Engineering Commons^™

Etching With Electron Beam Generated Plasmas, D. Leonhardt, Scott G. Walton, Christopher Muratore, Richard F. Fernsler, R. A. Meger

Chemical and Materials Engineering Faculty Publications

A modulated electron beam generated plasma has been used to dry etch standard photoresist materials and silicon. Oxygen–argon mixtures were used to etch organic resist material and sulfur hexafluoride mixed with argon or oxygen was used for the silicon etching. Etch rates and anisotropy were determined with respect to gas compositions, incident ion energy (from an applied rf bias) and plasma duty factor. For 1818 negative resist and i-line resists the removal rate increased nearly linearly with ion energy (up to 220 nm/min at 100 eV), with reasonable anisotropic pattern transfer above 50 eV. Little change in etch rate was …

Effect Of Plasma Flux Composition On The Nitriding Rate Of Stainless Steel, Christopher Muratore, Scott G. Walton, D. Leonhardt, Richard F. Fernsler, David D. Blackwell, R. A. Meger

Chemical and Materials Engineering Faculty Publications

The total ion flux and nitriding rate for stainless steel specimens exposed to a modulated electron beam generated argon-nitrogen plasma were measured as a function of distance from the electron beam axis. The total ion flux decreased linearly with distance, but the nitriding rate increased under certain conditions, contrary to other ion flux/nitriding rate comparisons published in the literature. Variation in ion flux composition with distance was explored with a mass spectrometer and energy analyzer as a possible explanation for the anomalous nitriding rate response to ion flux magnitude. A transition in ion flux composition from mostly N2 1 to …

Modeling, Fabrication, And Optimization Of Niobium Cavities, Robert A. Schill Jr., Mohamed Trabia, William Culbreth

Transmutation Sciences Materials (TRP)

One of the key technologies for the deployment of acceleratordriven transmutation systems is the accelerator itself. Elliptical superconducting niobium cavities are used to increase the efficiency of the high-power accelerators needed to support the transmutation mission.

One of the major sources of energy loss from a superconducting accelerator cavity is a process known as multiple impacting (or “multipacting”) of electrons. This phenomenon limits the maximum amount of energy and power that the niobium cavity can store. As a result, the maximum power available for accelerating the desired charge, as well as the overall performance of the accelerator is reduced. Furthermore, …

Fundamental And Applied Experimental Investigations Of Corrosion Of Steel By Lbe Under Controlled Conditions: Kinetics, Chemistry, Morphology, And Surface Preparation: Quarterly Report, Allen L. Johnson, John Farley, Dale L. Perry

Transmutation Sciences Materials (TRP)

This project has four components:

(1) the fabrication of a materials test apparatus with unique capabilities,

(2) comparative studies of steel corrosion under gas phase conditions comparable to the Lead Bismuth Eutectic (LBE) oxygen control conditions,

(3) isotope labeling studies, and

(4) collaborative efforts with other workers in the field.

Development Of Titanium Nitride/Molybdenum Disulphide Composite Tribological Coatings For Cryocoolers, Anil Pai

Electronic Theses and Dissertations

Hydrogen is a clean and sustainable form of carrier of energy that can be used in mobile and stationary applications. At present hydrogen is produced mostly from fossil sources. Solar photoelectrochemical processes are being developed for hydrogen production. Storing hydrogen can be done in three main ways: in compressed form, liquid form and by chemical bonding. Near term spaceport operations are one of the prominent applications for usage of large quantities of liquid hydrogen as a cryogenic propellant. Efficient storage and transfer of liquid hydrogen is essential for reducing the launch costs. A Two Stage Reverse Turbo Brayton Cycle (RTBC) …

Phenomenology And Experimental Observations In High Temperature Ternary Interdiffusion, Abby Lee Elliott

Electronic Theses and Dissertations

A new method to extract composition dependent ternary interdiffusion coefficients from a single diffusion couple experiment is presented. The calculations involve direct determination of interdiffusion fluxes from experimental concentration profiles and local integration and differentiation of Onsager's formalism. This new technique was applied to concentration profiles obtained from selected semi-infinite, single-phase diffusion couple experiments in the Cu-Ni-Zn, Fe-Ni-Al, and Ni-Cr-Al systems. These couples exhibit features such as uphill diffusion and zero flux planes. The interdiffusion coefficients from the new technique along with coefficients reported from other methods are graphed as functions of composition. The coefficients calculated from the new technique …

