum level of less than 5 × 10⁻⁶. -4 Pa; simultaneously turn on the DC power source to preheat, control the Ar gas flow rate at 100 SCCM, and clean the gas pipeline.

[0069] (9) Ignition and pre-sputtering. Turn on the power source to ignite. After the glow stabilizes, adjust the Ar gas flow rate to stabilize the working pressure at 4.0 Pa and the DC power at 400 W. At this time, keep the shielding plate and baffle closed and perform pre-sputtering for 6 minutes to remove contaminants adsorbed on the target surface.

[0070] (10) Deposition of Au nano-coating. Open the shielding disk and baffle, and use the noble metal Au target to sputter Au nano-coating on the Cr-C coating surface. The preparation process parameters are: Ar gas flow rate of 50 SCCM, working pressure of 2.0 Pa, negative bias voltage of -300 V, DC power of 200 W, substrate temperature of room temperature, and deposition time of 7 min.

[0071] (11) After coating is completed, shut down the equipment. Turn off the substrate rotation, power source, substrate heating, and Ar gas cylinder. Increase the Ar gas flow rate to extract the residual gas in the pipeline. After the flow meter shows a flow rate of 0, sequentially close the shut-off valve, gate valve, and flow meter, and decelerate the molecular pump. After the molecular pump speed reaches 0, turn off the mechanical pump.

[0072] (12) Take out the sample. Open the inflation valve. After inflation is complete, open the chamber, take out the prepared coating sample, and place it in a vacuum drying oven for later use.

[0073] Example 2:

[0074] (1) Grinding the substrate. Use 400, 600, 800, 1000, 1500 and 2000 grit sandpaper to grind the upper and lower surfaces of the stainless steel sheet in sequence. The purpose is to remove the oxide layer on the stainless steel surface and increase the roughness of the substrate surface to make the coating adhesion stronger.

[0075] (2) Cleaning the substrate. The polished stainless steel sheet was ultrasonically cleaned for 30 minutes each with acetone, anhydrous ethanol and deionized water. Finally, the substrate was dried and fixed on the sample holder in the vacuum chamber.

[0076] (3) Install the target material. Install the high-purity graphite target (99.999%, δ60mm×5mm) on the target position where the radio frequency power source is turned on, and evenly place 10 high-purity Ti sheets (99.999%, 8mm×8mm) in the sputtering ring of the graphite target to form a Ti-C composite target composed of graphite target and Ti sheets.

[0077] (4) Evacuate the vacuum chamber and clean the pipes. A two-stage pumping system consisting of a mechanical pump and a molecular pump is used to achieve a vacuum level of less than 5 × 10⁻⁶. -4 Pa; turn on the RF power source and preheat for 30 minutes; at the same time, control the Ar gas flow rate at 150 SCCM and clean the gas pipeline.

[0078] (5) Ignition and pre-sputtering. Turn on the power source to ignite. After the glow stabilizes, adjust the Ar gas flow rate to stabilize the working pressure at 6.0 Pa and the sputtering power at 300 W. At this time, keep the shielding disk and baffle closed and perform pre-sputtering for 30 minutes to remove contaminants adsorbed on the target surface.

[0079] (6) Deposition of Ti-C hybrid coating. Open the shielding disk and baffle, and use Ti-C composite target to sputter Ti-C hybrid coating on stainless steel surface. The preparation process parameters are: 10 Ti wafers, Ar gas flow rate of 125 SCCM, working pressure of 5.0 Pa, substrate temperature of 100 ℃, RF power of 200 W, and deposition time of 30 min.

[0080] (7) Replace the target material. Replace the Ti-C composite target with a high-purity Pd target (99.999%, φ60mm×5mm).

[0081] (8) Evacuate the vacuum chamber and clean the pipes. A two-stage pumping system consisting of a mechanical pump and a molecular pump is used to achieve a vacuum level of less than 5 × 10⁻⁶. -4 Pa; simultaneously turn on the DC power source to preheat, control the Ar gas flow rate at 150 SCCM, and clean the gas pipeline.

[0082] (9) Ignition and pre-sputtering. Turn on the power source to ignite. After the glow stabilizes, adjust the Ar gas flow rate to stabilize the working pressure at 6.0 Pa and the DC power at 300 W. At this time, keep the shielding plate and baffle closed and perform pre-sputtering for 10 minutes to remove contaminants adsorbed on the target surface.

[0083] (10) Deposition of Pd nano-coating. Open the shielding disk and baffle, and use a noble metal Pd target to sputter a Pd nano-coating on the Ti-C coating surface. The preparation process parameters are: Ar gas flow rate of 100 SCCM, working pressure of 4.0 Pa, negative bias voltage of -200 V, DC power of 300 W, substrate temperature of room temperature, and deposition time of 3 min.

[0084] (11) After coating is completed, shut down the equipment. Turn off the substrate rotation, power source, substrate heating, and Ar gas cylinder. Increase the Ar gas flow rate to extract the residual gas in the pipeline. After the flow meter shows a flow rate of 0, sequentially close the shut-off valve, gate valve, and flow meter, and decelerate the molecular pump. After the molecular pump speed reaches 0, turn off the mechanical pump.

