Engineering Commons^™

Syntheses, Photophysics, & Application Of Porphyrinic Metal-Organic Frameworks, Zachary L. Magnuson

USF Tampa Graduate Theses and Dissertations

Porphyrins are a group of heterocyclic macrocycles that play crucial roles in various biological processes such as electron transfer, catalysis, and sensing. Hemoglobin, which carries oxygen in the blood of mammals, and chlorophyll, which drives photosynthesis in plants and algae, are both porphyrins. The ability of porphyrins to bind metal ions and their unique electronic and photophysical properties make them an excellent platform for designing functional materials for various applications, often drawing inspiration from their function in nature. Metal-organic frameworks (MOFs) are a class of porous materials that have been extensively studied in recent years due to their high surface …

Restoration And Modification Of A Sputter Tool For The Deposition Of A Zno Guiding Layer Via Rf Sputtering, Matthew Watson

USF Tampa Graduate Theses and Dissertations

In this thesis, a novel sputter tool was restored and modified to deposit a ZnO film for future applications as a guiding layer on a surface acoustic wave (SAW) device. Some restorations and modifications included a water chiller being sized and added to the tool, leak checks to establish an ultra-high vacuum of 10-6 Torr, then finally heat lamps for temperature control were installed. Once modified, one of the preexisting magnetrons was utilized to deposit a ZnO via RF sputtering onto a quartz substrate. The layer was characterized via energy-dispersive X-ray spectroscopy which showed the existence of Zn on the …

The Influence Of Bipolar Electrochemical Cell Geometry On The Studies Of Pitting Corrosion, Amin Kazem Ghamsari

USF Tampa Graduate Theses and Dissertations

Bipolar electrochemistry (BPE) is a technique that provides a wireless alternative totraditional electrochemistry to elicit redox reactions. It has been utilized in different applications, including studying localized corrosion, gradient electrodeposition, propulsion of micromotors, and water treatment. The popularity of the method is not solely dependent on its wirelessness but more due to the simultaneous presence of cathodic and anodic poles on the same surface, which also begets its name as bipolar. The concept of the method is based on the polarization of conductive objects in an electric field in the presence of an electrolyte. In BPE, instead of controlling the …

Development Of An Automated Platform For Sensing And Differentiating Vapor-Phase Btex Constituents, Jonathan Samuelson

USF Tampa Graduate Theses and Dissertations

Light aromatic hydrocarbons are an inevitable byproduct of fossil fuel extraction, refinement, distribution, and use. The four lightest and most prevalent of these are benzene, toluene, ethylbenzene, and xylene, which are known collectively as BTEX. In spite of their chemical similarity these species have markedly different effects on human health and substantially different concentrations are permitted by OSHA in workplaces and by the EPA in ambient air and groundwater. Real-time detection, identification, and quantification of these species is therefore of great importance wherever they see industrial use.This work represents the continuation and advancement of a line of research in which …

Impedance Analysis Of Anodized Aluminum And Structural Bridge Tendons, Justin Silnutzer

USF Tampa Graduate Theses and Dissertations

This is a two-part thesis with the overall investigation technique being electrochemical impedance spectroscopy (EIS). In the first part, EIS is used to estimate the layer thickness of anodized aluminum oxide. This required the development of an appropriate electrical circuit model; that with parameters that correspond to physical properties of the oxide. In this work, it was found that for thicker oxides of which the outer porous layer is greater than 12 microns, impedance may be used to estimate the outer layer thickness. However, further research is required to understand the role of outer porous layer structure on the impedance …

Magnetic And Structural Effects In Interfacial Magnetism: Molecular Magnets And Ferrimagnetic Alloys, Jenae E. Shoup

USF Tampa Graduate Theses and Dissertations

Magnetic thin films are important for technological applications such as giant magnetoresistance,spin valves and magnetic tunnel junctions. A key feature for these applications to be possible is the interface between two materials. We will be studying two types of thin film magnetism; interfaces between molecular carbon, C60, and non-magnetic/ferromagnetic material and two layers of ferrimagnetic rare earth/ transition metal alloys (RE/TM) that have similar composition to engineer a magnetic tunable interface.

