SEARCH · Search NASA
Results for “salt concentration”
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.
Kinetic study of hydrogen transport in graphite under molten fluoride salt environment
Here, in this work, a kinetic model, which describes the reactions occurring during the hydrogen charging process on a graphite surface, was optimized on Electrochemical Impedance Spectroscopic (EIS) to study the entry of hydrogen into graphite in high temperature molten FLiNaK salt. The results show that the rate constants of k 1 increases with decreasing applied potential (becoming more negative), and k 2 and k 3 are independent of the applied potential. At the same charging potential, all the three rate constants are independent of the water concentration in the FLiNaK salt. The surface coverage of absorbed hydrogen increases with decreasing the charging potential and increasing the moisture content in the salt. The adsorption efficiency of hydrogen increases with increasingly charging potential and decreases with increasing moisture content of the FLiNaK salt. These results demonstrate that EIS is a promising technique for measuring the kinetic parameters for hydrogen transport in graphite under molten fluoride salt environment.
Investigation of impurity driven corrosion behavior in molten 2LiF-BeF 2 salt
A 1000 -h corrosion experiment of 316H stainless steel at 700 °C investigated the role of metal fluoride impurities CrF 2 and FeF 2 in LiF-BeF 2 (66-34 mole %) (FLiBe) salt. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) demonstrated the ability to measure changes in the concentration of these fluorides in FLiBe salt. Cyclic voltammetry (CV) showed the potential for real-time quantitative concentration measurement of corrosion products in the molten salt. Materials characterization revealed that both impurity species influence the dissolution of Cr from the alloy. The collective results from these analysis methods advance the understanding of the influence impurities have on materials corrosion.
Comparing Experimentally-Measured Sand’s Times with Concentrated Solution Theory Predictions in a Polymer Electrolyte
We compare the electrochemically measured Sand’s time, the time required for the cell potential to diverge when the applied current density exceeds the limiting current, with theoretical predictions for a 0.47 M poly(ethylene oxide) (5 kg mol −1 )/LiTFSI electrolyte. The theoretical predictions are made using concentrated solution theory which accounts for both concentration polarization and polymer motion, using independently measured parameters that depend on concentration, c : conductivity ( κ ), salt diffusion coefficient ( D ), cationic transference number with respect to the solvent velocity ( t + 0 ), thermodynamic factor 1 + dln f ± dln c , and partial molar volume of the salt ( V ̅ ); f ± is the mean molar activity coefficient of the salt. We find quantitative agreement between experimental data and theoretical predictions. We derive a generalized analytical expression for Sand’s time for electrolytes based on dilute solution theory. This expression correctly predicts the divergence of the Sand’s time at the limiting current, in agreement with experimental data and concentrated solution theory predictions. When the applied current is large compared to the limiting current, the analytical expression approaches the standard expression for Sand’s time used in the literature.
Comparative geochemistry of flowback chemistry from the Utica/Point Pleasant and Marcellus formations
Flowback/Produced fluid samples were collected from several wells from two Utica/Point Pleasant (UPP) sites (UPPW and UPPS) in Ohio, and one Marcellus (Marcellus Shale Energy and Environment Laboratory (MSEEL)) site in West Virginia over a period of approximately two years. Although these formations have different ages, depositional environments, diagenetic histories, and geochemical and mineralogical compositions (i.e. the UPP is significantly more carbonate rich than the Marcellus which is more siliceous), analysis of trends in fluid species over time shows that, overall, the TDS and major solubilized elements (Na, Ca, Cl) in the UPP and Marcellus brines are remarkably similar. Total dissolved solutes (TDS) in these brines ranged from approximately 40 to 250 g/L salt, and in general, concentrations increased with time elapsed since natural gas well completion and stimulation. The behavior of Na, Br, and Cl suggests that the produced water signatures from these formations are largely derived from the native formational brines which display evidence of originating from evaporated seawater. There is a strong correlation between Cl and Br, indicating that both species behave conservatively, and the similarity among each of these brines suggests no appreciable contribution of salt from halite dissolution because Br is excluded from the halite structure. Cl/Br ratios in the brines range from ~80 to 120 (mg/L/mg/L). Other elements, such as K, which readily reacts between fluids and ion exchange sites on clays, generally exhibit conservative behavior for an individual site, but show significant variations among each of the different well pads. The concentrations of Sr and Ba vary dramatically among well sites, and increase with respect to Cl- over time, suggesting increasing solubilization, presumably from desorption from clay minerals or dissolution of carbonates or sulfates from the source formation(s). The UPPW well site has very low Ba due to high-sulfate input fluid, which resulted in precipitation of barite/celestite in the brines. In contrast the UPPS well site had elevated Sr (~ 3500 mg/L), presumably due to the use of Sr-rich recycled brine used in hydraulic fracturing. The Marcellus site had the highest Ba concentrations (up to 10 g/L) and highest Ba/Sr ratios in the fluids, due to the high concentration of barium in the Marcellus target (~ 1000 ppm, as compared to ~200 ppm in the UPP). These observations suggest that solutes in the FP fluids are derived from native brines, water-rock interactions that have occurred over geologic time scales, as well as some contribution from contemporaneous reactions in the subsurface. The results also show that the composition of the injected fluid can influence flowback fluid chemistry and possibly production efficiency.
