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At least 379 records · Page 21

Chalcocarbogels as High-Capacity and Cycle-Stable Electrode Materials for Lithium and Sodium Ion Batteries

The low capacities of commercial Li ion batteries and cycle instabilities of amorphous metal sulfide based batteries impose constraints on their utilization for large-scale energy storage. We report here the acid-free, room-temperature (RT), and solution-based synthesis of a chalcogenide–carbonaceous hybrid aerogel, termed as “chalcocarbogel”, comprising molybdenum sulfide (MoS x ) and graphene oxide (GO). The chalcocarbogel is a nanoparticle-aggregated, porous, amorphous gel consisting of Mo 3 S 13 and Mo 2 S 12 -like structures as determined by synchrotron X-ray PDF, XANES, and EXAFS. The MoS x -GO chalcocarbogel demonstrates high specific capacities of ~1215 and ~807 mAh g –1 for Li/MoS x -GO and Na/MoS x -GO cells, respectively, for a 50 mAg –1 discharge rate during the first cycle. After the activation cycles, the MoS x -GO chalcocarbogel stabilizes, maintaining high specific capacities of approximately ~700 mAh g –1 for Li/MoS x -GO and ~473 mAh g –1 for Na/MoS x -GO cells, while continuously cycling. Importantly, the MoS x -GO aerogel reported here serves as a promising platform to develop chalcocarbogels for applications spanning both Li and Na ion batteries.

25 ENERGY STORAGE↗

Soil Analysis Micro-Mission Concepts Derived from the MSP 2001 Mars Environmental Compatibility Assessment (MECA)

The Mars Environmental Compatibility Assessment (MECA) will evaluate the Martian environment for soil and dust-related hazards to human exploration as part of the Mars Surveyor Program 2001 Lander. The integrated MECA payload contains a wet-chemistry laboratory, a microscopy station, an electrometer to characterize the electrostatic environment, and arrays of material patches to study abrasion and adhesion. Heritage will be all-important for low cost micro-missions, and adaptations of instruments developed for the Pathfinder, '98 and '01 Landers should be strong contenders for '03 flights. This talk has three objectives: (1) Familiarize the audience with MECA instrument capabilities; (2) present concepts for stand-alone and/or mobile versions of MECA instruments; and (3) broaden the context of the MECA instruments from human exploration to a comprehensive scientific survey of Mars. Due to time limitations, emphasis will be on the chemistry and microscopy experiments. Ion-selective electrodes and related sensors in MECA's wet-chemistry laboratory will evaluate total dissolved solids, redox potential, pH, and the concentration of many soluble ions and gases in wet Martian soil. These electrodes can detect potentially dangerous heavy-metal ions, emitted pathogenic gases, and the soil's corrosive potential, and experiments will include cyclic voltammetry and anodic stripping. For experiments beyond 2001, enhancements could allow multiple use of the cells (for mobile experiments) and reagent addition (for quantitative mineralogical and exobiological analysis). MECA's microscopy station combines optical and atomic-force microscopy (AFM) in an actively focused, controlled illumination environment to image particles from millimeters to nanometers in size. Careful selection of substrates allows controlled experiments in adhesion, abrasion, hardness, aggregation, magnetic and other properties. Special tools allow primitive manipulation (brushing and scraping) of samples. Soil particle properties including size, shape, color, hardness, adhesive potential (electrostatic and magnetic), will be determined using an array of sample receptacles and collection substrates. The simple, rugged atomic-force microscope will image in the submicron size range and has the capability of performing a particle-by-particle analysis of the dust and soil. Future implementations might enhance the optical microscopy with spectroscopy, or incorporate advanced AFM techniques for thermogravimetric and chemical analysis.

