KR20140094736A - Method for manufacturing corrosion resistant and conductive nano carbon coating and fuel cell bipolar plate thereby - Google Patents

Abstract

The present invention etches an oxide film formed on the surface of a stainless steel material by plasma etching to activate the surface layer and prevent a problem of decreasing conductivity thereof. Also the present invention coats the etched surface of the oxide film with metal nitride, such as CrN or TiN, to a nanoscale thickness and then coats the metal nitride to a nanoscale thickness to form a coating layer having high conductivity and corrosion resistance with high productivity. Therefore, it is possible to mass-produce a fuel cell bipolar plate, an electrode material, and a stainless steel material with improved conductivity and corrosion resistance.

Description

TECHNICAL FIELD [0001] The present invention relates to a corrosion-resistant and conductive nano-carbon coating method using stainless steel as a base material, and a fuel cell separator using the same. BACKGROUND ART < RTI ID = 0.0 >

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a special surface treatment method using stainless steel as a base material to provide both conductivity and corrosion resistance. More specifically, the present invention relates to a nanocarbon coating method, and a PEMFC (Polymer Electrolyte Membrane Fuel Cell) Plate, an electrode material having excellent conductivity and corrosion resistance, and the like.

Stainless steel is a material that is used very frequently and can be applied to a wide variety of materials due to its complementary properties or specific physical properties. Particularly, it is attracting attention as a base material of a fuel cell separator and can be used as an electrode material if the corrosion resistance is further enhanced. It is also required that various properties are required for reinforcement of other properties.

Fuel cells are one of the environmentally friendly renewable energy sources based on the combustion reaction in which hydrogen and oxygen react in the presence of a catalyst to generate water and energy. Electrical energy can be generated without special pollutants, and it has the advantage of showing very high efficiency by adding heat generated.

The fuel cell separator is a necessary component for such a fuel cell. The physical properties that the fuel cell separator needs to have include strength, corrosion resistance, gas barrier property, conductivity and dimensional accuracy. Further, considering the practicality of the fuel cell itself, the fuel cell separator requires a manufacturing process design suitable for mass production.

At present, the fuel cell separator plate developed in accordance with the above-mentioned requirements is being developed in a competitive manner centering on the two basic materials by resin coating the carbon material and surface treatment of the metal material, and Korean Patent No. 10-1000697 Discloses a technique of using a carbon coating containing fluorine (F) in a stainless steel material and JP 2010-287542 A describes a technique of coating a carbon layer by coating a stainless steel material with a Cr intermediate layer to improve conductivity . This technique is also difficult to apply to actual mass production with a relatively thick film having a thickness of the carbon layer of 0.5 占 퐉 to 2 占 퐉.

When stainless steel is used as the base material, it must be excellent in corrosion resistance as well as in conductivity, and these two characteristics are practically incompatible. In the past, surface modification of the stainless steel base material by nitriding has been the mainstream in the past, but satisfactory results have not been obtained in terms of cost and physical properties.

While trying to ignore the cost and concentrate only on improvement of physical properties, gold coating is applied to the stainless steel, but this is also difficult to commercialize.

FIG. 1 shows the contact resistance and corrosion current measurement results of the carbon coating on stainless steel according to the temperature. It is necessary to select the coating temperature for optimizing the both, in which the fuel cell separator plates having both physical quantities should be low. FIG. 2 shows contact resistance and corrosion current measurement results according to the thickness of the carbon coating. As the film thickness increases, the contact resistance and the corrosion current decrease. However, thickening the increase of the film thickness leads to a problem of mass production because the productivity is lowered, so it is necessary to keep the film thickness thin and maintain excellent characteristics.

On the other hand, in the case of stainless steel, since Cr is added to the surface of the oxide layer to form a natural coating for improving the corrosion resistance, the adhesion of the coating layer and deterioration of the conductivity must be improved in the surface treatment.

Also, in the case of carbon coating, when the thickness of the coating is made thick and desired physical properties are provided, there is a problem in that the reality is poor due to the characteristics of the fuel cell separator, which requires mass production and low production cost.

Therefore, an object of the present invention is to provide a method of manufacturing a stainless steel base material by carbon coating a stainless steel base material, thereby improving the characteristics of the stainless steel base material and improving the corrosion resistance and conductivity, And to provide a method of manufacturing the same, and a method for manufacturing the same, which can realize a corrosion-resistant and conductive nano-carbon coating method and a fuel cell separator according to the method.

