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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

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↗
DOE OSTI2023

Resolving Nanoscale Processes during Carbon Mineralization Using Identical Location Transmission Electron Microscopy

Basalt reservoirs offer the potential for carbon mineralization, aiding in achieving net-zero emissions. However, debates persist about microscopic crystallization mechanisms due to limited characterization techniques under high-temperature and pressure conditions. By using Identical Location Transmission Electron Microscopy (IL-TEM) and cryo-TEM, this study reveals nanoscale interfacial carbonation processes of forsterite and diopside nanoparticles in water-saturated supercritical carbon dioxide under realistic reservoir conditions. Further, both minerals undergo preferential metal cation dissolution into a thin water film, forming porous Si-rich amorphous layers, supporting the leached layer mechanism as the dominant mineral reactivity process. Diopside’s amorphous layer has lower porosity and growth rate relative to forsterite, likely related to the connectivity of silicate tetrahedra. Kinetically favorable nesquehonite and aragonite nanocrystals form on the amorphous layers. These findings support the development of accurate reservoir simulations and help enable commercial-scale carbon storage deployment.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Silicate Melting and Vaporization During Rocky Planet Formation

Collisions that induce melting and vaporization can have a substantial effect on the thermal and geochemical evolution of planets. However, the thermodynamics of major minerals are not well known at the extreme conditions attained during planet formation.We obtained new data at the Sandia Z Machine and use published thermodynamic data for the major mineral forsterite (Mg 2 SiO 4 ) to calculate the specific entropy in the liquid region of the principal Hugoniot.We use our calculated specific entropy of shocked forsterite, and revised entropies for shocked silica, to determine the critical impact velocities for melting or vaporization upon decompression from the shocked state to 1 bar and the triple points, which are near the pressures of the solar nebula.We also demonstrate the importance of the initial temperature on the criteria for vaporization. Applying these results to N-body simulations of terrestrial planet formation, we find that up to 20% to 40% of the total system mass is processed through collisions with velocities that exceed the criteria for incipient vaporization at the triple point. Vaporizing collisions between small bodies are an important component of terrestrial planet formation.

58 GEOSCIENCES↗
DOE OSTI2023

The environmental controls on efficiency of enhanced rock weathering in soils

Abstract Enhanced rock weathering (ERW) in soils is a promising carbon removal technology, but the realistically achievable efficiency, controlled primarily by in situ weathering rates of the applied rocks, is highly uncertain. Here we explored the impacts of coupled biogeochemical and transport processes and a set of primary environmental and operational controls, using forsterite as a proxy mineral in soils and a multiphase multi-component reactive transport model considering microbe-mediated reactions. For a onetime forsterite application of ~ 16 kg/m 2 , complete weathering within five years can be achieved, giving an equivalent carbon removal rate of ~ 2.3 kgCO 2 /m 2 /yr. However, the rate is highly variable based on site-specific conditions. We showed that the in situ weathering rate can be enhanced by conditions and operations that maintain high CO 2 availability via effective transport of atmospheric CO 2 (e.g. in well-drained soils) and/or sufficient biogenic CO 2 supply (e.g. stimulated plant–microbe processes). Our results further highlight that the effect of increasing surface area on weathering rate can be significant—so that the energy penalty of reducing the grain size may be justified—only when CO 2 supply is nonlimiting. Therefore, for ERW practices to be effective, siting and engineering design (e.g. optimal grain size) need to be co-optimized.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Carbon mineralization pathways in interfacial adsorbed water nanofilms

