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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Ion Exchange Column Thermal Modeling: Prevention of Process Effluent Boiling - 18577

The Savannah River Site treats and disposes of legacy high-level waste, which resulted from 60 years of nuclear material production, medical research, and other nuclear related work. Complex mixtures of soluble and insoluble solids occupy tanks of which the South Carolina Department of Health and Environmental Control recognizes as the single largest environmental risk state-wide. The risk is reduced through removal, treatment, and solidification of decontaminated salt waste. Presently, SRS decontaminates the soluble salt component of the waste, a solution containing actinides and cesium, via implementation of the Actinide Removal Process and the Modular Caustic Side Solvent- Extraction Unit. Caustic solvent extraction is set to increase in scale by late 2018, with startup of the newly constructed Salt Waste Processing Facility. In conjunction with Salt Waste Processing Facility startup, Savannah River Remediation has been tasked by the Department of Energy to demonstrate modular ion exchange technology. The Tank Closure Cesium Removal project aims to demonstrate the feasibility of modular ion exchange processes for future Department of Energy applications. The Tank Closure Cesium Removal system is scheduled to begin operation in mid-2018. Dissolved salt solution, or influent, will be fed through a filter and ion exchange columns in lead-lag configuration, producing effluent. The effluent is fed to a separate high-level waste tank, for future disposition at Salt-stone Production Facility. Once the demonstration project is complete, the loaded ion exchange columns will be purged, dried, and placed in interim safe storage, awaiting final disposition. The ion exchange media selected for the Tank Closure Cesium Removal system is Honeywell UOP IONSIV{sup C} R-9120. The media is a prime candidate for separation of cesium from radioactive high-level waste. UOP R-9120{sup C} is inorganic and has high capacity, selectivity, and affinity for cesium. During operation, influent is fed to the ion exchange columns, contacting UOP R-9210{sup C} packed within the media vessel. Contact initiates loading of isotopes, and given ample time the solid phase (ion exchange media) and solution achieve thermodynamic equilibrium. UOP R-9120{sup C} is a prime candidate for separation of cesium and dissolved fission products. Although the properties of UOP R-9120{sup C} are favorable for separation, the same properties lead to accumulation of a heat source in the ion exchange bed. Cesium-137 and its daughter product, barium-137 m, generate a clear majority of heat (i.e. ∼ 94%). During operation salt solution flows through each column and transports heat from the ion exchange bed. Once operation is terminated, the effluent contained within the porous bed volume becomes essentially static. In the absence of engineering controls, the heat generated may boil the effluent. Rapid vaporization of aqueous salt solution would lead to bed over pressurization. Over pressurization and an associated release of high-level waste would result in adverse impacts to human health and the environment. This paper focuses on modeling the heat transfer associated with the Tank Closure Cesium Removal system ion exchange column. The model evaluates the maximum heat generation and the associated radionuclide loadings that prevent boiling within of the media vessel, under no flow conditions. A safety significant control, maintaining loadings less than the established loading limit ensures associated impacts to human health and the environment are prevented. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2019

