Silicone resins, filled with phosphates and other oxide fillers, yield upon firing in air at 1100 °C, a product resembling Biosilicate^® glass-ceramics, one of the most promising systems for tissue engineering applications. The process requires no preliminary synthesis of parent glass, and the polymer route enables the application of direct ink writing (DIW) of silicone-based mixtures, for the manufacturing of reticulated scaffolds at room temperature. The thermal treatment is later applied for the conversion into ceramic scaffolds. The present paper further elucidates the flexibility of the approach. Changes in the reference silicone and firing atmosphere (from air to nitrogen) were studied to obtain functional composite biomaterials featuring a carbon phase embedded in a Biosilicate^®-like matrix. The microstructure was further modified either through a controlled gas release at a low temperature, or by the revision of the adopted additive manufacturing technology (from DIW to digital light processing).

Vitrification of municipal solid waste incineration (MSWI) bottom ash is an effective method to produce a chemically stable glass, with metal recovery. In order to justify the high costs of this process, the vitrified residue can then be upcycled into potential marketable products. In this study, vitrified bottom ash was successfully converted into strong and chemically stable porous glass-ceramics by the combination of alkali activation and sintering. After the activation of the glass in a NaOH solution of low molarity, foams were easily produced by intensive mechanical stirring, with the aid of a surfactant, and stabilized by gelation. The obtained open-celled material was further consolidated by a sintering treatment, at 800-900 °C. The addition of recycled soda-lime glass allowed activation at low molarity and sintering at lower temperature, but it reduced the mechanical properties and the stabilization of heavy metals. On the other hand, the increase in molarity of the alkaline solution increased the porosity and also the strength of foams from vitrified bottom ash.