SEARCH · Search NASA

Results for “transition metal silicates”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

49 records · Page 3

All sources NASA NTRS DOE OSTI

NASA NTRS2013

The W-W02 Oxygen Fugacity Buffer at High Pressures and Temperatures: Implications for f02 Buffering and Metal-silicate Partitioning

Oxygen fugacity (fO2) controls multivalent phase equilibria and partitioning of redox-sensitive elements, and it is important to understand this thermodynamic parameter in experimental and natural systems. The coexistence of a metal and its oxide at equilibrium constitutes an oxygen buffer which can be used to control or calculate fO2 in high pressure experiments. Application of 1-bar buffers to high pressure conditions can lead to inaccuracies in fO2 calculations because of unconstrained pressure dependencies. Extending fO2 buffers to pressures and temperatures corresponding to the Earth's deep interior requires precise determinations of the difference in volume (Delta) V) between the buffer phases. Synchrotron x-ray diffraction data were obtained using diamond anvil cells (DAC) and a multi anvil press (MAP) to measure unit cell volumes of W and WO2 at pressures and temperatures up to 70 GPa and 2300 K. These data were fitted to Birch-Murnaghan 3rd-order thermal equations of state using a thermal pressure approach; parameters for W are KT = 306 GPa, KT' = 4.06, and αKT = 0.00417 GPa K-1. Two structural phase transitions were observed for WO2 at 4 and 32 GPa with structures in P21/c, Pnma and C2/c space groups. Equations of state were fitted for these phases over their respective pressure ranges yielding the parameters KT = 190, 213, 300 GPa, KT' = 4.24, 5.17, 4 (fixed), and αKT = 0.00506, 0.00419, 0.00467 GPa K-1 for the P21/c, Pnma and C2/c phases, respectively. The W-WO2 buffer (WWO) was extended to high pressure by inverting the W and WO2 equations of state to obtain phase volumes at discrete pressures (1-bar to 100 GPa, 1 GPa increments) along isotherms (300 to 3000K, 100 K increments). The slope of the absolute fO2 of the WWO buffer is positive with increasing temperature up to approximately 70 GPa and is negative above this pressure. The slope is positive along isotherms from 1000 to 3000K with increasing pressure up to at least 100 GPa. The WWO buffer is at a higher fO2 than the IW buffer at pressures lower than 40 GPa, and the magnitude of this difference decreases at higher pressures. This qualitatively indicates an increasingly lithophile character for W at higher pressures. The WWO buffer was quantitatively applied to W metal-silicate partitioning by using the WWO-IW buffer difference in combination with literature data on W metal-silicate partitioning to model the exchange coefficient (KD) for the Fe-W exchange reaction. This approach captures the pressure dependence of W metal-silicate partitioning using the WWO-IW buffer difference and models the activities of the components in the silicate and metallic phases using an expression of the Gibbs excess energy of mixing. Calculation of KD along a peridotite liquidus predicts a decrease in W siderophility at higher pressures that supports the qualitative behavior predicted by the WWO-IW buffer difference, and agrees with findings of others. Comparing the competing effects of temperature and pressure on W metal-silicate partitioning, our results indicate that pressure exerts a greater effect.

Shofner, G. A.↗

DOE OSTI2020

Linking low and high temperature NO oxidation mechanisms over Brønsted acidic chabazite to dynamic changes of the active site

The oxidation of NO over Brønsted acid sites in chabazite (CHA) zeolites shows an atypical temperature dependence; at low temperature the apparent activation energy is negative, but it becomes positive as the temperature exceeds a transition temperature. To explain this behavior we used density functional theory and statistical mechanics to investigate high and low temperature mechanisms for this reaction and propose a dynamic active site change in response to temperature variation. Our simulations show that the apparent activation barrier in the low temperature regime is more negative over Brønsted acidic CHA as compared to the siliceous zeolite framework. This effect is attributed to further enthalpic stabilization of the transition states by physical interaction with the H-CHA Brønsted acid sites. At elevated temperature, our calculations support both the existence and the significant catalytic role of NO+ in providing a modified active site. The temperature dependent transformation of the active site from H-CHA to NO-CHA sites may occur via two plausible ion-exchange mechanisms that define a transition temperature for the reaction. This transition temperature can be tuned by incorporating different trivalent metal atoms (B, Al, Ga or In) within the CHA framework. We found the lowest transition temperature for H-[In] CHA and H-[Ga]CHA. Here, the ability to control the dynamic response of the active site and the associated switch between low and high temperature mechanism with negative and positive apparent activation energy, respectively, is of fundamental interest for the design of zeolite catalysts operating in the presence of NO.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

