Materials & Coatings

Polyimide Aerogels With Three-Dimensional Cross-Linked Structure

These aerogels are suited for use as insulation as well as adsorbent beds for chemical separators, and as platforms for solid-state sensors.

Polyimide aerogels with three-dimensional cross-linked structure are made using linear oligomeric segments of polyimide, and linked with one of the following into a 3D structure: trifunctional aliphatic or aromatic amines, latent reactive end caps such as nadic anhydride or phenylethynylphenyl amine, and silica or silsesquioxane cage structures decorated with amine. Drying the gels supercritically maintains the solid structure of the gel, creating a polyimide aerogel with improved mechanical properties over linear polyimide aerogels.

Posted in: Briefs, TSP, Materials, Insulation, Materials properties, Nanotechnology, Polymers

Alumina Paste Layer as a Sublimation Suppression Barrier for Yb₁₄MnSb₁₁

This material can be applied to any thermoelectric couples requiring sublimation suppression.

Sublimation is a major cause of degradation of thermoelectric power generation systems. Most thermoelectric materials tend to have peak values at the temperature where sublimation occurs. A sublimation barrier is needed that is stable at operating temperatures, inert against thermoelectric materials, and able to withstand thermal cycling stress.

Posted in: Briefs, TSP, Materials, Nuclear energy, Thermal management, Thermal management, Aluminum alloys, Insulation

Silica/Polymer and Silica/Polymer/Fiber Composite Aerogels

These materials resist compression better than pure silica aerogels do.

Aerogels that consist, variously, of neat silica/polymer alloys and silica/polymer alloy matrices reinforced with fibers have been developed as materials for flexible thermal-insulation blankets. In comparison with prior aerogel blankets, these aerogel blankets are more durable and less dusty. These blankets are also better able to resist and recover from compression — an important advantage in that maintenance of thickness is essential to maintenance of high thermal-insulation performance. These blankets are especially suitable as core materials for vacuum-insulated panels and vacuum-insulated boxes of advanced, nearly seamless design. (Inasmuch as heat leakage at seams is much greater than heat leakage elsewhere through such structures, advanced designs for high insulation performance should provide for minimization of the sizes and numbers of seams.)

Posted in: Briefs, TSP, Materials, Composite materials, Fabrics, Fibers, Insulation, Polymers, Silicon alloys

High-Temperature Solid Lubricant Coating

NASA PS400 is a solid lubricant coating invented for high-temperature tribological applications. This plasma-sprayed coating is a variant of the previously patented PS304 coating, and has been formulated to provide higher density, smoother surface finish, and better dimensional stability.

Posted in: Briefs, TSP, Materials, Lubricants, Coatings Colorants and Finishes, Coatings, colorants, and finishes, Composite materials, Materials properties, Tribology

Exfoliated Graphite Nano-Reinforcements With Surface Modifications to Improve Dispersability

Exfoliated graphite nanoflakes are a potential low-cost source of nano-reinforcement for making polymer composites with unique properties. The chemical nature of the graphitic surface leads to a low-surface energy as produced. This makes the nanoflakes difficult to disperse in polymer resins and makes it difficult to make high-quality composites. To improve nanoflake dispersability in various polymers, two surface treatments were selected to modify the chemical structure of the graphite nanoflakes.

Posted in: Briefs, TSP, Materials, Fabrication, Composite materials, Graphite, Nanomaterials, Resins

MicroGel® for Passivation of Pigment Degradation

MicroGel® is a unique, highly porous xero-gel silica formed using sol-gel techniques. The starting materials used are designed per guidance from molecular dynamic calculations, and are made up of mixed alkali silicates rather than normally used single alkali silicates that are gelled with appropriate mineral acid at controlled temperature and time.

Posted in: Briefs, TSP, Materials, Fabrication, Composite materials, Materials properties, Silicon alloys

Producing Synthetic Agglutinates in Simulated Lunar Regolith

Method helps in the study of Lunar material.

A method was developed of synthesizing agglutinates as components of simulated Lunar regolith. The method is needed for further development of Lunar-exploration capabilities because natural Lunar regolith contains agglutinates that contribute significantly to its mechanical and thermophysical properties. Agglutinates are particles that, in the Lunar case, are aggregates of smaller regolith particles (mineral grains, glasses, and even older agglutinates) bonded together by vesicular, flow-banded glass.

Posted in: Briefs, Materials, Soils, Glass, Materials identification, Test procedures

Modeling of Failure for Analysis of Triaxial Braided Carbon Fiber Composites

Better understanding of triaxial braided composites will lead to improved aerospace and automotive structures.

In the development of advanced aircraft-engine fan cases and containment systems, composite materials are beginning to be used due to their low weight and high strength. The design of these structures must include the capability of withstanding impact loads from a released fan blade. Relatively complex triaxially braided fiber architectures have been found to yield the best performance for the fan cases. To properly work with and design these structures, robust analytical tools are required that can be used in the design process.

Posted in: Briefs, TSP, Materials, CAD / CAM / CAE, CAD, CAM, and CAE, Failure modes and effects analysis, Composite materials, Fibers, Fans, Jet engines

Selective Functionalization of Carbon Nanotubes: Part II

Different species are deposited at different distances.

An alternative method of low-temperature plasma functionalization of carbon nanotubes provides for the simultaneous attachment of molecular groups of multiple (typically two or three) different species or different mixtures of species to carbon nanotubes at different locations within the same apparatus. This method is based on similar principles, and involves the use of mostly the same basic apparatus, as those of the methods described in “Low-Temperature Plasma Functionalization of Carbon Nanotubes” (ARC-14661-1), NASA Tech Briefs, Vol. 28, No. 5 (May 2004), page 45.

Posted in: Briefs, Materials, Joining, Gases, Materials properties, Nanomaterials

Catalyst for Carbon Monoxide Oxidation

This catalyst forms carbon dioxide in a high-powered, pulsed CO2 laser.

In many applications, it is highly desirable to operate a CO2 laser in a sealed condition, for in an open system the laser requires a continuous flow of laser gas to remove the dissociation products that occur in the discharge zone of the laser, in order to maintain a stable power output. This adds to the operating cost of the laser, and in airborne or space applications, it also adds to the weight penalty of the laser. In a sealed CO2 laser, a small amount of CO2 gas is decomposed in the electrical discharge zone into corresponding quantities of CO and O2. As the laser continues to operate, the concentration of CO2 decreases, while the concentrations of CO and O2 correspondingly increase. The increasing concentration of O2 reduces laser power, because O2 scavenges electrons in the electrical discharge, thereby causing arcing in the electric discharge and a loss of the energetic electrons required to boost CO2 molecules to lasing energy levels. As a result, laser power decreases rapidly.

Posted in: Briefs, TSP, Materials, Lasers, Lasers, Carbon monoxide, Catalysts

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