Interaction of Iron with Alumina Refractory Under Flash Ironmaking Conditions

A novel flash ironmaking technology (FIT) based on the direct reduction of iron ore concentrate by a reducing gas such as hydrogen, natural gas, or coal gas has been developed at the University of Utah. A proper choice of refractories is expected to play an important role in the development of FIT and its scale-up. In this work, the interaction of iron with alumina refractory under flash ironmaking conditions has been investigated. A thermodynamic basis for the interaction phenomena has been developed by considering the Fe-Al-O system, and a kinetic model based on solid-state diffusion is proposed to describe the growth of the hercynite (FeAl{sub 2}O{sub 4}) spinel formed as a result of the interaction between Fe, O (from H{sub 2}O and CO{sub 2}), and Al{sub 2}O{sub 3}. Experiments were conducted with Fe powders and pure Al{sub 2}O{sub 3} in the temperature range 1200 to 1500 °C under gas atmospheres relevant to flash ironmaking, and the reacted samples were analyzed using XRD, SEM-EDX, and EPMA techniques. The analyses of reacted samples confirmed the formation of the hercynite (FeAl{sub 2}O{sub 4}) spinel phase and the thickness of the FeAl{sub 2}O{sub 4} spinel as measured using elemental line scans in SEM-EDX and EPMA varied in the range of 0.5 to 1.3 mm. Results showed that the proposed model suitably describes the growth of the hercynite spinel layer, which obeyed the parabolic rate law at all temperatures. The parabolic rate constants were obtained and the diffusion-controlled growth of the FeAl{sub 2}O{sub 4} layer strongly depended on temperature. Furthermore, using the kinetic model, an expression for the effective diffusivity ( (D{sub eff})-bar ) was obtained and its values at the experimental temperatures were determined. The solid-state diffusion was an activated process, as expected, with an activation energy value of 231 kJ/mol.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Structure and microwave dielectric characteristics of lithium-excess Ca{sub 0.6}Nd{sub 0.8/3}TiO{sub 3}/(Li{sub 0.5}Nd{sub 0.5})TiO{sub 3} ceramics

Graphical abstract: - Highlights: • Dense ceramics were fabricated by the conventional solid-state route. • Excess-Li addition lowers sintering temperature. • Excess-Li addition improves the relative density and microwave dielectric properties. - Abstract: Compositions based on (1−x)Ca{sub 0.6}Nd{sub 8/3}TiO{sub 3}−x(Li{sub 1/2}Nd{sub 1/2})TiO{sub 3} + yLi (CNLNTx + yLi, x = 0.30–0.60, y = 0–0.05), suitable for microwave applications have been developed by systematically adding excess lithium in order to tune the microwave dielectric properties and lower sintering temperature. Addition of 0.03 excess-Li simultaneously reduced the sintering temperature and improved the relative density of sintered CNLNTx ceramics. The excess Li addition can compensate the evaporation of Li during sintering process and decrease the secondary phase content. The CNLNTx (x = 0.45) ceramics with 0.03 Li excess sintered at 1190 °C have single phase orthorhombic perovskite structure, together with the optimum combination of microwave dielectric properties of ε{sub r} = 129, Q × f = 3600 GHz, τ{sub f} = 38 ppm/°C. Obviously, excess-Li addition can efficiently decrease the sintering temperature and improve the microwave dielectric properties. The high permittivity and relatively low sintering temperatures of lithium-excess Ca{sub 0.6}Nd{sub 0.8/3}TiO{sub 3}/(Li{sub 0.5}Nd{sub 0.5})TiO{sub 3} ceramics are ideal for the development of low cost ultra-small dielectric loaded antenna.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Piezochromism and structural and electronic properties of benz[a]anthracene under pressure

We report a combined experimental and theoretical study of the high pressure behavior of a herringbone-type hydrocarbon benz[a]anthracene (BaA) using fluorescence spectroscopy, X-ray diffraction, optical absorption, photoconductivity measurements, and first-principles density functional theory (DFT) calculations. The ambient-pressure molecular solid phase of BaA was found to be stable up to ~15.0 GPa. Increasing the external pressure within this region would induce a reversible piezochromic colour change in the sample, from yellow-green to light brown. The reversibility of the colour change was confirmed by both optical observations and fluorescence measurements. Further compression beyond 15 GPa leads to polymerization of the sample and formation of an amorphous hydrogenated carbon. The low pressure crystalline phase is not recoverable when the sample is decompressed from pressure above 15 GPa. DFT investigation of the structures at zero temperature suggests that the formation of a crystalline polymeric phase can take place between 30 and 117 GPa, however the kinetic barriers hinder the process at low pressure regions. The phase transition is therefore suggested to proceed along a gradual transition path to an amorphous phase at a lower reaction threshold, activated by finite temperature effects. Optical absorption measurements reveal that the band gap of BaA decreases at high pressure, from 2.4 eV at 0.5 GPa to 1.0 eV at 50.6 GPa. The DFT calculations further suggest that the band gap of BaA in the molecular phase could reduce to ~0.1 eV at 117 GPa. Photoconductivity measurements show a continuous increase of photocurrent in the molecular phase region, which most likely originated from the increase of carrier mobility under pressure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Effect of surface free energies on the heterogeneous nucleation of water droplet: A molecular dynamics simulation approach

