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Chevrel Phases as Potential Thermoelectric Materials

Scattering of phonons by loosely bound atoms reduces thermal conductivity. Crystalline phases of compounds of general composition (Cuw, CuxFey, or Tiz)Mo6Se8 [where w

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Alkyl Pyrocarbonate Electrolyte Additives for Li-Ion Cells

Beneficial properties of films that form on carbon anodes are enhanced. Alkyl pyrocarbonates have been found to be useful as electrolyte additives for improving the low-temperature performances of rechargeable lithium-ion electrochemical cells. The beneficial effects of these and other additives have been investigated, along with various electrolyte formulations, in continuing research directed toward extending the range of practical operating temperatures from the present lower limit of –20 °C down to –40 °C, and even lower if possible. This research at earlier stages was reported in a number of NASA Tech Briefs articles; namely, “Update on Electrolytes for Low-Temperature Lithium Cells” (NPO-20407), Vol. 24, No. 1, (January 2000), page 56; “Lithium Alkoxide Electrolyte Additives for Lithium-Ion Cells” (NPO-20607), Vol. 25, No. 6 (June 2001), page 52; “Aliphatic Ester Electrolyte Additives for Lithium-Ion Cells” (NPO-20601), Vol. 25, No. 6 (June 2001), page 53; and “Ethyl Methyl Carbonate as a Cosolvent for Lithium-Ion Cells” (NPO-20605), Vol. 25, No. 6 (June 2001), page 53.

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Fluorinated Alkyl Carbonates as Cosolvents in Li-Ion Cells

These solvents offer advantages with respect to performance and safety. Partially fluorinated alkyl carbonate liquid compounds have been found to be excellent electrolyte cosolvents for rechargeable lithium-ion electrochemical cells. The benefits afforded by these and other ingredients of electrolyte solutions in rechargeable Li-ion cells have been investigated in continuing research directed toward extending the range of practical operating temperatures of the cells (from +40 °C down to –40 °C, and possibly even as low as –60 °C). Fluorinated solvents were perceived to be especially attractive in that they will result in inherently safer cells, due to their low flammability. This research at earlier stages was reported in a number of previous NASA Tech Briefs articles; namely, “Update on Electrolytes for Low-Temperature Lithium Cells” (NPO-20407), Vol. 24, No. 1, (January 2000), page 56; “Lithium Alkoxide Electrolyte Additives for Lithium-Ion Cells” (NPO- 20607), Vol. 25, No. 6 (June, 2001), page 52; “Aliphatic Ester Electrolyte Additives for Lithium-Ion Cells” (NPO-20601), Vol. 25, No. 6 (June, 2001), page 53; “Ethyl Methyl Carbonate as a Cosolvent for Lithium-Ion Cells” (NPO-20605), Vol. 25, No. 6 (June, 2001), page 53; and “Alkyl Pyrocarbonate Electrolyte Additives for Li-Ion Cells” (NPO-20775), which precedes this article.

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Diaminobenzoquinones as Corrosion-Inhibiting Additives

Protection can extend beyond edges of paints to adjacent unpainted areas. Non-polymeric N,N´-di-N-hydrocarbyl- 2,5-diamino-1,4-benzoquinones (where the hydrocarbyl substituents are alkyl or aryl) have been found to be useful as corrosion-inhibiting additives for paints and other conventional coating materials that are applied to steel and other metals. Prior coating additives made from reactions of benzoquinones with diamines are polymeric. Such polymers are expensive and difficult to make. Moreover, being polymers, they cannot diffuse much and hence are believed not to protect uncoated areas of metal against corrosion. In contrast, when used in proper concentrations, the present non-polymeric diaminobenzoquinones provide enhanced protection that extends somewhat from the edges of coats into uncoated areas — an important advantage in situations in which there are imperfections (e.g., gaps, scratches, and blisters) in coats of paint.

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Nanolaminate Mirrors With Integral Figure-Control Actuators

A report discusses the development of thin-shell curved mirrors comprised of metallic multilayer nanolaminate substrates that contain integral inplane actuators for controlling surface figure with micron-level precision. These mirrors, intended for incorporation into scientific imaging systems, would have areal mass densities of

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Flat Membrane Device for Dehumidification of Air

Water vapor is not condensed; instead, it is transported to vacuum. A device based on the transport of water through a membrane to a vacuum has been developed for dehumidifying a stream of air in the life-support system of a spacecraft or space suit. The device could also be adapted to terrestrial use in dehumidification of air in an air-conditioning stream or drying of air or another gas in a chemical processing stream. The design of this device is an advance in that it decreases (relative to prior designs) the weight, power consumption, and volume of the dehumidifier in the life-support system or other gas-circulation system in which the device is used. In the case of a spacecraft or space suit, the design thereby also increases safety and health margins. Although the membranes in the device must be replaced periodically and a vacuum source is essential for its operation, no other dehumidifier works as well in a spacecraft or space suit.

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Protective Solid Electrolyte Films for Thin Li-Ion Cells

These films would simplify fabrication and afford greater flexibility in design. Thin films of Li2CO3 are under consideration for use as passivating layers between electrodes and solid electrolytes in advanced thin-film lithium-ion electrochemical cells. By suppressing undesired chemical reactions as described below, the Li2CO3 films could help to prolong the shelf lives, increase the specific energies, and simplify the fabrication of the cells. Batteries comprising one or more cells of this type could be used as sources of power in such miniature electronic circuits as those in “smart” cards, implantable electronic medical devices, sensors, portable communication devices, and hand-held computers.

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