Bulletin of the American Physical Society
2019 Annual Meeting of the APS Four Corners Section
Volume 64, Number 16
Friday–Saturday, October 11–12, 2019; Prescott, Arizona
Session E05: Materials II |
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Chair: Andri Gretarsson, ERAU Room: STEM 105 |
Friday, October 11, 2019 2:48PM - 3:00PM |
E05.00001: Crystal Structure of Ni$^{\mathrm{\mathbf{2+}}}_{\mathrm{\mathbf{3}}}$\textbf{[Fe}$^{\mathrm{\mathbf{3+}}}$\textbf{(CN)}$_{\mathrm{\mathbf{6}}}$\textbf{]}$_{\mathrm{\mathbf{2}}}$\textbf{.}\textbf{\textit{n}}\textbf{H}$_{\mathrm{\mathbf{2}}}$ O Prussian Blue Analogue Md Minuddin, Seyedayat Ghazisaeed, Boris Kiefer, Heinz Nakotte The Prussian Blue Analogue (PBA), Ni$^{\mathrm{2+}}_{\mathrm{3}}$[Fe$^{\mathrm{3+}}$(CN)$_{\mathrm{6}}$]$_{\mathrm{2}}$.$n$H$_{\mathrm{2}}$O, was previously reported to crystallize in the cubic F-43m structure. However, our Density-Functional-Theory (DFT) calculations for this PBA predicted the existence of an alternative tetragonal P-4m2 structure, which is energetically degenerate with the F-43m structure. The computations also suggested that maximum possible water molecules per formula unit is $n=$7. To verify our computed structure, we synthesized this PBA using the chemical precipitation method and we performed X-ray (XRD) and neutron diffraction (ND) measurements. Rietveld refinement of the XRD data satisfies the framework structure but they are insensitive to the position of light elements such as H. Rietveld refinement of ND data were also unable to solve the issue as H has high incoherent scattering cross section. To test hydrogen positions experimentally, we synthesized a deuterized sample of this PBA since D has much smaller incoherent scattering cross section compared to H for ND studies. As H$_{\mathrm{2}}$O and D$_{\mathrm{2}}$O have almost same bond lengths and bond angles, the same framework structure is expected for the deuterized sample. We will present the current state of our analysis of our ND data for the deuterized PBA using the Rietveld refinement package GSAS II. [Preview Abstract] |
Friday, October 11, 2019 3:00PM - 3:12PM |
E05.00002: Constant Voltage Conductivity Measurements of a Critical Temperature Transition in Low Density Polyethylene Megan Loveland, Zachary Gibson, Brian Wood, JR Dennison Temperature-dependent constant voltage conductivity measurements of the highly disordered insulating polymeric material low density polyethylene (LDPE) were made to investigate a transition of electrical transport mechanisms from variable range hopping to multiple trapping at a critical temperature. Such a transition is evidenced as a change of slope in a double logarithmic plot of conductivity versus temperature at the critical temperature, $T_{c}$. Below $T_{c}$ variable range hopping, with a T$^{\mathrm{-1/4}}$ dependence, is the dominant mechanism; above $T_{c}$ multiple trapping mechanisms, with linear T$^{\mathrm{-1}}$ dependence dominate. To investigate this transition, the sample temperature, $T$, was varied from \textasciitilde 230 K to 300 K, based on prior experimental evidence which estimated $T_{c}$ to be \textasciitilde 268 K, along with theoretical models which predict $T_{c}_{\mathrm{\thinspace }}$\textasciitilde 255 K. A constant voltage conductivity system was used, with current measured in parallel plate geometry with a steady voltage applied across 25 \textmu m thin film LDPE samples using Ohm's law. Experiments were conducted \textit{in vaccu}, with a lower bound in measurable conductivities of \textasciitilde 1$\cdot $10$^{\mathrm{-21}}$ ($\Omega $-cm)$^{\mathrm{-1}}$ due to fA current resolution. Transitions seen in other electron transport measurements and related structural phase transitions at comparable temperatures are discussed. [Preview Abstract] |
Friday, October 11, 2019 3:12PM - 3:24PM |
E05.00003: Quantifying Materials Surface Conditions Through Secondary Electron Yield Measurements Phil Lundgreen, JR Dennison Secondary electron yields (SEY) are heavily influenced by surface conditions, including roughness, oxidation, and contamination. For common elemental conducting materials such as Cu, numerous yield measurements found in the literature are found to vary significantly. In an effort to categorize and characterize variations in these studies parameters for an empirically-based model of SEY curves written in a reduced format for yield, $\delta $(E)/ $\delta_{\mathrm{max}}$, versus incident energy, E/E$_{\mathrm{max}}$ have been employed. The four SEY fitting parameters of interest include the maximum yield, $\delta_{\mathrm{max}}$ at energy, E$_{\mathrm{max}}$ and the exponents for power-law behavior at low and high energy limits. Evaluation of numerous yield measurements from prior studies gathered in the form of a user-friendly SEY database show discernible correlations between the parameters and these surface conditions. Establishing such trends allow for semi-quantitative predictions of Cu under varying surface conditions. Knowledge of how SEY will vary for different technical materials used in spacecraft construction, plasma devices, or other applications and how these materials' surface conditions evolve with prolonged exposure to extreme environments can increase modeling accuracy of electron emission and system charging. Specifically, applications for the survivability of spacecraft in the space environment over mission lifetimes are discussed. [Preview Abstract] |
