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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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At least 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Deep Learning Potential For Investigation of Chemical Conversion of CO2 at Air-Reactive Deep Eutectic Solvent Interface

Capturing CO2 from air is urgent to battle against the climate change. Traditional CO2 capture by alkaline solution or aqueous amine has high regeneration cost, equipment corrosion, and amine leakage. Deep eutectic solvents (DESs) are promising alternatives with low corrosion, non-toxicity, and biodegradable nature. Functionalized DESs can capture and convert CO2 at low partial pressures. Developing reactive DESs for efficient CO2 capture needs a foundational understanding of the reaction-transport coupling of CO2 at the air-DES interface. In this study, we develop a deep learning potential (DLP) to investigate the absorption and reaction of CO2 at the air-DES interface (DES: 1-ethyl-3-methylimidazolium 2-cyanopyrrolide ([Emim][2-CNpyr]) and ethylene glycol (EG)). The DLP model allows us to simulate chemical reactions at a lower computational cost with ab initio accuracy. By analyzing reaction free energy surfaces, molecular interactions among CO2, DES components and reaction products, and transport of CO2 through the interface, we identify three main reaction pathways of CO2 at the interface: forming carboxylate with [Emim], carbamate with [2-CNpyr], and carbonate with EG. The mechanistic understanding of CO2 chemisorption at the interface will facilitate the development of novel direct air capture technology using DESs.

Nguyen, Manh Tien↗
DOE OSTI2016

Determination of Activity of Neodymium(III) in Molten Eutectic LiCl-KCl using Electrochemical Methods

The pyrochemical recycling of actinides is a promising option for closing the nuclear fuel cycle. The technology is particularly attractive for recycle of metallic and molten salt fuels. The Republic of Korea is also taking a serious look at the application of pyrochemical treatment of used oxide fuel from Pressurized Water Reactors (PWR). The science behind pyrochemical recycling is being actively studied at the various national labs and universities. The Rare Earth Drawdown process is proposed to be included in a commercial pyrochemical recycling facility in order to minimize the amount of waste generated from the processing that will require permanent disposal in a geological repository. This process involves selective extraction of rare earth elements from electro-refiner salt. The salt can then be further processed to selectively remove Group I-II active metals and eventually be recycled back to the electro-refiner. The preferred method of separation of the rare earths from the salt is using electrolysis due to its inherent selectivity and ease of operation. The purpose of this study is to evaluate the effects of the presence of cesium (Group I) on the electrochemical behavior of neodymium in a molten eutectic LiCl-KCl salt. The activity and by extension the activity coefficient of a species determines many of the key electrochemical properties such as apparent reduction potential. In this study, we have undertaken a series of experiments to experimentally determine the activity coefficient of the dissolved neodymium(III) ions as a function of concentration, both in the presence and absence of cesium. This was done using a first of its kind electrochemical cell. Previously, activity of dissolved species has been determined using electrochemical cells in which equilibrium potentials are measured for the Nd/Nd(III) versus a Ag/AgCl reference electrode. There are several issues associated with such an approach. These electrodes are associated with several sources of errors; indeterminate values of Standard Reduction Potentials of (E{sup θ}) for Ag and Nd in molten salts, unknown liquid junction potentials and potential drifts. These uncertainties contribute errors to the experimental measurements. For this study, we employed a Nd/LiCl-KCl-NdCl{sub 3(Saturatedelectrode)}. There are several advantages with using such an electrode. If the expanded Nernst Equation is written for the aforementioned electrochemical cell, all of the terms cancel out except the activity term. This enables us to directly experimentally measure the activity of the species in solution. When we use a saturated NdCl{sub 3} reference electrode, the activity that is measured is defined as the activity versus a 'Saturated Solid State'. To determine the activity coefficients, we need to determine the activity versus the 'Liquid Standard Sate'. To convert the activity from solid standard state to liquid standard state, we correct for it using the hypothetical Gibbs free energy of fusion for neodymium chloride. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Conceptual design of inverted core lead bismuth eutectic fast reactor for marine applications

