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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Characterizing the localization of organic C on mineral surfaces: a correlative microscopy/spectroscopy approach

It is estimated that organic carbon (OC) in soils exceeds the amount of OC in atmosphere and in vegetation pools combined.1 Given the current changes in climate and increasing temperatures in the environment, the fraction of OC sequestered in soils and sediments is more sensitive to decomposition and release as CO 2 in the atmosphere. Evidence implies that sorption and association of dissolved OC with inorganic soil components, i.e., soil minerals, is a key mechanism that contributes to stabilization and retention of OC in soil environment. Studies have shown a direct correlation between sorption of dissolved OC and soil mineral surface properties and their surface area. In addition, properties of organic compounds such as chemical structure and functional groups play a significant role in interaction of dissolved organic species with mineral surfaces. Association of OC with minerals via ligand exchange reactions, polyvalent tertiary bonding, or complexation with metal ions, is found to be preferential and dependent on the organic compounds’ functional groups.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Engineering Electrical Conductivity in Stable Zirconium-Based PCN-222 MOFs with Permanent Mesoporosity

Electrically conductive metal–organic frameworks (MOFs) featuring zirconium-based nodes are of great interest for electrochemical and optoelectronic applications due to their exceptional thermal and chemical stability, although the number of such MOFs remains limited. Here in this paper, we demonstrate that electron deficient molecules such as transition metal(IV) bis(dicarbollide) (TM IV (C 2 B 9 H 11 ) 2 ; TM IV CB for short, where TM = Ni, Pd, and Pt) or C 60 , spatially infiltrated in the microporous channels of the zirconium-based porphyrinic MOFs PCN-222 and PCN-222-Zn, generate highly stable and electrically conductive frameworks in which the mesopores remain accessible to other guests. Solid-state density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations indicate incorporation of Ni IV CB and C 60 in the MOF micropores is energetically and structurally feasible. Interestingly, in contrast to the free species, strong donor–acceptor interactions between the MOF and Ni IV CB restrain it to a single conformation. Calculated electronic structures and charge-hopping conduction probabilities illustrate that efficient charge-transfer (CT) from photoexcited linkers to the guest molecules facilitates charge hopping in the framework, making the MOFs electrically conductive. The donor–acceptor conjugates also enhance exciton dissociation at their heterojunctions, fostering the formation of long-lived electron-trapped states with potential utility for photo- and electrochemical devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

(Fe, Cr)(OH) 3 Coprecipitation in Solution and on Soil: Roles of Surface Functional Groups and Solution pH

The simultaneous precipitation of (Fe, Cr)(OH) 3 nanoparticles in solution (homogeneous) and on soil surfaces (heterogeneous), which controls Cr transport in soil and aquatic systems, was quantified for the first time in the presence of model surfaces, i.e., bare and natural organic matter (NOM)-coated SiO 2 and Al 2 O 3 . Various characterization techniques were combined to explore the surface-ion-precipitate interactions and the controlling mechanisms. (Fe, Cr)(OH) 3 accumulation on negatively charged SiO 2 was mainly governed by electrostatic interactions between hydrolyzed ion species or homogeneous (Fe, Cr)(OH) 3 and surfaces. The elevated pH through protonation of Al 2 O 3 surface hydroxyls resulted in higher Cr/Fe ratios in both homogeneous and heterogeneous coprecipitates. Here, due to ignorable NOM adsorption onto SiO 2 , the amounts of (Fe, Cr)(OH) 3 precipitates on bare/NOM-SiO 2 were similar; contrarily, attributed to favored NOM adsorption onto Al 2 O 3 and consequently carboxyl association with metal ions or (Fe, Cr)(OH) 3 nanoparticles, remarkably more heterogeneous precipitates harvested on NOM-Al 2 O 3 than bare-Al 2 O 3 . With the same solution supersaturation, the total amounts of homogeneous and heterogeneous precipitates were similar irrespective of the substrate type. With lower pH, decreased electrostatic forces between substrates and precipitates shifted (Fe, Cr)(OH) 3 distribution from heterogeneous to homogeneous phases. The quantitative knowledge of (Fe, Cr)(OH) 3 distribution and the controlling mechanisms can assist in better Cr sequestration in natural and engineered settings.

