Materials Science and Engineering Commons^™

Boron-Rich Semiconducting Boron Carbide Neutron Detector, Andrew D. Harken, Ellen E. Day, Brian W. Robertson, Shireen Adenwalla

Shireen Adenwalla Papers

Data on the neutron detection capabilities of a variety of boron carbide/Si heterojunction diodes is presented. The pulse height spectra are compared with previously measured conversion layer devices and the variations in shape and position of the peaks are discussed.

The Effects Of Humidity On The Dielectric Response In Ferroelectric Polymer Films Made By Langmuir-Blodgett Deposition, Kristin L. Kraemer, Alexander V. Sorokin, Christina M. Othon, Stephen Ducharme, Vladimir M. Fridkin

Stephen Ducharme Publications

No abstract provided.

Undergraduate Course In Environmental Design And Manufacturing, Andrew S. Borchers, Trevor S. Harding, Terri Lynch-Carls, Benjamin Redekop, Craig Hoff, Jackie El-Sayed, Daryl Doyle

Materials Engineering

This paper is a progress report on the development of an undergraduate course in environmental design and manufacturing. The importance of the topic is clear from National Academy of Engineering statements regarding the need to incorporate content on sustainable technology. The multidisciplinary team includes academic faculty from engineering, science, liberal studies, and business in collaboration with industry partners. The team's approach is to create a case-based course by adapting existing educational modules from Ford Motor Company. The group has received National Science Foundation funding for this project (DUE-0511322), and the project is currently in its beginning phases.

Cheating In College And The Workplace: An Examination Of Engineering Undergraduates' Ethical Behavior, Trevor S. Harding, Donald D. Carpenter, Cynthia J. Finelli

Materials Engineering

Research has demonstrated that engineering undergraduates report higher rates of cheating than those in other disciplines and that students who cheat in college are more likely to make unethical decisions as professionals. Therefore, better understanding the decision-making processes of engineering students and professionals who engage in dishonest behavior could lead to effective college-level interventions to cheating that have a positive impact on the ethical behavior of future professionals. To explore the relationship between academic and professional ethical behavior, the authors launched the Work Experience Study (WES) that examines students’ decision-making in situations where they are tempted to engage in unethical …

Nanomagnetic Structures: Fabrication And Interactions, David J. Sellmyer, Y. C. Sui, Yinfan Xu, M. L. Yan, Kory D. Sorge, Ralph Skomski

Materials Research Science and Engineering Center: Faculty Publications

Magnetic nanostructures with desirable properties such as monodispersed size and crystallographic texturing can be fabricated by a number of synthetic techniques. In this paper, we discuss methods for creating nanoclusters with fine control of individual properties and their interactions, as well as a promising chemical technique that provides control of several properties simultaneously. Current and potential applications also will be addressed.

Mercury And C2B10 Icosahedra Interaction, Carolina C. Ilie, Petru Lunca-Popa, Jiandi Zhang, Bernard Doudin, Peter A. Dowben

Materials Research Science and Engineering Center: Faculty Publications

We contrast the interaction of mercury with adsorbed orthocarborane films and semiconducting (dehydrogenated) boron carbide. Photoemission spectra reveal small shifts in orthocarborane (C₂B₁₀H₁₂) molecular orbital binding energies as well as the shift in mercury 5d_5/2shallow core level binding energies, suggesting only small interaction between mercury and the molecular film. Mercury does, however, interact with decomposed orthocarboranes i.e. semiconducting boron carbide.

Efficiency In Steel Melting: Ladle Development, Kent D. Peaslee, Semen Naumovich Lekakh, Todd P. Sander, Jeffrey D. Smith

Materials Science and Engineering Faculty Research & Creative Works

Effective ladle design and use is important for steel casting production. In foundry operations, the ladle temperature of the liquid steel is typically 150 to 250°F above the steel's melting point to compensate for the heat losses in small ladles and the associated high cooling rates from the large surface area to volume ratios. Higher superheat is also necessary to provide sufficient steel fluidity to properly fill the mold cavity. In spite of the relatively short time that the steel is in contact with the ladle lining, the huge thermal gradients in the lining drive high values of heat flow …

