Modeling and quantitative nanocalorimetric analysis to assess interdiffusion in a Ni/Al bilayer

Abstract

A computational model is developed to describe the evolution of the temperature field in a nanocalorimeter that comprises inert material layers on which a nanoscale Ni/Al bilayer has been deposited. The model incorporates a reduced continuum description of mixing and heat release in the Ni/Al bilayer, and of the energy equation in the inert layers. Due to the small thicknesses of individual layers that are several orders of magnitude smaller than the corresponding length, a simplified, transient, homogeneous representation of the temperature field can be adopted. The resulting lumped model is valid over short enough timescales, which are nonetheless sufficiently large to capture the formation reaction. By using experimental observations of the evolution of the temperature on the surface of the nanocalorimeter, the model is used to estimate the transient heat release rate. Assuming an Arrhenius model for the mixing between Ni and Al, the estimated heat release rate is used to determine the Arrhenius pre-exponent and activation energy of the atomic diffusivity. Computed results indicate that the present approach provides a promising means of characterizing atomic diffusion rates. Limitations arise, however, due to the low amplitudes of the heat release term at low temperature, and also due to phase-change effects, which make the heat release rate unobservable in the neighborhood of the melting temperature of individual constituents. For the present system, reliable estimates are extracted for temperatures ranging from about 600 K to the Al melting temperature.

Ignition of Nanocomposite Thermites by Electric Spark and Shock Wave

“…Most of the quantitative measurements reported to date and characterizing reactions leading to ignition of reactive nanomaterials have relied on thermal analysis [2][3][4][5][6][7][8][9][10]. Measurements associated with faster processes have also been reported, including time-resolved mass spectrometry following ignition of nano-thermites [11][12][13], micro- [14] and nano-calorimetry [15,16], and measurements of optical emission and pressure generated by the material coated on an electrically heated filament [17,18]. In all of the above measurements, the heating rates were sufficiently low and the ignition delays were sufficiently long to ensure the temperature uniformity within the ignited nanocomposite structure.…”

Combustion synthesis in nanostructured reactive systems

“…the con- 115 solidation process that involves the reaction between the compo-116 nents. However, during reactive sintering the technologies try to 117 avoid the self-propagation reaction at any point of the consolidated 133 and composites, approaches ten thousand. Thus it is not possible 134 to even briefly overview all of the latest achievements in this field.…”

Scanning AC nanocalorimetry study of Zr/B reactive multilayers

“…[11][12][13][14][15] . Nanocalorimetry makes it possible to conduct such studies on extremely small samples over a very wide range of heating rates [15][16][17][18][19][20] .…”

“…[11][12][13][14][15] . Nanocalorimetry makes it possible to conduct such studies on extremely small samples over a very wide range of heating rates [15][16][17][18][19][20] . DC nanocalorimetry, in particular, can be used to make accurate calorimetry measurements at heating and cooling rates in the 4,000-40,000 K/s range, whereas AC ° nanocalorimeters were developed [20][21][22][23] to enable measurements for scan rates below 4,000K/s, bridging the gap between traditional calorimetry and DC nanocalorimetry.…”