The Synthesis, Microstructure And Properties Of Bifunctional Micro-PCMs With Crystalline Titanium Dioxide Shell And N-Eicosane Core

Energy supply is increasingly intense in modern society. Energy storage technology is an effective way to improve energy efficiency. By using the technology, the energy can be temporarily stored in hot or cold materials for future needs. Phase change materials (PCMs), who own advantages of approximate isothermal heat storage/release and high heat storage capacity, have captured much attention in energy storage areas. In generally, PCMs are packaged in capsules in practical application to avoid its inherent defects in thermal energy storage system. Morever, the thermal conductivity can also be enhanced. PCMs own well properties such as temperature regulating, crush resistance and heat storage, and therefore show broad applied prospects in areas of textile, building, biological medicine and military, and so on. In this research, we developed a novel method to synthesis a kind of bifunctional micro-PCMs with an inorganic shell material which possessed unique properties and expanded the application of miro-PCMs. In this paper, we employed n-eicosane as core material and brookite-TiO2 as shell, and successfully synthesized bifunctional micro-PCMs with functions of temperature regulating as well as photocatalytic effectiveness. Microstructures observation and properties characterization were carried out through a variety of ways. Main works were as follows:1. Bifunctional micro-PCMs with crystalline titanium dioxide shell and n-eicosane core were synthesized in O/W reactant system with SDS as emulsifier, NaF as crystallization inducer and formamide as solvent.2. A series of micro-PCMs were obtained by changing the ratio of raw materials. The FT-IR, EDX and XPS measures were taken to confirm its chemical compositions. The spherical core-shell structure could be observed through SEM and TEM, proving the synthsis of target products. The sizes of the particles were around 1.5-2.5 μm. DSC characterizations showed high heat storage capacity. Both the encapsulation efficiency and energy storage efficiency were boosted as the rise of the n-eicosane/TBT mass ratio. The subcooling degree of the obtained microencapsules were less. The test of DSC heating-cooling cycles demonstrated that the encapsulated n-eiscosane performed good phase change performances and durability. The results of TGA characterizations proved well thermal stability of the microencapsules. Moreover, the higher mass ratio of TBT/n-eicosane, the better thermal stability of the products.3. Exploring the effects of the amount of NaF added on the crystal structure and crystallinity of TiO2 shell. The XRD spectra showed that the TiO2 shells were amorphous under no NaF or under small amount of NaF. The brookit-TiO2 were discovered when we increased the concentration of NaF. Meanwhile, the more NaF, the higher crystallinity of TiO2 shell. The crystallinity of TiO2 shell didn’t chang any more when NaF added incresed to a certain degree. From discussions above, we concluded that NaF promoted the phase change of TiO2 shell from morphous to brookit.4. The photodegradation measurement and antimicrobial activity measurement demonstrated that the synthsised micro-PCMs owned both good heat storage ability and good photocatalytic effectiveness. It was a new type of bifunctional micro-PCMs.