Materials Science and Engineering Commons^™

Rbd2po4: Room Temprature Synthesis, Chemical And Structural Stablity Upon Heating, Masoud Mollaee

Open Access Theses & Dissertations

Monoclinic RbD2PO4 polycrystals were synthesized via the room temperature crystallization of RbH2PO4 dissolved in D2O. Powder x-ray diffraction (XRD) data collected at T=25 ºC indicate that this deuterated compound crystallizes in space group P21/m with unit cell parameters a=7.688í?, b=6.192í?, c=4.781í? and β=109.02°, and is isomorphic with the intermediate-temperature phase of its hydrogenated counterpart rubidium dihydrogen phosphate (RDP). We found no evidence of previously reported [Phase Transitions 80, 17 (2007)] polymorphic phase transition in rubidium dideuterium phosphate (DRDP) upon heating from room temperature to 210 ºC. All lattice parameters vary smoothly within this temperature range, demonstrating that the P21/m phase …

Thin Film Growths Of Znte And Cdte On Various Substrates Using A Novel Close Space Sublimation Reactor Css4, Damian Marrufo

Open Access Theses & Dissertations

Thin films of CdTe have been grown on CdS in a variety of methods for use in thin film photovoltaic systems. Limits to the efficiency of CdTe/CdS solar cells have been attributed to defects in the lattice that occur between the interface of CdS and CdTe due to a lattice mismatch. A close space sublimation (CSS) reactor known as the CSS4 was designed and fabricated in UTEP to deposit complex layers of CdTe and ZnTe on top of a CdS film that is grown via chemical bath deposition in order to obtain a CdTe photovoltaic. Unfortunately, the original design and …

A Novel Method For The Curing Of Metal Particle Loaded Conductive Inks And Pastes, David Adrian Roberson

Open Access Theses & Dissertations

The emerging technology of printed microelectronics involving the use of conductive inks in conjunction with standard printing techniques offers a fast and low waste method for creating microelectronics compared with standard manufacturing processes. A clear path to the creation of flexible electronics is present due to the ease of printing on flexible substrates. Moreover, creation of novel 3D structural electronics is possible via the integration of printing technologies and additive manufacturing (AM) techniques.

A key obstacle to the manufacturing of flexible and structural electronics comes from the temperature restrictions imposed by the substrates, which are typically polymeric. This hindrance has …

Structure Morphology And Optical Properties Of Nanocrystalline Ga2o3 Thin Films, Sampath Kumar Samala

Open Access Theses & Dissertations

Gallium Oxide thin films were produced by sputter deposition by varying the substrate temperature (T_s) in a wide range (T_s=25-800 oC) and under variable deposition time. The structural characteristics and optical properties of Ga₂O₃ films were evaluated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), Rutherford backscattering spectrometry (RBS) and spectrophotometric measurements. The effect of growth temperature is significant on the chemistry, crystal structure and morphology of Ga₂O₃ films. XRD and SEM analyses indicate that the Ga₂O₃ films grown at lower temperatures were …

The Effect Of Al, Mo, And B On The Oxidation Behavior Of Three Nb-Based Alloys, Victoria Rae Rangel

Open Access Theses & Dissertations

Extensive work has been undertaken to develop niobium based structural alloys for high temperature applications. These developments have led to the increase in engine operating temperatures and better performance efficiency. New materials including alloys based on metals with higher melting points such as molybdenum and niobium with silicon are now being examined as a better alternative to nickel base superalloys. Materials with a niobium silicide based composites have the potential for higher temperature capabilities. The oxidation behavior of Nb-20Cr-10Si and Nb-20Cr-10Si-5Al has been studied in a range of temperature from 700 to 1400°C in static air. Isothermal oxidation experiments indicate …

The Effects Of Uncommon Silicides On The Oxidation Of Alloys From The Nb-Cr-Si System, Daniel Brendan Voglewede

Open Access Theses & Dissertations

Niobium based alloys are being tapped as potential successors to current nickel base superalloys in high temperature applications. In the aerospace industry, high temperature materials are constantly being pushed to higher temperature regimes in order to improve engine efficiency however current superalloys cannot be pushed further due to melting temperature limitations. Niobium, being a refractory metal, can withstand much higher temperatures than nickel however its oxidation properties are woefully inadequate.