Hecht, M. H.↗

Radiation-induced alteration of sandstone concrete aggregate

This study investigates the alteration of felsic sandstone-type rock, which is used as a coarse aggregate in concrete, subject to the effects of gamma-ray and neutron irradiation. The effects of three gamma-ray doses (27, 55, and 108 MGy) and four neutron fluence levels (1.22, 2.19, 6.99, and 14.30 × 10 19 n/cm 2 , $E$ ≥ 0.01 MeV) were investigated. Quartz and albite were found to be the major rock-forming minerals, with microcline intermediates, chlorite, and muscovite as the minors. Gamma rays caused no significant changes to the physical properties of the sandstone aggregates, even at high doses (108 MGy). In contrast, neutron irradiation caused alterations that became more pronounced at higher neutron fluences. The solid was confirmed to expand through metamictization of the rock-forming minerals. Quartz and muscovite were the most affected phases, whereas albite and microcline intermediates were only slightly affected, and chlorite was almost unaffected. The decrease in density was measured by He and water pycnometry, and this value was almost reproduced by calculations using the rock-forming mineral composition of the pristine sample measured using X-ray powder diffraction/Rietveld analysis and the cell volume change of the major forming minerals. In addition, light optical microscopy and scanning electron microscopy images confirmed the presence of intergranular and intragranular cracks. Intergranular cracks appeared to have initiated from the quartz grains, which expanded significantly. The intragranular cracks were frequently observed in the albite and microcline intermediates. These cracks can be described as radial cracks starting from the expanding quartz, caused by enforced displacement for deformation consistency with quartz expansion. The crack area ratio quantified by SEM image analysis corresponds to the discrepancy of the volume expansion difference calculated by He or water pycnometry and dimensional change measurements. In conclusion, an evaluation of solid expansion and crack openings in aggregates is important to estimate concrete degradation.

36 MATERIALS SCIENCE↗

White Laue and powder diffraction studies to reveal mechanisms of HCP-to-BCC phase transformation in single crystals of Mg under high pressure

Mechanisms of hexagonal close-packed (HCP) to body-centered cubic (BCC) phase transformation in Mg single crystals are observed using a combination of polychromatic beam Laue diffraction and monochromatic beam powder diffraction techniques under quasi-hydrostatic pressures of up to 58 ± 2 GPa at ambient temperature. Although experiments were performed with both He and Ne pressure media, crystals inevitably undergo plastic deformation upon loading to 40–44 GPa. The plasticity is accommodated by dislocation glide causing local misorientations of up to 1°–2°. The selected crystals are tracked by mapping Laue diffraction spots up to the onset of the HCP to BCC transformation, which is determined to be at a pressure of 56.6 ± 2 GPa. Intensity of the Laue reflections from HCP crystals rapidly decrease but no reflections from crystalline BCC phase are observed with a further increase of pressure. Nevertheless, the powder diffraction shows the formation of 110 BCC peak at 56.6 GPa. The peak intensity increases at 59.7 GPa. Upon the full transformation, a powder-like BCC aggregate is formed revealing the destructive nature of the HCP to BCC transformation in single crystals of Mg.

36 MATERIALS SCIENCE↗

Achieving Balanced Crystallization Kinetics of Donor and Acceptor by Sequential-Blade Coated Double Bulk Heterojunction Organic Solar Cells

Sequential deposition has great potential to achieve high performance in organic solar cells due to the resulting well-controlled vertical phase separation. In this work, double bulk heterojunction organic solar cells are fabricated by sequential-blade cast in ambient conditions. Probed by the in situ grazing incidence X-ray diffraction and in situ UV–vis absorption measurements, the seq-blade system exhibits a different tendency from each of the binary films during the film formation process. Due to the extensive aggregation of FOIC, the binary PBDB-T:FOIC film displays a strong and large phase separation, resulting in low current density (J sc) and unsatisfactory power conversion efficiency. In the seq-blade cast system, the bottom layer PBDB-T:IT-M produces many crystal nuclei for the top layer PBDB-T:FOIC, so the PBDB-T molecules are able to crystallize easily and quickly. Balanced crystallization kinetics between polymer and small molecule and an ideal percolation network in the film are observed. In addition, the balanced crystallization kinetics are favorable toward realizing lower recombination loss through charge transport processes.

