Polymer and Organic Materials Commons^™

Silicone Tadpole: Research Into Soft Bodies, Danielle Fernandez

Mechanical Engineering Undergraduate Honors Theses

In this thesis, research is conducted in the area of soft robotics by building a soft tadpole that can deform with a specific air pressure. The goal is to mimic the motion of an organic tadpole in respect to its S-shaped tail movement. The angle of deformation, derived from material mechanic theories, ranges from 45 to 80 degrees for this type of movement. The design includes a head compartment which acts as a tank to transfer nitrogen pressure and a tail section that receives the said pressure and bends as a result. The tail section was designed with two rows …

Investigation Of Critical Technologies Of Chemical Vapor Deposition For Advanced (Si)Gesn Materials, Joshua Matthew Grant

Graduate Theses and Dissertations

The development of new materials for efficient optoelectronic devices from Group IV elements is the heart of Group IV photonics. This has direct ties to modern technology as the foundation for the electronics industry is silicon. This has driven the development of silicon-based optoelectronics using these other Group IV materials as silicon is a poor optical material due to its indirect band gap when compared to the III-V semiconductors that are used by most of the optoelectronics industry. While efforts have been made to integrate III-V materials onto silicon substrates, the incompatibility with the complementary metal oxide semiconductor process has …

Mesoscale Computational Studies Of Thin-Film Bijels, Joseph M. Carmack

Graduate Theses and Dissertations

Bijels are a relatively new class of soft materials that have many potential applications in the technology areas of energy, medicine, and environmental sustainability. They are formed by the arrest of binary liquid spinodal decomposition by a dispersion of solid colloidal nanoparticles. This dissertation presents an in-depth simulation study of Bijels constrained to thin-film geometries and in the presence of electric fields. We validate the computational model by comparing simulation results with previous computational modeling and experimental research. In the absence of suspended particles, we demonstrate that the model accurately captures the rich kinetics associated with diffusion-based surface-directed spinodal decomposition. …

Effects Of Surface-Directed Spinodal Decomposition On Binary Thin-Film Morphology, Michael Brian Wise

Graduate Theses and Dissertations

Preferential wetting can have a significant impact on the kinetics of phase separation in certain systems. The depletion of the wetting component can simply alter domain growth rates or change the structure entirely. In this thesis, we employ a Cahn-Hilliard model to study the evolution of binary thin-films with symmetric surface wetting. Three possible morphologies were identified: discrete, bicontinuous, and a novel quasi-2D bicontinuous structure in which both phases retain continuity throughout the volume as well as on the center xy plane. Using a continuity factor, regions of film thickness versus blend composition were classified as producing a certain morphology. …

Structure And Property Of Polymers And Biopolymers From Molecular Dynamic Simulations, Xiaoquan Sun

Graduate Theses and Dissertations

Natural and synthetic polymers and biopolymers have been studied for a variety of applications in food emulsion, biopharmaceutical purification, tissue engineering, and biosensor. The structure and property of polymers and biopolymers are critically important to determine their functions. Molecular dynamics (MD) simulations have a unique advantage to explore the structure and property of polymers and biopolymers from the molecular level. In the dissertation, MD simulations were conducted to study the mechanisms of various biological and chemical processes controlled by polymers and biopolymers based on real-world experimental results.

Seven heptapeptides have been screened from a peptide library in our earlier study …

Phase Field Model Of Thermally Induced Phase Separation (Tips) For The Formation Of Porous Polymer Membranes, Ashley Green, Aria Green

Mechanical Engineering Undergraduate Honors Theses

Most membrane research and development has been done through experimental work, which can be costly and time consuming. An accurate computational model would greatly reduce the need for these experiments. The focus of the research presented in this paper is to create an accurate computational model for membrane formation using thermally induced phase separation (TIPS). A phase field model is employed to create this model including the Cahn Hilliard Equation and Flory Huggins Theory. This model produced computational results that correspond well with theoretical and experimental results. The model was then adapted to correspond to the PVDF/DPC polymer-solvent system by …

Self-Assembled Barium Titanate Nanoscale Films By Molecular Beam Epitaxy, Timothy Allen Morgan

