Fabrication,Characterization And Thermal Regulation Mechanism Of Phase Change Microcapsules-filled Cement Composites

Facing upon the increasingly severe energy crisis, one of the key issues for reducing the building energy consumption is to pursue high-performance thermal energy storage technologies based on phase-change materials. In this study, in order to solve the problems of leakage, supercolling, phase separation and volume variation, etc. during their practical application, a novel cement composite incorporated with flaky graphite-doped microencapsulated phase-change materials(FGD-MPCMs) was developed. Various techniques, such as field emission-scanning electron microscopy(FE-SEM), optical microscopy(OM), X-ray diffraction(XRD), differential scanning calorimetric(DSC) and thermo gravimetric analysis(TGA) were used to analyze the composite structure and thermal performances. The results indicate that the spherical microcapsules are well dispersed in the cement matrix. When combined within the cement, the thermal stability of the microcapsules was highly improved, and the inclusion of greater amounts of FGD-MPCMs further increased the latent heat of the composite. Results from the infrared thermograph and the model room test suggested that the composite filled with FGD-MPCMs is capable of reducing indoor temperature fluctuation and exhibits good potential for application in buildings to enhance energy savings and thermal comfort.The mechanical properties of the cement composites were affected with the increase of FGD-MPCMs dosage and the porosity of the composites. In spite of this, the compressive strength and flexural strength of the cement composite with 30 wt% FGD-MPCMs could still reach to as high as 14.2 MPa and 4.1 MPa, respectively.Therefore, in order to endow the cement composite with thermal energy storage ability without sacrificing its mechanical strength, carbon fibers, in this study, were first incorporated into the MPCMs-filled composite system. As a result, the mechanical properties of the cement composites were enhanced with the increase of carbon fibers dosage. Compared to the pure cement specimen, after 3-day fast curing the compressive strength and flexural strength of the composite with 1.5 wt% carbon fibers increased 16.8 % and 31.2 %, respectively, while after 28-day standard curing, the values changes to 12.1 % and 17.3 %, respectively.Furthermore, thermal conductivity of the cement composites have also been improved by incorporated carbon fibers. When the mass percentages of carbon fibers is 1.5 wt%, thermal conductivity of the cement composites can reach to as high as 0.80 Wm-1K-1, which is 25.81 % higher than the one with 20 wt% FGD-MPCMs and only12.49 % lower than the raw cement.