• Development and assessment of a novel osmotic heat engine for energy generation from low-grade heat

      Cath, Tzahi Y.; Hickenbottom, Kerri Leah; Heeley, Michael B.; Munakata Marr, Junko; Sullivan, Neal P.; Balistreri, Edward J. (Edward Jay) (Colorado School of Mines. Arthur Lakes Library, 2015)
      Development of clean energy technologies that maximize efficiency and minimize resource consumption is a necessary component for a clean and secure energy future. The osmotic heat engine (OHE) is a closed-loop, membrane based process that utilizes low-grade heat and salinity-gradient energy between two streams for electrical energy generation. The OHE couples pressure retarded osmosis (PRO), an osmotically driven membrane process, with membrane distillation (MD), a thermally driven membrane process. In PRO, water permeates via osmosis through a semi-permeable membrane from a low concentration feed stream into a higher concentration brine (draw solution). The permeate stream becomes pressurized on the high concentration side of the membrane and a mechanical device (e.g., turbine generator set) is used to convert the hydraulic pressure to electrical energy. The MD process utilizes low-grade heat to reconcentrate the diluted brine from the PRO process and to produce a deionized water stream; these streams are then resupplied to the PRO process in the OHE. High power-density (power generated per unit area of membrane) of the PRO membrane is essential to maximize the efficiency and minimize the capital and operating costs of the OHE. Likewise, high separation efficiency is needed in the MD process to effectively reconcentrate the diluted draw solution. Thus, robust PRO membranes that can support high pressure, have high water flux, low reverse salt flux, low structural parameter, and a good membrane support structure are essential. The MD process must also be able to withstand high operating temperatures (> 60 ºC) and feed water concentrations, and have low pore wetting propensity. Additionally, the use of highly soluble ionic organic and inorganic draw solutions can increase PRO power densities while achieving high MD water fluxes, thus increasing efficiencies and decreasing costs of OHE. Therefore, the objective of this dissertation is to develop and demonstrate at the laboratory scale and through modeling work a novel, closed-loop, hybrid membrane-based system that converts low-grade heat to electrical energy. The performance of several membranes used for PRO and the effect of spacer configuration on membrane performance was evaluated. The performance of MD in concentrating hypersaline brines was evaluated and scale mitigation techniques were investigated to restore water flux and sustain the desalination process. Several ionic organic and inorganic draw solutions were evaluated as working fluids in the OHE, and their performance was assessed in terms of PRO power density and reverse salt diffusion, and MD separation and thermal efficiency and membrane pore wetting. The experimental data was used to develop a system model that evaluates system efficiency, net power output, and costs. Modeling results were used to perform an environmental life-cycle assessment using GaBi, a life-cycle assessment software. Although, at its current state of technology, OHE electricity generation costs ($0.48 per kWh) are not competitive with conventional U.S. grid energy costs ($0.04 per kWh), system environmental impacts are an order of magnitude lower. Furthermore, with future improvements to membrane technology and OHE process performance, electricity generation costs for the OHE as an energy storage device ($0.12 per kWh) could be comparable to on-peak demand charges in Southern California ($0.15 per kWh), thus making the OHE an attractive energy storage device.
    • Development of vascular injury models to measure the interactions between platelets, endothelial cells and nitric oxide under physiological flow conditions

      Neeves, Keith B.; Sylman, Joanna; Dorgan, John R.; Reynolds, Melissa M.; Krebs, Melissa D.; Liang, Hongjun (Colorado School of Mines. Arthur Lakes Library, 2015)
      The formation of a stable clot is a balance between pro- and antithrombotic biochemical mechanisms coupled to biophysical mechanisms mediated by local hemodynamics. A disruption in this balance leads to excessive clotting, or thrombosis, which is the leading cause of death in the United States. Blood clots form at the site of a vascular injury by platelet adhesion, activation, and aggregation coupled to a network of reactions called coagulation. Endothelial cells (EC) that line blood vessels also help regulate clot formation by secretion of platelet inhibitors such as nitric oxide (NO), supporting the activated protein C anticoagulation pathway, and expression of adhesive ligands that promote blood cell adhesion. The relative roles of these EC-mediated pro- and antithrombotic pathways for different types of injuries and in different vascular beds are largely unknown, despite detailed knowledge of the biochemistry and molecular biology of these pathways. Specifically, there is little known about the distribution of EC-secreted platelet inhibitor at the site of a focal injury, and how the transport of those inhibitors is influenced by blood flow. In this thesis, microfluidic vascular injury models and the finite element method were used to measure and model how the spatial and temporal distribution of NO and EC activation affect platelet function. NO is a free radical synthesized and released by the endothelium in a shear stress dependent manner that modulates platelet function. The flux of NO at the site of an injury is unknown. In my first study, synthetic NO-releasing polymers were used to mimic endothelial function, in which the NO flux was decoupled from the shear stress. I studied collagen-mediated platelet adhesion and aggregation over a range of physiological shear rates and NO fluxes. NO was found to induce measureable inhibition of platelet aggregation at fluxes of 0.33× 10-10 mol cm-2 min-1 to 2.5× 10-10 mol cm-2 min-1 at shear rates of 200-500 s-1. A computational model of NO transport was developed to determine the mass transfer limitations of NO in mediating platelet inhibition. The NO distribution was found to be reaction limited in the platelet rich layer, formed when RBC develop a core and there is margination of platelets to the vessel wall, and transport limited in the RBC core. The outcome of this study was the first report to isolate the shear rate dependent effect of NO on platelet aggregation. It is generally accepted that NO inhibition of platelets occurs primarily through soluble guanylyl cyclase (sGC)-dependent pathways. But, recent studies suggested that sGC-independent mechanisms might also mediate inhibition at millimolar NO donor concentration. In this study, I used the NO-releasing polymer system described above to determine the relative role of sGC dependent and independent signaling. Platelets treated with a small molecule inhibitor of sGC showed the existence of an independent pathway at an NO flux of 6.8×10-10 mol cm-2 min-1 at 200-500 s-1 which corresponded to an NO concentration of 65 – 240 nM. This outcome of this study is the first report of a sGC independent pathway in flowing whole blood. Endothelial cells (EC) inhibit and promote platelet activation in a shear stress dependent manner. Previous studies of EC-platelet interactions use chemical activators to indiscriminately activate entire monolayers of EC. In this study, I focally activated EC with heat using surface microelectrodes to create a well-defined injury zone of activated EC supporting platelet adhesion surrounded by quiescent EC inhibiting platelet activation. A computational model of the heat transfer was built to determine the in situ temperature increases directly under the cells at each voltage, which dictated whether the EC remained quiescent, became activated, or were killed. Platelet adhesion was supported between activated EC by EC-derived von Willebrand factor and laminin. We expect this model will be useful in ongoing studies of platelet-EC interactions. EC-derived NO contributes to platelet inhibition but it is unknown under which conditions it is the most important. Using the previously established EC-based focal injury model, the platelet aggregate formation was measured in the presence and absence of an endothelial nitric oxide synthase inhibitor. It was hypothesized that NO inhibits the cross-talk between upstream and downstream injuries by inhibiting platelet activation in a shear stress dependent manner. NO was found to have a pronounced effect in a dual injury configuration and when EC were conditioned by shear stress for days prior to the injury. Overall, the relationship between clot size and EC function under physiological flow conditions was determined by creation of a series of microfluidic focal vascular injury models which allowed for spatial and temporal control of NO release and EC activation.
    • Enhanced monitoring of hazardous waste site remediation: electrical conductivity tomography and citizen monitoring of remediation through the EPA's Community Advisory Group Program

