The word “nanoparticle” nominally elicits a vision of an isolated sphere; however, the vast bulk of nanoparticulate material exists in an aggregated state. This can have significant implications for applications such as combustion, catalysis, and optical excitation, where particles are exposed to high temperature and rapid heating conditions. In such environments, particles become susceptible to morphological changes which can reduce surface area, often to the detriment of functionality. Here, we report on thermally-induced coalescence which can occur in aluminum nanoparticle aggregates subjected to rapid heating (106–1011 K/s). Using dynamic transmission electron microscopy, we observed morphological changes in nanoparticle aggregates occurring in as little as a few nanoseconds after the onset of heating. The time-resolved probes reveal that the morphological changes initiate within 15 ns and are completed in less than 50 ns. The morphological changes were found to have a threshold temperature of about 1300 ± 50 K, as determined by millisecond-scale experiments with a calibrated heating stage. The temperature distribution of aggregates during laser heating was modeled with various simulation approaches. The results indicate that, under rapid heating conditions, coalescence occurs at an intermediate temperature between the melting points of aluminum and the aluminum oxide shell, and proceeds rapidly once this threshold temperature is reached.
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28 February 2014
Research Article|
February 25 2014
In situ imaging of ultra-fast loss of nanostructure in nanoparticle aggregates
Garth C. Egan;
Garth C. Egan
1
Department of Materials Science, University of Maryland
, College Park, Maryland 20742, USA
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Kyle T. Sullivan;
Kyle T. Sullivan
2
Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory
, 7000 East Avenue, Livermore, California 94550, USA
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Thomas LaGrange;
Thomas LaGrange
2
Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory
, 7000 East Avenue, Livermore, California 94550, USA
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Bryan W. Reed;
Bryan W. Reed
2
Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory
, 7000 East Avenue, Livermore, California 94550, USA
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Michael R. Zachariah
Michael R. Zachariah
a)
3
Department of Chemical and Biomolecular Engineering, University of Maryland
, College Park, Maryland 20742, USA
4
Department of Chemistry and Biochemistry, University of Maryland
, College Park, Maryland 20742, USA
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a)
Author to whom correspondence should be addressed. Electronic mail: mrz@umd.edu
J. Appl. Phys. 115, 084903 (2014)
Article history
Received:
December 12 2013
Accepted:
February 17 2014
Connected Content
A related article has been published:
Comment on “In situ imaging of ultra-fast loss of nanostructure in nanoparticle aggregates” [J. Appl. Phys. 115, 084903 (2014)]
Citation
Garth C. Egan, Kyle T. Sullivan, Thomas LaGrange, Bryan W. Reed, Michael R. Zachariah; In situ imaging of ultra-fast loss of nanostructure in nanoparticle aggregates. J. Appl. Phys. 28 February 2014; 115 (8): 084903. https://doi.org/10.1063/1.4867116
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