Speaker: Prof. Yucang Li, RMIT University
Time: 10:00, September 2, 2019
Venue: Room on the 3rd Floor, Building B5, University Town Campus
Abstract: Selective laser melting (SLM) was used for the fabrication of a new β Ti35Zr28Nb alloy and its scaffolds for biomedical applications. The SLM-manufactured porous scaffolds included an FCCZ structure (face centered cubic unit cell with longitudinal struts) and an FBCCZ structure (face and body centered cubic unit cell with longitudinal struts), exhibiting porosity values of 83.2% and 49.9%, respectively. The SLM-manufactured bulk samples showed a very similar elastic modulus in the longitudinal and transverse directions, but significantly higher yield strength in the transverse direction than in the longitudinal direction. However, both porous FCCZ and FBCCZ structures exhibited significantly higher elastic modulus and plateau strength in the longitudinal direction than in the transverse direction. The FCCZ scaffolds showed a longitudinal elastic modulus of 1.1 GPa and plateau strength of 27 MPa, and a transverse elastic modulus of 0.7 GPa and plateau strength of 8 MPa; while the FBCCZ scaffolds showed a longitudinal elastic modulus of 1.3 GPa and plateau strength of 58 MPa, and a transverse elastic modulus of 1.0 GPa and plateau strength of 45 MPa. These mechanical properties of the SLM-manufactured porous structures fall within the ranges of the mechanical properties of trabecular bone. The SLM-manufactured β-Ti35Zr28Nb alloy showed good corrosion properties. The MTS assay revealed that both the FCCZ and FBCCZ scaffolds displayed cell viability at the same level as that of the control. SEM observation indicated that osteoblast-like cells attached, grew, and spread in a healthy way on the surfaces of both the FCCZ and FBCCZ scaffolds, demonstrating the excellent biocompatibility of these materials. Overall, the SLM-manufactured Ti35Zr28Nb scaffolds possess promising potential for use as hard-tissue implant materials due to their appropriate mechanical properties, good corrosion resistance, and biocompatibility.
Magnesium (Mg) based alloys have been extensively considered for their use as biodegradable implant materials. However, controlling their corrosion rate in the physiological environment of the human body is still a significant challenge. One of the most effective approaches to address this challenge is to strategically design new Mg alloys with enhanced corrosion resistance, biocompatibility, and mechanical properties. Our research has developed new series of Mg-zirconium (Zr)-strontium (Sr)-rare earth element (REE) alloys for biodegradable implant applications. Research results indicate that Sr and Zr additions can refine the grain size and enhance the corrosion and biological behaviours of the Mg alloys. Furthermore, the addition of holmium (Ho) and dysprosium (Dy) to Mg-Zr-Sr alloys resulted in enhanced mechanical strength and decreased degradation rate. In addition, less than 5 wt.% Ho and Dy additions to Mg-Zr-Sr alloys led to enhancement of cell adhesion and proliferation of osteoblast cells on the Mg-Zr-Sr-Ho/Dy alloys.
Biography: Associate Professor Yuncang Li obtained his PhD in Materials Science Engineering from Deakin University in 2004 and then took up a research position in Biomaterials Engineering at Deakin University until the end of 2014. He joined School of Engineering, RMIT University in 2015. He was awarded an Australian Research Council (ARC) Future Fellowship in 2016. Dr Li has won a number of national competitive grants including ARC and National Health and Medical Research Council (NHMRC) projects. His research focuses on developing metallic biomaterials for medical applications. He published over 160 journal papers, 1 book and 15 book chapters and filed 5 patents. He has expertise in microstructure-mechanical property relationships, corrosion, and biocompatibility, surface modification, nanostructured metals and alloys, and metal foams.