The purpose of this study is to ascertain whether increased silicon additions can improve niobium oxidation properties by: forming ternary silicides with better oxidation properties and by preventing the formation …

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 …

Development Of Advanced Polymer Nanocomposite Capacitors, Miguel Mendoza

Open Access Theses & Dissertations

The current development of modern electronics has driven the need for new series of energy storage devices with higher energy density and faster charge/discharge rate. Batteries and capacitors are two of the most widely used energy storage devices. Compared with batteries, capacitors have higher power density and significant higher charge/discharge rate. Therefore, high energy density capacitors play a significant role in modern electronic devices, power applications, space flight technologies, hybrid electric vehicles, portable defibrillators, and pulse power applications. Dielectric film capacitors represent an exceptional alternative for developing high energy density capacitors due to their high dielectric constants, outstanding breakdown voltages, …

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 …

Applications Of Density Functional Theory In Materials Science And Engineering, Manuel Alvarado

Open Access Theses & Dissertations

Density Functional Theory (DFT) is a powerful tool that can be used to model various systems in materials science. Our research applies DFT to two problems of interest. First, an organic/inorganic complex dye system known as a Mayan pigment is modeled to determine chemical binding sites, verifying each model with physical data such as UV/Vis spectra. Preliminary studies on palygorskite-based mayan pigments (mayacrom blue, mayacrom purple) show excellent agreement with experimental studies when using a dimer dye geometry binding with tetrahedrally-coordinated aluminum impurity sites in palygorksite. This approach is applied to a sepiolite-based organic/inorganic dye system using thioindigo attached to …

Raman And Infrared Study Of Electrospun Plla/Pcl Nanofiber Blends For Use In Tissue Engineering, Jose Luis Enriquez Carrejo

Open Access Theses & Dissertations

Recently, the biomedical engineering field has developed at a very fast pace as improved techniques and materials become available to promote its growth. Consequently, the research in polymeric biomaterials has been highly stimulated by this trend. The goal of the current research is to demonstrate the usefulness of the Raman scattering, Raman mapping, and infrared absorption spectroscopies to tissue engineering, by spectroscopically characterizing blends of PLLA and PCL polymers, which were prepared by electrospinning with and without cell addition. The proposed use of these blends is as primary biomaterials in biodegradable scaffolds used in tissue engineering. Both Raman and infrared …

Development Of A Multi-Material, Multi-Technology Fdm System For Process Improvement Experimentation, David Espalin

Open Access Theses & Dissertations

Over the last three decades, developments within the area of Additive Manufacturing (AM) have resulted in novel technologies capable of producing highly customized, complex part geometries in a fraction of the lead time required by traditional manufacturing methods (e.g., injection molding, metal casting). In particular, fused deposition modeling (FDM), a material extrusion AM process, can produce parts using production-grade thermoplastics like acrylonitrile butadiene styrene, polycarbonate, and polyetherimide. Additionally, non-commercial materials (e.g., polycaprolactone, ceramic loaded polymers, carbon nanotube loaded polymers) have been processed using FDM in part to demonstrate the potential diversity in material selection.

Recently, a myriad of personal 3D …

The Effect Of Al And B Additions On The Oxidation Behavior Of Alloys From The Nb-Cr-Si System, Nydia Judit Esparza

Open Access Theses & Dissertations

Nickel based superalloys have been developed to perform substantially in industry however as technology develops, the need and desire to increase service temperatures to improve efficiency and performance is pushing the capabilities of these alloys. These aspired requirements entail the research and development of new structural materials that surpass the abilities of nickel alloys. Research in Nb-based alloys is underway as Nb alloys have shown to be a promising alternative with similar density but higher melting temperatures than the Ni alloys. However, because Nb has poor oxidation properties extensive studies are necessary to develop an alloy that can perform as …

A Study Of Wo3 And W0.95ti0.05o3 Thin Films Using Comparative Spectroscopy, James Heyward Howard