PRODUCTION OF GLASS-TO-METAL SEALS USING ADDITIVE MANUFACTURING TECHNIQUES

Glass-to-metal (GtM) seals are hermetic barriers between glass and metal components, often used in the electronic and vacuum industries. Creating the seals traditionally requires heating all the components to the glass melting temperature, where the glass will flow and bond to the metal. Due to the manufacturing constraints of the individual components and sealing conditions there are geometric and material restrictions. Additive manufacturing techniques were used to make GtM seals to reduce these restrictions. Hermetic, single pin seals were produced using printed metal shells, by selective laser melting (SLM), and digital light processing (DLP) printed glass preforms. Glass preforms were printed with photosensitive resin mixed with a silicate sealing glass powder in a 1:2 weight ratio. Thermal analysis, TGA/DSC, and screening experiments were used to determine an organic removal schedule. Video techniques determined a sintering schedule by producing a densification curve at different isothermal holds which were fit with a viscous sintering model. Single pin seals were also produced use a laser assisted manufacturing (LAM) process as an alternative to the conventional furnace sealing process. A Nd:YAG laser was focused on a solid glass preform, heating the glass to form the glass-metal bond. The sealing glass was doped with a transition metal oxide, Fe2O3 or CuO, to increase absorption of the laser wavelength. The interface of hermetic LAM seals were analyzed using electron microscopy, compared to conventional prepared seals, finding a reduction of interfacial morphologies.

Read, Aaron Reece↗

NASA NTRS1992

Terrestrial magma ocean and core segregation in the earth

According to the recent theories of formation of the earth, the outer layer of the proto-earth was molten and the terrestrial magma ocean was formed when its radius exceeded 3000 km. Core formation should have started in this magma ocean stage, since segregation of metallic iron occurs effectively by melting of the proto-earth. Therefore, interactions between magma, mantle minerals, and metallic iron in the magma ocean stage controlled the geochemistry of the mantle and core. We have studied the partitioning behaviors of elements into the silicate melt, high pressure minerals, and metallic iron under the deep upper mantle and lower mantle conditions. We employed the multi-anvil apparatus for preparing the equilibrating samples in the ranges from 16 to 27 GPa and 1700-2400 C. Both the electron probe microanalyzer (EPMA) and the Secondary Ion Mass spectrometer (SIMS) were used for analyzing the run products. We obtained the partition coefficients of various trace elements between majorite, Mg-perovskite, and liquid, and magnesiowustite, Mg-perovskite, and metallic iron. The examples of the partition coefficients of some key elements are summarized in figures, together with the previous data. We may be able to assess the origin of the mantle abundances of the elements such as transition metals by using the partitioning data obtained above. The mantle abundances of some transition metals expected by the core-mantle equilibrium under the lower mantle conditions cannot explain the observed abundance of some elements such as Mn and Ge in the mantle. Estimations of the densities of the ultrabasic magma Mg-perovskite at high pressure suggest existence of a density crossover in the deep lower mantle; flotation of Mg-perovskite occurs in the deep magma ocean under the lower mantle conditions. The observed depletion of some transition metals such as V, Cr, Mn, Fe, Co, and Ni in the mantle may be explained by the two stage process, the core-mantle equilibrium under the lower mantle conditions in the first stage, and subsequent downwards separation of the ultrabasic liquid (and magnesiowustite) and flotation of Mg-perovskite in the lower mantle.