Spectroscopic Insight on Neodymium Solvation in Lithium Borohydride-Supported Electrolyte
Borohydride-based electrolytes have recently emerged as promising media for the electrodeposition of electropositive metals, including rare earth (RE) elements. While the presence of supporting alkali metal cations and RE counteranions provides essential electrochemical conductivity for achieving fast metal electrodeposition, interactions between the host ligand and solvated neodymium (Nd) complexes remain unclear. This study provides insights into the coordination structure of a concentrated and directly solvated Nd salt in a lithium borohydride-supported electrolyte. Our spectroscopic results indicate that the RE coordination environment is significantly influenced by the solvation mechanism, which can vary between metathesis and complexation pathways, primarily dictated by stoichiometric factors. Under dilute conditions, nearly complete metathesis of anions leads to a high coordination number for the host ligand (borohydride), consistent with the previously reported solvated Nd speciation in chlorine-free electrolytes. In contrast, concentrated dissolution of the Nd salt in the supported electrolyte is dominated by a complexation pathway featuring a Li-ion-paired complex with a low coordination number of the host ligand. Density functional theory (DFT) calculations indicated that the observed blue shift in the borohydride vibration was the result of an increase in electron density drawn into the terminal B–H interbond region from the hydride as the coordination changed from Li to Nd. In conjunction with DFT results, vibrational analyses allowed correlation of the experimental shifts associated with changes in Nd ligation and coordination spheres, further consolidating the prevalence of highly chloride-coordinated species under concentrated conditions. In conclusion, the outcomes of this work illuminate the distinctive and heterogeneous coordination structures that the electroactive RE species can adopt at high concentrations in lithium borohydride-supported electrolytes, as a key step to comprehend the reported metal electrodeposition performance in these media.
Assessment of Flow-Enhanced Electrochemical Sensor Testing and Deployments
The goal of our activities in FY24 was to enable advanced materials accountancy for molten salt reactors (MSRs) through the development and optimization of robust flow-enhanced electrochemical sensors (FEES) using a safeguards-focused sensor testing platform called the modular flow instrumentation testbed (MFIT). Flow-enhanced electrochemical sensors are a type of electroanalytical sensor that have been developed at Argonne National Laboratory to be installed directly into MSR flow conduits to make measurements of the salt composition. These sensors represent a significant improvement in capabilities compared to earlier electroanalytical sensors that instead can only be operated in quiescent conditions. Previous work has focused on testing of the FEES in flowing conditions provided by the MFIT to assess the accuracy and precision of the sensor measurements. This year, the FEES technical readiness was increased by (1) demonstrating the use of optimized sensor techniques to achieve measurements in very high-concentration MSR-relevant salts, (2) leveraging new multimodal sensors and automation approaches to reduce measurement uncertainties, and (3) fabricating and deploying sensors to industrial partners to improve their ability to make measurements in challenging environments. Additionally, we also ran the sensors during complex system operations involving combined flow and purification activities to demonstrate safeguards-relevant measurements during online processing for MSRs.
