Phase transitions in ε-FeOOH at high pressure and ambient temperature
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99 GENERAL AND MISCELLANEOUS↗
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Recovery of Rare Earths, Precious Metals and other Critical Materials from Geothermal Waters with Advanced Sorbent Structures - CRADA 355 (Abstract)
The ability to recover valuable trace level minerals from geothermal brines using high-performance solid-phase sorbents will be explored and developed. A compressive range of sorbent materials will be screened for application to metal extraction from geothermal brines. Preferred sorbents from extraction of trace levels of rare earths (REs), precious metals (PMs), and other critical/strategically valuable materials (CMs) such as Zn, Mn, Te, Sc, Se and U from geothermal brines will be identified. For the preferred sorbents PNNL will determine the volumes they are capable of providing efficient extraction from. The thermal and chemical limits (including, acid, sulfur, salt) for performance of the preferred sorbent materials will be determined; with a target of at least 125°C and perhaps as high as 400° C. Sorbent form factors (including, packed bed, membrane, mats) that can function efficiently and be installed cost effectively in geothermal energy plants will be assessed for chemical and economic viability. Material regeneration and cyclic utilization will be demonstrated, targeting hundreds to thousands of cycles. Options for recovery and purification (including, selective separation of heavy REs) of collected materials will be explored. A techno-economic analysis (TEA) will be performed to assess the best approach to provide a value-added extraction process for geothermal energy systems. The sorbent materials and engineering analysis will be applicable to other industrial processes in which secondary recovery of valuable materials could provide economic benefit.
15 GEOTHERMAL ENERGY↗
Uranyl oxalate species in high ionic strength environments: stability constants for aqueous and solid uranyl oxalate complexes
Uranyl ion, UO 2 2+ , and its aqueous complexes with organic and inorganic ligands can be the dominant species for uranium transport on the Earth surface or in a nuclear waste disposal system if an oxidizing condition is present. As an important biodegradation product, oxalate, C 2 O 4 2– , is ubiquitous in natural environments and is known for its ability to complex with the uranyl ion. Oxalate can also form solid phases with uranyl ion in certain environments thus limiting uranium migration. Therefore, the determination of stability constants for aqueous and solid uranyl oxalate complexes is important not only to the understanding of uranium mobility in natural environments, but also to the performance assessment of nuclear waste disposal. In this work, we developed a thermodynamic model for the UO 2 2+ –Na + –H + –Cl – –ClO 4 – –C 2 O 4 2– –NO 3 – –H 2 O system to ionic strength up to ~11 mol•kg –1 . We constrained the stability constants for UO 2 C 2 O 4 (aq) and UO 2 (C 2 O 4 ) 2 2– at infinite dilution based on our evaluation of the literature data over a wide range of ionic strengths up to ~11 mol•kg –1 . We also obtained the solubility constants at infinite dilution for solid uranyl oxalates, UO 2 C 2 O 4 •3H 2 O, based on the solubility data over a wide range of ionic strengths. The developed model will enable for the accurate stability assessment of oxalate complexes affecting uranium mobility under a wide range of conditions including those in deep geological repositories.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
Data for Roebuck et al. (2025), "Differences in dissolved organic matter composition between rivers and estuaries is conserved across freshwater and saltwater coastal regions"
Dissolved organic matter (DOM) in coastal surface waters influences local water quality and is an important component of biogeochemical cycling in coastal systems, but the processes that alter DOM composition along lower reaches of rivers and estuarine waters are poorly understood. Roebuck et al. (2025) leveraged a spatially distributed community sampling effort in coastal ecosystems across two regions to identify broad spatial drivers of surface water DOM composition and identify transferable trends between saltwater and freshwater coastal systems. Samples were collected by community members from 47 locations within the mid-Atlantic and Great Lakes coastal regions.This dataset includes:* A selection of commonly reported absorbance and fluorescence peaks normalized to dissolved organic carbon concentrations* Parallel factor output from the EC1 fluorescence datasets* A selection of commonly reported absorbance and fluorescence peaks * Spectral indices output from matlab script for absorbance and fluorescence datasets* CO2sys calculations of pH changes under varying temperatures and a constant salinity, DIC, and alkalinity concentrationAll data files are plain-text CSV (comma separated value) and no special software is required to read them.
