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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Ballistic Ejection of Microdroplets from Overpacked Interfacial Assemblies

Spontaneous emulsification, resulting from the assembly and accumulation of surfactants at liquid–liquid interfaces, is an interfacial instability where microdroplets are generated and diffusively spread from the interface until complete emulsification. Here, it is shown that an external magnetic field can modulate the assembly of paramagnetic nanoparticle surfactants (NPSs) at liquid–liquid interfaces to trigger an oversaturation in the areal density of the NPSs at the interface, as evidenced by a marked reduction in the interfacial tension, γ, and corroborated with a magnetostatic continuum theory. Despite the significant reduction in γ, the presence of the magnetic field does not cause stable interfaces to become unstable. Upon rapid removal of the field, however, an explosive ejection of a plume of microdroplets from the surface occurs, a dynamical interfacial instability which is termed explosive emulsification. Further, this explosive event rapidly reduces the areal density of the NPSs to its pre-field level, stabilizing the interface. The ability to externally suppress or trigger the explosive emulsification and controlled generation of tens of thousands of microdroplets, uncovers an efficient energy storage and release process, that has potential applications for controlled and directed delivery of chemicals and remotely controlled soft microrobots, taking advantage of the ferromagnetic nature of the microdroplets.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Evaluation of Drilling Performance at The Geysers with Machine Learning Methods Using Geologic Data

A recent well, GDC-36, was drilled in The Geysers Geothermal Field served in a Department of Energy-industry to demonstrate improved drilling performance with polycrystalline diamond compact (PDC) bits. Both PDC and roller cone drill bits were used to drill this well. Key challenges encountered during drilling included lost circulation in the mud-drilled section, and bit damage interfacial severity in the deeper, air-drilled section. The objective of this study is to evaluate the drilling performance in relation to the local geological characteristics using machine learning methods. By applying K-clustering to the sonic log data, we were able to identify areas correlated with measured lost circulation. Also, the boundaries defined by clustering of the mineralogical and lithological data from the mud logs correlate well with interfacial severity during drilling. A random forest model was employed to build correlation between drilling data and rock strength. The confined compressive strength (CCS) of the rock in the training of the machine learning model was inferred from the dipole sonic log. The R-squared of the testing data is 0.78, and the RMSE (Root Mean Squared Error) is 0.06. The trained model was used to forecast rock strength for the section where sonic log data are not available. CCS could also be inferred from mud logs provided the relationship between mineralogy and rock strength is established through core testing data.

15 GEOTHERMAL ENERGY↗
DOE OSTI2024

Interface Modifications of Lithium Metal Anode for Lithium Metal Batteries

Lithium metal batteries (LMBs) enable much higher energy density than lithium–ion batteries (LIBs) and thus hold great promise for future transportation electrification. However, the adoption of lithium metal (Li) as an anode poses serious concerns about cell safety and performance, which has been hindering LMBs from commercialization. To this end, extensive effort has been invested in understanding the underlying mechanisms theoretically and experimentally and developing technical solutions. In this review, we devote to providing a comprehensive review of the challenges, characterizations, and interfacial engineering of Li anodes in both liquid and solid LMBs. Finally, we expect that this work will stimulate new efforts and help peer researchers find new solutions for the commercialization of LMBs.

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↗
NASA NTRS1986

Fractography of unidirectional graphite-epoxy as a function of moisture, temperature and specimen quality

Optical microscopy and SEM have been used to examine the tensile failure surfaces of (0-deg)8 T300/5208 graphite-epoxy specimens, and fractography is employed to determine how moisture content and temperature, together with specimen preparation, affect failure modes. A low energy failure morphology is noted in defective specimens; specimens made from nondefective prepregs appeared to exhibit a decrease in flaw sensitivity and increasing strength with either temperature or moisture, although moisture also seemed to increase interfacial debonding between filament and matrix. The combination of temperature and moisture degraded performance by increasing interfacial debonding, and rendering the epoxy more prone to fracture.

Clements, L. L.↗
NASA NTRS1984

Enhanced adhesion by high energy bombardment

Films (12) of gold, copper, silicon nitride, or other materials are firmly bonded to insulator substrates (12) such as silica, a ferrite, or Teflon (polytetrafluorethylene) by irradiating the interface with high energy ions. Apparently, track forming processes in the electronic stopping region cause intermixing in a thin surface layer resulting in improved adhesion without excessive doping. Thick layers can be bonded by depositing or doping the interfacial surfaces with fissionable elements or alpha emitters.

