Ti material for fuel cell separator and manufacturing method thereof

Abstract

Disclosed herein is a method of manufacturing a Ti material for a fuel cell separator, the method comprising rolling a Ti feedstock of a pure Ti material or Ti alloy material, depositing and coating Ti ion particles on the Ti feedstock by physical vapor deposition (PVD), and an oxidation heat treatment to form a conductive oxide layer of a TiO2-x (0 < x < 1) structure around the Ti ion particles deposited by the deposition coating. According to the present disclosure, Ti materials may be used to achieve corrosion resistance and electrical conductivity.

Description

Technical Field

[0001] The present disclosure relates to a Ti material applied to a fuel cell separator and a method for manufacturing the same. Background Art

[0002] A fuel cell separator is a component that allows hydrogen and oxygen to diffuse evenly within the fuel cell stack and allows water and heat generated during the power generation process to be removed.

[0003] The oxide form of Ti in a common oxidizing environment (such as heat treatment or anodizing) is TiO 2 , its structure exists in the form of rutile, anatase, brookite, amorphous, or a mixture thereof, depending on the oxidation conditions (temperature / time / pressure / solution, etc.). TiO 2 It exists on the surface of Ti as a raw material in the form of a stable oxide, forming a passivation layer, which exhibits very good corrosion resistance in a normal environment. This can be considered to be due to the presence of a very fine (within a few nanometers) oxide film layer (such as Cr 2 O 3 ) and achieve corrosion resistance in a similar manner.

[0004] Ti material is considered as a metal separator material for fuel cells because it has excellent mechanical properties (rigidity), large-scale production (stamping), and excellent corrosion resistance compared to other metals in the operating environment of the fuel cell. However, although the above-mentioned oxide film layer present on the surface of Ti is used to provide corrosion resistance to the material, it also has insulating properties, which makes it impossible to ensure the conductivity that the separator should have, so the Ti material itself is not suitable.

[0005] Therefore, the method of applying a conductive coating to the surface of a Ti material is mainly used as a method of applying the Ti material as a separator for a fuel cell. Another method is to use TiO 2 The conductivity of oxides. Through a specific process, TiO 2 can be converted to an O-deficient oxide layer structure, or TiO formed under controlled conditions can be used 2-x To maintain the inherent corrosion resistance of Ti while achieving electrical properties (conductivity) similar to carbon (C). Recently, technologies that utilize these properties have been actively researched and have potential applications in various fields such as electrode materials, catalysts, solar panels, biomaterials, and water electrolysis.

[0006] As we all know, TiO 2-x The reason for the conductivity is that when the rutile TiO 2When local defects of O atoms are induced in the structure to form a regular crystal shear structure, this type of defect structure provides a path for electron movement, thereby generating conductivity. According to what has been described in the literature and patents so far, the formation of TiO 2-x The method can be divided into two forms. The first method is to directly form TiO from the raw material Ti 2-x , in which TiO is formed by heat treatment at a specific temperature and time using a reducing agent in an atmosphere with controlled oxygen partial pressure and vacuum degree 2-x (Patent Documents 1, 2 and 3), and the second method is to directly form TiO by coating 2-x , wherein dry TiO is deposited using PVD or CVD in a reducing atmosphere 2-x Coating or coating containing TiO 2-x The sol-gel coating material is wet coated.

[0007] However, it is rare to find a coating designed to simultaneously meet corrosion resistance and conductivity for use in fuel cell separators, and even harder to find commercially. In order to make a commercially viable TI separator, the requirements of manufacturing process and cost, large-scale production and uniform quality, and long-term performance and durability need to be met. To do this, there are many technical challenges that need to be overcome.

[0008] For example, in the case of the first method, the TiO 2-x The heat treatment condition is to maintain a high temperature of about 600 to 1000°C for a long time under a restricted atmosphere (vacuum, low oxygen partial pressure and reducing gas). Therefore, there are limitations in terms of manufacturing process and cost. The case of coating by the second method is advantageous in terms of uniform quality and productivity. However, in terms of durability, since the Ti oxide layer is not produced by the raw material, when applied to the separator, there are many cases where durability is not satisfied, such as peeling of the coating in the corrosive environment of long-term fuel cell operation. In addition, in separators for fuel cells, the requirements for commercially viable manufacturing costs and durability levels are getting higher and higher.

[0009] Examples of patents that have considered and applied all of these aspects to separators using Ti as a raw material include Patent Documents 1, 2, 3, 4, etc. These development patents generally use TiO prepared from Ti raw materials. 2-x In the case of Patent Document 1 (U.S. Patent Registration No. 10199661), a uniform TiO2 layer is formed on a Ti raw material by pickling or other methods. 2 The oxide layer was then treated with a reducing plasma (using H 2 gas) or 300℃ vacuum heat treatment to form TiO2-x Then, a chemical bonding layer (Ti-OC, N) is formed by a CVD method, and C is coated on the oxide layer. However, the TiO formed by the reduction plasma and low temperature vacuum heat treatment method 2-x The corrosion resistance of the oxide layer is lower than that of the Ti oxide layer of the raw material formed under high temperature (oxidation) heat treatment conditions. In addition, since the process needs to be carried out under a vacuum atmosphere, the large-scale production and manufacturing cost are limited in terms of the manufacturing process under normal production environment conditions.

[0010] In this regard, Patent Document 2 (Japanese Patent Publication No. 2019-133862) adopts a method of forming TiO on the surface of the raw material by oxidative heat treatment under high temperature and low oxygen partial pressure conditions. 2-x Furthermore, the C-containing nanocomposite coating is performed before the oxidative heat treatment so that it is designed so that during the growth of the oxide layer during the heat treatment, the C nanocomposite is embedded in the TiO 2-x The oxide layer is formed in the TiO2 layer, and the thickness of the oxide layer is limited to 40 to 100 nm. However, since the oxygen partial pressure (3 to 30 Pa) and temperature conditions proposed in the patent correspond to an unbalanced state to form TiO2, the 2-x The conditions are such that the heat treatment time needs to be as short as less than one minute within a limited temperature range. The reason for this is believed to be the formation of TiO on the surface of the raw material. 2-x , which is the formation of TiO under given temperature-oxygen partial pressure conditions 2 The oxide compound is in a transition state during the process. Although the TiO formed by high temperature oxidation heat treatment is 2-x The layer can improve the corrosion resistance to a certain extent, but due to the principle of forming the conductive oxide layer and the limitations of the process conditions (due to the time limit of the roll-to-roll coil heat treatment), there are limitations in ensuring further corrosion resistance. Generally, in order to further improve the corrosion resistance of Ti materials, high-temperature oxidation heat treatment or positive electrode oxidation treatment is often performed, but the method of existing patent document 2 cannot apply higher heat treatment temperature and time conditions to improve corrosion resistance.

[0011] That is, conductive TiO 2-x Layer formation is possible only under the proposed time-temperature conditions, while outside this range, due to the TiO 2 Insufficient or excessive growth of the oxide layer reduces the conductivity, making it difficult to apply to separators. In the case where the oxide layer contains C, the TiO grown by corrosion 2The conductivity can be compensated to a certain extent, but when the corrosion is carried out in a more severe corrosive environment or under long-term tolerance conditions, the effect will be lost because the C-containing oxide layer or raw material falls off with the corrosion. Therefore, in the corrosive environment of fuel cells requiring high durability, it is necessary to form a conductive oxide layer with stronger corrosion resistance on the Ti separator material itself, while developing a coating method that can maintain performance.

[0012] In this regard, Patent Document 3 (Japanese Patent Publication No. 2019-214781) proposes a method of forming TiO by performing oxidative heat treatment or anodic oxidation in the atmosphere from the beginning. 2 The method of applying C to the TiO oxide layer and then performing heat treatment in an oxygen-deficient atmosphere or vacuum. This is concentrated on the Ti oxide layer, and during the heat treatment, C diffuses into the TiO 2 In the layer, TiO 2 Oxide reduction to Ti 2 O 3 and TiO, thereby ensuring conductivity and corrosion resistance. In particular, the upper limit value of the initial oxide layer is limited to 120nm to prevent the resistance from increasing at an oxide layer thickness greater than 120nm. Although this method can further increase the thickness of the oxide layer for ensuring corrosion resistance compared to conventional methods, since the method of forming the conductive oxide layer relies on the diffusion of C from the outermost layer of the oxide layer to the interior thereof, there is a limitation in setting the conditions for the additional oxide layer thickness for higher corrosion resistance. In addition, considering the area where the conductive oxide layer is located, direct exposure to a corrosive environment cannot be avoided from the beginning, which may involve the problem of gradual degradation of performance over time.

[0013] To summarize the basic problems of each of the patents described so far in terms of corrosion resistance, both methods have significant limitations in terms of heat treatment temperature and time conditions for setting the thickness of the conductive oxide layer to improve the corrosion resistance of the separator. In the case of Patent Document 2, since TiO2 needs to be formed on the surface of the Ti raw material by chemical reaction of the raw material Ti with gas under thermodynamic non-equilibrium conditions (in a roll-to-roll process), the corrosion resistance of the separator is improved. 2-x Therefore, there are restrictions on the temperature and time of the heat treatment. In the case of Patent Document 3, since it is necessary to induce TiO by diffusing C from the oxide layer of the Ti raw material under given temperature and time conditions, 2 The reduction reaction of the oxide layer is limited, so there is a limit to the thickness of the initial oxide layer. In addition, in terms of manufacturing process, both methods have the disadvantage of performing a secondary heat treatment process in a vacuum atmosphere, and in each case, large-scale production requires special production facilities that are generally difficult to commercialize and facilities above a certain scale, which may also be a factor in increasing costs.

