Hydrothermal Preparation Of Carbonated Hydroxyapatite Powder And Biomimetic Deposition Of Carbonated Hydroxyapatite Coating

Carbonated hydroxyapatite (CHA) has excellent biocompatibility and bioactivity, so it's considered to be the best bone substitute. The preparation of CHA nanopowder is a key to prepare CHA biomaterials. Ti and its alloys have excellent mechanics and biocompatibility. The composite materials synthesized through introducing CHA coatings onto Ti and its alloys not only have the good methanics properies of Ti and its alloys but have the excellent biological properties of CHA. So the preparation of CHA nanopowder and CHA coatings have been hot-topic in recent years.Needle-like AB-type CHA nanocystal was prepared by hydrothermal method. The carbonate content of CHA nanocystal was 8.9%, similaring to the apatite nanocystal in human bone. We used 0.25mol·L^-1 Ca(NO₃)₂, 0.15mol·L^-1 (NH₄)₃PO₄ and 0.15mol·L^-1 urea solutions as reagents, and the reaction mixture was hydrothermal treated at 200℃ for 8 hours.In this paper, we described the synthesis of CHA coating in a biomimetic route by functionalizing the pure titanium substrate with Si-OH groups by preparing silica films on it by a sol-gel method, the depositon mechanism of apatite was also discussed here. The results show that sol prepared at pH=3 with an TEOS:H₂O:EtOH ratio of 1:4:11(molar ratio) is suitable for plating silica films on titanium substrate when aged for 10 hours at 70℃. Titanium coated with three silica films was immersed in 1.5SBF for 10 days, and then there was a compact CHA layer deposited on the surface of the films. Calcium enriched silica films were obtained through introducing Ca²⁺ into silica sol. The results show that the deposition period of CHA could be shortened to 7 days after introducing CaO into silica films, and it's hopeful to settle the problem that the biomimetic deposition of CHA layer needs a very long time at present.