Materials Science and Engineering Commons^™

Conducting Polymer Based Gel Electrolytes For Ph Sensitivity, Aditya Jagannath Kashyap

USF Tampa Graduate Theses and Dissertations

The evaluation of concentration of ions and molecules with the help of biosensors have been regarded as an emerging technology. Bio and chemical sensors have a variety of applications in the field of medicine, military, environmental and food industries alike. With an estimated investment growth of over 4.31% in the development of pH sensors in the next five year, the objective of a developing a robust measurement system is all the more required. The scope of this research is to evaluate the ability of conducting polymer-based gel electrolytes for pH sensitivity, as a function of the transistor characteristics using an …

Synthesis And Characterization Of LaXBa1-XFeYAl1-YO3, Perovskite Oxides, For Co2 To Co Conversion, Hanzhong Shi

USF Tampa Graduate Theses and Dissertations

As the greenhouse gas effect becomes more serious, it is important to find an effective way to reduce carbon dioxide emissions and/or convert it to value-added products. Based on the catalytic requirements, convert CO₂ to CO using perovskite-type oxides which are suitable for reverse water-gas shift chemical looping (RWGS-CL). The resulting carbon monoxide can be subsequently used for chemical energy storage in the form of hydrocarbon-based fuels and chemicals. This research focuses on the synthesis of the La_xBa_1-xFe_yAl_1-yO₃ perovskite-type oxides, which can form oxygen vacancies, or active sites for CO …

Evaluation Of Novel Hemocompatible Surface Coatings For Extracorporeal Life Support: A Biocompatible Alternative To Systemic Anticoagulation, Teryn Rose Roberts

USF Tampa Graduate Theses and Dissertations

Extracorporeal life support (ECLS) is a class of technologies used to support or replace the function of failing organs. During ECLS, blood is withdrawn from systemic circulation and circulated through an artificial organ or “treatment membrane” that performs the function of the failing organ, prior to return to systemic circulation. While ECLS provides life-saving therapy to wide patient populations from pre-term infants to combat-wounded soldiers, this therapy is limited due to secondary thrombotic and bleeding complications that result from: 1) exposure of blood to the foreign surfaces in the device circuit and 2) administration of anticoagulant drugs to prevent clot …

The Feasibility Of High Strength Stainless Steel In Prestressing Applications For Pile Design, Cara Morton

USF Tampa Graduate Theses and Dissertations

Approximately 50% of the Nation’s infrastructure was built over 40 years ago for a 50 year service life according to the National Association of Corrosion Engineers [72]. To mitigate the cost of major repair or replacement at 50 years, AASHTO now requires all new bridge construction to have a 100 year service life. One of the main challenges in achieving this goal is avoiding corrosion, especially in warm, saltwater environments like those found in the Southeastern United States. Elements that cross the waterline (piles) are a weak link the infrastructure. Good quality concrete easily maintains a service life of 75+ …

The Effect Of Processing Conditions On The Energetic Diagram Of Cdte Thin Films Studied By Photoluminescence, Shamara P. Collins

USF Tampa Graduate Theses and Dissertations

The photovoltaic properties of CdTe-based thin films depend on recombination levels formed in the CdTe layer and at the heterojunction. The localized states are resultant of structural defects (metal sublattice, chalcogen sublattice, interstitial), controlled doping, deposition process, and/or post-deposition annealing. The photoluminescence study of CdTe thin films, from both the bulk and heterojunction, can reveal radiative states due to different defects or impurities. Identification of defects allows for potential explanation of their roles and influence on solar cell performance. A thorough understanding of the material properties responsible for solar cell performance is critical in further advancing the efficiency of devices. …

Computational Discovery Of Energetic Polynitrogen Compounds At High Pressure, Brad A. Steele

USF Tampa Graduate Theses and Dissertations

High-nitrogen-content energetic compounds containing multiple N-N bonds are an attractive alternative towards developing new generation of environmentally friendly, and more powerful energetic materials. High-N content translates into much higher heat of formation resulting in much larger energy output, detonation pressure and velocity upon conversion to large amounts of non-toxic, strongly bonded N2 gas. This thesis describes recent advances in the computational discovery of group-I alkali and hydrogen polynitrogen materials at high pressures using powerful first-principles evolutionary crystal structure prediction methods. This is highlighted by the discovery of a new family of materials that consist of long-sought after all-nitrogen N􀀀 5 …

In Situ Extrinsic Doping Of Cdte Thin Films For Photovoltaic Applications, Imran Suhrid Khan

USF Tampa Graduate Theses and Dissertations

The Cadmium Telluride thin film solar cell is one of the leading photovoltaic technologies. Efficiency improvements in the past decade made it a very attractive and practical source of renewable energy. Considering the theoretical limit, there is still room for improvement, especially the cell’s open circuit voltage (VOC). To improve VOC, the p-type carrier concentration and minority carrier lifetime of the CdTe absorber needs to be improved. Both these parameters are directly related to the point defect distribution of the semiconductor, which is a function of deposition stoichiometry, dopant incorporation and post-deposition treatments.

