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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Pressure-Induced Reduction of Dicyanamide by Samarium(II) in a Coordination Polymer

A samarium(II) coordination polymer, [Sm(2.2.2- cryptand)(dca)]I (dca− = dicyanamide), has been prepared from the reaction of SmI2 with tetrabutylammonium dicyanamide and 2.2.2- cryptand. The structure consists of [Sm(2.2.2-cryptand)] 2+ cations bridged by dicyanamide to form corrugated 1D chains. Single crystals of this compound have been studied spectroscopically using UV−vis−NIR and Raman spectroscopy as a function of pressure to reveal a pressureinduced two-electron reduction of dicyanamide by Sm 2+ to cyanide and cyanamide and Sm 3+ between 5 and 8 GPa. High-pressure single-crystal diffraction studies reveal a phase change at 2.6 ± 0.1 GPa, where a polymorph exhibiting a smaller Sm 2+ ···N C bond angle and shorter Sm 2+ ···C distance was observed. These observations provide mechanistic insight into the reduction of dicyanamide into cyanide and cyanamide by pressurized samarium(II).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Continuous Evolution of Eu 2+ /Eu 3+ Mixed Valency Driven by Pressure and Temperature

Continuous mixed valency involving Eu 2+ and Eu 3+ in Eu 4 Bi 6 Se 13 can be induced under applied pressure or at reduced temperatures. The monoclinic structure of Eu 4 Bi 6 Se 13 , crystallizing in the P2 1 /m space group (No. 11), features linear chains of Eu atoms aligned along the b-axis. Magnetic susceptibility measurements, conducted both parallel and perpendicular to the b-axis and analyzed using Curie–Weiss theory, alongside high-pressure partial fluorescence yield (PFY) data from X-ray absorption spectroscopy (XAS), indicate the material’s propensity to adopt a mixed-valent state. Within this state, the trivalent Eu 3+ configuration becomes increasingly favored as the pressure rises or the temperature decreases.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

High-Pressure Effects on an Octa-Hydrated Curium Complex: An Experimental and Theoretical Investigation

An octa-hydrated curium compound [Cm(H 2 O) 8 ](Hdtp)(dtp)·H 2 O (Cm1,H 2 dtp = 2,3-di(tetrazol-5-yl)pyrazine) along with its lanthanide analogues [Ln(H 2 O) 8 ](Hdtp)-(dtp)·H 2 O (Ln1, Ln 3+ = La 3+ –Nd 3+ , Sm 3+ –Lu 3+ ) were synthesized and characterized using single crystal X-ray diffraction and spectroscopic methods. Bond length analysis of VIII Cm(III)–OH 2 (where VIII refers to the coordination number) was compared to VIII Ln(III)–OH 2 (Ln 3+ = Nd 3+ and Sm 3+ ), indicating similar VIII M(III)–OH 2 bond lengths owing to the similar eight-coordinate ionic radii of these VIII M(III) cations. Owing to the reduced coordination number, the VIII Cm(III)–OH 2 bond lengths were shorter than previously reported IX Cm(III)–OH 2 bonds in [Cm(H 2 O) 9 ](CF 3 SO 3 ) 3 . The octa-aquo complexes were also characterized by solid-state UV–vis–NIR spectroscopy in addition to variable-temperature and variable-pressure photoluminescence. Variable-pressure absorption spectra of Cm1 were compared with Ln1 and show that the Cm(III) f → f transitions have a stronger dependence on pressure than that observed in Ln1 (Ln 3+ = Nd 3+ and Sm 3+ ). The experimental and computational analyses reveal that the monotonic decrease in the computed energy difference between the ground state and the first excited state corresponds to the observed red shift of the photoluminescence peak. This is accompanied by a gradual reduction in the average Cm(III)–OH 2 bond length and a delocalization of spin densities, alongside an intensified interaction involving the 5f orbitals under increasing pressure. Furthermore, these changes accommodate the new geometry and collectively modify the energy landscape, resulting in peak broadening and quenching.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Symmetrization of Strong Hydrogen Bond under High Pressure in Bihydroxide-Ion-Containing NaCu 2 (SO 4 ) 2 ·H 3 O 2 Revealed by Experimental Charge Density, Single-Crystal Electron Diffraction, and Neutron Diffraction Studies

