Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “silver”

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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Cycles till failure of silver-zinc cells with completing failures modes: Preliminary data analysis

One hundred and twenty nine cells were run through charge-discharge cycles until failure. The experiment design was a variant of a central composite factorial in five factors. Preliminary data analysis consisted of response surface estimation of life. Batteries fail under two basic modes; a low voltage condition and an internal shorting condition. A competing failure modes analysis using maximum likelihood estimation for the extreme value life distribution was performed. Extensive diagnostics such as residual plotting and probability plotting were employed to verify data quality and choice of model.

Sidik, S. M.↗
NASA NTRS1980

Isotopically anomalous silver in the Santa Clara and Pinon iron meteorites

The isotopic composition and concentration of Ag and the concentration of Pd have been determined in the Santa Clara and Pinon iron meteorites. It is shown that these meteorites contain isotopically anomalous Ag with an excess of Ag-107 relative to normal Ag, confirming earlier findings. Using an improved procedure for cleaning the sample surface from terrestrial Ag, a new concentration of 1.4 x 10 to the 11th atoms of Ag-109/g meteorite is established which is an order of magnitude below the levels found earlier. As a result ratios of Ag-107/Ag-109 were found which are enriched in Ag-107 by 60 percent to 160 percent. The existence of an excess Ag-107 in these two meteorites, which have high Pd-108/Ag-109 ratios of about 7 x 10 to the 4th is established.

Kaiser, T.↗
NASA NTRS1981

Pioneer 10 at Silver Au Describes Sun's atmosphere

Almost 4 billion kilometers from the Sun, Pioneer 10's findings paint a detailed picture of the solar atmosphere. The heliosphere is now believed to be a huge magnetic bubble created by the solar wind and gets its tear-shape from streamlining due to the motion of the solar system through the interstellar gas. The skin of the bubble, the region between stellar and interstellar gas, is believed to lie between 50 and 100 AU from the Sun. The solar wind drags the Sun's magnetic field with it. The bubble, probably extends far beyond Pluto, and is believed to breathe, expanding and contracting like a giant cosmic lung with each 11 year cycle. The most recent findings show that as storms on the Sun build up toward maximum solar activity, they send out shock waves throughout the bubble which cause ripples. This long lived solar storm turbulence accelerates low energy cosmic ray particles coming in from the galaxy, deflecting them out of the solar system, and shielding the planets. As distance from the Sun increases, more and more cosmic ray particles penetrate the heliosphere.

Source record↗
NASA NTRS1980

Fast ion transport in silver halide solid solutions and multiphase systems

The incorporation of homovalent ions, e.g., I(-) in AgBr, leads to a substantial increase in ionic conductivity sigma. The charge compensation concept does not explain the enhancement. AgBr + 30 mol. % AgI exhibits sigma approximately 7/omega/cm at 380 C, which is approximately 170% larger than that of alpha-AgI, the best known superionic conductor, at its melting point. The purely elastic displacement caused by the foreign ion is suggested to be the origin of such a unique behavior. Furthermore, AgI-AgBr two-phase systems display sigma approximately 10 to the 3rd times higher than predicted by the classical theories.

Shahi, K.↗
NASA NTRS1981

Spallogenic rare gases in iron meteorites with anomalous silver

He, Ne, and Ar have been measured in seven iron meteorites for which anomalous Ag isotopic compositions were reported, in order to determine if Ag-107 excesses could be related to galactic cosmic-ray bombardment of these meteorites. The results show that no correlation exists between Ag-107 excess and either the fluence or the energy spectrum of the particles producing spallogenic rare gases. Cosmic-ray-produced Ag-107 estimated from Ar-38 concentrations can account for only about 1 percent of the observed excess. Elimination of cosmic-ray bombardment as a production mechanism for Ag-107 excess strengthens the conclusion that the excess Ag-107 is the decay product of short-lived Pd-107 (half life 6.5 million years). The iron meteorite Pinon is shown to contain trapped rare gases with He-4/Ne-20 approximately 600.

