Materials & Coatings
Filter

# Catalysts for Efficient Production of Carbon Nanotubes

### Some alloys have been found to work at lower temperatures.

Several metal alloys have shown promise as improved catalysts for catalytic thermal decomposition of hydrocarbon gases to produce carbon nanotubes (CNTs). Heretofore almost every experiment on the production of carbon nanotubes by this method has involved the use of iron, nickel, or cobalt as the catalyst. However, the catalytic-conversion efficiencies of these metals have been observed to be limited. The identification of better catalysts is part of a continuing program to develop means of mass production of high-quality carbon nanotubes at costs lower than those achieved thus far (as much as $100/g for purified multi-wall CNTs or$1,000/g for single-wall CNTs in year 2002).

Posted in: Briefs, TSP, Materials

# Amorphous Silk Fibroin Membranes for Separation of CO₂

Amorphous silk fibroin has shown promise as a polymeric material derivable from natural sources for making membranes for use in removing CO2 from mixed-gas streams. For most applications of silk fibroin, for purposes other than gas separation, this material is used in its highly crystalline, nearly natural form because this form has uncommonly high tensile strength. However, the crystalline phase of silk fibroin is impermeable, making it necessary to convert the material to amorphous form to obtain the high permeability needed for gas separation.

Posted in: Briefs, Materials, Biomaterials, Fibers, Materials properties, Polymers, Tensile Strength

# Use of Atomic Oxygen for Increased Water Contact Angles of Various Polymers for Biomedical Applications

### Improved polymer hydrophilicity is beneficial for cell culturing and implant growth.

The purpose of this study was to determine the effect of atomic oxygen (AO) exposure on the hydrophilicity of nine different polymers for biomedical applications. Atomic oxygen treatment can alter the chemistry and morphology of polymer surfaces, which may increase the adhesion and spreading of cells on Petri dishes and enhance implant growth. Therefore, nine different polymers were exposed to atomic oxygen and water-contact angle, or hydrophilicity, was measured after exposure. To determine whether hydrophilicity remains static after initial atomic oxygen exposure, or changes with higher fluence exposures, the contact angles between the polymer and water droplet placed on the polymer’s surface were measured versus AO fluence. The polymers were exposed to atomic oxygen in a 100-W, 13.56-MHz radio frequency (RF) plasma asher, and the treatment was found to significantly alter the hydrophilicity of non-fluorinated polymers.

Posted in: Briefs, MDB, TSP, Briefs, TSP, Coatings & Adhesives, Materials, Bio-Medical, Medical, Medical equipment and supplies, Materials properties, Oxygen, Polymers

# Convergence Nanoparticles for Multi-Modal Biomedical Imaging

### This technique enables detection, sensing, navigation, and actuation in a single nanosystem.

A project is underway to develop a novel, versatile, multi-functional convergence nanoparticle system that utilizes inorganic nanoparticles for advanced biomedical applications. Inorganic nanoparticles exhibit improved optical, magnetic, and electronic properties compared to classical bulk materials, making them useful as key components for futuristic nano-device applications.

Posted in: Briefs, MDB, TSP, Briefs, TSP, Coatings & Adhesives, Materials, Bio-Medical, Diagnostics, Medical, Imaging and visualization, Medical equipment and supplies, Materials properties, Nanotechnology

# Droplet-Based Production of Liposomes

A process for making monodisperse liposomes having lipid bilayer membranes involves fewer, simpler process steps than do related prior methods. First, a microfluidic, cross-junction droplet generator is used to produce vesicles comprising aqueous-solution droplets contained in single-layer lipid membranes. The vesicles are collected in a lipid-solvent mix that is at most partially soluble in water and is less dense than is water. A layer of water is dispensed on top of the solvent. By virtue of the difference in densities, the water sinks to the bottom and the solvent floats to the top. The vesicles, which have almost the same density as that of water, become exchanged into the water instead of floating to the top. As there are excess lipids in the solvent solution, in order for the vesicles to remain in the water, the addition of a second lipid layer to each vesicle is energetically favored.

