Titanium plate material for fuel cell separators with excellent surface conductivity and durability and its manufacturing method

Abstract

The present invention aims to provide a fuel cell separator material that simultaneously ensures manufacturing cost, conductivity, and durability by adjusting the composition of the titanium (Ti) base material and easily forming a conductive oxide layer on the surface coating layer, and does not require additional coating. [Solution] A titanium separator plate material with excellent surface conductivity and durability is disclosed. The titanium plate material for a fuel cell separator plate according to the present invention comprises a Ti base material consisting of, by mass%, 0.001 to 0.09% Si, the remainder Ti, and unavoidable impurities, and a surface coating layer in which the contents of Ti, Si, and O measured by X-ray angle-resolved photoelectron spectroscopy using an Al-Kα X-ray source at a photoelectron takeoff angle of 45° are each greater than 0%. The surface coating layer is characterized by satisfying the following formula (1): Formula (1): 0.2 ≦ Si(at.%) / [Ti(at.%)+Si(at.%)] ≦ 0.8

Description

[Technical Field]

[0001] The present invention relates to a titanium plate for a fuel cell separator having excellent surface conductivity and durability, and a manufacturing method thereof. More particularly, the present invention relates to a titanium plate for a fuel cell separator having excellent surface conductivity and durability, which can omit a coating process and has excellent durability and surface conductivity even in a high-voltage operating environment of a fuel cell, and a manufacturing method thereof. [Background technology]

[0002] The present invention is a result of the following research project. (National research and development project that supported this invention) (Project unique number) 1415170001 (Project number) 20012130 (Ministry name) Ministry of Trade, Industry and Energy (Name of issue management (specialized) organization) Korea Institute for Industrial Technology Evaluation and Management (Research project name) Next-generation fuel cell system technology development project for hydrogen vehicles (Research title) Development of high-performance separators based on lightweight alternative materials (Contribution rate) 1 / 1 (Name of the organization carrying out the project) POSCO Corporation (Research period) 2020.05.01 ~ 2024.12.31

[0003] Titanium has excellent corrosion resistance and is being considered as a material for fuel cell separator plates. However, although the corrosion resistance is ensured by the passivation film formed on the surface layer, it has the drawback of being unable to ensure low contact resistance due to its semiconducting properties.

[0004] To solve this problem, Patent Document 1 discloses a technique of coating the surface of titanium with graphite powder, but this technique has problems such as a difficult manufacturing process and impeded conductivity due to peeling.

[0005] On the other hand, Patent Document 2 discloses a technique for forming a thin film layer of a precious metal on the surface of a metal member, but this technique has the problem of high manufacturing costs.

[0006] Furthermore, Patent Document 3 discloses a technology for forming a phase containing a Ti2O3 phase on the surface of titanium, but this requires a carbon reduction treatment step in the manufacturing process, and there is a limit to how well the electrical conductivity can be ensured.

[0007] Furthermore, Patent Document 4 discloses a process of applying carbon black to the surface of a titanium substrate and then heat treating it, but this requires an additional process of applying carbon black, which increases the manufacturing cost. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 5342462 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-105523 [Patent Document 3] Korean Patent Publication No. 10-2019-0095472 [Patent Document 4] Japanese Patent Application Publication No. 2019-133863 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to provide a fuel cell separator material that simultaneously ensures manufacturing cost, conductivity, and durability by adjusting the composition of the titanium (Ti) base material and easily forming a conductive oxide layer on the surface coating layer, and does not require additional coating. [Means for solving the problem]

[0010] The titanium plate material for a fuel cell separator of the present invention comprises a Ti base material consisting of, by mass%, 0.001 to 0.09% Si, the remainder Ti, and unavoidable impurities, and a surface coating layer in which the contents of Ti, Si, and O measured by X-ray angle-resolved photoelectron spectroscopy using an Al-Kα X-ray source at a photoelectron takeoff angle of 45° each exceed 0%, The surface coating layer is characterized by satisfying the following formula (1):

[0011] Formula (1): 0.2 ≦ Si(at.%) / [Ti(at.%)+Si(at.%)] ≦ 0.8

[0012] The thickness of the surface coating layer of the titanium plate material for a fuel cell separator of the present invention can be 3 to 1000 nm.

