Actions for FUNCTIONALLY GRADED ALUMINA

Email RIS file
Bookmark
Report an Issue

FUNCTIONALLY GRADED ALUMINA/MULLITE COATINGS FOR PROTECTION OF SILICON CARBIDE CERAMIC COMPONENTS FROM CORROSION [electronic resource].

Published
Washington, D.C. : United States. Dept. of Energy, 1997.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description
21 pages : digital, PDF file
Additional Creators
Federal Energy Technology Center (U.S.), United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information
Access Online

Availability

I Want It
I Want It

Finding items...

Restrictions on Access
Free-to-read Unrestricted online access
Summary
The main objective of this research project is the formulation of processes that can be used to prepare compositionally graded alumina/mullite coatings for protection from corrosion of silicon carbide components (monolithic or composite) used or proposed to be used in coal utilization systems (e.g., combustion chamber liners, heat exchanger tubes, particulate removal filters, and turbine components) and other energy-related applications. Mullite will be employed as the inner (base) layer and the composition of the film will be continuously changed to a layer of pure alumina, which will function as the actual protective coating of the component. Chemical vapor deposition reactions of silica, alumina, and aluminosilicates (mullite) through hydrolysis of aluminum and silicon chlorides in the presence of CO₂ and H₂ will be employed to deposit compositionally graded films of mullite and alumina. Our studies will include the kinetic investigation of the silica, alumina, and aluminosilicate deposition processes, characterization of the composition, microstructure, surface morphology, and mechanical behavior of the prepared films, and modeling of the various deposition processes. During this six-month reporting period, we continued the work on the development and construction of the thermogravimetric chemical vapor deposition system that we intend to employ for studying the deposition of alumina, silica, and aluminosilicates (such as mullite) from mixtures of metal chlorides in H₂ and CO₂. Specifically, we worked on the development of the tubular flow reactor that will be used for producing aluminum chloride for delivery to the chemical vapor deposition system and of the vapor and gas supply system. Various problems arising from condensation of aluminum chlorides in some sections of the supply line were resolved, and we expect to perform experiments using mixtures containing AlCl₃ in the next reporting period. Preliminary experiments on the deposition of SiO₂ from mixtures of methyltrichlorosilane (MTS) or tetrachlorosilane in H₂ and CO₂ were carried out, and the results showed that the deposition rates from MTS were much higher than those from SiCl₄ and comparable to those reported in the literature for alumina deposition from AlC₃-H₂-CO₂ mixtures of similar composition. It was thus decided to employ MTS as silicon source in our codeposition experiments, and a comprehensive investigation of thermodynamic equilibrium in the Al/Si/Cl/C/O/H system for compositions corresponding to MTS-AlCl₃-H₂-CO₂ mixtures was conducted so as to identify the boundaries of the region of the space of operating parameters and conditions where preparation of functionally graded mullite/alumina coatings through CVD from metal chloride, CO₂, and H₂ is feasible. The results showed that deposition of silica, alumina, mullite, and other aluminosilicates is feasible in a broad range of operating conditions from the equilibrated gas phase, but temperatures above 1148 K have to employed to obtain deposits of alumina and mullite if the solid phases are also at equilibrium with each other.
Report Numbers
E 1.99:de--fg22-96pc96208--02
de--fg22-96pc96208--02
Subject(s)
Other Subject(s)
Note
Published through SciTech Connect.
10/01/1997.
"de--fg22-96pc96208--02"
Type of Report and Period Covered Note
Semiannual; 03/01/1997 - 08/31/1997
Funding Information
FG22-96PC96208
View MARC record | catkey: 14454027