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Full-Text Articles in Physics

Design And Control Of A Peristaltic Pump To Simulate Left Atrial Pressure In A Conductive Silicone Model, Jeremy Collins May 2021

Design And Control Of A Peristaltic Pump To Simulate Left Atrial Pressure In A Conductive Silicone Model, Jeremy Collins

Mechanical Engineering Undergraduate Honors Theses

According to the CDC, atrial fibrillation is responsible for more than 454,000 hospitalizations and approximately 158,000 deaths per year. A common treatment for atrial fibrillation is catheter ablation, a process in which a long flexible tube is guided through the femoral artery and to the source of arrhythmia in the heart, where it measures the electrical potential at various locations and converts problematic heart tissue to scar tissue via ablation. This paper details the design and control of a low-cost ($400) peristaltic pump system using repetitive control to replicate blood pressure in the left atrium in a conductive ...


Simulation Of Optical Properties Of Dielectric Layers From Visible To Near Infrared Spectral Range, Andrew Cochran, Cory Conkel Apr 2021

Simulation Of Optical Properties Of Dielectric Layers From Visible To Near Infrared Spectral Range, Andrew Cochran, Cory Conkel

ONU Student Research Colloquium

Optical properties of dielectrics play a critical role in various applications including the design and manufacture of optical components & devices such as detectors, filters, imagers, lenses, optical coatings, photonic crystals, sensors and waveguides, and solar cells. Radiative properties of varying thicknesses of different dielectrics such as Aluminum Oxide (Al2O3), Silicon Dioxide (SiO2), Indium Tin Oxide (ITO), Magnesium Fluoride (MgF2) and Silicon Nitride (Si3N4) have been simulated and compared in the range of visible to near infrared by mathematical modelling using MATLAB simulations. The results of the evolution of the radiative properties, as a function of dielectric material thickness, on silicon ...


Origin Of Magnetism In Γ-Fesi 2 /Si(111) Nanostructures, Liwei D. Geng, Sahil Dhoka, Ilan Goldfarb, Ranjit Pati, Yongmei M. Jin Mar 2021

Origin Of Magnetism In Γ-Fesi 2 /Si(111) Nanostructures, Liwei D. Geng, Sahil Dhoka, Ilan Goldfarb, Ranjit Pati, Yongmei M. Jin

Michigan Tech Publications

Magnetism has recently been observed in nominally nonmagnetic iron disilicide in the form of epitaxial γ-FeSi2 nanostructures on Si(111) substrate. To explore the origin of the magnetism in γ-FeSi2/Si(111) nanostructures, we performed a systematic first-principles study based on density functional theory. Several possible factors, such as epitaxial strain, free surface, interface, and edge, were examined. The calculations show that among these factors, only the edge can lead to the magnetism in γ-FeSi2/Si(111) nanostructures. It is shown that magnetism exhibits a strong dependency on the local atomic structure of the edge. Furthermore, magnetism can be enhanced ...


Anisotropic Superconductivity In The Spin-Vortex Antiferromagnetic Superconductor Cak(Fe0.95ni0.05)(4)As-4, José Benito Llorens, Edwin Herrera, Víctor Barrena, Beilun Wu, Niclas Heinsdorf, Vladislav Borisov, Roser Valentí, William R. Meier, Sergey L. Bud’Ko, Paul C. Canfield, Isabel Guillamón, Hermann Suderow Feb 2021

Anisotropic Superconductivity In The Spin-Vortex Antiferromagnetic Superconductor Cak(Fe0.95ni0.05)(4)As-4, José Benito Llorens, Edwin Herrera, Víctor Barrena, Beilun Wu, Niclas Heinsdorf, Vladislav Borisov, Roser Valentí, William R. Meier, Sergey L. Bud’Ko, Paul C. Canfield, Isabel Guillamón, Hermann Suderow

Ames Laboratory Accepted Manuscripts

High critical temperature superconductivity often occurs in systems where an antiferromagnetic order is brought near T=0 K by slightly modifying pressure or doping. CaKFe4As4 is a superconducting, stoichiometric iron-pnictide compound showing optimal superconducting critical temperature with Tc as large as 35 K. Doping with Ni induces a decrease in Tc and the onset of spin-vortex crystal (SVC) antiferromagnetic order, which consists of spins pointing inwards to or outwards from alternating As sites on the diagonals of the in-plane square Fe lattice. Here we study the band structure of CaK(Fe0.95Ni0.05)4As4 (Tc=10 K, TSVC=50 K ...


