Dip coated silicon-substituted hydroxyapatite films

Silicon-substituted hydroxyapatites have been deposited onto Ti6Al4V substrates by sol-gel technology. The Ca-10(PO4)(6-x-y)(SiO4)(x)(CO3)(y)(OH)(2-x+y) coatings obtained, with silicon contents up to x = 1 (2.8 wt.%), show a homogeneous and crack-free surface of composed of particles smaller than 20 nm. The silicon enters into the apatite structure in the form 4 groups that partially substitute the PO43- groups. The Si content and the Ca/P molar ratio of the coatings agree with those originally introduced in the sols. Layers with thicknesses around 600 nm show adhesion strengths superior to 20 MPa as determined by a pull-out test. The formation of an apatite layer onto these coatings after immersion in a simulated body fluid is enhanced by the presence of silicon. (C) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.