A coated substrate is provided that comprises: a substrate; and a barrier coating comprising a compound having the formula: Ln.sub.2ABO.sub.8, where Ln comprises scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, or mixtures thereof; A comprises Si, Ti, Ge, Sn, Ce, Hf, Zr, or a combination thereof; and B comprises Mo, W, or a combination thereof. In one embodiment, B comprises Mo. A gas turbine is also provided that comprises the coated substrate described above.

An article comprises a substrate comprising a ceramic matrix composite; a first layer disposed over the substrate, the first layer comprising a substantially interconnected silicon source material, and a secondary material; and a second layer disposed over the first layer, the second layer comprising a membrane material in mass transfer communication with the silicon source material.

An article comprises a substrate comprising a ceramic matrix composite; a first layer disposed over the substrate, the first layer comprising a substantially interconnected silicon source material, and a secondary material; and a second layer disposed over the first layer, the second layer comprising a membrane material in mass transfer communication with the silicon source material.

In some examples, a braze material includes a first set of particles, a second set of particles, and a polymeric binder. The first set of particles includes a braze powder, where the braze powder comprises an Si-containing alloy. The first set of particles defines an average or median particle diameter between about 1 μm and about 40 μm. The second set of particles includes at least one of SiC or a transition metal carbide, where the second set of particles has a multimodal particle size distribution.

In some examples, a braze material includes a first set of particles, a second set of particles, and a polymeric binder. The first set of particles includes a braze powder, where the braze powder comprises an Si-containing alloy. The first set of particles defines an average or median particle diameter between about 1 μm and about 40 μm. The second set of particles includes at least one of SiC or a transition metal carbide, where the second set of particles has a multimodal particle size distribution.

Systems and methods for forming an oxidation protection system on a composite structure are provided. In various embodiments, an oxidation protection system disposed on a substrate may comprise a boron-silicon-glass layer or a boron layer and a silicon layer. The boron-silicon-glass layer, boron layer, the silicon layer, or a pretreatment layer may include an oxygen reactant compound.

Systems and methods for forming an oxidation protection system on a composite structure are provided. In various embodiments, an oxidation protection system disposed on a substrate may comprise a boron-silicon-glass layer or a boron layer and a silicon layer. The boron-silicon-glass layer, boron layer, the silicon layer, or a pretreatment layer may include an oxygen reactant compound.

Coated components, along with methods of their formation, are provided. The coated component includes a ceramic substrate having a surface; an intermediate layer on the surface of the ceramic substrate; and an environmental barrier coating on the intermediate layer. The intermediate layer includes a carbon-sink material that inhibits accumulation of free carbon from a carbon-containing species within the intermediate layer, the ceramic substrate, or both.

Methods for preparing an environmental barrier coating and the resulting coating are provided. The methods and products include the incorporation of a continuous ceramic inner layer and a segmented ceramic outer layer on a CMC component. The segmented ceramic outer layer may be formed by thermal spray techniques. The coating is more stable at higher temperatures and provides for a longer lifetime of the coated component.

Methods for preparing an environmental barrier coating and the resulting coating are provided. The methods and products include the incorporation of a continuous ceramic inner layer and a segmented ceramic outer layer on a CMC component. The segmented ceramic outer layer may be formed by thermal spray techniques. The coating is more stable at higher temperatures and provides for a longer lifetime of the coated component.