Properties of Highly Porous Hydroxyapatite Obtained by the Gelcasting of Foams

Abstract

Open‐cell hydroxyapatite (HA) foams, produced through the novel technique of gelcasting foams with relative porosities ranging from 0.72 to 0.90, were characterized for pore‐size distribution, surface area, permeability, compressive strength, elastic modulus, and microstructural features. The porous structure, which is composed of an array of spherical cells interconnected through windows, had a mode pore diameter in the range 17–122 μm, as demonstrated by mercury porosimetry. The BET specific surface area increased from 1.5 to 3.8 m2/g as the sample porosity increased. The compressive strength and elastic modulus were in the range 1.6–5.8 MPa and 3.6–21.0 GPa, respectively. The permeability constants, k1 (Darcian) and k2 (non‐Darcian), were strongly dependent on porosity fraction and varied widely, from 1.22 × 10−11 to 4.31 × 10−10 m2 and from 1.75 × 10−6 to 8.06 × 10−5 m, respectively. This combination of properties make the HA foams suitable for a variety of potential applications in the biomedical field, preferentially nonloading, including materials for bone repair, carriers for controlled drug‐delivery systems, and matrixes for tissue engineering.