Avoided Ferromagnetic Quantum Critical Point In Pressurized La5 Co2 Ge3, Li Xiang, Elena Gati, Sergey L. Bud’Ko, Scott M. Saunders, Paul C. Canfield Feb 2021

Avoided Ferromagnetic Quantum Critical Point In Pressurized La5 Co2 Ge3, Li Xiang, Elena Gati, Sergey L. Bud’Ko, Scott M. Saunders, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

We present the pressure-temperature phase diagram La5Co2Ge3 up to ∼5 GPa, which was constructed from magnetization, resistivity, and specific heat measurements. At ambient pressure, La5Co2Ge3 is an itinerant ferromagnet with a Curie temperature TC∼ 4 K. Upon increasing pressure up to ∼1.7 GPa, TC is suppressed down to ∼3 K. Upon further increasing pressure, our results suggest that La5Co2Ge3 enters a different low-temperature ground state. The corresponding transition temperature T∗ has a nonmonotonic pressure dependence up to ∼5 GPa. Our results demonstrate that the ferromagnetic quantum critical point in La5Co2Ge3 is avoided by the appearance of a different, likely ...


Temperature Dependence Of London Penetration Depth Anisotropy In Superconductors With Anisotropic Order Parameters, Vladimir G. Kogan, Ruslan Prozorov Feb 2021

Temperature Dependence Of London Penetration Depth Anisotropy In Superconductors With Anisotropic Order Parameters, Vladimir G. Kogan, Ruslan Prozorov

Ames Laboratory Accepted Manuscripts

We study the effects of anisotropic order parameters on the temperature dependence of London penetration depth anisotropy γ λ ( T ) . After MgB 2 , this dependence is commonly attributed to distinct gaps on multiband Fermi surfaces in superconductors. We have found, however, that the anisotropy parameter may depend on temperature also in one-band materials with anisotropic order parameters Δ ( T , k F ) ; a few such examples are given. We have also found that for different order parameters, the temperature dependence of Δ ( T ) / Δ ( 0 ) can be represented with good accuracy by the interpolation suggested by Einzel [J. Low Temp. Phys ...


Study Of Structural, Transport And Magneto-Crystalline Anisotropy In La1−Xsrxmno3 (0.30 ≤ X ≤ 0.40) Perovskite Manganites, Ganesha Channagoudra, Shalabh Gupta, Vijaylakshmi Dayal Feb 2021

Study Of Structural, Transport And Magneto-Crystalline Anisotropy In La1−Xsrxmno3 (0.30 ≤ X ≤ 0.40) Perovskite Manganites, Ganesha Channagoudra, Shalabh Gupta, Vijaylakshmi Dayal

Ames Laboratory Accepted Manuscripts

In this paper we present structural, transport, magnetic and magneto-crystalline anisotropy of La1−xSrxMnO3 (х = 0.30, 0.33, 0.36, and 0.40) synthesized using the solid-state reaction method. The X-ray diffraction pattern of the samples is well indexed to the rhombohedral structure with R3c space group. Lattice parameters and unit cell volume are found to decrease monotonically upon increasing Sr2+ concentration at La3+ site. X-ray photoelectron spectroscopy confirms the presence of Mn4+ and Mn3+, the ratio of which (Mn4+/Mn3+) increases from 0.44 to 0.64 with increasing Sr2+ concentration. From the ρ(T) and M(T ...


