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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

An Experimental Validation of a Revised Paschen's Law Relating to the ESD of Aerospace Vehicle Surfaces

This work seeks to experimentally validate a modified Paschen law which takes into account the effects of electron-ion pair removal between two electrodes within a dynamic gas medium. A test facility has been designed and fabricated in order to create supersonic flow conditions within the test section. Custom designed electrodes are mounted into the test section at desired gap distances. A power supply is utilized to charge the electrodes until discharge occurs. The discharge voltage of the electrode is recorded over a range of pressures within the test section. An operational pressure range is calculated using isentropic flow and normal shock relations at the desired Mach numbers. These values are plotted against the modified Paschen curve as a function of Mach number, electrode gap distance, and pressure as a means of validation.

ESD↗
DOE OSTI2016

StimuFrac Compressibility as a Function of CO2 Molar Fraction

Compressibility values were obtained in a range of pressures at 250degC by employing a fixed volume view cell completely filled with PAA aqueous solution and injecting CO2 at constant flow rate (0.3mL/min). Pressure increase as a function of supercritical CO2 (scCO2) mass fraction in the mixture was monitored. The plot shows the apparent compressibility of Stimufrac as a function of scCO2 mass fraction obtained in a pressure range between 2100-7000 psi at 250degC. At small mass fractions of scCO2 the compressibility increases probably due to the dissolution/reaction of CO2 in aqueous PAA and reaches a maximum at mCO2/mH2O = 0.06. Then, compressibility decreases showing a linear relationship with scCO2 mass fraction due to the continuous increase in density of the binary fluid associated to the pressure increase.

15 GEOTHERMAL ENERGY↗
DOE OSTI2017

Iodine Gas Adsorption in Nanoporous Materials: A Combined Experiment–Modeling Study

Here, we present a combined experimental and Grand Canonical Monte Carlo (GCMC) modeling study on the adsorption of iodine in three classes of nanoporous materials: activated charcoals, zeolites, and metal–organic frameworks (MOFs). Iodine adsorption profiles were measured for the first time in situ, with a uniquely designed sorption apparatus. It was determined that pore size and pore environment are responsible for a dynamic adsorption profile, correlated with distinct pressure ranges. At pressures below 0.3 atm, iodine adsorption is governed by a combination of small pores and extra-framework components (e.g., Ag+ ions in the zeolite mordenite). At regimes above 0.3 atm, the amount of iodine gas stored relates with an increase in pore size and specific surface area. GCMC results validate the trends noted experimentally and in addition provide a measure of the strength of the adsorbate–adsorbent interactions in these materials.

Sava Gallis, Dorina F.↗
DOE OSTI2013

Gram-scale, high-yield synthesis of a robust metal-organic framework for storing methane and other gases

We have synthesized and characterized a new metal-organic framework (MOF) material, NU-125, that, in the single-crystal limit, achieves a methane storage density at 58 bar (840 psi) and 298 K corresponding to 86% of that obtained with compressed natural gas tanks (CNG) used in vehicles today, when the latter are pressurized to 248 bar (3600 psi). More importantly, the deliverable capacity (58 bar to 5.8 bar) for NU-125 is 67% of the deliverable capacity of a CNG tank that starts at 248 bar. (For crystalline granules or powders, particle packing inefficiencies will yield densities and deliverable capacities lower than 86% and 67% of high-pressure CNG.) This material was synthesized in high yield on a gram-scale in a single-batch synthesis. Methane adsorption isotherms were measured over a wide pressure range (0.1-58 bar) and repeated over twelve cycles on the same sample, which showed no detectable degradation. Adsorption of CO2 and H-2 over a broad range of pressures and temperatures are also reported and agree with our computational findings.

Wilmer, CE↗
NASA NTRS2000

High Resolution and Large Dynamic Range Resonant Pressure Sensor Based on Q-Factor Measurement

A pressure sensor has a high degree of accuracy over a wide range of pressures. Using a pressure sensor relying upon resonant oscillations to determine pressure, a driving circuit drives such a pressure sensor at resonance and tracks resonant frequency and amplitude shifts with changes in pressure. Pressure changes affect the Q-factor of the resonating portion of the pressure sensor. Such Q-factor changes are detected by the driving/sensing circuit which in turn tracks the changes in resonant frequency to maintain the pressure sensor at resonance. Changes in the Q-factor are reflected in changes of amplitude of the resonating pressure sensor. In response, upon sensing the changes in the amplitude, the driving circuit changes the force or strength of the electrostatic driving signal to maintain the resonator at constant amplitude. The amplitude of the driving signals become a direct measure of the changes in pressure as the operating characteristics of the resonator give rise to a linear response curve for the amplitude of the driving signal. Pressure change resolution is on the order of 10(exp -6) torr over a range spanning from 7,600 torr to 10(exp -6) torr. No temperature compensation for the pressure sensor of the present invention is foreseen. Power requirements for the pressure sensor are generally minimal due to the low-loss mechanical design of the resonating pressure sensor and the simple control electronics.