Griffith, Joseph E.↗
DOE OSTI2024

Bottlebrush Block Copolymers at the Interface of Immiscible Liquids: Adsorption and Lateral Packing

Amphiphilic bottlebrush block copolymers (BBCPs), having a hydrophilic bottlebrush polymer (BP) linked covalently to a hydrophobic BP, were found to segregate to liquid-liquid interfaces to minimize the free energy of the system. The key parameter influencing the outcome of the experiments is the ratio between the degree of polymerization of the backbone (NBB) and that of the side-chain brushes (NSC). Specifically, a spherical, star-like configuration results when NBB < NSC, while a cylindrical, bottlebrush-like shape is preferred when NBB > NSC. Dynamic interfacial tension (γ) and fluorescence recovery after photobleaching (FRAP) measurements show that the BBCP configuration influences the areal density and in-plane diffusion at the fluid interface. The characteristic relaxation times associated with BBCP adsorption (τA) and reorganization (τR) were determined by fitting time-dependent interfacial tension measurements to a sum of two exponential relaxation functions. Both τA and τR initially increased with NBB up to 92 repeat units, due to the larger hydrodynamic radius in solution and slower in-plane diffusivity, attributed to a shorter cross-sectional diameter of the side-chains near the block junction. This trend reversed at NBB = 190, with shorter τA and τR attributed to increased segregation strength and exposure of the bare water/toluene interface due to tilting and/or wiggling of the backbone chains, respectively. The adsorption energy barrier decreased with higher NBB, due to a reduced BBCP packing density at the fluid interface. In conclusion, this study provides fundamental insights into macromolecular assembly at fluid interfaces, as it pertains to unique bottlebrush block architectures.

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

Highly tunable structure-by-design polymer brush membranes for organic solvent nanofiltration

Synthetic polymeric nanofiltration membrane processes offer an alternate low-energy option to energy-intensive distillation to fractionate similar size organic solvents for chemical, petroleum, food and biotechnology industries. Here, in this study, we synthesize and test a new class of structure-by-design hydrophilic polymeric brush membranes, that address the limitations of commercial polymer membranes, are tunable and exhibit commercially relevant filtration performance. Because these brush membranes are grafted by Single Electron Transfer-Living Radical Polymerization (SET-LRP) and replace statistically random phase inversion or interfacial polymerization used for synthesizing commercial polymer membranes, their porous structure can be remodeled by varying their morphology and chemistry. We graft hydroxyethyl methacrylate (HEMA) brush structures with short and long crosslinkers, demonstrate two competing phenomena - pore stiffening and opening - and obtain high selectivity at reasonable permeability for commercially relevant methanol/toluene separation. This new class of stable, tunable, and scalable membranes offers exciting opportunities to reduce energy for separation of organic solvents.

42 ENGINEERING↗
DOE OSTI2024

Controlling Interfacial Charge Separation Energetics and Kinetics

The overall goal is to probe electron transfer kinetics of the Marcus inverted region at interfaces. This project specifically uses a dye‐semiconductor interface with a reversible electron transfer reagent in solution where the semiconductor conduction band and electron transfer reagent ideally have a potential energy difference firmly within the Marcus inverted region. The goals of this project are: (Goal 1) Identify dye design elements that give dyes with low energy ground‐state oxidation potentials while retaining desirable electron transfer kinetics at the semiconductor interface. (Goal 2) Identify dye designs with excited‐state oxidation potentials set to fixed energies through molecular design while the dye ground‐state oxidation potentials are varied to allow for the evaluation of varied electron transfer reagents/redox shuttles (RS) with different free energies for electron transfer. (Goal 3) Within the context of the functionality identified in goals 1 and 2, goal 3 seeks to design dyes with features maximizing charge carrier lifetimes by minimizing recombination losses at metal oxide interfaces with high voltage systems. (Goal 4) Probe electron transfer kinetics in a high voltage‐dye sensitized solar cell with both the oxidized dye and RS firmly within the Marcus inverted region with regard to the TiO2 CB. (Goal 5) Identify tailored sensitizer/redox shuttle pairs with desirable electron transfer kinetics in defined spectral regions capable of “banding off” incident solar irradiation to give high voltage multijunction systems capable of exceeding the Shockley‐Queisser limit and powering catalytic processes.

14 SOLAR ENERGY↗
DOE OSTI2020

Towards a high-performance garnet-based solid-state Li metal battery: A perspective on recent advances

Garnet-based solid-state Li metal batteries have been widely considered one of the most promising next-generation energy storage systems. However, the performance of these batteries is plagued by various limitations caused by the solid-state electrolyte (SSE). The poor wetting of lithium on the garnet surface diminishes the contact between the anode and electrolyte, leading to extremely high anode interfacial resistance. Similarly, the point-to-point contact between the cathode and electrolyte leads to high impedance on the cathode side. Moreover, although the SSE serves a firm barrier separating the anode and cathode, lithium dendrites can still grow through, causing a short circuit. Lastly, the solid/solid interface cannot be well maintained under cycling at high current density and capacity. Recently, remarkable progress has been achieved in garnet electrolyte to resolve these problems towards the aim of a high-performance solid-state Li metal battery. In this perspective, we highlight various recent advances in the field of garnet-based solid-state battery, including improving the anode/electrolyte interface, lithium dendrite detection, reducing cathode impedance, and electrolyte architecture design.

