Iowa State College
University of South Florida
University of Nebraska at Lincoln
Montana Tech Library
California Polytechnic State University, San Luis Obispo
Quattrone Nanofabrication Facility
University of Akron Main Campus
Studies On Stable Crack Growth,
2017
United Arab Emirates University
Studies On Stable Crack Growth, Mohammed Juma Humaid Al-Ghafri
Theses
The goal of this work is to experimentally investigate the stable crack growth (SCG) fracture behavior of AISI 4340 alloy steel. A series of mode I and mixed mode SCG fracture tests were carried out on 8 mm thick compact tension (CT) specimens subjected to quasistatic loading. The wire cutting technique was used to introduce a pre-notch/ pre-crack of 0.05 mm root radius to the specimen. Five different loading angles Ψ between the loading axis and the crack surface were employed; 90° (mode I), 75°, 65°, 60° and 50°. Five different ratios of original crack length to specimen width ...
Fifty-Plus-Year Postflight Analysis Of First Fluid Experiment Aboard A Spacecraft,
2017
Portland State University
Fifty-Plus-Year Postflight Analysis Of First Fluid Experiment Aboard A Spacecraft, Mark M. Weislogel, Yongkang Chen, William J. Masica, Fred J. Kohl, Robert D. Green
Mark M. Weislogel
This year marks the 55th anniversary of the first fluid physics experiment performed aboard a spacecraft during the Mercury-Atlas 7 mission. Since then, NASA has conducted over 80 fluids physics experiments aboard a variety of spacecraft, many of which have enhanced the understanding of large-length-scale capillary phenomena relevant to liquid management in the weightless state. As both celebration and demonstration, the Mercury-Atlas 7 fluids experiment is revisited in light of the current understanding of large-length-scale capillary fluidics. Employing a modern numerical tool, a rich variety of experimental outcomes are discovered that were not observed during the flight experiment. Interestingly, experimental ...
Plasticization And Reinforcement In A Boron Cage Compound Polyurethane Nanocomposite: A Dielectric Study,
2017
Iowa State University
Plasticization And Reinforcement In A Boron Cage Compound Polyurethane Nanocomposite: A Dielectric Study, J. Liu, X. Zhang, D. E. Bowen, Nicola Bowler
Nicola Bowler
In order to control and modify the physical properties of nanocomposite systems, it is essential to understand the nano-filler/polymer structure–property relationships. Boron cage compounds (BCCs) are a class of icosahedral, closed cage molecules that are of interest due to their high boron content, their inherent neutron absorbing/shielding properties, their potential ability to act as molecular nano-particles and their ability to significantly improve the thermal stability of polymers in which they have been incorporated. When the BCC n-hexylcarborane is blended with a polybutadiene (PBD)/polyurethane (PU) segmented copolymer (EN8) an increase in the glass transition (Tg) temperature of ...
Single-Step, Atmospheric Pressure Chemical Vapor Deposition Of Methylammonium Bismuth Iodide Thin Films,
2017
Washington University in St. Louis
Single-Step, Atmospheric Pressure Chemical Vapor Deposition Of Methylammonium Bismuth Iodide Thin Films, Xiao Chen
Engineering and Applied Science Theses & Dissertations
Lead halide perovskites (CH3NH3PbI3 and its variants) are promising solar cell absorber materials. Though the reported power conversion efficiencies of lead halide perovskite solar cells (up to 21%) are competitive with commercial silicon solar cells, lead toxicity in these perovskites present a challenge to further scale-up and eventual commercialization. Recently, bismuth (Bi3+) based organic halide perovskite has drawn attention as a substitution for lead-free perovskites, since it is a non-toxic 6p-block element, isoelectronic with Pb2+. Methylammonium bismuth iodide ((CH3NH3)3Bi2I9) is reported for its non-toxic constituents ...
Electrothermal Lifetime Prediction Of Polyimide Wire Insulation With Application To Aircraft,
2017
Iowa State University
Electrothermal Lifetime Prediction Of Polyimide Wire Insulation With Application To Aircraft, Peter R. Hondred, Nicola Bowler, Michael R. Kessler
Nicola Bowler
This work investigates the electrothermal lifetime of a commonly used polyimide wire insulation material, Kapton®, through the use of thermogravimetry (TG) and breakdown voltage testing. From TG, an isoconversional model-free kinetic evaluation was used to obtain a relationship between the activation energies of degradation for Kapton as a function of weight loss. By relating the electrical life theory and the TG theory through the model defined by Toop (IEEE Trans. Dielectr. Electr. Insul. 1971, 6, 2), the electrothermal lifetime of Kapton has been calculated for conditions of 12 and 14.7 kV over a temperature range of 250–400°C ...
