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All sources NASA NTRS DOE OSTI

DOE OSTI2021

Insight into SEI Growth in Li-Ion Batteries using Molecular Dynamics and Accelerated Chemical Reactions

The performance of lithium-ion batteries (LIB) using organic electrolytes strongly depends on the formation of a stable solid electrolyte interphase (SEI) film. Elucidating the dynamic evolution and spatial composition of the SEI can be very useful to study the stability of SEI components and help optimize the formation cycles of LIB. We propose a classical molecular dynamics simulation protocol for predicting the first stages of SEI formation using a reaction method involving the decomposition of EC and LiPF 6 molecules in the electrolyte. We accelerate the formation of SEI components near the anode surface by increasing the probability of reactions, implemented through a geometry matching scheme, followed by a force-field reconfiguration. We observe the formation of gases (C 2 H 4 ), inorganic (Li 2 CO 3 and LiF) and organic (LEDC) components. Finally, this protocol shows promise to be able to evaluate the effects of varying electrolyte compositions and additives on SEI layer structure and composition.

25 ENERGY STORAGE↗

DOE OSTI2024

Trace Adsorptive Removal of PFAS from Water by Optimizing the UiO‐66 MOF Interface

Abstract The confluence of pervasiveness, bioaccumulation, and toxicity in freshwater contaminants presents an environmental threat second to none. Exemplifying this trifecta, per‐ and polyfluoroalkyl substances (PFAS) present an alarming hazard among the emerging contaminants. State‐of‐the‐art PFAS adsorbents used in drinking water treatment, namely, activated carbons and ion‐exchange resins, are handicapped by low adsorption capacity, competitive adsorption, and/or slow kinetics. To overcome these shortcomings, metal–organic frameworks (MOFs) with tailored pore size, surface, and pore chemistry are promising alternatives. Thanks to the compositional modularity of MOFs and polymer–MOF composites, herein we report on a series of water‐stable zirconium carboxylate MOFs and their low‐cost polymer‐grafted composites as C 8 –PFAS adsorbents with benchmark kinetics and “parts per billion” removal efficiencies. Bespoke insights into the structure–function relationships of PFAS adsorbents are obtained by leveraging interfacial design principles on solid sorbents, creating a synergy between the extrinsic particle surfaces and intrinsic molecular building blocks.

Ilić, Nebojša↗

DOE OSTI2022

Linking Friction Scales from Nano to Macro via Avalanches

Abstract Steady-state fluctuations in the friction force of molybdenum disulfide (MoS 2 ), a prototypical lamellar solid, were analyzed experimentally for newton-scale forces and computationally via molecular dynamics simulations for nanonewton-scale forces. A mean field model links the statics and the dynamics of the friction behavior across these eight orders of magnitude in friction force and six orders of magnitude in friction force fluctuations (i.e., avalanches). Both the statistics and dynamics of the avalanches match model predictions, indicating that friction can be characterized as a series of avalanches with properties that are predictable over a wide range of scales.

Salners, Tyler (ORCID:0000000332647944)↗

DOE OSTI2022

Graph-component approach to defect identification in large atomistic simulations

In this work, the graph-theoretical concept of connected components is employed to extract the evolution of defect configurations in a polycrystalline aluminum structure containing ~8.3 million atoms. This graph-component approach is applied to reveal details of defect formation, transport, and transformation in the polycrystalline Al under large shear deformation. Building upon standard nearest neighbor analysis, graph theory and associated tools are used to reduce the multi-million-atom system into discrete component subgraphs that represent distinct structural defects. This method allows the automated identification, characterization, and tracking of defective regions within large volumes of data representing atomic-scale processes. Such analysis elucidates relationships between external stimuli, such as strain, and defect distributions, which have a large influence on material properties. The Graph Analytics for Large Atomistic Simulations (GALAS) codebase that implements this analysis, together with user guidance, is openly available at https://github.com/pnnl/galas.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Fluorinated co-solvent promises Li-S batteries under lean-electrolyte conditions

