Thermal barrier coating compositions, methods of manufacture thereof and articles comprising the same

1. A process for coating a component, comprising:

applying a bond coat on a substrate of a component;

applying a thermal barrier material to the bond coat; and

applying a coating containing polynuclear aluminum oxide/hydroxide clusters, to the thermal barrier material; wherein the polynuclear aluminum oxide/hydroxide clusters are Al 13 Keggin clusters having the formula [AlO 4 Al 12 (OH) 24 (H 2 O) 12 ] 7+ , or are Al 13 Keggin complexes of salts of the Al 13 Keggin clusters, wherein the Al 13 Keggin complex has the formula {[AlO 4 Al 12 (OH) 24 (H 2 O) 12 ] 7+ *7NO 3 − }.

2. The process of claim 1 , wherein the Al 13 Keggin complex has the formula {[AlO 4 Al 12 (OH) 24 (H 2 O) 12 ] 7+ *7NO 3 − }.

3. The process of claim 1 , further comprising obtaining the Al 13 Keggin clusters or the Al 13 Keggin complexes by base neutralization of an aluminum salt solution, where the salt solution comprises a total aluminum concentration of about 0.02 to about 2.0 moles/liter, to obtain an (OH − /Al) mole ratio of about 2.1 to about 2.6.

4. The process of claim 1 , further comprising obtaining the Al 13 Keggin clusters or the Al 13 Keggin complexes by base neutralization of an aluminum salt solution, where the salt solution comprises a total aluminum concentration of about 0.02 to about 2.0 moles/liter, to obtain an (OH − /Al) mole ratio of about 2.2 to about 2.4.

5. The process of claim 1 , further comprising preparing the coating from a solution that comprises the Al 13 Keggin clusters or the Al 13 Keggin complexes in an amount of about 0.007 to about 0.07 moles/liter of the solution; where the solution comprises water or an organic solvent.

6. The process of claim 5 , further comprising precipitating the Al 13 Keggin clusters or the Al 13 Keggin complexes from a solution and collecting the Al 13 Keggin clusters or the Al 13 Keggin complexes by filtration, and drying the solution to form Al 13 Keggin cluster and/or Al 13 Keggin complex powder.

7. The process of claim 6 , further comprising dissolving the Al 13 Keggin cluster or Al 13 Keggin complex powder in water with a polymeric binder to form the coating.

8. The process of claim 1 , wherein the coating is applied by painting, spraying, electrostatic spraying, or spin-coating.

9. The process of claim 1 , further comprising drying the Al 13 Keggin clusters to form a pre-condensed coating of hydrated pseudo-boehmite (AlOOH*H 2 O), aluminum trihydroxide, or a combination thereof.

10. The process of claim 1 , further comprising heat treating the coating to form a fully dense transition alumina coating selected from the group consisting of χ-Al 2 O 3 , η-Al 2 O 3 and γ-Al 2 O 3 that has a thickness of about 1 to about 1000 nanometers.

11. The process of claim 1 , further comprising coagulating the Al 13 Keggin clusters or the Al 13 Keggin complexes with an aqueous solution of sodium silicate, where the sodium silicate is present in an amount of about 0.01 to about 0.1 moles/liter to form a hydroxy aluminosilicate compound, where the sodium silicates comprise sodium meta-silicate, sodium orthosilicate, disodium disilicate, or a combination thereof.

12. The process of claim 11 , wherein an Al/Si atomic ratio ranges from about 5:1 to 15:1.

13. The process of claim 11 , wherein the coating comprises the Al 13 Keggin cluster and the hydroxy aluminosilicate compound and wherein the coating is applied by dipping, painting, spraying, electrostatic spraying, spin-coating, or a combination thereof.