The development of an inverted core fast reactor aims to generate 60 MWth for about 30 Effective Full Power Years without refueling. The reactor design is a transportable reactor using UO{sub 2} fuel and lead-bismuth-eutectic cooled designed for marine applications and is intended to improve the reactor performances compared to the normal core design: better condition for passive cooling system capability by lower core pressure drop, taking advantage of potential power uprate from the lower maximum fuel temperature. Systematic design processes are presented in this work: fuel pin geometry selection, fuel assembly (FA) design, and core design. A relationship between pressure drops, coolant velocity, maximum fuel temperature, coolant channel diameter, and fuel volume fraction was introduced in a single graph used as a tool to select fuel pin geometry. Fuel fabrication capability also took place in consideration of FA design which led to 7 holes per FA, and two-dimensional temperature distribution studies were also carried out. Core design processes including radial zoning, axial zoning, and core optimization were conducted using Monte Carlo code MCS, which is UNIST CORE laboratory in-house code. The current core design uses 3 fuel enrichment levels and 3 FA types to control the local power distribution and power shift during its lifetime. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2020

Multi-Step Crystallization of Self-Organized Spiral Eutectics

A method for the solidification of metallic alloys involving spiral self-organization is presented as a new strategy for producing large-area chiral patterns with emergent structural and optical properties, with attention to the underlying mechanism and dynamics. This study reports the discovery of a new growth mode for metastable, two-phase spiral patterns from a liquid metal. Crystallization proceeds via a non-classical, two-step pathway consisting of the initial formation of a polytetrahedral seed crystal, followed by ordering of two solid phases that nucleate heterogeneously on the seed and grow in a strongly coupled fashion. Crystallographic defects within the seed provide a template for spiral self-organization. These observations demonstrate the ubiquity of defect-mediated growth in multi-phase materials and establish a pathway toward bottom-up synthesis of chiral materials with an inter-phase spacing comparable to the wavelength of infrared light. Given that liquids often possess polytetrahedral short-range order, our results are applicable to many systems undergoing multi-step crystallization.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Ceramic Rolling and Annealing on Mechanical Properties of AlCoCrFeNi{sub 2.1} Eutectic High-Entropy Alloys

It was firstly proved that AlCoCrFeNi{sub 2.1} could optimize the strength-ductility combination by ceramic rolling at room temperature. The technique greatly enhanced the strength of the materials at the price of slight ductility, which is different from the previous studies. When the thickness reduction was 23.06%, the yield strength and compressive strength were 1611.42 and 2212.99 MPa, respectively, with the plastic strain of 28.36%. Such an excellent combination of strength and ductility was attributed to the distribution of the residual stress, the high hydrostatic stress and the shear bands in ceramic rolling process. The plastic strain of the material increased to 38.54%, and the strength reduced to 1900.73 MPa after annealing at 800 °C for 1 h. A lot of like-flower patterns of recrystallized ultrafine grain were observed after annealing at 800 °C due to the sluggish diffusion in HEAs and the effect of ceramic rolling. In addition, after annealing at 800 °C, the fracture mode changed to shearing fracture of microvoid aggregation from cleavage/quasi-cleavage fracture of as-rolled sample due to the deposition of the second phase in the tested sample.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Ion transport in non-aqueous electrolyte mixtures of zinc chloride deep eutectic solvent (DES) and molecular solvents

For this work, the ion dynamics of null solvents 1ZnCl 2 :4EtG and 1ChCl:1ZnCl 2 :6EtG incorporating 1M water, propylene carbonate (PC) or acetonitrile (AcN) were investigated using 1 H NMR spectra and spin-lattice relaxation time (T 1 ) measurements combined with ionic conductivity, density, and viscosity, all as a function of temperature. Results show that the inclusion of all co-solvents increased the available free volume of the mixtures and followed the trend H 2 O ≤ PC < AcN. 1 H NMR spectra and T 1 inferred the presence of multiple ionic species with varying rates of mobilities. These dynamic heterogeneities were displayed by the broad T 1 minima – especially for the 1ZnCl 2 :4EtG mixtures – and asymmetrically broadened linewidths. T 1 results also revealed selective interaction sites between the hydrogen bond donors and acceptors, as well as with the co-solvents.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Investigation on Reaction Probabilities for Cyclic Voltammetry of Zirconium in LiCl-KCl Eutectic Molten Salt via Reverse-Engineering Method

