Special Coverage

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
Converting from Hydraulic Cylinders to Electric Actuators
Automating Optimization and Design Tasks Across Disciplines

Progress Toward Sequestering Carbon Nanotubes in PmPV

A report reopens the discussion of “Sequestration of Single-Walled Carbon Nanotubes in a Polymer” (MSC-23257), NASA Tech Briefs, Vol. 31, No. 12 (December 2007), page 38. To recapitulate: Sequestration of single-walled carbon nanotubes (SWNTs) in molecules of poly(m-phenylenevinylene-co-2,5-dioctyloxy- p-phenylenevinylene) [PmPV] is a candidate means of promoting dissolution of single-walled carbon nanotubes (SWNTs) into epoxies for making strong, lightweight epoxy-matrix/carbon-fiber composite materials. Bare SWNTs cannot be incorporated because they are not soluble in epoxies. One can render SWNTs soluble by chemically attaching various molecular chains to them, but such chemical attachments weaken them. In the present approach, one exploits the tendency of PmPV molecules to wrap themselves around SWNTs without chemically bonding to them. Attached to the backbones of the PmPV molecules are side chains that are soluble in, and chemically reactive with, epoxy precursors, and thus enable suspension of SWNTs in epoxy precursors. At time of the cited prior article, there had been only partial success in functionalizing the side chains to make them sufficiently soluble and reactive. The instant report states that a method of functionalization has been developed.

Posted in: Briefs, TSP, Materials

Functionalizing CNTs for Making Epoxy/CNT Composites

Functionalization of carbon nanotubes (CNTs) with linear molecular side chains of polyphenylene ether (PPE) has been shown to be effective in solubilizing the CNTs in the solvent components of solutions that are cast to make epoxy/CNT composite films. (In the absence of solubilization, the CNTs tend to clump together instead of becoming dispersed in solution as needed to impart, to the films, the desired CNT properties of electrical conductivity and mechanical strength.) Because the PPE functionalizes the CNTs in a non-covalent manner, the functionalization does not damage the CNTs. The functionalization can also be exploited to improve the interactions between CNTs and epoxy matrices to enhance the properties of the resulting composite films.

Posted in: Briefs, Materials

Fluoroester Co-Solvents for Low-Temperature Li⁺ Cells

Both low-temperature performance and high-temperature resilience are improved.

Electrolytes comprising LiPF6 dissolved in alkyl carbonate/fluoroester mixtures have been found to afford improved low-temperature performance and greater high-temperature resilience in rechargeable lithium-ion electrochemical cells. These and other electrolytes comprising lithium salts dissolved mixtures of esters have been studied in continuing research directed toward extending the lower limit of operating temperatures of such cells. This research at earlier stages, and the underlying physical and chemical principles, were reported in numerous previous NASA Tech Briefs articles.

Posted in: Briefs, TSP, Materials

Improved Aerogel Vacuum Thermal Insulation

Multilayer structures offer reduced effective thermal conductivity.

An improved design concept for aerogel vacuum thermal-insulation panels calls for multiple layers of aerogel sandwiched between layers of aluminized Mylar (or equivalent) poly(ethylene terephthalate), as depicted in the figure. This concept is applicable to both the rigid (brick) form and the flexible (blanket) form of aerogel vacuum thermal-insulation panels.

Posted in: Briefs, TSP, Materials, Performance upgrades, Fabrication, Insulation

Using Volcanic Ash To Remove Dissolved Uranium and Lead

Experiments have shown that significant fractions of uranium, lead, and possibly other toxic and/or radioactive substances can be removed from an aqueous solution by simply exposing the solution, at ambient temperature, to a treatment medium that includes weathered volcanic ash from Pu’u Nene, which is a cinder cone on the Island of Hawaii. Heretofore, this specific volcanic ash has been used for an entirely different purpose: simulating the spectral properties of Martian soil.

Posted in: Briefs, Materials, Environmental technologies, Soils, Waste management, Hazardous materials

Cyclic Oxidation Behavior of CuCrAl Cold-Sprayed Coatings for Reusable Launch Vehicles

The next generation of reusable launch vehicles is likely to use GRCop-84 [Cu-8(at.%)Cr-4%Nb] copper alloy combustion liners. The application of protective coatings on GRCop-84 liners can minimize or eliminate many of the environmental problems experienced by uncoated liners and significantly extend their operational lives and lower operational cost. A newly developed Cu-23 (wt.%) Cr-5% Al (CuCrAl) coating, shown to resist hydrogen attack and oxidation in an as-cast form, is currently being considered as a protective coating for GRCop-84. The coating was deposited on GRCop-84 substrates by the cold spray deposition technique, where the CuCrAl was procured as gas-atomized powders. Cyclic oxidation tests were conducted between 773 and 1,073 K to characterize the coated substrates.

Posted in: Briefs, TSP, Materials, Aluminum alloys, Chromium alloys, Coatings Colorants and Finishes, Coatings, colorants, and finishes, Copper alloys, Materials properties, Launch vehicles

Ceramic Fiber Structures for Cryogenic Load-Bearing Applications

Woven or braided fibers resist embrittlement under cryogenic conditions, enabling ultralow-temperature applications.

This invention is intended for use as a load-bearing device under cryogenic temperatures and/or abrasive conditions (i.e., during missions to the Moon). The innovation consists of small-diameter, ceramic fibers that are woven or braided into devices like ropes, belts, tracks, or cables. The fibers can be formed from a variety of ceramic materials like silicon carbide, carbon, aluminosilicate, or aluminum oxide. The fiber architecture of the weave or braid is determined by both the fiber properties and the mechanical requirements of the application. A variety of weave or braid architectures is possible for this application. Thickness of load-bearing devices can be achieved by using either a 3D woven structure, or a layered, 2D structure. For the prototype device, a belt approximately 0.10 in. (0.25 cm) thick, and 3.0 in. (7.6 cm) wide was formed by layering and stitching a 2D aluminosilicate fiber weave. The circumferential length of the 2D, layered belt was approximately 36 in. (91 cm).

Posted in: Briefs, TSP, Materials, Ceramics, Fibers, Materials properties, Spacecraft

Elastomer Reinforced With Carbon Nanotubes

Elastomers are reinforced with functionalized, single-walled carbon nanotubes (SWNTs) giving them high- breaking strain levels and low densities. Cross-linked elastomers are prepared using amine-terminated, poly(dimethylsiloxane) (PDMS), with an average molecular weight of 5,000 daltons, and a functionalized SWNT.

Posted in: Briefs, Materials

Improving Heat Flux Performance of Flat Surface in Spray-Cooling Systems

A method has been developed for improving heat flux performance relative to flat surfaces in spray-cooling systems. Similar enhancement techniques have been used for convective heat transfer, but, to the best knowledge at the time of this reporting, never spray cooling of foam. Previous studies have shown that spray-cooling heat flux enhancements may be attained using enhanced surfaces. However, most enhanced surface spray-cooling studies have been limited to extended and/or embedded surface structures. This study investigates the effect of foam on spraycooling heat flux.

Posted in: Briefs, Materials, Thermal management, Thermal management, Cooling, Foams

Treating Fibrous Insulation To Reduce Thermal Conductivity

A chemical treatment reduces the convective and radiative contributions to the effective thermal conductivity of porous fibrous thermal-insulation tile. The net effect of the treatment is to coat the surfaces of fibers with a mixture of transition-metal oxides (TMOs) without filling the pores. The TMO coats reduce the cross-sectional areas available for convection while absorbing and scattering thermal radiation in the pores, thereby rendering the tile largely opaque to thermal radiation.

Posted in: Briefs, TSP, Materials

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