14 SOLAR ENERGY↗

Asymmetric Alkoxy and Alkyl Substitution on Nonfullerene Acceptors Enabling High‐Performance Organic Solar Cells

Abstract In this paper, a strategy of asymmetric alkyl and alkoxy substitution is applied to state‐of‐the‐art Y‐series nonfullerene acceptors (NFAs), and it achieves great performance in organic solar cell (OSC) devices. Since alkoxy groups can have a significant influence on the material properties of NFAs, alkoxy substitution is applied to the Y6 molecule in a symmetric manner. The resulting molecule (named Y6‐2O), despite showing improved open‐circuit voltage ( V oc ), yields extremely poor performance due to low solubility and excessive aggregation properties, a change that is due to the conformational locking effect of alkoxy groups. In contrast, asymmetric alkyl and alkoxy substitution on Y6, yields a molecule named Y6‐1O that can maintain the positive effect of V oc improvement and obtain reasonably good solubility. The resulting molecule Y6‐1O enables highly efficient nonfullerene OSCs with 17.6% efficiency and the asymmetric side‐chain strategy has the potential to be applied to other NFA‐material systems to further improve their performance.

Chen, Yuzhong↗

Experiment K-7-18: Effects of Spaceflight in the Muscle Adductor Longus of Rats Flown in the Soviet Biosatellite Cosmos 2044: A Study Employing Neural Cell Adhesion Molecules (N-CAM) Immunocytochemistry and Conventional Morphological Techniques (Light and Electron Microscopy) - Part 1

The effects of spaceflight upon the 'slow' muscle adductor longus was examined in rats flown in the Soviet Biosatellite COSMOS 2044. Three groups - synchronous, vivarium and basal served as controls. The techniques employed included standard methods for light microscopy, N-CAM immunocytochemistry and electron microscopy. Light microscopic observations revealed myofiber atrophy, contraction bands and segmental necrosis accompanied by cellular infiltrates composed of macrophages, leucocytes and mononuclear cells. N-CAM immunoreactivity was seen (N-CAM-IR) on the myofiber surface, satellite cells and in regenerating myofibers reminiscent of myotubes. Ultrastructural alterations included Z band streaming, disorganization of myofibrillar architecture, sarcoplasmic degradation, extensive segmental necrosis with preservation of the basement membrane, degenerative phenomena of the capillary endothelium and cellular invasion of necrotic areas. Regenerating myofibers were identified by the presence of increased amounts of ribosomal aggregates and chains of polyribosomes associated with myofilaments that displayed varied distributive patterns. The principal electron microscopic changes of the neuromuscular junctions consisted of a decrease or absence of synaptic vesicles, degeneration of axon terminals, increased number of microtubules, vacant axonal spaces and axonal sprouting. The present observations indicate that major alterations such as myofibrillar disruption and necrosis, muscle regeneration and denervation and synaptic remodeling at the level of the neuromuscular junction may take place during spaceflight.

Daunton, N. G.↗

Convective flow effects on protein crystal growth

The experimental setup for the in-situ high resolution optical monitoring of protein crystal growth/dissolution morphologies was substantially improved. By augmenting the observation system with a temperature-controlled enclosure, laser illumination for the interferometric microscope, and software for pixel by pixel light intensity recording, a height resolution of about two unit cells for lysozyme can now be obtained. The repartitioning of Na(+) and Cl(-) ions between lysozyme solutions and crystals was studied. Quite unexpectedly, it was found that the longer crystals were in contact with their solution, the lower was their ion content. The development of a model for diffusive-convective transport and resulting distribution of the growth rate on facets was completed. Results obtained for a realistic growth cell geometry show interesting differences between 'growth runs' at 1g and 0g. The kinematic viscosity of lysozyme solutions of various supersaturations and salt concentrations was monitored over time. In contrast to the preliminary finding of other authors, no changes in viscosity were found over four days. The experimental setup for light scattering investigations of aggregation and nucleation in protein solutions was completed, and a computer program for the evaluation of multi-angle light scattering data was acquired.