[0014] The above information disclosed in the related art is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not constitute the related art that is already known to a person of ordinary skill in the art. Summary of the invention

[0015] The present disclosure is intended to solve the above-mentioned problems, and the present disclosure is intended to provide a Ti material for a fuel cell separator and a method of manufacturing the same, the fuel cell separator being able to ensure corrosion resistance and electrical conductivity using the Ti material.

[0016] According to one aspect of the present disclosure, a method for manufacturing a Ti material for a fuel cell separator is provided, the method comprising rolling a Ti raw material of a pure Ti material or a Ti alloy material, depositing and coating Ti ion particles on the Ti raw material by physical vapor deposition (PVD), and oxidative heat treatment to form TiO around the Ti ion particles deposited by the deposition coating. 2-x (0<x<1) structured conductive oxide layer.

[0017] In addition, part of the surface oxide layer of the Ti raw material may be covered by the Ar from the deposition coating. + Ion etching.

[0018] Here, by deposition coating, a Ti ion deposition layer can be formed on the surface oxide layer, on the etched surface of the Ti raw material, and on the inner side below the surface oxide layer of the Ti raw material, and an atomic mixed zone in which Ti of the surface oxide layer and deposited Ti ion particles are mixed can be formed.

[0019] Furthermore, the oxidation heat treatment may be performed in an atmospheric state, and the Ti element and Ti ion particles of the surface oxide layer may react with oxygen through the oxidation heat treatment to form an atmospheric heat-treated oxide layer.

[0020] More specifically, during the oxidative heat treatment, TiO 2-x The (0<x<1) structured conductive oxide layer may be formed by diffusion rearrangement between over-deposited Ti particles in the Ti ion deposition layer, defects, and O particles introduced from the atmosphere or existing in the surface oxide layer.

[0021] In addition, the method may further include: coating C particles on the surface oxide layer and the Ti ion deposition layer after the deposition coating, wherein the C particles may diffuse into the surface oxide layer and the Ti ion deposition layer through the oxidation heat treatment.

[0022] In addition, the method may further include performing Ar heat treatment or vacuum heat treatment on the Ti raw material after rolling.

[0023] Meanwhile, the acceleration voltage of the deposition coating may be 80 to 250 eV.

[0024] Furthermore, the area fraction (coverage %) of the Ti ion deposition layer on the Ti raw material surface may be 50% to 90%.

[0025] In addition, the thickness of the conductive oxide layer may be 50 to 500 nm.

[0026] In addition, the heat treatment temperature of the oxidation heat treatment may be 580 to 750° C., and the holding time may be 1 to 10 minutes.

[0027] Next, according to another aspect of the present disclosure, a Ti material for a fuel cell separator is provided, the Ti material comprising: a Ti raw material made of a pure Ti material or a Ti alloy material; a surface oxide layer formed on the Ti raw material; a Ti ion deposition layer, wherein Ti ion particles are deposited and coated on the Ti raw material and the surface oxide layer by physical vapor deposition (PVD); and a TiO2 layer formed around the deposited Ti ion particles. 2-x (0<x<1) structure formed conductive oxide layer.

[0028] In addition, a Ti ion deposition layer can be formed on a Ti raw material in which a portion of the surface oxide layer is oxidized by Ar from PVD. + Ion etching and exposure.

[0029] In addition, a Ti ion deposition layer may be formed on the surface oxide layer, on the etched surface of the Ti raw material, and on the inner side below the surface oxide layer of the Ti raw material, and an atomic mixed zone may be formed in which Ti of the surface oxide layer and deposited Ti ion particles are mixed.

[0030] In addition, the Ti material may further include an atmospheric heat-treated oxide layer formed on the surface of the surface oxide layer and the surface of the etched Ti raw material by reacting Ti elements and Ti ion particles of the surface oxide layer with oxygen through oxidation heat treatment.

[0031] In addition, by oxidative heat treatment, TiO can be formed by diffusion rearrangement between over-deposited Ti particles in the Ti ion deposition layer, defects, and O particles introduced from the atmosphere or existing in the surface oxide layer. 2-x (0<x<1) structured conductive oxide layer.

[0032] In addition, the Ti material may further include C particles coated on the surface oxide layer and the Ti ion deposition layer and then diffused into the inside of the surface oxide layer and the Ti ion deposition layer through oxidation heat treatment.

[0033] Furthermore, the Ti raw material may be Ar heat-treated or vacuum heat-treated.

[0034] Meanwhile, the area fraction (coverage %) of the Ti ion deposition layer on the Ti raw material surface may be 50% to 90%.

[0035] In addition, the thickness of the conductive oxide layer may be 50 to 500 nm.

[0036] According to the present disclosure, the following advantages are achieved.

[0037] First, the process is simple, and the coating is performed by applying an existing and widely commercialized process, which reduces costs and is suitable for large-scale production. The Ti separator coating implemented in the present disclosure mainly includes a PVD process and a heat treatment process. First, the Ti ion etching performed in the PVD process is a commonly used simple PVD process, rather than requiring additional equipment or being possible only under specific conditions like other conventional methods. In the case of the heat treatment process, the conductive oxide layer can be simply achieved using an ordinary heat treatment furnace under atmospheric conditions, rather than the conventional method of forming TiO from a Ti raw material. 2-x The method must be carried out under controlled atmospheric conditions such as low oxygen partial pressure and vacuum environment.

[0038] Secondly, compared with other methods, it has the advantage of achieving higher conductivity, which is conducive to improving and maintaining fuel cell performance. This allows the boundary between the conductive oxide layer and the raw material to remain unchanged, while using the oxide layer of the raw material to give the Ti material conductivity. Therefore, compared with the conventional method where there is a boundary, the contact resistance can be more effectively reduced. This can be achieved by physical deposition and heat treatment of Ti, which is the same element as the raw material, so that the conductive oxide layer is continuously distributed at the boundary of the raw material and the oxide layer (Ti ion atom mixing zone), thereby eliminating or minimizing the boundary resistance.

[0039] Third, compared with conventional methods, a coating was developed using a principle different from existing concepts to achieve a conductive oxide layer with excellent durability (corrosion resistance). In conventional methods, the oxidation reaction of Ti is controlled, or TiO is induced by using a reducing medium. 2 The reduction reaction to form TiO 2-x , forming a conductive oxide layer directly from Ti raw material. However, the disadvantage of these methods is that the process conditions for forming the conductive oxide layer are very limited, resulting in no further improvement in corrosion resistance or a weak structure. In contrast, in the present disclosure, heat treatment conditions can be set, which can further improve corrosion resistance by forming a conductive oxide layer through a diffusion rearrangement-based process, and a structurally corrosion-resistant conductive oxide layer can be formed. In addition, it can be seen that the post-forming treatment part of the coating material is also advantageous in terms of corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1An overview of a method of manufacturing the Ti material for a fuel cell separator of the present disclosure is shown.

[0041] Figure 2 , Figure 3 and Figure 4 pass Figure 1 The manufacturing method in FIG. 1 sequentially shows the Ti material for a fuel cell separator according to an embodiment of the present disclosure.

[0042] Figure 5 and Figure 6 pass Figure 1 The manufacturing method in FIG. 1 sequentially shows the Ti material for a fuel cell separator according to additional embodiments of the present disclosure.

[0043] Figure 7 and Figure 8 is a surface cross section of an embodiment of the rolling and heat treatment (Ar atmosphere) steps of the manufacturing method according to the present disclosure.

[0044] Fig. 9 and Fig.10 is a surface cross section according to another embodiment of the rolling and heat treatment steps.

[0045] Fig.11 and Fig.12 An overview of the Ti ion etching step of the manufacturing method of the present disclosure is shown.

[0046] also, Fig.13 , Fig.14 and Fig.15 The Ti material for a fuel cell separator according to an embodiment of the present disclosure is sequentially shown, in which an Ar heat-treated Ti raw material is applied through a manufacturing method.

[0047] Fig.16 , Fig.17 and Fig.18 The Ti material for a fuel cell separator according to an embodiment of the present disclosure is sequentially shown, in which a vacuum heat-treated Ti raw material is applied through a manufacturing method.

[0048] Fig.19 , Fig. 20 , Fig.21 and Fig. 22 is a TEM cross-sectional view of an oxide layer according to an embodiment of the present disclosure.

[0049] Fig.23 , Fig.24 , Fig.25 and Fig.26 is a surface XPS depth profile through oxidation heat treatment conditions according to an embodiment of the present disclosure.

[0050] Fig. 27 and Fig.28 is a RAMAN spectrum through oxidative heat treatment conditions according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0051] Hereinafter, embodiments of the present disclosure will be described in detail with reference to exemplary drawings, and since these embodiments as examples can be implemented in various forms by those skilled in the art to which the present disclosure pertains, they are not limited to the embodiments described herein.

[0052] In order to fully understand the present disclosure, its operating advantages and objectives to be achieved by implementing the present disclosure, it is necessary to explain exemplary embodiments of the present disclosure and the contents disclosed in the accompanying drawings with reference to the accompanying drawings.

[0053] Furthermore, in the description of the present disclosure, when it is determined that the description may unnecessarily obscure the subject matter of the present disclosure, the repeated description of well-known related arts will be reduced or omitted.

[0054] Figure 1 An overview of the method for manufacturing the Ti material for fuel cell separator of the present disclosure is shown. In addition, Figures 2 to 4 pass Figure 1 The manufacturing method in the embodiment of the present disclosure sequentially shows the Ti material for the fuel cell separator, and Figure 5 and Figure 6 pass Figure 1 The manufacturing method in the figure sequentially shows the Ti material for a fuel cell separator according to additional embodiments of the present disclosure.

[0055] In the following, reference Figures 1 to 6 , a Ti material for a fuel cell separator and a method for manufacturing the same according to the present disclosure will be described.

