Decomposition Kinetics

By the kinetic description of decomposition reactions of solids one usually understands analysis of isothermal ??t curves which characterize the evolution of the degree of decomposition of the reactant (or of the product yield) ? with time t. Such an analysis reduces essentially to choosing the equation that fits best the real kinetic curves. The set of equations derived from different models describing the mechanisms of separate stages (induction, acceleration, and deceleration), or of their combination, is well known and provides a basis for what is presently called formal kinetics [1–8]. The information obtained in this way on the contribution of these stages to the observed kinetics is used to develop mechanisms and schemes for the evolution of the decomposition process with time. This approach is not capable, however, of yielding any data on the thermochemical characteristics of a reaction (including the composition and stoichiometry of the products, the enthalpy and the entropy of the process) and on how the decomposition rate is affected by experimental conditions, such as the temperature and the presence of gaseous products in the reaction system.