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High-Efficiency, Easy-to-Manufacture Engineered Nanomaterials for Thermoelectric Applications

Materials can be produced in thin/thick film form while maintaining film quality and stoichiometric balance. Marshall Space Flight Center, Alabama Stated generally, reducing the dimensionality of bulk-scale thermoelectric (TE) materials is theoretically and practically understood to be a viable route for maintaining/increasing phonon scattering, and maintaining/increasing electrical conductivity — necessary conditions for improving thermoelectric merit. Solution deposition of thin, anisotropic films of nanoscale particles of known TE materials is a route toward obtaining such low-dimensional materials with increased TE merit.

Posted in: Materials, Briefs

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Refractory Open-Cell Foam Fuel Matrix for High-Efficiency Nuclear Thermal Propulsion

A fuel form for fission applications is functional at extremely high temperatures with minimal erosion or fission product losses. Marshall Space Flight Center, Alabama A tricarbide foam fuel material has been developed that can operate at temperatures near 3,000 °C, without substantial hydrogen erosion, while providing highly efficient heat transfer to the coolant or propellant. A tricarbide foam fuel matrix of zirconium carbide (ZrC), niobium carbide (NbC), and uranium carbide (UC) has been successfully deposited and hydrogen tested. It shows that high-temperature, high-porosity foams can be produced that resist hydrogen corrosion and prevent the diffusion of fission products from the matrix. Chemical vapor deposition (CVD) technology was applied to nuclear materials systems that may be used in thermal propulsion and very high-temperature gas reactors.

Posted in: Materials, Briefs

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Hydrazine Absorbent/Detoxification Pad

This hydrazine-degrading pad has applications in hazardous-material emergency response situations. Lyndon B. Johnson Space Center, Houston, Texas A new chemistry was developed for existing hydrazine absorbent/detoxification pads. Enhancements include faster reaction rates, weight reduction, a color change that indicates spill occurrence, and another color change that indicates successful hydrazine degradation. The previous spill control pad, using copper oxide on the silica gel substrate as the reactant, affected only 50 percent degradation of hydrazine after 9 hours. The new prototypes have been found to degrade hydrazine from 95 to 99.9 percent in only 5 minutes, and to below detection limits within 90 minutes.

Posted in: Materials, Briefs, TSP

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Nanotechnology Approach to Lightweight, Multifunctional Polyethylene Composite Materials

Potential uses include personal armor, implantable prosthetics, and cut-resistant fabrics such as gloves worn by chefs and scuba divers. Langley Research Center, Hampton, Virginia Of several ideas being pursued by NASA for the reduction of radiation dosage to astronauts, the use of ultra-high-molecular-weight polyethylene (UHMWPE)-based composite materials for both radiation shielding and micrometeorite shielding appears to be particularly appealing. UHMWPE has long been understood to provide superior radiation shielding following encounters with energetic nucleons due to its high hydrogen content. Meanwhile, impacts of micrometeorites with UHMWPE tend to vaporize it, rather than causing spallation of the shield material, which then creates additional potentially damaging micrometeorites. Less widely appreciated is the high specific strength of UHMWPE and UHMWPE fibers, which provide structural integrity to the composite. Amongst thermoplastics, UHMWPE has the highest impact strength and is also highly resistant to abrasion. Despite this highly appealing combination of properties, UHMWPE’s key mechanical properties can be improved by forming composites with other nanostructured materials, leading to further performance increases and weight reductions. Such composites will increase the ability of UHMWPE structures to withstand micrometeorite impacts and maintain the structural integrity of a pressurized environment.

Posted in: Materials, Briefs, TSP

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Electrostrictive Polymers

These lightweight and durable materials enable sensing and actuation devices. Langley Research Center, Hampton, Virginia A new class of electroactive polymeric blend materials has been created that offers both sensing and actuation dual functionality. The blend is comprised of two components where one has sensing capability, and the other has actuating capability. These innovative materials provide significant field-induced strain, high mechanical output force, and exceptional strain energy density. These electrostrictive polymers are conformable, lightweight, and durable. The processing system to fabricate these polymers is simple and can be manipulated to control and optimize the materials’ mechanical and electrical properties.

Posted in: Materials, Briefs, TSP

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Researchers Build 'Invisible' Materials with Light

Metamaterials have a wide range of potential applications, including sensing and improving military stealth technology. Before cloaking devices can become reality on a larger scale, however, researchers must determine how to make the right materials at the nanoscale. Using light is now shown to be an enormous help in such nano-construction. A new technique uses light like a needle to thread long chains of particles. The development could help bring sci-fi concepts, such as cloaking devices, one step closer to reality.The technique developed by the University of Cambridge team involves using unfocused laser light as billions of needles, stitching gold nanoparticles together into long strings, directly in water for the first time. The strings can then be stacked into layers one on top of the other, similar to Lego bricks. The method makes it possible to produce materials in much higher quantities than can be made through current techniques. SourceAlso: See other Sensors tech briefs.

Posted in: Photonics, Lasers & Laser Systems, Materials, Sensors, Nanotechnology, Defense, News

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Spongelike Structure Converts Solar Energy into Steam

A new material structure developed at MIT generates steam by soaking up the sun.The structure — a layer of graphite flakes and an underlying carbon foam — is a porous, insulating material structure that floats on water. When sunlight hits the structure’s surface, it creates a hotspot in the graphite, drawing water up through the material’s pores, where it evaporates as steam. The brighter the light, the more steam is generated.The new material is able to convert 85 percent of incoming solar energy into steam — a significant improvement over recent approaches to solar-powered steam generation.“Steam is important for desalination, hygiene systems, and sterilization,” says Hadi Ghasemi, a postdoc in MIT’s Department of Mechanical Engineering, who led the development of the structure. “Especially in remote areas where the sun is the only source of energy, if you can generate steam with solar energy, it would be very useful.”SourceAlso: See other Energy tech briefs.

Posted in: Materials, Solar Power, Energy Harvesting, Energy, News

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