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Title: Characterization of self-propagating formation reactions in Ni/Zr multilayered foils using reaction heats, velocities, and temperature-time profiles

We report on intermetallic formation reactions in vapor-deposited multilayered foils of Ni/Zr with 70 nm bilayers and overall atomic ratios of Ni:Zr, 2 Ni:Zr, and 7 Ni:2 Zr. The sequence of alloy phase formation and the stored energy is evaluated at slow heating rates (~1 K/s) using differential scanning calorimetry (DSC) traces to 725ºC. All three chemistries initially form a Ni-Zr amorphous phase which crystallizes first to the intermetallic NiZr. The heat of reaction to the final phase is 34-36 kJ/mol atom for all chemistries. Intermetallic formation reactions are also studied at rapid heating rates (greater than 105 K/s) in high temperature, self-propagating reactions which can be ignited in these foils by an electric spark. We find that reaction velocities and maximum reaction temperatures (Tmax) are largely independent of foil chemistry at 0.6 ± 0.1 m/s and 1220 ± 50 K, respectively, and that the measured Tmax is more than 200 K lower than predicted adiabatic temperatures (Tad). The difference between Tmax and Tad is explained by the prediction that transformation to the final intermetallic phases occurs after Tmax and results in the release of 20-30 % of the total heat of reaction and a delay in rapid cooling.
Authors:
 [1] ;  [1] ;  [1] ;  [1]
  1. Johns Hopkins University, Baltimore, MD (United States). Dept. of Materials Science and Engineering
Publication Date:
OSTI Identifier:
1076478
Grant/Contract Number:
FG02-09ER46648
Type:
Accepted Manuscript
Journal Name:
Journal of Applied Physiology (1948)
Additional Journal Information:
Journal Name: Journal of Applied Physiology (1948); Journal Volume: 109; Journal Issue: 1; Journal ID: ISSN 0021-8987
Research Org:
Johns Hopkins University, Baltimore, MD (United States). Dept. of Materials Science and Engineering
Sponsoring Org:
USDOE SC Office of Biological and Environmental Research (SC-23)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY exothermic reactions, intermetallic formation, multilayers, pyrometry