Cathodic Deposition Of Bioceramic Coating On Titanium Surface Preparation

With the aged population increasing, the need for artificial biomaterials increasingly enhanced in orthopedic, dental surgery and hard-tissue repaired areas. Bioactive ceramic-coated metal has the predominance of both metal and ceramics, so it is considered as a kind of the most promising bone replacement material.At present, many methods have been applied to prepare bioactive coatings. Among which, the cathodic electrodeposition has its special advantages, such as low operation temperature and high ability to coat on irregular objects. But the main problem of the electrodeposition, the coating being loose and prone to desquamat, is caused by the violent evolution of H2 bubbles from reduction of water on the surface of the substrate.The reduction potential of H2O2 is more positive than that of water. In our work, H2O2 was used to modify electrolyte in order to inhibited H2 evolution and improve the quality of the coatings. The influences of pH value, the amount of H2O2, electrolyte temperature, loading time, cathodic potential and cathodic current density on depositing calcium phosphate coating were investigated. The coating is tested by XRD?SEM and FTIR technology.The results showed that:High initial pH value is beneficial for depositing hydroxyapatite (HAp) coatings. The coating prepared at pH=5.5 is denser and the intensity of XRD diffraction peaks of hydroxyapatite is stronger than those at pH=2.5.The intensity of diffraction peaks of hydroxyapatite increases with the loading time, and SEM photos indicate coverage also increases. At the same time, the claval crystals of about 0.015 um turn into the flake-shaped crystals of about 0.5 Mm.With the rising of electrolyte temperatures, the cathodic current density increases gradually. The crystals, which form a network structure, keeps flake-shaped while the crystal size reduced. But when the electrolyte temperature exceeds 70, the electrolyte becomes unstableand, accordingly, the deposition process becomes difficulty to conduct.When the amount of H2O2 addition increases from 1% to 9%, the current density increases gradually, and the morphology of hydroxyapatite crystal change greatly from amorphous to larger flake crystals, eventually to small ones. Increased H2O2 addition causes an increase in HAp XRD diffraction intensity.A high constant cathodic potential causes a high current density and produces a dense coatings. The irregular flake-shaped crystals also turn into needle ones. When a constant cathodic current is applied, the similar phenomena appear.The results showed that the high quality coatings can be deposited under such conditions: T=70, pH=5.5, =-0.8V (vs SCE), and H2O2 addition=6%. The adhesion strength between coatings and substrate reaches 12.73MPa.