Materials

Using ALD To Bond CNTs to Substrates and Matrices

CNT-based field emitters could be made more durable. Atomic-layer deposition (ALD) has been shown to be effective as a means of coating carbon nanotubes (CNTs) with layers of Al2O3 that form strong bonds between the CNTs and the substrates on which the CNTs are grown. It should also be possible to form strong CNT/ substrate bonds using other coating materials that are amenable to ALD — for example, HfO2, Ti, or Ta. Further, it has been conjectured that bonds between CNTs and matrices in CNT/matrix composite materials could be strengthened by ALD of suitable coating materials on the CNTs.

Posted in: Materials, Briefs

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Polymer-Based Composite Catholytes for Li Thin-Film Cells

It should be possible to increase charge capacities and cycle lives. Polymer-based composite catholyte structures have been investigated in a continuing effort to increase the charge/ discharge capacities of solid-state lithium thin-film electrochemical cells. A cell according to this concept contains the following layers (see figure): An anode current-collecting layer, typically made of Cu; An Li metal anode layer; A solid electrolyte layer of Li3.3PO3.8N0.22 (“LiPON”) about 1 to 2 μm thick; The aforementioned composite catholyte layer, typically about 100 μm thick, consisting of electronically conductive nanoparticles in an Li-ion- conductive polymer matrix; and A metallic cathode current collector, typically made of Mo and about 0.5 μm thick.

Posted in: Materials, Briefs, TSP

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Chemical Passivation of Li+-Conducting Solid Electrolytes

Such passivation could enable long-life lithium rechargeable cells. Plates of a solid electrolyte that exhibits high conductivity for positive lithium ions can now be passivated to prevent them from reacting with metallic lithium. Such passivation could enable the construction and operation of high-performance, long-life lithium-based rechargeable electrochemical cells containing metallic lithium anodes. The advantage of this approach, in comparison with a possible alternative approach utilizing lithium-ion graphitic anodes, is that metallic lithium anodes could afford significantly greater energy-storage densities.

Posted in: Materials, Briefs, TSP

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Nickel-Based Superalloy Resists Embrittlement by Hydrogen

This alloy also exhibits high strength and ductility. A nickel-based superalloy that resists embrittlement by hydrogen more strongly than does nickel alloy 718 has been developed. Nickel alloy 718 is the most widely used superalloy. It has excellent strength and resistance to corrosion as well as acceptably high ductility, and is recognized as the best alloy for many high- temperature applications. However, nickel alloy 718 is susceptible to embrittlement by hydrogen and to delayed failure and reduced tensile properties in gaseous hydrogen. The greater resistance of the present nickel- based superalloy to adverse effects of hydrogen makes this alloy a superior alternative to nickel alloy 718 for applications that involve production, transfer, and storage of hydrogen, thereby potentially contributing to the commercial viability of hydrogen as a clean-burning fuel.

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Composite Cathodes for Dual-Rate Li-Ion Batteries

A battery could have both high charge capacity and high rate capacity. Composite-material cathodes that enable Li-ion electrochemical cells and batteries to function at both high energy densities and high discharge rates are undergoing development. Until now, using commercially available cathode materials, it has been possible to construct cells that have either capability for high-rate discharge or capability to store energy at average or high density, but not both capabilities. However, both capabilities are needed in robotic, standby-power, and other applications that involve duty cycles that include long-duration, low-power portions and short-duration, high-power portions.

Posted in: Materials, Briefs, TSP

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Organic/Inorganic Polymeric Composites for Heat-Transfer Reduction

Organic/inorganic polymeric composite materials have been invented with significant reduction in heat-transfer properties. Measured decreases of 20–50 percent in thermal conductivity versus that of the unmodified polymer matrix have been attained. These novel composite materials also maintain mechanical properties of the unmodified polymer matrix. The present embodiments are applicable, but not limited to: racing applications, aerospace applications, textile industry, electronic applications, military hardware improvements, and even food service industries. One specific application of the polymeric composition is for use in tanks, pipes, valves, structural supports, and components for hot or cold fluid process systems where heat flow through materials is problematic and not desired.

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Special Polymer/Carbon Composite Films for Detecting SO2

These films offer distinct advantages over prior SO2-sensor materials. A family of polymer/ carbon films has been developed for use as sensory films in electronic noses for detecting SO2 gas at concentrations as low as 1 part per million (ppm). Most previously reported SO2 sensors cannot detect SO2 at concentrations below tens of ppm; only a few can detect SO2 at 1 ppm. Most of the sensory materials used in those sensors (especially inorganic ones that include solid oxide electrolytes, metal oxides, and cadmium sulfide) must be used under relatively harsh conditions that include operation and regeneration at temperatures >100 °C. In contrast, the present films can be used to detect 1 ppm of SO2 at typical operating temperatures between 28 and 32 °C and can be regenerated at temperatures between 36 and 40 °C.

Posted in: Materials, Briefs, TSP

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