Isoconversional Methods in Thermodynamic Principles.

Area of Science:

• Materials Science
• Chemical Thermodynamics
• Analytical Chemistry

Background:

• Thermogravimetric analysis (TGA) is crucial for studying material decomposition.
• Understanding the thermodynamic underpinnings of TGA methods is essential for accurate analysis.
• Isothermal and dynamic TGA methods have distinct thermodynamic characteristics.

Purpose of the Study:

• To present the thermodynamic aspects of isothermal and dynamic thermogravimetric analysis.
• To model isoconversional variants of dynamic TGA methods.
• To propose a framework for quantifying thermodynamic differences between TGA methods.

Main Methods:

• Thermodynamic analysis of isothermal and dynamic TGA.
• Application of de Donder's extent of reaction principles.
• Introduction of 'off-distance' (D = ΔΔ G) for thermodynamic quantification.

Main Results:

• Isothermal and dynamic TGA methods exhibit similar energetic grouping but different activity.
• Isoconversional dynamic TGA methods demonstrate opposing thermodynamic effects.
• Enthalpy dominates isothermal and dynamic methods; entropy dominates isoconversional methods.

Conclusions:

• A unified thermodynamic perspective on TGA methods is presented.
• The 'off-distance' parameter effectively quantifies thermodynamic behavior.
• Distinguishing between enthalpy-driven and entropy-driven processes in TGA is clarified.