Rosenberger, Franz↗

Integrating Characteristic Arctic Vegetation in a Land Surface Model Improves Representation of Carbon Dynamics Across a Tundra Landscape: Modeling Archive

This modeling archive is in support of the Next-Generation Ecosystem Experiments in the Arctic (NGEE Arctic) publication "Integrating Characteristic Arctic Vegetation in a Land Surface Model Improves Representation of Carbon Dynamics Across a Tundra Landscape", by Murphy et al. (2025). This archive contains model input files and outputs from landscape-scale simulations conducted using ELM, the land model component of the Department of Energy’s Energy Exascale Earth System Model (E3SM), at the Council NGEE Arctic field site (Council Road mile marker 71) on Alaska’s Seward Peninsula. Input data and model output from two sets of ELM simulations are provided. The first set of simulations were conducted with the two default ELM Arctic plant functional types (PFTs; broadleaf deciduous boreal shrub and a C3 grass) and the second set of simulations were conducted with a set of nine Arctic-specific PFTs including nonvascular mosses and lichens, graminoids, forbs, evergreen dwarf shrubs, three height classes of deciduous shrubs (dwarf, low, and low to tall), and deciduous alder shrubs (Sulman et al., 2021). Parameter names and major parameter changes in the Arctic-specific PFT configuration are described in Sulman et al. (2021) and archived in the Sulman et al. (2021) dataset (see below). Simulations were spatially explicit, covering an approximately 6.4X3.3 km domain at the Council site with a spatial resolution of 100 m for a total of 2,112 simulated grid cells under each ELM PFT configuration. The modeling archive contains meteorological forcing (seven *.nc files and one *.txt file), a domain definition file (one *.nc files), land surface configuration files (two *.nc files), parameter files (two *.nc files), annual ELM output files spanning 1980-2014 (68 *.nc files), and a User’s Guide (*pdf file). Additional information on the provided files is in the “Modeling Archive Contents” section of the User’s Guide. Model outputs are aggregated to the column scale (i.e. PFT-specific outputs are not provided here).

Murphy, Bailey [ORNL] (ORCID:0000000203995221)↗

Polymerized small molecular acceptor based all-polymer solar cells with an efficiency of 16.16% via tuning polymer blend morphology by molecular design

All-polymer solar cells (all-PSCs) based on polymerized small molecular acceptors (PSMAs) have made significant progress recently. Here, we synthesize two A-DA’D-A small molecule acceptor based PSMAs of PS-Se with benzo[c][1,2,5]thiadiazole A’-core and PN-Se with benzotriazole A’-core, for the studies of the effect of molecular structure on the photovoltaic performance of the PSMAs. The two PSMAs possess broad absorption with PN-Se showing more red-shifted absorption than PS-Se and suitable electronic energy levels for the application as polymer acceptors in the all-PSCs with PBDB-T as polymer donor. Cryogenic transmission electron microscopy visualizes the aggregation behavior of the PBDB-T donor and the PSMA in their solutions. In addition, a bicontinuous-interpenetrating network in the PBDB-T:PN-Se blend film with aggregation size of 10~20 nm is clearly observed by the photoinduced force microscopy. The desirable morphology of the PBDB-T:PN-Se active layer leads its all-PSC showing higher power conversion efficiency of 16.16%.

14 SOLAR ENERGY↗

Oxygen Vacancy Evolution at Li x V 2 O 5 /LiPON Solid State Electrochemical Interfaces Using Depth Resolved Cathodoluminescence Spectroscopy

The formation of oxygen vacancies at buried LiPON/ Li x V 2 O 5 interfaces has been observed on a near-nanometer scale and nondestructively using depth-resolved cathodoluminescence spectroscopy (DRCLS) and interfacial markers. Before electrochemical cycling, as-deposited LiPON/Li x V 2 O 5 exhibits a 1.6 eV defect optical emission, which density functional theory calculations identify as originating from oxygen vacancies. This defect appears first within a few nanometers of the buried LiPON/Li x V 2 O 5 interface without cycling, indicating that spontaneous O diffusion from the Li x V 2 O 5 lattice into LiPON may have caused these interface-localized oxygen vacancy defects. DRCLS measured the intensity and spatial distribution of this oxygen vacancy signal as a function of electrochemical cycling in a LiPON/Li x V 2 O 5 half-cell, showing oxygen vacancy signal increasing and moving deeper into the electrode with increased cycle number. Significant electrochemical irreversibility was also observed, with poor Coulombic efficiency and a 15% drop in capacity over 50 cycles. Theoretical simulations predict that the presence of oxygen vacancies increases the energy barrier for lithium diffusion significantly, indicating that this aggregation of oxygen vacancies could be another battery degradation mechanism accompanying lithiation induced phase changes.

