Characterization of eggshell-derived hydroxyapatite on Ti6Al4V metal substrate coated by sol-gel method

The aim of this work was to synthesize hydroxyapatite (HAp) by sol-gel route using eggshell and triethyl phosphite as calcium and phosphorus precursors, respectively. After the preparation of homogeneous solution with aging period for 24 h, hydroxyapatite (HAp) sol-gel coatings were made on Ti6Al4V substrate. Polyethylene glycol (PEG) and triethanolamine (TEA) were added to HAp solution to enhance morphological structure of coatings. PEG- and TEA-added solutions and coatings were labeled as P-Hap and T-Hap, respectively. The coating process was carried out by spin coating method, and the coated samples were heated up to 600 degrees C for 1 h. Phase development of coatings and dried powder and morphologies of coatings upon heat treatment were detected by XRD and SEM, respectively. Thermal behavior of obtained powder were investigated with DTA/TGA. Surface roughness was determined by XP2 surface profilometer. It was found that all the samples at RT showed amorphous structure and transformed at 600 degrees C to well-crystallized HAp-phase with no beta-TCP. Morphological results indicated that T-HAp coating showed the best morphology with crack-free uniform porous structure, which is necessary for biocompatible implants. P-HAp coating showed non-uniform porous structure with large cracks, whereby HAp coatings had similar structure to T-HAp coatings but with much less porosity.