Materials Science and Engineering Commons^™

Power Maximization For Pyroelectric, Piezoelectric, And Hybrid Energy Harvesting, Murtadha A. Shaheen

Theses and Dissertations

The goal of this dissertation consists of improving the efficiency of energy harvesting using pyroelectric and piezoelectric materials in a system by the proper characterization of electrical parameters, widening frequency, and coupling of both effects with the appropriate parameters.

A new simple stand-alone method of characterizing the impedance of a pyroelectric cell has been demonstrated. This method utilizes a Pyroelectric single pole low pass filter technique, PSLPF. Utilizing the properties of a PSLPF, where a known input voltage is applied and capacitance C_p and resistance R_p can be calculated at a frequency of 1 mHz to 1 Hz. …

Effects Of Antidepressants On Human Mesenchymal Stem Cell Differentiation On Clinically Relevant Titanium Surfaces, Nancy B. Ayad

Theses and Dissertations

Selective Serotonin Reuptake Inhibitors (SSRIs) are the most frequently prescribed class of drugs worldwide and are implemented in the treatment of depression and other psychiatric disorders. SSRIs relieve depressive symptoms by modulating levels of the neurotransmitter serotonin in the brain. SSRIs block the function of the serotonin transporter, thereby increasing concentrations of extracellular serotonin. However, serotonin levels in the neurons of the brain only account for 5% while the remaining 95% is present outside the brain. Serotonin receptors and transporter are located on bone resident cells (mesenchymal stem cells (MSCs)), osteoblasts and osteoclasts, and serotonergic activity is believed to affect …

Surface Modification Techniques For Increased Corrosion Tolerance Of Zirconium Fuel Cladding, James Carr

Theses and Dissertations

Corrosion is a major issue in applications involving materials in normal and severe environments, especially when it involves corrosive fluids, high temperatures, and radiation. Left unaddressed, corrosion can lead to catastrophic failures, resulting in economic and environmental liabilities. In nuclear applications, where metals and alloys, such as steel and zirconium, are extensively em- ployed inside and outside of the nuclear reactor, corrosion accelerated by high temperatures, neu- tron radiation, and corrosive atmospheres, corrosion becomes even more concerning. The objec- tives of this research are to study and develop surface modification techniques to protect zirconium cladding by the incorporation of a …

Drying Methods For The Fabrication Of Polymer Foam Material, Dalton Echard

Theses and Dissertations

This is a report on the study of the drying of nanoporous polymer foam material fabricated by photolithogtaphic methods. Three drying methods were employed, which were air drying, supercritical drying and freeze drying. After fabrication and drying, physical properties of the polymer foams were measured. These measurements included density of the material, Young’s modulus, surface area, and the shape of the skeletal particles. The measurements determined the effect of the polymer concentration and the effect of drying methods. It was determined that polymer concentration had a much larger effect on the properties of the materials than the drying method.

The Dawn Of New Quantum Dots: Synthesis And Characterization Of Ge1-Xsnx Nanocrystals For Tunable Bandgaps., Richard J. Esteves

Theses and Dissertations

Ge_1-xSn_x alloys are among a small class of benign semiconductors with composition tunable bandgaps in the near-infrared spectrum. As the amount of Sn is increased the band energy decreases and a transition from indirect to direct band structure occurs. Hence, they are prime candidates for fabrication of Si-compatible electronic and photonic devices, field effect transistors, and novel charge storage device applications. Success has been achieved with the growth of Ge_1-xSn_x thin film alloys with Sn compositions up to 34%. However, the synthesis of nanocrystalline alloys has proven difficult due to larger discrepancies (~14%) in …

Beyond Conventional C-Plane Gan-Based Light Emitting Diodes: A Systematic Exploration Of Leds On Semi-Polar Orientations, Morteza Monavarian

Theses and Dissertations

Despite enormous efforts and investments, the efficiency of InGaN-based green and yellow-green light emitters remains relatively low, and that limits progress in developing full color display, laser diodes, and bright light sources for general lighting. The low efficiency of light emitting devices in the green-to-yellow spectral range, also known as the “Green Gap”, is considered a global concern in the LED industry. The polar c-plane orientation of GaN, which is the mainstay in the LED industry, suffers from polarization-induced separation of electrons and hole wavefunctions (also known as the “quantum confined Stark effect”) and low indium incorporation efficiency that …

Diagnostics And Degradation Investigations Of Li-Ion Battery Electrodes Using Single Nanowire Electrochemical Cells, Naveen Kumar Reddy Palapati, Naveen Kumar Reddy Palapati

Theses and Dissertations

Portable energy storage devices, which drive advanced technological devices, are improving the productivity and quality of our everyday lives. In order to meet the growing needs for energy storage in transportation applications, the current lithium-ion (Li-ion) battery technology requires new electrode materials with performance improvements in multiple aspects: (1) energy and power densities, (2) safety, and (3) performance lifetime. While a number of interesting nanomaterials have been synthesized in recent years with promising performance, accurate capabilities to probe the intrinsic performance of these high-performance materials within a battery environment are lacking. Most studies on electrode nanomaterials have so far used …