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Room-Temperature Homogeneous Nucleation Synthesis And Thermal Stability Of Nanometer Single Crystal Ceo2, X.-D. Zhou, Wayne Huebner, Harlan U. Anderson 2018 Missouri University of Science and Technology

Room-Temperature Homogeneous Nucleation Synthesis And Thermal Stability Of Nanometer Single Crystal Ceo2, X.-D. Zhou, Wayne Huebner, Harlan U. Anderson

Wayne Huebner

Nanometer (about 4~5nm) CeO2 single crystals were first synthesized by room-temperature homogeneous nucleation; the size was determined by electron microscopy and specific surfaced area of the particles. Modeling revealed that the surface energy of as-synthesized nanometer single crystals was in the range of 2.8-3.7J/m2. Crystal growth mechanisms change over the temperature regimes, from boundary diffusion over low-temperature regime (Eα=0.16eV) to bulk diffusion (Eα=0.50eV) over high-temperature region.


Pm Manufacturing Research Boosted By Continuous Sintering Furnace, Joseph William Newkirk 2018 Missouri University of Science and Technology

Pm Manufacturing Research Boosted By Continuous Sintering Furnace, Joseph William Newkirk

Joseph William Newkirk

University of Missouri-Rolla has recently acquired a Fluidtherm laboratory continuous sintering furnace. Custom designed and built for PM research, the furnace will allow current efforts in sintering development, pressure gas quenching of PM steels, optimisation of toughness and fatigue properties of PM parts, and production of metal matrix composites to be enhanced and extended.


Corrosion Resistant Nickel-Based Alloy, Joseph William Newkirk, Sanhong Zhang 2018 Missouri University of Science and Technology

Corrosion Resistant Nickel-Based Alloy, Joseph William Newkirk, Sanhong Zhang

Joseph William Newkirk

A nickel based, high silicon alloy exhibits very high corrosion resistance in high temperature sulfuric acid environments. The alloy may be cast and is sufficiently ductile to be fabricated and machined. The alloy is ductile and has sufficient resistance to mechanical and thermal shock to be reliable in service when used as rotating parts.


Comparison Of Thermal Properties Of Laser Deposition And Traditional Welding Process Via Thermal Diffusivity Measurement, Yu Yang, Omoghene Osaze Obahor, Yaxin Bao, Todd E. Sparks, Jianzhong Ruan, Jacquelyn K. Stroble, Robert G. Landers, Frank W. Liou, Joseph William Newkirk 2018 Missouri University of Science and Technology

Comparison Of Thermal Properties Of Laser Deposition And Traditional Welding Process Via Thermal Diffusivity Measurement, Yu Yang, Omoghene Osaze Obahor, Yaxin Bao, Todd E. Sparks, Jianzhong Ruan, Jacquelyn K. Stroble, Robert G. Landers, Frank W. Liou, Joseph William Newkirk

Joseph William Newkirk

Laser deposition is an effective process for mold and die repair. In order to improve the part repair quality??the process impact on thermal diffusivity and thermal conductivity needs to be understood for laser deposited, welded and virgin H13. In this paper, H13 tool steel samples were made by laser deposition, welding and virgin H13 and then cut into pieces. Experiments were conducted to investigate the thermal diffusivity and conductivity. A laser flash method is used to test these samples. The future work and opportunities are also summarized. Keywords: Laser Flash, laser deposition, tool steel, H13


An Investigation Of The Effect Of Direct Metal Deposition Parameters On The Characteristics Of The Deposited Layers, Tarak A. Amine, Joseph William Newkirk, Frank W. Liou 2018 Missouri University of Science and Technology

An Investigation Of The Effect Of Direct Metal Deposition Parameters On The Characteristics Of The Deposited Layers, Tarak A. Amine, Joseph William Newkirk, Frank W. Liou

Joseph William Newkirk

Multilayer direct laser deposition (DLD) is a fabrication process through which parts are fabricated by creating a molten pool into which metal powder is injected as particles. During fabrication, complex thermal activity occurs in different regions of the build; for example, newly deposited layers will reheat previously deposited layers. The objective of this study was to provide insight into the thermal activity that occurs during the DLD process. This work focused on the effect of the laser parameters of newly deposited layers on the microstructure and mechanical properties of the previously deposited layers in order to characterize these effects to ...


