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Galvanic Porous Silicon: Processing And Characterization For Nanoenergetics, Collin R. Becker 2010 University of Colorado at Boulder

Galvanic Porous Silicon: Processing And Characterization For Nanoenergetics, Collin R. Becker

Mechanical Engineering Graduate Theses & Dissertations

Porous silicon (PS) is a silicon (Si) based material composed of pores with diameters ranging from several nanometers to several micrometers. Typically PS is formed by electrochemically etching a Si wafer in a hydrofluoric acid (HF) based electrolyte. This route requires a custom built etch cell and a power supply and is difficult to integrate with the batch processing techniques of conventional Microsystems fabrication. In the first part of this work, a galvanic etching approach is used to fabricate PS in which neither a power supply nor custom etch cell are required. Galvanic etching methods are developed to fabricate thick ...


Localized Mechanical Deformation And Dissolution Of 45s5 Bioglass, Ding Li 2010 University of Kentucky

Localized Mechanical Deformation And Dissolution Of 45s5 Bioglass, Ding Li

University of Kentucky Doctoral Dissertations

Bioactive glasses react with the human physiological solution in control of their biofunctionality. The stress state in bioactive glasses determines the chemomechanical reaction and their biofunctionality. Using the microindentation technique, the effect of the indentation deformation on the surface damage and material dissolution of 45S5 bioglass was investigated.

The indentation-induced residual stresses were calculated. Complete anelastic recoveries of the indentation depths and the impression marks were observed for the first time, which was likely driven by the stored strain energy over the anelastic deformation zone. The indentation-induced local surface damages were revealed before and after the immersion tests in phosphate ...


Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D. 2010 University of Nebraska at Lincoln

Studies Of Dynamic Crack Propagation And Crack Branching With Peridynamics, Youn Doh Ha Ph.D., Florin Bobaru Ph.D.

Faculty Publications from the Department of Engineering Mechanics

In this paper we discuss the peridynamic analysis of dynamic crack branching in brittle materials and show results of convergence studies under uniform grid refinement (m-convergence) and under decreasing the peridynamic horizon (δ-convergence). Comparisons with experimentally obtained values are made for the crack-tip propagation speed with three different peridynamic horizons.We also analyze the influence of the particular shape of themicro-modulus function and of different materials (Duran 50 glass and soda-lime glass) on the crack propagation behavior. We show that the peridynamic solution for this problem captures all the main features, observed experimentally, of dynamic crack propagation and branching, as ...


Validation Of Tool Mark Comparisons Obtained Using A Quantitative, Comparative, Statistical Algorithm, L. Scott Chumbley, Max D. Morris, M. James Kreiser, Charles Fisher, Jeremy Craft, Lawrence Genalo, Stephen Davis, David Faden, Julie Kidd 2010 Iowa State University

Validation Of Tool Mark Comparisons Obtained Using A Quantitative, Comparative, Statistical Algorithm, L. Scott Chumbley, Max D. Morris, M. James Kreiser, Charles Fisher, Jeremy Craft, Lawrence Genalo, Stephen Davis, David Faden, Julie Kidd

Ames Laboratory Publications

A statistical analysis and computational algorithm for comparing pairs of tool marks via profilometry data is described. Empirical validation of the method is established through experiments based on tool marks made at selected fixed angles from 50 sequentially manufactured screwdriver tips. Results obtained from three different comparison scenarios are presented and are in agreement with experiential knowledge possessed by practicing examiners. Further comparisons between scores produced by the algorithm and visual assessments of the same tool mark pairs by professional tool mark examiners in a blind study in general show good agreement between the algorithm and human experts. In specific ...


Electronic And Magnetic Structure Of (Crcl 3 ) 3, M. Grodzicki, B. Mallick, Anja V. Mudring 2010 Iowa State University

Electronic And Magnetic Structure Of (Crcl 3 ) 3, M. Grodzicki, B. Mallick, Anja V. Mudring

Anja V. Mudring

Electronic structure calculations in the local spin-density approximation have been carried out on the recently synthesized trimer (CrCl 3 ) 3 exhibiting antiferromagnetic ordering below T N =55 K. The calculated magnetic coupling constant, the paramagnetic Curie temperature, and the decrease of the magnetic moment below T N are well reproduced by the calculations. An interpretation of the spin structure is given that is consistent with all experimental data currently available.


