Colloidal forming of macroporous calcium pyrophosphate bioceramics in 3D-printed molds

A technique for colloidal forming of Ca₂P₂O₇ macroporous bioceramics, based on low-pressure injection molding (LPIM) of a glycerol-water slip containing Ca₂P₂O₇ and Ca(Н₂PO₄)₂ into a plastic mold fabricated via FDM 3D-printing, was proposed. Chemical reaction between the solid phases of the water containing slip - Ca₂P₂O₇ and Ca(Н₂PO₄)₂, resulting in brushite (CaHPO₄·2H₂O) formation, led to consolidation of the casting and preserved its complex architecture in the course of mold burning-out. Macroporous ceramics of Kelvin structure (70% macropores with the sizes from 2 up to 4 mm), based on a pre-defined composition with 10 wt% Ca(PO₃)₂ and sintered in liquid-phase regime, demonstrated a compressive strength of 1.4 ± 0.1 MPa at a density of 22 ± 2%. In vitro tests on bioactivity in SBF solution, as well as on resorption of the ceramics in model solution of citric acid, were carried out.