Phase transformations, heat evolution, and atomic diffusion during slow heating of Al-rich Al/Zr multilayered foils

Fisher, Kaitlynn; Barron, Sara C.; Bonds, M.; Knepper, Robert; Livi, Kenneth J. T.; Campbell, Geoffrey H.; Browning, Nigel D.; Weihs, Timothy P.

doi:10.1063/1.4850915

Cited by 17 publications

(20 citation statements)

References 54 publications

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“…32 In particular, the latter indicated that the velocity bilayer curve for Ni-Al multilayer exhibits an anomalous velocity plateau, similar to what is observed experimentally with the Zr-Al system. 23 The study in Ref. 32 also suggested a thermal mechanism for the occurrence of this anomaly and observed that for the Ni/Al system the plateau occurs at bilayers such that w=d % 5%, where w is the premix width.…”

Section: Propagation Velocitymentioning

confidence: 99%

“…Consequently, the range of measured premixed widths can be quite wide. 23 We have not attempted a systematic analysis of the impact of w over the range of possible values, but have rather restricted our attention to two representative values, w ¼ 0.5 nm and w ¼ 0.8 nm. These values lie within a typical range of experimentally measured premixed widths and are sufficiently separated so as to lead to significant variations within the range of bilayers considered.…”

Section: Propagation Velocitymentioning

confidence: 99%

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

Vohra

Winokur

Overdeep

et al. 2014

Journal of Applied Physics

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A computational model of anaerobic reactions in metallic multilayered systems with an equimolar composition of zirconium and aluminum is developed. The reduced reaction formalism of M. Salloum and O. M. Knio, Combust. Flame 157(2): 288–295 (2010) is adopted. Attention is focused on quantifying intermixing rates based on experimental measurements of uniform ignition as well as measurements of self-propagating front velocities. Estimates of atomic diffusivity are first obtained based on a regression analysis. A more elaborate Bayesian inference formalism is then applied in order to assess the impact of uncertainties in the measurements, potential discrepancies between predictions and observations, as well as the sensitivity of predictions to inferred parameters. Intermixing rates are correlated in terms of a composite Arrhenius law, which exhibits a discontinuity around the Al melting temperature. Analysis of the predictions indicates that Arrhenius parameters inferred for the low-temperature branch lie within a tight range, whereas the parameters of the high-temperature branch are characterized by higher uncertainty. The latter is affected by scatter in the experimental measurements, and the limited range of bilayers where observations are available. For both branches, the predictions exhibit higher sensitivity to the activation energy than the pre-exponent, whose posteriors are highly correlated.

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Section: Propagation Velocitymentioning

confidence: 99%

Section: Propagation Velocitymentioning

confidence: 99%

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

Vohra

Winokur

Overdeep

et al. 2014

Journal of Applied Physics

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“…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].…”

Section: Introductionmentioning

confidence: 99%

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

Overdeep

Livi

Allen

et al. 2015

Combustion and Flame

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a b s t r a c tIn this study, we explore the effect of magnesium content on the ability of reactive nanocomposite foils to generate heat, by comparing three chemistries: Al:Zr, Al-8Mg:Zr, and Al-38Mg:Zr. These correspond to foils with alternating aluminum and zirconium layers where the Al is either pure, an 8 at.%Mg alloy, or a 38 at.%Mg alloy, respectively. Measurements performed in a specially designed bomb calorimeter show that Al-8Mg:Zr foils perform the best, generating the greatest gravimetric heat in air, oxygen, and nitrogen environments. Both Mg-containing foils release a visible plume of particles and vapor upon reacting, which was recorded with a high speed camera. This ejected mass includes Mg vapor and particles of all three metals. Both the vapor and particles oxidize rapidly in air, resulting in single metal-oxide particles. The reacted foils, particularly the Al-8Mg:Zr samples, contain voids and higher levels of oxygen and nitrogen throughout their thicknesses than reacted Al:Zr foils. To explain the higher heats of reaction for the Al-8Mg:Zr foils, we suggest that the out-diffusion and evaporation of Mg generates a high concentration of vacancies that enhance oxygen and nitrogen diffusion throughout the foil, thereby increasing the degree of oxidation and nitridation.

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“…Following recent experimental observations [38,39], the model assumes that the formation reaction is essentially complete prior to the start of the oxidation process. Thus, the initial foil temperature at the start of oxidation can be approximated as the adiabatic temperature corresponding to the anaerobic formation reaction.…”

Section: Model Formulationmentioning

confidence: 99%