Beyond Simple Dilution: Superior Conductivities from Cosolvation of Acetonitrile/LiTFSI Concentrated Solution with Acetone
Concentrated solutions of Li salts in acetonitrile are promising alternative electrolytes for the next generation of Li batteries as they may exhibit superior electrochemical properties. However, the reduced mobility of the chemical species is a barrier yet to be overcome, and for this, we explore the utilization of acetone as a cosolvent. Although acetone is a polar compound, we find that its addition to the LiTFSI/acetonitrile solution does not follow the trends expected for a simple dilution process. At a low concentration, acetone subtly shifts acetonitrile from the first to extended solvation sheaths of the ions. Still, most of the original structure of the solution is preserved, and mobile high-concentration clusters are formed in the solution. At higher concentrations, the cosolvation promotes cation–anion interactions but with a different nature from those in the original solution and still allows for a further increase in conductivity. Additionally, the non-coordinating fraction of acetonitrile acquires features resembling the pure solvent, which is a possible additional facilitating factor for ionic diffusion.
Development of High Temperature (>700°C) Molten Salt Pump Technology for Generation 3 Solar Power Tower Systems
Bearings are required for long-shafted pumps historically used in concentrating solar thermal power applications. For molten chloride salts, bearings for such service conditions are not commercially available, nor has a design been demonstrated to work. Therefore, a project was sponsored by the Department of Energy’s Solar Energy Technologies Office for the development and demonstration of a submerged bearing for use in chloride salt pumps. This project’s tasks covered the tribological testing of candidate materials and the design, fabrication, testing, and post-test analysis of full-scale salt-compatible bearings. This work expands upon previous work. The effects of potential particulate in the salt were investigated through tribological bench testing. Through 11 tests, the MgO particulate size and concentration in a molten chloride salt were varied, and the effects on friction, wear rate, and wear characteristics were recorded. Novel journal bearings for chloride salt service were designed and fabricated based on these results. The bearings were of a relevant scale (i.e., for a 1.5 in. pump shaft) to demonstrate the technology with respect to further scale-up. The bearings were made of Haynes 244 and Yttria Partially Stabilized Zirconia. A custom bearing test rig, salt tanks, and associated infrastructure (e.g., heaters, tanks, transfer lines, gas flow control) were designed, procured, and installed. A few issues were encountered in the system fabrication process, resulting in delay of the project schedule. The system was successfully fabricated and assembled. Heating, cover gas, and pump motor systems were integrated into the control logic. This progress of the bearing test system represents a significant step forward towards demonstrating this promising technology. Nevertheless, the project ended before testing of the full-scale bearings could be performed.
Extended thermodynamic model for high salinity produced waters
To support the development of desalination processes for high salinity produced waters, we developed a comprehensive thermodynamic model that reliably predicts the thermodynamic properties and phase behavior of produced water. Here this study extends a previously developed thermodynamic model for the aqueous hexary oceanic salt system by incorporating the Sr 2+ and Ba 2+ ions. Based on the electrolyte nonrandom two-liquid theory, the model requires two adjustable binary interaction parameters for each water-electrolyte and electrolyte-electrolyte pair that has a common ion. The binary interaction parameters for the electrolyte-electrolyte pairs involving Sr 2+ and Ba 2+ ions were identified using thermodynamic and salt solubility data. The model was validated for temperatures from 273.15 K to 473.15 K and electrolyte concentrations from infinite dilution to salt saturation. Extension of the model to include HCO 3 − , CO 3 2− , and CO 2 is currently in progress.
Facility to Alleviate Salt Technology Risks (FASTR): Design Report
The Facility to Alleviate Salt Technology Risks (FASTR) is a versatile, high-temperature (>600°C) molten chloride salt test facility designed to enable a variety of testing to advance the Generation 3 (Gen 3) Concentrated Solar Power (CSP) molten salt technology. FASTR includes a salt preparation system and a forced flow test loop with a suite of instrumentation. The FASTR loop is capable of 725°C operation and flow rates of 3–7 kg/s, and it includes heated and cooled sections and swappable components to enable testing of future vendor-supplied hardware. The salt preparation system supplies large batches (e.g., 200 kg) of clean salt for use in the FASTR forced convection loop. This report summarizes the design and capabilities of FASTR in its as-built form as of December 2022.
