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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Determination of the Structures of Lignin Subunits and Nanoparticles in Solution by Small‐Angle Neutron Scattering: Towards Improving Lignin Valorization

Abstract Lignin nanoparticles (LNPs) are usually produced from lignin solution through supersaturation. The structure of the lignin in solution is still poorly understood due to structural variability of isolated lignins. Here, lignins were extracted from different plants to establish a general pattern of their structure in several lignin solvents. Lignin molecules (lignin subunits) and larger aggregates were observed in dimethyl sulfoxide (DMSO), ethylene glycol (EG) and 0.1 N NaOD solutions by small‐angle neutron scattering (SANS). It was proposed that the aggregates were composed of lignin subunits with a higher molecular weight and a higher ratio of the aliphatic to phenolic hydroxyl groups. The size, shape, and compactness are important factors that affect the uses of the LNPs, which were obtained from the SANS data for the first time. A discrepancy in the radius between SANS and DLS was discovered, pointing to a large hydration shell around the LNPs in aqueous solutions. The cytotoxicity of the corncob lignin, kraft lignin, and their LNPs were measured and compared.

Zhang, Xin↗
DOE OSTI2021

1,3,5-Trichloro-2,4,6-Trinitrobenzene: The Elusive Impurity Standard

1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is an insensitive high explosive synthesized in two steps; 1,3,5-trichloro-2,4,6-trinitrobenzene (TCTNB) is the only intermediate. Due to solubility limitations, TATB is often dissolved in dimethylsulfoxide (DMSO) for liquid chromatography-mass spectrometry (LC–MS) analyses; however, DMSO is capable of participating in a wide variety of reactions. Intending to use it as an impurity standard, TCTNB was dissolved in DMSO. A stark color change from colorless to yellow accompanied by wavelength and ion chromatogram changes occurred over 24 hours. Three compounds were identified as causing the color change. All three were present in both acetone and DMSO solutions, but, overtime the absorbance spectra of the DMSO solution changed indicating an underlying reaction occurs between these compounds and DMSO. The chemical formulas of impurities present in the TCTNB sample as well as reaction products are identified via quadrupole time of flight mass spectrometry. The chemical structures are also proposed. The combination of the solvent system, ionization technique, and halogenated/nitrated aromatic ring structures resulted in substitutions of both the chlorine and nitro groups to hydroxyl groups. Furthermore, three proposed structures were closely related to TCTNB, but only one was detected at a consistent mass and absorbance wavelength in both acetone and DMSO. This compound had undergone a chlorine to hydroxyl substitution and should be utilized for TCTNB detection.

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

Nonflammable Lithium Metal Full Cells with Ultra-high Energy Density Based on Coordinated Carbonate Electrolytes

Coupling thin Li metal anodes with high-capacity/high-voltage cathodes such as LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) is a promising way to increase lithium battery energy density. Yet, the realization of high-performance full cells remains a formidable challenge. Here, we demonstrate a new class of highly coordinated, nonflammable carbonate electrolytes based on lithium bis(fluorosulfonyl)imide (LiFSI) in propylene carbonate/fluoroethylene carbonate mixtures. Utilizing an optimal salt concentration (4 M LiFSI) of the electrolyte results in a unique coordination structure of Li + -FSI - -solvent cluster, which is critical for enabling the formation of stable interfaces on both the thin Li metal anode and high-voltage NCM811 cathode. Under highly demanding cell configuration and operating conditions (Li metal anode = 35 μm, areal capacity/charge voltage of NCM811 cathode = 4.8 mAh cm -2 /4.6 V, and anode excess capacity [relative to the cathode] = 0.83), the Li metal-based full cell provides exceptional electrochemical performance (energy densities = 679 Wh kg cell -1 /1,024 Wh L cell -1 ) coupled with nonflammability.

