Claims
- 1. An article comprising:
a silicon-containing substrate; and a modified mullite coating comprising mullite and a modifier component that reduces cracks in the modified mullite coating.
- 2. The article of claim 1, wherein said modifier component comprises a lower thermal expansion component than mullite that imparts a closer coefficient of thermal expansion match between said modified mullite coating and said silicon-containing substrate.
- 3. The article of claim 1, wherein said modifier component forms a phase in said modified mullite coating that reduces thermal stress in the modified mullite coating by reducing the elastic modulus of said modified mullite coating.
- 4. The article of claim 1, wherein said modifier component forms a phase in said modified mullite coating that arrests the propagation of cracks in said modified mullite coating.
- 5. The article of claim 1, wherein said modifier component comprises an alkaline earth aluminosilicate.
- 6. The article of claim 1, wherein said modifier component comprises a modifier component of the formula MO.Al2O3.xSiO2, where M is an alkaline earth element and 1≦x≦3.
- 7. The article of claim 1, wherein said modifier component comprises barium feldspar (BaO.Al2O3.2SiO2), strontium feldspar (SrO.Al2O3.2SiO2) or a combination of barium feldspar (BaO.Al2O3.2SiO2), and strontium feldspar (SrO.Al2O3.2SiO2).
- 8. The article of claim 1, wherein said modifier component comprises a monoclinic celsian crystalline phase.
- 9. The article of claim 1, wherein said modifier component comprises barium strontium aluminosilicate (BSAS), calcium aluminosilicate (CAS), yttrium silicate (YS) or a combination thereof.
- 10. The article of claim 1, wherein said modifier component comprises an NZP (NaZr2P3O12) modifier.
- 11. The article of claim 10, wherein said modifier component comprises NaZr2P3O12, Ba1 25Zr4P5 5SiO0 5O24, Ca0 5Sr0 5Zr4(PO4)6 or Ca0 6Mg0 4Sr4(PO4)6.
- 12. The article of claim 1, wherein said modifier component comprises a calcium aluminate or an aluminum titanate.
- 13. The article of claim 1, wherein said modifier component comprises 3Ca0.5.5 Al2O3, or Al2O3.TiO2.
- 14. The article of claim 1, wherein said modifier component comprises cordierite (2MgO.2Al2O3.5SiO2), fused silica (SiO2) silicon (Si), or mixture thereof.
- 15. The article of claim 1, wherein said silicon-containing substrate is a monolithic or composite silicon carbide/silicon ceramic.
- 16. The article of claim 1, wherein said silicon-containing substrate is a monolithic or composite silicon nitride.
- 17. The article of claim 1, further comprising an external environmental/thermal barrier coating applied to said modified mullite coating.
- 18. The article of claim 17, wherein said modified mullite coating functions as a bond coating between said external environmental/thermal barrier coating and said silicon-containing substrate.
- 19. The article of claim 17, wherein said thermal barrier coating comprises yttria-stabilized zirconia, scandia-stabilized zirconia, calcia-stabilized zirconia, magnesia-stabilized zirconia, alumina or alumina silicate.
- 20. The article of claim 2, wherein a volume faction of the modifier component in the modified mullite coating is proportionate to a ratio of a difference between a coefficient of thermal expansion of the silicon-containing substrate and the coefficient of thermal expansion of a mullite to a difference between a coefficient of thermal expansion of the modifier component and the coefficient of thermal expansion of the mullite.
- 21. A method of forming an article, comprising; forming a silicon-containing substrate; and applying a modified mullite coating comprising mullite and a modifier component that reduces cracks in the modified mullite coating.
- 22. The method of claim 21, further comprising annealing said modified mullite coating to convert a glass phase of said modifier component to a phase compatible with said mullite.
- 23. The method of claim 21, further comprising applying an external environmental/thermal barrier coating onto said modified mullite coating.
- 24. The method of claim 21, wherein said modifier component comprises a lower thermal expansion component than mullite that imparts a closer coefficient of thermal expansion match between said modified mullite coating and said silicon-containing substrate.
