The Biocompatibility Of Zr-based Bulk Metallic Glasses

In this thesis, a Ni-free Zr46(Cu4.5/5.5Ag1/5.5)46Al8bulk metallic glass (BMG) hasbeen studied in details in terms of microstructure, mechanical properties, corrosionresistance in simulated body fluids, in vitro cytotoxicity and in vivo biocompatibility,in order to evaluate its potential as a biomedical materials. Meanwhile, forcomparison, the related properties of Zr-Cu-Ni-Al, Zr-Ti-Ni-Cu-Al, Ti-Zr-Ni-Cu-BeBMGs, pure Ti and Ti-6Al-4V alloy have been studied as well.The microstructure and thermal properties of bulk metallic glasses have beenstudied by using X-ray diffraction (XRD), transmission electron microscope (TEM)and differential scanning calorimetry (DSC). The calculation results of theautocorrelation function (ACF) of high-resolution TEM (HRTEM) imagesdemonstrated that with the increase in the sample diameter, the BMG possessed moreordered atomic configuration and thus less free volume. The structural relaxationpeak just below the glass transition temperature of the DSC curve also showed thatthe free volume of BMG decreases with increasing the sample diameter.The Zr46(Cu4.5/5.5Ag1/5.5)46Al8BMG exhibited a higher hardness and bettercompression plasticity than other studied BMG, pure Ti and Ti-6Al-4V alloy. Thehardness of the BMG was closely correlated with Tg, namely, the higher the Tg, thelarger the hardness. In addition, with the increase of the free volume, the plasticdeformation capacity of BMG increases as well.The friction tests have been performed on the selected BMGs, pure Ti andTi-6Al-4V alloys. The results indicated that the wear resistance of alloys increaseswith the increasing of sample diameter. That means, the Zr46(Cu4.5/5.5Ag1/5.5)46Al8BMG with larger sample size has the smaller friction coefficient and the moreshallow morphology. Among the studied BMGs, pure Ti and Ti-6Al-4V alloy, theZr46(Cu4.5/5.5Ag1/5.5)46Al8BMG had the best wear resistance performance.The biocorrosion measurements of the selected BMGs, pure Ti and Ti-6Al-4Valloy have been performed in simulated physiological fluid. A layer of passive filmwas formed in the surface of the alloy sample during the corrosion tests, andZr46(Cu4.5/5.5Ag1/5.5)46Al8BMG presented the best corrosion resistance among thestudied alloys. The immersion test results in the simulated body fluid (SBF) showedthat the deposit appeared in the surface of the alloy sample after a period ofimmersion, and the Ca/P atomic ratio of the surface deposit ofZr46(Cu4.5/5.5Ag1/5.5)46Al8BMG sample was close to that for the natural bone, whichpresented a better bioactivity. The results from the L929cells culture indicated that theZr46(Cu4.5/5.5Ag1/5.5)46Al8BMG exhibit cytotoxicity of Grade1,which verified thematerials for use in further biomedical applications. The biocompatibility of BMGwas also evaluated in vivo by implanting the BMG samples into white rabbits, whichindicated that the BMG can integrate with the bone tissue closely and enriched moreCa, P elements, which showed an excellent biocompatibility.