Engineering Commons^™

Boron Induced Surface Modification Of Transition Metals, Raghasudha Vangaveti

Theses

Boronizing is a thermo-chemical surface treatment of metals in which boron atoms diffuse into the metal substrate and form hard metallic borides. As a result of boronizing, several properties such as hardness, wear resistance, corrosion resistance, and high temperature oxidation resistance improve which make the metal substrate more suitable for industrial applications. These boronized parts are used in many industrial applications like ingot moulds, crucibles, biomedical implants, die-casting moulds, magnetic head applications, drawing dies etc.

The objective of this work was to investigate the influence of boronizing on the properties of transition metals. Three transition metals, tantalum, niobium and tungsten …

Electrochemical Corrosion Testing Of Boronized And Unboronized Steels, Kranthi K. Pallegar

Theses

Boronizing is a thermo-chemical surface coating technique with which surface properties of materials are enhanced substantially. One of these properties is corrosion resistance. Corrosion resistance testing has been performed in many ways right from the traditional weight loss methods to the latest electrochemical techniques. These electrochemical techniques are more reliable and less time consuming and hence are widely accepted for corrosion testing in the industry.

In the present work, direct current (D.C) corrosion testing studies of both boronized and unboronized steels have been discussed. Three types of steels, AISI 1018, AISI 4340 and AISI 304 stainless steel, were considered for …

High Temperature Heat Exchanger Project: Quarterly Progress Report October 1, 2005 Through December 31, 2005, Anthony Hechanova

Publications (NSTD)

• Liquid Salt Technical Working Group Meeting. The first meeting of the Liquid Salt Technical Working Group was held on October 28, 2005 at the Pratt Whitney Rocketdyne facility in Canoga Park, CA. 20 experts from academia, industry, and national laboratories participated to discuss current state of knowledge and research needs for high temperature liquid salt applications.
• Nuclear Hydrogen Initiative Semi-annual Review. Several participants from the UNLVRF University Consortium gave technical presentations at the NHI Semi-annual Review meeting in Rockville, MD, November 9-10, 2005.
• Quarterly Collaboration Meeting. The University of Nevada, Las Vegas hosted a UNLVRF HTHX Project quarterly meeting December …

Dynamic Sulfur Tolerant Process And System With Inline Acid Gas-Selective Removal For Generating Hydrogen For Fuel Cells, Surjit Randhava, W. S. Winston Ho, Richard L. Kao, Elias H. Camara

Chemical and Materials Engineering Faculty Patents

This invention relates to a sulfur tolerant, dynamic, compact, lightweight fuel process and system that is capable of converting sulfur bearing carbonaceous fuels to hydrogen rich gases suitable for fuel cells or chemical processing applications. The process and system is based on the AHR and WGS reactions, followed by cleanup of byproduct sulfur-containing gases and carbon oxides that would otherwise poison the fuel cell electrocatalyst. Advantageously, this is accomplished via an ASMS and a methanator or an AWMR. The process and system preferably uses a special sulfur tolerant catalysts and hardware designs that enable the conversion in an energy efficient …

Sub-Surface Corrosion Research On Rock Bolt System, Perforated Ss Sheets And Steel Sets For The Yucca Mountain Repository — Quarterly Technical Report No. 6, Dhanesh Chandra, Jaak J.K. Daemen

Publications (YM)

This report encompasses the work done for this fourth quarter of the year 2005, in accordance to cooperative agreement of University of Nevada system for the Task 019 “Subsurface Corrosion Research on Rock Bolt System, Perforated SS Sheets and Steel Sets for the Yucca Mountain Repository”, the overall objective of which is to conduct corrosion research and predict the durability of rock-bolts and other underground metallic roof supports. We have started oxidation tests using Thermogravimetric Analyzer (TGA), and Potentiodynamic tests to determine the corrosion rates of rock bolts, other support materials including bench mark materials. In this quarter, we have …

The Microstructure And Grain Size Of Jet Electroplated Copper Films In Damascene Trench Features, Andrew Tzanavaras, Gregory Young, Stacy H. Gleixner

Faculty Publications

The brightening additive level and dc current density of electroplating baths are two parameters that affect the gap-filling capability and the degree of impurity incorporation in electroplated copper films. Additive incorporation can inhibit grain growth during the room temperature recrystallization process and therefore affect the final grain size. This investigation explores the grain size and microstructure of dc jet-electroplated copper films in 0.35 and 0.50μm Damascene trenches as a function of current density and brightening additive level after first receiving a high-temperature anneal. Unlike a previous study that explored these variables in blanket Cu films [ J. Electrochem. Soc. , …

