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At least 1,063 records · Page 59

Structure, dynamics and stability of water/scCO 2 /mineral interfaces from ab initio molecular dynamics simulations

Here, the interface between a solid and a complex multi-component liquid forms a unique reaction environment whose structure and composition can significantly deviate from either bulk or liquid phase and is poorly understood due the innate difficulty to obtain molecular level information. Feldspar minerals, as typified by the Ca-end member Anorthite, serve as prototypical model systems to assess the reactivity and ion mobility at solid/water-bearing supercritical fluid (WBSF) interfaces due to recent X-ray based measurements that provide information on water-film formation, and cation vacancies at these surfaces. Using density functional theory based molecular dynamics, which allows the evaluation of reactivity and condensed phase dynamics on equal footing, we report on the structure and dynamics of water nucleation and surface aggregation, carbonation and Ca mobilization under geologic carbon sequestration scenarios (T = 323 K and P = 90 bar). We find that water has a strong enthalpic preference for aggregation on a Ca-rich, O-terminated anorthite (001) surface, but entropy strongly hinders the film formation at very low water concentrations. Carbonation reactions readily occur at electron-rich terminal Oxygen sites adjacent to cation vacancies, when in contact with supercritical CO 2 . Cation vacancies of this type can form readily in the presence of a water layer that allows for facile and enthalpicly favorable Ca 2+ extraction and solvation. Apart from providing unprecedented molecular level detail of a complex three component (mineral, water and scCO 2 ) system), this work highlights the ability of modern capabilities of AIMD methods to begin to qualitatively and quantitatively address structure and reactivity at solid-liquid interfaces of high chemical complexity. This work was supported by the US Department of Energy, Office of Fossil Energy (M.-S. L., B. P. M. and V.-A. G.) and the Office of Basic Energy Science, Division of Chemical Sciences, Geosciences and Biosciences (R.R.), and performed at the Pacific Northwest National Laboratory (PNNL). PNNL is a multi-program national laboratory operated for DOE by Battelle. Computational resources were provided by PNNL’s Platform for Institutional Computing (PIC), the W. R. Wiley Environmental Molecular Science Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research located at PNNL and the National Energy Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

A High‐Energy‐Density Potassium Battery with a Polymer‐Gel Electrolyte and a Polyaniline Cathode

Abstract A safe, rechargeable potassium battery of high energy density and excellent cycling stability has been developed. The anion component of the electrolyte salt is inserted into a polyaniline cathode upon charging and extracted from it during discharging while the K + ion of the KPF 6 salt is plated/stripped on the potassium‐metal anode. The use of a p‐type polymer cathode increases the cell voltage. By replacing the organic‐liquid electrolyte in a glass‐fiber separator with a polymer‐gel electrolyte of cross‐linked poly(methyl methacrylate), a dendrite‐free potassium anode can be plated/stripped, and the electrode/electrolyte interface is stabilized. The potassium anode wets the polymer, and the cross‐linked architecture provides small pores of adjustable sizes to stabilize a solid‐electrolyte interphase formed at the anode/electrolyte interface. This alternative electrolyte/cathode strategy offers a promising new approach to low‐cost potassium batteries for the stationary storage of electric power.

Gao, Hongcai↗

Mild Acetylation and Solubilization of Ground Whole Plant Cell Walls in EmimAc: A Method for Solution-State NMR in DMSO-d6

Lignocellulosic biomass is mainly composed of polysaccharides and lignin. The complexity and diversity of the plant cell wall polymers makes it difficult to isolate the components in pure form for characterization. Many current approaches to analyzing lignocellulose structure, which involve sequential extraction and characterization of the resulting fractions, are time-consuming and labor-intensive. The present study describes a new and facile system for rationally derivatizing and dissolving coarsely ground plant cell wall materials. Using ionic liquids (EmimAc) and dichloroacetyl chloride as a solvent/reagent produced mildly acetylated whole cell walls without significant degradation. The acetylated products were soluble in DMSO-d6 from which they can be characterized by solution-state two-dimensional nuclear magnetic resonance (2D NMR) spectrometry. A distinct advantage of the procedure is that it realizes the dissolution of whole lignocellulosic materials without requiring harsh ball-milling, thereby allowing the acquisition of high-resolution 2D NMR spectra to revealing structural details of the main components (lignin and polysaccharides). The method is therefore beneficial to understanding the composition and structure of biomass aimed at its improved utilization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Ionization electron signal processing in single phase LArTPCs. Part II. Data/simulation comparison and performance in MicroBooNE

