Calcium phosphate crystal growth under controlled atmosphere in electrochemical deposition

Abstract

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.