Materials & Coatings

Adjustable Membrane Mirrors Incorporating G-Elastomers

Lightweight, flexible, large-aperture mirrors of a type being developed for use in outer space have unimorph structures that enable precise adjustment of their surface figures. A mirror of this type includes a reflective membrane layer bonded with an electrostrictive grafted elastomer (G-elastomer) layer, plus electrodes suitably positioned with respect to these layers. By virtue of the electrostrictive effect, an electric field applied to the G-elastomer membrane induces a strain along the membrane and thus causes a deflection of the mirror surface. Utilizing this effect, the mirror surface figure can be adjusted locally by individually addressing pairs of electrodes.

Posted in: Briefs, Materials, Mirrors, Calibration, Electronic control units, Elastomers
Read More >>

High-Temperature Crystal-Growth Cartridge Tubes Made by VPS

Mechanical properties and maximum useful temperature exceed those of tungsten-alloy tubes.

Cartridge tubes for use in a crystal-growth furnace at temperatures as high as 1,600°C have been fabricated by vacuum plasma spraying (VPS). These cartridges consist mainly of an alloy of 60 weight percent molybdenum with 40 weight percent rhenium, made from molybdenum powder coated with rhenium. This alloy was selected because of its high melting temperature (≈2,550°C) and because of its excellent ductility at room temperature. These cartridges are intended to supplant tungsten/nickel-alloy cartridges, which cannot be used at temperatures above ≈1,300°C.

Posted in: Briefs, Materials, Fabrication, Manufacturing equipment and machinery, Spraying, Alloys, Heat resistant materials
Read More >>

Hall-Effect Thruster Utilizing Bismuth as Propellant

A laboratory-model Hall-effect spacecraft thruster was developed that utilizes bismuth as the propellant. Xenon was used in most prior Hall-effect thrusters. Bismuth is an attractive alternative because it has a larger atomic mass, a larger electron- impact- ionization cross-section, and is cheaper and more plentiful.

Posted in: Briefs, Materials, Propellants, Spacecraft fuel, Rocket engines, Performance tests
Read More >>

Coated Glass for Transparent Heating Elements

This coated glass can be used in high-humidity and high-altitude applications such as architectural and aircraft windows.

Applying an electric current to specially coated glass results in radiant heat energy. This process creates a transparent heating element with near- uniform surface temperatures. Manufacturing the heating element requires an ordinary pane of float glass. A fluorine-doped tin oxide coating (SnO2:F) measuring 0.25 micron thick is applied to one surface of the glass during fabrication. The coating conducts electricity, has a very tightly controlled resistance, has no appreciable color or structure, and is quite transparent. The coating has low emissivity properties that help contribute to the efficiency of the heated glass.

Posted in: Briefs, Materials, Heat transfer, Fabrication, Coatings, colorants, and finishes, Conductivity, Glass
Read More >>

Method of Cross-Linking Aerogels Using a One-Pot Reaction Scheme

A document discusses a new, simplified method for cross-linking silica and other oxide aerogels, with a polymeric material to increase strength of such materials without adversely affecting porosity or low density. The usual process is long and arduous, requiring multiple washing and soaking steps to infiltrate oxide with the polymer precursor after gelation. Additionally, diffusion problems can result in aerogel monoliths that are not uniformly cross-linked.

Posted in: Briefs, Materials, Forming, Nanomaterials, Nanotechnology, Polymers
Read More >>

CO₂ Sensors Based on Nanocrystalline SnO₂ Doped With CuO

Miniature CO2 sensors could be mass-produced inexpensively.

Nanocrystalline tin oxide (SnO2) doped with copper oxide (CuO) has been found to be useful as an electrical-resistance sensory material for measuring the concentration of carbon dioxide in air. SnO2 is an n-type semiconductor that has been widely used as a sensing material for detecting such reducing gases as carbon monoxide, some of the nitrogen oxides, and hydrocarbons. Without doping, SnO2 usually does not respond to carbon dioxide and other stable gases. The discovery that the electrical resistance of CuO-doped SnO2 varies significantly with the concentration of CO2 creates opportunities for the development of relatively inexpensive CO2 sensors for detecting fires and monitoring atmospheric conditions. This discovery could also lead to research that could alter fundamental knowledge of SnO2 as a sensing material, perhaps leading to the development of SnO2-based sensing materials for measuring concentrations of oxidizing gases.

Posted in: Briefs, TSP, Materials, Sensors and actuators, Conductivity, Copper alloys, Nanotechnology, Refractory materials, Tin alloys
Read More >>

Coating Reduces Ice Adhesion

Developed for the space shuttle, this coating may be used on aircraft and automobiles.

The Shuttle Ice Liberation Coating (SILC) has been developed to reduce the adhesion of ice to surfaces on the space shuttle. SILC, when coated on a surface (foam, metal, epoxy primer, polymer surfaces), will reduce the adhesion of ice by as much as 90 percent as compared to the corresponding uncoated surface. This innovation is a durable coating that can withstand several cycles of ice growth and removal without loss of anti-adhesion properties.

Posted in: Briefs, Materials, Coatings, colorants, and finishes, Durability, Icing and ice detection, Reusable launch vehicles and shuttles
Read More >>

Hybrid Multifoil Aerogel Thermal Insulation

Aerogel used in place of astroquartz makes lighter, more efficient insulation.

This innovation blends the merits of multifoil insulation (MFI) with aerogel-based insulation to develop a highly versatile, ultra-low thermally conductive material called hybrid multifoil aerogel thermal insulation (HyMATI). The density of the opacified aerogel is 240 mg/cm3 and has thermal conductivity in the 20 mW/mK range in high vacuum and 25 mW/mK in 1 atmosphere of gas (such as argon) up to 800 ºC. It is stable up to 1,000 ºC. This is equal to commercially available high-temperature thermal insulation. The thermal conductivity of the aerogel is 36 percent lower compared to several commercially available insulations when tested in 1 atmosphere of argon gas up to 800 ºC.

Posted in: Briefs, TSP, Materials, Conductivity, Insulation, Nanomaterials
Read More >>

Directed Growth of Carbon Nanotubes Across Gaps

Single-walled carbon nanotubes grow aligned along applied electric fields.

An experiment has shown that when single- walled carbon nanotubes (SWNTs) are grown by chemical vapor deposition in the presence of an electric field of suitable strength, the nanotubes become aligned along the electric field. In an important class of contemplated applications, one would exploit this finding in fabricating nanotube transistors; one would grow SWNTs across gaps between electrodes that would serve, subsequently, as source and drain contacts during operation of the transistors.

Posted in: Briefs, TSP, Materials, Transistors, Fabrication, Chemicals, Nanomaterials
Read More >>

Nanotip Carpets as Antireflection Surfaces

Reflectance less than 10–3 is readily achieved.

Carpetlike random arrays of metal-coated silicon nanotips have been shown to be effective as antireflection surfaces. Now undergoing development for incorporation into Sun sensors that would provide guidance for robotic exploratory vehicles on Mars, nanotip carpets of this type could also have many uses on Earth as antireflection surfaces in instruments that handle or detect ultraviolet, visible, or infrared light.

Posted in: Briefs, TSP, Materials, Optics, Materials properties, Nanomaterials
Read More >>

The U.S. Government does not endorse any commercial product, process, or activity identified on this web site.