Scholarship & Research
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Item Characterization of manganese sulfide inclusion surfaces in 1018 carbon steels and interfacial studies of graphene coated copper surfaces(Montana State University - Bozeman, College of Letters & Science, 2021) Rieders, Nathaniel Frederic; Co-chairs, Graduate Committee: Recep Avci and Yves U. IdzerdaManganese sulfide inclusions are known to be sites of localized corrosion in steels, however little is know concerning the physical and chemical properties of inclusion surfaces. Some inclusions have been observed to be more corrosively active than others. In an effort to distinguish between active and inactive inclusions, this work utilizes surface sensitive electron spectroscopies and microscopies to characterize manganese sulfide inclusion interfaces in 1018 carbon steels. A method was developed to measure variations in surface potential with a high degree of spatial resolution using an Auger microscope. It was found that manganese sulfide inclusion surfaces are heterogeneous and possess discrete manganese oxide and copper sulfide phases. Valence band Auger spectroscopy was used to distinguish between various Mn and Fe chemical species. Surface potential measurements indicate that inclusions are more noble than the surrounding steel surface. TEM analysis indicates a high defect content at the inclusion/steel interface. It is hypothesized that active and inactive inclusions can be distinguished via the availability of sulfur. Graphene on copper surfaces were characterized for use as a protective coating against corrosion using surface sensitive spectroscopies. A feature in the copper Auger transition was found to be unique to graphene, and used to identify its presence and degree of substrate coupling. Localized oxidation of the copper substrate was observed to correlate with low surface potential regions, believed to be intercalated oxygen, which enhances the reactivity of the graphene overlayer. Intercalated Cl was observed to inhibit substrate oxidation, and reduce the reactivity of the graphene overlayer. The intercalation of water was observed to occur at room temperature, and molecularly adsorb to the copper surface at temperatures up to 200 C, indicating that graphene inhibits dissociation of water. Distribution of intercalated water was observed using Auger spectroscopy. It is suggested that doping of graphene is an effective strategy for use as an anticorrosive coating on heterogeneous surfaces.Item An investigation of a prefabricated steel truss girder bridge with a composite concrete deck(Montana State University - Bozeman, College of Engineering, 2018) Kuehl, Tyler William; Chairperson, Graduate Committee: Damon FickSteel truss girder bridges are an efficient and aesthetic option for highway crossings. Their relatively light weight compared with steel plate girder systems make them a desirable alternative for both material savings and constructability. A prototype of a welded steel truss girder constructed with an integral concrete deck has been proposed as a potential alternative for accelerated bridge construction (ABC) projects in Montana. This system consists of a prefabricated welded steel truss girder topped with a concrete deck that can be cast at the fabrication facility (for ABC projects) or in the field after erection (for conventional projects). To investigate possible solutions to the fatigue limitations of certain welded member connections in these steel truss girders, bolted connections between the diagonal tension members and the top and bottom chords of the steel truss girders were evaluated. A 3D finite element model was used to more accurately represent the distribution of lane and truckloads to the individual steel truss girders. This distribution was compared to an approximate factor calculated using an equivalent moment of inertia with expressions for steel plate girders from AASHTO. A 2D analytical model was used to investigate the fatigue strength of the bolted and welded connections for both a conventional cast in place deck system and an accelerated bridge deck system (cast integral with the steel truss girder). Truss members and connections for both construction alternatives were designed using loads from AASHTO Strength I, Fatigue I, Fatigue II, and Service II load combinations. A comparison was made between the two steel truss girder configurations and 205 ft. steel plate girder used in a previously designed bridge over the Swan River. Material and fabrication estimates suggest the cost of the conventional and accelerated construction methods is 10% and 26% less, respectively, than the steel plate girder designed for the Swan River crossing.Item Corrosion of mild steel under an anaerobic biofilm(Montana State University - Bozeman, College of Letters & Science, 1990) Lee, Whonchee; Chairperson, Graduate Committee: William G. Characklis; Eric Grimsrud (co-chair)Item The corrosion of mild steel : a new interpretation of ac impedance spectra of corroding mild steel(Montana State University - Bozeman, College of Letters & Science, 1995) Morrison, Michael LeeItem The role of secondary precipitates and sulfate reducing bacteria in microbially influenced steel corrosion : implications for fuel tank degradation(Montana State University - Bozeman, College of Letters & Science, 2013) Maday, Christine Anne; Chairperson, Graduate Committee: David W. MogkMicrobially influenced corrosion causes wide reaching economic impacts. One example is the United States Navy's recent setbacks after converting to biofuels. The presence sulfate reducing bacteria in fuel tanks has caused contamination of biofuel and accelerated corrosion processes although the exact mechanism is not well understood. Steel corrosion processes include precipitation of secondary minerals in the form of iron sulfides and oxides. Interaction of sulfate reducing bacteria with secondary precipitates has not been previously investigated. The purpose of this study is to document microbe-mineral interaction and characterize products of such interaction. One iron oxide, goethite, and two iron sulfides, pyrrhotite and pyrite, were chosen as analogues to alteration products associated with steel corrosion. These minerals were polished and characterized with an array of analytical techniques prior to and after exposure to sulfate reducing bacteria, Desulfovibrio indonensiensis. X-ray diffraction was performed to confirm mineral phase. Standard scanning electron microscopy and field emission scanning electron microscopy were used to obtain secondary and backscatter electron images to display cell attachment and discriminate phases. Spot analyses using energy dispersive spectroscopy was used to obtain elemental information to help identify phase of mineral substrate, mineral inclusions, and secondary precipitate on the surface. Surface chemistry was further investigated with x-ray photoelectron spectroscopy to identify chemical states of elements present. The x-ray diffraction data confirmed goethite and pyrite to be free of significant contamination. Pyrrhotite, however, had other minerals associated with the sample. Backscatter images of the sample confirmed goethite to be slightly heterogonous, pyrrhotite to have greater heterogeneity and pyrite to be completely homogenous. After exposure to Desulfovibrio indonensiensis for a period of 7, 14, and 30 days, the samples were analyzed again. Goethite was found to be inert with respect to bacteria while pyrrhotite and pyrite had cell attachment and overlying precipitate indicating microbe-mineral interaction. The results of this study indicate the negative feedback mechanism associated with sulfate reducing bacteria and goethite. Sulfide minerals can create a positive feedback mechanism for the corrosion process if localized sites of oxidation occur on the secondary precipitates to allow for sulfate reducing bacteria interaction.