25 ENERGY STORAGE↗
DOE OSTI2021

High-salinity brine desalination with amine-based temperature swing solvent extraction: A molecular dynamics study

Solvent extraction desalination (SED) is a promising technique for efficiently treating high salinity brines. However, only a few studies in the literature have investigated the influence of the molecular characteristics of the organic solvents on the emergent performance of the separation process. Thus, in this work we investigate the influence of the molecular structure of four different secondary amines on the desalination process of a concentrated aqueous solution of NaCl. Molecular dynamics simulations and free energy calculations are used to obtain the thermodynamic and structural properties of the pure solvent bulk phase, as well as a homogeneous solvent-water bulk mixture. Furthermore, solvent-water and solvent-brine interfacial systems are used to explicitly analyze the water partitioning behavior in the relevant temperature range for SED. The water solubilization in these secondary amines is found to be an exothermic process. Additionally, although the hydrogen-bonding interaction between the water and solvent molecules are beneficial, this interaction is not necessarily the dominant factor for ranking the water solubility performance of the different solvents. Finally, the excess volume of mixing of the bulk solvent-water mixture, as well as the electrostatic surface features of the solvents are also found to provide important clues for screening solvent behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Navigating Large Chemical Spaces Using Graph Theory and Integer Programming

Navigating and analyzing large chemical spaces are necessary to accelerate the design and discovery of new molecules and chemical processes. In this work, we introduce a computational framework that integrates graph theory and integer programming to enable the efficient navigation of large chemical spaces. Our framework represents the chemical space as a graph, wherein nodes represent molecules and edges represent the degree of similarity or connectivity based on domain-specific information. Using the graph representation, we identify representative molecules by computing the so-called minimum dominating set (MDS), which in our context is the minimum set of molecules that is connected to all other molecules. We present a suite of solution strategies for the MDS problem including heuristic and rigorous integer programming (IP) approaches. We show that these approaches allow us to capture physicochemical properties and domain-specific logic and constraints, facilitating the identification of molecules with the target properties. We demonstrate the effectiveness of the proposed approach by navigating the chemical space of per- and polyfluoroalkyl substances (PFAS); this comprises approximately 15,000 molecular structures. We compare our framework against traditional dimensionality reduction and clustering methods such as t-SNE and K-means clustering.

Chemical structure↗
DOE OSTI2020

Exploiting Machine Learning to Efficiently Predict Multidimensional Optical Spectra in Complex Environments

The excited-state dynamics of chromophores in complex environments determine a range of vital biological and energy capture processes. Time-resolved, multidimensional optical spectroscopies provide a key tool to investigate these processes. Although theory has the potential to decode these spectra in terms of the electronic and atomistic dynamics, the need for large numbers of excited-state electronic structure calculations severely limits first-principles predictions of multidimensional optical spectra for chromophores in the condensed phase. In this work, we leverage the locality of chromophore excitations to develop machine learning models to predict the excited-state energy gap of chromophores in complex environments for efficiently constructing linear and multidimensional optical spectra. By analyzing the performance of these models, which span a hierarchy of physical approximations, across a range of chromophore–environment interaction strengths, we provide strategies for the construction of machine learning models that greatly accelerate the calculation of multidimensional optical spectra from first principles.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A Holistic Approach for Elucidating Local Structure, Dynamics, and Speciation in Molten Salts with High Structural Disorder

To examine ion solvation, exchange, and speciation for minority components in molten salts (MS) typically found as corrosion products, we propose a multimodal approach combining extended X-ray absorption fine structure (EXAFS) spectroscopy, optical spectroscopy, ab initio molecular dynamics (AIMD) simulations, and rate theory of ion exchange. Going beyond conventional EXAFS analysis, our method can accurately quantify populations of different coordination states of ions with highly disordered coordination environments via linear combination fitting of the EXAFS spectra of these coordination states computed from AIMD to the experimental EXAFS spectrum. In a case study of dilute Ni(II) dissolved in the ZnCl 2 +KCl melts, our method reveals heterogeneous distributions of coordination states of Ni(II) that are sensitive to variations in temperature and melt composition. These results are fully explained by the difference in the chloride exchange dynamics at varied temperatures and melt compositions. Finally, this insight will enable a better understanding and control of ion solubility and transport in MS.

