Materials Science and Engineering Commons^™

Synergistic And Antagonistic Effect Of Sulfur-Based Additives On The Performance Of Greases With Zddp And Ptfe, Arunya Suresh

Material Science and Engineering Theses - Archive

Lithium-base greases constitute about 50% of the grease market. The current trend is towards developing greases with longer working life and wider application flexibility. To address this concern, greases are blended with antiwear and extreme pressure (EP) additives that serve to reduce wear and increase the operating life of the machinery by creating a low strength, shearable film on the moving surfaces. In the current study, greases were developed to address the need for both performance as prescribed by the ASTM standards D2266 and D2596, respectively. The actual bearing conditions vary significantly with load, rpm and duration of test. These …

Corrosion And Leaching Study Of Low Copper (I) Oxide Paints For Antifouling Application, Hansika Parekh

Material Science and Engineering Theses - Archive

Global environmental concern/economy challenges necessitate innovation of AFP's with novel additives offering improved corrosion protection, and biofouling resistance. Dispersing large proportions (40-70%) of Cu/Cu2O in paints although inexpensive produces excessive leaching & heavy accumulation of copper in marine. This study aims at formulating AFP's with reduced Cu2O levels along with novel additives, targeting controlled copper release around 15 ug/cm2/day. In the present study several formulations were prepared using Viscoplex (PAMA in mineral oil), Ionomer ED-SPAN and CuDDP. Substitute ocean water was prepared to simulate marine environmental conditions and perform leaching studies of different formulations. A variety of preliminary elimination tests …

Solar Selective Optical Coating Made With Metal Nanopaticles For Photovoltaic Thermal Applications, Xin Wang

Material Science and Engineering Theses - Archive

The goal of this research is to fabricate solar selective reflector with suitable optical properties and high thermal and chemical stability for using in the photovoltaic thermal window. While the reflector allows some transmittance in visible spectrum, the mid/far infrared light needs to be reflected back into the window minimizing the IR radiation loss. Nickel/alumina composite was proposed as the solar selective reflector. This thesis consists of two parts - one part concerning the fabrication and characterization of solar selective reflector and another dealing with an optical modeling to simulate the optical properties of the solar selective reflector. The alumina …

Influence Of Magnesium Nitrate On The Corrosion Performance Of Sol-Gel Coated Aa2024-T3 Aluminium Alloy, Rajath Varma, Brendan Duffy, John Cassidy

Articles

Traditional anti-corrosion technology has relied heavily on using reducible metal species, predominantly hexavalent chromium (Cr(VI)), for protecting reactive metal alloys such as aluminium which is extensively used in the aerospace sector. However, the impending changes in the use of Cr(VI) in Europe and the United States have forced aerospace manufacturers to examine alternative materials for protecting aluminium. One of the most promising alternatives being investigated are organosilane based sol-gels containing anticorrosion additives. In this work the anti-corrosion properties of magnesium (II) nitrate (Mg(NO3)2) as a inhibitor was investigated at different concentrations (0.1% - 1.0 wt %) in a methyltriethoxysilane (MTEOS) …

Anti Wetting Additives For Aluminosilicate Refractories In Molten Aluminum Contact Applications, Devdutt Pramod Shukla

Doctoral Dissertations

"Aluminosilicate based refractories are widely used in furnace installations for melting aluminum because they are inexpensive, readily available and generally exhibit the properties desired from a refractory material. However, they face severe corrosion and degradation issues due to the extremely reducing nature of molten aluminum alloys. Isothermal static cup testing is widely used as a tool to evaluate the performance of refractories against penetration by molten aluminum alloys. Various testing methods were reviewed and an upgraded static cup test was recommended. Commercially available aluminosilicate refractories were tested using this method and their results were studied in order to understand the …

A Computational Study On Novel Carbon-Based Lithium Materials For Hydrogen Storage And The Role Of Carbon In Destabilizing Complex Metal Hydrides, Mohammed Minhaj Ghouri

Doctoral Dissertations

One of the major impediments in the way of the realization of hydrogen economy is the storage of hydrogen gas. This involves both the storage for stationary applications as well as that of storage onboard vehicles for transportation applications. For obvious reasons, the system targets for the automotive applications are more stringent. There are many approaches which are still being researched for the storage of hydrogen for vehicular applications. Among them are the high pressure storage of hydrogen gas and the storing of liquid hydrogen in super insulated cryogenic cylinders. While both of them have been demonstrated practically, the high …

