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# Ultrastable Mg, Zn, Ca BMGs

Abstract

The aims of this thesis are to produce and examine biodegradable thin film metallic glasses (TFMGs) and the recently discovered ultrastable metallic glass (SMG) films for biomedical applications. To ensure full biocompatibility the films will be composed entirely of essential mineral MgZnCa alloys.

The literature review provides an overview of metallic glass formation and processing, thin films and deposition methods, initial understandings of ultrastable glasses, and biomedical requirements with a focus on biodegradation.

The films will be deposited onto various substrates via magnetron sputtering and pulse laser deposition (PLD) techniques. The master alloys and deposition targets will be prepared via induction furnace melting and copper mould gravity casting of pure base element Mg, Zn, and Ca (99.8wt% pure or better).

The initial results have shown the Mg$$_{65}$$Zn$$_{30}$$Ca$$_{5}$$ alloy is relatively brittle, with most targets fracturing during casting or shaping operations. The targets which were produced without failure were examined via DSC and found to be at best primarily crystalline in structure. This should be expected as this alloy’s critical casting thickness is similar to the thickness of the mould utilised.

Going forward XRD analysis will be used to definitively establish the targets’ structures, and the target manufacturing process will be refined (current method is not efficient ). Numinous thin film metallic glass specimens will be produced via sputtering/PLD and evaluated; hopefully leading to publications and attendance at conferences.

# INTRODUCTION

Current pharmaceutical technology relays on re-dosing of drugs, often with treatments being readminister several times per day or week. Coating pharmaceuticals with tailored bioabsorbable films designed to degrade over time could allow for a slow controlled release of drug packages such as antibiotics, antimicrobials, and analgesics (painkillers). These medical devices could be implanted during surgeries, eliminating the needs for daily drug administration.

Thin film metallic glasses (TFMGs) are one technology which may make this possible. These novel amorphous metallic materials been demonstrated to significantly modify substrate properties such as hardness, wear residence, surface finish, fatigue and corrosion residence, and even ductility. Recently ultrastable metallic glass (SMG) films have been discovered which display improved thermal and kinetic stabilities, and often reduced entropy relative to the more established TFMGs. Many properties of SMGs have not yet been characterised and it is not yet known if in additional to improved stability if they may offer greater improvements in substrate property modification. The application of these films onto drug delivery systems, or even orthopaedic devices, could provide great potential for improvements in wound healing and pain management practices.

The aims of this thesis are to produce and investigate quality TFMGs and SMGs for biomedical applications. Thin films of established bulk metallic glass (BMG) compositions, such as Mg$$_{65}$$Zn$$_{30}$$Ca$$_{5}$$ will be deposited onto various substrates including; BMGs of similar film composition, Polycaprolactone (PCL) scaffolds, and dissolvable NaCl substrate (to allow base film to be studied independently). The properties and characteristics of the films as well as their property modification effects on the different substrates will be investigated, and the characterised films compared with their BMG counterparts.

Example Equation Formatting $\nabla_{\rm rad} = \frac{3F\kappa}{4acg}\frac{P}{T^4} > \nabla_{\rm ad}.$