Dynamics Of Poly(Methyl Methacrylate)–Montmorillonite Nanocomposites: A Dielectric Study,
2017
Iowa State University
Dynamics Of Poly(Methyl Methacrylate)–Montmorillonite Nanocomposites: A Dielectric Study, Weixing Sun, Li Li, Michael R. Kessler, Nicola Bowler
Nicola Bowler
The effect of varying amounts of montmorillonite (MMT) filler (in weight ratios of 100/0, 100/5, and 100/10) on the molecular dynamics and polarization of atactic poly(methyl methacrylate) (PMMA) is investigated using broad-band dielectric spectroscopy from 10−2 to 106 Hz and at temperatures from 30 to 140 °C. The experimental data were analyzed with the sum of Havriliak–Negami (HN) functions and a power-law conduction term. The characteristic frequency, activation energies, and dielectric strength of PMMA/MMT nanocomposites were analyzed. As MMT content increases, a Maxwell–Wagner–Sillars (MWS) relaxation emerges in the nanocomposites and the ...
Comparison Of Pm-Hip To Cast Alloy 625 For Nuclear Applications,
2017
Purdue University
Comparison Of Pm-Hip To Cast Alloy 625 For Nuclear Applications, Alexander L. Bullens, Keyou Mao, Janelle P. Wharry, Esteban Bautista
The Summer Undergraduate Research Fellowship (SURF) Symposium
PM-HIP, or Powder Metallurgy and Hot Isostatic Pressing, metals have been a low cost alternative to forged and cast structural metals within various industries. The nuclear industry has recently developed interest in PM-HIP alloys, but further research needs to be done to quantify their mechanical properties and characterize the microstructure. Specifically, we must understand the mechanical and microstructural evolution of PM-HIP materials after long-term operation at the elevated temperatures that PM-HIP components will experience in service. We focus on Ni-base alloy Inconel 625, and compare the PM-HIP version to the cast version. Our methodology consists of annealing samples to various ...
Modelling Catalytic Structures With Python And Ase,
2017
St. Mary's College of Maryland
Modelling Catalytic Structures With Python And Ase, Tommie L. Day, Peilin Liao, Pilsun Yoo
The Summer Undergraduate Research Fellowship (SURF) Symposium
Voltaic cells hold great potential as a source of clean electricity generation. These fuel sources are more efficient than combustion engines, and they do not produce environmentally harmful by-products. The electrochemical reaction which occurs within the cell is typically catalyzed by platinum, which increases the cost. The search for a better performing, less expensive catalyst is hindered by the lack of a complete, predictive theory of catalysis. Using Quantum Espresso and the Atomic Simulation Environment library for Python, we created a tool for nanoHUB.org which can visually and computationally model catalytic surfaces. This tool can simulate nanoparticles and metallic ...
Cylindrical Shell Based Phase Transforming Cellular Materials: Designing A Recoverable Energy Dissipating Material,
2017
Purdue University
Cylindrical Shell Based Phase Transforming Cellular Materials: Designing A Recoverable Energy Dissipating Material, Gordon F. Jarrold, David Restrepo, Nilesh Mankame, Pablo Zavattieri
The Summer Undergraduate Research Fellowship (SURF) Symposium
Energy dissipating materials are used in a variety of impact events to protect more important parts of a system; one example of this is a football player’s helmet protecting a brain. A major drawback to classic energy dissipating materials however is that they dissipate energy through plastic deformation, meaning that after a single use, permanent deformations will prevent the material from being reusable to the same capacity as initially. We have designed a 1D cellular material in which geometric phase transformations in cylindrical shell elements are the primary energy dissipating mechanism, allowing for recoverability after use while keeping high ...
Investigating Tantalum As A Plasma-Facing Component For Nuclear Fusion Reactors,
2017
Purdue University
Investigating Tantalum As A Plasma-Facing Component For Nuclear Fusion Reactors, Arvind Sundaram, Jitendra K. Tripathi, Theodore J. Novakowski, Ahmed Hassanein Ph. D.
