Isothermal Kinetics Model for Solid–Solid Reaction of Powders Through Surface Area and Size Distribution of Particles

Several industrial processes, such as those in metallurgical, chemical, ceramic, and cement industries, often involve solid–solid reactions. The solid reactions at high temperatures are often limited or controlled by solid diffusion, and some models have been suggested to describe the reaction behaviors. A model considering the particle shape, surface area, particle size distribution, and diffusion rate of reactants was established to develop a quantitative representation of the solid–solid reaction of powders in a binary reactant system. In this model, the interface of particles was divided into reaction and nonreaction surfaces, and the particle shape was divided into first- and second-level shapes. The area of the reaction interface was calculated, and the concentration distribution of the reactants was numerically expressed. The simulated kinetics curves of fractional conversion α with time for different average particle sizes and diffusion coefficients were shown to be useful for evaluating the kinetics of solid–solid reactions. The simulated kinetics curves and experimental data from the references were compared, and a good accuracy was achieved.