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At least 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Carbon-carbon interactions in warm dense titanium carbide

Encouraged by experimental reports of diamond precipitation in carbon-containing materials under warm dense matter conditions and in shock compression experiments, we examine the behavior of carbon in TiC using density functional theory-molecular dynamics simulations. Two polymorphs of TiC are considered, the ambient-pressure B1 ($Fm$$\overline{3}$$m$) structure in which C-C interactions are prevented by geometric constraints, and a high-pressure Cmcm structure in which C atoms condense into zigzag chains. Chemistry-inspired bonding analyses confirm the covalently bound nature of these chains and further illuminate important interatomic interactions in both structures. Upon melting of B1 TiC, new short-range C-C interactions develop in the liquid, while the pre-existing C-C interactions in Cmcm TiC persist in the liquid. Here, the resulting carbon networks in the melt provide a promising environment for eventual diamond nucleation.

Ab initio molecular dynamics↗
DOE OSTI2024

IDAES-PSE 2.5.0 Release

The Institute for the Design of Advanced Energy Systems (IDAES) Integrated Platform is a versatile computational environment offering extensive process systems engineering (PSE) capabilities for optimizing the design and operation of complex, interacting technologies and systems. IDAES enables users to efficiently search vast, complex design spaces to discover the lowest cost, most environmentally sustainable solutions while supporting the full process modeling lifecycle, from conceptual design to dynamic optimization and control. The extensible, open platform empowers users to create models of novel processes and rapidly develop custom analyses, workflows, and end-user applications. IDAES-PSE 2.5.0 Release Highlights Upcoming Changes IDAES will be switching to the new Pyomo solver interface in the next release. Whilst this will hopefully be a smooth transition for most users, there are a few important changes to be aware of. The new solver interface uses a different version of the IPOPT writer (“ipopt_v2”) and thus any custom configuration options you might have set for IPOPT will not carry over and will need to be reset. By default, the new Pyomo linear presolver will be activated with ipopt_v2. Whilst are working to identify any bugs in the presolver, it is possible that some edge cases will remain. IDAES will begin deploying a new set of scaling tools and APIs over the next few releases that make use of the new solver writers. The old scaling tools and APIs will remain for backward compatibility but will begin to be deprecated. New Models, Tools and Features New diagnostics check for near-parallel variables and constraints. New diagnostics tools for identifying causes of infeasibility in models. New example for creating a custom model of a liquid-liquid extractor unit operation. Bug Fixes Fixed bug in Gibbs reactor that caused it to appear to have additional spurious degrees of freedom. Fixed bug in the Modular Property Framework that would cause errors when trying to use phase-based material balances with phase equilibria. Fixed bug in Modular Properties Framework that caused errors when initializing models with non-vapor-liquid phase equilibria. Testing and Robustness Deployed the IDAES Diagnostics Toolbox to confirm that there are no structural or numerical issues in the core model libraries. Additional robustness tests for core model, and some associated improvements in the converge tester class. Fixed a number of issues that were causing unexpected warnings to be emitted during testing. Deprecations and Removals Removed examples for RIPE tool which has not been supported for a number of releases.

AS↗
DOE OSTI2021

Material Control & Accountancy for Molten Salt Reactors (FY2021 Report)

There is significant domestic and international interest, investment, and research and development momentum to pursue advanced nuclear reactor technologies. Molten salt reactor (MSR) concepts display the largest variability in fuel type and design features among the current advanced concepts. MSRs have been proposed with various core designs, sizes (power), and fuel cycles. Salt-fueled molten salt systems represent the only advanced reactor type with fuel that is not in a solid form during operation. These “liquid-fueled” MSRs are unique from perspectives of fuel fabrication, spent irradiated fuel and waste components, licensing, and material control and accountability (MC&A) including the potential of fissile material holdup. The liquid fuel salt is the defining distinction in comparison to other advanced reactors that propose TRI-structural ISOtropic particle fuel pebbles, various coolant options (e.g., molten salts or metals, high temperature gas), or small modular alternatives using solid fuel variants including both light water reactors and non-light water reactors. MSRs are appealing to the nuclear energy industry because of the diverse reactor characteristics they can support including various neutron energy spectra, fueling requirements, fuel cycles, and/or fuel utilization. However, because of the significant deviation and diversity of a salt-fueled system compared to traditional solid fuel light water-cooled reactors (LWRs), the history, regulatory licensing framework, modeling capabilities, and supporting engineering technology are either lacking or, in some cases, nonexistent. Therefore, the research community is actively supporting advanced MSR development on many of these fronts in particular to assist MSR vendors with licensing requirements. ORNL is leading the research and development of respective MC&A approaches for salt-fueled MSRs. This report summarizes the research performed at Oak Ridge National Laboratory (ORNL) under the US Department of Energy, Office of Nuclear Energy, Advanced Reactor Safeguards (ARS) program to investigate safeguards and security by design concepts, licensing and regulatory considerations, and dynamic system-level modeling to understand radioisotope concentrations for salt-fueled MSRs. The report builds upon the previous research and literature, identifies the MC&A challenges inherent to a salt-fueled MSR, reviews current regulatory frameworks for LWRs and their applicability towards salt-fueled MSRs, summarizes the status and progress of an MSR dynamic modeling tool, and discusses a prospective MC&A approach based on the Molten Salt Demonstration Reactor (MSDR) model.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2023