Preparation And Characterization Of Pt/Γ-Al2o3 Model Catalyst On Nial Alloy, Zhongfan Zhang, Long Li, Lin-Lin Wang, Sergio I. Sanchez, Ross V. Grieshaber, Qi Wang, Duane D. Johnson, Anatoly I. Frenkel, Ralph G. Nuzzo, Judith C. Yang 2010 University of Pittsburgh

Preparation And Characterization Of Pt/Γ-Al2o3 Model Catalyst On Nial Alloy, Zhongfan Zhang, Long Li, Lin-Lin Wang, Sergio I. Sanchez, Ross V. Grieshaber, Qi Wang, Duane D. Johnson, Anatoly I. Frenkel, Ralph G. Nuzzo, Judith C. Yang

Duane D. Johnson

Numerous studies of heterogeneous catalysis systems clearly demonstrate that the metal nanoparticle (NPs)/support interaction is significant in determining the catalytic chemistry. Theoretical simulations have been performed to understand the metal/support interactions [1,2]. For example, theorists discovered that electronic and oxygen defects of γ-Al2O3 anchor the active particles [1]. Platinum NPs dispersed on γ-alumina is one of the most widely used heterogeneous catalysts and Pt performs extremely well as a catalyst for the oxygen-reduction reaction used in fuel cell industries. Hence, we chose Pt/γ-Al2O3 as a model heterogeneous catalyst system to investigate the metal NPs/support interface ...


Interphase Energies Of Hcp Precipitates In Fcc Metals: A Density-Functional Theory Study In Al-Ag, Daniel Finkenstadt, Duane D. Johnson 2010 United States Naval Academy

Interphase Energies Of Hcp Precipitates In Fcc Metals: A Density-Functional Theory Study In Al-Ag, Daniel Finkenstadt, Duane D. Johnson

Duane D. Johnson

Density-functional theory (DFT) calculations of interphase boundary energies relevant to hexagonal-close-packed (hcp) γ-precipitate formation were performed within approximate unit cells that mirror the experimental conditions in face-centered-cubic (fcc) Al-Ag solid solutions. In Al-rich, fcc Al-Ag, γ precipitates are observed to form rapidly with large (300+) aspect ratios even though the Al stacking-fault energy is high (approximately 130 mJ/m2), which should suppress hcp ribbon formation according to standard arguments. Our DFT results show why high-aspect ratio plates occur and why previous estimates based on Wulff construction were orders of magnitude less than observed values. Using DFT, we obtain a Gibbs ...


Communication Prev. Article Next Article Table Of Contents Chains Of Face-Sharing {Zpr6} Octahedra With Alternating Endohedral Iridium Atoms And Chloride Ions In {(Ir,Cl)Pr6}Cl10, Nina Herzmann, Matthias Bruhmann, Anja V. Mudring, Gerd Meyer 2010 Iowa State University

Communication Prev. Article Next Article Table Of Contents Chains Of Face-Sharing {Zpr6} Octahedra With Alternating Endohedral Iridium Atoms And Chloride Ions In {(Ir,Cl)Pr6}Cl10, Nina Herzmann, Matthias Bruhmann, Anja V. Mudring, Gerd Meyer

Anja V. Mudring

The most impressive feature of the crystal structure of IrPr6Cl11 is chains of face-sharing {Pr6} octahedra that encapsulate, alternatingly, iridium atoms and chloride ions, according to the formulation {(Ir,Cl)Pr6}Cl10. An alternative description of the structure is the connection of isolated {IrPr6} clusters that are surrounded in a mixed {ZR6}Xi12/{ZR6}Xi8 type by chlorido ligands with a rather complex connectivity, {IrPr6}(Cli−a−a4/3Cla−i−a8/3Cli−a6/2Cla−i6/2)e(Cli−i2/2)f, to a three-dimensional structure of tetragonally packed cluster-complex chains.


Isogeometric Shell Analysis: The Reissner–Mindlin Shell, D. J. Benson, Y. Bazilevs, Ming-Chen Hsu, T.J.R. Hughes 2010 University of California, San Diego

Isogeometric Shell Analysis: The Reissner–Mindlin Shell, D. J. Benson, Y. Bazilevs, Ming-Chen Hsu, T.J.R. Hughes

Ming-Chen Hsu

A Reissner–Mindlin shell formulation based on a degenerated solid is implemented for NURBS-based isogeometric analysis. The performance of the approach is examined on a set of linear elastic and nonlinear elasto-plastic benchmark examples. The analyses were performed with LS-DYNA, an industrial, general-purpose finite element code, for which a user-defined shell element capability was implemented. This new feature, to be reported on in subsequent work, allows for the use of NURBS and other non-standard discretizations in a sophisticated nonlinear analysis framework.


