The Preparation And Characterization Of Apatite Coatings By Microwave Assisted Method

Titanium(Ti)metal and its alloys have been universally used in the dental and orthopedic fields,as well as biomedical implant materials,because of their excellent mechanical compatibility and good corrosion resistance.However,it is common knowledge that bones do not bond directly to Ti and its alloys as they get encapsulated by fibrous tissues after implantation,which hinders their clinical applications.Magnesium(Mg)and its alloys have been regarded as promising biodegradable materials used as bone implants due to the elastic modulus similar to human bone,low density and biocompatibility.However,the corrosion rate of magnesium and its alloys in chloride containing environment,such as human body fluid,is very fast,which could lead to the loss of mechanical integrity before the effective healing of the fractured bone.Hence,it is important to improve the bioactivity of Ti alloys and reduce the corrosion rate of Mg alloys.A novel surface modification method i.e.microwave-assisted coating method could greatly shorten the time of coating preparation.In this paper,dense and uniform apatite coatings were prepared on Ti6Al4V titanium substrates using microwave assisted aqueous chemical method.During the preparation process,some parameters were optimized,such as alkali time,heat treatment,Ca/P molar ratio of the microwave solution.Results showed that during the microwave process,alkali treatment followed by heat treatment to the titanium substrates would promote the rapid deposition of hydroxyapatite to form coating.And the morphologies of the apatite coatings could be adjusted by the Ca/P molar ratio of the microwave solution.After immersion test in simulated body fluid(SBF),the coated titanium alloy exhibits a good bioactivity by quickly inducing the formation of apatite depositions.Dense and uniform magnesium phytic acid/hydroxyapatite composite coatings were rapidly prepared on AZ31 magnesium alloy substrates by chemical conversion and microwave assisted method.During the preparation process,some parameters were optimized,such as pH value of phytic acid solution,time and temperature of phytic acid treatment,pH value of microwave solution and microwave time.The corrosion resistance and the bioactivity were characterized by electrochemical tests and immersion tests.Results showed that the thickness of the composite coating was~7μm,and the coating was dense.The charge transfer resistance of the coated sample was 32000Ω·cm~2 and the corrosion current density was 1.03μA/cm~2.Meanwhile,the composite coating could induce apatite deposition quickly and effectively improve the long-term corrosion resistance of magnesium alloy in SBF.