Process for the production of a self-healing coating, bipolar plate and fuel cell

Abstract

The application discloses a preparation process of a self-healing coating, a bipolar plate and a fuel cell, and comprises the following steps: providing a substrate and pretreating the substrate; and depositing a self-healing coating doped with a metal with a repairing function on the surface of the pretreated substrate, wherein the self-healing coating at least comprises a substrate contact layer and an anti-corrosion layer which are sequentially formed on the substrate. Compared with the prior art, the self-healing coating has the metal with the repairing function in the substrate contact layer, which can rapidly react with oxygen to form a dense oxide film during work, so that the coating has the self-healing ability and the anti-corrosion performance of the coating is improved.

Description

Technical Field

[0001] This invention relates to the field of fuel cells and their fabrication technology, and in particular to a process for preparing a self-healing coating, as well as bipolar plates and fuel cells. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) not only possess the high efficiency, pollution-free, noise-free, and continuous operation characteristics of general fuel cells, but also have advantages such as high power density, low operating temperature, fast start-up, and long service life. They have broad application prospects in electric vehicles, portable power sources, and other fields, and have attracted increasing attention from more and more countries and enterprises.

[0003] As a key component of proton exchange membrane fuel cells (PEMFCs), bipolar plates are currently the mainstream material. While graphite bipolar plates offer good corrosion resistance, electrical conductivity, and thermal conductivity, their high porosity, low mechanical strength, and poor processing performance, coupled with their weight accounting for 70%–80% of the fuel cell stack's weight and 40%–60% of its cost, make them a more promising material for PEMFC commercialization. Metal bipolar plates, on the other hand, offer superior strength, better processing performance, and gas impermeability, allowing them to block oxidants and reductants. They can also be manufactured in very thin layers (as thin as 0.1 mm–0.3 mm), significantly improving the specific energy and specific power of the fuel cell while substantially reducing bipolar plate costs. However, metal materials are prone to corrosion or passivation in the fuel cell's operating environment, leading to reduced battery performance. Currently, preparing corrosion-resistant, low-contact-resistance coatings on the surface of metal bipolar plates is the primary method to address this issue.

[0004] Existing protective coatings for metal bipolar plates mainly include precious metal coatings, cermet coatings, and conductive polymer coatings. While coatings made from precious metals and their compounds offer good protection, the high cost of precious metals increases the manufacturing cost of PEMFCs. Coatings made from conductive polymers suffer from chemical instability and insufficient adhesion to the substrate for practical applications. Coatings made from cermet materials offer advantages such as high conductivity and good chemical stability, meeting the requirement of both corrosion resistance and conductivity for metal bipolar plate surface coatings. However, the main process for preparing cermet coatings is physical vapor deposition (e.g., magnetron sputtering), which results in inherent defects that are difficult to avoid. These defects include porosity and cracks, allowing the electrolyte to directly contact the bipolar plate substrate, leading to substrate corrosion. Furthermore, the poor adhesion between the coating and the substrate makes the coating prone to failure under frequent start-stop conditions in PEMFCs, thus reducing fuel cell performance. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a preparation process for a self-healing coating, as well as a bipolar plate and a fuel cell, to solve the problems of easy corrosion of the substrate and poor adhesion between coatings in the prior art.

[0006] To achieve the above objectives, one technical solution of the present invention provides a preparation process for a self-healing coating, comprising the following steps:

[0007] A substrate is provided and the substrate is pretreated;

[0008] A self-healing coating doped with a repairing metal is deposited on the surface of a pretreated substrate, wherein the self-healing coating comprises at least a substrate contact layer and an anti-corrosion layer sequentially stacked on the substrate.

[0009] Furthermore, the step of depositing a self-healing coating doped with a metal having repair capabilities on the pretreated substrate surface includes the following sub-steps:

[0010] Using a metal with repair function as a target material, a metal with repair function is sputtered onto the surface of the substrate to form the substrate contact layer.