This work focuses on a reverse-engineering program design for the cyclic voltammetry (CV) method to help illustrating, enhancing, and providing robustness in detection probability of the reactions during an electrorefining process. Analyzing the reactions from CV plots for 1.07, 2.49, and 4.98 wt% of zirconium chloride (ZrCl{sub 4}) in a LiCl-KCl molten salt at 773 K under different scan rates from Hoover's study has been accomplished. The results provide the current (Amp) versus potential (V) to investigate the optimum probability of the reactions at each peak. All simulations have been done through the commercial software MATLAB by using various experimental values existing in the literature as a first guess (e.g., the diffusion coefficients, and formal potentials). Preliminary results indicate that the zirconium reactions at each peak from cathodic to anodic side for 1.07 wt% are as followed: combination of Zr{sup +2}/Zr and Zr{sup +4}/ Zr{sup +2} at approximately -1.15 V, Zr{sup +2}/Zr at -1.5 V, Zr{sup +4}/Zr at -1.85 V, 70% Zr/Zr{sup +4} and 30% Zr/Zr{sup +2} at -0.5 V, and Zr{sup +2}/ Zr{sup +4} at - 0.25 V. These mentioned peaks are similar for 2.49 wt% at different voltages. In addition, the highest anodic peak for 4.98 wt% is found to be a combination of 30% Zr/Zr{sup +4} and 70% Zr/Zr{sup +2}. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2017

Electrochemical Behavior of Lanthanum in Molten LiF-NaF-KF 'Flinak' Eutectic Salt

In order to develop the Fluoride High- Temperature Reactor, an emerging Gen-IV reactor concept, a primary coolant cleanup system must be developed to allow online reprocessing of the primary molten fluoride salt. This research is focused on the determination of electrochemical properties of rare earths (REs) in molten fluoride salt related to the FHR. The FHR utilizes two fluoride salts. These fluoride salts are LiF-NaF-KF (46.5-11.5-42 mol%), melting point 454 deg. C, also known as 'Flinak', and LiFBeF{sub 2} (33-67 mol%), melting point 459 deg. C, also known as 'Flibe'. Flibe is selected as the primary coolant salt due to its low neutron cross-section (Li{sup 7}-enriched), superior heat transfer properties, and low melting point. However, due to the beryllium content in Flibe, it is highly toxic to humans and Flinak is preferred for the secondary and tertiary coolant salts. The work presented here is specifically focused on the behavior of lanthanum trifluoride (LaF{sub 3}) in molten Flinak. Furthermore, updated data and analysis regarding the electrochemical behavior of dysprosium trifluoride (DyF{sub 3}) is also presented. Previous work related to this topic was presented at the 2016 ANS winter conference. The goal of this research is to develop a contaminant cleanup system for the primary loop of the FHR.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2023

Time dependent chlorination of CeO 2 , La 2 O 3 and Nd 2 O 3 by ZrCl 4 dissolved in eutectic LiCl–KCl

Partial chlorination of CeO 2 , La 2 O 3 , and Nd 2 O 3 was achieved using ZrCl 4 dissolved in molten LiCl-KCl at 450°C over a period of 4-5 hr. ZrCl 4 was pre-volatilized into an argon stream to maintain a constant vapor pressure for equilibration with the salt. This approach was effective at maintaining the ZrCl 4 concentration at the solubility limit of 1.3 mol% in the molten salt throughout the duration of two of the chlorination experiments and within about 60% of the solubility limit in the third experiment. Based on the analysis of salt samples, fractional conversion after four hours of reaction for CeO 2 , and five hours for La 2 O 3 , and Nd 2 O 3 were calculated to be 0.97, 0.28, and 0.65 respectively. Assuming a shrinking core diffusion-limited model, the diffusivity of ZrCl 4 through the hypothesized ZrO 2 layer was calculated for the chlorination of CeO 2 , La 2 O 3 , and Nd 2 O 3 were 1.76 x 10 -10 cm 2 /sec, 7.85 x 10 -12 cm 2 /sec, and 7.42 x 10 -12 cm 2 /sec, respectively. Given the extremely low values calculated for diffusivity, it was concluded that the process is chemical reaction rate limited and that a complete reaction of each rare earth oxide could be achieved. Furthermore, a chemically controlled shrinking core model was shown to also fit the experimental data closely.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