Materials & Coatings

4-Vinyl-1,3-Dioxolane-2-One as an Additive for Li-Ion Cells

Low-temperature charge/discharge capacity is increased. Electrolyte additive 4-vinyl-1, 3-dioxolane-2-one has been found to be promising for rechargeable lithium-ion electrochemical cells. This and other additives, along with advanced electrolytes comprising solutions of LiPF6 in various mixtures of carbonate solvents, have been investigated in a continuing effort to improve the performances of rechargeable lithium-ion electrochemical cells, especially at low temperatures. In contrast to work by other researchers who have investigated the use of this additive to improve the high-temperature resilience of Li-ion cells, the current work involves the incorporation of 4-vinyl-1,3-dioxolane-2-one into quaternary carbonate electrolyte mixtures, previously optimized for low-temperature applications, resulting in improved low temperature performance.

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


Aerogel/Particle Composites for Thermoelectric Devices

Shrinkage is reduced through addition of titania powder. Optimizing solution chemistry and the addition of titania and fumed silica powder reduces shrinkage. These materials would serve to increase thermal efficiency by providing thermal insulation to suppress lateral heat leaks. They would also serve to prolong operational lifetime by suppressing sublimation of certain constituents of thermoelectric materials (e.g., sublimation of Sb from CoSb3) at typical high operating temperatures. [The use of pure silica aerogels as cast-in-place thermal-insulation and sublimation-suppression materials was described in “Aerogels for Thermal Insulation of Thermoelectric Devices” (), NASA Tech Briefs, Vol. 30, No. 7 (July 2006), page 50.]

Posted in: Briefs, TSP, Materials, Powder metallurgy, Composite materials, Insulation, Reliability


Vaporizable Scaffolds for Fabricating Thermoelectric Modules

Thermoelectric legs would be separated by precise gaps. A process for fabricating thermoelectric modules with vacuum gaps separating the thermoelectric legs has been conceived, and the feasibility of some essential parts of the process has been demonstrated. The vacuum gaps are needed to electrically insulate the legs from each other. The process involves the use of scaffolding in the form of sheets of a polymer to temporarily separate the legs by the desired distance, which is typically about 0.5 mm. During a bonding subprocess that would take place in a partial vacuum at an elevated temperature, the polymer would be vaporized, thereby creating the vacuum gaps. If desired, the gaps could later be filled with an aerogel for thermal insulation and to suppress sublimation of thermoelectric material, as described in “Aerogels for Thermal Insulation of Thermoelectric Devices” (), NASA Tech Briefs, Vol. 30, No. 7 (July, 2006), page 50.

Posted in: Briefs, TSP, Materials, Fabrication, Insulation, Polymers, Electro-thermal engines


Stability Enhancement of Polymeric Sensing Films Using Fillers

Enhanced stability of polymer sensing films is achieved by adding colloidal fillers.Experiments have shown the stability enhancement of polymeric sensing films on mixing the polymer with colloidal filler particles (submicron-sized) of carbon black, silver, titanium dioxide, and fumed silicon dioxide. The polymer films are candidates for potential use as sensing media in micro/nano chemical sensor devices. The need for stability enhancement of polymer sensing films arises because such films have been found to exhibit unpredictable changes in sensing activity over time, which could result in a possible failure of the sensor device.

Posted in: Briefs, TSP, Materials, Sensors and actuators, Composite materials, Materials properties, Nanotechnology, Polymers


Nanotube Dispersions Made With Charged Surfactant

Dispersions (including monodispersions) of nanotubes in water at relatively high concentrations have been formulated as prototypes of reagents for use in making fibers, films, and membranes based on single-walled carbon nanotubes (SWNTs). Other than water, the ingredients of a dispersion of this type include one or more charged surfactant( s) and carbon nanotubes derived from the HiPco™ (or equivalent) process. Among reagents known to be made from HiPco™ (or equivalent) SWNTs, these are the most concentrated and are expected to be usable in processing of bulk structures and materials. Test data indicate that small bundles of SWNTs and single SWNTs at concentrations up to 1.1 weight percent have been present in water plus surfactant. This development is expected to contribute to the growth of an industry based on applied carbon nanotechnology. There are expected to be commercial applications in aerospace, avionics, sporting goods, automotive products, biotechnology, and medicine.

Posted in: Briefs, Materials, Water, Fabrication, Materials properties, Nanotechnology


Aerogels for Thermal Insulation of Thermoelectric Devices

Energy-conversion efficiencies would be increased and operational lifetimes prolonged. Silica aerogels have been shown to be attractive for use as thermal insulation materials for thermoelectric devices. It is desirable to thermally insulate the legs of thermoelectric devices to suppress lateral heat leaks that degrade thermal efficiency. Aerogels offer not only high thermal insulation effectiveness, but also a combination of other properties that are especially advantageous in thermoelectric device applications.

Posted in: Briefs, TSP, Materials, Insulation, Electro-thermal engines


Low-Density, Creep Resistant Single Crystal Superalloys

Weights of aircraft turbine rotors could be reduced significantly. Several recently formulated nickelbase superalloys have been developed with excellent high-temperature creep resistance, at lower densities than those of currently used nickel-base superalloys. These alloys are the latest products of a continuing effort to develop alloys that have even greater strength-toweight ratios, suitable for use in turbine blades of aircraft engines. Mass densities of turbine blades exert a significant effect on the overall weight of aircraft. For a given aircraft, a reduction in the density of turbine blades enables design reductions in the weight of other parts throughout the turbine rotor, including the disk, hub, and shaft, as well as supporting structures in the engine. The resulting total reduction in weight can be 8 to 10 times that of the reduction in weight of the turbine blades.

Posted in: Briefs, TSP, Materials, Product development, Heat resistant alloys, Nickel alloys, Fans, Rotary engines, Lightweighting


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