Materials & Coatings

Predicting Properties of Unidirectional-Nanofiber Composites

A theory for predicting mechanical, thermal, electrical, and other properties of unidirectional- nanofiber/matrix composite materials is based on the prior theory of micromechanics of composite materials. In the development of the present theory, the prior theory of micromechanics was extended, through progressive substructuring, to the level of detail of a nanoscale slice of a nanofiber. All the governing equations were then formulated at this level.

Posted in: Briefs

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Heterogeneous Superconducting Low-Noise Sensing Coils

Electrically superconductive outer layers are supported by highly thermally conductive skeletons. A heterogeneous material construction has been devised for sensing coils of super-conducting quantum interference device (SQUID) magnetometers that are subject to a combination of requirements peculiar to some advanced applications, notably including low-field magnetic resonance imaging for medical diagnosis. The requirements in question are the following:

Posted in: Briefs, TSP

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Progress Toward Making Epoxy/Carbon-Nanotube Composites

A modicum of progress has been made in an effort to exploit single-walled carbon nanotubes as fibers in epoxy-matrix/fiber composite materials. Two main obstacles to such use of carbon nanotubes are the following: (1) bare nanotubes are not soluble in epoxy resins and so they tend to agglomerate instead of becoming dispersed as desired; and (2) because of lack of affinity between nanotubes and epoxy matrices, there is insufficient transfer of mechanical loads between the nanotubes and the matrices.

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Electrocatalytic Reduction of Carbon Dioxide to Methane

A room-temperature electrocatalytic process that effects the overall chemical reaction CO2 + 2H2O → CH4 + 2O2 has been investigated as a means of removing carbon dioxide from air and restoring oxygen to the air. The process was originally intended for use in a spacecraft life-support system, in which the methane would be vented to outer space. The process may also have potential utility in terrestrial applications in which either or both of the methane and oxygen produced might be utilized or vented to the atmosphere.

Posted in: Briefs, TSP

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Oxide Fiber Cathode Materials for Rechargeable Lithium Cells

LiCoO2 and LiNiO2 fibers have been investigated as alternatives to LiCoO2 and LiNiO2 powders used as lithium-intercalation compounds in cathodes of rechargeable lithium-ion electrochemical cells. In making such a cathode, LiCoO2 or LiNiO2 powder is mixed with a binder [e.g., poly(vinylidene fluoride)] and an electrically conductive additive (usually carbon) and the mixture is pressed to form a disk. The binder and conductive additive contribute weight and volume, reducing the specific energy and energy density, respectively.

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Method of Cross-Linking Aerogels Using a One-Pot Reaction Scheme

A document discusses a new, simplified method for cross-linking silica and other oxide aerogels, with a polymeric material to increase strength of such materials without adversely affecting porosity or low density. The usual process is long and arduous, requiring multiple washing and soaking steps to infiltrate oxide with the polymer precursor after gelation. Additionally, diffusion problems can result in aerogel monoliths that are not uniformly cross-linked.

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Coated Glass for Transparent Heating Elements

This coated glass can be used in high-humidity and high-altitude applications such as architectural and aircraft windows. Applying an electric current to specially coated glass results in radiant heat energy. This process creates a transparent heating element with near- uniform surface temperatures. Manufacturing the heating element requires an ordinary pane of float glass. A fluorine-doped tin oxide coating (SnO2:F) measuring 0.25 micron thick is applied to one surface of the glass during fabrication. The coating conducts electricity, has a very tightly controlled resistance, has no appreciable color or structure, and is quite transparent. The coating has low emissivity properties that help contribute to the efficiency of the heated glass.

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