Carbon mineralization in humidified carbon dioxide offers a promising route to mitigate anthropogenic emissions in a world stressed by water security. Despite its technological importance, our understanding of carbonation in water-poor environments lags, as traditional dissolution-precipitation pathways struggle to explain the adsorbed water nanofilm-mediated reactivity. Here, we utilize in operando X-ray diffraction (XRD) and advanced molecular simulations to investigate nanoconfined reactions driving forsterite carbonation, the magnesium-rich olivine. By examining magnesium ion dissolution and transport in atomistic simulations of the forsterite-water-carbon dioxide interface and comparing these with the in operando XRD activation energies, we identify both processes as rate-limiting at saturation. Our simulations reveal a mechanistic view of interfacial carbonation, where dissolution and precipitation are mediated by anomalous quasi two-dimensional diffusion. The transport process involves intermittent diffusive hopping in the desorbed state, separated by crawling events that are spatially short but temporally long. This understanding transcends carbon mineralization, with implications for understanding the transport of contaminants in geosystems, the design of multifunctional materials, water desalination, and molecular recognition systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Emerging investigator series: ion diffusivities in nanoconfined interfacial water films contribute to mineral carbonation thresholds

The dynamics and reactivity of nanoconfined fluids play critical roles across a wide range of environmental and technological systems, though reaction mechanisms and kinetics are not well understood. Here, the carbonation kinetics of forsterite (Mg 2 SiO 4 ) exposed to 90 atm supercritical carbon dioxide at 35–65 °C and 85–100% relative humidity (RH) was monitored with in situ X-ray diffraction, and partner molecular dynamics simulations were used to describe the free energy landscape of Mg 2+ adsorption and diffusion on forsterite surfaces covered in water films 3–10 monolayers thick. The collective findings reveal how decreasing the water film thickness by ~1.4 monolayers, from ~0.92 to ~0.64 nm, inhibited reaction rates by up to 97%, promoted anhydrous Mg-carbonate (magnesite, MgCO 3 ) precipitation, and more than doubled the apparent activation energy of carbonation. The transport simulations suggest that four monolayers are required to enable sufficiently facile Mg 2+ diffusion, helping explain previously observed water film thickness-dependent reactivity thresholds.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Reactive force fields for aqueous and interfacial magnesium carbonate formation

Here we develop Mg/C/O/H ReaxFF parameter sets for two environments: an aqueous force field for magnesium ions in solution and an interfacial force field for minerals and mineral–water interfaces. Since magnesium is highly ionic, we choose to fix the magnesium charge and model its interaction with C/O/H through Coulomb, Lennard-Jones, and Buckingham potentials. We parameterize the forcefields against several crystal structures, including brucite, magnesite, magnesia, magnesium hydride, and magnesium carbide, as well as Mg 2+ water binding energies for the aqueous forcefield. Then, we test the forcefield for other magnesium-containing crystals, solvent separated and contact ion-pairs and single-molecule/multilayer water adsorption energies on mineral surfaces. We also apply the forcefield to the forsterite–water and brucite–water interface that contains a bicarbonate ion. We observe that a long-range proton transfer mechanism deprotonates the bicarbonate ion to carbonate at the interface. Free energy calculations show that carbonate can attach to the magnesium surface with an energy barrier of about 0.22 eV, consistent with the free energy required for aqueous Mg–CO 3 ion pairing. Also, the diffusion constant of the hydroxide ions in the water layers formed on the forsterite surface are shown to be anisotropic and heterogeneous. These findings can help explain the experimentally observed fast nucleation and growth of magnesite at low temperature at the mineral–water–CO 2 interface in water-poor conditions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Metasomatic alteration of coarse‐grained igneous calcium‐aluminum‐rich inclusions from CK3 carbonaceous chondrites

