(546g) Synthesis and Reactive Characterization of Aluminum Combined with Aluminum Iodate Hexahydrate Crystals [Al(H2O)6 ](IO3)3(HIO3)2

A crystalline aluminum iodate acid salt has been synthesized from aluminum particles dissolved in iodic acid solution. The precipitate from solution is aluminum iodate hexahydrate [Al(H₂O)₆ ](IO₃)₃(HIO₃)₂, as confirmed by X-ray diffraction (XRD) analysis. The method of synthesis first dissolves iodine oxide in water, creating an IO₃^- solution with pH < 0.2. Aluminum nanoparticles are added to the IO₃^-solution and aluminum iodate hexahydrate (AIH) crystals precipitate. The bulk density of the crystalline AIH and Al composite is dependent on the initial water to aluminum concentration ratio during synthesis. Reactivity is characterized in terms of flame speed with measurements purposefully designed to capture less than 1% light emission, resulting in speeds as high as 3200 m/s for AIH + Al composite with a calculated density of 3.43 g/cc. AIH increases reactivity in Al energetic materials by replacing the Al₂O₃ passivation layer that naturally forms on Al particles with AIH. AIH is a reactive salt and the energy released form the formation of Al₂O₃ is significantly less than the energy released form the formation of Al₂O₃ from unreacted Al in the core of Al particles. Al₂O₃ acts as a heat sink and oxygen diffusion barrier and replacement of the Al₂O₃ passivation layer with AIH significantly reduces the apparent activation energy of Al oxidation. The reaction to form Al₂O₃ from AIH is extremely over oxidized (15.5 moles of extra oxygen for every mole of AIH) and replacement of the Al₂O₃ passivation layer with AIH increase the amount of available oxygen and reduces the distance between unreacted Al in the core and oxidizer. The combined effects of reducing apparent activation energy and reduced distance between fuel and oxidizer result in flame speeds as high as 3200 m/s in AIH mixtures. Reactivity is affected by the concentrations of AIH, Al, β-HIO₃, and HI₃O₈ of AIH mixtures. At an ER of 1.0, reactivity increases as concentration of β-HIO₃ and HI₃O₈ increase. When concentrations of β-HIO₃ and HI₃O₈ increase, AIH concentration decreases from 75wt% to 60wt%. The increase in reactivity at an ER of 1.0 could be a result of increased density from higher concentrations of iodic acids or could be a result of reduced concentration of AIH.