Theses and Dissertations at Montana State University (MSU)
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/732
Browse
8 results
Search Results
Item Evaluation of methanotrophic activity and growth in a methanotrophic-heterotrophic co-culture(Montana State University - Bozeman, College of Engineering, 2021) Kilic, Ayse Bengisu; Chairperson, Graduate Committee: Ellen G. Lauchnor; Erika J. Espinosa-Ortiz, Brent M. Peyton and Ellen Lauchnor were co-authors of the article, 'Methane-based bioreactor configurations in value-added product development: a review' submitted to the journal 'Journal of bioscience and bioengineering' which is contained within this thesis.; Erika J. Espinosa-Ortiz, Brent M. Peyton and Ellen Lauchnor were co-authors of the article, 'Evaluation of methanotrophic activity and growth in a methanotrophic-heterotrophic co-culture' submitted to the journal 'Engineering in life sciences' which is contained within this thesis.Methane is a potent greenhouse gas (GHG) and accounts for 20-30% of the GHG emissions globally. In nature, methane is utilized as a sole carbon and energy source by a group of bacteria referred to as methanotrophs. Methanotrophs have been reported to have the ability to form close associations with other microorganisms such as heterotrophic bacteria in the environment. Therefore, understanding methanotrophic activity and growth in a microbial consortium with heterotrophic bacteria is of interest from an environmental and biotechnology perspective. In this study, a methanotroph; Methylocystis sp. NLS7 and a heterotrophic bacterium, Pseudomonas chlororaphis, were co-cultivated in a methane-fed bioreactor with a dialysis membrane device used to separate the species physically. It was hypothesized that the co-culture would exhibit enhanced methanotrophic activity and microbial growth of NLS7 in NLS7- P. chlororaphis co-culture. The methane-oxidation rate and microbial growth rate of NLS7 were evaluated as a functional response variable to the presence of P. chlororaphis. In addition, the effects of NLS7 growth were evaluated on the growth of P. chlororaphis. Our findings indicated that the presence of P. chlororaphis does not have any beneficial effects on Methylocystis sp. NLS7 activity and growth. However, the growth of P. chlororaphis in the co-culture with solely methane as a carbon source indicated that P. chlororaphis is likely gaining carbon and energy from by-products of methane oxidation by Methylocystis sp. NLS7 since P. chlororaphis could not utilize methane as a carbon and energy source. The results of this study give us an important insight into the activity and the growth of methanotrophic consortia in methane-driven ecosystem.Item The electrochemical oxidation of lithium-ammonia solutions(Montana State University - Bozeman, College of Engineering, 1968) Bennett, John EdwinItem Analysis and characterization of surface oxides on intermetallic alloys of zirconium using auger electron spectroscopy(Montana State University - Bozeman, College of Engineering, 1991) Mirpuri, Rajesh G.Item Wet air oxidation of sediments contaminated with polychlorinated biphenyls (PCBs)(Montana State University - Bozeman, College of Engineering, 2002) Ray, Justin MichaelItem A study in the oxidation of Kraft black liquor(Montana State University - Bozeman, College of Engineering, 1966) Shah, Bharat KeshavlalItem A study in the oxidation of Kraft black liquor(Montana State University - Bozeman, College of Engineering, 1969) Zadick, F. J.Item A fundamental study of hot corrosion and interdiffusion of chromium, aluminum, and silicon coatings on a nickel-201 substrate(Montana State University - Bozeman, College of Engineering, 2014) Gill, Zachery Edward; Co-chairpersons, Graduate Committee: Paul E. Gannon and Roberta AmendolaModern turbine engine systems require increased efficiency and durability. To achieve these goals, high-temperature materials with high-strength, low-cost and non-strategic compositions are needed. In advanced turbine applications, combustor liners, blades and vanes are exposed to corrosive combustion byproducts, such as alkali salts, at temperatures up to ~1700°C with high gas velocities, entrained particulates, and other foreign objects at pressures of up to 3 MPa (30 atm). These extreme conditions can drive a dangerous phenomenon known as "hot corrosion", an accelerated form of oxidation that occurs when metals and metal alloys are heated in the temperature range 700-900°C in the presence of alkali salts. An increased understanding of the fundamental behaviors of common high temperature alloys and their degradation mechanisms is therefore critical for the production of reliable components. In this study a model substrate, Nickel 201, was coated on one side with Cr, Al, or Si thin films (~1 micron) via magnetron sputtering physical vapor deposition (PVD). Uncoated and PVD coated samples were then exposed to laboratory air at 700°C and 900°C and to an environment similar in composition to atmospheres found in post combustion turbine systems, comprised of air/SO 2 gas mixture, at 700°C. The exposures were conducted over time intervals observing coating-substrate interactions and surface oxide development. Identical samples were subjected to the same exposures with addition of a deposit of sodium sulfate (Na 2SO 4), a model alkali salt. Sample mass gains were recorded and resulting oxide compositions assessed as a function of exposure time using microscopy techniques on sample surfaces and cross sections. The development of intermetallic species was determined by X-ray diffraction. At 700°C, coated and uncoated samples displayed different oxidation behaviors. Under laboratory air, no hot-corrosion occurred. While at 700°C in air/SO 2 exposures, evidence for hot corrosion on deposited samples was observed. When sodium sulfate was introduced at 900°C, coated and uncoated samples displayed rapid corrosion consistent with hot corrosion. The oxidation processes and coating/substrate inter-diffusion phenomena are presented and discussed in the context of establishing basic approaches to improve the fundamental understanding of hot corrosion, and the protection mechanisms of high temperature materials.Item Oxidation behavior of (Co,Mn) 3O 4 coatings on preoxidized stainless steel(Montana State University - Bozeman, College of Engineering, 2011) Hoyt, Kathryn Olivia; Chairperson, Graduate Committee: Paul E. GannonAs global energy challenges grow, alternative energy technologies like fuel cells are being investigated. Solid Oxide Fuel Cells (SOFCs) provide the advantages of high energy conversion efficiency, low emissions, fuel flexibility and both portable and stationary application. High material cost and need for longer material lifespan still impede the wider use of SOFCs. To produce substantial voltage, planar SOFCs are joined into stacks using interconnects. Interconnects both separate and connect each individual fuel, separating gas flow and conducting current. For SOFCs that operate at less than 800°C, metal alloys are being considered for the interconnect, particularly ferritic stainless steel. Ceramic coatings are being explored to improve the surface conductivity over time and significantly reduce Cr volatility from the steel. In addition, the coating must have a matching coefficient of thermal expansion (CTE) and be compatible with electrode and seal materials. One promising coating is (Co,Mn) 3O 4 spinel, which is deposited using various techniques, resulting in different thicknesses, compositions and microstructures. In this study, stainless steel 441HP samples were subjected to three levels of preoxidation prior to coating with 2 micron CoMn alloy using magnetron sputtering. Samples were subsequently annealed to Co 1.5Mn 1.5O 4 in 800°C air. Oxidation behaviors were evaluated as a function of exposure to laboratory air and dual atmospheres (3% H 2O and H 2 on one side, 3% H 2O and air on the other) and area specific resistance (ASR) measurements in lab air, all at 800°C. In addition, chemical and phase composition, mass gain, and adhesion were investigated using a complimentary suite of analytical techniques. Preoxidation was found to inhibit Fe transport from the stainless steel into the coating and exhibited a substantially thinner surface oxide layer after oxidation. Preoxidized samples also maintained slightly lower ASR values after 1650 hours in 800°C air compared to non-preoxidized samples. Oxidation behaviors, their possible mechanisms, and implications for SOFC interconnects will be presented and discussed.