Polymer-Derived Si-Al-C-N Ceramics:Oxidation, Hot-Corrosion, And Structural Evolution, Yiguang Wang

Electronic Theses and Dissertations

Polymer-derived ceramics are a new class of materials synthesized by thermal decomposition of polymer precursors. Previous studies have shown that the materials exhibit excellent thermo-mechanical properties and can be stable at temperatures up to 2000oC. Furthermore, the novel polymer-to-ceramics process enables the manipulation of the ceramic structures at the atomic/nano level by designing the chemistry of polymer precursors and controlling the pyrolysis conditions, thereby, the properties of ceramics. In this dissertation, oxidation/hot-corrosion behavior and the structural evolution of Si-Al-C-N ceramics have been studied. The structural evolution and crystallization behavior of the SiCN and SiAlCN ceramics are investigated using FT-IR, XRD, …

Fast And Slow Magnetization Processes In Magnetic Recording Media, Jian Zhou, Ralph Skomski, Steven A. Michalski, Roger D. Kirby, David J. Sellmyer

Materials Research Science and Engineering Center: Faculty Publications

Information loss due to thermal activation is a major concern in ultrahigh-density magnetic recording media. The usually considered mechanism is thermally activated magnetization reversal over micromagnetic energy barriers. However, micromagnetic approaches ignore local anisotropy fluctuations, which translate into a time-dependent reduction of the remanent magnetization. The effect is negligibly small in macroscopic magnets but becomes important on a scale of a few nanometers.

Spin-Polarized Electronic Structure, Arti Kashyap, Renat F. Sabirianov, Sitaram Jaswal

Materials Research Science and Engineering Center: Faculty Publications

This chapter is devoted to the electronic structure of nanoscale metallic magnets. After an introduction to methods of electronic structure calculations, we review how recent trends translate into the description of magnetic nanostructures. Among the considered structures are nanowires, small particles, surfaces and interfaces, and multilayers, and emphasis is on magnetic properties such as moment and magnetization, interatomic exchange, and anisotropy.

One of the goals of computational nanoscience is to calculate physical and chemical properties from first principles. This requires the knowledge of the electronic structures of the materials system in question. The density-functional theory (DFT) makes a huge step …

"Introduction" To Advanced Magnetic Nanostructures, David J. Sellmyer, Ralph Skomski

Materials Research Science and Engineering Center: Faculty Publications

The nanostructures considered here are magnetic and characterized by structural length scales ranging from a few interatomic distances to about one micrometer. The basic length unit is the nanometer (1 nm = 10^–3 μm = 10^–9 m), corresponding to about four interatomic Fe-Fe distances. Magnetic nanostructures pose experimental challenges, exhibit interesting physical phenomena, and have many present or potential applications. An important aspect is that structural lengths affect, but only partly determine, the magnetic length scales encountered in the structures. Examples are domains in semihard nanoparticles, where both the domain size and the domain-wall thickness may be smaller …

A Measurement Of Electron-Wall Interactions Using Transmission Diffraction From Nanofabricated Gratings, Brett E. Barwick, Glen Gronniger, Lu Yuan, Sy-Hwang Liou, Herman Batelaan

Materials Research Science and Engineering Center: Faculty Publications

Electron diffraction from metal coated freestanding nanofabricated gratings is presented, with a quantitative path integral analysis of the electron-grating interactions. Electron diffraction out to the 20th order was observed indicating the high quality of our nanofabricated gratings. The electron beam is collimated to its diffraction limit with ion-milled material slits. Our path integral analysis is first tested against single slit electron diffraction, and then further expanded with the same theoretical approach to describe grating diffraction. Rotation of the grating with respect to the incident electron beam varies the effective distance between the electron and grating bars. This allows the measurement …

Polymer-Derived Ceramics: Electronic Properties And Application, Weixing Xu

Electronic Theses and Dissertations

In this work, we studied the electronic behavior of polymer-derived ceramics (PDCs) and applied them for the synthesis of carbon nanotube reinforced ceramic nanocomposites and ceramic MEMS (Micro-Electro-Mechanical Systems) structures. Polymer-derived SiCN ceramics were synthesized by pyrolysis of a liquid polyureasilazane with dicumyl peroxide as thermal initiator. The structural evolution during pyrolysis and post-annealing was studied using FTIR, solid state NMR and Raman. The results revealed that the resultant ceramics consisted of SiCxNx-4 as major building units. These units were connected with each other through C-C/C=C bonds or by shearing N/C. The amount of sp2 free carbon strongly depends on …

