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Results for “Ions and properties”

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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Ion temperature troughs induced by a meridional neutral air wind in the night-time equatorial topside ionosphere

A mathematical model was constructed to calculate O(+) and H(+) concentrations, field-aligned velocities, and electron temperatures in the night-time equatorial topside ionosphere. The model is used to establish the ability of F-region neutral air winds to produce observed ion temperature distributions, and to study the properties of ion temperature troughs as functions of altitude, latitude, and ionospheric composition. The O(+) - H (+) transition height represents an altitude limit above which the ion cooling from adiabatic expansion of the plasma is very small; the northern and southern edges of the ion temperature troughs are restricted to the limiting dip altitudes determined by magnetic field line geometry and by the functional form of the F-region neutral wind velocity.

Bailey, G. J.↗
DOE OSTI2021

Electrospun Separator Based on Sulfonated Polyoxadiazole with Outstanding Thermal Stability and Electrochemical Properties for Lithium-Ion Batteries

Traditional polyolefin separators used in lithium-ion batteries (LIBs) are seriously limited by the issues of inferior security and poor electrolyte wettability. Most of the very promising candidate separators based on heat-resistant polymers are, however, inherently difficult to process. Herein, a unique sulfonated aromatic heterocyclic polymer, lithiated poly(diphenyl ether oxadiazole) sulfonate (Li-SPEOD), was synthesized through a simple one-pot method and further electrospun to act as a novel separator (es-Li-SPEOD) for LIBs. In this work, the prepared Li-SPEOD possesses a high degree of sulfonation with a high molecular weight (M w = 4.31 × 10 5 ). The es-Li-SPEOD separator exhibits excellent mechanical and fire-resistance properties and is able to maintain dimensional stability at a temperature of even up to 400 °C in air. The ionic conductivity (3.57 mS cm –1 ) and lithium-ion transference number (0.37) of the es-Li-SPEOD with an electrochemical stability window of 4.5 V vs Li + /Li can be improved by 382.4 and 32.1%, respectively, compared to those of Celgard-2500 in the LiPF 6 electrolyte. The enhanced rate capability and cycle performance of the LiFePO 4 –Li half-cell are therefore obtained. Moreover, the es-Li-SPEOD displays an outstanding dendrite-suppressing effect for the lithium metal anode. This research proves that the Li-SPEOD-based separator has a broad application perspective in next-generation lithium batteries.

25 ENERGY STORAGE↗
NASA NTRS1984

Dual ion beam deposition of carbon films with diamondlike properties

A single and dual ion beam system was used to generate amorphous carbon films with diamond like properties. A methane/argon mixture at a molar ratio of 0.28 was ionized in the low pressure discharge chamber of a 30-cm-diameter ion source. A second ion source, 8 cm in diameter was used to direct a beam of 600 eV Argon ions on the substrates (fused silica or silicon) while the deposition from the 30-cm ion source was taking place. Nuclear reaction and combustion analysis indicate H/C ratios for the films to be 1.00. This high value of H/C, it is felt, allowed the films to have good transmittance. The films were impervious to reagents which dissolve graphitic and polymeric carbon structures. Although the measured density of the films was approximately 1.8 gm/cu cm, a value lower than diamond, the films exhibited other properties that were relatively close to diamond. These films were compared with diamondlike films generated by sputtering a graphite target.

Mirtich, M. J.↗
DOE OSTI2021

The In Situ Ion Irradiation Toolbox: Time-Resolved Structure and Property Measurements

Abstract The dynamic interactions of ions with matter drive a host of complex evolution mechanisms, requiring monitoring on short spatial and temporal scales to gain a full picture of a material response. Understanding the evolution of materials under ion irradiation and displacement damage is vital for many fields, including semiconductor processing, nuclear reactors, and space systems. Despite materials in service having a dynamic response to radiation damage, typical characterization is performed post-irradiation, washing out all information from transient processes. Characterizing active processes in situ during irradiation allows the mechanisms at play during the dynamic ion-material interaction process to be deciphered. In this review, we examine the in situ characterization techniques utilized for examining material structure, composition, and property evolution under ion irradiation. Covering analyses of microstructure, surface composition, and material properties, this work offers a perspective on the recent advances in methods for in situ monitoring of materials under ion irradiation, including a future outlook examining the role of complementary and combined characterization techniques in understanding dynamic materials evolution.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Dual-band Ion-scale Waves in the Solar Wind: Statistical Properties and Comparison with Single-band Ion-scale Waves

