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Fox, Robert V

Publications and source records attributed to Fox, Robert V.

4 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Investigation of Rare Earth Elements Mobility Using Molecular Dynamics

Rare Earth Elements (REE) are critical many applications such as electronics, permanent magnets, agricultural etc. Effective separation of REEs is a challenge due to their similarities in chemical and physical properties. Current separation processes are costly and environmentally detrimental. Therefore, research on REEs mobility in water-based solvents is necessary to design effective separation processes. In this research, the key kinetic and thermodynamic parameters, including diffusion coefficient and hydration shell are determined under the influence of external electric field. The diffusion coefficient of metal ions increases due to electric field in pure water.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2022

Investigation of Rare Earth Elements Mobility Using Molecular Dynamics

Rare Earth Elements (REE) are critical many applications such as electronics, permanent magnets, agricultural etc. Effective separation of REEs is a challenge due to their similarities in chemical and physical properties. Current separation processes are costly and environmentally detrimental. Therefore, research on REEs mobility in water-based solvents is necessary to design effective separation processes. In this research, the key kinetic and thermodynamic parameters, including diffusion coefficient and hydration shell are determined under the influence of external electric field. The diffusion coefficient of metal ions increases due to electric field in pure water.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2022

Ligand-Assisted Separation of Rare Earth Elements via Capillary Electrophoresis

Rare earth elements (REEs) are a class of critical materials vital in applications such as EVs, batteries, and defense weapons systems. These elements are found primarily in ores, and due to their similar chemical behavior, the challenge remains to find an effective means of separation. The addition of ligands of varying charge, size, denticity, etc. can help to increase separation, yet the mechanistic behavior and factors influencing separation are still poorly understood. Here, iminodiacetic acid (IDA) is used to exploit and maximize differences in electrophoretic mobilities between adjacent REEs. Mobilities and diffusion coefficients of REEs in aqueous media are measured via CE and are compared to MD and FEM simulations.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Water Interplays during Dysprosium Electrodeposition in Pyrrolidinium Ionic Liquid: Deconvoluting the Pros and Cons for Rare Earth Metallization

The electrochemical production of rare earth metals (REMs) in ionic liquids (ILs) has received much attention as a promising, sustainable and replacement to the molten salt electrolysis. Water additives have been recently suggested as a strategy to overcome the limitations of the ionic liquid process, but without complete assessment of its overall viability for the REMs production. In this regard, a full investigation of water impact on dysprosium (Dy) electrodeposition in pyrrolidinium triflate (BMPyOTf) ionic liquid was carried out. Water introduction was revealed to involve an interplay of implications on the electrodeposition process, including coordination, speciation, reduction pathways, interfacial dynamics, nucleation and metal stability and purity. In highly dry conditions, the reduction occurs at very negative potentials (-3.3V) in a consecutive pathway, resulting in negligible metal electrodeposition (low rate and efficiency) at the electrode surface. Initial water introduction (<30% molar fraction) leads to partitioning of the Dy complex between water and IL coordinated speciation, giving rise to an additional wave at more positive potentials (-2.4V). Probing and quantification of the heterogeneous Dy speciation by spectroscopic analyses enabled the uncovering of the reduction mechanism and accurate evaluation of the mass transport properties. While lowering the reduction thermodynamics, water addition also improved the nucleation, deposition rate and faradaic efficiency. In spite of these benefits, stripping voltammetric analysis also indicated substantial chemical reactivity of the deposited Dy metal with water additives and/or electrolyte components, under extended timescales. Surface characterization of the obtained product confirmed limited Dy metal stability (mostly oxidized/fluorinated) and purity (~60%) in the studied system. Moreover, high water introduction (>30% molar fraction) was shown to trigger a fast hydrogen evolution reaction (HER), downgrading the robustness of system efficiency. We report the overall impact of water additives seems to engender both promoting and mitigating effects on the Dy electrodeposition process, making the case for more innovative strategies to be sought.

36 MATERIALS SCIENCE↗