Laser Metallization And Doping For Silicon Carbide Diode Fabrication And Endotaxy, Zhaoxu Tian

Electronic Theses and Dissertations

Silicon carbide is a promising semiconductor material for high voltage, high frequency and high temperature devices due to its wide bandgap, high breakdown electric field strength, highly saturated drift velocity of electrons and outstanding thermal conductivity. With the aim of overcoming some challenges in metallization and doping during the fabrication of silicon carbide devices, a novel laser-based process is provided to direct metallize the surface of silicon carbide without metal deposition and dope in silicon carbide without high temperature annealing, as an alternative to the conventional ion implantation, and find applications of this laser direct write metallization and doping technique …

Development Of Thermally Processed Nanocomposites With Controlled Surfaces, Petya Georgieva

Electronic Theses and Dissertations

The ever increasing need for technology development requires the integration of inexpensive, light weight and high strength materials which are able to meet the high standards and specifications for various engineering applications. The intention of this work is to show that the suitable material selection and the utilization of plasma spray processing can be of potential interest to a large number of industrial, biomedical and everyday life applications. This research demonstrates also that plasma processing is a promising engineering tool for multifunctional coatings and near-net-shape manufacturing. Further, the theoretical and experimental results are combined in order to explain the mechanisms …

Magnetic Properties Of Sputter Deposited Fe-Based Amorphous Thin Films For Resonator Application, Chaitali China

Electronic Theses and Dissertations

In this study we investigate the magnetic properties of Fe-based amorphous thin films. Fe1-x-y-zBxSiyCz, Fe80-xNixB20, Fe80-xMnxB20, and Fe73-xMnxB27 films were deposited on silicon and glass substrates in a DC and RF magnetron sputtering system. Inductive magnetic measurements were performed to investigate the magnetic properties, including induced anisotropy and magnetostriction, of the as-deposited and annealed films using an M-H Looper. The chemical composition of the films was characterized using secondary ion mass spectroscopy (SIMS). The physical thickness of the films was determined by use of a stylus profilometer. The M-H Looper studies indicated that the induced anisotropy (Hk) depends strongly on …

Fundamental Aspects Of Regenerative Cerium Oxide Nanoparticles And Their Applications In Nanobiotechnology, Swanand Patil

Electronic Theses and Dissertations

Cerium oxide has been used extensively for various applications over the past two decades. The use of cerium oxide nanoparticles is beneficial in present applications and can open avenues for future applications. The present study utilizes the microemulsion technique to synthesize uniformly distributed cerium oxide nanoparticles. The same technique was also used to synthesize cerium oxide nanoparticles doped with trivalent elements (La and Nd). The fundamental study of cerium oxide nanoparticles identified variations in properties as a function of particle size and also due to doping with trivalent elements (La and Nd). It was found that the lattice parameter of …

Synthesis, Processing And Characterization Of Nanocrystalline Titanium Dioxide, Shipeng Qiu

Electronic Theses and Dissertations

Titanium dioxide (TiO2), one of the basic ceramic materials, has found a variety of applications in industry and in our daily life. It has been shown that particle size reduction in this system, especially to nano regime, has the great potential to offer remarkable improvement in physical, mechanical, optical, biological and electrical properties. This thesis reports on the synthesis and characterization of the nanocrystalline TiO2 ceramic in details. The study selected a simple sol-gel synthesis process, which can be easily controlled and reproduced. Titanium tetraisopropoxide, isopropanol and deionized water were used as starting materials. By careful control of relative proportion …

Preparation Of Efficient Cuin1-Xgaxse2-Ysy/Cds Thin-Film Solar Cells By Optimizing The Molybdenum Back Contact And Using Diethylselenide As Selenium Precursor, Ankur Kadam

Electronic Theses and Dissertations

High efficiency CuIn1-xGaxSe2-ySy (CIGSS)/CdS thin-film solar cells were prepared by optimizing the Mo back contact layer and optimizing the parameters for preparing CIGSS absorber layer using diethylselenide as selenium source. The Mo film was sputter deposited on 2.5 cm x 10 cm soda-lime glass using DC magnetron sputtering for studying the adhesion and chemical reactivity with selenium and sulfur containing gas at maximum film growth temperature. Mo being a refractory material develops stresses, nature of which depends on the deposition power and argon pressure. It was found that the deposition sequence with two tensile stressed layers deposited at 200W and …

Designing And Modeling Of A New Continuous Steelmaking Process, Jörg Peter

Doctoral Dissertations

"Continuous steel production has the potential to lower the cost of steelmaking as compared to current batch operations. However, experiences from past attempts to develop and commercialize continuous steelmaking processes show that there are several engineering hurdles to overcome. The objective of this research was the development of a fully continuous steelmaking process that would incorporate the lessons from past experiences, address the foreseen challenges, and meet the requirements to justify the possible replacement of the current EAF-LMF steelmaking route.

