Now showing items 21-40 of 229

    • Accelerating the discovery and optimization of thermoelectric materials

      Toberer, Eric; Ortiz, Brenden R.; Ohno, Timothy R.; Zimmerman, Jeramy D.; Stevanovic, Vladan (Colorado School of Mines. Arthur Lakes Library, 2018)
      Widespread application of the Materials Genome Initiative (MGI) promises to revolutionize the discovery and realization of next-generation materials for a diverse set of applications. Fundamental to the success of the MGI is the synergistic effect of computational and experimental material science, wherein computation serves as a guide for experimentation, as opposed to the \textit{ex-post-facto} approach which has dominated the literature in the prior decades. The field of thermoelectrics, in particular, has historically been dominated by experimental work motivated largely by chemical intuition. Complex coupling between scattering phenomena, electronic transport, and thermal transport renders optimization in thermoelectric systems difficult, both experimentally and computationally. We have formulated a computationally inexpensive metric, deemed $\beta_{SE}$, which was applied in a high-throughput computational survey of over 40,000 compounds. This metric was validated and refined through the experimental work within this thesis. Our survey revealed many intriguing material classes, two of which were examined experimentally in detail: 1) the n-type Zintl phases, and 2) the quaternary diamond-like semiconductors. The n-type Zintl phases are a particularly interesting example of where chemical intuition and historical precedent can mislead the discovery of new materials. The p-type Zintl phases are a well-known and historically successful family of thermoelectric materials. The thermoelectric community has long-held that Zintl phases must be p-type due to the proclivity of the typical chemistries to form alkali or alkali-earth vacancies. However, our computational search indicated that the n-type Zintl phases should both outnumber and outperform their p-type counterparts. We proceeded to discover and dope two n-type Zintls, KAlSb$_4$ and KGaSb$_4$, finding them to be promising thermoelectric materials. The quaternary diamond-like (DLS) semiconductors are another class of materials identified through our search. The quaternary materials were predicted to exhibit both high electronic mobility and low lattice thermal conductivity, properties that are generally inversely related to each other. We experimentally investigated the 3x3 matrix of compositions Cu$_2$(Zn,Cd,Hg)(Si, Ge, Sn)Te$_4$, finding the Hg-containing DLS to have an unusually high electronic mobility and abnormally low lattice thermal conductivity- ideal for thermoelectrics. However, while computations predict high performance when doped n-type, all of the quaternary DLS present as degenerately doped p-type semiconductors. To overcome the degenerate p-type doping, applied the concept of ``phase boundary mapping'' to reduce the carrier concentration nearly 5 orders of magnitude through intrinsic defect manipulation alone. Our work within the quaternary DLS demonstrated that material discovery in thermoelectrics is also an optimization problem with many dimensions -- which is onerous to perform using classical synthesis techniques. The complex optimization problem presented by the DLS was the impetus for the last study presented in this work. We demonstrated that high-throughput experimental synthesis (particularly with bulk ceramics) has the potential to dramatically increase the rate of material optimization, potentially allowing better synergy with existing high-throughput computational efforts. Together, our work ultimately moves the field of thermoelectrics towards the vision described by the MGI. We have produced new metrics for understanding thermoelectric materials, identified potential materials for thermoelectric applications, and built-upon existing experimental techniques to accelerate material optimization. Together these efforts have begun to unravel the complex structure-property relations that dictate thermoelectric performance.
    • Geomechanical property changes with hydrous pyrolysis in Mahogany oil shale in Green River Formation

      Tutuncu, Azra; Mohanraj, Keerthikanand; Ozkan, E.; Ermila, Mansur A.; Lewan, MIchael (Colorado School of Mines. Arthur Lakes Library, 2018)
      The formation characteristics of organic-rich shales have proven to be affected by mineralogical composition, total organic content, water concentration, and bedding-plane orientation along with other parameters. However, it is not known with good accuracy what types of influence thermal maturation has on the immature organic matter on geomechanical properties of the formations. In order to quantify the behavior of the oil shale samples under thermal maturation, it is imperative to understand its elastic properties. Thus, it becomes vital to understand the shale’s elastic properties via geomechanical analysis of the selected core samples. In this experimental study, vertical core samples of Mahogany shale in Green River formation from the Anvil Points mine site were selected. These samples possess immature organic content consisting of Type-I kerogen. This study consists of an experimental investigation to comprehend if thermal maturation of immature organic matter has an impact on the geomechanical properties of shale formation. Hydrous pyrolysis experiments were conducted to represent the four different stages of petroleum formation: temperature ranges that represent the bitumen generation (300°C), bitumen generation and initial oil generation (330°C), oil generation (360°C) and the oil cracking to gas (390°C). The samples were tested in these four different temperature states were analyzed later for the changes in their geomechanical properties. The geomechanical properties are evaluated in terms of dynamic elastic properties and resistivity. Unfortunately, the pyrolyzed samples had sustained a heavy loss of their mechanical strength and integrity due to the expansion because of the samples undergoing thermal maturation resulting in their infringement. The weakening prevented us from analyzing the changes in static properties. However, investigation of the changes in dynamic elastic properties and resistivity was possible. The samples were evaluated for dynamic elastic properties before and after pyrolysis to note the variations that it had undergone during the process of thermal maturation that was artificially induced by hydrous pyrolysis. In this research study, we analyze the thermal maturation effects on the geomechanical properties of the oil shale plugs via the analysis of elastic properties and resistivity measurements. The post analysis of the thermally matured core plugs, we found a prominent decrease in the elastic properties such as the Young’s, bulk and shear modulus. We conclude that thermal maturation of organic-rich samples results in mechanical weakening of the sample. Correspondingly, resistivity data were a function of organic richness and temperature. An analytical comparison of the elastic properties of formations across the globe for a comprehensive evaluation of the differences amongst them is also carried out. The results of the study indicate that thermal maturation tends to decrease the mechanical integrity and strength of the rock. The generation of petroleum products due to the maturation of organic products results in pore volume expansion, which causes fracture development and most often the failure of the sample. The behavior of resistivity tends to be dependent on the amount of organic matter expelled during the thermal maturation as well as the amount of organic matter withheld in the core plug, which relatively makes them temperature dependent, as the organic matter expelled is a function of the temperature.
    • Photoautotrophic growth of eukaryotic microalgae and electron detours under deficient sink stress