Expansive Open Fermi Arcs And Connectivity Changes Induced By Infrared Phonons In Zrte5, Lin-Lin Wang Feb 2021

Expansive Open Fermi Arcs And Connectivity Changes Induced By Infrared Phonons In Zrte5, Lin-Lin Wang

Ames Laboratory Accepted Manuscripts

Expansive open Fermi arcs covering most of the surface Brillouin zone (SBZ) are desirable for detection and control of many topological phenomena, but they have generally been reported for Kramers-Weyl points, or unconventional chiral fermions, pinned at time-reversal invariant momentum in chiral materials. Here using first-principles band structure calculations, we show that for conventional Weyl points in ZrTe5 with the chirality of +1/−1 near the BZ center at general momentum induced by one of the infrared phonons—the second lowest B1u mode for breaking inversion symmetry—they can also form expansive open Fermi arcs across the SBZ boundary to ...


Surface Acoustic Waves Increase Magnetic Domain Wall Velocity, Anil Adhikari, Shireen Adenwalla Jan 2021

Surface Acoustic Waves Increase Magnetic Domain Wall Velocity, Anil Adhikari, Shireen Adenwalla

Shireen Adenwalla Papers

Domain walls in magnetic thin films are being explored for memory applications and the speed at which they move has acquired increasing importance. Magnetic fields and currents have been shown to drive domain walls with speeds exceeding 500 m/s. We investigate another approach to increase domain wall velocities, using high frequency surface acoustic waves to create standing strain waves in a 3 micron wide strip of magnetic film with perpendicular anisotropy. Our measurements, at a resonant frequency of 248.8 MHz, indicate that domain wall velocities increase substantially, even at relatively low applied voltages. Our findings suggest that the ...


Generation Of Excited Species In A Streamer Discharge, Shirshak K. Dhali Jan 2021

Generation Of Excited Species In A Streamer Discharge, Shirshak K. Dhali

Electrical & Computer Engineering Faculty Publications

At or near atmospheric pressure, most transient discharges, particularly in molecular gases or gas mixture containing molecular gases, result in a space charge dominated transport called a streamer discharge. The excited species generation in such discharges forms the basis for plasma chemistry in most technological applications. In this paper, we simulate the propagation of streamers in atmospheric pressure N2 to understand the energy partitioning in the formation of various excited species and compare the results to a uniform Townsend discharge. The model is fully two-dimensional with azimuthal symmetry. The results show a significantly larger fraction of the energy goes ...


Prediction Of Spin Polarized Fermi Arcs In Quasiparticle Interference In Cebi, Zhao Huang, Christopher Lane, Chao Cao, Guo-Xiang Zhi, Yu Liu, Christian E. Matt, Brinda Kuthanazhi, Paul C. Canfield, Dmitry Yarotski, A. J. Taylor, Jian-Xin Zhu Dec 2020

Prediction Of Spin Polarized Fermi Arcs In Quasiparticle Interference In Cebi, Zhao Huang, Christopher Lane, Chao Cao, Guo-Xiang Zhi, Yu Liu, Christian E. Matt, Brinda Kuthanazhi, Paul C. Canfield, Dmitry Yarotski, A. J. Taylor, Jian-Xin Zhu

Ames Laboratory Accepted Manuscripts

We predict that CeBi in the ferromagnetic state is a Weyl semimetal. Our calculations within density functional theory show the existence of two pairs of Weyl nodes on the momentum path (0,0,kz) at 15meV above and 100meV below the Fermi level. Two corresponding Fermi arcs are obtained on surfaces of mirror-symmetric (010)-oriented slabs at E=15meV and both arcs are interrupted into three segments due to hybridization with a set of trivial surface bands. By studying the spin texture of surface states, we find the two Fermi arcs are strongly spin polarized but in opposite directions, which ...