Ohtani, Eiji↗

NASA NTRSDate not supplied

Understanding the Response of Common Spacecraft Shields to Hypervelocity Impacts of Meteorite and Other Terrestrial Analog Materials

Micrometeoroid and orbital debris (MMOD) populations can vary significantly in composition, density, and homogeneity. Hypervelocity testing campaigns intended to design and optimize MMOD shields for spacecraft are recognizing the need to investigate shield response from different types of impactors that span the range of densities observed in the MMOD population, such as nylon, Al, Al 2 O 3 , steel, and Cu. These tests, however, still pre-dominantly employ spherical and homogenous projectiles. Adding any compositional or mineralogical complexity to the impactor, such as what would be expected from a polymineralic micrometeoroid, for ex-ample, will be concomitant with a more complex shockwave structure in the projectile after it impacts the outer surface of any type of MMOD shield. The magnitude of these complexities will depend on how varied the mineralogy of the projectile is, but in the case of a metal-bearing chondrite, the disparate shock impendence between adjacent metal and silicate grains will potentially create localized areas of shock focusing (local increase in nominal shock pressure), or shock shadowing (local decrease in nominal shock pressure). The response of a MMOD shield is generally predicted using a ballistic limit equation – a semiempirical curve, derived from hypervelocity testing data, that denotes a particle diameter (for a given set of impact conditions such as projectile density and impact angle) when a shield will fail as a function of impact speed. These curves exhibit inflection points as a function of impact speed that represent when the projectile experiences sufficient pressure to fragment, melt, or vaporize. The introduction of shock focusing and shadowing in a heterogenous projectile will add uncertainty to the predicted pressures needed to go through each transition, leading to increased uncertainty in the expected performance of the MMOD shield. Therefore, it is necessary to explore the performance of MMOD shields in hypervelocity tests against more complex, natural projectile materials. To this end we have conducted a comparative test series to begin investigating the impact damage caused by meteoritic and terrestrial-analog projectiles, to that of spherical Al projectiles of similar mass.

Impact testing↗

NASA NTRS1998

Development of In-Fiber Reflective Bragg Gratings as Shear Stress Monitors in Aerodynamic Facilities

Bragg gratings centered at nominal wavelengths of 1290 nm and 1300 run were inscribed in a 9/125 microns germano-silicate optical fiber, using continuous wave frequency doubled Ar+ laser radiation at 244 nm. Such gratings have been used extensively as temperature and strain monitors in smart structures. They have, however, never been used for measuring aerodynamic shear stresses. As a test of their sensitivity as shear stress monitors, a Bragg fiber attached to a metal plate was subjected to laminar flows in a glass pipe. An easily measurable large flow-induced wavelength shift (Delta Lambda(sub B)) was observed in the Bragg reflected wavelength. Thereafter, the grating was calibrated by making one time, simultaneous measurements of Delta Lambda(sub B) and the coefficient of skin friction (C(sub f)) with a skin friction balance, as a function of flow rates in a subsonic wind tunnel. Onset of fan-induced transition in the tunnel flow provided a unique flow rate for correlating Delta Lambda(sub B) and (C(sub f) values needed for computing effective modulus of rigidity (N(sub eff)) of the fiber attached to the metal plate. This value Of N(sub eff) is expected to remain constant throughout the elastic stress range expected during the Bragg grating aerodynamic tests. It has been used for calculating the value of Cf at various tunnel speeds, on the basis of measured values of Bragg wavelength shifts at those speeds.

Parmar, Devendra S.↗

NASA NTRS2022

Fayalite Formation Through Hydrothermal Experiments: Insights into Early Fluid-assisted Aqueous Alteration Processes on Asteroids