[0011] Furthermore, in the step of sputtering a metal with repair function onto the surface of the substrate using a metal with repair function as a target to form the substrate contact layer, a pulsed DC bias voltage is applied to the substrate and the substrate contact layer is formed using a DC magnetron sputtering process. The thickness of the substrate contact layer is 0.1 to 0.3 μm, and during sputtering, the pulsed DC bias voltage is -50 to 200 V, the metal target is a 2 to 5 inch planar target, the sputtering power of the metal target is 100 to 200 W, and the sputtering time of the metal target is 15 to 30 min.

[0012] Furthermore, the step of depositing a self-healing coating doped with a repairing metal on the pretreated substrate surface also includes the following steps:

[0013] A corrosion-resistant layer is co-sputtered with the metal having repair function using nitrogen or carbon elements outside the substrate contact layer, and bonded to the substrate contact layer.

[0014] Furthermore, in the step of co-sputtering an anti-corrosion layer bonded to the substrate contact layer with nitrogen or carbon elements and the metal with repair function outside the substrate contact layer, the specific method for forming the anti-corrosion layer using nitrogen elements is as follows:

[0015] The sputtering parameters of the metal target are maintained and nitrogen gas is introduced into the deposition chamber. The metal target and nitrogen gas are used to deposit a metal nitride bonded to the substrate contact layer outside the substrate contact layer using a reactive sputtering process to form the anti-corrosion layer. During the reactive sputtering process, the flow rate of the nitrogen gas is 40-80 sccm.

[0016] Furthermore, in the step of co-sputtering an anti-corrosion layer bonded to the substrate contact layer using nitrogen or carbon elements and the metal with repair function, the anti-corrosion layer formed using carbon elements includes an intermediate layer and a carbon layer sequentially stacked on the substrate contact layer; the specific method for forming the anti-corrosion layer using carbon elements is as follows:

[0017] A middle layer that bonds to the substrate contact layer is co-sputtered outside the substrate contact layer using element C and the metal with repair function;

[0018] A carbon layer bonded to the intermediate layer is sputtered outside the intermediate layer using element C.

[0019] Furthermore, in the step of co-sputtering an intermediate layer bonded to the substrate contact layer using element C and the metal with repair function outside the substrate contact layer, the specific method for forming the intermediate layer is as follows:

[0020] Turn on the carbon target and simultaneously adjust the sputtering power of the metal target and the carbon target. Using the metal target and the carbon target, a metal carbide bonded to the substrate contact layer is deposited outside the substrate contact layer using a magnetron co-sputtering process to form the intermediate layer. During the magnetron co-sputtering process, the sputtering power of the metal target and the sputtering power of the carbon target are linearly inversely proportional. The sputtering power of the carbon target is 100-200W, and the sputtering time of the carbon target is 15-30min.

[0021] Furthermore, in the step of sputtering a carbon layer bonded to the intermediate layer using element C, the specific method for forming the carbon layer is as follows:

[0022] A carbon layer bonded to the intermediate layer is deposited outside the intermediate layer by periodically changing the bias voltage. During the deposition process, the high bias voltage is 600V and the low bias voltage is 150V. The number of cycles for changing the high and low bias voltages is 10 to 20. The duration of the high and low bias voltages scales proportionally with the number of cycles. The deposition time of the carbon layer is less than or equal to 2 hours.

[0023] To solve the above-mentioned technical problems, another technical solution of the present invention provides a bipolar plate, including a substrate and a self-healing coating formed on the surface of the substrate by the self-healing coating preparation process described above, which is doped with a metal having repair function.

[0024] To solve the above-mentioned technical problems, another technical solution of the present invention provides a fuel cell, including a bipolar plate having a self-healing coating formed with a metal doped with repair function, wherein the self-healing coating formed on the bipolar plate is prepared by the self-healing coating preparation process described above, or the bipolar plate is a bipolar plate as described above.

[0025] This invention pre-prepares a substrate contact layer consisting of a metal with repair function deposited on a substrate. When the fuel cell operates in a high-temperature, corrosive environment, the metal with repair function in the substrate contact layer reacts with the oxygen introduced during fuel cell operation under a high potential, causing the metal with repair function to be oxidized. This forms a dense oxide film on the substrate contact layer, sealing the pores and cracks generated during the coating preparation process and preventing the electrolyte from penetrating into the corrosive substrate. As a result, the coating exhibits self-healing ability and improves corrosion resistance.

