Search NASA⌕ Search

SEARCH · Search NASA

Results for “solution processability”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,369 records · Page 76
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Causal Analysis Report for "Demolition of Historic and Yet-to-be-Determined Radar Towers at TTR Without Completing Required NEPA Process"

Two radar towers at the Tonopah Test Range (TTR), Contraves Towers 22-00 and 12-00, were torn down prior to completion of the required National Environmental Policy Act (NEPA) process. National Technology and Engineering Solutions of Sandia, LLC, (NTESS) submission of the NEPA checklist triggered a Sandia Field Office (SFO) review of the proposed work scope and was to include a required consultation between SFO and the Nevada State Historic Preservation Office (SHPO) to assess any adverse effect(s) on historic properties or contributing element(s) to a historic district and, if so, determine a resolution. Following the consultation, SFO provides approval/denial of the proposed work detailed on the submitted NEPA checklist. Contraves Tower 22-00 is a historic structure, as formally determined by the SFO in consultation with the SHPO. The historical eligibility of Contraves Tower 12-00 is yet to be determined. On February 13, 2018, NTESS notified SFO that Contraves Tower 22-00 at TTR was torn down in May 2017 prior to completion of the required the NEPA process, including consultation with the SHPO. NTESS submitted two NEPA checklists to SFO in 2016 for the removal of several structures no longer required by NTESS. The first NEPA checklist listed three historic structures (one of which was Contraves Tower 22-00) and SFO determination on whether consultation with the SHPO is necessary as well as approval/denial of the NEPA checklist is pending. The second NEPA checklist listed five non-historic structures, one of which was Contraves Tower 12-00. SFO approved the NEPA checklist covering non historic structures except for the Contraves Tower 12-00, as the Contraves Tower 12-00 requires further consultation with the SHPO by SFO. Only after completion of the consultation would SFO determine approval/denial on the remaining property cited within the NEPA checklist. In late January 2018, NTESS personnel discovered that Contraves Tower 22-00 was no longer listed in the Facility Information Management System (FIMS). Upon further investigation, NTESS personnel verified that the Contraves Tower 22-00 had been removed in May 2017. During the initial extent of condition, it was discovered that Contraves Tower 12-00 had also been torn down in May 2017 as part of this same destruction and demolition (D&D) activity. Both Contraves Towers 22-00 and 12-00) had been torn down prior to completion of the NEPA process, including consultation with the SHPO.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2016

Removal of TcO 4 – from Representative Nuclear Waste Streams with Layered Potassium Metal Sulfide Materials

Many efforts have focused on the sequestration and immobilization of 99Tc because the radionuclide is highly mobile in oxidizing environments and presents serious health risks due to its radiotoxicity and long half-life (t1/2 = 213 000 a). One of the more common methods for Tc removal from solution and immobilization in solids is based on reducing Tc from highly soluble Tc(VII) to sparingly soluble Tc(IV). In order to remove solution Tc through this reduction process, the Tc-sequestering solid must contain a reducing agent and, ideally, the Tc-sequestering material would function in a large range of chemical environments. For long-term stability, the reduced Tc would preferentially be incorporated into the resulting mineral structure instead of simply being sorbed onto the mineral surface. Here, we report results obtained from batch sorption experiments performed in anoxic and oxic conditions with two sulfide-containing potassium metal sulfide (KMS) materials, known as KMS-2 and KMS-2-SS. In deionized water in anoxic conditions after 15 d of contact, KMS-2 is capable of removing ~45% of Tc and KMS-2-SS is capable of removing ~90% of Tc. The improved performance of KMS-2-SS compared to KMS-2 in deionized water in anoxic conditions appears to be linked both to a higher pH resulting from the batch sorption experiments performed with KMS-2-SS and a higher overall purity of KMS-2-SS. Both materials perform even better in highly caustic (pH~13.5), high ionic strength (8.0 M) simulated Hanford low-activity waste solutions, removing more than 90% Tc after 15 d of contact in anoxic conditions. Post-reaction solids analysis indicate that Tc(VII) is reduced to Tc(IV) and that Tc(IV) is bonded to S atoms in the resulting KMS-2 structure in a Tc2S7 form. In contrast to previous ion exchange experiments with other KMS materials, the batch sorption experiments examining Tc removal cause the initially crystalline KMS materials to lose much of their initial long-range order.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2019