In minerals and inorganic compounds, strong hydrogen bonding can lead to the formation of complex ionic species such as the H 3 O 2 – bihydroxide anion and Zundel cation H 5 O 2 + . We studied [NaCu 2 (SO 4 ) 2 ·H 3 O 2 ] natrochalcite, which contains bihydroxide anions and undergoes hydrogen bond symmetrization at the lowest pressure reported so far among inorganic compounds. Hydrogen bond symmetrization leads to changes in the bulk modulus, seismic wave velocities, and proton mobility and plays a primary role in high-temperature superconductivity, but its characteristics are not well understood due to a lack of systematic studies and limitations of experimental methods sensitive to this subtle change. In this work, we applied experimental charge density analysis based on in situ single-crystal X-ray diffraction data, along with the single-crystal neutron and electron diffraction experiments, to probe the behavior of hydrogen atoms during the hydrogen bond symmetrization process under high-pressure conditions. On the way to the symmetrical H-bonding, natrochalcite undergoes a series of complex redistributions of electron density, which we trace with multipole refinement and detailed analysis of changes in the Laplacian of electron density values. Additionally, we deconvoluted the equation of state (volume of the unit cell vs pressure relation) into the atomic equation of states describing dependencies of atomic charges or volumes vs pressure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Pressure-Induced Stabilization of Terbium(IV) in CsTb(CrO 4 ) 2 Characterized by X-ray Absorption Spectroscopy

Single crystals of CsTb(CrO 4 ) 2 and CsDy(CrO 4 ) 2 , where the lanthanide metals are in the trivalent state under ambient conditions, have been investigated under high-pressure conditions on the gigapascal scale utilizing a diamond anvil cell. These compounds were characterized by single-crystal X-ray diffraction in addition to high-pressure solid-state UV-vis-NIR spectroscopy, Raman spectroscopy, and Tb L 3 -edge highenergy- resolution fluorescence-detected X-ray absorption near-edge structure (HERFD-XANES). The high-pressure UV-vis-NIR spectra reveal strong broadening of the metal-to-ligand charge transfer band to lower energies, associated with a visible color change from yellow to dark red/black. Clear evidence for the stabilization of Tb 4+ under high pressure is provided by the appearance of a second edge feature characteristic of Tb 4+ , starting at 19.62 GPa in the high-pressure L 3 -edge HERFD-XANES at around 7528 eV. This represents the first example of Tb 4+ being stabilized by high pressure and expands upon the limited chemistry of terbium in the tetravalent state.

Anions↗
DOE OSTI2026

Single-Atom Nickel Dispersed on Mo 2 TiC 2 T x MXene for Upcycling of Polyolefins via Catalytic Hydropyrolysis for Fuels and Lubricants

Plastic waste has been a major social and environmental problem. Chemical upcycling of plastic waste into transportation fuels or lubricant oil has emerged as an attractive and promising approach to convert plastic waste into valuable products. However, conventional catalyst systems often require high-pressure hydrogen, prolonged residence time, and the use of noble metal catalysts. Here, we present zero-valent nickel single atoms on Mo-based MXenes (Ni/Mo 2 TiC 2 T x ) for effective hydrogenation of polyolefins. In situ spectroscopic and microscopic characterizations demonstrate the formation of Ni–Mo and Ni–C bonds at a low Ni loading, resulting in the formation of dispersed intercalated Ni atoms. The catalysts were then employed to convert polyethylene into fuels and lubricant molecules under atmospheric hydrogen pressure, short vapor residence time (τ < 1 s), and mild reaction temperature (300 °C). We further demonstrated the possibility of tuning the Ni structure by changing the Ni loading, attributed to the strong metal–support interactions (MSIs) with the Mo 2 TiC 2 T x support. Under optimized conditions, 22.5 C% gasoline, 12.0 C% diesel, 19.2 C% jet fuel (JP-8), and 37.4 C% lubricant were produced over 0.5% Ni/Mo 2 TiC 2 T x . This work highlights the potential of utilizing MSIs of Mo 2 TiC 2 T x MXenes to synthesize single-atom catalysts (SACs) for upcycling plastic waste into higher-value products.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Implications of high-pressure oxygen hydrates on radiolytic oxygen in Jovian icy moons