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

Redox-homogeneous, gel electrolyte-embedded high-mass-loading cathodes for high-energy lithium metal batteries

Lithium metal batteries have higher theoretical energy than their Li-ion counterparts, where graphite is used at the anode. However, one of the main stumbling blocks in developing practical Li metal batteries is the lack of cathodes with high-mass-loading capable of delivering highly reversible redox reactions. To overcome this issue, here we report an electrode structure that incorporates a UV-cured non-aqueous gel electrolyte and a cathode where the LiNi 0.8 Co 0.1 Mn 0.1 O 2 active material is contained in an electron-conductive matrix produced via simultaneous electrospinning and electrospraying. This peculiar structure prevents the solvent-drying-triggered non-uniform distribution of electrode components and shortens the time for cell aging while improving the overall redox homogeneity. Moreover, the electron-conductive matrix eliminates the use of the metal current collector. When a cathode with a mass loading of 60 mg cm -2 is coupled with a 100 µm thick Li metal electrode using additional non-aqueous fluorinated electrolyte solution in lab-scale pouch cell configuration, a specific energy and energy density of 321 Wh kg -1 and 772 Wh L -1 (based on the total mass of the cell), respectively, can be delivered in the initial cycle at 0.1 C (i.e., 1.2 mA cm -2 ) and 25 °C.

25 ENERGY STORAGE↗
DOE OSTI2021

Mass action model of solution activity via speciation by solvation and ion pairing equilibria

Abstract Solutes and their concentrations influence many natural and anthropogenic solution processes. Electrolyte and solution models are used to quantify and predict such behavior. Here we present a mechanistic solution model based on mass action equilibria. Solvation and ion pairing are used to model speciated solute and solvent concentrations such that they correlate to a solution’s vapor pressure (solvent activity) according to Raoult’s law from dilute conditions to saturation. This model introduces a hydration equilibrium constant ( K ha ) that is used with either an ion dissociation constant ( K id ) or a hydration modifier ( m ) with an experimentally determined ion dissociation constant, as adjustable parameters to fit vapor–liquid equilibrium data. The modeled solvation equilibria are accompanied by molecular dynamics (MD) studies that support a decline in the observed degree of solvation with increased concentration. MD calculations indicate this finding is a combination of a solvent that solvates multiple solutes, and changes in a solute’s solvation sphere, with the dominant factor changing with concentration. This speciation-based solution model is lateral to established electrostatics-based electrolyte theories. With its basis in mass action, the model can directly relate experimental data to the modeled solute and solvent speciated concentrations and structures.

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

Spontaneous formation of anisotropic microrods from paraffin wax in an aqueous environment

The construction of functional nano-/micro-architectures through self-assembly and self-organization of organic molecules and polymeric materials plays an important role in the development of many technologies. In this study, we report the spontaneous formation of uniform polymer microrods with lengths of up to a few tens of micrometers from paraffin wax. Through a solvent attrition approach, colloidal structures of paraffin wax are introduced into water. After the initial growth stage, the microrods undergo morphological transformation and end-to-end aggregation, processes likely driven by thermodynamics to create equilibrium structures with minimal interfacial energies. Here, the polymer microrods can effectively absorb hydrophobic nanoparticles, indicating their potential to serve as host materials for functional components. The formation of polymer microrods from paraffin wax and their spontaneous growth mechanism discovered in this study may provide new insights to the self-assembly of microstructures.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Exploring the use of the pentaphenylcyclopentadienyl ligand in uranium chemistry: the crystal structure of (C

