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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Passive films on magnesium anodes in primary batteries

The characteristics of the passive films over Mg anodes, which essentially govern the voltage delay of the latter, have been determined nondestructively from an analysis of the transient and steady-state response of the electrode potential to low amplitude galvanostatic polarization under various experimental conditions viz., with different corrosion inhibitor coatings on Mg, after various periods of ageing of anode in solutions containing corrosion inhibitors, at various low temperatures etc. Using these parameters, the kinetics of film build-up or dissolution under these conditions have been monitored. The morphology of the anode film has been verified with scanning electron microscopy. Similar transients at low temperatures point out a steep rise in the film resistivity which is essentially responsible for the severe voltage delay. Finally, possible application of this technique in secondary Li batteries to improve cycling characteristics of the Li anode has been pointed out.

Ratnakumar, B. V.↗
NASA NTRS1995

HTS thin films: Passive microwave components and systems integration issues

The excellent microwave properties of the High-Temperature-Superconductors (HTS) have been amply demonstrated in the laboratory by techniques such as resonant cavity, power transmission and microstrip resonator measurements. The low loss and high Q passive structures made possible with HTS, present attractive options for applications in commercial, military and spacebased systems. However, to readily insert HTS into these systems improvement is needed in such areas as repeatability in the deposition and processing of the HTS films, metal-contact formation, wire bonding, and overall film endurance to fabrication and assembly procedures. In this paper we present data compiled in our lab which illustrate many of the problems associated with these issues. Much of this data were obtained in the production of a space qualified hybrid receiver-downconverter module for the Naval Research Laboratory's High Temperature Superconductivity Space Experiment 2 (HTSSE-2). Examples of variations observed in starting films and finished circuits will be presented. It is shown that under identical processing the properties of the HTS films can degrade to varying extents. Finally, we present data on ohmic contacts and factors affecting their adhesion to HTS films, strength of wire bonds made to such contacts, and aging effects.

Miranda, F. A.↗
NASA NTRS1995

HTS Thin Films: Passive Microwave Components and Systems Integration Issues

The excellent microwave properties of the High-Temperature-Superconductors (HTS) have been amply demonstrated in the laboratory by techniques such as resonant cavity, power transmission and microstrip resonator measurements. The low loss and high Q passive structures made possible with HTS, present attractive options for applications in commercial, military and space-based systems. However, to readily insert HTS into these systems, improvement is needed in such areas as repeatability in the deposition and processing of the HTS films, metal-contact formation, wire bonding, and overall film endurance to fabrication and assembly procedures. In this paper, we present data compiled in our lab which illustrate many of the problems associated with these issues. Much of this data were obtained in the production of a space qualified hybrid receiver-downconverter module for the Naval Research Laboratory's High Temperature Superconductivity Space Experiment II (HTSSE-II). Examples of variations observed in starting films and finished circuits will be presented. It is shown that under identical processing the properties of the HTS films can degrade to varying extents. Finally, we present data on ohmic contacts and factors affecting their adhesion to HTS films, strength of wire bonds made to such contacts, and aging effects.

Miranda, F. A.↗
NASA NTRS2000

Electrolyte and Electrode Passivation for Thin Film Batteries

Passivation films for thin film batteries have been prepared and the conductivity and voltage stability window have been measured. Thin films of Li2CO3 have a large voltage stability window of 4.8V, which facilitates the use of this film as a passivation at both the lithium anode-electrolyte interface at high cathodic potentials.

passivation thin film batteries↗
NASA NTRS1995

Aspects of passive magnetic levitation based on high-T(sub c) superconducting YBCO thin films

Passive magnetic levitation systems reported in the past were mostly confined to bulk superconducting materials. Here we present fundamental studies on magnetic levitation employing cylindrical permanent magnets floating above high-T(sub c) superconducting YBCO thin films (thickness about 0.3 mu m). Experiments included free floating rotating magnets as well as well-established flexible beam methods. By means of the latter, we investigated levitation and drag force hysteresis as well as magnetic stiffness properties of the superconductor-magnet arrangement. In the case of vertical motion of the magnet, characteristic high symmetry of repulsive (approaching) and attractive (withdrawing) branches of the pronounced force-displacement hysteresis could be detected. Achievable force levels were low as expected but sufficient for levitation of permanent magnets. With regard to magnetic stiffness, thin films proved to show stiffness-force ratios about one order of magnitude higher than bulk materials. Phenomenological models support the measurements. Regarding the magnetic hysteresis of the superconductor, the Irie-Yamafuji model was used for solving the equation of force balance in cylindrical coordinates allowing for a macroscopic description of the superconductor magnetization. This procedure provided good agreement with experimental levitation force and stiffness data during vertical motion. For the case of (lateral) drag force basic qualitative characteristics could be recovered, too. It is shown that models, based on simple asymmetric magnetization of the superconductor, describe well asymptotic transition of drag forces after the change of the magnet motion direction. Virgin curves (starting from equilibrium, i.e. symmetric magnetization) are approximated by a linear approach already reported in literature only. This paper shows that basic properties of superconducting thin films allow for their application to magnetic levitation or - without need of levitation forces, e.g. microgravity - magnetic damping devices.