We present a comprehensive statistical analysis of ion-scale waves including dual-band ion-scale waves (DBIWs) observed by the Parker Solar Probe in the solar wind. DBIWs are characterized by the simultaneous occurrence of distinct left- and right-handed polarized wave packets at higher and lower frequencies, respectively, in the spacecraft frame, implying the presence of bidirectionally propagating L-mode waves. We identify and compare DBIWs to single-band ion-scale waves (SBIWs) and investigate their spatial distributions, background magnetic field conditions, and associated inertial range turbulence characteristics. We find that DBIWs exhibit a strong preferential occurrence at heliocentric distances between 0.2 and 0.25 au (equivalently 43 and 54 R S ) in contrast to SBIWs, the occurrence rate of which peaks closer to the Sun and decreases with the heliocentric distance. DBIWs are also preferentially observed under conditions of strong Alfvénic turbulence, characterized by low magnetic compressibility and perpendicular-dominant fluctuations. These findings support a scenario in which stochastic ion heating via sufficiently large perpendicular Alfvénic fluctuation generates the ion temperature anisotropies required to excite bidirectional ion cyclotron waves. This work advances our understanding of kinetic wave generation in the solar wind and its connection to large-scale turbulence.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1975

Alkali oxide-tantalum, niobium and antimony oxide ionic conductors

The phase equilibrium relations of four systems were investigated in detail. These consisted of sodium and potassium antimonates with antimony oxide and tantalum and niobium oxide with rubidium oxide as far as the ratio 4Rb2O:llB2O5 (B=Nb, Ta). The ternary system NaSbO3-Sb2O4-NaF was investigated extensively to determine the actual composition of the body centered cubic sodium antimonate. Various other binary and ternary oxide systems involving alkali oxides were examined in lesser detail. The phases synthesized were screened by ion exchange methods to determine mobility of the mobility of the alkali ion within the niobium, tantalum or antimony oxide (fluoride) structural framework. Five structure types warranted further investigation; these structure types are (1) hexagonal tungsten bronze (HTB), (2) pyrochlore, (3) the hybrid HTB-pyrochlore hexagonal ordered phases, (4) body centered cubic antimonates and (5) 2K2O:3Nb2O5. Although all of these phases exhibit good ion exchange properties only the pyrochlore was prepared with Na(+) ions as an equilibrium phase and as a low porosity ceramic. Sb(+3) in the channel interferes with ionic conductivity in this case, although relatively good ionic conductivity was found for the metastable Na(+) ion exchanged analogs of RbTa2O5F and KTaWO6 pyrochlore phases.

Roth, R. S.↗
NASA NTRS1983

New calculation of the properties of the positronium ion

The positronium negative ion Ps(-), the system composed of two electrons and a positron, has been reinvestigated theoretically. Using a Hylleraas wave function with two nonlinear parameters and more than 200 linear terms, excellent values of binding energy and annihilation lifetime of the particle-stable 1Se ground state have been obtained. In addition, the question of stability of the 3Pe state discussed by Mills has been examined and it is agreed with his conclusion that the state is probably not stable against breakup into Ps(n = 2) + e(-). Improved limits on the critical 'positron' mass for binding the 3Pe state have also been obtained.

Bhatia, A. K.↗
NASA NTRS1992

Optical fiber spectroscopy: A study of the luminescent properties of the europium ion for thermal sensors