- 25. The method of claim 21, wherein said modifier component forms a phase in said modified mullite coating that reduces thermal stress in the modified mullite coating by reducing the elastic modulus of said modified mullite coating.
- 26. The method of claim 21, wherein said modifier component forms a phase in said modified mullite coating that arrests the propagation of cracks in said modified mullite coating.
- 27. The method of claim 21, wherein said modifier component comprises alkaline earth aluminosilicates.
- 28. The method of claim 21, wherein said modifier component comprises a modifier component of the formula MO.AL2O3.2SiO2, where M is an alkaline earth element.
- 29. The method of claim 21, wherein said modifier component comprises barium feldspar (BaO.Al2O3.2SiO2), strontium feldspar (SrO.Al2O3.2SiO2) or a combination of barium feldspar (BaO.Al2O3.2SiO2), and strontium feldspar (SrO.Al2O3.2SiO2).
- 30. The method of claim 21, wherein said modifier component comprises a monoclinic celsian crystalline phase.
- 31. The method of claim 21, wherein said modifier component comprises barium strontium aluminosilicate (BSAS), calcium aluminosilicate (CAS), yttrium silicate (YS) or a combination thereof.
- 32. The method of claim 21, wherein said modifier component comprises an NZP modifier.
- 33. The method of claim 32, wherein said modifier component comprises NaZr2P3O12, Ba1 25Zr4P5 5Si0 5O24, Ca0 5Sr0.5Zr4(PO4)6 or Ca0 6Mg0 4Sr4(PO4)6.
- 34. The method of claim 21, wherein said modifier component comprises a calcium aluminate or an aluminum titanate.
- 35. The method of claim 21, wherein said modifier component comprises 3Ca0.5.5 Al2O3, or Al2O3.TiO3.
- 36. The method of claim 21, wherein said modifier component comprises cordierite (2MgO.2Al2O3.5SiO2), fused silica (SiO2) or silicon (Si).
- 37. The method of claim 21, comprising adding a volume faction of the modifier component in the modified mullite coating is proportionate to a ratio of a difference between a coefficient of thermal expansion of the silicon-containing substrate and the coefficient of thermal expansion of a mullite to a difference between a coefficient of thermal expansion of the modifier component and the coefficient of thermal expansion of the mullite.
- 38. The method of claim 21, comprising applying said modified mullite coating by thermal spray, high velocity oxy-fuel (HVOF) spray, vapor deposition, physical vapor deposition (PVD) or solution technique.
- 39. The method of claim 21, comprising applying said modified mullite coating by air plasma spray, vacuum plasma spray or low pressure plasma spray.
- 40. The method of claim 21, comprising applying said modified mullite coating by chemical vapor deposition.
- 41. The method of claim 21, comprising applying said modified mullite coating by sol-gel, slurry coating or colloidal suspension coating.
- 42. The method of claim 21, comprising forming the modified mullite coating by first forming a starting powder of the coating and modifier component by ball milling.
- 43. The method of claim 21, comprising forming the modified mullite coating by a sol-gel or colloidal process.
- 44. A method for making a coated article comprising forming a silicon/silicon carbide composite having silicon carbide-containing fibers; applying a modified mullite coating comprising mullite and barium strontium aluminosilicate (BSAS), that reduces cracks in the modified mullite coating; and optionally applying a yttria-stabilized zirconia coating to the modified mullite coating.
- 45. A coated article comprising a silicon/silicon carbide composite having silicon carbide-containing fibers; a modified mullite coating comprising mullite and barium strontium aluminosilicate (BSAS), that reduces cracks in the modified mullite coating; and optionally a yttria-stabilized zirconia coating on the modified mullite coating.
Government Interests
[0001] This invention was made with government support under Contract No. NAS3-26385 awarded by NASA. The government may have certain rights in the invention.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60083158 |
Apr 1998 |
US |
Divisions (1)
|
Number |
Date |
Country |
Parent |
09299419 |
Apr 1999 |
US |
Child |
10233359 |
Sep 2002 |
US |