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Results for “backing layers”

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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Chalcogen back surface field layer

Kesterite photovoltaic devices having a back surface field layer are provided. In one aspect, a method of forming a photovoltaic device includes: forming a complete photovoltaic device having a substrate, an electrically conductive layer on the substrate, an absorber layer on the electrically conductive layer, a buffer layer on the absorber layer, and a transparent front contact on the buffer layer; removing the substrate and the electrically conductive layer from the complete photovoltaic device to expose a backside surface of the absorber layer; forming a passivating layer on the backside surface of the absorber layer; and forming a high work function back contact on the passivating layer. A photovoltaic device having a passivating layer is also provided.

14 SOLAR ENERGY↗
NASA NTRS1964

Variable-transparency wall regulates temperatures of structures

An effective temperature regulating wall consists of one layer /e.g., one of the paraffins/ relatively opaque to thermal radiation in the solid state and transparent to it in the molten state and placed between two transparent layers. A mirror coating is applied to back layer.

Osullivan, W. J., Jr.↗
NASA NTRS2005

Secondary polymer layered impregnated tile

A low density organic polymer impregnated preformed fibrous ceramic article includes a plurality of layers. A front layer includes ceramic fibers or carbon fibers or combinations of ceramic fibers and carbon fibers, and is impregnated with an effective amount of at least one organic polymer. A middle layer includes polymer impregnated ceramic fibers. A back layer includes ceramic fibers or carbon fibers or combinations of ceramic fibers and carbon fibers, and is impregnated with an effective amount of at least one low temperature pyrolyzing organic polymer capable of decomposing without depositing residues.

Huy K Tran↗
NASA NTRS2005

Secondary polymer layered impregnated tile

A low density organic polymer impregnated preformed fibrous ceramic article includes a plurality of layers. A front layer includes ceramic fibers or carbon fibers or combinations of ceramic fibers and carbon fibers, and is impregnated with an effective amount of at least one organic polymer. A middle layer includes polymer impregnated ceramic fibers. A back layer includes ceramic fibers or carbon fibers or combinations of ceramic fibers and carbon fibers, and is impregnated with an effective amount of at least one low temperature pyrolyzing organic polymer capable of decomposing without depositing residues.

Tran, Huy K.↗
NASA NTRS2004

Flexible Shields for Protecting Spacecraft Against Debris

A report presents the concept of Flexshield a class of versatile, lightweight, flexible shields for protecting spacecraft against impacts by small meteors and orbiting debris. The Flexshield concept incorporates elements of, but goes beyond, prior spacecraft-shielding concepts, including those of Whipple shields and, more recently, multi-shock shields and multi-shock blankets. A shield of the Flexshield type includes multiple outer layers (called bumpers in the art) made, variously, of advanced ceramic and/or polymeric fibers spaced apart from each other by a lightweight foam. As in prior such shields, the bumpers serve to shock an impinging hypervelocity particle, causing it to disintegrate vaporize, and spread out over a larger area so that it can be stopped by an innermost layer (back sheet). The flexibility of the fabric layers and compressibility of the foam make it possible to compress and fold the shield for transport, then deploy the shield for use. The shield can be attached to a spacecraft by use of snaps, hook-and-pile patches, or other devices. The shield can also contain multilayer insulation material, so that it provides some thermal protection in addition to mechanical protection.

Christiansen, Eric L.↗
NASA NTRS1993

Hypervelocity particle penetration in multi-layered thermal blankets

Micrometeoroid and related hypervelocity particle impacts into 0.04-sq m samples cut from Scheldahl G411500 thermal blankets (STB) covering trays D05 and D07 in the NASA-LDEF satellite are characterized in detail. These impacts usually produced unique penetration features that generally consist of a delamination zone extending tens of penetration-hole diameters, separating the Teflon layer from the silver/Inconel film and the paint backing layers. When viewed from the space-facing side, the penetration holes are usually surrounded by rings or concentric halos within the delamination zone and radial cracks extending from the ejecta-rim surrounding the hole to the edge of the delamination zone. The phenomena responsible for the formation of these features are examined.

Liu, Jean↗
NASA NTRS2000

HSPES membrane electrode assembly

An improved fuel cell electrode, as well as fuel cells and membrane electrode assemblies that include such an electrode, in which the electrode includes a backing layer having a sintered layer thereon, and a non-sintered free-catalyst layer. The invention also features a method of forming the electrode by sintering a backing material with a catalyst material and then applying a free-catalyst layer.

