Multilayer article characterized by low coefficient of thermal expansion outer layer

A multilayer article comprising:

• a substrate comprising a compound selected from the group consisting of a ceramic compound, a Si-containing metal alloy and combinations thereof, with the proviso that said substrate excludes C/C composites;
• an outer layer;
• and
• at least one intermediate layer located between said outer layer and said substrate, wherein said outer layer comprises a rare earth silicate having a low coefficient of thermal expansion less than 8×10−6/° C. and formula RE2O3.—SiO2, where RE is a rare earth element selected from the group consisting of Sc, Dy, Ho, Er, Tm, Yb, Lu, Eu, Gd, Tb and combinations thereof,
• wherein said rare earth silicate, is characterized by an X1 phase having the low coefficient of thermal expansion, where RE is selected from the group consisting of Eu, Gd, Tb and combinations thereof.

A multilayer article comprising:

• a substrate comprising a compound selected from the group consisting of a ceramic compound, a Si-containing metal alloy and combinations thereof, with the proviso that said substrate excludes C/C composites;
• an outer layer;
• and
• at least one intermediate layer located between said outer layer and said substrate,
• wherein said outer layer comprises a rare earth silicate having a low coefficient of thermal expansion less than 8×10−6/° C. and a formula selected from the group consisting of
• (a) RE2O3.SiO2,
• (b) 2RE2O3.3SiO2,
• (c) RE2O3.2SiO2, and combinations thereof, where RE is a rare earth element selected from the group consisting of Sc, Dy, Ho, Er, Tm, Yb, Lu, Eu, Gd, Tb and combinations thereof,
• comprising a silicon-containing layer comprising at least one of Si and a Si-containing alloy located between the at least one said intermediate layer and said substrate.

A multilayer article comprising:

• a substrate comprising a compound selected from the group consisting of a ceramic compound, a Si-containing metal alloy and combinations thereof;
• an outer layer;
• and
• at least one intermediate layer located between said outer layer and said substrate,
• wherein said outer layer comprises a hafnia-containing composite oxide comprising hafnia and a compound selected from the group consisting of barium strontium aluminosilicate, calcium aluminosilicate, magnesium aluminosilicate, rare earth silicate, niobium oxide, titania and combinations thereof.

A multilayer article comprising:

• a substrate comprising a compound selected from the group consisting of a ceramic compound, a Si-containing metal alloy and combinations thereof;
• an outer layer;
• and
• at least one intermediate layer located between said outer layer and said substrate,
• wherein the at least one said intermediate layer comprises a compound selected from one of (1) mullite and (2) mullite and a compound selected from the group consisting of barium strontium aluminosilicate, calcium aluminosilicate, magnesium aluminosilicate and combinations thereof, and
• wherein said outer layer comprises at least one of a) hafnia and b) a hafnia-containing composite oxide comprising hafnia and a compound selected from the group consisting of mullite, barium strontium aluminosilicate, calcium aluminosilicate, magnesium aluminosilicate, rare earth silicate, alumina, tantalum oxide, niobium oxide, silica, titania and combinations thereof.

A multilayer article comprising:

• a Substrate comprising a compound selected from the group consisting of a ceramic compound, a Si-containing metal alloy and combinations thereof;
• an outer layer, and
• at least one intermediate layer located between said outer layer and said substrate,
• wherein the at least one said intermediate layer comprises a chemical barrier layer located near said outer layer, said chemical barrier layer comprising a compound selected from the group consisting of mullite, hafnia, hafnium silicate, scandium silicate, ytterbium silicate and combinations thereof, and
• wherein said outer layer comprises at least one of a) hafnia and b) a hafnia-containing composite oxide comprising hafnia and a compound selected from the group consisting of mullite, barium strontium aluminosilicate, calcium aluminosilicate, magnesium aluminosilicate, rare earth silicate, alumina, tantalum oxide, niobium oxide, silica, titania and combinations thereof.

