Papers by Keyword: γ-Al₂O₃

Abstract: The purpose of this work was hydrogen permeation of ceramic or metal/ceramic membrane using γ-Al2O3 by synthesizing. The γ-Al2O3 was synthesized by using the sol-gel process with aluminum isopropoxide and primary distilled water as the precursor and solvent. The γ-Al2O3-based membranes were prepared using HPS. The phase transformation, thermal evolution, surface are and morphology of γ-Al2O3 and γ-Al2O3-based membranes were characterized by XRD, TG-DTA, BET and FE-SEM. The hydrogen permeation of γ-Al2O3-based membranes was examined at room temperature comparing with other paper using nickel composited membrane on alumina ceramic support.

Abstract: Slurry iron aluminide coatings are very resistant to steam oxidation at 600-650º C. These coatings can be used to protect new generation Ultra Super Critical (USC) steam power plant ferritic/martensitic steel components. The microstructure of the initially deposited coating changes as a function of time, mainly due to coating-substrate interdiffusion, going from mostly Fe2Al5 to FeAl, causing the precipitation of AlN in those substrates containing a minimum content of N and moreover, developing Kirkendall porosity at the coating-substrate interface. Steam oxidation at 650º C causes the formation of a protective thin layer of hexagonal χ-Al2O3 phase along with some α- and γ-Al2O3 after the first few hours of exposure. However, despite the relatively low temperature, and after several thousands hours the protective layer was mostly composed of α-Al2O3. A study of the evolution of the microstructure of slurry aluminide coatings deposited on P92 and exposed to steam at 650º C has been carried out by scanning and transmission electron microscopy and X ray diffraction.