In order to understand the effects of the earliest fluid-assisted hydration processes on asteroids, we performed one hydrothermal experiment using three different reactants (FeO-rich amorphous silicates, iron metal powder, and water) at conditions informed by our current state of knowledge of asteroidal alteration. This experiment provides, for the first time, clear evidence that the growth of fayalite can occur during hydrotherma lalteration, as described previously in meteorites. These newly formed fayalite crystals are elongated and porous, similar to the ones described in CV3, CK, and ordinary chondrites. The results show that (1) fayalite could form even if chemical equilibrium was not reached in the experiment, at a water to rock mass ratio (0.4 W/R at the beginning of the experiment) higher than the values calculated to be thermodynamically viable at equilibrium(W/R > 0.2); (2) the composition and the texture of the reactants changed during the hydrothermal alteration process, suggesting that the reactants, especially the amorphous silicates, underwent dissolution and reprecipitation; (3) fayalite can form at low temperature(220°C), which is at the transition between hydrothermal alteration and fluid-assisted metamorphism in chondrites. The results are consistent with previous mineralogical observations and thermodynamic models, which suggest that fayalite crystals are formed on asteroidal parent bodies by the interaction between a hydrothermal fluid and disequilibrium assemblages that compose the pristine materials that condensed in the early solar nebula. This experiment suggests that two variables play a very important role in the formation off ayalite during the hydrothermal growth (W/R mass ratio and the fluid composition). These results are similar to the recent observations of the fine-grained matrix of ordinary chondrites.

E Dobrică↗

DOE OSTI2021

The TESS-Keck Survey. II. An Ultra-short-period Rocky Planet and Its Siblings Transiting the Galactic Thick-disk Star TOI-561

We report the discovery of TOI-561, a multiplanet system in the galactic thick disk that contains a rocky, ultra-short-period planet. This bright (V = 10.2) star hosts three small transiting planets identified in photometry from the NASA TESS mission: TOI-561 b (TOI-561.02, P = 0.44 days, R {sub p} = 1.45 ± 0.11 R {sub ⊕}), c (TOI-561.01, P = 10.8 days, R {sub p} = 2.90 ± 0.13 R {sub ⊕}), and d (TOI-561.03, P = 16.3 days, R {sub p} = 2.32 ± 0.16 R {sub ⊕}). The star is chemically ([Fe/H] = −0.41 ± 0.05, [α/Fe] = +0.23 ± 0.05) and kinematically consistent with the galactic thick-disk population, making TOI-561 one of the oldest (10 ± 3 Gyr) and most metal-poor planetary systems discovered yet. We dynamically confirm planets b and c with radial velocities from the W. M. Keck Observatory High Resolution Echelle Spectrometer. Planet b has a mass and density of 3.2 ± 0.8 M {sub ⊕} and 5.5{sub −1.6}{sup +2.0} g cm{sup −3}, consistent with a rocky composition. Its lower-than-average density is consistent with an iron-poor composition, although an Earth-like iron-to-silicates ratio is not ruled out. Planet c is 7.0 ± 2.3 M {sub ⊕} and 1.6 ± 0.6 g cm{sup −3}, consistent with an interior rocky core overlaid with a low-mass volatile envelope. Several attributes of the photometry for planet d (which we did not detect dynamically) complicate the analysis, but we vet the planet with high-contrast imaging, ground-based photometric follow-up, and radial velocities. TOI-561 b is the first rocky world around a galactic thick-disk star confirmed with radial velocities and one of the best rocky planets for thermal emission studies.

47 OTHER INSTRUMENTATION↗

DOE OSTI2020

Advances in catalytic production processes of biomass-derived vinyl monomers

Plastic industries currently source the majority of monomers from crude oil substances. Although we have witnessed a significant interest of companies in the utilization of sustainable feedstock materials for bio-based compound synthesis in the past decade, the transition to photosynthetic or chemosynthetic plant-based production in a circular carbon economy is largely slow due to complex biomass processing, costs and related reaction factors. The upgrade of the separated platform chemicals with a deeper supporting understanding of processes, models and a root–cause analysis about the underlying distribution challenges of engineered transformation mechanisms, catalyzed conversion pathways and selectivity would be beneficial to advance applied scientific development, bio-refining and manufacturing output amount. This review provides a summary, assessment and perspective for three important polymer-forming vinyl molecules, i.e. acrylic acid, methacrylic acid and styrene. These provide a backbone to produce acrylates, polystyrene, resins, rubbers, protective surface coatings, adhesives, textiles and other obtained copolymers. A succinct analytical overview on the thermo-catalytic intermediate routes for property-wise drop-in alternatives is presented. Sugars, acrolein, allyl alcohol, ethylbenzene, glycerol, 3-hydroxypropionic acid, isobutene, itaconic acid and lactic acid are considered as the main starting reactants. Catalysts span mixed metal oxides, silicates, native or impregnated zeolite frameworks (HBEA, HZSM, and MFI) and hetero-poly acids as well as homogeneous base hydroxides or platinum group metals, supported on carbon, alumina and sulfates. Finally, the article concludes with a brief state sum-up of the results, topics and opportunities for systematic future research or scaling.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Equations of state, phase relations, and oxygen fugacity of the Ru-RuO 2 buffer at high pressures and temperatures