An Objective and Efficient Method for Assessing the Impact of Reduced-Precision Calculations On Solution Correctness

Recent studies have shown that reducing the precision of floating-point calculations in an atmospheric model can improve the models' computational performance without affecting model fidelity, but code changes are needed to accommodate lower precision, and a small number of calculations might need to retain higher precision to prevent undue round-off error. For complex and computationally expensive systems like the Energy Exascale Earth System Model (E3SM), a method is needed to objectively assess the quality of the lower-precision simulations and to quickly identify problematic code pieces This paper demonstrates that solution correctness can be evaluated through a simple and quantitative error metric based on time step convergence. The proposed test method can unambiguously detect the accumulation of precision error and objectively assess its impact on solution accuracy. Since fast physical processes are known to affect key features of the multi-year mean climate in an atmospheric model, we show that the convergence test applied to short simulations can provide useful information about the impact of reduced precision on a model’s long-term behavior. In contrast, the traditional way of climate model evaluation requires multi-year simulations and involves inspecting many physical quantities for statistical significance in the presence of natural variability. The simplicity, computational efficiency, and objectivity of the proposed method makes it very attractive for high-resolution model development. The method is also expected to be applicable to other models that numerically solve time evolution equations.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Savannah River Site H-Canyon Collaborative Advanced Technology Demonstration (ATD) Program Review - 19499

The purpose of the Department of Energy-Environmental Management Office of Technology Development's (DOE-EM TD) Science of Safety (SOS) Robotics Initiative is to pull innovative commercial off the shelf (COTS) and near ready technologies to the field to expedite remaining EM mission clean up and enhance worker safety. A goal of this program is to demonstrate to DOE facilities the value of these available new technologies and their potential uses to solve difficult problems. In support of this goal, the Savannah River Site (SRS) H-Canyon Air Exhaust (HCAEX) tunnel biannual inspection task has been selected to demonstrate and evaluate the benefit of pulling advanced technology solutions to EM facilities. This is a highly collaborative task facilitated by SRNL and engaging SRS H-Canyon facility stakeholders, National Laboratory robotic and concrete inspection SMEs and university robotic and sensor researchers. Presently, the SRS HCAEX tunnel inspection consists of a visual examination to evaluate the structural integrity of the tunnel. Personal access is prohibited in the tunnel due to extreme conditions, thus the examination is accomplished remotely by deploying cameras mounted on a robotic crawler deployed into the tunnel. While the ability to see inside the tunnel in recent years has been highly valuable, it is desirable to have a better understanding of the environment to support a more thorough structural analysis and for long term planning purposes. This higher order of understanding can be accomplished through advanced COTS sensors and tools and those currently in development and near ready. The advanced technologies selected for demonstration will be evaluated for hosting on the FY19 HCAEX tunnel inspection crawler platform. The HCAEX ATD task is expected to be performed over a two-year period with year one now concluding. At WM2018, we presented the H-Canyon stakeholder's high priority inspection and remote handling needs, the collaboration team and the planned process of developing an integrated solution. This presentation will review the initial scope and inspection needs, then discuss the past year's progress to address these needs. The discussion includes the results of the Concrete Integrated Product Team (CIPT) formed to evaluate promising concrete NDE inspection technologies and a Lidar based tunnel mapping sensor suite solution. Highlighted in the discussion will be the engagement and pulling of university developed research and development to include student engagement through the formation and hosting of the SRNL Robotics and Sensors Intern team and collaboration with MSIPP funded Robotic Arm Concrete NDT Inspection University researchers. Lastly, the path forward to complete the demonstration will be presented. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2022

Structural analyses of amorphous calcium carbonate before and after removing strontium ions from an aqueous solution