Magnetic Properties Of Gd Intermetallics, L. Petit, Z. Szotek, J. Jackson, M. Lüders, Durga Paudyal, Yaroslav Mudryk, Vitalij K. Pecharsky, K. A. Gschneidner, J. B. Staunton 2018 Daresbury Laboratory

Magnetic Properties Of Gd Intermetallics, L. Petit, Z. Szotek, J. Jackson, M. Lüders, Durga Paudyal, Yaroslav Mudryk, Vitalij K. Pecharsky, K. A. Gschneidner, J. B. Staunton

Ames Laboratory Accepted Manuscripts

Using first-principles calculations, based on disordered local moment theory, combined with the self-interaction corrected local spin density approximation, we study magnetic interactions in GdX intermetallics for X = Cu, Zn, Ga, Cd, and Mg. Our predicted magnetic orders and ordering temperatures both at zero and other pressures agree well with experiments including the large increase in the Curie temperature of GdCd under pressure that is shown by our own experimental measurements. From our results it emerges that the Ruderman-Kittel-Kasuya-Yosida interaction on its own can not explain the observed behaviour under pressure, and that the magnetic ordering mechanism is strongly influenced by ...


Effect Of Stacking Fault Energy On Mechanism Of Plastic Deformation In Nanotwinned Fcc Metals, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King, Richard A. Lesar 2018 The Ames Laboratory

Effect Of Stacking Fault Energy On Mechanism Of Plastic Deformation In Nanotwinned Fcc Metals, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King, Richard A. Lesar

Richard Alan Lesar

Starting from a semi-empirical potential designed for Cu, we have developed a series of potentials that provide essentially constant values of all significant (calculated) materials properties except for the intrinsic stacking fault energy, which varies over a range that encompasses the lowest and highest values observed in nature. These potentials were employed in molecular dynamics (MD) simulations to investigate how stacking fault energy affects the mechanical behavior of nanotwinned face-centered cubic (FCC) materials. The results indicate that properties such as yield strength and microstructural stability do not vary systematically with stacking fault energy, but rather fall into two distinct regimes ...


Modeling Of Ti-W Solidification Microstructures Under Additive Manufacturing Conditions, Matthew R. Rolchigo, Michael Mendoza, Peyman Samimi, David A. Brice, Peter C. Collins, Richard Lesar 2018 Iowa State University

Modeling Of Ti-W Solidification Microstructures Under Additive Manufacturing Conditions, Matthew R. Rolchigo, Michael Mendoza, Peyman Samimi, David A. Brice, Peter C. Collins, Richard Lesar

Richard Alan Lesar

Additive manufacturing (AM) processes have many benefits for the fabrication of alloy parts, including the potential for greater microstructural control and targeted properties than traditional metallurgy processes. To accelerate utilization of this process to produce such parts, an effective computational modeling approach to identify the relationships between material and process parameters, microstructure, and part properties is essential. Development of such a model requires accounting for the many factors in play during this process, including laser absorption, material addition and melting, fluid flow, various modes of heat transport, and solidification. In this paper, we start with a more modest goal, to ...


Microstructures And Grain Refinement Of Additive-Manufactured Ti-Xw Alloys, Michael Mendoza, Peyman Samimi, David A. Brice, Brian Martin, Matthew R. Rolchigo, Richard Lesar, Peter C. Collins 2018 Iowa State University

Microstructures And Grain Refinement Of Additive-Manufactured Ti-Xw Alloys, Michael Mendoza, Peyman Samimi, David A. Brice, Brian Martin, Matthew R. Rolchigo, Richard Lesar, Peter C. Collins

Richard Alan Lesar

It is necessary to better understand the composition–processing–microstructure relationships that exist for materials produced by additive manufacturing. To this end, Laser Engineered Net Shaping (LENS™), a type of additive manufacturing, was used to produce a compositionally graded titanium binary model alloy system (Ti-xW specimen (0 ≤ x ≤ 30 wt pct), so that relationships could be made between composition, processing, and the prior beta grain size. Importantly, the thermophysical properties of the Ti-xW, specifically its supercooling parameter (P) and growth restriction factor (Q), are such that grain refinement is expected and was observed. The systematic, combinatorial study of this binary ...