Practical lithium-sulfur batteries stipulate the use of a lean-electrolyte and a high Coulombic efficiency of the lithium metal anode. In this work, we employ 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether as a co-solvent in the electrolyte of Li-S batteries to meet the demands. The co-solvent fosters the formation of a LiF-rich solid electrolyte interphase on lithium metal anode, as revealed by Ab initio molecular dynamics and Femtosecond Stimulated Raman spectroscopy. The co-solvent results in an average Coulombic efficiency of 99.4% for lithium plating/stripping cycles. Full cells with a capacity ratio of 2 between lithium anode and the S@PAN cathode (3 gs cm –2 ) exhibited a stable cycle life over 100 cycles at an electrolyte/sulfur ratio of 2 µL mg –1 , validating the high Coulombic efficiency of the lithium anode and demonstrating the compatibility of the electrolyte with both electrodes. To enhance the energy density, we prepared a hybrid cathode composed of 45 wt.% VS 2 mixed with ZnS-coated Li 2 S@graphene as the cathode. Based on the mass of both electrodes and the electrolyte, the full cell delivers an energy density of 483 Wh kg –1 , which demonstrates viable Li-S batteries with the lean-electrolyte.

25 ENERGY STORAGE↗

DOE OSTI2020

Ion irradiation and modification: The role of coupled electronic and nuclear energy dissipation and subsequent nonequilibrium processes in materials

Understanding material responses to energy deposition from energetic charged particles is important for defect engineering, ion-beam processing, ion-beam analysis and modification, geologic aging, space exploration, and nuclear applications. As an incident ion penetrates a solid, its energy is transferred to electrons and to atomic nuclei of the solid. Much of this electronic energy deposition is subsequently transferred to the atomic structure via electron–phonon (e–ph) coupling, leading to local inelastic thermal spikes in which energy dissipation is influenced by the local environment. In addition, intense ionization can lead to high densities of localized electronic excitations in wide-bandgap materials and ceramics that can affect defect dynamics and atomic mobility. Specifically, energy exchange between electrons and atomic nuclei, along with localized electronic excitations, can lead to substantial competitive (ionization-induced annealing), additive (both electronic and nuclear energy depositions contributing to damage production), and synergistic (more damage than the sums of separate damage processes) effects. Although nonmonotonic effects of the e–ph coupling strength and athermal processes are demonstrated for pre-existing defects and residual damage during ion–solid interactions, there is limited understanding of when such electronic effects must be considered in atomic-scale models of damage production and evolution in a broad variety of materials. Complex ceramics and chemically disordered solid solution alloys with different constituent elements allow a systematic evaluation of defect dynamics and irradiation performance with increasing complexity. Current knowledge regarding tuning of bonding characteristics and chemical disorder to control atomic-level dynamics is reviewed. Although a lack of fundamental understanding obstructs the advancement of reliable predictions for ion beam material modification, it highlights challenges and opens research opportunities. Insights into the complex electronic and atomic correlations with extreme energy deposition will strengthen our ability to design materials and predict ion-irradiation-induced damage in a radiation environment, and they may pave the way to better control fundamental processes and design new material functionalities for advanced technologies.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Femtosecond diffraction and dynamic high pressure science

Solid-state material at high pressure is prevalent throughout the Universe, and an understanding of the structure of matter under such extreme conditions, gleaned from x-ray diffraction, has been pursued for the best part of a century. The highest pressures that can be reached to date (2 TPa) in combination with x-ray diffraction diagnosis have been achieved by dynamic compression via laser ablation. The past decade has witnessed remarkable advances in x-ray technologies, with novel x-ray Free-Electron-Lasers (FELs) affording the capacity to produce high quality single-shot diffraction data on timescales below 100 fs. We provide a brief history of the field of dynamic compression, spanning from when the x-ray sources were almost always laser-plasma based, to the current state-of-the art diffraction capabilities provided by FELs. We give an overview of the physics of dynamic compression, diagnostic techniques, and the importance of understanding how the rate of compression influences the final temperatures reached. We provide illustrative examples of experiments performed on FEL facilities that are starting to give insight into how materials deform at ultrahigh strain rates, their phase diagrams, and the types of states that can be reached. We emphasize that there often appear to be differences in the crystalline phases observed between the use of static and dynamic compression techniques. We give our perspective on both the current state of this rapidly evolving field and some glimpses of how we see it developing in the near-to-medium term.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2025

