Materials & Coatings

Regenerable Trace-Contaminant Sorbent for the Primary Life Support System (PLSS)

This technology has applications in air-revitalization systems on spacecraft, submarines, automobiles, and commercial aircraft. Lyndon B. Johnson Space Center, Houston, Texas The NASA objective of expanding the human experience into the far reaches of space requires the development of regenerable life support systems. This work addresses the development of a regenerable air-revitalization system for trace-contaminant (TC) removal for the spacesuit used in extravehicular activities (EVAs). Currently, a bed of granular activated carbon is used for TC control. The carbon is impregnated with phosphoric acid to enhance ammonia sorption, but this also makes regeneration difficult, if not impossible. Temperatures as high as 200 °C have been shown to be required for only partial desorption of ammonia on time scales of 18,140 hours. Neither these elevated temperatures nor the long time needed for sorbent regeneration are acceptable. Thus, the activated carbon has been treated as an expendable resource, and the sorbent bed has been oversized in order to last throughout the entire mission.

Posted in: Briefs, TSP

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Lithium Fluoride as a Polysulfide Shuttle Inhibitor for Lithium Sulfur Chemistry

This invention imparts properties such as reinforcement, enhanced tensile strength, and/or electrical and thermal conductivity to composites. Lyndon B. Johnson Space Center, Houston, Texas In a lithium sulfur cell, the reduction of sulfur to lithium sulfide is a critical series of reactions that provides a large theoretical capacity of 1,672 mAh/g sulfur. One of many challenges in this system is the solubility of generated lithium polysulfides during the charge/discharge process. These polysulfides derived from the reduction of elemental sulfur are soluble in organic electrolytes, and can be reduced at the anode, causing an undesired reaction. Polysulfide species can also accumulate at the surface of the cathode and be further reduced to lower-order polysulfides such as Li2S2 or Li2S. The insulating nature of these lower-order polysulfides blocks the electron pathway on the carbon cathode.

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Fibers of Aligned Single-Wall Carbon Nanotubes and Process for Making the Same

This invention imparts properties such as reinforcement, enhanced tensile strength, and/or electrical and thermal conductivity to composites. Lyndon B. Johnson Space Center, Houston, Texas Single-wall carbon nanotubes (SWNTs) are fullerenes of closed-cage carbon molecules typically arranged in hexagons and pentagons. Commonly known as “buckytubes,” these cylindrical carbon structures have extraordinary properties, including high electrical and thermal conductivity, as well as high strength and stiffness. With intrinsic strength estimated to be on the order of 100 times that of steel, SWNTs are a possible strengthening reinforcement in composite materials. The intrinsic electronic properties of SWNTs also make them electrical conductors and useful in applications involving field mission devices such as flat-panel displays, and in polymers used for radio frequency interference and electromagnetic shielding that require electrical conductance properties.

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Enhancing MRI Contrast by Geometrical Confinement of Small Imaging Agents Within Nanoporous Particles

Lyndon B. Johnson Space Center, Houston, Texas Magnetic resonance imaging (MRI) has evolved into one of the most powerful, non-invasive diagnostic imaging techniques in medicine and biomedical research. The superior resolution and in-depth anatomical details provided by MRI are essential for early diagnosis of many diseases. Chemical contrast agents (CAs) have been widely used for improving the sensitivity and diagnostic confidence in MRI.

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Purifying Nanomaterials by Dissolving Excess Reactants and Catalysts in Ferric Chloride

Liquid phase temperature salts dissolve metallic catalysts like Fe, Co, or Ni, and “wash” them away. John H. Glenn Research Center, Cleveland, Ohio Physical and chemical properties of nanomaterials are known to be significantly different from those having larger crystallites (i.e. bigger than nano), but with the same chemical compositions. Optimal uses of these new nanomaterial properties will likely result in engineering materials that are better than what is available today. Before this can happen, characterization of the physical and chemical properties of nanomaterials is needed.

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White, Electrically Conductive, Radiation-Stable, Thermal Control Coating

Goddard Space Flight Center, Greenbelt, Maryland A highly reflective, white conductive coating system was developed using a layered approach with a combination of commercially available white conductive pigments within a conductive binder system. The top coating is a space-stable, radiation-resistant, highly reflective coating that has been tailored to provide optimum reflectance properties and meet vacuum thermal surface resistivities. The combined layer is a mixture of a highly reflective, electrically dissipative coating and a moderately reflective but highly conductive pigment in a conductive binder. A second, underlying layer of conductive white coating offers optimum adhesion to metal substrates and the topcoat. The system vacuum resistivity at room temperature is approximately 1 × 109 ohms/sq, and has a solar absorptance of less than 0.13 as measured on a Cary 5000 spectrophotometer.

Posted in: Briefs, TSP, Thermoelectrics, Coatings & Adhesives

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Plasma-Assisted Thin Film Coatings to Create Highly Hydrophobic Porous Structures

Multiple samples can be coated in this manner. John H. Glenn Research Center, Cleveland, Ohio Gas-distribution layers (GDLs) are water-management structures used in fuel cells and electrolyzers. GDLs are critical components that prevent flooding of the fuel cell electrode by product water, thus preserving open channels for reactant gas to reach the electrode. Typically, GDLs are electrically conductive papers (metal or carbon) having a fine pore structure. Extremely fine pores in some GDL materials are difficult to fully infiltrate with Teflon (PTFE). These materials are typically wet-proofed by coating with hydrophobic materials (e.g. PTFE). This is usually accomplished by immersing the raw paper in a PTFE emulsion. Completeness of wet-proofing by immersion in emulsion can be limited, because fine pores will filter out the PTFE particles.

Posted in: Briefs, TSP, Coatings & Adhesives

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