Self-propagating reactions in Al/Zr multilayers: Anomalous dependence of reaction velocity on bilayer thickness

Abstract

Effect of varying bilayer spacing distribution on reaction heat and velocity in reactive Al/Ni multilayers J. Appl. Phys. 105, 083504 (2009); 10.1063/1.3087490Modeling of the self-propagating reactions of nickel and aluminum multilayered foils Deposition and characterization of a self-propagating CuO x / Al thermite reaction in a multilayer foil geometry High temperature, self-propagating reactions are observed in vapor-deposited Al/Zr multilayered foils of overall atomic ratios 3 Al:1 Zr and 2 Al:1 Zr and nanoscale layer thicknesses; however, the reaction velocities do not exhibit the inverse dependence on bilayer thickness that is expected based on changes in the average diffusion distance. Instead, for bilayer thicknesses of 20-30 nm, the velocity is essentially constant at $7.7 m/s. We explore several possible explanations for this anomalous behavior, including microstructural factors, changes in the phase evolution, and phase transformations in the reactant layers, but find no conclusive explanations. We determine that the phase evolution during self-propagating reactions in foils with a 3 Al:1 Zr stoichiometry is a rapid transformation from Al/Zr multilayers to the equilibrium intermetallic Al 3 Zr compound with no intermediate crystalline phases. This phase evolution is the same for foils of 90 nm bilayer thicknesses and foils of bilayer thicknesses in the range of 27 nm to 35 nm. Further, for foils with a bilayer thickness of 90 nm and a 3 Al:1 Zr overall chemistry, the propagation front is planar and steady, in contrast to unsteady reaction fronts in foils with 1 Al:1 Zr overall chemistry and similar bilayer thicknesses. V C 2013 AIP Publishing LLC. [http://dx.

Reactive multilayers fabricated by vapor deposition: A critical review

“…Surveying the systems listed in Table 1, it is apparent that, in general, highly exothermic systems propagate at increased rates. Rapid reactions with speeds N 10 m/s have been observed in 2Ni/3Al [58], Pt/Al [60], Ni(V)/1100 Al [70], Ru/ Al [144], 3Nb/Si [67], Zr/2Al [147], Zr/3Al [147], Sc/Au [90], Y/Au [90], Ti/2B [148], CuO/Al [76], and Ti/C [146] multilayers of different total thicknesses. Equiatomic Pt/Al self-propagates at the highest reported rates, up to 100 m/s, even when adhered to substrates [60], while low exothermicity Ni/Ti [101] is an example system that propagates at low rates.…”

“…For example, the Ni-Al system has been evaluated for 3:1, 3:2, 1:1, 2:3, and 1:3 Ni/Al ratios, and each exhibits a rapid, propagating exothermic reaction that moves through the entire substance [58,63,65]. Reactive Pt-Al [60], Ti-Al [59,145,146], Ni(V)-Zr [142,153], and Zr-Al [147] multilayers also span large ranges of composition. In some studies, an alloy target is used for deposition.…”

Using magnesium to maximize heat generated by reactive Al/Zr nanolaminates

“…If the heat generated within an ignition zone is enough to initiate rapid mixing in the surrounding layers, then the reaction will self-propagate throughout the entire system. This idea has been applied to systems with different microstructures and chemistries [1][2][3], including core-shell particles [4][5][6][7][8], powder compacts [9][10][11][12][13][14], mechanically activated foils and powders [15][16][17][18][19], and vapor-deposited laminate foils [2,[20][21][22][23][24][25][26][27][28].…”

Interdiffusion in amorphous AlxZr1-x alloys

“…In other studies where Al/Zr multilayers were prepared for the investigation of the solid state amorphisation in crystalline Al/Zr 75,76 and of the crystallisation of amorphous Al/ Zr, 77,78 a similar asymmetry of the interface width, as detected in this study, was observed.…”