Åkermanite glass microspheres: Preparation and perspectives of sinter-crystallization

Glass microspheres with the exact stoichiometry of åkermanite (Ca2MgSi2O7), one of the most promising modern bioceramics, were produced by the flame synthesis method. The distinctive high cooling rate was found to prevent the crystallization; the size of amorphous microbeads could be correlated with the size of partially crystallized precursor powders, deriving from conventional melt quenching and milling. The glass microspheres were characterized in terms of crystallization and sintering behavior, in the perspective of applications in additive manufacturing of åkermanite-based scaffolds. The results showed that merwinite (Ca3MgSi2O8) is the primary product of glass devitrification; only in a second stage, merwinite reacts with the residual glass and yields åkermanite. The rapid crystallization, implying limited viscous flow sintering, was tested as an opportunity to create components with complex porosity distribution.