According to the present invention, the oxide film formed on the surface of the stainless steel base material is etched by plasma etching to activate the surface layer and prevent the problem of deterioration of conductivity, and a metal nitride such as CrN or TiN is etched on the oxide film- Coated with a nano-sized thickness, coated with a carbon layer to a thickness of nano-size, and a coating layer excellent in both conductivity and corrosion resistance was produced with high productivity.

That is,

Etching the oxide coating of the stainless steel base material;

Depositing a metal nitride buffer layer in a nano-sized thickness on the surface of the base material on which the oxide film is etched;

And depositing a conductive carbon layer on the buffer layer to have a nano-sized thickness. The present invention also provides a method of manufacturing a nano-carbon coating layer having corrosion resistance and conductivity.

The present invention also provides a method of manufacturing a nano-carbon coating layer having corrosion resistance and conductivity, wherein the etching of the oxide coating of the stainless steel base material is performed by plasma etching.

The metal nitride buffer layer may be formed by supplying a metal target and a nitrogen gas into a chamber, applying a voltage to the metal arc, and applying a bias voltage to the base material at 300 to 500 ° C The present invention also provides a method for producing a nano-carbon coating layer having corrosion resistance and conductivity.

Further, the present invention is characterized in that, in the above, the coating of the conductive carbon layer is carried out by applying a voltage to the ion gun, applying the bias voltage to the base material, and setting the temperature to 200 to 600 ° C. The present invention also provides a method for producing a nano-carbon coating layer.

The bias voltage may be DC, AC, or a pulse voltage having a frequency of 0.1 kHz to 500 kHz, and the thickness of the conductive carbon layer is 1 to 150 nm. A method of manufacturing a nano carbon coating layer having corrosion resistance and conductivity is provided.

The present invention also provides a method of manufacturing a semiconductor device, comprising the steps of: etching an oxide film; Depositing a metal nitride buffer layer; And depositing the conductive carbon layer in a nano-sized thickness, each of which is carried out by constructing a process chamber, wherein each process chamber is arranged in-line such that the steps proceed in-situ. A method of manufacturing a nano-carbon coating layer having conductivity is provided.

The etching of the oxide film is performed by plasma etching using an ion gun, and the position of the ion gun is moved so as to narrow the gap between the ion gun and the surface of the base material, Wherein the nano-carbon coating layer has improved corrosion resistance and conductivity.

Further, according to the present invention,

Characterized in that the oxide coating of the stainless steel base material is etched and the metal nitride buffer layer is deposited thereon and the conductive carbon layer is again deposited thereon in a nano-sized thickness, in a stainless steel reinforced with corrosion resistance and conductivity .

The present invention also provides a stainless steel reinforced with corrosion resistance and conductivity, wherein the metal nitride film contains CrN or TiN and the thickness thereof is 1 to 20 nm.

The present invention also provides a stainless steel reinforced with corrosion resistance and conductivity, wherein the conductive carbon layer is 1 to 150 nm.

Further, the present invention is characterized in that the stainless steel reinforced with corrosion resistance and conductivity as described above is a fuel cell separator or an electrode material.

Further, according to the present invention,

A first chamber in which an ion gun is installed to etch an oxide film of a stainless steel base material with a plasma;

A second chamber having a metal arc for coating a metal nitride layer on the surface of the stainless steel base material after the oxide film etching process in the first chamber; And

A third chamber provided with an ion gun for coating a conductive carbon layer with a nanosize thickness on a surface of a stainless steel base material coated with a metal nitride film in the second chamber; Wherein the step of coating the conductive carbon layer and the step of coating the conductive carbon layer are carried out in-situ in a batch.

According to the present invention, since the natural oxide film of the stainless steel base material is etched with a plasma and then coated, the effect of improving the conductivity by coating treatment is excellent, and CrN or TiN is coated on the etched surface with nano- The carbon layer is coated again with a nano-sized thickness, and the corrosion current can be largely lowered while keeping the contact resistance low, and since the thickness of the coating is extremely thin in the nano size, the inline process is possible and the productivity is also very good. Accordingly, it is possible to provide a mass production fuel cell separator, an electrode material, or a reinforced special stainless steel material.