36 MATERIALS SCIENCE↗

Engineered Catalyst Support with Improved Durability at Higher Weight Percentage of Platinum

Proton Exchange Membrane (PEM) fuel cells are a suitable electrochemical power source for heavy duty vehicle (HDV) applications due to their high efficiency and durability. The cathode of the fuel cell uses a higher geometric loading of platinum (∼0.2 to 0.4 mg Pt /cm 2 ) for the electrocatalysis of the kinetically sluggish Oxygen Reduction Reaction (ORR) which requires higher weight percent loading of the metal (∼50%) on the carbon support to decrease the catalyst layer thickness and hence, the reactant transport losses. The conventionally used supports for platinum catalyst, such as the KetjenBlack TM type high surface area carbon (HSC) features limited mesopore area for the dispersion of Pt nanoparticles leading to increased aggregation and poor durability. Here, we show a new class of carbon materials known as the Engineered Catalyst Support (ECS) developed by Pajarito Powder with higher mesopore fraction for the dispersion of higher weight percentage of Pt nanoparticles. ECS materials can disperse up to 50% Pt by weight of the catalyst thereby enabling lower catalyst layer thickness with higher performance retained after durability test. A comprehensive set of physico-chemical and electrochemical studies in membrane electrode assembly (MEA) are reported to understand the performance and durability of Pt/ECS catalysts.

08 HYDROGEN↗

Iridium Surface Oxide Affects the Nafion Interface in Proton-Exchange-Membrane Water Electrolysis

Proton-exchange-membrane water electrolyzer (PEMWE) catalyst layers consist of aggregates of catalyst particles (typically iridium) and ionomer (typically Nafion). Prior work suggests that the oxide form of Ir affects the kinetics of the oxygen-evolution reaction. However, because most catalyst-benchmarking studies are conducted ex situ in liquid electrolytes, it remains unclear how the ionomer is influenced by the catalyst oxide and affects overall cell performance. Using a suite of experimental techniques, we conduct fundamental investigations into model ink (catalyst and ionomer dispersed in solution) and thin-film systems to inform cell-level overpotential analysis as a function of three forms of Ir (metallic Ir m , oxyhydroxide IrOOH, and oxide IrO 2 ). Furthermore, nafion on Ir m has a high degree of phase separation and higher swelling, likely improving the ionic conductivity. Additionally, Nafion binds most strongly to IrOOH, likely yielding reduced kinetic overpotentials. These findings highlight the intricacies of the ionomer/Ir interface and provide insight into all catalyst-layer systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

"EGM" (Electrostatics of Granular Matter): A Space Station Experiment to Examine Natural Particulate Systems

A granular-materials experiment is being developed for a 2002 launch for Space Station deployment. The experiment is funded by NASA HQ and managed through NASA Lewis Research Center. The experiment will examine electrostatic aggregation of coarse granular materials with the goals of (a) obtaining proof for an electrostatic dipole model of grain interactions, and (b) obtaining knowledge about the way aggregation affects the behavior of natural particulate masses: (1) in unconfined dispersions (clouds such as nebulae, aeolian dust palls, volcanic plumes), (2) in semi-confined, self-loaded masses as in fluidized flows (pyroclastic surges, avalanches) and compacted regolith, or (3) in semi-confined non-loaded masses as in dust layers adhering to solar cells or space suits on Mars. The experiment addresses both planetary/astrophysical issues as well as practical concerns for human exploration of Mars or other solar system bodies. Additional information is contained in the original.

Marshall, J.↗

An assay for intermolecular exchange of alpha crystallin

An affinity column of alpha crystallin linked to cyanogen bromide-activated Sepharose was developed to study the exchange of alpha subunits. Alpha crystallin bound to the Sepharose-alpha complex was dissociated with 8 mol/l urea, followed by quantitation using high-performance reverse-phase liquid chromatography. The time course of binding at 37 degrees C showed a hyperbolic binding pattern reaching equilibrium between 6-18 hr. Under these conditions, binding of beta and gamma crystallins to the same matrix was less than 10% of the alpha values, as was binding of alpha to glycine-coupled Sepharose. This assay was used to demonstrate changes in the subunit exchange of alpha crystallins present in high molecular weight versus lower molecular weight aggregates of the human lens. These results show that this binding procedure was a specific reproducible assay that might be used to study intermolecular interactions of the alpha crystallins.

