Thermal and structural characterization of TiO2 and TiO2/polymer micro hollow spheres

Micro hollow spheres, synthesized by the coating of tetradecane filled microcapsules with titanium dioxide, are characterized using thermal gravimetry (TG), infrared spectroscopy (IR), Hg-porosimetry and scanning electron microscopy (SEM). The investigations show a strong dependence of the coating efficiency on the initial pH (precipitation in water or dilute sulfuric acid) as well as the specific capsule surface present in solution. Since the process is dominated by heterogeneous precipitation, the coating efficiency is governed by the counteracting processes of capsule-TiO2 and TiO2-TiO2 agglomeration. TG-IR analysis of the capsules shows the vaporization of tetradecane prior to the decomposition of the polymeric wall to carbon monoxide, carbon dioxide and water. After the extraction or calcination of the core microcapsules, stable inorganic and organic-inorganic hollow spheres are obtained.