Effect Of Stacking Fault Energy On Mechanism Of Plastic Deformation In Nanotwinned Fcc Metals, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King, Richard A. Lesar 2018 The Ames Laboratory

Effect Of Stacking Fault Energy On Mechanism Of Plastic Deformation In Nanotwinned Fcc Metals, Valery Borovikov, Mikhail I. Mendelev, Alexander H. King, Richard A. Lesar

Alexander H. King

Starting from a semi-empirical potential designed for Cu, we have developed a series of potentials that provide essentially constant values of all significant (calculated) materials properties except for the intrinsic stacking fault energy, which varies over a range that encompasses the lowest and highest values observed in nature. These potentials were employed in molecular dynamics (MD) simulations to investigate how stacking fault energy affects the mechanical behavior of nanotwinned face-centered cubic (FCC) materials. The results indicate that properties such as yield strength and microstructural stability do not vary systematically with stacking fault energy, but rather fall into two distinct regimes ...


Double Hysteresis Loops At Room Temperature In Nanbo3-Based Lead-Free Antiferroelectric Ceramics, Xiaoli Tan, Zunping Xu, Xiaoming Liu, Zhongming Fan 2018 Iowa State University

Double Hysteresis Loops At Room Temperature In Nanbo3-Based Lead-Free Antiferroelectric Ceramics, Xiaoli Tan, Zunping Xu, Xiaoming Liu, Zhongming Fan

Xiaoli Tan

Polarization-field double hysteresis loops have hardly ever been observed at room temperature in polycrystalline NaNbO3, one of a few lead-free antiferroelectric compounds. In this Letter, it is shown that the exposure of a modified NaNbO3 ceramic to bipolar electric fields of ±160 kV/cm at 100°C can preserve the double hysteresis loops at room temperature. These double hysteresis loops can still be observed after 125 days room temperature aging with some decay in maximum polarization. Frequency dependence analysis suggests that the double hysteresis loops originate from the antiferroelectric ↔ ferroelectric phase transition, not the charged defects. A novel electrical treatment ...


Nonequilibrium Polarization Dynamics In Antiferroelectrics, M. M. Vopson, Xiaoli Tan 2018 University of Portsmouth

Nonequilibrium Polarization Dynamics In Antiferroelectrics, M. M. Vopson, Xiaoli Tan

Xiaoli Tan

A nonequilibrium statistical domain nucleation model of polarization dynamics in less understood antiferroelectric systems is introduced. Predictions of the model have been successfully tested experimentally using an antiferroelectric Pb0.99Nb0.02[( Zr0.57Sn0.43) Ti-0.94(0.06)] O-0.98(3) polycrystalline ceramic. We determined the activation energy of the domain nucleation process for this particular antiferroelectric sample to be W-b = 1.07 eV and the critical volume of the polar nucleus V * = 98 x 10(-27)m(3), which corresponds to a linear length scale of 2.86 nm.


Modeling The Interphase Of A Polymer-Based Nanodielectric, Connor S. Daily, Weixing Sun, Michael R. Kessler, Xiaoli Tan, Nicola Bowler 2018 Iowa State University

Modeling The Interphase Of A Polymer-Based Nanodielectric, Connor S. Daily, Weixing Sun, Michael R. Kessler, Xiaoli Tan, Nicola Bowler

Xiaoli Tan

A three-phase theoretical model is proposed that is suitable for describing the effective permittivity of polymer-matrix composites containing spherical nanoparticles. The model accounts for the presence of an interphase region, which surrounds each nanosphere, whose permittivity is allowed to be different from that of the matrix polymer. The nanoparticles themselves are approximated as hard (non-overlapping) spheres, whereas the interphase regions of neighboring nanoparticles are permitted to overlap. The volume fraction of the interphase region is computed by assuming that the nanoparticles are arranged on the nodes of a simple-cubic lattice. The effective permittivity of the composite is subsequently computed via ...


