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At least 199 records · Page 11

Ion redistributions at interfaces facilitate nucleation and growth of branched Ag 3 PO 4 polypods

Branched structures are of spectacular interest due to their improved light-harvesting, direct carrier transportation pathway, high surface area, and controllable electronic structures. Understanding their growth mechanisms and controlling factors enables the design of materials with improved functions. Interfaces of liquid-solid and air-liquid are known to change the chemical and physical properties of the liquid solution. However, their role in crystal growth, especially of branched structures, is seldom investigated. In this work we synthesized branched silver phosphate polypods in a thin layer of aqueous solution at room temperature taking advantage of the unique properties near the interfaces. The branched crystals nucleate and grow with a liquid thickness of 810 µm or below requiring the presence of both the gas-liquid and liquid-solid interfaces. The hydrophilicity of the solid substrate also facilitates nucleation and growth. Our results indicate that the synergism of long-range electric fields (ion distributions) at the interfaces promotes not only the nucleation and growth of silver phosphate but also the formation of branched structures. This work can be a reference for facilitating crystal nucleation and growth and controlling structures with specific morphologies, such as branched ones, by understanding and mimicking the properties at the interfaces.

36 MATERIALS SCIENCE↗

All‐Solid‐State Batteries With Mechanically Stable Interfaces Consisting of a Zero‐Strain Cation‐Disordered Rocksalt Cathode

Interface stabilization is critical to the development of working all‐solid‐state batteries. Rigid cathode/solid electrolyte interfaces often disintegrate due to anisotropic volume change of cathode‐active materials, resulting in irreversible capacity loss. Herein, we demonstrate that Li 1.211 Mo 0.467 Cr 0.3 O 2 (LMCO), a pioneering cation‐disordered rocksalt oxide (DRX) cathode that has intrinsically small volume change upon lithium intercalation, can be integrated with a thiophosphate‐based solid electrolyte for all‐solid‐state batteries. Interface stability of the all‐solid LMCO cell was investigated by electrochemical impedance spectroscopy, X‐ray micro‐computed tomography, and electron microscopy. Since LMCO was initially synthesized as a layered phase exhibiting a large volume change, interface disintegration can be observable in the early cycles. As layered LMCO phase‐transformed into DRX LMCO in subsequent cycles, reintegration of the interfaces occurs within a pressurized cell as a result of its zero‐stain behavior. Consequently, the DRX LMCO cathode maintains interface integrity, and thus electrical wiring, over an extended number of cycles, leading to improved capacity retention with small internal cell resistance.

DRX↗

A Many-Body Perturbation Theory Approach to Energy Band Alignment at the Crystalline Tetracene–Silicon Interface

Hybrid inorganic–organic semiconductor (HIOS) interfaces are of interest for new photovoltaic devices operating above the Shockley–Queisser limit. Predicting energy band alignment at the interfaces is crucial for their design, but represents a challenging problem due to the large scales of the system, the energy precision required and a wide range of physical phenomena that occur at the interface. To tackle this problem, many-body perturbation theory in the non-self-consistent GW approximation, orbital relaxation corrections for organic semiconductors, and line-up potential method for inorganic semiconductors which allows for tractable and accurate computing of energy band alignment in crystalline van-der-Waals hybrid inorganic–organic semiconductor interfaces are used. In this work, crystalline tetracene physisorbed on the clean hydrogen-passivated 1 × 2 reconstructed (100) silicon surface is studied. Using this computational approach, it is found that the energy band alignment is determined by an interplay of the mutual dynamic dielectric screening of two materials and the formation of a dipole layer due to a weak hybridization of atomic/molecular orbitals at the interface. The significant role of the exchange-correlation effects in predicting band offsets for the hybrid inorganic–organic semiconductor interfaces is also emphasized.