[0056] The present disclosure develops a material coating technology for a Ti separator for a fuel cell, which is more efficient in terms of performance and manufacturing process by using a combination of a PVD process and a heat treatment process. The technology is a non-equilibrium process, rather than an equilibrium process method that uses only oxidation, reduction reaction or diffusion process like the existing method, and its principle is to form a conductive oxide layer on the Ti material. Therefore, compared with the existing technology, in terms of performance, higher corrosion resistance and conductivity will be ensured, while also having performance suitable for pre-coating and post-forming processes. In addition, by implementing the technology using commonly commercialized equipment under simple conditions, this development has been made, making the manufacturing process a process more suitable for the commercialization of Ti separators.

[0057] The present disclosure relates to a Ti material for a metal fuel cell separator and a method for manufacturing the same, as well as coating and surface treatment of the Ti material. Ti is a pure Ti material such as grade 1 or 2 or an alloy thereof, and the material may be in a state in which a material having a thickness of 0.3 mm or more that has been heat-treated from BA (bright annealing: a heat treatment process using nitrogen, hydrogen, argon or a mixture of these gases (these gases are non-oxidizing gases), similar to a stainless steel bright annealing process) is further rolled to a thickness (0.08 to 0.1 mm) required for the application separator (non-heat-treated) or a state in which the material is further heat-treated to ensure mechanical properties suitable for forming a separator after further rolling. In the present disclosure, the material is used in a heat-treated state to obtain mechanical properties suitable for press forming before coating.

[0058] Next, as a coating method, indoor sheet or roll-to-roll coil coating is performed using a PVD (physical vapor deposition) device (ion etching and vapor deposition coating), and then an oxidative heat treatment is performed to form a conductive oxide layer on the surface of the coated Ti separator. In this case, a heat treatment furnace capable of furnace atmosphere control (such as vacuum and oxygen partial pressure) can be used, but generally, a heat treatment furnace performed in an atmospheric state is acceptable.

[0059] Then, through molding and machining, fuel cell separators for the negative and positive electrodes can be manufactured.

[0060] More specifically refer to Figures 2 to 4 , the material of the Ti raw material 11 as the Ti raw material is pure titanium or a titanium alloy. The pure titanium used here refers to a material containing 98.8% or more Ti. For example, pure titanium may be one of the pure titanium materials in ASTM grade 1, 2, 3 or 4, which are very economical and easy to process. A titanium alloy is a material containing 70% or more Ti and having a balance of alloy elements and impurity elements. In the present invention, pure titanium is preferably used as the base metal as a material more suitable for the separator.

[0061] Regarding the PVD and heat treatment processes, the original purpose of the PVD technology is to form a physically uniform thin film layer on the material to be coated (target) together with the reaction gas in a vacuum plasma atmosphere. However, the purpose of the PVD process in the present disclosure is to simultaneously introduce artificial over-deposition and structural disorder of the Ti element into the surface of the Ti raw material and the oxide layer region on the surface of the raw material, so as to form a conductive TiO on the surface of the Ti raw material. 2-x Therefore, during the heat treatment, conductive TiO can be formed by diffusion rearrangement (restoration of structural disorder) between over-deposited Ti particles, defects, and O particles (introduced from the atmosphere or present in the oxide layer on the surface of the base metal) in the local area of ​​the deposited Ti particles. 2-x (0<x<1). An example is shown below.

[0062] Ti(s)+(2n-1)TiO 2 (s)→2Ti n O 2n-1(s)

[0063] nTiO 2 +V o →Ti n O 2n-1

[0064] PVD methods that can achieve the above process include ion plating, bias sputtering, ion beam assisted deposition (IBAD), etc. The advantages of these methods are that in the deposition of Ti + ions, Ar + The ions collide simultaneously, which not only partially removes (etches) the oxide layer on the surface, but also transfers energy to the Ti ion deposited layer 13 and the Ti raw material 11 below the surface, resulting in the displacement of the crystal structure and the consistent formation of an atomic mixed layer between the deposited Ti ion particles 21 and the Ti raw material 11. Then, after heat treatment, a conductive oxide layer 15 with good corrosion resistance and adhesion is formed in this area.

[0065] Hereinafter, the PVD process will be referred to as "Ti ion etching".

[0066] Hereinafter, the structure of the Ti conductive oxide layer is described in more detail. First, the surface oxide layer 12 of the Ti raw material 11 is formed by a process of rolling to a thickness suitable for use as a separator material, and undergoes a heat treatment process to ensure formability. The surface oxide layer 12 of the Ti raw material 11 may include all states in which the BA heat-treated raw material has been 1) rolled only to a thickness of 0.08 to 0.15t (unheated material) and after rolling, 2) subjected to Ar heat treatment in a low oxygen atmosphere, or 3) subjected to vacuum heat treatment. All three states have TiO on the surface of the raw material. 2 A surface oxide layer 12 is formed, but the thickness and structure of this layer may vary throughout the process.

[0067] Figures 7 to 10 The cross-section and EDS composition mapping photos of the surface oxide layer of the heat-treated Ti raw material are shown in Figure 2. Figures 7 and 8 is an Ar heat-treated Ti raw material having a surface oxide layer of 100 to 200 nm, and Figures 9 and 10 The vacuum heat-treated titanium raw material has a surface oxide layer of less than 10 nm. That is, the thickness of the surface oxide layer ranges from several nanometers to several hundred nanometers, and the thickness becomes thinner and more uniform in the order of non-heat treatment, Ar heat treatment and vacuum heat treatment.

[0068] Next, Ti ion particles 21 etched by Ti ions are distributed inside and at the surface boundary of the surface oxide layer 12 of the Ti raw material 11. During the PVD process, these Ti ion particles 21 are also deposited on the surface oxide layer of the Ti raw material and on the surface of the Ti raw material 11. + Ion bombardment removes the oxide layer on the raw material surface.

[0069] Including the surface oxide layer of Ti raw material, + Ion bombardment (such as vacancies, intrusion of Ti ions, lattice displacement defects, etc.) partially removes the surface oxide layer 12 of the Ti raw material 11 to form a disordered region with irregular structure near the surface. In this region, the Ti ions diffuse the collision energy with the Ti ion deposition layer 13 to generate an atomic mixing zone (atomic mixing zone) close to the raw material surface.

[0070] The atomic mixed region refers to the region where the Ti particles deposited by PVD and the raw material Ti are in a mixed state. This layer has a gradient pattern from the inside of the raw material to the surface, which depends on the deposition depth of the Ti ions and is used to maintain the bonding force between the conductive oxide layer 15 and the raw material.

[0071] Next, when a heat treatment process is performed, a conductive oxide layer 15 is formed in the region around the Ti ion-deposited particles.

[0072] During the heat treatment, the Ti / TiO 2 As the fraction increases, the oxide layer structure changes from TiO 2 Rearrange to Ti 1+x O 2 (For convenience, the chemical symbols of the conductive oxide formed on the structure by diffusion rearrangement of over-deposited Ti particles and defects will be represented as such.)

[0073] In addition, when the penetration depth of Ti ion deposition reaches the surface and the area below the raw material, the excessive deposition of Ti particles and Ar + The diffusion rearrangement of defects formed by ion collision forms Ti in the atomic mixing zone. 1+x O 2 (0<x<1). TiO2 is formed around the Ti ion deposition particles from the outer oxide layer to the atomic mixing zone of the raw material. 1+x O 2 A conductive oxide layer 15 is formed in the region.

[0074] Next, in the outermost oxide layer existing in the Ti raw material 11, there is an atmospheric heat-treated oxide layer 16, which is produced by the reaction of Ti elements diffused outward from the raw material during the heat treatment and the Ti ion deposition particles themselves with oxygen, and this area is also formed by some Ti ion deposition particles and Ti 1+X O 2 Zone Mixing. Depending on the heat treatment temperature and time conditions, the atmospheric heat treated oxide layer 16 thus formed can be used to impart a higher corrosion resistance to the separator.

[0075] In contrast, Figure 5 and Figure 6 The case with C coating is shown. Figure 3 When C coating is performed after Ti ion etching in the PVD process, such as Figure 6 As shown, the C particles 22 diffuse into the oxide layer during the oxidation heat treatment and are included in the oxide layer, or are combined with the Ti ion particles 21 or the raw material Ti diffused outward. 2 The ions may induce further reduction reactions in the layer or contribute to the conductivity itself.

[0076] Next, Fig.11 and Fig.12 An overview of the Ti ion etching step of the manufacturing method disclosed herein is shown. In addition, Figures 13 to 15 The Ti material for a fuel cell separator according to an embodiment of the present disclosure is shown in sequence, wherein an Ar heat-treated Ti raw material is applied by a manufacturing method, and Figures 16 to 18 The Ti material for a fuel cell separator according to an embodiment of the present disclosure is sequentially shown, in which a vacuum heat-treated Ti raw material is applied through a manufacturing method.

[0077] With reference to this, the steps of the manufacturing method of the present disclosure will be described in more detail.

[0078] 1) Ti ion etching by PVD device

[0079] In the present disclosure, the purpose of the PVD process is to artificially introduce over-deposition and structural disorder of Ti in the interface region between the surface of the Ti raw material 11 and the surface oxide layer 12 by methods such as ion plating, bias sputtering or ion beam assisted deposition (IBAD). To this end, the PVD process steps include Ti ion etching and C-PVD processes, which can be performed only by Ti ion etching or by Ti ion etching and C-PVD together, depending on the characteristics required for the separator for the fuel cell.

