Materials & Coatings

Detecting Airborne Mercury by Use of Polymer/Carbon Films

These films can be operated and regenerated at mild temperatures.

Films made of certain polymer/carbon composites have been found to be potentially useful as sensing films for detecting airborne elemental mercury at concentrations on the order of tens of parts per billion or more. That is to say, when the polymer/carbon composite films are exposed to air containing mercury vapor, their electrical resistances decrease by measurable amounts. Because airborne mercury is a health hazard, it is desirable to detect it with great sensitivity, especially in enclosed environments in which there is a risk of a mercury leak from lamps or other equipment.

Posted in: Briefs, Materials, Chemicals, Composite materials, Polymers, Hazardous materials, Test equipment and instrumentation

Composite Silica Aerogels Opacified With Titania

Thermal insulation is enhanced by reducing the radiative contribution to heat transfer.

A further improvement has been made to reduce the high-temperature thermal conductivities of the aerogel-matrix composite materials described in “Improved Silica Aerogel Composite Materials” (NPO-44287), NASA Tech Briefs, Vol. 32, No. 9 (September 2008), page 50. Because the contribution of infrared radiation to heat transfer increases sharply with temperature, the effective high-temperature thermal conductivity of a thermal-insulation material can be reduced by opacifying the material to reduce the radiative contribution. Therefore, the essence of the present improvement is to add an opacifying constituent material (specifically, TiO2 powder) to the aerogel-matrix composites.

Posted in: Briefs, TSP, Materials

Multiplexed Colorimetric Solid-Phase Extraction

This analytical platform enables simultaneous determination of trace analytes in water.

Multiplexed colorimetric solid-phase extraction (MC-SPE) is an extension of colorimetric solid-phase extraction (CSPE) — an analytical platform that combines colorimetric reagents, solid phase extraction, and diffuse reflectance spectroscopy to quantify trace analytes in water. In C-SPE, analytes are extracted and complexed on the surface of an extraction membrane impregnated with a colorimetric reagent. The analytes are then quantified directly on the membrane surface using a hand-held diffuse reflectance spectrophotometer. Importantly, the use of solid-phase extraction membranes as the matrix for impregnation of the colorimetric reagents creates a concentration factor that enables the detection of low concentrations of analytes in small sample volumes.

Posted in: Briefs, Materials

Graphite Non-Wovens as Functional Layers in Diagnostic Test Kits

Blood-handling diagnostic test strips can be used for diabetes testing and monitoring, and testing for other diseases.

The separation of serum or plasma from whole blood is of overriding importance in clinical chemistry. In particular, many diagnostic detection reactions of blood components proceed without impairment only after the red blood corpuscles have been separated off. This particularly applies to color reactions that are evaluated either by reflectometry or visually, or also electrochemically.

Posted in: Briefs, MDB, Briefs, Coatings & Adhesives, Materials, Bio-Medical, Medical, Patient Monitoring, Fluids and secretions, Medical equipment and supplies, Graphite, Test equipment and instrumentation

Using Ozone To Clean and Passivate Oxygen-Handling Hardware

A proposed method of cleaning, passivating, and verifying the cleanliness of oxygen-handling hardware would extend the established art of cleaning by use of ozone. As used here, “cleaning” signifies ridding all exposed surfaces of combustible (in particular, carbon-based) contaminants. The method calls for exposing the surfaces of the hardware to ozone while monitoring the ozone effluent for carbon dioxide. The ozone would passivate the hardware while oxidizing carbon-based residues, converting the carbon in them to carbon dioxide. The exposure to ozone would be continued until no more carbon dioxide was detected, signifying that cleaning and passivation were complete.

Posted in: Briefs, Materials, Carbon dioxide, Oxygen equipment, Oxygen equipment, Hardware

Two-Piece Screens for Decontaminating Granular Material

These are more effective than are single-piece screens.

Two-piece screens have been designed specifically for use in filtering a granular material to remove contaminant particles that are significantly wider or longer than are the desired granules. In the original application for which the two-piece screens were conceived, the granular material is ammonium perchlorate and the contaminant particles tend to be wires and other relatively long, rigid strands. The basic design of the two-piece screens can be adapted to other granular materials and contaminants by modifying critical dimensions to accommodate different grain and contaminant-particle sizes.

Posted in: Briefs, Materials, Product development, Materials properties, Particulate filters

Metal Standards for Waveguide Characterization of Materials

Metal waveguide inserts can be tailored to have known scattering parameters.

Rectangular-waveguide inserts that are made of non-ferromagnetic metals and are sized and shaped to function as notch filters have been conceived as reference standards for use in the rectangular- waveguide method of characterizing materials with respect to such constitutive electromagnetic properties as permittivity and permeability. Such standards are needed for determining the accuracy of measurements used in the method, as described below.

Posted in: Briefs, TSP, Materials, Waveguides, Waveguides, Conductivity, Materials properties, Metals, Test equipment and instrumentation, Test procedures

Large-Format Carbon Nanotube Sheets Fabricated With Chemical Vapor Deposition

Non-woven, textile-like sheets of carbon nanotubes can be created without post-processing.

Carbon nanotube (CNT) sheets, yarns, and their derivative products are beginning to emerge in the marketplace. A productive and scalable manufacturing method utilizes a chemical vapor deposition process for making very-large-format CNT non-woven, textile-like sheets directly from the reactor without post-processing.

Posted in: Briefs, Materials, Fabrication, Chemicals, Nanomaterials

Filtering Water by Use of Ultrasonically Vibrated Nanotubes

Water molecules could flow through; larger molecules and other particles could not.

Devices that could be characterized as acoustically driven molecular sieves have been proposed for filtering water to remove all biological contaminants and all molecules larger than water molecules. Originally intended for purifying wastewater for reuse aboard spacecraft, these devices could also be attractive for use on Earth in numerous settings in which there are requirements to obtain potable, medical-grade, or otherwise pure water from contaminated water supplies. These devices could also serve as efficient means of removing some or all water from chemical products — for example, they might be useful as adjuncts or substitutes for stills in the removal of water from alcohols and alcoholic beverages. These devices may be constructed using various materials, such as ceramics, metallics, or polymers, depending on end-use requirements.

Posted in: Briefs, Materials, Water reclamation, Nanotechnology, Acoustics, Acoustics

Improvements in Production of Single-Walled Carbon Nanotubes

Continuous mass production in fluidized-bed reactors now appears feasible.

A continuing program of research and development has been directed toward improvement of a prior batch process in which single-walled carbon nanotubes are formed by catalytic disproportionation of carbon monoxide in a fluidized-bed reactor. The overall effect of the improvements has been to make progress toward converting the process from a batch mode to a continuous mode and to scaling of production to larger quantities. Efforts have also been made to optimize associated purification and dispersion post processes to make them effective at large scales and to investigate means of incorporating the purified products into composite materials. The ultimate purpose of the program is to enable the production of high-quality single-walled carbon nanotubes in quantities large enough and at costs low enough to foster the further development of practical applications.

Posted in: Briefs, Materials

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