Thresholds for igniting exothermic reactions in Al/Ni multilayers using pulses of electrical, mechanical, and thermal energy

Abstract

We use pulses of electrical, mechanical, and thermal energy to determine the ignition thresholds of self-propagating reactions in Al/(Ni-7 V) and Al/Inconel multilayers. The energy density and power density required to initiate reactions in a Al/(Ni-7 V) foil with a 50 nm bilayer is compared for all three techniques to demonstrate the importance of heat loss on ignition thresholds and its dependence on the test volume and the surrounding thermal resistance. In addition, ignition is shown to occur at temperatures as low as 232 °C when heat losses are very small suggesting that ignition can be controlled by atomic mixing in the solid state. The experiments demonstrate that the ignition threshold drops with increasing ignition volume, and it rises with increasing bilayer spacing and with increasing intermixed thickness. These trends are also supported by an analytical model we derive to predict the effects of ignition volume, multilayer microstructure, and physical properties on the ignition threshold. We calculate an activation energy of 77.3 ± 1.3 kJ/mol for solid state mixing based on measured ignition temperatures.

X-ray reflectivity measurement of interdiffusion in metallic multilayers during rapid heating

“…This is consistent with recent measurements (at temperatures similar to ours) by Grieseler and co-workers who reported E a = 120 kJ mol À1 and also assumed a grain boundary diffusion mechanism (Grieseler et al, 2014). Another point of comparison is an activation energy for solid-state interdiffusion of 77 AE 1 kJ mol À1 calculated by Fritz and co-workers based on the ignition threshold for self-propagating reactions in Al/Ni-V multilayers very similar to those considered here (Fritz et al, 2013). All of these numbers are reasonably consistent with our measured values of $ 90 kJ mol À1 .…”

Properties of reactive Al:Ni compacts fabricated by radial forging of elemental and alloy powders

“…Exothermic formation reactions that generate intermetallic compounds and heat have been studied extensively [1][2][3][4][5][6][7][8] and can occur in compacts of homogeneous [1][2][3][4][5][6][7][8], composite [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] or core shell particles [29][30][31], or in layered films [32][33][34][35][36][37][38][39][40] or foils [41][42][43]…”

Development of a reduced model of formation reactions in Zr-Al nanolaminates

“…Note that heat loss by radiation has been neglected in the ignition model 34 in light of the limited range of the temperature measurements, and that heat losses to the surroundings are considered to be dominated by natural convection. 32 Conductive heat loss to the copper blocks (see experimental set-up in Ref.…”

“…2. Following the analysis developed by Fritz et al, 34 the ignition temperatures are exploited to estimate the activation energy of atomic diffusion in the low temperature regime. For the equimolar Zr-Al system, it is estimated to be approximately 53 kJ/mol, accurate within 61.3 kJ/mol.…”