The Fha And The Bg / Bg-the Fha Composite Coating And Its Biological Activity Study

Titanium alloy/HA composite bioactive ceramic coating not only has good mechanical properties, but also has good biological activity, has being the focus of the field of hard tissue replacement materials research, fluorine substituted hydroxyapatite (FHA) formed by F- substituted some parts of OH" in hydroxyapatite has lower solubility, longer lifetime, better thermal stability than HA in human body fluids the has become a new hotspot in recent years. Electrophoretic deposition (EPD) is widely used in preparating a variety of functional metal/ceramic composite material with fast deposition rate, low cost, suitable for complex substrate surface and so on. Therefore, the authors used X-ray diffraction, scanning electron microscopy, spectroscopy, thermal analysis, thermal expansion, universal testing machine, electrochemical workstation and the equality of means of days to study the influnce of the concentration of reactants, F doped and calcination temperature fabrication process parameters on the FHA powder phase composition, crystal lattice parameters, cell volume and density and thermal stability; the influnce of heat treatment temperature of the FHA powder, heat treatment temperature of the coating, and substrate pretreatments on the morphology of FHA surface and the adhesive force of coatings, and optimizating heat-treatment of BG/BG-FHA coatings; researching the corrosion resisting propertity and biological activity of FHA and the BG/BG-FHA composite coating by SBF experimental study. Main contents and conclusions are as follows:1) CaF2 phase is detected when reactant concentration of F" increases from 0.5 mol/L to 1.0mol/L, unit cell volume of F0.75HA increases linearly and density decreases linearly with the heat treatment temperature from 70℃to 1250℃, doping F leads to the nonlinear decrease of a axis lattice parameters.2) Doping F improves the thermal stability of FHA at high temperature., and the stability can be gradually improved with the inrease of F content; Sintering density of FHA bulk increases with small amount of F doping (x=0.25), but decreases when F doping content more than x=0.25.Thermal expansion coefficient (CET) of FHA decreases with the increase of F content, and the CET of FA is 12.21×10-6/K, lowered by 10.7% compared to HA at 1100℃. The growth ability of new apatite forming on FHA bulk surface proved by the SBF soaking experiment is: FHA>HA>FA.3) Powder treated at a certain crystallization temperature treatment (700℃) used for coating after electrophoretic deposition obtained with a more compact structure; a certain temperature (700℃) heat treatment will enhance the coating adhesion strength, phase change of coating increased at high temperature (900℃), resulting in deterioration of bond properties. coatings pretreated by alkali treatment after acid treatment obtains more reasonable structure, with more binding force. Overall, FHA coatings obtain poor coating adhesion.4) After heat treatment, chemical reaction occur between glass and titanium alloy substrate of the coating, coating and matrix bond according to chemical metallurgical; the formation of mesh porous structure coating after heat treatment has good biological activity; optimization of the coating heat treatment was:annealing temperature:750℃, holding time: 12min; Cooling-down method:With furnace cooling. Coating after heat treatment optimization with a larger binding capacity (> 20MPa).5) Considered the passivation current anode current, the width of passivation potential and free corrosion potential value as reference standards, the corrosion resistance of several coatings in descending order: FHA coating> BG/BG-FHA coating> alkali treatment substrate >acid treatment substrate;titanium alloy substrate gain weight significantly in the late immersion, which results from saturated NaCl deposited on the surface; the mass of the FHA coating has increased because alternating deposition of apatite and NaCl has been carried out on the surface after immersion; the mass of BG/BG-FHA coating gain slightly because dissolution and deposition reaction proceed more equivalent.6) Corrosion resistance in descending order: FHA coating>BG/BG-FHA coating>alkali treatment substrate>acid treatment substrate; There is almost no deposition of calcium phosphate on the surface of pretreated substrate, bone-like calcium deficiency apatite,which grown like petal, several hundred nanometers length, formed on the surface of FHA coating after soaking, showing excellent biological activity. Carbonate substituted fluoride hydroxyapatite and calcium deficiency apatite formed on the surface of BG/BG-FHA coating after immersion. The coating and substrate combined closely after immersion, without interface cracks and pores, indicating BG/BG-FHA coating has good mechanical properties and biological activity.