Preparation Of Micro-arc Oxidation HA Coatings On Titanium Alloys And Its Biological Histocompatibility

At present, ceramic materials on titanium alloys by surface modification is importantfor implant materials. This kind of material, hydroxylapatite（HA） containing coatings ontitanium alloys, not only has good mechanical properties,but also has excellent bioactivityand biocompatibility. For titanium alloys, there are many surface treatment methods suchas the electrophoretic deposition and anodic oxidation. Though these methods can producefilms on titanium alloys, they have several shortcomings such as low bonding strengthbetween substrate and the film layer and hard to produce HA phase. Micro-arc oxidation（MAO）, as a effective surface modification technology,can produce films contained HA ontitanium alloys, and has high bonding force to reach the standard.Recently, hydro-thermal treatment and alkali-thermal treatment mostly are used forthe research about preparation of HA containing coatings on Titaniumalloys by MAO. Dueto the extension of the production cycle, these methods are not conducive to theproduction.In this paper, we will apply MAO to produce ceramic films contained HA on thesurface of titanium alloys by adjusting the formula of the electrolyte. There are Ca andCa（H₂PO₄）₂in the electrolyte which is a new type of electrolyte to fabricate oxidationcoatings. Firstly,In different parameters of electrolyte and oxidation time, we will test thephase composition, the thickness of films,The surface morphology, the content of elementsby X-ray diffraction, scanning electron microscopy and so on. Then the surface roughness,the3-D morphology, the bonding force between substrate and coating will be detected andanalysed. Finally,we will make a valuation about biological histocompatibility for ceramicfilms contained HA by the experiment of the implants embedding in the muscle tissue ofanimals.The results showed that the perfect HA phase was found when the PH of theelectrolyte was5⁶, Ca/P was2:1, the electrolyte concentration was above0.17mol/LCa,citric acid content was0.6times of Ca（H₂PO₄）₂, and other electrical parameters were anodic current density in10A/dm², the pulse frequency in150HZ, the duty cycle in12%,the positive pulse number in10. The crystal phases of the MAO films were mainlycomposed of HA phase, calcium phosphate and rutile. Citric acid could not only promotethe formation of HA, but also reduce the content of Al and V on the surface of the MAOfilms. The HA peak of XRD, the thickness of films and the surface roughness increasedwith the increase of the electrolyte concentration and oxidation time, but the rutile peakgradually was reduced. The surface morphology observation showed that with the increaseof the electrolyte concentration and oxidation time, there were so many ceramic particleson the surface of MAO coatings. Although the bonding force between substrate andcoating could be reduced with the increase of oxidation time, the bonding forces wereabove4N up to a good combination. The results about the experiment of the implantsembedding in the muscle tissue of animals showed that compared with the titanium alloywithout the surface treatment, a large number of proliferation and inflammatory cells werenot found on the muscle tissue around the sample of ceramic films contained HA. Therewere some muscle fibers and new elements of N and S on the surface of coatings by Theanslysis of SEM and the energy of dispersive spectrum（EDS）.The surface of itanium alloys can be derictly produced biological ceramic filmscontained HA by MAO in this paper, this material has excellent biologicalhistocompatibility by the experiment of the implants embedding in the muscle tissue ofanimals.