Department of Physics

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Author: search.filters.author.Dr. Abdul SattarSubject: search.filters.subject.FA15

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    The Effects of Mn –Substitution on the Structural and Magnetic Parameters of Zn Ferrites Synthesized by Sol Gel Method
    (Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) Khursheed Amin; CIIT/Fa15-RPH-015/LHR; Dr. Abdul Sattar; LHR TP 6844
    Single phase Mn substituted Zn ferrites with chemical formula Zn1-xMnxFe2O4 (x= 0.0, 0.1, 0.2 and 0.3) were synthesized by means of Sol-gel auto-combustion technique. The samples were sintered at 700oC and then characterized by different experimental techniques such as X-ray diffraction (XRD),Fourier transform infrared spectroscopy(FTIR),Scanning electrons microscope(SEM),Vibrating sample magnetometer(VSM) andVector network analysis (VNA). The single phase formation of all the samples was confirmed by the XRD analysis. Lattice parameter (a), volume (V) and X-ray density (Dx) as a function of Mn contents were calculated from XRD patterns. Scanning electron microscopy reveals that the grain size of all the ferrites is found to be in the range of 200nm-250nm. FTIR spectra give us idea about different functional groups present in a material and nature of molecular bonds in the substance. Vibrating sample magnetometer (VSM) was used to determine M-H loops of all the samples. The value of coercivity is found to be several hundred oersteds which indicate that the material is soft spinel ferrite in nature. In addition, high frequency parameters (direct and real permittivity, permeability, conductivity and loss tangent) were studied as a function of frequency (1GHz-6GHz) for a selected sample.
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    Atomistic simulation of silica-based glasses using molecular dynamics
    (Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) Muhammad Umer; CIIT/FA15-RPH-026/LHR; Dr. Abdul Sattar; LHR TP 6842
    Silica based glasses are being utilized ubiquitously in different disciplines of everyday life. Addition of modifiers in silica based glasses varies their physical and chemical properties. In this dissertation the preparation of silica based ternary glasses SiO2 CaO-ZrO2 using molecular dynamic simulation has been done. The structures of different silica based glasses with compositions 70SiO2-(30-x)CaO-xZrO2 (x=0,5,10,15,20,25,30) were generated using MD simulations following melt quench method. Pedone‟s potential is used to meet the requirement of molecular dynamics simulations. The radial distribution function analysis suggests that the clustering of the silica tetrahedral glass network increases with the concentration of calcium. The different concentrations of CaO and ZrO2 noticeably change the glass transition temperature of different compositions of glasses. The structural analysis of our ternary glasses equips us with the information of oxygen-silicon coordination number and the Qn species found in the prepared glasses. The appearance of different ratios of Qn species in our glasses is because of the changing concentration of CaO and ZrO2 in the composition.
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    Study of the structural evolution in phosphate glasses using Molecular Dynamics simulations
    (Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) Hafsa Javed; CIIT/FA15-RPH-002/LHR; Dr. Abdul Sattar; LHR TP 6843
    This thesis presents the study of the structural changes in ternary zinc magnesium glasses. Compositional effects on the structural properties of the ternary zinc magnesium phosphate glasses were studied for the development of the glasses with the improved chemical durability. The basic methodology for the study is molecular dynamics simulations. The short range structures in glasses were examined using the pair distribution function, angular distribution function and coordination number analysis. Also the glass transition temperature was measured for different compositions. The short range structure of the simulated glasses was observed and the results were validated with the results obtained from simulations and the experimentally measured data. It was found that the backbone structure of the phosphate is not affected by the change in composition. As the zinc oxide was replaced by the magnesium oxide the chemical durability of the glass was increased. The results for the glass transition temperature show an increase in transition temperature with the replacement of MgO by ZnO. It indicates the formation of more chemically impervious bonds with increase in magnesium oxide content. The glass with the enhanced chemical durability will be more impervious to the aqueous attack.