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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 NTRS1978

Inversion of the resonance line of Sr/+/ produced by optically pumping Sr atoms

A description is presented of an experiment which demonstrates the selective production of excited-state ions by an optical absorption from neutrals. An inversion on the resonance line of Sr(+) was produced by laser excitation of a two-electron transition, followed by ionization of one of the excited electrons by the same laser. A pulsed, mode-locked laser operating at 2680 A was used to excite atoms from the Sr ground level. The same laser then ionized the excited atoms. The 2680-A pump beam was generated by frequency doubling the output of a synchronously pumped mode-locked dye laser in a KDP crystal. It is pointed out that the reported results are significant for the construction of vacuum-ultraviolet and X-ray lasers. Many of the proposed methods for making such lasers depend on the selective production of excited-state ions.

Green, W. R.↗
NASA NTRS1983

In-flight acoustic test results for the SR-2 and SR-3 advanced-design propellers

Several advanced-design propellers, previously tested in the wind tunnel at the Lewis Research Center, have been tested in flight at the Dryden Flight Research Facility. The flight-test propellers were mounted on a pylon on the top of the fuselage of a JetStar airplane. Acoustic data for the advanced-design SR-2 and SR-3 propellers at Mach numbers to 0.8 and helical-tip Mach numbers to 1.15 are presented; maximum blade-passage frequency sound-pressure levels are also compared.

Lasagna, P. L.↗
DOE OSTI2020

Combined Cr and S poisoning behaviors of La 1-x Sr x MnO 3±δ and La 1-x Sr x Co 1-y FeyO 3-δ cathodes in solid oxide fuel cells

Although the individual effects of airborne Cr and S contaminants on SOFC cathode performance degradation have been extensively studied, the combined effects of Cr and S contaminants remain largely unexplored. Under the real SOFC operating condition where the Cr and S species coexist, their effects may compete, affecting the poisoning behavior. Here, our investigation reveals that the combined Cr and S poisoning behavior of LSCF remains different from those of individual Cr and S poisonings, while the combined poisoning mechanism of LSM is equivalent to the sum of those of individual Cr and S effects. For LSCF electrode, gaseous Cr species are deposited mainly at the LSCF/GDC interface by electrochemical reduction, rather than forming SrCrO 4 on LSCF surfaces (as in the case of Cr-only poisoning), indicating no reaction between Cr vapors and SrO on the LSCF surface. Thermodynamic analysis demonstrates that the SrO on LSCF surface absorbs SO 2 (g) and thereby loses the Cr-gettering effect, allowing Cr vapors to flow through LSCF and to reach the LSCF/GDC interface where the Cr deposition occurs. Unlike LSCF, LSM electrode shows cumulative effects of Cr and S, as Cr accumulation occurs at the triple-phase boundary and S absorption takes place at localized Sr-rich regions.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Bayesian analysis of the 86 Sr ⁢(𝛼,𝛼) reaction to constrain the 86 Sr ⁢(𝛼,𝑛) cross section at astrophysical energies

The alpha optical model potential (𝛼-OMP ) is a phenomenological approach used to describe elastic scattering where multiple reaction channels are open. It is one of the most critical inputs for the calculation of thermonuclear reaction rates in explosive stellar environments, but uncertainties within the 𝛼-OMP lead to imprecise predictions hindering comparisons between calculations and observations. In order to improve the precision of the 𝛼-OMP, additional nuclear physics data are required. In this paper, a measurement of the 86 Sr (𝛼, 𝛼) elastic scattering cross section at multiple energies is reported. Here, a local optical potential is constructed via a fully Bayesian analysis of the elastic scattering data. The resulting uncertainties on the low-energy cross sections relevant to nuclear astrophysics are then calculated and shown to be on the order of 50%.

59 ≤ A ≤ 89↗
DOE OSTI2020

Absence of μ SR evidence for magnetic order in the pseudogap phase of Bi 2 + x Sr 2 - x CaCu 2 O 8 + δ

We present an extended zero-field muon spin relaxation (ZF-$µSR$) study of overdoped $Bi_{2+x}Sr_{2-x}\,CaCu_2O_{8+δ}$ (Bi2212) single crystals, intended to elucidate the origin of weak quasistatic magnetism previously detected by $µSR$ in the superconducting and normal states of optimallydoped and overdoped samples. New results on heavily-overdoped single crystals show a similar monotonically decreasing ZF-$µSR$ relaxation rate with increasing temperature that persists above the pseudogap (PG) temperature $T^*$ and does not evolve with hole doping ($p$). Additional measurements using an ultra-low background apparatus confirm that this behavior is an intrinsic property of Bi2212, which cannot be due to magnetic order associated with the PG phase. Instead we show that the temperature-dependent relaxation rate is most likely caused by structural changes that modify the contribution of the nuclear dipole fields to the ZF-$µSR$ signal. Finally, our results for Bi2212 emphasize the importance of not assuming the nuclear-dipole field contribution is independent of temperature in ZF-$µSR$ studies of high-temperature (high-$T_c$) cuprate superconductors, and do not support a recent $µSR$ study of $YBa_2Cu_3O_{6+x}$ that claims to detect magnetic order in the PG phase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2020

