Materials & Coatings

High-Temperature SMAs for Actuator Applications

Work output is comparable to conventional SMA alloys but with transition temperatures significantly exceeding those of conventional materials. Compositions and production processes have been developed for making NiTi-based shape-memory alloys (SMAs) that can be tailored for use as actuator materials at temperatures exceeding those of conventional alloys. Whereas conventional shape-memory alloys are limited to use at temperatures well below 100 °C due to low transformation temperatures, these high-temperature shape-memory alloys (HTSMAs) have transformation temperatures exceeding 300 °C while maintaining many of the other attributes associated with NiTi alloys, most importantly high work output (see Figure 1). Other attractive properties of this family of NiTiPt HTSMAs include usefully high values of tensile ductility, relatively narrow hysteresis, good oxidation resistance up to 600 °C, and excellent thermal and dimensional stability. Just as important, these alloys can be readily processed into various structural forms such as thin rod and fine-diameter wire by conventional processes (see Figure 2). These materials hold promise for expanding the variety of applications in which SMAbased actuators could be used.

Posted in: Briefs, TSP, Materials

Read More >>

Low-Pt-Content Anode Catalyst for Direct Methanol Fuel Cells

The costs of fuel-cell anodes could be reduced substantially. Combinatorial experiments have led to the discovery that a nanophase alloy of Pt, Ru, Ni, and Zr is effective as an anode catalyst material for direct methanol fuel cells. This discovery has practical significance in that the electronic current densities achievable by use of this alloy are comparable or larger than those obtained by use of prior Pt/Ru catalyst alloys containing greater amounts of Pt. Heretofore, the high cost of Pt has impeded the commercialization of direct methanol fuel cells. By making it possible to obtain a given level of performance at reduced Pt content (and, hence, lower cost), the discovery may lead to reduction of the economic impediment to commercialization.

Posted in: Briefs, TSP, Materials

Read More >>

Atomized BaF2-CaF2 for Better-Flowing Plasma-Spray Feedstock

Water atomization is better suited to high-volume production of metal fluoride than conventional methods. Atomization of a molten mixture of BaF2 and CaF2 has been found to be superior to crushing of bulk solid BaF2- CaF2 as a means of producing eutectic BaF2-CaF2 powder for use as an ingredient of the powder feedstock of a hightemperature solid lubricant material known as PS304. Developed to reduce friction and wear in turbomachines that incorporate foil air bearings, PS304 is applied to metal substrates by plasma spraying. The constituents of PS304 are:

Posted in: Briefs, TSP, Materials

Read More >>

Nanophase Nickel-Zirconium Alloys for Fuel Cells

Corrosion resistance can be achieved at lower cost. Nanophase nickel- zirconium alloys have been investigated for use as electrically conductive coatings and catalyst supports in fuel cells. Heretofore, noble metals have been used because they resist corrosion in the harsh, acidic fuel-cell interior environments. However, the high cost of noble metals has prompted a search for less-costly substitutes.

Posted in: Briefs, TSP, Materials

Read More >>

SiO2/TiO2 Composite for Removing Hg From Combustion Exhaust

This material could remove mercury from exhaust streams of coal-burning power plants. Pellets made of a high-surface-area composite of silica and titania have shown promise as means of removing elemental mercury from flue gases. With further technical development and commercialization, this material could become economically attractive as a more-effective, less-expensive alternative to activated carbons for removing mercury from exhaust streams of coal-burning power plants, which are the sources of more than 90 percent of all anthropogenic airborne mercury.

Posted in: Briefs, Materials

Read More >>

Lightweight Tanks for Storing Liquefied Natural Gas

These tanks are also relatively inexpensive. Single-walled, jacketed aluminum tanks have been conceived for storing liquefied natural gas (LNG) in LNG-fueled motor vehicles. Heretofore, double- wall steel tanks with vacuum between the inner and outer walls have been used for storing LNG. In comparison with the vacuum-insulated steel tanks, the jacketed aluminum tanks weigh less and can be manufactured at lower cost. Costs of using the jacketed aluminum tanks are further reduced in that there is no need for the vacuum pumps heretofore needed to maintain vacuum in the vacuum-insulated tanks.

Posted in: Briefs, Materials

Read More >>

Hybrid Wound Filaments for Greater Resistance to Impacts

PBO fibers are used in addition to high-strength carbon fibers. The immediately preceding article includes an example in which a composite overwrap on a pressure vessel contains wound filaments made of a hybrid of high-strength carbon fibers and poly(phenylene benzobisoxazole) [PBO] fibers. This hybrid material is chosen in an effort to increase the ability of the pressure vessel to resist damage by lowspeed impacts (e.g., dropping of tools on the vessel or bumping of the vessel against hard objects during installation and use) without significantly increasing the weight of the vessel. Heretofore, enhancement of the impact resistances of filament-wound pressure vessels has entailed increases in vessel weight associated, variously, with increases in wall thickness or addition of protective materials.

Posted in: Briefs, Materials

Read More >>

The U.S. Government does not endorse any commercial product, process, or activity identified on this web site.