Ignition in ternary Ru/Al-based reactive multilayers : Effects of chemistry and stacking sequence

Abstract

While self-propagating reactions in metallic multilayers have been known since the early 1990s, the vast majority of research has been conducted on binary systems comprising either elemental or alloyed layers. The properties of reaction and ignition in these samples are, for a given composition, mainly determined by the bilayer thickness as main design parameter. Here, we present how the stacking sequence is established as an additional design parameter when going from binary to ternary layered systems. The basis for this study is reactive Ru/Al multilayers which are extended to ternary samples by introducing a third element (Ni, Pt, or Hf) as a third, individual component. It is shown that exothermic solid state reactions at the layer interfaces and grain boundaries control the ignition temperature. Furthermore, the stacking sequence determines the specific volume density of phase boundaries and, thus, the magnitude of contribution of these reactions to the process of ignition. While the addition of hafnium is found to have little to no effect on ignition, nickel and platinum lower the ignition temperatures by up to 150 °C (Ni) and 230 °C (Pt), respectively. This can be attributed to the exothermic formation of Ni2Al9, amorphous a-(Al,Pt), and Pt2Al3 which are formed at temperatures significantly lower than that of RuAl6 which is the driving reaction for ignition in binary Ru/Al multilayers.