Various icy moons, such as Europa and Ganymede, have thin oxygen atmospheres and exhibit spectral features attributed to oxygen held in their surface ices. The oxygen forms from the radiolysis of water. The interiors of these bodies are subject to high pressures and it is not known how deep into icy moons oxygen-bearing ices can penetrate, or the structures formed by the oxygen–water system at high pressure. Here, we show that oxygen hydrates are stable to 2.6 GPa, allowing them to penetrate deep into icy moons, both above and below proposed sub-surface liquid-water oceans. Similarities between oxygen and hydrogen hydrates indicate potentially enhanced recombination rates, transforming them back into water and offering a resolution to the discrepancy between predicted and measured radiolysis rates. In addition to the low-pressure CS-II clathrate, our results find three high-pressure phases in the oxygen–water system: an ST clathrate, a C 0 hydrate, and a filled ice isomorphous with methane hydrate III. This shows a vast storage potential for molecular oxygen in icy moons and indicates that Europa could still be absorbing oxygen into its crustal ice.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Synthesis, structure, and stability of a novel 2 H -azirine under pressure

We have synthesized 2,3-diphenyl-2H-azirine, a strained unsaturated heterocyclic compound, and examined its high-pressure behavior to above 10 GPa using diamond anvil cell techniques. Single crystal X-ray diffraction at ambient conditions reveals that the crystal structure is hexagonal and consists of interesting helices surrounding voids in the structure. A continuous shift of the Raman and infrared vibrational spectra with increasing pressure is observed, indicating that the molecular structure is preserved to at least 8 GPa at room temperature. High-pressure synchrotron powder X-ray diffraction shows that the hexagonal structure persists, with a smooth compression of the a and c parameters to 10 GPa. The structural stability under pressure is attributed to the reduction in void size within the helical framework despite the inherent strain and reactivity of the molecule. The channels in the structure could encapsulate small molecules for gas or energy storage applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

High-pressure neutron powder diffraction study of an arsenolite deuterium inclusion compound: structure and formation kinetics

High-pressure variable-temperature neutron powder diffraction was employed to investigate the synthesis and structural properties of arsenolite (As 4 O 6 ), a cubic arsenic( III ) oxide polymorph, and its inclusion compound with deuterium. The compound forms with the stoichiometry As 4 O 6 ·2D 2 , consistent with earlier findings. At 295 K and 1.96(2) GPa, D 2 molecules occupy the 16c site (0, 0, 0) and are aligned along the <111> direction. The diffraction data suggest that the D 2 molecules at this site become rotationally disordered upon decompression to 0.78(2) GPa at 120 K, while no occupancy is observed at the 8a position (⅛, ⅛, ⅛) under any of the studied conditions. The kinetic data of the high-pressure inclusion compound synthesis at 1.56(2) and 1.96(2) GPa were analyzed using the Avrami model. The Avrami exponent, 0.135(16), remains invariant with pressure, demonstrating that the reaction topochemistry is unaffected by compression. Similarly, the reaction rates, 0.29(3) and 0.23(3) min −0.135 at 1.56(2) and 1.96(2) GPa, respectively, exhibit negligible pressure dependence and suggest a surprisingly low activation volume of 1.6 cm 3 mol −1 for the reaction. These results provide detailed insight into the structural dynamics and kinetics of deuterium inclusion in arsenolite under high pressure.

