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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Robust constrained tension control for high-precision roll-to-roll processes

Tension control is critical for maintaining good product quality in most roll-to-roll (R2R) production systems. Previous work has primarily focused on improving the disturbance rejection performance of tension controllers. Here, a robust linear parameter-varying model predictive control (LPV-MPC) scheme is designed to enhance the tension tracking performance of a pilot R2R system for deposition of materials used in flexible thin film applications. The performance of a tension controller may degrade due to disturbances associated with model uncertainties and the slowly-changing dynamics in R2R systems. We introduce a method that separately treats these two sources of disturbance. The controller utilizes an incremental model to eliminate the errors caused by the mismatch between the nominal model and the actual system. A tube-based MPC formulation combined with scheduled parameters adequately updates models and corrects for the time-varying dynamics. Constraints on the rated motor torque are incorporated in the MPC to maintain the controller reliability and avoid machine failures. We illustrate the operation of our control algorithm through simulation of an actual R2R system. The controller outperforms the benchmarks in terms of fast transient response and offset-free tension tracking. Furthermore, it also demonstrates immunity from variations due to parametric uncertainties.

42 ENGINEERING↗
DOE OSTI2021

Uranium(VI) attenuation in a carbonate-bearing oxic alluvial aquifer

Uranium minerals are commonly found in soils and sediment across the United States at an average concentration of 2–4 mg/kg. Uranium occurs in the environment primarily in two forms, the oxidized, mostly soluble uranium(VI) form, or the reduced, sparingly soluble reduced uranium(IV) form. Here we describe subsurface geochemical conditions that result in low uranium concentrations in an alluvial aquifer with naturally occurring uranium in soils and sediments in the presence of complexing ligands under oxidizing conditions. Groundwater was saturated with respect to calcite and contained calcium (78–90 mg/L) with elevated levels of carbonate alkalinity (291–416 mg/L as HCO 3 -). X-ray adsorption near edge structure (XANES) spectroscopy identified that sediment-associated uranium was oxidized as a uranium(VI) form (85%). Calcite was the predominant mineral by mass in the ultrafine fraction in uranium-bearing sediments (>16 mg/kg). Furthermore, groundwater geochemical modeling indicated calcite and/or a calcium-uranyl-carbonate mineral such as liebigite in equilibrium with groundwater. The δ 13 C (0.57‰ ± 0.15‰) was indicative of abiotic carbonate deposition. Thus, solid-phase uranium(VI) associated with carbonate is likely maintaining uranium(VI) groundwater levels below the maximum contaminant level (MCL; 30 µg/L), presenting a deposition mechanism for uranium attenuation rather than solely a means of mobilization.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2026

How alkyl branching shapes structure in imidazolium and pyrrolidinium NTf 2 ionic liquids

High-energy X-ray scattering experiments and molecular dynamics (MD) simulations were carried out on ionic liquids (ILs) consisting of 1-alkyl-3-methylimidazolium and 1-alkyl-1-methylpyrrolidinium cations. These cations were paired with bis(trifluoromethylsulfonyl)amide anions and identical alkyl tails were used for both cationic species. The goal of this work is to investigate how the nanoscale structure of the ionic liquid changes with the length and with the degree of branching of the alkyl tail, for ILs having a common anion. We investigate spatial correlations in the intermolecular region, focusing on the intrinsic charge-charge interactions that characterize all ionic liquids, as well as the nanoscale domain segregation that is present in IL species with significant nonpolar components.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Calcium-organic matter fouling in nanofiltration: Synchrotron-based X-ray fluorescence and absorption near-edge structure spectroscopy for speciation