Posted in: Briefs, MDB, Briefs, Manufacturing & Prototyping, Coatings & Adhesives, Materials, Bio-Medical, Medical

# Integrated Multilayer Insulation

### IMLI offers several potential advantages over conventional MLI.

Integrated multilayer insulation (IMLI) is being developed as an improved alternative to conventional multilayer insulation (MLI), which is more than 50 years old. A typical conventional MLI blanket comprises between 10 and 120 metallized polymer films separated by polyester nets. MLI is the best thermal-insulation material for use in a vacuum, and is the insulation material of choice for spacecraft and cryogenic systems. However, conventional MLI has several disadvantages: It is difficult or impossible to maintain the desired value of gap distance between the film layers (and consequently, it is difficult or impossible to ensure consistent performance), and fabrication and installation are labor-intensive and difficult. The development of IMLI is intended to overcome these disadvantages to some extent and to offer some additional advantages over conventional MLI.

Posted in: Briefs, Materials, Performance upgrades, Product development, Insulation

# Polyimide/Glass Composite High-Temperature Insulation

### This composite was found to exhibit an unexpectedly high degree of fire resistance.

Lightweight composites of RP46 polyimide and glass fibers have been found to be useful as extraordinarily fire-resistant electrical-insulation materials. RP46 is a polyimide of the polymerization of monomeric reactants (PMR) type, developed by NASA Langley Research Center. RP46 has properties that make it attractive for use in electrical insulation at high temperatures. These properties include high-temperature resistance, low relative permittivity, low dissipation factor, outstanding mechanical properties, and excellent resistance to moisture and chemicals. Moreover, RP46 contains no halogen or other toxic materials and when burned it does not produce toxic fume or gaseous materials.

Posted in: Briefs, Materials, Composite materials, Glass fibers, Insulation, Polymers, Fire prevention

# Damage Detection and Self-Repair in Inflatable/Deployable Structures

### Integrated sensors and self-repairing materials provide structural health management.

Inflatable/deployable structures are under consideration for applications as varied as expansion modules for the International Space Station to destinations for space tourism to habitats for the lunar surface. Monitoring and maintaining the integrity of the physical structure is critical, particularly since these structures rely on non-traditional engineering materials such as fabrics, foams, and elastomeric polymers to provide the primary protection for the human crew. The closely related prior concept of monitoring structural integrity by use of built-in or permanently attached sensors has been applied to structures made of such standard engineering materials as metals, alloys, and rigid composites. To effect monitoring of flexible structures comprised mainly of soft goods, however, it will be necessary to solve a different set of problems — especially those of integrating power and data-transfer cabling that can withstand, and not unduly interfere with, stowage and subsequent deployment of the structures. By incorporating capabilities for self-repair along with capabilities for structural health monitoring, successful implementation of these technologies would be a significant step toward semi-autonomous structures, which need little human intervention to maintain. This would not only increase the safety of these structures, but also reduce the inspection and maintenance costs associated with more conventional structures.

Posted in: Briefs, Materials, Finite element analysis, On-board diagnostics, On-board diagnostics (OBD), Maintenance, repair, and service operations, Elastomers, Fabrics, Gases

# Nanocomposite Strain Gauges Having Small TCRs

### Usefully large gauge factors and acceptably small drifts should also be attainable.

Ceramic strain gauges in which the strain-sensitive electrically conductive strips made from nanocomposites of noble metal and indium tin oxide (ITO) are being developed for use in gas turbine engines and other power-generation systems in which gas temperatures can exceed 1,500°F (about 816°C). In general, strain gauges exhibit spurious thermally induced components of response denoted apparent strain. When temperature varies, a strain-gauge material that has a nonzero temperature coefficient of resistance (TCR) exhibits an undesired change in electrical resistance that can be mistaken for the change in resistance caused by a change in strain. It would be desirable to formulate strain-gauge materials having TCRs as small as possible so as to minimize apparent strain.

Posted in: Briefs, TSP, Materials, Sensors and actuators, Ceramics, Composite materials, Nanotechnology, Semiconductors, Gas turbines