Facility to Alleviate Salt Technology Risks (FASTR): Commissioning Update
The Facility to Alleviate Salt Technology Risks (FASTR) is a versatile, high-temperature (>600°C) molten chloride salt test facility designed to enable a variety of testing to advance the Generation 3 (Gen 3) concentrated solar power (CSP) molten salt technology. FASTR includes a salt preparation system and a forced flow test loop with a suite of instrumentation. The FASTR loop is capable of operating at 725°C with flow rates of 3–7 kg/s, and it includes heated and cooled sections and swappable components to facilitate testing future vendor-supplied hardware. The salt preparation system supplies large batches of clean salt for use in the FASTR forced circulation loop. This report summarizes the shakedown and initial operation of the FASTR forced circulation loop through December 2022.
Anion-tethered Single Lithium-ion Conducting Polyelectrolytes through UV-induced Free Radical Polymerization for Improved Morphological Stability of Lithium Metal Anodes
Single Li + ion conducting polyelectrolytes (SICs), which feature covalently tethered counter-anions along their backbone, have the potential to mitigate dendrite formation by reducing concentration polarization and preventing salt depletion. However, due to their low ionic conductivity and complicated synthetic procedure, the successful validation of these claimed advantages in lithium metal (Li 0 ) anode batteries remains limited. In this study, we fabricated a SIC electrolyte using a single-step UV polymerization approach. The resulting electrolyte exhibited a high Li + transference number (t + ) of 0.85 and demonstrated good Li + conductivity (6.3×10 -5 S/cm at room temperature), which is comparable to that of a benchmark dual ion conductor (DIC, 9.1×10 -5 S/cm). Benefitting from the high transference number of SIC, it displayed a three-fold higher critical current density (2.4 mA/cm 2 ) compared to DIC (0.8 mA/cm 2 ) by successfully suppressing concentration polarization-induced short-circuiting. Additionally, the t + significantly influenced the deposition behavior of Li0, with SIC yielding a uniform, compact, and mosaic-like morphology, while the low t + DIC resulted in a porous morphology with Li 0 whiskers. Using the SIC electrolyte, Li 0 ||LiFePO 4 cells exhibited stable operation for 4500 cycles with 70.5 % capacity retention at 22 °C.
Anion-tethered Single Lithium-ion Conducting Polyelectrolytes through UV-induced Free Radical Polymerization for Improved Morphological Stability of Lithium Metal Anodes
Single Li + ion conducting polyelectrolytes (SICs), which feature covalently tethered counter-anions along their backbone, have the potential to mitigate dendrite formation by reducing concentration polarization and preventing salt depletion. However, due to their low ionic conductivity and complicated synthetic procedure, the successful validation of these claimed advantages in lithium metal (Li 0 ) anode batteries remains limited. In this study, we fabricated a SIC electrolyte using a single-step UV polymerization approach. The resulting electrolyte exhibited a high Li + transference number (t + ) of 0.85 and demonstrated good Li + conductivity (6.3×10 -5 S/cm at room temperature), which is comparable to that of a benchmark dual ion conductor (DIC, 9.1×10 -5 S/cm). Benefitting from the high transference number of SIC, it displayed a three-fold higher critical current density (2.4 mA/cm 2 ) compared to DIC (0.8 mA/cm 2 ) by successfully suppressing concentration polarization-induced short-circuiting. Additionally, the t + significantly influenced the deposition behavior of Li 0 , with SIC yielding a uniform, compact, and mosaic-like morphology, while the low t + DIC resulted in a porous morphology with Li 0 whiskers. In conclusion, using the SIC electrolyte, Li 0 ||LiFePO 4 cells exhibited stable operation for 4500 cycles with 70.5 % capacity retention at 22 °C.