25 ENERGY STORAGE↗
DOE OSTI2021

Controlled exposure of CuO thin films through corrosion-protecting, ALD-deposited TiO 2 overlayers

Ultra-thin film coatings are used to protect semiconductor photoelectrodes from the harsh chemical environments common to photoelectrochemical energy conversion. These layers add contact transfer resistance to the interface that can result in a reduction of photoelectrochemical energy conversion efficiency of the photoelectrode. Here, we describe the concept of a partial protection layer, which allows for direct chemical access to a small fraction of the semiconductor underlayer for further functionalization by an electrocatalyst. The rest of the interface remains protected by a stable, inert protection layer. CuO is used as a model system for this scheme. Atomic layer deposition (ALD)-prepared TiO 2 layers on CuO thin films prepared from electrodeposited Cu 2 O allow for the control of interfacial morphology to intentionally expose the CuO underlayer. The ALD-TiO 2 overlayer shrinks during crystallization, while Cu 2 O in the underlayer expands during oxidation. As a result, the TiO 2 protection layer cracks to expose the oxidized underlying CuO layer, which can be controlled by preceding thermal oxidation. Furthermore, this work demonstrates a potentially promising strategy for the parallel optimization of photoelectrochemical interfaces for chemical stability and high performance.

14 SOLAR ENERGY↗
DOE OSTI2026

Passivation‐Induced Species Dynamics and Microstructural Evolution in Solid‐State Lithium–Sulfur Cathodes

Solid-state lithium–sulfur (SSLS) batteries offer high theoretical energy density, yet their practical viability is hindered by poor sulfur utilization and limited rechargeability. At the core of this challenge lies the passivating nature of Li 2 S, which restricts ionic and electronic transport, suppresses interfacial activity, and severely impedes the reversibility of electrochemical reactions. In this study, we elucidate the mechanistic origins of these limitations by resolving how charge and discharge species form, grow, and spatially evolve within the cathode microstructure under varied current densities and electrode compositions. By resolving the species distribution at the particle scale and coupling it with Raman spectroscopy and X-ray diffraction, we demonstrate how Li 2 S formation induces localized surface passivation that progressively limits electrochemical accessibility within the cathode microstructure. Sulfur utilization is found to be strongly governed by the interplay between sulfur loading, residual porosity, and interfacial architecture. High sulfur contents result in buried, electrochemically isolated domains due to poor solid electrolyte (SE) percolation, while low sulfur contents trigger SE degradation via parasitic reactions. The resulting sulfur-porosity maps delineate the mechanistic boundaries between reversible and transport-limited regimes, offering actionable design guidance for SSLS cathodes with enhanced sulfur utilization.

electrode microstructure↗
DOE OSTI2024

A dynamically bare metal interface enables reversible magnesium electrodeposition at 50 mAh cm −2

Understanding and facilitating pure magnesium nucleation/growth electrodeposition behavior with ultrahigh Coulombic efficiency is complicated by the phenomenon of solid electrolyte interphase (SEI) formation in state-of-the-art, halogen-free magnesium electrolytes. Defining the electrolyte properties necessary to achieve ideal electrodeposition/stripping (E/S) thus remains elusive. Here, in this work, we reveal for the first time, rapid magnesium electrodeposition behavior that forms densely aligned, micron-sized thin platelets by establishing a dynamic bare magnesium/electrolyte interface during high-rate net plating. This effectively “SEI-free” interface allows facile magnesium diffusion and migration in stripping with near-unity E/S efficiency under demanding conditions over long-term cycling. The intrinsic electrolyte stability of the salt/solvent at the molecular level is the key to forming such an interface. The efficacy of the dynamic bare interface and an electrodeposited, free-standing magnesium anode is demonstrated in a high-areal-capacity full cell. These findings provide new design principles and fundamental understanding of interfacial chemistry in multivalent metal batteries.