Abstract We report on the primary and secondary mineralogies of three coarse‐grained igneous calcium‐aluminum‐rich inclusions (CAIs) (Compact Type A [CTA], Type B [B], and forsterite‐bearing type B [FoB]) from the Northwest Africa (NWA) 5343 (CK3.7) and NWA 4964 (CK3.8) carbonaceous chondrites, compare them with the mineralogy of igneous CAIs from the Allende (CV3.6) chondrite, and discuss the nature of the alteration processes that affected the CK and CV CAIs. The primary mineralogy and mineral chemistry of the CK3 CAIs studied are similar to those from Allende; however, primary melilite and anorthite are nearly completely absent. Although the secondary minerals identified in CK CAIs (Al‐diopside, andradite, Cl‐apatite, clintonite, forsterite, ferroan olivine, Fe,Ni‐sulfides, grossular, ilmenite, magnetite, plagioclase, spinel, titanite, and wadalite) occur also in the Allende CAIs, there are several important differences: (i) In addition to melilite and anorthite, which are nearly completely replaced by secondary minerals, the alteration of CK CAIs also affected high‐Ti pyroxenes (fassaite and grossmanite) characterized by high Ti 3+ /Ti 4+ ratio and spinel. These pyroxenes are corroded and crosscut by veins of Fe‐ and Ti‐bearing grossular, Fe‐bearing Al,Ti‐diopside, titanite, and ilmenite. Spinel is corroded by Fe‐bearing Al‐diopside and grossular. (ii) The secondary mineral assemblages of grossular + monticellite and grossular + wollastonite, commonly observed in the Allende CAIs, are absent; the Fe‐bearing grossular + Fe‐bearing Al‐diopside ± Fe,Mg‐spinel, Fe‐bearing grossular + Fe,Mg‐olivine ± Fe,Mg‐spinel, and Ca,Na‐plagioclase + Fe‐bearing Al‐diopside + Fe‐bearing grossular assemblages are present instead. These mineral assemblages are often crosscut by veins of Fe‐bearing Al‐diopside, Fe,Mg‐olivine, Fe,Mg‐spinel, and Ca,Na‐plagioclase. The coarse‐grained secondary grossular and Al‐diopside often show multilayered chemical zoning with distinct compositional boundaries between the layers; the abundances of Fe and Ti typically increase toward the grain edges. (iv) Sodium‐rich secondary minerals, nepheline and sodalite, commonly observed in the peripheral portions of the Allende CAIs, are absent; Ca,Na‐plagioclase is present instead. We conclude that coarse‐grained igneous CAIs from CK3.7–3.8 s and Allende experienced an open‐system multistage metasomatic alteration in the presence of an aqueous solution–infiltration metasomatism. This process resulted in localized mobilization of all major rock‐forming elements: Si, Ca, Al, Ti, Mg, Fe, Mn, Na, K, and Cl. The metasomatic alteration of CK CAIs is more advanced and occurred under higher temperature and higher oxygen fugacity than that of the Allende CAIs.

Geochemistry & Geophysics↗
DOE OSTI2026

Computer simulation of reaction and transport of core-scale serpentinization of Fe-bearing olivine and evolution of geological hydrogen

We present reactive flow and transport simulations of core-scale serpentinization of forsteritic, Fe-bearing olivine under hydrothermal conditions. The model captures fluid flow, evolving porosity–permeability, and redox-controlled H 2 production in a cylindrical core over 55 days at 245 °C and 37 bar. Key processes include olivine dissolution, precipitation of serpentine and magnetite, and oxidation of Fe2+ to Fe 3+ . Here, results show strong coupling among flow velocity, alteration front propagation, and spatially heterogeneous H 2 generation. Elevated H2 concentrations align with inlet-localized magnetite precipitation, consistent with experiments. Secondary mineral formation reduces porosity and permeability, altering transport pathways. Reactive flow at the fluid–solid interface governs H 2 generation rates and distribution. Dissolved SiO2 promotes serpentine and talc formation by suppressing brucite, while bicarbonate extends reaction duration and moderates surface complexation effects.

Geologic hydrogen↗
DOE OSTI2022

Chrome-free qandilite (Mg 2 TiO 4 ) refractory aggregates: Role of titania source and evaluation of thermal expansion coefficient

As used chrome-based refractories may contain toxic Cr 6+ , the chrome-free Mg 2 TiO 4 phase is being considered which is known to improve hot strength and resistance to thermal shock and slag corrosion. As in situ Mg 2 TiO 4 formation generates porosity, preformed aggregates are desirable. Dilatometric studies revealed that when dead burned magnesia is combined with industrial anatase instead of rutile, it expanded less (1% versus 7.2%) and the reaction occurred earlier (965°C compared to 1120°C). After sintering at 1,600°C, rutile produced an aggregate with 3.8% open porosity, whereas anatase led to 0 % porosity and a bulk density of 3.24g/cm 3 with a thermal expansion coefficient (70–1,600°C) of 13.5×10 -6 K -1 . Moreover, replacing rutile by anatase eliminates the undesirable MgTiO 3 phase. The anatase-based aggregate consisted of a Mg 2 TiO 4 matrix with residual unreacted MgO and an intergranular, refractory CaTiO 3 phase. In conclusion, the rutile-based aggregate was deemed unsuitable due to a low-melting microstructure of forsterite contiguous with CaTiO 3 .