[0026] Meanwhile, this invention uses a metal with repair function as the inner layer in contact with the substrate, and the formed metal nitride or metal carbide as the outer anti-corrosion layer. During sputtering, the inner substrate contact layer can form chemical bonds with the substrate on both sides and the outer anti-corrosion layer, bonding the substrate and the anti-corrosion layer to form the basis of the coating's self-healing ability. The outer anti-corrosion layer possesses excellent electrical conductivity, thus enabling the coating to have both anti-corrosion and conductive properties, thereby improving the performance of the fuel cell. Furthermore, the bipolar plate prepared using this invention has a similar thermal diffusivity among its substrate, the metal with repair function, and the metal carbide or metal nitride, reducing stress between the membrane layers and improving the bonding force between them. This prevents membrane failure during operation, enhances the coating's durability, and further improves the performance of the fuel cell. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0028] Figure 1 This is a flowchart of the preparation process of the self-healing coating of the present invention.

[0029] Figure 2 for Figure 1 The flowchart for step S2.

[0030] Figure 3 The polarization test curves of the self-healing coating with self-repairing ability prepared by the present invention and the coating prepared by conventional process are shown.

[0031] Figure 4 The electrostatic potential test curve of the self-healing coating with self-repairing ability prepared in this invention at 0.6V is shown.

[0032] Figure 5 The electrostatic potential test curve of the self-healing coating with self-repairing ability prepared in this invention at -0.1V.

[0033] Figure 6 This is a flowchart of the preparation process of the self-healing coating in Embodiment 1 of the present invention.

[0034] Figure 7 This is a flowchart of the preparation process of the self-healing coating in Embodiment 2 of the present invention. Detailed Implementation

[0035] The following detailed description illustrates the specific implementation method:

[0036] like Figure 1 The diagram shows a flowchart of a self-healing coating preparation process according to an embodiment of the present invention. Specifically, the preparation process of the self-healing coating includes the following steps:

[0037] S1: Provide a substrate and preprocess the substrate.

[0038] A substrate is provided and pretreated to remove particles, oil, organic residues, and oxides adhering to the substrate, thereby improving the adhesion of subsequent coating growth and increasing the reliability of the bond between the coating and the substrate. In this embodiment, the substrate is a metal substrate to increase the strength and processing performance of the bipolar plate and to block oxidants and reducing agents during operation, thereby improving the performance of the bipolar plate.

[0039] Specifically, during the pretreatment of the substrate, firstly, the surface of the substrate is sanded and polished to a mirror finish or near-mirror finish using sandpaper to remove oxide layers, particles, etc., and to improve the smoothness and gloss of the substrate surface, thereby improving the surface properties of the substrate. In this embodiment, the sandpaper is preferably 800-1200 grit silicon carbide sandpaper, and mechanical grinding and polishing, electrolytic polishing, etc., can be used during the sanding and polishing process. Then, the sanded and polished substrate is placed in an ultrasonic cleaning device, and isopropanol and distilled water are used as cleaning agents to ultrasonically clean the substrate. After that, high-pressure air is used to blow away any remaining water stains on the substrate to remove impurities, oil, and organic residues from the pores of the substrate. In this embodiment, the ultrasonic cleaning power of the substrate is 50-70KW, and the cleaning time is 10-30 minutes. Finally, the ultrasonically cleaned substrate is placed in a magnetron sputtering device, and under vacuum, the substrate surface is sputtered cleaned with pulsed DC bias and argon plasma to further remove oxides and contaminants from the substrate surface. At the same time, the bombardment of argon ions can also increase the surface roughness of the substrate and increase the specific surface area, thereby increasing the adhesion between the coating and the substrate in the subsequent film formation process. In this embodiment, the pulsed DC bias is set to -600 to 700V during sputtering cleaning.

[0040] Understandably, in some other embodiments, when cleaning the substrate, the cleaning agent may also be an organic solvent with good grease-dissolving ability, such as acetone solution, alcohol, etc., and the cleaning method is not limited to ultrasonic cleaning, but may also be cleaning by soaking, boiling, etc.