      Munakata Marr, Junko; Hort, Ryan D.; Revil, André, 1970-; Figueroa, Linda A.; Singha, Kamini; Gianquitto, Tina (Colorado School of Mines. Arthur Lakes Library, 2015)
      In situ chemical oxidation using permanganate has become a common method for degrading trichloroethene (TCE) in contaminated aquifers. Its effectiveness, however, is dependent upon contact between the oxidant and contaminant. Monitoring permanganate movement after injection is often hampered by aquifer heterogeneity and insufficient well coverage. Time lapse electrical conductivity tomography increases the spatial extent of monitoring beyond well locations. This technique can create two- or three-dimensional images of the electrical conductivity within the aquifer to monitor aquifer chemistry changes caused by permanganate injection and oxidation reactions. In-phase and quadrature electrical conductivity were measured in homogeneous aqueous and porous media samples to determine the effects of TCE and humate oxidation by permanganate on both measures of conductivity. Further effects of clean sand, 10% kaolinite (v/v), and 10% smectite (v/v) on both types of conductivity were studied as well. Finally, in-phase electrical conductivity was measured over time after injecting permanganate solution into two-dimensional tanks containing artificial groundwater with and without TCE to observe the movement of the permanganate plume and its interaction with TCE and to examine the effectiveness of time-lapse conductivity tomography for monitoring the plume's movement. In-phase electrical conductivity after oxidation reactions involving permanganate, TCE, and humate could be accurately modeled in homogeneous batch samples. Use of forward modeling of in-phase conductivity from permanganate concentrations may be useful for improving recovery of conductivity values during survey inversion, but further work is needed combining the chemistry modeling with solute transport models. Small pH-related quadrature conductivity decreases were observed after TCE oxidation, and large quadrature conductivity increases were observed as a result of sodium ion addition; however, quadrature conductivity could not be related to concentrations of permanganate or reaction products. Additionally, EPA Superfund sites participating in the Community Advisory Group (CAG) program were examined to determine how communities may have benefitted from the program. While CAG participation was correlated with slower achievement of EPA cleanup milestones, many CAGs successfully achieved five standardized social goals. CAGs that achieved these social goals varied in composition but were similar in their focus on community outreach and ability to extend their influence beyond CAG meetings.
    • Origin and evolution of the southeastern Merrimack belt, Massachusetts

      Kuiper, Yvette; Charnock, Robert David; Kelly, Nigel; Pfaff, Katharina (Colorado School of Mines. Arthur Lakes Library, 2015)
      The Ordovician to Early-Devonian metasedimentary Merrimack belt of the southeastern New England Appalachian Mountains is deformed by multiple generations of folds that may have been a result of the Acadian (~421-395 Ma) and/or Alleghanian (~315-290 Ma) orogenies. The adjacent Nashoba terrane to the southeast was deformed primarily during the Acadian orogeny, and does not show much evidence for Alleghanian deformation and metamorphism, suggesting that the deformation in the Merrimack belt may also be largely a result of the Acadian orogeny. However, existing 40Ar/39Ar geochronology results suggest that the deformation in the Merrimack belt is largely Alleghanian. Potentially Pennsylvanian units in the Merrimack belt were investigated to determine if deformation was a result of the Alleghanian orogeny. Along the southeastern margin of the Merrimack belt in Massachusetts the Harvard Conglomerate is noncomformably on top of the Ayer Granodiorite at Pin Hill, MA. The Vaughn Hill Conglomerate (previously considered the Harvard Conglomerate), is adjacent to the Vaughn Hill Formation at Vaughn Hill. The Vaughn Hill Formation may lie at the base of the Merrimack belt. Detailed structural mapping was carried out on the four units and compared with deformation in selected units of the southeastern Merrimack belt. Detrital zircon U-Pb LA-ICP-MS geochronology was carried out on the metasedimentary units and U-Pb CA-TIMS zircon geochronology on the Ayer Granodiorite, in order to constrain the ages of the units and the deformation. The maximum depositional ages are ~463 Ma for the Vaughn Hill Formation, ~415 Ma for the Harvard Conglomerate, and ~416 Ma for the Vaughn Hill Conglomerate. The Ayer Granodiorite at Pin Hill is ~420 Ma. The Vaughn Hill Formation is interpreted as representing a time of continued deposition after deposition of the metasedimentary units of the Nashoba terrane, and forms the base of the Merrimack belt. Previously, the metasedimentary units of the Nashoba terrane and the Merrimack belt were thought to be unrelated as they are now separated by the Clinton-Newbury fault zone, which juxtaposed upper amphibolite facies rocks of the Nashoba terrane with greenschist facies rocks of the southeastern Merrimack belt. The difference in metamorphic grade can be explained by observed normal movement along the Clinton-Newbury fault zone. The Vaughn Hill Formation contains a significant population of ~560-530 Ma zircon interpreted to have been sourced from peri-Ganderian arc-derived sediment recycled from the Nashoba terrane. The Vaughn Hill Formation also contains a significant population of ~645-630 zircon from peri-Ganderian arcs not recorded in the peri-Ganderian Nashoba terrane. The Vaughn Hill Formation either received this sediment from ~645-630 Ma arcs now exposed in the northern New England Appalachian Mountains via an interconnected basin, or from ~645-630 Ma peri-Ganderian arc sediment that was present between the Merrimack belt and the Laurentian margin at ~463 Ma, and that is now buried and/or subducted. The Harvard and Vaughn Hill conglomerates contain a significant population of ~430 Ma zircon grains interpreted to be sourced from local igneous sources and older zircon grains from recycled Merrimack belt metasedimentary units, and are the youngest metasedimentary units in the Merrimack belt, with the exception of the Pennsylvanian Coal Mine Brook Formation. Based on new results, significant deformation in the southeastern Merrimack belt must be younger than ~415 Ma and may still be Acadian or Alleghanian. Based on new and existing structural analysis and on prior 40Ar/39Ar geochronology data, it is likely that bedding-parallel axial planar cleavage of early isoclinal folds (D1) is related to the Acadian orogeny. These are overprinted by m- to km-scale, close to tight, generally steeply NNW-dipping folds (D2), and subhorizontal to recumbent chevron to rounded folds (D3). D2-3 are likely post-Acadian and may be a result of the Alleghanian orogeny.
    • Nitrogen injection in progressively sealed longwall gobs and the formation of a complete and dynamic seal