74 ATOMIC AND MOLECULAR PHYSICS↗

Geophysical methods reveal the soil architecture and subsurface stratigraphic heterogeneities across land-lake interfaces along Lake Erie

Abstract Purpose The land-lake interface is a unique zone where terrestrial and aquatic ecosystems meet, forming part of the Earth’s most geochemically and biologically active zones. The unique characteristics of this interface are yet to be properly understood due to the inherently high spatiotemporal variability of subsurface properties, which are difficult to capture with the traditional soil sampling methods. Geophysical methods offer non-invasive techniques to capture variabilities in soil properties at a high resolution across various spatiotemporal scales. Methods We combined electromagnetic induction (EMI), electrical resistivity tomography (ERT), and ground penetrating radar (GPR) with data from soil cores and in situ sensors to investigate hydrostratigraphic heterogeneities across land-lake interfaces along the western basin of Lake Erie. Results EMI revealed high spatial heterogeneities in ECa distribution across the land-lake interfaces, with higher values in the wetland and transition zones compared to the upland zone. Soil ECa maps matched soil maps from a public database with the hydric soil units delineated as high conductivity zones (ECa > 40 mS/m). ERT and GPR showed vertical variation in soil properties with clear stratigraphic boundaries, and correlation of ERT profiles with lithologs from piezometers revealed the stratigraphic units of silt–clay and till sequence down to 3.5 m depth which are consistent with the surficial geology of the study area. Conclusions These results validate the use of multiple geophysical methods for extrapolating soil properties and mapping stratigraphic structures at land-lake interfaces, thereby providing the missing information required to improve the earth system model (ESM) of coastal interfaces.

54 ENVIRONMENTAL SCIENCES↗

Effects of three-dimensional Cu/Nb interfaces on strengthening and shear banding in nanoscale metallic multilayers

Manipulation of the atomic-scale structure of two-dimensional (2D) interfaces have been shown to provide nanocomposites with enhanced strength, deformability, and radiation damage resistance. In comparison with 2D interfaces, here we investigate the mechanical response of nanocomposites containing three-dimensional (3D) Cu/Nb interfaces consisting of a chemical/structural gradient separating pure Cu and Nb layers, through which the lattice mismatch between face-centered cubic Cu and body-centered cubic Nb is accommodated over a distance of several nanometers. Furthermore, it is demonstrated that 3D interfaces increase the yield and flow strength by 50% and 22%, respectively, over composites containing 2D interfaces at similar layer thicknesses. After 14% compressive strain, the onset of shear banding results in co-deformation of both Cu and Nb phases within and outside of the shear band. We conclude with a discussion of the role of interface structure in shear band formation and growth in 3D Cu/Nb.

3-dimensional interface↗

Characterization of the atomic-level structure of γ-alumina and (111) Pt/γ-alumina interfaces

The atomic-level structure of platinum/γ-alumina interfaces is characterized in a model system of dense γ-alumina embedded with faceted Pt NPs produced by implantation of platinum ions into sapphire followed by thermal annealing in air at 800 °C. Aberration-corrected scanning transmission electron microscopy (STEM) was used to collect atomic-resolution images, which are compared to STEM image simulations of two experimentally-based bulk models of γ-alumina by Smrčok et al. and Zhou and Snyder. A density functional theory (DFT) based model of (111) interfaces with different chemical terminations (O, Al 1 , Al 2 ) of the γ-alumina developed by Oware Sarfo et al. is also compared to experimental STEM data from Pt/γ-alumina interfaces. Further, the Smrčok γ-alumina model provides a better fit than the Zhou structure to the bulk of the γ-alumina. The oxygen-terminated Oware Sarfo model best fits the experimental data and is a very good model close to the interface. However, the fit of the interface model to the experimental data is poorer beyond the third atomic layer in the γ-alumina. This is attributed to compromises required in the design of the model to limit the cell size and computational time for DFT calculations. Understanding the accuracy and limits of the structural models of γ-alumina and Pt/γ-alumina interfaces is important to further the understanding of the structure/property relationships in this system.