Materials Data on Sr(IO)2 by Materials Project

Sr(OI)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Sr sites. In the first Sr site, Sr is bonded in a 9-coordinate geometry to four O and four I atoms. There are a spread of Sr–O bond distances ranging from 2.50–2.53 Å. There are a spread of Sr–I bond distances ranging from 3.43–3.71 Å. In the second Sr site, Sr is bonded in a 9-coordinate geometry to four O and five I atoms. There are a spread of Sr–O bond distances ranging from 2.51–2.53 Å. There are a spread of Sr–I bond distances ranging from 3.47–3.83 Å. In the third Sr site, Sr is bonded in a 9-coordinate geometry to four O and four I atoms. There are a spread of Sr–O bond distances ranging from 2.51–2.53 Å. There are a spread of Sr–I bond distances ranging from 3.43–3.70 Å. In the fourth Sr site, Sr is bonded in a 9-coordinate geometry to four O and five I atoms. There are a spread of Sr–O bond distances ranging from 2.50–2.53 Å. There are a spread of Sr–I bond distances ranging from 3.46–3.85 Å. There are eight inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.38 Å. In the second O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.37 Å. In the third O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.38 Å. In the fourth O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.37 Å. In the fifth O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. In the sixth O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. In the seventh O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. In the eighth O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. There are eight inequivalent I sites. In the first I site, I is bonded in a distorted water-like geometry to two Sr and one I atom. The I–I bond length is 3.31 Å. In the second I site, I is bonded in a 2-coordinate geometry to three Sr and one I atom. The I–I bond length is 3.27 Å. In the third I site, I is bonded in a distorted water-like geometry to two Sr and one I atom. The I–I bond length is 3.28 Å. In the fourth I site, I is bonded in a 2-coordinate geometry to three Sr and one I atom. The I–I bond length is 3.30 Å. In the fifth I site, I is bonded in a distorted rectangular see-saw-like geometry to two Sr and two I atoms. The I–I bond length is 2.88 Å. In the sixth I site, I is bonded in a 4-coordinate geometry to two Sr and two I atoms. The I–I bond length is 2.88 Å. In the seventh I site, I is bonded in a distorted rectangular see-saw-like geometry to two Sr and two I atoms. In the eighth I site, I is bonded in a 4-coordinate geometry to two Sr and two I atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr(IO)2 by Materials Project

Sr(OI)2 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are four inequivalent Sr sites. In the first Sr site, Sr is bonded to four O and three I atoms to form distorted edge-sharing SrI3O4 pentagonal bipyramids. There are a spread of Sr–O bond distances ranging from 2.47–2.50 Å. There are a spread of Sr–I bond distances ranging from 3.35–3.51 Å. In the second Sr site, Sr is bonded in a 2-coordinate geometry to four O and five I atoms. There are a spread of Sr–O bond distances ranging from 2.48–2.72 Å. There are a spread of Sr–I bond distances ranging from 3.40–4.02 Å. In the third Sr site, Sr is bonded in a 2-coordinate geometry to four O and four I atoms. There are a spread of Sr–O bond distances ranging from 2.48–2.70 Å. There are a spread of Sr–I bond distances ranging from 3.43–3.65 Å. In the fourth Sr site, Sr is bonded in a 4-coordinate geometry to four O and four I atoms. There are a spread of Sr–O bond distances ranging from 2.46–2.52 Å. There are a spread of Sr–I bond distances ranging from 3.31–3.94 Å. There are eight inequivalent O sites. In the first O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.38 Å. In the second O site, O is bonded in a T-shaped geometry to two equivalent Sr and one O atom. The O–O bond length is 1.40 Å. In the third O site, O is bonded in a distorted T-shaped geometry to two equivalent Sr and one O atom. The O–O bond length is 1.42 Å. In the fourth O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. The O–O bond length is 1.37 Å. In the fifth O site, O is bonded in a 3-coordinate geometry to two equivalent Sr and one O atom. In the sixth O site, O is bonded in a 4-coordinate geometry to two equivalent Sr, one O, and one I atom. The O–I bond length is 2.36 Å. In the seventh O site, O is bonded in a 4-coordinate geometry to two equivalent Sr, one O, and one I atom. The O–I bond length is 2.34 Å. In the eighth O site, O is bonded in a distorted T-shaped geometry to two equivalent Sr and one O atom. There are eight inequivalent I sites. In the first I site, I is bonded in a 4-coordinate geometry to three Sr and one I atom. The I–I bond length is 3.34 Å. In the second I site, I is bonded in a distorted single-bond geometry to one Sr, one O, and one I atom. The I–I bond length is 3.17 Å. In the third I site, I is bonded in a distorted single-bond geometry to one Sr, one O, and one I atom. In the fourth I site, I is bonded in a 2-coordinate geometry to three Sr and one I atom. In the fifth I site, I is bonded in a distorted bent 120 degrees geometry to two Sr and one I atom. The I–I bond length is 3.29 Å. In the sixth I site, I is bonded in a 2-coordinate geometry to two Sr and one I atom. The I–I bond length is 3.29 Å. In the seventh I site, I is bonded in a 2-coordinate geometry to two Sr and one I atom. In the eighth I site, I is bonded in a distorted bent 120 degrees geometry to two Sr and one I atom.

36 MATERIALS SCIENCE↗