Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4995937 | Thermochimica Acta | 2017 | 10 Pages |
â¢Kinetic analysis of solid-state reactions involving surface nucleation is discussed.â¢Surface nucleation and anisotropic growth kinetic models are presented.â¢Shape of the particles, direction of growth and localization of the rate-determining step are considered.â¢Eighteen models are proposed according to realistic assumptions.â¢Importance of particles size or particle size distribution is put in evidence.
Nucleation-growth models for the kinetic analysis of gas-solid reactions in which nucleation proceeds at the surface of the particles are reported. The growth of the nuclei is assumed to be anisotropic, i.e. with a very fast surface rate compared to the bulk one. The nucleation and growth processes are assumed to occur with, respectively, an areic frequency γ (nb. nuclei mâ2 sâ1) and an areic reactivity Ï (mol mâ2 sâ1), both depending only on the thermodynamic variables (such as temperature, partial pressures â¦) established during the reaction. Depending on the shape of the particles, the direction of growth and the localization of the rate-determining step, eighteen analytical expressions of kinetic rate are obtained. The importance of particle size is also put in evidence.