Experimental studies and measurements of inclusions in diamonds show that ferric iron components are increasingly stabilized with depth in the mantle. To determine the thermodynamic stability of such components, their concentration needs to be measured at known oxygen fugacities. The metal-oxide pair Ru and RuO 2 are ideal as an internal oxygen fugacity buffer in high-pressure experiments. Both phases remain solid to high temperatures and react minimally with silicates, only exchanging oxygen. To calculate oxygen fugacities at high pressure and temperature, however, requires information on the phase relations and equation of state properties of the solid phases. We have made in situ synchrotron X-ray diffraction measurements in a multi-anvil press on mixtures of Ru and RuO 2 to 19.4 GPa and 1473 K with which we have determined phase relations of the RuO 2 phases and derived thermal equations of state (EoS) parameters for both Ru and RuO 2 . Rutile-structured RuO 2 was found to undergo two phase transformations, first at ~7 GPa to an orthorhombic structure and then above 12 GPa to a cubic structure. The phase boundary of the cubic phase was constrained for the first time at high pressure and temperature. We have derived a continuous Gibbs free energy expression for the tetragonal and orthorhombic phases of RuO 2 by fitting the second-order phase transition boundary and P-V-T data for both phases, using a model based on Landau theory. The transition between the orthorhombic and cubic phases was then used along with EoS terms derived for both phases to determine a Gibbs free energy expression for the cubic phase. We have used these data to calculate the oxygen fugacity of the Ru + O 2 = RuO 2 equilibrium, which we have parameterized as a single polynomial across the stability fields of all three phases of RuO 2 . The expression is log 10 f O 2 (Ru – RuO 2 ) = (7.782 – 0.00996P + 0.001932P 2 – 3.76 × 10 –5 P 3 ) + (–13 763 + 592P – 3.955P 2 )/T + (–1.05 × 10 6 – 4622P)/T 2 , which should be valid from room pressure up to 25 GPa and 773–2500 K, with an estimated uncertainty of 0.2 log units. Our calculated fO 2 is shown to be up to 1 log unit lower than estimates that use previous expressions or ignore EoS terms.

Armstrong, Katherine↗

DOE OSTI2025

Linking Manganese Fractions and Organic Carbon in Soils of Contrasting Land Use Systems

Manganese (Mn) is an essential micronutrient that influences carbon (C) cycling by binding or oxidizing soil organic matter. Mn fractions in soil and their plant availability depend largely on soil pH, which is commonly altered by agricultural practices. Fractions of Mn in soils range from readily available (e.g., bioavailable Mn, exchangeable Mn) to stabilized (e.g., Mn-oxide minerals, Mn contained in silicates). Furthermore, the distribution of soil Mn with depth was assessed in contrasting land use systems (organic agriculture, conventional agriculture, and unmanaged forest) using a sequential extraction method that targets Mn fractions ranging in bioavailability. Both agricultural sites had similar amounts of total Mn but had available Mn (1–7% of total Mn) lower than that of the unmanaged forested site (15% of total Mn). Manganese and organic C were generally positively correlated, but this relationship depended on soil depth, Mn fractions, and concentrations, while land management change had little influence.