(Fe, Cr)(OH)3 distribution↗
DOE OSTI2023

Effect of Anions on the Delithiation of [Li–Al] Layered Double Hydroxides: Thermodynamic Insights

The utilization of lithium aluminum [Li–Al] layered double hydroxides (LDHs) is explored for direct lithium extraction (DLE) from geothermal brines and minerals. Following extraction, the Li + ions need to be removed from the LDH structure and converted into LiOH or Li 2 CO 3 products, making them suitable for battery applications. The research investigates the delithiation of [Li–Al-X] LDHs (where X = Cl – , OH – , and SO 4 2– ), which were synthesized and dried under different conditions. Herein the study aims to understand how the choice of anions and drying conditions affects the delithiation process. To determine the stability of these [Li–Al] LDHs, high-temperature oxide melt solution calorimetry is employed. The results reveal that the stability of LDHs varies significantly based on postdrying conditions, anion choice, and the water content in the interlayer. The order of stability, as indicated by the enthalpy of formation values, is found to be OH-LDH-O > OH-LDH-A > SO 4 -LDH-O > SO4-LDH-A > Cl-LDH-O > Cl-LDH-A. This trend is attributed to the interactions among the interlayer species and the metal hydroxide layers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Insights into the Interaction of Redox Active Organic Molecules and Solvents with the Pristine and Defective Graphene Surfaces from Density Functional Theory

A systematic study is reported on the interaction of two representative redox active organic molecules and two solvent molecules with pristine and defective graphene surfaces as a model of an electrode surface of a redox flow battery (RFB). The redox active molecules include a catholyte, 2,5-di-tert-butyl-1,4-dimethoxybenzene (DDB), and an anolyte molecule, benzothiadiazole (BTZ), and the solvent molecules include acetonitrile (MeCN) and ethylene carbonate (EC). The graphene defects investigated include a single vacancy, double vacancy, zigzag step edge, and armchair step edge. Computations suggest that the interactions of all molecules with a pristine graphene surface are relatively weak (0.2 to 0.8 eV) and dominated by van der Waals effects; therefore, these molecules are chemically stable upon interacting with pristine nondefective graphene. The BTZ, DDB, MeCN, and EC molecules interact strongly (1.5 to 5.5 eV) with the single vacancy and zigzag step edges of graphene that leads to the possible decomposition of the molecules with strength of interaction in the order of MeCN > BTZ > DDB > EC and MeCN > EC > BTZ > DDB, respectively. Calculations show that the BTZ, DDB, MeCN, and EC molecules interact less strongly (0.2 to 1.4 eV) to the double vacancy and armchair step edge than to the single vacancy and zigzag step edge. The binding energies of the molecules were significantly reduced when interacting with the passivated defects, suggesting that the passivation of the defects could help prevent unwanted chemical interactions between the neutral molecules and the electrode surface. In all organic RFBs, one of the crucial bottlenecks is the stability of the constituent molecules with the electrode material, and this study provides insights into the chemical interaction of selected candidate species with a model carbon electrode.