Coupled Electrical And Magnetic Properties In (La,Sr)Feo3-Δ, X.-D. Zhou, Qingsheng Cai, Jinbo Yang, M. S. Kim, William B. Yelon, William Joseph James, Y.-W. Shin, B. J. Scarfino, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

This article is aimed at studying the temperature dependence oxygen nonstoichiometry, magnetic moments, Fe³⁺ fraction, Néel temperature and conductivity of (La,Sr)FeO_3-δ. It is found that the magnetic properties in La_0.60 Sr_0.40 Fe_3-δ is determined by Fe³⁺ and its concentration, and the conductance is resulted from Fe⁴⁺ ions, which act as electron holes. Both of magnetic and electrical properties were directly governed by oxygen nonstoichiometry (δ). when δ=0.2, the compound has maximum Fe³⁺, the saturation magnetic moments and Néel temperature are 3.8 µB and 410 °C, both at the highest level, …

Continuous Solidification Of Yba2cu3o7−X By Isothermal Undercooling, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Growth kinetics and microstructural development of single crystal YBa₂Cu₃O_7−x (Y123) superconductors, prepared by a melt texturing method under isothermal undercooling conditions, were investigated. At small undercooling, ΔT = 6 K, the initial growth of Y123 crystal was terminated at a size of ∼8 mm × 8 mm in the semisolid phase before the entire sample was fully solidified through the peritectic reaction. With incremental increase of ΔT, the growth of the crystal continued so that the whole sample (22 mm diameter and 8 mm thickness) solidified as a single crystal. Termination of the crystal growth …

Microstructural And Mechanical Characterization Of Al-Al2o3 Nanocomposites Synthesized By High-Energy Milling, Balaji Prabhu

Electronic Theses and Dissertations

The twin objectives of the investigation were (i) to synthesize Al/Al2O3 metal matrix composites (MMCs) with uniform distribution of the Al2O3 reinforcement in the Al matrix and (ii) to evaluate the effect of volume fraction and size of the reinforcement on the mechanical behavior of MMCs. This was achieved by successful synthesis of Al-Al2O3 MMCs with volume fractions of 5, 10, 20, 30, and 50%, and particle sizes of 50 nm, 150 nm, and 5 µm of Al2O3 synthesized from blended component powders by a high-energy milling technique. A uniform distribution of the Al2O3 reinforcement in the Al matrix was …

Nondestructive Evaluation Of Thermal Barrier Coatings With Thermal Wave Imaging And Photostimulated Luminescence Spectroscopy, Barbara Franke

Electronic Theses and Dissertations

Gas Turbine manufacturers strive for increased operating temperatures of gas turbine engines to improve efficiency and performance. One method of increasing the temperature beyond material limits is by applying thermal barrier coatings (TBCs) to hot section components. TBCs provide a thermal gradient between the hot gases and metallic substrate, and allow an increase in turbine inlet temperatures of 100-150ºC. However, spallation of TBCs can cause catastrophic failure of turbine engines by incipient melting of the substrate. To prevent such an occurrence, non-destructive evaluation (NDE) techniques are critical for quality control, health monitoring, and life assessment of TBCs. Two techniques in …

Vibrational Behavior Of The MN+1AxN Phases From First-Order Raman Scattering (M=Ti,V,Cr, A=Si, X=C,N), Jonathan E. Spanier, Surojit Gupta, Maher S. Amer, Michel W. Barsoum

Mechanical and Materials Engineering Faculty Publications

We report on the Raman spectra of Ti₃SiC₂ (312), M2AlC(211) (M=Ti, V, Cr, and Nb) and Ti4AlN3 (413), as representative compounds from the family of Mn+1AXn phases. Intense and narrow first-order Raman peaks are observed, and we present an analysis of the spectra based on symmetry considerations and from results of first-principles calculations of phonon frequencies. The agreement between experimental and calculated mode energies is excellent. The identification of the modes enables application of Raman scattering as a diagnostic tool for the detailed study of the structural and physical properties of this family of compounds and their …

Investigation Of Ferroelectricity In Newly Synthesized Nitrile Polymer Systems, Matt Poulsen, Stephen Ducharme, Alexander V. Sorokin, Sahadeva Reddy, James M. Takacs, Y. Wen, Jihee Kim, Shireen Adenwalla