The reaction of UI3 with NaC5Ph5 in THF generated (η5-C5Ph5)UI2(THF)2 which was characterized by X-ray crystallography. The complex has a four-legged piano stool structure with a 2.539 Å U– (C5Ph5 ring centroid) distance that is slightly longer than the 2.504 Å distance in (η5-C5Me5)UI2(THF)3 which has a larger formal coordination number. Although the synthesis of the mono-cyclopentadienyl complex was facile, no bis-cyclopentadienyl complexes were isolated from reactions using two equivalents of the pentaphenylcyclopentadienyl ligand per uranium. In one UI3/2NaC5Ph5 synthesis, the X-ray crystal structure of (THF)3Na(η5-C5Ph5) was obtained. Attempts to reduce (η5-C5Ph5)UI2(THF)2 did not give evidence for a UII product. KC8 reductions of the in situ reaction of NdI3 and NaC5Ph5, analogous to the synthesis of (η5-C5Ph5)UI2(THF)2, yielded an X-ray crystal structure of a solvent-separated ion pair (SSIP), [K(18-crown-6)(THF)2][C5Ph5].

Chemistry↗
DOE OSTI2023

Packed Column Simulations

CO2 Capture CFD (C3FD) dataset contains STAR-CCM+ simulations of a CO2-capturing solvent flowing across packing structures in a column. This dataset contains 50 2D and 50 3D simulations, each of which spans 500 timesteps. The 2D and 3D simulation meshes have 150,073 and 3,129,815 nodes, respectively. Each node contains information about its physical location, liquid volume fraction, momentum, and node type.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2025

PFSA-Ionomer Dispersions to Thin-Films: Interplay Between Sidechain Chemistry and Dispersion Solvent

In fuel-cell catalyst layers (CLs), ionomers exists as nanoscale thin-films binding catalyst particles, wherein ionic and gaseous species transport to catalyst sites. To improve film function, ionomers have been designed based on the prototypical perfluorosulfonic acid (PFSA). Since CLs are fabricated through solution-based processing of inks, understanding how ink/dispersion solvent impacts ionomer interactions and function is important to guide future ionomer design. Herein, PFSA and its chemical derivatives are characterized from dispersion (in solvent) to thin film (cast on support) to investigate the impact of solvent water content on ionomer dispersion (structure, acidity) and resulting film properties. Dispersion characterization reveals that secondary aggregate structure depends on the sidechain chemistry, but all PFSA-based ionomers evolve similarly as dispersion becomes water-rich. The differences in aggregation alter ionomer adsorption and thin film morphology. Further, hydrophilic domain spacing and orientation are affected primarily by sidechain chemistry, and modulated by solvent composition. Thin-film conductivity correlates with hydration and nanodomain alignment, signifying the role of morphology in properties. Overall, this work provides insights into how chemistry can be used to coarse-tune structure–property relationships, while processing solvent is for fine-tuning of dispersion-film interplay for controlling CL-ionomer function, which can be translated to other chemistries and ink formulations.

25 ENERGY STORAGE↗
DOE OSTI2025

Toward Computation-Guided Design of Tunable Organic-Inorganic CdS Quantum Dot Binary Superlattices

Combining the advantages of structural programmability in sequence-defined biomimetic molecules and the controllable packing geometry in nanoparticle superlattices, we demonstrate a self-assembled organic-inorganic superlattice whose structure can be altered with the slightest change in the sequence of the organic counterpart. Here, oleate-coated CdS quantum dots (QDs) form a square-packed superlattice with a 1:1 molar equivalence of a di-block amphiphilic peptoid (Nbrpe6Dig) in chloroform. In contrast, no apparent structure is observed in the organic solvent alone. Based on theoretical evidence, we show that the assembly is a binary superlattice where both the CdS QDs and the peptoids serve as building blocks and further predict a correlation between the superlattice structure and the peptoid sequence. The computationally guided prediction is validated by experiments where superlattice transformation is observed with modified peptoids. The mechanism identified in our work inspires new ways to control and tune organic-inorganic hybrid nanomaterial self-assembly.