Development of a Novel Magnesium Alloy for Thixomolding® of Automotive Components (Final Report)

Magnesium (Mg) alloy die-castings are increasingly used in the automobile industry to achieve cost effective mass reduction, especially in systems where multiple components can be integrated into a single thin wall die-casting. However, there are several component quality restrictions in thin-walled Mg die castings, including variability in dimensional accuracy, part-to-part variation in mechanical properties, and porosity in the final part, which has limited the continued growth of die-cast components in the automobile industry. An alternative to die-casting is the process of thixomolding®. While the die-casting process relies on filling a mold at high speeds with the alloy in the completely molten state, the thixomolding® process fills a mold with a thixotropic alloy in a semi-solid slurry state at a temperature between the liquidus and solidus temperatures. Ideally, the material should be ~30–65% solid rather than being completely liquid at the beginning of the injection process. Advantages of the thixomolding® process include a finer grain structure, lower porosity, improved dimensional accuracy, improved part-to part consistency, improved mechanical properties, particularly ductility in the component, the ability to reduce wall thickness for mass savings, and longer tool life due to lower process temperatures. The objective of this collaborative project between Oak Ridge National Laboratory, FCA US LLC, and Leggera Technologies was to develop one or more novel Mg alloys more suitable for thixomolding® automotive structural components than the current die-casting alloys used for this process. The primary interest was to improve ductility while maintaining tensile and fatigue strengths, as these are properties that are critical for use in body and chassis structural applications. Since good corrosion resistance is also desirable for this application, this property was also considered when evaluating promising alloy compositions. An initial evaluation of existing components thixomolded® using AM60 was performed and microstructure, and tensile properties were evaluated for the baseline alloy. Targets were established for ease of processing (characterized by the melting range defined as the difference between the liquidus and the solidus), strength, and ductility. Computational modeling was used to identify promising alloys and selected alloys were cast in laboratory scale heats. Properties measured from laboratory scale heats were used to down-select two alloys for further evaluation and component fabrication. Two alloys were prepared in industrial scale heats, cut into small pieces (chips), and thixomolding® trials were initiated. Trial components were successfully fabricated using one alloy composition, but it was concluded that further refinement of the thixomolding® process parameters are required to successfully fabricate component using second alloy. Microstructure and mechanical properties were evaluated on the material removed from the fabricated component and properties were compared to the baseline alloy. Although mechanical properties of the alloys showed improvement over the baseline alloy, it was determined that modifications to the thixomolding® process would result in better microstructure control with further improvement in properties leading to successful commercialization. A provisional patent application has already been filed on the new alloys developed as part of the project.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Emergent discrete space-time crystal of Majorana-like quasiparticles in chiral liquid crystals

Time crystals spontaneously break the time translation symmetry, as recently has been frequently reported in quantum systems. Here we describe the observation of classical analogues of both 1+1-dimensional and 2+1-dimensional discrete space-time crystals in a liquid crystal system driven by a Floquet electrical signal. These classical time crystals comprise particle-like structural features and exists over a wide range of temperatures and electrical driving conditions. The phenomenon-enabling period-doubling effect comes from their topological Majorana-like quasiparticle features, where periodic inter-transformations of co-existing topological solitons and disclinations emerge in response to external stimuli and play pivotal roles. Our discrete space-time crystals exhibit robustness against temporal perturbations and spatial defects, behaving like a time-crystalline analogues of a smectic phase. Our findings show that the simultaneous symmetry breaking in time and space can be a widespread occurrence in numerous open systems, not only in quantum but also in a classical soft matter context.