[0080] Ti ion etching is a process in which Ar +Ion bombardment and Ti ion deposition process. When Ti ionized in plasma + When ions are accelerated with high voltage and deposited on a surface, Ar + The ions also collide with the raw material, removing oxides from the surface and causing surface structural disorder (lattice displacement, vacancies, etc.) of the raw material. This collision energy helps to homogenize the Ti deposit layer and diffuse the deposited Ti particles into the raw material for forming an atomic mixing layer (see Fig.11 and Fig.12 ). In this way, during the heat treatment, a diffusion rearrangement between the defects in the local area of ​​the interface of the physically over-deposited Ti particles and the deposited Ti particles and the O particles introduced from the surface oxide layer of the raw material or from the atmosphere is achieved, and in the process of restoring this structural disorder, the conductive TiO 2-x That is, as a method for making the Ti oxide layer conductive, in the conventional method (forming TiO by reaction of Ti and O under heat treatment conditions of reducing gas or low oxygen partial pressure), 2-x method, or by using a reduction catalyst such as C to TiO 2 Reduction to TiO 2-x In the method of using a chemical reaction under specific conditions, a TiO 2 The lack of O in the structure leads to the formation of TiO 2-x , and in this development, the fraction of Ti particles in TiO 2 The Ti particles are then rearranged by diffusion to form Ti 1+x O 2 To impart conductivity.

[0081] Utilizing this diffusion rearrangement mechanism, TiO can only be formed under low oxygen partial pressure and limited temperature and time conditions. 2-x , which is the same as the conventional patent or literature method, can only be achieved by atmospheric heat treatment, and can reduce the restrictions on heat treatment temperature and time conditions, by strengthening the outermost TiO 2 The oxide layer (i.e., protective layer) is used to achieve additional improvement in corrosion resistance. In addition, no special pretreatment process is required to control impurities before coating, and it can be applied relatively independently of the state of the oxide layer surface of the Ti raw material, thereby reducing the various conditions of Ti raw material pretreatment constraints required for the separator process so far.

[0082] In addition, under the atmospheric heat treatment conditions of the subsequent process, Ti ion etching inhibits the uneven growth of the Ti oxide layer, which is beneficial to the control and condition establishment of the oxidation heat treatment process. Generally, the growth of the Ti oxide layer by heat treatment is achieved by the reaction of Ti diffused outward from the raw material with external O. However, in the case of Ti ion etching, in addition to forming the outermost oxide layer, a certain amount of O introduced from the atmosphere is absorbed into the disordered region by ion bombardment with Ti deposited on the surface of the raw material, and is consumed to form Ti. 1+x O 2 This provides the temperature and time conditions for the heat treatment required to more reliably ensure the target resistance value.

[0083] In the present disclosure, the purpose of the Ti ion etching process is not to form a general coating, but to increase the fraction of Ti particles in the oxide layer and surface of the raw material, while introducing defects during the heat treatment process to promote the diffusion and rearrangement of Ti particles, thereby forming TiO 2-x Therefore, in order to ensure that the Ar + The atomic mixing zone is formed by the collision effect of ions and the binding force of Ti ions located on the surface of the raw material. The acceleration voltage can be in the range of 80 to 800V, and a more suitable voltage can be in the range of 180 to 250eV. At an acceleration voltage greater than the above range, Ar + The ions may not cause a collision effect on the surface of the raw material and the Ti deposition layer, but penetrate into the raw material, and the Ti ions may also be injected into the raw material instead of being located on the surface of the raw material, which makes it difficult to form the conductive oxide layer 15. In addition, at an acceleration voltage less than the above range, when Ar + When the collision effect of ions is not sufficient to form the conductive oxide layer 15 by heat treatment, or when an atomic mixing zone is not formed due to insufficient Ti ion bombardment energy, there may be a problem of reduced corrosion resistance and durability of the formed processing parts due to insufficient bonding force of the conductive oxide layer 15.

[0084] For the Ti ion etching time, Ti ion etching is performed for 1 to 4 minutes so that the coverage (%) of Ti ion deposition is not excessive or insufficient, and more preferably 2 to 3 minutes. When the coverage of Ti ion deposition exceeds the above time, the formation of the conductive oxide layer 15 may become difficult because the oxidation of the external Ti ion deposition particles during the heat treatment increases the resistance, and the diffusion of O particles into the oxide layer is blocked by the oxide layer. In a shorter time than the above, the amount of deposited Ti ions becomes insufficient, making it difficult to expect to form the conductive oxide layer 15 by increasing the Ti fraction inside the oxide layer or on the surface of the raw material, and even if a conductive oxide is formed, the proportion of the insulating oxide on the outside becomes relatively high within the same heat treatment time, making it difficult to ensure stable conductivity. As a result, depending on the acceleration voltage and time of Ti ion etching, the area fraction (coverage %) of the Ti ion deposition covering the surface of the raw material is suitable to be 50% to 90% of the total surface of the raw material, and the thickness of 50 to 200nm is suitable. The thickness of the conductive oxide layer 15 formed from the periphery of the Ti ion deposition to the atomic mixing zone can be at least 50 to 500nm. Table 1 below shows the change in contact resistance with Ti ion etching time and oxidation heat treatment, and Figures 15 to 20 Graph showing the change in contact resistance as heat treatment proceeds for each Ti feedstock condition.

[0085] Figures 13 to 15 The Ti raw material after Ar heat treatment is shown. Fig.13 The Ti raw material before heat treatment is shown. Fig.14 The Ti raw material subjected to oxidation heat treatment for 3 minutes and Fig.15 The Ti raw material after oxidative heat treatment for 5 minutes is shown. Figures 16 to 18 It is a Ti raw material that has been vacuum heat treated. Fig.16 shows the situation before heat treatment, Fig.17 The case of oxidative heat treatment for 3 minutes is shown, and Fig.18 The case where the oxidative heat treatment was performed for 5 minutes is shown.

[0086] Table 1

[0087]

[0088] 2) Oxidation heat treatment

[0089] The oxidation heat treatment process is used to impart conductivity and corrosion resistance to the separator surface after Ti ion etching. In the present disclosure, the oxidation heat treatment can be performed by atmospheric heat treatment rather than under specially controlled atmospheric conditions, and can be performed by controlling the gas type and oxygen partial pressure to obtain a more stable quality. The process sequentially includes heating the separator by exposing the separator to be heat treated to a target temperature, then maintaining the separator at the corresponding temperature for a period of time, and then air cooling.

[0090] The process of ensuring conductivity is made possible by inducing outward diffusion of Ti atoms of the raw material and diffusion of Ti atoms over-deposited by Ti ion deposition during the oxidation heat treatment temperature-time, which converts the TiO 2 oxide layer or TiO further prepared by heat treatment 2 The structure of the oxide layer changes to Ti 1+x O 2 Therefore, in terms of ensuring conductivity, the oxidation heat treatment temperature-time conditions are determined by the deposition of Ti atoms in TiO 2 The energy and diffusion rate required for diffusion in the oxide layer and the formation of Ti by the diffusion and rearrangement of Ti and O particles 1+x O 2 According to the experimental results, the heat treatment temperature range of 580 to 750°C and the holding time of 1 to 10 minutes are suitable for this process, and the results are shown in Table 2.

[0091] When the heat treatment temperature is lower than 580° C., the energy required for diffusion may be insufficient, and when it exceeds 750° C., the rapid growth of the oxide layer may increase the resistance. In addition, a holding time of less than 1 minute may not provide sufficient time for diffusion and rearrangement, and a holding time of more than 10 minutes may cause excessive growth of the oxide layer, making it impossible to achieve the target conductivity.

[0092] The corrosion resistance conditions of the separator can be set within the temperature and time range that ensures the target conductivity. Generally, the corrosion resistance or oxidation resistance of Ti materials can be further improved by heat treatment, which is related to the thickness, composition and structure of the Ti oxide layer. 2-x In the chemical bonding state, it is known that Ti 2 O 3, TiO, etc. have better corrosion resistance than non-stoichiometric compound states (TiO 1.8, 1.9...). The corrosion resistance of Ti raw materials that have been anodized or oxidatively heat treated is better than that of untreated Ti. The present disclosure also confirms that within the range of ensuring conductivity, when subjected to higher temperatures and longer holding times, better corrosion resistance can be achieved in a fuel cell corrosive environment. This is particularly evident in corrosion evaluations under harsh conditions, where a heat treatment time of 5 to 10 minutes in the range of 680 to 720°C has a high discriminant power for corrosion resistance.

[0093] It can be seen that in the case of C coating, the inflow of O into the oxide layer is blocked at the outermost part of the coating due to the C layer, so Ti 1+x O 2 The formation of is delayed, and the reduction in contact resistance occurs slightly later. It is believed that this is because the reduction in contact resistance is caused by the influx of O and the diffusion of Ti ion deposition particles at a given temperature from the moment when C diffuses into the oxide layer. Therefore, considering the delay time caused by the C coating, it is preferably maintained for about 1 to 3 minutes compared to when there is no C layer. As described above, it was found that the corrosion resistance is more significant when maintained for a long time at high temperature, in which case the heat treatment time and temperature conditions are preferably within the range of 680 to 720°C for 5 to 10 minutes.

[0094] Table 2

[0095]

[0096] Hereinafter, aspects of the conductive oxide layer and the corrosion resistance enhancement are described.

[0097] 1) Formation of conductive oxide layer

[0098] Generally, it is known that TiO 2-x The formation under controlled atmosphere (oxygen partial pressure, temperature, etc.) depends on the reaction of O and Ti at the boundary between the raw material and the oxide layer, which is affected by the diffusion rate of O and Ti elements in the oxide layer on the surface of the raw material. 2 The diffusion rate in the oxide layer is high, while the diffusion rate of Ti is relatively low, so when the amount of O supplied to the oxide layer during heat treatment is limited, the fraction of Ti diffused outward from the raw material in the boundary region between the raw material and the oxide layer becomes relatively high, and TiO is formed by local O deficiency in the oxidation reaction of Ti. 2-x The TiO formed as described above 2-x The phases are realized through an equilibrium process that depends on the diffusion and chemical reactions of Ti and O atoms.