Guńka, Piotr A. [Warsaw University of Technology (↗
DOE OSTI2026

A study of silver acetate under extreme conditions

With the aim of exploring chemical systems that may undergo metallization when irradiated with hard X-rays, we selected silver acetate (AgC 2 H 3 O 2 ) for the subject of this study. X-ray-induced decomposition of silver acetate under ambient and high-pressure conditions was observed in a diamond anvil cell (DAC), leading to the formation of metallic nanograins of silver at ambient pressure and 1.65 GPa. At 4 GPa, no decomposition was observed. The Avrami kinetics equation also provides information about novel structural formation at ambient pressure and 1.65 GPa. By modeling of the XRD data, it was found that the size of the silver nanocrystallites formed at 1.65 GPa pressure steadily increased to ∼5 nm after 600 min of X-ray irradiation as determined by applying the Scherrer equation to the diffraction peak widths. Time-resolved X-ray diffraction (XRD) revealed pressure-dependent kinetics, demonstrating that coupling pressure with irradiation enables controlled photochemical pathways in this model system. Concurrent with previous studies, the application of high pressure (HP) can be considered as a means of controlling X-ray synthetic photochemistry.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Structure of ice VII with Hirshfeld atom refinement

In the refinement of the crystal structures of ice, the best results obtained so far have been with neutron diffraction because the most troublemaking aspects are the hydrogen atoms. In nine out of twenty ice structures, the hydrogen atoms are disordered, which makes proper refinement more difficult. In our previous paper describing the structure of ice VI we proved that, using Hirshfeld atom refinement (HAR) based on synchrotron X-ray data, it is possible to obtain results comparable with those from neutron experiments. In this work, we investigate another structure of high-pressure disordered ice, cubo-ice (ice VII). Single crystals of cubo-ice were grown under pressure in diamond anvil cells. X-ray diffraction measurements were conducted at a synchrotron source facility (APS, University of Chicago, USA) as well as on our regular in-house laboratory diffractometer with Ag radiation. The data collected were further refined with HAR. Comparison of the structural parameters obtained with those derived from neutron diffraction showed very good agreement in terms of bond lengths and fairly good agreement in terms of hydrogen atom ADPs. We were also able to perform unconstrained refinements with various split-atom models.

Chemistry↗
DOE OSTI2025

High-Pressure Electrides: A Quantum Chemical Perspective

It has long been assumed that all matter will adopt simple close-packed lattices and become metallic under pressure, in accordance with the Thomas–Fermi–Dirac (TFD) model. However, this model struggles to explain pressure-driven complex structural transitions that have been observed in elements, including sodium, challenging our conventional understanding of compressed matter. Moreover, in stark contrast to the TFD model, first-principles calculations suggest that various elements and compounds become electrides under pressure. Electrides, characterized by concentrations of charge density at interstitial regions, can be thought of as ionic compounds where electrons behave as the anions. Though ambient-pressure molecular electrides have been extensively studied via experiments and computations, high-pressure electrides (HPEs) are not well-understood. The identification and characterization of HPEs have been, to date, based purely on theory, including topological analysis of the electron density and the electron localization function. Here, we review these theoretical analysis tools and suggest guidelines that can be used to classify systems as electrides. Moreover, we describe models used to rationalize the electronic structure of HPEs, drawing parallels with ambient-pressure molecular systems, and encourage the development of experimental techniques that provide evidence for the theoretically calculated charge localization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Department of Transportation PHMSA Aerosol Spray Project: Phase-0

This report discusses the work conducted at Sandia National Laboratories during the preliminary phase (Phase-0) of the Department of Transportation (DOT) Pipeline and Hazardous Materials Safety Administration (PHMSA) project tasked to better understand what happens to a high-pressure liquid canister or vessel during a fire in which an accidental instantaneous release occurs. Phase 0 had two main objects: (1) to establish a methodology for the high temperature and pressure spray vessel release and (2) to characterize the spray droplet formation. For this test series, diagnostic equipment such as the Malvern Spraytec, high-speed photometric cameras, pencil gauges, and thermocouples were used. Additionally, the effect of surface tension on the particle size distribution was evaluated with 1-liter of distilled water and with the same including the addition of 0.5% soap/water mixture. Results from this effort indicated that the plume formed from the instantaneous release in all conditions primarily included two distinct particle size distributions including 217-312µm and 0.53µm on average. Soapy water formed a higher concentration of smaller mist (0.53µm) than distilled water, potentially due to decreased surface tension with the added surfactant. Though results showed good correlation to certain particle size distributions it is encouraged to conduct additional tests like this with a wider range of liquids with different properties, which could affect the overall particle size distribution when released.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Effect of Preparation Conditions of Fe@SiO2 Catalyst on Its Structure Using High-Pressure Activity Studies in a 3D-Printed SS Microreactor

