Aluminosilicate-Based Oxide Composite Coating and Bond Coat for Silicon-Based Ceramic Substrates

• US 20100255289A1
• Filed: 01/24/2007
• Published: 10/07/2010
• Est. Priority Date: 01/25/2006
• Status: Abandoned Application

• Current Assignee: Balakrishnan G. Nair, Charles Lewinsohn, Qiang Zhao
• Original Assignee: Balakrishnan G. Nair, Charles Lewinsohn, Qiang Zhao
• Inventors: Zhao, Qiang, Lewinsohn, Charles, Nair, Balakrishnan G.
• Application Number:
  US11/626,804
• Publication Number:
  US 20100255289A1
• Time in Patent Office: Days
• US Class Current: 428/325
• CPC Class Codes: C04B 2235/3208 Calcium oxide or oxide-forming salts thereof, e.g. lime
• CPC Class Codes: C04B 2235/80 Phases present in the sintered or melt-cast ceramic products other than the main phase
• CPC Class Codes: C04B 2235/9607 Thermal properties, e.g. thermal expansion coefficient
• CPC Class Codes: C04B 35/195 Alkaline earth aluminosilicates, e.g. cordierite or anorthite
• CPC Class Codes: C04B 35/565 based on silicon carbide
• CPC Class Codes: C04B 35/584 based on silicon nitride
• CPC Class Codes: C04B 35/806 The matrix of the ceramic products consisting of non-oxides only
• CPC Class Codes: C04B 41/009 characterised by the material treated
• CPC Class Codes: C04B 41/4539 as a emulsion, dispersion or suspension
• CPC Class Codes: C04B 41/4554 the coating or impregnating material being an organic or organo-metallic precursor of an inorganic material
• CPC Class Codes: C04B 41/5024 Silicates C04B41/5022 takes precedence; silico-fluorides C04B41/5018
• CPC Class Codes: C04B 41/5037 Clay, Kaolin
• CPC Class Codes: C04B 41/5042 Zirconium oxides or zirconates; Hafnium oxides or hafnates
• CPC Class Codes: C04B 41/5059 Silicon carbide
• CPC Class Codes: C04B 41/5066 Silicon nitride
• CPC Class Codes: C04B 41/52 Multiple coating or impregnating multiple coating or impregnating with the same composition or with compositions only differing in the concentration of the constituents, is classified as single coating or impregnation
• CPC Class Codes: C04B 41/522 Multiple coatings, for one of the coatings of which at least one alternative is described
• CPC Class Codes: C04B 41/89 for obtaining at least two superposed coatings having different compositions
• CPC Class Codes: Y10T 428/252 Glass or ceramic [i.e., fired or glazed clay, cement, etc.] [porcelain, quartz, etc.]

Abstract

An article is disclosed in one embodiment of the invention as including a silicon-based ceramic substrate and a top coat. A bond coat is provided between the silicon-based ceramic substrate and the top coat. The bond coat is derived from a mixture containing preceramic polymer precursors, such as polycarbosilanes, polycarbosilazanes, or other silicocarbon polymers and pyrolyzed preceramic polymer precursors. A filler material may also be included in the mixture to modify the coefficient of thermal expansion (CTE) of the bond coat to more closely match the CTE of the silicon-based ceramic substrate, top coat, or both.

Claims

1. An article comprising:

a silicon-based ceramic substrate;

a top coat; and

a bond coat between the silicon-based ceramic substrate and the top coat, the bond coat derived from a mixture comprising a preceramic polymer precursor, a pyrolyzed preceramic polymer precursor, and a filler material selected to modify the coefficient of thermal expansion (CTE) of the bond coat to more closely match the CTE of at least one of the silicon-based ceramic substrate and the top coat.

2. The article of claim 1, wherein the preceramic polymer precursor is selected from the group consisting of polycarbosilanes, polycarbosilazanes, and silicocarbon polymers.

3. The article of claim 1, wherein the preceramic polymer precursor is a liquid.

4. The article of claim 1, wherein the pyrolyzed preceramic polymer precursor is a solid.

5. The article of claim 4, wherein the pyrolyzed preceramic polymer precursor is provided in powder form with an average particle size of less than five microns.

