Engineering Science and Materials Commons^™

Design And Development Of Transition Metal-Based Electrocatalysts For Environmentally Friendly And Efficient Hydrogen Evolution Reactions (Her), Navid Attarzadeh

Open Access Theses & Dissertations

Hydrogen fuel is a clean energy source primarily because it emits no carbon dioxide (CO2). Sustainable energy alternatives have attracted the scientific community and policymakers as concerns over global warming and depletion of fossil fuels have increased significantly. Substituting H2 gas as a primary source for our daily energy consumption under the guideline of the hydrogen economy concept has not progressed as anticipated because of inadequate efficiency associated with the generation (electrolyzer) and utilization (fuel cell) devices. However, there are challenges associated with hydrogen that must be overcome for it to become a truly sustainable and widespread energy source. The …

The Qualification Of Sealability And Creep Relaxation Of Additively Manufactured Zytel Gaskets For Pem Fuel Cells, Robert Lazarin

Open Access Theses & Dissertations

The purpose of this thesis is to study the feasibility of low-cost additive manufacturing of gaskets for proton exchange membrane fuel cells exposed to extreme temperature conditions ranging from -55°C to 100°C. With the growing popularity and decreasing costs of additive manufacturing technologies, specifically Material Extrusion (ME), research is being conducted to determine the feasibility of ME components. Thermally cycled PEMFCs may exhibit accelerated gasket deterioration, therefore, the mechanical stability of material extruded gaskets following a harsh thermal cycle must be assessed. The feasibility of the material extruded gaskets will be proven by manufacturing optimization and mechanical testing. The target …

Suitability Of Low-Cost Additive Manufacturing For Polymer Electrolyte Fuel Cells, David Alexander

Open Access Theses & Dissertations

The purpose of this dissertation is to study the feasibility of low-cost additive manufacturing to fabricate polymer electrolyte fuel cell bipolar plate materials. Traditional manufacturing techniques include molding, milling, hollow embossing, hydro-forming, rolling, and electromagnetic forming. These processes are employed when a design has been selected due to higher costs at low volumes. The combination of high initial costs and bipolar plates being the most expensive component of the polymer electrolyte fuel cell creates incentive to mitigate this obstacle. The feasibility of low-cost additive manufactured bipolar plates will be proven by fabrication, post-processing, and characterization of printed test specimen. The …

A Study Of The Frustrated Honeycomb Battery Material Na2ni2teo6, Nathan Christopher Episcopo

Open Access Theses & Dissertations

The P2-type layered hexagonal compound Na2Ni2TeO6 with Ni2+ on a honeycomb lattice was synthesized by the standard solid-state route. Structural characterization chemical phase purity was confirmed by Rietveld refinement of laboratory and synchrotron data. The crystal structure refines well in the P63/mcm space group. Single crystal growth trials using the self-flux-melt method were conducted with limited success. The magnetic transition temperature pertaining to Ni2+ lattice was confirmed by analysis of specific heat capacity to be . The magnetic susceptibility remains largely unchanged in magnetic field of and external pressure of . There is an almost linear response in isothermal magnetization …

Fabrication And Testing Of Cfrp Composites With Embedded Piezoelectric Particles For Temperature Sensing And Energy Harvesting, Emilio Tarango Valles

Open Access Theses & Dissertations

As a part of this world's continuous evolution and technological advancements, smart materials and functional composites have become an attractive topic. In many cases, these new functional composites are replacing the traditional engineering material due to their customizable mechanical properties. This Thesis analyzes and demonstrates the signal response, sensing capabilities and structural properties from Carbon/Glass Fiber Reinforced Plastic Composites (CFRP) with embedded Lead Zirconate Titanate Particles (PZT). The added PZT particles function as actuators, giving the composites a functionality. The PZT quantity inside each composite was variated to study better and characterize the mechanical and electrical properties; the variations were …

Processing And Property Evaluation Of Tungsten-Based Mixed Oxides For Photovoltaics And Optoelectronics, Mirella Vargas

Open Access Theses & Dissertations

Tungsten Oxide (WO3) films and low-dimensional structures have proven to be promising candidates in the fields of photonics and electronics. WO3 is a well-established n-type semiconductor characterized by unique electrochromic behavior, an ideal optical band gap that permits transparency over a wide spectral range, and high chemical integrity. The plethora of diverse properties endow WO3 to be highly effective in applications related to electrochromism, gas sensing, and deriving economical energy. Compared to the bulk films, a materials system involving WO3 and a related species (elements or metal oxides) offer the opportunity to tailor the electrochromic response, and an overall enhancement …