Graduate Theses and Dissertations

One challenge of investigating ferroelectrics at the nanoscale has been controlling the stoichiometry during growth. Historically, the growth of barium titanate (BaTiO3) by molecular beam epitaxy has relied on a growth technique called shuttered RHEED. Shuttered RHEED controls the stoichiometry of barium titanate through the precise deposition of alternating layers of BaO and TiO2. While this approach has achieved 1% control of stoichiometry, finding self-limiting mechanisms to lock-in stoichiometry has been the focus of the growth community. The Goldschmidt tolerance factor predicts an unstable perovskite when barium sits in the titanium lattice site. The BaO-TiO2 phase diagram predicts a low-solubility …

Phase Transitions In Monochalcogenide Monolayers, Mehrshad Mehboudi

Graduate Theses and Dissertations

Since discovery of graphene in 2004 as a truly one-atom-thick material with extraordinary mechanical and electronic properties, researchers successfully predicted and synthesized many other two-dimensional materials such as transition metal dichalcogenides (TMDCs) and monochalcogenide monolayers (MMs). Graphene has a non-degenerate structural ground state that is key to its stability at room temperature. However, group IV monochalcogenides such as monolayers of SnSe, and GeSe have a fourfold degenerate ground state. This degeneracy in ground state can lead to structural instability, disorder, and phase transition in finite temperature. The energy that is required to overcome from one degenerate ground state to another …

Membranes For Food And Bioproduct Processing, Alexandru Marius Avram

Graduate Theses and Dissertations

Modified membranes for process intensification in biomass hydrolysis

Production of biofuels and chemicals from lignocellulosic biomass is one of the leading candidates for replacement of petroleum based fuels and chemicals. However, conversion of lignocellulosic biomass into fuels and chemicals is not cost effective compared to the production of fuels and chemicals from crude oil reserves. Some novel and economically feasible approaches involve the use of ionic liquids as solvents or co-solvents, since these show improved solvation capability of cellulose over simple aqueous systems. Membranes offer unique opportunities for process intensification which involves fractionation of the resulting biomass hydrolysate leading to …

Interactive Physics And Characteristics Of Photons And Photoelectrons In Hyperbranched Zinc Oxide Nanostructures, Garrett Edward Torix

Graduate Theses and Dissertations

As is commonly known, the world is full of technological wonders, where a multitude of electronic devices and instruments continuously help push the boundaries of scientific knowledge and discovery. These new devices and instruments of science must be utilized at peak efficiency in order to benefit humanity with the most advanced scientific knowledge. In order to attain this level of efficiency, the materials which make up these electronics, or possibly more important, the fundamental characteristics of these materials, must be fully understood. The following research attempted to uncover the properties and characteristics of a selected family of materials. Herein, zinc …

The Effect Of Process Parameters And Surface Condition On Bond Strength Between Additively Manufactured Components And Polymer Substrates, Bharat Bhushan Chivukula

Graduate Theses and Dissertations

Additive patching is a process in which printers with multiple axes deposit molten material onto a pre-defined surface to form a bond. Studying the effect of surface roughness and process parameters selected for printing auxiliary part on the bond helps in improving the strength of the final component. Particularly, the influence of surface roughness, as established by adhesion theory, has not been evaluated in the framework of additive manufacturing (AM). A full factorial design of experiments with five replications was conducted on two levels and three factors, viz., layer thickness, surface roughness, and raster angle to examine the underlying effects …

Spotlight On Graphene Research From The Middle East, Kathleen A. Lehman

University Libraries Faculty Publications and Presentations

In an extension to the 2011 article “Reviews of Science for Science Librarians: Graphene” (Lehman 2011), this paper seeks to continue exploring the trend of graphene research but limits its focus to the research production of countries in the Middle East. In addition to reporting on the research output of this group of countries, this article will also examine the most prolific Middle Eastern graphene authors,their supporting institutions and funding agencies, the most cited publications from this group, the journals most used for publication of their work, and the general trend in graphene research growth in the Middle East. As …

Metal Assisted Nanowire Growth For Silicon Nanowire/Amorphous Silicon Composite Solar Cell, Asmaa Ali Sadoon

