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dc.contributor.advisorChairperson, Graduate Committee: Paul E. Gannonen
dc.contributor.authorTatar, Gregory Stevenen
dc.date.accessioned2019-03-14T13:55:37Z
dc.date.available2019-03-14T13:55:37Z
dc.date.issued2018en
dc.identifier.urihttps://scholarworks.montana.edu/xmlui/handle/1/15107en
dc.description.abstractStainless steels are often used in high temperature (greater than or equal to 500°C) applications such as solid oxide fuel cells (SOFCs), combustion engine exhaust systems, and various power/chemical plant process equipment. At high temperatures and in oxidizing conditions, chromium containing oxides, such as chromia (Cr2O 3), form protective surface layers on the underlying stainless steel. Reactive evaporation of these surface layers, however, may form volatile chromium species such as CrO 2 (OH) 2 and CrO 3, compromise the protection of stainless steels, and cause deleterious downstream effects. Such effects include SOFC performance degradation and hazardous materials generation. This study focuses on both the reactive evaporation and reactive condensation processes and their dependencies on materials and environmental conditions. First, the corrosion behaviors of stainless steels were investigated in a variety of exposure conditions and then the nature of chromium vapor condensation was investigated on ceramic surfaces under various conditions. Ferritic stainless steel samples (T409) were examined after 700°C exposures (94 h) to dry or wet air or nitrogen, and with or without contacting aluminosilicate fibers. Surface compositions and structures were characterized using field emission scanning electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffraction. The fibers had a substantial impact on corrosion behaviors; likely serving as a mass transport barrier for corrosive gas species. Observed corrosion behaviors under these different environments and their potential mechanisms are presented and discussed. Additionally, quantification of chromium content on fibers was performed using inductively coupled plasma mass spectroscopy. Fibers were observed to collect chromium in dry/moist air consistent with the formation of CrO 3 and CrO 2(OH) 2, respectively, and their subsequent reactive condensation. To better understand the reactive condensation of volatile chromium species onto various ceramic surfaces, volatile chromium species were generated from chromium containing sources at 500-900°C and flowed past samples of aluminosilicate fibers, alumina, mica, and quartz wool at temperatures ranging from 100-900°C for 24-150 hours. The ceramic surfaces were characterized using x-ray photoelectron spectroscopy. Analysis of Cr 2p 3/2 peak positions revealed the influence of temperature, material, and exposure time on the oxidation states of surface chromium compounds, and extent of chromium deposition. Potential mechanisms are proposed to help explain the observed trends.en
dc.language.isoenen
dc.publisherMontana State University - Bozeman, College of Engineeringen
dc.subject.lcshEvaporationen
dc.subject.lcshCondensationen
dc.subject.lcshChromiumen
dc.subject.lcshStainless steelen
dc.subject.lcshCorrosion and anti-corrosivesen
dc.subject.lcshSolid oxide fuel cellsen
dc.titleReactive evaporation of chromium from stainless steel and the reactive condensation of chromium vapor species on ceramic surfacesen
dc.typeDissertationen
dc.rights.holderCopyright 2018 by Gregory Steven Tataren
thesis.degree.committeemembersMembers, Graduate Committee: Roberta Amendola; Stepen W. Sofie; Robert Walker.en
thesis.degree.departmentChemical & Biological Engineering.en
thesis.degree.genreDissertationen
thesis.degree.namePhDen
thesis.format.extentfirstpage1en
thesis.format.extentlastpage185en
mus.data.thumbpage145en


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