[0099] Formation of TiO2-x One of the other methods is to use PVD equipment to deposit TiO 2 The surface of the oxide layer is Ar + A method of sputtering followed by heat treatment under vacuum.

[0100] The principle used is that after the Ar + During the process of sputtering artificially introducing structural disorder in the oxide layer and the crystal structure of the raw material surface, TiO is formed due to the increased diffusion rate of the Ti element and local O deficiency. 2-x Such Ar + Sputtering involves a non-equilibrium process. However, TiO 2 Layer reduction to TiO 2-x Only by repeated Ar + This can be achieved by sputtering or by heat treatment at high temperature (>1000°C) for several hours under vacuum.

[0101] As mentioned above, TiO 2-x Important factors in the formation reaction are 1) the diffusion rate of Ti and 2) the relative ratio of Ti to O at the boundary between the feedstock and the oxide layer. + When the ions collide with the surface of the Ti raw material, the TiO 2 The oxide layer and the crystal structure of the Ti raw material cause a certain degree of disorder. + In addition to ion etching, when Ti ions are deposited on the surface of the raw material at an acceleration voltage of tens to hundreds of eV, TiO 2 The ratio of Ti content inside the oxide layer and on the surface of the raw material may be forced to increase. + During ion etching and Ti ion deposition, due to Ar + The defect energy accumulated by ion bombardment, including vacancies, interstitials, and atomic displacements, can promote the diffusion of Ti and O atoms (especially having the effect of reducing the activation E required for Ti diffusion). In addition, during the heat treatment, the artificially added Ti particles interfere with the Ti and O rearrangement process, resulting in the formation of TiO 2 That is, for the stoichiometric deviation from TiO 2 Lack of or removal of O, conductive oxide (Ti 1+x O 2 ) is formed by artificial (PVD method) over-deposited Ti particles and diffusion rearrangement of defects in the crystal structure rather than by structural changes through balanced diffusion and chemical reactions.

[0102] In summary, the conductive oxide layer is formed by artificially introducing over-deposited Ti particles and structural defects at the boundary between the oxide layer and the Ti raw material surface during Ti ion etching, and then performing heat treatment under appropriate temperature and time conditions to restore the defects through the diffusion and rearrangement of Ti and O to form a structurally conductive non-stoichiometric Ti oxide, i.e., Ti 1+x O 2 To achieve.

[0103] Therefore, even without heat treatment at high temperature (>1000°C) for several hours as in conventional methods, TiO can be formed within a few minutes by segregation of these elements using a non-equilibrium process of PVD at a relatively low temperature (600 to 700°C). 2-x or Ti 1+x O 2 In addition, since the diffusion rearrangement phenomenon of Ti and O elements in the existing Ti raw material oxide layer and the raw material surface is used, vacuum or low oxygen partial pressure conditions required for oxidation or reduction reactions as in conventional methods are not required, and even by heat treatment in the atmospheric state, TiO can be formed. 2-x or Ti 1+x O 2 To ensure conductivity.

[0104] In the present disclosure, the reason why Ti particles are deposited by Ti ion etching methods (such as ion plating, bias sputtering or IBAD) instead of ion implantation is that in the case of ion implantation, the surface properties of the deposited particles change during the process of penetrating into the raw material, while Ti ion etching can form a fine coating without changing the surface properties of the raw material. That is, the oxide layer of the raw material can be maintained and used to more effectively form a conductive oxide layer, and since the method is used as coating and sputtering at the same time, the Ti ion deposited particles can be distributed inside the oxide layer on the surface of the raw material, outside the surface of the raw material, and even inside some raw materials to form an atomic mixing layer. When the Ti ion deposited particles exist continuously by gradually transitioning from the oxide layer to the atomic mixing zone under the surface of the raw material, the stress caused by the formation of the deposited layer can be minimized, and the advantage is that the adhesion of the coating remains excellent even after heat treatment. Therefore, even in the coating method of the diaphragm with a [pre-coating-post-treatment] method, such as a roll-to-roll PVD process, a more durable conductive oxide layer structure can be achieved.

[0105] Another advantage of this method of forming a conductive oxide layer is that, compared with conventional methods, higher conductivity can be ensured, which is relatively independent of the thickness of the oxide layer formed on the surface by heat treatment. In conventional methods, since the boundary between the conductive oxide layer and the raw material is discontinuous, or there is a fine insulating boundary layer, the resistance increases accordingly, and when the thickness of the oxide layer on the surface exceeds a certain level (about 100 to 200nm), the conductivity tends to decrease rapidly. However, since the position of the conductive oxide layer is distributed by Ti ion deposition from the atomic mixing zone in contact with the raw material body to the boundary between the raw material and the oxide layer on the surface and the outer oxide layer continuously exist, there is no boundary between the raw material and the conductive oxide layer, therefore, even if the thickness of the oxide layer is thicker than other conventional methods, the method disclosed in the present invention also shows higher conductivity. This result can be confirmed from the measured values ​​of the contact resistance of the embodiments and comparative examples in Table 1.

[0106] 2) Enhanced corrosion resistance

[0107] Another advantage of the method for forming a conductive coating by Ti ion etching and heat treatment according to the present disclosure is that it has very excellent corrosion resistance in a fuel cell corrosive environment compared to a coating for a Ti separator achieved by conventional methods. This enhanced corrosion resistance can be described by the formation position, shape and structure of the conductive oxide layer.

[0108] Location of the conductive oxide layer

[0109] By converting the Ti oxide layer into TiO 2 Modified to TiO 2-x The location of the conductive oxide layer produced during the process of imparting conductivity varies slightly depending on the method and process. For example, conventional TiO 2-xThe formation process is achieved by the raw material Ti diffusing outward in a vacuum and reducing atmosphere to react Ti and O from the surface, or by the reduction reaction occurring from the outermost layer of the oxide layer mediated by applying a reducing agent directly to the surface of the oxide layer. In both cases, the oxide layer of the Ti raw material is used, which has excellent corrosion resistance compared with other methods using heterogeneous material coatings. However, due to this method, the location of the conductive oxide layer exists at the outermost side and is therefore directly exposed to the corrosive environment. In the former case, there is a boundary between the surface of the raw material and the conductive oxide layer formed thereon, which may increase the resistance when the conductive oxide layer is self-dissipated in the long-term harsh fuel cell corrosion environment, while in the latter case, the conductive oxide layer exists at the outermost side and is therefore preferentially attacked by the corrosive environment, which may lead to loss of function. However, in the present disclosure, the conductive oxide layer is formed near the surface of the raw material, that is, the innermost side of the entire oxide layer, and is formed at the boundary of the oxide layer through Ti ion etching and heat treatment processes. Therefore, the conductive oxide layer is not exposed to the external corrosive environment, but is protected from the influence of the external oxide layer formed by heat treatment, and can be maintained for a longer time in a harsh corrosive environment.

[0110] Shape of conductive oxide layer

[0111] The corrosion resistance of metal materials is also closely related to the shape of the oxide layer on the surface of the raw material. When the oxide layer contains many defects, such as microcracks or porous structures, these defects provide diffusion paths for corrosive anions and oxygen in a corrosive environment, causing these elements to adsorb and corrode at the interface of the raw material and the oxide layer, thereby losing its effectiveness as a protective layer. In particular, when there is a clear boundary between the raw material and the coating or between the raw material and the oxide layer, the current coupling phenomenon caused by the difference in the electrochemical potential of the two regions promotes the delamination of the coating or oxide layer. Generally, the oxide layer on the surface of Ti materials that have undergone atmospheric oxidation heat treatment to improve the corrosion resistance of Ti consists of porous TiO 2 The oxide layer and the inner surface of the dense and thin TiO 2 +TiO 2-x The inner layer is composed of two layers, and in a harsh corrosive environment containing aggressive negative ions, the corrosion resistance is mainly determined by the inner layer.

[0112] Even if the conductive oxide layer formed by the reaction of Ti and O on the surface of the raw material according to the conventional method has TiO 2 +TiO 2-xStructure, due to the extremely limited temperature and time conditions of the oxidation heat treatment, it may not be possible to ensure sufficient thickness, and the boundary between the raw material and the oxide layer is distinguished, which has limitations in increasing corrosion resistance. However, when the conductive oxide layer is realized by Ti ion deposition and heat treatment as in the present disclosure, there is no boundary between the raw material and the conductive oxide layer, because the atomic mixed area is converted into a conductive oxide layer and contained in the raw material, and a dense layer is formed by increasing the Ti fraction and diffusion and rearrangement rather than by oxidation reaction growth. Therefore, compared with other methods, it is possible to have excellent corrosion resistance in terms of structural shape. In addition, since the conductive oxide layer formed in this way has excellent bonding with the raw material, it is possible to minimize the deterioration of the corrosion resistance of the treated part, which is a fragile part in the [pre-coating-post-formation] method.

[0113] Structure of surface oxide layer (heat treatment conditions)

[0114] According to the temperature and time of oxidation heat treatment, TiO 2 It may exist in the form of anatase, rutile, or a mixture of the two. In terms of corrosion resistance, the relative trend of these structures is that the rutile structure is more inert than the anatase structure, thus having excellent corrosion resistance, and it is reported that with increasing heat treatment time, TiO in the temperature range of 500 to 650 ° C 2 The oxide layer has higher corrosion protection performance. In addition, with the increase of oxidation heat treatment temperature, the TiO 2 The structure of TiO2 gradually changes from anatase > anatase + rutile > rutile, which may have higher corrosion resistance. However, in the previously disclosed patent method, the method of forming the conductive oxide layer is carried out by chemical reaction of Ti and O under limited oxygen partial pressure, so the temperature and time conditions of heat treatment are very limited. That is, under conditions exceeding this range, TiO2 2 The growth of will quickly reduce the conductivity, which has limitations in ensuring additional corrosion resistance by oxidative heat treatment. However, in the present disclosure, since the conductive oxide layer is formed by structural rearrangement through the diffusion of Ti and O atoms, rather than by a chemical reaction between Ti-O as in the conventional method, heat treatment can be performed within a relatively wide temperature and time range even in the atmosphere. In other words, the method of ensuring conductivity by the method of the present invention enables heat treatment at higher temperatures and longer times, which can maximize the rutile fraction of the outer Ti oxide layer, thereby further maximizing corrosion resistance. However, it is pointed out again here that the range of heat treatment conditions for achieving conductivity is determined within the temperature-time range, as referenced in the table, within which range, due to the TiO generated on the outer surface 2The increased resistance due to the oxide layer does not reduce the target conductivity.

