NATURE AND PHILOSOPHY OF THERMAL-PROCESSES IN MINERALS AND INORGANIC MATERIALS

Solid-state thermal processes have their own specificity, distinguishi ng them from the processes in gases and liquids. This specificity incl udes, among others, their limited reversibility and the limited or mod ified role of chemical affinity as the main driving force indicating t he direction of real solid-state processes. The consequency is the for mation of metastable compounds or phases during heating, as intermedia te steps towards the state of thermodynamic equilibrium. They are a re sults of the particular properties of the rigid internal structure of minerals and materials as the thermal reaction medium. The peculiariti es of thermal reactions of solids are presented on the example of thos e of oxides (silicates and berates) with polymeric structures. The sig nificance of crystal-chemical factors for the prediction or explanatio n of the course of high-temperature processes, as complementing the th ermodynamic factors, is discussed.