Department of Physics
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Item Magnetosonic Weaves for Anisotropic Non- Extensive Distributions(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) MUHAMMAD ZEEWAQAR MANZOOR; CIIT/FA15-RPH-024/LHR; Dr. Muhammad Fraz Bashir,; LHR TP 6983The magnetosonic wave instability is studied by using the kinetic theory taking the non- extensive anisotropic distribution which follows the Tsallis statistics. The temperature anisotropy may also serve as a source of free energy, which can make different waves unstable depending upon whether the anisotropy ratio is either greater (A>1) or smaller (A<1) than one. In this work, the marginal stability analysis of the magnetosonic wave instability in non-extensive anisotropic plasma is obtained using the exact numerical analysis to explain the Bale diagram obtained from the solar wind data at 1 AU for Non- extensive counterstreaming distribution. The effect of non-extensivity parameter q and the temperature anisotropy on the growth rate and the real frequency is discussed by using the exact numerical analysis. Different functional which depend on the counterstreaming parameter P have been considered. The appearance of counterstreams has a strong effect on the marginal instability conditions of the firehose and the mirror modes. The marginal instability conditions of these modes very precisely depend on the functional dependence of the parameter P. An extremely interesting new physical result has been obtained in the case P=P₁. In this case, the counterstreams affect both magnetosonic modes, making the plasma unstable at low values of || . With increasing the parameter P₀₁ the mirror and the firehose modes becomes more unstable, and the region of the plasma stability turns out to be limited from all sides. Such a behavior is obviously very similar to that found in the solar wind plasma, where the observed data form a rhombic-shaped region in the A- || plane. Thus the effects of Non-extensivity parameter q on the marginal stability curve are highlighted to better model the Bale- diagram Non-extensivity counterstreaming index q as compared to the usual Maxwellian distribution.Item Investigation of Sr-substituted BaFe2O4 Synthesized by Sol-Gel Method(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) Jawaria Shaheen; FA15-RPH-010; Dr. Mukhtar Ahmad; LHR TP 6985In the present work, Sr-substituted samples of single phase spinel mono ferrites with formula Ba1-xSrxFe2O4 (x = 0.00, 0.33, 0.67, 1.00) were synthesized using sol-gel auto combustion method. A sample with x = 0.00 was chosen to heat treat at different temperatures (at 100oC, 300oC, 400oC, 600oC and 700oC for 4h) in order to confirm the single phase formation of the samples. The sample heat treated at these temperatures was then investigated by X-ray diffraction (XRD) analysis. The results show that single phase sample can be successfully synthesized at a temperature of 600oC which is much lower than the same structured samples reported in earlier literature. All the synthesized compositions of these samples were then sintered at 700°C for 4h for better crystallinity. These samples were then investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), vibrating sample magnetometery (VSM), Vector network analysis (VNA). X-ray diffraction analysis reveals that single-phase monobarium ferrites can be obtained at 600°C-700°C temperature for 4h. From XRD patterns, different structural parameters such as lattice parameters (a,b,c), cell volume (V) and X-ray diffraction density as a function of Sr2+ ions at Ba2+ sites were calculated. Scanning electron microscopy results show that the grain size increases as the temperature is increased because it is well known that increased heat treatment promotes the grain growth in ferrites. Fourier transform infrared spectroscopy analysis gives us information about different groups of chemical compounds present in our material. From M-H loops of the samples (with x=0.0, 0.33, 0.67 and 1.00) measured by VSM, different magnetic parameters such as saturation magnetization (Ms), remanance (Mr), coercivity (Hc) and magnetic moment (nB) were calculated. The value of coercivity (Hc) increases as the Sr substitution was increased in ferrite materials. In addition, the variation of different dielectric parameters (real permittivity, imaginary permittivity, real permeability, imaginary permeability, ac conductivity and loss tangent) as a function of frequency (-6GHz) has been discussed in the present work.Item Theoretical and Experimental Study of Mixed Ionic Electronic Materials (MIEC) for Electrochemical Functional Nano-Composite Layer(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) Muhammad Khurram Qureshi; CIIT/FA15-RPH-014/LHR; Dr. Rizwan Raza; LHR TP 6984Due to the increased demand of energy there would be a stern dispute in the near future as the efficient energy resources are soon to be ceased. To overcome such a challenging disagreement, we have to put our attention towards such novel energy conversion and efficient technology which can strengthen us against such problem. Fuel cells are promising devices for clean and efficient power generation. The electrolyte free fuel cell (EFFC) is an innovative, high-energy conversion and efficient generation of fuel cells which directly convert the chemical energy into electrical energy. In this research the mixed ionic and electronic conducting material will be equipped by desired route for EFFC production. MIEC is basically responsible for the performance of EFFC. EFFC with only one homogenous layer Nano-composite material comprises upon ionic and electronic conductors which will overwhelm the mechanically and chemically compatible issues. The designed material was examined experimentally and theoretically. The single homogenous layer consist upon mixed conducting Nano-composite material certifies the better performance, high efficiency and reliability. Diverse electrochemical measurements are used to investigate the performance and efficiency of prepared EFFC material. The conductivity of MIEC is investigated with 2 probe and 4 probe method. After that, the mixed conductivity was separated out with the help of ion blocking and Heb-Wagner