FOS: Physical sciences↗
DOE OSTI2025

In Situ Surface Reconstruction via Lithium Residue Regulation for Direct Recycling of Ni-Rich Cathodes

Surface stability is crucial for the long cycling performance of Ni-rich cathodes, as it dictates and governs side reactions, preserves crystal integrity, and mitigates capacity degradation during cycling. For spent Ni-rich cathodes targeted for one-step direct recycling, constructing a robust and stable surface is particularly challenging because prior cycling induces severe structural and morphological degradation. Here, in this study, we introduce an in situ surface reconstruction strategy that converts surface lithium residues into a protective layer via a direct liquid-phase coating with ammonium dihydrogen phosphate (ADP). During the process, residual lithium remaining after the hydrothermal relithiation is removed, while a conformal lithium phosphate (Li 3 PO 4 , LPO) layer is formed to act as both a chemical barrier and a structural stabilizer. This dual function enhances cycling stability and rate capability in regenerated cathodes, and the approach is applicable to various Ni-rich compositions including spent LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) and scrap LiNi 0.866 Mn 0.066 Co 0.05 Al 0.018 O 2 (NCMA). Its scalability and compositional versatility make it a promising route for sustainable regeneration of high-performance cathode materials.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Ionic-content-driven restructuring of spirobisindane ionene networks: implications for mechanics, self-healing, and gas transport

Polymers of intrinsic microporosity (PIMs) offer exceptional gas permeability but remain brittle and susceptible to physical aging, limiting their durability in separation applications. Here, we introduce a reconfigurable microporous polymer network that uniquely integrates permanent PIM microporosity with autonomous, intrinsic self-healing driven by imidazolium-based ionic motifs. Spirobisindane units generate the intrinsic free-volume architecture, while an imidazolium-containing polyamide ionene supplies dynamic ionic and hydrogen-bonding interactions that reorganize under mild activation. Incorporation of imidazolium-based ionic liquids further tunes cohesion, mobility, and densification, enabling the network to relax, re-associate, and retain microporosity without structural collapse. Through a comprehensive multiscale approach combining spectroscopy, scattering, thermal and mechanical characterization with all-atom molecular dynamics and density functional theory calculations, we elucidate how ionic content, as a single control parameter that reshapes free-volume distributions, modulates local coordination environments, and governs relaxation and healing kinetics. At intermediate ionic loadings, the networks achieve rapid, repeatable self-healing while maintaining CO$_2$ selectivity, demonstrating an optimal balance between segmental mobility and structural integrity. By establishing how hierarchical ionic interactions couple structure, dynamics, and transport in microporous ionene networks, this work provides generalizable design rules for adaptive soft-matter systems that require simultaneous mechanical resilience, reconfigurability, and selective gas transport.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Reinforcement learning based hybrid bond-order coarse-grained interatomic potentials for exploring mesoscale aggregation in liquid–liquid mixtures

Exploring mesoscopic physical phenomena has always been a challenge for brute-force all-atom molecular dynamics simulations. Although recent advances in computing hardware have improved the accessible length scales, reaching mesoscopic timescales is still a significant bottleneck. Coarse-graining of all-atom models allows robust investigation of mesoscale physics with a reduced spatial and temporal resolution but preserves desired structural features of molecules, unlike continuum-based methods. Here, we present a hybrid bond-order coarse-grained forcefield (HyCG) for modeling mesoscale aggregation phenomena in liquid–liquid mixtures. The intuitive hybrid functional form of the potential offers interpretability to our model, unlike many machine learning based interatomic potentials. We parameterize the potential with the continuous action Monte Carlo Tree Search (cMCTS) algorithm, a reinforcement learning (RL) based global optimizing scheme, using training data from all-atom simulations. The resulting RL-HyCG correctly describes mesoscale critical fluctuations in binary liquid–liquid extraction systems. cMCTS, the RL algorithm, accurately captures the mean behavior of various geometrical properties of the molecule of interest, which were excluded from the training set. The developed potential model along with the RL-based training workflow could be applied to explore a variety of other mesoscale physical phenomena that are typically inaccessible to all-atom molecular dynamics simulations.