Amorphous calcium carbonate (ACC) is a precursor of crystalline calcium carbonate; hence, its structural information at the atomic level is very important for controlling the morphology of crystalline calcium carbonate. In this study, we attempted to elucidate the process of Sr extraction from aqueous solution by using ACC for the purpose of removal of radioactive Sr from the contaminated water leaked after the Fukushima Daiichi nuclear accident. Here, the pair distribution functions, g(r) obtained by X-ray and neutron diffraction (ND) measurements show that ACC has a structure partially similar to that of monohydrocalcite, suggesting that ACC is transferred to the crystalline calcium carbonate starting from its crystal nucleus. Rietveld analysis of the ND data showed that the ACC that removed Sr was crystallized to calcite. However, the Sr–O coordination analyzed using extended X-ray absorption fine structure (EXAFS) implies that the local environment of O around Sr is similar to that in crystalline calcium carbonate aragonite.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Unfolding bovine α-lactalbumin with T-jump: Characterizing disordered intermediates via time-resolved x-ray solution scattering and molecular dynamics simulations

The protein folding process often proceeds through partially folded transient states. Therefore, a structural understanding of these disordered states is crucial for developing mechanistic models of the folding process. Characterization of unfolded states remains challenging due to their disordered nature, and incorporating multiple methods is necessary. Combining the time-resolved x-ray solution scattering (TRXSS) signal with molecular dynamics (MD), we are able to characterize transient partially folded states of bovine α-lactalbumin, a model system widely used for investigation of molten globule states, during its unfolding triggered by a temperature jump. We track the unfolding process between 20 μs and 70 ms and demonstrate that it passes through three distinct kinetic states. The scattering signals associated with these transient species are then analyzed with TRXSS constrained MD simulations to produce protein structures that are compatible with the input signals. Without utilizing any experimentally extracted kinetic information, the constrained MD simulation successfully drove the protein to an intermediate molten globule state; signals for two later disordered states are refined to terminal unfolded states. From our examination of the structural characteristics of these disordered states, we discuss the implications disordered states have on the folding process, especially on the folding pathway. Finally, we discuss the potential applications and limitations of this method.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Nonequilibrium DMFT + CPA for correlated disordered systems

We present a solution for the nonequilibrium dynamics of an interacting disordered system. The approach adapts the combination of the equilibrium dynamical mean-field theory and the equilibrium coherent potential approximation methods to the nonequilibrium many-body formalism, using the Kadanoff-Baym-Keldysh complex time contour, for the dynamics of interacting disordered systems away from equilibrium. We use our time domain solution to obtain the equilibrium density of states of the disordered interacting system described by the Anderson-Hubbard model, bypassing the necessity for the cumbersome analytical continuation process. We further apply the nonequilibrium solution to the interaction quench problem for an isolated disordered system. Here, the interaction is abruptly changed from zero (noninteracting system) to another constant (finite) value at which it is subsequently kept. We observe via the time dependence of the potential, kinetic, and total energies the effect of disorder on the relaxation of the system as a function of final interaction strength. Finally, the real-time approach has the potential to shed light on the fundamental role of disorder in the nonequilibrium dynamics of interacting quantum systems.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Radiation Effects in Innovative Structural Materials