Phase-Field Simulation Of Microstructural Development Induced By Interdiffusion Fluxes Under Multiple Gradients, Rashmi Mohanty

Electronic Theses and Dissertations

The diffuse-interface phase-field model is a powerful method to simulate and predict mesoscale microstructure evolution in materials using fundamental properties of thermodynamics and kinetics. The objective of this dissertation is to develop phase-field model for simulation and prediction of interdiffusion behavior and evolution of microstructure in multiphase binary and ternary systems under composition and/or temperature gradients. Simulations were carried out with emphasis on multicomponent diffusional interactions in single-phase system, and microstructure evolution in multiphase systems using thermodynamics and kinetics of real systems such as Ni-Al and Ni-Cr-Al. In addition, selected experimental studies were carried out to examine interdiffusion and microstructure …

Crystallography Open Database – An Open-Access Collection Of Crystal Structures, Saulius Grazulis, Daniel Chateigner, Robert T. Downs, A. F. T. Yokochi, Miguel Quirós, Luca Lutterotti, Elena Manakova, Justas Butkus, Peter Moeck, Armel Le Bail

Physics Faculty Publications and Presentations

The Crystallography Open Database (COD), which is a project that aims to gather all available inorganic, metal–organic and small organic molecule structural data in one database, is described. The database adopts an openaccess model. The COD currently contains 80,000 entries in crystallographic information file format, with nearly full coverage of the International Union of Crystallography publications, and is growing in size and quality.

Experimental Study Of The Response Of Semiconductor Detectors For Edxrf Analysis., Sunil Kumar Valaparla

Open Access Theses & Dissertations

This present work relates to the study and characterization of the response function of an energy-dispersive x-ray spectrometer. The problems of energy, efficiency and resolution calibration of the system operating in the energy (5-60 keV) range are discussed. We present the operation characteristics of the portable pyro-electric x-ray generator (COOL-X) and the application of the calibrated response spectrum in the elemental analysis using X-ray Fluorescence (XRF).

We study the response of the Si(Li)-Pin XR-100CR semiconductor detector to low energy photons. The photopeak efficiency was determined experimentally by using radioisotopes and compared against a theoretical efficiency curve. The efficiency for gamma …

Inclusion Modification In Steel Castings Using Automated Inclusion Analysis, Vintee Singh

Masters Theses

"The objective of this research is to study the effects of changing the melt and ladle practices (deoxidation, slag, refractory types, etc.) in steel foundries on the cleanliness and toughness of steel castings. This study used an automated inclusion analyzer ASPEX PICA-1020, which provides a rapid and accurate method for determining the composition, size, number, and spacing of the inclusions present in steel samples. The first step in this research was to complete a series of industrial tests to benchmark the current foundry ladle practices with respect to cleanliness of the cast steel. Trials were conducted at steel foundries using …

Three-Dimensional Hydrogel Cell Culture Systems For Modeling Neural Tissue, John P. Frampton

Legacy Theses & Dissertations (2009 - 2024)

Two-dimensional (2-D) neural cell culture systems have served as physiological models for understanding the cellular and molecular events that underlie responses to physical and chemical stimuli, control sensory and motor function, and lead to the development of neurological diseases. However, the development of three-dimensional (3-D) cell culture systems will be essential for the advancement of experimental research in a variety of fields including tissue engineering, chemical transport and delivery, cell growth, and cell-cell communication. In 3-D cell culture, cells are provided with an environment similar to tissue, in which they are surrounded on all sides by other cells, structural molecules …

Complex Electronic States In Double-Layered Ruthenates (Sr1−Xcax)3ru2o7, Zhe Qu, Jin Peng, David Fobes, Leonard Spinu, Zhiqiang Mao

Physics Faculty Publications

The magnetic ground state of (Sr_1−xCa_x)₃Ru₂O₇ (0≤x≤1) is complex, ranging from an itinerant metamagnetic state (0≤x<0.08) to an unusual heavy-mass nearly ferromagnetic (FM) state (0.08<x<0.4), and finally to an antiferromagnetic (AFM) state (0.4≤x≤1). In this report we elucidate the electronic properties for these magnetic states, and show that the electronic and magnetic properties are strongly coupled in this system. The electronic ground state evolves from an AFM quasi-two-dimensional metal for x=1.0 to an Anderson localized state for 0.4≤x<1.0 (the AFM region). When the magnetic state undergoes a transition from the AFM to the nearly FM state, the electronic ground state switches to a weakly localized state induced by magnetic scattering for 0.25≤x<0.4, and then to a magnetic metallic state with the in-plane resistivity ρ_ab∝T^α (α>2) for 0.08<x<0.25. The system eventually transforms into a Fermi-liquid ground state when the magnetic ground state enters the itinerant metamagnetic state for x<0.08. When x approaches the critical composition (x∼0.08), …

