Development of multifunctional microencapsulated phase change materials with composite titania-polyurea (TiO2-PUA) shell with visible light photocatalysis property for building applications
Date of Issue2018
School of Civil and Environmental Engineering
Phase change material (PCM) is capable of saving energy consumption in the cooling and heating of building, because it is a class of substances with a high heat of fusion which, melt and solidify at a certain temperature. For PCM, the microencapsulation is best way to facilitate PCM addition into composite material, and allows PCM work properly and endurably. TiO2 is a potential candidate for the multifunctional PCM microcapsule shell because of its desirable thermal conductivity, and mechanical and photocatalytic properties. Owing to stability, low cost and nontoxicity, it is regarded as the ideal product to be incorporated into building materials to impart the self-cleaning to reduce the maintenance cost. The self-cleaning property of engineered cementitious composites (ECC) with TiO2 is demonstrated in this work firstly. The fabrication is proposed to obtain multifunctional PCM-TiO2 microcapsules which can comfort the building temperature and exert self-cleaning. This work presents a facile approach to synthesize microencapsulated phase change materials (MEPCMs) with composite titania-polyurea (TiO2-PUA) shell. MEPCM microcapsules with PUA shell were first synthesized through interfacial polymerization followed by deposition of TiO2 by means of the liquid phase deposition (LPD). Results show that the MEPCMs have a well-defined core-shell structure with around 73 wt.% of core fraction and dense composite TiO2-PUA shell, which is thermally stable and durable and effectively lowers the evaporation and prevents leakage of the core material even after repeated heating and cooling. The MEPCMs also show mitigated supercooling, faster thermal response, and high thermal storage capacity. It is demonstrated that TiO2 on the shell of PCM microcapsule can photocatalytically decompose the RhB under visible light irradidation. Through characterization using XPS and photoluminescence, it is found that F-doping enables TiO2-PUA-PCM microcapsule show photocatalysis under visible light. Compared with pure synthesized powder and commercial anatase TiO2, The TiO2 microcapsules have highest photocatalysis efficiency under artificial visible light. The microcapsule fabricated at higher temperature exhibits better photocatalysis effficiency. Microcapsules with smaller size show improvement in photocatalysis. The TiO2-PUA-PCM microcapsule successfully demonstrates the energy storage and photocatalysis in the mixture with cement. It indicates that the TiO2-PUA-PCM MEPCMs can successfully impart the function to the mixture with cement. With the increase of TiO2-PUA-PCM MEPCMs in mixture with cement, the self-cleaning function and energy storage capability improve correspondingly. Also, mixing with cement barely affect the performance efficiency of MEPCM in self-cleaning and temperature modulation.