Resume

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        My research focused on molecular dynamic simulation of aluminosilicate glasses in the hope of understanding the properties of assemblies of molecules in terms of their structure and the microscopic interactions between them. This serves as a complement to conventional experiments, enabling us to learn something new, something that can not be found out in other ways.

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Master Resume 

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           Dy 3+ -doped alkaline earth aluminosilicate glasses of the molar composition 35 MO – 10Al 2 O 3 – 55 SiO 2 (M=Ba, Sr, Ca, and Mg) were prepared by using the melt quenching technique. Differential scanning calorimetry (DSC) measurements of these glasses were carried out. Direct and indirect optical band gaps were calculated based on the glasses UV absorption spectra. The Judd-Ofelt (J-O) theory was used to evaluate the three intensity parameters from the experimental oscillator strengths. Using the J-O intensity parameters, several radiative properties such as spontaneous transition probabilities (A R ), radiativebranching ratios (β R ), and radiative lifetimes (τ R ) were determined. The photoluminescence spectra obtained by the excitation wavelength of 349 nm show three emission bands at 482,574 and 660 nm corresponding to the 4 F 9/2 → 6 H (15/2, 13/2, 11/2) transitions, respectively. From the visible emission spectra yellow to blue (Y/B) intensity ratios and chromaticity coordinates were calculated. The lifetimes of the 4 F 9/2 metastable state were also measured. All properties are discussed in relation to the influence of the different network modifyer ions on the structure of the glasses.

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Thesis Resume 

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Understanding the atomic structure of glasses is critical for developing new generations of materials with important technical applications. In particular, the local environment of rare-earth ions and their distribution and clustering is of great relevance for applications of rare earth-containing glasses in photonic devices.
In this work, the structure of Gd 2 O 3 doped lithium and potassium aluminosilicate glasses is investigated as a function of their network modifier oxide to aluminum oxide ratio using molecular
dynamics simulations. The applied simulation procedure yields a set of configurations, the so-called inherent structures, of the liquid state slightly above the glass transition temperature. The generation of a large set of inherent structures allows a statistical sampling of the medium-range order of the Gd 3+ ions with less computational effort compared to other simulation methods. The resulting medium-range atomic structures of network former and modifier ions are in good agreement with experimental results and simulations of similar glasses. It was found that increasing NMO/Al ratio increases the network modifier coordination number with non-bridging oxygen sites and reduces the overall stability of the network structure. The fraction of non-bridging oxygen sites in the vicinity of Gd 3+ ions increases considerably with decreasing field strength and increasing concentration of the network modifier ions. These correlations could be confirmed even if the simulation results of alkaline earth aluminosilicate glasses are added to the analysis. In addition, the structure
predictions generally indicate a low driving force for the clustering of Gd 3+ . Here, network modifier ions of large ionic radii reduce the probability of Gd–O–Gd contacts.

 Publications  

 

1) M.Zekri, A.Herrmann, R.Turki, C.Rüssel, R.Maâlej, K.Damak

Experimental and theoretical studies of Dy3+ doped alkaline earth aluminosilicate glasses 

Journal of Luminescence, 212, 354-360,  

DOI: 10.1016/j.jlumin.2019.04.041

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2) Rim Turki, Mohamed Zekri, Andreas Herrmann, Christian Rüssel, Ramzi Maalej, Kamel Damak

Optical properties of peralkaline aluminosilicate glasses doped with Sm3+.

Journal of Alloys and Compounds 07/2019; 

DOI: 10.1016/j.jallcom.2019.07.255