Novel Endohedral Derivatives Of Sc3n@C2n (N = 34, 40) And Unique Tether Controlled Bis-Functionalization Of Fullerenes, Maira Raquel Ceron Hernandez

Open Access Theses & Dissertations

Since the discovery of fullerenes in 1985, their exohedral functionalization has been necessary to increase their solubility and explore their properties and potential applications in materials science and medicinal chemistry. This Thesis provides a short overview of the importance of electronic, size and shape complementarity in determining the structures of specific endohedral fullerene compounds. This is followed by a description of a new method for the separation of scandium nitride endohedral fullerenes Sc3N@C2n (n = 34, 39 and 40), and their monofunctionalization.

We also present the regioselective synThesis of easily isolable bis-derivatives of C60, C70, and M3N@Ih-C80 (M = Sc, …

Alkali Promoted Molybdenum (Iv) Sulfide Based Catalysts, Development And Characterization For Alcohol Synthesis From Carbon Monoxide And Hydrogen, Belinda Delilah Molina

Open Access Theses & Dissertations

For more than a century transition metal sulfides (TMS) have been the anchor of hydro-processing fuels and upgrading bitumen and coal in refineries worldwide. As oil supplies dwindle and environmental laws become more stringent, there is a greater need for cleaner alternative fuels and/or synthetic fuels. The depletion of oil reserves and a rapidly increasing energy demand worldwide, together with the interest to reduce dependence on foreign oil makes alcohol production for fuels and chemicals via the Fischer Tropsch synthesis (FTS) very attractive. The original Fischer-Tropsch (FT) reaction is the heart of all gas-to-liquid technologies; it creates higher alcohols and …

Growth And Analysis Of Micro And Nano Cdte Arrays For Solar Cell Applications, Brandon Adrian Aguirre

Open Access Theses & Dissertations

CdTe is an excellent material for infrared detectors and photovoltaic applications. The efficiency of CdTe/CdS solar cells has increased very rapidly in the last 3 years to ~20% but is still below the maximum theoretical value of 30%. Although the short-circuit current density is close to its maximum of 30 mA/cm2, the open circuit voltage has potential to be increased further to over 1 Volt. The main limitation that prevents further increase in the open-circuit voltage and therefore efficiency is the high defect density in the CdTe absorber layer. Reducing the defect density will increase the open-circuit voltage above 1 …

Thermal Barrier Coatings (Tbc's) For High Heat Flux Thrust Chambers, Christopher Michael Bradley

Open Access Theses & Dissertations

The last 30 years materials engineers have been under continual pressure to develop materials with a greater temperature potential or to produce configurations that can be effectively cooled or otherwise protected at elevated temperature conditions. Turbines and thrust chambers produce some of the harshest service conditions for materials which lead to the challenges engineers face in order to increase the efficiencies of current technologies due to the energy crisis that the world is facing. The key tasks for the future of gas turbines are to increase overall efficiencies to meet energy demands of a growing world population and reduce the …

High Pressure Synchrotron X-Ray Diffraction Studies Of Superprotonic Transitions In Phosphate Based Solid Acids, Juan Daniel Hermosillo

Open Access Theses & Dissertations

Certain phosphate based solid acids, such as CsH2PO4 and RbH2PO4, have been shown to exhibit an abrupt, several-order-of-magnitude increase in their proton conductivity when heated above a temperature threshold. This so called superprotonic behavior allows the above-mentioned materials to function as fuel cell electrolytes at temperatures between 150C and 300C, a remarkable application that attracted significant interest especially from the automobile industry. Yet, the microscopic structures and dynamic mechanisms responsible for this behavior are not fully understood. In fact, until very recently, the very nature of the superprotonic behavior has been debate, with some groups attributing the steep proton enhancement …

Hafnia-Based Nanostructured Thermal Barrier Coatings For Next Generation Gas Turbine Technology, Mohammed Noor-A-Alam

Open Access Theses & Dissertations

Extensive efforts have been directed in the last several decades towards improving thermodynamic efficiency of industrial gas turbines for power generation plants. The central theme of the efforts is to increase the turbine operating temperature and, thus, allowing higher efficiency. Thermal barrier coatings (TBC) constitute an advanced technology to protect the metallic surface from high temperature exposure for long time operation. The TBCs protect the gas turbine components from high temperature and allows further increase in engine operating temperature which subsequently increases the efficiency of the gas turbine power plant. However, the current TBC materials are capable of allowing the …