Synthysis Of Polymer/Nano-Droplet Composites From Reverse Microemulsion Polymerization, Liehui Ge

Master's Theses and Doctoral Dissertations

L₁ and L₂ domains of the water/AOT/MMA ternary system were investigated at 22±1°C. Free radical polymerizations were conducted in L₂ domain. Only opaque polymer rods were obtained. Acrylamide, a water soluble monomer, plays a role of co-surfactant which greatly expands the L₂ domain. However, polymerizations only yielded opaque material. SEM showed images of phase separation.

MDOS (2-Methacryloyloxy)ethyl trimethylammonium bis(2-ethylhexyl) sulfosuccinate, was synthesized by ion exchange method. L₁ and L₂ domains of the water/MDOS/MMA ternary system were also investigated at 22±1°C. Free radical polymerizations were conducted in L₂ domain. Transparent polymer was produced. The …

Chemical Solution Deposition Of Electronic Oxide Films, Robert W. Schwartz, Theodor Schneller, Rainer Waser

Materials Science and Engineering Faculty Research & Creative Works

The chemical solution deposition (CSD) technique as a highly flexible method for the fabrication of electronic oxide thin films is reviewed. Various chemical aspects of different approaches are discussed, including sol-gel, hybrid, and metallo-organic decomposition (MOD) routes, which all have been successfully applied for the deposition of this class of materials. Principles of the selection and properties of the educts, the mechanism of film crystallization, and tailoring of microstructure through manipulation of deposition parameters are reported. the role of thermodynamics on the phase transformation process is also reviewed. Finally, some of the applications for chemical solution-derived thin films currently under …

Thermal Efficiency Of Steel Melting, Kent D. Peaslee, Semen Naumovich Lekakh, Bradley Randall

Materials Science and Engineering Faculty Research & Creative Works

This paper presents the results of energy consumption measurements at steel foundries using induction and/or electric arc furnace melting. Statistical methods, infrared thermography, and numerical investigations were used for analysis of heat losses. The influence of different melting practices on energy losses was examined. Industrial experiments in isothermal holding of liquid steel in induction furnaces under different power inputs were used for evaluation of the real values of heat losses by radiation from liquid steel and conductivity through lining. Average values and statistical distributions of energy consumptions for melting steel are presented in this article.

Evaluation Of Microstructure And Superplasticity In Friction Stir Processed 5083 Al Alloy, Indrajit Charit, Rajiv S. Mishra

Materials Science and Engineering Faculty Research & Creative Works

Friction stir processing (FSP) has been developed as a potential grain refinement technique. In the current study, a commercial 5083 Al alloy was friction stir processed with three combinations of FSP parameters. Fine-grained microstructures with average grain sizes of 3.5-8.5 µm were obtained. Tensile tests revealed that the maximum ductility of 590 was achieved at a strain rate of 3 x 10^-3 s^-1 and 530 °C in the 6.5-µm grain size FSP material, whereas for the material with 8.5-µm grain size, maximum ductility of 575 was achieved at a strain rate of 3 x 10^-4 s^{-1 …}

High Gradient Multilayer Insulator Technology, Harlan U. Anderson, Stephen E. Sampayan, G. J. Caporaso, W. C. Nunnally, D. M. Sanders, J. A. Watson, Mike L. Krogh

Materials Science and Engineering Faculty Research & Creative Works

We are investigating a novel insulator concept that involves the use of alternating layers of conductors and insulators with periods less than 1 mm. These structures perform 1.5 to 4 times better than conventional insulators in long pulse, short pulse, and alternating polarity applications. We have surveyed our ongoing studies by investigating the performance under long pulse electron beam, short pulse, and full reversing conditions.

Ferroelectricity At Molecular Level, L. M. Blinov, A. V. Bune, Peter A. Dowben, Stephen Ducharme, Vladimir M. Fridkin, S. P. Palto, K. A. Verkhovskaya, G. V. Vizdrik, S. G. Yudin

Stephen Ducharme Publications

he synthesis of ultrathin ferroelectric nanostructures by the Langmuir-Blodgett method and their properties are reviewed. It is shown that ferroelectricity exists in one monolayer of the ferroelectric P(VDF-TrFE) copolymer, i.e., at the molecular level. The specific characteristics of switching of ultrathin ferroelectric films are established.

