Azadi, Ava

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Azadi, Ava

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  • Publication
    The Effect of Powder Size and Morphology on the Sinterability of Bioresorbable Mg-Sr/Ca Alloys
    (2024-03-07)
    Azadi, Ava 
    ;
    O'Cearbhaill, Eoin D. 
    ;
    Celikin, Mert 
    Possessing outstanding biocompatibility and bioresorbability, magnesium (Mg) alloys with strontium (Sr) and calcium (Ca) additions have shown potential to be used as temporary implants in orthopaedic applications. Having a low elastic modulus (45 GPa) close to the human bone lowers the stress shielding effects. Low temperature Additive Manufacturing (AM) techniques (e.g., Fused Deposition Modelling) have potential to be used for the fabrication of complex Mg components while avoiding safety concerns associated with high temperature AM. However, low sinterability of common Mg-alloys is the main limiting factor. The objective of this work is to investigate the effect of powder particle size / morphology on the sinterability of Mg-Ca/Sr based alloys produced via powder metallurgy. Laser Diffraction and Scanning Electron Microscopy (SEM) were used to characterize particle size and morphology. The study also focused on assessing the role of liquid phase sintering (LPS) mechanism by thermodynamic calculations and microstructural characterisation (SEM). Porosity measurements using density analysis and image processing were employed to determine the effects of powder size and morphology on sinterability of the alloys. It was found that the non-homogeneous particle size distribution with more spherical powder particles, facilitated the compaction and accordingly higher densification was obtained. This was achieved for powders milled at higher speeds (900 rpm), resulting in significantly lower porosity levels (~ 6-8 %) compared to the dry-milled state (~40-60 %).
      178
  • Publication
    Development of Magnesium-Strontium/Calcium (Mg-Sr/Ca)-Based Alloys with Improved Sinterability for Next-Generation Biomedical Implants
    (Springer, 2023-02-06)
    Celikin, Mert 
    ;
    Azadi, Ava 
    ;
    Kim, Hyeonseok 
    ;
    Vaughan, Ted 
    ;
    O'Cearbhaill, Eoin D. 
    The use of biodegradable magnesium (Mg) alloys for bone fixation devices has potential to improve patients’ quality of life by avoiding the necessary secondary operations conducted regularly for the removal of implants fabricated from conventional non-resorbable alloys. Mg-alloys have excellent biocompatibility and biodegradability along with a low modulus of elasticity which will decrease bone-shielding effects. However, low corrosion resistance and relatively poor mechanical performance limit the use of Mg-based alloys for biomedical applications. This study focuses on the processing of Mg-Ca- and Mg-Sr-based alloys via powder metallurgical route. Thermodynamic calculations are used to predict the liquid phase fractions in order to optimise sinterability and porosity levels. Materials characterisation was conducted to validate the thermodynamic modeling results using optical and scanning electron microscopy (SEM/EDS) as well as X-ray Diffraction (XRD).
      126