The single-phase liquid argon time projection chamber (LArTPC) provides a large amount of detailed information in the form of fine-grained drifted ionization charge from particle traces. To fully utilize this information, the deposited charge must be accurately extracted from the raw digitized waveforms via a robust signal processing chain. Enabled by the ultra-low noise levels associated with cryogenic electronics in the MicroBooNE detector, the precise extraction of ionization charge from the induction wire planes in a single-phase LArTPC is qualitatively demonstrated on MicroBooNE data with event display images, and quantitatively demonstrated via waveform-level and track-level metrics. Improved performance of induction plane calorimetry is demonstrated through the agreement of extracted ionization charge measurements across different wire planes for various event topologies. In addition to the comprehensive waveform-level comparison of data and simulation, a calibration of the cryogenic electronics response is presented and solutions to various MicroBooNE-specific TPC issues are discussed. This work presents an important improvement in LArTPC signal processing, the foundation of reconstruction and therefore physics analyses in MicroBooNE.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Flavor, transverse momentum, and azimuthal dependence of charged pion multiplicities in semi-inclusive deep-inelastic scattering with 10.6 GeV electrons

Measurements of semi-inclusive deep-inelastic scattering multiplicities for 𝜋 + and 𝜋 − from proton and deuteron targets are reported on a grid of hadron kinematic variables 𝑧, 𝑃 𝑇 , and 𝜙* for leptonic kinematic variables in the range 0.3<𝑥<0.6 and 3<𝑄 2 <5GeV 2 . Data were acquired in 2018 and 2019 at Jefferson Lab Hall C with a 10.6 GeV electron beam impinging on 10-cm-long liquid hydrogen and deuterium targets. Scattered electrons and charged pions were detected in the High Momentum Spectrometer and Super High Momentum Spectrometer, respectively. The multiplicities were fitted for each bin in (𝑥,𝑄 2 ,𝑧,𝑃𝑡) to extract the 𝜙*—independent 𝑀 0 and the azimuthal modulations ⟨cos⁡(𝜙*)⟩ and ⟨cos⁡(2⁢𝜙*)⟩. The 𝑃𝑡 dependence of the 𝑀 0 results was found to be remarkably consistent for the four cases studied: 𝑒⁢𝑝→𝑒⁢𝜋 + ⁢𝑋, 𝑒⁢𝑝→𝑒⁢𝜋 − ⁢𝑋, 𝑒⁢𝑑→𝑒⁢𝜋 + ⁢𝑋, 𝑒⁢𝑑→𝑒⁢𝜋 − ⁢𝑋 over the range 0GeV<𝑃 𝑡 <0.4GeV, as were the multiplicities evaluated near 𝜙*=180∘ over the extended range 0GeV<𝑃 𝑡 <0.7GeV. The Gaussian widths of the 𝑃 𝑡 dependence exhibit a quadratic increase with 𝑧. The cos⁡(𝜙*) modulations were found to be consistent with zero for 𝜋 + , in agreement with previous world data, while the 𝜋 − moments were, in many cases, significantly greater than zero. The cos⁡(2⁢𝜙*) modulations were found to be consistent with zero. The higher statistical precision of this dataset of about 20 000 individual multiplicity values, compared with previously published data, should allow improved determinations of quark transverse momentum distributions and higher twist contributions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Growth of Compound Semiconductors in a Low Gravity Environment: Microgravity Growth of PbSnTe

