KR20190048872A - Coating composition for interconnector surface treatment of solide oxide feul cell and preparation method thereof - Google Patents

Abstract

The present invention relates to a coating composition for a solid oxide fuel cell metal separation plate and a manufacturing method thereof, which are a main component of the coating composition for a solid oxide fuel cell metal separation plate for manufacturing a metal separation plate having excellent corrosion resistance and low contact resistance. The present invention prevents dust from being generated and is possible to form a uniform coating layer when performing spray coating.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition for a solid oxide fuel cell metal separator,

The present invention relates to a coating composition for a solid oxide fuel cell metal separator and a method of manufacturing the same, and is a main component of a coating composition for a solid oxide fuel cell metal separator for producing a metal separator having excellent corrosion resistance and low contact resistance, To a powder for plasma spray coating capable of forming a uniform coating film upon spray coating without generating dust, and a method for producing the same.

Solid oxide fuel cells generally operate at the highest temperature of the fuel cell (700-1000), and because all components are solid, they are simpler in structure than other fuel cells, and the electrolyte loss and replenishment and corrosion problems There is no noble metal catalyst, and it is easy to supply fuel through direct internal reforming. In addition, it has an advantage that it can generate thermal hybrid power using waste heat because it discharges gas at a high temperature. Due to these advantages, researches on solid oxide fuel cells are actively being carried out.

Solid Oxide Fuel Cell (SOFC) is an electrochemical energy conversion device composed of an oxygen ion conductive electrolyte, an air electrode (anode) and a fuel electrode (cathode) located on both sides thereof. In the air electrode, oxygen ions generated by the reduction reaction of oxygen move to the fuel electrode through the electrolyte and react with hydrogen supplied to the fuel electrode to generate water. At this time, electrons are generated in the fuel electrode and electrons are consumed in the air electrode. When the electrodes are connected to each other, electricity flows. However, since the electric power generated in one unit cell based on the air electrode, the electrolyte and the fuel electrode is considerably small, a large amount of electric power can be output by constructing the fuel cell by stacking (stacking) a plurality of unit cells, And can be applied to various power generation systems. For the stacking, it is necessary that the air electrode of one unit cell and the fuel electrode of another unit cell be electrically connected, and a metal separator is used for this purpose.

The metal separator is a core component of a solid oxide fuel cell (SOFC) that functions to separate fuel and air while electrically connecting unit cells. Metal separator plates for SOFCs must meet the requirements of high electronic conductivity, chemical stability in an oxidizing / reducing atmosphere, low reactivity with other materials, similar thermal expansion coefficient, low gas permeability. The use of metal separators can replace the existing ceramic interconnect material LaCrO ₃ at SOFC operating temperatures of 600 to 800. The metal separator has an excellent mechanical strength and can serve as an excellent support for ceramic materials with low strength and has a high electrical conductivity, which can reduce the resistance of the SOFC cell and the stack. In general, metal containing chromium (Cr) is preferred as a metal separator because chromium oxide (Cr ₂ O ₃ ) having high conductivity is formed on the surface of the metal separator in an SOFC operating environment.

In addition, since the metal separator plate must electrically connect each unit cell, sufficient conductivity must be provided. Also, since the environment inside the fuel cell is an environment in which hydrogen ion concentration is high and is easily corroded at a high temperature, the metal separator plate should have sufficient corrosion resistance. Japanese Patent Application Laid-Open Nos. 2003-276249 and 2003-272653 disclose a technique of performing very thin gold plating on the surface of a metal separator for cost reduction. However, since the gold-plated part has a low hardness, when the metal separator contacts the electrode, damage such as scratches may occur and corrosion may occur.

Another method for producing a metal separator having excellent corrosion resistance, low contact resistance, and high productivity is plasma spray coating of the metal separator using a suitable nano powder. However, in this case, depending on the physical properties of the nanopowder, there is a problem that dust is generated or that the nanopowder does not uniformly feed on the coating, resulting in a non-uniform coating film.

Accordingly, the present inventors have completed the present invention after having repeatedly studied nano powders applicable to plasma spray coating which can solve the above problems and their manufacturing methods.

An object of the present invention is to provide a coating composition for a solid oxide fuel cell metal separator for producing a metal separator having excellent corrosion resistance and low contact resistance.

Another object of the present invention is a powder for plasma spray coating which is contained in a coating composition for a solid oxide fuel cell metal separator.

It is another object of the present invention to provide a method for producing a plasma spray coating powder which is less dusty and can form a uniform coating film upon plasma spray coating.