Calcium (Ca)-enhanced organic matter (OM) fouling of nanofiltration (NF) membranes leads to reduced flux during desalination and requires frequent cleaning. Fouling mechanisms are not fully understood, which limits the development of targeted fouling control methods. This study employed synchrotron-based X-ray fluorescence (XRF) and X-ray absorption near-edge structure (XANES) spectroscopy to quantify the spatial distribution and mass of Ca deposition as well as changes in the Ca coordination environment characteristic of specific fouling mechanisms, respectively. Bench-scale filtration experiments were performed using feed solutions containing Ca and ten different types of organic matter (OM), as well as the common scalants, calcium carbonate (CaCO 3 ) and calcium sulfate (CaSO 4 ). Osmotic backwash (OB) was performed at regular intervals for fouling control. Ca-OM aggregation resulted in greater flux decline and lower flux recovery during OB than Ca conditioning of membranes followed by filtration of feed solution with OM. Linear combination fitting (LCF) of XANES absorption spectra from fouled membranes indicated that Ca-OM aggregation preferentially occurred for OM types that exhibited both high carboxylic group and negative charge density. Consequently, these OM types exhibited greater deposition of Ca and TOC on the membrane surface when compared to other OM types. For the coexistence of scalants and OM, Ca speciation within the fouling layer was characteristic of both Ca bound to the membrane (i.e. potential bridging, charge screening) as well as Ca-OM aggregation and deposition mechanisms, while a range of crystal polymorphs were observed to occur simultaneously. XRF and XANES represent powerful tools for the elucidation of NF fouling mechanisms by quantification of Ca deposition as well as Ca speciation. Fouling control methods should target OM types with high carboxyl group density and negative charge to neutralize or eliminate interactions with Ca.

42 ENGINEERING↗
DOE OSTI2026

Organic colloid composition in variable-redox porewaters within a mountainous floodplain

Redox gradients, often driven by changes in sediment moisture levels in porous, heterogeneous groundwater systems, create dynamic conditions that may promote the production and transport of colloids within natural waters. While much research has focused on the inorganic composition of colloids, the organic composition remains less well understood. Organic matter (OM) in colloids may associate with minerals, complex metal ions, and serve as an electron donor for microbial respiration; therefore, its composition is of high interest. We examined the composition of porewater OM along a redox gradient in a riparian soil located along the Slate River in Crested Butte, Colorado, USA as a function of depth (90, 130, 200, and 350 cm below ground surface). All depths were oxic to suboxic, except 200 cm, where the products of iron and sulfate reduction were observed concomitant with an increase in dissolved and/or colloidal OM, pH, alkalinity, and conductivity. We investigated the composition of porewater using correlated scanning transmission X-ray microscopy and transmission electron microscopy. We observed a change in the OM chemistry from carboxylate-rich at the 200 cm depth (where it was also enmeshed with non-crystalline iron) to phenol- and substituted-aromatic-rich at other depths. Radiocarbon dating revealed carbon in porewater at 200 cm was younger than depths above and below. Soil porewater can flow down into the underlaying gravel bed during baseflow conditions, thus we speculate whether riparian porewater could transport iron- and carboxylate-rich organic colloids into surrounding surface waters through the gravel bed conduit.

Alpine floodplain↗
DOE OSTI2021

Location-Dependent Cobalt Deposition in Smartphone Cells upon Long-Term Fast-Charging Visualized by Synchrotron X-ray Fluorescence

In this work, we investigate the transition-metal dissolution of the layered cathode material LiCoO 2 upon repeated fast-charging of three smartphone batteries from different manufacturers using synchrotron micro X-ray fluorescence (μ-XRF). Using this spatially resolved technique, dissolution of Co and subsequent location-dependent deposition on the anode are observed. μ-XRF mapping of selected parts of the anode electrode sheets, such as electrode folds and edges of the jelly roll, reveals the difference in the way Co is deposited on specific regions of the anode electrode. While some folds show no depositions, edges of the anode show gradually accumulating Co depositions. Furthermore, careful quantification of the dissolved Co reveals that the capacity loss scales with the amount of deposited Co on the anode, that is, total Co loss from within the cathode. Soft X-ray absorption spectroscopy of the Co depositions on the anode shows that Co is mainly deposited in a reduced 2 + state. While optimization of the fast-charging protocol mitigates Li plating on the anode, no significant difference in the amount of deposited Co can be observed between an optimized and a nonoptimized fast-charging algorithm.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Mercury Removal from Contaminated Water by Wood-Based Biochar Depends on Natural Organic Matter and Ionic Composition

