1. Exothermic reactions in Co/Al nanolaminates.
- Author
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Adams, D. P., Hodges, V. C., Bai, M. M., Jones, E., Rodriguez, M. A., Buchheit, T., and Moore, J. J.
- Subjects
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VAPOR-plating , *STOICHIOMETRY , *HIGH temperatures , *SURFACE roughness , *CRYSTALS , *MICROSTRUCTURE , *MAGNETRONS , *SPUTTERING (Physics) - Abstract
Vapor-deposited Co/Al nanolaminates having a net equiatomic stoichiometry exhibited rapid, high-temperature synthesis. When ignited locally, 7.5-μm-thick Co/Al foils were characterized by self-sustained propagating reactions with flame front speeds between ∼0.5 and 9 m/s. Speed was largely affected by bilayer thickness and premixed volume fraction, consistent with previous studies of other exothermic multilayers. Cobalt aluminide foils reacted by self-propagating synthesis developed a variety of rough surface morphologies characterized by a large amplitude (peak-to-valley ∼1.0 μm), multiperiod, wavelike structure. High-temperature reaction was also stimulated by rapid global heating. Tests revealed low ignition temperatures (Tig)∼240–460 °C compared with previous Co–Al powder reactant experiments. Ignition temperature was influenced by bilayer thickness. All foils ignited by global heating and those reacted in a self-propagating mode developed a single-phase B2 (CsCl-type) crystal structure. Thick Co/Al nanolaminates were used successfully to join a few different materials including metalized Al2O3 (by soldering) and polyetheretherketone (by direct attachment). [ABSTRACT FROM AUTHOR]
- Published
- 2008
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