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Time-Resolved Mass Spectrometry of Nano-Al and Nano-Al/CuO Thermite under Rapid Heating: A Mechanistic Study
journal contribution
posted on 2012-12-27, 00:00 authored by Guoqiang Jian, Nicholas
W. Piekiel, Michael R. ZachariahAluminum nanoparticles (Al-NPs) and nano-Al/CuO thermite
were investigated
in a rapid heating environment by temperature jump time-of-flight
mass spectrometry. Upon rapid heating (105 to 106 K/s), Al-containing vapor species (Al and Al2O) are observed
to slowly increase with increasing temperature, followed by a rapid
increase in concentration at ∼2030 K. The temporal evolution
of Al, Al2O species observed in time-resolved mass spectra
of rapid heated Al-NPs supports the hypothesis that Al containing
species diffuse outward through the oxide shell under high heating
rate conditions. The rapid rise in Al-containing species above 2030
K, which is below the bulk melting point of Al2O3, implies that the penetration of Al into the shell probably decreases
its melting point. The measurements lead to an effective overall diffusion
coefficient of ∼10–10 cm2/s. Time-resolved
mass spectra of nano-Al/CuO thermite show for the first time the existence
of Al, Al2O, AlO, and Al2O2 intermediate
reaction products, with Al2O the main intermediate oxidation
product, in agreement with thermochemical calculations.