Synthesis of Mn‐P‐Na Based Nanocrystallite Composites and Investigation of Their Thermal Behavior Towards Heat Storage and Dissipation Applications

ABSTRACT In this study, we report the synthesis, characterization, and thermal behavior of sodium hydroxide based two manganese‐phosphate nanocrystallite composites, MnPNa 1 = Mn 2 (PO 4 )OH. 0.2H 3 PO 4 . 0.1NaOH.H 2 O (calcined) and MnPNa 2 = Mn 2 (PO 4 )OH. 2H 2 O. 0.8H 3 PO 4 . 0.1NaOH. H 2 O (non‐calcined), and the molecular weights of the composites are estimated to be 247.40 and 360.20 g/mol, respectively. Comprehensive characterization was carried out, which includes elemental analysis, X‐ray powder diffraction, thermogravimetric analysis, derivative thermogravimetry, Fourier Transform Infrared (FT‐IR) Spectrometry, and scanning electron microscopy. Confirmation of the different functional groups within the composites was done through FT‐IR analysis. Differential scanning calorimetry analyses revealed distinct thermal behaviors: MnPNa 1 exhibited consistent exothermic properties, making it suitable as a heat dissipation material (HDM) with high stability across a broad temperature range. In contrast, MnPNa 2 displayed a high specific heat capacity (Cp) of 1.23 J/g·K, highlighting its potential as a sensible heat storage material. The crystallinity of MnPNa 1 (89.83%) further supports its stability and application in heat dissipation technologies, while MnPNa 2 's smaller crystallite size enhances its surface interactions for efficient heat storage. The crystallite sizes of MnPNa 1 and MnPNa 2 are found to be 25.5 and 18.8 nm, respectively.