Department of Physics
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Item Study of Streaming Dust Acoustic Instability in Quantum Plasma(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2018) Asif Zahoor; FA16-RPH-031; Dr. Muhammad Jamil; LHR TP 5240In this thesis a study related to Streaming Dust Acoustic Instability in Quantum Plasma is done. In this investigation starting from equation of motion containing Fermi Pressure, Bohm Potential and Exchange Correlation term we use quantum hydrodynamic (QHD) model to derive a general expression for dielectric constant which led to the final dispersion relation. A graphical discussion is also made by considering real part which shows the phase speed of DAWs whereas the imaginary part give the growth rate. The graphical results are obtained by varying the mass of dust particles, number density of electrons and by taking different streaming speed. This research is expecting a great scope in astrophysical quantum plasmasItem Study of Dust Acoustic Waves with Dust Charge Fluctuation in Quantum Plasm(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2018) Rubina; FA16-RPH-016; Dr. Muhammad Jamil; LHR TP 5230In this dissertation, the time-dependent charge fluctuation of dust particles have been studied in quantum dusty plasmas. The dust acoustic wave has been taken as the perturbation of the plasma system. The quantum fluid model consisting upon momentum balance equation, continuity equation and gravitational Poisson’s equation has been employed to solve for the dispersion relation. The instability of the wave in the form of damping is observed. It is noticed that the dust acoustic wave went to damp for the whole spectrum of k on varying ion-thermal temperature, electron number density and dust radii.Item Investigation of Doped (III-V) Group Elements Emissive Layer for Visible LED Applications(2019) Aqsa Hashmi; CIIT/FA17-RPH-043/LHR; Dr. Farah Alvi; LHR TP 5728This study Sb2S3 was prepared by applying hydrothermal technique with different concentration of Ag as a doping impurity to improve its optical and electrical properties to be used in optoelectronics for LED applications. FTIR spectra was used to analyze the vibrations of chemical bonds present in the different groups in the sample. The intensity of the peaks is reduced with the increase in doping concentration, this is because the strength of chemical bonds decreases because of intermolecular transition of groups present in the sample. Optical properties were studied by UV-Vis and PL spectroscopy. UV-vis spectra was used to calculate bandgap that comes out between 2.5-1.9 eV. The bandgap was reduced with the increase in doping concentration of Ag which indicate its good compatibility for LED applications. IV measurements were used to analyze IV characteristics of the samples and to find out the turn on voltage of the device. SEM results were helpful in analyzing the surface morphology of the samples and measuring the particle size. The device was characterized by electroluminescence spectra which confirmed the red emission from LEDs having emissive layers of undoped and doped Sb2S3. So the materials have bright future for visibe LED applications.Item Hybrid Ion Conductors Membrane for CO2 Separation(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2018) TAUQEER AHMAD; SP16-RPH-028; LHR TP 5246; Dr. Ghazanfar AbbasCO2 is emitted in a very large amount per year by the different fossil fuel industries for the generation of energy which is the major origin of GHG in the climate. CO2 emission is a major worldwide problem of today. Different works have been done for the reduction of CO2 emission gas and numerous types of works are under process. In our project the major focus is to separate the CO2 by hybrid ion conductors membrane of solid oxide fuel cell. For this purpose, GDC/Li2CO3-Na2CO3 (LN-GDC) nanocomposite electrolyte material was synthesized with molar ratio 1:3 by co precipitation method. The sample was dried in oven and filtered by suction pump followed by sintering at temperature 700oC in a digital furnace. The prepared sample LN-GDC was further characterized by different techniques; XRD, SEM, FTIR including conductivity measurements by four probes DC method. The XRD and SEM results confirm that the synthesized material lies in nano scale, homogeneous and dense in nature. However, the major study was focused to analyze the CO2 separation from this membrane so the sample was further reformed in polymer membrane and chloroform was used as a solvent for the preparation of dense hybrid membrane. This modified prepared hybrid membrane is used for the separation of CO2 gasItem Study of Shafranov Shift by the Simplest Grad Shafranov Equation Solution for Various Tokamaks(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2012) Kanwal