REFLECTED SHOCK IGNITION AND COMBUSTION OF ALUMINUM AND NANOCOMPOSITE THERMITE POWDERS

• Published in: Combustion science and technology 2007-03, Vol.179 (3), p.457-476
• Main Authors: BAZYN, T., GLUMAC, N., KRIER, H., WARD, T. S., SCHOENITZ, M., DREIZIN, E. L.
• Format: Article
• Language: English
• Subjects: Applied sciences; Combustion. Flame; Energy; Energy. Thermal use of fuels; Exact sciences and technology; ignition; Miscellaneous; nanothermites; shock tube; Theoretical studies. Data and constants. Metering
• ISSN: 0010-2202; 1563-521X
• DOI: 10.1080/00102200600637261

A comparison of the ignition and combustion characteristics of Al-Fe 2 O 3 and Al-MoO 3 nanocomposite powders and two sizes of aluminum powder in inert and oxidizing environments was performed in the region behind a reflected shock in a shock tube. Radiation intensity was monitored by photometry, and temporal information on the particle temperatures was obtained using high-speed pyrometry. In addition, emission spectra were collected to identify intermediate species produced during combustion. In inert environments, both thermite materials showed evidence of ignition within 1-2 ms at 1400 and 1800 K. Particle temperatures during reaction ranging from 2700-3350 K were observed, with Al-MoO 3 having generally higher temperatures than Al-Fe 2 O 3 . Addition of oxygen in the ambient environment reduced ignition times and increased combustion temperatures to 3350-3800 K as well, suggesting that heterogeneous reactions can enhance the combustion performance of the thermite materials. In air at 3 atm, the nanocomposite thermites and nanoscale aluminum all showed extremely rapid ignition: on the microsecond time scale and under 2000 K. The bulk of the material, however, ignited and burned on much longer time scales of the order of 1 millisecond. Bulk nanocomposites were found to ignite as quick or more quickly than bulk, agglomerated nanoscale aluminum and significantly faster than a 5-10 micron aluminum powder.