All-optical control of charge-trapping defects in rare-earth doped oxides

Abstract Charge-trapping defects in crystalline solids play important roles in applications ranging from microelectronics, optical storage, sensing and quantum technologies. On one hand, depleting trapped charges in the host matrix reduces charge noise and enhances coherence of solid-state quantum emitters. On the other hand, stable charge traps can enable high-density optical storage systems. Here we report all-optical control of charge-trapping defects via optical charge trapping (OCT) spectroscopy of a rare-earth ion doped oxide (Y 2 O 3 ). Charge trapping is realized by low intensity optical excitation in the 200–375 nm range. Charge detrapping or depletion is carried out by optically stimulated luminescence (OSL) under 532 nm stimulation. Using a Pr-doped Y 2 O 3 polycrystalline ceramic host matrix, we observe charging pathways via the inter-band optical absorption of Y 2 O 3 and via the 4f-5d transitions of Pr 3+ . We demonstrate effective control of the density of trapped charges within the Y 2 O 3 matrix at ambient environment. These results point to a viable method for controlling the local charge environment in rare-earth doped crystals via all-optical means, and pave the way for further development of efficient optical storage technologies with ultrahigh storage capacity, as well as for the localized control of quantum coherence in rare-earth doped solids.

França, Leonardo V. S. [Pritzker School of Molecul↗

NASA NTRS1969

Solid state television camera system Patent

Solid state television camera system consisting of monolithic semiconductor mosaic sensor and molecular digital readout systems

Broderick, J. C.↗

NASA NTRS1972

Nucleic acid hybridization with RNA immobilized on filter paper.

RNA has been immobilized in a manner suitable for use in molecular hybridization experiments with dissolved RNA or DNA by a nonaqueous solid-phase reaction with carbonyldiimidazole and RNA 'dry coated' on cellulose or, preferably, on previously activated phosphocellulose filters. Immobilization of RNA does not appear to alter its chemical character or cause it to acquire affinity for unspecific RNA or DNA. The versatility and efficiency of this method make it potentially attractive for use in routine analytical or preparative hybridization experiments, among other applications.

Saxinger, W. C.↗

NASA NTRS1972

Cost analysis of carbon dioxide concentrators

A methodology is developed to predict the relevant contributions of the more intangible cost elements encountered in the development of flight-qualified hardware and is used to predict the costs of three carbon dioxide concentration systems. The cost and performance data from Gemini, Skylab, and other programs are utilized as a basis for establishing the cost estimating relationships. The concentration systems analyzed are the molecular sieves C02 concentrator, the hydrogen-depolarized concentrator, and the regenerable solid desiccant concentrator. Besides the cost estimates for each system, their comparative criteria including relative characteristics, operational differences, and development status are considered.

Yakut, M. M.↗

NASA NTRS1975

Liquid ethylene-propylene copolymers

Oligomers are prepared by heating solid ethylene-propylene rubber in container that retains solid and permits liquid product to flow out as it is formed. Molecular weight and viscosity of liquids can be predetermined by process temperature. Copolymers have low viscosity for given molecular weight.