Gutierrez, Roman C.↗
NASA NTRS1980

An ICR study of an association reaction at low pressure

The reactions of the gaseous ion CH3+ with HCN are investigated, using the ion cyclotron resonance technique. The pressure range of the experiment was 1 x 10 to the -6 to 3 x 10 to the -4 Torr with a rate coefficient of 2 x 10 to the -10 cu cm/sec. Good agreement was found between rate coefficients determined in the trapping mode at the low end of the pressure range and the drift mode at the high end of the pressure range. It is shown that the association reaction of CH3 with HCN follows second order kinetics throughout the entire pressure range of the experiment. The reaction is interpreted in terms of both a saturated three-body and a radiative association mechanism. Some explanations for the disagreement of the rate coefficient with that reported previously are also given.

Mcewan, M. J.↗
NASA NTRS1974

Development of acoustically lined ejector technology for multitube jet noise suppressor nozzles by model and engine tests over a wide range of jet pressure ratios and temperatures

An experimental program comprising model nozzle and full-scale engine tests was undertaken to acquire parametric data for acoustically lined ejectors applied to primary jet noise suppression. Ejector lining design technology and acoustical scaling of lined ejector configurations were the major objectives. Ground static tests were run with a J-75 turbojet engine fitted with a 37-tube, area ratio 3.3 suppressor nozzle and two lengths of ejector shroud (L/D = 1 and 2). Seven ejector lining configurations were tested over the engine pressure ratio range of 1.40 to 2.40 with corresponding jet velocities between 305 and 610 M/sec. One-fourth scale model nozzles were tested over a pressure ratio range of 1.40 to 4.0 with jet total temperatures between ambient and 1088 K. Scaling of multielement nozzle ejector configurations was also studied using a single element of the nozzle array with identical ejector lengths and lining materials. Acoustic far field and near field data together with nozzle thrust performance and jet aerodynamic flow profiles are presented.

Atvars, J.↗
NASA NTRS2007

Validation of the Aura Microwave Limb Sounder middle atmosphere water vapor and nitrous oxide measurements

The quality of the version 2.2 (v2.2) middle atmosphere water vapor and nitrous oxide measurements from the Microwave Limb Sounder (MLS) on the Earth Observing System (EOS) Aura satellite is assessed. The impacts of the various sources of systematic error are estimated by a comprehensive set of retrieval simulations. Comparisons with correlative data sets from ground-based, balloon and satellite platforms operating in the UV/visible, infrared and microwave regions of the spectrum are performed. Precision estimates are also validated, and recommendations are given on the data usage. The v2.2 H2O data have been improved over v1.5 by providing higher vertical resolution in the lower stratosphere and better precision above the stratopause. The single-profile precision is ~0.2–0.3 ppmv (4–9%), and the vertical resolution is ~3–4 km in the stratosphere. The precision and vertical resolution become worse with increasing height above the stratopause. Over the pressure range 0.1–0.01 hPa the precision degrades from 0.4 to 1.1 ppmv (6–34%), and the vertical resolution degrades to ~12–16 km. The accuracy is estimated to be 0.2–0.5 ppmv (4–11%) for the pressure range 68–0.01 hPa. The scientifically useful range of the H2O data is from 316 to 0.002 hPa, although only the 82–0.002 hPa pressure range is validated here. Substantial improvement has been achieved in the v2.2 N2O data over v1.5 by reducing a significant low bias in the stratosphere and eliminating unrealistically high biased mixing ratios in the polar regions. The single-profile precision is ~13–25 ppbv (7–38%), the vertical resolution is ~4–6 km and the accuracy is estimated to be 3–70 ppbv (9–25%) for the pressure range 100–4.6 hPa. The scientifically useful range of the N2O data is from 100 to 1 hPa.

Atlas, E.↗
NASA NTRS1986

Kinetics and mechanism of the IO + IO reaction

The flash photolysis-absorption technique has been used to measure the rate constant for the reaction IO + IO over the temperature range 250-373 K and pressure range 20-700 torr of N2. The rate constant for the overall reaction was found to be independent of pressure and equal to 1.73 x 10 to the -12th exp (1020 + or - 200)/T cu cm/molecule s. Branching ratios for the reaction channels forming 2I + O2, I2 + O2, and I2O2, were found to be pressure dependent, with the I2 channel accounting for less than 5 percent of the total reaction over the observed pressure range. A stable reaction product was observed between 230 and 300 nm which was formed on a long time scale compared to IO disappearance. The rate constant for the reaction I + O3 + yields to IO + O2 was measured at 298 K and found to be (9.5 + or - 1.5) x 10 to the -13th cu cm/molecule s.

