Tech Briefs

Instrumentation for Sensitive Gas Measurements

Measurements are based on cavity-enhanced absorption.

Posted in: Test & Measurement, Briefs

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Apparatus for Testing Flat Specimens of Thermal Insulation

An improved design affords flexibility for testing under diverse conditions.

Posted in: Test & Measurement, Briefs, TSP

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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: Test & Measurement, Briefs, TSP

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Miniature Laser Doppler Velocimeter for Measuring Wall Shear

Interference fringes are configured for sensitivity to a velocity gradient.

Posted in: Test & Measurement, Briefs, TSP

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Sol-Gel Process for Making Pt-Ru Fuel-Cell Catalysts

Relative to another process, this one takes less time and yields better results. A sol-gel process has been developed as a superior alternative to a prior process for making platinum-ruthenium alloy catalysts for electro-oxidation of methanol in fuel cells. The starting materials in the prior process are chloride salts of platinum and ruthenium. The process involves multiple steps, is time-consuming, and yields a Pt-Ru product that has relatively low specific surface area and contains some chloride residue. Low specific surface area translates to incomplete utilization of the catalytic activity that might otherwise be available, while chloride residue further reduces catalytic activity (“poisons” the catalyst). In contrast, the sol-gel process involves fewer steps and less time, does not leave chloride residue, and yields a product of greater specific area and, hence, greater catalytic activity.

Posted in: Materials, Briefs, TSP

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Corrosion-Prevention Capabilities of a Water-Borne, Silicone- Based, Primerless Coating

Some formulations are better for steel, some for aluminum. Comparative tests have been performed to evaluate the corrosion-prevention capabilities of an experimental paint of the type described in “Water-Borne, Silicone-Based, Primerless Paints,” NASA Tech Briefs, Vol. 26, No. 11 (November 2002), page 30. To recapitulate: these paints contain relatively small amounts of volatile organic solvents and were developed as substitutes for traditional anticorrosion paints that contain large amounts of such solvents. An additional desirable feature of these paints is that they can be applied without need for prior application of primers to ensure adhesion.

Posted in: Materials, Briefs

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Making Activated Carbon for Storing Gas

Solid disks of microporous activated carbon, produced by a method that enables optimization of pore structure, have been investigated as means of storing gas (especially hydrogen for use as a fuel) at relatively low pressure through adsorption on pore surfaces. For hydrogen and other gases of practical interest, a narrow distribution of pore sizes <2 nm is preferable. The present method is a variant of a previously patented method of cyclic chemisorption and desorption in which a piece of carbon is alternately (1) heated to the lower of two elevated temperatures in air or other oxidizing gas, causing the formation of stable carbon/oxygen surface complexes; then (2) heated to the higher of the two elevated temperatures in flowing helium or other inert gas, causing the desorption of the surface complexes in the form of carbon monoxide. In the present method, pore structure is optimized partly by heating to a temperature of 1,100 °C during carbonization. Another aspect of the method exploits the finding that for each gas-storage pressure, gas-storage capacity can be maximized by burning off a specific proportion (typically between 10 and 20 weight percent) of the carbon during the cyclic chemisorption/desorption process.

Posted in: Materials, Briefs

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