      Posewitz, Matthew C.; Thomas, Dylan C.; Domaille, Dylan; Trewyn, Brian (Colorado School of Mines. Arthur Lakes Library, 2018)
      Eukaryotic microalgae have been an attractive target for use in the bioeconomy for over 70 years because of their ability to efficiently generate biomass from CO2, sunlight, seawater, and fertilizer. In this thesis, I will demonstrate the isolation of a promising new industrial alga, Picochlorum celeri, which has one of the highest maximum growth rates ever reported. The organism’s hallmark is a high chlorophyll concentration, a dynamic antenna regulated by light, and a high net oxygen evolution rate. In addition to this new biotechnology strain, a starchless mutant of the model organism, Chlamydomonas reinhardtii, was photosynthetically characterized which unmasked water-water cycles cause by uncoupled light reactions and carbon metabolism. In this analysis, the apparent maximal rate of Flavodiiron proteins was calculated as they activate under light transitions as well as the usage of the Plastid terminal oxidase under both inactive carbon metabolic stress and nitrogen deficiency.
    • Development of single element detection imaging systems and femtosecond laser micromachining for additive manufacturing processes

      Squier, Jeff A.; Worts, Nathan G.; Durfee, Charles G.; Toberer, Eric; Navarre-Sitchler, Alexis K. (Colorado School of Mines. Arthur Lakes Library, 2018)
      The development of ultrafast laser imaging and micromachining systems for use in integrated material modification and additive manufacturing setups is discussed. This thesis is organized into seven Chapters. The first chapter presents a brief overview and introduction of ultrafast lasers and the benefits of using them for linear and nonlinear microscopy and imaging as well as amplified laser material modification. Chapter two demonstrates the many capabilities of the amplified ultrafast laser machining system in the context of additive manufacturing (AM). The significant results here include the ability to process AM components by creating a surface finish to a certain specification, generating micro-cone structures on the surface for modifying wetting characteristics, and writing nanogratings onto the components for encoding numerical counterfeiting information. Chapter three shows the results of using the ultrafast laser micromachining in combination with spatial frequency modulated imaging (SPIFI) to produce enhanced resolution images in multiple linear and nonlinear modalities. Chapter four extends SPIFI to a previously unknown capability in which the imaging system is constructed in such a way as to acquire interferometric axial sensitivity. This is significant as it opens up the world of surface metrology and imaging the phase content of objects with enhanced resolution. The fifth chapter highlights an imaging system where SPIFI is used to gain enhanced resolution in multiple dimensions simultaneously. Chapter six provides a review of a focusing technique called simultaneous spatial and temporal focusing (SSTF) which can be utilized in a wide range of microscopy and micromachining applications and mitigates many problems ultrafast lasers have when interacting with materials and acquiring images. The final chapter provides general conclusions and an outlook to the future of using amplified ultrafast lasers to provide in-situ process monitoring for additive and subtractive manufacturing.
    • Influence of dolerites on coal rank, maturity and total gas content in coal bed methane play, Botswana

      Milkov, Alexei V.; Bulguroglu, Muhammed Emin; Sonnenberg, Stephen A.; Monecke, Thomas (Colorado School of Mines. Arthur Lakes Library, 2018)
      Coal bed methane (CBM) is the gas adsorbed into the solid matrix of the coal. Botswana’s energy has heavily been depending on coals. In order to explore CBM potential of Botswana, Kubu Energy Resources (a joint venture between Sasol and Origin Energy) drilled nine coreholes in three different license areas, which cover a total area of 3000 km2 in 2013. Due to extensive magmatic activity that happened about 180 million years ago, Botswana has abundant dolerite sills. In this thesis, I studied the subsurface geology of the Kubu’s license areas to understand the influence of dolerites on coal beds and CBM potential. I used well-logs to reveal lateral and vertical variations in lithology and created structure and isopach maps to understand variations in stratigraphy and structural setting. Coal rank, maturity and total gas content data were provided from Kubu Energy. I used the 1D basin modelling software Genesis (version 5.7) by Zetaware Inc. to build burial and thermal history models and to understand the thermal influence of dolerites on the surrounding sediments, coals and CBM. Thermal influence of sills depends on their thickness. Dolerite sills thicker than 15 m have thermal influence ratio 1:0.55 above the sill and 1:0.48 below the sill, i.e., they affect sediments at the distance about half of their own thickness. Dolerite sills thinner than 5 m have thermal influence ratio 1:5.2 above the sill and 1:6.1 below the sill, i.e., they affect sediments at the distances 5-6 times larger than their own thickness. Timing of the intrusion is also important. Less deposition time results in relatively higher maturity values in the surrounding sediments. Intrusions deposited almost instantaneously have the largest thermal effect on the surrounding sediments. As expected, coal rank, maturity (vitrinite reflectance) and gas content increase towards the contacts of dolerite sills with surrounding rocks. In this study, non-heat affected samples display lower total gas content values than typical productive CBM plays in the U.S basins. However, heat-affected coals in Botswana have gas content in the range of typical productive CBM plays in the U.S basins.
    • Advanced thermoplastic composites for wind turbine blade manufacturing