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

Reactive Transport Modeling of Mineral Precipitation and Carbon Trapping in Discrete Fracture Networks

In this study we use numerical experiments to analyze reactive flow and transport behavior in discrete intersecting fracture networks, focusing on (a) how reaction-induced changes in physical and chemical properties affect flow connectivity and (b) how fracture networks developed in the Earth's critical zone contribute to carbon sequestration via mineral weathering reactions. In the first part of the study, we used two-dimensional reactive flow and transport simulations to analyze the impacts of mixing in a natural discrete fracture network. We concluded that reaction-induced changes can substantially alter the flow connectivity, especially at fracture intersections. The second set of simulations considered the problem of natural weathering of fractured mafic and ultramafic rocks in the partially saturated Earth's critical zone as a function of infiltration rates, fracture permeability, and partially saturated flow parameters. As a model system, we considered an incongruent reaction network with dissolution of forsterite and precipitation of magnesite. The behavior is complex in terms of the rate-controlling processes because of the multicomponent nature of the system as shown by the grid Peclet number: the CO 2 behavior is gas diffusion-controlled in the partially saturated zone, while the rate of water flow via the Damkӧhler number controls Mg 2+ transport through the fracture network. The amounts of carbon that can be trapped are modest, but the naturally fractured domain considered here provides a useful “base case” against which various engineered solutions can be compared.

58 GEOSCIENCES↗
DOE OSTI2026

Aperture and roughness govern iron oxide passivation in olivine fractures during carbon mineralization

Efficient carbon dioxide mineralization in silicate-rich formations depends on reaction rates within fracture networks, yet the role of fracture microstructure remains poorly constrained. We investigated how fracture aperture and surface roughness influence mineralization by reacting synthetic forsteritic olivine fractures with controlled apertures (0.5–1.6 millimeters) and roughness (6–16 micrometers) with supercritical carbon dioxide at 13.7 megapascals and 185 degrees Celsius. Optical microscopy and Raman spectroscopy showed that rougher fracture surfaces promoted iron oxide precipitation, which passivated olivine surfaces, limiting magnesium availability for carbonate formation while removing iron as a reactant. These effects were more pronounced in smaller-aperture fractures. A geochemical model incorporating surface topography and passivation reproduced the observed trends, confirming that increased roughness can reduce reactivity despite greater surface area. Our results demonstrate that fracture microstructure strongly influences iron oxide passivation and carbon dioxide mineralization, with important implications for predicting long-term performance of engineered carbon dioxide storage systems.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

Low temperature and limited water activity reveal a pathway to magnesite via amorphous magnesium carbonate

Forsterite carbonated in thin H 2 O films to magnesite via amorphous magnesium carbonate during reaction with H 2 O-bearing liquid CO 2 at 25 °C. This novel reaction pathway contrasts with previous studies that were carried out at higher H 2 O activity and temperature, where more highly hydrated nesquehonite was the metastable intermediate.

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

Nanoconfinement matters in humidified CO 2 interaction with metal silicates

With enigmatic observations of enhanced reactivity of wet CO 2 -rich fluids with metal silicates, the mechanistic understanding of molecular processes governing carbonation proves critical in designing secure geological carbon sequestration and economical carbonated concrete technologies. Here, we use the first principle and classical molecular simulations to probe the impact of nanoconfinement on physicochemical processes at the rock–water–CO 2 interface. We choose nanoporous calcium–silicate–hydrate (C–S–H) and forsterite (Mg 2 SiO 4 ) as model metal silicate surfaces that are of significance in cement chemistry and geochemistry communities, respectively. We show that while a nanometer-thick interfacial water film persists at unsaturated conditions consistent with in situ infrared spectroscopy, the phase behavior of the water–CO 2 mixture changes from its bulk counterpart depending on the surface chemistry and nanoconfinement. We also observe enhanced solubility at the interface of water and CO 2 phases, which could amplify the CO 2 speciation rate. Additionally, through free energy calculations, we show that CO 2 could be found in a metastable state near the C–S–H surface, which can potentially react with surface water and hydroxyl groups to form carbonic acid and bicarbonate. These findings support the explicit consideration of nanoconfinement effects in reactive and non-reactive pore-scale processes.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

