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Glass/Ceramic Composites for Sealing Solid Oxide Fuel Cells

Ceramic fillers in a glass contribute to strength and fracture toughness. A family of glass/ceramic composite materials has been investigated for use as sealants in planar solid oxide fuel cells. These materials are modified versions of a barium calcium aluminosilicate glass developed previously for the same purpose. The composition of the glass in mole percentages is 35BaO + 15CaO + 5Al2O3 + 10B2O3 + 35SiO2. The glass seal was found to be susceptible to cracking during thermal cycling of the fuel cells.

Posted in: Materials, Briefs, TSP

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Composite Elastic Skins for Shape-Changing Structures

Anisotropic stiffness properties can be tailored for specific applications. Composite elastic skins having tailorable mechanical properties have been invented for covering shape-changing (“morphable”) structures. These skins are intended especially for use on advanced aircraft that change shapes in order to assume different aerodynamic properties.

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Oxygen-Permeable, Hydrophobic Membranes of Silanized α-Al2O3

These membranes perform better than do organic polymer oxygen-diffusion membranes. Membranes made of silanized alumina have been prepared and tested as prototypes of derivatized ceramic membranes that are both highly permeable to oxygen and hydrophobic. Improved oxygen-permeable, hydrophobic membranes would be attractive for use in several technological disciplines, including supporting high-temperature aqueous-phase oxidation in industrial production of chemicals, oxygenation of aqueous streams for bioreactors, and oxygenation of blood during open-heart surgery and in cases of extreme pulmonary dysfunction. In comparison with organic polymeric oxygen-permeable membranes now commercially available, the derivatized ceramic membranes are more chemically robust, are capable of withstanding higher temperatures, and exhibit higher oxygen-diffusion coefficients.

Posted in: Materials, Briefs

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Thermoelectric Inhomogeneities in (Ag1-SbTe2)x(PbTe)1-x

A document presents a study of why materials of composition (Ag1–ySbTe2)0.05 (PbTe)0.95 [0=y=1] were previously reported to have values of the thermoelectric figure of merit [ZT (where Z = a2/??, a is the Seebeck coefficient, ? is electrical resistivity, ? is thermal conductivity, and T is absolute temperature)] ranging from 2. In the study, samples of (AgSbTe2)0.05(PbTe)0.95, (Ag0.67SbTe2)0.05 (PbTe)0.95, and (Ag0.55SbTe2)0.05(PbTe)0.95 were prepared by melting followed, variously, by slow or rapid cooling. Analyses of these samples by x-ray diffraction, electron microscopy, and scanning microprobe measurements of the Seebeck coefficient led to the conclusion that these materials have a multiphase character on a scale of the order of millimeters, even though they appear homogeneous in x-ray diffraction and electron microscopy. The Seebeck measurements showed significant variations, including both n-type and p-type behavior in the same sample. These variations were found to be consistent with observed variations of ZT. The rapidly quenched samples were found to be less inhomogeneous than were the furnace-cooled ones; hence, rapid quenching was suggested as a basis of research on synthesizing more nearly uniform high-ZT samples.

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SiC Composite Turbine Vanes

Y-cloth was conceived to provide fiber reinforcement for sharp trailing edges. Turbine inlet guide vanes have been fabricated from composites of silicon carbide fibers in silicon carbide matrices. A unique design for a cloth made from SiC fibers makes it possible to realize the geometric features necessary to form these vanes in the same airfoil shapes as those of prior metal vanes.

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Polymer Electrolytes for Rechargeable Lithium Batteries

Cyanoresins would be blended and complexed with Li salts. Polymeric electrolytes for rechargeable lithium-based electrochemical cells and batteries would be made by blending and complexing cyanoresins with lithium salts, according to a proposal. In particular, polymeric electrolytes for separators, carbon-composite anodes, and cathodes would be formulated from appropriate blends of different polymers that are mutually insoluble and do not chemically react with each other. As a result, each polymeric component would retain its specific desired characteristics in high-energy-density batteries that would be capable of long cycle lives and high charge/discharge rates. For example, one polymeric component could provide high ionic conductivity and charge-carrier concentration while another polymeric component would provide structural integrity. Conceivably, a lithium battery made with such materials could exhibit an energy density of 80 W×h/lb for more than 1,000 charge/discharge cycles. Batteries like this could be used in applications ranging from geosynchronous satellites to electric vehicles to small consumer electronic equipment.

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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:

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