      Samaniuk, Joseph R.; Dorgan, John R.; Cousins, Dylan S.; Stebner, Aaron P.; Knauss, Daniel M.; Neeves, Keith B. (Colorado School of Mines. Arthur Lakes Library, 2018)
      Fiber-reinforced polymer composites are an intriguing class of engineering materials that are increasingly exploited in the construction, aerospace, and energy sectors. Their high specific properties make them an ideal design choice where traditional engineering materials like metals are too heavy, or where unreinforced polymers are not stiff or strong enough. Furthermore, their anisotropic nature can be exploited for unique applications such as airfoils in aircraft wings or wind turbines. However, most structural composites use thermosetting polymers as their matrix, which presents several issues. Foremost is that thermosets cannot be easily recycled, so massive amounts of composite waste are landfilled at the end of a part’s service life. Secondly, thermoset subcomponents of a larger structure can only be joined using adhesives. Conversely, thermoplastic composites enable recycling after a part is retired from service and facilitate thermal joining of multi-part structures. Liquid infusible thermoplastic resins are beginning to emerge for use in vacuum-assisted resin transfer molding, which is the method of manufacture for wind turbine blades. While infusible thermosetting resins have been well characterized, basic characterization of rheological and kinetic behavior for thermoplastic resins is lacking. The present work provides important experimental development and data aimed at characterization of infusible thermoplastic resin systems. A novel thermoplastic biobased resin system is also developed, which has potential for commercial use.
    • Direct reliability-based design (d-RBD) of shallow wind turbine foundations

      Griffiths, D. V.; Ben Hassine, Jomâa; Johnson, Kathryn E.; Kiousis, Panagiotis Demetrios, 1956-; Guerra, Andres (Colorado School of Mines. Arthur Lakes Library, 2018)
      Wind turbine foundations transfer dynamic and highly eccentric loads to variable soils. The design of such foundations involves the verification of multiple limit states to ensure proper operation of the turbine and avoid catastrophic failures. An optimal foundation design minimizes cost while meeting all relevant limit states at quantifiable and acceptable risks. This dissertation explores three common limit states that are relevant to the design of shallow, gravity based, wind turbine foundations using a fully-probabilistic Monte Carlo Simulation (MCS) method, termed in this work as the direct Reliability Based Design (d-RBD) method. The three limit states are foundation tilt, rotational stiffness and bearing capacity. For each of these limit states, design variables are randomized using predefined probability density functions. The d-RBD method involves running Monte Carlo Simulations to produce realizations covering potential combinations of design decision variables such as foundation dimensions (e.g. width and/or depth). The d-RBD method uses Bayesian conditional probability theory to select the geometry combinations that meet the predefined target probability of failure. With this approach, a single MCS run is needed to identify pools of acceptable designs for each limit state from which an optimal design meeting all limit states can be selected. This dissertation introduces d-RBD as a direct, fully probabilistic design procedure that offers important advantages over global factor (ASD/WSD) or partial factor (LSD/LRFD) design methods. For each of the limit states under consideration, d-RBD is used to highlight the cost of uncertainty, rank the design variables by their importance and assess the effects of pertinent variability assumptions. The findings from this work are relevant to ongoing efforts to develop international and U.S. standards for the design of wind turbine support structures and their foundations.
    • Underground cable ampacity: a fresh look at addressing the future electric grid

      Sen, Pankaj K.; Malmedal, Keith; Bates, Carson; Porter, Jason M.; Arkadan, Abd A.; Ammerman, Ravel F. (Colorado School of Mines. Arthur Lakes Library, 2018)
      Underground power cables serve a critical purpose in electric power applications and the electric grid. Many have experienced the frustration of a power outage resulting from a failed cable. This dissertation addresses underground electric power cable ampacity and provides analytical, experimental, and operational test results for underground cables. The motivation for this work stems from challenges facing the industry in determining cable ampacity due to the uncertainty in soil thermal resistivity and soil thermal stability. Analytical results compare multiple software models. Experimental results consist of radial temperature measurements of a buried cable at 3 heat rates for 5 to 21 days. Operational results include measurements of 1 kV DC combiner circuits installed at a 10 MW photovoltaic (PV) power plant. There are numerous methodologies for calculating ampacity that can result in substantial differences. Some of these differences stem from the concern of soil dry-out described as soil thermal stability. This dissertation proposes a method to address using a soil parameter called the Non-Drying Heat Rate. Experimental results indicate that soil around a cable dries based on the magnitude of heat flux and length of time but not directly proportional to the cable diameter as proposed in the Law of Times. A set of experiments was performed on a direct buried cable to compare with the Neher-McGrath method and commercially available software programs. The results show the Neher-McGrath calculations and CYMCAP software outputs overestimated the measured temperature with a mean error of 4% ± 10% for the 6 experiments performed. Soil drying was not predicted to occur based on the non-drying heat rate measurements, and the experimental results confirmed this. A PV power plant design was used as a case study concluding that the measurements for the DC combiner cables were significantly lower than the calculated temperatures. It illustrates the need for an industry accepted standard that provides a clear methodology for addressing soil thermal resistivity and soil thermal stability. This dissertation makes the following contributions: 1. Illustrates the need for an industry standard that addresses soil thermal stability 2. Proposes the non-drying heat rate method to address soil thermal stability 3. Indicates that the Neher-McGrath method is conservative by experimentation 4. Indicates no soil drying occurred during experimentation, as predicted by the non-drying heat rate method 5. Provides cable temperature measurements of an operational PV power plant
    • Catalytic coatings for vanadium-based hydrogen membranes