Electron Irradiation Effects On Ferroelectric Copolymer Langmuir-Blodgett Films, Christina M. Othon, Stephen Ducharme

Stephen Ducharme Publications

The effect of irradiation on the ferroelectric properties of Langmuir-Blodgett films of the copolymer poly(vinylidene fluoride-trifluorethelene) is investigating using 1.26 MeV electrons with dosages from 16 to 110 Mrad. Irradiation causes a systematic decrease in the phase transition temperature, coercive field and polarization of these thin films.

Exploration Of Artificial Multiferroic Thin-Film Heterostructures Using Composition Spreads, K.-S. Chang, M. A. Aronova, C.-L. Lin, M. Murakami, M.-H. Yu, Jason R. Hattrick-Simpers, O. O. Famodu, S. Y. Lee, R. Ramesh, M. Wuttig, I. Takeuchi, C. Gao, L. A. Bendersky

Faculty Publications

We have fabricated a series of composition spreads consisting of ferroelectric BaTiO₃ and piezomagnetic CoFe₂O₄ layers of varying thicknesses modulated at nanometer level in order to explore artificial magnetoelectricthin-film heterostructures. Scanning microwavemicroscopy and scanning superconducting quantum interference device microscopy were used to map the dielectric and magnetic properties as a function of continuously changing average composition across the spreads, respectively. Compositions in the middle of the spreads were found to exhibit ferromagnetism while displaying a dielectric constant as high as ≈120.

Corrosion Of Steel By Lead Bismuth Eutectic, John Farley, Allen L. Johnson, Dale L. Perry

Transmutation Sciences Materials (TRP)

There is an active international interest in lead-bismuth eutectic and similar liquid lead systems because of the relevance to the transmutation of nuclear waste, fast reactors, and spallation neutron sources. A successful program in nuclear waste processing that includes transmutation in accelerator-driven systems and fast reactors, would significantly decrease the space requirements for geological repositories.

Materials in these systems must be able to tolerate high neutron fluxes, high temperatures, and chemical corrosion. For lead bismuth eutectic (LBE) systems, there is an additional challenge because the corrosive behaviors of materials in LBE are not well understood. Most of the available information …

Environment-Induced Degradation And Crack-Growth Studies Of Candidate Target Materials, Ajit K. Roy

Transmutation Sciences Materials (TRP)

The primary objective of this task is to evaluate the effect of environmental and mechanical parameters on environment induced degradations of candidate target structural materials for applications in spallation-neutron-target systems, such as accelerator-driven systems for the transmutation of waste. The materials selected for evaluation and characterization are martensitic stainless steels including Alloys HT-9, EP-823 and Type 422 stainless steel (SS).

More recently, this experimental program has been expanded to evaluate the effect of molten lead-bismuth eutectic (LBE) on the corrosion behavior of target structural materials in the presence of oxygen. Since the Materials Performance Laboratory (MPL) at UNLV currently cannot …

Modeling Corrosion In Oxygen Controlled Lbe Systems With Coupling Of Chemical Kinetics And Hydrodynamics, Samir Moujaes, Yitung Chen

Transmutation Sciences Materials (TRP)

The corrosion of structural materials is a major concern for the use of lead-bismuth eutectic (LBE) systems for nuclear applications such as in transmuter targets or fast reactors. Corrosion in liquid metal systems can occur through various processes, including, for example, dissolution, formation of inter-metallic compounds at the interface, and penetration of liquid metal along grain boundaries. Predicting the rate of these processes depends on numerous system operational factors: temperature, system geometry, thermal gradients, solid and liquid compositions, and velocity of the liquid metal, to name a few. Corrosion, along with mechanical and/or hydraulic factors, often contributes to component failure. …

Development Of A Mechanistic Understanding Of High-Temperature Deformation Of Alloy Ep-823, Ajit K. Roy, Brendan O'Toole

Transmutation Sciences Materials (TRP)

The focus of this work is to determine the effect of elevated temperatures on the tensile properties of Alloy EP-823 and other martensitic alloys having similar compositions. The information obtained through this work describing the mechanism of elevated-temperature deformation will assist in developing suitable target structural materials possessing enhanced LBE corrosion resistance at process temperatures, allowing the continued development and eventual deployment of these technologies.

