Bulletin of the American Physical Society
Joint Spring 2014 Meeting of the Texas Sections of the APS, AAPT, and Zone 13 of the SPS
Volume 59, Number 2
Thursday–Saturday, March 20–22, 2014; Abilene, Texas
Session F3: Condensed Matter and NanoScience |
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Room: Hunter Welcome Center C |
Friday, March 21, 2014 2:30PM - 2:42PM |
F3.00001: The use of Multi-Wall Carbon Nanotubes in the area of Nanoenergetic Materials Patricia Martinez, Mkhitar Hobosyan, Anvar Zakhidov, Karen Martirosyan A new type of nanoenergetic wires were produced by spin- twist multi-walled carbon nanotube (MWCNT) sheets with Al-I$_{2}$O$_{5}$, a nanoenergetic material (NM) whose volumetric energy is two orders of magnitude greater than that of Trinitrotoluene (TNT) and has a detonation velocity of approximately 2500 m/s. MWCNT's sheets are a promising material in the area of NM because of their unique intrinsic properties such as high heat dispassion, low resistivity, high tensile stress and elasticity which help to achieve better self-propagating and strong nanoenergetic wires. The ignition of the NM/MWCNT wire shows a well- defined detonation of the NM along the MWCNT matrix. Due to the high thermal dissipation in the MWCNT, they do not burn, but rather direct the thermal energy of the detonation along the twisted coils, slowing the speed of propagation. This property can be further explored in the creation of new reinforced composites using NM as a micro and even nanoscale welder. The thread-like structure of the NM/MWCNT composite wires allows the utilization of textile technologies to create complex weaves which can be used as nanoexplosive fabrics with desired energetic properties for local heating, welding, targeted iodine release, and other properties as will be discussed in this work. [Preview Abstract] |
Friday, March 21, 2014 2:42PM - 2:54PM |
F3.00002: A Novel Approach for Betavoltaic Devices Utilizing Nitrogen Doped Graphene Powder as an Electrode Kyle Drake Betavoltaic devices were created based on the direct energy conversion method patented by Paul Rappaport in 1953. Betavoltaic devices are potential alternatives to current next generation batteries and fuel cells. A betavoltaic cell consists of a radioisotope that emits beta particles (electrons) and a semiconducting material. In the betavoltaic device the radioisotope emits a beta particle which passes through the semiconductor creating many electron-hole pairs (EHPs) causing a current to be produced. Current betavoltaic devices utilize high band gap semiconductors such as gallium arsenide, silicon carbide, and gallium phosphide. In this research, graphene will be used as a substitute for the semiconducting material used in current betavoltaic devices. Graphene is a new material which due to its remarkable electronic properties, is currently being investigated for possible applications in many fields. The purpose of this research is to incorporate graphene's properties as a semiconductor for use as an electrode in betavoltaic devices. [Preview Abstract] |
Friday, March 21, 2014 2:54PM - 3:06PM |
F3.00003: Correlations of Positron Annihilation Spectroscopy with TOC, XRF and XRD for Barnett Shale Core Fnu Ameena, Helge Alsleben, C.A. Quarles Measurements are reported of both positron lifetime and Doppler broadening parameters on 14 samples of Barnett shale core selected from 196 samples ranging from depths of 6107 to 6402 feet. The Barnett shale core was taken from EOG well Two-O-Five 2H located in Johnson county. The selected samples are dark clay-rich mudstone consisting of fine grained clay minerals.~ The samples are varied in shape, typically a few inches long and about 1/2 inch in width and thickness, and are representative of the predominant facies in the core.~~ X-ray fluorescence (XRF),~ X-ray diffraction (XRD), petrographic analysis and geochemical analysis of total organic carbon (TOC) were already available for each of the selected samples. Correlations between the S parameter and the average positron lifetime and the TOC, XRF and XRD parameters will be discussed. The observed correlations suggest that positron spectroscopy may be a useful tool in characterizing shale. [Preview Abstract] |
Friday, March 21, 2014 3:06PM - 3:18PM |
F3.00004: Modeling of the trajectories of positrons and electrons in a Time of Flight Positron annihilation induced Auger Electron Spectrometer (TOF-PAES) Randall Gladen, Prasad Joglekar, Alex Weiss Described herein is a simulation of the trajectories of the positrons in a Time of Flight Positron annihilation induced Auger Electron Spectroscopy (TOF-PAES) system using SIMION. In addition to positrons, the trajectories of the Auger and secondary electrons from the sample to the detector are simulated for a range of energies and emerging angles from the sample. The data collected from the implementation of this simulation will provide a better understanding of the dynamics of the positron beam, as well as the trajectories of the emitted electrons, allowing for greater optimization of the PAES system. Also discussed will be the simulation of proposed future additions to the PAES system, such as cylindrical geometry ExB plates in place of the rectangular geometry plates that are currently in place, and how these will affect the positron beam. The results of these simulations will be considered when constructing future PAES systems. [Preview Abstract] |
