Thermal analysis by variable temperature infrared spectroscopy with a button sample holder and Peltier...

Area of Science:

• Materials Science
• Analytical Chemistry
• Spectroscopy

Background:

• Infrared spectroscopy is a powerful tool for material characterization.
• Accurate temperature control is crucial for studying dynamic material processes.
• Existing methods may have limitations in heating/cooling rates and sample handling.

Purpose of the Study:

• To develop and validate a novel apparatus for variable temperature infrared spectroscopy.
• To enable rapid and precise temperature cycling of neat samples.
• To demonstrate the apparatus's capability in analyzing temperature-dependent material transformations.

Main Methods:

• Utilized stacked Peltier thermoelectric devices for controlled sample heating and cooling.
• Implemented a button sample holder for neat samples.
• Achieved heating/cooling rates of 2 °C s⁻¹ between 0 and 150 °C.
• Employed temperature step heating/cooling profiles and linear ramp heating.

Main Results:

• Demonstrated high measurement sensitivity, detecting <1% intensity variations for a 10 °C increment.
• Successfully correlated spectral changes with heating/cooling of α-quartz.
• Accurately determined the melting point of ibuprofen.
• Quantified thermal decomposition kinetics (isoconversion effective activation energies) of acetylsalicylic acid.

Conclusions:

• The developed apparatus provides accurate and sensitive variable temperature infrared spectroscopy.
• It effectively distinguishes between reversible and irreversible sample changes.
• The system is suitable for analyzing phase transitions, decomposition, and other temperature-dependent phenomena in various materials.