Process parameter optimisation for manufacturing porous bioactive silicate glass microspheres via flame spheroidisation: The goldilocks effect

This study investigated the influence of flame spheroidisation process parameters for successfully manufacturing solid (dense) and highly porous microspheres from Food and Drug Administration approved bioactive 45S5 glass and 45S5 with addition of viscosity modifiers (i.e. 2 and 5 mol% borax and V2O5), compared against successfully processed phosphate glass microspheres (termed P40). Characterisation studies performed included thermal analysis (SDT), glass viscosity measurements using high temperature rotational viscometry and hot stage microscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. This study revealed that aside from intrinsic material properties (i.e. melt temperature and viscosity profiles), process parameters including starting glass particle size, cooling rate and gas flow rates were important factors in achieving the desired porous glass microsphere morphology. Considering the above influential factors, a processing model has been proposed for the manufacture of highly porous microspheres from bioactive silicate glasses.