Villa, I. M.↗
NASA NTRS1983

The isotopic composition and concentration of Ag in iron meteorites and the origin of exotic silver

The isotopic composition of Ag and the concentration of Ag and Pd in Canyon Diablo (IA), Grant (IIIB), Santa Clara, Tlacotepec and Warburton Range (IVB), Pinon and Deep Springs (anom) were analyzed. Troilite from Santa Clara and from Grant was also studied. With the exception of IA, all the meteorites were enriched in Ag-107 by about 2%-212% and the ratio of Ag-107/Ag-109 in the metal phase was found to be greater than the terrestrial value. Ag of anomalous isotopic composition was found to be common in all IVB and anomalous meteorites. A correlation of Ag-107/Ag-109 with Pd/Ag was established except for the iron meteorite of Santa Clara. The excess Ag-107 is thought to result from the decay of Pd-107. The Grant data appear to represent a Pd-107-Ag-107 isochron and indicate that the cooling rate at elevated temperatures was rapid enough to preserve the isotopic differences between metal and troilite. The data suggest that Ag in Santa Clara is made up of almost pure Ag-107 produced from Pd-107 decay and Ag-109 produced by nuclear reactions with only a small amount of 'normal' Ag. This indicates an intense energetic particle bombardment history in the early solar system which occurred after the formation of small planetary bodies.

Kaiser, T.↗
NASA NTRS1984

MOD silver metallization for photovoltaics

Photovoltaic cells require back side metallization and a collector grid system on the front surface. Both front and back surface metallizations should have good adhesion, low contact resistance, low sheet resistance, long term stability, and their deposition methods should not degrade the n-p junction. Advantages and disadvantages of different deposition methods are discussed.

Vest, G. M.↗
NASA NTRS1985

Ink jet printing of silver metallization for photovoltaics

Progress was made in the continuing development of the ink jet printing system for thick film circuits. The unit being used is a prototype ink jet printer. One of the first tasks completed was the complete documentation of this ink jet printing system as it existed. It was determined that this was an essential step in deciding what modifications were needed to the system and how these modifications would be implemented. Design modification studies were started for electronic, mechanical, and programming aspects of the ystem. The areas needeing improvement were discussed and applicable changes decided upon. Some improvments were completed. Although the general areas needing improving were identified and some changes decided upon, the exact details of how other changes can be implemented are yet been decided.

Vest, R. W.↗
NASA NTRS1986

Preventing Delamination of Silverized FEP Films

Edge treatment inhibits attack by moisture. New technique prevents delamination by sealing edges where delamination starts. Samples of aluminum/FEP/silver laminate survive humidity tests and other environmental tests when edges of layers are covered by epoxy bead. Untreated laminates, in contrast, deteriorated seriously during such tests.

Domnikov, L.↗
NASA NTRS1986

Channel waveguides in glass via silver-sodium field-assisted ion exchange

Multimode channel waveguides have been formed in sodium aluminosilicate glass by field-assisted diffusion of Ag(+) ions from vacuum-evaporated Ag films. The two-dimensional refractive index profiles of the waveguides were controlled by varying the diffusion time, the diffusion temperature, and the electric field strength. Estimates of the diffusion rate through a strip aperture were obtained, assuming the electric field was strong 120-240 V/mm. The maximum change in refractive index in the sodium aluminosilicate glasses was estimated near 65 percent of the change in soda-lime silicate glass. The physical properties of the glasses are given in a table.

Forrest, K.↗
NASA NTRS1985

Analysis of normal and transparent silver Teflon

Samples of Inconel/silver/Teflon exposed to solar radiation, and atomic oxygen on Solar Max were microcharacterized. Those samples exposed to atomic oxygen from the metallic side had become transparent while those exposed from the Teflon side remained reflective. The difference between the transparent and non-transparent material was determined. Microcharacterization of these Inconel/silver/Teflon samples was performed using scanning electron microscopy with windowless energy dispersive X ray analysis, secondary ion mass spectrometry, and X ray photoelectron spectroscopy.

Stuckey, W. K.↗
NASA NTRS1987

Permeation of oxygen through high purity, large grain silver

The permeation of high purity, large grain Ag membranes by oxygen has been studied over the temperature range 400 to 800 C. The permeability was found to be quite linear and repeatable, but the magnitude was 3.2 times smaller than that determined by past research. Since previous investigators studied substantially less pure Ag and conducted experiments within much poorer vacuum environments (which indicates that their grain boundary density was much greater), the data presented here suggest oxygen transport through the membrane is primarily by grain boundary diffusion. The diffusivity measurements were found to exhibit two distinct linear regions, one above and one below a critical temperature of 630 C. The high-temperature data have an activation energy (11.1 kcal/mole) similar to that reported by others, but the low-temperature data have a higher activation energy (15.3 kcal/mole), which can be explained by impurity trapping in the grain boundaries. Vacuum desorption of the oxygen-saturated Ag was found to occur at a threshold of 630 C, which is consistent with the onset of increased mobility within the grain boundaries.

