Niti Shape Memory Alloy Electrochemical Methods Preparation Of Ha Bioactive Coating

Artificial bone materials is a kind of important substitute materials for body and a kind of biomaterials which is usually used in the modern life of the physical bone structure. It is required that the artificial materials should not only have a excellent biocompatibility , strength and tenacity but also have the ability to endure the impact fatigue and be able to bear the fretting. Because the bone apparatus is a kind of special apparatus in body. They are always endured the wallops from body and also likely to glide relatively due to the pressure from body. Nowadays the new titanium alloy is most extensively used in the substitute operation for use as bone implants. NiTi shape memory alloy has been become one of the most extensively used biomaterials due to its excellent mechanical properties, good corrosion resistance, high biocompatibility, special pseudoelasticity and shape as well as volume memory effect. But as the biomaterials of implants its bioactivity is not very good. Hydroxyapatite (HA) is known for being osteoconductive that has found various clinical applications because it has a similar composition as the calcium phosphate in the bone. However it lack the mechanical strength that is required for load bearing implants. Due to its brittleness and fragility, it cannot undergo loads other than compressive. As a result, manufacturing HA as a coating on the surface of titanium alloy is the best effective approach of combining the bioactivity of HA and the strength of the titanium alloy.The experiment device was designed and HA coatings on the surface of NiTi shape memory alloy were prepared via electrochemical deposition from aqueous electrolytes containing Ca and P ions at low temperature and then treated with alkaline solution. The morphologies and constitutions of the coatings were analyzed by SEM and XRD, respectively. The effects of experiment parameters on the phase constitution and the structure morphologies of the coating was studied. The results show that when the pHwas 3-4, deposition voltage at about 6V , and the temperature at 55-60 ℃, the electrochemical deposited coatings was made of CaHPO4·2H2O completely, then was transformed into HA after treated by alkaline solution. The coating featured a homogeneous and compact appearance when the surface of the NiTi substrate was pre-treated and the electrolytes contained organic solvent. Under a certain situation the morphologies of the coating transformed from traditional acicular shape into piece - layer shape and the mechanism of the morphologies transformation was canvassed . It was thought that the exist of electric field and other physical and chemic factor broke the structure symmetry of the growth cell of HA.The biocompatibility experiment of NiTi/HA coating materials was carried out compared with NiTi, Ti6A14V and 1Cr18Ni9Ti. The results showed that HA coating improved the cell activity and biocompatibility of NiTi shape memory alloy matrix and stimulated cartilage cell forming.