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Results for “RECOMBINATION COEFFICIENT”

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 NTRS1983

Catalytic recombination of nitrogen and oxygen on iron-cobalt-chromia spinel

The energy-transfer catalytic recombination coefficient for nitrogen and oxygen recombination on iron-cobalt-chromia spinel is inferred from stagnation-point heat flux measurements in dissociated arc-jet flow. This material was coated on several Space Shuttle Orbiter thermal protection tiles. The resulting coefficients are correlated with an Arrhenius model for convenience, and these expressions may be used to account for catalytic recombination in predictions of the heat flux on the spinel-coated tiles flown on several Space Shuttle Orbiter flights. The results are compared with those inferred by Rakich, Stewart, and Lanfranco from an Orbiter flight and arc-jet experiments. Good agreement is obtained for oxygen recombination, but agreement for nitrogen is poor.

Scott, C. D.↗
NASA NTRS1996

Surface Catalytic Efficiency of Advanced Carbon Carbon Candidate Thermal Protection Materials for SSTO Vehicles

The catalytic efficiency (atom recombination coefficients) for advanced ceramic thermal protection systems was calculated using arc-jet data. Coefficients for both oxygen and nitrogen atom recombination on the surfaces of these systems were obtained to temperatures of 1650 K. Optical and chemical stability of the candidate systems to the high energy hypersonic flow was also demonstrated during these tests.

Stewart, David A.↗
NASA NTRS1995

Hydrocarbon Ions in the Ionospheres of Titan and Jupiter

Two examples are given of models of ion chemistry in reducing atmospheres: Titan, which is a satellite of Saturn, and Jupiter, the largest of the gas giants. In both ionospheres, layers of hydrocarbon and/or C, H, and N-containing ions have been predicted to appear, with larger ions dominating at lower altitudes. Altitude profiles are presented for individual C1- and C2-hydrocarbon ions and larger ions that are represented for example, as C(x)H(y)(+) and C(x)H(y)N(x)(+). The accuracy of the predictions is, however, limited by the availability of information about the chemistry of these ions. In addition to rate coefficients and product channels for ion-molecule reactions, dissociative recombination coefficients and branching ratios are needed for many hydrocarbon and and related ions.

Fox, J. L.↗
NASA NTRS1988

Electron-temperature dependence of the recombination of electrons with O4(+) ions

The coefficient for recombination of O4(+) ions with electrons has been measured as a function of Te by analyzing electron- and ion-density decays in microwave-generated afterglow plasmas in neon-oxygen mixtures. Te values in the afterglow were elevated above those of the neutral species and ions by continuous application of microwave power. The data analysis included effects on the Te arising from inelastic collisions of electrons with the minority oxygen molecules and spatial nonuniformities of Te due to the spatially nonuniform microwave heating field. Over the temperature range Te = 143-5500 K the recombination coefficients were found to have a Te exp -z dependence, with z = 0.48 + 0.1 or - 0.05. While the values of the recombination coefficients for this dimer ion are an order of magnitude larger than those of the monomer ions, the temperature dependence is close to the Te exp -0.5 dependence predicted and often observed for diatomic ions.

Dulaney, J. L.↗
DOE OSTI2025

Unusually Strong Near‐Infrared Photoluminescence of Highly Transparent Bulk InSe Flakes

Abstract Bulk γ‐InSe has a direct bandgap of 1.24 eV, which corresponds to near infrared wavelengths ( λ = 1.0 µm) useful in optoelectronic applications from biometric detectors to silicon photonics. However, its potential for optoelectronic applications is largely untapped due in part to the lack of quantitative studies of its optical properties. Here, the unusually low absorptance and high photoluminescence quantum efficiency of single‐crystalline InSe flakes with thickness in the hundreds of nanometers are studied. InSe emits brightly at room temperature from its direct bandgap with a peak photoluminescence quantum yield (PLQY) of 20%, despite displaying indirect bandgap like low absorption coefficient due to the symmetry of its crystal structure. By performing pump‐dependent PLQY measurements, the radiative and nonradiative recombination coefficients are extracted, including the Shockley‐Read‐Hall and Auger coefficients. Finally, a proof‐of‐concept alternating current electroluminescent device at low temperature is demonstrated to show the promise of InSe in optoelectronic technology such as highly transparent, bright NIR light sources.

