Example:

Figure: Reaction progress (TG, normalized signals) of hydromagnesite decomposition as a function of time under differing temperature modes (marked on the curves).


Figure: Temperature profiles in isothermal and oscillatory temperature modes (24 h period)
1/ Temperature variations 230°C ± 40°C
2/ Temperature variations 230°C ± 20°C
3/ Isothermal 230°C

In the above figures, the arithmetic mean temperature (230°C) of the oscillatory temperature modes is the same for all experiments, however, the differences in the amplitudes greatly influence the reaction progress (see first figure). The prediction of the decomposition of hydromagnesite at 230°C with ± 40°C amplitude and 24h period indicates that after one year the sample will be almost fully decomposed. For the same mean temperature (230°C) and period (24h) but different amplitudes (20°C and 0°C for the isothermal conditions), hydromagnesite will decompose much less in this period of time (reaction extents are about 37 and 34%, respectively). Total decomposition for the 20 °C amplitude is reached within about 4 years whereas under isothermal conditions, about 9 years are required.


Comments:

The kinetic parameters calculated from the non-isothermal experiments allow prediction of the reaction progress at any temperature mode: isothermal, non-isothermal and intermediate intervals in the heating rate, expressed, e.g. in an oscillatory temperature mode. Examples of predictions of the reaction progress in an oscillatory temperature mode (widely applied in temperature-modulated calorimetry) are given above. A temperature-modulated mode increases the basic understanding of the characterization of materials in different fields [16-18]. Presented examples indicate that the prediction of some of the thermal characteristics under this mode is possible using conventional non-isothermal experiments.