Formation of hollow vitreous and semi-crystalline microspheres in slag flame spraying

Slags may be flame sprayed to produce hollow vitreous or semi-crystalline microspheres. Feedstock compositions, as well as the heating and cooling kinetics, determine the properties of the final product. These kinetics were estimated by finite element modeling of the thermal and kinematical history of different slags throughout a flame and compared with the morphology and crystallinity of the yielded microspheres. The formation mechanism of hollow spheres is also discussed.