A BG/HA Graded Coating Prepared By Electrophoresis Codeposition In The Acetic Acid Medium

T16A14V alloy has good biocompatibility and excellent mechanical property. It has been extensively used in the orthopedic sursery and the substitution of hard body tissues. But Ti6A14V alloy has no bioactivity. It can not form a strong and long-term stable combination with the bone. The bioactivity of the T16A14V alloy surface can be improved by preparing HA coating on it. But there is a big tensile stress ,caused by the difference of the thermal expansion coefficient,at the interface between the HA coating and the substrate. In addition,the microstructure of the HA coating is not compact. The HA coating is easily broken off from the substrate because of the interface corrosion,caused by the body fluid,and the cycle load. The preparation of the BG/HA bioactive graded coating on the surface of Ti6A14V is an effective way to alleviate the heat stress.In this study,a kind of BG (Na2O10wt%-CaO15wt%-SiO248wt%-P2O55wt% -82631 Owt%-TiO26wt%-CaF26wt%) ,whose thermal expansion coefficient is bigger than that of Ti6A14V at high temperature and contrary at low temperature,had been developed by formulating recipes and adjusting composition according the empirical formula of the relationship of the enamel expansion coefficient and its composition. The expansion coefficient of the BG matches that of T16A14V alloy. Its fusion temperature is low (<700) and the chemical stabilization is good. The HA powder had been prepared by Sol-Gel method. The BG powder and HA powder were used as the stuff of the coating. The dispersing and the charging of the BG and HA particles in non-aqueous medium had been studied. The surfaces of both the BG particles and HA particles can take the positive electrical charge when they are dispersed in the acetic acid. That is the premise of the BG/HA electrophoresis codeposition. The laws of the electrophoresis deposition of the BG and HA particles were found by the study on each of their deposition under the different conditions. The electrophoresis codeposition of the BG and HA particles had been studied and the BG/HA graded coating,which is compact in the bottom layer and porous near the surface layer,had been prepared on the surface of the dental implant after the low temperature heat treatment (about 740 ) and fast firing (50-80/min,heatpreservation time was 5-8min.).The mechanical property,phase,the adhesion state of the interface ,and the microstructure of all kinds of coatings (BG coating,BG/HA composite coating,BG/HA graded coating) were analyzed by the routine and modern testing means (XRD,IR,SEM,ED AX,XPS and EMPA etc.).The shear strength of the coating hadbeen tested by a new method-the flat bottom cone shear testing. It was foundthat there was a close relationship between the adhesion strength of the BG coating and the surface roughness of the titanium alloy and the firing temperature. The chemical state of the elements Ti and Si at the coating interface varied. The chemical bond and the mechanical occluding make the BG coating form a strong adhesion with the titanium alloy. The HA particles were diffused in the BG phase. The gluing-tensioning strength of the BG coating is 40-SOMPa. The shear strength of the BG coating reaches above 35MPa. The HA content in the surface layer of the BG/HA graded coating has an important effect on the adhesion of coating. The shear strength of the coating comes down with increase of the HA content. The shear strength of the coating is 15-20MPa when the HA content in the surface layer is about 30%.