Characterization And Cytotoxic Assessment Of Ballistic Aerosolized Particulates For Tungsten Alloy Penetrators Interacting With Steel Targets, Brenda Ivette Machado

Open Access Theses & Dissertations

The aerosolized particulates produced during an impact of depleted uranium munitions can potentially contaminate extensive areas around the impact sites and cause a wide spectrum of civilian and military damage. Thus materials such as WHA have been prompted for consideration. The present research is concerned with the regular collection of aerosol particulates associated with ballistic WHA rod penetration into rolled homogeneous steel (RHA) or other related steel armor as armor plate sequences. Particulate size characterization via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) along with chemical compositions via energy dispersive spectroscopy (EDS) were the focus of this research. …

Fabrication And Characterization Of Zirconium Oxide Thin Films, Vemnkata Rama Sesha Ravi Kumar Vemuri

Open Access Theses & Dissertations

Zirconium oxide (ZrO2) is an important material with a potential for a wide range of technological applications. The outstanding chemical stability, electrical and mechanical properties, high dielectric constant, and wide band gap of ZrO2 make it suitable for several industrial applications in the field of optics, electronics, magneto-electronics, and optoelectronics. ZrO2 is frequently used as a high refractive index material in multilayer optical coatings in high power laser systems. ZrO2 is employed in super plastic structural ceramics that demonstrate excellent strength and fracture toughness. ZrO2 has been considered as a promising dielectric to replace SiO2 in advanced metal oxide semiconductor …

Metal Induced Crystallization Of Silicon Thin Films, Sandeep Kumar Raju Sangaraju

UNLV Theses, Dissertations, Professional Papers, and Capstones

Low temperature crystallization of thin film silicon is important for many industrial applications including flat panel displays and silicon thin film solar cells. Unfortunately this remains a major challenge since crystallization temperature of silicon is above 1,000 degrees Celsius, thus limiting to substrates that can tolerate high temperatures. The inability to deposit crystalline thin films on glass substrates is the reason why flat panel display industry uses amorphous silicon for LCD active matrix displays. Thus the ability to deposit crystallized thin film silicon at low temperatures will have significant impact on thin film silicon applications. It has been observed that …

Multicomponent Interdiffusion In Austenitic Ni-, Fe-Ni-Base Alloys And L12-Ni3al Intermetallic For High-Temperature Applications, Narayana Garimella

Electronic Theses and Dissertations

Interdiffusion in multicomponent-multiphase alloys is commonly encountered in many materials systems. The developments of multicomponent-multiphase alloys require control of microstructure through appropriate heat treatment, involving solid-state transformations, precipitation processes, and surface modification, where the interdiffusion processes play a major role. In addition, interdiffusion processes often control degradation and failure of these materials systems. Enhanced performance and reliable durability always requires a detailed understanding of interdiffusion. In this study, ternary and quaternary interdiffusion in Ni-Cr-X (X = Al, Si, Ge, Pd) at 900°C and 700°C, Fe-Ni-Cr-X (X = Si, Ge) at 900°C, and Ni3Al alloyed with Ir, Ta and Re at …

Formation Of Lyotropic Liquid Crystals Through The Self-Assembly Of Bile Acid Building Blocks, Karan Tamhane

Electronic Theses and Dissertations

Liquid crystalline materials (LCMs) have gained much popularity over the past century. The thermotropic forms of these materials have been extensively studied and employed in a range of innovative applications. The lyotropic liquid crystal systems that have been studied in the past have often been formed by the organization of natural and synthetic small molecules in solutions. In this study, we use self-assembled supramolecular structures as building blocks to fabricate lyotropic liquid crystals. We investigate the self-assembly of a naturally occurring bile acid called lithocholic acid (LCA), to form supramolecular fibrous and tubular structures in basic aqueous solutions. We control …

Electronic Properties And Microstructures Of Amorphous Sicn Ceramics Derived From Polymer Precursors, Tao Jiang

