3D Electron Microscopy Investigations of Human Dentin and Ion Beam Irradiation Effect on Biocompatible Anatase TiO2 Using Focused Ion Beam Based Techniques
Materials Science and Engineering, MSc. Thesis Defense, 2015
Prof. Dr. Mehmet Ali Gülgün (Thesis Advisor), Assoc. Prof. Melih Papila, Prof. Dr. Sedat Alkoy
Date & Time: 29th December, 2015 – 11 AM
Place: SUNUM G111
Keywords : Focused Ion Beam, 3D Reconstruction, Electron Tomography, Ion Beam Irradiation, Human Dentin, Anatase TiO2
The concept of this study, as well as three dimensional reconstruction of human dentin in micro and nano size; involves also the irradiation effects and modification of anatase TiO2 surface by gallium focused ion beam and investigating the different aspects of modified surface by means of Scanning Electron Microscopy (SEM), Raman spectroscopy and Energy Dispersive Spectroscopy (EDS). The aforementioned procedures can successfully be carried out using a dual-beam system consisting of high-resolution scanning electron microscope (HR-SEM), focused ion beam (FIB) columns, attachments such as gas injection systems (GIS), and detectors for elemental analysis (EDS). However, the ion beam irradiation causes some artifacts as long as other beneficial modifications on material’s surface especially on biocompatible materials such as TiO2. Therefore, in this work we tried to consider these kinds of limitations as well as the advantages of using focused ion beam for nanostructuring, ion implantation etc.
In the first part of this study, high-resolution electron microscopy techniques, such as Focused Ion Beam (FIB), Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HRTEM) revealed micro and nano features within human dentin with high definition and accuracy. The samples were prepared using FIB based advanced nanostructuring processes in a dual-beam instrument. The related secondary electron (SE) image tomographs were acquired by means of stacking the images from FIB slice-series for monitoring micro-sized dentinal tubules, whereas FIB-structured pin-like samples were investigated at the TEM to observe the collagen fibrils at the nanoscale. The complimentary analysis helped to reveal the microstructure and morphology of human dentin in three dimensions in detail.
In the second part of the study, surface morphology and microstructural evolution upon low energy ion irradiation of anatase TiO2 were investigated by in situ focused Ga+ ion beam/scanning electron microscopy. A surface roughening through pore formation, coalescence and eventually nanoneedle formation was induced on TiO2 surface. The mechanism of nanoneedle formation was investigated. In addition, Raman spectroscopy and EDS analysis of irradiated surface revealed the gallium implantation during direct milling. Gas assisted etching was investigated in this study in order to reveal the enhancement of surface milling in presence of assisting gas.