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ThesisItem Open Access Study of electrical and magnetic properties of cobalt based metallic glasses and composite material(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2005-07) Agrawal, Rati; Kushwaha, R.P.S.There are many materials of commercial importance; composite materials and metallic glasses are two such important materials among them. Wide variety of technological and industrial applications of these materials motivates the present work. Cobalt based metallic glass of nominal composition Co60B12Si12Fe4Mo2Ni1 and cobalt based composite material prepared by varying concentration of cobalt metal powder in plaster of paris was used for investigating their electrical and magnetic properties. For cobalt based composite material change in A.C. magnetic susceptibility with both frequency and concentration have been taken into account. Similarly temperature and concentration dependence of electrical resistivity of composite material was investigated. From experimental results obtained, A.C. magnetic susceptibility was found to decrease with frequency for all concentrations and increase in susceptibility was observed when plotted with concentration. when electrical resistivity of cobalt based composite material was investigate for its temperature dependence, slight decrease in resistivity or a dip was observed for all the concentrations i.e. for all the samples with different concentrations of cobalt metal powder in plaster of paris. Energy losses in the samples were also measured by studying their hysteresis loops for two different frequencies.ThesisItem Open Access Study of the role of pair transfer processes on isotope effect in superconducting TTF[Ni(dmit)2]2 systems(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2004-06) Pant, Manju; AjayIn the present investigation, we have studied the role of interband pair transfer processes on isotope effect in layered TTF[Ni(dmit)2]2 systems. For this purpose we have considered two chain Hubbard model that includes the intra and intermolecular vibrations in the presence of electron Coulomb energy and the electron transfer energy between the chains. Such a model calculations will be applicable for the organic superconductors where molecular layered structures are available. We obtained the expressions for the superconducting order parameter, transition temperature and finally the isotope effect coefficient ( ) using double time Greens’s function equations of motion technique within BCS mean field approximation. Finally the numerical analysis show that isotope effect coefficient ( ) depends on the intra and interlayer molecular vibrations, the pair transfer processes and also on the superconducting transition temperature (Tc) in layered organic superconductors like TTF[Ni(dmit)2]2 . On the basis of our model calculations we have predicted the effects of the pair transfer processes, the density of states at Fermi level and the chemical pressure on the isotope effect coefficient which need to be tested through rigorous experimental investigations on these systems.ThesisItem Open Access Study of thermo-elastic properties of nanomaterials under high pressure and high temperature(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2008-05) Jeewan Chandra; Gupta, B.R.K.T he study based on the EOS at high-pressure and high temperature is of fundamental interest because they permit interpolation and extrapolation in to the regions in which the experimental data are not available adequately. The Present work describes the theoretical study of thermo-elastic properties especially compression, thermal expansion, bulk modulus, thermal expansion coefficient of some of the nanomaterials by making use of Equation of State. For different class of solids a lot of numbers of equation of states are available. Among the number of isothermal and isobaric EOS described earlier, we prefer isothermal Usual Tait’s Equation of State (UTE) and isobaric Singh and Gupta Integral form of Equation of State (IFEOS) because of their simple and straightforward applications in high pressure and high temperature physics. We have reported the results obtained for thermo physical properties of nanomaterials i.e. n-SnO2, n-CeO2, n-PbS, n-MgO, nCuO, n-AlN, n-ZnO, n-NiO, n-TiO2, n-Ni, n-Ti, n-(Ni+Fe), n-Mo, individual single wall carbon nanotube (SWCNT), under effect of high temperatures and high pressures. The variation of compression (V/V0), isothermal bulk modulus (KT) and relative isothermal expansion coefficient ǂ(P)/ǂ0) with pressure have plotted and shown in tables, for nanocrystalline n-SnO2 with three particle sizes 3nm, 8nm and 14nm, n-CeO2, nanocrystalline MgO ( 100nm and 200nm), n-CuO, n-PbS ( 2.6nm, 5.4nm and 8.8nm), n-Ni(20nm and 62nm), n-Mo and n-AlN n-TiO2( 35nm and 6nm) and nZnO using Usual Tait’s equation of state. We have also calculated temperature dependence of thermal expansivity (ǂT), relative volume thermal expansion (V/V0) and bulk modulus (KT) of nanomaterials { n-ZnO, n-TiO2 anatase, n-NiO, n-Ni, n(Ni+Fe), n-Ti, and SWCNT(armchair CNT (5, 5), and zig-zag CNT (9, 0); both in axial as well as radial directions)}using IFEOS at different temperature and atmospheric pressure. The Integral form of Equation of State( IFEOS) is entirely free from the use of potentials and need only three input parameters such as Anderson Gruneisen parameter( 0 TDž ), volume thermal expansion coefficient(ǂ0) at zero pressure, reference temperature, and the thermo-elastic parameter k which can be calculated from the slope of the graph between log(DžT) and log(T/T0). The calculated values are plotted with temperature and compared to available experimental data in order to compare the present results. All the results have been presented graphically. It may be noted here that the calculated values are in close agreement to the experimental data. Thus it is emphasized here that the Integral form of Equation of State (IFEOS) and Usual Taits Equation of State(UTE) successfully explains the thermo-elastic properties nanomaterials.ThesisItem Open Access Influence of the third dimension on the electronic spectra and out-of-plane transport behaviour in bilayered high Tc cuprates in normal state(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2008-01) Tewari, Bhagya Sindhu; AjayThesisItem Open Access Study of thermophysical properties of different class of solids under high pressure and high temperature(G.B. Pant University of Agriculture and Technology, Pantnagar (Uttarakhand), 2005) Devlal, Kamal; Gupta, B.R.K.ThesisItem Open Access Heavy ion irradiation induced effects on MgB2 thin films(Govind Ballabh Pant University of Agriculture and Technology;Pantnagar, 2006) Ravindra Kumar; Agrawal, H.M.ThesisItem Open Access Study of mechanical properties of nanomaterials under high temperature and high pressure(Govind Ballabh Pant University of Agriculture and Technology;Pantnagar, 2006) Srivastava, Ajeet Kumar; Gupta, B.R.K.ThesisItem Open Access Study of the spectral properties of layered high Tc Cuprate superconductors(G.B.Pant University Of Agriculture And Technology Pantnagar : Uttaranchal, 2005) Pathak, Kumar Pradeep; AjayThesisItem Open Access Study of non-equilibrium effects and some systematics in (n, 2n) reactions(Govind Ballabh Pant University of Agriculture and Technology;Pantnagar, 2006) Prajapati; Agrawal, H.M.