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

Droplet bioprinting of acellular and cell-laden structures at high-resolutions

Advances in digital light projection(DLP) based (bio) printers have made printing of intricate structures at high resolution possible using a wide range of photosensitive bioinks. A typical setup of a DLP bioprinter includes a vat or reservoir filled with liquid bioink, which presents challenges in terms of cost associated with bioink synthesis, high waste, and gravity-induced cell settling, contaminations, or variation in bioink viscosity during the printing process. Here, we report a vat-free, low-volume, waste-free droplet bioprinting method capable of rapidly printing 3D soft structures at high resolution using model bioinks and model cells. A multiphase many-body dissipative particle dynamics model was developed to simulate the dynamic process of droplet-based DLP printing and elucidate the roles of surface wettability and bioink viscosity. Process variables such as light intensity, photo-initiator concentration, and bioink formulations were optimized to print 3D soft structures (∼0.4–3 kPa) with a typical layer thickness of 50 µm, an XY resolution of 38 ± 1.5 μm and Z resolution of 237 ± 5.4 µm. To demonstrate its versatility, droplet bioprinting was used to print a range of acellular 3D structures such as a lattice cube, a Mayan pyramid, a heart-shaped structure, and a microfluidic chip with endothelialized channels. Droplet bioprinting, performed using model C3H/10T1/2 cells, exhibited high viability (90%) and cell spreading. Additionally, microfluidic devices with internal channel networks lined with endothelial cells showed robust monolayer formation while osteoblast-laden constructs showed mineral deposition upon osteogenic induction. Overall, droplet bioprinting could be a low-cost, no-waste, easy-to-use, method to make customized bioprinted constructs for a range of biomedical applications.

DLP↗
DOE OSTI2021

Exploring the composition, phase separation and structure of AgFe alloys for magneto-optical applications

Bimetallic alloys with large discrepancies in atomic radii and crystal structure typically yield systems that are highly immiscible, even at high temperatures. The Ag x Fe 1−x binary system has limited solid and liquid solubility and thus phase separated Ag + Fe alloys should result. Furthermore, Ag has interesting plasmonic properties and Fe is a strong ferromagnet, thus magneto-plasmonic nanoparticles/films should result due to their phase separation. We have leveraged a combinatorial sputter deposition to synthesize thin films with a large Ag x Fe 1−x (0.19 < x < 0.84) phase space to correlate the composition and structure to the optical and magnetic properties for both as-deposited and annealed compositions.

Bimetallic alloys↗
DOE OSTI2024

Normal mode description of phases of matter: Application to heat capacity

Understanding thermodynamics in liquids at the atomic level is challenging because of strong atomic interactions and lack of spatial symmetry. Recent prior theoretical works have focused on describing heat capacity of liquids in terms of phonon-like excitations but often rely on fitting factors and assumptions. In this work, we propose characterizing various phases in terms of instantaneous normal modes (INMs) of structural snapshots from molecular dynamics simulations of single-element systems over wide ranges of temperature and pressure. We use the INMs to build a mode-level microscopic description of heat capacity and demonstrate that heat capacity of liquids can be described by a combination of both solidlike and gaslike degrees of freedom, leading to a more unified framework to fundamentally describe heat capacity of all three phases of matter: solid, liquid, and gas. Published by the American Physical Society 2024

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Microbe-Encapsulated Silica Gel Biosorbents for Selective Extraction of Scandium from Coal Byproducts

Establishing an inexpensive and environmentally friendly scandium (Sc) supply is critical for the development of clean energy technologies. However, refining Sc from Sc-bearing sources using current technologies poses economic and environmental challenges due to its low concentration relative to base metals and chemically similar lanthanides. In this work, we developed a biosorption-based flow-through process for extraction of Sc from low-grade feedstocks. A novel biosorbent material was synthesized by encapsulating Arthrobacter nicotianae, a bacterium that selectively adsorbs Sc, within a porous silica matrix. Through the use of several complementary microscopy techniques, we demonstrated a highly porous biosorbent structure with a high cell-loading density and a homogenous cell distribution. Batch adsorption assays revealed selective Sc adsorption over lanthanides and common based metals, with the exception of Fe(III), as evidenced by separation factors greater than 50. The MESG particles were packed into fixed-bed columns to enable adsorption under flow-through conditions, which demonstrated effective Sc extraction at flow rates up to 0.08 cm/s and high stability for reuse; greater than 95% of the adsorption capacity was maintained after 10 consecutive adsorption/desorption cycles. When applied to a lignite coal leachate, whose Fe content was depleted through pH-mediated precipitation, the MESG particles yielded Sc breakthrough at 30 bed volumes, whereas all other metals broke through after only a few bed volumes. Following desorption, an eluate with a 124-fold increase in Sc purity was achieved relative to the lignite leachate with Sc constituting 96.4% of the total REEs. This study established a rapid, facile, and scalable cell immobilization approach that enables the use of microbial biomass for Sc recovery from low-grade sources.

