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2006

Iowa State University

Materials Science and Engineering

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Synthesis And Characterization Of Hydrated Rubidium Thio-Hydroxosilicogermanates Using Mechanochemical Hydrothermal Synthesis, Carly R. Nelson, Sarah Olson, Steven A. Poling, Steve W. Martin Dec 2006

Synthesis And Characterization Of Hydrated Rubidium Thio-Hydroxosilicogermanates Using Mechanochemical Hydrothermal Synthesis, Carly R. Nelson, Sarah Olson, Steven A. Poling, Steve W. Martin

Materials Science and Engineering Publications

The synthesis, structure, and proton conductivity of the hydrated thio-hydroxosilicogermanates RbzGexSi1-xSz(OH)4-z·yH2O (2 ≤ z ≤ 3; 0 < y < 1.7) are reported. X-ray diffraction indicates that the z = 2 materials are amorphous and show no unreacted starting materials, which is consistent with the mechanochemical hydrothermal evaporation−precipitation synthesis method. Infrared spectroscopy shows a fully reacted system where both silicon and germanium central anions have vibrational modes at 950, 780, 667, and 450 cm-1 associated with asymmetric modes for Si−O, Ge−O, Si−S, and Ge−S chemical bonds, respectively. O−H stretching and bending modes are present at ...


Modeling Of The Size Effects On The Behavior Of Metals In Microscale Deformation Processes, Gap-Yong Kim, Jun Ni, Muammer Koc Dec 2006

Modeling Of The Size Effects On The Behavior Of Metals In Microscale Deformation Processes, Gap-Yong Kim, Jun Ni, Muammer Koc

Gap-Yong Kim

For the accurate analysis and design of microforming process, proper modeling of material behavior at the micro/mesoscale is necessary by considering the size effects. Two size effects are known to exist in metallic materials. One is the “grain size” effect, and the other is the “feature/specimen size” effect. This study investigated the feature/specimen size effect and introduced a scaling model which combined both feature/specimen and grain size effects. Predicted size effects were compared with three separate experiments obtained from previous research: a simple compression with a round specimen, a simple tension with a round specimen, and ...


Effect Of Chain Architecture And Surface Energies On The Ordering Behavior Of Lamellar And Cylinder Forming Block Copolymers, V. Khanna, Eric W. Cochran, A. Hexemer, G. E. Stein, G. H. Fredrickson, E. J. Kramer, X. Li, J. Wang, S. F. Hahn Dec 2006

Effect Of Chain Architecture And Surface Energies On The Ordering Behavior Of Lamellar And Cylinder Forming Block Copolymers, V. Khanna, Eric W. Cochran, A. Hexemer, G. E. Stein, G. H. Fredrickson, E. J. Kramer, X. Li, J. Wang, S. F. Hahn

Eric W. Cochran

We investigate the effect of surface energy and chain architecture on the orientation of microdomains in relatively thick films (600-800 nm) of lamellar and cylindrical block copolymers of poly(cyclohexylethylene) (C) and poly(ethylene) (E). The E block has 26 ethyl branches per 1000 backbone carbon atoms. Melt surface energies of the C and E blocks are 22.3 and 20.9 mJ/m 2, respectively. Grazing-incidence small-angle X-ray scattering (GISAXS), scanning force microscopy (SFM), and cross-sectional transmission electron microscopy (TEM) show that cylindrical and lamellar CEC triblock copolymers orient their microdomains normal to the surface throughout the film thickness ...


Elastic Properties Of Gd5si2ge2 Studied With An Ultrasonic Pulse-Echo Technique, O. Svitelskiy, A. Suslov, Deborah L. Schlagel, Thomas A. Lograsso, Karl A. Gschneidner Jr., Vitalij K. Pecharsky Nov 2006

Elastic Properties Of Gd5si2ge2 Studied With An Ultrasonic Pulse-Echo Technique, O. Svitelskiy, A. Suslov, Deborah L. Schlagel, Thomas A. Lograsso, Karl A. Gschneidner Jr., Vitalij K. Pecharsky

Ames Laboratory Publications

We present the results of a study of the elastic properties of Gd5Si2Ge2, an alloy with giant magnetocaloric, magnetostrictive, and colossal magnetoresistive properties. Sound wave velocities measured in a number of different geometries allowed us to determine the whole elastic tensor for the monoclinic phase of this material. The anisotropy of the crystal is explored using the polar plots of the variations in the main crystallographic planes of the sound speed, the Young’s modulus, the shear modulus, and the linear compressibility. The effect of hydrostatic pressure on the Gd5Si2Ge2 ...