      Wolden, Colin Andrew; Way, J. Douglas; Fuerst, Thomas F.; Wilcox, Jennifer; Liguori, Simona; Pylypenko, Svitlana (Colorado School of Mines. Arthur Lakes Library, 2018)
      Vanadium is a cheaper and highly permeable alternative to palladium as a dense metallic hydrogen membrane. However, catalytic surface coatings must be applied to vanadium surfaces to enable the transport of molecular hydrogen. These coatings facilitate dissociation and recombination kinetics of molecular hydrogen and protect vanadium from oxidation. Palladium is the most common coating, but suffers from high material costs and interdiffusion with vanadium in the presence of hydrogen at and above 400 °C. In this work, alternative surface catalysts that operate via a spillover transport mechanism were investigated for membrane operation at temperatures > 400 °C. Membrane performance of the various group V metals (vanadium, niobium, and tantalum) was studied with the application of Mo2C. Vanadium provided the best hydrogen permeability and mechanical stability, and therefore remained the focus of this thesis. Low temperature operation (< 600 °C) of Mo2C/V membranes revealed a robust resistance to embrittlement which was onset by transport limitations in the Mo2C. TiC was also tested as a coating and produced high fluxes up to 0.71 mol m-2 s-1 at 650 °C and 1 MPa transmembrane pressure. The effect of hydrogen isotopes on permeation at high temperature (600 – 700 °C) was tested on the TiC/V membranes. Protium permeated 1.12 – 1.34 times faster than deuterium, yet no isotopic effect on solubility was measured. A challenge with both Mo2C and TiC coatings was the competitive adsorption of CO2 and N2 which inhibited hydrogen transport. However, this was resolved with the addition of thin Pd films over the carbide layers. Aside from transition metal carbides, a simple air treatment produced catalytically active V2O3 on the surface of vanadium. The surface oxide yielded similar fluxes to Mo2C, yet, was only stable at 550 °C. Density functional theory simulations revealed superior energetic properties for hydrogen adsorption and dissociation on the V2O¬3 (0001) surface compared to other V oxide states. Lastly, vanadium sputter conditions and fabrication of composite Pd/V/Pd membranes on porous ceramic supports were studied to enable tubular geometries.
    • Redox cycles with doped calcium manganites for high-temperature thermochemical energy storage in concentrating solar power

      Jackson, Gregory; Imponenti, Luca; O'Hayre, Ryan P.; Kee, R. J.; Braun, Robert J. (Colorado School of Mines. Arthur Lakes Library, 2018)
      Redox cycles with reducible perovskite oxides of the form ABO$_3$ can provide thermochemical energy storage (TCES) with higher energy density and storage temperatures than molten-salt systems for large-scale energy storage in concentrating solar power (CSP). Perovskites from earth abundant cations are desirable for cost-effective solutions, but such materials must demonstrate appropriate thermodynamics for high specific TCES and favorable kinetics for heat-driven reduction and exothermic re-oxidation. This dissertation explores the thermodynamics and kinetics of doped CaMnO$_{3-\delta}$ particles for TCES redox cycles where particles are heated and reduced in N$_2$ ($P_{\text{O2}} \approx 10^{-4}$ bar) to high temperatures (700 to $1000^{\circ}$C) in a solid-particle solar receiver. Chemical and sensible energy stored in the reduced perovskite particles is released as needed to a supercritical CO$_2$ power cycle via re-oxidation and cooling of the material. Thermodynamics of Ca$_{1-x}$Sr$_x$MnO$_{3-\delta}$ ($x=0.05$ and $0.1$) and CaCr$_y$Mn$_{1-y}$O$_{3-\delta}$ ($y=0.05$ and $0.1$) are characterized through thermogravimetric analysis and calorimetry. Results indicate Ca$_{1-x}$Sr$_x$MnO$_{3-\delta}$ compositions can store over 200 kJ kg$^{-1}$ more specific energy storage compared to inert particulate TES media for $T \ge 900^\circ$C; the specific energy storage potential of Ca$_{0.9}$Sr$_{0.1}$MnO$_{3-\delta}$ at $T=900^\circ$C and $P_\text{O2}=10^{-4}$ bar is 706 kJ kg$^{-1}$. Challenges are expected achieving these high values of energy storage in a transport-limited receiver with low residence time for CSP. Redox kinetics are explored in a packed bed reactor with rapid heating capabilities. Results in isothermal tests show that oxidation is significantly faster than reduction. Modeling of packed bed experiments indicate that reduction at $T \ge 800^\circ$C is limited by build-up of oxygen in the gas phase and equilibrium thermodynamics between the solid and gas phases. Long-term redox cycling tests, which simulate a nominal TCES cycle, demonstrate excellent chemical stability for all materials. A standard deviation of 1.9\% on the extent of reduction over 1000 cycles was observed for Ca$_{0.9}$Sr$_{0.1}$MnO$_{3-\delta}$. Modeling efforts of the packed bed experiments allow for characterization of redox kinetics, to be implemented in computational models for system component design. One of the most promising compositions, Ca$_{0.9}$Sr$_{0.1}$MnO$_{3-\delta}$, is implemented in a 1-D receiver model to explore designs and operating conditions for perovskite-based energy storage systems.
    • Factors predictive of roof instability in addition to the existing CMRR criteria at two case study coal mines