Biochars can remove potentially toxic elements, such as inorganic mercury [Hg(II)] from contaminated waters. However, their performance in complex water matrices is rarely investigated, and the combined roles of natural organic matter (NOM) and ionic composition in the removal of Hg(II) by biochar remain unclear. Here, we investigate the influence of NOM and major ions such as chloride (Cl – ), nitrate (NO 3 – ), calcium (Ca 2+ ), and sodium (Na + ) on Hg(II) removal by a wood-based biochar (SWP700). Multiple sorption sites containing sulfur (S) were located within the porous SWP700. In the absence of NOM, Hg(II) removal was driven by these sites. Ca 2+ bridging was important in enhancing removal of negatively charged Hg(II)-chloro complexes. In the presence of NOM, formation of soluble Hg-NOM complexes (as seen from speciation calculations), which have limited access to biochar pores, suppressed Hg(II) removal, but Cl – and Ca 2+ could still facilitate it. The ability of Ca 2+ to aggregate NOM, including Hg-NOM complexes, promoted Hg(II) removal from the dissolved fraction (<0.45 μm). Hg(II) removal in the presence of Cl – followed a stepwise mechanism. Weakly bound oxygen functional groups in NOM were outcompeted by Cl – , forming smaller-sized Hg(II)-chloro complexes, which could access additional intraparticle sorption sites. Therein, Cl – was outcompeted by S, which finally immobilized Hg(II) in SWP700 as confirmed by extended X-ray absorption fine structure spectroscopy. We conclude that in NOM containing oxic waters, with relatively high molar ratios of Cl – : NOM and Ca 2+ : NOM, Hg(II) removal can still be effective with SWP700.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Wildfire Produces Transient Minerals: Speciation, Reactivity, and Fate of Iron and Manganese in Surface Soils Post Wildfire

Wildfire leads to the deposition of an ash layer at the land surface. This material typically has alkaline properties, abundant pyrogenic carbon, and elevated metal concentrations compared to surface soils. Here, we compare ash and surface soils collected three weeks and two years after the Glass Fire (St. Helena, California, USA) to determine how wildfire affects the speciation and reactivity of iron (Fe) and manganese (Mn), two micronutrients that influence many soil processes. Synchrotron-based analyses revealed that wildfire generated stable Fe oxides like maghemite (γ-Fe 2 O 3 ) and hematite (α-Fe 2 O 3 ) that likely derived from surface soil or mineral dust rather than the vegetation, and Mn oxides such as hausmannite (Mn 3 O 4 ) and bixbyite (Mn 2 O 3 ) that derived primarily from aboveground biomass. However, these pyrogenic minerals were absent in soils collected two years after the fire. Their loss from the soil surface may result from a combination of erosion, translocation to deeper soil layers, and chemical weathering. The latter hypothesis is supported by the enhanced mobilization of Fe and Mn from ash upon the addition of pyoverdine, a model biogenic ligand. The increased mobility of micronutrients from fire-derived minerals in ash in response to microbial and root exudation may facilitate postfire soil and vegetation recovery.

bixbyite↗
DOE OSTI2026

Enhanced Manganese Oxidation at the Biofilm–Fluid Interface Drives Pore-Scale Patterns in Mineral Precipitation