Sander, S. P.↗
DOE OSTI2019

Fluorine chemistry at extreme conditions: possible synthesis of $HgF_4$

By irradiating a pressurized mixture of a fluorine-bearing compound ($XeF_2$) and $HgF_2$ with synchrotron hard x-rays (>7 keV) inside a diamond anvil cell, we have observed dramatic changes in the far-infrared spectrum within the 30-35 GPa pressure range which suggest that we may have formed $HgF_4$ in the following way: $XeF_2 \xrightarrow{hv} Xe + F_2$ (photochemically) and $HgF_2 + F_2 \rightarrow HgF_4$ (30 GPa < P < 35 GPa). This lends credence to recent theoretical calculations by Botana et al. that suggest that Hg may behave as a transition metal at high pressure in an environment with an excess of molecular fluorine. The spectral changes were observed to be reversible during pressure cycling above and below the above mentioned pressure range until a certain point when we suspect that molecular fluorine diffused out of the sample at lower pressure. Upon pressure release, $HgF_2$ and trace $XeF_2$ were observed to be remaining in the sample chamber suggesting that much of the $Xe$ and $F_2$ diffused and leaked out from the sample chamber. Received: 29 October 2018, Accepted: 18 January 2019; Edited by: A. Goñi, A. Cantarero, J. S. Reparaz; DOI: http://dx.doi.org/10.4279/PIP.110001 Cite as: M Pravica, S Schyck, B Harris, P Cifligu, E Kim, B Billinghurst, Papers in Physics 11, 110001 (2019). This paper, by M Pravica, S Schyck, B Harris, P Cifligu, E Kim, B Billinghurst, is licensed under the Creative Commons Attribution License 4.0.

Pravica, Michael G.↗
DOE OSTI2014

Exploration of stable compounds, crystal structures, and superconductivity in the Be-H system

Using first-principles variable-composition evolutionary methodology, we explored the high-pressure structures of beryllium hydrides between 0 and 400 GPa. We found that BeH{sub 2} remains the only stable compound in this pressure range. The pressure-induced transformations are predicted as Ibam→P3{sup -}m1→R3{sup -}m→Cmcm→P4/nmm, which occur at 24, 139, 204 and 349 GPa, respectively. P3{sup -}m1 and R3{sup -}m structures are layered polytypes based on close packings of H atoms with Be atoms filling all octahedral voids in alternating layers. Cmcm and P4/nmm contain two-dimensional triangular networks with each layer forming a kinked slab in the ab-plane. P3{sup -}m1 and R3{sup -}m are semiconductors while Cmcm and P4/nmm are metallic. We have explored superconductivity of both metal phases, and found large electron-phonon coupling parameters of λ = 0.63 for Cmcm with a T{sub c} of 32.1-44.1 K at 250 GPa and λ = 0.65 for P4/nmm with a T{sub c} of 46.1-62.4 K at 400 GPa. The dependence of T{sub c} on pressure indicates that T{sub c} initially increases to a maximum of 45.1 K for Cmcm at 275 GPa and 97.0 K for P4/nmm at 365 GPa, and then decreases with increasing pressure for both phases.

36 MATERIALS SCIENCE↗
DOE OSTI2015

High-pressure protein crystallography of hen egg-white lysozyme

The crystal structure of hen egg-white lysozyme (HEWL) was analyzed under pressures of up to 950 MPa. The high pressure modified the conformation of the molecule and induced a novel phase transition in the tetragonal crystal of HEWL. Crystal structures of hen egg-white lysozyme (HEWL) determined under pressures ranging from ambient pressure to 950 MPa are presented. From 0.1 to 710 MPa, the molecular and internal cavity volumes are monotonically compressed. However, from 710 to 890 MPa the internal cavity volume remains almost constant. Moreover, as the pressure increases to 950 MPa, the tetragonal crystal of HEWL undergoes a phase transition from P4{sub 3}2{sub 1}2 to P4{sub 3}. Under high pressure, the crystal structure of the enzyme undergoes several local and global changes accompanied by changes in hydration structure. For example, water molecules penetrate into an internal cavity neighbouring the active site and induce an alternate conformation of one of the catalytic residues, Glu35. These phenomena have not been detected by conventional X-ray crystal structure analysis and might play an important role in the catalytic activity of HEWL.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1985

Propagation of detonations in hydrazine vapor

In the range of greater hydrazine vapor pressure, detonation speed depends exclusively on the extent of the ammonia decomposition in the second reaction stage. As vapor pressure decreases, the ammonia disintegration speed becomes increasingly slower and the reaction reached in the reaction zone increasingly decreases until finally, in the vapor pressure range between 53 and 16 Torr, the contribution of the second stage to detonation propagation disappears, and only the first stage remains active. Since the disintegration speed of the hydrazine in this pressure range has decreased markedly as well, no level, but rather only spinning, detonations occur. Temporary separations of the impact front and the reaction zone in the process lead to fluctuations of the detonation speed.