A multilayer article comprising:

• a substrate comprising a compound selected from the group consisting of a ceramic compound, a Si-containing metal alloy and combinations thereof;
• an outer layer;
• and
• at least one intermediate layer located between said outer layer and said substrate,
• wherein said outer layer comprises at least one of a) hafnia and b) a hafnia-containing composite oxide comprising hafnia and a compound selected from the group consisting of mullite, barium strontium aluminosilicate, calcium aluminosilicate, magnesium aluminosilicate, rare earth silicate, alumina, tantalum oxide, niobium oxide, silica, titania and combinations thereof, and
• further comprising a mullite chemical barrier layer disposed between the at least one said intermediate layer and said substrate.

A multilayer article comprising:

• a substrate comprising a compound selected from the group consisting of a ceramic compound, a Si-containing metal alloy and combinations thereof;
• an outer layer comprising:
• a zirconia-containing oxide comprising zirconia and a compound selected from the group consisting of silica, titania, tantalum oxide and combinations thereof;
• and
• at least one intermediate layer located between said outer layer and said substrate,
• wherein the at least one said intermediate layer comprises a compound selected from one of (1) mullite and (2) mullite and a compound selected from the group consisting of barium strontium aluminosilicate, calcium aluminosilicate, magnesium aluminosilicate and combinations thereof.

A multilayer article comprising:

• a substrate comprising a compound selected from the group consisting of a ceramic compound, a Si-containing metal alloy and combinations thereof;
• an outer layer comprising:
• a zirconia-containing oxide comprising zirconia and a compound selected from the group consisting of silica, titania, tantalum oxide and combinations thereof;
• and
• at least one intermediate layer located between said outer layer and said substrate,
• wherein the at least one said intermediate layer comprises a chemical barrier layer located near said outer layer, said chemical barrier layer comprising a compound selected from the group consisting of mullite, hafnia, hafnium silicate, scandium silicate, ytterbium silicate and combinations thereof.

A multilayer article comprising:

• a substrate comprising a compound selected from the group consisting of a ceramic compound, a Si-containing metal alloy and combinations thereof;
• an outer layer;
• and
• at least one intermediate layer located between said outer layer and said substrate,
• wherein said outer layer comprises a zirconia-containing oxide comprising zirconia and a compound selected from the group consisting of silica, titania, tantalum oxide and combinations thereof,
• wherein said outer layer has a coefficient of thermal expansion of not greater than 6×10−6/° C. and said outer layer and said intermediate layer are effective to inhibit penetration of water vapor to said substrate at a temperature of at least 1300° C., and
• a mullite chemical barrier layer disposed between the at least one said intermediate layer and said substrate.

A multilayer article comprising:

• a substrate comprising a compound selected from the group consisting of a ceramic compound, a Si-containing metal alloy and combinations thereof;
• an outer layer;
• and
• at least one intermediate layer located between said outer layer and said substrate,
• wherein said outer layer consists of a zirconia-containing oxide comprising zirconia and a compound selected from the group consisting of silica, titania, tantalum oxide and combinations thereof.

A multilayer article comprising:

• a substrate comprising a compound selected from the group consisting of a ceramic compound, a Si-containing metal alloy and combinations thereof;
• an outer layer comprising:
• a zirconia-containing oxide comprising zirconia and a compound selected from the group consisting of silica, titania, tantalum oxide and combinations thereof;
• and
• at least one intermediate layer located between said outer layer and said substrate,
• wherein the at least one said Intermediate layer comprises:
• a compound selected from one of (1) mullite and (2) mullite and a compound selected from the group consisting of barium strontium aluminosilicate, calcium aluminosilicate, magnesium aluminosilicate and combinations thereof;
• and
• a chemical barrier layer located near said outer layer, said chemical barrier layer comprising a compound selected from the group consisting of mullite, hafnia, hafnium silicate, scandium silicate, ytterbium silicate and combinations thereof.