Posterminaries: After Nabarro, Alexander H. King Nov 2006

Posterminaries: After Nabarro, Alexander H. King

Alexander H. King

With the passing of Frank Nabarro in July of this year, we have lost one of the founding fathers of materials science. His name appears in many of the textbooks from which we train our students today, and also on the spines of several volumes on dislocation theory, including his classic monograph on the subject. He rightly stands among the gods of our field. Ninety years old at his death, he was a sprightly dancer at the frontiers of knowledge, right up to the end.


Modeling Of The Semi-Solid Material Behavior And Analysis Of Micro-/Mesoscale Feature Forming, Gap-Yong Kim, Muammer Koc, Rhet Mayor, Jun Ni Oct 2006

Modeling Of The Semi-Solid Material Behavior And Analysis Of Micro-/Mesoscale Feature Forming, Gap-Yong Kim, Muammer Koc, Rhet Mayor, Jun Ni

Gap-Yong Kim

One of the major challenges in simulation of semi-solid forming is characterizing the complex behavior of a material that consists of both solid and liquid phases. In this study, a material model for an A356 alloy in a semi-solid state has been developed for high solid fractions (>0.6) and implemented into a finite element simulation tool to investigate the micro-/mesoscale feature formation during the forming process. Compared to previous stress models, which are limited to expressing the stress dependency on only the strain rate and the temperature (or the solid fraction), the proposed stress model adds the capability ...


An Experimental Investigation On Semi-Solid Forming Of Micro/Meso-Scale Features, Gap-Yong Kim, Jun Ni, Rhett Mayor, Heesool Kim Oct 2006

An Experimental Investigation On Semi-Solid Forming Of Micro/Meso-Scale Features, Gap-Yong Kim, Jun Ni, Rhett Mayor, Heesool Kim

Gap-Yong Kim

The potentials of semi-solid forming technology have generated much interest regarding its application in micromanufacturing. This study investigates the feasibility of using semi-solid forming technology to produce parts with micro/meso features. An experimental setup has been developed to study the effects of die/punch temperature, initial solid fraction, punch speed, and workpiece shape on the semi-solid forming process. A part has been produced for a microreactor application and has been analyzed with an optical measurement system for feature formation. The results indicated complex interaction among the process parameters and the material flow, which affected the final pin formation. The ...


Method Of Making Active Magnetic Refrigerant Materials Based On Gd-Si-Ge Alloys, Alexandra O. Pecharsky, Karl A. Gschneidner Jr., Vitalij K. Pecharsky Oct 2006

Method Of Making Active Magnetic Refrigerant Materials Based On Gd-Si-Ge Alloys, Alexandra O. Pecharsky, Karl A. Gschneidner Jr., Vitalij K. Pecharsky

Iowa State University Patents

An alloy made of heat treated material represented by Gd5(SixGe1−x)4 where 0.47≦x≦0.56 that exhibits a magnetic entropy change (−ΔSm) of at least 16 J/kg K, a magnetostriction of at least 2000 parts per million, and a magnetoresistance of at least 5 percent at a temperature of about 300K and below, and method of heat treating the material between 800 to 1600 degrees C. for a time to this end.


Semicrystalline Thermoplastic Elastomeric Polyolefins: Advances Through Catalyst Development And Macromolecular Design, Atsushi Hotta, Eric W. Cochran, Janne Ruokolainen, Vikram Khann, Glenn H. Fredrickson, Edward J. Kramer, Yong-Woo Shin, Fumihiko Shimizu, Anna E. Cherian, Phillip D. Hustad, Jeffrey M. Rose, Geoffrey W. Coates Oct 2006

Semicrystalline Thermoplastic Elastomeric Polyolefins: Advances Through Catalyst Development And Macromolecular Design, Atsushi Hotta, Eric W. Cochran, Janne Ruokolainen, Vikram Khann, Glenn H. Fredrickson, Edward J. Kramer, Yong-Woo Shin, Fumihiko Shimizu, Anna E. Cherian, Phillip D. Hustad, Jeffrey M. Rose, Geoffrey W. Coates

