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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Stabilization of Miscible Aqueous Phases via Diffusion‐Controlled Multifunctional Nanoparticle‐Ligand Complexation

Liquid‐in‐liquid structuring by harnessing miscible aqueous domains can be achieved by inducing thermodynamically defined phase separation using aqueous solutions of incompatible solutes, where immiscibility is dictated by the concentrations of the solutes. For instance, in aqueous two‐phase systems (ATPSs), the interfacial tension between the two different aqueous solutions is so small that it stabilizes the phase‐separated domains, but not their shape, thus falling short of designing tunable, robust structures. Here, we introduce a diffusion‐controlled strategy that enables liquid‐in‐liquid compartmentalization absent a thermodynamically defined interface or bulk liquid‐liquid phase separation using a barrier formed in situ at the initial contact boundary of an aqueous dispersion of multifunctional nanoparticles and a solution of multifunctional ligands in pure water or a water/alcohol mixture. The nanoparticles and ligands are entropically driven to disperse uniformly but interact at the initial contact boundary more rapidly than bulk mixing, forming a layer that establishes a barrier akin to a semi‐permeable membrane and allows the formation of tubular compartments. A wealth of opportunities is enabled by the proposed technique, where examples in separations, soft electronic devices, and ultralight porous electromagnetic shielding materials are shown.

cryogels↗
DOE OSTI2019

Dendrite–Free Potassium Metal Anodes in a Carbonate Electrolyte

Potassium (K) metal anodes suffer from a challenging problem of dendrite growth. In this study, it is demonstrated that a tailored current collector will stabilize the metal plating–stripping behavior even with a conventional KPF 6 –carbonate electrolyte. A 3D copper current collector is functionalized with partially reduced graphene oxide to create a potassiophilic surface, the electrode being denoted as rGO@3D–Cu. Potassiophilic versus potassiophobic experiments demonstrate that molten K fully wets rGO@3D–Cu after 6 s, but does not wet unfunctionalized 3D–Cu. Electrochemically, a unique synergy is achieved that is driven by interfacial tension and geometry: the adherent rGO underlayer promotes 2D layer–by–layer (Frank–van der Merwe) metal film growth at early stages of plating, while the tortuous 3D–Cu electrode reduces the current density and geometrically frustrates dendrites. The rGO@3D–Cu symmetric cells and half–cells achieve state–of–the–art plating and stripping performance. Here, the symmetric rGO@3D–Cu cells exhibit stable cycling at 0.1–2 mA cm –2 , while baseline Cu prematurely fails when the current reaches 0.5 mA cm –2 . The half–cells cells of rGO@3D–Cu (no K reservoir) are stable at 0.5 mA cm –2 for 10 000 min (100 cycles), and at 1 mA cm –2 for 5000 min. The baseline 3D–Cu, planar rGO@Cu, and planar Cu foil fails after 5110, 3012, and 1410 min, respectively.

25 ENERGY STORAGE↗
DOE OSTI2025

Shape‐Evolving Structured Liquids

Migration, division, and reconfiguration - functions essential to living systems - are driven by active processes. Developing synthetic mimics is an outstanding challenge. Lipid bilayers that bound natural systems are locally deformed by active species, e.g., microtubules, but the resulting non-equilibrium shapes relax when active species motion ceases, and the shape changes lack immediate control. A fully synthetic system is described, driven by active particles encapsulated by a reconfigurable nanoparticle-surfactant membrane that undergoes shape fluctuations reminiscent of living cells. These shape changes are preserved after particle activity stops. Surfactant concentration tunes the interfacial tension over three orders of magnitude, making on-demand shape evolution possible. Directional migration, division, and reconfiguration across multiple scales are possible, leading to a new class of biomimetic, reconfigurable, and responsive materials, paving the way for autonomous synthetic machines.

Kim, Paul Y↗
DOE OSTI2020

Empirical correlations for prediction of minimum miscible pressure and near-miscible pressure interval for oil and CO 2 systems

