Production of porous calcium phosphate (CaP) ceramics with highly elongated pores using carbon-coated polymeric templates

This study reports a new way of enhancing the compressive strength of porous calcium phosphate (CaP) ceramics by creating highly elongated pores. These elongated pores were produced by casting a CaP/camphene slurry into stretched polymeric sponges with a thick carbon coating layer used as a template. The sample produced after sintering at 1250 °C for 3 h showed a highly elongated porous structure with a porosity of 38 ± 1.2 vol%, where elongated pores with a size of 512 ± 96 μm were formed as a replica of the template. In addition, CaP walls with a thickness of 841 ± 239 μm were fully densified without any noticeable defects due to the high CaP content of 40 vol% in the CaP/camphene slurry. The compressive strength of the sample was as high as 21 ± 4.9 MPa when tested parallel to the direction of pore elongation, which is much higher than that (12 ± 2.4 MPa) of the sample tested normal to the direction of pore elongation. The sample also showed good biocompatibility, as assessed by the in vitro cell test using a pre-osteoblast cell line.