Heterogeneous nucleation of water droplet on surfaces with different solid-liquid interaction intensities is investigated by molecular dynamics simulation. The interaction potentials between surface atoms and vapor molecules are adjusted to obtain various surface free energies, and the nucleation process and wetting state of nuclei on surfaces are investigated. The results indicate that near-constant contact angles are already established for nano-scale nuclei on various surfaces, with the contact angle decreasing with solid-liquid interaction intensities linearly. Meanwhile, noticeable fluctuation of vapor-liquid interfaces can be observed for the nuclei that deposited on surfaces, which is caused by the asymmetric forces from vapor molecules. The formation and growth rate of nuclei are increasing with the solid-liquid interaction intensities. For low energy surface, the attraction of surface atoms to water molecules is comparably weak, and the pre-existing clusters can depart from the surface and enter into the bulk vapor phase. The distribution of clusters within the bulk vapor phase becomes competitive as compared with that absorbed on surface. For moderate energy surfaces, heterogeneous nucleation predominates and the formation of clusters within bulk vapor phase is suppressed. The effect of high energy particles that embedded in low energy surface is also discussed under the same simulation system. The nucleation preferably initiates on the high energy particles, and the clusters that formed on the heterogeneous particles are trapped around their original positions instead of migrating around as that observed on smooth surfaces. This feature makes it possible for the heterogeneous particles to act as fixed nucleation sites, and simulation results also suggest that the number of nuclei increases monotonously with the number of high energy particles. The growth of nuclei on high energy particles can be divided into three sub-stages, beginning with the formation of a wet-spot, increase of contact angle with near-constant contact line, and finally growth with constant contact angle. The growth rate of nuclei also increases with the size of high energy particles.

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

Simulation of Particulate Transport for Delivery of Solid Amendments into the Subsurface: FY24 Status Report

For particulate-based amendments to be viable for field-scale remediation at the Hanford Site (e.g., 200 DV-1 Operable Unit), particles need to be delivered a sufficient radial distance from an injection well and retained at concentrations high enough for effective treatment. An accurate description of the particle radius of influence (ROI) is critical for developing an overall remediation strategy. However, field-scale particle simulations are currently limited due to insufficient simulation capabilities and a lack of experimental data to validate and parameterize particle transport models. To help build toward field-scale deployment, this fiscal year (FY) we have (1) developed a pre screening tool to estimate particle transport, (2) implemented particle transport models within PFLOTRAN, and (3) conducted preliminary estimations of particle ROI. While field-scale numerical simulations will ultimately be necessary before remedy design and field implementation, we have developed a pre-screening tool that offers valuable estimations of expected particle injectability and ROI in a 1-D system. The advantage of the tool is that it does not require extensive laboratory experiments and instead makes predictions based solely on routine laboratory measurements. This tool can assist in down-selection and decision-making by identifying which particle amendment systems are worth pursuing in future laboratory experiments, such as 1-D column tests and beyond. With any system, scaling up from the lab to the field presents challenges. Currently, there is no field data available for model calibration or validation. However, the theoretical particle models being developed herein are the best tools available to guide progress toward field deployment. To help bridge this gap and verify model predictions, larger-scale lab experiments are being proposed. To advance simulation capabilities, six particle transport models are being integrated into the reactive transport simulator PFLOTRAN. These include colloid filtration theory (CFT) and five additional particle transport models (M1-M5). Each model, from M1 to M5, progressively incorporates additional particle transport and retention processes. Ultimately, the simplest model capable of accurately describing 1-D column data will be selected and parameterized. During FY24, the CFT and M1 model have been fully implemented within PFLOTRAN. Using an existing 1 D column experiment, the two currently implemented particle transport models (CFT and M1), and associated parameters, were fit to this experiment. While simpler model formulations are helpful for estimations, these formulations could not fully describe particle transport and retention behavior in the previous 1-D column experiment. Thus, additional complexities will need to be considered, which will be accounted for in the M2-M5 model formulations. Additionally, because a viscous, shear thinning fluid was required to keep particles in suspension, considerations for flow will also need to also be accounted for. Therefore, a new immiscible two-phase flow mode is currently being implemented in PFLOTRAN. With some modifications, this new flow module could also support simulation of non-Newtonian liquid amendments, foams, and emulsions. We also estimated the expected ROI of solid amendments using 1-D simulations. The average predicted ROI was approximately 15 ft for micron-sized zero valent iron (mZVI) suspended in xanthan gum (XG). Using the pre screening tool and ROI estimates, additional amendment-delivery laboratory characterization and experiments are proposed. The results from additional experiments can be used to validate and parametrize particulate transport model formulations, which will ultimately provide predictive capabilities for field amendment-delivery systems.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Mixed sodium nickel-manganese sulfates: Crystal structure relationships between hydrates and anhydrous salts

