Engineering Commons^™

Mixed Ion-Polaron Transport In Na2o-Pbo-Fe2o3-P2o5 Glasses, A. Moguš-Milanković, A. Šantić, Signo Tadeu Dos Reis, K. Furić, D. E. Day

Materials Science and Engineering Faculty Research & Creative Works

The electrical and dielectric properties of the xNa₂O · (100 - x) · [28.3PbO · 28.7Fe₂O₃ · 43.0P₂O₅] (0 ≤ x ≤ 30) glasses were measured by impedance spectroscopy in the frequency range from 0.01 Hz to 3 MHz and the temperature range from 303 to 473 K. the conductivity for glasses containing ≤15 mol% Na₂O is predominantly electronic and is controlled by electron hopping between Fe(II) and Fe(III) ions. in these glasses the sodium ions have such a low mobility, caused by ion-polaron interaction, that they make no …

Study Of Ceramic Slurries For Investment Casting With Ice Patterns, Qingbin Liu, Ming-Chuan Leu, Harish Jose, Von Richards

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Ice patterns generated by rapid freeze prototyping or a molding process can be used to make ceramic investment molds for metal castings. Due to the use of ice, the ceramic slurries must be poured around the pattern and cured at sub-freezing temperatures. Success of this process depends greatly on the mold strength after the gelation of the slurries. This paper describes the experimental results of the mold strength after the gelation of the slurries under different compositions. The parameters considered include mixing time, alumino-silicate vs. fused silica ratio, volume of binder, and volume of catalyst. The strength of the gelled …

Wavelenght-Dispersive X-Ray Flourescence Accuration, H. Widyatmoko

Makara Journal of Technology

Wavelenght–Dispersive X-Ray Flourescence Accuration. X-Fuorescence spectrometry is a method, which is increasingly applied in the geochemical analysis. X-Fuorescence spectrometry is classified under two categories – WDXRF (wavelenght – dispersive X-ray fluorescence spectrometer) and EDXRF (energy-dispersive X – ray fluorescence spectrometer). WDXRF can be configured as a sequential spectrometer , a simultaneous spectrometer or a hibrid instrument, which combines the advantages of the simultaneous and sequential spectrometers into one instrument. Each instrument is different in some characteristics, and each has applications for which it is specifically suited. In this investigation sequential spectrometer PW 1450 was used to analyze the major, minor …

Secondary Flow Experimental Study For Axial Compressor Cascade Strong Stagger With And Without Tip- Clearance: Static Pressure Distribution On Blade Surface, Syamsuri Syamsuri

Makara Journal of Technology

Secondary Flow Experimental Study for Axial Compressor Cascade Strong Stagger With and Without Tip- Clearance: Static Pressure Distribution on Blade Surface. The performance of blade cascade is influenced by the growth and boundary layer’s separation along blade surface and endwall (casing and hub). The secondary flow which happens near hub and casing compressors is three dimentional flow separation phenomenon comes from interaction blade boundary layer with casing and hub boundary layers in the compressor. The secondary flow causes secondary losses, blockage effect, and turning angle (deflection) distribution along blade span. The result of the research shows that the increase of …

Effect Of Photoperiodicity On Co2 Fixation By Chlorella Vulgaris Buitenzorg In Bubble Column Photobioreactor For Food Supplement Production, Anondho Wijanarko, Dianursanti Dianursanti, Arief Budi Witarto, Roekmijati Widaningroem Soemantojo

Makara Journal of Technology

To reduce the level of CO2 content in air, effort on converting CO2 to useful products is required. One of the alternatives includes CO2 fixation to produce biomass using Chlorella vulgaris Buitenzorg. Chlorella vulgaris Buitenzorg is applied for production of food supplement. Chlorella vulgaris Buitenzorg is also easy to handle due to its superior adaptation. Currently, Chlorella vulgaris Buitenzorg has been analyzed by some experts for its cellular composition, its ability to produce high quality biomass and the content of essential nutrition. A series of experiments was conducted by culturing Chlorella vulgaris Buitenzorg using Beneck medium in bubbling column photobioreactor. …

Synthesize Of Emulsion Polymer Latex For Sub-Grade Cbr Improvement In The Road Construction, Keba Moto, V. Julian, Syamsudin Syamsudin, T. A. Wiradi, S. R. Wijaya

Makara Journal of Technology

Synthesize of emulsion polymer latex for sub-grade CBR improvement in the road construction. Latex polymer for California Bearing Ratio (CBR) enhancement in sub-grade soil of road building has been prepared by emulsion polymerizations technique. The prepared polymer then characterize by Fourier Transform Infrared (FTIR). For application purpose, CBR test was done to the compacted polymer added-soil. The CBR test is done also for both soaked and unsoaked samples. It is found that our latex polymer is better then other imported latex polymer. For the latex polymer, which is design to have Temperatur glass (Tg) around 9.8-19.6o, indicating the formation of …

46th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 46th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-endorsed by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, August 1-5, 2004.

