Materials

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.

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Multifunctional Deployment Hinges Rigidified by Ultraviolet

These hinges provide both structural support and electrical connections.

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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.

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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.

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Formulating Precursors for Coating Metals and Ceramics

A protocol has been devised for formulating low-vapor-pressure precursors for protective and conversion coatings on metallic and ceramic substrates.

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Making Macroscopic Assemblies of Aligned Carbon Nanotubes

Nanotubes are aligned and manipulated with the help of magnetic and/or electric fields. A method of aligning and assembling single-wall carbon nanotubes (SWNTs) to fabricate macroscopic structures has been invented. The method entails suspending SWNTs in a fluid, orienting the SWNTs by use of a magnetic and/or electric field, and then removing the aligned SWNTs from suspension in such a way as to assemble them while maintaining the alignment.

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Using Iron To Treat Chlorohydrocarbon Contaminated Soil

Prompt chemical remediation is followed by longer-term enhanced bioremediation. A method of in situ remediation of soil contaminated with chlorinated hydrocarbon solvents involves injection of nanometer-size iron particles. This method should not be confused with a similar method, involving injection of emulsified iron particles, reported in “Treatment To Destroy Chlorohydrocarbon Liquids in the Ground” (KSC-12246), NASA Tech Briefs, Vol. 27, No. 6 (June 2003), page 56. Like that method, this method is implemented in a process that is safe, yields environmentally benign end products, takes less time and costs less than do traditional pump-and-treat processes, and is both less expensive and less environmentally disruptive than are cleanup processes that involve excavation, trans-port to facilities for incineration or other treatment, and reburial in landfills.

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