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Full-Text Articles in Engineering

Non-Collinear Magnetic Textures Studied By Neutron Scattering, Nan Tang May 2023

Non-Collinear Magnetic Textures Studied By Neutron Scattering, Nan Tang

Doctoral Dissertations

Non-collinear magnetic structures, where the magnetic moments do not align along a single axis, can lead to interesting physical phenomena and potential device applications. In this dissertation, two specific non-collinear magnetic textures are studied which includes soft/hard bilayer and skyrmions. Soft/hard magnetic bilayer thin films have been widely used in data storage technologies and permanent magnet applications. Here, we use polarized neutron reflectometry (PNR) to study magnetic configuration in soft-hard bilayer heterostructure thin films designed with different sample geometry and material properties under a range of temperatures and fields. Comparing the PNR results to the micromagnetic simulations reveals that the …


Synthesis And Assembly Of Polymer Materials At Interfaces, Xiaoshuang Wei Oct 2022

Synthesis And Assembly Of Polymer Materials At Interfaces, Xiaoshuang Wei

Doctoral Dissertations

The overarching goal of the thesis is to understand growth and assembly of polymer materials at interfaces. Chapter 2 and Chapter 3 study simultaneous polymer growth and assembly at fluid interfaces, where in-situ photopolymerization and vapor phase deposition were utilized to grow polymers, respectively. Chapter 4 leverages capillary condensation to pattern polymer growth at solid substrates. Chapter 1 provides background information on polymer materials at interfaces, and vapor phase deposition method (initiated chemical vapor deposition, iCVD) to grow polymers. This chapter also reviews polymer thin film wetting, and colloidal assemblies at interfaces. In Chapter 2, we demonstrate the preparation …


Contributions To The Performance Of Thin Film Capacitors For High Reliability Applications, Daniel Krueger Jan 2021

Contributions To The Performance Of Thin Film Capacitors For High Reliability Applications, Daniel Krueger

Doctoral Dissertations

"Capacitors are critical devices in microelectronic assemblies that must be incorporated into electronic systems through a variety of ways such as integrated or discrete devices. This work has developed new thin film capacitors deposited directly onto multichip module or printed circuit board surfaces to benefit from closer integration that enhances system performance for use in high reliability applications. The capacitors serve as filters or provide tuning and energy storage functions. Unexpected performance was observed during development that included low adhesion of the films to the substrates, higher effective dielectric constants than reported in literature, and low yields. Three publications resulted …


Development Of Functional Biomaterials Using Protein Building Blocks, Li-Sheng Wang Mar 2019

Development Of Functional Biomaterials Using Protein Building Blocks, Li-Sheng Wang

Doctoral Dissertations

Proteins have intrinsic molecular properties that are highly useful for materials applications, especially for biomaterials. My research has focused on translating these molecular properties to materials surface behavior. In one approach, I developed a fluorous-based thermal treatment strategy to generate stable thin films from a variety of naturally abundant proteins. The different surface properties generated from the choice of protein were utilized to modulate cell-surface interactions, prevent bacterial adhesions, and control drug loading/release. I have used nanoimprint lithography to generate patterned protein films for cell alignment. Coupling with inkjet printing deposition, I have fabricated mixed protein films with spatial and …


Fabrication Of Functional Nano-Structured Materials And Devices Using Supercritical Fluids, Shengkai Li Nov 2017

Fabrication Of Functional Nano-Structured Materials And Devices Using Supercritical Fluids, Shengkai Li

Doctoral Dissertations

Nano-structured materials possess unconventional properties and enable miniaturization of devices. However, fabrications of such materials and devices are challenging and in many cases cumbersome, and development of nanofabrication techniques are essential to realizing novel designs and commercializing scientific ideas. Supercritical fluids possess a unique combination of gas-like diffusion properties and liquid-like dissolution power, and are suitable reaction media for fabricating materials at the nanometer scale. This dissertation focuses on developing supercritical fluids-related techniques for fast and large-scale fabrication of novel composite materials and devices. Using supercritical fluid deposition (SFD) technique, cobalt thin films were deposited on a variety of substrates, …


Morphology Evolution Mechanisms Of Low Band Gap Polymer-Based Photovoltaics, Sunzida Ferdous Nov 2015

Morphology Evolution Mechanisms Of Low Band Gap Polymer-Based Photovoltaics, Sunzida Ferdous

