Materials & Coatings

Electroceramic Actuators for Operation at Low Temperatures

Relatively large strokes are produced at temperatures between 30 and 60 K.

Electrostrictive ceramic actuators that can function at low temperatures have been developed for controlling the shapes of mirrors in the Next Generation Space Telescope (NGST). On Earth, electrostrictive ceramic actuators may be useful for fine control of the positions of objects in cryogenic laboratory apparatuses and in industrial cryogenic (including superconducting) systems.

Posted in: Briefs, TSP, Materials, Optics, Sensors and actuators, Ceramics

Improved Low-Temperature Performance of Li-Ion Cells Using New Electrolytes

This technology has utility in high-power batteries for electric vehicles.

As part of the continuing efforts to develop advanced electrolytes to improve the performance of lithiumion cells, especially at low temperatures, a number of electrolyte formulations have been developed that result in improved low-temperature performance (down to –60 °C) of 26650 A123Systems commercial lithium- ion cells. The cell type/design, in which the new technology has been demonstrated, has found wide application in the commercial sector (i.e., these cells are currently being used in commercial portable power tools). In addition, the technology is actively being considered for hybrid electric vehicle (HEV) and electric vehicle (EV) applications.

Posted in: Briefs, TSP, Materials, Battery cell chemistry, Lithium-ion batteries, Electrolytes

Wider-Opening Dewar Flasks for Cryogenic Storage

Dewar flasks have been proposed as containers for relatively long-term (25 days) storage of perishable scientific samples or other perishable objects at a temperature of –175 °C. The refrigeration would be maintained through slow boiling of liquid nitrogen (LN2). For the purposes of the application for which these containers were proposed, (1) the neck openings of commercial off-the-shelf (COTS) Dewar flasks are too small for most NASA samples; (2) the round shapes of the COTS containers give rise to unacceptably low efficiency of packing in rectangular cargo compartments; and (3) the COTS containers include metal structures that are too thermally conductive, such that they cannot, without exceeding size and weight limits, hold enough LN2 for the required long-term-storage.

Posted in: Briefs, Materials, Performance upgrades, Containers, Storage, Refrigerants

Supercapacitor Electrolyte Solvents With Liquid Range Below –80 °C

New formulations extend operation into lower temperatures.

A previous NASA Tech Brief [“Low-Temperature Supercapacitors” (NPO-44386) NASA Tech Briefs, Vol. 32, No 7 (July 2008), page 32] detailed ongoing efforts to develop non-aqueous supercapacitor electrolytes capable of supporting operation at temperatures below commercially available cells (which are typically limited to charging and discharging at ≥40 °C). These electrolyte systems may enable energy storage and power delivery for systems operating in extreme environments, such as those encountered in the Polar regions on Earth or in the exploration of space. Supercapacitors using these electrolytes may also offer improved power delivery performance at moderately low temperatures (e.g., –40 to 0 °C) relative to currently available cells, offering improved cold-cranking and cold-weather acceleration capabilities for electrical or hybrid vehicles.

Posted in: Briefs, Materials

Silicon Oxycarbide Aerogels for High-Temperature Thermal Insulation

A high-performance, silicon oxycarbide (SiOC) aerogel material is suitable for use as thermal insulation at temperatures approaching 1,200 °C. These aerogel composites were created using cost-effective and commercially available polymeric precursors (the polymethylsiloxane resin, SOC-A35, from Starfire Systems), thus enabling scaleup and mass commercialization. The SiOC aerogels exhibited bulk densities and thermal conductivities that rival traditional silica-based aerogels. Prolonged exposure to temperatures above 1,000 °C had virtually no effect on the thermal conductivity, surface area, pore volume, or pore diameter of SiOC aerogels.

Posted in: Briefs, Materials, Conductivity, Insulation, Polymers, Silicon alloys, Durability

Designs and Materials for Better Coronagraph Occulting Masks

Optical density and phase profiles are achromatized over a broad wavelength range.

New designs, and materials appropriate for such designs, are under investigation in an effort to develop coronagraph occulting masks having broad-band spectral characteristics superior to those currently employed. These designs and materials are applicable to all coronagraphs, both ground-based and spaceborne. This effort also offers potential benefits for the development of other optical masks and filters that are required (1) for precisely tailored spatial transmission profiles, (2) to be characterized by optical-density neutrality and phase neutrality (that is, to be characterized by constant optical density and constant phase over broad wavelength ranges), and/or (3) not to exhibit optical-density-dependent phase shifts.

Posted in: Briefs, Materials, Design processes, Optics, Sun and solar, Materials identification

Advanced Liquid-Cooling Garment Using Highly Thermally Conductive Sheets

This garment provides metabolic heat rejection applicable to surgical cooling vests, combat fatigues, and firefighter and hazmat suits.

This design of the liquid-cooling garment for NASA spacesuits allows the suit to remove metabolic heat from the human body more effectively, thereby increasing comfort and performance while reducing system mass. The garment is also more flexible, with fewer restrictions on body motion, and more effectively transfers thermal energy from the crewmember’s body to the external cooling unit. This improves the garment’s performance in terms of the maximum environment temperature in which it can keep a crewmember comfortable.

Posted in: Briefs, MDB, TSP, Briefs, TSP, Coatings & Adhesives, Materials, Bio-Medical, Medical, Human factors, Thermal management, Spacesuits

Extended Shelf Life for PMR Polyimide Resins and Prepregs

Secondary alcohols are used in place of primary alcohols.

An improved class of formulations for PMR polyimide resins retards the imidization that undesirably occurs during handling and storage. While imidization is desired at the final (deliberate polymerization) stage of production of a polyimide, imidization results in premature aging when it occurs during earlier stages of synthesis, shipping, prepregging, and fabrication layup. By retarding imidization at storage and handling temperatures, the improved class of formulations increases both shelf life and the upper limit of allowable temperature for handling and storage prior to final polymerization.

Posted in: Briefs, TSP, Materials, Performance upgrades, Storage, Resins, Durability

Silica-Filled EPDM Rubbers as Ablative Insulating Materials

These materials are intended to replace other materials that will soon be unavailable.

Silica-filled polymers made from ethylene propylene diene monomer (EPDM) have been found to be useful as ablative thermal-insulation materials. These polymers have been investigated as candidates to replace some previously developed polymeric ablative rocket-engine insulating materials that will soon become commercially unavailable. Although these materials have been developed specifically for use in and on solid-fuel rocket motors, they may also be useful in terrestrial applications in which there are requirements for protection against high temperatures for short times.

Posted in: Briefs, Materials, Elastomers, Heat resistant materials, Insulation, Rocket engines

Statistical Sampling of Tide Heights Study

The goal of the study was to determine if it was possible to reduce the cost of verifying computational models of tidal waves and currents. Statistical techniques were used to determine the least number of samples required, in a given situation, to remain statistically significant, and thereby reduce overall project costs. Commercial, academic, and Federal agencies could benefit by applying these techniques, without the need to “touch” every item in the population. For example, the requirement of this project was to measure the heights and times of high and low tides at 8,000 locations for verification of computational models of tidal waves and currents. The application of the statistical techniques began with observations to determine the correctness of submitted measurement data, followed by some assumptions based on the observations.

Posted in: Briefs, Materials, Computational fluid dynamics, Mathematical models, Statistical analysis, Water, Marine vehicles and equipment

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