Studying exothermic reactions in the Ni-Al system at rapid heating rates using a nanocalorimeter

Abstract

Heats of reaction and heat capacity changes were measured using scanning nanocalorimetry for a nickel and aluminum bilayer where initial heating rates of 104 K/s were achieved. Multiple exotherms were observed on the initial heating, but the number of intermediate exotherms decreased with increasing heating rate. The final phase was the B2 NiAl intermetallic. Results from the nanocalorimeter were compared with a conventional differential scanning calorimeter (operating at 0.7 K/s) to understand the effect of significant (10 000×) increases in heating rate on the phase transformation sequence. The high heating rate in the nanocalorimeter delays reaction initiation, causes the exothermic peaks to shift to higher temperatures, and appears to suppress the formation of intermediate, metastable phases. Potential explanations for this apparent suppression are discussed.

Low-Temperature Synthesis of Ultra-High-Temperature Coatings of ZrB2 Using Reactive Multilayers

“…Calorimetry has been used extensively to examine the thermodynamics and kinetics of multilayer reactions [12][13][14][15][16][17][18][19][20] . Nano-calorimetry sensors can significantly enhance the study of these solid-state reactions because of their extraordinary sensitivity and extremely small thermal mass [21][22][23] …”

In situ transmission electron microscopy investigation of the interfacial reaction between Ni and Al during rapid heating in a nanocalorimeter

“…This sandwich structure is the smallest symmetric repeat unit of a multilayer with a 100 nm bilayer spacing and matches the structure used in previous nanocalorimetry investigations of the Al/Ni reaction. 26 10 nm of Al 2 O 3 was deposited on both sides of the Al/Ni/Al stack to serve as a passivation layer and diffusion barrier. This sample geometry is illustrated in the upper-left of Fig.…”

Correlating ignition mechanisms of aluminum-based reactive materials with thermoanalytical measurements

“…Validating the estimate illustrated in Fig. 22, peak positions detected by the nanocalorimeter were close to those predicted based on the Kissinger processing of earlier DSC results with similar nanofoils [18]. Furthermore, absolute reaction enthalpies were evaluated and compared with those detected by DSC at much lower heating rates.…”

“…A newly developed semiconductor based nanocalorimeter was used to characterize reactions in AleNi nanofoils [18]. NieAl bilayers with thickness varied from 25 to 60 nm were directly deposited onto a thin Si-based sensitive element.…”

“…(a) Temperature vs. time profile for the first and second heating pulses. (b) Heating rate vs. temperature obtained by differentiating the curves in (a) with respect to time[18].…”