54 ENVIRONMENTAL SCIENCES↗
Alkaline-Earth Chalcogenide Nanocrystals: Solution-Phase Synthesis, Surface Chemistry, and Stability
Increasing demand for effective energy conversion materials and devices has renewed interest in semiconductors comprised of earth-abundant and biocompatible elements. Alkaline-earth sulfides doped with rare earth ions are versatile optical materials. However, relatively little is known about controlling the dimensionality, surface chemistry, and inherent optical properties of the undoped versions of alkaline-earth monoand polychalcogenides. Here, we describe the colloidal synthesis of alkaline-earth chalcogenide nanocrystals through the reaction of metal carboxylates with carbon disulfide or selenourea. Systematic exploration of the synthetic phase space allows us to tune particle sizes over a wide range using a mixture of commercially available carboxylate precursors. Solid-state NMR spectroscopy confirms the phase purity of the selenide compositions. Surface characterization reveals that bridging carboxylates and amines preferentially terminate the surface of the nanocrystals. While these materials are colloidally stable in the mother solution, the selenides are susceptible to oxidation over time, eventually degrading to selenium metal through polyselenide intermediates. As part of these investigations, we have developed the colloidal syntheses of barium di- and triselenides, two among few reported nanocrystalline alkaline-earth polychalcogenides. Electronic structure calculations reveal that both materials are indirect band gap semiconductors. The colloidal chemistry presented here may enable the synthesis of more complex, multinary chalcogenide materials containing alkaline-earth elements.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Extraction and Separation of Rare-Earth Elements from Coal Fly Ash and Leachate using a Recyclable Ionic Liquid
Coal fly ash (CFA) can be a promising source for recovering rare-earth elements (REEs), as it contains a broad range of REEs with average concentrations frequently exceeding those in traditional rare earth mines. Recent research from our group has demonstrated that REEs can be preferentially extracted from CFA solids using a recyclable ionic liquid (IL), betainium bis-(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]). When CFA was heated with the mixture of IL and an aqueous solution above 65°C, most leached REEs partitioned into the IL phase and were separated from the bulk elements. Subsequent acid stripping of the REE-loaded IL removed the REEs and regenerated the IL for reuse in multiple extraction cycles. This IL-based REE-CFA recovery method has been applied to ten CFA samples derived from different coal sources, including ash recovered from disposal ponds. Analysis of 34 elements confirmed the process consistently achieved high REE recovery efficiency, with strong selectivity over bulk and trace elements across diverse CFA types. In addition to the IL-solid extraction, the performance of [Hbet][Tf2N] in extracting REEs from fly-ash leachates have been evaluated by four commonly used leaching reagents, including HCl, HNO3, H2SO4, and citrate. During the IL-leachate extraction, [Hbet][Tf2N] was mixed and heated with a Class C fly ash leachate generated from each leaching reagent, followed by an acid stripping. It was observed that the partitioning and recovery of REEs increased as the leachate pH increased from 3 to 11. Among the investigated leachates, HCl and citrate proved to be the most compatible with IL extraction, exhibiting a slightly higher REE recovery and a lower non-REE co-extraction compared to the IL-solid extraction. Sc, Y, Nd, Sm, Gd, Dy, and Yb consistently showed a high recovery rate from both CFA solids and leachates. Notably, Pr, Tb, and Ho, which were not previously leached from the CFA solids, were partially recovered from the leachates. Overall, our studies revealed the strong potential of [Hbet][Tf2N] for effectively recovering REEs from leachates, highlighting its applicability as a sustainable strategy for other aqueous REE feedstocks. Furthermore, a techno-economic analysis will be performed to quantify the economic viability of the IL-based REE recovery method and guide future process improvement.