Schoenhuber, P.↗
NASA NTRS1961

Microwave Reflectivity of Deposited Aluminum Films for Passive Relay Communications

Reflectivity measurements from 400 Mc/sec to 10 kMc/sec on 2,200 A thick aluminum deposited on 1/2-mil-thick Mylar film show this material to be a very good reflector of radio waves. Measurements made under conditions of stress and temperature which would be encountered by a communications sphere, such as Project Echo (1960 Iota), showed very little deterioration of the high reflectivity. packaging effects also caused very little reflectivity change. Under conditions of severe temperature cycling, aluminum removal and decreased reflectivity occurred.

Cuddihy, William F.↗
NASA NTRS2004

Measurement of Thin Film Integrated Passive Devices on SiC through 500 C

Wireless communication in jet engines and high temperature industrial applications requires FD integrated circuits (RFICs) on wide bandgap semiconductors such as Silicon Carbide (SiC). In this paper, thin-film NiCr resistors, MIM capacitors, and spiral inductors are fabricated on a high purity semi-insulating 4H-SiC substrate. The devices are experimentally characterized through 50 GHz at temperatures of up to 500 C and the equivalent circuits are deembedded from the measured data. It is shown that the NiCr resistors are stable within 10% to 300 C while the capacitors have a value stable within 10% through 500 C.

Schwartz, Zachary D.↗
NASA NTRS1980

Coating of plasma polymerized film

Plasma polymerized thin film coating and the use of other coatings is suggested for passivation film, thin film used for conducting light, and solid body lubrication film of dielectrics of ultra insulators for electrical conduction, electron accessories, etc. The special features of flow discharge development and the polymerized film growth mechanism are discussed.

Morita, S.↗
NASA NTRS1986

Four-micron period ion-implanted bubble test circuits

Packaged magnetic bubble test circuits made with 4-micron period ion-implanted circuits were operated over -55 to +110 C. The circuits used bidirectional transfer and nondestructive detection and were made on bismuth-containing magnetic garnet films. Passivated circuits that incorporated an improved transfer conductor design were operated on films with higher Gilbert damping parameters. Potential advantages to using films with lower bubble aspect ratios for ion-implanted circuits are discussed. However nondestructive read-out detection was not realized with these 'flat' bubbles.

Nelson, T. J.↗
NASA NTRS1983

Cleaning chemistry of InSb(100) molecular beam epitaxy substrates

InSb has been used as a substrate for molecular beam epitaxy. For good epitaxial growth, a substrate surface which is smooth and clean on an atomic scale is required. Chemical cleaning procedures provide an oxide film to passivate the surface. This film is then desorbed by in situ heating. The material forming the film should, therefore, have a high vapor pressure at some temperature less than the substrate melting temperature. A chloride film appears to satisfy the latter requirement. The present investigation is, therefore, concerned with the formation of a chloride film rather than an oxide film. Carbon contamination has been found to cause problems in chemical cleaning procedures. The level of carbon contamination found in the case of chloride film formation, is therefore compared with the corresponding level observed in procedures using oxide films. It appears that a chloride film grown in connection with a short exposure time to a Cl2 plasma is preferable to other passivation films studied.

Vasquez, R. P.↗
NASA NTRS1981

Secondary lithium batteries for space applications

Secondary lithium cells which use a LiAsF6-2-Me-THF electrolyte and a TiS2 intercalatable cathode exhibit encouraging cycle life at ambient temperature. Electrochemical and surface analytical studies indicate that the electrolyte is unstable in the presence of metallic lithium, leading to the formation of a lithium passivating film composed of lithium arsenic oxyfluorides and lithium fluorsilicates. The lithium cyclability remains as the most important problem to solve. Different electrolyte solvents, such as sulfolane, exhibit promising characteristics but lead to new compatibility problems with the other cell component materials.

Carter, B.↗
NASA NTRS1983

Friction and wear of iron in sulfuric acid

Elemental iron sliding on aluminum oxide in aerated sulfuric acid concentrations ranging from very dilute (0.000007 N; i.e., 4 ppm) to very concentrated (96 percent acid) was studied. Load and reciprocating sliding speeds were kept constant. With the most dilute acid of 0.7 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent, the high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid, and decreased somewhat at 50 percent in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It is apparent that the normal passivating film was being worn away and a galvanic cell established which rapidly attached to the wear area.

Rengstorff, G. W. P.↗
NASA NTRS1984

Interaction of sulfuric acid corrosion and mechanical wear of iron

Friction and wear experiments were conducted with elemental iron sliding on aluminum oxide in aerated sulfuric acid at concentrations ranging from very dilute (0.00007 N; i.e., 4 ppm) to very concentrated (96 percent acid). Load and reciprocating sliding speed were kept constant. With the most dilute acid concentration of 0.00007 to 0.0002 N, a complex corrosion product formed that was friable and often increased friction and wear. At slightly higher concentrations of 0.001 N, metal losses were essentially by wear alone. Because no buildup of corrosion products occurred, this acid concentration became the standard from which to separate metal loss from direct corrosion and mechanical wear losses. When the acid concentration was increased to 5 percent (1 N), the well-established high corrosion rate of iron in sulfuric acid strongly dominated the total wear loss. This strong corrosion increased to 30 percent acid and decreased somewhat to 50 percent acid in accordance with expectations. However, the low corrosion of iron expected at acid concentrations of 65 to 96 percent was not observed in the wear area. It was apparent that the normal passivating film was being worn away and a galvanic cell established that rapidly attacked the wear area. Under the conditions where direct corrosion losses were highest, the coefficient of friction was the lowest.

Rengstorff, G. W. P.↗