Although near-miscible CO 2 flooding has recently received considerable attention, no criteria are available to predict its applicability to a specific reservoir. Evaluating the viability of near-miscible flooding requires experimental exploration of a specific region in pressure–temperature space. The near-miscible pressure field is bounded on one side in P, T space by the MMP (minimum miscible pressure). This paper provides robust empirical correlations to estimate the MMP for both pure and impure CO 2 and for prediction of the near-miscible pressure region for CO 2 -oil. Many slim tube analyses, lacking high density data points, systematically underestimate the MMP, when the near miscible region is not accounted for. They are based on 147 published data sets that include: slim tube experimental determination of MMP; interfacial tension (IFT) between oil and CO 2 ; concentration of solution gas; and purity of the CO 2 . This paper is the first to begin a systematic exploration of the pressure-temperature space within which near-miscible effects characterize CO 2 floods. Our new correlations provide a basis for identifying and investigating the nature of near miscible effects associated with existing CO 2 floods. For a case study of an offshore field we determined that lower and upper pressure boundaries for effective near-miscible flooding, are 0.87 MMP and 1.07 MMP at reservoir temperatures. The proposed model is the first empirical correlation for the prediction of near-miscible pressure region, it will provide the basis for both screening the relative potential of oil reservoirs for economically viable miscible or near-miscible CO 2 -flooding.

42 ENGINEERING↗
DOE OSTI2022

The effect of original and initial saturation on residual nonwetting phase capillary trapping efficiency

Injection of supercritical carbon dioxide (CO 2 ) into geological formations is a strategy for both atmospheric greenhouse gas reduction (climate change mitigation) and enhanced oil recovery. To understand CO 2 trapping efficiency, the capillary trapping behaviors that immobilize subsurface fluids were analyzed at the pore-scale using pairs of proxy fluids representing the range of in situ nonwetting and wetting fluid properties encountered in geologic storage reservoirs. The pairs of fluids were cycled through imbibition and drainage processes using a flow cell apparatus containing a sintered glass bead column. Computed x-ray microtomography (microCT) was used to identify immobilized nonwetting fluid after imbibition and drainage events. From microCT images, the trapped residual (post-secondary imbibition) nonwetting phase was spatially correlated to both the original (post-primary imbibition) and the initial (post-primary drainage) nonwetting phase; this relationship is referred to here as the original saturation dependence (SO-dependence) and initial saturation dependence (SI-dependence), respectively. Significant trends of decreasing SO- and SI-dependence with increasing wetting and nonwetting fluid phase viscosities were observed. This finding implies that the amount of CO 2 injected and ultimately trapped is dependent on the nonwetting phase (e.g. oil or gas) already present in the formation, as well as on the manner in which supercritical CO 2 is initially injected, which are factors not considered in current trapping models. To explore the potential effect that varying viscosity and interfacial tension (IFT) might have on this process, we report on a variety of fluid pairs with different viscosities and IFT.

42 ENGINEERING↗
DOE OSTI2022

Viscoelastic necking dynamics between attractive microgels

Hypothesis: Microgels can deform and interpenetrate and display colloid/polymer duality. The effective interaction of microgels in the collapsed state is governed by the interplay of polymer–solvent interfacial tension and bulk elasticity. A connecting neck is shown to mediate microgel interaction, but its temporal evolution has not been addressed. Here we hypothesize that the necking dynamics of attractive microgels exhibits liquid-like or solid-like behavior over different time and length scales. Experiments: We simulate the merging and pinching of attractive microgels with different crosslinking densities in explicit solvent using dissipative particle dynamics. The temporal coalescence dynamics of microgels is investigated and compared with simple liquid and polymeric droplets. We model the neck growth on long time scales using Maxwell model of polymer relaxation and compare the theoretical prediction with simulation data. The mechanical strength of the neck is characterized systematically via simulated pinch-off of microgels by steered molecular dynamics. Findings: We evidence a crossover in the coalescence dynamics reflecting the viscoelastic signature of microgels. In contrast to the common knowledge that viscoelastic materials respond elastically on short time scales, the early expansion of the microgel neck exhibits a linear behavior, similar to the viscous coalescence of liquid droplets. However, the late regime with arrested dynamics resembles sintering of solid particles. Through an analytical model relating microgel dynamics to neck growth, we show that the long-term behavior is governed by stress relaxation of the polymers in the neck region and predict an exponential decay in the rate of growth, which agrees favorably with the simulation. Different from coalescence, the thread thinning in microgel breakup primarily highlights its polymeric characteristics.

