Materials & Coatings

Composite-Material Structures for Absorbing Crash Energy

These structures can be fabricated relatively easily and inexpensively. Improved lightweight composite-material structures have been invented to protect persons and equipment during aircraft and ground-vehicle crashes. These structures are designed to hold their initial shapes and sustain rated loads under normal operating conditions and, during crashes, to undergo sustained deformation with high stroke efficiency at tailored crush loads to absorb kinetic energy. The advantages offered by these structures over prior crash-energy-absorbing structures, including composite-material ones, are that these structures can be fabricated by use of relatively simple, cost-effective techniques and the designs of the structures can readily be adapted to a variety of applications.

Posted in: Materials, Briefs, TSP

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Nematic Cells for Digital Light Deflection

Smectic A (SmA) prisms can be made in a variety of shapes and are useful for visible spectrum and infrared beam steerage. Smectic A (SmA) materials can be used in non-mechanical, digital beam deflectors (DBDs) as fillers for passive birefringent prisms based on decoupled pairs of electrically controlled, liquid crystalline polarization rotators, like twisted nematic (TN) cells and passive deflectors. DBDs are used in free-space laser communications, optical fiber communications, optical switches, scanners, and in-situ wavefront correction.

Posted in: Materials, Photonics, Briefs, TSP

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Improved Silica Aerogel Composite Materials

Shrinkage and cracking are greatly reduced. A family of aerogel-matrix composite materials having thermal-stability and mechanical-integrity properties better than those of neat aerogels has been developed. Aerogels are known to be excellent thermal- and acoustic-insulation materials because of their molecular-scale porosity, but heretofore, the use of aerogels has been inhibited by two factors: Their brittleness makes processing and handling difficult. They shrink during production and shrink more when heated to high temperatures during use. The shrinkage and the consequent cracking make it difficult to use them to encapsulate objects in thermal-insulation materials.

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Making More-Complex Molecules Using Superthermal Atom/Molecule Collisions

Atoms adsorbed on cold surfaces react with energetic impinging atoms. A method of making more-complex molecules from simpler ones has emerged as a by-product of an experimental study in outer-space atom/ surface collision physics. The subject of the study was the formation of CO2 molecules as a result of impingement of O atoms at controlled kinetic energies upon cold surfaces onto which CO molecules had been adsorbed. In this study, the O/CO system served as a laboratory model, not only for the formation of CO2 but also for the formation of other compounds through impingement of rapidly moving atoms upon molecules adsorbed on such cold interstellar surfaces as those of dust grains or comets. By contributing to the formation of increasingly complex molecules, including organic ones, this study and related other studies may eventually contribute to understanding of the origins of life.

Posted in: Briefs, TSP

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Flat Membrane Device for Dehumidification of Air

Water vapor is not condensed; instead, it is transported to vacuum. A device based on the transport of water through a membrane to a vacuum has been developed for dehumidifying a stream of air in the life-support system of a spacecraft or space suit. The device could also be adapted to terrestrial use in dehumidification of air in an air-conditioning stream or drying of air or another gas in a chemical processing stream. The design of this device is an advance in that it decreases (relative to prior designs) the weight, power consumption, and volume of the dehumidifier in the life-support system or other gas-circulation system in which the device is used. In the case of a spacecraft or space suit, the design thereby also increases safety and health margins. Although the membranes in the device must be replaced periodically and a vacuum source is essential for its operation, no other dehumidifier works as well in a spacecraft or space suit.

Posted in: Materials, Briefs

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Nano-Engineered Catalysts for Direct Methanol Fuel Cells

Small particle sizes and large surface areas can be produced economically and consistently. Nano-engineered catalysts, and a method of fabricating them, have been developed in a continuing effort to improve the performances of direct methanol fuel cells as candidate power sources to supplant primary and secondary batteries in a variety of portable electronic products. In order to realize the potential for high energy densities (as much as 1.5 W•h/g) of direct methanol fuel cells, it will be necessary to optimize the chemical compositions and geometric configurations of catalyst layers and electrode structures. High performance can be achieved when catalyst particles and electrode structures have the necessary small feature sizes (typically of the order of nanometers), large surface areas, optimal metal compositions, high porosity, and hydrophobicity.

Posted in: Materials, Briefs, TSP

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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.

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