Fischer–Tropsch synthesis (FTS) in a 3D-printed stainless steel (SS) microchannel microreactor was investigated using Fe@SiO2 catalysts. The catalysts were prepared by two different techniques: one pot (OP) and autoclave (AC). The mesoporous structure of the two catalysts, Fe@SiO2 (OP) and Fe@SiO2 (AC), ensured a large contact area between the reactants and the catalyst. They were characterized by N2 physisorption, H2 temperature-programmed reduction (H2-TPR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron microscopy (XPS), and thermogravimetric analysis–differential scanning calorimetry (TGA-DSC) techniques. The AC catalyst had a clear core–shell structure and showed a much greater surface area than that prepared by the OP method. The activities of the catalysts in terms of FTS were studied in the 200–350 °C temperature range at 20-bar pressure with a H2/CO molar ratio of 2:1. The Fe@SiO2 (AC) catalyst showed higher selectivity and higher CO conversion to olefins than Fe@SiO2 (OP). Stability studies of both catalysts were carried out for 30 h at 320 °C at 20 bar with a feed gas molar ratio of 2:1. The Fe@SiO2 (AC) catalyst showed higher stability and yielded consistent CO conversion compared to the Fe@SiO2 (OP) catalyst.

Biochemistry & Molecular Biology↗
NASA NTRS1994

Hydrogen and related materials at high density: Physics, chemistry and planetary implications

Recent studies of low-Z molecular materials including hydrogen to multimegabar pressures (less than 300 GPa) have uncovered a range of phenomena relevant to understanding the nature of the interiors of the outer planets and their satellites. Synchrotron x ray diffraction measurements (to 42 GPa) have been used to determine the crystal structure of the solid (hexagonal-close packed) and equation of state. Sound velocities in fluid and solid hydrogen (to 24 GPa) have been inverted to obtain elastic constants and aggregate bulk and shear moduli. In addition, an improved intermolecular potential has been determined which fits both static and shock-wave data. Use of the new potential for the molecular envelope of Jupiter suggests the need for major revisions of existing Jovian models or a reanalysis of reported free oscillations for the planet. Studies at higher pressures (greater than 100 GPa) reveal a sequence of pressure-induced symmetry-breaking transitions in molecular hydrogen, giving rise to three high-pressure phases (1, 2, and 3). Phase 1 is the rotationally disordered hcp phase which persists from low pressure to well above 100 GPa at high temperature (e.g., 300 K). Phase 2 is a low-temperature, high-pressure phase (transition at 100 GPa and 77 K in H2) with spectral features indicative of partial rotational ordering and crystallographic distortion. The transition to Phase 3 at 150 GPa is accompanied by a weakening of the molecular bond, gradual changes in orientational ordering, strong enhancement of the infrared intramolecular vibrational absorption, and strong intermolecular interactions similar to those of ambient-pressure network solids. Studies of the phase diagram reveal a triple point near 130 K and 160 GPa. Higher pressure measurements of vibrational spectra place a lower bound of approximately 250 GPa on the predicted transition pressure for dissociation of molecular hydrogen to form a monatomic metal.

