Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ARGON”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Argon-40-argon-39 dating of Apollo sample 15555.

An age of 3.33 (plus or minus 0.05) b.y. was obtained for Apollo 15 sample 15555 by argon-40-argon-39 dating. The age of rock 15555, a basalt from the rim of Hadley Rille, establishes an upper limit to the age of the rille. The basalt flows filling the Hadley Rille section of the Imbrium basin postdate the formation of the basin - as measured by the Apollo 14 samples of the Fra Mauro formation - by at least 500 m.y. Therefore, the mare basalts cannot be simple impact melts but rather must result from some igneous activity on the moon.

Alexander, E. C., Jr.↗
NASA NTRS1973

Argon in Apollo 15 green glass spherules /15426/ - Ar-40-Ar-39 age and trapped argon

The results of thermal-release argon analyses of neutron-irradiated green glass spherules separated from the lunar sample 15426 are discussed. It is shown that the gas-retention age determined by the Ar-40-Ar-39 method is similar to that of local mare basalts, and differs from the ages of Appenine Front samples recovered from the same region as 15426. Trapped argon is present in near-surface regions of the spherules, and can be resolved into at least two components requiring separate origins: a shallow (0.1 micron) component with Ar-40/Ar-39 not less than 30, and a deeper (2.0 micron) component with an Ar-40/Ar-39 ratio of 2.9. The ratio of trapped Ar-40 to Ar-36 is higher than in any lunar soil samples, and suggests that the trapped gas was implanted early in the spherules history.

Podosek, F. A.↗
NASA NTRS1995

Concerning Apparent Similarity of Structures of Fluoropolymer Surfaces Exposed to an Argon Plasma or Argon Ion Beam

X-ray photoelectron spectroscopy (XPS) C(sub 1s) spectra of fluoropolymers exposed to either an argon plasma or argon ion beam show remarkable similarity, implying that the surface-modification reactions for these two processes likely proceed through comparable mechanisms, revolving predominantly ion-surface interactions. The importance of working with a monochromatized x-ray source for XPS analysis of the surface-modified fluoropolymers is once again emphasized.

Golub, Morton A.↗
NASA NTRS1979

Tissue gas and blood analyses of human subjects breathing 80% argon and 20% oxygen

Eight human volunteers, individually studied in a hyperbaric chamber, breathed: (1) air at 1 ATA; (2) 80% argon and 20% oxygen at 1 ATA for 30 min; (3) air at 1 ATA for 30 min; (4) 100% O2 at 1 ATA for 30 min; (5) air at 1 ATA for 30 min; (6) 100% O2 at 2 ATA for 60 min; and (7) 80% argon and 20% oxygen at 1 ATA for 30 min. Oxygen, carbon dioxide, nitrogen, and argon tensions were measured in muscle and subcutaneous tissue by mass spectroscopic analyses. Venous blood obtained at regular intervals was analyzed for coagulation and fibrinolytic factors. Inert gas narcosis was not observed. After breathing argon for 30 min, muscle argon tensions were almost three times the subcutaneous tensions. Argon wash-in mirrored nitrogen wash-out. Argon wash-in and wash-out had no effect on tissue PO2 or PCO2. Coagulation and fibrinolytic changes usually associated with vascular bubbles were absent.

Horrigan, D. J.↗
NASA NTRS1971

Dissociation-excitation reactions of argon metastables with carbon dioxide.

Results of a study showing that a metastable argon-carbon dioxide reaction results in dissociation of carbon dioxide and electronic excitation of one of the products, carbon monoxide or oxygen. A flow system using a 2450-MHz discharge was used to produce metastable argon atoms. Metastable argon in the afterglow was confirmed by adding nitrogen to the afterglow. Without addition of carbon dioxide no argon line emission, or any other emission, is observed from the reaction zone. Absence of argon line emission produced by recombination indicates the absence of charged species.

Starr, W. L.↗
NASA NTRS1984

Etching of diamond with argon and oxygen ion beams

The angular dependences of the sputter yield of (100) single crystal diamond under argon and oxygen ion beams were investigated. For argon ion beams a large increase in the sputter yield was observed as the angle of incidence was increased from the normal, with a maximum occurring at approximately 60 deg from the normal. The magnitude of the increase and the angle at which the maximum was observed were dependent on the ion energy and species. The shape of the yield versus angle of incidence curve indicated the presence of a highly damaged surface layer. Large deviations from this curve were observed where ion incidence was along channeling directions. Studies with oxygen ion beams showed almost no angular dependence for 500 eV ions while at an energy of 1000 eV the angular dependence was similar to that for argon ions. At normal incidence the yield for 500 eV oxygen ions was seven times larger than that for 500 eV argon ions. For 1000 eV oxygen and argon ions the corresponding ratio is only 2.5. Implications for mechanisms of inert and reactive ion etching are discussed. Application of the data to ion beam shaping of diamond tips for ultrahigh pressure research is discussed.

Whetten, T. J.↗
NASA NTRS1991

Solution and shock-induced exsolution of argon in vitreous carbon

To add to the knowledge of noble gas solution and exsolution in carbonaceus material, experiments were performed on vitreous carbon. Ar-rich vitreous carbon samples were prepared under vapor-saturated conditions using argon as the pressurizing medium. Solubility data were obtained for temperatures of 773 to 973 K and pressures of 250 to 1500 bars. Up to 7 wt pct Ar was dissolved in the carbon. The solubility data were compared to a thermodynamic model of argon atoms dissolving into a fixed population of 'holes' in the carbon. Two variations of the model yielded estimates of the enthalpy of solution of Ar in vitreous carbon equal to about -4700 cal/mole. Preliminary shock experiments showed that 28 percent of the total argon was released by driving 4 GPa shocks into the argon-rich carbon. It was demonstrated that shock-induced argon loss is not simply caused by the impact-induced diminution of grain size. The present value of shock pressure required for partial impact devolatilization of Ar from carbon is below the range (5-30 GPa) at which H2O is released from phyllosilicates.

Gazis, Carey↗
NASA NTRS1974

Argon in the Martian atmosphere

Heretofore undetected argon may be a significant constituent of the Martian atmosphere with a partial pressure of 1.8 mbar. The addition of argon to the 5.5 plus or minus 0.8 mbar of CO2, deduced from ground-based spectroscopy, is consistent with the values of total pressure deduced from the Mariner radio occulation measurements. The presence of argon in the Martian atmosphere contributes to the cooling of the upper thermosphere and exosphere and may explain the difference between predicted and observed temperatures. The argon concentrations predicted here may be related to the recent observation of several tens of per cent of an inert gas, deduced from Mars-6 data.

Levine, J. S.↗
NASA NTRS1980

Lunar cold traps and their influence on argon-40

In polar areas of the moon the maximum temperatures reached in some permanently shaded areas are well below the temperature required to retain water ice for billions of years, and cold enough to hold other volatiles for shorter periods. Aside from water, the most significant lunar volatiles are the radiogenic gases, of which argon-40 is the most easily detected, both in situ and as retrapped ions in rocks returned from the surface on the moon. Argon-40 escapes from the moon at a surprisingly high rate that is between 3% and 6% of its total production. Its brief lifetime in the lunar exosphere is marked by numerous adsorption/desorption events. Collisions with the lunar surface in cold, permanently shaded areas lead to long term storage, forming reservoirs of trapped gas that may be disturbed occasionally to produce sudden increases in atmospheric argon. It is postulated that this may explain at least part of the time variations in Apollo 17 mass spectrometer measurements of argon that were previously attributed to internal processes associated with the release of radiogenic gases from the moon.

Hodges, R. R., Jr.↗