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Studies On Stable Crack Growth, Mohammed Juma Humaid Al-Ghafri 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 ...


Effect Of Chain Rigidity On Network Architecture And Deformation Behavior Of Glassy Polymer Networks, Kyler Reser Knowles 2017 University of Southern Mississippi

Effect Of Chain Rigidity On Network Architecture And Deformation Behavior Of Glassy Polymer Networks, Kyler Reser Knowles

Dissertations

Processing carbon fiber composite laminates creates molecular-level strains in the thermoset matrix upon curing and cooling which can lead to failures such as geometry deformations, micro-cracking, and other issues. It is known strain creation is attributed to the significant volume and physical state changes undergone by the polymer matrix throughout the curing process, though storage and relaxation of cure-induced strains remain poorly understood. This dissertation establishes two approaches to address the issue. The first establishes testing methods to simultaneously measure key volumetric properties of a carbon fiber composite laminate and its polymer matrix. The second approach considers the rigidity of ...


Half-Metallic Co-Based Quaternary Heusler Alloys For Spintronics: Defect- And Pressure-Induced Transitions And Properties, Enamullah, D. D. Johnson, K. G. Suresh, Aftab Alam 2017 Indian Institute of Technology Bombay

Half-Metallic Co-Based Quaternary Heusler Alloys For Spintronics: Defect- And Pressure-Induced Transitions And Properties, Enamullah, D. D. Johnson, K. G. Suresh, Aftab Alam

Duane D. Johnson

Heusler compounds offer potential as spintronic devices due to their spin polarization and half-metallicity properties, where electron spin-majority (minority) manifold exhibits states (band gap) at the electronic chemical potential, yielding full spin polarization in a single manifold. Yet, Heuslers often exhibit intrinsic disorder that degrades its half-metallicity and spin polarization. Using density-functional theory, we analyze the electronic and magnetic properties of equiatomic Heusler (L21) CoMnCrAl and CoFeCrGe alloys for effects of hydrostatic pressure and intrinsic disorder (thermal antisites, binary swaps, and vacancies). Under pressure, CoMnCrAl undergoes a metallic transition, while half-metallicity in CoFeCrGe is retained for a limited range. Antisite ...


Origin Of Magnetic Anisotropy In Doped Ce2co17 Alloys, Liqin Ke, D. A. Kukusta, Duane D. Johnson 2017 Ames Laboratory

Origin Of Magnetic Anisotropy In Doped Ce2co17 Alloys, Liqin Ke, D. A. Kukusta, Duane D. Johnson

Duane D. Johnson

Magnetocrystalline anisotropy (MCA) in doped Ce2Co17 and other competing structures was investigated using density functional theory. We confirmed that the MCA contribution from dumbbell Co sites is very negative. Replacing Co dumbbell atoms with a pair of Fe or Mn atoms greatly enhance the uniaxial anisotropy, which agrees quantitatively with experiment, and this enhancement arises from electronic-structure features near the Fermi level, mostly associated with dumbbell sites. With Co dumbbell atoms replaced by other elements, the variation of anisotropy is generally a collective effect and contributions from other sublattices may change significantly. Moreover, we found that Zr doping promotes the ...


Large Energy Product Enhancement In Perpendicularly Coupled Mnbi/Cofe Magnetic Bilayers, T. R. Gao, L. Fang, S. Fackler, S. Maruyama, X. H. Zhang, L. L. Wang, T. Rana, P. Manchanda, A. Kashyap, K. Janicka, A. L. Wysocki, A. T. N'Diaye, E. Arenholz, J. A. Borchers, B. J. Kirby, B. B. Maranville, K. W. Sun, M. J. Kramer, V. P. Antropov, D. D. Johnson, R. Skomski, J. Cui, I. Takeuchi 2017 University of Maryland at College Park

