Hydrothermal growth of hydroxyapatite single crystals under natural convection

Whiskerlike-shaped hydroxyapatite single crystals with the calcium-deficien t nature were hydrothermally grown under natural convection by using a temp erature-gradient-applied pressure vessel. With this method, crystals grew t hinner with a smaller tapering angle than those grown under the nonconvecti on, Maximum length of the crystals grown under natural convection was 8.3 n m. The grown crystals survived without fracture through at least ten times maximum indentation (25 mu m) of the three-point bending tests, showing the maximum bending angle of 62 degrees. Average tensile strength of the cryst als was 410.0 MPa.