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Reactive Additives for Phenylethynyl-Containing Resins

Processability is improved. Phenylethynyl containing reactive additive (PERA) compounds and mixtures have been found to be useful for improving the processability of oligomers, polymers, cooligomers, and copolymers that contain phenylethynyl groups. The additives can be incorporated in different forms:

Posted in: Materials, Briefs

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Multicomponent, Rare-Earth-Doped Thermal-Barrier Coatings

Thermal conductivities are reduced while maximum use temperatures are increased. Multicomponent, rare-earth-doped, perovskite-type thermal-barrier coating materials have been developed in an effort to obtain lower thermal conductivity, greater phase stability, and greater high-temperature capability, relative to those of the prior thermal-barrier coating material of choice, which is yttriapartially stabilized zirconia. As used here, “thermal-barrier coatings” (TBCs) denotes thin ceramic layers used to insulate air-cooled metallic components of heat engines (e.g., gas turbines) from hot gases. These layers are generally fabricated by plasma spraying or physical vapor deposition of the TBC materials onto the metal components.

Posted in: Materials, Briefs

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Development of Carbon-Nanotube/Polymer Composites

A report presents a short discussion of one company’s effort to develop composites of carbon nanotubes in epoxy and other polymer matrices.

Posted in: Materials, Briefs

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Modifications of a Composite-Material Combustion Chamber

Two short reports discuss modifications of a small, lightweight combustion chamber that comprises a carbon/carbon composite outer shell and an iridium/rhenium inner liner. The first report discusses chamber design modifications made as results of hot-fire tests and post-test characterization. The modifications were intended to serve a variety of purposes, including improving fabrication, reducing thermal-expansion mismatch stresses, increasing strength-to-weight ratios of some components, and improving cooling of some components. The second report discusses (1) the origin of stress in the mismatch between the thermal expansions of the Ir/Re liner and a niobium sleeve and flange attached to the carbon/carbon shell and (2) a modification intended to relieve the stress. The modification involves the redesign of an inlet connection to incorporate a compressible seal between the Ir/Re liner and the Nb flange. A nickel alloy was selected as the seal material on the basis of its thermal-expansion properties and its ability to withstand the anticipated stresses, including the greatest stresses caused by the high temperatures to be used in brazing during fabrication.

Posted in: Materials, Briefs

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Multifunctional Deployment Hinges Rigidified by Ultraviolet

These hinges provide both structural support and electrical connections.

Posted in: Materials, Briefs, TSP

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Nanostructured MnO2-Based Cathodes for Li-Ion/Polymer Cells

Experiments show promise for increasing energy densities. Nanostructured MnO2-based cathodes for Li-ion/polymer electrochemical cells have been investigated in a continuing effort to develop safe, highenergy-density, reliable, low-toxicity, rechargeable batteries for a variety of applications in NASA programs and in mass-produced commercial electronic equipment. Whereas the energy densities of state-of-the-art lithium-ion/polymer batteries range from 150 to 175 W·h/kg, the goal of this effort is to increase the typical energy density to about 250 W·h/kg. It is also expected that an incidental benefit of this effort will be increases in power densities because the distances over which Li ions must diffuse through nanostructured cathode materials are smaller than those through solid bulk cathode materials.

Posted in: Materials, Briefs

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Multi-Layer Laminated Thin Films for Inflatable Structures

Laminates offer advantages over equal-thickness monolayer sheets. Special-purpose balloons and other inflatable structures would be constructed as flexible laminates of multiple thin polymeric films interspersed with layers of adhesive, according to a proposal. In the original intended application, the laminate would serve as the envelope of the Titan Aerobot — a proposed robotic airship for exploring Titan (one of the moons of Saturn). Potential terrestrial applications for such flexible laminates could include blimps and sails.

Posted in: Materials, Briefs, TSP

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