Rhein, R. A.↗

NASA NTRS1998

Carbon-13 Labeling Used to Probe Cure and Degradation Reactions of High- Temperature Polymers

High-temperature, crosslinked polyimides are typically insoluble, intractible materials. Consequently, in these systems it has been difficult to follow high-temperature curing or long-term degradation reactions on a molecular level. Selective labeling of the polymers with carbon-13, coupled with solid nuclear magnetic resonance spectrometry (NMR), enables these reactions to be followed. We successfully employed this technique to provide insight into both curing and degradation reactions of PMR-15, a polymer matrix resin used extensively in aircraft engine applications.

Meador, Mary Ann B.↗

NASA NTRS2010

Formation, Structure and Properties of Amorphous Carbon Char from Polymer Materials in Extreme Atmospheric Reentry Environments

Amorphous carbonaceous char produced from the pyrolysis of polymer solids has many desirable properties for ablative heat shields for space vehicles. Molecular dynamics simulations are presented to study the transformation of the local atomic structure from virgin polymer to a dense, disordered char [1]. Release of polymer hydrogen is found to be critical to allow the system to collapse into a highly coordinated char structure. Mechanisms of the char formation process and the morphology of the resulting structures are elucidated. Thermal conductivity and mechanical response of the resulting char are evaluated [2]. During reenty, the optical response and oxidative reactivity of char are also important properties. Results of ab initio computations of char optical functions [3] and char reactivity [4] are also presented.

Lawson, John W.↗

DOE OSTI2021

Phenol-containing polyester multiphase polymer blend materials

A solid multiphase polymer blend material comprising: (i) a polyphenolic substance having a molecular weight of at least 500 g/mol; and (ii) a polyester having a molecular weight of at least 500 g/mol; wherein at least a portion of the polyphenolic substance is covalently bonded directly or through a linking moiety to the polyester. Methods for producing the blend material are also described, e.g., homogeneously melt blending a mixture comprising components (i) and (ii) under conditions resulting in covalent attachment of at least a portion of the polyphenolic substance directly or through a linking moiety to the polyester. Methods for producing objects made of the blend material by melt extrusion are also described.

Bova, Anthony S.↗

DOE OSTI2022

Phenol-containing polyester multiphase polymer blend materials

Bova, Anthony S.↗

NASA NTRSDate not supplied

Determination of Interfacial Energy for Solid-State Precipitation

Precipitation of strengthening phases from solid state is a critical process for many materials. For example, the high-temperature creep resistance of Ni-based superalloys is governed by ’ precipitates. However, the interfacial energy which controls the precipitation is expensive to determine experimentally. For simulations, the atomic nature of precipitation events necessitates using Molecular Dynamics (MD) so relying on fitting to a-priori experimental behavior is not required. However, the solid-state precipitation takes orders of magnitude longer time than is accessible for traditional MD simulation. Taking inspiration from Kinetic Monte-Carlo (KMC) methods for simulating diffusion on a rigid lattice, we have developed a hybrid KMC-MD approach to enable simulation of solid-state precipitation (and determination of the interfacial energy). Implementing these methods in LAMMPS, we calculated the interfacial energy for the ’ precipitation out of a super-saturated  phase in Ni-based superalloys. The resulting interfacial energy value for the Ni-Al system is well within the accuracy of experimental values, demonstrating the capability of this method. Enabling the calculation of the interfacial energy without a-priori experimental knowledge of the precipitation unlocks a more efficient ICME-based approach for guiding annealing protocols in Ni-based superalloys and other solid-state precipitation systems.

Precipitation↗

NASA NTRS1991

Influence of mass diffusion on the stability of thermophoretic growth of a solid from the vapor phase

The stability of solid planar growth from a binary vapor phase with a condensing species dilute in a carrier gas is examined when the ratio of depositing to carrier species molecular mass is large and the main diffusive transport mechanism is thermal diffusion. It is shown that a deformation of the solid-gas interface induces a deformation of the gas phase isotherms that increases the thermal gradients and thereby the local mass deposition rate at the crests and reduces them at the valleys. The initial surface deformation is enhanced by the modified deposition rates in the absence of appreciable Fick/Brownian diffusion and interfacial energy effects.

Castillo, J. L.↗