      Brune, Jürgen F.; Marts, Jonathan; Bogin, Gregory E.; Dagdelen, Kadri; Grubb, John W.; Wilson, William (Colorado School of Mines. Arthur Lakes Library, 2015)
      Methane ignition and spontaneous combustion of coal are two common ventilation hazards associated with longwall coal mining. Methane is a coal mine gas emitted from the surrounding strata and the seams themselves as part of the mining process. Methane is diluted by the mine ventilation system used to provide fresh air to the face. Methane air mixtures become explosive between the lower explosive limit of 5.5% methane and the upper explosive limit of 14% methane. Mixtures with higher methane contents will burn as a diffusion flame. Methane ignition has been the cause of several recent mine tragedies including the Upper Big Branch Mine explosion in April 2010 and the Pike River Mine explosion in November 2010. Spontaneous combustion is an exothermic reaction involving coal and oxygen. The initiation of spontaneous combustion is dependent on oxygen concentration and residence time in addition to other factors. If the heat from the reaction is not dissipated the heating can proceed to thermal runaway or a fire that may result in fatalities, equipment losses and or mine closure. Recent spontaneous combustion events have resulted in the temporary closure and loss of longwall equipment and reserves at the Elk Creek Mine from a fire that was discovered in January 2013 and the Soma Mine Disaster that resulted in over 300 fatalities from an explosion that is suspected to have initiated from a spontaneous combustion fire. The investigation is still on going. The focus of this dissertation is to investigate the use of nitrogen to both reduce explosive gas volumes and to reduce the spontaneous combustion potential by diluting oxygen ingress behind the longwall shields. This research will investigate the quantity of nitrogen injection, the injection location and the method of face ventilation to determine the effectiveness of each variable in mitigating the hazards discussed above. The hypothesis is that a back return scheme in conjunction with progressive nitrogen injection creates a safer work environment than a traditional U-Type ventilation scheme in terms of both explosive gas and spontaneous combustion hazards. Knowledge regarding the porous media distribution of the caved gob is required for modeling the gas distributions. Previous findings regarding porous media distribution of the gob and nitrogen injection are presented and discussed in a literature review. A geo-mechanical model was developed to determine the porous media distribution for an active longwall panel. A numerical fluid flow and gas dilution model was developed using the porous media distribution and utilized to study the validity of the hypothesis. Nitrogen injection amount and location was varied for both U-Type and back return face ventilation schemes to determine the effectiveness of each on the desired hazard mitigation. Important conclusions drawn from the research include the following findings. Porous media distributions are noticeably different for static panels compared to active panels simulated by utilizing a method of stepped extraction for the geo-mechanical model. These differences are especially apparent immediately inby the face. There is a point of diminishing returns for nitrogen injection quantity for both face ventilation methods. It was found that nitrogen injection closer to the face provides more diluting and inertization effectiveness that locations further inby. A back return with sufficient nitrogen injection directly inby the face provided the optimal dilution and inertization scheme. Although a back return increases oxygen ingress and creates a larger volume of explosive gas the oxygen can be diluted rapidly through a nitrogen induced, complete dynamic seal stretching from headgate to tailgate. In addition the explosive gas region is moved further inby and away from the active workings of the face in the back return scheme. These findings partially satisfy the hypothesis that implementing a back return provides a safer working environment compared to standard U-Type ventilation. The explosive potential risk has been reduced although spontaneous combustion indicator gases should be closely monitored and the nitrogen injection system well maintained due to the increased oxygen ingress.
    • Electric-field assembly of colloids with anisotropic interactions

      Wu, Ning; Ma, Fuduo; Wu, David T.; Marr, David W. M.; Liberatore, Matthew W.; Furtak, Thomas E. (Thomas Elton), 1949- (Colorado School of Mines. Arthur Lakes Library, 2015)
      Assembly of colloidal particles has been a hot research topic for past two decades. Scientifically, these studies have significantly enriched our fundamental understanding in the physics of soft materials, including crystal nucleation and growth, phase transition, and glass formation. Practically, the assembled structures can uniquely interact with a broad range of electromagnetic waves and they are envisioned as important building blocks for metamaterials or photonic crystals with exotic properties. Previous studies, however, lack the diversity in the assembled structures, precise tunability of the colloidal interactions, and systematic investigation of different types of anisotropy. In this thesis, we apply external electric fields to manipulate and assemble anisotropic particles, particles that possess asymmetric properties in geometry, surface functionality, or chemical composition. We have obtained new and rich structures assembled from both spherical particles with anisotropic interactions and dimers with anisotropic material properties. Spherical colloids can acquire anisotropic dipolar interactions under AC electric fields and assemble into a variety of well-defined oligomers. Colloidal dimers with equal lobe sizes also show rich phase behavior and different assembly regimes. In particular, the formation of two dimensional close-packed crystals of perpendicularly aligned dimers shows promise in fabricating 3D photonic crystals based on dimer-like colloids. When dimers are asymmetric, the pair interaction is orientation-dependent. At low frequencies, two to four lying dimers associate closely with a central standing dimer and form chiral clusters. At high frequencies, we observe a series of novel structures that closely resemble one- and two-dimensional antiferromagnetic lattices. In addition to various types of equilibrium structures, we also discover a new particle propulsion mechanism that arises from the unbalanced electrohydrodynamic flow surrounding an asymmetric dielectric dimer when we tune the lobe size, chemical composition, and zeta potential on two lobes differently. Both the propulsion direction and speed can be conveniently modulated by field strength and frequency. The propulsion mechanism revealed here is not limited to colloidal dimers and should be universal for other types of asymmetric particles. Such knowledge is important for both building intelligent colloidal robots and studying the out-of-equilibrium behavior of active matter.
    • Fundamental study on the effects of heterogeneity on trapping of dissolved CO2 in deep geological formations through intermediate-scale testing and numerical modeling, A

