Abstract
There have been persistent challenges in thermal spraying of nanoparticles feedstock for making nanostructured coatings with desired mechanical strength. Here we report fabrication of nanostructured titania coatings by atmospheric plasma spraying of hollow titania spheres, and microstructures and photocatalytic activities of the coatings are examined. The hollow microspheres are ~ 50 μm in diameter and possess a mesoporous shell of 1-3 μm in thickness. The coatings show micro-nano hybrid structures with well-retained titania nanoparticles and agglomerated granules. High anatase content is achieved in the coatings, suggesting that constrained heating of the particles effectively prevents the transformation from anatase to rutile. The spherical characteristics of the organic materials in the feedstock powder play dominant roles in regulating the physicochemical characteristics of the coatings for photocatalytic performances. These results would provide insight into large-scale thermal spray fabrication of nanostructured coatings using appropriately designed hollow spherical powder.