Theses and Dissertations (Physics)

Functionalized multiwall carbon nanotubes for electronic and magnetic applications

Thu, 12 Nov 2020 00:00:00 GMT

Functionalized multiwall carbon nanotubes for electronic and magnetic applications Oke, James Ayodele In this work, SiO2, MWCNTs, MWCNTs:SiO2, MWCNTs-TiO2, and MWCNTs:TiO2:SiO2 nanomaterials were synthesized and characterized by the use of different techniques to ascertain novelty of the nanomaterials and also to establish their suitability for several electrical, electronic and magnetic based device applications. The results, in general, indicate that the nanocomposites were well prepared and the properties of MWCNTs can be tuned by introducing SiO2, TiO2, and a composite of SiO2 and TiO2 in its matrix. This tunability of properties leading to the suitability of the material for various applications has been explained in this work

Measurement of Heavy Ion induced X-ray production cross sections in metallic targets at MeV energies

Sat, 20 Apr 2019 00:00:00 GMT

Measurement of Heavy Ion induced X-ray production cross sections in metallic targets at MeV energies Masekane, Masedi Carington Experimental X-ray production cross sections (i.e. probability of X-ray generation in a target by an incoming MeV ion) are useful not only for fundamental ion beam – matter interaction studies, but also for the development of new ion beam materials analysis techniques such as Heavy Ion Particle Induced X-ray Emission (HI-PIXE) spectroscopy. Unfortunately, while theoretical predictions of X-ray production cross sections due to light (Z<6) projectile ions are generally in good agreement with experiment, this is not the same for heavier projectiles. Experimental studies show that heavy ions induce higher X-ray yields in targets compared to light ions of the same velocity, which implies higher sensitivity for Heavy Ion PIXE. There is therefore a need for substantial experimental data to improve theoretical models. This dissertation presents measurements carried out at the iThemba Laboratory for Accelerator Based Sciences (LABS) to determine X-ray production cross sections in Vanadium (V), Zirconium (Zr) and Tin (Sn) metal oxide films due to carbon and chlorine MeV ion beams at an ion velocity range of 0.1-1.0 MeV/u. The measured cross sections are compared to predictions by the modified Plane Wave Born Approximation (PWBA) and the ECPSSR theory that takes into account; the energy loss (E) of the projectile due to Coulomb deflection (C) by the target atom, and the perturbed-stationary state (PSS) and relativistic nature (R) of the target atoms’ inner shell. The observed agreements and discrepancies between experiment and theory are discussed in terms of the atomic ionization mechanisms for each projectile-target collision

Electronic, electrical and magnetic properties of graphene oxide functionalized with gold and iron nanoparticles

Fri, 01 Jan 2021 00:00:00 GMT

Electronic, electrical and magnetic properties of graphene oxide functionalized with gold and iron nanoparticles Idisi, David Omoefe In the current project, GO was synthesized and functionalized with gold and iron oxide nanoparticles. Several characterization techniques were performed to study the change in the microstructural, electronic, electrical and magnetic properties of rGO due to functionalization. The obtained results from the study showed weak ferromagnetic and superparamagnetic features for rGO:Au-NP and supermagnetism for rGO-ATAFe 2O3 nanocomposites. The source of the observed magnetic features were mainly attributed to defects induced into rGO by oxygen moieties, Au and Fe atoms bonding on the edge and basal planes of GO. The charge storage behavior and magnetic properties of rGO:Au-NP composite indicate that the material can be useful for applications in ferro-electric and memory devices. The rGO:Fe2O3 nanocomposite can find potential in magnetic resonance imaging contrast agent application due to the observed superparamagnetic properties.

Graphene oxide functionalised with conducting and non-conducting polymer materials for spintronic and biomedical applications

Tue, 23 Mar 2021 00:00:00 GMT

Graphene oxide functionalised with conducting and non-conducting polymer materials for spintronic and biomedical applications Ganya, Elison Soul We have synthesised graphene oxide (GO) using Hummer’s method which was further reduced (rGO) by hydrazine hydrate. We used the reverse micelle process to functionalise graphene oxide (GO) to synthesise P-GO and its subsequent reduction produced P-rGO. The synthesised GO was coated with poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) conducting polymer (CP) to obtain CP-GO which was subsequently reduced using hydrazine hydrate to form CP-rGO. We used Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), ultra-violet photoelectron spectroscopy (UPS), X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) techniques to study the electronic and structural properties of GO, rGO, P-GO, P-rGO, CP-GO and CP-rGO nanocomposites for biological/biomedical applications. The magnetic properties of the nanocomposites were investigated using the superconducting quantum interference device (SQUID). The electrical conductivity of the CP-GO nanocomposites was found to be ~104 times higher than that of GO. The P-rGO nanocomposites exceptionally show an over-trebled magnetic response of 9.6 × 10-3 emu/g as compared to the CP-GO of 2.9 × 10-3 emu/g, respectively at 2 K. Functionalisation of GO with polyacrylate improves the magnetic properties for P-GO and P-rGO due to increase in defect density, sp3-type bonding and improved magnetic coupling of magnetic moments emanating from the presence of nitrogen species. The presence of polyacrylate and PEDOT:PSS contribute to the successful modification of the electronic and magnetic behaviour of the nanocomposites thereby qualifying them for potential biological/biomedical applications.