1 is a graph showing changes in contact resistance and corrosion current depending on the coating temperature of the carbon coating material.
2 is a graph showing changes in contact resistance and corrosion current depending on the coating film thickness of the carbon coating material.
3 is a layered cross-sectional view showing the surface treatment and coating layer construction for a stainless steel base material according to the present invention.
4 is a schematic view of a carbon layer coating using an ion gun according to the present invention.
FIG. 5 is a schematic diagram showing plasma etching of a base material, a metal nitride layer coating, and a nano carbon layer coating in accordance with the present invention.
FIG. 6 is a graph showing the contact resistance and the corrosion current of a specimen completed by the coating process according to the present invention in comparison with the prior art.
7 is a view illustrating a method for measuring a contact resistance of a specimen in which a coating process is completed according to the present invention.
FIG. 8 is a graph showing the etching rate according to the distance between the ion gun and the base material in the process of etching the oxide film of the base material by the plasma etching according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention makes it possible to use a stainless steel as a base material to form a coating layer capable of further strengthening corrosion resistance and conductivity and to use it as a fuel cell separator or to produce a special stainless steel reinforced with electrode material or stainless steel itself.

To this end, the natural oxide layer of stainless steel is removed by plasma etching, and a metal nitride layer is laminated on the etched surface to a thickness of about 1 to 20 nm to further strengthen the corrosion resistance of stainless steel. Due to the plasma etching process, the oxide film covered on the surface of the stainless steel is removed to further improve the conductivity. At the same time, fine irregularities of about several nm are formed on the entire surface to be activated, Thereby enhancing adhesion.

And a metal nitride film having excellent corrosion resistance such as CrN and TiN is coated on the activated surface very thinly on the order of 1 to 20 nm to reinforce the corrosion resistance which can be weakened by the conductivity enhancement. Since the metal nitride film has conductivity different from the oxide film, the corrosion resistance can be improved without deteriorating the conductivity.

Then, a conductive nano carbon coating layer 300 having a thickness of 1 to 150 nm is formed thereon to further enhance the conductivity thereof while maintaining corrosion resistance. After completion of the entire process, the layer is formed as shown in FIG.

The etch process and the carbon coating process are performed using ion guns that produce high energy ions as well as plasma etching efficiency and provide excellent film quality and high productivity (deposition rate). Also, the thin film of nanosize thickness Can be produced.

Namely, the nano-carbon coating which improves the corrosion resistance and the conductivity both in the stainless steel base material is constituted by an inline coating system including the ion gun, thereby achieving mass production (see FIG. 6). Through the in-line coating system, both the plasma etching step, the metal nitride film coating step and the conductive nanocarbon coating layer 300 formation step proceed in-situ. The reason why the inline coating system can be constructed is that the plasma etching process and the carbon coating process of the present invention both use a high-efficiency ion gun, thereby exhibiting sufficient physical properties with a nano-sized thickness. This is because when the conductive carbon is coated using the conventional PVD process, the film quality is not dense and there is a risk of peeling, so it is necessary to form a thick film having a thickness of 500 nm to several μm. Therefore, it takes a long time more than 5 hours, The present invention has improved the situation in which the system was not meaningful. In particular, if lowering the manufacturing cost such as the fuel cell separator is the key to the commercialization of the technology, mass production of the manufacturing process and the system can be said to have great significance in terms of technology and economy. The ion gun used in the present invention can obtain a high bonding force and a deposition rate unlike the conventional CVD process. In order to increase the bonding strength and the microstructure density, ion guns capable of imparting particle energies as high as 700 eV have been used so as to have economical efficiency and mass productivity [Andrew, S., Mike, A., Michael , K., Ken, N., Colin, Q., "Iustrial Ion Sources and Their Application for DLC Coating," presented at the SVC 42nd Annual Technical Conference, USA, April 17-22, 1999. Considering that the particle energy of the conventional PACVD process is as low as 2 to 3 eV, the generation of high energy particles by the ion gun of the present invention greatly improves the process efficiency and the quality of the film quality. Robertson, J., "Diamond-like amorphous carbon," Materials Science and Engineering R 37: 129-281,

Hereinafter, a method of manufacturing a fuel cell bipolar plate according to an embodiment of the present invention will be described in detail with reference to detailed process conditions.

First, the stainless steel processed as the base material of the fuel cell separator is prepared and cleaned. The cleaning can be performed according to a known technique using chemicals such as distilled water and isopropyl alcohol.

