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First-Principles Study, Fabrication And Characterization Of (Zr0.25nb0.25ti0.25v0.25)C High-Entropy Ceramics, Beilin Ye, Tongqi Wen, Manh Cuong Nguyen, Luyao Hao, Cai-Zhuang Wang, Yanhui Chu 2019 South China University of Technology

First-Principles Study, Fabrication And Characterization Of (Zr0.25nb0.25ti0.25v0.25)C High-Entropy Ceramics, Beilin Ye, Tongqi Wen, Manh Cuong Nguyen, Luyao Hao, Cai-Zhuang Wang, Yanhui Chu

Ames Laboratory Accepted Manuscripts

The formation possibility of a new (Zr0.25Nb0.25Ti0.25V0.25)C high-entropy ceramics (ZHC-1) was first analyzed by the first-principles calculations and thermodynamical analysis and then it was successfully fabricated by hot pressing sintering technique. The first-principles calculation results showed that the mixing enthalpy of ZHC-1 was 5.526 kJ/mol and the mixing entropy of ZHC-1 was in the range of 0.693R–1.040R. The thermodynamical analysis results showed that ZHC-1 was thermodynamically stable above 959 K owing to its negative mixing Gibbs free energy. The experimental results showed that the as-prepared ZHC-1 (95.1% relative density ...


Determination Of Conversion Factors For Various Calibration Geometries Using Barium-133 In A Silver Zeolite Cartridge, Amin Hamideh 2019 Louisiana State University

Determination Of Conversion Factors For Various Calibration Geometries Using Barium-133 In A Silver Zeolite Cartridge, Amin Hamideh

LSU Master's Theses

Iodine-131 (I-131) is a major fission product among other radionuclides released during a nuclear incident. This radioiodine has a half-life of 8.02 days and the primary organ of uptake through ingestion or inhalation is the thyroid gland. For these reasons, nuclear power plants must routinely monitor I-131 through air sampling. Currently, there are two adsorbing media to collect I-131: activated charcoal and silver zeolite cartridges. Silver zeolite cartridges are generally used during a post nuclear incident due to its affinity for iodine while not adsorbing noble gases such as krypton-85 and xenon-135. After an air sample is taken from ...


A Neutron Diffraction Demonstration Of Long-Range Magnetic Order In The Quasicrystal Approximant Dycd6, D. H. Ryan, J. M. Cadogan, Tai Kong 2019 McGill University

A Neutron Diffraction Demonstration Of Long-Range Magnetic Order In The Quasicrystal Approximant Dycd6, D. H. Ryan, J. M. Cadogan, Tai Kong

Ames Laboratory Accepted Manuscripts

We have used neutron powder diffraction to demonstrate the existence of long-range antiferromagnetic order of Ising-like Dy moments in the DyCd6 quasicrystal approximant phase. This cubic compound undergoes a slight distortion to a monoclinic cell at low temperatures. The Neel temperature is 18.0(2) K and the magnetic order of the Dy sublattice may be described in the parent cubic Im (3) over bar structure using a combination of two propagation vectors, k(1) = [0 0 0] and k(2) = [1/2 0 1/2], yielding 'anti-I' order. Alternatively, when referred to the monoclinic C2/c cell, the magnetic ...


Connection Between Mott Physics And Crystal Structure In A Series Of Transition Metal Binary Compounds, Nicola Lanatà, Tsung-Han Lee, Yong-Xin Yao, Vladan Stevanović, Vladimir Dobrosavljević 2019 Aarhus University

Connection Between Mott Physics And Crystal Structure In A Series Of Transition Metal Binary Compounds, Nicola Lanatà, Tsung-Han Lee, Yong-Xin Yao, Vladan Stevanović, Vladimir Dobrosavljević

Ames Laboratory Accepted Manuscripts

The choice that a solid system “makes” when adopting a crystal structure (stable or metastable) is ultimately governed by the interactions between electrons forming chemical bonds. Here we analyze six prototypical binary transition metal compounds and shed light on the connection between Mott physics and the behavior of the energy as a function of the spatial arrangement of the atoms in these systems. Remarkably, we find that the main qualitative features of this complex behavior in the Mott phase of these systems can be traced back to the fact that the strong d-electron correlations influence substantially the charge transfer ...


