The Study On Preparation Of Hydroxyapatite Layers On Titanium By Dual Calcium And Phosphorus Ion Implantation

The ion implantation surface modification has prominent advantages in improving the tissue bonding properties of dental implants and artificial joints for the high adhesion of the HAp coating to its substrate. Calcium ions were implanted with the metal vapor vacuum arc (MEVVA) ion implanter in the present study. The surface structure, biological activity, corrosion resistance and other surface properties of titanium after dual calcium and phosphorus ion implantation were also investigated. In addition, a combination of dual ion implantation and hydrothermal treatment were performed to obtain HAp coatings on titanium.In this work, Ca ion and P ion were implanted into pure titanium substrate in amounts of 2×10¹⁷ and 1×10¹⁷ ions/cm² at the ion energy of 110 keV and 80 keV respectively. The EDS and AES analyses indicate that, both Ca and P ions have a depth of about 250 nm, and the ratio of Ca/P is close to 1.7. Moreover, the pre-oxidation at 450°C and the sequence that first P ion then Ca ion implantation could enhance the ion content implanted and maintain a more appropriate ratio of Ca/P. XRD, XPS and TEM analyses prove that CaO, P2O5, CaTiO₃, P, TiP and other new substances are introduced to the surface. It is presumed that CaP4O11 and more P2O5 are formed on the pre-oxidized samples. The study also indicates that the surface roughness, microhardness and the Young's modulus are also improved upon the dual ions implantation samples.The hydrothermal treatment was performed on every sample, and globular HAp particles were formed on the two pre-oxidized samples, especially the one first P ion then Ca ion implantation, which is proved by SEM,EDS,XRD and FTIR analyses. Moreover, the temperature and air pressure also have remarkable influence on the formation of HAp. It is observed that the diameter of HAp particles achieves 1μm when hydrothermal treated at 200°C and 1.55 MPa.The surface morphology of Ca ion and/or P-ion implanted samples and hydrothermal treated samples after soaked in SBF for 7 days were also examined in order to examine the improvement of titanium's biological activity. The HAp deposited on Ca ion implanted samples was more homogeneous than that P ion implanted. The dual ions implanted samples also had global deposits. The samples pre-oxidized got a refiner and more homogeneous HAp particles. Additionally, better effect of grain refining was observed on the hydrothermal treated samples, which is attributed to the huge amount of nucleating sites provided by the HAp layer and the increase of surface energy and hydroxyl as a result of hydrothermal treatment. Corrosion resistance test tells that the P-ion-implanted samples had the highest corrosion-resistant followed by the dual ion-implantated ones.