Rigid Object Tracking Algorithms For Low-Cost Ar Devices, Timothy Garrett, Saverio Debernardis, Rafael Radkowski, Carl K. Chang, Michele Fiorentino, Antonio E. Uva, James H. Oliver 2018 Iowa State University

Rigid Object Tracking Algorithms For Low-Cost Ar Devices, Timothy Garrett, Saverio Debernardis, Rafael Radkowski, Carl K. Chang, Michele Fiorentino, Antonio E. Uva, James H. Oliver

James H. Oliver

Augmented reality (AR) applications rely on robust and efficient methods for tracking. Tracking methods use a computer-internal representation of the object to track, which can be either sparse or dense representations. Sparse representations use only a limited set of feature points to represent an object to track, whereas dense representations almost mimic the shape of an object. While algorithms performed on sparse representations are faster, dense representations can distinguish multiple objects. The research presented in this paper investigates the feasibility of a dense tracking method for rigid object tracking, which incorporates the both object identification and object tracking steps. We ...


Comparison Of Natural Feature Descriptors For Rigid-Object Tracking For Real-Time Augmented Reality, France Franco Bermudez, Sheneeka Ward, Christian Santana Diaz, Rafael Radkowski, Timothy Garrett, James H. Oliver 2018 Inter American University of Puerto Rico

Comparison Of Natural Feature Descriptors For Rigid-Object Tracking For Real-Time Augmented Reality, France Franco Bermudez, Sheneeka Ward, Christian Santana Diaz, Rafael Radkowski, Timothy Garrett, James H. Oliver

James H. Oliver

This paper presents a comparison of natural feature descrip- tors for rigid object tracking for augmented reality (AR) applica- tions. AR relies on object tracking in order to identify a physical object and to superimpose virtual object on an object. Natu- ral feature tracking (NFT) is one approach for computer vision- based object tracking. NFT utilizes interest points of a physcial object, represents them as descriptors, and matches the descrip- tors against reference descriptors in order to identify a phsical object to track. In this research, we investigate four different nat- ural feature descriptors (SIFT, SURF, FREAK, ORB) and their ...


Quantum Tricritical Point In The Temperature-Pressure-Magnetic Field Phase Diagram Of Cetige3, Udhara S. Kaluarachchi, Valentin Taufor, Sergey Bud’ko, Paul C. Canfield 2018 Iowa State University and Ames Laboratory

Quantum Tricritical Point In The Temperature-Pressure-Magnetic Field Phase Diagram Of Cetige3, Udhara S. Kaluarachchi, Valentin Taufor, Sergey Bud’Ko, Paul C. Canfield

Ames Laboratory Accepted Manuscripts

We report the temperature-pressure-magnetic-field phase diagram of the ferromagnetic Kondo-lattice CeTiGe 3 determined by means of electrical resistivity measurements. Measurements up to ∼ 5.8 GPa reveal a rich phase diagram with multiple phase transitions. At ambient pressure, CeTiGe 3 orders ferromagnetically at T C = 14 K. Application of pressure suppresses T C , but a pressure-induced ferromagnetic quantum criticality is avoided by the appearance of two new successive transitions for p > 4.1 GPa that are probably antiferromagnetic in nature. These two transitions are suppressed under pressure, with the lower-temperature phase being fully suppressed above 5.3 GPa. The critical pressures ...


Depolymerization Of Post-Consumer Polylactic Acid Products, David A. Grewell, Gowrishankar Srinivasan, Eric W. Cochran 2018 Iowa State University

Depolymerization Of Post-Consumer Polylactic Acid Products, David A. Grewell, Gowrishankar Srinivasan, Eric W. Cochran

Eric W. Cochran

Presented in this study is a novel recycling strategy for poly(lactic acid) (PLA) in which the depolymerization is rapidly promoted by the base–catalyzed hydrol–/alcohol–ysis of the terminal ester bonds under mild conditions. Post–consumer PLA water bottles were cut into approximately 6 × 2 mm plastic chips and heated to 50–60×C in water, ethanol, or methanol as the depolymerization medium. A variety of carbonate salts and alkaline metal oxides were screened as potential catalysts. High–power ultrasound was also investigated as a means to accelerate the PLA decomposition. Both mass loss and HPLC analysis of ...