Environment-Induced Degradations In A Target Structural Material For Transmutation Applications, Ramprashad Prabhakaran

UNLV Theses, Dissertations, Professional Papers, and Capstones

This investigation is focused on the evaluation of stress corrosion cracking (SCC) and localized corrosion behavior of Type 422 stainless steel in aqueous environments at ambient and elevated temperature. The results of constant load SCC testing using smooth specimens showed no failure in the neutral solution but a threshold stress of 97 ksi was observed in the 90°C acidic environment. SCC testing by the slow-strain-rate test method indicate that the time-to-failure, true failure stress and ductility parameters were gradually reduced with increasing temperature, showing more pronounced effect in the acidic solution. The application of a controlled cathodic potential showed further …

Experimental Investigation Of Time Dependent Behavior Of Welded Topopah Spring Tuff, Lumin Ma

Publications (YM)

Four types of laboratory tests have been performed. Specimens were attained from four lithophysal zones of the welded Topopah Spring Tuff unit at Yucca Mountain, Nevada: upper lithophysal, middle nonlithophysal, lower lithophysal and lower nonlithophysal zones. Two types of tests are conducted to study time-dependent behavior: constant strain rate and creep tests. Sixty five specimens from the middle nonlithophysal zone were tested at six strain rates: 10 , 10 , 10 , 10 , 10 , and 10 . Test durations range from 2 seconds to 7 days. Fourteen specimens from middle nonlithophysal, lower lithophysal and lower nonlithophysal zones are …

Embrittlement And Localized Corrosion In Alloy Ht-9, Sudheer Sama

UNLV Theses, Dissertations, Professional Papers, and Capstones

This investigation is focused on the evaluation of stress corrosion cracking (SCC), hydrogen embrittlement (HE) and localized corrosion susceptibility of Alloy HT -9 in neutral and acidic solutions at 30, 60 and 90°C. Constant-load and slow-strain-rate (SSR) testing techniques were used to evaluate the SCC and HE behavior of this alloy by using smooth and notched tensile specimens. Hydrogen effect on the cracking behavior was evaluated by applying cathodic (negative) potential to the test specimens. Localized corrosion susceptibility was evaluated by cyclic potentiodynamic polarization technique. The results of constant load SCC testing showed a threshold stress at 80% of the …

Field-Controlled Domain-Wall Resistance In Magnetic Nanojunctions, John D. Burton, Arti Kashyap, Mikhail Ye. Zhuravlev, Ralph Skomski, Evgeny Y. Tsymbal, Sitaram Jaswal, O.N. Mryasov, R.W. Chantrell

Materials Research Science and Engineering Center: Faculty Publications

The electrical resistance of a constrained domain wall in a nanojunction is investigated using micromagnetic modeling and ballistic conductance calculations. The nanojunction represents two ferromagnetic electrodes connected by a ferromagnetic wire of 10 nm in length and of a few nanometers in cross section. We find that the anisotropy of the electrodes favors a localization of the domain wall within the constriction (wire) revealing a positive domain-wall resistance. An applied magnetic field moves the domain wall toward one of the electrodes and reduces its width. This compression of the domain wall leads to a sizeable enhancement of the domain-wall resistance.

Environment-Induced Degradation And Crack-Growth Studies Of Candidate Target Materials: Annual Progress Report (May 2003 – May 2004), Ajit K. Roy

Transmutation Sciences Materials (TRP)

As indicated in the original proposal, the primary objective of this task was to evaluate the effect of hydrogen on environment-assisted cracking of candidate target structural materials for applications in spallation-neutron-target (SNT) systems such as accelerator production of tritium (APT) and accelerator transmutation of waste (ATW). The materials selected for evaluation and characterization were martensitic stainless steels including Alloy EP 823, HT-9, and Type 422 stainless steel. The susceptibility to stress corrosion cracking (SCC) of these materials were evaluated in neutral and acidic aqueous environments using smooth and notched tensile specimens under constant-load (CL) and slow-strain-rate (SSR) conditions. Further, the …

Fabrication, Characterization, And Modeling Of Organic Capacitors, Schottky Diodes, And Field Effect Transistors, Mo Zhu

Doctoral Dissertations

The objectives of this project are to fabricate, characterize, and model organic microelectronic devices by traditional lithography techniques and Technology Computer Aided Design (TCAD).