Stephen Ducharme Publications

The ferroelectric and piezoelectric properties of newly synthesized polymer systems have been studied. To date PVDF and its copolymers P(VDF-TrFE) have provided the bulk of the knowledge pertaining to ferroelectricity in polymers. Recently, ultrathin ferroelectric films of P(VDF-TrFE) 70:30 have been fabricated using the Langmuir-Blodgett technique [4]. In this study, various new polymers have been synthesized by chemically altering the PVDF structure. This alteration was performed in order to enhance the amphiphilic nature of the polymer and thus improve the LB film quality and control. Various chemical groups have been used to replace the electropositive hydrogen and electronegative fluorine found …

Investigations Of The Kinetics Of Liquid Droplets On Soil Substrates Using A Novel Approach: Contact Ratio, Abdelhafiz “Moh’D Adnan” Herbawi

Theses

In view of young’s equation, in which the contact angle “ϑ” and the liquid surface tension γ_lv are the only measurable parameters, the contact angle has been widely conceived as a thermodynamic quantity. Accordingly “ϑ” has been the main focus of most theoretical and experimental investigations. The rate of change in the contact angle has been commonly used as the relevant parameter of spreading dynamics in spite of difficulties associated with contact angle measurements that are well recognized in the literature. Considering that the velocity of the contact line is the pertinent quantity for spreading, it is therefore reasonable …

Microwave Processing Of Fiber Reinforced Composites (Optimization Of Glass Reinforced Epoxy Curing Process), Mohamed Osama Ali

Theses

Microwave curing of polymer matrix composites has proven to be an attractive substitute for conventional thermal curing. Industrial applications are currently developed including telecommunications, aerospace, food industry, enhancement concrete setting, composites manufacturing, and many others. Many universities and research centers around the globe are endeavoring to make use of this technology to the most. Common research objectives include homogeneity of the cure, the acceleration of cure kinetics, cure reaction mechanism, and enhancement of mechanical properties. In order to efficiently utilize this form of energy, precise control over power, temperature, and time were applied to achieve set goals: reduce cure time …

Effect Of Bond Thickness On Lifetime Of Adhesive Joints, Ehab Mohammed El-Said El-Refaai Shehab

Theses

The aim of this research was to study the effect of bond thickness on the fracture energy and the lifetime of an adhesively bonded system and develop a model to predict the lifetime of adhesive joints. An approach based on fracture mechanics was employed to assess aluminum/epoxy bond lifetime. An experimental investigation was carried out using double cantilever beam (DCB) specimens with various bond thicknesses under mode 1.

This study describes an approach to predict the rate of crack propagation using Paris' power law. The approach used elevated temperatures to accelerate the crack propagation under constant loads. The elevated temperatures …

Ductile Crack Growth Emanating From Sharp Notes In A Low Alloy Steel, Aladdin I. Abu-Assi

Theses

Stable crack growth behavior emanating from a sharp notch is investigated. Material chosen for tests was EN 34 NiCrMo6 low alloy steel (akin to 4340/4330). Tests were carried out on CT specimens for various angles and ratios to obtain load vs, load-line displacement, Ρ-Δ_LL, curves. Experimental results were analyzed. A normalization approach of Ρ-Δ_{LL curves has been attempted and all experimental curves were represented as a single characteristic curve. Such approach has been also applied on experimental data available from other experimental investigations and results were encouraging, as it may address transferability issue. Fracture surfaces were …}

Investigation Of Epoxy Resin Spreading On Glass Surfaces, Haneen Nemer Al-Dahdooh

Theses

The spreading of a small epoxy resin droplet (l.5tL) on a glass surface was examined with the objective of developing a new type of hydrophobic polymer coated glass which has the ability to reduce heat gain inside a building. The study covered three main aspects; the spreading kinetics of epoxy resin on a glass surface, the hydophopicity of the developed polymer-coated glass surface, and the reduction of solar radiation of this surface, As wettability and spreading phenomena arc a fundamental prerequisite for coating, the spreading kinetics of different curing agent concentrations (15:200, 18:200, 21:200) of epoxy resin on the glass …

Thermal And Mechanical Properties Of Polyethylene-Polypropylene Blends, Rania Omar Akkad

