Calcium phosphate crystal growth under controlled atmosphere in electrochemical deposition

Cathodic deposition of calcium phosphate (Ca-P) on titanium was studied under controlled atmospheres. Electrochemical deposition was conducted in a sealed electrochemical cell with a controlled flow of nitrogen, carbon dioxide or compressed air. The Ca-P phases of the depositions on titanium were examined by X-ray diffraction, Fourier transform-infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. Experimental results showed that hydroxyapatite (HA) deposition occurs under a pure nitrogen atmosphere, while octacalcium phosphate (OCP) deposition occurs under a carbon dioxide atmosphere. The atmosphere in the electrochemical cell effectively maintained constant levels of pH value in the electrolyte during the deposition process. A HA/OCP layered structure on titanium was obtained by controlling the atmosphere. The electrochemical deposition process of Ca-P can be explained by the thermodynamic and kinetics theory of the Ca-P precipitation from an aqueous supersaturated solution.