Structure and mechanical properties of β-TCP scaffolds prepared by ice-templating with preset ice front velocities

Anisotropic scaffolds with the typical structure of lamellar, aligned and continuous pores were successfully achieved by the directional solidification of water-based β-tricalcium phosphate (β-TCP) suspensions. Adjustable porosities from 49 to 82%, tunable pore widths from 8 to 50 μm and linked ceramic cells with wall thicknesses from 4 to 30 μm were obtained. Correlated compressive strengths reached from 0.4 MPa (82% porosity, low solidification velocity of 10 μm s−1) to 40 MPa (49% porosity, high solidification velocity of 30 μm s−1). At a given scaffold porosity, the compressive strength increased by more than twofold with increasing solidification velocity due to attendant structural changes. Thus, the key to controlling structural sizes, besides the trivial control of porosity through the water content in the initial suspension, is to control the solidification velocity. In this study, an analytical solution of the heat conduction equation was used as a novel approach to control the solidification velocity during the process. The relationships between processing conditions and resulting structure as well as between structure and mechanical properties were elucidated and discussed.