Tech Briefs

Nickel-Tin Electrode Materials for Nonaqueous Li-Ion Cells

Capacity densities exceed those of materials now commercially available for the same purpose. Experimental materials made from mixtures of nickel and tin powders have shown promise for use as the negative electrodes of rechargeable lithium-ion electrochemical power cells. During charging (or discharging) of a lithiumion cell, lithium ions are absorbed into (or desorbed from, respectively) the negative electrode, typically through an intercalation or alloying process. The negative electrodes (for this purpose, designated as anodes) in state-of-the-art Li-ion cells are made of graphite, in which intercalation occurs. Alternatively, the anodes can be made from metals, in which alloying can occur. For reasons having to do with the electrochemical potential of intercalated lithium, metallic anode materials (especially materials containing tin) are regarded as safer than graphite ones; in addition, such metallic anode materials have been investigated in the hope of obtaining reversible charge/discharge capacities greater than those of graphite anodes. However, until now, each of the tin-containing metallic anode formulations tested has been found to be inadequate in some respect.

Posted in: Briefs, Materials

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Patched Off-Axis Bending/Twisting Actuators for Thin Mirrors

Two documents present updates on thin-shell, adjustable, curved mirrors now being developed for use in spaceborne imaging systems.  These mirrors at an earlier stage of development were reported in “Nanolaminate Mirrors With Integral Figure-Control Actuators” (NPO-30221), NASA Tech Briefs, Vol. 26, No. 5 (May 2002), page 80. To recapitulate: These mirrors comprise metallic film reflectors on nanolaminate substrates that contain “in-plane” actuators for controlling surface figures with micronlevel precision. The actuators are integral parts of the mirror structures, typically fabricated as patches that are bonded onto the rear (nonreflective) surfaces of the mirror shells. The current documents discuss mathematical modeling of mirror deflections caused by actuators arranged in unit cells distributed across the rear mirror surfaces. One of the documents emphasizes an actuator configuration in which a mirror surface is divided into hexagonal unit cells. Each unit cell contains four rectangular actuator patches in an off-axis cruciform pattern to induce a combination of bending and twisting. For deflections to reduce certain optical aberrations, it is found that, relative to other configurations, this configuration involves a smaller areal density of actuators.

Posted in: Briefs, TSP, Materials

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Automation of Vapor-Diffusion Growth of Protein Crystals

High-throughput experiments are accelerated through automation of routine operations.Some improvements have been made in a system of laboratory equipment developed previously for studying the crystallization of proteins from solution by use of dynamically controlled flows of dry gas. The improvements involve mainly (1) automation of dispensing of liquids for starting experiments, (2) automatic control of drying of protein solutions during the experiments, and (3) provision for automated acquisition of video images for monitoring experiments in progress and for post-experiment analysis.

Posted in: Briefs, Medical

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Miniature Laser Doppler Velocimeter for Measuring Wall Shear

Interference fringes are configured for sensitivity to a velocity gradient.

Posted in: Briefs, TSP, Test & Measurement

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Quadrupole Ion Mass Spectrometer for Masses of 2 to 50 Da

H2, He, O2, and Ar can be quantitated at low concentrations in N2

Posted in: Briefs, TSP, Test & Measurement

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Apparatus for Testing Flat Specimens of Thermal Insulation

An improved design affords flexibility for testing under diverse conditions.

Posted in: Briefs, TSP, Test & Measurement

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Instrumentation for Sensitive Gas Measurements

Measurements are based on cavity-enhanced absorption.

Posted in: Briefs, Test & Measurement

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