Engineering Commons^™

Application Of Geophysics And Remote Sensing Techniques For Economic Mineral Exploitation In Libya, Awad Abdussalam Henish Lemnifi

Doctoral Dissertations

“This study investigates crustal thickness and properties within the north central Africa region. Results obtained from 15 seismic stations belonging to the Libyan Center for Remote Sensing and Space Science are reported, in addition to 3 seismic stations publically available, using receiver functions, the first P-to-S receiver function investigation of the 410 km and 660 km depth discontinuities bounding the mantle transition zone (MTZ), and P wave tomography methods. The results from the first method show crustal thicknesses ranging from 24 km to 36 km (with uncertainties ranging between ±0.10 km and ±0.90 km). More specifically, crustal thickness ranges from …

Transition Metal Chalcogenide Hybrid Systems As Catalysts For Energy Conversion And Biosensing, Siddesh Umapathi

Doctoral Dissertations

"Generation of hydrogen and oxygen through catalyst-aided water splitting which has immense applications in metal air batteries, PEM fuel cells and solar to fuel energy production, has been one of the critical topics in recent times. The state of art oxygen evolution reaction (OER), oxygen reduction reaction (ORR), hydrogen evolution reaction (HER) catalysts are mostly comprised of precious metals. The current challenge lies in replacing these precious metal-based catalysts with non-precious earth-abundant materials without compromising catalytic efficiency.

This research explores mixed metal selenides containing Fe-Ni, Fe-Co and RhSe which were hydrothermally synthesized and/or electrodeposited and tested for OER and ORR …

Minimizing The Negative Effect Of Pumping On Scc Freeze-Thaw Durability, Daniel Galvez-Moreno

Doctoral Dissertations

“The durability of concrete must be ensured to reduce the carbon footprint of the production of portland cement. If concrete is properly designed to preserve its integrity under adverse exposure conditions, the service life of the material can be extended with minimum maintenance. Nevertheless, bad handling, placing, finishing or curing practices can abate the durability potential and service life of even the best mix design. Pumping concrete is a very efficient placing technique that offers significant cost reduction and versatility at the jobsite, but it also has the potential of altering the air void system parameters, which are key to …

Enhanced Electrochemical Performance Of Li-Ion Battery Cathodes By Atomic Layer Deposition, Yan Gao

Doctoral Dissertations

”Li-ion battery now plays an irreplaceable role in supplying green and convenient energy. In this work, atomic layer deposition (ALD) was used to modify Li-ion battery cathode particles for performance enhancement.

An ultrathin and conductive CeO₂ ALD film was deposited on Li-rich layered cathode particles, of which the specific capacity and cyclic stability were significantly improved. On the same cathode particles, FeO_x ALD and post-annealing resulted in a stable and conductive surface spinel phase to improve the performance.

Synergetic TiN coating and Ti doping were performed on a LiFePO₄ (LFP) cathode and extended its cycle life. The …

Forming And Processing Of Advanced Fiber Reinforced Polymer Composites, Robert Meinders

Doctoral Dissertations

“Composite materials are commonly used in industry to manufacture strong and lightweight structures. Composites feature a large degree of flexibility in materials selection and manufacturing processes to tailor the strength of manufactured parts. This study examines different manufacturing aspects of composites. In Part I, the fabrication of composite parts using the compression forming process is examined. During compression forming, metal dies are used to apply large deformations to prepreg material to fabricate composite parts. The high stresses and deformations of this process can yield manufacturing defects. T650/5320-1 prepreg is subjected to material characterization to develop simulations of large deformation forming …

Structured Catalysts Designed And Manufactured By 3d-Printing Technique For Functional Integration Of Catalytic Systems, Fatima Magzoub

Doctoral Dissertations

"Microporous zeolites are widely used as heterogeneous catalysts in a wide variety of chemical and petrochemical industries to produce value-added chemicals and fuels, owing to their large surface area, acid-base properties, high thermal stability, and excellent shape-selectivity.

The overall goal of this research was to shape engineer composite zeolites and fine-tune their physiochemical properties to improve the catalytic production of dimethyl ether (DME) and light olefins that are typically used as substitution to diesel fuel and polymer precursors, respectively. Specifically, HZSM-5 and silicalite-1 zeolites were formulated into monolithic contactors using 3D printing technique, followed by subsequent SAPO-34 crystals growth through …

Additive Manufacturing Of Customized Lithium-Ion Batteries: Process Fundamentals And Applications, Xiaowei Yu

Doctoral Dissertations

“In the pasting decades, considerable efforts have been spent in developing the next-generation lithium-ion batteries (LIBs), from advanced active materials to new manufacturing methods. The development of additive manufacturing (AM) has brought new opportunities to LIBs. In this work, two AM methods are introduced for fabricating electrodes of LIBs. The first method is aerosol printing, which is a solvent-based wet additive method. Whereas the second method is a solvent-free, dry printing method. The commonly used materials for current collectors and active materials (including cathodes and anodes) of LIBs are aerosol printed and the electrochemical functionalities of the printed materials are …

Analysis And Modeling Of Power Supply Induced Jitter For High Speed Driver And Low Dropout Voltage Regulator, Yin Sun

Doctoral Dissertations

”With the scaling of power supply voltage levels and improving trans-conductance of drivers, the sensitivity of drivers to power supply induced delays has increased. The power supply induced jitter (PSIJ) has become one of the major concerns for high-speed system. In this work, the PSIJ analysis and modeling method are proposed for high speed drivers and the system with on-die low dropout (LDO) voltage regulator. In addition, a jitter-aware target impedance concept is proposed for power distribution network (PDN) design to correlate the PSIJ with PDN parasitic.

The proposed PSIJ analysis model is based on the driver power supply rejection …

Investigation Of Urea Decomposition And Deposit Formation In Diesel Exhaust After-Treatment System, Anand Alembath

Doctoral Dissertations

“Urea-selective catalytic reduction (SCR) system has proved to be an effective solution to reduce NO_x emissions in commercial vehicle (CV) diesel engines. A significant challenge in urea injection is to comprehend its decomposition chemistry that leads to formation of undesired deposits in the exhaust system unit. Due to complex interaction of multi-phase fluid flow and transport processes, significant uncertainty is associated with the identification of interacting factors that control the deposit initiation and its growth. To meet the future ultra-low NO_x emissions and to deliver ammonia without deposit formation, there is an imminent need to develop the urea-SCR …

Nanoengineered Core-Shell Structures Using Tubile Halloysite Clay, Yusuf A. Darrat

Doctoral Dissertations

Halloysite nanotubes are a versatile nanomaterial that can be used in a wide variety of applications. They have a unique structure which could be described as a flat material that consists of silica on one side and alumina on the other; this structure is rolled up in a way naturally forming an internal 10-15 nm lumen and interlayer spacing. This could lead to many potential applications for example incorporating halloysite as a template material or as a support structure. They are an inexpensive clay material that is available in large quantities (thousands of tons), so they may be practically used …