The emanation method and the method of surface labelling have been applied to study thermal processes. Using these methods,
processes which are not connected with thermal effects can be analysed. In certain cases, for example in the study of poorly
crystalline, or amorphous phases, these methods are even more sensitive than thermographic and X-ray techniques. The method
of surface labelling is advantageous in cases when it is impossible to activate the samples by the parent isotope of the gas
during the process of their preparation.
Diffusion of220Rn in ionic solids as affected by non-equilibrium defects, radiation damage, mechanical treatment and nonstoichiometry is
discussed. Ferric oxide (alpha), zinc oxide and titanium dioxide (rutile) are used to demonstrate the application of the emanation
thermal analysis for studying the respective effects.
The theoretical background for the use of radon diffusion as a probe of microstructure changes in solids is given. The high sensitivity of the emanation thermal analysis (ETA) in the study of solid state processes especially interactions taking place on surfaces and in the near surface layers is described. The increasing sensitivity of the method towards bulk processes with rising temperature is theoretically shown. The background considerations to be used in the mathematical modeling of temperature dependences of the radon release from solids on heating (i.e. simulated ETA curves) are presented. Various models for radon diffusion and various functions describing the annealing of structure irregularities, which served as diffusion paths for radon, were used in the modeling. It was shown, that ETA is able to characterize microstructure changes in the surface layers of the thickness from several nanometers to several micrometers.
In the Emanation Thermal Analysis the release of inert gas atoms previously incorporated in the sample is measured. Results
of the statistical modelling of the inert gas release during thermal decomposition of solids are presented. The updated model
supposing three components in the solid-state reaction system including the formation of an intermediate metastable component
on the surface of the newly formed component was proposed for the modelling of the ETA curves. The release of inert gas atoms
previously incorporated into the sample is used as a probe of microstructure changes. The random nucleation mechanism was
considered in the modelling. The model can be used in modelling ETA curves of solid-solid, solid-gas and solid-liquid interactions
where the existence of metastable intermediate component is supposed.