Large Energy Product Enhancement In Perpendicularly Coupled Mnbi/Cofe Magnetic Bilayers, T. R. Gao, L. Fang, S. Fackler, S. Maruyama, X. H. Zhang, L. L. Wang, T. Rana, P. Manchanda, A. Kashyap, K. Janicka, A. L. Wysocki, A. T. N'Diaye, E. Arenholz, J. A. Borchers, B. J. Kirby, B. B. Maranville, K. W. Sun, M. J. Kramer, V. P. Antropov, D. D. Johnson, R. Skomski, J. Cui, I. Takeuchi

Duane D. Johnson

We demonstrate substantial enhancement in the energy product of MnBi-based magnets by forming robust ferromagnetic exchange coupling between a MnBi layer and a thin CoFe layer in a unique perpendicular coupling configuration, which provides increased resistance to magnetization reversal. The measured nominal energy product of 172kJ/m3 at room temperature is the largest value experimentally attained for permanent magnets free of expensive raw materials. Our finding shows that exchange-coupled MnBi/CoFe magnets are a viable option for pursuing rare-earth-free magnets with energy products approaching those containing rare-earth elements.


Chapter 14 – Evolutionary Algorithms Applied To Electronic-Structure Informatics: Accelerated Materials Design Using Data Discovery Vs. Data Searching, Duane D. Johnson 2017 Iowa State University

Chapter 14 – Evolutionary Algorithms Applied To Electronic-Structure Informatics: Accelerated Materials Design Using Data Discovery Vs. Data Searching, Duane D. Johnson

Duane D. Johnson

We exemplify and propose extending the use of genetic programs (GPs) – a genetic algorithm (GA) that evolves computer programs via mechanisms similar to genetics and natural selection – to symbolically regress key functional relationships between materials data, especially from electronic structure. GPs can extract structure–property relations or enable simulations across multiple scales of time and/or length. Uniquely, GP-based regression permits “data discovery” – finding relevant data and/or extracting correlations (data reduction/data mining) – in contrast to searching for what you know, or you think you know (intuition). First, catalysis-related materials correlations are discussed, where simple electronic-structure-based rules are revealed ...


Intrinsic Magnetic Properties In R(Fe1−Xcox)11tiz(R=Yand Ce;Z=H,C,And N), Liqin Ke, Duane D. Johnson 2017 Ames Laboratory

Intrinsic Magnetic Properties In R(Fe1−Xcox)11tiz(R=Yand Ce;Z=H,C,And N), Liqin Ke, Duane D. Johnson

Duane D. Johnson

To guide improved properties coincident with reduction of critical materials in permanent magnets, we investigate via density functional theory (DFT) the intrinsic magnetic properties of a promising system, R(Fe1−xCox)11TiZ with R=Y, Ce and interstitial doping (Z=H,C,N). The magnetization M, Curie temperature TC, and magnetocrystalline anisotropy energy K calculated in local density approximation to DFT agree well with measurements. Site-resolved contributions to K reveal that all three Fe sublattices promote uniaxial anisotropy in YFe11Ti, while competing anisotropy contributions exist in YCo11Ti. As observed in experiments on R(Fe1−xCox)11Ti, we find a complex ...


Asymmetric Mass Acquisition In Labi: Topological Semimetal Candidate, Yun Wu, Tai Kong, Lin-Lin Wang, Duane D. Johnson, Daixiang Mou, Lunan Huang, Benjamin Schrunk, Sergey L. Bud'ko, Paul C. Canfield, Adam Kaminski 2017 Iowa State University

Asymmetric Mass Acquisition In Labi: Topological Semimetal Candidate, Yun Wu, Tai Kong, Lin-Lin Wang, Duane D. Johnson, Daixiang Mou, Lunan Huang, Benjamin Schrunk, Sergey L. Bud'ko, Paul C. Canfield, Adam Kaminski

Duane D. Johnson

We use our high resolution He-lamp-based, tunable laser-based angle-resolved photoemission spectroscopy measurements and density functional theory calculations to study the electronic properties of LaBi, a binary system that was proposed to be a member of a new family of topological semimetals. Both bulk and surface bands are present in the spectra. The dispersion of the surface state is highly unusual. It resembles a Dirac cone, but upon closer inspection we can clearly detect an energy gap. The bottom band follows roughly a parabolic dispersion. The dispersion of the top band remains very linear, “V” -shape like, with the tip approaching ...


