Study of the kinetics of the mechanism of solid-state reactions at increasing temperatures

A method of comparing the kinetics of isothermal solid-state reactions based on the classical equation for analysis of nucleation-and-growth processes is described. In this method, plots of In In (1-α) vs In (time), where α is the fraction reacted, are used to distinguish reaction mechanisms. Even nonintegral slopes obtained for values of the fraction reacted from 0.15 to 0.50 may indicate whether the reaction rate is diffusion- or phase-boundary-controlled. The problems of ascertaining zero time and self-cooling (or heating) of the reacting sample can be observed in the analysis but do not cause severe difficulties in interpretation, as they can for analyses based on reduced-time plots. The analysis is applied to the dehydroxylation of kaolinite and of brucite and the decomposition of BaCO3.

Method of Comparing Solid‐State Kinetic Data and Its Application to the Decomposition of Kaolinite, Brucite, and BaCO3

Master plot methods based on the integral and/or the differential forms of the kinetic equation describing solid-state reactions have been redefined by using the concept of the generalized time, θ, introduced by Ozawa. This redefinition permits the application of these master plots to the kinetic analysis of solid-state reactions, whatever the type of temperature program used for recording the experimental data. In isothermal conditions, a single curve is enough to construct the experimental master plots. In nonisothermal conditions, the knowledge of both α as a function of temperature and activation energy is required for calculating the master plot curves from the experimental data. Practical usefulness of the present master plot methods is examined, and exemplified by being applied to the thermal decomposition of ZnCO3 under isothermal, linear nonisothermal, and nonlinear nonisothermal conditions.

Kinetic Analysis of Solid-State Reactions: The Universality of Master Plots for Analyzing Isothermal and Nonisothermal Experiments

https://pure.tue.nl/ws/files/1715165/620302.pdf

Multiphase diffusion in binary and ternary solid-state systems

A review of the structure, and fundamental mechanisms and kinetics of the leaching of chalcopyrite.

Many solid state reactions can be represented by equations of the type F(α) =kt, where α is the fraction of material reacted in time, t. These equations can be expressed in the form F(α) =A(t/t0.5) where t0.5 is the time for 50% reaction and A is a calculable constant depending on the form of F(α). Numerical tables are given of F(α) in relation to α, and to (t/t0.5), for nine equations corresponding to reactions which are diffusion controlled, or are reaction-rate controlled, or obey first order kinetics, or follow the equations of Avrami and Erofe'ev. The application of the tables to the analysis of experimental data is described.

B. N. Narahari Achar

Papers

Numerical Data for Some Commonly Used Solid State Reaction Equations