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Use of Solvent-Free Conditions/Dry Mixing for Functionalizing Carbon Nanotubes

Lyndon B. Johnson Space Center, Houston, Texas Two methods have been developed for functionalizing carbon nanotubes in solvent-free conditions. In one method, purified single-walled carbon nanotubes (SWNTs) and a diazonium salt are added to a metal vial, which is loaded with a stainless steel ball bearing. The metal vial is clamped into a mill mixer, and is mixed for one hour. The unreacted diazonium salt is then dissolved in a volume of acetonitrile that efficiently solubilizes the salt to remove the unreacted functionalization reagent. The functionalized nanotubes are then collected by filtration.

Posted in: Materials, Briefs

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Synthesis of Novel Copoly(alkyl ether imide)s With Unique Surface Properties

These materials have potential applications in marine biofouling, biomedical devices, microfluidics, corrosion and stain resistance, ice and water adhesion, and drag reduction. Langley Research Center, Hampton, Virginia Copoly(alkyl ether imide)s were synthesized for the purposes of tailoring surface chemistry. Alkyl ether oligomers with amine end groups were synthesized from the hydroxyl-terminated species, and subsequently reacted with aromatic dianhydrides and diamines to make the copolymers. Films were solution-cast from the copolymers and exhibited reduced surface energy and increased surface fluorine content at extremely low loadings relative to the imide matrix. These copolymers are currently being evaluated for mitigation of particle adhesion and fouling from exposure to various particle and biological contaminants. Additionally, the surface migration of the oxetane segments can be used as a shuttle to bring other designed chemical constituents to the surface.

Posted in: Materials, Briefs

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Inkjet-Assisted Creation of Self-Healing Layers Between Composite Plies

Inkjet printing provides the ability to rapidly transfer this technology into a prepreg manufacturing process. University of Sheffield, United Kingdom A self-healing advanced composite system was designed and optimized using minimum self-healing (SH) agent (~0.02%) deposited in microscopically ordered arrays through inkjet printing, to arrest cracks along interfaces between plies (see figure). The approach consisted of depositing thermoplastic, low-viscosity microdroplets with chemically and mechanically comparable properties to epoxy matrix in aerospace-grade composites onto fiber-reinforced epoxy prepregs before curing. The SH agents remained arrested and encapsulated between epoxy plies without direct contact with neighboring microdroplets. This ensured consistent integrity of the composite while preserving the SH capability.

Posted in: Materials, Briefs

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Fail-Safe Accumulator for Internal Active Thermal Control Loops

Lyndon B. Johnson Space Center, Houston, Texas Spacecraft internal active thermal control systems (ATCSs) typically use water or a water mixture as their working fluid. A gas-charged bellows accumulator pressurizes the system and provides liquid inventory control. If only a single internal ATCS loop is used, the accumulator represents a single-point failure that can result in a loss of crew. To protect against this possibility, the normal practice is to add a second, fully redundant loop. A redundant loop requires duplication of cold plates, heat exchangers, and plumbing, even though these items are themselves highly reliable. Duplicating these reliable piece parts to protect against accumulator failure adds significant mass to the spacecraft.

Posted in: Mechanical Components, Briefs

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Rocket Vent Design With Variable Flow Control and Rain Protection

Rugged design will ensure operation from pre-flight through flight. Marshall Space Flight Center, Alabama This innovation is a rocket purge vent design that can control and balance flow across multiple vents and across very large gas flow ranges while keeping water or other undesirable gases from entering into the vented space. When changing purge rates, this device adapts to the different flow rates to maintain a very low internal delta pressure. It provides a vent design that can withstand high winds and blowing rain without allowing water entry. With the rugged design, it can operate during all rocket operational phases, from pre-flight operations through flight. This design is useful for any device needing a one-way valve type purge or general air vent where rain and gas reverse entry must not occur.

Posted in: Mechanical Components, Briefs

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Turbo-Brayton Converter for Fission Surface Power Applications

John H. Glenn Research Center, Cleveland, Ohio Producing electric power for space applications is challenging. Although short-term missions can use batteries or fuel cells, these sources are not practical for durations longer than one month. Photovoltaics become less attractive as the distance from the Sun increases, and they are ineffective in Sun-shadowed environments. For these types of missions, thermal-to-electric converters can produce electric power from nuclear heat sources. Potential converter technologies include thermoelectric, Stirling, Brayton, Rankine, thermophotovoltaic, and alkali metal thermal to electric conversion (AMTEC).

Posted in: Mechanical Components, Briefs

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Vibration Ring

John H. Glenn Research Center, Cleveland, Ohio Machine vibration often originates with rotating driveline components such as rotors, gears, bearings, and fans. Such vibration is the source of unwanted noise and can be destructive to the machine. The vibration ring is a mechanism that provides an indirect damping effect, and is rigid enough to be mounted within the driveline. The mechanical structure of the vibration ring responds to vibratory excitation by stressing an embedded piezoelectric material. The material generates an electric charge, which is dissipated though an electric circuit. The net result is a reduction of vibration energy.

Posted in: Mechanical Components, Briefs

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