The extreme radiation environments and demanding structural conditions of next-generation fission and proposed fusion reactors will require high performance materials with very high radiation resistance. Although conventional structural materials such as ferritic/ martensitic steels offer several attractive features, there is value in exploring alternative materials systems that may offer unprecedented radiation stability while also offering good thermomechanical properties. As noted elsewhere, options for designing radiation resistance include (a) the traditional approach of introducing a very high sink strength for recombination of radiation-induced vacancies and interstitials (e.g., Ti-modified stainless steels or 'nano-cluster-strengthened ferritic alloys', (b) utilizing materials with immobile vacancies at the operating temperature (e.g., silicon carbide), and (c) utilizing certain classes of materials that inherently exhibit superior resistance to radiation defect retention and accumulation (e.g., ferritic steels). Three relatively new but promising structural materials systems were selected for investigation, based on their favorable unirradiated mechanical properties and potential for good stability under irradiation: High entropy alloys (HEAs), bulk metallic glass (BMG), and MAX phase ceramics. The high configurational entropy in HEAs might alter point defect (solute and radiation defects) diffusion processes, thus potentially enhancing the recombination of radiation-produced damage. Therefore, HEAs offer the potential of a new class of materials for radiation resistance category (c) mentioned previously. A variety of BMGs such as Zr{sub 52.5}Cu{sub 17.9}Ni{sub 14.6}Al{sub 10}Ti{sub 5} offer good mechanical properties including fracture toughness values that may exceed 100 MPa-m{sup 1/2} and near net shape fabrication potential. The lack of crystallinity in BMGs prohibits the formation of conventional Frenkel pair defects under irradiation and therefore offer the possibility of another new material system for radiation resistance category (c). MAX phase ceramics (e.g., Ti{sub 3}SiC{sub 2}, Ti{sub 3}AlC{sub 2}, Ti{sub 2}AlC) have good mechanical properties and contain a nano-laminate structure that could provide a very high point defect sink strength. Due to their refractory nature, many of the MAX phase ceramics may exhibit negligible vacancy mobility up to high temperatures. Therefore, MAX phase ceramics offer the potential to provide radiation resistance in either categories (a) and (b), depending on the operating temperature. For this study, a novel 27%Fe-27%Mn-28%Ni-18%Cr single phase face centered cubic high entropy alloy was synthesized that exhibited good strength and ductility over a wide temperature range. Zr{sub 52.5}Cu{sub 17.9}Ni{sub 14.6}Al{sub 10}Ti{sub 5} (BAM-11) was selected as a prototypic advanced BMG. Several MAX phase ceramics (e.g., Ti{sub 3}SiC{sub 2}, Ti{sub 3}AlC{sub 2}, Ti{sub 2}AlC) that have good unirradiated thermal and mechanical properties were also investigated. The irradiation damage behaviors of these three novel materials systems have been studied after fission neutron at ∼75 deg. C up to 1 dpa and Ni ion irradiation at 25- 700 deg. C up to 30 dpa (lower temperatures and doses for the BMGs). All three sets of materials generally exhibited good radiation stability within certain temperature regimes. For example, the BMG exhibited only minor (<10%) change in strength that appeared to saturate after a dose of ∼1 dpa. A key shortcoming of current BMGs are that they can not be used at temperatures >>300 deg. C due to glass to crystalline transition at elevated temperature. The MAX phase ceramics irradiated at 400-700 deg. C appeared to be in the 'low temperature' regime where vacancies are immobile and therefore the radiation hardening saturated at relatively low doses. The Ti{sub 3}SiC{sub 2} MAX phase exhibited the best overall radiation stability over a wide temperature range. The HEA exhibited fine scale dislocation loop formation, no observable cavity swelling and reduced amounts of Cr depletion compared to traditional austenitic Fe-Cr-Ni alloys after ion irradiation, which suggests suppressed point defect and solute diffusion behavior. (authors)

36 MATERIALS SCIENCE↗
DOE OSTI2017

AMORE Mo-99 Spike Test Results

With funding from the National Nuclear Security Administrations Material Management and Minimization Office, Argonne National Laboratory (Argonne) is providing technical assistance to help accelerate the U.S. production of Mo-99 using a non-highly enriched uranium (non-HEU) source. A potential Mo-99 production pathway is by accelerator-initiated fissioning in a subcritical uranyl sulfate solution containing low enriched uranium (LEU). As part of the Argonne development effort, we are undertaking the AMORE (Argonne Molybdenum Research Experiment) project, which is essentially a pilot facility for all phases of Mo-99 production, recovery, and purification. Production of Mo-99 and other fission products in the subcritical target solution is initiated by putting an electron beam on a depleted uranium (DU) target; the fast neutrons produced in the DU target are thermalized and lead to fissioning of U-235. At the end of irradiation, Mo is recovered from the target solution and separated from uranium and most of the fission products by using a titania column. The Mo is stripped from the column with an alkaline solution. After acidification of the Mo product solution from the recovery column, the Mo is concentrated (and further purified) in a second titania column. The strip solution from the concentration column is then purified with the LEU Modified Cintichem process. A full description of the process can be found elsewhere [1–3]. The initial commissioning steps for the AMORE project include performing a Mo-99 spike test with pH 1 sulfuric acid in the target vessel without a beam on the target to demonstrate the initial Mo separation-and-recovery process, followed by the concentration column process. All glovebox operations were tested with cold solutions prior to performing the Mo-99 spike tests. Two Mo-99 spike tests with pH 1 sulfuric acid have been performed to date. Figure 1 shows the flow diagram for the remotely operated Mo-recovery system for the AMORE project. There are two separate pumps and flow paths for the acid and base operations. The system contains three sample ladders with eight sample loops per ladder for target mixing; column loading, including acid and water washes; and column stripping, including the final water wash.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