36 MATERIALS SCIENCE↗

Multi-material hydrodynamics with algebraic sharp interface capturing

A finite volume method for Eulerian multi-material hydrodynamics with sharp interface capturing is presented here. The pressure-temperature non-equilibrium multi-material system with finite-rate pressure relaxation in mixed-cells is considered here. This pressure closure facilitates material-property-dependent pressure relaxation, rather than instantaneous pressure equilibration, which in turn allows the use of unsplit high-order time-integrators. A modified tangent of hyperbola for interface capturing (THINC) method is used to reconstruct multi-material (> 2) interfaces, on three-dimensional unstructured meshes. A simple modification which extends the THINC reconstruction to interfaces between more than two materials is proposed. It is demonstrated that the modified THINC can capture multi-material interfaces within 2–4 tetrahedral cells. Since no geometric reconstructions are required by the THINC method, the presented multi-material method is algorithmically simple, and computationally efficient. Consistent reconstructions of conserved quantities at material interfaces ensure that conservation and closure laws are satisfied at the discrete level. Through a suite of test problems solved on unstructured meshes, it is demonstrated that the presented method is a promising candidate for accurate and efficient multi-material hydrodynamics computations.

97 MATHEMATICS AND COMPUTING↗

Influence of processing on secondary phase formation and microstructural evolution at U-10Mo alloy and Zr interlayer interfaces

Thermo-mechanical processing of uranium-10 wt. % molybdenum (U-10Mo) fuel plates leads to microstructure changes at the U-10Mo/Zr interfaces. Secondary phases formed at this interface are particularly important to interfacial bond strength, process optimization, and maintaining structural integrity of the U-10Mo fuel plates during irradiation. In this work, we determined the phases and phase transformation products occurring at the interface of the U-10Mo fuel and Zr interlayer when the fuel plate is subjected to short and long hot isostatic pressure times. Interfacial morphology, structure and composition of phases formed, and relative hardness across the U-10Mo/Zr interfaces were studied using a multi-length scale, multi-modal characterization approach involving electron microscopy, atom probe tomography, and atomic force microscopy. Here, results highlight that the extent of phase transformations, secondary phase formation, and hardness variability across interfaces can be controlled by modifying processing parameters. Phase diagram construction and thermodynamic calculations were performed using the Thermocalc software to identify expected phases formed at interfaces during the maximum hold temperature of 560 °C experienced during HIP.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Conversion of ethanol to 1,3–butadiene over Ag–ZrO 2 /SiO 2 catalysts: The role of surface interfaces

A series of Ag–ZrO 2 /SiO 2 catalysts with different metal–support interfaces were synthesized in an effort to elucidate the roles of specific interfaces in controlling the ethanol to 1,3–butadiene conversion and selectivity. According to the results of detailed characterizations (e.g. CO/pyridine–DRIFTS, XPS, TEM, NH 3 –TPD, and 1 H MAS NMR), it was found that the Ag–O–Si interfaces significantly enhanced the dehydrogenation of ethanol while the presence of ZrO 2 improved the interaction between Ag and ZrO 2 /SiO 2 , creating more Ag δ+ active sites. In this research, the high dispersion of ZrO 2 on SiO 2 generated abundant Zr–O–Si interfaces with medium and weak Lewis acidity, promoting the condensation of acetaldehyde to crotonaldehyde. These Zr–O–Si interfaces in close interaction with Ag δ+ species played a critical role in the enhanced H transfer during the MPV reduction of crotonaldehyde to crotyl alcohol. The synergies among the interfaces resulted in retarded ethanol dehydration reactivity, balanced ethanol dehydrogenation and condensation reactions, and a subsequent high 1,3–butadiene yield.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Nonlinear Interface Reduction for Time-Domain Analysis of Hurty/Craig-Bampton Superelements with Frictional Contact

