Self-propagating reactions in Al/Zr multilayers: Anomalous dependence of reaction velocity on bilayer thickness

Journal Article · Sat Dec 14 04:00:00 EST 2013 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4840915· OSTI ID:22217778

Barron, S. C.; Kelly, S. T.; Kirchhoff, J.; Knepper, R.; Fisher, K.; Hufnagel, T. C.; Weihs, T. P. ^[1]; Livi, K. J. T. ^[2]; Dufresne, E. M.; Fezzaa, K. ^[3]; Barbee, T. W. ^[4]

---

1. Department of Materials Science and Engineering, Johns Hopkins University, Baltimore, Maryland 21218 (United States)
2. Department of Earth and Planetary Sciences, Integrated Imaging Center, Johns Hopkins University, Baltimore, Maryland 21218 (United States)
3. Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
4. Condensed Matter and Materials Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

High temperature, self-propagating reactions are observed in vapor-deposited Al/Zr multilayered foils of overall atomic ratios 3 Al:1 Zr and 2 Al:1 Zr and nanoscale layer thicknesses; however, the reaction velocities do not exhibit the inverse dependence on bilayer thickness that is expected based on changes in the average diffusion distance. Instead, for bilayer thicknesses of 20-30 nm, the velocity is essentially constant at ∼7.7 m/s. We explore several possible explanations for this anomalous behavior, including microstructural factors, changes in the phase evolution, and phase transformations in the reactant layers, but find no conclusive explanations. We determine that the phase evolution during self-propagating reactions in foils with a 3 Al:1 Zr stoichiometry is a rapid transformation from Al/Zr multilayers to the equilibrium intermetallic Al{sub 3}Zr compound with no intermediate crystalline phases. This phase evolution is the same for foils of 90 nm bilayer thicknesses and foils of bilayer thicknesses in the range of 27 nm to 35 nm. Further, for foils with a bilayer thickness of 90 nm and a 3 Al:1 Zr overall chemistry, the propagation front is planar and steady, in contrast to unsteady reaction fronts in foils with 1 Al:1 Zr overall chemistry and similar bilayer thicknesses.

• OSTI ID: 22217778
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 22 Vol. 114; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
77 NANOSCIENCE AND NANOTECHNOLOGY
ALUMINIUM
COMBUSTION
FABRICATION
FOILS
LAYERS
MICROSTRUCTURE
NANOSTRUCTURES
PHASE TRANSFORMATIONS
STOICHIOMETRY
THICKNESS
VAPOR DEPOSITED COATINGS
VELOCITY
ZIRCONIUM