Howard, Jason D.↗
DOE OSTI2023

High-Sensitivity Low-Energy Ion Spectroscopy with Sub-Nanometer Depth Resolution Reveals Oxidation Resistance of MoS 2 Increases with Film Density and Shear-Induced Nanostructural Modifications of the Surface

For decades, density has been attributed as a critical aspect of the structure of sputter-deposited nanocrystalline molybdenum disulfide (MoS 2 ) coatings impacting oxidation resistance and wear resistance. Despite its importance, there are few examples in the literature that explicitly investigate the relationship between the density and oxidation behaviors of MoS 2 coatings. Aging and oxidation are primary considerations for the use of MoS 2 coatings in aerospace applications as they inevitably experience prolonged storage in water and oxygen-rich environments prior to use. Oxidation that is either limited to the first few nanometers or through the bulk of the coating can result in seizure due to high initial coefficients of friction or component failure from excessive wear. High-sensitivity low-energy ion spectroscopy (HS-LEIS) and Rutherford backscattering spectrometry (RBS) are both used to understand the extent of oxidation throughout the first ~10 nanometers of the surface of pure sputtered nanocrystalline MoS 2 coatings after high-temperature aging and how it is impacted by the density of coatings as measured by RBS. Results show that low-density coatings (ρ = 3.55 g/cm 3 ) exhibit a more columnar microstructure and voiding, which act as pathways for oxidative species to penetrate and interact with edge sites, causing severe surface and subsurface oxidation. Furthermore, HS-LEIS of surfaces sheared prior to oxidation reveals that the oxidation resistance of low-density MoS 2 coatings can be significantly improved by shear-induced reorientation of the surface microstructure to a basal orientation and elimination of pathways for oxygen into the bulk through compaction of surface and subsurface voids.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Ethanol-Induced Condensation and Decondensation in DNA-Linked Nanoparticles: A Nucleosome-like Model for the Condensed State

Inspired by the conventional use of ethanol to induce DNA precipitation, ethanol condensation has been applied as a routine method to dynamically tune “bond” lengths (i.e., the surface-to-surface distances between adjacent nanoparticles that are linked by DNA) and thermal stabilities of colloidal crystals involving DNA-linked nanoparticles. However, the underlying mechanism of how the DNA bond that links gold nanoparticles changes in this class of colloidal crystals in response to ethanol remains unclear. Here, we conducted a series of all-atom molecular dynamic (MD) simulations to explore the free energy landscape for DNA condensation and decondensation. Our simulations confirm that DNA condensation is energetically much more favorable under 80% ethanol conditions than in pure water, as a result of ethanol’s role in enhancing electrostatic interactions between oppositely charged species. Moreover, the condensed DNA adopts B-form in pure water and A-form in 80% ethanol, which indicates that the higher-order transition does not affect DNA’s conformational preferences. We further propose a nucleosome-like supercoiled model for the DNA condensed state, and we show that the DNA end-to-end distance derived from this model matches the experimentally measured DNA bond length of about 3 nm in the fully condensed state for DNA where the measured length is 16 nm in water. Altogether, this study provides an atomistic understanding of the mechanism underlying ethanol-induced condensation and water-induced decondensation, while our proposed nucleosome-like model allows the design of new strategies for interpreting experimental studies of DNA condensation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Molecular insight into the anion effect and free volume effect of CO 2 solubility in multivalent ionic liquids

For many years, experimental and theoretical studies have investigated the solubility of CO 2 in a variety of ionic liquids (ILs), but the overarching absorption mechanism is still unclear. Currently, two different factors are believed to dominate the absorption performance: (a) the fractional free volume (FFV) accessible for absorption; and (b) the nature of the CO 2 interactions with the anion species. The FFV is often more influential than the specific choice of the anion, but neither mechanism provides a complete picture. Herein, we have attempted to decouple these mechanisms in order to provide a more definitive molecular-level perspective of CO 2 absorption in IL solvents. We simulate a series of nine different multivalent ILs comprised of imidazolium cations and sulfonate/sulfonimide anions tethered to benzene rings, along with a comprehensive analysis of the CO 2 absorption and underlying molecular-level features. We find that the CO 2 solubility has a very strong, linear correlation with respect to FFV, but only when comparisons are constrained to a common anion species. The choice of anion results in a fundamental remapping of the correlation between CO 2 solubility and FFV. Overall, the free volume effect dominates in the ILs with smaller FFV values, while the choice of anion becomes more important in the systems with larger FFVs. Our proposed mechanistic map is intended to provide a more consistent framework for guiding further IL design for gas absorption applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Prediction of the structures and heats of formation of MO 2 , MO 3 , and M 2 O 5 for M = V, Nb, Ta, Pa

