Preparation of Spherical Titania Nanoparticles by CO2 Laser Evaporation and Process‐Integrated Particle Coating

Abstract

The CO2 laser vaporization (LAVA) method was used to prepare titania nanopowders. Because this versatile method does not require special precursors, a coarse anatase raw powder was applied as starting material. Powder samples produced under varied process parameters were characterized by transmission electron microscopy (TEM), X‐ray diffraction measurements, and Brunauer–Emmett–Teller surface area measurements. The laser‐generated powders consist of spherical, single crystalline and pure anatase nanoparticles, merely softly agglomerated by weak van der Waals forces. Using TEM analysis, the influence of the process parameters on the resulting particle size distribution was investigated. The results are discussed with respect to the particle formation by gas phase condensation. The potential of a process integrated, i.e. in situ, coating procedure for the surface modification of the anatase nanoparticles is demonstrated. As an exemplary representative of organic layer materials stearic acid was chosen. The organic coating was characterized by TEM and Raman spectrometry. Because of the unavoidable soft agglomeration the coating covers entire agglomerates rather than individual primary particles. Thus, the influence of the LAVA process parameters on the agglomerate sizes was systematically studied using a scanning mobility particle sizer.