Kinetics of solid-gas reactions characterized by scanning AC nano-calorimetry with application to Zr oxidation

Abstract

Scanning AC nano-calorimetry is a recently developed experimental technique capable of measuring the heat capacity of thin-film samples of a material over a wide range of temperatures and heating rates. Here we describe how this technique can be used to study solid-gas phase reactions by measuring the change in heat capacity of a sample during reaction. We apply this approach to evaluate the oxidation kinetics of thin-film samples of zirconium in air. The results confirm parabolic oxidation kinetics with an activation energy of 0.59±0.03 eV. The nano-calorimetry measurements were performed using a device that contains an array of micromachined nano-calorimeter sensors in an architecture designed for combinatorial studies. We demonstrate that the oxidation kinetics can be quantified using a single sample, thus enabling high-throughput mapping of the composition-dependence of the reaction rate. a)

Crystallization behavior upon heating and cooling in Cu50Zr50 metallic glass thin films

“…The samples were heated to approximately 1,300 K at average heating rates varying from 13 K/s to 21,000 K/s, and then cooled to room temperature at a rate of approximately 5,000 K/s. Previous work has demonstrated that under these experimental conditions sample oxidation effects are negligible [27].…”

Scanning AC Nanocalorimetry and Its Applications

“…The technique can be applied to study a broad range of reactions, e.g. high temperature solid-gas reactions of thin-film materials, or the reaction kinetics under a wide range of scanning rates, just to name a few [24,25].…”

“…If we assign all droplets with volume v i (and thus a surface or interfacial area of s i ) in the distribution to group i, and if we denote the number of droplets and the nucleation frequency per droplet in that group by n i and , respectively, the rate of nucleation then follows the law of radioactive decay [70] 20) provided the number of droplets is sufficiently large. For bulk nucleation, the expected nucleation frequency is given by 25) where m is the total number of groups in the distribution and V is the total volume of i I droplets at a given time. Equations (4.24) and (4.25) are very general and hold for any temperature history, but they are not very useful in the analysis of experimental data because it is difficult to resolve the nucleation frequency for islands of different size.…”