Superelasticity And Cryogenic Linear Shape Memory Effects Of Cafe2as2, John T. Sypek, Hang Yu, Keith J. Dusoe, Gil Drachuck, Hetal Patel, Amanda M. Giroux, Alan I. Goldman, Andreas Kreyssig, Paul C. Canfield, Serguei L. Bud’ko, Christopher R. Weinberger, Seok-Woo Lee 2018 University of Connecticut

Superelasticity And Cryogenic Linear Shape Memory Effects Of Cafe2as2, John T. Sypek, Hang Yu, Keith J. Dusoe, Gil Drachuck, Hetal Patel, Amanda M. Giroux, Alan I. Goldman, Andreas Kreyssig, Paul C. Canfield, Serguei L. Bud’Ko, Christopher R. Weinberger, Seok-Woo Lee

Paul C. Canfield

Shape memory materials have the ability to recover their original shape after a significant amount of deformation when they are subjected to certain stimuli, for instance, heat or magnetic fields. However, their performance is often limited by the energetics and geometry of the martensitic-austenitic phase transformation. Here, we report a unique shape memory behavior in CaFe2As2, which exhibits superelasticity with over 13% recoverable strain, over 3 GPa yield strength, repeatable stress–strain response even at the micrometer scale, and cryogenic linear shape memory effects near 50 K. These properties are acheived through a reversible uni-axial phase transformation mechanism, the tetragonal ...


Pressure Induced Half-Collapsed-Tetragonal Phase In Cakfe4as4, Udhara Kaluarachchi, Valentin Taufour, Aashish Sapkota, Vladislav Borisov, Tai Kong, W. R. Meier, Karunakar Kothapalli, Benjamin G. Ueland, Andreas Kreyssig, Roser Valenti, Robert J. McQueeney, Alan I. Goldman, Sergey L. Bud'ko, Paul C. Canfield 2018 Iowa State University and Ames Laboratory

Pressure Induced Half-Collapsed-Tetragonal Phase In Cakfe4as4, Udhara Kaluarachchi, Valentin Taufour, Aashish Sapkota, Vladislav Borisov, Tai Kong, W. R. Meier, Karunakar Kothapalli, Benjamin G. Ueland, Andreas Kreyssig, Roser Valenti, Robert J. Mcqueeney, Alan I. Goldman, Sergey L. Bud'ko, Paul C. Canfield

Paul C. Canfield

We report the temperature-pressure phase diagram of CaKFe4As4 established using high-pressure electrical resistivity, magnetization, and high-energy x-ray diffraction measurements up to 6 GPa. With increasing pressure, both resistivity and magnetization data show that the bulk superconducting transition of CaKFe4As4 is suppressed and then disappears at p≳4 GPa. High-pressure x-ray data clearly indicate a phase transition to a collapsed tetragonal phase in CaKFe4As4 under pressure that coincides with the abrupt loss of bulk superconductivity near 4 GPa. The x-ray data, combined with resistivity data, indicate that the collapsed tetragonal transition line is essentially independent of pressure, occurring at 4.0 ...


Dirac Node Arcs In Ptsn4, Yun Wu, Lin-Lin Wang, Eundeok Mun, Duane D. Johnson, Daixiang Mou, Lunan Huang, Youngbin Lee, Serguei L. Bud’ko, Paul C. Canfield, Adam Kaminski 2018 Iowa State University and Ames Laboratory

Dirac Node Arcs In Ptsn4, Yun Wu, Lin-Lin Wang, Eundeok Mun, Duane D. Johnson, Daixiang Mou, Lunan Huang, Youngbin Lee, Serguei L. Bud’Ko, Paul C. Canfield, Adam Kaminski

Paul C. Canfield

In topological quantum materials1–3 the conduction and valence bands are connected at points or along lines in the momentum space. A number of studies have demonstrated that several materials are indeed Dirac/Weyl semimetals4–8 . However, there is still no experimental confirmation of materials with line nodes, in which the Dirac nodes form closed loops in the momentum space2,3 . Here we report the discovery of a novel topological structure—Dirac node arcs—in the ultrahigh magnetoresistive material PtSn4 using laser-based angle-resolved photoemission spectroscopy data and density functional theory calculations. Unlike the closed loops of line nodes, the Dirac ...


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