One of the most unexpected spin-related properties of C60 is the emergence of room-temperature ferromagnetism in multilayer films of C60 and non-ferromagnetic transition metals such as Cu or Mn …

Block Copolymer Directed Self-Assembly: Exploring The Efficacy Of Applications In Semiconductor Fabrication, Jakin Bryce Delony

USF Tampa Graduate Theses and Dissertations

Over the course of the past 80 years, semiconductor devices have become increasingly ubiquitous in everyday life.From constructing mainframes that encompassed entire rooms during the 1940s, to inventing personal computers in the 1980s, to developing progressively faster smartphones and wearable technology in the 2010s, the primary driving force behind the Digital Revolution has been increasing transistor counts, and thus computing power, via incremental improvements in optical lithography. In 1965, Intel co-founder Gordon Moore boldly predicted that the transistor density of semiconductor devices would double approximately every 18-24 months. While this prediction -- now colloquially referred to as Moore's Law -- …

Crystal Structure Prediction Of Materials At Extreme Conditions, Ashley S. Williams

USF Tampa Graduate Theses and Dissertations

The prediction of the structure of a crystal given only the constituent elements is one of the greatest challenges in both materials science and computational science alike. If one were to try to predict a novel crystal by brute force, meaning by arranging the atoms in every possible position of the unit cell and optimizing the geometry to find the energy minima of the potential energy surface, the amount of computer resources required to complete the calculation on the timescale of a few years would vastly exceed the currently installed computational capacity of the entire world. Fortunately, several methods have …

The Photophysical Studies Of Transition Metal Polyimines Encapsulated In Metal Organic Frameworks (Mof’S), Jacob M. Mayers

USF Tampa Graduate Theses and Dissertations

Light harvesting systems provide a platform that converts solar energy into other forms of energy. One of the most common examples of photon capturing and conversion into chemical energy is observed in photosynthetic organisms in both Eurkaroyic and Prokaryotic domains. Nature provides a model for successful light harvesting platforms which includes the compartmentalization of antenna complexes that contain separated donor and acceptor pairs that participate in efficient electron transfer processes. In order to mimic such systems, crystalline porous materials that exhibits regular cavities and pore dimensions provides an excellent starting place. Metal organic frameworks (MOFs) are a class of porous …

Spin Coupling In Magnetic Core - Shell Nanoparticles, Corisa Kons

USF Tampa Graduate Theses and Dissertations

Magnetic nanoparticles (NPs) have garnered much interest due to the unique properties that emergewhen compared to their bulk counterparts. In particular, core-shell (CS) NPs offer the ability to tailor the magnetic properties of the system through careful selection of core and shell constituent materials. In this work, the magnetic ordering of CS NPs with contrast in core/shell features (moment, anisotropy, coercivity, etc.) have been investigated using a combination of X-ray magnetic circular dichroism spectroscopy (XMCD) and polarized small angle neutron scattering (SANS). First, temperature-dependent analyses of XMCD and SANS studies were carried out for CS NPs featuring a core composed …

Investigation Of Immobilized Enzymes In Confined Environment Of Mesoporous Host Matrices, Xiaoliang Wang

USF Tampa Graduate Theses and Dissertations

Enzyme immobilization in metal-organic frameworks (MOFs) as a promising strategy, is attracting the interest of scientists from different disciplines with the expansion of MOF’s development. Different from other traditional host materials, their unique strengths of high surface areas, large yet adjustable pore sizes, functionalizable pore walls, and diverse architectures make MOFs an ideal platform to investigate hosted enzymes, which is critical to the industrial and commercial process. In addition to the protective function of MOFs, the extensive roles of MOFs in the enzyme immobilization are being well-explored by making full use of their remarkable properties like well-defined structure, high porosity, …

Design Of Acoustic Wave Sensor System For Detection Of Btex In Gas Phase, Veselinka Mitevska

USF Tampa Graduate Theses and Dissertations

Benzene, toluene, ethylbenzene, and xylene are classified as volatile organic compounds (VOC), which if present at higher concentrations can cause acute and/or chronic health effects. To protect people from VOCs, the occupational safety and health agency (OSHA) established short term and eight-hour workday exposure limits. The short time levels of exposure for BTEX materials are 5 ppm, 150 ppm, 125 ppm, and 150 ppm, for benzene, toluene, ethylbenzene, and xylene respectively. The eight-hour workday exposure for these same materials are 1 ppm for benzene, 200 ppm for toluene, 100 ppm for ethylbenzene and 100 ppm for xylene. Although there are …

Multi-Material Hybrid Additive And Subtractive Manufacturing Of Photonic Devices, Roger Brandon Tipton

USF Tampa Graduate Theses and Dissertations

Optoelectronics focuses on the application of electronic devices that utilize forms of electromagnetic radiation including visible light and other wavelengths including ultraviolet and infrared. Optoelectronics typically include devices that emit light and detect light. Devices created using this technology include light-emitting diodes, laser diodes, photoresistors, photodiodes, solar cells, phototransistors, and fiber optics. Fiber optic interconnects are interesting devices in that they are used in conjunction with optoelectronic devices to transmit information between individual optoelectronic components.