[0041] S2: Prepare a self-healing coating on the substrate surface.

[0042] The substrate is then placed in a magnetron sputtering apparatus. A self-healing coating doped with the repair-functional metal is deposited sequentially on the pretreated substrate surface, using both a metal with repair function as the target alone and a combination of the metal with repair function and nitrogen (N) or carbon (C) as the target. This self-healing coating, during operation, rapidly combines with oxygen to undergo an oxidation reaction, generating oxides of the repair-functional metal. This seals the pores and cracks generated during the coating's fabrication process, preventing electrolyte from seeping into the coating and corroding the substrate. In this embodiment, the repair-functional metal is a metal element capable of rapidly combining with oxygen in the strongly acidic environment of a fuel cell to generate stable metal oxides, such as Cr, Ti, Ta, and Nb.

[0043] In this embodiment, the self-healing coating includes at least a substrate contact layer and an anti-corrosion layer sequentially stacked on the substrate. The substrate contact layer is formed by depositing a metal with repair capabilities. As the basis for the self-healing coating's self-healing ability, when the bipolar plate operates in a high-temperature corrosive environment, the metal with repair capabilities in the substrate contact layer reacts rapidly with oxygen under the high potential of the corresponding electrode to form a dense oxide film, thus repairing inherent defects generated during the coating's preparation process and preventing electrolyte corrosion of the substrate. The anti-corrosion layer is formed by reacting the metal with N or C elements to form metal nitrides or metal carbides, and covers the substrate contact layer. It not only has anti-corrosion properties but also excellent conductivity. Furthermore, the substrate, the substrate contact layer (i.e., the metal with repair capabilities), and the anti-corrosion layer (i.e., the metal carbide or metal nitride) have similar thermal diffusivity, which reduces stress between the layers, thereby improving the adhesion between them and preventing failure during operation, thus enhancing the coating's durability.

[0044] like Figure 2 As shown, step S2 specifically includes the following sub-steps:

[0045] S21: Sputtering a substrate contact layer onto the surface of the substrate.

[0046] Specifically, the substrate is held in a magnetron sputtering apparatus and fixed. A magnetron sputtering process is employed, and a pulsed DC bias is applied to the substrate. A metal with repair function is used as the sputtering target to sputter and deposit a metal with repair function directly in contact with the substrate, forming a substrate contact layer. This creates a metallic bond between the substrate surface and the metal with repair function, resulting in a self-healing coating with good electrical conductivity. In this embodiment, the thickness of the sputtered substrate contact layer is 0.1–0.3 μm, and during sputtering, the pulsed DC bias is set to -50–200V. A planar target with a size of 2–5 inches is selected, the sputtering power of the metal target is 100–200W, and the sputtering time is 15–30 minutes.

[0047] S22: An anti-corrosion layer is formed by sputtering on the surface of the substrate contact layer.

[0048] Specifically, the substrate is kept in position and fixed in the magnetron sputtering equipment. An anti-corrosion layer bonded to the substrate contact layer is deposited by co-sputtering N or C elements with the metal with repair function outside the substrate contact layer. This forms chemical bonds between the N or C elements and the metal with repair function to enhance the bonding force between the anti-corrosion layer and the substrate contact layer and prevent coating failure.

[0049] In this embodiment, when the anti-corrosion layer is formed by co-sputtering nitrogen with a metal having repair function, the anti-corrosion layer is a metal nitride formed by the reaction of nitrogen and the metal with repair function during sputtering. Specifically, during sputtering, the sputtering parameters of the metal target are maintained, and nitrogen gas is introduced into the deposition chamber of the magnetron sputtering equipment. The metal target and nitrogen gas are used to deposit a metal nitride bonded to the substrate contact layer outside the substrate contact layer using a reactive sputtering process to form the anti-corrosion layer. In this embodiment, the flow rate of the nitrogen gas is 40-80 sccm.