Treated Hfo2 Based Rram Devices With Ru, Tan, Tin As Top Electrode For In-Memory Computing Hardware, Yuvraj Dineshkumar Patel Dec 2020

Treated Hfo2 Based Rram Devices With Ru, Tan, Tin As Top Electrode For In-Memory Computing Hardware, Yuvraj Dineshkumar Patel

Theses

The scalability and power efficiency of the conventional CMOS technology is steadily coming to a halt due to increasing problems and challenges in fabrication technology. Many non-volatile memory devices have emerged recently to meet the scaling challenges. Memory devices such as RRAMs or ReRAM (Resistive Random-Access Memory) have proved to be a promising candidate for analog in memory computing applications related to inference and learning in artificial intelligence. A RRAM cell has a MIM (Metal insulator metal) structure that exhibits reversible resistive switching on application of positive or negative voltage. But detailed studies on the power consumption, repeatability and retention ...


Low-Temperature Crystal Structure And Mean-Field Modeling Of Erxdy1−Xal2 Intermetallics, Yaroslav Mudryk, Bruno P. Alho, Paula O. Ribeiro, Vitalij K. Pecharsky Dec 2020

Low-Temperature Crystal Structure And Mean-Field Modeling Of Erxdy1−Xal2 Intermetallics, Yaroslav Mudryk, Bruno P. Alho, Paula O. Ribeiro, Vitalij K. Pecharsky

Ames Laboratory Accepted Manuscripts

Low-temperature crystal structure of the ErxDy1−xAl2 alloys with x = 0.45, 0.67, 0.90 was examined using temperature-dependent powder X-ray diffraction. The Er-rich sample, Er0.9Dy0.1Al2, exhibits a rhombohedral distortion associated with the magnetic ordering that occurs around 20 K. The rhombohedral distortion is suppressed in Er0.67Dy0.33Al2, while a weak low-temperature tetragonal distortion is observed in Er0.45Dy0.55Al2. The mean-field theory supports the correlation between the type of structural distortion and the variable easy ...


3-D Fabry–Pérot Cavities Sculpted On Fiber Tips Using A Multiphoton Polymerization Process, Jonathan W. Smith, Jeremiah C. Williams, Joseph S. Suelzer, Nicholas G. Usechak, Hengky Chandrahalim Dec 2020

3-D Fabry–Pérot Cavities Sculpted On Fiber Tips Using A Multiphoton Polymerization Process, Jonathan W. Smith, Jeremiah C. Williams, Joseph S. Suelzer, Nicholas G. Usechak, Hengky Chandrahalim

Faculty Publications

This paper presents 3-D Fabry–Pérot (FP) cavities fabricated directly onto cleaved ends of low-loss optical fibers by a two-photon polymerization (2PP) process. This fabrication technique is quick, simple, and inexpensive compared to planar microfabrication processes, which enables rapid prototyping and the ability to adapt to new requirements. These devices also utilize true 3-D design freedom, facilitating the realization of microscale optical elements with challenging geometries. Three different device types were fabricated and evaluated: an unreleased single-cavity device, a released dual-cavity device, and a released hemispherical mirror dual-cavity device. Each iteration improved the quality of the FP cavity's reflection ...


Characterization Of Fiber Bragg Grating Based, Geometry-Dependent, Magnetostrictive Composite Sensors, Edward Lynch Dec 2020

Characterization Of Fiber Bragg Grating Based, Geometry-Dependent, Magnetostrictive Composite Sensors, Edward Lynch

Theses and Dissertations

Optical sensors based on geometry dependent magnetostrictive composite, having potential applications in current sensing and magnetic field sensing are modeled and evaluated experimentally with an emphasis on their thermal immunity from thermal disturbances. Two sensor geometries composed of a fiber Bragg grating (FBG) embedded in a shaped Terfenol-D/epoxy composite material, which were previously prototyped and tested for magnetic field response, were investigated. When sensing magnetic fields or currents, the primary function of the magnetostrictive composite geometry is to modulate the magnetic flux such that a magnetostrictive strain gradient is induced on the embedded FBG. Simulations and thermal experiments reveal ...