The present contribution provides new structural and spectroscopic data on the formation of solid solutions between hydrated and dehydrated sulfate salts of sodium-nickel and sodium-manganese in a whole concentration range: Na{sub 2}Ni{sub 1−x}Mn{sub x}(SO{sub 4}){sub 2}·yH{sub 2}O, 0≤ x≤1.0. Using powder XRD, electron paramagnetic resonance spectroscopy (EPR), IR and Raman spectroscopy it has been found that double sodium-nickel and sodium-manganese salts form solid solutions Na{sub 2}Ni{sub 1−x}Mn{sub x}(SO{sub 4}){sub 2}·4H{sub 2}O with a blödite-type of structure within a broad concentration range of 0≤x≤0.49, while the manganese rich compositions Na{sub 2}Ni{sub 1−x}Mn{sub x}(SO{sub 4}){sub 2}·2H{sub 2}O (0.97≤x≤1.0) crystallize in the kröhnkite-type of structure. The Ni-based blödites Na{sub 2}Ni{sub 1−x}Mn{sub x}(SO{sub 4}){sub 2}·4H{sub 2}O dehydrate between 140 and 260 °C into anhydrous salts Na{sub 2}Ni{sub 1−x}Mn{sub x}(SO{sub 4}){sub 2}, 0≤ x≤0.44, with a structure where Ni{sub 1−x}Mn{sub x}O{sub 6} octahedra are bridged into pairs by edge- and corner sharing SO{sub 4}{sup 2−} groups. Both TEM and EPR methods show that the Ni{sup 2+} and Mn{sup 2+} ions are homogenously distributed over three crystallographic positions of the large monoclinic cell. The dehydration of the kröhnkite phase Na{sub 2}Ni{sub 1−x}Mn{sub x}(SO{sub 4}){sub 2}·2H{sub 2}O yields the alluaudite phase Na{sub 2+δ}Mn{sub 2-δ/2}(SO{sub 4}){sub 3}, where the Na-to-Mn ratio decreases and all Ni{sup 2+} dopants are released from the structure. The process of the dehydration is discussed in terms of structural aspects taking into account the distortion degree of the Ni,MnO{sub 6} and SO{sub 4} polyhedra. - Graphical abstract: Thermal dehydration of the blödite phase Na{sub 2}Ni{sub 1−x}Mn{sub x}(SO{sub 4}){sub 2}·4H{sub 2}O (0≤ x≤0.49) yields nickel-manganese sulfates Na{sub 2}Ni{sub 1−x}Mn{sub x}(SO{sub 4}){sub 2} (0≤ x≤0.44) with a large monoclinic cell, while the alluaudite phase Na{sub 2+δ}Mn{sub 2-δ/2}(SO{sub 4}){sub 3} is obtained from the kröhnkite phase Na{sub 2}Ni{sub 1−x}Mn{sub x}(SO{sub 4}){sub 2}·2H{sub 2}O (0.97≤x≤1.0). - Highlights: • Blödite phases accommodate Mn{sup 2+} ions. • Blödite structure is transformed to a super-cell structure. • The kröhnkite phase accommodates only limited amounts of Ni{sup 2+} ions.