Eric W. Cochran

We report the design, synthesis, morphology, phase behavior, and mechanical properties of semicrystalline, polyolefin-based block copolymers. By using living, stereoselective insertion polymerization catalysts, syndiotactic polypropylene-block-poly(ethylene-co-propylene)-block-syndiotactic polypropylene and isotactic poly propylene-block-regioirregular poly propylene-block- isotactic polypropylene triblock copolymers were synthesized. The volume fraction and composition of the blocks, as well as the overall size of the macromolecules, were controlled by sequential synthesis of each block of the polymers. These triblock copolymers, with semicrystalline end-blocks and mid-segments with low glass-transition temperatures, show significant potential as thermoplastic elastomers. They have low Young's moduli, large strains at break, and better than 90 ...


Sum Frequency Generation Vibrational Spectroscopic And High-Pressure Scanning Tunneling Microscopic Studies Of Benzene Hydrogenation On Pt(111), Kaitlin M. Bratlie, Max O. Montano, Lucio D. Flores, Matti Paajanen, Gabor A. Somorjai Oct 2006

Sum Frequency Generation Vibrational Spectroscopic And High-Pressure Scanning Tunneling Microscopic Studies Of Benzene Hydrogenation On Pt(111), Kaitlin M. Bratlie, Max O. Montano, Lucio D. Flores, Matti Paajanen, Gabor A. Somorjai

Kaitlin M. Bratlie

Sum frequency generation (SFG) vibrational spectroscopy and high-pressure scanning tunneling microscopy (HP-STM) have been used in combination for the first time to study a catalytic reaction. These techniques have been able to identify surface intermediates in situ during benzene hydrogenation on a Pt(111) single-crystal surface at Torr pressures.


Hydrogen And Deuterium Exchange On Pt(111) And Its Poisoning By Carbon Monoxide Studied By Surface Sensitive High-Pressure Techniques, Max Montano, Kaitlin M. Bratlie, Miquel Salmeron, Gabor A. Somorjai Oct 2006

Hydrogen And Deuterium Exchange On Pt(111) And Its Poisoning By Carbon Monoxide Studied By Surface Sensitive High-Pressure Techniques, Max Montano, Kaitlin M. Bratlie, Miquel Salmeron, Gabor A. Somorjai

Kaitlin M. Bratlie

Catalytic hydrogen/deuterium exchange on a platinum (111) single crystal and its poisoning with carbon monoxide was studied using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), sum frequency generation vibrational spectroscopy (SFG), and mass spectrometry under reaction conditions at pressures in the mTorr to atmospheric range. At 298 K and in the presence of 200 mTorr of hydrogen and 20 mTorr of deuterium the surface is catalytically active, producing HD with activation energy of 5.3 kcal/mol. Addition of 5 mTorr of CO stops the reaction completely. In situ STM images reveal an ordered surface structure of chemisorbed ...


Persistence Of 5:3 Plates In Re5(Sixge1-X)4 Alloys, O. Ugurlu, L. Scott Chumbley, C. R. Fisher Oct 2006

Persistence Of 5:3 Plates In Re5(Sixge1-X)4 Alloys, O. Ugurlu, L. Scott Chumbley, C. R. Fisher

Materials Science and Engineering Publications

Studies of RE5(SixGe1-x)4 alloys, where RE equals rare earth, have revealed a second-phase having a thin-plate morphology in essentially every alloy examined, independent of exact composition and matrix crystal structure. Identified as having a composition approximating Gd5(SixGe1-x)3 and a hexagonal crystal structure in the Gd-based system, it has been suggested that the observed thin-plate second phases seen in this family of rare earth alloys are all most likely of the form RE5(SixGe1-x)3. A number of interesting observations suggest that the formation of ...


Comment On “Structural Stability Of Complex Hydrides: Libh4 Revisited”, Duane D. Johnson, Nikolai A. Zarkevich Sep 2006

Comment On “Structural Stability Of Complex Hydrides: Libh4 Revisited”, Duane D. Johnson, Nikolai A. Zarkevich

Duane D. Johnson

A Comment on the Letter by Zbigniew Łodziana and Tejs Vegge, Phys. Rev. Lett. 93, 145501 (2004).