[0050] When the anti-corrosion layer is formed by co-sputtering carbon with a metal having repair function, the anti-corrosion layer includes an intermediate layer and a carbon layer sequentially stacked on the substrate contact layer. The intermediate layer is a metal nitride generated by the reaction of carbon with the metal having repair function. Specifically, during the sputtering process, firstly, the carbon target is turned on, and the sputtering power of the metal target and the carbon target is simultaneously adjusted. Using the metal target and the carbon target, a metal carbide bonded to the substrate contact layer is deposited outside the substrate contact layer using a magnetron co-sputtering process to form the intermediate layer. In this embodiment, when adjusting the sputtering power of the metal target and the carbon target, the sputtering power of the metal target and the sputtering power of the carbon target are linearly inversely proportional (i.e., when the sputtering power of the metal target decreases linearly, the sputtering power of the carbon target increases linearly). The sputtering power of the carbon target is 100-200W, and the sputtering time of the carbon target is 15-30min. Then, a carbon layer bonded to the intermediate layer is deposited outside the intermediate layer by periodically changing the bias voltage. The intermediate layer and the carbon layer together form the anti-corrosion layer. In this embodiment, when periodically changing the bias voltage, the high bias voltage is 600V and the low bias voltage is 150V. The number of cycles for changing the high and low bias voltages is 10 to 20. The duration of the high and low bias voltages scales proportionally with the number of cycles. The deposition time of the carbon layer is less than or equal to 2 hours.

[0051] In this embodiment, due to the different materials and preparation processes used in preparing the anti-corrosion layer, the structure of the self-healing coating is different. When the anti-corrosion layer is prepared using nitrogen element and a metal with repair function, the self-healing coating is a two-layer structure including a metal-metal nitride with repair function. When the anti-corrosion layer is prepared using carbon element and a metal with repair function, the self-healing coating is a three-layer structure including a metal-metal carbide-carbon layer with repair function. However, due to the presence of the metal with repair function (i.e., the substrate contact layer), both can achieve the purpose of self-repair.

[0052] like Figure 3As shown, the polarization test curves of the self-healing coating with self-repairing ability prepared by the present invention and the coating prepared by the traditional process are shown. Curve ① is the polarization test curve of the coating without self-repairing ability prepared by the traditional process, and curve ② is the polarization test curve of the self-healing coating with self-repairing ability prepared by the process of the present invention. It can be clearly seen from the figure that the self-corrosion voltage of curve ② is positively shifted and the self-corrosion current is reduced, indicating that the self-healing coating of the present invention has better anti-corrosion performance.

[0053] like Figure 4 and Figure 5 The figures show the electrostatic potential test curves of the self-healing coating with self-repairing ability prepared according to the present invention at 0.6V and -0.1V, respectively. It can be clearly seen from the figures that the corrosion current is much less than 10. -6 A / cm 2 It meets DOE requirements.

[0054] The self-healing coating preparation process of this embodiment involves pre-preparing a substrate contact layer on the substrate, which is a substrate contact layer obtained by depositing a metal with repair function. This serves as the basis for the self-healing coating's self-healing capability. When the fuel cell operates in a high-temperature corrosive environment, the metal with repair function in the substrate contact layer reacts rapidly with the oxygen introduced during the fuel cell's operation under the influence of a high potential, forming a dense oxide film on the substrate contact layer. This film seals the pores and cracks generated during the coating preparation process, preventing the electrolyte from penetrating into the corrosive substrate. As a result, the coating exhibits self-healing ability and improves its corrosion resistance.

[0055] Another embodiment of the present invention provides a bipolar plate, the bipolar plate comprising a substrate and a self-healing coating formed outside the substrate, the self-healing coating being fabricated based on the self-healing coating fabrication process described in the above embodiments. Specifically, the self-healing coating comprises a substrate contact layer and an anti-corrosion layer sequentially deposited on the surface of the substrate; the substrate contact layer is formed by depositing a metal with repair function, which serves as the basis for the self-healing coating's self-healing capability. When the bipolar plate operates in a high-temperature corrosive environment, the metal with repair function in the substrate contact layer reacts rapidly with oxygen under the high potential of the corresponding electrode to form a dense oxide film, thereby repairing inherent defects generated during the coating fabrication process and preventing electrolyte corrosion of the substrate. The anti-corrosion layer is formed by the reaction of a metal with repair function and N or C elements to form metal nitrides or metal carbides, and covers the substrate contact layer. It not only has anti-corrosion properties, but also excellent electrical conductivity. At the same time, the substrate, the substrate contact layer (i.e., the metal with repair function), and the anti-corrosion layer (i.e., the metal carbide or metal nitride) have similar thermal diffusivity coefficients, which reduces the stress between the film layers, thereby improving the bonding force between the film layers, preventing the film layers from failing during operation, and thus enhancing the durability of the coating.

