Thermal characterization of agar encapsulated in TiO2 sol-gel

Thermal effusivity evolution as a function of time, of aqueous emulsions of agar encapsulated in a TiO2 matrix synthesized by the sol-gel method, was monitored during dehydration at ambient conditions. Measurements of thermal effusivity were performed by the photoacoustic technique using a conventional cell. The results show sigmoidal growth as a function of time during the dehydration process. The data analysis shows two dehydration stages; in the first one, samples prepared at pH 7.5 show a lower dehydration time than samples prepared at pH 7. But, when the dehydration process continues, it is slowed down in the sample prepared at pH 7.5. FT-IR absorption and Raman spectroscopy are used to verify the strong interaction between the TiO2 matrix and the agar.