Investigation of the thermal storage mechanism of porous TiO2 enhanced phase change materials
The application of phase change materials in thermal energy storage technology is often limited by unstable shape and low thermal conductivity.In the present work,a novel phase change materials for in situ encapsulation of titanium dioxide were synthesized by a one-step method based on the hydrolysis reaction of tetrabutyl titanate.The encapsulation process of phase change materials does not require any curing agents or organic solvents and does not emit any pollutants.Moreover,the material exhibits excellent shape stability and leak resistance,and has a high latent heat(115 J/g).Further study revealed anomalous bimodal phase change behavior in the incompletely dried samples.Taking the drying time as a variable,it was found that the synergistic effect of the residual nonparaffinic liquid phase material and titanium dioxide in the sample promoted the growth of(110+111)crystal structure,which increased the average crystallite spacing of the paraffin waxes during the crystallization process,and further led to an imbalance of the(110+111)crystallite to 020 crystallite ratio during the crystallization process of encapsulated paraffin waxes.This further leads to an imbalance in the ratio of the(110+111)crystal face and the 020 crystal face during the crystallization process of the encapsulated paraffin wax,and eventually an abnormal bimodal phase transition phenomenon appears in the differential scanning calorimetry(DSC)curve.
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