Collaboration on SBIR/TTO Phase II Project for Optical QC Device and Collaboration on SBIR/TTO Phase II-b Project for Advanced Quality Inspection Device Development: Cooperative Research and Development CRADA Number CRD-16-00652 (Final Report)

The overall goal of this program is to develop and commercialize a turnkey quality control solution for the entire PEM fuel cell manufacturing process including membrane, gas diffusion layers, catalyst, and assembled systems. This quality control solution is unique to each customer’s specific needs but includes a suite of in-line quality control systems for roll-to-roll manufacturing that can target thin, transparent membrane as well as opaque membrane, catalyst, and GDLs. The Phase II developed the CPNUVV system for thin, transparent membrane that operates using polarized filters to enhance defect resolution and determine thickness. However, PEM material manufacturers want a complete, turnkey solution for all components of the PEM fuel cell. In the Phase IIB, Mainstream will partner with NREL, and transition reflectance technology NREL developed (US Patent 9,234,843) to operate in real-time on a web-line to develop a total solution to PEM quality control. The device will identify and mark defects as well as monitor materials thickness in real-time to improve line efficiency and to reduce waste. The research performed at NREL under this CRADA increases the basis of knowledge about optical inspection methods, how they perform with regards to fuel cell component materials, and how they can be implemented in in-line, real-time configurations to provide quality inspection for roll-to-roll (R2R) manufacturing. Methods explored were found to be sensitive to catalyst loading in electrodes on both membrane and gas diffusion media substrates and to membrane thickness, across a broad range of thickness. The latter capability is novel and now patented and provides a previously unstudied and undemonstrated capability for R2R manufacturing of membranes.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2026

Elucidating microstructural evolution and hardness variation across friction self-piercing riveted Al-7055 using synchrotron X-ray scattering and advanced microscopy techniques

Friction self-piercing riveting (FSPR) is a unique hybrid joining technique that combines the advantages of mechanical interlocking, frictional heat, and solid-state joining (if metallurgically compatible) to produce crack free joints in high strength and/or low-ductility alloys at room temperature. Here, in the current study, Al-7055 sheets were joined using FSPR for lightweight automotive applications and significant microhardness variations were observed across the joint cross-section. A detailed microstructural characterization at multiple length scales was carried out using advanced electron microscopy and X-ray scattering techniques to provide a fundamental understanding of the process-structure-property relationships. The relative contributions of microstructural characteristics at various length scales (i.e., grain size, dislocation density, solute concentration, precipitate nature) to strengthening were estimated using existent formulations (i.e., Hall-Petch, Taylor, precipitate bypass/shear equations) and correlated to the observed microhardness values across different regions. Small-angle X-ray scattering and scanning transmission electron microscopy revealed significant changes in the size and volume fraction of precipitate species, i.e., GP-I Zones, η′, and Mg/Zn solute co-clusters, depending on the process region. It was observed that the dissolution of the small η′/GP-I zones (T ∼ 150–200 °C) in the heat-affected zone were the key reason for the hardness drop. Further, it was shown that solid-solution, dislocation, grain size and solute co-cluster strengthening played a key role in the thermo-mechanically affected zone and grain-refined zone (GRZ). Finally, these observations were leveraged along with the Zener-Holloman relationship and grain size in the GRZ to estimate the peak joining temperature of the GRZ (∼ 350 °C) near the steel rivet.

aluminum 7xxx alloy↗
DOE OSTI2021

Identification and Online Updating of Dynamic Models for Demand Response of an Industrial Air Separation Unit

