Kinetics of thermal expansion of illite-based ceramics in the dehydroxylation region during heating

Abstract

The kinetics of the illite dehydroxylation is investigated using data from non-isothermal thermodilatometric experiments. An illitic clay with more than 70 % of illite was thermally treated under several heating rates from 1 to 15 °C min−1 in the dehydroxylation region. Model-free and nonlinear model-fitting methods were used to analyze the data, and their results are discussed. The dehydroxylation of the trans-vacant and cis-vacant illite layers can be described by the Avrami–Erofeev model with the exponent values 1.010 and 2.1, respectively, and the apparent activation energies of 119 and 184 kJ mol−1, respectively. The obtained kinetic parameters were used for the calculation of an optimal heating regime in order to achieve a constant thermal expansion rate in the dehydroxylation region for an illite-based ceramic body.