Zulfiqar; FA10-MSPHY-005; Dr. Muhammad Asif; LHR TP 3515Plasma internal energy is not conserved on a magnetic surface if nonlinear flows are considered. The Magnetohydrodynamic equilibrium in an axisymmetric plasma is described by the Grad Shafranov equation in terms of the magnetic flux. A generalized Grad Shafranov type equation has been used. Specific functional forms of plasma internal energy and current are used. A simplest analytic solution of the Grad Shafranov equation is used. This solution is over constrained both in shape and in plasma current. We demonstrate that the Shafranov shift for this solution is independent of plasma current for various tokamaks. We studied the dependence of Shafranov shift on various plasma parameters and found that Shafranov shift depends on parameters such as major radius, minor radius, aspect ratio and inverse aspect ratio. The Shafranov shift shows a direct relation with major radius „ ‟. The value of Shafranov shift increases with the increase in value of major radius. Similarly for minor radius „a‟ there exist a direct relation between Shafranov shift and minor radius. And inverse aspect ratio „a/ ‟ is also varies directly with Shafranov shift. For the case of aspect ratio Shafranov shift is inversely related to the aspect ratio „ ‟Item Study of Shafranov Shift by the Simplest Grad Shafranov Equation Solution for Various Tokamaks(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2012) Kanwal Zulfiqar; CIIT/FA10-MSPHY-005/LHR; Dr. Muhammad Asif; LHR TP 3515Plasma internal energy is not conserved on a magnetic surface if nonlinear flows are considered. The Magnetohydrodynamic equilibrium in an axisymmetric plasma is described by the Grad Shafranov equation in terms of the magnetic flux. A generalized Grad Shafranov type equation has been used. Specific functional forms of plasma internal energy and current are used. A simplest analytic solution of the Grad Shafranov equation is used. This solution is over constrained both in shape and in plasma current. We demonstrate that the Shafranov shift for this solution is independent of plasma current for various tokamaks. We studied the dependence of Shafranov shift on various plasma parameters and found that Shafranov shift depends on parameters such as major radius, minor radius, aspect ratio and inverse aspect ratio. The Shafranov shift shows a direct relation with major radius „ ‟. The value of Shafranov shift increases with the increase in value of major radius. Similarly for minor radius „a‟ there exist a direct relation between Shafranov shift and minor radius. And inverse aspect ratio „a/ ‟ is also varies directly with Shafranov shift. For the case of aspect ratio Shafranov shift is inversely related to the aspect ratio „ ‟.Item Electron transport properties of stacked 2 dimensional materials(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2017) Ali Raza; SP15-RPH-003; Dr. Abdul Sattar; LHR TP 6856Graphene; a material with a high carrier mobility, having zero band gap drawback. Whereas, Boron Nitride with an insulating behavior, having a wide band gap opening. To control the band gap of grapheme without affecting the carrier mobility, Graphene/ Boron Nitride (grapheme/BN) hetero bilayers (HBLs) are formed. In these HBLs the layer of graphene is already doped with BN as well. First Principles calculations show that the band gap and electron effective mass can be modulated according to the need by just changing their stacking arrangement and the inter layer spacing between BN and hybrid layer of graphene. The results show that the tunability of graphene band gap have a linear dispersion relation with handsome band gap opening for a specific stable stacking pattern and this is a promising feature for futuristic Nano devices.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 Synthesis And Characterization Of Lead Based(Library Information Services, COMSATS University Islamabad, Lahore Campus, 2019) Muhammad Faizan; CIIT/FA17-RPH-025/LHR; Dr. Muhammad Amir Razaq; LHR TP 5720To overcome the needs of energy the production and storage of energy has become the critical problem therefore most research topics around the world are related to the work on storage devices [1]. Lead acid batteries (LABs) are the most oldest among the secondary rechargeable batteries. The first lead acid battery was invented in 1859. In these days getting power for various applications from LABs has become a popular way. These batteries include two types of electrodes and an electrolyte. One of the electrodes is positive and the other is negative. The reaction between these components is the basic cause of the generation of power. Due to having fast response, high cyclic efficiency about (63-90%) and low cost these batteries playing a vital role in all type of industries [2, 3, 4, 5].