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Cleaning Carbon Nanotubes by Use of Mild Oxygen Plasmas

Mildness of the plasmas is the key to cleaning without destruction. Experiments have shown that it is feasible to use oxygen radicals (specifically, monatomic oxygen) from mild oxygen plasmas to remove organic contaminants and chemical fabrication residues from the surfaces of carbon nanotubes (CNTs) and metal/CNT interfaces. A capability for such cleaning is essential to the manufacture of reproducible CNT-based electronic devices.

Posted in: Materials, Briefs, TSP

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Designing Cure Cycles for Matrix/Fiber Composite Parts

This methodology enables production of void-free laminates. A methodology has been devised for designing cure cycles to be used in the fabrication of matrix/fiber composite parts (including laminated parts). As used here, “cure cycles” signifies schedules of elevated temperature and pressure as functions of time, chosen to obtain desired rates of chemical conversion of initially chemically reactive matrix materials and to consolidate the matrix and fiber materials into dense solids. Heretofore, cure cycles have been designed following an empirical, trial-and-error approach, which cannot be relied upon to yield optimum results. In contrast, the present methodology makes it possible to design an optimum or nearly optimum cure cycle for a specific application.

Posted in: Materials, Briefs

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Combustion Synthesis of Ca3(PO4)2 Net-Shape Surgical Implants

More-biocompatible materials are produced in fewer processing steps. ASelf-propagating high-temperature combustion synthesis (SHS) is the basis of a method of making components of porous tricalcium phosphate [Ca3(PO4)2] and related compounds in net sizes and shapes for use as surgical implants that are compatible with bone. Ca3(PO4)2-based materials are among those preferred for use in orthopedic, restorative, and reconstructive surgery. As explained below, the SHS method offers advantages over prior methods of manufacturing Ca3(PO4)2-based surgical implants.

Posted in: Materials, Briefs, TSP

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Thermally Stable Piezoelectric and Pyroelectric Polymers

Neither mechanical nor solvent treatment is necessary for orientation of polymer molecules. A class of thermally stable piezoelectric and pyroelectric polymers, and an improved method of making them, have been invented. These polymers can be used as substrates for a wide variety of electro- mechanical transducers, sensors, and actuators.

Posted in: Materials, Briefs

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MoO3 Cathodes for High-Temperature Lithium Thin-Film Cells

Cycle lives of these cathodes exceed those of LiCoO2 and LiMn2O4 cathodes. MoO3 has shown promise as a cathode material that can extend the upper limit of operating temperature of rechargeable lithium thin-film electrochemical cells. Cells of this type are undergoing development for use as energy sources in cellular telephones, wireless medical sensors, and other, similarly sized portable electronic products. The LiCoO2 and LiMn2O4 cathodes heretofore used in these cells exhibit outstanding cycle lives (of the order of hundreds of thousands of cycles) at room temperature, but operation at higher temperatures reduces their cycle lives substantially: for example, at a temperature of 150 °C, cells containing LiCoO2 cathodes lose half their capacities in 100 charge/discharge cycles.

Posted in: Materials, Briefs, TSP

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Ion-Conducting Organic/Inorganic Polymers

Properties can be tailored through a choice of starting alkoxysilane and diamine ingredients. Ion-conducting polymers that are hybrids of organic and inorganic moieties and that are suitable for forming into solidelectrolyte membranes have been invented in an effort to improve upon the polymeric materials that have been used previously for such membranes. Examples of the prior materials include perfluorosulfonic acid-based formulations, polybenzimidazoles, sulfonated polyetherketone, sulfonated naphthalenic polyimides, and polyethylene oxide (PEO)-based formulations. Relative to the prior materials, the polymers of the present invention offer greater dimensional stability, greater ease of formation into mechanically resilient films, and acceptably high ionic conductivities over wider temperature ranges. Devices in which films made of these ion-conducting organic/ inorganic polymers could be used include fuel cells, lithium batteries, chemical sensors, electrochemical capacitors, electrochromic windows and display devices, and analog memory devices.

Posted in: Materials, Briefs, TSP

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Lithium Dinitramide as an Additive in Lithium Power Cells

This inorganic additive appears to act as a superior SEI promoter. Lithium dinitramide, LiN(NO2)2 has shown promise as an additive to nonaqueous electrolytes in rechargeable and non-rechargeable lithium-ion-based electrochemical power cells. Such non-aqueous electrolytes consist of lithium salts dissolved in mixtures of organic ethers, esters, carbonates, or acetals. The benefits of adding lithium dinitramide (which is also a lithium salt) include lower irreversible loss of capacity on the first charge/discharge cycle, higher cycle life, lower self-discharge, greater flexibility in selection of electrolyte solvents, and greater charge capacity.

Posted in: Materials, Briefs

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