Theses

The thermal and mechanical characteristics of thermally treated and untreated pure polyethylene (PE), pure polypropylene (PP) and their blends were investigated. Injection-moulded samples containing 100:00,75:25,50:50,25:75 and 00:100 weight percentage of PE:PP, were prepared and thermally treated at 100°C for 0, 2, 4, 7, 14 days. The treated samples were subjected to differential scanning calorimetry (DSC), thermogravimetry (TG & DTG), infrared spectral analysis (IR) and tensile tests in order to study the effect of thermal treatment and blending ratios on their thermal and mechanical properties. The results indicate that addition of PE causes the melting temperature (T_m) of PP …

Approaches Toward Integrating Functionality Into Structural Materials, Rajiv S. Mishra

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

Efficiency In Steel Melting: Opportunities And Progress, Kent D. Peaslee, Semen Naumovich Lekakh, Von Richards, Jay Triplett

Materials Science and Engineering Faculty Research & Creative Works

This paper summarizes the findings from a study of melting efficiency in steel foundries and provides examples of material and energy savings from improvements in technology and melting practices. This study is based on information gathered at 19 Steel Founders Society of America member foundries and includes a combination of historical data and industrial measurements by the research team. Information and data were collected on the type of melting equipment, melting practices, energy use and ladle practices. The data was statistically analyzed using STATGRAPHICS commercial software. A multiple regression analysis allowed evaluation of the influence of the melting furnace (type, …

Study Of The Electronic Structure Of Cafeo₃, Jinbo Yang, M. S. Kim, Qingsheng Cai, X.-D. Zhou, Harlan U. Anderson, William Joseph James, William B. Yelon

Materials Science and Engineering Faculty Research & Creative Works

We have studied the charge disproportionation phenomenon in CaFeO3 using the local-spin density approximation with the on-site Coulomb interaction parameter U and exchange parameter J. The calculation reveals that the total number of the 3d electrons is about 5.1 for both Fe(1)(Fe5+) and Fe(2)(Fe3+) atoms, and that there are about 0.25 electron holes in the O-2p band. Therefore, the charge disproportionation can be more accurately described as 2d5L(Fe4+)=d5L2(Fe5+)+d5(Fe3+), where L denotes a hole in the oxygen 2p band, instead of 2d4(Fe4+)=d3(Fe5+)+d5(Fe3+). The hybridization between the Fe-3d and O-2p orbitals is stronger for Fe(1) than for Fe(2) due to the shorter …

Alloy Recovery And Control In Steel Melting, Kent D. Peaslee, Darryl S. Webber, Semen Naumovich Lekakh, Bradley Randall

Materials Science and Engineering Faculty Research & Creative Works

Alloy recovery plays an important role in steel melting economics because the cost of alloying additives such as ferroalloys and pure non-ferrous metals is significantly higher than the cost of steel scrap. Recovery of alloying additives also influences the reproducibility of steel properties from heat to heat. This paper reviews alloy recovery and final chemistry distributions at seven steel foundries and preliminary laboratory studies of alloy dissolution in ladles. Melting and alloy practices were observed for several plant trial heats in each of the foundries. Alloying and chemistry data were collected for an additional 20 - 155 heats at each …

Elevated Temperature Deformation Behavior Of Nanostructured Al-Ni-Gd-Fe Alloys, X. L. Shi, Rajiv S. Mishra, T. J. Watson

Materials Science and Engineering Faculty Research & Creative Works

The elevated temperature deformation behavior of nanostructured Al89Ni3Gd7Fe1 alloy was characterized. Tensile strength was 760 MPa at 373 K. Ductility of the alloy increases with increasing strain rate at 573 K. At high temperatures (623-673 K), the operative deformation mechanism is dislocation-climb controlled.