      Illangasekare, T. H.; Agartan Karacaer, Elif; Navarre-Sitchler, Alexis K.; Singha, Kamini; Tilton, Nils; Cihan, Abdullah (Colorado School of Mines. Arthur Lakes Library, 2015)
      Climate change due to CO2 build up in the atmosphere has been studied for many years. Carbon capture and storage (CCS) is a technology to reduce the atmospheric emissions of CO2 produced from large point sources like power plants. The captured CO2 is deposited into the subsurface formation, such as deep saline aquifers, in the case of geologic sequestration of CO2. The earliest application of CO2 sequestration in subsurface formations was back to the early 1970s in order to increase oil production. Environmental benefits of CO2 storage to reduce greenhouse gas emissions to the atmosphere have been considered since the 1980s and studied in detailed since the 1990s. In deep geologic formations, CO2 is trapped through a number of mechanisms including structural, capillary, dissolution, and mineral trapping to achieve secure and long-term storage which reduces the risk of leakage. The fundamental understanding of these mechanisms should be improved in order to develop strategies on the trapping in the target formation. Heterogeneity of the formation is another factor that plays a key role for the stable trapping at the injection and post-injection periods, and makes it challenging to understand the relative contribution of each mechanism to storage. The main goal of this study is to investigate the role of heterogeneity on the trapping of dissolved CO2 for the secure and long-term storage in the deep saline formations via well-controlled laboratory experiments and numerical modeling. The small and intermediate-scale laboratory experiments were performed using surrogate fluid combinations showing identical density characteristics with dissolved CO2 and brine under ambient pressure and temperature conditions. The more complex packing configurations and field-scale applications were simulated using the numerical model. The results of experimental and numerical modeling studies suggested that the contribution of convective mixing to the stable trapping of dissolved CO2 depends on the geometry, distribution, and hydraulic properties of the geologic features in the formations. In multilayered systems, convective mixing and diffusion controlled trapping contribute to dissolution trapping; however the impact of each mechanisms depends on the permeability and thickness of the low-permeability layers. On the other hand, the intralayer heterogeneity present in low-permeability layers enhances mixing, and the long-term trapping in these layers depends on distribution of the materials. The effective strategies can be developed to enhance trapping by taking the advantage of natural heterogeneity of the formation. These conclusions are relevant when investigating stable trapping of dissolved CO2 in deep saline formations.
    • Three-dimensional modeling of complex salt wall terminations in the Paradox Basin: implications for salt structure evolution, compartmentalizing fault trends and petroleum exploration

      Trudgill, Bruce, 1964-; Lehmann, Katie; Carr, Mary; Sarg, J. F. (J. Frederick) (Colorado School of Mines. Arthur Lakes Library, 2015)
      The Paradox Basin, located in southeastern Utah and southwestern Colorado, is a stunning geologic area for salt tectonics research. Characterized by the halite-rich Pennsylvanian Paradox Formation, this region provides pristine examples of the many structural and stratigraphic relationships associated with evolving salt structures. Formed during the Ancestral Rocky Mountain orogeny (ARM), the basin displays the complex development of the Colorado Plateau throughout the past ~320-300 million years. Unlike other ARM basins, the Paradox Basin was substantially influenced by the dynamic evolution of the Paradox Formation. The northwest-southeast-striking salt structures in the Paradox Basin exhibit unusual morphologies, which has been attributed to compartmentalization of the basin by northeast-southwest-trending Precambrian basement structures. This has resulted in the abrupt or abnormal terminations of these salt structures observed in the basin today. Previously, minimal research was conducted on these salt wall terminations, perhaps due to their complex, three-dimensional geometries. However, study of these salt wall terminations is essential to understanding the evolution of the salt walls and the adjacent stratigraphy. Three-dimensional modeling of the Castle Valley and Gypsum Valley salt wall terminations reveals: (1) pre-existing Precambrian basement structures directly influenced the flow of the Paradox salt, generating the unusual salt wall terminations in the Paradox Basin; (2) asymmetry across the salt wall flanks, resulting in different amounts of accommodation and stratigraphic thicknesses; (3) the important relationship between eolian deposition of the White Rim Sandstone and the timing of the rise of the Castle Valley salt wall; (4) the amount of faulting along salt wall terminations and the resulting compartmentalization; (5) the development of multiple halokinetic sequences in response to passive diapirism of the Gypsum Valley salt wall; (6) growth faulting at Klondike Ridge associated with failure of the stratigraphy to imitate the salt wall termination; (7) the potential to better predict White Rim Sandstone petroleum reservoirs throughout the basin; (8) the possibility of new petroleum plays along the southern flank of the Gypsum Valley salt wall termination. The results of this study indicate that modeling of salt wall terminations is essential to understanding the complexity associated with salt structures. Furthermore, these models provide insight into other systems and may help with improved petroleum exploration and production. In areas such as the Gulf of Mexico, diapiric Jurassic Louann Salt produces irregularly shaped salt structures. The study of the salt wall terminations would be more applicable in these instances than the study of the central, linear parts of the salt walls. Therefore, this study illustrates the significance of three-dimensional models in developing a better understanding of the Paradox Basin and other salt systems.
    • Communication and localization of an autonomous mobile robot

      Han, Qi; Sweatt, Marshall Roy; Steele, John P. H.; Yang, Dejun (Colorado School of Mines. Arthur Lakes Library, 2015)
      Removing humans from dangerous situation by shifting them to a supervisory role has existed for decades. Oil and gas refineries are beginning to shift to this line of thought, as equipment is monitored electronically; however, accidents still occur when operators must physically verify alerts before actions can be taken. A mobile robotic system is a suitable analog for this process. The operator can remotely perform inspection tasks from an operator control station through a mobile robotic system; however, communication between the operator and the robot is paramount. If communication is ever lost, the human operator will be exposed to the dangers of the environment. In an autonomous system, localization of the mobile robot is key - if the operator tells the robot to move from location A to location B, the robot needs to know exactly where it is at all times to avoid causing damage to the environment or itself. The work in this thesis focuses on the WiFi communication and localization of a mobile robot. First, extensive experiments are conducted to understand the relationship of received signal strength, bandwidth, link quality, and distance for both indoor and outdoor environments in a 2.4 GHz WiFi network. Findings from these empirical studies are then used to determine both single and k-coverage of a given area. Single-coverage is required to ensure that at every point in the region of interest, communication can occur between the mobile robotic system and the operator control station. Coverage is then expanded to k-coverage to provide a more robust network for localization. Algorithms are implemented to determine a minimal 3-coverage deployment that ensures a minimum threshold distance between neighboring access points. Channel allocation is determined through a graph coloring approach where two heuristics are implemented and their results are compared. WiFi localization is implemented through RSSI fingerprinting, a matching heuristic, where a new approach is considered for determining the k-closest neighbors. The results from WiFi localization are then fused with dead reckoning, and a fiducial marker system using an extended Kalman filter and a validation gate. An accuracy of 0.43 m is achieved with the hybrid localization technique.
    • Observed loading behavior during cross passage construction for Brisbane Airport Link project