Open Access Theses & Dissertations

Tungsten oxide (WO3) is important and well-studied in materials science, particularly for sensor applications. In this research work, we consider the innovation of adding Ti to thin films of this material. Since the characteristics of any such material are strongly dependent on the conditions and methods used in its deposition, the main objective of this project is to provide a detailed spectroscopic characterization by Raman scattering, infrared absorption, and X-ray photoelectron spectroscopy (XPS) of WO3 and of W0.95Ti0.05O3. This characterization will be based on comparison of the morphology and composition of WO3-based thin films, grown by radio frequency magnetron reactive …

Development Of Nanocomposites For Energy Storage Devices, Md Ashiqur Rahaman Khan

Open Access Theses & Dissertations

With the ever-increasing need in improving the performance and operation life of future mobile devices, developing higher power density energy storage devices has been receiving more attention. Lithium ion battery (LIB) and capacitor are two of the most widely used energy storage devices and have attracted increasing interest from both industrial and academic fields. Batteries have higher power density than capacitor but significantly longer charge/discharge rates. In order to further improve the performance of these energy storage devices, one of the approaches is to use high specific surface area nano-materials. Among all the nano-materials developed so far, one-dimensional nanowires are …

Nanoprobe I-V Characterization Of Cdte/Cds Micro And Nano-Patterned Solar Cells, Heber Prieto

Open Access Theses & Dissertations

This thesis presents a novel way to characterize micro and nano patterned cadmium telluride thin film solar cells via a nano-probe system. A historical review of CdTe-based solar cells is presented first followed by review of the technology developed to produce the patterned CdTe cells. A detailed presentation is then provided on the use of a Zyvex nanoprobing system to characterize the patterned solar cells. The I-V response of micro- and nano-patterned solar cells stimulated under different e-beam conditions is presented and analyzed. Suggestions of how to improve the technique are provided. This work documents, for the first time, the …

The Influence Of Build Parameters On The Microstructure During Electron Beam Melting Of Ti6al4v, Karina Puebla

Open Access Theses & Dissertations

With the demand of devices to replace or improve areas, such as: electronic, biomedical and aerospace industries. Improvements in these areas of engineering have been in need due to the customer’s needs for product properties requirements. The design of components must exhibit better material properties (mechanical or biocompatible) close to those of any given product. Rapid prototyping (RP) technologies that were originally designed to build prototypes may now be required to build functional end-use products. To carry out the transition, from RP to rapid manufacturing (RM), the available materials utilized in RP must provide the performance required for RM. The …

Oxidation Of Borides And Carbides With Y2o3 And Ta Additions, Salvador Manuel Rodriguez

Open Access Theses & Dissertations

The study presented here describes an investigation of an oxidation scale of a fully-sintered Y2O3-ZrB2-TiC composite exposed in air at 1173K. Upon oxidation of the boride/carbide, a ZrO2-TiO2 was expected to form similar to the ZrO2-SiO2 dual scale of an oxidized ZrB2-SiC. The 47wt% Y2O3-38wt%ZrB2-16wt%TiC composite formed a dual scale consisting primarily of an Y2O3-ZrO2-TiC inner scale with an outer scale of ZrO2-TiO2-Y2O3.

The samples oxidized with a parabolic layer growth allowing the calculation of the effective diffusion coefficient indicating that the oxidation was controlled by oxygen ingress through primarily the ZrO2-Y2O3 phase. The oxygen potential between the inner layer …

Preparation And Characterization Of Iron Oxide And Hydroxide Based Nanomaterials, Guillermo Carbajal Franco

Open Access Theses & Dissertations

Iron (Fe) oxides and hydroxides are common and abundant materials. They exhibit diverse crystal structures, properties and phenomena by virtue of which they find a wide range of scientific and technological applications. Controlled growth and manipulation of the specific structure and electronic behavior to meet the requirements of a given application is a challenging problem in view of many possible phases and composition of the resulting materials. The preparation method and experimental conditions will, therefore, significantly affect the properties and performance of Fe oxides and hydroxides. The goal of the project is to obtain Fe-based oxide/hydroxide catalytic materials and to …

Fundamental Studies Of Co-Base Superalloy Biomedical Prototypes Fabricated By Electron Beam Melting: Microstructures And Microstructural Architecture, Sara M. Gaytan

Open Access Theses & Dissertations

Rapid prototyping, especially electron beam melting (EBM) technology by ARCAM have proven to provide outstanding microstructural and mechanical properties on different alloys fabricated by this technology. Being a computer designed driven technology, complex components, that are hard or even impossible to fabricate by traditional manufacturing techniques, can be fabricated by layer-by-layer EBM technology.