Graduate Theses and Dissertations

Solar cells are photovoltaic devices that convert the energy of light to electricity by the photovoltaic effect. Crystalline silicon-based solar cells are the most dominant solar cells in the market today due to the high efficiency and relatively low cost. However, the cost of such solar cell is still high due to the large amount of material that is consumed in fabricating such a device. Polycrystalline/amorphous thin films and nanomaterial technologies have emerged to reduce the high cost of c-Si based solar cells and increase the efficiency. In this research, we combined these two technologies to propose and fabricate silicon …

Wear Resistant Polydopamine/Ptfe Nanoparticle Composite Coating For Dry Lubrication Applications, Samuel George Beckford

Graduate Theses and Dissertations

This dissertation presents an investigation into the effect of nanoparticle fillers and a polydopamine adhesive primer on the tribological performance of thin PTFE films. The principal objective of this investigation was to reduce wear in PTFE films, an issue which precludes the use of PTFE films in tribological applications requiring high durability. The friction and wear of the composite films were evaluated using a ball-on-flat configuration in linear reciprocating motion. It was found that the use of a polydopamine adhesive primer reduces the wear of PTFE films more than 600 times. X-ray photoelectron spectroscopy (XPS) results show that a tenacious …

Phase Transformation In Monolayer Molybdenum Disulphide With And Without Defects Under Tension Predicted By Atomistic Simulations, Khanh Quoc Dang

Graduate Theses and Dissertations

In addition to its use as a solid lubricant, molybdenum disulphide (MoS2) has gained recent attention as a possible substitute for silicon as it is increasingly difficult to keep shrinking down electronic devices made of silicon, the conventional electronic material. When thinned down to atomic thickness, monolayer MoS2 possesses very unique and promising electronic and electrical properties. Unlike electronic and electrical properties, knowledge of the mechanical properties and role of structural defects on these properties of monolayer MoS2 is unexplored. For this thesis, the two main objectives are (1) to gain insight about the failure mechanism of monolayer MoS2 by …

Friction And Wear Of Polytetrafluoroethylene/Graphene Oxide Composite Thin Films, Justin Kyle Carter

Graduate Theses and Dissertations

Polytetrafluoroethylene (PTFE) is a commonly used solid lubricant due to its low coefficient of friction and chemical inertness. As a polymer, PTFE suffers from high wear and low adhesion to substrates limiting its use as a thin film. Thin PTFE films are ideal candidates for solid lubrication in micro-machines and bearing applications. The main goal of this work is to enhance the durability of thin PTFE films through the addition of few layered graphene oxide (GO) as filler. In order to address adhesion issues, the addition of an adhesive layer of polydopamine (PDA) between stainless steel substrates and thin PTFE …

Crack Growth Behavior Under Creep-Fatigue Conditions Using Compact And Double Edge Notch Tension-Compression Specimens, Santosh B. Narasimha Chary

Graduate Theses and Dissertations

The American Society for Testing and Materials (ASTM) has recently developed a new standard for creep-fatigue crack growth testing, E 2760-10, that supports testing compact specimens, C(T), under load controlled conditions. C(T) specimens are commonly used for fatigue and creep-fatigue crack growth testing under constant-load-amplitude conditions. The use of these specimens is limited to positive load ratios. They are also limited in the amount of crack growth data that can be developed at high stress intensity values due to accumulation of plastic and/or creep strains leading to ratcheting in the specimen. Testing under displacement control can potentially address these shortcomings …

Design And Fundamental Understanding Of Minimum Quantity Lubrication (Mql) Assisted Grinding Using Advanced Nanolubricants, Parash Kalita

Graduate Theses and Dissertations

Abrasive grinding is widely used across manufacturing industry for finishing parts and components requiring smooth superficial textures and precise dimensional tolerances and accuracy. Unlike any other machining operations, the complex thermo-mechanical processes during grinding produce excessive friction-induced energy consumption, heat, and intense contact seizures. Lubrication and cooling from grinding fluids is crucial in minimizing the deleterious effects of friction and heat to maximize the output part quality and process efficiency. The conventional flood grinding approach of an uneconomical application of large quantities of chemically active fluids has been found ineffective to provide sufficient lubrication and produces waste streams and pollutants …