Static And Dynamical Properties Of Multiferroics, Sayed Omid Sayedaghaee Dec 2020

Static And Dynamical Properties Of Multiferroics, Sayed Omid Sayedaghaee

Theses and Dissertations

Since the silicon industrial revolution in the 1950s, a lot of effort was dedicated to the research and development activities focused on material and solid-state sciences. As a result, several cutting-edge technologies are emerging including the applications of functional materials in the design and enhancement of novel devices such as sensors, highly capable data storage media, actuators, transducers, and several other types of electronic tools. In the last two decades, a class of functional materials known as multiferroics has captured significant attention because of providing a huge potential for new designs due to possessing multiple ferroic order parameters at the ...


Using Numerical Methods To Screen Magnetocaloric Materials In An Active Magnetic Regenerative Cycle, Huseyin Ucar, Durga Paudyal, Ozdal Boyraz Dec 2020

Using Numerical Methods To Screen Magnetocaloric Materials In An Active Magnetic Regenerative Cycle, Huseyin Ucar, Durga Paudyal, Ozdal Boyraz

Ames Laboratory Accepted Manuscripts

A 2-dimensional numerical model of a room temperature operating Active Magnetic Regenerator (AMR) that comprises of a regenerator, hot and cold heat exchangers, heat transfer fluid is developed. The regenerator is made of a magnetocaloric material (MCM) which heats up upon applying a magnetic field, H, and cools down when the field is removed; thus, making it the most essential part of an AMR. The model takes experimentally measured ∆Tad(H,T) and the Cp(H,T) data as input and provides quantitative performance metrics of the magnetic cooling system, such as ∆Tspan and the cooling load, as output. With ...


Magnetic Detwinning And Biquadratic Magnetic Interaction In Eufe2as2 Revealed By Eu-153 Nmr, Qing-Ping Ding, N. S. Sangeetha, William R. Meier, Mingyu Xu, Sergey L. Bud’Ko, Paul C. Canfield, David C. Johnston, Yuji Furukawa Nov 2020

Magnetic Detwinning And Biquadratic Magnetic Interaction In Eufe2as2 Revealed By Eu-153 Nmr, Qing-Ping Ding, N. S. Sangeetha, William R. Meier, Mingyu Xu, Sergey L. Bud’Ko, Paul C. Canfield, David C. Johnston, Yuji Furukawa

Ames Laboratory Accepted Manuscripts

In the nematic state of iron-based superconductors, twin formation often obscures the intrinsic, anisotropic, in-plane physical properties. Relatively high in-plane external magnetic fields Hext greater than the typical laboratory-scale magnetic fields 10–15 T are usually required to completely detwin a sample. However, recently a very small in-plane Hext∼0.1 T was found to be sufficient for detwinning the nematic domains in EuFe2As2. To explain this behavior, a microscopic theory based on biquadratic magnetic interactions between the Eu and Fe spins has been proposed. Here, using 153Eu nuclear magnetic resonance (NMR) measurements below the Eu2+ ordering temperature, we show ...


Laser-Induced Modifications In Two-Dimensional Materials, Tariq Afaneh Nov 2020

Laser-Induced Modifications In Two-Dimensional Materials, Tariq Afaneh

Graduate Theses and Dissertations

Atomically thin two-dimensional (2D) materials have attracted a growing interest in the lastdecade from the fundamental point of view as well as their potential applications in functional devices. Due to their high surface-to-volume ratio, the physical properties of 2D materials are very sensitive to the environmental factor such as surrounding media and illumination conditions (e.g. light-mater interaction). In the first part of this dissertation I will present recent advances in developing laser-assisted methods to tune the physical properties of 2D transition metal dichalcogenides (TMDs). We demonstrate laser-assisted chemical modification ultrathin TMDs, locally replacing selenium by sulfur atoms. The photo-conversion ...


