Titania Nanocoating on MnCO3 Microspheres via Liquid-Phase Deposition for Fabrication of Template-Assisted Core–Shell- and Hollow-Structured Composites

A novel class of core–shell- and hollow-structured MnCO3/TiO2 composites was synthesized by titania nanocoating on MnCO3 microspheres via two-step liquid-phase deposition at room temperature. Morphological change from core–shell to hollow microparticles was possible in the prepared samples by controlling prereaction time of MnCO3 and [NH4]2TiF6. Upon the prereaction process, the core of the core–shell MnCO3/TiO2 became highly porous, and a honeycomb-like surface that resembled the orientation of self-assembled MnCO3 nanocrystals was developed. The MnCO3 core was completely removed after 6 h prereaction. Calcination at 600 °C resulted in the transformation of both core–shell- and hollow-structured composites to Mn2O3/TiO2 anatase microspheres that retained their original morphologies. X-ray diffraction, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and electron probe microanalysis were employed for microsphere characterization. As th...