Organic microelectronics is becoming a promising field due to its number of advantages in low-cost fabrication for large area substrates. There have been growing studies in organic electronics and optoelectronics. In this project, several organic microelectronic devices are studied with the aid of experimentation and numerical modeling.

Organic metal-insulator-metal (MIM) and metal-insulator-semiconductor (MIS) capacitors consisting of insulating polymer poly(4-vinylphenol) (PVP) have been fabricated by spin-coating, photo lithography, and reactive ion etching techniques. Based on the fabricated …

The Effect Of Transition Metal Additions On The Microstructure And Properties Of Nanocomposite Pr–Fe–B Permanent Magnets, Jeffrey E. Shield, Yi Liu, R. Marr, Z. Chen, Baomin Ma

Materials Research Science and Engineering Center: Faculty Publications

Permanent magnets with the general composition Pr₉ (Fe_0.95Co_0.05)_85.5M_0.5B₅, where M denotes a transition metal, have been produced by melt spinning. The effect on the microstructure and magnetic properties of eight different alloying elements has been examined. The grain size and distribution have been correlated to the maximum energy product obtained. The grain size of the Pr₉ (Fe_0.95Co_0.05) _85.5B₅ control alloy was determined to be 17.5 nm, and it was found that the grain size was not significantly reduced compared to the control …

Domain-Wall Pinning At Inhomogenities Of Arbitrary Cross-Sectional Geometry, Ralph Skomski, Jian Zhou, Arti Kashyap, David J. Sellmyer

Materials Research Science and Engineering Center: Faculty Publications

Abstract—The coercivity of cellular Sm-Co based permanent magnets is investigated by model calculations. The grain boundaries responsible for the pinning coercivity are modeled as planar inhomogenities with arbitrary cross-sectional geometry. The calculation yields a physically transparent integral equation for the pinning energy, whose derivative is the pinning force. The theory rationalizes experimental data on a semiquantitative level, but without adjustable parameters, and bridges the gap between smooth concentration gradients and abrupt interfaces. Explicit results are obtained for sinoidal profiles, for very thin grain boundaries, and for profiles intermediate between attractive and repulsive pinning. The corrections predicted by the present model …

Magnetization Reversal And Giant Coercivity In Sm-Co/Cu-Ti Particulate Films, Jian Zhou, Arti Kashyap, Yi Liu, Ralph Skomski, David J. Sellmyer

Materials Research Science and Engineering Center: Faculty Publications

Highly coercive granular SmCo/CuTi films were produced by thermal processing of sputtered SmCo₅ (CuTi) multilayers and investigated experimentally and theoretically. Electron microscopy shows that the processed films consist of spherical grains that have diameters of 5–10 nm and are embedded in a matrix. Both the grains and the matrix phase exhibit the CaCu₅ structure, but the matrix is probably Cu-rich. The films have high coercivities of up to 50.4 kOe at 300 K. Analytical calculations and micromagnetic simulations yield a transition from a nucleation-type weak-interaction regime to a discrete-pinning-type strong-interaction regime. The transition occurs at packing fractions similar …

L10 Ordered Fept:C Composite Films With (001) Texture, M. L. Yan, Renat F. Sabiryanov, Yinfan Xu, Xingzhong Li, David J. Sellmyer

Materials Research Science and Engineering Center: Faculty Publications

Highly textured (001) FePt:C nanocomposite thin films, deposited directly on thermally oxidized Si wafers, are obtained by multilayer deposition plus subsequent thermal annealing. Nanostructures, crystalline orientations, interactions, and magnetic properties are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), magnetic force microscopy, and magnetic measurements. The formation of the ordered L1₀ phase is confirmed by XRD, and only visible (00 ) peaks indicate a high degree of the (001) texture. TEM observation reveals that FePt grains are embedded in the C matrix and appear to be well isolated.

Nanostructure And Magnetic Properties Of Fept :C Cluster Films, Yinfan Xu, M. L. Yan, David J. Sellmyer

Materials Research Science and Engineering Center: Faculty Publications

Magnetic properties and nanostructure of FePt : C cluster-deposited films with C volume fraction of 7%, 14%, 33%, and 45% have been studied. As-deposited FePt : C films were prepared by a multilayer method in which FePt layers were deposited from a cluster source employing a gas-aggregation technique and C layers from a normal sputtering gun. In the as-deposited films, FePt clusters with fcc structure are embedded in the C matrix. The high anisotropy FePt L1₀ cluster structure was realized in the films via post-deposition annealing and the nanostructure of the films was observed by high-resolution transmission electron microscope …