Dynamic Observation Of Dendritic Quasicrystal Growth Upon Laser-Induced Solid-State Transformation, Insung Han, Joseph T. Mckeown, Ling Tang, Cai-Zhuang Wang, Hadi Parsamehr, Zhucong Xi, Ying-Rui Lu, Matthew J. Kramer, Ashwin J. Shahani Nov 2020

Dynamic Observation Of Dendritic Quasicrystal Growth Upon Laser-Induced Solid-State Transformation, Insung Han, Joseph T. Mckeown, Ling Tang, Cai-Zhuang Wang, Hadi Parsamehr, Zhucong Xi, Ying-Rui Lu, Matthew J. Kramer, Ashwin J. Shahani

Ames Laboratory Accepted Manuscripts

We report the laser-induced solid-state transformation between a periodic “approximant” and quasicrystal in the Al-Cr system during rapid quenching. Dynamic transmission electron microscopy allows us to capture in situ the dendritic growth of the metastable quasicrystals. The formation of dendrites during solid-state transformation is a rare phenomenon, which we attribute to the structural similarity between the two intermetallics. Through ab initio molecular dynamics simulations, we identify the dominant structural motif to be a 13-atom icosahedral cluster transcending the phases of matter.


High Layer Uniformity Of Two-Dimensional Materials Demonstrated Surprisingly From Broad Features In Surface Electron Diffraction, Shen Chen, Michael Horn Von Hoegen, Patricia A. Thiel, Adam Kaminski, Benjamin Schrunk, Thanassis Speliotis, Edward Henry Conrad, Michael C. Tringides Nov 2020

High Layer Uniformity Of Two-Dimensional Materials Demonstrated Surprisingly From Broad Features In Surface Electron Diffraction, Shen Chen, Michael Horn Von Hoegen, Patricia A. Thiel, Adam Kaminski, Benjamin Schrunk, Thanassis Speliotis, Edward Henry Conrad, Michael C. Tringides

Chemistry Publications

Paradoxically a very broad diffraction background, named the Bell-Shaped-Component (BSC), has been established as a feature of graphene growth. Although the BSC has been present in the earlier literature it has been ignored. Recent diffraction studies as a function of electron energy have shown that the BSC is not related to scattering interference. The BSC is a very strong effect, but its origin is still unclear. Here, additional experiments are carried out as a function of temperature while monitoring changes in the intensity of different spots over the range that single-layer-graphene (SLG) grows. Quantitative fitting of the profiles shows that ...


Reinvestigation Of The Intrinsic Magnetic Properties Of (Fe1-Xcox)(2)B Alloys And Crystallization Behavior Of Ribbons, Tej Nath Lamichhane, Olena Palasyuk, Vladimir P. Antropov, Ivan A. Zhuravlev, Kirill D. Belashchenko, Ikenna C. Nlebedim, Kevin W. Dennis, Anton Jesche, Matthew J. Kramer, Sergey L. Bud’Ko, R. William Mccallum, Paul C. Canfield, Valentin Taufour Nov 2020

Reinvestigation Of The Intrinsic Magnetic Properties Of (Fe1-Xcox)(2)B Alloys And Crystallization Behavior Of Ribbons, Tej Nath Lamichhane, Olena Palasyuk, Vladimir P. Antropov, Ivan A. Zhuravlev, Kirill D. Belashchenko, Ikenna C. Nlebedim, Kevin W. Dennis, Anton Jesche, Matthew J. Kramer, Sergey L. Bud’Ko, R. William Mccallum, Paul C. Canfield, Valentin Taufour

Physics and Astronomy Publications

New determination of the magnetic anisotropy from single crystals of (Fe1-xCox)(2)B alloys are presented. The anomalous temperature dependence of the anisotropy constant is discussed using the standard Callen-Callen theory, which is shown to be insufficient to explain the experimental results. A more material specific study using first-principles calculations with disordered moments approach gives a much more consistent interpretation of the experimental data. Since the intrinsic properties of the alloys with x = 0.3 - 0.35 are promising for permanent magnets applications, initial investigation of the extrinsic properties are described, in particular the crystallization of melt spun ribbons with ...


