Development of nanoenergetic materials based on Al/I 2 O 5 system K.S. Martirosyan*, L. Wang, and D. Luss Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX, USA, 77204 *kmartirossian@uh.edu ABSTRACT We studied the gas generation and thermal wave behavior during the detonation of a novel nanoenergetic mixture of iodine oxide and aluminum. The ignition of a homogeneous mixture of iodine pentoxide (78 wt. %) and aluminum nanoparticles (22 wt. %) occurs in the range of 605-620 °C. It generates a high discharge pressure (~11 MPa) and a shock wave with a velocity of ~2000 m/s. The pressure very rapidly rose to its peak during ~ 4 μs with a ΔP/Δt of up to 2750 GPa/s. The ignition temperature exceeded by at least 100 °C those of conventional thermite systems implying that the Al/I 2 O 5 nano mixtures can be safely stored and handled. The activation energy for the nanoscale reaction of 3I 2 O 5 +10Al=5Al 2 O 3 +6I was estimated to be 152 kJ/mol. The maximum pressure x volume (PV-value) obtained by a 0.5 g mixture was ~3.8 kPa.m 3 . This compares well with the highest reported value of 3.9 kPa.m 3 for the Bi 2 O 3 /Al mixture for the same sample mass. Keywords: nanoenergetic materials, gas generation, detonation, thermite, activation energy, rapid pressure rise. 1 INTRODUCTION Metastable Intermolecular Composites (MIC) also known as Nanoenergetic Materials (NM) have potential applications as propellants, explosives and primers and currently are the subject of extensive research [1, 2]. They can have higher energy densities than conventional explosives [3-8] and can generate shock wave with velocities of up to 2500 m/s [9-11]. These materials are mainly mixtures of two nanoparticles components, one of which is defined as a fuel and the second as oxidizer. The use of nanoscale particles instead of micro particles increases the intimate contact between the fuel and oxidizer. This decreases mass transport limitations which increases the reaction rate and reactivity of the mixtures. Thermodynamic calculations of the adiabatic temperature, equilibrium composition, and reaction enthalpy help select an MIC mixture from a large number of candidate thermite mixtures. Among numerous thermodynamically feasible MIC mixtures the most widely investigated are Al/Fe 2 O 3 , Al/MoO 3 , Al/WO 3 , Al/CuO and Al/Bi 2 O 3 nano systems [3- 11]. Recent advances in the integration of nanoenergetic components into micro-electro-mechanical systems (MEMs) suggest a possible development of “nanoenergetics-on-a-chip” devices, which will have many potential applications in digital propulsion systems. Recently we developed Nanoenergetic Gas-Generators (NGG) [11-14] and have shown that Al/Bi 2 O 3 and Al/I 2 O 5 nanocomposites can release up to seven times more gas product during explosion among traditional thermite compositions. Our long term research focuses on the finding and characterization of new NGG materials that rapidly release vigorous amount of gases and have high PV-values (pressure x volume). We describe here a novel potential MIC mixture based on Al/I 2 O 5 that releases a large amount of gaseous products and generates a fast moving thermal wave during the explosion. 2 EXPERIMENTAL 2.1 Sample preparation The enthalpy of the reaction 3I 2 O 5 + 10Al = 5Al 2 O 3 + 6I + (-ΔH=6.22kJ/g) (1) is higher than those of the following common stoichiometric thermite mixtures: Al/Fe 2 O 3 (3.97 kJ/g), Al/MoO 3 (4.72 kJ/g), Al/WO 3 (2.92 kJ/g), Al/CuO (4.09 kJ/g) and Al/Bi 2 O 3 (2.12 kJ/g). The adiabatic temperature this reaction accounting for phase changes was estimated to be 3253 K [15]. This indicates that following ignition this reaction can propagate in a self sustaining manner. The aluminum and iodine pentoxide powders were purchased from Sigma-Aldrich Co and stored in a glove box under (99.9 % pure) nitrogen to prevent contamination by any air impurities. The reactants were thoroughly mixed in hexane under a nitrogen environment for up to 8 h in a rotary mixing and grinding machine. The hexane was used as a mixing agent to prevent buildup of an electrostatic charge on the particles surface that may lead to ignition and/or explosion of the powders during the mixing and handling. The mixing of the reactants in hexane under nitrogen environment prevents the partial oxidation of the Al nano particles and averts the need to reduce the active metal. In most experiments we used aluminum nanoparticles with an average particle size of ~100 nm. This powder is not very active in air and can be safely NSTI-Nanotech 2010, www.nsti.org, ISBN 978-1-4398-3402-2 Vol. 2, 2010 137