42 ENGINEERING↗
Efficient Capture and Release of the Rare-Earth Element Neodymium in Aqueous Solution by Recyclable Covalent Organic Frameworks
Rare-earth elements (REEs) are present in a broad range of critical materials. The development of solid adsorbents for REE capture could enable the cost-effective recycling of REE-containing magnets and electronics. In this context, covalent organic frameworks (COFs) are promising candidates for REE adsorption due to their exceptionally high surface area. Despite having attractive physical properties, COFs are heavily underutilized for REE capture applications due to their limited lifecycle in aqueous acidic environments, as well as synthetic challenges associated with the incorporation of ligands suitable for REE capture. Here, in this work, we show how the Ugi multicomponent reaction can be leveraged to postsynthetically modify imine-based COFs for the introduction of a diglycolic acid (DGA) moiety, an efficient scaffold for REE capture. The adsorption capacity of the DGA-functionalized COF was found to be more than 40 times higher than that of the pristine imine COF precursor and more than four times higher than that of the next-best reported DGA-functionalized solid support. This rationally designed COF has appealing characteristics of high adsorption capacity, fast and efficient capture and release of the REE ions, and reliable recyclability, making it one of the most promising adsorbents for solid–liquid REE ion extractions reported to date.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Orthorhombic distortion drives orbital ordering in the antiferromagnetic 3$d$ 1 Mott insulator PrTiO 3
The orbital, which represents the shape of the electron cloud, very often strongly influences the manifestation of various exotic phenomena, e.g., magnetism, metal-insulator transition, colossal magnetoresistance, unconventional superconductivity, etc. in solid-state systems. The observation of the antiferromagnetism in $RE$TiO 3 ($RE$ = rare-earth) series has been puzzling since the celebrated Kugel-Khomskii model of spin-orbital superexchange predicts ferromagnetism in an orbitally degenerate $d$ 1 system. Further, the existence of the orbitally ordered vs. orbital liquid phase in both antiferromagnetic and paramagnetic phase have been unsettled issues thus far. To address these longstanding questions, we investigate single crystalline film of PrTiO 3 . Our synchrotron x-ray diffraction measurements confirm the retention of bulklike orthorhombic ($D_{2h}$) symmetry in the thin film geometry. We observe similar x-ray linear dichroism signal in both paramagnetic and antiferromagnetic phase, which can be accounted by ferro-orbital ordering (FOO). While the presence of $D_{2h}$ crystal field does not guarantee lifting of orbital degeneracy always, we find it to be strong enough in these rare-earth titanates, leading to the FOO state. Thus, our work demonstrates the orthorhombic distortion is the driving force for the orbital ordering of antiferromagnetic $RE$TiO 3 .
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Mixing of Condensable Constituents with H–He during the Formation and Evolution of Jupiter
Simulations of Jupiter's formation are presented that incorporate mixing of H–He with denser material entering the planet as solids. Heavy compounds and gas mix substantially when the planet becomes roughly as massive as Earth, because incoming planetesimals can fully vaporize. Supersaturation of vaporized silicates causes the excess to sink as droplets, but water remains at higher altitudes. Because the mean molecular weight decreases rapidly outward, some of the compositional inhomogeneities produced during formation can survive for billions of years. After 4.57 Gyr, our Jupiter model retains compositional gradients; proceeding outward, one finds (i) an inner heavy-element core, the outer part derived from hot supersaturated rain-out; (ii) a composition-gradient region, containing most of the heavy elements, where H–He abundance increases outward, reaching about 0.9 mass fraction at 0.3 of the radius, with silicates enhanced relative to water in the lower parts and depleted in the upper parts; (iii) a uniform-composition region (neglecting He immiscibility) that is enriched over protosolar and contains most of the planet’s mass; and (iv) an outer region where cloud formation (condensation) of heavy constituents occurs. This radial compositional profile has heavy elements more broadly distributed than predicted by classical formation models but less diluted than suggested by Juno-constrained gravity models. The compositional gradients in the region containing the bulk of the heavy elements prevent convection, in both our models and those fitting current gravity, resulting in a hot interior where much of the accretion energy remains trapped.