High Thermoelectric Efficiency In Monolayer Pbi2 From 300 K To 900 K, Bo Peng, Haodong Mei, Hezhu Shao, Ke Xu, Gang Ni, Qingyuan Jin, Costas M. Soukoulis, Heyuan Zhu 2019 Fudan University

High Thermoelectric Efficiency In Monolayer Pbi2 From 300 K To 900 K, Bo Peng, Haodong Mei, Hezhu Shao, Ke Xu, Gang Ni, Qingyuan Jin, Costas M. Soukoulis, Heyuan Zhu

Ames Laboratory Accepted Manuscripts

By using a first-principles approach, monolayer PbI2 is found to have great potential in thermoelectric applications. The linear Boltzmann transport equation is applied to obtain the perturbation to the electron distribution by different scattering mechanisms. The mobility is mainly limited by the deformation-potential interaction with long-wavelength acoustic vibrations at low carrier concentrations. At high concentrations, ionized impurity scattering becomes stronger. The electrical conductivity and Seebeck coefficient are calculated accurately over various ranges of temperature and carrier concentration. The lattice thermal conductivity of PbI2, 0.065 W m−1 K−1 at 300 K, is the lowest among other 2D thermoelectric ...


Local Structure Origin Of Ultrafast Crystallization Driven By High-Fidelity Octahedral Clusters In Amorphous Sc0.2sb2te3, Chong Qiao, Y. R. Guo, S. Y. Wang, Ming Xu, Xiangshui Miao, Cai-Zhuang Wang, Kai-Ming Ho 2019 Fudan University

Local Structure Origin Of Ultrafast Crystallization Driven By High-Fidelity Octahedral Clusters In Amorphous Sc0.2sb2te3, Chong Qiao, Y. R. Guo, S. Y. Wang, Ming Xu, Xiangshui Miao, Cai-Zhuang Wang, Kai-Ming Ho

Ames Laboratory Accepted Manuscripts

Phase-change material Sc0.2Sb2Te3 (SST) can remarkably boost the writing speed of memory devices due to the extremely fast crystallization. It was demonstrated that the fast crystallization is because Sc stabilizes the 4-fold rings which act as precursors of nuclei in the amorphous phase. In this work, by using first-principles molecular dynamics simulations, we studied the local structures in the liquid and amorphous SST at various temperatures. The results reveal that Sc-centered configurations are almost in the form of stable octahedral clusters, which enhances the local order of the amorphous phase. Different from Sb- and Te-centered clusters which have lower ...


Effects Of Dopants On The Glass Forming Ability In Al-Based Metallic Alloy, Yang Sun, Feng Zhang, Lin Yang, Huajing Song, Mikhail I. Mendelev, Cai-Zhuang Wang, Kai-Ming Ho 2019 Ames Laboratory

Effects Of Dopants On The Glass Forming Ability In Al-Based Metallic Alloy, Yang Sun, Feng Zhang, Lin Yang, Huajing Song, Mikhail I. Mendelev, Cai-Zhuang Wang, Kai-Ming Ho

Ames Laboratory Accepted Manuscripts

The effect of dopants on the metallic glass forming ability is usually considered based on the analysis of changes in the liquid structure or thermodynamics. What is missing in such considerations is an analysis of how a dopant changes the properties of the crystal phases which can form instead of the glass. In order to illuminate this aspect we performed molecular dynamics simulations to study the effects of Mg and Sm dopants on the crystal nucleation in Al. The simulation data were found to be consistent with the experimental observations that addition of Mg to Al does not lead to ...


Ultrafast Nonlinear Transparency Driven At A Telecom Wavelength In An Organic Semiconductor System, Joong-Mok Park, Di Cheng, Aaron Patz, Liang Luo, Fadzai Fungura, Ruth Shinar, Kai-Ming Ho, Joseph Shinar, Jigang Wang 2019 Iowa State University and Ames Laboratory

Ultrafast Nonlinear Transparency Driven At A Telecom Wavelength In An Organic Semiconductor System, Joong-Mok Park, Di Cheng, Aaron Patz, Liang Luo, Fadzai Fungura, Ruth Shinar, Kai-Ming Ho, Joseph Shinar, Jigang Wang

Ames Laboratory Accepted Manuscripts

Ultrafast laser-induced transparency is demonstrated using femtosecond (fs) pump-probe experiments in the organic P3HT:PCBM (donor:acceptor) blend structure. For above band gap pumping, ultrafast transient signals strongly depend on the probe photon energy. Most intriguingly, for below band gap pumping at 0.95 eV, or 1.3 µm at a telecom wavelength, a huge transmission increase up to 30% only during the laser pulse ∼100 fs is observed as a pump-driven, quasi-instantaneous suppression of absorption for the high photon-energy energy probe beam. We attribute the observed laser-driven transparency to dynamic Franz-Keldysh effect, at least one order of magnitude stronger ...