Microstructural and mechanical properties are compared for an EBM femoral knee component prototype with a traditionally-fabricated and body-removed femoral knee implant. Block and cylindrical shape components fabricated by EBM were also analyzed for this project. The alloy utilized for these components is Co-26Cr-6Mo-0.2C characterized by the standards …

Ballistic Projectile Metallurgical Issues And Fundamentals: Aerosol Production In Rod Penetration Erosion And Erosion Phenomena Associated With Railgun Development, Brenda Ivette Machado

Open Access Theses & Dissertations

The issue is derived from ballistic erosion as it relates to nanoparticle production and respiration of these particles as a health concern ballistic erosion and ballistic erosion as it relates to railgun performance. A common thread between these two issues is dynamic recrystallization (DRX). DRX has been demonstrated to be the dominant mechanism for solid-state flow associated with ballistic projectile/target penetration and interaction, friction-stir welding phenomena, and other high-strain rate deformation phenomena.

Aerosol particulates collected on filters from ballistic penetration and erosion events for W-Ni-Co and W-Ni-Fe kinetic energy rod projectiles penetrating steel target plates were observed to be highly …

Microstructural Architecture Developed In The Fabrication Of Solid And Open-Cellular Copper Components By Additive Manufacturing Using Electron Beam Melting, Diana Alejandra Ramirez

Open Access Theses & Dissertations

The fabrication of Cu components were first built by additive manufacturing using electron beam melting (EBM) from low-purity, atomized Cu powder containing a high density of Cu2O precipitates leading to a novel example of precipitate-dislocation architecture. These microstructures exhibit cell-like arrays (1-3µm) in the horizontal reference plane perpendicular to the build direction with columnar-like arrays extending from ~12 to >60 µm in length and corresponding spatial dimensions of 1-3 µm. These observations were observed by the use of optical metallography, and scanning and transmission electron microscopy. The hardness measurements were taken both on the atomized powder and the Cu components. …

Effect Of Process Parameter On Temperature Distribution, Microstructure, And Mechanical Properties Of Self-Reacting Friction Stir Welded Aluminum Alloy 6061-T651, Monica Adriana Torres

Open Access Theses & Dissertations

Self-reacting friction stir welding is the latest FSW tool configuration developed, it employs two shoulders--one on top and one on the bottom of the workpiece-- this tool configuration offers many advantages over conventional welding techniques. However, the current lack of information and specifications limits its understanding and application. This investigation analyzed the effect of process parameters on temperature distribution, microstructure evolution, and final mechanical properties of 6061-T651 SR-FS welds. A factorial experiment was carried out, in which three-process parameters were analyzed--rotational speed, travel speed, and tool plunge force-- three levels were analyzed for each parameter, except for a tool plunge …

Fabrication And Characterization Of Nanocrystalline Yttrium Oxide Thin Films For Electronic Device Applications, Mudavakkat Vikas Haridas

Open Access Theses & Dissertations

This thesis presents the optimization of growth conditions for fabricating nanocrystalline Yttrium Oxide (Y2O3) thin films on silicon and optical grade, high quality quartz substrates in order to study its structural, optical and electrical properties for electronic device applications.

Commercially Y2O3 has proven to be difficult to fabricate at high quality due to its high temperature growth requirements and the need to alter established fabrication methods for electronic devices. A high temperature requirement for high quality poses a problem for research and analysis. This calls upon for an optimization of the growth conditions to facilitate fabrication of thin films for …

The Effect Of Cr, Si And B On The Oxidation Behavior On Three Nb-Based Alloys, David Alvarez

Open Access Theses & Dissertations

Nb-based alloys are of particular interest to replace the current Ni-based superalloys for high-temperature structural applications. One important limitation to improve the efficiency of gas-turbine engines is the temperature limit of current materials being used. By allowing the temperature to increase, the efficiency will increase. Nb-based alloys have high melting points and adequate mechanical properties but the oxidation resistance is still inadequate.