Short-Range Anisotropic Ferromagnetic Correlations In The Paramagnetic And Antiferromagnetic Phases Of Gd5ge4, Zhong W. Ouyang, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., Deborah L. Schlagel, Thomas A. Lograsso Sep 2006

Short-Range Anisotropic Ferromagnetic Correlations In The Paramagnetic And Antiferromagnetic Phases Of Gd5ge4, Zhong W. Ouyang, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., Deborah L. Schlagel, Thomas A. Lograsso

Ames Laboratory Publications

Signatures of short range anisotropic ferromagnetic correlations and ferromagnetic clustering, manifested as unusually large hysteresis and other anomalies of the low magnetic field dc magnetization and ac magnetic susceptibility, have been observed in both the antiferromagnetic and paramagnetic states of single crystal Gd5Ge4. Ferromagnetic correlations, which are most pronounced in a weak magnetic field applied along the b axis, are readily suppressed by fields exceeding ∼5 kOe and are believed to be related to a Griffiths-like phase that develops in Gd5Ge4 below TG≅240 K.


Mixed Anion Materials And Compounds For Novel Proton Conducting Membranes, Steven A. Poling, Carly R. Nelson, Steve W. Martin Sep 2006

Mixed Anion Materials And Compounds For Novel Proton Conducting Membranes, Steven A. Poling, Carly R. Nelson, Steve W. Martin

Iowa State University Patents

The present invention provides new amorphous or partially crystalline mixed anionchalcogenide compounds for use in proton exchange membranes which are able to operate over a wide variety of temperature ranges, including in the intermediate temperature range of about 100 ° C. to 300° C., and new uses for crystallinemixed anion chalcogenide compounds in such proton exchange membranes. In one embodiment, the proton conductivity of the compounds is between about 10−8 S/cm and 10−1 S/cm within a temperature range of between about −60 and300° C. and a relative humidity of less than about 12%.


Structure Effects Of Benzene Hydrogenation Studied With Sum Frequency Generation Vibrational Spectroscopy And Kinetics On Pt(111) And Pt(100) Single-Crystal Surfaces, Kaitlin M. Bratlie, Christopher J. Kliewer, Gabor A. Somorjai Sep 2006

Structure Effects Of Benzene Hydrogenation Studied With Sum Frequency Generation Vibrational Spectroscopy And Kinetics On Pt(111) And Pt(100) Single-Crystal Surfaces, Kaitlin M. Bratlie, Christopher J. Kliewer, Gabor A. Somorjai

Kaitlin M. Bratlie

Sum frequency generation (SFG) surface vibrational spectroscopy and kinetic measurements using gas chromatography have identified at least two reaction pathways for benzene hydrogenation on the Pt(100) and Pt(111) single-crystal surfaces at Torr pressures. Kinetic studies at low temperatures (310-370 K) show that benzene hydrogenation does not proceed through cyclohexene. A Langmuir-Hinshelwood-type rate law for the low-temperature reaction pathway is identified. The rate-determining step for this pathway is the addition of the first hydrogen atom to adsorbed benzene for both single-crystal surfaces, which is verified by the spectroscopic observation of adsorbed benzene at low temperatures on both the Pt ...


Posterminaries: The Scales Of Judgement, Alexander H. King Sep 2006

Posterminaries: The Scales Of Judgement, Alexander H. King

Alexander H. King

Materials scientists are generally well-versed in physics, and physics, above all, is a science of measurements. The first instinct of a physicist is to parse a problem in terms of its measurables in the dimensions of mass, length, and time, and it is the shifting of attention down the scale of length that particularly characterizes our present times as the Nano Age.


Tailorable Polymer Waveguides For Miniaturized Bio-Photonic Devices Via Two-Polymer Microtransfer Molding, Jae-Hwang Lee, Zhuo Ye, Kristen P. Constant, Kai-Ming Ho Aug 2006

Tailorable Polymer Waveguides For Miniaturized Bio-Photonic Devices Via Two-Polymer Microtransfer Molding, Jae-Hwang Lee, Zhuo Ye, Kristen P. Constant, Kai-Ming Ho

Materials Science and Engineering Conference Papers, Posters and Presentations

Traditional optical fibers have been developed to achieve novel characteristics for both macro- and micro-applications. Inorganic optical waveguides using two-dimensional photonic crystals and silicon-on-insulator technology are examples of recent trends for macro- and micro-scale optical applications, respectively. As bio-photonics devices operate mostly with visible light, visible-transparent materials such as metal oxides and polymers are preferred as the guiding medium. Although polymers have tremendous potential because of their enormous variation in optical, chemical and mechanical properties, their application for optical waveguides is limited by conventional lithography. We present a non-optical lithographic technique, called two-polymer microtransfer molding, to fabricate polymer nano-waveguides, on-chip ...