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

Thermo-mechanical behavior of hypoeutectic Ni-Y-Zr alloys

Microstructure refinement and optimized alloying can improve metallic alloy performance: stable nanocrystalline (NC) alloys with immiscible second phases, e.g., Cu-Ta, are stronger than unstable NC alloys and their coarse-grained (CG) counterparts, but higher melting point matrices are needed. Hypoeutectic, CG Ni-Y-Zr alloys were produced via arc-melting to explore their potential as high-performance materials. Microstructures were studied to determine phases present, local composition and length scales, while heat treatments allowed investigating microstructural stability. Alloys had a stable, hierarchical microstructure with ~250 nm ultrafine eutectic, ~10 µm dendritic arm spacing and ~1 mm grain size. Hardness and uniaxial compression tests revealed that mechanical properties of Ni-0.5Y-1.8Zr (in wt%) were comparable to Inconel 617 despite the small alloying additions, due to its hierarchical microstructure. Here, uniaxial compression at 600 °C showed that ternary alloys outperformed Ni-Zr and Ni-Y binary alloys in flow stress and hardening rates, which indicates that the Ni 17 Y 2 phase was an effective reinforcement for the eutectic, which supplemented the matrix hardening due to increased solubility of Zr. Results suggest that ternary Ni-Y-Zr alloys hold significant promise for high temperature applications.

36 MATERIALS SCIENCE↗
DOE OSTI2017

In Situ Tracking Kinetic Pathways of Li + /Na + Substitution during Ion-Exchange Synthesis of Li x Na 1.5– x VOPO 4 F 0.5

Ion exchange is a ubiquitous phenomenon central to wide industrial applications, ranging from traditional (bio)chemical separation to the emerging chimie douce synthesis of materials for batteries and other energy applications. The exchange process is complex, involving substitution and transport of different ions under non-equilibrium conditions, and thus difficult to probe, leaving a gap in mechanistic understanding of kinetic exchange pathways toward final products. Herein, we report in situ tracking kinetic pathways of Li + /Na + substitution during solvothermal ion-exchange synthesis of Li x Na 1.5-x VOPO 4 F 0.5 (0 ≤ x ≤ 1.5), a promising multi-Li polyanionic cathode for batteries. The real-time observation, corroborated by first-principles calculations, reveals a selective replacement of Na + by Li + , leading to peculiar Na + /Li + /vacancy orderings in the intermediates. Contradicting the traditional belief of facile topotactic substitution via solid solution reaction, an abrupt two-phase transformation occurs and predominantly governs the kinetics of ion exchange and transport in the 1D polyanionic framework, consequently leading to significant difference of Li stoichiometry and electrochemical properties in the exchanged products. The findings may help to pave the way for rational design of ion exchange synthesis for making new materials.