Qi, Xin↗
DOE OSTI2024

Anode Upcycling via Tailored Solvent Treatment

To achieve a truly closed-loop direct recycling process for lithium-ion batteries, all component materials must be recovered. To date, direct recycling method development has primarily focused on the high-value transition-metal cathode materials, while the inherently lower-value graphite has been challenging to recover in a cost-effective manner. However, end-of-life graphite contains a unique engineered value due to the presence of the solid electrolyte interphase (SEI). Growth of the SEI during the cell's active lifetime stabilizes the electronically reactive graphite surface through an irreversible consumption of Li, and thus necessitates both excess lithiation of the cathode and a costly and time-intensive formation procedure during manufacturing. An optimized pre-formed SEI that capitalizes on existing SEI components from end-of-life batteries has the potential to significantly reduce cathode lithiation requirements and eliminate the critical bottleneck of formation cycling during cell remanufacturing. Further, retaining Li at the anode obviates the need for a separate Li leaching and recovery step, improving the overall efficiency of the direct recycling line. In this work, we present a novel approach to "upcycling" spent graphite through use of tailored chemical treatment to remove adverse (i.e., highly resistive and/or poorly passivating) SEI species while retaining beneficially passivating components. We have explored a rational set of solvents spanning a range of polarity, proticity, and molecular size to evaluate structure-property-performance relationships between applied solvent(s), removed and remaining SEI species, and electrochemical response of the resulting graphite product. Further, we have developed and optimized a robust and holistic analysis procedure that couples symmetric-cell electrochemical testing, multi-modal materials characterization, and advanced electrochemical modeling. These analysis results inform a set of correlative metrics for graphite performance relative to both solvent properties and upcycled SEI composition. We demonstrate effective tunability in the residual SEI composition by varying solvent identity and concentration, and report on several promising solvent systems that achieve comparable or performance to pristine graphite.

anode recycling↗
DOE OSTI2025

Epoxide Alcoholysis over M-BEA Zeolites: Effects of Alcohol Chain Length on Rates and Regioselectivities

The structures of nucleophilic reactants affect their coordination behavior among solvent molecules and kinetics of reactions with surface intermediates within the confines of fluidfilled pores of zeolites and other microporous materials. Consequently, rates and regioselectivities of diverse chemistries may depend sensitively on nucleophile identity in manners not observed for classic fluid phase reactions. Here, we examine the impact of varying the primary alcohol (ROH) chain length on the kinetics of 1,2-epoxybutane (C 4 H 8 O) ring-opening within Brønsted (Al-BEA) and Lewis acid (Zr-BEA) zeolites. Turnover rates increase by factors of ∼6 (Al-BEA) and 4-fold (Zr-BEA) between methanol and 1-hexanol, yet the reaction mechanisms remain comparable. Despite modest rate differences, apparent activation enthalpies calculated from rates and activities of solvated reactants decrease linearly by 12 (Al-BEA) to 33 kJ mol −1 (Zr- BEA) with increased proton affinity, which suggests bond formation energies for the nucleophile strongly influence rate increases. The molecular interpretation of these trends demonstrates, however, that the solvation of ring-opening transition states by zeolite pore structures and solvent molecules also governs rates. The impact of local solvating interactions appears most directly as changes in regioselectivities, which tend to enhance terminal alcohol formation with increasing ROH chain length. Regioselectivities largely do not vary with differences in fluid composition for a given ROH. The addition of H 2 O increases the number of hydrogen bonds among reactive species, and trends in regioselectivities imply that the decreased hydrogen bonding ability of longer chain ROH, and not the nucleophile strength or steric bulk, determines the regioselectivities of the resulting products. This work provides direct experimental evidence that nucleophilicity and hydrogen bonding influence reaction barriers and regioselectivities in zeolitecatalyzed epoxide ring-opening, offering pathways to better control reaction kinetics.

acidic zeolites↗