Anomalous Ionic Conductivity Increase In Li2s + Ges2 + Geo2 Glasses, Youngsik Kim, Jason Salenga, Steve W. Martin Aug 2006

Anomalous Ionic Conductivity Increase In Li2s + Ges2 + Geo2 Glasses, Youngsik Kim, Jason Salenga, Steve W. Martin

Materials Science and Engineering Publications

Numerous studies of the ionic conductivities in oxide-doped chalcogenaide glasses have shown the anomalous result that the ionic conductivity actually increases significantly (by more than a factor of 10 in some cases) by the initial addition of an oxide phase to a pure sulfide glass. After this initial sharp increase, the conductivity then monotonically decreases with further oxide addition. While this behavior is important to the application of these glasses for Li batteries, no definitive understanding of this behavior has been elucidated. To examine this effect further and more completely, the ionic conductivities of 0.5Li2S + 0.5[(1 − x ...


Magnetism Of (Dy0.5er0.5)Al2 Single Crystal In Ac And Dc Magnetic Fields, Evgenii M. Levin, Karl A. Gschneidner Jr., Thomas A. Lograsso, Deborah L. Schlagel Aug 2006

Magnetism Of (Dy0.5er0.5)Al2 Single Crystal In Ac And Dc Magnetic Fields, Evgenii M. Levin, Karl A. Gschneidner Jr., Thomas A. Lograsso, Deborah L. Schlagel

Ames Laboratory Publications

The temperature (4.2–90 K), ac magnetic field (1.25–50 Oe), frequency (5–125 Hz), and bias dc magnetic field (0–10 kOe) dependencies of the real and imaginary components of the ac magnetic susceptibility, and the temperature (4.2–250 K) and dc magnetic field(0.1–50 kOe) dependencies of the dc magnetic susceptibility and magnetization of a(Dy0.5Er0.5)Al2 single crystal have been studied. Isothermal magnetization measurement in a dc magnetic field indicates that (Dy0.5Er0.5)Al2 orders ferromagnetically at 37 K. The ac ...


An Experimental Study Of Effects Of Overlaying Tissues On Hifu Lesion, Tao Long, Viren R. Amin, Ronald A. Roberts, R. Bruce Thompson, Scott R. Mcclure, Timothy Ryken Aug 2006

An Experimental Study Of Effects Of Overlaying Tissues On Hifu Lesion, Tao Long, Viren R. Amin, Ronald A. Roberts, R. Bruce Thompson, Scott R. Mcclure, Timothy Ryken

Center for Nondestructive Evaluation Conference Papers, Posters and Presentations

Understanding the effect of overlaying tissues on HIFU lesion is crucial for estimating HIFU dose distribution at a target tissue. We have run a series of experiments to systematically observe the effects of the overlaying tissues on the HIFU beam and ultimately the lesion created in the target tissue. First, we mapped out the HIFU transducer beam (in low power) under water without and with different overlaying tissue layers. Then, we performed a series of experiments in high power to create lesions in target tissues (e.g., liver) without and with overlaying tissues (e.g. muscle). The lesions are characterized ...


Characterization Of Aperiodic And Periodic Thin Cu Films Formed On The Five-Fold Surface Of I-Al70pd21mn9 Using Medium-Energy Ion Scattering Spectroscopy, J. A. Smerdon, J. Ledieu, R. Mcgrath, T. C. Q. Noakes, P. Bailey, M. Draxler, C. F. Mcconville, Thomas A. Lograsso, A. R. Ross Jul 2006

Characterization Of Aperiodic And Periodic Thin Cu Films Formed On The Five-Fold Surface Of I-Al70pd21mn9 Using Medium-Energy Ion Scattering Spectroscopy, J. A. Smerdon, J. Ledieu, R. Mcgrath, T. C. Q. Noakes, P. Bailey, M. Draxler, C. F. Mcconville, Thomas A. Lograsso, A. R. Ross

Ames Laboratory Publications

The elucidation of the local atomic structure of a pseudomorphic film of Cu deposited on the five-fold surface of i-Al70Pd21Mn9using medium-energy ion scattering spectroscopy is reported. Monte Carlo calculations, using the VEGAS code, have been utilized to simulate the blocking of 100 keV He+ ions scattered from the overlayer. The coordinates of the Cu atoms in the overlayer derived from this procedure are consistent with a structure occurring in five rotational domains. Each domain consists of nanoscale strips of fcc Cu(100) with the ⟨110⟩ azimuth aligned along the five-fold directions of the quasicrystalline ...


