Phase Conversion of Ice‐Templated α‐Tricalcium Phosphate Scaffolds into Low‐Temperature Calcium Phosphates with Anisotropic Open Porosity

Abstract

The current study aims to extend the material platform for anisotropically structured calcium phosphates to low‐temperature phases such as calcium‐deficient hydroxyapatite (CDHA) or the secondary phosphates monetite and brushite. This is achieved by the phase conversion of highly porous α‐tricalcium phosphate (α‐TCP) scaffolds fabricated by ice‐templating into the aforementioned phases by hydrothermal treatment or incubation in phosphoric acid. Prior to these steps, α‐TCP scaffolds are either sintered for 8 h at 1400 °C or remain in their original state. Both nonsintered and sintered α‐TCP specimens are converted into CDHA by hydrothermal treatment, while a transformation into monetite and brushite is achieved by incubation in phosphoric acid. Hydrothermal treatment for 72 h at 175 °C increases the porosity in nonsintered samples from 85% to 88% and from 75% to 88% in the sintered ones. An increase in the specific surface area from (1.102 ± 0.005) to (9.17 ± 0.01) m2 g−1 and from (0.190 ± 0.004) to (2.809 ± 0.002) m2 g−1 due to the phase conversion is visible for both the nonsintered and sintered samples. Compressive strength of the nonsintered samples increases significantly from (0.76 ± 0.11) to (5.29 ± 0.94) MPa due to incubation in phosphoric acid.