Optoelectronics are typically produced by traditional lithography methods including etching, writing, and printing on rigid silicon substrates for fabricating devices. Other techniques like glass or …

Polyethyleneimine-Based High Yield Fluorescent Soluble Covalent Organic Framework, Haonan Wang

USF Tampa Graduate Theses and Dissertations

In this thesis, we report a novel covalent organic framework (COF) with fluorescence and water-soluble features, F-COF-PT with high gravimetric yield (~ 89%), that was generated by the reactions of branched polyethyleneimine (PEI) and 1,3,6,8-Tetrabromopyrene (TBP). The surface area and pore volume were about up to 63.2 m2/g and 0.41 m3/g. The prepared COFs maintained the TBP fluorescent performance in water solutions at 440-460 nm. Furthermore, Cu(II) ion solution would impact the quenching activity with F-COF-PT3, and NaOH treated F-COF-PT3 has the 5.6 m2/g capacity of uptake CO2. Finally, the zeta potential and particle diameter of original and treated F-COF-PT3s …

Plasma Treatment Of High-Density Polyethylene, Linear Low-Density Polyethylene, And Polyvinyl Chloride Geomembranes By Air And Oxygen, Merve Koca Uyar

USF Tampa Graduate Theses and Dissertations

High-density polyethylene (HDPE), linear low-density polyethylene (LLDPE), and polyvinyl chloride (PVC) geomembranes were treated with air and oxygen plasma. The purpose of air and oxygen plasma treatment of geomembrane surface is to increase the surface wettability of these materials, thereby increasing adhesive properties. Increasing adhesive properties enables a surface to be coated with a desired material with antibacterial, antioxidant, and UV resistant characteristics, without changing bulk material properties. To protect the geomembranes from oxidation degradation, UV degradation and biological degradation, it is important to increase the antibacterial, antioxidant, and UV resistant properties of geomembrane. Before and after the plasma treatments …

Material And Topographically Optimized Thermal Dissipation For High-Performance Electronic Devices Utilizing Vapor Chambers, Derek Joseph Daniels

USF Tampa Graduate Theses and Dissertations

Advances in materials science and engineering in the field of thermal transport and dissipation enable the use of higher-performance electronic devices that are smaller and generate more heat. Phase change thermal transport systems such as heat pipes and vapor chambers enable passive dissipation from devices that generate excessive heat without the need for actively pumped cooling systems. Properly designed vapor chamber enabled systems easily exceed the thermal conductivity of manufactured diamond at a small fraction of the cost.[1][2][3] While heat pipe phase change systems are generally one-dimensional with a limited cross section, vapor chambers are generally two-dimensional with a small …

Texturing In Bi2Te3 Alloy Thermoelectric Materials: An Applied Physics Investigation, Oluwagbemiga P. Ojo

USF Tampa Graduate Theses and Dissertations

Thermoelectric devices provide the means for direct conversion between heat and electricity. The device conversion efficiency, or performance, is directly related to the thermoelectric figure of merit, ZT, of the working materials. Bismuth telluride alloys are the materials currently in use in most thermoelectric devices for near room temperature solid-state refrigeration and power conversion applications. The vast majority of publications in the literature on thermoelectricity report on investigations towards developing new materials with enhanced thermoelectric properties, however Bi₂Te₃ alloys have been used in thermoelectric devices for decades.

