Search NASA⌕ Search

SEARCH · Search NASA

Results for “THICK FILM”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

An experimental evaluation of the Hamrock and Dowson minimum film thickness equation for fully flooded EHD point contacts

Fifty-seven measurements of the minimum lubricant film separating the elastohydrodynamically lubricated point contact of a steel crowned roller and a flat sapphire disk were made by an optical interferometry technique. The data collected were used to evaluate the Hamrock and Dowson minimum EHD film thickness model over a practical range of contact ellipticity ratio where the major axis of the contact ellipse is aligned both parallel and perpendicular to the direction of motion. A statistical analysis of the measured film thickness data showed that on the average the experimental data averaged 30 percent greater film thickness than the Hamrock and Dowson model predicts.

Koye, K. A.↗
NASA NTRS1980

Some limitations in applying classical EHD film thickness formulas to a high-speed bearing

Elastohydrodynamic film thickness was measured for a 20-mm ball bearing using the capacitance technique. The bearing was thrust loaded to 90, 448, and 778 N. The corresponding maximum stresses on the inner race were 1.28, 2.09, and 2.45 GPa. Test speeds ranged from 400 to 14,000 rpm. Film thickness measurements were taken with four different lubricants: (a) synthetic paraffinic, (b) synthetic paraffinic with additives, (c) neopentylpolyol (tetra) ester meeting MIL-L-23699A specifications, and (d) synthetic cycloaliphatic hydrocarbon traction fluid. The test bearing was mist lubricated. Test temperatures were 300, 338, and 393 K. The measured results were compared to theoretical predictions using the formulas of Grubin, Archard and Cowking, Dowson and Higginson, and Hamrock and Dowson. There was good agreement with theory at low dimensionless speed, but the film was much smaller than theory predicts at higher speeds. This was due to kinematic starvation and inlet shear heating effects.

Coy, J. J.↗
NASA NTRS1980

Some limitations in applying classical EHD film-thickness formulae to a high-speed bearing

Elastohydrodynamic film thickness was measured for a 20 mm ball bearing using the capacitance technique. The bearing was thrust loaded to 90, 448, and 778 N. The corresponding maximum stresses on the inner race were 1.28, 2.09, and 2.45 GPa. Test speeds ranged from 400 to 14,000 rpm. Film thickness measurements were taken with four different lubricants: (1) synthetic paraffinic; (2) synthetic paraffinic with additives; (3) neopentylpolyol (tetra) ester; and (4) synthetic cycloaliphatic hydrocarbon traction fluid. The test bearing was mist lubricated. Test temperatures were 300, 338, and 393 K. The measured results were compared to theoretical predictions and are presented.

Coy, J. J.↗
DOE OSTI2023

Determination of film thicknesses of metal oxides prepared by atomic layer deposition on SBA-15

ZrO 2 and CeO 2 films were grown in SBA-15 by Atomic Layer Deposition (ALD) to loadings of 0.92 g oxide/g SBA-15. Scanning Transmission Electron Microscopy (STEM) with Energy Dispersive Spectra (EDS) showed that the oxides grew uniformly inside the mesopores. Film thicknesses were then analyzed as a function of the number of ALD cycles using three methods: 1) mass changes assuming bulk densities for the films; 2) changes in pore size from Barret-Joyner-Halenda (BJH) analysis with N 2 adsorption isotherms; and 3) small-angle X-ray scattering (SAXS). Film thicknesses assuming bulk densities were between 6 and 8 times smaller than those obtained from BJH analysis. SAXS analysis gave film thicknesses that were approximately twice that obtained from bulk densities. Here, possible explanations of the discrepancies between these methods are discussed.

36 MATERIALS SCIENCE↗
NASA NTRS1995

Percolation effect in thick film superconductors: Using a Bi(Pb)SrCaCuO based paste to prepare a superconducting planar transformer

A thick film superconductor paste has been developed to study the properties of granulated superconductor materials, to observe the percolation effect and to confirm the theory of the conducting mechanism in the superconducting thick films. This paste was also applied to make a superconducting planar transformer. Due to the T(sub c) and advantageous current density properties the base of the past was chosen to be of Bi(Pb)SrCaCu) system. For contacts a conventional Ag/Pt paste was used. The critical temperature of the samples were between 110 K and 115 K depending on the printed layer thickness. The critical current density -at the boiling temperature of the liquid He- was between 200 - 300 A/sq cm. The R(T) and V(I) functions were measured with different parameters. The results of the measurements have confirmed the theory of conducting mechanism in the material. The percolation structure model has been built and described. As an application, a superconducting planar thick film transformer was planned and produced. Ten windings of the transformer were printed on one side of the alumina substrate and one winding was printed on the other side. The coupling between the two sides was possible through the substrate. The samples did not need special drying and firing parameters. After the preparation, the properties of the transformer were measured. The efficiency ans the losses were determined. Finally, some fundamental advantages and problems of the process were discussed.