      Walton, Gabriel; Holley, Elizabeth A.; Young, Meriel; Brune, Jürgen F.; Santi, Paul M. (Paul Michael), 1964- (Colorado School of Mines. Arthur Lakes Library, 2018)
      Roof falls remain one of the greatest hazards facing underground coal miners (Barczak et al., 2000; Razani et al., 2013; Oraee et al., 2016). In 2017 there were 91 lost-time injuries from roof falls (in US underground coal mines). A further 48 roof falls were reported in US underground coal mines with no lost days (MSHA, 2018). These numbers have certainly decreased over the last century (MSHA, 2018), but the goal of zero injuries still remains. Assessing the likelihood of roof falls is therefore highly important and will have a direct effect on the prevention of accidents caused by them. One method developed to help assess roof instability in underground coal mines is the Coal Mine Roof Rating (CMRR). The CMRR is a field-based empirical method which is straightforward to use and gives a quantitative interpretation of coal mine roof geology. The CMRR classification system was developed by Molinda and Mark (1994) to quantify the geological description of mine roof into a single value which could be used in engineering design. It provides an excellent starting point, but it does not necessarily include all the factors that may influence roof stability, nor is it widely used in the Western US. This thesis research uses two underground longwall coal mines located in the Western US (Mine A and Mine B) as case studies to investigate which parameters are indicative of roof falls at these mines. It also evaluates whether the CMRR is applicable to them, and if not, why this might be. A data set was collected at 30 sites in each mine. This data set included the CMRR, a record of the roof stability and a series of non-CMRR parameters thought to also be potentially indicative of roof stability but which are not included in the CMRR. These data were then statistically analyzed for correlation between CMRR and roof stability. The correlation between roof stability and the non-CMRR parameters collected was also evaluated. To further evaluate how influential each parameter already included in the CMRR is at each mine, each constituent of the CMRR was removed in turn and a modified CMRR was calculated. This modified CMRR was then evaluated for correlation with roof stability. At Mine A, the correlation between the CMRR and roof stability was found to be statistically significant (significance threshold α = 0.05), with a p value of 0.0073. Logistic regression analyses showed the CMRR to be reasonably predictive of roof stability at Mine A. Faulting, along with depth of cover and slope angle of surface topography were found to be the most significant non-CMRR parameters to correlate with roof stability at Mine A. At Mine B, the correlation between the CMRR and roof stability was not found to be statistically significant (p value = 0.95) against a significance threshold of α=0.05. The logistic regression analyses also showed the CMRR to have little predictive capability on roof stability at Mine B. At Mine B, location at an intersection and depth of cover were found to be significantly correlated with roof stability. The CMRR is therefore moderately effective at Mine A but not effective at Mine B. This is thought to be due, at least in part, to the unusual topography above Mine B, with differential erosion resulting in a landscape of flat plateaus and sharp river valleys. It is suggested that these sudden changes in slope and topography lead to in-situ stress rotation and the development of shear stresses near the excavation at Mine B. This, combined with a lack of major discontinuities such as slickensides, which are central to the CMRR system, likely explains why the CMRR is much less effective at predicting roof stability at Mine B compared to Mine A. Mine A was also found to more closely match the geological conditions of the mines in the CMRR reference database than Mine B. The majority of the coal seams sampled in the CMRR reference database are located in the Appalachian or Illinois basins. The Appalachian Basin is a foreland basin with a complex geological structure and a high incidence of faulting. This is similar to the regional geology at Mine A. The Illinois basin as a whole more closely matches the geological setting at Mine B; both are located in broad, gentle structural depressions. However, the Illinois Basin coal seam most frequently sampled in the CMRR reference database is one with notable faulting and a roof geology which is complex and laterally inconsistent. This is the opposite of the geological conditions in the roof at Mine B, which are laterally uniform and continuous. It is likely that the CMRR is not applicable at Mine B because the geological conditions there are not captured in the CMRR reference database.
    • Catalytic upgrading of muconates for renewable chemical applications

      Richards, Ryan; Vardon, Derek R.; Settle, Amy E.; Koh, Carolyn A. (Carolyn Ann); Trewyn, Brian; Posewitz, Matthew C. (Colorado School of Mines. Arthur Lakes Library, 2018)
      Due to growing awareness of environmental impacts and the economic volatility of petroleum, there has been a drastic increase in research towards biomass-derived, sustainable alternatives to petroleum-based processes and products. Notably, commodity chemicals for production of commercial products are exclusively manufactured using feedstocks derived from crude oil refining and currently account for over one third of the worldwide industrial energy demand. As the market demand for petrochemicals are only forecasted to grow, development and advancement of renewable chemical processes is timely. Lignocellulosic biomass presents as a promising alternative source for these aromatic monomers due to the diverse structure and inherently high oxygen content within its components: lignin, cellulose, and hemicellulose. However, significant research is needed in order to realize the use of lignocellulosic biomass as a platform for such chemical products and to push these renewable chemical processes toward industrial and commercial relevance. This work focuses on the catalytic conversions of cis,cis-muconic acid (cis,cis-2,4-hexadienedioic acid), a polyunsaturated C6 dicarboxylic acid that can be microbiologically produced from lignocellulosic biomass streams. The state of catalysis for Diels-Alder reactions involved in upgrading schemes of muconic acid and other biomass-derived products to drop-in and functional alternative commodity monomers is reviewed and evaluated, followed by concentrated studies into the iodine-catalyzed isomerization of cis,cis¬-dimethyl muconate to the Diels-Alder active isomer, trans,trans-dimethyl muconate. Finally, an investigation into the use of atomic layer deposition to enhance the leaching resistance and thermal stability of supported platinum group metal catalysts during condensed phase hydrogenation of muconic acid to adipic acid is presented.
    • Tectonic evolution of Taranaki Basin, offshore New Zealand, The

