Ceramic felt material for high-temperature fuel cells

1. An inorganic felt material for a molten carbonate fuel cell gasket, comprising:

cubic zirconia stabilized by at least one Group IIA material; wherein:

the cubic zirconia is present at a concentration of 80-87 mol % in the inorganic felt material;

yttrium is present at a concentration of at least 8 mol % in the inorganic felt material;

the at least one Group IIA material comprises calcium, present at a concentration of no greater than 5 mol %, and magnesium, present at a concentration of no greater than 10 mol % in the inorganic felt material; and

the concentrations of yttrium, calcium, and magnesium in the inorganic felt material satisfy equations (1), (2), and (3):

16≤ x+ 2 y+z≤ 20  (1)

8≤ x/ 2+ y+z≤ 13  (2)

y≤ 5,  (3)

wherein x=mol % yttrium, y=mol % calcium, and z=mol % magnesium; and

the inorganic felt material exhibits a carbonate uptake rate of 2.0 wt. % or less after 100 hours operation in contact with a molten carbonate electrolyte at 650° C.

2. The inorganic felt material of claim 1 , wherein the at least one Group IIA material is present in a concentration of 2 mol % to 15 mol %.

3. The inorganic felt material of claim 1 , wherein x, y, and z, respectively, are as follows:

x= 10; y= 4; z= 2; or

x= 8; y= 4; z= 4.

4. A method for fabricating an inorganic felt material for a molten carbonate fuel cell gasket, comprising:

(a) saturating an organic felt material with an inorganic salt solution comprising 84-87 mol % of a zirconium-based compound, 8-10 mol % of a yttrium-based compound, 3-4 mol % of a calcium-based compound, and 2-10 mol % of a magnesium-based compound, wherein the concentrations of the zirconium-based compound, the yttrium-based compound, the calcium-based compound, and the magnesium-based compound are expressed in terms of mol %, relative to the total moles of inorganic salts present in the inorganic salt solution;

(b) removing excess inorganic salt solution;

(c) drying the organic felt material to form a structure comprising at least one zirconium-based inorganic layer over the organic felt material;

(d) heat-treating the structure to remove the organic felt material and form a zirconia felt layer;

(e) repeating (a)-(d) a plurality of times to form a plurality of zirconia felt layers;

(f) stacking the plurality of zirconia felt layers to a predetermined thickness; and

(g) sintering the plurality of zirconia felt layers at a temperature in the range of 1500° C. to 1625° C. to form the inorganic felt material;

wherein:

the inorganic felt material comprises cubic zirconia stabilized by at least one Group IIA material;

the cubic zirconia is present at a concentration of 80-87 mol % in the inorganic felt material;

yttrium is present at a concentration of at least 8 mol % in the inorganic felt material;

the at least one Group IIA material comprises calcium, present at a concentration of no greater than 5 mol %, and magnesium, present at a concentration of no greater than 10 mol % in the inorganic felt material; and

the concentrations of yttrium, calcium, and magnesium in the inorganic felt material satisfy equations (1), (2), and (3):

(1) 16≤x+2y+z≤20

(2) 8≤x/2+y+z≤13

(3) y≤5,

wherein x=mol % yttrium, y=mol % calcium, and z=mol % magnesium; and

the molten carbonate fuel cell gasket exhibits a carbonate uptake rate of 2.0 wt. % or less after 100 hours operation in contact with a molten carbonate electrolyte at 650° C.

5. The method of claim 4 , wherein the drying occurs at a temperature in the range of 50° C. to 150° C. and for a time in the range of 0.5 hrs to 1.5 hrs.

6. The method of claim 4 , wherein the heat-treating occurs at a temperature in the range of 50° C. to 150° C. and for a time in the range of 24 hrs to 72 hrs.

7. The method of claim 4 , wherein the stacking occurs at a temperature in the range of 800° C. to 1200° C.

8. The method of claim 4 , further comprising:

cooling the inorganic felt material at a temperature in the range of 900° C. to 1100° C. and for a time in the range of 1.0 hrs to 10 hrs.

9. The method of claim 4 , wherein the inorganic salt solution comprises 84 mol % of the zirconium-based compound, 8-10 mol % of the yttrium-based compound, 4 mol % of the calcium-based compound, and 2-4 mol % of the magnesium-based compound.

10. The method of claim 4 , wherein x, y, and z, respectively, are as follows:

x= 10; y= 4; z= 2; or

x= 8; y= 4; z= 4.

11. The method of claim 4 , wherein x=8; y=4; and z=4.

12. The method of claim 11 , wherein the carbonate uptake rate is 0.2 wt. % or less after 100 hours operation in contact with a molten carbonate electrolyte at 650° C.