[0013] Furthermore, the titanium plate material for fuel cell separators of the present invention has a surface contact resistance of 10 mΩcm. 2 It can be as follows:

[0014] The method for producing a titanium plate material for a fuel cell separator of the present invention includes the steps of: providing a Ti base material containing, by mass%, 0.001 to 0.09% Si, the remainder Ti, and unavoidable impurities; Melting the Ti base material, hot rolling it, and cold rolling it; The rolled Ti base material was -30 10 from the bar -10 and forming a surface coating layer by heat-treating the substrate in a 500 to 900°C atmosphere controlled by bar for 10 seconds to 1 hour. The surface coating layer has a Ti, Si, and O content of more than 0%, as measured by X-ray angle-resolved photoelectron spectroscopy using an Al-Kα X-ray source at a photoelectron takeoff angle of 45°; The surface coating layer is characterized by satisfying the following formula (1):

[0015] Formula (1): 0.2 ≦ Si(at.%) / [Ti(at.%)+Si(at.%)] ≦ 0.8

[0016] In addition, in the method of the present invention for producing a titanium plate for a fuel cell separator, the thickness of the surface coating layer can be set to 3 to 1000 nm.

[0017] Furthermore, the method for producing a titanium plate material for a fuel cell separator of the present invention is capable of reducing the surface contact resistance to 10 mΩcm. 2It can be as follows: [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a titanium plate material for fuel cell separator plates that has excellent surface conductivity and durability when used for fuel cell separator plates. [Brief explanation of the drawings]

[0019] [Figure 1] 1 shows a comparison of the surface coating layer components observed when measuring the comparative example and the inventive example by X-ray angle-resolved photoelectron spectroscopy using an Al-Kα X-ray source under the condition of a photoelectron takeoff angle of 45°. [Figure 2] 1 is an image of the surface layer and base material of Example 1 observed with a transmission electron microscope. DETAILED DESCRIPTION OF THE INVENTION

[0020] The following describes preferred embodiments of the present invention. However, the embodiments of the present invention can be modified into various other forms, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the art.

[0021] The terms used in this application are merely used to describe specific examples. Thus, for example, singular expressions include plural expressions unless the context clearly dictates otherwise. Note that the terms "comprise" or "include" used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not intended to preclude the presence of other features, steps, functions, components, or combinations thereof.

[0022] The titanium plate material for a fuel cell separator of the present invention comprises a Ti base material consisting of, by mass%, 0.001 to 0.09% Si, the remainder being Ti and unavoidable impurities, and a surface coating layer in which the contents of Ti, Si, and O measured by X-ray angle-resolved photoelectron spectroscopy using an Al-Kα X-ray source at a photoelectron takeoff angle of 45° each exceed 0%, The surface coating layer can satisfy the following formula (1).

[0023] Formula (1): 0.2 ≦ Si(at.%) / [Ti(at.%)+Si(at.%)] ≦ 0.8

[0024] The inventors have conducted research to ensure the conductivity of the surface coating layer formed on the surface without a separate coating process, and have found the composition of the Ti base material and the elemental conditions that allow the surface coating layer to have conductivity. Specifically, the titanium plate material developed by the inventors, which contains 0.001 to 0.09% Si in the base material, has the Si component concentrated in the surface layer under temperature conditions with low oxygen partial pressure, resulting in TiSi x O y It was discovered that when it is formed in oxide form, it can have conductivity. The reason for this conductivity is believed to be due to the Si doping effect, which lowers the band gap energy and changes it to a conductor.

[0025] The reason why the lower limit of the Si content of the base material is set to 0.001% by mass or more is that this is the minimum content value at which the Si doping effect, which indicates the conductivity of the surface layer, can be exhibited, and the reason why the upper limit is set to 0.09% is that exceeding 0.09% may have an adverse effect on the formability of the material, so the upper limit is set to 0.09%.

