The Preparation And Evaluation Of Hydroxyapatite Coating On Commercial Pure Titanium

Hydroxyapatite (HA), because of its best biocompatibility, innocuity, safe and canconduct the growth of bone, has been widely used as bone substitute material in clinical. Butpure hydroxyapatite has poor mechanical properties, such as low flexural strength, brittleness,and poor fatigue resistance, which limited its application in environment. Titanium and itsalloys and other metals have light texture, high fracture toughness, and excellentbiocompatibility can be used to replace femur or tibia bones, which can endure high load; butthese metals can only integrate with bone and not form a solid combination with bone. Forthis reason, people coated HA on the surface of these metals or alloys to form compositematerial. This composite material not only has biological activity and biocompatibility of HA,but also has strong mechanical properties of metal, so it has a high value for surgicalapplication.In this dissertation, HA coating was synthesized by bionic mineralization method on thesurface of commercial pure titanium (CP Ti), which was firstly treated by high energy shotpeening (HESP) and polished. The surface morphology and composition of the coating wereanalyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), Electron ProbeMicroanalyzer (EPMA) and infrared spectroscopy (FTIR), and the effect of high energy shotpeening to Ti substrate and hydroxyapatite coating was discussed. The results indicated thatHA coating was synthesized by biomimetic method and the ratio of Ca/P is 1.30. Thetechniques of HESP enhanced the chemical reactivity of the Ti substrate, and accelerated thedeposition rate of HA. Surface roughness increasement narrowed the coating cracks, andenhanced the cohesion between the substrate and coating.This dissertation mainly uses sol-gel method to coat HA coating on titanium substratewhich was firstly pretreated by HESP and polishing. The change of contact angles of thepolished substrate before and after NaOH treatment was measured by equipment. The resultshow that HA coating can be dip-coated by sol-gel method on the two substrates, thethickness of the coating can be increased by increasing the dip-coat times. Comparing withthe substrate without NaOH treatment, HA can easier coat on the surface of the substrate afterNaOH treatment, which is due to the NaOH treatment increased the surface free energy andactivity of the substrate. Especially,γ~p/γ~d increased from 0.235 to 0.727, and HA precursor isbenefited for coating on the surface, decreased dip-coating time; the thickness of the coating is uniform; the cohesion of substrate with coating is also enhanced. Compare with thepolished substrate, HA can dip-coat on the HESP substrate easier, and the cohesion of coatingand substrate is high, enhanced from 10 MPa of polished sample to 30MPa of HESP sample.