42 ENGINEERING↗
DOE OSTI2022

Dissolving Nonionic Surfactants in CO 2 to Improve Oil Recovery in Unconventional Reservoirs via Wettability Alteration

CO 2 injection is a promising method for enhanced oil recovery (EOR) in unconventional shale reservoirs. Here, in this work, we postulate that CO 2 EOR may be improved by the dissolution of surfactants into CO 2 . Although CO 2 is a relatively good solvent for oil, we show that CO 2 and Eagle Ford oil are immiscible at compositions above 70 wt % CO 2 , even at pressures as high as 62 MPa. The presence of a CO 2 –oil interface at reservoir conditions indicates that the addition of a surfactant has the potential to improve oil recovery–via wettability alteration from oil-wet to CO 2 -wet, CO 2 –oil interfacial tension (IFT) reduction, or both. Three nonionic surfactants (branched tridecyl ethoxylate Indorama SURFONIC TDA-9, branched nonylphenol ethoxylate Indorama SURFONIC N-100, and linear dodecyl ethoxylate Indorama SURFONIC L12-6) were evaluated for CO 2 -solubility, shale wettability alteration, effect on CO 2 –oil IFT, ability to generate CO 2 –oil foams, and ability to increase oil extraction from Eagle Ford, Mancos, and Bakken shale cores. Each surfactant dissolved in CO 2 up to 1 wt % at pressures and temperatures commensurate with CO 2 EOR. CO 2 -dissolved surfactants did not significantly affect CO 2 –oil IFT or generate CO2–oil foams, but they did induce a dramatic change in the contact angle of an oil droplet on an oil-aged shale chip in CO 2 from strongly oil-wet (11°) toward intermediate CO 2 –oil wettability (82°) (at 80 °C, 27.6 MPa). The branched tridecyl ethoxylated surfactant, SURFONIC TDA-9, afforded the highest oil recovery in core soaking experiments–75%, compared to 71% by pure CO 2 . Analysis of oil extracts by gas chromatography revealed that heavier oil components were produced when the surfactant was added to CO 2 . These results indicate that CO 2 -dissolved surfactants may increase oil recovery from shale by wettability alteration from oil-wet toward CO 2 -wet.

04 OIL SHALES AND TAR SANDS↗
DOE OSTI2020

High Pressure Infiltration/Expulsion of Aqueous NaCl in Planar Hydrophobic Nanopores

Pressure-driven permeation of water in a poorly wettable material results in a conversion of mechanical work into surface free energy representing a new form of energy storage, or absorption. When water is replaced by a concentrated electrolyte solution, the storage capacity of a nanoporous medium becomes comparable to high-end supercapacitors. The addition of salt can also reduce the hysteresis of the infiltration/expulsion cycle. Our molecular simulations provide a theoretical perspective into the mechanisms involved in the process, and underlying structures and interactions in compressed nanoconfined solutions. Specifically, we consider aqueous NaCl in planar confinements of widths of 1.0 nm and 1.64 nm and pressures of up to 3 kbar. Open ensemble Monte Carlo simulations utilizing fractional exchanges of molecules for efficient additions/removal of ions have been utilized in conjunction with pressure-dependent chemical potentials to model bulk phases under pressure. Confinements open to these pressurized bulk, aqueous electrolyte phases show reversibility at narrow pore sizes and irreversibility in wider ones, consistent with experiment, as well as strong hysteresis at both pore size. The addition of salt results in significant increases in the solid/liquid interfacial tension in narrower pores and associated infiltration and expulsion pressures. Furthermore, these changes are consistent with strong desalination effects at the lower pore size observed irrespective of external pressure and initial concentration.

25 ENERGY STORAGE↗
DOE OSTI2026

Adsorption of Mixed Micelles of Polysorbate 80 and Oleic Acid to the Air–Water Interface

The solubilization of long chain amphiphiles with limited solubility into mixed micelles composed of highly soluble surfactants plays a crucial role in modulating the stability and functionality of formulations in pharmaceutical and food systems. Subsequently, the mixed micelles adsorb from solution to the air−water surface, defining the transport mechanism of the insoluble amphiphiles to the interface. We use X-ray reflectivity to measure the composition and provide insight into the structure of these mixed monolayers, and, alongside interfacial tension measurements, we provide an understanding of how the bulk composition determines the surface composition and the dynamics of tension reduction. We use a model system consisting of an insoluble fatty acid, oleic acid (OA), and a soluble micelle-forming surfactant, polysorbate 80 (PS80). PS80 forms spherical micelles, and, above the critical micelle concentration (cmc), OA is readily solubilized inside the micelles. We show that the adsorption of PS80/OA mixed micelles to the air−water interface rapidly reduces the tension and lowers the equilibrium tension in proportion to the OA concentration. X-ray reflectivity data, fit using Parratt-slab models, quantitively demonstrates that the monolayers become enriched with OA, and we show how the OA intercalates into the PS80 monolayers.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Toward Lithium Recovery Using Modular (and Membraneless) Phase Separation and Extraction (MPSE) Technology with Ionic Liquid (IL) Solvents: Effect of Coatings

