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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 253 records · Page 14

Development of an all-metal thick-film cost-effective metallization system for solar cells

Screened electrodes made from fluorocarbon activated copper paste and silver fluoride activated copper paste, tape adhesion and scratch tests were studied. Experiments were conducted with variations in past parameters, firing conditions, including gas ambients, furnace furniture, silicon surface and others. A liquid medium intended to provide transport during the carbon fluoride decomposition, is incorporated in the paste.

Ross, B.↗

Method and apparatus for convection control of metallic halide vapor density in a metallic halide laser

An apparatus is disclosed in which a reservoir containing copper chloride is heated so that the copper chloride is maintained in a liquid form. The apparatus includes a means for flowing a buffer gas (which in the exemplary embodiment is neon) over the liquid copper chloride to provide a mixture of copper chloride vapor and neon above the liquid copper chloride. A conduit provides fluid communication between the reservoir containing the copper chloride vapor/neon mixture and the laser. The copper chloride vapor density in the laser is related to the liquid copper chloride temperature and the neon flow rate through the reservoir. In accordance with a further feature of the exemplary embodiment, neon is also provided directly to the laser in order to provide a further means of controlling the copper chloride vapor density in the laser.

Pivirotto, T. J.↗

Development of an all-metal thick film cost effective metallization system for solar cells

Electrodes made with pastes produced under the previous contract were analyzed and compared with raw materials. A needle-like structure observed on the electroded solar cell was identified as eutectic copper-silicon, a phase considered to benefit the electrical and metallurgical properties of the contact. Electrodes made from copper fluorocarbon and copper silver fluoride also contained this phase but had poor adhesion. A liquid medium, intended to provide transport during carbon fluoride decomposition was incorporated into the paste resulting in better adhesion. The product survived preliminary environmental tests. A 2 cm by 2 cm solar cell made with fluorocarbon activated copper electrodes and gave 7% AMI efficiency (without AR coating). Both silver fluoride and fluorocarbon screened paste electrodes can be produced for approximately $0.04 per watt.

Ross, B.↗

Molecular orbital studies in oxidation: Sulfate formation and metal-metal oxide adhesion

The chemical mechanisms for sulfate formation from sodium chloride and sulfur trioxide, which is a product of jet fuel combustion was determined. Molten sodium sulfate leads to hot corrosion of the protective oxide layers on turbine blades. How yttrium dopants in nidkel-aluminum alloys used in turbine blades reduce the spalling rate of protective alumina films and enhance their adhesion was also determined. Two other fulfate mechanisms were deduced and structure of carbon monoxide on a clean chronium and clean platinum-titanium alloys surfaces was determined. All studies were by use of the atom superposition and electron delocalization molecular orbital (ASED-MO) theory. Seven studies were completed. Their titles and abstracts are given.

Anderson, A. B.↗

Behavior of ceramic particles at the solid-liquid metal interface in metal matrix composites

Directional solidification results were obtained in order to investigate particle behavior at the solid-liquid interface in Al-2 pct Mg (cellular interface) and Al-6.1 pct Ni (eutectic interface) alloys. It is found that particles can be entrapped in the solid if adequate solidification rates and temperature gradients are used. Model results showed critical velocity values slightly higher than those obtained experimentally.

Stefanescu, D. M.↗

Theoretical study of the effect of an AlGaAs double heterostructure on metal-semiconductor-metal photodetector performance

The sizing and efficiency of an aircraft is largely determined by the performance of its high-lift system. Subsonic civil transports most often use deployable multi-element airfoils to achieve the maximum-lift requirements for landing, as well as the high lift-to-drag ratios for take-off. However, these systems produce very complex flow fields which are not fully understood by the scientific community. In order to compete in today's market place, aircraft manufacturers will have to design better high-lift systems. Therefore, a more thorough understanding of the flows associated with these systems is desired. Flight and wind-tunnel experiments have been conducted on NASA Langley's B737-100 research aircraft to obtain detailed full-scale flow measurements on a multi-element high-lift system at various flight conditions. As part of this effort, computational aerodynamic tools are being used to provide preliminary flow-field information for instrumentation development, and to provide additional insight during the data analysis and interpretation process. The purpose of this paper is to demonstrate the ability and usefulness of a three-dimensional low-order potentialflow solver, PMARC, by comparing computational results with data obtained from 1/8 scale wind-tunnel tests. Overall, correlation of experimental and computational data reveals that the panel method is able to predict reasonably well the pressures of the aircraft's multi-element wing at several spanwise stations. PMARC's versatility and usefulness is also demonstrated by accurately predicting inviscid threedimensional flow features for several intricate geometrical regions.

Salem, Ali F.↗

An Investigation on the Use of a Laser Ablation Treatment on Metallic Surfaces and the Influence of Temperature on Fracture Toughness of Hybrid Co-Cured Metal-PMC Interfaces

Hybrid composite laminates that contain alternating layers of titanium alloys and carbon fabric reinforced polyimide matrix composites (PMC) are excellent candidates for light-weight, high-temperature structural materials for high-speed aerospace vehicles. The delamination resistance of the hybrid titanium-PMC interface is of crucial consideration for structural integrity during service. Here, we report the first investigations on the use of laser ablation in combination with sol-gel treatment technique on Ti/NiTi foil surfaces in co-cured hybrid polyimide matrix composite laminates. Mode-I and mode-II fracture toughness of the hybrid Ti/NiTi-PMC interface as a function of temperature were determined via experimental testing and finite element analysis.

Connell, John↗

Functionally Graded Metal-Metal Composite Structures

Methods and devices are disclosed for creating a multiple alloy composite structure by forming a three-dimensional arrangement of a first alloy composition in which the three-dimensional arrangement has a substantially open and continuous porosity. The three-dimensional arrangement of the first alloy composition is infused with at least a second alloy composition, where the second alloy composition comprises a shape memory alloy. The three-dimensional arrangement is consolidated into a fully dense solid structure, and the original shape of the second alloy composition is set for reversible transformation. Strain is applied to the fully dense solid structure, which is treated with heat so that the shape memory alloy composition becomes memory activated to recover the original shape. An interwoven composite of the first alloy composition and the memory-activated second alloy composition is thereby formed in the multiple alloy composite structure.

Brice, Craig A.↗