Kindler, Andrew↗
DOE OSTI2015

Rectification and tunneling effects enabled by Al{sub 2}O{sub 3} atomic layer deposited on back contact of CdTe solar cells

Atomic layer deposition (ALD) of Aluminum oxide (Al{sub 2}O{sub 3}) is employed to optimize the back contact of thin film CdTe solar cells. Al{sub 2}O{sub 3} layers with a thickness of 0.5 nm to 5 nm are tested, and an improved efficiency, up to 12.1%, is found with the 1 nm Al{sub 2}O{sub 3} deposition, compared with the efficiency of 10.7% without Al{sub 2}O{sub 3} modification. The performance improvement stems from the surface modification that optimizes the rectification and tunneling of back contact. The current-voltage analysis indicates that the back contact with 1 nm Al{sub 2}O{sub 3} maintains large tunneling leakage current and improves the filled factor of CdTe cells through the rectification effect. XPS and capacitance-voltage electrical measurement analysis show that the ALD-Al{sub 2}O{sub 3} modification layer features a desired low-density of interface state of 8 × 10{sup 10 }cm{sup −2} by estimation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1991

Making Ultrathin Solar Cells

Process produces extremely thin silicon solar cells - only 50 micrometers or less in thickness. Electrons and holes have less opportunity to recombine before collected at cell surfaces. Efficiency higher and because volume of silicon small, less chance of radiation damage in new cells. Initial steps carried out at normal thickness to reduce breakage and avoid extra cost of special handling. Cells then thinned mechanically and chemically. Final cell includes reflective layer on back surface. Layer bounces unabsorbed light back into bulk silicon so it absorbs and produces useful electrical output.

Cogan, George W.↗
NASA NTRS1996

Effect of variations in the doping profiles on the properties of doped multiple quantum well avalanche photodiodes

The purpose of this study is to use both theoretical and experimental evidence to determine the impact of doping imbalance and symmetry on the physical and electrical characteristics of doped multiple quantum well avalanche photodiodes (APD). Theoretical models have been developed to calculate the electric field valence and conduction bands, capacitance-voltage (CV), and carrier concentration versus depletion depth profiles. The models showed a strong correlation between the p- and n-doping balance inside the GaAs wells and the number of depleted stages and breakdown voltage of the APD. A periodic doping imbalance in the wells has been shown to result in a gradual increase (or decrease) in the electric field profile throughout the device which gave rise to partially depleted devices at low bias. The MQW APD structures that we modeled consisted of a 1 micron top p(+)-doped (3 x 10(exp 18) cm(exp -3)) GaAs layer followed by a 1 micron region of alternating layers of GaAs (500 A) and Al(0.42)Ga(0.58)As (500 A), and a 1 micron n(+) back layer (3 x 10(exp 18) cm(exp -3)). The GaAs wells were doped with p-i-n layers placed at the center of each well. The simulation results showed that in an APD with nine doped wells, and where the 50 A p-doped layer is off by 10% (p = 1.65 x 10(exp 18) cm(exp -3), n = 1.5 x 10(exp 18) cm(exp -3)), almost half of the MQW stages were shown to be undepleted at low bias which was a result of a reduction in the electric field near the p(+) cap layer by over 50% from its value in the balanced structure. Experimental CV and IV data on similar MBE grown MQW structures have shown very similar depletion and breakdown characteristics. The models have enabled us to better interpret our experimental data and to determine both the extent of the doping imbalances in the devices as well as the overall p- or n-type doping characteristics of the structures.

Menkara, H. M.↗
NASA NTRS2016

Multilayer Active Shell Mirrors for Space Telescopes

A novel active mirror technology based on carbon fiber reinforced polymer (CFRP) substrates and replication techniques has been developed. Multiple additional layers are implemented into the design serving various functions. Nanolaminate metal films are used to provide a high quality reflective front surface. A backing layer of thin active material is implemented to provide the surface-parallel actuation scheme. Printed electronics are used to create a custom electrode pattern and flexible routing layer. Mirrors of this design are thin (< 1.0 mm), lightweight (2.7 kg/m2 ), and have large actuation capabilities. These capabilities, along with the associated manufacturing processes, represent a significant change in design compared to traditional optics. Such mirrors could be used as lightweight primaries for small CubeSat-based telescopes or as meter-class segments for future large aperture observatories. Multiple mirrors can be produced under identical conditions enabling a substantial reduction in manufacturing cost and complexity. An overview of the mirror design and manufacturing processes is presented. Predictions on the actuation performance have been made through finite element simulations demonstrating correct abilities on the order of 250−300× for astigmatic modes with only 41 independent actuators. A description of the custom metrology system used to characterize the active mirrors is also presented. The system is based on a Reverse Hartmann test and can accommodate extremely large deviations in mirror figure (> 100 µm PV) down to sub-micron precision. The system has been validated against several traditional techniques including photogrammetry and interferometry. The mirror performance has been characterized using this system, as well as closed-loop figure correction experiments on 150 mm dia. prototypes. The mirrors have demonstrated post-correction figure accuracies of 200 nm RMS (two dead actuators limiting performance).