Temperature And Magnetic-Field Dependence Of The Elastic Constants Of Ni-Mn-Al Magnetic Heusler Alloys, Xavier Moya, Lluís Mañosa, Antoni Planes, Thorsten Krenke, Mehmet Acet, Michel Morin, Jerel L. Zarestky, Thomas A. Lograsso Jul 2006

Temperature And Magnetic-Field Dependence Of The Elastic Constants Of Ni-Mn-Al Magnetic Heusler Alloys, Xavier Moya, Lluís Mañosa, Antoni Planes, Thorsten Krenke, Mehmet Acet, Michel Morin, Jerel L. Zarestky, Thomas A. Lograsso

Ames Laboratory Publications

We report on measurements of the adiabatic second-order elastic constants of the off-stoichiometric Ni54Mn23Al23 single-crystalline Heusler alloy. The variation in the temperature dependence of the elastic constants has been investigated across the magnetic transition and over a broad temperature range. Anomalies in the temperature behavior of the elastic constants have been found in the vicinity of the magnetic phase transition. Measurements under applied magnetic field, both isothermal and variable temperature, show that the value of the elastic constants depends on magnetic order, thus giving evidence for magnetoelastic coupling in this alloy system.


In Situ Transmission Electron Microscopy Study Of The Nanodomain Growth In A Sc-Doped Lead Magnesium Niobate Ceramic, W. Qu, X. Zhao, Xiaoli Tan Jul 2006

In Situ Transmission Electron Microscopy Study Of The Nanodomain Growth In A Sc-Doped Lead Magnesium Niobate Ceramic, W. Qu, X. Zhao, Xiaoli Tan

Materials Science and Engineering Publications

Sc doping enhances the B-site 1:1 cation ordering in the Pb(Mg1/3Nb2/3)O3ceramic. At low doping levels, the electrical polar domains remain at the nanometer scale and the relaxor ferroelectric behavior persists. The electric field-induced relaxor to normal ferroelectric phase transition process was directly observed with an in situtransmission electron microscopy technique in a Sc-doped Pb(Mg1/3Nb2/3)O3 polycrystalline sample. It was found that the phase transition started at the grain boundary and took two steps to complete: the gradual coalescence of the polar nanodomains and the abrupt formation of the large wedge-shaped ferroelectric ...


Magnetic Anisotropy And Magnetic Phase Diagram Of Gd5ge4, Zhong W. Ouyang, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., Deborah L. Schlagel, Thomas A. Lograsso Jul 2006

Magnetic Anisotropy And Magnetic Phase Diagram Of Gd5ge4, Zhong W. Ouyang, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., Deborah L. Schlagel, Thomas A. Lograsso

Ames Laboratory Publications

The magnetization of single crystal Gd5Ge4, which in a zero magnetic field orders antiferromagnetically at 128 K, indicates a reversible spin-flop transition when the magnetic field is along the c axis and the absence of similar transformations when the magnetic field vector is perpendicular to the c axis. This anisotropic behavior is due to variation of magnetization energy between the c axis and the a or b axes of the orthorhombic crystal caused by a different alignment of the Gd moments with respect to the magnetic field vector. The anisotropy of the antiferromagnetic state diminishes with the ...


The Effect Of A Modified Downcomer On The Hydrodynamics In An External Loop Airlift Reactor, Samuel T. Jones, Theodore J. Heindel Jul 2006

The Effect Of A Modified Downcomer On The Hydrodynamics In An External Loop Airlift Reactor, Samuel T. Jones, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Gas holdup and superficial liquid velocity in the downcomer and riser are studied for an external loop airlift reactor with an area ratio of 1:16. Two downcomer configurations are investigated consisting of the downcomer open or closed to the atmosphere. Experiments for these two configurations are carried out over a range of superficial gas velocities from UG = 0.5 to 20 cm/s using three aeration plates with open area ratios of 0.62, 0.99 and 2.22%. These results are compared to a bubble column operated with similar operating conditions. Experimental results show that the gas holdup ...