Dong, Ziye↗
DOE OSTI2023

Role of Complexation Strength on the Photophysical and Transport Properties of Semiconducting Charged Polymer Complexes

The high polymer fraction in complexes of conjugated and insulating polyelectrolytes offers unique opportunities for the fabrication of conductive thick films and bulk structures. The electrostatic interactions in these systems further provide a handle for controlling their structure and properties. The impact of charge-mediated complexation strength on the photophysical and electronic transport properties in blends of conjugated polyelectrolytes (CPEs) with oppositely charged polymeric ionic liquids (PILs) was examined. Complexes were formed with varying frequency of charged repeat units, from 50 to 100%, on an anionic polythiophene-based CPE and a complimentary cationic PIL. In highly charged complexes, the intimate mixing between the CPE and the PIL reduced the structural disorder along the CPE backbone, enhancing its intrachain conjugation and interchain stacking. In weakly charged complexes (<90%), these chain planarization effects were absent and microphase separation occurred. At all charge fractions examined, the electrical conductivity of an acid-doped complex was higher than that of the unblended constituent CPE. Further, the highest electrical conductivity, near 1 S cm –1 , was found for a charge fraction of 100%. These results demonstrate the potential for designing effective polymeric conductors using electrostatic complexation.

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

Non-classical crystallization in soft and organic materials

Classical nucleation and crystal growth theories describe how nuclei form, become stable after reaching a critical size and then enlarge through monomer attachment. More than two decades ago, non-classical pathways have been proposed for various types of (bio)molecules and materials, which can substantially alter the crystallization kinetics and outcomes. Direct observation of non-classical crystallization of inorganic nanomaterials, including metastable structure-mediated and particle attachment-based pathways that usually occur on the nanoscale, was enabled by in situ liquid-phase electron microscopy. However, it was not until recently that the crystallization dynamics of beam-sensitive soft materials were directly imaged with sufficient spatial resolution, and a level of microstructural understanding of defects and interfaces emerged. This article provides a high-level review of the non-classical crystallization pathways discovered in soft and organic materials and a forward-looking guide for future research. We first analyse how the characteristics of soft materials affect their crystallization pathways and kinetics. We then identify technical approaches to studying the crystallization trajectories of soft materials and discuss strategies to properly select and apply them to different systems. Breakthroughs made in understanding the crystallization of small organic molecules, (bio)macromolecules, colloids and reticular framework materials are examined. Lastly, we provide an outlook on the challenges in elucidating soft material crystallization pathways and the opportunities for assisting the design and synthesis of new materials and structures.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Fabrication of a Nb-Ti Superconducting Closed-Loop Coil for the Next-Generation 45 GHz ECR Ion Source MARS-D

Electron Cyclotron Resonance Ion Sources (ECRISs) that utilize Nb-Ti superconducting coils for 28 GHz frequencies have been operating effectively for over twenty years. However, transitioning to higher frequencies demands stronger magnetic fields, and the conventional racetrack-and-solenoid ECRIS structures have reached their maximum capability with Nb-Ti. To address this, a Mixed Axial and Radial field System Demonstrator (MARS-D) is being developed at Lawrence Berkeley National Laboratory (LBNL). This system features an innovative Closed-Loop Coil (CLC) design that optimizes the use of the conductor fields, enabling the application of Nb-Ti in the next-generation 45 GHz ECRISs. The fabrication of the hexagonal CLC is particularly challenging due to its complex winding path and shape, the stiffness of the Nb-Ti superconducting wire, and the small bending radius. Here, to address these challenges, a series of unique fixtures and tools, as well as a pre-over-bending method, were developed for winding the CLC. To validate the winding fixtures, tools, procedures, and materials used in the coil assembly, a 4-layer practice CLC was wound, epoxy-impregnated, and then cold-tested using liquid nitrogen. The full-size MARS-D CLC is in the process of winding. This paper presents the structure of the MARS-D CLC, the winding fixtures and tools, the winding procedures, the quality control, the impregnation, the test results, and the potential future improvements.