The design of the new process consists of five interconnected vessels. Preheated scrap would be continuously charged, melted, and superheated …

Nanodot-Based Organic Memory Devices, Zhengchun Liu

Doctoral Dissertations

In this study, resistor-type, diode-type, and transistor-type organic memory devices were investigated, aiming at the low-cost plastic integrated circuit applications. A series of solution-processing techniques including spin-coating, inkjet printing, and self-assembly were employed to fabricate these devices.

The organic resistive memory device is based on a novel molecular complex film composed of tetracyanoquinodimethane (TCNQ) and a soluble methanofullerene derivative [6,6]-phenyl C61-butyric acid methyl ester (PCBM). It has an Al/molecules/Al sandwich structure. The molecular layer was formed by spin-coating technique instead of expensive vacuum deposition method. The current-voltage characteristics show that the device switches from the initial 'low' conduction state to …

Low Temperature Co-Fired Ceramics For Micro-Fluidics, John Youngsman, Brian Marx, Martin Schimpf, Scott Wolter, Jeff Glass, Amy Moll

Materials Science and Engineering Faculty Publications and Presentations

The miniaturization of analytical instruments and packaging of novel sensors is an area that has attracted significant research interest and offers many opportunities for product commercialization. Low Temperature Co-fired Ceramics (LTCC) is a materials system composed of alumina and glass in an organic binder. LTCC is a good choice for sensor development because of the ease of incorporating features in the ‘green’ or unfired state such as electrical traces, fluidic pathways and passive electrical components. After a firing cycle, what remains is a robust, monolithic device with features embedded in the package. In order for LTCC to be a successful …

Vibration Testing Of Repaired Lead-Tin/Lead-Free Solder Joints, Matthew O'Keefe, S. Vetter, D. Murry, J. Smith, P. Amick, Martin G. Perez, D. W. Kleine, Richard S. Colfax

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

Effect Of Nozzle Base Material On The Rate Of Clogging During The Continuous Casting Of Aluminum-Killed Steels, Luis Trueba, Kent D. Peaslee, Jeffrey D. Smith, Musa Karakus

Materials Science and Engineering Faculty Research & Creative Works

One approach to solving the problem of nozzle clogging during the continuous casting of aluminum-killed steels is through careful selection of nozzle materials. in this study, the rate of clogging was measured while casting steel through simulated nozzles produced from alumina, zirconia, magnesia, zirconia-graphite, and alumina-graphite - three common base materials and two common carbon-containing nozzle materials. Spent nozzles were characterized using optical and cathodoluminescence microscopy. Interactions between the nozzles and steel were not observed in the alumina, zirconia, and zirconia-graphite nozzles. Slight interactions were observed in the magnesia nozzles as alumina inclusions within the steel interacted with the nozzle …

Electrochemical Deposition And Characterization Of Fe₃O₄ Films Produced By The Reduction Of Fe(Iii)-Triethanolamine, Hiten M. Kothari, Elizabeth A. Kulp, Steven J. Limmer, Philippe Poizot, Eric W. Bohannan, Jay A. Switzer

Chemistry Faculty Research & Creative Works

In this paper, we demonstrate that films of magnetite, Fe₃O₄, can be deposited by the electrochemical reduction of a Fe(III)-triethanolamine complex in aqueous alkaline solution. the films were deposited with a columnar microstructure and a [100] preferred orientation on stainless steel substrates. In-plane electrical transport and magnetoresistance measurements were performed on the films after they were stripped off onto glass substrates. the resistance of the films was dependent on the oxygen partial pressure. We attribute the increase in resistance in O₂ and the decrease in resistance in Ar to the oxidation and reduction of grain …

Segmental Dynamics Of Poly(Isopropyl Acrylate)-D7 On Silica, Piyawan Krisanangkura, Frank D. Blum

