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

In this study, we report the synthesis, characterization, and thermal behavior of sodium hydroxide based two manganese-phosphate nanocrystallite composites, MnPNa₁ = Mn₂(PO₄)OH. 0.2H₃PO₄. 0.1NaOH.H₂O (calcined) and MnPNa₂ = Mn₂(PO₄)OH. 2H₂O. 0.8H₃PO₄. 0.1NaOH. H₂O (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: MnPNa₁ exhibited consistent exothermic properties, making it suitable as a heat dissipation material (HDM) with high stability across a broad temperature range. In contrast, MnPNa₂ 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 MnPNa₁ (89.83%) further supports its stability and application in heat dissipation technologies, while MnPNa₂'s smaller crystallite size enhances its surface interactions for efficient heat storage. The crystallite sizes of MnPNa₁ and MnPNa₂ are found to be 25.5 and 18.8 nm, respectively.