25 ENERGY STORAGE↗
DOE OSTI2017

In Situ Observation of Oxygen Vacancy Dynamics and Ordering in the Epitaxial LaCoO 3 System

Vacancy dynamics and ordering underpin the electrochemical functionality of complex oxides and strongly couple to their physical properties. In the field of the epitaxial thin films, where connection between chemistry and film properties can be most clearly revealed, the effects related to oxygen vacancies are attracting increasing attention. Here, we report a direct, real-time, atomic level observation of the formation of oxygen vacancies in the epitaxial LaCoO 3 thin films and heterostructures under the influence of the electron beam utilizing scanning transmission electron microscopy (STEM). In the case of LaCoO 3 /SrTiO 3 superlattice, the formation of the oxygen vacancies is shown to produce quantifiable changes in the interatomic distances, as well as qualitative changes in the symmetry of the Co sites manifested as off-center displacements. The onset of these changes was observed in both the [100]pc and [110]pc orientations in real time. Additionally, annular bright field images directly show the formation of oxygen vacancy channels along [110]pc direction. In the case of 15 u.c. LaCoO 3 thin film, we observe the sequence of events during beam-induced formation of oxygen vacancy ordered phases and find them consistent with similar processes in the bulk. Moreover, we record the dynamics of the nucleation, growth, and defect interaction at the atomic scale as these transformations happen. These results demonstrate that we can track dynamic oxygen vacancy behavior with STEM, generating atomic-level quantitative information on phase transformation and oxygen diffusion.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A rapid molecular precursor solid-state route to crystalline Fe 2 GeS 4 nanoparticles

Iron germanium sulfide (Fe 2 GeS 4 ) recently emerged as a potential thin film solar photovoltaic absorber. The introduction of the third element—germanium (Ge)—viewed as a solution for overcoming multiple barriers of a photovoltaic pyrite, confers stability to Fe 2 GeS 4 at elevated temperatures, typically required for accomplishing grain growth in Gen 2 thin film PV. A facile synthesis of Fe 2 GeS 4 nanoparticles from molecular precursors, comprising mechanical mixing of starting materials followed by a two-hour annealing in a sulfur-rich atmosphere is presented herein. Further processing of the resulting Fe 2 GeS 4 nanopowders at elevated temperatures demonstrates high thermal stability of Fe 2 GeS 4 (up to 500 °C), in comparison with pyrite, which shows onset of pyrrhotite upon heating above 160 °C. Based on the secondary crystalline phases formed, here we propose a mechanism of decomposition of Fe 2 GeS 4 at high temperatures. Films fabricated with Fe 2 GeS 4 were further annealed and revealed that Fe 2 GeS 4 withstands high temperatures in thin film.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Kinetic model for quartz and spinel dissolution during melting of high-level-waste glass batch

The dissolution of quartz particles and the growth and dissolution of crystalline phases during the conversion of batch to glass potentially affects both the glass melting process and product quality. Crystals of spinel exiting the cold cap to molten glass below can be troublesome during the vitrification of iron-containing high-level wastes. To estimate the distribution of quartz and spinel fractions within the cold cap, we used kinetic models that relate fractions of these phases to temperature and heating rate. Fitting the model equations to data showed that the heating rate, apart from affecting quartz and spinel behavior directly, also affects them indirectly via concurrent processes, such as the formation and motion of bubbles. Because of these indirect effects, it was necessary to allow one kinetic parameter (the pre-exponential factor) to vary with the heating rate. The resulting kinetic equations are sufficiently simple for the detailed modeling of batch-to-glass conversion as it occurs in glass melters. The estimated fractions and sizes of quartz and spinel particles as they leave the cold cap, determined in this study, will provide the source terms needed for modeling the behavior of these solid particles within the flow of molten glass in the melter.