Virtual prototyping in engineering design relies today on modern numerical models of contacting structures with accurate resolution of interface mechanics, which strongly affect the system-level stiffness and energy dissipation due to frictional losses. High-fidelity modeling within the localized interfaces is required to resolve local quantities of interest that may drive design decisions. The high-resolution finite element meshes necessary to resolve inter-component stresses tend to be computationally expensive, particularly when the analyst is interested in response time histories. The Hurty/Craig-Bampton (HCB) transformation is a widely used method in structural dynamics for reducing the interior portion of a finite element model while having the ability to retain all nonlinear contact degrees of freedom (DOF) in physical coordinates. These models may still require many DOF to adequately resolve the kinematics of the interface, leading to inadequate reduction and computational savings. This study proposes a novel interface reduction method to overcome these challenges by means of system-level characteristic constraint (SCC) modes and properly orthogonal interface modal derivatives (POIMDs) for transient dynamic analyses. Both SCC modes and POIMDs are computed using the reduced HCB mass and stiffness matrices, which can be directly computed from many commercial finite element analysis software. Comparison of time history responses to an impulse-type load in a mechanical beam assembly indicate that the interface-reduced model correlates well with the HCB truth model. Localized features like slip and contact area are well-represented in the time domain when the beam assembly is loaded with a broadband excitation. The proposed method also yields reduced-order models with greater critical timestep lengths for explicit integration schemes.

42 ENGINEERING↗

Modular multi-interface nanocrystals for enhanced ethanol oxidation electrocatalysis

Electrochemical processes that utilize biomass-derived ethanol as a source of electrons and protons offer a sustainable energy strategy, yet their practical implementation is limited by sluggish ethanol oxidation reaction (EOR) kinetics and catalyst poisoning. Here, in this study, we report a modular multi-interface nanocrystal catalyst comprising core/shell Co 2 P/Pd and Pd-Au heterostructured interfaces that exhibit complementary functions for the enhanced EOR catalysis. The Co 2 P/Pd interface boosts Pd atom utilization and lowers the kinetic barriers for ethanol-to-acetate conversion, while the Pd-Au interface effectively alleviates CO poisoning caused by C–C bond cleavage of ethanol. In-depth analyses using in situ attenuated total reflectance-surface-enhanced infrared absorption spectroscopy, differential electrochemical mass spectrometry, and density functional theory calculations elucidate the mechanistic roles of these interfaces. The optimized Co 2 P/Pd-Au 0.08 nanorods achieve an excellent mass activity, underscoring the potential of modular, multi-interface nanocrystals for advancing EOR catalysis and offering a generalizable strategy for broader catalytic innovations.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Tailoring Interfaces in Solid-State Batteries Using Interfacial Thermochemistry and Band Alignment

Solid-state lithium ion batteries have enhanced thermal stability compared to batteries using liquid electrolytes. Although their practical implementation is limited by undesired side reactions between the electrode and electrolyte, different modification strategies have been proposed to stabilize these reactive interfaces. These approaches have been primarily based upon bulk materials properties, however, which may not necessarily be representative of the chemistry at the solid/solid interface. In this work, first principles calculations and X-ray scattering experiments are used to elucidate molecular-level reactivity and develop design principles for tailored interfaces based on surface and interfacial properties. Because of its well-known instability, the interface between the Li metal anode and the lithium lanthanum titanate (LLTO) solid electrolyte is applied as a model system. Density functional theory calculations are used to describe bulk, surface, and interfacial thermochemistry of the Li/LLTO system, and interfacial reconstruction is probed using ab initio molecular dynamics. These simulations of the Li/LLTO interface demonstrate facile decomposition concomitant with reduction of Ti 4+ ions. Based on further insights from computational analysis of the surface band edge positions, La 2 O 3 is proposed as an interlayer coating and is shown to provide an energetic barrier for interfacial charge transfer and decomposition reactions from X-ray reflectivity measurements and theoretical calculations. The findings in this work suggest that design strategies based on surface and interfacial properties can be used to kinetically stabilize electrode/electrolyte interfaces in solid-state batteries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Self-Assembly of Silica Nanoparticles at Water–Hydrocarbon Interfaces: Insights from In Operando Small-Angle X-ray Scattering Measurements and Molecular Dynamics Simulations