[0056] In addition, another embodiment of the present invention provides a fuel cell, wherein the fuel cell comprises a self-healing coating prepared by the self-healing coating preparation process of the above embodiments or comprises the above-mentioned bipolar plate. Specifically, the fuel cell includes a bipolar plate with a self-healing coating. Of course, the fuel cell also includes other necessary components (such as cells, electrodes, etc.) besides the bipolar plate, and the aforementioned necessary components can all be implemented using existing structures, which will not be described in detail here. Thus, by using the fuel cell of the present invention, after final assembly, under high temperature and phosphoric acid corrosion environment, when the fuel cell is working normally, after oxygen is introduced to the cathode, the high potential generated at the cathode causes the metal with repair function to quickly combine with oxygen and undergo an oxidation reaction to form a dense oxide film, repairing the inherent defects generated during the preparation of the self-healing coating; at the same time, since the substrate, the metal with repair function and the metal nitride or metal carbide in the self-healing coating have similar thermal diffusivity, the bonding force between each film layer is improved, thereby enabling the fuel cell to have both excellent corrosion resistance and stable electrochemical performance.

[0057] The preparation process of the self-healing coating of the present invention will be further described in detail below with specific examples. In describing the present invention, an SS316L stainless steel substrate, a Cr metal with repair function, and either a CrN metal nitride or a CrC metal carbide will be used as examples. Of course, it is understood that in other embodiments, the substrate can also be made of other metallic materials, such as aluminum, titanium, nickel, etc.; the metal with repair function is not limited to Cr metal, but can also be one or more of other metal elements with repair function such as Cr, Ti, Ta, Nb, etc.; and the metal nitride and metal carbide can also be corresponding metal nitrides and metal carbides formed by combining other metal elements with repair function with N and C elements.

[0058] Example 1

[0059] like Figure 6 The diagram shows a flowchart of the preparation process of the self-healing coating in this embodiment. The self-healing coating prepared in this embodiment comprises a Cr-CrN two-layer structure. The specific steps of the preparation process of the self-healing coating in this embodiment are as follows:

[0060] S101: Provide an SS316L stainless steel substrate and pretreat the SS316L stainless steel substrate.

[0061] First, an SS316L stainless steel base is provided.

[0062] Then, use 1000-grit silicon carbide sandpaper to grind and polish the surface of the SS316L stainless steel substrate to a mirror finish.

[0063] Next, the SS316L stainless steel substrate after grinding and polishing is placed in an ultrasonic cleaning device. The power of the ultrasonic cleaning device is adjusted to 65KW. Isopropanol and distilled water are used as cleaning agents to ultrasonically clean the SS316L stainless steel substrate for 30 minutes. After that, high-pressure air is used to blow away the water stains remaining on the SS316L stainless steel substrate.

[0064] Finally, the ultrasonically cleaned SS316L stainless steel substrate was placed in a magnetron sputtering device, and sputtered cleaned with argon plasma under vacuum with a pulsed DC bias voltage of -600 to 700V, thus completing the pretreatment of the SS316L stainless steel substrate.

[0065] S102: A Cr metal layer is sputtered onto the surface of an SS316L stainless steel substrate.

[0066] The SS316L stainless steel substrate was placed and fixed in the magnetron sputtering equipment. The magnetron sputtering process was used, and a pulsed DC bias voltage of -50 to 200V was applied to the SS316L stainless steel substrate. The sputtering power was set to 150W, and the Cr metal target was turned on. The Cr metal target was a 3-inch planar target. A 0.2μm thick Cr metal layer was sputtered and deposited on the surface of the SS316L stainless steel substrate as the substrate contact layer. The sputtering time was 30 minutes.