Batch melting, Cold cap, Quartz, Spinel, Waste gla↗
DOE OSTI2022

Thermodynamic modeling of adsorption at the liquid-solid interface

Adsorptive separation techniques are significantly energy efficient in comparison to conventional thermal separation techniques such as distillation. Despite extensive research and development activities undertaken for mixed-gas adsorption, the use of adsorption techniques for the separation of multicomponent liquid mixtures is still limited. A major barrier is the lack of accurate adsorption thermodynamic models, which form the scientific foundation of process simulation of such systems, making the translation to industrial scale challenging. In this work, we have rigorously computed the surface excess of adsorption for six binary liquid mixtures on silica gel at 303 K using the frameworks of the generalized Langmuir isotherm (gL) and the adsorbed solution theory (AST). The six binary liquid mixtures were formed by the pair-wise combinations of four components: benzene, 1,2-dichloroethane, cyclohexane, and n-heptane. We have based our calculations by considering simultaneous equilibria of three phases: saturated vapor phase, bulk liquid phase, and adsorbed phase. Further, the composition of the corresponding saturated vapor phase was estimated by the Nonrandom Two-Liquid activity coefficient model and experimental vapor-liquid equilibria data. The activity coefficients of the adsorbed phase, the central issue of multicomponent adsorption thermodynamics, were calculated using the adsorption Nonrandom Two-Liquid activity coefficient model. Devoid of simplifying assumptions, gL and AST provide rigorous thermodynamic frameworks for adsorption equilibria of multicomponent liquid mixtures.

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

Structural, Optical, and Dielectric Studies on Sr-Doped Biferroic YCrO{sub 3}

In this work, the solid-state synthesis of Y{sub 1-x}Sr{sub x}CrO{sub 3} (x = 0.0, 0.1) samples has been reported. The X-ray diffraction data analysis confirmed that the synthesized samples have crystallized into the orthorhombic phase with the assigned space group Pbnm. The Rietveld refinement of the XRD data confirmed the structure and other related parameters. The slight variation in the lattice parameters and negligible shift in the reflection peaks reveals the uniform dispersion of Sr at Y-site in the parent YCrO{sub 3} matrix. The dielectric characterization revealed the good dielectric nature of the prepared samples which decreases with Sr doping. Field emission scanning electron microscopy (FE-SEM) revealed that an agglomeration type process has taken place in the sample preparation. Fourier transform infrared (FTIR) characterization witnessed the formation of orthorhombic phase of the samples under study displaying sharp absorption bands corresponding to Cr–O stretching, Y/Sr–O stretching, and O–Cr–O deformation vibration, respectively. UV-Vis spectroscopy analysis revealed the dual direct allowed bandgap of the samples assigned to the Cr{sup 3+} ion transition in the ground level.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Modeling and simulation of vascular tumors embedded in evolving capillary networks

Here in this work, we present a coupled 3D–1D model of solid tumor growth within a dynamically changing vascular network to facilitate realistic simulations of angiogenesis. Additionally, the model includes erosion of the extracellular matrix, interstitial flow, and coupled flow in blood vessels and tissue. We employ continuum mixture theory with stochastic Cahn–Hilliard type phase-field models of tumor growth. The interstitial flow is governed by a mesoscale version of Darcy’s law. The flow in the blood vessels is controlled by Poiseuille flow, and Starling’s law is applied to model the mass transfer in and out of blood vessels. The evolution of the network of blood vessels is orchestrated by the concentration of the tumor angiogenesis factors (TAFs); blood vessels grow towards the increasing TAFs concentrations. This process is not deterministic, allowing random growth of blood vessels and, therefore, due to the coupling of nutrients in tissue and vessels, makes the growth of tumors stochastic. We demonstrate the performance of the model by applying it to a variety of scenarios. Numerical experiments illustrate the flexibility of the model and its ability to generate satellite tumors. Simulations of the effects of angiogenesis on tumor growth are presented as well as sample-independent features of cancer.