      Mooney, Michael A.; Kuyt, W. John; Nelson, Priscilla P.; Shiling, Pei (Colorado School of Mines. Arthur Lakes Library, 2015)
      The analysis and design of cross passages for twin bored tunnel projects provides unique challenges when considering the 3D geometry, geotechnical behavior, and interaction between the internal tunnel structures and the ground. Current practice involves complicated modeling to approximate the cross passage behavior and facilitate design of the necessary support structures, often consisting of a combination of geotechnical solutions (e.g. grouting, ground freeze), excavation support (shotcrete, spiling, rock bolting), and structural solutions (internal props) to maintain the mainline tunnels and the opening space. However, little work has been done to validate these solutions with field data from construction projects. The Center for Underground Construction and Tunneling at the Colorado School of Mines has been provided with strain gauge field data for the Brisbane Airport Link, courtesy of Arup, one of the design firms on the project. A thorough evaluation of this data has been conducted to establish the development of forces in the mainline tunnel structures (segments and propping) throughout the cross passage excavation sequence. Results from the gauges have been compared to basic analytical and numerical solutions for validation. The observed behavior of the cross passages during excavation was established. Key mechanisms driving behavior include the effects of prop installation and jacking on the segmental lining, the unloading effect observed with geological excavation, the development of stresses due to soil arching, and the effects of locked-in lateral stresses around the tunnels. The influence of the two-layer heterogeneous geology of the project was determined to be a key factor in driving the majority of these behaviors. The analysis is concluded with a discussion of the importance of each mechanism to potential future design of cross passages and potential future developments for cross passage instrumentation schemes.
    • PT evolution of Sentinel Cu deposit, northwestern Zambia

      Kelly, Nigel; Hitzman, Murray Walter; Meighan, Corey James; Wendlandt, Richard F.; Kuiper, Yvette (Colorado School of Mines. Arthur Lakes Library, 2015)
      The Sentinel Cu deposit, located on the eastern margin of Kabompo Dome within the Domes Region of northwest Zambia, is hosted in Neoproterozoic metasedimentary rocks of the Katangan Supergroup. Copper sulfide minerals in the deposit are intergrown with metamorphic minerals formed during the latest Neoproterozoic to early Cambrian Lufilian event, interpreted to be associated with the latter stages of Gondwana assembly. This study examines the interrelated roles of metamorphism and metasomatism in the host rocks to the deposit to help better resolve their P-T history. The results have implications for improved understanding of the tectonothermal evolution of the Domes Region. Whole-rock geochemistry of the Sentinel Phyllite (ore host) indicates that Mg must have been added during syn-metamorphic metasomatism. Quartz veins with copper sulfides also contain kyanite, phlogopite, and Mg-chlorite suggesting these minerals formed by a series of metasomatic reactions requiring the addition of Mg from an aqueous fluid. Based on regional geology, the source of Mg is likely both residual basinal fluids developed during evaporite formation and possibly brines derived from evaporite dissolution. In order to constrain the temperatures of metamorphism/metasomatism at Sentinel three independent thermobarometry approaches including garnet-biotite Fe-Mg exchange thermometry and trace element thermometry (Ti-in-quartz and Zr-in-rutile) were applied. Ti-in-quartz thermometry conducted on quartz from vein and matrix domains within the Sentinel Phyllite, and quartz from matrix domains of rocks from the surrounding stratigraphy record similar temperatures of ~450°C across >500 meters of stratigraphic section. These conditions are interpreted to reflect closure to Ti diffusion during retrograde cooling. Zr-in-rutile thermometry conducted on rutile in quartz veins within the Sentinel Phyllite, and rutile in matrix domains of rocks from the surrounding stratigraphy, records temperature conditions of ~550°C. Rimward increases in Zr concentrations of rutile from veins in the carbonaceous and less carbonaceous phyllites suggest that Zr-in-rutile temperatures record conditions of growth along a path of increasing temperature and not retrograde re-equilibration due to deformation. Temperature estimates from garnet-biotite thermometry are broadly consistent with temperature estimates calculated from Zr-in-rutile thermometers, but give estimates up to and exceeding 600°C. Taken together, the data suggest that metamorphic mineral assemblages in the Sentinel rocks equilibrated at conditions similar to those accompanying vein formation, and that peak metamorphic temperatures were at or above 600°C. Application of Grt-Bt-Pl-Qtz (GBPQ) and Grt-Als-Qtz-Pl (GASP) barometry conducted at Sentinel fall into two groups: ~9-10 kbars and ~7 kbars, with lower pressures for samples with more calcic plagioclase. The most elevated pressures pertain to more albitic plagioclase core compositions from quartz-feldspar-biotite schists, and not necessarily compositions in chemical equilibrium with garnet. Therefore, re-equilibration of more albite-rich plagioclase with garnet to form more anorthitic rims at or below 7 kbars is viable. In the Sentinel area, kyanite appears to be texturally overprinted by talc, and is interpreted to also be related to syn-metamorphic Mg metasomatism. This observation indicates that the talc-kyanite-quartz schist, which is regionally extensive, cannot be considered a “whiteschist” (senso stricto) formed during high-pressure metamorphism. Similarly, high pressure metamorphism associated with kyanite-bearing schists bounding the Sentinel Phyllite is likely related to re-equilibration of a more albite-rich plagioclase at or below 7 kbars. These observations may also have implications for regionally extensive garnet-kyanite bearing schists and gneisses observed in the Domes Region, which indicate ~7 kbars is likely a robust maximum estimate for peak pressures accomopanying metamorphism, rather than the higher pressure estimates of previous studies. The new data suggest that minimal structural thickening during the Lufilian event together with an elevated geotherm could explain the observed mineral assemblages. Copper sulfide minerals are rare in the matrix of the host phyllites at Sentinel, suggesting that Cu in quartz veins is not a remobilization of a pre-existing Cu enrichment within the carbonaceous protolith to the phyllite. Therefore, the Sentinel Cu deposit should be considered a ‘syn-metamorphic’ Cu deposit. Sulfide minerals are intergrown with or form inclusions in rutile. Temperatures of ~550-600°C reflected by rutile growth within the Sentinel Phyllite are likely close to the peak temperatures of ore deposition.
    • Evaluating mesoporous materials for potential drug delivery and catalytic applications

