Characterization of self-propagating formation reactions in Ni/Zr multilayered foils using reaction heats, velocities, and temperature-time profiles

Abstract

We report on intermetallic formation reactions in vapor-deposited multilayered foils of Ni/Zr with 70 nm bilayers and overall atomic ratios of Ni:Zr, 2 Ni:Zr, and 7 Ni:2 Zr. The sequence of alloy phase formation and the stored energy is evaluated at slow heating rates (∼1 K/s) using differential scanning calorimetry traces to 725 °C. All three chemistries initially form a Ni–Zr amorphous phase which crystallizes first to the intermetallic NiZr. The heat of reaction to the final phase is 34–36 kJ/mol atom for all chemistries. Intermetallic formation reactions are also studied at rapid heating rates (greater than 105 K/s) in high temperature, self-propagating reactions which can be ignited in these foils by an electric spark. We find that reaction velocities and maximum reaction temperatures (Tmax) are largely independent of foil chemistry at 0.6±0.1 m/s and 1220±50 K, respectively, and that the measured Tmax is more than 200 K lower than predicted adiabatic temperatures (Tad). The difference between Tmax and Tad is explained by the prediction that transformation to the final intermetallic phases occurs after Tmax and results in the release of 20%–30% of the total heat of reaction and a delay in rapid cooling.

Reactive multilayers fabricated by vapor deposition: A critical review

“…A different product phase has been reported for 3Ni/Al [63], Pt/Al [60], Ti/2B [148], Zr/2Si [56], Ni .91 V .09 /Zr [153], and 7Ni .91 V .09 /2Zr [153] multilayers. Many of these systems (e.g., 7Ni .91 V .09 /2Zr) form a single product phase irrespective of their bilayer thickness.…”

“…A few studies have measured the rate of temperature rise associated with a passing wavefront and estimate this to be~10 6 K/s [167,168]. Peak temperatures in steady reaction wavefronts vary with reactive multilayer composition, but are generally well above 1000 K. A survey of bimetallic systems reveals a low flame temperature of~1250 K in 2Ni .91 V .09 /Zr [142,153], and a high flame temperature of 1875 K for Zr/3Al [141]. Much higher temperatures can be expected in Pt/Al and various thermite systems when reacted near adiabatic conditions.…”

“…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].…”

Physiochemical Characterization of Iodine (V) Oxide Part II: Morphology and Crystal Structure of Particulate Films

“…Aside from multi-layer physical or chemical vapor deposition [13][14][15][16][17], these methods generally involve some sort of a carrier fluid to combine, intermix, and transport the reagent materials to the deposition substrate. Wide ranging methods are available to control the morphology and fuel-oxidizer intimacy of the particles in the films such as self-assembly [18], aerogel, sol-gel based, or aerosol spray pyrolysis [19,20], and core-shell encapsulation [21,22].…”