Use Of Positron Annihilation Spectroscopy For Stress-Strain Measurements, Ajit K. Roy

Transmutation Sciences Materials (TRP)

Metals and alloys, when subjected to tensile loading beyond a limiting value, can undergo plastic deformation resulting in lattice defects such as voids and dislocations. These imperfections may interact with the crystal lattice, producing a higher state of internal stresses characterized by reduced ductility. Residual stresses can also be generated in welded structures due to rapid rate of solidification, and dissimilar metallurgical microstructures between the weld and the base metals. Premature failures can be experienced in engineering metals and alloys due to the presence of these residual stresses. Specific thermal treatments commonly known as stress relief operations can relieve these …

Development Of Nanostructure Based Corrosion-Barrier Coatings On Steel For Transmutation Applications: Quaterly Report, Biswajit Das

Transmutation Sciences Materials (TRP)

During the past quarter, this project employed one graduate student and two undergraduate student researchers and made the following accomplishments :

• Acquisition of steel samples for experiments

• Design and fabrication of specialized anodization apparatus to accommodate steel samples

• Investigation of adhesiveness of aluminum on steel

• Investigation of effects of anodizing acids on steel to identify most appropriate acid and a suitable barrier material

Stress Corrosion Cracking Of Target Material, Mohammad K. Hossain

Transmutation Sciences Materials (TRP)

The primary objective of this paper is to evaluate the effect of hydrogen on environment assisted cracking of candidate target materials for transmutation applications. Transmutation refers to transformation of long-lived actinides and fission products from spent nuclear fuels (SNF), and occurs when the nucleus of an atom changes because of natural radioactive decay, nuclear fission, nuclear fusion, neutron capture, or other related processes. Martensitic Alloy EP 823 was selected to be the candidate alloy for this investigation. During the initial phase, the stress corrosion cracking (SCC) behavior of this alloy was evaluated in neutral (pH: 6-7) and acidic (pH: 2-3) …

Interaction Between Metal Fission Products And Triso Coating Materials: A Study Of Chemical Bonding And Interdiffusion, Clemens Heske

Fuels Campaign (TRP)

The goal of this project is to elucidate the chemical bonding and interface formation of metal fission products with the coating materials used in state-of-the-art TRISO fuel particles. Particular emphasis is placed on an analysis of intermediate chemical phases at the interface, the intermixing/diffusion behavior, and the electronic interface structure as a function of material choice (metal and coating materials), temperature, and external stress. Furthermore, we intend to assess the chemical state of some of the metal fission products. The findings are expected to give valuable information about failure mechanisms of TRISO particles and fission product transport. Secondly, through simulating …

Interaction Between Metal Fission Products And Triso Coating Materials: A Study Of Chemical Bonding And Interdiffusion: 3rd Quarter Report, 2004, Clemens Heske

Fuels Campaign (TRP)

The goal of this project, which started in May 2004, is to elucidate the chemical bonding and interface formation of metal fission products with the coating materials used in state-of-the-art TRISO fuel particles. Particular emphasis is placed on an analysis of intermediate chemical phases at the interface, the intermixing/diffusion behavior, and the electronic interface structure as a function of material choice (metal and coating materials), temperature, and external stress.

In detail, this project is devoted to studying the interface formation of Pd, Ag, and Cs with SiC and pyrolytic carbon. Using the TRISO coating materials and single crystal references as …

Interaction Between Metal Fission Products And Triso Coating Materials: A Study Of Chemical Bonding And Interdiffusion: 4th Quarter Report, 2004, Clemens Heske

Fuels Campaign (TRP)

The goal of this project, which started in May 2004, is to elucidate the chemical bonding and interface formation of metal fission products with the coating materials used in state-of-the-art TRISO fuel particles. Particular emphasis is placed on an analysis of intermediate chemical phases at the interface, the intermixing/diffusion behavior, and the electronic interface structure as a function of material choice (metal and coating materials), temperature, and external stress. In detail, this project is devoted to studying the interface formation of Pd, Ag, and Cs with SiC and pyrolytic carbon. In order to study the properties of the relevant interfaces, …