The Summer Undergraduate Research Fellowship (SURF) Symposium
Nuclear fusion is a potential source for producing unlimited environment-friendly energy. Tungsten (W) is selected as the primary candidate material for plasma facing component in nuclear fusion reactors due to its high melting temperature (3695 K), low sputtering erosion yield and strong mechanical properties. However, recent investigations on W have confirmed that it undergoes severe surface morphology changes during low energy He plasma and/or ion irradiation similar to a harsh fusion environment. Additionally, our previous studies indicate that tantalum (Ta) may show better resistance to the harsh radiation environment and is therefore worthy of investigation. Hydrogen retention properties, specifically ...
Microstructure Evolution During Compaction Of Powder Blends,
2017
Howard University
Microstructure Evolution During Compaction Of Powder Blends, Ayush Giri, Marcial Gonzalez, Yasasvi Bommire
The Summer Undergraduate Research Fellowship (SURF) Symposium
Powder compaction is a manufacturing technology used to transform powder particles into a solid material with unique anisotropic microstructure and low porosity. It is widely used by pharmaceutical companies to manufacture tablets with desired properties. These properties are the result of the microstructure obtained during the compaction process. Therefore, it is imperative to understand the mechanics underneath the constituent granular particles that eventually contribute to properties of the manufactured tablets. Computational simulation tools have been developed in the past to study powder compaction for pharmaceutical tablets. However, most of the already existing tools limit their scope to study individual particles ...
Irradiation-Induced Nanocluster Evolution,
2017
William Penn University
Irradiation-Induced Nanocluster Evolution, Didier Ishimwe, Matthew J. Swenson, Janelle P. Wharry
The Summer Undergraduate Research Fellowship (SURF) Symposium
Oxide dispersion strengthened steel (ODS) and commercial ferritic-martensitic (F-M) alloys are widely accepted candidate structural materials for designing advanced nuclear reactors. Nanoclusters embedded in the steel matrix are key microstructural features of both alloy types. Irradiation from nuclear fusion and fission affects the morphology of these nanoparticles, altering the performance of the alloys and potentially decreasing their usable lifetime. Thus, it is important to understand the effect of irradiation on these nanoparticles in order to predict long-term nuclear reactor performance. It was found that the evolution of nanoclusters in each material is different depending on the experimental irradiation parameters. The ...
Understanding Powder Compaction With Single Particle Measurements,
2017
Purdue University
Understanding Powder Compaction With Single Particle Measurements, Wentao Chen, Ankit Agarwal, Marcial Gonzalez
The Summer Undergraduate Research Fellowship (SURF) Symposium
Powder compaction is the process of transforming granular media into a solid body with a high relative density (low porosity) and a unique anisotropic microstructure. It is critical to understand the physical mechanisms of the compaction process in order to identify powder properties and optimal process parameters for achieving desired properties of the final product. Tools that can simulate particle rearrangement and deformation during the compaction process are usually developed to guide such fundamental understanding. This study aims at understanding powder compaction using particle mechanics approach. Specifically, it employs the nonlocal contact formulation to predict the contact behavior of a ...
Effect Of Particle Interactions On Powder Flow Behavior,
2017
Universidad de Los Andes - Colombia
Effect Of Particle Interactions On Powder Flow Behavior, Ivana A. Penagos, Carolina P. Mora, Teresa Carvajal
The Summer Undergraduate Research Fellowship (SURF) Symposium
The study of powder flow behavior is essential for the development of processing technologies in many industries. In fact, powders have a major function in diverse types of manufacturing, such as pharmaceuticals, foods, chemicals, materials, minerals and cosmetics. This leads to an increasing demand for the development of reliable methods to assess powder flow problems in industry. This research intends to provide a general insight into how surface interactions and particle properties may alter powder flowability. The materials used for this study were lactose, starch, milk powder, cocoa and chocolate. These vary in their interparticle forces as well as on ...
Simulating Dynamic Failure Of Polymer-Bonded Explosives Under Periodic Excitation,
2017
Liberty University
Simulating Dynamic Failure Of Polymer-Bonded Explosives Under Periodic Excitation, Rachel Kohler, Camilo Duarte Cordon, Marisol Koslowski
The Summer Undergraduate Research Fellowship (SURF) Symposium
Accidental mishandling of explosive materials leads to thousands of injuries in the US every year. Understanding the mechanisms behind the detonation process is crucial to prevent such accidents. In polymer-bonded explosives (PBX), high-frequency mechanical excitation generates thermal energy and can lead to an increase in temperature and vapor pressure, and potentially the initiation of the detonation process. However, the mechanisms behind this energy release, such as the effects of dynamic fracture and friction, are not well understood. Experimental data is difficult to collect due to the different time scales of reactions and vibrations, so research is aided by running simulations ...
