Glass-ceramic foams and reticulated scaffolds by sinter-crystallization of a hardystonite glass

In the present investigation, we focused on a glass-based route to hardystonite ceramics, which represent one of the most promising classes of biomaterials, in the form of highly porous scaffolds. A glass corresponding to the stoichiometry of a hardystonite solid solution (Ca₂Zn_0.85Mg_0.15Si₂O₇) was first synthesized and reduced in the form of fine powders (<40 μm). Highly crystallized samples were obtained by sinter-crystallization, in air, at 1000–1200 °C, starting from highly porous green bodies (porosity >70 vol%), obtained by direct foaming or stereolithography of specifically formulated suspensions. More precisely, foams were obtained by intensive mechanical stirring (with the help of a surfactant) of suspensions undergoing gelation, in weakly alkaline aqueous solutions. Reticulated structures with complex non-stochastic geometry, on the other hand, were obtained by digital light processing of glass powders suspended in a photosensitive organic binder. The intensive crystallization caused an excellent retention of the shapes generated at room temperature. The uniform microstructures, all comprising quite dense struts, favored the mechanical properties (with crushing strength well exceeding 2 MPa, with open porosity above 65 vol%).