| With the development of society,our country has gradually entered an aging society.The aging of the body will cause the continuous decline and disease of body tissues and organs.There is a huge demand for products that grow year by year.Therefore,in terms of extending people's life span and improving people's quality of life,researches on new biological materials or surface treatments to improve the biological properties of materials are the development direction of future biomedical materials.The Ti and Ti alloys have excellent corrosion resistance and good biocompatibility,and are now widely used in biomedical materials.However,Ti and Ti alloys also have defects such as poor wear resistance when implanted into the human body as implants.These defects also limit the development of Ti and Ti alloys in biomedical materials.Therefore,proper surface treatment for Ti and Ti alloys is particularly important.Among many surface treatment technologies,micro-arc oxidation is widely used because of its low cost and low pollution.In particular,micro-arc oxidation can be used for surface treatment of irregularly shaped objects,which is why micro-arc oxidation is used in biomedical implants.It provides favorable conditions for the application of materials.Although micro-arc oxidation technology can form high wear resistance and corrosion resistant coatings on Ti and Ti alloys used in biomedical applications,the coatings still appear uneven microstructures and coating thicknesses.Thus,this article first uses micro-arc oxidation to prepare the bio-oxidation film layer containing Ca and P elements.In order to avoid the defects of the traditional micro-arc oxidation film layer,ultrasonic-assisted micro-arc oxidation is used to improve the forming quality of the film.The effect of ultrasound assistance on the microstructure and structure of the micro-arc oxidation film was studied with XRD,and the effect of microscopic changes on the macroscopic properties was explored through electrochemical experiments and friction and wear experiments.In the first work of this thesis,the effect of ultrasonic assistance on the microstructure and performance of the coating was studied by using ultrasonic assistance with different durations.The influences of ultrasonic with different durations on the coating microstructures and resultant properties were systematically investigated.The positive effects of ultrasonic,such as cavitation effect,sound flow effect,and mechanical effect,accelerate the cooling rate of electrolyte and promote the uniformity of the solute on the sample surface.Therefore,the produced coatings with ultrasonic assistance exhibit uniform microstructures with fewer cracks and thereby better performances.For instance,the ultrasonic-assisted coating with a 15-min duration shows a lower mass loss(by 25.1%)compared with the counterpart without ultrasonic assistance in the tribology test;the ultrasonic-assisted one with 15-min duration also reveals a lower corrosion current density(0.103?A cm-2)than the counterpart(0.238?A cm-2)in Hank's solution.In order to further enhance the biological performance of the implant,ultrasonic-assisted micro-arc oxidation and hydrothermal treatment are combined to form a composite of hydroxyapatite.Using SEM to study the difference in the microscopic morphology of the coating before and after hydrothermal treatment,and compare the formation of hydroxyapatite crystals generated after the ultrasonic-assisted sample hydrothermal treatment,and explore the difference of ultrasonic-assisted components of coatings by XRD.In in vitro experiments,the differences in the biological properties of the samples were compared.In this experiment,ultrasonic-assisted micro-arc oxidation can deposit more Ca elements,and at the same time can promote the formation of Ti O2.The content of Ti O2 increases by 10.81%,and the coating becomes thicker(38.32%);avoid surface heterogeneous areas,making the coating smoother and the elements uniform.After the hydrothermal treatment,more hydroxyapatite was generated on the surface of the ultrasonic-assisted coating,the content increased by 36.69%,and the distribution and microscopic morphology were more uniform.In vitro experiments showed that compared with samples without ultrasound assistance(14.45×104 cm-2),the number of MG63 cells on the ultrasound-assisted micro-arc oxidation coating was larger(16.15×104 cm-2).After hydrothermal treatment,the number of MG63 cells on samples without ultrasound assistance was greatly reduced.Meanwhile,the biological activity of the coating can be improved due to the formation of hydroxyapatite crystals.There are denser and more uniform HA crystals on the surface of the ultrasonic-assisted sample after the hydrothermal treatment,which also leads to an increase in the ALP activity of the coating.Therefore,the ALP activity of the film after the ultrasonic-assisted micro-arc oxidation sample hydrothermal treatment is the highest among all the samples(2.01 U/ml). |
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