Geng, Jamie↗
NASA NTRS1987

Nitrogen recombination on high-temperature reusable surface insulation and the analysis of its effect on surface catalysis

The energy transfer catalytic recombination coefficients for nitrogen and oxygen on a borosilicate glass are determined in nitrogen and air hypersonic arc jet streams. These data, obtained from a reacting boundary-layer analysis with first-order surface reaction kinetics, compare well with earlier results from a Goulard frozen boundary-layer model up to 1600 K. The apparent surface recombination rates increase up to 1600 K, then begin to decrease. To illustrate the effects of temperature and nitrogen dissociation on energy transfer to the glass, a diffusional heat-flux is calculated using the present results from 1450 K up to 1850 K. This diffusional heat-flux is the contribution to the total heating rate by atom recombination, and is used to compare the present results with coefficients from three previous studies.

Kolodziej, Paul↗
NASA NTRS1962

Recombination and Mobility of Nuclear Radiation Induced Ionization in Liquid Hydrogen

In the present experiment, a stationary radioactive source (Kr-85) was allowed to produce ionization at a particular location in a flowing stream of liquid hydrogen. By measurement of the ionization collected at various points downstream for various velocities we were able to measure independently the recombination coefficient and the ionic mobility. In addition, we were able to obtain an approximate value of E, the fraction of the volumetric ionization rate which is available for volume recombination and production of ion currents.

Ionization↗
NASA NTRS1984

Recombination of electrons with H3(+) and H5(+) ions

A microwave afterglow-mass spectrometer apparatus is used to determine the dissociative recombination coefficients for capture of electrons by H3(+) and H5(+) ions as a function of electron temperature. At an ion and neutral temperature of 240 K, the coefficient for H3(+) is found to vary slowly with the electron temperature at first, decreasing from 1.6 x 10 to the -7th cu cm/s at an electron temperature of 240 K to 1.2 x 10 to the -7th cu cm/s at an electron temperature of 500 K; at electron temperatures ranging from 500 to 3000 K, the coefficient falls as the reciprocal of the electron temperature. It is noted that the results, which have an uncertainty of + or - 20 percent, agree satisfactorily over the common energy range (0.03-0.36 eV) with the recombination cross sections determined in merged beam measurements by Auerbach et al. (1977). Attention is also given to the implication of the results for modeling planetary atmospheres and interstellar clouds.

Macdonald, J. A.↗
NASA NTRS1977

The rate coefficient for the O/+/ + N2 reaction in the ionosphere

The rate coefficient for the reaction O(+) + N2 yields NO(+) + N is determined as a function of temperature from the photochemistry of NO(+) for both day and night conditions by using a large sample of simultaneous measurements of ion and neutral concentrations and temperatures made by the Atmosphere Explorer C satellite. The results cover the ion temperature range from 500 to 1200 K. Using recent flow-drift-tube results, the rate coefficient is calculated as a function of ion temperature and mean ion drift velocity for ionospheric conditions. The satellite and laboratory determinations are found to be in good agreement. Using this temperature dependence, an earlier determination of the dissociative recombination coefficient of NO(+) with electrons is refined.

Torr, M. R.↗
NASA NTRS1984

Non-catalytic surfaces for metallic heat shields

The magnitude of the atom recombination coefficients needed for metal heat shield surfaces on Shuttle-type vehicles is analyzed and discussed. Prior work which identifies surfaces having low catalytic activity is reviewed. Arc tunnel tests to evaluate catalytic activity are described and the difficulties of such tests are discussed. Results are presented which show major differences between atom recombination and atom exchange from molecules. Results of surface analysis show that bulk and surface composition of a coating are different.

Swann, R. T.↗