Silica Nanoparticle-Based Coatings With Superhydrophilic And Superhydrophobic Properties, Robert Andrew Fleming

Graduate Theses and Dissertations

Superhydrophilic and superhydrophobic surfaces have potential for implementation into a variety of fields, including self-cleaning surfaces, anti-fogging transparent materials, and biomedical applications. In this study, sandblasting, oxygen plasma treatments, silica nanoparticle films, and a low surface energy fluorocarbon film were employed to change the natural surface wettability of titanium, glass, and polyethylene terephthalate (PET) substrates, with an aim to produce superhydrophilic and superhydrophobic behavior. The effects of these surface modifications are characterized by water contact angles (WCAs), surface wetting stability, surface morphology and roughness, surface elemental composition, and optical transmittance measurements. The results show that stable superhydrophilic and superhydrophobic surfaces …

Design, Fabrication, Testing Of Cnt Based Isfet And Characterization Of Nano/Bio Materials Using Afm, Zhuxin Dong

Graduate Theses and Dissertations

A combination of Carbon Nanotubes (CNTs) and Ion Selective Field Effect Transistor (ISFET) is designed and experimentally verified in order to develop the next generation ion concentration sensing system. Micro Electro-Mechanical System (MEMS) fabrication techniques, such as photolithography, diffusion, evaporation, lift-off, packaging, etc., are required in the fabrication of the CNT-ISFET structure on p-type silicon wafers. In addition, Atomic Force Microscopy (AFM) based surface nanomachining is investigated and used for creating nanochannels on silicon surfaces. Since AFM based nanomanipulation and nanomachining is highly controllable, nanochannels are precisely scratched in the area between the source and drain of the FET where …

Pulse Sharpening Effects Of Thin Film Ferroelectric Transmission Lines, Robert J. Sleezer

Graduate Theses and Dissertations

Advances in material science have resulted in the development of electrically nonlinear high dielectric thin film ferroelectrics, which have led to new opportunities for the creation of novel devices. This dissertation investigated one such device: a low voltage nonlinear transmission line (NLTL). A finite element simulation of ferroelectric transmission lines showed that NLTLs are capable of creating shockwaves. Additionally, if the losses are kept sufficiently low, it was shown that voltage gain should be possible. Furthermore, a method of accounting for material dispersion was developed. Results from simulations including material dispersion showed that temporal solitons might be possible from a …

Titanium Aluminum Nitride Films Deposited By Ac Reactive Magnetron Sputtering: Study Of Positioning Effect In An Inverted Cylindrical Magentron Sputtering System, George C. Vandross Ii

Graduate Theses and Dissertations

TiAlN films were deposited on glass substrates by AC magnetron sputtering at 2 kW with constant Argon and Nitrogen gas flow rates to study the effects of positioning on the deposited films. The deposition system used was an ICM-10 IsoFlux cylindrical magnetron sputtering chamber. The samples were placed in different positions and tilts with respect to the location of the Titanium and Aluminum targets in the chamber. It was found that with change in position and application of tilts, deposited films acquired different physical and chemical properties. It is believed that the differences in these properties were caused by to …

A Silicon Carbide Based Solid-State Fault Current Limiter For Modern Power Distribution Systems, Erik Darnell Johnson

Graduate Theses and Dissertations

The fault current limiter represents a developing technology which will greatly improve the reliability and stability of the power grid. By reducing the magnitude of fault currents in distribution systems, fault current limiters can alleviate much of the damage imposed by these events. Solid-state fault current limiters in particular offer many improved capabilities in comparison to the power system protection equipment which is currently being used for fault current mitigation. The use of silicon carbide power semiconductor devices in solid-state fault current limiters produces a system that would help to advance the infrastructure of the electric grid.