6. The article of claim 1, wherein the silicon-based ceramic substrate comprises a material selected from the group consisting of silicon nitride, silicon carbide, and a silicon-based ceramic matrix composite.

7. The article of claim 1, wherein the mixture further comprises an inert filler, the inert filler comprising at least one of material of the silicon-based ceramic substrate to promote adhesion to the silicon-based ceramic substrate, and material of the top coat to promote adhesion to the top coat.

8. The article of claim 1, wherein the mixture further comprises an active filler material selected to react with the preceramic polymer precursor and pyrolyzed preceramic polymer precursor to increase the volume of the bond coat material.

9. The article of claim 8, wherein the active filler material is selected from the group consisting of TiSi₂, TiH₂, Fe, Al, and Ni.

10. The article of claim 1, wherein the mixture further comprises at least one of solvents and organic additives to control the rheology of the mixture.

11. The article of claim 1, wherein the filler material comprises at least one of Al₂O₃, ZrO₂, Fe, Cu, Ni, Mo, Al, Ti, TiH₂, TiSi₂C, and MgO.

12. A bond coat slurry comprising:

a polymer preceramic precursor;

a pyrolyzed polymer preceramic precursor; and

a filler material selected to adjust the coefficient of thermal expansion of a bond coat produced from the bond coat slurry.

13. The bond coat slurry of claim 12, wherein the preceramic polymer precursor is selected from the group consisting of polycarbosilanes, polycarbosilazanes, and silicocarbon polymers.

14. The bond coat slurry of claim 12, wherein the preceramic polymer precursor is a liquid.

15. The bond coat slurry of claim 12, wherein the pyrolyzed preceramic polymer precursor is a solid.

16. The bond coat slurry of claim 15, wherein the pyrolyzed preceramic polymer precursor is a solid powder with an average particle size of less than five microns.

17. The bond coat slurry of claim 12, further comprising an inert filler material selected to promote bonding to at least one of a silicon-based ceramic substrate and a top coat.

18. The bond coat slurry of claim 12, further comprising an active filler material selected to react with the preceramic polymer precursor and pyrolyzed preceramic polymer precursor to increase the volume of the bond coat material.

19. The bond coat slurry of claim 18, wherein the active filler material is selected from the group consisting of TiSi₂, TiH₂, Fe, Al, and Ni.

20. The bond coat slurry of claim 12, further comprising at least one of solvents and organic additives to control the rheology of the bond coat slurry.

21. The article of claim 12, wherein the filler material comprises at least one of Al₂O₃, ZrO₂, Fe, Cu, Ni, Mo, Al, Ti, TiH₂, TiSi₂C, and MgO.

22. A method for applying an environmental barrier coating to a silicon-based ceramic substrate, the method comprising:

preparing a bond coat slurry, the bond coat slurry comprising a mixture containing a polymer preceramic precursor and a pyrolyzed polymer preceramic precursor;

wetting a silicon-based ceramic substrate with the bond coat slurry; and

pyrolyzing the bond coat slurry to create a bond coat on the silicon-based ceramic substrate.

23. The method of claim 22, wherein preparing a bond coat slurry comprises preparing multiple bond coat slurries for applying multiple bond coats to the silicon-based ceramic substrate.

24. The method of claim 22, further comprising wetting the bond coat with a top coat slurry.

25. The method of claim 24, wherein wetting the bond coat with a top coat slurry comprises wetting the bond coat with multiple top coat slurries to apply multiple top coats to the bond coat.

26. The method of claim 24, further comprising sintering the top coat slurry to create a top coat on the bond coat.

27. The method of claim 26, wherein pyrolyzing and sintering are conducted simultaneously.

28. The method of claim 26, wherein pyrolyzing and sintering are conducted consecutively.

29. The method of claim 26, wherein sintering comprises heating to a temperature above 1200°

C.

30. The method of claim 22, wherein pyrolyzing comprises heating to a temperature below 1200°

C.

31. The method of claim 22, wherein wetting comprises at least one of dip coating, spraying, painting, screen printing, and spin coating the silicon-based ceramic substrate with the bond coat slurry.