Next, the cleaned base material is put into a chamber, and a natural oxide film such as chromium oxide formed on the surface of the stainless steel is etched by plasma etching. An ion gun is prepared for plasma etching, and an inert gas such as Ar or nitrogen (N ₂ ) is added thereto, and a plasma of 0.1 to 5 kW (pulse power, AC power, or DC power) Impacts the surface of the base material with ions to etch the oxide film naturally formed on the surface of the stainless steel and activate the surface itself. At this time, a bias voltage is applied to the base material to attract the ions, so that the etching effect can be efficiently performed. As shown in FIG. 6, the ion gun is disposed on both the upper surface and the rear surface of the base material so that both surfaces of the base substrate can be etched at the same time. In the etching process, the etching rate varies depending on the distance between the surface of the base material and the ion gun The ion gun is movable so as to be etched so as to move the ion gun close to the base material (see FIG. 6).

That is, the relationship between the etching rate y 300 / x, where x is the distance between the ion gun and the surface of the base material is derived. In this embodiment, when the distance between the ion gun and the sample is reduced from 10 cm to 3 cm, There was an effect.

In this embodiment, a 250 W DC power was applied to the ion gun and a bias voltage of -100 V was applied to the base material for about 5 minutes. FIG. 9 shows FESEM analysis results of the substrate surface before and after the etching process, and the surface became flat after etching. The surface roughness after etching was 20%.

After the plasma etching process is completed, a buffer layer is formed on the surface of the activated base material to enhance the corrosion resistance. That is, the CrN or TiN-based metal nitride layer is coated in a nano size. The process may be a process used for forming the coating, such as PVD or PECVD, and may be performed at a temperature ranging from room temperature to 500 ° C, preferably 300 to 500 ° C, a process pressure of 10 ^-2 to 10 ^-5 torr . In this embodiment, the metal target and the nitrogen gas are supplied to the chamber and the PECVD process using a metal arc is performed. A metal nitride film such as CrN or TiN is coated with an extremely thin film of about 1 to 20 nm. , Temperature, etc., but it is preferable to set it to not more than 10 to 30 seconds and not more than 5 minutes per one base material.

In this embodiment, a voltage applied to a metal arc was 10 to 30 V at a DC voltage, a current was 30 to 200 A, and a bias voltage of 0 to -100 V was applied to the base metal for forming a metal nitride film. Note that sputtering may occur if a bias voltage higher than the above is applied under the above conditions. The formation of the metal nitride film improves the corrosion resistance of the stainless steel base material from which the oxide film is etched. When CrN or TiN is formed, the metal nitride film has conductivity as a whole, thereby improving the physical properties as a whole with the high conductive layer to be formed thereafter.

Next, a hydrocarbon-based gas may be supplied as a carbon source, or a graphite target may be used, and a conductive carbon layer may be deposited by a PVD or PECVD process. In the case of this embodiment, it was formed by a method using an ion gun. The process may be performed at a temperature of 200 to 1000 캜, preferably 300 to 600 캜, by using a heater, and a hydrocarbon gas (for example, To maintain the process pressure at 10 < ^-2 > to 10 < ^-5 > torr, and the conductive carbon layer thickness is deposited to 1 to 150 nm, preferably 5 to 100 nm. The deposition process of the conductive carbon layer is schematically shown in Fig. At this time, it is preferable to apply a bias voltage to the base material. The bias voltage can be applied in DC, AC, or pulse frequency (0.1 kHz to 500 kHz) with a negative voltage of 0 to -800 V, which prevents charge accumulated in the metal separator during conductive nanocarbon coating The bonding force between the metal separator and the carbon black is improved.

Through this process, as seen from the energy and temperature conditions of the carbon itself, the carbon layer is crystallized at the same time as the deposition due to the heat energy applied from the outside and the electric energy applied to the base material, Thereby forming an aged carbon layer. Since the conductive nano carbon coating layer 300 exhibiting conductivity is formed in a very thin nano-sized thickness, the process time is very short, and 360 coating processes can be performed per hour, so that the fuel cell separator 300 Can be produced.

Conventionally, compared to the case where the thickness of the carbon layer is set to 500 nm or more, in this embodiment, a thickness of 60 nm or less including a CrN layer for corrosion resistance and a carbon layer for conductivity is formed so that a coating layer having a much thinner overall thickness is formed, .

