An article includes a substrate, an intermediate coating on the substrate, and an environmental barrier coating (EBC) on the intermediate coating. The substrate includes a ceramic, ceramic matrix composite (CMC), or superalloy. The EBC includes a rare earth disilicate. When the intermediate coating is at an initial state, such as prior to exposure to an oxidating environment, the intermediate coating includes a bond coat on the substrate and a reactive layer on the bond coat. The bond coat includes silicon, while the reactive layer includes a rare earth monosilicate or rare earth oxide. In response to oxidation of a portion of the silicon of the bond coat to form silicon dioxide, a portion of the rare earth monosilicate or rare earth oxide of the reactive layer is configured to react with at least a portion of the silicon dioxide to form a converted layer that includes a rare earth disilicate.

An article includes a substrate, an intermediate coating on the substrate, and an environmental barrier coating (EBC) on the intermediate coating. The substrate includes a ceramic, ceramic matrix composite (CMC), or superalloy. The EBC includes a rare earth disilicate. When the intermediate coating is at an initial state, such as prior to exposure to an oxidating environment, the intermediate coating includes a bond coat on the substrate and a reactive layer on the bond coat. The bond coat includes silicon, while the reactive layer includes a rare earth monosilicate or rare earth oxide. In response to oxidation of a portion of the silicon of the bond coat to form silicon dioxide, a portion of the rare earth monosilicate or rare earth oxide of the reactive layer is configured to react with at least a portion of the silicon dioxide to form a converted layer that includes a rare earth disilicate.

A nuclear reactor structure configuring a pebble accommodating space of a pebble bed type nuclear reactor includes a core material including graphite and a ceramic/ceramic composition material covering a surface of the core material. According to a core material processing step (A) of processing the core material including graphite into a quadrangular prism, a bottom surface of which is an approximately isosceles trapezoid, a step (B) of obtaining a base material by covering the core material with an aggregate including a ceramic fiber, and a CVD step (C) of putting the base material into a CVD reactor and forming a SiC matrix in gaps of the aggregate, thereby forming a ceramic/ceramic composite material on a surface of the core material, the nuclear reactor structure capable of enhancing durability, preventing cracking, etc. from occurring, and preventing exposure of graphite as the core material from occurring, can be provided.

A nuclear reactor structure configuring a pebble accommodating space of a pebble bed type nuclear reactor includes a core material including graphite and a ceramic/ceramic composition material covering a surface of the core material. According to a core material processing step (A) of processing the core material including graphite into a quadrangular prism, a bottom surface of which is an approximately isosceles trapezoid, a step (B) of obtaining a base material by covering the core material with an aggregate including a ceramic fiber, and a CVD step (C) of putting the base material into a CVD reactor and forming a SiC matrix in gaps of the aggregate, thereby forming a ceramic/ceramic composite material on a surface of the core material, the nuclear reactor structure capable of enhancing durability, preventing cracking, etc. from occurring, and preventing exposure of graphite as the core material from occurring, can be provided.

Methods for forming a nucleation layer on a substrate. In some embodiments, the processing method comprises sequential exposure to a first reactive gas comprising a metal precursor and a second reactive gas comprising a halogenated silane to form a nucleation layer on the surface of the substrate.

A method for manufacturing a SiC epitaxial wafer according to one aspect of the present invention includes separately introducing, into a reaction space for SiC epitaxial growth, a basic N-based gas composed of molecules containing an N atom within the molecular structure but having neither a double bond nor a triple bond between nitrogen atoms, and a Cl-based gas composed of molecules containing a Cl atom within the molecular structure, and mixing the N-based gas and the Cl-based gas at a temperature equal to or higher than the boiling point or sublimation temperature of a solid product generated by mixing the N-based gas and the Cl-based gas.

A method for manufacturing a SiC epitaxial wafer according to one aspect of the present invention includes separately introducing, into a reaction space for SiC epitaxial growth, a basic N-based gas composed of molecules containing an N atom within the molecular structure but having neither a double bond nor a triple bond between nitrogen atoms, and a Cl-based gas composed of molecules containing a Cl atom within the molecular structure, and mixing the N-based gas and the Cl-based gas at a temperature equal to or higher than the boiling point or sublimation temperature of a solid product generated by mixing the N-based gas and the Cl-based gas.

Provided is a method capable of manufacturing a metal carbonitride film or a metalloid carbonitride film at low temperature. A metal carbonitride film or a metalloid carbonitride film is formed using as a nitrogen source at least one of an N-trialkylsilyl-1,2,3-triazole compound and a 1,2,4-triazole compound represented by the following general formula (1):

##STR00001## where Rs are the same or different, each represent a hydrogen atom, a linear, branched or cyclic alkyl group of 1 to 5 carbon atoms or a trialkylsilyl group of 1 to 5 carbon atoms, and, depending on circumstances, bond to each other to form a ring.

A method for manufacturing a part coated with a protective coating includes: forming a protective coating across all or part of the surface of a part, wherein the part includes a refractory alloy including a niobium matrix containing metal silicide inclusions, wherein the protective coating is formed by a pack carburization method from a cement including: i. a mixture A of (Nb.sub.xTi.sub.1-x).sub.3M.sub.3CrSi.sub.6 and M.sub.0.6Cr.sub.0.4Si where M denotes Fe, Co or Ni and x is between 0 and 1, or ii. a mixture B of M′Si, NbSi.sub.2 and Nb.sub.4M′.sub.4Si.sub.7 where M′ denotes Fe, Co or Ni.

An investment casting system includes a core having at least one fine detail, a shell positioned relative to said core, and a strengthening coating applied at least to the at least one fine detail.