79 ASTRONOMY AND ASTROPHYSICS↗
Structurally Driven Selective Adsorption of Hydrocarbons by Metal Substitution in Isostructural Rare-Earth Metal–Organic Frameworks
The design and realization of highly selective nanoporous materials are necessary to target critical separations across industries. By leveraging pore size, pore shape, and linker functionalization, the design of nanoporous solid adsorbents will enable the rapid production of energy efficient separation materials for high-value gas mixtures. This study uses a combination of modeling, synthesis, and gas adsorption testing to investigate a new class of small-pore isostructural rare-earth (RE) 2,5-dihydroxyterephthalic acid (DOBDC) metal–organic frameworks (MOFs) (RE: Pr-, Gd-, Er-, Yb; DOBDC = 2,5-dihydroxyterephthalic acid) and their adsorption selectivity for acetylene/ethylene mixtures. Density functional theory simulations identified that selective binding of acetylene over ethylene in the Gd-, Er-, and Yb-DOBDC MOFs was due to hydrogen-bonding between acetylene and the linker hydroxyl. Adsorption experiments validated the computational results by identifying mechanisms that control the acetylene/ethylene adsorption selectivity and high acetylene adsorption. Furthermore, dynamic column breakthrough experiments with the Gd-DOBDC MOF validated the simulations and indicated that ethylene can be separated from acetylene in a mixture containing 1 vol % acetylene and 39 vol % ethylene (balance argon). In conclusion, the results highlight the complexity of gas binding in functional porous materials and how combining modeling and experiment enables a fundamental understanding of gas–framework interactions that can be leveraged for the design of future separation materials.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Towards green synthesis of Mn 4+ -doped fluoride phosphors: a review
Mn 4+ -doped fluoride phosphors are attractive for application in white solid-state lighting devices because their distinct red emission can improve the color rendering index, while the earth-abundance of Mn 4+ ions can reduce the production cost. However, highly hazardous HF is used as the fluoride source in the synthesis processes, which requires extreme caution. In this review, we introduce various methods for synthesizing Mn 4+ -doped fluoride phosphors, categorized according to the presence or absence of HF in the synthesis. The underlying optical properties of the phosphors fabricated using the various methods are discussed. In addition, in the discussion of each method, we emphasize on the key factors and strategies for developing phosphors. Finally, this review highlights perspectives on and future directions for the safe synthesis of Mn 4+ -doped fluoride phosphors to achieve solid-state lighting devices with superior optical properties.
36 MATERIALS SCIENCE↗
Dopant segregation in YAG single crystal fibers grown by the laser heated pedestal growth technique
In this work, we report self-segregation of dopants in a crystal matrix within a single crystal (SC) fiber. Neodymium and holmium-doped yttrium aluminum garnet (YAG) fibers were grown using the Laser Heated Pedestal Growth (LHPG) technique and cross-sectional dopant concentration was measured using electron-probe micro-analysis. It was observed that the degree of auto-segregation of the rare-earth dopant depended on the difference in ionic size of the dopant ion and the Y 3+ ion in the YAG matrix. While holmium showed little tendency to self-segregate, the concentration of neodymium ions varied as much as 25% across the cross-section of the fiber. Strong correlation between the dopant concentration profile and fiber draw speed was also demonstrated. Since the local refractive index depends on the concentration of dopants, a refractive index profile can be achieved by a dopant profile across the fiber cross-section. Engineered index profiles can be realized by varying growth conditions, dopants, crystal matrix, etc. Such an approach is promising in applications such as the development of monolithic SC fibers with graded-index profiles.
