Determination of Parabolic Rate Constants from a Local Analysis of Mass-Gain Curves

Abstract

A method is proposed to allow a more accurateevaluation of thermogravimetric data to identifydiffusion or partial diffusion control of scalingkinetics. This method is based on the fitting ofmass-gain data to a parabola over a short time interval.The translation of the time interval over the entiretest time period provides an actual instantaneousparabolic rate constant independently of any transient stage or simultaneous reaction steps. Theusefulness and limitations of this procedure areillustrated from oxidation tests performed on severalmetallic materials (pure nickel, single-crystalsuperalloys, and NbTi-Al alloy).