Ion implantation of calcium and zinc in magnesium for biodegradable implant applications

In this study, magnesium was implanted with calcium-ion and zinc-ion at fluences of 10(15), 10(16), and 10(17) ion.cm(-2), and its in vitro degradation behaviour was evaluated using electrochemical techniques in simulated body fluid (SBF). Rutherford backscattering spectrometry (RBS) revealed that the implanted ions formed layers within the passive magnesium-oxide/hydroxide layers. Electrochemical impedance spectroscopy (EIS) results demonstrated that calcium-ion implantation at a fluence of 10(15) ions.cm(-2) increased the polarisation resistance by 24%, but higher fluences showed no appreciable improvement. In the case of zinc-ion implantation, increase in the fluence decreased the polarisation resistance. A fluence of 10(17) ion.cm(-2) decreased the polarisation resistance by 65%, and fluences of 10(15) and 10(16) showed only marginal effect. Similarly, potentiodynamic polarisation results also suggested that low fluence of calcium-ion decreased the degradation rate by 38% and high fluence of zinc-ion increased the degradation rate by 61%. All the post-polarized ion-implanted samples and the bare metal revealed phosphate and carbonate formation. However, the improved degradative behaviour in calcium-ion implanted samples can be due to a relatively better passivation, whereas the reduction in degradation resistance in zinc-ion implanted samples can be attributed to the micro-galvanic effect

Biocompatibility and biodegradation studies of a commercial zinc alloy for temporary mini-implant applications

In this study, the biocompatibility and in vitro degradation behaviour of a commercial zinc-based alloy (Zn-5 Al-4 Mg) were evaluated and compared with that of pure zinc for temporary orthopaedic implant applications. Biocompatibility tests were conducted using human alveolar lung epithelial cells (A549), which showed that the zinc alloy exhibits similar biocompatibility as compared to pure zinc. In vitro degradation evaluation was performed using weight loss and electrochemical methods in simulated body fluid (SBF) at 37 degrees C. Weight loss measurements revealed that the degradation of the zinc alloy was slightly lower during the initial immersion period (1-3 days), but marginally increased after 5 and 7 days immersion as compared to pure zinc. Potentiodynamic polarisation experiments showed that the zinc alloy exhibits higher degradation rate than pure zinc. However, electrochemical impedance spectroscopy analysis suggests that pure zinc is susceptible to localized degradation, whereas the zinc alloy exhibited passivation behaviour. Post-degradation analysis revealed localized degradation in both pure zinc and the zinc alloy

Ion Implantation of Calcium and Zinc in Magnesium for Biodegradable Implant Applications

In this study, magnesium was implanted with calcium-ion and zinc-ion at fluences of 1015, 1016, and 1017 ion·cm−2, and its in vitro degradation behaviour was evaluated using electrochemical techniques in simulated body fluid (SBF). Rutherford backscattering spectrometry (RBS) revealed that the implanted ions formed layers within the passive magnesium-oxide/hydroxide layers. Electrochemical impedance spectroscopy (EIS) results demonstrated that calcium-ion implantation at a fluence of 1015 ions·cm−2 increased the polarisation resistance by 24%, but higher fluences showed no appreciable improvement. In the case of zinc-ion implantation, increase in the fluence decreased the polarisation resistance. A fluence of 1017 ion·cm−2 decreased the polarisation resistance by 65%, and fluences of 1015 and 1016 showed only marginal effect. Similarly, potentiodynamic polarisation results also suggested that low fluence of calcium-ion decreased the degradation rate by 38% and high fluence of zinc-ion increased the degradation rate by 61%. All the post-polarized ion-implanted samples and the bare metal revealed phosphate and carbonate formation. However, the improved degradative behaviour in calcium-ion implanted samples can be due to a relatively better passivation, whereas the reduction in degradation resistance in zinc-ion implanted samples can be attributed to the micro-galvanic effect

Design of low-cost organic light emitting diodes

This project focused on reducing the production cost of organic light emitting diodes and organic semiconductors through intuitive engineering design. Included in the thesis is a comprehensive, bottom-up method of design, synthesis, fabrication and analysis of both a set of luminescent materials and semiconductor device structure for use in organic light emitting diodes. The results demonstrate the viability of the method and reveal novel findings about the "thermally activated delayed fluorescence" phenomenon and its application in organic light emitting diodes