An article that includes a substrate; a first layer including yttria and zirconia or hafnia, where the first layer has a columnar microstructure and includes predominately the zirconia or hafnia; a second layer on the first layer, the second layer including zirconia or hafnia, ytterbia, samaria, and at least one of lutetia, scandia, ceria, neodymia, europia, and gadolinia, where the second layer includes predominately zirconia or hafnia, and where the second layer has a columnar microstructure; and a third layer on the second layer, the third layer including zirconia or hafnia, ytterbia, samaria, and a rare earth oxide including at least one of lutetia, scandia, ceria, neodymia, europia, and gadolinia, where the third layer has a dense microstructure and has a lower porosity than the second layer.

An article that includes a substrate; a first layer including yttria and zirconia or hafnia, where the first layer has a columnar microstructure and includes predominately the zirconia or hafnia; a second layer on the first layer, the second layer including zirconia or hafnia, ytterbia, samaria, and at least one of lutetia, scandia, ceria, neodymia, europia, and gadolinia, where the second layer includes predominately zirconia or hafnia, and where the second layer has a columnar microstructure; and a third layer on the second layer, the third layer including zirconia or hafnia, ytterbia, samaria, and a rare earth oxide including at least one of lutetia, scandia, ceria, neodymia, europia, and gadolinia, where the third layer has a dense microstructure and has a lower porosity than the second layer.

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 method for producing a building material includes a first step of applying a first ultraviolet-curable paint onto an inorganic material containing a woody reinforcement and incompletely curing the first ultraviolet-curable paint, a second step of applying a second ultraviolet-curable paint and completely curing the second ultraviolet-curable paint, a third step of polishing the completely cured second ultraviolet-curable paint to smoothen a surface of the completely cured second ultraviolet-curable paint, and a fourth step of applying an enamel paint and curing the enamel paint. In the second step, the second ultraviolet-curable paint is applied while the first ultraviolet-curable paint is incompletely cured.

A method for producing a building material includes a first step of applying a first ultraviolet-curable paint onto an inorganic material containing a woody reinforcement and incompletely curing the first ultraviolet-curable paint, a second step of applying a second ultraviolet-curable paint and completely curing the second ultraviolet-curable paint, a third step of polishing the completely cured second ultraviolet-curable paint to smoothen a surface of the completely cured second ultraviolet-curable paint, and a fourth step of applying an enamel paint and curing the enamel paint. In the second step, the second ultraviolet-curable paint is applied while the first ultraviolet-curable paint is incompletely cured.

A method for coating a substrate includes spraying a combination of powders. The combination of powders includes: Hf.sub.0.5Si.sub.0.5O.sub.2; Zr.sub.0.5Si.sub.0.5O.sub.2; and, optionally, at least one of HfO.sub.2 and ZrO.sub.2. A molar ratio of said Hf.sub.0.5Si.sub.0.5O.sub.2 and HfO.sub.2 combined to said Zr.sub.0.5Si.sub.0.5O.sub.2 and ZrO.sub.2 combined is from 2:1 to 4:1. A molar ratio of said Hf.sub.0.5Si.sub.0.5O.sub.2 to said HfO.sub.2 is at least 1:3.

A thermal barrier coating includes a highly porous layer and a dense layer. The highly porous layer is formed on a heat-resistant base, is made of ceramic, has pores, has a layer thickness of equal to or larger than 0.3 mm and equal to or smaller than 1.0 mm, and has a pore ratio of equal to or higher than 1 vol % and equal to or lower than 30 vol %. The dense layer is formed on the highly porous layer, is made of ceramic, has a pore ratio of equal to or lower than 0.9 vol % that is equal to or lower than the pore ratio of the highly porous layer, and has a layer thickness of equal to or smaller than 0.05 mm.

A coating method includes depositing a slurry including a coarsely particulate ceramic and a finely particulate ceramic on a base material configured with an oxide-based ceramics matrix composite such that a proportion of coarse particles decreases towards a surface of the base material; forming a bond coating by performing a heat treatment on the base material on which the slurry has been deposited; and forming a top coating by thermally spraying a ceramic onto the bond coating. The oxide-based ceramics matrix composite is an alumina silica type oxide-based ceramics matrix composite. The coarsely particulate ceramic and the finely particulate ceramic are alumina-based powder.

A coating method includes depositing a slurry including a coarsely particulate ceramic and a finely particulate ceramic on a base material configured with an oxide-based ceramics matrix composite such that a proportion of coarse particles decreases towards a surface of the base material; forming a bond coating by performing a heat treatment on the base material on which the slurry has been deposited; and forming a top coating by thermally spraying a ceramic onto the bond coating. The oxide-based ceramics matrix composite is an alumina silica type oxide-based ceramics matrix composite. The coarsely particulate ceramic and the finely particulate ceramic are alumina-based powder.

The disclosure describes a method for forming a surface layer of a ceramic matrix composite (CMC) article. The technique includes depositing a slurry on a surface of an infiltrated CMC. The slurry includes a carrier material, a binder, a plasticizer, and solid particles. The solid particles include a plurality of fine ceramic particles defining a fine particle average size less than about 5 micrometers. The method further includes drying the slurry to form an article having an outer surface layer that includes the solid particles on the infiltrated CMC. The method further includes machining at least a portion of the outer surface layer of the article. The method further includes infiltrating the article with a molten infiltrant to form a composite article.