Electrocrystallization kinetics of hydroxyapatite and calcium phosphate coatings under magnetic field

A. L. Daltin - A. Ahmed Chekkat - P. Millet - J. P. Chopart

LISM LRC CEA, Université de Reims Champagne Ardenne, B.P. 1039, 51687 Reims Cedex 2, France

Abstract
Calcium phosphate compounds have been synthesized on a T6Al4V substrate by potentiostatic deposition under a magnetic field. The electrolyte bath used for electrodeposition was based on an aqueous solution with Ca(NO₃)₂, 4H₂O and NH₄H₂PO₄ and several Ca/P ratios. Electrocrystallization kinetics of calcium phosphate coatings under magnetic field superimposition has been investigated. Analyses of the transient current curves reveal progressive nucleation with or without magnetic field superimposition. Attention has been given to the morphologies and structures obtained under natural and forced magnetohydrodynamic convection. X-ray diffraction has been used to analyze the compositions of the obtained specimens. Calcium deficient hydroxyapatite has been identified. The Ca/P atomic ratios from EDX analysis are in good accordance with XRD results. Morphology has been observed by a scanning electron microscope. Needle shape crystallites have been obtained. Many volcano-like structures due to the presence of hydrogen bubbles formed during deposition are present on coatings obtained without superimposition of magnetic field. With magnetohydrodynamic convection due to the Lorentz force, this phenomenon can be suppressed. Tables 1, Figs 9, Refs 14.