Friday, March 21, 2014 3:18PM - 3:30PM |
F3.00005: Raman Spectroscopy of 3-D Graphene Robert Friedfeld, Jonathan Belew, Matthew Pusko, Kyle Drake Purified powders and three dimensional freestanding graphene foam were assessed analytically through Raman Spectroscopy. Samples were tested in a number of solvents in order to identify the most stable dispersions. Purified powders were shown to be inferior to the ``as received'' 3D graphene foam as quantified through the above analytical methods. Graphene foams are reported here to represent a highly pure form of graphene that may be dispersed in solution in order to form thin films that retain the same quantifiable qualities as the solid starting material. [Preview Abstract] |
Friday, March 21, 2014 3:30PM - 3:42PM |
F3.00006: Role of plastic deformation in shock-induced phase transitions Punam Ghimire, Ramon Ravelo Large-scale molecular dynamics simulations of shocked wave propagation in metallic single crystals exhibit high elastic limits and are ideally suited for investigating the role defect nucleation and multiplication play on the kinetics of phase transformations. For phase transformations which proceed at pressures below the theoretical elastic-plastic transition pressure no plasticity accompanies the phase change. For cases where plastic deformation precedes the phase transformation, the defect-mediated phase transition proceeds nominally at faster rates than defect-free ones. We examined the effect of plastic deformation and shock propagation direction on shock-induced phase transformation employing large scale non-equilibrium molecular dynamics simulations. The atomic interactions were modeled utilizing embedded atom method (EAM) models, which exhibit a targeted $fcc \longrightarrow bcc$ phase transformation below and above the plastic deformation thresholds. [Preview Abstract] |
Friday, March 21, 2014 3:42PM - 3:54PM |
F3.00007: Probing the Ground State of alpha-Plutonium with Density Functional Theory Thomas Bates, Raymond Atta-Fynn Plutonium, Pu, has six different crystalline states as a function temperature. The room temperature phase, known as alpha-Plutonium ($\alpha $-Pu), is a low-symmetry, monoclinic crystal, with distorted internal bonds. The $\alpha $-Pu monoclinic crystal has several degrees of freedom so theoretical calculations on $\alpha $-Pu often assume experimental lattice parameters and atomic positions to avoid optimizing the degrees of freedom. The key assumption in such calculations is that the experimental and theoretical lattice parameters and internal positions are similar. However, there is a possibility that differences exist between the theoretical ground structure and experimental structure. In this talk, the use of density functional theory (DFT) and several atomistic configurations of $\alpha $-Pu to investigate the differences between the optimized theoretical structures and the experimental structure will be discussed. [Preview Abstract] |
Friday, March 21, 2014 3:54PM - 4:06PM |
F3.00008: Positronium formation at the Surface of a Topological Insulator Thomas Bates, Alex Weiss This research is focused on the study of the emission of positronium, Ps, at the surface of a topological insulator, Ba2 T2 Se. Ps is the hydrogen like bound state of an electron and its antiparticle, the positron. Here report on experiments in which a low energy ($\sim$ 10eV) positron beam was used to deposit positrons at the sample surface. The energy spectrum of the gamma rays resulting from positron and electron annihilation was measured using a NaI(Tl) gamma detection system. The gamma spectrum was analyzed to determine the fraction of free Ps emitted into the vacuum from the surface. Our results indicate that the amount of free Ps emitted increases as the sample temperature is increased providing evidence that a portion of the positrons are bound in a surface state and annihilate at the surface at low temperatures. The existence of such a bound surface state suggests that positron annihilation spectroscopy could be used to obtain surface specific information regarding the electron momentum and spin distributions at the surfaces of topological insulators. [Preview Abstract] |
Friday, March 21, 2014 4:06PM - 4:18PM |
F3.00009: Atomistic Modeling of Uranium (IV) Ion Interaction with Water Austin McDonald, Raymond Atta-Fynn A fundamental understanding of the interaction of toxic heavy metal ions with the biosphere, particularly water, is important for their remediation from the environment. Predicting the behavior of such ions in water requires a detailed atomic and molecular scale understanding of the ion-water interaction. In this talk, we will describe the process for modeling the interaction of the U$^{4+}$ ion with water using static first principles and classical molecular dynamics methods. The hydrations shell structure of U$^{4+\, }$and other properties such as the radial distribution function, solvent angular tilts, and ion diffusion will be discussed and compared to available experimental and theoretical data. [Preview Abstract] |
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