Date of Award

2013

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Metallurgical Engineering

First Advisor

Kumar, Dr. Dhananjay

Abstract

Magnesium has emerged as a revolutionary biodegradable metal for use as an orthopedic material, it has several advantages over the permanent metallic materials currently in use, including eliminating the effects of stress shielding, improving biocompatibility and degradation properties, thus removing the requirement of a second surgery for implant removal. Due to the rapid degradation of magnesium, it is necessary to control the corrosion rates of the materials to match the rates of bone healing. This dissertation reports on the effect of doping on the properties of β-tricalcium phosphate (β-TCP). It also reports on its application as a thin film coating on magnesium alloys for implant applications. Adding various dopants to β-TCP significantly influences critical properties. In this study, discs were fabricated in two compositions: (i) undoped β-TCP, (ii) β-TCP doped with 1.0 wt % MgO, 0.5 wt % ZnO, and 1.0 wt % TiO2. Films were fabricated from these compositions using the pulsed laser deposition (PLD) technique. These coatings were then characterized for corrosive, hardness, and cytocompatibility. The XRD patterns of the coating confirm the amorphous nature of the films. The presence of the metal oxides in β-TCP improved ceramic densification. The application of these doped coatings was also found to increase the hardness by 88 %, the modulus of elasticity by 66 %, and improve corrosion resistance of the magnesium alloy substrate; with a 2.4 % improvement in Ecorr and 95 % decrease in icorr. Cell viability was studied using an osteoblast precursor cell line MC3T3-E1 to assure that the biocompatibility of these ceramics was not altered due to the dopants. Long-term biodegradation studies were conducted by measuring weight change and surface microstructure as a function of time in simulated body fluid. The results suggest that these coatings could be used for bioresorbable implants with improved corrosion resistance and increased hardness.

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