Morphological regulation and crystal growth of hydrothermal-electrochemically deposited apatite

Apatite was deposited on commercially pure titanium plates using a hydrothermal-electrochemical method in an electrolyte containing calcium and phosphate ions. Needle-like apatites were synthesized in 43 kinds of condition with different electrolyte temperatures (90–200°C), current densities (5.0–25.0 mA/cm2), and current loading times (10–120 min). The length of one side of the hexagonal apatite and longitudinal length of them were determined through field-emission-type scanning electron microscopic photographs. The size of needle-like apatites remarkably increased with the electrolyte temperature and current loading time, and slightly changed with current density. Multivariate analysis revealed that both size and shape of apatite needle on titanium substrate can be regulated accurately by systematic control of the electrolyte temperature, current density, and current loading time. These results revealed that hydrothermal-electrochemical deposition of apatite consists of two processes: nucleation and crystal growth, which strongly depend on the electrolyte temperature and current density.