In this work, a single-channel slope-plate Modular and Membrane-less Phase Separation and Extraction (MPSE) device was fabricated using 3D printing. The slope-plate was designed with an insertable glass slide to enable surface modification with coatings. Self-assembled monolayers (SAMs) and perfluoropolyether (Zdol) coatings were applied to tailor surface wettability and enhance phase separation. Using a model biphasic system of water and hexadecane, both coatings significantly improved the separation efficiency compared to the uncoated device by promoting selective wetting. Building on these results, lithium extraction from a simulated saline solution was investigated using 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf₂]) as the ionic liquid (IL) extractant. The IL effectively extracted Li⁺ from the aqueous phase in bulk extraction, demonstrating its potential for lithium recovery. However, the low interfacial tension between the IL and aqueous phases posed challenges for phase separation. The application of SAM and Zdol coatings effectively mitigated this issue. Overall, integrating tailored surface chemistry with the slope-plate MPSE design shows great promise as an efficient and scalable platform for studying liquid–liquid separation and optimizing ionic liquid–based extraction processes for lithium recovery from saline sources.

3D printing↗
DOE OSTI2022

Understanding and Manipulating Helical Nanofilaments in Binary Systems with Achiral Dopants

Here, in this paper, we report the relationship between helical pitch of the helical nanofilament (HNF) phase formed by bent-core molecule NOBOW and the concentration of achiral dopants 5CB and octane, using linearly polarized resonant soft X-ray scattering (RSoXS). Utilizing theory-based simulation, which fits well with the experiments, the molecular helices in the filament were probed and the superstructure of helical 5CB directed by groove of HNFs was observed. Quantitative pitch determination with RSoXS reveals that helical pitch variation is related to 5CB concentration with no temperature dependence. Doping rodlike immiscible 5CB led to a pitch shortening of up to 30%, which was attributed to a change in interfacial tension. By shedding light not only on phase behavior of binary systems but also enabling control over pitch length, our work may benefit various applications of HNF-containing binary systems, including optical rotation devices, circularly polarized light emitters, and chirality transfer agents.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Insights into a Greener Stimuli-Responsive Fracturing Fluid for Geothermal Applications

StimuFracTM, is a non-toxic stimuli-responsive fracturing fluid consisting on a CO2-reactive polymer which has shown at the lab-scale to consistently fracture rock cores at significantly lower net pressures in a range of representative geothermal pressure/temperature conditions. In this work, we report on the two main mechanisms responsible for fracturing rock at lower net pressures with this novel fracturing fluid. The first mechanism is the additional work / overpressure generated by aqueous polymer solution during its CO2-triggered volume expansion. The second mechanism is associated to a reduction in pore invasion pressure as a result of the lower interfacial tension of StimuFrac. This reduction in pore invasion pressure results in a reduction in fracturing net pressure as previously reported. The results presented in this work illustrate the potential of StimuFrac as a greener and less-energy intensive fracturing fluid for geothermal and fossil energy production.

Fernandez, Carlos A.↗
DOE OSTI2021

Mesoscale Frank–Kasper Crystal Structures from Dendron Assembly by Controlling Core Apex Interactions

Single-component polymeric materials open up a great potential for self-assembly into mesoscale complex crystal structures that are known as Frank-Kasper (FK) phases. Predicting the packing structures of the soft-matter spheres, however, remains a challenge even when the molecular design is precisely known. Here, we investigate the role of the molecules' enthalpic interaction in determining the low-symmetry crystal structures. To this end, we synthesize architecturally asymmetric dendrons by varying their apex functionalities and examine the packing structures of the second-generation (G2) dendritic wedges. Our work shows that weakening the hydrogen bonding of the dendron apex makes the particles softer and smaller, and leads to the formation of various FK structures at lower temperatures, including the new observation of a FK C14 phase in the cone-shaped dendron systems. As a consequence of the free energy balance between the particle's interfacial tension and the chain's stretching, various packing structures are mainly tuned by designing the hydrogen bonding interaction.