CdTe films were deposited by the Elemental …

Direct Print Additive Manufacturing Of Optical Fiber Interconnects, Roger B. Tipton

USF Tampa Graduate Theses and Dissertations

High performance communications, sensing and computing systems are growing exponentially as modern life continues to rely more and more on technology. One of the factors that are currently limiting computing and transmission speeds are copper wire interconnects between devices. Optical fiber interconnects would greatly increase the speed of today’s electronic devices. In this study it has been demonstrated that by using a new Direct Print Additive Manufacturing (DPAM) process of Fused Deposition Modeling (FDM) of plastic and micro-dispensing of pastes and inks, we can 3D print single and multi-mode optical fibers in a controlled manner such that compact, 3-dimensional optical …

Non-Precious Metal Catalysts For Oxygen Reduction Reaction In Alkaline Solutions, Zhewen Yin

USF Tampa Graduate Theses and Dissertations

Mesoporous WO3 powders were prepared via sol-gel processing synthesis using nonionic surfactant Pluronic (P-123) as the template. The influences of heating temperature on the pore structure and properties of WO3 powders were investigated. Three kinds of modifications were compared and evaluated after finding out the best heating condition. Different amount of lanthanum was doped into mesoporous WO3 to improve its Oxygen Reduction Reaction (ORR) activity. Several factors contributing to the increase of catalytic performance were discussed. Vulcan carbon powder was also used as a support to increase the catalysts’ electrical conductivity as well as dispersity. The component, microstructure and specific …

Supported Perovskite-Type Oxides: Establishing A Foundation For Co2 Conversion Through Reverse Water-Gas Shift Chemical Looping, Bryan J. Hare

USF Tampa Graduate Theses and Dissertations

Perovskite-type oxides show irrefutable potential for feasible thermochemical solar-driven CO₂ conversion. These materials exhibit the exact characteristics required by the low temperature reverse water-gas shift chemical looping process. These properties include structural endurance and high oxygen redox capacity, which results in the formation of numerous oxygen vacancies, or active sites for CO₂ conversion. A major drawback is the decrease in oxygen self-diffusion with increasing perovskite particle size. In this study, the La_0.75Sr_0.25FeO₃ (LSF) perovskite oxide was combined with various supports including popular redox materials CeO₂ and ZrO₂ along with more abundant …

Manipulating Electromagnetic Waves With Enhanced Functionalities Using Nonlinear And Chiral Metamaterials, Sinhara Rishi Malinda Silva

USF Tampa Graduate Theses and Dissertations

Metamaterials are artificial structures, which periodically arranged to exhibit fascinating electromagnetic properties, not existing in nature. A great deal of research in the field of metamaterial was conducted in a linear regime, where the electromagnetic responses are independent of the external electric or magnetic fields. Unfortunately, in linear regime the desired properties of metamaterials have only been achieved within a narrow bandwidth, around a fixed frequency. Therefore, nonlinearity is introduced into metamaterials by merging meta-atoms with well-known nonlinear materials. Nonlinear metamaterials are exploited in this dissertation to introduce and develop applications in microwave frequency with broadband responses. The nonlinearity was …

Growth, Characterization, And Function Of Ferroelectric, Ferromagnetic Thin Films And Their Heterostructures, Mahesh Hordagoda

USF Tampa Graduate Theses and Dissertations

With recent trends in miniaturization in the electronics sector, ferroelectrics have gained popularity due to their applications in non-volatile RAM. Taking one step further researchers are now exploring multiferroic devices that overcome the drawbacks of ferroelectric (FE) and ferromagnetic (FM) RAM’s while retaining the advantages of both. The work presented in this dissertation focuses on the growth of FE and FM thin film structures. The primary goals of this work include, (1) optimization of the parameters in the pulsed laser deposition (PLD) of FE and FM films and their heterostructures, (2) development of a structure-property relation that leads to enhancements …