Easy Access To Ultra Long-Time Stable, Luminescent Europium(Ii) Fluoride Nanoparticles In Ionic Liquids, Nina von Prondzinski, Joanna Cybinska, Anja V. Mudring 2010 Iowa State University

Easy Access To Ultra Long-Time Stable, Luminescent Europium(Ii) Fluoride Nanoparticles In Ionic Liquids, Nina Von Prondzinski, Joanna Cybinska, Anja V. Mudring

Anja V. Mudring

Physical vapour deposition into ionic liquids allows for the first time the synthesis of a reduced lanthanide halide on the nanoscale. The obtained EuF2 nanoparticles show a bright blue luminescence and form long-time stable-colloidal solutions in the ionic liquids.


Factors Controlling Ductility In Ultrafine Grain Aluminum Alloys Under Monotonic And Cyclic Loading, Partha Sarathi De 2010 Missouri University of Science and Technology

Factors Controlling Ductility In Ultrafine Grain Aluminum Alloys Under Monotonic And Cyclic Loading, Partha Sarathi De

Doctoral Dissertations

"Ultrafine grained (UFG) Al processed by severe plastic deformation (SPD) methods are characterized by high strength and a limited uniform ductility. Friction stir processing (FSP), an offshoot of friction stir welding has emerged as a new technique to produce UFG alloys. FSP-UFG Al alloys show a distinctly different behavior with higher uniform elongation and improved high cycle fatigue life as compared to other SPD processed variants. The objective of this work was to study the microstructural basis for such mechanical behavior in FSP-UFG Al alloys.

To study the mechanical behavior of FSP Al alloys, a subsize bending fatigue and uniaxial ...


Borate Based Bioactive Glass Scaffolds For Hard And Soft Tissue Engineering, Steven B. Jung 2010 Missouri University of Science and Technology

Borate Based Bioactive Glass Scaffolds For Hard And Soft Tissue Engineering, Steven B. Jung

Doctoral Dissertations

"The main objectives of this dissertation were to evaluate bioactive borate glass scaffolds for hard and soft tissue applications and determine the potential toxicity of the borate glasses on the adjacent and systemic tissues. Porous randomly oriented fiber scaffolds composed of bioactive borate glass were implanted in subcutaneous soft tissue sites and in calvaria defects of laboratory rats and no signs of toxicity (necrotic tissue, increase in macrophages or other immune cells) were detected in any of the adjacent tissues (hard or soft). Systemic organs (kidney and liver) of laboratory rats implanted with bioactive borate scaffolds were analyzed for possible ...


Ceramic Dielectrics For High Energy Density Capacity Application, Sheng Chao 2010 Missouri University of Science and Technology

Ceramic Dielectrics For High Energy Density Capacity Application, Sheng Chao

Doctoral Dissertations

"The objective of this dissertation is to investigate the relationship between the processing parameters, microstructural development, defect chemistry and electrical properties of titanium oxide (TiO₂) dielectrics for high energy density capacitor applications. The effects of aliovalent dopants on the dielectric properties of TiO₂ ceramics were investigated, aiming to further improve the desired dielectric properties especially at elevated temperatures (up to 200°C). Due to the segregation of acceptor type impurities in the starting powders, space charge polarization took place in TiO₂ ceramics with relative large grain size (>̲500nm), leading to high dielectric loss and low energy storage efficiency. Increased ratio ...


Zinc Iron Phosphate Glasses For Enameling Applications, Sagnik Saha 2010 Missouri University of Science and Technology

Zinc Iron Phosphate Glasses For Enameling Applications, Sagnik Saha

Masters Theses

"New compositions of low temperature black glasses were developed that are suitable as frits for enameling soda-lime silicate (S-L-S) glass substrates. Zinc iron phosphate glasses are of interest for this application because they possess dilatometric low softening points (under 600ºC) and have coefficients of thermal expansion that are compatible with S-L-S glass (in the range 90-110x10⁻⁷/ºC). The development of compositions with excellent chemical durability, particularly in acidic conditions, is also desired. Compositional modification were made to the (Na₂O+K₂O)·ZnO·MnO·Fe₂O₃·P₂O₅ glass system using design of experiments. The compositional boundaries used in the design were based ...