Microbial oxidation of manganese (Mn) from aqueous Mn(II) to solid-phase Mn(III, IV) minerals catalyzes Mn(II) removal in natural and engineered porous systems. However, little is known about the spatiotemporal evolution of Mn biomineralization in confined spaces that experience simultaneous Mn(II) delivery and Mn oxide precipitation. Here, we combine time-lapse microscopy, image analysis, and mass spectrometry to quantify the extent and rate of Mn biomineralization by Pseudomonas putida GB-1 in an optically transparent two-dimensional porous medium. We found that Mn(II) oxidation initially occurred within biofilms but shifted over time toward the edges of biofilms in contact with pore fluid. Minerals precipitated outside of the initial biofilm footprint likely due to surface-mediated oxidation of Mn(II) by nascent biogenic Mn oxides, reinforcing a gradient in mineral accumulation from the Mn(II) source near the reactor inlet to the outlet. The rate of mineral precipitation outside the biofilm footprint surpassed the rate of mineral accumulation inside biofilms within 6 h and accounted for two-thirds of the total Mn oxide mass in the pore space at the end of the experiment. This work advances a mechanistic understanding of coupled biotic and abiotic Mn oxidation in porous environments while providing a novel platform to quantify microbe-mineral-fluid interactions.

Biofilms↗
DOE OSTI2023

Biosynthesis of Haloterpenoids in Red Algae via Microbial-like Type I Terpene Synthases

Red algae or seaweeds produce highly distinctive halogenated terpenoid compounds, including the pentabromochlorinated monoterpene halomon that was once heralded as a promising anticancer agent. The first dedicated step in the biosynthesis of these natural product molecules is expected to be catalyzed by terpene synthase (TS) enzymes. Recent work has demonstrated an emerging class of type I TSs in red algal terpene biosynthesis. However, only one such enzyme from a notoriously haloterpenoid-producing red alga (Laurencia pacifica) has been functionally characterized and the product structure is not related to halogenated terpenoids. Herein, we report 10 new type I TSs from the red algae Portieria hornemannii, Plocamium pacificum, L. pacifica, and Laurencia subopposita that produce a diversity of halogenated mono- and sesquiterpenes. Here we used a combination of genome sequencing, terpenoid metabolomics, in vitro biochemistry, and bioinformatics to establish red algal TSs in all four species, including those associated with the selective production of key halogenated terpene precursors myrcene, trans-β-ocimene, and germacrene D-4-ol. These results expand on a small but growing number of characterized red algal TSs and offer insight into the biosynthesis of iconic halogenated algal compounds that are not without precedence elsewhere in biology.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Water or Anion? Uncovering the Zn 2+ Solvation Environment in Mixed Zn(TFSI) 2 and LiTFSI Water-in-Salt Electrolytes

Applications of aqueous zinc batteries for grid-scale energy storage are limited by their poor reversibility and the competing water splitting reaction. The recent invention of a water-in-salt (WIS) electrolyte concept provides a new route enabling a stable and highly reversible aqueous zinc battery chemistry. In the present work, a mixed zinc bis(trifluoromethane sulfonyl)imide (Zn(TFSI) 2 ) and LiTFSI WIS electrolyte was studied using X-ray total scattering, X-ray absorption, and Fourier transform infrared spectroscopy in conjunction with classical molecular dynamics simulations. It was found that, in the highly concentrated WIS electrolyte consisting of 1 m Zn(TFSI) 2 and 20 m LiTFSI, Zn 2+ cations are mainly solvated by six waters in their first solvation shell, while the TFSI – anions are completely excluded. This ion solvation picture is fundamentally different from the previous understandings. The results suggest that additional studies are needed to fully understand the unusual stability and reversibility of zinc-WIS electrolyte-based batteries.

25 ENERGY STORAGE↗
DOE OSTI2026

Depolymerization of Vinyl Polymers

Depolymerization is a promising approach to reduce plastic waste by regenerating monomers from polymers, presenting a compelling solution to maintain a circular polymer economy. However, vinyl polymers with all-carbon backbones are especially difficult to depolymerize due to significant thermodynamic and kinetic barriers. Developments in reversible-deactivation radical polymerization and catalytic methods demonstrate how tuning polymer structure and reaction conditions can address these challenges. This Viewpoint revisits early studies on radical depolymerization and recent advances enabling monomer recovery at lower temperatures. Exciting current trends to utilize depolymerization as a strategy for tuning polymer material properties and upcycling waste polymer to high-value products are discussed. Finally, we outline key directions to make vinyl polymer depolymerization scalable, efficient, and economically viable.

depolymerization↗