| 主权项 |
1. An environmental barrier coating for high temperature ceramic components, the barrier coating comprising:
a bond coat layer comprising silicon; an optional silica layer; at least one transition layer consisting of about 85% to about 99% by volume of a primary transition material comprising mullite or a mullite/BSAS mixture, optionally a first sintering aid dissolved in the primary transition material and 1% to about 15% by volume of a first secondary material; an outer layer consisting of about 1% to about 15% by volume of a second secondary material, about 85% to about 100% by volume of a primary outer material comprising BSAS, and optionally a second sintering aid dissolved in the primary outer material; and the first and second sintering aids being selected from water soluble sintering aids and solvent soluble sintering aids, the water soluble sintering aids being chosen from the group consisting of rare earth nitrate, rare earth acetate, rare earth chloride, rare earth oxide, ammonium phosphate, phosphoric acid, polyvinyl phosphonic acid, and combinations thereof, the solvent soluble sintering aids being chosen from the group consisting of solvent soluble rare earth sources and solvent soluble phosphorous sources, and the first and second secondary materials being chosen from the group consisting of rare earth oxides, rare earth disilicates, rare earth monosilicates, rare earth elements, rare earth containing aluminosilicate glasses, rare earth and alkaline earth containing aluminosilicate glasses, rare earth aluminates, phosphorous pentoxide, phosphorous containing aluminosilicate glasses, phosphorous and alkaline earth containing aluminosilicate glasses, aluminum orthophosphate, aluminum oxide, and combinations thereof; wherein the transition layer is produced by sintering a transition layer slurry comprising particles of the primary transition material and particles of the first sintering aid, and the sintering step consolidates the particles of the primary transition material in the presence of the first sintering aid and forms the first secondary material as a reaction product of the first sintering aid and the primary transition material; wherein the outer layer is produced by sintering an outer layer slurry comprising particles of the primary outer material and particles of the second sintering aid, and the sintering step consolidates the particles of the primary outer material in the presence of the second sintering aid and forms the second secondary material as a reaction product of the second sintering aid and the primary outer material; and wherein the transition layer has a porosity of less than 10% by volume, and the outer layer has a porosity of less than 10% by volume. |