Structures for the mono-, di-, and tri-bridge isomers of M 2 O 5 as well as those for the MO 2 and MO 3 fragments for M = V, Nb, Ta, and Pa were optimized at the density functional theory (DFT) level. Single point CCSD(T) calculations extrapolated to the complete basis set (CBS) limit at the DFT geometries were used to predict the energetics. Here, the lowest energy dimer isomer was the di-bridge for M = V and Nb and the tri-bridge for M = Ta and Pa. The di-bridge isomers were predicted to be composed of MO 2 + and MO 3 - fragments, whereas the mono- and tri-bridge are two MO 2 + fragments linked by an O 2 - . The heats of formation of M 2 O 5 dimers, as well as MO 2 and MO 3 neutral and ionic species were predicted using the Feller–Peterson–Dixon (FPD) approach. The heats of formation of the MF 5 species were calculated to provide additional benchmarks. Dimerization energies to form the M 2 O 5 dimers are predicted to become more negative going down group 5 and range from -29 to -45 kcal mol -1 . The ionization energies (IEs) for VO 2 and TaO 2 are essentially the same at 8.75 eV whereas the IEs for NbO 2 and PaO 2 are 8.10 and 6.25 eV, respectively. The predicted adiabatic electron affinities (AEAs) range from 3.75 eV to 4.45 eV for the MO 3 species and vertical detachment energies from 4.21 to 4.59 eV for MO 3 - . The calculated M[double bond, length as m-dash]O bond dissociation energies increase from 143 kcal mol -1 for M = V to ~170 kcal mol -1 for M = Nb and Ta to ~200 kcal mol -1 for M = Pa. The M–O bond dissociation energies are all similar ranging from 97 to 107 kcal mol -1 . Natural bond analysis provided insights into the types of chemical bonds in terms of their ionic character. Pa 2 O 5 is predicted to behave like an actinyl species dominated by the interactions of approximately linear PaO 2 + groups.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Ionization wave propagation in a He plasma jet in a controlled gas environment

Characterizing ionization wave propagation in low temperature plasma jets is critical to predicting production of reactive species and plasma–surface interactions for biomedical applications and surface functionalization. In this work, results from optical emission and laser induced fluorescence measurements of the ionization wave in a He plasma jet operating in a controlled gas environment are discussed and used for comparison with numerical modeling. Additionally, the ionization wave was observed using ICCD (Intensified Charge Coupled Device) imaging and characterized by time and spatially resolved electron density measurements using laser-collision-induced fluorescence. The plasma jet was initially characterized using pure He (nominally at 200 Torr), while varying pressure and voltage. When operating in pure He, the ionization wave broadly expands exiting the plasma tube. Increasing the operating pressure reduces the speed and isotropic expansion of the ionization wave. Furthermore, the jet operated with a humid He shroud was also studied. The humid He shroud results in the electron density increasing and having an annular profile due to the lower ionization potential of H2O compared to He and localized photoionization in the mixing region. Numerical modeling highlighted the importance of resonance radiation emitted by excited states of He, photoelectron emission from the quartz tube, and the kinetic behavior of the electrons produced by photoionization ahead of the ionization front.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2025

Molecular understanding of ion transport in a zwitterionic electrolyte

Zwitterions (ZIs) are unique molecules that carry both positive and negative charges, resulting in overall charge neutrality and high dielectric constants. These distinctive properties have enabled broad applications of zwitterionic functionality, including the emerging use of ZIs in lithium-ion battery electrolytes. As a contribution to this developing field, we use all-atom molecular dynamics simulations to investigate the ion transport mechanisms in amorphous mixtures of a zwitterionic liquid containing a range of LiTFSI salt concentrations. Furthermore, the local coordination environment around the Li + ions plays a strong role in governing ionic conductivity, as well as the enhancement of Li + transport numbers with increasing salt concentration. Addition of small amounts of water leads to increased conductivity and ion mobilities due to the water coordinating with the Li + ions, which reduces direct interactions with larger charged species.

