Surface Silanization Treatment Of Biomedical Magnesium Alloy And Its Structure And Properties

Magnesium alloy is considered to be the most promising biodegradable metal implant material due to its good mechanical compatibility,biocompatibility and complete degradability.However,due to the low standard electrode potential,it is highly ·prone to corrosion and releases hydrogen gas in the complex body fluid environment,and will generate bubbles around the tissue to form vesicles,which hinder the heal:ing process of the wound.This shortcoming restricts the clinical application of magnesium alloy.In order to solve the problem of excessive corrosion rate of magnesium alloy in the body,the silane coupling agent is a special green non-polluting organic compound to treat the magnesium alloy surface and reduce the corrosion rate of magnesium alloy.The silane coupling agent with good corrosion resistance was selected by experiment,and the effects of different roughness,doped hydroxyapatite(HA)and ultrasonic dispersion on the structure and corrosion resistance of the film were studied.The silanized magnesium alloy sample is prepared by a sol-gel method,that is,the magnesium alloy substrate is immersed in a fully hydrolyzed silane solution or a modified silane solution for a certain period of time to form a silane film.The samples were observed and analyzed by Scanning Electron Microscope,Fourier Transform Infrared spectroscopy,Energy Dispersive Spectrometer,etc.;the bonding strength of the samples was tested by tensile test;the corrosion characteristics of the film were analyzed by electrochemical workstation;finally,the corrosion process of sample is simulated by simulating body fluid immersion.The optimum hydrolysis pH of the silanes(BTSE,BTSPS,GPTMS)obtained from preliminary experiment is between 6.5-7.0,the hydrolysis alcohol-water ratio was 85:15,the curing time and temperature were 60 min and 100 ?,respectively.After silicidation of magnesium alloy,the corrosion current of the sample is reduced by 2 orders of magnitude and the corrosion voltage is increased by 0.2V.The overall protection performance of GPTMS in the selected silane coupling agent is the best,followed by BTSPS and finally BTSE.The surface roughness of the substrate has a certain influence on the growth of the silane film layer.When the surface is rough,gradually reducing the surface roughness can effectively promote the growth of the film layer;when the surface is smooth,continuing to reduce the surface roughness of the substrate has no significant effect on the growth of the film.When the composite film is doped with HA,the overall corrosion protection performance is reduced,and the amount of HA added has a certain influence on the corrosion resistance.When the addition amount is 3g/L,the corrosion protection is relatively well.By ultrasonic treatment of HA,the particles are dispersed,the particle size is reduced,and the silane film layer has good bonding property,and the corrosion protection performance of the film layer can be effectively improved.