[0067] S103: A CrN layer is formed by sputtering on the surface of a Cr metal layer.

[0068] The SS316L stainless steel substrate is kept in position and fixed in the magnetron sputtering equipment. The sputtering parameters of the Cr metal target are maintained and nitrogen gas is introduced into the deposition chamber of the magnetron sputtering equipment. A CrN layer bonded to the Cr metal layer is deposited outside the Cr metal layer to form the anti-corrosion layer. The flow rate of nitrogen gas is 60 sccm when it is introduced.

[0069] The self-healing coating prepared in this embodiment has a two-layer structure composed of Cr-CrN from the inside out. When the inner Cr metal layer is working in a high-temperature corrosive environment, the Cr metal can react rapidly with the oxygen introduced during the operation of the fuel cell under the action of high potential to form a dense oxide film, thereby making the coating exhibit self-healing ability and improving corrosion resistance.

[0070] Example 2

[0071] like Figure 7 The diagram shows a flowchart of the preparation process of the self-healing coating in this embodiment. The self-healing coating prepared in this embodiment includes a Cr-CrC-C three-layer structure. The specific steps of the preparation process of the self-healing coating in this embodiment are as follows:

[0072] S201: Provide an SS316L stainless steel substrate and pretreat the SS316L stainless steel substrate.

[0073] First, an SS316L stainless steel base is provided.

[0074] Then, use 1000-grit silicon carbide sandpaper to grind and polish the surface of the SS316L stainless steel substrate to a mirror finish.

[0075] Next, the SS316L stainless steel substrate after grinding and polishing is placed in an ultrasonic cleaning device. The power of the ultrasonic cleaning device is adjusted to 65KW. Isopropanol and distilled water are used as cleaning agents to ultrasonically clean the SS316L stainless steel substrate for 30 minutes. After that, high-pressure air is used to blow away the water stains remaining on the SS316L stainless steel substrate.

[0076] Finally, the ultrasonically cleaned SS316L stainless steel substrate was placed in a magnetron sputtering device, and sputtered cleaned with argon plasma under vacuum with a pulsed DC bias voltage of -600 to 700V, thus completing the pretreatment of the SS316L stainless steel substrate.

[0077] S202: A Cr metal layer is sputtered onto the surface of an SS316L stainless steel substrate.

[0078] The SS316L stainless steel substrate was placed and fixed in the magnetron sputtering equipment. The magnetron sputtering process was used, and a pulsed DC bias voltage of -50 to 200V was applied to the SS316L stainless steel substrate. The sputtering power was set to 150W, and the Cr metal target was turned on. The Cr metal target was a 3-inch planar target. A 0.2μm thick Cr metal layer was sputtered and deposited on the surface of the SS316L stainless steel substrate as the substrate contact layer. The sputtering time was 30 minutes.

[0079] S203: A CrC layer is formed by sputtering on the surface of a Cr metal layer.

[0080] The SS316L stainless steel substrate remains in its fixed position within the magnetron sputtering equipment. The carbon target is activated, and the sputtering power of both the Cr metal target and the carbon target is adjusted synchronously. Specifically, the sputtering power of the Cr metal target is linearly decreased while the sputtering power of the carbon target is linearly increased, to deposit a CrC layer as an intermediate layer outside the Cr metal layer. In this embodiment, the sputtering power can be linearly adjusted by regulating the sputtering currents of the Cr metal target and the carbon target. The sputtering time is 30 minutes.

[0081] S204: A graphite carbon layer is formed by sputtering on the surface of a CrC layer.

[0082] The bias voltage applied to the SS316L stainless steel substrate was periodically changed between a high bias voltage of 600V and a low bias voltage of 150V, with the number of cycles set to 10. The deposition time was 1.8h with the low bias voltage of 150V and 0.2h with the high bias voltage, in order to deposit a graphite carbon layer outside the CrC layer, thereby forming an anti-corrosion layer.