Heinrich, H. J.↗
DOE OSTI2017

Evolutionary optimization of PAW data-sets for accurate high pressure simulations

We examine the challenge of performing accurate electronic structure calculations at high pressures by comparing the results of all-electron full potential linearized augmented-plane-wave calculations, as implemented in the WIEN2k code, with those of the projector augmented wave (PAW) method, as implemented in Quantum ESPRESSO or Abinit code. In particular, we focus on developing an automated and consistent way of generating transferable PAW data-sets that can closely produce the all electron equation of state defined from zero to arbitrary high pressures. The technique we propose is an evolutionary search procedure that exploits the ATOMPAW code to generate atomic data-sets and the Quantum ESPRESSO software suite for total energy calculations. We demonstrate different aspects of its workability by optimizing PAW basis functions of some elements relatively abundant in planetary interiors. In addition, we introduce a new measure of atomic data-set goodness by considering their performance uniformity over an extended pressure range. - Highlights: • An attempt made to achieve the AE-FLAPW accuracy, at the favorable computational efficiency of the PAW approach for an outspread pressure range. • Provided an automatic and consistent route for developing efficient and transferable PAW data-sets. • Explicated an improved measure for the goodness of data-sets by including uniformity of the data-set performance over an extended pressure range.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Toward an international practical pressure scale: A proposal for an IPPS ruby gauge (IPPS-Ruby2020)

At the 26 th AIRAPT conference in 2017, a task group was formed to work on an International Practical Pressure Scale (IPPS). This report summarizes the activities of the task group toward an IPPS ruby gauge. We have selected three different approaches to establishing the relation between pressure ( P ) and ruby R1-line shift ( Δλ ) with three groups of optimal reference materials for applying these approaches. Using a polynomial form of the second order, the recommended ruby gauge (referred as Ruby2020) is expressed by: P [ G P a ] = 1.87 ( ± 0.01 ) × 10 3 Δ λ λ 0 1 + 5.63 ( ± 0.03 ) Δ λ λ 0 , where λ 0 is the wavelength of the R1-line near 694.25 nm at ambient condition. In June of 2020, the Executive Committee of AIRAPT endorsed the proposed Ruby2020. Finally, we encourage high-pressure practitioners to utilize Ruby2020 within its applicable pressure range (up to 150 GPa), so that pressure data can be directly compared across laboratories and amended consistently as better scales emerge in the future.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Efficient Lithium Metal Cycling over a Wide Range of Pressures from an Anion-Derived Solid-Electrolyte Interphase Framework

Advanced electrolytes were developed to improve the cyclability of lithium (Li) metal anodes, yet their working mechanisms remain unclear. Here, we study the Li cycling performance under different pressures in a 1 M Li bis(fluorosulfonyl)imide/fluorinated 1,4-dimethoxybutane electrolyte. A consistently long cycle life is achieved over a wide range of pressures (30–600 psi). We find that this is due to a completely different Li plating mode with more favorable deposition morphologies compared to that in a conventional carbonate electrolyte, which exhibits increasing cycle stability with increased pressure. We show that this is enabled by the properties of an anion-derived residual solid-electrolyte interphase (rSEI) framework on the electrode surface, an undercharacterized structure with profound implications for Li metal cycling. This anion-derived rSEI chemistry is likely the key to a prolonged cycle life of Li metal batteries and should be vigorously addressed in future electrolyte designs.

25 ENERGY STORAGE↗
DOE OSTI2018

Electron density and gas density measurements in a millimeter-wave discharge

Electron density and neutral gas density have been measured in a non-equilibrium air breakdown plasma using optical emission spectroscopy and two-dimensional laser interferometry, respectively. A plasma was created with a focused high frequency microwave beam in air. Experiments were run with 110 GHz and 124.5 GHz microwaves at powers up to 1.2 MW. Microwave pulses were 3 microsec. long at 110 GHz and 2.2 microsec. long at 124.5 GHz. Electron density was measured over a pressure range of 25 to 700 Torr as the input microwave power was varied. Electron density was found to be close to the critical density over the pressure range studied and to vary weakly with input power. Neutral gas density was measured over a pressure range from 150 to 750 Torr at power levels high above the threshold for initiating breakdown. The two-dimensional structure of the neutral gas density was resolved. Intense, localized heating was found to occur hundreds of nanoseconds after visible plasma formed. This heating led to neutral gas density reductions of greater than 80% where peak plasma densities occurred. Spatial and temporal structure of gas heating at atmospheric pressure were found to agree well with numerical simulations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