      Trewyn, Brian; Joglekar, Madhura; Maupin, C. Mark; Posewitz, Matthew C.; Yang, Yongan (Colorado School of Mines. Arthur Lakes Library, 2015)
      Mesoporous silica nanoparticles (MSN) have attracted significant attention in the past decade due to their unique properties such as high surface area, tunable pore size, large pore volume, controllable particle morphology and ease of surface functionalization. They have been extensively researched for their application as a potential targeted drug delivery carrier. Some research has also focussed on developing MSN-based hard templating strategies for the synthesis of other mesoporous materials such as mesoporous carbon nanoparticles (MCN) with diverse properties. In order to safely employ MSN as a drug delivery vehicle, considerations in hemocompatibility become essential and critical. The research presented in this dissertation demonstrates the effects and interaction of various morphologies of MSN on human RBC membrane at biologically relevant concentrations. The addition of organic functionality on the surface of these MSNs has been known to produce profound effects on their interaction with the human RBC membrane. The effects of two types of lipid bilayer coatings on the surface of MSN with the human RBC membrane have been systematically investigated. It has been demonstrated that a small change in the composition of the lipid bilayer coating on the MSN surface can transform the MSN-based drug delivery system from being seriously incompatible to being largely hemocompatible. The utility of MSN can be further enhanced by using it as a hard template for the synthesis of other mesoporous nanomaterials such as MCN. Herein, large-pore mesoporous silica nanoparticles (l-MSN) have been utilized for the development of monodispersed MCN with high surface areas and well-defined morphology. The morphology can be tuned by making small changes in the reaction parameters. Furthermore, a highly selective covalent surface functionalization approach for the modification of MCN has been developed for tethering functional groups and single-site catalysts on the surface of MCN. A copper-based single-site catalyst covalently anchored on the surface of MCN has been demonstrated to be highly active for organic transformation such selective benzyl alcohol oxidation under environmentally benign conditions. The surface modification strategy for MCN has been furthered exploited to anchor platinum-based single-site catalysts on its surface. For the first time, these MCN-based heterogenous catalysts have been used for the electrochemical oxidation of methane at low temperature (80°C) in a proton exchange membrane fuel cell demonstrating unprecedented activities. In general, the fundamental studies on hemocompatibility and the development of MSN as a platform for the synthesis of monodispersed MCN with its selective surface modification approach will not only bring new insights for the application of MSN as an intravascular drug-delivery vehicle but also assist in the design of novel MCN-based systems templated from MSN for catalytic, electrocatalytic and biological applications.
    • Structure-constrained image-guided inversion of geophysical data

      Revil, André, 1970-; Zhou, Jieyi; Hale, Dave, 1955-; Sava, Paul C.; Tenorio, Luis; Maxwell, Reed M. (Colorado School of Mines. Arthur Lakes Library, 2015)
      The regularization term in the objective function of an inverse problem is equivalent to the "model covariance" in Tarantola's wording. It is not entirely reasonable to consider the model covariance to be isotropic and homogenous, as done in classical Tikhonov regularization, because the correlation relationships among model cells are likely to change with different directions and locations. The structure-constrained image-guided inversion method, presented in this thesis, aims to solve this problem, and can be used to integrate different types of geophysical data and geological information. The method is first theoretically developed and successfully tested with electrical resistivity data. Then it is applied to hydraulic tomography, and promising hydraulic conductivity models are obtained as well. With a correct guiding image, the image-guided inversion results not only follow the correct structure patterns, but also are closer to the true model in terms of parameter values, when compared with the conventional inversion results. To further account for the uncertainty in the guiding image, a Bayesian inversion scheme is added to the image-guided inversion algorithm. Each geophysical model parameter and geological (structure) model parameter is described by a probability density. Using the data misfit of image-guided inversion of the geophysical data as criterion, a stochastic (image-guided) inversion algorithm allows one to optimize both the geophysical model and the geological model at the same time. The last problem discussed in this thesis is, image-guided inversion and interpolation can help reduce non-uniqueness and improve resolution when utilizing spectral induced polarization data and petrophysical relationships to estimate permeability.
    • Effect of hydration on the mechanical properties of anion exchange membranes

      Liberatore, Matthew W.; Herring, Andrew M.; Vandiver, Melissa A.; Knauss, Daniel M.; Wolden, Colin Andrew; Way, J. Douglas; Wu, Ning (Colorado School of Mines. Arthur Lakes Library, 2015)
      Anion exchange membranes (AEM) are promising solid polymer electrolytes for use in alkali fuel cells and electrochemical conversion devices. The dynamic nature of the fuel cell environment requires that AEMs operate at a range of hydration levels. Water sorption is critical for ion conduction, but excess water uptake causes dimensional swelling and mechanical instability. Ion conduction is slower in AEMs, compared to proton exchange membranes (PEM), making it important to minimize overall transport resistance by reducing membrane thickness; however, maintaining mechanical durability is difficult as thickness is reduced. Achieving an AEM with high conductivity and good mechanical durability is a difficult balance, which was the focus of this thesis. Various polymer chemistries were investigated with respect to ion conduction, morphology, swelling, and mechanical properties as potential AEMs. The success of perfluorosulfonic acid PEMs inspired synthesis of perfluorinated AEMs, but cation functionalization was low, and proved chemically unstable, resulting in poor performance. Random polyiosoprene copolymers with high ion concentration were solution processed into films and subsequently crosslinked to generate solid AEMs. Diblock copolymers were studied due to their ability to phase separate into organized morphologies for efficient ion transport, but polymer chemistry greatly influenced mechanical performance. A polystyrene based diblock resulted in stiff, brittle AEMs with insufficient strength, but a polyethylene based diblock AEM produced large, flexible films. Mechanical performance was investigated by extensional and dynamic mechanical testing. The addition of cation functionalities increased membrane stiffness, leading to brittle films. Water in the membrane acts as a plasticizer increasing elasticity and elongation, but also weakening membranes. Changing polymer chemistry to a polyethylene based diblock and optimizing casting conditions produced large (~300 cm2) area membranes of consistent (10 um) thickness. These membranes were flexible and showed good mechanical performance. Mechanical softening, due to hydration level, was identified by dynamic mechanical analysis. Conductivity measured as a function of humidity suggested increased ion conduction correlated with the hygromechanical softening point. Understanding the relationship between ion conduction and mechanical properties is critical to the development of robust, well-performing AEMs for use in fuel cells and electrochemical devices.
    • Investigating the effectiveness of using basement heat flow as a tool for modeling the thermal history of a basin in a 1D basin model

