Synergistic effect of stearic acid/bismuth oxychloride/cupric oxide for thermal storage applications: preparation, stability, rheological and thermophysical analysis

The present study reports the preparation of nanophase change materials (NPCMs) using a two-step method with an optimized ratio of 0.5 wt% of nanoparticles for thermal storage applications. Bismuth oxychloride (BiOCl), cupric oxide (CuO), and a mixture of BiOCl/CuO (composite) were used as nanoparticles, and stearic acid was used as the PCM. The crystallography, chemical/functional groups and morphologies of the prepared NPCMs have been analysed by XRD, FT-IR and SEM, respectively. Observations revealed that the presence of nanoparticles in NPCMs did not affect crystal formation or chemical disruption of molecular interactions. TGA was used to analyse the thermal stability and rate of deterioration of the NPCMs. The deterioration of the PCM occurs at 243 degrees C with a weight loss of 1.3% while 0.5 wt% concentrated BiOCl, CuO, and composite NPCMs exhibit weight losses of 1.8%, 2.3%, and 3.4%, respectively at 257 degrees C, 262 degrees C and 258 degrees C. In the DSC study, the phase-changing attributes of the NPCMs manifested in the onset temperature range between 53.4 degrees C and 59.8 degrees C. The potential enthalpy of the PCM is 209.1 kJ kg-1, whereas those of the 0.5 wt% concentrated BiOCl, CuO, and composite NPCMs are 204.6, 198.3, and 201.7 kJ kg-1, respectively. However, the enhanced thermal conductivities of 0.5 wt% concentrated BiOCl, CuO, and the composite NPCMs are 0.18, 0.22, and 0.20 W/(m.degrees C), respectively, which are 5.9%, 29.4% and 17.6% greater than that of PCM. Additionally, the congruent melting rate increased by 31% for 0.5 wt% CuO concentrated NPCM; therefore, it is a potential candidate than other NPCMs/PCM. Cyclic tests were conducted to assess the reliability of the NPCMs, and compatible results were obtained even after 500 cycles. The findings of this work indicate that all the prepared NPCMs could be a viable option for practical applications, including thermal comfort buildings, solar heating, and electronic cooling.