The contact resistance and the corrosion current were measured for the fuel cell separator thus fabricated. The conductive carbon layer was directly etched with a thickness of 50 nm without CrN or TiN buffer layer without etching the natural coating of the stainless steel base material, The contact resistance and the corrosion current were measured. As a result, as shown in Fig. 6, the contact resistance was 13.2 mΩcm ² @ 10 kgf / cm ² and the corrosion current was 9.13 μA / cm ^{2 in the} specimen of the comparative example on the left, but the contact resistance was 13.7 mΩcm ² @ cm ² and the corrosion current is 0.42 μA / cm ² , it can be seen that the contact resistance is kept at the same level and the corrosion current is greatly lowered. This means that the fuel cell separator according to the present invention has good conductivity and excellent corrosion resistance and can satisfy mass productivity.

Fig. 7 illustrates a method of measuring the contact resistance of the fuel cell bipolar plate manufactured in this embodiment. Psalter A current of 10 kg per cm ² was applied to current collectors at the upper and lower ends, and the voltage across both ends was measured to determine the contact resistance between the separator and the GDL (gas diffusion layer). The contact resistance is measured by measuring the contact resistance in the state where the separator is located between the GDLs, and then the contact resistance of the GDL is separately measured to obtain the difference between the two values.

It is needless to say that the corrosion-resistant electrode material and the special stainless steel can be manufactured in substantially the same manner as described above for the production of the fuel cell separator using the nano-carbon coating in the above embodiment, and other materials.

It is to be understood that the invention is not limited to the disclosed embodiment, but is capable of many modifications and variations within the scope of the appended claims. It is self-evident.

100: base metal
200: metal nitride layer
300: (conductive) nano carbon layer
400: plasma source

Claims (12)

Etching the oxide coating of the stainless steel base material;
Depositing a metal nitride buffer layer on the surface of the base material on which the oxide film is etched;
And depositing a conductive carbon layer on the buffer layer to a nano-sized thickness. The method of manufacturing a nano-carbon coating layer having corrosion resistance and conductivity according to claim 1, The method for manufacturing a nano carbon coating layer according to claim 1, wherein the etching of the oxide coating of the stainless steel base material is performed by plasma etching. The method according to claim 1, wherein the metal nitride buffer layer is formed by supplying a metal target and nitrogen gas into a chamber, applying a voltage to the metal arc, applying a bias voltage to the base material, Wherein the nano-carbon coating layer has corrosion resistance and conductivity. The nano carbon coating layer according to claim 1, wherein the coating of the conductive carbon layer is performed by applying a voltage to the ion gun, applying the bias voltage to the base material, and setting the temperature to 200 to 600 占 폚. ≪ / RTI > 5. The method of claim 4, wherein the bias voltage is a pulse voltage of DC to AC of 0 to -800 V or a frequency of 0.1 kHz to 500 kHz, and the thickness of the conductive carbon layer is 1 to 150 nm. Wherein the nano-carbon coating layer is formed on the surface of the substrate. The method of claim 1, further comprising: etching the oxide coating; Depositing a metal nitride buffer layer; And depositing the conductive carbon layer to a nano-sized thickness, each of which is performed by constructing a process chamber, wherein each process chamber is arranged in-line and the steps are progressed in-situ collectively Wherein the nano-carbon coating layer has a corrosion resistance and a conductivity. 7. The method of claim 1 or 6, wherein the step of etching the oxide film is performed by plasma etching using an ion gun, and the position of the ion gun is configured to be movable so as to narrow the gap between the ion gun and the surface of the base material, Wherein the nano-carbon coating layer has improved corrosion resistance and conductivity. Characterized in that an oxide film of a stainless steel base material is etched and a metal nitride buffer layer is deposited thereon and a conductive carbon layer is again deposited thereon in a nano-sized thickness. 8. The stainless steel according to claim 7, wherein the metal nitride film contains CrN or TiN, and the thickness of the metal nitride film is 1 to 20 nm. 10. The stainless steel according to claim 8 or 9, wherein the conductive carbon layer is between 1 and 150 nm in corrosion resistance and conductivity. The stainless steel reinforced with corrosion resistance and conductivity according to claim 10, wherein the stainless steel is a fuel cell separator or an electrode material. A first chamber in which an ion gun is installed to etch an oxide film of a stainless steel base material with a plasma;
A second chamber having a metal arc for coating a metal nitride layer on the surface of the stainless steel base material after the oxide film etching process in the first chamber; And
A third chamber provided with an ion gun for coating a conductive carbon layer with a nanosize thickness on a surface of a stainless steel base material coated with a metal nitride film in the second chamber; And the conductive carbon layer is continuously in-situ. The apparatus for manufacturing a nano-carbon coating layer having corrosion resistance and conductivity according to claim 1,

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