C2-Neb: The Nudged Elastic Band Method With Two Climbing Images, Validated On The Martensitic Transformation In Niti Shape Memory Alloy, Nikolai A. Zarkevich, Duane D. Johnson 2017 Ames Laboratory

C2-Neb: The Nudged Elastic Band Method With Two Climbing Images, Validated On The Martensitic Transformation In Niti Shape Memory Alloy, Nikolai A. Zarkevich, Duane D. Johnson

Duane D. Johnson

The nudged-elastic band (NEB) method is modified with concomitant two climbing images (C2-NEB) to find a transition state (TS) in complex energy landscapes, such as those with serpentine minimal energy path (MEP). If a single climbing image (C1-NEB) successfully finds the TS, C2-NEB finds it with higher stability and accuracy. However, C2-NEB is suitable for more complex cases, where C1-NEB misses the TS because the MEP and NEB directions near the saddle point are different. Generally, C2-NEB not only finds the TS but guarantees that the climbing images approach it from the opposite sides along the MEP, and it estimates ...


A Ship-In-A-Bottle Strategy To Synthesize Encapsulated Intermetallic Nanoparticle Catalysts: Exemplified For Furfural Hydrogenation, Raghu V. Maligal-Ganesh, Chaoxian Xiao, Tian Wei Goh, Lin-Lin Wang, Jeffrey Gustafson, Yuchen Pei, Zhiyuan Qi, Duane D. Johnson, Shiran Zhang, Franklin Feng Tao, Wenyu Huang 2017 Iowa State University

A Ship-In-A-Bottle Strategy To Synthesize Encapsulated Intermetallic Nanoparticle Catalysts: Exemplified For Furfural Hydrogenation, Raghu V. Maligal-Ganesh, Chaoxian Xiao, Tian Wei Goh, Lin-Lin Wang, Jeffrey Gustafson, Yuchen Pei, Zhiyuan Qi, Duane D. Johnson, Shiran Zhang, Franklin Feng Tao, Wenyu Huang

Duane D. Johnson

Intermetallic compounds are garnering increasing attention as efficient catalysts for improved selectivity in chemical processes. Here, using a ship-in-a-bottle strategy, we synthesize single-phase platinum-based intermetallic nanoparticles (NPs) protected by a mesoporous silica (mSiO2) shell by heterogeneous reduction and nucleation of Sn, Pb, or Zn in mSiO2-encapsulated Pt NPs. For selective hydrogenation of furfural to furfuryl alcohol, a dramatic increase in activity and selectivity is observed when intermetallic NPs catalysts are used in comparison to Pt@mSiO2. Among the intermetallic NPs, PtSn@mSiO2 exhibits the best performance, requiring only one-tenth of the quantity of Pt used ...


Removal Of Chlorine From Chlorine-Nitrogen Mixture In A Film Of Liquid Water, Sarwan S. Sandhu 2017 University of Dayton

Removal Of Chlorine From Chlorine-Nitrogen Mixture In A Film Of Liquid Water, Sarwan S. Sandhu

Sarwan S. Sandhu

In industry there are many examples of absorption of a gas with or without chemical reaction in the liquid phase. In physical absorption, a particular gaseous component is removed from a gas mixture due to its larger solubility in the liquid phase solvent. The removal of butane and pentane from a refinery gas mixture by a heavy oil in the liquid phase is an example of physical absorption. In absorption with chemical reaction, the gaseous component to be removed transfers across the gas-liquid interface due to a difference in the bulk chemical potentials or concentrations in the two phases. The ...


