Ultrasonication Induced Engineering of Emulsion Stability for Developing Advanced Oleic Acid Microencapsulated Phase Change Material ( PCM ) Systems

ABSTRACT

The present study investigated the effect of the ultrasonication assisted emulsification process on the stability of the oleic acid‐based‐oil‐in‐water emulsions for developing calcium carbonate based microencapsulated phase change materials (MEPCM). The effects of ultrasonic power, treatment time, and surfactant concentration on particle size, zeta potential, and emulsion stability index (ESI) were optimized using a Taguchi L9 orthogonal array coupled with ANOVA. The optimum conditions (80% ultrasonic power, 10 min treatment time, and 1.5 wt% surfactant concentration) yielded particle size of 174 nm, zeta potential of −36 mV and ESI of 95%. Stable MEPCM were synthesized through in situ precipitation and FTIR, XRD, SEM and EDX analysis confirmed the successful encapsulation of oleic acid within compact shell of CaCO ₃ consisting of calcite and vaterite phases. DSC analysis confirmed phase change characteristics retention after encapsulation, with ultrasonication‐treated MEPCM exhibiting melting temperature of 12.9°C and latent heat of fusion of 22.29 J/g. The encapsulated systems showcased moderate encapsulation efficiency (32.56%), and high thermal storage capability (97.95%). Thermal cycling studies revealed excellent thermal reliability with 91.97% latent heat retention after 200 heating–cooling cycles. Ultrasonication‐treated MEPCM displayed lower breakage rate (2.34%), lower leakage rate (1.56%) and higher actual core loading (45.28%) in comparison to untreated samples. Thermal conductivity was significantly enhanced from 0.146 W/m K for pure oleic acid to 1.064 W/m K after encapsulation due to the thermally conductive CaCO ₃ shell. The results confirm that ultrasonication assisted emulsion engineering is an effective strategy for developing thermally and structurally stable MEPCM for passive thermal energy storage applications.