Abstract: An article for use in aggressive environments is presented. In one embodiment, the article comprises a substrate and a self-sealing and substantially hermetic sealing layer disposed over the bondcoat. The substrate may be any high-temperature material, including, for instance, silicon-bearing ceramics and ceramic matrix composites. A method for making such articles is also presented. The method comprises providing a substrate; disposing a self-sealing layer over the substrate; and heating the sealing layer to a sealing temperature at which at least a portion of the sealing layer will flow.

Abstract: Multiphase ceramic nanocomposites having at least three phases are disclosed. Each of the at least three phases has an average grain size less than about 100 nm. In one embodiment, the ceramic nanocomposite is substantially free of glassy grain boundary phases. In another embodiment, the multiphase ceramic nanocomposite is thermally stable up to a temperature of at least about 1500° C. Methods of making such multiphase ceramic nanocomposites are also disclosed.

Abstract: Multiphase ceramic nanocomposites having at least three phases are disclosed. Each of the at least three phases has an average grain size less than about 100 nm. In one embodiment, the ceramic nanocomposite is substantially free of glassy grain boundary phases. In another embodiment, the multiphase ceramic nanocomposite is thermally stable up to a temperature of at least about 1500° C. Methods of making such multiphase ceramic nanocomposites are also disclosed.

Abstract: Articles for use in a high temperature environment, and methods for protecting articles in such environments, are provided. The article comprises a substrate comprising silicon; a bondcoat comprising silicon, disposed over the substrate; an intermediate barrier disposed over the bondcoat, the barrier comprising at least one layer, wherein the at least one layer comprises a rare-earth silicate and is substantially free of mullite; and a topcoat disposed over the intermediate barrier, the topcoat comprising a rare-earth monosilicate. The method comprises providing a substrate, the substrate comprising silicon; disposing a bondcoat comprising silicon over the substrate; disposing an intermediate barrier over the bondcoat, the barrier comprising at least one layer, wherein the at least one layer comprises a rare-earth silicate and is substantially free of mullite; and disposing a topcoat over the intermediate barrier, the topcoat comprising a rare-earth monosilicate.

Abstract: A material and an article comprising the material are presented. The material comprises a plurality of structural components. The structural components are configured in a series of increasing structural component size classes. The series has a base unit size class and at least one modular size class, and a component of the at least one modular size class comprises a plurality of components of the next smaller size class in the series. The structural components of the base unit size class comprise at least one bulk phase, and the structural components are bonded together at interfaces. Mechanical damage originating within a modular size class structural component is energetically favored to propagate in a distributed fashion among the plurality of structural components contained within the modular size class structural component.

Abstract: A material and an article comprising the material are presented. The material comprises a plurality of structural components. The structural components are configured in a series of increasing structural component size classes. The series has a base unit size class and at least one modular size class, and a component of the at least one modular size class comprises a plurality of components of the next smaller size class in the series. The structural components of the base unit size class comprise at least one bulk phase, and the structural components are bonded together at interfaces. Mechanical damage originating within a modular size class structural component is energetically favored to propagate in a distributed fashion among the plurality of structural components contained within the modular size class structural component.