Preparation Of The Amorphous Calcium Phosphate Coating On Titanium By Electrochemical Deposition And Its Evolution Mechanism

Preparation of the amorphous phosphate calcium (ACP) coating on titanium by electrochemistry deposition (ECD) was comprehensively investigated. The homogeneous and controllable ACP coating was obtained by controlling the process parameters and adding Mg2+ into the electrolyte. Its amorphous structure was confirmed by transmission electron microscope (TEM) together with grazing reflection absorption infrared spectroscopy (IR) spectrometer. Then its excellent biodegradation and biological activity were confirmed by the dissolution behavior and cell response experiment. Additionally, the evolution of ACP to hydroxyapatite (HAp) and its mechanism were investigated in the alkaline environment, and the converted nano-hydroxyapatite is expected to explore new application of the electrochemistry deposited ACP.In the process of ECD, the formation of ACP coating was controlled by the current density, deposition temperature, component and concentration of the electrolyte. The specific effect of these factors were analysed by SEM, FITR and TEM. Among these factors, Mg2+ in the electrolyte is indispensable. Besides, the homogeneous ACP can be obtained at slight current density, degraded temperature and high concentration.ACP will convert to the crystallized HAP in the liquid environment due to its unstable nature. The cited alkaline environment will accelerate the evolution process without the interference of the external ions such as Ca and P. The evolution was investigated by SEM, FTIR, TEM and HR-TEM. It was commonly proved that the HAp nucleus will from on the interface of ACP/solution and the nutrition for their growth will be supported by the ACP. But the final configuration of the converted HAp depended on the solution condition. In our experiment, the converted nano-hydroxyapatite is constructed by the units similar to ACP’s. The nano-hydroxyapatite is crystallized by rearrangement of these units without the mesophase such as octacalcium phosphate (OCP). Additionally, the converted HAP coating in our study was nano-sized which is expected to be applied in the field of teeth implantation.Compared with the electrochemisty deposited HAP, the Ca2+ release from ACP coating is higher. And cell response suggests that the ACP coating may stimulate the proliferation of mouse pre-osteoblast cells. Furthermore, higher alkaline phosphatase (ALP) activity and osteocalcin expression indicate more effective stimulating which will promote the early healing of the bone. It is expected to avoid the fracture induced by the weak combination between the coating and titanium substrate.