(605b) Understanding Ignition in Metallic Reactive Laminate Materials

Understanding how to control the ignition of reactive materials is important to the mining, demolition, bonding, and military industries. The ignition of reactive materials can be accomplished in a variety of means including mechanical impact, electrical spark, and direct heat transfer. Most ignition techniques have involved localized heating where heat losses away from the heat source can affect ignition thresholds. Here, we consider results from both local heating experiments and global heating experiments where heat losses are negligible. In addition, we utilize electrical, thermal, and mechanical methods of delivering heat to the reactive material. The various results suggest that the ignition condition is controlled by three heating parameters: the uniformity of heating, the heating rate and the heating time (or ignition temperature). As the heating mode varies from global to localized, a higher energy density is required to ignite due to increasing heat losses. For very localized heating the power density controls ignition. The activation energies and pre-exponential diffusion constants obtained by uniformly heating Ni/Al and Zr/Al nanolaminate reactive material will be presented. The experimentally determined thermodynamic and kinetic parameters for the Ni/Al system confirm the values used in numerical models that predict the reaction velocity of reactive materials with different reactant spacings.