      Trudgill, Bruce, 1964-; Coleman, Robert D.; Milkov, Alexei V.; Kuiper, Yvette (Colorado School of Mines. Arthur Lakes Library, 2018)
      The sedimentary architecture of the Taranaki Basin, located primarily offshore of northwestern New Zealand, reveals the structural and stratigraphic response to the region’s polyphase tectonic history. Using Schlumberger’s Petrel software, 2D and 3D seismic data are structurally and stratigraphically interpreted and depth-converted, and three depth-converted regional cross-sections are sequentially restored through 14 time horizons using Midland Valley’s Move. The structural restoration process incorporates paleobathymetry, isostatic corrections, decompaction, unfaulting, and unfolding, and yields extension and shortening rates from the deepwater to proximal Taranaki Basin. Measured Middle Cretaceous to Paleocene extension rates total 7.0% in the Northern Taranaki Basin, 5.1% in the Central Taranaki Basin, and 1.8% in the Southern Taranaki Basin; the temporal and spatial distribution of extension provides evidence of two-phase rifting. Eocene initiation of Pacific Plate subduction resulted in anomalously high post-rift subsidence, 0.10% shortening across the Northern Taranaki Basin, little to no shortening in the Central Taranaki Basin, and 1.6% shortening across the Southern Taranaki Basin. The Southern Taranaki Basin, which has experienced a higher magnitude of transpressional stress, has seen the greatest variety of shortening-related deformation in the basin. The distribution of strain in the basin is compared with previous research in the region, which reveals that the style of convergence-driven compressional strain is less varied in the Taranaki Basin, where the Taranaki Fault System has accommodated much of the basin shortening, than the nearby Reinga Basin; basement terranes and the spatial relationship between basin location and extinct and active Southwest Pacific subduction zones are presented as the underlying controls on strain distribution. Convergence-related shortening generally occurred in a systematic and sequential manner, migrating north-to-south, and the direction of principal compressive stress has rotated clockwise. Miocene to Recent back-arc extension of 0.44% is measured in the Northern Taranaki Basin, 0.17% in the Central Taranaki Basin, and is not observed in the Southern Taranaki Basin. Extension measured in this study is synthesized with previous research and presented from a rotating block model perspective, demonstrating a general north-south temporal migration of extension. The distribution of ultimate recoverable oil reserves are compared to the areal extent of shortening-related structures in the basin. Approximately 93% of New Zealand’s oil reserves are located within the extent of shortening delineated in this study, and it is proposed that convergence-related structural deformation provides a key control on the distribution of hydrocarbon accumulations in the basin.
    • Exfoliated hexagonal boron nitride based anti-corrosion polymer nano-composite coatings for carbon steel in a saline environment

      Mishra, Brajendra; Alabdullah, Fadhel T.; Liu, Stephen; De Moor, Emmanuel; Ranville, James F. (Colorado School of Mines. Arthur Lakes Library, 2018)
      Polymer coating is the most suitable route to protect the metallic surfaces, and it has many purposes including anti-static coating, electromagnetic shielding, anti-reflective and anti-corrosion properties. The long term performance of the metallic surface can be achieved by polymer coatings. The discovery of nanoparticles introduced a new class of materials having higher surface area, high-performance polymer nano-composites appear attainable. For polymer anti-corrosion coatings, in addition to the inherited barrier effect provided by pure polymer films, the film blocking properties can be improved using plate-like nano-fillers. Incorporating fillers, such as graphene nano-platelets, has proven effective as anti-corrosion coating. These coatings usually improve the barrier, mechanical, electrical, optical, rheological, adhesion properties, and resistance against the environmental degradation; However, polymer coatings loaded with graphene displayed long-term enhanced corrosion after erupting the barrier due to inherited electrical conductivity and higher position in the galvanic series. Herein, we exfoliated the hexagonal boron nitride (h-BN) from micro particles into nano-sheets and incorporated it as fillers at different concentration in polymer coatings to enhance the barrier properties. For comparison, graphene nano-platelets were also used. Transmission electron micrographs confirmed the exfoliation of hexagonal boron nitride (h-BN). For exfoliation, we selected two different particles size i.e., 0.07 µm and 5.0 µm. The barrier properties of the coatings were determined in 3.5 % NaCl during different times of immersion, via different electrochemical techniques such as open circuit potential, electrochemical impedance spectroscopy and potentiodynamic. The coatings containing exfoliated h-BN (5.0 µm) particles exhibited improved resistance for longer periods of immersion compared to graphene nano-platelets. The improved corrosion properties can be attributed to the high aspect ratio, plate-like shape and electrically insulated nature of the exfoliated (h-BN) nano-sheets. Specifically, the thesis will be composed of the following steps: 1) preparation of exfoliated hexagonal boron nitride (h-BN) from different particles and synthesis of anti-corrosion coating by dispersion of fillers in polymer matrix via solvent blending, 2) electrochemical techniques for the determination of anticorrosion properties and 3) characterization of exfoliated nano-sheets and nanocomposites.
    • Dynamic contingency analysis of a power system under natural disaster conditions

      Mohagheghi, Salman; Silva, Deborath; Arkadan, Abd A.; Nayeri, Payam (Colorado School of Mines. Arthur Lakes Library, 2018)
      In September 2017, one of the most devastating natural disasters occurred in the island of Puerto Rico. A hurricane of category 5 with wind speeds reaching as high as 175mph hit the island. This Hurricane, named Maria, impacted the island greatly and left the population without power for weeks, some even for months. The government declared a humanitarian crisis on the island. The challenging part of the power grid in Puerto Rico is its location and the fact that it does not have a tie to the rest of the U.S. electric grid. This means the grid needs to be self-sufficient and cannot rely on external help. Even though natural disasters are inevitable, their impact on the power grid can be reduced by making the grid more resilient. To do this, it is necessary to identify the vulnerable parts of the network to be reinforced. In the case of a hurricane for instance, this could be strengthening the vulnerable transmission line towers, raising the overhead conductors to higher heights in areas with a high risk of inundation, protecting the substations from being flooded by the surge water, or deploying more distributed energy resources in order to enable islanded operation. This goal of this research is to analyze the vulnerabilities of the Puerto Rico power grid and identify the weaknesses and vulnerabilities. This is achieved by studying both static and dynamic operation of the system in order to identify the components that need to be reinforced. Doing this may help the grid against potential future disasters either by allowing it to withstand the event completely or by shortening the duration and/or scope of outages.
    • Ultrasonic and electrical properties of hydrate-bearing sediments