Chemistry Faculty Research & Creative Works

For a polymer film deposited on a surface, the strength of the surfacesegment interaction affects the mobility of polymer-chain segments. The selfconsistent field lattice model of Scheutjens and Fleer,1 based on mean-field lattice models of polymer at interfaces,2 has been used to describe the distribution of conformations of polymers on surfaces. Adsorbed-polymer segments may be classified as belonging to loops, trains or tails. There are different techniques used to study the molecular motion of the polymer including modulated differential scanning calorimetry (MDSC)3 and nuclear magnetic resonance (NMR).4,5 in this work, solid-state deuterium (2H) NMR was used to characterize the polymer …

Segmental Dynamics In Poly(Methyl Acrylate) On Silica: Molecular-Mass Effects, Burak Metin, Frank D. Blum

Chemistry Faculty Research & Creative Works

The effect of molecular mass on the segmental dynamics of poly(methyl acrylate) (PMA) adsorbed on silica was studied using deuterium quadrupole-echo nuclear magnetic resonance (NMR) and modulated differential scanning calorimetry. Samples adsorbed on silica (all about 1.5 mg PMA/m2 silica) were shown to have more restricted segmental mobility, and higher Tg's, than the corresponding bulk PMA samples. Around the glass-transition region, adsorbed samples exhibited segmental mobility, which could be classified as heterogeneous due to a superposition of more-mobile and less-mobile components present in the deuterium NMR spectra. This heterogeneity was consistent with a motional gradient with more-mobile segments near the …

Nanobiomagnetics, Diandra Leslie-Pelecky, V. Labhasetwar, R. H. Kraus Jr.

Materials Research Science and Engineering Center: Faculty Publications

The application of nanomagnetic materials to biological systems has produced significant advances in research, diagnosis, and treatment of numerous pathologies. This chapter summarizes the major applications of magnetic materials: magnetic targeting, drug and gene delivery, magnetic separation, the use of magnetic beads in manipulating single molecules, as contrast agents in magnetic resonance imaging, and for hyperthermia. Biocompatibility requirements for magnetic materials used in these applications are reviewed.

“Nanobiomagnetism” is the intersection of nanomagnetism and medicine that focuses on biological systems and/or processes. Magnetism is an inherent facet of life, from iron in blood to the ability of magnetotactic bacteria, birds, …

Understanding And Control Of Lateral Contraction In Stamping Lithography, Zheng Li, Li Tan, Gang-Yu Liu

Materials Research Science and Engineering Center: Faculty Publications

Thin film contraction under external mechanical stress can be used to miniaturize size and increase density of patterned features on top. Nonlinear Finite Element Analysis is used to provide guidance on this contraction process. It was found that the substrate contraction causes stress accumulation along interfaces between protruded features and substrate. These stress accumulation complexes the control of profile changes on patterned features and suggest a design of patterned features arranged beyond a critical distance to avoid cross-interference.

Magnetic Aging, Ralph Skomski, Jian Zhou, Roger D. Kirby, David J. Sellmyer

Materials Research Science and Engineering Center: Faculty Publications

Thermally activated magnetization reversal is of great importance in areas such as permanent magnetism and magnetic recording. In spite of many decades of scientific research, the phenomenon of slow magnetization dynamics has remained partially controversial. It is now well-established that the main mechanism is thermally activated magnetization reversal, as contrasted to eddy currents and structural aging, but the identification of the involved energy barriers remains a challenge for many systems. Thermally activated slow magnetization processes proceed over energy barriers whose structure is determined by the micromagnetic free energy. This restricts the range of physically meaningful energy barriers. An analysis of …

Effects Of Ion-Beam Irradiation On The L10 Phase Transformation And Their Magnetic Properties Of Fept And Ptmn Films (Invited), Chih-Huang Lai, Sheng-Huang Huang, Cheng-Han Yang, C.C. Chiang, Sy_Hwang Liou, David J. Sellmyer, M. L. Yan, L. Yuan, T. Yokata

Materials Research Science and Engineering Center: Faculty Publications

In this paper, we illustrate how to modify the structure and magnetic properties of L1₀ FePt and PtMn films using ion-beam irradiation. Highly ordered L1₀ FePt and PtMn phases were achieved directly by using 2 MeV He-ion irradiation without conventional post-annealing. A high ion-beam current density (~μA/cm² ) was used to achieve direct beam heating on samples. This irradiation-induced heating process provides efficient microscopic energy transfer and creates excess point defects, which significantly enhances the diffusion and promotes the formation of the ordered L1₀ phase. In-plane coercivity of FePt films greater than 5700 Oe could be …