University Physics I: Classical Mechanics, Julio Gea-Banacloche 2019 University of Arkansas, Fayetteville

University Physics I: Classical Mechanics, Julio Gea-Banacloche

Open Educational Resources

This is a textbook for the first semester of University Physics for scientists and engineers. It covers classical mechanics, and a brief introduction to thermodynamics. The presentation and approach are similar to Mazur’s “The Principles and Practice of Physics,” in that conservation laws are introduced before forces, and one-dimensional systems thoroughly covered before moving to two dimensions. Although the course is “calculus based,” the book has been written with the understanding that many students may be taking calculus simultaneously as a corequisite, so the use of calculus is relatively sparse.

This revised version (Fall 2019) takes into account a ...


Mechanisms Of Enhanced Thermal Stability Of Polarization In Lead-Free (Bi 1/2na 1/2) 0.94ba 0.06tio 3/Zno Ceramic Composites, Zhongming Fan, Lin Zhou, Tae-Hoon Kim, Ji Zhang, Shan-Tao Zhang, Xiaoli Tan 2019 Iowa State University

Mechanisms Of Enhanced Thermal Stability Of Polarization In Lead-Free (Bi 1/2na 1/2) 0.94ba 0.06tio 3/Zno Ceramic Composites, Zhongming Fan, Lin Zhou, Tae-Hoon Kim, Ji Zhang, Shan-Tao Zhang, Xiaoli Tan

Ames Laboratory Accepted Manuscripts

(Bi 1/2Na 1/2)TiO 3-based solid solutions, one of the major systems of lead-free piezoelectric ceramics, exhibit a low thermal depolarization temperature ( T d~100°C). It was reported that by incorporating 30 mol% ZnO particles to form a ceramic composite of (Bi 1/2Na 1/2) 0.94Ba 0.06TiO 3/ZnO, the depolarization process can be shifted up to ~250 °C. In the present work, a variety of advanced transmission electron microscopy techniques, including in situ heating, annular bright-field, high-angle annular dark-field, geometric phase analysis, energy-dispersive spectrum and electron energy-loss spectroscopy, are employed to investigate the ...


Nonlinearity In The Dark: Broadband Terahertz Generation With Extremely High Efficiency, Ming Fang, Nian-Hai Shen, Wei E. I. Sha, Zhixiang Huang, Thomas Koschny, Costas M. Soukoulis 2019 Iowa State University and Ames Laboratory

Nonlinearity In The Dark: Broadband Terahertz Generation With Extremely High Efficiency, Ming Fang, Nian-Hai Shen, Wei E. I. Sha, Zhixiang Huang, Thomas Koschny, Costas M. Soukoulis

Ames Laboratory Accepted Manuscripts

Plasmonic metamaterials and metasurfaces offer new opportunities in developing high performance terahertz emitters and detectors beyond the limitations of conventional nonlinear materials. However, simple meta-atoms for second-order nonlinear applications encounter fundamental trade-offs in the necessary symmetry breaking and local-field enhancement due to radiation damping that is inherent to the operating resonant mode and cannot be controlled separately. Here we present a novel concept that eliminates this restriction obstructing the improvement of terahertz generation efficiency in nonlinear metasurfaces based on metallic nanoresonators. This is achieved by combining a resonant dark-state metasurface, which locally drives nonlinear nanoresonators in the near field, with ...


Nonvolatile Voltage Controlled Molecular Spin State Switching, G. Hao, A. Mosey, X. Jiang, A. J. Yost, K. R. Sapkota, G. T. Wang, X. Zhang, J. Zhang, A. T. N'Diaye, R. Cheng, X. Xu, P. A. Dowben 2019 University of Nebraska - Lincoln

Nonvolatile Voltage Controlled Molecular Spin State Switching, G. Hao, A. Mosey, X. Jiang, A. J. Yost, K. R. Sapkota, G. T. Wang, X. Zhang, J. Zhang, A. T. N'Diaye, R. Cheng, X. Xu, P. A. Dowben

Xiaoshan Xu Papers

Voltage-controlled room temperature isothermal reversible spin crossover switching of [Fe{H2B(pz)2}2(bipy)] thin films is demonstrated. This isothermal switching is evident in thin film bilayer structures where the molecular spin crossover film is adjacent to a molecular ferroelectric. The adjacent molecular ferroelectric, either polyvinylidene fluoride hexafluoropropylene or croconic acid (C5H2O5), appears to lock the spin crossover [Fe{H2B(pz)2}2(bipy)] molecular complex largely in the low or high spin state depending on the direction of ferroelectric polarization. In both a planar two terminal diode structure and ...


