Contact-Point Models for Solid-Solid Reaction Kinetics: A Parameter Estimation and Derived Insights

A consistent description of solid-solid reactions needs to consider the spatially discontinuous nature of contact between the reactant particles, for which the contact-point framework, as proposed in the recent literature, is the appropriate framework to use. Among the models in this genre, only the model proposed by Dalvi and Suresh [AIChE J. 2011, 57 (5), 1329-1338] shows the correct asymptotic behavior. The model has two parameters (the diffusivity of B in the product phase and the initial contact area parameter), which have to be fitted from experimental conversion-time data. In this paper, we provide a methodology to separately and independently estimate the two parameters from kinetic data from experiments on pellets with different numbers of contact points. The methodology has been tested on the calcia-C(12)A(7), system, with the parameter values as well as their temperature dependence being determined over a temperature range of 1200 to 1350 degrees C. Results show that the initial contact area parameter is sensitive to the number of contact points and decreases with an increase in temperature. An attempt has been made to rationalize the observed behavior on the basis of sintering theories.

Automated summary

A consistent description of solid-solid reactions considering the spatially discontinuous nature of contact between the reactant particles is proposed. The paper provides a methodology to estimate two parameters separately from kinetic data and tested it on the calcia-C(12)A(7) system, showing the sensitivity of the initial contact area parameter to the number of contact points and temperature.