In order to accomplish the above object, the present invention provides a method for preparing an aqueous solution, comprising the steps of: 1) dissolving a manganese compound and a copper compound in distilled water to prepare a Mn aqueous solution and an aqueous Cu solution; 2) mixing the Mn aqueous solution and the Cu aqueous solution at a volume ratio of 3: 1 to 1: 1 to prepare a first mixture; 3) adding the first mixture to an inorganic base aqueous solution; 4) filtering, washing and drying the precipitate produced in step 3); 5) heat treating the dried powder produced in the step 4) at 450 to 600 ° C; 6) mixing the calcined powder produced in the step 5) with an aqueous solution, and then pulverizing and preparing a slurry; 7) spray drying the slurry to produce spherical granular powder; And 8) heat-treating the powder produced in the step 7) at a temperature of 800 to 900 ° C. and sintering the powder.

The present invention also provides a powder for plasma spray coating produced by the method for producing plasma spray coating powder and a coating composition for a metal separator comprising the same. A preferable solid oxide fuel cell metal separator can be manufactured by forming a coating layer with the above composition on a separator plate base made of metal.

The embodiments of the present invention are described in order to more fully explain the present invention to those skilled in the art, and the following embodiments may be modified into various other forms, It is not limited to the embodiment. Rather, these embodiments are provided so that this disclosure will be more faithful and complete, and will fully convey the scope of the invention to those skilled in the art.

In the drawings, the thickness and size of each layer are exaggerated for convenience and clarity of description, and the same reference numerals refer to the same elements in the drawings. As used herein, the term " and / or " includes any and all combinations of one or more of the listed items.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" include singular forms unless the context clearly dictates otherwise. Also, " comprise " and / or " comprising " when used herein should be interpreted as specifying the presence of stated shapes, numbers, steps, operations, elements, elements, and / And does not preclude the presence or addition of one or more other features, integers, operations, elements, elements, and / or groups.

According to an embodiment of the present invention, there is provided a method for preparing a copper alloy, comprising the steps of: 1) dissolving a manganese compound and a copper compound in distilled water to prepare a Mn aqueous solution and an aqueous Cu solution; 2) mixing the Mn aqueous solution and the Cu aqueous solution at a volume ratio of 3: 1 to 1: 1 to prepare a first mixture; 3) adding the first mixture to an inorganic base aqueous solution; 4) filtering, washing and drying the precipitate produced in step 3); 5) heat treating the dried powder produced in the step 4) at 450 to 600 ° C; 6) mixing the calcined powder produced in the step 5) with an aqueous solution, and then pulverizing and preparing a slurry; 7) spray drying the slurry to produce spherical granular powder; And 8) heat-treating the powder produced in the step 7) at a temperature of 800 to 900 ° C. and sintering the powder.

The manufacturing method is based on Co-precipitation method, which is excellent in economical efficiency among various nanopowder production technologies and can be easily controlled and manufactured. The present invention is further characterized in that a sintering step in the above step is further applied do.

The metal elements of the manganese compound and the copper compound are excellent in corrosion resistance and easy to bond with oxygen, nitrogen and carbon. In addition, adhesion to a metal substrate is improved, and good conductivity and corrosion resistance can be exhibited for a long period even in a high temperature and acidic atmosphere. Further, by forming the coating to a thickness of 4 nm or more, it is possible to prevent formation of pinholes and prevent corrosion of the substrate and elution of the metal.

According to one embodiment of the invention, as the manganese compound is manganese sulfate (MnSO _4), manganese chloride (MnCl _2), manganese nitrate (Mn (NO _{3) 2),} and manganese acetate (Mn (CH ₃ COO) ₂ Preferably, the manganese chloride is a hydrate of the manganese chloride according to a commercial production form.

According to one embodiment of the invention, the copper compound is copper sulfate (CuSO _4), copper chloride (CuCl _2), copper nitrate (Cu (NO _{3) 2)} and copper acetate _{(Cu (CH 3 COO) 2} ) , And is preferably a copper chloride. The hydrate of the copper chloride may be used according to commercial production mode.

According to an embodiment of the present invention, the volume ratio of the Mn aqueous solution to the Cu aqueous solution in the step of mixing Mn aqueous solution and Cu aqueous solution is preferably 3: 1 to 1: 1, more preferably 3: 2 to 1: 1. If the amount of the manganese compound is less than the above ratio, a stable surface film can not be formed and a problem of corrosion resistance may be caused. If the amount of the manganese compound is larger than the above ratio, the expected effect is not large compared to the cost.

According to an embodiment of the present invention, the step of heat-treating in step 5) is preferably heat-treated for 2-4 hours. Further, in one embodiment of the present invention, the step of heat-treating and sintering in step 8) is preferably heat-treated for 2-4 hours. If the heating time is exceeded or less than the above-mentioned time, desired physical properties including hardness and the like may not be obtained.

