TY - JOUR
T1 - Toward design of the pre-stressed nano- and microscale aluminum particles covered by oxide shell
AU - Levitas, Valery I.
AU - Dikici, Birce
AU - Pantoya, Michelle L.
N1 - Funding Information:
The authors gratefully acknowledge support from the National Science Foundation under contract CBET-0755236, managed by Drs. Phillip Westmoreland and Arvind Atreya and the Office of Naval Research under contracts N00014-08-1-1262 and N00014-08-1-0104 all managed by Dr. Clifford Bedford.
PY - 2011/7
Y1 - 2011/7
N2 - Prediction based on the recently developed melt-dispersion mechanism of reaction for nanometric (nano) and micrometer (micron) scale aluminum (Al) particles suggests a possible increase in particle reactivity if the alumina shell is pre-compressed and the Al core is pre-expanded. This prediction was checked experimentally by measuring the flame speed for Al and molybdenum trioxide (MoO3) thermites in a semi-confined tube. Pre-stressing was produced by heating particles to several elevated temperatures, holding them at a temperature for 10min to relax thermal stresses, and cooling them at several rates to room temperature. For the optimal thermal treatment conditions (heating to 105°C and cooling at 0.13°C/s), flame propagation speed increased by 31% for nanoparticles and for 41% for micron particles. Cooling at 0.06°C/s after heating to 105°C and cooling at 0.06°C/s and 0.13°C/s after heating to 170°C either did not change the flame speed or increased it significantly less. Results are quantitatively consistent with the theoretical predictions based on the melt-dispersion mechanism.
AB - Prediction based on the recently developed melt-dispersion mechanism of reaction for nanometric (nano) and micrometer (micron) scale aluminum (Al) particles suggests a possible increase in particle reactivity if the alumina shell is pre-compressed and the Al core is pre-expanded. This prediction was checked experimentally by measuring the flame speed for Al and molybdenum trioxide (MoO3) thermites in a semi-confined tube. Pre-stressing was produced by heating particles to several elevated temperatures, holding them at a temperature for 10min to relax thermal stresses, and cooling them at several rates to room temperature. For the optimal thermal treatment conditions (heating to 105°C and cooling at 0.13°C/s), flame propagation speed increased by 31% for nanoparticles and for 41% for micron particles. Cooling at 0.06°C/s after heating to 105°C and cooling at 0.06°C/s and 0.13°C/s after heating to 170°C either did not change the flame speed or increased it significantly less. Results are quantitatively consistent with the theoretical predictions based on the melt-dispersion mechanism.
KW - Alumina shell
KW - Flame propagation rate
KW - Internal stresses
KW - Melt-dispersion mechanism
UR - http://www.scopus.com/inward/record.url?scp=79955907409&partnerID=8YFLogxK
U2 - 10.1016/j.combustflame.2010.12.002
DO - 10.1016/j.combustflame.2010.12.002
M3 - Article
AN - SCOPUS:79955907409
SN - 0010-2180
VL - 158
SP - 1413
EP - 1417
JO - Combustion and Flame
JF - Combustion and Flame
IS - 7
ER -