Hemley, R. J.↗
NASA NTRS2000

Measurements and Modeling of Nitric Oxide Formation in Counterflow, Premixed CH4/O2/N2 Flames

Laser-induced fluorescence (LIF) measurements of NO concentration in a variety of CH4/O2/N2 flames are used to evaluate the chemical kinetics of NO formation. The analysis begins with previous measurements in flat, laminar, premixed CH4/O2/N2 flames stabilized on a water-cooled McKenna burner at pressures ranging from 1 to 14.6 atm, equivalence ratios from 0.5 to 1.6, and volumetric nitrogen/oxygen dilution ratios of 2.2, 3.1 and 3.76. These measured results are compared to predictions to determine the capabilities and limitations of the comprehensive kinetic mechanism developed by the Gas Research Institute (GRI), version 2.11. The model is shown to predict well the qualitative trends of NO formation in lean-premixed flames, while quantitatively underpredicting NO concentration by 30-50%. For rich flames, the model is unable to even qualitatively match the experimental results. These flames were found to be limited by low temperatures and an inability to separate the flame from the burner surface. In response to these limitations, a counterflow burner was designed for use in opposed premixed flame studies. A new LIF calibration technique was developed and applied to obtain quantitative measurements of NO concentration in laminar, counterflow premixed, CH4/O2/N2 flames at pressures ranging from 1 to 5.1 atm, equivalence ratios of 0.6 to 1.5, and an N2/O2 dilution ratio of 3.76. The counterflow premixed flame measurements are combined with measurements in burner-stabilized premixed flames and counterflow diffusion flames to build a comprehensive database for analysis of the GRI kinetic mechanism. Pathways, quantitative reaction path and sensitivity analyses are applied to the GRI mechanism for these flame conditions. The prompt NO mechanism is found to severely underpredict the amount of NO formed in rich premixed and nitrogen-diluted diffusion flames. This underprediction is traced to uncertainties in the CH kinetics as well as in the nitrogen oxidation chemistry. Suggestions are made which significantly improve the predictive capability of the GRI mechanism in near-stoichiometric, rich, premixed flames and in atmospheric-pressure, diffusion flames. However, the modified reaction mechanism is unable to model the formation of NO in ultra-rich, premixed or in high-pressure, nonpremixed flames, thus indicating the need for additional study under these conditions.

Thomsen, D. Douglas↗
NASA NTRS2001

Real-Time Optical Monitoring of Flow Kinetics and Gas Phase Reactions Under High-Pressure OMCVD Conditions

This contribution addresses the real-time optical characterization of gas flow and gas phase reactions as they play a crucial role for chemical vapor phase depositions utilizing elevated and high pressure chemical vapor deposition (HPCVD) conditions. The objectives of these experiments are to validate on the basis of results on real-time optical diagnostics process models simulation codes, and provide input parameter sets needed for analysis and control of chemical vapor deposition at elevated pressures. Access to microgravity is required to retain high pressure conditions of laminar flow, which is essential for successful acquisition and interpretation of the optical data. In this contribution, we describe the design and construction of the HPCVD system, which include access ports for various optical methods of real-time process monitoring and to analyze the initial stages of heteroepitaxy and steady-state growth in the different pressure ranges. To analyze the onset of turbulence, provisions are made for implementation of experimental methods for in-situ characterization of the nature of flow. This knowledge will be the basis for the design definition of experiments under microgravity, where gas flow conditions, gas phase and surface chemistry, might be analyzed by remote controlled real-time diagnostics tools, developed in this research project.

Dietz, N.↗
NASA NTRS2004

High-Fidelity Three-Dimensional Simulation of the GE90

A full-engine simulation of the three-dimensional flow in the GE90 94B high-bypass ratio turbofan engine has been achieved. It would take less than 11 hr of wall clock time if starting from scratch through the exploitation of parallel processing. The simulation of the compressor components, the cooled high-pressure turbine, and the low-pressure turbine was performed using the APNASA turbomachinery flow code. The combustor flow and chemistry were simulated using the National Combustor Code (NCC). The engine simulation matches the engine thermodynamic cycle for a sea-level takeoff condition. The simulation is started at the inlet of the fan and progresses downstream. Comparisons with the cycle point are presented. A detailed look at the blockage in the turbomachinery is presented as one measure to assess and view the solution and the multistage interaction effects.

Turner, Mark G.↗