Characterization Of Iron Phthalocyanine As The Cathode Active Material For Lithium-Ion Batteries, Sarwan S. Sandhu, Joseph P. Fellner 2017 University of Dayton

Characterization Of Iron Phthalocyanine As The Cathode Active Material For Lithium-Ion Batteries, Sarwan S. Sandhu, Joseph P. Fellner

Sarwan S. Sandhu

The developed thermodynamic functions for the determination of Gibbs free energy, enthalpy, and entropy of formation of solid lithium-iron phthalocyanine (LixFePc) from solid lithium and iron phthalocyanine as a function of x, defined as g-moles of the intercalated lithium per g-mole of iron phthalocyanine, at a fixed set of temperature and pressure conditions are presented. In addition, a proposed expression for the evaluation of lithium diffusion coefficient in solid iron phthalocyanine as a function of both x and temperature, and the experimental results from the ongoing research/development work on the lithium/iron phthalocyanine cells are included.


Negahban Group Report: Saw-Tooth Shear Response Of Aged Poly(Methyl Methacrylate) (Pmma), Mehrdad Negahban 2017 University of Nebraska - Lincoln

Negahban Group Report: Saw-Tooth Shear Response Of Aged Poly(Methyl Methacrylate) (Pmma), Mehrdad Negahban

Mechanical & Materials Engineering Faculty Publications

Results for isothermal saw-tooth shear loading experiments conducted on annealed and oven-cooled poly(methyl methacrylate) (PMMA) at temperatures between 50oC and 140oC. The experiments were conducted 1996.


Defect Engineering: A Path Toward Exceeding Perfection, Hamed Attariani, Kasra Momeni, Kyle Adkins 2017 Wright State University - Lake Campus

Defect Engineering: A Path Toward Exceeding Perfection, Hamed Attariani, Kasra Momeni, Kyle Adkins

Hamed Attariani

Moving to nanoscale is a path to get perfect materials with superior properties. Yet defects, such as stacking faults (SFs), are still forming during the synthesis of nanomaterials and, according to common notion, degrade the properties. Here, we demonstrate the possibility of engineering defects to, surprisingly, achieve mechanical properties beyond those of the corresponding perfect structures. We show that introducing SFs with high density increases the Young’s Modulus and the critical stress under compressive loading of the nanowires above those of a perfect structure. The physics can be explained by the increase in intrinsic strain due to the presence ...


Degradation Of Azo Dyes Under Different Wavelengths Of Uv Light With Chitosan-Sno2 Nanocomposites, Mohammad Mansoob Khan Dr, R Saravanan, Vinod Kumar Gupta 2017 Universiti Brunei Darussalaam

Degradation Of Azo Dyes Under Different Wavelengths Of Uv Light With Chitosan-Sno2 Nanocomposites, Mohammad Mansoob Khan Dr, R Saravanan, Vinod Kumar Gupta

Dr. Mohammad Mansoob Khan

In this study, synthesis of novel binary chitosan-SnO2 nanocomposites is reported. Different physical and chemical techniques were used to characterize and analyze the characteristics of the chitosan-SnO2 nanocomposites as photocatalysts. The prepared novel photocatalysts were used to degrade the model dyes such as methyl orange (MO) and rhodamine B (RhB) under different wavelengths (254, 310 and 365 nm) of UV light. The photocatalytic degradation results suggest that the prepared binary chitosan-SnO2(50:50) nanocomposite shows superior degradation efficiency compared with pure SnO2and binary chitosan-SnO2 (75:25) nanocomposite owing to its high crystallinity, high surface ...


