Materials

Protective Skins for Aerogel Monoliths

Viscous polymer precursors are applied, then polymerized before they can percolate in. A method of imparting relatively hard protective outer skins to aerogel monoliths has been developed. Even more than aerogel beads, aerogel monoliths are attractive as thermal-insulation materials, but the commercial utilization of aerogel monoliths in thermal-insulation panels has been inhibited by their fragility and the consequent difficulty of handling them. Therefore, there is a need to afford sufficient protection to aerogel monoliths to facilitate handling, without compromising the attractive bulk properties (low density, high porosity, low thermal conductivity, high surface area, and low permittivity) of aerogel materials. The present method was devised to satisfy this need.

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Ceramic Paste for Patching High-Temperature Insulation

Repairs can be performed by use of simple techniques. A ceramic paste that can be applied relatively easily, either by itself or in combination with one or more layer(s) of high temperature ceramic fabrics, such as silicon carbide or zirconia, has been invented as a means of patching cracks or holes in the reinforced carbon-carbon forward surfaces of a space shuttle in orbit before returning to Earth. The paste or the paste/fabric combination could also be used to repair rocket-motor combustion chambers, and could be used on Earth to patch similar high-temperature structures.

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Electrically Conductive Anodized Aluminum Surfaces

These coatings are highly adherent, transparent, and relatively inexpensive. Anodized aluminum components can be treated to make them sufficiently electrically conductive to suppress discharges of static electricity. The treatment was conceived as a means of preventing static electric discharges on exterior satin-anodized aluminum (SAA) surfaces of spacecraft without adversely affecting the thermal-control/optical properties of the SAA and without need to apply electrically conductive paints, which eventually peel off in the harsh environment of outer space. The treatment can also be used to impart electrical conductivity to anodized housings of computers, medical electronic instruments, telephone-exchange equipment, and other terrestrial electronic equipment vulnerable to electrostatic discharge.

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Composite Solid Electrolyte Containing Li+- Conducting Fibers

Li+-ion conductivities are greater than those achieved before. Improved composite solid polymer electrolytes (CSPEs) are being developed for use in lithium-ion power cells. The matrix components of these composites, like those of some prior CSPEs, are highmolecular- weight dielectric polymers [generally based on polyethylene oxide (PEO)]. The filler components of these composites are continuous, highly-Li+- conductive, inorganic fibers.

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Making Activated Carbon by Wet Pressurized Pyrolysis

Thermomechanical instabilities and associated frequency instabilities are reduced. A wet pressurized pyrolysis (wet carbonization) process has been invented as a means of producing activated carbon from a wide variety of inedible biomass consisting principally of plant wastes. The principal intended use of this activated carbon is room-temperature adsorption of pollutant gases from cooled incinerator exhaust streams.

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Perovskite Superlattices as Tunable Microwave Devices

Interfacial interactions between paraelectric materials induce quasi-ferroelectric behavior. Experiments have shown that superlattices that comprise alternating epitaxial layers of dissimilar paraelectric perovskites can exhibit large changes in permittivity with the application of electric fields. The superlattices are potentially useful as electrically tunable dielectric components of such microwave devices as filters and phase shifters.

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Reliability and Design Considerations for Long Life Using Mica Capacitors in High-Voltage Apps

Over the last 40 years, a series of misconceptions regarding mica capacitor applications has led novice users to consistently over- derate wound or rolled mica/ epoxy dielectric capacitors. Mica, K2A13(Si04)3, a complex aluminum silicate in dielectric form, has been successfully used for many years as an integral part of high- voltage (2KVDC to 50KVDC) capacitor manufacturing — particularly in the 50pF to 5μF value range. Mica has unrivaled physical and electrical properties in comparison to other capacitor dielectrics, especially ceramic. Mica is extremely stable. Capacitance will change only -2% at -54°C and to +3% at +125°C. Mica is an excellent insulator, and is resistant to high temperature, thermal shock, mechanical shock, and vibration.

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