In this thesis, an investigation of crystallographic texturing on large …

Development Of Carbon And Silicon Carbide Based Microelectrode Implantable Neural Interfaces, Chenyin Feng

USF Tampa Graduate Theses and Dissertations

The use of neural modulation techniques to treat nervous system disorders, as well as neural recording to study brain function, continues to be of intense interest around the world. Due to the need to treat diseases such as Parkinson’s, dementia, depression and return normal function to patients suffering from nervous system damage and trauma, neural implants continue to be developed globally. One of these devices, the microelectrode implantable neural interface (mINI), has been rapidly developed, thanks to advanced semiconductor fabrication processes. However, the long-term reliability of present-day devices has still to be demonstrated and is delaying the application of this …

Preparation And Characterization Of Single Layer Conducting Polymer Electrochromic And Touchchromic Devices, Sharan Kumar Indrakar

USF Tampa Graduate Theses and Dissertations

Electrochromic devices (ECDs) have triggered great interest because of their potential applicability in energy-efficient buildings and low power display systems, including reflective type smart windows/mirrors and wearable-flexible devices. In the past decades, electrochromic technologies with different device structures and materials have been proposed. The idea of employing a simple device structure with a durable, cost effective electrolyte is crucial to designing and manufacturing high-performance ECDs. With this idea in mind, this thesis describes the various efforts to develop a simple ECD comprising of a composite single active layer gel electrolyte, sandwiched between two transparent conducting electrodes, lasting over 10,000 cycles …

Corrosion Propagation Of Stainless Steel Reinforced Concrete, Nelly Sofía Orozco Martínez

USF Tampa Graduate Theses and Dissertations

Structural durability is a growing concern in global infrastructure. The infrastructure report card released by the American Society of Civil Engineers (ASCE) indicates that approximately 9.1% of the total bridges in the United States were structurally deficient in 2016. In addition, it suggests that about 40% of the total bridges in the country are now 50 years or older. This issue becomes even more critical in structures exposed to aggressive environments such as marine structures. Thus, federal and regional efforts are now being directed towards infrastructural durability improvement to improve the long-term cost-efficiency of civil infrastructure.

Corrosion prevention strategies may …

Sulfate Optimization In The Cement-Slag Blended System Based On Calorimetry And Strength Studies, Mustafa Fincan

USF Tampa Graduate Theses and Dissertations

Optimization of sulfur trioxide (SO³) content is typically conducted for plain cements (OPC-based) paste or mortar systems using compressive strength testing and isothermal calorimetry for quality control. The objective of these procedures is to ensure adequate strength and set properties by controlling the time of occurrence of the aluminate peak by adjusting the SO³ content by incremental addition of sulfate in the form of hemihydrate at three or more levels, at the same time attempting to maximize either strength or heat of hydration at 1 and 3 days. The inclusion of supplementary cementitious materials such as blast …

Fabrication And Characterization Methods Of Self-Cleaning Coatings For Solar Panels Application, Mohammed Khaleel M Alhussain

USF Tampa Graduate Theses and Dissertations

Transparent self-cleaning coatings with superhydrophobic and superhydrophilic behavior are of great interest in a wide range of industrial applications such as automotive, solar panels, windows, and optical devices. Each has its uses, properties, and characteristics. For the use of these coatings on solar panels, certain features are important in maintaining the efficiency of the panels in different weather conditions and reducing the operation and maintenance cost, such as self-cleaning, high transparency, antifouling, anti-fogging, and anti-icing. Herein, we have investigated the fabrication of self-cleaning coatings using two simple methods and ways to improve their characteristics. In the first method, a hydrophobic …

The Effect Of Cement And Blast Furnace Slag Characteristics On Expansion Of Heat-Cured Mortar Specimens, Jair G. Burgos

USF Tampa Graduate Theses and Dissertations

Delayed ettringite formation (DEF) is a durability issue that typically occurs in concrete exposed to high temperatures at an early age such as precast elements and massive concrete structural elements. There are many advantages to precast concrete such as its quality control, better safety control, and reusable forms, which make them cheaper than casting on site [1]. Heat curing of precast concrete is conducted to obtain high early-strength. However, in doing so, durability issues can arise in the form of internal sulfate attack also known as DEF, if the internal temperature of concrete exceeds 70°C. Past this threshold, ettringite decomposes …

Conversion From Metal Oxide To Mof Thin Films As A Platform Of Chemical Sensing, Meng Chen

USF Tampa Graduate Theses and Dissertations

Chemical sensor is working as a widely used device which can be applied to the detection of specific chemicals that are existing in the environment especially in gas phase. The detection of combustible and toxic chemicals can be extremely important in the field of both industrial and civil activities. The chemical sensor is commonly operating by utilizing a chemical or physical interaction between the specific chemical compound and the sensing functional unit, to obtain an electronic signal caused by the property change and realize the chemical detection. Traditional chemical gas sensors such as catalytic gas sensor, thermal conductivity gas sensor, …