Reverse Hartmann↗
DOE OSTI2021

Methods for fabricating thin film III-V compound solar cell

The present invention utilizes epitaxial lift-off in which a sacrificial layer is included in the epitaxial growth between the substrate and a thin film III-V compound solar cell. To provide support for the thin film III-V compound solar cell in absence of the substrate, a backing layer is applied to a surface of the thin film III-V compound solar cell before it is separated from the substrate. To separate the thin film III-V compound solar cell from the substrate, the sacrificial layer is removed as part of the epitaxial lift-off. Once the substrate is separated from the thin film III-V compound solar cell, the substrate may then be reused in the formation of another thin film III-V compound solar cell.

Pan, Noren↗
DOE OSTI2015

Material identification in x-ray microscopy and micro CT using multi-layer, multi-color scintillation detectors

We demonstrate that a dual-layer, dual-color scintillator construct for microscopic CT, originally proposed to increase sensitivity in synchrotron imaging, can also be used to perform material quantification and classification when coupled with polychromatic illumination. We consider two different approaches to data handling: (1) a data-domain material decomposition whose estimation performance can be characterized by the Cramer-Rao lower bound formalism but which requires careful calibration and (2) an image-domain material classification approach that is more robust to calibration errors. The data-domain analysis indicates that useful levels of SNR (>5) could be achieved in one second or less at typical bending magnet fluxes for relatively large amounts of contrast (several mm path length, such as in a fluid flow experiment) and at typical undulator fluxes for small amount of contrast (tens of microns path length, such as an angiography experiment). The tools introduced could of course be used to study and optimize parameters for a wider range of potential applications. The image domain approach was analyzed in terms of its ability to distinguish different elemental stains by characterizing the angle between the lines traced out in a two-dimensional space of effective attenuation coefficient in the front and back layer images. As a result, this approach was implemented at a synchrotron and the results were consistent with simulation predictions.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Experimental Study of High-Velocity Projectile Impact Welding

The purpose of this study is to investigate the effect of various parameters on the welding process with high-velocity projectiles. For carrying out Impact Spot Welding tests, a single stage compressed gas gun impact test facility was used to launch flat- and conical-nosed projectiles within the velocity range from 100 to 150 m/s and performed. Different types of materials such as steel, copper, brass, and aluminum alloy were used. In the present experimental study, the steel plate with a thickness of 4 mm was considered as a back layer and the other plates made of copper, brass, and aluminum alloy were considered as front layers. Different gaps of 0.1, 0.2, and 0.5 mm were considered between the layers. The shape of the welded interface was studied by Scanning Electron Microscopy (SEM). The depth of penetration in the specimen and the kinetic energy of the projectiles were calculated. The experimental results showed that a complete bonding has occurred in the collision zone, especially in the central areas.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Spin-pseudospin intertwined excitation at the ν = 1 bilayer quantum Hall state investigated by nuclear-spin relaxation

We investigate the electron spin degree of freedom at the imbalanced density bilayer ν = 1 quantum Hall states using the resistively detected nuclear-spin-lattice relaxation rate 1/T{sub 1}. Our measurements reveal a continuous change in 1/T{sub 1} for σ = 1 to 0, suggesting that the balanced density ν = 1 state also exhibits electron-spin fluctuations. Moreover, the value of 1/T{sub 1} in the back layer (the layer from which electrons are transferred to the front layer) increases at intermediate density imbalance states. This indicates that the low-energy electron-spin mode, similar to a mode observed in Skyrmion crystals, might extend across the two layers.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1982

Superabsorbent Multilayer Fabric

Material contains gel-forming polymer and copolymer that absorb from 70 to 200 times their weight of liquid. Superabsorbent Polymer and Copolymer form gels to bind and retain liquid in multiply fabric. Until reaction between liquid and absorbent masses forms gel, backing layer retains liquids within fabric; also allows material to "breathe." Possible applications include baby diapers, female hygiene napkins, and hospital bedpads. Might also have uses in improvement of dry soil.

Coreale, J. V.↗
NASA NTRS1995

A Neural Network/Acoustic Emission Analysis of Impact Damaged Graphite/Epoxy Pressure Vessels

Acoustic emission (AE) signal analysis has been used to measure the effects of impact damage on burst pressure in 5.75 inch diameter, inert propellant filled, filament wound pressure vessels. The AE data were collected from fifteen graphite/epoxy pressure vessels featuring five damage states and three resin systems. A burst pressure prediction model was developed by correlating the AE amplitude (frequency) distribution, generated during the first pressure ramp to 800 psig (approximately 25% of the average expected burst pressure for an undamaged vessel) to known burst pressures using a four layered back propagation neural network. The neural network, trained on three vessels from each resin system, was able to predict burst pressures with a worst case error of 5.7% for the entire fifteen bottle set.

Walker, James L.↗