method. These two techniques were used to study the ionic and electronic conductivity of MIEC. Similarly, the optical, mechanical, vibrational, structural characteristics and important parameters were investigated with the help of multiple techniques The working and electrochemical performance of prepared EFFC was studied at Nano level to explain the working principle of as prepared EFFC. Theoretical model and simulations of pItem Effect of Changing Fundamental Constants on Helium Abundance during Big Bang Nucleosynthesis(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) Raza ur Rehman Mir; CIIT/FA15-RPH-033/LHR; Dr. Shabana Nisar; LHR TP 6941Effect of Changing Fundamental Constants on Helium Abundance during Big Bang NucleosynthesisItem Fabrication and Characterization of Tin Oxide Based Flexible Composites for Energy Storage Applications(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) NAEEM MUNIR; CIIT/FA15-RPH-030/LHR; Dr.M Aamir Razaq; LHR TP 6986Tin Oxide (SnO2) is excessively used for energy storage applications due to wide potential, transparency and thermal stability. Several methods are reported for fabrication of SnO2 nano structures e.g. electro spinning, chemical vapor deposition process, self assembly, homogeneous precipitation method, thermal decomposition and hydrothermal method. Hydrothermal method is advantageous due to low cost, template free, environment friendly and low temperature. In this study, SnO2 is fabricated via hydrothermal method and furthermore composites with CuO, ZnO and lignocelluloses fiber are synthesized for development of electrochemically efficient and flexible paper electrodes for energy storage. X-Ray diffraction, Scanning Electron Microscopy (SEM), FTIR and Cyclic Voltammetry measurements of fabricated composites were employed to characterize the morphology, structural and electrochemical characteristics. SEM reveals the nano-petal and nanorods morphology of SnO2 and CuO, respectively. XRD measurements confirm the fabrication of SnO2, SnO2/CuO and ZnSnO3 by JCD cards (41-1445), (48-1548) and (34-1451) respectively. Cyclic Voltammetry confirm the electrochemical kinetics of fabricated composites which are highly feasible for super capacitors and batteries.Item 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 6844Single 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.Item 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 6842Silica 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.Item Ordinary Mode Instability in Non-extensive Anisotropic Plasma(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) MUHAMMAD SHERAZ MISALI; CIIT/FA15-RPH-001/LHR; Dr. Muhammad Fraz Bashir; LHR TP 6836The distribution function has different forms in the different region of space plasmas. These change in the distribution significantly affects the dispersion properties of the waves especially their free energy source (if exist) can make the wave unstable under certain conditions. These instabilities as an effect of free energy source is a great deal of interest in space plasma community to their application to different solar wind problems e.g., particle acceleration etc. The non-extensive distribution have received renewed attention due to the better agreement with the space plasma observations as compared to the Maxwellian distribution. The temperature anisotropy makes the wave unstable based depending upon whether the anisotropy ratio (A=Tx/Tz) is either greater (A>1) or smaller (A<1) than one. The Bale diagram obtained by the solar wind data is clear indication of this relation showing four different region of anisotropy plasma beta space. These different regions are bounded by the instabilities. Davidson and Wu first discussed the electromagnetic ordinary (O) mode instability can become unstable for anisotropy ratio greater than one and high plasma beta. Ibscher et al. revisited the work and obtained the marginal and threshold conditions of the o-mode instability for electron for the bi Maxwellian distributions and extended to the solar wind proton anisotropy and related to the Bale-diagram. The exact numerical analysis contrary to the above theoretical result is predicted by Hadi et al. and clearly proved that the lower bound of the Bale-diagram is bounded by the O mode instability in the counter-streaming plasmas. In this work, the marginal instability threshold condition of ordinary mode(O-mode) is obtained using the exact numerical analysis to explain the bale-diagram obtained from the solar wind data at 1AU for Non extensive distributions. It is shown that the lower bound of the Bale-diagram is bounded by the O-mode instability. The effects of non-extensivity parameter q on the marginal stability curve are also highlighted to better model the Bale-diagram through Non extensity index q as compared to the usual Maxwellian distribution.Item 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 6843This 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.Item Synthesis and Characterization of Nickel-Copper Doped M-type Hexagonal Ferrites for High Frequency and Energy Storage Applications(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) Ahmed Iftikhar Qureshi; CIIT/FA15-RPH-031/LHR; Dr. Majid Niaz Akhtar; LHR TP 6832Nanoparticles of Ni-Cu doped M-type hexagonal ferrites (Ba0.5Sr0.5NixCuxFe12-2xO19) have been prepared from Microemulsion technique. FTIR (fourier transform infrared spectroscopy), XRD (x-ray diffraction), SEM (scanning electron microcopy), VNA (vector network analyzer), UV-VIS (ultraviolet visible region) are used to characterized the materials for their structure, morphology, grain size and grain boundary, electromagnetic and optical properties of the M-type hexagonal ferrite sintered material. FTIR confirms the formation of M-type hexagonal ferrites that describes the bonding mechanism. XRD confirms the single phase crystalline material with ‘a’= 5.88 Angstrom and ‘c’=23.039 Angstrom. SEM shows a grain size of 0.25µm to 0.55µm, VNA confirm the dielectric and electric properties of M-type hexagonal ferrites. DC electrical resistivity and dielectric constant are increased which shows the material is a good candidate for high frequency and good capacitance for energy storage devices.