Commissioning Of An Arc-Melting/Vacuum Quench Furnace Facility For Fabrication Of Ni-Ti-Fe Shape Memory Alloys, And The Characterization, Jagat Singh

Electronic Theses and Dissertations

Shape memory alloys when deformed can produce strains as high as 8%. Heating results in a phase transformation and associated recovery of all the accumulated strain, a phenomenon known as shape memory. This strain recovery can occur against large forces, resulting in their use as actuators. The goal of this project is to lower the operating temperature range of shape memory alloys in order for them to be used in cryogenic switches, seals, valves, fluid-line repair and self-healing gaskets for space related technologies. The Ni-Ti-Fe alloy system, previously used in Grumman F-14 aircrafts and activated at 120 K, is further …

The Role Of The Solid Substrate On The Spreading Kinetics Of A Liquid Droplet, Bashar Jalal Sasa

Theses

Classic hydrodynamic wetting theory leads to a linear relationship between spreading speed and the capillary force, being determined only by the surface tension of the liquid and its viscosity.

The theory appears in good agreement with results generated from experiments conducted on the spreading of Polydimethylsiloxanes (PDMS) on soda-lime glass substrate and fails to account for the behavior of other liquids. This thesis examines the role played by the solid substrate on the spreading kinetics of liquid droplets. The set of experiments whose results are presented below used different types of liquids with various properties of surface tension and viscosity …

Material Selection For A Composite Hip Joint, Ahmed Abdullah Ali Al-Hosani

Theses

The use of biomaterials in orthopedic surgery has been successfully acceptable in the current medical practice. Total hip joint replacement (THR) is one of the most popular and successful operations in orthopedics. Total hip replacement (THR) has been using metal prosthesis for many years. However, the use of metal implants has two major disadvantages. The first disadvantage is that the stiffness of the metallic prosthesis is relatively high compared to the surrounding, load carrying bone. The elastic moduli of titanium and cobalt-chromium alloy are 110 and 210 GPa, respectively. Whereas the elastic modulus of cortical bone ranges from 15 to …

Preparation And Characterization Of Thermally Stabilized Ceria And Ceria Containing Materials, Leena Ali Rashid Al-Kaabi

Theses

Ceria, CeO₂, is one of the most important catalytic materials that can play multiple roles owing to its ability to release and uptake oxygen under catalytic reaction conditions with the preservation of it fluorite structure. Textural and thermal stability is a critical issue in determining the promoting and metal supporting functions of CeO₂ in its catalytic applications in the three way catalysis. Therefore, significant efforts have been made by industry on finding ways to improve the thermal stability of ceria both by modification of the synthesis of CeO₂ and by looking at possible stabilizers.

In the …

Salt Balance, Fresh Water Residence Time And Budget For Non-Conservative Materials For Makoba Bay During Wet Season, As Ngusaru, Aj Mmochi

Tanzania Journal of Science

Water and salt budgets suggest that in order to balance the inflow and outflow of water at Makoba bay, there is net flux of water from the bay to the open ocean during wet season. Residual salt fluxes between the bay and the open ocean indicate advective salt export. Exchange of water between the bay with the open ocean plays a role of replacing exported salt via mixing. Calculated freshwater residence time for the bay is 63 days during wet season. Budget results for non-conservative materials indicate net DIP flux from the ocean to the bay and a net DIN …

Surface Titration Of Colloidal Alpha-Alumina, J. W. Ntalikwa

Tanzania Journal of Engineering and Technology (TJET)

The surface charge density (σ₀) of colloidal alumina (α-Al₂O₃) suspended in 1:1 electrolytes (NaCl, NaNO₃, CsCl and CsNO₃) at different electrolyte concentration (c₀) was determined using acid-base titration. The data were described in terms of the Triple Layer Model (TLM) of electric double layer. It was observed that the polarity of σ₀ could be varied through a point of zero charge (PZC) by varying the pH of the suspension. The PZCs were observed to occur at pH = 7.8 ± 0.1, 7.6 ± 0.2, 8.5 ± 0.1 and 8.3 ± 0.1 in NaCl, NaNO₃, CsCl and CsNO₃, respectively. It was …