Exotic Inverse Kinetic Isotopic Effect in the Thermal Decomposition of Levitated Aluminum Iodate Hexahydrate Particles

Aluminum iodate hexahydrate ([Al(H2O)6](IO3)3(HIO3)2; AIH) represents
a novel, oxidizing material for energetic applications. Recently,
AIH was synthesized to replace the aluminum oxide passivation layer
of aluminum nanoenergetic materials (ALNEM). The design of reactive
coatings for ALNEM-doped hydrocarbon fuels in propulsion systems requires
fundamental insights of the elementary steps of the decomposition
of AIH. Here, through the levitation of single AIH particles in an
ultrasonic field, we reveal a three-stage decomposition mechanism
initiated by loss of water (H2O) accompanied by an unconventional
inverse isotopic effect and ultimate breakdown of AIH into gaseous
elements (iodine and oxygen). Hence, AIH coating on aluminum nanoparticles
replacing the oxide layer would provide a critical supply of oxygen
in direct contact with the metal surface thus enhancing reactivity
and reducing ignition delays, further eliminating decades-old obstacles
of passivation layers on nanoenergetic materials. These findings demonstrate
the potential of AIH to aid in the development of next-generation
propulsion systems.