The growth of the alloy compound semiconductor lead tin telluride (PbSnTe) was chosen for a microgravity flight experiment in the Advanced Automated Directional Solidification Furnace (AADSF), on the United States Microgravity Payload-3 (USNP-3) in February, 1996 and on USNW- 4 in November, 1997. The objective of these experiments was to determine the effect of the reduction in convection, during the growth process, brought about by the microgravity environment. The properties of devices made from PbSnTe, an alloy of PbTe and SnTe, are dependent on the ratio of the elemental components in the starting crystal. Compositional uniformity in the crystal is only obtained if there is no significant mixing in the liquid during growth. The technological importance of PbSnTe lies in its band gap versus composition diagram which has a zero energy crossing at approximately 40% SnTe. This facilitates the construction of long wavelength (greater than 6 gm) infrared detectors and lasers. The properties and utilization of PbSnTe are the subject of other papers. 1,2 PbSnTe is also interesting from a purely scientific point of view. It is, potentially, both solutally and thermally unstable due to the temperature and density gradients present during growth. Density gradients, through thermal expansion, are imposed in directional solidification because temperature gradients are required to extract heat. Solutal gradients occur in directional solidification of alloys due to segregation at the interface. Usually the gradients vary with both experiment design and inherent materials properties. In a simplified one dimensional analysis with the growth axis parallel to the gravity vector, only one of the two instabilities work at a time. During growth, the temperature in the liquid increases ahead of the interface. Therefore the density, due to thermal expansion, is decreasing in that direction. However, the phase diagram shows that the lighter SnTe is preferentially rejected at the interface. This causes the liquid density to increase with distance away from the interface.

Fripp, A. L.↗

Monodisperse porous polymer particles containing macrocyclic ether as a new class of sorbent for SR(II) separation

Strontium{sup 90} is one of the typical fission products that may be found in high level liquid waste (HLLW). Separation of Sr{sup 90} prior to the vitrification is beneficial to the final treatment of solid radioactive waste. In this study, a new class of sorbent for Sr(II) was developed by loading the macrocyclic ether DtBuCH18C6 into the monodisperse porous polymer particles (MPPPs). The MPPPs are well-known as a promising chromatographic material due to the uniform particle size, porous morphology, good compatibility with organic extractants, and rigid matrix. The structure and micro-morphology of the sorbent particles were characterized. The adsorption behavior towards Sr(II) in HNO{sub 3} media was investigated by both batch and column experiments. High adsorption efficiency and selective separation of Sr(II) was obtained. The sorbent particles can be recycled for at least several times before obvious lose of the adsorption ability. This kind of sorbent possesses the potential to be used for strontium separation in radioactive liquid waste.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Ionic-liquid-Assisted Fabrication of Lignocellulosic Thin Films with Tunable Hydrophobicity

Thin films with enhanced water repellency and mechanical strength can be fabricated from renewable lignocellulosic feedstock as a replacement for petrochemical-derived synthetic polymers, such that it minimizes life cycle impact on the environment and human health. In this work, hybrid poplar wood, either untreated (control) or pretreated with hot water at 160 °C for 20 min (HWE-20), 60 min (HWE-60), and 90 min (HWE-90), was dissolved in 1-ethyl-3-methylimidazolium acetate and regenerated to fabricate thin films. The HWE-90 films were enriched in lignin by 74%, specifically on the surface, which along with hemicellulose depletion imparted hydrophobicity (108° water contact angle) when compared to the control (56°), HWE-20 (77°), and HWE-60 (84°) films. They also exhibited 86% reduced water vapor sorption hysteresis and 75% improved storage modulus compared to the control. Thus, we demonstrate how to tune the lignocellulosic film properties via a combination of hot water pretreatment and ionic liquid dissolution.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

A semi-empirical power-law model for the dip-coating of a substrate into a particle-containing, non-Newtonian, complex fluid system

The apparent viscosity of a particle suspension of ZrSi 2 particles, polyhydromethylsiloxane (PHMS) preceramic polymer and n-Octane solvent, used to process polymer-derived ceramic composite coatings, is shown by viscometric experiments to be shear-thinning. The suspension is dip-coated onto substrates and the measured entrained coating thickness, h 0 , is observed to be a power-law function of U, the substrate extraction speed, as h 0 = 0.5051U 0.5 . The experimentally observed semi-empirical model is directly compared to the results of a variety of theoretically derived Landau-Levich scaling laws and other models that have similar liquids and that include other effects. None of these cases predicts the scaling observed in these experiments. A correction factor is introduced to quantify the difference between the semi-empirical model with existing theoretical models. Possible explanations for the observed scaling behavior are presented.

