Physico-Geometrical Kinetics of Solid-State Reactions in an Undergraduate Thermal Analysis Laboratory

An undergraduate kinetic experiment of the thermal decomposition of solids by microscopic observation and thermal analysis was developed by investigating a suitable reaction, applicable techniques of thermal analysis and microscopic observation, and a reliable kinetic calculation method. The thermal decomposition of sodium hydrogen carbonate is selected as the suitable reaction for the student experiments, because its physico-geometrical reaction mechanism is approximately described by the two-dimensional phase boundary controlled model, and its reaction kinetics are less sensitive to the measurement conditions of thermal analyses. On the basis of simple microscopic observations of this reaction, development of the physico-geometrical reaction model and derivation of the kinetic model function are imposed on students. The kinetic analysis is also performed using the kinetic rate data recorded by a single thermogravimetric run under modulated temperature conditions. This reduces the time spent in the laboratory and enables the application of a two-step kinetic calculation that provides reliable kinetic results. From the results, students can interpret the kinetics, which are closely related to the physico-geometrical characteristics of the reaction. A one-day undergraduate course in a thermal analysis laboratory is proposed from research and trials conducted in our university.