ECR ion sources↗
DOE OSTI2020

Dendrite-free Al recycling via electrodeposition using ionic liquid electrolytes: The effects of deposition temperature and cathode surface roughness

In this report, the electrodeposition of Al from aluminum scrap alloys (A2020) on copper cathode substrates with varied surface roughness under different deposition temperatures was studied using low-temperature AlCl 3 -1-butyl-3-methyl-imidazolium chloride (BMIC) ionic liquid electrolytes. The bulk electrodeposition of Al was carried out under a voltage of 1.5 V at a stirring rate of 120 rpm using a fixed ionic liquid electrolyte concentration (molar ratio AlCl 3 : BMIC = 2:1). The effects of deposition temperature (range from 80 °C to 140 °C) and surface roughness of Cu cathode substrates (polished by 320, 600, 800, 1200 grits SiC sandpapers and mirror polishing process) on the morphology of deposited Al, current density, current efficiency and energy consumption, were investigated. The Al deposits were characterized using scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), profilometer, and electrochemical measurements for current density, current efficiency, and energy consumption. It is demonstrated that the deposition temperature and surface roughness of Cu electrodes play a critical role in the nucleation and growth of Al deposits. Higher deposition temperature promotes the diffusion and/or migration of Al 2 Cl 7 - ions and then enhances the current density and efficiency during the electrodeposition of Al. Smoother surface of Cu electrodes is preferred for the formation of dendrite-free Al deposits. Typically, on the mirror polished Cu electrode, no Al dendrite structure was observed, and only plate-like Al deposits were formed at the deposition temperature of 100 °C. Pure metallic Al was successfully deposited on Cu electrodes in AlCl 3 + BMIC ionic liquid electrolytes for all experiments with a current efficiency range from 72% to 99% and energy consumption of 4.6–6.3 kW h/kg Al.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Structural and chemical changes in hardwood cell walls during early stages of flash pyrolysis

Volatile products from thermal decomposition of lignocellulosic biomass have been well characterized, but the solid- and liquid-phase reactions during the early stages of decomposition are largely unknown. Here the initial solid-phase biomass thermal deconstruction reactions were analyzed in situ and with high particle heating rates, delineating how these processes occur. A variety of instrumentation was used to quantify the extent and relative rates of deconstruction, demonstrating that biopolymers resist the thermally energetic conditions to differing degrees, even when ensconced in biomass cell walls. Hemicellulose and the more frangible lignin components decompose and volatilize more readily than cellulose, which temporarily enriches biomass with cellulose. These chemical changes manifest in larger cell wall structural and mechanical property transformations. In all, this investigation concludes that these solid-phase reactions strongly influence the production rates of volatile species and will require additional study before these processes can be modeled precisely to improve yields of desired product.

09 BIOMASS FUELS↗
DOE OSTI2023

Tracking Molecular Transport Across Oil/Aqueous Interfaces: Insight into “Antagonistic” Binding in Solvent Extraction

Liquid/liquid (L/L) interfaces play a key, yet poorly understood, role in a range of complex chemical phenomena where time-evolving interfacial structures and transient supramolecular assemblies act as gatekeepers to function. Here, for this study, we employ surface-specific vibrational sum frequency generation combined with neutron and X-ray scattering methods to track the transport of dioctyl phosphoric acid (DOP) and di-(2-ethylhexyl) phosphoric acid (DEHPA) ligands used in solvent extraction at buried oil/aqueous interfaces away from equilibrium. Our results show evidence for a dynamic interfacial restructuring at low ligand concentrations in contrast to expectation. These time-varying interfaces arise from the transport of sparingly soluble interfacial ligands into the neighboring aqueous phase. These results support a proposed “antagonistic” role of ligand complexation in the aqueous phase that could serve as a holdback mechanism in kinetic liquid extractions. These findings provide new insights into interfacially controlled chemical transport at L/L interfaces and how these interfaces vary chemically, structurally, and temporally in a concentration-dependent manner and present potential avenues to design selective kinetic separations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