Grain boundary corrosion of highly porous ceramic TiO2 foams is reduced by annealing and quenching

Porous bioceramics, such as scaffolds, can be used for bone regeneration. Bioceramics are instantly attacked by body fluids, macrophages and osteoclasts during stages of bone repair. Acidic microenvironments generated by these cells may amplify the well-known effect of grain boundary dissolution. Grain boundary corrosion in such porous scaffolds can have significant impact on the mechanical strength due to the high surface area of the scaffold. Corrosive media were found to significantly affect the mechanical strength of highly porous TiO2 scaffolds. Compressive strength decreased significantly after 12 h in an aqueous acidic solution with a reduction to 35 ± 10% after 8 weeks immersion time. Following post-sintering heat treatments by combining air quenching and annealing, the strength was maintained throughout a corrosion period of 8 weeks in acidic environment. Impurity segregation to the grain boundaries and thus, susceptibility to grain boundary corrosion was reduced by the synergistic effect of both heat treatments.