Classical molecular dynamic simulations↗
DOE OSTI2025

Volatiles from the necrophagous fly Cochliomyia macellaria (Diptera: Calliphoridae) as indicators of Salmonella exposure

Blow flies (Diptera: Calliphoridae) are crucial in forensic investigations due to their association with both living and dead humans and other animals. Additionally, their interactions with various resources and potential as vectors of pathogens of humans and other animals, thus, make them potential tools for biosurveillance. This study investigated the potential of monitoring volatile organic compounds (VOCs) emitted by blow flies exposed to Salmonella as a method for pathogen surveillance. Adult blow flies ( Cochliomyia macellaria ) were exposed, or not, to Salmonella enterica . Following exposure, VOCs released by the blow flies were collected and analyzed using gas chromatography-mass spectrometry (GC-MS). Results indicate a treatment by time interaction (P < 0.01). Indicator species analysis identified a single compound significantly associated with S. enterica exposure (P = 0.02), Nonane, 2,2,4,4,6,8,8-heptamethyl, potentially indicating an immune system response. Given a compound indicating exposure was detected, future research should determine if more replicates could detect more differences after Salmonella ingestion. This research highlights the potential of blow flies as biosurveillance tools and the potential value of volatiles for assessing their exposure to pathogens.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

Aberration-corrected STEM imaging of 2D materials: Artifacts and practical applications of threefold astigmatism

High-resolution scanning transmission electron microscopy (HR-STEM) with spherical aberration correction enables researchers to peer into two-dimensional (2D) materials and correlate the material properties with those of single atoms. The maximum intensity of corrected electron beam is confined in the area having sub-angstrom size. Meanwhile, the residual threefold astigmatism of the electron probe implies a triangular shape distribution of the intensity, whereas its tails overlap and thus interact with several atomic species simultaneously. The result is the resonant modulation of contrast that interferes the determination of phase transition of 2D materials. Here, we theoretically reveal and experimentally determine the origin of resonant modulation of contrast and its unintended impact on violating the power-law dependence of contrast on coordination modes between transition metal and chalcogenide atoms. The finding illuminates the correlation between atomic contrast, spatially inequivalent chalcogenide orientation, and residual threefold astigmatism on determining the atomic structure of emerging 2D materials.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Complete Genome Sequence of Human Oral Saccharibacterium “ Candidatus Nanosynbacter sp. HMT352” Strain KC1

“Cand. Nanosynbacter sp. HMT352” strain KC1 is an ectoparasitic saccharibacterium/TM7 that was co-isolated from a human saliva sample with its obligate bacterial host, Schaalia odontolytica. The genome of strain KC1 enables studies of the mechanisms and evolution of interspecies interactions and, for oral species, studies of their potential roles in health and disease.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Inferring microbial co-occurrence networks from amplicon data: a systematic evaluation

Microbes commonly organize into communities consisting of hundreds of species involved in complex interactions with each other. 16S ribosomal RNA (16S rRNA) amplicon profiling provides snapshots that reveal the phylogenies and abundance profiles of these microbial communities. These snapshots, when collected from multiple samples, can reveal the co-occurrence of microbes, providing a glimpse into the network of associations in these communities. However, the inference of networks from 16S data involves numerous steps, each requiring specific tools and parameter choices. Moreover, the extent to which these steps affect the final network is still unclear. In this study, we perform a meticulous analysis of each step of a pipeline that can convert 16S sequencing data into a network of microbial associations. Through this process, we map how different choices of algorithms and parameters affect the co-occurrence network and identify the steps that contribute substantially to the variance. We further determine the tools and parameters that generate robust co-occurrence networks and develop consensus network algorithms based on benchmarks with mock and synthetic data sets. The Microbial Co-occurrence Network Explorer, or MiCoNE (available at https://github.com/segrelab/MiCoNE) follows these default tools and parameters and can help explore the outcome of these combinations of choices on the inferred networks. We envisage that this pipeline could be used for integrating multiple data sets and generating comparative analyses and consensus networks that can guide our understanding of microbial community assembly in different biomes.