[0115] Next, detailed conditions of the PVD process for the Ti separator coating for fuel cells implemented by the present disclosure are described in Table 3, and manufacturing conditions and performance evaluation results of Examples and Comparative Examples for forming the conductive oxide layer and verifying corrosion resistance are shown in Table 4. Details of the manufacturing conditions in each case are as follows.

[0116] Example 1

[0117] The Ti raw material used was BA heat-treated grade 1 material, rolled to 0.1t, and then heat-treated in an Ar atmosphere at 650°C for about 1 to 2 minutes. -6 At a vacuum degree of 100°C and a temperature of 100±10°C, Ti ion etching was performed in a PVD chamber at BIAS180eV for 2 minutes and left for 24 hours to form a natural oxide film on the surface after coating. Oxidation heat treatment was performed in a conventional induction heating heat treatment furnace under atmospheric atmosphere: ① 600°C for 10 minutes, ② 620°C for 7 minutes, and ③ 690°C for 5 minutes, then taken out and air-cooled in the atmosphere.

[0118] Example 2

[0119] The raw materials and oxidation heat treatment conditions were the same as in Example 1, and in the PVD process, C deposition after Ti ion etching was performed at BIAS 180 eV for 2 minutes as in Example 1.

[0120] Example 3

[0121] The Ti raw material used is a sample that was subjected to vacuum heat treatment (vacuum degree 10 to 30 Pa, 650 to 700°C, and heat treatment for about 1 to 2 minutes) after rolling 0.1t BA heat-treated grade 1 material, and then subjected to the same PVD-Ti ion etching process as in Example 1, and then subjected to oxidation heat treatment in air at ① 650°C for 5 minutes and ② 690°C for 5 minutes, respectively.

[0122] Comparative Example 1-①

[0123] The Ti raw material used was a BA heat-treated Ti grade 1 material, which was rolled to 0.1t as is (without heat treatment). The PVD process was carried out under the same process conditions as in Example 2, and then vacuum heat treated at 600°C for 10 minutes (vacuum degree 10 to 30 Pa, temperature rise 20°C / min for 30 minutes, maintained at 600°C for 10 minutes, and chamber cooling for 3 hours).

[0124] Comparative Example 1-②

[0125] On the same raw material as in Comparative Example 1-①, a PVD process was performed under the same conditions as in Example 1, followed by Ti ion etching (BIAS 180 / 70, for 2 minutes), followed by TiO 2 Deposition (BIAS100eV, O 2 100cc, 2 minutes) and C deposition (BIAS 180eV, 2 minutes). The heat treatment was the same as in Comparative Example 1-①, using vacuum heat treatment.

[0126] Comparative Example 2

[0127] Pure Ti material treated by BA 2 SO 4 Acid pickling and vacuum reduction heat treatment to form TiO on the surface 2-x Then, C coating is performed after plasma pretreatment in the CVD process. In this case, by adding C 2 H 2 In addition, N 2 To induce TiO(C,N) bonding as a method of attaching C to the surface of the Ti oxide layer. (Temperature 300℃ / pressure 10Pa / C 2 H 2 Gas containing N / voltage DC 2.0kV)

[0128] Comparative Example 3

[0129] The solution dispersed with C nanocomposite after plasma pretreatment was applied on the surface of the vacuum heat-treated Ti 1 grade material by a roll coater. Then, an oxidative heat treatment was performed at 600 to 620°C for 10 to 30 seconds under a low oxygen partial pressure of 10 to 30 Pa. The TiC compound present on the surface was then cleaned and reheated under vacuum at 580 to 600°C for about 1 minute to absorb TiC into the raw material.

[0130] Table 3

[0131]

[0132] Table 4

[0133]

[0134]

[0135] In the corrosion appearance, ○ is good, △ is partial corrosion, and × is complete corrosion.

[0136] Next, the results of the durability test of the embodiment of the present disclosure are described.

[0137] The corrosion test was conducted under conditions simulating the fuel cell environment, and the constant potential corrosion evaluation was divided into general and severe conditions. The conditions for each evaluation method are shown in Table 5 below. (Evaluation equipment: constant potential instrument)

[0138] Table 5

[0139]

[0140] Contact resistance measurement was performed for each Example and Comparative Example by inserting an evaluation sample between gas diffusion layers (GDL) and calculating the contact resistance by measuring the voltage applied to the sample by current at a pressure of 1.0 MPa. In this way, the contact resistance was compared before and after the corrosion evaluation.

[0141] The results of the formation of the conductive oxide layer are described.

[0142] In order to more clearly distinguish + The mechanism and location of the conductive oxide layer formed by ion sputtering and Ti ion deposition, as in Example 3, Ti ion etching is performed on the Ti raw material in a vacuum heat-treated state with a very sparse initial surface oxide layer (the thickness of the surface oxide layer in the vacuum heat-treated state is within about 10 nm. Fig. 9 ). Then the contact resistance between the Ti ion etched sample and the raw material was measured as a function of the heat treatment temperature and time conditions, as shown in Table 6. TEM, X-ray photoelectron spectroscopy (XPS) and RAMAN analysis were performed on each of the cases a), b), c) and d) to observe the changes in the composition and structure of the Ti oxide layer according to the heat treatment conditions. ( Figure 23 to Figure 28 )

[0143] As described above, the reason for examining the tendency of Ti oxide formation using a raw material having a small initial surface oxide layer is to confirm the mechanism of forming a conductive oxide layer by Ti ion etching while excluding the oxide layer existing on the surface of the initial raw material as much as possible. + Ion etching and Ti ion deposition were performed in an attempt to more clearly examine the phenomenon of the formation of a conductive oxide layer by diffusion rearrangement between over-deposited Ti elements and defects and O particles in the atomic mixing zone close to the surface of the raw material.

[0144] It can be seen from the results in Table 6 that when the heat treatment temperature and time required for the diffusion rearrangement of elements and defects in the conductive oxide layer are insufficient, the contact resistance after heat treatment increases, which is considered to be due to the initial Ti oxide layer formed in the outermost layer. However, after Ti ion etching, when the heat treatment exceeds 670°C for 5 minutes or 690°C for 3 minutes, the contact resistance drops rapidly and reaches a level of 0 to 1, which is a significantly different trend compared to the heat treatment results of the raw material without Ti ion etching under the same conditions.

[0145] Table 6

[0146]

[0147] Figures 19 to 22 The TEM cross-sectional photographs and heat treatment conditions of each material are shown in Table 6. The Ti raw material heat-treated in vacuum has a very thin oxide layer thickness of less than 10 nm, but after heat treatment at 690°C for 3 minutes ( Fig. 22 ), it can be seen that an oxide layer of about 300 nm has grown. The appearance of the oxide layer consists of an inner porous layer and an outer coarse-grained crystalline oxide layer, and the boundary between the oxide layer and the raw material formed by heat treatment is clearly divided. When Ti ion etching is performed on the surface of the vacuum heat-treated raw material, a Ti ion deposition layer of about 20 to 100 nm (average 50 nm) is formed ( Fig.19 ). However, since the deposition time is limited to 2 minutes to further promote the formation of the conductive oxide layer, the shape of the layer (coverage <80%) has a relatively regular curved or irregular shape. In particular, it can be seen that the area in contact with the raw material is an atomic mixed layer formed by Ar and Ti ion bombardment, and the boundary with the raw material is almost indistinguishable. Fig. 20 and Fig.21 The following are cross-sectional photographs of the oxide layer subjected to oxidation heat treatment at 650°C for 5 minutes (1800 mΩ) and 690°C for 5 minutes (0-1 mΩ) respectively. Fig. 22 In the figure, a cross section of the oxide layer heat-treated at 650°C for 5 minutes is examined. There is a Ti ion deposition layer on the raw material, and an oxide layer is formed thereon by heat treatment, and the outer oxide layer almost completely covers the Ti ion deposition layer. It can also be seen that the Ti ion deposition layer maintains almost the same thickness and shape as before the heat treatment. That is, it can be seen that the heat treatment temperature-time condition is not sufficient to cause diffusion rearrangement between Ti ion particles, defects, and O, and it can be inferred that due to the external TiO 2 As the oxide layer grows, the contact resistance increases significantly. Fig.21 In the cross section of the oxide layer in the state of heat treatment at 690°C for 5 minutes, it is observed that the thickness of the outer oxide layer and the Ti ion deposition layer grow and expand simultaneously, and the boundary between the Ti ion deposition layer and the oxide layer formed on the outside disappears due to diffusion. That is, it is believed that under the corresponding heat treatment conditions, the conductive oxide layer is formed by the diffusion rearrangement process between the oxide layer formed on the outside, the over-deposited Ti particles, the surrounding defects and the O particles to form Ti 1+ x O 2 .