Finite-Strain Scale-Free Phase-Field Approach To Multivariant Martensitic Phase Transformations With Stress-Dependent Effective Thresholds, Hamed Babaei, Valery I. Levitas Nov 2020

Finite-Strain Scale-Free Phase-Field Approach To Multivariant Martensitic Phase Transformations With Stress-Dependent Effective Thresholds, Hamed Babaei, Valery I. Levitas

Aerospace Engineering Publications

A scale-free phase-field model for martensitic phase transformations (PTs) at finite strains is developed as an essential generalization of small-strain models in Levitas et al. (2004) and Idesman et al. (2005). The theory includes finite elastic and transformational strains and rotations as well as anisotropic and different elastic properties of phases. The gradient energy term is excluded, and the model is applicable for any scale greater than 100 nm. The model tracks finite-width interfaces between austenite and the mixture of martensitic variants only; volume fractions of martensitic variants are the internal variables rather than order parameters. The concept of the ...


Comparative Study Of Silk-Based Magnetic Materials: Effect Of Magnetic Particle Types On The Protein Structure And Biomaterial Properties., Ye Xue, Samuel Lofland, Xiao Hu Oct 2020

Comparative Study Of Silk-Based Magnetic Materials: Effect Of Magnetic Particle Types On The Protein Structure And Biomaterial Properties., Ye Xue, Samuel Lofland, Xiao Hu

Faculty Scholarship for the College of Science & Mathematics

This study investigates combining the good biocompatibility and flexibility of silk protein with three types of widely used magnetic nanoparticles to comparatively explore their structures, properties and potential applications in the sustainability and biomaterial fields. The secondary structure of silk protein was quantitatively studied by infrared spectroscopy. It was found that magnetite (Fe3O4) and barium hexaferrite (BaFe12O19) can prohibit β-sheet crystal due to strong coordination bonding between Fe3+ ions and carboxylate ions on silk fibroin chains where cobalt particles showed minimal effect. This was confirmed by thermal analysis, where a high temperature degradation peak was found above 640 °C in ...


Stacking Faults And Alternate Crystal Structures For The Shape-Memory Alloy Niti, M. Krcmar, German D. Samolyuk, James R. Morris Oct 2020

Stacking Faults And Alternate Crystal Structures For The Shape-Memory Alloy Niti, M. Krcmar, German D. Samolyuk, James R. Morris

Ames Laboratory Accepted Manuscripts

We use ab initio calculations to study the role of stacking faults in connecting the high-temperature B2 and the theoretically predicted low-temperature B33 NiTi phases. In contrast with prior work, we describe the B2 -> B33 phase transformation in terms of alternate bilayer shifts by 1/2[100] on the (011)(B2) plane, obtaining a viable pathway; the same mechanism could also work with the B19 parent phase. We then examine B33-like structures built from alternate stacking sequences of B19 bilayers, constructed to have monoclinic tilt angles close to the experimentally reported NiTi B19' martensite, and find four low-energy stacking-fault variants ...


Crystal Structure And Physical Properties Of Yb2in And Eu2-Xybxin Alloys, F. Guillou, H. Yibole, R. Hamane, V. Hardy, Y. B. Sun, J. J. Zhao, Yaroslav Mudryk, Vitalij K. Pecharsky Oct 2020

Crystal Structure And Physical Properties Of Yb2in And Eu2-Xybxin Alloys, F. Guillou, H. Yibole, R. Hamane, V. Hardy, Y. B. Sun, J. J. Zhao, Yaroslav Mudryk, Vitalij K. Pecharsky

Ames Laboratory Accepted Manuscripts

While binary RE2In, where RE = rare earth, have been reported a few decades ago, recent investigations revealed intriguing new physical insights. For instance, the discovery of a nearly ideal first-order ferromagnetic transition in Eu2In calls for further exploration of structures and properties of RE2In, in particular for the least-documented RE = Eu and Yb cases. Here, we investigate Eu2-xYbxIn pseudobinaries with nominal values of x = 0.25, 0.5, 0.75, 1, 1.5, 2 by powder x-ray diffraction (including as function of temperature from 100 to 375 K for Yb2In), magnetization (5-300 K), as well as electrical resistivity (5-300 K ...


