Mechanical Engineering Commons^™

Enhanced Biofouling Properties Of Polyethersulfone Membranes Using Multi-Functional Thermo-Responsive Polymers For Ultra-Filtration Applications, Homa Ghasemi

Theses and Dissertations

The accumulation and growth of microorganisms on a membrane surface, known as membrane biofouling, has been a significant issue in the effective use of membrane technology for water and wastewater treatment. To overcome these challenges, this study aimed to modify the surface of a polyethersulfone (PES) membrane through the use of a multi-functionalized thermo-responsive polymer. The primary objectives of chemical treatment on membrane surfaces are to enhance surface hydrophilicity and provide anti-bacterial/biocidal properties.To evaluate the effectiveness of these modifications, the performance of the modified membranes was tested for their ability to resist biofouling through filtration of bovine serum albumin (BSA), …

Understanding Heterostructure Chemiresistive Gas Sensing At Room Temperature, Yale Wang

Theses and Dissertations

Chemiresistive sensors are the most widely investigated gas sensors due to their ease in fabrication, cost-effectiveness, simplicity of operation, and offer advances in miniaturization. Up to date, typical and well-researched resistive-type sensing materials include semiconductor metal oxides, noble metals, carbon-based nanomaterials (e.g., graphene and carbon nanotubes), and conducting polymers. Gas sensors based on a single material were found difficult to meet the practical requirements for multi-sensing properties, including sensitivity, selectivity, speed of response/recovery, stability, limit of detection, and room temperature operation. Rational design through a combination of chemically or electronically dissimilar nanomaterials is an effective route to enhancing gas sensing …

Designing And Investigating A Novel Biodegradable-Nontoxic Mg-Mn-Zn-Na-K Alloying System, Murtatha Mohammed Jamel

Theses and Dissertations

Magnesium has been studied extensively due to the promising potential of using magnesium alloys in different applications, especially for biomedical implantation devices and other medical applications. This growing interest is due to the abundance of magnesium metal in the Earth's crust, as well as the fact that magnesium is 37% less dense than aluminum, has good mechanical properties, and is a nontoxic element with good biocompatibility. However, most Mg-based alloys contain alloying elements that are added to improve the mechanical properties but have toxic characteristics. At the same time a number of these alloys are still used in medical applications. …

Application Of Survival Analysis Techniques To Probabilistic Assessment Of Fatigue In Steel Bridges, Azam Nabizadehdarabi

Theses and Dissertations

The fatigue of engineering materials under repetitive loading is a significant issue affecting the design and durability of components and systems in a variety of engineering-related applications including civil, mechanical, aerospace, automotive, and electronics. Many factors can affect the service life of a component or system under repetitive loading, such as the type of structure, loading, connection details, stress state, peak stress or stress range, surface condition, temperature, and environmental exposure. Currently, there is no comprehensive probabilistic approach that can systematically address all the factors that contribute to fatigue on a single mathematical platform. However, advanced analysis techniques developed for …

Optimizing Self-Healing Wind Turbine Blades Utilizing Dicyclopentadiene Infused Vascular Networks, Giovanni Lewinski

Theses and Dissertations

Self-healing wind turbine blades can reduce costs associated with maintenance, repair, and energy compensation. Self-healing is the ability to sustain and recover from damage autonomously. The self-healing presented in this paper uses the reaction of two agents Dicyclopentadiene, DCPD, and Grubbs’ first-generation catalyst, henceforward known as a catalyst to fuel this recovery. DCPD is housed as a liquid isolated from the catalyst until a damaging event occurs, causing the two agents to mix and solidify to form the thermoset Polydicyclopentadiene, PDCPD. We discuss the efforts made to optimize the self-healing properties of wind turbine blades and provide new systems to …

In Silico Analysis Of Advanced Processing Methods For Light-Weight Alloys Powders, Marjan Nezafati

Theses and Dissertations

Light-weight Al and Mg-based metal-matrix nanocomposites (MMNCs) are lauded as one of the most promising structural materials for vehicle, military, and construction applications. These MMNCs are often synthesized using the powder metallurgy (PM) process under liquid nitrogen cryogenic environments to control the grain sizes. It is believed that proper incorporation of the nitrogen species into the bulk lattice during processing could strongly enhance the mechanical properties of MMNCs by forming N-rich dispersoids. In this work, using the density-functional theory (DFT), the adsorption, absorption and diffusion behavior of nitrogen molecule/atoms have been studied and related to t Al and Mg MMNC …

Graphene-Based Lubrication For Tribological Applications: Nanolubricants And Self-Lubricating Nanocomposites, Emad Omrani

Theses and Dissertations

In this work, the effects of graphene nanoplatelets (GNPs) additives on tribological properties of aluminum are investigated. The objective of this research is to investigate and explain the enhancement mechanisms of GNPs at the contact surface during tribological testing. The graphene nanoplatelets are studied both as an oil additive (Chapter I) and as a reinforcement (Chapter II) experimentally. The coefficient of friction (COF) and wear rate were identified using a pin-on-disk test setup.