[0026] The composition of the surface coating layer to exhibit conductivity can satisfy the following formula (1):

[0027] Formula (1): 0.2 ≦ Si(at.%) / [Ti(at.%)+Si(at.%)] ≦ 0.8

[0028] In order to show the conductive properties due to Si doping, the lower limit of formula (1) is set to 0.2 or more. If it exceeds 0.8, the conductive properties will change to semiconducting properties due to the concentration of Si, resulting in poor conductivity, so the upper limit is limited to 0.8 or less.

[0029] The composition of the surface coating layer essentially contains Ti, Si, and O, but may further contain one or more of C and N, and may optionally contain 0.06% or less of Fe.

[0030] The surface coating layer of the present invention may have a thickness of 3 to 1000 nm.

[0031] The inventors limited the coating thickness to 3 to 1000 nm because they discovered that the thickness of the surface coating layer that maintains conductivity in a fuel cell environment must be at least 3 nm; if the thickness is less than 3 nm, destruction of the surface coating layer will result in a decrease in performance due to the restoration of the TiO2 coating layer. Therefore, the maximum thickness of the formed surface coating layer was limited to 1000 nm, which is the limit value at which defects such as cracks will not occur when the separator plate forming process is applied after the titanium plate is manufactured.

[0032] The titanium base material may be made of a pure titanium material or a titanium alloy, and must essentially contain, by mass %, 0.001 to 0.09% Si.

[0033] According to the present invention, the titanium plate material for fuel cell separators has a surface contact resistance of 10 mΩcm. 2 It can be the following:

[0034] According to the present invention, a method for manufacturing a titanium plate for a fuel cell separator includes the steps of: providing a Ti base material containing, by mass%, 0.001 to 0.09% Si, the remainder Ti, and unavoidable impurities; A step of melting a Ti base material, a step of hot rolling it, and a step of cold rolling it; The rolled Ti substrate was -30 10 from the bar -10 and forming a surface coating layer by heat-treating the substrate in a 500 to 900°C atmosphere controlled by bar for 10 seconds to 1 hour. The surface coating layer has a Ti, Si, and O content of more than 0% when measured by X-ray angle-resolved photoelectron spectroscopy using an Al-Kα X-ray source at a photoelectron takeoff angle of 45°; A method for producing a titanium plate material for a fuel cell separator, wherein the surface coating layer satisfies the following formula (1):

[0035] Formula (1): 0.2 ≦ Si(at.%) / [Ti(at.%)+Si(at.%)] ≦ 0.8

[0036] Oxygen partial pressure 10 -30 bar~10 -10 The reason for limiting the time to form the surface coating layer to 10 seconds to 1 hour in an atmosphere of 500 to 900°C at 10 bar is that -10 When the oxygen partial pressure is 10 bar or less, the atmosphere is such that Si can be diffused into the Ti, O compound layer on the surface and doped, and this is the maximum oxygen partial pressure condition under which Si diffusion is possible. -30 This is because, if the pressure is less than bar, creating the atmosphere requires high manufacturing costs using excess hydrogen, CO, CO2, methane, propane gas, etc. The heating temperature is limited to 500°C or higher to diffuse Si, and the upper limit is set to 900°C because excessive grain growth above 900°C reduces formability. In addition, the heating maintenance time is set taking into account the minimum and maximum maintenance times required for Si doping in the surface coating layer.

[0037] The present invention will now be described in more detail with reference to preferred embodiments thereof. [Example]

[0038] The following 30 kg ingots were vacuum melted, hot rolled, annealed, and cold rolled to produce cold-rolled titanium plates (0.2 mm thick) having the composition shown in Table 1.

[0039] [Table 1]

[0040] Table 2 below shows the composition of the surface coating layer and the results of property evaluation of the titanium plate material after atmospheric heating exposure following cold rolling.

