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Title: A slice of an aluminum particle: Examining grains, strain and reactivity

Abstract

The Combustion Institute Micron-scale aluminum (Al) particles are plagued by incomplete combustion that inhibits their reactivity. One approach to improving reactivity is to anneal Al particles to increase dilatational (volumetric) strain which has also been linked to increased combustion performance. While optimal annealing temperatures have been identified (roughly 300 °C), little is known about cooling rate effects on particle combustion performance. This study examines the effect of quenching after annealing Al microparticles to 100, 200 and 300 °C on intra-particle dilatational strain and reactivity. Synchrotron X-ray diffraction analysis of the particles reveals the cooling rates in the range from 0.007 to 0.38 K/s have little effect on the dilatational strain of the aluminum-core, alumina-shell particles. The annealed and quenched Al particles were then combined with a metal oxidizer (copper oxide) to examine reactivity. Flame propagation experiments follow the same trend: flame speeds are unchanged until a critical annealing temperature of 300 °C is reached and performance is maintained for each annealing temperature regardless of cooling rate. These results show that altering the mechanical properties and combustion performance of Al particles is strongly dependent on the annealing temperature and unchanged with variation in cooling rate. The contributions from elastic and plastic deformation mechanisms on strainmore » are also considered and additional experimental results are shown on the microstructure of an Al particle. Focused ion beam milling of an Al particle to electron transparency was combined with transmission electron microscope imaging in order to examine the microstructure of the Al particles. This confirmed that the Al microparticles have a polycrystalline structure shown by grains all exceeding 100 nm in size.« less

Authors:
ORCiD logo [1]; ORCiD logo [1];  [1];  [1];  [1];  [2]
  1. Texas Tech Univ., Lubbock, TX (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1377556
Alternate Identifier(s):
OSTI ID: 1358976
Grant/Contract Number:
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Combustion and Flame
Additional Journal Information:
Journal Volume: 173; Journal Issue: C; Journal ID: ISSN 0010-2180
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; aluminum; annealing; quenching; combustion; pre-stress; synchrotron XRD; FIB; TEM; powder metallurgy

Citation Formats

McCollum, Jena, Smith, Dylan K., Hill, Kevin J., Pantoya, Michelle L., Warzywoda, Juliusz, and Tamura, Nobumichi. A slice of an aluminum particle: Examining grains, strain and reactivity. United States: N. p., 2016. Web. doi:10.1016/j.combustflame.2016.09.002.
McCollum, Jena, Smith, Dylan K., Hill, Kevin J., Pantoya, Michelle L., Warzywoda, Juliusz, & Tamura, Nobumichi. A slice of an aluminum particle: Examining grains, strain and reactivity. United States. doi:10.1016/j.combustflame.2016.09.002.
McCollum, Jena, Smith, Dylan K., Hill, Kevin J., Pantoya, Michelle L., Warzywoda, Juliusz, and Tamura, Nobumichi. Mon . "A slice of an aluminum particle: Examining grains, strain and reactivity". United States. doi:10.1016/j.combustflame.2016.09.002. https://www.osti.gov/servlets/purl/1377556.
@article{osti_1377556,
title = {A slice of an aluminum particle: Examining grains, strain and reactivity},
author = {McCollum, Jena and Smith, Dylan K. and Hill, Kevin J. and Pantoya, Michelle L. and Warzywoda, Juliusz and Tamura, Nobumichi},
abstractNote = {The Combustion Institute Micron-scale aluminum (Al) particles are plagued by incomplete combustion that inhibits their reactivity. One approach to improving reactivity is to anneal Al particles to increase dilatational (volumetric) strain which has also been linked to increased combustion performance. While optimal annealing temperatures have been identified (roughly 300 °C), little is known about cooling rate effects on particle combustion performance. This study examines the effect of quenching after annealing Al microparticles to 100, 200 and 300 °C on intra-particle dilatational strain and reactivity. Synchrotron X-ray diffraction analysis of the particles reveals the cooling rates in the range from 0.007 to 0.38 K/s have little effect on the dilatational strain of the aluminum-core, alumina-shell particles. The annealed and quenched Al particles were then combined with a metal oxidizer (copper oxide) to examine reactivity. Flame propagation experiments follow the same trend: flame speeds are unchanged until a critical annealing temperature of 300 °C is reached and performance is maintained for each annealing temperature regardless of cooling rate. These results show that altering the mechanical properties and combustion performance of Al particles is strongly dependent on the annealing temperature and unchanged with variation in cooling rate. The contributions from elastic and plastic deformation mechanisms on strain are also considered and additional experimental results are shown on the microstructure of an Al particle. Focused ion beam milling of an Al particle to electron transparency was combined with transmission electron microscope imaging in order to examine the microstructure of the Al particles. This confirmed that the Al microparticles have a polycrystalline structure shown by grains all exceeding 100 nm in size.},
doi = {10.1016/j.combustflame.2016.09.002},
journal = {Combustion and Flame},
number = C,
volume = 173,
place = {United States},
year = {Mon Sep 12 00:00:00 EDT 2016},
month = {Mon Sep 12 00:00:00 EDT 2016}
}

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