Materials & Coatings

Ionic Liquids to Replace Hydrazine

Customized ionic liquids offer better safety and convenience than traditional propellants.

A method for developing safe, easy-to-handle propellants has been developed based upon ionic liquids (ILs) or their eutectic mixtures. An IL is a binary combination of a typically organic cation and anion, which generally produces an ionic salt with a melting point below 100 °C. Many ILs have melting points near, or even below, room temperature (room temperature ionic liquids, RTILs). More importantly, a number of ILs have a positive enthalpy of formation. This means the thermal energy released during decomposition reactions makes energetic ILs ideal for use as propellants. Unlike traditional, storable propellants like hydrazine, ILs also exhibit near-zero vapor pressure. This makes them safer to handle because it eliminates hazardous inhalation — the primary pathway — as a route for toxicity in humans. Thus, ILs are ideal candidates for replacing hydrazine, which is expensive and dangerous, and poses significant handling difficulties.

Posted in: Briefs, TSP, Materials, Alternative fuels, Hydrazines, Liquid propellants, Chemicals, Thermal testing
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Variable Emittance Electrochromics Using Ionic Electrolytes and Low Solar Absorptance Coatings

One of the last remaining technical hurdles with variable emittance devices or skins based on conducting polymer electrochromics is the high solar absorptance of their top surfaces. This high solar absorptance causes overheating of the skin when facing the Sun in space. Existing technologies such as mechanical louvers or loop heat pipes are virtually inapplicable to micro (< 20 kg) and nano (< 5 kg) spacecraft.

Posted in: Briefs, TSP, Materials, Thermal management, Thermal management, Coatings Colorants and Finishes, Coatings, colorants, and finishes, Electrolytes, Polymers, Satellites
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Biomedical Textile Material Selection and Performance Considerations in Device Design

Biocompatible materials are increasingly being refined for incorporation in therapeutic applications.

Biomedical textile structures incorporate a wide array of biocompatible materials, including advanced polymers and metals in a range of sizes and thicknesses with varying material characteristics and performance properties. Promising substrates, now in development, add to the diversity of biomedical textile structure options. This versatility puts device designers within reach of developing highly complex, ultra-sophisticated components that can be used in a number of therapeutic applications, including orthopedics, cardiovascular, tissue engineering, neurology, and general surgery.

Posted in: Briefs, MDB, Briefs, Coatings & Adhesives, Materials, Bio-Medical, Implants & Prosthetics, Medical, Medical equipment and supplies, Biomaterials, Materials identification, Metals, Polymers, Textiles
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SCAFTEX® Non-Woven Bio-Textile for Implantable Devices

With the ability to encourage cellular in-growth, this material may become increasingly important to orthopedic reconstruction.

Classic tissue engineering utilizes absorbable non-woven biomedical textiles from a variety of fibers to aid in cell growth and proliferation, and medical device companies rely on these materials for implantable devices that must degrade over time. Non-woven bio-textiles such as SCAFTEX® and others have become the material of choice for many tissue engineering and regenerative medicine applications, and with superior surface area, high void volume, and excellent permeability, they are now also increasingly used in a wide variety of restorative applications ranging from orthopedic reconstruction and wound management to cosmetic surgery.

Posted in: Briefs, MDB, Briefs, Coatings & Adhesives, Materials, Bio-Medical, Implants & Prosthetics, Medical, Prostheses and implants, Suppliers, Biomaterials, Textiles
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A Model of Reduced Kinetics for Alkane Oxidation Using Constituents and Species for N-Heptane

The reduction of elementary or skeletal oxidation kinetics to a subgroup of tractable reactions for inclusion in turbulent combustion codes has been the subject of numerous studies. The skeletal mechanism is obtained from the elementary mechanism by removing from it reactions that are considered negligible for the intent of the specific study considered. As of now, there are many chemical reduction methodologies.

Posted in: Briefs, Materials, Analysis methodologies, Mathematical models, Chemicals, Combustion and combustion processes
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Thermally Conductive Tape Based on Carbon Nanotube Arrays

To increase contact conductance between two mating surfaces, a conductive “tape” has been developed by growing dense arrays of carbon nanotubes (CNTs, graphite layers folded into cylinders) on both sides of a thermally conductive metallic foil. When the two mating surfaces are brought into contact with the conductive tape in between, the CNT arrays will adhere to the mating surface. The van der Waals force between the contacting tubes and the mating surface provides adhesion between the two mating surfaces. Even though the thermal contact conductance of a single tube-to-tube contact is small, the tremendous amount of CNTs on the surface leads to a very large overall contact conductance.

Posted in: Briefs, Materials, Joining, Adhesives and sealants, Conductivity, Nanomaterials, Thermal testing
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Lightweight, Ultra-High-Temperature, CMC-Lined Carbon/Carbon Structures

This refractory composite material is applicable to defense vehicles, combustion chambers, rocket nozzles, hot gas generators, and valves using both liquid and solid propellants.

lished engineering material used extensively in aerospace. The beneficial properties of C/C include high strength, low density, and toughness. Its shortcoming is its limited usability at temperatures higher than the oxidation temperature of carbon — approximately 400 °C. Ceramic matrix composites (CMCs) are used instead, but carry a weight penalty. Combining a thin laminate of CMC to a bulk structure of C/C retains all of the benefits of C/C with the high temperature oxidizing environment usability of CMCs.

Posted in: Briefs, TSP, Materials, Ceramics, Composite materials, Heat resistant materials, Lightweight materials, Nanomaterials, Spacecraft
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Two Catalysts for Selective Oxidation of Contaminant Gases

One oxidizes halocarbons and ammonia; the other oxidizes ammonia.

Two catalysts for the selective oxidation of trace amounts of contaminant gases in air have been developed for use aboard the International Space Station. These catalysts might also be useful for reducing concentrations of fumes in terrestrial industrial facilities — especially facilities that use halocarbons as solvents, refrigerant liquids, and foaming agents, as well as facilities that generate or utilize ammonia.

Posted in: Briefs, Materials, Catalysts, Air supply, Air supply, Gases, Hazardous materials, Spacecraft
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Nanoscale Metal Oxide Semiconductors for Gas Sensing

A report describes the fabrication and testing of nanoscale metal oxide semiconductors (MOSs) for gas and chemical sensing. This document examines the relationship between processing approaches and resulting sensor behavior. This is a core question related to a range of applications of nanotechnology and a number of different synthesis methods are discussed: thermal evaporation-condensation (TEC), controlled oxidation, and electrospinning. Advantages and limitations of each technique are listed, providing a processing overview to developers of nanotechnology-based systems.

Posted in: Briefs, TSP, Materials, Sensors and actuators, Sensors and actuators, Gases, Nanotechnology, Semiconductors
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Carbon Nanofibers Synthesized on Selective Substrates for Nonvolatile Memory and 3D Electronics

This method can impact the application of carbon nanofiber tubes in 3D electronics applications.

A plasma-enhanced chemical vapor deposition (PECVD) growth technique has been developed where the choice of starting substrate was found to influence the electrical characteristics of the resulting carbon nanofiber (CNF) tubes. It has been determined that, if the tubes are grown on refractory metallic nitride substrates, then the resulting tubes formed with dc PECVD are also electrically conducting.

Posted in: Briefs, Materials, Electronic equipment, Electronic equipment, Conductivity, Nanomaterials
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