Mg full cell↗
DOE OSTI2022

How Water Attacks MXene

Two-dimensional (2D) transition metal carbides and nitrides (MXenes) have shown outstanding performances in electrochemical energy storage and many other applications. However, the stability of MXene remains a concern, especially its quick degradation in aqueous solutions under ambient conditions. Here, we report on the water/Ti 3 C 2 O 2 -MXene interfacial chemistry from first-principles molecular dynamics simulations at room temperature. Surprisingly, we find that the water molecules can attack the basal plane of Ti 3 C 2 O 2 and pull the surface Ti atoms out, thereby reconstructing the surface. Further, by tracking close encounters of water molecules and surface Ti atoms on the basal plane of Ti 3 C 2 O 2 , we show that the attack is initiated by the chemisorption of a water molecule on a surface Ti atom, followed by the breaking of Ti–C bonds and deprotonation of the water molecule, leading to the formation of Ti–OH on the Ti 3 C 2 O 2 surface and a hydronium ion in the aqueous phase. Our finding highlights the susceptibility of Ti 3 C 2 O 2 MXene to water attack, supporting recent experimental observations. Furthermore, we demonstrate that preventing close encounters of water molecules and the surface Ti atoms is key to the stability of the basal plane and can be realized by negatively charging the surface (thereby reorienting the O atoms of water away from the surface) or converting the surface O to -OH groups (thereby shifting the water layer further away from the surface). Our insights and approach highlight the importance of the reactivity of water when interfacing with 2D materials such as MXenes.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Determining the Structure-Property Relationships of Quasi-Two-Dimensional Semiconductor Nanoplatelets.

We report a theoretical study of CdSe nanoplatelets aimed at identifying the main factors determining their photophysical properties. Using atomic configurations optimized with density functional theory calculations, we computed quasiparticle and exciton binding energies of nanoplatelets with two to seven monolayers. We employed many body perturbation theory at the GW level and solved the Bethe-Salpeter equation to obtain absorption spectra and excitonic properties. Our results, which agree well with recent experiments, were then used to design a model that allows us to disentangle the effects of quantum confinement, strain induced by passivating ligands, and dielectric environment on the electronic properties of nanoplatelets. We found that, for the model to accurately reproduce our first principle results, it is critical to account for surface stress and consider a finite potential barrier and energy-dependent effective masses when describing quantum confinement. Our findings call into question previous assumptions on the validity of an infinite barrier to describe carrier confinement in nanoplatelets, suggesting that it may be possible to optimize interfacial charge transfer and extraction by appropriately choosing passivating ligands. The model developed here is generalizable to core-shell platelets and enables the description of system sizes not yet directly treatable by first-principles calculations.

Greenwood, Arin R.↗
DOE OSTI2026

Final Technical Report for DE-SC0021049: Manipulating interfacial reactivity with atomically layered heterostructures

This final technical report summarizes the work accomplished in this DOE Early Career Research Program project that has established moiré superlattice materials and two-dimensional (2D) heterostructures as a highly tunable platform for controlling heterogeneous charge transfer (ET) kinetics at solid-liquid interfaces. By precisely engineering van der Waals heterostructures of atomically thin 2D materials, particularly bilayer and trilayer graphene with controlled twist angles, this project demonstrated systematic control of interfacial charge transfer rates spanning three orders of magnitude. This research addresses fundamental questions about how electronic structure, charge localization, and atomic layer-dependent properties govern charge transfer at electrochemical interfaces, with broad implications for energy conversion, electrocatalysis, and next-generation electrochemical devices.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Photosynthetic Biohybrid System for Enhanced Abiotic N 2 -to-NH 3 Conversion under Ambient Conditions

Photosynthetic biohybrid systems (PBSs) offer an eco-friendly approach to transforming solar energy into value-added products by integrating biological entities with inorganic semiconductors. However, the chemical conversion capacity of most PBSs has inherent limitations, as whole-cell bacteria and isolated enzymes require fine-tuning of environmental conditions. Here, in this study, we report a new PBS developed by introducing free-standing ceria nanoparticles into the purple membrane (PM) of Halobacterium salinarum archaea, which can unidirectionally transfer charge carriers in response to incident photons, even after separation from living archaea at various conditions. Our microscopy, spectroscopy, and synchrotron X-ray scattering analyses confirm that the electrostatic assembly between ceria and PM creates seamless interfacial contact, thereby enhancing the photocatalytic capacity of ceria. Although the conversion of dinitrogen (N 2 ) to ammonia (NH 3 ) is thermodynamically challenging due to the triple bond in N 2 and a series of charge-transfer reactions, our PM–ceria (PMC) hybrid nanoparticle efficiently produces NH 3 by reducing N 2 using solar energy even under atmospheric pressure and room temperature while simultaneously converting glycerol into value-added derivatives. Additionally, our PMC nanoparticle involves neither toxic/precious metals nor bioengineering processes to achieve enhanced photocatalytic N 2 -to-NH 3 conversion. This study sheds light on the new aspect of PBSs by employing PM to potentially resolve the global energy and environmental challenges posed by the conventional Haber–Bosch process.

Jang, Jinhyeong [Argonne National Laboratory (ANL)↗