Tuning Degradation And Cell Adhesion In Next Generation Resorbable Implants, Ufuomaroghene Ikoba

USF Tampa Graduate Theses and Dissertations

Osteoarthritic and bone degenerative diseases are expected to grow immensely as the aging population, 65 years and older increases. Orthopedic implants are one sub-class of medical devices that are used to treat bone breaks and fractures. Traditionally, internal fixation implants are manufactured using titanium or stainless steel. Magnesium, a bioresorbable and biodegradable material, has been proposed as an alternative to titanium and stainless steel. The goal of this research is to control the degradation behavior of magnesium implants by developing crystallized thin poly(lactic acid) copolymer films as protective coatings. To do this, this work was divided into two aims. Aim …

Urine Volume Reduction During Long-Duration Cave Exploration By A Light-Weight And Portable Forward Osmosis System, Sebastian Engelhardt, Katey E. Bender, Jörg Vogel, Stephen E. Duirk, Francisco B. Moore, Hazel A. Barton

International Journal of Speleology

The preservation of caves is a challenge during long-duration cave expeditions where human waste can add significant nitrogen to the cave ecosystem. Since the removal of urine that accumulates during a multi-day caving trip is not always feasible due to weight and volume constraints, a light-weight and portable filtration system that is capable of reducing urine volume would be desirable. In this study we tested the Aquaporin Inside hollow fiber membrane in a forward osmosis (FO) setup to evaluate its capability to reduce urine volume while rejecting nitrogenous compounds using different draw solution chemistries and water recovery rates. As a …

Laser-Induced Modifications In Two-Dimensional Materials, Tariq Afaneh

USF Tampa Graduate Theses and Dissertations

Atomically thin two-dimensional (2D) materials have attracted a growing interest in the lastdecade from the fundamental point of view as well as their potential applications in functional devices. Due to their high surface-to-volume ratio, the physical properties of 2D materials are very sensitive to the environmental factor such as surrounding media and illumination conditions (e.g. light-mater interaction). In the first part of this dissertation I will present recent advances in developing laser-assisted methods to tune the physical properties of 2D transition metal dichalcogenides (TMDs). We demonstrate laser-assisted chemical modification ultrathin TMDs, locally replacing selenium by sulfur atoms. The photo-conversion process …

Sustainable Non-Noble Metal Based Catalysts For High Performance Oxygen Electrocatalysis, Swetha Ramani

USF Tampa Graduate Theses and Dissertations

Current energy crisis has dramatically shifted the focus of technological advancements towards clean and renewable forms of energy. Continued dependence and utilization of fossil fuels has created global awareness on harmful greenhouse gas emissions and climate change. A need for sustainable technology has gained a lot of significance in the recent years. This has led to the development of devices and technologies that rely on environmentally friendly electrochemical conversion and storage of energy. One such advancement that generates electrical energy from chemical reactions is known as fuel cell technology. While fuel cells have demonstrated potential in replacing the conventional technologies …

Van Der Waals Epitaxy Of Ultrathin Early Transition Metal (Ti & V) (Di)Selenides: Charge And Magnetic Order In The Ultrathin Limit, Manuel Bonilla Lopez

USF Tampa Graduate Theses and Dissertations

Since the isolation of graphene in 2004, two-dimensional (2D) layered materials, specially the transition metal dichalcogenides (TMDs), have attracted immense interest from theoreticians and experimentalist due to the diversity of properties presented in this family of materials. The main reason for the interest in such materials has been the observation of emergent properties as a consequence of the reduced dimensions, i.e. the monolayer regime. Initially the monolayer regime was obtained via the scotch-tape method. The implementation of exfoliation techniques was successful since layered 2D materials are composed of stacked layers held together by weak van der Walls forces that permits …

Additive Manufactured And Laser Enhanced Optical Fiber On Flexible Kapton Substrate, Dianhao Hou

USF Tampa Graduate Theses and Dissertations

This thesis mainly focuses on the realization of laser enhancing additive manufactured optical fibers on the flexible substrate based on previous work on the rigid surface, and the exploration of their loss at different bend status by optical transmission test. Optical fibers are successfully fabricated using polymethyl methacrylate by fused deposition modeling technology within Norland Optical Adhesive 1369 which is chosen as the cladding material and micro-dispensed on the Kapton substrate. The Laser cutting technology and scanning electron microscope have been used to enhance and characterize the flatness of two end facets of samples, respectively. The optical adhesive and PMMA …