      Prasad, Manika; Pohl, Mathias; Dugan, Brandon; Collett, T. S.; Waite, William F.; Koh, Carolyn A. (Carolyn Ann); Tutuncu, Azra (Colorado School of Mines. Arthur Lakes Library, 2018)
      There is a need to estimate the amount of gas hydrates occurring in the subsurface to establish the potential of natural gas hydrates as, for example, gas resource, geo-hazards, or climate change factors. Controlled laboratory measurements of the seismic properties of pure hydrate and hydrate-bearing sediment are critical to calibrate seismic and more importantly well-logging methods used to estimate gas hydrate accumulations. In general, the presence of hydrates is accompanied by an increase in acoustic velocity and attenuation. The stiffening effect of hydrate formation in unconsolidated sediment strongly depends on hydrate habit: hydrate formation along the grain surfaces increases velocities already at low (Sh ~ 3%) hydrate saturation, whereas hydrate located in the pore space will increase velocity only at high (Sh > 20%) hydrate saturation. I measured ultrasonic P- and S-wave velocity and attenuation in pure tetrahydrofuran (THF) hydrate and THF hydrate-bearing sediment as functions of pressure and temperature. In addition, I measured complex electrical conductivity in a methane hydrate-bearing sandstone during multiple cycles of hydrate formation and dissociation. These combined measurements allow us to understand the effect of hydrate growth on geophysical properties, interactions between sediment – water – hydrate and hydrate – water interfaces, and provide a better understanding of why an increase in hydrate saturation in sediment is accompanied by an increase in wave attenuation in well log data. The ultrasonic measurements show that presence of liquid water between hydrate grains increases attenuation in pure THF hydrates and sand-clay mixtures with varying hydrate saturation (0, 40, 60, and 80%). The observations suggest that trapped water within the hydrate causes the heightened attenuation. A comparison with laboratory data obtained using methane as a hydrate former verifies that acoustic properties of THF hydrate-bearing sediments are comparable to the methane hydrate-bearing sediments found in nature, demonstrating that THF hydrate is an appropriate proxy for methane hydrate. After an increase in pressure from 435 to 2175psi, the loss-diagram shows that samples with various hydrate saturation (0, 40, 60, and 80%) converge to the same linear behavior; as the hydrate saturations increase, the Ki - µi ratios decrease, implying a change in loss mechanisms. These findings help make a better prediction on the effects of hydrate saturation in the subsurface on the sediment properties and can be used to interpret field seismic observations. Similar to acoustic attenuation, electrical conductivity is sensitive to the existence and amount of free water. Hydrate formation results in a thin hydrate layer along the grains. The conductivity data suggest that small layers of unreacted free water are present between the thin layer of hydrate and the sediment grains. This is very important because residual water has a significant effect on wave attenuation. Hydrate formation consumes pure H2O which, during the onset of hydrate formation, results in an increase of temperature due to the exothermic reaction. This is observed as a sudden increase in electrical conductivity. Further cooling results in the observed decrease in conductivity. The reverse effect is detected during hydrate dissociation. Combined, these two processes could be used to monitor the hydrate formation or dissociation front in the subsurface.
    • Experimental methods of flowsheet development for hard drive recycling by preferential degradation and physical separation

      Taylor, Patrick R.; Ott, Brandon; Spiller, D. Erik; Anderson, Corby G. (Colorado School of Mines. Arthur Lakes Library, 2018)
      Neodymium-iron-boride magnet recycling by applying mineral processing practices of liberation and separation to hard disk drives is designed, discussed, and evaluated. Magnetic material, observed to be brittle, is liberated from the hard drive constructed mostly of malleable metals by preferential degradation of the magnet material. The process developed is shown to recover greater than ninety-five percent of the neodymium-iron-boride magnet material in the feed with a product grade of up to over 80 percent magnet material by mass. The process is designed to co-produce stainless steel, aluminum, nickel alloy, carbon steel, and printed circuit board concentrates as contributors to the recycle value of hard drives. The value of materials enclosed in hard drives is explored and discussed. Economic evaluation of this process, including estimation of capital and operating expenditures coupled with revenue based on demonstrated recovery of valuable materials, shows a positive net present value at various depreciation rates up to thirty percent.
    • Measurements and modeling of gas hydrates formation in inhibited systems: high pressure, high salinity, and mixture of inhibitors

