Preparation And Investigation On Biological Activity Of Cacium Phosphate Coatings On AZ91Magnesium Alloy

At present, the clinical bone implant materials are mainly stainless steel, titaniumand chrome base alloy. But, these materials’ density, and elastic modulus don’tmatch with human bone.And because these materials belong to heavy metal，itcontains heavy metal elements,it’s bad to people’s health。. the refractory, need totake out a second time and need a surgery.It has bad effect to physical and mentalhealth and a second surgery increase economic burden. On the other hand, these metalmaterials’ density, the elastic modulus are very different from the human bone, and itcause stress shielding effect and make the growth of bone slowly. At present,magnesium alloy material began to have been used as bone implant for study.Magnesium alloy has the small density, good mechanical properties, high strength,close to human body bone elastic modulus, easily degradable, etc. But the chemiscalproperty of the magnesium alloy is live, the corrosion resistance is poor, so itscorrosion resistance needs to be improved. On the other hand, a layer of coating, onthe surface of magnesium alloys with biological activity of membrane can promotebone growth.This thesis is about preparing bioactive calcium phosphate film in the liquid ofcalcium phosphate on the surface of AZ91surface。The method is controlling thevariable. under the condition ovariable in other conditions constant, join differentcontents of nitrobenzene between sulfonic acid sodium, sodium molybdate and indifferent pH value the preparation phosphating film. With scanning electronmicroscopy (sem) of phosphating film surface morphology, polarization curveanalysis its corrosion resistance.The conclusion were that the difficulties betweensulfonic acid sodium can promote the role of film, but much more content alsoinfluence the quality of film, affect corrosion resistance. Sodium molybdate increasednuclear particle shape, promote the film。 too much of the content of sodiummolybdate in solution formed undissolved molybdenum acid calcium, reduce thecalcium ion content, affects the film. Again, through the experiment proves that the pH value of film also have the enormous influence. When the pH value of2.5thefollowing, the film’s quality was poor, the acidity because too big, magnesium alloycorrosion speed too fast, the speed of the film is less than the corrosion rate, make themembrane layer on the map.From the energy spectrum analysis, it’s included that the membrane of thechemical composition, and atom percentage content, the main components of thephosphate film is calcium phosphate. By XRD on membrane layer diffraction analysis,object is determined, it is concluded that the main components of the film is calciumphosphate.On the other hand, this paper studies the formation mechanism of phosphate film.In different reaction time,10s,30s,60s,2min,5min,10min,20min,30min, toget membrane layer, and carry on the scanning electron microscopy (SEM) of theanalysis of the microstructure, draw of calcium phosphate film first formed on thebeta phase into nuclear particle, α gradually to expand on that. It’s included that,phosphate film appear dynamic balance stage more than30min, magnesium matrixcorrosion speed and film speed phase equilibrium stage, the corrosion resistance andthe impact is not big, so the best film time is30min.