Synthesis And Property Of Paraffin@TiO₂ And Paraffin@TiO₂/GO Microcapsule Phase Change Materials

Phase change material?PCM?has great development potential as energy storage material.As an organic PCM,paraffin has many advantages such as high energy storage density,stable chemical property,non-corrosion and low cost,which is the most widely used PCM for energy storage.However,paraffin has the problems of low thermal conductivity and leakage during the phase change process,which limits its further application in thermal energy storage.Encapsulating paraffin with inorganic shell material not only can prevent the leakage of paraffin,but also can effectively improve the thermal conductivity of paraffin.Meanwhile,modifying the microcapsule with graphene oxide can further improve the light absorption performance and thermal conductivity of microcapsule composite,which enables the microcapsule composite to efficiently store and utilize solar energy.In this study,paraffin@TiO₂ and paraffin@TiO₂/GO microcapsule PCM were synthesized by in-situ hydrolysis and polycondensation of tetrabutyl titanate in a nonaqueous oil-in-water emulsion.The chemical composition,crystalline structure,morphology and microstructure of paraffin@TiO₂ and paraffin@TiO₂/GO microcapsules were characterized by Fourier transform infrared spectroscopy?FT-IR?,X-ray diffractometer?XRD?,Raman spectroscopy?Raman?,scanning electron microscopy?SEM?and transmission electron microscopy?TEM?.The thermal properties of the microcapsules were measured by differential scanning calorimeter?DSC?and thermo-gravimetric analyzer?TGA?.The thermal conductivity,heat storage capability,light absorption property and photo-thermal conversion performance of the corresponding microcapsule slurries were researched.The paraffin@TiO₂ microcapsules were regular spherical shape with the average diameters of 2-5?m with a smooth shell.There was no chemical reaction between paraffin core and TiO₂ shell material.The paraffin@TiO₂ composite had similar phase change behaviors as those of pure paraffin.Typical sample froze at 52.24oC and melt at 60.41oC,the freezing and melting latent heat of the typical sample were 110.42 J/g and 107.54 J/g,respectively,of which the encapsulation ratio achieved to 54.58%.The thermal stability of paraffin was improved by the protection of TiO₂ shell.The paraffin@TiO₂ composite had good thermal cycling performance.The paraffin@TiO₂/GO microcapsules were regular spherical particles with average diameters of 2-5?m,there was just a physical interaction between paraffin,TiO₂ and graphene oxide.When the mass percent of grahene oxide in the paraffin@TiO₂/GO composites were 0.1%,0.2%and 0.3%,the encapsulation ratios of paraffin were 56.76%,41.99%and 37.93%,respectively.The paraffin@TiO₂/GO composite had good thermal stability.The thermal conductivity and light absorption property of the microcapsule was improved by the graft of graphene oxide.The thermal conductivity,heat storage capability and photo-thermal conversion performance of the paraffin@TiO₂/GO slurry was great enhanced.On the basis of the above results,the paraffin@TiO₂/GO microcapsule PCM was promising to be used in solar energy collector system.