[0041] [Table 2]

[0042] The cold-rolled plates of the examples were cut into 10cm x 10cm pieces, ultrasonically cleaned in acetone for one hour in the laboratory, and then heat-treated in a furnace controlled with a low oxygen partial pressure. The atmosphere was controlled using Ar, hydrogen, CO, CO2, methane, and propane gases to maintain a low oxygen partial pressure. Oxygen partial pressure measurements were performed using a Metlor oxygen partial pressure meter. After heat treatment, the test pieces were analyzed for the composition of the surface coating layer by X-ray angle-resolved photoelectron spectroscopy using an Al-Kα X-ray source with a photoelectron takeoff angle of 45°. Figure 1 shows the composition of the surface coating layer. As shown in Examples 1 to 4, Si was detected in the surface layer, and the relative component ratios are shown in Table 2.

[0043] FIG. 2 shows an image of the surface coating layer and the base material of Example 1 observed with a transmission electron microscope, and the thickness of the surface coating layer was observed and investigated.

[0044] To evaluate contact resistance, the measurement sample was cut into 5cm x 5cm pieces, and carbon paper (GDL) / test piece / carbon paper (GDL) / test piece / carbon paper (GDL) was placed inside the upper and lower Cu plates, and after applying current to the Cu plate, a voltage terminal was connected to the test piece to evaluate the initial contact resistance.The test piece for which the initial contact resistance was evaluated was immersed in a 0.05M sulfuric acid + 2ppm hydrofluoric acid solution for 100 hours to evaluate durability in the fuel cell operating environment, and the contact resistance was re-evaluated to see if there was any change.

[0045] Inventive Examples 1 to 4 satisfy the composition and the oxygen partial pressure in the atmosphere is 10 -30 10 from the bar -10When the test is carried out in an atmosphere of 500 to 900°C at 10 bar for 10 seconds to 1 hour, and formula (1) satisfies 0.1 to 3, the initial surface contact resistance and the contact resistance after the durability test are 10 mΩ cm 2 The following was satisfied:

[0046] On the other hand, in Comparative Examples 1 to 3, the oxygen partial pressure in the atmosphere was 10 -10 bar, and formula (1) was less than 0.2, so the initial surface contact resistance and the contact resistance after the durability test were 10 mΩ cm 2 exceeded.

[0047] Although exemplary embodiments of the present invention have been described above, the present invention is not limited thereto, and it will be understood by those skilled in the art that various changes and modifications can be made without departing from the concept and scope of the claims set forth below.

Claims

1. A Ti base material consisting of, in mass%, 0.001 to 0.09% Si, the remainder Ti, and unavoidable impurities; a surface coating layer in which the contents of Ti, Si, and O measured by X-ray angle-resolved photoelectron spectroscopy using an Al-Kα X-ray source at a photoelectron takeoff angle of 45° are each greater than 0%, The titanium plate material for a fuel cell separator, wherein the surface coating layer satisfies the following formula (1): Formula (1): 0.2≦Si(at.%) / [Ti(at.%)+Si(at.%)]≦0.8

2. 2. The titanium plate material for a fuel cell separator according to claim 1, wherein the surface coating layer has a thickness of 3 to 1000 nm.

3. Surface contact resistance is 10 mΩcm ２ 2. The titanium plate material for fuel cell separators according to claim 1, wherein:

4. Providing a Ti base material consisting of, in mass%, 0.001 to 0.09% Si, the remainder Ti, and unavoidable impurities; Melting the Ti base material, hot rolling it, and cold rolling it; The rolled Ti base material was －３０ 10 minutes from the bar －１０ and forming a surface coating layer by heat-treating the substrate for 10 seconds to 1 hour in a 500 to 900°C atmosphere controlled at bar; The surface coating layer has a Ti, Si, and O content of more than 0%, as measured by X-ray angle-resolved photoelectron spectroscopy using an Al-Kα X-ray source under a photoelectron takeoff angle of 45°; The method for producing a titanium plate for a fuel cell separator, wherein the surface coating layer satisfies the following formula (1): Formula (1): 0.2≦Si(at.%) / [Ti(at.%)+Si(at.%)]≦0.8

5. 5. The method for manufacturing a titanium plate for a fuel cell separator according to claim 4, wherein the surface coating layer has a thickness of 3 to 1000 nm.

6. Surface contact resistance is 10 mΩcm ２ 5. The method for manufacturing a titanium plate for a fuel cell separator according to claim 4, wherein the following is true:

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