36 MATERIALS SCIENCE↗

Underwater plasma breakdown characteristics with respect to highly pressurized drilling applications

Deep earth drilling is a key technique to extract oil, gas, and geothermal heat from the earth. Many complex energy focusing methods have been explored as an alternative approach to reach these resources but most of them require high energy. However, by utilizing short time span liquid plasma discharges, energy focusing can be achieved within traditional drilling systems. These discharges induce a rapid expansion process and a resulting shockwave. It is believed that this focused energy will lower the required cutting force to progress through the rock. Lowering the required cutting force will allow for lower drill bit wear, quicker rate of penetration, and an overall cost savings of the project. Plasma breakdown characteristics at drilling relevant pressures, ranging from 1 to 350 atm, were studied. A resistance–capacitance circuit with an air gapped spark switch was utilized to generate pulsed plasma between the pressurized electrodes. It was found that the required breakdown voltage increases as the pressure increases. It was also found that a plasma channel formation and an associated breakdown may or may not occur between the electrodes at different pressures due to variation in required breakdown voltages. Breakdown time-lag in the dielectric medium (tap water, 780 μS cm –1 ) increased as the pressure was increased, which indicated a higher voltage drop at higher pressures (>100 atm). The plasma generated cavitation bubble with an associated shockwave occurred as pressures were increased. However, the bubble radius and the bubble duration decreased as the pressure was increased. The plasma generated shockwave speeds fall within the expected speed of sound in water. Lastly, preliminary rock cracking tests were performed on granite at high pressures (340 and 272 atm) and it was found that plasma is able to create cracks in the rock.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

Partial molar properties from molecular simulation using multiple linear regression

Partial molar volumes, energies, and enthalpies can be computed from NpT-Gibbs ensemble simulations through a post-processing procedure that leverages fluctuations in composition, total volume, and total energy of a simulation box. By recording the instantaneous box volumes V and instantaneous number of molecules N i of each of n species for M frames, a large M ×n matrix N is constructed, as well as the M × 1 vector V. The 1 × n vector of partial molar volumes V¯ may then be solved using N • V¯=V. A similar construction permits calculation of partial molar energies using M instantaneous measurements of the total energy of the simulation box, and N • U¯=U. Partial molar enthalpies may be derived from U¯, V¯, and pressure p. These properties may be used to calculate enthalpy and entropy of transfer (absorption, extraction, and adsorption) for species in complex mixtures. The method is demonstrated on three systems in the NpT-Gibbs ensemble: a highly compressible natural gas condensate of methane, n-butane, and n-decane, the liquid-phase adsorption of 1,5-pentanediol and ethanol onto the MFI zeolite, and a relatively incompressible mixture of ethanol, n-dodecane, and water at liquid-liquid equilibrium. Property predictions are compared to those from numerical differentiation of simulation data sequentially changing the composition and from equations of state. Here, the method can also be extended to reaction equilibria in a closed system and is applied to a reactive first-principles Monte Carlo simulation of compressed nitrogen/oxygen.

