Preparation, Characterization And Property Of The Microarc Oxidation Of Medical Zirconium Material And Niobium Material

Zr and Nb are great potential medical metallic materials, since they have little negative effects on human body and equipped with exc€ellent mechanical properties. But it is needed to produce a bioactive film on the surface of Zr and Nb in order to inprove the bonding properties between them and the human body, because both Zr and Nb are Bio-inert materials. Micro-arc oxide (MAO) technique is a proved technique to improve the bioactivity of Ti, but it's on the starting stage to imply this technique in improving the bioactivity of Zr and Nb. This article firstly prepared porous MAO coatings containing Ca and P in-situ on the Zr and Nb. Then the electric parameters (voltage, current, duty cycle and frequency) feature and thier effects on the films'thickness, morphology, phase composition and contents of Ca, P in the films were researched, The effects of electric parameters on MAO films were quantitatively investigated by variance analysis method, The mechanism of electric parameters' effects on MAO films was discussed from the angle of total pulse energy. After that, the bioactivity and related mechanical properties of MAO coatings were detected through body fluid immersion test, nano-indentation test and scratch test.The results show that porous films form on the medical Zr and Nb base material after MAO. The films, combined well with the base material, are composed by compact layer and porosity layer. The MAO films in the phosphate solution including Ca are mainly composed of O, Ca and P elements, the contents of which decrease from the film surface to the base material. The MAO film on Zr base material is composed of m-Zr02 and t-ZrO2, while the MAO film on Nb base material is composed of amorphous Nb2O5. The biological activity of MAO films on Zr and Nb performs well, and the elastic modulus decrease remarkably.The mechanism and effects of electrical parameters on MAO on Zr and Nb is identical.(1)The electrical parameters affect the MAO film thickness, phase compositon and surface morphology by changing the pulse total energy. With the increasing anode voltage or current density, the film thickness increases with parabola, the diameter of micro-hole increases, the number of micro-hole per unit decreases, the film becomes coarser, and the width of cracks increases. With the duty cycle increasing, the thickness sightly increases, but the increasing rate becomes small. With the increasing frequency, the thickness change is not obvious. At high frequency, the micro-hole diameter is smaller and a little more compact, but the change is not obvious. According to the variance analysis, the effect sequence of electrical parameters on the thickness is:voltage>current density>duty cycle>frequency, the effect of frequency can be neglected.(2) The electrical parameters affect the anode's diffusion volecity and cathod's motion volecity by changing the voltage and electric field strength. Furthermore, the relative elements content is changed. With the increasing voltage, current dencity, or duty cycle, the content of Ca and P increase, the mole ratio of Ca and P increases, but the effect of duty cycle is smaller. The effect of frequency on the relative content is smaller. The relative content and mole ratio can be changed by designing and controlling of the electric parameters.(3)With the time increasing, the thickness of MAO films increase as an exponent curve under constant voltage mode, and the thickness increases as a linearity curve under constant current mode. It is more conducive to controlling the growing rate of MAO films under the constant current mode...