Electronic Theses and Dissertations

Polymer-derived ceramics (PDCs) are a new class of high-temperature materials synthesized by thermal decomposition of polymeric precursors. These materials possess many unique features as compared with conventional ceramics synthesized by powder metallurgy based processing. For example, PDCs are neither amorphous nor crystalline. Instead, they possess nano-domain structures. Due to the direct chemical-to-ceramic processing, PDCs can be used for making components and devices with complex shapes. Thus, understanding the properties and structures of these materials are of both fundamental and practical interest. In this work, the structures and electronic behavior of polymer-derived amorphous silicon carbonitrides (SiCNs) were investigated. The materials were …

Characterization And Aqueous Colloidal Processing Of Tungsten Nano-Powders, Zhengtao Yang

Electronic Theses and Dissertations

Extensive attention has been paid to consolidate nanoparticles into nanocrystalline components that possess better properties than their coarse-grained counterparts. Nanocrystalline monolithic tungsten (W) has been envisaged to possess better properties than coarse-grained tungsten and to improve the performance of many military components. Commercially available nano-W powders were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and Brunauer, Emmett, and Teller (BET) measurement. While the bulk of nano-W powders consisted of bcc-W as confirmed by XRD and TEM, much of their surface consisted of WO3 with traces of …

Sintering Additives For Nanocrystalline Titania And Processing Of Porous Bone Tissue Engineering Scaffolds, Arun Menon

Electronic Theses and Dissertations

Titania (Titanium dioxide, TiO2) has been researched as a promising biomaterial due to its excellent biocompatibility. However, the main limitation of titania is its poor mechanical properties which limit its use in many load-bearing applications. In this thesis report, the properties of titania were improved by doping with small quantities of MgO, ZnO and SiO2 as sintering additives. Nanocrystalline powder was selected, as it possesses outstanding properties over conventional coarse-grained powders due to reduced grain size. Nanocrystalline anatase powder of size 5-15 nm was synthesized via a simple sol-gel technique. Small quantities of dopants were introduced into pure titania powder, …

Classical Size Effect In Copper Thin Films: Impact Of Surface And Grain Boundary Scattering On Resistivity, Tik Sun

Electronic Theses and Dissertations

Surface and grain boundary electron scattering contribute significantly to resistivity as the dimensions of polycrystalline metallic conductors are reduced to, and below, the electron mean free path. A quantitative measurement of the relative contributions of surface and grain boundary scattering to resistivity is very challenging, requiring not only the preparation of suitably small conductors having independent variation of the two relevant length scales, namely, the sample critical dimension and the grain size, but also independent experimental quantification of these two length scales. In most work to date the sample grain size has been either assumed equal to conductor dimension or …

Quench Factor Analysis Of Wrought And Cast Aluminum Alloys, Vishwanath Gandikota

Masters Theses

"Mechanical property variation across the cross section of heat treatable aluminum alloys is a major concern. To minimize such variation, a proper understanding of kinetic transformations and estimation of mechanical properties is required. The Jominy end quench test has been used successfully to study the effect of quench rate on the final heat treated properties of wrought and cast aluminum alloys. This test produces varying cooling rates along the length of a cylindrical sample cooled with water at one end. Jominy bars of wrought and cast aluminum alloys were solutionized, endquenched, and aged to T6 temper condition after delays of …

Morphology And Cathode Optimization For Efficient Polymer Bulk Heterojunction Solar Cells, Yi Yang

Material Science and Engineering Theses - Archive

Efficiency of polymer bulk heterojunction solar cell is highly dependent on the active layer morphology and can be controlled by specific experimental conditions. In this work, the influences of P3HT:PCBM blend composition, solution concentration, and the thermal annealing on the cell performance are presented. The maximum of Jsc and FF are reached when the weight percentage of PCBM in the blend is 60 % under which both high density of donor and accepter interfaces expecting the formation of efficient percolated electron transport paths. 36 mg/ml is found to be the optimum solution concentration for P3HT:PCBM blend and it can be …

Effect Of Aging On The Transformation Of Phases In Solder Joint Of Pbga Packaging, Jeong-Min Kim

Material Science and Engineering Theses - Archive

This study investigates the microstructural characteristics of 3.0Ag-0.5Cu-Sn (SAC305) solder joint as in assembled state, and their evolution with aging treatment at 100 and 150°C for various hours. Specific aim of the study is 1) to understand thermodynamic stability of as-reflowed microstructure (β-Sn dendrite, inner dendrite Cu6Sn5 intermetallic (IMC) compound, and the eutectic structure), 2) to find direction of their change with aging, and 3) to relate interfacial reaction to such evolution in microstructures. This investigation is spurred by the findings made in a separate study where fatigue resistance of solder joint and failure location shows markedly keen dependence on …