74 ATOMIC AND MOLECULAR PHYSICS↗

Final Report: In-Situ TEM Observations of Degradation Mechanisms in Next-Generation High-Energy Density Lithium-Ion Battery Systems

This project originally sought to characterize nanoscale processes associated with the degradation of next-generation high energy density lithium-ion battery electrodes via in-situ transmission electron microscopy (TEM). The research also focused on developing the experimental techniques necessary for investigating electrochemical systems by in-situ transmission electron microscopy and providing a framework for understanding and quantifying electron beam effects that influence experimental results. In line with these goals, this project demonstrated and published the first in-situ TEM cycling of a Li-ion battery electrode in commercially relevant non-aqueous electrolyte: a technique subsequently adopted by a number of researchers in the field. Experiments performed on Sn anodes, demonstrated porosity evolution during Li dealloying as a mechanism for strain accommodation during the first cycle, and observed partially reversible crystalline to amorphous phase transitions associated with Li insertion and extraction in subsequent cycles. Complementary study of in-situ dealloying in a simple model, Au-Cu, was also performed. We also published the earliest quantitative measurements of electron beam effects in aqueous and non-aqueous liquids. Specifically, we utilized a model system to quantify the fraction of incident electron beam that contributed to charge transfer mediated reactions in non-aqueous liquid, since such liquids are primarily dose sensitive. We also quantified the evolution of model aqueous chemistries as a function of dose rate and chemical potential to better understand the reaction mechanisms active in liquids exposed to electron beams. The original project goals included the use of controlled environments to simulate different battery operational conditions. To aid such experiments, we developed new experimental apparatuses and techniques to perform in-situ liquid cell TEM under controlled temperature, including heating and cooling. We demonstrated this capability in aqueous systems; specifically understanding phase selection and solid-liquid interface interactions with particles during water crystallization and hydrothermal precipitation kinetics of ZnO. We also published the first demonstration of in-situ TEM based high-field (plasma) experiments and in-situ TEM of aqueous photochemistry, which demonstrated an previously unrecognized early growth mode transition during Au sputtering and delocalization of gas bubble nucleation during water splitting, respectively. In addition to the scientific results, this portion of the project greatly expanded the range of systems that can be characterized in realistic environments at the nanoscale via in-situ TEM. Unfortunately, commercial battery electrolytes are quite sensitive to electron dose. This limits the time of acquisition and/or the spatial resolution of the experiments. The same problem has been encountered in all subsequent publications in the field. The major problem, relative to the project original goals, is that long term cycling is challenging to characterize and the desired high resolution or analytical capabilities are limited. In line with our original goals to characterize battery reaction and degradation mechanisms under controlled electrochemical cycling, we developed a completely new type of Li-ion electrochemical cell that has been useful for both structural and analytical characterization. To date, we have demonstrated this platform for in-situ cycling of Li-ion batteries during scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and x-ray photoelectron spectroscopy (XPS). In-situ AES has been found to be a quite powerful tool to characterize the chemical evolution of Li-ion batteries cycled in-situ and much of our effort in the final project period has focused on charactering Li-ion cathodes using the technique. We utilized in-situ SEM to propose a new mechanism for Li whisker/dendrite formation and show the importance of diffusion mediated stress relaxation in fracture of Sn anode particles. A combination of in-situ XPS and AES was used to clarify the CuO anode reaction mechanism. In the final project period, we have gained new insights into surface reactions occurring on cathodes at high voltage using in-situ AES. Specifically, we have discovered that many of the SEI formation reactions typically attributed to electrolyte decomposition are actually more fundamental to the electrode material surface thermodynamics in the presence of an arbitrary carbon source. These insights greatly affect how we understand and control surface degradation induced capacity fade at cathodes. Finally, we have made some effort to apply this novel in-situ platform to TEM characterization and believe this is a fruitful avenue for future research.

25 ENERGY STORAGE↗

First Measurements of the Parity-Violating and Beam-Normal Single-Spin Asymmetries in Elastic Electron-Aluminum Scattering