      Sum, Amadeu K.; Hu, Yue; Sampaio, Jorge; Krebs, Melissa D.; Carreon, Moises A.; Rao, Ishan (Colorado School of Mines. Arthur Lakes Library, 2018)
      As energy demands continuously increase, oil and gas fields delve into ultra-deep water, which leads to severe operating conditions in terms of pressure, temperature, and water salinity. These conditions pose significant flow assurance challenges, especially gas hydrate formation and scale deposition. Reliable prediction of hydrate phase equilibrium at extreme conditions, in terms of high salinity and high pressure, is necessary for development and operations in ultra-deep water oil and gas production. However, according to the literature review, no open literature studies exist for the hydrate phase equilibria in brine systems above 69 MPa (10,000 psia) due to the challenges associated with experimental designs, safety issues and pitting corrosion problems. As a result, current hydrate prediction tools commonly used are not fully benchmarked and become unreliable at the extreme conditions of very high pressure and high salinity. In this study, experimental data on methane hydrate phase equilibria containing electrolytes, sodium chloride (NaCl), potassium chloride (KCl), and ammonium chloride (NH4Cl) were measured for concentrations up to about 10 wt% at pressure below 10.3 MPa through both isochoric and differential scanning calorimetry (DSC) method with stepwise heating. The results from both methods show good agreement with each other, which proves the accuracy and reliability of experimental methods and measurements. Moreover, the effect of the cation in the electrolyte on the hydrate inhibition strength is identied through the measurements, showing that hydrate inhibition strength by the sodium cation was slightly stronger than that of potassium and ammonium cations due to smaller ionic size for Na+. With validating the reliability of both methods used for measurement of hydrate phase equilibria and identifying the limitation of DSC method in salt concentration, a unique system capable to operate up to 207 MPa has been designed and set up considering safety issues and corrosion problems to measure hydrate dissociation conditions with isochoric method. Due to no data in open literature, the measurements of both structure I and structure II hydrate in single and mixed salts, including NaCl, KCl, CaCl2, MgCl2 and CaBr2, as well as mixed organic inhibitor and salts, such as MEG and CaBr2, become valuable for benchmarking existing prediction tools and improving prediction methods. In addition, the increased stability of methane hydrate at high pressure is discovered through the measurement of methane hydrate phase equilibria with fresh water. It is explained and understood by studying the effect of pressure on macroscopic and microscopic properties of water, methane gas and hydrate through both thermodynamic calculations and molecular simulations. As the interplay of hydrates and salt precipitation is fundamentally important due to the possible co-precipitation of two solids, both phase behavior and kinetics for gas hydrates formation/dissociation are studied by the developed experimental system. The measurements of both three phase (liquid – hydrates – gas) and four-phase (liquid – hydrates – solid salts – gas) equilibria with under-saturated and over-saturated NaCl and KCl solutions, separately, elucidates that the equilibrium boundary moves to lower temperature and higher pressure as the salt concentration increased up to the limit of saturation in the solution, and was unchanged from the conditions at saturation with four phases (liquid – hydrates – solid solids – gas) in equilibrium. Moreover, observed unusual inflection points in the pressure trace as a factor of time for the kinetic experiments, demonstrating that (i) hydrates can still form even with salt precipitated and (ii) the formation of hydrates and salt precipitation are competing effects. Finally, to bridge the gap between the measured data and its applicability, a simple but robust correlation (Hu-Lee-Sum correlation) has been developed to capture the hydrate suppression temperature at a given pressure, for not only high salinity brines, but also systems with mixed thermodynamic hydrate inhibitors (THIs). Due to its inherent property of generality and simplicity, it is a useful tool for the flow assurance engineer to accurately estimate hydrate dissociation temperature at given conditions with the average absolute deviation smaller than 2.0 K. Therefore, this comprehensive study, including measurements and prediction of hydrate phase equilibria, as well as kinetic experiments of hydrate growth rate, at extreme conditions, in terms of high pressure, high salinity and mixture of inhibitors, plays an important role on ultra-deepwater oil and gas production which go beyond hydrate management in pipe flow, such as, setting depth of surface-controlled subsurface safety valve (SCSSV) and identification of effective risk mitigation.
    • Uncertainty quantification in seismic imaging

      Sava, Paul C.; Pawelec, Iga; Wakin, Michael B.; Trainor-Guitton, Whitney; Snieder, Roel, 1958- (Colorado School of Mines. Arthur Lakes Library, 2018)
      To make informed decisions, one has to consider all available knowledge about the assessed problem. An important part of the decision-making process is understanding uncertainties and how they influence the outcome. In seismic exploration, many decisions are based on interpretations of seismic images, which are affected by multiple sources of uncertainty. Thus, image uncertainty quantification is an important, albeit challenging task. In this thesis, I focus on two uncertainty sources that affect seismic imaging: data uncertainty and velocity uncertainty. I quantify the seismic data uncertainty using theoretical analysis applied to two field experiments with repeated shots. My analysis reveals that amplitude distributions for each data sample as a function of time and position are not Gaussian and that the uncertainty of a seismic event is proportional to its mean amplitude. I also find that seismic events excited by the source are highly repeatable, but small changes of the source position impact the amplitude response, highlighting the importance of geometry repeatability for the lapse studies. Velocity uncertainty also has a large impact on image uncertainty, as it affects reflector positioning and the focusing of seismic events. By examining two subsalt imaging scenarios with geological uncertainty caused by the salt body physical properties, I demonstrate that image uncertainty, expressed as a function of the image amplitude or as a function of the reflector location, is the largest under the salt: the image amplitude distributions are two times broader under the salt than away from it. The confidence index maps are a useful tool to convey the information about image amplitude uncertainty to an interpreter, while the location uncertainty reveals uncertain directions and is affected by acquisition geometry. The main challenges facing uncertainty quantification in seismic imaging include integration of different sources of uncertainty and reducing the computational cost of the analysis. My analysis leads to recommendations about possible approaches towards these challenges, with emphasis on using sparsity to reduce the dimensionality of the problem.
    • Identification of parameters for predicting long-runout landslides in the western United States

      Santi, Paul M. (Paul Michael), 1964-; Lockyear, Russell A.; Walton, Gabriel; Zhou, Wendy (Colorado School of Mines. Arthur Lakes Library, 2018)
      No existing research provides an integrated analysis of the key parameters that contribute to long-runout landslides in the Western United States. This study begins the task by assembling a dataset of geological, topographical, and hydrological parameters for landslides from eight study areas. Six measures of mobility were analyzed and two (landslide height drop to runout length ratio, H/L and landslide runout length, L) were selected for further use. Analysis of the correlations of the measured parameters with H/L and L was performed to quantify how well they predict these two mobility measures. The initial slope angle was found to match H/L for small landslides that did not experience a break in slope. Landslides in concave topography, landslides on previously moved material, and landslides in confined topography were found to possess lower H/L values, indicating higher mobility. Finally, landslides occurring on previously moved material and landslides in confined topography were found to possess larger values of L.