Abstract

The reaction kinetics of three different Zr–Nb alloys with Zr-0.7 wt% Nb, Zr-2.5 wt% Nb, and Zr-5 wt% Nb
were investigated using the thermogravimetric technique in the temperature range of 723-790 K. Analysis of the
oxidation curves revealed that, at all oxidation temperatures, the reaction follows initially parabolic and then
linear oxidation reaction mechanism. The X-ray powder diffraction pattern of the oxidation products revealed
the formation of ZrO0.27 and Nb0.20Zr0.80O2.10 at each temperature. The rate constants were evaluated using rate
equation and the activation energy by Arrhenius equation in both the parabolic and linear regions of each alloy.
The activation energies of Zr-0.7 wt% Nb, Zr-2.5 wt% Nb, and Zr-5 wt% Nb alloys in the parabolic region are
225, 222, and 198 kJ/mol, respectively, whereas in the linear region, the activation energies of the corresponding
alloys are 156, 136, and 123 kJ/mol.