      Boak, Jeremy; Jacob, Dayna; Trudgill, Bruce, 1964-; Leonard, Jay E. (Colorado School of Mines. Arthur Lakes Library, 2015)
      The goal of this project is to investigate the effectiveness of using Basement Heat Flow and Platte River Associates, Inc. (PRA) 2014 approach of finding the sediment-water/air interface temperatures to estimate the thermal history. This was carried out by creating 1D wells models in the Williston, Uinta, Paradox, and Norwegian North Sea basins in the BasinMod® software. These models were also used to investigate the effects of different tectonic histories, erosion estimates, and thermal properties of kerogen on thermal indicators in the basin. Multiple scenarios with different settings were carried out on each well model until a model that matched the measured data was produced. A thermal history in each basin was successfully derived. The most reasonable models for the Williston Basin that matched the measured data included either a failed Tertiary rift or a basement conductivity anomaly in order to explain high maturities in the basin center although there is little to no evidence to support either theory. The models for both the Uinta and Paradox basins included thinning of the mantle lid followed by thickening of the crust during the Tertiary due to their location on the Colorado Plateau. Thinning the mantle lid during the Tertiary and having a thin present day mantle lid thickness of 60km was crucial for the maturation of the source rocks in the Uinta Basin model. The temperature histories in these two basins were slightly different because of their different locations on the Colorado Plateau and the deposition of highly conductive salt in the Paradox Basin. In these three basins (Williston, Uinta, Paradox), the rapid deposition of shale in the Cretaceous Western Interior Seaway created a thermal blanket that either enhanced or hindered maturation of source rocks. For the well models in the North Sea, a thinner mantle lid during the Tertiary was required to mature the source rocks; therefore the models that included a rifting or thinning event later than the Permo-Triassic rift event best matched the measured data. Other conclusions made from the model 1) constrain the amount of erosion in the Williston, Uinta, and Paradox basins, and 2) determine that including the thermal properties of kerogen in the well models would not impact the thermal history especially in thin source rock with lower TOC content. The Basement Heat Flow tool and Platte River Associates, Inc. (PRA) 2014 approach of finding the sediment-water/air interface temperatures were effective in estimating the thermal history. This process of determining the tectonic history of the basin can be complicated by anomalies and hydrodynamic flow but the other factors included in the calculations of the subsurface temperatures and heat flux are valuable in determining the thermal history of the basin.
    • Quantitative interpretation of airborne gravity gradiometry data for mineral exploration

      Li, Yaoguo; Martinez, Cericia D.; Hitzman, Murray Walter; Dagdelen, Kadri; Sava, Paul C.; Krahenbuhl, Richard A. (Colorado School of Mines. Arthur Lakes Library, 2015)
      In the past two decades, commercialization of previously classified instrumentation has provided the ability to rapidly collect quality gravity gradient measurements for resource exploration. In the near future, next-generation instrumentation are expected to further advance acquisition of higher-quality data not subject to pre-processing regulations. Conversely, the ability to process and interpret gravity gradiometry data has not kept pace with innovations occurring in data acquisition systems. The purpose of the research presented in this thesis is to contribute to the understanding, development, and application of processing and interpretation techniques available for airborne gravity gradiometry in resource exploration. In particular, this research focuses on the utility of 3D inversion of gravity gradiometry for interpretation purposes. Towards this goal, I investigate the requisite components for an integrated interpretation workflow. In addition to practical 3D inversions, components of the workflow include estimation of density for terrain correction, processing of multi-component data using equivalent source for denoising, quantification of noise level, and component conversion. The objective is to produce high quality density distributions for subsequent geological interpretation. I then investigate the use of the inverted density model in orebody imaging, lithology differentiation, and resource evaluation. The systematic and sequential approach highlighted in the thesis addresses some of the challenges facing the use of gravity gradiometry as an exploration tool, while elucidating a procedure for incorporating gravity gradient interpretations into the lifecycle of not only resource exploration, but also resource modeling.
    • Theoretical electronic structure of structurally modified graphene

      Wu, Zhigang; Dvorak, Marc David; Ciobanu, Cristian V.; Lusk, Mark T.; Wood, David M.; Bernard, James; Wei, Su-Huai (Colorado School of Mines. Arthur Lakes Library, 2015)
      Graphene has emerged as a promising replacement for silicon in next-generation electronics and optoelectronic devices. If graphene is to be used in semiconductor devices, however, it must acquire an electronic band gap. Numerous approaches have been proposed to control the band gap of graphene, including the periodic patterning of defects. However, the mechanism for band gap opening and the associated physics in graphene patterned with defects remain unclear. Using both analytic theory and first-principles calculations, we show that periodic patterning of defects on graphene can open a large and tunable band gap, induce strong absorption peaks at optical wavelengths, and host a giant band gap quantum spin Hall phase. First, a geometric rule is analytically derived for the arrangements of defects that open a band gap in graphene, with one ninth of all possible patterns opening a band gap. Next, we perform ab-initio density functional calculations to compare the effects of structural vacancies, hexagonal BN dopants, and passivants on the electronc structure of graphene. Qualitatively, these three types of structural defects behave the same, with only slight differences in their resulting band structures. By adjusting the shape of structural defects, we show how to move the Dirac cones in reciprocal space in accordance with the tight-binding model for the anistropic honeycomb lattice, while the fundamental mechanism for band gap opening remains the same. To quantitatively predict the band gap and optical properties of these materials, we employ many-body perturbation theory with Green's functions (GW/Bethe-Salpeter equation) to directly include electron-electron and electron-hole interactions. Structurally modified graphene shows a strong renormalization of the fundamental band gap over single particle descriptions, and a strong electron-hole interaction as indicated by strong exciton binding energies (> 0.5 eV). Finally, we show that structurally modified graphene can host a topologically insulating phase if spin-orbit interactions are included. Tight-binding calculations show that an insulating graphene nanomesh is also a quantum spin Hall insulator with a giant bulk band gap, an extremely valuable material for next-generation spintronics.
    • Study of thermoelectric properties of graphene materials, A