Experimental Study On Thermal Treatment Of Used Printed Wiring Boards (Pwbs), Xiangjun Zuo 2010 Missouri University of Science and Technology

Experimental Study On Thermal Treatment Of Used Printed Wiring Boards (Pwbs), Xiangjun Zuo

Masters Theses

The availability of cheaper and better electronic products as a result of the rapid innovation in technology in past decades has driven the production of e-waste forward. Printed wiring board (PWB) is a component made of one or more layers of insulating material with electrical conductors. The existing processes of recycling PWBs use pyrometallurgical or hydrometallurgical methods, which generate atmospheric pollution. Green recycling has obvious benefits to decrease the amount of PWBs. Green recycling includes two features, 1) little or zero pollution of toxic gases and heavy metals, and 2) efficient (quick and economical) recycling.

The aim of this work ...


About The Chemistry Of The Terminating 5f-Planes In I-Alpdmn : A Comparison Between Models And Surface Studies, M. Quiquandon, Baris Unal, Patricia A. Thiel, D. Gratias 2010 LEM CNRS-ONERA

About The Chemistry Of The Terminating 5f-Planes In I-Alpdmn : A Comparison Between Models And Surface Studies, M. Quiquandon, Baris Unal, Patricia A. Thiel, D. Gratias

Chemistry Conference Papers, Posters and Presentations

Structural arguments are proposed that support the hypothesis that the equilibrium 5f-surfaces of i-AlPdMn icosahedral alloys are actual cuts of the bulk structure with almost pure Al termination planes [1, 2] corresponding to actual bulk properties with no need for possible Al segregation on the surface. Most of the 5f termination planes in i-AlPdMn are made of two close planes containing essentially Al at the upper one and Al and Pd at the second one (see for instance [3]). Here, perfect unrelaxed structural models that differ only in the chemical distribution of the atomic species are devised, close to the ...


Foundry Parameters For Casting High-Aluminum Lightweight Steel In Complex Shapes, Angella Marie Schulte 2010 Missouri University of Science and Technology

Foundry Parameters For Casting High-Aluminum Lightweight Steel In Complex Shapes, Angella Marie Schulte

Masters Theses

"This work investigated the liquid metal treatment and molding practices for Fe- 30wt.%Mn-9wt.%Al-1wt.%Si-0.9wt.%C-0.5wt.%Mo steel. The goal of this research was to determine the process conditions that would produce a tough Fe-Mn-Al-C alloy and the appropriate mold design to produce a defect-free P900 plate.

Notch toughness of age-hardenable Fe-Mn-Al-C alloys decreases as phosphorus increases. Thermodynamic calculations and experimental work show that additions of Ca followed by Ce can be used to mitigate the deleterious effects of phosphorus, and the addition of Ar-stirring can be used to decrease the number of harmful aluminum nitride inclusions ...


Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev 2010 Western Kentucky University

Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev

Mathematics Faculty Publications

We study long-wave Marangoni convection in a layer heated from below. Using the scaling k=O Bi, where k is the wave number and Bi is the Biot number, we derive a set of amplitude equations. Analysis of this set shows presence of monotonic and oscillatory modes of instability. Oscillatory mode has not been previously found for such direction of heating. Studies of weakly nonlinear dynamics demonstrate that stable steady and oscillatory patterns can be found near the stability threshold.


Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev 2010 Institute of Continuous Media Mechanics

Oscillatory And Monotonic Modes Of Long-Wave Marangoni Convection In A Thin Film, Sergey Shklyaev, Mikhail Khenner, Alexei Alabuzhev

Mathematics Faculty Publications

We study long-wave Marangoni convection in a layer heated from below. Using the scaling k=O Bi, where k is the wave number and Bi is the Biot number, we derive a set of amplitude equations. Analysis of this set shows presence of monotonic and oscillatory modes of instability. Oscillatory mode has not been previously found for such direction of heating. Studies of weakly nonlinear dynamics demonstrate that stable steady and oscillatory patterns can be found near the stability threshold.


Production And Characterization Of Novel Air Filtration Media, Elizabeth Skomra 2010 Clemson University

Production And Characterization Of Novel Air Filtration Media, Elizabeth Skomra

All Dissertations

HEPA and ULPA filtration systems have proven to be an advantageous instrument in removing common contaminants from the air. However, an increased pressure drop due to the build-up of particulates on the filters results in its inevitable decrease in performance. Improving current filtration systems would include increasing collection efficiency all the while either maintaining or reducing the differential pressure drop in order to extend the life of the filter. One method of improving collection efficiency would be viable by increasing the amount of surface area within the filter media by glass fibers because of their inherent quality of being smaller ...


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