In one embodiment of the present invention, the inorganic base in the step 3) includes, but is not limited to, alkali metal hydroxides including sodium hydroxide (NaOH) and potassium hydroxide (KOH), inorganic bases such as ammonium carbonate or alkali metal carbonate (S). A preferred inorganic base is sodium bicarbonate, but is not limited thereto. When sodium bicarbonate was used, the detection rate of Cu in the filtrate after coprecipitation was remarkably low. The detection of Cu in the filtrate means that Mn ₂ O ₃ is produced rather than Mn ₂ CuO ₄ due to the lack of Cu, which can be confirmed by the XRD results shown in FIG.

In one embodiment of the present invention, the plasma spray coating powder produced by the method of the present invention is prepared by pulverization and slurry after the first heat treatment (calcining step), spray drying the slurry to prepare a granular powder, The hardness is increased through the secondary heat treatment (sintering process), so that it is not cracked or dust is generated during the operation, and uniform spraying is possible by feeding uniformly during plasma spray coating.

According to an embodiment of the present invention, a separator plate material made of metal; And a coating layer formed of a coating composition for a solid oxide fuel cell metal separator including the powder for plasma spray coating.

As the material of the separator plate base material, any material that can be used for the metal separator plate for fuel cells can be used without limitation. Examples thereof include stainless steel, aluminum, titanium or nickel, or at least one of aluminum, May be provided. However, since the separator plate itself does not exhibit a satisfactory level of corrosion resistance and electrical conductivity characteristics in a harsh environment of high temperature and high humidity of the fuel cell, in order to compensate for this, in the coating composition for a solid oxide fuel cell metal separator, A coating layer is formed on the surface of the base material. This coating can improve the electrical conductivity, corrosion resistance, etc. of the metal separator.

The present invention provides a method for producing a plasma spray coating powder which is less dusty and capable of forming a uniform coating film upon plasma spray coating, and a powder for plasma spray coating produced by such a manufacturing method is provided.

FIG. 1 is an enlarged microphotograph of a powder for plasma spray coating produced by a manufacturing method according to an embodiment of the present invention, which is a comparison between powder before sintering and powder after sintering. (Powder (a) before sintering, powder (b) after sintering)
2 is XRD data of embodiments in which the inorganic base component is different in the coprecipitation step. (Example 1: Sodium Bicarbonate, Example 2: Sodium Carbonate, Example 3: Ammonia Water, Example 4: Ammonium Bicarbonate, Example 5: Ammonium Carbonate)

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood that both the foregoing description and the following detailed description are exemplary, explanatory and are intended to be illustrative, and not restrictive. The scope of the invention is defined by the appended claims rather than by the foregoing description. will be.

Example 1 Sintered Process for producing Mn ₂ CuO ₄ spinel material powder for plasma spray coating.

Copper (II) -chloride dehydrate and Manganese (II) -chloride tetrahydrate were each dissolved in distilled water in 50% solution. Cu aqueous solution was mixed with 40-45% of the aqueous solution of Mn, and then the raw material solution was added to a 7-9% aqueous solution of sodium bicarbonate 5-7 times as much as the raw material solution. The resulting precipitate was filtered, washed and dried (90-110 DEG C for 8 hours). The dried powder was subjected to a first heat treatment (450-600 DEG C for 2 hours), and the calcined powder was mixed with distilled water in a 40-55% aqueous solution and ground by a ball mill to prepare a slurry. The balls were filtered and the slurry was spray dried to produce spherical granular powder. The powder was subjected to a secondary heat treatment (sintering) at 800-900 ° C for 2 hours to obtain a sintered powder.

Example 2 Sintered Process for producing Mn ₂ CuO ₄ spinel material powder for plasma spray coating.

The procedure of Example 1 was repeated except that sodium carbonate was used as an inorganic base in Step 3 of Example 1 above.

Example 3 Sintered Process for producing Mn ₂ CuO ₄ spinel material powder for plasma spray coating.

The procedure of Example 1 was repeated except that ammonia water was used as a base in the third step of Example 1 above.

Example 4 Sintered Process for producing Mn ₂ CuO ₄ spinel material powder for plasma spray coating.

Was prepared in the same manner as in Example 1, except that ammonium bicarbonate was used as an inorganic base in Step 3 of Example 1 above.

Example 5 Sintered Process for producing Mn ₂ CuO ₄ spinel material powder for plasma spray coating.

The procedure of Example 1 was repeated except that ammonium carbonate was used as an inorganic base in Step 3 of Example 1 above.

Comparative Example 1 Process for producing Mn ₂ CuO ₄ spinel material powder for plasma spray coating.

A powder was prepared in the same manner as in Example 1 except that the second heat treatment step was not carried out.