[0085] (12) Take out the sample. Open the inflation valve. After inflation is complete, open the chamber, take out the prepared coating sample, and place it in a vacuum drying oven for later use.

[0086] Example 3:

[0087] (1) Grinding the substrate. Use 400, 600, 800, 1000, 1500 and 2000 grit sandpaper to grind the upper and lower surfaces of the stainless steel sheet in sequence. The purpose is to remove the oxide layer on the stainless steel surface and increase the roughness of the substrate surface to make the coating adhesion stronger.

[0088] (2) Cleaning the substrate. The polished stainless steel sheet was ultrasonically cleaned for 22 minutes each with acetone, anhydrous ethanol and deionized water. Finally, the substrate was dried and fixed on the sample holder in the vacuum chamber.

[0089] (3) Install the target material. Install the high-purity graphite target (99.999%, δ60mm×5mm) on the target position where the radio frequency power source is turned on, and evenly place 6 high-purity Nb sheets (99.999%, 8mm×8mm) in the sputtering ring of the graphite target to form an Nb-C composite target composed of the graphite target and Nb sheets.

[0090] (4) Evacuate the vacuum chamber and clean the pipes. A two-stage pumping system consisting of a mechanical pump and a molecular pump is used to achieve a vacuum level of less than 5 × 10⁻⁶. -4 Pa; turn on the RF power source and preheat for 22 minutes; at the same time, control the Ar gas flow rate at 125 SCCM and clean the gas pipeline.

[0091] (5) Ignition and pre-sputtering. Turn on the power source to ignite. After the glow stabilizes, adjust the Ar gas flow rate to stabilize the working pressure at 5.0 Pa and the sputtering power at 400 W. At this time, keep the shielding disk and baffle closed and perform pre-sputtering for 22 minutes to remove contaminants adsorbed on the target surface.

[0092] (6) Deposition of Nb-C hybrid coating. Open the shielding disk and baffle, and use an Nb-C composite target to sputter an Nb-C hybrid coating on the stainless steel surface. The preparation process parameters are: 6 Nb wafers, Ar gas flow rate of 100 SCCM, working pressure of 4.0 Pa, substrate temperature of 300 °C, RF power of 300 W, and deposition time of 40 min.

[0093] (7) Replace the target material. Replace the Nb-C composite target with a high-purity precious metal Pt target (99.999%, δ60mm×5mm).

[0094] (8) Evacuate the vacuum chamber and clean the pipes. A two-stage pumping system consisting of a mechanical pump and a molecular pump is used to achieve a vacuum level of less than 5 × 10⁻⁶. -4 Pa; simultaneously turn on the DC power source to preheat, control the Ar gas flow rate at 125 SCCM, and clean the gas pipeline.

[0095] (9) Ignition and pre-sputtering. Turn on the power source to ignite. After the glow stabilizes, adjust the Ar gas flow rate to stabilize the working pressure at 5.0 Pa and the DC power at 350 W. At this time, keep the shielding plate and baffle closed and perform pre-sputtering for 8 minutes to remove contaminants adsorbed on the target surface.

[0096] (10) Deposition of Pt nanocoating. Open the shielding disk and baffle, and use a noble metal Pt target to sputter a noble metal Pt nanocoating on the Nb-C coating surface. The preparation process parameters are: Ar gas flow rate of 75 SCCM, working pressure of 3.0 Pa, negative bias voltage of -250 V, DC power of 250 W, substrate temperature of room temperature, and deposition time of 5 min.

[0097] (11) After coating is completed, shut down the equipment. Turn off the substrate rotation, power source, substrate heating, and Ar gas cylinder. Increase the Ar gas flow rate to extract the residual gas in the pipeline. After the flow meter shows a flow rate of 0, sequentially close the shut-off valve, gate valve, and flow meter, and decelerate the molecular pump. After the molecular pump speed reaches 0, turn off the mechanical pump.

[0098] Remove the sample. Open the inflation valve. After inflation is complete, open the chamber, remove the prepared coating sample, and place it in a vacuum drying oven for later use.

