Corrosion resistant chemical vapor deposited coatings for SiC and Si3N4

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dc.contributor.authorGraham, David W.en
dc.contributor.committeechairBrown, Jesse J. Jr.en
dc.contributor.committeememberGordon, Ronald S.en
dc.contributor.committeememberHirschfeld, Deidre A.en
dc.contributor.departmentMaterials Science and Engineeringen
dc.date.accessioned2014-03-14T21:46:38Zen
dc.date.adate2009-09-29en
dc.date.available2014-03-14T21:46:38Zen
dc.date.issued1993-04-09en
dc.date.rdate2009-09-29en
dc.date.sdate2009-09-29en
dc.description.abstractSilicon carbide and silicon nitride turbine engine components are susceptible to hot corrosion by molten sodium sulfate salts which are formed from impurities in the engine's fuel and air intake. Several oxide materials were identified which may be able to protect these components from corrosion and preserve their structural properties. Ta20, coatings were identified as one of the most promising candidates. Thermochemical calculations showed that the chemical vapor deposition(CVD) of tantalum oxide from O2 and TaCI5 precursors is thermodynamically feasible over a range of pressures, temperatures, and reactant concentrations. The deposition of Ta205, as a single phase is predicted in regions of excess oxygen, where the reaction is predicted to yield nearly 100% efficiency. CVD experiments were carried out to deposit tantalum oxide films onto SiC substrates. Depending on the deposition conditions, a variety of coating morphologies have been produced, and conditions have been identified which produce dense, continuous Ta205 deposits. Preliminary corrosion tests on these coatings showed no apparent degradation of the CVD deposited tantalum oxide coatings. The feasibility of depositing ZrTi04 as a coating material was also investigated based on thermochemical considerations. Since no data were available for this material, thermodynamic values were estimated. Thermochemical calculations indicated the chemical vapor deposition of zirconium titanate from O2, ZrCl4, and TiCl4 occurs over a range of temperatures in a very narrow region of the phase diagram. Deviations from the single phase region predicted the codeposition of either Zr02 or Ti02 with ZrTi04. These results suggested that the chemical vapor deposition of ZrTi04 may be difficult from a process handling perspective. Additionally, the process is predicted to be very inefficient, leaving substantial amounts of unreacted chlorides in the reactor exhaust.en
dc.description.degreeMaster of Scienceen
dc.format.extentviii, 71 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-09292009-020327en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-09292009-020327/en
dc.identifier.urihttp://hdl.handle.net/10919/44944en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V855_1993.G734.pdfen
dc.relation.isformatofOCLC# 28513962en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V855 1993.G734en
dc.subject.lcshCoating processesen
dc.subject.lcshCoatingsen
dc.subject.lcshSilicon carbideen
dc.subject.lcshSilicon nitrideen
dc.subject.lcshTurbines -- Corrosionen
dc.titleCorrosion resistant chemical vapor deposited coatings for SiC and Si3N4en
dc.typeThesisen
dc.type.dcmitypeTexten
thesis.degree.disciplineMaterials Science and Engineeringen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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