[0083] The self-healing coating prepared in this embodiment has a three-layer structure composed of Cr-CrC-C from the inside out. When the inner Cr metal layer is working in a high-temperature corrosive environment, the Cr metal can react rapidly with the oxygen introduced during the operation of the fuel cell under the action of high potential to form a dense oxide film, thereby enabling the coating to exhibit self-healing ability and improve corrosion resistance.

Claims

1. A process for the preparation of a self-healing coating, characterized in that, The method comprises the following steps: providing a substrate and pretreating the substrate; forming a self-healing coating layer doped with a metal having a repairing function on the surface of the pretreated substrate, wherein the self-healing coating layer comprises at least a substrate contact layer and an anti-corrosion layer which are sequentially stacked on the substrate; and forming the substrate contact layer by sputtering a metal having a repairing function on the surface of the substrate as a target material to form the substrate contact layer in contact with the substrate; in the step of forming the substrate contact layer, a pulsed direct current bias is applied to the substrate and a direct current magnetron sputtering process is used to form the substrate contact layer, the thickness of the substrate contact layer is 0.1-0.3 μm, and in the sputtering process, the pulsed direct current bias is -50-200 V, the metal target material is a 2-5 inch planar target material, the sputtering power of the metal target material is 100-200 W, and the sputtering time of the metal target material is 15-30 min; in the step of forming the anti-corrosion layer, N element or C element is used to co-sputter an anti-corrosion layer combined with the substrate contact layer outside the substrate contact layer and the metal having a repairing function; and the specific method for forming the anti-corrosion layer by using N element is as follows: the sputtering parameters of the metal target material having a repairing function are kept unchanged, nitrogen gas is introduced into the deposition cavity, and a metal nitride combined with the substrate contact layer is deposited outside the substrate contact layer by using the metal target material and nitrogen gas and a reaction sputtering process to form the anti-corrosion layer; in the reaction sputtering process, the flow rate of the nitrogen gas is 40-80 sccm; the anti-corrosion layer formed by using C element comprises an intermediate layer and a carbon layer which are sequentially stacked on the substrate contact layer; and the specific method for forming the anti-corrosion layer by using C element is as follows: an intermediate layer combined with the substrate contact layer is co-sputtered outside the substrate contact layer by using C element and the metal having a repairing function; a carbon layer combined with the intermediate layer is sputtered outside the intermediate layer by using C element; the specific method for forming the intermediate layer is as follows: the carbon target material is turned on, and the sputtering power of the metal target material and the carbon target material is adjusted synchronously, a metal carbide combined with the substrate contact layer is deposited outside the substrate contact layer by using the metal target material and the carbon target material and a magnetron co-sputtering process to form the intermediate layer; in the magnetron co-sputtering process, the sputtering power of the metal target material and the sputtering power of the carbon target material are in a linear inverse relationship, the sputtering power of the carbon target material is 100-200 W, and the sputtering time of the carbon target material is 15-30 min.

2. The process for the preparation of a self-healing coating according to claim 1, characterized in that, in the step of sputtering a carbon layer combined with the intermediate layer outside the intermediate layer by using C element, the specific method for forming the carbon layer is as follows: a carbon layer combined with the intermediate layer is deposited outside the intermediate layer by using a method of periodically changing the bias voltage, in the deposition process, the high bias voltage is 600 V, the low bias voltage is 150 V, the number of changing cycles of the high and low bias voltages is 10-20, the duration time of the high and low bias voltages is scaled by a factor of the number of changing cycles, and the deposition time of the carbon layer is less than or equal to 2 h.

3. A bipolar plate, characterized by The coating includes a substrate and a self-healing coating formed on the surface of the substrate using the self-healing coating preparation process as described in any one of claims 1 to 2, which is doped with a metal having repair function.

4. A fuel cell comprising a bipolar plate formed with a self-healing coating layer doped with a metal having a healing function, characterized by The self-healing coating of the metal doped with repair function formed on the bipolar plate is prepared by the self-healing coating preparation process as described in any one of claims 1 to 2, or the bipolar plate is the bipolar plate as described in claim 3.

Images