To achieve tunable controls on the interactions of siliceous materials in subsurface environments bearing water and hydrocarbons, it is essential to determine the influence of hydrocarbon–water interfaces on the self-assembly of the silica particles. The hydrophilic silica particle have a tendency to aggregate on the water front of the interface. Self-assembly of silica nanoparticles proceeds via the migration of these nanoparticles to the water–hydrocarbon interface followed by aggregation at the interface. Fractal-like morphologies of assembled silica nanoparticles at water–hydrocarbon interfaces are observed. Rapid assembly of the hydrophilic silica nanoparticles at water–hydrocarbon interfaces corresponds to an overall reduction in the surface tension of water–toluene and water–heptane systems. These studies demonstrate the silica aggregation that is the precursor of silica polymerization, or nucleation and growth is influenced by the presence of hydrocarbons in subsurface geologic environments. These insights were derived from in operando ultrasmall and small-angle X-ray scattering (USAXS/SAXS) measurements, cryo-scanning electron microscopy (Cryo-SEM) imaging, and classical molecular dynamics simulations. As a result, these studies are intended to inform current and future efforts aimed at tuning silica reactivity in subsurface geologic environments to enhance permeability, the design and use of silica-based proppants to enhance fractures, and the development of effective strategies to control silica-based scaling behavior in subsurface reservoirs.

42 ENGINEERING↗

Reorganization of Water at Aqueous Aluminum Chloride (AlCl 3 ) Interfaces: Vibrational Sum Frequency Generation and Molecular Dynamics Simulations

AlCl 3 hydration states and complexation are not well understood both in solutions and at the air–aqueous interface despite their potential significance in natural waters and their industrial and energy-related applications. Here, we investigated Al 3+ and Cl – ion behaviors in an AlCl 3 aqueous bulk solution and at the air–aqueous interface using interface-selective vibrational sum frequency generation (SFG), Raman and infrared spectroscopies, molecular dynamics (MD) simulation, as well as molecular-informed reduced modeling. Our reduced modeling reveals relatively long-range effects for Al 3+ as compared to monovalent ions such as Na + indicating that the interfacial depth of trivalent ions can be significantly larger than that of monovalent ions at the air–water interface. MD simulations reveal interfacial stratification and multiple layering of the ions. Compression of the Al 3+ and Cl – distributions with increasing concentrations from 0.5 to 2.5 m is also observed in the subsurface regions. Significant SSP- and PPP-polarized SFG OH spectral intensity increases are observed from 0.5 to 1.5 m and 0.5 to 2.5 m, respectively, indicative of interfacial depth increases and a change in average orientation above 1.5 m. Extensive evaluation of SFG spectra, Fresnel-corrected using several approaches, shows the same trends. The nonmonotonic trend points to a changing structure in surface and subsurface water orientation and hydrogen bonding environment generally consistent with the MD simulation of stratification and water orientation changes. Furthermore, solvent-shared ion pairing is implicated with MD simulation radial distribution analysis and consistent with infrared spectral identification of the hexaaqua aluminum ion in the solution phase. Spectral evidence of a strong Al 3+ hydration shell and the acidic behavior of the Al 3+ ions is obvious in the Raman and infrared spectra of the bulk solution. In conclusion, we show that the MD dipole potential is directly related to the MD second-order susceptibility of the interface, χ SFG–MD (2) , both of which correlate up to ∼35 Å with the spectral observations of increasing and then saturating intensities, suggesting that both ion stratification and interfacial depth determine the water orientations at an air–water interface of 1-3 electrolyte solutions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Electron Trapping and Ion Leaching at the Li-Modified Quartz–Water Interface

Electrons and ions at metal oxide-water interfaces have a critical role in many phenomena and applications, thus making their properties of considerable interest. We here investigate the behavior of a lithium impurity at the water interface with Li-doped SiO 2 using hybrid density functional based ab initio molecular dynamics simulations. We find that the excess electron donated by the lithium dopant localizes on a surface silicon atom and is partially solvated at the aqueous interface. While the position of the excess electron does not change during our ~60 ps simulation, the lithium cation diffuses from its initial position in the SiO 2 subsurface toward the interface and eventually leaches out of the oxide surface and becomes solvated by four water molecules, forming an aqueous Li+- electron complex at the interface. The degree of interaction between the localized electron and the lithium ion controls not only the energy level of the excess electron but also the extent of structural distortion and hydrogen-bonding at the interface. The results of our study can be relevant for understanding the initial stages of glass corrosion, where alkali ions are leached from the surface region by interactions with water.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Structure of Molten Alkali Chlorides at Charged Interfaces and the Prediction and Interpretation of Their X-ray Reflectivity