Organometal Halide Perovskite Solar Absorbers And Ferroelectric Nanocomposites For Harvesting Solar Energy, Chaminda Lakmal Hettiarachchi

USF Tampa Graduate Theses and Dissertations

Organometal halide perovskite absorbers such as methylammonium lead iodide chloride (CH₃NH₃PbI₃-_xCl_x), have emerged as an exciting new material family for photovoltaics due to its appealing features that include suitable direct bandgap with intense light absorbance, band gap tunability, ultra-fast charge carrier generation, slow electron-hole recombination rates, long electron and hole diffusion lengths, microsecond-long balanced carrier mobilities, and ambipolarity. The standard method of preparing CH₃NH₃PbI₃-_xCl_x perovskite precursors is a tedious process involving multiple synthesis steps and, the chemicals being used (hydroiodic acid …

Understanding Gas Sorption Mechanisms In Metal–Organic Materials Via Computational Experimentation, Katherine A. Forrest

USF Tampa Graduate Theses and Dissertations

Metal–organic materials (MOMs), a type of porous crystalline structure composed of organic ligands jointed with metal ions, have captured the interest of scientists as potentially useful in gas sorption applications. Some of the most crucial avenues of investigation are in H2 storage (for use as a clean burning fuel source) and CO2 capture and sequestration (to remove the greenhouse gas from the environment).

A major advantage of MOMs for such applications is their high variability in terms of physical dimensions and chemical moieties, based on composition and synthesis conditions, making them potentially customizable for specific application if necessary structural characteristics …

Two Dimensional Layered Materials And Heterostructures, A Surface Science Investigation And Characterization, Yujing Ma

USF Tampa Graduate Theses and Dissertations

The isolation of single layers of van der Waals materials has shown that their properties can be significantly different compared to their bulk counterparts. These observations, illustrates the importance of interface interactions for determining the materials properties even in weakly interacting materials and raise the question if materials properties of single layer van der Waals materials can be controlled by appropriate hetero-interfaces. To study interface effects in monolayer systems, surface science techniques, such as photoemission spectroscopy and scanning probe microscopy/spectroscopy, are ideally suited. However, before these characterization methods can be employed, approaches for the synthesis of hetero-van der Waals systems …

Photopolymerization Synthesis Of Magnetic Nanoparticle Embedded Nanogels For Targeted Biotherapeutic Delivery, Daniel Jonwal Denmark

USF Tampa Graduate Theses and Dissertations

Conventional therapeutic techniques treat the patient by delivering a biotherapeutic to the entire body rather than the target tissue. In the case of chemotherapy, the biotherapeutic is a drug that kills healthy and diseased cells indiscriminately which can lead to undesirable side effects. With targeted delivery, biotherapeutics can be delivered directly to the diseased tissue significantly reducing exposure to otherwise healthy tissue. Typical composite delivery devices are minimally composed of a stimuli responsive polymer, such as poly(N-isopropylacrylamide), allowing for triggered release when heated beyond approximately 32 °C, and magnetic nanoparticles which enable targeting as well as provide a mechanism for …

Enhanced Visible Light Photocatalytic Remediation Of Organics In Water Using Zinc Oxide And Titanium Oxide Nanostructures, Srikanth Gunti

USF Tampa Graduate Theses and Dissertations

The techniques mostly used to decontaminate air as well as water pollutants have drawbacks in terms of higher costs, require secondary treatment, and some methods are very slow. So, emphasis has been given to water though the use of photocatalysts, which break organic pollutants to water and carbon dioxide and leave no trace of by-products at the end. Photocatalytic remediation aligns with the waste and wastewater industries’ zero waste schemes with lower cost, eco-friendly and sustainable treatment technology. The commonly used photocatalysts such as titanium oxide (TiO₂), zinc oxide (ZnO), tungsten oxide (WO₃) have band gap …

Interference Of Light In Multilayer Metasurfaces: Perfect Absorber And Antireflection Coating, Khagendra Prasad Bhattarai

USF Tampa Graduate Theses and Dissertations

We have studied several metamaterials structures with multiple layers by explaining them theoretically and verifying experimentally. The engineered structures we have designed work either as a perfect absorber or antireflection coating. The multilayer model as we call it Three Layer Model (TLM) has been developed, which gives the total reflection and transmission as a function of reflection and transmission of individual layers. By manipulating the amplitude and phase of the reflection and the transmission of the individual layers, we can get the required functionality of the optoelectronic devices. To get zero reflection in the both perfect absorber and the antireflection …