Sali, Robert↗
NASA NTRS1982

Film thickness measurement for spiral groove and Rayleigh step lift pad self-acting face seals

One Rayleigh step lift pad and three spiral groove self-acting face seal configurations were tested to measure film thickness and frictional torque as a function of shaft speed. The seals were tested at a constant face load of 73 N (16.4 lb) with ambient air at room temperature and atmospheric pressure as the fluid medium. The test speed range was from 7000 to 17,000 rpm. The measured film thickness was compared with theoretical data from mathematical models. The mathematical models overpredicted the measured film thickness at the lower speeds of the test speed range and underpredicted the measured film thickness at the higher speeds of the test speed range.

Dirusso, E.↗
DOE OSTI2021

Development of 4.0 μm thick film REBCO tapes with length over 10 m by Ohmic heating technique

High-temperature superconducting REBCO (RE-(Gd,Y)Ba 2 Cu 3 O 7-δ ) coated conductor has an immense potential to enable magnetic fields above 20 T because of its high current-carrying capacity, high irreversibility field, and good mechanical properties. Advanced metal organic chemical vapor deposition (A-MOCVD) reactor with ohmic heating has been developed to grow long-length, thick film REBCO tapes in a single pass with superior in-field performance. Multiple long-length 5% Zr doped REBCO tapes with film thickness ranging from 1-4 µm have been produced in an A-MOCVD reactor. The critical current density (J c ) of these conductors has been examined by scanning hall probe microscopy. REBCO coated conductors with ~4 µm thickness exhibit magnetization J c >1.5 MA/cm 2 at 65 K, 1.5 T and 5.4 MA/cm 2 at 4.2 K, 13 T. As a result, the microstructure, out-of-plane and in-plane texture of REBCO coated conductors are also presented.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1979

Elastohydrodynamic film thickness measurements of artificially produced nonsmooth surfaces

Optical interferometry is used to measure the elastohydrodynamic (EHD) film thickness associated with artificially produced nonsmooth surfaces. The nonsmooth surfaces are produced by modifying the surfaces of highly-polished balls with irregularities in the form of multiple grooves and dents. By closely spacing these irregularities it is possible not only to produce depressions on the surface of the balls but also to generate pseudo asperities. The average roughness wavelength of this artificially-produced, nonsmooth, surface approximates the average fundamental roughness wavelength found on surfaces of some mechanical elements operating under concentrated contact. By comparing the measured film thickness profiles to the stylus traces of the irregularities, it was possible to observe the local deformations associated with micro-EHD pressure generation. In both pure rolling and pure sliding conditions the artificially-produced asperities are deformed and complete separation exists between them and the mating surface. Such findings demonstrate the importance of local surface topography and resulting micro-EHD effects on the film thickness between rough surfaces in concentrated contact. Sliding data are presented which demonstrate a severe constriction, caused by the irregularities, at the exit of the Hertzian region.

Cusano, C.↗
NASA NTRS1981

The effects of artificially-produced defects on the film thickness distribution in sliding EHD point contacts

Effects of artificially produced dents and grooves on the elastohydrodynamic film thickness profile in a sliding point contact are investigated using optical interferometry. Defects on the surface of a highly polished ball are held stationary at various locations within the vicinity of the contact region while the disk is rotating. It is shown that defects can dramatically change the film thickness which exists when no defects are present in or near the contact, and it is shown that the change in thickness is mainly a function of the position of the defects in the inlet region, the geometry of the defects, the orientation of the defects in the case of grooves, and the depth of the defect relative to the central film thickness.

Cusano, C.↗
NASA NTRS1974

Traction and film thickness measurements under starved elastohydrodynamic conditions

Results of traction and film thickness measurements made for a point contact geometry under starved elastohydrodynamic rolling and sliding conditions are reviewed. These results indicate that the variation of film thickness with the location of the inlet lubricant boundary under combination rolling and sliding behaves identically with that found previously under pure rolling conditions. The maximum shear rate is shown to depend on the degree of starvation and has no theoretical limit. The relative increase in traction due to starvation is influenced by thermal and fluid rheological conditions within the Hertz region.

Wedeven, L. D.↗
NASA NTRS1977

Laser drilling of vias in dielectric for high density multilayer LSHI thick film circuits

A design analysis of a high density multilevel thick film digital microcircuit used for large scale integration is presented. The circuit employs 4 mil lines, 4 mil spaces and requires 4 mil diameter vias. Present screened and fired thick film technology is limited on a production basis to 16 mil square vias. A process whereby 4 mil diameter vias can be fabricated in production using laser technology was described along with a process to produce 4 mil diameter vias for conductor patterns which have 4 mil lines and 4 mil spacings.