This research focuses on the oxidation behavior of three Nb-based alloys to study the effect of Cr and Si variation and look at the effect of Boron. Boron can form a glassy borosilicate which is viscous at high …

Development And Characterization Of The Oxidation Behavior Of Various High Temperature Niobium Based Alloys, Benedict Isabel Portillo

Open Access Theses & Dissertations

The oxidation response of various niobium based refractory alloys from the Nb-Mo-Si-B-X alloy system has been examined at temperatures between 700 and 1400°C in air. The development of these alloys was part of an ongoing effort to develop and discover a new materials system capable of replacing nickel based super alloys. Additions of titanium were found to provide limited oxidation resistance. A discontinuous layer of TiO2 was observed to from at temperatures above 1100°C. Alloys containing titanium additions were observed to suffer from pest oxidation at low and intermediate temperatures due to the development of Nb2O5. Poor oxidation resistance at …

An Ab-Initio Study Of The Elastic Properties Of Important Group Iv Diborides At High Temperatures, Manny Gonzales

Open Access Theses & Dissertations

Presented is an ab-initio Molecular Dynamics (MD) study, employing the Density Functional Theory (DFT), of the lattice parameter, thermal expansion coefficients and elastic constants of ZrB₂, TiB₂ and HfB₂ as a function of temperature. The MD trajectories provide the equilibrium lattice parameters at finite temperatures, and the gradient of the energy from these equilibrium solutions is then used to calculate the components of the stiffness tensor. The results for ZrB₂ are shown to agree well with reported experimental results for the lattice parameters and elastic constants as a function of temperature.

Sensitivity Analysis Of The Johnson-Cook Plasticity Model For Hypervelocity Impacts: A Hydro-Code Study, Carlos David Castellanos

Open Access Theses & Dissertations

Computer simulations have been in use for decades in the modeling of hypervelocity impacts and general large deformation problems. Several computer codes have been developed to simulate this type of problems under a variety of geometric configurations and for any number of materials. These codes make use of several constitutive material models to simulate the response of the material under a variety of thermo-mechanical conditions. The Johnson-Cook constitutive model is widely used in the simulation hypervelocity impacts for the simulation of crater formation and even perforation of target structures. This thesis presents the results of a sensitivity study of this …

Selection Process, Modified Impact Testing And Failure Analysis Of An Electron-Beam-Melted Ti-6al-4v 3d Tessellation Based On The Eulerian Path Of The First Stellation Of The Rhombic Dodecahedron Open Unit Cell, Hugo Lopez

Open Access Theses & Dissertations

Ti-6Al-4V lattice block structures manufactured through the electron beam melting (EBM) process are a promising field in design and research due to great advantages that the alloy, the process and the final product offer. Three lattice block structures were manufactured through the electron beam process using an ARCAM A2 machine. The structures were designed using the MATERIALIZE^TM software and were designed around different types of unit cells. Compression testing was performed and one unit cell was selected due to its anisotropic behavior for modified impact testing. The same unit cell was used and it was scaled up to add …

Processing Of Zrb2-Zrc-Zrxsiy Ceramic By Reactive Metal Penetration, Nischel B. Maheswaraiah

Open Access Theses & Dissertations

The processing of ZrB2-ZrC-ZrxSiy composite by reactive metal penetration was investigated as a successor to the ZrB2-SiC composites for hypersonic vehicles application, which cannot be used for extended time at temperatures greater than 1600C due to formation of SiO and CO gases. Zirconium (Zr), zirconium disilicide (ZrSi2), and boron carbide (B4C) were reacted in graphite crucibles for 60, 120, 180, and 240 minutes. Microscopy and x-ray diffraction (XRD) deduced the formation of a heterogeneous microstructure of ZrB2-ZrC-ZrxSiy precipitates surrounded by a solidified Zr-Si melt. Unreacted boron carbide was observed in samples held at 1860C for 60 minutes and 120 minutes, …