NASA Discipline Cell Biology↗

Observed Enhancement of Reflectivity and Electric Field in Long-Lived Florida Anvils

A study of two long-lived Florida anvils showed that reflectivity greater than 20 dBZ increased in area, thickness and sometimes magnitude at mid-level well downstream of the convective cores. In these same regions electric fields maintained strengths greater than 10 kV m(sup -1) for many tens of minutes and became quite uniform over tens of kilometers. Millimetric aggregates persisted at 9 to 10 km for extended times and distances. Aggregation of ice particles enhanced by strong electric fields might have contributed to reflectivity growth in the early anvil, but is unlikely to explain observations further out in the anvil. The enhanced reflectivity and existence of small, medium and large ice particles far out into the anvil suggest that an updraft was acting, perhaps in weak convective cells formed by instability generated from the evaporation and melting of falling ice particles. We conclude that charge separation must have occurred in these anvils, perhaps at the melting level but also at higher altitudes, in order to maintain fields greater than 10 kV m(sup -1) at 9 to 10 km for extended periods of time over large distances. We speculate that charge separation occurred as a result of ice-ice particle collisions (without supercooled water being present) via either a noninductive or perhaps even an inductive mechanism, given the observed broad ice particle spectra, the strong pre-existing electric fields and the many tens of minutes available for particle interactions. The observations, particularly in the early anvil, show that the charge structure in these anvils was quite complex.

Dye, James E.↗

Observed Enhancement of Reflectivity and Electric Field in Long-Lived Florida Anvils

A study of two long-lived Florida anvils showed that reflectivity >20 dBZ increased in area, thickness and sometimes magnitude at mid-level well downstream of the convective cores. In these same regions electric fields maintained strengths >10 kV m1 for many tens of minutes and became quite uniform over tens of kilometers. Millimetric aggregates persisted at 9 to 10 km for extended times and distances. Aggregation of ice particles enhanced by strong electric fields might have contributed to reflectivity growth in the early anvil, but is unlikely to explain observations further out in the anvil. The enhanced reflectivity and existence of small, medium and large ice particles far out into the anvil suggest that an updraft was acting, perhaps in weak convective cells formed by instability generated from the evaporation and melting of falling ice particles. We conclude that charge separation must have occurred in these anvils, perhaps at the melting level but also at higher altitudes, in order to maintain fields >10 kV m 1 at 9 to 10 km for extended periods of time over large distances. We speculate that charge separation occurred as a result of ice-ice particle collisions (without supercooled water being present) via either a non-inductive or perhaps even an inductive mechanism, given the observed broad ice particle spectra, the strong pre-existing electric fields and the many tens of minutes available for particle interactions. The observations, particularly in the early anvil, show that the charge structure in these anvils was quite complex.

Dye, James E.↗

Energy efficiency and biological interactions define the core microbiome of deep oligotrophic groundwater

While oligotrophic deep groundwaters host active microbes attuned to the low-end of the bioenergetics spectrum, the ecological constraints on microbial niches in these ecosystems and their consequences for microbiome convergence are unknown. Here, we provide a genome-resolved, integrated omics analysis comparing archaeal and bacterial communities in disconnected fracture fluids of the Fennoscandian Shield in Europe. Leveraging a dataset that combines metagenomes, single cell genomes, and metatranscriptomes, we show that groundwaters flowing in similar lithologies offer fixed niches that are occupied by a common core microbiome. Functional expression analysis highlights that these deep groundwater ecosystems foster diverse, yet cooperative communities adapted to this setting. We suggest that these communities stimulate cooperation by expression of functions related to ecological traits, such as aggregate or biofilm formation, while alleviating the burden on microorganisms producing compounds or functions that provide a collective benefit by facilitating reciprocal promiscuous metabolic partnerships with other members of the community. We hypothesize that an episodic lifestyle enabled by reversible bacteriostatic functions ensures the subsistence of the oligotrophic deep groundwater microbiome.

54 ENVIRONMENTAL SCIENCES↗