Segmental Dynamics In Poly(Methyl Acrylate)-D3 On Strongly And Weakly Adsorbing Silica Surfaces, Burak Metin, Frank D. Blum

Chemistry Faculty Research & Creative Works

The segmental dynamics of a polymer on a solid surface appears to be significantly different than that in bulk. The strength of the interaction between polymer segments and a solid surface is likely to be an important factor affecting the segmental mobility of the polymers. Studies of polymers on a weakly adsorbing surface would provide additional understanding of their motional characteristics on surfaces. In a recent NMR study by Rivillon et al., chain dynamics was seen to be different for samples, even when there was no specific interaction with the surface. Peanasky et al. have found a restricted segmental dynamics …

Fourier Transform Infrared Analysis Of Hydroxyl Content Of Hydrothermally Processed Heteroepitaxial Barium Titanate Films, Sandeep K. Patil, Nipun Shah, Frank D. Blum, M. N. Rahaman

Chemistry Faculty Research & Creative Works

The concentration of hydroxyl (-OH) groups in epitaxial barium titanate (BaTiO3) films (thickness ≈ 200 nm), deposited on single-crystal strontium titanate (SrTiO3) at 150 °C by a hydrothermal technique, was investigated using x-ray photoelectron spectroscopy and Fourier transform infrared (FTIR) spectroscopy. After hydrothermal treatment, a broad FTIR resonance for the hydroxyl groups indicated a significant concentration of surface -OH groups in the films. The as-deposited films were subsequently treated hydrothermally with D2O, and the kinetics of the exchange reaction between -OH incorporated into the film and -OD from the D2O were studied using FTIR. For reactions carried out intermittently, the …

Effect Of Plasticizer On Pvac-D3 Dynamics Using 2h Solid-State Nmr, Rakesh R. Nambiar, Frank D. Blum

Chemistry Faculty Research & Creative Works

Poly(vinyl acetate) (PVAc) is an important polymer for use in many applications due to its various bulk and surface characteristics. The structure of poly(vinyl acetate) results in a relatively low glass transition temperature (Tg) and makes it important for processing and applications such as paints, adhesives, thin films and surface coatings. Poly(vinyl acetate) can also be easily plasticized, widening its range of applications. The term "plasticizer" refers to a species that will decrease Tg of a polymer.1 Polymer-plasticizer systems have been studied for years and continue to be of current interest. The effects of polymer-plasticizer interactions2 and plasticizer structure3 on …

The Stability And Oxidation Resistance Of Iron- And Cobalt-Based Magnetic Nanoparticle Fluids Fabricated By Inert-Gas Condensation, Nguyen H. Hai, Raymond Lemoine, Shaina Remboldt, Michelle A. Strand, Steve Wignall, Jeffrey E. Shield, Diandra Leslie-Pelecky

Materials Research Science and Engineering Center: Faculty Publications

Magnetic nanoparticle fluids have numerous biomedical applications, including magnetic imaging, drug delivery, and hyperthermia treatment for cancer. Ideal magnetic nanoparticle fluids have well-separated, biocompatible nanoparticles with a small size distribution that form a stable colloid. We have combined inert-gas condensation, which produces nanoparticles with low polydispersity, with deposition directly into a surfactant-laden fluid to prevent agglomeration. Iron, cobalt, and iron-nitride nanoparticle fluids fabricated using inert-gas condensation have with mean particle sizes from 5-50 nm and remain stable over long periods of time. Iron and cobalt nanoparticles oxidize on exposure to air, with oxidation rates dependent on surfactant type and concentration. …

Research Experiences For Teachers In Materials Science: A Case Study, Michelle A. Strand, Steve Wignall, Diandra Leslie-Pelecky

Materials Research Science and Engineering Center: Faculty Publications

The National Science Education Standards encourage teachers to become involved in research as ‘representatives of science in the classroom’. The Research Experiences for Teachers program affiliated with the Materials Research Science and Engineering Center at the University of Nebraska involves teachers in research on nanoscale magnetic and electronic structures over a summer. Two teachers and a sponsoring researcher share their experiences and what they believe are necessary elements for successful RET experiences.

Multiscale Phenomena In Bruggeman Composites, Ralph Skomski, Jiangyu Li, Jian Zhou, David J. Sellmyer

Materials Research Science and Engineering Center: Faculty Publications

Mechanical, magnetic, and transport properties of arbitrary inhomogeneous composites are investigated by a Bruggeman-type mean-field approach. The theory yields materials parameters as functions of the volume fractions, geometries, and materials constants of the phases. Each system is described by a single response parameter g, which is equal to the percolation threshold of the composite. For macroscopic systems, the approach yields very simple expressions, but nanoscale and multiferroic effects yield relatively complicated corrections to g. In the respective cases, the parameter g depends on the length scale of the composite and has the character of a combination of magnetic, electric, and …