A ceramic component is generally provided that includes a silicon-based layer comprising a silicon-containing material (e.g., a silicon metal and/or a silicide) and about 0.001% to about 85% of an In-containing compound. For example, the silicon-based layer can be a bond coating directly on the surface of the substrate. Alternatively or additionally, the silicon-based layer can be an outer layer defining a surface of the substrate, with an environmental barrier coating on the surface of the substrate. Gas turbine engines are also generally provided that include such a ceramic component.

An assembly for use in a gas turbine engine and method for making the same are described herein. The assembly comprising a CMC component, a metallic component spaced apart from the CMC component, and a spacer. The spacer having a first surface in contact with the CMC and a second surface opposite the first surface in contact with the metallic component, the spacer comprising a CMC substantially free of silicon metal with a porosity of between about 5 percent and about 40 percent by volume to chemically isolate the CMC component from the metallic component.

A durable light weight, high temperature acoustic CMC liner system. A thin ceramic matrix composite skin, also referred to as a facesheet, forms an outer layer of a cell in the CMC liner system, forming the boundary with the flow of hot gases in the exhaust. A backplate forms the opposite boundary for the cell. The truss structure is formed between the backplate and the facesheet and provides the cell with strength. When the CMC system replaces the metal liner, the backplate thickness is increased so that it is about the thickness of the liner system that it replaces. The truss structure extends between the backplate and the facesheet, forming channels or volumetric spaces. These channels or volumetric spaces are filled with high temperature air permeable acoustic materials that attenuate sound propagated by cooling air in the acoustic range.

A process of producing a ceramic matrix composite component. The process includes positioning a plurality of ceramic matrix composite plies on top of one another and forming a cavity therein. At least a portion of the cavity includes a terminal diameter sufficiently small to permit infiltration of a densifying material. The plurality of ceramic matrix composite plies are densified to form a densified body. The densifying results in the portion of the cavity including the terminal diameter being filled with densifying material and the cavity is present in the densified body. A ceramic matrix composite having cavities therein is also disclosed.

A compound is generally provided that has the formula: Ln.sub.3-xB.sub.xM.sub.5-yB.sub.yO.sub.12, where Ln comprises Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or a mixture thereof; x is 0 to about 1.5; M comprises Ga, In, Al, Fe, or a combination thereof; y is 0 to about 2.5; and x+y is greater than 0. A composition is also provided that includes a silicon-containing material (e.g., silicon metal and/or a silicide) and the boron-doped refractory compound having the formula described above, such as about 0.001% to about 85% by volume of the boron-doped refractory compound.

An article includes a substrate, a bond coat on the substrate, and a multilayer environmental barrier coating (EBC) on the bond coat. The multilayer EBC includes a first EBC layer defining a first thickness and a second EBC layer defining a second thickness. The first EBC layer includes a first rare earth disilicate and a first concentration of a sintering aid that includes alumina. The second EBC layer includes a second rare earth disilicate and a second concentration of the sintering aid that includes alumina, less than the first concentration of the sintering aid.

A ceramic matrix composite article includes a chemical vapor infiltration ceramic matrix composite base portion including ceramic fiber reinforcement material in a ceramic matrix material having between 0% and 5% free silicon. The ceramic matrix composite article further includes a melt infiltration ceramic matrix composite covering portion including a ceramic fiber reinforcement material in a ceramic matrix material having a greater percentage of free silicon than the chemical vapor infiltration ceramic matrix composite base portion.

A method for forming a ceramic matrix composite article includes laying up a first group of plies; laying up a second group of plies, the first and second groups of plies being adjacent to each other; compacting the first group of plies and the second group of plies in the same processing step; and performing a first infiltration process on the first group of plies. The method also includes performing a second infiltration process on the second group of plies, the first infiltration process being one of a melt infiltration process or a chemical vapor infiltration process, and the second infiltration process being the other of the melt infiltration process or the chemical vapor infiltration process.

A seal system a ceramic component having a surface region defining a first surface roughness, a metallic component situated adjacent the surface region, and a coating system disposed on the surface region. The coating system includes a silicon-containing layer on the surface region and a barrier layer on the silicon-containing layer. The silicon-containing layer has a surface in contact with the barrier layer. The barrier layer has a surface in contact with the metallic component. The surface of the barrier layer has a second surface roughness that is less than the first surface roughness. The barrier layer limits interaction between silicon of the silicon-containing layer and elements of the metallic component. The barrier layer has a coefficient of thermal expansion that is within about 60% of a coefficient of thermal expansion of the ceramic component. A gas turbine engine and a method are also disclosed.

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.