Al/CuO reactive nanolaminate ignition was studied using temperature jump (T-Jump) heating for rates greater than 105 K/s. Multilayer samples were sputter deposited onto thin platinum filaments in alternating layers of Al and CuO. The filaments were resistively heated in a time-of-flight mass spectrometer (ToF-MS), while ignition and reaction were observed with high-speed video. A total deposited thickness of 1800 nm was maintained for all samples, while the number of bilayers was varied from 1 to 12. Increasing this value decreased the diffusion distances and increased the amount of interfacial area across which reaction could occur, while keeping the overall energy of the system constant. From 2 to 6 bilayers, the ignition temperature decreased from 1250 to 670 K and the overall reactivity increased. Past 6 bilayers, the ignition temperature only decreased slightly and there was little impact on the overall reactivity. This behavior is consistent with a mass-transport model where the predominant diffusing species exhibits a low activation energy (50 kJ/mol). Ignition temperature, which depends upon bilayer thickness, is found to be a good predictor of flame speed.

No abstract

No abstract

A new expression is derived for interpreting differential scanning calorimetry curves for solidstate reactions with diffusion controlled kinetics. The new form yields an analytic expression for temperature at the maximum peak height that is similar to a Kissinger analysis, but that explicitly accounts for laminar, cylindrical and spherical multi-layer system geometries. This expression was used to analyze two reactive multi-layer nano-laminate systems, a Zr/CuO thermite and an Al-Ni aluminide, that include systematically varied layer thicknesses. This new analysis scales DSC peak temperatures against sample geometry, which leads to geometry-independent inherent activation energies and prefactors. For the Zr-CuO system, the DSC data scales with the square of the bi-layer thickness, while for the Ni-Al system the DSC data scales with the thickness. This suggests distinct reaction mechanims between these systems.

Abstract