The fundamental properties of molten salts have been the subject of research that spans a century. Yet, in the past few years, there has been an unprecedented surge in interest for these systems in the bulk and under confinement by walls and interfaces including under applied potentials. This is driven by the prospect of exciting and very practical energy technologies, including those in the solar and nuclear fields. This article sets to answer two simple but fundamental questions. How does the liquid structure of alkali chlorides change at a real interface when it is charged? Also, how would such changes on the liquid side of the interface be detected in X-ray reflectivity experiments? We use an interface mimicking conductive diamond, which because of its lattice spacing, is an excellent choice for reflectivity experiments. The reason for our interest in X-ray reflectivity is that, as opposed to electrochemical measurements alone, this is likely the only technique in which atomic level information at the liquid side of the interface can be gained under the extreme temperature environments of molten salts. As it will become apparent, the interpretation of reflectivity results in terms of atomic positions is complex when multiple species with different X-ray contrasts on the liquid side are considered. A theoretical scheme termed “the peaks and antipeaks analysis of reflectivity” originally introduced in our prior work (J. Phys. Chem. C2019, 123 (8), 4914–4925) is expanded to interpret the structural changes at the interface as a function of applied electrical bias.

36 MATERIALS SCIENCE↗

Aqueous Interfaces in Chemical Separations

Chemical separations play a vital role in refinery and reprocessing of critical materials, such as platinum group metals, rare earths, and actinides. The choice of separation system─whether it is liquid–liquid extraction (LLE), sorbents, or membranes─depends on specific needs and applications. In almost all separation processes, the desired metal ions adsorb or transfer across an aqueous interface, such as the solid/liquid interface in sorbents or oil/water interfaces in LLE. Despite these separation technologies being extensively used for decades, our understanding of the molecular-scale mechanisms governing ion adsorption and transport at interfaces remains limited. This knowledge gap presents a significant challenge in meeting the increasing demands for these critical materials due to their growing use in advanced technologies. Fortunately, recent advancements in surface-specific experimental and computational techniques offer promising avenues to bridge this gap and facilitate the development of next-generation separation systems. Interestingly, unanswered questions regarding interfacial phenomena in chemical separations hold great relevance to various fields, including energy storage, geochemistry, and atmospheric chemistry. Therefore, the model interfacial systems developed for studying chemical separations, such as amphiphilic molecules assembled at a solid/water, air/water, or oil/water interface, may have far-reaching implications, extending beyond separations and opening doors to addressing a wide range of scientific inquiries. This perspective discusses recent interfacial studies elucidating amphiphile–ion interactions in chemical separations of metal ions. Finally, these studies provide direct, molecular-scale information about solute and solvent behavior at aqueous interfaces, including multivalent and complex ions in highly concentrated solutions, which play key roles in LLE of critical materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Surface Energies and Structure of Salt–Brine Interfaces

Permeability of salt formations is controlled by the equilibrium between the salt–brine and salt–salt interfaces described by the dihedral angle, which can change with the composition of the intergranular brine. In this work, classical molecular dynamics (MD) simulations were used to investigate the structure and properties of the salt–brine interface to provide insight into the stability of salt systems. Mixed NaCl–KCl brines were investigated to explore differences in ion size on the surface energy and interface structure. Nonlinearity was noted in the salt–brine surface energy with increasing KCl concentration, and the addition of 10% KCl increased surface energies by 2–3 times (5.0 M systems). Size differences in Na+ and K+ ions altered the packing of dissolved ions and water molecules at the interface, impacting the surface energy. Additionally, ions at the interface had lower numbers of coordinating water molecules than those in the bulk and increased hydration for ions in systems with 100% NaCl or 100% KCl brines. Ultimately, small changes in brine composition away from pure NaCl altered the structure of the salt–brine interface, impacting the dihedral angle and the predicted equilibrium permeability of salt formations.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