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Results for “effective conductivity”

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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Aerodynamic results of support system interference effects tests conducted in NASA/ARC 6 by 6-foot supersonic wind tunnel using an 0.015-scale model of the configuration 14OA/B SSV orbiter (OA59), volume 1

An experimental aerodynamic investigation was conducted in the NASA/ARC 6- by 6-foot supersonic wind tunnel on an 0.015-scale configuration 140A/B SSV Orbiter model. The primary objective was to determine the extent aerodynamic simulation is compromised by sting base mounting with MPS nozzles removed. Both a conventional sting (through the base) and an alternate model mounting system were utilized. The alternate mounting system consisted of a non-metric blade strut, which approximated the vertical tail and entered the model through the upper aft section of its fuselage. The model was tested both in and out of the presence of a dummy sting with and without MPS nozzles when on the alternate mounting system. Data were obtained at Mach numbers from 0.6 through 2.0, a Reynolds number of 2.5 million per foot, angles of attack from -4 through 14 degrees, angles of sideslip from -15 through 15 degrees, elevon deflections of 0 and 15 degrees, and bodyflap deflections of -11.7, 0, and 16.3 degrees.

Campbell, J. H., II↗
NASA NTRS1978

Ultraviolet effects on conductive coated coverglasses

Experiments on the International Sun-Earth Explorer required that the outer surface of the spacecraft be conductive. For the solar panels this was accomplished by using solar cell coverglasses coated with indium-oxide and interconnected to ground. This paper presents results of ultraviolet tests performed as part of the overall qualification program for cell assemblies using these coverglasses. The samples were exposed under vacuum at a controlled temperature to 5000 equivalent sun hours. Coverglass transmission curves and cell assembly current-voltage curves were measured before and after the test. Observed degradations were of the order of 1 percent more for conductively coated coverglasses than for coverglasses without conductive coatings.

Bass, J. A.↗
NASA NTRS1978

Ultraviolet effects on conductive coated coverglasses

Experiments on the International Sun-Earth Explorer required that the outer surface of the spacecraft be conductive. For the solar panels this was accomplished by using solar cell coverglasses coated with indium-oxide and interconnected to ground. This paper presents results of ultraviolet tests performed as part of the overall qualification program for cell assemblies using these coverglasses. The samples were exposed under vacuum at a controlled temperature to 5000 equivalent sun hours. Coverglass transmission curves and cell assembly current-voltage curves were measured before and after the test. Observed degradations were of the order of 1 percent more for conductively coated coverglasses than for coverglasses without conductive coatings.

Bass, J. A.↗
NASA NTRS1985

Effect of conductivity and concentration on the sample stream in the transverse axis of a continuous flow electrophoresis chamber

The resolution of continuous flow electrophoresis systems is generally measured by the spread of the sample bands in the direction of the electrophoretic migration. This paper evaluates the cross section of the sample bands in the plane perpendicular to the flow and shows that the spread in the direction perpendicular to the migration increased significantly with the applied electric field. Concentrated samples of monodisperse latex particles and vinyltoluene T-butylstyrene particles in sample buffers of different electrical conductivities were used to map the shape of the sample bands relative to the zero electric field case. As the electric field was applied, the sample band spread from an initial diameter of only one-third the chamber thickness until it approached the chamber walls where electroosmosis significantly reduced the resolution of separation. It can be shown, however, that it is possible to minimize these distortions by careful sample preparation and experiment design.

Miller, Teresa Y.↗
NASA NTRS1991

Effective thermal conductivity of composites with fibre-matrix debonding

Debonding of the fiber-matrix interface is a major cause for the degradation of the mechanical properties and the loss of thermal conductivity of fiber-reinforced composites. This paper discusses two analytical approaches for modeling the thermal conduction problem of composites. One is based on the concept of modeling the thermal barrier by an equivalent heat transfer coefficient at the fiber-matrix interface, as described by Hasselman and Johnson (1987) and Benveniste and Miloh (1986). The other approach, suggested by Hatta and Taya (1986), is by treating a composite with debonded interface as a coated-fiber composite. The major advantage of the latter aproach is that the thickness of the fiber coating can be realistically modeled depending upon the extent of degradation of the composite with the thermal conductivity of the coating as that of air.

Fadale, T. D.↗
NASA NTRS1992

Heat transfer in vertical Bridgman growth of oxides - Effects of conduction, convection, and internal radiation

In the present investigation of crystalline phase internal radiation and heat conduction during the vertical Bridgman growth of a YAG-like oxide crystal, where transport through the melt is dominated by convection and conduction, heat is also noted to be conducted through ampoule walls via natural convection and enclosure radiation. The results of a quasi-steady-state axisymmetric Galerkin FEM indicate that heat transfer through the system is powerfully affected by the optical absorption coefficient of the crystal. The coupling of internal radiation through the crystal with conduction through the ampoule walls promotes melt/crystal interface shapes that are highly reflected near the ampoule wall.

Brandon, S.↗
DOE OSTI2021

Ion‐Conducting, Electron‐Blocking Layer for High‐Performance Solid Electrolytes

Lithium metal batteries bring greater promise for energy density, often relying on solid‐state electrolytes to meet critical benchmarks. However, Li dendrite formation is a prevailing problem that limits the cycle life and Coulombic efficiency of solid‐state Li metal batteries. For the first time, a thin (<100 nm) layer of electronically insulating, ionically conducting lithium phosphorus oxynitride (LiPON) is applied using atomic layer deposition between a Li anode and garnet Li 7 La 3 Zr 2 O 12 (LLZO). The performance of a conformal LiPON layer as an electron barrier in symmetric Li‐LLZO cells is observed through potential step chronoamperometry, galvanostatic cycling, electron microscopy, and various spectroscopic techniques. The LiPON‐coated LLZO achieves 100 times lower electronic conductance than LLZO alone. Cycling carried out at 0.1 mA cm −2 for 100 cycles demonstrates that suppression of electron pathways into the bulk solid electrolyte improves the cycle life of a lithium metal cell. These findings suggest an electronic conductivity effect in solid‐state electrolytes. A strategy is demonstrated to design thin‐film (LiPON)‐modulated bulk solid‐state electrolytes (LLZO) capable of maintaining high ionic conductivity and electrochemical stability while reducing the effective electronic conductivity, which results in significantly decreased dendrite formation, improved cycle life, and greater interfacial integrity between the electrolyte and a Li anode.

Hitz, Emily M.↗
NASA NTRSDate not supplied

Ceramic Aerogels for Space High Temperature Applications

Aerogels play an important role in thermal insulation systems for space application. They are light-weight materials with low thermal conductivity, effectively suppressing heat transfer by conduction, convection, and radiation. Silica aerogels sinter at 600°C and polymer aerogels generally decompose below 450°C, meaning they are not suitable for high temperature insulation needs. This presentation will detail aluminosilicate aerogels, YSZ aerogel, and YbSZ aerogels that we have designed and developed for space high temperature thermal insulation applications. Aluminosilicate aerogels can be used up to 1100°C without losing the mesoporous structure, whereas YSZ aerogels and YbSZ aerogels can be used up to 1000°C. With further modification using SiO 2 coatings, they also can be used at 1100°C by maintaining the mesoporous structure. Ceramic felts, mats, or papers were used to reinforce those aerogels in composites that do not flake and can be flexible. Hydrophobicity was also achieved by manipulation of the surface of those aerogels and their composites.

Haiquan Guo↗