Ignition and Combustion Characteristics of Laser Irradiated

This experimental study investigates low power (3 W) laser ignition and the subsequent burning characteristics of consolidated Al/CuxO nanoparticle pellets and loose nanolaminate flakes. The effects of laser absorption, packing density (bulk porosity), and material properties on ignition are quantified, while simplified numerical models are used to examine their predominance. It is found that ignition of consolidated Al/CuO pellets is controlled by their effective thermal conductivity, such that ignition delay (approximately 1 to 100 ms) is minimized in the most porous specimen. However, the burning rate of these pellets is a compromise between the availability of reactive interfaces and the porosity allowing for gas expansion. On the other hand, ignition of loose Al/Cu2O nanolaminate flakes is predominately controlled by power absorption in the laser irradiated layer made of Al or Cu2O, especially when the thickness of the Cu2O layer is smaller than 60 nm. Ignition delay (approximately 0.1 to 1 ms) is tunable by adjusting the thickness of the top Cu2O layer, which absorbs more radiation compared to a top Al layer. Moreover, the burning rate of the nanolaminate samples is a compromise between the layer thickness for power absorption and the equivalence ratio that controls the extent of Al/CuxO reactions.