Crops↗

NASA NTRS2023

Microstructural Changes and Pb Mobility During the Zircon to Reidite Transformation: Implications for Planetary Impact Chronology

Impact events modify and leave behind a complex history of rock metamorphism on terrestrial planets. Evidence for an impact event may be recorded in physical changes to minerals, such as mineral deformation and formation of high P-T polymorphs, but also in the form of chemical fingerprints, such as enhanced elemental diffusion and isotopic mixing. Here we explore laboratory shock-induced physical and chemical changes to zircon and feldspar, the former of which is of interest because its trace elements abundances and isotope ratios are used extensively in geochemistry and geochronology. To this end, a granular mixture of Bishop Tuff sanidine and Kuehl Lake zircon, both with well characterized Pb isotope compositions, was prepared and then shocked via a flat plate accelerator. The peak pressure of the experiment, as calculated by the impedance matching method, was ~24 GPa although a broader range of P-T conditions is anticipated due to starting sample porosity. Unshocked and shocked materials were characterized via scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and Raman spectroscopy. These methods show that the starting zircon material had abundant metamict regions, and the conversion of the feldspar to glass in the post-shock material. Analyses of the shocked product also yielded multiple occurrences of the high-pressure ZrSiO 4 polymorph reidite, with some domains up to 300 μm across. The possibility of U-Pb system disturbance was evaluated via laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and secondary ion mass spectrometry (SIMS). The isotopic data reveal that disturbance of the U-Pb geochronometer in the reidite was minimal (<2% for the main U-Pb geochronometers). To better constrain the P-T conditions during the shock experiment, we complement impedance matching pressure calculations with iSALE2D impact simulations. The simulated results yield a range of P-T conditions experienced during the experiment and show that much of the sample may have reached >30 GPa, which is consistent with formation of reidite. In the recovered shocked material, we identified lamellae of reidite, some of which interlock with zircon lamellae. Reidite {112} twins were identified, which we interpret to have formed to reduce stress between the crystal structure of the host zircon and reidite. These two findings support the interpretation that shear transformation enabled the transition of zircon to reidite. The size and presence of reidite found here indicate that this phase is probably common in impact-shocked crustal rocks that experienced ~25 to ~35 GPa, especially when the target material has porosity. Additionally, shock loading of the zircon and transformation to reidite at these pressures in porous materials is unlikely to significantly disturb the U-Pb system in zircon and that the reidite inherits the primary U and Pb elemental and isotopic ratios from the zircon.

Bishop Tuff↗

DOE OSTI2025

Carbonation and Sulfidation of Mg- and Ni-Containing Solutions: Implications for Carbon Mineralization and Critical Element Recovery

Carbonation of alkaline earth metals ( e.g. , magnesium (Mg)) and sulfidation of nickel (Ni) are promising methods to achieve concurrent carbon mineralization and selective Ni recovery. However, the coexistence of alkaline earth metals and Ni from silicate ores or mining wastewater complicates the carbonation and sulfidation owing to cation coprecipitation. To better understand simultaneous metal carbonation and Ni-sulfide formation, we used Mg- and Ni-containing solutions and systematically investigated the Mg and Ni coprecipitates’ phase transformation during sequential/concurrent carbonation and sulfidation. During a single carbonation process, hydromagnesite dehydrated and formed magnesite over time. Nickel bicarbonate formed and became a Mg–Ni carbonate solid solution because of their similar ionic radii. During a single sulfidation process, the pH did not affect Ni-sulfide formation, but it controlled Mg behavior. Specifically, at pH 9.6, brucite formed, while at pH 7.8, Mg 2+ remained in the solution. For the sequential carbonation–sulfidation process, Ni-carbonate formed during carbonation converted to Ni-sulfide because of the low Ni-sulfide K sp . For the sulfidation–carbonation process, Ni-sulfide remained the same even after carbonation and Mg-carbonate precipitates. For the concurrent carbonation and sulfidation process, Mg-carbonate and Ni-sulfide formed simultaneously. Finally, this study develops a scientific foundation of carbonation and sulfidation processes, benefiting coupled CO 2 storage and sulfide-enabled resource recovery.

54 ENVIRONMENTAL SCIENCES↗