Magnetization Processes In Melt-Spun Sm-Co-Based Alloys With The Tbcu7-Type Structure, A. Hsiaoa, S. Aich, L. H. Lewis, Jeffrey E. Shield

Materials Research Science and Engineering Center: Faculty Publications

The initial magnetization processes in melt-spun Sm-Co alloys with remanent ratios above 0.7 have been studied. Alloys of (Sm_(1/(6+x) Co _(5+x)/(6+x) ) ₉₄Nb₃C₃ (x = 067, 1.7, 2.3 and 3) alloys modified with Nb and C were melt spun at wheel speeds of 20 and 40 m/s, and the compositions span the range between the Sm₂Co₁₇ and SmCo_{5 stoichiometries. Structurally, all alloys formed in the TbCu7-type structure, although a small amount of Sm2Co7 was observed in Sm-rich samples, and a small amount of fcc Co formed …}

Artificial Neural Network Modeling Of Rf Mems Resonators, Yongjae Lee, Yonghwa Park, Feng Niu, Bonnie Bachman, K. C. Gupta, Dejan Filipovic

Economics Faculty Research & Creative Works

In this article, a novel and efficient approach for modeling radio‐frequency microelectromechanical system (RF MEMS) resonators by using artificial neural network (ANN) modeling is presented. In the proposed methodology, the relationship between physical‐input parameters and corresponding electrical‐output parameters is obtained by combined circuit/full‐wave/ANN modeling. More specifically, in order to predict the electrical responses from a resonator, an analytical representation of the electrical equivalent‐network model (EENM) is developed from the well‐known electromechanical analogs. Then, the reduced‐order, nonlinear, dynamic macromodels from 3D finite‐element method (FEM) simulations are generated to provide training, validating, and testing datasets for the ANN model. The developed ANN …

Spectroscopic And Microscopic Investigation Of The Corrosion Of 316/316l Stainless Steel By Lead-Bismuth Eutectic (Lbe) At Elevated Temperatures: Importance Of Surface Preparation, Allen L. Johnson, Denise Parsons, Julia Manzerova, Dale L. Perry, Daniel Koury, Brian D. Hosterman, John Farley

Transmutation Sciences Materials (TRP)

The corrosion of steel by lead–bismuth eutectic (LBE) is an important issue in proposed nuclear transmutation schemes. Russian scientists at the IPPE exposed steel samples to oxygen-controlled LBE at temperatures up to 823 K and exposure times up to 3000 h. We have characterized these post-exposure steel samples and unexposed controls, using scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDAX) and X-ray photoelectron spectroscopy (XPS). Previous researchers have investigated the corrosion by LBE of steel of varying composition. In the present work, we compared two samples having the same composition (standard nuclear grade 316/316L) but different surface preparation: a cold-rolled …

High Temperature Heat Exchanger Project: Quarterly Progress Report April 1, 2004 Through June 30, 2004, Anthony Hechanova

Publications (NSTD)

UNLV hosted a meeting on NHI Materials and Heat Exchanger Design on Monday, May 17. Paul Pickard (Sandia National Lab) and Bill Corwin (Oak Ridge National Lab) facilitated the meeting. The purpose of the meeting was to summarize the hydrogen materials and heat exchanger requirements and priorities for UNLV staff and their collaborators to support the research proposal solicitation for the UNLV Research Foundation HTHX program. Attendance was heavier than anticipated and required a change of venue to accommodate the crowd of over 30.

Use Of Collaborative Learning Exercises To Increase Student Motivation And Learning In An Introduction To Materials Engineering Course, Stacy Gleixner, Hilary Lackritz

Faculty Publications

A collection of collaborative, in-class exercises have been designed for use in a freshmen/sophomore level Introduction to Materials Science and Engineering class. The activities are team based problems that include open ended design problems, calculation questions, and thought problems on unanswered research questions. The activities have been designed with the goal of having one or two a week embedded in a more traditional lecture setting. The exercises relate to the topics covered in most standard Introduction to Materials classes (crystal structure, mechanical properties, polymers, phase diagrams…). Each activity is designed specifically to engage the students in the lecture and excite …

Travelogue From The Materials World: A First Week Laboratory Activity, Katherine C. Chen, Blair London, Linda Vanasupa, Timothy T. Orling, Lisa Christensen

Materials Engineering

A fun, yet educational, laboratory activity was developed for the first week of an introductory Materials Engineering laboratory in order to set the stage for the rest of the quarter. The class is broken up into 8 teams, and each team performs a different experiment during each lab period. The teams then rotate lab experiments each week in a round robin manner, and thus teamwork is an important component of the class. In order to quickly promote team bonding the very first week, each team goes on a materials scavenger hunt together. A variety of materials-related items are to be …

