Fabrication and characterization of thin nano-hydroxyapatite coatings on titanium

Titanium is the most commonly used metallic material in the manufacture of orthopedic implants, and hydroxyapatite (HA) is bioactive and biocompatible when used as bone substitutes. To achieve better biocompatibility and excellent mechanical performance of prostheses, HA coating is often fabricated on titanium surfaces. The present study used dip-coating techniques to fabricate HA coating of organic sol-gel of Ca(NO3)(2.4)H2O and PO(CH3)(3) and inorganic sol of Ca(NO3)(2).4H(2)O and (NH4)(2).HPO4.Scanning electron microscopy (SEM) and grazing-incidence X-ray diffraction (XRD) have been used to characterize the morphology and the distributions of crystallite size and micro-strains of the coatings. After firing at 400 degreesC, the apatite structure of coatings on titanium began to appear. Warren-Averbach Fourier transfer analysis of the diffuse reflections indicated that the mean crystallite size increased and micro-strain decreased significantly with the rise in firing temperature. In the range of 400-600 degreesC, the effect of firing temperatures on mean crystallite size and micro-strain of both coatings was obvious. Precursor types of HA coating significantly affected the aggregating size of particles of nano-HA coatings, which were 25-40 nm for organic sol-gel and approximately 100 run for inorganic sol. The morphology of interfaces between coating and titanium indicated thin nano-HA coatings with thickness 2 mum for organic sol-gel and 5 mum for inorganic sol were intact and homogenous. The effect of firing temperatures on aggregating size of particles of both coatings was not obvious. (C) 2004 Elsevier B.V. All rights reserved.