Motion Of Phase Boundary During Antiferroelectric–Ferroelectric Transition In A Pbzro3-Based Ceramic, Binzhi Liu, Xinchun Tian, Lin Zhou, Xiaoli Tan Oct 2020

Motion Of Phase Boundary During Antiferroelectric–Ferroelectric Transition In A Pbzro3-Based Ceramic, Binzhi Liu, Xinchun Tian, Lin Zhou, Xiaoli Tan

Materials Science and Engineering Publications

The in situ biasing transmission electron microscopy technique is employed to investigate the nucleation and growth of the ferroelectric phase during the electric field-induced phase transition in Pb0.99{Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98}O3, a PbZrO3-based antiferroelectric ceramic. The first-order displacive phase transition is found to be highly reversible with the initial antiferroelectric domain configuration almost completely recovered upon removal of the applied field. In the forward transition from the antiferroelectric to ferroelectric phase, {100}c facets are dominant on the phase boundary; while in the reverse transition from the ferroelectric to antiferroelectric phase ...


Conductivity Reversal In Silicon Doped With S And Zn, Abdulaziz Shavkatovich Mavlyanov, Nurullo Zikrillayev, Maruf Khaqqulov, Erkin Khaltursunov, Farhod Shakarov Sep 2020

Conductivity Reversal In Silicon Doped With S And Zn, Abdulaziz Shavkatovich Mavlyanov, Nurullo Zikrillayev, Maruf Khaqqulov, Erkin Khaltursunov, Farhod Shakarov

Acta of Turin Polytechnic University in Tashkent

Based on experimental results of investigation of type of conductivity of silicon samples doped with sulfur at Т=1250°С, and thereafter with zinc at T=1200°С, the authors put forward the hypothesis about self-assembly of “binary” elementary cells where atoms of elements of group II (Zn) and IV (S) allegedly form ZnS-type compounds in Si. The thermodynamic conditions required for buildup of such elementary cells and assembly of various associations in the basic lattice of silicon including self-assembly of ZnS clusters were theoretically determined and experimentally justified.


Substitutional And Interstitial Doping In Laco5 System For The Development Of Hard Magnetic Properties: A First Principles Study, Huseyin Ucar, Renu Choudhary, Durga Paudyal Sep 2020

Substitutional And Interstitial Doping In Laco5 System For The Development Of Hard Magnetic Properties: A First Principles Study, Huseyin Ucar, Renu Choudhary, Durga Paudyal

Ames Laboratory Accepted Manuscripts

We investigate here the changes in the electronic structure at the transition metal sites of the RE-TM5 structure (RE = Rare Earth, TM = Transition Metal) while doping the interstitial sites with nitrogen. LaCo5 compound is taken as the baseline compound owing to its critically needed intrinsic magnetic properties such as magneto-crystalline anisotropy energy (MAE) of ≈5 meV/fu [1] due to the contributions from the cobalt network. In addition, because of the lack of 4f electrons in lanthanum, complications originating from the treatment of the 4f localized electrons are absent in this compound; making it an ideal reference material to all ...


Viable Materials With A Giant Magnetocaloric Effect, Nikolai A. Zarkevich, Vladimir I. Zverev Sep 2020

Viable Materials With A Giant Magnetocaloric Effect, Nikolai A. Zarkevich, Vladimir I. Zverev

Ames Laboratory Accepted Manuscripts

This review of the current state of magnetocalorics is focused on materials exhibiting a giant magnetocaloric response near room temperature. To be economically viable for industrial applications and mass production, materials should have desired useful properties at a reasonable cost and should be safe for humans and the environment during manufacturing, handling, operational use, and after disposal. The discovery of novel materials is followed by a gradual improvement of properties by compositional adjustment and thermal or mechanical treatment. Consequently, with time, good materials become inferior to the best. There are several known classes of inexpensive materials with a giant magnetocaloric ...