The shock physics of giant impacts: Key requirements for the equations of state

We discuss major challenges in modeling giant impacts between planetary bodies, focusing on the equations of state (EOS). During the giant impact stage of planet formation, rocky planets are melted and partially vaporized. However, most EOS models fail to reproduce experimental constraints on the thermodynamic properties of the major minerals over the required phase space. Here, we present an updated version of the widely-used ANEOS model that includes a user-defined heat capacity limit in the thermal free energy term. Our revised model for forsterite (Mg 2 SiO 4 ), a common proxy for the mantles of rocky planets, provides a better fit to material data over most of the phase space of giant impacts. We discuss the limitations of this model and the Tillotson equation of state, a commonly used alternative model.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Interference microscopy study of the preplasma formed on an iron target surface exposed to high-power femtosecond laser pulses

The characteristic scale of spread of the plasma formed on the surface of a bulk iron target irradiated by a femtosecond laser pulse with an intensity of 10{sup 16} W cm{sup −2} is measured by time-resolved interference microscopy using femtosecond pulses emitted by a Cr : forsterite laser system with an intensity contrast of 10{sup 7}. The chosen technique is demonstrated to be efficient in such measurements. It is shown experimentally that, as a result of laser pulse impact, the displacement of a plasma layer with a density exceeding critical does not exceed 30 nm. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Focused‐beam X‐ray fluorescence and diffraction microtomographies for mineralogical and chemical characterization of unsectioned extraterrestrial samples

Abstract This study describes the application of new synchrotron X‐ray fluorescence (XRF) and diffraction (XRD) microtomographies for the 3‐D visualization of chemical and mineralogical variations in unsectioned extraterrestrial samples. These improved methods have been applied to three compositionally diverse chondritic meteorite samples that were between 300 and 400 μm in diameter, including samples prepared from fragments of the CR2 chondrite LaPaz Icefield (LAP) 02342, H5 chondrite MacAlpine Hills (MAC) 88203, and the CM2 chondrite Murchison. The synchrotron‐based XRF and XRD tomographies used are focused‐beam techniques that measure the intensities of fluorescent and diffracted X‐rays in a sample simultaneously during irradiation by a high‐energy microfocused incident X‐ray beam. Measured sinograms of the emitted and diffracted intensities were then tomographically reconstructed to generate 2‐D slices of XRF and XRD intensity through the sample, with reconstructed pixel resolution of 1–2 μm, defined by the resolution of the focused incident X‐ray beam. For sample LAP 02342, primary mineral phases that were visualized in reconstructed slices using these techniques included isolated grains of α‐Fe, orthopyroxene, and olivine. For our sample of MAC 88203, XRF/XRD tomography allowed visualization of forsteritic olivine as a primary mineral phase, a vitrified fusion crust at the sample surface, identification of localized Cr‐rich spinels at spatial resolutions of several micrometers, and imaging of a plagioclase‐rich glassy matrix. In the sample of Murchison, major identifiable phases include clinoenstatite‐ and olivine‐rich chondrules, variable serpentine matrix minerals and small Cr‐rich spinels. Most notable in the tomographic analysis of Murchison is the ability to quantitatively distinguish and visualize the complex mixture of serpentine‐group minerals and associated tochilinite–cronstedtite intergrowths. These methods provide new opportunities for spatially resolved characterization of sample texture, mineralogy, crystal structure, and chemical state in unsectioned samples. This provides researchers an ability to characterize such samples internally with minimal disruption of sample micro‐structures and chemistry, possibly without the need for sample extraction from some types of sampling and capture media.

Geochemistry & Geophysics↗