Inventive manufacture of CrB.sub.2—Al.sub.2O.sub.3 composites is based on pressureless sintering. According to typical inventive practice, CrB.sub.2 powder and Al.sub.2O.sub.3 powder are mixed together in selected volumetric proportions so that the volume of the CrB.sub.2 does not exceed 50% of the overall volume of the CrB.sub.2—Al.sub.2O.sub.3 mixture. The CrB.sub.2—Al.sub.2O.sub.3 mixture is shaped into a green body. The green body is pressureless sintered in a non-oxidizing atmosphere at a firing temperature in the approximate range between 1600° C. and 2050° C. The present invention succeeds in preparing, via pressureless sintering, a proportionality-associated range of compositions in the CrB.sub.2—Al.sub.2O.sub.3 system, which is a potentially “advanced” ceramic system. A typical inventively fabricated CrB.sub.2—Al.sub.2O.sub.3 composite is inventively configured in a complex shape, and has “advanced” material (e.g., mechanical) properties that are favorable for a contemplated application. Inventive manufacture of ceramic-ceramic composites is thus dually attributed, and uncommonly so, with complex shape-ability and advanced capability.

Inventive manufacture of CrB.sub.2—Al.sub.2O.sub.3 composites is based on pressureless sintering. According to typical inventive practice, CrB.sub.2 powder and Al.sub.2O.sub.3 powder are mixed together in selected volumetric proportions so that the volume of the CrB.sub.2 does not exceed 50% of the overall volume of the CrB.sub.2—Al.sub.2O.sub.3 mixture. The CrB.sub.2—Al.sub.2O.sub.3 mixture is shaped into a green body. The green body is pressureless sintered in a non-oxidizing atmosphere at a firing temperature in the approximate range between 1600° C. and 2050° C. The present invention succeeds in preparing, via pressureless sintering, a proportionality-associated range of compositions in the CrB.sub.2—Al.sub.2O.sub.3 system, which is a potentially “advanced” ceramic system. A typical inventively fabricated CrB.sub.2—Al.sub.2O.sub.3 composite is inventively configured in a complex shape, and has “advanced” material (e.g., mechanical) properties that are favorable for a contemplated application. Inventive manufacture of ceramic-ceramic composites is thus dually attributed, and uncommonly so, with complex shape-ability and advanced capability.

A method for enhancing optical properties of sintered, zirconia ceramic bodies and zirconia ceramic dental restorations is provided. The porous or pre-sintered stage of a ceramic body is treated with two different yttrium-containing compositions and sintered, resulting in sintered ceramic bodies having enhanced optical properties. The enhanced optical properties may be substantially permanent, remaining for the useful life of the sintered ceramic body.

A method for enhancing optical properties of sintered, zirconia ceramic bodies and zirconia ceramic dental restorations is provided. The porous or pre-sintered stage of a ceramic body is treated with two different yttrium-containing compositions and sintered, resulting in sintered ceramic bodies having enhanced optical properties. The enhanced optical properties may be substantially permanent, remaining for the useful life of the sintered ceramic body.

The disclosure describes articles and techniques that include an airfoil having a hybrid coating system to provide improved particle impact resistance and improve CMAS attack resistance on the pressure side of the airfoil and improved thermal load protection on the suction side of the airfoil. An example article for a gas turbine engine may include a substrate, and a hybrid environmental barrier coating (EBC) including a relatively dense EBC layer on a first portion of the substrate and a relatively porous EBC layer on a second portion of the substrate, where the first portion of the substrate is different from the second portion of the substrate, and wherein at least a portion of the relatively porous EBC layer overlaps at least a portion of the relatively dense EBC layer in an overlap region.

The disclosure describes articles and techniques that include an airfoil having a hybrid coating system to provide improved particle impact resistance and improve CMAS attack resistance on the pressure side of the airfoil and improved thermal load protection on the suction side of the airfoil. An example article for a gas turbine engine may include a substrate, and a hybrid environmental barrier coating (EBC) including a relatively dense EBC layer on a first portion of the substrate and a relatively porous EBC layer on a second portion of the substrate, where the first portion of the substrate is different from the second portion of the substrate, and wherein at least a portion of the relatively porous EBC layer overlaps at least a portion of the relatively dense EBC layer in an overlap region.

A method for enhancing optical properties of sintered, zirconia ceramic bodies and zirconia ceramic dental restorations is provided. The porous or pre-sintered stage of a ceramic body is treated with two different yttrium-containing compositions and sintered, resulting in sintered ceramic bodies having enhanced optical properties. The enhanced optical properties may be substantially permanent, remaining for the useful life of the sintered ceramic body.

A method for enhancing optical properties of sintered, zirconia ceramic bodies and zirconia ceramic dental restorations is provided. The porous or pre-sintered stage of a ceramic body is treated with two different yttrium-containing compositions and sintered, resulting in sintered ceramic bodies having enhanced optical properties. The enhanced optical properties may be substantially permanent, remaining for the useful life of the sintered ceramic body.

An airfoil includes an airfoil wall that defines a leading end, a trailing end, and suction and pressure sides that join the leading end and the trailing end. The airfoil wall is formed of a silicon-containing ceramic. A first environmental barrier topcoat is disposed on the suction side of the airfoil wall, and a second, different environmental barrier topcoat is disposed on the pressure side of the airfoil wall. The first topcoat is vaporization-resistant and the second topcoat is resistant to calcium-magnesium-aluminosilicate.

An airfoil includes an airfoil wall that defines a leading end, a trailing end, and suction and pressure sides that join the leading end and the trailing end. The airfoil wall is formed of a silicon-containing ceramic. A first environmental barrier topcoat is disposed on the suction side of the airfoil wall, and a second, different environmental barrier topcoat is disposed on the pressure side of the airfoil wall. The first topcoat is vaporization-resistant and the second topcoat is resistant to calcium-magnesium-aluminosilicate.