3D–1D coupled blood flow models↗
DOE OSTI2023

Real-time imaging of acoustic waves in bulk materials with X-ray microscopy

The dynamics of lattice vibrations govern many material processes, such as acoustic wave propagation, displacive phase transitions, and ballistic thermal transport. The maximum velocity of these processes and their effects is determined by the speed of sound, which therefore defines the temporal resolution (picoseconds) needed to resolve these phenomena on their characteristic length scales (nanometers). Here, we present an X-ray microscope capable of imaging acoustic waves with subpicosecond resolution within mm-sized crystals. We directly visualize the generation, propagation, branching, and energy dissipation of longitudinal and transverse acoustic waves in diamond, demonstrating how mechanical energy thermalizes from picosecond to microsecond timescales. Bulk characterization techniques capable of resolving this level of structural detail have previously been available on millisecond time scales—orders of magnitude too slow to capture these fundamental phenomena in solid-state physics and geoscience. As such, the reported results provide broad insights into the interaction of acoustic waves with the structure of materials, and the availability of ultrafast time-resolved dark-field X-ray microscopy opens a vista of new opportunities for 3D imaging of materials dynamics on their intrinsic submicrosecond time scales.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Content-aware foveated camera for multi-target tracking

Modern image sensors deliver substantial space-time bandwidth, yet indiscriminate acquisition often overwhelms memory, computation, and downstream perception. We present a content-aware, multi-foveated camera that dynamically reallocates sensing and magnification to multiple regions of interest (ROIs). A phase-only spatial light modulator (SLM) serves as a solid-state, inertia-free beam-steering and lens element, enabling per-frame field-of-view (FOV) reconfiguration and content-aware target tracking. By interleaving frames across foveae, our system preserves a wide-FOV situational context while refreshing each ROI at high rates, thereby reducing data volume without degrading task performance. We constructed a prototype employing a single-SLM, single-sensor architecture and demonstrated its application in real-time multi-object tracking with dynamic ROI maintenance across multiple viewpoints. The approach offers a general pathway to integrate detection, tracking, and segmentation algorithms in the acquisition loop, shifting workload from post hoc processing to intelligent capture.

Zang, Zihan [Univ. of California, Los Angeles, CA ↗
DOE OSTI2022

Metal fluxes at the sediment–water interface in a free water surface constructed wetland

Metal biogeochemistry in the sediment, water, and the sediment–water interface (SWI) was studied in a free water surface constructed wetland. Concentrations of labile copper (Cu), zinc (Zn), sulfate, chloride, and dissolved organic carbon (DOC) were measured with the diffusive gradients in thin film (DGT) and peeper. A good agreement between peeper- and DGT-measured metals was observed for Cu (regression r 2 = 0.3, 95% CI of the slopes > 0), but not for Zn (95% CI of the slopes overlapped with 0), which was attributed to the different complexed compounds between Cu and Zn in porewater. The depth profile of labile metals in sediment porewater varied with time and was consistent with the solid-phase metal deposition, showing higher concentrations in the surface layer (3 to –3 cm) than in the bottom layer (–4 to –13 cm). The depth-averaged labile Cu and Zn concentrations measured by DGT were 1.0 and 3.1 µg/L, and labile sulfate, chloride, and DOC concentrations measured by peeper were 1.8, 3.6, and 2.1 mg/L, respectively. A sharp decrease in sulfate occurred in September when sulfate concentrations became the lowest among sampling months. This was caused by the seasonal sulfur cycles in the wetland, where the dominant sulfur reaction is sulfate reduction in warm seasons and sulfide oxidation in cold seasons. Different metal-removal mechanisms were observed in the two wetland cells; sulfur dynamics controlled the removal processes in the cell without frequent disturbance but failed to influence metal removal in the cell with frequent disturbance due to the interruption of anoxic layers. The flux ratios that compare labile element concentrations between the water column and the SWI (R-Cu, R-Zn, R-DOC, R-sulfate, and R-chloride) were generated to determine metal diffusive fluxes at the interface. Labile Zn was mostly transported from the water to the SWI during all seasons (R-Zn < 1 for all months except January). Labile Cu moved from the SWI to the water during the warm months (R-Cu < 1), which was explained by the bioturbation-induced transport of organic matter based on the positive correlations between R-Cu and R-DOC. In general, sediment can serve either as a sink or a source depending on the environmental conditions, metal speciation, and presence of living organisms. Here, metal flux at the SWI is a key component in the biogeochemical cycling of a constructed wetland.

54 ENVIRONMENTAL SCIENCES↗