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Title: Impact ignition and combustion of micron-scale aluminum particles pre-stressed with different quenching rates

Pre-stressing aluminum (Al) particles by annealing and quenching alters dilatational strain and is linked to increased particle reactivity. The quenching rate associated with pre-stressing is a key parameter affecting the final stress state within the Al particle, with faster quenching rates theoretically favoring a higher, more desirable stress state. Micron scale Al particles are annealed to 573 K, then quenched at different rates (i.e., 200 and 900 K/min), mixed with bismuth oxide (Bi2O 3), and the Al + Bi2O 3 mixtures are examined under low-velocity, drop-weight impact conditions. Both quenching rates showed increased impact ignition sensitivity (i.e., between 83% and 89% decrease in ignition energy). However, the slower quenching rate showed a 100% increase in pressurization rate compared to untreated particles, while the faster quenching rate showed a 97% increase in peak pressure, indicating that these two quenching rates affect Al particles differently. Surprisingly, synchrotron X-ray diffraction data show that the 200 K/min quenched particles have a higher dilatational strain than the untreated particles or the 900 K/min quenched particles. Results are rationalized with the help of a simple mechanical model that takes into account elastic stresses, creep in the alumina shell, and delamination of shell from the core. Themore » model predicts that Al powder quenched at 200 K/min did not experience delamination. In contrast, Al quenched at 900 K/min did not have creep but does have delamination, and under impact, delamination led to major fracture, greater oxygen access to the core, and significant promotion of reaction. Thus, the increase in quenching rate and shell-core delamination are more important for the increase in Al reactivity than pre-stressing alone.« less
Authors:
 [1] ; ORCiD logo [2] ;  [3] ; ORCiD logo [1]
  1. Texas Tech Univ., Lubbock, TX (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
  3. Iowa State Univ., Ames, IA (United States); Ames Lab., Ames, IA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 124; Journal Issue: 11; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING
OSTI Identifier:
1477385
Alternate Identifier(s):
OSTI ID: 1471264

Hill, Kevin J., Tamura, Nobumichi, Levitas, Valery I., and Pantoya, Michelle L.. Impact ignition and combustion of micron-scale aluminum particles pre-stressed with different quenching rates. United States: N. p., Web. doi:10.1063/1.5044546.
Hill, Kevin J., Tamura, Nobumichi, Levitas, Valery I., & Pantoya, Michelle L.. Impact ignition and combustion of micron-scale aluminum particles pre-stressed with different quenching rates. United States. doi:10.1063/1.5044546.
Hill, Kevin J., Tamura, Nobumichi, Levitas, Valery I., and Pantoya, Michelle L.. 2018. "Impact ignition and combustion of micron-scale aluminum particles pre-stressed with different quenching rates". United States. doi:10.1063/1.5044546.
@article{osti_1477385,
title = {Impact ignition and combustion of micron-scale aluminum particles pre-stressed with different quenching rates},
author = {Hill, Kevin J. and Tamura, Nobumichi and Levitas, Valery I. and Pantoya, Michelle L.},
abstractNote = {Pre-stressing aluminum (Al) particles by annealing and quenching alters dilatational strain and is linked to increased particle reactivity. The quenching rate associated with pre-stressing is a key parameter affecting the final stress state within the Al particle, with faster quenching rates theoretically favoring a higher, more desirable stress state. Micron scale Al particles are annealed to 573 K, then quenched at different rates (i.e., 200 and 900 K/min), mixed with bismuth oxide (Bi2O3), and the Al + Bi2O3 mixtures are examined under low-velocity, drop-weight impact conditions. Both quenching rates showed increased impact ignition sensitivity (i.e., between 83% and 89% decrease in ignition energy). However, the slower quenching rate showed a 100% increase in pressurization rate compared to untreated particles, while the faster quenching rate showed a 97% increase in peak pressure, indicating that these two quenching rates affect Al particles differently. Surprisingly, synchrotron X-ray diffraction data show that the 200 K/min quenched particles have a higher dilatational strain than the untreated particles or the 900 K/min quenched particles. Results are rationalized with the help of a simple mechanical model that takes into account elastic stresses, creep in the alumina shell, and delamination of shell from the core. The model predicts that Al powder quenched at 200 K/min did not experience delamination. In contrast, Al quenched at 900 K/min did not have creep but does have delamination, and under impact, delamination led to major fracture, greater oxygen access to the core, and significant promotion of reaction. Thus, the increase in quenching rate and shell-core delamination are more important for the increase in Al reactivity than pre-stressing alone.},
doi = {10.1063/1.5044546},
journal = {Journal of Applied Physics},
number = 11,
volume = 124,
place = {United States},
year = {2018},
month = {9}
}

Works referenced in this record:

Mechanochemical mechanism for fast reaction of metastable intermolecular composites based on dispersion of liquid metal
journal, April 2007
  • Levitas, Valery I.; Asay, Blaine W.; Son, Steven F.
  • Journal of Applied Physics, Vol. 101, Issue 8, Article No. 083524
  • DOI: 10.1063/1.2720182