[0148] By examining the boundary region between the Ti raw material and the oxide layer, it can be seen that when the Ti raw material was heat treated at 690 °C for 3 minutes, a crystalline oxide layer with a porous shape was grown on the surface of the raw material ( Fig. 22 It can be seen that after Ti ion etching, the Ti ion deposited layer ( Fig. 20 The enlarged photo in the figure has a fuzzy grain boundary and almost maintains the amorphous phase of the Ti ion deposition state before heat treatment ( Fig.19 However, after heat treatment at 690°C for 5 minutes ( Fig.21 ), a dense oriented grain structure was observed, which is different from the oxide layer formed on the Ti raw material. This is believed to be due to the formation of the conductive oxide layer through crystallization of diffusion rearrangement of Ti, O particles and defects at the boundary between the raw material and Ti ion deposition (i.e., atomic mixing zone) after Ti ion etching and heat treatment under certain time and temperature conditions. In addition, it can be seen that the boundary between the conductive oxide layer formed by Ti ion deposition and the raw material maintains continuity without any obvious distinction, so that the conductive oxide layer achieved by the present disclosure can have excellent bonding and corrosion resistance with the raw material. For the above phenomenon, XPS depth distribution and Raman spectroscopy were performed to analyze the composition of the Ti oxide constituting the oxide layer according to the depth and structural changes caused by the heat treatment conditions, and the results are shown in Figure 23 to Figure 26 as well as Fig. 27 and Fig.28 middle.

[0149] As a result of XPS analysis, it can be seen that when Ti ion etching is performed on the surface of the raw material, the Ti oxide layer is only partially present, and the fraction of Ti on the surface increases ( Fig.23 ). It can be seen that as a result of heat treatment at 650°C for 5 minutes ( Fig.24 ), on the outside of the oxide layer, except for TiO 2 In addition, Ti 2 O 3 and TiO oxides, which is similar to the results of the oxidative heat treatment of the raw materials ( Fig.26 ). However, when Fig.24 and Fig.25 As shown in Figure 2, when Ti ion etching is performed, the fraction of TiO in the oxide layer after heat treatment tends to remain slightly higher than that of the raw material ( Fig.26), which seems to be due to the increase in the fraction of Ti due to Ti ion deposition. In addition, in the case of condition b), unlike d), the distribution diagram of Ti oxide up to a certain depth is not linear and appears jagged, and this is considered to be due to the local difference in the Ti content at each location caused by Ti ion deposition. Unlike conditions d) or b) of the raw material, under the heat treatment condition c) where the contact resistance decreases rapidly, the obvious difference observed in the XPS results is that when sufficient heat treatment is performed after Ti ion etching, the new TiO 2 part, that is, it is assumed to be TiO 2-x The components form a certain depth in the direction from the inside of the oxide layer to the main body of the raw material, such as Fig. 27 This is the XPS result under the same heat treatment conditions (d) of the Ti raw material ( Fig.26 ) or at lower temperature conditions (b) after Ti ion etching ( Fig.24 ). In other words, it can be inferred that the difference in contact resistance is caused by the TiO 2-x The conductive oxide layer is formed inside the oxide layer. It is believed that the conductive oxide layer is formed below the surface of the raw material by a heat treatment process after Ti ion etching. + Defects formed by ion bombardment and over-deposited Ti particles by Ti ion etching are formed by diffusion rearrangement processes with O inside the raw material rather than by chemical reactions between O and Ti in the atmosphere on the surface of the raw material. Fig.24 As shown, the TiO 2 The reason why the oxide profile also shows jaggedness is that the distribution and depth of the disordered and atomic mixed regions formed inside the raw material during Ti ion etching cannot be locally uniform, so the Ti 1+x O 2 The distribution trend of the conductive oxide layer also follows this trend.

[0150] Fig. 27 and 28 RAMAN analysis results are shown to examine the changes in the composition of the oxide layer in response to Ti ion etching.

[0151] The oxide layer in the initial vacuum heat treatment state is very sparse, and due to the Ti of the raw material, it is difficult to obtain Raman analysis information about the Ti oxide, but the rutile peak is roughly visible, and it can be seen that the surface oxide layer exposed to the atmosphere at room temperature after Ti ion etching exists in an amorphous state with some anatase, such as Fig. 27A) in the middle. However, it can be seen that after heat treatment according to the conditions in Table 6, the structure changes to a structure with some common rutile-based anatase, although there are slight differences in each case (the main peaks of rutile-type titanium oxide appear at 240, 443 and 610, while other peaks appear at 319, 707 and 818). However, by examining the relationship between the change of the main peaks in the Raman spectrum with temperature and heat treatment time and the phenomenon of rapid resistance drop, it can be seen that the peaks of condition c) 690°C for 5 minutes have more obvious intensity compared with condition b) 650°C for 5 minutes, and the positions of the shifted main peaks return to the original positions (rutile 240 and 443), and new peaks such as 172 and 319 appear at positions that did not exist before.

[0152] In a conventional reducing atmosphere, TiO 2-x The formation of TiO 2 The oxide layer widens or deviates from the original position due to the change from stoichiometric structure to non-stoichiometric structure due to O deficiency, that is, the introduction of O vacancies in the lattice. However, in the current development, it has been shown that the disordered state caused by the initial Ti deposition and ion bombardment appears as a broad peak in the Raman spectrum, but after heat treatment, except for TiO 2 In addition to the formation of , as the crystal structure gradually recovers through the diffusion rearrangement process, the shape of the peak becomes obvious and the shifted peak returns to the original position. However, in condition c) where the contact resistance decreases rapidly, the intermediate peak 173 that belongs to neither anatase nor rutile and the secondary peak 319 of rutile can be seen ( Fig.28 This is considered to be a peak derived from the newly formed conductive oxide layer through diffusion rearrangement within the oxide layer. Considering that in the Ti raw material heat treated at the same temperature and similar time ( Fig.28 D)) and under the conditions of heat treatment at lower temperature and same time after Ti ion etching ( Fig.28 The peaks in condition B)) do not appear, and the appearance of these peaks in condition c) is considered to be evidence of the formation of a conductive oxide layer by Ti ion etching, and the XPS Fig.25 The results for the conditions in also confirmed this correlation.

[0153] Next, the results of the corrosion resistance evaluation will be described.

[0154] In order to verify the corrosion resistance of the coating of the present disclosure, a constant potential corrosion evaluation was performed on each of Examples 1 and 2 and Comparative Examples 1, 2 and 3, and then the corrosion appearance and contact resistance changes after the evaluation were measured. The constant potential corrosion evaluation was divided into 1) a general corrosion evaluation corresponding to a general fuel cell operating potential and environment, and 2) a severe corrosion evaluation that verifies higher durability than the general corrosion evaluation, and the results are shown in Table 7.

[0155] Table 7

[0156]

[0157]

[0158] 1) As a result of the general corrosion evaluation, the change in contact resistance before and after the evaluation was favorable for all embodiments and comparative examples, with the exception of Comparative Example 1-2, with no significant increase. However, when comparing the corrosion appearance, it can be seen that for Examples 1-1 and 2-1 and Comparative Example 3, no damage due to surface corrosion was observed, but for the remaining Comparative Examples, the coating on the surface was partially corroded and delaminated. This is a result indicating that although both the embodiments and comparative examples use a raw material Ti oxide layer to achieve conductivity, corrosion resistance may vary depending on the implementation. Among these, it can be seen that Comparative Example 1-2 shows the worst corrosion resistance, not only because of delamination due to corrosion, but also because of the increased contact resistance after the evaluation. Comparative Example 1-2 is a TiO 2 C deposition was performed on the surface of the oxide layer and then TiO was reduced by vacuum heat treatment. 2 The results are even worse than those of Comparative Example 1-1 in which C deposition was performed after Ti ion etching. From these results, it can be seen that when the conductive oxide layer exists in the outermost position and is directly exposed to a corrosive environment, its corrosion resistance may be worse. In addition, titanium carbide (coating delamination due to TiC corrosion) that may be formed during C application and heat treatment may be another reason for the decrease in corrosion resistance.

[0159] According to the existing patent, in the case of Comparative Examples 1 and 2, the corrosion resistance is determined by the oxide layer formed by the reduction heat treatment conditions, but is limited by the phenomenon that further corrosion resistance is ensured by increasing the thickness of the oxide layer under conditions higher than a specific temperature and time. On the contrary, the reason why the corrosion resistance of Examples 1-1 and 2-1 and Comparative Example 3 is superior to that of Comparative Examples 1-1, 1-2 and Comparative Example 2 under general corrosion evaluation conditions can be considered to be due to the higher temperature under the heat treatment conditions for forming the Ti oxide layer. In the case of Comparative Examples 1-1 and 1-2, the vacuum heat treatment after C coating does not contribute to the formation of the Ti oxide layer required for corrosion resistance, while in the case of Comparative Example 2, the heat treatment temperature for forming the conductive oxide layer before C coating is quite low, about 300°C. However, it can be seen that the Ti oxide layer formed at around 600°C as in Examples 1 and 2 and Comparative Example 3 exhibits more excellent corrosion resistance.

[0160] Examples 1-1 and 2-1 and Comparative Example 3 were subjected to severe corrosion evaluation, confirming that they have better corrosion resistance. However, in this section, the results of Examples 1-2 and 2-2 with slightly changed heat treatment conditions are shown, although there is almost no difference in the evaluation results. As can be seen from the results, the appearance of the evaluation parts is damaged or partially delaminated by corrosion. However, as a result of comparing the contact resistance before and after the evaluation, the contact resistance of Examples 1-2 and 2-2 remains the same as the initial state, while the contact resistance of Comparative Example 3 increases significantly. In Comparative Example 3, the reason for the increase in resistance while the coating is delaminated due to surface corrosion is that the conductive oxide layer formed on the surface of the Ti raw material under the severe corrosion evaluation conditions is removed due to corrosion. On the contrary, in the case of Examples 1-2 and 2-2, even if the outer oxide layer is removed beyond a certain level due to the progress of surface corrosion, the reason why the contact resistance remains unchanged can be considered that the position of the conductive oxide layer does not exist outside the oxide layer, but is distributed inside the oxide layer and at or below the boundary with the surface of the raw material (body), so that even if the outer oxide layer is partially corroded, the conductivity remains unchanged. This is considered to be a factor that makes the coating method of the present invention more durable due to the formation position and shape of the conductive oxide layer, as described previously for the mechanism of forming the conductive oxide layer by the Ti ion etching and heat treatment method.

