Materials

LiCoPO4 Cathode Layers for Thin-Film Batteries

Highest voltage thin-film batteries ever reported are demonstrated at low current densities. LiCoPO4 has been found to be a promising active cathode material for high-energy-density, thin-film, rechargeable electrochemical power cells. The potential of the charge/discharge plateau of a cell containing an LiCoPO4 cathode is 4.8 V — a value that compares favorably with the corresponding value of 3.8 V of a state-of-the art cell containing an LiCoO2 cathode.

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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.

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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:

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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.

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Bonding by Hydroxide-Catalyzed Hydration and Dehydration

Room-temperature process can be varied to suit optical and non-optical applications. A simple, inexpensive method for bonding solid objects exploits hydroxidecatalyzed hydration and dehydration to form silicatelike networks in thin surface and interfacial layers between the objects. (Silicatelike networks are chemical-bond networks similar to, but looser than, those of bulk silica). The method can be practiced at room temperature or over a wide range of temperatures.

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Making High-Tensile-Strength Amalgam Components

Instead of spheroids or flakes, wires are used as the solid constituents. Structural components made of amalgams can be made to have tensile strengths much greater than previously known to be possible. Amalgams, perhaps best known for their use in dental fillings, have several useful attributes, including room- temperature fabrication, corrosion resistance, dimensional stability, and high compressive strength. However, the range of applications of amalgams has been limited by their very small tensile strengths. Now, it has been discovered that the tensile strength of an amalgam depends critically on the sizes and shapes of the particles from which it is made and, consequently, the tensile strength can be greatly increased through suitable choice of the particles.

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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.

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