Doctoral Dissertations

An optimal nanoscale phase separation between the donor (generally, a conjugated polymer) and the acceptor (generally, a fullerene derivative) materials is one of the major requirements for obtaining high efficiency organic photovoltaic (OPV) device. Recent methods of controlling such nanostructure morphology in a bulkheterojunction (BHJ) OPV device involve addition of a small amount of solvent additive to the donor and acceptor solutions. The idea is to retain the acceptor materials into the solution for a longer period of time during the film solidification process, thus allowing the donor material to crystallize earlier. The ultimate morphology resulting from the solvent casting …


Effect Of Processing History And Material Properties On The Growth Of Wrinkle Amplitude, Yu-Cheng Chen Nov 2015

Effect Of Processing History And Material Properties On The Growth Of Wrinkle Amplitude, Yu-Cheng Chen

Doctoral Dissertations

Wrinkling has been employed by many organisms to form unique topography, such as fingerprints, gut villi, and surface of flower petal cells. The wavy wrinkle structure provides friction enhancement, surface area increase, optical, and wetting properties improvement. Inspired by Nature, scientists have created wrinkles synthetically and proposed numerous uses for them. However, wrinkling surfaces encounters limitations on achieving massive area and high amplitude-to-wavelength ratio (aspect ratio). The three phase contact line wrinkling technique creates well-defined wrinkles in a continuous fashion, and has great potential to scale-up for massive production. In addition to the velocity dependent adhesion force, we find the …


Quantum Tuning Of Plasmons In Ultrathin Metal Films, Ao Teng Aug 2014

Quantum Tuning Of Plasmons In Ultrathin Metal Films, Ao Teng

Doctoral Dissertations

The surface plasmon is a coherent charge density oscillation localized at a metal surface. It can couple with light and the resulting plasmon-polariton hybrid mode is confined to volumes that are much smaller than the classical diffraction limit of light. Nano-plasmonics is a rapidly evolving field where light manipulation at the nanoscale may lead to novel applications. However, as the size of plasmonic devices approaches the quantum-size regime, the macroscopic picture of plasmon may no longer be valid. To elucidate the influence of the discretization of the single particle spectrum on the collective plasmon response, we performed a systematic study …


Thin Film Combinatorial Synthesis Of Advanced Scintillation Materials, Jonathan Daniel Peak Dec 2010

Thin Film Combinatorial Synthesis Of Advanced Scintillation Materials, Jonathan Daniel Peak

Doctoral Dissertations

The development and application of a combinatorial sputtering thin film technique to screen potential scintillation material systems was investigated. The technique was first benchmarked by exploring the binary lutetium oxide-silicon oxide material system, which successfully identified the luminescence phases of the system, Lu2SiO5 (LSO) and Lu2Si2O7 (LPS). The second application was to optimize the activator concentration in cerium doped LSO. The successfully optimized cerium concentration in the thin film LSO of 0.34 atomic percent was much greater than the standard cerium concentration in single crystal LSO. This lead to an intensive study based on temperature dependent steady-state and lifetime photoluminescence …


A Hybrid Finite Element-Finite Difference Method For Thermal Analysis In A Double-Layered Thin Film, Teng Zhu Apr 2000

A Hybrid Finite Element-Finite Difference Method For Thermal Analysis In A Double-Layered Thin Film, Teng Zhu

Doctoral Dissertations

Thin film technology is of vital importance in microtechnology applications. For instance, thin films of metals, of dielectrics such as SiO2, or Si semiconductors are important components of microelectronic devices. The reduction of the device size to the microscale has the advantage of enhancing the switching speed of the device. The reduction, on the other hand, increases the rate of heat generation that leads to a high thermal load on the microdevice. Heat transfer at the microscale with an ultrafast pulsed-laser is also a very important process for thin films. Hence, studying the thermal behavior of thin films or of …


A Thin-Film Micromanufactured Oxygen Microelectrode, James Clay Mcguyer Jr. Oct 1999

A Thin-Film Micromanufactured Oxygen Microelectrode, James Clay Mcguyer Jr.

Doctoral Dissertations

The methods for production of recessed oxygen microelectrodes developed by Whalen, et al. (1967) and improved upon by Linsenmeier, et al. (1987) are dated production methods by the standards of sensor production of the current time. The production process for this type of polarographic oxygen sensing electrode has remained unchanged for over 10 years, and is a time consuming, extremely low-yield process. The goal of this project has been to use the techniques of micromanufacturing available at the Institute for Micromanufacturing at Louisiana Tech University to construct a recessed oxygen microelectrode with a batch process that has higher yield than …