Friday, October 11, 2019 3:24PM - 3:36PM |
E05.00004: Finding Ways to Stabilize Potential New Superalloys Tyler Whitaker, Brayden Bekker, Gus Hart The ability to create something new and interesting depends heavily on the materials available to us. The search for new superalloys provides many opportunities in energy production and structural integrity. By using high-throughput methods, we are able to find potential quaternary additions to known metastable ternary superalloys. We use density functional theory (DFT) to find a list of elements that could stabilize each ternary alloy. We then use a machine-learned interatomic potentials (called moment tensor potential, or MTP) to explore the stability of the superalloy phases in the quaternary systems found from DFT. Through these steps, we are able to find the quaternary compositions the most stable superalloy phases when synthesized. [Preview Abstract] |
Friday, October 11, 2019 3:36PM - 3:48PM |
E05.00005: The Rational Search for Strong Biocompatible Alloys Wade Kloppenburg, Jaime Moya, Emilia Morosan, Ka'ai Kauwe, Taylor Sparks, Boris Kiefer Materials design, namely the identification of material sets that simultaneously show combinations of desired chemical/physical properties remains challenging. Here we discuss a strategy to find new biomaterials for reconstructive surgery. The relevant design attributes for this application are simultaneous high material strength and ductility. In this respect, it has previously been shown that bulk $\beta $Au$_{\mathrm{0.25}}$Ti$_{\mathrm{0.75\thinspace }}$can be stabilized in a phase with a Vicker's hardness that is 3-4 times higher than that for any other Au/Ti ratio. Our Density-Functional-Theory (DFT) computations of the ideal material strength in Au-Ti alloys show the same trend and allow to connect glide system and electronic structure. We expand previous equilibrium computations and discuss the effect of deformation on the electronic structure, a key to rationalize the unusually high strength of this alloy. Combining crystal structure and electronic structure we data mined AFLOW for similar materials. Based on the search results we predict the existence of several novel high strength alloys with possible applications in reconstructive surgery. [Preview Abstract] |
Friday, October 11, 2019 3:48PM - 4:00PM |
E05.00006: A Unified Description of the Electrical Properties of Low-Density Polyethylene via the Dispersion Parameter Zachary Gibson, Megan Loveland, JR Dennison Low-density polyethylene is a prototypical highly disordered insulating material. This ubiquitous polymer has a variety of applications from spacecraft charging to high voltage DC power cable insulation. Therefore, the electrical properties are of great interest. The dispersion parameter, which originally appeared in a semi-empirical model to describe anomalies in permittivity data, is central to an understanding of these electrical properties. This parameter depends linearly on either temperature (low field regime) or on electric field (high field regime) and is scaled by the reciprocal of a characteristic energy. When the dispersion parameter reaches one, a transition from dispersive to non-dispersive transport occurs. Scher and Montroll spurred an ``anomalous to obvious phase transition'' by describing the anomalous transit times in dispersive materials with use of long-tailed hopping-time distribution functions characterized by the dispersion parameter. Direct measurements of the evolution of embedded charge distributions via pulsed electroacoustic measurements show a dispersive to non-dispersive transport transition occurs at an electric field strength of \textasciitilde 10$^{\mathrm{8}}$ V/m. Measurements of the temperature transition in constant voltage conductivity data measured by our group and extensive data from the literature are presented and described in terms of the dispersion parameter. Other models and measurements---including those for AC and DC conductivity, radiation induced conductivity, charge decay, and electrostatic breakdown---also depend on the dispersion parameter. [Preview Abstract] |
Friday, October 11, 2019 4:00PM - 4:12PM |
E05.00007: The Entropy Paradox in the Chapman-Jouguet Theory of Detonation David Dunlap, Osmar Aguirre The Chapman-Jouguet theory of detonation waves (circa 1905) predicts propagation speeds in gaseous systems to within 2{\%} of experimental values in most cases. In spite of this success, the theory was criticized early on by investigators who claimed that the accuracy of the CJ solution was just a lucky accident. The solution represents an entropy minimum of the final state, which is thermodynamically unstable. We show, however, that the original entropy-minimum argument was made erroneously, thus resolving a 100-year-old paradox. [Preview Abstract] |
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