Ignition and Combustion Characteristics of Nanoscale Al/AgIO₃: A Potential Energetic Biocidal System

Abstract

The authors investigated the ignition and reaction of Al/AgIO₃ thermites for potential use in biocidal applications. Rapid-heating wire experiments were performed to measure the ignition temperature and investigate the thermal decomposition of the oxidizer using a T-Jump/TOF Mass Spectrometer and an optical emission setup. Combustion experiments inside a constant-volume pressure cell were also carried out, and the relative performance was compared with other thermite systems. The ignition temperature in air at atmospheric pressure was found to be 1215 ± 40 K. The AgIO₃ was found to significantly outperform CuO and Fe₂O₃ oxidizers in pressurization tests, and this is attributed to the enhanced gas release as the AgIO₃ thermally decomposes to release iodine in addition to oxygen. The reacted product was collected to investigate the final state of the products. Transmission electron microscopy and X-ray diffraction were performed to show that the major Ag product species was AgI, and not elemental Ag and I₂. The AgI was found to be surface exposed to the environment, existing primarily as agglomerated spherical nanoparticles, and was found in some cases to coat the Al₂O₃ after the reaction.

Keywords:

• Biocide
• Combustion
• Ignition
• Nanothermite
• Silver iodate
• Thermite

ACKNOWLEDGMENTS

This work was funded by the Defense Threat Reduction Agency Basic Research Program. The authors also thank Kelvin Higa, Dan Kline, and Dan Bliss at the Naval Air Warfare Center for preparation of some of the thermite materials, and assistance with SEM/EDX and DSC-TGA analysis. They thank Dr. William Fourney for use of the high-speed camera. The authors acknowledge the support of the Maryland NanoCenter and its NispLab. The NispLab is supported in part by the NSF as a MRSEC Shared Experimental Facility.

Notes

^a Al₂O₃ involves dissociation into several gaseous products (e.g., AlO, Al₂O, O, O₂), rather than molecular Al₂O₃.

^b The product libraries do not contain some volatile species such as AlOI or AgI, and this may slightly affect the value.