Recently, there has been interest in developing a distributed temperature sensor integrated into an optical fiber. Such a system would allow embedding of the optical fiber within or on a structural material to provide for continuous monitoring of the material's temperature. Work has already begun on the development of a temperature sensor using the temperature dependent emission spectra from the lanthanide rare earths doped into crystalline hosts. The lifetime, the linewidth and the integrated intensity of this emission are each sensitive to changes in the temperature and can provide a basis for thermometry. One concept for incorporating this phenomena into an optical fiber based sensor involves bonding the optically active material to the cladding of an optical fiber and allowing the luminescent light to couple into the the fiber by the evanescent wave. Experimental work developing this concept has already been reported. Measurements of the linewidth of Eu3+:Y2O3, diffused into a fiber, made by Albin clearly show a strong and regular dependence on temperature over the range of 300 to 1000 K. We report here on a study of the temperature dependence of the lineshape of the emission at 611 nm using the data in references. We focus attention on understanding the general behavior of the Eu3+:Y2O3 system. Building upon understanding of this system we will be able to establish the physical criterial for a good optical fiber based temperature sensor and then to examine available data on other lanthanide rare earths and transition metal ions to determine the best luminescent system for temperature sensing in an optical fiber.

Buoncristiani, A. Martin↗
NASA NTRS1994

Radiative properties of molecular nitrogen ions produced by helium Penning ionization and argon effects

The development of hypersonic aerospace vehicles requires a better understanding on the thermal and chemical nonequilibrium kinetics of participating species in shock layers. The computational fluid dynamic (CFD) codes developed for such flowfields overestimate the radiation in the spectral region of 300 - 600 nm. A speculation for this overestimation is that inclusion of Ar, CO2, and H2O at the upper atmosphere flight region makes a significant impact on radiative kinetics of molecular nitrogen ions. To define the effects of minority species on the radiative kinetics of N2(+), an experimental setup was made by using the helium Penning ionization. The vibrational and rotational temperature were measured by mapping the vibrational and rotational distributions of N2(+) emission with high spectroscopic resolution and absolute intensity measurements. Measured vibrational temperatures were in the range from 18,000 to 36,000 K, and rotational temperatures were in the range from 300 to 370 K. The irradiance of 391.44 nm line and rotational and vibrational temperatures were analyzed to define argon and CO2 effects on the N2(+) emission. When Ar or CO2 is injected with N2, the rotational temperature did not change. The irradiances were reduced by 34 percent and 78 percent for the 50 percent of mixture of Ar and CO2, respectively. The vibrational temperatures were increased by 24.1 percent and 82.9 percent for the 50 percent of mixture of Ar and CO2, respectively. It appears that there are no significant effects from small concentrations of Ar and CO2 at the upper atmosphere flight region.

Miller, George, III↗
NASA NTRS2006

Optical Properties of Tm(3+) Ions in Alkali Germanate Glass

Tm-doped alkali germanate glass is investigated for use as a laser material. Spectroscopic investigations of bulk Tm-doped germanate glass are reported for the absorption, emission and luminescence decay. Tm:germanate shows promise as a fiber laser when pumped with 0.792 m diodes because of low phonon energies. Spectroscopic analysis indicates low nonradiative quenching and pulsed laser performance studies confirm this prediction by showing a quantum efficiency of 1.69.

Walsh, Brian M.↗
NASA NTRS1978

Sensitivity of 30-cm mercury bombardment ion thruster characteristics to accelerator grid design

The design of ion optics for bombardment thrusters strongly influences overall performance and lifetime. The operation of a 30 cm thruster with accelerator grid open area fractions ranging from 43 to 24 percent, was evaluated and compared with experimental and theoretical results. Ion optics properties measured included the beam current extraction capability, the minimum accelerator grid voltage to prevent backstreaming, ion beamlet diameter as a function of radial position on the grid and accelerator grid hole diameter, and the high energy, high angle ion beam edge location. Discharge chamber properties evaluated were propellant utilization efficiency, minimum discharge power per beam amp, and minimum discharge voltage.

Rawlin, V. K.↗
NASA NTRS1978

Sensitivity of 30-cm mercury bombardment ion thruster characteristics to accelerator grid design

The design of ion optics for bombardment thrusters strongly influences overall performance and lifetime. The operation of a 30-cm thruster with accelerator grid open area fractions ranging from 43 to 24 percent, was evaluated and compared with previously published experimental and theoretical results. Ion optics properties measured included the beam current extraction capability, the minimum accelerator grid voltage to prevent backstreaming, ion beamlet diameter as a function of radial position on the grid and accelerator grid hole diameter, and the high energy, high angle ion beam edge location. Discharge chamber properties evaluated were propellant utilization efficiency, minimum discharge power per beam amp, and minimum discharge voltage.

Rawlin, V. K.↗