16S rRNA↗
DOE OSTI2020

Electrochemical Behavior of Copper Ion Complexed with Nanoparticle Organic Hybrid Materials

Nanoscale Organic Hybrid Materials (NOHMs) have unique properties that show potential for their use as novel electrolytes that can interact with redox active species. In this work, we probe the effects of adding poly(ethyleneimine)-based NOHMs (NOHM-I-PEI) on copper ion electrochemical reactions. As NOHM-I-PEI is added to a solution containing Cu(II), the voltammetric peak current decreases. This is likely caused by strong complex formation between the PEI nitrogen and the copper, similar to complexation observed in solutions of the polymer with copper. Upon copper addition to a NOHM-I-PEI solution, the pH decreases from 10.1, plateauing at pH = 5.3 at ~3:1 N:Cu ratio indicating that Cu(II) displaces protons. The UV–visible spectra exhibit a Cu-PEI peak, the intensity of which levels off at ~2.8 N:Cu. Acid titration of the N-moieties of the PEI reveals three inflections corresponding to N-environments in the PEI. Upon controlling the pH of the solution by buffering, the "sequestration" of Cu(II) is found to occur when there are unprotonated nitrogens present in the NOHM-I-PEI system; this phenomenon is also supported by UV-vis results. Furthermore, this work highlights the potential of and the design of NOHMs to carry charged electroactive species in solutions along with key factors to control for optimal function.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Cluster Expansion Analysis of Atomic Order in Li-Ion Battery Cathode Material LiCo y Ni 1-y O 2

A modified cluster-expansion treatment was developed recently to analyze atomic order in LiCo y Ni 1-y O 2 , a model cathode material for Li-ion batteries. In this treatment, referred to as a “spin-atom” cluster expansion, the occupant of a lattice site is identified by its spin state as well as its atomic species. Further, Effective Cluster Interaction (ECI) coefficients are derived from a large training data set (i.e., the set of atomic arrangements for which DFT calculations are performed) which is filtered by an anomaly detection algorithm to eliminate poorly converged DFT calculations. The cluster expansion incorporates Li-Ni (LN) exchange as well as intralayer Co-Ni (CN) exchange. Monte Carlo simulations based on the cluster expansion were applied to the Ni-rich part of the phase diagram. The simulations predict a miscibility gap between y = 0.05 and y = 0.65.

25 ENERGY STORAGE↗
DOE OSTI2021

Microwave Synthetic Routes for Shape-Controlled Catalyst Nanoparticles and Nanocomposites

The use of microwave irradiation for the synthesis of inorganic nanomaterials has recently become a widespread area of research that continues to expand in scope and specialization. The growing demand for nanoscale materials with composition and morphology tailored to specific applications requires the development of facile, repeatable, and scalable synthetic routes that offer a high degree of control over the reaction environment. Microwave irradiation provides unique advantages for developing such routes through its direct interaction with active reaction species, which promotes homogeneous heat distribution, increased reaction rates, greater product quality and yield, and use of mild reaction conditions. Many catalytic nanomaterials such as noble metal nanoparticles and intricate nanocomposites have very limited synthetic routes due to their extreme temperature sensitivity and difficulty achieving homogeneous growth. This work presents recent advances in the use of MW irradiation methods to produce high-quality nanoscale composites with controlled size, morphology, and architecture.

59 BASIC BIOLOGICAL SCIENCES↗