Special Coverage

NASA Supercomputer Simulations Reveal 'Noisy' Aerodynamics
Robotic Gripper Cleans Up Space Debris
Soft Robot “Walks” on Any Terrain
Defense Advanced Research Projects Agency
Using Microwaves to Produce High-Quality Graphene
Transducer-Actuator Systems for On-Machine Measurements and Automatic Part Alignment
Wide-Area Surveillance Using HD LWIR Uncooled Sensors
Heavy Lift Wing in Ground (WIG) Cargo Flying Boat
Technique Provides Security for Multi-Robot Systems
Bringing New Vision to Laser Material Processing Systems
NASA Tests Lasers’ Ability to Transmit Data from Space

Biologically Inspired Purification and Dispersion of SWCNTs

A biologically inspired method has been developed for (1) separating single-wall carbon nanotubes (SWCNTs) from other materials (principally, amorphous carbon and metal catalysts) in raw production batches and (2) dispersing the SWCNTs as individual particles (in contradistinction to ropes and bundles) in suspension, as required for a number of applications. Prior methods of purification and dispersal of SWCNTs involve, variously, harsh physical processes (e.g., sonication) or harsh chemical processes (e.g., acid reflux). These processes do not completely remove the undesired materials and do not disperse bundles and ropes into individual suspended SWCNTs. Moreover, these processes cut long SWCNTs into shorter pieces, yielding typical nanotube lengths between 150 and 250 nm.

Posted in: Briefs, TSP, Materials

Quantifying Airborne Hydrogen in Nearly Real Time

An indirect method of measuring small concentrations of hydrogen gas in air in nearly real time has been devised to circumvent the difficulty of performing such measurements directly. In this method, a sample of air suspected of containing hydrogen is first enclosed in a suitable container, and its humidity is measured. The enclosed sample is then exposed to ultraviolet light (typically at a wavelength of 254 nm), which photolyzes the hydrogen to water vapor. The exposure time needed for photolysis is of the order of minutes, the exact value depending on the shape and size of the sample container.

Posted in: Briefs, TSP, Materials

Silicon Nanowire Growth at Chosen Positions and Orientations

It is now possible to grow silicon nanowires at chosen positions and orientations by a method that involves a combination of standard microfabrication processes. Because their positions and orientations can be chosen with unprecedented precision, the nanowires can be utilized as integral parts of individually electronically addressable devices in dense arrays.

Posted in: Briefs, TSP, Materials, Fabrication, Nanotechnology, Semiconductors, Silicon alloys

Detecting Airborne Mercury by Use of Palladium Chloride

Palladium chloride films have been found to be useful as alternatives to the gold films heretofore used to detect airborne elemental mercury at concentrations of the order of parts per billion (ppb). Somewhat more specifically, when suitably prepared palladium chloride films are exposed to parts-per-billion or larger concentrations of airborne mercury, their electrical resistances change by amounts large enough to be easily measurable. Because airborne mercury adversely affects health, it is desirable to be able to detect it with high sensitivity, especially in enclosed environments in which there is a risk of leakage of mercury from lamps or other equipment.

Posted in: Briefs, TSP, Materials

Detecting Airborne Mercury by Use of Gold Nanowires

Like the palladium chloride (PdCl2) films described in the immediately preceding article, gold nanowire sensors have been found to be useful for detecting airborne elemental mercury at concentrations on the order of parts per billion (ppb). Also like the PdCl2 films, gold nanowire sensors can be regenerated under conditions much milder than those necessary for regeneration of gold films that have been used as airborne-Hg sensors. The interest in nanowire sensors in general is prompted by the expectation that nanowires of a given material covering a given surface may exhibit greater sensitivity than does a film of the same material because nanowires have a greater surface area.

Posted in: Briefs, TSP, Materials, Sensors and actuators, Sensors and actuators, Air pollution, Metals, Nanotechnology, Hazardous materials

Electrolytes for Low-Temperature Operation of Li-CFₓ Cells

A report describes a study of electrolyte compositions selected as candidates for improving the low-temperature performances of primary electrochemical cells that contain lithium anodes and fluorinated carbonaceous (CFx) cathodes. This study complements the developments reported in “Additive for Low-Temperature Operation of Li-(CF)n Cells” (NPO-43579) and Li/CFx Cells Optimized for Low-Temperature Operation (NPO-43585), which appear elsewhere in this issue of NASA Tech Briefs.

Posted in: Briefs, TSP, Materials

Polyimide-Foam/Aerogel Composites for Thermal Insulation

Composites of specific types of polymer foams and aerogel particles or blankets have been proposed to obtain thermal insulation performance superior to those of the neat polyimide foams. These composites have potential to also provide enhanced properties for vibration dampening or acoustic attenuation. The specific type of polymer foam is denoted “TEEK-H,” signifying a series, denoted “H,” within a family of polyimide foams that were developed at NASA’s Langley Research Center and are collectively denoted “TEEK” (an acronym of the inventors’ names).

Posted in: Briefs, Materials, Thermal management, Thermal management, Performance upgrades, Composite materials, Foams, Insulation

Yb₁₄MnSb₁₁ as a High-Efficiency Thermoelectric Material

Yb14MnSb11 has been found to be well-suited for use as a p-type thermoelectric material in applications that involve hot-side temperatures in the approximate range of 1,200 to 1,300 K. The figure of merit that characterizes the thermal-to-electric power-conversion efficiency is greater for this material than for SiGe, which, until now, has been regarded as the state-of-the art high-temperature p-type thermoelectric material. Moreover, relative to SiGe, Yb14MnSb11 is better suited to incorporation into a segmented thermoelectric leg that includes the moderate-temperature p-type thermoelectric material CeFe4Sb12 and possibly other, lower-temperature p-type thermoelectric materials.

Posted in: Briefs, Materials

Room-Temperature Ionic Liquids for Electrochemical Capacitors

A document discusses room-temperature ionic liquids (RTILs) used as electrolytes in carbon-nanotube-based, electrochemical, double-layer capacitors. Unlike the previous electrolyte (EtNB4 in acetonitrile), the RTIL used here does not produce cyanide upon thermal decomposition and does not have a moisture sensitivity.

Posted in: Briefs, TSP, Materials, Capacitors, Capacitors, Electrolytes, Nanotechnology

Ultra-Lightweight Self- Deployable Nanocomposite Structure for Habitat Applications

A document discusses self-deployable, rigidized structures that are ultra-lightweight and have gas barrier properties, space durability, and high impact resistance. Developed here are microcellular-foamed sandwich structures made from nanocomposite shape memory polymers (SMPs) with Cold-Hibernated Elastic Memory (CHEM) deployed technique for space structural components including space habitats. This type of foam sandwich also does not suffer from the toxicity problems of conventional foams, and has higher mechanical properties than those processed with conventional techniques. This design can be compacted into a very small volume for launch. Once deployed, the microcellular structure can use the heat from the Sun to recover 98 to 100 percent of its shape.

Posted in: Briefs, TSP, Materials

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