TY - JOUR
T1 - Exothermic surface chemistry on aluminum particles promoting reactivity
AU - Mulamba, Oliver
AU - Pantoya, Michelle L.
N1 - Publisher Copyright:
© 2014 Elsevier B.V. All rights reserved.
PY - 2014
Y1 - 2014
N2 - The exothermic surface chemistry associated with the alumina passivation shell surrounding aluminum (Al) particles and fluorine from fluoropolymer materials is investigated. In particular, polytetrafluo-roethylene (PTFE) has been synthesized with varying chain lengths and combined with nanometric Al fuel particles. The Al-PTFE kinetics were analyzed using equilibrium diagnostics including differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) for calorific and phase change behavior coupled with additional flame speed measurements. The objective was to understand the effects of varying PTFE molecular structure on the kinetic and energy propagation behaviors of these composites. Results showed a pre-ignition reaction (PIR) with longer chained PTFE samples and not with the shorter chained PTFE samples. The PIR is attributed to fluorine dislodging hydroxyls from the alumina (Al 2 O 3 ) passivation surface and forming Al-F structures. Composites exhibiting the PIR correspondingly result in significantly higher flame speeds. The PIR surface chemistry may contribute to promoting the melt dispersion mechanism (MDM) responsible for propagating energy in nano Al reactions. Composites with a PIR also have higher heats of combustion in both the PIR and main reaction exotherms. These results help elucidate the influence of molecular scale surface chemistry on macroscopic energy propagation.
AB - The exothermic surface chemistry associated with the alumina passivation shell surrounding aluminum (Al) particles and fluorine from fluoropolymer materials is investigated. In particular, polytetrafluo-roethylene (PTFE) has been synthesized with varying chain lengths and combined with nanometric Al fuel particles. The Al-PTFE kinetics were analyzed using equilibrium diagnostics including differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) for calorific and phase change behavior coupled with additional flame speed measurements. The objective was to understand the effects of varying PTFE molecular structure on the kinetic and energy propagation behaviors of these composites. Results showed a pre-ignition reaction (PIR) with longer chained PTFE samples and not with the shorter chained PTFE samples. The PIR is attributed to fluorine dislodging hydroxyls from the alumina (Al 2 O 3 ) passivation surface and forming Al-F structures. Composites exhibiting the PIR correspondingly result in significantly higher flame speeds. The PIR surface chemistry may contribute to promoting the melt dispersion mechanism (MDM) responsible for propagating energy in nano Al reactions. Composites with a PIR also have higher heats of combustion in both the PIR and main reaction exotherms. These results help elucidate the influence of molecular scale surface chemistry on macroscopic energy propagation.
KW - Alumina surface reactions
KW - Aluminum particles
KW - DSC-TGA
KW - Flame speeds
KW - Polytetrafluoroethylene
KW - Pre ignition reaction
UR - http://www.scopus.com/inward/record.url?scp=84922783072&partnerID=8YFLogxK
U2 - 10.1016/j.apsusc.2014.07.112
DO - 10.1016/j.apsusc.2014.07.112
M3 - Article
AN - SCOPUS:84922783072
SN - 0169-4332
VL - 315
SP - 90
EP - 94
JO - Applied Surface Science
JF - Applied Surface Science
IS - 1
ER -