Advancements in Technology for Controlling Fiber Orientation in Composite Parts

The performance of a composite part is primarily determined by the orientation of fibers in the plies. Designers wishing to exploit the full potential of composite materials, while avoiding manufacturing problems and part failures, must define and control fiber orientation. Anticipating true fiber orientation for a single ply is seldom intuitive, and predicting the behavior of an entire laminate made of tens or hundreds of plies is nearly impossible.

Posted in: Briefs, Materials, Fabrication, Composite materials, Fibers


Low-EC-Content Electrolytes for Low-Temperature Li-Ion Cells

Electrolytes comprising LiPF6 dissolved at a concentration of 1.0 M in three different mixtures of alkyl carbonates have been found well suited for use in rechargeable lithium-ion electrochemical cells at low temperatures. These and other electrolytes have been investigated in continuing research directed toward extending the lower limit of practical operating temperatures of Li-ion cells down to –60 °C. This research at earlier stages was reported in numerous previous NASA Tech Briefs articles, the three most recent being "Ethyl Methyl Carbonate as a Cosolvent for Lithium-Ion Cells" (NPO-20605), Vol. 25, No. 6 (June 2001), page 53; "Alkyl Pyrocarbonate Electrolyte Additives for Li-Ion Cells" (NPO-20775), Vol. 26, No. 5 (May 2002), page 37; and "Fluorinated Alkyl Carbonates as Cosolvents in Li-Ion Cells (NPO-21076), Vol. 26, No. 05 (May 2002), page 38. The present solvent mixtures, in terms of volume proportions of their ingredients, are 1 ethylene carbonate (EC) + 1 diethyl carbonate (DEC) + 1 dimethyl carbonate (DMC) + 3 ethyl methyl carbonate (EMC); 3EC + 3DMC + 14EMC; and 1EC + 1DEC + 1DMC + 4EMC. Relative to similar mixtures reported previously, the present mixtures, which contain smaller proportions of EC, have been found to afford better performance in experimental Li-ion cells at temperatures <–20 °C.

Posted in: Briefs, TSP, Materials, Battery cell chemistry, Lithium-ion batteries, Electrolytes


Alkaline Capacitors Based on Nitride Nanoparticles

One key to success is an oxygen-free, plasma-assisted nitride-synthesis process.High-energy-density alkaline electrochemical capacitors based on electrodes made of transition-metal nitride nanoparticles are undergoing development. Transition-metal nitrides (in particular, Fe3N and TiN) offer a desirable combination of high electrical conductivity and electrochemical stability in aqueous alkaline electrolytes like KOH. The high energy densities of these capacitors are attributable mainly to their high capacitance densities, which, in turn, are attributable mainly to the large specific surface areas of the electrode nanoparticles. Capacitors of this type could be useful as energy-storage components in such diverse equipment as digital communication systems, implanted medical devices, computers, portable consumer electronic devices, and electric vehicles.

Posted in: Briefs, TSP, Materials, Capacitors, Energy storage systems, Conductivity, Electrolytes


Polymer Electrolytes for Rechargeable Lithium Batteries

Cyanoresins would be blended and complexed with Li salts.Polymeric electrolytes for rechargeable lithium-based electrochemical cells and batteries would be made by blending and complexing cyanoresins with lithium salts, according to a proposal. In particular, polymeric electrolytes for separators, carbon-composite anodes, and cathodes would be formulated from appropriate blends of different polymers that are mutually insoluble and do not chemically react with each other. As a result, each polymeric component would retain its specific desired characteristics in high-energy-density batteries that would be capable of long cycle lives and high charge/discharge rates. For example, one polymeric component could provide high ionic conductivity and charge-carrier concentration while another polymeric component would provide structural integrity. Conceivably, a lithium battery made with such materials could exhibit an energy density of 80 W×h/lb for more than 1,000 charge/discharge cycles. Batteries like this could be used in applications ranging from geosynchronous satellites to electric vehicles to small consumer electronic equipment.

Posted in: Briefs, TSP, Materials, Battery cell chemistry, Lithium-ion batteries, Conductivity, Electrolytes, Polymers


Lightweight Foam Pads for Helmets

Special formulations are selected to obtain desired properties. Special foam pads have been developed for use in helmets. The foams in these pads have been formulated to obtain a combination of light weight, resistance to oxidation, flame retardance, superior shock-absorbing properties, and physical comfort during long use. In the original application, the pads are intended especially for use in supporting the heads of reclining astronauts during launch, providing a slight upward tilt so that the astronauts can see critical panels, switches, and checklists more easily. Modified versions of the pads and foams may be useful on Earth in helmets for motorcyclists, athletes, and others.

Posted in: Briefs, TSP, Materials, Human factors, Foams, Helmets


Water-Borne, Silicone-Based, Primerless Paints

These paints dry to form flexible anticorrosion coats.Water-borne, silicone- based paints for protecting metal structures against corrosion have been developed as substitutes for traditional anticorrosion paints that contain large amounts of volatile organic solvents. It is desirable to reduce the volatile-organic-compound (VOC) contents of paints in order to reduce the associated pollution, toxicity, flammability, and problem of compliance with environmental regulations. The VOC contents of the present water-borne, silicone-based paints are less than 200 g/L. An additional desirable feature of these paints is that they can be applied without need for prior application of primers to ensure adhesion.

Posted in: Briefs, Materials


PM Gamma Titanium Aluminide and Fabrication Techniques

Lightweight, high temperature-resistant parts can be manufactured economically.A γ titanium aluminide alloy produced by a powder-metal (PM) process, and techniques for fabricating sheets and sheet-metal components from the alloy, have been developed. The alloy and techniques, used together, are expected to satisfy a need for relatively economical manufacture of lightweight, high-temperature-resistant components of propulsion systems, control surfaces, and general structures of advanced aircraft and spacecraft. The specific strength of the alloy is similar to the specific strengths of superalloys, while its specific stiffness is greater and its density is smaller. For applications in the temperature range of 500 to 800 °C, this alloy can be used in place of superalloys, thereby making it possible to reduce weights of components by as much as 50 percent.

Posted in: Briefs, TSP, Materials


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