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

Impacts of Pore Network-Scale Wettability Heterogeneity on Immiscible Fluid Displacement: A Micromodel Study

The mixed-wet nature of reservoir formations imposes a wide range of rock wettability from strong resident-fluid wetting to strong invading-fluid wetting. The characteristics of two-phase flow in porous media composed of mixed-wetting surfaces remain poorly understood. In this study, we investigated the displacement of resident ethylene glycol (EG) by hexane in two mixed-wet micromodels of identical 2.5-D geometry heterogeneity, with uniformly or heterogeneously distributed patches strongly wetting to hexane. These patches are mixed among pores with unaltered EG-wetting surfaces. Along with control tests in the originally EG-wet micromodel, here we show the classic fingering and transitions in flow regimes at $logCa$ (capillary number) from -7.2 to -3.9. Moreover, pore-scale distributions of wettability and their spatial correlation influence displacement efficiency. In the two mixed-wet micromodels, we found (a) an increase of steady-state hexane saturation at the end of experiments by up to 0.12 in the capillary fingering regime and a decrease of at most by 0.06 in the viscous fingering regime, compared to the EG-wet micromodel, and (b) dispersed and fragmented hexane distribution after displacement. Brine drainage during supercritical CO 2 (scCO 2 ) injections in these micromodels occurs with lower wettability contrasts, and under similar viscosity ratios and interfacial tensions resulted in higher displacement efficiency relative to displacement of EG by hexane. While mixed-wettability can enhance displacement efficiency compared to uniform wettability, the dynamics of immiscible fluids in strong mixed-wet reservoirs are expected to be less pronounced in contributing to the efficiency of geological CO 2 sequestration, oil recovery, and remediation of hydrocarbon-contaminated aquifers.

2.5-D micromodel↗
DOE OSTI2022

Entropically engineered formation of fivefold and icosahedral twinned clusters of colloidal shapes

Fivefold and icosahedral symmetries induced by multiply twinned crystal structures have been studied extensively for their role in influencing the shape of synthetic nanoparticles, and solution chemistry or geometric confinement are widely considered to be essential. Here we report the purely entropy-driven formation of fivefold and icosahedral twinned clusters of particles in molecular simulation without geometric confinement or chemistry. Hard truncated tetrahedra self-assemble into cubic or hexagonal diamond colloidal crystals depending on the amount of edge and vertex truncation. By engineering particle shape to achieve a negligible entropy difference between the two diamond phases, we show that the formation of the multiply twinned clusters is easily induced. The twinned clusters are entropically stabilized within a dense fluid by a strong fluid-crystal interfacial tension arising from strong entropic bonding. Our findings provide a strategy for engineering twinning behavior in colloidal systems with and without explicit bonding elements between particles.

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

Effects of grain size and small-scale bedform architecture on CO 2 saturation from buoyancy-driven flow

Small-scale (mm-dm scale) heterogeneity has been shown to significantly impact CO 2 migration and trapping. To investigate how and why different aspects of small-scale heterogeneity affect the amount of capillary trapping during buoyancy-driven upward migration of CO 2 , we conducted modified invasion percolation simulations on heterogeneous domains. Realistic simulation domains are constructed by varying two important aspects of small-scale geologic heterogeneity: sedimentary bedform architecture and grain size contrast between the matrix and the laminae facies. Buoyancy-driven flow simulation runs cover 59 bedform architecture and 40 grain size contrast cases. Simulation results show that the domain effective CO 2 saturation is strongly affected by both grain size and bedform architecture. At high grain size contrasts, bedforms with continuous ripple lamination at the cm scale tend to retain higher CO 2 saturation than bedforms with discontinuous or cross lamination. In addition, the “extremely well sorted” grain sorting cases tend to have lower CO 2 saturation than expected for cross-laminated domains. Finally, both a denser CO 2 phase and greater interfacial tension increase CO 2 saturation. Again, variation in fluid properties seems to have a greater effect on CO 2 saturation for cross-laminated domains. This result suggests that differences in bedform architecture can impact how CO 2 saturation values respond to other variables such as grain sorting and fluid properties.

58 GEOSCIENCES↗
DOE OSTI2020

Nano-layer deposition of metal oxides via a condensed water film

Abstract Nanocoatings on solids can be achieved by various processes, including sol-gel and atomic layer deposition. However, challenges remain for achieving uniform nanocoatings on nanoscale substrates at a large scale. Here, we report a versatile and fundamentally different technique, termed condensed layer deposition, for depositing conformal metal oxide nanocoatings on nanoparticles and nanofibers. This approach involves water in liquid hydrocarbons condensing as a nanoscale water film on the substrate surface, enabled by interfacial tension between polar water and nonpolar liquid hydrocarbons. Chemical precursors are then added, which react with the condensed water film to form a metal oxide nanocoating. We demonstrate this for titania, alumina, and niobia on substrates including carbon nanotubes, iron oxide particles and carbon black. Condensed layer deposition can achieve oxide nanocoatings on a variety of substrates with tunable thickness, in one pass, at room temperature.

36 MATERIALS SCIENCE↗