Demand-response operation of air separation units requires frequent changes in production rate(s), and scheduling calculations must explicitly consider process dynamics to ensure feasibility of the solutions. To this end, scale-bridging models (SBMs) approximate the scheduling-relevant dynamics of a process and its controller in a low-order representation. In contrast to previous works that have employed nonlinear SBMs, this paper proposes linear SBMs, developed using time-series analysis, to facilitate online scheduling computations. Using a year-long industrial dataset, we nd that compact linear SBMs are suitable approximations over typical scheduling horizons, but that their accuracies are unpredictable over time. We introduce a strategy for online updating of the SBMs, based on Kalman ltering schemes for online parameter estimation. The approach greatly improves the accuracy of SBM predictions and will enable the use of linear SBM-based demand-response scheduling in the future.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2026

Plan It Together: Optimizing Across Generation, Transmission, Distribution, and Distributed Energy Resources

Integrated planning holds the promise of unlocking lower total system cost solutions by connecting previously siloed planning processes. This article summarizes the state of bulk and local grid planning today and details multiple new analytical approaches that can enable more holistic planning methods to develop comprehensive solutions to generation, transmission, distribution, and distributed energy resource needs. These include both iterative approaches as well as cooptimization techniques. In addition to the benefits of these methods, the technical and institutional challenges and associated solutions are also discussed.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2019

Tank 9H Salt Solution Supernatant Characterization in Support of Potential Operating Strategies of Tank 9H Supernatant Through the Tank Closure Cesium Removal System

Savannah River Remediation (SRR) recently initiated an ion exchange process to remove radioactive cesium from dissolved salt solution in Tank 10H, known as Tank Closure Cesium Removal (TCCR). As part of that ongoing campaign, the salt in Tank 9H will be dissolved and transferred to Tank 10H for processing through the TCCR system, and SRR requested the characterization of the dissolved salt solution in Tank 9H prior to the transfer to Tank 10H. On July 18, 2019, Savannah River Remediation Engineering (SRR-E) delivered two variable depth Tank 9H salt solution samples, identified as samples HTF-9-19-74 and HTF-9-19-75 (combined total sample volume of about 400 mL) to the Savannah River National Laboratory (SRNL) for characterization. These two Tank 9H variable depth samples (HTF-9-19-74 and HTF-9-19-75 taken at ~180” and 42”, respectively) were retrieved from Riser 7 after hydro-lancing activities were complete. Approximately 4200 gallons of water were added to the tank during this activity. This report presents the analytical characterization results for the Tank 9H salt solution variable depth samples HTF-9-19-74 and HTF-9-19-75 and contains mainly the filtrate analytical results for anions, elements, mass spectral data, total cesium characterization results and select radionuclide results, along with the X-ray diffraction characterization of the solid fractions from the liquid /solid separation of the variable depth salt solutions. Most of these analyses were performed in duplicate with the percent relative standard deviation (%RSD), a measure of the variability between each duplicate data set expressed as a percentage, used to estimate the analytical result quality for each analyte.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2016

Evaluating geothermal and hydrogeologic controls on regional groundwater temperature distribution

Described is a one-dimensional (1-D) analytic solution is developed for heat transport through an aquifer system where the vertical temperature profile in the aquifer is nearly uniform. The general anisotropic form of the viscous heat generation term is developed for use in groundwater flow simulations. The 1-D solution is extended to more complex geometries by solving the equation for piece-wise linear or uniform properties and boundary conditions. A moderately complex example, the Eastern Snake River Plain (ESRP), is analyzed to demonstrate the use of the analytic solution for identifying important physical processes. For example, it is shown that viscous heating is variably important and that heat conduction to the land surface is a primary control on the distribution of aquifer and spring temperatures. Use of published values for all aquifer and thermal properties results in a reasonable match between simulated and measured groundwater temperatures over most of the 300 km length of the ESRP, except for geothermal heat flow into the base of the aquifer within 20 km of the Yellowstone hotspot. Previous basal heat flow measurements (110 mW/m 2 ) made beneath the ESRP aquifer were collected at distances of > 50 km from the Yellowstone Plateau, but a higher basal heat flow of 150 mW/m 2 is required to match groundwater temperatures near the Plateau. As a result, the ESRP example demonstrates how the new tool can be used during preliminary analysis of a groundwater system, allowing efficient identification of the important physical processes that must be represented during more-complex 2-D and 3-D simulations of combined groundwater and heat flow.

