High-speed preparation of biocompatible ceramic coatings by laser CVD

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In the present study, calcium base oxides, e.g. CaTiO_3, α-TCP and HAp films were prepared by metalorganic chemical vapor deposition (MOCVD) and laser enhanced CVD (LCVD). Effects of preparation conditions on the crystal phase, microstructure and deposition rate were investigated. Furthermore, the bone conductivity and biocompatibility were evaluated by the formation behavior of apatite on those films in a Hanks'' solution.CaTiO_3, α-TCP and HAp films were obtained first by MOCVD. Apatite wholly covered the surface of CaTiO_3 films with a smooth surface after 6 weeks, CaTiO_3 films with a complicated surface after 3 days, α-TCP films after 2 weeks and HAp films after 6 hours. The apatite predominantly formed at the micro-sized hollows, indicating significant effect of surface morphology on the apatite formation rate except of the intrinsic bone conductivity of the ceramics films.HAp and α-TCP films were obtained also by LCVD at a high deposition rate. Laser power (P_L) showed significant effect on the crystal phase of Ca-P-O films: at P_L=200W α-TCP formed in wide conditions, at P_L=150W α-TCP formed at high temperatures and HAp formed at low temperatures, at P_L=100W HAp in a main phase formed in wide conditions. Any film showed a dense microstructure. The deposition rate increased with increasing the precursor concentration, deposition temperature, laser power and total pressure in chamber (P_<tot>), showing the highest value of 1200μm/h at P_L=200W and P_<tot>=0.6 kPa. Apatite formed on the Hap films prepared by LCVD in Hanks'' solution after 6 hours.In a summary, it is confirmed that CaTiO_3, α-TCP and HAp films can be prepared by chemical vapor deposition, and the effects of preparation conditions on the crystal phase, microstructure and deposition rate were clarified. The CaTiO_3, α-TCP and HAp films prepared by CVD were proved to have excellent bone conductivity by revealing high apatite formation rate in pseudo body solutions.