Thermal enhancement of salt-based phase change materials using silica and mesoporous silica nanoparticles for thermal energy storage

Abstract Enhancing the thermal properties of phase change materials is critical for improving the efficiency of thermal energy storage (TES) systems. In this work, silica (SNs) and mesoporous silica nanoparticles (MSNs) were synthesized via a sol–gel method and incorporated into potassium nitrate (KNO 3 ) at varying mass fractions (0.1–2.5 mass%) to evaluate their impact on thermo-physical performance. The nanostructures were characterized using FTIR, XRD, HRTEM, and SEM, confirming the formation of amorphous silica phases, spherical particle morphology, and well-dispersed mesoporous structures. Thermal characterization using differential scanning calorimetry showed that 0.5 mass% MSNs enhanced the specific heat of KNO 3 by 15.97% (solid) and 22.4% (liquid), with a corresponding TES capacity increase of 11.11%. Similarly, 1.0 mass% SNs increased specific heat by 7.14% and 10.2%, with a TES improvement of 3.4%. Thermal conductivity measured at 25 °C reached maximum values of 0.77 W m −1 K −1 for SNs and 0.79 W m −1 K −1 for MSNs at 1.0 mass% loading; however, further increases in nanoparticle content caused a decline due to agglomeration, reduced effective interfacial area, and increased thermal resistance. These results demonstrate that low concentrations of silica-based nanoparticles, especially 0.5 mass% MSNs, can significantly enhance both heat storage and heat transfer characteristics of KNO 3 , making them promising candidates for next-generation TES materials in solar thermal and high-temperature energy applications.