58 GEOSCIENCES↗
DOE OSTI2018

Stable Formamidinium-Based Perovskite Solar Cells via In Situ Grain Encapsulation

Formamidinium (FA)-based lead iodide perovskites have emerged as the most promising light-absorber materials in the prevailing perovskite solar cells (PSCs). However, they suffer from the phase-instability issue in the ambient atmosphere, which is holding back the realization of the full potential of FA-based PSCs in the context of high efficiency and stability. Herein, the tetraethylorthosilicate hydrolysis process is integrated with the solution crystallization of FA-based perovskites, forming a new film structure with individual perovskite grains encapsulated by amorphous silica layers that are in situ formed at the nanoscale. The silica not only protects perovskite grains from the degradation but also enhances the charge-carrier dynamics of perovskite films. The underlying mechanism is discussed using a joint experiment-theory approach. Through this in situ grain encapsulation method, PSCs show an efficiency close to 20% with an impressive 97% retention after 1000-h storage under ambient conditions.

14 SOLAR ENERGY↗
DOE OSTI2024

Ion‐Specific Interactions Engender Dynamic and Tailorable Properties in Biomimetic Cationic Polyelectrolytes

Abstract Biomaterials such as spider silk and mussel byssi are fabricated by the dynamic manipulation of intra‐ and intermolecular biopolymer interactions. Organisms modulate solution parameters, such as pH and ion co‐solute concentration, to effect these processes. These biofabrication schemes provide a conceptual framework to develop new dynamic and responsive abiotic soft material systems. Towards these ends, the chemical diversity of readily available ionic compounds offers a broad palette to manipulate the physicochemical properties of polyelectrolytes via ion‐specific interactions. In this study, we show for the first time that the ion‐specific interactions of biomimetic polyelectrolytes engenders a variety of phase separation behaviors, creating dynamic thermal‐ and ion‐responsive soft matter that exhibits a spectrum of physical properties, spanning viscous fluids to viscoelastic and viscoplastic solids. These ion‐dependent characteristics are further rendered general by the merger of lysine and phenylalanine into a single, amphiphilic vinyl monomer. The unprecedented breadth, precision, and dynamicity in the reported ion‐dependent phase behaviors thus introduce a broad array of opportunities for the future development of responsive soft matter; properties that are poised to drive developments in critical areas such as chemical sensing, soft robotics, and additive manufacturing.

Aubrecht, Filip J.↗
DOE OSTI2016

The Key Role of U 28 in the Aqueous Self‐Assembly of Uranyl Peroxide Nanocages

Abstract For 11 years now, the structural diversity and aesthetic beauty of uranyl–peroxide capsules have fascinated researchers from the diverse fields of mineralogy, polyoxometalate chemistry, and nuclear fuel technologies. There is still much to be learned about the mechanisms of the self‐assembly process, and the role of solution parameters including pH, alkali template, temperature, time, and others. Here we have exploited the high solubility of the UO 2 2+ /H 2 O 2 /LiOH aqueous system to address the effect of the hydroxide concentration. Important techniques of this study are single‐crystal X‐ray diffraction, small‐angle X‐ray scattering, and Raman spectroscopy. Three key phases dominate the solution speciation as a function of time and the LiOH/UO 2 2+ ratio: the uranyl–triperoxide monomer [UO 2 (O 2 ) 3 ] 4− and the two capsules [(UO 2 )(O 2 )(OH)] 24 24− (U 24 ) and [(UO 2 )(O 2 ) 1.5 ] 28 28− (U 28 ). When the LiOH/U ratio is around three, U 28 forms rapidly and this cluster can be isolated in high yield and purity. This result was most surprising and challenges the hypothesis that alkali templating is the most important determinant in the cluster geometry. Moreover, analogous experiments with KOH, NH 4 OH, and TEAOH (TEA=tetraethylammonium) also rapidly yield U 28 , which suggests that U 28 is the kinetically favored species. Complete mapping of the pH–time phase space reveals only a narrow window of the U 28 dominance, which is why it was previously overlooked as an important kinetic species in this chemical system, as well as others with different counterions.

Falaise, Clément↗