Materials

Liquid Silicone Rubber Takes the Heat

Our comprehensive white paper on liquid silicone rubber provides a detailed look at the injection-molding process and offers guidelines to achieve better molded LSR parts. While there are some shared similarities to thermoplastic injection molding, LSR is a thermoset material with a unique set of design characteristics.

Posted in: Materials, White Papers

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Elevated-Temperature, Highly Emissive Coating for Energy Dissipation of Large Surfaces

This coating can be used in high-temperature rocket nozzles, control surfaces, industrial furnaces, and transfer lines. Marshall Space Flight Center, Alabama This coating demonstrates high emittance above 80% or better at broad wavelengths within the infrared spectrum. It has shown to have an extremely stable emittance at lower wavelengths within the infrared (IR) spectrum, where energy dissipation is critical at elevated temperatures. The coating has demonstrated increases in surface texturing, and ultimately an increase in emissivity when exposed to temperatures up to 2,050 °F (≈1,120 °C). It is also stable at continuous run, elevated temperatures, and shows no signs of spalling or erosion.

Posted in: Materials, Coatings & Adhesives, Briefs

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Catalyst for Treatment and Control of Post-Combustion Emissions

This oxidation/reduction catalyst can be used in diesel and natural gas applications, and in nonautomotive pollution sources. Langley Research Center, Hampton, Virginia Emissions from fossil-fuel combustion contribute significantly to smog, acid rain, and global warming problems, and are subject to stringent environmental regulations. These regulations are expected to become more stringent as state and regional authorities become more involved in addressing these environmental problems. Better systems are needed for catalytic control.

Posted in: Materials, Coatings & Adhesives, Briefs

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Thermally Activated Crack Healing Mechanism for Metallic Materials

A thin metallic film of a low-melting-temperature healing agent is used. Langley Research Center, Hampton, Virginia A thermally activated healing mechanism is proposed and experimentally validated to mitigate crack propagation damage in metallic materials. The protected structure is coated with a thin metallic film of a low-melting-temperature healing agent. To heal or mitigate crack damage, the structure is heated to the melting temperature of the healing agent, allowing it to flow into the crack opening. Once in the crack mouth, the healing agent has two benefits: (1) by adhering to the crack surfaces, the healing agent bridges the crack, reducing the amount of load at the crack tip; and (2) any voluminous substance in the crack mouth causes crack closure (premature crack-face contact during cyclic loading) that also reduces the crack-tip loading.

Posted in: Materials, Coatings & Adhesives, Briefs

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Subsurface Imaging of Nanocomposites

Applications include sensors and actuators, aerospace structures, and tissue infusion in medical areas. Langley Research Center, Hampton, Virginia A nondestructive method that is based on modified atomic force ultrasonic microscopy (AFUM) methods has been developed for characterizing nanomaterials. The technology allows imaging and quantifying of material properties at the surface and subsurface levels. The technology reveals the orientation of nanotubes within a composite structure and offers the ability to determine subsurface characteristics without destroying the nanomaterial structure. The method is widely applicable for basic nanomaterials characterization, including distribution and orientation of particles in a nanocomposite, localized elastic constants and changes in elastic constants, adhesive surface properties, sound velocity, and material damping coefficient.

Posted in: Materials, Coatings & Adhesives, Briefs

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Self-Healing Glass Sealants for Solid Oxide Fuel Cells and Electrolyzer Cells

Operational requirements are 600 to 1,000 °C for thousands of hours. John H. Glenn Research Center, Cleveland, Ohio A solid oxide fuel cell (SOFC) is an electrochemical device that converts chemical energy into electrical power. A solid oxide electrolyzer cell (SOEC) operates in a reverse mode of SOFC, and produces O2 and H2 gases. SOFCs are being developed for a broad range of applications including portable electronic devices, automobiles, power generation, and aeronautics. The salient features of SOFCs are all-solid construction and high-temperature electrochemical reaction-based operation, resulting in clean and efficient power generation from a variety of fuels. SOFCs of two different designs, tubular and planar, are currently under development. Planar SOFCs offer several advantages such as simple manufacturing and relatively short current path, resulting in higher power density and efficiency. However, planar SOFCs and SOECs require hermetic seals. Various glass and glass-ceramics based on borates, phosphates, and silicates are being examined for SOFC seals. Silicate glasses are expected to perform superior to the borate and phosphate glasses as sealing materials.

Posted in: Materials, Coatings & Adhesives, Briefs

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Micromachined Thermopile Arrays with Novel Thermo-electric Materials

Goddard Space Flight Center, Greenbelt, Maryland Future missions to outer planets will have stringent limits on payload mass. Thermal imaging instruments to map planetary surfaces will be part of those payloads, and, consequently, will have to be compact and low mass. For thermal instruments, another key requirement will be state-of-the-art, highly sensitive detectors. Thermopiles are prime candidates for high-resolution thermal mapping in the far-infrared (17- to 250-μm wavelength) spectral range. Thermopile detector arrays can be made to be very lightweight and compact. Furthermore, they require very few ancillary components (e.g., readout electronics, optics, amplifiers), which can add to instrument volume and mass. The implementation of thermopiles on these missions is likely because they (1) generate an output voltage that is proportional to the incoming radiation within the spectral range being mapped; (2) do not require an electrical bias or an optical chopper; (3) have negligible 1/f noise; (4) are radiation hard; and (5) have a reported specific detectivity of 1 × 109 cm·Hz1/2/W at room temperature.

Posted in: Materials, Coatings & Adhesives, Briefs

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