Arctic warming by abundant fine sea salt aerosols from blowing snow
Abstract The Arctic warms nearly four times faster than the global average, and aerosols play an increasingly important role in Arctic climate change. In the Arctic, sea salt is a major aerosol component in terms of mass concentration during winter and spring. However, the mechanisms of sea salt aerosol production remain unclear. Sea salt aerosols are typically thought to be relatively large in size but low in number concentration, implying that their influence on cloud condensation nuclei population and cloud properties is generally minor. Here we present observational evidence of abundant sea salt aerosol production from blowing snow in the central Arctic. Blowing snow was observed more than 20% of the time from November to April. The sublimation of blowing snow generates high concentrations of fine-mode sea salt aerosol (diameter below 300 nm), enhancing cloud condensation nuclei concentrations up to tenfold above background levels. Using a global chemical transport model, we estimate that from November to April north of 70° N, sea salt aerosol produced from blowing snow accounts for about 27.6% of the total particle number, and the sea salt aerosol increases the longwave emissivity of clouds, leading to a calculated surface warming of +2.30 W m −2 under cloudy sky conditions.
Poly(lactic- co -glycolic acid) Nanoparticles as Delivery Systems for the Improved Administration of Radiotherapeutic Anticancer Agents
This letter reports the development of poly(lactic- co -glycolic acid) (PLGA) nanoparticles (NPs) as delivery systems that could potentially encapsulate and improve the administration of radiotherapeutic anticancer agents. Different metal ions (Ba, Gd, and Ce) were used as surrogates of α-emitting radionuclides ( 223 Ra, 225 Ac, and 227 Th), and their encapsulation within the PLGA NPs ( D h < 300 nm) was evaluated. The initial concentration of metal ions, the metal salt (nitrate vs chloride), and the presence of chelators influenced the concentration of surrogate ions within the PLGA NPs. This letter shows the potential of PLGA NPs to encapsulate radionuclides, particularly α-emitters, for their application in nuclear medicine.
Average hydrodynamic radius analysis reveals critical solvation thresholds in high-concentration lithium electrolytes
Understanding the solvation structures of lithium salts in carbonate- and ether-based electrolytes is central to explaining the exceptional stability of high-concentration electrolytes (HCEs) and localized high-concentration electrolytes (LHCEs). Conventional techniques such as vibrational spectroscopy and one-dimensional NMR provide only limited information, typically restricted to coordination ratios and ion-pair distributions, without revealing the actual size and mass of solution complexes. Here, in this study, we introduce an average hydrodynamic radius (AHR) analysis based on internally referenced DOSY NMR, which enables direct estimation of the average volume and molecular weight of lithium–solvent complexes in solution. Using LiFSI–EMC and LiFSI–EMC–TTE electrolytes, we demonstrate that the onset of effective lithium metal stabilization and aluminum corrosion suppression coincides with the formation of very large complexes, whose average volume exceeds 300 times that of free EMC molecules. This finding supports a new “blocking mechanism,” wherein bulky solvated complexes impede direct solvent access to reactive surfaces. The AHR analysis thus not only clarifies the fundamental origin of HCE and LHCE effectiveness, but also provides a broadly applicable experimental framework for probing complex solvation structures and guiding rational electrolyte design.
Material Selection and Corrosion Studies of Candidate Bearing Materials for Use in Molten Chloride Salt
Molten chloride salts are being given strong consideration for use in heat transfer and storage in concentrating solar power (CSP) systems as well as in some nuclear reactor applications. Containment of the molten salt, particularly at the highest temperatures, is a major material concern and has received considerable study. Another material issue is the pumps that will be required to move the molten salt along with the bearing materials that will be required to have sufficient corrosion resistance as well as wear resistance in the high temperature salt. A pair of coordinated studies in our laboratory has addressed the corrosion, and the wear issues of candidate bearing materials including the selection of candidate materials as well as their performance in a molten sodium chloride-potassium chloride-magnesium chloride salt environment. This work addresses the selection of candidate materials and their chemical compatibility with the molten salt. The studies have identified material pairs that have suitable properties for use as bearings that would be immersed in molten chloride salt.