Unusual Perpendicular Anisotropy In Co2Tisi Films, Yunlong Jin, Shah R. Valloppilly, Parashu R. Kharel, Rohit Pathak, Arti Kashyap, Ralph Skomski, David J. Sellmyer 2019 University of Nebraska-Lincoln

Unusual Perpendicular Anisotropy In Co2Tisi Films, Yunlong Jin, Shah R. Valloppilly, Parashu R. Kharel, Rohit Pathak, Arti Kashyap, Ralph Skomski, David J. Sellmyer

David Sellmyer Publications

Thin films of Co2TiSi on MgO are investigated experimentally and theoretically. The films were produced by magnetron sputtering on MgO(001) and have a thickness of about 100 nm. As bulk Co2TiSi, they crystallize in the normal cubic Heusler (L21) structure, but the films are slightly distorted (c/a = 1.0014) and contain some antisite disorder. The films exhibit a robust perpendicular anisotropy of 0.5 MJ m3. This result is surprising for several reasons. First, surface and interface anisotropies are too small to explain perpendicular anisotropy in such rather thick films. Second, Co ...


Noncollinear Spin Structure In Fe3+Xco3−Xti2 (X = 0, 2, 3) From Neutron Diffraction, Haohan Wang, Balamurugan Balamurugan, Rabindra Pahari, Ralph Skomski, Yaohua Liu, Ashfia Huq, D. J. Sellmyer, Xiaoshan Xu 2019 University of Nebraska - Lincoln

Noncollinear Spin Structure In Fe3+Xco3−Xti2 (X = 0, 2, 3) From Neutron Diffraction, Haohan Wang, Balamurugan Balamurugan, Rabindra Pahari, Ralph Skomski, Yaohua Liu, Ashfia Huq, D. J. Sellmyer, Xiaoshan Xu

Xiaoshan Xu Papers

Neutron powder diffraction has been used to investigate the spin structure of the hard-magnetic alloy Fe3+xCo3−xTi2 (x = 0, 2, 3). The materials are produced by rapid quenching from the melt, they possess a hexagonal crystal structure, and they are nanocrystalline with crystallite sizes D of the order of 40 nm. Projections of the magnetic moment onto both the crystalline c axis and the basal plane were observed. The corresponding misalignment angle exhibits a nonlinear decrease with x, which we explain as a micromagnetic effect caused by Fe-Co site disorder. The underlying physics is ...


Straintronic Nanomagnetic Devices For Non-Boolean Computing, Md Ahsanul Abeed 2019 Virginia Commonwealth University

Straintronic Nanomagnetic Devices For Non-Boolean Computing, Md Ahsanul Abeed

Theses and Dissertations

Nanomagnetic devices have been projected as an alternative to transistor-based switching devices due to their non-volatility and potentially superior energy-efficiency. The energy efficiency is enhanced by the use of straintronics which involves the application of a voltage to a piezoelectric layer to generate a strain which is ultimately transferred to an elastically coupled magnetostrictive nanomaget, causing magnetization rotation. The low energy dissipation and non-volatility characteristics make straintronic nanomagnets very attractive for both Boolean and non-Boolean computing applications. There was relatively little research on straintronic switching in devices built with real nanomagnets that invariably have defects and imperfections, or their adaptation ...


M2 Factor Of A Vector Schell-Model Beam, Milo W. Hyde IV, Mark F. Spencer 2019 Air Force Institute of Technology

M2 Factor Of A Vector Schell-Model Beam, Milo W. Hyde Iv, Mark F. Spencer

Faculty Publications

Extending existing scalar Schell-model source work, we derive the M2 factor for a general electromagnetic or vector Schell-model source to assess beam quality. In particular, we compute the M2 factors for two vector Schell-model sources found in the literature. We then describe how to synthesize vector Schell-model beams in terms of specified, desired M2 and present Monte Carlo simulation results to validate our analysis.