Abstracts, Review Of Progress In Quantitative Nondestructive Evaluation (Portland, Or, July 20–August 4, 2006), Center For Nondestructive Evaluation, Iowa State University Jun 2006

Abstracts, Review Of Progress In Quantitative Nondestructive Evaluation (Portland, Or, July 20–August 4, 2006), Center For Nondestructive Evaluation, Iowa State University

Review of Progress in Quantitative Nondestructive Evaluation

Abstracts of papers presented at the 2006 Review of Progress in Quantitative Nondestructive Evaluation (QNDE) conference held in Portland, Oregon from July 30–August 4, 2006.


In Situ Sum Frequency Generation Vibrational Spectroscopy Observation Of A Reactive Surface Intermediate During High-Pressure Benzene Hydrogenation, Kaitlin M. Bratlie, Lucio D. Flores, Gabor A. Somorjai May 2006

In Situ Sum Frequency Generation Vibrational Spectroscopy Observation Of A Reactive Surface Intermediate During High-Pressure Benzene Hydrogenation, Kaitlin M. Bratlie, Lucio D. Flores, Gabor A. Somorjai

Kaitlin M. Bratlie

Sum frequency generation surface vibrational spectroscopy and kinetic measurements using gas chromatography have been used to identify a reactive surface intermediate in situ during hydrogenation of benzene on a Pt(111) single crystal surface at Torr pressures. Upon adsorption at 310 K, both chemisorbed and physisorbed benzene coexist on the surface, a result which has not previously been observed. Kinetic measurements show a linear compensation effect for the production of both cyclohexane and cyclohexene. From these data the isokinetic temperature was identified and correlated to the chemisorbed benzene species, which were probed by means of vibrational spectroscopy. Additionally, chemisorbed benzene ...


Variation Of Magnetostriction With Temperature In Tb5si2.2ge1.8 Single Crystal, A. P. Ring, H. L. Ziegler, Thomas A. Lograsso, Deborah L. Schlagel, J. E. Snyder, David C. Jiles Apr 2006

Variation Of Magnetostriction With Temperature In Tb5si2.2ge1.8 Single Crystal, A. P. Ring, H. L. Ziegler, Thomas A. Lograsso, Deborah L. Schlagel, J. E. Snyder, David C. Jiles

Ames Laboratory Conference Papers, Posters, and Presentations

The Tb5(SixGe4−x) alloy system is similar to the better known Gd5(SixGe4−x), except it has a more complex magnetic and structural phase diagram. Gd5(SixGe1−x)4 has received much attention recently due to its giant magnetocaloric effect, colossal magnetostriction and giant magnetoresistance in the vicinity of a first order combined magnetic-structural phase transition. The magnetostriction changes that accompany the phase transitions of single crystal Tb5(Si2.2Ge1.8) have been investigated at temperatures between 20 and150 K by measurements of ...


Magnetostructural Transitions And Adiabatic Temperature Variation In Polycrystal And Single-Crystal Ni2mnga Alloys, C. P. Sasso, M. Pasquale, L. Giudici, S. Besseghini, E. Villa, L. H. Lewis, Thomas A. Lograsso, Deborah L. Schlagel Apr 2006

Magnetostructural Transitions And Adiabatic Temperature Variation In Polycrystal And Single-Crystal Ni2mnga Alloys, C. P. Sasso, M. Pasquale, L. Giudici, S. Besseghini, E. Villa, L. H. Lewis, Thomas A. Lograsso, Deborah L. Schlagel

Ames Laboratory Conference Papers, Posters, and Presentations

The magnetocaloric response of off-stoichiometric Ni2MnGa polycrystal and single-crystal samples with a Curie temperature coincident with the martensitic transition temperature was investigated. The direct measurement of temperature change (ΔTad) during an adiabatic transformation under a maximum field variation ΔH = 5.6×106 A/m (7 T) was performed. The polycrystalline sample shows a maximum ΔTad ≈ 1.5 K at a temperature close to the structural transition. The value of ΔTad and the 20 K span of the ΔTad peak encourage further studies of the effect of microstructure on ...