Claims

1. A method for preparing multifunctional M-C / G composite coating, characterized in that: The steps are as follows: The target material is installed on the target position connected to the radio frequency power source, the metal substrate is fixed on the sample holder in the vacuum chamber, and the M-C mixed coating is prepared on the surface of the metal substrate by using a multi-point co-sputtering method, wherein M represents Cr, Ti or Nb metal; The radio frequency power for preparing the M-C mixed coating is 200-400 W; Then, the G noble metal coating nano-coating is prepared on the surface of the M-C mixed coating by using a negative bias sputtering method, so as to obtain an M-C / G composite coating; The negative bias for preparing the G noble metal coating nano-coating is -200 to -300 V, and the direct current power is 200-300 W; In the method for preparing the M-C mixed coating on the surface of the metal substrate, the target material is uniformly placed in the sputtering ring belt of the graphite target, and the M-C composite target composed of the graphite target and the metal sheet is formed; In the method for preparing the ultra-thin G nano-coating on the surface of the M-C mixed coating by using the negative bias sputtering method, a negative bias is applied, the target material is a high-purity G target, and the deposition time is not more than 7 minutes; the G target includes Au, Pd or Pt noble metal; The M-C mixed coating is a stoichiometric ratio adjustable mixed coating, which is composed of sp2 bonded elemental C, sp3 bonded elemental C, elemental M, M carbide and M oxide; the G nano-coating is an ultra-thin noble metal nano-coating with a surface that is dense, flat and has a thickness of not more than 20 nm; The M-C / G composite coating is used for enhancing corrosion resistance, reducing contact resistance and improving hydrophobic characteristics on the surface of a metal bipolar plate.

2. The method for preparing multifunctional M-C / G composite coating according to claim 1, characterized in that: The method for preparing the M-C mixed coating on the surface of the metal substrate by using the multi-point co-sputtering method is as follows: Purging the tube by vacuum: vacuum to less than 5 x 10 -4 Pa, open the radio frequency power source to preheat for 15-30 minutes; at the same time, control the Ar gas flow to be 100-150 SCCM to purge the gas pipeline; Starting and pre-sputtering: the power source is started, the Ar gas flow is adjusted to stabilize the working pressure at 4.0-6.0 Pa, and the sputtering power is 300-500 W; at this time, the shutter disc and the baffle are kept closed, and the pre-sputtering is performed for 15-30 minutes to remove the contaminants adsorbed on the surface of the target material; Depositing the M-C mixed coating: the shutter disc and the baffle are opened, the Ar gas flow is 75-125 SCCM, the working pressure is 3.0-5.0 Pa, the substrate temperature is room temperature-300 °C, and the deposition time is 30-50 minutes, so that the M-C composite target is sputtered to obtain the M-C mixed coating on the surface of the metal substrate; The vacuumizing is performed by using a two-stage gas extraction system composed of a mechanical pump and a molecular pump.

3. The method for preparing the multifunctional MC / G composite coating according to claim 1, characterized in that: The method for preparing the ultra-thin G nano-coating on the surface of the M-C mixed coating by using the negative bias sputtering method is as follows: Vacuum pumping, cleaning pipeline: vacuum pumping makes the vacuum degree of vacuum chamber less than 5 × 10 -4 Pa; at the same time, open the direct current power source to preheat, control the Ar gas flow at 100-150 SCCM, and clean the gas pipeline; Starting and pre-sputtering: the power source is started, the Ar gas flow is adjusted to stabilize the working pressure at 4.0-6.0 Pa, and the direct current power is 300-400 W; at this time, the shutter disc and the baffle are kept closed, and the pre-sputtering is performed for 6-10 minutes to remove the contaminants adsorbed on the surface of the target material; Depositing the G nano-coating: the shutter disc and the baffle are opened, the Ar gas flow is 50-100 SCCM, the working pressure is 2.0-4.0 Pa, the substrate temperature is room temperature, and the deposition time is 3-7 minutes, so that the G target is sputtered to obtain the ultra-thin G nano-coating on the surface of the M-C coating; The vacuumizing is performed by a two-stage air exhaust system composed of a mechanical pump and a molecular pump.

4. The method for preparing the multifunctional MC / G composite coating according to claim 1, characterized in that: Before multi-point co-sputtering is adopted, the surface of the metal substrate is pretreated, including grinding the substrate and cleaning the substrate; the cleaning of the substrate is that the ground stainless steel sheet is cleaned by ultrasonic cleaning with acetone, anhydrous ethanol and deionized water respectively for 15-30 minutes, and finally the substrate is dried by blowing; the grinding of the substrate is that the upper and lower surfaces of the stainless steel sheet are ground by using sandpaper with a mesh of 400, 600, 800, 1000, 1500 and 2000 in sequence, so as to remove the oxide layer on the surface of the stainless steel, increase the roughness of the surface of the substrate and make the adhesion of the coating stronger.

5. The method for preparing the multifunctional MC / G composite coating according to claim 1, characterized in that: The multiple pieces of metal M pieces are 2-10 pieces of 99.999% high-purity metal M pieces.

6. The method for preparing the multifunctional MC / G composite coating according to claim 1, characterized in that: The purity of the graphite target and the G target is 99.999%.

7. The multifunctional M-C / G composite coating prepared by the method according to any one of claims 1-6, characterized in that: The coating is a double-layer composite coating including a bottom layer M-C mixed coating and a top layer G nano coating, and the performance of the M-C / G composite coating meets the American DOE standard. The multiple pieces of metal M pieces are 2-10 pieces of 99.999% high-purity metal M pieces. The purity of the graphite target and the G target is 99.999%. The coating is a double-layer composite coating including a bottom layer M-C mixed coating and a top layer G nano coating, and the performance of the M-C / G composite coating meets the American DOE standard.

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