Interactive Demonstrations And Laboratories Using Shape Memory Alloys, Wendy C. Crone, Eric J. Voss, Katherine C. Chen

Materials Engineering

Shape memory alloys (SMAs) constitute a unique class of materials that undergo a reversible phase transformation allowing the material to display dramatic stress-induced and temperature-induced deformations that are recoverable. Nickel titanium (NiTi) is a shape memory alloy used in a wide variety of biomedical, aerospace, automotive and other applications. The austenite-martensite phase transformation that occurs in these alloys with changes in temperature or applied stress is responsible for the unique properties of this material. The unusual behavior of SMAs provides an exciting way to engage students and can be incorporated into a variety of courses under topics such as phase …

The Structure Of The High-Energy Spin Excitations In A High-Transition-Temperature Superconductor, S. M. Hayden, H. A. Mook, Pengcheng Dal, T. G. Perring, F. Doǧan

Materials Science and Engineering Faculty Research & Creative Works

In conventional superconductors, lattice vibrations (phonons) mediate the attraction between electrons that is responsible for superconductivity. The high transition temperatures (high-Tc) of the copper oxide superconductors has led to collective spin excitations being proposed as the mediating excitations in these materials. The mediating excitations must be strongly coupled to the conduction electrons, have energy greater than the pairing energy, and be present at Tc. The most obvious feature in the magnetic excitations of high-Tc superconductors such as YBa 2Cu3O6+x is the so-called 'resonance'. Although the resonance may be strongly coupled to the superconductivity, it is unlikely to be the main …

The Influence Of Academic Dishonesty On Ethical Decision- Making In The Workplace: A Study Of Engineering Students, Trevor S. Harding, Donald D. Carpenter, Cynthia J. Finelli, Honor J. Passow

Materials Engineering

According to studies conducted over the past four decades, engineering students self-report high frequencies of academic dishonesty (cheating) while in college. Research on college students in all fields has indicated that such behavior is more common among students who participate in academic dishonesty at the high school level and that it is correlated with other deviant or unethical behaviors, such as petty theft and lying. If, in fact, such correlations do exist, one might hypothesize that there is also a relationship between academic dishonesty in college and deviant or unethical behavior in professional practice. Placing this relationship in the context …

Life Cycle Assessment As A Tool For Green Manufacturing Education, Trevor S. Harding

Materials Engineering

The design and production of engineering products that have a reduced impact on the environment and human health has increasingly become a strategic goal of corporations. Consequently, starting engineers will need to be educated in green design techniques. One method that is particularly attractive to engineers is Life Cycle Assessment (LCA). LCA is an objective approach to evaluating the environmental burden of a product, process or activity by identifying and quantifying material and energy usage and waste outputs at every life stage. LCA involves three steps: identification of scope of analysis, life cycle inventory, and impact analysis. Such an approach …

Does Academic Dishonesty Relate To Unethical Behavior In Professional Practice? An Exploratory Study, Trevor S. Harding, Donald D. Carpenter, Cynthia J. Finelli, Honor J. Passow

Materials Engineering

Previous research indicates that students in engineering self-report cheating in college at higher rates than those in most other disciplines. Prior work also suggests that participation in one deviant behavior is a reasonable predictor of future deviant behavior. This combination of factors leads to a situation where engineering students who frequently participate in academic dishonesty are more likely to make unethical decisions in professional practice. To investigate this scenario, we propose the hypotheses that (1) there are similarities in the decision-making processes used by engineering students when considering whether or not to participate in academic and professional dishonesty, and (2) …

Structural And Magnetic Properties Of Mrsr₂Y₁.₅Ce₀.₅Cu₂Oz (M-1222) Compounds With M = Fe And Co, V. P. S. Awana, Anurag Gupta, H. Kishan, Satish K. Malik, William B. Yelon, J. Lindén, M. Karppinen, H. Yamauchi, Darshan C. Kundaliya

Physics Faculty Research & Creative Works

The MSr2Y1.5Ce0.5Cu2Oz (M-1222) compounds, with M = Fe and Co, have been synthesized through a solid-state reaction route. Both compounds crystallize in a tetragonal structure (space group 14/mmm). A Rietveld structural refinement of the room-temperature neutron diffraction data for Fe-1222 reveals that nearly half the Fe remains at the M site, while the other half goes to the Cu site in the CuO2 planes. Existence of Fe at two different lattice sites is also confirmed by 57Fe Mössbauer spectroscopy from which it is inferred that ~50% of the total Fe occupies the Cu site in the CuO2 planes as Fe3+, …