Geopolymer Applications And Material Specifications In Railway Industry, Sakdirat Kaewunruen 2017 University of Birmingham

Geopolymer Applications And Material Specifications In Railway Industry, Sakdirat Kaewunruen

Sakdirat Kaewunruen

Geopolymer has been developed in the past decades and its applications in civil infrastructures start to gain popularity by replacing high-carbon concrete materials with the greener material. However, the application and uses of geopolymer concrete in railway industry are not common. It is because the material design and mixture did not fully accommodate the sub-system and systemic requirements for rail operations and maintenance. In this presentation, the emphasis is placed on the promising solutions to solve the sustainability issue and applicability for geopolymer concrete in railway environments. The review of railway infrastructures and their design and operational requirements are highlighted ...


Sustainable And Self-Sensing Concrete, Sakdirat Kaewunruen, Maaninder Singh, Ange-Therese Akono, Tetsuya Ishida 2017 University of Birmingham

Sustainable And Self-Sensing Concrete, Sakdirat Kaewunruen, Maaninder Singh, Ange-Therese Akono, Tetsuya Ishida

Sakdirat Kaewunruen

The majority of civil infrastructure is constructed using concrete materials and currently concrete production is at all time high resulting in significant carbon dioxide emissions. Furthermore, concrete structures have low tensile strength and low ductility increasing the risk of failure. Therefore concrete is currently neither environmentally nor economically sustainable. In this study, the experimental investigation has been highly promising in identifying a solution to solve the sustainability issue regarding concrete. Our critical literature showed that there have been successful in identifying the most optimum solution to solve the issue of carbon dioxide emissions related to concrete production but concrete structures ...


Physical Properties Of Single Crystalline R Mg 2 Cu 9 ( R = Y , Ce − Nd , Gd − Dy , Yb ) And The Search For In-Plane Magnetic Anisotropy In Hexagonal Systems, Tai Kong, William R. Meier, Qisheng Lin, Scott M. Saunders, S. L. Bud’ko, Rebecca Flint, Paul C. Canfield 2017 Iowa State University

Physical Properties Of Single Crystalline R Mg 2 Cu 9 ( R = Y , Ce − Nd , Gd − Dy , Yb ) And The Search For In-Plane Magnetic Anisotropy In Hexagonal Systems, Tai Kong, William R. Meier, Qisheng Lin, Scott M. Saunders, S. L. Bud’Ko, Rebecca Flint, Paul C. Canfield

Qisheng Lin

Single crystals ofRMg2Cu9 (R = Y, Ce-Nd, Gd-Dy, Yb) were grown using a high-temperature solution growth technique and were characterized by measurements of room-temperature x-ray diffraction, temperature-dependent specific heat, and temperature- and field-dependent resistivity and anisotropic magnetization. YMg2Cu9 is a nonlocal- moment-bearing metal with an electronic specific heat coefficient, γ ∼ 15 mJ/mol K2. Yb is divalent and basically non-moment-bearing in YbMg2Cu9. Ce is trivalent in CeMg2Cu9 with two magnetic transitions being observed at 2.1 K and 1.5 K. PrMg2Cu9 does not exhibit any magnetic phase transition down to 0.5 K. The other members being studied (R = Nd ...


Dual Mechanism For Toughening And Sustained Aminoglycoside Elution From A Polyphosphate Hydrogel, Dwight D. Lane, Russell J. Stewart PhD 2017 University of Utah

Dual Mechanism For Toughening And Sustained Aminoglycoside Elution From A Polyphosphate Hydrogel, Dwight D. Lane, Russell J. Stewart Phd

Biomedical Engineering Western Regional Conference

No abstract provided.


Redesign Of Computer Keyboards For Hospital And Consumer Use, Kent Williams, Brian Jensen, Anton Bowden 2017 Brigham Young University - Provo

Redesign Of Computer Keyboards For Hospital And Consumer Use, Kent Williams, Brian Jensen, Anton Bowden

Biomedical Engineering Western Regional Conference

Application of carbon nanotube coatings to computer keyboards in order to reduce the spread of bacteria in hospitals and homes.

Keywords: carbon nanotube, bacteria, antimicrobial, keyboard, design, MRSA, biofilm


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