Core-Shell Copper And Nickel Nanofoam: Uniform Electroplating And Properties,
2017
Washington State University
Core-Shell Copper And Nickel Nanofoam: Uniform Electroplating And Properties, Hassan Zbib, David Bahr
The Summer Undergraduate Research Fellowship (SURF) Symposium
Characterizing materials on the nanoscale is a key factor to enhance nanotechnology in diverse applications, ranging from electronics to energy fields. However, controlling the structure of the material at the nanoscale or mimicking the nanoscale features of a structure that already exists requires linking processing conditions to the nanostructure. This work focuses on solids that show porous patterns at the nano-micro scale; these are often called cellular solids and classified into two categories: honeycombs and foams. This study focuses on nanofoams; with ligament dimensions in the sub-micron scale. Electrospinning has been developed to produce nanofoam structures of polymers with controlled ...
Atomistic Simulations Of Novel Nanoscale Semiconductor Devices: Resistance Switches And Two-Dimensional Transistors,
2017
Texas A & M University - College Station
Atomistic Simulations Of Novel Nanoscale Semiconductor Devices: Resistance Switches And Two-Dimensional Transistors, Joseph P. Anderson, Mahbubul Islam, David Guzman, Alejandro Strachan
The Summer Undergraduate Research Fellowship (SURF) Symposium
As transistors get smaller, we are achieving record levels of memory density. However, there is a limit to how small transistors can be made before their functionality breaks down. Thus alternatives to traditional transistor technology are needed. The two such technologies we examined are: resistance switching devices, which reversibly grow metal filaments through a dielectric, and two-dimensional transistors, which are capable of breaking through the scalability limit of traditional transistors. In order to design resistance switching devices which create filaments with some level of consistency, the dynamics of the filament formation need to be explored. Herein we model this process ...
Improving Methods Of Doping On Black Phosphorus,
2017
Electrocal and Computer Engineering
Improving Methods Of Doping On Black Phosphorus, Yuqin Duan, Adam Charnas, Jingkai Qin, Peide Ye
The Summer Undergraduate Research Fellowship (SURF) Symposium
Black phosphorus (BP) is a 2D semiconducting material with high carrier mobility. It is usually p-type due to oxidation states near its valence band. Although achieved through other growth methods, n-type doping has not yet been accomplished through the modern chemical vapor transport (CVT) growth method. To address this issue, small amounts of tellurium were added to Red Phosphorus to act as a dopant during the CVT growth process in addition to tin(Sn) and tin(IV) iodide, which facilitate growth. The chemicals are heated up to 600°C and precisely cooled in a 21-hour process, during which BP crystals ...
Study Of Persistent Slip Bands Formed By Low Cycle Fatigue On Nickel-Based Superalloys At Room Temperature,
2017
Wesleyan College
Study Of Persistent Slip Bands Formed By Low Cycle Fatigue On Nickel-Based Superalloys At Room Temperature, Anjola Uprety, Sae Matsunaga, Michael S. Titus Dr., Michael D. Sangid Dr., Alberto W. Mello Dr.
The Summer Undergraduate Research Fellowship (SURF) Symposium
The ability of Ni-based superalloys to withstand temperatures in excess of 11000C makes them useful for applications in the hottest components in jet engines, gas turbines, and thrust engines. Increasing the efficiency of these gas turbine engines helps to reduce the fossil fuel consumption and the production of greenhouse gasses. A common mode of failure in these Ni-based superalloys is low cycle fatigue, in which narrow regions of high dislocation density, which are known as persistent slip bands (PSBs), can develop and lead to crack initiation. A detailed understanding of the formation and structure of PSBs has eluded ...
Structure-Force Field Generator For Molecular Dynamics Simulations,
2017
Universidad de Los Andes - Colombia
Structure-Force Field Generator For Molecular Dynamics Simulations, Carlos M. Patiño, Lorena Alzate, Alejandro Strachan
The Summer Undergraduate Research Fellowship (SURF) Symposium
Atomistic and molecular simulations have become an important research field due to the progress made in computer performance and the necessity of new and improved materials. Despite this, first principle simulations of large molecules are still not possible because the high computational time and resources required. Other methods, such as molecular dynamics, allow the simplification of calculations by defining energy terms to describe multiple atom interactions without compromising accuracy significantly. A group of these energy terms is called a force field, and each force field has its own descriptions and parameters. The objective of this project was to develop a ...