Structural, Magnetic And Surface Properties Of Rf Magnetron Sputtered Undoped Lanthanum Mangnite Thin Films, Varad Rajan Sakhalkar

Material Science and Engineering Theses - Archive

In the present study, polycrystalline and epitaxial undoped Lanthanum Manganite (LMO) thin films were deposited by using RF magnetron sputtering on three substrates, Si (100), MgO (100) and LaAlO₃ (100) to study the influence of the misfit strain at the substrate/film interface. The effect of processing conditions on the synthesis of LMO films was studied by conducting deposition on Si wafer. Films were characterized by X-Ray Diffraction (XRD), Atomic Force Microscope (AFM), Energy Dispersive Spectroscopy (EDS) and Superconducting Quantum Interference Device (SQUID) to investigate the influence of processing parameters on their structure and properties. Based on the initial study on …

Maxwell Garnett Rule For Dielectric Mixtures With Statistically Distributed Orientations Of Inclusions, Marina Koledintseva, Richard E. Dubroff, Robert W. Schwartz

Electrical and Computer Engineering Faculty Research & Creative Works

An analytical model of an effective permittivity of a composite taking into account statistically distributed orientations of inclusions in the form of prolate spheroids will be presented. In particular, this paper considers the normal Gaussian distribution for either zenith angle, or azimuth angle, or for both angles describing the orientation of inclusions. The model is an extension of the Maxwell Garnett (MG) mixing rule for multiphase mixtures. The resulting complex permittivity is a tensor in the general case. The formulation presented shows that the parameters of the distribution law for orientation of inclusions affect the frequency characteristics of the composites, …

Low-Temperature Growth Of Inn On Si(100) By Femtosecond Pulsed Laser Deposition, M. A. Hafez, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

InN films were grown on Si(100) using femtosecond pulsed laser deposition. Laser induced breakdown of ammonia was used to generate atomic nitrogen for InN growth. An indium buffer layer was initially deposited on the Si substrate at low temperature followed by an InN intermediate layer. The crystal quality and surface morphology were investigated by reflection high-energy electron diffraction during growth and atomic force microscopy and x-ray diffraction after growth. The results showed that the In (2×1) initial buffer layer improved the quality of the InN film. High quality InN films were grown at a temperature of ∼350 °C.

Electronic And Structural Properties Of Molybdenum Thin Films As Determined By Real Time Spectroscopic Ellipsometry, J. D. Walker, H. Khatri, V. Ranjan, Jian Li, R. W. Collins, S. Marsillac

Electrical & Computer Engineering Faculty Publications

Walker, J.D., Khatri, H., Ranjan, V., Li, J., Collins, R.W., & Marsillac, S. (2009). Electronic and structural properties of molybdenum thin films as determined by real-time spectroscopic ellipsometry. Applied Physics Letters, 94(14). doi: 10.1063/1.3117222

Yttrium And Hydrogen Superstructure And Correlation Of Lattice Expansion And Proton Conductivity In The Bazr0.9y0.1o2.95 Proton Conductor, A. Braun, A. Ovalle, V. Pomjakushin, A. Cervellino, S. Erat, Wayne C. Stolte, T. Graule

Chemistry and Biochemistry Faculty Research

Bragg reflections in Y-resonant x-ray diffractograms of BaZr_0.9Y_0.1O_2.95 (BZY10) reveal that Y is organized in a superstructure. Comparison with neutron diffraction superstructure reflections in protonated/deuterated BZY10 suggests that both superstructures are linked, and that protons move in the landscape imposed by the Y. The thermal lattice expansion decreases abruptly for protonated BZY10 at T≥648±20 K, coinciding with the onset of lateral proton diffusion and suggesting a correlation of structural changes and proton conductivity. The chemical shift in the Y L₁-shell x-ray absorption spectra reveals a reduction from Y³⁺ toward Y²⁺ upon …

Preliminary Investigation Of Metallurgical Structure And Mechanical Properties Of Cast Iron With High Aluminum Content, Pavel Bizyukov

Dissertations and Theses @ UNI

The problem addressed in this study analyzed various properties of cast iron with high aluminum content. This grade of cast iron was projected for use in the automotive industry. The benefits provided with high aluminum content are lower specific gravity and relatively inexpensive source materials with the potential of achieving high temperature properties.

The purpose of the study was to select suitable source materials and determine an effective melting technique, to investigate metallurgical structure and mechanical properties at given chemical composition, and, finally, to provide elaborate results.

The design of the experiment included the following steps: (a) selection and preparation …