Browsing Doctoral Degrees (Physics) by Title
Now showing items 1-20 of 47
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The anomalous low state of the X-ray binary system Hercules X-1
(University of the Free State, 2008)The lightcurve of Hercules X-1 (Her X-1) shows a peculiar 35-day modulation of the X-ray flux cycling between low and high states. The 35-day modulation is believed to result from the occultation of the neutron star by a ... -
Characterization of Gd2O2S: Tb³+ phosphor powder and thin films
(University of the Free State, 2011-06)Under Ultra violet (UV), cathode-ray and X-ray excitation, terbium activated rare earth oxysulphide (Gd2O2S:Tb3+) phosphors shows bright green luminescence. Due to its superior luminescent performance, Gd2O2S:Tb3+ phosphor ... -
Characterization of SrAl₂O₄:Eu²⁺,Dy³⁺ nano thin films prepared by pulsed laser deposition
(University of the Free State, 2010-11)English: Thin films of SrAl2O4:Eu2+,Dy3+ phosphor were deposited on silicon (Si (100)) substrates using a 248 nm KrF pulsed laser. Deposition parameters, namely; substrate temperature, pulse repetition rate, number of laser ... -
A combined ab initio and experimental study of lanthanides and/or transition metal doped oxides
(University of the Free State (Qwaqwa Campus), 2017-01)Ab initio modelling techniques have produced a notable contribution in analysing semiconductor metal oxides properties by use of first principles. These techniques have transformed to a high level of accuracy, owing to the ... -
Degradation of ZnS:Cu,Au,Al phosphor powder and thin films under prolonged electron bombardment
(University of the Free State, 2001-10)Auger electron spectroscopy (AES) and cathodoluminescence (CL), both excited by the same electron beam, were used to monitor changes in surface composition and luminous efficiency during electron bombardment. ZnS:Cu,Al,Au ... -
Effect of broadband excitation ions in the luminescence of Ln.³+ doped SrF₂ nanophosphor for solar cell application
(University of the Free State, 2015-06)SrF2:Pr3+-Yb3+ phosphor powder was previously investigated for down-conversion application in solar cells. The rst surface, structural and optical characterization results indicated that the Pr3+-Yb3+ couple requires a ... -
Effect of host anion or cation substitution on the luminescence and stability of lanthanum oxide based phosphors doped with bismuth
(University of the Free State, 2022-01)LaOCl:Bi3+ phosphor powders were successfully prepared via the solid-state reaction method and compared to LaOBr:Bi3+. Photoluminescence measurements revealed that the phosphors displayed ultraviolet emission around 344 ... -
Experimental studies and modelling of surface loss during segregation
(University of the Free State, 2015-01)Afrikaans: Metallurgiese produkte speel ‘n onontbeerlike rol in die alledaagse lewe. Die soeke na metale met beter eienskappe soos sterkte, slytasie- en korrosieweerstand asook metodes om vervaardigingskostes en – tye te ... -
Gamma-ray production in the Be-type star-pulsar binary system PSR B1259-63
(University of the Free State, 2012-01-30)English: The high-mass binary system PSR B1259-63/LS 2883 is one of only six known gamma-ray binaries, and the only one where the compact object is known from the direct observation of a pulsed radio signal to be a 48 ms ... -
Growth of antimony on copper : a scanning tunneling microscopy study
(University of the Free State, 2012-01)English: The thesis deals with adsorption, self–assembly and surface reactions of Sb atoms on solid Cu(111) substrates. It is of genuine interest in materials science and technology to develop strategies and methods for ... -
An image guided adaptive radiotherapy strategy for cervix cancer treatment based on equivalent uniform dose
(University of the Free State, 2021-11)Aim: This study aims to develop an image-guided adaptive strategy to compensate for temporal effects of tumour shrinkage and organ motion in cervix cancer treatment based on the equivalent uniform dose (EUD). The strategy ... -
Investigation of the luminescent properties of metal quinolates (Mqx) for use in OLED devices
(University of the Free State, 2014-01)Since Tang and VanSlyke developed the first organic light emitting diode (OLED) in the late 80’s using tris-(8-hydroxyquinoline) aluminium (Alq3) as both the emissive and electron transporting layer, a lot of research has ... -
An investigation on surface segregation of S in Fe and a Fe-Cr alloy using computational models and experimental methods
(University of the Free State, 2014-11)English: A systematic investigation is conducted to determine the influence of the microscopic effects of the bcc Fe lattice on the segregation parameters, Q, D0, ΔG and Ω. These microscopic effects include the dependence ... -
'n ISS studie van die (110), (111) en (100)-enkel-kristalvlakke van NiAI
(University of the Free State, 2000-11)English: In this study the [110]-, the [111]- and the [1OO]-single crystal surfaces of Ni Al were investigated. The aim was to firstly harmonize the existing knowledge of these surfaces and secondly to create a clear and ... -
Kinetic Monte Carlo simulation of the growth of gold nanostructures on a graphite substrate
(University of the Free State, 2006-06)Nanotechnology has, without a doubt, ushered in a new era of technological convergence and holds the promise of making a profound impact on the way research in physics, chemistry, materials science, biotechnology etc. are ... -
Luminescence enhancement of phosphors by doping with silver
(University of the Free State, 2015-10)Phosphor materials doped with noble metals have attracted considerable attention for the past fifty years due to their possible applications in lighting and solar cells with improved efficiency, biology, lasers and novel ... -
Luminescence from lanthanide ions and the effect of co-doping in silica and other hosts
(University of the Free State, 2012-07)Amorphous silica powders doped with lanthanide ions were synthesised by the sol-gel method and their cathodoluminescence (CL) and photoluminescence (PL) emissions were compared. Interesting differences depending on the ... -
Luminescence investigation of trivalent rare earth ions in sol-gel derived SiO₂ and ZnO co-doped SiO₂:Pr³⁺
(University of the Free State, 2011-05)Tb3+-Pr3+ , Ce3+-Pr3+ , and Eu3+-Pr3+ ion pairs co-doped in SiO2 were successfully synthesized using a sol gel method to produce rare earth activated oxide nanophosphors. Green emitting ZnO nanoparticles were also successfully ... -
Luminescence investigations of CaS:Eu2+ powder and pulsed laser deposited thin films for application in light emitting diodes
(University of the Free State, 2015-06)The main objective of this thesis was to investigate the luminescent properties of commercial CaS:Eu2+ powder and pulsed laser deposited thin films for application in light emitting diodes. X-ray diffraction (XRD), X-ray ... -
Luminescence properties of Gd2O3:Bi3+ co-doped Ln3+ as powder and thin films phosphor for solar cell application
(University of the Free State, 2021-11)The main aim of this project is to study the luminescence properties of Gd2O3:Bi3+ co-doped Ln3+(Yb3+ and Er3+) phosphor powder and thin films to improve the energy conversion efficiency of photovoltaics (PV) by using the ...