Study on Physicochemical and Thermal Properties of Tetrabutylammonium-Based Cation Ionic Salts Induced by Al₂O₃ Additive for Thermal Energy Storage Application

• Main Authors: Inge M. Sutjahja, Surjani Wonorahardjo, Surjamanto Wonorahardjo
• Format: Article
• Language: English
• Published: MDPI AG 2020-09-01
• Series: Inorganics
• Subjects: tetrabutylamonium bromide; tetrabutylamonium hexafluorophosphate; aluminium oxide additive; infrared (IR); decomposition and melting temperature; heat of fusion
• Online Access: https://www.mdpi.com/2304-6740/8/9/51
• ISSN: 2304-6740

The physicochemical and thermal properties of tetrabutylammonium bromide (TBA-Br) and tetrabutylammonium hexafluorophosphate (TBA-PF₆), and their change with the addition of Al₂O₃, were investigated using infrared (IR) spectroscopy and by simultaneously conducting thermal thermogravimetric (TG) analysis and differential thermal analysis (DTA) to obtain the differential scanning calorimetry (DSC) thermogram. The change in the IR data is characterized by the growth of a large peak in the range of 3500 cm⁻¹ and the reduction of peaks below 1000 cm⁻¹ with the additive concentration. The decomposition temperature determined from the peak in the DTG curve is nearly constant for TBA-Br, and it decreases with the addition of Al₂O₃ for TBA-PF₆, although it does not depend on the concentration of the additives. The DTA curve of ionic salts with the addition of Al₂O₃ shows additional peaks, which indicates a change in the sample’s temperature at disorder or phase transitions. The variation in the melting temperature with additive concentration is similar to that of decomposition temperature. The maximum heat of fusion value was approximately 67 kJ kg⁻¹ for the doped TBA-Br and TBA-PF₆ but was achieved at a different additive concentration. This is due to the additional disorder in the system induced by the dissolution of Al₂O₃.