A Study Of Corrosion Monitoring Techniques Used In Urls For Metals, Sirui Li

USF Tampa Graduate Theses and Dissertations

With the increasing use of fission-type nuclear power generation, particularly high-levels radioactive nuclear waste are generated, so the safe use of nuclear energy requires proper disposal of high-level radioactive nuclear waste. The selected treatment method is deep geological disposal. Therefore, underground research laboratory (URL) to prepare for deep geological disposal will also be carried out. Corrosion of metallic materials, which are closely related to the safety of URL, is the focus of this research project. This study selected monitoring techniques for URL and developed a rough monitoring scheme for temperature and resistivity in URL. In this study, corrosion-temperature and corrosion-resistivity …

Effects Of Microstructure And Alloy Concentration On The Corrosion And Tribocorrosion Resistance Of Al-Mn And We43 Mg Alloys, Hesham Y. Saleh Mraied

USF Tampa Graduate Theses and Dissertations

The design of new engineering materials resistant to both wear damage and corrosion degradation becomes increasingly demanding in complex service conditions. Unfortunately, there is typically a tradeoff between wear and corrosion resistance, even for important passive metals such as Al alloys. This is because the presence of precipitates hardens the material but at the same time lead to unfavorable galvanic coupling between the precipitates and the matrix, resulting in accelerated corrosion. This work showed that Al (or Mg) supersaturated solid solution formed using non-equilibrium methods exhibited enhanced corrosion resistance without compromising strength. For Al, alloying with Mn up to ~ …

Engineered Nanocomposite Materials For Microwave/Millimeter-Wave Applications Of Fused Deposition Modeling, Juan De Dios Castro

USF Tampa Graduate Theses and Dissertations

A variety of high-permittivity (high-k) and low-loss ceramic-thermoplastic composite materials as fused deposition modeling (FDM) feedstock, based on cyclo-olefin polymer (COP) embedded with sintered ceramic fillers, have been developed and investigated for direct digital manufacturing (DDM) of microwave components. The composites presented in this dissertation use a high-temperature sintering process up to 1500°C to further enhance the dielectric properties of the ceramic fillers. The electromagnetic (EM) properties of these newly developed FDM composites were characterized up to the Ku-band by using the cavity perturbation technique. Several models for prediction of the effective relative dielectric permittivity of composites based …

Reduced Dimensionality Effects In Gd-Based Magnetocaloric Materials, Hillary Faith Belliveau

USF Tampa Graduate Theses and Dissertations

Magnetic refrigeration based on the magnetocaloric effect (MCE) is a promising alternative to conventional gas compression based cooling techniques. Understanding impacts of reduced dimensionality on the magnetocaloric response of a material such as Gadolinium (Gd) or its alloys is essential in optimizing the performance of cooling devices, which is also the overall goal of this thesis. We have determined, in the first part of the thesis, that laminate structures of pure Gd produced by magnetron sputtering have several disadvantages. The target material (pure Gd), ultra-high vacuum components, and the electrical energy it takes to run the manufacturing process are all …

Confinement Effects And Magnetic Interactions In Magnetic Nanostructures, Kristen Lee Stojak Repa

USF Tampa Graduate Theses and Dissertations

Multifunctional nanocomposites are promising for a variety of applications ranging from microwave devices to biomedicine. High demand exists for magnetically tunable nanocomposite materials. My thesis focuses on synthesis and characterization of novel nanomaterials such as polymer nanocomposites (PNCs) and multi-walled carbon nanotubes (MWCNTs) with magnetic nanoparticle (NP) fillers.

Magnetite (Fe₃O₄) and cobalt ferrite (CoFe2O4) NPs with controlled shape, size, and crystallinity were successfully synthesized and used as PNC fillers in a commercial polymer provided by the Rogers Corporation and poly(vinylidene fluoride). Magnetic and microwave experiments were conducted under frequencies of 1-6 GHz in the presence of …

Experimental And Computational Study On Fracture Mechanics Of Multilayered Structures, Hai Thanh Tran

USF Tampa Graduate Theses and Dissertations

Many devices in electronics are in the form of multilayered structures. These structures can fail catastrophically if they contain defects or cracks. Enhancing their fracture properties is therefore critical to improve the reliability of the systems. The interface-dominated fracture mechanics of multilayered structure was studied using experiments and finite element (FE) modeling by considering two examples: thin films on polymer substrates in flexible electronics and Cu leadframe/epoxy molding compound (EMC) in micro-electronics packaging.