Fig. 2 shows the XRD results of the examples prepared in Examples 1 to 5 above. Example 1 In a further embodiment, except for nopeunde in after co-precipitation filtrate by the relatively Cu detected amount, which means that due to a Cu deficiency, the Mn ₂ O ₃ instead of Mn ₂ CuO ₄ that the relatively more generated, these results It may affect the physical properties of the metal separator during the manufacture of the metal separator.

[ Manufacturing Example 1] Production of metal separator

1) Separation plate Of base metal  Produce

A metal separator for fuel cells was fabricated by using stainless steel (316L, thickness 0.1mm) as a separator plate specimen base material. In preparing the metal separator for fuel cells, wet cleaning was first performed using acetone for 5 minutes, wet cleaning was performed using ethanol for 5 minutes, and dry cleaning was performed using plasma etching using argon gas .

2) Coating

The coating composition including the powder prepared in Example 1 was coated on the stainless steel surface using a spray coating method and dried at 180 for 10 seconds. Lt; / RTI > for 10 minutes.

[ Comparative Example 1] Production of metal separator plate

A metal separator was prepared in the same manner as in Preparation Example 1, except that the powder prepared in Comparative Example 1 was used in place of the powder prepared in Example 1.

Experimental Example  One Contact resistance measurement

A contact resistance measurement device was used to measure the contact resistance between the metal separator plate and the carbon paper by the modified Davies method to obtain an optimized constant for cell clamping to measure the contact resistance of the metal separator for fuel cells. Respectively.

Contact Resistance (㏁㎠) Production Example 1 20.6 Comparative Example 1 16.1

In the contact resistance measurement experiment for measuring the contact resistance according to the presence or absence of the metal element, Production Example 1 was performed at 20.6 ㏁ cm ² , But Comparative Example 1 shows 16.1 MΩcm ² , Which is a value decreased by 16 to 22% as compared with that of Production Example 1.

Experimental Example  2 Measurement of corrosion current

EG & G 273A was used as a measuring device to measure the corrosion current. The corrosion durability test was compared and evaluated by the corrosion current data of 0.6V vs SCE (Saturated Calomel Electrode) in a cathode environment similar to the driving atmosphere of PEFC (Polymer Electrolyte Fuel Cell).

Corrosion current (mA / cm 2) Production Example 1 2.4 Comparative Example 1 8.1

The metal separator prepared in Preparation Example 1 had a low corrosion current value of 2.4, but in Comparative Example 1, it showed a high corrosion current value of 8.1. It can be understood that the metal separator of Production Example 1 has higher corrosion resistance than Comparative Example 1 that the corrosion current value is high.

Claims (12)

1) preparing a Mn aqueous solution and an aqueous Cu solution by dissolving a manganese compound and a copper compound in distilled water, respectively;
2) mixing the Mn aqueous solution and the Cu aqueous solution at a volume ratio of 3: 1 to 1: 1 to prepare a first mixture;
3) adding the first mixture to an inorganic base aqueous solution;
4) filtering, washing and drying the precipitate produced in step 3);
5) heat treating the dried powder produced in the step 4) at 450 to 600 ° C;
6) mixing the calcined powder produced in the step 5) with an aqueous solution, and then pulverizing and preparing a slurry;
7) spray drying the slurry to produce spherical granular powder; And
8) heat-treating the powder produced in the step 7) at 800 to 900 ° C. and sintering the powder. The method according to claim 1,
The manganese compound being selected from the group consisting of manganese sulfate (MnSO _4), manganese chloride (MnCl _2), manganese nitrate (Mn (NO _{3) 2),} and manganese acetate _{(Mn (CH 3 COO) 2} ) Wherein the plasma spray coating method comprises the steps of: The method according to claim 1,
It is selected from the group consisting of the above copper compound with copper sulfate (CuSO _4), copper chloride (CuCl _2), copper nitrate (Cu (NO _{3) 2)} and copper acetate _{(Cu (CH 3 COO) 2} ) Wherein the plasma spray coating method comprises the steps of: The method according to claim 1,
Wherein the volume ratio of the Mn aqueous solution and the Cu aqueous solution in the second step is 3: 2 to 1: 1. The method according to claim 1,
Wherein the step of heat treating in step 5) is heat-treated for 2-4 hours. The method according to claim 1,
Wherein the step of heat-treating and sintering in step 8) is heat-treated for 2 to 4 hours. The method according to claim 1,
Wherein the inorganic base in step 3) is sodium bicarbonate. 3. The method of claim 2,
Wherein the manganese compound is manganese chloride (MnCl ₂ ). The method of claim 3,
Wherein the copper compound is copper chloride (CuCl ₂ ). The powder for plasma spray coating according to any one of claims 1 to 9, which is produced by the process for producing a plasma spray coating powder. 11. A coating composition for a metal separator comprising a powder for plasma spray coating according to claim 10. Separating plate base material made of metal; And
And a coating layer formed from the coating composition for a metal separator according to claim 11.

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