The Q weak collaboration has made the first measurements of the elastic parity-violating and beam-normal single-spin asymmetries from the 27 Al nucleus. Both are the result of ancillary measurements conducted during the Q weak experiment at Jefferson Lab. The goal of the experimental was to determine the proton's weak charge, Q p W , via a measurement of the elastic parity-violating electron-proton scattering asymmetry. During the experiment, ancillary measurements were made with different beam configurations on a separate aluminum alloy target, in an effort to directly measure the aluminum background coming from the experiment's liquid hydrogen target cell. This dissertation discusses three primary results: the parity-violating 27 Al asymmetry analysis used to correct for the aluminum target background in the final Q weak analysis, its extended analysis leading to the extraction of the pure elastic parity-violating 27 Al asymmetry, and the determination of the elastic beam-normal single-spin 27 Al asymmetry. The parity-violating result was also used to make a semi model-independent determination of 27 Al neutron distribution radius, an important test for models used to describe neutron-rich matter. The beam-normal single-spin asymmetry stands to possibly shed light on an observed disagreement between theory and a previous measurement performed on 208 Pb, as 27 Al is the next highest atomic mass nucleus to have this observable measured. The elastic parity-violating 27 Al asymmetry was found to be 1.927 +/- 0.173 ppm at (Q 2 ) = 0.0236 +/- 0.0001 GeV 2 . This measured parity-violating asymmetry implies a 27 Al neutron distribution radius of 3.024 +/- 0.104 fm. Calculating the difference between this radius and the 27 Al proton distribution radius yields the neutron skin, which was found to be 0.092 +/- 0.104 fm. This skin value is consistent with zero, within its uncertainty, and it confirms the naive expectation for a light nucleus like 27 Al. The beam-normal single-spin 27 Al asymmetry was found to be -16.322 +/- 2.679 ppm at &lang;Q&rang; = 0.154 GeV. This value agrees with the previous observed trend of beam-normal single-spin asymmetries measured from light nuclei, which motivates the need for future measurements of higher atomic mass nuclei.

Source record↗

Effect of purity on adsorption capacities of a Mars-like clay mineral at different pressures

There has been considerable interest in adsorption of carbon dioxide on Marslike clay minerals. Some estimates of the carbon dioxide reservoir capacity of the martian regolith were calculated from the amount of carbon dioxide adsorbed on the ironrich smectite nontronite under martian conditions. The adsorption capacity of pure nontronite could place upper limits on the regolith carbon dioxide reservoir, both at present martian atmospheric pressure and at the postulated higher pressures required to permit liquid water on the surface. Adsorption of carbon dioxide on a Clay Mineral Society standard containing nontronite was studied over a wide range of pressures in the absence of water. Similar experiments were conducted on the pure nontronite extracted from the natural sample. Heating curves were obtained to help characterize and determine the purity of the clay sample.

Jenkins, Traci↗

Variable Gravity Effects on the Cooling Performance of a Single Phase Confined Spray

The objective of this paper is to discuss the testing of a spray cooling experiment designed to be flown on NASA's KC-135 Reduced Gravity Testing Platform. Spray cooling is an example of a thermal management technique that may be utilized in high flux heat acquisition and high thermal energy transport concepts. Many researchers have investigated the utility of spray cooling for the thermal management of devices generating high heat fluxes. However, there has been little research addressing the physics and ultimate performance of spray cooling in a variable gravity environment. An experimental package, consisting of a spray chamber coupled to a fluid delivery loop system, was fabricated for variable gravity flight tests. The spray chamber contains two opposing nozzles spraying on target Indium Tin Oxide (ITO) heaters. These heaters are mounted on glass pedestals, which are part of a sump system to remove unconstrained liquid from the test chamber. Liquid is collected in the sumps and returned to the fluid delivery loop. Thermocouples mounted in and around the pedestals are used to determine both the heat loss through the underside of the IT0 heater and the heat extracted by the spray. A series of flight tests were carried out aboard the KC-135, utilizing the ability of the aircraft to produce various gravity conditions. During the flight tests, for a fixed flow rate, heat input was varied at 20, 30, 50, and 80W with variable gravities of 0.01, 0.16, 0.36, and 1.8g. Flight test data was compared to terrestrial baseline data in addition to analytical and numerical solutions to evaluate the heat transfer in the heater and support structure . There were significant differences observed in the spray cooling performance as a result of variable gravity conditions and heat inputs. In general, the Nussult number at the heater surface was found to increase with decreasing gravity conditions for heat loads greater than 30W.

Michalak, Travis↗