[0161] Table 8 shows the results of severe corrosion evaluation as a function of temperature and time to verify the oxidative heat treatment conditions that can further improve the corrosion resistance of Examples 1 and 2.

[0162] Table 8

[0163]

[0164] ※Corrosion degree appearance - O: Good, Δ: Local corrosion, X: Complete corrosion) As a result of severe corrosion evaluation for each condition, after the evaluation of Examples 1 and 2, the contact resistance did not increase, but the phenomenon of oxide layer delamination due to surface corrosion was more obvious in Example 2 with C deposition compared to Example 1. In the case of Example 1, surface oxide layer corrosion decreased with increasing temperature and time, and it was confirmed that when heat treatment was performed at 690°C for 5 minutes as in Example 1-3, oxide layer delamination hardly occurred. In Example 2, oxide layer corrosion occurred very obviously at a temperature of 690°C or less regardless of the heat treatment conditions, but when heat treatment was performed at 690°C for 5 minutes as in Example 2-3, the oxide layer delamination phenomenon tended to be significantly reduced. This is believed to be due to the structure of the outer titanium oxide layer being closer to that of rutile at 690°C for 5 minutes or more, which increases corrosion resistance, just as at temperatures of 500 to 650°C, the titanium oxide layer structure changes from anatase (active) to rutile (inert) as the heat treatment time increases, which increases corrosion resistance. These results can also be found in Fig. 27 and Fig.28 As can be seen in the Raman analysis results. Fig.28 In the case of (F), where the Ti raw material was heat treated at 600°C for 3 minutes, the surface oxide layer was mainly anatase structure and contained some rutile, but Fig.28 In the case of (D), where the Ti raw material is heat treated at 690°C for 3 minutes, it can be seen that the surface oxide layer changes to an almost rutile structure. It can be seen that the rutile peak is more clearly expressed at higher temperatures, and the position of the peak also moves toward the original rutile peak, even when comparing the Ti raw material heat treated at 650°C for 5 minutes after Ti ion etching ( Fig.28 B) and heat treated at 690℃ for 5 minutes ( Fig.28The same is true for the sample of C). Therefore, in the present disclosure, since the principle of forming a conductive oxide layer is different from the conventional method, the temperature and time can be controlled by performing an oxidative heat treatment in the atmosphere as in Examples 1 and 2, thereby improving corrosion resistance while maintaining conductivity. Conventional methods require that the oxide layer responsible for conductivity and corrosion resistance be located in one area at the same time. Therefore, when the structure of the oxide layer changes to meet the increased corrosion resistance, the conductivity decreases, which limits the setting of the heat treatment conditions. For example, in the case of Comparative Example 2, the conductivity of the oxide layer can only be ensured by performing an oxidative heat treatment at 600°C for 1 minute under a low oxygen partial pressure, but it is difficult to further improve the corrosion resistance by heat treatment because the structure is mainly composed of anatase phase, and when deviating from the proposed heat treatment temperature and time conditions, anatase becomes less conductive. However, the present disclosure is relatively less constrained by the external atmospheric environment and temperature, because according to the method, the conductive oxide layer is not only located inside the entire oxide layer and close to the surface of the raw material, but also formed by diffusion rearrangement inside the material rather than by the redox reaction between Ti and O under the external atmospheric environment. That is, during the heat treatment, the inner conductive oxide layer is formed separately from the oxide layer formed on the outer side. Therefore, by controlling the heat treatment temperature and time, the structure of the outer oxide layer that can be used as a protective layer can be changed to a structure that is more resistant to corrosion environments.

[0165] Meanwhile, the present disclosure includes the following improved embodiments.

[0166] Improved Example 1

[0167] In addition to the Ti target, a TiSi-based alloy target containing Si (2 to 30%) may be used to ensure the target contact resistance and corrosion resistance.

[0168] For example, TiSi ion etching, TiSiO 2 Deposition coating or TiSiO 2 The results of deposition coating + C deposition coating followed by heat treatment are shown in Table 9 below.

[0169] Table 9

[0170]

[0171] Improved Example 2

[0172] In addition to Ti ion etching, when [Ti ion etching TiO 2 [Deposition coating], under some heat treatment conditions, the target contact resistance and a certain level of corrosion resistance can be achieved, and the results are shown in Table 10 below.

[0173] Improved Example PVD process conditions:

[0174] -Ti or TiSi ion etching conditions: acceleration voltage 180eV for 2 minutes;

[0175] -TiO 2 or TiSiO 2 Deposition conditions: acceleration voltage 100 eV, O 2 Gas 100 sccm, 2 min;

[0176] -C deposition conditions: acceleration voltage 100 eV, duration 2 minutes.

[0177] Table 10

[0178] Coating <![CDATA[TiSiO 2 +C coating]]> <![CDATA[Ti ion / TiO 2 +C coating]]> Heat Treatment 610℃10min. 610℃10min. Before evaluation (Ω) 1 to 2 0 to 1 After constant potential corrosion evaluation (Ω) 3 to 5 2 to 3

[0179] Although the present disclosure has been described with reference to the exemplary drawings, it is obvious to those skilled in the art that the present disclosure is not limited to the above-described embodiments, and various changes and modifications may be made without departing from the spirit and scope of the present disclosure. Therefore, the examples of changes or modifications belong to the claims of the present disclosure, and the scope of the present disclosure should be interpreted based on the claims.

Claims

1. A method for manufacturing a Ti material for a fuel cell separator, the method comprising the following steps: Ti raw material for rolling pure Ti material or Ti alloy material; Depositing and coating Ti ion particles on the Ti raw material by physical vapor deposition; and Oxidative heat treatment to form TiO around the Ti ion particles deposited by the deposition coating 2-x (0<x<1) structured conductive oxide layer.

2. The method according to claim 1, wherein the Ar from the deposition coating + A portion of the surface oxide layer of the Ti raw material is ion-etched, and the surface of the Ti raw material is bombarded by ions.

3. The method according to claim 2, wherein: Through the deposition coating, a Ti ion deposition layer is formed on the surface oxide layer, on the etched surface of the Ti raw material, and on the inner side below the surface oxide layer of the Ti raw material, and an atomic mixing zone is formed in which the Ti of the raw material and the deposited Ti ion particles are mixed.

4. The method according to claim 3, wherein the oxidative heat treatment is carried out in an atmospheric state, and The Ti element of the surface oxide layer and the Ti ion particles react with oxygen through the oxidative heat treatment to form an atmospheric heat-treated oxide layer.

5. The method according to claim 3, wherein in the oxidation heat treatment, the TiO is formed by diffusion rearrangement between Ti particles excessively deposited in the Ti ion deposition layer, defects, and O particles introduced from the atmosphere or existing in the surface oxide layer. 2-x (0<x<1) structured conductive oxide layer.

6. The method according to claim 3, further comprising the steps of: coating C particles on the surface oxide layer and the Ti ion deposition layer after the deposition coating, The C particles diffuse into the surface oxide layer and the interior of the Ti ion deposition layer through the oxidation heat treatment. The method according to claim 3 , wherein the accelerating voltage of the deposition coating is 80 to 800 eV. 8 . The method according to claim 7 , wherein an area fraction of the Ti ion deposition layer on the surface of the Ti raw material is 50% to 90%.

9. The method according to claim 3, wherein the conductive oxide layer has a thickness of 50 to 500 nm.

10. The method according to claim 3, wherein the heat treatment temperature of the oxidation heat treatment is 580 to 750°C, and the holding time is 1 to 10 minutes.

11. A Ti material for a fuel cell separator, the Ti material comprising: Ti raw material made of pure Ti material or Ti alloy material; A surface oxide layer formed on the Ti raw material; Ti ion deposition layer, wherein Ti ion particles are deposited and coated on the Ti raw material and the surface oxide layer by physical vapor deposition; and Around the deposited Ti ion particles, TiO 2-x (0<x<1) structure formed conductive oxide layer.

12. The Ti material according to claim 11, wherein the Ti ion deposition layer is formed on the Ti raw material, in which a portion of the surface oxide layer is formed by Ar from the physical vapor deposition. + Ion etching and exposure.

13. The Ti material according to claim 12, wherein the Ti ion deposition layer is formed on the surface oxide layer, on the etched surface of the Ti raw material, and on the inner side below the surface oxide layer of the Ti raw material, and an atomic mixing zone is formed, in which the Ti of the raw material and the deposited Ti ion particles are mixed.

14. The Ti material according to claim 13, further comprising: The atmospheric heat-treated oxide layer is formed on the surface oxide layer and on the surface of the etched Ti raw material by reacting the Ti element of the surface oxide layer and the Ti ion particles with oxygen through oxidation heat treatment.

15. The Ti material according to claim 13, wherein The TiO is formed by the oxidation heat treatment through diffusion rearrangement between the Ti particles over-deposited in the Ti ion deposition layer, defects and O particles introduced from the atmosphere or existing in the surface oxide layer. 2-x (0<x<1) structured conductive oxide layer.

16. The Ti material according to claim 13, further comprising: The C particles are coated on the surface oxide layer and the Ti ion deposition layer and then diffused into the surface oxide layer and the inside of the Ti ion deposition layer through oxidation heat treatment. The Ti material according to claim 13 , wherein the Ti raw material is subjected to Ar heat treatment or vacuum heat treatment. 18 . The Ti material according to claim 13 , wherein an area fraction of the Ti ion deposition layer on the surface of the Ti raw material is 50% to 90%. The Ti material according to claim 13 , wherein the conductive oxide layer has a thickness of 50 to 500 nm.

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