Reaction kinetics of nanometric aluminum and iodine pentoxide Cory Farley • Michelle Pantoya NATAS2009 Special Issue Ó Akade ´miai Kiado ´, Budapest, Hungary 2010 Abstract Owing to increasing threats of biological attacks, new methods for the neutralization of spore- forming bacteria are currently being examined. Thermites may be an effective method to produce high-temperature reactions, and some compositions such as aluminum (Al) and iodine pentoxide (I 2 O 5 ) also have biocidal properties. This study examines the thermal degradation behavior of I 2 O 5 mixed with micron and nanometer scale aluminum (Al) particles. Differential scanning calorimetry (DSC) and thermogravimetric (TG) analyses were performed in an argon environment on both particle scales revealing a non- reaction for micron Al and a complex multistep reaction for the nanometer scale Al. Results show that upon I 2 O 5 decomposition, iodine ion sorption into the alumina shell passivating Al particles is the rate-controlling step of the Al–I 2 O 5 reaction. This pre-ignition reaction is unique to nano-Al mixtures and attributed to the significantly higher specific surface area of the nanometric Al particles which provide increased sites for I - sorption. A similar pre- ignition reaction had previously been observed with fluo- ride ions and the alumina shell passivating Al particles. Keywords Biocidal Reactions  Halogen decomposition  Aluminum combustion  Thermite decomposition Introduction The increase of organized terrorist cells around the world poses a growing threat to the United States and many other countries. For these terrorist cells, chemical and biological weapons make highly effective terror weapons against civilians and weapons of intimidation against soldiers [1]. While large scale chemical weapon production requires a large chemical plant, biological weapons can be produced in basements and hospitals around the world [1]. Of the organisms that could cause enough disease and death to cripple a region, anthrax poses one of the greatest threats [2]. Bioweapon attacks from agents such as anthrax would be difficult to predict, detect, or prevent [2]. Therefore, com- plete elimination of the bacterial spore while in a storage bunker can effectively prevent great loss of life and psy- chological trauma induced from undergoing a terror attack. Popular methods for the destruction of spore-forming bac- teria such as anthrax involve either ultraviolet radiation [3] or an oxidation agent such as peroxide [2]. An assault on a bunker storing anthrax containers does not lend itself to a prolonged ultraviolet radiation exposure. Oxidation of anthrax spores is a slow process with necessary exposure times of up to an hour for effective neutralization [3]. Thermites consist of a mixture of Al and a metal oxide, which produces a highly exothermic reaction when ignited [4]. With flame temperatures over 2000 K, thermites may act as a quick, effective sterilization tool when prolonged exposure to a neutralization agent is not a viable option. A common oxidizer is iron (III) oxide, Fe 2 O 3 [5]; however, for bacterial sterilization, I 2 O 5 was selected due to iodine’s bactericidal properties [6]. Iodine pentoxide is produced by heating iodic acid to 200 °C in a stream of dry air [7]. The remaining powder is stable and produces a thermite reac- tion when combined with Al fuel. When I 2 O 5 and Al react, the products are alumina (Al 2 O 3 ) and iodine, via Eq. 1. 10Al þ 3I 2 O 5 ! 5Al 2 O 3 þ 3I 2 ð1Þ This study examines the kinetics for nanometer and micron scale Al particles reacting with I 2 O 5 in a thermal C. Farley  M. Pantoya (&) Department of Mechanical Engineering, Texas Tech University, Lubbock, TX 79409-1021, USA e-mail: michelle.pantoya@ttu.edu; mpantoya@gmail.com 123 J Therm Anal Calorim (2010) 102:609–613 DOI 10.1007/s10973-010-0915-5