COMPOSITE COATING LAYER FOR HOT BALANCE OF PLANT IN SOLID OXIDE FUEL CELL

Abstract

A composite coating layer for a solid oxide fuel cell member according to the present disclosure includes a nickel layer that coats at least a portion of the surface of the solid oxide fuel cell member, and a lanthanum oxide layer that coats at least a portion of the surface of the nickel layer, and thereby, has an effect of suppressing the volatilization of chromium from the solid oxide fuel cell member even under high temperature and long-term conditions.

Claims

1. A composite coating layer for a solid oxide fuel cell member, the composite coating layer comprising: a nickel layer that coats at least a portion of the surface of the solid oxide fuel cell member; and a lanthanum oxide layer that coats at least a portion of the surface of the nickel layer.

2. The composite coating layer of claim 1, wherein: the solid oxide fuel cell member is a metal material member containing chromium.

3. The composite coating layer of claim 1, wherein: the nickel layer contains 99.0 wt. % or more of nickel based on the total weight of the nickel layer.

4. The composite coating layer of claim 1, wherein: the nickel layer has a thickness of 50 nm to 200 nm.

5. The composite coating layer of claim 1, wherein: lanthanum oxide of the lanthanum oxide layer is La.sub.2O.sub.3.

6. The composite coating layer of claim 1, wherein: the lanthanum oxide layer contains 99.0 wt. % or more of lanthanum oxide based on the total weight of the lanthanum oxide layer.

7. The composite coating layer of claim 1, wherein: the lanthanum oxide layer has a thickness of 100 nm to 10,000 nm.

8. A solid oxide fuel cell member coated with the composite coating layer of claim 1.

9. The solid oxide fuel cell member of claim 8, wherein: the solid oxide fuel cell member is a metal material member containing chromium.

10. The solid oxide fuel cell member of claim 8, wherein: the solid oxide fuel cell member is a member of a peripheral auxiliary device of the solid oxide fuel cell.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 shows the visual observation results of Quartz Wool for the degree of chromium volatilization of the cylindrical SUS of Example 1 of the present disclosure;

[0032] FIG. 2 shows the visual observation results of Quartz Wool for the degree of chromium volatilization of the cylindrical SUS of Comparative Example 1 of the present disclosure;

[0033] FIG. 3 shows the visual observation results of Quartz Wool for the degree of chromium volatilization of the cylindrical SUS of Comparative Example 2 of the present disclosure; and

[0034] FIG. 4 shows the microstructure shape and EDS results of the cylindrical SUS of Example 1 of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] Hereinafter, Examples and Experimental Examples of the present disclosure will be described in detail. These Examples and Experimental Examples are for explaining the present disclosure more specifically, and the scope of the present disclosure is not limited to these Examples and Experimental Examples.

Example 1

[0036] A coating layer was formed on SUS 430 used for manufacturing a solid oxide fuel cell stack by the following method.

[0037] Step 1) Surface Treatment

[0038] Cylindrical SUS (diameter: ¾ inch) was polished by using #320 light sandpaper. Then, the cylindrical SUS was exposed to a hydrofluoric acid (HF) aqueous solution diluted to a concentration of 1% for 4 hours, thereby performing surface treatment.

[0039] Step 2) Formation of Nickel Layer

[0040] Then, the Ni coating layer was introduced through the electroplating method. Specifically, boric acid was dissolved in a 1M nickel sulfate aqueous solution and a 0.2M nickel chloride aqueous solution to adjust the pH to about 4.0. The cylindrical SUS treated in step 1 was added as a negative electrode thereto, and a current of 5.4 A/dm.sup.2 was applied to the cylindrical SUS at 50° C. At this time, the positive electrode was placed in nickel to perform a nickel electroplating. After electroplating, the cylindrical SUS was completely dried.

[0041] Step 3) Formation of Lanthanum Oxide Layer

[0042] Then, the cylindrical SUS treated in step 2 was immersed in 1M La nitrate aqueous solution, and then a voltage was applied. Specifically, deposition was carried out under deposition conditions of −1.1 V, total deposition charge of 4.0 C, and about 20 minutes, and it was confirmed that a stable La.sub.2O.sub.3 oxide was coated onto the surface. All deposition processes were performed at normal temperature (23° C.) and normal pressure (1 atm).

