Date of Defense
24-11-2025 11:00 AM
Location
F1-1043
Document Type
Dissertation Defense
Degree Name
Doctor of Philosophy in Mechanical & Aerospace Engineering
College
COE
Department
Mechanical and Aerospace Engineering
First Advisor
Prof. Abdel-Hamid. I. Mourad
Keywords
Biocorrosion studies; metallic glass alloys; cytotoxicity studies; cell culture; antimicrobial studies; electrochemical analysis; molecular dynamic simulations.
Abstract
The relentless pursuit of advanced biomaterials that synergistically combine high mechanical strength, exceptional corrosion resistance, and inherent biocompatibility is critical for next-generation medical implants. This research addresses this challenge through the development and multi-faceted evaluation of a novel library of Zr-Co-Ti-based metallic glasses (MGs); Zr60Co30Ti10, Zr55Co35Ti10, and Zr50Co40Ti10, fabricated via melt-spinning. The alloys were confirmed to be fully amorphous by X-ray diffraction (XRD), a structure underpinned by exceptional thermal stability, with the Zr60 composition exhibiting a larger supercooled liquid region (Δ𝑇𝑥) of 149.68 °C, a hallmark of a strong glass former. This amorphous nature conferred outstanding mechanical properties, with nanoindentation revealing a high hardness of 9–9.5 GPa paired with a moderate elastic modulus (85–115 GPa), mitigating the risk of stress-shielding and positioning them favourably against bone. The electrochemical performance of these MGs was rigorously assessed across a physiologically relevant spectrum of environments, including acidic (HCl), neutral (NaCl), alkaline (NaOH), and simulated body fluids (SBFs) such as Artificial Saliva Solution (ASS), Artificial Blood Plasma (ABP), Phosphate-Buffered Saline (PBS), and Hank’s Balanced Salt Solution (HBSS). Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) unveiled extraordinary corrosion resistance, with passive current densities on the order of 10-11 A/cm² and charge transfer resistance often exceeding 1006 Ω·cm². A compelling composition dependent hierarchy emerged. The Zr60Co30Ti10 (Zr60) alloy demonstrated consistently superior and versatile performance, particularly excelling in neutral and alkaline conditions. Intriguingly, while the Zr55Co35Ti10 (Zr55) and Zr50Co40Ti10 (Zr50) alloys showed enhanced resistance in highly alkaline environments (pH12), a reversal of the Zr60 trend, their overall performance remained secondary. This superior corrosion resistance was further validated against other melt-spun MG systems like Cu51Zr30Hf14Ag5 and Zr38Co34Al10Cu10Ti8. Post-corrosion analysis via SEM, EDS, and XPS confirmed the formation of stable, dense passive films rich in ZrO₂ and TiO₂, effectively hindering ion release. The biological efficacy of these alloys confirmed a crucial dual functionality. In vitro cytocompatibility assays using L-929 fibroblast cells confirmed excellent cell viability and proliferation, indicating minimal cytotoxic response. Furthermore, the MGs exhibited significant inherent antibacterial properties, drastically reducing biofilm formation against pathogenic strains of Listeria monocytogenes and Escherichia coli compared to conventional medical alloys. Molecular dynamics simulations provided profound atomistic insights, revealing a dominance of full icosahedral clusters via Voronoi tessellation and a split-second peak in the radial distribution function (RDF), which fundamentally justify the high glass-forming ability and the observed combination of properties. The common neighbour analysis (CNA) further confirmed the amorphous structure of the simulated Zr-Co-Ti based MG alloy (Zr60). The synergistic integration of exceptional corrosion resistance, optimal mechanical properties, dual functionality in promoting cell growth while inhibiting bacteria, and a robust amorphous structure establishes this novel Zr-Co-Ti based MG alloy system, particularly the Zr60Co30Ti10 composition, as a future candidate for demanding biomedical applications.
Included in
BIO-CORROSION STUDIES ON NOVEL Zr‑Co‑Ti BASED METALLIC GLASS ALLOYS FOR BIOMEDICAL IMPLANT APPLICATIONS
F1-1043
The relentless pursuit of advanced biomaterials that synergistically combine high mechanical strength, exceptional corrosion resistance, and inherent biocompatibility is critical for next-generation medical implants. This research addresses this challenge through the development and multi-faceted evaluation of a novel library of Zr-Co-Ti-based metallic glasses (MGs); Zr60Co30Ti10, Zr55Co35Ti10, and Zr50Co40Ti10, fabricated via melt-spinning. The alloys were confirmed to be fully amorphous by X-ray diffraction (XRD), a structure underpinned by exceptional thermal stability, with the Zr60 composition exhibiting a larger supercooled liquid region (Δ𝑇𝑥) of 149.68 °C, a hallmark of a strong glass former. This amorphous nature conferred outstanding mechanical properties, with nanoindentation revealing a high hardness of 9–9.5 GPa paired with a moderate elastic modulus (85–115 GPa), mitigating the risk of stress-shielding and positioning them favourably against bone. The electrochemical performance of these MGs was rigorously assessed across a physiologically relevant spectrum of environments, including acidic (HCl), neutral (NaCl), alkaline (NaOH), and simulated body fluids (SBFs) such as Artificial Saliva Solution (ASS), Artificial Blood Plasma (ABP), Phosphate-Buffered Saline (PBS), and Hank’s Balanced Salt Solution (HBSS). Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) unveiled extraordinary corrosion resistance, with passive current densities on the order of 10-11 A/cm² and charge transfer resistance often exceeding 1006 Ω·cm². A compelling composition dependent hierarchy emerged. The Zr60Co30Ti10 (Zr60) alloy demonstrated consistently superior and versatile performance, particularly excelling in neutral and alkaline conditions. Intriguingly, while the Zr55Co35Ti10 (Zr55) and Zr50Co40Ti10 (Zr50) alloys showed enhanced resistance in highly alkaline environments (pH12), a reversal of the Zr60 trend, their overall performance remained secondary. This superior corrosion resistance was further validated against other melt-spun MG systems like Cu51Zr30Hf14Ag5 and Zr38Co34Al10Cu10Ti8. Post-corrosion analysis via SEM, EDS, and XPS confirmed the formation of stable, dense passive films rich in ZrO₂ and TiO₂, effectively hindering ion release. The biological efficacy of these alloys confirmed a crucial dual functionality. In vitro cytocompatibility assays using L-929 fibroblast cells confirmed excellent cell viability and proliferation, indicating minimal cytotoxic response. Furthermore, the MGs exhibited significant inherent antibacterial properties, drastically reducing biofilm formation against pathogenic strains of Listeria monocytogenes and Escherichia coli compared to conventional medical alloys. Molecular dynamics simulations provided profound atomistic insights, revealing a dominance of full icosahedral clusters via Voronoi tessellation and a split-second peak in the radial distribution function (RDF), which fundamentally justify the high glass-forming ability and the observed combination of properties. The common neighbour analysis (CNA) further confirmed the amorphous structure of the simulated Zr-Co-Ti based MG alloy (Zr60). The synergistic integration of exceptional corrosion resistance, optimal mechanical properties, dual functionality in promoting cell growth while inhibiting bacteria, and a robust amorphous structure establishes this novel Zr-Co-Ti based MG alloy system, particularly the Zr60Co30Ti10 composition, as a future candidate for demanding biomedical applications.