A solid-state fault …

Atomistic Simulations Of Defect Nucleation And Intralayer Fracture In Molybdenum Disulphide During Nanoindentation, James A. Stewart

Graduate Theses and Dissertations

Molybdenum disulphide (MoS2) is a layered, hexagonal crystal that has a very low coefficient of friction. Due to this low coefficient of friction, MoS2 has become a well-known solid lubricant and liquid lubricant additive. As such, nanoparticles of MoS2 have been proposed as an additive to traditional liquid lubricants to provide frictional properties that are sensitive to different temperature and pressure regimes. However, to properly design these MoS2 nanoparticles to be sensitive to different temperature and pressure regimes, it is necessary to understand the mechanical response of crystalline MoS2 under mechanical loading. Specifically, the fundamental mechanism associated with the nucleation …

Semiconductor Nanocrystals: From Quantum Dots To Quantum Disks, Zheng Li

Graduate Theses and Dissertations

The bottom-up colloidal synthesis opened up the possibility of finely tuning and tailoring the semiconductor nanocrystals. Numerous recipes were developed for the preparation of colloidal semiconductor nanocrystals, especially the traditional quantum dots. However, due to the lack of thorough understanding to those systems, the synthesis chemistry is still on the empirical level. CdS quantum dots synthesis in non-coordinating solvent were taken as a model system to investigate its molecular mechanism and formation process, ODE was identified as the reducing agent for the preparation of CdS nanocrystals, non-injection and low-temperature synthesis methods developed. In this model system, we not only proved …

Cross-Linked Pdms Expansion Due To Submersion In Liquid And Supercritical Co2, Teng Yang

Graduate Theses and Dissertations

Characterization of micro/nano-copper particles impregnated Polydimethylsiloxane (PDMS) submersed in supercritical carbon dioxide (scCO2) was studied. The purpose of this investigation was to advance micro-corrosion sensor technology utilizing PDMS and micro-metal particle composite as the sensing element currently under-development. One of the key challenges encountered was the removal of the native oxides inherently existing on the metal particles. Numerous techniques were experimented with to counter this problem at the UA Engineered Micro/Nano Systems Laboratory (EMNSL), with swell-based protocols being identified as the most promising solution. In terms of compatibility to Micro-electro-mechanical Systems (MEMS) fabrication, CO2 is often used in the release …

Electrospun Polycaprolactone Nanofiber Scaffolds For Tissue Engineering, Andreas Haukas

Graduate Theses and Dissertations

Stem cell and tissue engineering offer us with a unique opportunity to research and develop new therapies for treating various diseases that are otherwise incurable using traditional medicines. However, development of these new therapies replies upon the establishment of in vitro cell culture and differentiation systems that mimic in vivo microenvironments required for cell-cell and cell-ECM interaction. The development of these cell culture systems depends upon the identification of appropriate biomaterials and cell sources. Biomaterials should be carefully selected and fabricated into scaffolds for supporting cell growth and differentiation. In this study, we explored the fabrication of 3D electrospun nanofiber …

Physiochemical And Nanomanipulation Studies Of Carbon Nanomaterials, Siva Naga Sandeep Chalamalasetty

Graduate Theses and Dissertations

Carbon nanomaterials are, without a doubt, one of man's wonder creations. Though these nanomaterials are a very recent trend, extraordinary electromechanical properties and the light weightiness of these nanomaterials attracted the attention of researchers. Although vast research has been done since the start of the US nanotechnology initiative, much effort was in the area of synthesis and characterization of the nanomaterials. However, most of the traditional macroscopic material's theories fail at the nanoscale level, and since the material properties are dependent on size and structure at nanoscale level, the behavior of the carbon nanomaterials in different environments needs attention. High …

Stability And Optimization Of Photoconductivity In Thermally Vacuum Evaporated Indium (Iii) Sulfide Thin Films, Gustavo Rehder, Robert Engelken, Randy Stidham, Richard Tanner, Lee Ketchum, Anil Baral

Journal of the Arkansas Academy of Science

Long term stability of photosensitivity versus time in indium (III) sulfide thin films thermally vacuum evaporated onto photocell-patterned printed circuit boards varies sensitively with several factors including contact metal type, contact metal diffusion and electromigration into the semiconductor, doping, and encapsulation method. Because of the significant photoconductivity and relative low toxicity and environmental impact of this compound semiconductor, it is important to better characterize these dependences toward commercial applications. We will report on measurements of photoconductivity vs. time as functions of such factors and evolving methods to stabilize this photoconductivity.

Plastic Mounting Technique For Herbaria, Albert Robinson Jr.

Journal of the Arkansas Academy of Science

No abstract provided.