Phenomenal Magneto-Elastoresistance Of Wte2: Strain Engineering Of Electronic And Quantum Transport Properties, Na Hyun Jo, Lin-Lin Wang, Peter P. Orth, Sergey L. Bud’ko, Paul C. Canfield 2019 Iowa State University and Ames Laboratory

Phenomenal Magneto-Elastoresistance Of Wte2: Strain Engineering Of Electronic And Quantum Transport Properties, Na Hyun Jo, Lin-Lin Wang, Peter P. Orth, Sergey L. Bud’Ko, Paul C. Canfield

Physics and Astronomy Publications

Elastoresistance describes the relative change of a material's resistance when strained. It has two major contributions: strain induced geometric and electronic changes. If the geometric factor dominates, like in ordinary metals such as copper, the elastoresistance is positive and rather small, i.e. typically of order 1. In a few materials, however, changes in electronic structure dominate, which gives rise to larger and even negative values, such as (-11) for Bi. Here, we report that the transition metal dichalcogenide (TMDC) WTe2 is a member of the second group, exhibiting a large and non-monotonic elastoresistance that is about (-20) near ...


High Energy Product Of Mnbi By Field Annealing And Sn Alloying, Wenyong Zhang, Balamurugan Balasubramanian, Parashu Kharel, Rabindra Pahari, Shah R. Valloppilly, Xingzhong Li, Lanping Yue, Ralph Skomski, David J. Sellmyer 2019 University of Nebraska - Lincoln

High Energy Product Of Mnbi By Field Annealing And Sn Alloying, Wenyong Zhang, Balamurugan Balasubramanian, Parashu Kharel, Rabindra Pahari, Shah R. Valloppilly, Xingzhong Li, Lanping Yue, Ralph Skomski, David J. Sellmyer

Faculty Publications from Nebraska Center for Materials and Nanoscience

Permanent-magnet materials are one cornerstone of today’s technology, abundant in disk drives, motors, medical equipment, wind generators, and cars. A continuing challenge has been to reconcile high permanent-magnet performance with low raw-material costs. This work reports a Mn-Bi-Sn alloy exclusively made from inexpensive elements, exhibiting high values of Curie-temperature, magnetization, anisotropy, coercivity, and energy product. The samples are produced by field annealing of rapidly quenched Sn-containing MnBi alloys, where the improvement of the magnetic properties is caused by the substitutional occupancy of the 2c sites in the hexagonal NiAs structure by Sn. The substitution modifies the electronic structure of ...


Comparative Study Of Topological Hall Effect And Skyrmions In Nimnin And Nimnga, Wenyong Zhang, Balamurugan Balasubramanian, Ahsan Ullah, Rabindra Pahari, Xingzhong Li, Lanping Yue, Shah R. Valloppilly, Andrei Sokolov, Ralph Skomski, David J. Sellmyer 2019 University of Nebraska-Lincoln

Comparative Study Of Topological Hall Effect And Skyrmions In Nimnin And Nimnga, Wenyong Zhang, Balamurugan Balasubramanian, Ahsan Ullah, Rabindra Pahari, Xingzhong Li, Lanping Yue, Shah R. Valloppilly, Andrei Sokolov, Ralph Skomski, David J. Sellmyer

Faculty Publications from Nebraska Center for Materials and Nanoscience

A nonequilibrium rapid-quenching method has been used to fabricate NiMnIn and NiMnGa alloys that are chemically and morphologically similar but crystallographically and physically very different. NiMnGa crystallizes in a Ni2In-type hexagonal structure, whereas NiMnIn is a cubic Heusler alloy. Both alloys yield a topological Hall effect contribution corresponding to bubble-type skyrmion spin structures, but it occurs in much lower magnetic fields in NiMnIn as compared to NiMnGa. The effect is unrelated to net Dzyaloshinskii-Moriya interactions, which are absent in both alloys due to their inversion-symmetric crystal structures. Based on magnetic-force microscopy, we explain the difference between the two alloys by ...


Structure And Magnetism Of Co2ge Nanoparticles, Onur Tosun, Frank M. Abel, Balamurugan Balasubramanian, Ralph Skomski, David J. Sellmyer, George C. Hadjipanayis 2019 University of Delaware

Structure And Magnetism Of Co2ge Nanoparticles, Onur Tosun, Frank M. Abel, Balamurugan Balasubramanian, Ralph Skomski, David J. Sellmyer, George C. Hadjipanayis

Faculty Publications from Nebraska Center for Materials and Nanoscience

The structural and magnetic properties of Co2Ge nanoparticles (NPs) prepared by the cluster-beam deposition (CBD) technique have been investigated. As-made particles with an average size of 5.5 nm exhibit a mixture of hexagonal and orthorhombic crystal structures. Thermomagnetic measurements showed that the as-made particles are superparamagnetic at room temperature with a blocking temperature (TB) of 20 K. When the particles are annealed at 823 K for 12 h, their size is increased to 13 nm and they develop a new orthorhombic crystal structure, with a Curie temperature (TC) of 815 K. This is drastically different ...


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