Comparative Example 1

[0043] A coating layer was formed by the same method, except that the Ni coating layer was introduced in Example 1, which was used as Comparative Example 1.

Comparative Example 2

[0044] A cylindrical SUS without any treatment was used as Comparative Example 2.

Experimental Example 1: Evaluation of Chromium Volatilization Inhibition Performance

[0045] Using the cylindrical SUS prepared above, the degree of chromium volatilization was evaluated as follows.

[0046] Specifically, a cylindrical SUS was placed in the middle of the quartz tube, and one end was filled with Quartz Wool so that the Cr component volatilized from the SUS could be collected. The prepared tube was loaded into the furnace, and after flowing 5000 sccm air at 850° C. and exposing it to a deteriorated environment for 200 hours to generate chromium vapor, and then condensed and collected in Quartz wool at low temperature (15° C., cooling water circulation).

[0047] Through the color that appears due to chromium volatilization, it was qualitatively confirmed whether or not it was collected. The content of the chromium component collected through ICP-MS analysis was quantitatively analyzed according to the type and presence of the coating layer.

[0048] First, as shown in FIG. 1, each Quartz Wool was observed with the naked eye. As shown in FIG. 1, it was confirmed that in Comparative Example 2, the green chromium powder was collected, while in Examples and Comparative Example 1, chromium volatilization was suppressed from the cylindrical SUS.

[0049] Subsequently, in order to make a more accurate comparison, the amount of volatilized chromium in Example 1 and Comparative Example 1 was confirmed by ICP-MS analysis, and calculated by the following Equation, and the results are shown in Table 1 below. In the following Equation, a control group was based on Comparative Example 2.

[00001]$\begin{array}{c}\mathrm{Rate}\mathrm{of}\mathrm{chromium}\\ \mathrm{volatilization}\mathrm{decreased}\left(\%\right)\end{array}=\frac{\begin{array}{c}\mathrm{Collection}\mathrm{amount}\mathrm{of}\\ \mathrm{chromium}\left(\mathrm{control}\mathrm{group}\right)\end{array}-\begin{array}{c}\mathrm{Collection}\mathrm{amount}\mathrm{of}\\ \mathrm{chromium}\left(\mathrm{experimental}\mathrm{group}\right)\end{array}}{\mathrm{Collection}\mathrm{amount}\mathrm{of}\mathrm{chromium}\left(\mathrm{control}\mathrm{group}\right)}\times 100$

TABLE-US-00001 TABLE 1 Rate of chromium volatilization decreased (%) Example 1 95.50% Comparative 53.91% Example 1

[0050] As shown in Table 1, it was confirmed that when only the La.sub.2O.sub.3 coating layer was present, chromium volatilization was decreased by 53.91%, but when an additional Ni coating layer was introduced, it shows a high rate of chromium volatilization decreased of 95.50%. Therefore, it was confirmed that when La.sub.2O.sub.3 was coated onto the Ni coating layer, the most uniform oxide coating layer was introduced to effectively suppress chromium volatilization.

Experimental Example 2: Observation of Composite Coating Layer

[0051] The composite coating layer of the cylindrical SUS prepared in Example 1 was observed as follows.

[0052] First, the cross section of the cylindrical SUS was observed by SEM, and the result is shown in (1) of FIG. 4. As shown in FIG. 4(1), the presence and thickness of several coating layers deposited on the SUS can be confirmed.

[0053] Moreover, the cylindrical SUS was observed by SEM-Energy Dispersive Spectroscopy. Specifically, when an electron beam was scanned into a cylindrical SUS, the excited electrons in the element of the specimen were stabilized and a specific X-ray was emitted. At this time, because the intrinsic X-ray energy emitted for each element is different, component analysis is possible with this value. Therefore, as shown in (2), (3), (5), and (6) of FIG. 4, only the emission X-ray of a specific element was analyzed for each element (Fe, La, Ni, Cr), and the results are shown respectively.

[0054] For example, it can be confirmed that Fe is yellow and is located in the lower portion of the substrate, La is a red color, and is coated onto the upper part of the substrate. In addition, (3) of FIG. 4 shows the distribution of all elements together, and the distribution of each element can be confirmed by comparing it with (1) of FIG. 4.