      Wu, Zhigang; Twombly, Chris; Lusk, Mark T.; Wood, David M. (Colorado School of Mines. Arthur Lakes Library, 2015)
      Graphene has very beneficial charge transport properties which make it an interesting potential thermoelectric material, but its thermoelectric efficiency is limited by large thermal conductivity. Nanostructuring graphene by incorporating periodic holes in the crystal structure produces graphene nanomesh with reduced thermal conductivity due to increased phonon scattering. The goal of this study was to investigate the thermoelectric properties of graphene nanomeshes and defected graphene using Density Functional Theory and semi-classical Boltzmann Transport Theory. We computed the Seebeck coefficient, electrical conductivity, and the electrical component of thermal conductivity from first principles. We first developed and verified the accuracy of our techniques using silicon. We then examined the properties of silicon nanowires in order to study systems with more complex geometry and to show that nanostructuring can improve thermoelectric properties. Our results agreed closely with previous experimental and theoretical studies of silicon systems. We then employed this suite of methods to study graphene, graphene nanomeshes, and periodically defected graphene. Our calculations for pristine graphene agreed closely with experimental measurements, proving that our methods work well with 2D systems. Our calculations suggest that there is up to a one order of magnitude increase in Seebeck coefficient for graphene nanomeshes compared to pristine graphene. This increase was found to be strongly dependent on a previously predicted geometrically based semimetal to semiconductor transition. We estimated a maximum ZT of 0.15-0.4 for graphene nanomeshes based on a simple scaling law for the thermal conductivity in these systems. The ZT value is strongly dependent on the purity and the quality of the graphene crystal lattice, which affects the relaxation time of charge carriers in these systems. We then studied defected graphene with partial hydrogen passivation and boron-nitride (BN) doping to further demonstrate the importance of the semimetal to semiconductor transition. We concluded that the geometrically based semimetal to semiconductor transition in graphene systems is responsible for improved thermoelectric properties, and helps explain strong disorder based reduction in efficiency reported in previous computational studies. Our study suggests that with further optimization nanostructured graphene could be a potential thermoelectric material.
    • Combination of hydrodynamic and optical forces for cell mechanical flow cytometry

      Marr, David W. M.; Neeves, Keith B.; Roth, Kevin B.; Squier, Jeff A.; Silverman, Anne K.; Wu, Ning (Colorado School of Mines. Arthur Lakes Library, 2015)
      Cell mechanical properties are a label-free biomarker capable of differentiating between healthy and diseased cells. Currently, cell deformability is measured by testing the mechanics of a suspension of cells to yield population averaged properties. This approach can mask the presence of sub-populations of diseased cells. Alternatively, individual cell measurements provide detailed information of individual cells, but are inherently low throughput, making data acquisition tedious and scale-up impractical. To address these issues, we propose using optical-based cell deformation techniques in microfluidic platforms to measure cell mechanical properties non-invasively, non-destructively and in a high-throughput manner (> 1 cell/s). In this thesis two different techniques are proposed: optical alignment compression (OAC) cytometry and optical stretching in flow. Both techniques combine optical and hydrodynamic forces in low Reynolds number flows. In OAC cytometry, an aligning optical trap is combined with extensional flow in a microfluidic device to allow hydrodynamic forces to cause measurable deformation through cell-cell collisions at the flow stagnation point. Results demonstrate the utility of optical-based testing by testing two red blood cell systems. To further examine optically based techniques, we employ optical forces to induce deformation. In optical stretching with improved laser imaging, a linear diode bar laser is aligned parallel to flow in a microfluidic device to deform cells that pass through the trap. The combination of optical and hydrodynamic forces at high flow rates allows for high-throughput measurements (~50 cells/s). Technique viability is tested with both red blood cells and neutrophils. By considering these two approaches we will characterize the interplay of optical and hydrodynamic forces and their contributions to cell deformation in optical-based cell mechanical property testing.
    • Effect of various deformation processes on the corrosion behavior of casing and tubing carbon steels in sweet environment, The

      Mishra, Brajendra; Elramady, Alyaa Gamal; Olson, D. L. (David LeRoy); Liu, Stephen; Madeni, Juan Carlos; Graves, Ramona M. (Colorado School of Mines. Arthur Lakes Library, 2015)
      The aim of this research project is to correlate the plastic deformation and mechanical instability of casing steel materials with corrosion behavior and surface change, in order to identify a tolerable degree of deformation for casing steel materials. While the corrosion of pipeline and casing steels has been investigated extensively, corrosion of these steels in sweet environments with respect to plastic deformation due to bending, rolling, autofrettage, or handling needs more investigation. Downhole tubular expansion of pipes (casings) is becoming standard practice in the petroleum industry to repair damaged casings, shutdown perforations, and ultimately achieve mono-diameter wells. Tubular expansion is a cold-drawing metal forming process, which consists of running conical mandrels through casings either mechanically using a piston or hydraulically by applying a back pressure. This mechanism subjects the pipes to large radial plastic deformations of up to 30 pct. of the inner diameter. It is known that cold-working is a way of strengthening materials such as low carbon steel, but given that this material will be subjected to corrosive environments, susceptibility to stress corrosion cracking (SCC) should be investigated. This research studies the effect of cold-work, in the form of cold-rolling and cold-expansion, on the surface behavior of API 5CT steels when it is exposed to a CO2-containing environment. Cold-work has a pronounced influence on the corrosion behavior of both API 5CT K55 and P110 grade steels. The lowest strength grade steel, API 5CT K55, performed poorly in a corrosive environment in the slow strain rate test. The ductile material exhibited the highest loss in strength and highest susceptibility to stress corrosion cracking in a CO2-containing environment. The loss in strength declined with cold-rolling, which can be ascribed to the surface compressive stresses induced by cold-work. On the other hand, API 5CT P110 grade steels showed higher susceptibility to SCC when they were cold-rolled and cold-expanded. The research found that surface compressive stresses have an effect on the SCC behavior of casing and tubing steels. The CO2 corrosion behavior and atomic processes at the corroding interface were investigated at laboratory temperature using electrochemical techniques. Cold-work was found to have an influence on the corrosion behavior of both API 5CT K55 and P110 grade steels. These behaviors were found to be material and process dependent. Surface evaluation techniques such as field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD) analysis did not detect formation of a protective scale. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) analysis both detected the appearance of a scale that was traced back to magnetite.