In the first example, aluminum-manganese (Al-Mn) thin films with Mn concentration up to 20.5 at.% were deposited on polyimide (PI) substrates. A variety of phases, including supersaturated …

Corrosion Characteristics Of Magnesium Under Varying Surface Roughness Conditions, Yahya Efe Yayoglu

USF Tampa Graduate Theses and Dissertations

The biggest challenge with magnesium alloy biodegradable implants is the rapid corrosion at the earlier stages of the healing process after implantation. In this research, the impact of surface roughness generated by different means on the corrosion rate of AZ31 magnesium alloy in a simulated biologic environment is investigated. In order to perform accurate experimentation, an in vitro setup is assembled that simulates the human body environment accurately has been prepared using Schinhammer’s in vitro immersion testing setup and Kokubo’s Simulated Body Fluid (SBF). For the immersion test of Mg in SBF, several surface texture groups of Mg have been …

Biomarker Detection At Risk Forecasting Level Using Metal-Enhanced Fluorescence Combined With Surface Acoustic Wave, Jun Liu

USF Tampa Graduate Theses and Dissertations

In this paper, metal-enhanced fluorescence (MEF) technique is used to lower the detection limit of carcinoembryonic antigen (CEA) which is able to be utilized in forecasting the risk of having certain kinds of cancers, especially colon and rectal cancer. By incubating silver nanocubes (Ag NCs) on the surface of the chips, the detection limit goes down to below 1ng/mL of CEA. Also, when combining MEF with surface acoustic wave (SAW) devices, the incubation time between antigen and antibody will decrease significantly with the fluorescence signal keeping similar or higher level.

Metal-Organic Frameworks As Potential Platforms For Carbon Dioxide Capture And Chemical Transformation, Wenyang Gao

USF Tampa Graduate Theses and Dissertations

The anthropogenic carbon dioxide (CO₂) emission into the atmosphere, mainly through the combustion of fossil fuels, has resulted in a balance disturbance of the carbon cycle. Overwhelming scientific evidence proves that the escalating level of atmospheric CO₂ is deemed as the main culprit for global warming and climate change. It is thus imperative to develop viable CO₂ capture and sequestration (CCS) technologies to reduce CO₂ emissions, which is also essential to avoid the potential devastating effects in future. The drawbacks of energy-cost, corrosion and inefficiency for amine-based wet-scrubbing systems which are currently used in industry, …

Effect Of Void Fraction On Transverse Shear Modulus Of Advanced Unidirectional Composites, Jui-He Tai

USF Tampa Graduate Theses and Dissertations

In composite materials, transverse shear modulus is a critical moduli parameter for designing complex composite structures. For dependable mathematical modeling of mechanical behavior of composite materials, an accurate estimate of the moduli parameters is critically important as opposed to estimates of strength parameters where underestimation may lead to a non-optimal design but still would give one a safe one.

Although there are mechanical and empirical models available to find transverse shear modulus, they are based on many assumptions. In this work, the model is based on a three-dimensional elastic finite element analysis with multiple cells. To find the shear modulus, …

Preparation And Characterization Of Van Der Waals Heterostructures, Horacio Coy Diaz

USF Tampa Graduate Theses and Dissertations

In this dissertation different van der Waals heterostructures such as graphene-MoS₂ and MoTe₂-MoS₂ were prepared and characterized. In the first heterostructure, polycrystalline graphene was synthesized by chemical vapor deposition and transferred on top of MoS₂ single crystal. In the second heterostructure, MoTe₂ monolayers were deposited on MoS₂ by molecular beam epitaxy.

Characterization of graphene-MoS₂ heterostructures was conducted by spin and angle resolve spectroscopy which showed that the electronic structure of the bulk MoS₂ and graphene in this van der Waals heterostructures is modified. For MoS₂ underneath the graphene, a band …

Al/Ti Nanostructured Multilayers: From Mechanical, Tribological, To Corrosion Properties, Sina Izadi

USF Tampa Graduate Theses and Dissertations

Nanostructured metallic multilayers (NMMs) are well-known for their high strength in smaller bilayer thicknesses. Six Al/Ti (NMM) with different individual layer thickness were tested for their mechanical hardness using a nanoindentation tool. Individual layer thicknesses were chosen carefully to cover the whole confined layer slip (CLS) model. Nano-hardness had a reverse relation with the square root of individual layer thickness and reached a steady state at ~ 5 nm bilayer thickness. Decreasing the layer bilayer thickness from ~ 104 nm to ~ 5 nm, improved the mechanical hardness up to ~ 101%. Residual stresses were measured using grazing incident X-ray …