Outlaw, R. A.↗
NASA NTRS1988

High-temperature processing of oxide superconductors and superconducting oxide-silver oxide composite

High temperature processing was found to partially convert the green 211 phase oxide to 123 phase. High Tc superconductivity was observed in Bi-Sr-Cu-O and Y-Sr-Cu-O systems prepared using the same heat treatment process. High temperature processing presents an alternative synthetic route in the search for new high Tc superconductors. An unusual magnetic suspension with enhancement in critical current density was observed in the 123 and AgO composite.

Wu, M. K.↗
NASA NTRS1992

Silver Teflon blanket: LDEF tray C-08

A study of the Teflon blanket surface at the edge of tray C-08 illustrates the complexity of the microenvironments on the Long Duration Exposure Facility (LDEF). The distribution of particulate contaminants varied dramatically over a distance of half a centimeter (quarter of an inch) near the edge of the blanket. The geometry and optical effects of the atomic oxygen erosion varied significantly over the few centimeters where the blanket folded over the edge of the tray resulting in a variety of orientations to the atomic oxygen flux. A very complex region of combined mechanical and atomic oxygen damage occurred where the blanket contacted the edge of the tray. A brown film deposit apparently fixed by ultraviolet light traveling by reflection through the Teflon film was conspicuous beyond the tray contract zone. Chemical and structural analysis of the surface of the brown film and beyond toward the protected edge of the blanket indicated some penetration of energetic atomic oxygen at least five millimeters past the blanket-tray contact interface.

Crutcher, E. Russ↗
NASA NTRS1992

Some results of the oxidation investigation of copper and silver samples flown on LDEF

The Long Duration Exposure Facility (LDEF) Mission provides a unique opportunity to study the long term effects of the space environment on materials. The LDEF has been deployed in orbit on 7 April 1984 by the shuttle Challenger in an almost circular orbit with a mean altitude of 477 km and an inclination of 28.5 degrees. It was retrieved from its decayed orbit of 335 km by the shuttle Columbia on 12 January 1990 after almost 6 years in space. The LDEF is a 12-sided, 4.267 m diameter, and 9.144 m long structure. The experiments, placed on trays, are attached to the twelve sides and the two ends of the spacecraft. The LDEF was passively stabilized with one end of the spacecraft always pointing towards the earth center and one of the sides (row 9) always facing the flight direction. The materials investigated originate from the Ultra-Heavy Cosmic Ray Experiment (UHCRE). The main objective is a detailed study of the charge spectra of ultraheavy cosmic-ray nuclei from zinc to uranium and beyond, using solid-state track detectors. Besides the aluminium alloy used for the experiment, UHCRE comprises several other materials. The results of space exposure for two of them, the copper grounding strips and the thermal covers (FEP Teflon/Ag/Inconel) painted black on the inner side (Chemglaze Z306), are presented.

Derooij, A.↗
NASA NTRS1993

Low resistance silver contacts to indium phosphide - Electrical and metallurgical considerations

The electrical and metallurgical behavior of the Ag-InP contact system has been investigated. Specific contact resistivity (Rc) values in the low 10 exp -6 Ohm sq cm range are readily achieved on n-InP (Si: 1.7 x 10 exp 18/cu cm) after sintering at 400 C for several minutes. The low Rc values, however, are shown to be accompanied by dissolution of InP into the metallization, resulting in device degradation. An analysis of the sinter-induced metallurgical interactions shows this system to be similar to the well-characterized Au-InP system, albeit with fundamental differences. The similarities include the dissociative diffusion of In, the reaction-suppressing effect of SiO2 capping, and especially, the formation of a phosphide layer at the metal-InP interface. The low post-sinter Rc values in the Ag-InP system may be due to the presence of a AgP2 layer at the metal-InP interface; low values of Rc can be achieved without incurring device degrading metallurgical interactions by introducing a thin AgP2 layer between the InP and the current carrying metallization.

Weizer, Victor G.↗