Claims
- 1. 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, wherein said modifier component comprises an alkaline earth aluminosilicate.
- 2. The method of claim 1, further comprising annealing said modified mullite coating to convert a glass phase of said modifier component to a phase compatible with said mullite.
- 3. The method of claim 1, further comprising applying an external environmental/thermal barrier coating onto said modified mullite coating.
- 4. The method 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.
- 5. The method 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.
- 6. The method 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.
- 7. The method 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 method of claim 1, wherein said modifier component comprises a monoclinic celsian crystalline phase.
- 9. The method of claim 1, wherein said modifier component comprises barium strontium aluminosilicate (BSAS), calcium aluminosilicate (CAS), or a combination thereof.
- 10. The method of claim 1, wherein said modifier component comprises cordierite (2MgO.2Al2O3.5SiO2).
- 11. The method of claim 1, comprising adding a volume fraction of the modifier component in the modified mullite coating 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.
- 12. The method of claim 1, comprising applying said modified mullite coating by thermal spray, high velocity oxy-fuel (HVOF) spray, vapor deposition, physical vapor deposition (PVD) or solution technique.
- 13. The method of claim 1, comprising applying said modified mullite coating by air plasma spray, vacuum plasma spray or low pressure plasma spray.
- 14. The method of claim 1, comprising applying said modified mullite coating by chemical vapor deposition.
- 15. The method of claim 1, comprising applying said modified mullite coating by sol-gel, slurry coating or colloidal suspension coating.
- 16. The method of claim 1, comprising forming the modified mullite coating by first forming a starting powder of the coating and modifier component by ball milling.
- 17. The method of claim 1, comprising forming the modified mullite coating by a sol-gel or colloidal process.
- 18. 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, said modifier component comprising a material having a formula of MO.Al2O3.2SiO2, where M is an alkaline earth element.
- 19. 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, wherein said modifier component comprises an NZP modifier.
- 20. The method of claim 19, wherein said modifier component comprises NaZr2P3O12, Ba1.25Zr4P5.5Si0.5O2.4, Ca0.5Sr0.5Zr4(PO4)6 or Ca0.6Mg0.4Sr4(PO4)6.
- 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, said modifier component comprising a calcium aluminate or an aluminum titanate.
- 22. The method of claim 21, wherein said modifier component comprises 3Ca0.5.5 Al2O3, or Al2O3.TiO3.
- 23. 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.
- 24. The method of claim 23 further comprising applying a yttria-stabilized zirconia coating to the modified mullite coating.
- 25. 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, said modifier component comprising yttrium silicate.
Parent Case Info
This application is a division of U.S. patent application Ser. No. 09/299,419, filed on Apr. 26, 1999, now U.S. Pat. No. 6,485,848, which claims the benefit under 35 U.S.C. 119(e) of provisional patent application having Ser. No. 60/083,158; filed on Apr. 27, 1998.
Government Interests
This invention was made with government support under Contract No. NAS3-26385 awarded by NASA. The government may have certain rights in the invention.
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Provisional Applications (1)
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