Invited Paper TF-ThA6
Reactive Nano Laminates with Tailored Yield

Thursday, October 31, 2013, 3:40 pm, Room 102 C

In this presentation we report on a series of reactive oxygen exchange nanolaminates between an oxygen source, CuO, and a reactive metal oxygen sink where the propensity for energy release is tailored by material selection and by multilayer geometry. These results suggest it is possible to create a class of energetic materials whose yield can be tailored for specific applications.

We demonstrate that by considering anion transport in the terminal oxide, we can produce multilayers that are unstable at room temperature, or those which require substantial thermal energy to ignite. We first explored this terminal phase hypothesis by comparing CuO-metal laminates with the reactive metals: Mg, Zr, and Al. Zr-CuO laminates were the least stable, owing to the fast oxygen transport through the ZrO₂ terminal oxide, while CuO-Al laminates were the most stable, owing to the excellent diffusion barrier properties associated with Al₂O₃. A second demonstration is made for laminates of CuO and Al_1-xTi_x where x is varied systematically between the pure end members. We identify a composition of ~ 35% Ti, above which the laminates react at room temperature and below which thermal energy in the range of 300 °C and above is require to initiate oxygen exchange. Calorimetry analysis is used to measure effective activation energies for each material combination in order to better understand the material property / energy release relationships.

In addition, we report the use of in situ XPS analysis to explore, with sub nm resolution, the interface chemistry of as deposited nanolaminates precursors to identify the limitations of interface abruptness in the as-prepared state. We find that in all cases CuO|reactive metal interfaces have an unavoidable minimum oxide thickness but this thickness depends on a number of factors including thermodynamic driving force for oxygen exchange, wetting, and oxygen diffusivity.