Formation of solid and hollow spherical particles by spray pyrolysis

Spray pyrolysis offers a number of opportunities for the synthesis of either solid or hollow spherical particles. As predicted by the evaporation model, particles with different shell thicknesses can be obtained depending on the concentration gradient at the onset of precipitation. If the precipitate shell has a sufficiently high permeability for removal of the remaining solvent, then the shell can be preserved and a hollow particle obtained. By drying at a lower temperature solid particles are readily formed from precursor salts but hollow particle formation by SP at these low temperatures imposes demanding heating rate requirements.