Cocca, T.↗
NASA NTRS1979

Elastohydrodynamic film thickness measurements of artificially-produced nonsmooth surfaces

Optical interferometry is used to measure the elastohydrodynamic (EHD) film thickness associated with artificially produced, nonsmooth surfaces. The nonsmooth surfaces are produced by modifying the surfaces of highly-polished balls with irregularities in the form of multiple grooves and dents. By closely spacing these irregularities, it is possible not only to produce depressions on the surface of the balls but also to generate pseudo asperities. The average roughness wavelength of this artificially-produced, nonsmooth surface approximates the average fundamental roughness wavelength found on surfaces of some mechanical elements operating under concentrated contact. By comparing the measured film thickness profiles to the stylus traces of the irregularities, it is possible to observe the local deformations associated with micro-EHD pressure generation. In both pure rolling and pure sliding conditions, the artificially-produced 'asperities' are deformed and complete separation exists between them and the mating surface. Such findings demonstrate the importance of local surface topography and resulting micro-EHD effects on the film thickness between rough surfaces in concentrated contact. In addition, sliding data are presented which demonstrate a severe constriction, caused by the irregularities, at the exit of the Hertzian region.

Cusano, C.↗
NASA NTRS1978

Minimum film thickness in elliptical contacts for different regimes of fluid-film lubrication

The film-parameter equations are provided for four fluid-film lubrication regimes found in elliptical contacts. These regimes are isoviscous-rigid; viscous-rigid; elastohydrodynamic of low-elastic-modulus materials, or isoviscous-elastic; and elastohydrodynamic, or viscous-elastic. The influence or lack of influence of elastic and viscous effects is the factor that distinguishes these regimes. The film-parameter equations for the respective regimes come from earlier theoretical studies by the authors on elastohydrodynamic and hydrodynamic lubrication of elliptical conjunctions. These equations are restated and the results are presented as a map of the lubrication regimes, with film-thickness contours on a log-log grid of the viscosity and elasticity parameters for five values of the ellipticity parameter. The results present a complete theoretical film-parameter solution for elliptical contacts in the four lubrication regimes.

Hamrock, B. J.↗
NASA NTRS2003

Quartz Microbalance Study of 400-angstrom Thick Films near the lambda Point

In a recent measurement we observed the thinning of an adsorbed helium film induced by the confinement of critical fluctuations a few millikelvin below the lambda point. A capacitor set-up was used to measure this Casimir effect. In this poster we will present our measurement of an adsorbed helium film of 400 angstroms near the lambda point with a quartz microbalance. For films this thick, we must take into account the non-linear dynamics of the shear waves in the fluid. In spite of the added complications, we were able to confirm the thinning of the film due to the Casimir effect and the onset of the superfluid transition. In addition, we observe a sharp anomaly at the bulk lambda point, most likely related to critical dissipation of the first sound. This work is carried out in collaboration with Rafael Garcia, Stephen Jordon and John Lazzaretti. This work is funded by NASA's Office of Biological and Physical Research under grant.

Chan, Moses H. W.↗
NASA NTRS2004

Implementation of a Thick-Film Composite Li-Ion Microcathode Using Carbon Nanotubes as the Conductive Filler

This paper describes the development of a thick-film microcathode for use in Li-ion microbatteries in order to provide increased power and energy per area. These cathodes take advantage of a composite porous electrode structure, utilizing carbon nanotubes (CNT) as the conductive filler. The use of carbon nanotubes was found to significantly reduce the measured resistance of the electrodes, increase active material accessibility, and improve electrode performance. In particular, the cycling and power performance of the thick-film cathodes was significantly improved, and the need for compression was eliminated. Cathode thickness and CNT content were optimized to maximize capacity and power performance. Power capability of >50 mW/sq cm (17 mA/sq cm) with discharge capacity of >0.17 mAh/sq cm was demonstrated. The feasibility of fabricating thick-film microcathodes capable of providing the power and capacity needed for use in autonomous microsensor systems was also demonstrated.

Lin, Qian↗
NASA NTRS1976

Discrete component bonding and thick film materials study

The bonding reliability of discrete capacitor chips bonded with solders and conductive epoxies was examined along with the thick film resistor materials consisting of iron oxide phosphate and vanadium oxide phosphates. It was concluded from the bonding reliability studies that none of the wide range of types of solders examined is capable of resisting failure during thermal cycling while the conductive epoxy gives substantially lower failure rates. The thick film resistor studies proved the feasibility of iron oxide phosphate resistor systems although some environmental sensitivity problems remain. One of these resistor compositions has inadvertently proven to be a candidate for thermistor applications because of the excellent control achieved upon the temperature coefficient of resistance. One new and potentially damaging phenomenon observed was the degradation of thick film conductors during the course of thermal cycling.

Kinser, D. L.↗