Mineral, organic, and synthetic oils are not always efficient enough to satisfy the demands of a high-performance lubricant; therefore, mixing additives with base fluids is an approach …

Synthesis And Characterization Of Transition Metal Oxide And Dichalcogenide Nanomaterials For Energy And Environmental Applications, Ren Ren

Theses and Dissertations

Transition metal oxides (TMOs) and transition metal dichalcogenides (TMDs) have gained immense interest recently for energy and environmental applications due to their exceptional structural, electronic, and optical properties. For example, titanium dioxide (TiO2) as one of the TMO photocatalysts has been widely studied due to its stability, non-toxicity, wide availability, and high efficiency. However, its wide bandgap significantly limits its use under visible light or solar light. Recent studies also show that semiconducting TMDs could be used as potential supercapacitor electrode materials and platinum (Pt)-free electrocatalysts for economical utilization of renewable energy, because the high cost and scarcity of Pt …

Microstructure, Wetting Angle And Corrosion Of Aluminum-Silicon Alloys, Shvetashva Suri

Theses and Dissertations

In this study the effect of composition, surface roughness and water droplet size on contact angle and corrosion properties of cast Aluminum-Silicon alloys containing Si from 5% to 50% have been examined. The water contact angle was measured on a given sample using a goniometer. In addition, the effect of surface roughness and droplet size on contact angle has been measured for alloys at a fixed composition. The microstructures can be found in this report with sizes of primary and eutectic Silicon as well as inter-particle spacing between Silicon. Contact angle measurements are accompanied with a photographic validation of the …

Advanced Self-Healing Polymer Composites For Wind Turbine Blades, Arun Kumar Koralagundi Matt

Theses and Dissertations

Wind energy is one of the prime sources of energy among the renewable sources of energy. Wind power has been one of the most promising sources of long-term, clean energy. Materials and design approach in commercial wind turbines have not seen a momentous change in the recent years. In this study, an intriguing bio-mimetic design approach is sought after, which is to heal damages as they arise in a composite material. Self-healing material systems in wind turbine blades have the potential to fulfill the requirement as an added safety mechanism to heal damages and prevent catastrophic failures. Effectively supplying healing …

Effects Of Surface Topography And Vibrations On Wetting: Superhydrophobicity, Icephobicity And Corrosion Resistance, Rahul Ramachandran

Theses and Dissertations

Concrete and metallic materials are widely used in construction and water industry. The interaction of both these materials with water and ice (or snow) produces undesirable results and is therefore of interest. Water that gets absorbed into the pores of dry concrete expands on freezing and can lead to crack formation. Also, the ice accretion on concrete surfaces such as roadways can have disastrous consequence. Metallic components used in the water industry undergo corrosion due to contact with aqueous corrosive solutions. Therefore, it is desirable to make concrete water/ice-repellent, and to make metallic surfaces corrosion-resistant.

Recent advances in micro/nanotechnology have …

Novel Substrate-Bound Hybrid Nanomaterials For Anode Electrodes In Lithium-Ion Batteries, Haejune Kim

Theses and Dissertations

Li-ion batteries (LIBs) are commercially dominant in electrochemical energy storage devices. Their wide applications as power sources, from portable electronics to electric vehicles/hybrid electric vehicles, are mainly attributed to their superior energy density based on unit volume and unit weight over other battery systems. Growing demands for lighter, longer-lasting, and more powerful devices spur the development of new electrode materials, because the performance of LIBs is highly dependent on the characteristics of electrodes. The ideal candidate for anode materials of LIBs should have high lithium storage capability and stable structure after repeated charge/discharge cycles. Since its first commercialization by Sony …

Characterization Of Carbon-Fiber Reinforced Polyetherimide Thermoplastic Composites Using Mechanical And Ultrasonic Methods, Mohannad A. Alhaidri

Theses and Dissertations

Continuous fiber-reinforced thermoplastics (CFRT) have the potential for being a mass-produced material for high-performance applications. The primary challenge of using CFRT is achieving fiber wet-out due to the high viscosity of thermoplastics. This results in higher temperatures and pressures required for processing the composites. Co-mingling thermoplastic fibers with a reinforcing fiber, potentially, can enable better wetting by reducing the distance the matrix needs to flow. This could result in shorter cycle times and better consolidation at lower temperatures and pressures. In this study, a polyetherimide (PEI) fiber was comingled with carbon fibers (CF). The resultant fibers were woven into fabrics …

Wetting, Superhydrophobicity, And Icephobicity In Biomimetic Composite Materials, Vahid Hejazi

Theses and Dissertations

Recent developments in nano- and bio-technology require new materials. Among these new classes of materials which have emerged in the recent years are biomimetic materials, which mimic structure and properties of materials found in living nature. There are a large number of biological objects including bacteria, animals and plants with properties of interest for engineers. Among these properties is the ability of the lotus leaf and other natural materials to repel water, which has inspired researchers to prepare similar surfaces. The Lotus effect involving roughness-induced superhydrophobicity is a way to design nonwetting, self-cleaning, omniphobic, icephobic, and antifouling surfaces. The range …

Modeling Of Instabilities And Self-Organization At The Frictional Interface, Vahid Mortazavi

Theses and Dissertations

The field of friction-induced self-organization and its practical importance remains unknown territory to many tribologists. Friction is usually thought of as irreversible dissipation of energy and deterioration; however, under certain conditions, friction can lead to the formation of new structures at the interface, including in-situ tribofilms and various patterns at the interface.

This thesis studies self-organization and instabilities at the frictional interface, including the instability due to the temperature-dependency of the coefficient of friction, the transient process of frictional running-in, frictional Turing systems, the stick-and-slip phenomenon, and, finally, contact angle (CA) hysteresis as an example of solid-liquid friction and dissipation. …

Material Behavior Characterization Of A Thin Film Polymer Used In Lithium-Ion Batteries, Michael James Martinsen

Theses and Dissertations

The use of lithium-ion batteries in the automotive industry has become increasingly popular. As more hybrid and electric vehicles take to the road an understanding of how these batteries will behave structurally will be of greater concern. Impact testing can give a valuable overview of the strengths and weaknesses of a battery's design, however, these tests can be time consuming, expensive, and dangerous. Finite element analysis can deliver a reliable low cost approximation of physical testing results. The accuracy of FE results depends greatly on the mathematical representation of the material properties of Li-ion battery components. In this study, the …