36 MATERIALS SCIENCE↗
Melting of magnesium oxide up to two terapascals using double-shock compression
Constraining the melting behavior of magnesium oxide, a major constituent of gaseous and rocky planets, is key to benchmarking their evolutionary models. Using a double-shock technique, we extended the MgO melt curve measurements to 2 TPa; this is twice the pressure achieved by previous melting experiments on any material. A temperature plateau is observed between 1218 and 1950 GPa in the second shock states, which is attributed to latent heat of melting. At 1950 GPa, the measured melting temperature is 17,600 K, 17% lower than recent theoretical predictions. Furthermore, the melting curve is steeper than that of MgSiO 3 , indicating that MgO is likely solid in the interior of Saturn-sized gas giants and extra-solar super-Earth planets.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Crystal Structure and Melting of Fe Shock Compressed to 273 GPa: In Situ X-Ray Diffraction
Abstract not provided
Turneaure, Stefan J.↗
Synthesis of mesoporous silica using a mineral silica source
Abstract Mesoporous silica has been applied in catalysis, separations, and drug delivery. It has generally been made using organosilicon precursors such as tetraethyl orthosilicate. For sustainability, it is necessary to find readily accessible mineral sources for making mesoporous silica. In this work, we demonstrate the successful synthesis of mesoporous silica with 10 nm average pore size using the mineral forsterite (Mg 2 SiO 4 ) as a silica source, providing a potentially cheaper and more Earth‐friendly route to making technologically important porous silica materials. Pure forsterite was synthesized by a solid‐state chemistry route at 1000°C and underwent dissolution–reprecipitation in aqueous hydrochloric acid containing the soft template surfactant, Pluronic P123. Variations of initial reaction pH (−0.2 to 0.6), reaction time (12–24 h), reaction temperature (50 to 90°C), and silica precursor (forsterite and fumed silica) were performed. The mesoporous silica aged at 70°C for 24 h had the highest porosity, with a surface area of 735 m 2 /g and a pore volume of 1.4 ml/g, comparable to mesoporous silica made using conventional starting materials. This novel geomimetic synthesis route supports the possibility of analogous formation of structured (mesoporous or zeolitic) silica in nature under abiotic or prebiotic conditions.
Materials Science↗
Ionically conductive powders and films, and methods of preparation
A solid ionically conductive composition (e.g., nanoparticles of less than 1 micron or a continuous film) comprising at least one element selected from alkali metal, alkaline earth metal, aluminum, zinc, copper, and silver in combination with at least two elements selected from oxygen, sulfur, silicon, phosphorus, nitrogen, boron, gallium, indium, tin, germanium, arsenic, antimony, bismuth, transition metals, and lanthanides. Also described is a battery comprising an anode, a cathode, and a solid electrolyte (corresponding to the above ionically conductive composition) in contact with or as part of the anode and/or cathode. Further described is a thermal (e.g., plasma-based) method of producing the ionically conductive composition. Further described is a method for using an additive manufacturing (AM) process to produce an object constructed of the ionically conductive composition by use of particles of the ionically conductive composition as a feed material in the AM process.
Kercher, Andrew K.↗
Erbium-Implanted WS 2 Flakes with Room-Temperature Photon Emission at Telecom Wavelengths
Optically addressable spin impurities in crystals along with device engineering provide an attractive route to realizing quantum technologies in the solid state, but reconciling disparate emitter and host material constraints for a given target application is often challenging. Rare-earth ions in two-dimensional (2D) materials could mitigate this problem given the atomic-like transitions of the emitters and the versatile nature of van der Waals systems. Here we combine ion implantation, confocal microscopy, and ab initio calculations to examine the photon emission of Er-doped WS 2 flakes. Optical spectroscopy reveals narrow, long-lived photoluminescence lines in the telecom band, which we activate after low-temperature thermal annealing. Spectroscopic and polarization-selective measurements show a uniform response across the ensemble, while the fluorescence brightness remains mostly unchanged with temperature, suggesting nonradiative relaxation channels are inefficient. Our results create opportunities for novel solid state devices coupling 2D-hosted, telecom-band emitters to photonic heterostructures separately optimized for photon manipulation.
77 NANOSCIENCE AND NANOTECHNOLOGY↗